bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of the matrix effect on the headspace solid‐phase microextraction (HS‐SPME) analysis of chlorophenols in wines
Authors: Insa Sara , Besalú Emili , Salvadó Victòria , Anticó Enriqueta 
Published: March 2007

AbstractIn this paper, we propose a comparative study to check the matrix effect on the extraction of three chlorophenols, 2,4,6‐trichlorophenol (TCP), 2,3,4,6‐tetrachlorophenol and pentachlorophenol, direct precursors of 2,4,6‐trichloroanisole, in synthetic and commercial wines (white and red wines). A rapid, simple and sensitive methodology based on solid‐phase microextraction (SPME) and GC with electron capture detection (GC‐ECD) and mass spectrometric detection (GC‐MS) was developed and the variables affecting the extraction process (temperature, time and salt content) were examined employing a factorial design at two levels. Since GC‐ECD does not allow the clear identification of target analytes in white wine, owing to overlapped interferences, GC‐MS/MS was used for subsequent examinations. Calibration curves were constructed in synthetic, white and red wine. Significant differences between the slopes of synthetic and red wine, with the exception of TCP, were observed. Analytical parameters were evaluated and satisfactory results were obtained, showing the usefulness of the headspace SPME (HS‐SPME) method for determining chlorophenolic compounds in wines.
HPLC retention behavior on hydride‐based stationary phases
Authors: Pesek Joseph J. , Matyska Maria T. , Larrabee Susan 
Published: March 2007

AbstractTwo stationary phases attached to a silica hydride surface, cholesterol and bidentate C18, are investigated with a number of pharmaceutically related compounds in order to illustrate the various retention mechanisms that are possible for these bonded materials. The test solutes range from hydrophilic to hydrophobic based on log P (octanol/water partition coefficient) and pKa values. The mobile phases consist of acidified (formic and perchloric acid) water/methanol or water/ACN mixtures. Of particular interest are the high organic content mobile phase compositions where the retention would increase if the bonded material was operating in the aqueous normal phase (ANP) mode. Plots of retention factor (k) versus mobile phase composition are used to elucidate the retention mechanism. A number of examples are presented where solutes are retained based on RP, ANP, or dual retention mechanisms. The silica hydride‐based stationary phases can also retain compounds in the organic normal phase.
On the long‐time stability of the Crank–Nicolson scheme for the 2D Navier–Stokes equations
Authors: Tone Florentina 
Published: March 2007

AbstractIn this article we study the stability for all positive time of the Crank–Nicolson scheme for the two‐dimensional Navier–Stokes equations. More precisely, we consider the Crank–Nicolson time discretization together with a general spatial discretization, and with the aid of the discrete Gronwall lemma and of the discrete uniform Gronwall lemma we prove that the numerical scheme is stable, provided a CFL‐type condition is satisfied. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Performance and numerical behavior of the second‐order scheme of precise time‐step integration for transient dynamic analysis
Authors: Ma Hang , Yin Feng , Qin Qing‐Hua 
Published: March 2007

AbstractSpurious high‐frequency responses resulting from spatial discretization in time‐step algorithms for structural dynamic analysis have long been an issue of concern in the framework of traditional finite difference methods. Such algorithms should be not only numerically dissipative in a controllable manner, but also unconditionally stable so that the time‐step size can be governed solely by the accuracy requirement. In this article, the issue is considered in the framework of the second‐order scheme of the precise integration method (PIM). Taking the Newmark‐β method as a reference, the performance and numerical behavior of the second‐order PIM for elasto‐dynamic impact‐response problems are studied in detail. In this analysis, the differential quadrature method is used for spatial discretization. The effects of spatial discretization, numerical damping, and time step on solution accuracy are explored by analyzing longitudinal vibrations of a shock‐excited rod with rectangular, half‐triangular, and Heaviside step impact. Both the analysis and numerical tests show that under the framework of the PIM, the spatial discretization used here can provide a reasonable number of model types for any given error tolerance. In the analysis of dynamic response, an appropriate spatial discretization scheme for a given structure is usually required in order to obtain an accurate and meaningful numerical solution, especially for describing the fine details of traction responses with sharp changes. Under the framework of the PIM, the numerical damping that is often required in traditional integration schemes is found to be unnecessary, and there is no restriction on the size of time steps, because the PIM can usually produce results with machine‐like precision and is an unconditionally stable explicit method. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Spline methods for the solution of hyperbolic equation with variable coefficients
Authors: Rashidinia J. , Mohammadi R. , Jalilian R. 
Published: March 2007

