bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermo-optical characteristics and concentration quenching effects in Nd3+doped yttrium calcium borate glasses
Authors: Santos D. R. S. , Santos C. N. , de Camargo A. S. S. , Silva W. F. , Santos W. Q. , Vermelho M. V. D. , Astrath N. G. C. , Malacarne L. C. , Li M. S. , Hernandes A. C. , Ibanez A. , Jacinto C.
Published: March 2011

In this work we present a comprehensive study of the spectroscopic and thermo-optical properties of a set of samples with composition xNd2O3-(5−x)Y2O3–40CaO-55B2O3 (0 ≤ x ≤ 1.0 mol%). Their fluorescence quantum efficiency (η) values were determined using the thermal lens technique and the dependence on the ionic concentration was analyzed in terms of energy transfer processes, based on the Förster–Dexter model of multipolar ion–ion interactions. A maximum η = 0.54 was found to be substantially higher than for yttrium aluminoborate crystals and glasses with comparable Nd3+ content. As for the thermo-optical properties of yttrium calcium borate, they are comparable to other well-known laser glasses. The obtained energy transfer microparameters and the weak dependence of η on the Nd3+ concentration with a high optimum Nd3+ concentration put this system as a strong candidate for photonics applications.
Optical properties of La-incorporated HfO2 upon crystallization
Authors: Wang Tuo , Wei Junwei , Downer Michael C. , Ekerdt John G.
Published: March 2011

The imaginary part of the dielectric constant (ε2) and the band gap energy (Eg) of as-deposited and crystallized HfO2 and La-incorporated HfO2 (La–HfO2) are extracted from spectroscopic ellipsometry. As-deposited amorphous HfO2 and La–HfO2 have similar absorption tails, which implies the existence of disorder in the amorphous film structure. Upon crystallization, the absorption tails are reduced and Eg increases for both HfO2 and La–HfO2. But disorder still exists and interband states form in pure HfO2, whereas disorder in crystalline La–HfO2 is largely reduced, which might be the result of La atoms incorporating into the HfO2 host, forming a new HfLaxOy network after crystallization.
Evolution of itinerant ferromagnetism in SrxPb1−xRuO3 (≤x≤1): Interplay between Jahn–Teller distortion and A-site disorder
Authors: Lu Hai-Shuang , Ju Sheng
Published: March 2011

Density functional theory with local spin density approximation is applied to study the evolution of ferromagnetism in SrxPb1−xRuO3 (0≤x≤1). Besides the enhanced Pb–O covalence and Pb–Ru hybridization, the Jahn–Teller effect, which favors the low-spin state (S=0) of Ru4+ in a stretched oxygen octahedra, is found to be the origin of the observed paramagnetism in PbRuO3. With the introduction of Sr, the Pb–Ru hybridization is weakened and an intermediate-spin state (S=1) is preferred via the opposite Jahn–Teller effect in a compressed oxygen octahedra, leading to the appearance of ferromagnetism for x>0.5. Our calculations provide a good explanation of recent experimental findings.
Growth study of Co thin film on nanorippled Si(100) substrate
Authors: K. V. Sarathlal , Kumar Dileep , Gupta Ajay
Published: March 2011

The growth behavior of Co thin film on nanorippled Si(100) substrate has been studied. A clear anisotropy in the growth behavior along and normal to the ripples has been observed, resulting in preferential coalescence of islands normal to the ripple wave vector. A preferential orientation of c-axis along the ripple wave vector is observed, which may be a result of minimization of magnetoelastic and anisotropic energies in the presence of internal stresses.
Enhanced visible and near-infrared optical absorption in silicon supersaturated with chalcogens
Authors: Pan Si H. , Recht Daniel , Charnvanichborikarn Supakit , Williams James S. , Aziz Michael J.
Published: March 2011

We show that single-crystal silicon supersaturated with sulfur (S), selenium (Se), or tellurium (Te) displays a substantially enhanced absorption coefficient for light with wavelengths of 400 to 1600 nm. Alloys were prepared in silicon on insulator wafers by ion implantation followed by nanosecond pulsed laser melting. Measurements of the absorption coefficient were made by direct transmission through freestanding thin films and by spectroscopic ellipsometry.
Dynamics of relaxation and fragmentation in size-selected icosahedral Arn[NO−(v = 1)] clusters
Authors: Shin H. K.
Published: March 2011

We study the vibrational relaxation and solvation dynamics in size-selected icosahedral Arn(NO−) at 300 K, where NO−(X3Σ−) is in v = 1 and n = 1–12, using a classical dynamics method and an interaction model consisting of detailed host–guest and host–host interactions. Two relaxation time scales are found: (i) the short-time (<200 ps), in which rate is nearly independent of cluster size, and (ii) the ns scale, in which a slow energy transfer process occurs between NO− vibration and argon modes at a rate (∼108 s−1) decreasing slightly from n = 12 to 6 and rapidly from n = 5 to 1 (∼106 s−1). In Ar12(NO−), less than one-quarter of the host atoms sampled evaporate, nearly 60% of evaporation occurring within 200 ps caused by rapid energy transfer from NO− at short time. The fraction of evaporation decreases nearly exponentially with increasing evaporation time, but ∼16% of evaporation still occurs on a time scale longer than 1 ns. Evaporation from one hemisphere of Ar12(NO−) dominates the rest. Final cluster sizes commonly produced from the fragmentation of Ar12(NO−) are n = 6–11 (evaporation of 6–1 atoms) and n = 12 (no evaporation).
Compression-induced failure of electroactive polymeric thin films
Authors: De Tommasi D. , Puglisi G. , Zurlo G.
Published: March 2011

