bluuebunny/crossref_metadata_2025 huggingface dataset:
Multiple mantle plume components involved in the petrogenesis of subduction‐related lavas from the northern termination of the Tonga Arc and northern Lau Basin: Evidence from the geochemistry of arc and backarc submarine volcanics
Authors: Falloon Trevor J. , Danyushevsky Leonid V. , Crawford Tony J. , Maas Roland , Woodhead Jon D. , Eggins Stephen M. , Bloomer Sherman H. , Wright Dawn J. , Zlobin Sergei K. , Stacey Andrew R.
Published: September 2007

We report new geochemical data for boninites and backarc basin‐type basalts recovered from the northern termination of the Tonga trench and Lau Basin. Boninitic pillow lavas, ranging from high‐Mg compositions to andesites and dacites, have been erupted within large submarine volcanic edifices (calderas and volcanoes) associated with active rifting of both the northern end of the Tofua volcanic arc and in a backarc position relative to the arc volcanoes on the northern Tonga Ridge. The mantle sources in the area are a complex mixture of (1) the “normal” Tongan mantle wedge source that has “Pacific”‐type isotopic signature with (2) the plume‐related components (EMI, EMII, and HIMU) and (3) an “Indian”‐type source upwelling beneath the backarc spreading. Some of these sources, such as the “normal” mantle wedge and variably depleted residual plume mantle, are fluxed by subduction components from the slab, which produces boninites, tholeiites, and mixtures thereof. Other mantle sources, such as “Indian”‐type backarc mantle and also some of the plume mantle, produce melts due to adiabatic decompression. These melts are variably mixed with each other and with the slab‐fluid fluxed subduction‐related melts to form the observed spectrum of magma compositions.
An expression for the overall oxygen isotope fractionation between the sum of dissolved inorganic carbon and water
Authors: Zeebe R. E.
Published: September 2007

Stable oxygen isotope fractionation factors (α's) between individual dissolved carbonate species (CO2(aq.), H2CO3, HCO3−, CO32−) and water, and their sum ( = [CO2(aq.)] + [H2CO3] + [HCO3−] + [CO32−]) and water are fundamental geochemical parameters. While values of , α, and have recently been examined, an overall mass balance for stable oxygen isotopes in the carbonate system still needs to be derived. The theoretical treatment of this mass balance is not trivial (in contrast to, e.g., stable carbon isotopes) because (1) oxygen is exchanged with H2O and (2) complications arise from the nature of the oxygen mole fractions. I use the recently reported individual α's to derive an expression for the overall oxygen isotope fractionation between and water. This allows the calculation of α(−H2O) at any given pH of the solution. The result differs from a relationship published earlier, and implications for previous studies are discussed. Numerical routines in MATLAB and Excel for the present calculation have been developed and are available as auxiliary material (Software S1). Applications of the expression include, for example, examination of biomineralization mechanisms and corrections to isotopic paleotemperature equations. The latter application can significantly alter reconstructions of Phanerozoic climate change.
Diagnosing a partly standing internal wave in Mamala Bay, Oahu
Authors: Martini K. I. , Alford M. H. , Nash J. D. , Kunze E. , Merrifield M. A.
Published: September 2007

An internal partly standing wave in Mamala Bay, Hawaii is studied using new observations and the Princeton Ocean Model (POM). Previous work suggested a convergence in the bay of east‐ and westbound waves emanating from Kaena Ridge and Makapuu Point, respectively. New energy flux measurements with shipboard ADCP/CTD confirm that Makapuu Point is the eastern source. After validating the POM results against observations, the model output is modally decomposed and compared with the expected theoretical patterns of kinetic and available potential energy, energy flux, and group velocity for a partly standing wave. Agreement is seen for the first baroclinic mode, which also contains most of the energy. The results confirm previous suggestions of standing wave dynamics in Mamala Bay.
Utilization of the AMSU high frequency measurements for improved coastal rain retrievals
Authors: Kongoli Cezar , Ferraro Ralph R. , Pellegrino Paul , Meng Huan , Dean Charles
Published: September 2007

This study describes a new rain estimation technique using Advanced Microwave Sounding Unit (AMSU) high frequency measurements and applicable over coastal regions. The existing operational AMSU rain retrieval algorithm utilizes the microwave window frequency measurements at 23, 31, 89 and 150 GHz. These measurements have limited applicability over coast due to ocean surface emissivity effects. This situation often leads to missing rain extent and thus rate retrievals over coastal regions. The new technique utilizes the higher window (89 and 150 GHz), opaque oxygen (53.6 GHz) and water vapor absorption (183 ± 1, ±3 and ±7 GHz) channels that are less impacted by surface emissivity variations. Rain extent is determined using a number of scattering measures computed from linear combinations of the brightness temperature at the selected high frequency channels. Next, the ice water path parameter is estimated from a quadratic relationship with the brightness temperature at the 183 ± 7 GHz water vapor absorption channel and the cosine of the local zenith angle. Rain rate is computed from ice water path. Evaluation and monitoring of the new technique integrated with the existing algorithm has indicated that the upgraded algorithm is robust and superior to the existing one over coast.
Deliquescence and hygroscopic growth of succinic acid particles measured with LACIS
Authors: Wex H. , Ziese M. , Kiselev A. , Henning S. , Stratmann F.
Published: September 2007

