bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alternating repetition time balanced steady state free precession
Authors: Leupold J. , Hennig J. , Scheffler K. 
Published: January 2006

AbstractA novel balanced SSFP technique for the separation or suppression of different resonance frequencies (e.g., fat suppression) is presented. The method is based on applying two alternating and different repetition times, TR1 and TR2. This RF scheme manipulates the sensitivity of balanced SSFP to off‐resonance effects by a modification of the frequency response profile. Starting from a general approach, an optimally broadened stopband within the frequency response function is designed. This is achieved with a TR2 being one third of TR1 and an RF‐pulse phase increment of 90°. With this approach TR2 is too short (∼1 ms) to switch imaging gradients and is only used to change the frequency sensitivity. Without a significant change of the spectral position of the stopband, TR1 can be varied over a range of values (∼2.5–4.5 ms) while TR2 and phase cycling is kept constant. On‐resonance spins show a magnetization behavior similar to balanced SSFP, but with maximal magnetization at flip angles about 10° lower than in balanced SSFP. The total scan time is increased by about 30% compared to conventional balanced SSFP. The new technique was applied on phantoms and volunteers to produce rapid, fat suppressed images. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.
Investigation of laser‐fired rear‐side recombination properties using an analytical model
Authors: Kray Daniel , Glunz Stefan 
Published: January 2006

AbstractThis paper presents the application of the analytical model for locally contacted rear sides recently published by Fischer to the determination of recombination losses of solar cells with fixed metallization fraction, but varying contact pitch. After the successful experimental validation of the model on oxide‐passivated solar cells with ohmic contacts, the model was used for a detailed investigation of rear sides prepared by the laser‐fired contacts (LFC) method. In this way the surface recombination velocity (SRV) at the very contact areas was extracted for a broad base doping range. The determined parameterization allows the calculation of the SRV of any LFC rear side concerning base doping and contact pitch. The excellent passivation quality of the alnealed oxide with LFC contacts is shown: on 1 (100) Ω cm FZ an effective SRV of only 35 (4·3) cm/s could be measured with 1000 µm contact pitch. Copyright © 2006 John Wiley & Sons, Ltd.
Reconstruction of central carbon metabolism in Sulfolobus solfataricus using a two‐dimensional gel electrophoresis map, stable isotope labelling and DNA microarray analysis
Authors: Snijders Ambrosius P. L. , Walther Jasper , Peter Stefan , Kinnman Iris , de Vos Marjon G. J. , van de Werken Harmen J. G. , Brouns Stan J. J. , van der Oost John , Wright Phillip C. 
Published: January 2006

AbstractIn the last decade, an increasing number of sequenced archaeal genomes have become available, opening up the possibility for functional genomic analyses. Here, we reconstructed the central carbon metabolism in the hyperthermophilic crenarchaeon Sulfolobus solfataricus (glycolysis, gluconeogenesis and tricarboxylic acid cycle) on the basis of genomic, proteomic, transcriptomic and biochemical data. A 2‐DE reference map of S. solfataricus grown on glucose, consisting of 325 unique ORFs in 255 protein spots, was created to facilitate this study. The map was then used for a differential expression study based on 15N metabolic labelling (yeast extract + tryptone‐grown cells (YT) vs. glucose‐grown cells (G)). In addition, the expression ratio of the genes involved in carbon metabolism was studied using DNA microarrays. Surprisingly, only 3 and 14% of the genes and proteins, respectively, involved in central carbon metabolism showed a greater than two‐fold change in expression level. All results are discussed in the light of the current understanding of central carbon metabolism in S. solfataricus and will help to obtain a system‐wide understanding of this organism.
Proteomic analysis of beryllium‐induced genotoxicity in an Escherichia coli mutant model system
Authors: Taylor‐McCabe Kirsten J. , Wang Zaolin , Sauer Nancy N. , Marrone Babetta L. 
Published: January 2006

