bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric and magnetic characteristics of LuFeMgO4 ceramics
Authors: Qin Ying , Wang Zhuo , Chen Xiang Ming , Liu Xiao Qiang
Published: October 2010

The magnetic and dielectric characteristics of LuFeMgO4 ceramics were investigated together with the crystal structure. The present ceramics were refined as a rhombohedral structure in space group R3¯m, and antiferromagnetic with a Néel temperature of 27 K. The slim hysteresis loop measured at 10 K demonstrated weak ferromagnetic ordering in LuFeMgO4 ceramics, which might be attributed to the canting angle in Fe moment. An obvious dielectric relaxation, which was well fitted by the modified Debye equation and Arrhenius law with an activation energy of 0.35 eV, was observed in the temperature range of 180–420 K. Moreover, the obtained dielectric constant was much larger than that reported previously. The dielectric relaxation could be strongly suppressed by oxygen annealing, indicating that oxygen vacancies played an important role in the dielectric response of LuFeMgO4 ceramics.
Energetic, mechanical, and vibrational stability of metastable OsC phase
Authors: Kong Yi , Zhao Dongdong , Zhou Laicai , Guo Haibo , Du Yong
Published: October 2010

The assessment of experimental and theoretical results shows controversy about the mechanical stability of OsC phases. The stability of WC-structured, NiAs-structured, and CoSn-structured OsC phases has been investigated by using first-principles calculations. Present results show that WC–OsC and NiAs–OsC are both unstable, energetically and vibrationally, at zero pressure. Further calculations show WC–OsC can be stabilized under high pressure but not NiAs–OsC, which is unstable even under very high pressure. It is found that the interaction between Os atoms in parallel x-y plane is responsible for the deep instability of NiAs structure, while the greatly increased interaction under high pressure between nearest C–Os atoms is responsible for the stabilization of WC–OsC under high pressure.
Luminescence of Ce3+ at two different sites in α-Sr2P2O7 under vacuum ultraviolet-UV and x-ray excitation
Authors: Hou Dejian , Han Bing , Chen Wanping , Liang Hongbin , Su Qiang , Dorenbos Pieter , Huang Yan , Gao Zhenhua , Tao Ye
Published: October 2010

A series of Ce3+ doped α-Sr2−2xCexNaxP2O7 phosphor compounds has been prepared using a high-temperature solid-state reaction technique. The luminescence properties under vacuum ultraviolet-UV and x-ray excitation were studied. Luminescence spectra reveal three UV-emitting peaks at about 310, 330, and 350 nm from which we conclude that Ce3+ occupies two distinct sites in α-Sr2P2O7. The influences of the doping concentration, the temperature, and the excitation wavelength on the luminescence of Ce3+ at the Ce(I) and Ce(II) sites together with the decay characteristics are discussed. The light yield under x-ray excitation is found to be around 10 000 photons/MeV.
Spin switch based on double spin-filter tunnel junction geometry
Authors: Miao G. X. , Moodera J. S.
Published: October 2010

Using the concept of spin filter tunneling, we propose a scheme to turn on and off the spin polarization of a transport current. This is achievable in a double spin filter tunneling geometry, where the net spin polarization of the transient current can be switched off when the two spin filters are aligned antiparallel to each other such that their filtering effects cancel out. When aligned parallel, the two spin filters strengthen each other and the transient current is thus highly spin polarized. This magnetic manipulation gives an additional degree of freedom to tune or even turn off a transport current’s spin polarization. We also show that, to some extent, the degree of spin polarization can be linearly varied with an applied bias voltage.
Influence of interdot hopping and intradot many-body interaction on conductance through parallel triple-quantum-dot device: Nonequilibrium Green’s function approach
Authors: Fu Hua-Hua , Yao Kai-Lun
Published: October 2010

By means of the nonequilibrium Green’s function technique, influence of interdot hoppings t’s and intradot many-body interaction U on electronic transport through parallel triple-quantum-dot (tQD) device in the Coulomb blockade regime are theoretically investigated. In the symmetrical tQD device with uniform interdot hopping t, as t increases starting from zero, the conductance is enhanced due to the opening of new channels for the electronic transport, but as t increases over its critical tc, the interdot hoppings have an opposite influence, which are well consistent with those obtained by the numerical renormalization-group method. The effect of the intradot electron interaction U on the electronic transport through the tQD device is strongly relative to the strength of t. For small t, U suppresses the electronic transport and the Coulomb blockade effect on the dots is dominant. However, for relatively strong t, a small U has a contribution to enhance the electronic transport through the device. These theoretical results can be applied to explain the recent experimental findings on a parallel tQD device. In the asymmetrical parallel tQD device, the symmetry-breaking in the interdot hoppings leads to the increasing on the electronic transport owing to the appearance of more resonance levels in the conductance spectrum. On the basis of this feature, it is proposed that we can obtain some devices with desirable transport properties, such as the molecular charge rectifier, through adjusting the interdot hoppings and the intradot many-body interaction.
All-optical injection and detection of ballistic charge currents in germanium
Authors: Loren Eric J. , Zhao Hui , Smirl Arthur L.
Published: October 2010

