bluuebunny/crossref_metadata_2025 huggingface dataset:
Short-term variations in Be stars observed by the CoRoT and Kepler space missions
Authors: Gutiérrez-Soto Juan , Neiner Coralie , Fabregat Juan , Lanza Antonino Francesco , Semaan Thierry , Rainer Monica , Poretti Ennio
Published: July 2011

The corot and kepler space missions are collecting very high-precision long-duration photometric data of many Be stars, allowing us to better understand the origin of their short-term variability and the link between these variations and the Be phenomenon. In this paper, we present a brief summary of the results obtained in the analysis of several Be stars observed with corot in terms of pulsations. In addition, we show that variations of the Be star HD 175869 can be explained as two active regions separated by 150 degrees or as unstable pulsating modes in a star with an extensive mixing in radiative layers corresponding to a core overshooting of 0.35Hp. A preliminary study of the photometric and spectroscopic variability seen in the B1.5IVe star HD 51193 is performed. Currently the kepler satellite is observing the only confirmed Be star in its field of view, namely KIC 6954726. From low-resolution spectra we derived a spectral type of B2.5Ve for this star and we studied the long-term variation of the emission in the Hα line. The 3.5-year kepler light curve will allow us to detect even more close frequencies than with corot and to perform a detailed analysis of the amplitude variations in a Be star.
The multiplicity of massive stars
Authors: Sana Hugues , Evans Christopher J.
Published: July 2011

Binaries are excellent astrophysical laboratories that provide us with direct measurements of fundamental stellar parameters. Compared to single isolated stars, multiplicity induces new processes, offering the opportunity to confront our understanding of a broad range of physics under the extreme conditions found in, and close to, astrophysical objects.

In this contribution, we will discuss the parameter space occupied by massive binaries, and the observational means to investigate it. We will review the multiplicity fraction of OB stars within each regime, and in different astrophysical environments. In particular we will compare the O star spectroscopic binary fraction in nearby open clusters and we will show that the current data are adequately described by an homogeneous fraction off≈ 0.44.

We will also summarize our current understanding of the observed parameter distributions of O + OB spectroscopic binaries. We will show that the period distribution is overabundant in short period binaries and that it can be described by a bi-modal Öpik law with a break point aroundP≈ 10 d. The distribution of the mass-ratios shows no indication for a twin population of equal mass binaries and seems rather uniform in the range 0.2 ≤q=M2/M1≤ 1.0.
Pulsations in massive stars: effect of the atmosphere on the strange mode pulsations
Authors: Godart Mélanie , Dupret Marc-Antoine , Noels Arlette , Aerts Conny , Simón-Díaz Sergio , Lefever Karolien , Puls Joachim , Montalban Josefina , Ventura Paolo
Published: July 2011

Recent space observations with CoRoT and ground-based spectroscopy have shown the presence of different types of pulsations in OB stars. These oscillations could be due to acoustic and gravity modes, solar-like oscillations or even other pulsations of large growth rates. We present a first attempt at interpreting the latter as strange modes.
Asteroseismology and rotation in the main sequence
Authors: Jendreieck Andressa , Pacheco Eduardo Janot , de Andrade Laerte B. P. , Suárez Juan Carlos
Published: July 2011

In this project, we study the effects of stellar rotation on the pulsation predictions for stars in the Main Sequence following the series δ Scu, γ Dor, SPB, Be and β Cep. The objects' rotation in this series span from a few km/s to a few hundreds of km/s. We will compare theoretical predictions yielded by the codes CESAM/FILOU with published data from the MOST and CoRoT satellites. A better diagnostic of the rotation effects on stellar pulsations will help to improve the oscillatory models.
Line profile variability and tidal flows in eccentric binaries
Authors: Koenigsberger Gloria , Moreno Edmundo , Harrington David M.
Published: July 2011

A number of binary systems display enhanced activity around periastron passage which may be caused by the tidal interactions. We have developed a time-marching numerical calculation from first principles that computes the surface deformations, the perturbed velocity field, the energy dissipation rates and the photospheric line-profiles in a rotating star with a binary companion in an eccentric orbit. The method consists of solving the equations of motion for a grid of elements covering the surface of star m1, subjected to gravitational, centrifugal, Coriolis, gas pressure and viscous shear forces (Moreno et al. 1999, Toledano et al. 2007, Moreno et al. 2011). At selected times during the orbital cycle, the velocities of surface elements on the visible hemisphere of the star are projected along the observer's line of sight and the photospheric line-profile calculation is performed (Moreno et al. 2005). Direct comparison with observational photospheric line profile variability is then possible, showing that the general features are reproduced (Harrington et al. 2009). In this poster we show the example of a highly eccentric system (e = 0.8, P = 15 d). The surface deformation changes rapidly from that of an “equilibrium tide” at periastron to one with smaller-scale structure shortly thereafter. The computed line profiles display the presence of large blue-to-red migrating “bumps” around periastron, with smaller scale structure appearing later in the orbital cycle. Because the growth rate of the surface perturbations increases very abruptly at periastron, instabilities are expected to arise which may cause the observed activity and mass-ejection events around this orbital phase.
Fundamental parameters of 4 massive eclipsing binaries in Westerlund 1
Authors: Koumpia Eugenia , Bonanos Alceste Z.
Published: July 2011

