bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improvement in toughness and crystallization of poly(L‐lactic acid) by melt blending with poly(epichlorohydrin‐co‐ethylene oxide)
Authors: Zhang Kunyu , Ran Xianghai , Wang Xuemei , Han Changyu , Han Lijing , Wen Xin , Zhuang Yugang , Dong Lisong 
Published: May 2011

AbstractMelt blending of poly(lactic acid) (PLA) and poly(epichlorohydrin‐co‐ethylene oxide) copolymers (ECO) was performed to improve the toughness and crystallization of PLA. Thermal and scanning electron microscopy analysis indicated that PLA and ECO were not thermodynamically miscible but compatible to some extent. The addition of a small amount of ECO accelerated the crystallization rate and increased the final crystallinity of PLA in the blends. Significant enhancement in toughness and flexibility of PLA were achieved by the incorporation of the ECO elastomer. When 20 wt% ECO added, the impact strength increased from 5 kJ/m2 of neat PLA to 63.9 kJ/m2, and the elongation at break increased from 5% to above 160%. The failure mode changed from brittle fracture of neat PLA to ductile fracture of the blend. Rheological measurement showed that the melt elasticity and viscosity of the blend increased with the concentration of ECO. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.
Effect of nanoclay addition on the foaming behavior of linear polypropylene‐based soft thermoplastic polyolefin foam blown in continuous extrusion
Authors: Zhai Wentao , Park Chul B. 
Published: May 2011

AbstractThe goal of this study is to fabricate a soft foam with high cell density and high foam expansion based on thermoplastic polyolefin (TPO), and to supply a potential candidate for soft thermoset foams. It was found that a linear polypropylene (PP)‐based TPO foam exhibited very poor cell morphology because of its weak melt strength. Nanoclay was introduced into the TPO to improve its foaming behavior. The extrusion foaming experiments demonstrated that the introduction of 0.5 wt% nanoclay significantly increased the cell morphology and expansion ratio of TPO/clay nanocomposite foams due to the enhanced cell nucleation and the possible cell coalescence suppression at low temperatures. At a high nanoclay content of 2.0 wt%, the cell density and foam expansion of foams increased continuously compared with the 0.5 wt% nanoclay addition. Our study suggested that it was possible to produce soft TPO foams with a well‐defined cell structure and high foam expansion using a continuous method, but that a proper PEOc content control was needed to maximize foam expansion. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
Co‐injection molding of immiscible polymers: Skin‐core structure and adhesion studies
Authors: Gomes M. , Martino D. , Pontes A.J. , Viana J.C. 
Published: May 2011

AbstractIn this article, the microstructure and the adhesion developed in co‐injected specimens obtained with polypropylene (PP; core) and polystyrene (PS; skin) were studied as a function of process conditions and additives used. The study shows that the incorporation of low amounts of fillers such as Nanoclays and styrene‐ethylene‐butadiene‐styrene (SEBS) copolymer to the core material, working as compatibilizers, improves the adhesion at lower and higher polymer melt temperatures, respectively. The authors concluded as well that the use of such fillers, also improves the reproducibility of the process. The adhesion was assessed by shear tests using double lap shear specimens. A data acquisition system was attached to the mold to evaluate the pressure inside the cavity. Results of the in‐mold pressure profiles corresponded well when compared with MoldFlow predictions, and demonstrated that the adhesion of both materials is also related to their behavior and shrinkage inside the mold. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.
Discovery of biomarker candidates for coronary artery disease from an APOE‐knock out mouse model using iTRAQ‐based multiplex quantitative proteomics
Authors: Jing Linhong , Parker Carol E. , Seo David , Hines Maria Warren , Dicheva Nedyalka , Yu Yanbao , Schwinn Debra , Ginsburg Geoffrey S. , Chen Xian 
Published: May 2011

