bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Bi doping on magnetic and magnetocaloric properties of La0.7−xBixSr0.3MnO3 (≤x≤0.4)
Authors: Barik S. K. , Mahendiran R.
Published: May 2010

We investigated the effect of Bi doping on magnetic and magnetocaloric properties of La0.7−xBixSr0.3MnO3 (x=0.0–0.4). It is shown that the low temperature ground state changes from a ferromagnet (x=0) to a charge-ordered antiferromagnet for x=0.4. While the paramagnetic-ferromagnetic (PM-FM) transition is second-order in x≤0.25, it changes into first-order for x=0.3 which is at the magnetic phase boundary. The changes in the magnetic ground state affect magnetic entropy. The magnitude of the isothermal magnetic entropy (|ΔSM|) at the FM Curie temperature increases from 4.56 J/kg K for x=0 to a maximum value of 5.02 J/kg K for x=0.05 and then decreases to nearly zero for x=0.4 at the charge order transition. In contrast to x≤0.25, the ΔSM of x=0.3 is magnetic history dependent and its temperature dependence exhibits a clear step at TCO=260 K followed by a plateau between 240 and 185 K. Although |ΔSM|=3.1 J/kg K of x=0.3 is small compared to other compositions, it has a high relative cooling power (325 J/kg) which is desirable for magnetic refrigeration over a wide temperature. The unusual magnetic and magnetocaloric properties of x=0.3 are attributed to the existence of short-range charge-orbital (CO) correlations in the PM state. It is suggested that harnessing competition between FM spin ordering and CO correlations may provide a strategy to enhance magnetic refrigeration capacity over a wide temperature range.
The influence of magnetic anisotropy on magnetoelectric behavior in conical spin ordered multiferroic state
Authors: Yao Xiaoyan , Lo Veng Cheong , Liu Jun-Ming
Published: May 2010

For the magnetism-driven multiferroic materials, the magnetic anisotropy plays an essential role in the magnetoelectric behavior. To understand the influence of magnetic anisotropy on multiferroic state resulting from the conical spin order, we have performed Monte Carlo simulation on a three-dimensional classical Heisenberg model in spinel lattice. The single-ion anisotropy from the easy-axis type to the easy-plane type is considered in the system, and the corresponding magnetoelectric behavior is investigated under a rotating external magnetic field (h). It is revealed that the magnetic anisotropy drags the orientation of conical spin structure slightly away from the direction of h, and distorts the conical spin structure as well. The balance between h and the anisotropy results in the anisotropic magnetoelectric properties during the rotation of h.
Theoretical investigation of the high pressure structure, lattice dynamics, phase transition, and thermal equation of state of titanium metal
Authors: Hu Cui-E , Zeng Zhao-Yi , Zhang Lin , Chen Xiang-Rong , Cai Ling-Cang , Alfè Dario
Published: May 2010

We report a detailed first-principles calculation to investigate the structures, elastic constants, and phase transition of Ti. The axial ratios of both α-Ti and ω-Ti are nearly constant under hydrostatic compression, which confirms the latest experimental results. From the high pressure elastic constants, we find that the α-Ti is unstable when the applied pressures are larger than 24.2 GPa, but the ω-Ti is mechanically stable at all range of calculated pressure. The calculated phonon dispersion curves agree well with experiments. Under compression, we captured a large softening around Γ point of α-Ti. When the pressure is raised to 35.9 GPa, the frequencies around the Γ point along Γ-M-K and Γ-A in transverse acoustical branches become imaginary, indicating a structural instability. Within quasiharmonic approximation, we obtained the full phase diagram and accurate thermal equations of state of Ti. The phase transition ω-Ti→α-Ti→β-Ti at zero pressure occurs at 146 K and 1143 K, respectively. The predicted triple point is at 9.78 GPa, 931 K, which is close to the experimental data. Our thermal equations of state confirm the available experimental results and are extended to a wider pressure and temperature range.
Photovoltage transients at fullerene-metal interfaces
Authors: Podolian A. , Kozachenko V. , Nadtochiy A. , Borovoy N. , Korotchenkov O.
Published: May 2010

Photovoltage (PV) transients are studied in C60–Pb and C60–Au thin films. The morphology of the C60 layers is characterized by x-ray diffraction and atomic force microscopy, which evidence the formation of a nanocrystalline C60 layer on polycrystalline Pb and Au underlayers. In contrast to Au substrate, Pb crystallites with a (111) texture are predominantly formed. The signs of the PV signals developed at the C60–Pb and C60–Au interfaces are found to be opposite due to very different workfunction values of the two metals. The evolution of the PV rise and decay curves with increasing light illumination intensity is completely different at the C60–Pb and C60–Au interfaces. The rise for the C60–Pb interface speeds up considerably with the increase in intensity, which is markedly different from the behavior at C60–Au, which exhibits nearly unchanged curve shapes. The PV decay time for C60–Au is also only weakly affected by varying light intensity. In contrast, increasing the illumination intensity causes the decay curves for C60–Pb to become multiexponential profiles, developing fast initial decays. The results are discussed in terms of different charge redistribution properties of C60 molecules adsorbed on Pb(111) and Au interfaces. The observed transformation of the PV decay curves is explained by the presence of interface states and a subsequent interplay of the charge redistribution properties of C60 molecules adsorbed on Pb(111). The results can be applied to sandwich structures containing organic-metal interfaces to account correctly for the interfacial charge transfer dynamics.
A single crystalline strontium titanate thin film transistor
Authors: Uchida Kosuke , Yoshikawa Akira , Koumoto Kunihito , Kato Takeharu , Ikuhara Yuichi , Ohta Hiromichi
Published: May 2010