Westerlund 1 is one of the most massive young clusters known in the Local Group, with an age of 3-5 Myr. It contains an assortment of rare evolved massive stars, such as blue, yellow and red supergiants, Wolf-Rayet stars, a luminous blue variable, and a magnetar, as well as 4 massive eclipsing binary systems (Wddeb, Wd13, Wd36, WR77o, see Bonanos 2007). The eclipsing binaries present a rare opportunity to constrain evolutionary models of massive stars, the distance to the cluster and furthermore, to determine a dynamical lower limit for the mass of a magnetar progenitor. Wddeb, being a detached system, is of great interest as it allows determination of the masses of 2 of the most massive unevolved stars in the cluster. We have analyzed spectra of all 4 eclipsing binaries, taken in 2007-2008 with the 6.5 meter Magellan telescope at Las Campanas Observatory, Chile, and present fundamental parameters (masses, radii) for their component stars.
The nature of the light variations of chemically peculiar stars CU Vir and HD 64740
Authors: Krtička Jiri , Marková Hana , Mikulášek Zdenek , Lüftinger Theresa , Bohlender David , Zverko Juraj , Žižňovský Jozef
Published: July 2011

The nature of the light variations of chemically peculiar stars was studied in detail only in a very few cases. To better understand the mechanisms of light variability of these stars, we study the light variations of the well-known magnetic chemically peculiar star CU Vir and one of the least amplitude variable stars HD 64740. We show that the light variability of these stars is induced by flux redistribution in spots of enhanced abundance of chemical elements (e.g., helium, silicon, iron or chromium), and by the stellar rotation. We conclude that this is a promising model for the explanation of the light variability of most chemically peculiar stars.
Long-term spectroscopic monitoring of LBVs and LBV candidates
Authors: Lobel Alex , Groh Jose H. , Torres Kelly , Gorlova Nadya
Published: July 2011

We present results of a long-term spectroscopic monitoring program (since mid 2009) of Luminous Blue Variables with the new HERMES echelle spectrograph on the 1.2m Mercator telescope at La Palma (Spain). We investigate high-resolution (R = 80,000) optical spectra of two LBVs, P Cyg and HD 168607, the LBV candidates MWC 930 and HD 168625, and the LBV binary MWC 314. In P Cyg we observe flux changes in the violet wings of the Balmer Hα, Hβ, and He i lines between May and Sep 2009. The changes around 200 to 300 km s−1 are caused by variable opacity at the base of the supersonic wind from the blue supergiant.

We observe in MWC 314 broad double-peaked metal emission lines with invariable radial velocities over time. On the other hand, we measure in the photospheric S ii λ5647 absorption line, with lower excitation energy of ~14 eV, an increase of the heliocentric radial velocity centroid from 37 km s−1 to 70 km s−1 between 5 and 10 Sep 2009 (and 43 km s−1 on 6 Apr 2010). The increase of radial velocity of ~33 km s−1 in only 5 days can confirm the binary nature of this LBV close to the Eddington luminosity limit.

A comparison with VLT-UVES and Keck-Hires spectra observed over the past 13 years reveals strong flux variability in the violet wing of the Hα emission line of HD 168625 and in the absorption portion of the Hβ line of HD 168607. In HD 168625 we observe Hα wind absorption at velocities exceeding 200 km s−1 which develops between Apr and June 2010.
The spectroscopic orbits and physical parameters of GG Car
Authors: Marchiano Paula E. , Brandi Elisande , Muratore Maria F. , Quiroga Claudio , Ferrer Osvaldo , García Lia
Published: July 2011

GG Car is a peculiar B type star with emission lines classified as a B[e] supergiant star. In this work we present a spectral analysis of this system based on spectra obtained at Casleo. We fit the spectral energy distribution adopting a model for the gas and dust circumstellar components and thus we obtain the physical parameters of the star and its environment.
The effects of μ gradients on pulsations of rapidly rotating stars
Authors: Reese Daniel R. , Lara Francisco Espinosa , Rieutord Michel
Published: July 2011

Recently, Reese et al. (2008), Lignières & Georgeot (2008) and Lignières & Georgeot (2009) showed that the frequencies of low-degree acoustic modes in rapidly rotating stars, also known as “island modes”, follow an asymptotic formula, the coefficients of which can be deduced from ray dynamics. We investigate how this asymptotic behaviour is affected by μ gradients by comparing pulsation spectra from models with and without such a discontinuity.
The resonant B1II + B1II binary BI 108
Authors: Rivinius Thomas , Mennickent Ronald E. , Kołaczkowski Zbigniew
Published: July 2011

BI 108 is a luminous variable star in the Large Magellanic Cloud classified B1 II. The variability consists of two resonant periods (3:2), of which only one is orbital, however. We discuss possible mechanisms responsible for the second period and its resonant locking.
Spectral and photometric study of Be Stars in the first exoplanet fields of CoRoT
Authors: Semaan Thierry , Martayan Christophe , Frémat Yves , Hubert Anne-Marie , Soto Juan Gutiérrez , Neiner Coralie , Zorec Juan
Published: July 2011

