bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Balmer discontinuity behavior of Be stars by the Monte Carlo method
Authors: Cruzado Alicia
Published: July 2011

For a given photospheric model, we study the behavior of the BD as different density and temperature distributions in the circumstellar envelope are assumed. For non spherically symmetric envelopes, we analyze the variation of the BD when the angle of observation varies. The radiation transfer through the medium is handled by means of the Monte Carlo method. We calculate the flux emitted by the star+envelope system in a small wavelength range around the BD. The calculations are made under LTE conditions.
Infrared continuum sizes of Be star disks
Authors: Gies Douglas R. , Touhami Yamina N. , Schaefer Gail H.
Published: July 2011

Long baseline interferometry now offers us the opportunity to measure the dimensions of Be star circumstellar disks across the spectrum. This includes the near-infrared continuum where the emission is dominated by bound-free and free-free emission from the ionized disk gas. Here we present the results of calculations of the disk sizes and continuum flux excesses for a simple version of the viscous decretion model of the disk. We compare these results to recent 18 μm flux measurements from the AKARI infrared satellite all-sky survey.
K- and L-band spectroscopy of Be stars
Authors: Granada Anahí , Arias María L. , Cidale Lydia S. , Mennickent Ronald E.
Published: July 2011

We describe the behaviour of IR hydrogen emission lines of a sample of Be stars and discuss the physical properties of the circumstellar envelopes of Be stars classified in Groups I and II (Mennickent et al. 2009). We find that while Humphreys and Pfund lines of Group I stars form in an optically thick envelope/disk, Group II stars show Pfund lines that form in an optically thick medium and Humphreys lines originating in optically thinner regions. The transition between Groups I and II could be understood in terms of the evolution of the circumstellar disk of the star and might bring clues on the mechanism originating the Be phenomenon.
The inhomogeneous wind of the LBV candidate Cyg OB2 No.12
Authors: Klochkova Valentina G. , Chentsov Eugene L. , Miroshnichenko Anatoly S.
Published: July 2011

We present the results of high-resolution spectroscopy of the extremely luminous star Cyg OB2 No. 12. We identified about 200 spectral features in the range 4552–7939 Å, including the interstellar Na I, K I lines and numerous very strong DIBs, along with the He I, C II, and Si II lines. An MK spectral type we derived for the object is B4.5±0.5 Ia+. Our analysis of the radial velocity data shows the presence of a gradient in the stellar atmosphere, caused by both atmospheric expansion and matter infall onto the star. The Hα emission displays broad Thompson wings, a slightly blue-shifted P Cyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.
Imaging “Pinwheel” nebulae with optical long-baseline interferometry
Authors: Millour Florentin , Driebe Thomas , Groh Jose H. , Chesneau Olivier , Weigelt Gerd , Liermann Adriane , Meilland Anthony
Published: July 2011

Dusty Wolf-Rayet stars are few but remarkable in terms of dust production rates (up to Ṁ = 10−6 M⊙/yr). Infrared excesses associated to mass-loss are found in the sub-types WC8 and WC9. Few WC9d stars are hosting a “pinwheel” nebula, indirect evidence of a companion star around the primary. While few other WC9d stars have a dust shell which has been barely resolved so far, the available angular resolution offered by single telescopes is insufficient to confirm if they also host “pinwheel” nebulae or not. In this article, we present the possible detection of such nebula around the star WR 118. We discuss about the potential of interferometry to image more “pinwheel” nebulae around other WC9d stars.
Images of unclassified and supergiant B[e] stars disks with interferometry
Authors: Millour Florentin , Meilland Anthony , Chesneau Olivier , Fernandes Marcelo Borges , Groh Jose H. , Driebe Thomas , Liermann Adrianne , Weigelt Gerd
Published: July 2011

B[e] stars are among the most peculiar objects in the sky. This spectral type, characterised by allowed and forbidden emission lines, and a large infrared excess, does not represent an homogenous class of objects, but instead, a mix of stellar bodies seen in all evolutionary status. Among them, one can find Herbig stars, planetary nebulae central stars, interacting binaries, supermassive stars, and even “unclassified” B[e] stars: systems sharing properties of several of the above. Interferometry, by resolving the innermost regions of these stellar systems, enables us to reveal the true nature of these peculiar stars among the peculiar B[e] stars.
Properties of the circumstellar dust in galactic FS CMa objects
Authors: Miroshnichenko Anatoly S. , Gray Richard O. , Bjorkman Karen S. , Rudy Richard J. , Lynch David K. , Carciofi Alex C.
Published: July 2011

FS CMa objects are a group of hot stars that exhibit the B[e] phenomenon. The group was defined a few years ago on the basis of the formerly known unclassified B[e] stars and newly discovered objects. One of their main features is the presence of hot circumstellar dust whose properties were unknown. We present IR spectra of nearly 20 FS CMa objects obtained with the Spitzer Space Telescope. Dusty features, such as broad silicate bands in emission and narrow bands that are usually explained by PAHs, are detected. The IR fluxes are compared to those detected by IRAS and MSX. Main results of the data analysis are briefly discussed.
Effect of Be-disk evolution on the global one-armed oscillations
Authors: Oktariani Finny , Okazaki Atsuo T.
Published: July 2011

