bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simulation of Rate Dependent Plasticity of Polymers
Authors: Shaban Ahmed , Mahnken Rolf 
Published: January 2007

AbstractPolycarbonate is an amorphous polymer which exhibits nonlinear deformation before failure. It shows a pronounced strength‐differential effect between compression and tension. Strain rate influences the mechanical response of the polycarbonate. In particular, the yield stress is increased with increasing strain rate. The concept of stress mode dependent weighting function is used in the proposed model to simulate the asymmetric effects for different loading speeds. In this concept, an additive decomposition of the flow rule is assumed into a sum of weighted stress mode related quantities. The characterization of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of the mode angle, such that stress mode dependent scalar weighting functions can be constructed. The resulting evolution equations are updated using a backward Euler scheme and the algorithmic tangent operator is derived for the finite element equilibrium iteration. The numerical implementation of the resulting set of constitutive equations is used in a finite element program for parameter identification. The proposed model is verified by showing a good agreement with the experimental data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the Springback of Sheet Metals at Large Deformations
Authors: Vladimirov Ivaylo N. , Reese Stefanie 
Published: January 2007

AbstractSheet metal forming simulations are increasingly replacing traditional build‐and‐break prototyping because they provide a less expensive and more rapid way to speed up product design time while improving quality and performance. Sheet metal is subjected to stretching, bending and unbending during forming, and an accurate prediction of the formability and springback of the sheet necessitates the use of an appropriate constitutive model.Use of isotropic hardening alone has been identified as a source of inaccurate springback prediction. In order to be able to describe the cyclic hardening behaviour and the Bauschinger effect, a large‐deformation elasto‐plastic material model with non‐linear kinematic hardening is discussed in the present work. The model is derived from a thermodynamical framework and is based on the multiplicative split of the deformation gradient. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vibrations and heating of inelastic solids under harmonic loading
Authors: Zhuk Yaroslav 
Published: January 2007

AbstractTwo problem statements for the investigation of the thermomechanical behavior of inelastic materials under harmonic loading are developed. The “complete” problem statement consists of universal balance equations of thermodynamics and constitutive equations derived from the general thermodynamic theory of viscoplastic solids with internal state variables. An approximate problem statement is derived by the application of modified harmonic linearizing technique to the complete system of equations. Thereby the subsystem of mechanical equations is formulated in the complex‐value form and material properties are described by means of amplitude‐dependent complex‐value moduli. The problems of vibration and dissipative heating of physically nonlinear solids are formulated. The main thermomechanical characteristics are analyzed for some classes of problems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preparative isolation and purification of geniposide from gardenia fruits by centrifugal partition chromatography
Authors: Kim Chul Young , Kim Jinwoong 
Published: January 2007

AbstractThe iridoid glycoside, geniposide was purified by centrifugal partition chromatography (CPC) with a two‐phase solvent system composed of ethyl acetate:isopropanol:water (3:2:5, v/v) from an 80% methanolic extract of fruits of Gardenia jasminoides. Preparative CPC yielded 56.2 mg of geniposide in a one‐step separation of 500 mg of extract, with a purity of 95% as determined by HPLC. Isolated geniposide was identified from its 1H‐NMR, 13C‐NMR and MS spectra. Copyright © 2006 John Wiley & Sons, Ltd.
Reprocessing acrylonitrile–butadiene–styrene plastics: Structure–property relationships
Authors: Bai Xiaojuan , Isaac D.H. , Smith K. 
Published: January 2007

AbstractAcrylonitrile–butadiene–styrene (ABS) plastics from computer equipment housings have been reprocessed, some under various conditions of temperatures and shearing rates and others for multiple numbers of cycles. Structural changes in these reprocessed materials were investigated by infrared spectroscopy (FTIR), gel permeation chromatography, and dynamic mechanical thermal analysis. Gas chromatography/mass spectrometry was used to analyze extracts from the ABS plastics. These studies were related to measurements of the mechanical properties of the reprocessed materials, and the fracture surfaces were examined using scanning electron microscopy. It was found that impact strength was much more significantly affected than tensile properties by reprocessing. Within the range of reprocessing parameters studied, temperature had a more significant effect than shear rate on mechanical properties. Significant reductions in impact strength and slight increases in stiffness and strength, particularly following reprocessing at the highest temperature of 270°C and multiple reprocessing, were linked to loss of small molecules (including lubricants), degradation (crosslinking and scission) of the rubber phase, and changes in the morphology seen in the fracture surfaces. POLYM. ENG. SCI., 47:120–130, 2007. © 2007 Society of Plastics Engineers
Immobilized Me2Si(C5Me4)(N‐tBu)TiCl2/(nBuCp)2ZrCl2 hybrid metallocene catalyst system for the production of poly(ethylene‐co‐hexene) with pseudo‐bimodal molecular weight and inverse comonomer distribution
Authors: Hong Sung Chul , Mihan Shahram , Lilge Dieter , Delux Lourant , Rief Ursula 
Published: January 2007

