bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Investigation of Physical and Geometrical Parameters in Close Binaries using the ASAS Database
Authors: Nedoroščik J. , Vaňko M. , Parimucha Š.
Published: April 2012

The main goal of this work was to find dependencies between Fourier coefficients, which were developed by light curve fitting with Fourier polynomials. The light curves were acquired from the ASAS database (All Sky Automated Survey). In this statistical research it was necessary to sort and modify these data, because light curves of eclipsing binaries are just part of a bigger database, which contains the light curves of pulsating variable stars, novas etc. It was required to phase and normalize all of our light curves, that it could be possible to use a program to fit light curves with Fourier coefficients. Thereafter, we were looking for relations between Fourier coefficients.
Long-Term Variability and Outburst Activity of FS Aurigae: Further Evidence for a Third Body in the System
Authors: Neustroev V. , Sjoberg G. , Tovmassian G. , Zharikov S. , Heras T. Arranz , Lake P. B. , Lane D. , Lubcke G. , Henden A. A.
Published: April 2012

FS Aurigae is famous for a variety of uncommon and puzzling periodic photometric and spectroscopic variabilities which do not fit well into any of the established sub-classes of cataclysmic variables. Here we present preliminary results of long-term monitoring of the system, conducted during the 2010-2011 observational season. We show that the long-term variability of FS Aur and the character of its outburst activity may be caused by variations in the mass transfer rate from the secondary star as the result of eccentricity modulation of a close binary orbit induced by the presence of a third body on a circumbinary orbit.
The Photometric Study of Neglected Short-Period Eclipsing Binary BS Vulpeculae
Authors: Zejda Miloslav , Mikulášek Zdeněk , Zhu Liying , Qian Shengbang , Liška Jiří
Published: April 2012

The preliminary results of a study of a neglected, relatively bright, short-periodic (P=0.48 d), near contact eclipsing binary BS Vulpeculae is given. We present our new complete (BVRI) light curves, and physical parameters of the system based on them, derived by the 2003 version of the Wilson–Van Hamme code.
Circumbinary Planets and the SOLARIS Project
Authors: Konacki Maciej , Sybilski Piotr , Kozłowski Stanisław K. , Ratajczak Milena , Hełminiak Krzysztof G.
Published: April 2012

Extrasolar planets in binary and multiple star systems have become a noticeable niche with about 50 planets among over 500 known. Here we however focus on a particular subset of exoplanets in binary star systems — circumbinary planets. They have the unique advantage that a search for circumbinary planets does also significantly contribute to the understanding of their parent stars. We review what is currently known about circumbinary planets and then introduce our two projects aimed at detecting circumbinary planets: The TATOOINE project to find circumbinary planets around non-eclipsing double-lined spectroscopic binary stars with precision radial velocities, and the SOLARIS project to detect circumbinary planets with the timing of eclipses of eclipsing binary stars. For the SOLARIS project, we were granted 2.6 million USD to establish a network of at least four robotic 0.5-m telescopes on three continents (Australia, Africa and South America) to carry out precision photometry of a sample of eclipsing binary stars. We expect that both projects will have a large impact also on the observational stellar astronomy.
Stellar Wobble Due to a Nearby Binary System
Authors: Morais M. H. M. , Correia A. C. M.
Published: April 2012

To date, there are several reported exoplanet detections within binary star systems. These findings are based on radial velocity data for the target star. However, the companion star could in turn have a companion of which we are not aware. We describe how this hidden binary system affects the radial velocity of the target star, mimicking a planet in some circumstances We also explain what can be done in practice in order to distinguish between these two effects.
Pipeline for Making Images of Gas Flows in Binary Stars
Authors: Richards Mercedes T. , Slobounov Elena , Conover Marshall , Fisher John , Cocking Alexander
Published: April 2012

The data collection and data analysis pipeline for the study and imaging of interacting binaries is outlined. This process includes the systematic collection of time-resolved spectra of individual systems, data reduction including subtraction of the stellar spectra, application of tomography codes to reveal images of the gas flows in 2D and 3D, comparison of the observed spectrum with synthetic spectra of the accretion disk and gas stream, and application of 3D visualization techniques.
Differential Rotation in Two RS CVn Systems: σ Gem and ζ And
Authors: Kővári Zsolt , Bartus János , Kriskovics Levente , Oláh Katalin , Vida Krisztián , Ribárik Orsolya , Strassmeier Klaus G.
Published: April 2012

The differentially rotating convective envelope is an indispensable element of the magnetic dynamo working in RS CVn-systems. Tidal coupling is responsible for maintaining fast rotation, and also the observed high level of magnetic activity. In this work, we compare the physical properties of two well known RS CVn-type binaries, that is the long-period system σ Gem and the ellipsoidal variable ζ And. For the comparison, we use the results obtained from processing time-series Doppler images. We also aim at understanding how differential rotation could be affected by tidal forces in such close binaries.
Polarimetry of Exoplanetary System CoRoT-2
Authors: Kostogryz N. M. , Yakobchuk T. M. , Vidmachenko A. P.
Published: April 2012

