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1
Garcia, Alexander Patricio. "Perfil do Orizicultor de abrangência da Região da Associação dos Municípios do Extremo Sul Catarinense." Universidade Federal de Pelotas, 2012. http://repositorio.ufpel.edu.br/handle/ri/1394.
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Previous issue date: 2012-12-07<br>The present work aimed to evaluate the producer of rice profile of the Association of Municipalities in the Catarinense Extreme Southern (AMESC) in relation to the utilization rate of certified seeds as well as the cultural practices in the pre-germinated rice cultivation system. For this work development, a questionnaire survey was applied to the farmers of the AMESC region, who cultivate rice into the pre germinated system. All municipalities that cultivate rice in the AMESC comprisement, had interviewed farmers. Forty-eight properties altogether, were searched; just four properties in each country. There was no survey in Balneário Arroio do Silva, Balneário Gaivota and Passo de Torres, where no rice is produced. The work showed that the utilization rate of certified seeds in the rural properties reached (79%), being above the average (53%) of the utilization rate of Brazil certified seeds for irrigated rice. It s possible to conclude the utilization rate of certified seeds in the AMESC region is higher than the Brazilian average. Such component of production contributes for a better productivity and rentability of the catarinense southern rice farmings.<br>O presente trabalho teve por objetivo avaliar o perfil do orizicultor da região de abrangência da Associação dos Municípios do Extremo Sul Catarinense (AMESC) quanto à taxa de utilização de sementes certificadas e às práticas culturais no sistema de cultivo de arroz pré germinado. Para o desenvolvimento deste trabalho, foi realizada uma pesquisa com a aplicação de um questionário aos produtores rurais da região da AMESC que cultivam arroz no sistema pré germinado. Todos os municípios que cultivam arroz da região de abrangência da AMESC tiveram produtores entrevistados, totalizando 48 propriedades pesquisadas, sendo aplicado o questionário em quatro propriedades por município. Não houve pesquisa nos municípios de Balneário Arroio do Silva, Balneário Gaivota e Passo de Torres pelo fato de não produzirem arroz. O trabalho mostrou que taxa de utilização de sementes certificadas nas propriedades rurais alcançou 79%, estando acima da média (53%) da taxa de utilização de sementes certificadas do Brasil para o arroz irrigado. É possível inferir que a região da AMESC possui uma taxa de utilização de sementes certificadas acima da média brasileira e que este componente da produção contribui para melhorar a produtividade e a rentabilidade das lavouras orizicolas sul catarinense.
2
Chen, Minliang [Verfasser]. "Novel approaches for in vivo evolution, screening and characterization of enzymes for metabolic engineering of Escherichia coli as hyper L-tryptophan producer / Chen Minliang." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1224270819/34.
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Chen, Minliang [Verfasser]. "Novel approaches for in vivo evolution, screening and characterization of enzymes for metabolic engineering of Escherichia coli as hyper L-tryptophan producer / Minliang Chen." München : Verlag Dr. Hut, 2021. http://d-nb.info/1232847674/34.
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4
Eismin, Ryan J., and Ryan J. Eismin. "Surface, Aggregation, and Phase Characterization of Microbially-Produced & Chemically-Synthesized Monorhamnolipids." Diss., The University of Arizona, 2017. http://hdl.handle.net/10150/623026.
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The purpose of this research has been to explore the native monorhamnolipid (mRL) mixture produced by Pseudomonas aeruginosa ATCC 9027, as well as newly- synthesized monorhamnolipid diastereomers (R,R)-Rha-C10-C10, (R,S)-Rha-C10-C10, (S,S)-Rha-C10-C10 and (S,R)-Rha-C10-C10, to understand their aggregation and phase behavior in aqueous solution. This work is in response to the consideration that biosurfactants offer a "greener" alternative to conventional surfactants. Relationships between chemical structure of the diastereomers and surface activity were studied using surface tension measurements. It was found that the critical aggregation concentration (CAC) values are lower for deprotonated (R,S)-Rha-C10-C10 and higher for protonated (R,S)-Rha-C10-C10 compared to the other diastereomers or the native mRL mixture. Furthermore, the 1:1:1:1 diastereomeric mixture has the overall lowest cross-sectional area for deprotonated rhamnolipids. Dynamic light scattering (DLS) was used to study the hydrodynamic radii (Rh) of the mRL aggregates and the four diastereomers in aqueous solution. In all five surfactants studied, each observed at pH 8.0 and 4.0, three aggregate populations were observed. For all deprotonated rhamnolipids the micelle, at a hydrodynamic radius of ~2 nm, was found to be in the highest abundance where the two lower abundant other population take on a lamellar aggregate structure. Data to support this were collected using fluorescence probing techniques. For the surfactants in the protonated state, pH 4.0, it was found that all form primarily lamellar structures, also confirmed using fluorescence probing. The average aggregation numbers (Nagg) of the micelles for the deprotonated native mRL mixture and the four diastereomers were studied using steady-state and time-resolved fluorescence quenching measurements. Somewhat unexpectedly, the Nagg values were observed to be a strong function of the rhamnolipid concentration for all systems. At low concentrations, pre-micellar aggregates with aggregation numbers too small for micelles were observed. A critical concentration is identified at which a critical aggregation number is defined; this is proposed to be the smallest fully-formed micelle in solution with values of ~25-30 molecules/micelle for the native mRL mixture and all four diastereomers. Thus, the aggregation properties of the native mRL mixture and the four diastereomers are generally similar at this critical concentration. However, the increase in aggregation number above this critical point varies for all the surfactants, where the (R,R)-Rha-C10-C10 diastereomer has the greatest increase in monomers with concentration and the (S,S) and (R,S) diastereomers have the lowest. The increased observed aggregation number is consistent with the computational work showing increased growth with concentration for the deprotonated rhamnolipid micelles. Furthermore, these computations have confirmed the ability of protonated rhamnolipids to form lamellar structures in solution. Fluorescence probing work was also used to study rhamnolipid phase behavior as a function of varying solution conditions, such as ionic strength, solution pH, surfactant concentration, and temperature. Steady-state fluorescence methods are utilized to probe the surfactant microenvironment using the polarity-sensitive dyes prodan and laurdan. By dissolving the dye within the rhamnolipid aggregates and observing their solvatochromic behavior, all surfactants studied are known to form more micellar aggregates at high pH and low surfactant concentration, whereas elongation of the micelle is observed at low pH and moderate to high surfactant concentration.
5
Jackson, Linda C. "Neutral solvent pulping product characterization." Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/11234.
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Zhou, Dan. "Characterization of carbon nanoclusters produced by arc-discharge." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187312.
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The research covered in this dissertation presents a systematic study for growth phenomena of carbon nanoclusters prepared by a arc discharge technique. Through a series of experiments, it has been found that morphology and yield of nanotubes strongly depend on the processing parameters. A low current density of 190 A/cm², a discharge voltage of 27 V, a high helium pressure of 550 torr, and a minimum electrode gap offered the best condition for synthesis of carbon nanotubes. According to a detailed study of carbon nanoclusters by TEM, the rich variety of growth phenomena, in particular non-concentric and complex branching phenomena are reported. These phenomena have demonstrated that the growth process of nanotubes is apparently more complex than what the existing growth models suggest. Further refinement and expansions of these models are important for technological exploitation of nanotubes and may be identified and guided by the present results. The reaction of foreign materials with carbon vapor in the arc results in their encapsulation into carbon cages, as well as the formation of other novel forms of carbon nanoclusters. Among more than eighteen elements introduced into the discharge in this study, B, Y, Zr, Nb, and Mo are most easily encapsulated in the form of their carbides into carbon nanoclusters. Through the detailed study, it has been found that the encapsulation occurs most easily in the materials with the incompletely-filled 4d electron shell for the refractory materials. Furthermore, it is reported that Fe, Co, Ni, or YC₂ working as catalysts stimulate the formation of single-walled nanotubes (SWTs), and mixtures of these catalysts greatly enhance the yield of SWTs. Based on morphologies of the star patterns of SWTs produced by an anode containing YC₂, their step-by-step growth mechanism is proposed. In addition to the SWTs, it has been found that Fe or Ni also stimulates the formation of strings of carbon nanobeads. A growth model for this phenomenon is presented. Finally, the conversion of carbon nanotubes into SiC whiskers is reported. In contrast to the conventional process, starting with nanotubes offers a high purity SiC whisker without any metal impurity.
7
Van, Reenen Carol A. (Carol Ann). "Characterization of bacteriocin 423 produced by Lactobacillus pentosus." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51652.
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Thesis (PhD)--University of Stellenbosch, 2000.<br>ENGLISH ABSTRACT: Worldwide, bacteriocins, particularly those produced by food-related lactic acid bacteria, are
receiving attention due to the possible use of these peptides as natural preservatives in food,
replacing potentially harmful chemical preservatives.
Bacteriocins are ribosomally synthesized proteins or peptides that inhibit closely related
microorganisms. Most bacteriocins produced by lactic acid bacteria are small, heat resistant
peptides that inhibit other Gram-positive bacteria, including food-borne pathogens such as
Listeria monocytogenes, Bacillus cereus, Clostridium perfringens and Staphylococcus aureus,
but do not inhibit Gram-negative bacteria, molds or fungi. Bacteriocins are produced as
inactive prepeptides that become active after the N-terminal leader peptide is cleaved off.
Small heat resistant bacteriocins are either lantibiotics (Class I), containing unusual posttranslationally
modified amino acids, or peptides that are non-Ianthionines (Class II). The
Class II bacteriocins are further divided into four different groups: Class lIa, the anti-listerial
bacteriocins containing the YGNGV consensus sequence in the N-terminal of the protein,
Class lib, bacteriocins consisting of two peptides, Class IIc, bacteriocins that are secreted via
the sec pathway, and Class lid, bacteriocins that do not belong in the previous three
subgroups.
