bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristic temperatures of exchange biased systems
Authors: Dobrynin A. N. , Prozorov R.
Published: August 2007

Characteristic temperatures in ferromagnetic-antiferromagnetic exchange biased systems are analyzed. In addition to usual blocking temperature of exchange bias, TB, and the Néel temperature of an antiferromagnet, TN, the inducing temperature of exchange bias, Tind, has been recently proposed. Tind is the temperature at which the direction of exchange anisotropy is established. We demonstrate that this temperature is, in general, different from TB and TN. Measurements of Tind, in addition to TB and TN, provide important information about exchange interactions in ferromagnetic-antiferromagnetic heterostructures.
Relaxation and dephasing of the intersubband transitions in n-type InAs∕AlSb multi quantum wells
Authors: Menzel S. , Zibik E. A. , Revin D. G. , Cockburn J. W. , Devenson J. , Teissier R. , Baranov A. N.
Published: August 2007

Intersubband electron relaxation and dephasing has been studied in InAs∕AlSb multi quantum wells using time resolved femtosecond spectroscopy. The authors have measured a relaxation time T1 of 3ps at T=300K (and 4.6ps at T=10K) for a transition energy of 260meV, which is in good agreement with our calculations. A dephasing time T2 of ∼320fs for optically excited electrons in the second subband was measured which determines the homogeneous broadening (∼4.1meV) of the absorption line.
Effect of GaP strain compensation layers on rapid thermally annealed InGaAs∕GaAs quantum dot infrared photodetectors grown by metal-organic chemical-vapor deposition
Authors: Fu L. , McKerracher I. , Tan H. H. , Jagadish C. , Vukmirović N. , Harrison P.
Published: August 2007

The effect of GaP strain compensation layers was investigated on ten-layer InGaAs∕GaAs quantum dot infrared photodetectors (QDIPs) grown by metal-organic chemical-vapor deposition. Compared with the normal QDIP structure, the insertion of GaP has led to a narrowed spectral linewidth and slightly improved detector performance. A more significant influence of GaP was observed after the structure was annealed at various temperatures. While a similar amount of wavelength tuning was obtained, the GaP QDIPs exhibited much less degradation in device characteristics with increasing annealing temperature.
High tunability of lead strontium titanate thin films using a conductive LaNiO3 as electrodes
Authors: Jain M. , Karan N. K. , Yoon J. , Wang H. , Usov I. , Katiyar R. S. , Bhalla A. S. , Jia Q. X.
Published: August 2007

Highly tunable films of dielectric PbxSr1−xTiO3 (with x=0.3 and 0.4) have been deposited on conductive LaNiO3 coated LaAlO3 substrates using a sol-gel technique. The processing condition was found to greatly influence the microstructure as well as the dielectric and electrical properties of the films. At room temperature, dielectric tunability values as high as 70% and 78.6% at an applied electric field of 223kV∕cm were achieved for the Pb0.3Sr0.7TiO3 and Pb0.4Sr0.6TiO3 films, respectively.
Strip-shaped samples in a microwave Corbino spectrometer
Authors: Scheffler Marc , Kilic Serife , Dressel Martin
Published: August 2007

The Corbino geometry, where a flat sample is pressed against an open end of a coaxial cable, is an established probe layout for broadband microwave spectroscopy. Here we show that besides the conventional case of the sample covering the complete Corbino probe, also strip-shaped samples can be studied with a Corbino spectrometer. This increases the sensitivity for highly conductive samples and furthermore opens the route for the study of anisotropic materials.
Inherent nanoscale structural instabilities near morphotropic boundaries in ferroelectric solid solutions
Authors: Rossetti George A. , Khachaturyan Armen G.
Published: August 2007

The special structural properties of ferroelectric solid solutions near morphotropic phase boundaries are explained on thermodynamic grounds. The authors show that vanishing of the orientational anisotropy in the simplest 2-4-6 Landau polynomial is sufficient to produce the appearance of a morphotropic boundary (MB) separating rhombohedral and tetragonal phases. Under this condition the polarization vector becomes unstable against rotation, resulting in a drastic decrease in domain wall energy and the formation of mixed nanodomains having a diffraction domain-averaged structure that may mimic diffraction from lower-symmetry monoclinic phases. The theory automatically predicts tricritical points on the line of paraelectric to ferroelectric transitions and continuity of thermodynamic properties across the MB.
Whispering gallery resonances in semiconductor micropillars
Authors: Astratov V. N. , Yang S. , Lam S. , Jones B. D. , Sanvitto D. , Whittaker D. M. , Fox A. M. , Skolnick M. S. , Tahraoui A. , Fry P. W. , Hopkinson M.
Published: August 2007

In this letter, the authors observe high quality (Q up to 20 000) whispering gallery modes (WGMs) with small modal volumes V∼0.3μm3 in 4–5μm Al(Ga)As∕GaAs micropillars by employing an experimental geometry in which both excitation and collection of emission are in a direction normal to the sidewalls of the pillars. They show that WGMs provide at least two times larger values of the figure of merit for strong coupling applications Q∕V compared to “photonic dot” states in pillars with comparable size.
Variable temperature Raman microscopy as a nanometrology tool for graphene layers and graphene-based devices
Authors: Calizo I. , Miao F. , Bao W. , Lau C. N. , Balandin A. A.
Published: August 2007

