bluuebunny/crossref_metadata_2025 huggingface dataset:
High‐resolution photoabsorption cross‐section measurements of SO2 at 160 K between 199 and 220 nm
Authors: Rufus J. , Stark G. , Thorne A. P. , Pickering J. C. , Blackwell‐Whitehead R. J. , Blackie D. , Smith Peter L.
Published: June 2009

Photoabsorption cross sections of sulfur dioxide over a range of temperatures are required to interpret observations and to support models of the atmospheres of Io and Venus. We report high‐resolution (λ/Δλ ≈ 450,000) photoabsorption cross‐section measurements by Fourier transform spectrometry of SO2 at 160 K in the wavelength region 199 to 220 nm, which encompasses the strongest features in the prominent 1B2 − 1A1 system. Our results are compared with literature values obtained at lower resolutions and with 295 K cross sections recorded earlier with the same instrument.
Comparison of morphological and biological control of exchange with transient storage zones in a field‐scale flume
Authors: Orr Cailin H. , Clark Jeffery J. , Wilcock Peter R. , Finlay Jacques C. , Doyle Martin W.
Published: June 2009

To determine how differences in geomorphologic setting influence spatial heterogeneity in transport and uptake of limiting nutrients, we investigated reach‐scale interactions between porous bed material textures, bed morphology, transient storage, and nutrient retention in a field‐scale flume (84 m × 2.75 m). Conservative salt tracer and soluble reactive phosphorous additions were used to quantify effects of plane bed and alternate bar morphologies, and clean gravel versus sandy gravel bed texture on reach‐scale nutrient retention and transient storage. We conducted experiments under light and dark conditions to clarify the role of benthic production on surface‐subsurface hydrologic interactions and the relative influence of increasing biomass on nutrient uptake rates. Mean water residence time varied by a factor of 8 across treatments (4–32 min) and transient storage volume varied strongly with sediment texture. The exchange rate coefficient was greatly influenced by presence of alternate channel bars. Phosphorus uptake had the tendency to change with total volume of sediment‐water interaction during dark conditions where periphyton abundance was low. However, under light conditions, periphyton growth clogged bed material pores and essentially eliminated exchange between the surface and subsurface. Uptake then was related to periphyton biomass accumulation rather than hydraulic or geomorphic parameters. The location and mechanism of stream nutrient retention may be more temporally and spatially dynamic than previously realized. Under clean bed conditions in streams (e.g., shaded riffles, streambeds following floods or in winter), nutrient uptake will be hyporheic dominated. Under high periphyton biomass conditions, nutrient uptake will be elevated in the surface sediments, minimal in the hyporheic, and thus benthic dominated.
Global Positioning System and solar radio burst forensics
Authors: Kintner P. M. , O'Hanlon B. , Gary D. E. , Kintner P. M. S.
Published: June 2009

On 6 December 2006, a solar radio burst associated with a class X6 solar flare demonstrated that GPS receiver operation is vulnerable to solar radio burst noise at 1.2 GHz and 1.6 GHz. Within 8 days, two more solar radio bursts confirmed the initial results. These solar radio bursts occurred at solar minimum when they were least expected. Given that measurements of solar radio bursts extend back to at least 1960, why did 40 years pass before anyone realized that solar radio bursts could be so intense or pose a potential threat to the continuous availability of GPS operations? An investigation has been conducted to see if archived solar radio burst data or GPS data could be used to detect intense solar radio bursts. With the exception of the intense solar radio bursts of December 2006, we find that when both GPS data and Radio Solar Telescope Network (RSTN) data are available, they agree within the limits presented by differing reception frequencies and unknown polarization. However, inconsistencies and lapses within the RSTN data set were also discovered, making it unlikely that we will ever know the true number of intense (>150,000 solar flux unit) solar radio bursts that may have occurred during the last 40 years.
Multiple phase screen calculation of wide bandwidth propagation
Authors: Knepp Dennis L. , Nickisch L. J.
Published: June 2009

This paper presents results from a two‐dimensional multiple phase screen (MPS) calculation that computes numerical realizations or sample functions of the electric field after propagation through the ionosphere. The MPS code solves the parabolic wave equation and allows for direct computation of realizations of the received signal. The ionization is represented by a series of random phase screens that characterize the severity and spectrum of the electron density fluctuations. For wide bandwidth signals, the MPS code is exercised for many frequencies over the bandwidth of the propagating signal; Fourier transform techniques are used to obtain the propagating signal in the time domain. The MPS simulation is quite general and may be applied to problems involving numerous, separated, layers of ionization characterized by spatially varying electron density power spectra. MPS techniques can handle all levels of ionospheric disturbances from the least severe, where only small phase fluctuations occur, to the most severe case of frequency selective scintillation. Several examples of propagating signals are presented that simultaneously show the development of the ionospheric transfer function and the impulse response function. The calculations are repeated, and the realizations are averaged to obtain the two‐frequency, two‐position mutual coherence function (MCF), Γ(x, f) and its Fourier transform S(q,τ), the generalized power spectrum. The wide bandwidth MPS results closely match results obtained from strong scatter theory as utilized in the phase screen diffraction method.
Thrust or detachment? Exhumation processes in the Aegean: Insight from a field study on Ios (Cyclades, Greece)
Authors: Huet Benjamin , Labrousse Loïc , Jolivet Laurent
Published: June 2009

