bluuebunny/crossref_metadata_2025 huggingface dataset:
Mala Bizta Sochal Klu: underground, alternative and commercial in Havana hip hop
Authors: Baker Geoff
Published: February 2012

The terms underground, alternative and commercial are widely used in discussions of popular music scenes in Havana and around the world. In Cuba, the words alternative and underground are often used interchangeably, in critical as well as popular discourse. I propose a working definition of, and a distinction between, these terms in Havana, since to render them synonymous reduces their usefulness. The distinction between underground and commercial, in contrast, is widely seen as self-evident, by critics as well as by fans. However, a simplistic dichotomy glosses over the interpenetration of these terms, which are of limited use as analytical categories. This discussion of terminology is grounded in an analysis of the politics of style in Havana hip hop.
The promotional state ‘after neo-liberalism’: ideologies of governance and New Zealand's pop renaissance
Authors: Scott Michael , Craig David
Published: February 2012

This article responds to Frith and Cloonan's (2008) call for researchers considering the relationship between the state and popular music to analyse more closely the ideologies of governance that undergird music policy. Building on Cloonan's ‘promotional state’ and drawing on recent New Zealand experience, this paper shows how New Zealand's Labour government (1999–2008) developed policies to support the export of ‘Kiwi’ pop which requires a reconsideration of state music policy as interventions in the market. The work of the New Zealand Music Commission in generating and coordinating working partnerships with diverse music industry actors illustrates emerging forms of ‘after neo-liberal’ ideology and governance, wherein state-related actors and musicians each and together adapt to market arrangements through supply side, social inclusion and new institutional policy settings and modalities. This article offers points of comparison to types of ideological and governing/institutional formations we can expect to see emerging in promotional states elsewhere.
Temporal variations of non‐volcanic tremor (NVT) locations in the Mexican subduction zone: Finding the NVT sweet spot
Authors: Husker Allen L. , Kostoglodov Vladimir , Cruz‐Atienza Victor M. , Legrand Denis , Shapiro Nikolai M. , Payero Juan S. , Campillo Michel , Huesca‐Pérez Eduardo
Published: February 2012

Epicentral locations of non‐volcanic tremors (NVT) in the Mexican subduction zone are determined from the peak of the energy spatial distribution and examined over time. NVT is found to occur persistently at a distance of ∼215 km from the trench, which we term the “Sweet Spot” because this region probably has the proper conditions (i.e., temperature, pressure, and fluid content) for the NVT to occur with minimum shear slip. High‐energy NVT episodes are also observed every few months, extending ∼190 km to ∼220 km from the trench with durations of a few weeks. During the 2006 slow slip event (SSE) the duration and the recurrence rate of the NVT episodes increased. Low‐energy episodes were also observed, independent from the high‐energy episodes, ∼150 km to ∼190 km from the trench during the 2006 SSE. Both the high and low energy episodes were made up of many individual NVT's that had a range of energy‐release‐rates. However, the highest energy‐release‐rates of the high‐energy episodes were consistently double those of the low‐energy episodes and the persistent activity at the Sweet Spot. We suggest that all of the high‐energy episodes are evidence of small, short repeat interval SSE. Given this model, the increased recurrence rate of the high‐energy NVT episodes during the 2006 long‐term SSE implies that short‐term SSE's also increase during the SSE and are therefore triggered by the SSE.
Validation study of the magnetically self‐consistent inner magnetosphere model RAM‐SCB
Authors: Yu Yiqun , Jordanova Vania , Zaharia Sorin , Koller Josef , Zhang Jichun , Kistler Lynn M.
Published: February 2012

The validation of the magnetically self‐consistent inner magnetospheric model RAM‐SCB developed at Los Alamos National Laboratory is presented here. The model consists of two codes: a kinetic ring current–atmosphere interaction model (RAM) and a 3‐D equilibrium magnetic field code (SCB). The validation is conducted by simulating two magnetic storm events and then comparing the model results against a variety of satellite in situ observations, including the magnetic field from Cluster and Polar spacecraft, ion differential flux from the Cluster/CODIF (Composition and Distribution Function) analyzer, and the ground‐based SYM‐H index. The model prediction of the magnetic field is in good agreement with observations, which indicates the model's capability of representing well the inner magnetospheric field configuration. This provides confidence for the RAM‐SCB model to be utilized for field line and drift shell tracing, which are needed in radiation belt studies. While the SYM‐H index, which reflects the total ring current energy content, is generally reasonably reproduced by the model using the Weimer electric field model, the modeled ion differential flux clearly depends on the electric field strength, local time, and magnetic activity level. A self‐consistent electric field approach may be needed to improve the model performance in this regard.
Evidence of a hydrological connection between the ice divide and ice sheet margin in the Aurora Subglacial Basin, East Antarctica
Authors: Wright A. P. , Young D. A. , Roberts J. L. , Schroeder D. M. , Bamber J. L. , Dowdeswell J. A. , Young N. W. , Le Brocq A. M. , Warner R. C. , Payne A. J. , Blankenship D. D. , van Ommen T. D. , Siegert M. J.
Published: February 2012