We report herein fabrication and characterization of a thin film transistor (TFT) using single crystalline strontium titanate (SrTiO3) film, which was grown by a pulsed laser deposition technique followed by the thermal annealing treatment in an oxygen atmosphere. Although TFTs on the as-deposited SrTiO3 films (polycrystalline epitaxial films) exhibited poor transistor characteristics, the annealed single crystalline SrTiO3 TFT exhibits transistor characteristics comparable with those of bulk single crystal SrTiO3 field-effect transistor: an on/off current ratio >105, subthreshold swing ∼2.1 V decade−1, and field-effect mobility ∼0.8 cm2 V−1 s−1. This demonstrates the effectiveness of the appropriate thermal annealing treatment of epitaxial SrTiO3 films.
Influence of nano-oxide layer on the giant magnetoresistance and exchange bias of NiMn/Co/Cu/Co spin valve sensors
Authors: Gupta Anoop , Mohanan Senthilnathan , Kinyanjui Michael , Chuvilin Andrey , Kaiser Ute , Herr Ulrich
Published: May 2010

NiMn is an interesting material for achieving a high exchange bias in spin valve systems. We investigated the influence of a nano-oxide layer (NOL) inserted in the pinned Co layer on the magnetotransport properties of NiMn/Co/Cu/Co spin valve sensors. The samples were annealed at 350 °C for 10 min to achieve the antiferromagnetic L10 ordered structure of NiMn. The NOL has been characterized by small angle x-ray reflectivity, transmission electron microscopy (TEM), and energy filtered TEM. The inclusion of the NOL leads to an increase in the giant magnetoresistance (GMR) by 20 % indicating a high degree of specular reflection at the NOL. For NOL positions close to the NiMn/Co interface, a decrease in the exchange bias field (Hex) is observed. The best combination of high GMR value and large Hex was found when the NOL was inserted in the center of the pinned Co layer.
On the low pressure shock initiation of octahydro-1,3,5,7–tetranitro-1,3,5,7-tetrazocine based plastic bonded explosives
Authors: Vandersall Kevin S. , Tarver Craig M. , Garcia Frank , Chidester Steven K.
Published: May 2010

In large explosive and propellant charges, relatively low shock pressures on the order of 1–2 GPa impacting large volumes and lasting tens of microseconds can cause shock initiation of detonation. The pressure buildup process requires several centimeters of shock propagation before shock to detonation transition occurs. In this paper, experimentally measured run distances to detonation for lower input shock pressures are shown to be much longer than predicted by extrapolation of high shock pressure data. Run distance to detonation and embedded manganin gauge pressure histories are measured using large diameter charges of six octahydro-1,3,5,7–tetranitro-1,3,5,7-tetrazocine (HMX) based plastic bonded explosives (PBX’s): PBX 9404; LX-04; LX-07; LX-10; PBX 9501; and EDC37. The embedded gauge records show that the lower shock pressures create fewer and less energetic “hot spot” reaction sites, which consume the surrounding explosive particles at reduced reaction rates and cause longer distances to detonation. The experimental data is analyzed using the ignition and growth reactive flow model of shock initiation in solid explosives. Using minimum values of the degrees of compression required to ignite hot spot reactions, the previously determined high shock pressure ignition and growth model parameters for the six explosives accurately simulate the much longer run distances to detonation and much slower growths of pressure behind the shock fronts measured during the shock initiation of HMX PBX’s at several low shock pressures.
Noncommutative Poisson boundaries of unital quantum operations
Authors: Lim Bunrith Jacques
Published: May 2010

In this paper, Poisson boundaries of unital quantum operations (also called Markov operators) are investigated. In the case of unital quantum channels, compact operators belonging to Poisson boundaries are characterized. Using the characterization of amenable groups by the injectivity of their von Neumann algebras, we will answer negatively some conjectures appearing in the work of Arias et al. [“Fixed points of quantum operations,” J. Math. Phys. 43, 5872 (2002)] about injectivity of the commuting algebra of the Kraus operators of unital quantum operations and their injective envelopes.
Comparison of kinetic theory models of laser ablation of carbon
Authors: Shusser Michael
Published: May 2010

The paper compares the predictions of three-dimensional kinetic theory models of laser ablation of carbon. All the models are based on the moment solution of the Boltzmann equation for arbitrary strong evaporation but use different approximations. Comparison of the model predictions demonstrated that the choice of the particular model has very little influence on the results. The influence of the heat conduction from the gas to the solid phase was also found to be negligible in this problem.
Temporally-resolved hydrodynamics in the vicinity of a vibrating ionic polymer metal composite
Authors: Prince Chekema , Lin Weiyang , Lin Jenny , Peterson Sean D. , Porfiri Maurizio
Published: May 2010

