bluuebunny/crossref_metadata_2025 huggingface dataset:
Like and cross‐polarized scatter cross sections for two‐dimensional, multiscale rough surfaces based on a unified full wave variational technique
Authors: Bahar Ezekiel
Published: July 2011

A variational method is used to select the specific, smooth decomposition of the total surface height spectral density function into surface height spectral density functions for the larger‐ and smaller‐scale surfaces. Using this decomposition, the total like and cross‐polarized scatter cross sections are expressed as weighted sums of physical optics scatter cross sections associated with the larger‐scale surfaces and the tilt‐modulated scatter cross sections for the smaller‐scale surfaces. This variational technique has been shown to be stationary over a wide range of the variational parameter. Since only the slopes of the larger‐scale surfaces tilt modulate the cross sections of the smaller‐scale surfaces, it is necessary to select surface height spectral density functions for the larger‐scale surfaces that do not require the introduction of artificial spatial cutoff wave numbers for the spectral density functions. The methods used to smoothly decompose the surface height spectral density functions result in no artificial rapid fluctuations in the corresponding surface height autocorrelation functions for the smaller‐ and larger‐scale surfaces. This method can be applied to the remote sensing of rough sea or land surfaces.
Comparison of spherical harmonic and B spline models for the vertical total electron content
Authors: Schmidt Michael , Dettmering Denise , Mößmer Matthias , Wang Yuanyuan , Zhang Jiantong
Published: July 2011

Most of the geodetic ionosphere models describe the electron density of the Earth's atmosphere by global maps of the vertical total electron content (VTEC) for fixed time intervals (e.g., 2 h) assuming a single‐layer model and using a spherical harmonic expansion up to a specific degree n. However, it is well known that spherical harmonic models are not suited for representing data of heterogeneous density and quality. As a consequence, data gaps cannot be handled appropriately. In this paper we present a different approach for modeling VTEC generally depending on space and time defining the 3‐D system of base functions as tensor products of trigonometric B spline functions for the longitude and two sets of endpoint‐interpolating B spline functions for latitude and time, respectively. We compare this approach to a spherical harmonic expansion with similar resolution and show how data gaps influence the accuracy of VTEC maps even in areas with good data coverage.
Determination of Mineralogical Contents of a Bangle Shard from an Indus Valley Settlement through X-ray Diffraction Analysis
Authors: Kayani Saheeb Ahmed , Siddiqui Rehan ul Haq
Published: July 2011

Some initial results of XRD testing of a bangle shard collected from Harrappa, an Indus Valley settlement located in Pakistan, are presented. The mineralogical structure of the bangle shard includes montmorillonite, gypsum, and quartz.
Molecular simulations to study the effect of pore geometry and structure on the adsorption of CH4/H2 mixtures in carbon pores
Authors: Kumar Vasanth , Müller Erich , Rodriguez-Reinoso Francisco
Published: July 2011

We used molecular simulations to study the effect of pore structure and geometry on the selectivity of carbon materials for the adsorption of methane from a mixture of methane and hydrogen at 50 bar and 298 K. We modeled hydrogen as a more realistic dumb-bell shaped fluid and methane as spherical Lennard-Jones sphere. The pore geometry studied includes the slit, nanotube, random carbon structure and carbon pores that mimic a foam structure. Our results confirm that both the pore size and pore structure have a significant effect on the selectivity for methane molecules. An array of nanotubes that have a closed structure has the highest selectivity for methane molecules, followed by carbon foam, slit and random pore structures. Energetic and packing effects at low and high pressures, respectively, influence the selectivity for methane. Reduction in entropy of hydrogen in smaller pores increases the selectivity for methane molecules.
Quantitative Nuclear Magnetic Resonance to Measure Fat Mass in Infants and Children
Authors: Andres Aline , Gomez‐Acevedo Horacio , Badger Thomas M.
Published: July 2011

Quantitative nuclear magnetic resonance (QMR) is being used in human adults to obtain measures of total body fat mass (FM) with high precision. The current study assessed a device specially designed to accommodate infants and children between 3 and 50 kg (EchoMRI‐AH). Body composition of 113 infants and children (3.3–49.9 kg) was assessed using dual‐energy X‐ray absorptiometry (DXA), air displacement plethysmography (ADP, PeaPod for infants ≤8 kg and BodPod for children ≥6 years) and QMR. Results were compared with the deuterium oxide dilution technique (D2O) and a four‐compartment model (4‐C). The percentages of compliance were: 98% QMR; 75% DXA; 94% BodPod; and 95% PeaPod. Although QMR precision was high (coefficient of variation = 1.42%), it overestimated FM ∼10% compared to the 4‐C model and underestimated FM by ∼4% compared to the deuterium method in children ≥6 years. QMR was less concordant with 4‐C or D2O models for infants ≤8 kg. Thus, a piece‐wise defined model for mathematically fitting the QMR data to the D2O data was employed and this adjustment improved the accuracy relative to D2O and 4‐C for infants. Our results suggest that the pediatric QMR with appropriate mathematical adjustment provides a fast and precise method for assessing FM longitudinally in infants and in children weighing up to 50 kg.
Four‐Year Weight Losses in the Look AHEAD Study: Factors Associated With Long‐Term Success
Authors: Wadden Thomas A. , Neiberg Rebecca H. , Wing Rena R. , Clark Jeanne M. , Delahanty Linda M. , Hill James O. , Krakoff Jonathan , Otto Amy , Ryan Donna H. , Vitolins Mara Z. ,   ; The Look AHEAD Research Group
Published: July 2011