Subglacial hydrology in East Antarctica is poorly understood, yet may be critical to the manner in which ice flows. Data from a new regional airborne geophysical survey (ICECAP) have transformed our understanding of the topography and glaciology associated with the 287,000 km2 Aurora Subglacial Basin in East Antarctica. Using these data, in conjunction with numerical ice sheet modeling, we present a suite of analyses that demonstrate the potential of the 1000 km‐long basin as a route for subglacial water drainage from the ice sheet interior to the ice sheet margin. We present results from our analysis of basal topography, bed roughness and radar power reflectance and from our modeling of ice sheet flow and basal ice temperatures. Although no clear‐cut subglacial lakes are found within the Aurora Basin itself, dozens of lake‐like reflectors are observed that, in conjunction with other results reported here, support the hypothesis that the basin acts as a pathway allowing discharge from subglacial lakes near the Dome C ice divide to reach the coast via the Totten Glacier.
Evolution of the Dynamic Changes in Functional Cerebral Oxidative Metabolism from Tissue Mitochondria to Blood Oxygen
Authors: Vazquez Alberto L , Fukuda Mitsuhiro , Kim Seong-Gi
Published: February 2012

The dynamic properties of the cerebral metabolic rate of oxygen consumption (CMRO2) during changes in brain activity remain unclear. Therefore, the spatial and temporal evolution of functional increases in CMRO2 was investigated in the rat somato-sensory cortex during forelimb stimulation under a suppressed blood flow response condition. Temporally, stimulation elicited a fast increase in tissue mitochondria CMRO2 described by a time constant of ~ 1 second measured using flavoprotein autofluorescence imaging. CMRO2-driven changes in the tissue oxygen tension measured using an oxygen electrode and blood oxygenation measured using optical imaging of intrinsic signal followed; however, these changes were slow with time constants of ~ 5 and ~ 10 seconds, respectively. This slow change in CMRO2-driven blood oxygenation partly explains the commonly observed post-stimulus blood oxygen level-dependent (BOLD) undershoot. Spatially, the changes in mitochondria CMRO2 were similar to the changes in blood oxygenation. Finally, the increases in CMRO2 were well correlated with the evoked multi-unit spiking activity. These findings show that dynamic CMRO2 calculations made using only blood oxygenation data (e.g., BOLD functional magnetic resonance imaging (fMRI)) do not directly reflect the temporal changes in the tissue's mitochondria metabolic rate; however, the findings presented can bridge the gap between the changes in cellular oxidative rate and blood oxygenation.
Cross-talk between TGFβ1 and EGFR signalling pathways induces TM4SF5 expression and epithelial–mesenchymal transition
Authors: Kang Minkyung , Choi Suyong , Jeong Soo-Jin , Lee Sin-Ae , Kwak Tae Kyoung , Kim Hyeonjung , Jung Oisun , Lee Mi-Sook , Ko Youra , Ryu Jihye , Choi Yoon-Ju , Jeong Doyoung , Lee Hyo Jeong , Ye Sang-Kyu , Kim Sung-Hoon , Lee Jung Weon
Published: February 2012

The EMT (epithelial–mesenchymal transition) is involved in fibrosis and cancer, and is regulated by different signalling pathways mediated through soluble factors, actin reorganization and transcription factor actions. Because the tetraspan (also called tetraspanin) TM4SF5 (transmembrane 4 L6 family member 5) is highly expressed in hepatocellular carcinoma and induces EMT, understanding how TM4SF5 expression in hepatocytes is regulated is important. We explored the mechanisms that induce TM4SF5 expression and whether impaired signalling pathways for TM4SF5 expression inhibit the acquisition of mesenchymal cell features, using human and mouse normal hepatocytes. We found that TGFβ1 (transforming growth factor β1)-mediated Smad activation caused TM4SF5 expression and EMT, and activation of the EGFR [EGF (epidermal growth factor) receptor] pathway. Inhibition of EGFR activity following TGFβ1 treatment abolished acquisition of EMT, suggesting a link from Smads to EGFR for TM4SF5 expression. Further, TGFβ1-mediated EGFR activation and TM4SF5 expression were abolished by EGFR suppression or extracellular EGF depletion. Smad overexpression mediated EGFR activation and TM4SF5 expression in the absence of serum, and EGFR kinase inactivation or EGF depletion abolished Smad-overexpression-induced TM4SF5 and mesenchymal cell marker expression. Inhibition of Smad, EGFR or TM4SF5 using Smad7 or small compounds also blocked TM4SF5 expression and/or EMT. These results indicate that TGFβ1- and growth factor-mediated signalling activities mediate TM4SF5 expression leading to acquisition of mesenchymal cell features, suggesting that TM4SF5 induction may be involved in the development of liver pathologies.
Optimizing the front end test stand high performance H− ion source at RAL
Authors: Faircloth D. , Lawrie S. , Gabor C. , Letchford A. , Whitehead M. , Wood T. , Perkins M.
Published: February 2012

