bluuebunny/crossref_metadata_2025_split huggingface dataset:
Block diagonalization of Laplacian matrices of symmetric graphs via group theory
Authors: Kaveh A. , Nikbakht M. 
Published: August 2006

AbstractIn this article, group theory is employed for block diagonalization of Laplacian matrices of symmetric graphs. The inter‐relation between group diagonalization methods and algebraic‐graph methods developed in recent years are established. Efficient methods are presented for calculating the eigenvalues and eigenvectors of matrices having canonical patterns. This is achieved by using concepts from group theory, linear algebra, and graph theory. These methods, which can be viewed as extensions to the previously developed approaches, are illustrated by applying to the eigensolution of the Laplacian matrices of symmetric graphs. The methods of this paper can be applied to combinatorial optimization problems such as nodal and element ordering and graph partitioning by calculating the second eigenvalue for the Laplacian matrices of the models and the formation of their Fiedler vectors. Considering the graphs as the topological models of skeletal structures, the present methods become applicable to the calculation of the buckling loads and the natural frequencies and natural modes of skeletal structures. Copyright © 2006 John Wiley & Sons, Ltd.
Direct correlation between proteins' folding rates and their amino acid compositions: An ab initio folding rate prediction
Authors: Ma Bin‐Guang , Guo Jian‐Xiu , Zhang Hong‐Yu 
Published: August 2006

AbstractDiscovering the mechanism of protein folding, in molecular biology, is a great challenge. A key step to this end is to find factors that correlate with protein folding rates. Over the past few years, many empirical parameters, such as contact order, long‐range order, total contact distance, secondary structure contents, have been developed to reflect the correlation between folding rates and protein tertiary or secondary structures. However, the correlation between proteins' folding rates and their amino acid compositions has not been explored. In the present work, we examined systematically the correlation between proteins' folding rates and their amino acid compositions for two‐state and multistate folders and found that different amino acids contributed differently to the folding progress. The relation between the amino acids' molecular weight and degeneracy and the folding rates was examined, and the role of hydrophobicity in the protein folding process was also inspected. As a consequence, a new indicator called composition index was derived, which takes no structure factors into account and is merely determined by the amino acid composition of a protein. Such an indicator is found to be highly correlated with the protein's folding rate (r > 0.7). From the results of this work, three points of concluding remarks are evident. (1) Two‐state folders and multistate folders have different rate‐determining amino acids. (2) The main determining information of a protein's folding rate is largely reflected in its amino acid composition. (3) Composition index may be the best predictor for an ab initio protein folding rate prediction directly from protein sequence from the standpoint of practical application. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Acoustic phonons in InSb probed by time‐resolved X‐ray diffraction
Authors: Morak A. , Kämpfer T. , Uschmann I. , Lübcke A. , Förster E. , Sauerbrey R. 
Published: August 2006

AbstractAcoustical phonons in InSb were induced with femtosecond light pulses and probed by diffraction of ultrashort X‐ray pulses in the crystal lattice. The time dependent transient X‐ray diffraction signal due to elastic lattice deformation was measured with subpicosecond resolution. The elastic lattice deformation depends on the temporal evolution of the energy transfer from excited electrons in the semiconductor into the lattice. As already shown in previous investigation a conventional thermoelastic model is not sufficient to describe this coupling process. Here a complex simulation including a two temperature model of the electron and lattice as well as the microscopic behavior of the electron plasma is applied to explain important effects like thermal carrier diffusion and band gap deformation found in the lattice deformation experiments. When this model is used, with realistic values for both pump laser fluences and bulk material constants, excellent agreement between the experimentally observed time dependent lattice deformation and calculated values is obtained throughout the observation period. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Band‐edge photoluminescence in CdTe
Authors: Horodyský P. , Grill R. , Hlídek P. 
Published: August 2006

