bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Imaging Strategies for Assessment of Cerebrovascular Involvement
Authors: Tang Cheuk Ying , Narula Jagat , Friedman Joseph I. 
Published: December 2012

AbstractThere is an important correlation between vascular risk factors and nonspecific imaging findings in the brain such as white‐matter hyperintensities. These vascular risk factors are also associated with dementia and lesser forms of cognitive impairment. One hypothesis is that these vascular risk factors lead to disruption of connective networks in the central nervous system that are supported by myelinated white‐matter fibers, which in turn lead to deficits in functional signaling between various brain regions. Another possibility is an alteration of the neurovascular coupling due to vascular risk factors. This reduced functional signaling contributes to the cognitive deficits in persons harboring these vascular risk factors. Lifestyle changes may restore some of these functional deficits through brain plasticity. It is imperative that preclinical diagnostic techniques are developed to identify these early brain changes in persons harboring vascular risk factors, as such efforts may improve primary and secondary prevention efforts. Recently developed imaging techniques may provide objective imaging biomarkers to measure the structural and functional brain changes in persons with vascular risk factors and resulting subclinical atherosclerotic disease. This article reviews a few of these novel imaging techniques. Mt Sinai J Med 79:674–682, 2012. © 2012 Mount Sinai School of Medicine
Generation of large finite‐element matrices on multiple graphics processors
Authors: Dziekonski A. , Sypek P. , Lamecki A. , Mrozowski M. 
Published: December 2012

SUMMARYThis paper presents techniques for generating very large finite‐element matrices on a multicore workstation equipped with several graphics processing units (GPUs). To overcome the low memory size limitation of the GPUs, and at the same time to accelerate the generation process, we propose to generate the large sparse linear systems arising in finite‐element analysis in an iterative manner on several GPUs and to use the graphics accelerators concurrently with CPUs performing collection and addition of the matrix fragments using a fast multithreaded procedure. The scheduling of the threads is organized in such a way that the CPU operations do not affect the performance of the process, and the GPUs are idle only when data are being transferred from GPU to CPU. This approach is verified on two workstations: the first consists of two 6‐core Intel Xeon X5690 processors with two Fermi GPUs: each GPU is a GeForce GTX 590 with two graphics processors and 1.5 GB of fast RAM; the second workstation is equipped with two Tesla C2075 boards carrying 6 GB of RAM each and two 12‐core Opteron 6174s. For the latter setup, we demonstrate the fast generation of sparse finite‐element matrices as large as 10 million unknowns, with over 1 billion nonzero entries.Comparing with the single‐threaded and multithreaded CPU implementations, the GPU‐based version of the algorithm based on the ideas presented in this paper reduces the finite‐element matrix‐generation time in double precision by factors of 100 and 30, respectively. Copyright © 2012 John Wiley & Sons, Ltd.
Investigation of elastic constants of polymer/nanoparticles composites using the brillouin spectroscopy and the mechanical homogenization modeling
Authors: Maurice Gérard , Rouxel Didier , Vincent Brice , Hadji Rachid , Schmitt Jean‐François , Taghite M'barek , Rahouadj Rachid 
Published: December 2012

AbstractA numerical model using homogenization techniques is proposed to simulate the evolution of elastic properties of nanocomposite polymer‐nanoparticles, depending on the concentration of nanoparticles and the rigidity of the particle–matrix interface. To validate this model, it was confronted to several physical systems having different interface behavior, the nanocomposite systems: poly(vinylidene fluoride trifluoroethylene)/Al2O3 (alumina nanoparticles incorporated into copolymer of vinylidene difluoride and trifluoroethylene to form nanocomposite), PMMA/CNT (carbon nanotube/poly(methyl methacrylate) composite) and PMMA/SiO2 with nanoparticles with or without surface treatment of silanization. For all these systems, the Young's modulus (nanoparticles and matrix) has been obtained experimentally from the elastic modulus C11 obtained by Brillouin spectroscopy. These macroscopic measurements coupled with the theoretical model allow a multiscale approach of the elastic behavior of nanocomposite systems, providing information on the global elastic properties of polymer‐nanoparticle material, and also indications about the strength of physical and chemical bonds between the nanoparticles and the matrix. Our results validate the hypothesis of the crucial role of the interface module, provided by numerical simulation which shows that incorporation of nanoparticles may lead to a strengthening or a weakening of the matrix. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.
Effect of molding condition and pellets material on the weld property of injection molded jute/polylactic acid
Authors: Wang Cuntao , Uawongsuwan Putinun , Yang Yuqiu , Hamada Hiroyuki 
Published: December 2012