The aim of the front end test stand project is to demonstrate that chopped low energy H− beams of high quality can be produced. The beam line currently consists of the ion source, a 3 solenoid low energy beam transport and a suite of diagnostics. A brief status report of the radio frequency quadrupole is given. This paper details the work to optimize the ion source performance. A new high power pulsed discharge power supply with greater reliability has been developed to allow long term, stable operation at 50 Hz with a 60 A, 2.2 ms discharge pulse and up to 100 A at 1.2 ms. The existing extraction power supply has been modified to operate up to 22 kV. Results from optical spectroscopy measurements and their application to source optimization are summarized. Source emittances and beam currents of 60 mA are reported.
Shot-to-shot reproducibility in the emission of fast highly charged metal ions from a laser ion source
Authors: Krása J. , Velyhan A. , Margarone D. , Krouský E. , Láska L. , Jungwirth K. , Rohlena K. , Ullschmied J. , Parys P. , Ryć L. , Wołowski J.
Published: February 2012

The generation of fast highly charged metal ions with the use of the sub-nanosecond Prague Asterix Laser System, operated at a fundamental wavelength of 1315 nm, is reported. Particular attention is paid to shot-to-shot reproducibility in the ion emission. Au and Pd targets were exposed to intensities up to 5 × 1016 W/cm2. Above the laser intensity threshold of ∼3 × 1014 W/cm2 the plasma is generated in a form of irregular bursts. The maximum energy of protons constituting the leading edge of the fastest burst reaches a value up to 1 MeV. The fast ions in the following bursts have energy gradually decreasing with the increasing burst number, namely, from a value of about 0.5 MeV/charge regardless of the atomic number and mass of the ionized species.
Upgraded vacuum arc ion source for metal ion implantation
Authors: Nikolaev A. G. , Oks E. M. , Savkin K. P. , Yushkov G. Yu. , Brown I. G.
Published: February 2012

Vacuum arc ion sources have been made and used by a large number of research groups around the world over the past twenty years. The first generation of vacuum arc ion sources (dubbed “Mevva,” for metal vapor vacuum arc) was developed at Lawrence Berkeley National Laboratory in the 1980s. This paper considers the design, performance parameters, and some applications of a new modified version of this kind of source which we have called Mevva-V.Ru. The source produces broad beams of metal ions at an extraction voltage of up to 60 kV and a time-averaged ion beam current in the milliampere range. Here, we describe the Mevva-V.Ru vacuum arc ion source that we have developed at Tomsk and summarize its beam characteristics along with some of the applications to which we have put it. We also describe the source performance using compound cathodes.
Polarity-dependent photoemission spectra of wurtzite-type zinc oxide
Authors: Williams Jesse , Yoshikawa Hideki , Ueda Shigenori , Yamashita Yoshiyuki , Kobayashi Keisuke , Adachi Yutaka , Haneda Hajime , Ohgaki Takeshi , Miyazaki Hiroki , Ishigaki Takamasa , Ohashi Naoki
Published: February 2012

The polar surfaces of wurtzite-type zinc oxide (ZnO) were characterized by x-ray photoemission spectroscopy to identify the origin of the polarity dependence of the valence band spectra. A characteristic sub-peak always appeared in the valence band spectra of the (0001) face regardless of the surface preparation conditions. It also appeared in the valence band spectra of the (101¯2) face, but only when the photoelectron take-off angle was parallel to the c-axis of ZnO. Our analysis demonstrates that this take-off angle dependency originates not from the surface state, photoelectron diffraction, or the presence of surfactants but from the crystal polarity.
${\cal {PT}}$
PT
symmetric, Hermitian and $\mathcal P$P-self-adjoint operators related to potentials in ${\cal {PT}}$PT quantum mechanics
Authors: Azizov Tomas Ya. , Trunk Carsten
Published: February 2012

In the recent years, a generalization H = p2 + x2(ix)ε of the harmonic oscillator using a complex deformation was investigated, where ε is a real parameter. Here, we will consider the most simple case: ε even and x real. We will give a complete characterization of three different classes of operators associated with the differential expression H: The class of all self-adjoint (Hermitian) operators, the class of all \documentclass[12pt]{minimal}\begin{document}${\cal {PT}}$\end{document}PT symmetric operators, and the class of all \documentclass[12pt]{minimal}\begin{document}$\mathcal P$\end{document}P-self-adjoint operators. Surprisingly, some of the \documentclass[12pt]{minimal}\begin{document}${\cal{ PT}}$\end{document}PT symmetric operators associated to this expression have no resolvent set.
Shear-induced particle migration and margination in a cellular suspension
Authors: Zhao Hong , Shaqfeh Eric S. G. , Narsimhan Vivek
Published: February 2012

We simulate the cross-flow migration of rigid particles such as platelets in a red blood cell (RBC) suspension using the Stokes flow boundary integral equation method. Two types of flow environments are investigated: a suspension undergoing a bulk shear motion and a suspension flowing in a microchannel or duct. In a cellular suspension undergoing bulk shear deformation, the cross-flow migration of particles is diffusional. The velocity fluctuations in the suspension, which are the root cause of particle migration, are analyzed in detail, including their magnitude, the autocorrelation of Lagrangian tracer points and particles, and the associated integral time scales. The orientation and morphology of red blood cells vary with the shear rate, and these in turn cause the dimensionless particle diffusivity to vary non-monotonically with the flow capillary number. By simulating RBCs and platelets flowing in a microchannel of 34 μm height, we demonstrate that the velocity fluctuations in the core cellular flow region cause the platelets to migrate diffusively in the wall normal direction. A mean lateral velocity of particles, which is most significant near the edge of the cell-free layer, further expels them toward the wall, leading to their excess concentration in the cell-free layer. The calculated shear-induced particle diffusivity in the cell-laden region is in qualitative agreement with the experimental measurements of micron-sized beads in a cylindrical tube of a comparable diameter. In a smaller duct of 10 × 15 μm cross section, the volume exclusion becomes the dominant mechanism for particle margination, which occurs at a much shorter time scale than the migration in the bigger channel.
A theoretical study of the CX2N radicals (X = F, Cl, Br): The effect of halogen substitution on structure, isomerization, and energetics
Authors: Puzzarini Cristina
Published: February 2012

