bluuebunny/crossref_metadata_2025 huggingface dataset:
NMR nuclear magnetic shielding anisotropy of linear molecules within the linear response within the elimination of the small component approach
Authors: Ruiz de Azúa Martín C. , Giribet Claudia G. , Melo Juan I.
Published: January 2011

The influence of the spin-Zeeman (SZ) operator in the evaluation of the spin-orbit effect on the nuclear magnetic shielding tensor in the context of the linear response within the elimination of the small component approach is critically discussed. It is shown that such term yields no contribution to the isotropic nuclear magnetic shielding constant, but it may be of great importance in the determination of individual tensor components, and particularly of the tensor anisotropy. In particular, an interesting relation between the SZ and orbital Zeeman contributions to the spin-orbit effect for the case of linear molecules is shown to hold. Numerical examples for the BrH, IH, and XeF2 molecules are presented which show that, provided the SZ term is taken into account, results of the individual shielding tensor components and the tensor anisotropy are in good agreement with those obtained by other theoretical methods, and particularly by the Dirac–Hartree–Fock approach.
Low thermal conductivity and enhanced thermoelectric performance of Gd-filled skutterudites
Authors: Liu Ruiheng , Chen Xihong , Qiu Pengfei , Liu Jinfeng , Yang Jiong , Huang Xiangyang , Chen Lidong
Published: January 2011

With Fe compensation, the heavy rare earth element Gd-filled GdyFexCo4−xSb12 (x<2) skutterudites have been successfully synthesized by melting-annealing approach. Fe substitution on the Co site brings two contrary effects on Gd filling: charge compensation which enhances the filling fraction of Gd, and Lattice expansion which is deleterious for the stability of filled compounds that contain smaller atoms. When Fe content is less than 1.7, pure GdyFexCo4−xSb12 compounds are obtained and the Gd maximum filling fraction (ymax) increases with Fe content. The power factor (S2σ) of the GdyFexCo4−xSb12 increases with Fe content. The lattice thermal conductivity is significantly depressed by Gd filling. The sample Gd0.41Fe1.48Co2.52Sb12 has a lattice thermal conductivity as low as 1.1 W m−1 K−1 at room temperature, and its figure of merit (ZT) reaches a maximum value of 0.83 at 700 K. At high temperature, thermal conductivity shows significant increase due to bipolar diffusion, which obstructs obtaining higher ZT.
Influence of transferred-electron effect on drain-current characteristics of AlGaN/GaN heterostructure field-effect transistors
Authors: Moradi Maziar , Valizadeh Pouya
Published: January 2011

An analytical model, with incorporation of transferred-electron effect, for drain-current characteristics of AlGaN/GaN heterostructure field-effect transistors (HFETs) is presented. The transferred-electron effect is often neglected in modeling the drain-current of III-V HFETs. The broad steady-state electron drift-velocity overshoot of GaN in comparison to other direct semiconductors such as GaAs and InP, in addition to the larger difference between the peak and saturation drift-velocity, and the wider band gap of this semiconductor suggest the importance of the incorporation of transferred-electron effect (i.e., steady-state drift-velocity overshoot) in modeling the drain-current of these devices. Simulation results are compared with the results of the adoption of a saturating drift transport model, which has been recently used in modeling the drain-current of these devices. Comparisons between the two models demonstrate the importance of the consideration of transferred-electron effect, especially as the Ohmic contact quality is improved.
Precessing vortices and antivortices in ferromagnetic elements
Authors: Lyberatos A. , Komineas S. , Papanicolaou N.
Published: January 2011

A micromagnetic numerical study of the precessional motion of the vortex and antivortex states in soft ferromagnetic circular nanodots is presented using Landau-Lifshitz–Gilbert dynamics. For sufficiently small dot thickness and diameter, the vortex state is metastable and spirals toward the center of the dot when its initial displacement is smaller than a critical value. Otherwise, the vortex spirals away from the center and eventually exits the dot which remains in a state of in-plane magnetization (ground state). In contrast, the antivortex is always unstable and performs damped precession resulting in annihilation at the dot circumference. The vortex and antivortex frequencies of precession are compared with the response expected on the basis of Thiele’s theory of collective coordinates. We also calculate the vortex restoring force with an explicit account of the magnetostatic and exchange interaction on the basis of the “rigid” vortex and “two-vortices side charges free” models and show that neither model explains the vortex translation mode eigenfrequency for nanodots of sufficiently small size.
Frequency-dependent electrical properties of ferroelectric BaTi2O5 single crystal
Authors: Masó Nahum , Yue XinYan , Goto Takashi , West Anthony R.
Published: January 2011

Analysis and modeling of impedance spectroscopy data of ferroelectric BaTi2O5 single crystal has been carried out at temperatures both below and above the ferroelectric Curie temperature, TC. The most appropriate equivalent circuit is found to consist of a parallel combination of a resistor (R), capacitor (C), and constant phase element (CPE). Below TC, the resistance R is too large to measure and the circuit simplifies to C–CPE. Above TC, R shows Arrhenius behavior with low values of conductivity, eg ∼4×10−7 S cm−1 at 800 K and high activation energy, 1.13(2) eV, and represents a thermally activated dc hopping process associated with leakage transport of either electrons or holes through the crystal lattice. C is frequency-independent, passes through a maximum at the ferroelectric–paraelectric transition temperature, TC∼475 °C, represents the limiting high frequency capacitance of the crystal and is attributed to the response of the individual dipoles that are responsible for the ferroelectricity. The A parameter of the CPE also passes through a maximum at TC, is not thermally activated in the same manner as R but shows similar temperature dependence to that of C. The physical origin of the CPE, with interlinked resistive and capacitive components, whose relative contributions are governed by the power law n parameter, may be associated with dipole-dipole interactions and reflect the time- and frequency-dependence of their cooperative nature.
Structural, electrical, and strain properties of stoichiometric 1−x−y(Bi0.5Na0.5)TiO3−x(Bi0.5K0.5TiO3)−y(Na0.5K0.5)NbO3 solid solutions
Authors: Singh Amrita , Chatterjee Ratnamala
Published: January 2011

