bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geodesic finite elements on simplicial grids
Authors: Sander Oliver 
Published: June 2012

SUMMARYWe introduce geodesic finite elements as a conforming way to discretize partial differential equations for functionsv: Ω → M, where Ω is an open subset ofandMis a Riemannian manifold. These geodesic finite elements naturally generalize standard first‐order finite elements for Euclidean spaces. They also generalize the geodesic finite elements proposed ford = 1 in a previous publication of the author. Our formulation is equivariant under isometries ofMand, hence, preserves objectivity of continuous problem formulations. We concentrate on partial differential equations that can be formulated as minimization problems. Discretization leads to algebraic minimization problems on product manifoldsMn. These can be solved efficiently using a Riemannian trust‐region method. We propose a monotone multigrid method to solve the constrained inner problems with linear multigrid speed. As an example, we numerically compute harmonic maps from a domain intoS2. Copyright © 2012 John Wiley & Sons, Ltd.
Surface properties and thermal stability of a novel low‐surface‐energy polybenzoxazine/clay nanocomposites
Authors: Dong Huijie , Xin Zhong , Lu Xin , Qu Li 
Published: June 2012

AbstractA novel type of polybenzoxazine (PB‐m)/clay nanocomposites were prepared from 2‐bis (3‐methyl‐3,4‐dihydro‐2H‐1,3‐benzoxazinyl) propane (B‐m) and di‐methyl, di‐octadecyl ammonium chloride (DODMAC)‐modified clay. Surface properties and thermal stability of the PB‐m/clay nanocomposites were characterized by contact angle measurement and thermogravimetry (TGA), respectively. It was found that the PB‐m/clay nanocomposites possess the lowest surface free energy (15.27 mJ/m2) after 8 h curing at 210°C, which is even lower than that of poly (tetrafluoroethylene) (21.0 mJ/m2), and the presence of the clay in the B‐m PB‐m matrix enhances the stability of the surface energy at 210°C. FTIR results show that the intercalated structures of PB‐m/clay nanocomposites have no influence on the hydrogen‐bonding network of the PB‐m during curing. Combining with the results of atomic force microscope, it can be concluded that the stability of surface energies of the PB‐m/clay nanocomposites is mainly affected by the migration and masking of clay. Also, TGA results show that the addition of clay improves the thermal stability of PB‐m. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Effect of solution pH on crack initiation and propagation in glass‐polyester pipes subjected to impact
Authors: Stamenović M. , Putić S. , Medjo B. , Rakin M. , Zrilić M. 
Published: June 2012

AbstractThe objective of this study was the determination of the influence of alkaline and acidic solutions on the impact properties of glass‐polyester composite pipes. First, the impact test was performed on virgin samples (without the influence of any liquid) to obtain knowledge about the original material properties. Subsequently, the specimens were soaked in water and in alkaline and acidic solutions: sodium hydroxide, ammonium hydroxide, phosphoric acid, and nitric acid. The specimens were left in each liquid for 3, 10, 30, and 60 days at room temperature. The impact toughness and the crack initiation and propagation energies were recorded for all samples. A comparison of the results was made based on the pH values of the aggressive media, as well as based on the original impact properties and number of days of treatment. This way, the service life of pipes for transport of theexamined solutions could be predicted. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Effect of maleic anhydride grafted polypropylene compatibilizer on the morphology and properties of polypropylene/multiwalled carbon nanotube composite
Authors: Ezat G. S. , Kelly A. L. , Mitchell S. C. , Youseffi M. , Coates P. D. 
Published: June 2012

AbstractThe effect of maleic anhydride grafted polypropylene (MA‐g‐PP) compatibilizer on the mechanical and electrical properties of a polypropylene‐carbon nanotube composite is presented. Commercially available grades of polypropylene homopolymer (PP) and multiwalled CNT (MCNT) were used to prepare composites (PP/MCNT) by melt compounding. The effects of maleic anhydride graft level and loading on material properties were investigated. The addition of MCNT without compatibilizer enhanced the mechanical properties of PP, whereas addition of both grades of MA‐g‐PP alone had a detrimental effect. When MA‐g‐PP was added as a compatiblizer to the PP/MCNT composite, flexural and tensile moduli increased, indicating that enhanced levels of MCNT dispersion within PP had been achieved. Strength of the nanocomposite decreased with the addition of both grades of MA‐g‐PP, possibly due to the deterioration of the mechanical properties of the polymer in the presence of lower molecular weight MA‐g‐PP. Electrical resistivity improved with both grades of MA‐g‐PP, with higher maleic anhydride graft levels having the most significant effect. Scanning electron microscopy analysis confirmed that the optimum state of dispersion was for the nanocomposite prepared with MA‐g‐PP with highest grafting level. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Investigation of the nanoscale mechanical properties of carbon fiber/epoxy resin interphase. I. analysis of fiber‐stiffening effect during the nanoindentation process based on numerical simulation
Authors: Li Yanxia , Li Min , Gu Yizhuo , Zhang Zuoguang , Guan Peiqiang 
Published: June 2012

