Gamma–ray spectroscopy with single–carrier collection in high–resistivity semiconductors

With the standard plane–parallel configuration of semiconductor detectors, good γ–ray spectra can only be obtained when both electrons and holes are completely collected. We show by calculations (and experiments) that with contacts of hemispherical configuration one can obtain γ–ray spectra of adequate resolution and with signal heights of nearly full amplitude even when only one type of carrier is collected. Experiments with CdTe detectors for which the µτ product for electrons is about 10^(3) times that of the holes confirm these calculations. The adoption of hemispherical contacts thus widens the range of high–resistivity semiconductors potentially acceptable for γ–ray detection at room temperature

Spatial and seasonal patterns and long term variability of the composition of the haze in the United States: an analysis of data from the IMPROVE network

July 1996.Principal investigators: William C. Malm, Marc L. Pitchford.Includes bibliographical references.This report describes data for the three year period, March 1992 through February 1995, of the Interagency Monitoring of Protected Visual Environments (IMPROVE) measurement program. IMPROVE is a cooperative visibility monitoring effort between the United States Environmental Protection Agency, (EPA) federal land management agencies, and state air agencies

Direct observation and imaging of a spin-wave soliton with p−p-like symmetry

The prediction and realization of magnetic excitations driven by electrical currents via the spin transfer torque effect, enables novel magnetic nano-devices where spin-waves can be used to process and store information. The functional control of such devices relies on understanding the properties of non-linear spin-wave excitations. It has been demonstrated that spin waves can show both an itinerant character, but also appear as localized solitons. So far, it was assumed that localized solitons have essentially cylindrical, $s-$like symmetry. Using a newly developed high-sensitivity time-resolved magnetic x-ray microscopy, we instead observe the emergence of a novel localized soliton excitation with a nodal line, i.e. with $p-$like symmetry. Micromagnetic simulations identify the physical mechanism that controls the transition from $s-$ to $p-$like solitons. Our results suggest a potential new pathway to design artificial atoms with tunable dynamical states using nanoscale magnetic devices

Re: Musings on malaria morbidity and mortality after the new Mosquirix® vaccine

Importance of pilot implementation and Phase IV studies and pending questions: The Malaria Vaccine Implementation Project (MVIP) is coordinated by the World HealthOrganisation (WHO) and led by African health authorities in Ghana, Kenya and Malawi. In Ghana, the MVIP is led by Ministry of Health/Ghana Health Service and evaluatedby a consortium of researchers from University of Ghana, University of Health and Allied Sciences, Agogo Malaria Centre, and the Research and Development Division of Ghana Health Service. The project is designed to address several outstanding questions related to the public health use of the vaccine. Additionally, Phase IV studies are ongoing to further assess the safety of the vaccine in Ghana (Kintampo and Navrongo) as a standardregulatory requirement for new vaccines. Indeed, this approach has been used for the introduction of other vaccines in Ghana such as the human papilloma virus vaccine.2 Specifically, the MVIP will provide data to the Ministry of Health and partners on how best to deliver the required four doses of the vaccine in routine settings; assess the vaccine’s full potential role in reducing childhood deaths; and establish the vaccine’s safety profile inthe context of routine use. Since the Phase III study was not intended to measure the impact of the vaccine on mortality, the data from MVIP will confirm or refute theimpact of the malaria vaccine on mortality as determined in the mathematical models outlined by Penny M et. al.

Foodborne illness among school children in Ga east, Accra

Background: A food borne illness was reported in Ga- East district of Greater Accra Region among school children in May, 2007 after eating food provided at school. The objective of the investigation was to determine the source, mode of contamination and the causative agent.Methods: A case-control study was conducted, cases were schoolchildren with abdominal symptoms and controls were children of the same sex and class without any symptom during the same period. The school children were selected by systematic sampling. Food handlers and the children were interviewed by a structured questionnaire. Food handlers were physically examined and their stools and blood examined. The kitchen for food preparation was inspected. Risks of food borne infection from the foods eaten were determined using attack rates .Results: The minimum, peak and maximum incubation periods were 2, 11 and 61 hours respectively. The source was rice and groundnut soup (with the highest attack rate difference). Stool and blood samples of food handlers were not infective. Storage facility for food items was poor. No food samples were available for organism isolation. A protocol to prevent such outbreaks was nonexistent.Conclusion: The short incubation period and symptoms presented suggest an infective origin. The storage of the meat may potentially have been the point of contamination. The study showed that the schoolchildren ate contaminated food although the investigation could not determine the causative agent. Protocols to prevent such outbreaks need to be developed for the schools.Keywords: Food borne, illness, contaminated food, school children, Accr