Structural isomers of the CX2N radicals, where X = F, Cl, and Br, have been investigated at high level of theory, i.e., using the coupled-cluster method in conjunction with correlation-consistent basis sets ranging in size from triple- to sextuple-zeta. Extrapolation to the complete basis-set limit as well as core-correlation effects and inclusion of higher excitations in the cluster operator have been considered for accurately evaluating geometries and energies. The effect of halogen substitution on molecular structure, isomer stability, and dissociation energy is addressed; in particular, only the F2CN, Cl2CN, Br2CN, and F2NC radicals of C2V symmetry are predicted to be stable with respect to dissociation.
Experimental investigation of geodesic acoustic mode spatial structure, intermittency, and interaction with turbulence in the DIII-D tokamak
Authors: Hillesheim J. C. , Peebles W. A. , Carter T. A. , Schmitz L. , Rhodes T. L.
Published: February 2012

Geodesic acoustic modes (GAMs) and zonal flows are nonlinearly driven, axisymmetric (m=0andn=0) E×B flows, which are thought to play an important role in establishing the saturated level of turbulence in tokamaks. Results are presented showing the GAM’s observed spatial scales, temporal scales, and nonlinear interaction characteristics, which may have implications for the assumptions underpinning turbulence models towards the tokamak edge (r/a>rsim0.75). Measurements in the DIII-D tokamak [Luxon, Nucl. Fusion 42, 614 (2002)] have been made with multichannel Doppler backscattering systems at toroidal locations separated by 180∘; analysis reveals that the GAM is highly coherent between the toroidally separated systems (γ>0.8) and that measurements are consistent with the expected m=0andn=0 structure. Observations show that the GAM in L-mode plasmas with ~2.5-4.5 MW auxiliary heating occurs as a radially coherent eigenmode, rather than as a continuum of frequencies as occurs in lower temperature discharges; this is consistent with theoretical expectations when finite ion Larmor radius effects are included. The intermittency of the GAM has been quantified, revealing that its autocorrelation time is fairly short, ranging from about 4 to about 15 GAM periods in cases examined, a difference that is accompanied by a modification to the probability distribution function of the E×B velocity at the GAM frequency. Conditionally-averaged bispectral analysis shows the strength of the nonlinear interaction of the GAM with broadband turbulence can vary with the magnitude of the GAM. Data also indicate a wavenumber dependence to the GAM’s interaction with turbulence.
Developed quantum turbulence and its decay
Authors: Skrbek L. , Sreenivasan K. R.
Published: February 2012

This article is primarily a review of our knowledge of the correspondence between classical and quantum turbulence, though it is interspersed with a few new interpretations. This review is deemed timely because recent work in quantum turbulence promises to provide a better understanding of aspects of classical turbulence, though the two fields of turbulence have similarities as well as differences. We pay a particular attention to the conceptually simplest case of zero temperature limit where quantum turbulence consists of a tangle of quantized vortex line and represents a simple prototype of turbulence. At finite temperature, we anchor ourselves at the level of two-fluid description of the superfluid state—consisting of a normal viscous fluid and a frictionless superfluid—and review much of the available knowledge on quantum turbulence in liquid helium (both He II and 3He-B). We consider counterflows in which the normal and superfluid components flow against each other, as well as co-flows in which the direction of the two fluids is the same. We discuss experimental methods, phenomenological results as well as key theoretical concepts.
Proof of rounding by quenched disorder of first order transitions in low-dimensional quantum systems
Authors: Aizenman Michael , Greenblatt Rafael L. , Lebowitz Joel L.
Published: February 2012

We prove that for quantum lattice systems in d ⩽ 2 dimensions the addition of quenched disorder rounds any first order phase transition in the corresponding conjugate order parameter, both at positive temperatures and at T = 0. For systems with continuous symmetry the statement extends up to d ⩽ 4 dimensions. This establishes for quantum systems the existence of the Imry–Ma phenomenon which for classical systems was proven by Aizenman and Wehr. The extension of the proof to quantum systems is achieved by carrying out the analysis at the level of thermodynamic quantities rather than equilibrium states.
On the design and applicability of nanowire solar cells using low-grade semiconductors
Authors: Gharghi Majid
Published: February 2012