First we investigate the spectral and photometric properties (colours, magnitudes) of a sample of faint Be stars observed in the first exoplanet fields of CoRoT (IR1, LRA1 and LRC1). We determine the fundamental parameters by fitting ESO-FLAMES/GIRAFFE spectra with synthetic models taking account for non-LTE effects. After that we correct these parameters from fast rotation effects. We also study the location of each star in the (logL vs logT) HR diagram. Second we start to analyse the CoRoT light curves to investigate further the possible correlation between the pulsating properties and the fundamental parameters of the stars.
Is macroturbulence in OB Sgs related to pulsations?
Authors: Simón-Díaz Sergio , Herrero Artemio , Uytterhoeven Katrien , Castro Norberto , Aerts Conny , Puls Joachim
Published: July 2011

As part of a long term observational project, we are investigating the macroturbulent broadening in O and B supergiants (Sgs) and its possible connection with spectroscopic variability phenomena and stellar oscillations. We present the first results of our project, namely firm observational evidence for a strong correlation between the extra broadening and photospheric line-profile variations in a sample of 13 Sgs with spectral types ranging from O9.5 to B8.
Eruptive outflow phases of massive stars
Authors: Smith Nathan
Published: July 2011

I review recent progress on understanding eruptions of unstable massive stars, with particular attention to the diversity of observed behavior in extragalatic optical transient sources that are generally associated with giant eruptions of luminous blue variables (LBVs). These eruptions are thought to represent key mass loss episodes in the lives of massive stars. I discuss the possibility of dormant LBVs and implications for the duration of the greater LBV phase and its role in stellar evolution. These eruptive variables show a wide range of peak luminosity, decay time, expansion speeds, and progenitor luminosity, and in some cases they have been observed to suffer multiple eruptions. This broadens our view of massive star eruptions compared to prototypical sources like Eta Carinae, and provides important clues for the nature of the outbursts. I will also review and discuss some implications about the possible physical mechanisms involved, although the cause of the eruptions is not yet understood.
η Carinae long-term variability
Authors: Damineli Augusto , Teodoro Mairan , Corcoran Michael F. , Groh Jose H.
Published: July 2011

We present preliminary results of our analysis on the long-term variations observed in the optical spectrum of the LBV star η Carinae. Based on the hydrogen line profiles, we conclude that the physical parameters of the primary star did not change in the last 15 years.
The Chandra survey of Carina OB stars
Authors: Gagné Marc , Fehon Garrett , Savoy Michael R. , Cohen David H. , Townsley Leisa K. , Broos Patrick S. , Povich Matthew S. , Corcoran Michael F. , Walborn Nolan R. , Moffat Anthony F.J. , Nazé Yael , Oskinova Lidia M.
Published: July 2011

We have combined 22 deep Chandra ACIS-I pointings to map over one square degree of the Carina complex. Our x-ray survey detects 69 of 70 known O-type stars and 61 of 130 known early B stars. The majority of single O stars display soft X-ray spectra and have a mean log LX/Lbol ≈ −7.5 suggesting shocks embedded in the O-star winds. Over OB stars show unusually high X-ray luminosities, high shock temperatures or time variability, not predicted for embedded wind shocks.
Hα19 in the galaxy M 33, a high-luminosity massive merging eclipsing binary
Authors: Goranskij Vitaly P. , Bersukova Elena
Published: July 2011

CCD photometry reveals a hot spot on the surface of the hot accretion gainer in this supergiant O type binary with a big accretion rate. This spot is as bright as 25000 Suns. The orbital period of this system is 33.108 days. The absorption-line spectrum contains multiple lines of He I, Si III and N II. The star is associated with H II region formed by bipolar gas outflow from the system.
High-angular resolution observations of the Pistol star
Authors: Martayan Christophe , Blomme Ronny , Le Bouquin Jean-Baptiste , Merand Anthony , Montagnier Guillaume , Selman Fernando , Girard Julien , Fox Andrew , Baade Dietrich , Frémat Yves , Lobel Alex , Martins Fabrice , Patru Fabien , Rivinius Thomas , Sana Hugues , Štefl Stanislas , Zorec Juan , Semaan Thierry
Published: July 2011

First results of near-IR adaptive optics (AO)-assisted imaging, interferometry, and spectroscopy of this Luminous Blue Variable (LBV) are presented. They suggest that the Pistol Star is at least double. If the association is physical, it would reinforce questions concerning the importance of multiplicity for the formation and evolution of extremely massive stars.
Determination of fundamental parameters and circumstellar properties for a sample of B[e] stars
Authors: Muratore María F. , Cidale Lydia S. , Arias María L. , Zorec Juan , Torres Andrea F.
Published: July 2011

We develop a simple model to derive theoretical continuum energy distributions for B[e] stars, consisting of a B star surrounded by an envelope made of gas and dust. We select a sample of B[e] objects for which we construct the observed energy distributions, from 0.1 to 100 μm, using available photometric and spectroscopic data. We present some preliminary fittings.
Overall properties of hot, massive stars in the X-ray domain
Authors: Nazé Yael
Published: July 2011