The onset of compression induces wrinkling in actuation devices based on electroactive polymer thin films, which leads to a sudden decrease in performances and, eventually, to failure. Inspired by the classical tension field theory for thin membranes, we provide a general framework for the analysis of the insurgence of in-plane compressions. Our main result is the analytical deduction of a voltage-dependent domain of tensile configurations in the principal stretches plane.
An improved dynamic Monte Carlo model coupled with Poisson equation to simulate the performance of organic photovoltaic devices
Authors: Meng Lingyi , Wang Dong , Li Qikai , Yi Yuanping , Brédas Jean-Luc , Shuai Zhigang
Published: March 2011

We describe a new dynamic Monte Carlo model to simulate the operation of a polymer-blend solar cell; this model provides major improvements with respect to the one we developed earlier [J. Phys. Chem. B 114, 36 (2010)] by incorporating the Poisson equation and a charge thermoactivation mechanism. The advantage of the present approach is its capacity to deal with a nonuniform electrostatic potential that dynamically depends on the charge distribution. In this way, the unbalance in electron and hole mobilities and the space-charge induced potential distribution can be treated explicitly. Simulations reproduce well the experimental I-V curve in the dark and the open-circuit voltage under illumination of a polymer-blend solar cell. The dependence of the photovoltaic performance on the difference in electron and hole mobilities is discussed.
Communication: X-ray scattering from ionic liquids with pyrrolidinium cations
Authors: Santos Cherry S. , Murthy N. Sanjeeva , Baker Gary A. , Castner Edward W.
Published: March 2011

We report the structure functions obtained from x-ray scattering experiments on a series of four homologous ionic liquids. The ionic liquids are 1-alkyl-1-methylpyrrolidinium cations paired with the bis(trifluoromethylsulfonyl)amide anion, with alkyl chain lengths of n = 4, 6, 8, and 10. The structure functions display two intense diffraction peaks for values of the scattering vector q in the range from 0.6 to 1.5 Å−1 for all samples. Both diffraction peaks shift to lower values of q for increasing temperature. First sharp diffraction peaks are observed in the structure functions for q < 0.5 Å−1 for liquids with n = 6, 8, and 10.
Dislocation engineering in SiGe heteroepitaxial films on patterned Si (001) substrates
Authors: Gatti R. , Boioli F. , Grydlik M. , Brehm M. , Groiss H. , Glaser M. , Montalenti F. , Fromherz T. , Schäffler F. , Miglio Leo
Published: March 2011

We demonstrate dislocation engineering without oxide masks. By using finite element simulations we show how nanopatterning of Si substrates with {111} trenches provides anisotropic elastic relaxation in a SiGe film, generates preferential nucleation sites for dislocation loops, and allows for dislocation trapping, leaving wide areas free of threading dislocations. These predictions are confirmed by atomic force and transmission electron microscopy performed on overcritical Si0.7Ge0.3 films. These were grown by molecular beam epitaxy on a Si(001) substrate patterned with periodic arrays of selectively etched {111}-terminated trenches.
Permanent tuning of quantum dot transitions to degenerate microcavity resonances
Authors: Gudat Jan , Bonato Cristian , van Nieuwenburg Evert , Thon Susanna , Kim Hyochul , Petroff Pierre M. , van Exter Martin P. , Bouwmeester Dirk
Published: March 2011

We demonstrate a technique for achieving spectral resonance between a polarization-degenerate micropillar cavity mode and an embedded quantum dot transition. Our approach is based on a combination of isotropic and anisotropic tensile strain effected by laser-induced surface defects, thereby providing permanent tuning. Such a technique is a prerequisite for the implementation of scalable quantum information schemes based on solid-state cavity quantum electrodynamics.
Temperature dependent x-ray diffraction study of lightly doped NaxWO3
Authors: Paul Sanhita , Mukherjee G. D. , Ghosh Anirudha , Oishi S. , Raj Satyabrata
Published: March 2011

Temperature dependent x-ray diffraction studies have been carried out on nonstoichiometric lightly doped sodium tungsten bronze (NaxWO3 for x=0.025). The investigation reveals a structural modification around 230 K. Although the high and low temperature phases are monoclinic but at low temperature the corner sharing WO6 octahedra get significantly distorted due to displacement of tungsten and oxygen atoms from its mean position. This structural modification induces polaron formation in Na0.025WO3 below 230 K.
Fast growth of graphene patterns by laser direct writing
Authors: Park J. B. , Xiong W. , Gao Y. , Qian M. , Xie Z. Q. , Mitchell M. , Zhou Y. S. , Han G. H. , Jiang L. , Lu Y. F.
Published: March 2011

Rapid single-step fabrication of graphene patterns was developed using laser-induced chemical vapor deposition (LCVD). A laser beam irradiates a thin nickel foil in a CH4 and H2 environment to induce a local temperature rise, thereby allowing the direct writing of graphene patterns in precisely controlled positions at room temperature. Line patterns can be achieved with a single scan without pre- or postprocesses. Surprisingly, the growth rate is several thousand times faster than that of general CVD methods. The discovery and development of the LCVD growth process provide a route for the rapid fabrication of graphene patterns for various applications.
Highly efficient organic photovoltaic devices using F-doped SnO2 anodes
Authors: Hu Ziyang , Zhang Jianjun , Hao Zhihong , Hao Qiuyan , Geng Xinhua , Zhao Ying
Published: March 2011