Nanowire based radial junction structure has been widely proposed to achieve high efficiency solar cells with low grade semiconductors, in particular silicon. We present a concise model based on the collection probability of photogenerated carriers to investigate the effect of size and geometry on the photovoltaic behavior in radial junction devices. The model provides a simple tool to obtain the optimal range of radius sizes depending on material and device parameters. We use the model to derive guideline for the design of cells made of low grade silicon. The analysis of the radial structure in upgraded metallurgical grade silicon reveals how nanowire devices lose the improved efficiency advantage quickly at radii below the minority carrier diffusion length.
Densification of chemical vapor deposition silicon dioxide film using oxygen radical oxidation
Authors: Kawase Kazumasa , Teramoto Akinobu , Umeda Hiroshi , Suwa Tomoyuki , Uehara Yasushi , Hattori Takeo , Ohmi Tadahiro
Published: February 2012

Silicon dioxide (SiO2) films formed by chemical vapor deposition (CVD) were treated with oxygen radical oxidation using Ar/O2 plasma excited by microwave. The mass density depth profiles, carrier trap densities, and current-voltage characteristics of the radical-oxidized CVD-SiO2 films were investigated. The mass density depth profiles were estimated with x ray reflectivity measurement using synchrotron radiation of SPring-8. The carrier trap densities were estimated with x ray photoelectron spectroscopy time-dependent measurement. The mass densities of the radical-oxidized CVD-SiO2 films were increased near the SiO2 surface. The densities of the carrier trap centers in these films were decreased. The leakage currents of the metal-oxide-semiconductor capacitors fabricated by using these films were reduced. It is probable that the insulation properties of the CVD-SiO2 film are improved by the increase in the mass density and the decrease in the carrier trap density caused by the restoration of the Si-O network with the radical oxidation.
Parallel density matrix propagation in spin dynamics simulations
Authors: Edwards Luke J. , Kuprov Ilya
Published: February 2012

Several methods for density matrix propagation in parallel computing environments are proposed and evaluated. It is demonstrated that the large communication overhead associated with each propagation step (two-sided multiplication of the density matrix by an exponential propagator and its conjugate) may be avoided and the simulation recast in a form that requires virtually no inter-thread communication. Good scaling is demonstrated on a 128-core (16 nodes, 8 cores each) cluster.
Robust interpolation between weak- and strong-correlation regimes of quantum systems
Authors: Cioslowski Jerzy
Published: February 2012

A robust interpolation between the weak- and strong-correlation regimes of quantum systems is presented. It affords approximants to the function E(ω) describing the dependence of the total energy (or other observable) on the coupling parameter ω that measures the correlation strength. The approximants conform to truncations of the asymptotic expansions of E(ω) at the ω → 0 and ω → ∞ limits with arbitrary (but given) numbers of terms. In addition, depending on the number of fitted parameters, they either reproduce or optimally (in the least-square or maximum-error sense) approximate the exact E(ω) at any given number of values of the coupling strength. Numerical tests demonstrate the high accuracy of even the low-order approximate expression for E(ω). The approximants, which do not suffer from spurious poles, possess a wide range of applicability that stems from their capability of accurately reproducing not only E(ω) but also its derivatives with respect to ω. They are equally useful for interpolation between the low- and high-temperature limits of energy and other quantities associated with various models of statistical thermodynamics. The new interpolation scheme is not applicable to the cases where the weak- and strong-correlation asymptotics involve non-analytic functions of ω or expressions dependent on logarithm of the coupling strength. Excluded are also the cases where the weak- and strong-correlation asymptotics pertain to de facto different states, e.g., the ground state of a homogeneous electron gas in three dimensions.
Local trace formulae and scaling asymptotics for general quantized Hamiltonian flows
Authors: Paoletti Roberto
Published: February 2012

A class of trace formulae in the Toeplitz quantization of Hamiltonian flows on compact symplectic manifolds is given a local intepretation in terms of certain scaling asymptotics near a symplectic fixed locus; these are reminiscent of the near diagonal asymptotics of equivariant Szegö kernels. In spectral theory, the distributional trace of a positive elliptic operator encapsulates information on the asymptotic distribution of its eigenvalues; a trace formula relates the singularities of the trace to Poincaré data of an appropriate Hamiltonian flow. This leads to the asymptotics of certain smoothing kernels, related to the Fourier transform of the trace of a wave operator. In Toeplitz quantization, we consider analogues of these, with the wave operator replaced by a quantized Hamiltonian flow, possibly composed with a family of zeroth order Toeplitz operators. We study the concentration of these smoothing kernels near the fixed loci of the linearized dynamics, and specifically how the Poincaré map controls their scaling asymptotics. This generalizes previous results on holomorphic flows.
Low-energy rotational inelastic collisions of H+ + CO system
Authors: Kumar T. J. Dhilip , Kumar Sanjay
Published: February 2012