This report provides a further analysis of the year 4 weight losses in the Look AHEAD (Action for Health in Diabetes) study and identifies factors associated with long‐term success. A total of 5,145 overweight/obese men and women with type 2 diabetes were randomly assigned to an intensive lifestyle intervention (ILI) or a usual care group, referred to as Diabetes Support and Education (DSE). ILI participants were provided approximately weekly group or individual treatment in year 1; continued but less frequent contact was provided in years 2–4. DSE participants received three group educational sessions in all years. As reported previously, at year 4, ILI participants lost an average of 4.7% of initial weight, compared with 1.1% for DSE (P < 0.0001). More ILI than DSE participants lost ≥5% (46% vs. 25%, P < 0.0001) and ≥10% (23% vs. 10%, P < 0.0001) of initial weight. Within the ILI, achievement of both the 5% and 10% categorical weight losses at year 4 was strongly related to meeting these goals at year 1. A total of 887 participants in ILI lost ≥10% at year 1, of whom 374 (42.2%) achieved this loss at year 4. Participants who maintained the loss, compared with those who did not, attended more treatment sessions and reported more favorable physical activity and food intake at year 4. These results provide critical evidence that a comprehensive lifestyle intervention can induce clinically significant weight loss (i.e., ≥5%) in overweight/obese participants with type 2 diabetes and maintain this loss in more than 45% of patients at 4 years.
Food Insecurity and Increased BMI in Young Adult Women
Authors: Gooding Holly C. , Walls Courtney E. , Richmond Tracy K.
Published: July 2011

Food insecurity has been associated with weight status in children and adults although results have been mixed. We aimed to identify whether food insecurity was associated with BMI in young adults and whether this association differed by gender and was modified by food stamp use and the presence of children in the home. Cross‐sectional data from wave 4 (2007–2008) of the National Longitudinal Study of Adolescent Health were analyzed. Multiple linear regression was used to investigate the association between food insecurity and BMI in gender stratified models of young adult women (n = 7,116) and men (n = 6,604) controlling for age, race/ethnicity, income, education, physical activity, smoking, alcohol use, the presence of children in the home, and food stamp use in young adulthood and/or adolescence. Food insecurity was more common in young adult women (14%) than young adult men (9%). After controlling for a variety of individual variables, food insecure women had a BMI that was on average 0.9 kg/m2 units higher than women who were food secure. This difference in BMI persisted after controlling for recent or past food stamp use and was not different among women with or without children in the household. No relationship was found between food insecurity and BMI in young adult men. Providers should inquire about food insecurity, especially when treating obesity, and policy initiatives should address the role of access to healthy food in those facing food insecurity.
Obesity Modifies the Relations Between Serum Markers of Dairy Fats and Inflammation and Oxidative Stress Among Adolescents
Authors: Wang Huifen , Steffen Lyn M. , Vessby Bengt , Basu Samar , Steinberger Julia , Moran Antoinette , Jacobs David R. , Hong Ching‐Ping , Sinaiko Alan R.
Published: July 2011

Pentadecanoic acid (15:0) and heptadecanoic acid (17:0), the dairy‐specific saturated fatty acids have been inversely, while inflammation and oxidative stress have been positively related to the risk of cardiovascular disease (CVD). Both fatty acid metabolism and inflammation and oxidative stress may be influenced by adiposity. In the current cross‐sectional analyses among adolescents (mean age 15 years), we determined whether overweight status modified the associations between dairy fatty acids (pentadecanoic acid (15:0) and heptadecanoic acid (17:0)) represented in serum phospholipids (PL) and markers of inflammation and oxidative stress. Six biomarkers for inflammation and oxidative stress were analyzed, including circulating adiponectin, C‐reactive protein (CRP), cytokines interleukin‐6 (IL‐6) and tumor necrosis factor‐α (TNF‐α), and urinary 15‐keto‐dihydro‐PGF2α (15‐keto) and 8‐iso‐PGF2α (F2‐iso). Generalized linear regression analyses, adjusted for age, gender, race, tanner score, total energy intake and physical activity, revealed that PL dairy fatty acids were inversely associated with CRP, F2‐iso and 15‐keto in overweight, but not in normal weight adolescents (all Pinteraction < 0.05). However, higher level of PL dairy fatty acids was associated with lower IL‐6 among all adolescents. Further adjustment for dietary intake of calcium, vitamin D, protein, total flavonoids, and ω‐3 fatty acids did not materially change the findings. Dairy‐specific saturated fats, i.e., 15:0 and 17:0 fatty acids, may contribute to the potential health benefits of dairy products, especially for overweight adolescents.
Heterogeneity Among White Adipose Tissue Depots in Male C57BL/6J Mice
Authors: Sackmann‐Sala Lucila , Berryman Darlene E. , Munn Rachel D. , Lubbers Ellen R. , Kopchick John J.
Published: July 2011