We consider the effect of density distribution evolution on the global one-armed oscillation modes in disks around Be stars. Previous studies of global oscillations in Be disks assumed a power-law density distribution of the disk. However, observational results show that some Be stars exhibit evidence of formation and dissipation of the equatorial disk. This causes the disk density distribution can be far from a power-law form. Performing calculations for several times in the disk formation and dissipation stages, we find one-armed modes confined to the inner part of the disk in both stages. In the disk formation stage, the oscillation frequency stays approximately constant after the disk is fully developed. In the dissipation stage of the Be disk, the local precession frequency is, in general, higher than in the disk formation stage. Thus, we expect that V/R periods become shorter as the innermost part of the disk starts to accrete.
Pulsations in Wolf-Rayet stars: observations with MOST
Authors: Chené André-Nicolas , Moffat Anthony F. J.
Published: July 2011

Photometry of Wolf-Rayet (WR) stars obtained with the first Canadian space telescope MOST (Microvariability and Oscillations of STars) has revealed multimode oscillations mainly in continuum light that suggest stellar pulsations could be a significant contributing factor to the mass-loss rates. Since the first clear detection of a pulsation period of P = 9.8h in WR123, two other stars have also shown periods of a few days, which must be related to stellar pulsations.
Seismic modelling of OB stars
Authors: Dupret Marc-Antoine , Godart Mélanie , Belkacem Kevin , Noels Arlette
Published: July 2011

A review of the ability of asteroseismology to probe the internal physics of OB stars is presented. The main constraints that can be obtained from the frequency spectrum in p- and g-modes pulsators are discussed. Next, we consider energetic aspects of the pulsations in OB stars and show how such study also allows to constrain their internal physics. The cases of p-mixed modes (β Cep stars), g-modes (SPB stars), strange modes and stochastically excited modes are considered.
Radial and nonradial oscillations of massive supergiants
Authors: Saio Hideyuki
Published: July 2011

Stability of radial and nonradial oscillations of massive supergiants is discussed. The kappa-mechanism and strange-mode instability excite oscillations having various periods in wide ranges of the upper part of the HR diagram. In addition, in very luminous (logL/L⊙≳ 5.9) models, monotonously unstable modes exist, which probably indicates the occurrence of optically thick winds. The instability boundary is not far from the Humphreys-Davidson limit. Furthermore, it is found that there exist low-degree (ℓ = 1, 2) oscillatory convection modes associated with the Fe-opacity peak convection zone, and they can emerge to the stellar surface so that they are very likely observable in a considerable range in the HR diagram. The convection modes have periods similar to g-modes, and their growth-times are comparable to the periods. Theoretical predictions are compared with some of the supergiant variables.
Very massive binaries in R 136
Authors: Chené André-Nicolas , Schnurr Olivier , Crowther Paul A. , Lajus Eduardo F. , Moffat Anthony F. J.
Published: July 2011

As recent observations have shown, luminous, hydrogen-rich WN5-7h stars (and their somewhat less extreme cousins, O3f/WN6 stars) are the most massive main-sequence stars known. However, not nearly enough very massive stars have been reliably weighed to yield a clear picture of the upper initial-mass function (IMF). We therefore have carried out repeated high-quality spectroscopy of four new O3f/WN6 and WN5-7h binaries in R136 in the LMC with GMOS at Gemini-South, to derive Keplerian orbits for both components, respectively, and thus to directly determine their masses. We also monitored binary candidates and other, previously unsurveyed stars, to increase the number of very massive stars that can be directly weighed.
Using the orbiting companion to trace WR wind structures in the 29d WC8d + O8-9IV binary CV Ser
Authors: David-Uraz Alexandre , Moffat Anthony F. J.
Published: July 2011

We have used continuous, high-precision, broadband visible photometry from the MOST satellite to trace wind structures in the WR component of CV Ser over more than a full orbit. Most of the small-scale light-curve variations are likely due to extinction by clumps along the line of sight to the O companion as it orbits and shines through varying columns of the WR wind. Parallel optical spectroscopy from the Mont Megantic Observatory is used to refine the orbital and wind-collision parameters, as well as to reveal line emission from clumps.
Spectroscopic follow-up of the colliding-wind binary WR 140 during the 2009 January periastron passage
Authors: Fahed Rémi , Moffat Anthony F. J. , Zorec Juan , Eversberg Thomas , Chené André-Nicolas , Alves Filipe , Arnold Wolfgang , Bergmann Thomas , Carreira Luis F. Gouveia , Dias Filipe Marques , Fernando Alberto , Gallego José Sánchez , Hunger Thomas , Knapen Johan H. , Leadbeater Robin , Morel Thierry , Rauw Grégor , Reinecke Norbert , Ribeiro José , Romeo Nando , dos Santos Eva M. , Schanne Lothar , Stahl Otmar , Stober Barbara , Stober Berthold , Viegas Nelson G. Correia , Vollmann Klaus , Corcoran Michael F. , Dougherty Sean M. , Pittard Julian M. , Pollock Andy M. T. , Williams Peredur M.
Published: July 2011

We present the results from the spectroscopic follow-up of WR140 (WC7 + O4-5) during its last periastron passage in january 2009. This object is known as the archetype of colliding wind binaries and has a relatively large period (≃8 years) and eccentricity (≃0.89). We provide updated values for the orbital parameters, new estimates for the WR and O star masses and new constraints on the mass-loss rates.
The WR/LBV system HD 5980: wind-velocity – brightness correlations
Authors: Koenigsberger Gloria , Georgiev Leonid , Hillier D. John , Morrell Nidia , Barbá Rodolfo , Gamen Roberto
Published: July 2011

