bluuebunny/crossref_metadata_2025 huggingface dataset:
The human xenobiotic‐metabolizing enzyme arylamineN‐acetyltransferase 1 (NAT1) is irreversibly inhibited by inorganic (Hg2+) and organic mercury (CH3Hg+): Mechanism and kinetics
Authors: Ragunathan Nilusha , Busi Florent , Pluvinage Benjamin , Sanfins Elodie , Dupret Jean-Marie , Rodrigues-Lima Fernando , Dairou Julien
Published: June 2010

Human arylamineN‐acetyltransferase 1 (NAT1) is a xenobiotic‐metabolizing enzyme that biotransforms aromatic amine chemicals. We show here that biologically‐relevant concentrations of inorganic (Hg2+) and organic (CH3Hg+) mercury inhibit the biotransformation functions of NAT1. Both compounds react irreversibly with the active‐site cysteine of NAT1 (half‐maximal inhibitory concentration (IC50) = 250 nM andkinact= 1.4 × 104M−1s−1for Hg2+and IC50= 1.4 μM andkinact= 2 × 102M−1s−1for CH3Hg+). Exposure of lung epithelial cells led to the inhibition of cellular NAT1 (IC50= 3 and 20 μM for Hg2+and CH3Hg+, respectively). Our data suggest that exposure to mercury may affect the biotransformation of aromatic amines by NAT1.
Heparin binding domain in vitronectin is required for oligomerization and thus enhances integrin mediated cell adhesion and spreading
Authors: Chillakuri Chandramouli R , Jones Céline , Mardon Helen J
Published: June 2010

MINT‐7905703: Vn (uniprotkb:P04004) and Vn (uniprotkb:P04004) bind (MI:0407) by molecular sieving (MI:0071)
SUFFERING INFERTILITY: THE IMPACT OF INFERTILITY ON WOMEN'S LIFE EXPERIENCES IN TWO NIGERIAN COMMUNITIES
Authors: LARSEN ULLA , HOLLOS MARIDA , OBONO OKA , WHITEHOUSE BRUCE
Published: June 2010

This paper examines the experiences of women with infertility in two Nigerian communities with different systems of descent and historically different levels of infertility. First, the paper focuses on the life experiences of individual women across the two communities and second, it compares these experiences with those of their fertile counterparts, in each community. In doing this, women who are childless are distinguished from those with subfertility and compared with high-fertility women. The research is based on interdisciplinary research conducted among the Ijo and Yakurr people of southern Nigeria, which included a survey of approximately 100 childless and subfertile women and a matching sample of 100 fertile women as well as in-depth ethnographic interviews with childless and subfertile women in two communities: Amakiri in Delta State and Lopon in Cross River State. The findings indicate that while there are variations in the extent to which childlessness is considered to be problematic, the necessity for a woman to have a child remains basic in this region.
Ecology of parasiteSycophilomorphasp. onFicus altissimaand its effect on the fig-fig wasp mutualism
Authors: PENG Y. Q. , ZHAO J. B. , HARRISON R. D. , YANG D. R.
Published: June 2010

Figs and their pollinating wasps are a classic example of an obligate mutualism. In addition, figs are parasitized by a suite of non-mutualistic wasps whose basic ecology is largely undescribed.Sycophilomorpha(subfamily Epichrysomallinae) fig wasps are ovule gallers and the genus contains only 1 described species. An undescribedSycophilomorphaspecies parasitizedFicus altissimaat Xishuangbana, Southwestern China. The wasp was observed ovipositing on the tiny immature figs that were still concealed beneath the involucral bracts. ASycophilomorphawasp oviposited on more than 1 fig and spent long time-periods to lay large clutches on a single fig. The wasps naturally occurred on all 7 sampled trees, but the occurrence of wasps was significantly different among trees, crops and months. These wasps were able to prevent unpollinated figs from being aborted, and their offspring were able to develop in the figs that otherwise had no pollinator wasps or seeds. TheSycophilomorphawasp had a detrimental effect on the fig–fig wasp mutualism. Figs in whichSycophilomorphawasps were present, produced significantly fewer seeds, pollinators and cheaters. However, the abundance ofSycophilomorphain a fig was only significantly negatively correlated with pollinator production and not seed or cheater production. Our study illustrates a previously unknown fig wasp niche and expands our understanding of factors that can affect the fig–fig wasp interaction.
Low secondary transmission of 2009 pandemic influenza A (H1N1) in households following an outbreak at a summer camp: relationship to timing of exposure
Authors: DOYLE T. J. , HOPKINS R. S.
Published: June 2010

Following an outbreak of 2009 pandemic influenza A (H1N1) at a residential summer camp for boys aged 10–16 years, we assessed secondary household transmission of the novel virus after their return home. Of 212 study participants who attended camp, 49 had confirmed or probable influenza for a primary attack rate of 23%. Of 87 exposed household contacts who did not attend camp, only three instances of probable transmission were observed, for a household secondary attack rate of 3·5%. All secondary cases occurred in households where the ill camp attendee returned home 1 day after onset of illness, with an attack rate of 14·3% in household contacts in this category. Returning home after peak infectivity to others and advanced warning prior to reintegration of sick individuals into the household probably contributed to the overall low secondary attack rate observed.
Current taxonomic composition of European genebank material documented in EURISCO
Authors: van Hintum Theo , Knüpffer Helmut
Published: June 2010

