bluuebunny/crossref_metadata_2025 huggingface dataset:
L p -Green potential estimates on noncompact Riemannian manifolds
Authors: Xiao Jie
Published: June 2010

We are concerned with Lp a priori estimates for the Green function of a regular domain of the Laplacian–Beltrami operator on any 3≤n-dimensional complete noncompact boundary-free Riemannian manifold via rough and sharp isoperimetric-type inequalities. Consequently, we are led to evaluate the critical limit of an induced monotone Green’s functional using the asymptotic behavior of the Lorentz norm deficit of the Green function at infinity, as well as the harmonic radius of a regular domain in the Riemannian manifold with both non-negative Ricci curvature and optimal isoperimetric inequality of Euclidean type.
Interface characteristics of n-n and p-n Ge/SiC heterojunction diodes formed by molecular beam epitaxy deposition
Authors: Gammon P. M. , Pérez-Tomás A. , Jennings M. R. , Shah V. A. , Boden S. A. , Davis M. C. , Burrows S. E. , Wilson N. R. , Roberts G. J. , Covington J. A. , Mawby P. A.
Published: June 2010

In this article, we report on the physical and electrical nature of Ge/SiC heterojunction layers that have been formed by molecular beam epitaxy (MBE) deposition. Using x-ray diffraction, atomic force microscopy, and helium ion microscopy, we perform a thorough analysis of how MBE growth conditions affect the Ge layers. We observe the layers developing from independent islands at thicknesses of 100 nm to flat surfaces at 300 nm. The crystallinity and surface quality of the layer is shown to be affected by the deposition parameters and, using a high temperature deposition and a light dopant species, the layers produced have large polycrystals and hence a low resistance. The p-type and n-type layers, 300 nm thick are formed into Ge/SiC heterojunction mesa diodes and these are characterized electrically. The polycrystalline diodes display near ideal diode characteristics (n<1.05), low on resistance and good reverse characteristics. Current-voltage (I-V) measurements at varying temperature prove that all the layers have two-dimensional fluctuations in the Schottky barrier height (SBH) due to inhomogeneities at the heterojunction interface. Capacitance-voltage analysis and the SBH size extracted from I-V analysis suggest strongly that interface states are present at the surface causing Fermi-level pinning throughout the bands. A simple model is used to quantify the concentration of interface states at the surface.
A simple method for measuring the superhydrophobic contact angle with high accuracy
Authors: Hung Yi-Lin , Chang Yao-Yuan , Wang Meng-Jiy , Lin Shi-Yow
Published: June 2010

A modified selected-plane method for contact angle (θ) measurement is proposed in this study that avoids the difficulty of finding the real contact point and image-distortion effects adjacent to the contact point. This method is particularly suitable for superhydrophobic surfaces. The sessile-drop method coupled with the tangent line is the most popular method to find the contact angle in literature, but it entails unavoidable errors in determining the air-solid base line due to the smoothness problem and substrate tilting. In addition, the tangent-line technique requires finding the actual contact point. The measurement error due to the base line problem becomes more profound for superhydrophobic surfaces. A larger θ deviation results from a more superhydrophobic surface with a fixed base line error. The proposed modified selected-plane method requires only four data points (droplet apex, droplet height, and two interfacial loci close to the air-solid interface), avoiding the problem of the sessile-drop-tangent method in finding the contact point and saving the trouble of the sessile-drop-fitting method for best fitting of the numerous edge points with the theoretical profile. A careful error analysis was performed, and a user-friendly program was provided in this work. This method resulted in an accurate θ measurement and a method that was much improved over the classical selected plane and the sessile-drop-tangent methods. The θ difference between this method and the sessile-drop-fitting method was found to be less than three degrees.
Automated high pressure cell for pressure jump x-ray diffraction
Authors: Brooks Nicholas J. , Gauthe Beatrice L. L. E. , Terrill Nick J. , Rogers Sarah E. , Templer Richard H. , Ces Oscar , Seddon John M.
Published: June 2010

A high pressure cell for small and wide-angle x-ray diffraction measurements of soft condensed matter samples has been developed, incorporating a fully automated pressure generating network. The system allows both static and pressure jump measurements in the range of 0.1–500 MPa. Pressure jumps can be performed as quickly as 5 ms, both with increasing and decreasing pressures. Pressure is generated by a motorized high pressure pump, and the system is controlled remotely via a graphical user interface to allow operation by a broad user base, many of whom may have little previous experience of high pressure technology. Samples are loaded through a dedicated port allowing the x-ray windows to remain in place throughout an experiment; this facilitates accurate subtraction of background scattering. The system has been designed specifically for use at beamline I22 at the Diamond Light Source, United Kingdom, and has been fully integrated with the I22 beamline control systems.
Arsenic decapping and half cycle reactions during atomic layer deposition of Al2O3 on In0.53Ga0.47As(001)
Authors: Shin Byungha , Clemens Jonathon B. , Kelly Michael A. , Kummel Andrew C. , McIntyre Paul C.
Published: June 2010