Results on two series of lead-free piezoelectric solid solutions of 1−x−y(Bi0.5Na0.5)TiO3−x(Bi0.5K0.5TiO3)−y(Na0.5K0.5)NbO3 (BNT-BKT-KNN) ceramics, synthesized in the vicinity of ferroelectric rhombohedral (x=0.17) and ferroelectric tetragonal (x=0.20) phase boundary of 1−x(BNT)–xBKT are presented. Orthorhombic KNN in stoichiometric proportion as third component with 0.0≤y≤0.06 is added to prepare these two series (i) with x=0.17 and (ii) with x=0.20. Addition of KNN up to a critical y is observed to improve tetragonality in both series and solid solubility of KNN was verified at least up to y=0.1 in this system. Depolarization temperature Td of these stoichiometric BNT-BKT-KNN series were found to be considerably lower than that of their parent BNT-BKT compositions. As a result of this, coexistence of polar and nonpolar phases for compositions at morphotropic phase boundary (MPB) were indicated at room temperature, resulting in pinched polarization versus electric field (P-E) loops and large strain (strain of ∼0.80% was observed for y=0.01 sample in ×20 series and strain of 0.50% was seen for y=0.04 sample in ×17 series) The MPB of ×17 and ×20 series found to be at y=0.04 and y=0.01, respectively.
Structure evolution of Zn cluster on graphene for ZnO nanostructure growth
Authors: Guo J. Y. , Xu C. X. , Gu B. X. , Sheng F. Y.
Published: January 2011

Monte Carlo simulations are carried out for Zn cluster supported on a suspended graphene to estimate the morphological evolution of the following growth of ZnO nanostructure. The metal–metal interactions are modeled with the tight-binding many-body potential and a Lennard-Jones potential is used to describe the metal-carbon interactions. The dynamic processes of Zn cluster in the temperature field decomposing and drifting effects are visualized through the simulation. Zn atoms make one regular atomic single layer on the graphene sheet at a relatively low temperature, which would act as orderly and high density catalytic nucleation sites. In the relatively high temperature, the Zn atomic single layer falls to pieces, the orderly and low density catalytic nucleation sites are formed. It is expected from these behaviors that the buffer layer of graphene provide a sound explanation for the formation of ordered orientated ZnO nanostructure.
Growth and structure of an ultrathin tin oxide film on Rh(111)
Authors: Yuhara J. , Tajima D. , Matsui T. , Tatsumi K. , Muto S. , Schmid M. , Varga P.
Published: January 2011

The oxidation of submonolayer tin films on a Rh(111) surface by O2 gas was studied using low energy electron diffraction, Auger electron spectroscopy, x-ray photoemission spectroscopy (XPS), and scanning tunneling microscopy. A uniform tin oxide monolayer film formed at oxidation temperatures around 500 °C and a partial pressure of 2×10−7 mbar O2. The tin oxide film had (2×2) periodicity on the Rh(111) surface, and the resulting tin coverage was determined to be 0.5 ML. Using XPS, the compositional ratio O/Sn was determined to be 3/2. XPS spectra showed a single component for the Sn and O peaks, indicating a uniform bonding environment. Finally, ab initio density-functional theory total energy calculations and molecular dynamics simulations were performed using the projector augmented wave method to determine the detailed structure of the tin oxide thin film.
Experimental evidence of resonant effective permittivity in a dielectric metamaterial
Authors: Lepetit T. , Akmansoy É. , Ganne J.-P.
Published: January 2011

We designed and fabricated a dielectric metamaterial consisting of one set of high permittivity resonators. We experimentally showed that this metamaterial exhibits resonant effective permittivity, issued from the second mode of Mie resonances of these resonators. Therefore, metamaterials consisting of high permittivity resonators may provide either effective permeability or permittivity issued from the first two modes of Mie resonances, respectively. This ensures that all-dielectric metamaterials involving two sets of matched high permittivity resonators may exhibit negative index issued from these two modes, notably up to the terahertz domain.
Plasmonic field enhancement of individual nanoparticles by correlated scanning and photoemission electron microscopy
Authors: Peppernick Samuel J. , Joly Alan G. , Beck Kenneth M. , Hess Wayne P.
Published: January 2011