We present the results of modelling the polarization resulting from the planetary transits and stellar spots in the system Corot-2 using the Monte Carlo method. The planetary transit was estimated to produce a polarization maximum at the limb of ~5 × 10−6, adopting solar center-to-limb polarization. Assuming different parameters of the spots, we evaluated the flux and polarization changes due to the stellar activity.
Hot Stars with Winds: The CMFGEN Code
Authors: Hillier D. John
Published: April 2012

cmfgen is an atmosphere code developed to model the spectra of a variety of objects – O stars, Wolf-Rayet stars, luminous blue variables, A and B stars, central stars of planetary nebula, and supernovae. The principal computational aim of cmfgen is to determine the temperature and ionization structure of the atmosphere, and the atomic level populations. Toward this end, we have developed several different radiative transfer modules that (a) solve the transfer equation for spherical geometry in the comoving frame, (b) solve the static transfer equation in the plane parallel approximation without, or with, a vertical velocity field, (c) solve the static transfer code for a spherical atmosphere allowing for all relativistic terms, (d) solve the time-dependent spherical transfer equation to first order in v/c for a homologous expansion, and (e) solve the time-dependent spherical transfer equation allowing for all relativistic terms. To achieve consistency between the radiation field, temperature structure, and level populations we use a linearization technique. Line blanketing is accurately treated while complex photoionization cross-sections, containing numerous resonances, can also be handled. Spectra, for comparison with observation, are computed using cmf_flux. Several other auxiliary programs have also been developed – these include diagnostic tools as well as programs that allow the effect on spectra of rotation and departures from spherical geometry to be investigated. In this presentation we will briefly describe cmfgen and auxiliary codes.
Comparison of Limb-Darkening Laws from Plane-Parallel and Spherically-Symmetric Model Stellar Atmospheres
Authors: Neilson Hilding R.
Published: April 2012

Limb-darkening is a fundamental constraint for modeling eclipsing binary and planetary transit light curves. As observations, for example from Kepler, CoRot, and Most, become more precise then a greater understanding of limb-darkening is necessary. However, limb-darkening is typically modeled as simple parameterizations fit to plane-parallel model stellar atmospheres that ignores stellar atmospheric extension. In this work, I compute linear, quadratic and four-parameter limb-darkening laws from grids of plane-parallel and spherically-symmetric model stellar atmospheres in a temperature and gravity range representing stars evolving on the Red Giant branch. The limb-darkening relations for each geometry are compared and are found to fit plane-parallel models much better than the spherically-symmetric models. Assuming that limb-darkening from spherically-symmetry model atmospheres are more physically representative of actual stellar limb-darkening than plane-parallel models, then these limb-darkening laws will not fit the limb of a stellar disk leading to errors in a light curve fit. This error will increase with a star's atmospheric extension.
Hydrodynamics of Decretion Disks of Rapidly Rotating Stars
Authors: Kurfürst Petr
Published: April 2012

During the evolution of hot stars, the equatorial rotational velocity can approach its critical value. Further increase in rotation rate is not allowed, consequently mass and angular momentum loss is needed to keep the star near and below its critical rotation. The matter ejected from the equatorial surface forms the outflowing viscous decretion disk. Models of outflowing disks of hot stars have not yet been elaborated in detail, although it is clear that such disks can significantly influence the evolution of rapidly rotating stars. One of the most important features is the disk radial temperature variation because the results will help us to specify the mass and angular momentum loss of rotating stars via decretion disks.
Multi-dimensional Modeling of Massive Binary Interaction in Eta Carinae
Authors: Groh J. H.
Published: April 2012

We summarize recent efforts from our group to constrain the nature of both stars in the Eta Carinae binary system and its orbital parameters by studying the influence of the companion star on the spectrum of the primary star. We find that the cavity in the dense wind of the primary star strongly affects multi-wavelength diagnostics such as the ultraviolet spectrum, the optical hydrogen lines, and the shape of the near-infrared continuum region. These diagnostics have been previously interpreted as requiring a latitude-dependent wind generated by a fast-rotating primary star, but the effects of the companion on them provide tenuous evidence that the primary star is a rapid rotator.
Creation of Neutral Disk-like Zone Around the Active Hot Star in Symbiotic Binaries
Authors: Cariková Zuzana , Skopal Augustin
Published: April 2012

We investigated the ionization structure of symbiotic binaries during their active phases. We found that a neutral disk-like zone around the hot star can be created as a result of its enhanced wind and fast, 200 - 300 km s−1, rotation. Calculated column densities of the neutral hydrogen atoms throughout the neutral zone and emission measures of the ionized part of the wind from the hot star are in a good agreement with those derived from observations.
Advances in Modeling Eclipsing Binary Stars in the Era of Large All-Sky Surveys with EBAI and PHOEBE
Authors: Prša A. , Guinan E. F. , Devinney E. J. , Degroote P. , Bloemen S. , Matijevič G.
Published: April 2012

