bluuebunny/crossref_metadata_2025 huggingface dataset:
A NOTE ON SCHRÖDINGER MAXIMAL OPERATORS WITH A COMPLEX PARAMETER
Authors: SJÖLIN PER , SORIA FERNANDO
Published: May 2010

Extending previous results of the first author, some new estimates are obtained for maximal operators of Schrödinger type with a complex parameter.
Hydrometeorological daily recharge assessment model (DREAM) for the Western Mountain Aquifer, Israel: Model application and effects of temporal patterns
Authors: Sheffer N. A. , Dafny E. , Gvirtzman H. , Navon S. , Frumkin A. , Morin E.
Published: May 2010

Recharge is a critical issue for water management. Recharge assessment and the factors affecting recharge are of scientific and practical importance. The purpose of this study was to develop a daily recharge assessment model (DREAM) on the basis of a water balance principle with input from conventional and generally available precipitation and evaporation data and demonstrate the application of this model to recharge estimation in the Western Mountain Aquifer (WMA) in Israel. The WMA (area 13,000 km2) is a karst aquifer that supplies 360–400 Mm3yr−1of freshwater, which constitutes 20% of Israel's freshwater and is highly vulnerable to climate variability and change. DREAM was linked to a groundwater flow model (FEFLOW) to simulate monthly hydraulic heads and spring flows. The models were calibrated for 1987–2002 and validated for 2003–2007, yielding high agreement between calculated and measured values (R2= 0.95; relative root‐mean‐square error = 4.8%; relative bias = 1.04). DREAM allows insights into the effect of intra‐annual precipitation distribution factors on recharge. Although annual precipitation amount explains ∼70% of the variability in simulated recharge, analyses with DREAM indicate that the rainy season length is an important factor controlling recharge. Years with similar annual precipitation produce different recharge values as a result of temporal distribution throughout the rainy season. An experiment with a synthetic data set exhibits similar results, explaining ∼90% of the recharge variability. DREAM represents significant improvement over previous recharge estimation techniques in this region by providing near‐real‐time recharge estimates that can be used to predict the impact of climate variability on groundwater resources at high temporal and spatial resolution.
Characterizing the recharge regime of the strongly exploited aquifers of the North China Plain by environmental tracers
Authors: von Rohden Christoph , Kreuzer Andreas , Chen Zongyu , Kipfer Rolf , Aeschbach‐Hertig Werner
Published: May 2010

We employed environmental tracers (3H‐3He, noble gases, stable isotopes 18O and 2H) to study groundwater recharge and residence times in the strongly exploited North China Plain aquifer system in the area of Shijiazhuang, the capital of the Hebei province. Groundwater in the unconfined parts of the piedmont plain contains tritium down to depths of about 100 m and exhibits 3H‐3He ages of less than 40 years. 3H‐3He ages correlate well with sampling depth but less so with distance along a transect from the mountains in the west through the recharge area in the piedmont plain, indicating a minor role of lateral inflow compared to spatially distributed recharge. The increase of groundwater age with increasing thickness of the saturated zone combined with the steady groundwater table descent over the last decades implies an effective recharge rate of around 0.3 m/yr, mostly due to infiltration of precipitation and irrigation water. Despite the recycling of irrigation water, a water balance deficit remains, causing depletion of the aquifers. Anthropogenic modifications of the natural recharge regime appear to be reflected by a trend of increasing stable isotope ratios in groundwater of the last decades.
Nutrients export by rivers to the coastal waters of Africa: Past and future trends
Authors: Yasin Jemal Adem , Kroeze Carolien , Mayorga Emilio
Published: May 2010

We analyze past and future trends in nitrogen (N), phosphorus (P), and carbon (C) export by rivers to the coastal waters of Africa as calculated by the Global Nutrient Export to WaterShed (NEWS) models for the period 1970–2050. Between 1970 and 2000 the total nutrient export by African rivers increased by 10–80%. For future years (2000–2050) we calculate an increase in the total loads of dissolved forms of N and P, but decreasing trends for dissolved organic C and particulate forms of N and P. There are large regions that deviate from these pan‐African trends. We explore the regional patterns and the underlying processes, in particular for the Nile, Zaire, Niger, and Zambezi. In the future, anthropogenic sources may, in large parts of Africa, become larger contributors to riverine nutrient loads than natural sources.
Intermittency of near‐bottom turbulence in tidal flow on a shallow shelf
Authors: Lozovatsky I. , Roget E. , Planella J. , Fernando H. J. S. , Liu Zhiyu
Published: May 2010

