The COBRA demonstrator at the LNGS underground laboratory Ebert, J.; Fritts, M.; Gehre, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2016, Letnik:
807
Journal Article
Recenzirano
Odprti dostop
The COBRA demonstrator, a prototype for a large-scale experiment searching for neutrinoless double beta-decay, was built at the underground laboratory Laboratori Nazionali del Gran Sasso (LNGS) in ...Italy. It consists of an array of 64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid design and a total mass of 380g. It is used to investigate the experimental challenges faced when operating CdZnTe detectors in low-background mode, to identify potential background sources and to show the long-term stability of the detectors. The first data-taking period started in 2011 with a subset of the detectors, while the demonstrator was completed in November 2013. To date, more than 250kgd of data have been collected. This paper describes the technical details of the experimental setup and the hardware components.
Events near the cathode and anode surfaces of a coplanar grid CdZnTe detector are identifiable by means of the interaction depth information encoded in the signal amplitudes. However, the amplitudes ...cannot be used to identify events near the lateral surfaces. In this paper a method is described to identify lateral surface events by means of their pulse shapes. Such identification allows for discrimination of surface alpha particle interactions from more penetrating forms of radiation, which is particularly important for rare event searches. The effectiveness of the presented technique in suppressing backgrounds due to alpha contamination in the search for neutrinoless double beta decay with the COBRA experiment is demonstrated.
The aim of the COBRA experiment is to prove the existence of neutrinoless double-beta-decay (0νββ-decay) and to measure its half-life. For this purpose a detector array made of cadmium-zinc-telluride ...(CdZnTe) semiconductor detectors is operated at the Gran Sasso Underground Laboratory (LNGS) in Italy. This setup is used to investigate the experimental issues of operating CdZnTe detectors in low-background mode and to identify potential background components, whilst additional studies are proceeding in surface laboratories. The experiment currently consists of monolithic, calorimetric detectors of coplanar grid design (CPG detectors). These detectors are 1 × 1 × 1 cm3 and are arranged in 4 × 4 detector layers. Ultimately four layers will be installed by the end of 2013, of which two are currently operating. To date 82.3 kg·days of data have been collected. In the region of interest for 116Cd around 2.8 MeV, the median energy resolution is 1.5% FWHM, and a background level near 1 counts/keV/kg/y has been reached. This paper gives an overview of the current status of the experiment and future perspectives.
Evolved Seasparrow Missile program Frazer, R K; Hanson Jr, J M; Leumas, M J ...
Johns Hopkins APL technical digest,
10/2001, Letnik:
22, Številka:
4
Journal Article
Recenzirano
The multinational effort to develop and field the Evolved Seasparrow Missile is nearing completion. The effort, supported by a consortium of the United States and allied nations, is a significant ...improvement to the existing Sparrow Missile. It will provide the fleets of these nations with an anti-missile capability against existing and projected threats that possess low-altitude, higher-velocity, and maneuver capabilities that stress present systems. This article traces the Evolved Seasparrow Missile's development from early definition efforts through engineering and manufacturing development into production transition and completion of the present at-sea developmental and operational testing that will prove its capabilities to support consortium fleet missions. (Author)
The COBRA demonstrator, a prototype for a large-scale experiment searching for neutrinoless double beta-decay, was built at the underground laboratory Laboratori Nazionali del Gran Sasso (LNGS) in ...Italy. It consists of an array of 64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid design and a total mass of 380g. It is used to investigate the experimental challenges faced when operating CdZnTe detectors in low-background mode, to identify potential background sources and to show the long-term stability of the detectors. The first data-taking period started in 2011 with a subset of the detectors, while the demonstrator was completed in November 2013. To date, more than 250kg d of data have been collected. This paper describes technical details of the experimental setup and the hardware components.
In a recent study, we showed that the earthworm species
Eisenia fetida, inhabiting an extremely high metal polluted compost heap on a wine farm, did not have elevated body loads of the metals but ...exhibited genotoxic tolerance when exposed to Cd in the laboratory (
Voua Otomo and Reinecke, 2010). To unravel the mechanism behind the surprisingly low metal body burdens on one hand and genotoxic tolerance on the other hand, we investigated the estimated bioavailability of these metals (Cu, Zn, Pb and Cd) using sequential extraction methods with CaCl
2 and di-ethylene-triamine-pentaacetic acid (DTPA) and allozyme polymorphism in this field population, a laboratory control as well as a long-term Cd exposed population. The amounts of mobile (extracted with CaCl
2) and mobilizable (extracted with DTPA) metals in relation to the total (extracted with nitric acid) metals were all below 0.05% for all four metals, suggesting low availability for uptake. The low availability of these metals could not be explained by physico-chemical properties of soil but by the phenomenon of aging of the metals. There was no difference in allozyme frequency between metal tolerant and non-metal tolerant populations of
E. fetida. This suggested that the tolerance found in earlier studies could be a mere physiological adaptation
► Reported metal tolerance and low metal accumulation in
Eisenia fetida were investigated. ► High total metal did not translate into high bioavailable contents in soil. ► Low metal bioavailability could not be explained by physico-chemical properties of soils. ► Allozyme polymorphism in the earthworms failed to point towards genetic adaptation.
