Academic literature on the topic 'Division of Biological Effects'
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Journal articles on the topic "Division of Biological Effects"
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Stamatakis, Michail, and Nikos V. Mantzaris. "Intrinsic noise and division cycle effects on an abstract biological oscillator." Chaos: An Interdisciplinary Journal of Nonlinear Science 20, no. 3 (September 2010): 033118. http://dx.doi.org/10.1063/1.3484868.
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COX, D. L., R. ENDRES, R. V. KULKARNI, M. LABUTE, and R. R. P. SINGH. "ELECTRON CORRELATION EFFECTS IN BIOLOGICAL MOLECULES." International Journal of Modern Physics B 16, no. 20n22 (August 30, 2002): 3377. http://dx.doi.org/10.1142/s0217979202014462.
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Allosteric (conformation changing) proteins with transition metal atoms are at the heart of much important biological function (e.g., myoglobin hemoglobin used for storing and transporting oxygen in the bloodstream). In the case of myoglobin and hemoglobin, oxygen ligation to the iron center induces a spin crossover (high to low) coupled to a structural change; apart from the role of Hunds' exchange in the spin crossover, electron interaction effects have been ignored. We argue that the spin crossover/structure change observed in the similarly structured but far simpler cobalt valence tautomer molecules1 necessitates an inclusion of underscreened Kondo like correlations for a complete description of the energetics of the transition and dynamics, e.g., for x-ray absorption data. We carry this study out with Varma-Yafet-Gunnarsson-Schonhammer wave functions, which, in chemistry language, are basis set restricted configuration interaction in character. We briefly review the applicability of such wave functions to the description of the putative Kondo molecules cerocene (Ce[(CH)5]2) and ytterbocene bipyridine (Yb[(CH)5]2(bipy)) and to the problem of electron transfer in biological molecules and organic conductors, where anomalous long range tunneling may occur. Research supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Division of Materials Research.
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Sokolova, Ekaterina, Natalia Menzorova, Victoria Davydova, Alexandra Kuz’mich, Anna Kravchenko, Natalya Mishchenko, and Irina Yermak. "Effects of Carrageenans on Biological Properties of Echinochrome." Marine Drugs 16, no. 11 (November 1, 2018): 419. http://dx.doi.org/10.3390/md16110419.
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Sea urchin pigment echinochrome A (Ech), a water-insoluble compound, is the active substance in the cardioprotective and antioxidant drug Histochrome® (PIBOC FEB RAS, Moscow, Russia). It has been established that Ech dissolves in aqueous solutions of carrageenans (CRGs). Herein, we describe the effects of different types of CRGs on some properties of Ech. Our results showed that CRGs significantly decreased the spermotoxicity of Ech, against the sea urchin S. intermedius sperm. Ech, as well as its complex with CRG, did not affect the division and development of early embryos of the sea urchin. Ech reduced reactive oxygen species production (ROS) in neutrophils, caused by CRG. The obtained complexes of these substances with pro- and anti-activating ROS formation properties illustrate the possibility of modulating the ROS induction, using these compounds. The CRGs stimulate the induction of anti-inflammatory IL-10 synthesis, whereas Ech inhibits this synthesis and increases the production of the pro-inflammatory cytokines IL-6 and TNFα. The inclusion of Ech, in the complex with the CRGs, decreases Ech’s ability to induce the expression of pro-inflammatory cytokines, especially TNFα, and increases the induction of anti-inflammatory cytokine IL-10. Thus, CRGs modify the action of Ech, by decreasing its pro-inflammatory effect. Whereas, the Ech’s protective action towards human epithelial HT-29 cells remains to be unaltered in the complex, with κ/β-CRG, under stress conditions.
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Lock, Judith E. "Transgenerational effects of parent and grandparent gender on offspring development in a biparental beetle species." Biology Letters 8, no. 3 (November 16, 2011): 408–11. http://dx.doi.org/10.1098/rsbl.2011.0920.
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Parental effects on offspring life-history traits are common and increasingly well-studied. However, the extent to which these effects persist into offspring in subsequent generations has received less attention. In this experiment, maternal and paternal effects on offspring and grand-offspring were investigated in the biparental burying beetle Nicrophorus vespilloides , using a split-family design. This allowed the separation of prenatal and postnatal transgenerational effects. Grandparent and parent gender were found to have a cumulative effect on offspring development and may provide a selection pressure on the division of parental investment in biparental species.
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Schlimpert, Susan, Sebastian Wasserstrom, Govind Chandra, Maureen J. Bibb, Kim C. Findlay, Klas Flärdh, and Mark J. Buttner. "Two dynamin-like proteins stabilize FtsZ rings duringStreptomycessporulation." Proceedings of the National Academy of Sciences 114, no. 30 (July 7, 2017): E6176—E6183. http://dx.doi.org/10.1073/pnas.1704612114.
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During sporulation, the filamentous bacteriaStreptomycesundergo a massive cell division event in which the synthesis of ladders of sporulation septa convert multigenomic hyphae into chains of unigenomic spores. This process requires cytokinetic Z-rings formed by the bacterial tubulin homolog FtsZ, and the stabilization of the newly formed Z-rings is crucial for completion of septum synthesis. Here we show that two dynamin-like proteins, DynA and DynB, play critical roles in this process. Dynamins are a family of large, multidomain GTPases involved in key cellular processes in eukaryotes, including vesicle trafficking and organelle division. Many bacterial genomes encode dynamin-like proteins, but the biological function of these proteins has remained largely enigmatic. Using a cell biological approach, we show that the twoStreptomycesdynamins specifically localize to sporulation septa in an FtsZ-dependent manner. Moreover, dynamin mutants have a cell division defect due to the decreased stability of sporulation-specific Z-rings, as demonstrated by kymographs derived from time-lapse images of FtsZ ladder formation. This defect causes the premature disassembly of individual Z-rings, leading to the frequent abortion of septum synthesis, which in turn results in the production of long spore-like compartments with multiple chromosomes. Two-hybrid analysis revealed that the dynamins are part of the cell division machinery and that they mediate their effects on Z-ring stability during developmentally controlled cell division via a network of protein–protein interactions involving DynA, DynB, FtsZ, SepF, SepF2, and the FtsZ-positioning protein SsgB.
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Helanterä, Heikki, Oliver Aehle, Maurice Roux, Jürgen Heinze, and Patrizia d'Ettorre. "Family-based guilds in the ant Pachycondyla inversa." Biology Letters 9, no. 3 (June 23, 2013): 20130125. http://dx.doi.org/10.1098/rsbl.2013.0125.
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High relatedness promotes the evolution of sociality because potentially costly cooperative behaviours are directed towards kin. However, societies, such as those of social insects, also benefit from genetic diversity, e.g. through enhanced disease resistance and division of labour. Effects of genetic diversity have been investigated in a few complex eusocial species. Here, we show that genetically based division of labour may also be important in ‘simple societies’, with fewer individuals and limited morphological caste differentiation. The ponerine ant Pachycondyla inversa has small colonies, headed by several unrelated queens. We show that nest-mate workers from different matrilines engage in different tasks, have distinct chemical profiles and associate preferentially with kin in the nest, while queens and brood stay together. This suggests that genetically based division of labour may precede the evolution of complex eusociality and facilitate the existence of low relatedness societies functioning as associations of distinct families that mutually benefit from group living.
