bluuebunny/crossref_metadata_2025 huggingface dataset:
Emplacement of Martian rampart crater deposits
Authors: Baloga Stephen M. , Fagents Sarah A. , Mouginis‐Mark Peter J.
Published: October 2005

We present a basic continuum flow model for the emplacement of the distal rampart crater deposits on Mars. Assuming cylindrical symmetry, analytic solutions of the volume and momentum conservation equations yield time‐dependent flow thickness and velocity profiles. The momentum equation has an inertial term, and a frictional resistance term that is proportional to the local volumetric flow rate. We find that only a few basic physical processes are necessary to form sharp distal ramparts. First, there must be sufficient material to form a continuum overland flow. Then, for simple choices of boundary conditions at the source of the flow, distal ramparts form naturally due to the cylindrical geometry, the inertia of the flow, and local frictional resistance. THEMIS images of rampart deposits show that the ejecta flow velocities were relatively slow, being diverted by preexisting obstacles even within ∼0.2 crater radii from the rim of the parent crater. To develop inferences about rampart deposit emplacement, we require measurements of the crater radius and flow distance, and assumptions about the maximum source flow velocity and depth. We measured nine clearly expressed rampart deposits for craters with diameters of 3.4–17.0 km. The model provides estimates of the emplacement time, the rampart width, and the shape of the radial flow depth profiles. We find that modest velocities of ∼27–116 m s−1, maximum source flow depths of 10–40 m, and emplacement durations of 12–31 min adequately explain the morphologies of selected rampart craters.
Quantifying the opal belt in the Atlantic and southeast Pacific sector of the Southern Ocean by means of 230Th normalization
Authors: Geibert Walter , Rutgers van der Loeff Michiel M. , Usbeck Regina , Gersonde Rainer , Kuhn Gerhard , Seeberg‐Elverfeldt Jens
Published: October 2005

A set of 114 samples from the sediment surface of the Atlantic, eastern Pacific and western Indian sectors of the Southern Ocean has been analyzed for 230Th and biogenic silica. Maps of opal content, Th‐normalized mass flux, and Th‐normalized biogenic opal flux into the sediment have been derived. Significant differences in sedimentation patterns between the regions can be detected. The mean bulk vertical fluxes integrated into the sediment in the open Southern Ocean are found in a narrow range from 2.9 g m−2 yr−1 (Eastern Weddell Gyre) to 15.8 g m−2 yr−1 (Indian sector), setting upper and lower limits to the vertically received fraction of open ocean sediments. The silica flux to sediments of the Atlantic sector of the Southern Ocean is found to be 4.2 ± 1.4 × 1011 mol yr−1, just one half of the last estimate. This adjustment represents 6% of the output term in the global marine silica budget.
Fast coronal mass ejection environments and the production of solar energetic particle events
Authors: Kahler S. W. , Vourlidas A.
Published: October 2005

The search continues for coronal environmental factors that determine whether a fast coronal mass ejection (CME) results in a solar energetic particle (SEP) event at 1 AU. From a plot of peak 20 MeV SEP intensities versus associated CME speeds we select for comparison two groups of fast, wide, western hemisphere CMEs observed with the LASCO coronagraph from 1998 to 2002. The SEP‐rich CME group produced the largest observed SEP events, and the SEP‐poor CME group produced the smallest or no observed SEP events. The major differences are that the SEP‐rich CMEs are brighter and more likely to be streamer blowouts and to follow colocated CMEs within 12 or 24 hours. The SEP‐poor CMEs are fainter and less likely to interact with streamers or to follow preceding colocated CMEs. Thus we confirm the recent result that the SEP event peak intensities are higher when the associated driver CMEs are preceded within a day by wide CMEs at the same locations. However, the enhanced brightness, and therefore mass, of the SEP‐rich CMEs appears to be their most dominant characteristic and suggests that either large longitudinal and latitudinal extents or high densities are needed for fast CMEs to produce SEPs.
Possible influence of the Antarctic Oscillation on tropical cyclone activity in the western North Pacific
Authors: Ho Chang‐Hoi , Kim Joo‐Hong , Kim Hyeong‐Seog , Sui Chung‐Hsiung , Gong Dao‐Yi
Published: October 2005

The present study investigates how large‐scale atmospheric circulation in the Southern Hemisphere (SH) modulates tropical cyclone (TC) activity in the western North Pacific (WNP) during a typhoon season (July, August, and September; boreal summer). The variation of the SH circulation of interest is the Antarctic Oscillation (AAO). In the positive phase of AAO relative to its negative phase, two anomalous highs develop over the western Pacific in both hemispheres: a huge anticyclone in southeastern Australia and a relatively weak anticyclone in the East China Sea. These teleconnection patterns are examined and compared with previous analyses. Related to the AAO variations, a statistically significant alteration of TC activities is found over the WNP. The difference in the mean TC passage numbers over the East China Sea (120°–140°E, 20°–40°N) between the eight highest‐AAO years and the eight lowest‐AAO years is as large as 2, equivalent to a 50–100% increase from the climatology. This change is primarily a result of more TCs forming over the eastern Philippine Sea. On the other hand, TC passage numbers slightly decrease over the South China Sea. These changes in TC activity are predominant in August and are consistent with changes in low‐level vorticity over the subtropical WNP. The influence of SH circulation variability on large‐scale environments and tropical convection in the subtropical NH suggest a possible usage of AAO variation for long‐range forecasting of TC activity over the WNP.
Assessing future nitrogen deposition and carbon cycle feedback using a multimodel approach: Analysis of nitrogen deposition
Authors: Lamarque J.‐F. , Kiehl J. T. , Brasseur G. P. , Butler T. , Cameron‐Smith P. , Collins W. D. , Collins W. J. , Granier C. , Hauglustaine D. , Hess P. G. , Holland E. A. , Horowitz L. , Lawrence M. G. , McKenna D. , Merilees P. , Prather M. J. , Rasch P. J. , Rotman D. , Shindell D. , Thornton P.
Published: October 2005