The massive eclipsing system HD 5980 in the Small Magellanic Cloud presented sudden ~1–3 mag eruptive events in 1993-1994, the nature of which is still unexplained. We recently showed that these brief eruptions occurred at the beginning of an extended high state of activity which is characterized by large emission-line intensities and that this high state is currently ending (Koenigsberger et al. 2010). Star A, the more massive member of the 19-day binary, is responsible for the spectacular spectral variations observed over the past 3 decades (see Figure 1). It has a He-enriched stellar wind and is over-luminous for its mass, implying an advanced evolutionary state (Koenigsberger et al. 1998). Data obtained over the past 3 decades show that Star A's wind speed slowed down as the system brightened. Also present in these data is a correlated increase in emission-line strength, visual and UV brigthness. The latter suggests that the high activity state in HD 5980 may be attributed to a bolometric luminosity increase, consistent with the results of Drissen et al. (2001). Hence, HD 5980 may be providing the important clues needed for understanding the behavior of other luminous blue variables and for understainding the evolutionary transition between massive O-type stars and Wolf-Rayet stars.
HD 150136: towards one of the most massive systems?
Authors: Mahy Laurent , Gosset Eric , Sana Hugues , Rauw Gregor , Fauchez Thomas , Nitschelm Christian
Published: July 2011

We present the preliminary results of an intensive monitoring devoted to HD 150136. Already quoted as an O3+O6 binary, we detected a third O-type component physically linked to the system, making it one of the nearest (1.3 kpc) most massive systems known until now (~134M⊙). To determine the physical parameters of this system, we applied a disentangling program to study individually the three components. It allows us to constrain their spectral types and to derive a new orbital solution for the short-period system.
Masses of the astrometric SB2 ζ Ori A
Authors: Rivinius Thomas , Hummel Christian A. , Stahl Otmar
Published: July 2011

We report the first dynamic mass for an O-type supergiant, the interferometrically resolved SB2 system ζ Ori A (O9.5Ib+B0/1). The separation of the system excludes any previous mass-transfer, ensuring that the derived masses can be compared to single star evolutionary tracks.
SC3-63371 and SC4-67145: two wind-interacting A+B binaries
Authors: Smith Myron A. , Mennickent Ronald E.
Published: July 2011

We report on two SMC objects with remarkable light curves and spectra. Both are in fact A I + B III binaries that exhibit interacting winds. We show a sketch of the geometry.
OB-stars as extreme condition test beds
Authors: Puls Joachim , Sundqvist Jon O. , Rivero González Jorge G.
Published: July 2011

Massive stars are inherently extreme objects, in terms of radiation, mass loss, rotation, and sometimes also magnetic fields. Concentrating on a (personally biased) subset of processes related to pulsations, rapid rotation and its interplay with mass-loss, and the bi-stability mechanism, we will discuss how active (and normal) OB stars can serve as appropriate laboratories to provide further clues.
Discussion – Normal and active OB stars as extreme condition test beds
Authors: Gagné Marc , Pacheco Eduardo Janot
Published: July 2011

Guillaume Dubus: As far as I can tell your model is exactly the same as standard models for high-mass x-ray binaries, the on difference is that you have a mechanism for generating γ rays. My question is, we know that there are dozens of other systems that are just LS 5039, so why are they not emitting γ rays?
Investigation of X-ray transient CI Cam as an unique star with the B[e]phenomenon
Authors: Barsukova Elena A. , Burenkov Alexandr N. , Klochkova Valentina G. , Goranskij Vitalij P. , Metlova Nataly V. , Kroll Peter , Miroshnichenko Anatoly S.
Published: July 2011

Double mode pulsations of the B4 component in the system of CI Cam were detected. The photometric 19.4 day orbital period of CI Cam was confirmed with the plates of the Sonneberg collection for a long period of time before the unique 1998 outburst. The amplitude of the periodic component of 0.08 mag before the outburst was larger than that of 0.03 mag after the outburst.
X-ray emission from hydrodynamical wind simulations in non-LTE models
Authors: Krtička Jiri , Feldmeier Achim , Oskinova Lidia M. , Kubát Jiri , Hamann Wolf-Rainer
Published: July 2011

Massive hot stars are strong sources of X-ray emission originating in their winds. Although hydrodynamical wind simulations that are able to predict this X-ray emission are available, the inclusion of X-rays in stationary wind models is usually based on crude approximations. To improve this, we use results from time-dependent hydrodynamical simulations of the line-driven wind instability to derive an analytical approximation of X-ray emission in the stellar wind. We use this approximation in our non-LTE wind models and find that an improved inclusion of X-rays leads to a better agreement between model ionization fractions and those derived from observations. Furthermore, the slope of the Lx-L relation is in better agreement with observations, albeit the X-ray luminosity is underestimated by a factor of three. We propose that a possible solution for this discrepancy is connected with the wind porosity.
X-Ray modeling of η Carinae & WR 140 from SPH simulations
Authors: Russell Christopher M. P. , Corcoran Michael F. , Okazaki Atsuo T. , Madura Thomas I. , Owocki Stanley P.
Published: July 2011

