bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spin‐dependent current through a ferromagnetic resonant tunnelling quantum well
Authors: Lebedeva N. , Kuivalainen P. 
Published: June 2005

AbstractWe study the nonequilibrium quantum transport through a ferromagnetic quantum well (FQW) coupled to two nonmagnetic leads. A formal expression for the spin‐polarized current is derived with the Keldysh nonequilibrium‐Green‐function technique. Then the retarded Green function for the FQW, which is needed in the general expression for the transmission coefficient T(E), is calculated by using Zubarev's double‐time‐Green‐function technique. The derived expression for T(E) includes, e.g., the shift and the life‐time broadening of the electronic states inside the FQW due to the tunnelling processes and the strong exchange interaction between the charge carrier spins and the localized spins of the magnetic electrons. Numerical results are presented for a simple FQW model structure consisting of a diluted III–V ferromagnetic semiconductor between the insulating barriers. A single resonant level inside the FQW is coupled to the nonmagnetic leads by tunnelling and to the ferromagnetic subsystem by the exchange interaction. Novel effects predicted by the model are discussed, such as the broadening of the resonant level due to the spin‐disorder scattering in a 2D‐hole gas and the large spontaneous spin‐splitting of the resonant level in a ferromagnetic phase transition. These effects are seen in the calculated T(E) and the spin current through the FQW, which show strong temperature and magnetic field dependences at temperatures close to the Curie temperature. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport through a four‐quantum‐dot ring
Authors: Li Hua , Lü Tianquan , Sun Punan 
Published: June 2005

AbstractThe nonequilibrium Keldysh Green's function technique is used to study the electronic transport property of a four‐quantum‐dot ring under dc bias. The formula for the dc current through the system is obtained. The transmission probability T(ω) as a function of electron energy ω and the differential conductance as a function of the chemical potential of the left reservoir are calculated. Both of them display oscillation structures. When the tunnel coupling amplitude between neighboring dots is sufficiently large, the resonant states of the system depend on the arrangement of single‐dot Fermi levels. In addition, the coupling amplitude to the two reservoirs can also influence the transport property of the system. When the single‐dot Fermi levels of the four dots are all aligned, the electronic spectrum of the system is found to fall within an interval centered at the single‐dot Fermi level with a width of twice the tunnel coupling amplitude between two neighboring dots. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomistic study of structural simulation and Curie temperature of R2Fe17–xTx (R = Tb, Ho, Er; T = Ti, V, Cr, Mn)
Authors: Qian Ping , Wang Qing‐Lin , Chen Nan‐Xian , Shen Jiang 
Published: June 2005

AbstractIn order to study the effect of ternary element T substitution on the structural properties of R2Fe17–xTx (R = Tb, Ho, Er; T = Ti, V, Cr, Mn), the phase stability and site preference are performed by using pair potentials based on lattice inversion technique. Our results indicate that the Ti, V, Cr and Mn atoms can stabilize R2Fe17–xTx with the hexagonal Th2Ni17‐type structure. Calculated site preference of these stabilizing elements T is found to be the 4f site, which is in agreement with the experiment. Moreover, the decrease of the Curie temperature TC with increasing Mn concentration is explained qualitatively by the exchange‐interaction model. The method utilized in the present investigation offers a rather easy and direct way to study the structural properties of intermetallics. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interfacial steps, dislocations, and inversion domain boundaries in the GaN/AlN/Si (0001)/(111) epitaxial system
Authors: Dimitrakopulos G. P. , Sanchez A. M. , Komninou Ph. , Kehagias Th. , Karakostas Th. , Nouet G. , Ruterana P. 
Published: June 2005

AbstractThe role of substrate steps in the introduction of transformations of interfacial structure and inversion domain boundaries is studied for the GaN/AlN/Si (0001)/(111) epitaxial system using topological analysis and high resolution transmission electron microscopy. This epitaxial system can exhibit distinct interfacial structures at the AlN/Si interface, and transformations from one to the other can be introduced by the steps on the substrate surface. The interfacial steps can exhibit dislocation character and they may accommodate the coexistence of energetically degenerate as well as distinct interfacial structures. A substrate step is identified as a potential cause for pinhole formation. Inversion domain boundaries accommodate interfacial transformations when they emanate from the epitaxial interface and can reduce the coherency dislocation character of interfacial steps. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Elastic and thermal properties of δ‐plutonium
Authors: Siethoff Hans 
Published: June 2005