AbstractThe interphase in fiber reinforced polymer composites is a narrow region around the fiber with the thickness in nanoscale, and its properties have a significant effect on the composite mechanical properties. Nanoindentation method was widely accepted for the measurement of the interphase properites. Different from the homogenous material, the modulus diffence between fiber and matrix is very obvious, it is difficult to get the intrinsic properties of the interphase just depending on the experimental data due to the fiber‐stiffening effect. A numerical method is developed to simulate the nanoindentation process, to understand the fiber‐stiffening effect during the nanoindentation process in the carbon fiber/epoxy composites. The predicted results reveal that the fiber impacts the indentation response in the vicinity region of the fiber. When the indent contacts the fiber, there will be a mutation in the load–displacement curve, and the fiber‐stiffening effect is obvious, which is less affected by the thickness and modulus of the interphase and the resin matrix modulus. If the interphase thickness is smaller than the distance of indent contacting the fiber, it is nearly impossible to get the intrinsic modulus of the interphase due to the effect of fiber. On the other hand, if the interphase thickness is larger than that, in the near region about 100 nm away the indent contacting the fiber, the indentation response can reflect the difference of the interphase modulus. The gradient of the curve, that is, the indentation force varying with the distance from the fiber surface, decreases with the increase in the interphase modulus. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers
Synthesis of novel high oil‐absorption resins of poly(methyl methacrylate–butyl methacrylate) by surface‐initiated atom transfer radical polymerization using activators regenerated by electron transfer for efficient removal of oil
Authors: Ji Naiyi , Chen Hou , Zong Guangxi , Wang Dongju 
Published: June 2012

AbstractOil‐absorption resins are considered one of the effective materials to separate organic chemical compounds from oily water. In this work, well‐defined high oil‐absorption resins of poly(methyl methacrylate–butyl methacrylate) grafted onto silica gel were prepared by surface‐initiated atom transfer radical polymerization using activators regenerated by electron transfer mediated by FeCl3/iminodiacetic acid. The grafted polymers were grown in a controlled manner. By considering the effect of different polymerization conditions, we prepared novel high oil‐absorption resins. The chemical structures of the resins were determined by Fourier transform IR spectroscopy. SEM and TGA were also used to characterize the resins. It was found that the resins had good heat‐resistant quality, higher oil absorbency and better oil retention and regeneration properties. The resins can absorb 31.2 g g−1 for tricholoromethane and 23.3 g g−1 for toluene. Copyright © 2012 Society of Chemical Industry
Immobilization of catalases on amidoxime polyacrylonitrile nanofibrous membranes
Authors: Feng Quan , Wang Qingqing , Tang Bin , Wei Anfang , Wang Xueqian , Wei Qufu , Huang Fenglin , Cai Yibing , Hou Dayin , Bi Songmei 
Published: June 2012

