bluuebunny/crossref_metadata_2025 huggingface dataset:
Where is the Light? Tracing the Evolution of Bulges and Disks since z ~ 0.8
Authors: Tasca Lidia A. M. , Tresse Laurence ,   COSMOS & zCOSMOS Collaboration
Published: December 2011

The chronology of galactic bulge and disk formation is studied by analysing the relative contributions of these components to the B band rest–frame luminosity density (LD) at two different cosmological epochs. The luminosity function (LF) of the bulge and disk components at z ~ 0.8 is computed on a galaxy subsample of the final zCOSMOS “bright” catalogue of roughly 20,000 objects with spectroscopic redshift in the COSMOS field. The comparison is then performed on galaxies in the local universe. Our preliminary results show that the LD in the disk component strongly decreases from ~ 80% at z ~ 0.8 to ~ 50% at z = 0, the bulges having a specular behaviour. The observational constraints provided in this work are aimed to discriminate among competing scenarios of galaxy formation and evolution. An appropriate comparison with hydrodynamical semianalytical models will be considered in a future study to understand further the formation and evolution of galaxies.
Re-assessment of the Accretion Disc Clock in Hercules X-1
Authors: Jurua E. , Still M. , Meintjes P. J. , Charles P. A. , Anguma S. K
Published: December 2011

The Galactic neutron star X-ray binary Her X-1 shows a 35-day photometric modulation. Detected across a broad energy range, the modulation is prevalent in X-rays, cycling between low and high states. Since the discovery of the 35-day cycle of Her X-1, the X-ray source has entered and returned from an extended anomalous low state on at least seven occasions. Employing Rossi X-ray Timing Explorer All-Sky Monitor observations, prior predictions that Her X-1 would return from the 2003 - 2004 anomalous low state with a new precession period and accretion luminosity are verified. However, the precession has not been as coherent over recent years as predicted. Potentially there have been more minor anomalous low states between 2004 and the present day.
Intra‐annual rainfall variability control on interannual variability of catchment water balance: A stochastic analysis
Authors: Zanardo S. , Harman C. J. , Troch P. A. , Rao P. S. C. , Sivapalan M.
Published: December 2011

We evaluate the extent to which within‐year rainfall variability controls interannual variability of catchment water balance. To this end, we analytically derive the probability density function of the annual Budyko evaporation index, B (i.e., the ratio of annual actual evapotranspiration to annual precipitation), by accounting for the stochastic nature of intra‐annual rainfall fluctuation and neglecting all other sources of variability. We apply our analytical model to 424 catchments located in different climatic regions across the conterminous United States to perform this assessment. In general, we found that the model is capable of explaining mean B but is less accurate in predicting its coefficient of variation. Nonetheless, in a significant number of catchments the model can provide adequate predictions of the probability density function of B. Clear geographic patterns can be distinguished in the residuals between observed and predicted statistics of B. Interannual variability is thus not always associated with random intra‐annual rainfall fluctuations. In some regions, other controls, such as seasonality and vegetation adaptations, are possibly more important. A sensitivity analysis of model parameters helped characterize the dominant controls on the distribution of B in terms of three dimensionless ratios that include climatic and soil characteristics. This study represents the first step in a diagnostic, data‐driven analysis of the climatic controls on the interannual variability of catchment water balance.
The global economic cycle and satellite‐derived NO2 trends over shipping lanes
Authors: de Ruyter de Wildt Martijn , Eskes Henk , Boersma K. Folkert
Published: December 2011

In recent years, space‐borne spectrometers have been used to detect shipping emissions of nitrogen oxides. Driven by economic growth, these emissions have been increasing for several decades, yet in few studies it has been attempted to detect trends in ship emitted NO2 from space. Here a method is presented that enhances the shipping signal in satellite measurements of NO2, which makes it possible to detect non‐linear trends on a monthly to yearly basis. The method removes variations in NO2measurements over shipping lanes that are not related to shipping and that obscure shipping trends. With this method we could detect non‐linear trends in NO2over major shipping lanes in the Mediterranean Sea, the Red Sea, the Indian Ocean and the South Chinese Sea. The shipping signal displays a large increase of 62–109% between 2003 and the summer of 2008 and a sharp decline of 12–36% afterwards, corresponding to the global economic recession of 2008‐2009. These two trends are detected over all four shipping lanes by several space‐borne spectrometers. Because of high correlations between satellite data mutually and between satellite data, shipping statistics and international trade volumes, we conclude that the detected trends are caused by actual changes in shipping emissions. This study therefore shows that it is possible to detect short‐term economic fluctuations in satellite measurements of NO2 over major shipping lanes.
The relation between ion temperature anisotropy and formation of slow shocks in collisionless magnetic reconnection
Authors: Higashimori K. , Hoshino M.
Published: December 2011