Transparent F-doped SnO2 (FTO) is used as an anode material in organic photovoltaics based on poly(3-hexylthiophene) and [6, 6]-phenyl C61-butlyric acid methyl ester. Power conversion efficiency of 4.41% is achieved under 100 mW/cm2 simulated AM 1.5G solar illumination, which is comparable to that (4.25%) of the reference cells fabricated on indium tin oxide (ITO) glass substrates. Our results indicate that FTO anodes are a viable alternative to ITO for photovoltaic devices for cost effective fabrication of organic photovoltaic devices.
Spreading sequences for fast switching process in spin-valve nanopillars
Authors: Carpentieri Mario , Ricci Marco , Burrascano Pietro , Torres Luis
Published: March 2011

A detailed study of the effects of binary spreading sequences (BSS) excitation in the magnetization dynamics of exchange-biased spin-valves driven by spin-transfer-torque has been carried out by full micromagnetic modeling. We show that the use of BSS allows to trigger the magnetization reversal by exciting its main precession modes. We compared our numerical results with the experimental ones reported by [Cui et al., Phys. Rev. B 77, 214440 (2008)], attaining quantitative agreement. Advantages of BSS as microwave source with respect to a sinusoidal signal are also reported and discussed.
Momentum transfer resolved memory in a magnetic system with perpendicular anisotropy
Authors: Seu Keoki A. , Roy S. , Su R. , Parks D. H. , Shipton E. , Fullerton E. E. , Kevan S. D.
Published: March 2011

We have used resonant, coherent soft x-ray scattering to measure wave vector resolved magnetic domain memory in Co/Pd multilayers. The technique uses angular cross correlation functions and can be applied to any system with circular annuli of constant values of scattering wave vector q. In our Co/Pd film, the memory exhibits a maximum at q=0.0384 nm−1 near initial reversal that decreases in magnitude as the magnetization is further reversed. The peak is attributed to bubble domains that nucleate reproducibly near initial reversal and which grow into a labyrinth domain structure that is not reproduced from one magnetization cycle to the next.
On the reality of the residual entropies of glasses and disordered crystals: Counting microstates, calculating fluctuations, and comparing averages
Authors: Goldstein Martin
Published: March 2011

In the course of an on-going debate on whether glasses or disordered crystals should have zero entropy at 0 K, i.e., whether the “residual entropy” assigned to them by calorimetric measurements is real, the view has been expressed by some who hold the zero entropy view that to measure entropy, all or an appreciable number of the microstates that contribute to the entropy must be visited. We show here that the entropy calculated on the basis of the number of microstates visited during any conceivable time of measurement would be underestimated by at least 20 orders of magnitude. We also examine and refute the claim that an ensemble average for glassy systems, which predicts a finite residual entropy, also predicts physically impossible properties. We conclude that calorimetrically measured residual entropies are real.
Impact of diffusionless anneal using dynamic surface anneal on the electrical properties of a high-k/metal gate stack in metal-oxide-semiconductor devices
Authors: Choi Changhwan , Lee Kam-Leung , Narayanan Vijay
Published: March 2011

The impact of diffusionless anneal using dynamic surface anneal (DSA) on the electrical properties of p-type metal-oxide-semiconductor devices with high-k gate dielectrics and metal gate was investigated by monitoring flatband voltage (VFB) and equivalent oxide thickness (EOT) change. Compared to rapid thermal anneal, DSA induces a positive VFB shift without EOT degradation. This finding is attributed to suppression of positively charged oxygen vacancies [Vo++] generation in high-k dielectrics due to the shorter thermal budget. Processing parameters including high-k dielectrics, TiN metal gate thickness, and Si cap deposition temperature significantly affect thermally induced-oxygen vacancies, leading to different VFB behaviors.
Silicone substrate with in situ strain relief for stretchable thin-film transistors
Authors: Graz Ingrid M. , Cotton Darryl P. J. , Robinson Adam , Lacour Stéphanie P.
Published: March 2011

We have manufactured stretchable thin-film transistors and interconnects directly onto an engineered silicone matrix with localized and graded mechanical compliance. The fabrication only involves planar and standard processing. Brittle active device materials are patterned on non deformable elastomer regions (strain <1% at all times) while interconnects run smoothly from “stiff” to “soft” elastomer. Pentacene thin-film transistors sustain applied strain up to 13% without electrical degradation and mechanical fracture. This integrated approach opens promising options for the manufacture of physically adaptable and transformable circuitry.
Carbon nanotube field-effect transistors with molecular interface
Authors: Chen Kan-Sheng , McGill Stephen A. , Xiong Peng
Published: March 2011

We report on a study of molecular modifications of the electronic characteristics of single-walled carbon nanotube (SWNT) field-effect transistors (FETs) through insertion of different organic self-assembled monolayers (SAMs) between the SWNT and an electrode. The changes induced by the molecular interface were elucidated using a device structure created by directed assembly of a single SWNT over three prepatterned electrodes, one of which had a SAM deposited via dip-pen nanolithography. The resulting direct comparison of two FETs sharing the same SWNT revealed pronounced modification of the transfer characteristics, on/off ratio, and threshold voltages due to the SWNT/molecule/metal junction. The effects are attributed primarily to the alteration of the electronic bands in the Au electrode and the SWNT, and the resulting changes in the effective Schottky barrier height/thickness, by the ordered and well-aligned molecular SAM.
Large optical Stark shifts in semiconductor quantum dots coupled to photonic crystal cavities
Authors: Bose R. , Sridharan D. , Solomon G. S. , Waks E.
Published: March 2011

