bluuebunny/crossref_metadata_2025 huggingface dataset:
Strong bulk plasma acceleration in Earth's magnetosheath: A magnetic slingshot effect?
Authors: Lavraud B. , Borovsky J. E. , Ridley A. J. , Pogue E. W. , Thomsen M. F. , Rème H. , Fazakerley A. N. , Lucek E. A.
Published: July 2007

In the near‐Earth environment, strong bulk plasma accelerations are frequently taken to be the diagnostic of the occurrence of magnetic reconnection. In this letter, we report new and unambiguous spacecraft observations and corresponding magnetohydrodynamic (MHD) simulation of strong bulk plasma acceleration in the terrestrial magnetosheath during low Alfvén Mach number solar wind conditions, which is demonstrably not associated with magnetic reconnection. We illustrate this effect with Cluster spacecraft data that show plasma accelerations up to speeds of 1040 km/s, while the ambient solar wind speed is only 650 km/s (i.e., in excess by 60%). Based on a comparison with global MHD simulations of the magnetosphere, we show that the acceleration results from enhanced magnetic forces exerted on the plasma by “stiff” magnetic flux tubes in a low‐β magnetosheath that result from the low Alfvén Mach number solar wind. The MHD simulations demonstrate that the acceleration is asymmetric, as well as the magnetopause shape, and is the result of both magnetic pressure gradient and tension forces, showing that this effect is not a simple analogy to a “slingshot effect” for which magnetic tension would dominate. Like magnetic reconnection, this mechanism is capable of producing strong plasma acceleration in the near‐Earth's environment. The low Alfvén Mach number solar wind condition leading to this mechanism is often characteristic of coronal mass ejections (CMEs).
Impact of the global warming on the fluvial thermal erosion over the Lena River in Central Siberia
Authors: Costard F. , Gautier E. , Brunstein D. , Hammadi J. , Fedorov A. , Yang D. , Dupeyrat L.
Published: July 2007

The hydrology of the Lena and its tributaries is characterized by an extremely episodic flow regime. Here we report recent climatic change in Central Siberia, and its impact on the fluvial thermal erosion. We point out three major changes since the 1980s: a marked reduction of the river ice thickness in winter, a pronounced increase of the water stream temperature in spring and a slight increase of the discharge during the break up (May–June). A GIS analysis based on aerial pictures and satellite images highlights the impact of the water warming on the frozen banks. The vegetated islands appear to be very sensitive to the water temperature increase, showing an acceleration of their head retreat (+21–29%). This suggests that recent global warming directly affects the fluvial dynamics and the erosional process of one of the largest arctic fluvial system.
Global observation of traveling atmospheric disturbances (TADs) in the thermosphere
Authors: Bruinsma Sean L. , Forbes Jeffrey M.
Published: July 2007

Densities derived from accelerometer measurements on the CHAMP satellite near 400 km are used to elucidate global‐scale characteristics of traveling atmospheric disturbances (TADs) in connection with 3 sudden injections of energy at high latitudes on 29 May 2003. Dayside TADs with typical amplitudes ∼20–30% propagate towards the equator from the northern hemisphere (southern hemisphere) auroral region with phase speeds of order 730 ms−1 (460 ms−1). Some evidence is found for TAD penetration from the northern to the southern Hemisphere, and for the first time for trans‐polar propagation. Nighttime TAD signatures are less well defined, but have phase speeds similar to the dayside TADs. The above day‐night and hemisphere differences possibly reflect dependencies on direction and intensity of the prevailing solar‐driven circulation, and on generation efficiency and ion drag dissipation with respect to solar zenith angle.
Evidence for magnetic reconnection initiated in the magnetosheath
Authors: Phan T. D. , Paschmann G. , Twitty C. , Mozer F. S. , Gosling J. T. , Eastwood J. P. , Øieroset M. , Rème H. , Lucek E. A.
Published: July 2007

We report Cluster spacecraft 1 observations of a reconnection exhaust embedded in the magnetosheath flow. The reconnection evidence consists of (1) accelerated plasma outflows, (2) interpenetrating ion beams, (3) reconnection inflows and (4) the associated tangential reconnection electric field. Furthermore, Hall magnetic fields were observed with no gaps in the middle of the exhaust. Together with the exhaust thickness being ∼ 10 ion skin depths, this implies that the spacecraft crossed through the ion diffusion region. The dimensionless reconnection rate determined independently using the plasma and electric field measurements was ∼0.07, implying fast reconnection. The same (but 36 times thicker) current sheet was observed upstream in the solar wind by the ACE and Wind spacecraft but without the reconnection signatures. These observations suggest that reconnection was initiated in the magnetosheath due to compression of the (non‐reconnecting) solar wind current sheet at the bow shock and against the dayside magnetopause.
Inhibition of HIV‐1 or bacterial activation of macrophages by products of HIV‐1‐resistant human cells
Authors: Li Guanhua , Aaron Sagiv , Kazmierczak Katarzyna , Lesner Adam , Li Yuchang , Ivanova Anna , Bentsman Galina , Potash Mary Jane , Simm Malgorzata
Published: July 2007

