Progress towards a lattice determination of (moments of) nucleon structure functions

Using unimproved and non-perturbatively O(a) improved Wilson fermions, results are given for the three lowest moments of unpolarised nucleon structure functions. Renormalisation, chiral extrapolation and the continuum limit of the matrix elements are briefly discussed. The simulations are performed for both quenched and two flavours of unquenched fermions. No obvious sign of deviation from linearity in the chiral extrapolations are found. (This is most clearly seen in our quenched unimproved data, which extends to lighter quark mass.) Possible quenching effects also seem to be small. The lowest moment thus remains too large, so it seems to be necessary to reach smaller quark masses in numerical simulations.Comment: 3 pages, Latex, 4 figures, Talk presented at Lattice2001(matrixelement

Perturbative Renormalization of Improved Lattice Operators

We derive bases of improved operators for all bilinear quark currents up to spin two (including the operators measuring the first moment of DIS Structure Functions), and compute their one-loop renormalization constants for arbitrary coefficients of the improvement terms. We have thus control over O(a) corrections, and for a suitable choice of improvement coefficients we are only left with errors of O(a^2).Comment: 4 pages, LaTeX + 1 eps file + epscrc2.sty (included). Talk given to the Lattice 97 International Symposium, 22-26 July 1997, Edinburgh, UK. Minor changes in notatio

Optical study of the vibrational and dielectric properties of BiMnO3

BiMnO3 (BMO), ferromagnetic (FM) below Tc = 100 K, was believed to be also ferroelectric (FE) due to a non-centro-symmetric C2 structure, until diffraction data indicated that its space group is the centro-symmetric C2/c. Here we present infrared phonon spectra of BMO, taken on a mosaic of single crystals, which are consistent with C2/c at any T > 10 K, as well as room-temperature Raman data which strongly support this conclusion. We also find that the infrared intensity of several phonons increases steadily for decreasing T, causing the relative permittivity of BMO to vary from 18.5 at 300 K to 45 at 10 K. At variance with FE materials of displacive type, no appreciable softening has been found in the infrared phonons. Both their frequencies and intensities, moreover, appear insensitive to the FM transition at Tc

particle size evaluation of total mixed rations in intensive beef production systems

AbstractSamples of total mixed ration (TMR) were collected periodically in 15 beef cattle farms and submitted to a nutritional and particle size evaluation. Samples of faeces were taken and analysed for pH, consistency, colour and visually ranked for corn residues (Corn Residue Index) from 4 (totally digested) to 0 (very high presence of maize residues). Dry matter (DM), crude protein (CP), and ash content of TMR for Limousine were higher than that for Charolaise while an opposite situation was observed for crude fiber (CF). Particle size analysis of TMR showed an higher content of small ( 19.0 mm) particles in Charolaise than in Limousine TMR. From May to September a general increase of larger fractions and a reduction of the smaller ones were observed, as a consequence of empirical practices of TMR formulation during summer. Faeces characteristics did not show any difference between breeds (overall mean pH: 6.00 vs 6.13; Corn Residue Index: 2.90 vs 3.24, respectively for Charolaise a..

Ash leachates from some recent eruptions of Mount Etna (Italy) and Popocatépetl (Mexico) volcanoes and their impact on amphibian living freshwater organisms

Leaching experiments were carried out on fresh ash samples from Popocatépetl 2012, Etna 2011, and Etna 2012 eruptions, in order to investigate the release of compounds in both double-deionized and lake (Lake Ohrid, FYR of Macedonia) waters. The experiments were carried out using different grain sizes and variable stirring times (from 30 min to 7 days). Results were discussed in the light of changing pH and release of compounds for the different leachates. In particular, Etna samples induced alkalinization, and Popocatépetl samples induced acidification of the corresponding leachates. The release of different elements does not show correlation with the stirring time, with the measured maximum concentrations reached in the first hours of washing. General inverse correlation with grain size was observed only for Na+, K+, Cl-, Ca2+, Mg2+, SO2-4 , and Mn2+, while the other analysed elements show a complex, scattering relationship with grain size. Geochemical modelling highlights leachates' saturation only for F and Si, with Popocatépetl samples sometimes showing saturation in Fe. The analysed leachates are classified as undrinkable for humans on the basis of European laws, due to excess in F-, Mn2+, Fe, and SO2-4 (the latter only for Popocatépetl samples). Finally, the Etna 2012 and Popocatépetl leachates were used for toxicity experiments on living biota (Xenopus laevis). They are mildly toxic, and no significant differences exist between the toxic profiles of the two leachates. In particular, no significant embryo mortality was observed; while even at high dilutions, the leachates produced more than 20% of malformed larvae

Higher-twist contributions to the Structure Functions coming from 4-fermion operators

We evaluate the contribution of a class of higher-twist operators to the lowest moment of the Structure Functions, by computing appropriate matrix elements of six four-fermion operators in the quenched approximation. Their perturbative renormalization constants and mixing coefficients are calculated in the 't Hooft-Veltman scheme of dimensional regularization, using codes written in the algebraic manipulation computer language FORM.Comment: Talk presented at LATTICE99(matrix elements), Pisa (Italy), June 29 - July 3; 3 pages; to be published in Nucl. Phys. B (Proc. Suppl.

O(a)O(a) Improvement for Quenched Wilson Fermions

We briefly describe some of our recent results for the mass spectrum and matrix elements using $O(a)$ improved fermions for quenched QCD. Where possible a comparison is made between improved and Wilson fermions.Comment: 6 pages, Latex, 11 figures, epsf.sty and buckow1.sty needed (buckow1.sty included). Talk presented at the 31st Ahrenshoop Symposium on the Theory of Elementary Particles, September 1997, Buckow, German