bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Peroxide Containing Maleinate Surface‐Active Monomers for Obtaining Reactive Polymers
Authors: Borzenkov Mykola , Hevus Orest 
Published: June 2012

AbstractNovel surface‐active monomers were synthesized by successive treatment of tert‐butylperoxy‐6‐hydroxyhexanoate with maleic anhydride, 1,3‐propane sultone and triethylamine or with maleic anhydride and poly(ethylene glycol) methyl ether. The surface‐active properties of monomers were studied. The critical micelle concentrations (cmc) as well as the surface tension at the cmc were determined for obtained monomers. The synthesized compounds were shown to be suitable reactive surfactants for obtaining styrene latexes.
Superparamagnetic Nanocomposites of Poly(vinyl alcohol‐graft‐acrylonitrile) as Carrier for Magnetically Assisted Release of Ciprofloxacin
Authors: Gupta Rashmi , Bajpai A.K. 
Published: June 2012

AbstractIn the present study also a superparamagnetic nanocomposite of Poly (vinyl‐ alcohol‐g‐acrylonitrile) has been designed by homogeneous impregnation of iron oxide nanoparticles into the graft polymer matrix. The so prepared nanocomposite was characterized by FT‐IR, TEM and XRD techniques and studied for water sorption behavior and magnetization properties. The superparamagnetic nanocomposite was loaded with an antibiotic drug, ciprofloxacin (CFx), and its release behavior was investigated under varying experimental conditions such as chemical composition of the matrix, pH of the release media, applied magnetic field and percent loading of the drug. The drug transport mechanism was also analyzed using Ficks power law. The drug loaded magnetic nanocomposite was also studied for antibacterial and in‐vitro blood compatible properties.
Thermal Properties Evolution of PCB FR4 Epoxy Composites for Mechatronic During Very Long Ageing
Authors: Lé‐Magda Mélanie , Dargent Eric , Youssef Boulos , Guillet Alain , Idrac Jonathan , Saiter Jean‐Marc 
Published: June 2012

AbstractVery long ageing times, up to 8000 h at 110 °C, were achieved on printed circuit boards PCB FR4 Laminate commonly used in automotive design. This composite is fabricated from glass fiber embedded in a flame retardant epoxy resin. Ageing is performed in an oven under air atmosphere at a temperature lower than the glass transition temperature, thus physical ageing must take place. Thermogravimetric analysis indicates that during heating, the flame retardant interacts first with O2 atmosphere for temperature higher than 180 °C. Fourier transform infrared spectroscopic analysis shows that chemical degradation of the samples due to oxidation occurs after ageing at 110 °C for time longer than 940 h. From thermally modulated differential scanning calorimetry analysis, two different modifications of the epoxy resin are evidenced: one fraction for which oxidation modified drastically the molecular structure and one fraction which is not yet oxidized. These two fractions had different molecular mobilities leading to different molecular relaxation processes at the glass transition.
Effect of Epoxidation of Diene Component of SBS Block Copolymer on Morphology and Mechanical Properties
Authors: Pandit Rajesh , Giri Jyoti , Michler Goerg H. , Lach Ralf , Grellmann Wolfgang , Youssef Boulos , Saiter Jean Marc , Adhikari Rameshwar 
Published: June 2012

AbstractIn this work, the polybutadiene (PB) block of an asymmetric lamellae forming polystyrene/polybutadiene based triblock copolymer was epoxidized to different extent in order to study its effect on morphology and mechanical behaviour of the copolymer. The products were analyzed by means of different microscopic techniques, Fourier transform infrared (FTIR) spectroscopy and microhardness measurements. It was found that the microphase separation behavior and hence the mechanical properties of the materials were drastically altered through epoxidation of the diene block of the styrene/diene triblock copolymer. With the increase in the extent of epoxidation the lamellar structure changed to distorted lamellae and then to disordered domains. Consequently, inhomogeneous mechanical performance of the samples was observed at higher degree of chemical modification.
Optical Properties of Swift Heavy Ion Beam Irradiated Polycarbonate/Polystyrene Composites Films
Authors: Rathore Bhupendra Singh , Gaur Mulayam Singh , Singh Kripa Shanker 
Published: June 2012