The higher‐order structure functions of vertical velocity fluctuations (transverse structure functions (TSF)) were employed to study the characteristics of turbulence intermittency in a reversing tidal flow on a 19 m deep shallow shelf of the East China Sea. Measurements from a downward‐looking, bottom‐mounted Acoustic Doppler Velocimeter, positioned 0.45 m above the seafloor, which spanned two semidiurnal tidal cycles, were analyzed. A classical lognormal single‐parameter (μ) model for intermittency and the universal multifractal approach (specifically, the two‐parameter (C1 and α) log‐Levy model) were employed to analyze the TSF exponent ξ(q) in tidally driven turbulent boundary layer and to estimate μ, C1, and α. During the energetic flooding tidal phases, the parameters of intermittency models approached the mean values of ≈ 0.24, 1 ≈ 0.15, and ≈ 1.5, which are accepted as the universal values for fully developed turbulence at high Reynolds numbers. With the decrease of advection velocity, μ and C1 increased up to μ ≈ 0.5–0.6 and C1 ≈ 0.25–0.35, but α decreased to about 1.4. The results explain the reported disparities between the smaller “universal” values of intermittency parameters μ and C1 (mostly measured in laboratory and atmospheric high Reynolds number flows) and those (μ = 0.4–0.5) reported for oceanic stratified turbulence in the pycnocline, which is associated with relatively low local Reynolds numbers Rλw. The scaling exponents ξ(2) of the second‐order TSF, relative to the third‐order structure function, was also found to be a decreasing function of Rλw, approaching the classical value of 2/3 only at very high Rλw. A larger departure from the universal turbulent regime at lower Reynolds numbers could be attributed to the higher anisotropy and associated intermittency of underdeveloped turbulence.
Solution convergence of flow over steep topography in a numerical model of canyon upwelling
Authors: Dawe Jordan T. , Allen Susan E.
Published: May 2010

The convergence as resolution is increased is examined for a numerical model simulation of upwelling over a continental shelf canyon. A series of idealized one‐ and two‐dimensional models are used to plot the dependence of bottom Ekman layer velocity structure and transport on model resolution. Using these results as a guide, a bottom Ekman layer‐resolving three‐dimensional numerical model is constructed. This model is used to simulate a laboratory model of canyon upwelling. Alongshore velocity, volume of fluid upwelled through the canyon onto the shelf, and change in depth of the canyon water are examined at three grid resolutions. Numerical model particle trajectories are compared with a laboratory model of canyon upwelling to validate the model. The results suggest that current computational cluster power is sufficient to accurately simulate all aspects of upwelling in a steep canyon with the exception of flow separation from the canyon wall.
Estimation of the particle flux from the convective mixed layer by large eddy simulation
Authors: Noh Yign , Nakada Satoshi
Published: May 2010

With an aim to estimate how much phytoplankton population remains within the mixed layer during winter and acts as seeds for blooming in the following spring, the downward particle flux from the convective mixed layer is investigated by analyzing the motion of a large number of Lagrangian particles in the ocean mixed layer simulated by large eddy simulation. It is found that W/ws decreases gradually from 1 to 0 with wd/ws, where W is the sedimentation rate, defined as the ratio of downward particle flux to the mean particle concentration within the mixed layer; ws is the terminal velocity of a particle settling in still fluid; and wd is the deepening velocity of the mixed layer depth (MLD). It is in contrast with the previous hypothesis that W = ws for wd > ws and W = 0 otherwise. The new parameterization W/ws = exp[−1.4(wd/ws)] leads to much higher particle concentration after winter than the previous estimation, when wd < ws. The present result suggests that the escape of particles from the mixed layer occurs stochastically, and its probability is determined by turbulence at the MLD and by the mixed layer deepening, both of which are represented by wd/ws.
Impacts of mineral dust on the vertical structure of precipitation
Authors: Li R. , Min Q.‐L.
Published: May 2010

Characteristics of precipitation vertical structure in deep convective cloud systems are compared using measurements from sensors on board multiple satellites over the equatorial Atlantic under dust‐laden and dust‐free conditions. Both case and statistical studies consistently show that the impacts of mineral dust on tropical cloud and precipitation systems are highly dependent on rain type. For convective rain, the pattern of rainfall profiles above the dust layer is mainly determined by updraft intensity. For similar updraft intensity, the convective rain at and below the dust layer exhibits enhancement of the breakup process of raindrops due to mineral dust and associated warm air with strong wind shear. For stratiform rain, dust‐induced microphysical effects are more evident. For similar storm height (or the rain top), precipitation at altitudes above 6 km is enhanced under dust‐laden conditions, suggesting an enhancement of ice heterogeneous nucleation. For warm rain with similar storm height, precipitation is systematically weaker under dust‐laden conditions. Furthermore, the ratio of precipitation water to the total amount of atmospheric hydrometeors is smaller under dust‐laden conditions. Our study suggests that mineral dust exhibits a second aerosol indirect effect on cloud and precipitation systems.
Investigation of cloud condensation nuclei properties and droplet growth kinetics of the water‐soluble aerosol fraction in Mexico City
Authors: Padró Luz T. , Tkacik Daniel , Lathem Terry , Hennigan Chris J. , Sullivan Amy P. , Weber Rodney J. , Huey L. Greg , Nenes Athanasios
Published: May 2010

We present hygroscopic and cloud condensation nuclei (CCN) relevant properties of the water‐soluble fraction of Mexico City aerosol collected upon filters during the 2006 Megacity Initiative: Local and Global Research Observations (MILAGRO) campaign. Application of κ‐Köhler theory to the observed CCN activity gave a fairly constant hygroscopicity parameter (κ = 0.28 ± 0.06) regardless of location and organic fraction. Köhler theory analysis was used to understand this invariance by separating the molar volume and surfactant contributions to the CCN activity. Organics were found to depress surface tension (10–15%) from that of pure water. Daytime samples exhibited lower molar mass (∼200 amu) and surface tension depression than nighttime samples (∼400 amu); this is consistent with fresh hygroscopic secondary organic aerosol (SOA) condensing onto particles during peak photochemical hours, subsequently aging during nighttime periods of high relative humidity. Changes in surface tension partially compensate for shifts in average molar volume to give the constant hygroscopicity observed, which implies the amount (volume fraction) of soluble material in the parent aerosol is the key composition parameter required for CCN predictions. This finding, if applicable elsewhere, may explain why CCN predictions are often found to be insensitive to assumptions of chemical composition and provides a very simple way to parameterize organic hygroscopicity in atmospheric models (i.e., κorg = 0.28ɛWSOC). Special care should be given, however, to surface tension depression from organic surfactants, as its nonlinear dependence with organic fraction may introduce biases in observed (and predicted) hygroscopicity. Finally, threshold droplet growth analysis suggests the water‐soluble organics do not affect activation kinetics.
Using long‐term water balances to parameterize surface conductances and calculate evaporation at 0.05° spatial resolution
Authors: Zhang Yongqiang , Leuning Ray , Hutley Lindsay B. , Beringer Jason , McHugh Ian , Walker Jeffrey P.
Published: May 2010

