bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conservation laws in disordered electron systems: Thermodynamic limit and configurational averaging
Authors: Janiš V. , Kolorenč J. 
Published: June 2004

AbstractWe discuss conservation of probability in noninteracting disordered electron systems. We argue that although the norm of the electron wave function is conserved in individual realizations of the random potential, we cannot extend this conservation law easily to configurationally averaged systems in the thermodynamic limit. A direct generalization of the norm conservation to averaged functions is hindered by the existence of localized states breaking translational invariance. Such states are elusive to the description with periodic Bloch waves. Mathematically this difficulty manifests itself via the diffusion pole in the electron–hole irreducible vertex. The pole leads to a clash with analyticity of the self‐energy, reflecting causality of the theory, when norm conservation is enforced by a Ward identity. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Monte Carlo method for propagating multi‐dimensional wave packets
Authors: Schröder Markus , Kleinekathöfer Ulrich 
Published: June 2004

AbstractA method for propagating multi‐dimensional wave packets in time using a product ansatz for the wave function is presented. Other than in the time‐dependent Hartree approach which is based on a variational scheme, the current method is based on the stochastic Ito calculus. The correlations between the different one‐dimensional wave functions are taken into account via stochastic processes such that on average the original Schrödinger equation is reproduced. Numerical tests of the proposed scheme have been performed in two and four dimensions. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin singlet excitons of composite fermions
Authors: Kramer B. , Merlo M. , Magnoli N. , Sassetti M. 
Published: June 2004

AbstractInteracting electrons in two degenerate Landau levels with opposite spins at total filling factor 1 are considered. Using the Chern–Simons gauge transformation, the system is mapped to composite fermions. These are non‐interacting on the average. The fluctuations of the Chern–Simons gauge field can introduce an effective interaction which is attractive for particle–hole pairs. The spin‐singlet ground state of such excitonic pairs is considered. At zero temperature, the pair‐breaking energy is estimated. It is given by the Fermi energy if the original interaction is sufficiently strong. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Few‐electron transfer reactions in donor–acceptor complexes and molecular wires
Authors: May V. , Petrov E. G. 
Published: June 2004

AbstractA unified description is presented for electron transfer reactions in molecular systems which proceed against the background of fast vibrational relaxation processes. By generalizing earlier treatments a common approach is developed which covers single‐ and two‐electron transfer as well as processes with the participation of even more electrons. Different types of reactions are discussed taking place either in donor–bridge–acceptor complexes or molecular wires attached to nanolectrodes. In particular, it is underlined that measuring the dependence of the transfer rate or of the stationary current on the length of the molecular system may represent an efficient way to uncover the concrete mechanism of charge transfer. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exponents of the localization length in the 2D Anderson model with off‐diagonal disorder
Authors: Eilmes Andrzej , A. Römer Rudolf 
Published: June 2004

AbstractWe study Anderson localization in two‐dimensional systems with purely off‐diagonal disorder. Localization lengths are computed by the transfer‐matrix method and their finite‐size and scaling properties are investigated. We find various numerically challenging differences to the usual problems with diagonal disorder. In particular, the divergence of the localization lengths close to the band centre is investigated in detail for bipartite and non‐bipartite lattices as well as different distributions of the off‐diagonal disorder. Divergence exponents for the localization lengths are constructed that appear to describe the data well down to at least 10−5. We find only little evidence for a crossover energy scale below which the power law has been argued to fail. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Random‐matrix model of resonant Rayleigh scattering in systems with exciton fine‐structure splitting
Authors: Runge Erich , Zimmermann Roland 
Published: June 2004

AbstractWe extend our recently developed local random‐matrix model of resonant Rayleigh scattering at the exciton transition in semiconductor nanostructure [Phys. Rev. B 69, 155307 (2004)] to systems with finite fine‐structure (exchange) splitting. A much richer phenomenology is found due to the interplay of two small characteristic energies, one being the exchange energy and the other given by the average energetic distance of two exciton state localized in the same spatial region. Three contributions to the Rayleigh signal can be distinguished by their temporal and angular behavior. They correspond to forward scattering, backscattering and a broad isotropic background. The change of their relative weight as function of average exchange energies provides further insight into the intimate connection of level repulsion and enhanced backscattering and the origin of the universal 2:3 ratio predicted in our earlier work. The time‐dependent Rayleigh signal is found to depend strongly on the polarization of excitation and detection. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluctuations of the Shannon capacity in a Rayleigh model of wireless communication
Authors: Stäring J. , Eriksson A. , Mehlig B. 
Published: June 2004