Taxonomy plays an essential role in genebank documentation. It is often the first level at which users search material, and it determines the protocols used in the management of collections. Especially, when plant genetic resources information is pooled in systems such as EURISCO, the European catalogue of ex situ plant genetic resources, problems regarding technical handling of taxonomic nomenclature, such as lack of standardization and low quality of data, become apparent. These problems were studied by analysing the content of EURISCO and mapping the taxon names in EURISCO on those used in the United States Department of Agriculture genebank system GRIN-Tax. Thus, the number of spelling errors and the level of standardization could be quantified and improved. An analysis of the content of EURISCO was made, showing a highly unbalanced distribution over crops: 50% of the accessions belong to ten genera only. Mapping EURISCO on the crops listed in Annex 1 of the International Treaty on Plant Genetic Resources for Food and Agriculture showed that 67% of the accessions in EURISCO belong to crops in that list.
Social fragmentation and economic growth: evidence from developing countries
Authors: OKEDIJI TADE O.
Published: June 2010

This paper proposes a composite measure of ethnic fragmentation, the Social Diversity Index (SDI) to capture inherent multidimensionality not captured in the prevalent Ethno-Linguistic Fractionalization Index (ELF). The SDI more accurately demonstrates the direct effects of hidden diversity values and the extent and corresponding costs of ethnic diversity on economic growth. A comparative empirical analysis of the results from 132 countries employing the SDI and the ELF Index, suggests that the SDI is more robustly correlated with growth, and does a moderately better job of explaining the effect of exogenous static ethnic diversity. However, the empirical effects of ethnic diversity on growth tend to diminish with the inclusion of additional macroeconomic variables.
Sources of new nitrogen in the Vietnamese upwelling region of the South China Sea
Authors: Bombar Deniz , Dippner Joachim W. , Doan Hai Nhu , Ngoc Lam Nguyen , Liskow Iris , Loick‐Wilde Natalie , Voss Maren
Published: June 2010

In the South China Sea, the southwest monsoon between June and September induces upwelling off the southern central Vietnamese coast. During field campaigns in July 2003 and 2004 we evaluated the importance of nitrate and nitrogen fixation as sources of new nitrogen for phytoplankton primary productivity, both in the actual upwelling zone and in the oligotrophic area farther offshore. Complementary to rate measurements of primary productivity, nitrate uptake, and nitrogen fixation, we determined vertical nitrate fluxes by Ekman upwelling (upwelling zone) and turbulent diffusion (offshore waters). Because of the influence of El Niño, upwelling was weaker in July 2003, with an average primary productivity of 28 ± 18 mmol C m−2 d−1, compared to 103 ± 25 mmol C m−2 d−1 in July 2004. Calculated upwelling nitrate fluxes of 17 ± 2 mmol N m−2 d−1 in July 2004 are consistent with N demands of primary productivity, if Redfield stoichiometry is assumed. In July 2003 upwelling fluxes of 14 ± 2 mmol N m−2 d−1 exceeded N demands, indicating that new production was not fully realized. Diffusive nitrate fluxes in offshore waters were determined in July 2003 and are of the order of 2.3 ± 0.6 mmol N m−2 d−1, based on the maximal diffusivities of 1 cm2 s−1 in the nitracline. Nitrogen fixation was a significant N source in offshore waters, but at lower rates in July 2003 (22–119 μmol N m−2 day−1) than in July 2004 (37–375 μmol N m−2 day−1), equaling 1%–5% and probably 2%–25% of the diffusive nitrate fluxes, respectively.
Laboratory simulations of Mars evaporite geochemistry
Authors: Moore Jeffrey M. , Bullock Mark A. , Newsom Horton , Nelson Melissa
Published: June 2010

Evaporite‐rich sedimentary deposits on Mars were formed under chemical conditions quite different from those on the Earth. Their unique chemistries record the chemical and aqueous conditions under which they were formed and possibly subsequent conditions to which they were subjected. We have produced evaporite salt mineral suites in the laboratory under two simulated Martian atmospheres: (1) present‐day and (2) a model of an ancient Martian atmosphere rich in volcanic gases. The composition of these synthetic Mars evaporites depends on the atmospheres under which they were desiccated as well as the chemistries of their precursor brines. In this report, we describe a Mars analog evaporite laboratory apparatus and the experimental methods we used to produce and analyze the evaporite mineral suites. The acidic, “paleo‐Mars” gas mixture was CO2 with trace amounts of SO2, N2O, and HCl to simulate an atmosphere influenced by volcanic emissions. Brines formed by the interaction of water with an SNC‐derived synthetic Mars mineral mix were produced under the acidic Mars atmospheric gas mixture. The brines were then desiccated under the two different simulated Mars conditions in the evaporite apparatus. Infrared reflectance spectroscopy and SEM microprobe analyses reveal that salts precipitated from the brine evaporated under simulated present Mars conditions were chemically different from those formed under the acidic Mars atmosphere conditions. The primary salt precipitated from the brine evaporated under present‐day Mars conditions was a hydrated calcium sulfate, with lesser amounts of a magnesium sulfate and aluminum sulfate. Salts precipitated from the brine evaporated under an acidic atmosphere were dominated by magnesium sulfates, with lesser amounts of Na2SO4. These experiments suggest ways that relative cation abundances in Martian sulfate‐bearing sediments can indicate the atmospheric and aqueous conditions under which they were formed. We conclude that the salts that make up the Meridiani sediments were probably formed by the interaction of water and igneous rocks at a high water‐to‐rock ratio, followed by desiccation under an atmosphere rich in acidic volcanic volatiles. The formation of Ca sulfates on Mars has most likely been due to the evaporation or freezing and sublimation of waters in equilibrium with an atmosphere much like the present.
Meddy dynamics and interaction with neighboring eddies southwest of Portugal: Observations and modeling
Authors: Carton X. , Daniault N. , Alves J. , Cherubin L. , Ambar I.
Published: June 2010