Despite the absence of large surveys, the recent X-ray observatories provide X-ray data for hundreds of massive stars (294 OB stars detected in the 2XMM catalog, 129 OB stars detected in the Chandra Carina Complex Project). Analyzing medium-resolution spectra led to new results on the relationship between the X-ray luminosity and the bolometric luminosity, as well as on the typical properties (plasma temperature, variability) of these objects.
Interaction between the Be star and the compact companion in TeV γ-ray binaries
Authors: Okazaki Atsuo T. , Nagataki Shigehiro , Naito Tsuguya , Kawachi Akiko , Hayasaki Kimitake , Owocki Stanley P. , Takata Jumpei
Published: July 2011

We report on the results from 3-D SPH simulations of TeV binaries with Be stars. Since there is only one TeV binary (B 1259-63) where the nature of the compact companion has been established, we mainly focus on this Be-pulsar system. From simulations of B 1259-63 around periastron, we find that the pulsar wind dominates the Be-star wind and strips off an outer part of the Be-star disk, causing a strongly asymmetric, phase-dependent structure of the circumstellar material around the Be star. Such a large modulation may be detected by optical, IR, and/or UV observations at phases near periastron. We also discuss the results from simulations of another TeV binary LS I+61 303, for which the nature of the compact object is not yet known.
Equatorial mass loss from Be stars
Authors: Georgy Cyril , Ekström Sylvia , Granada Anahí , Meynet Georges
Published: July 2011

Be stars are thought to be fast rotating stars surrounded by an equatorial disc. The formation, structure and evolution of the disc are still not well understood. In the frame of single star models, it is expected that the surface of an initially fast rotating star can reach its keplerian velocity (critical velocity). The Geneva stellar evolution code has been recently improved, in order to obtain some estimates of the total mass loss and of the mechanical mass loss rates in the equatorial disc during the whole critical rotation phase. We present here the first results of the computation of a grid of fast rotating B stars evolving towards the Be phase, and discuss the first estimates we obtained.
Descriptive and Analytical Epidemiology of Accidents in Five Categories of Sport Aviation Aircraft
Authors: van Doorn Robert R. A. , de Voogt Alex J.
Published: July 2011

The present study reports and compares causes of, and factors contributing to, 2,118 documented accidents of sport aviation represented by diverse aircraft types including balloons and blimps, gliders, gyroplanes, and ultralights. For the 26-year period, accidents were aircraft-specific regarding damage, injury severity, and human errors. The likelihood of fatal injuries in sport aviation accidents differs per aircraft category and is related to the phase of flight in which the accident originates and the involvement of aircraft-specific human errors. Results show that amateur-built aircraft are a specific subgroup.
Seeing the Big Picture of Mishaps
Authors: Branford Kate
Published: July 2011

The analysis of major accidents in safety-critical systems requires a “big-picture” approach, with the capacity to accommodate contributing factors from within the organisations involved and from dysfunctional interactions between different parts of the broader system. Rasmussen’s AcciMap approach is useful in this regard, as it illustrates how multiple factors throughout the system combined to produce an accident. This article describes the application of this technique to the Überlingen mid-air collision and draws on this application to discuss the benefits of the AcciMap Approach. These include its capacity to incorporate contributing factors from all system levels and illustrate their interrelationships succinctly; to depict the activities of front-line workers within the context in which they occurred; and to aid safety recommendation development.
Integrating Safety and Crew Resource Management (CRM) Aspects in the Recurrent Training of Cabin Crew Members
Authors: Ritzmann Sandrina , Kluge Annette , Hagemann Vera , Tanner Margot
Published: July 2011

Recurrent training of cabin crew should include theoretical and practical instruction on safety as well as crew resource management (CRM) issues. The endeavors of Swiss International Air Lines Ltd. and Swiss Aviation Training Ltd. to integrate CRM and safety aspects into a single training module were evaluated. The objective of the integration was to make CRM more tangible and ease acquisition of competencies and transfer of CRM training content to practice by showing its relevance in relation to safety tasks. It was of interest whether the integrated design would be mirrored in a more favorable perception by the trainees as measured with a questionnaire. Participants reacted more positively to the integrated training than to stand-alone CRM training, although the integrated training was judged as being slightly more difficult and less oriented toward instructional design principles. In a range of forced-choice questions, the majority of participants opted for an integrated training format because it was seen as livelier and more interesting and also more practically relevant. For the forthcoming training cycle, a better alignment of training with instructional principles and an even higher degree of training integration by using simulator scenarios are striven for.
A New Scale to Evaluate Disruptive Passenger Management by Cabin Crew
Authors: Piñar-Chelso María José , Fernández-Castro Jordi
Published: July 2011

