Дисертації з теми "Structure regeneration"
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1
Toma, Jeremy Steven. "Immunohistochemical analyses of nervous system structure, development and regeneration." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/31284.
Анотація:
Specific aspects of nervous system structure, development, and regeneration were
investigated in two separate studies. The first study was concerned with development of
sensory root entry zones. Sensory information enters the central nervous system (CNS)
via root entry zones where sensory axons span a glial environment consisting of Schwann
cells in the peripheral nervous system (PNS) and astrocytes and oligodendrocytes in the
CNS. Little is known about the postnatal development of the glial elements of many root
entry zones. I sought to establish a comparative developmental timecourse of the glial
elements in the postnatal (PO, P3, P7, P14) and adult rat of three root entry zones: the
spinal nerve dorsal root entry zone, the trigeminal root entry zone, and the vagal dorsal
root entry zone. I compared entry zone development based on the expression of antigens
in peripheral glia, central glia, and the PNS extracellular matrix. While all three root
entry zones had reached maturity by PI4, the glial elements comprising the PNS-CNS
interface of the trigeminal root entry zone and the vagal dorsal root entry zone matured
earlier than those of the spinal nerve dorsal root entry zone.
This study revealed unexpected expression patterns of certain glial antigens. For
example, the antibody used to label mature oligodendrocytes (RIP) labelled Schwann cell
cytoplasm. I sought to follow up on this observation and characterized RTP
immunoreactivity in peripheral glia in the second study. In uninjured rats, RIP
demarcated paranodal regions of myelinated axons and clearly defined Schmidt-
Lantermann incisures. Robust RIP immunoreactivity was present in Remak bundles.
Low levels of RIP immunoreactivity were detectable in satellite cells surrounding dorsal
root ganglion (DRG) neurons and in terminal Schwann cells at neuromuscular junctions.
These results suggested a correlation between RIP immunoreactivity and amount of
axoglial contact. Injury induced sympathetic sprouting and pericellular basket formation
in the DRG was conducted to further examine this correlation. All perineuronal
sympathetic sprouts infiltrated heavily RlP-immunoreactive satellite cell sheaths. RIP
immunoreactivity was absent from placodal-derived olfactory ensheathing cells,
suggesting that correlation between axoglial contact and RIP immunoreactivity is
confined to peripheral glia of neural crest origin.Science, Faculty of
Zoology, Department of
Graduate
2
Koon, Chung Lun. "Studies of coke deposition, structure and regeneration during catalytic processing." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306081.
3
Castro, Diaz Miguel. "Universal characterisation of coke structure and distribution for hydrocarbon conversion process catalysts." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268476.
4
Welling, Pirjo. "Regeneration by seeds and vegetation structure in alpine plant communities, subarctic Finland /." Oulu : Oulun Yliopisto, 2002. http://herkules.oulu.fi/isbn951426861X/.
5
Franks, Katrin. "The structure and properties of soluble phosphate based glasses." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326227.
6
Ioras, Ioan Florin. "The impacts of livestock grazing on plant communities and soil structure in semi-natural Norway spruce stands (Picea abies (L.) Karsten) in the Piatra Craiului massif." Thesis, Brunel University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323725.
7
Brudvig, Lars Andrew. "Effects of restoration on Midwestern oak savanna biodiversity, structure, and oak regeneration." [Ames, Iowa : Iowa State University], 2007.
8
Welling, P. (Pirjo). "Regeneration by seeds and vegetation structure in alpine plant communities, subarctic Finland." Doctoral thesis, University of Oulu, 2002. http://urn.fi/urn:isbn:951426861X.
Анотація:
Abstract
The aims were to examine the importance of regeneration by seeds, the
influence of plant traits and disturbances, and the role of seed-seedling
conflicts in regeneration and in the determination of vegetation structure.
The study was carried out at in a subarctic alpine area (Kilpisjärvi
69°01'N 20°50E', Finland).
Seed bank and seedling densities were high in many plant communities
(ranges 99 -1109 viable seeds/m2 and 0.2-227
seedlings/m2, respectively). Effective seedling
recruitment is reflected in vegetation as a high proportion of plants with
poor or no vegetative reproduction ability. This development may take place
in meadows and snowbeds where herbs (e.g. Gnaphalium
supinum, Sibbaldia procumbens,
Veronica alpina and Viola
biflora) are abundant. On the other hand, the low proportion of
these plants in heath vegetation reflects ineffective seedling
recruitment.
Floristic similarities between the consecutive phases in the
regeneration pathway may be low despite effective seedling recruitment.
Clonality, large and small seed sizes and appendaged diaspores limit the
movement of species from phase to phase.
Generally, disturbances facilitate effective regeneration by seeds.
Grazing promotes species with large seed banks and is therefore one reason
for high seed bank densities. Freezing and melting processes negate a
negative influence of altitude on seed bank densities in the phase of
seedlings. However, if disturbances are severe and continuous and the soil
is compact, unstable or dry, disturbances are not beneficial. The same is
true if there is a shift in the species composition of seedlings from gaps
to closed vegetation. This phenomenon occurred in a rich meadow.
Seed-seedling conflicts limit regeneration by seeds in low-herb
snowbeds and Ranunculus glacialis-Gymnomitrion
snowbeds. Vegetative reproduction and infrequent pulses of seedling
recruitment negate an influence of short-term seedling recruitment on the
spatial structure of vegetation. Extreme conditions, such as low
temperatures, instability of the soil and late snowmelt modify the
influence of factors that are important in more moderate conditions.
To conclude, all transitions limit regeneration by seeds. However,
favourable conditions (e.g. moist conditions in a meadow) partly eliminate
the obstacles against seedling emergence. Regeneration by seeds therefore
has a major impact on the dynamics and structure of vegetation. In heath
vegetation, where bare soils are dry and the moss cover is thick, large
seed banks and seed rains do not guarantee effective seedling recruitment.
The regeneration process is reduced in the early phases, and plants that reproduce primarily by seeds have a minor role in vegetation. The accumulation of seed banks is effective in these circumstances.
9
Kapoor, Saurabh. "Alkali-free bioactive glasses for bone regeneration." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/13951.
Анотація:
Doutoramento em Ciência e Engenharia dos MateriaisBioactive glasses and glass-ceramics are a class of third generation biomaterials which elicit a special response on their surface when in contact with biological fluids, leading to strong bonding to living tissues. The purpose of the present study was to develop diopside based alkali-free bioactive glasses in order to achieve good sintering behaviour, high bioactivity, and a dissolution/ degradation rates compatible with the target applications in bone regeneration and tissue engineering. Another aim was to understand the structure-property relationships in the investigated bioactive glasses. In this quest, various glass compositions within the Diopside (CaMgSi2O6) – Fluorapatite (Ca5(PO4)3F) – Tricalcium phosphate (3CaO•P2O5) system have been investigated. All the glasses were prepared by melt-quenching technique and characterized by a wide array of complementary characterization techniques. The glass-ceramics were produced by sintering of glass powders compacts followed by a suitable heat treatment to promote the nucleation and crystallization phenomena. Furthermore, selected parent glass compositions were doped with several functional ions and an attempt to understand their effects on the glass structure, sintering ability and on the in vitro bio-degradation and biomineralization behaviours of the glasses was made. The effects of the same variables on the devitrification (nucleation and crystallization) behaviour of glasses to form bioactive glass-ceramics were also investigated. Some of the glasses exhibited high bio-mineralization rates, expressed by the formation of a surface hydroxyapatite layer within 1–12 h of immersion in a simulated body fluid (SBF) solution. All the glasses showed relatively lower degradation rates in comparison to that of 45S5 Bioglass®. Some of the glasses showed very good in vitro behaviour and the glasses co-doped with zinc and strontium showed an in vitro dose dependent behaviour. The as-designed bioactive glasses and glass–ceramic materials are excellent candidates for applications in bone regeneration and for the fabrication of scaffolds for tissue engineering.
Os vidros e vitrocerâmicos bioactivos fazem parte da chamada terceira geração de biomateriais, i.e., materiais que estimulam uma resposta especial quando em contacto com fluidos biológicos, capaz de conduzir ao estabelecimento de ligações fortes entre a sua superfície e os tecidos vivos. O presente estudo visou o estudo e desenvolvimento de vidros bioactivos à base de diópsido e isentos de metais alcalinos que apresentem um bom comportamento na sinterização, elevados índices de bioactividade, e taxas de dissolução / degradação compatíveis com as almejadas aplicações em regeneração óssea e em engenharia de tecidos. Procurou-se ainda entender as relações entre a estrutura e as propriedades dos vidros bioactivos estudados. De acordo com esta perspectiva, estudaram-se várias composições de vidros bioactivos pertencentes ao sistema Diópsido (CaMgSi2O6) – Fluorapatite (Ca5(PO4)3F) – Fosfato de tricálcico (3CaO•P2O5). Todas as composições vítreas foram preparados por fusão, seguida de fritagem em água fria, e caracterizados através de um conjunto de técnicas complementares de caracterização. Os vitrocerâmicos foram obtidos por sinterização das fritas de vidro moídas e compactadas, seguida de tratamento térmico adequado para promover os fenómenos de nucleação e cristalização. Além disso, algumas composições vítreas seleccionadas foram dopadas com vários iões funcionais e os seus efeitos na estrutura vítrea, na sua propensão para a sinterização, e nos comportamentos in vitro em termos de biodegradação e bio-mineralização foram avaliados. Os efeitos das mesmas variáveis no processo de devitrificação (nucleação e cristalização) dos vidros e formação de materiais vitrocerâmicos foram também investigados. Algumas composições de vítreas apresentaram taxas de bio-mineralização elevadas, expressas através da formação de camadas superficiais de hidroxiapatite após 1-12 h de imersão num fluido fisiológico simulado (SBF). Todas as composições vítreas apresentaram taxas de degradação mais baixas quando comparadas com a do 45S5 Bioglass®. Alguns vidros bioactivos revelaram comportamentos in vitro excelentes, sendo a taxa de biomineralização dos co-dopados com zinco e estrôncio dependente da dose incorporada de dopantes. Os materiais estudados demostraram boa aptidão para aplicações em regeneração óssea e para o fabrico de estruturas de suporte em engenharia de tecidos.
10
Borth, Eric B. "Drivers of Larch Forest Regeneration in Siberia." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1562939303944601.
11
Sire, Jean-Yves. "Structure, formation et regeneration des ecailles d'un poisson teleosteen, hemichromis bimaculatus (perciforme, cichlide)." Paris 7, 1987. http://www.theses.fr/1987PA077162.