We demonstrate large cavity-enhanced optical Stark shifts for a single quantum dot (QD) coupled to a photonic crystal cavity. A maximum Stark shift of 20 GHz is observed for a QD detuned by 104 GHz from the cavity mode. These Stark shifts are attained with extremely low cavity field energies of only ten photons. The changes in the QD emission wavelength are monitored via nonresonant transfer between the QD and cavity mode. Experimental results are compared to theoretical predictions based on the solution to the full master equation and found to be in excellent agreement.
Communication: Identification of the molecule–metal bonding geometries of molecular nanowires
Authors: Demir Firuz , Kirczenow George
Published: March 2011

Molecular nanowires in which a single molecule bonds chemically to two metal electrodes and forms a stable electrically conducting bridge between them have been studied intensively for more than a decade. However, the experimental determination of the bonding geometry between the molecule and electrodes has remained elusive. Here we demonstrate by means of ab initio calculations that inelastic tunneling spectroscopy (IETS) can determine these geometries. We identify the bonding geometries at the gold–sulfur interfaces of propanedithiolate molecules bridging gold electrodes that give rise to the specific IETS signatures that were observed in recent experiments.
Histology of the gastrointestinal tract of the northern brown bandicoot, Isoodon macrourus (Marsupialia:Peramelidae)
Authors: O'Hara Patricia J. , Murray Peter J. , Klieve Athol V.
Published: March 2011

Published information on the histology of the gastrointestinal tract of peramelids is limited, with previous research only examining portions of the tract. We examined the histological structure of the gastrointestinal tract of eight adult I. macrourus from stomach to colon. The organisation of the tissue layers of the gastrointestinal tract was comparable to other mammals. In contrast to previous research, the long villi in the small intestine, which accounts for half of the total length of the gastrointestinal tract in an adult I. macrourus, were folded in a zig-zag formation. The purpose of this morphological strategy is unclear.
Additional records of small mammals in northern South Australia
Authors: Allen B. , Read J. L. , Medlin G.
Published: March 2011

Analysis of prey remains found in predator scats is a valuable tool for assessing the distribution and status of small mammal populations. As part of a large-scale dingo research project in northern South Australia, the prey remains found in 1845 dingo scats were analysed. A range of species were identified as expected, though, of particular interest, additional records of Rattus villosissimus, Notomys fuscus and Pseudomys australis were obtained. Our R. villosissimus records confirm the contemporary range of this species in the north-eastern pastoral zone, while our N. fuscus records support other recent records of this species in the same area. Our P. australis record indicates that an isolated population of this species exists in the Strzelecki Desert, ~400 km east of the nearest known population. The status of these populations remains unknown, including the risk of dingo predation to them.
Spectral Characteristics of the 2dFGRS–NVSS Galaxies
Authors: Jackson C. A. , Londish D. M.
Published: March 2011

We have analysed the 2dF spectra of a sample of galaxies common to the 2dF Galaxy Redshift Survey (2dFGRS, Colless 1999) and the NRAO VLA Sky Survey (NVSS, Condon et al. 1998). Our sample comprises 88 galaxies selected by Sadler et al. (1999) from 30 2dFGRS fields observed in 1998. In this paper we discuss how this and future, much larger, samples of 2dFGRS–NVSS galaxies can be interpreted via analysis of those galaxies with strong narrow emission lines. Using diagnostic line ratio measurements, we confirm the majority of the eyeball classifications of Sadler et al. (1999), although many galaxies show evidence of being ‘composite’ galaxies—mixtures of AGN plus starburst components.
HI Multibeam Survey Techniques
Authors: Staveley-Smith Lister
Published: March 2011

The parameters of the HI Parkes All-Sky Surveys (HIPASS), as proposed by the Multibeam Survey Working Group, are described, as are the advantages and disadvantages of various multibeam observing techniques, including telescope scanning. The best techniques, in terms of minimising the variance in image sensitivity, are calculated. Some of the observing techniques may be applicable to other multibeam surveys.
The Bruny Island Radio Spectrometer
Authors: Erickson W. C.
Published: March 2011

A radio spectrometer has been built on Bruny Island, south of Hobart, for the study of solar bursts in the rarely observed frequency range from 3 to 20 MHz. This spectrometer is an adaptive device that employs digital techniques to avoid most of the strong terrestrial interference prevalent in this frequency range. The residual interference that cannot be avoided is excised during off-line processing. As a result, successful observations are made down to the minimum frequency that can propagate through the ionosphere to the antenna. This minimum frequency depends upon the zenith distance of the Sun and it is usually between 4 and 8 MHz.
The Wisconsin Hα Mapper (WHAM): A Brief Review of Performance Characteristics and Early Scientific Results
Authors: Reynolds R. J. , Tufte S. L. , Haffner L. M. , Jaehnig K. , Percival J. W.
Published: March 2011