Whether back‐arc extension in the Aegean is symmetric or asymmetric at the regional scale is a key question to the understanding of the dynamics of back‐arc extension. New field observations, structural analysis of finite and instantaneous strain, and their relationship with metamorphism on Ios island (Cyclades) lead us to investigate the significance of the South Cycladic Shear Zone (SCSZ). Two successive tectonometamorphic events have been documented in the hanging wall and the footwall of the SCSZ. First, penetrative top‐to‐the‐south shearing is observed in the upper Cycladic Blueschists and the lower Cycladic Basement close to their contact. It is expressed in the hanging wall by shear bands and pressure shadows associated to blueschist facies minerals, contemporaneous with overthrusting of the Cycladic Blueschists over the basement unit. Second, large extensional top‐to‐the‐north shear zones lately crosscut the whole stack. These constraints allow us to reinterpret the kinematics of the Aegean domain during synorogenic and postorogenic periods. When replaced in the reconstructed geometry of the Hellenic Eocene orogenic wedge, the observed top‐to‐the‐south thrusting is coeval with extensional shear zones observed in Syros that could represent the roof of the Cycladic Blueschists. An extrusion structure is then proposed for the exhumation of the Cycladic Blueschists in the subduction zone. Top‐to‐the‐north asymmetric extension together with the Andros‐Tinos‐Mykonos and Paros‐Naxos detachments can be correlated to Oligo‐Miocene extension in the back‐arc domain.
Force measurements between particles and the air‐water interface: Implications for particle mobilization in unsaturated porous media
Authors: Shang Jianying , Flury Markus , Deng Youjun
Published: June 2009

Capillary forces acting at the air‐water interface play an important role in colloid fate and transport in subsurface porous media. We quantified capillary forces between different particles (sphere, cylinder, cube, disk, sheet, and natural mineral particles) and a moving air‐water interface. The particles had different sizes and contact angles (ranging from 14° to 121°). Theoretical calculations using the Young‐Laplace equation were used to support and generalize the experimental data. When the air‐water interface moved over the particles, there were strong capillary forces acting on the particles in the direction of the moving interface. The measured maximum capillary forces were similar to those calculated by the Young‐Laplace equation. The larger the contact angles and the larger the particle size, the stronger were the capillary forces. Particles with irregular shape and sharp edges experienced greater forces than smooth particles. Generalization of the results indicates that capillary forces exerted by a moving air‐water interface can readily exceed attractive Derjaguin‐Landau‐Verwey‐Overbeek (DLVO) and gravity forces for typical subsurface particles, and a moving air‐water interface is therefore an effective mechanism for mobilization of particles in porous media. Particles in the colloidal size range are particularly susceptible for mobilization by a moving air‐water interface.
Does sedimentary 231Pa/230Th from the Bermuda Rise monitor past Atlantic Meridional Overturning Circulation?
Authors: Lippold Jörg , Grützner Jens , Winter Diane , Lahaye Yann , Mangini Augusto , Christl Marcus
Published: June 2009

Ocean circulation may have undergone reductions and reinvigorations in the past closely tied to regional climate changes. Measurements of 231Pa/230Th ratios in a sediment core from the Bermuda Rise have been interpreted as evidence that the Atlantic Meridional Overturning Circulation (AMOC) was weakened or completely eliminated during a period of catastrophic iceberg discharges (Heinrich‐Event 1, H1). Here we present new data from the Bermuda Rise that show further 231Pa/230Th peaks during Heinrich‐2 (H2) and Heinrich‐3 (H3). Additionally, a tight correlation between diatom abundances (biogenic silica) and 231Pa/230Th is discovered in this core. Our results redirect the interpretation of 231Pa/230Th from the Bermuda Rise as a proxy for ocean circulation towards a proxy that reacts highly sensitive to changes of particle composition and water mass properties.
Higher surface mass balance of the Greenland ice sheet revealed by high‐resolution climate modeling
Authors: Ettema Janneke , van den Broeke Michiel R. , van Meijgaard Erik , van de Berg Willem Jan , Bamber Jonathan L. , Box Jason E. , Bales Roger C.
Published: June 2009

High‐resolution (∼11 km) regional climate modeling shows total annual precipitation on the Greenland ice sheet for 1958–2007 to be up to 24% and surface mass balance up to 63% higher than previously thought. The largest differences occur in coastal southeast Greenland, where the much higher resolution facilitates capturing snow accumulation peaks that past five‐fold coarser resolution regional climate models missed. The surface mass balance trend over the full 1958–2007 period reveals the classic pattern expected in a warming climate, with increased snowfall in the interior and enhanced runoff from the marginal ablation zone. In the period 1990–2007, total runoff increased significantly, 3% per year. The absolute increase in runoff is especially pronounced in the southeast, where several outlet glaciers have recently accelerated. This detailed knowledge of Greenland's surface mass balance provides the foundation for estimating and predicting the overall mass balance and freshwater discharge of the ice sheet.
Growing season methyl bromide and methyl chloride fluxes at a sub‐arctic wetland in Sweden
Authors: Hardacre C. J. , Blei E. , Heal M. R.
Published: June 2009

