bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of functional group on the mechanical properties of PA6/SiO2 composites
Authors: Liu Juan , Yi Hongling , Lin Heng , Wei Ting , Zheng Baicun
Published: February 2014

The polyamide‐6 materials were mixed with nano‐silica modified by γ‐glycidoxypropyltrimethoxysilane (GPS) via a melt blending process. The idea was to study the correlation between content of GPS and PA6/silica interfacial interactions as well as mechanical properties of PA6/silica composites. The epoxy groups in GPS could react with –COOH and –NH2 in PA6 to produce the covalent bond and hydrogen bonding based on FTIR chart, TG analysis, and TEM analysis results. The DSC results show that nanosilica could encourage the formation of the hydrogen bonded structure of the α‐PA6 crystals. However, the over GPS could confine the motion of polyamide‐6 and decrease the generation of α‐PA6 crystals resulted the decrease of mechanical properties. So the amount of epoxy groups grafted on nano‐silica has a threshold effect on strength of PA6. POLYM. COMPOS., 35:435–440, 2014. © 2013 Society of Plastics Engineers
Amine‐functionalized poly(styrene) microspheres as thermoplastic toughener for epoxy resin
Authors: Chaudhary S. , Surekha P. , Kumar D. , Rajagopal C. , Roy P. K.
Published: February 2014

In this article, the potential of amine‐functionalized poly(styrene) (PS) microspheres as toughening agent for epoxy resin has been explored. PS microspheres were prepared by suspension polymerization, where the monomer concentration and stirring speed was varied to control the microsphere dimensions (52–183 µm). The obtained microspheres were chemically functionalized with an aim to improve its dispersion within the epoxy matrix. The amine groups generated on the microsphere surface offer a potential site of covalent linkage with the epoxy matrix, thereby resulting in increased compatibility and improved properties. Epoxy composites containing varying amounts of microspheres (1–7% w/w) were prepared and their mechanical properties were evaluated under both quasi‐static as well as dynamic conditions. The amination of poly(styrene) (APS) led to improved dispersion of the rigid microspheres in the epoxy matrix, which was evident from higher impact strength and fracture energies (GIC) as compared to its neat analogs. The izod impact strength and GIC increased by 33% and 150%, respectively, on introduction of 3% APS. This was accompanied with an increase in the tensile modulus and strength of the epoxy resin. Further increase in loading led to agglomeration of the microspheres, which in turn resulted in lowering of impact strength and toughness. Excellent agreement was found between the experimentally measured modulae and the predictions made on the basis of Halpin–Tsai and Lewis–Neilson models. Fracture surface morphology was studied to arrive at the principal toughening mechanisms behind the experimental findings. POLYM. COMPOS., 36:174–183, 2015. © 2014 Society of Plastics Engineers
Medication use in adults living in Brasilia, Brazil: a cross‐sectional, population‐based study
Authors: Galvao Tais F. , Silva Marcus T. , Gross Raz , Pereira Mauricio G.
Published: February 2014

Purpose

To assess the prevalence of medicine use in adults of Brasilia and to elucidate the associated factors.

Methods

A cross‐sectional study was conducted with adults (18 to 65 years) living in Brasilia, who were selected using a two‐stage probabilistic sampling and interviewed in their home, from February to May 2012. The primary outcome was the use of medicines in the last 7 days. A Poisson regression with robust variance was employed to adjust for covariates following a hierarchical model.

Results

The study included 1820 individuals (11% losses), 60% of which were women, and the mean age was 37 ± 12.6 years. The prevalence of drug consumption was 35.7% (95% confidence interval [95%CI]: 33.5%–37.9%). Medicine consumption was significantly higher in women (prevalence ratio [PR] = 1.54; 95%CI: 1.28–1.85); unemployed or retired people (PR = 1.35; 95%CI: 1.15–1.59); people with hypertension (PR = 2.33; 95%CI: 2.00–2.71), diabetes (PR = 1.46; 95%CI: 1.22–1.74), depression (PR = 1.32; 95%CI: 1.13–1.53), or other chronic diseases (PR = 1.50; 95%CI: 1.26–1.79); and study participants who had a recent medical consultation (PR = 1.49; 95%CI: 1.29–1.71). Medication use was significantly higher at older ages. The participants obtained about half of the drugs from the Brazilian public health system, but this access was significantly different according to the economic class.

Conclusions

Medication use was common among adults living in Brasilia and is associated with sex, age, health conditions, and access to healthcare. Copyright © 2014 John Wiley & Sons, Ltd.
Influence of Regular Physical Activity on Warfarin Dose and Risk of Hemorrhagic Complications
Authors: Shendre Aditi , Beasley Timothy Mark , Brown Todd M. , Hill Charles E. , Arnett Donna K. , Limdi Nita A.
Published: February 2014

Objective

To determine the influence of regular physical activity on stable warfarin dose and risk of major hemorrhage in patients on chronic anticoagulation therapy.

Design

Regular physical activity (maintained over > 80% of visits) was ascertained by self‐report at initiation of warfarin therapy (target international normalized ratio [INR] = 2–3) in 1272 patients, with changes documented at monthly anticoagulation clinic visits in a population‐based prospective cohort. Multi‐variable linear regression and survival analysis, respectively, were used to assess influence on warfarin and risk of hemorrhage.