AbstractNatural fibers such as jute fiber and biodegradable poly(lactic acid) (PLA) polymer are very good choices for environmental friendly material. Multi‐gate injection is often used to meet the demand of mass production of injection moldings, therefore weld line is inevitable. The presence of weld lines not only detracts from the surface quality but also significantly reduces the mechanical strength of injection‐molded parts. Although it is not always easy to completely eliminate weld lines, the weld strength could be improved through suitable adjustment of molding conditions such as melt temperature, mold temperature, hold pressure, injection speed, and so on. In this study, three kinds of pellets materials were prepared: long fiber pellets (LFT), the re‐compounding pellets (RP), and LFT50:RP50 hybrid mixtures (LFT/RP). Tensile test was carried out to investigate the effect of different pellets and holding pressures on the mechanical property of welded jute/PLA specimens. And the interfacial shear strength of non‐welded jute/PLA specimens was calculated with Kelly‐Tyson Formula. Fiber separation and fiber dispersion in RP became better than that of LFT which resulted in a better interfacial property. Weld strength of RP and hybrid LFT/RP specimens was improved by 43.34% and 16.46% than that of LFT specimen, respectively. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Color changes due to thermal ageing and artificial weathering of pigmented and textured ABS
Authors: Iannuzzi Giovanna , Mattsson Britta , Rigdahl Mikael 
Published: December 2012

AbstractAcrylonitrile–butadiene–styrene copolymers (ABS) are known to be sensitive towards ageing which can lead to color changes, primary interest in this study. The color changes were expressed in terms of the CIELAB color system. ABS plaques were subjected to heat ageing and artificial weathering. Uncolored ABS and dark gray colored specimens were employed. The pigmented ABS plaques were also imposed with different surface textures. In general, the uncolored material suffered from the most severe discoloration and the artificial weathering produced the strongest effect. For both types of specimens, a clear yellowing took place. Both the pigment system and the surface texture affected the color development during the ageing test. The latter can be of significant importance in certain applications when components with different surface textures are placed adjacent to each other. The surface micro‐hardness increased with increasing ageing time and its change followed that of the discoloration. Chemical changes of the surface layers were characterized by FTIR and were in accordance with results reported in the literature; i.e., an increase of the bands associated with carbonyl groups with increasing ageing time and a decrease of the bands associated with the polybutadiene phase clearly indicated chemical degradation due to ageing treatments. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers
Sensitization of zinc oxide photoanode with an indoline dye
Authors: Onwona‐Agyeman Boateng , Nakao Motoi , Kumara Gamaralalege Rajanya Asoka , Karunarathne Sedari Mudiyanselage Migara Lakshitha , Anuradha Sepalage Gaveshana , Dematage Nilupulee 
Published: December 2012

ABSTRACTA dye‐sensitized solar cell (DSC) made of nanoporous ZnO film on aluminum‐doped zinc oxide (ZnO/AZO) transparent substrate has higher solar‐to‐electric energy conversion efficiency than a DSC consisting of nanoporous ZnO film deposited on conventional fluorine‐doped tin oxide (ZnO/FTO) transparent substrate. The ZnO/AZO DSC gave an overall conversion efficiency of 7.2% whereas the ZnO/FTO yielded a conversion efficiency of 4.5%. The film‐substrate orientation and higher light harvesting of the nanoporous ZnO film on the AZO after heating in air are mainly attributed to the higher energy conversion efficiency of the ZnO/AZO DSC. Copyright © 2012 John Wiley & Sons, Ltd.
Photostimulated detection of defect formation in BaF2 under irradiation of synchrotron radiation
Authors: Watanabe Masayuki , Azuma Junpei , Asaka Shuji , Tsujibayashi Toru , Arimoto Osamu , Nakanishi Shunsuke , Itoh Hiroshi , Kamada Masao 
Published: December 2012