AbstractPolycarbonate/polystyrene composites films were irradiated by 55 MeV Carbon ion beam with fluence ranging from 1 × 1011 to 1 × 1013 ions/cm2. The polymer composites films were prepared by solution mixing method. The effects of ion beam on structural, optical and surface morphology of PC/PS composites films were investigated by X‐ray diffraction (XRD), UV‐visible spectroscopy (UV‐vis), Fourier Transform Infrared Spectroscopy (FT‐IR) and Optical Microscope. The XRD pattern shows the average crystallite size, percentage of crystallinity and inter‐chain separation, which decreases with increase in ion fluences. UV‐vis spectra show that the energy band gap and transmittance decreases while number of carbon atoms increases with fluences. The FT‐IR spectra evidenced very small change in cross linking and chain scissoring at high ion fluences, while the optical microscopy shows a color change with ion fluence.
Conductivity Study on PEO Based Polymer Electrolytes Containing Hexafluorophosphate Anion: Effect of Plasticizer
Authors: Sharma Jitender Paul , Yamada K. , Sekhon S. S. 
Published: June 2012

AbstractPEO based polymer electrolytes containing ammonium hexafluorophosphate (NH4PF6) and hexafluorophosphoric acid (HPF6), both with PF anion have been studied. The effect of the addition of propylene carbonate (PC) to PEO‐NH4PF6 and PEO‐HPF6 has been observed to increase in ionic conductivity which is attributed to an increase in free ion concentration due to the dissociation of ion aggregates present at higher acid/salt concentrations. The plasticized polymer electrolytes containing HPF6 show relatively higher conductivity (σmax = 1.02 × 10−4 S/cm at 10 wt% HPF6) as compared to electrolytes containing NH4PF6 (σmax = 1.09 × 10−5 S/cm at 10 wt% NH4PF6). Presence of free ions, ion aggregates and their dissociation with the addition of PC has been studied by Fourier Transform Infrared Spectroscopy (FTIR). The change in amorphous phase with PC content was also studied by X‐Ray Diffraction (XRD). The variation of conductivity with temperature shows Vogel–Tammen–Fulcher (VTF) behavior, which is associated with the highly amorphous nature of electrolytes. 1H Nuclear magnetic Resonance (NMR) spectra at different temperatures shows line narrowing and suggests the onset of long range ion diffusional motion. Change in surface morphology of polymer electrolytes with the addition of PC is also checked by Scanning Electron Microscopic (SEM) studies.
High Density Polyethylene Containing Antibacterial Silver Nanoparticles for Medical Applications
Authors: Ziąbka Magdalena , Mertas Anna , Król Wojciech , Bobrowski Andrzej , Chłopek Jan 
Published: June 2012

AbstractHigh density polyethylene (HDPE) and composites with silver nanoparticles were processed via extrusion and injection moulding. The materials thus produced were tested against Gram‐positive Staphylococcus aureus and Gram‐negative Escherichia coli. The release of silver ions Ag+ from composites was measured by means of ICP‐MS method. Surface parameters such as wettability and roughness were determined because of their effect on the most important processes at biomaterial interface. Scanning electron microscopy was used to investigate the microstructure. Durability tests of polymer and composite materials were carried out in a simulated biological solution by monitoring the pH and electrical conductivity, mass changes as well as the longitudinal ultrasonic wave measurements. Antibacterial tests prove that nanosilver modified materials have bactericidal activity against tested bacteria. Biological durability studies reveal stable behavior of incubated materials. Spectrometric analysis shows that the amount of silver release depends on the immersion time and the amount of nanopowder introduced into the polymer matrix.
Cardiovascular physiology in premotor Parkinson's disease: A neuroepidemiologic study
Authors: Jain Samay , Ton Thanh G. , Perera Subashan , Zheng Yan , Stein Phyllis K. , Thacker Evan , Strotmeyer Elsa S. , Newman Anne B. , Longstreth Will T. 
Published: June 2012

