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Search Results: 1 - 10 of 466122 matches for " Oscar A;Greiner "
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Prevalence of blood parasites in Tyrannidae (flycatchers) in the Eastern plains of Colombia
Matta, Nubia E;Basto, Natalia;Gutierrez, Rafael;Rodríguez, Oscar A;Greiner, Ellis C;
Memórias do Instituto Oswaldo Cruz , 2004, DOI: 10.1590/S0074-02762004000300005
Abstract: blood samples from 159 birds of the new-world family tyrannidae (the flycatchers) from the eastern plains of colombia, were examined for haematozoa parasites, in 1999-2000. haematozoa were detected in six of 20 species. the overall prevalence was 10.1%. the most common parasites detected were microfilariae, followed by trypanosoma and plasmodium. the highest prevalence (9.6%) was found in the ochre-bellied flycatcher (mionectes oleaginea). mixed infections with more than one genus of blood parasite were rare and most infections encountered were of low intensity. the results of this study suggest an important role of ecologically diverse conditions determining composition, transmission, and prevalence of a blood parasite fauna, presumably through host interaction population density. some new host parasite relationship records are presented.
The X-ray spectrum of LSI+61o303
J. Greiner,A. Rau
Physics , 2001, DOI: 10.1051/0004-6361:20010826
Abstract: It had been proposed earlier that the hard X-ray and gamma-ray radiation of the Be/X-ray system LSI+61o303 could be due to inverse Compton scattering of optical photons from the Be star by the same electron population which also produces the radio emission. Recently, Apparao (2001) has calculated this inverse Compton emission in more detail, and predicted that the X-ray spectrum should show a break at around 20 keV. We investigated archival RXTE data, but do not find such a break in the 2--25 keV range. The implications of this finding are shortly discussed.
Broadband X-ray Spectroscopy of GRS 1915+105
A. Rau,J. Greiner
Physics , 2000,
Abstract: We analyzed RXTE data of GRS 1915+105 of X-ray low states between 1996 and 1998. The X-ray spectrum is dominated by the power law component. We found (i) that the power law is pivoting at 10-30 keV, (ii) that the power law slope correlates with radio flux, (iii) three different groups of 3-10 keV residuals, (iv) that one of these residual groups correlates with the power law slope.
S 10947 Aql = RX J2009.8+1557: A probable RS CVn star which sometimes stops its eclipses
G. A. Richter,J. Greiner
Physics , 2000,
Abstract: We report the discovery of a new variable star, called S 10947 Aql, as the likely optical counterpart of RX J2009.8+1557. The optical variability pattern as well as the detected X-ray emission suggest that it is a chromospherically active binary of the RS Canum Venaticorum type. We discovered an occasional disappearance of the eclipsing minima as well as large variations in the eclipse amplitude. We discuss possible causes of this peculiarity.
A model-independent analysis of the dependence of the anomalous J/psi suppression on the number of participant nucleons
A. P. Kostyuk,W. Greiner
Physics , 2003, DOI: 10.1088/0954-3899/29/10/102
Abstract: A recently published experimental dependence of the J/psi to Drell-Yan ratio on the measured, by a zero degree calorimeter, forward energy E_ZDC in Pb+Pb collisions at the CERN SPS is analyzed. Using a model-independent approach it is shown that the data are at variance with an earlier published experimental dependence of the same quantity on the transverse energy of neutral hadrons E_T. The discrepancy is related to a moderate centrality region: 100 < N_p < 200 (N_p is the number of participant nucleons) and is peculiar only to the data obtained within the `minimum bias' analysis (using the `theoretical Drell-Yan'). This could result from systematic experimental errors in the minimum bias sample. A possible source of the errors is discussed.
