Diameter Effect In Initiating Explosives, Numerical Simulations

The ability to safely machine small pieces of HE with the femtosecond laser [1][2][3] allows diameter effect experiments to be performed in initiating explosives in order to study the failure diameter, the reduction of the detonation velocity and curvature versus the diameter. The reduced diameter configuration needs to be optimized, so that the detonation products of the first cylinder will not affect the measurement of the detonation velocity of the second cylinder with a streak camera. Different 2D axi-symmetrical configurations have been calculated to identify the best solution using the Ignition and Growth reactive flow model for LX16 Pellet [4] with Ls-Dyna

Epididymal specific, selenium-independent GPX5 protects cells from oxidative stress-induced lipid peroxidation and DNA mutation

Can selenium (Se) independent, epididymal-specific glutathione peroxidase 5 (GPX5) protect CHO-K1 cells from oxidative damage and, more specifically, from lipid peroxidation and DNA mutation?CHO-K1 cells expressing GPX5 have increased resistance to oxidative challenge and, more specifically, decreased levels of lipid peroxidation and decreased levels of the downstream DNA lesion 8-oxo-7,8-dihydroguanine (8-oxodG) compared with control cells.GPX5 associates with sperm during transit of the epididymis, and has been postulated to protect sperm from peroxide-mediated attack. However, its function as an active glutathione peroxidase has been questioned due to substitution of the classical selenocysteine residue at its active site. Indirect evidence for a functional role for GPX5 has been provided by in vivo studies, in particular from the GPX5 knockout mouse whereby offspring sired by GPX5(/) males have a higher rate of spontaneous abortion and developmental defects, attributed to increased oxidative injury (8-oxodG) to sperm DNA, but only when the GPX5(/) males are over 1 year of age. Interestingly, we have previously shown severely reduced levels of GPX5 in humans.To look more directly at its role in protection against oxidative damage, we have used an in vitro system, generating a CHO-K1 mammalian cell line expressing recombinant rat GPX5.We have used the recombinant CHO-K1 cells to determine whether GPX5 is able to protect these cells from an administered oxidative challenge, using a range of approaches. We compared the viability of GPX5-expressing cells with control cells by both MTT and trypan blue exclusion assays. We next investigated whether GPX5 protects the cells specifically from lipid peroxidation, by using the fluorescent reporter molecule C11-BODIPY(581/591), and thus from downstream DNA mutation, by comparing levels of the DNA lesion 8-oxodG. We also investigated whether GPX5 can be transferred to rat sperm via epididymosomes.GPX5-expressing CHO-K1 cells had increased viability compared with control cells following oxidative challenge (P 0.005). We also found that GPX5-expressing CHO-K1 cells had significantly lower levels of C11-BODIPY(581/591) oxidation, and hence lipid peroxidation, compared with control cells. Levels of 8-oxodG DNA damage were also markedly lower in the nuclei of GPX5-expressing cells than in control cells. Finally, we showed that GPX5 can be transferred to rat sperm via epididymosomes.GPX5 is not active in glutathione peroxidase assays using H2O2 as the substrate. However, the related non-mammalian Se-independent GPXs show preference for electron donors other than glutathione, with a number utilizing thioredoxin as a reducing equivalent. Hence, the in vitro activity of GPX5 needs to be assessed using a range of alternative substrates and electron donors. GPX5 is secreted by the epididymis and associates with the sperm plasma membrane. We showed that this transfer can occur via epididymosomes; however, the mechanism for transfer and the identity of a potential binding partner in the sperm membrane needs to be determined. Finally, our study utilized an in vitro system that needs to be translated to human sperm.Our study supports an important role for GPX5 as an antioxidant, possibly acting as a phospholipid hydroperoxidase and participating in the maintenance of cell and DNA integrity.This project was funded in part by the BBSRC. The authors declare no conflict of interest.</p

Positive selection of an MHC class-I restricted TCR in the absence of classical MHC class I molecules

The H-2L(d) alloreactive 2C T cell receptor (TCR) is commonly considered as being positively selected on the H-2K(b) molecule. Surprisingly, 2C TCR(+) CD8(+) single-positive T cells emerge in massive numbers in fetal thymic organ culture originating from 2C transgenic, H-2K(b)D(b−/−) (2C(+)K(b)D(b−/−)) but not in fetal thymic organ culture from β(2)-microglobulin(−/−) 2C transgenic animals. Mature CD8(+) T cells are observed in newborn but not in adult 2C(+)K(b)D(b−/−) mice. These CD8(+) T cells express the α(4)β(7) integrin, which allows them to populate the intestine, a pattern of migration visualized by intrathymic injection of FITC and subsequent accrual of FITC-labeled lymphocytes in the gut. We conclude that the 2C TCR is reactive not only with H-2L(d) and H-2K(b), but also with nonclassical MHC class I products to enable positive selection of 2C(+) T cells in the fetal and newborn thymus and to support their maintenance in the intestine

An Investigation into intermittency

The results of an investigation based on ALEPH data,e + e − → hadrons at s√=91 GeV, into fluctuations in rapidity space are presented. It is found that the behaviour of the factorial moments is well represented by the Lund parton shower model. An estimate is made of the scale of fluctuations needed to describe the data. Differential moments are introduced and are used to demonstrate that within the average represented by the traditional factorial moments the pattern of fluctuations is itself a strong function of rapidity. This pattern is shown to be primarily associated with the emission of hard gluons. The implied structure between the hadron clusters and partons is explored by the use of transverse mass moments. It is concluded that the principal features of the one-dimensional factorial moments, differential moments and transverse mass moments have their origin in theO(α s ) matrix element, kinematic boundaries and the method of selection of the event axis