In this paper, we study the hydrodynamics induced by an ionic polymer metal composite (IPMC) cantilever vibrating in a quiescent fluid. Time-resolved particle image velocimetry is used to measure the velocity field in the vicinity of the vibrating IPMC strip and a control volume analysis is utilized to estimate the thrust production per unit IPMC width. The governing fluid dynamics dimensionless parameters are varied parametrically to ascertain the influence of the Reynolds number, the peak tip displacement to IPMC length ratio, and the IPMC aspect ratio. It is found that the Reynolds number is the dominant parameter in determining the thrust produced by the IPMC, while the relative tip displacement and aspect ratio play secondary roles. An increase in the relative tip displacement has a minimal effect on the produced thrust, while an increase in the aspect ratio results in a mild decrease in thrust production. It is further found that estimating the thrust from the mean velocity field significantly underpredicts the thrust estimate.
Thermophotonic heat pump—a theoretical model and numerical simulations
Authors: Oksanen Jani , Tulkki Jukka
Published: May 2010

We have recently proposed a solid state heat pump based on photon mediated heat transfer between two large-area light emitting diodes coupled by the electromagnetic field and enclosed in a semiconductor structure with a nearly homogeneous refractive index. Ideally the thermophotonic heat pump (THP) allows heat transfer at Carnot efficiency but in reality there are several factors that limit the efficiency. The efficient operation of the THP is based on the following construction factors and operational characteristics: (1) broad area semiconductor diodes to enable operation at optimal carrier density and high efficiency, (2) recycling of the energy of the emitted photons, (3) elimination of photon extraction losses by integrating the emitting and the absorbing diodes within a single semiconductor structure, and (4) eliminating the reverse thermal conduction by a nanometer scale vacuum layer between the diodes. In this paper we develop a theoretical model for the THP and study the fundamental physical limitations and potential of the concept. The results show that even when the most important losses of the THPs are accounted for, the THP has potential to outperform the thermoelectric coolers especially for heat transfer across large temperature differences and possibly even to compete with conventional small scale compressor based heat pumps.
Amplification of a fast wave by extracting both the kinetic energy and electrostatic potential energy of a large-orbit relativistic electron beam in a coaxial electrostatic wiggler
Authors: Zhang Shi-Chang
Published: May 2010

Nonlinear model and simulation technique of the interaction and energy transfer between a fast wave and a large-orbit relativistic electron beam in a coaxial electrostatic wiggler are presented. Unlike the situations in a magnetostatic-wiggler free-electron laser (MWFEL) and in an electron cyclotron maser (ECM), the electrostatic potential of the electrons plays an important role and participates in the energy exchange between the wave and the electron beam. Compared to MWFEL and ECM, the coaxial electrostatic-wiggler configuration has a distinguishing peculiarity that besides the electron-beam’s kinetic energy, its electrostatic potential energy can be effectively transferred to the fast wave. Simulation shows that wave could be amplified with ultrahigh gain by extracting both the kinetic energy and electrostatic potential energy of the electron beam.
Highly sensitive parylene membrane-based ac-calorimeter for small mass magnetic samples
Authors: Lopeandia A. F. , André E. , Garden J.-L. , Givord D. , Bourgeois O.
Published: May 2010

We report the microfabrication and operation of a highly sensitive ac-calorimeter designed to characterize small mass magnetic systems operating at very low frequencies (from 0.1 to 5 Hz) in a temperature range from 20 to 300 K. The calorimetric cell is built in the center of a 500 nm thick polymeric membrane of parylene C held up by a Cu frame. On both sides of the membrane defining a three layer structure, electrical leads, heater, and thermometer are deposited as thin film layers of NbNx, with different nitrogen contents, taking benefit of the poor thermal conductance of niobium nitride to thermally isolate the system. This suspended structure ensures very low heat capacity addenda with values in the μJ/K over the 1 mm2 area of the measurement cell. The structuring of the membrane along with suspending of the sensing part only by the parylene bridges leads to a highly reduced thermal link. The calorimeter has been characterized as a function of frequency, temperature, and magnetic field. The thermal link measured is really small reaching values well below 10−8 W/K at 50 K. With these characteristics the frequency of adiabaticity is typically around few hertz and energy exchanges as small as 1 pJ can be detected. Measurements have been performed on Co/Au thin films and on the GdAl2 microcrystal where the ferromagnetic phase transition is clearly evidenced.
Abel transform analysis of ion storage ring imaging data
Authors: Zhaunerchyk Vitali
Published: May 2010

In this paper a new approach to analyze dissociative recombination product distance distributions measured at ion storage rings is presented. This approach is based on an Abel transform and the validity is demonstrated for the imaging data obtained from the CRYRING experiments on the dissociative recombination of H2+ and CO+. The reported method is generally valid for the data analysis of high resolution merged beams experiments such as DESIREE where isotropic fragment distributions can be expected.
A low temperature scanning tunneling microscopy system for measuring Si at 4.2 K
Authors: Dreyer Michael , Lee Jonghee , Wang Hui , Barker Barry
Published: May 2010

In this paper we describe our low temperature scanning tunneling microscopy system with ultrahigh vacuum sample preparation capabilities. The main focus lies on the specialized silicon preparation facility which is the most unusual part. Other special solutions such as sample transport will also be described in detail. Finally, we demonstrate the ability to prepare high quality silicon (111) and (100) surfaces.
New interpolation algorithm for evaluation a spatial profile of plasma densities in radio frequency discharges
Authors: Oh Se-Jin , Jang Sung-Ho , Kim Young-Cheol , Chung Chin-Wook
Published: May 2010