We have recently described the molecular basis of HIV‐1 resistance factor (HRF)‐mediated anti‐viral activity in primary and transformed CD4 T cells. HRF(+) cell culture supernatants or partially purified HRF were found to incapacitate the formation of the NF‐κB/DNA complex, which is indispensable for long terminal promoter‐driven transcription of virus genes. In this study, we tested whether HRF might have much broader activity against other organisms whose pathogenesis is linked to NF‐κB activation. Specifically, we tested the effects of HRF on the NF‐κB‐mediated responses of primary macrophages to HIV‐1 or several bacterial antigens. We found that exposure to HRF inhibited HIV‐1 expression in macrophages and also induced the production of HRF‐like activity by macrophages, which prevented replication of virus in HIV‐1‐infected peripheral blood lymphocytes cultured in the adjacent compartment. We investigated the mechanism of this inhibition and found that HRF impeded NF‐κB/DNA binding in macrophages induced by either HIV‐1 or lipopolysaccharide from several bacteria species, resulting in impaired tumor necrosis factor‐alpha responses to these organisms.
The vicious cycle of apoptotic β‐cell death in type 1 diabetes
Authors: Kaminitz Ayelet , Stein Jerry , Yaniv Isaac , Askenasy Nadir
Published: July 2007

Autoimmune insulitis, the cause of type 1 diabetes, evolves through several discrete stages that culminate in β‐cell death. In the first stage, antigenic epitopes of B‐cell‐specific peptides are processed by antigen presenting cells in local lymph nodes, and auto‐reactive lymphocyte clones are propagated. Subsequently, cell‐mediated and direct cytokine‐mediated reactions are generated against the β‐cells, and the β‐cells are sensitized to apoptosis. Ironically, the β‐cells themselves contribute some of the cytokines and chemokines that provoke the immune reaction within the islets. Once this vicious cycle of autoimmunity is fully developed, the fate of the β‐cells in the islets is sealed, and clinical diabetes inevitably ensues. Differences in various aspects of these concurrent events appear to underlie the significant discrepancies in experimental data observed in experimental models that simulate autoimmune insulitis.
Coordinating TLR‐activated signaling pathways in cells of the immune system
Authors: Banerjee Ashish , Gerondakis Steve
Published: July 2007

Toll‐like receptor (TLR) signaling leads to the activation of mitogen‐activated protein kinase and nuclear factor‐κB signaling pathways. While the upstream signaling events initiated at the level of adaptors and the activation of the downstream signaling pathways have received a lot of attention, our understanding of how these signaling pathways are coordinated to regulate gene expression is poorly understood. This review gives a selective overview on our current understanding of signaling downstream of TLRs, with an emphasis on how the upstream kinases like the mitogen‐activated protein kinase kinase kinases (TAK1 and Tpl2) and inhibitor of κ‐B kinase (IKK) coordinate the signaling events that steer the course of an immune response.
Status and conservation of the giant muntjac Megamuntiacus vuquangensis, and notes on other muntjac species in Laos
Authors: Timmins R. J. , Evans T. D. , Khounboline Khamkhoun , Sisomphone Chainoi
Published: July 2007

The large-antlered, or giant, muntjac Megamuntiacus vuquangensis wasdescribed from Vietnam in 1994 and found concurrently in the Annamite Mountains and nearby hill ranges of central and southern Laos. The northerly and southerly range limits are still unknown. It may occupy a wide range of habitats and is found sympatrically with the common muntjac Muntiacus muntjak. Another muntjac species, the taxonomic affinity of which is as yet undetermined, was recently discovered to occur within its range. The large-antlered muntjac is probably not threatened with extinction in the near future, but in view of its restricted range and threats from habitat degradation and hunting, it should be classified as Vulnerable in the Red Data Book. Its future in Laos is largely dependent on the recently created protected-areas system to maintain large tracts of habitat and reduce hunting pressure.
Diradicals, antiaromaticity, and the pseudo-Jahn-Teller effect: Electronic and rovibronic structures of the cyclopentadienyl cation
Authors: Wörner H. J. , Merkt F.
Published: July 2007

The electronic and rovibronic structures of the cyclopentadienyl cation (C5H5+) and its fully deuterated isotopomer (C5D5+) have been investigated by pulsed-field-ionization zero-kinetic-energy (PFI-ZEKE) photoelectron spectroscopy and ab initio calculations. The vibronic structure in the two lowest electronic states of the cation has been determined using single-photon ionization from the X̃E1″2 ground neutral state and 1+1′ resonant two-photon ionization via several vibrational levels of the ÃA2″2 excited state. The cyclopentadienyl cation possesses a triplet ground electronic state (X̃+A2′3) of D5h equilibrium geometry and a first excited singlet state (ã+E2′1) distorted by a pseudo-Jahn-Teller effect. A complete analysis of the E⊗e Jahn-Teller effect and of the (A+E)⊗e pseudo-Jahn-Teller effect in the ã+E2′1 state has been performed. This state is subject to a very weak linear Jahn-Teller effect and to an unusually strong pseudo-Jahn-Teller effect. Vibronic calculations have enabled us to partially assign the vibronic structure and determine the adiabatic singlet-triplet interval (1534±6cm−1). The experimental spectra, a group-theoretical analysis of the vibronic coupling mechanisms, and ab initio calculations were used to establish the topology of the singlet potential energy surfaces and to characterize the pseudorotational motion of the cation on the lowest singlet potential energy surface. The analysis of the rovibronic photoionization dynamics in rotationally resolved spectra and the study of the variation of the intensity distribution with the intermediate vibrational level show that a Herzberg-Teller mechanism is responsible for the observation of the forbidden ã+E2′1←ÃA2″2 photoionizing transition.
New construction for a QMA complete three-local Hamiltonian
Authors: Nagaj Daniel , Mozes Shay
Published: July 2007

