2,594 research outputs found
Simulation of Heavily Irradiated Silicon Pixel Sensors and Comparison with Test Beam Measurements
Charge collection measurements performed on heavily irradiated p-spray DOFZ
pixel sensors with a grazing angle hadron beam provide a sensitive
determination of the electric field within the detectors. The data are compared
with a complete charge transport simulation of the sensor which includes signal
trapping and charge induction effects. A linearly varying electric field based
upon the standard picture of a constant type-inverted effective doping density
is inconsistent with the data. A two-trap double junction model implemented in
the ISE TCAD software can be tuned to produce a doubly-peaked electric field
which describes the data reasonably well. The modeled field differs somewhat
from previous determinations based upon the transient current technique. The
model can also account for the level of charge trapping observed in the data.Comment: 8 pages, 11 figures. Talk presented at the 2004 IEEE Nuclear Science
Symposium, October 18-21, Rome, Italy. Submitted to IEEE Transactions on
Nuclear Scienc
Correction to: Between a rock and a hard place: dilemmas regarding the purpose of public universities in South Africa
Correction to: Between a rock and a hard place: dilemmas regarding the purpose of public universities in South Africa (Higher Education, (2019), 77, 4, (567-583), 10.1007/s10734-018-0291-9)
Unveiling the nature of the highly obscured AGN in NGC5643 with XMM-Newton
We present results from an XMM-Newton observation of the nearby Seyfert 2
galaxy NGC5643. The nucleus exhibits a very flat X-ray continuum above 2 keV,
together with a prominent K-alpha fluorescent iron line. This indicates heavy
obscuration. We measure an absorbing column density N_H in the range 6-10 x
10^{23} atoms/cm/cm, either directly covering the nuclear emission, or covering
its Compton-reflection. In the latter case, we might be observing a rather
unusual geometry for the absorber, whereby reflection from the inner far side
of a torus is in turn obscured by its near side outer atmosphere. The nuclear
emission might be then either covered by a Compton-thick absorber, or
undergoing a transient state of low activity. A second source (christened "X-1"
in this paper) at the outskirts of NGC5643 optical surface outshines the
nucleus in X-rays. If belonging to NGC5643, it is the third brightest (L_X ~ 4
x 10^{40} erg/s) known Ultra Luminous X-ray source. Comparison with past large
aperture spectra of NGC 5643 unveils dramatic X-ray spectral changes above 1
keV. We interpret them as due to variability of the active nucleus and of
source X-1 intrinsic X-ray powers by a factor >10 and 5, respectively.Comment: 11 LATEX pages, 12 figures, to appear in Monthly Notices of the Royal
Astronomical Societ
On-Sensor Data Filtering using Neuromorphic Computing for High Energy Physics Experiments
This work describes the investigation of neuromorphic computing-based spiking
neural network (SNN) models used to filter data from sensor electronics in high
energy physics experiments conducted at the High Luminosity Large Hadron
Collider. We present our approach for developing a compact neuromorphic model
that filters out the sensor data based on the particle's transverse momentum
with the goal of reducing the amount of data being sent to the downstream
electronics. The incoming charge waveforms are converted to streams of
binary-valued events, which are then processed by the SNN. We present our
insights on the various system design choices - from data encoding to optimal
hyperparameters of the training algorithm - for an accurate and compact SNN
optimized for hardware deployment. Our results show that an SNN trained with an
evolutionary algorithm and an optimized set of hyperparameters obtains a signal
efficiency of about 91% with nearly half as many parameters as a deep neural
network.Comment: Manuscript accepted at ICONS'2
Relationships between High-Resolution Computed Tomography, Lung Function and Bacteriology in Stable Bronchiectasis