Анотація:
Les differents aspects de la biologie de l'ecaille elasmoide ont ete precises chez le cichlide hemichromis bimaculatus, a l'aide de techniques histo/morphologiques et experimentales. Les resultats permettent de considerer ce materiel comme un modele favorable pour l'etude: de la mise en place d'une matrice collagenique orientee, de la mineralisation d'une telle trame organique, d'interactions epidermo-dermiques (en ontogenese ou en regeneration) et de l'origine phylogenetique de l'ecaille elasmoide
12
Minor, Jesse, Donald Falk, and Greg Barron-Gafford. "Fire Severity and Regeneration Strategy Influence Shrub Patch Size and Structure Following Disturbance." MDPI, 2017. http://hdl.handle.net/10150/624330.
Анотація:
Climate change is increasing the frequency and extent of high-severity disturbance, with potential to alter vegetation community composition and structure in environments sensitive to tipping points between alternative states. Shrub species display a range of characteristics that promote resistance and resilience to disturbance, and which yield differential post-disturbance outcomes. We investigated differences in shrub patch size and stem density in response to variations in fire severity, vegetation community, and post-disturbance reproductive strategies in Sky Island forested ecosystems in the southwestern United States. Patterns in shrub structure reflect the effects of fire severity as well as differences among species with alternate post-fire reproductive strategies. Increased fire severity correlates with larger patch sizes and greater stem densities; these patterns are observed across multiple fire events, indicating that disturbance legacies can persist for decades. High severity fire produces the largest shrub patches, and variance in shrub patch size increases with severity. High severity fire is likely to promote expansion of shrub species on the landscape, with implications for future community structure. Resprouting species have the greatest variability in patch structure, while seeding species show a strong response to disturbance: resprouting species dominateatlowdisturbanceseverities,andobligateseedersdominatehighseverityareas. Differential post-fire reproductive strategies are likely to generate distinct patterns of vegetation distribution following disturbance, with implications for community composition at various scales. Shrub species demonstrate flexible responses to wildfire disturbance severity that are reflected in shrub patch dynamics at small and intermediate scales.
13
Schiffman, Paula M. "Environmental determinism and forest structure and composition: a naturally replicated experiment." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/37397.
14
Willems, Nancy. "Forest structure and regeneration dynamics of podocarp/hardwood forest fragments, Banks Peninsula, New Zealand." Lincoln University, 1999. http://hdl.handle.net/10182/1301.
Анотація:
Although species maintenance in small forest fragments relies on successful regeneration and recruitment, few studies have examined the effects of fragmentation on regeneration processes. New Zealand's podocarp species rely on large disturbance openings operating across a vegetated landscape to stimulate regeneration. Clearance of vegetation that results in small fragments of forest removes regeneration opportunities for podocarps by destroying the intact vegetation mosaic, and as a result may exclude disturbances of the scale necessary for podocarp regeneration. Fragmentation alters the disturbance regime of the landscape, with important implications for the regeneration of podocarps on Banks Peninsula. The four remaining lowland podocarp-hardwood fragments on Banks Peninsula were sampled to determine the structure and regeneration patterns of podocarps and to assess their long term viability. Density, basal area, and size and age class distributions were used to examine current composition, and in conjunction with spatial analysis, to identify past regeneration patterns and infer likely future changes in composition and population structure. Podocarp size and age class structures for three of the four fragments were characteristically even-sized and relatively even-aged (eg; Prumnopitys taxifolia c. 350 to 600 years), with little or no regeneration for approximately the last 200 years (old-growth fragments). Regeneration of the current podocarp canopy in the old-growth fragments may have been stimulated by flooding. The fourth younger fragment showed much more recent regeneration with Prumnopitys taxifolia, Podocarpus totara and Dacrycarpus dacrydioides mostly 80-160 years old, and substantial populations of seedlings and saplings, probably as a result of anthropogenic fire. In the absence of major disturbance the podocarp component in forest fragments on Banks Peninsula is likely to decline with composition shifting towards dominance by hardwood species. There is some evidence to suggest that canopy collapse will stimulate some podocarp regeneration within the fragments, however it appears to be unlikely that podocarps will persist on Banks Peninsula indefinitely within the fragments studied. There is an urgent need for more quantitative research in New Zealand fragmentation literature, and a need for more emphasis on processes. Banks Peninsula offers potential for a more landscape scale approach in forest management, and the maintenance of regenerating scrub in pockets about the Peninsula may offer the regeneration opportunities for podocarps that are lacking within protected fragments. My study took a quantitative approach in examining the effects of forest fragmentation on the demographics of podocarps and compositional change in forest fragments on Banks Peninsula.
15
Klinka, Karel. "Structure and regeneration of old-growth stands in the engelmann spruce - subalpine fir zone." Forest Sciences Department, University of British Columbia, 1998. http://hdl.handle.net/2429/661.
Анотація:
Old-growth stands are important for management,
conservation, wildlife, recreation, and maintaining biological
diversity in forested landscapes. However, we are lacking
the information needed to adequately identify and
characterize old-growth stands. This is especially true for
high elevation, interior forests. The characterization of stand
structure and regeneration pattern will help in the
development of site-specific guidelines for identifying old growth
stands and restoring some of the old-growth
characteristics in managed stands.
This pamphlet presents a synopsis of a study investigating
stand structure and regeneration of old-growth stands in the
Moist Cold Engelmann Spruce - Subalpine Fir (ESSFmc)
Subzone near Smithers, B.C. The three stands selected for
the study were located on zonal sites, each in different
watersheds, and the stands were established after fire. The
criteria used for selection were: i) absence of lodgepole
pine, ii) presence of advanced regeneration, and iii) abundant
snags and coarse woody debris. These stands were presumed
to represent the old-growth stage of stand development or
the final (climax) stage of secondary succession.
16
Dunn, Ingrid. "Structure, Composition, and Regeneration of Cross Timbers Forest Fragments in Different Land Use Contexts." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc799466/.
Анотація:
Throughout its current range, the Cross Timbers forest ecosystem is vulnerable to land-use change. In this study, we examined the surrounding land use matrix on the vegetation structure, composition and regeneration of six Cross Timbers forest fragments in Denton County, Texas (north of the Dallas-Fort Worth metroplex). Two fragments adjacent to agricultural land, two to residential neighborhoods, and two formally protected forest sites were selected. In summer 2015, five 100 m2 plots were randomly established in each fragment at least 200 meters from the edge. In each plot, all live and dead trees ≥ 3 cm diameter were identified and their height and diameter at breast height (DBH at 1.3 m aboveground) measured. Evidence of dumping (presence of trash) was recorded as an index of human frequentation. Differences in vegetation structure among the forest fragments were found. Most notably, fragments adjacent to agriculture contained 25% to 50% fewer trees per hectare than all other sites (Kruskal-Wallis, p < 0.02), especially trees <10 cm DBH. However, residential fragments had fewer trees that were ≥15 cm DBH compared to the other fragments, indicating that these are the youngest of the forest patches surveyed. Trash was observed in 60% of plots surveyed at residential forest sites, showing high levels of human frequentation compared to the protected and agricultural forest sites. Agricultural sites contained the lowest number of recorded tree species and were most similar to each other, sharing 91% of species. These findings indicate that surrounding land use affects forest structure and composition, consequently affecting valuable ecosystem services including wildlife habitat, aesthetics and recreation.
17
Klinka, Karel, Bob Brett, and Christine Chourmouzis. "Regeneration patterns in the Mountain hemlock zone." Forest Sciences Department, University of British Columbia, 1997. http://hdl.handle.net/2429/685.
Анотація:
The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old.
Understanding regeneration patterns in the MH zone has become increasingly important as logging continues towards higher elevations of the zone where snowpacks are deeper.
18
Aladin, Kaderbatcha Darwesh Mohideen. "Nanoscale structure-property and macroscale biomechanical function of nucleus pulposus in health, disease and regeneration." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45197143.
19
Steele, Kyle Lindsay. "Restoring forest composition and structure of riparian corridors in the Missouri Ozarks." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5690.
Анотація:
Thesis (M.S.)--University of Missouri-Columbia, 2008.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 14, 2009) Includes bibliographical references.
20
Crechet, Jean-Bernard. "Regeneration du complexe actif ras. Gtp relations structure-fonction de la proteine ras2 de saccharomyces cerevisiae." Paris 11, 1992. http://www.theses.fr/1992PA112029.
Анотація:
La conversion du complexe ras. Gdp en ras. Gtp constitue l'etape d'activation des produits ras dans le controle de la croissance et de la differenciation cellulaire. Chez saccharomyces cerevisiae, des analyses genetiques ont suggere que le produit du gene cdc25 pourrait exercer une fonction d'echange des nucleotides guanyliques sur les proteines ras1 et ras2 qui assurent le controle positif de l'activite adenylate cyclase. Les produits de deux suppresseurs extrageniques du defaut fonctionnel du cdc25 ont ete etudies: la proteine ras2t152i animee d'une propriete intrinseque d'echange accelere des nucleotides, et le produit carboxy-terminal du gene sdc25 (c-sdc25) qui possede une forte homologie avec la region correspondante du cdc25 et presente les proprietes d'un facteur d'echange des nucleotides sur les proteines ras de levure et de mammiferes. L'intervention combinee du facteur c-sdc25 et du domaine catalytique de la proteine gap, activatrice de la gtpase des produits ras a mis en evidence in vitro, le role de ces deux elements a effets regulateurs opposes dans la modulation de l'activite adenylate cyclase dependante de ras2. Les consequences biologiques de plusieurs mutations introduites dans le gene ras2 et les effets de ces substitutions sur les proprietes biochimiques de la proteine ont permis de preciser l'importance de certaines regions de ras2 dans le mecanisme d'activation conduisant a l'acquisition de sa conformation gtp liee et dans l'interaction avec sa cible, l'adenylate cyclase
21
Vallés, Lluch Ana. "P(EMA-co-HEA)/SiO2 hybrid nanocomposites for guided dentin tissue regeneration: structure, characterization and bioactivity." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/3795.
Анотація:
Se sintetizaron nanocompuestos híbridos en bloque de poli(etil metacrilato-co-hidroxietil acrilato) 70/30 wt%/sílice, P(EMA-co-HEA)/SiO2, con distintas proporciones de sílice hasta el 30 wt%. El procedimiento de síntesis consistió en la copolimerización de los monómeros orgánicos durante la polimerización sol-gel simultánea de tetraetoxisilano, TEOS como precursor de sílice.
El TEOS se hidroliza eficientemente y condensa dando lugar a sílice, y presenta una distribución homogénea en forma de agregados inconexos de nanopartículas de sílice elementales en los híbridos con bajos contenidos de sílice (<10 wt%) o redes continuas interpenetradas con la red orgánica tras la coalescencia de los agregados de sílice (>10 wt%). La red polimérica orgánica se forma en los poros producidos en el interior de las nanopartículas elementales de sílice, y también en los poros formados entre los agregados de nanopartículas.
