A 10B-based neutron detector with stacked Multiwire Proportional Counters and macrostructured cathodes

We present the results of the measurements of the detection efficiency for a 4.7 \r{A} neutron beam incident upon a detector incorporating a stack of up to five MultiWire Proportional Counters (MWPC) with Boron-coated cathodes. The cathodes were made of Aluminum and had a surface exhibiting millimeter-deep V-shaped grooves of 45{\deg}, upon which the thin Boron film was deposited by DC magnetron sputtering. The incident neutrons interacting with the converter layer deposited on the sidewalls of the grooves have a higher capture probability, owing to the larger effective absorption film thickness. This leads to a higher overall detection efficiency for the grooved cathode when compared to a cathode with a flat surface. Both the experimental results and the predictions of the GEANT4 model suggests that a 5-counter detector stack with coated grooved cathodes has the same efficiency as a 7-counter stack with flat cathodes. The reduction in the number of counters in the stack without altering the detection efficiency will prove highly beneficial for large-area position-sensitive detectors for neutron scattering applications, for which the cost-effective manufacturing of the detector and associated readout electronics is an important objective. The proposed detector concept could be a technological option for one of the new chopper spectrometers and other instruments planned to be built at the future European Spallation Source in Sweden. These results with macrostructured cathodes generally apply not just to MWPCs but to other gaseous detectors as well.Comment: 14 pages, 9 figure

A Novel FibroScan Examination Dedicated to Spleen Stiffness Measurement.

Esophageal varices (EVs) are among the most severe complications of cirrhosis, with a prevalence of 50% to 60% among cirrhotic patients. International guidelines therefore recommend that cirrhotic patients should be screened for the presence of EVs. The main objective of this study was to introduce a new spleen-dedicated FibroScan (Echosens, Paris, France) examination and to assess its performance in detecting large EVs (grade 2 and 3). This novel examination has been validated in simulation and phantom studies and has been used in a population of patients with chronic liver disease. The study described here suggests that the novel spleen-dedicated FibroScan examination performs better than the standard FibroScan for the detection of large EVs (area under the curve = 0.70 for the standard examination and 0.79 [p <0.01] for the spleen examination), but further clinical studies are needed to investigate the role of spleen stiffness in the management of cirrhotic patients

Synchronisation of egg hatching of brown hairstreak (Thecla betulae) and budburst of blackthorn (Prunus spinosa) in a warmer future

Synchronisation of the phenology of insect herbivores and their larval food plant is essential for the herbivores’ fitness. The monophagous brown hairstreak (Thecla betulae) lays its eggs during summer, hibernates as an egg, and hatches in April or May in the Netherlands. Its main larval food plant blackthorn (Prunus spinosa) flowers in early spring, just before the leaves appear. As soon as the Blackthorn opens its buds, and this varies with spring temperatures, food becomes available for the brown hairstreak. However, the suitability of the leaves as food for the young caterpillars is expected to decrease rapidly. Therefore, the timing of egg hatch is an important factor for larval growth. This study evaluates food availability for brown hairstreak at different temperatures. Egg hatch and budburst were monitored from 2004 to 2008 at different sites in the Netherlands. Results showed ample food availability at all monitored temperatures and sites but the degree of synchrony varied strongly with spring temperatures. To further study the effect of temperature on synchronisation, an experiment using normal temperatures of a reference year (T) and temperatures of T + 5°C was carried out in climate chambers. At T + 5°C, both budburst and egg hatch took place about 20 days earlier and thus, on average, elevated temperature did not affect synchrony. However, the total period of budburst was 11 days longer, whereas the period of egg hatching was 3 days shorter. The implications for larval growth by the brown hairstreak under a warmer climate are considered.

CMB Polarimetry using Correlation Receivers with the PIQUE and CAPMAP Experiments

The Princeton IQU Experiment (PIQUE) and the Cosmic Anisotropy Polarization MAPper (CAPMAP) are experiments designed to measure the polarization of the Cosmic Microwave Background (CMB) on sub-degree scales in an area within 1 degree of the North Celestial Pole using heterodyne correlation polarimeters and off-axis telescopes located in central New Jersey. PIQUE produced the tightest limit on the CMB polarization prior to its detection by DASI, while CAPMAP has recently detected polarization at l~1000. The experimental methods and instrumentation for these two projects are described in detail with emphasis on the particular challenges involved in measuring the tiny polarized component of the CMB.Comment: 70 pages, 13 tables, 18 figures. Accepted by ApJS; tentative publication ApJS July 2005, v159