The aim of this work was to design an observational scale to enable the evaluation of cabin crew management of disruptive passengers, from the point of view of both safety and service quality; and to analyze the role of cabin crews’ emotional intelligence and self-efficacy in efficient intervention in such situations. Five judges (two experts and three clients) evaluated 18 cabin crew members using this scale, comprising 29 indicators (which measure nonverbal and verbal communication, expressed emotion, service quality, safety, realism, and overall execution) in four scenarios: in other words, two situations (a passenger who put his suitcase next to one of the emergency exits; and another who went to smoke in the toilet) and the remaining two types of disruptive passengers (Category Type I or II according to the US Federal Aviation Administration’s classification), in which they role played interactions with two actors playing the roles of passengers. It was found that performance was negatively correlated with perceived emotional intelligence, but positively with emotional intelligence, ability, and experience. Implications for crew resource management and service quality of cabin crew are discussed. The scale could be used for investigation, selection, and training purposes.
Seasonal cycle of near‐surface freshwater budget in the western tropical Atlantic
Authors: Romanova V. , Köhl A. , Stammer D.
Published: July 2011

We investigate differences of the ocean response in the Amazon domain to the seasonal variability of the river discharge that are either introduced via assimilating climatological temperature and salinity or by specifying seasonally varying river runoff. The role of the seasonal cycle of the Amazon freshwater discharge for the evolution of the barrier layer (BL) in the western tropical Atlantic and on the freshwater budget is estimated. During the experiments, three different runoff fields are being applied, including a time‐mean runoff, a seasonally varying runoff, and one that results from the GECCO assimilation approach. The simulation forced with a seasonal Amazon discharge appears to be closer to the constrained solution and moves away from the run with a constant runoff, demonstrating that the seasonal variability of the Amazon is an essential contributor in the freshwater forcing of the western tropical Atlantic. The modeled time‐mean BL thickness seems to be overestimated by the model relative to the data. On the seasonal timescale, the simulated spatial mean BL is found to vary between 13 and 30 m, with a maximum occurring in July, following the Amazon high discharge period in May. Analyzing the freshwater content balance, we find integrated near‐surface freshwater import from the western tropical Atlantic interior of around 0.20 Sv in October–November at 38°W and cumulative freshwater export out of the domain with a maximum of around 0.4 Sv in June as an effect of the Amazon flood in May.
Communications/Navigation Outage Forecasting System observational support for the equatorial E × B drift velocities associated with the four‐cell tidal structures
Authors: Araujo‐Pradere Eduardo A. , Anderson David N. , Fedrizzi Mariangel , Stoneback Russell
Published: July 2011

Previous studies have established the existence of a four‐cell longitude pattern in equatorial F region ionospheric parameters such as total electron content and electron densities and in daytime, equatorial E × B drift velocities. This paper, for the first time, quantifies the longitude gradients in E × B drift associated with the four‐cell tidal structures and confirms that these sharp gradients exist on a day‐to‐day basis. For this purpose, we use the Ion Velocity Meter (IVM) sensor on the Communications/Navigation Outage Forecasting System (C/NOFS) satellite to obtain the daytime, vertical E × B drift velocities at the magnetic equator as a function of longitude, local time, and season. The IVM sensor measures the E × B drift velocity in three dimensions; however, we only use the E × B drift observations perpendicular to B in the meridional plane. These observations can be used to obtain the vertical E × B drifts at the magnetic equator by mapping along the geomagnetic field line. The period initially selected for this work covers several days in October, March, and December 2009. We find, on a day‐to‐day basis, that (1) sharp E × B drift gradients of −1.3 m s−1 deg−1 exist in the western Pacific sector during equinox, (2) sharp E × B drift gradients of +3 m s−1 deg−1 are observed in the eastern Pacific sector during equinox, and (3) sharp E × B drift gradients of −1.7 m s−1 deg−1 exist in the eastern Pacific sector during December solstice.
Multiscale error analysis, correction, and predictive uncertainty estimation in a flood forecasting system
Authors: Bogner K. , Pappenberger F.
Published: July 2011

River discharge predictions often show errors that degrade the quality of forecasts. Three different methods of error correction are compared, namely, an autoregressive model with and without exogenous input (ARX and AR, respectively), and a method based on wavelet transforms. For the wavelet method, a Vector‐Autoregressive model with exogenous input (VARX) is simultaneously fitted for the different levels of wavelet decomposition; after predicting the next time steps for each scale, a reconstruction formula is applied to transform the predictions in the wavelet domain back to the original time domain. The error correction methods are combined with the Hydrological Uncertainty Processor (HUP) in order to estimate the predictive conditional distribution. For three stations along the Danube catchment, and using output from the European Flood Alert System (EFAS), we demonstrate that the method based on wavelets outperforms simpler methods and uncorrected predictions with respect to mean absolute error, Nash‐Sutcliffe efficiency coefficient (and its decomposed performance criteria), informativeness score, and in particular forecast reliability. The wavelet approach efficiently accounts for forecast errors with scale properties of unknown source and statistical structure.
Shade estimation over streams using distributed temperature sensing
Authors: Petrides A. C. , Huff J. , Arik A. , van de Giesen N. , Kennedy A. M. , Thomas C. K. , Selker J. S.
Published: July 2011