AbstractNear band‐gap photoluminescence (PL) and absorption of bulk crystals of CdTe were measured over a wide range of temperatures (4–500 K). It is demonstrated that the high‐temperature (above 150 K) PL intensity correlates with a lower quality of the samples and quasiparticle localization induced by the crystal potential fluctuations. The influence of the high absorption coefficient at the free‐exciton resonance energy on the PL spectra is analytically studied by solving the diffusion‐recombination equation. We show that the reabsorption of the radiation by the free‐exciton states creates two illusory PL maxima. No dead surface layer is needed to explain reabsorption effects. The room‐temperature PL maximum matches neither the free‐exciton resonance nor the band‐gap energy. The high temperature PL is explained by the recombination of electrons and holes localized on potential fluctuations. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theory of the cubic‐tetragonal phase transition in PbTiO3
Authors: El‐frikhe Es‐saïd , Toumanari Ahmed , Khatib Driss 
Published: August 2006

AbstractThe phase transition in PbTiO3 is discussed quantitatively from the microscopic free energy based upon the mean field approximation, where the Ti ions shift is considered as the order parameter in the lattice having the spontaneous deformation. From our calculation of the microscopic free energy, the ionic shift of the Ti ion and the coefficient of the expanded free energy, we concluded that the transition temperature and the order of cubic‐tetragonal transition are well explained by this model. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of neutron diffraction on the spinel system with long and short range order
Authors: Hamedoun M. , Talbi F. , Masrour R. , Bouslykhane K. , Hourmatallah A. , Benzakour N. 
Published: August 2006

AbstractThe diluted spinels systems ZnCr2x Al2–2x S4 have been studied by means of neutron diffraction in the concentration range0.3 ≤ x ≤ 1. For this compound, several powders samples with different heat treatment and a single crystal were studied. A helical structure with, wave vector k1 = [0, 0, 0.79] and mk1 ⊥ [001] is built up in a second‐order phase transition. At T 0 = 12 K, a first order transition takes place and the helical structure begins to transform into two collinear structure corresponding to k2 = [${1 \over 2}$, ${1 \over 2}$, 0], mk2//[1$ \bar 1 $0] and k3 = [1, ${1 \over 2}$, 0] mk3//[001]. For x ≤ 0.8, no long‐range magnetic ordering was detected, reflecting the presence of a spin glass state (SG). By using the high‐temperature series expansions (HTSE), we have deduced the magnetic phase diagrams. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effects of magnetic field on the removal of organic compounds and metals by coagulation and flocculation
Authors: Duangduen C. , Nathaporn A. , Kitiphatmontree M. 
Published: August 2006

AbstractThe effects of magnetic field (MF) were studied using surface water from the Pra Ram IX reservoir. Dissolved organic carbon (DOC) removal was improved by exposure of untreated water to MF for up to 5 hours duration. MF was found to alter the physico‐chemical properties of some involved substances. Optimum DOC removal (15‐20%) was observed after 30‐40 minutes of exposure. Flocculation was also improved in the presence of MF. The removal of DOC, iron, heavy metals (As, Zn) was the best with an optimum ferric chloride dosage of 50 mg/L and exposure to 0.35Tesla magnetic field for 30 min. However, Ca removal was not affected by this treatment. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decoherence effects due to exciton‐phonon interaction in CdSe quantum dots: Contribution of the piezoelectricity and deformation potential couplings
Authors: Sellami Karim , Jaziri Sihem 
Published: August 2006

AbstractWe analyse decoherence effects of an exciton in II‐VI semiconductor quantum dot. We calculate the scattering rate of excitons by acoustic phonons laying a foundation for work on understanding carrier relaxation in quantum dots providing then a basis for studying decoherence phenomena in these systems. We considered two exciton‐acoustic phonons scattering mechanisms the standard deformation potential coupling and the piezoelectric coupling. The latter was found to be relatively important in large dots. We discuss the influence of an external applied magnetic field and the dot size on the scattering rate. We show that it depends strongly on the quantum dot size, then using a modulated external magnetic field the interaction of the exciton and acoustic phonon modes can be modified in a wide range. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of the electrolytic super alloys Ni‐Fe
Authors: Bouhouch L. , Fadel M. , Hilali E. 
Published: August 2006