All optical techniques are used to inject and to study the relaxation dynamics of ballistic charge currents in clean germanium at room temperature without the application of external contacts or the use of externally applied fields. Ballistic currents are injected by the quantum interference between the transition amplitudes for direct one and two photon absorption of a pair of phase-locked and harmonically related ultrafast laser pulses. The transport of carriers following ballistic injection is temporally and spatially resolved using optical differential transmission techniques that are sensitive to the relative optical phase of the two injection pulses. The electron-hole dynamics are determined by the initial ballistic injection velocity, momentum relaxation, and space charge field effects. The injection process in Ge is similar to that in direct band gap materials but the indirect nature of Ge complicates the monitoring of the carrier dynamics, allowing the holes to play a more prominent role than in direct gap materials. The latter opens the possibility of following the hole (as opposed to the electron) dynamics.
Diffusion model for Knudsen-type compressor composed of periodic arrays of circular cylinders
Authors: Taguchi Satoshi
Published: October 2010

A rarefied gas flow in a long porous channel having a periodic structure that is consisting of alternately arranged porous media and gaps, the former of which contains a periodic array of parallel circular cylinders, is considered for the case in which the channel is infinitely wide. The cylinder arrays have a periodic temperature distribution with the same period as the structure. Under the assumption that the length of each cylinder array and that of each gap are much larger than the period of the cylinders in the array, a fluid-dynamic system describing the overall behavior of the gas in the channel is derived from the kinetic system composed of the Bhatnagar–Gross–Krook equation and the diffuse reflection boundary condition. The derived system is composed of a diffusion model for each cylinder array, whose isothermal version has been reported previously [S. Taguchi and P. Charrier, Phys. Fluids 20, 067103 (2008)], a set of fluid-dynamic equations for each gap, and the macroscopic connection conditions at each junction between an array and a gap. Then, the fluid-dynamic system is applied to a long channel consisting of many cylinder arrays and gaps. Some numerical results demonstrating the pumping effect of the flow are presented.
Atomic structure of steps on 180° ferroelectric domain walls in PbTiO3
Authors: Angoshtari Arzhang , Yavari Arash
Published: October 2010

Using the method of anharmonic lattice statics, we calculate the equilibrium structure of steps on 180° ferroelectric domain walls (DWs) in PbTiO3. We consider three different types of steps: (i) Ti–Ti step that joins a Ti-centered DW to a Ti-centered DW, (ii) Pb–Pb step that joins a Pb-centered DW to a Pb-centered DW, and (iii) Pb–Ti step that joins a Pb-centered DW to a Ti-centered DW. We show that atomic distortions due to these steps broaden a DW but are localized, i.e., they are confined to regions with dimensions of a few lattice spacings. We see that a step locally thickens the DW; the defective DW is two to three times thicker than the perfect DW depending on the step type. We also observe that steps distort the polarization distribution in a mixed Bloch–Néel like way; polarization rotates out of the DW plane near the steps. Our calculations show that Pb–Pb steps have the lowest static energy.
Graphene-based ultrafast diode
Authors: Dragoman D. , Dragoman M. , Plana R.
Published: October 2010

We present a graphene-based ballistic diode, which is able to rectify an incident signal due to an oblique gate positioned between the two terminals of the device. The operating point of the diode can be controlled by the applied gate voltage, whereas the current-voltage dependence of the device can be changed by varying the inclination angle of the gate. In particular, the ideality factor of the graphene-based diode can take values higher or lower than 1 by modifying this inclination angle. The rectifying properties of the graphene diode are thus tunable, in deep contrast with semiconductor-based diodes.
Interface energy and its influence on interface fracture between metal and ceramic thin films in nanoscale
Authors: Liang L. H. , You X. M. , Ma H. S. , Wei Y. G.
Published: October 2010

A theoretical model about the size-dependent interface energy between two thin films with different materials is developed by considering the chemical bonding contribution based on the thermodynamic expressions and the structure strain contribution based on the mechanical characteristics. The interface energy decreases with reducing thickness of thin films, and is determined by such available thermodynamic and mechanical parameters as the melting entropy, the melting enthalpy, the shear modulus of two materials, etc. The predicted interface energies of some metal/MgO and metal/Al2O3 interfaces based on the model are consistent with the results based on the molecular mechanics calculation. Furthermore, the interface fracture properties of Ag/MgO and Ni/Al2O3 based on the atomistic simulation are further compared with each other. The fracture strength and the toughness of the interface with the smaller structure interface energy are both found to be lower. The intrinsic relations among the interface energy, the interface strength, and the fracture toughness are discussed by introducing the related interface potential and the interface stress. The microscopic interface fracture toughness is found to equal the structure interface energy in nanoscale, and the microscopic fracture strength is proportional to the fracture toughness.
Impact response of cobalt over the 300–1400 K temperature range
Authors: Zaretsky E. B.
Published: October 2010

The yield and tensile (spall) strengths and the dynamic viscosity of 99.95% pure cobalt were studied in a series of interferometer-instrumented planar impact experiments over the 300 to 1423 K temperature range. The spall strength of cobalt declines monotonously from 3.2 GPa at 300 K to 0.8 GPa at 1400 K. The dynamic yield strength grows linearly with temperature in both the hcp and fcc cobalt phases. The hcp to fcc transformation at 690 K is accompanied by an abrupt twofold drop of the yield strength. The similarity between the temperature dependence of the cobalt’s dynamic viscosity and of the yield strength suggests that both properties are controlled by the interaction of the dislocations with the oncoming phonon flow (phonon drag).
Magnetically induced structural reorientation in magnetite studied by nuclear magnetic resonance
Authors: Chlan V. , Kouřil K. , Štěpánková H. , Řezníček R. , Štěpánek J. , Tabiś W. , Król G. , Tarnawski Z. , Kąkol Z. , Kozłowski A.
Published: October 2010

