Electronic properties of Pt-W substitutionally random alloys

Summary We have investigated the electronic states of some Pt-W alloys by means of the relativistic KKR-CPA theory in order to gain some insights on the many interesting physical properties of such a system. In particular we were interested in studying the role of the Fermi surface topology in the ordering phenomena shown by this alloy. It turns out that the broadening of the states at the Fermi energy makes the Fermi surface concept questionable. Reasons for that are understood in terms of our scheme and approximations, even though to give an exhaustive answer one should pursue the full-charge self-consistency obtainable in the SCF-KKR-CPA theory.     

The effect of agitation speed,enzyme loading and substrate concentration on enzymatic hydrolysis of cellulose from brewer’s spent grain

Brewer’s spent grain components (cellulose, hemicellulose and lignin) were fractionated in a two-step chemical pretreatment process using dilute sulfuric acid and sodium hydroxide solutions. The cellulose pulp produced was hydrolyzed with a cellulolytic complex, Celluclast 1.5 L, at 45 °C to convert the cellulose into glucose. Several conditions were examined: agitation speed (100, 150 and 200 rpm), enzyme loading (5, 25 and 45 FPU/g substrate), and substrate concentration (2, 5 and 8% w/v), according to a 2³ full factorial design aiming to maximize the glucose yield. The obtained results were interpreted by analysis of variance and response surface methodology. The optimal conditions for enzymatic hydrolysis of brewer’s spent grain were identified as 100 rpm, 45 FPU/g and 2% w/v substrate. Under these conditions, a glucose yield of 93.1% and a cellulose conversion (into glucose and cellobiose) of 99.4% was achieved. The easiness of glucose release from BSG makes this substrate a raw material with great potential to be used in bioconversion processes.     

Pure rotational spectra of PbSe and PbTe: potential function, Born-Oppenheimer breakdown, field shift effect and magnetic shielding

The pure rotational spectra of 41 isotopic species of PbSe and PbTe have been measured in their X 1Sigma+ electronic state with a resonator pulsed-jet Fourier transform microwave spectrometer. The molecules were prepared by laser ablation of suitable target rods and stabilised in supersonic jets of noble gas. Global multi-isotopologue analyses yielded spectroscopic Dunham parameters Y01, Y11, Y21, Y31, Y02, and Y12 for both species, as well as effective Born-Oppenheimer breakdown (BOB) coefficients delta01 for Pb, Se and Te. Unusual large values of the BOB parameters for Pb have been rationalized in terms of finite nuclear size (field shift) effect. A direct fit of the same data sets to an appropriate radial Hamiltonian yielded analytic potential energy functions and BOB radial functions for the X 1Sigma+ electronic state of both PbSe and PbTe. Additionally, the magnetic hyperfine interactions produced by the uneven mass number A nuclei 207Pb, 77Se, 123Te, and 125Te were observed, yielding first determinations of the corresponding nuclear spin-rotation coupling constants.     

A new method to calculate the thermodynamical properties of liquids from accurate speed-of-sound measurements

In this work, a new method for the determination of the thermodynamical properties of fluids, based on experimental speed-of-sound measurements, is described. This method consists in the solution of recursive equations (REM, Recursive Equations Method) for the determination of the density ρ(p,T) and specific heat capacity at constant pressure c_p(p,T), using the initial values of density ρ(p₀,T) and isobaric specific heat capacity c_p(p₀,T) known at a reference pressure p₀, as a function of the temperature, if the speed-of-sound function, u(p,T), is known, at least over a certain temperature and pressure range. A complete uncertainty analysis has also been developed. As an example of the good performances of this analysis method, firstly density and isobaric specific heat capacity have been calculated for water and the results have been compared with those predicted by the International Association for the Properties of Water and Steam 95 Formulation (IAPWS-95), as delivered by Wagner and Pruss. One more application has been made starting from experimental speed-of-sound values in pure acetone. These results have been compared with those calculated by the most advanced numerical integration methods and with the prevision of the dedicated NIST equation of state (EoS) by Lemmon and Span.