We present a new way of encoding a quantum computation into a three-local Hamiltonian. Our construction is novel in that it does not include any terms that induce legal-illegal clock transitions. Therefore, the weights of the terms in the Hamiltonian do not scale with the size of the problem as in previous constructions. This improves the construction by Kempe and Regev [Quantum Inf. Comput. 3, 258–264 (2003); e-print quant-ph∕0302079] who were the first to prove that three-local Hamiltonian is complete for the complexity class QMA, the quantum analog of NP. Quantum k-SAT, a restricted version of the local Hamiltonian problem using only projector terms, was introduced by Bravyi (e-print quant-ph∕0602108) as an analog of the classical k-SAT problem. Bravyi proved that quantum 4-SAT is complete for the class QMA with one-sided error (QMA1) and that quantum 2-SAT is in P. We give an encoding of a quantum circuit into a quantum 4-SAT Hamiltonian using only three-local terms. As an intermediate step to this three-local construction, we show that quantum 3-SAT for particles with dimensions 3×2×2 (a qutrit and two qubits) is QMA1 complete. The complexity of quantum 3-SAT with qubits remains an open question.
Accurate experimental determination of the Poisson’s ratio of GaN using high-resolution x-ray diffraction
Authors: Moram M. A. , Barber Z. H. , Humphreys C. J.
Published: July 2007

An accurate Poisson’s ratio value of 0.183±0.003 for a typical c-axis-oriented GaN film grown by metal-organic vapor-phase epitaxy deposition has been determined using a wafer bending apparatus combined with high-resolution x-ray diffraction lattice parameter measurements. The precision of this method has improved ten fold over typical methods used for thin film samples, enabling future study of the effects of doping, compositional changes, or structural defects on the Poisson’s ratio of GaN. The obtained Poisson’s ratio value is lower than most calculated values, which is attributed to the presence of strain-relieving edge dislocations in the GaN sample. Unstrained film lattice parameters can also be found using this method, and are shown to be a=3.1884±0.0002Å and c=5.1850±0.0002Å (assuming an unstrained c∕a ratio of 1.6262). A brief review of Poisson’s ratio and unstrained lattice parameter values for GaN in the literature is also given.
Collisionless magnetic reconnection in large-scale electron-positron plasmas
Authors: Daughton William , Karimabadi Homa
Published: July 2007

One of the most fundamental questions in reconnection physics is how the dynamical evolution will scale to macroscopic systems of physical relevance. This issue is examined for electron-positron plasmas using two-dimensional fully kinetic simulations with both open and periodic boundary conditions. The resulting evolution is complex and highly dynamic throughout the entire duration. The initial phase is distinguished by the coalescence of tearing islands to larger scale while the later phase is marked by the expansion of diffusion regions into elongated current layers that are intrinsically unstable to plasmoid generation. It appears that the repeated formation and ejection of plasmoids plays a key role in controlling the average structure of a diffusion region and preventing the further elongation of the layer. The reconnection rate is modulated in time as the current layers expand and new plasmoids are formed. Although the specific details of this evolution are affected by the boundary and initial conditions, the time averaged reconnection rate remains fast and is remarkably insensitive to the system size for sufficiently large systems. This dynamic scenario offers an alternative explanation for fast reconnection in large-scale systems.
Large eddy simulation of vortex breakdown/flame interaction
Authors: Duwig Christophe , Fuchs Laszlo
Published: July 2007

The dynamics of a swirl-stabilized premixed flame is studied using large eddy simulation (LES). A filtered flamelet model is used to account for the subgrid combustion. The model provides a consistent and robust reaction-diffusion expression for simulating the propagation of turbulent premixed flames correctly. The numerical results were found to be relatively insensitive to small changes in the inflow boundary conditions and to the numerical mesh employed. Furthermore, the results were found to agree well with the available experimental data both for velocity and scalar fields. In addition, unsteady flame features [i.e., precessing vortex core (PVC)] were identified and compared with experimental data. The agreement between LES results and experimental data, in terms of flame dynamics, was also good. Increasing swirl did not affect the flame strongly but a decrease of swirl number was shown to change the flame shape and suppress the PVC. The PVC and flame dynamics were studied using proper orthogonal decomposition (POD) allowing us to identify and isolate the PVC from smaller-scale turbulence. The POD results indicate that the PVC corresponds to a helical wave consisting of two counter-rotating helices. A dynamical reduced model was also derived do describe the flame response to the PVC.
Gallium-doped zinc oxide films as transparent electrodes for organic solar cell applications
Authors: Bhosle V. , Prater J. T. , Yang Fan , Burk D. , Forrest S. R. , Narayan J.
Published: July 2007

We report microstructural characteristics and properties of gallium-doped ZnO films deposited on glass by pulsed laser deposition. The Zn0.95Ga0.05O film deposited at 200 °C and 1×10−3 Torr showed predominant ⟨0001⟩ orientation with a metallic behavior and a resistivity of 2×10−4 Ω cm at room temperature. Low resistivity of the ZnGaO films has been explained in terms of optimal combination of carrier concentration and minimized scattering, and is correlated with the microstructure and the deposition parameters. Power conversion efficiency comparable to indium tin oxide-based devices (1.25±0.05%) is achieved on a Zn0.95Ga0.05O∕Cu-phthalocyanine∕C60 double-heterojunction solar cell.
Shear-induced diffusion in dilute suspensions of spherical or nonspherical particles: Effects of irreversibility and symmetry breaking
Authors: Lopez Mauricio , Graham Michael D.
Published: July 2007