AbstractWe consider a Rayleigh model [Foschini and Gans, Wirel. Pers. Commun. 6, 311 (1998)] for the Shannon capacity characterising wireless information transfer in a network of antennae. In this model, the capacity C is a linear statistic of the channel matrix of the network. We use this fact to calculate the variance [C] of the Shannon capacity. We find that the expected value 〈C〉 of the Shannon capacity is typical, that is the coefficient of variation $\sqrt {{\rm var} [C]}/\langle C \rangle$ is small. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Erythrocyte osmotic fragility test for screening of alpha‐thalassemia‐1 and beta‐thalassemia trait in pregnancy
Authors: Sirichotiyakul S. , Tantipalakorn C. , Sanguansermsri T. , Wanapirak C. , Tongsong T. 
Published: June 2004

AbstractObjectives: To evaluate the sensitivity and specificity of osmotic fragility test (OFT) as a screening test in predicting the severe thalassemia trait (α‐thalassemia‐1 & β‐thalassemia). Methods: A descriptive analysis and diagnostic test of non‐anemic pregnant women attending antenatal care clinic, Maharaj Nakorn Chiang Mai, during April, and July 2002 was made. Blood samples were collected from 446 singleton pregnancies with no obvious medical complication such as iron deficiency anemia. OFT was performed in the same day, using 0.45% glycerin saline solution and the cut‐off value of less than 60% was used for an abnormal test. Quantitative HbA2 test and PCR (SEA type) were done as a gold standard to confirm the diagnosis of β‐thalassemia trait and α‐thalassemia‐1 trait, respectively. Results: The main outcome measures were sensitivity, specificity, positive and negative predictive value of OFT. If the OFT cut‐off value of less than 60% was considered positive, the test had a sensitivity, specificity, positive and negative predictive value of 97.6%, 72.9%, 33.6%, and 99.5%, respectively. Conclusion: OFT has high sensitivity in detection of α‐thalassemia‐1 trait or β‐thalassemia trait and due to its simplicity with very low cost it may, therefore, be considered as a screening test in a wide population.
Properties of the two neuromuscular compartments in a split bipennate muscle
Authors: Pereira Barry P. , Kumar V. Prem , Lim Aymeric Y. T. , Tan Jessie A. C. , Tan Bee‐Leng 
Published: June 2004

AbstractBipennate muscles may be split along their distal aponeurosis, dividing each into two compartments. These sub‐muscle units may be used in tendon transfers. This paper presents the contractile properties of the two sub‐units of the flexor carpi ulnaris in a macaca fascicularis, after it was split by up to 80% of its length. The sub‐muscle units were electrically stimulated and found to have independent isometric contraction, with minimal contraction recorded from the non‐stimulated sub‐unit. Also, the sum of the forces measured from each unit when stimulated individually, was found to be greater than the force of the whole muscle, given the same isometric conditions. The distal aponeurosis which is common allows force transmission between the compartments. Splitting the muscle along this distal aponeurosis alters this function and the force capacity of the muscle, providing a new potential for using the sub‐units as grafts for tendon transfers. © 2004 Orthopaedic Research Society. Published y Elsevier Ltd. All rights reserved.
Biosynthesis of UDP-GlcA, a key metabolite for capsular polysaccharide synthesis in the pathogenic fungus Cryptococcus neoformans
Authors: BAR-PELED Maor , GRIFFITH Cara L. , ORY Jeramia J. , DOERING Tamara L. 
Published: June 2004

UDP-glucose dehydrogenase catalyses the conversion of UDP-glucose into UDP-GlcA, a critical precursor for glycan synthesis across evolution. We have cloned the gene encoding this important enzyme from the opportunistic pathogen Cryptococcus neoformans. In this fungus, UDP-GlcA is required for the synthesis of capsule polysaccharides, which in turn are essential for virulence. The gene was expressed in Escherichia coli and the 51.3-kDa recombinant protein from wild-type and five mutants was purified for analysis. The cryptococcal enzyme is strongly inhibited by UDP-xylose and NADH, has highest activity at pH 7.5 and demonstrates Km (app) values of 0.1 and 1.5 mM for NAD+ and UDP-glucose respectively. Its activity was significantly decreased by mutations in the putative sites of NAD+ and UDP-glucose binding. Unlike previously reported eukaryotic UDP-glucose dehydrogenases, which are hexamers, the cryptococcal enzyme is a dimer.
Enzymic and structural characterization of nepenthesin, a unique member of a novel subfamily of aspartic proteinases
Authors: ATHAUDA Senarath B. P. , MATSUMOTO Koji , RAJAPAKSHE Sanath , KURIBAYASHI Masayuki , KOJIMA Masaki , KUBOMURA-YOSHIDA Nobuko , IWAMATSU Akihiro , SHIBATA Chiaki , INOUE Hideshi , TAKAHASHI Kenji 
Published: June 2004