With the launch of NASA's Kepler mission, stellar astrophysics in general, and the eclipsing binary star field in particular, has witnessed a surge in data quality, interpretation possibilities, and the ability to confront theoretical predictions with observations. The unprecedented data accuracy and an essentially uninterrupted observing mode of over 2000 eclipsing binaries is revolutionizing the field. Amidst all this excitement, we came to realize that our best models to describe the physical and geometric properties of binaries are not good enough. Systematic errors are evident in a large range of binary light curves, and the residuals are anything but Gaussian. This is crucial because it limits us in the precision of the attained parameters. Since eclipsing binary stars are prime targets for determining the fundamental properties of stars, including their ages and distances, the penalty for this loss of accuracy affects other areas of astrophysics as well. Here, we propose to substantially revamp our current models by applying the lessons learned while reducing, modeling, and analyzing Kepler data.
Application of the GDDSYN Method in the Era of KEPLER, CoRoT, MOST and BRITE
Authors: Mochnacki Stefan W.
Published: April 2012

The precision of observations using observatories in space exceeds by a factor of 100 the accuracy of the light curve and line profile synthesis methods developed decades ago. Furthermore, physical effects too small to detect using ground based observations, such as aberration and Doppler beaming, become important when observing from space.

The GDDSYN method, developed by Hendry and Mochnacki, is both accurate and efficient, and is useful in the new context of space-based observations. Using a geodesic distribution of triangular surface elements varying little in size, it provides an alternative to the Wilson-Devinney code used at the heart of PHOEBE, and is adaptable to the new physical effects which are now observable. Tests and improvements are discussed.
New Light Curve Analysis for Large Numbers of Eclipsing Binaries III. SMC and Galactic Center
Authors: Kang Young-Woon , Hong Keong Soo , Rittipruk Pakakaew
Published: April 2012

We improved the method of light curve analysis for large numbers of eclipsing binaries. Current methods require a week to analyze the light curves of an eclipsing binary for its physical and orbital parameters. Therefore, we developed a new method to treat large numbers of light curves of eclipsing binaries. We tested the new method by analyzing more than 14 hundred light curves and 9 hundred light curves discovered by OGLE in the Small Magellanic Cloud and Galactic center, respectively.
Modelling Light Curves of Systems with Non-Circular Accretion Disks: KU Cyg
Authors: Zola S. , Szymanski T.
Published: April 2012

We present a code which can be used to simulate the light curve of a binary system harbouring a non-circular accretion disk, and show that such a system geometry can produce light curves with asymmetric minima and different heights of the maxima. We have applied this code to check for the possible existence of a non-circular accretion disk, as suggested by Smak & Plavec (1997), in the Algol-type binary KU Cyg. We compare the best solutions for two sets of multicolour light curves, obtained within circular and non-circular disk models.
The Long History of the Rossiter-McLaughlin Effect and its Recent Applications
Authors: Albrecht Simon
Published: April 2012

In this talk I will review the Rossiter-McLaughlin (RM) effect; its history, how it manifests itself during stellar eclipses and planetary transits, and the increasingly important role its measurements play in guiding our understanding of the formation and evolution of close binary stars and exoplanet systems.
The BANANA Survey: Spin-Orbit Alignment in Binary Stars
Authors: Albrecht Simon , Winn J. N. , Fabrycky D. C. , Torres G. , Setiawan J.
Published: April 2012

Binaries are not always neatly aligned. Previous observations of the DI Herculis system showed that the spin axes of both stars are highly inclined with respect to one another and the orbital axis. Here, we report on our ongoing survey to measure relative orientations of spin-axes in a number of eclipsing binary systems.

These observations will hopefully lead to new insights into star and planet formation, as different formation scenarios predict different degrees of alignment and different dependencies on the system parameters. Measurements of spin-orbit angles in close binary systems will also create a basis for comparison for similar measurements involving close-in planets.
VO-KOREL: A Fourier Disentangling Service of the Virtual Observatory
Authors: Škoda Petr , Hadrava Petr , Fuchs Jan
Published: April 2012

VO-KOREL is a web service exploiting the technology of the Virtual Observatory for providing astronomers with the intuitive graphical front-end and distributed computing back-end running the most recent version of the Fourier disentangling code KOREL.

The system integrates the ideas of the e-shop basket, conserving the privacy of every user by transfer encryption and access authentication, with features of laboratory notebook, allowing the easy housekeeping of both input parameters and final results, as well as it explores a newly emerging technology of cloud computing.

While the web-based front-end allows the user to submit data and parameter files, edit parameters, manage a job list, resubmit or cancel running jobs and mainly watching the text and graphical results of a disentangling process, the main part of the back-end is a simple job queue submission system executing in parallel multiple instances of the FORTRAN code KOREL. This may be easily extended for GRID-based deployment on massively parallel computing clusters.