During the SEMANE 2000 experiment southwest of Portugal, two meddies were found in near contact. These meddies had hydrological radii of about 20 and 30 km, thickness of 900 m, maximum temperatures of 12.45°C and 13.45°C, and maximum salinities of 36.52 and 36.78. The smaller meddy with more pronounced thermohaline anomalies was clearly double cored (at 750 and 1300 m depths) while the wider one was more diffuse and more homogeneous. The associated geostrophic velocities (referenced at 2000 m) locally reached 0.5 m/s in the smaller meddy, and 0.2 m/s in the wider one. Three RAFOS floats and two deep‐drogued surface drifters, seeded in the two meddies, rapidly gathered in the more intense meddy. This meddy trajectory, revealed by the float motion, was first eastward, then southward. Maps of sea level anomaly indicate that this motion did not correspond to the long‐term evolution of the initial positive sea level anomaly signature of the meddies, and that neighboring cyclones must have played a role in the meddy evolution. To determine the role of each eddy in the observed evolution, several scenarios were studied with a three‐layer quasi‐geostrophic numerical model. The interaction of two meddies in isolation did not result in the observed meddy trajectories on the long term. The interaction of these two meddies with successive neighboring cyclones provided a more realistic trajectory of the meddy containing the floats.
Multidecadal CO2 uptake variability of the North Atlantic
Authors: Löptien Ulrike , Eden Carsten
Published: June 2010

The multidecadal variability of air‐sea CO2 fluxes in the North Atlantic under preindustrial atmospheric CO2 conditions is simulated, using a coupled biogeochemical/circulation model driven by long‐term surface forcing reconstructed from the leading modes of sea level pressure observations from 1850 to 2000. Heat fluxes are of great importance for the multidecadal CO2 fluctuations, about equal in magnitude to wind stress, in contrast to their less prominent role for CO2 flux variability on interannual timescales. Another difference, compared to higher frequencies, is the dominance of the North Atlantic Oscillation in driving the variability of the air‐sea CO2 fluxes. Two spatially distinct regimes lead to large anomalies in the CO2 fluxes but compensate to a large degree. The first regime is advective and has its clear signature southeast of Greenland while the second one, in the vicinity of the Labrador Sea and off Newfoundland, is convective. In both regimes, the multidecadal CO2 fluctuations are driven mainly by variations in temperature, salinity, and DIC content at the sea surface while the role of the biological pump is of minor importance in this particular model. The magnitude of the simulated multidecadal CO2 uptake changes is on the order of 0.02 Pg C/yr and amounts to 10–15% of the estimated annual anthropogenic CO2 uptake of the North Atlantic.
Variations on morphology and elemental composition of mineral dust particles from local, regional, and long‐range transport meteorological scenarios
Authors: Coz Esther , Gómez‐Moreno Francisco J. , Casuccio Gary S. , Artíñano Begoña
Published: June 2010

Mineral dust is the second major source of PM10 in Madrid, reaching up to 80% of the PM10 mass during certain long‐range dust transport events. Three different types of scenarios have been found to be associated with the high particle concentration episodes in the city: local anthropogenic, regional recirculation, and African dust transport processes. The present study focuses on the characterization of the individual mineral dust particles related to some chemical and morphological features during these three types of episodes, with special attention to local and regional episodes. To achieve this purpose, four different samples were selectively collected during the 2004–2005 period campaigns, one corresponding to each type of scenario and other sample from an Atlantic ventilated one. Meteorological situation, dust source identification, impact on ambient concentrations, size range distribution, and particle individual analysis have been characterized for each of them. Elemental composition and morphology of more than 30,000 mineral particles were analyzed by computer‐controlled scanning electron microscopy. Particles were grouped into clusters based on their elemental composition, and the aspect ratio (AR) of each cluster or category was compared for each type of episode. The AR was related to the mineralogical crystal structure of each chemical cluster. The dates chosen for microscopy analysis were in good agreement in size distribution and chemical composition with the average of the dates in the entire campaign and with those from previous campaigns. Major differences between local/regional and long‐range transported mineral dust were found in the relative abundance between carbonates and silicates, with much higher abundance of calcium carbonates in the first ones. These differences between silicate and carbonate contents were consistent with the results found in previous campaigns and were directly related to the composition of the parent topsoil by studying the Ca/Si ratios of similar episodes recorded all over the Iberian Peninsula. Differences in morphology were also found for these scenarios. The predominance of calcium carbonate under regional and local influence is scientifically relevant since this mineral is known to react with both SO2 and HNO3 in the atmosphere. Larger average AR values were found for dust particles from long‐range transport, and smaller average AR values were found for particles from local and regional resuspended dust. The increasing average AR value has been linked to the silicate cluster presence, whereas a reduction has been observed within the carbonate cluster.
Integrated assessment of changes in freshwater inflow to the Arctic Ocean
Authors: Dyurgerov Mark , Bring Arvid , Destouni Georgia
Published: June 2010