In this study, we present the results of nitrogen deposition on land from a set of 29 simulations from six different tropospheric chemistry models pertaining to present‐day and 2100 conditions. Nitrogen deposition refers here to the deposition (wet and dry) of all nitrogen‐containing gas phase chemical species resulting from NOx (NO + NO2) emissions. We show that under the assumed IPCC SRES A2 scenario the global annual average nitrogen deposition over land is expected to increase by a factor of ∼2.5, mostly because of the increase in nitrogen emissions. This will significantly expand the areas with annual average deposition exceeding 1 gN/m2/year. Using the results from all models, we have documented the strong linear relationship between models on the fraction of the nitrogen emissions that is deposited, regardless of the emissions (present day or 2100). On average, approximately 70% of the emitted nitrogen is deposited over the landmasses. For present‐day conditions the results from this study suggest that the deposition over land ranges between 25 and 40 Tg(N)/year. By 2100, under the A2 scenario, the deposition over the continents is expected to range between 60 and 100 Tg(N)/year. Over forests the deposition is expected to increase from 10 Tg(N)/year to 20 Tg(N)/year. In 2100 the nitrogen deposition changes from changes in the climate account for much less than the changes from increased nitrogen emissions.
A general model to estimate hourly and daily solar radiation for hydrological studies
Authors: Yang Kun , Koike Toshio
Published: October 2005

As an important input for hydrological models and snowmelting models, surface solar radiation can be estimated from sunshine duration by the Ångström‐Prescott model. This model has site‐dependent parameters and thus needs calibrations when applied to individual regions. The calibrations are particularly difficult in highland and mountainous areas because of unavailability of radiation measurements. In this study, a simple model that can explicitly account for radiative transfer processes in the atmosphere is developed to estimate hourly and daily solar radiation. Its inputs are surface meteorological data (sunshine duration, air temperature, and relative humidity), so it can be easily applied to hydrological modeling. The radiation model is compared with the Food and Agricultural Organization radiation model and globally and locally calibrated Ångström‐Prescott models at a number of sites in various climate and elevation regions, and it is suggested that the new model is more general and more accurate, especially for estimating hourly solar radiation. The source code of this model is available from the authors upon request.
Gender Differences in Adjustment to Bereavement: An Empirical and Theoretical Review
Authors: Stroebe Margaret , Stroebe Wolfgang , Schut Henk
Published: October 2005

The loss of a marital partner results in substantial increases in morbidity and mortality among both men and women, but the effects are relatively greater for widowers than for widows in the acute grieving period. Evidence is reviewed, and explanations of the pattern are examined. An interpretation in terms of gender differences in social support (cf. M. Stroebe & W. Stroebe, 1983 ), although plausible, has not yet been empirically confirmed. Likewise, with respect to gender differences in coping styles, women are more confrontive and expressive of their emotions than men, but there has been little validation of the generally accepted grief work hypothesis (working through grief by women brings about their better recovery). Cognitive processes underlying effective coping with bereavement are analyzed, and a stressor-specific framework, the dual-process model of coping with loss, is suggested to help explain gender differences in health outcomes.
Life Reflection: A Social–Cognitive Analysis of Life Review
Authors: Staudinger Ursula M.
Published: October 2005

Life review and reminiscence are 2 concepts used to describe the phenomenon of people reflecting on their lives. Rather than used synonymously, these 2 concepts need to be distinguished on the basis of a social–cognitive process analysis. For that purpose, life reflection is introduced as a new term. Evidence shows that life reflection is a social–cognitive process that begins in adolescence and continues across the life span. It serves different functions across the life span, but at all ages it contributes to self-insight and a self-critical perspective. Striving for new insights about oneself and about life in general is challenging and taxing. Reflecting together with a trusted person, thus, may facilitate the process. A study testing and supporting some of these propositions is reported. Results are discussed in the context of lifespan theory.
New Perspectives on Autobiographical Memory: The Integration of Narrative Processing and Autobiographical Reasoning
Authors: Singer Jefferson A. , Bluck Susan
Published: October 2005

Researchers from diverse psychological subdisciplines have increasingly turned their attention to the storied aspect of human thought. Narrative processing and autobiographical reasoning are 2 forms of this conscious thought. Narrative processing is the tendency to create thought units that use vivid imagery, sequential plots, characters, and salient goals. Autobiographical reasoning consists of interpreting and evaluating remembered experiences. Both forms of thought are discussed in D. P. McAdams's (2001) personality theory and D. B. Pillemer's (2001) cognitive research. S. Bluck and T. Habermas (2001) highlight developmental aspects of narrative processing and autobiographical reasoning, particularly in adolescent identity formation. U. M. Staudinger (2001) illustrates how autobiographical reasoning about memories and life stories serves as a springboard for wisdom at different stages of the life cycle. Implications for integrating subdisciplines of psychology are discussed.
Performance in Planning: Processes, Requirements, and Errors
Authors: Mumford Michael D. , Schultz Rosemary A. , Van Doorn Judy R.
Published: October 2005