We perform a two‐dimensional simulation by using an electromagnetic hybrid code to study the formation of slow‐mode shocks in collisionless magnetic reconnection in low beta plasmas, and we focus on the relation between the formation of slow shocks and the ion temperature anisotropy enhanced at the shock downstream region. It is known that as magnetic reconnection develops, the parallel temperature along the magnetic field becomes large in association with the anisotropic plasma sheet boundary layer ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shocks. On the basis of our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X‐type region, but the ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance ∣x∣ ≥ 115 λi from the neutral point.
Distribution and metabolism of dimethylsulfoniopropionate (DMSP) and phylogenetic affiliation of DMSP‐assimilating bacteria in northern Baffin Bay/Lancaster Sound
Authors: Motard‐Côté J. , Levasseur M. , Scarratt M. G. , Michaud S. , Gratton Y. , Rivkin R. B. , Keats K. , Gosselin M. , Tremblay J.‐É. , Kiene R. P. , Lovejoy C.
Published: December 2011

We determined the distribution and bacterial metabolism of dimethylsulfoniopropionate (DMSP) and dimethylsulfide (DMS) in the two dominant surface water masses in northern Baffin Bay/Lancaster Sound during September 2008. Concentrations of particulate DMSP (DMSPp; 5–70 nmol L−1) and the DMSPp:Chl a ratios (15–229 nmol μg−1) were relatively high, suggesting the presence of DMSP‐rich phytoplankton taxa. Photosynthetic picoeukaryotes and total prokaryotes were tenfold and threefold more abundant in Baffin Bay surface water (BBS) than in Arctic surface water (AS), respectively. Heterotrophic bacterial production (0.07–2.5μC L−1 d−1) and bacterial turnover rate constants for dissolved DMSP (DMSPd) were low (0.03–0.11 h−1) compared with the values previously reported in warmer and more productive environments. Nonetheless, a relatively large proportion (12%–31%) of the DMSP metabolized by the bacteria was converted into DMS. Additionally, between 40% and 65% of the total bacterial cells incorporated sulfur from DMSPd, with Gammaproteobacteriaand non‐Roseobacter Alphaproteobacteria (AlfR‐) contributing proportionally more to total DMSP‐incorporating cells. The contribution of AlfR‐ to the total prokaryotic community was 50% higher in BBS than in AS, while the bacterial rate constants for DMSPd turnover were 78% higher in BBS than in AS. These results show that the two different Arctic water masses host specific microbial assemblages that result in distinct affinity for DMSP.
The dynamics of wind‐driven intraseasonal variability in the equatorial Indian Ocean
Authors: Nagura Motoki , McPhaden Michael J.
Published: December 2011

Variability in the equatorial Indian Ocean on intraseasonal time scales (defined as periods of 30–110 days) is investigated using satellite and in situ observations and a simple analytical linear long‐wave equatorial β‐plane model. Despite the extreme simplicity of the model, which includes just the two gravest baroclinic mode Kelvin waves and first meridional mode Rossby waves, simulated surface zonal velocity and sea surface height compare very well with observations. Both observations and model are characterized by a red shift in the velocity spectrum relative to the wind forcing spectrum, which is attributable to a combination of factors, including (1) the near resonant excitation of Kelvin waves by eastward propagating winds, (2) constructive interference between wind‐forced waves and Rossby waves reflected from the eastern boundary, and (3) the favored excitation of low‐frequency waves whose zonal wavelengths are long compared to the zonal fetch of the wind. We decomposed variability in two broad period bands, namely, 30–70 days and 70–110 days, for detailed analysis. At periods of 30–70 days, zonal velocity tends to be stationary in the directly forced region along the equator owing to the competing contributions of Kelvin and Rossby waves. In contrast, at 70–110 day periods, zonal velocity propagates westward despite eastward propagation of zonal wind stress because of the combined influence of eastern boundary generated and wind‐forced Rossby waves. Kelvin waves reflected from the western boundary are negligibly small, indicating that basin mode resonances are not prominent as has been previously suggested.
Inactivation of ceramide transfer protein during pro-apoptotic stress by Golgi disassembly and caspase cleavage
Authors: Chandran Suchismita , Machamer Carolyn E.
Published: December 2011

The mammalian Golgi apparatus is composed of multiple stacks of cisternal membranes organized laterally into a polarized ribbon. Furthermore, trans-Golgi membranes come in close apposition with ER (endoplasmic reticulum) membranes to form ER–trans-Golgi contact sites, which may facilitate transfer of newly synthesized ceramide from the ER to SM (sphingomyelin) synthase at the trans-Golgi via CERT (ceramide transfer protein). CERT interacts with both ER and Golgi membranes, and together with Golgi morphology contributes to efficient SM synthesis. In the present study, we show that Golgi disassembly during pro-apoptotic stress induced by TNFα (tumour necrosis factor α) and anisomycin results in decreased levels of CERT at the Golgi region. This is accompanied by a caspase-dependent loss of full-length CERT and reduction in de novo SM synthesis. In vitro, CERT is cleaved by caspases 2, 3 and 9. Truncated versions of CERT corresponding to fragments generated by caspase 2 cleavage at Asp213 were mislocalized and did not promote efficient de novo SM synthesis. Thus it is likely that during cellular stress, disassembly of Golgi structure together with inactivation of CERT by caspases causes a reduction in ceramide trafficking and SM synthesis, and could contribute to the cellular response to pro-apoptotic stress.
Quantum chemistry and catalysis
Authors: Slater John C. , Johnson Keith H.
Published: December 2011