The colliding wind binary (CWB) systems η Carinae and WR140 provide unique laboratories for X-ray astrophysics. Their wind-wind collisions produce hard X-rays that have been monitored extensively by several X-ray telescopes, including RXTE. To interpret these RXTE X-ray light curves, we apply 3D hydrodynamic simulations of the wind-wind collision using smoothed particle hydrodynamics (SPH). We find adiabatic simulations that account for the absorption of X-rays from an assumed point source of X-ray emission at the apex of the wind-collision shock cone can closely match the RXTE light curves of both η Car and WR140. This point-source model can also explain the early recovery of η Car's X-ray light curve from the 2009.0 minimum by a factor of 2-4 reduction in the mass loss rate of η Car. Our more recent models account for the extended emission and absorption along the full wind-wind interaction shock front. For WR140, the computed X-ray light curves again match the RXTE observations quite well. But for η Car, a hot, post-periastron bubble leads to an emission level that does not match the extended X-ray minimum observed by RXTE. Initial results from incorporating radiative cooling and radiative forces via an anti-gravity approach into the SPH code are also discussed.
Interferometric survey of Be stars with the CHARA array
Authors: Touhami Yamina N. , Gies Douglas R. , Schaefer Gail H. , Richardson Noel D. , Williams Stephen J. , Grundstrom Erika D. , McSwain M. Virginia
Published: July 2011

We present the first spatially resolved observations of circumstellar envelopes of 25 bright northern Be stars. The survey was performed with the CHARA Array interferometer in the K-band at intermediate and long baselines. The interferometric visibilities are well fitted by a viscous disk model where the gas density steeply decreases with the radius. Physical and geometrical parameters such as the density profile, the inclination, and the position angles of the circumstellar disks are determined. We find that the density radial exponent ranges between n ≈ 2.4 − 3.2, which is consistent with previous IRAS measurements. We have also obtained simultaneous optical and near-IR spectrophotometric measurements, and found that the model reproduces well the observed disk IR-continuum excess emission. By combining the projected rotational velocity of the Be star with the disk inclination derived from interferometry, we give estimates of the equatorial rotational velocities of these Be stars.
Non-thermal radio emission from colliding-wind binaries: modelling Cyg OB2 No. 8A and No. 9
Authors: Volpi Delia , Blomme Ronny , De Becker Michael , Rauw Gregor
Published: July 2011

Some OB stars show variable non-thermal radio emission. The non-thermal emission is due to synchrotron radiation that is emitted by electrons accelerated to high energies. The electron acceleration occurs at strong shocks created by the collision of radiatively-driven stellar winds in binary systems. Here we present results of our modelling of two colliding wind systems: Cyg OB2 No. 8A and Cyg OB2 No. 9.
Concluding Remarks
Authors: Maeder André
Published: July 2011

Highlights of this outstanding meeting are emphasized, as well as important open questions for future research.
Pilot Candidate Selection Method
Authors: Carretta Thomas R.
Published: July 2011

In 1993, the US Air Force implemented the Pilot Candidate Selection Method (PCSM) as an additional indicator of pilot training aptitude. PCSM scores have been shown to be related to several pilot training criteria including graduation/elimination, flying grades, class rank, and number of flight hours needed to complete training ( Carretta & Ree, 2003 ). The PCSM composite is still in use today, but the scores that contribute to it have changed. The study reported here examined the predictive validity of the current composite versus several training performance measures for 883 students attending Specialized Undergraduate Pilot Training (SUPT). Results indicated that the PCSM composite remained predictive of flying training performance despite changes in test content and flying training. After correction for multivariate range restriction and dichotomization of the graduation/elimination criterion, the correlation between the PCSM composite and T-6 completion was .53. This is consistent with the value of .46 reported by Carretta and Ree (2003) for an earlier version of the PCSM composite. Its predictiveness can be attributed to the measurement of factors that have consistently shown a relation to flying performance: cognitive ability, aviation job knowledge/experience, and psychomotor ability.
How Do Astronaut Candidate Profiles Differ From Airline Pilot Profiles?
Authors: Maschke Peter , Oubaid Viktor , Pecena Yvonne
Published: July 2011

Sixteen years after the second Europe-wide astronaut selection campaign, the European Space Agency started the third campaign by putting out a call for new astronauts in 2008. Due to extreme environmental conditions, expensive scientific experiments, and high public interest, not only are the psychological requirements on a high level, but they are also wide in variety: Besides cognitive and psychomotor requirements, greater importance than in comparable campaigns was put on personality and behavioral aspects, especially regarding interpersonal aspects. The psychological selection was conducted in two steps: Phase 1 concentrated mainly on performance tests and Phase 2 focused on personality and interpersonal behavior. Out of the 902 tested candidates, 46 fulfilled the psychological requirements. Significant differences were found between the astronaut candidates and the general population as well as airline pilot candidates.
An integrated dynamic modeling framework for investigating the impact of climate change and variability on irrigated agriculture
Authors: Rowan Timothy S. C. , Maier Holger R. , Connor Jeff , Dandy Graeme C.
Published: July 2011

Many hydrologic systems are likely to be affected by climate change. This is of particular importance given that agricultural production systems are inextricably linked to the hydrologic systems they rely upon. Although irrigation is often employed as a method to dampen the effect of short‐term variation in climatic inputs to agricultural production, sources of irrigation water are not immune to long‐term climatic change. Irrigation water use decisions are most often made at the farm level. It is at this scale that the economic and social impacts of climate change will be manifest. This paper presents an integrated stochastic dynamic modeling framework that can be used to investigate the viability of irrigated farms under alternative climate change scenarios. The framework is applied to a theoretical farm in the Murray Darling Basin, Australia, under four potential future climate scenarios. It is found that neglecting interannual variability in climatic inputs to agriculture consistently underestimates the reduction in farm viability caused by climate change and that multiyear sequences of climate states strongly influence estimates of farm profitability.
Multivariate calibration of a water and energy balance model in the spectral domain
Authors: Pauwels Valentijn R. N. , De Lannoy Gabriëlle J. M.
Published: July 2011

