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The National Enforcement Investigations Center of the EPA provides support services for the enforcement activities of the Agency. Recently, we have analyzed hazardous wastes as part of efforts to enforce the Resource Conservation and Recovery Act and the Superfund Act. Sample preparation for inorganic elemental analysis is a difficult and time-consuming step. Thus, it would be desirable to be able to use x-ray fluorescence methods which require relatively little sample preparation for the analysis of solid hazardous wastes. A major problem to be overcome is the need to calibrate for a large variety of samples. However, a compensating factor is that the error will be largely determined by the sampling error and the measurement accuracy is not quite so critical.
A result of Haglund implies that the
-bigraded Hilbert series of the space of diagonal harmonics is a
-Ehrhart function of the flow polytope of a complete graph with netflow vector
. We study the
-Ehrhart functions of flow polytopes of threshold graphs with arbitrary netflow vectors. Our results generalize previously known specializations of the mentioned bigraded Hilbert series at
. As a corollary to our results, we obtain a proof of a conjecture of Armstrong, Garsia, Haglund, Rhoades, and Sagan about the
-Ehrhart function of the flow polytope of a complete graph with an arbitrary netflow vector.
Here, we introduce a new radiocarbon (14C) extraction line operating at the University of Bern, which was designed and built for the extraction of in situ 14C from meteorites. With this system, we achieved two important developments compared to other systems. First, using the MICADAS gas-interface system, 14C can directly be measured from the collected CO2 gas, i.e., without graphitization of the sample. Second, meteorite sample masses as low as ~0.05 g can be used for high precision and reproducibility. Prior to extraction in an oxygen atmosphere held at a pressure of ~20–30 mbar in an iridium crucible at 1600°C for 40 min, samples were preheated for 1 h in a constant oxygen flow at 500°C and continuous pumping. Gas purification followed the method described previously (e.g., Hippe et al. 2009). While the blank levels for preheated samples are low (<2×104 14C atoms), the blanks for non-preheated samples are high, therefore those results cannot be used. We also report preliminary results for the L-chondrite JaH 073. The terrestrial age of 17.7±0.4 ka is in good agreement with previous results for the same sample of this meteorite, confirming that the extraction line, the gas purification system, and the AMS measurements are all reliable.
The author - with his collaborators - already in years 1995-96 have shown - purely from the analyses of the observations - that the gamma-ray bursts (GRBs) can be till redshift 20. Since that time several other statistical studies of the spatial distribution of GRBs were provided. Remarkable conclusions concerning the star-formation rate and the validity of the cosmological principle were obtained about the regions of the cosmic dawn. In this contribution these efforts are surveyed.
At present there are in use three different models to characterize the large scale structure of the universe. The clustering model (Soneira and Peebles, 1978) assumes that the superclusters are high density islands in a low density sea. The void model (Joeveer and Einasto, 1978), on the other hand, assumes that the voids are isolated low density islands in a high density sea. The sponge model (Gott et al., 1986) assumes that high and low density regions occupy equal volumes, and that the high and low density regions are both connected. The straightforward way to decide among these three models is the direct investigation of the spatial distribution of the galaxies. Nevertheless, there is an essentially different observational method that may also be useful to obtain some information about these models. The X-ray background radiation (XRB) is due either to the bremsstrahlung of hot intergalactic gas, or to the sum of the radiation of unresolved discrete sources (E.G. Boldt 1987). If the “discrete” origin is correct, then obviously the actual number of sources, and hence their total intensity, may vary from one part of the sky to another. Thus, in this case one has the possibility to estimate the number of sources in a given volume from the observed isotropy of the XRB. For example, Hamilton and Helfand (1987) suggest that the number of sources must be larger than 5000/(degree)2. Any such estimate needs several assumptions. In the previous works one usually assumed that the sources were distributed completely randomly; see, e.g. Fabian (1972). Nevertheless, if the XRB is generated by young galaxies (Bookbinder et al. 1980), it is not excluded that the sources of the SRB are also grouped similarly to galaxies. Because in this case the distribution of sources of the XRB is not completely random, one may expect a different type of fluctuations in the intensity of the XRB. In addition, since the grouping may be quite different for the three structure models, the expected fluctuations may also be different. There is a chance to discriminate among them using the observed isotropy of XRB. The basic observational datum concerning the isotropy of the XRB is well-known: the fluctuations in the intensity are smaller than 3%, if 3° × 3° pixels are used Shafer (1983).