AbstractBeryllium is the second lightest metal, has a high melting point and high strength‐to‐weight ratio, and is chemically stable. These unique chemical characteristics make beryllium metal an ideal choice as a component material for a wide variety of applications in aerospace, defense, nuclear weapons, and industry. However, inhalation of beryllium dust or fumes induces significant health effects, including chronic beryllium disease and lung cancer. In this study, the mutagenicity of beryllium sulfate (BeSO4) and the comutagenicity of beryllium with a known mutagen 1‐methyl‐3‐nitro‐1‐nitrosoguanidine (MNNG) were evaluated using a forward mutant detection system developed in Escherichia coli. In this system, BeSO4 was shown to be weakly mutagenic alone and significantly enhanced the mutagenicity of MNNG up to 3.5‐fold over MNNG alone. Based on these results a proteomic study was conducted to identify the proteins regulated by BeSO4. Using the techniques of 2‐DE and oMALDI‐TOF MS, we successfully identified 32 proteins being differentially regulated by beryllium and/or MNNG in the E. coli test system. This is the first study to describe the proteins regulated by beryllium in vitro, and the results suggest several potential pathways for the focus of further research into the mechanisms underlying beryllium‐induced genotoxicity.
The phosphate‐starvation response in Vibrio cholerae O1 and phoB mutant under proteomic analysis: Disclosing functions involved in adaptation, survival and virulence
Authors: von Krüger Wanda Maria Almeida , Santos Lery Leticia Miranda , Soares Marcia Regina , Saloum de Neves‐Manta Fernanda , Batista e Silva Celia Maria , da Costa Neves‐Ferreira Ana Gisele , Perales Jonas , Bisch Paulo Mascarello 
Published: January 2006

AbstractA proteomic analysis of a wild‐type and of a phoB mutant showed that Vibrio cholerae expresses genes of two major regulons in response to phosphate starvation. The Pho regulon, expressed by the wild‐type, allowed the cells to adapt to the new environment. Induction of the general stress regulon was mainly observed in the phoB mutant as a strategy to resist stress and survive. Some functions of the adaptative and survival responses play roles in the pathogenicity of the bacteria. Among the members of the Pho regulon, we found a porin described as an important factor for the intestinal colonisation. Other functions not obviously related to phosphate metabolism, expressed preferentially by the wild‐type cells, have also been implicated in virulence. These findings might explain the lack of virulence of the phoB mutant. The Pho regulon picture of V. cholerae, however, will not be complete until minor members and membrane proteins are identified. Among the phosphate‐starvation induced genes we have found 13 hypothetical ones and for some of them functions have been assigned. The majority of the genes identified here have not been described before, thus they could be used to expand the proteomic reference map of V. cholerae El Tor.
Protein profiling the effects of in vitro hyperoxic exposure on fetal rabbit lung
Authors: Henschke Phillip , Vorum Henrik , Honoré Bent , Rice Gregory Edward 
Published: January 2006

AbstractThe aim of this study was to test the hypothesis that acute in vitro exposure of prematurely delivered fetal rabbit lungs to hyperoxic conditions will induce the expression of an adaptive cassette of proteins that mediates antioxidant and inflammatory processes. To test this hypothesis, ex situ fetal rabbit lung explants were prepared from New Zealand white rabbits delivered by cesarean section on day 29 of gestation and incubated under air (21% O2; 5% CO2) or hyperoxic (95% O2; 5% CO2) atmospheres. Total tissue protein was extracted following incubation and subjected to 2‐DE. Using this technique, 1500–2000 protein spots were resolved per gel. Treatment‐dependent, differentially expressed proteins were identified by image analysis (Melanie II) and MALDI‐TOF MS and MALDI‐MS/MS. The analysis identified 12 protein spots that were differentially expressed by 1.5‐fold or more (p<0.05) by exposure to hyperoxic conditions. Six of these differentially expressed proteins were identified as vimentin, annexin I, inorganic pyrophosphatase, prohibitin, an N‐terminal fragment of ATP synthase and heat shock protein 27. The data obtained are consistent with the roles of these proteins in mediating cellular response to oxidative stress and in regulating cell proliferation.
The tegument surface membranes of the human blood parasite Schistosoma mansoni: A proteomic analysis after differential extraction
Authors: Braschi Simon , Curwen Rachel S. , Ashton Peter D. , Verjovski‐Almeida Sergio , Wilson Alan 
Published: January 2006