The short introduction into underlying technologies is given, briefly mentioning advantages as well as bottlenecks of the design used.
Towards a Theory for the Atmospheres, Structure, and Evolution of Giant Exoplanets
Authors: Burrows Adam
Published: April 2012

In this short review, I summarize some of the salient features of the emerging theory of exoplanets in general, and of giant exoplanets in particular. A focus is on the characterization of transiting planets at primary and secondary eclipse, but various other related topics are covered, if only briefly. A theme that clearly emerges is that a vibrant new science of comparative exoplanetology is being born.
Variability of Young Massive Stars in the Arches Cluster
Authors: Markakis K. , Bonanos A. Z. , Pietrzynski G. , Macri L. , Stanek K. Z.
Published: April 2012

We present preliminary results of the first near-infrared variability study of the Arches cluster, using adaptive optics data from NIRI/Gemini and NACO/VLT. The goal is to discover eclipsing binaries in this young (2.5 ± 0.5 Myr), dense, massive cluster for which we will determine accurate fundamental parameters with subsequent spectroscopy. Given that the Arches cluster contains more than 200 Wolf-Rayet and O-type stars, it provides a rare opportunity to determine parameters for some of the most massive stars in the Galaxy.
Photoionization Models of the Eskimo Nebula: Evidence for a Binary Central Star?
Authors: Danehkar A. , Frew D. J. , Parker Q. A. , De Marco O.
Published: April 2012

The ionizing star of the planetary nebula NGC 2392 is too cool to explain the high excitation of the nebular shell, and an additional ionizing source is necessary. We use photoionization modeling to estimate the temperature and luminosity of the putative companion. Our results show it is likely to be a very hot (Teff ≃ 250 kK), dense white dwarf. If the stars form a close binary, they may merge within a Hubble time, possibly producing a Type Ia supernova.
Magnetic Activity of Two Similar Subgiants in Binaries with Very Different Mass Ratios: EI Eri and V711 Tau
Authors: Oláh Katalin , Kővári Zsolt , Vida Krisztián , Strassmeier Klaus G.
Published: April 2012

We use more than three decades-long photometry to study the activity patterns on the two fast-rotating subgiant components in EI Eri (G5IV) and V711 Tau (K1IV). From yearly mean rotational periods from the light curves, we find that EI Eri, with well-measured solar-type differential rotation, always has spots from the equator to high latitudes. The measured differential rotation of V711 Tau is controversial, and in any case is very small. The spots on the K1IV star in V711 Tau seem to be tidally locked. The physical parameters of the two systems are similar, with one remarkable difference: EI Eri has a low mass M4-5 dwarf companion, whereas V711 Tau has a G5V star in the system, thus their mass centers are in very different positions. This may modify the whole internal structure of the active stars, causing marked differences in their surface features.
Structure Coefficients for Use in Stellar Analysis
Authors: Inlek Gulay , Budding Edwin
Published: April 2012

We give new values of the structural coefficients ηj, and related quantities, for realistic models of distorted stars in close binary systems. Our procedure involves numerical integration of Radau's equation for detailed structural data for stellar models taken from the EZWeb compilation of the Department of Astronomy, University of Wisconsin-Madison.
Gas Dynamic Simulations of Inner Regions of Protoplanetary Disks in Young Binary Stars
Authors: Fateeva A. M. , Bisikalo D. V. , Kaygorodov P. V. , Sytov A. Y.
Published: April 2012

We have carried out 2D and 3D numerical simulations (Kaigorodov et al 2010, Fateeva et al. 2011, Sytov et al. 2011) of accretion processes in binary T Tauri stars (TTSs) DQ Tau, UZ Tau E, V4046 Sgr, GW Ori, RoXs 42C using a finite-difference Roe-Osher-Einfeld TVD scheme. The morphology of the flow pattern for UZ Tau E is shown in Fig. 1 (left panel). The flow structure includes accretion disks surrounding the components, bow-shocks in front of both the components, a shock wave (“bridge”) between the circumstellar accretion disks and a gap containing rarefied gas in the inner part of the protoplanetary disk.
The Coming Water Crisis: A Common Concern of Humankind
Authors: Weiss Edith Brown
Published: April 2012

This essay argues that fresh water, its availability and use, should now be recognized as ‘a common concern of humankind’, much as climate change was recognized as a ‘common concern of humankind’ in the1992United Nations Framework Convention on Climate Change, and conservation of biodiversity was recognized as a ‘common concern of humankind’ in the1992Convention on Biological Diversity. This would respond to the many linkages between what happens in one area with the demand for and the supply of fresh water in other areas. It would take into account the scientific characteristics of the hydrological cycle, address the growing commodification of water in the form of transboundary water markets and virtual water transfers through food production and trade, and respect the efforts to identify a human right to water.
Impact of reduced near‐field entrainment of overpressured volcanic jets on plume development
Authors: Saffaraval Farhad , Solovitz Stephen A. , Ogden Darcy E. , Mastin Larry G.
Published: April 2012