A bacteriocin producing lactic acid bacterium was isolated in our laboratory from
traditionally home fermented South African sorghum beer. The producing bacterium was
found to be a facultative heterofermentative Lactobacillus sp. and was identified as
Lactobacillus plantarum or Lactobacillus pentosus by using the API 50 CHL carbohydrate
fermentation system and numerical analysis of total soluble cell protein patterns. RAPD-PCR
analysis identified the strain as L. plantarum, but 16S rRNA sequencing confirmed its
identification as L. pentosus.
The bacteriocin, first designated plantaricin 423 and later bacteriocin 423, was identified as
a Class lIa small heat resistant anti-listerial bacteriocin containing the YGNGV consensus
motif. Bacteriocin 423 inhibited a variety of Gram-positive bacteria, including Lactobacillus
spp., Leuconostoc spp., Oenococcus oeni, Pediococcus spp., Enterococcus spp.,
Propionibacterium spp., Staphylococcus spp., Bacillus spp., Clostridium spp. and Listeria spp.
The bacteriocin was inactivated by proteolytic enzymes and active over a wide pH range (pH
1-10). Bacteriocin 423 lost 50 % of its activity after autoclaving for 15 min at 121°C, but was
not affected by lesser heat treatments.
Bacteriocin production was increased by optimizing the growth medium, which consisted of
glucose, tryptone, yeast extract, potassium phosphate, sodium acetate, ammonium citrate, manganese sulphate, Tween 80 and casamino acids.
The bacteriocin was found to be plasmid-encoded. Genetic analysis of the bacteriocin
operon indicated a high percentage of homology to the operon of another Class lIa
bacteriocin, pediocin PA-1, although the structural genes of the two bacteriocins were
markedly different. The structural gene of bacteriocin 423 was amplified by PCR and cloned
into a yeastJE. coli vector between the ADH1 promoter and terminator sequences and fused
in-frame to the MFa1 secretion signal sequence. Saccharomyces cerevisiae transformed with
this plasmid expressed the bacteriocin.
The sequence of prebacteriocin 423 (MMKKIEKL TEKEMANIIGGKYYGNGVTCGKHSCSVN
WGOAFSCSVSHLANFGHGKC) is similar, but not identical to any other reported Class lIa
anti-listeria I peptide.<br>AFRIKAANSE OPSOMMING: Bakteriosiene, veral dié wat deur melksuurbakterieë geproduseer word, wek belangstelling
as gevolg van die moontlike gebruik van hierdie natuurlike antimikrobiese proteiëne as
preserveermiddels in voedselprodukte, in plaas van potensieël gevaarlike chemiese
preserveermiddels.
Bakteriosiene is ribosomaal-vervaardigde proteiëne wat naverwante bakterieë inhibeer.
Die meeste bakteriosiene wat deur melksuurbakterieë geproduseer word, is klein en
hittebestand. Hierdie bakteriosiene inhibeer ander Gram-positiewe bakterieë, insluitend
patogene soos Listeria monocytogenes, Bacillus cereus, Clostridium perfringens en
Staphylococcus aureus, maar inhibeer nie Gram-negatiewe bakterieë, giste of swamme nie.
Bakteriosiene word as onaktiewe prepeptiede geproduseer, wat ge-aktiveer word wanneer die
N-terminale leierpeptied afgesplits word. Klein hittebestande bakteriosiene is óf lantibiotika
(Klas I), met ongewone aminosure, óf normale peptiede (Klas II). Laasgenoemde klas kan
verder in vier groepe verdeel word. Klas lIa is anti-listeriese bakteriosiene met fn YGNGVaminosuurvolgorde
in die N-terminale kant van die peptied. Klas lib sluit in bakteriosiene wat
uit twee peptiede bestaan. Klas lie is sec-afhanklike bakteriosiene, en Klas lid sluit in al die
bakteriosiene wat nie in die eerste drie groepe geklassifiseer kan word nie.
'n Bakteriosien-produserende melksuurbakterie is uit tradisionele tuisgefermenteerde Suid-
Afrikaanse sorghumbier geïsoleer. Die bakterie is as 'n fakultatief heterofermentatiewe
Lactobacillus sp. geïdentifiseer. Die bakterie is verder as 'n Lactobacillus plantarum of
Lactobacillus pentosus geïdentifiseer deur middel van die API 50 CHL-koolhidraat
fermentasiesisteem en numeriese analiese van totale oplosbare selproteiënprofiele. Met
RAPD-PCR analiese is die organisme as L. plantarum geïdentifiseer, maar 168 rRNA
nukleotiedopeenvolging het die identiteit van die organisme as L. pentosus bevestig.
Bakteriosien 423, aanvanklik geklassifiseer as plantaricin 423, is fn klein Klas lIa,
hittebestande en anti-listeriese bakteriosien met die YGNGV motief, wat verskeie Grampositiewe
bakterieë inhibeer. Bakteriosien 423 het verskeie Gram-positiewe organismes
geïnhibeer, onder andere Lactobacillus spp., Leuconostoc spp., Oenococcus oeni,
Pediococcus spp., Enterococcus spp., Propionibacterium spp., Staphylococcus spp., Bacillus
spp., Clostridium spp., en Listeria spp. Proteolitiese ensieme inaktiveer die bakteriosien. Die
peptied was oor 'n pH reeks van 1-10 aktief. Outoklavering vir 15 min by 121°C het die
aktiwiteit van die peptied halveer, maar die bakteriosien is nie geïnaktiveer met ander
hittebehandelings nie.
Produksie van die bakteriosien is verhoog deur die groeimedium te optimiseer. Die groeimedium het bestaan uit glukose, triptoon, gisekstrak, kaliumfosfaat, natriumasetaat,
ammoniumsitraat, mangaansulfaat, Tween 80 en casaminosure.
Die bakteriosien se genetiese determinante is op In plasmied gesetel. Genetiese analiese
van die bakteriosien operon het 'n hoë homologie met In ander Klas lIa bakteriosien, pediocin
PA-1, getoon, maar die strukturele gene van die twee bakteriosiene verskil merkbaar. Die
strukturele geen van bakteriosien 423 is met PKR ge-amplifiseer en in 'n gistE. coli-vektor
tussen die ADH1 promotor- en termineerderopeenvolgings, in leesraam met die MFa1
sekresiesein, gekloneer. Saccharomyces cerevisiae wat met hierdie plasmied getransformeer
is, het bakteriosien 423 uitgedruk. Die aminosuurvolgorde van prebakteriosien 423
(MMKKIEKL TEKEMANIIGGKYYGNGVTCGKHSCSVNWGOAFSCSVSHLANFGHGKC) is verwant
aan, maar nie identies aan, ander Klas lIa anti-listeriese peptiede.
8
Van, der Merwe Iansha (Iansha Rosalia) 1975. "Characterization of thoeniicin 447 produced by Propionibacterium thoenii." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52729.
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Thesis (MSc)--University of Stellenbosch, 2002.<br>ENGLISH ABSTRACT: Antimicrobial peptides continue to be one of the most important classes of food additives.
The food industry is especially interested in the application of naturally occuring and
biologically derived preservatives. Among the metabolites of industrial importance produced
by propionibacteria are peptides called bacteriocins. Bacteriocins are ribosomally synthesized
peptides with antagonistic activity against closely related microorganisms. Many
microorganisms associated with food produce bacteriocins, which have stimulated interest in
the use of these peptides as natural food preservatives. Numerous bacteriocins are produced
by lactic acid bacteria, but only a few have been reported for propionibacteria. Since
propionic acid bacteria have GRAS (generally regarded as safe) status, their metabolic
compounds should be safe for human consumption.
Propionibacterium thoenii 447, isolated from Emmentaler cheese, produces a
bacteriocin-like peptide, named thoeniicin 447, with a narrow spectrum of activity. The
peptide displays a bactericidal mode of action against Lactobacillus delbrueckii subsp.
bulgaricus and a bacteriostatic action against Propionibacterium acnes.
Optimal bacteriocin production was detected during the early stationary growth phase.
The peptide is resistant to heat treatments of 60°C and 80°C for 15 and 30 min and to 100°C
for 15 min, but loses 80% of its activity after autoclaving (10 min at 121°C). Thoeniicin 447
remains active after incubation in buffers with pH values ranging from 1-10. The peptide is
inactivated by pepsin, pronase, a-chymotrypsin, trypsin and Proteinase K. Thoeniicin 447
was partially purified by ammonium sulfate precipitation, followed by SP-Sepharose cation
exchange chromatography. The estimated size of thoeniicin 447, according to tricine-SDSPAGE,
is approximately 6 kDa. Based on DNA sequencing, the mature peptide is 7130 Da in
size and homologous to propionicin Tl produced by P. thoenii strain 419.
Thoeniicin 447 is a relatively small, cationic and heat-stable peptide and can therefor be
classified as a member of class II bacteriocins. These features are very similar to those of
bacteriocins produced by lactic acid bacteria. However, no unique classification system has
been proposed for bacteriocins of propionibacteria.