AbstractMe2Si(C5Me4)(N‐tBu)TiCl2, (nBuCp)2ZrCl2, and Me2Si(C5Me4)(N‐tBu)TiCl2/(nBuCp)2ZrCl2 catalyst systems were successfully immobilized on silica and applied to ethylene/hexene copolymerization. In the presence of 20 mL of hexene and 25 mg of butyloctyl magnesium in 400 mL of isobutane at 40 bar of ethylene, Me2Si(C5Me4)(N‐tBu)TiCl2 immobilized catalyst afforded poly(ethylene‐co‐hexene) with high molecular weight ([η] = 12.41) and high comonomer content (%C6 = 2.8%), while (nBuCp)2ZrCl2‐immobilized catalyst afforded polymers with relatively low molecular weight ([η] = 2.58) with low comonomer content (%C6 = 0.9%). Immobilized Me2Si(C5Me4)(N‐tBu)TiCl2/(nBuCp)2ZrCl2 hybrid catalyst exhibited high and stable polymerization activity with time, affording polymers with pseudo‐bimodal molecular weight distribution and clear inverse comonomer distribution (low comonomer content for low molecular weight polymer fraction and vice versa). The polymerization characteristics and rate profiles suggest that individual catalysts in the hybrid catalyst system are independent of each other. POLYM. ENG. SCI., 47:131–139, 2007. © 2007 Society of Plastics Engineers
Development of wood‐substituted composites from highly filled polybenzoxazine–phenolic novolac alloys
Authors: Rimdusit Sarawut , Kampangsaeree Natcha , Tanthapanichakoon Wiwut , Takeichi Tsutomu , Suppakarn Nitinat 
Published: January 2007

AbstractHighly filled wood‐substituted composites from matrices based on polymer alloys of benzoxazine resin (BA‐a) and phenolic novolac resin using Hevea brasiliensis woodflour as a filler were developed. The results reveal that phenolic novolac resin can significantly reduce the curing temperature of the neat benzoxazine resin, thereby minimizing the degradation of woodflour filler during processing. The limiting oxygen indices (LOIs) of all the BP alloys were above the self‐extinguishable limit i.e. >26. In addition, the LOI values were found to moderately increase whereas the rate of burning decreased as the novolac fraction in the resin mixtures increased. Furthermore, a solvent resistance experiment and thermogravimetric analysis revealed that the suitable phenolic novolac content should not exceed 20 wt%, to avoid the presence of unreacted phenolic in the alloy networks. The outstanding mechanical performance of the resulting wood composites is attributed to the strong interfacial interaction between the BP alloys and the woodflour filler. POLYM. ENG. SCI., 47:140–149, 2007. © 2007 Society of Plastics Engineers
Polymerization of vinyl compounds in the presence of perfluoroisopropenyl ester
Authors: Narita Tadashi , Hamana Hiroshi , Sekiya Fumiaki , Nojima Yasuyuki 
Published: January 2007

AbstractTo report a new polymerization reaction phenomenon, this article examines the polymerization of butyl vinyl ether and N‐vinylcarbazole in the presence of 2‐benzoxypentafluoropropene [CF2C(CF3)OCOC6H5 or BPFP]. The homopolymer of butyl vinyl ether was produced in the presence of a catalytic amount of BPFP in high yields. N‐Vinylcarbazole, which is a monomer well‐known for producing its homopolymer under cationic polymerization conditions, also yielded its homopolymer in the presence of BPFP. It was concluded that some cationic species would be yielded by the addition of BPFP. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 908–910, 2007.
Crystal‐state 3D‐structural characterization of novel, Aib‐based, turn and helical peptides
Authors: Crisma Marco , Andreetto Erika , De Zotti Marta , Moretto ALessandro , Peggion Cristina , Formaggio Fernando , Toniolo Claudio 
Published: January 2007