We present an integrated and updated quantitative estimation of the river discharge and the meltwater flux and mass contributions from glaciers to the Arctic Ocean and to sea level rise. The average meltwater fluxes from mountain glaciers and ice caps and the Greenland ice sheet have increased markedly, by 56 km3/yr water equivalent (w.e.) and 160 km3/yr w.e., respectively, from the period 1961–1992 to the period 1993–2006, reaching in total 700–800 km3/yr w.e. in 2000–2006. Terrestrial runoff is on the order of 2.4 × 103 km3/yr and remains significantly larger than the glacier meltwater flux. The terrestrial runoff increase from 1961–1992 to 1993–2006 is 87 km3/yr, which is small in relative terms, but in absolute terms it is of the same order of magnitude as the meltwater increase from glaciers. The total contribution to sea level rise from glaciers draining to the Arctic Ocean has increased from 0.27 mm/yr (1961–1992) to about 0.64 mm/yr (1993–2006). In some years of the 1993–2006 period, the glacier contribution to sea level rise reached almost 1 mm/yr.
Nighttime chemical evolution of aerosol and trace gases in a power plant plume: Implications for secondary organic nitrate and organosulfate aerosol formation, NO3 radical chemistry, and N2O5 heterogeneous hydrolysis
Authors: Zaveri Rahul A. , Berkowitz Carl M. , Brechtel Fred J. , Gilles Mary K. , Hubbe John M. , Jayne John T. , Kleinman Lawrence I. , Laskin Alexander , Madronich Sasha , Onasch Timothy B. , Pekour Mikhail S. , Springston Stephen R. , Thornton Joel A. , Tivanski Alexei V. , Worsnop Douglas R.
Published: June 2010

Nighttime chemical evolution of aerosol and trace gases in a coal‐fired power plant plume was monitored with the Department of Energy Grumman Gulfstream‐1 aircraft during the 2002 New England Air Quality Study field campaign. Quasi‐Lagrangian sampling in the plume at increasing downwind distances and processing times was guided by a constant‐volume balloon that was released near the power plant at sunset. While no evidence of fly ash particles was found, concentrations of particulate organics, sulfate, and nitrate were higher in the plume than in the background air. The enhanced sulfate concentrations were attributed to direct emissions of gaseous H2SO4, some of which had formed new particles as evidenced by enhanced concentrations of nucleation‐mode particles in the plume. The aerosol species were internally mixed and the particles were acidic, suggesting that particulate nitrate was in the form of organic nitrate. The enhanced particulate organic and nitrate masses in the plume were inferred as secondary organic aerosol, which was possibly formed from NO3 radical‐initiated oxidation of isoprene and other trace organic gases in the presence of acidic sulfate particles. Microspectroscopic analysis of particle samples suggested that some sulfate was in the form of organosulfates. Microspectroscopy also revealed the presence of sp2 hybridized C = C bonds, which decreased with increasing processing time in the plume, possibly because of heterogeneous chemistry on particulate organics. Constrained plume modeling analysis of the aircraft and tetroon observations showed that heterogeneous hydrolysis of N2O5 was negligibly slow. These results have significant implications for several issues related to the impacts of power plant emissions on air quality and climate.
Where do winds drive the Antarctic Circumpolar Current?
Authors: Allison L. C. , Johnson H. L. , Marshall D. P. , Munday D. R.
Published: June 2010

The strength of the Antarctic Circumpolar Current (ACC) is believed to depend on the westerly wind stress blowing over the Southern Ocean, although the exact relationship between winds and circumpolar transport is yet to be determined. Here we show, based on theoretical arguments and a hierarchy of numerical modeling experiments, that the global pycnocline depth and the baroclinic ACC transport are set by an integral measure of the wind stress over the path of the ACC, taking into account its northward deflection. Our results assume that the mesoscale eddy diffusivity is independent of the mean flow; while the relationship between wind stress and ACC transport will be more complicated in an eddy‐saturated regime, our conclusion that the ACC is driven by winds over the circumpolar streamlines is likely to be robust.
Magnetization reversal of the hard stack in antiferromagnetically coupled soft and hard Co/Pt multilayer stacks: Exploring via minor-loop measurements on the soft stack
Authors: Zhang F. , Liu Z. Y. , Han X. Y. , Xu B. , He H. L. , Yu D. L. , Tian Y. J.
Published: June 2010

In the antiferromagnetically coupled soft and hard Co/Pt multilayer stacks of [Pt(6 Å)/Co(4 Å)]1/Pt(36 Å)/[Co(4 Å)/Pt(6 Å)]2 with perpendicular anisotropy, the minor-loop measurement of the soft stack is highly sensitive to the presence of domains in the hard stack. Through the minor-loop measurements, it is determined that the magnetization reversal likely occurs via two main stages in the hard stack, in the first one through the nucleation of small down domains and in the second one via the fast growth of nucleated down domains. In comparison to the major-loop measurement, the minor-loop measurement has revealed a much higher saturation field for the hard stack.
Electron scattering from roughness-induced fluctuations in the donor density in ZnO surface quantum wells
Authors: Quang Doan Nhat , Tuan Le , Tien Nguyen Thanh
Published: June 2010

We present the theory of an ad hoc mechanism for electron scattering in heavily-doped zinc oxide (ZnO) surface quantum wells (SFQWs). We show that the carriers must be extra scattered in the in-plane from roughness-induced fluctuations in the donor density. In combination with the normal scattering from roughness-induced fluctuations in the potential barrier position, this gives rise to an effective roughness-related process, referred to as combined surface roughness (CSR) scattering. The CSR scattering is determined by both the roughness and doping profiles. The fluctuating donor density dominates CSR scattering at small angles and is important for large correlation length. The electron mobility in heavily-doped ZnO SFQWs is ruled by CSR scattering. This enables a successful explanation of the mobility data of accumulation layers near the ZnO surface at extremely high electron densities, which has not been explained so far.
Force induced melting of the constrained DNA
Authors: Singh Amit Raj , Giri D. , Kumar S.
Published: June 2010

