bluuebunny/crossref_metadata_2025 huggingface dataset:
A three‐dimensional Moho depth model for the Tien Shan from EGM2008 gravity data
Authors: Steffen Rebekka , Steffen Holger , Jentzsch Gerhard
Published: August 2011

The Tien Shan in Central Asia is the largest intracontinental mountain range in the world, but it is 1500 km away from the collision zone between the Indian and Eurasian plates. This region has been and still is the focus of numerous geoscientific studies, mainly because of its evolutionary history and its unique position in the Eurasian lithosphere plate. So far, mainly seismological data have been used to explore the origin of and ongoing seismic activity in this region, but only one study has investigated terrestrial gravity data. In this study, a new gravity data set, EGM2008, is used to determine the crust‐mantle boundary (Mohorovičić discontinuity, Moho) of the Tien Shan using inversion of gravity data. In addition, an isostatic Moho is calculated from topographic data, which by comparison to the results of the gravity inversion illuminates the effects of isostatic compensation. The results of the gravity inversion generally agree with results of previous seismic studies and indicate that the Tien Shan has a mountain root with a thickness of about 75 km. Furthermore, the Moho is shallow under the basins, e.g., in the Tarim and Ili basins. The comparison with the isostatic Moho indicates an over‐compensation of the orogen and an under‐compensation of the basins. The over‐compensation results from the former subduction of the Tarim Basin terrane in the south. The under‐compensation of the Tarim Basin is generated by support of the terrane between the Tien Shan in the north and the Pamir mountains, Tibet and Himalayas in the south.
Renegotiating GM crop regulation
Authors: Kuzma Jennifer , Kokotovich Adam
Published: August 2011

Targeted genetic modification, which enables scientists to genetically engineer plants more efficiently and precisely, challenges current process‐based regulatory frameworks for genetically modified crops.
Ocean time-series reveals recurring seasonal patterns of virioplankton dynamics in the northwestern Sargasso Sea
Authors: Parsons Rachel J , Breitbart Mya , Lomas Michael W , Carlson Craig A
Published: August 2011

There are an estimated 1030 virioplankton in the world oceans, the majority of which are phages (viruses that infect bacteria). Marine phages encompass enormous genetic diversity, affect biogeochemical cycling of elements, and partially control aspects of prokaryotic production and diversity. Despite their importance, there is a paucity of data describing virioplankton distributions over time and depth in oceanic systems. A decade of high-resolution time-series data collected from the upper 300 m in the northwestern Sargasso Sea revealed recurring temporal and vertical patterns of virioplankton abundance in unprecedented detail. An annual virioplankton maximum developed between 60 and 100 m during periods of summer stratification and eroded during winter convective mixing. The timing and vertical positioning of this seasonal pattern was related to variability in water column stability and the dynamics of specific picophytoplankton and heterotrophic bacterioplankton lineages. Between 60 and 100 m, virioplankton abundance was negatively correlated to the dominant heterotrophic bacterioplankton lineage SAR11, as well as the less abundant picophytoplankton, Synechococcus. In contrast, virioplankton abundance was positively correlated to the dominant picophytoplankton lineage Prochlorococcus, and the less abundant alpha-proteobacteria, Rhodobacteraceae. Seasonally, virioplankton abundances were highly synchronous with Prochlorococcus distributions and the virioplankton to Prochlorococcus ratio remained remarkably constant during periods of water column stratification. The data suggest that a significant fraction of viruses in the mid-euphotic zone of the subtropical gyres may be cyanophages and patterns in their abundance are largely determined by Prochlorococcus dynamics in response to water column stability. This high-resolution, decadal survey of virioplankton abundance provides insight into the possible controls of virioplankton dynamics in the open ocean.
Bacteriocyte-associated gammaproteobacterial symbionts of the Adelges nordmannianae/piceae complex (Hemiptera: Adelgidae)
Authors: Toenshoff Elena R , Penz Thomas , Narzt Thomas , Collingro Astrid , Schmitz-Esser Stephan , Pfeiffer Stefan , Klepal Waltraud , Wagner Michael , Weinmaier Thomas , Rattei Thomas , Horn Matthias
Published: August 2011

Adelgids (Insecta: Hemiptera: Adelgidae) are known as severe pests of various conifers in North America, Canada, Europe and Asia. Here, we present the first molecular identification of bacteriocyte-associated symbionts in these plant sap-sucking insects. Three geographically distant populations of members of the Adelges nordmannianae/piceae complex, identified based on coI and ef1alpha gene sequences, were investigated. Electron and light microscopy revealed two morphologically different endosymbionts, coccoid or polymorphic, which are located in distinct bacteriocytes. Phylogenetic analyses of their 16S and 23S rRNA gene sequences assigned both symbionts to novel lineages within the Gammaproteobacteria sharing <92% 16S rRNA sequence similarity with each other and showing no close relationship with known symbionts of insects. Their identity and intracellular location were confirmed by fluorescence in situ hybridization, and the names ‘Candidatus Steffania adelgidicola’ and ‘Candidatus Ecksteinia adelgidicola’ are proposed for tentative classification. Both symbionts were present in all individuals of all investigated populations and in different adelgid life stages including eggs, suggesting vertical transmission from mother to offspring. An 85 kb genome fragment of ‘Candidatus S. adelgidicola’ was reconstructed based on a metagenomic library created from purified symbionts. Genomic features including the frequency of pseudogenes, the average length of intergenic regions and the presence of several genes which are absent in other long-term obligate symbionts, suggested that ‘Candidatus S. adelgidicola’ is an evolutionarily young bacteriocyte-associated symbiont, which has been acquired after diversification of adelgids from their aphid sister group.
An additional step in the transmission of Yersinia pestis?
Authors: Easterday W Ryan , Kausrud Kyrre L , Star Bastiaan , Heier Lise , Haley Bradd J , Ageyev Vladimir , Colwell Rita R , Stenseth Nils Chr
Published: August 2011