Los nanohíbridos con contenidos de sílice intermedios (10-20 wt%) exhibieron las propiedades más equilibradas e interesantes: i) refuerzo mecánico de la matriz orgánica conseguida gracias a redes de sílice continuas e interpenetradas, ii) buena capacidad de hinchado debida a la expansión de la red orgánica no impedida todavía por un esqueleto de sílice rígido, y a un número alto de grupos silanol terminales hidrófilos (concentraciones inorgánicas en los alrededores de la coalescencia), y iii) mayor reactividad superficial debido a un contenido relativo bastante elevado de grupos polares silanol terminales disponibles en las superficies.
La 'bioactividad' o capacidad de los materiales en bloque de formar hidroxiapatita (HAp) sobre sus superficies fue estudiada in vitro sumergiéndolos en fluido biológico simulado (simulated body fluid, SBF). La formación de la capa de HAp viene controlada por el mecanismo y el tiempo de inducción a la nucleación de la misma, que dependen a su vez de la estructura de la sílice.Vallés Lluch, A. (2008). P(EMA-co-HEA)/SiO2 hybrid nanocomposites for guided dentin tissue regeneration: structure, characterization and bioactivity [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/3795
Palancia
22
Thompson, Buckley Rodger. "Urban [infra]structure : using neglected infrastructure as a framework for the regeneration of inner city voids." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/53347.
Анотація:
November of 2014 saw the approval and commission of Tshwane's 2055 vision for the city (Tshwane municipality, 2013: 6). It seeks the restructuring and rejuvenation of the inner city in an attempt to remedy a state of stasis resulting from urban decentralization and fragmentation. Although Tshwane's proposal has potential, its formal exclusive nature and prioritization of the city centre has initiated a process of decay in the informal zones of the urban periphery. This process of decay is particularly evident within the city block of Brown Street. Once a place where many a union march started, Brown Street now exists as a shadow of its former self (Valeska, 2013). A lack of supporting infrastructure and appropriate spatial conditions have facilitated a sharp increase in crime. The consequent privation of safety has, in turn, prompted vacancies of onsite industries. (Valeska, 2013). The loss of formal economic infrastructure (energy) alongside the simultaneous degradation of adjoining infrastructure has inevitably led to the decay of this city block.
This dissertation focuses on the possibility of rehabilitating and regenerating the decaying "in-between" (Woods, 1997: 13) spaces of the city block within its urban periphery. A theoretical approach to transformation is proposed, which, instead of opting for demolition, seeks to expand on existing systems. Therefore, by harnessing site potential, the project suggests that the neglected infrastructure become part of a regenerative machine; a system of components that will stimulate the re-investment and development of the city block. The main intention of the [infra]structure is to establish a coordinated relationship between the formal and informal of the city, the vision and the void. The goal is to create an organized centrality, where fragmented realities are brought together harmoniously using the neglected infrastructures as mediator.Mini Dissertation (MArch(Prof))--University of Pretoria, 2016.
tm2016
Architecture
MArch(Prof)
Unrestricted
23
Loewenstein, Edward F. "An analysis of the size- and age-structure of a managed uneven-aged oak forest /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9717178.
24
Naficy, Cameron Edwards. "Changes in forest structure and composition associated with unique land use histories:." [Missoula, Mont.] : The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-12012008-173306/unrestricted/Naficy_Cameron_Thesis.pdf.
25
Busby, Sebastian Upton. "Forest Structure, Composition, and Regeneration after High-Severity and Rapidly Repeated Wildfires in the Central Cascade Range." PDXScholar, 2019. https://pdxscholar.library.pdx.edu/open_access_etds/5127.
Анотація:
Within mid-to-high elevation conifer forests in the Cascade Range, wildfire extent, severity, and frequency are expected to rise due to increasingly drier forest fuels under climate change. Considering dominant species composition, existing forests may be poorly adapted to absorb stress and recover following altered wildfire patterns. We tested the hypothesis that increased fire activity may disrupt the recovery of upper-montane and subalpine forest types by quantifying post-fire forest structure and conifer regeneration after spatially large, severe, and rapidly repeated wildfires in the Central Cascade Range. A stratified random sampling design was used to select field plots (n=122) and drivers of conifer regeneration were modeled using logistic and negative binomial regression models.
Median conifer regeneration was very poor among sample plots that experienced either a single high-severity fire (49 seedlings/ha) or rapid reburn (14-28 seedlings/ha). Distance to seed source primarily drove seedling abundance, with shade-tolerant species abundance being most sensitive to increasing seed source distances and dry, exposed, post-fire environmental conditions. Rapidly repeated fire increased the size of high-severity patches by killing live seed source trees spared during an initial fire, with chronological sequence of burn severity promoting regeneration of all conifer species or primarily fast growing, fire-adapted pines. Low-seedling densities, a general lack of seed source, and future warming trends suggest these forests affected by expansive high-severity and/or repeated wildfire will transition into a patchy, low-density forest state. This early-seral state ecosystem will be composed of fire-adapted pines farther from live seed source and incorporate a patchwork of shrubby grassland that in turn, may be more resilient to frequent wildfire than prior forests. If future wildfire patterns manifest as expected in the Cascade Range, recovering mid-to-high elevation forests may begin resembling their drier, lower-elevation mixed-conifer counterparts in structure and composition.
26
Pires, Flauzino Neto Wilson. "Etude morphologique des nanocristaux de cellulose et application nanocomposite." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI003/document.
Анотація:
Puisque cette thèse présente deux études indépendantes sur les nanocristaux de cellulose, le résumé a été divisé en deux sections qui font référence aux chapitres II et III, respectivement.Investigation morphologique et structurelle des nanocristaux de cellulose I et II préparés par hydrolyse à l'acide sulfuriqueLe but du travail de recherche présenté dans le chapitre II était de produire, de caractériser et de comparer les CNC obtenus à partir de la pâte de bois d'eucalyptus en utilisant trois méthodes différentes: i) l'hydrolyse classique à l'acide sulfurique (CN-I), ii) l'hydrolyse acide de la cellulose précédemment mercerisée par traitement alcalin (MCN-II), et iii) la solubilisation de la cellulose dans l'acide sulfurique et la recristallisation subséquente dans l'eau (RCN-II). Les trois types de CNC préparés présentent des morphologies et des structures cristallines différentes. Lorsque les conditions d'hydrolyse acide sont mises en place de telle sorte que les domaines cristallins dans la pâte de bois initial et la cellulose mercerisée (WP et MWP, respectivement) sont préservés (60 wt% H2SO4, 45°C, 50 min), les nanocristaux résultants conservent la nature fibrillaire des fibres d’origine (c'est-à-dire que l'axe de la chaîne est parallèle au grand axe des particules aciculaires) et leur type allomorphe initial (I pour WP et II pour la MWP). Dans les deux cas, les particules sont principalement composées de quelques cristallites élémentaires liées latéralement. Les nanocristaux unitaires dans les CNC préparés à partir de cellulose mercerisée (MCN-II) sont plus courts, mais plus larges que ceux préparés à partir des fibres de cellulose I (CN-I). Si des conditions plus sévères sont considérées (64 wt% H2SO4, 40°C, 20 min), ce qui entraîne la dépolymérisation et la dissolution de la cellulose native, les chaînes courtes recristallisent en rubans de Cell-II lors de la régénération dans l'eau à température ambiante. Dans ces rubans tortueux, l'axe de la chaîne serait perpendiculaire au grand axe du nanocristal et parallèle à son plan basal.La structure moléculaire et cristalline unique des nano-rubans implique qu'un nombre plus élevé d'extrémités de chaîne réductrice sont situées à la surface des particules, ce qui peut être important pour des modifications chimiques subséquentes et pour de potentielles applications spécifiques telles que la biodétection et la bio-imagerie. Donc, cette étude permet de mieux comprendre la structure cristalline et la morphologie de la CNC obtenue par régénération à l'acide sulfurique.Propriétés mécaniques de nanocomposites de caoutchouc naturel renforcé avec des nanocristaux de cellulose à facteur de forme élevé extraits de la coque de sojaDans cette étude, les CNCs ont été isolés des coques de soja à partir d’un traitement par hydrolyse avec de l'acide sulfurique. Ces CNCSH ont été utilisés comme phase de renfort dans une matrice NR par casting à différents taux de charge, à savoir 1, 2.5 et 5% en poids. Les effets des CNCSH sur la structure ainsi que sur les propriétés thermiques et mécaniques du NR ont été étudiés. Par exemple, en ajoutant seulement 2,5% en poids de CNC, le module de conservation en traction du nanocomposite à 25 °C est environ 21 fois plus élevé que celui de la matrice NR non chargée. Cet effet de renfort est supérieur à celui observé pour les CNCs extraits d'autres sources. Il peut être attribué non seulement au facteur de forme élevé de ces CNCs, mais aussi à la rigidité du réseau percolant de nanoparticules formé au sein de la matrice polymère. De plus, il a été constaté que la sédimentation des CNC pendant la mise en œuvre du film nanocomposite par casting joue un rôle crucial sur les propriétés mécaniques. Une contribution importante de ce travail est de mettre en évidence l'importance de la sédimentation des CNCs, pendant l'étape d'évaporation sur les propriétés mécaniques des nanocomposites, ce qui est rarement mentionné dans la littératureSince this thesis presents two independent studies on cellulose nanocrystals, the abstract was divided in two sections referring to chapters II and III, respectively.Comprehensive morphological and structural investigation of cellulose I and II nanocrystals prepared by sulfuric acid hydrolysisCellulose nanocrystals (CNCs) were produced from eucalyptus wood pulp using three different methods: i) classical sulfuric acid hydrolysis (CN-I), ii) acid hydrolysis of cellulose previously mercerized by alkaline treatment (MCN-II), and iii) solubilization of cellulose in sulfuric acid and subsequent recrystallization in water (RCN-II). The three types of CNCs exhibited different morphologies and crystal structures that were characterized using complementary imaging, diffraction and spectroscopic techniques. CN-I corresponded to the type I allomorph of cellulose while MCN-II and RCN-II corresponded to cellulose II. CN-I and MCN-II CNCs were acicular particles composed of a few laterally-bound elementary crystallites. In both cases, the cellulose chains were oriented parallel to the long axis of the particle, although they were parallel in CN-I and antiparallel in MCN-II. RCN-II particles exhibited a slightly tortuous ribbon-like shape and it was shown that the chains lay perpendicular to the particle long axis and parallel to their basal plane. The unique molecular and crystal structure of the RCN-II particles implies that a higher number of reducing chain ends are located at the surface of the particles, which may be important for subsequent chemical modification. While other authors have described nanoparticles prepared by regeneration of short-chain cellulose solutions, no detailed description was proposed in terms of particle morphology, crystal structure and chain orientation. Was provide such a description in the present document.Mechanical properties of natural rubber nanocomposites reinforced with high aspect ratio cellulose nanocrystals isolated from soy hullsCellulose nanocrystals (CNCs) were isolated from soy hulls by sulfuric acid hydrolysis. The resulting CNCs were characterized using TEM, AFM, WAXS, elemental analysis and TGA. The CNCs have a high crystallinity, specific surface area and aspect ratio. The aspect ratio (around 100) is the largest ever reported in the literature for a plant cellulose source. These CNCs were used as a reinforcing phase to prepare nanocomposite films by casting/evaporation using natural rubber as matrix. The mechanical properties were studied in both the linear and non-linear ranges. The reinforcing effect was higher than the one observed for CNCs extracted from other sources. It may be assigned not only to the high aspect ratio of these CNCs but also to the stiffness of the percolating nanoparticle network formed within the polymer matrix. Moreover, the sedimentation of CNCs during the evaporation step was found to play a crucial role on the mechanical properties
27
Arthurson, Kathy. "Social exclusion as a policy framework for the regeneration of Australian public housing estates /." Title page, contents and abstract only, 2001. http://web4.library.adelaide.edu.au/theses/09PH/09pha791.pdf.