Planning is not only an aspect of our day-to-day lives, it represents a critical aspect of performance on many high-level tasks. Although few of us would dispute the need for planning, the psychology of planning remains relatively undeveloped. With this point in mind, the intent in the present article was to review the available literature on planning. The authors begin by examining alternative models of planning and delineating their implications for performance. Subsequently, the findings obtained in various studies of planning are reviewed with respect to 8 key questions ranging from when planning is useful to how errors in planning should be minimized. The implications of current answers to these questions are discussed in terms of research needs and development of a more comprehensive theoretical understanding of performance in planning.
Bad is Stronger than Good
Authors: Baumeister Roy F. , Bratslavsky Ellen , Finkenauer Catrin , Vohs Kathleen D.
Published: October 2005

The greater power of bad events over good ones is found in everyday events, major life events (e.g., trauma), close relationship outcomes, social network patterns, interpersonal interactions, and learning processes. Bad emotions, bad parents, and bad feedback have more impact than good ones, and bad information is processed more thoroughly than good. The self is more motivated to avoid bad self-definitions than to pursue good ones. Bad impressions and bad stereotypes are quicker to form and more resistant to disconfirmation than good ones. Various explanations such as diagnosticity and salience help explain some findings, but the greater power of bad events is still found when such variables are controlled. Hardly any exceptions (indicating greater power of good) can be found. Taken together, these findings suggest that bad is stronger than good, as a general principle across a broad range of psychological phenomena.
IT to Support Knowledge Sharing in Communities, towards a Social Capital Analysis
Authors: Huysman Marleen , Wulf Volker
Published: October 2005

Ignoring the informal, non-canonical nature of knowledge sharing, including people's motivation, ability and opportunity to share knowledge, is one of the key causes of resistance to use knowledge-sharing tools. In order to improve knowledge sharing supported by information technology (IT), tools need to be embedded in the social networks of which it is part. This has implications for our knowledge on the design requirements of such socially embedded IT. The paper reviews tools that are designed for the purpose to foster social capital. We will then discuss what is needed for an IS design theory related to knowledge communities and how such a theory could incorporate social capital theory.
Modeling triblock surfactant-templated mesostructured cellular foams
Authors: Bhattacharya Supriyo , Gubbins Keith E.
Published: October 2005

Lattice Monte Carlo simulations are used to understand the role of surfactant self-assembly in the synthesis of templated mesoporous materials with ultralarge pores. Our system consists of model triblock surfactants in the presence of oil, water, and inorganic oxide. Depending on the temperature and component concentrations, these systems phase separate, and the surfactant-rich phase forms structures such as cylinders, lamellae, and spheres ordered in repetitive arrangements. In the absence of oil, the structures are cylindrical with diameters of 100Å, but increasing oil concentration produces ultralarge spheres with diameters above 500Å. Our results closely resemble the cylinder to sphere transition associated with the synthesis of the mesostructured cellular foams (MCFs). Pore size distributions of our model structures are qualitatively comparable with the pore size distributions of MCFs obtained from adsorption experiments. We also observe an increase in average pore size with oil concentration, which is consistent with the experimental reportings.
Dissipative dynamics of a system passing through a conical intersection: Ultrafast pump-probe observables
Authors: Gelman David , Katz Gil , Kosloff Ronnie , Ratner Mark A.
Published: October 2005

The dynamics of a system incorporating a conical intersection, in the presence of a dissipative environment, is studied with the purpose of identifying observable ultrafast spectroscopic signatures. A model system consisting of two vibronically coupled electronic states with two nuclear degrees of freedom is constructed. Dissipation is treated by two different methods, Lindblad semigroup formalism and the surrogate Hamiltonian approach. Pump-probe experimental expectation values such as transient emission and transient absorption are calculated and compared to the adiabatic and diabatic population transfer. The ultrafast population transfer reflecting the conical intersection is not mirrored in transient absorption measurements such as the recovery of the bleach. Emission from the excited state can be suppressed on the ultrafast time scale, but the existence of a conical intersection is only one of the possible mechanisms that can provide ultrafast damping of emission.
Electronic excitation energies of molecules in solution within continuum solvation models: Investigating the discrepancy between state-specific and linear-response methods
Authors: Corni S. , Cammi R. , Mennucci B. , Tomasi J.
Published: October 2005

In a recent article [R. Cammi, S. Corni, B. Mennucci, and J. Tomasi, J. Chem. Phys. 122, 104513 (2005)], we demonstrated that the state-specific (SS) and the linear-response (LR) approaches, two different ways to calculate solute excitation energies in the framework of quantum-mechanical continuum models of solvation, give different excitation energy expressions. In particular, they differ in the terms related to the electronic response of the solvent. In the present work, we further investigate this difference by comparing the excitation energy expressions of SS and LR with those obtained through a simple model for solute-solvent systems that bypasses one of the basic assumptions of continuum solvation models, i.e., the use of a single Hartree product of a solute and a solvent wave function to describe the total solute-solvent wave function. In particular, we consider the total solute-solvent wave function as a linear combination of the four products of two solute states and two solvent electronic states. To maximize the comparability with quantum-mechanical continuum model the resulting excitation energy expression is recast in terms of response functions of the solvent and quantities proper for the solvated molecule. The comparison of the presented expressions with the LR and SS ones enlightens the physical meaning of the terms included or neglected by these approaches and shows that SS agrees with the results of the four-level model, while LR includes a term classified as dispersion in previous treatments and neglects another related to electrostatic. A discussion on the possible origin of the LR flaw is finally given.
Wall intersection of ion orbits induced by fast transport of pedestal plasma over an electrostatic potential hill in a tokamak plasma edge
Authors: Hahn S. H. , Ku Seunghoe , Chang C. S.
Published: October 2005