Plague, caused by the bacterium Yersinia pestis, is a mammalian vector-borne disease, transmitted by fleas that serve as the vector between rodent hosts. For many pathogens, including Y. pestis, there are strong evolutionary pressures that lead to a reduction in ‘useless genes’, with only those retained that reflect function in the specific environment inhabited by the pathogen. Genetic traits critical for survival and transmission between two environments, the rodent and the flea, are conserved in epizootic/epidemic plague strains. However, there are genes that remain conserved for which no function in the flea–rodent cycle has yet been observed, indicating an additional environment may exist in the transmission cycle of plague. Here, we present evidence for highly conserved genes that suggests a role in the persistence of Y. pestis after death of its host. Furthermore, maintenance of these genes points to Y. pestis traversing a post-mortem path between, and possibly within, epizootic periods and offering insight into mechanisms that may allow Y. pestis an alternative route of transmission in the natural environment.
Disgust Sensitivity, Obesity Stigma, and Gender: Contamination Psychology Predicts Weight Bias for Women, Not Men
Authors: Lieberman Debra L. , Tybur Josh M. , Latner Janet D.
Published: August 2011

Recent research has established a link between disgust sensitivity and stigmatizing reactions to various groups, including obese individuals. However, previous research has overlooked disgust's multiple evolved functions. Here, we investigated whether the link between disgust sensitivity and obesity stigma is specific to pathogen disgust, or whether sexual disgust and moral disgust—two separate functional domains—also relate to negative attitudes toward obese individuals. Additionally, we investigated whether sex differences exist in the manner disgust sensitivity predicts obesity stigma, whether the sexes differ across the subtypes of obesity bias independent of disgust sensitivity, and last, the association between participants' BMI and different subtypes of obesity stigma. In study 1 (N = 92), we established that obesity elicits pathogen, sexual, and moral disgust. In study 2, we investigated the relationship between these types of disgust sensitivity and obesity stigma. Participants (N = 387) reported their level of disgust toward various pathogen, sexual, and moral acts and their attitudes toward obese individuals. For women, but not men, increased pathogen disgust sensitivity predicted more negative attitudes toward obese individuals. Men reported more negative general attitudes toward obese individuals whereas women reported greater fear of becoming obese. The sexes also differed in how their own BMI related to the subtypes of obesity stigma. These findings indicate that pathogen disgust sensitivity plays a role in obesity stigma, specifically for women. Defining the scope of disgust's activation in response to obesity and its relationship with other variables can help identify possible mechanisms for understanding and ultimately alleviating prejudice and discrimination.
Evaluation of Specific Metabolic Rates of Major Organs and Tissues: Comparison Between Nonobese and Obese Women
Authors: Wang ZiMian , Ying Zhiliang , Bosy‐Westphal Anja , Zhang Junyi , Heller Martin , Later Wiebke , Heymsfield Steven B. , Müller Manfred J.
Published: August 2011

Elia (1992) identified the specific resting metabolic rates (Ki) of major organs and tissues in young adults with normal weight: 200 for liver, 240 for brain, 440 for heart and kidneys, 13 for skeletal muscle, 4.5 for adipose tissue and 12 for residual mass (all units in kcal/kg per day). The aim of the present study was to assess the applicability of Elia's Ki values for obese adults. A sample of young women (n = 80) was divided into two groups, nonobese (BMI <29.9 kg/m2) and obese (BMI 30.0–43.2 kg/m2). This study was based on the mechanistic model: REE = σ (Ki × Ti), where REE is whole‐body resting energy expenditure measured by indirect calorimetry and Ti is the mass of individual organs and tissues measured by magnetic resonance imaging. For each organ/tissue, the corresponding Elia's Ki value was analyzed respectively for nonobese and obese groups by using stepwise univariate regression analysis. Elia's Ki values were within the range of 95% confidence intervals (CIs) in the nonobese group. However, Elia's Ki values were outside the right boundaries of 95% CIs in the obese group and a corresponding obesity‐adjusted coefficient was calculated as 0.98, indicating that Elia's values overestimate Ki by 2.0% in obese adults. Obesity‐adjusted Ki values were 196 for liver, 235 for brain, 431 for heart and kidneys, 12.7 for skeletal muscle, 4.4 for adipose tissue, and 11.8 for residual mass. In conclusion, although Elia's Ki values were validated in nonobese women, obesity‐adjustments are appropriate for application in obese women.
Lower Than Predicted Resting Metabolic Rate Is Associated With Severely Impaired Cardiorespiratory Fitness in Obese Individuals
Authors: Miller Wendy M. , Spring Thomas J. , Zalesin Kerstyn C. , Kaeding Kaylee R. , Janosz Katherine E. Nori , McCullough Peter A. , Franklin Barry A.
Published: August 2011

