bluuebunny/crossref_metadata_2025_split huggingface dataset:
Speed‐ and topography‐dependent boundary friction characteristics of steel
Authors: Aoki Saiko , Suzuki Akihito , Masuko Masabumi 
Published: June 2010

AbstractA novel tribometer that undergoes significant changes at ultra‐slow (>5.0 µm s−1) to moderate (<20 cm s−1) sliding speeds was developed in order to study the friction‐speed characteristics of steel lubricated with oil. Three different surface topographies were applied to the specimens, and the friction characteristics with an additive‐free base oil (MO91) and a stearic acid‐formulated oil (StA/MO91) were studied to understand the effects of surface textures on the lubrication performance of an adsorbed molecular layer formed by StA. Friction reduction behaviour of the adsorbed layer observed in the transverse direction was attributed to microscopic hydrodynamic action that maintained the load‐carrying performance of the adsorbed layer. Copyright © 2010 John Wiley & Sons, Ltd.
Biodegradable and Electroactive TEMPO‐Substituted Acrylamide/Lactide Copolymers
Authors: Zhuang Xiuli , Zhang Han , Chikushi Natsuru , Zhao Changwen , Oyaizu Kenichi , Chen Xuesi , Nishide Hiroyuki 
Published: June 2010

AbstractCopolymers composed of PLA and PTAm were prepared by a macromonomer approach. The PLA bearing vinyl group at chain end was copolymerized with 2,2,6,6‐tetrametylpiperidine‐4‐ylacrylamide. The resulted copolymers were oxidized by a peroxide to give PTAm‐g‐PLA. The structures of the copolymers were confirmed by NMR and FTIR spectroscopy. The comparison of 1H NMR results and SQUID measurements demonstrated that the oxidation of the PTAm fragment proceeded almost to completion. An MTT assay, cell adhesion and spreading evaluation showed that the copolymers exhibited improved cytocompatibility as compared to the PTAm homopolymer due to the introduction of the biocompatible PLA moiety.magnified image
Vinyl‐Type Polymerization of Alkylester‐Substituted Norbornenes Without Endo/Exo Separation
Authors: Müller Kerstin , Jung Youngsuk , Yoon Do Y. , Agarwal Seema , Greiner Andreas 
Published: June 2010

AbstractThe vinyl‐type homo‐ and copolymerization of 9‐norborn‐5‐en‐2yl‐nonane acid ethyl ester and 2‐hexyl‐5‐norbornen was investigated. Both monomers were polymerized using di‐µ‐chlorobis(6‐methoxybicyclo[2.2.1]hept‐2‐ene‐endo‐5σ,2π)palladium(II) and AgSbF6 as catalysts. Poly(2‐hexyl‐5‐norbornene) is soluble in common organic solvents and has a Tg of 252 °C. Poly(9‐norborn‐5‐en‐2yl‐nonane acid ethyl ester) shows swelling in solvents like THF, chlorobenzene or chloroform and has a Tg of 136 °C. The solubility of the copolymers depends on the amount of 9‐norborn‐5‐en‐2yl‐nonane acid ethyl ester. E‐modulus measurements of copolymers with different amounts of ester showed an increase of flexibility when increasing the content of 9‐norborn‐5‐en‐2yl‐nonane acid ethyl ester in the copolymer. magnified image
Electrospinning of Continuous Aligning Yarns with a ‘Funnel’ Target
Authors: Afifi Amalina M. , Nakano Shigeyuki , Yamane Hideki , Kimura Yoshiharu 
Published: June 2010

AbstractA new electrospinning set‐up is described for continuous aligning of poly(L‐lactide) yarn. It comprises a slowly rotating grounded ‘funnel’ target and a winder placed right up to the funnel. A charged polymer jet is ejected from a nozzle. The electrospun fibers are first accumulated on the mouth plane of the funnel to form a web. The web is then pulled upward and guided to a winder on which twisted fibers are continuously wound as a bundle. Each filament of the bundle is slanted at about 45° relative to the collecting direction, and its average diameter is 6.0 ± 1.9 µm. The drawn fiber shows improved tensile properties as a result of the increased molecular orientation. The morphologies of the twisted fibers before and after drawing are compared.magnified image
Preparation and Subsequent Shaping of Cellulose Acetates Using Ionic Liquids
Authors: Kosan Birgit , Dorn Susann , Meister Frank , Heinze Thomas 
Published: June 2010