Carnivorous plants are known to secrete acid proteinases to digest prey, mainly insects, for nitrogen uptake. In the present study, we have purified, for the first time, to homogeneity two acid proteinases (nepenthesins I and II) from the pitcher fluid of Nepenthes distillatoria (a pitcher-plant known locally as badura) and investigated their enzymic and structural characteristics. Both enzymes were optimally active at pH approx. 2.6 towards acid-denatured haemoglobin; the specificity of nepenthesin I towards oxidized insulin B chain appears to be similar, but slightly wider than those of other APs (aspartic proteinases). Among the enzymic properties, however, the most notable is their unusual stability: both enzymes were remarkably stable at or below 50 °C, especially nepenthesin I was extremely stable over a wide range of pH from 3 to 10 for over 30 days. This suggests an evolutionary adaptation of the enzymes to their specific habitat. We have also cloned the cDNAs and deduced the complete amino acid sequences of the precursors of nepenthesins I and II (437 and 438 residues respectively) from the pitcher tissue of N. gracilis. Although the corresponding mature enzymes (each 359 residues) are homologous with ordinary pepsin-type APs, both enzymes had a high content of cysteine residues (12 residues/molecule), which are assumed to form six unique disulphide bonds as suggested by computer modelling and are supposed to contribute towards the remarkable stability of nepenthesins. Moreover, the amino acid sequence identity of nepenthesins with ordinary APs, including plant vacuolar APs, is remarkably low (approx. 20%), and phylogenetic comparison shows that nepenthesins are distantly related to them to form a novel subfamily of APs with a high content of cysteine residues and a characteristic insertion, named ‘the nepenthesin-type AP-specific insertion’, that includes a large number of novel, orthologous plant APs emerging in the gene/protein databases.
Characterization of the ATP-hydrolysing activity of α-sarcoglycan
Authors: SANDONÀ Dorianna , GASTALDELLO Stefano , MARTINELLO Tiziana , BETTO Romeo 
Published: June 2004

α-Sarcoglycan is a glycoprotein associated with the dystrophin complex at sarcolemma of skeletal and cardiac muscles. Gene defects in α-sarcoglycan lead to a severe muscular dystrophy whose molecular mechanisms are not yet clear. A first insight into the function of α-sarcoglycan was obtained by finding that it is an ATP-binding protein and that it probably confers ability to hydrolyse ATP to the purified dystrophin complex [Betto, Senter, Ceoldo, Tarricone, Biral and Salviati (1999) J. Biol. Chem. 274, 7907–7912]. In the present study, we present definitive evidence showing that α-sarcoglycan is an ATP-hydrolysing enzyme. The appearance of α-sarcoglycan protein expression was correlated with the increase in ecto-nucleotidase activity during differentiation of C2C12 cells. Approx. 25% of ecto-nucleotidase activity displayed by the C2C12 myotubes was inhibited by preincubating cells with an antibody specific for the ATP-binding motif of α-sarcoglycan. This demonstrates that α-sarcoglycan substantially contributes to total ecto-nucleotidase activity of C2C12 myotubes. To characterize further this activity, human embryonic kidney 293 cells were transfected with expression plasmids containing α-sarcoglycan cDNA. Transfected cells exhibited a significant increase in the ATP-hydrolysing activity that was abolished by the anti-α-sarcoglycan antibody. The enzyme had a substrate specificity for ATP and ADP, did not hydrolyse other triphosphonucleosides, and the affinity for ATP was in the low mM range. The ATPase activity strictly required the presence of both Mg2+ and Ca2+ and was completely inhibited by suramin and reactive blue-2. These results show that α-sarcoglycan is a Ca2+, Mg2+-ecto-ATPDase. The possible consequences of the absence of α-sarcoglycan activity in the pathogenesis of muscular dystrophy are discussed.
Identification of a dehydrogenase acting on D-2-hydroxyglutarate
Authors: ACHOURI Younes , NOËL Gaëtane , VERTOMMEN Didier , RIDER Mark H. , VEIGA-DA-CUNHA Maria , van SCHAFTINGEN Emile 
Published: June 2004