The objective of this paper is to explore the possibility of using multiple variables in the calibration of hydrologic models in the spectral domain. A simple water and energy balance model was used, combined with observations of the energy balance and the soil moisture profile. The correlation functions of the model outputs and the observations for the different variables have been calculated after the removal of the diurnal cycle of the energy balance variables. These were transformed to the frequency domain to obtain spectral density functions, which were combined in the calibration algorithm. It has been found that it is best to use the square root of the spectral densities in the parameter estimation. Under these conditions, spectral calibration performs almost equally as well as time domain calibration using least squares differences between observed and simulated time series. Incorporation of the spectral coefficients of the cross‐correlation functions did not improve the results of the calibration. Calibration on the correlation functions in the time domain led to worse model performance. When the meteorological forcing and model calibration data are not overlapping in time, spectral calibration has been shown to lead to an acceptable model performance. Overall, the results in this paper suggest that, in case of data scarcity, multivariate spectral calibration can be an attractive tool to estimate model parameters.
A quick guide to writing a solid peer review
Authors: Nicholas Kimberly A. , Gordon Wendy S.
Published: July 2011

Scientific integrity and consensus rely on the peer review process, a defining feature of scientific discourse that subjects the literature forming the foundation of credible knowledge in a scientific field to rigorous scrutiny. However, there is surprisingly little training in graduate school on how to develop this essential skill [Zimmerman et al., 2011] or discussion of best practices to ensure that reviewers at all levels efficiently provide the most useful review. Even more challenging for the novice peer reviewer is that journals also vary widely in their review guidelines. Nonetheless, the goals of peer review are crystal clear: to ensure the accuracy and improve the quality of published literature through constructive criticism. To make the peer review process as efficient and productive as possible, you may want to consider a few useful approaches to tackling major steps throughout your review, from contemplating a review request and reading and assessing the manuscript to writing the review and interacting with the journal's editors (see Figure 1). These tips are particularly relevant for graduate students or other first‐time reviewers, but they may also be useful to experienced reviewers and to journal editors seeking to enhance their publication's processes.
Understanding sources, sinks, and transport of marine debris
Authors: Law Kara Lavender , Maximenko Nikolai
Published: July 2011

Fifth International Marine Debris Conference: Hydrodynamics of Marine Debris; Honolulu, Hawaii, 20 March 2011; Ocean pollution in the form of marine debris, especially plastic debris, has received increasing public and media attention in recent years through striking but frequently inaccurate descriptions of “;garbage patches.” Marine debris is composed of all manufactured materials, including glass, metal, paper, fibers, and plastic, that have been deliberately dumped or that accidentally entered the marine environment. Marine debris is most visible on beaches, but it has been observed in all oceans and in such remote locations as on the deep seabed and floating in the middle of subtropical ocean gyres. While many initiatives have been developed to solve this pollution problem through prevention and cleanup efforts, there is relatively little scientific information available to assess the current status of the problem or to provide metrics to gauge the success of remediation measures. With this in mind, a full‐day workshop entitled “Hydrodynamics of Marine Debris” was convened at the Fifth International Marine Debris Conference in Hawaii, bringing together observational scientists and oceanographic modelers to outline the steps necessary to quantify the major sources and sinks of marine debris and the pathways between them. The ultimate goal in integrating the two approaches of study is to quantify the basinscale and global inventory of marine debris by closing the associated mass budgets.
Boos receives 2010 James R. Holton Junior Scientist Award: citation
Authors: Webster Peter J.
Published: July 2011

William R. Boos received the 2010 James R. Holton Junior Scientist Award at the 2010 AGU Fall Meeting, held 13–17 December in San Francisco, Calif. The award recognizes outstanding research contributions by a junior atmospheric scientist within 3 years of his or her Ph.D.
Boos receives 2010 James R. Holton Junior Scientist Award: response
Authors: Boos William R.
Published: July 2011

William R. Boos received the 2010 James R. Holton Junior Scientist Award at the 2010 AGU Fall Meeting, held 13–17 December in San Francisco, Calif. The award recognizes outstanding research contributions by a junior atmospheric scientist within 3 years of his or her Ph.D.
Surge in North Atlantic hurricanes due to detectors, not climate change
Authors: Schultz Colin
Published: July 2011

A spate of research has indicated there may be a link between climate change and the prevalence of North Atlantic tropical cyclones. In a new paper, researchers note upon closer inspection that the prominent upswing in tropical cyclone detections beginning in the midtwentieth century is attributable predominantly to the detection of “shorties” tropical cyclones with durations of less than 2 days. That the apparent surge in cyclone activity could be attributable to changes in the quality and quantity of detections has gained ground as a potential alternative explanation. Using a database of hurricane observations stretching back to 1878, Villarini et al. try to tease out any detectable climate signal from the records. The authors note that between 1878 and 1943 there were 0.58 shorty detections per year, and between 1944 and 2008 there were 2.58 shorty detections per year. This increase in shorties, which the authors propose may be related to the end of World War II and the dawn of air‐based reconnaissance and weather tracking, was not mirrored by an increase in tropical cyclone activity for storms longer than 2 days. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2010JD015493, 2011
Virtual screening to design drug molecules for human proto oncogene Fyn kinase
Authors: Mannekumar Manne , Sravana lakshmi Pasupuleti , Vani Priyadarshini Ikkurthi , Pradhan Dibyabhaba , Umamaheswari Amineni
Published: July 2011

