The immune system and the impact of zinc during aging

The trace element zinc is essential for the immune system, and zinc deficiency affects multiple aspects of innate and adaptive immunity. There are remarkable parallels in the immunological changes during aging and zinc deficiency, including a reduction in the activity of the thymus and thymic hormones, a shift of the T helper cell balance toward T helper type 2 cells, decreased response to vaccination, and impaired functions of innate immune cells. Many studies confirm a decline of zinc levels with age. Most of these studies do not classify the majority of elderly as zinc deficient, but even marginal zinc deprivation can affect immune function. Consequently, oral zinc supplementation demonstrates the potential to improve immunity and efficiently downregulates chronic inflammatory responses in the elderly. These data indicate that a wide prevalence of marginal zinc deficiency in elderly people may contribute to immunosenescence

Magnetocaloric effect and magnetic properties of Tb0.9Sn0.1MnO3

The magnetocaloric effect in magnetic materials is of great interest nowadays. In this article we present an investigation about the magnetic properties near the magnetic transition in a polycrystalline sample of a manganite Tb0.9Sn0.1MnO3. Particularly, we are interested in describing the nature of the magnetic interactions and the magnetocaloric effect in this compound. The temperature dependence of the magnetization was measured to determine the characteristics of the magnetic transition and the magnetic entropy change was calculated from magnetization curves at different temperatures. The magnetic solid is paramagnetic at high temperatures. We observe a dominant antiferromagnetic interaction below T-n=38 K for low applied magnetic fields; the presence of Sn doping in this compound decreases the Neel temperature of the pure TbMnO3 system. A drastic increase in the magnetization as a function of temperature near the magnetic transition suggests a strong magnetocaloric effect. We found a large magnetic entropy change Delta S-M(T) of about -4 J/kg K at µ0H=3 T. We believe that the magnetic entropy change is associated with the magnetic transition and we interpret it as due to the coupling between the magnetic field and the spin ordering. This relatively large value and broad temperature interval (about 35 K) of the magnetocaloric effect make the present compound a promising candidate for magnetic refrigerators at low temperatures. (c) 2007 American Institute of Physics

Influence of branching density on the cross-linkability of ethylene-octene copolymers

Ethylene-octene copolymers (EOCs) with two different octene contents (20 and 35 wt%) and the same melt flow index (3 g per 10 min) were cross-linked using various levels (0.3, 0.5 and 0.7 wt%) of dicumyl peroxide at different temperatures. Cross-linking and degradation were analyzed by rubber process analyzer (RPA) within a temperature range of 150-200 °C. The highest s′ max (maximum elastic torque) and the lowest tan(delta) were found for EOC-20 with low-octene content at all cross-linking temperatures. Lower peroxide efficiency was observed in the case of the high-octene copolymer. Increased degradation was observed with increasing cross-linking temperature. High-octene EOC was found to be more vulnerable to degradation. According to dynamic mechanical analysis, the storage modulus (M′) and the glass transition temperature (T g) obtained from the tan(delta) peaks were found to decrease with increasing octene content. The differential scanning calorimetry (DSC) results show that the octene content has an inverse effect on the crystallinity (X) and melting point (T m) - due to the reduction in the average number of consecutive ethylene units. Creep testing at 150 °C confirmed the cross-linkability results obtained by RPA and the gel content analyses. Increased β-scission due to high numbers of tertiary carbon atoms present in the chain has resulted in the poorer cross-linking and inferior properties of high-octene EOC. © 2013 The Society of Polymer Science, Japan (SPSJ) All rights reserved