Abstract. The Wisconsin Hα Mapper (WHAM) is a recently completed facility for the detection and study of faint optical emission lines from diffuse ionised gas in the disk and halo of the Galaxy. WHAM consists of a 15 cm diameter Fabry–Perot spectrometer coupled to a 0·6 m ‘telescope’, which provide a 1° diameter beam on the sky and produce a 12 km s−1 resolution spectrum within a 200 km s−1 spectral window. This facility is now located at Kitt Peak in Arizona and operated remotely from Madison, Wisconsin, 2400 km distant. Early results include a velocity-resolved Hα map of a 70° × 100° region of the sky near the Galactic anticentre, the first detections of Hα emission from the M I and A high velocity clouds, and the first detections of [O I] λ6300 and other faint ‘diagnostic’ lines from the warm ionised medium. Through the summer of 1998, WHAM will be devoted almost exclusively to a survey of the northern sky, which will provide maps of the distribution and kinematics of the diffuse HII through the optical Hα line in a manner that is analogous to earlier sky surveys of the HI made through the 21 cm line.
Galaxies Detected by the Dwingeloo Obscured Galaxies Survey
Authors: Rivers A. J. , Henning P. A. , Kraan-Korteweg R. C.
Published: March 2011

The Dwingeloo Obscured Galaxies Survey (DOGS) is a 21-cm blind survey for galaxies hidden in the northern ‘Zone of Avoidance’ (ZOA): the portion of the optical extragalactic sky which is obscured by dust in the Milky Way. Like the Parkes southern hemisphere ZOA survey, the DOGS project is designed to reveal hidden dynamically important nearby galaxies and to help ‘fill in the blanks’ in the local large scale structure. To date, 36 galaxies have been detected by the Dwingeloo survey; 23 of these were previously unknown [no corresponding sources recorded in the NASA Extragalactic Database (NED)]. Among the interesting detections are three nearby galaxies in the vicinity of NGC 6946 and 11 detections in the Supergalactic plane crossing region. VLA follow-up observations have been conducted for several of the DOGS detections.
HI Study of the NGC 6744 System
Authors: Ryder Stuart D. , Walsh Wilfred , Malin David
Published: March 2011

We present the preliminary results of our 5-configuration, 20-pointing mosaic with the Australia Telescope Compact Array of the neutral hydrogen in the nearby spiral galaxy NGC 6744. The bulk of the HI resides in a ‘ring’ underlying the outer optical disk, with 2 HI spiral arms extending further out to almost 1·5 optical radii. The velocity field is fairly regular, apart from evidence for streaming motions along the HI arms, and the influence of the companion IB(s)m galaxy NGC 6744A. We associate a cloud of HI at a heliocentric velocity of 846 km s−1 with another companion object, ESO 104–g44. Our attempts to construct a mass model for NGC 6744 suffer from poor resolution in the inner disk, and the uncertainty in the total HI flux of NGC 6744. We anticipate that HIPASS observations will be crucial in resolving the latter issue.
Structural insights into conformational changes of a cyclic nucleotide-binding domain in solution from
Mesorhizobium loti
K1 channel
Authors: Schünke Sven , Stoldt Matthias , Lecher Justin , Kaupp U. Benjamin , Willbold Dieter
Published: March 2011

Cyclic nucleotide-sensitive ion channels, known as HCN and CNG channels, are activated by binding of ligands to a domain (CNBD) located on the cytoplasmic side of the channel. The underlying mechanisms are not well understood. To elucidate the gating mechanism, structures of both the ligand-free and -bound CNBD are required. Several crystal structures of the CNBD from HCN2 and a bacterial CNG channel (MloK1) have been solved. However, for HCN2, the cAMP-free and -bound state did not reveal substantial structural rearrangements. For MloK1, structural information for the cAMP-free state has only been gained from mutant CNBDs. Moreover, in the crystal, the CNBD molecules form an interface between dimers, proposed to be important for allosteric channel gating. Here, we have determined the solution structure by NMR spectroscopy of the cAMP-free wild-type CNBD of MloK1. A comparison of the solution structure of cAMP-free and -bound states reveals large conformational rearrangement on ligand binding. The two structures provide insights on a unique set of conformational events that accompany gating within the ligand-binding site.
Elevating the temperature regime of the large magnetocaloric effect in a Ni–Mn–In alloy towards room temperature
Authors: Sharma V K , Chattopadhyay M K , Sharath Chandra L S , Roy S B
Published: March 2011

We have prepared a Ni50(Mn,2%Cr)34In16 alloy by substituting Mn by Cr in a Ni50Mn34In16 alloy. A large isothermal magnetic entropy change is observed across the austenite–martensite phase transition in this new alloy for a moderate field change of 50 kOe. In comparison with the parent Ni50Mn34In16 alloy where the peak in isothermal entropy change amounts to nearly 19 J kg−1 K−1, in this Ni50(Mn,2%Cr)34In16 alloy the peak value of the isothermal entropy change is much larger, 24.4 J kg−1 K−1. Moreover, this large magnetocaloric effect in the Ni50(Mn,2%Cr)34In16 alloy occurs at ambient temperature near 294 K as compared with the temperature regime of the magnetocaloric effect being near 240 K in the parent Ni50Mn34In16 alloy. Thus the partial substitution of Mn by Cr in the Ni50Mn34In16 alloy is shown to be an effective method for enhancing the potential of the alloy system for near-room temperature applications.
Optimization of exchange-biased Heusler alloys
Authors: Endo H , Hirohata A , Nakayama T , Grady K O'
Published: March 2011

