First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen.

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.

A sample holder for simultaneous Raman and neutron vibrational spectroscopy.

We have built a sample holder (called a center stick or sample stick) for performing simultaneous Raman and neutron vibrational spectroscopy on samples of material at the VISION neutron vibrational spectrometer of the Spallation Neutron Source at Oak Ridge National Laboratory. This equipment holds material samples in the neutron beam within the cryogenic environment of the VISION spectrometer, allowing for samples to be studied at temperatures as low as 5 K. It also provides the capability for gas to be loaded to or evacuated from the sample while it is loaded at VISION. The optical components for directing and filtering light are located within the cryogenic volume, in physical proximity to the sample. We describe the construction of this sample holder and discuss our first measurements of simultaneous Raman and neutron vibrational spectra. The samples that we report on were of 4-nitrophenol at a temperature of 20 K and of cryogenic hydrogen of a number of different orthohydrogen fractions.

New Pulsed Cold Neutron Beam Line for Fundamental Nuclear Physics at LANSCE.

The NPDGamma collaboration has completed the construction of a pulsed cold neutron beam line on flight path12 at the Los Alamos Neutron Science Center (LANSCE). We describe the new beam line and characteristics of the beam. We report results of the moderator brightness and the guide performance measurements. FP12 has the highest pulsed cold neutron intensity for nuclear physics in the world.

Measurement of Parity Violation in np Capture: the NPDGamma Experiment.

The NPDGamma experiment will measure the parity-violating directional gamma ray asymmetry A γ in the reaction [Formula: see text]. Ultimately, this will constitute the first measurement in the neutron-proton system that is sensitive enough to challenge modern theories of nuclear parity violation, providing a theoretically clean determination of the weak pion-nucleon coupling. A new beam-line at the Los Alamos Neutron Science Center (LANSCE) delivers pulsed cold neutrons to the apparatus, where they are polarized by transmission through a large volume polarized (3)He spin filter and captured in a liquid para-hydrogen target. The 2.2 MeV gamma rays from the capture reaction are detected in an array of CsI(Tl) scintillators read out by vacuum photodiodes operated in current mode. We will complete commissioning of the apparatus and carry out a first measurement at LANSCE in 2004-05, which would provide a statistics-limited result for A γ accurate to a standard uncertainty of ±5 × 10(-8) level or better, improving on existing measurements in the neutron-proton system by a factor of 4. Plans to move the experiment to a reactor facility, where the greater flux would enable us to make a measurement with a standard uncertainty of ±1 × 10(-8), are actively being pursued for the longer term.

Commissioning of the NPDGamma Detector Array: Counting Statistics in Current Mode Operation and Parity Violation in the Capture of Cold Neutrons on B 4 C and (27) Al.

The NPDGamma γ-ray detector has been built to measure, with high accuracy, the size of the small parity-violating asymmetry in the angular distribution of gamma rays from the capture of polarized cold neutrons by protons. The high cold neutron flux at the Los Alamos Neutron Scattering Center (LANSCE) spallation neutron source and control of systematic errors require the use of current mode detection with vacuum photodiodes and low-noise solid-state preamplifiers. We show that the detector array operates at counting statistics and that the asymmetries due to B4C and (27)Al are zero to with- in 2 × 10(-6) and 7 × 10(-7), respectively. Boron and aluminum are used throughout the experiment. The results presented here are preliminary.

Refinements in primary rumen epithelial cell incubation techniques.

The objectives of this study were to 1) determine if the number of rumen epithelial cells in primary cell incubation affects the rate of metabolite production, and 2) determine the optimum mode of data expression to standardize reporting criteria. Sections of rumen epithelial tissue were excised from five Holstein heifers and subjected to serial tryptic digestion to isolate cells. Isolated cells had a mean viability of 86% (+/- 1.29) and were incubated at concentrations of 0.5, 1, 5, 10, 20, and 40 million cells per flask. Oxidation of [1-14C]butyrate to 14CO2 and production of acetoacetate (ACAC), beta-hydroxybutyrate (BHBA), lactate, and pyruvate were measured for cell dilution comparisons. Cell number, cell dry matter, cell crude protein, epithelial wet tissue weight, body weight, and metabolic body weight were measured to generate 12 different forms of data expression. Coefficients of variation were calculated for each type of expression. Expressing data per cell number resulted in the lowest variation. Oxidation of [1-14C]butyrate to 14CO2 and pyruvate production per million cells did not significantly differ between treatments for 90-min incubation. Acetoacetate and lactate concentrations were greatest at 0.5 and 1 million cells/flask, respectively, with no differences between 5 to 40 million cells/flask. Production of BHBA for 1 million cells/flask was greater than 0.5 and 40 million cells/flask, but did not change between cell concentrations 5 to 20 million. The BHBA:ACAC concentration ratios for 0.5 and 1 million cell dilutions were both 1.1 to 1 indicating low mitochondrial redox potentials. Concomitantly, lactate:pyruvate ratios for 0.5 and 1 million cells were greater than other cell dilutions, indicating a high cytosolic redox potential. The suggested range of rumen epithelial cells to include in incubations is 5 to 20 million cells/flask. This will minimize experimental error associated with using low cell numbers and the potential for reduced metabolite production caused by incubating large cell quantities. When rumen tissue taken from animals of the same species, size, and stage of development; data adjusted by cell number is preferred. However, it is recommended that cell protein, cell DM, and animal metabolic weight be included to facilitate future comparison between species and laboratories.

Eicosapentaenoic acid and gamma-linolenic acid induce apoptosis in HL-60 cells.

Enteral nutrition with eicosapentaenoic acid (EPA; 20:5 n-3) and gamma-linolenic acid (GLA; 18:3 n-6) decreased pulmonary inflammation by reducing neutrophil counts and chemotactic factors in bronchoalveolar lavage fluid during acute respiratory distress syndrome (ARDS). We hypothesize that the anti-inflammatory effects of EPA and GLA may be due, in part, to induction of neutrophil apoptosis. The purpose of this study was to determine whether EPA and GLA, alone or in combination, trigger apoptotic cell death in the human promyelocytic leukemia HL-60 cell line. HL-60 cells were incubated with 10, 20, 50, and 100 micromol/L EPA, GLA, or various combinations of EPA and GLA for 2, 4, 8, 12, and 24 hs. Oleic acid (18:1 n-9) was used as a fatty acid control. Flow cytometry using dual staining with propidium iodide and annexin V-FITC assessed apoptosis, necrosis, and viability. Apoptosis was verified by DNA fragmentation as assessed by agarose gel electrophoresis. EPA, GLA, and various combinations of EPA and GLA significantly induced apoptosis and reduced cell viability in HL-60 cells. Viability was significantly reduced to the same extent with the combination of 50 micromol/L EPA\20 micromol/L GLA compared with 100 micromol/L EPA. These data indicate that EPA and GLA, alone or in combination, reduce cell survival by induction of apoptosis. Thus, induction of apoptosis by select dietary n-3 (EPA) and n-6 (GLA) polyunsaturated fatty acids may be the mechanism of the resolution of pulmonary inflammation in ARDS.