As a member of the genus Propionibacterium, P. thoenii 447 is generally regarded as
safe. This, together with the narrow spectrum of activity, particularly the action against P.
acnes, heat tolerance of thoeniicin 447 and its activity over a wide pH range renders the
peptide suitable for possible pharmaceutical applications.<br>AFRIKAANSE OPSOMMING: Antimikrobiese middels sal deurgaans beskou word as een van die belangrikste klasse van
voedsel bymiddels. Die voedselindustrie is veral geïnteresseerd in die toepassing van
preserveermiddels van 'n meer natuurlike en biologiese oorsprong. Onder die metaboliese
produkte van industriële belang wat deur propionibakterieë geproduseer word is
antimikrobiese peptiede (bakteriosiene). Bakteriosiene is ribosomaal-gesintetiseerde peptiede
met 'n antagonistiese aktiwiteit teenoor naverwante bakterieë. Verskeie bakteriosiene word
deur melksuurbakterieë geproduseer, terwyl slegs enkele vir propionibakterieë beskryf is.
Baie van hierdie propionibakterieë word in die algemeen as veilig beskou en het GRAS status.
Die metaboliete wat hulle produseer behoort dus veilig vir menslike gebruik te wees.
Propionibacterium thoenii 447 is uit Emmentaler kaas geisoleer en produseer 'n
bakteriosien-agtige peptied, naamlik thoeniicin 447 met 'n beperkte spektrum van aktiwiteit.
Die peptied het 'n bakteriosidiese werking teenoor Lactobacillus delbrueckii subsp.
bulgaricus en 'n bakteriostatiese werking teenoor Propionibacterium acnes.
Optimum bakteriosien produksie is verkry tydens die vroeë stationêre groeifase. Die
peptied is bestand teen hittebehandelings van 60°C en 80°C vir 15 en 30 min, asook 100°C vir
15 min, maar verloor 80% van sy aktiwiteit na outoklavering (lOmin by 121°C). Die peptied
blyaktief na inkubasie in buffers van pH 1-10. Die peptied word deur pepsien, pronase, uchymotripsien,
tripsien en Proteinase K geïnaktiveer.
Thoeniicin 447 is met behulp van ammoniumsulfaat-presipitasie, gevolg deur SPSepharose
katioon-uitruilchromatografie gedeeltelik gesuiwer. Skeiding op "n trisien-SDS
poliakrielarnied-jel het 'n aktiewe band van ongeveer 6 kDa getoon. Volgens die DNA
volgorde bepaling is thoeniicin 447, 7130 Da in grootte en homoloog aan Propionicin Tl,
geisoleer vanaf P. thoenii stam 419.
Thoeniicin 447 is 'n relatiewe klein, kationiese en hitte-bestande peptied en kan op grond
hiervan as 'n lid van die klas II bakteriosiene geklassifiseer word. Hierdie eienskappe is
soortgelyk aan die eienskappe van bakteriosiene geproduseer deur melksuurbakterieë. Tot op
hede is geen klassifikasiesisteem vir die bakteriosiene van propionibakterieë voorgestel nie.
As 'n lid van die genus Propionibacterium, word P. thoenii 447 in die algemeen as veilig
beskou. Dit, tesame met die nou spektrum van aktiwiteit, veral teenoor P. acnes, die
hittetoleransie van thoeniicin 447, asook die aktiwiteit oor 'n wye pH-grens, maak die peptied
geskik vir moontlike farmaseutiese toepassings.
9
Bargo, Johnny E. "Mechanical property characterization of recycled thermoplastics." Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1473.
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Thesis (M.S.)--West Virginia University, 2000.<br>Title from document title page. Document formatted into pages; contains xvii, 143 p. : ill. (some col.) Includes abstract. Includes bibliographical references (p. 104-105).
10
Van, Staden Anton Du Preez. "In vitro and In vivo characterization of Amyloliquecidin, a novel two-component lantibiotic produced by Bacillus amyloliquefaciens." Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96656.
Full textAbstract:
Thesis (PhD)--Stellenbosch University, 2015.<br>ENGLISH ABSTRACT: Antimicrobial resistance is one of the major problems faced by the medical industry today. The ability of bacteria to rapidly acquire resistance against antibiotics and the over prescription and inappropriate use of antibiotics further exacerbate this crisis. Few new antimicrobials are, however, making it through the drug discovery pipeline. The search and development of novel and effective antimicrobials is therefore of the utmost importance.
Lantibiotics are ribosomally synthesized cationic antimicrobial peptides with extensive post-translational modifications. They are active against a wide range of Gram-positive bacteria, including antibiotic-resistant strains. They are characterized by the presence of lanthionine and methyllanthionine rings and have been suggested as alternatives or for use in conjunction with antibiotics against resistant pathogens. Staphylococcus aureus is the most common bacteria isolated from skin and soft tissue infections (SSTIs). Strains of S. aureus have emerged with resistance against antibiotics with the most common being methicillin-resistant S. aureus (MRSA). Several lantibiotics are active against MRSA in vivo and have even shown superior activity to traditional antibiotics. Lantibiotics therefore show much promise for the treatment of SSTIs caused by resistant- and non-resistant S. aureus.
In this study the bacterially diverse soil of the Fynbos in the Western Cape was screened for novel antimicrobials. Two antimicrobial producing Bacillus strains were isolated, Bacillus clausii AD1 and Bacillus amyloliquefaciens AD2. Both of these strains produce lantibiotics with B. clausii AD1 producing a known lantibiotic, clausin. B. amyloliquefaciens AD2 produces a novel two-component lantibiotic which was designated amyloliquecidin. The lantibiotic operon of amyloliquecidin was sequenced and annotated. All the genes required for successful production of amyloliquecidin are present in the operon. Amyloliquecidin was characterized in vitro and along with clausin is active against clinical strains of S. aureus (including MRSA), Enterococcus spp., Listeria spp. and beta-haemolytic streptococci. Amyloliquecidin has remarkable stability at physiological pH compared to nisin and clausin. A comparative in vivo murine infection model was used to evaluate the effectiveness of amyloliquecidin, nisin, clausin and Bactroban (commercial S. aureus topical treatment) in treating wound infections caused by S. aureus. All the lantibiotics proved to be just as effective as the Bactroban treatment. Furthermore, the tested lantibiotics did not have a negative influence on the wound closure rates of infected and non-infected wounds. Bactroban had a negative effect on wound healing compared to the lantibiotics.
To our knowledge amyloliquecidin is the third two-component lantibiotic isolated from Bacillus. This study represents the first to test the effectiveness of amyloliquecidin in vivo and is one of a handful to test lantibiotics as topical treatments.<br>AFRIKAANSE OPSOMMING: Antimikrobiese weerstandbiedende bakterieë is op die oomblik een van die grootste probleme in die mediese veld. Die antibiotika krisis word vererg deur die vermoë van bakterieë om vinnig weerstand op te bou teen antibiotika, asook die alledaagse misbruik van antibiotika. Daar is ook ʼn tekort in die hoeveelheid antibiotika wat na die finale fases van ontwikkeling gaan. Om die oorhand teen antibiotika-weerstandige bakterieë te kry is dit van uiterste belang dat meer effektiewe antibiotika ontdek word.
Lantibiotika is kationiese antimikrobiese peptiede wat deur die ribosoom gesintetiseer word en bevat ʼn verskeidenheid van modifikasies wat na translasie ingebou word. Hulle word gekarakteriseer deur lanthionien en metiellanthionien ringe. Lantibiotika is aktief teen ʼn verskeidenheid Gram-positiewe bakterieë en kan in kombinasie met antibiotika, of as alternatief gebruik word. Staphylococcus aureus is die mees algemene bakterium wat geassosieer word met vel en sagte weefsel infeksies (VSWIs). Staphylococcus aureus met weerstand teen antibiotika is ook al geïsoleer, die mees algemene weerstandige ras is methisillien-weerstandige S. aureus (MWSA). Lantibiotika is wel aktief teen MWSA in vitro en in vivo, met van hulle wat tot beter aktiwiteit as die voorgeskrewe antibiotika het. Lantibiotika kan dus gebruik word as behandeling vir VSWIs wat veroorsaak word deur weerstandige S. aureus, asook teen nie-weerstandige rasse.
In hierdie studie was die bakteriese diverse grond van die Fynbos in die Wes-kaap ondersoek vir bakterieë wat antimikrobiese middels produseer. Twee Bacillus rasse, Bacillus clausii AD1 en Bacillus amyloliquefaciens AD2, wat antimikrobiese middels produseer, is geïsoleer. Bacillus clausii AD1 produseer ʼn bekende lantibiotikum, naamlik clausin. Bacillus amyloliquefaciens AD2 produseer ʼn nuwe twee-komponent lantibiotikum, amyloliquecidin. Die lantibiotikum operon wat verantwoordelik is vir die produksie van amyloliquecidin is geïdentifiseer en geannoteer. Die operon bevat al die gene benodig vir die biosintese van amyloliquecidin. Amyloliquecidin is in vitro gekarakteriseer en het aktiwiteit teen ʼn verskeidenheid Gram-positiewe bakterieë. Amyloliquecidin en clausin is aktief teen S. aureus (insluitend MWSA), Enterococcus spp., Listeria spp. en beta-hemolitiese streptococci wat vanaf infeksies geïsoleer is. Amyloliquecidin is baie stabiel by filologiese pH en aansienlik meer stabiel as nisin en clausin. Die effektiwiteit van nisin, clausin en amyloliquecidin in die behandeling van muis vel infeksies veroorsaak deur S. aureus was vergelyk met die kommersiële behandeling Bactroban. Al drie lantibiotika het die verspreiding van S. aureus
met die selfde effektiwiteit as Bactroban belemmer. Geen van die lantibiotika het ʼn negatiewe effek op wond genesing nie. Bactroban, inteendeel, belemmer wond genesing.
So ver ons weet is amyloliquecidin die derde twee-komponent lantibiotikum wat uit Bacillus geïsoleer is. Die studie is ook die eerste om die effektiwiteit van amyloliquecidin in vivo te rapporteer, asook ook een van die min studies wat kyk na lantibiotika as behandeling vir topikale infeksies.