AbstractAmidoxime polyacrylonitrile (AOPAN) nanofibrous membranes were generated by the reaction between electrospun polyacrylonitrile nanofibrous membranes and hydroxylamine hydrochloride. AOPAN nanofibrous membranes were further modified by Fe(III) chelation for immobilizing catalases with coordination bonds. The surface morphologies of the nanofibrous membranes and immobilized catalases were observed by field emission scanning electron microscopy. Chelation of Fe(III) onto AOPAN nanofibrous membranes was studied by the Langmuir isothermal adsorption model. It was found that the maximum amount of coordinated Fe(III) (qm) was 4.5045 mmol g−1 (dry nanofibrous membranes) and the binding constant (Kl) was 0.0698 L mmol−1. The amounts of immobilized enzymes were determined by the method of Bradford. Kinetic parameters were analyzed for both immobilized and free catalases. The value of Vmax (7122.6 µmol mg−1 min−1) for the immobilized catalases was smaller than that for the free catalases (9203.2 µmol mg−1 min−1), and the Km for the immobilized catalases was larger. The immobilized catalases showed better resistance to pH and temperature change than the free catalases, and the storage stability of immobilized catalases was higher than that of free catalases. As for reusability, the immobilized catalases retained 71% of their activity after eight repeated uses. © 2012 Society of Chemical Industry
Photodegradation of azo‐dyes in aqueous solution by polyacrylonitrile nanofiber mat‐supported metalloporphyrins
Authors: Shao Linjun , Xing Guiying , Lv Weixi , Yu Huijun , Qiu Mingxi , Zhang Xian‐Man , Qi Chenze 
Published: June 2012

AbstractElectrospinning has been employed to fabricate uniform polyacrylonitrile and polyacrylonitrile copolymer nanofiber mats supporting metalloporphyrins (MTPP; M: Zn(II), Cu(II), Ni(II), Co(II), Fe(III) and Pd(II); TPP: meso‐tetraphenylporphyrin). The nanofiber mat‐supported metalloporphyrins are shown as efficient photocatalysts for the degradation of various azo‐dyes in aqueous solutions under visible light irradiation. The effect of transition metals on azo‐dye photodegradation has been examined. The nanofiber mat‐supported copper–porphyrin and iron–porphyrin complexes are among the most effective photocatalysts for azo‐dye degradation. Immobilization of the metalloporphyrins onto the nanofiber mats greatly facilitates the recovery and reuse of the expensive and toxic photocatalysts. Most interestingly, there are no significant degradations of the photocatalytic activities of the recycled photocatalysts. © 2012 Society of Chemical Industry
Wide bandgap Cu(In,Ga)Se2 solar cells with improved energy conversion efficiency
Authors: Contreras Miguel A. , Mansfield Lorelle M. , Egaas Brian , Li Jian , Romero Manuel , Noufi Rommel , Rudiger‐Voigt Eveline , Mannstadt Wolfgang 
Published: June 2012

ABSTRACTWe report on improvements to the energy conversion efficiency of wide bandgap (Eg > 1.2 eV) solar cells on the basis of CuIn1−xGaxSe2. Historically, attaining high efficiency (>16%) from these types of compound semiconductor thin films has been difficult. Nevertheless, by using (a) the alkaline‐containing high‐temperature EtaMax glass substrates from Schott AG, (b) elevated substrate temperatures of 600–650 °C, and (c) high vacuum evaporation from elemental sources following National Renewable Energy Laboratory's three‐stage process, we have been able to improve the performance of wider bandgap solar cells with 1.2 < Eg < 1.45 eV. The current density–voltage (J–V) data we present includes efficiencies >18% for absorber bandgaps of ~1.30 eV and efficiencies of ~16% for bandgaps up to ~1.45 eV. In comparing J–V parameters in similar materials, we establish gains in the open‐circuit voltage and, to a lesser degree, the fill factor value, as the reason for the improved performance. The higher voltages seen in these wide gap materials grown at high substrate temperatures are due to reduced recombination. We establish the existence of random and discrete grains within the CIGS absorbers that yield limited or no generation/collection of minority carriers. We also show that interfacial recombination is the main mechanism limiting additional enhancements to open‐circuit voltage and therefore performance. Solar cell results, absorber materials characterization, and experimental details and discussion are presented. Copyright © 2012 John Wiley & Sons, Ltd.
Fabrication of grid type dye sensitized solar modules with 7% conversion efficiency by utilizing commercially available materials
Authors: Wei Tzu‐Chien , Lan Jo‐Lin , Wan Chi‐Chao , Hsu Wen‐Chi , Chang Ya‐Huei 
Published: June 2012