Raman microscopy of graphene was carried out over the temperature range from 83to373K. The number of layers was independently confirmed by the quantum Hall measurements and atomic force microscopy. The values of the temperature coefficients for the G and 2D-band frequencies extracted from Raman spectra of the single-layer graphene are −(1.6±0.2)×10−2cm−1∕K and −(3.4±0.4)×10−2cm−1∕K, respectively. The G peak temperature coefficients of the bilayer graphene and bulk graphite are −(1.5±0.06)×10−2cm−1∕K and −(1.1±0.04)×10−2cm−1∕K, respectively. The results are important for the application of Raman microscopy as a nanometrology tool for the graphene-based devices operating at various temperatures.
Supersymmetry and Lie groups
Authors: Trzetrzelewski Maciej
Published: August 2007

We construct all vacuum states of N=2 supersymmetric Yang-Mills quantum mechanics [for SU(N) group] and discuss their origin from the SU(N) real cohomology.
Demonstration of critical coupling in microfiber loops wrapped around a copper rod
Authors: Guo Xin , Li Yuhang , Jiang Xiaoshun , Tong Limin
Published: August 2007

The authors demonstrate critical coupling condition in microfiber loops wrapped around a copper rod. The critical coupling condition is achieved by tuning the coupling coefficient to balance the circulation loss. A maximum extinction of 30dB has been obtained around the critical coupling point with a quality factor of about 4000. The resonance wavelength can be tuned by applying an electric current through the copper rod. The copper rod, usually deemed as a high-loss medium for handling light at optical frequency, serves as a low-index robust support for achieving critical coupling in the microfiber loops with acceptable loss.
Self-seeded growth and ultraviolet photoresponse properties of ZnO nanowire arrays
Authors: Ghosh R. , Dutta M. , Basak D.
Published: August 2007

The authors report on the self-seeded growth of ZnO nanowire (NW) arrays on glass substrates by a simple solvothermal method using two different sol concentrations for the seed layer formation. The formations of hexagonal-shaped NWs with diameter of 20–60nm on the seed layer for 0.1M sol and mostly of trapezoidal-shaped NWs with base width of 135nm on the seed layer for 0.03M sol have been explained considering the longitudinal and transversal growths of ZnO NWs. The photocurrent behavior of ZnO NW arrays in air as well as in vacuum is analyzed in terms of adsorbed oxygen and water molecules.
Effect of nitric oxide on gain and output power of a non-self-sustained electric discharge pumped oxygen-iodine laser
Authors: Hicks A. , Bruzzese J. , Lempert W. R. , Rich J. W. , Adamovich I. V.
Published: August 2007

This letter discusses the effect of nitric oxide on gain and output power of a pulser-sustainer discharge excited oxygen iodine laser. Adding small amounts of NO to the laser mixture (a few hundreds of ppm) considerably increases gain and output power due to (i) O atom titration and resultant slower I* atom quenching and (ii) improved stability of the dc sustainer discharge, which allows stable operation at significantly higher discharge powers. Gain on the 1315nm iodine atom transition and laser power in the M=3 transverse laser cavity are 0.049%∕cm and 1.24W, at a flow temperature of T=100K.
High efficient and low color-temperature white light-emitting diodes with Tb3Al5O12:Ce3+ phosphor
Authors: Chen Yibo , Gong Menglian , Wang Gang , Su Qiang
Published: August 2007

High efficient Tb3Al5O12:Ce3+ (TAG:Ce3+) phosphors were prepared in a solid-state reaction method with various fluxes. The results show that addition of proper flux can decrease the phase-forming temperature of the TAG crystals and improve the morphology as well as enhance the photoluminescence of the phosphors greatly. High efficient and low color-temperature white light-emitting diodes (WLEDs) were fabricated with the TAG:Ce3+ phosphor. Good performances of the WLEDs indicate that a mixture of H3BO3 and LiF is an excellent flux for synthesis of TAG:0.04Ce3+ phosphor and is beneficial to the fabrication of high efficient WLEDs.
Sense determination of micropipes via grazing-incidence synchrotron white beam x-ray topography in 4H silicon carbide
Authors: Chen Y. , Dhanaraj G. , Dudley M. , Sanchez E. K. , MacMillan M. F.
Published: August 2007

Computer modeling using the ray-tracing method has been used to simulate the grazing-incidence x-ray topographic images of micropipes in 4H silicon carbide recorded using the pyramidal (11−28) reflection. Simulation results indicate that the images of micropipes appear as white features of roughly elliptical shape, canted to one side or other of the g vector depending on the dislocation sense. Observed images compare well with the simulations, demonstrating that the direction of cant provides a simple, nondestructive, and reliable way to reveal the senses of micropipes. Sense assignment has been validated using back-reflection reticulography.
Scaling in back-illuminated GaN avalanche photodiodes
Authors: Minder K. , Pau J. L. , McClintock R. , Kung P. , Bayram C. , Razeghi M. , Silversmith D.
Published: August 2007

Avalanche p-i-n photodiodes of various mesa areas were fabricated on AlN templates for back illumination for enhanced performance through hole-initiated multiplication, and the effects of increased area on device performance were studied. Avalanche multiplication was observed in mesa sizes up to 14063μm2 under linear mode operation. Uniform gain and a linear increase of the dark current with area were demonstrated.
Thermally driven defect formation and blocking layers at metal-ZnO interfaces
Authors: Mosbacker H. L. , Zgrabik C. , Hetzer M. J. , Swain A. , Look D. C. , Cantwell G. , Zhang J. , Song J. J. , Brillson L. J.
Published: August 2007