Volcanic plumes are often studied using one‐dimensional analytical models, which use an empirical entrainment ratio to close the equations. Although this ratio is typically treated as constant, its value near the vent is significantly reduced due to flow development and overpressured conditions. To improve the accuracy of these models, a series of experiments was performed using particle image velocimetry, a high‐accuracy, full‐field velocity measurement technique. Experiments considered a high‐speed jet with Reynolds numbers up to 467,000 and exit pressures up to 2.93 times atmospheric. Exit gas densities were also varied from 0.18 to 1.4 times that of air. The measured velocity was integrated to determine entrainment directly. For jets with exit pressures near atmospheric, entrainment was approximately 30% less than the fully developed level at 20 diameters from the exit. At pressures nearly three times that of the atmosphere, entrainment was 60% less. These results were introduced into Plumeria, a one‐dimensional plume model, to examine the impact of reduced entrainment. The maximum column height was only slightly modified, but the critical radius for collapse was significantly reduced, decreasing by nearly a factor of two at moderate eruptive pressures.
Distal deposition of tephra from the Eyjafjallajökull 2010 summit eruption
Authors: Stevenson J. A. , Loughlin S. , Rae C. , Thordarson T. , Milodowski A. E. , Gilbert J. S. , Harangi S. , Lukács R. , Højgaard B. , Árting U. , Pyne‐O'Donnell S. , MacLeod A. , Whitney B. , Cassidy M.
Published: April 2012

The 2010 Eyjafjallajökull lasted 39 days and had 4 different phases, of which the first and third (14–18 April and 5–6 May) were most intense. Most of this period was dominated by winds with a northerly component that carried tephra toward Europe, where it was deposited in a number of locations and was sampled by rain gauges or buckets, surface swabs, sticky‐tape samples and air filtering. In the UK, tephra was collected from each of the Phases 1–3 with a combined range of latitudes spanning the length of the country. The modal grain size of tephra in the rain gauge samples was 25 μm, but the largest grains were 100 μm in diameter and highly vesicular. The mass loading was equivalent to 8–218 shards cm−2, which is comparable to tephra layers from much larger past eruptions. Falling tephra was collected on sticky tape in the English Midlands on 19, 20 and 21st April (Phase 2), and was dominated by aggregate clasts (mean diameter 85 μm, component grains <10 μm). SEM‐EDS spectra for aggregate grains contained an extra peak for sulphur, when compared to control samples from the volcano, indicating that they were cemented by sulphur‐rich minerals e.g. gypsum (CaSO4⋅H2O). Air quality monitoring stations did not record fluctuations in hourly PM10 concentrations outside the normal range of variability during the eruption, but there was a small increase in 24‐hour running mean concentration from 21–24 April (Phase 2). Deposition of tephra from Phase 2 in the UK indicates that transport of tephra from Iceland is possible even for small eruption plumes given suitable wind conditions. The presence of relatively coarse grains adds uncertainty to concentration estimates from air quality sensors, which are most sensitive to grain sizes <10 μm. Elsewhere, tephra was collected from roofs and vehicles in the Faroe Islands (mean grain size 40 μm, but 100 μm common), from rainwater in Bergen in Norway (23–91 μm) and in air filters in Budapest, Hungary (2–6 μm). A map is presented summarizing these and other recently published examples of distal tephra deposition from the Eyjafjallajökull eruption. It demonstrates that most tephra deposited on mainland Europe was produced in the highly explosive Phase 1 and was carried there in 2–3 days.
Scale interactions near the foothills of Himalayas during CAIPEEX
Authors: Prabha Thara V. , Karipot Anandakumar , Axisa D. , Kumari B. Padma , Maheskumar R. S. , Konwar M. , Kulkarni J. R. , Goswami B. N.
Published: April 2012

Scale interactions associated with small scale (<100 km) dynamics might play a crucial role in the distribution of aerosol in the Himalayan foothills region. Turbulence measurements from a horizontal flight path during Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) are used to illustrate the scale interactions in the vertically sheared flow below the high‐level subtropical westerly jet, which is important in the transport of pollution. Data analysis reveals the three dimensional property of large eddies that scale 10–12 km near the slopes, which could bring pollution from the valley to the Tibetan Plateau through a circulation adhering to the slopes. This circulation has a subsidence region away from the slopes and may also contribute to the buildup of pollution in elevated layers over the Plains. The vertical velocity and temperature spectra from research flight data showed clear indications of (−5/3) slope in the mesoscale range. The isotropic behavior of the velocity spectra was noticed for cloud‐free traverses, while this behavior is distorted for cloudy conditions with the enhancement of energy at smaller scales as well as with low frequency gravity wave generation. A high‐resolution cloud allowing model simulation over the flight path is used to examine the representation of these dynamical interactions in the numerical model. Based on the analysis of observational data and model inferences, a conceptual understanding of the flow in the region close to the foot hills and its role in the distribution of aerosol and cloud condensation nuclei is presented.
Recent changes in tropospheric water vapor over the Arctic as assessed from radiosondes and atmospheric reanalyses
Authors: Serreze Mark C. , Barrett Andrew P. , Stroeve Julienne
Published: April 2012