AbstractDue to the lack of precise markers indicative of its occurrence and progression, coronary artery disease (CAD), the most common type of heart diseases, is currently associated with high mortality in the United States. To systemically identify novel protein biomarkers associated with CAD progression for early diagnosis and possible therapeutic intervention, we employed an iTRAQ‐based quantitative proteomic approach to analyze the proteome changes in the plasma collected from a pair of wild‐type versus apolipoprotein E knockout (APOE−/−) mice which were fed with a high fat diet. In a multiplex manner, iTRAQ serves as the quantitative ‘in‐spectra’ marker for ‘cross‐sample’ comparisons to determine the differentially expressed/secreted proteins caused by APOE knock‐out. To obtain the most comprehensive proteomic data sets from this CAD‐associated mouse model, we applied both MALDI and ESI‐based mass spectrometric (MS) platforms coupled with two different schemes of multidimensional liquid chromatography (2‐D LC) separation. We then comparatively analyzed a series of the plasma samples collected at 6 and 12 wk of age after the mice were fed with fat diets, where the 6‐ or 12‐wk time point represents the early or intermediate phase of the fat‐induced CAD, respectively. We then categorized those proteins showing abundance changes in accordance with APOE depletion. Several proteins such as the γ and β chains of fibrinogen, apolipoprotein B, apolipoprotein C‐I, and thrombospondin‐4 were among the previously known CAD markers identified by other methods. Our results suggested that these unbiased proteomic methods are both feasible and a practical means of discovering potential biomarkers associated with CAD progression.
Proteomic profiling between CNE‐2 and its strongly metastatic subclone S‐18 and functional characterization of HSP27 in metastasis of nasopharyngeal carcinoma
Authors: Li Guo‐Ping , Wang Hua , Lai Yiu‐Kay , Chen Shao‐Chun , Lin Marie C. M. , Lu Gang , Zhang Jing‐Fang , He Xiao‐Guang , Qian Chao‐Nan , Kung Hsiang‐Fu 
Published: May 2011

AbstractMetastasis to secondary sites remains the leading cause of nasopharyngeal carcinoma (NPC)‐associated death. In order to identify the candidate protein(s) responsible for the differential metastatic capacity, the protein expression profiling between NPC cell line CNE‐2 and its highly metastatic subclone S‐18 were compared by 2‐DE. In total, 18 spots were differentially expressed between these two cell lines. Among all, seven proteins were identified with further MS analysis. Western blotting further validated upregulation of HSP27 and ezrin, and downregulation of valosin containing protein and keratin 18 in S‐18. Moreover, the knockdown of HSP27 was found to significantly decrease the invasive ability of S‐18. On the other hand, overexpression of HSP27 in NP460 cells, which generated little endogenous HSP27 and less invasive, was noted to gain enhanced metastatic capability. Real‐time PCR confirmed that the transcriptional levels of NF‐κB and MMP9, MMP11 were downregulated after inhibition of HSP27 in S‐18, which implicated that HSP27 enhanced the metastatic property of NPC cells probably via the NF‐κB‐mediated activation of MMPs. The findings in this work provided us a platform for further elucidating the underlying mechanisms of NPC metastasis and demonstrated that HSP27 would be a valid target for anti‐cancer drug development.
The Role of Interannual Climate Variability in Controlling Solifluction Processes, Endalen, Svalbard
Authors: Harris Charles , Kern‐Luetschg Martina , Christiansen Hanne H. , Smith Fraser 
Published: May 2011

ABSTRACTA continuous record is presented of active layer processes at Endalen, Svalbard, over the period 2005–08. The monitored slope has a gradient of around 7° and in 2005, active layer depth was 94 cm, but this increased by around 14 cm over the next three years. The presence of an ice‐rich transient layer proved highly significant in determining the timing and profiles of solifluction movement. Frost heaving was 4.2 cm in 2005–06, 6.6 cm in 2006–07 and 3.2 cm in 2007–08, but thaw settlement exceeded frost heave in each year, giving a net total ground surface lowering of 6.2 cm. In winter, segregation ice was concentrated within the upper and lower active layer, leaving the central parts ice‐poor. During the summers of 2006 and 2008, thawing of the transient layer was associated with artesian pore pressures at 90 cm depth and basal soil shearing, but in 2007, when the thaw front failed to reach the ice rich basal zone, pore pressures during thaw were sub‐hydrostatic and no basal shearing was observed. Solifluction shear strain during thaw settlement resulted in downslope surface displacements of 2.3 cm in 2005–06, 1.2 cm in 2006–07 and 1 cm in 2007–08. Copyright © 2011 John Wiley & Sons, Ltd.
Toward accurate prediction of pKa values for internal protein residues: The importance of conformational relaxation and desolvation energy
Authors: Wallace Jason A. , Wang Yuhang , Shi Chuanyin , Pastoor Kevin J. , Nguyen Bao‐Linh , Xia Kai , Shen Jana K. 
Published: May 2011