28
Maradiaga, Rodriguez Dalila del Carmen. "Comparing the structure and composition of riparian woodlands in three northeast Kansas lake watersheds." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/15041.
Анотація:
Master of ScienceDepartment of Horticulture, Forestry, and Recreation Resources
Charles Barden
Riparian forests are more effective than other land cover types at stabilizing stream banks during high water events. Tree trunks and roots can slow flood-waters, thus retaining sediment deposition within riparian areas instead of downstream in reservoirs. This project is part of a larger, multi-agency study on reducing sedimentation of federal reservoirs. Between August 2010 and May 2012, riparian forests were assessed in the watersheds of three northeast Kansas lakes: Atchison County, Banner Creek, and Centralia City. The predominant land use in those watersheds is agricultural, with Atchison and Centralia watersheds dominated by cropland and Banner dominated by grassland. Plot dimensions were 50ft by 30ft (1500 ft[superscript]2) measured from the top of the streambank outward to the extent of the predetermined active channel width (ACW). Forty-four plots were assessed across the three watersheds. Data collected in each plot were used to determine the basal area (BA) in ft[superscript]2 per acre, trees per acre (TPA), tree height by crown class, and quadratic mean diameter (QMD) by species. Results showed some trends in BA and TPA among the three watersheds, however differences were not significant. The average BA of trees in riparian woodlands in the Centralia watershed was 155 ft[superscript]2 (dominated by cottonwood (Populus deltoides) with some honeylocust (Gleditsia triacanthos)); the Atchison and Banner watersheds showed an average BA of 120 ft[superscript]2. The Atchison watershed was dominated by honeylocust and walnut (Juglans nigra) but the Banner watershed was dominated by bur oak (Quercus macrocarpa) and hackberry (Celtis occidentalis). However, the Atchison watershed had the most TPA (194), as well as the tallest trees of the three watersheds. The Atchison watershed had the highest QMD in oak, whereas the Banner and Centralia watersheds had the highest QMD in cottonwood. Banner watershed had more plots with seedlings, whereas Atchison watershed had more plots with saplings. Overall, forest regeneration primarily comprised hackberry seedlings and saplings, with hickory saplings more common in the Banner watershed. For each watershed, the composition and structure of riparian vegetation differed but not significantly.
29
Yamamoto, Kazuhiro, and Koji Tsuneyoshi. "A study on the cell structure and the performances of wall-flow diesel particulate filter." Elsevier, 2012. http://hdl.handle.net/2237/20049.
30
Sippola, Anna-Liisa. "Forest structure and biodiversity in northern boreal forests : effects of regeneration cutting on flying beetles and wood-decomposing fungi." Helsinki : University of Helsinki, 2001. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/sippola/.
31
Klinka, Karel. "Natural regeneration on clearcuts at the lower limit of the mountain hemlock zone." Forest Sciences Department, University of British Columbia, 1997. http://hdl.handle.net/2429/654.
Анотація:
The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous
forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska
yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old.
Early regeneration failures followed slashburning and the planting of unsuitable species. Currently, the most successful and feasible option for reforesting cutovers is natural
regeneration with a mix of the three main tree species, but uncertainties remain about the temporal and spatial pattern of regeneration, changes in species composition, and the time
required for stand establishment after cutting. Our study addressed these concerns by examining regeneration patterns on 6 sites that were clearcut 11-12 years prior to sampling and left to regenerate naturally. The sites were located at the lower
limits of the zone in the Tetrahedron Range, near Sechelt, at elevations from 1060-1100m.
32
Regelbrugge, Jon Charles Victor. "Effects of wildfire on the structure and composition of mixed oak forests in the Blue Ridge of Virginia." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/76340.
Анотація:
Canopy mortality. species abundance. and the species composition and origin of regeneration in mixed oak forests were studied following a 1900 ha man-caused early growing season wildfire in Shenandoah National Park. in the Blue Ridge Physiographic Province. Virginia. Pre-fire stands were dominated by chestnut. scarlet, and northern red oaks growing on medium quality sites (50 year upland oak site index 16-20 m). Permanent vegetation plots were established in four stands for each of high and low levels of fire intensity. and unburned stands. High-intensity fire killed 67% of the basal area and 81% of the trees, whereas low-intensity fire resulted in mortality of 8% of the basal area and 15% of the trees. The mean height of stem-bark char accounted for 91% and 95% of the variation in percent of the basal area and number of trees killed by fire, respectively. Logistic regression models were developed to predict the probability of fire-induced individual tree mortality (top-kill) as a function of DBH and height of stem-bark char for chestnut oak, scarlet and northern red oaks, pignut hickory, blackgum. and red maple. Blackgum and chestnut oak were the most fire resistant species studied. High-intensity fire resulted in the development of a new stand, whereas low-intensity fire resulted in thinning of the overstory and understory. Most species present in pre-fire stand reproduced via basal sprouts, chestnut oak sprouts were the most abundant stems taller than 1 m two growing seasons after high-intensity fire. Tree-of-heaven was the only species to regenerate by seed and able to match the height growth of oak basal sprouts. This research suggests that oaks are capable of replacing themselves on medium quality sites following wildfire-induced canopy removal in 55 to 60 year old stands.Master of Science
33
Rismanchian, Omid. "Evidence-based spatial intervention for regeneration of deteriorating urban areas : a case of study from Tehran, Iran." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/8023.
Анотація:
Throughout the urban development process over the last seven decades in Tehran, the capital city of Iran, many self-generated neighbourhoods have developed in which the majority of the residents are low-income families. On one hand, the main spatial attribute of these deprived neighbourhoods is spatial isolation from the surrounding, more affluent areas, which is accompanied by inadequate urban infrastructure and a lack of accessibility and permeability. On the other hand, the Tehran City Revitalisation Organisation - the governmental sector which is in charge of the deprived areas - is incapable of conducting urban regenerations without investment from the private sector, and is seeking methods to create ‘socio-economic stimulant zones’ to attract private sector participation in regeneration programmes. In this regard, this research investigates the notion of ‘spatial isolation’ which in return causes socio-economic isolation as highlighted in the literature. The research suggests that in order to develop feasible regeneration programmes, which can meet the interest of both people and government, and release the deprived area from isolation both spatially and socio-economically, the regeneration plans should focus on public open space developments as ‘socio-economic stimulant zones’. With regard to this idea, the research highlights the street as a ‘social arena’ – not arteries or thoroughfares – as the type of public open space in which its development could not only release the deprived areas from spatial isolation, but could also direct more pedestrian movement to and through the deprived neighbourhoods, making more opportunities for the creation of socio-economic interactions. In this respect, the theory of ‘natural movement’ and theories and literature of ‘integrated public open spaces’ form the theoretical framework of the research to support this idea. For further investigation, two case studies, one as the deprived area and one as the control area, have been chosen, and the spatial pattern of the city and the two cases have been analysed in regard to the notion of ‘spatial isolation’ through Space Syntax using Depthmap software and GIS. Also, the correlation between the distribution pattern of commercial land uses and syntactic measures across the city of Tehran is investigated to identify the potential streets in which to create commercial opportunities. Afterwards, in order to study the street life and the variety of activities the streets can afford, a few locally integrated streets in the deprived case have been chosen. At this stage, nineteen behaviours have been observed and classified in five major classes including the necessary, social, optional, hazardous, and occasional activities, and the correlation with syntactic measures are studied. Moreover, the methods of developing a route filtering system and a transformability index for identifying the most suitable streets for the creation of a pedestrian friendly network are discussed, using an example of a deprived area, integrating it with the surrounding urban fabric to create the ‘socio-economic stimulant zones’. The results show that by identifying the underlying spatial pattern of the urban fabric, it is possible to release the deprived areas from its spatial isolation through developing a street network without causing urban fragmentation. This approach could also form a cost-effective basis for developing a pedestrian friendly street network as one of the ‘socio-economic stimulant zones’, which the Tehran City Revitalisation Organisation is looking for; the type of streets that not only support the necessary activities and transportation, but could also facilitate socio-economic interaction.
34
Aksamit, Dawn N. "Exotic Invasive Plants on Private Woodlands of Virginia: Effects on forest composition, structure, and wildlife habitat." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/30975.
Анотація:
Exotic invasive plants have become a significant issue in the Southeastern United States for private landowners. These plants possess characteristics that allow for rapid growth and easy adaptation to many growing conditions, often outcompeting native vegetation and altering wildlife habitat, especially in disturbed areas. Disturbance, including access roads, trails, harvest sites, powerline corridors, and fence rows, is common on private land. Private landowners are often left to combat these problems without many monetary or expertise resources that are available to federal lands. Three field sites, each in a different physiographic province in Virginia, were surveyed for exotic invasive populations and sampled with nested overstory, understory, and regeneration plots and wildlife point intercept transects using paired plots during the summers of 2006 and 2007. Species richness of the overstory and understory did differ, but native percent understory cover and sapling density remained unchanged. Tree density and forest basal area were reduced with presence of exotic invasive plants. Regeneration diversity and density decreased in areas of exotic plant invasion. Eastern cottontail habitat suitability increased with the presence of exotic invasive plants. Suitability of habitat for the gray squirrel, downy woodpecker food, black-capped chickadee reproduction, and eastern wild turkey cover declined with the occurrence of exotic invasive plants. Twenty three of thirty seven total invasive plots were within twenty feet of a disturbance area. Continual assessment of impacts will help provide a better understanding of the nature of exotic invasive plants to landowners and may help them to manage and prevent plant invasions.Master of Science
35
Slyder, Jacob Brake. "Population Structure and Biophysical Density Correlates of Whitebark Pine (Pinus albicaulis) at Two Treelines in the Northern Rocky Mountains." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/42522.