An edge localized mode event is known to transport a significant portion of pedestal plasma across the separatrix and increase the divertor heat load to a possibly intolerable level in a tokamak fusion reactor. In the present work, a large random-walk transport is introduced in a plasma edge in a guiding-center orbit following code XGC [C. S. Chang, S. H. Ku, and H. Weitzner, Phys. Plasmas 11, 2649 (2004)] to understand the effect of edge radial electric-field shear on the wall-intersection location of large-transport orbits. It is found that without an edge radial electric field, Er, the majority of large-diffusion-induced ion orbital loss is to the outer divertor near the separatrix surface. However, with a large negative Er in the plasma edge with the ion grad-B drift into the single-null divertor, ion orbits with their kinetic energy less than the potential energy shift their wall-intersection locations to the inner divertor, while those with their kinetic energy higher than the potential energy retain their wall intersections at the outer divertor. If the ion grad-B is away from the single-null divertor, the ion orbital loss is always to the outer wall.
Runaway electrons in a fully and partially ionized nonideal plasma
Authors: Ramazanov T. S. , Turekhanova K. M.
Published: October 2005

This paper reports on a study of electron runaway for a nonideal plasma in an external electric field. Based on pseudopotential models of nonideal fully and partially ionized plasmas, the friction force was derived as a function of electron velocities. Dependences of the electron free path on plasma density and nonideality parameters were obtained. The impact of the relative number of runaway electrons on their velocity and temperature was considered for classical and semiclassical models of a nonideal plasma. It has been shown that for the defined intervals of the coupled plasma parameter, the difference between the relative numbers of runaway electron values is essential for various plasma models.
Growth precursors for a-C:H film deposition in pulsed inductively coupled methane plasmas
Authors: Bauer M. , Schwarz-Selinger T. , Jacob W. , von Keudell A.
Published: October 2005

Film deposition in pulsed inductively coupled plasmas is investigated using methane as precursor gas. The densities of neutrals as well as ion and radical fluxes are quantified using mass spectrometry. Plasma composition is uniquely determined by the mean dissipated energy per source gas molecule in the plasma, Emean. Film growth rates are measured by in situ real-time ellipsometry. The contributions of individual precursors to film growth are discussed quantitatively by comparing absolute net growth fluxes of reactive species with deposited carbon atoms. It is shown that chemisorption of CH3 or implantation of energetic carbonaceous ions cannot explain the observed growth rates. Instead, film deposition occurs either by incorporation of CH radicals at small values of Emean(<10eV) or by incorporation of unsaturated hydrocarbon radicals such as C2H3 or C2H at intermediate values of Emean(10<Emean<100eV). Film growth depends strongly on incorporation of carbonaceous ions only at larger values of Emean(>100eV).
Interaction of dust grains in strong collision plasmas: Diffusion pressure of nonequilibrium charge carriers
Authors: Vishnyakov V. I.
Published: October 2005

The formation of the nonequilibrium charge carriers in the space-charge layer at the interphase boundary in thermal collision plasmas has been studied. It has been shown that the flux of the nonequilibrium charge carriers determines the diffusional pressure on the interphase boundary, which provides for the existence of the force, directed to the area of greater plasma perturbation. The comparison of the electrostatic and diffusional pressures shows the possibility of the balance of the forces and the formation of the ordered structures of dust grains in a complex strong collision plasma.
Wavelet representation of plasma particle dynamics in stationary electrostatic waves
Authors: Tanriverdi Sevim , Psimopoulos Michalis
Published: October 2005

The dynamics of plasma particles in the presence of a stationary electrostatic wave is studied by expanding the motion of each particle in powers of the wave amplitude. The coefficients of this expansion are wavelets in velocity space that gradually transform into well-behaved singular functions for t⪢to; to=(m∕k2T)1∕2. The force exerted on the plasma and the rate of kinetic energy transferred to the plasma by the wave are obtained by averaging the amplitude expansion over initial conditions. Higher-order terms show that nonlinear wave-plasma interactions are governed by a universal function M(τ) which is independent of the velocity distribution and depends only on τ=t∕tosc; tosc=(m∕kqEo)1∕2. It is found that the short-time (t≈tosc) behavior of M(τ) describing the transition between linear and nonlinear regimes is given by M(τ)=1−(τ4∕234!)+(41τ8∕278!). Also, using an implicit expansion of the particle motion, a global component Mo(τ)=(4∕τ2)J1(τ2∕2), 0⩽τ<∞, of the universal function is obtained.
Modulated-bath ac calorimetry using modified commercial Peltier elements
Authors: Lortz Rolf , Abe Satoko , Wang Yuxing , Bouquet Frédéric , Tutsch Ulrich , Junod Alain
Published: October 2005

