470 research outputs found
Evaluation of Spacecraft Technology Programs (Effects on Communication Satellite Business Ventures), Volume 2
The computational procedures used in the evaluation of spacecraft technology programs that impact upon commercial communication satellite operations are discussed. Computer programs and data bases are described
Description of a subset of single events from the BATSE gamma ray burst data
About 15 percent of the gamma ray bursts in the Burst and Transient Source Experiment (BATSE) data exhibit a simple light curve consisting mainly of a single pulse without fine substructures. In 12 of the burst profiles, the pulse shapes show a linear rise and decay. Three events have a distinct sharp rise followed by a long, almost exponential decay. Searches based on only a sharp rise selection criterion resulted in five more grbs with different profile complexities. In one case, we identify an envelope of fast oscillations with a long, softer tail lasting about 100 seconds. The majority of events were detectable at energies above 300 keV, with tentative estimates for fluences that vary between 4.0 x 10(exp -8) and 5.4 x 10(exp -6) ergs/sq cm. We describe here their general characteristics (durations, rise-decay times) and their hardness ratios
Hospital-Reported Pneumococcal Susceptibility to Penicillin
Geographic variation in drug susceptibility among isolates of Streptococcus pneumoniae has influenced national treatment guidelines for community-acquired pneumonia. Whether individual hospital susceptibility data provide reliable and valid information for providers is unclear. We examined the geographic and temporal variability in hospital-reported rates of pneumococcal susceptibility. We surveyed all 52 hospitals that provided acute adult care in the five counties surrounding Philadelphia and collected data on levels of penicillin susceptibility among all pneumococcal blood isolates from 1998 to 2000. In 1998, pneumococcal nonsusceptibility to penicillin varied from 0% to 67% of all blood isolates across the 33 hospitals with ≥10 isolates in that year. Hospital location did not correlate with the level of reported pneumococcal susceptibility (p = 0.8). In addition, correlations were not significant in reported pneumococcal susceptibility to penicillin within individual hospitals during the 3 years
Monitoring Cen X-3 with BATSE
The eight uncollimated BATSE Large Area Detectors (LAD's) provide the ability to monitor pulsed hard x ray sources on a nearly continuous basis. Using data from the LAD's, the pulse timing and pulsed flux of the 4.8 second period binary x ray pulsar Centaurus X-3 was analyzed over a two month period. The methods and initial results of this analysis, which includes both data folded onboard GRO and 1.024 second resolution discriminator rates folded on the ground, are presented
Do Gamma-Ray Burst Sources Repeat?
The demonstration of repeated gamma-ray bursts from an individual source
would severely constrain burst source models. Recent reports (Quashnock and
Lamb 1993; Wang and Lingenfelter 1993) of evidence for repetition in the first
BATSE burst catalog have generated renewed interest in this issue. Here, we
analyze the angular distribution of 585 bursts of the second BATSE catalog
(Meegan et al. 1994). We search for evidence of burst recurrence using the
nearest and farthest neighbor statistic and the two-point angular correlation
function. We find the data to be consistent with the hypothesis that burst
sources do not repeat; however, a repeater fraction of up to about 20% of the
observed bursts cannot be excluded.Comment: ApJ Letters, in press, 13 pages, including three embedded figures.