We present results of a combined two-photon photoemission and scanning electron microscopy investigation to determine the electromagnetic enhancement factors of silver-coated spherical nanoparticles deposited on an atomically flat mica substrate. Femtosecond laser excitation of the nanoparticles produces intense photoemission, attributed to near-resonant excitation of localized surface plasmons. Enhancement factors are determined by comparing the respective two-photon photoemission yields measured for single nanoparticles and the surrounding flat surface. For p-polarized, 400 nm (∼3.1 eV) femtosecond radiation, a distribution of enhancement factors is found with a large percentage (67%) of the nanoparticles falling within a median range. A correlated scanning electron microscopy analysis demonstrated that the nanoparticles typifying the median of the distribution are characterized by spherical shapes and relatively smooth silver film morphologies. In contrast, the largest enhancement factors were produced by a small percentage (7%) of particles that displayed silver coating defects that altered the overall particle structure. Comparisons are made between the experimentally measured enhancement factors and previously reported calculations of the localized near-field enhancement for isolated silver nanoparticles.
Investigation of oxygen-related defects and the electrical properties of atomic layer deposited HfO2 films using electron energy-loss spectroscopy
Authors: Jang Jae Hyuck , Jung Hyung-Suk , Kim Jeong Hwan , Lee Sang Young , Hwang Cheol Seong , Kim Miyoung
Published: January 2011

The electrical properties of hafnium dioxide (HfO2) thin films are often attributed to the oxygen composition and oxygen-related defects; however, there have been few systematic studies on the electronic structures of such oxygen atoms. In this study, we used electron energy-loss spectroscopy to identify the influence of the electronic states of the oxygen atoms in HfO2 thin films by comparing HfO2 samples for different oxygen source pulse time during atomic-layer deposition (ALD). Although all samples by ALD have higher oxygen content in the film than that in the reference stoichiometric HfO2 sample, variations in the local symmetry of amorphous HfO2 thin films were significantly affected by oxygen source pulse time. Moreover, leakage currents of high-oxygen content HfO2 samples with longer O3 pulse time decreased considerably, compared with those of low-oxygen content HfO2 samples with shorter O3 pulse time, in which oxygen-related defects were observed by the Vfb shift under constant voltage stress. After postdeposition annealing (PDA), the electronic structure of oxygen atoms in HfO2 films was affected by the initial oxidation states in the amorphous HfO2 films. Furthermore, after PDA, polycrystalline HfO2 in high-oxygen content samples was mostly of the monoclinic phase, whereas the metastable tetragonal phase was readily formed in low-oxygen content HfO2.
Magnetoresistance in nanostructured Tb/Ti and Tb/Si multilayers
Authors: Svalov A. V. , Kurlyandskaya G. V. , Vas’kovskiy V. O. , Sorokin A. N. , Diercks D.
Published: January 2011

Magnetic, magnetoresistive and structural properties were studied for [Tb/Ti]n and [Tb/Si]n multilayers which were prepared by rf-sputtering. The thickness of the Tb layers varied from 1.5 to 12 nm. The thickness of 2 nm nonmagnetic spacers of Ti or Si was kept constant. Both anisotropic and isotropic magnetoresistance was observed in [Tb/Ti]n and [Tb/Si]n multilayers. A decrease in the thickness of the terbium layers led to a decrease in the anisotropic contribution to the total magnetoresistance. The negative isotropic magnetoresistanse in [Tb/Ti]n and [Tb/Si]n multilayers can be attributed to the giant magnetoresistance (GMR) and/or high field isotropic magnetoresistance. The structure of the samples of both types enabled the existence of the GMR effect.
Electrical potential modulation of dynamic film properties of aqueous surfactant solutions through a nanogap
Authors: Xie Guoxin , Luo Jianbin , Liu Shuhai , Guo Dan
Published: January 2011

The effect of external electrical potentials (EEPs) on aqueous surfactant films nanoconfined in a ball-plate configuration has been investigated by measuring the dynamic film thickness with an interferometer. Experimental results indicate that the film formation properties of the surfactant solutions in the nanogap under applied EEPs are strongly dependent on the interfacial adsorbed surfactant structure. Effective control over the film formation properties by applying EEPs depends on the signs of the charges on the solid surface and the surfactant headgroups, the surfactant concentration, and the magnitude of EEPs. Remarkable alterations of the film formation properties in the nanogap by EEPs can be observed except when the surface charge is the same in sign as the headgroups and the surfactant concentration is above the critical micelle concentration. Mechanisms of these phenomena have been discussed in this work.
Strong pulse asymmetry in quantum-dot mode-locked semiconductor lasers
Authors: Radziunas Mindaugas , Vladimirov Andrei G. , Viktorov Evgeny A. , Fiol Gerrit , Schmeckebier Holger , Bimberg Dieter
Published: January 2011

We describe the formation of a strong pulse asymmetry in mode-locked quantum-dot edge-emitting two-section semiconductor lasers. A mode decomposition technique reveals the role of the superposition of different modal groups. The results of theoretical analysis are supported by the experimental data.
Disorder induced Coulomb gaps in graphene constrictions with different aspect ratios
Authors: Terrés B. , Dauber J. , Volk C. , Trellenkamp S. , Wichmann U. , Stampfer C.
Published: January 2011

We present electron transport measurements on lithographically defined and etched graphene nanoconstrictions with different aspect ratios including different lengths (l) and widths (w). A roughly length-independent disorder induced effective energy gap can be observed around the charge neutrality point. This energy gap scales inversely with the width even in regimes where the length of the constriction is smaller than its width (l<w). In very short constrictions, we observe both resonances due to localized states or charged islands and an elevated overall conductance level (0.1−1e2/h), which is strongly length-dependent in the gap region. This makes very short graphene constrictions interesting for highly transparent graphene tunneling barriers.
Growth and electrical properties of Al-catalyzed Si nanowires
Authors: Choi Seok-Youl , Fung Wayne Y. , Lu Wei
Published: January 2011

