Occupational Exposure to Solar UVB and Seasonal Monitoring of Serum Levels of 25-hydroxy Vitamin D3: A Case–Control Study

To characterize the relationship between occupational sun exposure and seasonal variations in serum 25-OH-D3, four consecutive measurements of 25-OH-D3, one per season, were taken in 122 outdoor and 104 indoor Israeli workers. Continuous UVB measurements, taken in Beer Sheva, Israel, provided the average daily standard erythema dose (SED) of ambient solar UVB. The average daily exposure of the outdoor and indoor workers to solar UVB was 4.4 ± 1.6 h (4.0–37.6 SED) and 0.9 ± 0.5 h (0.6–8.2 SED), respectively. At each season mean 25-OH-D3 were significantly higher among outdoor workers than among indoor workers. Mean 25-OH-D3 increased significantly from spring to autumn in both gender and occupational groups. Adjusting for confounders, high (>median) 25-OH-D3 among males was significantly associated with occupational sun exposure in the autumn (odds ratio [OR] 4.31; 95% confidence interval [CI] 1.4–13.3), and among females in the spring (OR 3.35; 95% CI 1.53–7.32). Among this working population optimal vitamin D status (≥30 ng mL⁻¹) was approached only in summer by males working either outdoor or indoor. In the rest of the year 25-OH-D3 ranged between ≥20.0 and 29.0 ng mL⁻¹. Monitoring 25-OH-D3 may disclose undesirable vitamin D status following reduced sun exposure for skin cancer prevention among outdoor workers.     

Finite difference approximation of a nonlinear integro-differential system

Finite difference approximation of the nonlinear integro-differential system associated with the penetration of a magnetic field into a substance is studied. The convergence of the finite difference scheme is proved. The rate of convergence of the discrete scheme is given. The decay of the numerical solution is compared with the analytical results proven earlier.     

Optimization and method validation of determining polyphenolic compounds by UFLC-DAD system using two biphenyl and pentafluorophenylpropyl columns

The development of efficient analytical methods for the identification and quantification of polyphenols in natural products is needed. The present study was aimed to optimize the polyphenols by UFLC using two different Ascentis express columns. Chromatographic separation was performed using UFLC-DAD connected with Ascentis Express Biphenyl column (system I) and Ascentis Express F5 pentafluorophenylpropyl (PFP) column (system II). Multistep gradient elution program was used in both analytical instruments to detect 34 compounds of different classes (phenolic acids, flavonoids, isoflavones, flavanols, flavonols and flavanones). The detection wavelength, linear calibration range, theoretical plate, tailing factor, limits of detection and of quantification were determined. The results were validated and the optimized method was proven to be precise, revealing good separation in the UFLC system II using Ascentis Express F5 PFP column. In conclusion, this study shows analytical preciseness and is useful in determining polyphenols in natural products.     

Building analytical three-field cosmological models

A difficult task to deal with is the analytical treatment of models composed of three real scalar fields, as their equations of motion are in general coupled and hard to integrate. In order to overcome this problem we introduce a methodology to construct three-field models based on the so-called “extension method”. The fundamental idea of the procedure is to combine three one-field systems in a non-trivial way, to construct an effective three scalar field model. An interesting scenario where the method can be implemented is with inflationary models, where the Einstein–Hilbert Lagrangian is coupled with the scalar field Lagrangian. We exemplify how a new model constructed from our method can lead to non-trivial behaviors for cosmological parameters.     

Allocation of Control Points in Stochastic Dynamic-Programming Models

The question of allocation of control points in stochastic dynamic-programming models from different areas is considered. A widely used approach is to choose equal time intervals between successive control points. Conditions under which this choice may cease to be optimal are discussed. Two different approaches to statement and solution of a production-control problem are presented.     

On the inertia of the Lyapunov transform AH+HA* for H >0

Given an arbitrary n×n matrix A with complex entries, we characterize all inertia triples (abc) that are attained by the Lyapunov transform AH+ HA^*, as H varies over the set of all n× n positive definite matrices.     

Some Aspects of the Distributional Properties of the Expected Value of Perfect Information (EVPI)

In this paper we examine the Expected Value of Perfect Information (EVPI), with respect to the underlying probability distribution. By the method of optimal control theory we show that for any given second and third moments the underlying distribution that maximizes the EVPI is a 2-spike distribution. We find that shifting the distribution mean from zero will decrease the associated EVPI. The EVPI is further analyzed when the underlying distribution is symmetric, centred at zero.     

One-dimensional perturbations of cyclic operators

It is shown that for a cyclic operator on a finite dimensional Hilbert space, arbitrary spectrum is obtainable by means of a one-dimensional perturbation.     

Manganese(III) biliverdin IX dimethyl ester: a powerful catalytic scavenger of superoxide employing the Mn(III)/Mn(IV) redox couple

A manganese(III) complex of biliverdin IX dimethyl ester, (MnIIIBVDME)2, was prepared and characterized by elemental analysis, UV/vis spectroscopy, cyclic voltammetry, chronocoulometry, electrospray mass spectrometry, freezing-point depression, magnetic susceptibility, and catalytic dismuting of superoxide anion (O2.-). In a dimeric conformation each trivalent manganese is bound to four pyrrolic nitrogens of one biliverdin dimethyl ester molecule and to the enolic oxygen of another molecule. This type of coordination stabilizes the +4 metal oxidation state, whereby the +3/+4 redox cycling of the manganese in aqueous medium was found to be at E1/2 = +0.45 V vs NHE. This potential allows the Mn(III)/Mn(IV) couple to efficiently catalyze the dismutation of O2.- with the catalytic rate constant of kcat = 5.0 x 10(7) M-1 s-1 (concentration calculated per manganese) obtained by cytochrome c assay at pH 7.8 and 25 degrees C. The fifth coordination site of the manganese is occupied by an enolic oxygen, which precludes binding of NO., thus enhancing the specificity of the metal center toward O2.-. For the same reason the (MnIIIBVDME)2 is resistant to attack by H2O2. The compound also proved to be an efficient SOD mimic in vivo, facilitating the aerobic growth of SOD-deficient Escherichia coli.