The widespread prevalence of obesity has lead to extensive research on white adipose tissue (WAT), which frequently uses the C57BL/6J mouse strain as a model. In many studies, results obtained in one WAT depot are often extrapolated to all WAT. However, functional differences among WAT depots are now becoming apparent. Thus, to identify the molecular mechanisms responsible for WAT depot‐specific differences under “normal” conditions, four C57BL/6J mouse WAT depots (inguinal, mesenteric, epididymal, and retroperitoneal) were analyzed. Depot proteomic profiles, along with weights, protein contents, adipocyte sizes and oxidative stress were determined. Mesenteric WAT had almost twice the protein content of the other depots analyzed. Mean adipocyte size was highest in epididymal and lowest in mesenteric and inguinal depots. The proteome of inguinal WAT displayed low levels of enzymes involved in ATP generation, glucose and lipid metabolism, and antioxidant proteins. Higher levels of these proteins were observed in mesenteric and epididymal WAT, with variable levels in the retroperitoneal depot. Some of these proteins showed depot‐specific correlations with plasma levels of insulin, leptin, and adiponectin. In agreement with the proteomic data, levels of the antioxidant protein heat shock protein β1 (HSPβ1) also were lower in inguinal WAT when analyzed by western blotting and immunohistochemistry. Also, lipid peroxidation products showed similar trends. Our results are consistent with lower triglyceride turnover and lower oxidative stress in inguinal than mesenteric and epididymal WAT. The observed WAT depot‐specific differences provide clues as to the mechanisms leading to these depots' respective diverse functions.
Role of BMI‐Associated Loci Identified in GWAS Meta‐Analyses in the Context of Common Childhood Obesity in European Americans
Authors: Zhao Jianhua , Bradfield Jonathan P. , Zhang Haitao , Sleiman Patrick M. , Kim Cecilia E. , Glessner Joseph T. , Deliard Sandra , Thomas Kelly A. , Frackelton Edward C. , Li Mingyao , Chiavacci Rosetta M. , Berkowitz Robert I. , Hakonarson Hakon , Grant Struan F.A.
Published: July 2011

Obesity is a serious health concern for children and adolescents, particularly in Western societies, where its incidence is now considered to have reached epidemic proportions. A number of genetic determinants of adult BMI have already been established through genome wide association studies (GWAS), most recently from the GIANT meta‐analysis of such datasets combined. In this current study of European Americans, we examined the 32 loci detected in that GIANT study in the context of common childhood obesity within a cohort of 1,097 cases (defined as BMI ≥95th percentile), together with 2,760 lean controls (defined as BMI <50th percentile), aged between 2 and 18 years old. Nine of these single‐nucleotide polymorphims (SNPs) yielded at least nominal evidence for association with common childhood obesity, namely at the FTO, TMEM18, NRXN3, MC4R, SEC16B, GNPDA2, TNNI3K, QPCTL, and BDNF loci. However, overall 28 of the 32 loci showed directionally consistent effects to that of the adult BMI meta‐analysis. We conclude that among the 32 loci that have been reported to associate with adult BMI in the largest meta‐analysis of BMI to date, at least nine also contribute to the determination of common obesity in childhood in European Americans, as demonstrated by their associations in our pediatric cohort.
Controllable giant dielectric constant in AlOx/TiOy nanolaminates
Authors: Li Wei , Chen Zhijun , Premnath Ramesh N. , Kabius Bernd , Auciello Orlando
Published: July 2011

Dielectric materials exhibiting high dielectric constants play critical roles in a wide range of applications from microchip energy storage embedded capacitors for implantable biomedical devices to energy storage capacitors for a new generation of renewable energy generation/storage systems. Instead of searching for new materials, we demonstrate that giant dielectric constants can be achieved by integrating two simple oxides with low dielectric constants into nanolaminate structures. In addition, the obtained dielectric constant values are highly tunable by manipulating the sub-layer thicknesses of the component oxides to control the number of interfaces and oxygen redistribution. The work reported here opens a new pathway for the design and development of high dielectric constant materials based on the nanolaminate concept.
Start-to-end modelling of a mode-locked optical klystron free electron laser amplifier
Authors: Dunning D. J. , Mc Neil B. W. J. , Thompson N. R. , Williams P. H.
Published: July 2011

A free electron laser (FEL) in a mode-locked optical klystron (MLOK) configuration is modelled using start-to-end simulations that simulate realistic electron beam acceleration and transport before input into a full three-dimensional FEL simulation code. These simulations demonstrate that the MLOK scheme is compatible with the present generation of radiofrequency accelerator designs. A train of few-optical cycle pulses is predicted with peak powers similar to those of the equivalent conventional FEL amplifier. The role of electron beam energy modulation in these results is explained and the limitations of some simulation codes discussed. It is shown how seeding the FEL interaction using a High Harmonic seed laser can improve the coherence properties of the output.
Electron-acoustic solitary waves in the presence of a suprathermal electron component
Authors: Danehkar Ashkbiz , Saini Nareshpal Singh , Hellberg Manfred A. , Kourakis Ioannis
Published: July 2011

