bluuebunny/crossref_metadata_2025 huggingface dataset:
CAN UNSTABLE PREFERENCES PROVIDE A STABLE STANDARD OF WELL-BEING?
Authors: Bykvist Krister
Published: March 2010

How do we determine the well-being of a person when her preferences are not stable across worlds? Suppose, for instance, that you are considering getting married, and that you know that if you get married, you will prefer being unmarried, and that if you stay unmarried, you will prefer being married. The general problem is to find a stable standard of well-being when the standard is set by preferences that are not stable. In this paper, I shall show that the problem is even worse: inconsistency threatens if we accept both that your desires determine what is good for you and that you must prefer what is better for you. After I have introduced a useful toy model and stated the inconsistency argument, I will go on to discuss a couple of unsuccessful theories and see what we can learn from their mistakes. One important lesson is that how you would have felt about a life had you never led it is irrelevant to the question of how good that life is for you. What counts is how you feel about your life when you are actually leading it. Another lesson is that a life can be better for you even if you would not rank it higher, if you were to lead it.
OPPORTUNITY AS MUTUAL ADVANTAGE
Authors: Sugden Robert
Published: March 2010

This paper argues that measurements of opportunity which focus on the contents of a person's opportunity set fail to capture open-ended aspects of opportunity that liberals should value. I propose an alternative conception of ‘opportunity as mutual advantage’ which does not require the explicit specification of opportunity sets, and which rests on an understanding of persons as responsible rather than rational agents. I suggest that issues of distributive fairness are best framed in terms of real income, and that meaningful measurements of real income are possible if opportunity as mutual advantage is ensured.
SMOOTH VARYING-COEFFICIENT ESTIMATION AND INFERENCE FOR QUALITATIVE AND QUANTITATIVE DATA
Authors: Li Qi , Racine Jeffrey S.
Published: March 2010

We propose a semiparametric varying-coefficient estimator that admits both qualitative and quantitative covariates along with a test for correct specification of parametric varying-coefficient models. The proposed estimator is exceedingly flexible and has a wide range of potential applications including hierarchical (mixed) settings, small area estimation, etc. A data-driven cross-validatory bandwidth selection method is proposed that can handle both the qualitative and quantitative covariates and that can also handle the presence of potentially irrelevant covariates, each of which can result in finite-sample efficiency gains relative to the conventional frequency (sample-splitting) estimator that is often found in such settings. Theoretical underpinnings including rates of convergence and asymptotic normality are provided. Monte Carlo simulations are undertaken to assess the proposed estimator’s finite-sample performance relative to the conventional semiparametric frequency estimator and to assess the finite-sample performance of the proposed test for correct parametric specification.
Westward Expansion, Preappointment Politics, and the Making of the Southern Slaveholding Supreme Court
Authors: Crowe Justin
Published: March 2010

In this article, I trace the historical lineage and dynamic processes leading to the creation of the Southern slaveholding Supreme Court of antebellum America. Supported by case studies of several Jeffersonian and Jacksonian era legislative battles over judicial reform, I argue that the complex, multistage creation of the Southern slaveholding Court—the Court that decided cases such asPrigg v. Pennsylvania, Dred Scott v. Sandford, andAbleman v. Booth—was the inadvertent result of certain institutional strictures concerning the size of the Court and the geographic organization of the federal circuit system. In so doing, I illustrate how the creation of a fundamentally Jacksonian but also disproportionately Southern and undeniably slaveholding Court was not simply about who was appointed but about the structures that determined who might be appointed, who could be appointed, and who should be appointed. It was these considerations, in turn, that shaped not only the makeup and composition of the Court during this tumultuous period of American political development but also the very character of the momentous decisions it was likely to make.
Therapie männlicher Sexualstörungen
Authors: Casella Roberto
Published: March 2010

Die primäre symptomatische Behandlung einer erektilen Dysfunktion stützt sich auf orale Phosphodiasterase Typ-5 Hemmer (Sildenafil, Vardenafil, Tadalafil). Der Patient sollte in der Handhabung dieser Medikamente genau instruiert und über mögliche Nebenwirkungen aufgeklärt werden. Diese Heilmittel zeigen ein sicheres Wirkungsprofil und dürfen auch bei Patienten mit stabilen kardiovaskulären Erkrankungen benützt werden. Erst beim Versagen einer oralen Therapie sollten urethral oder intrakavernös applizierbares Alprostadil sowie Erektionshilfesysteme (Vakumpumpe) zur Anwendung kommen. Bei eindeutig funktioneller Ursache und/oder Beziehungsproblematik ist eine Sexual- und/oder Paartherapie zu diskutieren. Schwellkörperprothesen werden in der Schweiz sehr selten implantiert, die Gefäßchirurgie ist am Aussterben. Eine Testosteronsubstitution findet selten Platz in der Behandlung der erektilen Dysfunktion. Zur Behandlung des frühzeitigen Samenergusses (Ejaculatio praecox) kommen sexualtherapeutische Konzepte („stop-start“ oder „squeeze“ Technik), topische Lokalanästhetika vor dem Koitus sowie die tägliche Einnahme selektiver Hemmer der Serotonin-Wiederaufnahme (Paroxetin, Fluoxetin, Sertralin; „off label use“) zur Anwendung. Dapoxetin ist ein schnellwirkender selektiver Hemmer der Serotonin-Wiederaufnahme, der kurz vor dem Koitus einzunehmen ist. Dieses Medikament ist in mehreren europäischen Ländern zugelassen und sollte in wenigen Monaten auf dem Schweizer Markt erscheinen.
Lymphadenopathie und Diabetes insipidus – Assoziation?
Authors: Zahnd  , Oestmann  , Ebnöther
Published: March 2010