Changes in tropospheric water vapor over the Arctic are examined for the period 1979 to 2010 using humidity and temperature data from nine high latitude radiosonde stations north of 70°N with nearly complete records, and from six atmospheric reanalyses, emphasizing the three most modern efforts, MERRA, CFSR and ERA‐Interim. Based on comparisons with the radiosonde profiles, the reanalyses as a group have positive cold‐season humidity and temperature biases below the 850 hPa level and consequently do not capture observed low‐level humidity and temperature inversions. MERRA has the smallest biases. Trends in column‐integrated (surface to 500 hPa) water vapor (precipitable water) computed using data from the radiosondes and from the three modern reanalyses at the radiosonde locations are mostly positive, but magnitudes and statistical significance vary widely between sites and seasons. Positive trends in precipitable water from MERRA, CFSR and ERA‐Interim, largest in summer and early autumn, dominate the northern North Atlantic, including the Greenland, Norwegian and Barents seas, the Canadian Arctic Archipelago and (on the Pacific side) the Beaufort and Chukchi seas. This pattern is linked to positive anomalies in air and sea surface temperature and negative anomalies in end‐of‐summer sea ice extent. Trends from ERA‐Interim are weaker than those from either MERRA or CFSR. As assessed for polar cap averages (the region north of 70°N), MERRA, CFSR and ERA‐Interim all show increasing surface‐500 hPa precipitable over the analysis period encompassing most months, consistent with increases in 850 hPa air temperature and 850 hPa specific humidity. Data from all of the reanalyses point to strong interannual and decadal variability. The MERRA record in particular shows evidence of artifacts likely introduced by changes in assimilation data streams. A focus on the most recent decade (2001–2010) reveals large differences between the three reanalyses in the vertical structure of specific humidity and temperature anomalies.
Seasonal to decadal scale variations in the surface velocity of Jakobshavn Isbrae, Greenland: Observation and model‐based analysis
Authors: Joughin Ian , Smith Ben E. , Howat Ian M. , Floricioiu Dana , Alley Richard B. , Truffer Martin , Fahnestock Mark
Published: April 2012

Using new data, we build upon the nearly two‐decade long record of observations from Jakobshavn Isbrae to investigate the processes driving its dynamic evolution. While winter flow speed has not increased substantially over the last three winters, there remains a strong seasonal variation in flow speed that coincides with a cycle of summer thinning and winter thickening. We relate changes in glacier speed to geometry through variations in basal traction and horizontal stresses, using ice‐flow models constrained by satellite and airborne observations. These results suggest that the bed provides little flow resistance along the main trough within about 20 km of the terminus. While the loss of buttressing from the retreat of grounded and floating ice likely contributed to the initial speedup, other processes are of comparable significance at seasonal to decadal time scales. From analysis of the models, we hypothesize that thinning‐induced change in basal effective pressure is the dominant process influencing near‐terminus behavior, while diffusive processes drive the upstream response. The apparent need for the terminus to thin to near flotation before it can calve may limit the rate at which retreat occurs. Our analysis of the processes controlling the speed suggests little potential for further large acceleration. Thinning and elevated speeds may continue at rates similar to present, however, putting the glacier on course to retreat to the head of its deep trough in about a century, at which point it likely would stabilize with a thinner terminus.
Persistence of soil organic matter in eroding versus depositional landform positions
Authors: Berhe Asmeret Asefaw , Harden Jennifer W. , Torn Margaret S. , Kleber Markus , Burton Sarah D. , Harte John
Published: April 2012

Soil organic matter (SOM) processes in dynamic landscapes are strongly influenced by soil erosion and sedimentation. We determined the contribution of physical isolation of organic matter (OM) inside aggregates, chemical interaction of OM with soil minerals, and molecular structure of SOM in controlling storage and persistence of SOM in different types of eroding and depositional landform positions. By combining density fractionation with elemental and spectroscopic analyses, we showed that SOM in depositional settings is less transformed and better preserved than SOM in eroding landform positions. However, which environmental factors exert primary control on storage and persistence of SOM depended on the nature of the landform position considered. In an annual grassland watershed, protection of SOM by physical isolation inside aggregates and chemical association of organic matter (complexation) with soil minerals, as assessed by correlation with radiocarbon concentration, were more effective in the poorly drained, lowest‐lying depositional landform positions, compared to well‐drained landform positions in the upper parts of the watershed. Results of this study demonstrated that processes of soil erosion and deposition are important mechanisms of long‐term OM stabilization.
Improving operational plume forecasts
Authors: Balcerak Ernie
Published: April 2012

Forecasting how plumes of particles, such as radioactive particles from a nuclear disaster, will be transported and dispersed in the atmosphere is an important but computationally challenging task. During the Fukushima nuclear disaster in Japan, operational plume forecasts were produced each day, but as the emissions continued, previous emissions were not included in the simulations used for forecasts because it became impractical to rerun the simulations each day from the beginning of the accident.Draxler and Rolph examine whether it is possible to improve plume simulation speed and flexibility as conditions and input data change. The authors use a method known as a transfer coefficient matrix approach that allows them to simulate many radionuclides using only a few generic species for the computation. Their simulations work faster by dividing the computation into separate independent segments in such a way that the most computationally time consuming pieces of the calculation need to be done only once. This makes it possible to provide real‐time operational plume forecasts by continuously updating the previous simulations as new data become available. They tested their method using data from the Fukushima incident to show that it performed well. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2011JD017205, 2012)
Sexual Functioning and Obesity: A Review
Authors: Kolotkin Ronette L. , Zunker Christie , Østbye Truls
Published: April 2012