AbstractProton uptake or release controls many important biological processes, such as energy transduction, virus replication, and catalysis. Accurate pKa prediction informs about proton pathways, thereby revealing detailed acid‐base mechanisms. Physics‐based methods in the framework of molecular dynamics simulations not only offer pKa predictions but also inform about the physical origins of pKa shifts and provide details of ionization‐induced conformational relaxation and large‐scale transitions. One such method is the recently developed continuous constant pH molecular dynamics (CPHMD) method, which has been shown to be an accurate and robust pKa prediction tool for naturally occurring titratable residues. To further examine the accuracy and limitations of CPHMD, we blindly predicted the pKa values for 87 titratable residues introduced in various hydrophobic regions of staphylococcal nuclease and variants. The predictions gave a root‐mean‐square deviation of 1.69 pK units from experiment, and there were only two pKa's with errors greater than 3.5 pK units. Analysis of the conformational fluctuation of titrating side‐chains in the context of the errors of calculated pKa values indicate that explicit treatment of conformational flexibility and the associated dielectric relaxation gives CPHMD a distinct advantage. Analysis of the sources of errors suggests that more accurate pKa predictions can be obtained for the most deeply buried residues by improving the accuracy in calculating desolvation energies. Furthermore, it is found that the generalized Born implicit‐solvent model underlying the current CPHMD implementation slightly distorts the local conformational environment such that the inclusion of an explicit‐solvent representation may offer improvement of accuracy. Proteins 2011. © 2011 Wiley‐Liss, Inc.
Anodic repassivation of low energy Au‐implanted ultra‐thin anodic Al2O3
Authors: Mardare Andrei Ionut , Melnikov Alexander , Wieck Andreas Dirk , Hassel Achim Walter 
Published: May 2011

AbstractUltrathin anodic alumina with a film thickness of 11 nm was implanted by Au atoms with low energy of 2, 5 or 10 keV. Stopping range simulations yielded three essentially different geometries ranging from surface near implantation over well penetrated oxide to near oxide metal interface implantation, covering the entire range of possible implantation modifications. This work aims at demonstrating how to perform band gap engineering in alumina not only on an energetic level but also targeting a certain geometrical position of the doping atoms by means of the implantation parameters. Beside the intended implantation the oxide destruction in the implantation path and its possible repair was of interest. The repassivation behaviour was considerably different showing a significant redox contribution of the gold nanoclusters on top of the simple oxide repassivation. Near surface implanted Au remained electrochemically active for low repassivation potentials. Higher repassivation potentials always buried the implanted Au atoms under anodic alumina. The repassivation charge determined allowed determining the volume destructed by the implantation.
Single walled carbon nanotubes functionalized with hydrides as potential hydrogen storage media: A survey of intermolecular interactions
Authors: Surya V. J. , Iyakutti K. , Venkataramanan N. S. , Mizuseki H. , Kawazoe Y. 
Published: May 2011

AbstractIn this paper, we have analyzed the intermolecular interactions between H2and single walled carbon nanotube (SWCNT)–hydride complexes and project their capability as a practicable hydrogen storage medium (HSM). In this respect, we have investigated the type of interactions namely van der Waals, electrostatic, and orbital interactions to understand the molecular hydrogen binding affinity of various systems. We found that the charge transfer effects coupled with induced electrostatic interactions are responsible for synergetic action of SWCNT and hydrides on adsorption of H2molecules at ambient conditions. Also we have calculated the thermodynamically usable capacity of hydrogen in all the systems. This study enables one to identify and design potential hydrogen storage materials.
Green high‐power light sources using InGaN multi‐quantum‐well structures for full conversion
Authors: Galler B. , Sabathil M. , Laubsch A. , Meyer T. , Hoeppel L. , Kraeuter G. , Lugauer H. , Strassburg M. , Peter M. , Biebersdorf A. , Steegmueller U. , Hahn B. 
Published: May 2011