Wir berichten über eine 62-jährige Patientin mit einer bekannten chronischen idiopathischen Myelofibrose, die eine akute Lymphadenopathie entwickelte. Zeitnah mit der Lymphadenopathie traten ein Diabetes insipidus, Osteolysen sowie ein Hautexanthem auf. Die klinische und radiologische Verdachtsdiagnose einer Langerhans-Zell-Histiozytose konnte schliesslich mittels wiederholter Biopsie betroffener Organe gesichert werden. Es wurde eine Therapie gemäss Empfehlung der Histiozytose-Gesellschaft eingeleitet.
Comment on “Variations of tropical upper tropospheric clouds with sea surface temperature and implications for radiative effects” by H. Su et al.
Authors: Rondanelli Roberto , Lindzen Richard S.
Published: March 2010

Using TRMM VIRS data, we attempt to replicate the analysis made by Su et al. (2008) to quantify the effect of methodological choices on the magnitude of the observed correlations between upper‐level cloud cover and SST. Using brightness temperature thresholds to identify upper‐level cloud, we recover a relatively small change in the normalized area of cirrus clouds with SST (∼−6%/K compared to ∼−2%/K found by Su et al. (2008)). We discuss the effect of several methodological choices on the magnitude of the signal, namely, the classification of cloudy regions into convective updrafts and anvil, the use of cloud weighted SST, and the truncation and sampling error of the orbital satellite data with respect to the evolution of mesoscale convective systems. Accounting for some of these methodological differences could resolve the discrepancy between the weak signal documented by Su et al. (2008) and the stronger signal documented originally by Lindzen et al. (2001) and others, including the results reported in this comment.
A GCM‐based analysis of circulation controls on δ18O in the southwest Yukon, Canada: Implications for climate reconstructions in the region
Authors: Field Robert D. , Moore G. W. K. , Holdsworth Gerald , Schmidt Gavin A.
Published: March 2010

To improve our understanding of paleoclimatic records in the southwest Yukon, we examined controls on precipitation δ18O using an isotopically‐equipped atmospheric general circulation model (GCM). Our results show that, particularly during the cool‐season, elevated δ18O is associated with a deeper Aleutian Low and stronger southerly moisture flow, while lower δ18O is associated with the opposite meteorological conditions. These results suggest that the large mid‐19th century shift towards lower δ18O values seen in paleoclimate records from the region was associated with a shift towards a weaker Aleutian Low. While in disagreement with a previous interpretation of this shift, it is consistent with records of glacial advance and tree‐ring growth during the same period, and observational studies of Aleutian Low controls on temperature and precipitation in the region.
Diffusion of relativistic runaway electrons and implications for lightning initiation
Authors: Dwyer Joseph R.
Published: March 2010

Using detailed Monte Carlo simulations, the diffusion coefficients for relativistic runaway electron avalanches in air are found for the range of electric field strengths applicable to thunderclouds. Diffusion causes runaway electron avalanches to spread perpendicular to and parallel to the avalanche direction, resulting in much smaller peak conductivities than would be inferred otherwise. The idea that runaway electron avalanches seeded by extensive cosmic ray air showers may initiate lightning has gained considerable popularity in recent years. However, using the diffusion coefficients calculated in this paper along with the avalanche multiplication limit from X‐ray and positron feedback, it is found that even 1017 eV cosmic ray air showers do not produce high enough conductivities to significantly alter the electric field inside a thundercloud. As a result, it will be shown that at present, no compelling theoretical argument exists to suggest that cosmic ray extensive air showers initiate lightning.
Cusp as a source for oxygen in the plasma sheet during geomagnetic storms
Authors: Kistler L. M. , Mouikis C. G. , Klecker B. , Dandouras I.
Published: March 2010

We have used the ion composition data from the CIS/CODIF instrument on Cluster to determine how the O+ population in the plasma sheet and the adjacent lobes changes during geomagnetic storms. The Cluster trajectory, which moves over the polar cap, into the lobe, and then into the plasma sheet on each orbit, allows us to track the changes in O+ in these regions for a prestorm orbit, main‐phase orbit, and recovery phase orbit. We find that changes in the O+ density and pressure in the plasma sheet are similar to those commonly observed in the ring current during a storm. The O+ is low prestorm. It increases by about a factor of 10 just prior to or during the early main phase of the storm, and is reduced, but usually not down to prestorm levels, in the recovery phase. The lobes contain tailward streaming O+ which originates in the “cleft ion fountain”. During the storms main phase, this population also increases. A detailed look at the main‐phase passes shows that a significant increase in the O+/H+ ratio is observed when this lobe population reaches the plasma sheet, and the tailward streaming O+ is observed continuously as the spacecraft moves from the lobe into the plasma sheet. The enhanced O+ in the lobe and the plasma sheet is observed for many hours during the storm. The inward convection of this population is likely a significant contributor to the storm time ring current.
An analytical model of capped turbulent oscillatory bottom boundary layers
Authors: Shimizu Kenji
Published: March 2010