In situ x-ray photoelectron spectroscopy was performed during thermal desorption of a protective As layer and subsequent atomic layer deposition (ALD) of Al2O3 on In0.53Ga0.47As(001). H2O dosing on the As-decapped surface caused formation of As oxides and As hydroxides, which were reduced by a subsequent trimethylaluminum (TMA) pulse. However, when a TMA pulse was performed first, the In0.53Ga0.47As(001) surface did not oxidize during subsequent ALD cycles, suggesting passivation by TMA adsorption at water-reactive sites. Scanning tunneling microscopy performed on a structurally-similar InAs(001) surface after H2O dosing revealed that surface defects are created by displacement of surface As atoms during oxidation. These surface defects act as interface states, consistent with the inferior capacitance-voltage characteristics of H2O-first ALD-Al2O3 capacitors compared to TMA-first samples.
Power loss by a two-dimensional hole gas in a Si/Si0.8Ge0.2 heterostructure over a wide temperature range
Authors: Kubakaddi S. S. , Katti V. S. , Lehmann D.
Published: June 2010

The average power loss of two-dimensional hole gas (2DHG) due to acoustic and optical phonons is calculated in a Si/Si0.8Ge0.2 heterostructure over a wide temperature range. The power loss of 2DHG due to acoustic phonons via deformation potential coupling and Pekar mechanism is calculated taking account of temperature dependent screening. The hole-acoustic phonon coupling is found to dominate hole power loss for Tc<70 K. The experimental power loss data for Tc<2 K is accounted for by Pekar mechanism and the data for 2 K<Tc<4.2 K is explained by the total contribution of these two mechanisms. Pekar mechanism is found to be important in these systems at very low Tc. Power loss calculation due to nonpolar optical phonons is carried out taking account of hot phonon effect and it is important and dominant for Tc>70 K. Hot phonon effect is found to reduce the power loss of 2DHG by a factor of about 1.5. The power loss calculations are carried out for different carrier concentrations and compared with those in GaAlAs/GaAs heterostructures.
Deuteration effect on tricritical phase transition of triglycine selenate: Calorimetric and dielectric measurements analyzed in the framework of Landau theory
Authors: Romero F. J. , Gallardo M. C. , Martín-Olalla J. M. , del Cerro J.
Published: June 2010

The ferroelectric phase transition of three single crystals of (TGSe)1−x(DTGSe)x has been described by using specific heat, latent heat, and dielectric permittivity measurements. Pure, half-deuterated, and highly-deuterated TGSe single crystals were analyzed. Transition temperature and latent heat increase with increasing deuteration. Irrespective of the degree of deuteration, a 2-4-6 Landau model is suitable to describe the phase transition. The fourth-rank prefactor in Landau potential is found to be very sensitive to deuteration while the second-rank and the sixth-rank prefactors smoothly change with composition. The pyroelectric figure of merit for these materials has also been derived from the theoretical model.
Long range intermolecular interactions between the alkali diatomics Na2, K2, and NaK
Authors: Zemke Warren T. , Byrd Jason N. , Michels H. Harvey , Montgomery John A. , Stwalley William C.
Published: June 2010

Long range interactions between the ground state alkali diatomics Na2–Na2, K2–K2, Na2–K2, and NaK-NaK are examined. Interaction energies are first determined from ab initio calculations at the coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory, including counterpoise corrections. Long range energies calculated from diatomic molecular properties (polarizabilities and dipole and quadrupole moments) are then compared with the ab initio energies. A simple asymptotic model potential ELR=Eelec+Edisp+Eind is shown to accurately represent the intermolecular interactions for these systems at long range.
Visualization of Tm dopant atoms diffused out of GaN quantum dots
Authors: Okuno H. , Rouvière J.-L. , Jouneau P.-H. , Bayle-Guillemaud P. , Daudin B.
Published: June 2010

GaN quantum dots doped with Tm atoms and embedded in AlN have been characterized by high-angle annular dark-field imaging using a scanning transmission electron microscope. Direct visualization of individual Tm atoms in AlN layers has been achieved. We have found that besides being present in GaN dots, Tm atoms also tend to segregate at AlN barriers. The Tm distribution is related to the capping mechanism of the dots with AlN. A visibility coefficient based on locally integrated, rather than peak, intensities is introduced to determine quantitatively the number of Tm atoms in a given atomic column. Experimental and simulated images show that this visibility presents a reduced sensitivity to the defocus or to the position of the Tm atom within the thin lamella.
Density functional approach to the description of fluids in contact with bilayers
Authors: Patrykiejew A. , Sokołowski S. , Ilnyskyi J. , Sokołowska Z.
Published: June 2010

We discuss an application of a density functional approach to describe a bilayer, or a simplified model of a membrane, that is built of tethered chain molecules. The bilayer integrity is maintained by tethering chain particles to two common sheets. We study the structure of a two-component mixture in contact with the bilayer, as well as the solvation force acting between two bilayers, immersed in a fluid. The fluid is a binary mixture involving the component that can cross freely the bilayer and the second impenetrable component. All the calculations are carried out for athermal system, in which only hard-core interactions are present.
Internal electric field influence on tunneling anisotropic magnetoresistance in epitaxial ferromagnet/n-GaAs junctions
Authors: Uemura Tetsuya , Harada Masanobu , Matsuda Ken-ichi , Yamamoto Masafumi
Published: June 2010

A strong voltage-dependent tunneling anisotropic magnetoresistance (TAMR) effect was observed in a fully epitaxial Co2MnSi/n-GaAs junction and a Co50Fe50/n-GaAs junction. Angular dependence of the tunnel resistance showed uniaxial-type anisotropic tunnel resistance between the [110] and [11¯0] directions in the (001) plane. The voltage at which the TAMR effect was suppressed was close to that at which the differential conductance reached a minimum in both samples, suggesting that the strength and/or the sign of the internal electric field at the Co2MnSi/n-GaAs and Co50Fe50/n-GaAs junctions could be related to the voltage-dependent TAMR effect through spin-orbit interaction.
Communications: Chain and double-ring polymeric structures: Observation of AlnH3n+1− (n=4–8) and Al4H14−
Authors: Li Xiang , Grubisic Andrej , Bowen Kit H. , Kandalam Anil K. , Kiran Boggavarapu , Gantefoer Gerd F. , Jena Puru
Published: June 2010