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Dong, Ren G., John Z. Wu, Xueyan S. Xu, Daniel E. Welcome, and Kristine Krajnak. "A Review of Hand–Arm Vibration Studies Conducted by US NIOSH since 2000." Vibration 4, no. 2 (June 15, 2021): 482–528. http://dx.doi.org/10.3390/vibration4020030.
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Studies on hand-transmitted vibration exposure, biodynamic responses, and biological effects were conducted by researchers at the Health Effects Laboratory Division (HELD) of the National Institute for Occupational Safety and Health (NIOSH) during the last 20 years. These studies are systematically reviewed in this report, along with the identification of areas where additional research is needed. The majority of the studies cover the following aspects: (i) the methods and techniques for measuring hand-transmitted vibration exposure; (ii) vibration biodynamics of the hand–arm system and the quantification of vibration exposure; (iii) biological effects of hand-transmitted vibration exposure; (iv) measurements of vibration-induced health effects; (iv) quantification of influencing biomechanical effects; and (v) intervention methods and technologies for controlling hand-transmitted vibration exposure. The major findings of the studies are summarized and discussed.
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Hynd, PI. "Effects of nutrition on wool follicle cell kinetics in sheep differing in efficiency of wool production." Australian Journal of Agricultural Research 40, no. 2 (1989): 409. http://dx.doi.org/10.1071/ar9890409.
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Wide phenotypic variation in fibre output per follicle was generated by selecting sheep (five South Australian strongwool Merinos, one finewool Merino and one Corriedale) on this basis, and by offering these sheep a low-protein diet for 9 weeks, followed by a high-protein diet for a further 8 weeks. Clean wool production was measured over the final 3 weeks of each period, while fibre diameter, the rate of length growth of fibres and a number of follicle characters were measured over the last 7 days of each period. The rate of division of follicle bulb cells and the total volume of the germinative region of the follicle was estimated by image-analysis of bulb sections in skin biopsy samples.With the change from the low-protein diet to the high-protein diet, the rate of clean fleece production was increased by 33% (P<0.002), reflecting an increase in fibre diameter (8%) and rate of length growth of fibres (26%); the volume of the germinative region of the average bulb increased 30% (P<0.012) and the rate of bulb cell division by 35% (P<0.004); cortical cell volume also did not change (923 8m3 v. 965 8m3; the average proportion of fibre cross-sectional area occupied by paracortical cells increased from 0.2 1 to 0.35 ( P < 0.01 0); the proportion of dividing cells entering the fibre cortex ranged from 0.25 to 0.42 (mean, 0.31) between sheep on the low-protein diet, and from 0.22 to 0.39 (mean, 0.32) when the animals were fed the high-protein ration; the effect of diet on cell distribution to fibre and inner root sheath was not significant (P<0.601).Phenotypic differences in fibre output were primarily related to differences in the rate of bulb cell division (r= 0.896, P < 0.001), but inclusion of a term for the proportion of bulb cells entering the fibre cortex, removed an additional, significant proportion of the variance. Cortical cell volume, on the other hand, was poorly related to fibre output.
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Yuan, Jintao, Zhiping Wei, Xinwei Xu, Dickson Kofi Wiredu Ocansey, Xiu Cai, and Fei Mao. "The Effects of Mesenchymal Stem Cell on Colorectal Cancer." Stem Cells International 2021 (July 24, 2021): 1–14. http://dx.doi.org/10.1155/2021/9136583.
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Colorectal cancer (CRC) is a common malignant tumor of the gastrointestinal tract with nonobvious early symptoms and late symptoms of anemia, weight loss, and other systemic symptoms. Its morbidity and fatality rate are next only to gastric cancer, esophageal cancer, and primary liver cancer among digestive malignancies. In addition to the conventional surgical intervention, other therapies such as radiotherapy and chemotherapy and new treatment methods such as biologics and microbiological products have been introduced. As a promising cell therapy, mesenchymal stem cell (MSC) has attracted extensive research attention. MSCs are early undifferentiated pluripotent stem cells, which have the common features of stem cells, including self-replication, self-division, self-renewal, and multidirectional differentiation. MSCs come from a wide range of sources and can be extracted from a variety of tissues such as the bone marrow, umbilical cord, and fat. Current studies have shown that MSCs have a variety of biological functions such as immune regulation, tissue damage repair, and therapeutic effects on tumors such as CRC. This review outlines the overview of MSCs and CRC and summarizes the role of MSC application in CRC.
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Geniole, Shawn N., Valentina Proietti, Brian M. Bird, Triana L. Ortiz, Pierre L. Bonin, Bernard Goldfarb, Neil V. Watson, and Justin M. Carré. "Testosterone reduces the threat premium in competitive resource division." Proceedings of the Royal Society B: Biological Sciences 286, no. 1903 (May 29, 2019): 20190720. http://dx.doi.org/10.1098/rspb.2019.0720.
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Like other animals, humans are sensitive to facial cues of threat. Recent evidence suggests that we use this information to dynamically calibrate competitive decision-making over resources, ceding more to high-threat individuals (who appear more willing/able to retaliate) and keeping more from low-threat individuals. Little is known, however, about the biological factors that support such threat assessment and decision-making systems. In a pre-registered, double-blind, placebo-controlled, cross-over testosterone administration study ( n = 118 men), we show for the first time that testosterone reduces the effects of threat on decision-making: participants ceded more resources to high-threat (versus low-threat) individuals (replicating the ‘threat premium’), but this effect was blunted by testosterone, which selectively reduced the amount of resources ceded to those highest in threat. Thus, our findings suggest that testosterone influences competitive decision-making by recalibrating the integration of threat into the decision-making process.
Dissertations / Theses on the topic "Division of Biological Effects"
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Kisiday, John D. (John David) 1970. "In vitro culture of a chondrocyte-seeded peptide hydrogel and the effects of dynamic compression." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29614.
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Thesis (Ph. D. in Bioengineering)--Massachusetts Institute of Technology, Biological Engineering Division, 2003.Includes bibliographical references.
Emerging medical technologies for effective and lasting repair of articular cartilage include delivery of cells or cell-seeded scaffolds to a defect site to initiate de novo tissue regeneration. Biocompatible scaffolds assist in providing a template for cell distribution and extracellular matrix accumulation in a three-dimensional geometry. In these studies, a self-assembling peptide hydrogel is evaluated as a potential scaffold for cartilage repair using a model bovine cell source. A seeding technique is developed for 3-D encapsulation of chondrocytes in a peptide hydrogel. The chondrocyte-seeded peptide hydrogel was then evaluated cellular activities in vitro under standard culture conditions and also when subjected to dynamic compression. During 4 weeks of culture in vitro, chondrocytes seeded within the peptide hydrogel retained their morphology and developed a cartilage-like ECM rich in proteoglycans and type II collagen, indicative of a stable chondrocyte phenotype. Time dependent accumulation of this ECM was paralleled by increases in material stiffness, indicative of deposition of mechanically-functional neo-tissue. Culture of chondrocyte-seeded peptide hydrogels in ITS-supplemented medium was investigated as an alternative to high serum culture. Low serum (0.2%), ITS-supplemented medium was found to maintain high levels of cell division and extracellular matrix synthesis and accumulation, as seen in high serum culture. Furthermore, low serum, ITS medium induced minimal chondrocyte de-differentiation on the surface of the hydrogel. This is in contrast to high serum culture, where surface de-differentiation and subsequent proliferation led to a 5-10 cell thick layer that stained positive for type I collagen.