AbstractChanges in cardiovascular physiology in Parkinson's disease (PD) are common and may occur prior to diagnostic parkinsonian motor signs. We investigated associations of electrocardiographic (ECG) abnormalities, orthostasis, heart rate variability, and carotid stenosis with the risk of PD diagnosis in the Cardiovascular Health Study, a community‐based cohort of older adults. ECG abnormality, orthostasis (symptomatic or asymptomatic), heart rate variability (24‐hour Holter monitoring), and any carotid stenosis (≥1%) by ultrasound were modeled as primary predictors of incident PD diagnosis using multivariable logistic regression. Incident PD cases were identified by at least 1 of the following: self‐report, antiparkinsonian medication use, and ICD‐9. If unadjusted models were significant, they were adjusted or stratified by age, sex, and smoking status, and those in which predictors were still significant (P ≤ .05) were also adjusted for race, diabetes, total cholesterol, low‐density lipoprotein, blood pressure, body mass index, physical activity, education level, stroke, and C‐reactive protein. Of 5888 participants, 154 incident PD cases were identified over 14 years of follow‐up. After adjusting models with all covariates, those with any ECG abnormality (odds ratio [OR], 1.45; 95% CI, 1.02–2.07; P = .04) or any carotid stenosis (OR, 2.40; 95% CI, 1.40–4.09; P = .001) at baseline had a higher risk of incident PD diagnosis. Orthostasis and heart rate variability were not significant predictors. This exploratory study suggests that carotid stenosis and ECG abnormalities occur prior to motor signs in PD, thus serving as potential premotor features or risk factors for PD diagnosis. Replication is needed in a population with more thorough ascertainment of PD onset. © 2012 Movement Disorder Society
Effect of through‐plane motion on left ventricular rotation: A study using slice‐following harmonic phase imaging
Authors: Brotman David , Zhang Ziheng , Sampath Smita 
Published: June 2012

AbstractNoninvasive quantification of regional left ventricular rotation may improve understanding of cardiac function. Current methods used to quantify rotation typically acquire data on a set of prescribed short‐axis slices, neglecting effects due to through‐plane myocardial motion. We combine principles of slice‐following tagged imaging with harmonic phase analysis methods to account for through‐plane motion in regional rotation measurements. We compare rotation and torsion measurements obtained using our method to those obtained from imaging datasets acquired without slice‐following. Our results in normal volunteers demonstrate differences in the general trends of average and regional rotation‐time plots in midbasal slices and the rotation versus circumferential strain loops. We observe substantial errors in measured peak average rotation of the order of 58% for basal slices (due to change in the pattern of the curve), −6.6% for midventricular slices, and −8.5% for apical slices; and an average error in base‐to‐apex torsion of 19% when through‐plane motion is not considered. This study concludes that due to an inherent base‐to‐apex gradient in rotation that exists in the left ventricular, accounting for through‐plane motion is critical to the accuracy of left ventricular rotation quantification. Magn Reson Med, 2013. © 2011 Wiley Periodicals, Inc.
Integration of the computational fluid dynamics technique with MRI in aortic dissections
Authors: Karmonik Christof , Partovi Sasan , Davies Mark G. , Bismuth Jean , Shah Dipan J. , Bilecen Deniz , Staub Daniel , Noon George P. , Loebe Matthias , Bongartz Georg , Lumsden Alan B. 
Published: June 2012

AbstractShort‐term and long‐term prognosis and their determining factors of Type III/Stanford B aortic dissections (TB‐AD), which separate the aorta distal at the origin of the subclavian artery into a true lumen and false lumen, have been elusive: One quarter of patients thought to be treated successfully, either by medical or by surgical means, do not survive 3 years. Unfavorable hemodynamic conditions are believed to lead to false lumen pressure increases and complications. A better characterization of TB‐AD hemodynamics may therefore impact therapeutic decision making and improve outcome. The large variations in TB‐AD morphology and hemodynamics favor a patient‐specific approach. Magnetic resonance imaging with its capability to provide high‐resolution structural images of the lumen and aortic wall and also to quantify aortic flow and kinetics of an exogenous tracer is a promising clinical modality for developing a deeper understanding of TB‐AD hemodynamics in an individual patient. With the information obtained with magnetic resonance imaging, computational fluid dynamics simulations can be performed to augment the image information. Here, an overview of the interplay of magnetic resonance imaging and computational fluid dynamics techniques is given illustrating the synergy of these two approaches toward a comprehensive morphological and hemodynamic characterization of TB‐AD. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Continuum large cracking in a rate‐dependent plastic–damage model for cyclic‐loaded concrete structures
Authors: Omidi Omid , Lotfi Vahid 
Published: June 2012