AbstractThe blood fluke Schistosoma mansoni can live for years in the hepatic portal system of its human host and so must possess very effective mechanisms of immune evasion. The key to understanding how these operate lies in defining the molecular organisation of the exposed parasite surface. The adult worm is covered by a syncytial tegument, bounded externally by a plasma membrane and overlain by a laminate secretion, the membranocalyx. In order to determine the protein composition of this surface, the membranes were detached using a freeze/thaw technique and enriched by sucrose density gradient centrifugation. The resulting preparation was sequentially extracted with three reagents of increasing solubilising power. The extracts were separated by 2‐DE and their protein constituents were identified by MS/MS, yielding predominantly cytosolic, cytoskeletal and membrane‐associated proteins, respectively. After extraction, the final pellet containing membrane‐spanning proteins was processed by liquid chromatographic techniques before MS. Transporters for sugars, amino acids, ions and other solutes were found together with membrane enzymes and proteins concerned with membrane structure. The proteins identified were categorised by their function and putative location on the basis of their homology with annotated proteins in other organisms.
Comparison of the mechanisms of reactions of β‐lactams and β‐sultams, including their reactions with some serine enzymes
Authors: Page Michael I. , Tsang Wing Y. , Ahmed Naveed 
Published: January 2006

AbstractThe strain energy of the four‐membered ring of β‐lactams is not released in the transition state to lower the activation energy of reactions involving ring‐opening. The alkaline hydrolysis of N‐aroyl β‐lactams occurs with competitive exo‐ and endocyclic CN ring fission, the ratio of which varies with the aryl substituent. β‐Sultams are four‐membered cyclic sulfonamides and are about 103 fold more reactive than analogous β‐lactams. Nucleophiles usually attack N‐acylsulfonamides at the carbonyl centre resulting in CN bond fission, but the hydrolysis of N‐acyl β‐sultams occurs with SN fission and opening of the four‐membered ring. The 3‐oxo‐β‐sultams are a unique combination of both β‐lactams and β‐sultams and therefore are susceptible to nucleophilic attack at either the acyl or the sulfonyl centre, but they hydrolyse with exclusive SN bond fission. β‐Sultams are novel inhibitors of the serine enzymes elastase, transpeptidase and β‐lactamase due to sulfonylation of the active‐site serine residue. Structure–activity relationships are used to identify differences in transition‐state structures between β‐sultams as inhibitors and β‐lactams as substrates. Copyright © 2006 John Wiley & Sons, Ltd.
Emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate and methyl methacrylate
Authors: Eslami Hormoz , Zhu Shiping 
Published: January 2006

AbstractThe emulsion atom transfer radical block copolymerization of 2‐ethylhexyl methacrylate (EHMA) and methyl methacrylate (MMA) was carried out with the bifunctional initiator 1,4‐butylene glycol di(2‐bromoisobutyrate). The system was mediated by copper bromide/4,4′‐dinonyl‐2,2′‐bipyridyl and stabilized by polyoxyethylene sorbitan monooleate. The effects of the initiator concentration and temperature profile on the polymerization kinetics and latex stability were systematically examined. Both EHMA homopolymerization and successive copolymerization with MMA proceeded in a living manner and gave good control over the polymer molecular weights. The polymer molecular weights increased linearly with the monomer conversion with polydispersities lower than 1.2. A low‐temperature prepolymerization step was found to be helpful in stabilizing the latex systems, whereas further polymerization at an elevated temperature ensured high conversion rates. The EHMA polymers were effective as macroinitiators for initiating the block polymerization of MMA. Triblock poly(methyl methacrylate–2‐ethylhexyl methacrylate–methyl methacrylate) samples with various block lengths were synthesized. The MMA and EHMA reactivity ratios determined by a nonlinear least‐square method were ∼0.903 and ∼0.930, respectively, at 70 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1914–1925, 2006
Structural prediction of peptides binding to MHC class I molecules
Authors: Bui Huynh‐Hoa , Schiewe Alexandra J. , von Grafenstein Hermann , Haworth Ian S. 
Published: January 2006

