30,165 research outputs found

    Synthesis of highly elastic biocompatible polyurethanes based on bio-based isosorbide and poly(tetramethylene glycol) and their properties.

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    Bio-based high elastic polyurethanes were prepared from hexamethylene diisocyanate and various ratios of isosorbide to poly(tetramethylene glycol) as a diol by a simple one-shot bulk polymerization without a catalyst. Successful synthesis of the polyurethanes was confirmed by Fourier transform-infrared spectroscopy and (1)H nuclear magnetic resonance. Thermal properties were determined by differential scanning calorimetry and thermogravimetric analysis. The glass transition temperature was -47.8℃. The test results showed that the poly(tetramethylene glycol)/isosorbide-based elastomer exhibited not only excellent stress-strain properties but also superior resilience to the existing polyether-based polyurethane elastomers. The static and dynamic properties of the polyether/isosorbide-based thermoplastic elastomer were more suitable for dynamic applications. Moreover, such rigid diols impart biocompatible and bioactive properties to thermoplastic polyurethane elastomers. Degradation tests performed at 37℃ in phosphate buffer solution showed a mass loss of 4-9% after 8 weeks, except for the polyurethane with the lowest isosorbide content, which showed an initial rapid weight loss. These polyurethanes offer significant promise due to soft, flexible and biocompatible properties for soft tissue augmentation and regeneration

    Auditory object cognition in dementia

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    The cognition of nonverbal sounds in dementia has been relatively little explored. Here we undertook a systematic study of nonverbal sound processing in patient groups with canonical dementia syndromes comprising clinically diagnosed typical amnestic Alzheimer's disease (AD; n = 21), progressive nonfluent aphasia (PNFA; n = 5), logopenic progressive aphasia (LPA; n = 7) and aphasia in association with a progranulin gene mutation (GAA; n = 1), and in healthy age-matched controls (n = 20). Based on a cognitive framework treating complex sounds as 'auditory objects', we designed a novel neuropsychological battery to probe auditory object cognition at early perceptual (sub-object), object representational (apperceptive) and semantic levels. All patients had assessments of peripheral hearing and general neuropsychological functions in addition to the experimental auditory battery. While a number of aspects of auditory object analysis were impaired across patient groups and were influenced by general executive (working memory) capacity, certain auditory deficits had some specificity for particular dementia syndromes. Patients with AD had a disproportionate deficit of auditory apperception but preserved timbre processing. Patients with PNFA had salient deficits of timbre and auditory semantic processing, but intact auditory size and apperceptive processing. Patients with LPA had a generalised auditory deficit that was influenced by working memory function. In contrast, the patient with GAA showed substantial preservation of auditory function, but a mild deficit of pitch direction processing and a more severe deficit of auditory apperception. The findings provide evidence for separable stages of auditory object analysis and separable profiles of impaired auditory object cognition in different dementia syndromes. (C) 2011 Elsevier Ltd. All rights reserved

    Investigating Dechlorane Plus (DP) distribution and isomer specific adsorption behavior in size fractionated marine sediments

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    In this study, Dechlorane Plus (DP) concentrations were analyzed in marine sediments (depth: similar to 10 cm) from two Korean industrial bays. Two sediments were fractionated into 5 sizes by using gravitational split-flow thin fractionation technique and DP distribution was investigated in different particle size fractions. Elevated DP levels in surface sediments were observed at the site closest to land and industrial area. The highest concentrations of DP were detected in the finest grain-size (< 10 mu m, 451.2 and 149.9 pg/g dry weight for the two bays). The fraction of anti-DP to the total DP (f(anti)) in the two fractionated samples increased with reduced grain-size and significantly correlated with organic carbon content (OC), which can be caused by preferential adsorption of anti-DP or higher biodegradation rates of syn-DP in the fine particles. To provide insight into such mechanism, simulated experiments were conducted using activated charcarbon (ACC) to adsorb DP dissolved in methanol and molecular descriptors of both isomers were estimated using Gaussian 03. The adsorption results revealed that syn-DP was preferentially adsorbed by ACC, suggesting syn-DP is more hydrophobic than anti-DP. The preferential adsorption of syn-DP by ACC also supported the hypothesis that the enrichment of anti-DP was more likely due to preferential biodegradation of syn-DP in the sediment. Molecular characterization of anti-DP and syn-DP showed that syn-DP had a higher dipole moment, slightly larger Van der Waals volume, but smaller maximal diameter, which might explain its higher uptake rate in biota. (C) 2014 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND licensX111411Ysciescopu

    A mechanism for robust circadian timekeeping via stoichiometric balance

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102189/1/msb201262.reviewer_comments.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102189/2/msb201262.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/102189/3/msb201262-sup-0001.pd

    Crystallization and preliminary crystallographic studies of an antimicrobial protein from Pharbitis nil

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    An antimicrobial protein from seeds of Pharbitis nil (Pn-AMP) which shows an antifungal activity towards several agriculturally important plant pathogens has been crystallized in the presence of equimolar N-acetylglucosamine with sodium citrate as precipitant. The crystal belongs to the hexagonal space group P6(1)22 (or P6(5)22), with unit-cell parameters a = b = 29.33 (5), c = 133.44 (12) Angstrom. Native data were collected using a crystal at 100 K to a resolution of 1.78 Angstrom.open2
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