AbstractIn this study, we developed the methods based on nonpolynomial cubic spline for numerical solution of second‐order nonhomogeneous hyperbolic partial differential equation. Using nonpolynomial cubic spline in space and finite difference in time directions, we obtained the implicit three level methods of O(k2 + h2) and O(k2 + h4). The proposed methods are applicable to the problems having singularity at x = 0, too. Stability analysis of the presented methods have been carried out. The presented methods are applied to the nonhomogeneous examples of different types. Numerical comparison with Mohanty's method (Mohanty, Appl Math Comput, 165 (2005), 229–236) shows the superiority of our presented schemes. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
A practical approach to control of nonlinear discrete‐time state‐delay systems
Authors: Boukas El‐Kébir , Mahmoud Magdi S. 
Published: March 2007

AbstractThe robust feedback stabilization of a class of nonlinear discrete‐time systems with unknown constant state‐delay and uncertain function of nonlinear perturbations is considered based on linear matrix inequality (LMI)‐based analysis and design procedures. In both cases of nominal and resilient feedback designs, the trade‐off between the size of the controller gains and the bounding factors is illuminated and incorporated into the design formalism. A dynamic output feedback controller is then designed for this class of systems. Seeking computational convenience, all the developed results are cast in the format of LMIs and several numerical examples are presented throughout the paper to demonstrate the advantages of the design methods. Copyright
© 2007 John Wiley & Sons, Ltd.
Deficiency of the autoimmune regulator AIRE in thymomas is insufficient to elicit autoimmune polyendocrinopathy syndrome type 1 (APS‐1)
Authors: Ströbel P , Murumägi A , Klein R , Luster M , Lahti M , Krohn K , Schalke B , Nix W , Gold R , Rieckmann P , Toyka K , Burek C , Rosenwald A , Müller‐Hermelink HK , Pujoll‐Borrell R , Meager A , Willcox N , Peterson P , Marx A 
Published: March 2007

AbstractThymomas are thymic epithelial neoplasms, associated with a variety of autoimmune disorders (especially myasthenia gravis), that apparently result from aberrant intra‐tumourous thymopoiesis and export of inefficiently tolerized T‐cells to the periphery. The autoimmune regulator (AIRE) drives the expression of self‐antigens in the thymic medulla and plays an essential role in ‘central’ tolerance in both humans and mice. However, while inactivating AIRE mutations result in the ‘autoimmune polyendocrinopathy syndrome type 1’ (APS‐1), its major features are not well reproduced in AIRE‐knock‐out mice. Therefore, alternative human disease scenarios with concomitant AIRE deficiency may be valuable tools to test conclusions drawn from mouse models. Here we show, in a large series, that ∼95% of thymoma patients are ‘chimeric’; expression of AIRE and major AIRE‐related autoantigens (eg insulin) were undetectable in their tumours but maintained in their remnant thymic tissue and lymph nodes. Notably, despite the AIRE‐deficient thymopoiesis in thymomas, disorders and autoantibodies typical of APS‐1 were distinctly uncommon in these patients. The one striking similarity was in the recently observed neutralizing anti‐type I interferon (IFN) antibodies, which are found at diagnosis in 100% of patients with APS‐1 and in ∼60% of patients with thymomas, as we show here. We conclude that APS‐1 type autoantigens must be protected from autoimmunity by mechanisms that do not extend to the muscle autoantigens so frequently targeted in thymoma patients but so rarely recognized in APS‐1. Thus our findings argue strongly for a tolerogenic function of AIRE beyond its role in negative T‐cell selection in human thymopoiesis, and/or for specific autoimmunization against muscle in thymomas. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Packaging of prions into exosomes is associated with a novel pathway of PrP processing
Authors: Vella LJ , Sharples RA , Lawson VA , Masters CL , Cappai R , Hill AF 
Published: March 2007