The nonlinear dynamics of electron-acoustic localized structures in a collisionless and unmagnetized plasma consisting of “cool” inertial electrons, “hot” electrons having a kappa distribution, and stationary ions is studied. The inertialess hot electron distribution thus has a long-tailed suprathermal (non-Maxwellian) form. A dispersion relation is derived for linear electron-acoustic waves. They show a strong dependence of the charge screening mechanism on excess suprathermality (through κ). A nonlinear pseudopotential technique is employed to investigate the occurrence of stationary-profile solitary waves, focusing on how their characteristics depend on the spectral index κ, and the hot-to-cool electron temperature and density ratios. Only negative polarity solitary waves are found to exist, in a parameter region which becomes narrower as deviation from the Maxwellian (suprathermality) increases, while the soliton amplitude at fixed soliton speed increases. However, for a constant value of the true Mach number, the amplitude decreases for decreasing κ.
Self-focusing and compression of laser pulses in partially stripped plasma
Authors: Jha Pallavi , Singh Vijay , Upadhyay Ajay K.
Published: July 2011

Propagation of a laser beam, having radial and axial Gaussian profile, in partially stripped plasma is analyzed. A wave equation, for the laser electric field driven by linear as well as nonlinear contributions due to atoms and plasma electrons, has been set up. A variational technique is used to obtain equations describing the evolution of the laser spot size and pulse length, and numerical methods are used to study their simultaneous evolution in partially stripped plasma.
Stabilized radiation pressure dominated ion acceleration from surface modulated thin-foil targets
Authors: Chen Min , Kumar Naveen , Pukhov Alexander , Yu Tong-Pu
Published: July 2011

The Rayleigh-Taylor instability in the radiation pressure dominated regime of ion acceleration is studied by means of multidimensional particle-in-cell simulations. It is shown that the growth of the long wavelength mode of the instability can be reduced by transverse diffusion of ions coming from the initial subwavelength modulations on the target front surface. Reduction in the growth of the instability keeps the target structure uniform along the transverse direction and opaque to the laser pulse for a longer duration, improving both the final peak energy and the spectral quality of the ions.
Dislocation nucleation from near surface void under static tensile stress in Cu
Authors: Pohjonen A. S. , Djurabekova F. , Nordlund K. , Kuronen A. , Fitzgerald S. P.
Published: July 2011

We examine a possible mechanism for the formation of protrusions on a metallic surface held in a sufficiently high electric field in the presence of a near-surface void. By means of molecular dynamics simulations we show that the high tensile stress exerted on a Cu {110} surface with a near-surface void can promote the nucleation of dislocations on the void surface. These dislocations cause slip along {111} crystallographic planes leading to mass transport in the volume above the void. We find a linear correlation between the radius of the void and the maximum depth for the growth to occur.
Organic photovoltaic bulk heterojunctions with spatially varying composition
Authors: Haney Paul M.
Published: July 2011

Models of organic bulk heterojunction photovoltaics, which include the effect of spatially varying composition of donor/acceptor materials, are developed and analyzed. Analytic expressions for the current-voltage relation in simplified cases show that the effect of varying blend composition on charge transport is minimal. Numerical results for various blend compositions, including the experimentally relevant composition of a donor-rich region near the cathode (a “skin layer” of donor material) show that the primary effect of this variation on device performance derives from its effect on photocharge generation. The general relation between the geometry of the blend and its effect on performance is given explicitly. The analysis shows that the effect of a skin layer on device performance is small.
Stacking in sediments of colloidal hard spheres
Authors: Marechal Matthieu , Hermes Michiel , Dijkstra Marjolein
Published: July 2011

We use computer simulations to investigate the crystallization dynamics of sedimenting hard spheres in large systems (hundreds of thousands of particles). We show that slow sedimentation results primarily in face-centered cubic (fcc) stacked crystals, instead of random hexagonal close packed or hexagonal close packed (hcp) crystals. We also find slanted stacking faults, in the fcc regions. However, we attribute the formation of fcc to the free energy difference between fcc and hcp and not to the presence of these slanted stacking faults. Although the free energy difference between hcp and fcc per particle is small (only 10−3 times the thermal energy), it can become considerable, when multiplied by the number of particles in each domain. The ratio of fcc to hcp obtained from dynamic simulations is in excellent agreement with well-equilibrated Monte Carlo simulations, in which no slanted stacking faults were found. Our results explain a range of experiments on colloids, in which the amount of fcc increases upon lowering the sedimentation rate or decreasing the initial volume fraction.
Effect of variable mass density on the kinematics of scalar gradient
Authors: Gonzalez M. , Paranthoën P.
Published: July 2011

Analysis of the equations for the orientation and norm of the gradient of a passive scalar shows that the kinematics of the scalar gradient may be deeply altered by non-solenoidal effects felt through the velocity gradient. While these effects are explicitly expressed in the equation for the gradient norm, the orientation equations are unaltered as compared to the incompressible case. In two-dimensional flows the behavior of the scalar gradient is governed by both the strain persistence parameter, r, and the ratio, δ/σ, of velocity divergence to the norm of the deviatoric part of the strain tensor. In particular, in the dilatational case, while large dilatation (δ/σ > 1) unconditionally lessens the scalar gradient, moderate dilatation (0 <δ/σ < 1) needs effective rotation (r ≠ 0) to drive the scalar gradient to decrease. In three-dimensional flows the analytic study needs the assumption that vorticity is aligned with a strain principal axis and leads to a more complex picture based on the strain persistence parameter, the velocity divergence and the strain eigenvalue corresponding to the strain direction parallel to vorticity. In this case, too, for moderate non-solenoidal dilatational effects, rotation appears to oppose the rise of the scalar gradient norm. Possible inferences of the analysis relevant to reacting flows with heat release are briefly discussed
Minimising wave drag for free surface flow past a two-dimensional stern
Authors: Ogilat Osama , McCue Scott W. , Turner Ian W. , Belward John A. , Binder Benjamin J.
Published: July 2011