The authors used depth-resolved cathodoluminescence spectroscopy and current-voltage measurements to probe the temperature-dependent formation of native point defects and reaction layers at metal-ZnO interfaces and their effect on transport properties. These results identify characteristic defect emissions corresponding to metal-Zn alloy versus oxide formation. Au alloys with Zn above its eutectic temperature, while Ta forms oxide blocking layers that reduce current by orders of magnitude at intermediate temperatures. Defects generated at higher temperatures and/or with higher initial defect densities for all interfaces produce Ohmic contacts. These reactions and defect formation with annealing reveal a thermodynamic control of blocking versus Ohmic contacts.
Multivariate Analysis of Trip-Chaining Behavior
Authors: Noland Robert B , Thomas John V
Published: August 2007

This paper examines the relationship between patterns of trip chaining and urban form. The goal is to examine whether lower density environments are related to more frequent reliance upon trip chaining and more complex tours. The analysis uses the 2001 National Household Travel Survey to evaluate household individual travel and trip characteristics alongside a basic measure of residential density. Two estimation techniques, the ordered probit and the negative binomial model, are used to evaluate the factors associated with the tendency to combine trips into more complex tours, measured as the number of stops. The results indicate that, accounting for key household and traveler characteristics, lower density environments lead both to a greater reliance upon trip chaining and to tours that involve more stops along the way. This is followed by a household level analysis of tour generation. Crane and Krizek have suggested that more accessible areas will tend to generate more tours. However, we found no evidence for this in our analysis.
Viewsphere: A GIS-Based 3D Visibility Analysis for Urban Design Evaluation
Authors: Yang Perry Pei-Ju , Putra Simon Yunuar , Li Wenjing
Published: August 2007

Previously, GIS-based visibility analysis has been conducted mainly in two dimensions, based on the concept of an isovist in the built environment or the concept of a viewshed in terrain and landscape analysis. The Viewsphere, a GIS approach towards 3D visibility analysis is proposed for measuring visible urban space quantitatively in a way that is different from its predecessors, the isovist and the viewshed. A test case of Singapore's urban space was conducted by evaluating the visibility of three alternative urban design scenarios and their potential impacts on the visual quality of open space. Both directional and nondirectional approaches were applied to the mapping of visibility based on the 2D and 3D indices. The proposition that 3D visibility indices are more effective than 2D indices was verified. The findings show that the 3D indices are sensitive to the changes of z-dimension.
Major influence of BrO on the NOx and nitrate budgets in the Arctic spring, inferred from Δ17O(NO3 - ) measurements during ozone depletion events
Authors: Morin S. , Savarino J. , Bekki S. , Cavender A. , Shepson P. B. , Bottenheim J. W.
Published: August 2007

Environmental context. Ozone depletion events (ODEs) in the Arctic lower atmosphere drive profound changes in the chemistry of nitrogen oxides (NOx) because of the presence of bromine oxide (BrO). These are investigated using the isotopic composition of atmospheric nitrate (NO3–), which is a ubiquitous species formed through the oxidation of nitrogen oxides. Since BrO is speculated to play a key role in the atmospheric chemistry of marine regions and in the free troposphere, our studies contribute to the improvement of the scientific knowledge on this new topic in atmospheric chemistry.
Abstract. The triple oxygen isotopic composition of atmospheric inorganic nitrate was measured in samples collected in the Arctic in springtime at Alert, Nunavut and Barrow, Alaska. The isotope anomaly of nitrate (Δ17O = δ17O–0.52δ18O) was used to probe the influence of ozone (O3), bromine oxide (BrO), and peroxy radicals (RO2) in the oxidation of NO to NO2, and to identify the dominant pathway that leads to the production of atmospheric nitrate. Isotopic measurements confirm that the hydrolysis of bromine nitrate (BrONO2) is a major source of nitrate in the context of ozone depletion events (ODEs), when brominated compounds primarily originating from sea salt catalytically destroy boundary layer ozone. They also show a case when BrO is the main oxidant of NO into NO2.
Experimental determination of the dissolution kinetics of zero-valent iron in the presence of organic complexants
Authors: Pierce Eric M. , Wellman Dawn M. , Lodge Alexander M. , Rodriguez Elsa A.
Published: August 2007

Environmental context. Iron metal is being considered as a material to be used for the treatment of groundwater contaminated with toxic metals and organics. Although time-dependant information is available, predicting the long-term behaviour of this material has been complicated by the build-up of rust or other alteration phases on the surface of Fe metal. In addition to the build-up of rust, changes to important environmental factors also complicate these types of predictions. The research discussed in this paper uses a non-traditional experimental technique to isolate the impact of specific environmental factors (i.e. pH, temperature) and organic complexants on the dissolution of Fe metal.