Evaporation from the land surface, averaged over successive 8 day intervals and at 0.05° (∼5 km) spatial resolution, was calculated using the Penman‐Monteith (PM) energy balance equation, gridded meteorology, and a simple biophysical model for surface conductance. This conductance is a function of evaporation from the soil surface, leaf area index, absorbed photosynthetically active radiation, atmospheric water vapor pressure deficit, and maximum stomatal conductance (gsx). The novelty of this paper is the use of a “Budyko‐curve” hydrometeorological model to estimate mean annual evaporation rates and hence a unique value of gsx for each grid cell across the Australian continent. First, the hydrometeorological model was calibrated using long‐term water balances from 285 gauged catchments. Second, gridded meteorological data were used with the calibrated hydrometeorological model to estimate mean annual average evaporation () for each grid cell. Third, the value of gsx for each cell was adjusted to equate calculated using the PM equation with from the hydrometeorological model. This closes the annual water balance but allows the PM equation to provide a finer temporal resolution for evaporation than is possible with an annual water balance model. There was satisfactory agreement (0.49 < R2 < 0.80) between 8 day average evaporation rates obtained using remotely sensed leaf area indices, the parameterized PM equation, and observations of actual evaporation at four Australian eddy covariance flux sites for the period 2000–2008. The evaporation product can be used for hydrological model calibration to improve runoff prediction studies in ungauged catchments.
Multiparameter quantification of gas release during weak Strombolian eruptions at Pacaya Volcano, Guatemala
Authors: Dalton Marika P. , Waite Gregory P. , Watson I. Matthew , Nadeau Patricia A.
Published: May 2010

Activity at Pacaya volcano, Guatemala is characterized by persistent degassing, coupled at times with lava effusion and/or coincident Strombolian‐style explosions. We used 0.25 Hz sample rate sulfur dioxide emission data from a UV camera and coincident infrasound recordings to investigate the link between varied emission rates and infrasound events. Degassing rates varied on two scales during this study; smaller, more rapid variations on the scale of 1 to 3 minutes are superimposed on larger, slower changes over 30 minutes to 1 hour. The acoustic record was dominated by repeated N‐shaped events characteristic of Strombolian explosions. Because of the high‐resolution of the gas measurements, we were able to calculate gas masses for individual explosions from both datasets and find the two estimates agree within an order of magnitude. The infrasound explosion records correlate with small pulses in degassing, but the longer‐term degassing trends may represent a deeper process.
Downward Arctic Oscillation signal associated with moderate weak stratospheric polar vortex and the cold December 2009
Authors: Wang Lin , Chen Wen
Published: May 2010

The climatic anomalies and related mechanism for the cold December 2009 in Northern Hemisphere are analyzed preliminarily. It is revealed that both anomalously low monthly mean temperature and more extreme cold days occurred over many areas of mid‐latitude Northern Hemisphere in this December. This cold condition can be accounted for by the extreme negative Arctic Oscillation (AO) at surface level, which is the lowest one for the past 31 years. It is shown that the negative surface AO in December is closely associated with the downward propagating anomalies from the stratosphere, implying the involvement of stratospheric processes in this cold month. Since the preceding stratospheric signal is not as strong as those reported in previous studies, it suggests that some relatively weaker stratospheric anomalies can also propagate downward and influence the troposphere.
Coercive force of nanocrystalline manganites
Authors: Prilipko S. Yu. , Akimov G. Ya. , Revenko Yu. F. , Varyukhin V. N. , Novokhatskaya A. A.
Published: May 2010

Samples of La0.7Mn1.3O3±Δ and (La0.65Sr0.35)0.8Mn1.2O3±Δ with particle sizes ranging from 6to200nm are obtained using cold isostatic pressing. The coercive force of the experimental samples is determined from the field dependences of the resistance and dynamic magnetic susceptibility. It is determined by two methods that the contribution of the surface layer to the magnetic characteristics of manganites is composition dependent. It is shown experimentally for the first time that the coercive force in manganites reaches its highest values with particle size of the order of 70nm for both compositions and vanishes completely for lanthanum manganite with ∼6nm particles as a result of reaching a superparamagnetic state.
Interaction of two substitutional impurity atoms in an hcp crystal
Authors: Belan V. I. , Landau A. I.
Published: May 2010