An analytical model of capped turbulent oscillatory bottom boundary layers (BBLs) is proposed using eddy viscosity of a quadratic form. The common definition of friction velocity based on maximum bottom shear stress is found unsatisfactory for BBLs under rotating flows, and a possible extension based on turbulent kinetic energy balance is proposed. The model solutions show that the flow may slip at the top of the boundary layer due to capping by the water surface or stratification, reducing the bottom shear stress, and that the Earth's rotation induces current and bottom shear stress components perpendicular to the interior flow with a phase lag (or lead). Comparisons with field and numerical experiments indicate that the model predicts the essential characteristics of the velocity profiles, although the agreement is rather qualitative due to assumptions of quadratic eddy viscosity with time‐independent friction velocity and a well‐mixed boundary layer. On the other hand, the predicted linear friction coefficients, phase lead, and veering angle at the bottom agreed with available data with an error of 3%–10%, 5°–10°, and 5°–10°, respectively. As an application of the model, the friction coefficients are used to calculate e‐folding decay distances of progressive internal waves with a semidiurnal frequency.
Helical circulations in the typhoon boundary layer
Authors: Ellis Ryan , Businger Steven
Published: March 2010

Low‐level wind data from the WSR‐88D in Guam obtained in Typhoon Dale (1996) and Typhoon Keith (1997) are analyzed for coherent structures. Consistent with the results of previous studies of Atlantic hurricanes, velocity anomalies associated with coherent structures were found in the boundary layer of both storms. A total of 99 cases of coherent structures, also known as roll vortices, were documented during a 6 h evaluation period for each storm. Storm‐relative roll location, roll vorticity, asymmetries in the upward and downward momentum fluxes, and signatures of circulations transverse to the mean flow associated with roll circulations were explored. The effects of terrain and convective precipitation systems, such as rainbands, on the occurrence of rolls were investigated. The results support and extend prior findings of roll observations, and can be used to help validate theoretical and numerical models of coherent structures within tropical cyclones. Moreover, the wind variations documented in this study may have application for wave runup and wind damage potential in tropical cyclones.
Mechanisms and feedback causing changes in upper stratospheric ozone in the 21st century
Authors: Oman L. D. , Waugh D. W. , Kawa S. R. , Stolarski R. S. , Douglass A. R. , Newman P. A.
Published: March 2010

Stratospheric ozone is expected to increase during the 21st century as the abundance of halogenated ozone‐depleting substances decrease to 1960 values. However, climate change will likely alter this “recovery” of stratospheric ozone by changing stratospheric temperatures, circulation, and abundance of reactive chemical species. Here we quantify the contribution of different mechanisms to changes in upper stratospheric ozone from 1960 to 2100 in the Goddard Earth Observing System chemistry‐climate model, using multiple linear regression analysis applied to simulations using either A1b or A2 greenhouse gas (GHG) scenarios. In both scenarios, upper stratospheric ozone has a secular increase over the 21st century. For the simulation using the A1b GHG scenario, this increase is determined by the decrease in halogen amounts and the GHG‐induced cooling, with roughly equal contributions from each mechanism. There is a larger cooling in the simulation using the A2 GHG scenario, but also enhanced loss from higher NOy and HOx concentrations, which nearly offsets the increase because of cooler temperatures. The resulting ozone evolutions are similar in the A2 and A1b simulations. The response of ozone caused by feedback from temperature and HOx changes, related to changing halogen concentrations, is also quantified using simulations with fixed‐halogen concentrations.
Traditional and microirrigation with stochastic soil moisture
Authors: Vico Giulia , Porporato Amilcare
Published: March 2010

Achieving a sustainable use of water resources, in view of the increased food and biofuel demand and possible climate change, will require optimizing irrigation, a highly nontrivial task given the unpredictability of rainfall and the numerous soil‐plant‐atmosphere interactions. Here we theoretically analyze two different irrigation schemes, a traditional scheme, consisting of the application of fixed water volumes that bring soil moisture to field capacity, and a microirrigation scheme supplying water continuously in order to avoid plant water stress. These two idealized irrigation schemes are optimal in the sense that they avoid crop water stress while minimizing water losses by percolation and runoff. Furthermore, they cover the two extremes cases of continuous and fully concentrated irrigation. For both irrigation schemes, we obtain exact solutions of the steady state soil moisture probability density function with random timing and amounts of rainfall. We also give analytical expressions for irrigation frequency and volumes under different rainfall regimes, evaporative demands, and soil types. We quantify the excess volumes required by traditional irrigation, mostly lost in runoff and deep infiltration, as a function of climate, soil, and vegetation parameters.
Control of cell cycle progression by phosphorylation of cyclin-dependent kinase (CDK) substrates
Authors: Suryadinata Randy , Sadowski Martin , Sarcevic Boris
Published: March 2010