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Zeybek, Asim. "Characterization of industrial powder metallurgy produced 410L ODS steel." Thesis, Open University, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580143.
Full text
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Tan, Chih-Lung. "A characterization of underwater sound produced by heavy precipitation." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242429.
Full textAbstract:
Thesis (M.S. in Physical Oceanography)--Naval Postgraduate School, December 1990.<br>Thesis Advisor(s): Nystuen, Jeffrey A. Second Reader: Medwin, Herman. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Descriptor(s): Bubbles, Sonograms, Underwater Sound, Acoustic Absorption, Rainfall Intensity, Wind, Light, Rates, Theses, Population, Correlation, Precipitation, Raindrops, Sound, Low Level, Acoustic Measurement, High Intensity, Atmospheric Precipitation, Spectrum Analysis, Acoustic Data, Low Frequency, Buoys, Mexico Gulf, Ocean Surface, High Rate, Ocean Waves, Clouds, Data Bases, Frequency. DTIC Identifier(s): Rainfall Rates. Author(s) subject terms: Rainfall Rate, Underwater Sound Spectrum, Sonograms. Includes bibliographical references (p. 55-57). Also available in print.
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ALMEIDA, CLARA MUNIZ DA SILVA DE. "CHARACTERIZATION OF MECHANICAL DEFECTS PRODUCED BY NANOINDENTATION IN INP." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2009. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13442@1.
Full textAbstract:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Nesta tese foi estudado o mecanismo de deformação mecânica de
semicondutores III-V, em especial do InP, através da criação de defeitos utilizando
um microscópio de força atômica e o indentador Triboscope. A liberdade de torção
da ponta do AFM dificulta o controle e a reprodutibilidade dos experimentos de
nanoindentação, por outro lado, através desta liberdade da técnica foi possível
medir a pressão necessária para a criação das primeiras discordâncias no cristal.
Foi realizado um estudo da deformação mecânica do óxido nativo presente na
superfície do InP(100) e do GaAs(001) através de indentações utilizando o
nanoindentador. Impressões plásticas residuais atribuídas à camada de óxido nativo
foram observadas na superfície dos semicondutores. O processo de deformação
plástica do InP foi estudado a partir de nanoindentações utilizando uma ponta
Berkovich e uma ponta conosférica. O processo de deformação do InP com a ponta
Berkovich apresenta descontinuidades para indentações realizadas com altas forças
que são associadas a sucessivos escorregamentos de planos {111} seguidos de
travamento das discordâncias. A distribuição de pressão na região indentada para a
ponta conosférica é isotrópica, permitindo uma melhor visualização da transição
elástico/plástico da deformação do material. Para essa ponta a deformação plástica
do InP é iniciada com um evento catastrófico, que aparece nas curvas de
indentação como uma descontinuidade. Foram observadas características ao redor
das indentações, indicando o aparecimento de discordâncias na superfície do
cristal. Microscopia eletrônica de transmissão foi utilizada para a observação das
seções transversais das indentações que apresentaram alta densidade de
discordâncias formadas pelos planos {111} escorregados.<br>In this thesis, the mechanical deformation mechanism of semiconductors
III-V was studied, especially for InP. Defects were produced by indentations using
an atomic force microscope and a Triboscope nanoindenter. The AFM tip torsion
during indentation difficult the control and the reproducibility of AFM
nanoindentation experiments. Nevertheless, the tip torsion allowed the
measurement of the materials Yield stress. A study of the mechanical deformation
mechanism of the native oxide that is presented in the surface of InP (100) and
GaAs (100) was done. The residual plastic impressions attributed to native oxides
were observed on the semiconductors surface. The plastic deformation process of
the InP was studied in nanoindentation experiments using a Berkovich and a
conosferical tip. The InP deformation mechanism observed with a Berkovich tip
presents discontinuities for indentations performed at high loads, that are
associated with successive slip of {111} planes along the <110> directions. The
pressure distribution on the indented region, applied by the conosferical tip, is
isotropic allowing a better visualization of the elastic/plastic transition in a material
deformation process. The plastic deformation of InP using this tip is initialized
with a catastrophic event, that appears in the indentation curves as a discontinuity.
Small cracks were observed around the indentations using both tips, suggesting
that some dislocations loops ends on the InP surface. Bigger cracks were observed
in indentations with the conosferical tip and they were attributed to material
fracture produced by the locking of dislocations near the surface. Transmission
electron microscopy was done in the nanoindentation cross section showing a high
density of defects created by the slip of the {111} planes.
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Fernandes, Vanda Filipa Silva. "Characterization of biodiesels produced from mixtures of vegetable oils." Master's thesis, Universidade de Aveiro, 2010. http://hdl.handle.net/10773/3141.
Full textAbstract:
Mestrado em Engenharia Química<br>Nos últimos anos o biodiesel tem recebido uma atenção notável devido à sua capacidade de substituir os combustíveis fósseis. É considerado um amigo do ambiente, devido às suas imensas vantagens. Este biocombustível é obtido a partir
de recursos renováveis, portanto é considerado biodegradável, CO2-neutro, nãotóxico e reduz significativamente as emissões gasosas com efeito de estufa.
É composto por uma mistura de ésteres mono alquílicos obtidos a partir de óleos vegetais, tais como, o óleo de soja, óleo de jatropha, óleo de colza, óleo de palma, óleo de girassol ou a partir de outras fontes como a gordura animal (sebo, banha),
restos de óleo e gorduras de cozinha. O processo mais comum para a sua produção é através de uma reacção de transesterificação, onde o óleo vegetal reage com um álcool de cadeia curta na presença de um catalisador.
Devido às suas propriedades muito semelhantes ao diesel, são mutuamente miscíveis e assim podem ser misturados em qualquer proporção em ordem a
melhorar as suas qualidades. O conhecimento das suas propriedades termofísicas como a densidade e viscosidade, que são afectadas pela temperatura, são muito importantes para a indústria automóvel.
Contudo, o biodiesel apresenta algumas desvantagens como elevada densidade,
viscosidade, ponto de turvação e escoamento/fluxação em comparação com diesel
fuel.
O seu comportamento a baixas temperaturas limita a sua aplicação em climas frios, sendo que este comportamento é influenciado pelas matérias-primas e álcool utilizado no processo de produção. Os biodieseis obtidos a partir de óleos com grande teor de ácidos gordos saturados induzem a um pior desempenho a baixas
temperaturas, visto que são compostos sólidos a temperaturas mais baixas.
Neste trabalho, misturas binárias e ternárias de biodiesel de soja, colza e palma, e diesel fuel foram preparadas e medidas as suas viscosidades dinâmicas e densidade em função da temperatura. Para prever as densidades e viscosidades a partir dos compostos puros são utilizadas regras de mistura.
O comportamento a baixas temperaturas dos três biodieseis foi estudado. Onde a composição da fase líquida e sólida e a fracção de sólidos a temperaturas abaixo do ponto de turvação foram analisadas. Aplicou-se um modelo termodinâmico para descrever estes sistemas multifásicos e outros sistemas idênticos. Duas versões do modelo preditivo UNIQUAC, juntamente com uma abordagem que assume uma completa miscibilidade dos componentes na fase sólida, são avaliados em relação aos dados de equilíbrio de fases experimentais medidos.
ABSTRACT: In recent years, biodiesel has received a notable attention due its ability to replace fossil fuels. It is considered an environmental friendly due their vast advantages. This biofuel is obtained from renewable resources, so it is considered biodegradable, CO2- neutral, non-toxic and significantly reduces the greenhouse gas emissions.
It is composed by a mixture of mono alkyl esters obtained from vegetable oil, such as, soybean oil, jatropha oil, rapeseed oil, palm oil, sunflower oil or from other sources like animal fat (beef tallow, lard), waste cooking oil and grasses. The most common process for its production is by a transesterification reaction, where the vegetable oil reacts with a short chain alcohol in presence of a catalyst.
Due to its properties very similar to diesel fuel, they are mutually miscible and so can be mixed in any proportion in order to improve its qualities. The knowledge of its thermophysical properties like density and viscosity, which are affected by
temperature, is very import for automotive industries.
However, biodiesel present some disadvantages like higher viscosity, density, cloud and pour point compared with diesel fuel.
Its behaviour at low-temperature limiting its application in cold climate and these behaviour is influenced by raw materials and the alcohol used in production process.
The biodiesel obtained from oils with a major level in saturated fatty acids esters induce a worse behaviour at low temperatures, since they are solid compounds at lower temperatures.
In this work, binary and ternary blends of biodiesel of soybean, rapeseed and palm, and diesel fuel were prepared and its dynamic viscosities and densities were measured in function of temperature. Mixing rules are used for predicting the densities and viscosities from pure compounds.
The low temperature behaviour of three biodiesel was studied. The liquid and solid phase compositions and solid fraction at temperatures below the cloud point were analyzed. A thermodynamic model was applied to describe these multiphase systems and other similar systems. Two versions of the predictive UNIQUAC model along with an approach that assuming complete immiscibility of the compounds in the solid
phase are evaluated against the experimental phase equilibrium data measured.
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Wise, Lynn V. "Characterization of sludges produced when using polyaluminum chloride coagulants." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/41514.
Full textAbstract:
The dewatering characteristics of polyaluminum chloride (Hyper⁺Ion 1050A) sludges were investigated using lab-scale tests including specific resistance to filtration (r*), capillary suction time (CST), and sludge pH. The effects of chemical conditioning (lime and cationic polymer) and mixing intensity (Gt) upon the sludge dewatering characteristics in a pilot-scale plate and frame press were also studied.
