1,043 research outputs found
Tests of the Rockwell Si:As Back-Illuminated Blocked-Impurity Band (BIBIB) detectors
Two arrays of Rockwell's Si:As back-illuminated blocked-impurity-band detectors were tested at the Max-Planck-Institute for Astronomy (MPIA) at low background and low temperature for possible use in the astronomical space experiment ISOPHOT. For these measurements special test equipment was put together. A cryostat was mechanically modified to accommodate the arrays and special peripheral electronics was added to a microprocessor system to drive the cold multiplexer and to acquire the output data. The first device, a 16x50 element array on a fan-out board was used to test individual pixels with a trans-impedance-amplifier at a photon background of 10(exp 8) Ph s(-1)cm(-2) and at temperatures of 2.7 to 4.4 K. The noise-equivalent-power NEP is in the range 5 - 7 x 10(exp -18) WHz(exp -1/2), the responsivity is less than or equal to 100 AW(exp -1)(f = 10 Hz). The second device was a 10x50 array including a cold readout electronics of switched FETs (SWIFET). Measurements of this array were done in a background range of 5 x 10(exp 5) to 5 x 10(exp 11) Ph s(exp-1)cm(exp-2) and at operating temperatures between 3.0 and 4.8 K. The NEP ranges from less than 10(exp -18) at the lowest background to 2 x 10(exp -16) WHz(exp -1/2) at the highest flux
Identification of human papillomavirus DNA in cutaneous lesions of Cowden syndrome
Background: Cowden syndrome (CS) or multiple hamartoma syndrome is a cancer-associated genodermatosis inherited in an autosomal dominant pattern. One of the diagnostic criteria is facial papules which are felt to be trichilemmomas, benign hair follicle tumors, which some consider to be induced by human papillomavirus (HPV). Objective: To search for HPV in skin tumors, especially trichilemmomas, from patients with CS. Methods: Skin lesions from patients with CS were classified histologically. Each tumor was then analyzed for HPV DNA by polymerase chain reaction with different primer sets; positive amplicons were typed by direct sequencing. Results: Twenty-nine biopsies from 7 patients with CS were investigated. Only 2 of 29 tumors clinically suspected of being trichilemmomas were confirmed histologically. In addition, 3 sclerotic fibromas, also typical of CS, were found, as well as 1 sebaceous hyperplasia. The other 23 lesions showed histological features of HPV-induced tumors in various stages of development. HPV DNA was found in 19 of 29 cutaneous lesions. Tumors without any histological signs of HPV induction were negative for HPV DNA. Two tumors which were histologically classified as common warts contained HPV types 27 and 28. All the 17 other HPV types belong to the group of epidermodysplasia-verruciformis-associated types. Conclusions: The majority of cutaneous lesions in CS contain HPV DNA. They may have a variety of histological patterns. Trichilemmomas are not clinically distinctive and can be difficult to identify in CS patients. Copyright (C) 2003 S. Karger AG, Basel
Recruitment kinetics of DNA repair proteins Mdc1 and Rad52 but not 53BP1 depend on damage complexity.
The recruitment kinetics of double-strand break (DSB) signaling and repair proteins Mdc1, 53BP1 and Rad52 into radiation-induced foci was studied by live-cell fluorescence microscopy after ion microirradiation. To investigate the influence of damage density and complexity on recruitment kinetics, which cannot be done by UV laser irradiation used in former studies, we utilized 43 MeV carbon ions with high linear energy transfer per ion (LET = 370 keV/”m) to create a large fraction of clustered DSBs, thus forming complex DNA damage, and 20 MeV protons with low LET (LET = 2.6 keV/”m) to create mainly isolated DSBs. Kinetics for all three proteins was characterized by a time lag period T(0) after irradiation, during which no foci are formed. Subsequently, the proteins accumulate into foci with characteristic mean recruitment times Ï(1). Mdc1 accumulates faster (T(0) = 17 ± 2 s, Ï(1) = 98 ± 11 s) than 53BP1 (T(0) = 77 ± 7 s, Ï(1) = 310 ± 60 s) after high LET irradiation. However, recruitment of Mdc1 slows down (T(0) = 73 ± 16 s, Ï(1) = 1050 ± 270 s) after low LET irradiation. The recruitment kinetics of Rad52 is slower than that of Mdc1, but exhibits the same dependence on LET. In contrast, the mean recruitment time Ï(1) of 53BP1 remains almost constant when varying LET. Comparison to literature data on Mdc1 recruitment after UV laser irradiation shows that this rather resembles recruitment after high than low LET ionizing radiation. So this work shows that damage quality has a large influence on repair processes and has to be considered when comparing different studies