Obese individuals have reduced cardiorespiratory fitness as compared with leaner counterparts. Regular exercise maintains or increases fitness and lean body mass. Lean body mass, in turn, has a direct impact on resting metabolic rate (RMR). Given these relationships, we sought to evaluate the association between RMR and cardiorespiratory fitness in obese individuals. We evaluated 64 obese individuals (78% female) with direct assessment of RMR and cardiorespiratory fitness via breath‐by‐breath measurement of oxygen consumption and carbon dioxide production at rest and during exercise. The mean age and BMI were 47.4 ± 12.2 years and 47.2 ± 9.2 kg/m2, respectively. The majority of subjects, 69%, had a measured RMR above that predicted by the Harris‐Benedict equation. Compared with the higher RMR group, those with a lower than predicted RMR had increased BMI, with values of 52.9 vs. 44.7 kg/m2, P = 0.001, respectively. Analysis of those demonstrating significant effort during cardiopulmonary exercise testing (peak respiratory exchange ratio ≥1.10) revealed a significantly higher peak oxygen uptake (VO2 peak) in the higher RMR group (17.3 ± 3.5 ml/min/kg) compared with the lower RMR group (13.6 ± 1.9 ml/min/kg), P = 0.003. In summary, a lower than predicted RMR was associated with a severely reduced VO2 peak and a higher BMI in this cohort. These data suggest that morbid obesity may be a vicious cycle of increasing BMI, reduced cardiorespiratory fitness, muscle deconditioning, and lower RMR. Collectively, these responses may, over time, exacerbate the imbalance between energy intake and expenditure, resulting in progressive increases in body weight and fat stores.
Polyamine homoeostasis as a drug target in pathogenic protozoa: peculiarities and possibilities
Authors: Birkholtz Lyn-Marie , Williams Marni , Niemand Jandeli , Louw Abraham I. , Persson Lo , Heby Olle
Published: August 2011

New drugs are urgently needed for the treatment of tropical and subtropical parasitic diseases, such as African sleeping sickness, Chagas' disease, leishmaniasis and malaria. Enzymes in polyamine biosynthesis and thiol metabolism, as well as polyamine transporters, are potential drug targets within these organisms. In the present review, the current knowledge of unique properties of polyamine metabolism in these parasites is outlined. These properties include prozyme regulation of AdoMetDC (S-adenosylmethionine decarboxylase) activity in trypanosomatids, co-expression of ODC (ornithine decarboxylase) and AdoMetDC activities in a single protein in plasmodia, and formation of trypanothione, a unique compound linking polyamine and thiol metabolism in trypanosomatids. Particularly interesting features within polyamine metabolism in these parasites are highlighted for their potential in selective therapeutic strategies.
Mutational analysis of allosteric activation and inhibition of glucokinase
Authors: Zelent Bogumil , Odili Stella , Buettger Carol , Zelent Dorothy K. , Chen Pan , Fenner Deborah , Bass Joseph , Stanley Charles , Laberge Monique , Vanderkooi Jane M. , Sarabu Ramakanth , Grimsby Joseph , Matschinsky Franz M.
Published: August 2011

GK (glucokinase) is activated by glucose binding to its substrate site, is inhibited by GKRP (GK regulatory protein) and stimulated by GKAs (GK activator drugs). To explore further the mechanisms of these processes we studied pure recombinant human GK (normal enzyme and a selection of 31 mutants) using steady-state kinetics of the enzyme and TF (tryptophan fluorescence). TF studies of the normal binary GK–glucose complex corroborate recent crystallography studies showing that it exists in a closed conformation greatly different from the open conformation of the ligand-free structure, but indistinguishable from the ternary GK–glucose–GKA complex. GKAs did activate and GKRP did inhibit normal GK, whereas its TF was doubled by glucose saturation. However, the enzyme kinetics, GKRP inhibition, TF enhancement by glucose and responsiveness to GKA of the selected mutants varied greatly. Two predominant response patterns were identified accounting for nearly all mutants: (i) GK mutants with a normal or close to normal response to GKA, normally low basal TF (indicating an open conformation), some variability of kinetic parameters (kcat, glucose S0.5, h and ATP Km), but usually strong GKRP inhibition (13/31); and (ii) GK mutants that are refractory to GKAs, exhibit relatively high basal TF (indicating structural compaction and partial closure), usually show strongly enhanced catalytic activity primarily due to lowering of the glucose S0.5, but with reduced or no GKRP inhibition in most cases (14/31). These results and those of previous studies are best explained by envisioning a common allosteric regulator region with spatially non-overlapping GKRP- and GKA-binding sites.
The yeast ABC transporter Pdr18 (ORF YNR070w) controls plasma membrane sterol composition, playing a role in multidrug resistance
Authors: Cabrito Tânia R. , Teixeira Miguel C. , Singh Ashutosh , Prasad Rajendra , Sá-Correia Isabel
Published: August 2011