Why do platinum, palladium, nickel and iron, as well as other Group-VIII transition metals, continually turn up as the active sites in catalysts? Why do certain enzymes and proteins—substances such as hemoglobin and ferredoxin that catalyze metabolic processes in living organisms—also appear to rely on transition metals for their action? How do catalysts work anyway, and could we design better ones? We are much nearer answering these questions and other related ones now that new methods, both theoretical and experimental, are available to investigate the electronic structure of complex molecules and materials of the type important to catalysis.
InGaAs-based bow-tie diode for spectroscopic terahertz imaging
Authors: Kašalynas I. , Venckevičius R. , Seliuta D. , Grigelionis I. , Valušis G.
Published: December 2011

Suitability of InGaAs-based bow-tie diodes for a spectroscopic terahertz imaging is demonstrated by inspecting explosive simulators packed in a thick plastic container. The transmission images were obtained within the frequency range of 0.58-2.52 THz at room temperature using optimized bow-tie diode connection scheme. Content of sucrose and tartaric acid in the test samples was discriminated. Measured absorbance was found to be in a good correlation with Fourier spectroscopy data. Performance of room temperature THz imaging using the bow-tie diode was compared versus a commercial pyro-electric sensor.
Redistribution of carbonyl stretch mode energy in isolated and solvated N-methylacetamide: Kinetic energy spectral density analyses
Authors: Jeon Jonggu , Cho Minhaeng
Published: December 2011

The vibrational energy transfer from the excited carbonyl stretch mode in N-deuterated N-methylacetamide (NMA-d), both in isolation and in a heavy water cluster, is studied with nonequilibrium molecular dynamics (NEMD) simulations, employing a quantum mechanical/molecular mechanical (QM/MM) force field at the semiempirical PM3 level. The nonequilibrium ensemble of vibrationally excited NMA-d is prepared by perturbing the positions and velocities of the carbonyl C and O atoms and its NEMD trajectories are obtained with a leap-frog algorithm properly modified for the initial perturbation. In addition to the time-domain analysis of the kinetic and potential energies, a novel method for the spectral analysis of the atomic kinetic energies is developed, in terms of the spectral density of kinetic energy, which provides the time-dependent changes of the frequency-resolved kinetic energies without the complications of normal mode analysis at every MD time step. Due to the QM description of the solute electronic structure, the couplings among the normal modes are captured more realistically than with classical force fields. The energy transfer in the isolated NMA-d is found to proceed first from the carbonyl bond to other modes with time scales of 3 ps or less, and then among the other modes over 3–21 ps. In the solvated NMA-d, most of the excess energy is first transferred to other intramolecular modes within 5 ps, which is subsequently dissipated to solvent with 7–19 ps time scales. The contribution of the direct energy transfer from the carbonyl bond to solvent was only 5% with ∼7 ps time scale. Solvent reorganization that leads to destabilization of the electrostatic interactions is found to be crucial in the long time relaxation of the excess energy, while the water intramolecular modes do not contribute significantly. Detailed mode-specific energy transfer pathways are deduced for the isolated and solvated NMA-d and they show that the energy transfer in NMA-d is a highly cooperative process among the intramolecular modes and there is no single dominant pathway with more than 30% of transient contribution.
Propagation of nonlinear dust magnetoacoustic waves in cylindrical geometry
Authors: Hussain S. , Mahmood S.
Published: December 2011

The cylindrical dust magnetoacoustic shocks in dissipative and solitons in non-dissipative dust-ion plasmas are studied. The dust particles are assumed to be fully negatively charged so that the density of electrons in comparison with dust and ions is negligible. The cylindrical Korteweg-de Vries Burgers and cylindrical Korteweg-de Vries equations are derived for dust magnetosonic waves by employing the reductive perturbation method. It is found that dust plasma parameters such as dust charge number, dust density, and ion temperature have strong influence on the profile of dust magnetoacoustic shocks and solitons. The results are also obtained numerically by using the data from laboratory experiments on dusty plasmas.
Simulating gyrokinetic microinstabilities in stellarator geometry with GS2
Authors: Baumgaertel J. A. , Belli E. A. , Dorland W. , Guttenfelder W. , Hammett G. W. , Mikkelsen D. R. , Rewoldt G. , Tang W. M. , Xanthopoulos P.
Published: December 2011

The nonlinear gyrokinetic code GS2 has been extended to treat non-axisymmetric stellarator geometry. Electromagnetic perturbations and multiple trapped particle regions are allowed. Here, linear, collisionless, electrostatic simulations of the quasi-axisymmetric, three-field period national compact stellarator experiment (NCSX) design QAS3-C82 have been successfully benchmarked against the eigenvalue code FULL. Quantitatively, the linear stability calculations of GS2 and FULL agree to within ∼10%.
Structural dynamics of surfaces by ultrafast electron crystallography: Experimental and multiple scattering theory
Authors: Schäfer Sascha , Liang Wenxi , Zewail Ahmed H.
Published: December 2011

