This paper reports on the development of a novel CMOS device employing lead-sensing bacteria to assay lead in drinking water. The objective of the PlomBOX project is to develop a low-cost sensor ...({\pounds}10) which can expedite access to on-demand assay methods and thus help mitigate lead intake through contaminated drinking water. The project follows three development paths: a) Certain bacteria can fluoresce or change colour when in the presence of lead. A genetically modified strain of Escherichia coli sensitive to lead concentrations up to 10 ppb is being developed. This constitutes the biosensor that fluoresces in proportion to the presence of lead. b) Bacteria response is imaged using a microprocessor (ESP32) with a camera module. This constitutes the optical metrology component of the PlomBOX. c) Data acquisition and control of the PlomBOX is achieved through a Bluetooth connection with the PlomApp, a custom-developed mobile phone application. Data are sent from the PlomApp to a database where a bespoke automated analysis software provides a result of the lead concentration in a sample of water. This paper reports on the instrumentation challenges of developing the electronics for the PlomBOX and on the first prototype.
This article reports the characterization of two High Purity Germanium detectors performed by extracting and comparing their efficiencies using experimental data and Monte Carlo simulations. The ...efficiencies were calculated for pointlike \(\gamma\)-ray sources as well as for extended calibration sources. Characteristics of the detectors such as energy linearity, energy resolution, and full energy peak efficiencies are reported from measurements performed on surface laboratories. The detectors will be deployed in a \(\gamma\)-ray assay facility that will be located in the first underground laboratory in Mexico, Laboratorio Subterráneo de Mineral del Chico (LABChico), in the Comarca Minera UNESCO Global Geopark
When monitoring a reactor site for nuclear nonproliferation purposes, the presence of an unknown or hidden nuclear reactor could be obscured by the activities of a known reactor of much greater power ...nearby. Thus when monitoring reactor activities by the observation of antineutrino emissions, one must discriminate known background reactor fluxes from possible unknown reactor signals under investigation. To quantify this discrimination, we find the confidence to reject the (null) hypothesis of a single proximal reactor, by exploiting directional antineutrino signals in the presence of a second, unknown reactor. In particular, we simulate the inverse beta decay (IBD) response of a detector filled with a 1 kT fiducial mass of Gadolinium-doped liquid scintillator in mineral oil. We base the detector geometry on that of WATCHMAN, an upcoming antineutrino monitoring experiment soon to be deployed at the Boulby mine in the United Kingdom whose design and deployment will be detailed in a forthcoming white paper. From this simulation, we construct an analytical model of the IBD event distribution for the case of one \(4\mathrm{\ GWt}\pm2\%\) reactor 25 km away from the detector site, and for an additional, unknown, 35 MWt reactor 3 to 5 km away. The effects of natural-background rejection cuts are approximated. Applying the model, we predict \(3\sigma\) confidence to detect the presence of an unknown reactor within five weeks, at standoffs of 3 km or nearer. For more distant unknown reactors, the \(3\sigma\) detection time increases significantly. However, the relative significance of directional sensitivity also increases, providing up to an eight week speedup to detect an unknown reactor at 5 km away. Therefore, directionally sensitive antineutrino monitoring can accelerate the mid-field detection of unknown reactors whose operation might otherwise be masked by more powerful reactors in the vicinity.
In previously treated head-and-neck cancer patients, p.o. administered
isotretinoin (13- cis retinoic acid) reduced the
occurrence of second aerodigestive tumors, including lung tumors, but
side ...effects made chronic therapy problematic. We reasoned that inhaled
isotretinoin might provide sufficient drug to the target cells for
efficacy while avoiding systemic toxicity, and we proceeded with the
pilot study reported here. Male A/J mice were given single i.p. doses
of urethane, a common experimental lung carcinogen, or
benzo a pyrene (BaP) or
4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), putative
major carcinogens in tobacco smoke. The following day, exposures to
isotretinoin aerosols for 45 min daily at 1.3, 20.7, or 481 μg/l were
initiated. After 2 weeks, the high dose caused severe toxicity on the
snout skin, necessitating a reduction of dose frequency to twice a
week. As a precaution, the mid dose was reduced to three exposures per
week. The weekly total deposited doses after the dose frequency
reductions were calculated to be 0.24, 1.6, and 24.9 mg/kg for the low,
mid, and high doses, of which 16% was estimated to be deposited in the
lungs. The weekly deposited pulmonary drug doses were calculated to be
0.01, 0.07, and 1.1% of a previously reported ineffective oral dose in
urethane-treated A/J mice. After 10–16 weeks, mice were sacrificed to
count areas of pulmonary hyperplasia and adenomas. For all carcinogens,
the mice exposed to the high isotretinoin dose showed reductions of
tumor multiplicity ranging from 56 to 80% ( P <
0.005). The mid dose was associated with reductions of tumor
multiplicity by 67 and 88% ( P < 0.005) in BaP-
and NNK-treated mice, respectively, and was tolerated until ∼12
weeks, when both these and the high-dose mice began losing weight. The
low-dose mice had nonsignificant reductions of 30%
( P < 0.13) and 16% ( P <
0.30) for BaP- and NNK-treated mice, respectively without any evidence
of side effects. For BaP- and NNK-treated mice, numbers of hyperplastic
areas directly correlated to dose level and inversely to tumor number,
suggesting arrested progression. Inhaled mid-dose isotretinoin caused
up-regulation of lung tissue nuclear retinoic acid receptors (RARs)
relative to vehicle-exposed mice, RARα (3.9-fold vehicle), RARβ
(3.3-fold), and RARγ (3.7-fold), suggesting that these receptors may
be useful biomarkers of retinoid activity in this system. The
encouraging results from this pilot study suggest that inhaled
isotretinoin merits evaluation in people at high risk for lung cancer.
