bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transparent copolyester/organoclay nanocomposites prepared by in situ intercalation polymerization: Synthesis, characterization, and properties
Authors: Tsai Yuhsin , Fan Cheng‐Hsing , Hung Chi‐Yuan , Tsai Fuu‐Jen 
Published: October 2010

AbstractIn this study, amorphous poly(ethylene terephthalate‐co‐1,3/1,4‐cyclohexylenedimethylene terephthalate) (PETG)/organoclay nanocomposites was synthesized by the in situ intercalation polymerization of terephthalic acid, ethylene glycol, 1,3/1,4‐cyclohexanedimethanol, and organoclay. The organoclay was obtained by modifying sodium montmorillonite (clay) with hexadecyl triphenylphosphonium bromide. The thermal, mechanical, optical, and gas barrier properties of these PETG nanocomposites with various organoclay contents (0–3 wt%) were discussed. The differential scanning calorimetry and X‐ray analyses revealed that all of the nanocomposites were amorphous. X‐ray diffraction and transmission electron micrographs showed that the organoclay was well dispersed in the polymer matrix, although some parts of the agglomerated layers remained on the scale of several hundreds of nanometers. The thermal stability and the mechanical property of the nanocomposites increased with organoclay content. The optical transmittances of nanocomposites that contained 0.5, 1, and 3 wt% of organoclay were 86.8%, 84.4%, and 77.4%, respectively. The oxygen transmission rate of the nanocomposite that contained 3 wt% of organoclay was about 50% of the PETG base polymer. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers
Predicting the risk of pre‐eclampsia between 11 and 13 weeks' gestation by combining maternal characteristics and serum analytes, PAPP‐A and free β‐hCG
Authors: Goetzinger Katherine R. , Singla Ashima , Gerkowicz Sabrina , Dicke Jeffrey M. , Gray Diana L. , Odibo Anthony O. 
Published: October 2010

AbstractObjectiveTo determine if a simplified model for predicting pre‐eclampsia (PEC) can be developed by combining first‐trimester serum analytes, pregnancy‐associated plasma protein A (PAPP‐A) and free beta human chorionic gonadotrophin (β‐hCG), and maternal characteristics.MethodsA retrospective cohort study of patients seen for first‐trimester aneuploidy screening from 2003 to 2009. The 5th, 10th, 90th, and 95th percentiles for the analyte multiples of the medians (MoMs) for our population were determined and evaluated for association with PEC. Univariate and backward stepwise logistic regression analyses were performed and the area under the receiver operating characteristic (ROC) curves [area under curve (AUC)] used to determine the best models for predicting PEC.ResultsAmong 4020 women meeting the inclusion criteria, outcome data was available for 3716 (93%). There were 293 cases of PEC. The final model identified a history of pre‐gestational diabetes [aOR 2.6, 95% confidence interval (CI) 1.7–3.9], chronic hypertension (cHTN) (aOR 2.6, 95% CI 1.7–3.9), maternal body mass index (BMI) > 25 (aOR 2.5, 95% CI 1.9–3.4), African American race (aOR 1.8, 95% CI 1.3–2.6), and PAPP‐A MoM < 10th percentile (aOR 1.6, 95% CI 1.1–2.4) to be significant predictors of PEC (AUC = 0.70, 95% CI 0.65–0.72).ConclusionLow first‐trimester PAPP‐A levels are associated with the development of PEC; however, the model was only modestly efficient in its predictive ability. Copyright © 2010 John Wiley & Sons, Ltd.
Production, cellular structure and thermal conductivity of microcellular (methyl methacrylate)–(butyl acrylate)–(methyl methacrylate) triblock copolymers
Authors: Reglero Ruiz Jose Antonio , Saiz‐Arroyo Cristina , Dumon Michel , Rodríguez‐Perez Miguel A , Gonzalez Leo 
Published: October 2010