We developed a type of ac microcalorimeter based on a modulated-bath technique for measuring the specific heat of small microgram samples in the temperature range from 30 to 300 K, and tested it in magnetic fields up to 14 T. The device is built from a modified commercial Peltier element. The temperature of its top plate can be modulated periodically by the Peltier effect, so that the oscillation is symmetrical about the temperature of the main bath. This avoids the problem of dc offsets which plague conventional ac calorimeters. The sample is attached to a thin thermocouple cross, acting as a weak thermal link to a platform. The absence of a heater reduces the background heat capacity (“addenda”) to a minimum. As an illustrative example of the performance of our device, the specific heat in fields up to 14 T of a small single crystal of the high-temperature superconductor Bi2.12Sr1.71Ca1.22Cu1.95Oy is determined.
Laser-field synchrotron radiation
Authors: Yu Wei , Li B. W. , Yu M. Y. , He F. , Ishiguro S. , Horiuchi R.
Published: October 2005

An electron with an appropriate initial velocity injected into an oncoming, ultraintense circularly polarized laser pulse can execute a circular relativistic motion at the peak of the laser pulse. The circulating electron then radiates in the same manner as that in the storage ring of a conventional synchrotron source. Owing to the extremely small orbit radius, the laser-field synchrotron radiation thus generated can be a compact source of radiation pulses at short wavelength and short duration.
Study of the hyperradiance from phase-locked soliton oscillators
Authors: Lin Chang , Zhang Xiu-lian
Published: October 2005

The hyperradiance from phase-locked soliton oscillators is investigated by using a family of solutions for the unperturbed sine-Gordon equation. Analytical descriptions for the emitted power from phase-locked soliton oscillators have been obtained for the two magnetically coupled long Josephson junctions operated in single-fluxon modes. We derive an intact mathematical expression and some simulation results of space-time action for the theory for superradiance from phase-locked oscillators.
Deep level emission from high-power diode laser bars detected by multispectral infrared imaging
Authors: Kozlowska Anna , Wawrzyniak Piotr , Tomm Jens W. , Weik Fritz , Elsaesser Thomas
Published: October 2005

Broadband imaging thermography is applied to investigate the infrared (IR) emission from high-power diode laser bars. We demonstrate the capabilities of a multispectral imaging system that operates in two optical channels, the near IR at 1.5–2μm and the mid IR at 2.4–5.5μm. In the near-IR region, deep level luminescence of the device contributes significantly to the thermo-images. A complementary measurement of the IR emission spectrum shows a broad defect band with maxima at E1=0.94eV and E2=1.05eV. Analysis of IR transients in both spectral channels makes a distinction of thermal radiation and deep level emission possible. In the mid IR, thermal radiation dominates, allowing for an analysis of thermal properties of the device with measurement times of fractions of a second only. This makes imaging thermography highly attractive for device screening.
On the performance and surface passivation of type II InAs∕GaSb superlattice photodiodes for the very-long-wavelength infrared
Authors: Hood Andrew , Razeghi Manijeh , Aifer Edward H. , Brown Gail J.
Published: October 2005

We demonstrate very-long-wavelength infrared type II InAs∕GaSb superlattice photodiodes with a cutoff wavelength (λc,50%) of 17μm. We observed a zero-bias, peak Johnson noise-limited detectivity of 7.63×109cmHz1∕2∕W at 77 K with a 90%–10% cutoff width of 17 meV, and quantum efficiency of 30%. Variable area diode zero-bias resistance-area product (R0A) measurements indicated that silicon dioxide passivation increased surface resistivity by nearly a factor of 5, over unpassivated photodiodes, and increased overall R0A uniformity. The bulk R0A at 77 K was found to be 0.08Ωcm2, with RA increasing more than twofold at 25 mV reverse bias.
Diffuse reverberant acoustic wave spectroscopy with absorbing scatterers
Authors: de Rosny Julien , Debever Claire , Conti Stephane , Roux Philippe
Published: October 2005

Strong interest has been shown on the propagation of transient ultrasonic waves inside a high reverberating cavity filled with moving scatterers. A diffuse model theoretically justifies that the elastic cross section and the dynamic of the scatterers can be deduced from field correlations. Recently, experiments have been performed to also obtain the inelastic cross section of the scatterers. In this letter, we propose justifying this extension within the diffuse model. Experimental results obtained inside a 1.5 liter reverberant water tank at 900 kHz central working frequency with spheres made of materials of different absorption are presented.
X-ray ferromagnetic resonance spectroscopy
Authors: Boero G. , Rusponi S. , Bencok P. , Popovic R. S. , Brune H. , Gambardella P.
Published: October 2005

We present a method to measure continuous-wave ferromagnetic resonance (FMR) spectra based on the core-level absorption of circularly polarized x rays. The technique is demonstrated by using a monochromatic x-ray beam incident on an yttrium–iron–garnet sample excited by a microwave field at 2.47 GHz. FMR spectra are obtained by monitoring the x-ray absorption intensity at the photon energy corresponding to the maximum of the magnetic circular dichroism effect at the iron L2,3 edges as a function of applied magnetic field. The x-ray FMR signal is shown to be energy dependent, which makes the technique element sensitive and opens up new possibilities to perform element-resolved FMR in magnetic alloys and multilayers.
Large dielectric tunability and microwave properties of Mn-doped (Ba,Sr)TiO3 thin films
Authors: Yuan Z. , Lin Y. , Weaver J. , Chen X. , Chen C. L. , Subramanyam G. , Jiang J. C. , Meletis E. I.
Published: October 2005