Succinic acid, a dicarboxylic acid which is only slightly soluble in water, was examined with regard to its deliquescence process and its hygroscopic growth in comparison with simple Köhler theory. Investigations were done at LACIS (Leipzig Aerosol Cloud Interaction Simulator), which can measure hygroscopic growth of aerosol particles at relative humidities up to values close to 100%. The deliquescence relative humidity of dry succinic acid particles with diameters of 200 nm was found at 99% (±0.2%). Deliquescence took place on a time scale faster than 0.3 seconds, for some measurements even faster than 0.15 seconds. Comparison of the measured equilibrium sizes of the succinic acid particles with modeled hygroscopic growth revealed evaporation of succinic acid from the deliquesced particles, an effect, which has been described in literature previously.
Influence of coast line on upper ocean's response to the tropical cyclone
Authors: Mahapatra D. K. , Rao A. D. , Babu S. V. , Srinivas Chamarthi
Published: September 2007

A 3‐dimensional Princeton Ocean Model has been configured for the east coast of India, which is applied to study the transformation of the upper ocean's response in the near‐coastal waters to the 1999 Orissa super cyclone in the Bay of Bengal at the time of landfall. It is well known that the sea surface temperature (SST) cooling is more towards the right of the storm track, because of the dominant wind stress forcing there. Consequently, the model simulated SSTs showed more cooling to the right of the storm track. However, it is found to be true only in the open ocean. The coastal dynamics transformed the scenario as the cyclone translated over the coastal waters owing to the impedance of the coast‐line to the circulation and shifted the region of maximum surface cooling to the left of the cyclone track. The satellite imageries during the period also endorsed the model simulations.
Global view of refilling of the plasmasphere
Authors: Sandel Bill R. , Denton Michael H.
Published: September 2007

We use observations by the IMAGE Extreme Ultraviolet Imager (EUV) to characterize the outflow of He+ from the ionosphere to the plasmasphere under quiet conditions. The view afforded by the IMAGE orbit encompasses the entire plasmasphere in a single exposure, enabling us to examine for the first time the globally‐averaged properties of plasmasphere refilling. We focus on a study period that begins with a moderate erosion event, and follow refilling during multiple orbits for a period of 69 hours. The inferred volume refilling rate, averaged over azimuth and time, ranges from ∼1 He+ cm−3 h−1 at L = 3.3 to ∼7 × 10−2 He+ cm−3 h−1 at L = 6.3 and is generally consistent with earlier, more local measurements. We show that the measured radial abundance profiles match those predicted by the Sheffield University Plasmasphere Ionosphere Model (SUPIM) for 2 ≤ L ≤ 4.
In situ observation and determination of liquid immiscibility in the Fe‐O‐S melt at 3 GPa using a synchrotron X‐ray radiographic technique
Authors: Tsuno Kyusei , Terasaki Hidenori , Ohtani Eiji , Suzuki Akio , Asahara Yuki , Nishida Keisuke , Sakamaki Tatsuya , Funakoshi Ken‐ichi , Kikegawa Takumi
Published: September 2007

We have performed in situ experiments on liquid immiscibility in Fe‐O‐S melts at 3 GPa and up to 2203 K using a synchrotron X‐ray radiographic technique. The difference between immiscible melts and a miscible melt can be clearly observed in radiographs. The immiscibility gap of the Fe‐O‐S melt shrinks with increasing temperature at 3 GPa. Two separated phases appeared from a miscible melt during quenching. Without in situ observations, the two phases observed in quench textures would be interpreted as either quench products from primary immiscible melts at high temperature, or those exsolved from a homogeneous melt to immiscible melts passing through the stability field of immiscible melts during quenching. In situ measurements are required in order to determine the immiscibility gap of the liquid Fe with light element(s). Our results have important implications for the formation and chemical composition of the cores of Earth and Mars.
A new index for the interplanetary merging electric field and geomagnetic activity: Application of the unified polar cap indices
Authors: Stauning Peter
Published: September 2007

The polar cap indices, PCN for the northern polar cap and PCS for the southern polar cap, are derived from analysis of magnetic variations in the polar caps. The indices mainly relate to the transpolar ionospheric electric currents generated by the interaction of the solar wind with the magnetosphere. The present paper discusses the relations between the PCN and PCS indices and the interplanetary merging electric field (MEF) with particular emphasis on the correlation of a combined PC index, PCC, with the MEF. The MEF parameter closely correlates with global disturbances such as magnetic storms that are caused by the impact on the magnetosphere of the enhanced solar wind following eruptive solar activity. The new PCC index resolves the ambiguity implied in having two index series to be proxy for the same merging electric field and to represent global magnetic activity. The paper examines the relations between the new polar cap index and the global magnetic activity level represented by the Dst index. It is shown that the Dst index correlates better with the PCC index than with the PCN and PCS indices or the auroral electrojet indices AU, AL, and AE.
IUPAC-NIST Solubility Data Series. 83. Acetonitrile: Ternary and Quaternary Systems
Authors: Skrzecz Adam , Lisov Nikolai I. , Sazonov Nikolai V.
Published: September 2007