We report the growth and electrical characterization of small-diameter, Al-catalyzed silicon nanowires. Large quantities of Si nanowires can be grown with a fast growth rate at a low temperature of 520 °C via a vapor-liquid-solid process using Al as catalyst. The use of high H2 partial pressure was found to effectively mitigate the Al catalyst oxidation problem, and higher SiH4 partial pressure was found to produce smaller diameter nanowires. Electrical measurements show that small diameter (d<∼25 nm) Al-catalyzed nanowires behave as p-type semiconductors with good gate response, while larger diameter Al-catalyzed nanowires behave as degenerately Al-doped semiconductors.
Finite temperature application of the corrected propagator method to reactive dynamics in a condensed-phase environment
Authors: Gelman David , Schwartz Steven D.
Published: January 2011

The recently proposed mixed quantum-classical method is extended to applications at finite temperatures. The method is designed to treat complex systems consisting of a low-dimensional quantum part (the primary system) coupled to a dissipative bath described classically. The method is based on a formalism showing how to systematically correct the approximate zeroth-order evolution rule. The corrections are defined in terms of the total quantum Hamiltonian and are taken to the classical limit by introducing the frozen Gaussian approximation for the bath degrees of freedom. The evolution of the primary system is governed by the corrected propagator yielding the exact quantum dynamics. The method has been tested on a standard model system describing proton transfer in a condensed-phase environment: a symmetric double-well potential bilinearly coupled to a bath of harmonic oscillators. Flux correlation functions and thermal rate constants have been calculated at two different temperatures for a range of coupling strengths. The results have been compared to the fully quantum simulations of Topaler and Makri [J. Chem. Phys. 101, 7500 (1994)] with the real path integral method.
On the role of evanescent modes and group index tapering in slow light photonic crystal waveguide coupling efficiency
Authors: Hosseini Amir , Xu Xiaochuan , Kwong David N. , Subbaraman Harish , Jiang Wei , Chen Ray T.
Published: January 2011

We investigate effects of different mechanisms on coupling efficiency between strip waveguides and the slow light mode in photonic crystal waveguides (PCWs). Both numerical simulations and experimental results show that group index (ng) tapering improves strip-PCW butt-coupling efficiency when compared to a direct coupling between a strip waveguide and a high-ng PCW. However, coupling efficiency is even higher when an intermediate low-ng PCW is used to couple from a strip waveguide to a high-ng PCW without an ng tapering. Our results suggest that the role of evanescent mode is more dominant in efficient coupling between two PCWs with large ng mismatch.
Faster and exact implementation of the continuous cellular automaton for anisotropic etching simulations
Authors: Ferrando N , Gosálvez M A , Cerdá J , Gadea R , Sato K
Published: January 2011

The current success of the continuous cellular automata for the simulation of anisotropic wet chemical etching of silicon in microengineering applications is based on a relatively fast, approximate, constant time stepping implementation (CTS), whose accuracy against the exact algorithm—a computationally slow, variable time stepping implementation (VTS)—has not been previously analyzed in detail. In this study we show that the CTS implementation can generate moderately wrong etch rates and overall etching fronts, thus justifying the presentation of a novel, exact reformulation of the VTS implementation based on a new state variable, referred to as the predicted removal time (PRT), and the use of a self-balanced binary search tree that enables storage and efficient access to the PRT values in each time step in order to quickly remove the corresponding surface atom/s. The proposed PRT method reduces the simulation cost of the exact implementation from to without introducing any model simplifications. This enables more precise simulations (only limited by numerical precision errors) with affordable computational times that are similar to the less precise CTS implementation and even faster for low reactivity systems.
Hasse-Weil zeta function of absolutely irreducible 𝑆𝐿₂-representations of the figure 8 knot group
Authors: Harada Shinya
Published: January 2011

Weil-type zeta functions defined by the numbers of absolutely irreducible

S
L

2

\mathrm {SL}_2

-representations of the figure

8
8

knot group over finite fields are computed explicitly. They are expressed in terms of the congruence zeta functions of reductions of a certain elliptic curve defined over the rational number field. Then the Hasse-Weil type zeta function of the figure

8
8

knot group is also studied. Its central value is written in terms of the Mahler measures of the Alexander polynomial of the figure

8
8

knot and a certain family of elliptic curves.
PhyloPro: a web-based tool for the generation and visualization of phylogenetic profiles across Eukarya
Authors: Xiong Xuejian , Song Hongyan , On Tuan , Lochovsky Lucas , Provart Nicholas J. , Parkinson John
Published: January 2011

Summary: With increasing numbers of eukaryotic genome sequences, phylogenetic profiles of eukaryotic genes are becoming increasingly informative. Here, we introduce a new web-tool Phylopro (http://compsysbio.org/phylopro/), which uses the 120 available eukaryotic genome sequences to visualize the evolutionary trajectories of user-defined subsets of model organism genes. Applied to pathways or complexes, PhyloPro allows the user to rapidly identify core conserved elements of biological processes together with those that may represent lineage-specific innovations. PhyloPro thus provides a valuable resource for the evolutionary and comparative studies of biological systems.