AbstractIt has been demonstrated in recent experimental and theoretical studies, that δ‐Pu exhibits highly anisotropic phonon properties. The present paper indicates, that properties related to low‐energy phonons such as Debye temperature and activation energy of self‐diffusion do not reflect these anisotropies, and obey the same laws as other face‐centred cubic metals. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin dynamics of exciton polaritons in microcavities
Authors: Shelykh I. A. , Kavokin A. V. , Malpuech G. 
Published: June 2005

AbstractIn this chapter we address a complex set of optical phenomena linked to the spin dynamics of exciton polaritons in semiconductor microcavities. When optically created, polaritons inherit the spin and dipole moment from the exciting light. Their state can be fully characterized by a so‐called “pseudospin” accounting for both spin and dipole moment orientation. However, from the very beginning of their life in a microcavity, polaritons start changing their pseudospin state under effect of effective magnetic fields of different nature and due to scattering with acoustic phonons, defects, and other polaritons. This makes pseudospin dynamics of exciton polaritons rich and complex. It manifests itself in non‐trivial changes in polarization of light emitted by the cavity versus time, pumping energy, pumping intensity and polarization. During the first years of theoretical research on exciton‐polariton relaxation the polarization has been simply neglected. Later it has been understood that the energy and momentum‐relaxation of exciton polaritons are spin‐dependent. It is typically the case in the regime of stimulated scattering when the spin polarizations of initial and final polariton state have a huge effect on the scattering rate between these states. It appeared that critical conditions for polariton Bose‐condensation are also polarization‐dependent. In particular, the stimulation threshold (i.e. the pumping power needed to have a population exceeding 1 at the ground state of the lower polariton branch) has been experimentally shown to be lower under linear than under circular pumping. These experimental observations have stimulated the theoretical research toward understanding of mutually dependent polarization‐ and energy‐relaxation mechanisms in microcavities. The authors of this chapter have been working on theoretical description of different specific effects of polariton spin‐dynamics in microcavities for years. Here we attempted to put together all fragments and to formulate a general approach to the problem that would allow then to consider a variety of particular cases. We start from reminding the main spin‐relaxation mechanisms known for free carriers and excitons. We then overview the most essential experimental results in this field before to present our original formalism which allowed us to interpret the key experimental findings. We are going to discuss only the strong coupling regime leaving aside all polarization effects in VCSELs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recursive generation of natural orbitals in a truncated orbital space
Authors: Li Xiangzhu , Paldus Josef 
Published: May 2005

AbstractWe describe a procedure that generates a subset of low‐lying natural orbitals. It employs a small truncated orbital space, whose dimension is essentially given by the number of natural orbitals we wish to generate. The method is somewhat related to the numerical renormalization group technique. The resulting low‐lying, optimal natural orbitals can then be used in the computation of one‐electron properties, as well as of the energy via a small‐scale configuration interaction (CI), yielding improved potential energy and property surfaces over those obtained with the same method using Hartree–Fock orbitals. The procedure is illustrated on a DZP model of water, considering both the dipole moment and the total energy at the equilibrium and symmetrically stretched geometries. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical study of the mechanism for spin‐forbidden quenching process O(1D) + CO2(1Σ) → O(3P) + CO2(1Σ)
Authors: Yang Guanghui , Yao Li , Zhang Xin , Meng Qingtian , Han Ke‐Li 
Published: May 2005

AbstractThe mechanism of the spin‐forbidden quenching process O(1D) + CO2(1Σ) → O(3P) + CO2(1Σ) was investigated by ab initio quantum chemistry methods. The calculations showed the singlet potential surface [O(1D)+CO2] is attractive where a strongly bound intermediate complex CO3 is formed in the potential basin without a transition state, whereas the complex CO3 that is formed on the triplet surface [O(3P)+CO3] must overcome a barrier. The complex channel was documented by searching minimum energy intersection points in the region of the bound complex CO3 and calculating spin‐orbit coupling at the point. A direct channel was proposed by a study of cross point of singlet and triplet PESs with different collision angles and calculations of spin‐orbit coupling at those cross points in a nonbound region of the [O(1D)+CO3] system. The mechanism of the energy transfer is discussed on the basis of the theoretical results. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Die Kalibrierung von Wärmeleitungsvakuummetern. The Calibration of Thermal Conductivity Vacuum Gauges
Authors: Breitenbach Jürgen 
Published: May 2005