Анотація:
This study analyzes the structure and biophysical correlates of density of two whitebark pine
(Pinus albicaulis) populations in the northern Rocky Mountains. Whitebark pine is a keystone
species and an important component of treeline ecosystem dynamics; however, subalpine populations
have declined nearly rangewide in recent decades. Though declines in subalpine forests have been
well documented in the literature, few studies have assessed population structure and habitat
requirements at treeline. Various disturbances have combined to impact whitebark pine populations
across its range, but the primary threat at treeline sites in the northern Rocky Mountains is white pine
blister rust, caused by the exotic fungal pathogen Cronartium ribicola. In this study, I aim to: 1)
assess population structure and regeneration within two geographically different treelines
experiencing contrasting levels of infection, and 2) examine associations among several biophysical
variables and whitebark pine density to better understand treeline habitat variability and regeneration
patterns. I used density-diameter curves and non-parametric Kruskal-Wallis tests to compare
population structure between sites, and developed generalized linear mixed models to assess
correlations between whitebark pine density and biophysical site variables. The results demonstrate
that despite very different ecosystems and blister rust infection rates, our two study sites have similar
population structure. Our model results highlight marked differences between populations in terms
of biophysical correlates of density. While correlations are similar within site, seedlings and saplings
have stronger correlations with biophysical variables than established trees.Master of Science
36
Mas, Vinyals Anna. "New design proposal to mimic the joint structure between bone and hyaline cartilage." Doctoral thesis, Universitat Ramon Llull, 2018. http://hdl.handle.net/10803/664480.
Анотація:
En el disseny de dispositius mèdics existeixen diversos casos en els quals és necessària la utilització de superfícies bioactives per aconseguir la integració òptima d’un implant amb el teixit que l’envolta. L’enginyeria de superfícies planteja diferents solucions, tot i així, per algunes aplicacions, l’obtenció d’una unió íntima entre el teixit i l’implant encara és un repte clínic. En aquest treball, presentem una tècnica que permet obtenir superfícies biomimètiques en qualsevol substrat que pugui ser sotmès a modificació per plasma.
Com a proba de concepte, hem aplicat la tecnologia desenvolupada en l’obtenció d’un scaffold heterogeni per la regeneració del teixit osteocondral, amb un gran potencial per ser utilitzat com a teràpia regenerativa. Un dels grans reptes en la regeneració osteocondral, és assolir un grau elevat de semblança amb l’estructura articular, des de l’òs subcondral fins a la superfície articular. La nostra metodologia permet la immobilització d’un hidrogel que imita el teixit cartilaginós a la superfície d’una plataforma bioceràmica, la qual reprodueix el teixit ossi. Aquesta última, actuarà com a suport mecànic i punt d’ancoratge a l’òs subcondral, a la vegada que proporcionarà un reservori de ions de calci i de fosfat que ajudaran a la creació del gradient de duresa present en les articulacions.
Així doncs, en aquesta tesi hem treballat en el disseny de les diferents parts que conformaran el scaffold. En primer lloc, per tal d’aprofundir en la creació del gradient de duresa, hem estudiat la bioactivitat de diferents substituts ossis bioceràmics comercials, els quals son candidats potencials per ser utilitzats en la construcció del scaffold. A continuació, hem validat la viabilitat del recobriment polimèric obtingut per PECVD en substrats bioceràmics i hem demostrat que no compromet la seva bioactivitat. A més, hem demostrat que la modificació superficial permet l’obtenció d’una interfície estable, que no es veu alterada per canvis fisiològics i permet l’autoensamblatge de l’hidrogel. Els estudis in vitro realitzats demostren que la tecnologia d’immobilització preserva la viabilitat cel·lular, i que la formulació permet la migració cel·lular a més de proporcionar un entorn adequat per la diferenciació condrogènica i osteogènica de cèl·lules mare mesenquimals.En el diseño de dispositivos médicos existen numerosos casos en los que es necesaria la utilización de superficies bioactivas para lograr la integración óptima de un implante con el tejido que le rodea. La ingeniería de superficies propone diferentes soluciones, sin embargo, en determinadas aplicaciones, la obtención de una unión íntima entre el tejido y el implante aún es un reto clínico. En el presente trabajo, presentamos una técnica que permite la obtención de superficies biomiméticas en cualquier sustrato que pueda ser sometido a modificación por plasma. Como prueba de concepto, hemos aplicado la tecnología desarrollada en la obtención de un scaffold heterogéneo para la regeneración del tejido osteocondral, con un gran potencial para ser usado como terapia regenerativa. Uno de los grandes retos en la regeneración osteocondral, es lograr un grado elevado de semejanza con la estructura articular, desde el hueso subcondral hasta la superficie articular. Nuestra metodología permite la inmovilización de un hidrogel que imita el tejido cartilaginoso en la superficie de una plataforma bioceràmica, la cual reproduce el hueso. Ésta última, actuará como soporte mecánico y punto de anclaje al hueso subcondral, a la vez que proporcionará un reservorio de iones de calcio y fosfato que ayudarán en la creación del gradiente de dureza presente en las articulaciones. Así pues, en esta tesis hemos trabajado en el diseño de las diferentes partes que conformaran el scaffold. En primer lugar, para profundizar en la creación del gradiente de dureza, hemos estudiado la bioactividad de diferentes sustitutos óseos biocerámicos comerciales, los cuales son candidatos potenciales para ser utilizados en la construcción del scaffold. A continuación, hemos validado la viabilidad del recubrimiento polimérico obtenido por PECVD en sustratos biocerámicos y hemos demostrado como no compromete su bioactividad. Además, hemos demostrado como la modificación superficial permite la obtención de una interfaz estable, que no se altera por cambios fisiológicos, la cual permite el autoensamblaje del hidrogel. Los estudios in vitro realizados demuestran que la tecnología de inmovilización preserva la viabilidad celular, y que la formulación permite la migración celular además de proporcionar un entorno adecuado para la diferenciación condrogénica y osteogénica de células madre mesenquimales.
In medical device engineering, there are several cases where there is an imperative need of obtaining bioresponsive surfaces to achieve an optimal integration of a certain biomaterial with the surrounding tissue. Surface engineering has provided different approaches, however for certain applications obtaining an intimate bonding between the tissue and the implant remains a clinical challenge. In this work, we present a newly developed technique that allows the obtention of biomimetic surfaces onto any substrate that can be subject to plasma modification. As a proof of concept, we have applied the technology to obtain a heterogeneous scaffold for osteochondral repair, which has a great potential to be used as regenerative therapy. One of the great challenges in osteochondral repair is achieving a high degree of mimicry of the whole joint structure, from the subchondral bone to the surface of hyaline cartilage. Our methodology allows the immobilization of a cartilage-like hydrogel onto a bone-like bioceramic platform by means of a polymeric coating. The bioceramic acts not only as mechanical support and anchoring point to the subchondral bone, but also it acts as a reservoir of calcium and phosphate ions, which through diffusion help in the creation of the stiffness gradient present in joints. Thus, in the present thesis, we have worked on the design of the different parts that will form the osteochondral heterogeneous scaffold. First, to gain insight into the stiffness gradient creation, we have studied the bioactivity of different commercially available bioceramic bone substitutes, which are potential candidates to be used as bone-like platform. Next, we have validated the viability of the polymeric coating obtained through PECVD in this type of biomaterials and shown how it does not compromise their bioactive properties. Moreover, we have demonstrated how the designed surface modification allows the obtention of a stable interface, which is not disrupted by physiological changes, that enables the subsequent self-assembly of a cartilage-like hydrogel. In vitro studies show how our immobilizing technology preserves cell viability, and that our hydrogel formulation enables cell migration as well as it provides a suitable environment for both chondrogenic and osteogenic differentiation of mesenchymal stem cells.
37
Fournier, Mylaine. "Structure et croissance d'un peuplement d'épinette noire (Picea mariana) issu d'une coupe d'une vingtaine d'années dans la région du Saguenay-Lac-Saint-Jean /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1997. http://theses.uqac.ca.
38
Spencer-Vellacott, Polly. "Landscape-scale genetic diversity in Fraxinus excelsior L. : genetic structure within and among populations and the influence of regeneration practices on genetic variation." Thesis, Bangor University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438831.
39
Bourdon, Laura. "Microstructures bioactives par électroimpression voie solvant pour la régénération tissulaire." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1244.
