Nucleon axial charge in (2+1)-flavor dynamical-lattice QCD with domain-wall fermions

We present results for the nucleon axial charge g{A} at a fixed lattice spacing of 1/a=1.73(3) GeV using 2+1 flavors of domain wall fermions on size 16;{3} x 32 and 24;{3} x 64 lattices (L=1.8 and 2.7 fm) with length 16 in the fifth dimension. The length of the Monte Carlo trajectory at the lightest m_{pi} is 7360 units, including 900 for thermalization. We find finite volume effects are larger than the pion mass dependence at m{pi}=330 MeV. We also find a scaling with the single variable m{pi}L which can also be seen in previous two-flavor domain wall and Wilson fermion calculations. Using this scaling to eliminate the finite-volume effect, we obtain g{A}=1.20(6)(4) at the physical pion mass, m_{pi}=135 MeV, where the first and second errors are statistical and systematic. The observed finite-volume scaling also appears in similar quenched simulations, but disappear when V>or=(2.4 fm);{3}. We argue this is a dynamical quark effect.     

A New Testing Machine for the Dynamic Characterization of High Strength Low Damping Fiber Materials

This work describes a novel method for measuring the damping, the elastic modulus and the non-linear behavior of high strength low damping fiber materials such as para-aramids, silicon carbide (SiC) and carbon. The method is based on resonant response characterization of a spring-mass system excited by a sine-wave forcing term which is applied as a vertical force to the suspended mass. The damping is obtained from the measured resonance quality factor Q, the elasticity modulus is calculated from the resonance frequency, and the non-linear coefficient is obtained with the backbone approach from resonance profile variations as a function of the forcing term amplitude. It is argued that the method is very sensitive, to the point that a maximum excitation amplitude of the order of a few percent of resistance is sufficient to obtain an estimate of the non-linear coefficient. This claim is supported by experimental results. A testing machine is also discussed, which provides the necessary sensitivity at such small excitation amplitudes and the capability of evaluating very small damping values, as expected in high strength low damping fiber materials. The sensitivity is guaranteed by an optical position sensor with sub-micron resolution. To evaluate small damping values, particular care has been taken to ensure that energy dispersions in the generator are much smaller than energy dispersions in the fibers themselves. Examples of dynamic characterization are shown for para-aramid, silicon carbide, and carbon fibers.     

Vapour-liquid-solid Growth and Characterisation of N-methylurea Crystals

A new growth method, based on a vapour-liquid-solid (VLS) mechanism, is reported for preparing single crystals of N-methylurea (NMU), a material which appears to be a good alternative to urea for non-linear optical applications in the “near UV-visible” region of the spectrum. Details of the growth procedure are given and it is shown that large single crystals, with volumes up to 7 ÷ 10 cm³, can be obtained with satisfactory reproducibility and very fast growth rate. Structural and optical characterisation, still preliminary, are reported, which evidence a crystalline quality comparable to that of urea and N-methylurea as previously grown with other growth techniques. Cryst. Res. Technol., Vol. 32, No. 1.     

Sustainable Approaches to the Synthesis of Metallophthalocyanines in Solution

This work aims to investigate more sustainable reaction conditions for the synthesis of metallophthalocyanines. Anisole, glycerol and their mixtures have been investigated as reaction media for the tetramerization of phthalonitriles. Acetates of three divalent first-transition metal cations, Co(II), Cu(II) and Zn(II), were used and several bases were tested, depending on the chosen substrates and reaction conditions, with a view to making the whole process more sustainable while ensuring its scalability. Unsubstituted phthalocyanines were synthesized to analyze the behavior of the different metal ions in terms of reactivity in the new reaction media, resulting in a general Cu > Co > Zn trend, while the nonpolar tetra-tert-butyl substitution was investigated to evaluate the synthesis of soluble derivatives in the new conditions. Furthermore, the potassium hydroxide (KOH)-aided statistical synthesis of the unsymmetrical 9(10), 16(17), 23(24)-tri-tert-butyl-2-iodophthalocyaninato zinc(II), starting from 4-tert-butylphthalonitrile and 4-iodophthalonitrile in a glycerol/anisole mixture, proceeded with a satisfactory 26% yield. Our results provide insights into the investigation of new reaction environments and the understanding of their strengths and weaknesses, with a view to further increasing the sustainability of the synthesis of metallomacrocycles with high added value while lowering their production cost.     

X‐ray Topographic Characterization of L‐Arginine Phosphate Monohydrate Crystals

L‐arginine phosphate monohydrate (LAP) organic crystals were investigated by X‐ray Lang topography. Selected topographs of nearly perfect seeded grown and self‐nucleated crystals show that typical defects inside are grown‐in and post‐growth dislocations, growth sector boundaries, and microbes, while their features are presented and discussed. No structural defects associated to the presence of step bunching on the (100) surface of the crystal have been observed by X‐ray topography.     

Prototype thermal detectors for a Re neutrino mass experiment

We report on a new method to measure the electron antineutrino mass, consisting of the end-point study of ¹⁸⁷Re β-spectrum (Q-value=2.6 keV) collected calorimetrically (source=detector approach) with high energy resolution and statistics. The proposed detector is a micro-bolometer, single or in an array structure, containing a total rhenium mass of 1 mg, operated at a temperature of a few tens of mK and able to reach 10 eV energy resolution. As phonon sensors, we are developing silicon thermistors doped by implantation; some tests are performed also with neutron transmutation doped germanium thermistors. We have obtained up to now promising energy resolutions down to 11 eV with tin absorbers (as test devices) and 70 eV with rhenium absorbers.     

Measure of low radioactive contamination and nuclear recoil quenching factor using cryogenic particle detectors

For double beta decay and dark matter experiments the determination of the radioactive contamination of materials used is of fundamental importance. The cryogenic particle detectors allow the realization of detectors with various types of materials and in this way the radioactivity is measured in a calorimetric approach with very high sensitivity. In particular a new complete analysis for different types of leads, modern and ancient roman, was realized and here presented. The detector sensitivity for a nuclear recoil event is a crucial point in the dark matter experiments. The nuclear recoil detection efficiency for cryogenic particle detectors was directly measured using two TeO₂ crystals facing one with other and performing a coincidence-anticoincidence analysis of the collected data. The determination of the quenching factor for low energy nuclear recoils in the TeO₂ cryogenic detectors shows that these devices are very sensitive to a possible dark matter particle interaction. In cryogenic detectors a nuclear recoil generates signals with the same amplitude of an electron with the same energy. The performed measure and the data analysis will be discussed in detail. Finally the experimental setup and the preliminary test of the new array of TeO₂ cryogenic detectors for double beta decay and dark matter search will be discussed in detail.