Methyl bromide and methyl chloride fluxes were measured at several sites in a sub‐arctic wetland near Abisko, Sweden (68°28′N 18°49′E) throughout the 2008 growing season. Averaged over 92 flux measurements the sub‐arctic wetland was found to be a small net sink for CH3Br, with mean (±1 sd) uptake of −25 (±20) ng m−2 h−1, but a small net source of CH3Cl with mean emissions of 400 (±1600) ng m−2 h−1. Seasonal trends were observed in both CH3Br and CH3Cl net fluxes, but diurnal trends for CH3Cl only, with peak emissions observed during the afternoon. CH3Cl fluxes differed significantly with hydrological status of measurement locations; however, no other substantial correlations were observed between fluxes and external parameters (air and soil temperature and PAR). This study shows that the single previous estimated sink flux for CH3Cl in tundra globally (derived from measurements in Alaska) requires revision, although not that for CH3Br.
P/CAF rescues the Bhlhe40-mediated repression of MyoD transactivation
Authors: Hsiao Sheng P. , Huang Kai M. , Chang Hsin Y. , Chen Shen L.
Published: June 2009

Previously, we found that MRFs (myogenic regulatory factors) regulated the expression of PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α) by targeting a short region, from nt −49 to +2 adjacent to the transcription initiation site, that contained two E-boxes. However, only the E2-box had significant affinity for MRFs, and the E1-box was predicted to be the target of Bhlhe40 (basic helix-loop-helix family, member e40, also known as Stra13, Bhlhb2, DEC1 and Sharp2), a transcriptional repressor implicated in the regulation of several physiological processes. In the present study, by using EMSA (electrophoresis mobility-shift assay), we confirmed that Bhlhe40 targeted the E1-box and formed a complex with the basic helix-loop-helix transcription factor MyoD (myogenic differentiation factor D) on the PGC-1α core promoter. We demonstrate that Bhlhe40 binds to the promoters of PGC-1α and myogenic genes in vivo and that Bhlhe40 represses the MyoD-mediated transactivation of these promoters. Furthermore, we found that this repression could be relieved by P/CAF (p300/CBP-associated factor) in a dose-dependent manner, but not by CBP [CREB (cAMP-response-element-binding protein)-binding protein]. Bhlhe40 interacted with P/CAF and this interaction disrupted the interaction between P/CAF and MyoD. These results suggest that Bhlhe40 functions as a repressor of MyoD by binding to adjacent E-boxes and sequestering P/CAF from MyoD.
Modulation of the proteolytic activity of the complement protease C1s by polyanions: implications for polyanion-mediated acceleration of interaction between C1s and SERPING1
Authors: Murray-Rust Thomas A. , Kerr Felicity K. , Thomas Adele R. , Wu Tina , Yongqing Tang , Ong Poh Chee , Quinsey Noelene S. , Whisstock James C. , Wagenaar-Bos Ineke C. , Freeman Craig , Pike Robert N.
Published: June 2009

The complement system plays crucial roles in the immune system, but incorrect regulation causes inflammation and targeting of self-tissue, leading to diseases such as systemic lupus erythematosus, rheumatoid arthritis and age-related macular degeneration. In vivo, the initiating complexes of the classical complement and lectin pathways are controlled by SERPING1 [(C1 inhibitor) serpin peptidase inhibitor, clade G, member 1], which inactivates the components C1s and MASP-2 (mannan-binding lectin serine peptidase 2). GAGs (glycosaminoglycan) and DXS (dextran sulfate) are able to significantly accelerate SERPING1-mediated inactivation of C1s, the key effector enzyme of the classical C1 complex, although the mechanism is poorly understood. In the present study we have shown that C1s can bind to DXS and heparin and that these polyanions enhanced C1s proteolytic activity at low concentrations and inhibited it at higher concentrations. The recent determination of the crystal structure of SERPING1 has given rise to the hypothesis that both the serpin (serine protease inhibitor)–polyanion and protease–polyanion interactions might be required to accelerate the association rate of SERPING1 and C1s. To determine what proportion of the acceleration was due to protease–polyanion interactions, a chimaeric mutant of α1-antitrypsin containing the P4–P1 residues from the SERPING1 RCL (reactive-centre loop) was produced. Like SERPING1, this molecule is able to effectively inhibit C1s, but is unable to bind polyanions. DXS exerted a biphasic effect on the association rate of C1s which correlated strongly with the effect of DXS on C1s proteolytic activity. Thus, whereas polyanions are able to bind C1s and modulate its activity, polyanion interactions with SERPING1 must also play a vital role in the mechanism by which these cofactors accelerate the C1s–SERPING1 reaction.
Differential contributions of Glu96, Asp102 and Asp111 to coagulation Factor V/Va metal ion binding and subunit stability
Authors: Song Jina , Talbot Kimberley , Hewitt Jeffrey , MacGillivray Ross T. A. , Pryzdial Edward L. G.
Published: June 2009