The Automatic Real-Time GRB Pipeline of the 2-m Liverpool Telescope
The 2-m Liverpool Telescope (LT), owned by Liverpool John Moores University,
is located in La Palma (Canary Islands) and operates in fully robotic mode. In
2005, the LT began conducting an automatic GRB follow-up program. On receiving
an automatic GRB alert from a Gamma-Ray Observatory (Swift, INTEGRAL, HETE-II,
IPN) the LT initiates a special override mode that conducts follow-up
observations within 2-3 min of the GRB onset. This follow-up procedure begins
with an initial sequence of short (10-s) exposures acquired through an r' band
filter. These images are reduced, analyzed and interpreted automatically using
pipeline software developed by our team called "LT-TRAP" (Liverpool Telescope
Transient Rapid Analysis Pipeline); the automatic detection and successful
identification of an unknown and potentially fading optical transient triggers
a subsequent multi-color imaging sequence. In the case of a candidate brighter
than r'=15, either a polarimetric (from 2006) or a spectroscopic observation
(from 2007) will be triggered on the LT. If no candidate is identified, the
telescope continues to obtain z', r' and i' band imaging with increasingly
longer exposure times. Here we present a detailed description of the LT-TRAP
and briefly discuss the illustrative case of the afterglow of GRB 050502a,
whose automatic identification by the LT just 3 min after the GRB, led to the
acquisition of the first early-time (< 1 hr) multi-color light curve of a GRB
afterglow.Comment: PASP, accepted (8 pages, 3 figures
The Moon at thermal infrared wavelengths: A benchmark for asteroid thermal models
Thermal-infrared measurements of asteroids are crucial for deriving the
objects' sizes, albedos, and also the thermophysical properties of the surface
material. Depending on the available data, a range of simple to complex thermal
models are applied to achieve specific science goals. However, testing these
models is often a difficult process and the uncertainties of the derived
parameters are not easy to estimate. Here, we make an attempt to verify a
widely accepted thermophysical model (TPM) against unique thermal infrared
(IR), full-disk, and well-calibrated measurements of the Moon. The data were
obtained by the High-resolution InfraRed Sounder (HIRS) instruments on board a
fleet of Earth weather satellites that serendipitously scan over the Moon. We
found 22 Moon intrusions, taken in 19 channels between 3.75 micron and 15.0
micron, and over a wide phase angle range from -73.1 deg to +73.8 deg. The
similarity between these Moon data and typical asteroid spectral-IR energy
distributions allows us to benchmark the TPM concepts and to point out
problematic aspects. The TPM predictions match the HIRS measurements within 5%
(10% at the shortest wavelengths below 5 micron when using the Moon's known
properties (size, shape, spin, albedo, thermal inertia, roughness) in
combination with a newly established wavelength-dependent hemispherical
emissivity. In the 5-7.5 micron and in the 9.5 to 11 micron ranges, the global
emissivity model deviates considerably from the known lunar sample spectra. Our
findings will influence radiometric studies of near-Earth and main-belt
asteroids in cases where only short-wavelength data (from e.g., NEOWISE, the
warm Spitzer mission, or ground-based M-band measurements) are available. The
new, full-disk IR Moon model will also be used for the calibration of IR
instrumentation on interplanetary missions (e.g., for Hayabusa-2) and weather
satellites.Comment: 21 pages, 9 figures, 7 tables, accepted for publication in Astronomy
& Astrophysics in March 202
ISOCAM observations of the L1551 star formation region
The results of a deep mid-IR ISOCAM survey of the L1551 dark molecular cloud
are presented. The aim of this survey is a search for new YSO (Young Stellar
Object) candidates, using two broad-band filters centred at 6.7 and 14.3
micron. Although two regions close to the centre of L1551 had to be avoided due
to saturation problems, 96 sources were detected in total (76 sources at 6.7
micron and 44 sources at 14.3 micron). Using the 24 sources detected in both
filters, 14 were found to have intrinsic mid-IR excess at 14.3 micron and were
therefore classified as YSO candidates. Using additional observations in B, V,
I, J, H and K obtained from the ground, most candidates detected at these
wavelengths were confirmed to have mid-IR excess at 6.7 micron as well, and
three additional YSO candidates were found. Prior to this survey only three
YSOs were known in the observed region (avoiding L1551 IRS5/NE and HL/XZ Tau).