The mutual solubility and liquid-liquid equilibria of acetonitrile ternary and quaternary systems with liquid solvents are reviewed. The solvents include water, inorganic compounds, and a variety of organic compounds such as hydrocarbons, halogenated hydrocarbons, alcohols, acids, esters, and nitrogen compounds. A total of 191 ternary and 35 quaternary systems whose properties were described in the chemical literature through 2000 are compiled. For 37 systems sufficient data were available to allow critical evaluation. All data are expressed as mass % and mole fractions as well as the originally reported units. Similar reviews of gas, liquid, and solid solubilities for other systems were published earlier in the International Union of Pure and Applied Chemistry Solubility Data Series. This is Volume 83 of this series.
Path-integral simulations beyond the adiabatic approximation
Authors: Schmidt J. R. , Tully John C.
Published: September 2007

Within the adiabatic approximation, it is trivial to generalize existing imaginary time path-integral techniques to the case of multiple electronic surfaces. However, there are many times where nonadiabatic effects can play an important role. To this end, we reformulate the well-known path-integral expressions to incorporate multiple potential surfaces, without necessitating the adiabatic approximation. We show that the resulting expression, like its adiabatic counterpart, can be interpreted in terms of a simple classical isomorphic system and thus is amenable to simulation through Monte Carlo techniques. We derive simple expressions to compute expectation values of a general operator in both the nuclear coordinate and electronic state, and demonstrate the existence of a simple internal diagnostic that can be used to evaluate the magnitude of equilibrium nonadiabatic effects.
Solution of the adjoint problem for instabilities with a deformable surface: Rosensweig and Marangoni instability
Authors: Bohlius Stefan , Pleiner Harald , Brand Helmut R.
Published: September 2007

We present a method to find the adjoint system of equations and the corresponding boundary conditions for free deformable surfaces. Motivated by the nonlinear discussion of the Rosensweig instability in ferrogels using the energy method, we treat the surface as dynamic and take the stationary limit only in the very end. We analyze the adjoint system of dynamic equations together with its corresponding boundary conditions and present as a solution the adjoint eigenvectors for the Rosensweig instability. The method is also applied to pure surface tension driven convection (Marangoni convection).
Nonequilibrium gyrokinetic fluctuation theory and sampling noise in gyrokinetic particle-in-cell simulations
Authors: Krommes John A.
Published: September 2007

The present state of the theory of fluctuations in gyrokinetic (GK) plasmas and especially its application to sampling noise in GK particle-in-cell (PIC) simulations is reviewed. Topics addressed include the Δf method, the fluctuation-dissipation theorem for both classical and GK many-body plasmas, the Klimontovich formalism, sampling noise in PIC simulations, statistical closure for partial differential equations, the theoretical foundations of spectral balance in the presence of arbitrary noise sources, and the derivation of Kadomtsev-type equations from the general formalism.
Comment on “Power loss in open cavity diodes and a modified Child-Langmuir law” [Phys. Plasmas 12, 093102 (2005)]
Authors: Swanekamp S. B. , Ottinger P. F.
Published: September 2007

In this Comment, it is shown that no modification of the Child-Langmuir law [Phys. Rev.32, 492 (1911); Phys. Rev. 2, 450 (1913)] is necessary to treat the space-charge-limited flow from a diode with an open boundary as reported in Phys. Plasmas 12, 093102 (2005). The open boundary condition in their simulations can be represented by a voltage source and a resistor whose value is the vacuum-wave impedance of the opening. The diode can be represented as a variable resistor whose value depends on the voltage drop across the diode (as measured by the line integral of E across the diode gap). This is a simple voltage-divider circuit whose analysis shows that the real diode voltage drops as the vacuum-wave impedance increases. Furthermore, it is shown that in equilibrium, the voltage drop between the anode and cathode is independent of the path chosen for the line integral of the electric field so that E=−∇Φ is valid. In this case, the equations of electrostatics are applicable. This clearly demonstrates that the electric field is electrostatic and static fields DO NOT RADIATE. It is shown that the diode voltage drops as the vacuum wave impedance increases and the current drops according to the Child-Langmuir law. Therefore, the observed drop in circuit current can be explained by a real drop in voltage across the diode and not an effective drop as claimed by the authors.
Ab initio finite field (hyper)polarizability computations on stoichiometric gallium arsenide clusters GanAsn (n=2–9)
Authors: Karamanis Panaghiotis , Bégué Didier , Pouchan Claude
Published: September 2007

We report reliable ab initio finite field (hyper)polarizability values at Hartree-Fock and second order Møller-Plesset perturbation theory (MP2) levels of theory for different geometrical configurations of small gallium arsenide clusters GanAsn with n=2–5. We relied on all-electron basis sets and pseudopotentials suitable for (hyper)polarizability calculations. In each case, we used structures that have been established in the literature after we optimized their geometries at B3LYP/cc-pVTZ-PP level of theory. Our results suggest that the first order hyperpolarizability (β) is much more sensitive to the special geometric features than the second order hyperpolarizability (γ). For the most stable configurations up to ten atoms the second order hyperpolarizability at MP2 level of theory varies between 15×104 and 32×104e4a04Eh−3. In addition, we examined the polarizability per atom evolution versus the cluster size for GanAsn with n=2–9. Our work extends earlier theoretical studies which were limited to eight atoms and exposes that the polarizability/atom of the most stable stoichiometric configurations up to Ga9As9 continues the monotonic downward trend with increasing size. Lastly, from the methodological point of view, our analysis shows that apart from polarizabilities, augmented pseudopotentials yield reliable first and second hyperpolarizability values as well.
Structural transition of PETN-I to ferroelastic orthorhombic phase PETN-III at elevated pressures
Authors: Tschauner O. , Kiefer B. , Lee Y. , Pravica M. , Nicol M. , Kim E.
Published: September 2007