Contact:  jparkin@sickkids.ca
Genomic characterization of asymptomatic Escherichia coli isolated from the neobladder
Authors: Sahl Jason W. , Lloyd Amanda L. , Redman Julia C. , Cebula Thomas A. , Wood David P. , Mobley Harry L. T. , Rasko David A.
Published: January 2011

The replacement of the bladder with a neobladder made from ileal tissue is the prescribed treatment in some cases of bladder cancer or trauma. Studies have demonstrated that individuals with an ileal neobladder have recurrent colonization by Escherichia coli and other species that are commonly associated with urinary tract infections; however, pyelonephritis and complicated symptomatic infections with ileal neobladders are relatively rare. This study examines the genomic content of two E. coli isolates from individuals with neobladders using comparative genomic hybridization (CGH) with a pan-E. coli/Shigella microarray. Comparisons of the neobladder genome hybridization patterns with reference genomes demonstrate that the neobladder isolates are more similar to the commensal, laboratory-adapted E. coli and a subset of enteroaggregative E. coli than they are to uropathogenic E. coli isolates. Genes identified by CGH as exclusively present in the neobladder isolates among the 30 examined isolates were primarily from large enteric isolate plasmids. Isolations identified a large plasmid in each isolate, and sequencing confirmed similarity to previously identified plasmids of enteric species. Screening, via PCR, of more than 100 isolates of E. coli from environmental, diarrhoeagenic and urinary tract sources did not identify neobladder-specific genes that were widely distributed in these populations. These results taken together demonstrate that the neobladder isolates, while distinct, are genomically more similar to gastrointestinal or commensal E. coli, suggesting why they can colonize the transplanted intestinal tissue but rarely progress to acute pyelonephritis or more severe disease.
Mapping of the interactions between partition proteins Delta and Omega of plasmid pSM19035 from Streptococcus pyogenes
Authors: Dmowski Michal , Jagura-Burdzy Grazyna
Published: January 2011

Formation of the segrosome, a nucleoprotein complex crucial for proper functioning of plasmid partition systems, involves interactions between specific partition proteins (ParA-like and ParB-like), ATP and specific DNA sequences (the centromeric sites). Although partition systems have been studied for many years, details of the segrosome formation are not yet clear. Organization of the pSM19035-encoded partition system is unique; in contrast with other knownparsystems, here, theδandωgenes do not constitute an operon. Moreover, Omega [a ParB-like protein which has a Ribbon-Helix-Helix (RHH) structure] recognizes multiple centromeric sequences located in the promoters ofδ,ωandcopS(copy-number control gene). The ParA-like protein Delta is a Walker-type ATPase. In this work, we identify the interaction domains and requirements for dimerization and hetero-interactions of the Delta and Omega proteins of pSM19035 plasmid. The RHH structures are involved in Omega dimerizationin vivoand its N-terminal unstructured part is indispensable for association with Delta, bothin vivoandin vitro. Omega does not need to form dimers to interact with Delta. ATP binding is not required for Delta dimerization but is important for interaction with Omegain vivo. Thein vitrointeraction between Delta and Omega depends on ATP but does not require the presence of specific DNA segments (the centromere) recognized by Omega. The C-terminal part of the Delta protein (aa 198–284) is indispensable for interaction with Omega. Delta most probably interacts with Omega as a dimer since two amino acid substitutions in a conserved region between the A′ and B motifs abolish both the dimerization of Delta and its interaction with Omega.
TolA mediates the differential detergent resistance pattern between the Salmonella enterica subsp. enterica serovars Typhi and Typhimurium
Authors: Lahiri Amit , Ananthalakshmi T. K. , Nagarajan Arvindhan G. , Ray Seemun , Chakravortty Dipshikha
Published: January 2011

The tol–pal genes are essential for maintaining the outer membrane integrity and detergent resistance in various Gram-negative bacteria, including Salmonella. The role of TolA has been well established for the bile resistance of Salmonella enterica subsp. enterica serovar Typhimurium. We compared the bile resistance pattern between the S.
enterica serovars Typhi and Typhimurium and observed that Typhi is more resistant to bile-mediated damage. A closer look revealed a significant difference in the TolA sequence between the two serovars which contributes to the differential detergent resistance. The tolA knockout of both the serovars behaves completely differently in terms of membrane organization and morphology. The role of the Pal proteins and difference in LPS organization between the two serovars were verified and were found to have no direct connection with the altered bile resistance. In normal Luria broth (LB), S. Typhi ΔtolA is filamentous while S. Typhimurium ΔtolA grows as single cells, similar to the wild-type. In low osmolarity LB, however, S. Typhimurium ΔtolA started chaining and S. Typhi ΔtolA showed no growth. Further investigation revealed that the chaining phenomenon observed was the result of failure of the outer membrane to separate in the dividing cells. Taken together, the results substantiate the evolution of a shorter TolA in S. Typhi to counteract high bile concentrations, at the cost of lower osmotic tolerance.
Transcriptional repressor CopR acts by inhibiting RNA polymerase binding
Authors: Licht Andreas , Freede Peggy , Brantl Sabine
Published: January 2011

CopR is a transcriptional repressor encoded by the broad-host-range streptococcal plasmid pIP501, which also replicates inBacillus subtilis.It acts in concert with the antisense RNA, RNAIII, to control pIP501 replication. CopR represses transcription of the essentialrepRmRNA about 10- to 20-fold. In previous work, DNA binding and dimerization constants were determined and the motifs responsible localized. The C terminus of CopR was shown to be required for stability. Furthermore, SELEX of thecopRoperator revealed thatin vivoevolution was for maximal binding affinity. Here, we elucidate the repression mechanism of CopR. Competition assays showed that CopR–operator complexes are 18-fold less stable than RNA polymerase (RNAP)–pII complexes. DNase I footprinting revealed that the binding sites for CopR and RNAP overlap. Gel-shift assays demonstrated that CopR andB. subtilisRNAP cannot bind simultaneously, but compete for binding at promoter pII. Due to its higher intracellular concentration CopR inhibits RNAP binding. Additionally, KMnO4footprinting experiments indicated that prevention of open complex formation at pII does not further contribute to the repression effect of CopR.
Electrical and Mechanical Characterizations of Nanocomposite Insulation for HTS Systems
Authors: Walsh Jennifer K. , Fabian Paul E. , Hooker Matthew W. , Lizotte Mark J. , Tuncer Enis , Sauers Isidor
Published: January 2011