(cont.) The effects of dynamic compression of chondrocyte-seeded peptide hydrogels were evaluated over long-term culture. A non-continuous loading protocol was identified in which proteoglycan, but not protein, synthesis increased over static, free-swelling culture. Increases in GAG matrix accumulation were observed after at least 8 days of loading, while hydroxyproline accumulation was unaffected by dynamic compression. These data demonstrated dynamic compression differentially regulated the synthesis of proteoglycans. Analysis of GAG loss to the medium indicated peak proteoglycan catabolism occurred immediately after the initiation of loading. This phenomenon was further explored using a modified loading protocol that increased GAG loss to the medium. Peak GAG loss to the medium was 2-fold higher than previously observed, resulting in GAG accumulation values significantly less than controls. Hydroxyproline accumulation was minimally affected by loading, demonstrating that dynamic compression also differentially regulated the catabolism of proteoglycans. Proteoglycan catabolism was not predominantly due to physical disruption accumulated extracellular matrix or loss of newly-synthesized molecules. Instead, the presence of MMPs in the medium that coincided with GAG loss suggest a potential enzymatic mechanism. These results demonstrate the potential of a self-assembling peptide hydrogel as a scaffold for the synthesis and accumulation of a true cartilage-like extracellular matrix ...
John D. Kisiday.
Ph.D.in Bioengineering
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Szafranski, Jon D. (Jon David). "Cartilage mechanobiology : the effects of loading on the fine structure and function of chondroitin sulfate glycosaminoglycans." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33871.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2005.Includes bibliographical references.
Chondroitin sulfate is a critical component of articular cartilage due to its contribution to the tissue's resistance to compressive deformation. Alterations in the biosynthesis of this molecule over time could impact the ability of the tissue to perform its necessary functions. Several factors have been shown to alter the biosynthesis of chondroitin sulfate in cartilage; among them are age, disease, depth of tissue, and mechanical compression. Specifically, mechanical compression has been shown to have a significant effect on the sulfation pattern and chain length and number in cartilage explant studies. The mechanisms that govern these alterations, however, have not been determined. The purpose of this study is to examine the effects of mechanical compression on chondroitin sulfate biosynthesis and analyze the roles of two possible mechanisms; enzyme transcription and organelle deformation. The effects of mechanical compression on the transcription rates of enzymes associated with the biosynthesis of chondroitin sulfate have not been previously studied. To perform this study in a bovine model, portions of the bovine genome had to be sequenced, PCR primers designed, and bulk expression levels determined. Static compression resulted in the significant up-regulation of two genes of interest: chondroitin sulfate and GalNAc 4S,6-sulfotransferase.
(cont.) Dynamic compression resulted in the significant up-regulation of the three sulfotransferases responsible for the bulk of sulfation in cartilage tissue. These results indicate a transient mechanotransduction reaction that differs based on the load regime. The effect of mechanical loading on the biosynthesis of chondroitin sulfate has been studied previously, however, this study seeks to examine more comprehensive loading regimes. Static compression and release resulted in an increase in 6-sulfation and a decrease in 4-sulfation that lasted to 48 hours after release of compression. Dynamic compression and release had the opposite effect on sulfation ratio, with an increase in 4-sulfation compared to 6-sulfation. The transcription changes seen in this study do not indicate the changes that occur in the end products of synthesis. Other factors may play a larger role, such as precursor availability or transport through the Golgi apparatus. Intracellular organelles react to static compression of the surrounding tissue in one of two manners. The majority of organelles deform much as the nucleus, proportionally in volume and shape to the cell. The Golgi apparatus appears to retain a significant portion of its volume relative to the cell and other organelles. In addition, it reforms structurally into a highly ordered stacked appearance.
(cont.) Osmotic forces within the Golgi may allow it to balance the osmotic load in the cytoplasm and resist compression and altered trafficking of the Golgi may in turn produce the altered appearance. Recent microscopy experiments on the Golgi apparatus utilizing two-photon microscopy have allowed us to examine the reaction of live tissue to static compression. These results illustrate the significant, but differing, effects of static and dynamic compression on the biosynthesis of chondroitin sulfate. The effects of these compression types on the transcription of enzymes responsible for this biosynthesis cannot fully explain the changes seen in newly synthesized chondroitin sulfate. Organelle reorganization has been shown to occur in response to static load and it is possible that altered organelle trafficking plays a role in this altered biosynthesis. Further studies are necessary to determine the final effect of the altered transcription and organelle structure on the manufacture of this important cartilage molecule.
by Jon D. Szafranski.
Ph.D.
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Wheeler, Cameron 1978. "Cartilage mechanobiology and transcriptional effects of combined mechanical compression and IGF-1 stimulation on bovine cartilage explants." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38613.
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Thesis (S.M.)--Massachusetts Institute of Technology, Biological Engineering Division, February 2007.Includes bibliographical references.
Background: Investigators have focused on mechano-regulation of upstream signaling and responses at the level of gene transcription, protein translation and post-translational modifications. Intracellular pathways including those involving integrin signaling, mitogen activated protein kinases (MAPKs), and release of intracellular calcium have been confirmed in several laboratories. Studies with IGF-1: Insulin-like growth factor-I (IGF-1) is a potent anabolic factor capable of endocrine and paracrine/autocrine signaling. Previous studies have demonstrated that mechanical compression can regulate the action of IGF-1 on chondrocyte biosynthesis in intact tissue; when applied simultaneously, these stimuli act by distinct cell activation pathways. Our objectives were to elucidate the extent and kinetics of the chondrocyte transcriptional response to combined IGF-1 and static compression in cartilage explants. Discussion: Clustering analysis revealed five distinct groups. TIMP-3 and ADAMTS-5, MMP-l and IGF-2, and IGF-1 and Collagen II, were all robustly co-expressed under all conditions tested. In comparing gene expression levels to previously measured aggrecan biosynthesis levels, aggrecan synthesis is shown to be transcriptionally regulated by IGF- 1, whereas inhibition of aggrecan synthesis by compression is not transcriptionally regulated.
(cont.) Conclusion: Many genes measured are responsive the effects of IGF-1 under 0% compression and 50% compression. Clustering analysis revealed strong co-expressed gene pairings. IGF-1 stimulates aggrecan biosynthesis in a transcriptionally regulated manner, whereas compression inhibits aggrecan synthesis in a manner not regulated by transcriptional activity.
by Cameron A. Wheeler.
S.M.