Setting

Outpatient anticoagulation clinic

Participants

1272 anticoagulated patients

Measurement and Main Results

There were 683 (53.7%) patients who were regularly physically active (≥ 30 min ≥ 3 times/week). Physically active patients required warfarin doses that were 6.9% higher (p=0.006) than in physically inactive patients after controlling for sociodemographic factors, vitamin K intake, clinical factors, and genetic variations.

The overall incidence of major hemorrhagic events was 7.6/100 person‐years (p‐yrs, 95% confidence interval [CI] 6.4–8.9) in our population. The incidence was lower for physically active patients (5.6/100 p‐yrs, 95% CI 4.2–7.2) than in inactive patients (10.3/100 p‐yrs, 95% CI 8.2–12.9, p=0.0004). Active patients had a 38% lower risk of hemorrhage (hazard ratio 0.62, 95% CI 0.42–0.98, p=0.03) compared with inactive patients.

Conclusions

Regular physical activity is associated with higher warfarin dose requirements and lower risk of hemorrhage. The influence of physical activity on drug response needs to be further explored, and the mechanisms through which it exerts these effects need to be elucidated.
Temperature accelerated life test on commercial concentrator III–V triple‐junction solar cells and reliability analysis as a function of the operating temperature
Authors: Espinet‐González P. , Algora C. , Núñez N. , Orlando V. , Vázquez M. , Bautista J. , Araki K.
Published: February 2014

A temperature accelerated life test on commercial concentrator lattice‐matched GaInP/GaInAs/Ge triple‐junction solar cells has been carried out. The acceleration of the aging has been accomplished by subjecting the solar cells at temperatures markedly higher than the nominal working temperature inside a concentrator, and the nominal photo‐current condition (820 X) has been emulated by injecting current in darkness. Three tests at different temperatures have been carried out. The failure distributions across the three test temperatures have been fitted to an Arrhenius–Weibull model. An Arrhenius activation energy of 1.59 eV was determined from the fit. The reliability functions and parameters of these solar cells at two nominal working conditions (80 and 100 °C) have been obtained. In both cases, the instantaneous failure rate function monotonically increases, that is, the failures are of the wear‐out kind. We have also observed that the reliability data are very sensitive to the nominal temperature condition. In fact, at a nominal working condition of 820 X and 80 °C, assuming that the concentration module works 5 h per day, the warranty time obtained for a failure population of 5% has been 113 years. However, for a nominal working condition of 820 X and 100 °C, the warranty time obtained for a failure population of 5% has been 7 years. Therefore, in order to offer a long‐term warranty, the working temperature could be a key factor in the design of the concentration photovoltaic systems. Copyright © 2014 John Wiley & Sons, Ltd.
Phosphorylation dynamics of membrane proteins from Arabidopsis roots submitted to salt stress
Authors: Vialaret Jérôme , Di Pietro Magali , Hem Sonia , Maurel Christophe , Rossignol Michel , Santoni Véronique
Published: February 2014

An excess of NaCl in the soil is detrimental for plant growth. It interferes with mineral nutrition and water uptake and leads to accumulation of toxic ions in the plant. Understanding the response of roots to NaCl stress may facilitate the development of crops with increased tolerance to this and other stresses. Since controls achieved at the posttranslational level are of critical importance for regulating protein function, the present work used a robust label‐free quantitative proteomic methodology to quantify phosphorylation events that affect root membrane proteins in Arabidopsis, in response to short‐term (up to 2 h) NaCl treatments. This work identified 302 proteotypic phosphopeptides including 77 novel phosphorylated sites. NaCl treatment significantly altered the abundance of 74 phosphopeptides, giving novel insights into the regulation of major classes of membrane proteins, including ATPases, sodium transporters, and aquaporins. The data provide a unique access to phosphorylation reprogramming of ionic equilibrium in plant cells under NaCl stress. The use of predictive bioinformatic tools for kinase motifs suggested that root membrane proteins are substrates of cAMP‐dependent protein kinase, cGMP‐dependent protein kinase, and protein kinase C families, also called AGC kinases, arguing for an important role of lipid signaling in abiotic stress responses. It also pointed to cross‐talks between protein kinase families during NaCl stress.
Synthesis and optical properties of poly(aryl ether ketone)s incorporating porphyrins in the backbones
Authors: Du Yinlong , Zhang Shuling , Jiang Xu , Zhu Kai , Geng Zhi , Fang Yu , Huo Pengfei , Liu Chuan , Song Yinglin , Wang Guibin
Published: February 2014

A series of novel soluble poly(aryl ether ketone)s (PAEKs) based on 5,10‐bis(4‐hydroxyphenyl)−15,20‐diphenylporphyrin (cis‐DHTPP), 4,4′‐(hexafluoroisopropylidene) diphenol (6FBPA) and 4,4′‐difluorobenzophenone (DFB) were synthesized and characterized by FT‐IR, 1H‐NMR, UV–vis and fluorescence spectroscopies. The intrinsic photophysical properties of porphyrins were preserved because of the absence of photoinduced electron transfer in the polymer chains. Investigation of the copolymers thermal properties indicated that these polymers had high glass transition temperatures and excellent thermal stabilities. The results of Z‐scan and optical limiting measurements manifested that incorporation of the porphyrin chromophore into the main chain engendered the novel PAEKs with superior nonlinear optical properties and optical limiting function, which could be effectively tuned by varying the molar ratio of porphyrin monomers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1282–1290
An approach to improve the efficiency of polymerization and enhance biological activity of poly(lactide‐co‐ethylene oxide fumarate) hydrogels
Authors: Lee Sherry , Zhong Xia , Ravarian Roya , Valtchev Peter , Dehghani Fariba
Published: February 2014