We report on a systematic study of ferromagnetic (F) Co2FeSi Heusler alloy films exchange-biased by antiferromagnetic (AF) IrMn. We have found that IrMn can produce an exchange-bias in the Heusler alloy with a loop shift of up to 200 Oe after optimized annealing. We also report on the effect of the insertion of a thin (<2 nm) layer of Mn at the interface. We have found that the insertion of a 0.5 nm thick Mn layer can increase the exchange-bias by a factor of two. Excessive annealing is found to decrease the exchange-bias dramatically and to disappear eventually. We believe this is due to Mn diffusion from the interface.
Effects of inter-molecular charge-transfer excitons on the external quantum efficiency of zinc-porphyrin/C60 heterojunction photovoltaic cells
Authors: Ryuzaki Sou , Kai Toshihiro , Toda Yasunori , Adachi Satoru , Onoe Jun
Published: March 2011

We have examined the structural effects of zinc-octaethylporphyrin [Zn(OEP)] films used as a donor on the external quantum efficiency (EQE) of organic heterojunction photovoltaic (OPV) cells [ITO/Zn(OEP)/C60/Al], and investigated what exactly causes the improvement of EQE. When the structure of the Zn(OEP) films changed from amorphous to crystalline, the maximum EQE increased from 36% to 42%, which is greater than that of around 35% for previously reported OPV cells using buffer materials (Peumans and Forrest 2001 Appl. Phys. Lett.
79 126). The crystallization of Zn(OEP) films is found to increase the number of inter-molecular charge-transfer (IMCT) excitons and to enlarge the mobility of carriers and IMCT excitons, thus significantly improving the EQE of the photoabsorption band under illumination due to the IMCT excitons.
1100 nm InGaAs/(Al)GaAs quantum dot lasers for high-power applications
Authors: Pavelescu E-M , Gilfert C , Weinmann P , Dănilă M , Dinescu A , Jacob M , Kamp M , Reithmaier J-P
Published: March 2011

InGaAs/(Al)GaAs quantum dot lasers emitting at 1100 nm are developed with a relatively low In content of 28% used for dot formation and an appropriate laser design to allow for high power emission. In comparison with an InGaAs QD laser with a similar design but a higher In content of 60% the newly developed lasers exhibit an improved temperature stability of the threshold current and internal quantum efficiency.
Tunnelling-based Faraday rotation effect enhancement
Authors: Dong Lijuan , Jiang Haitao , Chen Hong , Shi Yunlong
Published: March 2011

The transmission and Faraday rotation effect of a heterostructure composed of an all-dielectric magnetophotonic crystal and a magneto-optical metal are theoretically studied. When impedance and phase matching conditions are satisfied in the heterostructure, the transmission and Faraday rotation effect can simultaneously be enhanced due to the slow-wave effect of the localized electric field at the interface between the magnetophotonic crystal and the magneto-optical metal layer.
Neutron-induced transmutation effects in W and W-alloys in a fusion environment
Authors: Gilbert M.R. , Sublet J.-Ch.
Published: March 2011

W and W-alloys are among the primary candidate materials for plasma-facing components in the design of fusion reactors, particularly in high-heat-flux regions such as the divertor. Under neutron irradiation W undergoes transmutation to its near-neighbours in the periodic table. Additionally He and H are particles emitted from certain neutron-induced reactions, and this is particularly significant in fusion research since the presence of helium in a material can cause both swelling and a strong increase in brittleness. This paper presents the results of inventory burn-up calculations on pure W and gives quantitative estimates for He production rates in both a fusion-reactor environment and under conditions expected in the ITER experimental device. Transmutation reactions in possible alloying elements (Re, Ta, Ti and V), which could be used to reduce the brittleness of pure W, are also considered. Additionally, for comparison, the transmutation of other fusion-relevant materials, including Fe and SiC, are presented.
Analysis of the factors determining the extraction of negative ion beams from plasma sources
Authors: Lishev St. , Shivarova A. , Tarnev Kh.
Published: March 2011

Based on the modified Poisson–Vlasov method this study presents an analysis on the negative hydrogen-ion-beam extraction from plasma sources. Both the extraction cell and the values of the current densities of the extracted electron and ion beams considered are from experiments carried out regarding ITER. The role of different factors—potential of the electrodes, plasma parameters before the extraction, initial velocity distribution of the extracted particles, space-charge effects of the co-extracted electrons and details of the shape of the electrodes—determining the beam quality is analysed. It is shown that optimum mutual effects of external and space-charge fields leading to the formation of slightly concave meniscus acting together with the extraction electrode as a weak convexo-convex lens ensure formation of well-converged beams. The results outline (i) strong relation of the potentials of the electrodes to the plasma parameters before the extraction and (ii) the influence of the initial velocity distribution of the extracted particles as well as of the negative charge accumulation in the extraction region due to the electron beam.
Stably weakly shadowing transitive sets and dominated splittings
Authors: Yang Dawei
Published: March 2011

We prove that for any

C
1

C^1

-stably weakly shadowing transitive set

Λ
\Lambda

, either

Λ
\Lambda

is a sink or a source or

Λ
\Lambda

admits a dominated splitting.
Continuity of translation operators
Authors: Athreya Krishna , Peters Justin
Published: March 2011

For a Radon measure

μ
\mu

on

R

,

\mathbb {R},

we show that

L

∞

(
μ
)

L^{\infty }(\mu )

is invariant under the group of translation operators

T
t

(
f
)
(
x
)
=

f
(
x
−
t
)

 
(
t
∈

R

)