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Radiation from relativistic jets in turbulent magnetic fields
Using our new 3-D relativistic electromagnetic particle (REMP) code
parallelized with MPI, we have investigated long-term particle acceleration
associated with an relativistic electron-positron jet propagating in an
unmagnetized ambient electron-positron plasma. The simulations have been
performed using a much longer simulation system than our previous simulations
in order to investigate the full nonlinear stage of the Weibel instability and
its particle acceleration mechanism. Cold jet electrons are thermalized and
ambient electrons are accelerated in the resulting shocks. The acceleration of
ambient electrons leads to a maximum ambient electron density three times
larger than the original value. Behind the bow shock in the jet shock strong
electromagnetic fields are generated. These fields may lead to the afterglow
emission. We have calculated the time evolution of the spectrum from two
electrons propagating in a uniform parallel magnetic field to verify the
technique.Comment: 3 pages, 2 figures, submitted for the Proceedings of The Sixth
Huntsville Gamma-Ray Burst Symposium 2008, Huntsville, AL, October 20-23,
200
A major outburst from the X-ray binary RX J0520.5-6932
We report on the analysis of 8 years of MAssive Compact Halo Objects (MACHO)
data for the source RX J0520.5-6932. A regular period of 24.4 days has been
confirmed, however this is manifest almost entirely in the red part of the
spectrum. A major outburst, lasting approximately 200 days, was observed which
increased the apparent brightness of the object by approximately 0.15
magnitudes without significantly altering its V-R colour index. This outburst
was also seen in X-ray data. The evidence from this analysis points to the
identification of this object as a Be/X-ray binary with a periodically variable
circumstellar disk and a very early optical counterpart.Comment: Paper has been accepted by MNRA
Otomatisasi Instalasi Pengolah Air Limbah (Ipal) Sistem Mobile Di Baristand Industri Surabaya
Berdasarkan UU RI No.32 Tahun 2009 Tentang Perlindungan dan Pengelolaan Lingkungan Hidup, maka setiap industri maupun instansi harus bertanggung jawab terhadap pengelolaan limbah yang dihasilkan dari kegiatannya. Sehubungan dengan adanya permasalahan keterbatasan lahan yang permanen, maka Baristand berupaya membantu dalam pemecahan terhadap permasalahan yang dihadapi industri dengan perekayasaan Mobil IPAL.Permasalahan yang ada di Mobil IPAL adalah adanya fluktuasi Karakteristik & volume Air limbah yg akan diproses, tergantung sumber limbahnya, hal tersebut menimbulkan kesulitan pada pengaturan pH serta Penambahan pereaksi. Sehingga dengan Otomatisasi diharapkan kinerja IPAL Mobil lebih effisien.Sistem otomatisasi di IPAL Mobil meliputi penetapan pH 7 dengan pH display dan pengaturan pemberian reagen secara manual. Pengaturan pH : 7 dengan proses air limbah secara sinambung yang dilengkapi dengan dozing pump menggunakan larutan H2SO4 10 %, pengontrolan pH dengan waktu respon dalam 30 detik
Calibration of the GLAST Burst Monitor detectors
The GLAST Burst Monitor (GBM) will augment the capabilities of GLAST for the
detection of cosmic gamma-ray bursts by extending the energy range (20 MeV to >
300 GeV) of the Large Area Telescope (LAT) towards lower energies by 2
BGO-detectors (150 keV to 30 MeV) and 12 NaI(Tl) detectors (10 keV to 1 MeV).
The physical detector response of the GBM instrument for GRBs is determined
with the help of Monte Carlo simulations, which are supported and verified by
on-ground calibration measurements, performed extensively with the individual
detectors at the MPE in 2005. All flight and spare detectors were irradiated
with calibrated radioactive sources in the laboratory (from 14 keV to 4.43
MeV). The energy/channel-relations, the dependences of energy resolution and
effective areas on the energy and the angular responses were measured. Due to
the low number of emission lines of radioactive sources below 100 keV,
calibration measurements in the energy range from 10 keV to 60 keV were
performed with the X-ray radiometry working group of the
Physikalisch-Technische Bundesanstalt (PTB) at the BESSY synchrotron radiation
facility, Berlin.Comment: 2 pages, 1 figure; to appear in the Proc. of the First Int. GLAST
Symp. (Stanford, Feb. 5-8, 2007), eds. S.Ritz, P.F.Michelson, and C.Meegan,
AIP Conf. Pro
The optical counterpart to gamma-ray burst GRB970228 observed using the Hubble Space Telescope
Although more than 2,000 astronomical gamma-ray bursts (GRBs) have been
detected, and numerous models proposed to explain their occurrence, they have
remained enigmatic owing to the lack of an obvious counterpart at other
wavelengths. The recent ground-based detection of a transient source in the
vicinity of GRB 970228 may therefore have provided a breakthrough. The optical
counterpart appears to be embedded in an extended source which, if a galaxy as
has been suggested, would lend weight to those models that place GRBs at
cosmological distances. Here we report the observations using the Hubble Space
Telescope of the transient counterpart and extended source 26 and 39 days after
the initial gamma-ray outburst. We find that the counterpart has faded since
the initial detection (and continues to fade), but the extended source exhibits
no significant change in brightness between the two dates of observations
reported here. The size and apparent constancy between the two epochs of HST
observations imply that it is extragalactic, but its faintness makes a
definitive statement about its nature difficult. Nevertheless, the decay
profile of the transient source is consistent with a popular impulsive-fireball
model, which assumes a merger between two neutron stars in a distant galaxy.Comment: 11 pages + 2 figures. To appear in Nature (29 May 1997 issue
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