Molecular dynamics computer simulation with a Lennard–Jones potential is used to investigate the interaction of two identical substitutional impurity atoms in an hcp crystal lattice. Different atomic radii of the impurities atoms, interaction energy of the atoms and the lattice atoms, and initial distances between the impurity atoms at zero temperature and pressure. It is found that in a number of cases for small distances between the impurity atoms not exceeding five interatomic distances these atoms attract one another contrary to the well-known laws of the continuum theory of elasticity. Good agreement between the computational results and the theory of elasticity obtains for short distances between impurity atoms.
Efficient computation of compliance matrices in redundant internal coordinates from Cartesian Hessians for nonstationary points
Authors: Brandhorst Kai , Grunenberg Jörg
Published: May 2010

We present an extension to the theory of compliance matrices, which is valid for arbitrary nonstationary points on the potential energy hypersurface. It is shown that compliance matrices computed as the inverse of the covariant Hessian matrix obey the same invariance properties with respect to different internal coordinate systems as they do for stationary points. Furthermore, we demonstrate how the computation of compliance matrices in arbitrary sets of redundant internal coordinates starting from a Cartesian Hessian can be achieved efficiently, and we discuss their potential usefullness in geometry optimization processes
Lattice distortion in hcp rare gas solids
Authors: Grechnev A. , Tretyak S. M. , Freiman Yu. A.
Published: May 2010

The lattice distortion parameter δ≡c∕a−8∕3 has been calculated as a function of molar volume for the hcp phases of He, Ar, Kr, and Xe. Results from both semi-empirical potentials and density functional theory are presented. Our study shows that δ is negative for helium in the entire pressure range. For Ar, Kr, and Xe δ changes sign from negative to positive as the pressure increases, growing rapidly in magnitude at higher pressures.
The temperature dependence of the inelastic scattering time in InGaN grown by MOVPE
Authors: Yildiz A. , Kasap M.
Published: May 2010

Low temperature electrical measurements of the resistivity, the Hall effect and the magnetoconductivity were performed on an InGaN sample having an electron concentration far above the critical value for the metal–insulator transition. The weak localization effect and a two-band model were used to analyze the magnetoconductivity data. The temperature dependence of the inelastic scattering time was extracted from the magnetoconductivity data at low temperatures. It was found that the inelastic scattering time is proportional to T−1.63, suggesting that electron–electron interactions are dominant.
Effect of impurities on the quantum plasticity of β-tin single crystals
Authors: Kirichenko G. I. , Natsik V. D. , Pustovalov V. V. , Soldatov V. P. , Shumilin S. É.
Published: May 2010

The effect of small additions (0.01at.%) of indium, cadmium, and zinc impurities on the temperature dependences of the plasticity characteristics of β-tin single crystals in the interval 0.5K<T<4.2K is studied. Plastic deformation of the samples occurred by means of dislocation slip in the system (100)⟨010⟩. It has been shown in previous work that Peierls barriers are the main obstacles to the motion of dislocations of this system in pure β-tin. There exists a threshold temperature Tg≈1.2K above which dislocations overcome barriers by means of thermal fluctuations (thermally activated plasticity) and below which by means of quantum-mechanical tunneling (quantum plasticity). The present investigation shows that for weak doping of β-tin by various types of impurities the influence of Peierls relief on dislocation mobility remains dominant at low temperatures but Tg shifts appreciably in the direction of high temperatures (δTg≈0.2–1K), i.e. the temperature interval of quantum plasticity becomes wider. The experimentally observed shift of the threshold temperature depends in a complicated manner on the size of the impurities atoms, which create local barriers for dislocation slip. Current theory cannot give an unequivocal interpretation of such a dependence.
Dissipation function of magnetic media
Authors: Bar’yakhtar V. G. , Danilevich A. G.
Published: May 2010

A general method of constructing a dissipation function is developed for disordered magnetic media and for magnetically ordered systems. As an example it is shown for a ferromagnet that not only the invariance with respect to uniform rotations of the body but also the law of conservation of magnetization must be taken into account in order to construct a dissipation function. It is found that in ferromagnets the dissipation term in the equations of motion for the magnetization is a sum of Bloch and Landau–Lifshitz–Gilbert relaxation terms. The region of applicability of the relaxation term in the Landau–Lifshitz form is determined. The damping of spin waves in a ferromagnet with tetragonal symmetry is calculated. A procedure is formulated for transitioning from a ferromagnet with lower symmetry to a ferromagnet with a continuous degeneracy parameter. In this case the relaxation process can be systematically described by means of the dissipation function described in this article. It is shown how the relaxation term of a general form for ferromagnets becomes the Bloch relaxation term for paramagnets. It is shown that the magnetization vector relaxes in two stages. First the magnetic moment relaxes in magnitude quite rapidly as a result of exchange enhancement and then the magnetization relaxes slowly to its equilibrium direction. The second stage qualitatively corresponds to the relaxation picture described by the Landau–Lifshitz model.
Calculation of interfacial properties using molecular simulation with the reaction field method: Results for different water models
Authors: Míguez J. M. , González-Salgado D. , Legido J. L. , Piñeiro M. M.
Published: May 2010