Human Fyn tyrosine kinase, a Src-family enzyme plays a pivotal role in the integrin mediated cell signaling pathway and is known to interact with several molecular signals including FAK and paxillin that accounts for morphogenic transformation leading to cancer. The present study was aimed to design a persuasive inhibitor for Fyn kinase. The crystal structure was optimized and energy minimized applying OPLS2001 force field in Maestro v9.0. The inhibitor binding site residues such as LEU-17, GLY-18, ASN-19, VAL-25, ALA-37, LYS-39, GLU-54, THR-82, GLU-83, TYR-84, MET-85, GLY-88, ALA-134, ASN-135, LEU-137, and ASP-148 were located from the Fyn kinase co-crystal structure with staurosporine. Three published inhibitors (staurosporine, Rosmarinic acid and dasatinib) of Fyn kinase were searched through high throughput virtual screening in Ligand.Info Metadatabase and generated 1163 structural analogues. Glide 5.5 docking was performed to predict the binding orientation of prepared ligand molecule into a grid of 20 x 20 x 20 Å created around the centroid of optimized Fyn kinase. Isomers and tautomers were generated for 1163 chemical entities through LigPrep. Ligands having reactive functional groups and poor ADME properties were rejected from the prepared dataset and docked into the predicted active site of human Fyn kinase through a systematic application of virtual screening using Glide v5.5. Five lead molecules with good XP GScores were obtained with their binding orientations, further XP Gscores were interrelated with the existing three published inhibitors. Lead1 (nor dihydroguaiaretic acid) was observed to have the lowest XP Gscore (-11.39 Kcal/mol) compared to three published inhibitors and blocked the Fyn kinase active site by forming hydrogen bonds and good Van der Waals contacts. Thus, nor dihydroguaiaretic acid would be useful as drug molecule if synthesized and tested in animal models.
Implantable Gastric Stimulator Does Not Prevent the Increase in Plasma Ghrelin Levels That Occurs With Weight Loss
Authors: Korner Judith , Nandi Anindita , Wright Suzanne M. , Waitman Jonathan , McMahon Donald J. , Bessler Marc , Aronne Louis J.
Published: July 2011

The SHAPE (Screened Health Assessment and Pacer Evaluation) trial was a 24 month randomized multicenter placebo‐controlled study to determine the efficacy of an implantable gastric stimulator (IGS) for weight loss. This report is an investigator‐initiated sub‐study at one site designed to assess whether IGS affects plasma levels of ghrelin and peptide YY (PYY). The device was implanted in all subjects but was activated in the Treatment group (n = 7, BMI = 41.5 ± 2.0 kg/m2) and remained inactive in the Control (n = 6, BMI = 39.5 ± 1.7 kg/m2) during the first 12 months. IGS was activated in both groups during months 12–24. Fasting venous blood was drawn at months 0, 12, and 24 and an oral glucose tolerance test (OGTT) was performed at month 12. Although there was no difference in weight loss at 6 months (Control: −6.6 ± 1.5% vs. Treatment: −6.2 ± 1.4%), at 24 months the Control group exhibited weight gain from baseline (+2.2 ± 1.5%) that was significantly different from the weight loss in the Treatment group (−1.9 ± 1.4%; P < 0.05). At 12 months, fasting ghrelin was significantly increased (P < 0.05) in the Treatment group (285 ± 35 to 336 ± 35 pg/ml; weight change, −4.9 ± 1.4%), but not in the Control (211 ± 36 to 208 ± 35 pg/ml; weight change, −3.4 ± 1.5%). No significant change was observed in postprandial suppression of plasma ghrelin or in fasting and postprandial PYY levels. In conclusion, IGS does not prevent the increase in fasting plasma ghrelin levels associated with weight loss. Further studies are needed to determine whether changes in technology can improve weight loss and maintenance, perhaps using gut hormones as biomarkers of possible efficacy.
Novel NADPH–cysteine covalent adduct found in the active site of an aldehyde dehydrogenase
Authors: Díaz-Sánchez Ángel G. , González-Segura Lilian , Rudiño-Piñera Enrique , Lira-Rocha Alfonso , Torres-Larios Alfredo , Muñoz-Clares Rosario A.
Published: July 2011

PaBADH (Pseudomonas aeruginosa betaine aldehyde dehydrogenase) catalyses the irreversible NAD(P)+-dependent oxidation of betaine aldehyde to its corresponding acid, the osmoprotector glycine betaine. This reaction is involved in the catabolism of choline and in the response of this important pathogen to the osmotic and oxidative stresses prevalent in infection sites. The crystal structure of PaBADH in complex with NADPH showed a novel covalent adduct between the C2N of the pyridine ring and the sulfur atom of the catalytic cysteine residue, Cys286. This kind of adduct has not been reported previously either for a cysteine residue or for a low-molecular-mass thiol. The Michael addition of the cysteine thiolate in the ‘resting’ conformation to the double bond of the α,β-unsaturated nicotinamide is facilitated by the particular conformation of NADPH in the active site of PaBADH (also observed in the crystal structure of the Cys286Ala mutant) and by an ordered water molecule hydrogen bonded to the carboxamide group. Reversible formation of NAD(P)H–Cys286 adducts in solution causes reversible enzyme inactivation as well as the loss of Cys286 reactivity towards thiol-specific reagents. This novel covalent modification may provide a physiologically relevant regulatory mechanism of the irreversible PaBADH-catalysed reaction, preventing deleterious decreases in the intracellular NAD(P)+/NAD(P)H ratios.
Anion channel sensitivity to cytosolic organic acids implicates a central role for oxaloacetate in integrating ion flux with metabolism in stomatal guard cells
Authors: Wang Yizhou , Blatt Michael R.
Published: July 2011