Extracts of frozen rat liver were found to catalyse the formation of 3H2O from DL-2-hydroxy[2-3H]glutarate. Three peaks of enzyme activities were observed on separation by chromatography on DEAE-Sepharose. The first and second peaks corresponded to an enzyme acting on L-2-hydroxyglutarate and the third peak corresponded to an enzyme acting on D-2-hydroxyglutarate, as indicated by competitive inhibition of the detritiation of the racemic radioactive compound by the unlabelled L- and D-isomers respectively. The enzyme acting on the D-form was further characterized. It was independent of NAD or NADP and it converted D-2-hydroxyglutarate into α-ketoglutarate, transferring electrons to artificial electron acceptors. It also oxidized D-lactate, D-malate and meso-tartrate and was stimulated by Zn2+, Co2+ and Mn2+, but not by Mg2+ or Ca2+. Subcellular fractionation indicated that it was present in the mitochondrial fraction. The enzyme was further purified by chromatography on Blue Trisacryl and phenyl-Sepharose, up to a stage where only a few bands were still visible by SDS/ PAGE. Among the four candidate polypeptides that were identified by MS, one corresponded to a predicted mitochondrial protein homologous with FAD-dependent D-lactate dehydrogenase. The corresponding human protein was expressed in HEK-293 cells and it was shown to catalyse the detritiation of DL-2-hydroxy[2-3H]glutarate with similar properties as the purified rat enzyme.
Thimerosal stimulates Ca2+ flux through inositol 1,4,5-trisphosphate receptor type 1, but not type 3, via modulation of an isoform-specific Ca2+-dependent intramolecular interaction
Authors: BULTYNCK Geert , SZLUFCIK Karolina , KASRI Nael Nadif , ASSEFA Zerihun , CALLEWAERT Geert , MISSIAEN Ludwig , PARYS Jan B. , DE SMEDT Humbert 
Published: June 2004

Thiol-reactive agents such as thimerosal have been shown to modulate the Ca2+-flux properties of IP3 (inositol 1,4,5-trisphosphate) receptor (IP3R) via an as yet unidentified mechanism [Parys, Missiaen, De Smedt, Droogmans and Casteels (1993) Pflügers Arch. 424, 516–522; Kaplin, Ferris, Voglmaier and Snyder (1994) J. Biol. Chem. 269, 28972–28978; Missiaen, Taylor and Berridge (1992) J. Physiol. (Cambridge, U.K.) 455, 623–640; Missiaen, Parys, Sienaert, Maes, Kunzelmann, Takahashi, Tanzawa and De Smedt (1998) J. Biol. Chem. 273, 8983–8986]. In the present study, we show that thimerosal potentiated IICR (IP3-induced Ca2+ release) and IP3-binding activity of IP3R1, expressed in triple IP3R-knockout R23-11 cells derived from DT40 chicken B lymphoma cells, but not of IP3R3 or [Δ1–225]-IP3R1, which lacks the N-terminal suppressor domain. Using a 45Ca2+-flux technique in permeabilized A7r5 smooth-muscle cells, we have shown that Ca2+ shifted the stimulatory effect of thimerosal on IICR to lower concentrations of thimerosal and thereby increased the extent of Ca2+ release. This suggests that Ca2+ and thimerosal synergetically regulate IP3R1. Glutathione S-transferase pull-down experiments elucidated an interaction between amino acids 1–225 (suppressor domain) and amino acids 226–604 (IP3-binding core) of IP3R1, and this interaction was strengthened by both Ca2+ and thimerosal. In contrast, calmodulin and sCaBP-1 (short Ca2+-binding protein-1), both having binding sites in the 1–225 region, weakened the interaction. This interaction was not found for IP3R3, in agreement with the lack of functional stimulation of this isoform by thimerosal. The interaction between the IP3-binding and transmembrane domains (amino acids 1–604 and 2170–2749 respectively) was not affected by thimerosal and Ca2+, but it was significantly inhibited by IP3 and adenophostin A. Our results demonstrate that thimerosal and Ca2+ induce isoform-specific conformational changes in the N-terminal part of IP3R1, leading to the formation of a highly IP3-sensitive Ca2+-release channel.
Pustulöse Hauterkrankungen des Neugeborenen
Authors: Fölster‐Holst Regina , Höger Peter 
Published: June 2004