Recent studies in ultrafast electron crystallography (UEC) using a reflection diffraction geometry have enabled the investigation of a wide range of phenomena on the femtosecond and picosecond time scales. In all these studies, the analysis of the diffraction patterns and their temporal change after excitation was performed within the kinematical scattering theory. In this contribution, we address the question, to what extent dynamical scattering effects have to be included in order to obtain quantitative information about structural dynamics. We discuss different scattering regimes and provide diffraction maps that describe all essential features of scatterings and observables. The effects are quantified by dynamical scattering simulations and examined by direct comparison to the results of ultrafast electron diffraction experiments on an in situ prepared Ni(100) surface, for which structural dynamics can be well described by a two-temperature model. We also report calculations for graphite surfaces. The theoretical framework provided here allows for further UEC studies of surfaces especially at larger penetration depths and for those of heavy-atom materials.
Effect of shocklets on the velocity gradients in highly compressible isotropic turbulence
Authors: Wang Jianchun , Shi Yipeng , Wang Lian-Ping , Xiao Zuoli , He Xiantu , Chen Shiyi
Published: December 2011

The effect of randomly generated shocklets on velocity gradients in a three-dimensional compressible isotropic turbulence was systematically studied. The forced flows obtained from high-resolution simulations had a turbulent Mach number of 1.0 and a Taylor microscale Reynolds number around 180. The shock detection algorithm developed by Samtaney et al. [“Direct numerical simulation of decaying compressible turbulence and shocklet statistics,” Phys. Fluids 13, 1415 (2001)] was applied to extract the shocklets. Using reference frames moving with the detected shocks, we obtained statistical properties of velocity and its gradients both upstream and downstream of the shocks. It was shown that the shocks induced flow modulation at a wide range of length scales, including the inertial subrange scales. The shocks intensified enstrophy in the shock regions and this enhanced enstrophy production was partially redistributed over various scales and dissipated by straining and viscous effects outside the shock regions. We also found that both the strain rate eigenvectors and eigenvalues were significantly altered by shocks. Furthermore, local modulation effects by the shocklets enlarged with the shocklet strength. The Helmholtz decomposition was performed to show that most statistics associated with the solenoidal component of velocity derivatives were insensitive to the formation of shocks, but those associated with the compressive component of velocity derivatives depended strongly on the shock formation and shock strength.
Inertial migration of deformable capsules in channel flow
Authors: Kilimnik Alex , Mao Wenbin , Alexeev Alexander
Published: December 2011

Using three-dimensional computer simulations, we study the cross-stream inertial migration of neutrally buoyant deformable particles in a pressure-driven channel flow. The particles are modeled as elastic shells filled with a viscous fluid. We show that the particles equilibrate in a channel flow at off-center positions that depend on particle size, shell compliance, and the viscosity of encapsulated fluid. These equilibrium positions, however, are practically independent of the magnitude of channel Reynolds number in the range between 1 and 100. The results of our studies can be useful for sorting, focusing, and separation of micrometer-sized synthetic particles and biological cells.
Study on characteristic parameters influencing laser-induced damage threshold of KH2PO4 crystal surface machined by single point diamond turning
Authors: Chen Mingjun , Li Mingquan , Cheng Jian , Jiang Wei , Wang Jian , Xu Qiao
Published: December 2011

It has fundamental meaning to find the elements influencing the laser-induced damage threshold (LIDT) of KH2PO4 (KDP) crystal and to provide suitable characterization parameters for these factors in order to improve the LIDT of KDP. Using single-point diamond turning (SPDT) to process the KDP crystal, the machined surface quality has important effects on its LIDT. However, there are still not suitable characteristic parameters of surface quality of KDP to correspond with the LIDT nowadays. In this paper, guided by the Fourier model theory, we study deeply the relationship between the relevant characteristic parameters of surface topography of KDP crystal and the experimental LIDT. Research results indicate that the waviness rather than the roughness is the leading topography element on the KDP surface machined by the SPDT method when the LIDT is considered and the amplitude of micro-waviness has greater influence on the light intensity inside the KDP crystal within the scope of dangerous frequencies between (180 μm)−1 and (90 μm)−1; with suitable testing equipment, the characteristic parameters of waviness amplitude, such as the arithmetical mean deviation of three-dimensional profile Sa or root mean square deviation of three-dimensional contour Sq, are able to be considered as suitable parameters to reflect the optical quality of the machined surface in order to judge approximately the LIDT of the KDP surface and guide the machining course.
Langmuir probe diagnostics of electron energy distributions with optical emission spectroscopy in capacitively coupled rf discharge in nitrogen
Authors: Abdel-Fattah E. , Bazavan M. , Sugai H.
Published: December 2011