Анотація:
Le dépôt localisé en électrofilage champ proche et voie solvant - ou appelé ici « électro-impression » - est une technique récente permettant de diriger le dépôt de filament en combinant un jet de polymère stable et un collecteur amovible comme une technique de fabrication additive. Ce travail de thèse a eu pour objectif de développer la technique d’électro-impression afin de produire des structures bioactives pour l’ingénierie tissulaire. Le développement de la technique a été initié par une étude fondamentale pour comprendre les mécanismes de stabilité du jet de polymère sous champ électrique. Il a alors été mis en évidence qu’en augmentant la viscoélasticité des solutions par augmentation de la concentration ou de la masse molaire du polymère, des jets stables sans lasso pouvaient être obtenus. Ces résultats permettent désormais de considérer un nombre de matériaux plus important pour l’électro-impression. Les mécanismes d’empilement de filament localisé ont ensuite été étudiés pour in-fine limiter l’apparition de défauts lorsque la structure accumule un nombre de couches important. Les essais préliminaires sur l’utilisation d’un air humide, d’un air ionisé ou des deux polarités du champ électrique ont montré des résultats prometteurs pour contrôler l’empilement de filaments. La protection et la libération de protéines à partir de filaments électrofilés est un défis toujours d’actualité pour l’ingénierie tissulaire. Ainsi, différentes formulations de polymères ont été testées afin de trouver un moyen de préserver au mieux la protéine. Une étude structurale d’une protéine modèle, l’albumine de sérum bovin (BSA), a été réalisée par dichroïsme circulaire afin de vérifier l’effet de la mise en forme sur l’activité de la protéine. Les résultats ont montré que la BSA est libérée à partir de filaments de poly acide (lactique-co-glycolique) (PLGA) selon une structure très proche de sa structure native ce qui laisse supposer que l’électrofilage n’a que peu perturbé les propriétés de la protéine. La cinétique de libération de la protéine à partir de filaments de PLGA a aussi montré que la protéine était libérée en plus grande quantité en présence de poly (éthylène glycol) (PEG). La bioactivité de structures fibreuses contenant des agents de croissance a ensuite été étudiée pour des applications de régénération hépatique et parodontale. Dans le premier cas, le potentiel de régénération hépatique de filaments de PLGA avec le facteur « hepatocyte growth factor » (HGF) n’a pas été testé mais les filaments ont induits des comportements reproductibles et intéressants sur des cellules hépatiques HepG2 en fonction de la teneur en HGF dans les filaments. Concernant la régénération parodontale, deux structures fibreuses organisées ont été testées : une structure composite de poly (caprolactone) (PCL) contenant des nanoparticules d’hydroxyapatite et une structure de filaments cœur-coquilles (PEG-PCL) contenant le facteur de croissance « cementum protein 1 » (CEMP1). Ces deux structures ont permis aux cellules du ligament parodontal de produire une matrice minéralisée ce qui n’a pas été observé sur les deux autres structures sans nanoparticules et sans CEMP1. Ces structures sont donc prometteuses pour la régénération de tissus durs du parodonte comme l’os ou le cémentDirect-writing electrospinning is a recent technique able to deposit fibers with a stable polymer jet on a moving collector similarly to additive manufacturing. The aim of this work was to develop the solvent-based direct-writing electrospinning technique and produce bioactive structures for tissue engineering applications. A first fundamental study have been carried out on the stability mechanism of the polymer jet under electric field. This study showed that stable jet without whipping behavior could be obtained by increasing polymer concentration or molecular weight and thus viscoelasticity. Those results give rise to a new strategy to optimize solution formulation and enlarge the number of materials used for direct-writing electrospinning. Mechanism of filaments stacking have also been studied in order to find solutions to produce higher organized structure without stacking defects. Preliminary tests showed that injection of humidified air, ionized air or the use of two polarities could reduce the number of stacking defects. Protection and release of protein from electrospun filaments is still a current challenge for tissue engineering. Then, different polymer formulation with a model protein, bovine serum albumin (BSA), was tested to find a way to preserve the protein. Secondary structure of bovine serum albumin (BSA) was investigated by circular dichroism to check protein activity. Released BSA in water from poly (lactic-co-glycolic acid) (PLGA) filament had a similar structure to its native one which means that electrospinning had a relatively low effect on BSA structure or that BSA show good structure reversibility. The kinetic release of BSA from PLGA filaments also showed that the presence of poly (ethylene glycol) (PEG) allow a higher amount of BSA to be released. The bioactive potential of filaments containing growth factors was tested for a hepatic and periodontal regeneration. The hepatic regenerative potential of PLGA filaments containing hepatocyte growth factors (HGF) could not been tested but a reproducible effect was noticed on hepatocyte cells HepG2 according to the amount of HGF in the filaments. Concerning the periodontal regeneration, periodontal ligament cells (PDLC) was cultured on different organized structures: a composite one made of poly (caprolactone) (PCL) and hydroxyapatite nanoparticles and the other one is made of core-shell PEG-PCL filaments containing cementum protein 1 (CEMP1). The two structures allowed the PDLC to produce a mineralized matrix which was not the case for the two other structures without nanoparticles and CEMP1. Thus, those bioactive structures showed promising regenerative potential for hard tissues like bone or cement
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Kundrat, Mary Elizabeth. "A Comprehensive Series for Predicting Bone Dynamics: Forecasting Osseous Tissue Formation using the Molecular Structure of a Biomaterial." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1282842002.
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Klinka, Karel, Gordon J. Kayahara, and Christine Chourmouzis. "Regeneration, growth and productivity of trees within gaps of old-growth forests on the outer coast (CWHvh2) of British Columbia." Forest Sciences Department, University of British Columbia, 2001. http://hdl.handle.net/2429/669.
Анотація:
Central to the issue of harvest feasibility on the outer BC coast (CWHvh) is the question of whether sites, once harvested, can be regenerated, and whether the time period for replacement and subsequent growth is economically and environmentally acceptable. Since low productivity sites have not been harvested in the past, there is a lack of data to answer this question. We tried to provide an answer by assessing regeneration following natural disturbances. Small scale gap disturbances are the norm within old-growth stands. If regeneration is not a problem in gaps, then we have some evidence that regeneration
should not be a problem upon implementation of our management practices. The objectives of this study were: (1) to develop baseline information on the mechanisms and the patterns of regeneration across a sequence of forest types; (2) to assess regeneration success with respect to productivity; and (3) to estimate future growth and productivity.
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Durán, Rangel Cristabel [Verfasser], and Albert [Akademischer Betreuer] Reif. "Forest gaps structure and tree regeneration in a montane Guayanan forest, Sierra de Lema, Venezuela = Lückenstruktur und Baumverjüngung in Nebelwäldern der Sierra de Lema, Venezuela." Freiburg : Universität, 2011. http://d-nb.info/1123466084/34.
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Murta, Marco Aur?lio Cardoso. "Compara??o do estrato regenerante entre bordas e interior de uma floresta estacional semidecidual em Capelinha ? MG." UFVJM, 2016. http://acervo.ufvjm.edu.br/jspui/handle/1/1093.
Анотація:
?rea de concentra??o: Conserva??o e restaura??o de ecossistemas.Submitted by Jos? Henrique Henrique (jose.neves@ufvjm.edu.br) on 2016-12-16T16:56:37Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) marco_aurelio_cardoso_murta.pdf: 1577952 bytes, checksum: bba2d96d1b722132b4b3335ae8d2a59e (MD5)
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Companhia Energ?tica de Minas Gerais (CEMIG)
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES)
A Mata Atl?ntica ? considerada um dos biomas mais importantes do mundo, um hotspot para conserva??o, sendo as a??es antr?picas as principais fontes de dist?rbios que alteram este ambiente. A regenera??o natural ? um processo muito importante que atua diretamente sobre a recupera??o e fun??es do ecossistema. Este estudo teve como objetivo descrever e comparar a composi??o flor?stica-estrutural da regenera??o natural em uma Floresta Estacional Semidecidual localizada na RPPN Fazenda Fartura em Capelinha-MG. Para tal, foram amostrados um trecho no interior do fragmento (INT) e dois trechos de bordas, sendo uma em contato com pastagem (BP) e outra com cafeicultura (BC). Para analisar a diversidade alfa (?) foi utilizado o ?ndice de Shannon (H?) e equabilidade de Pielou (J?) e beta (?) pela similaridade flor?stica entre os trechos foi averiguada por meio de diagramas de Venn e dos ?ndices de Jaccard e Czekanowski. Foi elaborada uma curva esp?cie-?rea para estimar a dimens?o da riqueza flor?stica de cada trecho e calculados seus estimadores ?jackknife?. Para verificar poss?veis prefer?ncias das esp?cies ao longo dos trechos foi realizada uma An?lise de Esp?cies Indicadoras (ISA). Para analisar a estrutura da vegeta??o foram calculados os par?metros fitossociol?gicos cl?ssicos, al?m das distribui??es de di?metro e altura. As vari?veis estruturais foram comparadas por meio do teste de Kruskal-Wallis e a posteriori um teste de Dunn. Na amostragem total foram registrados 1.561 indiv?duos (230 no INT, 588 na BP e 743 na BC), identificados em 42 fam?lias bot?nicas, 87 g?neros e 162 esp?cies (78 no INT, 87 na BP e 89 na BC). As fam?lias com maior riqueza foram Myrtaceae, Fabaceae, Lauraceae, Rubiaceae, Melastomataceae e Annonaceae. Os resultados demonstraram que os trechos tem alt?ssima diversidade, muito acima do padr?o normalmente encontrado na literatura, com uma baixa similaridade flor?stica. De maneira geral, a estrutura da vegeta??o foi caracterizada por um maior n?mero de indiv?duos finos e pequenos. Os trechos apresentam ambientes distintos, cada um com diferentes hist?ricos de uso, variabilidade ambiental e tipos de dist?rbios, estes fatores possivelmente, foram os principais condicionantes que influenciaram os padr?es flor?sticos-estruturais da regenera??o natural na comunidade amostrada. As informa??es deste estudo evidenciaram a grande import?ncia da RPPN Fazenda Fartura para a conserva??o da Mata Atl?ntica, assim como, da necessidade de que mais estudos sejam realizados em escala espa?o-temporal.
Disserta??o (Mestrado) ? Programa de P?s-Gradua??o em Ci?ncia Florestal, Universidade Federal dos Vales do Jequitinhonha e Mucuri, 2016.
The Atlantic Forest is considered one of the most important biomes of the world, a hotspot for conservation, and human actions are the main sources of disturbances that change this environment. Natural regeneration is a very important process that acts directly on the recovery and ecosystem functions. This study aimed to describe and compare the floristic-structural composition of natural regeneration in a Semideciduous Forest located in the RPPN Fazenda Fartura in Capelinha-MG. For this, we sampled a stretch inside the fragment (INT) and two sections of edges, one in contact with pasture (BP) and the other with coffee (BC). To analyze the diversity alpha (?), we used Shannon Index (H') and evenness of Pielou (J') and beta (?) through floristic similarity between sections was determined through Venn diagrams and indices of Jaccard and Czekanowski. We developed the species-area curve to estimate the size of the floristic richness of each sections and its estimators calculated ?jackknife?. To check for possible preferences of the species along the sections we performed Indicator Species Analysis (ISA). To analyze the structure of the vegetation, we calculated the classical phytosociological parameters, besides diameter and height distribution. We compared the structural variables through Kruskal-Wallis test and retrospectively a Dunn test. In the total sampling, we registered 1,561 individuals (230 in INT, 588 in BP and 743 in BC), identified in 42 botanical families, 87 genera and 162 species (78 in INT, 87 in BP and 89 in BC). Families with greater richness were Myrtaceae, Fabaceae, Lauraceae, Rubiaceae, Melastomataceae and Annonaceae. The results showed that the sections have high diversity, well above the standard normally found in the literature, with a low floristic similarity. In general, the vegetation structure was characterized by a higher number of thin and small individuals. The sections have different environments, each with different historical use, environmental variability and types of disturbances, these factors possibly were the main constraints that influenced the floristic-structural patterns of natural regeneration in the sampled community. The information from this study showed the importance of RPPN Fazenda Fartura for the conservation of the Atlantic Forest, as well as the need for more studies to be performed in a spatiotemporal scale.
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Jelena, Kiurski. "Mehanizmi starenja katalizatora za hidrodesulfurizaciju." Phd thesis, Univerzitet u Novom Sadu, Tehnološki fakultet Novi Sad, 1997. https://www.cris.uns.ac.rs/record.jsf?recordId=71439&source=NDLTD&language=en.