Abstract. The geochemical cycling of iron, the reactivity of iron minerals and, more recently, the reactivity of zero valent iron (α-Fe), have been the subject of numerous investigations for over more than three decades. These investigations provide a wealth of knowledge regarding the effect of pH, temperature, chelating agents etc. on the reactivity and mechanism(s) of dissolution for α-Fe and iron oxide/oxyhydroxide minerals. However, most investigations have been conducted under static conditions that promote the formation of a partially oxidised surface film (e.g. passivating layer). In the presence of a passivating layer, the proposed dissolution mechanisms are vastly different and are based on the composition of the partially oxidised surface film. The objective of this study was to quantify the dissolution of α-Fe under conditions that maintain the pO2 at a relatively constant level and minimise the formation of a passivating layer on the metal surface. Single-pass flow-through tests were conducted under conditions of relatively constant dissolved O2 [O2(aq)] over the pH(23°C) range from 7 to 12 and temperature range from 23 to 90°C in the presence of ethylenediamine tetraacetic acid (EDTA) and ethylenediamine di-O-hydroxyphenylacetic acid (EDDHA) to maintain dilute conditions and minimise the formation of a partially oxidised surface film and Fe-bearing secondary phase(s) during testing. Although more information is needed, these results suggest the adsorption of EDTA and EDDHA, or the diffusion of the oxidised Fe–organic complex from the surface of α-Fe, is the rate-limiting step in the dissolution reaction. Results also suggest that the rate of dissolution is independent of pH, has a non-linear dependence on the concentration of organic complexant, and the forward dissolution rate for α-Fe is as much as three orders of magnitude greater than when a passive film and corrosion products are present.
Global dust teleconnections: aerosol iron solubility and stable isotope composition
Authors: Waeles Matthieu , Baker Alex R. , Jickells Tim , Hoogewerff Jurian
Published: August 2007

Environmental context. Iron is an essential component of many enzyme systems of marine plants (phytoplankton), but in large areas of the global ocean iron is in such short supply as to hinder phytoplankton growth. This is of major environmental interest because phytoplankton growth can remove carbon from the atmosphere. This contribution seeks to improve the understanding of how dust transported through, and processed within, the atmosphere helps to supply usable iron to the plants of the remote ocean.
Abstract. Soil dust mobilised from arid regions is transported through and processed within the atmosphere before deposition to marine and terrestrial ecosystems remote from the source regions. This process represents a significant source of iron to the oceans, which creates feedback loops throughout the Earth’s system. The very limited solubility of iron from dust makes the determination of this solubility, how it varies and how this may influence ocean biogeochemistry of considerable importance. In this short communication we summarise a series of recent studies of mechanisms that control solubility and then consider how these results influence the inputs of iron to the oceans and their isotopic signature.
Atmospheric variation of nitrous acid at different sites in Europe
Authors: Acker Karin , Möller Detlev
Published: August 2007

Environmental context. Nitrous acid (HNO2) is an important source of the hydroxyl radical (OH•), the most important daytime oxidising species that contributes to the formation of ozone as well as of other secondary pollutants in the troposphere. Understanding the sources and sinks of HNO2 is of crucial interest for accurately modelling the chemical composition of the troposphere and predicting future trace gas concentrations.
Abstract. Nitrous acid and several other atmospheric components and variables were continuously measured during complex field experiments at seven different suburban and rural sites in Europe. HNO2 is mainly formed by heterogeneous processes and is often accumulated in the nighttime boundary layer. Our results confirm that the photolysis of HNO2 is an important source of the hydroxyl radical, not only in the early morning hours but also throughout the entire day, and is often comparable with the contribution of ozone and formaldehyde photolysis. At all research sites unexpectedly high HNO2 mixing ratios were observed during the daytime (up to several hundred ppt, or pmol mol–1). Moreover, surprisingly, the HNO2 mixing ratio at the three mountain sites often showed a broad maximum or several distinct peaks at midday and lower mixing ratios during the night. Assuming a quickly established photo-equilibrium between the known significant gas phase reactions, only a few ppt HNO2 should be present around noon. The ratio of known sources to sinks indicates a missing daytime HNO2 source of 160–2600 ppt h–1 to make up the balance. Based on these values and on production mechanisms proposed in the literature we hypothesise that the daytime mixing ratio levels may only be explained by a fast electron transfer onto adsorbed NO2.
SOX9 is a key player in ultraviolet B-induced melanocyte differentiation and pigmentation
Authors: Passeron Thierry , Valencia Julio C. , Bertolotto Corine , Hoashi Toshihiko , Le Pape Elodie , Takahashi Kaoruko , Ballotti Robert , Hearing Vincent J.
Published: August 2007

SOX (
SRY
type HMG box) proteins are transcription factors that are predominantly known for their roles during development. During melanocyte development from the neural crest, SOX10 regulates microphthalmia-associated transcription factor, which controls a set of genes critical for pigment cell development and pigmentation, including dopachrome tautomerase and tyrosinase. We report here that another SOX factor, SOX9, is expressed by melanocytes in neonatal and adult human skin and is up-regulated by UVB exposure. We demonstrate that this regulation is mediated by cAMP and protein kinase. We also show that agouti signal protein, a secreted factor known to decrease pigmentation, down-regulates SOX9 expression. In adult and neonatal melanocytes, SOX9 regulates microphthalmia-associated transcription factor, dopachrome tautomerase, and tyrosinase promoters, leading to an increase in the expression of these key melanogenic proteins and finally to a stimulation of pigmentation. SOX9 completes the complex and tightly regulated process leading to the production of melanin by acting at a very upstream level. This role of SOX9 in pigmentation emphasizes the poorly understood impact of SOX proteins in adult tissues.
The two oxidized forms of the trinuclear Cu cluster in the multicopper oxidases and mechanism for the decay of the native intermediate
Authors: Yoon Jungjoo , Liboiron Barry D. , Sarangi Ritimukta , Hodgson Keith O. , Hedman Britt , Solomon Edward I.
Published: August 2007