Measurements with a rf compensated Langmuir probe and optical emission spectroscopy are carried out in capacitively coupled rf (13.56 MHz) pure nitrogen N2 discharges at fixed rf voltage over a wide range of pressure, 30 to 400 mTorr. The electron energy probability function (EEPF) measured below 100 mTorr resembles a bi-Maxwellian-type distribution. At pressure range of 100-200 mTorr, the EEPF has non-Maxwellian distribution with a “dip” near 4.5 eV. At the highest pressure of 400 mTorr, the EEPF evolves into a Druyvestein-like distribution and the “dip” disappears. The electron density significantly decreases with increase in the N2 pressure. On the other hand, the electron temperatures gradually decrease with an increase in N2 pressure, reaching minimum at 150 mTorr, beyond which it abruptly increases. Such evolution of the EEPFs shape with gas pressure has been discussed in terms of non-local electron kinetics and heating mode transition. The emission intensities of nitrogen (0-0) band of second positive system at 337.1 nm and (0-0) band of first negative systems at 391.4 nm are used to determine the dependence of their radiative states N2(C3Πu) and N2+(B2Σu+) with nitrogen pressure. It is observed that the pressure influences the radiative states differently owing to their different populating mechanisms. The vibrational temperature Tνib and rotational temperature Trot are measured for the sequence (Δν=-2) of N2 second positive system (C3Π→B3Πg) using the method of comparing the measured and calculated spectra with a chi-squared minimization procedure. It was found that both Tνib and Trot have similar dependences with N2 pressure; peaked at 100 mTorr beyond which it monotonically decreases with increase in the N2 pressure. The correlation between the observed maximum value of Tνib around 100 mTorr and the detected “dip” in the EEPF in the same pressure range has been discussed.
Accurate variational calculations of the ground 2P
o(1s22s22p) and excited 2S(1s22s2p2) and 2P
o(1s22s23p) states of singly ionized carbon atom
Authors: Bubin Sergiy , Adamowicz Ludwik
Published: December 2011

In this article we report accurate nonrelativistic variational calculations of the ground and two excited states of C+ ion. We employ extended and well optimized basis sets of all-electron explicitly correlated Gaussians to represent the wave functions of the states. The optimization of the basis functions is performed with a procedure employing the analytic gradient of the energy with respect to the nonlinear parameters of the Gaussians. The calculations explicitly include the effects due to the finite nuclear mass. The calculated transition energies between the three states are compared to the experimentally derived values. Finally, we present expectation values of some small positive and negative powers of the interparticle distances and contact densities.
Magnetic frustration and short-range ordering in cubic defect spinel MgMnO3
Authors: Seehra M. S. , Singh V. , Thota S.
Published: December 2011

Magnetic properties of bulk MgMnO3, a cubic defect spinel with the structure 4MgMnO3=3[Mg2+][Mg+2 1/3Mn4+ 4/3◻1/3]O4, are reported. For T > 150 K, magnetization M vs T data fits the Curie-Weiss law with μ ≃ 4μB expected for Mn4+ and θ ≃ −40 K indicating antiferromagnetic Mn4+-Mn4+coupling. For T < 150 K, a blocking temperature TB ≃ 15 K is observed below which coercivity increases with decreasing T. The electron magnetic resonance spectra yield a single broad line with g ≃ 1.9 whose linewidth increases with decreasing T leading to a peak at TB. As predicted in spinels with magnetic ions only on the B-sites, these observations suggest a magnetically frustrated state with short-range order only.
A study of the impact of dislocations on the thermoelectric properties of quantum wells in the Si/SiGe materials system
Authors: Watling Jeremy R. , Paul Douglas J.
Published: December 2011

Thermoelectric materials generate electricity from thermal energy using the Seebeck effect to generate a voltage and an electronic current from a temperature difference across the semiconductor. High thermoelectric efficiency ZT requires a semiconductor with high electronic conductivity and low thermal conductivity. Here, we investigate the effect of scattering from threading dislocations of edge character on the thermoelectric performance of individual n and p-channel SiGe multiple quantum well structures. Our detailed physical simulations indicate that while the thermal and electrical conductivities decrease with increasing dislocation scattering/density, the Seebeck coefficient actually increases with increasing threading dislocation density above 106 cm−2 at room temperature, due to an increase in the entropy associated with each carrier. The collective result of these individual effects, is that the present Si-based quantum well designs can tolerate scattering by a threading dislocation density up to ∼108 cm−2, well within the capabilities of modern growth techniques, before significant reductions in ZT due to scattering from threading dislocations is observed.
Voltage modulated electro-luminescence spectroscopy to understand negative capacitance and the role of sub-bandgap states in light emitting devices
Authors: Bansal Kanika , Datta Shouvik
Published: December 2011

Voltage modulated electroluminescence spectra and low frequency (≤100 kHz) impedance characteristics of red electroluminescent diodes under forward bias are investigated. Light emission under periodic voltage modulation tracks the onset of observed negative capacitance for each modulation frequency. Active participation of sub-bandgap defects including the shallower states in minority carrier recombination dynamics is sought to explain the results. The phenomenon of negative capacitance is understood as a necessary dielectric response to compensate any irreversible transient changes in the injected minority carrier reservoir due to radiative recombinations mediated by slowly responding sub-bandgap defects. Experimentally measured variations of the in-phase component of modulated electroluminescence spectra with forward bias levels and with modulation frequencies support the dynamic influence of these sub-bandgap states in the radiative recombination process. Predominant negative sign of the in-phase component of voltage modulated electroluminescence signal further confirms the bi-molecular nature of light emission. Effect of these states on the net density of minority carriers available for radiative recombination is discussed. These sub-bandgap states can even supress the external quantum efficiency of such devices under high frequency operation commonly used in optical communication.
Thermal diffusion of nitrogen into ZnO film deposited on InN/sapphire substrate by metal organic chemical vapor deposition
Authors: Shi K. , Zhang P. F. , Wei H. Y. , Jiao C. M. , Jin P. , Liu X. L. , Yang S. Y. , Zhu Q. S. , Wang Z. G.
Published: December 2011