Stomatal guard cells play a key role in gas exchange for photosynthesis and in minimizing transpirational water loss from plants by opening and closing the stomatal pore. The bulk of the osmotic content driving stomatal movements depends on ionic fluxes across both the plasma membrane and tonoplast, the metabolism of organic acids, primarily Mal (malate), and its accumulation and loss. Anion channels at the plasma membrane are thought to comprise a major pathway for Mal efflux during stomatal closure, implicating their key role in linking solute flux with metabolism. Nonetheless, little is known of the regulation of anion channel current (ICl) by cytosolic Mal or its immediate metabolite OAA (oxaloacetate). In the present study, we have examined the impact of Mal, OAA and of the monocarboxylic acid anion acetate in guard cells of Vicia faba L. and report that all three organic acids affect ICl, but with markedly different characteristics and sidedness to their activities. Most prominent was a suppression of ICl by OAA within the physiological range of concentrations found in vivo. These findings indicate a capacity for OAA to co-ordinate organic acid metabolism with ICl through the direct effect of organic acid pool size. The findings of the present study also add perspective to in vivo recordings using acetate-based electrolytes.
Small artery function 2 years postpartum in women with altered glycaemic distributions in their preceding pregnancy
Authors: Banerjee Moulinath , Anderson Simon G. , Malik Rayaz A. , Austin Clare E. , Cruickshank J. Kennedy
Published: July 2011

GDM (gestational diabetes mellitus) is associated with later adverse cardiovascular risk. The present study examined the relationship between glycaemia during pregnancy and small artery function and structures approx. 2 years postpartum. Women were originally enrolled in the HAPO (Hyperglycaemia and Adverse Pregnancy Outcome) study from which they were classified by their glycaemic distribution during pregnancy as controls (in the lower half of the distribution), UQ (upper quartile; in the UQ of the glycaemic distribution) or having had overt GDM. Subcutaneous arteries from a gluteal fat biopsy taken at follow-up 2 years later were examined using wire myography. Small artery structure, stiffness and vasoconstrictor responses were similar across groups. Maximal endothelium-dependent dilation in response to carbachol was impaired in arteries from both GDM (43.3%, n=8 and P=0.01) and UQ (51.7%, n=13 and P=0.04) women despite generally ‘normal’ current glycaemia (controls, 72.7% and n=8). Inhibition of NOS (nitric oxide synthase) significantly reduced maximum endothelium-dependent dilation in controls but had no effect on arteries from UQ and GDM women, suggesting impaired NOS activity in these groups. Endothelium-independent dilation was unaffected in arteries from previous GDM and UQ women when compared with the control group. Multiple regression analysis suggested that BMI (body mass index) at biopsy was the most potent factor independently associated with small artery function, with no effect of current glycaemia. Overweight women with either GDM or marginally raised glycaemia during pregnancy (our UQ group) had normal vascular structure and stiffness, but clearly detectable progressively impaired endothelium-dependent function at 2 years follow-up. These results suggest that vascular pathology, which may still be reversible, is detectable very early in women at risk of decline into Type 2 diabetes mellitus.
Control of noise and exhaust emissions from dual fuel engines
Authors: Al-Omari Salah B. , Selim Mohamed Y. E. , Al-Aseery A. A. J.
Published: July 2011

An experimental investigation has been carried out to examine the effects of adding water vapor to the intake air of a dual fuel engine on the performance, combustion noise, and emission of CO, HC gases, and smoke opacity. Dual fuel engine is a diesel engine using a small amount (5%) of liquid diesel fuel as a pilot fuel and burns a liquefied petroleum gas as the main fuel. The addition of water vapor to the combustion chamber of a diesel engine has known effects on reducing the dangerous emission of nitrogen oxides. Yet it is not currently clear for the dual fuel engine how much the sacrifice is of engine performance, noise, and other exhaust emissions. Experimental procedures conducted using a Ricardo diesel version variable compression research engine are discussed. Results from testing dual fuel engine with varying the added water vapor to fuel ratios and other design and operating parameters are presented and discussed. The addition of water vapor to the intake air affected the performance, combustion noise, and exhaust emissions.
Kinetic Alfven wave instability in a Lorentzian dusty plasma: Non-resonant particle approach
Authors: Rubab N. , Erkaev V. , Biernat H. K. , Langmayr D.
Published: July 2011