AbstractThis paper will be devoted to the study of the magnetic properties of the layers of Ni100–xFex alloys, obtained by electrolytic deposit. The chemical composition of these alloys varies, according to the content of both constituents nickel and iron, from 50 at% to 90 at% of nickel, for a layer thickness of about 10 μm. We have started a systematic study in order to determine the influence of the atomic composition of nickel on specific magnetization to saturation and the hysteresis loops, as well as the thermomagnetic effects. During our investigations, we noted that, firstly specific magnetization to saturation grows almost linearly with the content of iron of alloy. Secondly, the hysteresis loops present all a low coercitive force and a strong susceptibility. Finally we underlined that the effect of the heat treatment is very strong for the low contents of iron of alloy. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phonon frequency calculations of GdBCO and PrBCO
Authors: Tavana A. , Khosroabadi H. , Akhavan M. 
Published: August 2006

AbstractAb initio frozen‐phonon calculations have been performed for k = 0 Ag Raman modes of superconducting GdBa2Cu3O7 and insulating PrBa2Cu3O7. We have used the generalized gradient approximation full‐potential linear augmented plane‐wave method in our calculations by Wien2k code. Results have been compared with other computational and experimental data for similar systems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time dependence of magnetization in Fe1–xCox fine particles
Authors: Zoriasatain S. , Sebt S.A. , Akhavan M. 
Published: August 2006

AbstractThe change of the applied field in a medium containing anisotropic magnetic grains, makes the number of magnetic moments in the field direction, and in the opposite direction to vary. Near H = H c, probability of transition between the two minimum energies (SW model) increases strongly and the magnetization of system varies rapidly. We measured the time dependence of magnetization for various Fe1–xCox samples, in the presence of some step fields. These samples were grown via solving iron, and cobalt salts with borohydride and then, heat treatment was accomplished on them. The results of time measurement of magnetization in step fields reveals a linear proportionality between coercivity and magnetic stability. We have analyzed these results using magnetization models. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Determination of the pinned vortex fraction in type‐II superconductors
Authors: Bouaaddi A. , Taoufik A. , Labrag A. , Bghour M. , Abaragh A. , Ramzi A. , Senoussi S. 
Published: August 2006

AbstractIn this article we intend to study the pinned vortex fraction in a type II superconductors. The sample used is the YBa2Cu3O7‐γ. This fraction pinned is determined from the comparison of the experimental results and the theoretical results previously definite. In continuation one will study the variations of this fraction according to the temperature of the applied magnetic field and the electric current crossing the sample. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Apical oxygen, 3D‐2D cross over and superconductivity in Sm2–xCexCuO4–δ
Authors: Boujida M. 
Published: August 2006

AbstractIn spite of the vast amount of experimental and theoretical articles accumulated in HTSC, the mechanism of the interaction driving charge carriers to form Cooper pairs below Tc is still unknown. The comparison of the normal state transport properties of YBa2Cu3O7–δ and the Sm2–xCexCuO4–δ [1, 2] might shed some light on the microscopic origin of HTSC. In comparison to the YBCO, the apical oxygen in Sm2–xCexCuO4–δ [3] destroys the superconductivity via the vertical ionic bonding which localizes the charge in the Cu‐O squares, however the hole transfer by moving O(4) towards the CuO2 planes, leads to the optimization of YBCO properties. The behaviour of C axis parameter vs the oxygen content cannot be explained by a BSC mechanism. The high amount of anisotropy ratio [4] is explained by the sheer square planes in NCCO system, i.e. without apical oxygen (SC with Tc maximum). From the data of the resistivity in the normal state, we conclude the observation of a 3D‐2D cross over only in Sm2–xCexCuO4–δ [2] and Nd2–xCexCuO4–δ [5] which is also related to its high anisotropy. The competition between anisotropy and superconductivity destroys the superconducting state in the 2D limit even in the ground state. In this material the superconductivity cannot be enhanced at high temperature because the compound is a quasi 2D system (sheer square planes of CuO2) and the cuprate superconductors is a genuine three‐dimensional (3D) phenomenon [6]. The Josephson coupling between the different layers is S‐I‐S for NCCO and S‐N‐S for YBCO, thus the Lawrence and Doniach model (LD) [7] with neighbouring layers coupled by the Josephson tunnelling is appropriate. In summary the behaviour of apical oxygen is intrinsically different in the two kinds of cuprates. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Neutron diffraction line broadening of twins in YBa2Cu3O6+x (0 < x < 1) at high temperatures
Authors: Khoshnevisan B. , Ross D. K. 
Published: August 2006