Phenomenon related to low symmetry phase of magnetite Fe3O4 below the Verwey transition is the switching of magnetic easy axis by external magnetic field connected with a structural transition. Results of nuclear magnetic resonance (NMR) studies of axis switching are presented, preceded by careful characterization by magnetic measurements. We detect changes in the F57e NMR spectra that evidence the structural transition interrelated with the axis switching. We also observe the switching process in time and analyze the dynamics of the phenomenon. Phenomenological approach according to Kolmogorov–Johnson–Mehl–Avrami is employed to find a link between the experimental data from magnetization measurements and NMR, showing that the effect observed by these two methods has the same origin. Additionally, NMR identifies separately the unswitched and switched phase during the switching process.
The magnetic domain configuration in Co/Ni/Co nanoscale antidot arrays
Authors: Cheng Ruihua , Justus B. L. , Rosenberg A. , McIlroy D. N. , Holman Z. , Zhang D. , Kranov Y.
Published: October 2010

We performed superconducting quantum interference devices and magnetic force microscopy (MFM) measurements on magnetic multilayer Co(60 Å)/Ni(90 Å)/Co(60 Å) nanoscale antidot samples. The antidot samples were fabricated on nanochannel glass substrates with different antidot diameters and the antidots ordered as a two dimensional hexagonal lattice structure. The results indicate that a self-organized domain structure is formed due to the pinning effect of the antidots. The strong uniaxial anisotropy of Co suppresses the shape anisotropy of the antidots and results in an uncommon domain structure. The field dependent MFM data reveal a reversal of magnetization.
Strong electron correlation in the decomposition reaction of dioxetanone with implications for firefly bioluminescence
Authors: Greenman Loren , Mazziotti David A.
Published: October 2010

Dioxetanone, a key component of the bioluminescence of firefly luciferin, is itself a chemiluminescent molecule due to two conical intersections on its decomposition reaction surface. While recent calculations of firefly luciferin have employed four electrons in four active orbitals [(4,4)] for the dioxetanone moiety, a study of dioxetanone [F. Liu et al., J. Am. Chem. Soc. 131, 6181 (2009)] indicates that a much larger active space is required. Using a variational calculation of the two-electron reduced-density-matrix (2-RDM) [D. A. Mazziotti, Acc. Chem. Res. 39, 207 (2006)], we present the ground-state potential energy surface as a function of active spaces from (4,4) to (20,17) to determine the number of molecular orbitals required for a correct treatment of the strong electron correlation near the conical intersections. Because the 2-RDM method replaces exponentially scaling diagonalizations with polynomially scaling semidefinite optimizations, we readily computed large (18,15) and (20,17) active spaces that are inaccessible to traditional wave function methods. Convergence of the electron correlation with active-space size was measured with complementary RDM-based metrics, the von Neumann entropy of the one-electron RDM as well as the Frobenius and infinity norms of the cumulant 2-RDM. Results show that the electron correlation is not correctly described until the (14,12) active space with small variations present through the (20,17) space. Specifically, for active spaces smaller than (14,12), we demonstrate that at the first conical intersection, the electron in the σ∗ orbital of the oxygen-oxygen bond is substantially undercorrelated with the electron of the σ orbital and overcorrelated with the electron of the carbonyl oxygen's p orbital. Based on these results, we estimate that in contrast to previous treatments, an accurate calculation of the strong electron correlation in firefly luciferin requires an active space of 28 electrons in 25 orbitals, beyond the capacity of traditional multireference wave function methods.
A novel chemical detector using colorimetric sensor array and pattern recognition methods for the concentration analysis of NH3
Authors: Luo Xiao-gang , Liu Ping , Hou Chang-jun , Huo Dan-qun , Dong Jia-le , Fa Huan-bao , Yang Mei
Published: October 2010

With a colorimetric sensor array comprising chemoresponsive dyes, a simple, rapid, and cost-effective integrated system for differentiating low-concentration gases was described. The system could be used to identify gases by detecting the color change information of the chemoresponsive dyes based on porphyrins before and after reaction with the target gas; the colorimetric sensor array images were collected by a charge coupled device and processed with image analysis to get the color changes of the dyes in the array. Temperature, humidity, and flux of the chamber could be detected and displayed on the personal computer screen. A low-concentration [30–210 ppb (parts per 109)] NH3 was detected by the system. This prototype successfully differentiated four concentration levels of NH3 in less than 1 min. Pattern recognition methods, such as the backpropagation neural network and the radial basis function neural network, validated the effect of the developed sensor system both with 100% classification with feature vectors at single time point as inputs.
Effect of twin spacing on the growth velocity of Si faceted dendrites
Authors: Yang Xinbo , Fujiwara Kozo , Gotoh Raira , Maeda Kensaku , Nozawa Jun , Koizumi Haruhiko , Uda Satoshi
Published: October 2010

The growth velocity of silicon ⟨110⟩ faceted dendrites as a function of the twin spacing was investigated by in situ observation. As the twin spacing increases, ⟨110⟩ dendrite growth velocity nonlinearly decreases. The theoretical ⟨110⟩ and ⟨112⟩ dendrite growth velocities were calculated on the basis of the modified re-entrant corner model, and the theoretical growth velocity of ⟨112⟩ dendrites was found to be slower than that of ⟨110⟩ dendrites under the same twin spacing. The theoretical ⟨110⟩ dendrite growth velocity fits quite well with the experimental results.
Mutual interaction of Faraday rotation and Cotton–Mouton phase shift in JET polarimetric measurements
Authors: Orsitto F. P. , Boboc A. , Gaudio P. , Gelfusa M. , Giovannozzi E. , Mazzotta C. , Murari A. ,   JET-EFDA Contributors
Published: October 2010