A new interpolation to estimate a spatial profile of plasma densities of unmeasured regions for two-dimensional probe diagnostics is proposed. Our algorithm is based on the plasma diffusion characteristics. From a comparison with a well known interpolation, Modified Shepard, it has been found that our method gives more accurate plasma density profile, especially at the edge region of the measurement substrate, and improves computational efficiency
Optical transmission of periodic annular apertures in metal film on high-refractive index substrate: The role of the nanopillar shape
Authors: Bouillard J.-S. , Einsle J. , Dickson W. , Rodrigo S. G. , Carretero-Palacios S. , Martin-Moreno L. , Garcia-Vidal F. J. , Zayats A. V.
Published: May 2010

The influence of annular aperture parameters on the optical transmission through arrays of coaxial apertures in a metal film on high refractive index substrates has been investigated experimentally and numerically. It is shown that the transmission resonances are related to plasmonic crystal effects rather than frequency cutoff behavior associated with annular apertures. The role of deviations from ideal aperture shape occurring during the fabrication process has also been studied. Annular aperture arrays are often considered in many applications for achieving high optical transmission through metal films and understanding of nanofabrication tolerances are important.
On-demand entanglement source with polarization-dependent frequency shift
Authors: Wang Xiang-Bin , Yang Cheng-Xi , Liu Yan-Bing
Published: May 2010

The polarization entanglement photon pairs generated from the biexciton cascade decay in a single semiconductor quantum dot is distorted due to the fine structure splitting. We show that, frequency of light can be shifted when it passes through an electro-optic modulator under voltage ramping. Based on this, we can realize polarization-dependent frequency shift and the hidden entanglement due to fine structure splitting can be revealed.
Giant resonance frequency tunable magnetoelectric effect in a device of Pb(Zr0.52Ti0.48)O3 drum transducer, NdFeB magnet, and Fe-core solenoid
Authors: Zeng Min , Or Siu Wing , Chan Helen Lai Wa
Published: May 2010

Magnetoelectric (ME) effect has been studied in a device of Pb(Zr0.52Ti0.48)O3 (PZT) drum transducer, NdFeB magnet, and Fe-core solenoid. A unique ME effect is found to originate from the magnetic force-induced effectively amplified piezoelectric effect. Under the application of a magnet with dimensions of ϕ22×7.6 mm2, a giant ME coefficient of 13.2 V/cm Oe and a power density of 16.4 μW∕Oe across a 14 kΩ resistor were obtained at the first order radial resonance frequency of 650 Hz. Importantly, with increasing magnet mass, the resonance frequency decreases, while the resonance ME effect first increases and then decreases, which means a tunable resonance ME effect.
Large exchange bias field in the Ni–Mn–Sn Heusler alloys with high content of Mn
Authors: Xuan H. C. , Cao Q. Q. , Zhang C. L. , Ma S. C. , Chen S. Y. , Wang D. H. , Du Y. W.
Published: May 2010

The exchange bias properties have been investigated in bulk Mn50Ni40−xSn10+x (x=0, 0.5, and 1) Heusler alloys with high content of Mn, in which the largest exchange bias field is up to 910 Oe for Mn50Ni40Sn10 alloy. In these alloys, the excess Mn atoms would occupy not only the Sn sites but also the Ni sites, and the moments of Mn on Sn or Ni sites are coupled antiferromagnetically to those on the regular Mn sites, respectively. The origin of this considerably large exchange bias field has been discussed.
Nonpolar resistive switching in the Pt/MgO/Pt nonvolatile memory device
Authors: Huang Hsin-Hung , Shih Wen-Chieh , Lai Chih-Huang
Published: May 2010

Nonpolar resistive switching (RS), which is the coexistence of unipolar and bipolar RS characteristics, in the Pt/MgO/Pt memory device with the nonforming nature is demonstrated. The nonforming nature is ascribed to the relatively high defect density of the MgO film deposited by using the ion beam sputtering in Ar atmosphere. The results of Auger electron spectroscopy and x-ray photoelectron spectroscopy analyses combing with the temperature dependence of resistance suggest that metallic Mg filaments are formed in the low resistance state. The voltage-polarity-independent RESET process implies that filaments may be ruptured by local Joule heating, leading to nonpolar characteristics.
Generation of ultrahigh frequency air microplasma in a magnetic loop and effects of pulse modulation on operation
Authors: Taghioskoui Mazdak , Perlow Joshua , Zaghloul Mona , Montaser Akbar
Published: May 2010

An atmospheric pressure air microplasma (APAMP) source was developed under ambient conditions using a magnetic loop at an operating frequency of 740 MHz. A self-igniting, stable APAMP was generated at 9.5 W. Pulse modulation (PM) was applied to the ultra high frequency signal. The effects of PM on self-ignition and operation of the APAMP source were studied by using a square wave modulating signal in the frequency range of 5–30 KHz. With the application of PM on the APAMP, in the best case, the plasma self-ignites and is sustained at 2.5 W.
Tunneling dynamics and spawning with adaptive semiclassical wave packets
Authors: Gradinaru V. , Hagedorn G. A. , Joye A.
Published: May 2010

Tunneling through a one-dimensional Eckart barrier is investigated using a recently developed propagation scheme based on semiclassical wave packets. This version of the time-dependent discrete variable representation method yields linear equations for the parameters, is fully adaptive, and does not require a frozen ansatz in order to approximate the exact solution of the Schrödinger equation accurately. We rely on an analytical result to derive a new algorithm to spawn a second family of semiclassical wave packets after the tunneling has occurred. Numerical results for a benchmark problem demonstrate the accuracy of the new method.
90° polarization rotator using a bilayered chiral metamaterial with giant optical activity
Authors: Ye Yuqian , He Sailing
Published: May 2010