Free surface flow past a two-dimensional semi-infinite curved plate is considered, with emphasis given to solving the shape of the resulting wave train that appears downstream on the surface of the fluid. This flow configuration can be interpreted as applying near the stern of a wide blunt ship. For steady flow in a fluid of finite depth, we apply the Wiener-Hopf technique to solve a linearised problem, valid for small perturbations of the uniform stream. Weakly nonlinear results obtained by a forced KdV equation are also presented, as are numerical solutions of the fully nonlinear problem, computed using a conformal mapping and a boundary integral technique. By considering different families of shapes for the semi-infinite plate, it is shown how the amplitude of the waves can be minimised. For plates that increase in height as a function of the direction of flow, reach a local maximum, and then point slightly downwards at the point at which the free surface detaches, it appears the downstream wavetrain can be eliminated entirely
Excited-state intramolecular proton transfer reaction modulated by low-frequency vibrations: An effect of an electron-donating substituent on the dually fluorescent bis-benzoxazole
Authors: Sepioł J. , Grabowska A. , Borowicz P. , Kijak M. , Broquier M. , Jouvet Ch. , Dedonder-Lardeux C. , Zehnacker-Rentien A.
Published: July 2011

Excited-state intramolecular proton transfer (ESIPT) reaction has been studied in a molecule showing dual fluorescence, the 2,5-bis(2-benzoxazolyl)-4-methoxyphenol (BBMP), and its isotopomers, where the methoxy, and alternatively, the OH group has been deuterated. Attention is focused on the influence of electron donating OCH3 substituent on fast excited state reaction. Comparison between the resonance-enhanced multiphoton ionization spectrum and the laser-induced excitation of the primary and phototautomeric emissions has been done. The geometry, electron density distribution, vibrational structure as well as the potential energy profiles in the S0 and S1 states of four possible rotameric forms of BBMP were calculated with application of the density functional theory (DFT). It allowed identifying the most probable conformer and assessing the role of low-frequency motions for the ESIPT efficiency.
Contact line dynamics on heterogeneous surfaces
Authors: Ren Weiqing , Weinan E
Published: July 2011

Contact line dynamics on rough or chemically heterogeneous surfaces has been a subject of great interest. Most previous work focused on the issue of contact angle hysteresis in the static limit. This paper is devoted to the study of contact line dynamics on a chemically patterned surface over a wide range of contact line speed. Numerical simulations are carried out for two immiscible fluids confined in a channel and driven by either the shear motion of the two confining walls or an external force. It is found that in the low-speed regime when the averaged contact line speed U≪γ/β*, with γ being the surface tension of the fluid interface and β* the friction coefficient at the contact line, the behavior of the contact line dynamics is very similar to that of the static limit, namely it undergoes a stick-slip motion and the contact angle exhibits hysteretic behavior. At finite speed, the stick-slip behavior gradually diminishes, and the contact line motion becomes more smooth. The effect of these microscale dynamics on the averaged force between the fluid and the solid is investigated. It is found that while the friction force increases linearly with the averaged contact line speed, the force at the contact line due to the defect decreases with U. It is non-zero in the static limit and this is the cause of the contact angle hysteresis. As a result, the total force at the contact line may become non-monotone as a function of the contact line speed. This gives rise to an unstable regime for the contact line dynamics, which is indeed observed in the simulation when the dynamics is driven by an external force.
Energetics of hydrogen in GeO2, Ge, and their interfaces
Authors: Xiong Ka , Lin Liang , Robertson John , Cho Kyeongjae
Published: July 2011

The energetics of interstitial hydrogen in GeO2, Ge, and their interfaces are calculated using a hybrid density functional. We find that interstitial atomic hydrogen unexpectedly behaves as a donor in GeO2, like H in ZnO but unlike H in SiO2. At Ge:GeO2 interfaces, the donor electron can transfer to the lower lying Ge conduction band, which stabilises the O-H bond/donor complex. This reduces the probability of passivating Ge dangling bond (Pb) centers at Ge:GeO2 interfaces.
Solvent effects on the conformation of DNA dodecamer segment: A simulation study
Authors: Shen X. , Gu B. , Che S. A. , Zhang F. S.
Published: July 2011

Different solvent temperatures with five kinds of counterions are used to investigate solvent effects on the DNA microscopic structure. The dodecamer d (CGCGAATTCGCG) DNA segment is merged into the solvents and its conformation transition is studied with the molecular dynamics simulations in detail. For the simple point charge model of water molecule with Na+ counterions, as temperature increases from 200 K to 343 K, the duplex DNA changes from stiff B form to a state between A form and B form, which we define as mixed (A-B) structure, with a double helix unwinding. To study the counterions effects, other four alkali cations, Li+, K+, Rb+, or Cs+ ions, are substituted for Na+ ions at 298 K and 343 K, respectively. For the cases of Li+, Rb+, and Cs+ ions, the duplex DNA becomes more flexible with sugar configuration changing form C2′-endo to C1′-endo type and the width and depth of minor groove at CpG and GpC steps moving towards A values, as the mass of the counterions decreasing. For the case of K+ ions, DNA-K+ interaction widens the width of minor and major grooves at ApA steps and TpT steps, respectively. It seems that the light ions (Li+ or Na+) prefer to interact with the free phosphate oxygen atoms while the heavier ions (Rb+ and Cs+) strongly interact with the base pairs.
Indium-free bottom electrodes for inverted organic solar cells with simplified cell architectures
Authors: Schmidt H. , Winkler T. , Baumann I. , Schmale S. , Flügge H. , Johannes H.-H. , Hamwi S. , Rabe T. , Riedl T. , Kowalsky W.
Published: July 2011