Ferroelectric Ba0.6Sr0.4TiO3 thin films with 2% Mn additional doping were grown on (001) MgO by pulsed laser deposition. The microstructural studies from x-ray diffraction and transmission electron microscopy indicate that the films are highly epitaxial with c-axis oriented and atomic sharp interface. Dielectric property measurements at 1 MHz and room temperature reveal that the as-grown films have outstanding dielectric properties with large tunability of 80% at 40KV∕cm, very large dielectric constant value of 3800, and extra low dielectric loss of only 0.001. The high frequency (10–30 GHz) dielectric measurements demonstrate that the films are excellent in both dielectric property and very low dielectric insertion loss. Compared with the pure BSTO films or traditional doping, the additional doping of Mn in BSTO thin films can significantly improve the dielectric property of the as-grown films.
Air-bridged lateral growth of an Al0.98Ga0.02N layer by introduction of porosity in an AlN buffer
Authors: Wang T. , Bai J. , Parbrook P. J. , Cullis A. G.
Published: October 2005

We demonstrated air-bridged lateral growth of an Al0.98Ga0.02N layer with significant dislocation reduction by introduction of a porous AlN buffer underneath via metalorganic chemical vapor deposition. By modifying growth conditions, a porous AlN layer and an atomically flat AlN layer have been obtained for comparison, confirmed by atomic force microscopy. An Al0.98Ga0.02N layer was subsequently grown on both the porous AlN layer and the atomically flat AlN layer under identical conditions. Significant dislocation reduction was achieved for the Al0.98Ga0.02N layer grown on the porous AlN buffer layer, compared to the layer grown on the atomically flat AlN layer, as observed by transmission electron microscopy. Clear bubbles from the layer grown on the porous AlN buffer layer have been observed, while in contrast, there was not any bubble from the layer on the flat AlN buffer, confirming the mechanism of lateral growth for dislocation reduction. Asymmetric x-ray diffraction studies also indicated that the crystal quality was dramatically improved using the porous AlN buffer layer.
Current-induced asymmetric transport in La0.8Ca0.2MnO3 epitaxial thin films
Authors: Hu F. X. , Gao J.
Published: October 2005

We investigated the influence of a dc current on the transport properties in La0.8Ca0.2MnO3 epitaxial thin films grown on SrTiO3 substrates. A prominent finding is the appearance of asymmetric transport properties, like the behavior of p-n junctions, in a wide temperature range from 10Kto300K after the films were applied by a dc current over a threshold value. The asymmetric behavior resulted from a relative weak excitation is unstable and even spontaneously disappears. By optimizing excitation condition, the rectifyinglike behavior turns to be more significant and stable. Applying a small ac current could make the asymmetric transport collapse, subsequently, conventional symmetric transport behaviors appear. Phase separation and the coexistent ferromagnetic phases with different orbital order are taken into account in the interpretation of the observed phenomena.
Empirical correlation finding the role of temperature and particle size for nanofluid (Al2O3) thermal conductivity enhancement
Authors: Chon Chan Hee , Kihm Kenneth D. , Lee Shin Pyo , Choi Stephen U. S.
Published: October 2005

In this letter, we report an experimental correlation [Eqs. (1a) and (1b) or (1c)] for the thermal conductivity of Al2O3 nanofluids as a function of nanoparticle size (ranging from 11nmto150nm nominal diameters) over a wide range of temperature (from 21to71°C). Following the previously proposed conjecture from the theoretical point-of-view (Jang and Choi, 2004), it is experimentally validated that the Brownian motion of nanoparticles constitutes a key mechanism of the thermal conductivity enhancement with increasing temperature and decreasing nanoparticle sizes.
Influence of the dielectric constant of a polyvinyl phenol insulator on the field-effect mobility of a pentacene-based thin-film transistor
Authors: Jang Yunseok , Kim Do Hwan , Park Yeong Don , Cho Jeong Ho , Hwang Minkyu , Cho Kilwon
Published: October 2005

The mobility of pentacene thin-film transistors (TFTs) is correlated with the dielectric properties of their insulators. We varied the dielectric properties of the poly(4-vinylphenol) insulators of such TFTs by changing the molar ratio of the prepolymer/cross-linking agent while keeping the surface potential of the insulator surface constant. It was found that the field-effect mobility of the pentacene TFTs increases with increases in the dielectric constant of the insulators. A small increase in the dielectric constant of the insulator (a 20% increase, 3.6–4.3) was found to result in a dramatic increase in the field-effect mobility of pentacene TFTs by a factor of 3 (0.26to0.81cm2∕Vs).
Profiling of genes expressed in peripheral blood mononuclear cells predicts glucocorticoid sensitivity in asthma patients
Authors: Hakonarson Hakon , Bjornsdottir Unnur S. , Halapi Eva , Bradfield Jonathan , Zink Florian , Mouy Magali , Helgadottir Hildur , Gudmundsdottir Asta S. , Andrason Hjalti , Adalsteinsdottir Asdis E. , Kristjansson Kristleifur , Birkisson Illugi , Arnason Thor , Andresdottir Margret , Gislason David , Gislason Thorarinn , Gulcher Jeffrey R. , Stefansson Kari
Published: October 2005