A bilayered chiral metamaterial is proposed to realize a 90° polarization rotator, whose giant optical activity is due to the transverse magnetic dipole coupling among the metallic wire pairs of enantiomeric patterns. By transmission through this thin bilayered structure of less than λ/30 thick, a linearly polarized wave is converted to its cross polarization with a resonant polarization conversion efficiency of over 90%. It is demonstrated that the chirality in the propagation direction makes this efficient cross-polarization conversion possible.
Radiation-induced metastable ordered phase in gallium nitride
Authors: Ishimaru Manabu
Published: May 2010

Energetic particle irradiation is one of the useful ways for realizing metastable phases far from the equilibrium state. In the present study, we performed electron-beam-irradiation into gallium nitride (GaN) with a wurtzite structure and examined its structural changes using transmission electron microscopy. It was found that superlattice Bragg reflections appear in the electron diffraction patterns of the irradiated GaN. This suggests that the wurtzite GaN transforms to another crystalline structure with atomic ordering.
Piezoelectric activity of relaxor-PbTiO3 based single crystals and polycrystalline ceramics at cryogenic temperatures: Intrinsic and extrinsic contributions
Authors: Li Fei , Zhang Shujun , Xu Zhuo , Wei Xiaoyong , Luo Jun , Shrout Thomas R.
Published: May 2010

The piezoelectric activity in [001] poled Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 crystals was investigated as a function of composition and temperature. The level of intrinsic and/or extrinsic contribution to the total piezoelectric activity was analyzed using Rayleigh method. The results revealed that though 95% of the observed piezoelectric activity in rhombohedral crystals was intrinsic (lattice), the properties decreased significantly with decreasing temperature. At −150 °C, the piezoelectric response decreased by 40%–55% for the compositions close to a morphotropic phase boundary (rhombohedral-monoclinic or monoclinic-tetragonal), while decreasing only 20%–30% for the compositions in the rhombohedral region. The piezoelectric properties of Pb(Mg1/3Nb2/3)O3–PbTiO3 polycrystalline ceramics were found to decrease by 75%, showing both intrinsic and extrinsic contributions play important role in the reduction in piezoelectricity at cryogenic temperatures for ceramics.
Two-photon absorption photocurrent in p-i-n diode embedded silicon microdisk resonators
Authors: Chen Hui , Poon Andrew W.
Published: May 2010

We demonstrate two-photon absorption (TPA) photocurrent in p-i-n diode embedded silicon microdisk resonators. Our experiments reveal TPA photocurrent spectra with peaks corresponding to the microdisk resonance modes. The photocurrents at resonance wavelengths exceed those at off-resonance wavelengths by up to three orders of magnitude. We study the microdisk photocurrent spectra with various p-i-n diode intrinsic region widths in the microdisk rim. We report TPA photovoltaic effect with maximum power generation efficiency of ∼0.3%.
Infrared spectra of OCS–C6H6, OCS–C6H6–He, and OCS–C6H6–Ne van der Waals complexes
Authors: Dehghany M. , Norooz Oliaee J. , Afshari Mahin , Moazzen-Ahmadi N. , McKellar A. R. W.
Published: May 2010

The infrared spectrum of weakly bound OCS–C6H6 is studied in the region of the ν1 fundamental band of OCS (∼2050 cm−1) using a tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. This is one of the first direct infrared observations of a benzene-containing van der Waals complex. A very simple band is observed, corresponding to the parallel transition of a symmetric top. It is shifted by −11.1 cm−1 with respect to the free OCS monomer. The isotopologues OCS–C13 C125H6 and OC S34–C6H6 are observed, and the derived structure has OCS located along the benzene C6 symmetry axis in an S-bonded configuration with a center of mass separation of 4.42 Å, in good agreement with previous microwave spectra. Similar bands are observed for the trimers OCS–C6H6–He and OCS–C6H6–Ne, whose structure is obtained by adding an on-axis rare gas atom to the other side of the benzene. However, the analogous band for OCS–C6H6–Ar is not detected, raising the possibility that the stable form of this trimer may not have the same symmetrical structure. A “mystery” feature is observed close to the OCS–C6H6 band origin and its possible assignment to a cluster such as OCS–(C6H6)3 is discussed.
Theoretical spectroscopy of acetylene dication and its deuterated species
Authors: Palaudoux J. , Jutier L. , Hochlaf M.
Published: May 2010

We mapped the six-dimensional potential energy surface of the electronic ground state of HCCH++(X Σg−3) dication using the coupled cluster approach. This potential energy surface is incorporated later into perturbative and full variational treatments to solve the nuclear motions. We derived a set of spectroscopic data for HCCH++, HCCD++, and DCCD++. Our calculations reveal the presence of anharmonic resonances even at low energies, which complicates their assignment by vibrational quantum numbers. In light of our theoretical vibrational spectra, we propose an assignment of the experimental vibrationally resolved valence double ionization spectra of HCCH, HCCD, and DCCD. These spectra are viewed to be mostly composed by a pure vibrational progression involving the CC stretching mode together with a second progression involving both the CC stretching and the bendings.
Deviations in Pedestrian Itineraries in Urban Areas: A Method to Assess the Role of Environmental Factors
Authors: Foltête Jean-Christophe , Piombini Amaud
Published: May 2010