Inverted organic bulk heterojunction solar cells employing a multilayer electrode comprising of a thin Ag layer embedded between layers of zinc tin oxide (ZTO) are compared to cells using an indium tin oxide electrode. The In-free ZTO/Ag/ZTO (ZAZ) electrodes exhibit a favorable work function of 4.3 eV and are shown to allow for excellent electron extraction even without a further interlayer. As a result, issues like transient cell characteristics known from cells comprising titania can be readily avoided. This renders ZAZ a perfectly suited bottom electrode for inverted organic solar cells with a simplified cell architecture.
Analysis of self-consistency effects in range-separated density-functional theory with Møller-Plesset perturbation theory
Authors: Fromager Emmanuel , Jensen Hans Jørgen Aa.
Published: July 2011

Range-separated density-functional theory combines wave function theory for the long-range part of the two-electron interaction with density-functional theory for the short-range part. When describing the long-range interaction with non-variational methods, such as perturbation or coupled-cluster theories, self-consistency effects are introduced in the density functional part, which for an exact solution requires iterations. They are generally assumed to be small but no detailed study has been performed so far. Here, the authors analyze self-consistency when using Møller-Plesset-type (MP) perturbation theory for the long range interaction. The lowest-order self-consistency corrections to the wave function and the energy, that enter the perturbation expansions at the second and fourth order, respectively, are both expressed in terms of the one-electron reduced density matrix. The computational implementation of the latter is based on a Neumann series which, interestingly, even though the effect is small, usually diverges. A convergence technique, which perhaps can be applied in other uses of Neumann series in perturbation theory, is proposed. The numerical results thus obtained show that, in weakly bound systems, self-consistency can be neglected since the long-range correlation does not affect the density significantly. Although MP is not adequate for multireference systems, it can still be used as a reliable analysis tool. Though the density change is not negligible anymore in such cases, self-consistency effects are found to be much smaller than long-range correlation effects (less than 10% for the systems considered). For that reason, a sensible approximation might be to update the short-range energy functional term while freezing its functional derivative, namely, the short-range local potential, in the wave function optimization. The accuracy of such an approximation still needs to be assessed.
Can quasiclassical trajectory calculations reproduce the extreme kinetic isotope effect observed in the muonic isotopologues of the H + H2 reaction?
Authors: Jambrina P. G. , García Ernesto , Herrero Víctor J. , Sáez-Rábanos Vicente , Aoiz F. J.
Published: July 2011

Rate coefficients for the mass extreme isotopologues of the H + H2 reaction, namely, Mu + H2, where Mu is muonium, and Heμ + H2, where Heμ is a He atom in which one of the electrons has been replaced by a negative muon, have been calculated in the 200–1000 K temperature range by means of accurate quantum mechanical (QM) and quasiclassical trajectory (QCT) calculations and compared with the experimental and theoretical results recently reported by Fleming et al. [Science 331, 448 (2011)]10.1126/science.1199421. The QCT calculations can reproduce the experimental and QM rate coefficients and kinetic isotope effect (KIE), kMu(T)/kHeμ(T), if the Gaussian binning procedure (QCT–GB) – weighting the trajectories according to their proximity to the right quantal vibrational action – is applied. The analysis of the results shows that the large zero point energy of the MuH product is the key factor for the large KIE observed.
Synthesis and processing of pseudo noise signals by spin precession in Y3 Fe5O12 films
Authors: Kolokoltsev Oleg V. , Ordóñez-Romero César L. , Qureshi Naser
Published: July 2011

A simple method for synthesis of phase shift keying (PSK) signals in the microwave frequency range is presented. It is shown that the signal coding and processing can be efficiently realized by spin excitations in thin ferrite films. PSK signals are constructed through control of magnetization precession in a magnetic material by a pulsed magnetic field, and their compression is performed by a spin-wave based correlator, eliminating the need for semiconductor circuitry.
Spin resolved photoelectron microscopy using a two-dimensional spin-polarizing electron mirror
Authors: Tusche C. , Ellguth M. , Ünal A. A. , Chiang C.-T. , Winkelmann A. , Krasyuk A. , Hahn M. , Schönhense G. , Kirschner J.
Published: July 2011

We report on an imaging spin-filter for electrons. The specular reflection of low-energy electrons at the surface of a tungsten single crystal is used to project a spin-filtered two-dimensional image onto a position sensitive detector. Spin-filtering is based on the spin-dependent reflectivity of electrons due to spin-orbit coupling in the scattering target, while a two-dimensional field of view, encoded in the angle of incidence, is conserved in the outgoing beam. We characterize the efficiency of the spin-filter by recording photoelectron emission microscopy images of the magnetic domain structure of 8 monolayers cobalt grown on copper (100).
Chip-size formation of high-mobility Ge strips on SiN films by cooling rate controlled rapid-melting growth
Authors: Toko Kaoru , Ohta Yasuharu , Tanaka Takanori , Sadoh Taizoh , Miyao Masanobu
Published: July 2011