We develop a simple model to study the effects of the applied force on the melting of a double stranded DNA (dsDNA). Using this model, we could study the stretching, unzipping, rupture and slippagelike transition in a dsDNA. We show that in absence of an applied force, the melting temperature and the melting profile of dsDNA strongly depend on the constrained imposed on the ends of dsDNA. The nature of the phase boundary of the force-temperature diagram, which separates the zipped and the open state for the shearinglike transition is remarkably different than the DNA unzipping.
Identification of the nature of trapping centers in polyspirobifluorene based diodes by using electrical characterization
Authors: Renaud Cédric , Nguyen Thien-Phap
Published: June 2010

The trap parameters in hole-only diodes using a blue emitting polyspirobifluorene copolymer were explored by using two complementary techniques such as: charge based deep level transient spectroscopy and thermally stimulated current. The trap analyses have been further completed by the measurements of the current-voltage characteristics as a function of the temperature. The use of unipolar structures allowed us to determine hole traps in the devices and further to identify electron traps in bipolar structures. Two hole traps which are located at 0.19 and 0.37 eV from the highest occupied molecular orbital, have been identified in blue polyspirobifluorene based devices. In bipolar diodes, four electron traps are determined and are located at 0.32, 0.58, 0.74, and 0.83 eV from the lowest unoccupied molecular orbital. We also showed that the use of a palladium electrode introduced new trap states of mean activation energy of 0.4 eV. As the nature of the cathode changes from Ba/Al to Pd, these traps are inferred to be related to the interface of polymer/Pd contact.
The influence of water on the structural and transport properties of model ionic liquids
Authors: Spohr Heidrun V. , Patey G. N.
Published: June 2010

Molecular dynamics simulations are used to investigate the influence of water on model ionic liquids. Several models, where the ions vary in size, and in the location of the charge with respect to the center of mass, are considered. Particular attention is focused on the variation in transport properties (diffusion coefficients, shear viscosity, and electrical conductivity) with water concentration. An effort is made to identify the underlying physical reasons for water’s influence. The results for our model ionic liquids fall loosely into two categories, depending on the molecular characteristics of the constituent ions. If the ion size disparity is not too large (cation:anion diameter ratio≲2:1), and if the ion charge location is such that directional ion pair bonds are relatively weak, then we find that the ionic diffusion coefficients and the electrical conductivity increase, and the viscosity decreases with increasing water concentration. This agrees with what is commonly observed experimentally for room temperature ionic liquids (RTILs). For these systems, we do not find changes in the equilibrium structure that can account for the strong influence of water on the transport properties. Rather, by varying the molecular mass of water in our simulations, we demonstrate that the dominant effect of water can be dynamical in origin. In RTIL-water mixtures, the molecular mass of water is generally much less than that of the ions it replaces. These lighter water molecules tend to displace much heavier counterions from the ion coordination shells. This reduces caging and increases the diffusivity, which leads to higher conductivities and lower viscosities. For models with a larger ion size disparity (3:1), or in charge-off-center systems, where strong directional ion pairs are important in the pure ionic liquid, the behavior can be quite different. In these systems, the diffusion coefficients and electrical conductivity can still display conventional behavior and increase when water is added even though the reasons for this can be more complex than in the simpler cases noted above. However, in these systems the viscosity can increase, sometimes quite steeply, with increasing water concentration. We trace this unusual behavior to the formation of associated structures, extended anion-water chains that can weave among the cations in the size disparate case, and strongly bound cation-water-anion clusters in the charge-off-center systems.
Physical and magnetic roughness at metal-semiconductor interface using x-ray and neutron reflectometry
Authors: Singh Surendra , Basu Saibal , Bhattacharya D. , Poswal A. K.
Published: June 2010

A difference in nuclear and magnetic roughness in Fe/Ge thin film was observed by specular polarized neutron reflectometry. The study also shows asymmetric magnetic scattering length density distributions at Fe on Ge and Ge on Fe interfaces. Using specular and diffuse x-ray reflectivity measurements we could estimate the depth of interdiffusion of Fe and Ge at two interfaces. We also observed that the interface magnetic moments are also strongly dependent on the crystalline state of Fe and Ge as well as the deposition sequence. The difference between nuclear and magnetic roughness at magnetic-semiconductor interfaces will play important role in spintronics.
Ion temperature gradient driven transport in tokamaks with square shaping
Authors: Joiner N. , Dorland W.
Published: June 2010

Advanced tokamak schemes which may offer significant improvement to plasma confinement on the usual large aspect ratio Dee-shaped flux surface configuration are of great interest to the fusion community. One possibility is to introduce square shaping to the flux surfaces. The gyrokinetic code GS2 [Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1996)] is used to study linear stability and the resulting nonlinear thermal transport of the ion temperature gradient driven (ITG) mode in tokamak equilibria with square shaping. The maximum linear growth rate of ITG modes is increased by negative squareness (diamond shaping) and reduced by positive values (square shaping). The dependence of thermal transport produced by saturated ITG instabilities on squareness is not as clear. The overall trend follows that of the linear instability, heat and particle fluxes increase with negative squareness and decrease with positive squareness. This is contradictory to recent experimental results [Holcomb et al., Phys. Plasmas 16, 056116 (2009)] which show a reduction in transport with negative squareness. This may be reconciled as a reduction in transport (consistent with the experiment) is observed at small negative values of the squareness parameter.
Effect of temperature on precision of chaotic oscillations in nickel electrodissolution
Authors: Wickramasinghe Mahesh , Kiss István Z.
Published: June 2010