Using Stokesian dynamics simulations, the shear-induced diffusivities due to pair collisions of identical spherical or nonspherical particles are considered, with the purpose to evaluate the effects of irreversibility and symmetry breaking. Results are compared to an approximate upper bound found by assuming that the particles leave the collision at their maximum separation. For spherical particles, the effects of surface roughness and a short-range repulsive force are considered. For nonspherical particles, a short-range repulsive force is used and effects of shape are considered. In general, it is found that at small repulsion (range of repulsive force, rc, equal to 10−6 the particle radius R), the shape of the particle has a large impact on the shear-induced diffusivity, so particles with broken symmetry have diffusivities that are up to five orders of magnitude larger than those of spheres. At high repulsion (rc=10−1R), however, the effect on the particle shape on the diffusivity is not as strong and all particles have diffusivities with the same order of magnitude.
A long plasma column in a flexible tube at atmospheric pressure
Authors: Hong Yong Cheol , Cho Soon Cheon , Kim Jong Hun , Uhm Han Sup
Published: July 2007

Atmospheric-pressure nonthermal plasma produced at a low frequency in a flexible dielectric tube in an argon gas flow is presented. The plasma system consists of a typical injection needle as a hot electrode, a Teflon® tube as a dielectric, and a high voltage power supply. The plasma column is stabilized in the Teflon® tube by flowing channels of argon gas through an injection needle. The column has a length of approximately 60cm with 3lpm of argon, and plasma exists throughout the Teflon® tube with an inner diameter of 1.6mm. The characteristics of the long plasma column are studied by preliminary observations.
High-resolution microwave spectrum of the weakly bound helium-pyridine complex
Authors: Tanjaroon Chakree , Jäger Wolfgang
Published: July 2007

High-resolution rotational spectra of the helium-pyridine dimer were obtained using a pulsed molecular beam Fourier transform microwave spectrometer. Thirty-nine R-branch N14 nuclear quadrupole hyperfine components of a- and c-type dipole transitions were observed and assigned. The following spectroscopic parameters were obtained: rotational constants A=3875.2093(48)MHz, B=3753.2514(45)MHz, and C=2978.4366(81)MHz; quartic centrifugal distortion constants DJ=0.12408(55)MHz, DJK=0.1200(43)MHz, DK=−0.2451(25)MHz, d1=0.00427(27)MHz, and d2=0.00016(10)MHz; sextic centrifugal distortion constants HJ=0.003053(35)MHz, HJK=−0.006598(47)MHz, and HK=0.00411(59)MHz; N14 nuclear quadrupole coupling constants χaa(N14)=−4.7886(76)MHz, χbb(N14)=1.4471(76)MHz, and χcc(N14)=3.3415(43)MHz. Our analyses of the rotational and N14 quadrupole coupling constants show that the He atom binds perpendicularly to the aromatic plane of C5H5N with a displacement angle of approximately 7.0° away from the c axis of the pyridine monomer, toward the nitrogen atom. Results from an ab initio structure optimization on the second order Møller-Plesset level are consistent with this geometry and gave an equilibrium well depth of 86.7cm−1.
Effect of beam prebunching on gain and efficiency in a free electron laser: Nonlocal theory
Authors: Bhasin Anuradha , Sharma Suresh C.
Published: July 2007

Beam prebunching on the free electron laser (FEL) offers considerable enhancement in growth rate, efficiency, and gain when the prebunched beam electrons are in the retarding zone and the electron beam is highly modulated implying the largest beam oscillatory velocity due to wiggler. A nonlocal theory of this process has been developed. The growth rate, efficiency, and gain were evaluated based on existing experimental parameters and compared with available theoretical/experimental results. Nonlocal effects reduce the linear growth rate of the FEL instability. The growth rate, efficiency, and gain of the FEL instability increase with the modulation index and has the largest value when the modulation index approaching unity in addition to the frequency and wave number of the prebunched beam are comparable to that of the radiation wave. The growth rate of the FEL instability scales as one-third power of the beam current in the Compton regime and one-fourth power in the Raman regime.
Self-oscillation mode due to fluid-structure interaction in a micromechanical valve
Authors: Ducloux Olivier , Talbi Abdelkrim , Gimeno Leticia , Viard Romain , Pernod Philippe , Preobrazhensky Vladimir , Merlen Alain
Published: July 2007

This letter presents an original actuation mode for a micromechanical valve based on the induction of a self-oscillation, provided by the strong coupling between a mobile mechanical part and the fluid flow. The presented structure consists of a rigid silicon pad processed on a flexible membrane, both located over a silicon microchannel with structured internal walls. A theoretical analysis, based on a combination of the small perturbations method and a numerical study, shows that a self-oscillation can be induced on the mobile part due to the hybridization of the first flexion and torsion resonance modes interacting with the gas flow. Characterization of the self-oscillating microvalve shows high performances without electric energy supply for control.
Correlation between non-180° domain structures in (1−x)PbA1∕3Nb2∕3O3−xPbTiO3 single crystals (A=Mg or Zn) under an applied [001] electric field
Authors: Topolov V. Yu. , Cao Hu , Viehland D.
Published: July 2007