High-quality Ge-on-insulators (GOIs) are essential structures for high-performance transistors on an Si platform. We developed a rapid-melting-growth process for amorphous Ge (a-Ge) by optimizing the cooling rate and the underlying insulating materials. The effects of the solidification process for molten Ge on hole generation and spontaneous nucleation in Ge were determined. In addition, nucleation in the a-Ge matrix was found to be drastically suppressed by substituting SiO2 underlayers with SiN underlayers. By combining high cooling rates (10.5–11.5 °Cs−1) and SiN underlayers, we obtained ultra-long single crystal GOI strips (1 cm) with high hole mobilities (> 1000 cm2V−1s−1). This chip-size formation of high-quality GOI will facilitate the development of advanced high-speed Ge-based devices.
In situ investigation of the early stage of TiO2 epitaxy on (001) SrTiO3
Authors: Radović M. , Salluzzo M. , Ristić Z. , Di Capua R. , Lampis N. , Vaglio R. , Granozio F. Miletto
Published: July 2011

We report on a systematic study of the growth of epitaxial TiO2 films deposited by pulsed laser deposition on Ti-terminated SrTiO3 (001) single crystals. By using in situ reflection high energy electron diffraction, low energy electron diffraction, x-ray photoemission spectroscopy, and scanning probe microscopy, we show that the stabilization of the anatase (001) phase is preceded by the growth of a few nanometers thick pseudomorphic SrxTiO2+y (x, y < 1) intermediate layer. The data demonstrate that the formation of this intermediate phase is related to the activation of a long range Sr migration from the SrTiO3 substrate into the film. Our results enrich the phase diagram of the Sr–Ti–O system under epitaxial strain opening a route for the study of the electronic and dielectric properties of the reported Sr-deficient SrTiO3 phase.
Heat conduction in chain polymer liquids: Molecular dynamics study on the contributions of inter- and intramolecular energy transfer
Authors: Ohara Taku , Chia Yuan Tan , Torii Daichi , Kikugawa Gota , Kosugi Naohiro
Published: July 2011

In this paper, the molecular mechanisms which determine the thermal conductivity of long chain polymer liquids are discussed, based on the results observed in molecular dynamics simulations. Linear n-alkanes, which are typical polymer molecules, were chosen as the target of our studies. Non-equilibrium molecular dynamics simulations of bulk liquid n-alkanes under a constant temperature gradient were performed. Saturated liquids of n-alkanes with six different chain lengths were examined at the same reduced temperature (0.7Tc), and the contributions of inter- and intramolecular energy transfer to heat conduction flux, which were identified as components of heat flux by the authors’ previous study [J. Chem. Phys. 128, 044504 (2008)10.1063/1.2821963], were observed. The present study compared n-alkane liquids with various molecular lengths at the same reduced temperature and corresponding saturated densities, and found that the contribution of intramolecular energy transfer to the total heat flux, relative to that of intermolecular energy transfer, increased with the molecular length. The study revealed that in long chain polymer liquids, thermal energy is mainly transferred in the space along the stiff intramolecular bonds. This finding implies a connection between anisotropic thermal conductivity and the orientation of molecules in various organized structures with long polymer molecules aligned in a certain direction, which includes confined polymer liquids and self-organized structures such as membranes of amphiphilic molecules in water.
Surface reconstruction precursor to melting in Au309 clusters
Authors: Chen Fuyi , Li Z. Y. , Johnston Roy L.
Published: July 2011

The melting of gold cluster is one of essential properties of nanoparticles and revisited to clarify the role played by the surface facets in the melting transition by molecular dynamics simulations. The occurrence of elaborate surface reconstruction is observed using many-body Gupta potential as energetic model for 309-atom (2.6 nm) decahedral, cuboctahedral and icosahedral gold clusters. Our results reveal for the first time a surface reconstruction as precursor to the melting transitions. The surface reconstruction lead to an enhanced melting temperature for (100) faceted decahedral and cuboctahedral cluster than (111) faceted icosahedral gold cluster, which form a liquid patch due to surface vacancy.
Assessing the delay of plastic relaxation onset in SiGe islands grown on pit-patterned Si(001) substrates
Authors: Boioli F. , Gatti R. , Grydlik M. , Brehm M. , Montalenti F. , Miglio Leo
Published: July 2011

The onset of plastic relaxation in SiGe islands grown on pit-patterned Si(001) substrates is investigated using elasticity theory solved by finite element methods. Larger critical island volumes with respect to the unpatterned case are predicted. A justification based on the qualitatively different stressors acting on the substrate in the presence of pits is provided. Experimental results in terms of critical SiGe-island volumes as a function of the Ge content are nicely reproduced by the model.
The density broadening in a sodium F=2 condensate detected by a pulse train
Authors: Han Jianing
Published: July 2011