Multicopper oxidases (MCOs) catalyze the 4e
−
reduction of O
2
to H
2
O. The reaction of the fully reduced enzyme with O
2
generates the native intermediate (NI), which undergoes a slow decay to the resting enzyme in the absence of substrate. NI is a fully oxidized form, but its spectral features are very different from those of the resting form (also fully oxidized), because the type 2 and the coupled-binuclear type 3 Cu centers in the O
2
-reducing trinuclear Cu cluster site are isolated in the resting enzyme, whereas these are all bridged by a μ
3
-oxo ligand in NI. Notably, the one azide-bound NI (NI
Az
) exhibits spectral features very similar to those of NI, in which the μ
3
-oxo ligand in NI has been replaced by a μ
3
-bridged azide. Comparison of the spectral features of NI and NI
Az
, combined with density functional theory (DFT) calculations, allows refinement of the NI structure. The decay of NI to the resting enzyme proceeds via successive proton-assisted steps, whereas the rate-limiting step involves structural rearrangement of the μ
3
-oxo-bridge from inside to outside the cluster. This phenomenon is consistent with the slow rate of NI decay that uncouples the resting enzyme from the catalytic cycle, leaving NI as the catalytically relevant fully oxidized form of the MCO active site. The all-bridged structure of NI would facilitate electron transfer to all three Cu centers of the trinuclear cluster for rapid proton-coupled reduction of NI to the fully reduced form for catalytic turnover.
New results of intersection numbers on moduli spaces of curves
Authors: Liu Kefeng , Xu Hao
Published: August 2007

We present a series of results we obtained recently about the intersection numbers of tautological classes on moduli spaces of curves, including a simple formula of then-point functions for Witten's τ classes, an effective recursion formula to compute higher Weil–Petersson volumes, several new recursion formulae of intersection numbers and our proof of a conjecture of Itzykson and Zuber concerning denominators of intersection numbers. We also present Virasoro and KdV properties of generating functions of general mixed κ and ψ intersections.
Human C-reactive protein slows atherosclerosis development in a mouse model with human-like hypercholesterolemia
Authors: Kovacs Alexander , Tornvall Per , Nilsson Roland , Tegnér Jesper , Hamsten Anders , Björkegren Johan
Published: August 2007

Increased baseline values of the acute-phase reactant C-reactive protein (CRP) are significantly associated with future cardiovascular disease, and some
in vitro
studies have claimed that human CRP (hCRP) has proatherogenic effects.
in vivo
studies in apolipoprotein E-deficient mouse models, however, have given conflicting results. We bred atherosclerosis-prone mice (
Apob
100/100
Ldlr
−/−
), which have human-like hypercholesterolemia, with hCRP transgenic mice (
hCRP
+/0
) and studied lesion development at 15, 30, 40, and 50 weeks of age. Atherosclerotic lesions were smaller in
hCRP
+/0
Apob
100/100
Ldlr
−/−
mice than in
hCRP
0/0
Apob
100/100
Ldlr
−/−
controls, as judged from the lesion surface areas of pinned-out aortas from mice at 40 and 50 weeks of age. In lesions from 40-week-old mice, mRNA expression levels of several genes in the proteasome degradation pathway were higher in
hCRP
+/0
Apob
100/100
Ldlr
−/−
mice than in littermate controls, as shown by global gene expression profiles. These results were confirmed by real-time PCR, which also indicated that the activities of those genes were the same at 30 and 40 weeks in
hCRP
+/0
Apob
100/100
Ldlr
−/−
mice but were significantly lower at 40 weeks than at 30 weeks in controls. Our results show that hCRP is not proatherogenic but instead slows atherogenesis, possibly through proteasome-mediated protein degradation.
Electron Transfer Dynamics in Solution Using Imaginary-time Split Operator Approach
Authors: Zhu Wen-juan , Han Miao-miao , Zhao Yi
Published: August 2007

An imaginary-time split operator approach is proposed to study electron transfer (ET) dynamics using Sumi-Marcus theory. The approach is applied to evaluate the intermolecular ET rate between oxazine 1 and N,N-dimethlaniline. By measuring the two average survival times of the donor state probability and the rate constant in long time limit, the full kinetics of the ET is revealed with a variety of sink functions. Several new properties for the ET have been found in numerical simulations.
Heat Capacity and Gruneisen Parameter for GaN with Zinc-Blende Structure
Authors: Sun Xiao-wei , Liu Zi-jiang , Song Ting , Liu Xiao-bin , Wang Cheng-wei , Chen Qi-feng
Published: August 2007

A shell model molecular dynamics method is used to investigate the behavior of the pressure-volume relationship, heat capacities at constant pressure and constant volume, Gruneisen parameter for GaN with zinc-blende cubic structure at high pressures and high temperatures. The interactions between Ga-Ga, Ga-N, and N-N are described with polarizable potential models which have assigned two different partially ionic charges to Ga and N by taking into account of the ionic character of GaN. It is shown that the calculated thermodynamic parameters at ambient condition are in good agreement with the available theoretical results. Compared with the results from first-principles calculations, the discrepancy of constant-volume heat capacity at lower temperature may be explained well with different approximation mechanisms. The properties of GaN with zinc-blende structure are summarized in the temperature range of 300-2000 K and pressure up to 40 GPa.
Theoretical Investigation of CH3CF2O2+HOO Reaction
Authors: Cheng Xue-li , Li Gui-xin , Wang Zuo-mao , Zhao Yan-yun , Sun Yi-feng
Published: August 2007