Walking has long been neglected in urban-mobility research, but it is now making its way into numerous studies using various approaches. Empirical data are often processed in well-known models of flow allocation to study the behaviour of pedestrians and to identify their preferences. However, these models assume that route choices are predetermined at the start of each trip and do not admit any possible intervening decision along these trips. We propose to overcome this limitation through a new method for the analysis of pedestrian behaviour. This method, which we call ‘deviation analysis’ consists of (1) identifying the intersections from which a pedestrian has chosen a route longer than the shortest path; (2) defining the segments of the network which diverge from each deviation; (3) testing the influence of the environmental variables of these segments on the choice of route by using a discrete choice model. Deviations are compared with the cases where pedestrians follow the shortest path (called ‘continuations’), which are assumed to be less strongly linked to environmental variables due to the ‘natural’ choice for minimising the distance travelled. This method is applied to a series of pedestrian trips recorded in the French city of Lille. Results show that the environmental variables used in this study contribute to explaining the route choices with more strength when the deviations involve a trip lengthening of at least 50 m. They also show that the influence of variables describing the visual aspect of urban landscape may influence the route choices and outline the positive role of the urban atmosphere linked to the commercial function of streets.
Evidence of the Impacts of Urban Sprawl on Social Capital
Authors: Nguyen Doan
Published: May 2010

Sprawl opponents have blamed sprawl for weakening linkages among the residents and social capital but there is a lack of empirical evidence to support their argument. This study examines the relationship between the county sprawl index and social-capital factors from the 2000 Social Capital Community Benchmark Survey data. Using 3-level hierarchical models, this study shows that for the US, urban sprawl may support some types of social capital while negatively impacting the others. Furthermore, changing urban form via population density and street accessibility at the county level may not be ideal to improve social capital.
A Classification of Perceptual Corrections of Perspective Distortions in Renaissance Painting
Authors: Verstegen Ian
Published: May 2010

In an attempt to address major debates in perspective studies, this study brings perceptual research to bear on the problem of the status of perspective in the Renaissance. Between one school that sees perspective as mathematically rigorous but imperfectly applied and another that regards perspective as an incoherent discipline, this study argues that errors in the use of perspective are consistent and can be classified into two tendencies: first, the tendency to normalize a foreshortened form towards frontality and, second, the tendency to flatten a three-dimensional object to reveal its hidden sides. These tendencies find confirmation both in the Renaissance doctrine of the judgment of the eye ( giudizio dell'occhio) as well as in Gestalt-oriented perceptual research. Numerous examples of their application are given with regard to the representation of human figures, architecture, and the relation of figures to space.
Perceptual Overestimation of Rising Intensity: Is Stimulus Continuity Necessary?
Authors: Olsen Kirk N , Stevens Catherine J
Published: May 2010

A “perceptual bias for rising intensity” (Neuhoff 1998, Nature395 123–124) is not dependent on the continuous change of a dynamic, looming sound source. Thirty participants were presented with pairs of 500 ms steady-state sounds corresponding to onset and offset levels of previously used dynamic increasing- and decreasing-intensity stimuli. Independent variables, intensity-change direction (increasing, decreasing), intensity region (high: 70–90 dB SPL, low: 50–70 dB SPL), interstimulus interval (ISI) (0 s, 1.8 s, 3.6 s), and timbre (vowel, violin) were manipulated as a fully within-subjects design. The dependent variable was perceived loudness change between each stimulus item in a pair. It was hypothesised that (i) noncontinuous increases of intensity are overestimated in loudness change, relative to decreases, in both low-intensity and high-intensity regions; and (ii) perceptual overestimation does not occur when end-levels are balanced. The hypotheses were partially supported. At the high-intensity region, increasing stimuli were perceived to change more in loudness than decreasing-intensity stimuli. At the low-intensity region and under balanced end-level conditions, decreasing-intensity stimuli were perceived to change more in loudness than increasing-intensity stimuli. A significant direction × region interaction varied as a function of ISI. Methodological, sensory, and cognitive explanations for overestimation in certain circumstances are discussed.
Sexual risk behaviours and HIV-1 prevalence among urban men who have sex with men in Cape Town, South Africa
Authors: Burrell Earl , Mark Daniella , Grant Robert , Wood Robin , Bekker Linda-Gail
Published: May 2010

Background: Distinct homosexual and heterosexual HIV epidemics have previously been recognised in South Africa. However, linked HIV prevalence and self-reported sexual risk behaviour data have not been reported for men who have sex with men (MSM) in Cape Town since 1986. Methods: We conducted a cross-sectional, anonymous, venue-based HIV risk behaviour and prevalence study of 542 self-identified MSM in greater Cape Town using a self-administered risk questionnaire and the OraSure® testing device to asses HIV-1 prevalence. Results: This sample had an overall HIV prevalence of 10.4% (56/539). We found that self-identifying as gay, homosexual or queer (adjusted odds ratio (AOR) 4.5, 95% confidence interval (CI) 1.0–20.0) and reporting ever having had a sexually transmissible infection diagnosis (AOR 4.3, 95% CI: 2.3–8.3) were significantly predictive of testing HIV-1 positive, while reporting unprotected anal intercourse with a known HIV-negative partner (AOR 0.4, 95% CI: 0.2–0.9) was significantly protective. Conclusion: These data suggest a mature epidemic with consistent high-risk taking among MSM in Cape Town, and significant associations of select self-reported risk behaviours and HIV-1 serostatus. There is a need for continued and robust HIV surveillance along with detailed risk behaviour trends over time to inform the development of targeted risk-reduction interventions for this population.
Distortions and stabilization of simple-cubic calcium at high pressure and low temperature
Authors: Mao Wendy L. , Wang Lin , Ding Yang , Yang Wenge , Liu Wenjun , Kim Duck Young , Luo Wei , Ahuja Rajeev , Meng Yue , Sinogeikin Stas , Shu Jinfu , Mao Ho-kwang
Published: May 2010