AbstractThe acetylation of cellulose in ionic liquids (ILs) and the subsequent dry/wet spinning of these processing solutions were investigated. The homogeneous acetylation in ILs was carried out using different molar ratios of acetic anhydride to the anhydroglucose unit (AGU). The obtained solutions of cellulose acetates were characterised analytically by means of rheological methods. DS and $\overline {DP}$ of the prepared cellulose acetates were determined. Furthermore the processing solutions of the acetylation were shaped by means of a dry/wet spinning process to fibres with varied properties. The resulting fibre properties were discussed in consideration of the DS and in comparison with unsubstituted cellulose fibres.magnified image
Towards Nanowriting on Plastics: Dip‐Pen Nanolithography of Acrylamido‐Functionalized Oligonucleotides on Polystyrene
Authors: Turri Stefano , Torlaj Luca , Levi Marinella 
Published: June 2010

AbstractModel high density DNA arrays have been realized by direct deposition with Dip‐Pen Nanolithography of acrylamido‐functionalized oligonucleotides (23‐mer) on spin‐coated, flat polystyrene surfaces. A highly specific interaction between the acrylamide end functionality and polystyrene was found. The surface morphology of the model array was studied by atomic force microscopy (AFM). Spots are clearly seen both in topography and demodulation modes. The array withstands the hybridization process with label free, complementary oligonucleotides and the following cleaning procedures. The final AFM characterization showed significant changes especially in demodulation images which may be an indication that molecular recognition between complementary oligos has occurred.magnified image
PNIPAM Copolymers Containing Light‐Responsive Chromophores: A Method Toward Molecular Logic Gates
Authors: Jochum Florian D. , Forst F. Romina , Theato Patrick 
Published: June 2010

AbstractA series of thermo‐responsive PNIPAM copolymers containing different amounts of fulgimide moieties has been synthesized via a polymer analogous reaction of poly(pentafluorophenyl acrylate). All copolymers were designed to exhibit a lower critical solution temperature (LCST) in water, which was only weakly dependent on the amount of incorporated chromophoric fulgimide groups. The copolymers showed a photocyclization of the fulgimide side groups upon irradiation with UV‐light accompanied with a color change. The closed form of the chromophore had a halftime of 136 min for the visible reisomerization and did not affect the LCST of the polymer. This led to the realization of a logic “NOT A” for the fulgimide containing PNIPAM, while a corresponding azobenzene containing PNIPAM resulted in a different logic “A implies B”.magnified image
Recyclable Spherical Polyelectrolyte Brushes Containing Magnetic Nanoparticles in Core
Authors: Chen Kaimin , Zhu Yan , Li Li , Lu Yan , Guo Xuhong 
Published: June 2010

AbstractSpherical polyelectrolyte brushes consisting of a magnetite/polystyrene nanocomposite core and a poly(acrylic acid) brush shell were prepared by photo‐emulsion polymerization. They are narrowly dispersed, superparamagnetic and redispersible after aggregating by external magnetic field, as determined by transmission electron microscopy, dynamic light scattering, thermal gravimetric analysis and a vibrating sample magnetometer. Magnetic control is thus introduced into nano‐sized spherical polyelectrolyte brushes to achieve recovery and controllable delivery in applications. This approach opens up the way for cost‐effective applications of spherical polyelectrolyte brushes.magnified image
Describing the Structure of a Randomly Hyperbranched Polymer
Authors: Konkolewicz Dominik , Gray‐Weale Angus , Perrier Sébastien 
Published: June 2010

AbstractThis paper describes random branching theory, a model for the solution structure of hyperbranched polymers. In this model, the hyperbranched polymer is assumed to be composed of units whose structure is simpler than the resulting polymer. These simple units can have any structure of chemical functionality, from monomers to linear chains or spherical particles. This paper outlines how this theory is constructed, describes the underlying assumptions and parameters, and summarizes the most basic form. It is shown how variations in the parameters change the behavior of the model, and described how to fit an experimental data series. This demonstrates how the model can be used to fit other data series, and how it can be used as a test for whether a polymer is randomly hyperbranched.magnified image
Single nucleotide polymorphisms in the hypoxia‐inducible factor‐1 gene and colorectal cancer risk
Authors: Knechtel Gudrun , Szkandera Joanna , Stotz Michael , Hofmann Günter , Langsenlehner Uwe , Krippl Peter , Samonigg Hellmut , Renner Wilfried , Langner Cord , Dehchamani Dadbeh , Gerger Armin 
Published: June 2010