Coulombic interactions in molecular simulation are usually computed using the Ewald summation technique. This method is reliable for homogeneous and inhomogeneous systems but remarkably time consuming. This means a serious shortcoming in cases where unusually long simulation runs are necessary, for instance, during the calculation of interfacial properties, a subject of increasing interest. In homogeneous systems, the reaction field (RF) method can be alternatively used, reducing not only the computation time but also the difficulty of its implementation. However, it cannot be applied for inhomogeneous systems, at least from a strict formal point of view. In this paper, an analysis of the discrepancies in the computation of interfacial properties of water using the RF method is performed using constant volume biphasic Monte Carlo simulations, considering several of the most popular models available. The results show good quantitative agreement, within the simulation uncertainty, with the values obtained from the Ewald sums method. This result states the applicability of the RF method for interfacial properties calculation for this type of molecules.
Vibrational characteristics of niobium diselenide and graphite nanofilms
Authors: Gospodarev I. A. , Eremenko V. V. , Kravchenko K. V. , Sirenko V. A. , Syrkin E. S. , Feodos’ev S. B.
Published: May 2010

The phonon spectra of niobium diselenide nanofilms, consisting of several structural elements of this compound, as well as graphite nanofilms starting with bigraphene are analyzed at the microscopic level. The partial contributions of the displacements of atoms along the strong and weak coupling directions (i.e. along and perpendicular to the layers) to the phonon density of states are calculated. The characteristic distinguishing features of the vibrational spectral of these structures are analyzed. The fact that our calculations are practically identical to the data obtained from neutron diffraction, acoustic, and optical experiments confirms that the description of the phonon spectra of the compounds is highly accurate. The temperature dependences of the mean-square shifts for bulk samples and nanofilms along different crystallographic directions, making it possible to evaluate the stability of the graphite and niobium diselenide nanofilms at low temperatures, are calculated for each compound studied.
Vortex manipulation in a superconducting matrix with view on applications
Authors: Milošević M. V. , Peeters F. M.
Published: May 2010

We show how a single flux quantum can be effectively manipulated in a superconducting film with a matrix of blind holes. Such a sample can serve as a basic memory element, where the position of the vortex in a k×l matrix of pinning sites defines the desired combination of n bits of information (2n=k×l). Vortex placement is achieved by strategically applied current and the resulting position is read out via generated voltage between metallic contacts on the sample. Such a device can also act as a controllable source of a nanoengineered local magnetic field for, e.g., spintronics applications.
Strain engineering in Si via closely stacked, site-controlled SiGe islands
Authors: Zhang J. J. , Hrauda N. , Groiss H. , Rastelli A. , Stangl J. , Schäffler F. , Schmidt O. G. , Bauer G.
Published: May 2010

The authors report on the fabrication and detailed structural characterization of ordered arrays of vertically stacked SiGe/Si(001) island pairs. By a proper choice of growth parameters, islands which have both large sizes and high Ge fraction are obtained in the upper layer. Finite element method calculations of the strain distribution reveal that (i) the Si spacer between a pair of islands can act as a lateral quantum dot molecule made of four nearby dots for electrons and (ii) the tensile strain in a Si cap deposited on top of the stack is significantly enhanced with respect to a single layer.
EPR in the molecular magnet {Cu6[(MeSiO2)6]2}⋅6DMF
Authors: Kobets M. I. , Dergachev K. G. , Khats’ko E. N. , Pashchenko V. A. , Savina Yu. A.
Published: May 2010

Resonance studies of single crystals of the molecular magnet {Cu6[(MeSiO2)6]2}⋅6DMF have been performed in a wide range of frequencies 18–142GHz and magnetic fields 0–7.5T at liquid-helium temperature. Two nonequivalent magnetic centers of copper nanoclusters with turn angle of the local axes (50±2)° have been found. The ground state of each magnetic center (magnetic molecules, containing a ring of six ferromagnetic interacting ions Cu2+ (S=1∕2)) can be represented as a system of energy levels with effective particle spin S=3 (ĝ=2.28,2.28,2.083), split by an axial magnetic field DSz2 (D∕h=9.76GHz).
Dielectric constants of atomically thin silicon channels with double gate
Authors: Kageshima Hiroyuki , Fujiwara Akira
Published: May 2010

Dielectric constants of Si (111) nanofilms with the double gate are studied in the full inversion regime by using the first-principles calculation. The calculations show that the dielectric constants are significantly smaller than that of the bulk. Further, the dielectric constants depend on the conduction type as well as on the film thickness. They also oscillate with a 2-bilayer-thickness for the p-channel case as the film thickness decreases. The suppressed dielectric constants are found in the channel center as well as in the channel surface. These findings open the way to artificial control of the dielectric constant in semiconductor nanostructures.
Charge carrier densities in chemically doped organic semiconductors verified by two independent techniques
Authors: Lehnhardt M. , Hamwi S. , Hoping M. , Reinker J. , Riedl T. , Kowalsky W.
Published: May 2010

The charge carrier density of the p-type doped organic semiconductor 2,7-bis(9-carbazolyl)-9,9-spirobifluorene is determined for varied doping concentrations. As p-type dopant molybdenum trioxide is used. We determine the carrier density by measuring the polaron induced optical absorption and by a capacitance-voltage analysis. We show that both results are in excellent agreement. An almost linear dependence of the charge carrier density on the doping concentration is observed. Carrier densities on the order of 1018 cm−3 at a dopant concentration of 1 mol % can be achieved. Overall, a low doping efficiency on the order of 2%–4.5% is evidenced.
Tunable fishnet metamaterials infiltrated by liquid crystals
Authors: Minovich Alexander , Neshev Dragomir N. , Powell David A. , Shadrivov Ilya V. , Kivshar Yuri S.
Published: May 2010