AbstractWärmeleitungsvakuummeter werden in zahlreichen Anwendungen zur Überwachung von Grob‐ und Feinvakuum eingesetzt. Zur Feststellung der Richtigkeit der Messwerte fordern moderne Quälitätsmanagementsysteme eine regelmäßige Kalibrierung. Das Kalibrierlabor des Deutschen Kalibrierdienstes (DKD) der Firma VACUUBRAND verfügt über die Messaufbauten bzw. Messverfahren zum Kalibrieren von Vakuummessgeräten im Messbereich 10‐3 bis 1000 mbar. Die Messtechnik und das Kalibrierverfahren werden anhand von Wärmeleitungsvakuummetern mit digitaler Anzeige erläutert. Neben allgemeinen Angaben zur Kalibrierung werden die Besonderheiten von Wärmeleitungsvakuummetern und deren Auswirkungen auf das Kalibrierverfahren hervorgehoben. Die Bedeutung der Messabweichung und der Messunsicherheit sowie die Interpretation des Kalibrierscheins werden für den Benutzer diskutiert.
Plasmagestützte Oberflächenfunktionalisierung komplex strukturierter, miniaturisierter Kunststoff‐Formteile. Plasma assisted surface functionalization of miniaturized plastic devices
Authors: Besch Wilfried , Schröder Karsten , Ohl Andreas 
Published: May 2005

AbstractFür die Vorbereitung von Kunststoffbauteilen für Beschichtungen, Fügeprozesse und ähnliche Zwecke mittels Oberflächenfunktionalisierung kommen unterschiedliche Verfahren in Betracht. Die Verfahren unterscheiden sich in ihren Leistungsmerkmalen deutlich, sowohl in Bezug auf die erzielbaren Oberflächeneffekte als auch hinsichtlich verfahrenstechnischer Gegebenheiten. Für die Funktionalisierung komplex strukturierter Kunststoff‐Formteile kann gezeigt werden, dass hier auf Niederdruckplasmen basierende Verfahren sowohl hinsichtlich der Qualität der Funktionalisierung als auch der Prozessführung Vorteile aufweisen. Für sehr kleine, filigrane und komplexe Bauteile wird die besondere Spaltgängigkeit von Plasmen zum entscheidenden Kriterium. Dazu angestellte Untersuchungen mit Hilfe von Gasphasen‐Pfropfreaktionen zeigen, dass auch in Spalten, deren Abmessungen weit unter dem für andere, alternative Prozesse zugänglichen Bereich liegen, gleichmäßige Behandlungen erreicht werden können.
Transcription factor XBP‐1 is expressed during osteoblast differentiation and is transcriptionally regulated by parathyroid hormone (PTH)
Authors: Zambelli A. , Mongiardini E. , Villegas S.N. , Carri N.G. , Boot‐Handford R.P. , Wallis G.A. 
Published: June 2005

AbstractX‐box‐binding protein 1 (XBP‐1) is a basic‐region leucine zipper protein in the cyclic AMP response element binding protein/activating transcription factor (CREB/ATF) family of transcription factors involved in different cell‐differentiation processes. We have investigated the expression of XBP‐1 in differentiating MC3T3‐E1 osteoblastic cells. Cultures were treated with ascorbic acid (AA) and β‐glycerophosphate (BGP) to induce differentiation. Under these conditions, the basal transcription of xbp‐1 increases at day 2 following induction, peaks at day 5 and decreases thereafter. This result showed that xbp‐1 gene is differentially expressed during MC3T3‐E1 cell differentiation. Detection of XBP‐1 by immunofluorescence at days 0 (control culture without AA and BGP), 8 and 21 showed that the protein has a major cytoplasmic perinuclear location. In addition, xbp‐1 is transcriptionally upregulated by parathyroid hormone within 2.5 h of treatment and decreases thereafter.
Human glutamylcysteine synthetase protects HEK293 cells against UV‐induced cell death through inhibition of c‐Jun NH2‐terminal kinase
Authors: Fan Yumei , Wu Dongmei , Jin Lina , Yin Zhimin 
Published: June 2005