The synthesis and purification of poly(lactide ethylene oxide fumarate) (PLEOF) involved using organic solvents and triethylamine, an acid scavenger that produces toxic complexes. These issues were addressed by using potassium carbonate as an alternative acid scavenger and CO2 gas expanded solution as a media for reaction. Conducting the reaction at these conditions resulted in reducing the number of stages for purification, enhancing the yield of polymerization by 31%, and increasing the fumarate fraction by 110% compared with conventionally produced polymers. Therefore, the capacity of polymer for crosslinking was significantly promoted that resulted in elevating the compression modulus of hydrogel by 119%. Eliminating the toxic chemical residues and strengthening the mechanical property of PLEOF led to enhancement in primary osteoblast cell proliferation on this hydrogel. The new strategy for the synthesis of PLEOF had paramount impact on the characteristics of this polymer and enhanced its biocompatibility for tissue engineering applications, particularly bone repair. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1291–1299
Carbon fibers prepared from tailored reversible‐addition‐fragmentation transfer copolymerization‐derived poly(acrylonitrile)‐co‐poly(methylmethacrylate)
Authors: Spörl Johanna M. , Ota Antje , Beyer Ronald , Lehr Thomas , Müller Alexandra , Hermanutz Frank , Buchmeiser Michael R.
Published: February 2014

Reversible‐addition fragmentation‐transfer (RAFT) polymerization of acrylonitrile (AN) was performed with 2‐(2‐cyano‐2‐propyl‐dodecyl)trithiocarbonate as RAFT agent and azobis(isobutyronitrile) as initiator. Linear polyacrylonitrile (Mn = 133,000 g/mol, PDI = 1.34) was prepared within 7 h in 86% isolated yield. High‐yield copolymerization with methyl methacrylate (MMA) was performed and copolymerization parameters were determined according to Kelen and Tüdös at 90 °C in ethylene carbonate yielding rAN = 0.2 and rMMA = 0.42. The molecular weights, polydispersity indices (PDIs), and MMA content of the copolymer were adjusted in a way that precursor fibers could be prepared via wet spinning. These precursor fibers had round cross‐sections and a dense morphology, showing tenacities of 40–50 cN/tex and elastic moduli of 900–1000 cN/tex at a fineness of 1 dtex and an elongation of 13–17%. Precursor fibers were oxidatively stabilized and then carbonized at different temperatures. A maximum tensile strength of 2.5 GPa was reached at 1350 °C. Thermal analysis, infrared and Raman spectroscopy, wide‐angle X‐ray scattering, scanning electron microscopy, and tensile testing were used to characterize the resulting carbon fibers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1322–1333
Triplet harvesting in poly(9‐vinylcarbazole) and poly(9‐(2,3‐epoxypropyl)carbazole) doped with CdSe/ZnS quantum dots encapsulated with 16‐(N‐carbazolyl) hexadecanoic acid ligands
Authors: Khetubol Adis , Van Snick Sven , Stanislovaityte Egle , Hassinen Antti , Coutiño‐González Eduardo , Vanderlinden Willem , Firdaus Yuliar , Fron Eduard , Vlasselaer Maarten , Simokaitiene Jurate , De Feyter Steven , Hens Zeger , Grazulevicius Juozas V. , Dehaen Wim , Van der Auweraer Mark
Published: February 2014

Semiconductor quantum dots (QDs) can be used as alternative for transition metal complexes to harvest the nonemissive triplet excitons in organic light‐emitting diodes (OLEDs). In search for a QD‐based OLED material generating blue emission, poly(9‐vinylcarbazole) (PVK) and poly(9‐(2,3‐epoxypropyl) carbazole) (PEPK) are chosen as host for blue‐emitting CdSe/ZnS core/shell QDs. The QDs are encapsulated with 16‐(N‐carbazolyl) hexadecanoic acid (C16), a ligand terminated by a carbazole moiety. As alternative for PVK, PEPK, where the lower molecular weight and less extensive excimer formation could promise a better film formation and more extensive exciton hopping, is explored. The efficiencies of singlet (
) and triplet (
) energy transfer to the C16 capped QDs are estimated by combining stationary photoluminescence spectra and fluorescence decays of pristine polymer films with those of polymer films doped with the QDs. At a loading of 30 wt % of the QDs,
increases from 12 ± 1% in PVK to 41 ± 2% in PEPK while
increases from 37 ± 22% in PVK to 72 ± 48% in PEPK. The investigation of the film morphology by atomic force microscopy confirms that the main factor limiting the triplet transfer efficiency in the PVK matrix is the clustering of the C16 capped QDs. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 539–551
M‐strings, elliptic genera and N = 4 string amplitudes
Authors: Hohenegger S. , Iqbal A.
Published: February 2014

We study mass‐deformed N = 2 gauge theories from various points of view. Their partition functions can be computed via three dual approaches: firstly, (p,q)‐brane webs in type II string theory using Nekrasov's instanton calculus, secondly, the (refined) topological string using the topological vertex formalism and thirdly, M theory via the elliptic genus of certain M‐strings configurations. We argue for a large class of theories that these approaches yield the same gauge theory partition function which we study in detail. To make their modular properties more tangible, we consider a fourth approach by connecting the partition function to the equivariant elliptic genus of ℂ2 through a (singular) theta‐transform. This form appears naturally as a specific class of one‐loop scattering amplitudes in type II string theory on T2, which we calculate explicitly.
Resonant enhancement of indirect exchange interaction in semiconductor heterostructures
Authors: Rozhansky I. V. , Averkiev N. S. , Krainov I. V. , Lähderanta E.
Published: February 2014