AbstractWith an incidence of about 300 000 new cases colorectal cancer (CRC) is the second leading cause of cancer‐related death in Europe and the United States. Environmental and genetic factors influence CRC risk. Hypoxia‐inducible factor‐1 (HIF‐1), a heterodimeric protein composed of two subunits, HIF‐1 alpha and HIF‐1 beta, plays a critical role in oxygen homeostasis and is involved in angiogenesis and cell proliferation. The gene for the HIF‐1 alpha subunit (HIF1A) carries two common missense mutations—P582S (rs11549465) and A588T (rs11549467)—which both have been related to increased trans‐activation capacity of HIF1A. In our case–control study we investigated the association between these polymorphisms and CRC risk. We investigated 381 patients with histologically confirmed CRC and 2156 control subjects. HIF1A genotypes were determined by exonuclease (TaqMan) assays. For determination of microvessel density (MVD) tumor sections were stained using a mouse monoclonal antibody recognizing the pan‐endothelial marker CD31. In a multivariate logistic regression analysis including age and sex neither the HIF1A 582S allele (Odds ratio: 1.204; 95% confidence interval 0.911–1.592; P = 0.193) nor the 588T allele was significantly associated with CRC (Odds ratio: 0.851; 95% confidence interval 0.444–1.631; P = 0.626). However, in an exploratory analysis, the HIF1A 588T allele was associated with tumor localization (P = 0.016) and tumor size (P = 0.003). MVD was similar in tumors of patients carrying HIF1A 588T allele and patients without this rare allele. We conclude that functional polymorphisms in the HIF1A gene do not modify CRC risk but maybe associated with clinic‐pathological features of the disease. © 2010 Wiley‐Liss, Inc.
Differential expression of nucleostemin, a stem cell marker, and its variants in different types of brain tumors
Authors: Malakootian Mahshid , Mowla Seyed Javad , Saberi Hooshang , Asadi Malek Hossein , Atlasi Yaser , Shafaroudi Afsaneh Malekzadeh 
Published: June 2010

AbstractNucleostemin (NS) is implicated in the control of stem and cancer cell proliferation. In the present study, we have examined the expression of NS and its spliced variants in various brain tumors. Total RNA was extracted from 59 brain tumor samples, and the expression of different NS spliced variants was measured by semi‐quantitative RT‐PCR. The subcellular distribution of NS protein in brain tumors was further examined by immunohistochemistry. Furthermore, to decipher the potential involvement of NS in brain tumorogenesis, its expression was knocked‐down by means of RNA interference (RNAi) in two malignant glioma (U‐87MG and A172), one astrocytoma (1321N1) and one medulloblastoma (DAOY) cell lines. The alterations in cell‐cycle progression of the treated cells were then analyzed by flow cytometry. Our data revealed that NS and its variants are widely expressed in different types of brain tumors. Among the NS spliced variants, variant “1” and variant “3” were detected in the majority of tumor samples, whereas variant “2” was only detectable in few samples. Moreover, the intensity of the expression was correlated with the grade of the tumors (P < 0.05). Accordingly, the expression was much higher in glial tumors compared to that of meningiomas. As expected, a nucleolar/nucleoplasmic localization of NS protein was observed in the examined tumor samples. RNAi results revealed a significant reduction of NS expression along with a moderate blockade of the cell cycle in G2/M and S phases of NS‐siRNA treated cells. All in all, our data suggest a potential role for NS in tumorogenesis of brain cancers. © 2010 Wiley‐Liss, Inc.
A simple low‐SAR technique for chemical‐shift selection with high‐field spin‐echo imaging
Authors: Ivanov Dimo , Schäfer Andreas , Streicher Markus N. , Heidemann Robin M. , Trampel Robert , Turner Robert 
Published: June 2010