This survey reveals 15 new YSO candidates, although several of these are
uncertain due to their extended nature either in the mid-IR or in the
optical/near-IR observations. Two of the sources with mid-IR excess are
previously known YSOs, one is a brown dwarf MHO 5 and the other is the well
known T Tauri star HH30, consisting of an outflow and an optically thick disk
seen edge on.Comment: 14 Pages, 8 Figure
ISOCAM observations of the rho Ophiuchi cloud: Luminosity and mass functions of the pre-main sequence embedded cluster
We present the results of the first extensive mid-infrared (IR) imaging
survey of the rho Ophiuchi embedded cluster, performed with the ISOCAM camera
on board the ISO satellite. The main molecular cloud L1688, as well as L1689N
and L1689S, have been completely surveyed for point sources at 6.7 and 14.3
micron. A total of 425 sources are detected including 16 Class I, 123 Class II,
and 77 Class III young stellar objects (YSOs). Essentially all of the mid-IR
sources coincide with near-IR sources, but a large proportion of them are
recognized for the first time as YSOs. Our dual-wavelength survey allows us to
identify essentially all the YSOs with IR excess in the embedded cluster down
to Fnu ~ 10 - 15 mJy. It more than doubles the known population of Class II
YSOs and represents the most complete census to date of newly formed stars in
the rho Ophiuchi central region. The stellar luminosity function of the
complete sample of Class II YSOs is derived with a good accuracy down to L=
0.03 Lsun. A modeling of this lumino- sity function, using available pre-main
sequence tracks and plausible star for- mation histories, allows us to derive
the mass distribution of the Class II YSOs which arguably reflects the IMF of
the embedded cluster. We estimate that the IMF in rho Ophiuchi is well
described by a two-component power law with a low- mass index of -0.35+/-0.25,
a high-mass index of -1.7 (to be compared with the Salpeter value of -1.35),
and a break occurring at M = 0.55+/-0.25 Msun. This IMF is flat with no
evidence for a low-mass cutoff down to at least 0.06 Msun.Comment: A&A Document Class -- version 5.01, 27 pages, 10 figures v2: typos
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Noise performance of microwave humidity sounders over their lifetime
The microwave humidity sounders Special Sensor Microwave Water Vapor Profiler (SSMT-2), Advanced Microwave Sounding Unit-B (AMSU-B) and Microwave Humidity Sounder (MHS) to date have been providing data records for 25 years. So far, the data records lack uncertainty information essential for constructing consistent long time data series. In this study, we assess the quality of the recorded data with respect to the uncertainty caused by noise. We calculate the noise on the raw calibration counts from the deep space views (DSVs) of the instrument and the noise equivalent differential temperature (NEÎT) as a measure for the radiometer sensitivity. For this purpose, we use the Allan deviation that is not biased from an underlying varying mean of the data and that has been suggested only recently for application in atmospheric remote sensing. Moreover, we use the bias function related to the Allan deviation to infer the underlying spectrum of the noise. As examples, we investigate the noise spectrum in flight for some instruments. For the assessment of the noise evolution in time, we provide a descriptive and graphical overview of the calculated NEÎT over the life span of each instrument and channel. This overview can serve as an easily accessible information for users interested in the noise performance of a specific instrument, channel and time. Within the time evolution of the noise, we identify periods of instrumental degradation, which manifest themselves in an increasing NEÎT, and periods of erratic behaviour, which show sudden increases of NEÎT interrupting the overall smooth evolution of the noise. From this assessment and subsequent exclusion of the aforementioned periods, we present a chart showing available data records with NEÎTâŻâ<ââŻ1âŻK. Due to overlapping life spans of the instruments, these reduced data records still cover without gaps the time since 1994 and may therefore serve as a first step for constructing long time series. Our method for count noise estimation, that has been used in this study, will be used in the data processing to provide input values for the uncertainty propagation in the generation of a new set of Fundamental Climate Data Records (FCDRs) that are currently produced in the project Fidelity and Uncertainty in Climate data records from Earth Observation (FIDUCEO)
An anomaly detector with immediate feedback to hunt for planets of Earth mass and below by microlensing
(abridged) The discovery of OGLE 2005-BLG-390Lb, the first cool rocky/icy
exoplanet, impressively demonstrated the sensitivity of the microlensing
technique to extra-solar planets below 10 M_earth. A planet of 1 M_earth in the
same spot would have provided a detectable deviation with an amplitude of ~ 3 %
and a duration of ~ 12 h. An early detection of a deviation could trigger
higher-cadence sampling which would have allowed the discovery of an Earth-mass
planet in this case. Here, we describe the implementation of an automated
anomaly detector, embedded into the eSTAR system, that profits from immediate
feedback provided by the robotic telescopes that form the RoboNet-1.0 network.
It went into operation for the 2007 microlensing observing season. As part of
our discussion about an optimal strategy for planet detection, we shed some new
light on whether concentrating on highly-magnified events is promising and
planets in the 'resonant' angular separation equal to the angular Einstein
radius are revealed most easily. Given that sub-Neptune mass planets can be
considered being common around the host stars probed by microlensing
(preferentially M- and K-dwarfs), the higher number of events that can be
monitored with a network of 2m telescopes and the increased detection
efficiency for planets below 5 M_earth arising from an optimized strategy gives
a common effort of current microlensing campaigns a fair chance to detect an
Earth-mass planet (from the ground) ahead of the COROT or Kepler missions. The
detection limit of gravitational microlensing extends even below 0.1 M_earth,
but such planets are not very likely to be detected from current campaigns.
However, these will be within the reach of high-cadence monitoring with a
network of wide-field telescopes or a space-based telescope.Comment: 13 pages, 4 figures and 1 table. Accepted for publication in MNRA
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