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A neutron lifetime measurement conducted at the Japan Proton Accelerator Research Complex (J-PARC) is counting the number of electrons from neutron decays with a time projection chamber (TPC). The $��$ rays produced in the TPC cause irreducible background events. To achieve the precise measurement, the inner walls of the TPC consist of $^6$Li-enriched lithium-fluoride ($^6$LiF) tiles to suppress the amount of $��$ rays. In order to estimate the amount of $��$ rays from the $^{6}{\rm LiF}$ tile, prompt gamma ray analysis (PGA) measurements were performed using germanium detectors. We reconstructed the measured $��$-ray energy spectrum using a Monte Carlo simulation with the stripping method. Comparing the measured spectrum with a simulated one, the number of $��$ rays emitted from the$^{6}{\rm LiF}$ tile was $(2.3^{+0.7}_{-0.3}) \times 10^{-4}$ per incident neutron. This is $1.4^{+0.5}_{-0.2}$ times the value assumed for a mole fraction of the $^{6}{\rm LiF}$ tile. We concluded that the amount of $��$ rays produced from the $^{6}{\rm LiF}$ tile is not more twice the originally assumed value., 14 pages, 11 figures, will be submitted to JINST

Hydrostatic pressure alters the free energy of proteins by a few kJ mol-1, with the amount depending on their partial molar volumes. Because the folded ground state of a protein contains cavities, it is always a state of large partial molar volume. Therefore pressure always destabilises the ground state and increases the population of partially and completely unfolded states. This is a mild and reversible conformational change, which allows the study of excited states under thermodynamic equilibrium conditions. Many of the excited states studied in this way are functionally relevant; they also seem to be very similar to kinetic folding intermediates, thus suggesting that evolution has made use of the 'natural' dynamic energy landscape of the protein fold and sculpted it to optimise function. This includes features such as ligand binding, structural change during the catalytic cycle, and dynamic allostery.

In a neutron lifetime measurement at the Japan Proton Accelerator Complex, the neutron lifetime is calculated by the neutron decay rate and the incident neutron flux. The flux is obtained due to counting the protons emitted from the neutron absorption reaction of ${}^{3}{\rm He}$ gas, which is diluted in a mixture of working gas in a detector. Hence, it is crucial to determine the amount of ${}^{3}{\rm He}$ in the mixture. In order to improve the accuracy of the number density of the ${}^{3}{\rm He}$ nuclei, we suggested to use the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction as a reference because this reaction involves similar kinetic energy as the ${}^{3}{\rm He}({\rm n},{\rm p}){}^{3}{\rm H}$ reaction and a smaller reaction cross section to introduce reasonable large partial pressure. The uncertainty of the recommended value of the cross section, however, is not satisfied with our requirement. In this paper, we report the most accurate experimental value of the cross section of the ${}^{14}{\rm N}({\rm n},{\rm p}){}^{14}{\rm C}$ reaction at a neutron velocity of 2200 m/s, measured relative to the ${}^{3}{\rm He}({\rm n},{\rm p}){}^{3}{\rm H}$ reaction. The result was 1.868 $\pm$ 0.003 (stat.) $\pm$ 0.006 (sys.) b. Additionally, the cross section of the ${}^{17}{\rm O}({\rm n},{\rm \alpha}){}^{14}{\rm C}$ reaction at the neutron velocity is also redetermined as 249 $\pm$ 6 mb., Comment: 22 pages, 11 figures

Pressure-dependent (13)C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure-independent compressibilities. CH(3), CH(2) and CH carbon shifts change on average by +0.23, -0.09 and -0.18 ppm, respectively, due to a combination of bond shortening and changes in bond angles, the latter matching one explanation for the gamma-gauche effect. In addition, there is a residue-specific component, arising from both local compression and conformational change. To assess the relative magnitudes of these effects, residue-specific shift changes for protein G were converted into structural restraints and used to calculate the change in structure with pressure, using a genetic algorithm to convert shift changes into dihedral angle restraints. The results demonstrate that residual (13)C alpha shifts are dominated by dihedral angle changes and can be used to calculate structural change, whereas (13)C beta shifts retain significant dependence on local compression, making them less useful as structural restraints.\ud \ud

We have investigated the effect of pressure and temperature on the structural and thermodynamic stability of a protein dihydrofolate reductase from a deep-sea bacterium Moritella profunda in its folate-bound form in the pressure range between 3 and 375 MPa and the temperature range between -5 and 30 degrees C. The on-line cell variable pressure 1H NMR spectroscopy has been used to analyze the chemical shift and signal intensity in one-dimensional 1H NMR spectra. Thermodynamic analysis based on signal intensities from protons in the core part indicates that the thermodynamic stability of Moritella profunda DHFR is relatively low over the temperature range between -5 and 30 degrees C (deltaG0=15.8 +/- 4.1 kJ/mol at 15 degrees C), but is well adapted to the living environment of the bacterium (2 degrees C and 28 MPa), with the maximum stability around 5 degrees C (at 0.1 MPa) and a relatively small volume change upon unfolding (deltaV= 66 +/- 19 ml/mol). Despite the relatively low overall stability, the conformation in the core part of the folded protein remains intact up to approximately 200 MPa, showing marked stability of the core of this protein.