A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, AlnHm−, exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in AlnHm− species was m=3n+1 for n=5–8, i.e., AlnH3n+1−, and m=3n+2 for n=4, i.e., Al4H14−, as observed in their mass spectra. These are the most hydrogen-rich aluminum hydrides to be observed thus far, transcending the 3:1 hydrogen-to-aluminum ratio in alane. Even more striking, ion intensities for AlnHm− species with m=3n+1 and m=3n+2 hydrogen atoms were significantly higher than those of nearby AlnHm− mass peaks for which m<3n+1, i.e., the ion intensities for AlnH3n+1− and for Al4H14− deviated from the roughly bell-shaped ion intensity patterns seen for most AlnHm− species, in which m ranges from 1 to 3n. Calculations based on density functional theory showed that AlnH3n+1− clusters have chain and/or double-ring polymeric structures.
What Visual Information is Used for Stereoscopic Depth Displacement Discrimination?
Authors: Nefs Harold T , Harris Julie M
Published: June 2010

There are two ways to detect a displacement in stereoscopic depth, namely by monitoring the change in disparity over time (CDOT) or by monitoring the interocular velocity difference (IOVD). Though previous studies have attempted to understand which cue is most significant for the visual system, none has designed stimuli that provide a comparison in terms of relative efficiency between them. Here we used two-frame motion and random-dot noise to deliver equivalent strengths of CDOT and IOVD information to the visual system. Using three kinds of random-dot stimuli, we were able to isolate CDOT or IOVD or deliver both simultaneously. The proportion of dots delivering CDOT or IOVD signals could be varied, and we defined the discrimination threshold as the proportion needed to detect the direction of displacement (towards or away). Thresholds were similar for stimuli containing CDOT only, and containing both CDOT and IOVD, but only one participant was able to consistently perceive the displacement for stimuli containing only IOVD. We also investigated the effect of disparity pedestals on discrimination. Performance was best when the displacement crossed the reference plane, but was not significantly different for stimuli containing CDOT only and those containing both CDOT and IOVD. When stimuli are specifically designed to provide equivalent two-frame motion or disparity-change, few participants can reliably detect displacement when IOVD is the only cue. This challenges the notion that IOVD is involved in the discrimination of direction of displacement in two-frame motion displays.
Visual Processing Asymmetries in Change Detection
Authors: Iyilikci Osman , Becker Cordula , Güntürkün Onur , Amado Sonia
Published: June 2010

Change detection is critically dependent on attentional mechanisms. However, the relation between an asymmetrical distribution of visuo-spatial attention and the detection of changes in visual scenes is not clear. Spatial tasks are known to induce a stronger activation of the right hemisphere. The effects of such visual processing asymmetries induced by a spatial task on change detection were investigated. When required to detect changes in the left and in the right visual fields, participants were significantly faster in detecting changes on the left than on the right. Importantly, this left-side superiority in change detection is not influenced by inspection time, suggesting a critical role of visual processing benefit for the left visual field.
NCEP - ECPC monthly to seasonal US fire danger forecasts
Authors: Roads J. , Tripp P. , Juang H. , Wang J. , Fujioka F. , Chen S.
Published: June 2010

Five National Fire Danger Rating System indices (including the Ignition Component, Energy Release Component, Burning Index, Spread Component, and the Keetch–Byram Drought Index) and the Fosberg Fire Weather Index are used to characterise US fire danger. These fire danger indices and input meteorological variables, including temperature, relative humidity, precipitation, cloud cover and wind speed, can be skilfully predicted at weekly to seasonal time scales by a global to regional dynamical prediction system modified from the National Centers for Environmental Prediction’s Coupled Forecast System. The System generates global and regional spectral model ensemble forecasts, which in turn provide required input meteorological variables for fire danger. Seven-month US regional forecasts were generated every month from 1982 to 2007. This study shows that coarse-scale global predictions were more skilful than persistence, and fine-scale regional model predictions were more skilful than global predictions. The fire indices were better related to fire counts and area burned than meteorological variables, although relative humidity and temperature were useful predictors of fire characteristics.
Beyond Landsat: a comparison of four satellite sensors for detecting burn severity in ponderosa pine forests of the Gila Wilderness, NM, USA
Authors: Holden Zachary A. , Morgan Penelope , Smith Alistair M. S. , Vierling Lee
Published: June 2010

Methods of remotely measuring burn severity are needed to evaluate the ecological and environmental impacts of large, remote wildland fires. The challenges that were associated with the Landsat program highlight the need to evaluate alternative sensors for characterising post-fire effects. We compared statistical correlations between 55 Composite Burn Index field plots and spectral indices from four satellite sensors varying in spatial and spectral resolution on the 2003 Dry Lakes Fire in the Gila Wilderness, NM. Where spectrally feasible, burn severity was evaluated using the differenced Enhanced Vegetation Index (dEVI), differenced Normalised Difference Vegetation Index (dNDVI) and the differenced Normalised Burn Ratio (dNBR). Both the dEVI derived from Quickbird and the dNBR derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) showed similar or slightly improved correlations over the dNBR derived from Landsat Thematic Mapper data (R2 = 0.82, 0.84, and 0.78 respectively). The relatively coarse resolution MODIS-derived NDVI image was weakly correlated with ground data (R2 = 0.38). Our results suggest that moderately high-resolution satellite sensors like Quickbird and ASTER have potential for providing accurate information about burn severity. Future research should develop stronger links between higher-resolution satellite data and burn severity across a range of environments.
Bare soil and rill formation following wildfires, fuel reduction treatments, and pine plantations in the southern Sierra Nevada, California, USA
Authors: Berg Neil H. , Azuma David L.
Published: June 2010