AbstractThe crystal‐state conformations of the hexapeptide amide Pht‐(Aib)6‐NH‐C(CH3)2‐O‐OtBu (7), the hexapeptide Ac‐L‐aIle‐(Aib)5‐OtBu (6), the pentapeptide Z‐(Aib)3‐L‐Glu(OtBu)‐Aib‐O‐(CH2)2‐(1)Nap (5), the tetrapeptides Z‐(Aib)2‐L‐His(Nτ‐Trt)‐Aib‐OMe (4 I) and Z‐(Aib)2‐L‐Nva‐Aib‐OtBu (4 II), the tripeptide Pyr‐(Aib)3‐OtBu (3 I), the dipeptide amides Pyr‐(Aib)2‐(4)NH‐TEMPO (3 II) and Piv‐(Aib)2‐NH‐C(CH3)2‐O‐OtBu (3 III), and the dipeptides Pht‐Aib‐βAc6c‐OtBu (2 I), Pht‐Aib‐NH‐C(CH3)2‐O‐OtBu (2 II) and Boc‐gGly‐mAib‐OH (2 III) have been determined by X‐ray diffraction analyses. All peptides investigated are characterized by one or more turn/helix forming Aib residues. Except the three short dipeptides, all are folded into CO···HN intramolecularly H‐bonded 310‐helices, or into various types of β‐turns. In the structure of 6, two independent molecules of opposite screw sense were observed in the asymmetric unit, generating diastereomeric 310‐helices. Copyright © 2007 European Peptide Society and John Wiley & Sons, Ltd.
Effect of Ca doping on the structure and scintillation properties of ZnWO4
Authors: Kraus H. , Mikhailik V. B. , Vasylechko L. , Day D. , Hutton K. B. , Telfer J. , Prots Yu. 
Published: January 2007

AbstractThe future application of ZnWO4 scintillator in a cryogenic search for rare events is the motivation for optimization of this material. We present results on the effect of Ca doping on the structure and scintillation properties of ZnWO4. X‐ray diffraction analysis revealed that there is no mixing in the CaWO4–ZnWO4 pseudobinary system due to a significant mismatch of the crystal structures of CaWO4 and ZnWO4. The lattice parameters of Ca‐doped ZnWO4 samples obtained from X‐ray powder diffraction data confirmed this finding. It is also shown that ZnWO4 retains the monoclinic wolframite structure when cooling, at 12 K exhibiting the following lattice parameters: a = 4.6826(2) Å, b = 5.7088(2) Å, c = 4.9230(2) Å and β = 90.541(2)°. The scintillation light yield of the Zn1−x Cax WO4 was measured using the multi‐photon counting technique and it is found that small concentrations of Ca (x = 0.001 – 0.02) cause no deterioration of this parameter. Ca doping of ZnWO4 is expected to facilitate production of a single‐crystalline scintillator. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An analysis of the resonant tunneling‐time based on the presence‐time formalism
Authors: del Barco O. 
Published: January 2007

AbstractWe analyze the tunneling‐time of a spatial wave packet which traverses a resonant structure by means of the presence‐time formalism. With this method we can evaluate the finite size effects of the corresponding energy probability distribution in the tunneling‐time. We show that these effects are not negligible and reduce the tunneling‐time by 25%. An expression for the resonant tunneling‐time is derived, 3ħ/2Γr, where Γr is the width of the resonance. We confirm numerically this result for two resonant structures: a superlattice with n cells and square‐barrier periodic potential, and an asymmetrical rectangular double‐barrier potential. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Blue‐shifted H‐bond in aromatic sulfines: An ab initio calculation
Authors: Roohi H. , Machiabadi B. 
Published: January 2007

AbstractThe intramolecular CH···OS H‐bond in the aromatic sulfines, HRCSO, was analyzed by NBO and QTAIM methods. The results of QTAIM analysis at the MP2/aug‐cc‐pVDZ level of theory show that the CH···OS H‐bond meets all the characteristics of an improper, blue shift hydrogen bond. NBO analysis at the MP2/6–31++G(d,p)//MP2/aug‐cc‐pVDZ level predicts a normal relationship between change of bond length and CH rehybridization. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007
Using hooves for high‐resolution isotopic reconstruction of bovine dietary history
Authors: Harrison Sabine M. , Zazzo Antoine , Bahar Bojlul , Monahan Frank J. , Moloney Aidan P. , Scrimgeour Charlie M. , Schmidt Olaf 
Published: January 2007