The Boulby Underground Germanium Suite (BUGS) comprises three low background, high-purity germanium detectors operating in the Boulby Underground Laboratory, located 1.1 km underground in the ...north-east of England, UK. BUGS utilises three types of detector to facilitate a high-sensitivity, high-throughput radioassay programme to support the development of rare-event search experiments. A Broad Energy Germanium (BEGe) detector delivers sensitivity to low-energy gamma-rays such as those emitted by 210Pb and 234Th. A Small Anode Germanium (SAGe) well-type detector is employed for efficient screening of small samples. Finally, a standard p-type coaxial detector provides fast screening of standard samples. This paper presents the steps used to characterise the performance of these detectors for a variety of sample geometries, including the corrections applied to account for cascade summing effects. For low-density materials, BUGS is able to radio-assay to specific activities down to 3.6 mBq/kg for 234Th and 6.6 mBq/kg for 210Pb both of which have uncovered some significant equilibrium breaks in the 238U chain. In denser materials, where gamma-ray self-absorption increases, sensitivity is demonstrated to specific activities of 0.9 mBq/kg for 226Ra, 1.1 mBq/kg for 228 Ra, 0.3 mBq/kg for 224Ra, and 8.6 mBq/kg for 40K with all upper limits at a 90% confidence level. These meet the requirements of most screening campaigns presently under way for rare-event search experiments, such as the LUX-ZEPLIN (LZ) dark matter experiment. We also highlight the ability of the BEGe detector to probe the X-ray fluorescence region which can be important to identify the presence of radioisotopes associated with neutron production; this is of particular relevance in experiments sensitive to nuclear recoils.
The XENON100 Detector Scovell, P R; XENON100 Collaboration
arXiv.org,
06/2012
Paper, Journal Article
Odprti dostop
XENON100 is a liquid xenon (LXe) time projection chamber built to search for rare collisions of hypothetical, weakly interacting massive particles (WIMPs). Operated in a low-background shield at the ...Gran Sasso underground laboratory in Italy, XENON100 has reached the unprecedented background level of \(<\)0.15 events/day/\kevr in the energy range below 100 \kevr in 30 kg of target mass, before electronic/nuclear recoil discrimination. It found no evidence for WIMPs during a dark matter run lasting for 100.9 live days in 2010, excluding with 90% confidence scalar WIMP-nucleon cross sections above 7x10\(^{-45}\) cm\(^{2}\) at a WIMP mass of 50 GeV/c\(^{2}\). A new run started in March 2011, and more than 200 live days of WIMP-search data have been acquired. Results of this second run are expected to be released in summer 2012.
The first loading of gadolinium (Gd) into Super-Kamiokande in 2020 was successful, and the neutron capture efficiency on Gd reached 50\%. To further increase the Gd neutron capture efficiency to ...75\%, 26.1 tons of \(\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O\) was additionally loaded into Super-Kamiokande (SK) from May 31 to July 4, 2022. As the amount of loaded \(\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O\) was doubled compared to the first loading, the capacity of the powder dissolving system was doubled. We also developed new batches of gadolinium sulfate with even further reduced radioactive impurities. In addition, a more efficient screening method was devised and implemented to evaluate these new batches of \(\rm Gd_2(\rm SO_4)_3\cdot \rm 8H_2O\). Following the second loading, the Gd concentration in SK was measured to be \(333.5\pm2.5\) ppm via an Atomic Absorption Spectrometer (AAS). From the mean neutron capture time constant of neutrons from an Am/Be calibration source, the Gd concentration was independently measured to be 332.7 \(\pm\) 6.8(sys.) \(\pm\) 1.1(stat.) ppm, consistent with the AAS result. Furthermore, during the loading the Gd concentration was monitored continually using the capture time constant of each spallation neutron produced by cosmic-ray muons,and the final neutron capture efficiency was shown to become 1.5 times higher than that of the first loaded phase, as expected.