We present an approach to calculate indirect exchange interaction between paramagnetic ions via free carriers in heterostructures. Unlike well‐known Ruderman–Kittel–Kasuya–Yosida (RKKY) theory the suggested method is not a perturbation theory and thus can be used in the wider variety of cases, especially when resonant effects are important. The method is applied to standard 1D and 2D indirect exchange problems. We further focus on calculation of indirect exchange interaction between two ions mediated by 2D free carriers gas separated by a tunnel barrier. The calculations show that if the ion bound state energy lies within the energy range occupied by the free 2D carriers, the indirect exchange interaction is strongly enhanced due to resonant tunneling and far exceeds what one would expect from the conventional RKKY approach.
The effects of spark plasma sintering consolidation on the ferromagnetic resonance spectra (FMR) of Ni–Zn ferrites
Authors: Ortega‐Zempoalteca R. , Flores‐Arias Y. , Vázquez‐Victorio G. , Gaudisson T. , Ammar S. , Vargas‐Osorio Z. , Acevedo‐Salas U. , Valenzuela R.
Published: February 2014

Magnetic nanoparticles (NPs) of magnetite and Ni–Zn ferrites, synthesized by the forced hydrolysis in a polyol method, were used as the starting material to consolidate them by means of the spark plasma sintering (SPS) method. The microstructural changes were analyzed by X‐ray diffraction, transmission electron microscopy (TEM), magnetic hysteresis loops, and ferromagnetic resonance (FMR) measurements. FMR spectra changed from a high resonance field and small linewidth for the nanoparticles to a spectrum with reduced resonance field with extremely broadened linewidths for the consolidated materials. These effects can be ascribed to the evolution from superparamagnetic NPs to the formation of a nanostructured ceramic structure with high grain‐to‐grain interactions and with increased randomly distributed anisotropy axes.
Enhanced photovoltaic performance of vapor–liquid–solid grown silicon nanowire array with radial heterojunction
Authors: Kohen D. , Morin C. , Faucherand P. , Brioude A. , Perraud S.
Published: February 2014

We present the fabrication of a vapor–liquid–solid grown silicon nanowire array solar cell with a radial heterojunction. Lithography defined Cu catalyst patterning is used to grow a periodic array of 300 nm diameter nanowires with a center‐to‐center distance of 800 nm. A conformal a‐Si:H layer is deposited on the nanowire surface to create the heterojunction and passivate the nanowire surface. Transparent conductive oxide and Ni–Al metal grid are then deposited to complete the solar cell fabrication. With a nanowire height of 1.6 µm, the solar cell has an open‐circuit voltage of 467 mV. This clear improvement of the open‐circuit voltage compared to previous works may be due to the conformal deposition of a‐Si:H and to the use of a Cu catalyst. The parameters limiting the solar cell performances are discussed and explained. This work opens up the possibility to fabricate silicon nanowire array solar cells on low‐cost substrates.
Importance of temporal symmetry in spatial discretization for geostrophic adjustment in semi‐implicit Z‐grid schemes
Authors: Caluwaerts Steven , Degrauwe Daan , Termonia Piet , Voitus Fabrice , Bénard Pierre , Geleyn Jean‐François
Published: February 2014

Among the dynamical cores of numerical weather prediction communities, many different discretization methods can be distinguished to solve the equations governing the motions in the atmosphere numerically. One of them, the Z‐grid approach, is based on solving the equations formulated in terms of divergence and vorticity on an Arakawa A‐grid, a grid where all the variables are defined at the same grid points. To permit an efficient semi‐implicit (SI) treatment, Z‐grid schemes were proposed in the literature that first perform SI time discretization on the momentum equations formulated in terms of velocity components in order to construct from this a discretized divergence equation. This publication shows that a careful formulation of such SI Z‐grid schemes is required to conserve appropriate dispersion relations for inertia–gravity, inertia–Lamb and Rossby waves. It is proven analytically for a two time‐level (2TL) SI Z‐grid scheme of the 1D shallow‐water equations that the spatial discretization must respect temporal symmetry, meaning that the spatial discretization must be identical in the implicit and explicit parts of the scheme. If not, the discretized waves are damped or amplified and their phase and group velocity may be seriously distorted. These findings are discussed in detail and both 1D and 2D numerical tests are carried out to demonstrate that a symmetric formulation is an important modelling constraint in order to obtain an appropriate geostrophic adjustment.
Tropical origin of the severe European winter of 1962/1963
Authors: Greatbatch R. J. , Gollan G. , Jung T. , Kunz T.
Published: February 2014