This work is devoted to the study of heterophase states in (1−x)PbA1∕3Nb2∕3O3−xPbTiO3 or PAN−xPT (A=Mg or Zn) single crystals under an electric field ‖E‖[001]. The possibility of elastically matched phases in the transformational sequences of Pm3m→P4mm→Cm, Pm3m→Cm, and P4mm→Cm are considered with regards to non-180° domains and changes in lattice parameters. Systems of diagrams linking domain types with interfaces between coexisting polydomain phases in PMN–0.28PT and PZN–0.045PT crystals are given. An important role of an intermediate P4mm phase in achieving stress accommodation has been identified by analysis of lattice parameters of PMN–0.28PT, and the elastic compatibility conditions between non-180° domain structures in the P4mm and Cm phases have been determined for various heterophase states. Two scenarios of changes in the lattice parameter aT in the P4mm phase of PMN–0.28PT have first been discussed to reveal possibilities of stress accommodation in heterophase states. It has been shown that the correlation between domain structures in different heterophase states of studied crystals stems from coordinated unit-cell behavior under ‖E‖[001].
Characterization of correlated line edge roughness of nanoscale line gratings using small angle x-ray scattering
Authors: Wang Chengqing , Jones Ronald L. , Lin Eric K. , Wu Wen-Li , Rice Bryan J. , Choi Kwang-Woo , Thompson George , Weigand Steven J. , Keane Denis T.
Published: July 2007

To meet the challenges in dimensional metrology as the minimum feature size in semiconductor devices approaches sub-35 nm length scales, we have been developing a nondestructive method using x rays termed critical dimension small angle x-ray scattering (SAXS). Its capacity to quantify the dimension of linewidth, pitch, line height, and sidewall angle of line gratings has been demonstrated. In this work, we have further extended its capabilities to quantify the correlated line-edge roughness (LER) and linewidth roughness (LWR). Model line grating patterns with controlled LER and LWR were prepared and measured using x ray, their results were analyzed with model calculations. The magnitude of LER/LWR deduced from x-ray results compares favorably with the scanning electron microscopy results obtained from the same samples. An apparent Debye–Waller factor, which can be deduced from the SAXS data without any detailed model-based calculations, is found to be a convenient parameter to quantify the amplitude of LER/LWR.
Thermoelectric properties of rare earth–ruthenium–germanium compounds
Authors: Kong H. , Shi X. , Uher C. , Morelli D. T.
Published: July 2007

We report our studies of the thermoelectric properties of a class of compounds of composition R3Ru4Ge13 (R=Y, Dy, Ho, and Lu). Magnetization measurements show that the R ion is in the trivalent state in each of these compounds. Each of these compounds displays a semiconductorlike rise in electrical resistivity with decreasing temperature. The magnitude of the resistivity is much larger than typical metals and is similar to that of a heavily doped semiconductor or semimetal. The Seebeck coefficient is positive throughout the temperature range of 2–800K with room temperature values of approximately 40μVK−1. The lattice thermal conductivity is remarkably low and exhibits a very flat temperature dependence. This is consistent with the observed internal disorder associated with the cagelike structure of these compounds. Cobalt substitution for ruthenium enhances the semiconductor character but does not improve the thermoelectric properties.
Magnetic and electronic properties of misfit-layered cobalt oxide (Ca1−δOH)xCoO2
Authors: Shizuya Mitsuyuki , Isobe Masaaki , Takayama-Muromachi Eiji
Published: July 2007

The magnetic and electronic properties of non- and hole-doped samples of misfit-layered cobalt oxide (Ca1−δOH)xCoO2 were investigated using the data obtained from measurements of the magnetization, specific heat, resistivity, and Seebeck coefficient. A Curie-Weiss-like behavior was observed for all samples. In a highly doped sample, a magnetic transition at 13K and metamagnetism, due to long-range antiferromagnetic ordering, were observed. This long-range ordering coexists with a nonordered paramagnetic moment, most likely enhanced by ferromagnetic fluctuations. Large Sommerfeld constants, γ=32 and 46mJmol−1K−2, were obtained from the specific heat of the doped samples. This indicates that a large effective mass of the carriers exists in the hole-doped phase of this compound. The observation of both the finite value of γ and the semiconducting resistivity indicates that the carrier is localized by the Anderson localization mechanism. The Seebeck coefficient decreases with hole doping. In low temperature, the Seebeck coefficients for the doped samples exhibit abrupt enhancements with decreasing temperature, which implies an existence of pseudogap.
The effects of annealing on the structural, optical, and vibrational properties of lattice-matched GaAsSbN∕GaAs grown by molecular beam epitaxy
Authors: Bharatan S. , Iyer S. , Nunna K. , Collis W. J. , Matney K. , Reppert J. , Rao A. M. , Kent P. R. C.
Published: July 2007

The structural, optical, and vibrational properties of a GaAsSbN epilayer lattice matched to GaAs with a band gap of 1eV have been investigated using a variety of characterization techniques. These layers have potential applications in GaAs based tandem solar cells that utilize the near infrared region of the solar spectrum. The epilayers were grown in an elemental solid source molecular beam epitaxy system with a rf plasma nitrogen source. The Sb and N compositions of the nearly lattice-matched layers are 6.8% and 2.6%, respectively, as determined by high resolution x-ray diffraction and secondary ion mass spectroscopy (SIMS) analysis. The high crystalline quality of the layers is attested by the presence of well resolved Pendellosung fringes on a triple axis (004) x-ray scan and dynamical truncation rods observed on the corresponding (004) reciprocal space map. The effects of in situ annealing in As ambient and ex situ annealing in N ambient on the low temperature photoluminescence (PL) characteristics are discussed. Ex situ (in situ) annealed samples display an 8K PL peak energy of 1eV with a full width at half maximum of 18meV (26meV). Raman spectral analysis, the temperature dependence of the PL peak energy, and SIMS profiles indicate that outdiffusions of N and As are suppressed in the in situ annealed samples and improvement in Ga–N bonding is observed, leading to higher PL intensities in these samples. In addition, indirect evidence of atomic scale ordering has been observed. The stability of these structures appears to be dependent on the annealing conditions.
Resonant microwave absorption determination of characteristic magnetic length in magnetic-field-annealed Vitroperm
Authors: Basheed G. A. , Kaul S. N. , Michels A.
Published: July 2007