Gene expression profiles were examined in freshly isolated peripheral blood mononuclear cells (PBMC) from two independent cohorts (training and test sets) of glucocorticoid (GC)-sensitive (n= 64) and GC-resistant (n= 42) asthma patients in search of genes that accurately predict responders and nonresponders to inhaled corticosteroids. A total of 11,812 genes were examined with high-density oligonucleotide microarrays in both resting PBMC (106 patients) and cells treatedin vitrowith IL-1β and TNF-α combined (88 patients), with or without GC. A total of 5,011 genes were expressed at significant levels in the PBMC, and 1,334 of those were notably up-regulated or down-regulated by IL-1β/TNF-α treatment. The expression changes of 923 genes were significantly reversed in GC responders in the presence of GC. The expression pattern of 15 of these 923 genes that most accurately separated GC responders (n= 26) from the nonresponders (n= 18) in the training set, based on the weighted voting algorithm, predicted the independent test set of equal size with 84% accuracy. The expression accuracy of these genes was confirmed by real-time-quantitative PCR, wherein 11 of the 15 genes predicted GC sensitivity at baseline with 84% accuracy, with one gene predicting at 81% in an independent cohort of 79 patients. We conclude that we have uncovered gene expression profiles in PBMC that predict clinical response to inhaled GC therapy with meaningful accuracy. Upon validation in an independent study, these results support the development of a diagnostic test to guide GC therapy in asthma patients.
Consequences of reproductive barriers for genealogical discordance in the European corn borer
Authors: Dopman Erik B. , Pérez Luisa , Bogdanowicz Steven M. , Harrison Richard G.
Published: October 2005

Speciation involves the origin of trait differences that limit or prevent gene exchange and ultimately results in daughter populations that form monophyletic or exclusive genetic groups. However, for recently diverged populations or species between which reproductive isolation is often incomplete, gene genealogies will be discordant, and most regions of the genome will display nonexclusive genealogical patterns. In these situations, genome regions for which one or both species are exclusive groups may mark the footprint of recent selective sweeps. Alternatively, such regions may include or be closely linked to “speciation genes,” genes involved in reproductive isolation. Therefore, comparisons of gene genealogies allow inferences about the genetic architectures of both reproductive isolation and adaptation. Contrasting genealogical relationships in sexually isolated pheromone strains of the European corn borer moth (
Ostrinia nubilalis
) demonstrate the relevance of this approach. Genealogies for five gene regions are discordant, and only one molecular marker, the sex-linked gene
Tpi
, has evidence for pheromone strain exclusivity.
Tpi
maps to a position on the sex chromosome that is indistinguishable from a major factor (
Pdd
) affecting differences in postdiapause development time. The major factor (
Resp
) determining male behavioral response to pheromone is also sex-linked, but maps 20-30 cM away. Exclusivity at
Tpi
may be a consequence of these linkage relationships because evidence from phenotypic variation in natural populations implicates both
Pdd
and
Resp
as candidates for genes involved in recent sweeps and/or reproductive isolation between strains.
Induction of a proinflammatory program in normal human thyrocytes by the
RET/PTC1
oncogene
Authors: Borrello Maria Grazia , Alberti Luisella , Fischer Andrew , Degl'Innocenti Debora , Ferrario Cristina , Gariboldi Manuela , Marchesi Federica , Allavena Paola , Greco Angela , Collini Paola , Pilotti Silvana , Cassinelli Giuliana , Bressan Paola , Fugazzola Laura , Mantovani Alberto , Pierotti Marco A.
Published: October 2005

Rearrangements of the
RET
receptor tyrosine kinase gene generating
RET
/
PTC
oncogenes are specific to papillary thyroid carcinoma (PTC), the most frequent thyroid tumor. Here, we show that the
RET
/
PTC1
oncogene, when exogenously expressed in primary normal human thyrocytes, induces the expression of a large set of genes involved in inflammation and tumor invasion, including those encoding chemokines (CCL2, CCL20, CXCL8, and CXCL12), chemokine receptors (CXCR4), cytokines (IL1B, CSF-1, GM-CSF, and G-CSF), matrix-degrading enzymes (metalloproteases and urokinase-type plasminogen activator and its receptor), and adhesion molecules (L-selectin). This effect is strictly dependent on the presence of the RET/PTC1 Tyr-451 (corresponding to RET Tyr-1062 multidocking site). Selected relevant genes (
CCL20
,
CCL2
,
CXCL8
,
CXCR4
,
L-selectin
,
GM-CSF
,
IL1B
,
MMP9
,
UPA
, and
SPP1
/
OPN
) were found up-regulated also in clinical samples of PTC, particularly those characterized by
RET
/
PTC
activation, local extrathyroid spread, and lymph node metastases, when compared with normal thyroid tissue or follicular thyroid carcinoma. These results, demonstrating that the
RET
/
PTC1
oncogene activates a proinflammatory program, provide a direct link between a transforming human oncogene, inflammation, and malignant behavior.
Drosophila
ATM and ATR checkpoint kinases control partially redundant pathways for telomere maintenance
Authors: Bi Xiaolin , Srikanta Deepa , Fanti Laura , Pimpinelli Sergio , Badugu RamaKrishna , Kellum Rebecca , Rong Yikang S.
Published: October 2005