As HTS wire technology continues to advance, a critical need has emerged for dielectric materials that can be used in superconducting components such as terminations, fault current limiters, transformers, and motors. To address this need, CTD is developing nanocomposite insulations based on epoxy and benzoxazine chemistries. Depending on part geometry, some processing methods are more efficient than others. For this reason, CTD is investigating both fiber-reinforced and filled resin systems for use in these applications. A thorough set of electrical testing including AC breakdown, breakdown as a function of thickness, and flashover shows promising performance characteristics. In addition, mechanical testing (short beam shear and compression) indicate that these new materials to have as good or better performance than G10.
Minimal residual disease assessment in childhood acute lymphoblastic leukaemia: a Swedish multi‐centre study comparing real‐time polymerase chain reaction and multicolour flow cytometry
Authors: Thörn Ingrid , Forestier Erik , Botling Johan , Thuresson Britt , Wasslavik Carina , Björklund Elisabet , Li Aihong , Lindström‐Eriksson Eleonor , Malec Maria , Grönlund Elisabeth , Torikka Kerstin , Heldrup Jesper , Abrahamsson Jonas , Behrendtz Mikael , Söderhäll Stefan , Jacobsson Stefan , Olofsson Tor , Porwit Anna , Lönnerholm Gudmar , Rosenquist Richard , Sundström Christer
Published: January 2011

Minimal residual disease (MRD) assessment is a powerful prognostic factor for determining the risk of relapse in childhood acute lymphoblastic leukaemia (ALL). In this Swedish multi‐centre study of childhood ALL diagnosed between 2002 and 2006, the MRD levels were analysed in 726 follow‐up samples in 228 children using real‐time quantitative polymerase chain reaction (RQ‐PCR) of rearranged immunoglobulin/T‐cell receptor genes and multicolour flow cytometry (FCM). Using an MRD threshold of 0·1%, which was the sensitivity level reached in all analyses, the concordance between RQ‐PCR and FCM MRD values at day 29 was 84%. In B‐cell precursor ALL, an MRD level of ≥0·1% at day 29 predicted a higher risk of bone marrow relapse (BMR) with both methods, although FCM was a better discriminator. However, considering the higher median MRD values achieved with RQ‐PCR, a higher MRD cut‐off (≥0·2%) improved the predictive capacity of RQ‐PCR. In T‐ALL, RQ‐PCR was notably superior to FCM in predicting risk of BMR. That notwithstanding, MRD levels of ≥0·1%, detected by either method at day 29, could not predict isolated extramedullary relapse. In conclusion, the concordance between RQ‐PCR and FCM was high and hence both methods are valuable clinical tools for identifying childhood ALL cases with increased risk of BMR.
What happens when things go wrong?
Authors: Brandom Barbara W. , Callahan Patrick , Micalizzi Dale Ann
Published: January 2011

When a patient is injured or dies during anesthesia care, both the family of the patient and the health care providers suffer. The family needs to know what happened. The family can benefit from personal contact with the involved physicians. Apology to the injured is very important. The health care providers must report adverse events. Systematic review of adverse events can provide improved patient safety. Mechanisms exist to support the health care providers recovering from these potentially devastating experiences, but useful support is often not immediately available.
Does consideration matter to China’s split share structure reform?
Authors: Lu Fei , Balatbat Maria , Czernkowski Robert
Published: January 2011

We investigate the share market response to China’s split share structure reform and find average negative daily return around the government announcement on 29 April 2005. However, there is a turnaround at individual companies’ decision to implement the reform where we find positive and significant average daily return, contingent on the type of consideration. We attribute this change in market sentiment to the company’s announcement that the reform will involve the payment of consideration to holders of tradable A‐shares. Our results also show that holders of tradable A‐shares earn significant abnormal daily returns when companies propose to pay in cash or warrants or combine any of these payment methods with bonus shares.
Metformin restores endothelial function in aorta of diabetic rats
Authors: Sena Cristina M , Matafome Paulo , Louro Teresa , Nunes Elsa , Fernandes Rosa , Seiça Raquel M
Published: January 2011

BACKGROUND AND PURPOSE

The effects of metformin, an antidiabetic agent that improves insulin sensitivity, on endothelial function have not been fully elucidated. This study was designed to assess the effect of metformin on impaired endothelial function, oxidative stress, inflammation and advanced glycation end products formation in type 2 diabetes mellitus.

EXPERIMENTAL APPROACH

Goto‐Kakizaki (GK) rats, an animal model of nonobese type 2 diabetes, fed with normal and high‐fat diet during 4 months were treated with metformin for 4 weeks before evaluation. Systemic oxidative stress, endothelial function, insulin resistance, nitric oxide (NO) bioavailability, glycation and vascular oxidative stress were determined in the aortic rings of the different groups. A pro‐inflammatory biomarker the chemokine CCL2 (monocyte chemoattractant protein‐1) was also evaluated.