SUMMARYFormulation and algorithmic treatment of a rate‐dependent plastic–damage model modified to capture large tensile cracking in cyclic‐loaded concrete structures are presented in detail for a three‐dimensional implementation. The plastic–damage model proposed by Lee and Fenves in 1998 was founded based on isotropic damaged elasticity in combination with isotropic multi‐hardening plasticity to simulate cracking and crushing of concrete under cyclic or dynamic loadings. In order that the model can capture large crack opening displacements, which are inevitable in plain concrete structures, the excessive increase in plastic strain causing unrealistic results in cyclic behaviors is prevented when the tensile plastic–damage variable controlling the evolution of tensile damage is larger than a critical value. In such a condition, the crack opening/closing mechanism becomes similar to discrete cracking. The consistent tangent operator required to accelerate convergence rate is also formulated for the large cracking state including viscoplasticity. The validation and performance of the modified algorithm implemented in a special finite element program is exemplified through several single‐element tests as well as three structural applications. The last example examines the model in the seismic fracture analysis of Koyna dam as a benchmark problem and the resulting crack profile is compared with the available experiment. The numerical experimentations well demonstrate that the developed model whose modification is necessary to properly simulate the cyclic behavior of plain concrete subjected to large tensile strains is robust and reasonably accurate. Copyright © 2012 John Wiley & Sons, Ltd.
A high‐order hybridizable discontinuous Galerkin method for elliptic interface problems
Authors: Huynh L.N. T. , Nguyen N.C. , Peraire J. , Khoo B.C. 
Published: June 2012

SUMMARYWe present a high‐order hybridizable discontinuous Galerkin method for solving elliptic interface problems in which the solution and gradient are nonsmooth because of jump conditions across the interface. The hybridizable discontinuous Galerkin method is endowed with several distinct characteristics. First, they reduce the globally coupled unknowns to the approximate trace of the solution on element boundaries, thereby leading to a significant reduction in the global degrees of freedom. Second, they provide, for elliptic problems with polygonal interfaces, approximations of all the variables that converge with the optimal order of k + 1 in the L2(Ω)‐norm where k denotes the polynomial order of the approximation spaces. Third, they possess some superconvergence properties that allow the use of an inexpensive element‐by‐element postprocessing to compute a new approximate solution that converges with order k + 2. However, for elliptic problems with finite jumps in the solution across the curvilinear interface, the approximate solution and gradient do not converge optimally if the elements at the interface are isoparametric. The discrepancy between the exact geometry and the approximate triangulation near the curved interfaces results in lower order convergence. To recover the optimal convergence for the approximate solution and gradient, we propose to use superparametric elements at the interface. Copyright © 2012 John Wiley & Sons, Ltd.
Permanent Visas and Temporary Jobs: Evidence from Postdoctoral Participation of Foreign PhDs in the United States
Authors: Lan Xiaohuan 
Published: June 2012

AbstractAbout 75 percent of U.S.‐trained, noncitizen PhDs in science and engineering work in the United States after graduation, and 54 percent of those who stay take postdoctoral positions. The probability of postdoctoral participation is substantially higher for temporary visa holders than for permanent visa holders because of visa‐related restrictions in the U.S. labor market. To identify the causal effects of visa status on entry into a postdoctoral position, this paper uses a unique shock to visa status generated by the Chinese Student Protection Act of 1992. Eligibility for the act is used as an instrumental variable for visa status. Two‐stage least‐square estimates show that permanent visa holders are 24 percent less likely to take postdoctoral positions than temporary visa holders. The effects of a permanent visa vary considerably across research fields, but for most fields, it reduces postdoctoral participation significantly.
Improved conductive atomic force microscopy measurements on organic photovoltaic materials via mitigation of contact area uncertainty
Authors: Nikiforov Maxim P. , Darling Seth B. 
Published: June 2012