In two previous publications (Mészáros and Mészáros 1988 “Paper I”; Bagoly, Mészáros, and Mészáros 1988 “Paper II”), we have studied the fluctuations of the X-ray background (XRB) expected if the XRB is produced by discrete sources distributed as galaxies. The distribution of matter was assumed to follow the large-scale structure in the form of spherical clusters (superclusters) or spherical voids. In Paper I the density contrast of XRB sources inside and outside structures was taken to be a step function of constant height, whereas in Paper II we introduced arbitrary density contrasts (independent of redshift) and allowed for a redshift evolution of the luminosity of the sources. This led to predicted angular fluctuations of the XRB, which, when we compared them with the HEAO–1 observational limit (Shafer 1983), allowed us to set limits on the type and density of structures.
The Cosmological Principle claims that in the large scale average the visible parts of the universe are isotropic and homogeneous. In year 1998 the author, together with his two colleagues, discovered that the BATSE’s short gamma-ray bursts are not distributed isotropically on the sky. This first discovery was followed by other ones confirming both the existence of anisotropies in the angular distribution of bursts and the existence of huge Gpc structures in the spatial distribution. All this means that these anisotropies should reject the Cosmological Principle, because the large scale averaging hardly can be provided. This was claimed in year 2009. The aim of this contribution is to survey these publications since 1998 till today.
The test of the isotropy in the angular distribution of the gamma-ray bursts collected in BATSE Catalog (Meegan C. A. et al. 2000) is a test of cosmological principle itself, because the gamma-ray bursts are at cosmological distances. Several articles of the authors study this question (Balázs L. G., Mészáros A., & Horváth I., Astron. Astrophys., 339, 1, 1998; Balázs L. G., Mészáros A., Horváth I., & Vavrek R., Astron. Astrophys. Suppl., 138, 417, 1999; Mészáros A., Bagoly Z., & Vavrek R. Astron. Astrophys., 354, 1, 2000; Mészáros A., Bagoly Z., Horváth I., Balázs L.G. & Vavrek R. Astrophys. J., 539, 98, 2000). The final conclusion concerning the validity of isotropy is complicated both by instrumental effects and by the fact that there are three subgroups of gamma-ray bursts (“short”, “intermediate”, “long”; separation is done with respect to the duration of bursts). The long bursts are surely up to z ⋍ 4 (z is the redshift); for the remaining two subclasses the redshifts are unknown. The done tests of isotropy suggest (after the elimination of instrumental effects) the existence of anisotropy for the intermediate subclass on the confidence level > 95%. On the other hand, for the remaining two subclasses the situation is unclear; there is no unambiguous rejection of isotropy for them yet on the higher than 95% confidence level. If the bursts of intermediate subclass are at high z-s (say, at z > 0.1), then the validity of cosmological principle would be in serious doubt.
Extensive observational campaigns of afterglow hunting have greatly enriched our understanding of the gamma-ray burst (GRB) phenomenon. Efforts have been made recently to explore some afterglow properties or signatures that will be tested by the on-going or the future observational campaigns yet come. These include the properties of GRB early afterglows in the temporal domain; the GeV-TeV afterglow signatures in the spectral domain; as well as a global view about the GRB universal structured jet configuration. These recent efforts are reviewed. Within the standard cosmological fireball model, the very model(s) responsible for the GRB prompt emission is (are) not identified. These models are critically reviewed and confronted with the current data.