Using powder x-ray diffraction and first-principles calculations, we provide evidence for a structural transition of PETN-I below 6GPa to an orthorhombic phase of space group P21212. The transition can be rationalized as shear-stress induced and ferroelastic, which involves a slight static displacement of the molecules that breaks the fourfold symmetry of PETN-I. Previously reported changes in the optical spectra reflect a lifting of the twofold degeneracy of modes in tetragonal PETN-I. The observed transition is expected to induce soft shear compliances along specific directions in PETN crystallites that may relate to the observed dependence of detonation pressure on crystal orientation.
Microwave Spectra of Molecules of Astrophysical Interest. XXV. Methylamine
Authors: Ilyushin V. , Lovas F. J.
Published: September 2007

The microwave spectrum of methylamine in its ground vibrational state is critically reviewed and supplemented with spectral frequency calculations derived from rotation-internal rotation-inversion analysis. The review covers the frequency range from 1to500GHz and includes the transitions with rotational quantum number J from 0 to 30. The calculated frequency with uncertainty at the 95% confidence limit along with the lower state energy and line strength are presented. For J⩽10 transitions and some J>10 transitions exhibiting large hyperfine splittings, the quadrupole hyperfine structure is also tabulated.
Oxidation of silicon: Further tests for the interfacial silicon emission model
Authors: Farjas J. , Roura P.
Published: September 2007

The classical description of Si oxidation given by Deal and Grove has well-known limitations for thin oxides (below 200 Å). Among the large number of alternative models published so far, the interfacial emission model has shown the greatest ability to fit the experimental oxidation curves. It relies on the assumption that during oxidation Si interstitials are emitted to the oxide to release strain and that the accumulation of these interstitials near the interface reduces the reaction rate there. The resulting set of differential equations makes it possible to model diverse oxidation experiments. In this paper, we have compared its predictions with two sets of experiments: (1) the pressure dependence for subatmospheric oxygen pressure and (2) the enhancement of the oxidation rate after annealing in inert atmosphere. The result is not satisfactory and raises serious doubts about the model’s correctness.
Type IIA photosensitivity and formation of pores in optical fibers under intense ultraviolet irradiation
Authors: Kukushkin S. A. , Shlyagin M. G. , Swart P. L. , Chtcherbakov A. A. , Osipov A. V.
Published: September 2007

Formation of the type IIA Bragg gratings in germanosilicate optical fibers is studied. We report the observation of such a type of gratings in the standard single-mode fiber (Corning SMF-28) under different experimental conditions. A mechanism for the type IIA photosensitivity in optical fibers is proposed which is based on nucleation and evolution of pores from vacancy-type defects in fiber areas where a high level of mechanical stress is induced under intense ultraviolet (UV) light. Evolution of fiber core temperature under influence of a single 20 ns light pulse from a KrF excimer laser was measured and compared with theoretical calculations. It was shown that transient thermoinduced stress in the fiber core can achieve a level sufficient for effective nucleation of pores. A theory describing formation of pores in optical fibers has been developed and was used to estimate the pore nucleation rate, concentration, and other parameters of pore evolution for different levels of UV fluence and fiber core stress.
High electrical resistance hot-pressed NdFeB magnet for low loss motors
Authors: Komuro Matahiro , Satsu Yuichi , Enomoto Yuji , Koharagi Haruo
Published: September 2007

Fluoride-coated hot-pressed NdFeB magnets with electrical resistivity of 1.4mΩcm, which is ten times larger than that of a noncoated sintered NdFeB magnet, were prepared using fluoride coating powders. The high resistive NdFeB magnets consist of coated powders and are sintered with a neodymium fluoride layer, which was grown using a fluoride solution. No degradation of coercivity was observed in the fluoride coated NdFeB powders. The increase in magnet temperature caused by an alternating magnetic field (Eddy currents) was eightfold with the use of a fluoride-treated magnet. Furthermore, the increase in temperature at the magnet’s rotor was reduced by 50% when the high resistive hot-pressed magnet was substituted for the conventional commercial magnet.
A transformation of carbon dioxide to nonmolecular solid at room temperature and high pressure
Authors: Kume Tetsuji , Ohya Yasuhisa , Nagata Masayuki , Sasaki Shigeo , Shimizu Hiroyasu
Published: September 2007

Raman and infrared absorption spectra of solid carbon dioxide (CO2) have been measured at high pressures up to 80GPa and room temperature. The broadening and weakening of lattice vibrational signals and the disappearance of molecular vibration were detected at 65GPa by means of the Raman and infrared absorption experiments, respectively. The present Raman spectral feature is exactly the same as that of amorphous CO2 synthesized around 600K and 60GPa [M. Santoro et al., Nature (London) 441, 857 (2006)]. It is demonstrated that the polymerization of CO2 proceeds even at room temperature and almost independently of temperature.
Properties of magnetic nanoparticles in the Brownian relaxation range for liquid phase immunoassays
Authors: Enpuku K. , Tanaka T. , Matsuda T. , Dang F. , Enomoto N. , Hojo J. , Yoshinaga K. , Ludwig F. , Ghaffari F. , Heim E. , Schilling M.
Published: September 2007