The eukaryotic cell cycle is a fundamental evolutionarily conserved process that regulates cell division from simple unicellular organisms, such as yeast, through to higher multicellular organisms, such as humans. The cell cycle comprises several phases, including the S-phase (DNA synthesis phase) and M-phase (mitotic phase). During S-phase, the genetic material is replicated, and is then segregated into two identical daughter cells following mitotic M-phase and cytokinesis. The S- and M-phases are separated by two gap phases (G1 and G2) that govern the readiness of cells to enter S- or M-phase. Genetic and biochemical studies demonstrate that cell division in eukaryotes is mediated by CDKs (cyclin-dependent kinases). Active CDKs comprise a protein kinase subunit whose catalytic activity is dependent on association with a regulatory cyclin subunit. Cell-cycle-stage-dependent accumulation and proteolytic degradation of different cyclin subunits regulates their association with CDKs to control different stages of cell division. CDKs promote cell cycle progression by phosphorylating critical downstream substrates to alter their activity. Here, we will review some of the well-characterized CDK substrates to provide mechanistic insights into how these kinases control different stages of cell division.
Structural investigation and thermodynamical properties of alkali calcium trihydrides
Authors: Vajeeston P. , Ravindran P. , Fjellvåg H.
Published: March 2010

The ground-state structure, equilibrium structural parameters, electronic structure, and thermodynamical properties of MCaH3 (M=Li, Na, K, Rb, and Cs) phases have been investigated. From the 104 structural models used as inputs for structural optimization calculations, the ground-state crystal structures of MCaH3 phases have been predicted. At ambient condition, LiCaH3, NaCaH3, and KCaH3 crystallize in hexagonal, monoclinic, and orthorhombic structures, respectively. The remaining phases RbCaH3 and CsCaH3 crystallize in a cubic structure. The calculated phonon spectra indicate that all the predicted phases are dynamically stable. The formation energy for the MCaH3 phases have been calculated along different reaction pathways. The electronic structures reveal that all these phases are insulators with an estimated band gap varying between 2.5 and 3.3 eV.
Label-free imaging of heme proteins with two-photon excited photothermal lens microscopy
Authors: Lu Sijia , Min Wei , Chong Shasha , Holtom Gary R. , Xie X. Sunney
Published: March 2010

Heme proteins, such as hemoglobins and cytochromes, play important roles in various biological processes. Here we employ the two-photon excited photothermal effect as a contrast mechanism to map heme proteins distribution. Particularly, both a thermal lens scheme and a high-frequency modulation are utilized to enhance the signal-to-noise ratio. We demonstrate label-free imaging of individual red blood cells, subcellular distribution of cytochromes in live mammalian cells, and the microvascular networks in mouse ear tissue and in a zebrafish gill.
Second law of thermodynamics and phonon-boundary conditions in nanowires
Authors: Sellitto A. , Alvarez F. X. , Jou D.
Published: March 2010

The restrictions placed by the second law of thermodynamics on the boundary conditions have a special interest in nanosystems, where the Knudsen boundary layer, whose width is of the order of the mean-free path of heat carriers, becomes comparable to the size of the whole system. Here we explore second-order boundary conditions and show that the constraints of the classical irreversible thermodynamics are too restrictive, and that other formalisms going beyond local-equilibrium approach yield more realistic constraints for hydrodynamic phonon flow along nanowires. Furthermore, our analysis suggests a transition to zero thermal conductivity for very thin nanowires due to phonon backscattering.
Evolution of ferroelectric domain structures embedded inside polycrystalline BaTiO3 during heating
Authors: Varlioglu Mesut , Ustundag Ersan , Tamura Nobumichi , Jones Jacob L.
Published: March 2010

The evolution of ferroelectric domains inside a single grain of a polycrystalline BaTiO3 ceramic was investigated under quasistatic heating by using polychromatic scanning x-ray microdiffraction. Four domain orientations were observed, three of which exhibited a classic of ∼90° ferroelastic relationship. The fourth domain orientation was found to be crystallographically related with one of the other orientations by a rotation of either 180.47° or 0.47°. While heating the polycrystalline BaTiO3 from room temperature to above the Curie temperature (125 °C), all four ferroelectric domain orientations rotated toward a paraelectric cubic orientation which was found to be at an intermediate orientation relative to the four domain orientations. The crystallographic relationships of the domains with respect to paraelectric phase were explained using a domain structure model by Nepochatenko.
MP2/CBS atomic and molecular benchmarks for H through Ar
Authors: Barnes Ericka C. , Petersson George A.
Published: March 2010

We extrapolate to the MP2/CBS limit with a sequence of optimized n-tuple-ζ augmented polarized basis sets (n=4, 5, 6, and 7) for the entire set of 72 atoms, positive and negative atomic ions, homonuclear diatomic molecules, and hydrides representing the first two rows of the Periodic Table. The second-order correlation energies agree with accurate (±0.01 mEh) numerical values (He, Be, Ne, Mg, Ar, Zn+2, and Kr) to within ±0.1%. These MP2/CBS limits of the 72 species can now be used as benchmarks to calibrate more approximate calculations using smaller basis sets.
Control of an electrowetting-based beam deflector
Authors: de Boer Bart , Suijver Freek , Megens Mischa , Deladi Szabolcs , Kuiper Stein
Published: March 2010