ZusammenfassungDas Spektrum pustulöser Hauterkrankungen im Neugeborenenalter ist groß. Es reicht von harmlosen, transitorischen Adaptationsstörungen bis zu systemischen, lebensbedrohlichen Erkrankungen. Bei 30 – 60 % der Neugeborenen treten Pusteln im Rahmen des harmlosen Erythema toxicum auf, dessen Genese bis heute nicht geklärt ist. Differentialdiagnostisch gilt es, hiervon die behandlungsbedürftigen pustulösen Hauterkrankungen abzugrenzen, die sowohl infektiöser als auch nicht‐infektiöser Genese sein können. Typische Erreger sind Malassezia furfur, Staphylokokken, Streptokokken, Candida spp. und Viren der Herpesgruppe.
Longitudinale Melanonychie bei Einnahme von Hydroxycarbamid
Authors: Neynaber Sven , Wolff Hans , Plewig Gerd , Wienecke Ralf 
Published: June 2004

ZusammenfassungVier Fallberichte von Patienten mit myeloproliferativem Syndrom, die zur Therapie Hydroxycarbamid (Synonyme: Hydroxyurea, Hydroxyharnstoff; Handelsnamen: Litalir®, Syrea®) einnehmen, und bei denen es einige Monate nach Beginn der Therapie zum Auftreten striärer, longitudinaler Pigmentierungen der Finger‐ und Fußnägel kommt. Hintergrund: Pigmentierungen von Finger‐ und Fußnägeln eröffnen ein weites Feld der Differentialdiagnosen. Sie können mikrobiologischer, melanozytärer, stoffwechselbedingter oder exogener Ursache sein. Patienten und Methodik: Wir berichten über drei weibliche und einen männlichen Patienten im Alter zwischen 62 und 87 Jahren mit myeloproliferativem Syndrom oder chronisch myeloischer Leukämie, die zur Behandlung über fünf bis zwölf Jahre Hydroxycarbamid Synonyme: Hydroxyurea, Hydroxyharnstoff; Handelsnamen: Litalir®, Syrea®) einnahmen oder noch einnehmen. Die vier Patienten haben einen Hauttyp II nach Fitzpatrick. Ergebnisse: Mehrere Monate nach Beginn der Einnahme kam es zu striären, longitudinalen Pigmentierungen an Finger‐ und Fußnägeln. Bei zwei Patienten wurde dieser Befund als Zufallsbefund diagnostiziert, während sich die anderen beiden Patienten wegen der Nagelpigmentierungen in hautfachärztliche Behandlung begaben.Bei zwei der Patienten kam es wenige Monate nach Absetzen von Hydroxycarbamid zum Verschwinden der longitudinalen Pigmentierung während bei einem Patienten die Melanonychie der Finger‐ und Fußnägel bestehen blieb. Eine Patientin konnte wegen fehlenden Kontaktes nicht nachkontrolliert werden. Schlußfolgerung: Beim Auftreten longitudinaler Melanonychie bei hämato‐onkologischen Patienten ist eine genaue Anamnese, insbesondere bezüglich der Medikamente wichtig, da durch Hydroxyharnstoff Pigmentierungen der Finger‐ und Fußnägel auftreten können. Nach wie vor müssen jegliche melanozytäre Pigmentierungen der Akren, die Ausdruck eines akrolentiginösen Melanoms sein können, diagnostisch ausgeschlossen werden.
THE BINDING OF PENICILLIN IN RELATION TO ITS CYTOTOXIC ACTION
Authors: Eagle Harry 
Published: June 2004

1. (a) Mammalian cells in tissue culture (mouse fibroblasts and malignant human uterine epithelium) did not concentrate penicillin from the culture medium. Even at low concentrations, the cellular accumulation was usually less than that in the surrounding fluid, and most of it was removed by washing. The radioactive material in such eluates was actively bactericidal, and was presumably in large part unchanged penicillin.
(b) Penicilloic acid, produced by the action of penicillinase, was bound to the same (limited) extent as the active antibiotic. In both these respects mammalian cells behaved like naturally penicillin-resistant bacteria, and unlike such penicillin-sensitive bacteria as Streptococcus pyogenes or Diplococcus pneumoniae.
2. Cell-free sonic extracts of the L strain had the same limited reactivity with penicillin as the intact cells. The relatively minute amounts bound by the cells are therefore not due to their impermeability, but instead reflect the inherently low reactivity of the cellular constituents with penicillin.
3. It is suggested that the relative non-toxicity of penicillin for the mammalian host, and for mammalian cells in tissue culture, may be related to this low order of reactivity with the antibiotic.