The paper presents a study of Faraday rotation (FR) angle and Cotton–Mouton (CM) phase shift measurements to determine their mutual interaction and the validity of the linear models presently used in equilibrium codes. Comparison between time traces of measurements and model calculations leads to the result that only an exact numerical solution of Stokes equations can reproduce in all the experimental data. As a consequence, approximated linear models can be applied only in a limited range of plasma parameters. In general, the nonlinear coupling between FR and CM is important for the evaluation of polarimetry parameters.
New frequency translation technique for FM-CW reflectometry
Authors: Meneses Luis , Cupido Luis , Manso M. E. ,   JET-EFDA Contributors
Published: October 2010

In broadband microwave reflectometry, coherent detection is widely used to obtain the phase information and to improve the systems sensitivity, both in diagnostics measuring the electronic density profile and plasma fluctuations. Coherent detection uses a translated version of the probing signal to guarantee a stable intermediate frequency. Here, a novel technique to generate the frequency translation by double frequency conversion is presented and its advantages over the commonly used single frequency conversion techniques employing image rejection mixers are discussed. The results obtained with the new frequency translator modules developed for the three JET FM-CW reflectometers, operating successfully at JET since mid-2009, are presented.
Neutron spectroscopy as a fuel ion ratio diagnostic: Lessons from JET and prospects for ITER
Authors: Ericsson G. , Conroy S. , Gatu Johnson M. , Andersson Sundén E. , Cecconello M. , Eriksson J. , Hellesen C. , Sangaroon S. , Weiszflog M. ,   JET EFDA Contributors
Published: October 2010

The determination of the fuel ion ratio nt/nd in ITER is required at a precision of 20%, time resolution of 100 ms, spatial resolution of a/10, and over a range of 0.01<nT/nD<10. We use simplified but realistic Monte Carlo models of ITER to assess the possibility to use neutron emission spectroscopy (NES) for such measurements. We show that NES meets the requirements for ion temperatures Ti>6 keV and for nT/nD<0.6. A crucial issue is the signal-to-background situation in the measurement of the weak 2.5 MeV emission from DD reactions in the presence of a background of scattered 14 MeV DT neutrons. Important experimental input and corroboration for this assessment are presented from the time-of-flight neutron spectrometer at JET where the presence of a strong component of backscattered neutrons is observed. Neutron emission components on ITER due to beam-thermal and tritium-tritium reactions can further enhance the prospects for NES.
Characterization of the Li beam probe with a beam profile monitor on JET
Authors: Nedzelskiy I. S. , Korotkov A. , Brix M. , Morgan P. , Vince J. ,   JET EFDA Contributors
Published: October 2010

The lithium beam probe (LBP) is widely used for measurements of the electron density in the edge plasma of magnetically confined fusion experiments. The quality of LBP data strongly depends on the stability and profile shape of the beam. The main beam parameters are as follows: beam energy, beam intensity, beam profile, beam divergence, and the neutralization efficiency. For improved monitoring of the beam parameters, a beam profile monitor (BPM) from the National Electrostatics Corporation (NEC) has been installed in the Li beam line at JET. In the NEC BPM, a single grounded wire formed into a 45° segment of a helix is rotated by a motor about the axis of the helix. During each full revolution, the wire sweeps twice across the beam to give X and Y profiles. In this paper, we will describe the properties of the JET Li beam as measured with the BPM and demonstrate that it facilitates rapid optimization of the gun performance.
Effect of electron-beam irradiation on graphene field effect devices
Authors: Childres Isaac , Jauregui Luis A. , Foxe Michael , Tian Jifa , Jalilian Romaneh , Jovanovic Igor , Chen Yong P.
Published: October 2010

Electron beam exposure is a commonly used tool for fabricating and imaging graphene-based devices. Here, we present a study of the effects of electron-beam irradiation on the electronic transport properties of graphene and the operation of graphene field-effect transistors (GFETs). Exposure to a 30 keV electron-beam caused negative shifts in the charge-neutral point (CNP) of the GFET, interpreted as due to n-doping in the graphene from the interaction of the energetic electron beam with the substrate. The shift in the CNP is substantially reduced for suspended graphene devices. The electron beam is seen to also decrease the carrier mobilities and minimum conductivity, indicating defects created in the graphene. The findings are valuable for understanding the effects of radiation damage on graphene and for the development of radiation-hard graphene-based electronics.
Selective excitation of LI2 by chirped laser pulses with all possible interstate radiative couplings
Authors: Chatterjee Souvik , Bhattacharyya S. S.
Published: October 2010