The dewatering characteristics of the Hyper⁺Ion sludges were found to be dependent upon the influent water turbidity conditions; specifically, the ratio of aluminum coagulant to total dry solids in the sludge. Lime was an effective conditioner for doses that produced a sludge pH value in the range of 11.5 to 11.8 which, again, was a direct function of the aluminum coagulant fraction in the sludge. Cationic polymer and a combination of lime and polymer were also effective conditioning schemes when the appropriate dose and mixing intensity were applied.<br>Master of Science
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MARQUES, MARCOS ALEXANDRE. "CHARACTERIZATION OF SURFACE DEFECTS ROLLED STEEL PRODUCTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4394@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>O estudo teve por objetivo investigar o mecanismo de
formação de trincas superficiais na direção longitudinal de
laminação em barras do aço 1538 DH adotado na fabricação de
componentes para a indústria automobilística. Tem-se
conseguido alguns avanços no entendimento dos mecanismos de
trincamento de produtos laminados, porém tais avanços não
permitem, até o presente momento, a eliminação total do
problema, o que vem causando o sucateamento de um
expressivo percentual de produtos siderúrgicos. No escopo
deste trabalho chegou-se a características
microestruturais do material que sugerem as causas do
trincamento durante o processo de laminação e, para tal,
realizou-se o mapeamento das trincas, análises por
microscopia ótica, classificação das inclusões,
caracterizações por microscopia eletrônica de varredura e
EDS, difração de raios-X, ensaios de tração, ensaios de
dureza e microdureza, bem como simulação de ciclos
térmicos. Os resultados destas análises indicaram que a
nucleação e posterior propagação das trincas podem estar
relacionadas à presença de precipitados de segunda fase em
regiões interdendríticas, o que causaria a fragilização do
contorno de grão durante laminação a quente.<br>The purpose of this study was to investigate the cracking
mechanism with regard to longitudinal surface cracks in
rolled 1538 DH steel bars used for the automotive industry.
Although some advances have been achieved concerning the
understanding of the cracking mechanism, the problem is not
yet totally eliminated and still causing the scraping of a
significant percentage of steel products. In the course of
this work it was possible to determine some microstructural
characteristics of the material which may lead to cracking
due to the rolling process. In this sense, it was necessary
to carry out an experimental procedure that included crack
mapping, optical microscopy, classification of the
inclusions, scanning electron microscopy, EDS analysis, X-
ray diffraction, tensile testing, hardness and microhardness
evaluation as well as thermal cycle simulations. The
results seem to suggest that the crack nucleation and crack
propagation are related to the presence of interdendritic
second phase particles which induce to grain boundary
embrittlement during hot rolling.
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D'Ugo, Lucia. "Characterization of hydrothermal carbonization products from woodchip." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9366/.
Full textAbstract:
L’idrotermocarbonizzazione è un processo che permette di convertire un’elevata quantità di materie prime solide in carbone. Ciò viene realizzato inserendo come sostanza in input, oltre alla materia prima iniziale, acqua liquida e, successivamente, riscaldando fino a 180°C, temperatura alla quale inizia la reazione esotermica ed il processo diventa di tipo stand-alone. Tale reazione presenta un tempo di reazione variabile nel range di 4÷12 h. I prodotti in uscita sono costituiti da una sostanza solida che ha le caratteristiche del carbone marrone naturale e un’acqua di processo, la quale è altamente inquinata da composti organici.
In questo elaborato viene illustrata una caratterizzazione dei prodotti in uscita da un impianto di idrotermo carbonizzazione da laboratorio, il quale utilizza in input pezzi di legno tagliati grossolanamente.
Inizialmente tale impianto da laboratorio viene descritto nel dettaglio, dopodiché la caratterizzazione viene effettuata attraverso DTA-TGA dei materiali in ingresso ed uscita; inoltre altre sostanze vengono così analizzate, al fine di confrontarle col char ed i pezzi di legno. Quindi si riporta anche un’analisi calorimetrica, avente l’obiettivo di determinare il calore di combustione del char ottenuto; attraverso questo valore e il calore di combustione dei pezzi di legno è stato possibile calcolare l’efficienza di ritenzione energetica del processo considerato, così come la densificazione energetica riscontrata nel materiale in uscita.
In aggiunta, è stata eseguita un’analisi delle specie chimiche elementari sul char ed il legno in modo da determinare i seguenti parametri: fattori di ritenzione e fattori di ritenzione pesati sulla massa in termini di concentrazione di C, H, N e S. I risultati ottenuti da tale analisi hanno permesso di effettuare una caratterizzazione del char.
Un tentativo di attivazione del char viene riportato, descrivendo la procedura di attivazione seguita e la metodologia utilizzata per valutare il buon esito o meno di tale tentativo di attivazione. La metodologia consiste di uno studio isotermo dell’adsorbimento di acido acetico sul char “attivato” attraverso una titolazione. I risultati sperimentali sono stati fittati usando le isoterme di Langmuir e Freundlich e confrontati con le capacità di adsorbimento del semplice char e di un campione di carbone attivo preso da un’azienda esterna.
Infine si è considerata l’acqua di processo, infatti un’analisi fotometrica ne ha evidenziato le concentrazioni di TOC, COD, ioni nitrato e ioni fosfato. Questi valori sono stati conseguentemente confrontati con i limiti italiani e tedeschi massimi ammissibili per acque potabili, dando quindi un’idea quantitativa della contaminazione di tale acqua di processo.
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Eken, Ali Erdem. "Characterization Of Magnetite Thin Films Produced By Sol-gel Processing." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609298/index.pdf.
Full textAbstract:
Magnetite (Fe3O4) thin films were prepared by a sol-gel process in which, a solution of iron (III) nitrate dissolved in ethylene glycol was applied on glass substrates by spin coating. Xerogel films were obtained by drying the coated films at 110 °<br>C. The films were sintered between 300 °<br>C and 450 °<br>C in order to observe the phases existing in the films at different temperatures. Coating solution showed Newtonian behaviour and viscosity was found as 0.0215 Pa.s. DTA analysis showed that, sintering temperature should be selected between 291 °<br>C and 350 °<br>C in order to produce magnetite thin films. Prepared magnetite thin films were characterized by XRD, SEM, AFM, TEM, VSM and UV-Vis spectrometer. In-plane grazing angle diffraction studies showed that magnetite phase was present upon sintering the films at 300 °<br>C. From the SEM studies, it was shown that films with defect free surfaces were obtained and by cross section studies, thickness of the films was found as ~10-200 nm. AFM images showed that no cracks or any other defects on the film surface were present. TEM results proved the existence of single phase magnetite in the produced films. UV-Vis spectrum results showed that transmittance of the films increases with decreasing sintering temperature and increasing spinning rate. Up to 96% transmittance was observed between the wavelengths of 900-1100 nm. Magnetic properties of magnetite thin films were also examined by VSM (Vibrating Sample Magnetometer) and ferromagnetic behaviour was shown using VSM data.
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Mena, Gómez Josué. "Porous GaN produced by CVD: progress in development and characterization." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/457707.
Full textAbstract:
El nitrur de gal·li (GaN) és un semiconductor amb una banda prohibida ampla amb aplicacions importants en els LED de la llum blanca, que són una alternativa atractiva a les fonts de llum convencionals a causa de la seva llarga vida útil, robustesa física, unitats de mida petita i un mínim impacte ambiental. El GaN, en la seva forma porosa, s'espera que millori l'extracció de llum d'aquests LEDs.
En els últims anys el GaN ha atret també l'atenció del món dels sensors, i molts prototips s'han fabricat utilitzant dispositius HEMT. S'espera que els sensors basats en GaN porós ampliïn la superfície de contacte contra la que l'analit pot interactuar, augmentant la sensibilitat dels dispositius. A més, la realització d'aquests sensors específics per a un analit concret es pot aconseguir funcionalizant la superfície del dispositiu.
L'objectiu principal d'aquesta tesi és optimitzar les condicions de creixement per a la fabricació de GaN porós, així com el creixement de InGaN porós, i GaN porós dopat amb Mg i Si per poder fabricar dispositius basats en la unió p-n. En aquesta tesi s'ha abordat també l'estudi de la funcionalització química amb silans i sals de diazoni de la superfície del GaN per tal de fabricar sensors més eficients i selectius.
Les partícules i les capes epitaxials nanoporoses de GaN es van sintetitzar en un sol pas mitjançant deposició química en fase vapor (CVD de les seves sigles en anglès) a través de la reacció directa entre el gal·li i l'amoníac. Per al dopat de les partícules i capes poroses, es van triar l’acetilacetonat de magnesi i l’acetat de silici com a precursors de Mg i Si, respectivament, per generar els semiconductors de tipus p i n, respectivament. Els resultats obtinguts mostren avenços prometedors per a la fabricació de dispositius porosos basats en les unions p-n i la funcionalització de superfícies de GaN per a aplicacions de detecció.<br>El nitruro de galio (GaN) es un semiconductor con una banda prohibida ancha con aplicaciones importantes en LEDs de luz blanca, que son una alternativa atractiva a las fuentes de luz convencionales debido a su larga vida útil, robustez física, unidades de pequeño tamaño y un impacto ambiental mínimo. El GaN, en su forma porosa, se espera que mejore la extracción de luz de estos LEDs.
En los últimos años el GaN ha atraído tambien la atención del mundo de los sensores, y muchos prototipos se han fabricado utilizando dispositivos HEMT. Se espera que los sensores basados en GaN poroso amplíen la superficie de contacto contra la que el analito puede interactuar, aumentando la sensibilidad de los dispositivos. Además, la realización de estos sensores específicos para un analito concreto se puede conseguir funcionalizando químicamente la superficie del dispositivo.