Chandra X-ray Observations of the Quadruply Lensed Quasar RX J0911.4+0551

We present results from X-ray observations of the quadruply lensed quasar RX J0911.4+0551 using data obtained with the Advanced CCD Imaging Spectrometer (ACIS) on board the Chandra X-ray Observatory. The 29 ks observation detects a total of ~404 X-ray photons (0.3 to 7.0 keV) from the four images of the lensed quasar. Deconvolution of the aspect corrected data resolves all four lensed images, with relative positions in good agreement with optical measurements. When compared to contemporaneous optical data, one of the lensed images (component A3) is dimmer by a factor of ~6 in X-rays with respect to the 2 brighter images (components A1 and A2). Spectral fitting for the combined images shows significant intrinsic absorption in the soft (0.2 to 2.4 keV) energy band, consistent with the mini-BAL nature of this quasar, while a comparison with ROSAT PSPC observations from 1990 shows a drop of ~6.5 in the total soft bandpass flux. The observations also detect ~157 X-ray photons arising from extended emission of the nearby cluster (peaked ~42" SW of RXJ0911.4+0551) responsible for the large external shear present in the system. The Chandra observation reveals the cluster emission to be complex and non-spherical, and yields a cluster temperature of kT = 2.3^{+1.8}_{-0.8} keV and a 2.0 to 10 keV cluster luminosity within a 1 Mpc radius of L_X = 7.6_{-0.2}^{+0.6} x 10^{43} ergs/s (error bars denote 90% confidence limits). Our mass estimate of the cluster within its virial radius is 2.3^{+1.8}_{-0.7} x 10^{14} solar, and is a factor of 2 smaller than, although consistent with, previous mass estimates based on the observed cluster velocity dispersion.Comment: 16 pages, 3 figures (figure 1 is color ps). Accepted by Ap

Detection of X-ray Emission from Gravitationally Lensed Submillimeter Sources in the Field of Abell 370

We report the detection by Chandra of SMM J02399-0134 and SMM J02399-0136, two distant (z=1.06 and z=2.81, respectively) submillimeter sources gravitationally magnified by the galaxy cluster Abell 370. These are high-significance (> 7-sigma) X-ray detections of the high-redshift submillimeter source population. The X-ray positions are coincident with the optical positions to within one arcsecond. The X-ray spectra, while of low signal-to-noise ratio, are quite hard. Absorbed power law models with fixed photon indices of $\Gamma=2.0$ imply local absorbing columns $>2 \times 10^{23}$ cm$^{-2}$ and unabsorbed luminosities $>10^{44}$ erg s$^{-1}$ in both sources. These results imply that nuclear activity is responsible for the bulk of the luminosity in SMM J02399-0134, and for at least 20% of the luminosity of SMM J02399-0136, consistent with previous optical observations. We also place an upper limit on the X-ray flux of a third submillimeter source, SMM J02400-0134. Considered together with previously published Chandra upper limits on X-ray flux from submillimeter sources, our results imply that $20^{+30}_{-16}$ % of submillimeter sources exhibit X-ray emission from AGN (90% confidence), consistent with expectations of their contribution to the diffuse X-ray background.Comment: Corrected typos in Figure 1 labels; Accepted for publication in ApJ Letters, 6 pages, 2 figures, latex requires emulateapj5.st

Self-erasing and rewritable wettability patterns on ZnO thin films

Self-erasing patterns allow a substrate to be patterned multiple times or could store temporary information for secret communications, and are mostly based on photochromic molecules to change the color of the pattern. Herein we demonstrate self-erasing patterns of wettability on thin ZnO films made by atomic layer deposition. Hydrophilic patterns are written using UV light and decay spontaneously, i.e. become hydrophobic, or are erased aided by vacuum conditions or heat. We demonstrate that these patterns can be applied for channels to confine flow of water without physical walls.Peer reviewe