ZnO film with high crystal quality was prepared on InN/sapphire substrate by metal organic chemical vapor deposition. The diffusion of nitrogen (N) into ZnO film was investigated via Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS), and low-temperature photoluminescence (LT-PL). AES revealed that some N atoms out-diffused into ZnO film after a rapid thermal annealing (RTA) process, while most of the In atoms remained in InN layers, which was confirmed by XPS. LT-PL spectra at 10 K further confirmed that N atoms diffused into the upper ZnO film and acted as acceptors after RTA. It might be an attractive way to obtain high-quality p-type ZnO:N on InN films by this thermal diffusion doping technique.
On the accuracy of classical and long wavelength approximations for phonon transport in graphene
Authors: Singh Dhruv , Murthy Jayathi Y. , Fisher Timothy S.
Published: December 2011

This paper presents a critical evaluation of the approximations usually made in thermal conductivity modeling applied to graphene. The baseline for comparison is thermal conductivity computations performed using a rigorous calculation of three-phonon scattering events and accounting for the anharmonicity of interatomic forces. Three central assumptions that underlie published theories are evaluated and shown to compromise the accuracy of thermal conductivity predictions. It is shown that the use of classical phonon occupation statistics in place of the Bose-Einstein distribution causes the overprediction of specific heat and the underprediction of phonon relaxation time; for ZA phonons, the classical approximation can underpredict the relaxation time by a factor of approximately 2 at room temperature across a broad frequency band. The validity of the long wavelength (Klemens) approximation in evaluating the strength of phonon scattering events is also examined, and the findings indicate that thermal conductivity is significantly underpredicted when long-wavelength approximations are made, with the most significant discrepancy occurring for ZA phonons. The neglect of Normal processes in thermal conductivity computations is evaluated and shown to produce a diverging thermal conductivity with increasing size.
Silicon two-dimensional phononic crystal resonators using alternate defects
Authors: Wang Nan , Hsiao Fu-Li , Palaniapan Moorthi , Lee Chengkuo
Published: December 2011

We present the numerical and experimental investigations of micromechanical resonators made by creating alternate defects with different central-hole radii (r′) in a two-dimensional (2-D) phononic crystal (PnC) slab. The PnC structures were fabricated by etching a square array of cylindrical air holes in a 10 μm thick free-standing silicon plate using a CMOS-compatible process. Preliminary experimental results show that the performance of the PnC resonators in terms of resonant frequency, Q factor, and insertion loss (IL) is highly dependent on r′. A Q factor of more than 3000 is achieved for the case of r′ = 6 μm while all the designed resonators with alternate defects have higher Q factor and lower IL than the resonators based on the normal Fabry-Perot structure due to the reduction in the mode mismatch.
Dynamically reconfigurable terahertz metamaterial through photo-doped semiconductor
Authors: Roy Chowdhury Dibakar , Singh Ranjan , O’Hara John F. , Chen Hou-Tong , Taylor Antoinette J. , Azad Abul K.
Published: December 2011

We demonstrate reconfigurable terahertz metamaterial (MM) in which constituent resonators can be switched from split-ring resonators (SRRs) to closed-ring resonators via optical excitation of silicon islands strategically placed in the split gap. Both the fundamental and the third-order resonance modes experience monotonic damping due to increasing conductive losses in the photo-doped silicon region. More importantly, increasing the optical fluence (>200 μJ/cm2) results in the excitation of the second-order resonance mode, which is otherwise forbidden in a split-ring resonator for the incidence polarization in our experiments. Such dynamical control of metamaterial resonances could be implemented in active terahertz devices to achieve additional functionalities.
Heritage Conservation and the Search for a New Governing Approach in Hong Kong
Authors: Chung Him
Published: December 2011

In this paper I examine the governance of Hong Kong through heritage conservation. The economic approach to governance, a legacy of British colonialism in Hong Kong, has been challenged by the Hong Kong people's attempt to reconstruct a new identity from the bottom up. This attempt has been translated into a public campaign against current heritage preservation policies, including plans to demolish or redevelop heritage buildings—the material bases of identity. Partly as a response to the public's growing awareness of local identity and culture, and partly to avoid an imminent governing crisis, the Hong Kong government has initiated the ‘Revitalising Historic Buildings through Partnership’ Scheme. Focusing on this scheme, I investigate how the Hong Kong government has attempted to tap into heritage resources to develop a new governing approach. Has a more inclusive governing system been developed? Addressing the strength and constraints of the scheme, I provide an initial evaluation of the scheme and its implications for governance.
Ghana's National Health Insurance Scheme: Helping the Poor or Leaving Them Behind?
Authors: Dixon Jenna , Tenkorang Eric Y , Luginaah Isaac
Published: December 2011