AbstractWe have discovered a simple and highly robust method for removal of chemical shift artifact in spin‐echo MR images, which simultaneously decreases the radiofrequency power deposition (specific absorption rate). The method is demonstrated in spin‐echo echo‐planar imaging brain images acquired at 7 T, with complete suppression of scalp fat signal. When excitation and refocusing pulses are sufficiently different in duration, and thus also different in the amplitude of their slice‐select gradients, a spatial mismatch is produced between the fat slices excited and refocused, with no overlap. Because no additional radiofrequency pulse is used to suppress fat, the specific absorption rate is significantly reduced compared with conventional approaches. This enables greater volume coverage per unit time, well suited for functional and diffusion studies using spin‐echo echo‐planar imaging. Moreover, the method can be generally applied to any sequence involving slice‐selective excitation and at least one slice‐selective refocusing pulse at high magnetic field strengths. The method is more efficient than gradient reversal methods and more robust against inhomogeneities of the static (polarizing) field (B0). Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Rapid multislice imaging of hyperpolarized 13C pyruvate and bicarbonate in the heart
Authors: Lau Angus Z. , Chen Albert P. , Ghugre Nilesh R. , Ramanan Venkat , Lam Wilfred W. , Connelly Kim A. , Wright Graham A. , Cunningham Charles H. 
Published: June 2010

AbstractHyperpolarization of spins via dynamic nuclear polarization (DNP) has been explored as a method to non‐invasively study real‐time metabolic rocesses occurring in vivo using 13C‐labeled substrates. Recently, hyperpolarized 13C pyruvate has been used to characterize in vivo cardiac metabolism in the rat and pig. Conventional 3D spectroscopic imaging methods require in excess of 100 excitations, making it challenging to acquire a full cardiac‐gated, breath‐held, whole‐heart volume. In this article, the development of a rapid multislice cardiac‐gated spiral 13C imaging pulse sequence consisting of a large flip‐angle spectral‐spatial excitation RF pulse combined with a single‐shot spiral k‐space trajectory for rapid imaging of cardiac metabolism is described. This sequence permits whole‐heart coverage (6 slices, 8.8‐mm in‐plane resolution) in any plane, allowing imaging of the metabolites of interest, [1‐ 13C] pyruvate, [1‐ 13C] lactate, and 13C bicarbonate, within a single breathhold. Pyruvate and bicarbonate cardiac volumes were acquired, while lactate images were not acquired due to low lactate levels in the animal model studied. The sequence was demonstrated with phantom experiments and in vivo testing in a pig model. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Fast methods for determining instabilities of elastic–plastic damage models through closed‐form expressions
Authors: Xue Liang , Belytschko Ted 
Published: June 2010

AbstractFast methods for determining the onset of instability for elastic–plastic damage models under multiaxial loading conditions are developed. On the basis of the general Hadamard instability criterion, we derive a closed‐form expression to determine the onset of instability, the bifurcation directions and the polarization vector. The results of the present analytical method are compared with solutions using a numerical minimization method. Excellent agreement and significantly faster computations are achieved for the onset of instability and the directions of the instability mode and the polarization vector when using these new methods. Copyright © 2010 John Wiley & Sons, Ltd.
A symmetric weak form of Biot's equations based on redundant variables representing the fluid, using a Helmholtz decomposition of the fluid displacement vector field
Authors: Hörlin N.‐E. 
Published: June 2010

AbstractA novel symmetric weak formulation of Biot's equations for linear acoustic wave propagation in layered poroelastic media is presented. The primary variables used are the frame displacement, the acoustic pore pressure, the scalar potential and the vector potential obtained from a Helmholtz decomposition of the fluid displacement. Also a symmetric weak form based on the frame displacement, the pore pressure and the fluid displacement is obtained as an intermediate result. hp finite element simulations of a double leaf partition based on this new weak formulation is verified against simulation results from the classical frame displacement, fluid displacement formulation and a frame displacement pore pressure formulation. All three formulations simulated, displays the same rate of convergence with respect to finite element bases polynomial degree. The novel formulation also extends a previously published frame displacement, pore pressure, scalar fluid displacement potential formulation with an implicit irrotational fluid displacement assumption to a full representation of Biot's equations. Copyright © 2010 John Wiley & Sons, Ltd.
A case of valgus ankle in an early Pleistocene hominin
Authors: DeSilva J. M. , Papakyrikos A. 
Published: June 2010