AbstractMicrocellular foaming of a (methyl methacrylate)–(butyl acrylate)–(methyl methacrylate) triblock copolymer was carried out by means of supercritical CO2 in a single‐step process. The experiments were performed at 40 °C using a pressure of 300 bar (30 MPa) during 24 h. The depressurization times were modified from 2 to 30 min, leading to cell sizes from 10 to 100 µm, and relative densities from 0.11 to 0.17. It was found that the key parameter to control cell size and density was depressurization time: longer depressurization times generated larger cell sizes and lower densities. The thermal conductivity of these materials was measured using the transient plane source technique, and it was found that this decreased as the density was reduced. Various models for the prediction of thermal conductivity by conduction were tested. It was found that all the models underestimated the experimental results due to a significant contribution of radiation heat flow for these materials. Copyright © 2010 Society of Chemical Industry
Preparation and characterization of polyimide/modified layered double hydroxide nanocomposites
Authors: Ahn Jinhee , Han Mijeong , Ha Chang‐Sik 
Published: October 2010

AbstractPolyimide (PI)/modified layered double hydroxide (m‐LDH) nanocomposites were prepared in this study. For this work, m‐LDHs were prepared from layered double hydroxides (LDHs) through an anionic exchange reaction with pyromellitic dianhydride (PMDA), succinic acid or terephthalic acid. PMDA and 4,4′‐oxydianiline were used to make the poly(amic acid) precursor for PI. X‐ray diffraction and transmission electron microscopy measurements confirmed that the PMDA‐modified LDH (PMH) and terephthalic acid‐modified LDH (TMH) were well dispersed in the PI matrix. For the succinic acid‐modified LDH, some of the LDH was intercalated with the succinic acid molecules but most maintained its original structure. Thus, the PI/PMH and PI/TMH nanocomposites exhibited improved mechanical, thermal and electrical properties compared to pure PI. The PMH has aromatic groups and is expected to have better π–π interactions with the PI chains than the other m‐LDHs. Thus, the PI/PMH nanocomposites exhibited the best properties among the nanocomposites investigated. Copyright © 2010 Society of Chemical Industry
Relationship between the molecular structure of alginates and their gelation in acidic conditions
Authors: Andriamanantoanina Hanta , Rinaudo Marguerite 
Published: October 2010

AbstractThe study reports examined the influence of chemical composition of blocks along alginate chains on the ability to form a gel in acidic conditions. For that purpose, GG (where G is α‐L‐guluronic acid) and MM (where M is β‐D‐mannuronic acid) blocks of high purity were obtained with good yield from algae recovered along Madagascar coasts; the molecular weight distribution and M/G ratio were determined. The alginates extracted from Sargassum species (SG1 and SG4) are particularly rich in G units. From the dependence of viscosity on pH for solutions of each type of block, it is established that cooperative interchain interactions based on hydrogen bond networks occur for GG blocks when the pH is lower than 3.41 with an optimum at pH = 2.68; MM blocks phase‐separate at pH ≤ 1.93. For a purified commercial alginate (M/G = 1.3) a gel is formed at pH < 3.05 and modulus G′ becomes maximum at pH = 2.28. From these data, it is concluded that gelation in acidic conditions is mainly based on GG blocks forming junction zones. It is shown that acid gels obtained from pre‐formed gels in the presence of calcium are stronger than when formed directly from the sodium salt form. In addition, the degree of swelling of these gels in the acid form is lower (50% lower) than in the calcium form; this is attributed to the screening of electrostatic repulsions in the gel when the pH is around the intrinsic pK of carboxylic groups and, eventually, to the establishment of hydrogen bond interactions involving M units. Copyright © 2010 Society of Chemical Industry
Plasma‐modified halloysite nanocomposites: effect of plasma modification on the structure and dynamic mechanical properties of halloysite–polystyrene nanocomposites
Authors: Shamsi Mohtashim H , Luqman Mohammad , Basarir Fevzihan , Kim Joon‐Seop , Yoon Tae‐Ho , Geckeler Kurt E 
Published: October 2010

AbstractPlasma polymerization of styrene was used to modify the hydrophilic surfaces of halloysite nanotubes to investigate the reinforcement effect of new hydrophobic surfaces on the dynamic mechanical properties of halloysite–polystyrene nanocomposites at various degrees of loading. Pristine and plasma‐modified halloysite–polystyrene nanocomposites were synthesized by solution blending and characterized using various techniques. The storage moduli and glass transition temperatures of the composites were analyzed using dynamic mechanical thermal analysis. It was found that the rubbery moduli increased substantially after plasma coating with styrene due to the compatibility of the new hydrophobic halloysite surfaces with the polystyrene polymer matrix. In addition, the rubbery moduli increased with increasing amount of clay. The glass transition temperatures of the composites did not change significantly with the amount of clay. The strengths of the plasma‐modified composites were also compared with those of recently reported halloysite–epoxy resin composites. Copyright © 2010 Society of Chemical Industry
Direct observation of minimum‐sized amyloid fibrils using solution NMR spectroscopy
Authors: Yoshimura Yuichi , Sakurai Kazumasa , Lee Young‐Ho , Ikegami Takahisa , Chatani Eri , Naiki Hironobu , Goto Yuji 
Published: October 2010