AbstractWe have investigated the defect formation processes of BaF2 single crystals under vacuum ultraviolet radiation with the use of combination spectroscopy of synchrotron radiation (SR) and laser. The defect formation efficiency was measured as a function of excitation photon energy of SR by means of a laser‐induced luminescence method. It was found that the efficiency depends significantly on the excitation photon energy. We show that the dependence can be explained in terms of the diffusive motion of hot conduction electrons generated by the photoexcitation. The relationship between the defect formation and the energy relaxation of core excitons is also discussed.
Effect of external pressure on Tc of as‐grown and thermally treated superconducting Rbx Fe2–ySe2 single crystals
Authors: Kanagaraj M. , Krzton‐Maziopa A. , Kalai Selvan G. , Pomjakushina E. , Conder K. , Weyeneth S. , Puzniak R. , Arumugam S. 
Published: December 2012

AbstractWe report on the effect of external pressure on the superconducting transition temperature (Tc) of as‐grown and thermally treated single crystals of superconducting iron chalcogenide Rb0.85Fe1.9Se2. The superconducting transition temperature of 27.1 K at ambient pressure for the as‐grown sample was found to increase up to 33.2 K for the sample annealed for 3 h at 215 °C in vacuum. An increase of Tc up to 28.2 K was observed for the as‐grown sample at a pressure of 0.83 GPa. For all the studied crystals, annealed in the temperature range between 215 °C and 290 °C, the external pressure seems to decrease the superconducting transition temperature and a negative pressure coefficient of Tc was observed. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Gate‐controlled metal–insulator transition in the LaAlO3/SrTiO3 system with sub‐critical LaAlO3 thickness
Authors: Lee Joon Sung , Seung Sang Keun , Lee Seung Ran , Chang Jung‐Won , Noh Hyunho , Baasandorj Lkhagvasuren , Shin Hyun Sup , Shim Seung‐Bo , Song Jonghyun , Kim Jinhee 
Published: December 2012

AbstractWe studied the electrical conduction in the LaAlO3/SrTiO3 (LAO/STO) interface electron system with a sub‐critical LAO layer thickness of ∼3.5 unit cells (uc). It was found that the true dividing point between metallic and insulating behaviour without gating lies near the LAO thickness of 3.5 uc. Our marginally metallic 3.5 uc sample showed a sharp transition to insulating state at temperatures which strongly depended on the applied negative back‐gate voltage. The superior gate‐controllability of the sample was attributed to its sheet carrier density which was an order of magnitude lower than those of conducting LAO/STO samples with 4 uc or more of LAO layers. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Measurement of δ18O values in arsenic and selenium oxyanions
Authors: Larese‐Casanova Philip , Blake Ruth E. 
Published: December 2012

RATIONALEPast stable isotopic studies of selenium and arsenic oxyanions within a biogeochemistry context have focused solely on selenium isotopes due to monoisotopic nature of arsenic and lack of attention to oxygen. A modern quantification method of δ18O values in selenate, selenite, arsenate, and arsenite is presented here, similar to methods for other inorganic oxyanions such as phosphate.METHODSDissolved oxyanions were recovered after precipitation with silver or barium cations within controlled pH ranges and purified by drying and roasting under vacuum. Oxygen isotope ratio measurements were performed on 250–450 micrograms of solids using continuous flow high‐temperature conversion elemental analyzer/isotope ratio mass spectrometry (CF‐TCEA/IRMS). Each Se and As solid was evaluated for reproducibility and stability of δ18O values and the usefulness of this method for evaluating aqueous phase Se and As oxyanion reactions was addressed.RESULTSOnly silver arsenate and barium selenate were shown to have stable, reproducible δ18O values over 5 months and were calibrated to the VSMOW scale. The method was applied to confirm complete exchange of oxygen isotopes between arsenate and solvent water at pH 7 which produced an O‐isotope fractionation between arsenate and water of 6.0‰. Furthermore, the method revealed the ability of oxygen in selenate to kinetically fractionate during reduction to elemental selenium by a green rust compound which produced a fractionation (20.9‰) larger than reported δ80/76Se values for similar reactions.CONCLUSIONSThe experimental and analytical conditions for δ18O analysis of Se and As oxyanions were detailed. δ18O analyses of As and Se oxyanions may be useful in biogeochemical studies for tracing chemical reaction pathways, determining environmental sources of Se, or diagnosing specific reaction mechanisms for As and Se oxyanions. Copyright © 2012 John Wiley & Sons, Ltd.
Discrimination of cyclic and linear oligosaccharides by tandem mass spectrometry using collision‐induced dissociation (CID), pulsed‐Q‐dissociation (PQD) and the higher‐energy C‐trap dissociation modes
Authors: Przybylski Cédric , Bonnet Véronique 
Published: December 2012