We investigate the effects of temperature on complexity features of chaotic electrochemical oscillations using the anodic electrodissolution of nickel in sulfuric acid. The precision of the “period” of chaotic oscillation is characterized by phase diffusion coefficient (D). It is shown that reduced phase diffusion coefficient (D/frequency) exhibits Arrhenius-type dependency on temperature with apparent activation energy of 108 kJ/mol. The reduced Lyapunov exponent of the attractor exhibits no considerable dependency on temperature. These results suggest that the precision of electrochemical oscillations deteriorates with increase in temperature and the variation of phase diffusion coefficient does not necessarily correlate with that of Lyapunov exponent. Modeling studies qualitatively simulate the behavior observed in the experiments: the precision of oscillations in the chaotic Ni dissolution model can be tuned by changes of a time scale parameter of an essential variable, which is responsible for the development of chaotic behavior.
Effects of pulse duration and areal density on ultrathin foil acceleration
Authors: Zhang Xiaomei , Shen Baifei , Ji Liangliang , Wang Fengchao , Wen Meng , Wang Wenpeng , Xu Jiancai , Yu Yahong
Published: June 2010

The influence of laser pulse duration and areal density of target in the interaction of a circularly polarized pulse with an ultrathin overdense foil is investigated. One-dimensional particle-in-cell simulation shows that with an appropriate laser-pulse rising front, the light pressure acceleration regime is effective even though the thin foil is transparent. As the laser intensity evolves, three stages in the acceleration process can be identified: at first the total reflection of the laser pulse, followed by partial reflection, and then near total reflection again due to the Doppler effect. The influences of the rising front of laser pulse and areal density of the ultrathin foil are investigated. It is found that an optimal laser pulse rising front exists for obtaining high (saturation) ion energy with the same laser energy within a short time. An optimal areal density also exists for obtaining the highest energy. For the same laser pulse, a higher areal density or a higher density with same areal density is more appropriate for obtaining a stationary state for making light pressure acceleration mechanism more effective.
String-fluid transition in systems with aligned anisotropic interactions
Authors: Brandt P. C. , Ivlev A. V. , Morfill G. E.
Published: June 2010

Systems with aligned anisotropic interactions between particles exhibit numerous phase transitions. A remarkable example of the fluid phase transition occurring in such systems is the formation of particle strings—the so-called “string” or “chain” fluids. We employ an approach based on the Ornstein–Zernike (OZ) equation, which allows us to calculate structural properties of fluids with aligned anisotropic interactions. We show that the string-fluid transition can be associated with the bifurcation of the “isotropic” correlation length into two distinct scales which characterize the longitudinal and transverse order in string fluids and, hence, may be used as a fingerprint of this transition. The comparison of the proposed OZ theory with the Monte Carlo simulations reveals fairly good agreement.
First-principles study of structural, electronic, and mechanical properties of the nanolaminate compound Ti4GeC3 under pressure
Authors: Li Chenliang , Wang Zhenqing
Published: June 2010

This paper investigates the pressure dependences of the structural, electronic, mechanical, and optical properties of the nanolaminate Ti4GeC3 compound using the first-principles method based on the density functional theory. The lattice parameters and atom positions of Ti4GeC3 in bulk form were predicted and show that Ti4GeC3 is more compressible in the c direction than along the a direction. The elastic constants, shear modulus and Young’s moduli of Ti4GeC3 were then calculated at various pressures. The results indicate that Ti4GeC3 is mechanically stable in the pressure range of 0–70 GPa and that its brittle-ductile transition occurs at 60 GPa. By examining the densities of states, we also found that Ti4GeC3 remains structurally stable for pressures up to 70 GPa. Moreover, the Ti–Ge bonding is softer than all the Ti–C bonding and indicates that the Ti–C bond is more resistant to deformation than the Ti–Ge bond. Finally, the reflectivity spectrum of Ti4GeC3 under various pressures was investigated. Based on the results, we found that Ti4GeC3 can be used as a coating on spacecrafts to avoid solar heating, but it is not suitable for use under high pressure conditions.
Electrical and optical properties of SnEuTe and SnSrTe films
Authors: Ishida Akihiro , Tsuchiya Takuro , Yamada Tomohiro , Cao Daoshe , Takaoka Sadao , Rahim Mohamed , Felder Ferdinand , Zogg Hans
Published: June 2010

The SnTe, Sn1−xEuxTe and Sn1−xSrxTe (x<0.06) films were prepared by hot wall epitaxy. The ternary alloy films prepared in cation rich condition had hole concentration around 1×1019 cm−3 with high mobility exceeding 2000 cm2/V s at room temperature. Optical transmission spectra were also measured in the temperature range from 100 to 400 K and compared with theoretical calculations. Optical transmission spectra of the SnTe were simulated successfully assuming bumped band edge structures. A band inversion model was proposed for the Sn1−xEuxTe and Sn1−xSrxTe systems, and the optical transmission spectra were also simulated successfully assuming the band inversion model.
Influence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions
Authors: Severac Fabrice , Cristiano Fuccio , Bedel-Pereira Elena , Fazzini Pier Francesco , Boucher Jonathan , Lerch Wilfried , Hamm Silke
Published: June 2010