We analyze numerically the optical response and effective macroscopic parameters of fishnet metamaterials infiltrated with a nematic liquid crystal. We show that even a small amount of liquid crystal can provide tuning of the structures due to reorientation of the liquid crystal director. This enables switchable optical metamaterials, where the refractive index can be switched from positive to negative by an external field. This tuning is primarily determined by the shift in the cut-off wavelength of the holes, with only a small influence due to the change in plasmon dispersion.
Tunable band gap in Bi(Fe1−xMnx)O3 films
Authors: Xu X. S. , Ihlefeld J. F. , Lee J. H. , Ezekoye O. K. , Vlahos E. , Ramesh R. , Gopalan V. , Pan X. Q. , Schlom D. G. , Musfeldt J. L.
Published: May 2010

In order to investigate band gap tunability in polar oxides, we measured the optical properties of a series of Bi(Fe1−xMnx)O3 thin films. The absorption response of the mixed metal solid solutions is approximately a linear combination of the characteristics of the two end members, a result that demonstrates straightforward band gap tunability in this system.
Interface effect on the photocurrent: A comparative study on Pt sandwiched (Bi3.7Nd0.3)Ti3O12 and Pb(Zr0.2Ti0.8)O3 films
Authors: Cao Dawei , Xu Jie , Fang Liang , Dong Wen , Zheng Fengang , Shen Mingrong
Published: May 2010

We investigated and compared the photoelectric behavior of the Pt sandwiched (Bi3.7Nd0.3)Ti3O12 (BNT) and Pb(Zr0.2Ti0.8)O3 (PZT) films deposited by sol-gel method. Based on the analysis of the photocurrent and I-V characteristics, the top and bottom Pt/film interface Schottky barriers are found to be more symmetric in BNT, compared to that in PZT. The photocurrents originated from the depolarization field due to the alignment of ferroelectric polarization are different, although the polarizations of the two films are about the same. The mechanism behind the origin of the different photocurrent behaviors between Pt/BNT/Pt and Pt/PZT/Pt capacitors was discussed.
Incorporation of the dopants Si and Be into GaAs nanowires
Authors: Hilse M. , Ramsteiner M. , Breuer S. , Geelhaar L. , Riechert H.
Published: May 2010

We studied the doping with Si and Be of GaAs nanowires (NWRs) grown by molecular beam epitaxy. Regarding the NW morphology, no influence was observed for Si doping but high Be doping concentrations cause a kinking and tapering of the NWRs. We investigated local vibrational modes by means of resonant Raman scattering to determine the incorporation sites of the dopant atoms. For Si doping, both donors on Ga sites and acceptors on As sites have been observed. Be was found to be incorporated as an acceptor on Ga sites. However, at high doping concentration, Be is also incorporated on interstitial sites.
Thin-film transistors based on p-type Cu2O thin films produced at room temperature
Authors: Fortunato Elvira , Figueiredo Vitor , Barquinha Pedro , Elamurugu Elangovan , Barros Raquel , Gonçalves Gonçalo , Park Sang-Hee Ko , Hwang Chi-Sun , Martins Rodrigo
Published: May 2010

Copper oxide (Cu2O) thin films were used to produce bottom gate p-type transparent thin-film transistors (TFTs). Cu2O was deposited by reactive rf magnetron sputtering at room temperature and the films exhibit a polycrystalline structure with a strongest orientation along (111) plane. The TFTs exhibit improved electrical performance such as a field-effect mobility of 3.9 cm2/V s and an on/off ratio of 2×102.
Linear polarization rotators based on dye-doped liquid crystal cells
Authors: Huang Chia-Yi , Tsai Hong-Yi , Wang Yi-Hong , Huang Chong-Ming , Lo Kuang-Yao , Lee Chia-Rong
Published: May 2010

Linear polarization rotator is fabricated by a single-side homogenously aligned dye-doped liquid crystal cell and linear variable neutral density filter (LVNDF). When a pump beam passing through the transmittance-linear region of LVNDF irradiates on the untreated surface, the surface LC director in the irradiation region is photoaligned into a continuous twist from 0° to 90°. Consequently, the bulk director gradually transits from a homogeneous to twist orientation. This device is capable of rotating the polarization of an input linearly polarized light depending on the beam position, exhibiting a large continuous twist region (5.6 mm) and high contrast ratio (∼1000:1).
Flexural deformation in a compositionally stepped ferrite and magnetoelectric effects in a composite with piezoelectrics
Authors: Mandal S. K. , Sreenivasulu G. , Petrov V. M. , Srinivasan G.
Published: May 2010

The nature of strain mediated magnetoelectric (ME) coupling is investigated in laminates of lead zirconate titanate (PZT) and compositionally stepped ferrite with grading of piezomagnetic coefficient. ME effects that could only be attributed to grading related bending strain are observed in a trilayer of ferrite and oppositely poled PZT. It is shown that in a bilayer, grading induced flexural strain counteracts bending moment due to structural asymmetry and enhances ME coupling by a factor of 2. A zero-bias field ME effect is observed in such laminates. The graded composites are of interest for self-biased magnetic field sensors.
Habitat and food partitioning of billfishes (Xiphioidei)
Authors: Shimose T. , Yokawa K. , Saito H.
Published: May 2010

