Backward particle production in neutrino neon interactions

Backward proton and pion production is studied in ν and \(\bar v\) charged current interactions in neon. The results are compared with other experiments and theory. The complete backward proton data is compatible with protons produced by reinteractions in the nucleus. However in events with only one proton, muon variables appear correlated to those for the backward proton, as expected by the two-nucleon correlation model.     

Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

Mechanism for semiquinone formation in the oxygen negative chemical ionization mass spectrometry of 2,3,7,8-tetrachlorodibenzo-p-dioxin

The high toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) has led to the development of selective and highly sensitive quantitative methods for mass spectral analysis. Analytical selectivity has been demonstrated for the oxygen negative chemical ionization (ONCI) reaction of TCDD in an oxygen-rich plasma. While the reaction product (4,5-dichloro-1,2-benzoquinone anion) of 2,3,7,8-TCDD and oxygen is well known, the mechanism of its formation has not been studied thoroughly. In this report the results of a study involving the reaction of ¹⁸O₂ with 2,3,7,8-TCDD under high pressure and low pressure ONCI conditions are reported. A mechanism is proposed which is compatible with the observation that one ¹⁸O atom is incorporated into the product anion.     

A fully automated nanoelectrospray tandem mass spectrometric method for analysis of Caco-2 samples

Caco-2 cells offer a means to rapidly screen permeability of drug candidates, allowing pharmaceutical companies to eliminate candidates unable to cross the intestinal barrier early in the discovery process. This screening process is typically performed by conventional liquid chromatography/tandem mass spectrometry (LC/MS/MS), which can require time-consuming method development. An alternative to LC/MS/MS, automated nanoelectrospray tandem mass spectrometry (nanoESI-MS/MS), is introduced. This novel approach requires an off-line ZipTip desalting step followed by automated nanoESI-MS/MS, using the NanoMate 100 and ESI Chip. In addition to reduced method development time, automated nanoESI-MS/MS also offers no carry-over between samples, low sample consumption, and ease-of-use as compared with conventional pulled-capillary nanoelectrospray. Furthermore, the infusion system described has the potential to be high-throughput. A comparison of Caco-2 samples analyzed both by LC/MS/MS and by automated nanoESI-MS/MS is presented. The permeability and recovery data of the two compounds analyzed in this study obtained from conventional LC/MS/MS and by automated nanoESI-MS/MS were in excellent agreement.     

Comparison of conventional and enhanced mass resolution triple-quadrupole mass spectrometers for discovery bioanalytical applications

A new triple-quadrupole mass spectrometry (MS) system with enhanced resolution capabilities has recently become available. In order to evaluate the performance of this new instrument for drug discovery assays, both the linearity and the limit of detection were compared in the positive electrospray ionization (ESI) mode with those of a conventional triple-quadrupole instrument supplied by the same manufacturer. For these studies, spiked mouse plasma standard samples were split and assayed by each instrument, which allowed for a direct comparison of the two systems. In the unit mass resolution mode, the new mass spectrometer was found to be at least ten-fold more sensitive than the conventional instrument. The sensitivity of the new mass spectrometer under the enhanced mass resolution mode was found to be even better by another factor of two. For the test compound, the linear dynamic range was found to be 0.05-5000 ng/mL for the new instrument as compared with 2.5-5000 ng/mL for the conventional mass spectrometer.     

Phase-field modeling of void evolution and swelling in materials under irradiation

Void swelling is an important phenomenon observed in both nuclear fuels and cladding materials in operating nuclear reactors. In this work we develop a phase-field model to simulate void evolution and void volume change in irradiated materials. Important material processes, including the generation of defects such as vacancies and self-interstitials, their diffusion and annihilation, and void nucleation and evolution, have been taken into account in this model. The thermodynamic and kinetic properties, such...     

A search for the exotic Ξ<Superscript>−−</Superscript> (1860) in the hyperon beam experiment WA89(1860) in the hyperon beam experiment WA89

We report on a high statistics search for the Ξ^??(1860) resonance in Σ^?-nucleus collisions at 340 GeV/c. No evidence for this resonance is found in our data sample which contains 676000 Ξ^? candidates above bakground. For the decay channel Ξ^??(1860)→Ξ^? π ^? and the kinematic range 0.15<xF<0.9 we find a 3σ upper limit for the production cross section of 3.1 and 3.5 μb per nucleon, for reactions with carbon and copper, respectively.     

Identification of mononitropyrenes and mononitrofluoranthenes in air particulate matter via fused silica gas,chromatography combined with negative ion atmospheric pressure ionization mass spectrometry

This paper describes the use of high resolution capillary gas chromatography combined with negative ion atmospheric pressure ionization mass spectrometry (NIAPIMS) for the analysis of an air particulate extract for mononitropyrenes and mononitrofluoranthenes, some of which are powerful bacterial mutagens. The results are compared to those obtained by the electron impact mass spectrometric analysis of the same sample In addition, the NIAPIMS method confirmed the identification of 4-nitropyrene in the ambient air sample.