The quantum mechanical state-to-state rotational excitation cross sections have been computed using the ab initio ground electronic state potential energy surface of the system [M. Mladenovic and S. Schmatz, J. Chem. Phys. 109, 4456 (1998)] computed at coupled-cluster single and double and triple perturbative excitations method using correlation-consistent polarized valence quadruple zeta basis set where the asymptotic potential have been computed using the dipole moment, quadrupole moment, and the molecular polarizability components and fitted to this interaction potential. The anisotropy of the surface has been analyzed in terms of the multipolar expansion coefficients for the rigid-rotor surface. The integral cross sections for rotational excitations have been computed by solving close-coupled equations at very low collision energies (5−200 cm−1) and the corresponding rates have been obtained for a range of low temperatures (5−175 K). The j = 0 → j′ = 1 rotational excitation cross section (and rate) is found to be the dominant followed by the j = 0 → j′ = 2 in these collision energies. The close-coupling, coupled-state, and infinite-order sudden approximations coupling calculations have been performed in the energy range of 0.1–1.0 eV using vibrational ground potential. The rotational cross sections have been obtained by performing computationally accurate close-coupling calculations at 0.1 eV using vibrationally averaged potential (v = 1) and compared with the results of vibrational ground potential.
A laser-induced fluorescence study of the jet-cooled nitrous oxide cation (N2O+)
Authors: Gharaibeh Mohammed A. , Clouthier Dennis J.
Published: February 2012

Laser-induced fluorescence and wavelength resolved emission spectra of the $\tilde A$Ã 2Σ+ − $\tilde X$X̃ 2Πi electronic transition of the jet-cooled nitrous oxide cation have been recorded. The ions were produced in a pulsed electric discharge at the exit of a supersonic expansion using a precursor mixture of N2O in high pressure argon. Both spin-orbit components of the $0_0^0$000 band were studied at high resolution and rotationally analyzed to provide precise molecular constants for the combining states. Emission spectra were obtained by laser excitation of the $0_0^0$000, $2_0^1$201, $3_0^1$301, and $2_0^2$202 absorption bands, providing extensive data on the ground state bending, stretching, and combination vibrational levels. These data were fitted to a Renner-Teller model including spin-orbit, anharmonic, and Fermi resonance terms. The observed energy levels and fitted parameters were found to be comparable to those in the literature predicted from an ab initio potential energy surface.
Low energy collisions of CN(X  2Σ+) with He in magnetic ﬁelds
Authors: Feng Eryin , Shao Xi , Yu Chunhua , Sun Chunyan , Huang Wuying
Published: February 2012

A theoretical investigation of the He–CN(2Σ+) complex is presented. We perform ab initio calculations of the interaction potential energy surface and carry out accurate calculations of bound energy levels of the complex including the molecular fine structure. We find the potential has a shallow minimum and supports seven and nine bound levels in complex with 3He and 4He, respectively. Based on the potential the quantum scattering calculation is then implemented for elastic and inelastic cross sections of the magnetically trappable low-field-seeking state of CN(2Σ+) in collision with 3He atom. The cold collision properties and the influence of the external magnetic field as well as the effect of the uncertainty of interaction potential on the collisionally induced Zeeman relaxation are explored and discussed in detail. The ratios of elastic to inelastic cross sections are large over a wide range of collision energy, magnetic field, and scaling factor of the potential, suggesting helium buffer gas loading and cooling of CN in a magnetic trap is a good prospect.

At the request of the authors, this article is being retracted effective 18 May 2012.
Cage occupancies in the high pressure structure H methane hydrate: A neutron diffraction study
Authors: Tulk C. A. , Klug D. D. , dos Santos A. M. , Karotis G. , Guthrie M. , Molaison J. J. , Pradhan N.
Published: February 2012

A neutron diffraction study was performed on the CD4 : D2O structure H clathrate hydrate to refine its CD4 fractional cage occupancies. Samples of ice VII and hexagonal (sH) methane hydrate were produced in a Paris–Edinburgh press and in situ neutron diffraction data collected. The data were analyzed with the Rietveld method and yielded average cage occupancies of 3.1 CD4 molecules in the large 20-hedron (51268) cages of the hydrate unit cell. Each of the pentagonal dodecahedron (512) and 12-hedron (435663) cages in the sH unit cell are occupied with on average 0.89 and 0.90 CD4 molecules, respectively. This experiment avoided the co-formation of Ice VI and sH hydrate, this mixture is more difficult to analyze due to the proclivity of ice VI to form highly textured crystals, and overlapping Bragg peaks of the two phases. These results provide essential information for the refinement of intermolecular potential parameters for the water–methane hydrophobic interaction in clathrate hydrates and related dense structures.
Michaelis-Menten kinetics in shear flow: Similarity solutions for multi-step reactions
Authors: Ristenpart W. D. , Stone H. A.
Published: February 2012

Models for chemical reaction kinetics typically assume well-mixed conditions, in which chemical compositions change in time but are uniform in space. In contrast, many biological and microfluidic systems of interest involve non-uniform flows where gradients in flow velocity dynamically alter the effective reaction volume. Here, we present a theoretical framework for characterizing multi-step reactions that occur when an enzyme or enzymatic substrate is released from a flat solid surface into a linear shear flow. Similarity solutions are developed for situations where the reactions are sufficiently slow compared to a convective time scale, allowing a regular perturbation approach to be employed. For the specific case of Michaelis-Menten reactions, we establish that the transversally averaged concentration of product scales with the distance x downstream as x5/3. We generalize the analysis to n-step reactions, and we discuss the implications for designing new microfluidic kinetic assays to probe the effect of flow on biochemical processes.
Gravity currents in a two-layer stratified ambient: The theory for the steady-state (front condition) and lock-released flows, and experimental confirmations
Authors: Flynn M. R. , Ungarish M. , Tan A. W.
Published: February 2012