The characterization of temporal and spatial distribution of sunlight is essential for understanding energy transport in natural ecosystems. Fiber‐optic distributed temperature sensing (DTS) allows meter resolution measurements of temperature at subminute resolution. The difference in temperature due to absorption and reflection of a pair of helically twisted black and white fiber‐optic cables was measured with a DTS to document areas exposed to sunlight over the Walla Walla River. A high correlation (R2 = 0.99) was found between DTS‐based results and manual field observations of effective shade. These preliminary results provide proof of the concept that this method can be used for estimating the effective shade at fine spatial resolutions. Potential shortcomings and the need for a more quantitative physical model are suggested for further research.
Verification of porosity predictors for fluvial sand‐gravel deposits
Authors: Frings Roy M. , Schüttrumpf Holger , Vollmer Stefan
Published: July 2011

Although porosity is a key property of sediment mixtures, little is known of the natural variations in porosity in fluvial systems. Porosity predictors can help to generate such information. The objective of this study was to determine the accuracy of porosity predictors for fluvial sand‐gravel mixtures. In order to do so, porosity measurements were done in the Rhine River, using a diving bell to allow undisturbed sampling under water. In addition, laboratory experiments were conducted, and porosity data from literature were reanalyzed. Measured porosity values range from 0.06 to 0.48. Our study shows that predictors based on the median grain size, the deviation from the Fuller curve, or the sediment standard deviation are unable to reproduce the observed variation in porosity. Predictors based on the entire grain size distribution perform better but are biased and have a large prediction error. This suggests that they do not account correctly for the grain size effect on porosity. On the other hand, parameters such as grain shape and the mechanism of deposition probably also have a distinct influence on porosity. Slightly more accurate predictions can be obtained with tailor‐made predictors for the river under interest. Multivariate regression analysis on the Rhine data set produced a predictor with two independent parameters: the sediment standard deviation and the number of grains smaller than 0.5 mm, representing grain mixing effects and adhesion effects, respectively. Despite the shortcomings, porosity predictors provide valuable insights in the spatial variation in porosity, which is demonstrated in a case study for the Rhine River.
Estimating surface flow paths on a digital elevation model using a triangular facet network
Authors: Zhou Qiming , Pilesjö Petter , Chen Yumin
Published: July 2011

This study attempts to develop a method for the simulation of surface flow paths on a digital elevation model (DEM). The objective is to use a facet‐based algorithm to estimate the surface flow paths on a raster DEM. A grid DEM was used to create a triangular facet network (TFN) over which the surface flow paths were determined. Since each facet in the network has a constant slope and aspect, the estimations of, for example, flow direction and divergence/convergence are less complicated compared to traditional raster‐based solutions. Experiments were undertaken by estimating the specific catchment area (SCA) over a number of mathematical surfaces, as well as on a real‐world DEM. Comparisons were made between the derived SCA by the TFN algorithm with some algorithms reported in the literature. The results show that the TFN algorithm produced the closest outcomes to the theoretical values of the SCA compared with other algorithms, deriving more consistent outcomes and being less influenced by surface shapes. The real‐world DEM test also shows that the TFN was capable of modeling flow distribution without noticeable “artifacts,” and its ability of tracking flow paths makes it an appropriate platform for dynamic surface flow simulation.
Open radar interferometry software for mapping surface Deformation
Authors: Sandwell David , Mellors Rob , Tong Xiaopeng , Wei Matt , Wessel Paul
Published: July 2011

Over the past 15 years, software for processing interferometric synthetic aperture radar (InSAR) data into maps of surface deformation has been developed and refined. The InSAR technique is commonly used to investigate deformation associated with earthquakes, volcanoes, withdrawal of crustal fluids, and coherent ice motions [Massonnet and Feigl, 1998]. The software, called Generic Mapping Tools Synthetic Aperture Radar (GMTSAR), is an open‐source (GNU General Public License) InSAR processing system designed for users familiar with Generic Mapping Tools (GMT) [Wessel and Smith, 1998]. The GMTSAR code is written in the C programing language and will run on any UNIX® computer. It requires installation of GMT and Network Common Data Format (NetCDF) and supports several fast Fourier transform libraries.
NASA focusing beyond space shuttle era
Authors: Showstack Randy
Published: July 2011

Although the NASA space shuttle Atlantis is set to close out the space shuttle era in July with the STS‐135 mission, this final shuttle mission will not mark the end of America's leadership in human spaceflight, NASA administrator Charles Bolden said in a 1 July speech at the National Press Club in Washington, D. C. “When I hear people say, or listen to media reports [that indicate], that the final shuttle flight marks the end of U.S. human spaceflight, I have to say, ‘these folks must be living on another planet.’ We are not ending human spaceflight; we are recommitting ourselves to it and taking the necessary and difficult steps today to ensure America's preeminence in human space exploration for years to come.”
Higher “normal” U.S. temperatures
Authors: Showstack Randy
Published: July 2011

Temperatures across the United States were approximately 0.5°F warmer on average from 1981 to 2010 than they were from 1971 to 2000, according to data about new climate “normals” released by the National Oceanic and Atmospheric Administration's National Climatic Data Center (NOAA NCDC) on 1 July. In the new normals the annual maximum and minimum temperatures for every state in the continental United States increased on average, according to NCDC director Thomas Karl. The normals, updated once each decade, are 30‐year baseline averages of climatological variables including average temperature and precipitation for more than 7500 locations across the United States, according to NOAA. They are useful for a number of purposes including assisting local weather forecasters in comparing daily weather conditions and helping farmers with crop selection and planting decisions.
Role of the seasonal cycle in coupling climate and carbon cycling in the subantarctic zone
Authors: Monteiro Pedro M. S. , Boyd Philip , Bellerby Richard
Published: July 2011