Blood coagulation FV (Factor V) is activated by thrombin-mediated excision of the B domain, resulting in a non-covalent heterodimer, FVa (activated FV). Previous studies implicated Glu96, Asp102 and Asp111 in the essential Ca2+-dependent FVa subunit interaction. In the present study, FV E96A, D102A and D111A were purified and evaluated for function, subunit dissociation and metal ion binding. Chromogenic and clotting assays in the presence of procoagulant vesicles showed that each variant was inhibited (∼20–40%). D111A was further inhibited (>90%) after cleavage by thrombin. Comparable function was observed on activated platelets. D111A inhibition correlated to spontaneous subunit dissociation and severely impaired Ca2+ binding. The Cu2+ interaction was also inhibited, suggesting interdependent Ca2+ and Cu2+ binding to FV. The parental FV (FV-810; wild-type human FV missing residues 811–1491) used here is fully active without proteolysis because the B domain is truncated. Therefore, a FVa-like functional configuration exists for intact D111A independent of normal metal ion interactions. Unlike D111A, the thrombin-mediated FVa derived from E96A and D102A had only moderately enhanced subunit dissociation upon chelation and had normal metal ion binding. For FV-810-, E96A- and D102A-derived FVa, loss of function after chelation significantly preceded subunit dissociation. This study defines the highly conserved segment spanning Glu96–Asp111 in FV as multifunctional. Of the three amino acids evaluated, Asp111 is essential and probably functions through direct and indirect effects on Ca2+ and Cu2+ interactions. Glu96 and Asp102 individually influence FV/FVa by more subtle effects, possibly at the metal ion-dependent subunit interface.
Directional light emission through a metallic nanostructure
Authors: Zhang Yongliang , Zhao Deyin , Zhou Chuanhong , Jiang Xunya
Published: June 2009

In this paper, we numerically investigate the highly directional beaming effect when a transverse magnetic plane wave passes through a metallic slit-bumps nanostructure by using the finite difference time domain method. We find that the narrow bump with width w∼0.1λspp can serve as a good light emitter and two arrays of narrow bumps with suitable separation can diffract the surface plasmons into highly directional collimated beams. The number and the direction of the beams can be controlled by adjusting the geometry parameters of the nanostructure. The structure with optimized parameters has practical applications as directional surface plasmon polaritons couplers in integrated photonic devices.
X-ray spectroscopy of buried layer foils irradiated at laser intensities in excess of 1020 W/cm2
Authors: Chen S. N. , Patel P. K. , Chung H.-K. , Kemp A. J. , Le Pape S. , Maddox B. R. , Wilks S. C. , Stephens R. B. , Beg F. N.
Published: June 2009

Observations of a rapid decrease in thermal temperature as a function of depth of solid targets irradiated with a short pulse, ultrahigh-intensity laser are reported. This phenomenon is investigated using the Titan short pulse laser with intensities greater than 1020 W/cm2 interacting with buried layer targets. The longitudinal temperature profile is determined by measuring K-shell spectra from a 0.4 μm copper tracer layer placed at various depths (i.e., 0–1.5 μm) within the 2.4 μm thick target. It is observed that the line ratios (He-like K-shell lines) as a function of temperature require a consideration of at least three parameters to analyze the K-shell spectra: hot electron population, time-dependent plasma conditions, and opacity. Here, the study of the effect of these three parameters on measured spectra in the short pulse high intensity laser-matter interactions using the atomic model FLYCHK [H.-K. Chung et al., High Energy Density Phys. 1, 3 (2005)] is presented.
High-speed electroluminescence modulation of a conjugated-polymer light emitting diode
Authors: Barlow Iain A. , Kreouzis Theo , Lidzey David G.
Published: June 2009

To maximize the electroluminescence (EL) switching rate that can be generated in an organic-based light emitting diode, we fabricated a device having an active area of 0.018 mm2 which is based on a 1:1 blend of the high charge-carrier mobility conjugated polymers poly[dioctylfluoreneco-N-(4-butylphenyl) diphenylamine] and poly[9,9′-dioctylfluorene-co-benzothiadiazole]. Our devices have a 50% cutoff frequency of 26 MHz and a maximum EL modulation rate of 63 MHz at a drive voltage of 3.8 V. Such switching rates are suitable for short-range video transmission via plastic optical fibers, suggesting possible applications as optical communication light sources.
The initial and final states of electron and energy transfer processes: Diabatization as motivated by system-solvent interactions
Authors: Subotnik Joseph E. , Cave Robert J. , Steele Ryan P. , Shenvi Neil
Published: June 2009

For a system which undergoes electron or energy transfer in a polar solvent, we define the diabatic states to be the initial and final states of the system, before and after the nonequilibrium transfer process. We consider two models for the system-solvent interactions: A solvent which is linearly polarized in space and a solvent which responds linearly to the system. From these models, we derive two new schemes for obtaining diabatic states from ab initio calculations of the isolated system in the absence of solvent. These algorithms resemble standard approaches for orbital localization, namely, the Boys and Edmiston–Ruedenberg (ER) formalisms. We show that Boys localization is appropriate for describing electron transfer [Subotnik et al., J. Chem. Phys. 129, 244101 (2008)] while ER describes both electron and energy transfer. Neither the Boys nor the ER methods require definitions of donor or acceptor fragments and both are computationally inexpensive. We investigate one chemical example, the case of oligomethylphenyl-3, and we provide attachment/detachment plots whereby the ER diabatic states are seen to have localized electron-hole pairs.
A reanalysis of the Ã A1″−X̃ A1′ transition of CFBr
Authors: Truscott Benjamin S. , Elliott Nicola L. , Western Colin M.
Published: June 2009