AbstractWe investigate the possibility to obtain efficient green light sources for high‐power applications by full luminescence conversion via InGaN/GaN multi‐quantum‐well (MQW) structures. Using an ultraviolet (UV) light‐emitting diode (LED) for optical pumping of a forty‐period (40x) MQW structure emitting in the green spectral range, we show that a luminous flux comparable to the best reported values for direct green LEDs can be achieved. The position of the efficiency maximum on the excitation density axis is shifted by an order of magnitude to an equivalent of 28 Acm–2 while maintaining comparable absolute values. We propose the concept of processing suitable platelets placed directly on a pump LED as a general experimental tool to determine absolute efficiency values of structures that cannot be pumped by electrical means (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AlN/GaN HEMTs with high‐κ ALD HfO2 or Ta2O5 gate insulation
Authors: Deen David , Storm David , Meyer David , Katzer D. Scott , Bass Robert , Binari Steven , Gougousi Theodosia 
Published: May 2011

AbstractAlN/GaN Metal‐Insulator‐Semiconductor High Electron Mobility Transistors (HEMTs) have been grown and fabricated which utilize a 6 nm thick atomic layer deposited film of either Ta2O5 or HfO2 for gate insulation. Drain, transfer, and gate current characteristics are compared between both structures, showing a measurable difference in threshold voltage and transconductance. The cause is highlighted by the results of capacitance‐voltage analysis which showed 10 MHz dielectric constants of 8.7 and 11.7 for the HfO2 and Ta2O5 films, respectively. Furthermore, interface trap state density was extracted by Terman's method and compared between films. HEMT small signal frequency performance was representative of the different sub‐micron gate lengths. Consideration of the compared electrical results suggests that at this stage in ALD development, Ta2O5 appears better suited for gate insulation of AlN/GaN HEMTs. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Drain bias stress and memory effects in AlGaN/GaN heterostructure field‐effect transistors with p‐GaN gate
Authors: Sugiyama Takayuki , Honda Yoshio , Yamaguchi Masahito , Amano Hiroshi , Oshimura Yoshinori , Iida Daisuke , Iwaya Motoaki , Akasaki Isamu 
Published: May 2011

AbstractWe measured the drain bias stress effects in normally off mode AlGaN/GaN (JHFETs) with a p‐GaN gate, whose AlGaN barrier was exposed to air by dry etching. A large current collapse and a memory effect decreased the drain current (IDS). IDS of an unpassivated sample became the off leakage level of normally off mode JHFETs at a drain stress bias of 15 V. On the other hand, IDS in SiN‐passivated JHFETs decreased at a slow rate upon applying drain stress bias. The decrease in IDS in SiN‐passivated JHFETs was almost the same as that in as‐grown HFETs. These drain stress and memory effects were perfectly deletable by light exposure, and were rewritable similarly in an EPROM. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hierarchical spatial modeling of uncertainty in air pollution and birth weight study
Authors: Gray Simone C. , Gelfand Alan E. , Miranda Marie Lynn 
Published: May 2011

AbstractIn environmental health studies air pollution measurements from the closest monitor are commonly used as a proxy for personal exposure. This technique assumes that air pollution concentrations are spatially homogeneous in the neighborhoods associated with the monitors and consequently introduces measurement error into a resultant model. To model the relationship between maternal exposure to air pollution and birth weight, we build a hierarchical model that accounts for the associated measurement error. We allow four possible scenarios, with increasing flexibility, for capturing this uncertainty. In the two simplest cases, we specify models with a constant variance term and a variance component that allows uncertainty in the exposure measurements to increase as the distance between maternal residence and the location of the closest monitor increases. In the remaining two models, we introduce spatial dependence using random effects. The models are illustrated using Bayesian hierarchical modeling techniques that relate pregnancy outcomes from the North Carolina Detailed Birth Records to air pollution data from the U.S. Environmental Protection Agency. Copyright © 2011 John Wiley & Sons, Ltd.
Defining and ranking effects of individual agents based on survival times of cancer patients treated with combination chemotherapies
Authors: Thall Peter F. , Liu Diane D. , Berrak Su G. , Wolff Johannes E. 
Published: May 2011