The reactions of CH3CF2O2 with HOO are important chemical cyclic processes of photochemical contamination. In this paper, the reaction pathways and reaction mechanism of CH3CF2O2+HOO are investigated extensively with the Gaussian 98 package at the B3LYP/6-311++G** basis sets. The use of vibrational mode analysis and electron population analysis to reveal the reaction mechanism is firstly reported. The study shows that CH3CF2CO2+HOO IM1 TS1 CH3CF2O2H+O2 channel is the energetically most favorable, CH3CF2CO2H and O2 are the principal products, and the formation of CH3OH and CF2O is also possible.
DSC Study on Cooperative Relaxation in 1,2-propanediol
Authors: Gao Cai , Wang Tie-jun , Liu Xiang-nong , Zhou Guo-yan , Hua Tse-chao
Published: August 2007

Cooling rate dependence of the cooperative relaxation in 1,2-propanediol was investigated in terms of the nonlinear Adam-Gibbs (AG) enthalpy relaxation theory using differential scanning calorimetry. The AG parameters were obtained using a curve-fitting method. The results indicated that the model parameters show strong dependence on the cooling rates. Those obtained at higher cooling rates are in good agreement with the published data. The fitting results were used to estimate the microscopic parameters of the cooperative rearranging region (CRR), in particular the size of the CRR (z*) and the configurational state available to it (W*). It was found that the W* recommended for polymers led to physically meaningless z* for 1,2-propanediol. Johari's method, which was based on the AG theory, yielded around 3 molecules in the CRR, but the W* was anomalistically higher than those of polymers. It is difficult to reconcile the Adam-Gibbs' z* with the results obtained using Donth's formula. An argument is presented that a new physical meaning should be given to conventional Adam-Gibbs' z* for molecular H-bond liquids.
Absorption Spectra and Photoreactivity ofp-Aminobenzophenone by Time-dependent Density Functional Theory
Authors: Cheng Xue-mei , Huang Yao , Ma Jian-yi , Li Xiang-yuan
Published: August 2007

The absorption spectral properties of para-aminobenzophenone (p-ABP) were investigated in gas phase and in solution by time-dependent density functional theory. Calculations suggest that the singlet states vary greatly with the solvent polarities. In various polar solvents, including acetonitrile, methanol, ethanol, dimethyl sulfoxide, and dimethyl formamide, the excited S1 states with charge transfer character result from * transitions. However, in nonpolar solvents, cyclohexane, and benzene, the S1 states are the result of n * transitions related to local excitation in the carbonyl group. The excited T1 states were calculated to have * character in various solvents. From the variation of the calculated excited states, the band due to * transition undergoes a redshift with an increase in solvent polarity, while the band due to n * transition undergoes a blueshift with an increase in solvent polarity. In addition, the triplet yields and the photoreactivities of p-ABP in various solvents are discussed.
Effect of Surface Impurities on Oscillation in NO+CO/Pt(100) Reaction System
Authors: Liu Jin-jun , Hua Da-yin , Jiang Luo-luo
Published: August 2007

A lattice gas model was proposed to explore the effect of inert surface impurities on the oscillation in the NO+CO reaction system on Pt(100). It was found that when the fraction of the impurities is small, the (11) phase resulting from the surface restructuring can form a connected phase and the system exhibits a global sustained oscillation. With the fraction of the impurities increasing, the (11) phase only can form many isolated patches and the spatial coherence between the local oscillators with a random phase relationship lost, and as a result, the sustained oscillation changes into a damped one. When the diffusion rate of adsorbed CO and NO increases, the synchronization between local oscillators is enhanced and the global sustained oscillation can appear again.
Study of (2, 0) Band ofA2u -X2g+ System of N2+ by Optical Heterodyne Detected Velocity Modulation Spectroscopy
Authors: Wu Yan-dan , Ben Jin-wen , Li Ling , Zheng Li-juan , Chen Yang-qin , Yang Xiao-hua
Published: August 2007

The (2, 0) band of the A2u-X2g+ system of N2 + was rotationally studied via optical heterodyne detected velocity modulation spectroscopy. Owing to the high sensitivity of the spectroscopy employed, the frequencies of 310 lines of this band were accurately determined. Moreover, those overlapped lines were also well determined via deconvolution method. A nonlinear least-squares fitting procedure using a standard Hamiltonian was applied to analyze this band. Therefore, the most accurate molecular constants were obtained.
First Principle Calculation of Electric and Magnetic Properties for New Half-metal Fe2ScO4
Authors: Liu Jun , Wang Xin-qiang , Liu Yu , Dong Hui-ning
Published: August 2007

The new half-metals Fe2ScO4 and FeSc2O4 were designed and their spinel structures were optimized based on the first-principle pseudo-potential method. Their electric and magnetic properties including molecular magnetic moments and electronic structures were calculated and analyzed, and then were compared with those of Fe3O4. The calculation showed that Fe2ScO4 and FeSc2O4 were both new ferromagnetic II B-type half-metals, but Fe3O4 was ferrimagnetic. The molecular magnetic moment of Fe2ScO4 is about 7.28 B, which is much larger than the 4.0 B of Fe3O4 and 3.96 B of Fe2ScO4. The molecular magnetic moment of Fe2ScO4 mainly came from the spin-polarization of Fe3d electrons. Also, the conductance of Fe2ScO4 was a little larger than that of Fe3O4. For Fe2ScO4, the average electronic structure of Sc on A-sites was Sc+3s23p43d2 and that of Fe on B-sites was Fe2+t2g3tg2t2g. It can be predicted that the new half-metal Fe2ScO4 has wider application ground in spin electronic instruments because of its larger magnetoresistance compared to Fe3O4 and FeSc2O4.
Characterization of C12A7-O Catalyst and Mechanism of Phenol Formation by Hydroxylation of Benzene
Authors: Dong Ting , Wang Zhao-xiang , Kan Tao , Li Quan-xin
Published: August 2007