A set of relaxation experiments using the European Centre for Medium‐Range Weather Forecasts (ECMWF) atmospheric model is used to analyze the severe European winter of 1962/1963. We argue that the severe winter weather was associated with a wave train that originated in the tropical Pacific sector (where weak La Niña conditions were present) and was redirected towards Europe, a process we suggest was influenced by the combined effect of the strong easterly phase of the Quasi‐Biennial Oscillation (QBO) and unusually strong easterly winds in the upper equatorial troposphere that winter. A weak tendency towards negative North Atlantic Oscillation (NAO) conditions in December, associated with extratropical sea‐surface temperature and sea‐ice anomalies, might have acted as a favourable preconditioning. The redirection of the wave train towards Europe culminated in the stratospheric sudden warming at the end of January 1963. We argue that in February the sudden warming event helped maintain the negative NAO regime, allowing the severe weather to persist for a further month. A possible influence from the Madden–Julian Oscillation, as well as a role for internal atmospheric variability, is noted.
Isomers and conformers of complexes of Ti(OiPr)4with cyclopentane‐1,2‐dione: NMR study and DFT calculations
Authors: Osadchuk Irina , Pehk Tõnis , Paju Anne , Lopp Margus , Öeren Mario , Tamm Toomas
Published: February 2014

1H and13C NMR spectra of Ti(OiPr)4complexes with 3‐methyl‐1,2‐cyclopentanedione in deuterochloroform solution reveal formation of different compounds, depending on the molar ratio of diketone and Ti‐isopropoxide. The obtained results were compared with the DFT calculations of these complexes. Both NMR study and theoretical calculations show that the most stable complex is formed with two dione and one single isopropoxide molecules. Detailed conformational analysis was required to find the relative energies of the isomers and conformers of the systems. A possibility of presence of multiple isomeric complexes, some of which come in enantiomeric pairs, was revealed. Possible abundances of the isomers were estimated on the basis of Boltzmann distribution. © 2014 Wiley Periodicals, Inc.
Evaluating immediate and long‐term impacts of qualitative group model building workshops on participants' mental models
Authors: Scott Rodney J. , Cavana Robert Y. , Cameron Donald
Published: February 2014

Group model building literature reports that participation causes mental model refinement and alignment, but no previous study appears to have examined whether these changes are enduring. This paper reports on a case study involving four groups using group model building tools that were evaluated immediately before, immediately after, and 12 months following a 3‐hour workshop. Each workshop used qualitative group model building to plan strategy implementation initiatives in a government department. A change of circumstances (merger and restructure) meant that the workshop conclusions were not implemented, providing a research opportunity to measure the enduring effects of group model building workshops. Statistical comparison of written responses suggests that participants' views on the workshop topic changed and became more alike through the workshop process, and that these changes were enduring even in the relative absence of reinforcing activities. Copyright © 2014 System Dynamics Society
Micro‐chemical investigation of thick W coating on AISI 420 martensitic steel
Authors: Balijepalli S. K. , Kaciulis S. , Lionetti S. , Maddaluno G. , Montanari R.
Published: February 2014

Tungsten is a favorable material for protecting mechanical components such as thermal shields and divertor parts from plasma damage in nuclear fusion reactors. A thick coating of W has been developed on AISI 420 martensitic stainless steel substrate by means of plasma spray technique. Plasma spraying has been used for its simplicity, the possibility to cover complex and extended surfaces and the relatively low cost. An appropriate interlayer has been optimized to increase the adhesion of W coating on the steel substrate and to provide a soft interface with intermediate thermal expansion coefficient for better thermo‐mechanical compatibility. The present work describes and discusses the results of micro‐chemical investigations on coating and interface by X‐ray photoelectron spectroscopy and Auger electron spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.
SIMS depth profiling analysis of P‐doped n‐type Si layer to develop the Si QD solar cell
Authors: Kim Tae Woon , Baek Hyun Jeong , Jang Jong Shik , Lee Seung Mi , Kim Kyung Joong
Published: February 2014

Doping of phosphorus in silicon is important for the formation of n‐type semiconducting material for the silicon‐based electronic devices. In this study, the diffusion behavior of P in a SiO2/InP‐doped Si multilayer film was investigated by SIMS depth profiling. It showed a clear preferential diffusion of P to the Si/SiO2 interface regions. This behavior will act as a negative factor for the active doping of P in silicon quantum dot (QD) solar cells. As a result, the conversion efficiency of a heterojunction Si QD solar cell with a P‐doped Si QD layer was much lower than that with a B‐doped Si QD layer. Copyright © 2014 John Wiley & Sons, Ltd.
High Detectivity Solar‐Blind High‐Temperature Deep‐Ultraviolet Photodetector Based on Multi‐Layered (l00) Facet‐Oriented β‐Ga2O3 Nanobelts
Authors: Zou Rujia , Zhang Zhenyu , Liu Qian , Hu Junqing , Sang Liwen , Liao Meiyong , Zhang Wenjun
Published: February 2014

Fabrication of a high‐temperature deep‐ultraviolet photodetector working in the solar‐blind spectrum range (190–280 nm) is a challenge due to the degradation in the dark current and photoresponse properties. Herein, β‐Ga2O3 multi‐layered nanobelts with (l00) facet‐oriented were synthesized, and were demonstrated for the first time to possess excellent mechanical, electrical properties and stability at a high temperature inside a TEM studies. As‐fabricated DUV solar‐blind photodetectors using (l00) facet‐oriented β‐Ga2O3 multi‐layered nanobelts demonstrated enhanced photodetective performances, that is, high sensitivity, high signal‐to‐noise ratio, high spectral selectivity, high speed, and high stability, importantly, at a temperature as high as 433 K, which are comparable to other reported semiconducting nanomaterial photodetectors. In particular, the characteristics of the photoresponsivity of the β‐Ga2O3 nanobelt devices include a high photoexcited current (>21 nA), an ultralow dark current (below the detection limit of 10−14 A), a fast time response (<0.3 s), a high Rλ (≈851 A/W), and a high EQE (∼4.2 × 103). The present fabricated facet‐oriented β‐Ga2O3 multi‐layered nanobelt based devices will find practical applications in photodetectors or optical switches for high‐temperature environment.
Human Adipose-Derived Stromal/Stem Cells Protect Against STZ-Induced Hyperglycemia: Analysis of hASC-Derived Paracrine Effectors
Authors: Kono Tatsuyoshi M. , Sims Emily K. , Moss Dan R. , Yamamoto Wataru , Ahn Geonyoung , Diamond Julie , Tong Xin , Day Kathleen H. , Territo Paul R. , Hanenberg Helmut , Traktuev Dmitry O. , March Keith L. , Evans-Molina Carmella
Published: February 2014