AbstractThe objective of this study was to ascertain whether sequential sampling and isotopic analysis of bovine hooves could be used to reconstruct the dietary history of cattle. A controlled, on‐farm experiment was conducted in which cattle were switched from a barley‐based diet to an isotopically different diet incorporating maize, urea and seaweed (the isotopic spacing between diets was 13.6‰ for δ13C and 8.0‰ for δ15N) and maintained on that diet for 168 days. Postmortem sampling of the cleaned anterior wall of the lateral, left front claw was carried out on five individuals using a micro‐drilling technique. From the first 60 mm of each claw, up to 41 samples with a spacing between them of less than 1 mm were collected. Bands were less than 1 mm deep and had a mean width of 1.2 mm. The hoof keratin showed a rapid increase followed by a slower increase in its δ13C and δ15N values following the diet switch, suggesting that C and N in hoof keratin originate from more than one pool. However, the response of the N isotope composition of the hoof was somewhat delayed compared with that of C. Estimated mean hoof growth rates for these cattle were 10.5 ± 2.3 mm per month and 6.7 ± 1.0 mm per month (±SD, n = 5) when receiving the barley‐based transition diet and the maize‐based experimental diet, respectively. These values are considerably higher than previous estimates obtained by visual methods and they suggest that diet may have a greater influence on hoof growth rates than seasonality. These results demonstrate that hooves are a suitable incremental tissue for high‐resolution isotopic reconstruction of the dietary history of bovine animals. Copyright © 2007 John Wiley & Sons, Ltd.
Quality management and method Validation in EDXRF analysis
Authors: Álvarez R. Padilla , Markowicz A. , Wegrzynek D. , Cano E. Chinea , Bamford S. A. , Torres D. Hernández 
Published: January 2007

AbstractOwing to the increased demands from society for reliable/certified analytical results, x‐ray fluorescence laboratories face an urgent need for quality management system (QMS) implementation, in particular complying with the general requirements for the competence of testing and calibration laboratories of the latest approved ISO standard (ISO/IEC 17025: 2005). Some specific features of energy dispersive x‐ray fluorescence (EDXRF) techniques require a careful interpretation of some concepts related to method validation and quality control. This paper presents some thoughts on how to assess the traceability of the results and to evaluate the characteristics of performance of the analytical methods, including linearity, working range, precision, trueness and detection limits. Typical examples of EDXRF analytical techniques are provided for illustration, as well as some recommendations to quantify the uncertainty of the results. Copyright © 2007 John Wiley & Sons, Ltd.
Reactions to dating violence among Latino teenagers: An experiment utilizing the Articulated Thoughts in Simulated Situations paradigm
Authors: Rayburn Nadine Recker , Jaycox Lisa H. , McCaffrey Daniel F. , Ulloa Emilio C. , Zander‐Cotugno Megan , Marshall Grant N. , Shelley Gene A. 
Published: January 2007

AbstractDating violence is a serious problem among adolescents and young adults. Understanding teens’ reactions to dating violence offers the potential to understand the factors that lead to perpetration of violent behavior and to elucidate prevention strategies. Knowledge concerning youth attitudes about dating violence is limited, and has largely come from self‐report questionnaires to date. We utilized the Articulated Thoughts in Simulated Situations (ATSS) paradigm to assessing Latino teens’ reactions to dating violence. Forty‐one 9th grade students were presented with four simulated dating violence scenarios, and articulated their thoughts in response to them. Teens’ reactions to dating violence differed on a variety of dimensions as a function of their gender, the gender of the perpetrator, and familiarity with the perpetrator.
Using C++ to Write Automation Controller Software
Authors: Berman Russell T. 
Published: January 2007