The first direct resonant microwave absorption determination of the thermal renormalization of exchange stiffness, average magnetic anisotropy constant, and characteristic magnetic length in “field-annealed” Vitroperm samples with an initial magnetic permeability of μi=20000 and 150 000 has been presented and discussed.
Electron detrapping characteristics in positive bias temperature stressed n-channel metal-oxide-semiconductor field-effect transistors with ultrathin HfSiON gate dielectrics
Authors: Zhu Shiyang , Nakajima Anri
Published: July 2007

Electrons trapped in the HfSiON gate dielectrics of n-channel metal-oxide-semiconductor field-effect transistors induced by positive bias temperature stress start to decay when the stress is interrupted or an opposite (recovery) voltage is applied. The decay begins with a quick detrapping within tens of nanoseconds followed by a slow detrapping. The quick detrapping depends on the recovery voltage and the trapping history, whereas the slow detrapping obeys approximately a logarithmic dependence on time with an almost identical slope before saturation. The observed detrapping behavior can be explained by a spatial and/or energetic distribution of trapped electrons in the HfSiON film. The device degradation under various dynamic stresses is found to be almost independent of frequency ranging from 0.001to1MHz, while it is slightly enhanced at 10MHz, probably due to insufficient recovery at the recovering half cycle.
Orientation-controlled molecule-by-molecule polymer wire growth by the carrier-gas-type organic chemical vapor deposition and the molecular layer deposition
Authors: Yoshimura Tetsuzo , Ito Shinji , Nakayama Tomohiro , Matsumoto Kotaro
Published: July 2007

The carrier-gas-type organic chemical vapor deposition (CG-OCVD) and the molecular layer deposition were developed for orientation-controlled molecule-by-molecule growth of conjugated polymer wires on a surface with self-assembled monolayer (SAM), which provides a feasible way to construct self-organized three-dimensional polymer wire networks. It was also found that, in CG-OCVD, growth saturation occurs for a substrate without SAM while no growth saturation for a substrate with SAM. The analysis of results in terms of reaction site densities on surfaces suggests vertical wire growth on a substrate with SAM and horizontal wire growth on a substrate without SAM.
Terahertz frequency bandpass filters
Authors: Gallant A. J. , Kaliteevski M. A. , Brand S. , Wood D. , Petty M. , Abram R. A. , Chamberlain J. M.
Published: July 2007

The design, measurement, and analysis of a range of artificial materials for use at terahertz frequencies are described. The chosen structures consist of arrays of cylindrical gold-plated pillars with period comparable to the wavelength of incident radiation. An ultraviolet (UV) micromachining approach to the fabrication of these high aspect-ratio pillars is described using the negative epoxy-based resin SU8. Lattice fence structures are also realized using the same method. Terahertz (THz) frequency time domain spectroscopy is performed on these structures in the range 200 GHz to 3.0 THz and the relative transmission of the structures is determined. The pass and stop bands are observed with peak transmission of up to 97%. Finite difference time domain simulations and complex photonic band structure calculations are shown to provide good descriptions of the electromagnetic properties of the structures and are used to interpret the observed transmission spectra.
Microstructure and strain relaxation of epitaxial PrScO3 thin films grown on (001) SrTiO3 substrates
Authors: Chen Y. B. , Katz M. B. , Pan X. Q. , Folkman C. M. , Das R. R. , Eom C. B.
Published: July 2007

We have studied the microstructure and strain relaxation of epitaxial PrScO3 films grown on miscut (001) SrTiO3 substrates by transmission electron microscopy. PrScO3 films grown on highly miscut (>1°) SrTiO3 substrates are single domain films, fully strain relaxed via interfacial misfit dislocations, small angle tilt boundaries, and antiphase boundaries bounded by partial dislocation. In contrast, strain in PrScO3 films on low miscut (<0.2°) SrTiO3 substrates is relaxed by misfit dislocation as well as the formation of six different crystallographic domains. The formation of single domain PrScO3 films on high angle miscut substrates could be due to interfacial strain-energy minimization.
Noncontact charge measurement of moving microparticles contacting dielectric surfaces
Authors: Nesterov Alexander , Löffler Felix , König Kai , Trunk Ulrich , Leibe Klaus , Felgenhauer Thomas , Stadler Volker , Bischoff Ralf , Breitling Frank , Lindenstruth Volker , Hausmann Michael
Published: July 2007

In this study examples for a noncontact procedure that allow the description of instant electric charging of moving microparticles that contact dielectric surfaces, for instance, of a flow hose are presented. The described principle is based on the measurement of induced currents in grounded metal wire probes, as moving particles pass close to the probe. The feasibility of the approach was tested with laser printer toner particles of a given size for different basic particle flow and charging conditions. An analytic description for the induced currents was developed and compared to observed effects in order to interpret the results qualitatively. The implementation of the presented procedure can be applied to transparent and nontransparent particle containers and flow lines of complex geometry which can be composed from the presented basic flow stream configurations.
Curvature effects on electronic properties of small radius nanotube
Authors: Zeng H. , Hu H. F. , Wei J. W. , Wang Z. Y. , Wang L. , Peng P.
Published: July 2007