AbstractWe report here on the nature of the twinning associated with the tetragonal to orthorhombic I (T/OI) phase transition in YBCO, for temperatures between 500 °C and 600 °C. In situ neutron diffraction measurements show the coexistence of the T and split OI peaks in the vicinity of the transition. However, by direct numerical simulation, we show that this is to be expected from the twinned OI structure when the separation of adjacent twinning planes and the orthorhombicity both approach zero. It is demonstrated that the observed hkl‐dependent peak broadening is consistent with this interpretation. A comparison of the measured and simulated peak shapes enables us to make an approximate estimate of the actual twin widths for a given orthorhombicity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The effect of phonon‐electron thermal decoupling on the low‐T thermal conductivity data of cuprates
Authors: Smith M. F. 
Published: August 2006

AbstractWe describe how the anomalous decrease in the thermal conductivity, which has been observed in several cuprates at sub‐Kelvin temperatures, occurs because of the thermal decoupling of phonons and electrons. In typical experimental conditions for these ultra‐low‐T thermal conductivity measurements, the initial heat current is provided to the electrons in the sample mainly by phonons. The phonon‐electron heat transfer rate falls rapidly with decreasing temperature and, below a characteristic temperature scale that we identify to be roughly 200 mK in typical cuprates, a heat‐current bottleneck develops. The electronic heat current thus becomes limited by electron‐phonon heat transfer and acquires an anomalous temperature dependence. This results in the apparent low‐T downturn of the thermal conductivity. We account for the temperature and magnetic field dependence of the low‐T thermal conductivity in both the normal and superconducting states, obtaining quantitative agreement with the data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Risks and Challenges of Surgical Glove Failure
Authors: Rabussay Dietmar , Korniewicz Denise M. 
Published: August 2006

ABSTRACTThe relationship between infection control standards and surgical gloving practices is an important issue in combating infectious disease. For their own and their patients' protection, health care personnel must rely on the barrier qualities of gloves more than ever before. Both surgical and examination gloves fail frequently, which puts health care providers and patients at risk of acquiring fluid‐borne pathogens. This paper discusses current guidelines, the risk of infection by viral and bacterial pathogens, controversial issues involving gloving practices, and recommendations to improve infection control practices. AORN J 66 (Nov 1997) 867‐888.
Decreasing Surgical Risks for Patients with Obstructive Sleep Apnea
Authors: Yantis Mary Ann 
Published: August 2006

ABSTRACTThe prevalence of obstructive sleep apnea (OSA) has only recently been appreciated, in part because the signs and symptoms of OSA were previously overlooked. The identification of this disorder is extremely important before surgery to allow appropriate airway management. This article presents a brief overview of sleep apnea, its symptoms, and potential consequences. Nursing interventions are given for the preoperative, intraoperative, and postoperative phases. A resource list of agencies and internet sites that reference OSA is included for additional information. AORN J 68 (July 1998) 50–55.
Managing the Patient with Perforated Intrathoracic Esophagus
Authors: Graling P.R. , Hetrick V.L. , Vaughan B. , Kiernan P.D. 
Published: August 2006