AbstractIt is challenging to investigate the structure and dynamics of amyloid fibrils at the residue and atomic resolution because of their high molecular weight and heterogeneous properties. Here, we used solution nuclear magnetic resonance (NMR) spectroscopy to characterize the conformation and flexibility of amyloid fibrils of β2‐microglobulin (β2m), for which direct observation of solution NMR could not be made. Ultrasonication led to fragmentation producing a solution of minimum‐sized fibrils with a molecular weight of around 6 MDa. In 1H‐15N heteronuclear single‐quantum correlation measurements, five signals, derived from N‐terminal residues (i.e., Ile1, Gln2, Arg3, Thr4, and Lys6), were newly detected. Signal strength decreased with the distance from the N‐terminal end. Capping experiments with the unlabeled β2m monomer indicated that the signals originated from molecules located inside the fibrils. Ultrasonication makes the residues with moderate flexibility observable by reducing size of the fibrils. Thus, solution NMR measurements of ultrasonicated fibrils will be promising for studying the structure and dynamics of fibrils.
Increased flexibility decreases antifreeze protein activity
Authors: Patel Shruti N. , Graether Steffen P. 
Published: October 2010

AbstractAntifreeze proteins protect several cold‐blooded organisms from subzero environments by preventing death from freezing. The Type I antifreeze protein (AFP) isoform from Pseudopleuronectes americanus, named HPLC6, is a 37‐residue protein that is a single α‐helix. Mutational analysis of the protein showed that its alanine‐rich face is important for binding to and inhibiting the growth of macromolecular ice. Almost all structural studies of HPLC6 involve the use of chemically synthesized protein as it requires a native N‐terminal aspartate and an amidated C‐terminus for full activity. Here, we examine the role of C‐terminal amide and C‐terminal arginine side chain in the activity, structure, and dynamics of nonamidated Arg37 HPLC6, nonamidated HPLC6 Ala37, amidated HPLC6 Ala37, and fully native HPLC6 using a recombinant bacterial system. The thermal hysteresis (TH) activities of the nonamidated mutants are 35% lower compared with amidated proteins, but analysis of the NMR data and circular dichroism spectra shows that they are all still α‐helical. Relaxation data from the two nonamidated mutants indicate that the C‐terminal residues are considerably more flexible than the rest of the protein because of the loss of the amide group, whereas the amidated Ala37 mutant has a C‐terminus that is as rigid as the wild‐type protein and has high TH activity. We propose that an increase in flexibility of the AFP causes it to lose activity because its dynamic nature prevents it from binding strongly to the ice surface.
Estimation of pharmacokinetic parameters with the R package PK
Authors: Jaki Thomas , Wolfsegger Martin J. 
Published: October 2010

AbstractThe study of the pharmacokinetic (PK) behavior of a compound is crucial to understand the absorbtion, distribution, metabolism and elimination of a drug by the body. PK studies involve measuring the concentration of the drug in the plasma or blood at several time points post drug administration. The classic complete data design samples each subject at all predefined time points. Ethical considerations and restrictions in blood volume, however, lead to incomplete data designs being frequently used instead. In serial sampling designs only one sample is taken from each subject, whereas batch designs take samples more than once from each subject, but not at all time points. In this manuscript the R package PK, which enables the computation of various PK parameters in complete and incomplete data designs, is introduced and some examples are given. Copyright © 2010 John Wiley & Sons, Ltd.
The role of the minimum clinically important difference and its impact on designing a trial
Authors: Chuang‐Stein Christy , Kirby Simon , Hirsch Ian , Atkinson Gary 
Published: October 2010