T_t(f)(x) = {f(x-t)}\ (t \in \mathbb {R})

if and only if

μ
\mu

is equivalent to the Lebesgue measure

m
m

. We also give necessary and sufficient conditions for

L
p

(
μ
)
,
 
1
≤
p
>
∞
,

L^p(\mu ),\ 1 \leq p > \infty ,

to be invariant under the group

{

T
t

}

\{ T_t\}

in terms of the Radon-Nikodým derivative w.r.t.

m
m

.
Positive combinations and sums of projections in purely infinite simple 𝐶*-algebras and their multiplier algebras
Authors: Kaftal Victor , Ng P. W. , Zhang Shuang
Published: March 2011

Every positive element in a purely infinite simple

σ
\sigma

-unital

C
∗

C^*

-algebra

A

\mathscr {A}

is a finite linear combination of projections with positive coefficients. Also, every positive

a
a

in the multiplier algebra

M

(

A

)

\mathscr M(\mathscr {A})

of a purely infinite simple

σ
\sigma

-unital

C
∗

C^*

-algebra

A

\mathscr {A}

is a finite linear combination of projections with positive coefficients. Furthermore, if the essential norm

‖
a

‖

e
s
s

>
1

\|a\|_{ess} > 1

, then

a
a

is a finite sum of projections in

M

(

A

)

\mathscr M(\mathscr {A})

. As a consequence, any positive element in the generalized Calkin Algebra

M

(

A

)

/

A

\mathscr M(\mathscr {A})/\mathscr {A}

or in

M

(

A

)

\mathscr M(\mathscr {A})

but not in

A

\mathscr {A}

is a positive scalar multiple of a finite sum of projections.
Abstract commensurators of profinite groups
Authors: Barnea Yiftach , Ershov Mikhail , Weigel Thomas
Published: March 2011

In this paper we initiate a systematic study of the abstract commensurators of profinite groups. The abstract commensurator of a profinite groupGGis a groupComm(G)\mathrm {Comm}(G)which depends only on the commensurability class ofGG. We study various properties ofComm(G)\mathrm {Comm}(G); in particular, we find two natural ways to turn it into a topological group. We also useComm(G)\mathrm {Comm}(G)to study topological groups which containGGas an open subgroup (all such groups are totally disconnected and locally compact). For instance, we construct a topologically simple group which contains the pro-22completion of the Grigorchuk group as an open subgroup. On the other hand, we show that some profinite groups cannot be embedded as open subgroups of compactly generated topologically simple groups. Several celebrated rigidity theorems, such as Pink’s analogue of Mostow’s strong rigidity theorem for simple algebraic groups defined over local fields and the Neukirch-Uchida theorem, can be reformulated as structure theorems for the commensurators of certain profinite groups.
Reliable Inference in Highly Stratified Contingency Tables: Using Latent Class Models as Density Estimators
Authors: Linzer Drew A.
Published: March 2011

Contingency tables are among the most basic and useful techniques available for analyzing categorical data, but they produce highly imprecise estimates in small samples or for population subgroups that arise following repeated stratification. I demonstrate that preprocessing an observed set of categorical variables using a latent class model can greatly improve the quality of table-based inferences. As a density estimator, the latent class model closely approximates the underlying joint distribution of the variables of interest, which enables reliable estimation of conditional probabilities and marginal effects, even among subgroups containing fewer than 40 observations. Though here focused on applications to public opinion, the procedure has a wide range of potential uses. I illustrate the benefits of the latent class model—based approach for greatly improved accuracy in estimating and forecasting vote preferences within small demographic subgroups using survey data from the 2004 and 2008 U.S. presidential election campaigns.
Changepoint Analysis of Binary and Ordinal Probit Models: An Application to Bank Rate Policy Under the Interwar Gold Standard
Authors: Park Jong Hee
Published: March 2011

In this paper, I introduce changepoint models for binary and ordered time series data based on Chib's hidden Markov model. The extension of the changepoint model to a binary probit model is straightforward in a Bayesian setting. However, detecting parameter breaks from ordered regression models is difficult because ordered time series data often have clustering along the break points. To address this issue, I propose an estimation method that uses the linear regression likelihood function for the sampling of hidden states of the ordinal probit changepoint model. The marginal likelihood method is used to detect the number of hidden regimes. I evaluate the performance of the introduced methods using simulated data and apply the ordinal probit changepoint model to the study of Eichengreen, Watson, and Grossman on violations of the “rules of the game” of the gold standard by the Bank of England during the interwar period.
Influence of Low Tidal Volume Ventilation on Time to Extubation in Cardiac Surgical Patients
Authors: Sundar Sugantha , Novack Victor , Jervis Karinne , Bender S. Patrick , Lerner Adam , Panzica Peter , Mahmood Feroze , Malhotra Atul , Talmor Daniel
Published: March 2011

Background

Low tidal volumes have been associated with improved outcomes in patients with established acute lung injury. The role of low tidal volume ventilation in patients without lung injury is still unresolved. We hypothesized that such a strategy in patients undergoing elective surgery would reduce ventilator-associated lung injury and that this improvement would lead to a shortened time to extubation

Methods

A single-center randomized controlled trial was undertaken in 149 patients undergoing elective cardiac surgery. Ventilation with 6 versus 10 ml/kg tidal volume was compared. Ventilator settings were applied immediately after anesthesia induction and continued throughout surgery and the subsequent intensive care unit stay. The primary endpoint of the study was time to extubation. Secondary endpoints included the proportion of patients extubated at 6 h and indices of lung mechanics and gas exchange as well as patient clinical outcomes.