Properties of magnetic nanoparticles in the Brownian relaxation region were studied. Using the magnetic nanoparticles that exhibit remanence, we measured the magnetic properties, such as static magnetization, magnetic relaxation, and alternating current susceptibility, in a solution. Comprehensive comparisons were made between the experimental results and the theoretical ones predicted from the Brownian relaxation. From the comparison, the distributions of the particle parameters, i.e., the magnetic moment and the relaxation time, were estimated. It was shown that all the magnetic properties can be well explained when we take into account the parameter distributions in the sample.
Phase structure, microstructure, and electrical properties of bismuth modified potassium-sodium niobium lead-free ceramics
Authors: Du Hongliang , Luo Fa , Qu Shaobo , Pei Zhibin , Zhu Dongmei , Zhou Wancheng
Published: September 2007

( K 0.5 Na 0.5 ) 1 − 3 x Bi x NbO 3 (KNBN) ceramics were prepared by conventional solid-state sintering without cold-isostatic pressing. The phase structure, microstructure, and electrical properties of KNBN ceramics are studied. The phase structure of KNBN ceramics (x=0.01) is pure perovskite phase with orthorhombic symmetry at room temperature. The addition of Bi3+ significantly improves electrical properties of (K0.5Na0.5)NbO3 ceramics while keeping the tetragonal-orthorhombic phase transition temperature above 170 °C. The KNBN (x=0.01) ceramics show the optimum electrical properties (d33=164 pC∕N, kp=0.47, Qm=120, TC=403 °C, TO-T=174 °C, Pr=30.1 μC∕cm2, and Ec=6.18 kV∕cm). Take into account electrical properties and the polymorphic phase transition temperature (TO-T), it can be concluded that the KNBN (x=0.01) ceramic is a promising lead-free piezoelectric candidate material for practical application. The related mechanisms for high piezoelectric properties in KNBN (x=0.01) ceramics are also discussed.
Size dependence of Si 2p core-level shift at Si nanocrystal/SiO2 interfaces
Authors: Kim Sung , Kim Min Choul , Choi Suk-Ho , Kim Kyung Joong , Hwang Han Na , Hwang Chan Cook
Published: September 2007

Synchrotron-radiation x-ray photoelectron spectroscopy (XPS) has been used to analyze size-dependent Si 2p core-level spectra of Si nanocrystals (NCs) embedded in SiO2. The Si0 and suboxide XPS peaks of Si NCs shift to higher binding energies with decreasing NC size, which is based on the resolved spectra fitted by using Gaussian-Lorentzian lines for the Si oxidation states. It is also found that the shell region around Si NC bordered by SiO2 consists of the three Si suboxide states, Si1+, Si2+, and Si3+, whose densities are also strongly dependent on NC size. These results suggest that the analysis of the Si 2p core-level shift by XPS is useful for characterizing the size effect of Si NC at the Si NC∕SiO2 interfaces.
Novel approach to Abel inversion
Authors: Paul R. K.
Published: September 2007

Simple yet versatile, physically valid emissivity functions for peaked and hollow profiles with only two determinable parameters are proposed for performing Abel inversion. The advantages of the proposed functions have been explored. The inversion is very fast, accurate, convenient, and viable, in contrast to the existing methods. The validation of these functions has been confirmed by using simulated data under various conditions. The error in the process has been computed and found to depend on the functional form of the model emissivity. A comprehensive comparison has been drawn with the existing method and it has been found to offer a definite advantage over the existing technique in some respects, especially for real time applications. Limitation of this technique has also been discussed. The soft x-ray and visible light emissivity profile of SINP tokamak has been successfully obtained by using this method.
Apparatus for measuring the finite load-deformation behavior of a sheet of epithelial cells cultured on a mesoscopic freestanding elastomer membrane
Authors: Selby John C. , Shannon Mark A.
Published: September 2007

Details are given for the design, calibration, and operation of an apparatus for measuring the finite load-deformation behavior of a sheet of living epithelial cells cultured on a mesoscopic freestanding elastomer membrane, 10μm thick and 5mm in diameter. Although similar in concept to bulge tests used to investigate the mechanical properties of micromachined thin films, cell-elastomer composite diaphragm inflation tests pose a unique set of experimental challenges. Composite diaphragm (CD) specimens are extremely compliant (E<50kPa), experience large displacements when subject to small inflation pressures (∼100Pa), and must be continuously immersed in a bath of liquid culture medium during the acquisition of load-deformation measurements. Given these considerations, we have constructed an inflation apparatus consisting of an air-piston-cylinder pump integrated with a modular specimen mounting fixture that constitutes a horizontally semi-infinite reservoir of liquid culture medium. In a deformation-controlled inflation test, pressurized air is used to inflate a CD specimen into the liquid reservoir with minimum disturbance of the liquid-air interface. Piston displacements and absolute pump chamber air pressures are utilized as feedback to cycle the displaced (or inflated) CD volume V in a 0.05Hz triangular or sinusoidal wave form (VMIN=0μl, VMAX⩽40μl) while simultaneously recording the inflation pressure acting at the fixed boundary of the specimen, p(r=a). Using a carefully prescribed six-cycle inflation test protocol, the apparatus is shown to be capable of measuring the [V,p(r=a)] inflation response of a cell-elastomer CD with random uncertainties estimated at ±0.45μl and ±2.5Pa, respectively.
Avalanche breakdown in surface modified silicon nanowires
Authors: Elfström Niklas , Linnros Jan
Published: September 2007