AbstractPeptide binding to class I major histocompatibility complex (MHCI) molecules is a key step in the immune response and the structural details of this interaction are of importance in the design of peptide vaccines. Algorithms based on primary sequence have had success in predicting potential antigenic peptides for MHCI, but such algorithms have limited accuracy and provide no structural information. Here, we present an algorithm, PePSSI (peptide‐MHC prediction of structure through solvated interfaces), for the prediction of peptide structure when bound to the MHCI molecule, HLA‐A2. The algorithm combines sampling of peptide backbone conformations and flexible movement of MHC side chains and is unique among other prediction algorithms in its incorporation of explicit water molecules at the peptide‐MHC interface. In an initial test of the algorithm, PePSSI was used to predict the conformation of eight peptides bound to HLA‐A2, for which X‐ray data are available. Comparison of the predicted and X‐ray conformations of these peptides gave RMSD values between 1.301 and 2.475 Å. Binding conformations of 266 peptides with known binding affinities for HLA‐A2 were then predicted using PePSSI. Structural analyses of these peptide‐HLA‐A2 conformations showed that peptide binding affinity is positively correlated with the number of peptide‐MHC contacts and negatively correlated with the number of interfacial water molecules. These results are consistent with the relatively hydrophobic binding nature of the HLA‐A2 peptide binding interface. In summary, PePSSI is capable of rapid and accurate prediction of peptide‐MHC binding conformations, which may in turn allow estimation of MHCI‐peptide binding affinity. Proteins 2006. © 2006 Wiley‐Liss, Inc.
Conductance phenomena in microcrystalline cellulose
Authors: Nilsson M. 
Published: January 2006

Abstract We have investigated the conduction phenomena in compacted tablets of cellulose with varying relative humidity (RH) with techniques such as Low Frequency Dielectric Spectroscopy (LFDS) and Transient Current (TC) at room temperature. Two exponential decaying regions in the transient current measurements indicate two ionic species contributing to the conduction mechanism. A high power‐law exponent of ∼9 for the conductance with moisture content has been found. The mobility initially decreases with RH up to monolayer coverage, and further water vapor increases the mobility, indicating a blocking of available positions for the charge carrier ions. When the amount of water molecules present in the tablet increases one order of magnitude, the number of charge carriers increases 5‐6 orders of magnitude, suggesting a transition from a power‐law increase to a linear effective medium theory for the conduction. The charge carrier dependence on RH suggests that a percolating network of water molecules adsorbed to 6‐OH units on the cellulose chain span through the sample. The conductivity mechanisms in cellulose are still not clear. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The intrinsic conductivity of nanosized semiconducting crystals
Authors: Huijbregts L. J. , Brom H. B. , Brokken‐Zijp J. C. M. , Michels M. A. J. , de Goeje M. , Yuan M. 
Published: January 2006

AbstractWe show how the dielectric response of powders of semiconducting nanocrystals can be used to extract the intrinsic conductivity of the nanocrystals. The method is applied to powders of nanocrystals of semiconductive aquocyanophthalocyaninatocobalt (III) (Phthalcon‐11), a promising filler material for conducting composites, and published data of silicon. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spreading resistance microscopy study of polyamidine thin films
Authors: Rentzsch R. , Ionov A. N. , Nikolaeva M. N. , Dunaevskii M. S. 
Published: January 2006

AbstractWe have observed that thin films of polyamidine may exhibit high conductivity in some locations on the polymer surface at low electrical field strength. The conductance which has been tested by spreading resistance mode of an atomic force microscope depended on the type of substrate. We consider that a critical density of charge inside the polymer is needed for its switching to the conductive state. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of the phononless hopping in a Coulomb glass
Authors: Matulewski J. , Baranovskii S. D. , Thomas P. 
Published: January 2006

AbstractThe phononless hopping conductivity of a disordered system with localized states is studied in a broad range of frequencies by straightforward computer simulations taking into account Coulomb interactions. At sufficiently low temperatures, the conductivity is determined by the zero‐phonon absorption of the photon by pairs of states. The laser frequency dependence of the conductivity is examined and compared with the analytical model of Efros and Shklovskii and with recent experimental data obtained on Si:P. The range of parameters is determined, for which the conductivity dependence on photon energy best reproduces the experimental results. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magneto‐transport in ferromagnetic granular networks
Authors: Vilchik Hagai , Frydman Aviad , Berkovits Richard 
Published: January 2006