AbstractHuman glutamylcysteine ligase catalytic subunit (GCLC) is the rate‐limiting enzyme for glutathione synthesis. The heavy subunit possesses all the catalytic activities. UV irradiation (UV‐C, 30 J/m2) induced apoptosis in HEK293 cells, but the morphological changes were inhibited significantly by expression of GCLC. MTS assay and flow cytometry results also indicated that GCLC and JNK1APF expression enhanced cellular resistance to UV irradiation. Western blotting showed that irradiation strongly activated the c‐Jun NH2‐terminal kinases (JNKs) and caspase‐3 as well as p38 in HEK293 cells. Interestingly, existing data show that GCLC blocks JNK1 phosphorylation but does not affect p38 phosphorylation. Therefore, overexpression of GCLC protected HEK293 cells against UV irradiation‐induced cell death by inhibiting the phosphorylation and activation of JNK1, concomitantly with the inhibition of caspase‐3 activation and p21WAF1‐luciferase activity downstream of JNK.
Juxtacortical Chondroma of the Hand: Treatment by Resection of the Tumour and the Adjacent Bone Cortex
Authors: TAKADA A. , NISHIDA J. , AKASAKA T. , SHIRAISHI H. , FURUMACHI K. , TAJIMA K. , OKADA K. , SHIMAMURA T. 
Published: June 2005

A recurrence of a juxtacortical chondroma of the finger after marginal excision prompted us to review the treatment of this condition. Although the recommended treatment is simple curettage or marginal excision, the reported recurrence rate is significantly higher for lesions in the hand than those in other locations and recurrences only occurred in patients who had local treatments which did not include excision of the adjacent bone cortex. We report five patients with juxtacortical chondroma of the fingers. The first patient underwent marginal excision without resection of the underlying bone cortex. The other four patients underwent intralesional, marginal or wide excisions of tumour with resection of the bone cortex underlying the lesion. Recurrence was only seen in the patient who did not undergo resection of the bone cortex. Resection of the underlying bone cortex after excision of this tumour may be advisable for the treatment of this tumour in the hand to reduce the rate of recurrence.
Super-shedding cattle and the transmission dynamics ofEscherichia coliO157
Authors: MATTHEWS L. , McKENDRICK I. J. , TERNENT H. , GUNN G. J. , SYNGE B. , WOOLHOUSE M. E. J. 
Published: June 2005

SUMMARYThe prevalence ofEscherichia coliO157 displays striking variability across the Scottish cattle population. On 78% of farms, in a cross-sectional survey of 952, no shedding ofE. coliO157 was detected, but on a small proportion, ∼2%, very high prevalences of infection were found (with 90–100% of pats sampled being positive). We ask whether this variation arises from the inherent stochasticity in transmission dynamics or whether it is a signature of underlying heterogeneities in the cattle population. A novel approach is taken whereby the cross-sectional data are viewed as providing independent snapshots of a dynamic process. Using maximum-likelihood methods to fit time-dependent epidemiological models to the data we obtain estimates for the rates of immigration and transmission ofE. coliO157 infection – parameters which have not been previously quantified in the literature. A comparison of alternative model fits reveals that the variation in the prevalence data is best explained when a proportion of the cattle are assumed to transmit infection at much higher levels than the rest – the so-called super-shedders. Analysis of a second dataset, comprising samples taken from 32 farms at monthly intervals over a period of 1 year, additionally yields an estimate for the rate of recovery from infection. The pattern of prevalence displayed in the second dataset also strongly supports the super-shedder hypothesis.
Visual pigment composition in zebrafish: Evidence for a
rhodopsin–porphyropsin interchange system
Authors: ALLISON W. TED , HAIMBERGER THEODORE J. , HAWRYSHYN CRAIG W. , TEMPLE SHELBY E. 
Published: June 2005

(article appeared in Visual Neuroscience (2004), 21,
945–952)As a result of a production error, the footnote to this article was
incorrect. It should have stated that “the authors are in
alphabetical order” instead of stating that “all authors
contributed equally to this paper.” Because of the nature of this
error, the online version has been corrected.
Statistics of protein library construction
Authors: Firth Andrew E. , Patrick Wayne M. 
Published: June 2005

Abstract
Summary: We have investigated the statistics associated with constructing and sampling large protein-encoding libraries. Using fairly simple statistics we have written algorithms for estimating the diversity in libraries generated by the most commonly used protocols, including error-prone PCR, DNA shuffling, StEP PCR, oligonucleotide-directed randomization, MAX randomization, synthetic shuffling, DHR, ADO and SISDC.
Availability: Web interface and C++ source code available at http://guinevere.otago.ac.nz/stats.html
Contact: aef@sanger.otago.ac.nz
Supplementary information: Complete mathematical notes, model assumptions and justification, users' guide and worked examples at above website.
Practical FDR-based sample size calculations in microarray experiments
Authors: Hu Jianhua , Zou Fei , Wright Fred A. 
Published: June 2005