AbstractBipedal locomotion is a defining character of the hominin lineage. A skeletal correlate of bipedality is a perpendicularly oriented tibia relative to the plane of the ankle joint, positioning the foot directly under the centre of mass. Non‐human primates, in contrast, possess a tibial shaft that tilts laterally away from the plane of the ankle joint (valgus ankle), which positions the foot in inversion and is adaptive for arboreal climbing. KNM‐ER 2596 is a small distal tibia from 1.9 mya sediments at Koobi Fora, Kenya. Though it possesses some morphologies functionally linked to bipedality, such as an expanded metaphysis, it also possesses a valgus tilt to the ankle. We test the competing hypotheses that the KNM‐ER 2596 tibia is from a cercopithecoid, a non‐human hominoid, or a pathological hominin. A survey of the orthopaedic literature and a comparative study of modern human and non‐human primate tibiae support the hypothesis that KNM‐ER 2596 is from a hominin. In order to investigate the non‐phylogenetic causes of valgus ankle, we examined human skeletal tibiae with valgus tilt secondary to fracture of the distal fibula. Untreated breaks of the lower third portion of the fibula during childhood can result in a valgus tilt to the distal tibia and occasionally other peculiar morphologies found in the KNM‐ER 2596 tibia such as a superoinferiorly atrophied medial malleolus. The morphology of this tibia is incompatible with hypotheses that it is from a cercopithecoid or a hominoid, and instead, we suggest that KNM‐ER 2596 belonged to a hominin that may have suffered a fracture of the lower left fibula as a juvenile. Copyright © 2010 John Wiley & Sons, Ltd.
Zum Bifurkationsverhalten stochastischer Systeme
Authors: Cichon Martin , Wedig Walter 
Published: June 2010

AbstractUntersucht werden nichtlineare stochastisch parametererregte Systeme mit Berechnung stationärer Verteilungsdichten durch Lösung der zugehörigen Fokker‐Planck‐Kolmogorow‐Gleichungen (FPK).Die Lösung kann nur in wenigen Sonderfällen exakt analytisch angegeben werden, andernfalls sind geeignete Methoden zur analytischen Näherung erforderlich. Die so erhaltenen Verteilungsdichten werden mit denjenigen aus Monte Carlo Simulationen verglichen und dienen zusätzlich der physikalischen Deutung der Ränder.
Adaptive finite element procedures for elastoplastic problems at finite strains
Authors: Koch A. , Miehe C. 
Published: June 2010

AbstractA major difficulty in the context of adaptive analysis of geometrically nonlinear problems is to provide a robust remeshing procedure that accounts both for the error caused by the spatial discretization and for the error due to the time discretization. For stability problems, such as strain localization and necking, it is essential to provide a step–size control in order to get a robust algorithm for the solution of the boundary value problem. For this purpose we developed an easy to implement step–size control algorithm. In addition we will consider possible a posteriori error indicators for the spatial error distribution of elastoplastic problems at finite strains. This indicator is adopted for a density–function–based adaptive remeshing procedure. Both error indicators are combined for the adaptive analysis in time and space. The performance of the proposed method is documented by means of representative numerical examples.
Fitting Yield Curve Models Using the Kalman Filter
Authors: Walther B. , May A. , Fischer T. 
Published: June 2010

AbstractWe consider several stochastic interest rate models relying on the classes of Gaussian and square root processes. In particular, we introduce both, the Vasicek and the Cox‐Ingersoll‐Ross model, with k factors. Kalman filter methods are applied in order to estimate the parameters of these models. A detailed empirical analysis based on data from the German debt securities market is performed. The models are compared with respect to the number of factors and the different model classes. As a result, we suggest the application of the Vasicek model with at least two factors and the Cox‐Ingersoll‐Ross model with two factors.
Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6
Authors: Ke Chenhao , Li Juan , Fang Keyi , Zhu Qiliang , Zhu Jin , Yan Qing 
Published: June 2010

AbstractA hyperbranched polyamine was prepared using an A2 + B3 approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.