The dipole-blockaded sodium clock transition has been detected by high resolution microwave spectroscopy, the multiple-pulse spectroscopy. This spectroscopic technique has been first used to detect the density broadening and shifting in a Sodium Bose Einstein Condensate (BEC) by probing the sodium clock-transition. Moreover, by narrowing the pulse-width of the pulses, some of the broadening mechanisms can be partially reduced. The results reported here are essential steps toward the ground-state quantum computing, few-body spectroscopy, spin squeezing and quantum metrology.
CYP9Q-mediated detoxification of acaricides in the honey bee (Apis mellifera)
Authors: Mao Wenfu , Schuler Mary A. , Berenbaum May R.
Published: July 2011

AlthoughApis mellifera, the western honey bee, has long encountered pesticides when foraging in agricultural fields, for two decades it has encountered pesticides in-hive in the form of acaricides to controlVarroa destructor, a devastating parasitic mite. The pyrethroid tau-fluvalinate and the organophosphate coumaphos have been used forVarroacontrol, with little knowledge of honey bee detoxification mechanisms. Cytochrome P450-mediated detoxification contributes to pyrethroid tolerance in many insects, but specific P450s responsible for pesticide detoxification in honey bees (indeed, in any hymenopteran pollinator) have not been defined. We expressed and assayed CYP3 clan midgut P450s and demonstrated that CYP9Q1, CYP9Q2, and CYP9Q3 metabolize tau-fluvalinate to a form suitable for further cleavage by the carboxylesterases that also contribute to tau-fluvalinate tolerance. These in vitro assays indicated that all of the three CYP9Q enzymes also detoxify coumaphos. Molecular models demonstrate that coumaphos and tau-fluvalinate fit into the same catalytic pocket, providing a possible explanation for the synergism observed between these two compounds. Induction of CYP9Q2 and CYP9Q3 transcripts by honey extracts suggested that diet-derived phytochemicals may be natural substrates and heterologous expression of CYP9Q3 confirmed activity against quercetin, a flavonoid ubiquitous in honey. Up-regulation by honey constituents suggests that diet may influence the ability of honey bees to detoxify pesticides. Quantitative RT-PCR assays demonstrated that tau-fluvalinate enhances CYP9Q3 transcripts, whereas the pyrethroid bifenthrin enhances CYP9Q1 and CYP9Q2 transcripts and represses CYP9Q3 transcripts. The independent regulation of these P450s can be useful for monitoring and differentiating between pesticide exposures in-hive and in agricultural fields.
Moderation and consistency of teacher judgement: Teachers’ views
Authors: Connolly Stephen , Klenowski Valentina , Wyatt‐Smith Claire Maree
Published: July 2011

Major curriculum and assessment reforms in Australia have generated research interest in issues related to standards, teacher judgement and moderation. This article is based on one related inquiry of a large‐scale Australian Research Council Linkage project conducted in Queensland. This qualitative study analysed interview data to identify teachers’ views on standards and moderation as a means to achieving consistency of teacher judgement. A complementary aspect of the research involved a blind review that was conducted to determine the degree of teacher consistency without the experience of moderation. Empirical evidence was gained that most teachers, of the total interviewed, articulated a positive attitude towards the use of standards in moderation and perceived that this process produces consistency in teachers’ judgements. Context was identified as an important influential factor in teachers’ judgements and it was concluded that teachers’ assessment beliefs, attitudes and practices impact on their perceptions of the value of moderation practice and the extent to which consistency can be achieved.
Absent presences: The recognition of social class and gender dimensions within peer assessment interactions
Authors: Crossouard Barbara
Published: July 2011

This article focuses on the discursive characteristics of peer assessment interactions, drawing upon recent research into formative assessment within a task design involving extended project‐based work tackled in groups by pupils. Case studies were conducted within two schools in socially deprived areas of Scotland. They included classroom observation, digital video and audio data collection, and a series of interviews with pupils and teachers. The task design created opportunities for interdisciplinary, collaborative learning and generated strong pupil engagement. However, a disjuncture is seen between the conflictual characteristics of peer assessment, which are suggested to have gendered and social class dimensions, and the discourses of teamwork and community‐building that were privileged in the classrooms observed. Although recognised more in research conversations, the article argues that teachers could be better supported in considering how social class and gender are implicated in peer assessment and in developing classroom discourse that addresses social equity issues.
Vocational education and training in the spotlight: back to the future for the UK's Coalition Government?
Authors: Fuller Alison , Unwin Lorna
Published: July 2011

This paper examines the Coalition Government's plans for vocational education and training for 14- to 19-year-olds in England. It argues that new types of educational institutions will enable the emergence of new forms of segmentation in which the vocational track is likely to become
split into 'technical education' and lower level 'practical learning'. Whilst the new government has increased funding for apprenticeship, it has so far failed to address the systemic problems which have kept this as a minority track for 16- to 18-year-olds. The paper argues that the government-commissioned
Wolf Review of 14–19 Vocational Education in England provides support for segmentation.
Rethinking general education in the English upper secondary system
Authors: Hodgson Ann , Spours Ken
Published: July 2011

The Secretary of State for Education's recent announcement of an English Baccalaureate at 16+ has opened up a debate about the nature of general education in the English upper secondary system. Drawing on evidence from national and local studies, we argue that it is important to see
general education in England, not only in terms of the curriculum, but also as the product of a range of inter-related factors, which together form a 'model'. Using this analytical framework, we describe and analyse the two models of general education associated with the New Labour and Coalition
administrations respectively. We conclude by suggesting a set of challenges and principles to inform the development of a third, curriculum-led model.