The laser induced fluorescence spectrum of the Ã A1″−X̃ A1′ transition of CFBr is presented, with selected bands recorded at sub-Doppler resolution, allowing the rotational constants to be fully determined. Analysis of dispersed fluorescence spectra and the pattern of B79r/B81r isotope splittings indicate that the origin must be shifted from previous assignments in the literature to 23 271.0 cm−1. This implies that only the lowest four vibrational levels in the Ã state have significant quantum yields for fluorescence, with all other levels strongly predissociated. Comparison with photofragment measurements implies that the Ã state is metastable, with a barrier to dissociation of ∼1000 cm−1.
Langevin thermostat for rigid body dynamics
Authors: Davidchack Ruslan L. , Handel Richard , Tretyakov M. V.
Published: June 2009

We present a new method for isothermal rigid body simulations using the quaternion representation and Langevin dynamics. It can be combined with the traditional Langevin or gradient (Brownian) dynamics for the translational degrees of freedom to correctly sample the canonical distribution in a simulation of rigid molecules. We propose simple, quasisymplectic second-order numerical integrators and test their performance on the TIP4P model of water. We also investigate the optimal choice of thermostat parameters.
Large amplitude double layers in a positively charged dusty plasma with nonthermal electrons
Authors: Djebli M. , Marif H.
Published: June 2009

A pseudopotential approach is used to investigate large amplitude dust-acoustic solitary structures for a plasma composed of positively charged dust, cold electrons, and nonthermal hot electrons. Numerical investigation for an adiabatic situation is conducted to examine the existence region of the wave. The negative potential of the double layers is found to be dependent on nonthermal parameters, Mach number, and electrons temperature. A range of the nonthermal parameters values exists for which two possible double layers for the same plasma mix at different Mach numbers and with significant different amplitudes. The present model is used to investigate localized structures in the lower-altitude Earth’s ionosphere.
Accurate noncontact calibration of colloidal probe sensitivities in atomic force microscopy
Authors: Chung Koo-Hyun , Shaw Gordon A. , Pratt Jon R.
Published: June 2009

The absolute force sensitivities of colloidal probes comprised of atomic force microscope, or AFM, cantilevers with microspheres attached to their distal ends are measured. The force sensitivities are calibrated through reference to accurate electrostatic forces, the realizations of which are described in detail. Furthermore, the absolute accuracy of a common AFM force calibration scheme, known as the thermal noise method, is evaluated. It is demonstrated that the thermal noise method can be applied with great success to colloidal probe calibration in air and in liquid to yield force measurements with relative standard uncertainties below 5%. Techniques to combine the electrostatics-based determination of the AFM force sensitivity with measurements of the colloidal probe’s thermal noise spectrum to compute noncontact estimates of the displacement sensitivity and spring constant are also developed.
Composition dependence of glass transition temperature and fragility. II. A topological model of alkali borate liquids
Authors: Mauro John C. , Gupta Prabhat K. , Loucks Roger J.
Published: June 2009

Glass transition temperature and fragility are two important properties derived from the temperature dependence of the shear viscosity of glass-forming melts. While direct calculation of these properties from atomistic simulations is currently infeasible, we have developed a new topological modeling approach that enables accurate prediction of the scaling of both glass transition temperature and fragility with composition. A key feature of our approach is the incorporation of temperature-dependent constraints that become rigid as a liquid is cooled. Using this approach, we derive analytical expressions for the composition (x) dependence of glass transition temperature, Tg(x), and fragility, m(x), in binary alkali borate systems. Results for sodium borate and lithium borate systems are in agreement with published values of Tg(x) and m(x). Our modeling approach reveals a natural explanation for the presence of the constant Tg regime observed in alkali borate systems.
Generalized expression for polarization density
Authors: Wang Lu , Hahm T. S.
Published: June 2009

A general polarization density which consists of classical and neoclassical parts is systematically derived via modern gyrokinetics and bounce kinetics by employing a phase-space Lagrangian Lie-transform perturbation method. The origins of polarization density are further elucidated. Extending the work on neoclassical polarization for long wavelength compared to ion banana width [M. N. Rosenbluth and F. L. Hinton, Phys. Rev. Lett. 80, 724 (1998)], an analytical formula for the generalized neoclassical polarization including both finite-banana-width and finite-Larmor-radius effects for arbitrary radial wavelength in comparison to banana width and gyroradius is derived. In additional to the contribution from trapped particles, the contribution of passing particles to the neoclassical polarization is also explicitly calculated. The generalized analytic expression agrees very well with the previous numerical results for a wide range of radial wavelength.
Approaching the Hartree–Fock limit by perturbative methods
Authors: Deng Jia , Gilbert Andrew T. B. , Gill Peter M. W.
Published: June 2009

We describe perturbative methods for improving finite-basis Hartree–Fock calculations toward the complete-basis limit. The best method appears to offer quadratic error reduction and preliminary numerical applications demonstrate that remarkably accurate Hartree–Fock energies can be obtained.
Mirror instability in space plasmas: Solitons and cnoidal waves
Authors: Istomin Ya. N. , Pokhotelov O. A. , Balikhin M. A.
Published: June 2009

The nonlinear theory of magnetic mirror instability (MI) in space plasmas is revisited. The nonlinear dynamics of the MI is analyzed using the perpendicular plasma pressure balance condition and the drift kinetic equation for the ion distribution function as the starting point. In contrast with previous studies we do not rely on the reductive perturbation method and kinetic effects have been included in the model at all stages. It is shown that the MI initially produces a depression in the magnetic field that has an explosive behavior as was predicted previously. However, this process rapidly terminates and reaches finally saturation with the formation of stationary solutions in the form of either soliton type magnetic holes, cnoidal waves, or linear oscillations.
A hybrid solid-liquid polymer photodiode for the bioenvironment
Authors: Antognazza M. R. , Ghezzi D. , Musitelli D. , Garbugli M. , Lanzani G.
Published: June 2009