Adipose-derived stromal/stem cells (ASCs) ameliorate hyperglycemia in rodent models of islet transplantation and autoimmune diabetes, yet the precise human ASC (hASC)-derived factors responsible for these effects remain largely unexplored. Here, we show that systemic administration of hASCs improved glucose tolerance, preserved β cell mass, and increased β cell proliferation in streptozotocin-treated nonobese diabetic/severe combined immunodeficient mice. Coculture experiments combining mouse or human islets with hASCs demonstrated that islet viability and function were improved by hASCs following prolonged culture or treatment with proinflammatory cytokines. Analysis of hASC-derived factors revealed vascular endothelial growth factor and tissue inhibitor of metalloproteinase 1 (TIMP-1) to be highly abundant factors secreted by hASCs. Notably, TIMP-1 secretion increased in the presence of islet stress from cytokine treatment, while TIMP-1 blockade was able to abrogate in vitro prosurvival effects of hASCs. Following systemic administration by tail vein injection, hASCs were detected in the pancreas and human TIMP-1 was increased in the serum of injected mice, while recombinant TIMP-1 increased viability in INS-1 cells treated with interleukin-1beta, interferon-gamma, and tumor necrosis factor alpha. In aggregate, our data support a model whereby factors secreted by hASCs, such as TIMP-1, are able to mitigate against β cell death in rodent and in vitro models of type 1 diabetes through a combination of local paracrine as well as systemic effects. Stem Cells  2014;32:1831–1842
Dirac‐exact relativistic methods: the normalized elimination of the small component method
Authors: Cremer Dieter , Zou Wenli , Filatov Michael
Published: February 2014

Dirac‐exact relativistic methods, i.e., 2‐ or 1‐component methods which exactly reproduce the one‐electron energies of the original 4‐component Dirac method, have established a standard for reliable relativistic quantum chemical calculations targeting medium‐ and large‐sized molecules. Their development was initiated and facilitated in the late 1990s by Dyall's development of the normalized elimination of the small component (NESC). Dyall's work has fostered the conversion ofNESCand related (later developed) methods into routinely used, multipurpose Dirac‐exact methods by which energies, first‐order, and second‐order properties can be calculated at computational costs, which are only slightly higher than those of nonrelativistic methods. This review summarizes the development of a generally applicable 1‐componentNESCalgorithm leading to the calculation of reliable energies, geometries, electron density distributions, electric moments, electric field gradients, hyperfine structure constants, contact densities and Mössbauer isomer shifts, nuclear quadrupole coupling constants, vibrational frequencies, infrared intensities, and static electric dipole polarizabilities. In addition, the derivation and computational possibilities of 2‐componentNESCmethods are discussed and their use for the calculation of spin‐orbit coupling (SOC) effects in connection with spin‐orbit splittings andSOC‐corrected energies are demonstrated. The impact of scalar relativistic and spin‐orbit effects on molecular properties is presented.WIREs Comput Mol Sci2014, 4:436–467.

This article is categorized under:

Electronic Structure Theory > Ab Initio Electronic Structure Methods
Mesoscale modeling of offshore wind turbine wakes at the wind farm resolving scale: a composite‐based analysis with the Weather Research and Forecasting model over Horns Rev
Authors: Jiménez Pedro A. , Navarro Jorge , Palomares Ana M. , Dudhia Jimy
Published: February 2014

The use of mesoscale modeling to reproduce the power deficits associated with wind turbine wakes in an offshore environment is analyzed. The study is based on multiyear (3 years) observational and modeling results at the Horns Rev wind farm. The simulations are performed with the Weather Research and Forecasting mesoscale model configured at a high horizontal resolution of 333 m over Horns Rev. The wind turbines are represented as an elevated momentum sink and a source of turbulent kinetic energy. Composites with different atmospheric conditions are extracted from both the observed and simulated datasets in order to inspect the ability of the model to reproduce the power deficit in a wide range of atmospheric conditions. Results indicate that mesoscale models such as Weather Research and Forecasting are able to qualitatively reproduce the power deficit at the wind farm scale. Some specific differences are identified. Mesoscale modeling is therefore a suitable framework to analyze potential downstream effects associated with offshore wind farms. Copyright © 2014 John Wiley & Sons, Ltd.
The role of margins in boosting and ensemble performance
Authors: Martinez Waldyn , Gray J. Brian
Published: February 2014