We present findings on the determinants of enrolment for Ghana's National Health Insurance Scheme (NHIS). With this study we contribute to the literature by providing one of the few quantitative analyses on a nationwide survey. Using data from the 2008 Ghana Demographic and Health Survey, we find that those from the poorest households remain significantly less likely to enrol in the NHIS compared with respondents from wealthy households, even after controlling for theoretically relevant variables. However, our analysis also shows that respondents in Northern Ghana, considered the poorest part of the country, are more likely to be enroled than those in Southern Ghana. The findings present a clear challenge to the original mandate of the NHIS as a propoor policy and suggest that health policy makers should consider expanding and clarifying the criteria for declaring a person as indigent and that the scheme be further evaluated for obstacles that may be hindering enrolment.
Investigating the Social Capital and Resource Acquisition of Entrepreneurs Residing in Deprived Areas of England
Authors: Lee Robert , Tüselmann Heinz , Jayawarna Dilani , Rouse Julia
Published: December 2011

Enterprise policy in England has focused extensively on funding and training aspiring entrepreneurs residing in deprived areas. These policy initiatives have been directed at increasing the capabilities of entrepreneurs residing in deprived areas without knowing about their social capital and access to resources. This study is based on a survey of entrepreneurs that have completed the New Entrepreneurship Scholarship training programme across the nine regions of England. The findings suggest that social capital helps explain the acquisition of resources entrepreneurs residing in deprived areas need to develop a new venture. However, there seems to be an overreliance on bonding ties for resource acquisition. Too much bonding can lead to redundant resources and ‘getting by’ and may limit growth. In light of these findings several recommendations are developed for the coalition government's Local Enterprise Partnerships policy and the future funding of entrepreneurship initiatives in deprived areas.
Alterations in systemic concentrations of progesterone during the early luteal phase affect RBP4 expression in the bovine uterus
Authors: Mullen Michael P. , Forde Niamh , Parr Mervyn H. , Diskin Michael G. , Morris Dermot G. , Nally Jarlath E. , Evans Alexander C. O. , Crowe Mark A.
Published: December 2011

Systemic progesterone affects the timing and duration of uterine endometrial gene and protein expression and has significant effects on conceptus development. The objective of the present study was to examine how changes in progesterone concentrations during the early luteal phase affect retinol-binding protein (RBP4) mRNA and protein concentrations in the uterus. Endometrial tissue and uterine flushings were recovered on Days 7 and 13 of the oestrous cycle in heifers with high, normal and low progesterone concentrations. RBP4 mRNA and protein concentrations were higher (P < 0.05) on Day 13 compared with Day 7 in heifers with high and control progesterone concentrations. However, there was no difference in RBP4 protein concentrations between Days 7 and 13 in heifers with low progesterone (P > 0.05). On Day 7, although heifers with low progesterone had lower RBP4 mRNA expression compared with controls (P < 0.05) there was no difference in protein concentrations between treatment groups. On Day 13, RBP4 mRNA was 2-fold higher (P < 0.001) in heifers with high and control progesterone compared with their low-progesterone counterparts and RBP4 protein concentrations were over 2-fold higher (P < 0.001) in heifers with high compared to low progesterone. In conclusion, progesterone modulates uterine RBP4 mRNA and protein abundance in a time- and concentration-dependent manner.
Environmental regulation of placental phenotype: implications for fetal growth
Authors: Vaughan O. R. , Sferruzzi-Perri A. N. , Coan P. M. , Fowden A. L.
Published: December 2011

Environmental conditions during pregnancy determine birthweight, neonatal viability and adult phenotype in human and other animals. In part, these effects may be mediated by the placenta, the principal source of nutrients for fetal development. However, little is known about the environmental regulation of placental phenotype. Generally, placental weight is reduced during suboptimal conditions like maternal malnutrition or hypoxaemia but compensatory adaptations can occur in placental nutrient transport capacity to help maintain fetal growth. In vivo studies show that transplacental glucose and amino acid transfer adapt to the prevailing conditions induced by manipulating maternal calorie intake, dietary composition and hormone exposure. These adaptations are due to changes in placental morphology, metabolism and/or abundance of specific nutrient transporters. This review examines environmental programming of placental phenotype with particular emphasis on placental nutrient transport capacity and its implications for fetal growth, mainly in rodents. It also considers the systemic, cellular and molecular mechanisms involved in signalling environmental cues to the placenta. Ultimately, the ability of the placenta to balance the competing interests of mother and fetus in resource allocation may determine not only the success of pregnancy in producing viable neonates but also the long-term health of the offspring.
The evolution of improved and simplified superovulation protocols in cattle
Authors: Mapletoft Reuben J. , Bó Gabriel A.
Published: December 2011