ABSTRACTA process to fabricate a parallel connection dye‐sensitized solar cell (DSSC) module has been developed using commercially available materials and screen printed silver grid. The process is not only simple but also easy to manipulate and therefore facilitates researchers in evaluating new materials in a module platform. By changing the design of the silver grid pattern, it was found that the performance of DSSC modules can be controlled. With the silver grid, DSSC modules have shown that a 7% conversion efficiency can be reached. Modules fabricated by this process, but with a non‐volatile electrolyte system, passed a 60 °C, 1000 h thermal aging test. Copyright © 2012 John Wiley & Sons, Ltd.
Highly Skilled Migration: What Differentiates the ‘Brains’ Who Are Drained from Those Who Return in the Case of Greece?
Authors: Labrianidis Lois , Vogiatzis Nikos 
Published: June 2012

ABSTRACTThe migration of highly educated population (brain drain) poses extremely significant impacts on origin countries' development, especially in cases in which, owing to their economic and social structures, these countries cannot promote the efficient allocation of their professionals. At the same time, the decision of those migrants to return home or remain abroad is affected by several factors. This paper aims to analyse this phenomenon by using primary data collected from Greece. Our findings indicate that it is not reasonable to expect that a large share of these people is likely to return, especially given the ongoing economic and social crises that further exacerbate the observed mismatch between supply and demand for a highly educated workforce in the country. These empirical results can assist the formulation of specific policy measures in order to reap the benefits of those individuals' presence abroad, which can undoubtedly enhance the developmental prospects of European countries. This study constitutes the first one on brain drain from Greece, while it is also the first study to compare highly skilled migrants who still work abroad to those who have returned. Copyright © 2012 John Wiley & Sons, Ltd.
The choice of the exchange‐correlation functional for the determination of the jahn–teller parameters by the density functional theory
Authors: Andjelković Ljubica , Gruden‐Pavlović Maja , Daul Claude , Zlatar Matija 
Published: June 2012

AbstractThe Jahn–Teller (JT) parameters for small, aromatic, organic radicals, CnHn (n = 4–7), bis(cyclopentadienyl)cobalt(II) (cobaltocene), a sodium cluster (Na3), a silver cluster (Ag3), the hexaflurocuprate(II) ion ([CuF6]4−), and tris(acetylacetonato)manganese(III) ([Mn(acac)3]) have been evaluated by the means of the multideterminantal density functional theory using the most common approximations, to clarify which type of exchange‐correlation functional should be used in analysis of the JT effect. The results are compared with available experimental and theoretical data. The choice of the functional strongly depends on the chemical system at hand, but to obtain fast and qualitatively reliable results, the local density approximation may be taken as satisfactory, regardless of the diversity of the systems prone to a JT distortion. © 2012 Wiley Periodicals, Inc.
Docking between natural peroxides and heme group by parametric method 6
Authors: Leite Franco Henrique Andrade , de Mesquita Carneiro José Walkimar , de Araujo Martha Teixeira , Comar Moacyr , Taranto Alex Gutterres 
Published: June 2012

AbstractArtemisinin (Qinghaosu) is a sesquiterpene lactone with an endoperoxide function being currently used against strains of Plasmodium falciparum. These compounds are supposed to act on heme leading to reduction of the peroxide bond and production of radicals that can kill the parasite. The main goal of this study was the identification of new potential antimalarial drugs from natural sources as well as to find possible correlations between in silico parameters and experimental data. Thus, the interactions of 51 peroxides with heme were studied by molecular docking following refinement by conformational analysis and semiempirical parametric method 6. As a result, correlation between complex energy and dissociation constant (Kd) was found to be significant. The results indicate that compounds 5 and 24 are promising antimalarial agent. © 2012 Wiley Periodicals, Inc.
Proteomic analysis of salt‐responsive ubiquitin‐related proteins in rice roots
Authors: Liu Chih‐Wei , Hsu Yu‐Kai , Cheng Yu‐Hsiang , Yen Hung‐Chen , Wu Yung‐Pei , Wang Chang‐Sheng , Lai Chien‐Chen 
Published: June 2012