Accelerated erosion commonly occurs after wildfires on forested lands. As burned areas recover, erosion returns towards prefire rates depending on many site-specific characteristics, including fire severity, vegetation type, soil type and climate. In some areas, erosion recovery can be rapid, particularly where revegetation is quick. Erosion recovery is less well understood for many fuel load reduction treatments. The rate of post-disturbance erosion recovery affects management options for forested lands, particularly when considering the combined ramifications of multiple disturbances on resource recovery rates (i.e. cumulative watershed effects). Measurements of percentage bare soil and rilling on over 600 plots in the southern Sierra Nevada with slopes less than 75% and within 1 km of roads were made between 2004 and 2006. Results suggest that after high-, moderate- or low-severity wildfire, rilling was seldom evident more than 4 years after fire. Percentage bare soil generally did not differ significantly between reference plots and wildfire plots greater than 6 years old. Little rilling was evident after treatment with a variety of fuel reduction techniques, including burning of machine- and hand-piled fuel, thinning, mastication, and crushing. Percentage bare soil at the fuel load reduction treatment plots also did not differ significantly from reference conditions. Percentage bare soil at pine plantation plots was noticeably higher than at reference sites.
Effect of fire severity on long-term occupancy of burned boreal conifer forests by saproxylic insects and wood-foraging birds
Authors: Nappi Antoine , Drapeau Pierre , Saint-Germain Michel , Angers Virginie A.
Published: June 2010

Fire severity can vary greatly within and among burns, even in the Canadian boreal forest where fire regimes consist mostly of stand-replacing fires. We investigated the effects of fire severity on the long-term occupancy of burns by (i) saproxylic insects and (ii) three wood-foraging birds. Based on observations made 6 to 11 years after fire in burned conifer forests that varied in fire severity in Quebec, Canada, our results indicate that low-severity portions of the burns likely provided snag conditions suitable for the long-term presence of deadwood-associated insects and birds. The black-backed woodpecker, a post-fire forest specialist, was still abundant 6 and 8 years after fire. This pattern was likely explained by the persistence of several saproxylic insect species that are associated with recently dead trees and by the positive effect of lower fire severity on the abundance of Arhopalus foveicollis, a cerambycid with a long life cycle in dead wood. The American three-toed woodpecker and the brown creeper, and their associated prey (Scolytinae beetles), were more abundant in burned stands of lower v. higher severity. We conclude that less severely burned snags and stands within high-severity burns may favour the long-term presence of trophic webs that involve saproxylic insects and wood-foraging birds in burned boreal forests.
Assessing crown fire potential in coniferous forests of western North America: a critique of current approaches and recent simulation studies
Authors: Cruz Miguel G. , Alexander Martin E.
Published: June 2010

To control and use wildland fires safely and effectively depends on creditable assessments of fire potential, including the propensity for crowning in conifer forests. Simulation studies that use certain fire modelling systems (i.e. NEXUS, FlamMap, FARSITE, FFE-FVS (Fire and Fuels Extension to the Forest Vegetation Simulator), Fuel Management Analyst (FMAPlus®), BehavePlus) based on separate implementations or direct integration of Rothermel’s surface and crown rate of fire spread models with Van Wagner’s crown fire transition and propagation models are shown to have a significant underprediction bias when used in assessing potential crown fire behaviour in conifer forests of western North America. The principal sources of this underprediction bias are shown to include: (i) incompatible model linkages; (ii) use of surface and crown fire rate of spread models that have an inherent underprediction bias; and (iii) reduction in crown fire rate of spread based on the use of unsubstantiated crown fraction burned functions. The use of uncalibrated custom fuel models to represent surface fuelbeds is a fourth potential source of bias. These sources are described and documented in detail based on comparisons with experimental fire and wildfire observations and on separate analyses of model components. The manner in which the two primary canopy fuel inputs influencing crown fire initiation (i.e. foliar moisture content and canopy base height) is handled in these simulation studies and the meaning of Scott and Reinhardt’s two crown fire hazard indices are also critically examined.
Economic analysis of geospatial technologies for wildfire suppression
Authors: Hesseln Hayley , Amacher Gregory S. , Deskins Aaron
Published: June 2010

Geospatial technologies used to fight large fires are becoming increasingly available, yet no rigorous study exists of their effects on suppression costs or fire losses, nor do we know whether these technologies allow more efficient combination of firefighting assets used to suppress fires. The high cost of these technologies merits an assessment of these values. Using data from all large-scale fires originating on US Forest Service land greater than 1620 ha in the Northern Rocky Mountains for the 2000–03 fire seasons, we estimate random parameter models of total fire expenditures, agency fire suppression costs, fire duration, and area burned. Site factors, geospatial technology use, and firefighting assets are used as explanatory variables in these regressions. In addition, stochastic cost frontier models are estimated for suppression costs to judge the efficiency of input use for fires with and without geospatial technology use. We find that although geospatial technology use does not appear to significantly increase suppression costs when other factors are controlled, it does seem to allow more efficient allocation of resources such as labour and capital by fire managers seeking to minimise the costs of controlling large fires. Both of these results suggest that the high cost of using these technologies may be offset by improvements in the use of costly firefighting assets by fire managers.
Effect of fire weather, fuel age and topography on patterns of remnant vegetation following a large fire event in southern California, USA
Authors: Blodgett Nell , Stow Douglas A. , Franklin Janet , Hope Allen S.
Published: June 2010