Ca-III, the first superconducting calcium phase under pressure, was identified as simple-cubic (sc) by previous X-ray diffraction (XRD) experiments. In contrast, all previous theoretical calculations showed that sc had a higher enthalpy than many proposed structures and had an imaginary (unstable) phonon branch. By using our newly developed submicrometer high-pressure single-crystal XRD, cryogenic high-pressure XRD, and theoretical calculations, we demonstrate that Ca-III is neither exactly sc nor any of the lower-enthalpy phases, but sustains the sc-like, primitive unit by a rhombohedral distortion at 300 K and a monoclinic distortion below 30 K. This surprising discovery reveals a scenario that the high-pressure structure of calcium does not go to the zero-temperature global enthalpy minimum but is dictated by high-temperature anharmonicity and low-temperature metastability fine-tuned with phonon stability at the local minimum.
Effect of follicle size on fertility in cattle.
Authors: Perry G.
Published: May 2010

Procedures that control the timing of ovulation are of enormous value in advancing the use of reproductive technologies in all species. Among cattle, most protocols that control the timing of ovulation utilize gonadotrophin-releasing hormone (GnRH) around the time of insemination. A luteinizing hormone (LH) surge and ovulation are induced with an injection of GnRH. However, GnRH results in the ovulation of a wide range of follicle sizes regardless of whether or not standing oestrus had been initiated. Among both heifers and cows, the relationship between follicle size and pregnancy success following a fixed-time insemination protocol was quadratic. Small follicles induced to ovulate resulted in lower pregnancy rates, increased embryonic/ foetal mortality, and a slower rise in subsequent concentrations of progesterone compared with cows induced to ovulate larger follicles. Among postpartum cows, there was no relationship between ovulatory follicle size and pregnancy status when cows spontaneously initiated standing oestrus and ovulated. Furthermore, animals that exhibited standing oestrus within 24 h of fixed-time insemination had greater pregnancy success compared with animals that did not exhibit standing oestrus, and cows that exhibited standing oestrus had greater circulating concentrations of estradiol compared with cows that did not. Therefore, follicular maturity at time of GnRH-induced ovulation can influence pregnancy success following a fixed-time insemination protocol.
Nutrient management in black pepper (
Piper nigrum
L.).
Authors: Srinivasan V. , Dinesh R. , Hamza S. , Parthasarathy V. A.
Published: May 2010

Black pepper is cultivated in a wide range of soils with varying pH and fertility. Ideal condition requires a friable soil rich in humus and essential plant nutrients, with good drainage. Among the nutrients consumed by black pepper, N uptake is the highest followed by K and Ca and the magnitude of the nutrients removed is in the order: N > K > Ca > Mg > P > S > Fe > Mn > Zn. Various sources and levels of manures and fertilizers were evaluated for improving soil nutrient status and uptake by black pepper. The optimum dose of nutrients to be applied for getting higher yield was standardized through crop response functions and nutrient ratios in soil and plant. The critical level of essential nutrients, management efforts to correct the deficiencies and practices to improve the nutrient use efficiency are discussed.
Andy Dillin: Using aging research to probe biology
Authors: Sedwick Caitlin
Published: May 2010

Dillin uses genetics to probe the pathways that control cellular and organismal longevity.
Cooperation of the Dam1 and Ndc80 kinetochore complexes enhances microtubule coupling and is regulated by aurora B
Authors: Tien Jerry F. , Umbreit Neil T. , Gestaut Daniel R. , Franck Andrew D. , Cooper Jeremy , Wordeman Linda , Gonen Tamir , Asbury Charles L. , Davis Trisha N.
Published: May 2010

The coupling of kinetochores to dynamic spindle microtubules is crucial for chromosome positioning and segregation, error correction, and cell cycle progression. How these fundamental attachments are made and persist under tensile forces from the spindle remain important questions. As microtubule-binding elements, the budding yeast Ndc80 and Dam1 kinetochore complexes are essential and not redundant, but their distinct contributions are unknown. In this study, we show that the Dam1 complex is a processivity factor for the Ndc80 complex, enhancing the ability of the Ndc80 complex to form load-bearing attachments to and track with dynamic microtubule tips in vitro. Moreover, the interaction between the Ndc80 and Dam1 complexes is abolished when the Dam1 complex is phosphorylated by the yeast aurora B kinase Ipl1. This provides evidence for a mechanism by which aurora B resets aberrant kinetochore–microtubule attachments. We propose that the action of the Dam1 complex as a processivity factor in kinetochore–microtubule attachment is regulated by conserved signals for error correction.
Tuba, a Cdc42 GEF, is required for polarized spindle orientation during epithelial cyst formation
Authors: Qin Yi , Meisen Walter H. , Hao Yi , Macara Ian G.
Published: May 2010