The benzene conversion and phenol selectivity from C6H6/O2/H2O over [Ca24Al28O64]4+4O(C12A7-O) catalyst were investigated using a flow reactor. The benzene conversion increases with the increase of temperature, and the phenol selectivity mainly depends on both reaction temperature and the composition of the mixtures. The changes of the catalyst structure before and after the reactions and the intermediates on the catalyst surface and in the bulk were investigated by XRD, EPR and FT-IR. The catalytic reactions do not cause any damage to the structure of the positively charged lattice framework C12A7-O, but part of the O and O2 species in the bulk of C12A7-O translate to OH after the reactions. The neutral species and anion intermediate were investigated by Q-MS and TOF-MS respectively. It is suggested that the active O and OH species played a key role in the process of phenol formation.
Growth of 3C-SiC Films on On-axis 6H-SiC Substrates by LPCVD
Authors: Zheng Hai-wu , Fu Zhu-xi , Lin Bi-xia , Li Xiao-guang
Published: August 2007

Cubic SiC (3C-SiC) films were deposited on on-axis 6H-SiC (0001) substrates by low-pressure chemical vapor deposition (LPCVD). The result of X-ray diffraction patterns shows that the 3C-SiC films were of good crystalline quality. The influence of the growth parameters (flow rates of the gas sources and growth temperature) on the growth rate of the SiC films is discussed. The results show that the transport of silane or its reaction products is the limiting factor for the growth. The surface morphology of the SiC films was observed by atomic force microscope imaging. From these results it can be concluded that the growth of the films is in agreement with a Stranski-Krastanov growth mode.
Effects of Neutron Irradiation on Superconducting Properties of GdBa2Cu3O7- Single Domain Superconductor
Authors: Zhang Hong , Li Guang , Zhou Tao-fei , Liu Yong , Li Xiao-guang , Chen Yu
Published: August 2007

The effects of neutron irradiation with a fluence of 1015 n/cm2 on the superconducting properties of GdBa2Cu3O7 single domain sample were studied. The point and cascade defects produced by the neutron irradiation were observed by high-resolution transmission electron microscopy. The cascade defects were found to have the sizes of about 4-7 nm which is comparable to the coherence lengths of high temperature superconductors. The point defects disappear while the cascades still exist through thermal annealing. The temperature dependence of magnetization for the magnetic field parallel to the crystallographic c axis shows that the neutron irradiation leads to a dramatic degradation of superconductivity for the as-irradiated sample, a decrease of critical current density (Jc), and the weakening of the fishtail effect in the Jc versus magnetic induction B curve. However, for the as-irradiated sample annealed in the flowing oxygen atmosphere, it shows that Jc under high magnetic fields is greatly enhanced, the fishtail shifts towards higher magnetic fields, and its superconductivity is partially recovered as well due to the remaining effective pinning centers of the cascades. These results suggest a prospective application for such a treated GdBa2Cu3O7 superconductor.
Novel patterning of nano-bioceramics: template-assisted electrohydrodynamic atomization spraying
Authors: Li X , Huang J , Edirisinghe M.J
Published: August 2007

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.
Radiative transfer: exact Rayleigh scattering series and a formula for daylight
Authors: Hannay J.H
Published: August 2007

Daylight, or sky light, is sunlight Rayleigh scattered by the atmosphere onto the ground. This random scattering propagation through clear air is governed by ‘radiative transfer’. Beyond the single-scattering approximation, the famous virtuoso analysis of Chandrasekhar formulated the problem and offered exact, but rather involved, and ultimately numerical, algorithms for its solution. However, there is no real difficulty in writing down directly the exact Rayleigh scattering series in integrals. Its practical utility is limited to fairly small thicknesses
T
of atmosphere (compared with the mean free path), but the Earth has just such. Here even the next order beyond single scattering (error order
T
2
) supplies a formula for the brightness and partial polarization of daylight across the sky, which captures the essential topology of the polarization pattern, and also remains uniformly valid in the small thickness limit, for all elevations of the Sun and viewing angles. The status of the mathematical polarization direction pattern invented by Berry, Dennis and Lee as the simplest fit to the required topology is clarified.
Asymptotic Green's function in homogeneous anisotropic viscoelastic media
Authors: Vavryčuk Václav
Published: August 2007

An asymptotic Green's function in homogeneous anisotropic viscoelastic media is derived. The Green's function in viscoelastic media is formally similar to that in elastic media, but its computation is more involved. The stationary slowness vector is, in general, complex valued and inhomogeneous. Its computation involves finding two independent real-valued unit vectors which specify the directions of its real and imaginary parts and can be done either by iterations or by solving a system of coupled polynomial equations. When the stationary slowness direction is found, all quantities standing in the Green's function such as the slowness vector, polarization vector, phase and energy velocities and principal curvatures of the slowness surface can readily be calculated.