Hole mobility degradation has been studied in high-dose boron-implanted ultrashallow junctions containing high concentrations of boron-interstitial clusters (BICs), combining an empirical method based on the self-consistent interpretation of secondary-ion-mass spectrometry (SIMS) and Hall measurements and liquid-nitrogen (LN2) to room temperature (RT) hole mobility measurements. It has been found that BICs act as independent scattering centers which have a strong impact on hole mobility in addition to the other scattering mechanisms such as lattice and impurities scattering. A mobility degradation coefficient α has been introduced, which gives information on the mobility degradation level in the analyzed junctions. In the case of very high concentrations of BICs (containing a boron density up to 8×1014 cm−2), measured hole mobilities were found to be ∼40% lower than corresponding theoretical values. BICs dissolution through multiple Flash anneals at high temperature (1300 °C) reduces the observe mobility degradation.
Threshold voltage control of InAlN/GaN heterostructure field-effect transistors for depletion- and enhancement-mode operation
Authors: Choi Suk , Kim Hee Jin , Lochner Zachary , Zhang Yun , Lee Yi-Che , Shen Shyh-Chiang , Ryou Jae-Hyun , Dupuis Russell D.
Published: June 2010

We describe a method to change the threshold voltage of heterostructure field-effect transistors (HFETs) using InxAl1−xN/GaN heterostructures by using polarization and strain modification in the InAlN barrier layer to realize enhancement-mode operation. The threshold voltage and electronic band structure of the heterostructures were calculated for different indium compositions in the InAlN layer. Band structure calculations predict the enhancement-mode operation of compressively strained InAlN/GaN HFETs with an indium composition higher than 0.25. Studies of InAlN/GaN HFETs with different In alloy compositions show that the sheet resistance increases and the carrier concentration decreases for the heterostructures with increasing indium composition due to changes in the compressive strain and polarization in the InAlN barrier layer. Fabricated HFETs show threshold voltages of −2.5, −0.75, and +0.2 V for In∼0.18Al∼0.82N/GaN, In∼0.22Al∼0.78N/GaN, and In∼0.25Al∼0.75N/GaN HFETs, respectively, corresponding to a shift from depletion-mode to enhancement-mode operation.
A time-independent Hermitian Floquet approach for high harmonic generation in H2+ and HD+: Effect of nonadiabatic interaction in HD+
Authors: Sarkar Chitrakshya , Bhattacharyya S. S. , Saha Samir
Published: June 2010

We have theoretically investigated the high harmonic generation (HHG) in H2+ and HD+ using a time-independent Hermitian nonperturbative three-dimensional Floquet approach for continuous wave monochromatic lasers of intensities of 2.59×1013, 4.0×1013, and 5.6×1013 W/cm2, and wavelengths of 1064, 532, and 355 nm. For the moderate intensities and the wavelengths used, the Keldysh parameter γ>1 and no tunnel ionization occurs. We have endeavored to explain the dynamics of HHG in H2+ and HD+ within the framework of transitions due to electronic as well as intrinsic (for HD+) dipole moments and the nuclear motion on the field coupled ground and the first excited electronic states of these single-electron molecular ions, without considering any ionization. To evaluate the HHG spectra, the resonance Floquet quasienergy and the Fourier components of the Floquet state corresponding to the initial vibrational-rotational level v=0, J=0 have been calculated by solving the time-independent close-coupled Schrödinger equation following the Floquet ansatz. For HD+, we have taken into account the symmetry breaking effect of the nonadiabatic interaction or coupling [beyond the Born–Oppenheimer (BO) dynamics] in our calculations of the HHG spectra and have compared the results with the HHG spectra of HD+ obtained with the BO approximation.
Effect of nitrogen bonding states on dipole at the HfSiO/SiON interface studied by photoemission spectroscopy
Authors: Toyoda S. , Kamada H. , Kikuchi A. , Kumigashira H. , Oshima M. , Iwamoto K. , Sukegawa T. , Liu Z.
Published: June 2010

We have investigated effect of nitrogen bonding states on dipole at the HfSiO/SiON interface using photoemission spectroscopy with synchrotron radiation. Significant increase in the valence-band discontinuity between HfSiO films on a Si substrate upon annealing is observed, which can be related to changes in the interface dipole. Chemical states and in-depth profiles analyses suggest diffusion of nitrogen atoms from the HfSiO/SiON interface to the substrate during annealing processes. It is found that the formation of the interface dipole strongly depends on the nitrogen bonding states and their distributions at the HfSiO/SiON interface.
Out-of-plane magnetic patterning on austenitic stainless steels using plasma nitriding
Authors: Menéndez E. , Stinville J.-C. , Tromas C. , Templier C. , Villechaise P. , Rivière J.-P. , Drouet M. , Martinavičius A. , Abrasonis G. , Fassbender J. , Baró M. D. , Sort J. , Nogués J.
Published: June 2010

A correlation between the grain orientation and the out-of-plane magnetic properties of nitrogen-enriched polycrystalline austenitic stainless steel surface is performed. Due to the competition between the magnetocrystalline anisotropy, the exchange and dipolar interactions, and the residual stresses induced by nitriding, the resulting effective magnetic easy-axis can lay along unusual directions. It is also demonstrated that, by choosing an appropriate stainless steel texturing, arrays of ferromagnetic structures with out-of-plane magnetization, embedded in a paramagnetic matrix, can be produced by local plasma nitriding through shadow masks.
The structure and growth direction of rare earth silicide nanowires on Si(100)
Authors: Eames C. , Probert M. I. J. , Tear S. P.
Published: June 2010