The Cdc42 guanosine triphosphatase is essential for cell polarization in several organisms and in vitro for the organization of polarized epithelial cysts. A long-standing question concerns the identity of the guanine nucleotide exchange factor (GEF) that controls this process. Using Madin–Darby canine kidney cells grown in Matrigel, we screened 70 GEFs by RNA interference. Of these, six positives were identified that caused a multilumen phenotype, including Tuba, a Cdc42-specific GEF localized below the apical cortex. Loss of Tuba abolishes Cdc42 enrichment at the apical cortex. Normal lumen formation is rescued by human Tuba or active Cdc42 but not by a GEF-negative Tuba mutant. Silencing Cdc42 causes a similar phenotype, including multilumen formation and reduced atypical protein kinase C (aPKC) activity. Lumen disorganization after depletion of Tuba or Cdc42 or inhibition of aPKC is caused by defective spindle orientation. Together, our findings implicate Tuba as a key activator of the Cdc42 GTPase during epithelial ductal morphogenesis, which in turn activates apical aPKC to ensure that spindles orient parallel to the lateral plane.
A Gαi–GIV Molecular Complex Binds Epidermal Growth Factor Receptor and Determines Whether Cells Migrate or Proliferate
Authors: Ghosh Pradipta , Beas Anthony O. , Bornheimer Scott J. , Garcia-Marcos Mikel , Forry Erin P. , Johannson Carola , Ear Jason , Jung Barbara H. , Cabrera Betty , Carethers John M. , Farquhar Marilyn G.
Published: May 2010

Cells respond to growth factors by either migrating or proliferating, but not both at the same time, a phenomenon termed migration-proliferation dichotomy. The underlying mechanism of this phenomenon has remained unknown. We demonstrate here that Gαiprotein and GIV, its nonreceptor guanine nucleotide exchange factor (GEF), program EGF receptor (EGFR) signaling and orchestrate this dichotomy. GIV directly interacts with EGFR, and when its GEF function is intact, a Gαi–GIV–EGFR signaling complex assembles, EGFR autophosphorylation is enhanced, and the receptor's association with the plasma membrane (PM) is prolonged. Accordingly, PM-based motogenic signals (PI3-kinase-Akt and PLCγ1) are amplified, and cell migration is triggered. In cells expressing a GEF-deficient mutant, the Gαi–GIV-EGFR signaling complex is not assembled, EGFR autophosphorylation is reduced, the receptor's association with endosomes is prolonged, mitogenic signals (ERK 1/2, Src, and STAT5) are amplified, and cell proliferation is triggered. In rapidly growing, poorly motile breast and colon cancer cells and in noninvasive colorectal carcinomas in situ in which EGFR signaling favors mitosis over motility, a GEF-deficient splice variant of GIV was identified. In slow growing, highly motile cancer cells and late invasive carcinomas, GIV is highly expressed and has an intact GEF motif. Thus, inclusion or exclusion of GIV's GEF motif, which activates Gαi, modulates EGFR signaling, generates migration-proliferation dichotomy, and most likely influences cancer progression.
Ubr1 and Ubr2 Function in a Quality Control Pathway for Degradation of Unfolded Cytosolic Proteins
Authors: Nillegoda Nadinath B. , Theodoraki Maria A. , Mandal Atin K. , Mayo Katie J. , Ren Hong Yu , Sultana Rasheda , Wu Kenneth , Johnson Jill , Cyr Douglas M. , Caplan Avrom J.
Published: May 2010

Quality control systems facilitate polypeptide folding and degradation to maintain protein homeostasis. Molecular chaperones promote folding, whereas the ubiquitin/proteasome system mediates degradation. We show here that Saccharomyces cerevisiae Ubr1 and Ubr2 ubiquitin ligases promote degradation of unfolded or misfolded cytosolic polypeptides. Ubr1 also catalyzes ubiquitinylation of denatured but not native luciferase in a purified system. This activity is based on the direct interaction of denatured luciferase with Ubr1, although Hsp70 stimulates polyubiquitinylation of the denatured substrate. We also report that loss of Ubr1 and Ubr2 function suppressed the growth arrest phenotype resulting from chaperone mutation. This correlates with increased protein kinase maturation and indicates partitioning of foldable conformers toward the proteasome. Our findings, based on the efficiency of this quality control system, suggest that the cell trades growth potential to avert the potential toxicity associated with accumulation of unfolded or misfolded proteins. Ubr1 and Ubr2 therefore represent E3 components of a novel quality control pathway for proteins synthesized on cytosolic ribosomes.
The Impact of Culture and Ethnicity on Women's Perceived Role in Society and Their Attendant Health Beliefs
Authors: Benson Jill , Maldari Toni , Williams Jan , Hanifi Hoda
Published: May 2010

Cultural background and ethnicity need to be at the forefront of a doctor's mind when thinking about the way women present and deal with health issues for themselves and their families. Despite the obvious fact that women make up about half the population, their health needs may be different to the expectations and processes of the model of care used by the majority of health professionals. Some of these differences are likely to be due to social structures but women's personal history and health beliefs in general will impact on their health care in ways that may lead them even further from achieving healthy outcomes. In general practices where a large proportion of the population is from different cultures, interacting with women with complex health care needs requires an awareness of the underlying beliefs of both doctor and patient. To understand a woman's health issues in her new country, the doctor must acknowledge that she may face discrimination at three levels: as a woman, as a migrant and as an ethnic minority.