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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1187-1205 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dynamic bulk modulus of elasticity has been measured for 14 different rubbery elastomers: three natural rubbers, five neoprenes, three polyurethanes, and one each of butyl, nitrile, and butadiene types. The measurements ranged in temperature from -10 to +40°C, at frequencies from 5 to 3000 Hz, but mostly in the range 100-1000 Hz, at 2.5 MPa pressure. Values of the real (storage) part of the modulus fell within 35% of the mean value of 2.9 GPa for all elastomers, whereas loss moduli were a few percent of the storage moduli. Master curves were obtained for two neoprenes, a polyurethane, and a butyl rubber. These were fitted by hyperbolic functions with four adjustable parameters. Effects of room-temperature aging in artificial sea water were also studied. Aging versus time profiles fell into two distinct forms. Natural rubbers were least stable, neoprenes were intermediate, and urethanes proved most stable in bulk modulus.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 20 (1992), S. 95-101 
    ISSN: 1059-910X
    Keywords: Phosphatidylcholine ; Docosane ; Kinetics ; Phase transitions ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: We describe a temperature-jump device that permits time-resolved studies of thin cryo-transmission electron microscopy specimens. The specimen is rapidly heated to induce a change in microstructure just prior to cryo-fixation. The apparatus consists of a xenon arc lamp equipped with a shutter controlled by timing circuitry, used in conjunction with an environmental specimen preparation chamber. The specimen is heated by exposure to focused light from the lamp, and then plunged into cryogen. Using a thermocouple constructed from an electron microscope grid, we show that temperature jumps of 30-60 K are achieved with exposure times of 150-450 milliseconds. Micrographs of dimyristoyl phosphatidylcholine (DMPC) vesicles and n-docosane films, subjected to these exposures, shew that the specimens are still at least 20-30 K above their initial temperature when they contact the cryogen. This method could be applied to a variety of biological and chemical systems which undergo structural changes activated by a rise in temperature.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 33 (1995), S. 1167-1172 
    ISSN: 0887-6266
    Keywords: gel electrophoresis ; DNA electromobility ; polymer configurations ; polymer mobility ; polymer conduction ; dispersive transport ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The statistical conformations of a length of polymer chain, such as DNA, trapped in a void within a gel under the influence of an external electric field, have been studied by the method of Green's functions. Based upon a rectangular box approximation for the void shape, the method gives an explicit analytical expression for the end-to-end distance (Rx) as a function of applied field strength, number of chain segments coiled within the void, and size of a chain segment. Results of calculations show that the field compresses the entrained coil into more compact configurations, as would be expected. Such compression is believed to affect the electrophoretic mobility of a long chain molecule like DNA in a dilute gel. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polarized Raman spectra of SmSI-type rhombohedral LuOCl were recorded at various polarization orientations. The polarized spectra were analyzed to determine the symmetry assignments of the Raman-active transitions. The Raman spectra of polycrystalline and single-crystal LuOCl are characterized by five features. Analysis of the intensity enhancements of the three lattice vibrations at 139, 272 and 496 cm-1 indicate an Eg symmetry, whereas those at 86, 139 and 473 cm-1 exhibit intensity enhancements which indicate an A1g symmetry.
    Additional Material: 1 Ill.
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  • 5
    Publication Date: 2015-11-22
    Description: Cymbomonas tetramitiformis —a marine prasinophyte—is one of only a few green algae that still retain an ancestral particulate-feeding mechanism while harvesting energy through photosynthesis. The genome of the alga is estimated to be 850 Mb–1.2 Gb in size—the bulk of which is filled with repetitive sequences—and is annotated with 37,366 protein-coding gene models. A number of unusual metabolic pathways (for the Chloroplastida) are predicted for C. tetramitiformis , including pathways for Lipid-A and peptidoglycan metabolism. Comparative analyses of the predicted peptides of C. tetramitiformis to sets of other eukaryotes revealed that nonphagocytes are depleted in a number of genes, a proportion of which have known function in feeding. In addition, our analysis suggests that obligatory phagotrophy is associated with the loss of genes that function in biosynthesis of small molecules (e.g., amino acids). Further, C. tetramitiformis and at least one other phago-mixotrophic alga are thus unique, compared with obligatory heterotrophs and nonphagocytes, in that both feeding and small molecule synthesis-related genes are retained in their genomes. These results suggest that early, ancestral host eukaryotes that gave rise to phototrophs had the capacity to assimilate building block molecules from inorganic substances (i.e., prototrophy). The loss of biosynthesis genes, thus, may at least partially explain the apparent lack of instances of permanent incorporation of photosynthetic endosymbionts in later-divergent, auxotrophic eukaryotic lineages, such as metazoans and ciliates.