Workshop on the Seasonal Cycle of the Carbon‐Climate System in the Southern Ocean; Cape Town, South Africa, 23–25 August 2010; There is increasing evidence in the Southern Ocean that mesoscales and seasonal scales play an important role in the coupling of ocean carbon cycling and climate. The seasonal cycle is one of the strongest modes of variability in different components of the carbon cycle in the Southern Ocean. It is also the mode that couples climate forcing to ecosystem responses such as productivity and ultimately biogeochemical signals including carbon export. However, not only are these scales of coupling poorly understood, but also there appear to be important regional differences in the way they couple climate to carbon. With this as an overarching theme, a workshop in South Africa brought together scientists working in the Southern Ocean, the waters south of Australia, New Zealand, and South Africa. The importance of the Subantarctic Zone (SAZ) as a carbon sink made it an ideal system on which to focus the workshop.
Eos is out of this world—literally
Authors: Richman Barbara T.
Published: July 2011

When the space shuttle Endeavour launched on its 25th and final flight, AGU member and astronaut Andrew J. Feustel took with him a special bit of cargo: an issue of Eos. The accompanying photograph with the image of Eos, taken on 23 May 2011, shows the 15 February issue of Eos floating in front of one of the International Space Station windows. Below and left of the issue is the wing of Endeavour; also visible is the radiator panel on the shuttle's payload bay door. The thin blue line to the right of the issue is Earth's atmosphere. The STS‐134 mission, the second to last space shuttle mission, launched on 16 May and returned to Earth on 1 June. It delivered the Alpha Magnetic Spectrometer (a particle physics experiment module) to the International Space Station along with two communications antennas, a high‐pressure gas tank, and parts for the two‐armed Special Purpose Dexterous Manipulator (Dextre) robot. The final shuttle mission, STS‐135, launched on 8 July.
Part of the Gulf of Mexico became greener after oil spill
Authors: Balcerak Ernie
Published: July 2011

Biological changes have been observed in the northeastern Gulf of Mexico since the April–July 2010 Deepwater Horizon oil spill, the largest offshore spill event in U.S. history. To overcome the difficulty of lack of sufficient field sampling data for a region‐wide impact assessment, Hu et al. used multiyear satellite measurements of ocean phytoplankton's “glow” under sunlight to document the surface ocean's biological changes. They observed that during August 2010, several weeks after the leaking oil well was capped, an area stretching more than 11,000 square kilometers in the northeastern Gulf of Mexico was especially green, caused by increased phytoplankton biomass. The area was greener than it had been during any previous August since 2002. The researchers' analyses of ocean circulation and other oceanographic and environmental data indicate that the increased greenness was probably caused by the oil spill. Their findings highlight the unique value of satellite technology in observing changes in the ocean as well as the need for an integrated and sustained ocean observing system. (Geophysical Research Letters, doi:10.1029/2011GL047184, 2011)
Improving model estimates of gross primary production
Authors: Schultz Colin
Published: July 2011

Balancing the global carbon budget is a daunting task complicated by the fact that even the most essential values elude direct observation. Gross primary production, the amount of carbon used by terrestrial vegetation to fuel its annual growth, is often estimated by extrapolation from observations using climate models, including the Community Land Model (CLM). Terrestrial ecosystems are an extremely important sink for atmospheric carbon, so any misrepresentations of gross primary production can have strong effects on the understanding of the global carbon budget and may also potentially affect lawmakers' ability to plan around it. The widely used model, which is now in its fourth major version and seeks to represent the interplay between vegetation and climate, is known to overestimate global gross primary production by around 35 petagrams per year when compared to estimates derived from observations and other models, a surplus equivalent to about 6 times the annual carbon emissions of the United States. (Journal of Geophysical Research‐Biogeosciences, doi:10.1029/2010JG001593, 2011)
Estimating the distribution of extreme events
Authors: Balcerak Ernie
Published: July 2011

Modeling the distribution of extreme events such as major floods, severe rainfall, and high wind speeds can be challenging. Researchers in many fields commonly use the generalized extreme value (GEV) distribution to characterize how these events are distributed over time. However, for many types of extreme events, there are limited data available, making it difficult to fit the GEV distribution. To help deal with this problem, Ailliot et al. generalized two common methods (maximum likelihood and method of moments) for estimating the parameters and high quantiles of the GEV distribution. Using simple parameter constraints, the scientists developed efficient and numerically robust estimation procedures that are suitable for automatic batch processing of many small‐to medium‐sized data sets. They illustrate their methods by applying them to annual maximum rainfall data in New Zealand. (Water Resources Research, doi:10.1029/2010WR009417, 2011)
Fundamental issues of modeling in a climate of change
Authors: Schultz Colin
Published: July 2011