The object-oriented programming language C++ is extremely well suited for writing automation control software. Because it is object-oriented, C++ provides elegant mechanisms for developing reusable interfaces. For example, programmers can leverage off-the-shelf graphics or communication packages, or they can instead develop their own libraries. Additionally, end users have the possibility of extending the functionality of their control software by developing their own device drivers or Laboratory Information Management System (LIMS) interfaces. Because C++ provides mechanisms for multithreading, programmers can use it to implement dynamic scheduling algorithms. Event-driven scheduling is often favored above static scheduling because it results in higher instrument utilization and provides better error-handling facilities.
Usability in the Lab: Techniques for Creating Usable Products
Authors: Barrington Sarah 
Published: January 2007

Laboratory automation and instrumentation vendors frequently claim usability among their long lists of features and benefits—but can they justify that claim? What makes a product usable and how do you design for usability? This article outlines an approach used to create usable products in other application areas, such as eCommerce and medical device development, and suggests that a similar approach could provide benefits for users and developers alike in the field of laboratory automation. The user-centered design process is summarized, together with a set of usability heuristics that can be applied during the design process and used to evaluate usability during development.
Meta‐analysis of six‐month memantine trials in Alzheimer's disease
Authors: Doody Rachelle Smith , Tariot Pierre N. , Pfeiffer Eric , Olin Jason T. , Graham Stephen M. 
Published: January 2007

BackgroundClinical trials have suggested benefits of memantine for all stages of Alzheimer's disease (AD). A meta‐analysis of memantine trials in outpatients with probable AD was conducted.MethodsSix randomized, placebo‐controlled trials fulfilled inclusion criteria. Cognitive, global, functional, behavioral, and safety measures were evaluated by using fixed or random effects models. Sensitivity analysis was performed to determine potential effects of disease severity and concomitant cholinesterase inhibitor use.ResultsOverall, memantine showed statistically significant, homogenous benefits on global and functional outcomes and statistically significant but heterogeneous benefit on cognition. In pooled moderate to severe AD studies, effects were significant and homogeneous on global, functional, and behavioral measures; in pooled mild to moderate studies, significant and homogeneous effects were found on global rating and cognition. Safety profiles suggested excellent safety and tolerability, with no differences between the severity groups.ConclusionsMemantine consistently benefited patients in all stages of AD and was well‐tolerated.
Early Pleistocene climate changes in the central Mediterranean region as inferred from integrated pollen and planktonic foraminiferal stable isotope analyses
Authors: Joannin Sébastien , Quillévéré Frédéric , Suc Jean-Pierre , Lécuyer Christophe , Martineau François 
Published: January 2007

AbstractVegetation inherited from a Pliocene subtropical climate evolved through obliquity oscillations and global cooling leading to modern conditions. An integrated, highly time-resolved record of pollen and stable isotopes (δ18O and δ13C of Globigerina bulloides) was obtained to understand vegetation responses to Early Pleistocene climate changes. Continental and marine responses are compared in the Central Mediterranean region with a particular consideration of environmental changes during anoxic events.Pollen data illustrate vegetation dynamics as follows: [1] development of mesothermic elements (warm and humid conditions); [2] expansion of mid- and high-altitude elements (cooler but still humid conditions); and [3] strengthening of steppe and herb elements (cooler and dry conditions). These successions correlate with precession. δ18O variations recorded by Globigerina bulloides define two cycles (MIS 43-40) related to obliquity. At northern low- to mid-latitudes, the pollen signal records temperature and wetness changes related to precession even during global climate changes induced by obliquity. This may result in unexpected increasing wetness during glacial periods, which has to be considered specific to the Central and Eastern Mediterranean region. Lastly, an analysis of anoxic events reveals that enhanced runoff is indicated by increasing frequency of the riparian trees Liquidambar and Zelkova.
Infrared Observations of Seyfert Galaxies and Quasars
Authors: G Neugebauer  
Published: January 2007

The infrared energy distributions of the Seyfert galaxies apparently contain three components: a galactic stellar component, a thermal component from heated dust, plus a nonthermal component. The appearance of the infrared energy distribution depends on which component dominates. There is also a correlation observed between the infrared energy distribution and the Khachikian Weedman class.
Preliminary data on bright quasars are given. The infrared energy distributions generally increase into the infrared with a power law slope of ∼ 1. In detail they differ from power laws with a significant fraction emitting most of their energy near 3 μm. No differences in radio loud and radio quiet are obvious from the infrared energy distributions. The variability of the quasars in the infrared is generally correlated with the variability in the visible, although significant exceptions have been observed.