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Villasenor, Jose Fernando. "HABITAT USE AND THE EFFECTS OF DISTURBANCE ON WINTERING BIRDS USING RIPARIAN HABITATS IN SONORA, MEXICO." The University of Montana, 2007. http://etd.lib.umt.edu/theses/available/etd-03282007-165836/.
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Riparian systems are important for breeding bird communities and are highly used as migratory corridors; however, their importance for wintering birds has not been assessed systematically. In order to assess the value of riparian areas for birds wintering in Sonora, data from 1,816 standard point counts were collected from 87 locations during January and February 2004-2006. A total of 253 species were detected across 14 vegetation types, including nine categories of riparian vegetation. The mean number of species and individuals detected per count was significantly higher in riparian vegetation than in non-riparian vegetation for migratory species, but not for residents. Riparian bird communities are different from those in non-riparian habitats, and contribute 22% of the regional avifauna's species.Anthropogenic disturbance has imposed significant changes in riparian habitats, and is known to have negative effects on biological communities. To assess the effects of human induced disturbance on wintering bird communities, I recorded community composition, relative abundance of species, and three indicators of bird condition in relatively undisturbed and highly disturbed sites at three river systems in Sonora. There is, in general, little effect of disturbance on the composition of wintering communities, with less than 20% of the most common species having significant differences in their abundances between relatively undisturbed and highly disturbed sites. Condition indicators were similar in the two disturbance levels, but the mean heterophil/lymphocyte ratio in the blood of sampled birds showed increased levels of physiological stress in disturbed sites. A more experimental approach is needed to determine the specific cause of the stress expression in leucocytes.
Modification of natural flooding regimes has modified riparian areas, as has been the case in the Colorado River Delta. I present a summary of the changes experienced by riparian systems and some of the measures implemented for riparian restoration in the southwestern United States, and then I compare the scenario with that in central Sonora, where some of the same stressors exist on riparian systems, but where traditional management practices have also mitigated some of the negative consequences of flow control along mid-sized river systems.
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Anderson, Michelle Louise. "The edge effect: lateral habitat ecology of an alluvial river flood plain." The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-10012008-134442/.
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We describe the ecology of off-channel or "lateral" habitats as key attributes of the Shifting Habitat Mosaic (SHM) of a river flood plain at the Nyack Research Natural Area in northwestern Montana. Our working hypothesis was that lateral habitats are important to the cycling of energy and materials within the SHM and contribute greatly to the productivity and biodiversity of the floodplain ecosystem. We produce a quantitative description of temperature variation across aquatic and terrestrial habitats at Nyack. Thermal patterns across lateral habitats indicate vast differences exist between lateral habitats in habitat suitability for aquatic organisms over an annual cycle. Existing thermal regimes favor life history diversification. We further document the impacts of flood disturbances on organic matter accumulation by aquatic primary producers in off-channel environments. We were able to show that the annual flood pulse disturbance was the major force controlling periphyton community biomass, nutrient status, and species composition, with secondary control by surface and groundwater mediated water chemistry fluctuations during lower flow periods. We end with a study relating biodiversity pattern and process to lateral habitat heterogeneity. Data supported our prediction that densities and diversity of organisms and food webs of the flood plain would be greatly increased if off-channel habitats as well as main channel habitats were included. Collectively, lateral habitats uniquely support 50% of the total documented aquatic biodiversity of the entire floodplain. We conclude that lateral habitats contribute significantly to the biocomplexity of alluvial floodplain ecosystems.
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Sachs, Karen Ph D. Massachusetts Institute of Technology. "Bayesian network models of biological signaling pathways." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/38865.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2006.Includes bibliographical references (p. 153-165).
Cells communicate with other cells, and process cues from their environment, via signaling pathways, in which extracellular cues trigger a cascade of information flow, causing signaling molecules to become chemically, physically or locationally modified, gain new functional capabilities, and affect subsequent molecules in the cascade, culminating in a phenotypic cellular response. Mapping the influence connections among biomolecules in a signaling cascade aids in understanding of the underlying biological process and in development of therapeutics for diseases involving aberrant pathways, such as cancer and autoimmune disease. In this thesis, we present an approach for automatically reverse-engineering the structure of a signaling pathway, from high-throughput data. We apply Bayesian network structure inference to signaling protein measurements performed in thousands of single cells, using a machine called a flow cytorneter. Our de novo reconstruction of a T-cell signaling map was highly accurate, closely reproducing the known pathway structure, and accurately predicted novel pathway connections. The flow cytometry measurements include specific perturbations of signaling molecules, aiding in a causal interpretation of the Bayesian network graph structure.
(cont.) However, this machine can measure only -4-12 molecules per cell, too few for effective coverage of a signaling pathway. To address this problem, we employ a number of biologically motivated assumptions to extend our technique to scale up from the number of molecules measured to larger models, using measurements of overlapping variable subsets. We demonstrate this approach by scaling up to a model of 11 variables, using 15 overlapping 4-variable measurements.
by Karen Sachs.
Ph.D.
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Shiva, V. A. "Scalable computational architecture for integrating biological pathway models." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42384.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007.MIT Institute Archives copy: DVD inserted in pocket on p. [3] of cover on v. 1.
"c2007"--p. ii.
Includes bibliographical references (v. 2, leaves 292-302).
A grand challenge of systems biology is to model the cell. The cell is an integrated network of cellular functions. Each cellular function, such as immune response, cell division, metabolism or apoptosis, is defined by an interconnected ensemble of biological pathways. Modeling the cell or even one cellular function requires a computational architecture that integrates multiple biological pathway models in a scalable manner while ensuring minimal effort to maintain the resulting integrated model. Scalable is defined as the ease in which more and more biological pathway models can be integrated. Current architectures for integrating biological pathway models are primarily monolithic and involve combining each biological pathway model's software source code to build one large monolithic model that executes on a single computer. Such architectures are not scalable for modeling complex cellular functions or the whole cell. We present Cytosolve, a new computational architecture that integrates a distributed ensemble of biological pathway models and computes solutions in a parallel manner while offering ease of maintenance of the integrated model. The individual biological pathway models can be represented in SBML, CellML or in any number of formats. The EGFR model of Kholodenko with known solutions is used to compare the Cytosolve solution and computational times with a known monolithic approach. A new integrative model of the interferon (IFN) response to virus infection is developed using Cytosolve. Each model within the integrated model, spans different time scales, is created by different authors from four countries and three continents across different disciplines, is written in different software codes, and is built on different hardware platforms.
(cont.) A new quantitative methodology and formalism is then derived for evaluating different types of monolithic and distributed architectures for integrating biological pathway models. As more biological pathway models develop in a disparate and decentralized manner, the Cytosolve architecture offers a unique platform to build and test complex models of cellular function, and eventually the whole cell.
by V.A. Shiva Ayyadurai.
Ph.D.
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Margolin, Yelena 1977. "Analysis of sequence-selective guanine oxidation by biological agents." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42381.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, February 2008.Vita.
Includes bibliographical references.