ABSTRACTThe thoracic perioperative specialty team members at Inova Fairfax Hospital, Falls Church, Va, designed guidelines to improve the management of patients with esophageal perforations. They performed a retrospective analysis of 41 patients who were diagnosed with thoracic esophageal perforations from Sept 1, 1979, through Sept 1, 1996. The review affirmed their philosophy of aggressive, surgical intervention for perforations, particularly for patients diagnosed early (ie, within 24 hours). The process of examining and communicating the results among OR nurses, anesthesia care providers, and surgeons resulted in the increased efficiency and appropriateness with which patients were incorporated into the hospital's surgical and medical treatment groups. AORN J 68 (July 1998) 56–67.
ArrayFusion: a web application for multi-dimensional analysis of CGH, SNP and microarray data
Authors: Yang Tsun-Po , Chang Ting-Yu , Lin Chi-Hung , Hsu Ming-Ta , Wang Hsei-Wei 
Published: August 2006

Abstract
Summary: ArrayFusion annotates conventional CGH results and various types of microarray data from a range of platforms (cDNA, expression, exon, SNP, array-CGH and ChIP-on-chip) and converts them into standard formats which can be visualized in genome browsers (Affymetrix™ Integrated Genome Browser and GBrowse in the HapMap Project). Converted files can then be imported simultaneously into a single genome browser to benefit a collective interpretation between different array results. ArrayFusion therefore provides a new type of tool facilitating the integration of CGH and array results to provide new experimental directions.
Availability:
Contact: hwwang@ym.edu.tw
Weighted quality estimates in machine learning
Authors: Budagyan Levon , Abagyan Ruben 
Published: August 2006

AbstractMotivation: Machine learning methods such as neural networks, support vector machines, and other classification and regression methods rely on iterative optimization of the model quality in the space of the parameters of the method. Model quality measures (accuracies, correlations, etc.) are frequently overly optimistic because the training sets are dominated by particular families and subfamilies. To overcome the bias, the dataset is usually reduced by filtering out closely related objects. However, such filtering uses fixed similarity thresholds and ignores a part of the training information.Results: We suggested a novel approach to calculate prediction model quality based on assigning to each data point inverse density weights derived from the postulated distance metric. We demonstrated that our new weighted measures estimate the model generalization better and are consistent with the machine learning theory. The Vapnik–Chervonenkis theorem was reformulated and applied to derive the space-uniform error estimates. Two examples were used to illustrate the advantages of the inverse density weighting. First, we demonstrated on a set with a built-in bias that the unweighted cross-validation procedure leads to an overly optimistic quality estimate, while the density-weighted quality estimates are more realistic. Second, an analytical equation for weighted quality estimates was used to derive an SVM model for signal peptide prediction using a full set of known signal peptides, instead of the usual filtered subset.Contact: levon@molsoft.com
Species Preferentiality of the Pollen Tube Attractant Derived from the Synergid Cell ofTorenia fournieri
Authors: Higashiyama Tetsuya , Inatsugi Rie , Sakamoto Sachio , Sasaki Narie , Mori Toshiyuki , Kuroiwa Haruko , Nakada Takashi , Nozaki Hisayoshi , Kuroiwa Tsuneyoshi , Nakano Akihiko 
Published: August 2006

AbstractThe synergid cell of Torenia fournieri attracts pollen tubes by a diffusible but yet unknown chemical attractant. Here we investigated the species difference of the attractant using five closely related species in two genera, namely T. fournieri, Torenia baillonii, Torenia concolor, Lindernia (Vandellia) crustacea, and Lindernia micrantha. These five species have an exserted embryo sac, and ablation experiments confirmed that their synergid cells attracted the pollen tube. When ovules of T. fournieri and one of the other species were cultivated together with pollen tubes of each species, pollen tubes were significantly more attracted to synergid cells of the corresponding species. The attraction was not affected by the close proximity of embryo sacs of different species. This suggests that the attractant is a species-preferential molecule that is likely synthesized in the synergid cell. The calcium ion, long considered a potential attractant, could not serve as the sole attractant in these species, because elevation of the calcium ion concentration did not affect the observed attraction. In vivo crossing experiments also showed that the attraction of the pollen tube to the embryo sac was impaired when pollen tubes of different species arrived around the embryo sac, suggesting that the species preferentiality of the attractant may serve as a reproductive barrier in the final step of directional control of the pollen tube.