El objetivo principal de esta tesis es optimizar las condiciones de crecimiento para la fabricación de GaN poroso, así como el crecimiento de InGaN poroso, y GaN poroso dopado con Mg y Si para poder fabricar dispositivos basados en la unión p-n en un futuro. En esta tesis se ha abordado también el estudio de la funcionalización química con silanos y sales de diazonio de la superficie del GaN con el fin de fabricar sensores más eficientes y selectivos.
Las partículas y las capas epitaxiales nanoporosas de GaN se sintetizaron en un solo paso mediante deposición química en fase vapor (CVD de sus siglas en ingles) a través de la reacción directa entre el galio y el amoníaco. Para el dopado de las partículas y capas porosas, se eligieron acetilacetonato de magnesio y acetato de silicio como precursores de Mg y Si, respectivamente, para generar los semiconductores de tipo p y n, respectivamente. Los resultados obtenidos muestran avances prometedores para la fabricación de dispositivos porosos basados en las uniones p-n y la funcionalización de superficies de GaN para aplicaciones de detección.<br>Gallium nitride (GaN) is a wide band gap semiconductor with important applications in white-light LEDs, which are an attractive alternative to conventional light sources due to its long operation lifetime, physical robustness, small-sized units, and minimal environmental impact. GaN, in its porous form, is expected to enhance the light extraction of these LEDs.
In the recent years GaN has also attracted the attention of the sensors world, and many prototypes have been fabricated using HEMT devices. Porous GaN based sensors are expected to enlarge the contact surface against which the analyte can interact, increasing the sensitivity of the devices. Moreover, making these sensors specific for a given target can be achieved by chemically functionalizating the surface of the device.
The main objective of this thesis is to optimize the growth conditions for the fabrication of porous GaN, as well as the growth of Mg- and Si-doped porous GaN and InGaN in order to be able to fabricate devices based on p.n junctions in the future. In this thesis, the study of the chemical functionalization with silanes and diazonium salts of the GaN surface in order to further fabricate efficient and selective sensors, has been also approached.
Nanoporous GaN particles and epitaxial layers were synthesized in a single step by chemical vapor deposition (CVD) through the direct reaction between gallium and ammonia. For the doping of the porous particles and layers magnesium acetylacetonate and silicone acetate were chosen as Mg and Si precursors, respectively, in order to generate the p- and n-type semiconductors, respectively. The obtained results show promising advances for the fabrication of porous p-n junction-based devices and the functionalization of GaN surfaces for sensing applications.
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Nichols, Kristine Ann. "Characterization of glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/86.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2003.<br>Thesis research directed by: Natural Resource Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Zhao, Yi 1961. "CHARACTERIZATION OF WOOD OIL PRODUCED BY EXTRUDER-FEEDER LIQUEFACTION PROCESS." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276484.
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This thesis describes the results of the analytical effort dealing with the products from the preliminary experimental runs using the Advanced Extruder Feeder Biomass Liquefaction Facility in the period from August 1985 to December 1986. Results of the analyses show that a low-oxygen crude wood oil could be produced over a wide range of temperatures, pressures, with or without carbon monoxide and with or without a sodium carbonate catalyst. The analytical procedures have been adapted to evaluate the crude wood oil by standard investigative procedures, including elemental analysis, nuclear magnetic resonance, infrared spectroscopy, gas chromatograph-mass spectrometry, and gas chromatography.
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Hart, Roger A. Bailey James E. Bailey James E. "Characterization of Vitreoscilla hemoglobin inclusion bodies produced in Escherichia coli /." Diss., Pasadena, Calif. : California Institute of Technology, 1991. http://resolver.caltech.edu/CaltechETD:etd-06272007-152616.
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Chen, Yinan. "Characterization of oxysterols produced in macrophages and mechanisms of regulation." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI102/document.
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Les macrophages jouent un rôle clé dans l'athérosclérose. Après la captation massive des LDL oxydées (oxLDL), les macrophages sous-endothéliaux sont chargés en cholestérol et se transforment ainsi en cellules spumeuses qui contribuent à la formation de la plaque d'athérome. Les oxystérols, produits d'oxydation du cholestérol, sont retrouvés en quantité importante dans les oxLDL. Au niveau cellulaire, ils sont impliqués dans la régulation de l'homéostasie du cholestérol, l'induction du stress oxydatif cellulaire et de la cytotoxicité. Notre travail montre que le cholestérol, associé aux LDL et d'origine cellulaire, est fortement oxydé par les macrophages lors d'une exposition aux oxLDL. Les principaux produits d'oxydation sont le 7-cétocholesterol et 7α/β-hydroxycholestérol. De plus, nous démontrons que ces oxystérols sont exportés hors des macrophages via les HDL, mais pas l'apoA1. Nous avons aussi caractérisé les oxystérols formés dans les HDL suite à des modifications oxydatives et les HDL issues de patients diabétiques. Nous avons en outre montré que ces modifications sont associées à une diminution de la capacité des HDL à exporter les oxystérols<br>Macrophages play a key role in atherosclerosis. After massive uptake of oxidized LDL (oxLDL), subendothelial macrophages are overloaded with cholesterol thereby leading to the formation of foam cells, which is one characteristic of atherogenesis. Oxysterols, the oxidation products of cholesterol, are one of major components of oxLDL; they are involved in the regulation of cholesterol homeostasis, induction of cellular oxidative stress and cytotoxicity. Our works show that both LDL derived-cholesterol and cellular cholesterol can be strongly oxidized in human THP1 and murine RAW macrophages, especially during exposure of oxLDL. The major oxidative products are 7-ketocholesterol and 7α/β-hydroxycholesterol. Moreover, we demonstrate that both oxysterols derived from LDL cholesterol and cellular cholesterol can be exported to HDL, whereas not to apoA1. Then, we studied the functionality of modified HDL and diabetic HDL on oxysterols efflux. A decrease of oxysterols efflux was observed with oxidized and glycoxidized HDL. Compared to the HDL of healthy controls, the HDL of diabetic subjects are less efficient to efflux oxysterols. Taken together, the increased production of oxysterols in presence of oxLDL and their lower efflux by modified HDL support the detrimental role of these oxidative compounds in pathophysiological conditions like diabetes
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Mukherjee, Chiranjit. "CHARACTERIZATION OF ARGENTOJAROSITE SYNTHESIZED WITH BIOLOGICALLY PRODUCED FERRIC SULFATE SOLUTIONS." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374139251.
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Davis, Brian Edward. "Characterization and calibration of stereolithography products and processes." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17677.
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Moskalyk, Loralyn Ann. "Characterization of gene products from female mosquito midguts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27842.pdf.
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Siomi, Mikiko. "Characterization of the fragile X syndrome gene products." Kyoto University, 1994. http://hdl.handle.net/2433/160849.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである<br>Kyoto University (京都大学)<br>0048<br>新制・論文博士<br>博士(農学)<br>乙第8739号<br>論農博第1951号<br>新制||農||691(附属図書館)<br>学位論文||H6||N2760(農学部図書室)<br>UT51-94-Z490<br>(主査)教授 小田 順一, 教授 左右 田健次, 教授 駒野 徹<br>学位規則第4条第2項該当
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Metaferia, Ineku Amhayesus. "Characterization of Steel Corrosion Products in Reinforced Concrete." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42128.
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Steel corrosion is one of the major distress mechanisms that causes the deterioration of reinforced concrete structures around the world. It is an electrochemical reaction between the reinforcing steel and the surrounding concrete that produces a mass loss of the metal. Through the process of corrosion in reinforced concrete, iron ions get oxidized to form corrosion products (CP). Although multiple experiments and studies have been developed to understand the rheological behavior of corrosion products, this topic stays inconclusive. This work aims to characterize corrosion products at micro-scale in order to trace the progress of the formation of rust, to determine its nature and to analyse its rheological behavior in reinforced concrete. An experimental procedure to produce CP in the laboratory is also presented in this research. In addition, material characterization methods have been used to identify the iron oxide phases present in CP, determine their viscosity and rheological behavior and to study how CP flows in a porous media. In order to identify the different stages in the corrosion process, the CP was analysed at 2, 4, 6 and 8 weeks. The experiments identified four phases of iron oxide for each period. Furthermore, it was found that CP behaves as a shear-thinning slurry and as a result, its viscosity decreases with the applied shear rate. In addition, the damage caused by CP on concrete depends on the w/c ratio of the concrete mix and the exposure time to a corroding environment. The rebar mass loss results show that CP is formed in layers around the rebar, and the flow of each CP layer can differ.
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Tu, Ya. "Recovery, drying and characterization of carotenoproteins from industrial lobster waste." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59936.
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Lobster waste (including the head and hard carapace, viscera, mandibles and gills) contains approximately 98 $ mu$g/g total astaxanthin, 23% protein, 20% chitin, 34% ash, and 2.2% crude fat on dry weight basis. Carotenoprotein, amounting to 16% of the dry matter was effectively recovered from lobster waste by a trypsin aided process. Air-dried carotenoproteins were enriched in protein by about 108-115%, in crude fat by 540-594% and in carotenoid pigment by about 147-329% as compared with the waste material. Furthermore, the ash and chitin levels in the products were considerably lower than those of the raw material.<br>Drying characteristics of carotenoprotein was evaluated in a modified air-drier using air temperature (45$ sp circ$C, 55$ sp circ$C or 65$ sp circ$C) and relative humidity (5% and 15%) as main factors. The study indicated that higher temperatures achieved faster drying rates of the product but adversely affected its nutritional composition and/or quality. The proximate compositions of carotenoprotein dried at 45$ sp circ$C and relative humidity of 5% or 15% were comparable with that obtained by freeze drying.<br>Thus, the process achieved a substantial reduction in the levels of anti-nutrients associated with lobster waste (i.e., ash and chitin) while elevating the levels of carotenoid pigments and essential nutrients such as protein and fat in the recovered product. These characteristics of the tray-dried carotenoprotein suggest that it could be used as an inexpensive source of pigment and protein in diets of cultured salmonid species.