We experimentally demonstrate the feasibility of a small, low-power beam deflector based on electrowetting. The beam deflector deflects light by refraction at the flat interface (meniscus) between two immiscible and density-matched liquids, namely, a nonpolar oil mixture and an aqueous salt solution. The liquids are contained in a square pyramidal frustum with electrode-covered faces. The electrodes can be separately driven by voltage sources in order to control the contact angle between the meniscus and the frustum faces. By controlling the voltage on all four electrodes, a flat meniscus is obtained that can be tilted independently in two perpendicular directions. We present a capacitance-based feedback driving scheme and demonstrate that it can be used for accurate control of the meniscus shape and tilt. Independent, continuous, and accurate beam steering through an angle of ±6° was achieved on two deflection axes.
Synchronized optical and electrical characterization of discotic liquid crystals thin films
Authors: Calò Annalisa , Stoliar Pablo , Cavallini Massimiliano , Geerts Yves H. , Biscarini Fabio
Published: March 2010

We describe a setup suitable for simultaneously measuring optical and electrical properties of a liquid crystal mesophase upon temperature variation, and the difference in the order parameters between the bulk and the interface with the substrate. It integrates high-resolution polarized light optical microscopy, temperature regulation, and electrical measurements in a controlled atmosphere with a software kernel that controls the instruments and synchronizes the data streams. A user-friendly interface allows us to program multistep experiments controlling all the instruments and data acquisition by a specifically designed scheduler. We tested our system on a thin film of alkoxy-substituted phthalocyanines deposited on a test pattern with interdigitated electrodes. We studied the optical and electrical behavior in the proximity of the bulk phase transition to isotropic liquid, identifying a few ordered monolayers anchored to the substrate above the transition temperature.
The thermal conductivity of aqueous nanofluids containing ceria nanoparticles
Authors: Beck Michael P. , Yuan Yanhui , Warrier Pramod , Teja Amyn S.
Published: March 2010

We present data for the thermal conductivity of nanofluids consisting of two sizes of ceria nanoparticles dispersed in water at 298 K. We also demonstrate that the effective thermal conductivity of these heterogeneous nanofluids can be described by a simple “mixing” rule that incorporates the size dependence of the thermal conductivity of the nanoparticles themselves. Our data follow the same trends with particle size as shown for alumina nanofluids in our previous work, and provide additional validation for that data.
Simulations of photoconductivity and lifetime for steady state and nonsteady state measurements
Authors: Schüler N. , Hahn T. , Schmerler S. , Hahn S. , Dornich K. , Niklas J. R.
Published: March 2010

Contact less measurements of the minority carrier “lifetime” and the photoconductivity are widely used to characterize the material quality and to investigate defects in a sample. In order to interpret these measurements correctly and to guarantee comparability between different methods, numerical simulation tools were developed. These simulations allow to account even for very complex defect models, thus, e.g., enabling the simulation of trapping effects. Contrary to the Shockley–Read–Hall model or the widely used simulation tool PC1D nearly no assumptions are made. Furthermore, nonsteady state solutions can be obtained. The simulation approach is explained in detail, along with simulations of the trapping effect on the measured lifetime for different injections, trap parameters, and measuring methods, demonstrating the capabilities of the here presented simulation tool. Temperature and injection dependent lifetime measurements were performed and it is shown how important sample parameters can be extracted using the simulation tool. Additionally an approach is presented to simulate lifetimes for thick samples, where a nonuniform carrier profile has to be taken into account. This enables a comparison of nonsteady state to steady-state lifetime measurement techniques even for thick samples such as ingots.
Thermal stability of the nanostructured BaTiO3 determined by long and short range interactions: A dual-shell model
Authors: Ma Shouzhi , Wang Xiaohui , Zhou Ji , Li Longtu , Sun Chang Q.
Published: March 2010

Although barium titanate (BaTiO3) ferroelectrics at the nanoscale has been extensively investigated, the physical origin of their unusual performance, in particular, the suppressed thermal stability remains yet unclear despite existing models from various perspectives. Based on the consideration of the short range bond order-length-strength correlation and the long range dipole-dipole interaction, we have developed a dual-shell model for the size and shape induced suppression of the Curie temperature for BaTiO3 nanocrystals. One surface shell of three atomic layers represents the short range interaction due to the shorter and stronger bonds between under-coordinated atoms, which intrinsically lowers the mean atomic cohesive energy of the crystal. The other shell with thickness of Kc (critical number of atomic layers) characterizes the long rang dipole-dipole interaction. If one moves a BaTiO3 unit cell from the center of the nanocrystal outwards, the unit cell will lose its ferroelectrics gradually upon reaching the Kc point. The modeling predictions have been verified by the presented experimental observations and results documented in the open literature. The least Kc has been optimized to be 9 for BaTiO3 spherical particles.
Strong dependence of spin dynamics on the orientation of an external magnetic field for InSb and InAs
Authors: Litvinenko K. L. , Leontiadou M. A. , Li Juerong , Clowes S. K. , Emeny M. T. , Ashley T. , Pidgeon C. R. , Cohen L. F. , Murdin B. N.
Published: March 2010