The action of multidrug efflux pumps in MDR (multidrug resistance) acquisition has been proposed to partially depend on the transport of physiological substrates which may indirectly affect drug partition and transport across cell membranes. In the present study, the PDR18 gene [ORF (open reading frame) YNR070w], encoding a putative PDR (pleiotropic drug resistance) transporter of the ATP-binding cassette superfamily, was found to mediate plasma membrane sterol incorporation in yeast. The physiological role of Pdr18 is demonstrated to affect plasma membrane potential and is proposed to underlie its action as a MDR determinant, conferring resistance to the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid). The action of Pdr18 in yeast tolerance to 2,4-D, which was found to contribute to reduce [14C]2,4-D intracellular accumulation, may be indirect, given the observation that 2,4-D exposure deeply affects the sterol plasma membrane composition, this effect being much stronger in a Δpdr18 background. PDR18 activation under 2,4-D stress is regulated by the transcription factors Nrg1, controlling carbon source availability and the stress response, and, less significantly, Yap1, involved in oxidative stress and MDR, and Pdr3, a key regulator of the yeast PDR network, consistent with a broad role in stress defence. Taken together, the results of the present study suggest that Pdr18 plays a role in plasma membrane sterol incorporation, this physiological trait contributing to an MDR phenotype.
Multi-field/multi-scale turbulence response to electron cyclotron heating of DIII-D ohmic plasmas
Authors: Wang G. , Peebles W. A. , Rhodes T. L. , DeBoo J. C. , Staebler G. M. , Hillesheim J. C. , Yan Z. , McKee G. R. , Petty C. C. , Solomon W. M. , Burrell K. H. , Doyle E. J. , Leonard A. W. , Schmitz L. , VanZeeland M. A. , White A. E. , Zeng L.
Published: August 2011

The multi-field/multi-scale core (ρ ∼ 0.5–0.8) turbulence response to electron cyclotron heating (ECH) of DIII-D Ohmic plasmas is reported for the first time. Long wavelength (low-k) electron temperature (T̃e/Te) and high-k density turbulence levels (ñe/ne) are observed to strongly increase during ECH. In contrast, low-k and intermediate-k ñe/ne showed little change, whereas the cross-phase between local low-k electron temperature and density fluctuations (αneTe) was significantly modified. The increase in the electron thermal diffusivity determined from power balance is consistent with the increased turbulent transport correlated with the measured increases in low-k T̃e/Te and high-k ñe/ne. Linear stability analysis using the trapped gyro-Landau fluid (TGLF) model indicates an enhanced growth rate for electron modes [e.g., trapped electron mode (TEM)] at low-k consistent with the observed modifications in T̃e/Te and αneTe. TGLF also predicts an increase in high-k electron mode growth rates for normalized wavenumbers kθρs > 7, where electron temperature gradient (ETG) modes exist, which is consistent with the observed increase in high-kñe/ne turbulence
Structure of the alkali-metal-atom + strontium molecular ions: Towards photoassociation and formation of cold molecular ions
Authors: Aymar M. , Guérout R. , Dulieu O.
Published: August 2011

The potential energy curves, permanent and transition dipole moments, and the static dipolar polarizability, of molecular ions composed of one alkali-metal atom and a strontium ion are determined with a quantum chemistry approach. The molecular ions are treated as effective two-electron systems and are treated using effective core potentials including core polarization, large gaussian basis sets, and full configuration interaction. In the perspective of upcoming experiments aiming at merging cold atom and cold ion traps, possible paths for radiative charge exchange, photoassociation of a cold lithium or rubidium atom and a strontium ion are discussed, as well as the formation of stable molecular ions.
Roles of particle-wall and particle-particle interactions in highly confined suspensions of spherical particles being sheared at low Reynolds numbers
Authors: Sangani Ashok S. , Acrivos Andreas , Peyla Philippe
Published: August 2011

The roles of particle-wall and particle-particle interactions are examined for suspensions of spherical particles in a viscous fluid being confined and sheared at low Reynolds numbers by two parallel walls moving with equal but opposite velocities. Both particle-wall and particle-particle interactions are shown to decrease the rotational velocity of the spheres, so that in the limit of vanishingly small gaps between the spheres and the walls, the spheres acquire a rotational slip relative to the walls. The presence of the walls also increases the particle stresslet and, therefore, the total viscous dissipation. In the limit of vanishingly small gaps, the increased viscous dissipation in the gaps between pairs of spheres aligned in the flow direction is largely compensated by the reduction in the dissipation in the gaps between the spheres and the walls due to a reduction in the rotational velocity of the spheres. As a result, the effect of short-range particle interactions on the stresslet is generally insignificant. On the other hand, the channel-scale particle interactions in the shear flow induced by the moving walls decrease the particle stresslet, primarily because the fraction of pairs of spheres that are aligned parallel to the flow (the presence of which in a shear flow reduces the stresslet) is relatively higher than in unbounded suspensions. Expressions are also derived for the total stress in dilute random suspensions that account for both the particle-wall and the channel-scale particle-particle interactions in determining the rotational velocities and stresses. The latter are shown to be consistent with recent numerical [Y. Davit and P. Peyla, Europhys. Lett. 83, 64001 (2008)] and experimental [P. Peyla and C. Verdier, Europhys. Lett. 94, 44001 (2011)] findings according to which, for a range of sphere radius to gap width ratios, the effect of particle-particle interactions is to decrease the total dissipation.
On the benefits of hysteresis effects for closed-loop separation control using plasma actuation
Authors: Benard N. , Cattafesta L. N. , Moreau E. , Griffin J. , Bonnet J. P.
Published: August 2011