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Krzysiak, Amanda J. "The isolation and characterization of natural products from marine plants and microorganisms /." Electronic version (PDF), 2006. http://dl.uncw.edu/etd/2006/krzysiaka/amandakrzysiak.pdf.
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Hayes, Brian J. "Characterization of Ti-6Al-4V Produced Via Electron Beam Additive Manufacturing." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822771/.
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In recent years, additive manufacturing (AM) has become an increasingly promising method used for the production of structural metallic components. There are a number of reasons why AM methods are attractive, including the ability to produce complex geometries into a near-net shape and the rapid transition from design to production. Ti-6Al-4V is a titanium alloy frequently used in the aerospace industry which is receiving considerable attention as a good candidate for processing via electron beam additive manufacturing (EBAM). The Sciaky EBAM method combines a high-powered electron beam, weld-wire feedstock, and a large build chamber, enabling the production of large structural components. In order to gain wide acceptance of EBAM of Ti-6Al-4V as a viable manufacturing method, it is important to understand broadly the microstructural features that are present in large-scale depositions, including specifically: the morphology, distribution and texture of the phases present. To achieve such an understanding, stereological methods were used to populate a database quantifying key microstructural features in Ti-6Al-4V including volume fraction of phases, a lath width, colony scale factor, and volume fraction of basket weave type microstructure. Microstructural features unique to AM, such as elongated grains and banded structures, were also characterized. Hardness and tensile testing were conducted and the results were related to the microstructural morphology and sample orientation. Lastly, fractured surfaces and defects were investigated. The results of these activities provide insight into the process-structure-properties relationships found in EBAM processed Ti-6Al-4V.
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Yesil, Mustafa. "Enhancing the inactivation of Escherichia coli O157:H7 by bacteriophage and gaseous ozone to improve postharvest fresh produce safety." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1512103801957122.
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Tseng, Michael. "Characterization of the vaccinia virus I3L gene product." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0003/MQ43227.pdf.
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Minami, Hideki. "Characterization of diamond-like carbon films produced by pulsed laser deposition." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0018/MQ47071.pdf.
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Siddiqui, Nazia. "Characterization of Mechanically and Enzymatically Produced Cellulose Nanofibers from Wood Pulp." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/SiddiquiN2008.pdf.
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Peraud, Olivier. "Isolation and characterization of a sponge-associated actinomycete that produces manzamines." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4114.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.<br>Thesis research directed by: Marine-Estuarine-Environmental Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Rashash, Diana M. C. "Identification and characterization of odorous metabolites produced by selected freshwater algae." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164628/.
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Tipler, Steven. "Characterization of a light petroleum fraction produced from automotive shredder residues." Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/323435/5/contratST.pdf.
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Wastes have a real potential as being players in the energy mix of tomorrow. They can have a high heating value depending on their composition, which makes them good candidates to be converted into liquid fuel via pyrolysis. Among the different types of wastes, automotive residues are expected to rocket due to the increasing number of cars and the tendency to build cars with more and more polymers. Moreover, the existing regulations concerning the recycling of end-of-life vehicles become more and more stringent. Unconventional fuels such as those derived from automotive shredder residues (ASR) have a particular composition which tends to increase the amount of pollutants comparing with conventional fuels. Relying on alternative combustion modes, such as reactivity controlled compression ignition (RCCI), is a solution to cope with these pollutants. In RCCI, two types of fuels are burned simultaneously, namely a light fraction with a low reactivity, and a heavy fraction with a high reactivity. The heavy fraction governs the ignition as it is injected directly in the cylinder close to the end of compression. A variation of its ignition delay could impact the quality of the combustion. Nevertheless, this issue can be tackled by adjusting the injection timing. As long as the low reactivity fuel is concerned, such a solution cannot be adopted as its reactivity depends on the initial parameters (equivalence ratio, inlet temperature, exhaust gas recirculation ratio). However, if the fuel is too reactive, it could create knock that have a dramatic impact on the engine, leading to damages. Thus, being able to predict its features is a key aspect for a safe usage. Predicting methods exist but had never been tested yet with fuels derived from automotive residues. With petroleum products, usual prediction methods stand at three different levels: the chemical composition, the properties, and the reactivity in an appliance. The fuel is studied at these three levels. First, the structure gives a good overview of the fuel auto-ignition. For instance, aromatics tend to have higher ignition delay time (IDT) than paraffins. Second, the octane numbers are good indicators of the fuel IDT and of the resistance toward knock. Precisely, the octane numbers depict the resistance of a fuel towards an end-gas auto-ignition. Last, the IDT was studied in a rapid compression machine and a surrogate fuel was formulated. Surrogate fuels substitute real fuels during simulations because real fuels cannot be modelled by kinetic mechanisms due to their complexity.The existing methods to estimate the composition were updated to predict the n-paraffin, iso-paraffin, olefin, napthene, aromatic and oxygenate(PIONAOx) fractions. A good accuracy was achieved compared with the literature. This new method requires the measurement of the specific gravity, of the distillation cut points, of the CHO atom fractions, of the kinematic viscosity and of the refractive index.Two methods to predict the octane numbers were developed based on Bayesian inference, principal component analysis (PCA) and artificial neural network (ANN). The first is a Bayesian method which modifies the pseudocomponent (PC) method. It introduces a correcting factor which corrects the existing formulation of the PC method to increase its accuracy. A precision of more than 2% is achieved. The second method is based on PCA and ANN. 41 properties are studied among which reduced set of principal variables are selected to predict the octane numbers. 10 properties calculated only with the distillation cut points, the CHO atom fraction and the specific gravity were selected to accurately predict the octane numbers.Measurements of the IDT in a rapid compression machine (RCM) of a fuel produced from ASR were realized. They are the first measurements insuch a machine ever made. This provide experimental data to the literature. Moreover, these experimental data were used to formulate a surrogate fuel. Surrogate fuels can be used to realize simulations under specific conditions. The current thesis investigates fuels derived from ASR. It was showed that this fuel can be burnt in engines as long as their properties are carefully monitored. Among others, the IDT is particularly important. Nevertheless, additional experimental campaigns and simulations in engine are required in order to correctly assess all of the combustion features of such a fuel in an engine.<br>Doctorat en Sciences de l'ingénieur et technologie<br>info:eu-repo/semantics/nonPublished
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Alomirah, Husam Fahd. "Separation and structural characterization of alpha-lactalbumin and beta-lactoglobulin from whey products." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38143.
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In most food applications, whey proteins are used, rather than the individual proteins and this accounts for the high functional variability among commercially available whey protein products, and limits their applications. The overall objective of this study was to investigate the structural and thermal properties of individual alpha-lactalbumin (alpha-Lac) and beta-lactoglobulin (beta-Lg) fractions isolated from different whey protein sources.<br>A common non-chromatographic process that isolate alpha-Lac and beta-Lg, with relatively high purity and yield from liquid whey (LW), whey protein concentrate (WPC) and whey protein isolate (WPI) using different chelating agents, was developed. The use of sodium citrate (NaC) and sodium hexametaphosphate (SHMP) were more effective than other chelating agents. Yield results indicated that 47 to 69% of beta-Lg originally present in the whey preparations was recovered, with purities ranging from 84 to 95%, and protein contents ranging from 40 to 99%, while the yields of alpha-Lac were 23 to 89%, with purities ranging from 83 to 90%, and protein contents ranging from 65 to 96% depending on the source of whey protein preparations and type of chelating agents.<br>Structural and thermal properties of beta-Lg and alpha-Lac isolated fractions were studied using polyacrylamide electrophoresis (native and SDS), RP-HPLC, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and electrospray ionization mass spectrometry (ESI-MS). Results showed that all beta-Lg and alpha-Lac isolated fractions exhibit increased thermal stability and reversibility over standard proteins and difference in thermal properties were dependent on protein source. The relative intensity of the 1692 cm-1 band in the beta-Lg isolated fractions was dependent on the nature of the chelating agent, and disappearance of this band occurred at temperature higher than that of beta-Lg standard, indicating increased thermal stability of beta-Lg isolated fractions. Denaturation of apo-alpha-Lac was related to the gradual decrease in the alpha-helix band and accompanied by the gain in intensity of 1653 and 1641 cm-1 bands, while denaturation of holo-alpha-Lac was associated by breakdown of beta-sheet structure and increase in turns and unordered structures.<br>Changes in charge state distribution (CSD), as measured by ESI-MS of beta-Lg and alpha-Lac in response to pH and storage time, were only qualitative and were of relatively low resolution at basic pH. The hydrogen/deuterium (H/D) exchange results demonstrated that the conformation of holo-alpha-Lac was more stable than that of apo-alpha-Lac and conformation of beta-Lg variant B was more stable than beta-Lg variant A. Kinetics of H/D exchange indicated that alpha-Lac and beta-Lg fractions isolated from different whey protein sources have the same or improved conformational stabilities compared to that of alpha-Lac and beta-Lg standard. The covalent binding of 3 or more hexose residues to alpha-Lac enhanced its conformational stability, but covalent binding of two hexose residues to beta-Lg resulted in less stable conformation.
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Piispanen, Peter. "Synthesis and characterization of surfactants based on natural products." Doctoral thesis, KTH, Chemistry, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3383.