Electron spin relaxation times have been measured in InSb and InAs epilayers in a moderate (<4 T) external magnetic field. A strong and opposite field dependence of the spin lifetime was observed for longitudinal (Faraday) and transverse (Voigt) configuration. In the Faraday configuration the spin lifetime increases because the D’yakonov–Perel’ dephasing process is suppressed. At the high field limit the Elliot–Yafet spin flip relaxation process dominates, enabling its direct determination. Conversely, as predicted theoretically for narrow band gap semiconductors, an additional efficient spin dephasing mechanism dominates in the Voigt configuration significantly decreasing the electron spin lifetime with increasing field.
Nonferromagnetic material inserted magnetostrictive patch bonding technique for torsional modal testing of a ferromagnetic cylinder
Authors: Park Chan Il , Kim Yoon Young
Published: March 2010

Torsional vibration testing requires pure torsional mode transduction. However, no reliable technique is available for exciting torsional vibrations in ferromagnetic cylinders for a relatively wide range of frequencies. A magnetostrictive patch bonding excitation method developed for nonferromagnetic cylinders, based on the magnetostrictive principle, may be considered for ferromagnetic cylinders. However, the direct bonding of a magnetostrictive patch onto a ferromagnetic cylinder fails because the applied magnetic field spreads to both the patch and the cylinder and thus generates unwanted modes of vibration such as longitudinal modes. Thus, a modified or new technique must be developed in order to concentrate the applied magnetic field mainly on the patch, while causing the patch deformation to fully transfer to the cylinder. This paper presents a modified magnetostrictive patch bonding excitation and measurement technique suitable for ferromagnetic cylinders. The key idea is to insert a nonferromagnetic material between the test cylinder and the magnetostrictive patch. Because the thickness of the material or the gap size critically affects the torsional vibration test by the magnetostrictive patch boding method, a series of numerical and experimental investigations to find the optimal gap size are conducted. Other factors affecting the developed modal testing method are also considered. The validity of the developed method is checked by comparing the experimentally obtained eigenfrequencies of a test ferromagnetic cylinder with the theoretical eigenfrequencies.
A spin- and angle-resolving photoelectron spectrometer
Authors: Berntsen M. H. , Palmgren P. , Leandersson M. , Hahlin A. , Åhlund J. , Wannberg B. , Månsson M. , Tjernberg O.
Published: March 2010

A new type of hemispherical electron energy analyzer that permits angle and spin resolved photoelectron spectroscopy has been developed. The analyzer permits standard angle resolved spectra to be recorded with a two-dimensional detector in parallel with spin detection using a mini-Mott polarimeter. General design considerations as well as technical solutions are discussed and test results from the Au(111) surface state are presented.
Role of the local structure and the energy trap centers in the quenching of luminescence of the Tb3+ ions in fluoroborate glasses: A high pressure study
Authors: Venkatramu V. , Babu P. , Martín I. R. , Lavín V. , Muñoz-Santiuste Juan E. , Tröster Th. , Sievers W. , Wortmann G. , Jayasankar C. K.
Published: March 2010

The concentration and pressure dependent luminescence properties of the Tb3+ ions in a lithium fluoroborate glasses have been studied by analyzing the deexcitation processes of the D54 level at ambient conditions as well as a function of pressure up to 35 GPa at room temperature. The luminescence spectra of Tb3+ ions have been measured as a function of pressure and observed a continuous redshift as well as a progressive increase in the magnitude of the crystal-field splittings for the D54→F73,4,5 transitions. Monitoring the D54→F75 transition, the luminescence decay curves have been measured and analyzed in order to understand the dynamics of the deexcitation of the Tb3+ ions in these glasses. At ambient conditions a nonexponential behavior has been found for doping concentrations as low as 0.1 mol % of Tb4O7, although no cross-relaxation channels exist to explain this behavior. The modelization of the energy transfer processes surprisingly shows that the nonexponential character of the decay curves of the D54 level with concentration or with pressure has to be ascribed to energy transfer to traps without migration of energy between Tb3+ ions. For all the experimental situations the nonexponential character of the decay curves is well described by the generalized Yokota–Tanimoto model with a dipole-dipole interaction between the Tb3+ ions and the nearby luminescence quenching traps. The luminescence properties observed with releasing pressure are slightly different to those obtained while increasing pressure suggesting a local structural hysteresis in the lithium fluoroborate glass matrix giving rise to the generation of a new distribution of environments for the Tb3+ ions.
Effect of surface bonding on semiconductor nanoribbon wiggling structure
Authors: Zhang Yu , Yu Minrui , Savage Donald E. , Lagally Max G. , Blick Robert H. , Liu Feng
Published: March 2010

SiGe nanomembranes and nanowires provide one important class of stretchable electronic materials. We have investigated a very interesting wiggling phenomenon of SiGe nanoribbons bonded to Si substrate as experimentally observed in a Hall-bar structure. Based on continuum linear stability analysis, we establish a scaling rule between the wiggling period and surface bonding area, in relation to the ratio of strain energy over the interfacial bonding energy.
Nucleation theory beyond the deterministic limit. I. The nucleation stage
Authors: Dubrovskii V. G. , Nazarenko M. V.
Published: March 2010