Oxidatively damaged DNA has been strongly associated with cancer, chronic degenerative diseases and aging. Guanine is the most frequently oxidized base in the DNA, and generation of a guanine radical cation (G'") as an intermediate in the oxidation reaction leads to migration of a resulting cationic hole through the DNA n-stack until it is trapped at the lowest-energy sites. These sites reside at runs of guanines, such as 5'-GG-3' sequences, and are characterized by the lowest sequence-specific ionization potentials (IPs). The charge transfer mechanism suggests that hotspots of oxidative DNA damage induced by electron transfer reagents can be predicted based on the primary DNA sequence. However, preliminary data indicated that nitrosoperoxycarbonate (ONOOCO2"), a mediator of chronic inflammation and a one-electron oxidant, displayed unusual guanine oxidation properties that were the focus of present work. As a first step in our study, we determined relative levels of guanine oxidation, induced by ONOOCO2 in all possible three-base sequence contexts (XGY) within double-stranded oligonucleotides. These levels were compared to the relative oxidation induced within the same guanines by photoactivated riboflavin, a one-electron reagent. We found that, in agreement with previous studies, photoactivated riboflavin was selective for guanines of lowest IPs located within 5'-GG-3' sequences. In contrast, ONOOCO2" preferentially reacted with guanines located within 5'-GC-3' sequences characterized by the highest IPs. This demonstrated that that sequence-specific IP was not a determinant of guanine reactivity with ONOOCO2". Sequence selectivities for both reagents were double-strand specific. Selectivity of ONOOCO2 for 5'-GC-3' sites was also observed in human genomic DNA after ligation-mediated PCR analysis.
(cont.) Relative yields of different guanine lesions produced by both ONOOCO2" and riboflavin varied 4- to 5-fold across all sequence contexts. To assess the role of solvent exposure in mediating guanine oxidation by ONOOCO2", relative reactivities of mismatched guanines with ONOOCO2" were measured. The majority of the mismatches displayed an increased reactivity with ONOOCO2 as compared to the fully matched G-C base-pairs. The extent of reactivity enhancement was sequence context-dependent, and the greatest levels of enhancement were observed for the conformationally flexible guanine- guanine (G-G) mismatches and for guanines located across from a synthetic abasic site. To test the hypothesis that the negative charge of an oxidant influences its reactivity with guanines in DNA, sequence-selective guanine oxidation by a negatively charged reagent, Fe+2-EDTA, was assessed and compared to guanine oxidation produced by a neutral oxidant, y-radiation. Because both of these agents cause high levels of deoxyribose oxidation, a general method to quantify sequence-specific nucleobase oxidation in the presence of direct strand breaks was developed. This method exploited activity of exonuclease III (Exo III), a 3' to 5' exonuclease, and utilized phosphorothioate-modified synthetic oligonucleotides that were resistant to Exo III activity. This method was employed to determine sequence-selective guanine oxidation by Fe+2-EDTA complex and y-radiation and to show that both agents produced identical guanine oxidation pattems and were equally reactive with all guanines, irrespective of their sequence-specific IPs or sequence context.
(cont.) This showed that negative charge was not a determinant of Fe+2-EDTA-mediated guanine oxidation. Finally, the role of oxidant binding on nucleobase damage was assessed by studying sequence-selective oxidation produced by DNA-bound Fe+2 ions in the presence of H202. We found that the major oxidation targets were thymines located within 5'-TGG-3' motifs, demonstrating that while guanines were a required element for coordination of Fe+2 to DNA, they were not oxidized. Our results suggest that factors other than sequence-specific IPs can act as major determinants of sequence-selective guanine oxidation, and that current models of guanine oxidation and charge transfer in DNA cannot be used to adequately predict the location and identity of mutagenic lesions in the genome.
by Yelena Margolin.
Ph.D.
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Canton, Bartholomew (Bartholomew John). "Engineering the interface between cellular chassis and synthetic biological systems." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44918.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 165-176).
The aim of my thesis is to help enable the engineering of biological systems that behave in a predictable manner. Well-established techniques exist to engineer systems that behave as expected. Here, I apply such techniques to two aspects of the engineering of biological systems. First, I address the design and construction of standard biological devices in a manner that facilitates reuse in higher-order systems. I describe the design and construction of an exemplar device, an engineered cell-cell communication receiver using standard biological parts (refined genetic objects designed to support physical and functional composition). I adopt a conventional framework for describing the behavior of engineered devices and use the adopted framework to design and interpret experiments that describe the behavior of the receiver. The output of the device is the activity of a promoter reported in units of Polymerases Per Second (PoPS), a common signal carrier. Second, I begin to address the coupling that exists between engineered biological systems and the host cell, or chassis. I propose that the coupling between engineered biological systems and the cellular chassis might be reduced if fewer resources were shared between the system and the chassis. I describe the construction of cellular chassis expressing both T7 RNA polymerases (RNAP) and orthogonal ribosomes that are unused by the chassis but are available for use by an engineered system. I implement a network in which the orthogonal ribosomal RNA and the gene encoding T7 RNAP are transcribed by T7 RNAP. In turn, the orthogonal ribosomes translate the T7 RNAP message. In addition, the T7 RNAP and orthogonal ribosomes express a repressor that inhibits transcription of both the T7 RNAP and orthogonal ribosomes.
(cont.) As a result, the orthogonal RNAP and ribosomes are auto-generating and self-regulating. The provision of resources unused by the cellular chassis and dedicated to an engineered biological system forms the beginnings of a biological virtual machine.
by Bartholomew Canton.
Ph.D.
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Frick, Lauren Elizabeth. "The versatile E. coli adaptive response protein AlkB mitigates toxicity and mutagenicity of etheno-, ethano-, and methyl-modified bases in vivo." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42382.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, 2007.Vita.
Includes bibliographical references.
The Escherichia coli AlkB protein is an exceptionally versatile DNA repair enzyme. Its expression is induced upon exposure to alkylating agents as part of the Ada-mediated adaptive response. This member of the ac-ketoglutarate/iron(II)-dependent dioxygenase family was originally discovered to reverse directly methylated lesions formed preferentially in single-stranded regions of DNA, such as 1-methyladenine and 3- methylcytosine. Repair proceeds via an oxidative demethylation pathway, in which the aberrant methyl group is hydroxylated and spontaneously lost as formaldehyde. Since these early studies, the list of lesions repaired by AlkB through this pathway has been extended to include 1-methylguanine, 3-methylthymine, 3-ethylcytosine, and 1-ethyladenine. Furthermore, the protein possesses a second, distinct chemical mechanism through which it can repair another class of lesions, the etheno-adducts formed by the reaction of DNA with metabolites of the carcinogen vinyl chloride or with breakdown products generated by lipid oxidation. In this case, direct repair proceeds through epoxidation of the etheno bond, creating an intermediate that hydrolyzes to a glycol form and finally releases the two-carbon bridge as glyoxal, restoring the unadducted adenine or cytosine. Thus, the AlkB protein bridges the repair of alkylative lesions with those induced by oxidative stress and embodies the multi-faceted protection required to preserve genomic stability and coding information despite the constant threats to which organisms are exposed.