We demonstrate that a prototypical semiconducting polymer, poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) maintains unaltered its optoelectronic properties throughout the various steps for neural preparation. Films of MEH-PPV, after prolonged immersion in water or buffer solution, are characterized by linear and nonlinear optical spectroscopy. Based on this result, we introduce a hybrid solid-liquid photodiode based on MEH-PPV, in which we use culturing media as liquid, ionic cathodes. The hybrid device is proposed as an active interface between living tissue and conducting polymers for cell diagnostic and neural implants.
Synergetic pyrolysis of high density polyethylene and Jatropha and Karanj cakes: A thermogravimetric study
Authors: Parekh Dharmendra B. , Rotliwala Yogesh C. , Parikh Parimal A.
Published: June 2009

Coprocessing behavior of mixtures of high density polyethylene (HDPE) and deoiled cakes of Jatropha and Karanja was studied by thermogravimetric analyses under dynamic conditions in the presence of nitrogen atmosphere and compared with those of individual materials. Experiments were carried out in the temperature range of ambient temperature to 900 °C at two heating rates (5 and 20 °C/min). Kinetic studies indicated activation energies for HDPE decomposition to be 235 and 258 kJ/mol at heating rates of 5 and 20 °C/min, respectively. Values of activation energy for pyrolysis of cakes of Jatropha and Karanj and those for cake-HDPE mixtures varied with the rate of heating as well as with the three temperature ranges. This variation has been explained based on the materials’ decomposition behavior. Reduction in activation energy for decomposition of the mixtures implies synergetic effects to be existing when two materials are coprocessed together.
Pairwise interactions between deformable drops in free shear at finite inertia
Authors: Olapade Peter Ojo , Singh Rajesh Kumar , Sarkar Kausik
Published: June 2009

Interactions between a pair of equal-size viscous drops in shear are numerically investigated at finite Reynolds number (Re=0.1–10). At low Reynolds number the simulation compares well with a previous experimental observation. Apart from the usual pairwise motion where drops driven by shear pass over each other (type I trajectory), finite inertia introduces a new type (type II) of reversed trajectory where drops approaching each other reverse their initial trajectories. The new trajectory is explained by a reversed streamline pattern observed around a single drop in an imposed shear, and is similar to what is also observed for rigid spheres at finite inertia. However, drop deformability introduces a nonuniform transition from one to the other type of trajectory—drops display type I trajectory for high and low capillary numbers and type II for intermediate capillary numbers. The phenomenon is explained by noting that increasing capillary number gives rise to competing effects—while it increases drop deformation and therefore increases resistance to sliding motion, it also increases drop flexibility, decreases inclination angle, and overall effect of the drop’s presence is reduced, all helping them to slide by. The nonuniform behavior—type II trajectory for an intermediate range of capillary numbers—occurs only at Reynolds number above a critical value. Further increase in Reynolds number increases the range of capillary numbers for type II trajectory. For type I trajectory, terminal cross-stream separation increases linearly with increasing inertia indicating an enhanced shear induced diffusion. Increasing initial streamwise separation aids in reversed (type II) trajectory due to increased overlap with the reversed streamline zone. Increasing cross-stream distance expectedly facilitates (type I) sliding motion. For passing drops (type I trajectory), terminal cross-stream separation is not appreciably affected by capillary number and initial drop separation.
The impact of hydration water on the dynamics of side chains of hydrophobic peptides: From dry powder to highly concentrated solutions
Authors: Russo Daniela , Teixeira José , Ollivier Jacques
Published: June 2009

Elastic and quasielastic neutron scattering experiments are used to investigate the dynamics of side chains in proteins, using hydrophobic peptides, from dry and hydrated powders up to solutions, as models. The changes of the internal dynamics of a prototypical hydrophobic amino acid, N-acetyl-leucine-methylamide, and alanine amino acids are investigated as a function of water/peptide molecular ratio. While previous results have shown that, in concentrated solution, when the hydrophobic side chains are hydrated by a single hydration water layer, the only allowed motions are confined and can be attributed to librational/rotational movements associated with the methyl groups. In the present work we observe a dynamical evolution from dry to highly hydrated powder. We also observe rotational and diffusive motions and a dynamical transition at ∼250 K for long side chain peptides while for peptides with short side chains, there is no dynamical transition but only rotational motions. With a local measurement of the influence of hydration water dynamics on the amino acid side chains dynamics, we provide unique experimental evidence that the structural and dynamical properties of interfacial water strongly influence the side chain dynamics and the activation of diffusive motions. We also emphasize that the side chain length has a role on the onset of dynamical transition.
Low temperature hydrogen desorption in MgAl thin films achieved by using a nanoscale Ta/Pd bilayer catalyst
Authors: Fritzsche Helmut , Ophus Colin , Harrower Chris T. , Luber Erik , Mitlin David
Published: June 2009