KEY RESULTS

High‐fat fed GK rats with hyperlipidaemia showed increased vascular and systemic oxidative stress and impaired endothelial‐dependent vasodilatation. Metformin treatment significantly improved glycation, oxidative stress, CCL2 levels, NO bioavailability and insulin resistance and normalized endothelial function in aorta.

CONCLUSION AND IMPLICATIONS

Metformin restores endothelial function and significantly improves NO bioavailability, glycation and oxidative stress in normal and high‐fat fed GK rats. This supports the concept of the central role of metformin as a first‐line therapeutic to treat diabetic patients in order to protect against endothelial dysfunction associated with type 2 diabetes mellitus.
Death ligand TRAIL, secreted by CD1a+ and CD14+ cells in blister fluids, is involved in killing keratinocytes in toxic epidermal necrolysis
Authors: de Araujo Elisabeth , Dessirier Valérie , Laprée Geneviève , Valeyrie‐Allanore Laurence , Ortonne Nicolas , Stathopoulos Efstathios N. , Bagot Martine , Bensussan Armand , Mockenhaupt Maja , Roujeau Jean‐Claude , Tsapis Andreas
Published: January 2011

Abstract:  Toxic epidermal necrolysis (TEN) is characterized by an acute detachment and destruction of keratinocytes, affecting large areas of the skin. It is often related to adverse drug reactions. Previous studies have shown that effector CD8+ T cells, which accumulate in the blister fluid, are functionally cytotoxic and act through a classical perforin/granzyme B pathway. It has recently been shown that these cytotoxic T cells also secrete granulysin peptide, which is lethal to keratinocytes. These cytotoxic T cells exert their killer activity against autologous keratinocytes in the presence of the drug. However, they are unlikely to be the only effectors of TEN. We therefore searched for soluble death factors in the blister fluids that might kill keratinocytes. We found that the amounts of interferon‐γ, TRAIL and TNF‐α proteins were significantly greater in TEN blister fluids than in all controls (normal sera, TEN sera, burns and Eosinophilic pustular folliculitis blister fluids) and TNF‐like weak inducer of apoptosis (TWEAK) amounts are also greater in all controls except burns. We showed that these proteins acted in synergy to induce the death of keratinocytes in vitro. We also found that TRAIL and TWEAK were secreted by CD1a+ and CD14+ cells present in the blister fluids. Thus, in addition to MHC class I‐restricted cytotoxic T lymphocytes (CTLs), which lyse keratinocytes, ligands secreted by non‐lymphoid cells capable of inducing keratinocyte death in an MHC class I‐independent manner, also seem to be present in the blister fluids of patients with TEN.
Inhibiting scar formation in vitro and in vivo by adenovirus‐mediated mutant Smad4: a preliminary report
Authors: Tan Wei‐Qiang , Gao Zheng‐Jun , Xu Jing‐Hong , Yao Hang‐Ping
Published: January 2011

Abstract:  The best characterized signalling pathway employed by transforming growth factor‐beta (TGF‐β) is the Smad pathway. We focused on Smad4, because it is essential for the activation of Smad‐dependent target genes. We aimed to explore the possibility of inhibiting scar formation after wounding by blocking TGF‐β signalling by means of a gene therapy approach using adenovirus‐mediated expression of mutant Smad4. The coding sequence of the dominant‐negative mutant Smad4ΔM4, which has a deletion in the linker region of Δ275–322, was introduced by homologous recombination into an adenovirus vector to generate the recombinant vector Ad‐ΔM4, which encoded Smad4ΔM4. Mouse fibroblast NIH 3T3 cells were transfected with Ad‐ΔM4 and cell proliferation, collagen protein production, and the expression of collagen type I and type III mRNA were evaluated in vitro using a cell proliferation test, western blot analysis, and RT‐PCR, respectively. Cell proliferation and the expression of collagen type I and type III mRNA and protein were all inhibited by the transfection of Ad‐ΔM4. In vivo, Ad‐ΔM4 was applied externally to wounds on rats, and histological examination and quantification of the scars were performed to evaluate the curative effect. The transfection of Ad‐ΔM4 successfully inhibited scar formation in rat wounds. In conclusion, Ad‐ΔM4 can block the TGF‐β signalling of mouse wound cells effectively. In addition, gene therapy with Ad‐ΔM4 can effectively inhibit wound scarring in rats and may potentially be applied to clinical treatment of scars.
Topical beta‐carotene protects against infra‐red‐light–induced free radicals
Authors: Darvin Maxim E. , Fluhr Joachim W. , Meinke Martina C. , Zastrow Leonhard , Sterry Wolfram , Lademann Juergen
Published: January 2011