The authors use the density functional theory associated with nonequilibrium Green function to calculate (2,2) and (3,3) single-walled nanotubes. The result of T(E) imply that π or π* band has been suppressed at certain electronic energy region result in the effect of curvature induce complex hybridization procedure. In view of the I-V characteristics of (2,2) tube, it is found that the current curve appears to have an oscillation behavior. These peculiar electronic transport properties of small diameter tube directly relate to a large curvature effect, which may be useful for the manufacture of electronic applications.
Directed assembly of nanowire contacts using electrodeposition
Authors: Ingole S. , Aella P. , Hearne Sean J. , Picraux S. T.
Published: July 2007

A maskless process for the directed assembly of Ni contacts to Si nanowires on prepatterned electrodes is reported. Microarrays of thin Au∕Cr electrodes were lithographically formed on oxidized Si substrates followed by electric-field assisted alignment of Si nanowires between the electrodes. The nanowire ends were then embedded in Ni by selective electrodeposition over the prepatterned electrodes. Annealing to 300°C provided good electrical contacts for transport through the doped nanowires. This approach provides a parallel, maskless method to establish metal contacts to the nanowires without the need of high resolution electron beam lithography for electrical and mechanical applications.
Epistasis between catechol-
O
-methyltransferase and type II metabotropic glutamate receptor 3 genes on working memory brain function
Authors: Tan Hao-Yang , Chen Qiang , Sust Steven , Buckholtz Joshua W. , Meyers John D. , Egan Michael F. , Mattay Venkata S. , Meyer-Lindenberg Andreas , Weinberger Daniel R. , Callicott Joseph H.
Published: July 2007

Dopaminergic and glutamatergic systems are critical components responsible for prefrontal signal-to-noise tuning in working memory. Recent functional MRI (fMRI) studies of genetic variation in these systems in catechol-
O
-methyltransferase (COMT) and in metabotropic glutamate receptor mgluR3 (GRM3), respectively, suggest that these genes influence prefrontal physiological signal-to-noise in humans. Here, using fMRI, we extend these individual gene findings to examine the combined effects of COMT and GRM3 on dissociable components of the frontoparietal working memory network. We observed an apparent epistatic interaction of these two genes on the engagement of prefrontal cortex during working memory. Specifically, the GRM3 genotype putatively associated with suboptimal glutamatergic signaling was significantly associated with inefficient prefrontal engagement and altered prefrontal-parietal coupling on the background of COMT Val-homozygous genotype. Conversely, COMT Met-homozygous background mediated against the effect of GRM3 genotype. These findings extend putative brain dopaminergic and glutamatergic relationships indexed by COMT and GRM3 to a systems-level interaction in human cortical circuits implicated in working memory dysfunction such as in schizophrenia.
Structural basis of antigenic escape of a malaria vaccine candidate
Authors: Dutta Sheetij , Lee Seung Yeon , Batchelor Adrian H. , Lanar David E.
Published: July 2007

Antibodies against the malaria vaccine candidate apical membrane antigen-1 (AMA-1) can inhibit invasion of merozoites into RBC, but antigenic diversity can compromise vaccine efficacy. We hypothesize that polymorphic sites located within inhibitory epitopes function as antigenic escape residues (AER). By using an
in vitro
model of antigenic escape, the inhibitory contribution of 24 polymorphic sites of the 3D7 AMA-1 vaccine was determined. An AER cluster of 13 polymorphisms, located within domain 1, had the highest inhibitory contribution. Within this AER cluster, antibodies primarily targeted five polymorphic residues situated on an α-helical loop. A second important AER cluster was localized to domain 2. Domain 3 polymorphisms enhanced the inhibitory contribution of the domain 2 AER cluster. Importantly, the AER clusters could be split, such that chimeras containing domain 1 of FVO and domain 2 + 3 of 3D7 generated antisera that showed similarly high level inhibition of the two vaccine strains. Antibodies to this chimeric protein also inhibited unrelated strains of the parasite. Interstrain AER chimeras can be a way to incorporate inhibitory epitopes of two AMA-1 strains into a single protein. The AER clusters map in close proximity to conserved structural elements: the hydrophobic trough and the C-terminal proteolytic processing site. This finding led us to hypothesize that a conserved structural basis of antigenic escape from anti-AMA-1 exists. Genotyping high-impact AER may be useful for classifying AMA-1 strains into inhibition groups and to detect allelic effects of an AMA-1 vaccine in the field.
Apoptosis regulation by Bcl-x
L
modulation of mammalian inositol 1,4,5-trisphosphate receptor channel isoform gating
Authors: Li Chi , Wang Xiaoli , Vais Horia , Thompson Craig B. , Foskett J. Kevin , White Carl
Published: July 2007