AbstractMotivation: Owing to the experimental cost and difficulty in obtaining biological materials, it is essential to consider appropriate sample sizes in microarray studies. With the growing use of the False Discovery Rate (FDR) in microarray analysis, an FDR-based sample size calculation is essential.Method: We describe an approach to explicitly connect the sample size to the FDR and the number of differentially expressed genes to be detected. The method fits parametric models for degree of differential expression using the Expectation–Maximization algorithm.Results: The applicability of the method is illustrated with simulations and studies of a lung microarray dataset. We propose to use a small training set or published data from relevant biological settings to calculate the sample size of an experiment.Availability: Code to implement the method in the statistical package R is available from the authors.Contact: jhu@mdanderson.org
Analysis of sulfur and selenium assimilation in Astragalus plants with varying capacities to accumulate selenium
Authors: Sors Thomas G. , Ellis Danielle R. , Na Gun Nam , Lahner Brett , Lee Sangman , Leustek Thomas , Pickering Ingrid J. , Salt David E. 
Published: June 2005

SummarySeveral Astragalus species have the ability to hyperaccumulate selenium (Se) when growing in their native habitat. Given that the biochemical properties of Se parallel those of sulfur (S), we examined the activity of key S assimilatory enzymes ATP sulfurylase (ATPS), APS reductase (APR), and serine acetyltransferase (SAT), as well as selenocysteine methyltransferase (SMT), in eight Astragalus species with varying abilities to accumulate Se. Se hyperaccumulation was found to positively correlate with shoot accumulation of S‐methylcysteine (MeCys) and Se‐methylselenocysteine (MeSeCys), in addition to the level of SMT enzymatic activity. However, no correlation was observed between Se hyperaccumulation and ATPS, APR, and SAT activities in shoot tissue. Transgenic Arabidopsis thaliana overexpressing both ATPS and APR had a significant enhancement of selenate reduction as a proportion of total Se, whereas SAT overexpression resulted in only a slight increase in selenate reduction to organic forms. In general, total Se accumulation in shoots was lower in the transgenic plants overexpressing ATPS, PaAPR, and SAT. Root growth was adversely affected by selenate treatment in both ATPS and SAT overexpressors and less so in the PaAPR transgenic plants. Such observations support our conclusions that ATPS and APR are major contributors of selenate reduction in planta. However, Se hyperaccumulation in Astragalus is not driven by an overall increase in the capacity of these enzymes, but rather by either an increased Se flux through the S assimilatory pathway, generated by the biosynthesis of the sink metabolites MeCys or MeSeCys, or through an as yet unidentified Se assimilation pathway.
Calcium regulation of chloroplast protein import
Authors: Chigri Fatima , Soll Jürgen , Vothknecht Ute C. 
Published: June 2005

SummaryThe majority of chloroplast proteins is nuclear‐encoded and therefore synthesized on cytosolic ribosomes. In order to enter the chloroplast, these proteins have to cross the double‐membrane surrounding the organelle. This is achieved by means of two hetero‐oligomeric protein complexes in the outer and inner envelope, the Toc and Tic translocon. The process of chloroplast import is highly regulated on both sides of the envelope membranes. Our studies indicate the existence of an undescribed mode of control for this process so far, at the same time providing further evidence that the chloroplast is integrated into the calcium‐signalling network of the cell. In pea chloroplasts, the calmodulin inhibitor Ophiobolin A as well as the calcium ionophores A23187 and Ionomycin affect the translocation of those chloroplast proteins that are imported with an N‐terminal cleavable presequence. Import of these proteins is inhibited in a concentration‐dependent manner. Addition of external calmodulin or calcium can counter the effect of these inhibitors. Translocation of chloroplast proteins that do not possess a cleavable transit peptide, that is outer envelope proteins or the inner envelope protein Tic32, is not affected. These results suggest that the import of a certain subset of chloroplast proteins is regulated by calcium. Our studies furthermore indicate that this regulation occurs downstream of the Toc translocon either within the intermembrane space or at the inner envelope translocon. A potential promoter of the calcium regulation is calmodulin, a protein well known as part of the plant's calcium signalling system.