The formulae for the exact and asymptotic Green's functions are numerically checked against closed-form solutions for isotropic and simple anisotropic, elastic and viscoelastic models. The calculations confirm that the formulae and developed numerical codes are correct. The computation of theP-wave Green's function in two realistic materials with a rather strong anisotropy and absorption indicates that the asymptotic Green's function is accurate at distances greater than several wavelengths from the source. The error in the modulus reaches at most 4% at distances greater than 15 wavelengths from the source.
Domain-decomposition method for the global dynamics of delay differential equations with unimodal feedback
Authors: Röst Gergely , Wu Jianhong
Published: August 2007

The dynamics generated by the delay differential equation

with unimodal feedback is studied. The existence of the global attractor is shown and bounds of the attractor are given. We find attractive invariant intervals and give sufficient conditions that guarantee that all solutions enter the domain where
f
′ is negative with respect to a positive equilibrium, so the results for delayed monotone feedback can be applied to describe the asymptotic behaviour of solutions. In particular, the existence of heteroclinic orbits from the trivial equilibrium to a periodic orbit oscillating around the positive equilibrium is established. Numerical examples using Nicholson's blowflies equation and the Mackey–Glass equation are provided to illustrate the main results.
ZSTK474 is an ATP‐competitive inhibitor of class I phosphatidylinositol 3 kinase isoforms
Authors: Kong Dexin , Yamori Takao
Published: August 2007

Class I phosphatidylinositol 3 kinases (PI3K) phosphorylate phosphatidylinositol 4,5‐bisphosphate to generate phosphatidylinositol 3,4,5‐trisphosphate. These molecules play an important role in fundamental cellular responses. Four isoforms of class I PI3K are known to have different functions, and abnormalities in their activities have been related to various diseases such as cancer and inflammation. We previously identified a novel PI3K inhibitor, ZSTK474, which showed potent antitumor activity in vivo against a human cancer xenograft without observable toxicity. However, the mode of its molecular action was not investigated in detail. Our previous study only suggested that ZSTK474 possibly competes with ATP for the ATP‐binding pocket of PI3Kγ. In the present study, we have used an in vitro homogenous time‐resolved fluorescence kinase assay to examine whether ZSTK474 is indeed an ATP‐competing inhibitor of PI3K, and also to determine whether the inhibitory activity of ZSTK474 was isoform‐specific. Lineweaver–Burk plot analysis revealed that ZSTK474 inhibits all four PI3K isoforms in an ATP‐competitive manner. Among all of the PI3K isoforms, PI3Kδ was inhibited most potently by ZSTK474 with a Ki of 1.8 nM, and the other isoforms were inhibited at higher doses. We have also used a kinase activity ELISA to determine whether ZSTK474 inhibits mammalian target of rapamycin, a key kinase acting downstream of PI3K to promote protein synthesis and cell proliferation. Even at a concentration of 100 µM, ZSTK474 inhibited mammalian target of rapamycin activity rather weakly. These results indicate that ZSTK474 is an ATP‐competitive pan‐class I PI3K inhibitor. (Cancer Sci 2007; 98: 1638–1642)
Adverse Effects of Alcohol in Pregnancy
Authors: Barrison I. G. , Waterson E. J. , Murray‐Lyon Iain M.
Published: August 2007

Alcohol consumption in pregnancy can produce a spectrum of abnormalities in the developing foetus, ranging from minor retardation of growth to the fully developed ‘foetal alcohol syndrome’. This syndrome comprises a constellation of physical and mental defects associated with a charateristic facial appearance that is found in children: born to chronic alcoholic women. Although it was thought to be extremely rare in the U.K., several case studies have recently appeared in the literature, and its incidence is probably increasing. In moderately drinking pregnant women increased rates of spontaneous abortion, stillbirth and congenital malformation as well as growth retardation have been reported, though some of these findings await confurmation. It is likely also that certain behavioural abnormalities are consequent on maternal alcohol intake. The major U.K. finding so far is that consumption of more than 100g alcohol per week in the early stages of pregnancy is associated with reduced birth weight. There is no doubt that alcohol is teratogenic in laboratory animals and that the effects are dose‐related. In humans the threshold dose necessary to produce damage to the foetus and the time in pregnancy that alcohol is particularly likely to have deleterious effects have not yet been established. In the present state of knowledge there are difficulties in recommending safe limits. It is obvious that abstinence before and during pregancy is the safest course, but one drink a day is unlikely to be harmful. Greater efforts are needed to educate women about the dangers of alcohol consumption in pregnancy.
The Costs of Alcohol Misuse
Authors: McDonnell Rebecca , Maynard Alan
Published: August 2007

The misuse of alcohol imposes costs on society in a variety of ways. This paper presents a conservative estimate of the total resource cost of alcohol misuse in England and Wales concentrating on four major areas: the costs to industry and the National Health Service, material damage costs and the costs of criminal activity. It is estimated the social cost of alcohol misuse is in excess of £1500 million (1983 prices). Much research needs to be undertaken to improve the poor epidemiological bases on which these estimates depend.
Patterns of Outcome: Drinking Histories over Ten Years Among a Group of Alcoholics
Authors: Taylor Colin , Brown David , Duckitt Anita , Edwards Griffith , Oppenheimer Edna , Sheehan Margaret
Published: August 2007

In a long‐term follow‐up study extending over 10 years of a cohort of 99 male alcoholics, interviews were achieved with 68 of them. Data obtained by personal recall are presented to illustrate the pattern of the men's drinking over the follow‐up period. The changes over time and the difference between individuals are discussed.