Analysis of the electromagnetic streaming instability is carried out which is related to the cross field drift of kappa distributed ions. The linear dispersion relation for electromagnetic wave using Vlasov-fluid equations in a dusty plasma is derived. Modified two stream instability (MTSI) in a dusty plasma has been discussed in the limit ωpd2/c2k⊥2≪1. Numerical calculations of the growth rate of instability have been carried out. Growth rates of kinetic Alfvén instability are found to be small as compared to MTSI. Maximum growth rates for both instabilities occur in oblique directions for V0≥VA. It is shown that the presence of both the charged dust particles and perpendicular ion beam sensibly modify the dispersion relation of low-frequency electromagnetic wave. The dispersion characteristics are found to be insensible to the superthermal character of the ion distribution function. Applications to different intersteller regions are discussed.
Dispersion relation for pure dust Bernstein waves in a non-Maxwellian magnetized dusty plasma
Authors: Deeba F. , Ahmad Zahoor , Murtaza G.
Published: July 2011

Pure dust Bernstein waves are investigated using non-Maxwellian kappa and (r,q) distribution functions in a collisionless, uniform magnetized dusty plasma. Dispersion relations for both the distributions are derived by considering waves whose frequency is of the order of dust cyclotron frequency, and dispersion curves are plotted. It is observed that the propagation band for dust Bernstein waves is rather narrow as compared with that of the electron Bernstein waves. However, the band width increases for higher harmonics, for both kappa and (r,q) distributions. Effect of dust charge on dispersion curves is also studied, and one observes that with increasing dust charge, the dispersion curves shift toward the lower frequencies. Increasing the dust to ion density ratio (nd0ni0) causes the dispersion curve to shift toward the higher frequencies. It is also found that for large values of spectral index kappa (κ), the dispersion curves approach to the Maxwellian curves. The (r,q) distribution approaches the kappa distribution for r = 0, whereas for r > 0, the dispersion curves show deviation from the Maxwellian curves as expected. Relevance of this work can be found in astrophysical plasmas, where non-Maxwellian velocity distributions as well as dust particles are commonly observed.
Electronic structures and work functions of BC3 nanotubes: A first-principle study
Authors: Su W. S. , Chang C. P. , Lin M. F. , Li T. L.
Published: July 2011

The electronic structures and work functions of the single-wall BC3 nanotubes are studied by the first-principle method. In contrast to the armchair nanotubes, the zigzag nanotubes are indirect-band semiconductors. The zigzag nanotubes can be further classified into two types, depending on the wave-vector characteristics of the conduction band minima. The bandgap energies of the armchair nanotubes are always smaller than that of the BC3 sheet, and increase with the nanotube diameter. For the two types of zigzag nanotubes, the bandgap energies are always larger than that of the BC3 sheet, and decrease with the nanotube diameters. Analysis of the bond angles between the neighboring atoms on the nanotube walls shows that the mixing of the π and σ electron orbitals exhibits opposite trends for the armchair and zigzag nanotubes. These trends are not only responsible for the above dependence of the electronic structures on the types and diameters of the nanotubes, but also give physical insight to the indirectness of the band-structures of the zigzag nanotubes. By the first-principle method, it is found that the work functions of both armchair and zigzag nanotubes scale linearly with 1/D2, D being the nanotube diameter. Moreover, it is found that the per-atom strain energies and the vacuum bandwidths of both armchair and zigzag nanotubes satisfy universal relations which also scale linearly in 1/D2.
Modeling of static electrical properties in organic field-effect transistors
Authors: Xu Yong , Minari Takeo , Tsukagoshi Kazuhito , Gwoziecki Romain , Coppard Romain , Benwadih Mohamed , Chroboczek Jan , Balestra Francis , Ghibaudo Gerard
Published: July 2011

A modeling of organic field-effect transistors’ (OFETs’) electrical characteristics is presented. This model is based on a one-dimensional (1-D) Poisson’s equation solution that solves the potential profile in the organic semiconducting film. Most importantly, it demonstrates that, due to the common open-surface configuration used in organic transistors, the conduction occurs in the film volume below threshold. This is because the potential at the free surface is not fixed to zero but rather rises also with the gate bias. The tail of carrier concentration at the free surface is therefore significantly modulated by the gate bias, which partially explains the gate-voltage dependent contact resistance. At the same time in the so-called subthreshold region, we observe a clear charge trapping from the difference between C-V and I-V measurements; hence a traps study by numerical simulation is also performed. By combining the analytical modeling and the traps analysis, the questions on the C-V and I-V characteristics are answered. Finally, the combined results obtained with traps fit well the experimental data in both pentacene and bis(triisopropylsilylethynyl)-pentacene OFETs.
Influence of Ce4+ ions on the structural and magnetic properties of NiFe2O4
Authors: Shirsath Sagar E. , Jadhav Santosh S. , Toksha B. G. , Patange S. M. , Jadhav K. M.
Published: July 2011

The effect of Ce4+ substitution in NiFe2O4, with a chemical formula Ni1-2xCexFe2O4 (0 ≤ x ≤ 0.25), ferrite prepared by a solid-state reaction is presented in this paper. Ce4+ ions enter the NiFe2O4 lattice by replacing Ni2+ and swell the lattice. This enlarges the lattice constant, which results in a moderate distortion of the lattice. The r.m.s. strain increases from 0.411 × 10−3 to 0.471 × 10−3 with increasing Ce4+ content. SEM images revealed that Ce4+ promotes grain growth in NiFe2O4. It was also revealed that x-ray density and porosity decreases, whereas a significant increase in the bulk density is observed with the Ce4+ content. Substitution of Ce4+ for Ni2+ caused a decrease in the saturation magnetization from 41.3 to 25.12 emu/g and a decrease in the Curie temperature of the nickel ferrite from 830 to 594 K, whereas the coercivity increased from 59.48 to 458.25 Oe.