We studied the effect of salinity on some life-cycle parameters in the collembolan
Folsomia candida, the enchytraeid
Enchytraeus doerjesi, and two earthworm species,
Eisenia fetida and
Aporrectodea ...caliginosa, using natural saline soil from Robertson, Western Cape, South Africa. Specimens of the four species were exposed to soils along a gradient of salinity with electrical conductivity (EC) ranging from 0.08 to 1.62
dS
m
−1, under controlled laboratory conditions for 28 days. The results showed that although survival of
E. doerjesi and
F. candida was not significantly affected in this salinity range, juvenile production was significantly affected at 1.03
dS
m
−1 and higher. For
E. doerjesi, absolute cessation of reproduction occurred at 1.31
dS
m
−1 while for
F. candida, it occurred at a higher EC of 1.62
dS
m
−1. For
E. fetida and
A. caliginosa, survival was significantly affected at and above 0.92 and 1.31
dS
m
−1, respectively, while total mortality occurred at 1.31 and 1.62
dS
m
−1, respectively. Both earthworm species only produced cocoons in control soils. Growth of
A. caliginosa was significantly affected at a lower EC (0.52
dS
m
−1) than that which affected the growth of
E. fetida (1.03
dS
m
−1). Thus, the sensitivity of these soil organisms to saline stress, based on survival and reproduction data increased in the order:
F. candida<
E. doerjesi<
A. caliginosa<
E. fetida. Further investigation and of more taxa, may support the findings of this study that suggest that earthworms could be useful as indicators of saline disturbance than other taxa.
We studied the avoidance behaviour of
Eisenia fetida and
Aporrectodea caliginosa in OECD artificial soil spiked with NaCl and in natural saline soil (of varying ionic constitutions) collected from ...Robertson Experimental Farm (ROBS) in Western Cape, South Africa. For each organism, the ecotoxicological test was performed using a two-chamber test over a period of 48
h. The results showed that in the OECD soil, the avoidance EC50 (the concentration/electrical conductivity at which there is effect on 50% of the organisms) for
A. caliginosa of 667
mg
kg
−1 NaCl was lower than 1164
mg
kg
−1 for
E. fetida. Similarly in ROBS soil, the avoidance EC50 for
A. caliginosa of 0.26
dS
m
−1 was lower than 0.56
dS
m
−1 in
E. fetida. These results indicated that
A. caliginosa showed better avoidance to salinity than
E. fetida irrespective of soil types or ionic constitution. When compared with literature data, EC50 values in avoidance tests were either lower or comparable to those of reproduction, which was the most sensitive life-cycle parameter. The only exception was the EC50 value for avoidance of
E. fetida in natural soil which was higher than for reproduction suggesting that the predictive value of the avoidance test for this species might be lower in natural soils. The variation in sensitivities of these earthworms could be as a result of differences in their eco-physiology. These findings suggest the relevance of the avoidance test as a suitable screening method showing first tendencies of saline stress on the habitat function of soils.
Xyloglucans are the main hemicellulosic polysaccharides found in the primary cell walls of dicots and nongraminaceous monocots, where they are thought to interact with cellulose to form a ...three-dimensional network that functions as the principal load-bearing structure of the primary cell wall. To determine whether two Arabidopsis thaliana genes that encode xylosyltransferases, XXT1 and XXT2, are involved in xyloglucan biosynthesis in vivo and to determine how the plant cell wall is affected by the lack of expression of XXT1, XXT2, or both, we isolated and characterized xxt1 and xxt2 single and xxt1 xxt2 double T-DNA insertion mutants. Although the xxt1 and xxt2 mutants did not have a gross morphological phenotype, they did have a slight decrease in xyloglucan content and showed slightly altered distribution patterns for xyloglucan epitopes. More interestingly, the xxt1 xxt2 double mutant had aberrant root hairs and lacked detectable xyloglucan. The reduction of xyloglucan in the xxt2 mutant and the lack of detectable xyloglucan in the xxt1 xxt2 double mutant resulted in significant changes in the mechanical properties of these plants. We conclude that XXT1 and XXT2 encode xylosyltransferases that are required for xyloglucan biosynthesis. Moreover, the lack of detectable xyloglucan in the xxt1 xxt2 double mutant challenges conventional models of the plant primary cell wall.
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