Large fire events in southern California have burned thousands of hectares over the past decade. Landscape pattern and natural system processes are shaped by these large conflagrations, thereby influencing the ecological structure and functioning of the region. Unburned vegetation remnants can be used to assess general fuel consumption and to provide valuable information regarding fire behaviour, weather effects and post-fire regeneration. For this study, post-fire unburned vegetation was mapped at a very fine spatial resolution based on semi-automatic classification of airborne large-format multispectral image data and compared across different fire environment zones within the 2003 Cedar Fire burn perimeter. Landscape metrics were used to characterise unburned vegetation patches for a section of the Cedar Fire affected by Santa Ana weather conditions and for a section of the fire that burned under non-Santa Ana weather conditions. Maps of remnant vegetation and associated landscape metrics were compared across these two sections and within shrubland community type, topography and age-class strata using inferential statistics. Key findings reveal more unburned vegetation in larger, rounder patches in the non-Santa Ana section. Pre-fire stand age greater than 6 years showed little effect on the amount or pattern of unburned vegetation within the Santa Ana section.
The initiation of fire spread in shrubland fuels recreated in the laboratory
Authors: Plucinski Matt P. , Anderson Wendy R. , Bradstock Ross A. , Gill A. Malcolm
Published: June 2010

Fire-prone shrub-dominated vegetation communities cover a considerable portion of Australia, including areas fringing urban development. Near urban interfaces, they are actively managed with prescribed fire to reduce the risk of wildfire (unplanned fire). Knowledge of the range of conditions that allow fires to spread or fail to do so is limited and can inconvenience fire managers when conducting prescribed burns. A series of experimental ignitions conducted in miniature shrublands reconstructed in the laboratory were used to investigate factors that influence ignition thresholds. The miniature shrublands were composed of foliage from the shrub Allocasuarina nana and were prepared over a range of moisture contents and densities. The impact of dead fuel within the aerial structure of the shrubs was also investigated, as was the presence and absence of wind and litter. The most important factors for spread initiation were identified using logistic regression analysis and classification tree modelling. The presence of litter, live fuel moisture content, shrub-layer density, presence of wind, and the amount and continuity of the dead elevated fuel were all found to influence spread sustainability. There was a negative interaction between shrub-layer density and live fuel moisture content, showing the effect of density to be less at higher moisture contents.
Metabolic cost as a unifying principle governing neuronal biophysics
Authors: Hasenstaub Andrea , Otte Stephani , Callaway Edward , Sejnowski Terrence J.
Published: June 2010

The brain contains an astonishing diversity of neurons, each expressing only one set of ion channels out of the billions of potential channel combinations. Simple organizing principles are required for us to make sense of this abundance of possibilities and wealth of related data. We suggest that energy minimization subject to functional constraints may be one such unifying principle. We compared the energy needed to produce action potentials singly and in trains for a wide range of channel densities and kinetic parameters and examined which combinations of parameters maximized spiking function while minimizing energetic cost. We confirmed these results for sodium channels using a dynamic current clamp in neocortical fast spiking interneurons. We find further evidence supporting this hypothesis in a wide range of other neurons from several species and conclude that the ion channels in these neurons minimize energy expenditure in their normal range of spiking.
(La,Sr)CoO3/ZnO nanofilm–nanorod diode arrays for photo-responsive moisture and humidity detection
Authors: Gao Haiyong , Cai Wenjie , Shimpi Paresh , Lin Hui-Jan , Gao Pu-Xian
Published: June 2010

Large scale (La,Sr)CoO3 (LSCO)/ZnO nanofilm–nanorod diode arrays have been successfully fabricated using a combination of hydrothermal synthesis and colloidal deposition. With well-controlled dimensionality, crystallinity, crystal structures and device structures, LSCO/ZnO nanofilm–nanorod diode arrays display an excellent rectifying current–voltage (I–V) characteristic under ±1 V bias with negligible leakage current upon reverse bias. These nanostructured diode arrays have been found to be sensitive to UV illumination and different relative humidities at room temperature upon forward bias. A negative photoconductivity response is revealed upon UV illumination on the diode arrays as a result of the desorption process of nanofilm–nanorod surface moisture. The forward current of LSCO/ZnO nanofilm–nanorod diodes increases significantly with increasing relative humidity. These unique nanostructured diode arrays could be useful as photo-responsive moisture and humidity detectors.
Cucumber power
Authors: Wibig Tadeusz
Published: June 2010

The flow of electricity from one body to another has been known by man since we first
learned how to gather an electric charge. In contrast to conventional wisdom, the process in
the general case is not easy to explain. It is different in plasma in the Sun or in your colour
TV display, in semiconductors inside your computer or TV set circuits, or in metals
such as aluminium or copper connecting your TV to the mains and to the world
outside. The electricity flow will also be different in electrolytes, for example,
those filling your body (and brain), should you carelessly try to follow the same
connections. Sometimes it depends on the amount of charge to be displaced, the shapes
of bodies or even on the condition of the body surface. To understand all this,
considerable knowledge of the structure and properties of matter is necessary.
Convergence of the random vortex method in two dimensions
Authors: Long Ding-Gwo
Published: June 2010

