An epimerasic activity on galactose induced by xylose inKluyveromyces sp

Production of galactose epimerase by anKluyveromyces sp. isolated from Kefir (dairy product) was investigated in batch culture. The microorganism was cultured in media with 1% galactose, 1% xylose, or 0.5% xylose plus 0.5% galactose, in Erlenmeyer flasks shaken at 200 rpm and maintained at 30°C. After 48 h, the biomass was harvested by centrifugation and permeated with 80% ethanol. Permeated cells were suspended in 0.1M sodium phosphate buffer pH 6.5. A part of this suspension was shaken for 17h at 140 rpm. The supernatant, free of cells, was separated. Partial characterization ofKluyveromyces sp. epimerase was carried out in the cellular suspension and the supernatant solution. Enzymatic activity, using galactose as substrate, was measured. The product of this reaction was measured by the use of glucose oxidase. The results indicated: (1) there was a strong effect of xylose on induction of epimerase activity; (2) the epimerase obtained was independent of the energetic cell activity; (3) the epimerase activity in whole cells was similar to the activity obtained from the supernatant; (4) epimerase showed a typical substrate-inhibition curve and dependence on magnesium; and (5) the best pH range was between 5.5 and 6.5 and the optimal temperature was 30°C.     

Rough Sets and the role of the monetary policy in financial stability (macroeconomic problem) and the prediction of insolvency in insurance sector (microeconomic problem)

This paper faces two questions related with financial stability. The first one is a macroeconomic problem in which we try to further investigate the role of monetary policy in explaining banking sector fragility and, ultimately, systemic banking crisis. It analyses a large sample of countries in the period 1981–1999. We find that the degree of central bank independence is one of the key variables to explain financial crisis. However, the effects of the degree of independence are not linear. Surprisingly, either a high degree of independence or a high degree of dependence are compatible with a situation of financial stability, while intermediate levels of independence are more likely associated with financial crisis. It seems that it is the uncertainty related with a non-clear allocation of monetary policy responsibilities that contributes to financial crisis episodes.     

Ds1(2536)+ decays and the structure of P-wave charmed strange mesons

We calculate the D s 1 (2536) + decays into D*K channels,including the decay D s 1 (2536) + → D + π-K + through a virtual D*0 in a constituent quark model.Widths and S/D amplitudes ratio are in agreement with the recent Belle and BABAR data,being the results sensitive to 1 P 1 and 3 P 1 mixture.     

Heat-diffusion maximal operators for Laguerre semigroups with negative parameters

We prove L^p boundedness for the maximal operator of the heat semigroup associated to the Laguerre functions, , when the parameter α is greater than -1. Namely, the maximal operator is of strong type (p,p) if p>1 and , when -1<α<0. If α?0 there is strong type for 1<p?∞. The behavior at the end points is studied in detail.     

Fission neutron spectrum averaged cross sections for threshold reactions on arsenic

Summary We have measured the cross sections, averaged over a ²³⁵U fission neutron spectrum, for the two high threshold reactions: ⁷⁵As(n,p)^75mGe and ⁷⁵As(n,2n)⁷⁴As. The measured averaged cross sections are 0.292±0.022 mb, referred to the 3.95±0.20 mb standard for the ²⁷Al(n,p)²⁷Mg averaged cross section, and 0.371±0.032 mb referred to the 111±3 mb standard for the ⁵⁸Ni(n,p)^58m+gCo averaged cross section, respectively. The measured averaged cross sections were also evaluated semi-empirically by numerically integrating experimental differential cross section data extracted for both reactions from the current literature. The calculations were performed for four different representations of the thermal-neutron-induced ²³⁵U fission neutron spectrum. The calculated cross sections, though depending on analytical representation of the flux, agree with the measured values within the estimated uncertainties.     

Stereoselective synthesis of (+)-boronolide

The delta-lactone boronolide (+)-1, a pharmacologically active, naturally occurring product, has been synthesized in enantiopure form with L-erythrulose as the chiral starting material. The key steps of the synthesis were a highly stereoselective aldol-reduction one-pot sequence, an indium-mediated diastereoselective aldehyde allylation, and a ring-closing metathesis.     

Excess enthalpies of binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol,and heptane at T = 298.15 K and 313.15 K

Experimental excess molar enthalpies of the ternary systems {dibutyl ether (DBE) + 1-butanol + heptane} and the corresponding binary systems at T = 298.15 K and T = 313.15 K at atmospheric pressure are reported. A quasi-isothermal flow calorimeter has been used to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data for the binary and ternary systems have been fitted using the Redlich–Kister equation, the NRTL and UNIQUAC models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.     

The crystal structure of a valinomycin•2Ca2+ complex and the multi-step solution equilibria in acetonitrile characterised by 1H NMR,UV–Vis,and mass spectrometry

Valinomycin is a well-known potassium-selective ion carrier, but the nature of its direct interaction with calcium ion, another biologically important cation, is also of considerable interest. We have determined the first crystal structure of a valinomycin–calcium complex, which crystallises exclusively as a 1:2 valinomycin:Ca²⁺ complex, [VCa₂(OTf)₂(H₂O)₂]²⁺ in the solid state (V = valinomycin, OTf = triflate). Along with the 1:2 complex, the solution phase 1:1 and 2:1 complexes have been characterised in acetonitrile by ¹H NMR and UV–Vis titration experiments. The molar absorptivity curves and binding equilibrium constants for these complexes have been determined by the global analysis of the UV–Vis titration data using the program SIVVU?.     

An interpolation theorem between one-sided Hardy spaces

In this paper we generalize an interpolation result due to J.-O. Strömberg and A. Torchinsky to the case of one-sided Hardy spaces. This generalization is important in the study of the weak type (1,1) for lateral strongly singular operators. We shall need an atomic decomposition in which for every atom there exists another atom supported contiguously at its right. In order to obtain this decomposition we have developed a rather simple technique to break up an atom into a sum of others atoms.