AbstractPrion diseases are fatal, transmissible neurodegenerative disorders associated with conversion of the host‐encoded prion protein (PrPC) into an abnormal pathogenic isoform (PrPSc). Following exposure to the infectious agent (PrPSc) in acquired disease, infection is propagated in lymphoid tissues prior to neuroinvasion and spread within the central nervous system. The mechanism of prion dissemination is perplexing due to the lack of plausible PrPSc‐containing mobile cells that could account for prion spread between infected and uninfected tissues. Evidence exists to demonstrate that the culture media of prion‐infected neuronal cells contain PrPSc and infectivity but the nature of the infectivity remains unknown. In this study we have identified PrPC and PrPSc in association with endogenously expressing PrP neuronal cell‐derived exosomes. The exosomes from our prion‐infected neuronal cell line were efficient initiators of prion propagation in uninfected recipient cells and to non‐neuronal cells. Moreover, our neuronal cell line was susceptible to infection by non‐neuronal cell‐derived exosome PrPSc. Importantly, these exosomes produced prion disease when inoculated into mice. Exosome‐associated PrP is packaged via a novel processing pathway that involves the N‐terminal modification of PrP and selection of distinct PrP glycoforms for incorporation into these vesicles. These data extend our understanding of the relationship between PrP and exosomes by showing that exosomes can establish infection in both neighbouring and distant cell types and highlight the potential contribution of differentially processed forms of PrP in disease distribution. These data suggest that exosomes represent a potent pool of prion infectivity and provide a mechanism for studying prion spread and PrP processing in cells endogenously expressing PrP. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Synthesis, photophysical properties, and electron paramagnetic resonance studies of new poly(bisbenzothiazole)s containing bulky pendant groups
Authors: Huang Wei , Yin Jie 
Published: March 2007

AbstractA new series of poly(bisbenzothiazole)s containing bulky pendant cyclohexylidene or 4‐tert‐butylcyclohexylidene group was synthesized. Their structures were characterized by NMR (1H, 13C), FTIR, and EA. These polymers exhibited good solubility, thermal stability, and an amorphous nature. The photophysical properties of them were investigated in detail by UV absorption spectroscopy and photoluminescence spectroscopy. Compared with poly(p‐phenylene benzobisthiazole), the absorption maxima of these polymers were all blue shifted, and their optical bandgaps were increased. The emission peaks, having different intensity, were also blue shifted. They both changed in shape and position gradually with the increasing concentration, which showed the evidence of aggregate formation. In addition, the degree of aggregation was decreased with the increasing size of bulky pendant group and the PL quantum yield could be improved by the introduction of bulky pendant group. The result of electron paramagnetic resonance studies showed the intrinsic paramagnetic defects in this class of polymers. A new soliton–antisoliton model was constructed to interpret these intrinsic paramagnetic signals. POLYM. ENG. SCI., 47:429–438, 2007. © 2007 Society of Plastics Engineers.
Effect of diisocyanate structures on the properties of liquid crystalline polyurethanes
Authors: Lee Mooyoung , Hong Sung Chul , Lee Sang‐Won 
Published: March 2007

AbstractThermotropic liquid crystalline polyurethanes (LCPUs) were synthesized through the polyaddition reaction of 2,4‐toluene diisocyanate (2,4‐TDI), 4,4′‐diphenylmethane diisocyanate (MDI), or o‐toluidine diisocyanate (ODI) with 4,4′‐bis(6‐hydroxyhexoxy)biphenyl, and the effect of the structures of the diisocyanates on the properties of LCPUs were investigated. Intrinsic viscosities of the polymers were in the range of 0.23–0.30 dL/g. Mesomorphic behavior of the polyurethanes were investigated by differential scanning calorimetry, polarized optical microscopy, and wide‐angle X‐ray scattering. Different mesomorphic behaviors were observed according to the different structural characteristics of diisocyanates. Polyurethanes employing 2,4‐TDI and MDI exhibited monotropic behaviors, while that with ODI showed enantiotropic behavior. POLYM. ENG. SCI., 47:439–446, 2007. © 2007 Society of Plastics Engineers.
Rheology studies of foam flow during injection mold filling
Authors: Qin X. , Thompson M.R. , Hrymak A.N. 
Published: March 2007