We have numerically explored the feasibility and the mechanism of population transfer to the excited E Σ1g electronic state of Li2 from the v=0 level of the ground electronic state X Σ1g using the A Σ1u state as an intermediate. In this system, the use of transform limited pulses with a frequency difference greater than the maximum Rabi frequency does not produce population transfer when all possible radiative couplings are taken into account. We have employed two synchronous pulses far detuned from the allowed transition frequencies, mainly with the lower frequency pulse positively chirped, and both pulses coupling the successive pair of states, X-A and A-E. The adiabaticity of the process has been investigated by a generalized Floquet calculation in the basis of 12 field dressed molecular states, and the results have been compared with those obtained from the full solution of time dependent Schrödinger equation. The conventional representation of the process in terms of three (or four) adiabatic potentials is not valid. It has been found that for cases of almost complete population transfer in full calculations with the conservation of the vibrational quantum number, adiabatic passage is attained with the 12 state Floquet model but not with the six state model. The agreement between the full calculations and the 12 state Floquet calculations is generally good when the transfer is adiabatic. Another characteristic feature of this work is the gaining of control over the vibrational state preparation in the final electronic state by careful tuning of the laser parameters as well as the chirp rate sign. This causes time dependent changes in the adiabatic potentials and nonadiabatic transfers can be made to occur between them.
High quality ion acceleration from a double-layer target dominated by the radiation pressure of a transversely Gaussian laser pulse
Authors: Hong Xue-Ren , Xie Bai-Song , Zhang Shan , Wu Hai-Cheng , Aimidula Aimierding , Zhao Xue-Yan , Liu Ming-Ping
Published: October 2010

The ion acceleration from a double-layer target irradiated by a transversely Gaussian laser pulse is investigated by theoretical analysis and particle-in-cell simulations. The main idea of the double-layer target is to match the transverse areal mass density of the target with the laser intensity profile by single ion specie with two densities or by two ion species. Two-dimensional particle-in-cell simulations show that the target deformation and the transverse instability are efficiently suppressed in the double-layer scheme, ions within the laser spot are uniformly accelerated and are well collimated in the forward direction, GeV/u monoenergetic ion beams with very low divergency are observed.
Dark-state polariton in magnetized plasma under electromagnetically induced transparency
Authors: Kawamori Eiichirou
Published: October 2010

This paper derives a wave equation in magnetized plasma under electromagnetically induced transparency (EIT) regime for probe electron cyclotron wave. The equation has a solution indicating a state analogous to “dark-state polaritons” [M. Fleischhauer and M. D. Lukin, Phys. Rev. Lett. 84, 5094 (2000)] in quantum atomic system. The state analogous to dark-state polaritons is a propagating coupled state of the probe-wave electric field and longitudinal plasma oscillation. The propagation of the coupled state can be stopped as its waveform is maintained if injection of pump wave is properly controlled in time domain. The “stop-light” is achieved by adiabatic transition from a state in which the probe-wave field is dominant to a state in which the longitudinal plasma oscillation is dominant. This study also recaptures a phenomenon analogous to “coherent population trap” in conventional EIT of quantum atomic system.
Dust-ion-acoustic wave oscillation in metallic multiwalled carbon nanotubes
Authors: Fathalian Ali , Nikjo Shahram
Published: October 2010

In this paper, a charged multiwalled carbon nanotube (MWCNT), which is surrounded by charged nanoparticles, is modeled as a cylindrical shell of electron-ion-dust plasma. By employing the classical electrodynamics formulations and linearized hydrodynamic model, the dispersion relation of the dust-ion-acoustic wave oscillations in the composed system is investigated. We obtain a new low-frequency electrostatic excitation in the MWCNTs, i.e., dust-ion-acoustic wave oscillations.
Ultrafast electrical charging and discharging of a single InGaAs quantum dot
Authors: Nannen J. , Kümmell T. , Bartsch M. , Brunner K. , Bacher G.
Published: October 2010

We report on ultrafast control of the charge state of a single InGaAs quantum dot in a charge-tunable p-i-n diode structure. Focused ion beam etching is employed to decrease the capacitance of the device to enable radio frequency operation. A time-resolved photoluminescence technique is demonstrated that allows monitoring the charge state with a time-resolution which is limited only by the radiative lifetime of the charged and neutral exciton, respectively. Experimental data show that the charge state can be manipulated on time scales shorter than the radiative lifetime of approximately 1.4 ns.
Thermocapillary-assisted pulling of thin films: Application to molten metals
Authors: Scheid Benoit , van Nierop Ernst A. , Stone Howard A.
Published: October 2010

We study the thermocapillary stabilization of a free liquid film as it is formed by being pulled out of a bath at constant speed. For sufficiently large stresses induced at the interface through a controlled temperature gradient, a continuous film of liquid can be processed. For negligible inertial effects, the film thickness only depends on the capillary length and on the strength of the surface tension variation. The theory suggests that very thin ribbons or foils of molten material can be drawn out of a melt over a wide range of thicknesses and at speeds relevant to manufacturing.
Investigation of high frequency performance limit of graphene field effect transistors
Authors: Pince Ercag , Kocabas Coskun
Published: October 2010

Extremely high field effect mobility together with the high surface coverage makes graphene a promising material for high frequency electronics application. We investigate the intrinsic high frequency performance limit of graphene field effect transistors limited by the charge impurity scattering. The output and transfer characteristics of graphene field effect transistors together with the high frequency performance are characterized as a function of impurity concentration and dielectric constant of the gate insulator. Our results reveal that graphene transistors could provide power gain at radio frequency band.
Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes
Authors: Kolbe Tim , Knauer Arne , Chua Chris , Yang Zhihong , Einfeldt Sven , Vogt Patrick , Johnson Noble M. , Weyers Markus , Kneissl Michael
Published: October 2010

