600 research outputs found
The digital data processing concepts of the LOFT mission
The Large Observatory for X-ray Timing (LOFT) is one of the five mission
candidates that were considered by ESA for an M3 mission (with a launch
opportunity in 2022 - 2024). LOFT features two instruments: the Large Area
Detector (LAD) and the Wide Field Monitor (WFM). The LAD is a 10 m 2 -class
instrument with approximately 15 times the collecting area of the largest
timing mission so far (RXTE) for the first time combined with CCD-class
spectral resolution. The WFM will continuously monitor the sky and recognise
changes in source states, detect transient and bursting phenomena and will
allow the mission to respond to this. Observing the brightest X-ray sources
with the effective area of the LAD leads to enormous data rates that need to be
processed on several levels, filtered and compressed in real-time already on
board. The WFM data processing on the other hand puts rather low constraints on
the data rate but requires algorithms to find the photon interaction location
on the detector and then to deconvolve the detector image in order to obtain
the sky coordinates of observed transient sources. In the following, we want to
give an overview of the data handling concepts that were developed during the
study phase.Comment: Proc. SPIE 9144, Space Telescopes and Instrumentation 2014:
Ultraviolet to Gamma Ray, 91446
Hyper-velocity impact test and simulation of a double-wall shield concept for the Wide Field Monitor aboard LOFT
The space mission LOFT (Large Observatory For X-ray Timing) was selected in
2011 by ESA as one of the candidates for the M3 launch opportunity. LOFT is
equipped with two instruments, the Large Area Detector (LAD) and the Wide Field
Monitor (WFM), based on Silicon Drift Detectors (SDDs). In orbit, they would be
exposed to hyper-velocity impacts by environmental dust particles, which might
alter the surface properties of the SDDs. In order to assess the risk posed by
these events, we performed simulations in ESABASE2 and laboratory tests. Tests
on SDD prototypes aimed at verifying to what extent the structural damages
produced by impacts affect the SDD functionality have been performed at the Van
de Graaff dust accelerator at the Max Planck Institute for Nuclear Physics
(MPIK) in Heidelberg. For the WFM, where we expect a rate of risky impacts
notably higher than for the LAD, we designed, simulated and successfully tested
at the plasma accelerator at the Technical University in Munich (TUM) a
double-wall shielding configuration based on thin foils of Kapton and
Polypropylene. In this paper we summarize all the assessment, focussing on the
experimental test campaign at TUM.Comment: Proc. SPIE 9144, Space Telescopes and Instrumentation 2014:
Ultraviolet to Gamma Ray, 91446
Use of Molybdenum in the Transplant Water for Burley Tobacco
The need for adding molybdenum to tobacco arises because contents in Kentucky soils generally are on the borderline of sufficiency and because amounts of available molybdenum in soil are low when soil pH is low. Soil pH in tobacco fields at midseason often is 0.5 to 1.0 pH unit lower than prior to fertilization. primarily because of the high rates of commercial fertilizers commonly applied to tobacco. This acidity greatly lowers the availability of molybdenum to tobacco plants. That is why we recommend the use of molybdenum when soil pH before fertilization is 6.4 or below
A 0535+26 in the August/September 2005 outburst observed by RXTE and INTEGRAL
In this Letter we present results from INTEGRAL and RXTE observations of the
spectral and timing behavior of the High Mass X-ray Binary A 0535+26 during its
August/September 2005 normal (type I) outburst with an average flux
F(5-100keV)~400mCrab. The search for cyclotron resonance scattering features
(fundamental and harmonic) is one major focus of the paper. Our analysis is
based on data from INTEGRAL and RXTE Target of Opportunity Observations
performed during the outburst. The pulse period is determined. X-ray pulse
profiles in different energy ranges are analyzed. The broad band INTEGRAL and
RXTE pulse phase averaged X-ray spectra are studied. The evolution of the
fundamental cyclotron line at different luminosities is analyzed. The pulse
period P is measured to be 103.39315(5)s at MJD 53614.5137. Two absorption
features are detected in the phase averaged spectra at E_1~45keV and
E_2~100keV. These can be interpreted as the fundamental cyclotron resonance
scattering feature and its first harmonic and therefore the magnetic field can
be estimated to be B~4x10^12G.Comment: 4 pages, 5 figures, accepted for publication in A&A Letter
Simulations of the X-ray imaging capabilities of the Silicon Drift Detectors (SDD) for the LOFT Wide Field Monitor
The Large Observatory For X-ray Timing (LOFT), selected by ESA as one of the
four Cosmic Vision M3 candidate missions to undergo an assessment phase, will
revolutionize the study of compact objects in our galaxy and of the brightest
supermassive black holes in active galactic nuclei. The Large Area Detector
(LAD), carrying an unprecedented effective area of 10 m^2, is complemented by a
coded-mask Wide Field Monitor, in charge of monitoring a large fraction of the
sky potentially accessible to the LAD, to provide the history and context for
the sources observed by LAD and to trigger its observations on their most
interesting and extreme states. In this paper we present detailed simulations
of the imaging capabilities of the Silicon Drift Detectors developed for the
LOFT Wide Field Monitor detection plane. The simulations explore a large
parameter space for both the detector design and the environmental conditions,
allowing us to optimize the detector characteristics and demonstrating the
X-ray imaging performance of the large-area SDDs in the 2-50 keV energy band.Comment: Proceedings of SPIE, Vol. 8443, Paper No. 8443-210, 201
Peculiar outburst of A 0535+26 observed with INTEGRAL, RXTE and Suzaku
A normal outburst of the Be/X-ray binary system A0535+26 has taken place in
August 2009. It is the fourth in a series of normal outbursts that have occured
around the periastron passage of the source, but is unusual by starting at an
earlier orbital phase and by presenting a peculiar double-peaked light curve. A
first "flare" (lasting about 9 days from MJD 55043 on) reached a flux of 440
mCrab. The flux then decreased to less than 220 mCrab, and increased again
reaching 440 mCrab around the periastron at MJD 55057. Target of Opportunity
observations have been performed with INTEGRAL, RXTE and Suzaku. First results
of these observations are presented, with special emphasis on the cyclotron
lines present in the X-ray spectrum of the source, as well as in the pulse
period and energy dependent pulse profiles of the source.Comment: 6 pages, Accepted for publication on PoS, Proceedings of "The Extreme
sky: Sampling the Universe above 10 keV", held in Otranto (Italy) in October
200
The Association of the COMT V158M Polymorphism with Endometrial/Ovarian Cancer in HNPCC Families Adhering to the Amsterdam Criteria
Catechol-O-methyltransferase (COMT) is vital for the conjugation of catechol estrogens that are produced during oestrogen metabolism. The efficiency of this process varies due to a polymorphism in COMT, which changes valine to methionine (V158M). The Met genotypes slow the metabolism of catechol oestrogens, which are agents that are capable of causing DNA damage through the formation of DNA adducts and reactive oxygen species (ROS) production. The slower metabolism of catechol oestrogens results in there being a higher circulating concentration of these oeastrogens and consequently greater probability of DNA damage. To determine whether metabolic inefficiencies of oeastrogen metabolism are associated with the development of malignancy in hereditary non-polyposis colorectal cancer (HNPCC), we studied the V158M polymorphism in COMT in a large cohort of 498 HNPCC patients from Australia and Poland that were either mutation positive (n = 331) or negative (n = 167) for mismatch repair (MMR) gene mutations (hMLH1 or hMSH2). HNPCC is a familial predisposition to colorectal cancer (CRC) and extracolonic cancers that include endometrial cancer
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