RATIONALECarbohydrates have essential functions in living organisms and cells, but, due to the presence of numerous linkage combinations, substituent sites and possible conformations, they are the class of biomolecules which exhibits the huge structural diversity found in nature. Thereby, due to such diversity and poor ionization, their structural deciphering by mass spectrometry is still a very challenging task.METHODSHere, we studied a series of linear and cyclic neutral oligosaccharides using electrospray with collision‐induced dissociation (CID), pulsed‐Q‐dissociation (PQD) and the higher‐energy C‐trap dissociation (HCD) feature of a linear ion trap Orbitrap hybrid mass spectrometer (LTQ‐Orbitrap). The collision energy necessary to obtain 50% fragmentation (CE50 values) in CID, PQD and HCD was used to correlate both size and structures.RESULTSThe default settings for activation time and/or activation Q are the most appropriate, except for HCD, where 100 ms instead of 30 ms gave more intense fragment ions. PQD exhibits a 2–8‐fold lower sensitivity than CID. HCD provides signals closer or slightly superior by 1.5‐fold than PQD, and offers a more balanced ion distribution through the spectrum. Furthermore, HCD offers the possibility to make fine adjustments of the energy via the eV scale to further increase the yield of low‐mass fragments.CONCLUSIONSThe complementarity of CID, PQD and HCD was clearly demonstrated by obtaining structural information on hexa‐, hepta‐ and octasaccharides. Together, these results clearly indicate the usefulness of the CID/HCD pair for further structural deciphering, and analysis of more complex structures such as multi‐antennary carbohydrates or glycoconjuguates alone or in mixture. Copyright © 2012 John Wiley & Sons, Ltd.
Study on noncovalent complexes of alkaloids with DNA duplex using electrospray ionization mass spectrometry
Authors: Ma Lei , Song Fengrui , Liu Zhiqiang , Liu Shuying 
Published: December 2012

RATIONALEDNA is an important molecular target in modern medicine research. Some DNA‐binding ligands have been used to treat numerous diseases. Therefore, understanding the interactions of different ligands with DNA and looking for new DNA agents are necessary to develop new drugs.METHODSElectrospray ionization mass spectrometry (ESI‐MS) in the negative ion mode was used to screen the noncovalent complexes between 11 alkaloids with double helix oligonucleotides at molar ratios 1:1 to 1:4. The relative binding affinities based on the fraction of bound DNA and sequence selectivities of alkaloids towards the duplex were also investigated by ESI‐MS. Moreover, tandem mass spectrometry of 5‐charged complex ions was used to try to determine DNA‐binding modes.RESULTSSix alkaloids showed complexation with the selected DNA duplex, i.e., berberine, coptisine, peimine, aconitine, oxysophoridine and cytisine. They showed their binding affinities with d(AACTCCCGGCACAC/GTGTGCCGGGAGTT) in the order of berberine > coptisine > peimine > aconitine, oxysophoridine > cytosine; additional experiments involving collision energy proved this result. Sequence selectivities were not apparent for coptisine, peimine, aconitine and oxysophoridine with four DNA duplexes. The complexes containing berberine and coptisine underwent the predominant loss of the G base. However, for complexes containing the other four alkaloids, they dissociated via the loss of neutral drug. The results confirmed that they may have different binding modes.CONCLUSIONSAccording to experiment data and structural information, the binding mode of individual drugs with DNA was speculated. It was noted that the bindings of alkaloids peimine, aconitine and oxysophoridine with DNA are discovered firstly. This may give a clue to design duplex‐binding ligands and be helpful for understanding biological activities of these alkaloids. Copyright © 2012 John Wiley & Sons, Ltd.
Development of high‐pressure probe electrospray ionization for aqueous solution
Authors: Rahman Md. Matiur , Chen Lee Chuin , Hiraoka Kenzo 
Published: December 2012