Boosting refers to methods that create a sequence of classifiers that perform at least slightly better than random (weak learners) and combine them into a highly accurate ensemble model (strong learners) through weighted voting. There is sufficient empirical evidence to suggest that the performance of boosting methods is superior to that of individual classifiers. In the bias–variance decomposition framework, it has been demonstrated that boosting algorithms typically reduce bias for learning problems, and in some instances reduce the variance. In addition, even when combining a large number of weak learners, boosting algorithms can be very robust to overfitting, in most instances having lower generalization error than other competing ensemble methodologies, such as bagging and random forests. To explain the successful performance of boosting methods, Schapire et al. (Boosting the margin: a new explanation for the effectiveness of voting methods. Ann Stat 1998, 26:1651–1686) developed a bound based on the margins of the training data, from which they concluded that larger margins should lead to lower generalization error. In this article, we examine the role of margins in boosting and ensemble method performance. WIREs Comput Stat 2014, 6:124–131. doi: 10.1002/wics.1292

This article is categorized under:

Statistical and Graphical Methods of Data Analysis > Bootstrap and Resampling

Statistical Learning and Exploratory Methods of the Data Sciences > Classification and Regression Trees (CART)
Telomeric noncoding RNA: telomeric repeat‐containing RNA in telomere biology
Authors: Cusanelli Emilio , Chartrand Pascal
Published: February 2014

Telomeres are nucleoprotein structures that cap the ends of eukaryotic chromosomes, protecting them from degradation and activation of DNA damage response. For this reason, functional telomeres are vital to genome stability. For years, telomeres were assumed to be transcriptionally silent, because of their heterochromatic state. It was only recently shown that, in several organisms, telomeres are transcribed, giving rise to a long noncoding RNA (lncRNA) called telomeric repeat‐containing RNA (TERRA). Several lines of evidence now indicate that TERRA molecules play crucial roles in telomere homeostasis and telomere functions. Recent studies have shown that the expression and regulation of TERRA are dynamically controlled by each chromosome end. TERRA has been involved in the regulation of telomere length, telomerase activity, and heterochromatin formation at telomeres. The correct regulation of the telomeric transcripts may be essential to genome stability, and altered TERRA levels associate with tumorigenesis and cellular senescence. Thus, the study of the molecular mechanisms of TERRA biogenesis and function may advance the understanding of telomere‐related diseases, including cancer and aging.

This article is categorized under:

Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs

RNA in Disease and Development > RNA in Disease
Prevalence of human‐caused mortality in an unhunted cougar population and potential impacts to management
Authors: Thompson Daniel J. , Jenks Jonathan A. , Fecske Dorothy M.
Published: February 2014

Cougar (Puma concolor) populations have expanded in many western areas of the United States. The Black Hills cougar population naturally recolonized the area and cohabitates within an ecosystem heavily dissected by roads and human activity. Assessing mortality characteristics and determining survival of cougar populations is critical for managing and conserving this species. Our objectives were to assess cause‐specific mortality and estimate survival of the Black Hills cougar population, in addition to assessing annual mortality through ancillary opportunistic methods. We captured and radiocollared cougars during 1999–2005 to assess survival and cause‐specific mortality. In addition to cause‐specific mortality, we also documented all known cougar mortality opportunistically throughout the study area in conjunction with the South Dakota Department of Game, Fish and Parks. We captured 31 independent‐aged cougars (n = 12 M, 19 F) for analyses. We opportunistically documented 85 mortality events of cougars in South Dakota during 1998–2005. Despite protection from hunting during our study, 61.5% of mortality was human‐induced, in contrast to other studies of unhunted cougar populations that generally attribute natural mortality as the primary mortality source. Male and female cougars exhibited relatively high survival through the course of the study; however, low sample sizes precluded rigorous comparisons of annual survival rates between sex and age cohorts. Proportionally, the largest contributors to cougar mortality were lethal removal by the state agency (e.g., depredation, human‐safety concerns) and vehicular trauma. Continued assessment of cause‐specific mortality and survival will be useful for evaluating effects of future manipulations of this population. The potential effects of human‐caused cougar mortalities should be considered when evaluating management strategies for cougars in landscapes with high propensity for human–cougar interactions. © 2014 The Wildlife Society.
In‐situ Stabilization of Tin Nanoparticles in Porous Carbon Matrix derived from Metal Organic Framework: High Capacity and High Rate Capability Anodes for Lithium‐ion Batteries
Authors: Shiva Konda , Jayaramulu Kolleboyina , Rajendra H. B. , Kumar Maji Tapas , Bhattacharyya Aninda J.
Published: February 2014

It is a formidable challenge to arrange tin nanoparticles in a porous matrix for the achievement of high specific capacity and current rate capability anode for lithium‐ion batteries. This article discusses a simple and novel synthesis of arranging tin nanoparticles with carbon in a porous configuration for application as anode in lithium‐ion batteries. Direct carbonization of synthesized three‐dimensional Sn‐based MOF: [K2Sn2(1,4‐bdc)3](H2O) (1) (bdc = benzenedicarboxylate) resulted in stabilization of tin nanoparticles in a porous carbon matrix (abbreviated as Sn@C). Sn@C exhibited remarkably high electrochemical lithium stability (tested over 100 charge and discharge cycles) and high specific capacities over a wide range of operating currents (0.2–5 Ag–1). The novel synthesis strategy to obtain Sn@C from a single precursor as discussed herein provides an optimal combination of particle size and dispersion for buffering severe volume changes due to Li‐Sn alloying reaction and provides fast pathways for lithium and electron transport.
Synthesis, Structure, and Luminescent Properties of Three Coordination Compounds Based on in situ Generated Tetrazolate and Carboxylate Ligands
Authors: Ma Huiqing , Xu Yuwen , Meng Qingguo , Zhang Liangliang , Wang Rongming , Sun Daofeng
Published: February 2014