AbstractUsing numerical simulations and analytical calculations we have examined the transport properties of a ferromagnetic granular systems. We model this complex network system by an ensemble of ferromagnetic conducting grains randomly located on a 2D plain. Quite surprisingly, the magneto‐resistance of a complex network can be approximated by the magneto‐resistance of a single pair of ferromagnetic grains, although our simulations show that the transport trajectories change from a quasi‐1D path through the system to a percolation network through the larger grains as the number of grain in the system increases. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Generalized pair approximation in the description of the ac conductivity of a dense disordered array of quantum dots
Authors: Zvyagin I. P. 
Published: January 2006

AbstractThe frequency dependence of the hopping conductivity of dense arrays of semiconductor quantum dots of size $ \bar a $ substantially exceeding the edge‐to‐edge separation $ \bar w $ between the neighboring quantum dots is considered. It is shown that at low frequencies in a wide frequency range the conductivity obeys a fractional power law and its magnitude depends on the structural characteristics of the material. The possibility of the deviations from universality related to the material structure is discussed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetoresistance and Hall effect of a 2DEG in GaAs/AlGaAs: electron interaction and ‘memory’ effects in the presence of a mixed disorder
Authors: Galaktionov E. A. , Savchenko A. K. , Ritchie D. A. 
Published: January 2006

AbstractWe have studied the corrections to the Drude conductivity and Hall constant of a high‐mobility twodimensional electron gas in a GaAs/AlGaAs heterostructure due to the electron‐electron interaction in the presence of a mixed disorder. A parabolic, negative, temperature‐dependent magnetoresistance (MR) and temperature‐dependent Hall constant are observed. We show that these effects can be explained in terms of the electron interaction theory and obtain the values of the Fermi‐liquid interaction parameter Fσo . In addition, a temperature independent, positive MR has been detected. This classical MR is also shown to be a consequence of the mixed disorder. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Disorder‐induced features of the transverse resistance in a Si‐MOSFET in the quantum Hall effect regime
Authors: Shlimak I. , Friedland K.‐J. , Ginodman V. , Kravchenko S.V. 
Published: January 2006

AbstractWe investigate two features of the transverse resistance Rxy in a Si‐MOSFET in the quantum Hall effect regime. The first, the “overshoot” phenomenon, is observed at filling factor ν = 3. In this case, when the magnetic field increases and the filling factor ν approaches ν = 3, Rxy overshoots its normal plateau value of 1/3(h /e 2). However, if magnetic field increases further, Rxy decreases to its normal value. This effect has been previously observed in other two‐dimensional systems, particularly, in a more perfect Si/SiGe heterostructure. Comparing the two Si systems, Si‐MOSFET and Si/SiGe, with similar electron density and different mobility clearly shows that the increase in disorder leads to significant enhancement of the overshoot. The second effect is reported here for the first time and is characteristic only of Si‐MOSFET. It was observed that when the filling factor approaches ν = 5, Rxy , which is already at the plateau of 1/4(h /e 2), abruptly decreases to 1/5(h /e 2) and then sharply returns to 1/4(h /e 2). This “deep” effect is more pronounced at higher electron concentration for which ν = 5 is achieved at stronger magnetic fields. The explanation is based on the assumption of the equality between the disorder–induced broadening of adjacent valley‐split Landau bands and the energy gap between them. In the narrow interval of magnetic fields near ν = 5, the gap increases sharply due to exchange enhancement of the valley splitting, which results in a corresponding drop in Rxy . (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interference quantum corrections in the low temperature microwave magnetoresistance of the nondegenerate Ge
Authors: Veinger A. I. , Zabrodskii A. G. , Tisnek T. V. , Goloshchapov S. I. 
Published: January 2006

AbstractThe first observation of low temperature magnetoresistance (MR) of interference nature in the case of a light doping is reported. This MR occurs in both n‐ and p‐type Ge samples in weak magnetic fields at frequency of 10 GHz and temperatures below 30 K. It is registered on the background of the classical MR effect associated with electrons in different valleys of n‐Ge and with different (heavy and light) holes of p‐Ge. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phononless inelastic transport through a disordered array of quantum wires
Authors: Chudnovskiy A. L. 
Published: January 2006

AbstractPhononless plasmon assisted transport through a long disordered array of finite length quantum wires is investigated analytically. Generically strong electron plasmon interaction in quantum wires results in a qualitative change of the temperature dependence of thermally activated resistance in comparison to phonon assisted transport. At high temperatures, the thermally activated resistance is determined by the Luttinger liquid interaction parameter of the wires. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)