(cont.) Herein, we exploit and characterize a pair of E. coli strains differing only in AlkB status to demonstrate the ability of AlkB to repair the etheno-lesions, the structural analog 1,N6-ethanoadenine (EA), and 3-methyluracil in vivo. Additionally, we establish the ability of the EA "repair product" to form interstrand cross-links in certain sequence contexts of duplex DNA. We also show that although the adaptive response proteins repair lesions generated by oxidative stress, oxidative agents do not induce expression of the response. Finally, we establish that certain hypothesized substrates for AlkB are not in fact repaired by the enzyme, nor are they repaired by another adaptive response protein, AidB. This work extends the current knowledge regarding the amazing ability of AlkB to protect cellular nucleic acids from damage arising from a diverse array of both endogenous and exogenous sources.
by Lauren Elizabeth Frick.
Ph.D.
Books on the topic "Division of Biological Effects"
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Kiefer, Jürgen. Biological Radiation Effects. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-83769-2.
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Laboratory, U. S. Army Research. Terminal Effects Division. [Adelphi, Md.?: ARL, 1998.
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National Research Council of Canada. Division of Biological Sciences. S.l: s.n, 1985.
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Horiguchi, Toshihiro, ed. Biological Effects by Organotins. Tokyo: Springer Japan, 2017. http://dx.doi.org/10.1007/978-4-431-56451-5.
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Stavroulakis, Peter, and Marko Markov. Biological effects of electromagnetic fields: Mechanisms, modeling, biological effects, therapeutic effects, international standards, exposure criteria. Berlin: Springer, 2003.
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1948-, Williams R. Sanders, and Wallace Andrew G. 1935-, eds. Biological effects of physical activity. Champaign, Ill: Human Kinetics Books, 1989.
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Stavroulakis, Peter, ed. Biological Effects of Electromagnetic Fields. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-662-06079-7.
Full textBook chapters on the topic "Division of Biological Effects"
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Lytle, Thomas. "Commercial Division." In Drug and Biological Development, 222–39. Boston, MA: Springer US, 2007. http://dx.doi.org/10.1007/978-0-387-69094-0_10.
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Shen, Zhenyao, Junfeng Niu, Ying Wang, Hongyuan Wang, and Xin Zhao. "Biological Effects." In Advanced Topics in Science and Technology in China, 67–96. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-34964-5_4.
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Aon, M. A., and S. Cortassa. "Dynamics of cell growth and division." In Dynamic Biological Organization, 322–60. Dordrecht: Springer Netherlands, 1997. http://dx.doi.org/10.1007/978-94-011-5828-2_9.
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Wataha, John. "Palladium, Biological Effects." In Encyclopedia of Metalloproteins, 1628–35. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-1533-6_573.
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D’Haese, Patrick C. "Aluminum, Biological Effects." In Encyclopedia of Metalloproteins, 47–53. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-1533-6_110.
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Wang, Jiangxue, Ying Hou, and Jiawei Ma. "Titanium, Biological Effects." In Encyclopedia of Metalloproteins, 2250–51. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-1533-6_200002.
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He, Xiao. "Scandium, Biological Effects." In Encyclopedia of Metalloproteins, 1882–84. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-1533-6_200024.
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He, Xiao. "Yttrium, Biological Effects." In Encyclopedia of Metalloproteins, 2338–40. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-1533-6_200039.
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Lotufo, Guilherme R., G. Allen Burton, Gunther Rosen, and John W. Fleeger. "Assessing Biological Effects." In SERDP/ESTCP Environmental Remediation Technology, 131–75. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-6726-7_6.
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Kiefer, Jürgen. "Late Somatic Effects." In Biological Radiation Effects, 319–35. Berlin, Heidelberg: Springer Berlin Heidelberg, 1990. http://dx.doi.org/10.1007/978-3-642-83769-2_20.
Full textConference papers on the topic "Division of Biological Effects"
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Ateshian, Gerard A., Kevin D. Costa, Evren U. Azeloglu, Barclay Morrison, and Clark T. Hung. "Continuum Modeling of Biological Tissue Growth by Cell Division." In ASME 2009 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2009. http://dx.doi.org/10.1115/sbc2009-205495.
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A framework is formulated for continuum modeling of biological tissue growth that explicitly addresses cell division, using a homogenized representation of cells and the extracellular matrix (ECM). The essential elements of this model rely on the description of the cell as containing a solution of water and osmolytes, and having osmotically inactive solid constituents that may be generically described as a porous solid matrix. The division of a cell into two nearly identical daughter cells normally starts with the duplication of cell contents during the synthesis phase, followed by cell division during the mitosis phase. Thus, ultimately, cell division is equivalent to doubling of the cell solid matrix and osmolyte content, and a resulting increase in water uptake via osmotic effects. In a homogenized representation of the tissue, the geometry of individual cells is not modeled explicitly, but their solid matrix and intracellular osmolyte content can be suitably incorporated into the analysis of the tissue response, thereby accounting for their osmotic effects. Thus, cell division can be described by the growth of these cell constituents, including the accumulation of osmotically active content, and the resultant uptake of water.
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Zhang, Muheng, and Yongsheng Lian. "Numerical Investigation of the Coulter Principle in a Microfluidic Device." In ASME 2013 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fedsm2013-16011.
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Coulter counters are analytical microfluidic instrument used to measure the size and concentration of biological cells or colloid particles suspended in electrolyte. The underlying working mechanism of Coulter counters is the Coulter principle which relies on the fact that when low-conductive cells pass through an electric field these cells cause disturbances in the measurement (current or voltage). Useful information about these cells can be obtained by analyzing these disturbances if an accurate correlation between the measured disturbances and cell characteristics. In this paper we use computational fluid dynamics method to investigate this correlation. The flow field is described by solving the Navier-Stokes equations, the electric field is represented by a Laplace’s equation in which the conductivity is calculated from the Navier-Stokes equations, and the cell motion is calculated by solving the equations of motion. The accuracy of the code is validated by comparing with analytical solutions. The study is based on a coplanar Coulter counter with three inlets that consist of two sheath flow inlet and one conductive flow inlet. The effects of diffusivity, cell size, sheath flow rate, and cell geometry are discussed in details. The impacts of electrode size, gap between electrodes and electrode location on the measured distribution are also studied.
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Beal, David N., Stephen Huyer, Daniel L. Macumber, and Anuradha M. Annaswamy. "Blade Tonal Noise Reduction Using Stator Trailing-Edge Articulation." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77446.
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The biologically-inspired method of trailing-edge articulation is investigated as a means of reducing tonal noise due to the stator wake / rotor blade interaction in underwater vehicles. This work is experimental in nature and conducted in the closed channel water tunnel at Naval Undersea Warfare Center in Newport, Rhode Island. Tail articulation is carried out with a life scale stator model with hinged flapping tail designed to (i) operate in freestream velocities corresponding to Reynolds number in the range 75,000 < Re < 300,000 and (ii) operate at frequencies up to 30 Hz in order to investigate the range of Strouhal number 0.0 < St < 0.35. Velocity measurements in the active stator wake are carried out by Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) in order to investigate the effects of tail articulation on the stator wake. Time averaged measurements of the stator wake by LDV show that Strouhal number of the tail articulation has a dominant effect on the time mean stator drag. Instantaneous phase-averaged measurements of the stator wake by PIV show three regimes of the stator wake as Strouhal number is increased; quasi-steady wake spreading, vortex roll up, and strong vortex wake. Ongoing experiments with an instrumented propeller will demonstrate the efficacy of stator trailing-edge articulation on reducing unsteady blade forces.