We consider the propagation of a gravity current of density ρc at the bottom of a two-layer stratified ambient in a horizontal channel of height H, in the high-Reynolds number Boussinesq domain. The study emphasizes theoretical-analytical modeling, however, experimental and Navier-Stokes simulation data are also presented and their comparison with theory is discussed. The stratification parameters are S = (ρ1 − ρ2)/(ρc − ρ2) where ρ is the fluid density, and φ = h1R/H where h1R is the (unperturbed) ambient interface height. Here, 1 and 2 denote, respectively, the lower and upper layer and c denotes the gravity current. The reduced gravity is defined as g′ = (ρc/ρ2 − 1)g. Rigorous results are obtained for the steady-state analogue of the classical problem of Benjamin [J. Fluid Mech. 31, 209 (1968)]10.1017/S0022112068000133, in which the half-infinite gravity current has thickness h and speed U. We thereby demonstrate that the Froude number \documentclass[12pt]{minimal}\begin{document}${\cal F}= U/(g^{\prime } h)^{1/2}$\end{document}F=U/(g′h)1/2 is a function of a = h/H, S, and φ. In general, two solutions (or modes) may be realized. Issues of energy dissipation, sub- vs. supercriticality with respect to long internal waves and, more generally, the influence of upstream-propagating disturbances are discussed. For a gravity current released from a lock of height h0 and length x0, we derive an approximate shallow-water model and show that the motion is in this case governed by Ξ = H/h0, S, and φ. Although the shallow-water model neglects motion in the ambient layers and ignores the impact of propagation on stratification, the gravity current front speed in the slumping stage is in excellent agreement with measured data. Our theoretical solutions are consistent with previous results (in particular, Holyer and Huppert [J. Fluid Mech. 100, 739 (1980)] and Tan et al. [Environ. Fluid Mech. 11, 203 (2011)]), but have the advantages of being (i) derived without reliance on adjustable constants and ad hoc closures; (ii) applicable to a significantly broader range of dimensionless parameters; and (iii) better assessed by comparison against measured data. The present one-layer shallow-water approximation turns out to be a simple and versatile extension of existing models for homogeneous and linearly stratified ambients, and can be straightforwardly incorporated into the available prediction tools for gravity currents.
Thermal-structural analysis of electron gun with control grid
Authors: Yao Lieming , Zhang Kai , Yu Hailong , Huang Tao , Li Bin
Published: February 2012

Steady state thermal-structural analysis of electron guns is essential due to the requirement of high reliability in beam performance. Temperatures and displacements for all the components of an electron gun with a control grid are computed. Steady-state thermal analysis has been carried out for various cathode temperatures and various intercepted powers on the control grid to determine the temperature of the control grid. These results are verified experimentally based on measured results from an assembled electron gun. Structural analysis of the electron gun is used to evaluate the deformation of the inner electrodes under the hot condition. The results show that the thermal stress slightly changes the characteristics of the gun. The obtained thermal deformation data can be helpful to modify the design dimensions and assembly of an electron gun.
Temperature and humidity effects on superhydrophobicity of nanocomposite coatings
Authors: Han Yeong Yong , Steele Adam , Loth Eric , Bayer Ilker , De Combarieu Guillaume , Lakeman Charles
Published: February 2012

This work investigates temperature and humidity effects on the superhydrophobicity of polyurethane/organoclay nanocomposites. Previous reports of superhydrophobic degradation at decreasing surface temperatures for both low and high humidity were generally conducted in open environments. However, the present setup allows a thermally homogeneous environment, i.e., the temperature of the nanocomposite, air and water droplet are equal with no spatial temperature gradients. In such conditions, results showed stable retention of superhydrophobicity for both low humidity (RH < 20%) cool-down and warm-up cycles (20 °C to −3 °C to 20 °C). Similar performance was also observed for a high humidity (RH > 80%) cool-down cycle, though superhydrophobicity degraded during the warm-up cycle, which was attributed to dew condensation.
Enhanced efficiency of organic light-emitting devices with metallic electrodes by integrating periodically corrugated structure
Authors: Bi Yan-Gang , Feng Jing , Li Yun-Fei , Jin Yu , Liu Yue-Feng , Chen Qi-Dai , Sun Hong-Bo
Published: February 2012

Photons trapped in form of surface-plasmon polariton (SPP) modes associated with the metallic electrode/organic interface results in a large energy loss in organic light-emitting devices (OLEDs). We demonstrate efficient outcoupling of SPP modes from one of two metal electrodes by integrating a periodic wavelength-scale corrugation into the device structure. 30% enhancement in efficiency has been obtained from the corrugated OLEDs with appropriate grating period. The efficient outcoupling of the SPPs has been verified by numerical simulations of both absorption spectra and field distribution.
Epitaxial Cr on n-SrTiO3(001)—An ideal Ohmic contact
Authors: Capan C. , Sun G. Y. , Bowden M. E. , Chambers S. A.
Published: February 2012