ABSTRACTPhysical processes that lead to conversion of light into electrical energy inside photovoltaic devices happen at the nanoscale. Therefore, understanding of electrical properties of photovoltaic materials at this length scale is of paramount importance for improvement of device performance. In this paper, we describe and validate a new framework for high‐resolution quantitative measurements of electrical and mechanical properties of compliant materials with sub‐100‐nm resolution. Previous approaches have generally suffered from uncertainty in the quantitative level of contact between the probe and the material being measured; the methodology presented here overcomes this obstacle. We use the broadly studied ITO/PEDOT:PSS/P3HT:PC61BM system as an example to illustrate variability of chemical composition and electrical properties of the active layer at hundred‐nanometers and micrometer length scales. Copyright © 2012 John Wiley & Sons, Ltd.
Research on perfectionism and achievement motivation: implications for gifted students
Authors: Fletcher Kathryn L. , Speirs Neumeister Kristie L. 
Published: June 2012

AbstractPerfectionism has been associated with a rigid adherence to impossibly high standards, an irrational importance on the attainment of these standards, and a tendency to overgeneralize failures. Researchers have primarily focused on how perfectionism predicts psychological adjustment; yet, recent research also indicates that perfectionism impacts students' achievement motivation. In this article, research on the relationship between perfectionism and achievement motivation in non‐gifted students is reviewed. Conclusions about perfectionism and achievement motivation in non‐gifted students will highlight directions for future research and implications for enhancing the achievement motivation of gifted students with perfectionism. © 2012 Wiley Periodicals, Inc.
Gifted native American students: Underperforming, under‐identified, and overlooked
Authors: Gentry Marcia , Fugate C. Matthew 
Published: June 2012

AbstractThere has been limited focus among researchers on the nature and needs of gifted Native American students in the past 30 years, and the work that has been done frequently generalizes findings across Native American cultures. This article reviews recent literature on Native American youth and on gifted Native American students; examines the current condition of education in the Diné (Navajo) Nation through a sociocultural motivation lens and based on work with one tribal community on this reservation; calls researchers and educators to action and to recognize that, as with all ethnic groups, many individual cultures exist within Native American populations; and offers suggestions for education personnel. © 2012 Wiley Periodicals, Inc.
Boron‐Based High Explosives
Authors: Koch Ernst‐Christian , Klapötke Thomas M. 
Published: June 2012

AbstractThe detonation velocity, detonation pressure, and cylinder expansion energy of a series of boron compounds including nitroalkylborates, and mixed amino‐nitrosusbtituted borazines, borazenes, iminoboranes, and azaboridines were calculated with Cheetah 2.0. The detonation velocity of the boron compounds is always superior to the all‐carbon analogues at the corresponding densities. Nitro‐substituted boron compounds bearing amino groups instead of hydrogen display even higher performance.
Electronic and spin transport properties of a benzene molecule connected to graphene leads
Authors: Simchi Hamidreza , Esmaeilzadeh Mahdi , Saani Mehdi Heidari 
Published: June 2012

AbstractElectronic and spin transport properties of a benzene molecule connected to semi‐infinite armchair and zigzag graphene nano‐ribbon leads are calculated using non‐equilibrium Green function (NEGF) method at zero bias regime. It is shown that, the molecule is conductive in a specific range of energy for both armchair and zigzag leads. This behavior is similar for both kinds of leads. In presence of Rashba spin–orbit interaction, the molecule shows spin filtering properties for both kinds of leads but these properties are not similar for armchair and zigzag leads. Also, a spin‐polarized current is seen in the molecule connected to zigzag leads. The benzene molecule with Rashba spin–orbit interaction can be considered as an excellent candidate for molecular electronic and spintronic devices which can have very small dimensions relative to the conventional semiconductor devices.