In higher eukaryotes, the ataxia telangiectasia mutated (ATM) and ATM and Rad3-related (ATR) checkpoint kinases play distinct, but partially overlapping, roles in DNA damage response. Yet their interrelated function has not been defined for telomere maintenance. We discover in
Drosophila
that the two proteins control partially redundant pathways for telomere protection: the loss of ATM leads to the fusion of some telomeres, whereas the loss of both ATM and ATR renders all telomeres susceptible to fusion. The ATM-controlled pathway includes the Mre11 and Nijmegen breakage syndrome complex but not the Chk2 kinase, whereas the ATR-regulated pathway includes its partner ATR-interacting protein but not the Chk1 kinase. This finding suggests that ATM and ATR regulate different molecular events at the telomeres compared with the sites of DNA damage. This compensatory relationship between ATM and ATR is remarkably similar to that observed in yeast despite the fact that the biochemistry of telomere elongation is completely different in the two model systems. We provide evidence suggesting that both the loading of telomere capping proteins and normal telomeric silencing requires ATM and ATR in
Drosophila
and propose that ATM and ATR protect telomere integrity by safeguarding chromatin architecture that favors the loading of telomere-elongating, capping, and silencing proteins.
Hepatitis B small surface antigen particles are octahedral
Authors: Gilbert Robert J. C. , Beales Lucy , Blond Donatienne , Simon Martha N. , Lin Beth Y. , Chisari Francis V. , Stuart David I. , Rowlands David J.
Published: October 2005

The infectious component of hepatitis B (HB) virus (HBV), the Dane particle, has a diameter of ≈44 nm and consists of a double-layered capsid particle enclosing a circular, incomplete double-stranded DNA genome. The outer capsid layer is formed from the HB surface antigen (HBsAg) and lipid, whereas the inner layer is formed from the HB core Ag assembled into an icosahedral structure. During chronic infection HBsAg is expressed in large excess as noninfectious quasispherical particles and tubules with ≈22-nm diameter. Here, we report cryo-EM reconstructions of spherical HBsAg particles at ≈12-Å resolution. We show that the particles possess different diameters and have separated them into two predominant populations, both of which have octahedral symmetry. Despite their differing diameters, the two forms of the particle have the same mass and are built through conformational switching of the same building block, a dimer of HBsAg. We propose that this conformational switching, combined with interactions with the underlying core, leads to the formation of HBV Dane particles of different sizes, dictated by the symmetry of the icosahedral core.
Cyclophilin A is required for TRIM5α-mediated resistance to HIV-1 in Old World monkey cells
Authors: Berthoux Lionel , Sebastian Sarah , Sokolskaja Elena , Luban Jeremy
Published: October 2005

The peptidyl-prolyl isomerase cyclophilin A (CypA) embraces an exposed, proline-rich loop on HIV-1 capsid (CA) and renders reverse transcription complexes resistant to an antiviral activity in human cells. A CypA fusion with TRIM5 that is unique to New World owl monkeys also targets HIV-1 CA, but this interaction potently inhibits infection. A similar block to HIV-1 infection in Old World monkeys is attributable to the α isoform of the TRIM5 orthologue in these species. To determine whether HIV-1 restriction by Old World monkey TRIM5α is modulated by the CA-CypA interaction, RNA interference was used to disrupt CypA in cells from African green monkeys and rhesus macaques. HIV-1 infectivity increased in response to CypA knock-down to the same extent that it increased in response to TRIM5 knock-down. CypA knock-down eliminated the HIV-1 stimulatory effect of cyclosporin A (CsA), a competitive inhibitor of the CypA-CA interaction, or of CA mutants that block binding to CypA but caused no change in titer of retroviruses that don't interact with CypA. Simultaneous knock-down of both CypA and TRIM5 caused minimal additional increase in titer, suggesting that CypA inhibits HIV-1 replication in these cells because it is required for CA recognition by TRIM5α. Finally, CsA increased HIV-1 titer in otherwise nonrestrictive feline cells but only after these cells were transduced with Old World monkey TRIM5α. Thus, CypA is required for HIV-1 restriction by Old World monkey orthologues of TRIM5α.
Task-specific disruption of perceptual learning
Authors: Seitz Aaron R. , Yamagishi Noriko , Werner Birgit , Goda Naokazu , Kawato Mitsuo , Watanabe Takeo
Published: October 2005

For more than a century, the process of stabilization has been a central issue in the research of learning and memory. Namely, after a skill or memory is acquired, it must be consolidated before it becomes resistant to disruption by subsequent learning. Although it is clear that there are many cases in which learning can be disrupted, it is unclear when learning something new disrupts what has already been learned. Herein, we provide two answers to this question with the demonstration that perceptual learning of a visual stimulus disrupts or interferes with the consolidation of a previously learned visual stimulus. In this study, we trained subjects on two different hyperacuity tasks and determined whether learning of the second task disrupted that of the first. We first show that disruption of learning occurs between visual stimuli presented at the same orientation in the same retinotopic location but not for the same stimuli presented at retinotopically disparate locations or different orientations at the same location. Second, we show that disruption from stimuli in the same retinotopic location is ameliorated if the subjects wait for 1 h before training on the second task. These results indicate that disruption, at least in visual learning, is specific to features of the tasks and that a temporal delay of 1 h can stabilize visual learning. This research shows that visual learning is susceptible to disruption and elucidates the processes by which the brain can consolidate learning and thus protect what is learned from being overwritten.