To determine the relationship between high-resolution computed tomography (HRCT) findings, lung function, and bacteriology in bronchiectasis, we conducted a retrospective study of 49 Korean patients with stable bronchiectasis. To quantify the extent and severity of bronchiectasis, we used a CT scoring system consisting of bronchial dilatation, bronchial wall thickening, the number of bronchiectatic segments, the number of bulla, and the number of emphysema segments. The presence of air-fluid levels and lung consolidation were also evaluated. The results of CT scoring, spirometry and sputum culture were analyzed. Patients with cystic bronchiectasis had higher CT score, more dilated lumen and lower forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), and FEV1/FVC than patients with cylindrical bronchiectasis. Patients with mixed ventilatory impairment had larger number of bronchiectatic segments than patients with obstructive ventilatory impairment. CT score and the number of bronchiectatic segments were significantly associated with FVC and FEV1, while CT score and the number of emphysema segments were significantly associated with FEV1/FVC. Twenty-one patients of 49 patients showed a positive sputum culture including 15 cases of Pseudomonas aeruginosa. The CT score was the most important predictor of lung function. The presence of air-fluid levels predicted bacterial colonization
On minor black holes in galactic nuclei
Small and intermediate mass black holes should be expected in galactic nuclei
as a result of stellar evolution, minor mergers and gravitational dynamical
friction. If these minor black holes accrete as X-ray binaries or
ultra-luminous X-ray sources, and are associated with star formation, they
could account for observations of many low luminosity AGN or LINERs. Accreting
and inspiralling intermediate mass black holes could provide a crucial
electromagnetic counterpart to strong gravitational wave signatures, allowing
tests of strong gravity. Here we discuss observational signatures of minor
black holes in galactic nuclei and we demonstrate that optical line ratios
observed in LINERs or transition-type objects can be produced by an ionizing
radiation field from ULXs. We conclude by discussing constraints from existing
observations as well as candidates for future study.Comment: 6 pages. MNRAS Letters (accepted
Breast cancer risk and drinking water contaminated by wastewater: a case control study
BACKGROUND: Drinking water contaminated by wastewater is a potential source of exposure to mammary carcinogens and endocrine disrupting compounds from commercial products and excreted natural and pharmaceutical hormones. These contaminants are hypothesized to increase breast cancer risk. Cape Cod, Massachusetts, has a history of wastewater contamination in many, but not all, of its public water supplies; and the region has a history of higher breast cancer incidence that is unexplained by the population's age, in-migration, mammography use, or established breast cancer risk factors. We conducted a case-control study to investigate whether exposure to drinking water contaminated by wastewater increases the risk of breast cancer. METHODS: Participants were 824 Cape Cod women diagnosed with breast cancer in 1988–1995 and 745 controls who lived in homes served by public drinking water supplies and never lived in a home served by a Cape Cod private well. We assessed each woman's exposure yearly since 1972 at each of her Cape Cod addresses, using nitrate nitrogen (nitrate-N) levels measured in public wells and pumping volumes for the wells. Nitrate-N is an established wastewater indicator in the region. As an alternative drinking water quality indicator, we calculated the fraction of recharge zones in residential, commercial, and pesticide land use areas. RESULTS: After controlling for established breast cancer risk factors, mammography, and length of residence on Cape Cod, results showed no consistent association between breast cancer and average annual nitrate-N (OR = 1.8; 95% CI 0.6 – 5.0 for ≥ 1.2 vs. < .3 mg/L), the sum of annual nitrate-N concentrations (OR = 0.9; 95% CI 0.6 – 1.5 for ≥ 10 vs. 1 to < 10 mg/L), or the number of years exposed to nitrate-N over 1 mg/L (OR = 0.9; 95% CI 0.5 – 1.5 for ≥ 8 vs. 0 years). Variation in exposure levels was limited, with 99% of women receiving some of their water from supplies with nitrate-N levels in excess of background. The total fraction of residential, commercial, and pesticide use land in recharge zones of public supply wells was associated with a small statistically unstable higher breast cancer incidence (OR = 1.4; 95% CI 0.8–2.4 for highest compared with lowest land use), but risk did not increase for increasing land use fractions. CONCLUSION: Results did not provide evidence of an association between breast cancer and drinking water contaminated by wastewater. The computer mapping methods used in this study to link routine measurements required by the Safe Drinking Water Act with interview data can enhance individual-level epidemiologic studies of multiple health outcomes, including diseases with substantial latency
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