Members of the Bcl-2 family of proteins regulate apoptosis, with some of their physiological effects mediated by their modulation of endoplasmic reticulum (ER) Ca
2+
homeostasis. Antiapoptotic Bcl-x
L
binds to the inositol trisphosphate receptor (InsP
3
R) Ca
2+
release channel to enhance Ca
2+
- and InsP
3
-dependent regulation of channel gating, resulting in reduced ER [Ca
2+
], increased oscillations of cytoplasmic Ca
2+
concentration ([Ca
2+
]
i
), and apoptosis resistance. However, it is controversial which InsP
3
R isoforms mediate these effects and whether reduced ER [Ca
2+
] or enhanced [Ca
2+
]
i
signaling is most relevant for apoptosis protection. DT40 cell lines engineered to express each of the three mammalian InsP
3
R isoforms individually displayed enhanced apoptosis sensitivity compared with cells lacking InsP
3
R. In contrast, coexpression of each isoform with Bcl-x
L
conferred enhanced apoptosis resistance. In single-channel recordings of channel gating in native ER membranes, Bcl-x
L
increased the apparent sensitivity of all three InsP
3
R isoforms to subsaturating levels of InsP
3
. Expression of Bcl-x
L
reduced ER [Ca
2+
] in type 3 but not type 1 or 2 InsP
3
R-expressing cells. In contrast, Bcl-x
L
enhanced spontaneous [Ca
2+
]
i
signaling in all three InsP
3
R isoform-expressing cell lines. These results demonstrate a redundancy among InsP
3
R isoforms in their ability to sensitize cells to apoptotic insults and to interact with Bcl-x
L
to modulate their activities that result in enhanced apoptosis resistance. Furthermore, these data suggest that modulation of ER [Ca
2+
] is not a specific requirement for ER-dependent antiapoptotic effects of Bcl-x
L
. Rather, apoptosis protection is conferred by enhanced spontaneous [Ca
2+
]
i
signaling by Bcl-x
L
interaction with all isoforms of the InsP
3
R.
Crystal structure of the electron transfer complex rubredoxin–rubredoxin reductase of
Pseudomonas aeruginosa
Authors: Hagelueken Gregor , Wiehlmann Lutz , Adams Thorsten M. , Kolmar Harald , Heinz Dirk W. , Tümmler Burkhard , Schubert Wolf-Dieter
Published: July 2007

Crude oil spills represent a major ecological threat because of the chemical inertness of the constituent
n
-alkanes. The Gram-negative bacterium
Pseudomonas aeruginosa
is one of the few bacterial species able to metabolize such compounds. Three chromosomal genes,
rubB
,
rubA1
, and
rubA2
coding for an NAD(P)H:rubredoxin reductase (RdxR) and two rubredoxins (Rdxs) are indispensable for this ability. They constitute an electron transport (ET) pathway that shuttles reducing equivalents from carbon metabolism to the membrane-bound alkane hydroxylases AlkB1 and AlkB2. The RdxR–Rdx system also is crucial as part of the oxidative stress response in archaea or anaerobic bacteria. The redox couple has been analyzed in detail as a model system for ET processes. We have solved the structure of RdxR of
P. aeruginosa
both alone and in complex with Rdx, without the need for cross-linking, and both structures were refined at 2.40- and 2.45-Å resolution, respectively. RdxR consists of two cofactor-binding domains and a C-terminal domain essential for the specific recognition of Rdx. Only a small number of direct interactions govern mutual recognition of RdxR and Rdx, corroborating the transient nature of the complex. The shortest distance between the redox centers is observed to be 6.2 Å.
Isolation, characterization, andin vitroandin vivodifferentiation of putative thecal stem cells
Authors: Honda Arata , Hirose Michiko , Hara Kenshiro , Matoba Shogo , Inoue Kimiko , Miki Himomi , Hiura Hitoshi , Kanatsu-Shinohara Mito , Kanai Yoshiakira , Kono Tomohiro , Shinohara Takashi , Ogura Atsuo
Published: July 2007

Although ovarian theca cells play an indispensable role in folliculogenesis by providing follicular structural integrity and steroid substrates for estrogen production, little information is available about their recruitment, growth, and differentiation because their immature forms have not been identified. We have isolated putative thecal stem cells with the ability to self-renew and differentiatein vivoandin vitro. They are similar to fibroblasts in morphology and proliferatein vitroas round colonies with a homogenous cell population. They were induced to differentiate into early precursors and steroidogenic cells in a stepwise manner after treatment with serum, luteinizing hormone, and paracrine factors from granulosa cells. At each differentiation step, these cells displayed appropriate gene expression and morphological markers and later secreted androstenedione. The fully mature morphology was achieved by coculture with isolated granulosa cells. When transplanted into the ovaries, the putative thecal stem cells colonized exclusively in the ovarian interstitium and the thecal layer of follicles as differentiated cells. Thus, thecal stem cells appear to be present in neonatal ovaries and can be isolated, purified, and induced to differentiatein vitro. Thecal stem cells could provide an invaluablein vitroexperimental system to study interactions among the oocytes, granulosa cells, and theca cells during normal folliculogenesis and to study ovarian pathology caused by theca cell dysfunction.
A missing link in the sea urchin embryo gene regulatory network:
hesC
and the double-negative specification of micromeres
Authors: Revilla-i-Domingo Roger , Oliveri Paola , Davidson Eric H.
Published: July 2007

Specification of sea urchin embryo micromeres occurs early in cleavage, with the establishment of a well defined regulatory state. The architecture of the gene regulatory network controlling the specification process indicates that transcription of the initial tier of control genes depends on a double-negative gate. A gene encoding a transcriptional repressor,
pmar1
, is activated specifically in micromeres, where it represses transcription of a second repressor that is otherwise active globally. Thus, the micromere-specific control genes, which are the target of the second repressor, are expressed exclusively in this lineage. The double-negative specification gate was logically required from the results of numerous prior experiments, but the identity of the gene encoding the second repressor remained elusive. Here we show that
hesC
is this gene, and we demonstrate experimentally all of its predicted functions, including global repression of micromere-specific regulatory genes. As logically required, blockade of
hesC
mRNA translation and global overexpression of
pmar1
mRNA have the same effect, which is to cause all of the cells of the embryo to express micromere-specific genes.