We used a nanoscale (5 nm Ta/5 nm Pd) bilayer catalyst to achieve remarkable desorption kinetics for thin films. Full hydrogen desorption occurred at 100 °C with a noticeable desorption even at room temperature. This is a significant improvement relative to the 175 °C needed to fully desorb an identical film with a single Pd layer acting as the catalyst. Neutron reflectometry confirmed that the Ta/Pd bilayer remained intact both after hydrogen absorption and following the hydrogen desorption. We used x-ray diffraction analysis to gather complementary information regarding the crystal structure of the as-synthesized, sorbed and desorbed film.
Magnetic properties of a dc metamaterial consisting of parallel square superconducting thin plates
Authors: Navau Carles , Chen Du-Xing , Sanchez Alvaro , Del-Valle Nuria
Published: June 2009

Cloaking a static magnetic field is becoming a real possibility after the recently proposed concept of dc metamaterials. Here, we present, by a model based on superconductivity first principles, accurate and systematic calculations for the susceptibility of a dc metamaterial consisting of parallel square superconducting thin plates. Since both magnetic and kinetic energies are considered, our model takes into account the effect of a penetration depth in the superconductors and therefore can be applied for high-temperature superconductors. Thus, from the calculated results, a device that can cloak a static magnetic field may be constructed based on high-temperature superconducting thin films.
Efficient semitransparent inverted organic solar cells with indium tin oxide top electrode
Authors: Schmidt H. , Flügge H. , Winkler T. , Bülow T. , Riedl T. , Kowalsky W.
Published: June 2009

We reported on highly efficient semitransparent polymer solar cells comprising a transparent sputtered indium tin oxide (ITO) top electrode. We used an inverted cell structure with titanium dioxide prepared by atomic layer deposition as electron selective layer and molybdenum oxide (MoO3) as hole extraction layer. Moreover, the MoO3 layer prevents damage to the organic active materials due to the ITO sputtering process. For the semitransparent device, power conversion efficiencies of 1.9% were achieved with a high transmittance of 80% in the red region of the visible spectrum.
Flexible organic thin film transistors with self-assembled benzimidazole-copper complex as gate insulator
Authors: Chen S. W. , Wang C. H. , Hwang J.
Published: June 2009

A self-assembled benzimidazole-copper complex (SABCC) is utilized as the gate insulating material for pentacene organic thin film transistors (OTFTs) fabricated on a flexible polyethylene terephthalate plastic substrate. The fabrication features of SABCC are self-assembling, water-based processing, and selectivity of deposition. The pentacene OTFTs exhibit reasonable device characteristics. Threshold voltage, carrier mobility, on/off current ratio, and subthreshold swing are determined to be ∼−4.2 V, ∼0.08 cm2 V−1 s−1, ∼4×103, and ∼4.4 V/decade, respectively. The water-based fabrication process of the SABCC gate insulator on copper electrodes may provide an opportunity for low cost OTFTs on flexible plastic substrates.
Petschek-like reconnection with uniform resistivity
Authors: Baty H. , Priest E. R. , Forbes T. G.
Published: June 2009

Using two-dimensional time dependent viscoresistive magnetohydrodynamic simulations, we report for the first time the existence of fast stationary magnetic reconnection with a spatially uniform plasma resistivity. This is achieved through the use of a nonuniform well tailored viscosity profile, following requirements deduced by Baty et al. [Phys. Plasmas 16, 012102 (2009)]. The quasisteady state exhibits the global features of a classical Petschek solution, with two pairs of standing slow-mode shocks attached to a central diffusion region and a fast-mode expansion of the inflowing plasma. The diffusion region is however influenced by the viscosity with a two-component structure, and the reconnection rate is observed to be slightly higher than nonviscous nonuniform resistive reconnection.
Negative thermal expansion of ReO3 in the extended temperature range
Authors: Chatterji Tapan , Hansen Thomas C. , Brunelli Michela , Henry Paul F.
Published: June 2009

We reported previously [T. Chatterji et al., Phys. Rev. B 78, 134105 (2008)] negative thermal expansion (NTE) in ReO3 in the limited temperature range from 2 to 220 K. Here we discovered NTE in ReO3 at higher-temperature region from 600 to 680 K. We determined the temperature variation in the lattice parameter and the unit cell volume of ReO3 by neutron diffraction. The temperature variation in the lattice parameter and the unit cell volume show two regions of NTE and two minima. We attribute the NTE of ReO3 to be the result of anharmonicity and anomalous softening of M3 phonon mode.
Cascade emissions of an erbium-ytterbium doped silica-zirconia nanostructured optical fiber under supercontinuum irradiation
Authors: Brasse Gurvan , Restoin Christine , Auguste Jean-Louis , Blondy Jean-Marc
Published: June 2009

An erbium-ytterbium doped silica-zirconia nanostructured optical fiber is elaborated by using the chemical sol-gel method and its waveguiding properties are studied. A supercontinuum irradiation of the so-fabricated fiber leads to an exotic cascade emission of photons at 515 and 640 nm, as well as a wide emission band between 530 and 590 nm. Upconversion mechanisms and downconversion mechanisms are finally highlighted to explain these phenomena.
Low-resistance smooth-surface Ti/Al/Cr/Mo/Au n-type Ohmic contact to AlGaN/GaN heterostructures
Authors: Lan Yung-Ling , Lin Hung-Cheng , Liu Hsueh-Hsing , Lee Geng-Yen , Ren Fan , Pearton Stephen J. , Chang Mao-Nan , Chyi Jen-Inn
Published: June 2009