Optical counterparts of ROSAT X-ray sources in two selected fields at low vs. high Galactic latitudes
J. Greiner,G. A. Richter
Physics , 2014, DOI: 10.1051/0004-6361/201322844
Abstract: The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. We investigate two ROSAT All-Sky Survey fields of size 10 * 10 degrees each, one at galactic latitude b = 83 deg (Com), the other at b = -5 deg (Sge), in order to optically identify the majority of sources. We used optical variability, among other more standard methods, as a means of identifying a large number of ROSAT All-Sky Survey sources. All objects fainter than about 12 mag and brighter than about 17 mag, in or near the error circle of the ROSAT positions, were tested for optical variability on hundreds of archival plates of the Sonneberg field patrol. The present paper contains probable optical identifications of altogether 256 of the 370 ROSAT sources analysed. In particular, we found 126 AGN (some of them may be misclassified CVs), 17 likely clusters of galaxies, 16 eruptive double stars (mostly CVs), 43 chromospherically active stars, 65 stars brighter than about 13 mag, 7 UV Cet stars, 3 semiregular resp. slow irregular variable stars of late spectral type, 2 DA white dwarfs, 1 Am star, 1 supernova remnant and 1 planetary nebula. X-ray emission is, expectedly, tightly correlated with optical variability, and thus our new method for optically identifying X-ray sources is demonstrated to be feasible.
Generalized KdV Equation for Fluid Dynamics and Quantum Algebras
A. Ludu,R. A. Ionescu,W. Greiner
Physics , 1996, DOI: 10.1007/BF02058238
Abstract: We generalize the non-linear one-dimensional equation of a fluid layer for any depth and length as an infinite order differential equation for the steady waves. This equation can be written as a q-differential one, with its general solution written as a power series expansion with coefficients satisfying a nonlinear recurrence relation. In the limit of long and shallow water (shallow channels) we reobtain the well known Korteweg-de-Vries equation together with its single-soliton solution.
Tropospheric Circulation Variability over Central and Southern South America  [PDF]
Oscar A. Frumento, Vicente R. Barros
Atmospheric and Climate Sciences (ACS) , 2014, DOI: 10.4236/acs.2014.45084
Abstract: Combined Empirical Orthogonal Function Analysis of low-level atmospheric circulation after filtering the synoptic scale was performed for the period 1981-2006 over Central and Southern South America. Modes with 40 and near 70 days frequency associated with swings in longitude of the South Pacific and South Atlantic Ocean heights were identified. Their extreme values were related to drought and to high anomalous precipitation associated to floods in South East South America (SESA). These modes were independent of other sources of variability of the Southern Hemisphere atmosphere, namely MJO (Madden-Julian Oscillation), ENSO (El Nino Southern Oscillation) and AAO (Antarctic Oscillation). Mode one, which in its positive phase has a circulation similar to the mean winter, has a trend that explains part of the winter warming observed since 1980’s in Central and Eastern Argentina. Variance was calculated for the intra-annual variability, the one associated to the inter-annual variability including trends and jumps, and that of the annual cycle. The partition of the total variance was roughly 70%, 10% and 20% respectively. This partition implies that predictability of the regional climate is more critically dependent on the predictability of the intra-annual variability than of the inter-annual variability.
Shear Viscosity to Entropy within a Parton Cascade
El, A.;Greiner, C.;Xu, Z.
High Energy Physics - Phenomenology , 2007,
Abstract: The shear viscosity is calculated by means of the perturbative kinetic partonic cascade BAMPS with CGC initial conditons for various saturation momentum scale Q_s. eta/s ~ 0.15 stays approximately constant when going from RHIC to LHC.
Effect of the Haar measure on the finite temperature effective potential of $SU(2)$ Yang-Mills theory
K. Sailer,A. Sch?fer,W. Greiner
Physics , 1995, DOI: 10.1016/0370-2693(95)00346-M
Abstract: Including the Haar measure we show that the effective potential of the regularized SU(2) Yang-Mills theory has a minimum at vanishing Wilson-line $W=0$ for strong coupling, whereas it develops two degenerate minima close to $W=\pm 1$ for weak coupling. This suggests that the non-abelian character of $SU(2)$ as contained in the Haar measure might be responsible for confinement.
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