A theoretical framework for analyzing the random vortex method is presented. It extends and modifies the analysis of the inviscid vortex method in a natural and unified manner. The rate of convergence of the random vortex method in two dimensions is obtained by analyzing the consistency error and justifying the stability estimate. The sampling error introduced by the random motions of finitely many vortices is the dominant component of the consistency error in terms of order. It is estimated by applying Bennett’s inequality.
Diameters and eigenvalues
Authors: Chung F. R. K.
Published: June 2010

We derive a new upper bound for the diameter of akk-regular graphGGas a function of the eigenvalues of the adjacency matrix. Namely, suppose the adjacency matrix ofGGhas eigenvaluesλ1,λ2,…,λn{\lambda _1},{\lambda _2}, \ldots ,{\lambda _n}with<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue lamda 1 EndAbsoluteValue greater-than-or-equal-to StartAbsoluteValue lamda 2 EndAbsoluteValue greater-than-or-equal-to midline-horizontal-ellipsis greater-than-or-equal-to StartAbsoluteValue lamda Subscript n Baseline EndAbsoluteValue">|λ1|≥|λ2|≥⋯≥|λn|\left | {{\lambda _1}} \right | \geq \left | {{\lambda _2}} \right | \geq \cdots \geq \left | {{\lambda _n}} \right |whereλ1=k{\lambda _1} = k,λ=|λ2|\lambda = \left | {{\lambda _2}} \right |. Then the diameterD(G)D(G)must satisfy\[D(G)≤⌈log⁡(n−1)/log(k/λ)⌉D(G) \leq \left \lceil {\log (n - 1)/{\text {log}}(k/\lambda )} \right \rceil\]. We will consider families of graphs whose eigenvalues can be explicitly determined. These graphs are determined by sums or differences of vertex labels. Namely, the pair{i,j}\left \{ {i,j} \right \}being an edge depends only on the valuei+ji + j(ori−ji - jfor directed graphs). We will show that these graphs are expander graphs with small diameters by using an inequality on character sums, which was recently proved by N. M. Katz.
Trace rings of generic matrices are Cohen-Macaulay
Authors: Van den Bergh Michel
Published: June 2010

In this paper, we prove that trace rings of generic matrics are Cohen-Macaulay (Theorem 7.3.6). This is done by relating this problem to a conjecture of Stanley about modules of invariants under a reductive group. We prove a slightly weakened version (Conjecture 3.4’) of this conjecture in special cases (Theorem 6.1.8). In particular, we obtain that Conjecture 3.4’ is true for

S

L
2

S{L_2}

(Remark 6.1.10).
A rigorous subexponential algorithm for computation of class groups
Authors: Hafner James L. , McCurley Kevin S.
Published: June 2010

Let

C
(
−
d
)

C( - d)

denote the Gauss Class Group of quadratic forms of a negative discriminant

−
d

- d

(or equivalently, the class group of the imaginary quadratic field

Q
(

−
d

)

Q(\sqrt { - d} )

). We give a rigorous proof that there exists a Las Vegas algorithm that will compute the structure of

C
(
−
d
)

C( - d)

with an expected running time of

L

(
d

)

2

+
o
(
1
)

L{(d)^{\sqrt 2 + o(1)}}

bit operations, where

L
(
d
)
=

exp

(

log

d

log

log

d

)

L(d) = {\text {exp}}(\sqrt {\log \,d\;\log \,\log \,d} )

. Thus, of course, also includes the computation of the class number

h
(
−
d
)

h( - d)

, the cardinality of

C
(
−
d
)

C( - d)

.
Negatively curved manifolds with exotic smooth structures
Authors: Farrell F. T. , Jones L. E.
Published: June 2010

Let

M
M

denote a compact real hyperbolic manifold with dimension

m
≥
5

m \geq 5

and sectional curvature

K
=
−
1

K = - 1

, and let

Σ
\Sigma

be an exotic sphere of dimension

m
m

. Given any small number

δ
>
0

\delta > 0

, we show that there is a finite covering space

M
^

\widehat {M}

of

M
M

satisfying the following properties: the connected sum

M
^

#
Σ

\widehat {M}\# \Sigma

is not diffeomorphic to

M
^

\widehat {M}

, but it is homeomorphic to

M
^

\widehat {M}

;

M
^

#
Σ

\widehat {M}\# \Sigma

supports a Riemannian metric having all of its sectional curvature values in the interval

[
−
1
−
δ
,
−
1
+
δ
]

[ - 1 - \delta , - 1 + \delta ]

. Thus, there are compact Riemannian manifolds of strictly negative sectional curvature which are not diffeomorphic but whose fundamental groups are isomorphic. This answers Problem 12 of the list compiled by Yau [22]; i.e., it gives counterexamples to the Lawson-Yau conjecture. Note that Mostow’s Rigidity Theorem [17] implies that

M
^

#
Σ

\widehat {M}\# \Sigma

does not support a Riemannian metric whose sectional curvature is identically -1 . (In fact, it is not diffeomorphic to any locally symmetric space.) Thus, the manifold

M
^

#
Σ

\widehat {M}\# \Sigma

supports a Riemannian metric with sectional curvature arbitrarily close to -1 , but it does not support a Riemannian metric whose sectional curvature is identically -1 . More complicated examples of manifolds satisfying the properties of the previous sentence were first constructed by Gromov and Thurston [11].
Symmetric decreasing rearrangement is sometimes continuous
Authors: Almgren Frederick J. , Lieb Elliott H.
Published: June 2010