RATIONALEProbe electrospray ionization (PESI) is a recently developed method that uses a sharp solid needle as electrospray emitter and the sample is loaded to the needle tip by repetitive movement of the needle probe. This method has been previously used for the analysis of sample with high salt concentration and real‐world samples without sample pretreatment. Although PESI is also applicable to aqueous solution, the ion signal stability and reproducibility were not satisfactory due to the spontaneous occurrence of corona discharge taking place on the metallic needle tip.METHODSIn the previous version of PESI, the ionization was performed under an open environment, thus ambient condition such as humidity and the presence of environmental contaminant also affected the performance of PESI. In this paper, we report a modified version of PESI in which the electrospray and the desolvation of charged droplets are performed inside an enclosed chamber which is pressurized to >1 atm with dry air.RESULTSUnder a super atmospheric condition, the dielectric strength of the ambient gas was enhanced and stable electrospray could to be initiated without the occurrence of corona discharge even for liquid sample with high surface tension such as pure water. A comparative study of atmospheric‐pressure PESI and high‐pressure PESI (HP‐PESI) had been performed to demonstrate the improvement of PESI in sensitivity and signal stability for the detection analytes in aqueous solution.CONCLUSIONSHP‐PESI offers a higher sensitivity and signal stability over PESI due to the absence of gaseous breakdown, better desolvation, and higher ion sampling rate by the mass spectrometer. Copyright © 2012 John Wiley & Sons, Ltd.
Identification of low molecular weight organic acids by ion chromatography/hybrid quadrupole time‐of‐flight mass spectrometry during Uniblu‐A ozonation
Authors: Amorisco Apollonia , Locaputo Vito , Pastore Carlo , Mascolo Giuseppe 
Published: December 2012

RATIONALEThe balance of organic nitrogen and sulfur during ozonation of organic pollutants often shows a lack of complete mineralization. It follows that polar and ionic by‐products are likely to be present that are difficult to identify by liquid chromatography/mass spectrometry (LC/MS).METHODSThe structural elucidation of low molecular weight organic acids arising from Uniblu‐OH ozonation has been investigated by ion chromatography/electrospray tandem mass spectrometry (IC/ESI‐MS/MS) employing a quadrupole time‐of‐flight mass spectrometer. Unequivocal elemental composition of the by‐products was determined by a combination of mass accuracy and high spectral accuracy.RESULTSThe employed identification strategy was demonstrated to be a powerful method of unequivocally assigning a single chemical composition to each identified compound. The exact mass measurements of [M–H]– ions allowed the elemental formulae and related structures of eighteen by‐products to be determined confidently. The main degradation pathways were found to be decarboxylation and oxidation. The experimental procedure allowed the identification of both nitrogen‐ and sulfur‐containing organic acid by‐products arising from Uniblu‐OH ozonation.CONCLUSIONSThe obtained results are of environmental relevance for the balance of organic nitrogen and sulfur during the ozonation of organic pollutants due to the lack of complete mineralization of the compounds containing these atoms. Copyright © 2012 John Wiley & Sons, Ltd.
Exploration of CP12 conformational changes and of quaternary structural properties using electrospray ionization traveling wave ion mobility mass spectrometry
Authors: Kaaki Wassim , Woudstra Mireille , Gontero Brigitte , Halgand Frédéric 
Published: December 2012

RATIONALECP12 is a small chloroplast protein involved in the Benson‐Calvin cycle. Since it was demonstrated that the CP12 protein shared different conformational properties between reduced and oxidized states we took advantage of the segregational properties of the Traveling Wave Ion Mobility (TWIM) guide to study subtle conformational changes related to redox changes.METHODSElectrospray ionization mass (ESI‐MS) spectra of the CP12 protein were recorded in the positive ion mode using an ESI source fitted on a quadrupole time‐of‐flight (QToF) hybrid mass spectrometer equipped with a TWIM cell (Synapt HDMS G1, Waters Corp., Manchester) under non‐denaturing conditions. Non‐covalent experiments were performed using the same instrument without the use of the TWIM device.RESULTSWhatever the CP12 form studied, our results showed that CP12 protein was represented by two conformers in equilibrium that displayed very slight differences. These observations led us to propose that CP12 protein structure is rather undergoing transient subtle structural changes than having two different conformational populations in solution. In addition, using non‐denaturing experiments, NAD and CP12 stoichiometry were determined with respect to the GAPDH tetramer and the redox state of CP12.CONCLUSIONSIn this study we showed that the use of the segregational property of the ion mobility (TWIM, Synapt G1 HDMS, Waters, Manchester, UK) allowed differentiation of subtle conformational changes between redox states of the CP12 protein. Standard non‐denaturing experiments revealed different binding stoichiometry according to the redox state of the CP12 protein. Copyright © 2012 John Wiley & Sons, Ltd.