    Electronic ISSN: 1759-6653
    Topics: Biology
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  • 6
    Publication Date: 2013-09-08
    Description: Bioenergetic dysfunction occurs in Alzheimer's disease (AD) and mild cognitive impairment (MCI), a clinical syndrome that frequently precedes symptomatic AD. In this study, we modeled AD and MCI bioenergetic dysfunction by transferring mitochondria from MCI, AD and control subject platelets to mtDNA-depleted SH-SY5Y cells. Bioenergetic fluxes and bioenergetics-related infrastructures were characterized in the resulting cytoplasmic hybrid (cybrid) cell lines. Relative to control cybrids, AD and MCI cybrids showed changes in oxygen consumption, respiratory coupling and glucose utilization. AD and MCI cybrids had higher ADP/ATP and lower NAD + /NADH ratios. AD and MCI cybrids exhibited differences in proteins that monitor, respond to or regulate cell bioenergetic fluxes including HIF1α, PGC1α, SIRT1, AMPK, p38 MAPK and mTOR. Several endpoints suggested mitochondrial mass increased in the AD cybrid group and probably to a lesser extent in the MCI cybrid group, and that the mitochondrial fission–fusion balance shifted towards increased fission in the AD and MCI cybrids. As many of the changes we observed in AD and MCI cybrid models are also seen in AD subject brains, we conclude reduced bioenergetic function is present during very early AD, is not brain-limited and induces protean retrograde responses that likely have both adaptive and mal-adaptive consequences.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 7
    Publication Date: 2016-01-07
    Description: Ciliated protists exhibit nuclear dimorphism through the presence of somatic macronuclei (MAC) and germline micronuclei (MIC). In some ciliates, DNA from precursor segments in the MIC genome rearranges to form transcriptionally active genes in the mature MAC genome, making these ciliates model organisms to study the process of somatic genome rearrangement. Similar broad scale, somatic rearrangement events occur in many eukaryotic cells and tumors. The 〈mds_ies_db〉 ( http://oxytricha.princeton.edu/mds_ies_db ) is a database of genome recombination and rearrangement annotations, and it provides tools for visualization and comparative analysis of precursor and product genomes. The database currently contains annotations for two completely sequenced ciliate genomes: Oxytricha trifallax and Tetrahymena thermophila .
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 8
    Publication Date: 2015-06-05
    Description: In this note, we prove a generalization of the ‘strange formula’ of Freudenthal and de-Vries for compact homogeneous spaces with positive Euler characteristic. As a corollary, we obtain a new proof of the original formula. We also apply our results to computing a topological invariant used to study hyper-Kähler structures.
    Print ISSN: 0033-5606
    Electronic ISSN: 1464-3847
    Topics: Mathematics
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  • 9
    Publication Date: 2015-12-04
    Description: One approach to extracting the global 21-cm signal from total-power measurements at low radio frequencies is to parametrize the different contributions to the data and then fit for these parameters. We examine parametrizations of the 21-cm signal itself, and propose one based on modelling the Ly α background, intergalactic medium temperature and hydrogen ionized fraction using tanh functions. This captures the shape of the signal from a physical modelling code better than an earlier parametrization based on interpolating between maxima and minima of the signal, and imposes a greater level of physical plausibility. This allows less biased constraints on the turning points of the signal, even though these are not explicitly fit for. Biases can also be alleviated by discarding information which is less robustly described by the parametrization, for example by ignoring detailed shape information coming from the covariances between turning points or from the high-frequency parts of the signal, or by marginalizing over the high-frequency parts of the signal by fitting a more complex foreground model. The fits are sufficiently accurate to be usable for experiments gathering 1000 h of data, though in this case it may be important to choose observing windows which do not include the brightest areas of the foregrounds. Our assumption of pointed, single-antenna observations and very broad-band fitting makes these results particularly applicable to experiments such as the Dark Ages Radio Explorer , which would study the global 21-cm signal from the clean environment of a low lunar orbit, taking data from the far side.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 10
    Publication Date: 2014-11-21
    Description: Brain bioenergetic function declines in some neurodegenerative diseases, this may influence other pathologies and administering bioenergetic intermediates could have therapeutic value. To test how one intermediate, oxaloacetate (OAA) affects brain bioenergetics, insulin signaling, inflammation and neurogenesis, we administered intraperitoneal OAA, 1–2 g/kg once per day for 1–2 weeks, to C57Bl/6 mice. OAA altered levels, distributions or post-translational modifications of mRNA and proteins (proliferator-activated receptor-gamma coactivator 1α, PGC1 related co-activator, nuclear respiratory factor 1, transcription factor A of the mitochondria, cytochrome oxidase subunit 4 isoform 1, cAMP-response element binding, p38 MAPK and adenosine monophosphate-activated protein kinase) in ways that should promote mitochondrial biogenesis. OAA increased Akt, mammalian target of rapamycin and P70S6K phosphorylation. OAA lowered nuclear factor B nucleus-to-cytoplasm ratios and CCL11 mRNA. Hippocampal vascular endothelial growth factor mRNA, doublecortin mRNA, doublecortin protein, doublecortin-positive neuron counts and neurite length increased in OAA-treated mice. 1 H-MRS showed OAA increased brain lactate, GABA and glutathione thereby demonstrating metabolic changes are detectable in vivo . In mice, OAA promotes brain mitochondrial biogenesis, activates the insulin signaling pathway, reduces neuroinflammation and activates hippocampal neurogenesis.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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