Finite mixture of regression models for censored data based on scale mixtures of normal distributions

Advances in Data Analysis and Classification - In statistical analysis, particularly in econometrics, the finite mixture of regression models based on the normality assumption is routinely used to...     

Standard molar enthalpies of formation of 5- and 6-nitroindazole

The present work reports the experimental determination of the standard (p ^o = 0.1 MPa) molar enthalpies of formation in the condensed and gaseous phases, at T = 298.15 K, of 5- and 6-nitroindazole. These results were derived from the measurements of the standard molar energies of combustion, using a static bomb calorimeter and from the standard molar enthalpies of sublimation derived by the application of Clausius–Clapeyron to the temperature dependence of the vapour pressures measured by the Knudsen effusion technique. The results are interpreted in terms of the energetic contributions of the nitro groups in the different positions of the aromatic ring.     

An all-atom force field for metallocenes

A new all-atom force field, for the molecular modeling of metallocenes was constructed. Quantum chemical calculations were performed to obtain several force field terms not yet defined in the literature. The remainder were transferred from the OPLS-AA/AMBER framework. The parametrization work included the obtention of geometrical parameters, torsion energy profiles, and distributions of atomic charges that blend smoothly with the OPLS-AA specification for a variety of organic molecular fragments. Validation was carried out by comparing simulated and experimental data for five different ferrocene derivatives in the crystalline phase. The present model can be regarded as a step toward a general force field for metallocenes, built in a systematic way, easily integrated with OPLS-AA, and transferable between different metal-ligand combinations.     

Enthalpy of formation of the cyclopentadienyl radical: photoacoustic calorimetry and ab initio studies

The gas-phase C-H bond dissociation enthalpy (BDE) in 1,3-cyclopentadiene has been determined by time-resolved photoacoustic calorimetry (TR-PAC) as 358 +/- 7 kJ mol(-1). Theoretical results from ab initio complete basis-set approaches, including the composite CBS-Q and CBS-QB3 procedures, and basis-set extrapolated coupled-cluster calculations (CCSD(T)) are reported. The CCSD(T) prediction for the C-H BDE of 1,3-cyclopentadiene (353.3 kJ mol(-1)) is in good agreement with the TR-PAC result. On the basis of the experimental and the theoretical values obtained, we recommend 355 +/- 8 kJ mol(-1) for the C-H BDE of 1,3-cyclopentadiene and 271 +/- 8 kJ mol(-1) for the enthalpy of formation of cyclopentadienyl radical.     

A calorimetric study of plant–plant and plant–soil interactions of extracts from Ixorhea tschudiana

The effect of the CHCl₃ and MeOH extracts from aerial parts from the Northwestern Argentina endemic species Ixorhea tschudiana Fenzl. on germination of the dicot tomato and the monoct onion and on soil microbial activity was studied by calorimetric and calorespirometric experiments. The CHCl₃ extract inhibited seedling growth of tomato which increased with increasing concentrations. Seeds imbibed with 250 mg dm^?3 extract germinated 24 h later than control and those imbibed with 100 and 500 mg dm^?3 extract. This was reflected in the calculated low specific seedling growth rate (p_SGΔH_B) as determined from calorespirometric experiments. On the other hand, seedlings obtained in 500 mg dm^?3 extract showed shorter and thicker hairy roots than control with significantly higher p_SGΔH_B. Probably, the extract induces inhibition of water uptake by seedling roots. Germination was reduced 50% in onion seeds imbibed with 500 mg dm^?3 CHCl₃ extract which apparently is due to higher rate of imbibition during the first stages as determined for calorimetry. On the other hand, 83 and 250 mg kg^?1 of the MeOH and CHCl₃ extract seem to selectively inhibit the growth of certain microorganisms and to enhance the activity of soil actinomycetes. Two actinobacteria were isolated from soil treated with these concentrations of both extracts: Kocuria sp. and Kocuria rosea; this latter species is known as a keratinolytic agent and seems to degrade complex carbon compounds of the soil and those incorporated by the MeOH extract. Both Kocuria specie seem to be beneficial for the soil converting substrate into biomass and thus I. tschudiana could be used as a soil phytoremediator.     

High-spin structure of yrast-band in 78Kr

Lifetime of levels up to 22⁺, have been measured in ⁷⁸Kr and an oblate shape is assigned to the ground state using the CSM and the configuration dependent shell correction calculations. Calculations further show that ⁷⁸Kr is highly γ-soft nucleus. The experimental Q _t values coupled with theoretical calculations indicate an oblate shape for ⁷⁸Kr at low spins and triaxial shape at higher spins     

Thermal stability of aDesulfovibrio gigas periplasmic hydrogenase in reverse micelles

The thermal and operational stabilities ofDesulfovibrio gigas periplasmic hydrogenase were studied at 30 and 50°C in aqueous and micellar media. At the lower temperature the hydrogenase was more stable in reverse micelles of a cationic surfactant. No inactivation was detected over almost 16 d of incubation of the hydrogenase in the reverse micellar solution, during which the enzyme lost around 50% of the initial enzymatic activity in the aqueous solution. At 50°C the hydrogenase was more stable in aqueous medium, because of the changes that occur with the temperature in the organic phase—precipitation of surfactant and solvent evaporation. It was found that only micellar solutions of this enzyme can be repeatedly used, since the hydrogenase is inactivated after the first cycle of oxireduction in aqueous medium. The effect of glycerol and the electron carrier methylviologen as stabilizers of hydrogenase activity was also investigated. The results are interpreted on the grounds of hydrogenase and surfactant electrostatic properties.