This work addresses theory of nucleation and condensation based on the continuous Fokker-Plank type kinetic equation for the distribution of supercritical embryos over sizes beyond the deterministic limit, i.e., keeping the second derivative with respect to size. The first part of the work treats the nucleation stage. It is shown that the size spectrum should be generally obtained by the convolution of the initial distribution with the Gaussian-like Green function with spreading dispersion. It is then demonstrated that the fluctuation-induced effects can be safely neglected at the nucleation stage, where the spectrum broadening due to the nonlinear boundary condition is much larger than the fluctuational one. The crossover between the known triangular and double exponential distributions under different conditions of material influx into the system is demonstrated. Some examples of size distributions at the nucleation stage in different regimes of material influx are also presented.
Subsystem constraints in variational second order density matrix optimization: Curing the dissociative behavior
Authors: Verstichel Brecht , van Aggelen Helen , Van Neck Dimitri , Ayers Paul W. , Bultinck Patrick
Published: March 2010

A previous study of diatomic molecules revealed that variational second-order density matrix theory has serious problems in the dissociation limit when the N-representability is imposed at the level of the usual two-index (P,Q,G) or even three-index (T1,T2) conditions [H. Van Aggelen et al., Phys. Chem. Chem. Phys. 11, 5558 (2009)]. Heteronuclear molecules tend to dissociate into fractionally charged atoms. In this paper we introduce a general class of N-representability conditions, called subsystem constraints, and show that they cure the dissociation problem at little additional computational cost. As a numerical example the singlet potential energy surface of Be B+ is studied. The extension to polyatomic molecules, where more subsystem choices can be identified, is also discussed.
Fast ion generation in the cathode plasma jet of a multipicosecond laser-triggered vacuum discharge
Authors: Moorti A. , Naik P. A. , Gupta P. D.
Published: March 2010

Ion generation in the cathode plasma jet of a moderate-current (∼2.3 kA), low-energy (≤20 J) vacuum spark discharge triggered by ∼27 ps, 10 mJ laser pulses is studied using time of flight technique. Fastest ion velocity and velocity corresponding to the peak of the time of flight signals for Al cathode were measured to be ∼5.25×108 cm/s (energy of ∼143 keV/u) and ∼8.1×107 cm/s (energy of ∼3.4 keV/u), respectively. Corresponding velocities in the case of ions generated from laser-produced Al plasma (energy of ∼550 mJ, intensity of ∼1014 W/cm2) were found to be much smaller, viz., ∼1.05×108 cm/s (energy of ∼5.75 keV/u) and ∼2.63×107 cm/s (energy of ∼0.36 keV/u), respectively. Study shows efficient acceleration of ions in a current-carrying cathode plasma jet of a small-energy multipicosecond laser-triggered spark discharge as compared with that in a high-energy multipicosecond laser-produced plasma plume.
High density flux of Co nanoparticles produced by a simple gas aggregation apparatus
Authors: Landi G. T. , Romero S. A. , Santos A. D.
Published: March 2010

Gas aggregation is a well known method used to produce clusters of different materials with good size control, reduced dispersion, and precise stoichiometry. The cost of these systems is relatively high and they are generally dedicated apparatuses. Furthermore, the usual sample production speed of these systems is not as fast as physical vapor deposition devices posing a problem when thick samples are needed. In this paper we describe the development of a multipurpose gas aggregation system constructed as an adaptation to a magnetron sputtering system. The cost of this adaptation is negligible and its installation and operation are both remarkably simple. The gas flow for flux in the range of 60–130 SCCM (SCCM denotes cubic centimeter per minute at STP) is able to completely collimate all the sputtered material, producing spherical nanoparticles. Co nanoparticles were produced and characterized using electron microscopy techniques and Rutherford back-scattering analysis. The size of the particles is around 10 nm with around 75 nm/min of deposition rate at the center of a Gaussian profile nanoparticle beam.
Time of flight elastic recoil detection analysis with a position sensitive detector
Authors: Siketić Zdravko , Radović Iva Bogdanović , Jakšić Milko , Skukan Natko
Published: March 2010

A position sensitive detection system based on the microchannel plate detector has been constructed and installed at the existing time of flight (TOF) spectrometer in order to perform a kinematic correction and improve the surface time/depth resolution of elastic recoil detection analysis (ERDA) system. The position resolution of the detector has been tested for different types of ions and anode voltages. TOF spectra of recoiled O ions from SiO2 and F from CaF2 were collected in coincidence with position sensitive detector signal. Kinematic correction of TOF spectra improved surface time/depth resolution by ∼20% for our system; however even higher improvements could be obtained in larger solid angle TOF-ERDA systems.
Corrected Article: “An error-controlled fast multipole method” [J. Chem. Phys. 131, 244102 (2009)]
Authors: Dachsel Holger
Published: March 2010

We present a two-stage error estimation scheme for the fast multipole method (FMM). This scheme can be applied to any particle system. It incorporates homogeneous as well as inhomogeneous distributions. The FMM error as a consequence of the finite representation of the multipole expansions and the operator error is correlated with an absolute or relative user-requested energy threshold. Such a reliable error control is the basis for making reliable simulations in computational physics. Our FMM program on the basis of the two-stage error estimation scheme is available on request.
Dielectric properties of colloidal Gd2O3 nanocrystal films fabricated via electrophoretic deposition
Authors: Mahajan S. V. , Dickerson J. H.
Published: March 2010