AbstractThe minimum clinically important difference (MCID) between treatments is recognized as a key concept in the design and interpretation of results from a clinical trial. Yet even assuming such a difference can be derived, it is not necessarily clear how it should be used. In this paper, we consider three possible roles for the MCID. They are: (1) using the MCID to determine the required sample size so that the trial has a pre‐specified statistical power to conclude a significant treatment effect when the treatment effect is equal to the MCID; (2) requiring with high probability, the observed treatment effect in a trial, in addition to being statistically significant, to be at least as large as the MCID; (3) demonstrating via hypothesis testing that the effect of the new treatment is at least as large as the MCID. We will examine the implications of the three different possible roles of the MCID on sample size, expectations of a new treatment, and the chance for a successful trial. We also give our opinion on how the MCID should generally be used in the design and interpretation of results from a clinical trial. Copyright © 2010 John Wiley & Sons, Ltd.
Juvenile coho salmon behavioural characteristics in Klamath river summer thermal refugia
Authors: Sutton R. , Soto T. 
Published: October 2010

ABSTRACTDuring the summer in the main‐stem Klamath River, juvenile salmonids respond positively to cooler tributary temperatures by congregating in large schools at the mouths of these tributaries, referred to as thermal refugia. The purpose of this paper is to summarize results from coho salmon (Oncorhynchus kisutch) thermal refugia studies conducted since 2006 in the Klamath River. Results showed that juvenile coho salmon started using thermal refugia when the Klamath River main‐stem temperature approached approximately 19 °C. The majority of the juvenile coho salmon within the studied thermal refugia were found in the slower velocity habitat associated with cover. Juvenile coho salmon counts in the studied thermal refugia dramatically decreased at temperatures >22–23 °C, suggesting that this approximates their upper thermal tolerance level. Although some juvenile coho salmon were very mobile, others chose, until smoltification, to rear in the mouths and lower reaches of non‐natal tributaries where thermal refugia occurred, apparently because of suitable habitat conditions. Information gained from these investigations will improve our knowledge of the life history of coho salmon in the Klamath River drainage and how they use the main‐stem river. Copyright © 2010 John Wiley & Sons, Ltd.
Nutrients and water level fluctuations: A study of three aquatic plants
Authors: Deegan B. M. , White S. D. , Ganf G. G. 
Published: October 2010

ABSTRACTWater holes characteristic of the middle sections of fragmented, lowland, semi‐arid rivers act as refuge areas for biota during low flow and drought. However, river regulation and catchment development has altered the hydrological and nutrient status of these refuges. A series of artificial ponds were used to imitate these habitats and experiments were designed to determine whether stochastically fluctuating water levels with maximum amplitude of 65 cm would counteract the influence of nutrient enrichment on the growth of three key aquatic plant species. The species (Cyperus gymnocaulos, Triglochin procerum and Typha domingensis) represented different functional groups that inhabit contrasting zones across the elevation gradient. Each species was grown at a different elevation within the experiment reflecting each species' elevation preference and supplied with the equivalent to 0, 10 or 30 g N m−2 year−1. Under a static water regime nutrient enrichment doubled the total biomass of all three species. In contrast under a fluctuating water regime, nutrient addition did not influence total biomass of either T. domingensis or T. procerum and the performance of C. gymnocaulos was reduced by ca. 30%. These data suggest that if environmental flows were managed to provide a natural stochastically fluctuating water regime, this would nullify the influence of nutrient enrichment and limit the distribution and spread of invasive species such as Typha, that exists under the current altered conditions. Copyright © 2010 John Wiley & Sons, Ltd.
Characterizing the Contribution of Stem/Progenitor Cells to Tumorigenesis in thePten−/−TP53−/− Prostate Cancer Model
Authors: Abou-Kheir Wassim G. , Hynes Paul G. , Martin Philip L. , Pierce Rachel , Kelly Kathleen 
Published: October 2010

