Search results for "electron capture"
showing 10 items of 90 documents
Discovery of an Exceptionally Strong β -Decay Transition of F20 and Implications for the Fate of Intermediate-Mass Stars
2019
A significant fraction of stars between 7 and 11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on ^{20}Ne in the degenerate oxygen-neon stellar core. However, because of the unknown strength of the transition between the ground states of ^{20}Ne and ^{20}F, it has not previously been possible to fully constrain the rate. By measuring the transition, we establish that its strength is exceptionally large and that it enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupte…
A new proposal for the determination of polychlorinated biphenyls in environmental water by using host-guest adsorption
2020
Abstract Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants whose wide industrial use has been banned over the years in most countries due to their persistence and bioaccumulation. In fact, the International Agency for Research on Cancer defined them in 2016 as carcinogenic to humans based on sufficient evidence of an increased risk of cancer, being children and pregnant or lactating women the most vulnerable population subgroups. In this work, a new alternative for the determination of polychlorinated biphenyls (PCB28, PCB52, PCB101, PCB138, PCB153, and PCB180) in water samples has been developed by using a cyclodextrin-containing silica microparticulated material as …
Microwave-assisted extraction of pyrethroid insecticides from soil
2004
Abstract An analytical method has been developed for the microwave-assisted extraction of synthetic pyrethroid insecticide residues in soils and their determination by gas chromatography with electron capture detector (ECD) and mass spectrometry (MS) detector. Clean soil samples were spiked with nine pyrethroids: tetramethrin, cyfluthrin, flucythrinate, deltamethrin, bifenthrin, permethrin, cypermethrin and fluvalinate were used for this study. Concentration levels were 50 ng g −1 for all the compounds studied except to sumitrin for which a 10 μg g −1 was evaluated. Two grams of sample were treated in a closed PTFE reactor with 10 mL toluene and 1 mL water and irradiated at 700 W during 9 m…
Possible detection of the doubleβ+/electron-capture decay
1993
The two-neutrino double [beta] decay matrix elements of [sup 58]Ni, [sup 96]Ru, [sup 106]Cd, and [sup 136]Ce are calculated in the framework of the quasiparticle random phase approximation and the corresponding double [beta][sup +]/electron-capture (EC) decay ([beta][sup +][beta][sup +]/[beta][sup +]EC/ECEC) half-lives are estimated. The calculated ground-state-to-ground-state half-lives range from 3.9[times]10[sup 23] to 6.4[times]10[sup 19] yr indicating that the double [beta][sup +]/EC decay could, in principle, be detected using currently known experimental techniques.
Analysis of pesticide residues in fruit and vegetables by matrix solid phase dispersion (MSPD) and different gas chromatography element-selective det…
1995
A comparison between different element selective detectors for the determination of organophosphorus and organochlorine pesticide residues, from fruit and vegetables, was performed by capillary GC with electron capture detector (ECD), nitrogen phosphorus detector (NPD), flame photometric detector (FPD) in the sulphur and phosphorus modes, and mass spectrometry detector (MSD) in selected ion monitoring (SIM) mode. Pesticides were extracted from the different foodstuffs by Matrix Solid Phase Dispersion (MSPD). Recoveries of 41–108 % with relative standard deviation of 2–14 % in the concentration range 0.5–10 μg L−1 were obtained in oranges, lemons, grapefruit, pears, plums, lettuces and tomat…
Double beta decays of 124Xe investigated in the QRPA framework
2013
The two-neutrino (2ν2β) and neutrinoless (0ν2β) double beta decays of 124Xe are investigated. Decays to the ground state, , and various 0+ and 2+ excited states in 124Te are considered. The corresponding nuclear matrix elements have been calculated by using the quasiparticle random-phase approximation combined with the multiple-commutator model. G-matrix-based effective nuclear interactions have been used in realistic single-particle model spaces. All possible channels, β+β+, β+EC, and ECEC, are discussed for both the 2ν2β and 0ν2β decays. The associated half-lives are computed, in particular the one corresponding to the resonant neutrinoless double electron capture transition to the 2790.4…
Application of matrix solid-phase dispersion to the determination of a new generation of fungicides in fruits and vegetables.
2002
A method based on matrix solid-phase dispersion (MSPD) and gas chromatography to determine eight fungicides in fruits and vegetables is described. Fungicide residues were identified and quantified using nitrogen-phosphorus detection and electron-capture detection connected in parallel and confirmed by mass spectrometric detection. The method required 0.5 g of sample, C18 bonded silica as dispersant sorbent, silica as clean-up sorbent and ethyl acetate as eluting solvent. Recoveries from spiked orange, apple, tomato, artichoke, carrot and courgette samples ranged from 62 to 102% and relative standard deviations were less than 15% in the concentration range 0.05-10 mg kg(-1). Detection and qu…
Production of highly charged ions of rare species by laser-induced desorption inside an electron beam ion trap
2019
This paper reports on the development and testing of a novel, highly efficient technique for the injection of very rare species into electron beam ion traps (EBITs) for the production of highly charged ions (HCI). It relies on in-trap laser-induced desorption of atoms from a sample brought very close to the electron beam resulting in a very high capture efficiency in the EBIT. We have demonstrated a steady production of HCI of the stable isotope 165Ho from samples of only 1012 atoms (∼300 pg) in charge states up to 45+. HCI of these species can be subsequently extracted for use in other experiments or stored in the trapping volume of the EBIT for spectroscopic measurements. The high efficie…
Suppression of Penning discharges between the KATRIN spectrometers
2020
The KArlsruhe TRItium Neutrino experiment (KATRIN) aims to determine the effective electron (anti)neutrino mass with a sensitivity of $0.2\textrm{ eV/c}^2$ (90$\%$ C.L.) by precisely measuring the endpoint region of the tritium $\beta$-decay spectrum. It uses a tandem of electrostatic spectrometers working as MAC-E (magnetic adiabatic collimation combined with an electrostatic) filters. In the space between the pre-spectrometer and the main spectrometer, an unavoidable Penning trap is created when the superconducting magnet between the two spectrometers, biased at their respective nominal potentials, is energized. The electrons accumulated in this trap can lead to discharges, which create a…
Sulfuric acid cleanup and KOH-ethanol treatment for confirmation of organochlorine pesticides and polychlorinated biphenyls: application to wastewate…
1987
Abstract The efficacy of sulfuric acid cleanup and KOH-ethanol hydrolysis confirmation was studied for 22 organochlorine pesticides and 2 polychlorinated biphenyls (PCBs). Mean recoveries for different treatment times are given. The method was applied to analysis of several wastewater samples by gas chromatography with electron capture detection. Organochlorine compounds were extracted by using separatory funnels and 15% diethyl ether in hexane as extractant. All the compounds studied could be analyzed except trifluralin, dichloran, dieldrin, and endrin, which were destroyed after treatment with concentrated H2S04. The pesticides found most commonly in the samples analyzed were fenson, tetr…