AbstractAn important problem in oncology is comparing chemotherapy (chemo) agents in terms of their effects on survival or progression‐free survival time. When the goal is to evaluate individual agents, a difficulty commonly encountered with observational data is that many patients receive a chemo combination including two or more agents. Because agents given in combination may interact, quantifying the contribution of each individual agent to the combination's overall effect is problematic. Still, if on average combinations including a particular agent confer longer survival, then that agent may be considered superior to agents whose combinations confer shorter survival. Motivated by this idea, we propose a definition of individual agent effects based on observational survival data from patients treated with many different chemo combinations. We define an individual agent effect as the average of the effects of the chemo combinations that include the agent. Similarly, we define the effect of each pair of agents as the average of the effects of the combinations including the pair. Under a Bayesian regression model for survival time in which the chemo combination effects follow a hierarchical structure, these definitions are used as a basis for estimating the posterior effects and ranks of the individual agents, and of all pairs of agents. The methods are illustrated by a data set arising from 224 pediatric brain tumor patients treated with over 27 different chemo combinations involving seven chemo agents. Copyright © 2011 John Wiley & Sons, Ltd.
Sample size and power determination in joint modeling of longitudinal and survival data
Authors: Chen Liddy M. , Ibrahim Joseph G. , Chu Haitao 
Published: May 2011

AbstractOwing to the rapid development of biomarkers in clinical trials, joint modeling of longitudinal and survival data has gained its popularity in the recent years because it reduces bias and provides improvements of efficiency in the assessment of treatment effects and other prognostic factors. Although much effort has been put into inferential methods in joint modeling, such as estimation and hypothesis testing, design aspects have not been formally considered. Statistical design, such as sample size and power calculations, is a crucial first step in clinical trials. In this paper, we derive a closed‐form sample size formula for estimating the effect of the longitudinal process in joint modeling, and extend Schoenfeld's sample size formula to the joint modeling setting for estimating the overall treatment effect. The sample size formula we develop is quite general, allowing for p‐degree polynomial trajectories. The robustness of our model is demonstrated in simulation studies with linear and quadratic trajectories. We discuss the impact of the within‐subject variability on power and data collection strategies, such as spacing and frequency of repeated measurements, in order to maximize the power. When the within‐subject variability is large, different data collection strategies can influence the power of the study in a significant way. Optimal frequency of repeated measurements also depends on the nature of the trajectory with higher polynomial trajectories and larger measurement error requiring more frequent measurements. Copyright © 2011 John Wiley & Sons, Ltd.
Attachment Insecurity, Responses to Critical Incident Distress, and Current Emotional Symptoms in Ambulance Workers
Authors: Halpern Janice , Maunder Robert G. , Schwartz Brian , Gurevich Maria 
Published: May 2011

AbstractAmbulance workers are exposed to critical incidents that may evoke intense distress and can result in long‐term impairment. Individuals who can regulate distress may experience briefer post‐incident distress and fewer long‐term emotional difficulties. Attachment research has contributed to our understanding of individual differences in stress regulation, suggesting that secure attachment is associated with effective support‐seeking and coping strategies, and fewer long‐term difficulties. We tested the effect of attachment insecurity on emotional distress in ambulance workers, hypothesizing that (1) insecure attachment is associated with symptoms of current distress and (2) prolonged recovery from acute post‐critical incident distress, coping strategies and supportive contact mediate this relationship. We measured (1) attachment insecurity, (2) acute distress, coping and social contact following an index critical incident and (3) current symptoms of post‐traumatic stress, depression, somatization and burnout and tested the hypothesized associations. Fearful‐avoidant insecure attachment was associated with all current symptoms, most strongly with depression (R = 0.38,p<0.001). Fearful‐avoidant attachment insecurity was also associated with maladaptive coping, reduced social support and slower recovery from social withdrawal and physical arousal following the critical incident, but these processes did not mediate the relationship between attachment insecurity and current symptoms. These findings are relevant for optimizing post‐incident support for ambulance workers. Copyright © 2011 John Wiley & Sons, Ltd.