AbstractLoss of PTEN is one of the most common mutations in prostate cancer, and loss of wild-type TP53 is associated with prostate cancer progression and castrate resistance. Modeling prostate cancer in the mouse has shown that while Pten deletion in prostate epithelial cells leads to adenocarcinoma, combined loss of Pten and TP53 results in rapidly developing disease with greater tumor burden and early death. TP53 contributes significantly to the regulation of stem cell self-renewal, and we hypothesized that loss of Pten/TP53 would result in measurable changes in prostate cancer stem/progenitor cell properties. Clonogenic assays that isolate progenitor function in primary prostate epithelial cells were used to measure self-renewal, differentiation, and tumorigenic potential. Pten/TP53 null as compared with wild-type protospheres showed increased self-renewal activity and modified lineage commitment. Orthotopic transplantation of Pten/TP53 null cells derived from protospheres produced invasive Prostatic Intraepithelial Neoplasia (PIN)/adenocarcinoma, recapitulating the pathology seen in primary tumors. Pten/TP53 null progenitors relative to wild type also demonstrated increased dependence on the AKT/mammalian target of rapamycin complex 1 (mTORC1) and androgen receptor (AR) pathways for clonogenic and tumorigenic growth. These data demonstrate roles for Pten/TP53 in prostate epithelial stem/progenitor cell function, and moreover, as seen in patients with castrate-resistant prostate cancer, suggest for the involvement of an AR-dependent axis in the clonogenic expansion of prostate cancer stem cells.
Serotonergic mechanism underlying tranylcypromine enhancement of nicotine self‐administration
Authors: Villégier Anne‐Sophie , Belluzzi James D. , Leslie Frances M. 
Published: October 2010

AbstractAlthough nicotine is generally considered to be the main psychoactive component of tobacco, growing evidence highlights the importance of nonnicotine compounds in smoking reinforcement. Monoamine oxidase (MAO) inhibition is a major consequence of smoking and MAO inhibitors, such as tranylcypromine, increase nicotine reinforcement. Tranylcypromine has multiple pharmacological effects, increasing monoamine release for a few hours immediately after its administration and blocking MAO activity for several days. To assess the relative role of these two actions, adult male rats were tested in consecutive daily 3‐h sessions for self‐administration of nicotine (3 μg kg−1inj−1, i.v.) either 20 or 1 h following administration of tranylcypromine (3 mg kg−1). Both paradigms were shown to produce highly significant inhibition of MAO activity. However, whereas animals readily acquired self‐administration when pretreated with tranylcypromine 1 h prior to testing, they did not with the longer pretreatment interval. Such animals did immediately acquire nicotine self‐administration when the tranylcypromine pretreatment interval was switched to 1 h prior to testing on Day 4, indicating that an acute effect of the MAO inhibitor was responsible for enhanced nicotine reinforcement. Several lines of evidence implicate serotonin (5‐HT) as the mediator of this enhancement: (1) Tranyclypromine‐enhanced nicotine reinforcement was blocked by the 5‐HT2receptor antagonists, ritanserin and ketanserin; (2) parachloroamphetamine (PCA), a 5‐HT releaser, also enhanced nicotine self‐administration in animals in which MAO activity was inhibited; (3) pretreatment with tranylcypromine increased PCA‐induced 5‐HT overflow in the nucleus accumbens. These findings suggest that MAO inhibition enhances serotonergic transmission, which serves a critical role in the reinforcing effects of nicotine. Synapse, 2011. © 2010 Wiley‐Liss, Inc.
Fear conditioning is associated with synaptogenesis in the lateral amygdala
Authors: Dalzell L. , Connor S. , Penner M. , Saari M.J. , Leboutillier J.C. , Weeks A.C.W. 
Published: October 2010

AbstractFear conditioning in the rat typically involves pairing a conditioned stimulus (tone) with an aversive unconditioned stimulus (foot shock) which elicits a freeze response. Although the circuitry that underlies this form of learning is well defined, potential synaptic changes associated with this form of learning have not been fully investigated. This experiment examined synaptic structural plasticity in the lateral amygdala which is critical for the acquisition of the conditioned fear response. Adult male rats were randomly allocated to either a paired, unpaired or tone only condition. One day after the initial fear conditioning session and 1 h after a probe trial confirmation of a conditioned fear response, the rats were perfused and the relevant tissue was embedded for electron microscopic analysis. Synaptic changes were quantified in the lateral amygdala using a stereological approach. The results showed a significant increase in the number of synapses in the conditioned animals compared to controls. This finding suggests that an increase in synaptic compliment in the amygdala may underlie the acquisition of the conditioned fear response. Synapse, 2011. © 2010 Wiley‐Liss, Inc.