Extensive data bases on Gamma-Ray Burst (GRB) properties such as the BATSE 3B catalog (Meegan et al. 1996) contain a wealth of statistical information. The nine entries of the 3B database for each GRB consist of two durations, T50, T90, which contain 50% and 90% of the burst energy, respectively; four fluences (time-integrated energy fluxes) F1, F2, F3, F4, defined over different energy channels; and three measures of the peak flux (each summed over the four energy channels), measured over three different resolution timescales (64 ms, 256 ms and 1024 ms). Thus the initial number of variables is n = 9. There is, of course, some incompleteness in the catalog. There are 625 GRBs having all 9 non-zero quantities, and only they are considered here.
The effect of strong magnetic fields (B ≳ 1011Gauss) upon various atomic line emission mechanisms in the X-ray range is considered, in particular for H and H-like or He-like ions, and a discussion of the detectability and significance of possible measurements is given. The cyclotron mechanism, the one- and two-photon scattering and the bremsstrahlung effects in a strong B are reviewed, as well as the role they play in determining X-ray spectra. These considerations are applied to typical models of X-ray pulsars and Gamma-ray bursters, contrasting observations of magnetic related features to the present theoretical understanding of these objects.
The discovery of the afterglows of gamma-ray bursts (GRB) at X-ray, optical and radio wavelengths heralds a new era in the investigation of these objects. This provides a quantum jump in the type of observational information available, providing much more severe constraints on models, and probably represents the light at the end of the tunnel for this long-standing puzzle of astrophysics.
The paper experimentally investigates indoor visible light communication (VLC) channels. The disturbances come from the light bulbs and other VLC systems. The paper demonstrates that the noisiest light bulbs are the fluorescent lamps which emit high frequency disturbances. Different light bulbs are examined to make an optimal carrier choice for the transmitted signal. In the next part of the paper several modulation schemes and two kinds of detector systems are compared. The paper represents also the advantages and disadvantages of receiver constructions with and without a lens. The optimum modulation for different application is investigated.
The star has to go on radiating and radiating and contracting and contracting until, I suppose, it gets down to a few km. radius, when gravity becomes strong enough to hold in the radiation, and the star can at last find peace. Dr. Chandrasekhar had got this result before, but he has rubbed it in in his latest paper; and, when discussing it with him, I felt driven to the conclusion that this was almost a reductio ad absurdum of the relativistic degeneracy formula.
(A. S. Eddington )
The emphasis of this chapter is on four parts of relativistic astrophysics in which general relativity plays a fundamental role. After briefly reviewing the early history of the subject, we discuss
The structure and stability of relativistic stars
Observational evidence for black holes
General relativistic astrophysics encompasses a broader arena, and separate chapters or parts of chapters in this volume are devoted to cosmology, gravitational waves, the inspiral and merger of compact binaries, and black-hole stability.
Relativistic astrophysics began in 1916 on the Russian front, where Karl Schwarzschild wrote two papers, one reporting the solution to the Einstein equation for an incompressible spherical star, the other presenting the celebrated vacuum Schwarzschild spacetime. Schwarzschild was dead within the year, and for the next 47 years his solutions had a twilight existence. In no known stars did general relativity play a significant role, and only a handful of papers in astronomy or astrophysics mentioned the work.
Although sparsely distributed, the exceptions to this neglect were remarkable. In 1931, shortly before Chadwick's discovery of the neutron and shortly after the first paper by Chandrasekhar  (following approximate computations by Anderson  and Stoner  on an upper mass limit of white dwarfs, Landau  submitted a paper that independently argued that there was an upper limit on the mass of a collection of degenerate fermions and speculated on the existence of stars with cores of nuclear density.
A sample of 427 gamma-ray bursts (GRBs) was observed by the RHESSI
satellite in Feb. 2002 - Apr. 2008. We calculated spectral lags and peak-count
rates for the first time and constructed a new observational database. This database is
statistically studied completing an earlier analysis of durations and hardness ratios.
First, we discuss properties of short-, intermediate-, and long-duration GRBs in terms of
peak-count rates and spectral lags. Second, we investigate the number of GRB groups using
model-based clustering method together with Kolmogorov-Smirnov (K-S) and Anderson-Darling
(A-D) tests. The results are: The inter. bursts have properties similar to short bursts.