The growth direction and the structure of rare earth silicide nanowires grown on the Si(100) surface have been calculated from first principles. The energies of the optimum structures show that a structure related to the tetragonal bulk phase is more favorable than the hexagonal model and that growth parallel to the dimer rows is lower in energy than growth across the dimer rows.
Effect of B-site Al-doping on electric polarization in DyMnO3
Authors: Zhang N. , Wang K. F. , Luo S. J. , Wei T. , Dong X. W. , Li S. Z. , Wan J. G. , Liu J.-M.
Published: June 2010

We investigate the effect of Al-doping on the multiferroicity of DyMn1−xAlxO3. It is indicated that a slight doping (0.005≤x≤0.01) can significantly enhance the electric polarization which will be suppressed as x>0.03. The possible mechanism for the polarization enhancement is the rearrangement of the Mn spiral spin order upon the Al-doping. Our work demonstrates that the ferroelectricity of DyMnO3 is sensitive to the B-site nonmagnetic doping, allowing an unusual enhancement of the electric polarization.
Enhanced photorefractive performance in CdSe quantum-dot-dispersed poly(styrene-co-acrylonitrile) polymers
Authors: Li Xiangping , van Embden Joel , Chon James W. M. , Evans Richard A. , Gu Min
Published: June 2010

This paper reports on the enhanced photorefractive behavior of a CdSe quantum-dot-dispersed less expensive polymer of poly(styrene-co-acrylonitrile). The capability of CdSe quantum dots used as photosensitizers and the associated photorefractive performance are characterized through a photocurrent experiment and a two-beam coupling experiment, respectively. An enhanced two-beam coupling gain coefficient of 12.2 cm−1 at 46 V/μm was observed owning to the reduced potential barrier. The photorefractive performance per CdSe quantum dot is three orders of magnitude higher than that in the sample sensitized by trinitrofluorenone in poly(styrene-co-acrylonitrile), and almost ten times higher than that in the CdSe quantum-dot-sensitized poly(N-vinylcarbazole) polymers.
Permanent electric dipole moment of copper monoxide, CuO
Authors: Zhuang Xiujuan , Frey Sarah E. , Steimle Timothy C.
Published: June 2010

A number of low-rotational lines of the A Σ2−←X Π23/2(0,0) subband of a molecular beam of copper monoxide, CuO, were recorded field free and in the presence of a static electric field. A set of optimized fine and hyperfine parameters for the A Σ2−(υ′=0) state was produced from the analysis of the field-free spectrum. The permanent electric dipole moments μ for the A Σ2−(υ=0) and X Π23/2(υ=0) states were determined to be 1.12(71) and 4.57(3) D, respectively, from the analysis of the observed Stark shifts. The error of the experimentally determined μ value for the X Π23/2(υ=0) state is approximately ten times less than that for the previously determined value: μ=4.45(30) D [T. C. Steimle et al., J. Chem. Phys. 87, 5670 (1987)]. The experimental μ values are compared with theoretical predictions.
Correlation between dynamic flow and thermodynamic glass transition in metallic glasses
Authors: Ke H. B. , Wen P. , Zhao D. Q. , Wang W. H.
Published: June 2010

We report the values of steps of heat capacity (ΔCp) during the glass transition in a variety of metallic glasses (MGs). It is found that ΔCp is around 13.69 J mol−1 K−1 and almost invariable for the MGs. Based on the Eyring’s theory [N. Hirai and H. Eyring, J. Polym. Sci. 37, 51 (1959)], the phenomenon corresponds to a critical reduced free volume value. This exhibits that the glass transition takes place when the reduced free volume approaches to ∼2.35% in the MG systems. The value, consistent with that of the yielding of MGs, confirms that temperature and stress are equivalent for fluidizing MGs. Our results give an implication to understanding the glass transition in MGs as a Lindemann-type melting behavior [F. A. Lindemann, Z. Phys. 11, 609 (1910)].
The electronic properties of graphene nanoribbons with boron/nitrogen codoping
Authors: Wang Zhiyong , Hu Huifang , Zeng Hui
Published: June 2010

The electronic properties of graphene nanoribbons with boron/nitrogen codoping at different sites are investigated by performing first-principles calculations based on density functional theory. The calculated results show that the band structures of these doping configurations have distinctly changed around the Fermi level with gradual increasing the distance between nitrogen atom and boron atom. Doping positions regulate the electronic structure of the graphene nanoribbons. Interestingly, our results exhibit both semiconducting and half-metallic behavior in response to the boron/nitrogen codoping at different sites without an applied electronic field, opening a possibility in spintronics device application.
One-step implementation of multiqubit conditional phase gating with nitrogen-vacancy centers coupled to a high-Q silica microsphere cavity
Authors: Yang W. L. , Yin Z. Q. , Xu Z. Y. , Feng M. , Du J. F.
Published: June 2010

The diamond nitrogen-vacancy (NV) center is an excellent candidate for quantum information processing, whereas entangling separate NV centers is still of great experimental challenge. We propose a one-step conditional phase flip with three NV centers coupled to a whispering-gallery mode cavity by virtue of the Raman transition and smart qubit encoding. As decoherence is much suppressed, our scheme could work for more qubits. The experimental feasibility is justified.