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Yang, Hongta. "Fundamentals, preparation, and characterization of superhydrophobic wood fiber products." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24796.
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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2008.<br>Committee Chair: Yulin Deng; Committee Member: Jeffery S. Hsieh; Committee Member: Sujit Banerjee; Committee Member: Zhong Lin Wang.
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Zhu, Xiaochun. "Characterization of Protein Modification by Products of Lipid Peroxidation." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1225734704.
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Austin, Rodney C. "PHYSICAL CHARACTERIZATION OF OROSOMUCOID GENE PRODUCTS I AND II." University of Cincinnati / OhioLINK, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ucin971364485.
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Ghilamicael, Amanuel Menghs. "Isolation and characterization of n-alkane utilizing bacteria, which produce biomulsifiers." Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/4265.
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Includes bibliographical references.<br>Bacterial strains were isolated by enrichment cultures from oil-contaminated soil samples. In the present study, several strains, capable of growing on crude oil, were isolated. Isolates were screened for their inherent abilities to produce bioemulsifiers when they were grown on hydrocarbon substrates.
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Němcová, Andrea. "Produkce vybraných kvasinkových metabolitů využitelných do potravinových doplňků." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-233400.
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Carotenoids are naturally occurring pigments of plants also produced in many bacteria, and fungi. They represent one of the widest group of natural antioxidants with significant biological effects and numerous of industrial applications. There is an increased interest in carotenoids as natural antioxidants for their ability to reduce chronic diseases, various pathological stages and aging. The area of their application concerns mainly food industry; however, they are used in chemical, pharmaceutical, and cosmetics industry as well. One possibility is study of potential of red yeasts that are able to convert various substrates into carotenoid pigments. In presented thesis carotenogenic yeast belonging to the genus Rhodotorula, Sporobolomyces and Cystofilobasidium were tested for ability to use of selected waste substrates and also random mutagenesis in order to increase the production of biomass and specific metabolites – carotenoids and other lipid-soluble substances. As alternative nutrient sources derived from waste substrates from agricultural and food production (rapeseed substrate, rice, wheat, apple fiber, pasta and lignocellusic materials) were tested. To selected production media extracellular hydrolytic enzymes or commercial enzymes degrading polysaccharide were added. All tested red yeast strains were able to utilize these substrates as the only carbon source and simultaneous produce carotenoid enriched biomass. In this work, characterization of carotenogenic yeast using molecular techniques was studied. For this usage, interspecific variables of strongly conserved sequences of genomic DNA, especially rDNA D1/D2 large ribosomal subunit and ITS1 and 5,8-ITS2 rDNA regions were amplified. These sequences were subjected analysed by DGGE method to compare differences of carotenogenic yeasts. Isolation procedure of the intact DNA were optimized for caryotypic yeast characterization by pulsed field gel electrophoresis (PFGE). The karyotype of tested yeasts contain visible differences between yeast species and genera.
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Younesi, Reza. "Characterization of Reaction Products in the Li-O2 Battery Using Photoelectron Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183887.
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The rechargeable Li-O2 battery has attracted interest due to its high theoretical energy density (about 10 times better than today’s Li-ion batteries). In this PhD thesis the cycling instability of the Li-O2 battery has been studied. Degradation of the battery has been followed by studying the interface between the electrodes and electrolyte and determining the chemical composition and quantity of degradation products formed after varied cycling conditions. For this in-house and synchrotron based Photoelectron Spectroscopy (PES) were used as a powerful surface sensitive technique. Using these methods quantitative and qualitative information was obtained of both amorphous and crystalline compounds. To make the most realistic studies the carbon cathode pore structure was optimised by varying the binder to carbon ratio. This was shown to have an effect on improving the discharge capacity. For Li-O2 batteries electrolyte decomposition is a major challenge. The stability of different electrolyte solvents and salts were investigated. Aprotic carbonate and ether based solvents such as PC, EC/DEC, TEGDME, and PEGDME were found to decompose during electrochemical cycling of the cells. The carbonate based electrolytes decompose to form a 5-10 nm thick surface layer on the carbon cathode during discharge which was then removed during battery charging. The degradation products of the ether based electrolytes consisted mainly of ether and carbonate based surface species. It is also shown that Li2O2 as the final discharge product of the cell is chemically reactive and decomposes carbonate and ether based solvents. The stability of lithium electrolyte salts (such as LiPF6, LiBF4, LiB(CN)4, LiBOB, and LiClO4) was also studied. The PES results revealed that all salts are unstable during the cell cycling and in contact with Li2O2. Decomposition layers thinner than 5 nm were observed on Li2O2. Furthermore, it is shown that the stability of the interface on the lithium anode is a chief issue. When compared to Li batteries (where oxygen levels are below 10 ppm) working in the presence of excess oxygen leads to the decomposition of carbonate based electrolytes to a larger degree.
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Mbonimpa, Eric Gentil. "Characterization of disinfection by-product precursors from Missouri streams." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/4908.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.<br>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 April 10, 2009) Includes bibliographical references.
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Dundar, Halil. "Characterization And Purification Of A Bacteriocin Produced By Leuconostoc Mesenteroides Subsp. Cremoris." Phd thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607812/index.pdf.
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In this study, a new bacteriocin isolated from a Leuconostoc mesenteroides subsp. cremoris strain was purified to homogeneity by pH mediated cell adsorption-desorption, solid phase extraction with Amberlite XAD-16, cation-exchange chromatography and hydrophobic interaction chromatography. The purification resulted in an electrophoretically pure protein that was smaller than 6 kDa as judged by SDS-PAGE. The bacteriocin was found to be very hydrophobic and cationic and could be adsorbed by synthetic calcium silicate due to its cationic and especially hydrophobic nature. It was observed that this bacteriocin was sensitive to &<br>#945<br>-amylase in addition to proteinase K, trypsine, pepsine and chymotrypsine and had a bactericidal mode of action with a concomitant cell lysis. The results indicated that bacteriocin produced by Leuconostoc mesenteroides subsp. cremoris was more stable to combined effect of pH and heat than nisin, lacticin 481, lacticin 3147 and lactococcin G and was bactericidal between pH 2.0-12. It was found that the bacteriocin produced by Leuconostoc mesenteroides subsp. cremoris was stable to organic solvents and could be extracted with chloroform containing solvents efficiently for purification.
The bacteriocin produced by Leuconostoc mesenteroides subsp. cremoris was found to have a strong inhibitory activity against Listeria innoqua, Listeria monocytogenes, Bacillus cereus, Enterococcus faecalis, Lactobacillus delbrueckii, Lactobacillus cremoris, other Leuconostoc meenteroides strains and gram-negative bacterium Pseudomonas fluorescens. Some of the insensitive bacteria were observed to be sensitive when high concentration of the bacteriocin was used.
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Richards, Abigail Marie. "Identification and structural characterization of siderophores produced by halophilic and alkaliphilic bacteria." Online access for everyone, 2007. http://www.dissertations.wsu.edu/Dissertations/Summer2007/A_Richards_072707.pdf.
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COSTA, ANTONIO MARIO LEAL MARTINS. "SYNTHESIS, MORPHOLOGICAL CONTROL AND CHARACTERIZATION OF NANOSTRUCTURED TITANATES PRODUCED FROM ILMENITE SAND." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23001@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO<br>PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO<br>Titanatos nanoestruturados contendo Fe em sua estrutura foram produzidos a partir do tratamento hidrotérmico alcalino de areia ilmenítica. Os parâmetros de síntese - concentração da solução de NaOH e temperatura - foram variados com o intuito de explorar as possibilidades morfológicas. Os produtos foram
caracterizados via microscopia eletrônica de varredura e de transmissão, adsorção de nitrogênio, espectroscopia por energia dispersiva de raios X, Mossbauer e de refletância difusa no UV-Visível. Foram observadas a formação de partículas, folhas e fitas, de acordo com os parâmetros de síntese. Estes resultados foram organizados em um diagrama relacionando a morfologia com os parâmetros de síntese, possibilitando a descrição de um controle morfológico. O Fe se apresentou de duas formas após a síntese: uma como partículas de hematita anexadas às folhas e fitas e a outra na forma de íons Fe3mais dentro das estruturas das folhas ocupando sítios de Ti. Isto teve influência direta sobre as propriedades óticas dos produtos, uma vez que os produtos contendo apenas folhasapresentaram uma alta absorção de fótons, enquanto uma diminuição gradativa foi observada com a formação de fitas e segregação do Fe da estrutura. A área superficial específica dos produtos diminui na medida em que as folhas se tornam fitas, fato que associado com os resultados obtidos para as propriedades óticas, tornam as folhas muito atrativas para aplicação como fotocatalisadores.<br>Nanostructured Fe-titanates were produced via alkaline hydrothermal
treatment of ilmenite sand. The synthesis parameters – NaOH solution concentration and temperature – were varied with the aim of exploring the possible morphologies. The produced titanates were characterized via scanning and transmission electron microscopy, nitrogen adsorption, energy dispersive Xray spectroscopy, Mössbauer and diffuse reflectance spectroscopy. Particles, sheets and ribbons were formed, depending on the synthesis parameters. The results were assembled in a morphological diagram linking the morphology with the synthesis parameters revealing the possibility of morphological control. Iron appeared in two different forms, after synthesis: either as hematite particles attached to sheets and ribbons or as Fe3more ions within the structure of the sheets, occupying Ti sites. This fact has direct influence in the product optical properties since the sheets have shown high photon absorption while a gradual decrease was observed with the ribbons formation. The specific surface area of products decreased when the sheets become ribbons. This fact, associated with the results obtained for the optical properties, makes the sheets very attractive as photocatalysts.