Epitaxial Cr metallizations grown on n-SrTiO3(001) by molecular beam epitaxy are shown to result in an ordered interface with Cr bound to O in the terminal TiO2 layer, no reduction of the SrTiO3, and a near-perfect Ohmic contact. Cr/n-SrTiO3(001) thus constitutes an ideal interface between a pure metal and wide gap oxide in which interface redox chemistry does not occur, and the Fermi level remains unpinned.
Mapping the electronic properties of individual graphene grain boundaries
Authors: Tapasztó Levente , Nemes-Incze Péter , Dobrik Gergely , Jae Yoo Kwon , Hwang Chanyong , Biró László P
Published: February 2012

Grain boundaries, the characteristic topological defects of chemical vapor deposition grown graphene samples, are expected to substantially alter the electronic properties of the unperturbed graphene lattice. However, there is very little experimental insight into the underlying mechanisms. Here, we systematically map the electronic properties of individual graphene grain boundaries by scanning tunneling microscopy and spatially resolved tunneling spectroscopy measurements. The tunneling spectroscopy data reveal that the conductivity inside the boundaries is markedly suppressed for both electron and hole-type charge carriers. Furthermore, graphene grain boundaries can give rise to n-type inversion channels within the p-doped graphene sheets, forming p-n junctions with sharp interfaces on the nanometer scale. These properties persist for grain boundaries of various configurations and are robust against structural disorder.
Magnetostructural phase transitions and magnetocaloric effects in MnNiGe1−xAlx
Authors: Samanta Tapas , Dubenko Igor , Quetz Abdiel , Temple Samuel , Stadler Shane , Ali Naushad
Published: February 2012

The thermomagnetic and magnetocaloric properties of the MnNiGe1−xAlx system have been investigated by magnetization and differential scanning calorimetry (DSC) measurements. The presence of first-order magnetostructural transitions (MSTs) from hexagonal ferromagnetic to orthorhombic antiferromagnetic phases has been detected for x = 0.085 and 0.09 at 193 K and 186 K, respectively. The values of latent heat (L = 6.6 J/g) and corresponding total entropy changes (ΔST = 35 J/kg K) have been evaluated for the MST (x = 0.09) from DSC measurements. The magnetic entropy change for x = 0.09 (ΔSM = 17.6 J/kg K for 5 T) was found to be comparable with well-known giant magnetocaloric materials, such as Gd5Si2Ge2, MnFeP0.45As0.55, and Ni50Mn37Sn13.
Beam-scanning planar lens based on graphene
Authors: Ju Xu Hong , Bing Lu Wei , Jiang Yun , Gao Dong Zheng
Published: February 2012

One of the most important advantages of graphene is the capability of dynamically tuning its conductivity by means of chemical doping or gate voltage. Based on this property, we propose a planar gradient index graphene-based lens transforming spherical waves of the transverse-magnetic (TM) surface plasmon polariton (SPP) wave to plane waves of the TM SPP wave with specific beam deflections. Using numerical simulations, it is confirmed that a single-atomic-layered graphene can be a platform for planar gradient-index lens, which can be applied to modulate the propagation of SPP waves.
Experimental generation of a radially polarized beam with controllable spatial coherence
Authors: Wang Fei , Cai Yangjian , Dong Yiming , Korotkova Olga
Published: February 2012

We have experimentally generated a radially polarized (RP) beam with controllable state of spatial coherence by using a rotating ground-glass plate and a radial polarization converter. Furthermore, experimental and theoretical analysis of the focusing properties of a partially coherent RP beam is carried out. Our results show that we can shape the beam profile of the focused RP beam by varying its initial spatial coherence, which is useful for material thermal processing and particle trapping. The experimental results are in complete agreement with the theoretical predictions.
Functionalizing the rear scatterer in a luminescent solar concentrator
Authors: Debije Michael G. , Dekkers Wouter
Published: February 2012

Luminescent solar concentrators (LSCs) are presented that use a rear scattering layer made of a phosphorescent material for improving the use of the incident solar light spectrum. Besides simply scattering incident light that passes through the waveguide proper, the phosphor can absorb blue light and emit this light at a wavelength more amenable to absorption by the fluorescent dye. Integrated emission energies from the LSCs may be increased using the phosphor scatterer 4%–40% depending on the concentration of dye in the waveguide when compared to standard white scatterers.
Factors contributing to the sustainability of alcohol and other drug interventions in Australian community health settings
Authors: MacLean Sarah , Berends Lynda , Mugavin Janette
Published: January 2012

This study identifies factors that support the sustainability of interventions implemented to enhance responses to alcohol and other drug misuse in Australian community health settings. Eight completed projects that had received time-limited funding were sampled to reflect a mix of project types, contexts and success in meeting funding objectives. Projects were investigated using a case study approach involving thematic analysis. Project records were analysed and interviews were conducted with stakeholders to identify intervention elements that continued after funding ceased, and factors that supported this sustainability. Key factors identified were: embedding changes in the operations of the agency; filling a critical gap in the sector; building support from key individuals and agencies; and planning realistically for future ownership. We argue that complexity theory provides a framework to understand both the context-bound nature of intervention sustainability and differences within the literature as to how sustainability is typologised. Each factor associated with intervention sustainability identified in this study reflects an astute understanding of project context and a capacity to adapt. These factors could assist people designing interventions with time-limited funding to maximise ongoing impact of interventions. They should optimally be implemented within an overall approach of flexibility and sensitivity to context.