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Krishnamoorthi, M., S. Sreedhara, and Pavan Prakash Duvvuri. "Modelling of Soot Formation and Experimental Study for Different Octane Number Fuels in Dual Fuel Combustion Engine With Diesel." In ASME 2020 Internal Combustion Engine Division Fall Technical Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icef2020-2914.
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Abstract This work investigates the effects of low reactivity fuel (LRF) on reactivity controlled compression ignition (RCCI) engine with fossil diesel. RCCI mode of combustion is a low temperature combustion (LTC) strategy which reduces both oxides of nitrogen (NOx) and soot emissions simultaneously. Syngas and methanol can be obtained from renewable biological resources and conventional coal. LRF (methanol, syngas and gasoline) has been supplied to the engine along with intake air and diesel is injected to initiate the combustion process. Test engine has been operated for different dual fuel modes at constant engine speed (1500 rpm) and load (80%). Closed cycle combustion simulations have been performed to complement the experimental results and in-cylinder dynamics. Particle size mimic (PSM) model has been used to investigate the soot particle number and mass-size distributions and mean particle size. Results confirmed that maximum gross indicated thermal efficiency (38%) has been observed in gasoline/diesel dual fuel mode. Compared to gasoline/diesel dual fuel mode, about 74% and 86%, lower soot and NOx emissions have been observed for methanol/diesel dual fuel mode, while about 46% and 52% lower soot and NOx emissions have been found in syngas/diesel mode. About 53% higher carbon monoxide emission has been observed for syngas/diesel case as compared to gasoline/diesel case. Predictions from soot modelling reveal that condensation mode, surface growth mode and nucleation mode particles are dominant in methanol, syngas and gasoline/diesel dual fuel modes respectively. Bigger primary soot particles (diameter > 35 nm, nanometre) have been observed for methanol/diesel mode and the gasoline/diesel mode shows a smaller size of primary particles.
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Chen, Larry, and Urmila Ghia. "Composite Solution Procedure for 3-D Flow Simulations on a Multi-Box Grid." In ASME 2006 2nd Joint U.S.-European Fluids Engineering Summer Meeting Collocated With the 14th International Conference on Nuclear Engineering. ASMEDC, 2006. http://dx.doi.org/10.1115/fedsm2006-98441.
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Fluid flows in biological systems are typically complex, due to factors such as non-Newtonian behavior of biochemical fluids and complex geometry, as well as the interaction of muscles and fluid. With the advent of modern computational technology, these problems are gradually resolved. The present research illustrates two such examples. Grid generation is essential for conducting numerical simulation of fluid flow. In the present research, a new grid generation technique is developed and implemented into a flow solver. This technique enables one to create a grid for complex geometry using only a single computational zone. The flow field can therefore be analyzed without iteration between zones. The numerical scheme developed for solving the grid generation equations is an extension of the traditional three-dimensional Douglass-Gunn Alternating-Direction Implicit (ADI) scheme. A unique feature of the demonstrated grid generation scheme is the concept of multi-box computational domains. In this scheme, the physical domain is mapped onto a multi-box geometry in the computational space, rather than a single box as the traditional methods do. Therefore, the numerical scheme is adjusted accordingly. Flow simulations were performed using the software INS3D, which employs the method of artificial compressibility. This method transforms the Navier-Stokes equations into a system of hyperbolic-parabolic equations, and then marches along the pseudo-time axis until the velocity field becomes divergence-free. Two biological flow problems were analyzed using the aforementioned method. The flow field in an arterial graft as well as in the Left atrium (LA) of the human heart was studied. The effect of Reynolds number and flow-division ratio is examined in the graft problem. The Reynolds number effect is demonstrated via the presence of a helical flow structure and the overall pressure drop. The flow-division ratio alters the flow field in a way that moves the stagnation points. The simulated flow field closely resembles that observed clinically. The steady-state simulation of the flow field in the left atrium of the human heart provided information about the long-term performance of the heart chamber. The simulation demonstrates the existence of low wall shear region, which is therefore susceptible to blood clot formation. This observation also agrees with the clinical findings. In summary, the present research demonstrates application of CFD techniques in the analysis of flow in a biological system. A new grid generation technique is realized, and proved to be useful in simulating these flows. The flow simulation results provide insights into the system, and may be useful for clinical reference.
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Wong, Voon-Loong, Katerina Loizou, Phei-Li Lau, Richard S. Graham, and Buddhika N. Hewakandamby. "Numerical Simulation of the Effect of Rheological Parameters on Shear-Thinning Droplet Formation." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21363.
Full textAbstract:
Immiscible non-Newtonian-Newtonian fluid systems in microfluidics constitute an essential study as non-Newtonian fluids consistently met in medical and biological systems. Although a large number of experimental investigations have been reported in this area, attempts to develop predictive models appear to be limited. This paper is an attempt to incorporate a non-Newtonian stress model together with front-tracking scheme used in computational fluid dynamics. A conservative two-phase level set method (LSM) was applied for capturing the droplet breakup dynamics and relevant hydrodynamics of shear-thinning carboxymethylcellulose (CMC) droplets. Our droplets comprise of 0.02wt% to 1.2wt% CMC solutions in a Newtonian continuous fluids system (olive oil) employed in a T-shaped microfluidic cell. A Carreau-Yasuda viscosity model for shear-thinning CMC droplets has been implemented. This shear-dependent constitutive model fitted well to our steady state non-linear shear measurements for polymeric CMC solutions, with asymptotic viscosities at zero and infinite shear rates, and with different degrees of shear thinning (η0/η∞) in steady state. The particular focus of this study was to systematically undergo parametric studies on the influence of rheological parameters of the specified model such as zero (η0) and infinite shear viscosity (η∞), and relaxation time (λ) on the droplet formation processes. The level set simulation predicted that the droplet diameter increases with increasing η0/η∞. The effect of η0/η∞ has been found to have more prominent impact on droplet diameter for higher CMC concentrations. The variation in droplet diameter becomes less significant at the higher degrees of shear-thinning for all concentrations of CMC dispersed solutions. In the limit of zero shear-thinning effect, the droplet diameter increases when the dispersed phase viscosity decreases. Additionally, the effect of λ on the droplet diameter is also discussed. The reciprocal of the characteristic relaxation time (1/λ) corresponds to a critical shear rate that indicates the onset shear rate for shear-thinning. As λ increases, the numerical studies clearly reveal that the droplet diameter is increasing until it reaches a plateau for larger values of λ. The influence of λ leads to a more significant impact on droplet diameter for higher CMC concentration. These findings will ultimately help in understanding the sensitivity of rheological parameters to the microdroplet formation.