Flow separation control by a non-thermal plasma actuator is considered for a NACA 0015 airfoil at a chord Reynolds number of 1.9 × 105. Static hysteresis in the lift coefficient is demonstrated for increasing and then decreasing sinusoidal voltage amplitude supplying a typical single dielectric barrier discharge actuator at the leading edge of the model. In addition to these open-loop experiments, unsteady surface pressure signals are examined for transient processes involving forced reattachment and natural separation. The results show that strong pressure oscillations in the relatively slow separation process, compared to reattachment, precede the ultimate massive flow separation. To enhance the contrast between the parts of the signal related to the attached flow and those related to the incipient separation, RMS estimate of filtered values of Cp is used to define a flow separation predictor that is implemented in feedback control. Two simple controllers are proposed, one based on a predefined threshold of the unsteady Cp and another that utilizes the flow separation predictor to identify incipient separation. The latter effectively leverages the hysteresis in the post-stall regime to reduce the electrical power consumed by the actuator while maintaining continuously attached flow.
Forward Raman compression via photonic band gap in metals or warm dense matter
Authors: Son S. , Moon Sung Joon
Published: August 2011

The group velocity of a light pulse in photonic band gap material could considerably deviate from the speed of light in vacuum. A forward stoke and a pump pulse of different speeds would enable the Raman compression in metals or the warm dense matter. A small window of the parameter regime, where the compression is feasible via the forward Raman scattering, is identified.
Analysis of electric field screening by the proximity of two knife-edge field emitters
Authors: Tang Wilkin , Shiffler Don , Cartwright Keith L.
Published: August 2011

The electric field of two semi-infinitely wide knife-edge cathodes with arbitrary separation is calculated by using a Schwarz–Christoffel transformation. This geometry could also represent a trench (or scratch) on a flat surface. It is found that the magnitude of the electric field on the knife-edge cathodes depends strongly on the ratio h/a, where h is the height of the knife-edge cathodes and 2a is the distance between the cathodes. When h/a increases, the magnitude of the electric field on the cathode’s surface decreases. This shows the screening of one cathode by another cathode; for example, keeping the height fixed and decreasing the distance between the cathodes, the field enhancement on the corner decreases. Analytic approximations for the divergent electric field in the immediate vicinity of the sharp edge are derived for the cases where h/a>>1, and h/a≪1. These results lead to insight on the relationship of the density of field emitter in field emitting arrays and field emission from rough surfaces.
Analytical drain current model reproducing advanced transport models in nanoscale cylindrical surrounding-gate (SRG) MOSFETs
Authors: Cheralathan M. , Iannaccone G. , Sangiorgi E. , Iñiguez B.
Published: August 2011

In this paper we extend a compact surrounding-gate MOSFET model to include the hydrodynamic transport and quantum mechanical effects, and we show that it can reproduce the results of 3D numerical simulations using advanced transport models. A template device representative for the cylindrical surrounding-gate MOSFET was used to validate the model. The final compact model includes mobility degradation, drain-induced barrier lowering, velocity overshoot, and quantum effects. Comparison between the compact model and the advanced transport modeling approaches shows good agreement within the practical range of drain voltages.
On the Green-functions of the classical off-shell electrodynamics under the manifestly covariant relativistic dynamics of Stueckelberg
Authors: Aharonovich I. , Horwitz L. P.
Published: August 2011

In previous papers derivations of the Green function have been given for 5D off-shell electrodynamics in the framework of the manifestly covariant relativistic dynamics of Stueckelberg (with invariant evolution parameter τ). In this paper, we reconcile these derivations resulting in different explicit forms, and relate our results to the conventional fundamental solutions of linear 5D wave equations published in the mathematical literature. We give physical arguments for the choice of the Green function retarded in the fifth variable τ.
Monte-Carlo simulations of light propagation in luminescent solar concentrators based on semiconductor nanoparticles
Authors: Şahin Derya , Ilan Boaz , Kelley David F.
Published: August 2011

Semiconductor nanoparticles have a wide absorption band and small reabsorption probability, which makes them great candidates for luminescent solar concentrators (LSCs). We use Monte-Carlo simulations of photon transport to predict the performance of LSCs based on “type-II” CdSe-CdTe quantum dots. These computations suggest that semiconductor-based LSCs can be highly efficient. The optimum performance is reached with a fairly long LSC with a photovoltaic cell covering only one edge. In addition, when the LSC has CdSe-CdTe nanorods that are aligned perpendicular to the top surface, the escape of photons from the top surface is significantly reduced. These results are encouraging for cost-effective LSC designs based on semiconductor nanoparticles.
Verification of collisionless sheath model of capacitive rf discharges by particle-in-cell simulations
Authors: Wang Ying , Lieberman Michael A. , Wu Alan C. F. , Verboncoeur John P.
Published: August 2011

A global model for high voltage rf argon capacitive discharges in the collisionless sheath regime is verified by particle-in-cell simulations, for both current- and voltage-driven sources. The ion energy distributions (IEDs) and the IED widths are investigated and show good agreement with a theoretical model, with proper adjustment of the dc bias voltage. The sensitivities of IEDs to sources (current or voltage driven) are described. It is found that for the same variations of rf source amplitudes, larger voltage shifts are expected in the IEDs for the current-driven than the voltage-driven cases. The effects of rf frequencies on IEDs are determined for a fixed rf voltage-driven source amplitude. The IEDs show a surprising independence of the rf frequencies, which can be understood reasonably well by the combined scalings of the global discharge model and IED theoretical model.
L
p
-bounds for quasi-geostrophic equations via functional analysis
Authors: de la Llave Rafael , Valdinoci Enrico
Published: August 2011