RATIONALEUbiquitination of proteins plays an important role in regulating a myriad of physiological functions in plants such as xylogenesis, senescence, cell cycle control, and stress response. However, only a limited number of proteins in plants have been identified as being ubiquitinated in response to salt stress. The relationships between ubiquitination and salt‐stress responses in plants are not clear.METHODSRice (Oryza sativa) seedlings from the same genetic background with various salt tolerances exposed to salt stress were studied. The proteins of roots were extracted then analyzed using western blotting against ubiquitin. Differentially expressed ubiquitinated proteins were identified by nanospray liquid chromatography/tandem mass spectrometry (nano‐LC/MS/MS) and quantified by label‐free methods based on the Exponentially Modified Protein Abundance Index (emPAI) and on the peak areas of XIC spectra derived from ubiquitinated peptides. In addition, we performed a gel‐based shotgun proteomic analysis to detect the ubiquitinated proteome that may be involved in response to salt stress.RESULTSThe expressions of ubiquitination on pyruvate phosphate dikinase 1, heat shock protein 81–1, probable aldehyde oxidase 3, plasma membrane ATPase, cellulose synthase A catalytic subunit 4 [UDP‐forming] and cyclin‐C1‐1 were identified and compared before and after salt treatment. The functions of those ubiquitinated proteins were further discussed for defence against salt stress. In addition, a large number of ubiquitinated proteins were successfully identified as well in this study.CONCLUSIONSThe ubiquitination of proteins affected the protective mechanisms in rice seedlings to resist the salt stress during the initial phase. The findings in the present study also demonstrate that the regulated mechanisms through protein ubiquitination are important for rice seedlings against salt stress. Copyright © 2012 John Wiley & Sons, Ltd.
Identification of the unknown transformation products derived from clarithromycin and carbamazepine using liquid chromatography/high‐resolution mass spectrometry
Authors: Calza P. , Medana C. , Padovano E. , Giancotti V. , Baiocchi C. 
Published: June 2012

RATIONALEA comprehensive study of the environmental fate of pollutants is more and more required, above all on new contaminants, i.e. pharmaceuticals. As high‐resolution mass spectrometry (HRMSn) may be a suitable analytical approach for characterization of unknown compounds, its performance was evaluated in this study.METHODSThe analyses were carried out using liquid chromatography (LC) (electrospray ionization (ESI) in positive mode) coupled with a LTQ‐Orbitrap analyzer. High‐resolution mass spectrometry was employed to assess the evolution of the drug transformation processes over time; accurate masses of protonated molecular ions and sequential product ions were reported with an error below 5 millimass units, which guarantee the correct assignment of their molecular formula in all cases, while their MS2 and MS3 spectra showed several structurally diagnostic ions that allowed characterization of the different transformation products (TPs) and to distinguish the isobaric species.RESULTSThe simulation of phototransformation occurring in the aquatic environment and identification of biotic and abiotic transformation products of the two pharmaceuticals were carried out in heterogeneous photocatalysis using titanium dioxide, aimed to recreate conditions similar to those found in the environmental samples. Twenty‐eight main species were identified after carbamazepine transformation and twenty‐nine for clarithromycin.CONCLUSIONSThis study demonstrates that HRMS, combined with LC, is a technique able to play a key role in the evaluation of the environmental fate of pollutants and allows elucidation of the transformation pathways followed by the two drugs. Copyright © 2012 John Wiley & Sons, Ltd.
Observation of ion coalescence in Orbitrap Fourier transform mass spectrometry
Authors: Gorshkov Mikhail V. , Fornelli Luca , Tsybin Yury O. 
Published: June 2012

RATIONALESimilar to other mass spectrometric technologies based on ion trapping in a spatially restricted area, the performance of Orbitrap Fourier transform mass spectrometry (FTMS) is affected by the interaction between the trapped ion clouds. One of the effects associated with Coulombic interaction inside the ion trap is the ion cloud coupling, known in ion cyclotron resonance (ICR) FTMS as coalescence, or a phase‐locking phenomenon. Nevertheless, the direct observation of ion coalescence has not been reported for Orbitrap FTMS yet.METHODSWe have performed experiments on ion coalescence with a pair of isobaric peptides in the state‐of‐the‐art hybrid linear ion trap high‐field compact Orbitrap Elite FT mass spectrometer using both standard and advanced signal processing modes.RESULTSFor the instrument configuration employed in this work we found that ion coalescence occurs when two singly charged peptides with the mass difference of 22 mDa and molecular weight of about 1060 Da have the total abundance of at least 7.5*104 charges.CONCLUSIONSWe experimentally demonstrate the existence of the ion coalescence phenomenon in Orbitrap FTMS for peptides for a wide range of total trapped ion population. Using the applicable modeling of the phase‐locking threshold we estimate the effect of ion coalescence on the performance of Orbitrap FTMS. Copyright © 2012 John Wiley & Sons, Ltd.