This paper deals with the operationR\mathcal {R}of symmetric decreasing rearrangement which mapsW1,p(Rn){{\mathbf {W}}^{1,p}}({{\mathbf {R}}^n})toW1,p(Rn){{\mathbf {W}}^{1,p}}({{\mathbf {R}}^n}). We show that even though it is norm decreasing,R\mathcal {R}is not continuous forn≥2n \geq 2. The functions at whichR\mathcal {R}is continuous are precisely characterized by a new property calledco-area regularity. Every sufficiently differentiable function is co-area regular, and both the regular and the irregular functions are dense inW1,p(Rn){{\mathbf {W}}^{1,p}}({{\mathbf {R}}^n}). Curiously,R\mathcal {R}is always continuous in fractional Sobolev spacesWα,p(Rn){{\mathbf {W}}^{\alpha ,p}}({{\mathbf {R}}^n})with0>α>10 > \alpha > 1.
The three-space problem for 𝐿¹
Authors: Talagrand Michel
Published: June 2010

We construct a subspace

X
X

of

L
1

{L^1}

such that

X
X

is an

l
1

{l^1}

-sum of spaces isomorphic to

l
1

{l^1}

but such that

L
1

/

X

{L^1}/X

does not contain a copy of

L
1

{L^1}

. We also construct two Banach spaces

E
1

{E_1}

,

E
2

{E_2}

that do not contain a copy of

L
1

{L^1}

but such that

E
1

×

E
2

{E_1} \times {E_2}

contains a copy of

L
1

{L^1}

. Moreover, the projections of

L
1

{L^1}

on each factor are one-to-one, and the images of the unit ball of

L
1

{L^1}

are closed. These examples settle questions of J. Lindenstrauss, P. Pelczynski, J. Bourgain, and H. P. Rosenthal.
Koszul complexes, harmonic oscillators, and the Todd class
Authors: Bismut Jean-Michel
Published: June 2010

In this paper, we construct secondary characteristic classes associated with a short exact sequence of holomorphic Hermitian vector bundles. These secondary invariants are generalized analytic torsion forms associated with a family of elliptic operators. They are calculated in terms of Bott-Chern forms and of a certain complicated characteristic class. In a joint calculation with C. Soulé, we relate this characteristic class to the arithmetic Todd genus of Gillet and Soulé.
Efficient computation of the Fourier transform on finite groups
Authors: Diaconis Persi , Rockmore Daniel
Published: June 2010

Let

G
G

be a finite group,

f
:
G
→

C

f:G \to {\mathbf {C}}

a function, and

ρ
\rho

an irreducible representation of

G
G

. The Fourier transform is defined as

f
^

(
ρ
)
=

Σ

s
∈
G

f
(
s
)
ρ
(
s
)

\hat f(\rho ) = {\Sigma _{s \in G}}f(s)\rho (s)

. Direct computation for all irreducible representations involves order

|
G
|

2

{\left | G \right |^2}

operations. We derive fast algorithms and develop them for the symmetric group

S
n

{S_n}

. There,

(
n
!

)
2

{(n!)^2}

is reduced to

n

(
n
!

)

a

/

2

n{(n!)^{a/2}}

, where

a
a

is the constant for matrix multiplication (2.38 as of this writing). Variations of the algorithm allow efficient computation for “small” representations. A practical version of the algorithm is given on

S
n

{S_n}

. Numerical evidence is presented to show a speedup by a factor of 100 for

n
=
9

n = 9

.
The Π¹₂-singleton conjecture
Authors: Friedman Sy D.
Published: June 2010

The real

0
#

=

Thy

⟨

L
,
ε
,

ℵ
1

,

ℵ
2

,
…

⟩

{0^\# } = {\operatorname {Thy}}\left \langle {L,\varepsilon ,{\aleph _1},{\aleph _2}, \ldots } \right \rangle

is a natural example of a nonconstructible definable real. Moreover

0
#

{0^\# }

has a definition that is absolute: for some formula

ϕ
(
x
)
,

0
#

\phi (x),{0^\# }

is the unique real

R
R

such that

L
[
R
]
⊨
ϕ
(
R
)

L[R] \vDash \phi (R)

. Solovay conjectured that there is a real

R
R

such that

0

>
L

R

>
L

0
#

0{ > _L}R{ > _L}{0^\# }

and

R
R

also has such an absolute definition. We prove his conjecture by constructing a

Π
2
1

\Pi _2^1

-singleton

R
R

,

0

>
L

R

>
L

0
#

0{ > _L}R{ > _L}{0^\# }

. A variant of our construction produces a countable nonempty

Π
2
1

\Pi _2^1

set of reals not containing a

Π
2
1

\Pi _2^1

-singleton. The latter result answers a question of Kechris.
The even cycle problem for directed graphs
Authors: Thomassen Carsten
Published: June 2010

If each arc in a strongly connected directed graph of minimum indegree and outdegree at least 3 is assigned a weight 0 or 1, then the resulting weighted directed graph has a directed cycle of even total weight. This proves a conjecture made by L. Lovász in 1975 and has applications to colour-critical hypergraphs, sign-nonsingular matrices, and permanents of matrices.
Twistors, Kähler manifolds, and bimeromorphic geometry. I
Authors: LeBrun Claude
Published: June 2010