Анотація:
Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).U ovom radu izvršena su ispitivanja deaktivacije katalizatora za hidrodesulfurizaciju (HDS), uz simulaciju starenja u laboratorijskim uslovima i paralelna ispitivanja katalizatora iz realnog industrijskog postrojenja. Širok interval uslova u laboratorijskoj simulaciji (temperatura, vreme tretmana, oksidacione i inertne atmosfere) pružio je osnov za ocenu uticaja različitih parametara na brzinu starenja katalizatora i definisanje kritičnih uslova, posebno pri regeneraciji katalizatora. Ispitivanja dva tipa HDS katalizatora, NiO-MoO3/y-Al2O3 i CoO- MoO3/y-Al2O3 i binarnih modelnih sistema NiO/ Al2O3, uz primenu komplementamih metoda za ispitivanje stukture i teksture čvrstih poroznih materijala, omogućila su uvid u mehanizme starenja u ovim složenim katalitičkim sistemima. Utvrđeno je da je oksidaciona atmosfera, posebno vodena para, kritičan faktor u kinetici stukturnih i teksturalnih promena u katalitičkom sistemu. Segregacija aktivne faze, interakcija sa nosačem, sinterovanje i gubitak aktivne faze iz sistema simultani su procesi koji dovode do trajne deaktivacije katalizatora. Visina radne temperature i moguća lokalna pregrevanja u sloju katalizatora, podstaknuta promenama difuzionih karakteristika kataličkog zrna, ključni su za destrukciju aktivne faze katalizatora, uz segregaciju prekursora oksidne faze molibdena, čiji je uticaj izrazit u fazi regeneracije. Intermedijarno prisustvo tečne faze oksida molidena, koja obliva površinu nosača, uslovljavajući intenzivno sinterovanje i ubrzanu interakciju izmedju ostalih faza u sistemu, predstavlja osnovni mehanizam u starenju katalizatora za HDS.Abstract was processed by technology for Optical character recognition (OCR).Deactivation studies of hydrodesulphurization catalysts were performed, based on both aging simulation in laboratory conditions and investigation of catalysts from an industrial HDS plant. Broad interval of conditions applied in laboratory simulation (temperature, treatment duration, oxidation and inert atmospheres) was the basis for evaluating the effect of different parameters on catalyst aging kinetics and defining critical conditions, with emphasis on regeneration procedure. The investigations of two catalyst types, NiO-MoO3/y-Al2O3 and C0O-MoO3/y-Al2O3, and NiO/Al2O3 binary model systems, using complementary methods for structural and textural investigations of porous solid systems, enabled the insight in aging mechanisms of these complex catalytic systems. The oxidation atmosphere, especially water vapor, is critical for the rate of structural and textural changes in the catalysts. Segregation in active phase, interaction with the support, sintering and loss of active component from the catalyst are the simultaneous processes bringing about the irreversible deactivation of the catalyst. The temperature gradient in working conditions and possible formation of hot spots in catalyst reactor bed, affected also by changes of diffusion characteristics of catalyst grain, are crucial factors for segregation of molybdenum oxide precursor, which effect is pronounced during regeneration. The mechanism of HDS catalyst aging is based on intermediary presence of moIybdenum oxide liquid phase on the support surface, facilitating intensive sintering and interactions of other phases of catalytic system.
45
Busse, Nielsen Anders. "Understanding and communicating forest stand structures : lifting barriers for nature-based forest management." Hørsholm : Forest & Landscape, 2006. http://www.sl.kvl.dk/upload/flr36.pdf.
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Silveira, Éliton Rodrigo da. "Recuperação da mata ciliar do córrego Tarumã (Tarumã, SP): aspectos estruturais, florísticos e ambientais de quatro diferentes modelos florestais, dez anos após o plantio." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-06022017-102458/.
Анотація:
A recomposição das matas ciliares pode vir a ser a solução mais eficaz e duradoura para reverter o acelerado processo de degradação dos recursos hídricos. Não há, no entanto, consenso sobre técnicas e espécies adequadas para a recomposição e nem critérios e indicadores para avaliar o êxito dos plantios. Esta pesquisa tratou do estudo de reflorestamento efetuado em 1990, às margens do córrego Tarumã, município de Tarumã, SP. No plantio foram utilizadas 29 espécies, sendo 28 nativas da região e uma introduzida de valor comercial (Pinus elliottii var. densa). As árvores foram plantadas em quatro módulos distintos, caracterizados por diferentes combinações de espécies, como segue: Módulo A - 100% pioneiras; Módulo B - 50% pioneiras + 50% não pioneiras; Módulo C - plantio misto aleatório de espécies nativas (pioneiras ou não) e módulo D - 100% Pinus. Avaliou-se a floresta formada, dez anos após o plantio, com base no desempenho das espécies plantadas e comparando-se os módulos entre si e com fragmento natural remanescente - (E), quanto à estrutura do estrato arbóreo, densidade, diversidade e riqueza florística da regeneração natural, características químicas do solo superficial e deposição de folhedo ao longo do ano. Verificou-se que há diferença entre os módulos de plantio para boa parte dos parâmetros avaliados. Do ponto de vista da estrutura da floresta, todos os módulos de plantio apresentam área basal, diâmetro médio e altura máxima inferiores ao fragmento natural. Por outro lado, a densidade do plantio foi superior à densidade da floresta natural e, mesmo com a mortalidade ao longo desses dez anos, a densidade nos diferentes módulos ainda é superior à da floresta natural (árvores com DAP maior ou igual 5 cm). Em síntese, dez anos não foram suficientes para que, nas condições ambientais deste experimento, a floresta plantada adquirisse a estrutura de uma floresta natural. Comparando-se entre si as espécies plantadas quanto ao seu desempenho, destacaram-se pela sua sobrevivência: Inga uruguensis, Croton urucurana e Schinus terebinthifolius. Pelo crescimento em altura e diâmetro, as espécies com melhor desempenho foram: Anadenanthera macrocarpa, Enterolobim contortisiliquum, Croton urucurana e Pinus elliottii var. densa. Comparando-se os quatro módulos entre si, verifica-se que o plantio misto aleatório apresentou maior densidade e riqueza de espécies em regeneração, seguido do plantio com 50% não pioneiras, plantio puro de pioneiras, e no último lugar, o plantio puro de Pinus. Predominam espécies zoocórias na regeneração natural, sendo que 62% das espécies não foram plantadas, devendo ter sido trazidas por dispersores. No que se diz respeito à ciclagem de nutrientes, o plantio puro de Pinus, embora tenha depositado a maior quantidade de folhedo/ha/ano, proporciona baixo retorno de nutrientes ao solo de modo geral, já que a concentração desses nutrientes no folhedo é baixa. Além disso, a análise química da camada superficial do solo mostrou que sob o Pinus o solo é mais ácido e há menor disponibilidade para a maior parte dos nutrientes, o modelo que mais se aproximou da floresta natural foi o plantio misto aleatório com essências nativas. No outro extremo, com piores resultados, esteve o plantio puro com Pinus elliottii var. densa, para as condições ambientais da área estudada.Riparian forests restoration can be the best way to stop the degradation process of the water resources. However, there is no agreement about how to do that, what are the best species and planting techniques and how to evaluate the planted forests. This study was based upon a planted riparian forest, along Tarumã River, Tarumã municipality, São Paulo State. Twenty nine species were planted, being 28 native and one introduced species. Trees were planted in four different species combinations, as follows: Module - A 100% pioneer species; Module - B 50% pioneer and 50% no pioneer species; Module - C mixed; Module - D 100% Pinus. The four modules were evaluated ten year after planting, considering: forest structure, density, richness and diversity of natural regeneration, litter deposition and chemical properties of surface soil. These results of the planted forest were compared with a forest remnant - (E) located close to the experimental area. Differences were found among treatments and in comparison with the natural forest, for most of the parameters considered. Basal area, DBH, and maximum height were lower than in the forest fragment. Trees density is still higher in the planted forest than in the natural one, even the mortality rates have been high. Ten years were not enough to make the planted forest structure similar to the natural forest. Comparing the planted species performance, there is a group of high survival rates: Inga uruguensis, Croton urucurana and Schinus terebinthifolius. Another group presented species with high increment in height and diameter: Anadenanthera macrocarpa, Enterolobium contortisiliquum, Croton urucurana and Pinus elliottii var. densa. Natural regeneration density and richness under the planted forest were also different among treatments, in decreasing order: mixed planting - 50% pioneer + 50% no pioneer - 100% pioneer - pure Pinus. Among the species surveyed, zoochory is the main dispersion syndrome and 62% of the species were not planted. They were, probably, brought by animal dispersers. Litter production was higher in pure Pinus planting than in the other treatrnents. However, nutrients concentration is lower than in treatments with native species. So, total quantity of mineral elements that return to the soil is higher in those forests planted with native species. In addition, chemical properties of surface soil under Pinus forests (H + AI, pH, Ca, Mg, etc.) are worse than under other treatments. This study leads to conclusion that, among the tested treatments, the mixed planting with native species (C) was the most similar to the native forest in structure, diversity and natural regeneration. The worst result, under the environmental conditions of this study, was obtained with the pure stand of Pinus elliottii var. densa.
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Melo, Antônio Carlos Galvão de. "Reflorestamentos de restauração de matas ciliares : análise estrutural e método de monitoramento no médio Vale do Paranapanema (SP)." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/18/18139/tde-29092005-150857/.