Three metal organic coordination compounds, namely, {[Cd2(L1)4]2·9H2O}n (1), {[Zn(L1)2·2H2O]2·H2O}n (2), and [Cu(L2)2]n (3), [L1 = 3‐chloro‐2‐(5H‐tetrazol‐5‐yl)pyridine; L2 = 3‐chloropicolinic acid], were hydrothermally synthesized, in which L1 and L2 were synthesized by in situ reactions. X‐ray diffraction analyses revealed that the 2D layer of complex 1 is built from a dinuclear CdII second building blocks, whereas complex 2 shows 0D structure, which is built based on two L1 ligands, one zinc ion, and two water molecules. 3 shows a 1D infinite rod‐shaped chain. Additionally, the solid‐state fluorescence properties for compound 1 and 2 are also presented.
Derivation and analysis of new stand‐level mortality models based on existing growth equations
Authors: Vassileva Stankova Tatiana , Diéguez‐Aranda Ulises
Published: February 2014

Considering that, the temporal trend in stocking, expressed as number of trees per unit area, is the opposite of that of growth, and that both trajectories are sigmoidal, we derived a temporal trajectory of density decrease by reversing the temporal trend of a generalized growth function. We derived and analysed twelve stand‐level mortality models by using four data sets from monospecific even‐aged stands. Stand dominant height rather than stand age was incorporated as an indicator of the growth stage and a careful examination of the models conformity with the essential logical properties of the stand‐level survival models was conducted. We first tested the models adequacy and general predictive performance by fitting them to parameterization data sets and subsequently assessing them with validation data. The regression equations were re‐fitted afterwards over the total data sets to make use of all available information in the final parameter estimates. Nine model formulations were successfully fitted and four of them were the most adequate in describing stand density decrease with dominant height growth. The site‐specific effect was incorporated in the newly derived models through the predictor variable and the stand‐specific starting density was accounted for through a specific model parameter. These new dominant height‐dependent mortality equations can be considered for inclusion in the framework of stand‐level growth models as transition functions.
The Lognormal Race: A Cognitive-Process Model of Choice and Latency with Desirable Psychometric Properties
Authors: Rouder Jeffrey N. , Province Jordan M. , Morey Richard D. , Gomez Pablo , Heathcote Andrew
Published: February 2014

We present a cognitive process model of response choice and response time performance data that has excellent psychometric properties and may be used in a wide variety of contexts. In the model there is an accumulator associated with each response option. These accumulators have bounds, and the first accumulator to reach its bound determines the response time and response choice. The times at which accumulator reaches its bound is assumed to be lognormally distributed, hence the model is race or minima process among lognormal variables. A key property of the model is that it is relatively straightforward to place a wide variety of models on the logarithm of these finishing times including linear models, structural equation models, autoregressive models, growth-curve models, etc. Consequently, the model has excellent statistical and psychometric properties and can be used in a wide range of contexts, from laboratory experiments to high-stakes testing, to assess performance. We provide a Bayesian hierarchical analysis of the model, and illustrate its flexibility with an application in testing and one in lexical decision making, a reading skill.
Synthesis and Tribological Properties of Air Plasma Polymerized Soybean Oil with N‐Containing Structures
Authors: Zhao Xiaoyun , Yang Jingyi , Tao Dehua , Xu Xinru
Published: February 2014

In this study, polymerized oils with different viscosity grades were synthesized by the polymerization of soybean oil (SO) in an air plasma environment. The results of the elemental analysis, infrared spectroscopy, and pyrolysis gas chromatography revealed that the carbonyl, organic amine, and nitrogen heterocyclic groups were incorporated into the molecule of the polymerized oil (PAIR9); the GPC chromatogram of this oil revealed that the product consisted of dimers and oligomers with higher molecular weights. The tribological behaviors of the polymerized oils were evaluated using a four‐ball friction and wear tester. The maximum non‐seizure loads of all the polymerized oils surpassed that of SO, and the PB value of PAIR9 reached 1,186 N. Meanwhile, PAIR9 exhibited much better anti‐wear performance when the tested loads were lower than 350 N. The worn surfaces lubricated by SO and PAIR9 were analyzed using the X‐ray photoelectron spectra (XPS). The results of the XPS analysis proved that during the frictional process, the polymerized oil could not only promote the adsorption of the oil on the metal surface because of the oxygen‐containing species (such as esters and carbonyl groups) with higher polarities but also promote the interactions with the metallic iron to form compact and stable tribochemical films containing organic nitrogen complexes.
Personality types during transition to young adulthood: How are they related to life situation and well‐being?
Authors: Leikas S. , Salmela‐Aro K.
Published: February 2014

The present longitudinal study examined personality types, their change, and their relations with life outcomes and well‐being in a sample of young Finns (N = 493) that was followed from age 15 to 23. The Big Five traits were measured at ages 20 and 23, and four personality types – Resilients, Overcontrollers, Anti‐Resilients, and “Averages” – emerged at both time points. Those with higher initial well‐being were more likely to be later classified as Resilients, whereas those with low and decreasing well‐being were more likely to be classified as Anti‐Resilients. At age 23, Anti‐Resilients were less likely to have reached normative educational goals than others, and more likely to be unemployed than others, but Overcontrollers were less likely to be in a romantic relationship than others. The results question the universality of the three‐type structure, but support the predictive validity of personality types.