The electrical conductance of semiconductor nanowires can be changed by charges present on the nanowire surface. At high surface charge density, however, the nanowire channel may be quenched leading to a large shift in the IDS-VDS characteristics. In this letter, the authors demonstrate that this shift in VDS is related to an avalanche effect in the nanowire. Silicon nanowires were fabricated in a top-down approach and the nanowire surface charge density was modified through buffer solutions of different pH values. Computer simulations using representative surface charge and interface charge densities clearly reproduce the data and unambiguously demonstrate the avalanche effect.
Growth of vertically aligned Si wire arrays over large areas (>1cm2) with Au and Cu catalysts
Authors: Kayes Brendan M. , Filler Michael A. , Putnam Morgan C. , Kelzenberg Michael D. , Lewis Nathan S. , Atwater Harry A.
Published: September 2007

Arrays of vertically oriented Si wires with diameters of 1.5μm and lengths of up to 75μm were grown over areas >1cm2 by photolithographically patterning an oxide buffer layer, followed by vapor-liquid-solid growth with either Au or Cu as the growth catalyst. The pattern fidelity depended critically on the presence of the oxide layer, which prevented migration of the catalyst on the surface during annealing and in the early stages of wire growth. These arrays can be used as the absorber material in novel photovoltaic architectures and potentially in photonic crystals in which large areas are needed.
High resolution transmission electron microscopy of InN
Authors: Bartel T. P. , Kisielowski C. , Specht P. , Shubina T. V. , Jmerik V. N. , Ivanov S. V.
Published: September 2007

Hexagonal InN layers were grown by molecular beam epitaxy and studied by high resolution electron microscopy and by photoluminescence spectroscopy. Inclusions of a few nanometers in diameter were found, which are among the smallest reported. Image simulation, beam sensitivity, and photoluminescence of the samples corroborate that these inclusions are indeed metallic indium. This letter provides evidence that nanoscopic metallic indium inclusions can be present in InN crystals and have a strong influence on its optical properties.
Effect of illumination-induced space charge on photocarrier transport in hydrogenated microcrystalline Si1−xGex p-i-n solar cells
Authors: Matsui Takuya , Chang Chia-Wen , Kondo Michio , Ogata Keisuke , Isomura Masao
Published: September 2007

Photocarrier transport in hydrogenated microcrystalline Si1−xGex (μc-Si1−xGex:H) p-i-n solar cells (0<x<0.42) is studied using spectral response measurement under various bias light illuminations. The solar cell composed of μc-Si0.8Ge0.2:H i layer reveals an injection-level-independent carrier collection, demonstrating a 6.1% conversion efficiency with infrared sensitivities higher than double-thickness μc-Si:H solar cells due to an enhanced optical absorption. However, the illumination of the solar cells for x>0.35, particularly in the wavelength range of <650nm, induces a strong carrier recombination near the p-i interface and a weak collection enhancement in the bulk, indicative of field distortion by the negative space charge generated near the p-i interface. This finding is consistently explained by the increased acceptorlike states in undoped μc-Si1−xGex:H for large Ge contents.
Integration of In2O3 nanoparticle based ozone sensors with GaInN∕GaN light emitting diodes
Authors: Wang Ch. Y. , Cimalla V. , Kups Th. , Röhlig C.-C. , Stauden Th. , Ambacher O. , Kunzer M. , Passow T. , Schirmacher W. , Pletschen W. , Köhler K. , Wagner J.
Published: September 2007

There is a high demand for compact low-cost ozone sensors. It has been shown recently that In2O3 nanolayers can act as ozone sensitive films activated at room temperature by ultraviolet light. In the present work, the authors integrate ultrathin layers of In2O3 nanoparticles and a GaInN∕GaN based blue light emitting diode (LED) on a single sensor chip. The integrated sensor was found to be sensitive to O3 concentrations as low as ∼40ppb. These results demonstrate that by integrating GaInN∕GaN based blue LEDs and metal oxide sensing layers back to back on a single chip, compact and robust gas sensors can be realized.
Carbon nanotube nanocontact in T-junction structures
Authors: Chiu Po-Wen , Roth Siegmar
Published: September 2007

The authors report transport measurements on naturally formed carbon nanotube T junctions with a semiconducting bar and a metallic stem. The T junctions provide a unique structure that allows them to compare the quasi-zero-dimensional (Q0D) contact formed at the junction node with the quasi-one-dimensional (Q1D) contact formed between the semiconducting bar and the lithographically defined gold. From the bias-induced barrier lowering, it shows that the Q1D contact behaves like an end-bonded contact which has extended depletion tail along the tube axis, while the Q0D case acts as a side contact which has constrained depletion perpendicular to the tube axis.
Radiatively limited dephasing of quantum dot excitons in the telecommunications wavelength range
Authors: Ishi-Hayase J. , Akahane K. , Yamamoto N. , Sasaki M. , Kujiraoka M. , Ema K.
Published: September 2007

The extremely long dephasing time of excitons in strain-compensated quantum dots at telecommunications wavelengths was measured using a polarization-dependent four-wave mixing technique. The use of a 150-layer-stacked structure enabled them to measure a four-wave mixing signal with a high signal-to-noise ratio, in spite of the fact that a high-sensitive heterodyne detection was not used. The large anisotropy of the dephasing time indicates the dominance of the radiative recombination process on dephasing. By simultaneously measuring the radiative lifetime using a pump-probe technique, they could directly estimate pure dephasing with an accuracy of better than 0.1μeV.
Controller-area-network bus control and monitor system for a radio astronomy interferometer
Authors: Woody David P. , Wiitala Bradley , Scott Stephen L. , Lamb James W. , Lawrence Ronald P. , Giovanine Curt , Fredsti Sancar J. , Beard Andrew , Pryke Clem , Loh Michael , Greer Christopher H. , Cartwright John K. , Gutierrez-Kraybill Colby , Bolatto Alberto D. , Muchovej Stephen J. C.
Published: September 2007