AbstractThis work studies the flow behavior of a developing two‐phase gas‐polymer suspension during injection into the instrumented mold cavity of an injection molding machine. In the experiments, blowing agent type and concentration were varied along with processing conditions, to generate controlled cell structures in two different polymers, low density polyethylene and thermoplastic polyolefin. Experimental results indicate that the rheological properties of two phase gas‐polymer suspensions were sensitive to shear rate, blowing agent concentration, melt temperature, and mold temperature. The viscosity of all gas‐polymer suspensions revealed a reduction compared with neat polymer melt in the presence of gas bubbles, because of the reduced volume fraction of polymer matrix. A two‐phase rheological model has been used for fitting with our experimental results for estimating the shear viscosity of two‐phase flow in the mold cavity of the injection molding machine. POLYM. ENG. SCI., 47:522–529, 2007. © 2007 Society of Plastics Engineers.
External and internal plasticization of cellulose acetate with caprolactone: Structure and properties
Authors: Vidéki Bianka , Klébert Szilvia , Pukánszky Béla 
Published: March 2007

AbstractCellulose acetate was modified with caprolactone in an internal mixer at temperatures between 120 and 220 °C, and reaction times between 5 and 45 min in the presence of tinoctoate catalyst. The effect of plasticization on the properties of the polymer was studied by dynamic mechanical analysis and tensile testing. The dynamic mechanical spectrum of cellulose acetate exhibits three main relaxation transitions. These can be assigned to segments (α), to smaller structural units of the main chain, probably individual glucose rings (β), and to hydroxyl or hydroxylmethyl groups (γ). Plasticization by caprolactone leads to the decrease of the glass transition temperature of CA, but also to the breakdown of relatively large segments to smaller structural units. Free hydroxyl groups interact with the plasticizer forming larger units with higher transition temperature. Grafting decreases the intensity of the γ‐transition peak. External plasticization creates a larger number of small structural units, but the external plasticizer is less efficient in the decrease of stiffness than grafted polycaprolactone chains. Internal plasticization is more advantageous because it leads to higher flexibility at larger strength than external plasticization, and the migration of the plasticizer is prevented at the same time. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 873–883, 2007
A new implicit solvent model for protein–ligand docking
Authors: Morreale Antonio , Gil‐Redondo Rubén , Ortiz Ángel R. 
Published: March 2007

AbstractA new implicit solvent model for computing the electrostatics binding free energy in protein–ligand docking is proposed. The new method is based on an adaptation of the screening coulombic potentials proposed originally by Hassan et al. (J Phys Chem B 2000;104:6490–6498). In essence, it relies on two basic assumptions; (i) solvent screening can be accounted for by means of radially dependent sigmoidal dielectric functions and; (ii) the effective atom Born radii can be expressed only as a function of the exposed atom surface. Parameters of the model other than radii and charges are generic. These were optimized for a dataset of 826 protein–ligand complexes, comprising both X‐ray complexes for 23 receptors as well as decoys generated by docking computations. We show that the new model provides satisfactory results when benchmarked against reference values based on the numerical solution of the Poisson equation, with a root mean square error of 4.2 kcal/mol over a range of ∼40 kcal/mol in electrostatics binding free energies, a cross‐validated r2 of 0.81, a slope of 0.97, and an intercept of 1.06 kcal/mol. We show that the model is appropriate for ligands of different sizes, polarities, overall charge, and chemical composition. Furthermore, not only the total value of the electrostatic contribution to the binding free energy, but also its components (coulombic term, receptor desolvation, and ligand desolvation) are reasonably well reproduced. Computation times of ∼0.030 s per pose are obtained on a single processor desktop workstation. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Optical and electronic conduction behavior in germanium ferrite additive with transition metal
Authors: Fayek S. A. , Balboul M. R. , El‐Ocker M. 
Published: March 2007