We give a proof of Lp-bounds for the quasi-geostrophic equation and other non-local equations. The proof uses mainly tools from functional analysis, notably the product formulas (also known as “operator splitting methods”) and the Bochner-Pollard subordination identities, hence it could be applicable to other equations.
Pressure induced high spin-low spin transition in FeSe superconductor studied by x-ray emission spectroscopy and ab initio calculations
Authors: Kumar Ravhi S. , Zhang Yi , Xiao Yuming , Baker Jason , Cornelius Andrew , Veeramalai Sathishkumar , Chow Paul , Chen Changfeng , Zhao Yusheng
Published: August 2011

FeSe is a simple binary system in the iron based superconducting family and exhibits a significant pressure induced increase in the superconducting transition temperature (Tc). In addition to pressure effect, spin fluctuations, magnetic ordering, and crystal structure all play vital roles in altering Tc. Even though various experiments and theoretical simulations explain the connection among them and superconductivity, the interplay between these important parameters is still not clearly understood. Here, we report the pressure effect on the spin state of Fe in FeSe superconductor studied using synchrotron x-ray emission spectroscopy at ambient and low temperatures down to 8 K near Tc. Pressure induced high spin to low spin transition was observed at both ambient and low temperatures with continuous suppression of Fe magnetic moments under increasing pressure. The spin transition is closely related to the pressure induced tetragonal to orthorhombic structural transition.
Ab initio investigation of structural, electronic, mechanical, and thermodynamic properties of AlSc2 intermetallic compound under pressure
Authors: Pang Mingjun , Zhan Yongzhong , Wang Haizhou , Jiang Wenping , Du Yong
Published: August 2011

The dependences of the structural, electronic, mechanical, and thermodynamic properties of AlSc2 compound on pressure were investigated for the first time by means of the first-principles method based on the density functional theory with generalized gradient approximation and local density approximation. It was found that the pressure has significant effects on the equilibrium volume, mechanical properties, electronic properties and the heat capacity. Our calculated structural data are in good agreement with the previous experimental and theoretical data results. The calculated elastic constants indicate that the AlSc2 compound is mechanically stable in the pressure range of 0–50 GPa. The Zener ratio A and linear compressibility coefficients kc/ka are used to estimate anisotropic elasticity. The isotropic bulk modulus B, shear modulus G, Young’s modulus E, and Poisson’s ratio ν of polycrystalline AlSc2 compound were determined using the Voigt-Reuss-Hill averaging scheme. The B/G, Poisson’s ratio and microhardness parameter are calculated. The band structure and density of states are also discussed. The Debye temperature can be obtained from the elastic constants and the sound velocities and the pressure has little influence. The temperature-dependent behavior of thermodynamical properties (internal energy, entropy, free energy, and heat capacity) at 0, 20, and 40 GPa have been obtained from phonon density of states.
Levinson's theorem for graphs
Authors: Childs Andrew M. , Strouse D J
Published: August 2011

We prove an analog of Levinson's theorem for scattering on a weighted (m + 1)-vertex graph with a semi-infinite path attached to one of its vertices. In particular, we show that the number of bound states in such a scattering problem is equal to m minus half the winding number of the phase of the reflection coefficient (where each so-called half-bound state is counted as half a bound state).
The whistler mode refractive index as a function of gyrofrequency
Authors: Albert J. M.
Published: August 2011

The refractive index for a constant-frequency whistler mode wave in an electron-proton plasma is considered as a function of position, through the local gyrofrequencies Ωe,i. The full cold plasma dispersion relation is used. The wave frequency can take any value up to the smaller of Ωe and the plasma frequency ωpe, but ωpe is allowed to take any fixed value, as is the wavenormal angle. It is rigorously established that the refractive index is a decreasing function of Ωe. One application of this is to finding locations of Landau and cyclotron resonances, to evaluate the effects of whistler mode waves on radiation belt electrons.
Note: Seesaw actuation of atomic force microscope probes for improved imaging bandwidth and displacement range
Authors: Torun H. , Torello D. , Degertekin F. L.
Published: August 2011

The authors describe a method of actuation for atomic force microscope (AFM) probes to improve imaging speed and displacement range simultaneously. Unlike conventional piezoelectric tube actuation, the proposed method involves a lever and fulcrum “seesaw” like actuation mechanism that uses a small, fast piezoelectric transducer. The lever arm of the seesaw mechanism increases the apparent displacement range by an adjustable gain factor, overcoming the standard tradeoff between imaging speed and displacement range. Experimental characterization of a cantilever holder implementing the method is provided together with comparative line scans obtained with contact mode imaging. An imaging bandwidth of 30 kHz in air with the current setup was demonstrated.
Communication maps computed for homodimeric hemoglobin: Computational study of water-mediated energy transport in proteins
Authors: Gnanasekaran Ramachandran , Agbo Johnson K. , Leitner David M.
Published: August 2011

Frequency-resolved communication maps provide a coarse-grained picture of energy transport in nanoscale systems. We calculate communication maps for homodimeric hemoglobin from Scapharca inaequivalvis and sample them to elucidate energy transfer pathways between the binding sites and other parts of the protein with focus on the role of the cluster of water molecules at the interface between the globules. We complement analysis of communication maps with molecular simulations of energy flow. Both approaches reveal that excess energy in one heme flows mainly to regions of the interface where early hydrogen bond rearrangements occur in the allosteric transition. In particular, energy is carried disproportionately by the water molecules, consistent with the larger thermal conductivity of water compared to proteins.
In-assisted desorption of native GaAs surface oxides
Authors: Li L. H. , Linfield E. H. , Sharma R. , Davies A. G.
Published: August 2011