We describe the design and implementation of a controller-area-network bus (CANbus) monitor and control system for a millimeter wave interferometer. The Combined Array for Research in Millimeter-wave Astronomy (CARMA) is a 15-antenna connected-element interferometer for astronomical imaging, created by the merger of two university observatories. Its new control system relies on a central computer supervising a variety of subsystem computers, many of which control distributed intelligent nodes over CANbus. Subsystems are located in the control building and in individual antennas and communicate with the central computer via Ethernet. Each of the CAN modules has a very specific function, such as reading an antenna encoder or tuning an oscillator. Hardware for the modules was based on a core design including a commercial CANbus-enabled single-board computer and some standard circuitry for interfacing to peripherals. Hardware elements were added or changed as necessary for the specific module types. Similarly, a base set of embedded code was implemented for essential common functions such as CAN message handling and time keeping and extended to implement the required functionality for the different hardware. Using a standard CAN messaging protocol designed to fit the requirements of CARMA and a well-defined interface to the high-level software allowed separate development of high-level code and embedded code with minimal integration problems. Over 30 module types have been implemented and successfully deployed in CARMA, which is now delivering excellent new science data.
Cryopreservation of epididymal alpaca (Vicugna pacos) sperm: a comparison of citrate-, Tris- and lactose-based diluents and pellets and straws
Authors: Morton Katherine M. , Bathgate Roslyn , Evans Gareth , Maxwell W. M. Chis
Published: September 2007

Epididymal spermatozoa were harvested from male alpacas and frozen after extension and cooling to 4°C in citrate-, Tris- and lactose-based diluents (Experiment 1) and as pellets in 0.25- and 0.5-mL straws on either dry ice or over liquid nitrogen vapour (Experiment 2) to determine the effects diluents and packaging on their motility and acrosome integrity. In Experiment 1, sperm motility was higher after cooling to 4°C and after freeze–thawing (0 but not 3 h post-thaw) for spermatozoa extended in the lactose- than the citrate- or Tris-based diluent (P < 0.05). Post-thaw acrosome integrity after cooling to 4°C and post-thaw (0 h) was reduced for spermatozoa frozen in citrate- compared with lactose- or Tris-based diluents, but was similar for all groups 3 h after thawing. In Experiment 2, sperm motility immediately after thawing was higher for pellet freezing than for 0.25- or 0.5-mL straws on dry ice or liquid nitrogen vapour (P < 0.05), although by 3 h post-thaw motility was similar for pellets and straws (P > 0.05). Acrosome integrity was similar for all groups immediately after thawing and 3 h post-thaw. Cryopreservation of epididymal alpaca spermatozoa is feasible, with retained motility and acrosome integrity post-thaw. Freezing as pellets in a lactose-based diluent is recommended.
Electrolyte distribution and yolk sac morphology in frozen hydrated equine conceptuses during the second week of pregnancy
Authors: Crews Laura J. , Waelchli Rudolf O. , Huang Cheng X. , Canny Martin J. , McCully Margaret E. , Betteridge Keith J.
Published: September 2007

To investigate how equine conceptuses expand rapidly despite the hypo-osmolality of their yolk sac fluid, 18 conceptuses, aged 8–12 days and 0.8–10.0 mm in diameter, were examined by cryoscanning electron microscopy and energy dispersive X-ray microanalysis to determine the distribution of Na, Cl and K in their fluids. No osmotic gradient was found between central and peripheral yolk sac fluid. In conceptuses ≥ 6 mm in diameter, the concentrations of both Na and K in the subtrophectodermal compartments were higher than those determined previously in uterine fluid, supporting the concept of osmotic intake of fluid from the uterine environment as far as the compartments. However, electrolyte concentrations in the compartments consistently exceeded those found in the yolk sac, making it likely that ‘uphill’ water transport, rather than a purely osmotic uptake, is involved in yolk sac fluid accumulation. We also speculate that capsule formation could actively contribute to conceptus expansion and thereby to fluid intake.
Evaluation of predator numerical responses
Authors: Hone Jim , Krebs Charles , O'Donoghue Mark , Boutin Stan
Published: September 2007

We evaluated hypotheses of the dynamics of predators (lynx) relative to prey (snowshoe hares) and predator abundance in the Yukon, Canada. The hypotheses were that predator (lynx) dynamics are influenced by prey density, or by both prey and predator densities. Annual lynx population growth rate (r), estimated from lynx counts, was positively related to previous hare density and negatively related to previous lynx density, as described by the best-fitting additive model (R2 = 0.85). Annual lynx growth rate (r) estimated from lynx tracks was positively related to the ratio of hares per lynx in the best-fitting model (R2 = 0.55). There was most support for the prey- and predator-dependent hypothesis of predator dynamics. Projected lynx tracks showed similar trends to observed abundance but lagged one year, emphasising the need for evaluation of projected predator trends.
Occurrence of small mammals in a fragmented landscape: the role of vegetation heterogeneity
Authors: Holland Greg J. , Bennett Andrew F.
Published: September 2007