Abstract:  The influence of stress factors on human skin induces the production of free radicals. Free radicals react immediately with antioxidants contained in the skin, giving rise to their depletion and with the surrounding molecules, resulting in their damage, disorganization and even destruction. High amounts of free radicals are produced in the upper skin layers, i.e. mainly in the epidermis, subsequent to sun irradiation. Irradiation of the skin in the infra‐red (IR) range of the spectra, applied at physiological doses, can produce free radicals. The magnitude of destruction of antioxidants, such as carotenoids, can serve as a marker of the extent of the stress factor, characterized by the quantity of produced free radicals. In this study, measurements on the degradation of cutaneous carotenoids following IR skin irradiation of 12 healthy volunteers (skin type II), with two IR sources (standard infrared radiator = SIR and water filter infrared = wIRA) were taken using resonance Raman spectroscopy. Topical application of the antioxidant beta‐carotene (2 mg/cm2) provided protection for the human skin when exposed to IR radiation. The magnitude of the degradation of dermal carotenoids after IR irradiation was significantly higher for SIR than for wIRA irradiation, for both non‐treated and cream‐treated skin areas. The amount of destroyed carotenoids after IR irradiation was higher in the case of pretreatment with beta‐carotene than for the untreated skin, indicating that the superficial part of antioxidants is most important for protecting against external stressors. The direct comparison of beta‐carotene content was significantly higher for the cream‐treated compared to untreated areas for all pairs: baseline, wIRA, after wIRA, baseline SIR and after SIR. Additionally, topically applied carotenoids as a single antioxidant component are less stable than the carotenoids in the skin incorporated by nutrition and accumulated in a mixture with different antioxidant substances. Resonance Raman spectroscopy can be used for the non‐invasive measurements of carotenoids, which can be rated as marker substances of redox processes.
New targets of pemphigus vulgaris antibodies identified by protein array technology
Authors: Kalantari‐Dehaghi Mina , Molina Douglas M. , Farhadieh Mandana , John Morrow W. , Liang Xiaowu , Felgner Philip L. , Grando Sergei A.
Published: January 2011

Abstract:  We performed partial evaluation of pemphigus vulgaris (PV) autoantibody profile using the protein array technology. The sera from seven patients with acute PV and five healthy donors were probed for the presence of autoantibodies characteristic of the organ‐non‐specific autoimmune disorders rheumatoid arthritis, lupus erythematosus, scleroderma, diabetes and some other autoimmune disorders, but not to desmosomal proteins. The array targeted 785 human genes amplified using Mammalian Gene Clone Collection with gene‐specific primers containing 20‐bp nucleotide extension complementary to ends of linear pXT7 vector. The array identified PV antibodies significantly (P < 0.05) differentially reactive with 16 antigens, most of which were cell‐surface proteins, such as CD2, CD31, CD33, CD36, CD37, CD40, CD54, CD66c and CD84 molecules, nicotinamide/nicotinic acid mononucleotide adenylyltransferase, immunoglobulin heavy chain constant region gamma 2 and others. Reactivity with Fc‐IgG helps explain an ability of the chimeric desmoglein constructs to absorb out all disease‐causing PV antibodies. Anti‐M1 muscarinic receptor antibody was also identified, consistent with the facts that while blockade of this receptor causes keratinocyte detachment, its activation is therapeutic in PV. Further proteomics analysis of PV antibodies should help elucidate the immunopathogenic mechanisms underlying keratinocyte detachment and blistering.
Distinct profile of the mitochondrial DNA common deletion in benign skin lesions
Authors: Hafner Christian , Kamenisch York , Landthaler Michael , Berneburg Mark
Published: January 2011

Abstract:  Mutations of mitochondrial (mt) DNA, particularly the 4977 bp long common deletion, are increased in aging tissues and preferentially found in chronologically and photoaged skin. Mutations of human mitochondrial DNA (mtDNA) have also been identified in malignant tumors of the skin and of other organs. However, benign skin lesions have not yet been investigated. We analyzed the frequency of the common deletion in 27 benign skin lesions [8 seborrheic keratoses (SK), 5 epidermal nevi (EN), 14 solar lentigos (SL)] by quantitative real‐time PCR, because SK and especially SL have been related to (photo)aged skin. All SK and four of five EN displayed reduced common deletion levels compared with adjacent normal skin. In contrast, 50% of SL revealed a higher percentage of the common deletion than the adjacent normal skin, and some SL showed very high absolute common deletion levels up to 14% of total mtDNA. Our results show that the amount of the common deletion is significantly different in benign skin lesions and raise further questions regarding the pathogenesis of SL and its possible role as a precursor lesion of SK.
Microdialysis documents changes in the micromilieu of psoriatic plaques under continuous systemic therapy
Authors: Salgo Rebekka , Thaçi Diamant , Boehncke Sandra , Diehl Sandra , Hofmann Matthias , Boehncke Wolf‐Henning
Published: January 2011

Abstract:  Microdialysis is a novel technique suitable to analyse soluble mediators in the skin compartment. We applied this methodical approach to monitor changes in the micromilieu of psoriatic plaques under therapy. Tissue fluid was collected from lesional and non‐lesional skin of three patients with severe plaque‐type psoriasis prior to as well as after 12 weeks of continuous oral therapy with fumaric acid esters. Concentrations of a spectrum of cytokines and adipokines were measured using a commercial fluorescent bead immunoassay. The procedure was well tolerated even without local anaesthesia. Prior to initiation of therapy, we found elevated levels for IL‐2, IL‐6, IL‐18, IL‐23, and resistin in lesional versus non‐lesional skin, whereas adiponectin levels were higher in non‐lesional skin. All patients showed significant clinical improvement under treatment, paralleled by reduced concentrations of IL‐6, IL‐18, IL‐23, and resistin, but not IL‐2 and adiponectin in lesional skin. Thus, we were able to demonstrate through microdialysis a shift in the micromilieu of psoriatic plaques, characterized by reduced levels of pro‐inflammatory mediators in three patients under effective systemic anti‐inflammatory therapy with fumaric acid esters. Our observations need to be confirmed by larger studies. This approach is limited by practical aspects as it is very time‐consuming, but suitable to directly explore pathomechanisms causing the psoriatic phenotype in general and insulin resistance in the skin compartment in particular.