We review the literature on the relationship between obesity and sexual functioning. Eleven population‐based studies, 20 cross‐sectional non‐population‐based studies, and 16 weight loss studies are reviewed. The consistency of findings suggests that the relationship between obesity and reduced sexual functioning is robust, despite diverse methods, instruments, and settings. In most population‐based studies, erectile dysfunction (ED) is more common among obese men than among men of recommended weight. Studies of patients in clinical settings often include individuals with higher degrees of obesity, with most studies showing a relationship between obesity and lower levels of sexual functioning, especially ED. The few studies that include both genders generally report more problems among women. Most studies of patients with comorbidities associated with obesity also find an association between obesity and reduced sexual functioning. Most weight loss studies demonstrate improvement in sexual functioning concurrent with weight reduction despite varying study designs, weight loss methods, and follow‐up periods. We recommend that future studies (i) investigate differences and similarities between men and women with respect to obesity and sexual functioning, (ii) use instruments that go beyond the assessment of sexual dysfunction to include additional concepts such as sexual satisfaction, interest, and arousal and, (iii) assess how and the degree to which obese individuals are affected by sexual difficulties. Given the high prevalence of obesity and the inverse association between body mass and sexual functioning, we also recommend that sexual functioning should be more fully addressed by clinicians, both in general practice and in weight loss programs.
Cultural Safety and the Curriculum: Recommendations for Global Practice
Authors: Penn Claire
Published: April 2012

The world is changing and so are our caseloads. In the context of increasing cultural and linguistic diversity, clinicians and educators face multiple, complex challenges. We should be able to develop the skills and attitudes needed to greet such diversity, adopt new techniques that allow for ecologically valid service delivery, provide relevant and ethical service with confidence and sensitivity, recognize the influence of culture on the disorders we treat, and understand both facilitators and barriers to care in multiple clinical contexts.
Rheology of fluids measured by correlation force spectroscopy
Authors: Radiom Milad , Robbins Brian , Honig Christopher D. F. , Walz John Y. , Paul Mark R. , Ducker William A.
Published: April 2012

We describe a method, correlation force spectrometry (CFS), which characterizes fluids through measurement of the correlations between the thermally stimulated vibrations of two closely spaced micrometer-scale cantilevers in fluid. We discuss a major application: measurement of the rheological properties of fluids at high frequency and high spatial resolution. Use of CFS as a rheometer is validated by comparison between experimental data and finite element modeling of the deterministic ring-down of cantilevers using the known viscosity of fluids. The data can also be accurately fitted using a harmonic oscillator model, which can be used for rapid rheometric measurements after calibration. The method is non-invasive, uses a very small amount of fluid, and has no actively moving parts. It can also be used to analyze the rheology of complex fluids. We use CFS to show that (non-Newtonian) aqueous polyethylene oxide solution can be modeled approximately by incorporating an elastic spring between the cantilevers.
A characteristic function to estimate the longitudinal dispersion coefficient in surface water flows over porous media
Authors: Nofuentes M. , Polo M. J.
Published: April 2012

One-dimensional modelling of solute transport in shallow water flows relies on an accurate approximation of the longitudinal dispersion coefficient, E, especially under transient conditions of the water flow during the solute residence time. Previous approaches have used expressions (e.g., the Rutherford equation) that allow the inclusion of spatiotemporal variability of E during the transport process, but their accuracy is reduced in marked transient regimes since the data were obtained from experimental work in rivers. This work proposes a different approach from experimental work with slow, shallow flows over porous media in fertigation essays, and provides us with a simple, parametric sigmoid function to estimate a priori effective values of E from simple measurements of flow characteristics and variables. The results have been successfully validated and compared to the Rutherford equation approach. Furthermore, the methodology to develop this characteristic function can be easily adapted for application in other practical cases.
Controlling light propagation with nanowires
Authors: Peng Y. , Kempa K.
Published: April 2012

We study the interaction of electromagnetic waves (EM) with metallic nanowire systems for frequencies not far from the surface plasma frequency (polaritonic range). We employ calculation and simulation to show that when excited at one end with axially polarized EM waves, nanowires can function as efficient waveguides of surface plasmon polaritons (SPPs). From the Fabry-Perot resonances of standing SPP waves, we study their dispersion relation and show that for a vanishing SPP wavelength it is identical to that for a planar metallic surface. Nanowire systems can be employed in various nanophotonic applications, and we assess this potential by studying propagation characteristics of these nano-waveguides and their interactions.
Perpendicular coupling to in-plane photonics using arc waveguides fabricated via two-photon polymerization
Authors: Lee Chee-Wei , Pagliara Stefano , Keyser Ulrich , Baumberg Jeremy J.
Published: April 2012

We demonstrate the concept of vertically standing arc waveguides to couple normally incident light into the plane of a photonic circuit or sensor array. The simple one-step direct write fabrication uses a low power picosecond microchip laser for two-photon polymerization with high-speed and low-cost. Arc waveguides with different arc radii and waveguide port diameters are obtained, with insertion loss down to 1.5 dB. This demonstration of a distinctly different architecture employing unsupported arc waveguides adds another dimension to photonic integration and opens up applications for environmental sensors, integrated microfluidics, bio-assay chips, as well as offering an alternate way of input/output-coupling to planar waveguides.
Chemical potential perturbation: Extension of the method to lattice sum treatment of intermolecular potentials
Authors: Moore Stan G. , Wheeler Dean R.
Published: April 2012