Superovulation protocols have improved greatly since the early days of bovine embryo transfer when purified gonadotrophins were not available, follicular wave dynamics were unknown physiological phenomena and prostaglandins were not available. Although superstimulatory protocols in cattle are normally initiated mid-cycle, elective control of follicular wave emergence and ovulation have had a great impact on the application of on-farm embryo transfer. However, the most common treatment for the synchronisation of follicular wave emergence involves the use of oestradiol, which cannot be used in many parts of the world. Therefore, the need for alternative treatments has driven recent research. An approach that has shown promise is to initiate follicle-stimulating hormone (FSH) treatments at the time of the emergence of the new follicular wave following ovulation induced by gonadotrophin-releasing hormone. Alternatively, it has been shown that it may be possible to ignore follicular wave status and, by extending the treatment protocol, induce subordinate follicles to superovulate. Finally, the short half-life of pituitary FSH necessitates twice-daily treatments, which are time-consuming, stressful and subject to error. Recent treatment protocols have permitted superstimulation with a single FSH treatment or two treatments 48 h apart, reducing the need for animal handling during gonadotrophin treatments.
Microorganisms and plants: a photosynthetic perspective.
Authors: Morgan-Kiss R. M. , Dolhi J. M.
Published: December 2011

This chapter discusses the potential impact of climate change on photosynthetic organisms residing in year-round cold environments, with emphasis on studies regarding microbial communities in cold habitats as well as research on microbial isolates of psychrophilic photoautotrophs, or the photopsychrophiles.
Impacts of cultivation of Kappaphycus alvarezii on coral reef environs of the Gulf of Mannar and Palk Bay, South-eastern India.
Authors: Patterson Edward J. K. , Bhatt J. R.
Published: December 2011

This chapter presents an assessment of the impact of K. alvarezii cultivation on coral reef environs in the Gulf of Mannar and Palk Bay in Mandapam, Tamil Nadu, India, from October 2008 to October 2010 using the line intercept transect method. Twenty meter transects were laid parallel to a series of islands at 0.5-2.0 m depth during high tide, the number of transects depending on the size of the reef. Six transects in Shingle Island, 15 in Krusadai Island, and 6 in Poomarichan Island were laid in each assessment, which was carried out regularly at quarterly intervals to identify changes in benthic community structure. Thirty local fishermen were interviewed for their views on recent trends in fish catch. Underwater observations revealed considerable quantities of K. alvarezii fragments on the dense seagrass beds along the Pamban Pass. Coral colonies invaded by K. alvarezii were destroyed because of the shadowing and smothering effects of fragments firmly attached to the coral colony and forming a thick mat that penetrated deeply up to 5-10 cm, preventing sunlight from reaching zooxanthallae. Invasion also adversely affected other reef-associated fauna, especially native fish species. K. alvarezii was not preferred by native herbivorous fishes, such as surgeon fish (acanthurids) and parrot fish (scarids), and this provided an opportunity for the invading alga to grow very rapidly without any predators. K. alvarezii cultivation, as practiced using rafts on the luxuriant seagrass beds, reduced the penetration of light essential for the healthy growth of seagrass. This activity ultimately affected the seagrass beds, resulting in stunted growth with reduced shoot density, a turbid environment and less associated biodiversity, particularly fish. Fishermen working on the catch revealed that native herbivorous fish species are gradually declining in the area as they do not appear to prefer K. alvarezii as their food source.
Resource utilization and beneficial aspects of invasive alien weeds with special reference to the Western Ghats, India.
Authors: Rao R. R. , Kavitha Sagar Kavitha Sagar , Sathyanarayana N.
Published: December 2011

This chapter describes the utilization of invasive weeds in the Western Ghats region of India as medicinal plants, ornamental plants, edible plants, fodder plants, hyperaccumulators for bioremediation, biofertilizers and timber source, among other uses.
Relative age effect and soccer refereeing: A ‘Strategic Adaptation’ of relatively younger children?
Authors: Delorme Nicolas , Radel Rémi , Raspaud Michel
Published: December 2011

Previous research suggested that the relative age effect (RAE) has a psychological influence on children and their decision to engage in a particular sport. Relatively younger children seem to have lower self‐esteem. Indeed, because of the disadvantages of being younger, it is assumed that these players experience more situations of failure and inferiority. Because of these negative performance cues, it is likely that these young players feel less competent, which eventually leads to a higher dropout rate. These children can also decide to participate in sports in which physical attributes are less important. This shift from one sport to another can be interpreted as a ‘strategic adaptation’. The purpose of this study was thus to investigate whether refereeing could be another form of ‘strategic adaptation’. If a child chooses a specific sport but then does not feel competent enough to be a player, refereeing might be an alternate path followed to stay in the environment of a sport they like. Given the minimal age limits for refereeing, two hypotheses were formulated: (1) ‘reversed’ RAE would be observed in district referees younger than 18 years old and (2) no RAE would be observed in district referees older than 18 years old, regional referees and national referees. The birthdates of all official male soccer referees (n=13,952) were collected from the federation database. Results show that the distribution of all district referees was significantly unbalanced (χ2=18.73, df=3, P<0.001) with an over‐representation of individuals who were born in the second half of the competitive year. As expected, this imbalance was exclusively located in district referees of 18 years old and less (χ2=8.03, df=3, P<0.05), while the distribution was uniform for adults (χ2=5.17, df=3, P<0.16). Concerning regional referees (χ2=2.09, df=3, P<0.554) and national referees (χ2=3.75, df=3, P<0.290), the results also provide support for our initial hypothesis as uniform distributions were found for both groups. This study brings to light new elements in the potential relationship between relative age and refereeing. Qualitative and/or longitudinal research is needed to confirm our quantitative data.