The polarization of the in-plane electroluminescence of (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in the ultraviolet-A and ultraviolet-B spectral range has been investigated. The intensity for transverse-electric polarized light relative to the transverse-magnetic polarized light decreases with decreasing emission wavelength. This effect is attributed to rearrangement of the valence bands at the Γ-point of the Brillouin zone with changing aluminum and indium mole fractions in the (In)(Al)GaN quantum wells. For shorter wavelength the crystal-field split-off hole band moves closer to the conduction band relative to the heavy and light hole bands and as a consequence the transverse-magnetic polarized emission becomes more dominant for deep ultraviolet light emitting diodes.
Structural and optical properties of InAs quantum dot chains grown on nanoimprint lithography structured GaAs with different pattern orientations
Authors: Hakkarainen T. V. , Tommila J. , Schramm A. , Tukiainen A. , Ahorinta R. , Dumitrescu M. , Guina M.
Published: October 2010

We use large-scale UV nanoimprint lithography prepatterned GaAs substrates for site-controlled growth of InAs quantum dot chains by molecular beam epitaxy. We demonstrate simultaneous fabrication of quantum dot chains with high optical quality along four different crystal orientations, [011], [011¯], [010], and [001]. We show that the [011¯], [010], and [001]-oriented quantum dot chains not only have similar morphology but also experience similar in-plane optical anisotropy, which tends to align along the axis of the quantum dot chain. Our optical and structural results show that InAs quantum dot chains could be a potential platform for nanophotonic waveguiding and integrated circuits.
Bernhard Hermann Neumann 1909 - 2002
Authors: Praeger Cheryl E.
Published: October 2010

Bernhard Hermann Neumann was born and educated in Berlin. He held doctorates from Berlin and Cambridge, and mathematical positions at universities in Cardiff, Hull, Manchester, and the Australian National University (ANU) in Canberra. Whereas his move to the UK in 1933 was a result of the difficulties he faced as a Jew in finding employment in Germany, his move to Australia in 1962 was to set up a new research Department of Mathematics at the Institute of Advanced Studies at the ANU. Bernhard Neumann was famous for both his seminal research work in algebra and his strong support of all endeavours in mathematics. His scholarly publications span more than seventy years. His honours include Fellowship of the Royal Society and of the Australian Academy of Science, appointment as Companion of the Order of Australia, and numerous honorary doctorates. To Bernhard it was important to share and spread the joy of doing mathematics.
A network connecting Runx2, SATB2, and the miR-23a∼27a∼24-2 cluster regulates the osteoblast differentiation program
Authors: Hassan Mohammad Q. , Gordon Jonathan A. R. , Beloti Marcio M. , Croce Carlo M. , Wijnen Andre J. van , Stein Janet L. , Stein Gary S. , Lian Jane B.
Published: October 2010

Induced osteogenesis includes a program of microRNAs (miRs) to repress the translation of genes that act as inhibitors of bone formation. How expression of bone-related miRs is regulated remains a compelling question. Here we report that Runx2, a transcription factor essential for osteoblastogenesis, negatively regulates expression of the miR cluster 23a∼27a∼24-2. Overexpression, reporter, and chromatin immunoprecipitation assays established the presence of a functional Runx binding element that represses expression of these miRs. Consistent with this finding, exogenous expression of each of the miRs suppressed osteoblast differentiation, whereas antagomirs increased bone marker expression. The biological significance of Runx2 repression of this miR cluster is that each miR directly targets the 3′ UTR of SATB2, which is known to synergize with Runx2 to facilitate bone formation. The findings suggest Runx2-negative regulation of multiple miRs by a feed-forward mechanism to cause derepression of SATB2 to promote differentiation. We find also that miR-23a represses Runx2 in the terminally differentiated osteocyte, representing a feedback mechanism to attenuate osteoblast maturation. We provide direct evidence for an interdependent relationship among transcriptional inhibition of the miR cluster by Runx2, translational repression of Runx2 and of SATB2 by the cluster miRs during progression of osteoblast differentiation. Furthermore, miR cluster gain of function (i.e., inhibition of osteogenesis) is rescued by the exogenous expression of SATB2. Taken together, we have established a regulatory network with a central role for the miR cluster 23a∼27a∼24-2 in both progression and maintenance of the osteocyte phenotype.
Cryo-EM structure and rRNA model of a translating eukaryotic 80S ribosome at 5.5-Å resolution
Authors: Armache Jean-Paul , Jarasch Alexander , Anger Andreas M. , Villa Elizabeth , Becker Thomas , Bhushan Shashi , Jossinet Fabrice , Habeck Michael , Dindar Gülcin , Franckenberg Sibylle , Marquez Viter , Mielke Thorsten , Thomm Michael , Berninghausen Otto , Beatrix Birgitta , Söding Johannes , Westhof Eric , Wilson Daniel N. , Beckmann Roland
Published: October 2010

Protein biosynthesis, the translation of the genetic code into polypeptides, occurs on ribonucleoprotein particles called ribosomes. Although X-ray structures of bacterial ribosomes are available, high-resolution structures of eukaryotic 80S ribosomes are lacking. Using cryoelectron microscopy and single-particle reconstruction, we have determined the structure of a translating plant (
Triticum aestivum
) 80S ribosome at 5.5-Å resolution. This map, together with a 6.1-Å map of a
Saccharomyces cerevisiae
80S ribosome, has enabled us to model ∼98% of the rRNA. Accurate assignment of the rRNA expansion segments (ES) and variable regions has revealed unique ES–ES and r-protein–ES interactions, providing insight into the structure and evolution of the eukaryotic ribosome.
Pineal-specific agouti protein regulates teleost background adaptation
Authors: Zhang Chao , Song Youngsup , Thompson Darren A. , Madonna Michael A. , Millhauser Glenn L. , Toro Sabrina , Varga Zoltan , Westerfield Monte , Gamse Joshua , Chen Wenbiao , Cone Roger D.
Published: October 2010