The groups of inter. and long bursts appear to be different. The inter. GRBs in the
RHESSI and Swift databases seem to be different
phenomena. This work is summary of Řípa et al. (2012).
Duplex stainless steels (DSS) may be defined as a category of steels with a two-phase ferritic–austenitic microstructure, which combines good mechanical and corrosion properties. However, these steels can undergo significant microstructural modification as a consequence of either thermo-mechanical treatments (ferrite decomposition, which causes σ- and χ-phase formation and nitride precipitation) or plastic deformation at room temperature [austenite transformation into strain-induced martensite (SIM)]. These secondary phases noticeably affect the properties of DSS, and therefore are of huge industrial interest. In the present work, SIM formation was investigated in a 2101 lean DSS. The material was subjected to cold rolling at various degrees of deformation (from 10 to 80% thickness reduction) and the microstructure developed after plastic deformation was investigated by electron backscattered diffraction, X-ray diffraction measurements, and hardness and magnetic tests. It was observed that SIM formed as a consequence of deformations higher than ~20% and residual austenite was still observed at 80% of thickness reduction. Furthermore, a direct relationship was found between microstructure and magnetic properties.
Peter Mészáros, Department of Physics and Center for Particle Astrophysics, 525 Davey Lab, Pennsylvania State University, University Park, PA 16802, USA,
Ralph A. M. J. Wijers, Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, Amsterdam, The Netherlands
As we have seen in the previous chapters, observational evidence combined with elementary theoretical considerations leads to the view that gamma-ray bursts (GRBs) and their afterglows result from dissipation of energy from an ultrarelativistic flow, which in turn is generated by a catastrophic event that injects a supernova-like amount of energy into a small volume. As discussed in Chapter 7, this dissipation can be both internal (when radial or angular differences in motion lead to heat production and subsequent radiation) and external (when the outflow interacts with its environment). The prevailing view attributes the prompt gamma-ray emission to the internal dissipation, and the afterglow to external dissipation, but the phenomena may overlap in time. A case in point is the so-called reverse-shock emission seen in optical wavelengths, during and soon after the prompt emission, and in radio wavelengths within the first days (Chapters 6 and 7), which is best explained as due to the reverse shock propagating back into the ejecta when they decelerate onto the external mass. The present chapter will deal with the physics of the external interaction of the outflow, regardless of how soon after the burst onset we see its emission.
There are some basic assumptions we make about the physics that dominates the behavior of our system. First, we will here treat only the spherically symmetric case. This is generally not correct, because GRBs are known to be highly collimated.
It is remarkable that the long gamma-ray bursts, as objects connected with the supernovae - i.e. with the end-stages of massive stars, trace the star formation rate. This connection is discussed in this contribution. The presentation is in essence a recapitulation of the article by Mészáros et al. (2006).
It is remarkable that the long gamma-ray bursts, as objects connected with the supernovae - i.e. with the end of the massive stars, trace the star formation rate. This connection is discussed in this contribution. The presentation is in essence a recapitulation of the article Mészáros A. et al. A&A, 2006, 455, 785.
The objective of this study was to compare linear models and survival analysis for genetic evaluation of ovulatory disorders, which included veterinary treatments of silent heat/anestrus and cystic ovaries. Data of 23 450 daughters of 274 Austrian Fleckvieh sires were analyzed. For linear model analyses, ovulatory disorders were defined as a binary response (presence or absence) in the time periods from calving to 150 days after calving and from calving to 300 days after calving. For survival analysis, ovulatory disorders were defined either as the number of days from calving to the day of the first treatment for an ovulatory disorder (uncensored record) or from calving to the day of culling, or the last day of the period under investigation (until 150 or 300 days after calving; censored record). Estimates of heritability were very similar (0.016 to 0.020) across methods and periods. Correlations between sire estimated breeding value from linear model and survival analysis were 0.98, whereas correlations between different time periods were somewhat lower (0.95 and 0.96). The results showed that the length of time period had a larger effect on genetic evaluation than methodology.