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Rivier, Nicolas, Xavier Arcenegui-Siemens, and Gudrun Schliecker. "CELL DIVISION AND EVOLUTION OF BIOLOGICAL TISSUES." In Proceedings of the Workshop. WORLD SCIENTIFIC, 1995. http://dx.doi.org/10.1142/9789814447089_0025.
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Pineda, Saira F., Arjan M. Kamp, D. Legendre, and Armando J. Blanco. "Axisymmetric Low-Reynolds Motion of Drops Through Circular Microchannels." In ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/icnmm2012-73198.
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Flow constituted by drops appears in a wide range of natural, biological and engineering situations. For example, liquid-liquid two phase flow inside capillaries constitutes a model commonly used to represent fluid flow in a petroleum reservoir. The typical modeling approach considers inertial forces negligible in comparison to viscous forces, allowing the use of Stokes equation to study flow dynamics. Very few numerical simulations have been made considering inertial effects. In this project, the flow of a periodic train of drops in a viscous suspending fluid, due to the influence of a fixed pressure gradient, was studied by numerical simulation considering the full Navier-Stokes equations. A numerical approach based on a Volume of Fluid (VOF) formulation was employed using JADIM software, developed by the Institut de Mécanique des Fluides de Toulouse, France. JADIM solves Navier-Stokes equations using a VOF finite volume method, second order in space and time using structured mesh. This two-fluid approach without reconstruction of the interface allows simulating two-phase flows with complex interface shapes. Densities of the drops equal to those of the suspending fluid and a constant interface tension were assumed. The effect of drop size, viscosity ratio, interfacial forces and system pressure gradient on the flow dynamics was studied. Parameters values were chosen to be representative for some particular viscous oil. The result validation shows an excellent agreement between both numerical results. However, there are relative differences between them due to the increase in flow velocity when drop relative size increase and validity of Stokes approach is questionable. Results show non-symmetric eddies in the continuum phase, in a referential frame fixed to the drop. The shape of eddies is strongly influenced by viscosity radio. Drop mobility decreases with increasing size. Additionally, drop mobility also decreases when the viscosity ratio increases. Extra pressure gradient of the system due to the presence of the drop shows a strong dependency on the size ratio between the drop and the pore. For size ratio lower than 0.5, the extra pressure gradient required to move the continuum phase is small. However, when drop to micro-channel ratio exceeds 0.5, the extra pressure gradient significantly increases when the drop size increases. Also, viscosity ratio affects on the system pressure loss, especially in cases where the viscosity ratio is high. The analysis of the capillary number effect on the dynamics of the two-phase system shows that it does not influence drop mobility for the drop sizes considered.
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Kumari, Suruchi, and S. Raghavan. "Biological effects of microwave." In 2014 International Conference on Information Communication and Embedded Systems (ICICES). IEEE, 2014. http://dx.doi.org/10.1109/icices.2014.7034127.
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Brown, Samuel J. "An Introduction to the ASME HPS Section 6000 “Hazardous Release Protection”: Historical Development of a Means to Reduce Risk From Pressure Systems Failure." In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1814.
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The history of the ASME Boiler and Pressure Vessel Codes and Standards tells us that they were a response in 1915 by the ASME to reduce the numerous explosive failures in the 19th Century that resulted in personnel injury and death, in addition to extensive property loss. The number and scope of ASME Pressure Vessel and Piping Codes and Standards have been issued to cover various applications and operating conditions as the needs have been identified. In the 1970’s, the subcommittee on high pressure technology of the OAC (Operations Applications Components) committee of the ASME Pressure Vessel and Piping Division petitioned the ASME Codes and Standards Council to form a standards committee to prepare a High Pressure Systems Standard that addresses the establishment of a performance criteria and protection criteria for the pressure system. A risk based criterion was provided as a basis for determining if the system design application (siting) exceeds or needs improved reliability for the safety of personnel. The Section 6000 (as well as Sections 1000 to 5000) was begun with a draft outline in 1981 and approved in 2002. Section 6000 “Hazardous Release Protection” of the HPS standard provides a risk based criterion to assess the pressure system internal and external kinetic energy and degenerative hazards and permits a number of ways to lower risk to personnel and structures (e.g., redesign of the pressure system, protection (reduction of consequences), improved inspection (reduction of event probability), etc.). The types of hazards considered are: pressure waves, missiles, foundation motion, radiant heat/fireballs, fire, biological effects, chemical effects, and ionizing radiation. This paper briefly examines: the history of the development of Section 6000, the motivating safety issues, the scope and intent of the various paragraphs of the ASME Section 6000 of the High Pressure System (HPS) standard, its relationship to Sections 1000 to 5000 of the HPS, and some incidences of system failures which identify a need for guidance regarding tolerable risk, other guidelines, standard and code development, and some references that document its development.
Reports on the topic "Division of Biological Effects"
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Dayton, Thomas, Charles Beason, M. K. Hitt, Walter Rogers, and Michael Cook. Biological Effects of Directed Energy. Fort Belvoir, VA: Defense Technical Information Center, November 2002. http://dx.doi.org/10.21236/ada408809.
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Selby, P. (Biological effects of atomic radiation). Office of Scientific and Technical Information (OSTI), June 1990. http://dx.doi.org/10.2172/6867425.
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Barr, S. H., ed. Division of Biological and Medical Research research summary 1984-1985. Office of Scientific and Technical Information (OSTI), August 1985. http://dx.doi.org/10.2172/6039516.
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Schoenbach, Karl H., Stephen J. Beebe, E. S. Buescher, and Shenggang Liu. Pulsed Electric Field Effects on Biological Cells. Fort Belvoir, VA: Defense Technical Information Center, November 2001. http://dx.doi.org/10.21236/ada399182.
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Ritchie, Glenn D., Marni Y. Bekkedal, Andrew J. Bobb, and Kenneth R. Still. Biological and Health Effects of JP-8 Exposure. Fort Belvoir, VA: Defense Technical Information Center, September 2001. http://dx.doi.org/10.21236/ada399728.
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Holman, Peter, and Albert W. Price. Chemical Biological Material Effects Database New User Guide. Fort Belvoir, VA: Defense Technical Information Center, February 2011. http://dx.doi.org/10.21236/ada539856.
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Reeves, Glen I., and David Auton. Biological Effects of Nuclear Explosions (BENE) Domain Guide. Fort Belvoir, VA: Defense Technical Information Center, September 2012. http://dx.doi.org/10.21236/ada570379.
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Grabow, Chad L. Implications and Effects of Advanced Biological and Biological/Chemical Weapons at the Operational Planning Level. Fort Belvoir, VA: Defense Technical Information Center, June 1991. http://dx.doi.org/10.21236/ada240460.
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McCarthy, Geraldine. Biological Effects of Calcium Hydroxyapatite Crystals in Breast Cancer. Fort Belvoir, VA: Defense Technical Information Center, August 2001. http://dx.doi.org/10.21236/ada413254.
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ARMY DUGWAY PROVING GROUND UT. Chemical, Biological, and Radiological Contamination Survivability: Material Effects Testing. Fort Belvoir, VA: Defense Technical Information Center, June 2012. http://dx.doi.org/10.21236/ada565279.
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