Numerical models, one of the dominant modes of performing scientific research, fit into two broad classes: operational models, which aim to produce tightly constrained estimates of future behavior using historical observations, and exploratory, or novelty‐seeking models, which aim to include as many physical dynamics as possible. Kumar suggests that in the face of human‐induced land use and climate changes, attempts need to be made to bridge the divide between the two types of models. He argues that climate and human‐driven forces could fundamentally alter hydrologic dynamics such that appeals to historical evidence could be rendered obsolete as a method of ensuring that a model is an accurate representation of reality. Using the hydrologic cycle as a platform, the author categorizes ways that novelty‐seeking models could be used to improve predictions of future behavior. He suggests that prioritizing the prediction of extreme events, normally a focus of novelty‐seeking models, could result in more physically realistic models and improved estimates of future behavior. (Water Resources Research, doi:10.1029/2010WR009769, 2011)
Improving global estimates of land surface properties
Authors: Schultz Colin
Published: July 2011

Large models often rely on numerical simplifications of complex or small‐scale processes, usually because the underlying mechanisms are not well understood or direct observations are unavailable. The values for these parameterizations can be tuned to fit observations or estimated through an inversion process, in which measurements of one easily observable parameter are used to calculate a related, but more elusive, physical quantity. However, remotely sensed data are specific to each instrument, so it is crucial to ascertain whether a new sensor's data can be used with a model. Using the Joint Research Centre Two‐stream Inversion Package (JRC‐TIP) inversion model, Pinty et al. provide a method of transforming satellite measurements of surface albedo made by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) satellite into a physically consistent set of radiative and structural surface variable values suitable for assimilation into climate models. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2010JD015372, 2011)
CD137 differentially regulates innate and adaptive immunity against Mycobacterium tuberculosis
Authors: Fernández Do Porto Darío A , Jurado Javier O , Pasquinelli Virginia , Alvarez Ivana B , Aspera Romina H , Musella Rosa M , García Verónica E
Published: July 2011

Protective immunity against Mycobacterium tuberculosis is primarily mediated by the interaction of antigen‐specific T cells and antigen presenting cells, which often depends on the interplay of cytokines produced by these cells. Costimulatory signals represent a complex network of receptor–ligand interactions that qualitatively and quantitatively influence immune responses. Thus, here we investigated the function of CD137 and CD137L, molecules known to have a central role in immune regulation, during human tuberculosis (TB). We demonstrated that M. tuberculosis antigen stimulation increased both CD137 and CD137L expression on monocytes and NK cells from TB patients and healthy donors, but only up‐regulated CD137 on T lymphocytes. Blockage of the CD137 pathway enhanced the levels of interferon (IFN)‐γ and tumor necrosis factor (TNF)‐α produced by monocytes and NK against M. tuberculosis. In contrast, CD137 blockage significantly decreased the specific degranulation of CD8+ T cells and the percentage of specific IFN‐γ and TNF‐α producing lymphocytes against the pathogen. Furthermore, inhibition of the CD137 pathway markedly increased T‐cell apoptosis. Taken together, our results demonstrate that CD137:CD137L interactions regulate the innate and adaptive immune response of the host against M. tuberculosis.
Adaphostin promotes caffeine-evoked autocrine Fas-mediated death pathway activation in Bcr/Abl-positive leukaemia cells
Authors: Liu Wen-Hsin , Chang Long-Sen
Published: July 2011

The present study was conducted to verify whether caffeine is beneficial for improving leukaemia therapy. Co-treatment with adaphostin (a Bcr/Abl inhibitor) was found to potentiate caffeine-induced Fas/FasL up-regulation. Although adaphostin did not elicit ASK1 (apoptosis signal-regulating kinase 1)-mediated phosphorylation of p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun N-terminal kinase), co-treatment with adaphostin notably increased p38 MAPK/JNK activation in caffeine-treated cells. Suppression of p38 MAPK and JNK abrogated Fas/FasL up-regulation in caffeine- and caffeine/adaphostin-treated cells. Compared with caffeine, adaphostin markedly suppressed Akt/ERK (extracellular-signal-regulated kinase)-mediated MKP-1 (MAPK phosphatase 1) protein expression in K562 cells. MKP-1 down-regulation eventually elucidated the enhanced effect of adaphostin on p38 MAPK/JNK activation and subsequent Fas/FasL up-regulation in caffeine-treated cells. Knockdown of p38α MAPK and JNK1, ATF-2 (activating transcription factor 2) and c-Jun by siRNA (small interfering RNA) proved that p38α MAPK/ATF-2 and JNK1/c-Jun pathways were responsible for caffeine-evoked Fas/FasL up-regulation. Moreover, Ca2+ and ROS (reactive oxygen species) were demonstrated to be responsible for ASK1 activation and Akt/ERK inactivation respectively in caffeine- and caffeine/adaphostin-treated cells. Likewise, adaphostin functionally enhanced caffeine-induced Fas/FasL up-regulation in leukaemia cells that expressed Bcr/Abl. Taken together, the results of the present study suggest a therapeutic strategy in improving the efficacy of adaphostin via Fas-mediated death pathway activation in Bcr/Abl-positive leukaemia.