We demonstrate In-assisted desorption of native GaAs surface oxides at substrate temperatures of 480–550 °C. The oxides are removed through production of volatile Ga and In suboxides, Ga2O, and In2O. Compared to a Ga-assisted desorption process, excess In is easily removed at low substrate temperature, favouring a clean, smooth surface. The feasibility of using In-assisted desorption for the regrowth of high quality quantum dot structures is shown.
Sequence correlations shape protein promiscuity
Authors: Lukatsky David B. , Afek Ariel , Shakhnovich Eugene I.
Published: August 2011

We predict analytically that diagonal correlations of amino acid positions within protein sequences statistically enhance protein propensity for nonspecific binding. We use the term “promiscuity” to describe such nonspecific binding. Diagonal correlations represent statistically significant repeats of sequence patterns where amino acids of the same type are clustered together. The predicted effect is qualitatively robust with respect to the form of the microscopic interaction potentials and the average amino acid composition. Our analytical results provide an explanation for the enhanced diagonal correlations observed in hubs of eukaryotic organismal proteomes [J. Mol. Biol. 409, 439 (2011)]10.1016/j.jmb.2011.03.056. We suggest experiments that will allow direct testing of the predicted effect.
Accurate quantum-mechanical rate constants for a linear response Azzouz-Borgis proton transfer model employing the multilayer multiconfiguration time-dependent Hartree approach
Authors: Craig Ian R. , Thoss Michael , Wang Haobin
Published: August 2011

The multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) method is applied to simulate the quantum dynamics and thermal rate constant of the Azzouz-Borgis model of proton transfer in a polar solvent. To this end, the original atomistic potential is mapped to a system-bath model. Employing the flux correlation function formalism and importance sampling techniques, accurate quantum mechanical rate constants are obtained, which provide a benchmark for evaluating approximate approaches to study the quantum dynamics of condensed-phase chemical reactions. Furthermore, the validity of the mapping procedure is discussed based on the comparison of the classical dynamics of the original atomistic Azzouz-Borgis model and the mapped system-bath model.
Dependence on composition of the optical polarization properties of m-plane InxGa1−xN commensurately grown on ZnO
Authors: Tamaki Hiroaki , Kobayashi Atsushi , Ohta Jitsuo , Oshima Masaharu , Fujioka Hiroshi
Published: August 2011

We have grown m-plane InxGa1−xN (x = 0.24-0.43) commensurately on m-plane ZnO by the use of a low temperature epitaxial growth technique and investigated its optical properties. We found that the critical thickness for strain relaxation in the InGaN films prepared by the present technique is at least one order of magnitude larger than those reported by the other techniques. Polarized optical absorption measurements revealed that the allowed optical transition between the conduction band and the topmost valence band in m-plane InxGa1−xN (x = 0.24−0.43) on ZnO is for light polarized along c-axis. We found that the valence band splitting energy strongly depends upon the In composition. The values of the deformation potentials of InN were determined as D3 = 2.4 eV, D4 = −6.3 eV, and D5 = −1.2 eV, by fitting the experimental results with theoretical calculations based on the k·p approach.
Substrate-dependent quasiparticle recombination time in superconducting resonators
Authors: Vercruyssen N. , Barends R. , Klapwijk T. M. , Muhonen J. T. , Meschke M. , Pekola J. P.
Published: August 2011

We demonstrate an increased quasiparticle recombination time in superconducting resonators on a SiNx membrane, compared to identical resonators on a SiNx/Si wafer. An interpretation is given using a thermal model of the membrane. Using an array of tunnel junctions to cool or heat the membrane, we show that the resonators on the membranes are extremely sensitive to small changes of the phonon temperature, which renders them excellent phonon thermometers with a noise level equivalent to 5μK/Hz. The experimental set-up is in principle an ideal platform to study the interplay of quasiparticles and phonon populations in superconductors.
Enhanced thermoelectric power factor with impurity-induced resonant level
Authors: Liu M. , Qin X. Y. , Liu C. S. , Zeng Z.
Published: August 2011

Based on the resonant level concept, we presented an analytic calculation for the enhancement of the thermoelectric properties of semiconductor materials with element doping. We show that the power factor can be significantly enhanced due to a resonant energy level introduced by some element lies in the host bands and near the Fermi level and band edge. Our calculations reveal that by choosing optimal parameters for the element doping, such as impurity level, and doping concentration, one can obtain an optimum power factor for improved thermoelectric performance.
Theoretical investigation of rotationally inelastic collisions of the methyl radical with helium
Authors: Dagdigian Paul J. , Alexander Millard H.
Published: August 2011