Most studies of habitat use by small mammals rely on data from trapping grids. Such studies pertain to habitat use by individuals, which may not reflect population-level requirements. To meet the challenge of landscape change, it is important to understand habitat use by populations across large geographic areas. We surveyed small mammals in 48 forest remnants across a 300 km2 study area, to investigate the influence of vegetation heterogeneity on regional distributions. Information-theoretic techniques were used to evaluate models of vegetation associations. Richness of native mammals was influenced by vegetation condition: disturbed sites supported fewer species. Models for individual species showed the agile antechinus, Antechinus agilis, to prefer structurally diverse forest vegetation, the long-nosed potoroo, Potorous tridactylus, to favour mesic shrub communities, the bush rat, Rattus fuscipes, to prefer complex low cover regardless of composition, the swamp rat, Rattus lutreolus, to favour reduced canopy cover, and the house mouse, Mus domesticus, to prefer disturbed vegetation. To satisfy the needs of all native species, a mosaic of natural vegetation is required. Degradation and simplification of forest vegetation have detrimental consequences. These results highlight the need to consider habitat quality, together with more traditional biogeographic variables, when investigating factors influencing patch occupancy by native fauna in modified landscapes.
Mechanism of positioning the cell nucleus in vertebrate photoreceptors
Authors: Tsujikawa Motokazu , Omori Yoshihiro , Biyanwila Janisha , Malicki Jarema
Published: September 2007

Organelles are frequently distributed in a nonrandom manner in a cell's cytoplasm. A particular distribution pattern often facilitates a specific function of a cell, whereas its aberrations can lead to cell death. We show that a mutation in the zebrafish
mikre oko
(
mok
) locus, which encodes dynactin 1 subunit of the dynactin complex, produces a severe displacement of the photoreceptor cell nucleus toward the synaptic terminus. Interference with the function of other dynein complex constituents, including p50/dynamitin, the Lis1 polypeptide, and the disruption of a nuclear envelope component of the
syne
gene family in vertebrate photoreceptors also result in the mispositioning of nuclei. Although the overall photoreceptor polarity is not affected, this phenotype is accompanied by a misdistribution of the Bardet–Biedl syndrome 4 polypeptide and a decreased photoreceptor survival. These findings reveal an important mechanism that regulates nuclear position in vertebrate neurons.
Impact of anthropogenic atmospheric nitrogen and sulfur deposition on ocean acidification and the inorganic carbon system
Authors: Doney Scott C. , Mahowald Natalie , Lima Ivan , Feely Richard A. , Mackenzie Fred T. , Lamarque Jean-Francois , Rasch Phil J.
Published: September 2007

Fossil fuel combustion and agriculture result in atmospheric deposition of 0.8 Tmol/yr reactive sulfur and 2.7 Tmol/yr nitrogen to the coastal and open ocean near major source regions in North America, Europe, and South and East Asia. Atmospheric inputs of dissociation products of strong acids (HNO3and H2SO4) and bases (NH3) alter surface seawater alkalinity, pH, and inorganic carbon storage. We quantify the biogeochemical impacts by using atmosphere and ocean models. The direct acid/base flux to the ocean is predominately acidic (reducing total alkalinity) in the temperate Northern Hemisphere and alkaline in the tropics because of ammonia inputs. However, because most of the excess ammonia is nitrified to nitrate (NO3−) in the upper ocean, the effective net atmospheric input is acidic almost everywhere. The decrease in surface alkalinity drives a net air–sea efflux of CO2, reducing surface dissolved inorganic carbon (DIC); the alkalinity and DIC changes mostly offset each other, and the decline in surface pH is small. Additional impacts arise from nitrogen fertilization, leading to elevated primary production and biological DIC drawdown that reverses in some places the sign of the surface pH and air–sea CO2flux perturbations. On a global scale, the alterations in surface water chemistry from anthropogenic nitrogen and sulfur deposition are a few percent of the acidification and DIC increases due to the oceanic uptake of anthropogenic CO2. However, the impacts are more substantial in coastal waters, where the ecosystem responses to ocean acidification could have the most severe implications for mankind.
R-Spondin1 regulates Wnt signaling by inhibiting internalization of LRP6
Authors: Binnerts Minke E. , Kim Kyung-Ah , Bright Jessica M. , Patel Sejal M. , Tran Karolyn , Zhou Mei , Leung John M. , Liu Yi , Lomas Woodrow E. , Dixon Melissa , Hazell Sophie A. , Wagle Marie , Nie Wen-Sheng , Tomasevic Nenad , Williams Jason , Zhan Xiaoming , Levy Michael D. , Funk Walter D. , Abo Arie
Published: September 2007

The R-Spondin (RSpo) family of secreted proteins act as potent activators of the Wnt/β-catenin signaling pathway. We have previously shown that RSpo proteins can induce proliferative effects on the gastrointestinal epithelium in mice. Here we provide a mechanism whereby RSpo1 regulates cellular responsiveness to Wnt ligands by modulating the cell-surface levels of the coreceptor LRP6. We show that RSpo1 activity critically depends on the presence of canonical Wnt ligands and LRP6. Although RSpo1 does not directly activate LRP6, it interferes with DKK1/Kremen-mediated internalization of LRP6 through an interaction with Kremen, resulting in increased LRP6 levels on the cell surface. Our results support a model in which RSpo1 relieves the inhibition DKK1 imposes on the Wnt pathway.