By considering deformations of the Moishezon twistor spaces of

C

P

2

#
⋅
⋅
⋅
#

C

P

2

\mathbb {C}{\mathbb {P}_2}\# \cdot \cdot \cdot \# \mathbb {C}{\mathbb {P}_2}

constructed in [20], we show that the blow up of

C

2

{\mathbb {C}^2}

at

n
n

points in general position admits an asymptotically flat scalar-flat Kähler metric in each Kähler class, at least provided that the given points are nearly collinear.
A rigorous time bound for factoring integers
Authors: Lenstra H. W. , Pomerance Carl
Published: June 2010

In this paper a probabilistic algorithm is exhibited that factors any positive integernninto prime factors in expected time at mostLn[12,1+o(1)]{L_n}[\tfrac {1}{2},1 + o(1)]forn→∞n \to \infty, where<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="upper L Subscript x Baseline left-bracket a comma b right-bracket equals exp left-parenthesis b left-parenthesis log x right-parenthesis Superscript a Baseline left-parenthesis log log x right-parenthesis Superscript 1 minus a Baseline right-parenthesis">Lx[a,b]=exp(b(log⁡x)a(loglog⁡x)1−a){L_x}[a,b] = {\text {exp}}(b{(\log x)^a}{({\text {log}}\log x)^{1 - a}}). Many practical factoring algorithms, including the quadratic sieve and the elliptic curve method, are conjectured to have an expected running time that satisfies the same bound, but this is the first algorithm for which the bound can be rigorously proved. Nevertheless, this does not close the gap between rigorously established time bounds and merely conjectural ones for factoring algorithms. This is due to the advent of a new factoring algorithm, the number field sieve, which is conjectured to factor any positive integernnin timeLn[13,O(1)]{L_n}[\tfrac {1}{3},O(1)]. The algorithm analyzed in this paper is a variant of the class group relations method, which makes use of class groups of binary quadratic forms of negative discriminant. This algorithm was first suggested by Seysen, and later improved by A. K. Lenstra, who showed that the algorithm runs in expected time at mostLn[12,1+o(1)]{L_n}[\tfrac {1}{2},1 + o(1)]if one assumes the generalized Riemann hypothesis. The main device for removing the use of the generalized Riemann hypothesis from the proof is the use of multipliers. In addition a character sum estimate for algebraic number fields is used, with an explicit dependence on possible exceptional zeros of the correspondingLL-functions. Another factoring algorithm using class groups that has been proposed is the random class groups method. It is shown that there is a fairly large set of numbers that this algorithm cannot be expected to factor as efficiently as had previously been thought.
EHBP-1 Functions with RAB-10 during Endocytic Recycling inCaenorhabditis elegans
Authors: Shi Anbing , Chen Carlos Chih-Hsiung , Banerjee Riju , Glodowski Doreen , Audhya Anjon , Rongo Christopher , Grant Barth D.
Published: June 2010

Caenorhabditis elegans RAB-10 functions in endocytic recycling in polarized cells, regulating basolateral cargo transport in the intestinal epithelia and postsynaptic cargo transport in interneurons. A similar role was found for mammalian Rab10 in MDCK cells, suggesting that a conserved mechanism regulates these related pathways in metazoans. In a yeast two-hybrid screen for binding partners of RAB-10 we identified EHBP-1, a calponin homology domain (CH) protein, whose mammalian homolog Ehbp1 was previously shown to function during endocytic transport of GLUT4 in adipocytes. In vivo we find that EHBP-1-GFP colocalizes with RFP-RAB-10 on endosomal structures of the intestine and interneurons and that ehbp-1 loss-of-function mutants share with rab-10 mutants specific endosome morphology and cargo localization defects. We also show that loss of EHBP-1 disrupts transport of membrane proteins to the plasma membrane of the nonpolarized germline cells, a defect that can be phenocopied by codepletion of RAB-10 and its closest paralog RAB-8. These results indicate that RAB-10 and EHBP-1 function together in many cell types and suggests that there are differences in the level of redundancy among Rab family members in polarized versus nonpolarized cells.
Sequential Counteracting Kinases Restrict an Asymmetric Gene Expression Program to early G1
Authors: Mazanka Emily , Weiss Eric L.
Published: June 2010

Gene expression is restricted to specific times in cell division and differentiation through close control of both activation and inactivation of transcription. In budding yeast, strict spatiotemporal regulation of the transcription factor Ace2 ensures that it acts only once in a cell's lifetime: at the M-to-G1 transition in newborn daughter cells. The Ndr/LATS family kinase Cbk1, functioning in a system similar to metazoan hippo signaling pathways, activates Ace2 and drives its accumulation in daughter cell nuclei, but the mechanism of this transcription factor's inactivation is unknown. We found that Ace2's nuclear localization is maintained by continuous Cbk1 activity and that inhibition of the kinase leads to immediate loss of phosphorylation and export to the cytoplasm. Once exported, Ace2 cannot re-enter nuclei for the remainder of the cell cycle. Two separate mechanisms enforce Ace2's cytoplasmic sequestration: 1) phosphorylation of CDK consensus sites in Ace2 by the G1 CDKs Pho85 and Cdc28/CDK1 and 2) an unknown mechanism mediated by Pho85 that is independent of its kinase activity. Direct phosphorylation of CDK consensus sites is not necessary for Ace2's cytoplasmic retention, indicating that these mechanisms function redundantly. Overall, these findings show how sequential opposing kinases limit a daughter cell specific transcriptional program to a brief period during the cell cycle and suggest that CDKs may function as cytoplasmic sequestration factors.