Rotationally inelastic collisions of the CH3 molecule in its ground $\tilde X^2 A^{\prime \prime} _2 $X̃2A2′′ electronic state have been investigated. We have determined a potential energy surface (PES) for the interaction of rigid CH3, frozen at its equilibrium geometry, with a helium atom, using a coupled-cluster method that includes all single and double excitations, as well as perturbative contributions of connected triple excitations [RCCSD(T)]. The anisotropy of the PES is dominated by repulsion of the helium by the hydrogen atoms. The dissociation energy De was computed to equal 27.0 cm−1. At the global minimum, the helium atom lies in the CH3 plane between two C–H bonds at an atom-molecule separation R = 6.52 bohr. Cross sections for collision-induced rotational transitions have been determined through quantum scattering calculations for both nuclear spin modifications. Rotationally inelastic collisions can cause a change in the rotational angular momentum n and its body-frame projection k. Because of the anisotropy of the PES due to the hydrogen atoms, there is a strong propensity for Δk = ±3 transitions. Thermal rate constants for state-specific total collisional removal have also been determined.
Determining concentration depth profiles in fluorinated networks by means of electric force microscopy
Authors: Miccio Luis A. , Kummali Mohammed M. , Montemartini Pablo E. , Oyanguren Patricia A. , Schwartz Gustavo A. , Alegría Ángel , Colmenero Juan
Published: August 2011

By means of electric force microscopy, composition depth profiles were measured with nanometric resolution for a series of fluorinated networks. By mapping the dielectric permittivity along a line going from the surface to the bulk, we were able to experimentally access to the fluorine concentration profile. Obtained data show composition gradient lengths ranging from 30 nm to 80 nm in the near surface area for samples containing from 0.5 to 5 wt. % F, respectively. In contrast, no gradients of concentration were detected in bulk. This method has several advantages over other techniques because it allows profiling directly on a sectional cut of the sample. By combining the obtained results with x-ray photoelectron spectroscopy measurements, we were also able to quantify F/C ratio as a function of depth with nanoscale resolution.
Link between crystal quality and electrical properties of metalorganic vapour phase epitaxy InxGa1−xN thin films
Authors: Gorge V. , Djebbour Z. , Migan-Dubois A. , Pareige C. , Longeaud C. , Pantzas K. , Moudakir T. , Gautier S. , Orsal G. , Voss P. L. , Ougazzaden A.
Published: August 2011

We report on the crystal quality of metalorganic vapour phase epitaxy-grown InGaN with indium content ranging from 0% to 20%. Absorbance measurements are fit to a model including band tails and a defect represented as a Brendel oscillator (R. Brendel, Appl. Phys. A 50, 587, 1990). Band tail absorbance, corresponding to contorted bonds, increases with increased In content. Above 10% of In, the presence of another defect, the concentration of which increases with In content, has been correlated with x-ray diffraction and Raman. We suggest that this defect corresponds to nitrogen vacancies, in agreement with a reported model for GaN.
Modulation of the thermodynamic, kinetic, and magnetic properties of the hydrogen monomer on graphene by charge doping
Authors: Huang Liang Feng , Ni Mei Yan , Zhang Guo Ren , Zhou Wang Huai , Li Yong Gang , Zheng Xiao Hong , Zeng Zhi
Published: August 2011

The thermodynamic, kinetic, and magnetic properties of the hydrogen monomer on doped graphene layers were studied by ab initio simulations. Electron doping heightens the diffusion potential barrier, while hole doping lowers it. However, both kinds of dopings heighten the desorption potential barrier. The underlying mechanism was revealed by investigating the effect of charge doping on the bond strength of graphene and on the electron transfer and the coulomb interaction between the hydrogen monomer and graphene. The kinetic properties of H and D monomers on doped graphene layers during both the annealing process (annealing time t0 = 300 s) and the constant-rate heating process (heating rate α = 1.0 K/s) were simulated. Macroscopic diffusion of hydrogen monomers on graphene can be achieved when the doping-hole density reaches 5.0 × 1013 cm−2. Both electron and hole dopings linearly reduce the total magnetic moment and exchange splitting, which was explained by a simple exchange model. The laws found in this work had been generalized to explain many phenomena reported in literature. This study can further enhance the understanding of the interaction between hydrogen and graphene and was expected to be helpful in the design of hydrogenated-graphene-based devices.
Note: Multi-point measurement of |B| in the gas-dynamic trap with a spectral motional Stark effect diagnostic
Authors: Lizunov A. A. , Den Hartog D. J. , Donin A. S. , Ivanov A. A. , Prikhodko V. V.
Published: August 2011

An upgraded spectral motional Stark effect diagnostic has been installed on the gas-dynamic trap (GDT) experiment to enable spatially resolved measurement of |B|. A new low-noise charge-coupled device detector, combined with enhancements of the diagnostic neutral beam, allows single-shot profile measurements. Previously only single-point motional Stark effect measurements were possible, and detector noise severely limited measurement precision, requiring multi-shot averaging. The plasma pressure profile in GDT is derived from the measured diamagnetic modification of |B| and used to examine the conditions of stable plasma confinement at high plasma pressure.
Composition and heavy component enrichment of free Ar-Kr and Kr-Xe clusters
Authors: Danilchenko A. G. , Kovalenko S. I. , Konotop A. P. , Samovarov V. N.
Published: August 2011

The composition of free Ar-Kr and Kr-Xe clusters produced by condensation of supersonic jets of gaseous mixtures with different amounts of krypton and xenon are studied in detail by electron diffraction for the first time. Analytic relationships are derived between the concentration of the heavy component in a cluster to the amount of it in the gaseous mixture and the pressure of the gas at the inlet to the supersonic nozzle (cluster size). Krypton and xenon enrichment of the clusters, involving a substantial increase in the amount of the heavy component compared to its concentration in the gas, is studied. Three substantially different atomic-molecular modes of cluster enrichment during cluster nucleation and growth are identified.