Results

Median ventilation time was not significantly different in the low tidal volume group; a median (interquartile range) of 450 (264-1,044) min was achieved compared with 643 (417-1,032) min in the control group (P = 0.10). However, a higher proportion of patients in the low tidal volume group was free of any ventilation at 6 h: 37.3% compared with 20.3% in the control group (P = 0.02). In addition, fewer patients in the low tidal volume group required reintubation (1.3 vs. 9.5%; P = 0.03).

Conclusions

Although reduction of tidal volume in mechanically ventilated patients undergoing elective cardiac surgery did not significantly shorten time to extubation, several improvements were observed in secondary outcomes. When these data are combined with a lack of observed complications, a strategy of reduced tidal volume could still be beneficial in this patient population.
Forward from the crossroads of ecology and evolution
Authors: Rowntree Jennifer K. , Shuker David M. , Preziosi Richard F.
Published: March 2011

Community genetics is a synthesis of community ecology and evolutionary biology. It examines how genetic variation within a species affects interactions among species to change ecological community structure and diversity. The use of community genetics approaches has greatly expanded in recent years and the evidence for ecological effects of genetic diversity is growing. The goal of current community genetics research is to determine the circumstances in which, and the mechanisms by which community genetic effects occur and is the focus of the papers in this special issue. We bring a new group of researchers into the community genetics fold. Using a mixture of empirical research, literature reviews and theoretical development, we introduce novel concepts and methods that we hope will enable us to develop community genetics into the future.
Coding potential and transcript analysis of fowl adenovirus 4: insight into upstream ORFs as common sequence features in adenoviral transcripts
Authors: Griffin Bryan D. , Nagy Éva
Published: March 2011

Recombinant fowl adenoviruses (FAdVs) have been successfully used as veterinary vaccine vectors. However, insufficient definitions of the protein-coding and non-coding regions and an incomplete understanding of virus–host interactions limit the progress of next-generation vectors. FAdVs are known to cause several diseases of poultry. Certain isolates of species FAdV-C are the aetiological agent of inclusion body hepatitis/hydropericardium syndrome (IBH/HPS). In this study, we report the complete 45667 bp genome sequence of FAdV-4 of species FAdV-C. Assessment of the protein-coding potential of FAdV-4 was carried out with the Bio-Dictionary-based Gene Finder together with an evaluation of sequence conservation among species FAdV-A and FAdV-D. On this basis, 46 potentially protein-coding ORFs were identified. Of these, 33 and 13 ORFs were assigned high and low protein-coding potential, respectively. Homologues of the ancestral adenoviral genes were, with few exceptions, assigned high protein-coding potential. ORFs that were unique to the FAdVs were differentiated into high and low protein-coding potential groups. Notable putative genes with high protein-coding capacity included the previously unreported fiber 1, hypothetical 10.3K and hypothetical 10.5K genes. Transcript analysis revealed that several of the small ORFs less than 300 nt in length that were assigned low coding potential contributed to upstream ORFs (uORFs) in important mRNAs, including the ORF22 mRNA. Subsequent analysis of the previously reported transcripts of FAdV-1, FAdV-9, human adenovirus 2 and bovine adenovirus 3 identified widespread uORFs in AdV mRNAs that have the potential to act as important translational regulatory elements.
Medial prefrontal cortex activation facilitates re-extinction of fear in rats
Authors: Chang Chun-hui , Maren Stephen
Published: March 2011

It has been suggested that reduced infralimbic (IL) cortical activity contributes to impairments of fear extinction. We therefore explored whether pharmacological activation of the IL would facilitate extinction under conditions it normally fails (i.e., immediate extinction). Rats received auditory fear conditioning 1 h before extinction training. Immediately prior to extinction, rats received microinfusions into the IL of the GABAA receptor antagonist, picrotoxin, or the NMDA receptor partial agonist, D-cycloserine. Although neither drug facilitated extinction, they both facilitated the subsequent re-extinction of fear when animals were trained in a drug-free state, suggesting that activating the IL primes behavioral extinction.
Gene Expression Profiling and Shared Promoter Motif for Cell Wall-Modifying Proteins Expressed in Soybean Cyst Nematode-Infected Roots
Authors: Tucker Mark L. , Murphy Charles A. , Yang Ronghui
Published: March 2011

We hypothesized that soybean cyst nematode (SCN; Heterodera glycines) co-opts part or all of one or more innate developmental process in soybean (Glycine max) to establish its feeding structure, syncytium, in soybean roots. The syncytium is formed within the vascular bundle by partial degradation of cell walls and membranes between adjacent parenchyma cells. A mature syncytium incorporates as many as 200 cells into one large multinucleated cell. Gene expression patterns for several cell wall-modifying proteins were compared in multiple tissues undergoing major shifts in cell wall integrity. These included SCN-colonized roots, root tips where vascular differentiation occurs, flooded roots (aerenchyma), adventitious rooting in hypocotyls, and leaf abscission zones. A search in the 5′ upstream promoters of these genes identified a motif (SCNbox1: WGCATGTG) common to several genes that were up-regulated in several different tissues. The polygalacturonase 11 promoters (GmPG11a/b) include the SCNbox1 motif. The expression pattern for GmPG11a was examined further in transgenic soybean containing a PG11a promoter fused to a β-glucuronidase (GUS) reporter gene. GUS expression was highest in cells undergoing radial expansion in the stele and/or cell wall dissolution. GUS staining was not observed in cortical cells where a lateral root tip or a growing nematode emerged through the root cortex.