Background adaptation is used by teleosts as one of a variety of camouflage mechanisms for avoidance of predation. Background adaptation is known to involve light sensing by the retina and subsequent regulation of melanophore dispersion or contraction in melanocytes, mediated by α-melanocyte–stimulating hormone and melanin-concentrating hormone, respectively. Here, we demonstrate that an agouti gene unique to teleosts,agrp2, is specifically expressed in the pineal and is required for up-regulation of hypothalamicpmchandpmchlmRNA and melanosome contraction in dermal melanocytes in response to a white background.floating head, a mutant with defective pineal development, exhibits defective up-regulation ofmchmRNAs by white background, whereasnrc, a blind mutant, exhibits a normal response. These studies identify a role for the pineal in background adaptation in teleosts, a unique physiological function for the agouti family of proteins, and define a neuroendocrine axis by which environmental background regulates pigmentation.
Chlorhexidine-Impregnated Cloths to Prevent Skin and Soft-Tissue Infection in Marine Recruits: A Cluster-Randomized, Double-Blind, Controlled Effectiveness Trial
Authors: Whitman Timothy J. , Herlihy Rachel K. , Schlett Carey D. , Murray Patrick R. , Grandits Greg A. , Ganesan Anuradha , Brown Maya , Mancuso James D. , Adams William B. , Tribble David R.
Published: October 2010

Background.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) causes skin and soft-tissue infection (SSTI) in military recruits.

Objective.

To evaluate the effectiveness of 2% Chlorhexidine gluconate (CHG)-impregnated cloths in reducing rates of SSTI and S. aureus colonization among military recruits.

Design.

A cluster-randomized (by platoon), double-blind, controlled effectiveness trial.

Setting.

Marine Officer Candidate School, Quantico, Virginia, 2007.

Participants.

Military recruits.

Intervention.

Application of CHG-impregnated or control (Comfort Bath; Sage) cloths applied over entire body thrice weekly.

Measurements.

Recruits were monitored daily for SSTI. Baseline and serial nasal and/or axillary swabs were collected to assess S. aureus colonization.

Results.

Of 1,562 subjects enrolled, 781 (from 23 platoons) underwent CHG-impregnated cloth application and 781 (from 21 platoons) underwent control cloth application. The rate of compliance (defined as application of 50% or more of wipes) at 2 weeks was similar (CHG group, 63%; control group, 67%) and decreased over the 6-week period. The mean 6-week SSTI rate in the CHG-impregnated cloth group was 0.094, compared with 0.071 in the control group (analysis of variance model rate difference, 0.025 ± 0.016; P = .14). At baseline, 43% of subjects were colonized with methicillin-susceptible S. aureus (MSSA), and 2.1% were colonized with MRSA. The mean incidence of colonization with MSSA was 50% and 61% (P = .026) and with MRSA was 2.6% and 6.0% (P = .034) for the CHG-impregnated and control cloth groups, respectively.

Conclusions.

CHG-impregnated cloths applied thrice weekly did not reduce rates of SSTI among recruits. S. aureus colonization rates increased in both groups but to a lesser extent in those assigned to the CHG-impregnated cloth Intervention. Antecedent S. aureus colonization was not a risk factor for SSTI. Additional studies are needed to identify effective measures for preventing SSTI among military recruits.

Clinical Trials Registration.

ClinicalTrials.gov identifier: NCT00475930.
Ertapenem-Resistant Enterobacteriaceae Risk Factors for Acquisition and Outcomes
Authors: Hyle E. P. , Ferraro M. J. , Silver M. , Lee H. , Hooper D. C.
Published: October 2010

Background and Objective.

Carbapenem resistance among Enterobacteriaceae is of concern because of increasing prevalence and limited therapeutic options. Limited research has been focused on understanding ertapenem resistance as a more sensitive marker for resistance to other carbapenems. We sought to determine risk factors for acquisition of ertapenem-resistant, meropenem-susceptible, or intermediate Enterobacteriaceae and to assess associated patient outcomes.

Design.

Retrospective case-control study among adult hospitalized inpatients.

Setting.

A 902-bed quaternary care urban hospital.

Results.

Sixty-two cases of ertapenem-resistant Enterobacteriaceae were identified from March 14, 2006, through October 31, 2007, and 62 unmatched control patients were randomly selected from other inpatients with cultures positive for ertapenem-susceptible Enterobacteriaceae. Thirty-seven (60%) of case patient isolates were Enterobacter cloacae, 20 (32%) were Klebsiella pneumoniae, and 5 (8%) were other species of Enterobacteriaceae. Risk factors for ertapenem-resistant Enterobacteriaceae infection included intensive care unit stay (odds ratio [OR], 4.6 [95% confidence interval {CI}, 2.0–10.3]), vancomycin-resistant Enterococcus colonization (OR, 7.1 [95% CI, 2.4–21.4]), prior central venous catheter use (OR, 10.0 [95% CI, 3.0–33.1]), prior receipt of mechanical ventilation (OR, 5.8 [95% CI, 2.1–16.2]), exposure to any antibiotic during the 30 days prior to a positive culture result (OR, 18.5 [95% CI, 4.9–69.9]), use of a β-lactam during the 30 days prior to a positive culture result (OR, 6.9 [95% CI, 3.0–16.0], and use of a carbapenem during the 30 days prior to a positive culture result (OR, 18.2 [95% CI, 2.6–130.0]). For the 62 case patients, 30-day outcomes from the time of positive culture result were 24 discharges (39%), 10 deaths (16%), and 28 continued hospitalizations (44%). The final end point of the hospitalization was discharge for 44 patients (71%) and death for 18 patients (29%).