A comparative study of the specific contact resistivity and surface morphology of Ti/Al/Ni/Au, Ti/Cr/Mo/Au, and Ti/Al/Cr/Mo/Au metal contact stacks on AlGaN/GaN heterostructures is reported. Compared to the conventional Ti/Al/Ni/Au contact, the Ti/Al/Cr/Mo/Au contact has much smoother surface and achieves minimum specific contact resistivity of 1.1×10−6 Ω cm2. This contact maintains its low contact resistivity after storage at 200 °C for 100 h in N2. The robustness of this contact is attributed to the Cr and Mo layers, which suppress the formation of Al–Au alloys in the contact stack.
Charge pumping method for photosensor application by using amorphous indium-zinc oxide thin film transistors
Authors: Liu Po-Tsun , Chou Yi-Teh , Teng Li-Feng
Published: June 2009

The study investigated the photoreaction behavior of amorphous indium-zinc oxide thin film transistor (a-IZO TFT), which was thought to be insensitive to visible light. The obvious threshold voltage shift was observed after light illumination, and it exhibited slow recovery while returning to initial status. The photoreaction mechanism is well explained by the dynamic equilibrium of charge exchange reaction between O2(g) and O2− in a-IZO layer. A charge pumping technique is used to confirm the mechanism and accelerate recoverability. Using knowledge of photoreaction behavior, an operation scheme of photosensing elements consist of a-IZO TFT is also demonstrated in this work.
Concurrent Validity of the PSYCH-6, a Very Short Scale for Detecting Anxiety and Depression, Among Oncology Outpatients
Authors: Clover Kerrie , Leigh Carter Gregory , Adams Catherine , Hickie Ian , Davenport Tracey
Published: June 2009

Objective: To improve the acceptability of screening for depression and anxiety among patients with cancer there is a need for scales that are both very short and accurate. To date no very short questionnaire has been found to provide optimal performance for screening in oncology populations and other candidates must be examined. This study examined the concurrent validity of a relatively new, very short scale, the six item PSYCH-6 subscale of the Somatic and Psychological Health Report (SPHERE-12), in an oncology outpatient population.

Methods: Cross-sectional survey of 340 oncology outpatients attending a regional hospital in Newcastle, Australia. The performance of the PSYCH-6 against the Hospital Anxiety and Depression Scale (HADS) was evaluated using correlation, Cohen's kappa, positive agreement and negative agreement.

Results: The PSYCH-6 subscale of the SPHERE-12, at a cut-off point of 3, had substantial agreement with the total score of the HADS (HADS-T; κ = 0.73, p < 0.001). Negative agreement (0.92) was marginally higher than positive agreement (0.80).

Conclusions: The PSYCH-6 scale of the SPHERE-12 at a cut-off point of 3 is an equivalent instrument to the HADS-T for detecting cases and excluding non-cases of anxiety and depression and is suitable for deployment in oncology populations.
Psychological Distress and its Correlates in Chinese Adolescents
Authors: Huang Jun Ping , Xia Wei , Sun Cai Hong , Zhang Hui Ying , Wu Li Jie
Published: June 2009

Objectives: The aim of the present study was to estimate the prevalence of severe psychological distress in Chinese adolescents, and to identify the demographic and psychosocial factors associated with psychological distress in this population.

Method: A multi-stage stratified sampling procedure was used to select a sample of adolescents (n = 3109) in Heilongjiang Province (Northeast of China), who were aged 13–18 years old. Psychological distress was measured by the Kessler Psychological Distress Scale (K10). A K10 score between 22 and 30 was defined as moderate psychological distress; a score of ≥ 31 was defined as severe psychological distress in this study.

Results: The rates of moderate and severe psychological distress were 27.9% and 12.2%, respectively in the participants. There were no statistical differences in severe psychological distress by gender. Multivariate analysis showed that family environmental variables, schooling variables, self-perception with life and appearance, perceived health and negative life events were significantly associated with psychological distress.

Conclusion: Severe psychological distress is prevalent in the Chinese adolescent population. Family dysfunction, higher academic pressure, poor relationship with others and negative self-perception are important risk factors associated with psychological distress in adolescents. More studies using the K10 scale are needed so that national and international comparisons can be made.
Epidemiology of Intentional Self-Harm Presenting to Four District Health Boards in New Zealand Over 12 Months, and Comparison with Official Data
Authors: Hatcher Simon , Sharon Cynthia , Collins Nicola
Published: June 2009

Objective: The aim of the present study was to describe the number and characteristics of people presenting with intentional self-harm to four district health boards in New Zealand and to compare this with official data.

Methods: People presenting with self-harm were identified by searching a mixture of electronic and written databases in each DHB.

Results: Over 12 months 1633 people presented a total of 2087 times to these four DHBs. The highest rates were in Northland, young women and Maori. Official figures significantly underestimate the number of people who present to hospital with intentional self-harm.

Conclusion: Considerably more people present to hospital with intentional self-harm in New Zealand than are recorded by official figures. This is important because reducing self-harm is a key part of the New Zealand health strategy. To achieve this, accurate measurement of self-harm rates is required. Encouraging improved reporting by DHBs is unlikely to work. It is suggested that dedicated monitoring sites be set up in representative DHBs to solve the problem of flawed official data collection.