Species composition and food habits of four istiophorid billfishes were investigated and compared in three different tropical areas of the eastern North Pacific Ocean by longline operations from September to November 2004. Sailfish Istiophorus platypterus, shortbill spearfish Tetrapturus angustirostris and blue marlin Makaira nigricans had specific habitat preferences and mainly occurred in the near‐continent area (13–16° N; 103–107° W), the open‐ocean area (16–18° N; 118–134° W) and the near‐equator area (5° N; 104–120° W). Small (<140 cm in lower jaw–fork length) striped marlin Kajikia audax mainly occurred in the near‐continent area; however, large (≥140 cm) individuals occurred throughout all three areas. Prey compositions of large K. audax in the three areas were different from one other reflecting the prey availability in each area. In the open‐ocean area, molid fishes were dominant in mass for both large K. audax (49%) and T. angustirostris (73%), and large K. audax also fed on ostraciid (33%) and scombrid fishes (15%). In the near‐continent area, tetraodontid fishes were dominant for large and small I. platypterus (54, 57%), and both large and small K. audax also fed on tetraodontid fishes (3, 12%). Large K. audax in this area fed mainly on scombrid fishes (86%). These results indicate that large K. audax show overlaps but little segregations of its prey with other billfishes. In the near‐equator area, stomach contents of large K. audax and M. nigricans were few and billfish prey items were thought to be scarce.
Understanding waiting lists as the matching of surgical capacity to demand: are we wasting enough surgical time?
Authors: Pandit J. J. , Pandit M. , Reynard J. M.
Published: May 2010

If surgical ‘capacity’ always matched or exceeded ‘demand’ then there should be no waiting lists for surgery. However, understanding what is meant by ‘demand’, ‘capacity’ and ‘matched’ requires some mathematical concepts that we outline in this paper. ‘Time’ is the relevant measure: ‘demand’ for a surgical team is best understood as the total min required for the surgery booked from outpatient clinics every week; and ‘capacity’ is the weekly operating time available. We explain how the variation in demand (not just the mean demand) influences the analysis of optimum capacity. However, any capacity chosen in this way is associated with only a likelihood (that is, a probability rather than certainty) of absorbing the prevailing demand. A capacity that suitably absorbs the demand most of the time (for example, > 80% of weeks) will inevitably also involve considerable waste (that is, many weeks in which there is spare, unused capacity). Conversely, a level of capacity chosen to minimise wasted time will inevitably cause an increase in size of the waiting list. Thus the question of how to balance demand and capacity is intimately related to the question of how to balance utilisation and waste. These mathematical considerations enable us to consider objectively how to manage the waiting list. They also enable us critically to analyse the extent to which philosophies adopted by the National Health Service (such as ‘Lean’ or ‘Six Sigma’) will be successful in matching surgical capacity to demand.
A genome scan for quantitative trait loci influencing carcass, post‐natal growth and reproductive traits in commercial Angus cattle
Authors: McClure M. C. , Morsci N. S. , Schnabel R. D. , Kim J. W. , Yao P. , Rolf M. M. , McKay S. D. , Gregg S. J. , Chapple R. H. , Northcutt S. L. , Taylor J. F.
Published: May 2010

To gain insight into the number of loci of large effect that underlie variation in cattle, a quantitative trait locus (QTL) scan for 14 economically important traits was performed in two commercial Angus populations using 390 microsatellites, 11 single nucleotide polymorphisms (SNPs) and one duplication loci. The first population comprised 1769 registered Angus bulls born between 1955 and 2003, with Expected Progeny Differences computed by the American Angus Association. The second comprised 38 half‐sib families containing 1622 steers with six post‐natal growth and carcass phenotypes. Linkage analysis was performed by half‐sib least squares regression with gridqtl or Bayesian Markov chain Monte Carlo analysis of complex pedigrees with loki. Of the 673 detected QTL, only 118 have previously been reported, reflecting both the conservative approach to QTL reporting in the literature, and the more liberal approach taken in this study. From 33 to 71% of the genetic variance and 35 to 56% of the phenotypic variance in each trait was explained by the detected QTL. To analyse the effects of 11 SNPs and one duplication locus within candidate genes on each trait, a single marker analysis was performed by fitting an additive allele substitution model in both mapping populations. There were 53 associations detected between the SNP/duplication loci and traits with −log10Pnominal≥ 4.0, where each association explained 0.92% to 4.4% of the genetic variance and 0.01% to 1.86% of the phenotypic variance. Of these associations, only six SNP/duplication loci were located within 8 cM of a QTL peak for the trait, with two being located at the QTL peak: SST_DG156121:c.362A>G for ribeye muscle area and TG_X05380:c.422C>T for calving ease. Strong associations between several SNP/duplication loci and trait variation were obtained in the absence of any detected linked QTL. However, we reject the causality of several commercialized DNA tests, including an association between TG_X05380:c.422C>T and marbling in Angus cattle.
Monoclonal gammopathy of undetermined significance: a consensus statement
Authors: Berenson James R. , Anderson Kenneth C. , Audell Robert A. , Boccia Ralph V. , Coleman Morton , Dimopoulos Meletios A. , Drake Matthew T. , Fonseca Rafael , Harousseau Jean‐Luc , Joshua Douglas , Lonial Sagar , Niesvizky Ruben , Palumbo Antonio , Roodman G. David , San‐Miguel Jesus F. , Singhal Seema , Weber Donna M. , Zangari Maurizio , Wirtschafter Eric , Yellin Ori , Kyle Robert A.
Published: May 2010