Conclusions.

Ertapenem-resistant Enterobacteriaceae are important nosocomial pathogens. Multiple mechanisms of resistance maybe in operation. Additional study of ertapenem resistance is needed.
Impact of International Nosocomial Infection Control Consortium (INICC) Strategy on Central Line–Associated Bloodstream Infection Rates in the Intensive Care Units of 15 Developing Countries
Authors: Rosenthal Victor D. , Maki Dennis G. , Rodrigues Camila , Álvarez-Moreno Carlos , Leblebicioglu Hakan , Sobreyra-Oropeza Martha , Berba Regina , Madani Naoufel , Medeiros Eduardo A. , Cuéllar Luis E. , Mitrev Zan , Dueñas Lourdes , Guanche-Garcell Humberto , Mapp Trudell , Kanj Souha S. , Fernández-Hidalgo Rosalía ,   International Nosocomial Infection Control Consortium Investigators
Published: October 2010

Background.

The International Nosocomial Infection Control Consortium (INICC) was established in 15 developing countries to reduce infection rates in resource-limited hospitals by focusing on education and feedback of outcome surveillance (infection rates) and process surveillance (adherence to infection control measures). We report a time-sequence analysis of the effectiveness of this approach in reducing rates of central line–associated bloodstream infection (CLABSI) and associated deaths in 86 intensive care units with a minimum of 6-month INICC membership.

Methods.

Pooled CLABSI rates during the first 3 months (baseline) were compared with rates at 6-month intervals during the first 24 months in 53,719 patients (190,905 central line–days). Process surveillance results at baseline were compared with intervention period data.

Results.

During the first 6 months, CLABSI incidence decreased by 33% (from 14.5 to 9.7 CLABSIs per 1,000 central line–days). Over the first 24 months there was a cumulative reduction from baseline of 54% (from 16.0 to 7.4 CLABSIs per 1,000 central line–days; relative risk, 0.46 [95% confidence interval, 0.33–0.63];P<.001). The number of deaths in patients with CLABSI decreased by 58%. During the intervention period, hand hygiene adherence improved from 50% to 60% (P<.001); the percentage of intensive care units that used maximal sterile barriers at insertion increased from 45% to 85% (P< .001), that adopted Chlorhexidine for antisepsis increased from 7% to 27% (P= .018), and that sought to remove unneeded catheters increased from 37% to 83% (P= .004); and the duration of central line placement decreased from 4.1 to 3.5 days (P< .001).

Conclusions.

Education, performance feedback, and outcome and process surveillance of CLABSI rates significantly improved infection control adherence, reducing the CLABSI incidence by 54% and the number of CLABSI-associated deaths by 58% in INICC hospitals during the first 2 years.
Improving Efficiency in Active Surveillance for Methicillin-Resistant Staphylococcus aureus or Vancomycin-Resistant Enterococcus at Hospital Admission
Authors: Morgan Daniel J. , Day Hannah R. , Furuno Jon P , Young Atlisa , Johnson J. Kristie , Bradham Douglas D. , Perencevich Eli N.
Published: October 2010

Objective.

Mandatory active surveillance culturing of all patients admitted to Veterans Affairs (VA) hospitals carries substantial economic costs. Clinical prediction rules have been used elsewhere to identify patients at high risk of colonization with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE). We aimed to derive and evaluate the clinical efficacy of prediction rules for MRSA and VRE colonization in a VA hospital.

Design and Setting.

Prospective cohort of adult inpatients admitted to the medical and surgical wards of a 119-bed tertiary care VA hospital.

Methods.

Within 48 hours after admission, patients gave consent, completed a 44-item risk factor questionnaire, and provided nasal culture samples for MRSA testing. A subset provided perirectal culture samples for VRE testing.

Results.

Of 598 patients enrolled from August 30, 2007, through October 30, 2009, 585 provided nares samples and 239 provided perirectal samples. The prevalence of MRSA was 10.4% (61 of 585) (15.0% in patients with and 5.6% in patients without electronic medical record (EMR)-documented antibiotic use during the past year; P < .01). The prevalence of VRE was 6.3% (15 of 239) (11.3% in patients with and 0.9% in patients without EMR-documented antibiotic use; P < .01 ). The use of EMR-documented antibiotic use during the past year as the predictive rule for screening identified 242.8 (84%) of 290.6 subsequent days of exposure to MRSA and 60.0 (98%) of 61.0 subsequent days of exposure to VRE, respectively. EMR documentation of antibiotic use during the past year identified 301 (51%) of 585 patients as high-risk patients for whom additional testing with active surveillance culturing would be appropriate.

Conclusions.

EMR documentation of antibiotic use during the year prior to admission identifies most MRSA and nearly all VRE transmission risk with surveillance culture sampling of only 51% of patients. This approach has substantial cost savings compared with the practice of universal active surveillance.