We investigated the dielectric characteristics of [Al/Gd2O3/Si] metal-oxide-semiconductor (MOS) capacitors, which were fabricated from films of gadolinium oxide (Gd2O3) nanocrystals used as the gate oxide layer. Electrophoretic deposition cast Gd2O3 nanocrystal films of different thicknesses by varying the concentration of the nanocrystal suspensions. Capacitance-voltage (C-V) measurements of the MOS capacitors exhibited hysteresis, which indicated potentially favorable charge-storage properties. The films’ dielectric constant (κ=3.90), calculated from the C-V data, led to the packing density of nanocrystals within the film (66%), which is in the glassy regime approximated by randomly closed packed spheres.
Latent dynamics of a protein molecule observed in dihedral angle space
Authors: Omori Satoshi , Fuchigami Sotaro , Ikeguchi Mitsunori , Kidera Akinori
Published: March 2010

Dihedral angles are alternative set of variables to Cartesian coordinates for representing protein dynamics. The two sets of variables exhibit extremely different behavior. Motions in dihedral angle space are characterized by latent dynamics, in which motion induced in each dihedral angle is always compensated for by motions of many other dihedral angles, in order to maintain a rigid globular shape. Using molecular dynamics simulations, we propose a molecular mechanism for the latent dynamics in dihedral angle space. It was found that, due to the unique structure of dihedral principal components originating in the globular shape of the protein, the dihedral principal components with large (small) amplitudes are highly correlated with the eigenvectors of the metric matrix with small (large) eigenvalues. Such an anticorrelation in the eigenmode structures minimizes the mean square displacement of Cartesian coordinates upon rotation of dihedral angles. In contrast, a short peptide, deca-alanine in this study, does not show such behavior of the latent dynamics in the dihedral principal components, but shows similar behaviors to those of the Cartesian principal components, due to the absence of constraints to maintain a rigid globular shape.
Tunneling spectroscopy of electron subbands in thin silicon-on-insulator metal-oxide-semiconductor field-effect transistors
Authors: Noborisaka J. , Nishiguchi K. , Kageshima H. , Ono Y. , Fujiwara A.
Published: March 2010

We report the tunneling spectroscopy of thin silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistors with tunneling gate oxide. When electrons are injected into a thin SOI well, the gate-tunneling current shows kink structures originating from quantized energy levels in the SOI well. From the theoretical consideration of the energy levels and their density of states, the observed features can be ascribed to electron tunneling into the in-plane fourfold degenerate valley subbands. Furthermore, inhomogeneous peak broadening of the kink structures in the experiment is well explained by the SOI thickness variation.
High quality Ge epitaxial layers in narrow channels on Si (001) substrates
Authors: Wang G. , Rosseel E. , Loo R. , Favia P. , Bender H. , Caymax M. , Heyns M. M. , Vandervorst W.
Published: March 2010

We demonstrate the selective growth of high quality Ge epitaxial layers in channels as narrow as 10 nm on patterned Si (001) substrates by a combination of low temperature growth and selective recrystallization using Ge melt and regrowth during a millisecond laser anneal. Filling narrow trenches at high growth temperature as required for obtaining high quality layers was shown to be prohibited by Ge outdiffusion due to the high Ge chemical potential in such narrow channels. At low temperature, a hydride-terminated surface is maintained which counteracts the outdiffusion of the Ge adatoms and provides excellent trench filling. The resulting low crystalline quality can be restored by a selective Ge melt and epitaxial regrowth using a millisecond laser anneal.
Note: Low density and long plasma channels generated by laser transversely ignited ablative capillary discharges
Authors: Liu Mingwei , Deng Aihua , Liu Jiansheng , Li Ruxin , Xu Jiancai , Xia Changquan , Wang Cheng , Shen Baifei , Xu Zhizhan , Nakajima K.
Published: March 2010

A technique is developed to reduce the jitter associated with ablative capillary discharges. A laser pulse propagating perpendicularly to the axis of the capillary and focused onto a copper wire creates a plasma that initiates the discharge. This transverse laser ignition method has several advantages over previous techniques employing a laser pulse collinear with the capillary, including increased capillary lifetime and simpler arrangement of the igniting and the driving pulses for laser-wakefield acceleration. Using this technique long, low density plasma channels are produced with low jitter.
A Lennard-Jones plus Coulomb potential for Al3+ ions in aqueous solutions
Authors: Faro Tatiana M. C. , Thim Gilmar P. , Skaf Munir S.
Published: March 2010

We developed a simple pair-additive Lennard-Jones plus Coulomb potential for molecular simulations of the trivalent cation Al3+ in water which accounts reasonably well for the behavior of aluminum aqueous solutions. The model predicts an octahedral first hydration shell containing 6 water molecules and a trigonal second shell with 12 molecules on average, in good agreement with the available experimentally determined structure. The peak positions of the cation-oxygen radial distribution function are only slightly compressed compared to the x-ray structure, the hydration enthalpy is 10% too low, and the cation self-diffusion coefficient and the single-particle second rank reorientational time are in excellent agreement with inelastic neutron scattering and NMR spectroscopy data, respectively. The model also captures the essential vibrational features of the hydrated [Al(H2O)6]3+ complex. It predicts the main O–Al–O bending mode frequency to within ∼5%, but significantly overestimates the frequency of the totally symmetric Al–O stretching mode. Overall, the accuracy of the proposed model is as good as the best available classical potentials, if not better in some aspects, with a much simpler functional form, which makes it an attractive alternative for computer simulations of Al3+ in more complex aqueous and biomolecular systems.