Abstract The effects of adding transition metals (Ni and Co) on the optical and electrical properties of four thin films Ni1.25Fe1.5Ge0.25O4, Ni1.5Fe1Ge0.5O4, Co1Fe1Ge0.5O4 and Co1.25Fe1.5Ge0.25O4 are reported. X‐ray diffraction was used to ascertain the amorphization nature of the deposited films. The optical absorption behavior of these films was studied from the transmission and reflection in the range 200–1100 nm. It was found that the optical band gap increases on increasing GeO2 and arises from direct forbidden transitions. The opposite trend was found with the band tail width of the localized state. Optical constant parameters such as refractive index and absorption index were obtained for the films. The results for the alternating‐current (ac) conductivity and the dielectric constant of the four films are presented over the temperature range 277–357 K and the frequency range 0.1 to 1000 kHz. The ac conductivity increases with temperature and frequency and decreases with the increase in Ni2+ or Co2+ content. The effect of composition and temperature on the dielectric constant was also studied. The frequency variation of the dielectric constant does not have a peak, unlike many semiconductor glasses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanoscale surface characterization of GaN nanowires correlated with metal contact characteristics
Authors: Koley G. , Lakshmanan L. , Wu H. , Cha Ho‐Young 
Published: March 2007

AbstractSurface electronic properties of GaN nanowires have been investigated using scanning probe microscopy and correlated with metal/nanowire contact characteristics. Surface current map of the nanowire was observed to be highly nonuniform, resulting from a large variation in surface barrier of the nanowire, on the order of a few tenths of an eV. The surface barrier non‐uniformity, which most likely determines the formation of an ohmic or Schottky contact, is increased dramatically with the nanowire surface deformation. Current–voltage characteristics and scanning gate microscopy of the nanowires also indicate significant carrier trapping at the nanowire and silicon dioxide surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some aspects of ion implantation technique in nanostructured materials
Authors: Mazzoldi P. , Mattei G. 
Published: March 2007

AbstractThe paper will discuss the synthesis of metal nanoclusters (NCs) composites, in silica matrix, in which the cluster concentration is below the percolation limit (dispersed clusters). Some case studies will be presented in which ion‐beam‐based techniques are exploited either for the synthesis, but also for the structural or compositional modification of composites. As regards the technological properties of the studied systems, some results will be presented about the nonlinear properties and energy transfer mechanisms in silica containing Erbium ions and molecular‐like metal structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport in defective ionic materials: from bulk to nanocrystals
Authors: Chadwick A. V. 
Published: March 2007

AbstractThis contribution reviews the current state of knowledge of atomic transport in ionic materials, a dominant theme of the EURODIM Conference series for nearly four decades. The early history of the subject is briefly reviewed followed by the important developments that occurred in the early post‐WWII period. That work was mainly based on studies of relatively simple binary ionic systems in the form of single crystals and laid the foundation for much of the current knowledge. An overview is given of more recent work on fast‐ion conductors where the materials are generally more complex and the aim is to produce good ionic conductors for applications as electrolyte membranes in batteries and fuel cells. This includes the development of computer simulation techniques that are now an almost essential part of any investigation of ionic transport. Finally, a brief summary is given of transport in nanocrystalline ionic materials (nanoionics) where enhanced ionic conduction has been reported with the potential for significantly improved devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defects and photorefraction: A relation with mutual benefit
Authors: Imlau M. 
Published: March 2007

AbstractIntrinsic and extrinsic defects are at the origin of photorefraction. Donor and acceptor defects define the properties of the photorefractive response in particular its dispersive behavior. This enables, e.g., targeted material design by incorporation of extrinsic defects in photorefractive media. Vice versa, defect physics benefits from photorefraction, i.e., photorefraction is successfully applied in defect studies and material analysis. Concepts for investigations make use of the great variety of nonlinear photorefractive phenomena. These include the appearance of a transient light‐induced absorption, two‐wave mixing at one‐dimensional photonic gratings, photo‐assisted self‐assembly of photonic gratings and space‐charge waves originating from oscillating photonic gratings. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)