On February 25, 2009, a panel of international experts on plasma cell dyscrasia and skeletal disease met to discuss monoclonal gammopathy of undetermined significance (MGUS). This non‐malignant B‐cell disorder is the most common plasma cell dyscrasia and is associated with an increased risk of developing serious B‐cell disorders. Individuals with MGUS also have an increased risk of osteoporosis and osteopenia associated with an increased likelihood of developing fractures especially in the vertebral column, peripheral neuropathy and thromboembolic events. The goal of the meeting was to develop a consensus statement regarding the appropriate tests to screen, evaluate and follow‐up patients with MGUS. The panel also addressed the identification and treatment of MGUS‐related skeletal problems, thromboembolic events and neurological complications. The following consensus statement outlines the conclusions and marks the first time that a consensus statement for the screening and treatment of MGUS has been clearly stated.
Allogeneic haematopoietic cell transplantation after nonmyeloablative conditioning in patients with T‐cell and natural killer‐cell lymphomas
Authors: Shustov Andrei R. , Gooley Theodore A. , Sandmaier Brenda M. , Shizuru Judith , Sorror Mohamed L. , Sahebi Firoozeh , McSweeney Peter , Niederwieser Dietger , Bruno Benedetto , Storb Rainer , Maloney David G.
Published: May 2010

Patients with T‐cell and natural killer‐cell lymphomas have poor outcomes. This study examined the role of allogeneic haematopoietic cell transplantation (allo‐HCT) after nonmyeloablative conditioning in this setting. Seventeen patients with T‐cell lymphoma or NK‐cell lymphoma, including three patients in first complete remission, received allo‐HCT after 2 Gy total‐body irradiation and fludarabine. The median age was 57 (range, 18–73) years. The median number of prior therapies was 3 (range, 1–7), six patients (35%) had failed prior autologous HCT, and five patients (29%) had refractory disease at the time of allograft. Postgrafting immunosuppression was provided with mycophenolate mofetil with ciclosporin or tacrolimus. After a median follow‐up of 3·3 (range, 0·3–8·0) years among surviving patients, the estimated probabilities of 3‐year overall and progression‐free survival were 59% and 53%, respectively, while the estimated probabilities of non‐relapse mortality and relapse at 3 years were 19% and 26%, respectively. Sixty‐five percent of patients developed grades 2–4 acute graft‐versus‐host disease and 53% of patients developed chronic graft‐versus‐host disease. Allo‐HCT after nonmyeloablative conditioning is a promising salvage option for selected patients with T‐cell and NK‐cell lymphomas. These results suggest that graft‐versus‐T‐cell lymphoma activity is responsible for long‐term disease control.
Glucocerebrosidase deficiency dramatically impairs human bone marrow haematopoiesis in an in vitro model of Gaucher disease
Authors: Berger Juliette , Lecourt Séverine , Vanneaux Valérie , Rapatel Chantal , Boisgard Stéphane , Caillaud Catherine , Boiret‐Dupré Nathalie , Chomienne Christine , Marolleau Jean‐Pierre , Larghero Jérôme , Berger Marc G.
Published: May 2010

One of the cardinal symptoms of type 1 Gaucher Disease (GD) is cytopenia, usually explained by bone marrow (BM) infiltration by Gaucher cells and hypersplenism. However, some cases of cytopenia in splenectomized or treated patients suggest possible other mechanisms. To evaluate intra‐cellular glucocerebrosidase (GlcC) activity in immature progenitors and to prove the conduritol B epoxide (CBE)‐induced inhibition of the enzyme, we used an adapted flow cytometric technique before assessing the direct effect of GlcC deficiency in functional assays. Among haematopoietic cells from healthy donors, monocytes showed the highest GlcC activity but immature CD34+ and mesenchymal cells also had significant GlcC activity. CBE greatly inhibited the enzyme activity of all cell categories. GlcC‐deficient CD34+ cells showed impaired ability to proliferate and differentiate in the expansion assay and had lower frequency of erythroid burst‐forming units, granulocyte colony‐forming units (CFU) and macrophage CFU progenitors, but the effect of GlcC deficiency on megakaryocyte CFU lineage was not significant. GlcC deficiency strongly impaired primitive haematopoiesis in long‐term culture. Furthermore, GlcC deficiency progressively impaired proliferation of mesenchymal progenitors. These data suggest an intrinsic effect of GlcC deficiency on BM immature cells that supplements the pathophysiology of GD and opens new perspectives of therapeutic approach.
Current therapeutic approaches for patients with myelodysplastic syndromes
Authors: Greenberg Peter L.
Published: May 2010

The myelodysplastic syndromes (MDS) are a heterogeneous spectrum of disorders requiring selective therapy based on patients’ specific clinical features, predominantly their prognostic subgroups, age and performance status. Guidelines for management of patients with MDS have been generated by a number of national panels. This review focuses on evidence‐based data supporting therapeutic approaches, which have also been recommended by the US National Comprehensive Cancer Network MDS Panel, with discussion of accessibility of recommended drugs in the US and in other countries. For lower risk disease (International Prognostic Scoring System Low and Intermediate‐1) therapy is aimed at haematological improvement whereas for higher risk disease (Intermediate‐2 and High) treatment focuses on altering disease natural history. Recent information regarding additional clinical and biological features has provided useful parameters for assessing disease prognosis that aid risk‐based management decisions. The rationale for use of low versus high intensity therapies with these agents, including allogeneic haematopoietic stem cell transplantation, is discussed in detail.