Анотація:
Devido à importância das matas ciliares muitos esforços e recursos têm sido despendidos para sua restauração. Como forma de aumentar a eficácia dos reflorestamentos, a partir de 1986 as instituições de pesquisa desenvolveram técnicas de reflorestamento fundamentadas na sucessão secundária das florestas tropicais. Neste estudo foi realizada análise estrutural de dez reflorestamentos implantados com base na sucessão secundária e com idades variando de um a 13 anos, comparados com uma área em regeneração natural há 23 anos, todos em região de floresta estacional semidecidual, no médio Vale do Rio Paranapanema, SP. Em cada área foram levantados parâmetros referentes à biomassa (densidade, área basal, altura, DAP e cobertura de copas), fitossociologia (riqueza, diversidade e similaridade) e regeneração natural (densidade, riqueza, diversidade, similaridade com o estrato arbóreo e com áreas naturais). Os reflorestamentos apresentaram evolução mais rápida de todos os parâmetros referentes à biomassa do que a área em regeneração natural, os mais velhos aproximando-se estruturalmente de uma mata ciliar madura e levando a concluir que, para a região dos estudos, o abandono de áreas à regeneração natural não é estratégia de restauração tecnicamente recomendável, embora às vezes possa ser a única saída economicamente viável. Nenhuma das variáveis dendrométricas apresentou correlação expressiva com a riqueza de espécies plantadas, e conclui-se que a opção por plantios com baixa densidade (até 1240 plantas/ha) e baixa riqueza (até 11 espécies) não interfere no desempenho do reflorestamento, em termos de formação de biomassa. O desempenho estrutural dos reflorestamentos pode ser manipulado através da escolha das espécies e da densidade diferenciada entre os grupos sucessionais. A estrutura vertical dos reflorestamentos mostrou-se influenciada pela composição do plantio, refletindo a importância dos grupos sucessionais. As espécies pioneiras e secundárias iniciais dominam o dossel e constituem-se nas espécies emergentes. Plantas em regeneração natural são observadas somente nos reflorestamentos com idade de sete anos ou mais e sua densidade e riqueza mostraram-se correlacionadas apenas com a idade do reflorestamento e a distância até o fragmento natural mais próximo, predominando as espécies de síndrome de dispersão zoocóricaRiparian forests are key to protect water resources and biodiversity, so that efforts and funds have been directed towards its restoration. In recent years, forest restoration research and technology have been based upon secondary succession, since this paradigm have been considered the best solution in terms of restoration efficacy. Nine areas, reforested on the basis of secondary succession with different ages (one to 13 years), as well as a naturally regenerated forest 23 years old, are compared in this study, in terms of stand structure. The parameters adopted in this analysis were related to biomass (density, basal area, height, DBH and crown cover), fitossociology (richness, diversity and similarity) and natural regeneration (density, richness, diversity and similarity with the arboreal stratum and neighbouring native forests). Planted forests presented a recovery process faster than the naturally regenerated forest, in terms of biomass. The eldest planted forest are structurally similar to mature riparian forests in the same environmental condition. On the basis of these results natural regeneration can not be recomended as a good technical solution to recover riparian forests. In some situations, however, this can be the only solution, since it has no costs. No correlation was found between the number of species planted and dendrometric parameters, so that richness and density of the planted forest had no influence on the forest biomass. Structural performance of the planted forest can be managed through species selection considering the proportion between early and late successional species, wich has a direct influence on the biomass. Pioneer and early secondary species dominate the canopy. Natural regeneration of arboreal species starts about seven years after planting. Both density and richness of naturally regenerated plants are correlated with the age of the forest and the distance to the nearest forest patch. Plants in natural regeneration are predominantly from zoocorichous species
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Souza, Pierre Farias de. "Estudos fitossociológicos e dendrométricos em um fragmento de caatinga, São José de Espinharas - PB." Universidade Federal de Campina Grande, 2012. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/968.
Анотація:
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O presente trabalho objetivou analisar a composição florística, caracterizar os parâmetros das estruturas horizontal, vertical, interna, paramétrica e de regeneração, ajustar modelos volumétricos para estimativas de volume de fustes, bem como estimar um fator de forma para fustes na vegetação de caatinga. A área de estudo se localiza no Assentamento Cachoeira, município de São José de Espinharas-PB. Foram utilizadas 49 parcelas de 400 m2 (20 x 20 m), sistematicamente distribuídas, com espaçamento entre parcelas de 300 x 300m, demarcadas com auxílio de GPS de navegação (Global Position System). Para a coleta dos dados de inventário, da regeneração e da estrutura interna (classe de vitalidade, qualidade de fuste, posição de copa e altura de bifurcação), foi seguido o Protocolo de Medição da Rede de Manejo da Caatinga. Para o estudo das estimativas volumétricas, foi utilizada uma amostra 225 fustes. Para cada fuste, foram tomados medições de circunferência a 0,30m do solo (C0.3o), circunferência na altura do peito (CAP) e altura total do maior fuste. Na cubagem rigorosa, o fuste foi medido em seções de (1 m), pelo método de Smalian, até um valor mínimo aproveitável em tomo de 1,5 cm de diâmetro, anotando-se, quando fosse o caso, a circunferência e o comprimento fracionário da seção final. Após as medições, foram obtidos os volumes totais por fuste. Foram utilizados os modelos de Schumacher e Hall (1933), o modelo de Spurr, na forma linearizada, e o modelo de Schumacher e Hall (1933), na forma não linear, todos eles com duas opções para a variável independente, diâmetro a 0,3 metros de altura do solo e diâmetro equivalente, totalizando seis modelos. O fator de forma foi estimado pela razão entre o volume real através da cubagem rigorosa por fuste e o volume cilíndrico, cuja base é a área seccional obtida pelo DAP a 1,30 m e altura do fuste. A tabulação, o processamento e as análises foram realizados utilizando-se os softwares Microsoft Office Excel 2007, Statistica e Mata Nativa 2.0. Foram encontradas, na área de estudo, 30 espécies e 15 famílias e 26 gêneros. A espécie Luetzelburgia bahiensis, listada neste trabalho, não consta em registros anteriores. Não há enciclopédias sobre sua ocorrência na vegetação da Paraíba. As espécies que apresentaram maior densidade foram: Croton blanchetianus, Poincianella pyramidalis, Mimosa tenuiflora, Combretum sp, Aspidosperma pyrifolium e Mimosa ophthalmocentra. A espécie de maior Vl(%) da área é a P. pyramidalis, com 23,46%. Na estrutura vertical, a segunda classe de altura apresentou maior distribuição de fustes em densidade da área em estudo. Na regeneração, as espécies C. blanchetianus, Combretum sp. e P. pyramidalis apresentaram maior densidade em fustes da área. As três primeiras classes diamétricas possuem o maior número de fustes da floresta, classe I 60,1%, classe II 28,25 % e Classe III 8,17 %, totalizando 96,53%. Acima de 71% dos fustes da caatinga apresentaram saudáveis. Foi obtido o valor de 0,87 para o fator de forma estudado. Os quatro primeiros modelos volumétricos apresentaram bons desempenhos para estimativas de volume de fustes da caatinga.
The present work aims to analyze the floristic composition, characterize the parameters of the horizontal, vertical, internal, parametric and regeneration structures, adjust volumetric models in order to obtain stem volume estimates as well as estimate a form factor for stems in caatinga vegetation. The study area is located in the Cachoeira Settlement, in the municipality of São José de Espinharas-PB. We used 49 sample with an area of 400 m2 (20 x 20 m), systematically distributed, spacing between plots of 300 x 300m, demarcated with the help of GPS navigation (Global Positioning System). To collect the inventory data, regeneration and the internal structure (Class of vitality, quality of stem, crown position and height of bifurcation), the Measurement Network Management of the Caatinga Protocol was followed. For the study of volumetric estimates, we used a 225 sample stem. For each stem, measurements of the circumference at 0.30 m above the ground (CO, 30), circumference at breast height (CAP) and total height of the largest stem were taken. In the rigorous scaling procedure, the stem was measured in sections (1 m), by the method of Smalian, up to a minimum usable value of about 1.5 cm diameter, taking notes, where appropriate, of the circumference and length fraction of the final section. After the measurements, the total volumes per stem were obtained. We used Schumacher and Hall (1933) models, Spurr model in the linear form, and the model in the Schumacher and Hall (1933), in the non-linear form, all of them with two options for the independent variable, diameter at 0.3 meters above the ground and equivalent diameter, totalizing six models. The form factor was estimated by the ratio between the actual volume obtained by stem rigorous scaling and cylindrical volume, whose base is the sectional area obtained by the DAP at 1.30 m and height of the stem. The tabulation, processing and analysis were carried out using the software Microsoft Office Excel 2007, Statistics and Mata Nativa 2.0. We found, in the study area, 30 species and 15 families and 26 genera. The species Luetzelburgia bahiensis, listed in this work, is not present in previous records. There is no record about its occurrence in the vegetation of Paraiba. The species with the highest density were: Croton blanchetianus, Poincianella pyramidalis, Mimosa tenuiflora, Combretum sp, Aspidosperma pyrifolium and Mimosa ophthalmocentra. The species with the largest VI (%) in the area is P. pyramidalis with 23,46 %. On the vertical structure, the second height class presented a greater steam distribution in density in the study area. In regeneration, the species C. blanchetianus, Combretum sp. and P. pyramidalis showed a higher steam density in the area. The first three diametric classes have the largest number of stems of the forest. Class I 60 1%, Class II 28,25% and Class III 8,17%, totalizing 96,53%. Over 71% of the stems in the caatinga were healthy. The obtained value was 0.87 for the studied form factor. The first four volumetric models showed good performance for volume estimates of stems in the caatinga.
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Barrocas, Eva de Gouveia. "Contribution to the study of holm oak stand dynamics." Master's thesis, Universidade de Évora, 2021. http://hdl.handle.net/10174/30090.
Анотація:
The holm oak is an emblematic species of the montado, a complex and biodiverse multifunctional, agro-silvopastoral system. Signs of the decline of the montado crown cover have been reported. This research followed an integrative approach to investigate how crown cover influences stand structure, natural regeneration, soil conditions, and litter layer in pure holm oak stands. Two new methodologies were created: STRUX Index that facilitates structure classification, and Natural Regeneration Classification that studies the viability of natural regeneration. The results showed that a higher crown cover was linked to uneven-aged structure, higher values of above-ground biomass, higher number of established natural regeneration, and a tendency for higher values of soil organic carbon and litter layer. Furthermore, it was observed a positive correlation between natural regeneration, litter layer, and soil organic carbon together with a negative correlation with soil pH This study brings a positive perspective on the preservation of holm oak stands; Contribuição para a dinâmica de povoamento em montado de azinho
A azinheira é uma espécie emblemática do montado, sistema agro-silvopastoril, multifuncional e de elevada biodiversidade. Como a área de montado regrediu nas últimas décadas, tornou-se urgente compreender a dinâmica dos montados de azinho. Através de uma abordagem integrada, foi estudada a contribuição do grau de coberto para a dinâmica da estrutura dos povoamentos. Duas novas metodologias foram criadas: o Índice STRUX, para a classificação da estrutura do povoamento, e a Classificação de Regeneração Natural, para avaliar a viabilidade e qualidade da regeneração natural. Os resultados indicaram que valores superiores de grau de coberto estão relacionados com a estrutura irregular, com mais biomassa florestal e com mais regeneração natural instalada. Foi observada uma correlação positiva entre a regeneração natural, a manta morta e o carbono orgânico e uma correlação negativa com o pH do solo. Este estudo contribuiu para uma perspetiva positiva sobre a resiliência do montado de azinho.
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Mansoorian, Mahfarid [Verfasser], Elke [Akademischer Betreuer] Pahl-Weber, Asef [Akademischer Betreuer] Bayat, Asef [Gutachter] Bayat, and Elke [Gutachter] Pahl-Weber. "Linking conflict and collaboration; bottom-up urban regeneration within top-down structure of urban policy in Istanbul and Tehran / Mahfarid Mansoorian ; Gutachter: Asef Bayat, Elke Pahl-Weber ; Elke Pahl-Weber, Asef Bayat." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1164076531/34.