The recently developed chemical potential perturbation (CPP) method [S. G. Moore and D. R. Wheeler, J. Chem. Phys. 134, 114514 (2011)10.1063/1.3561865] is extended to the lattice (Ewald) sum treatment of intermolecular potentials. The CPP method predicts chemical potentials for a range of composition points using the local (position-dependent) pressure tensor of an inhomogeneous system. When computing the local pressure tensor, one can use the Irving-Kirkwood (IK) or Harasima (H) contours of distributing the pressure. We compare these two contours and show that for a planar interface, the homogeneous pressure and resulting chemical potential can be approximated with the CPP method using either the IK or the H contour, though with the lattice sum method the H contour has much greater computational efficiency. The proposed methods are validated by calculating the chemical potentials of the Lennard-Jones fluid and extended simple point-charge (SPC/E) water, and results show a high level of agreement with respective equations of state.
Phase diagram of magnetic domain walls in spin valve nano-stripes
Authors: Rougemaille N. , Uhlíř V. , Fruchart O. , Pizzini S. , Vogel J. , Toussaint J. C.
Published: April 2012

We investigate numerically the transverse versus vortex phase diagram of head-to-head domain walls in Co/Cu/Py spin valve nano-stripes (Py: permalloy), in which the Co layer is mostly single domain while the Py layer hosts the domain wall. The range of stability of the transverse wall is shifted towards larger thickness compared to single Py layers, due to a magnetostatic screening effect between the two layers. An approached analytical scaling law is derived, which reproduces faithfully the phase diagram.
Spatial displacement correlations in polymeric systems
Authors: Puosi F. , Leporini D.
Published: April 2012

The spatial correlations of the monomer displacements are studied via molecular-dynamics simulations of a melt of fully flexible, unentangled polymer chains with different length, interacting potential, density, and temperature. Both the scalar and the vector characters of the correlations are considered and their extension quantified in terms of suitable dynamical correlation lengths. Displacements performed at both short, i.e., vibrational, and long times, i.e., comparable to the structural relaxation time, are investigated. On both time scales the spatial correlations are modulated according to the radial distribution function g(r) to an extent which is determined by the character of the correlations, the time scale of the displacements and the structural slowing down. The spatial correlations of the short-time displacements have clear directional character. The modulus correlations of the long-time displacements are more marked, especially for sluggish states. Analogous findings are found by experiments on colloids. By inspecting the dynamical heterogeneities of states with slowed-down dynamics, it is observed that fast monomers exhibit correlations which are stronger and more differing from the bulk than the slow ones. It is shown that states with identical average vibrational monomer displacement exhibit identical spatial correlations of the monomer displacements pertaining to the subsets of the fast and the slow monomers characterizing both the short-time and the long-time dynamical heterogeneities.
Anisotropic hot electron emission from fullerenes
Authors: Johansson J. O. , Fedor J. , Goto M. , Kjellberg M. , Stenfalk J. , Henderson G. G. , Campbell E. E. B. , Hansen K.
Published: April 2012

Photoelectron spectra for fullerenes C60 and C70 ionized using 800 nm laser pulses with pulse durations from 120 to 1000 fs show thermal electron kinetic energy distributions but they also exhibit angular anisotropy with respect to the laser light polarization. The effective temperature of electrons, measured along the laser polarization direction, is significantly higher than in the perpendicular direction. We explain this observation by considering that the emission of the thermal electrons is uncorrelated with the phase of the laser pulse, unlike directly ionized electrons, and, depending on the time of emission, they may experience an additional “kick” from the vector potential of the laser field when they are emitted from the molecule.
Role of three-body interactions in formation of bulk viscosity in liquid argon
Authors: Lishchuk S. V.
Published: April 2012

With the aim of locating the origin of discrepancy between experimental and computer simulation results on bulk viscosity of liquid argon, a molecular dynamic simulation of argon interacting via ab initio pair potential and triple-dipole three-body potential has been undertaken. Bulk viscosity, obtained using Green-Kubo formula, is different from the values obtained from modeling argon using Lennard-Jones potential, the former being closer to the experimental data. The conclusion is made that many-body inter-atomic interaction plays a significant role in formation of bulk viscosity.
Reversible switching of room temperature ferromagnetism in CeO2-Co nanoparticles
Authors: Sacanell J. , Paulin M. A. , Ferrari V. , Garbarino G. , Leyva A. G.
Published: April 2012

We investigated the reversible ferromagnetic (FM) behavior of pure and Co doped CeO2 nanopowders. The as-sintered samples displayed an increasing paramagnetic contribution upon Co doping. Room temperature FM is obtained simply by performing thermal treatments in vacuum at temperatures as low as 500 °C and it can be switched off by performing thermal treatments in oxidizing conditions. The FM contribution is enhanced as we increase the time of the thermal treatment in vacuum. Those systematic experiments establish a direct relation between ferromagnetism and oxygen vacancies and open a path for developing materials with tailored properties.