Equilibrium spherically curved 2D Lennard-Jones systems

To learn about basic aspects of nano-scale spherical molecular shells during their formation, spherically curved two-dimensional N-particle Lennard-Jones systems are simulated, studying curvature evolution paths at zero-temperature. For many N-values (N<800) equilibrium configurations are traced as a function of the curvature radius R. Sharp jumps for tiny changes in R between trajectories with major differences in topological structure correspond to avalanche-like transitions. For a typical case, N=25, equilibrium configurations fall on smooth trajectories in state space which can be traced in the E-R plane. The trajectories show-up with local energy minima, from which growth in N at steady curvature can develop.Comment: 10 pages, 2 figures, to be published in Journal of Chemical Physic

Incidence and risk factors of open-angle glaucoma : the Rotterdam study

__Abstract__ Glaucoma is one of the poorest understood and defined eye diseases among those known since our era. Despite two millennia of writing about glaucoma, a straightforward and clear-cut definition is not available worldwide. In essence, glaucoma is an eye disease characterized by loss of retinal ganglion cells and their axons. Clinically, this loss becomes apparent by cupping, also called excavation, of the optic disc and concomitant visual field loss. There are many subgroups of glaucoma, separated by causes, genetics, or morphology, and within each group there may be tens of different glaucoma types. From the start, I would like to point out that this thesis focuses on primary open-angle glaucoma. This is glaucoma in which the persons have open angles in their anterior eye chamber, through which the intraocular fluid leaves the eye. Moreover, all causes of secondary glaucoma, such as inflammation, medication, and systemic disorders, should have been eliminated with a reasonable amount of certainty. Since open-angle glaucoma cases with pseudoexfoliation were not specifically excluded at baseline of the Rotterdam study, we prefer to refer to open-angle glaucoma instead of primary open-angle glaucoma although during follow-up, no pseudoexfoliation was observed

Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to $25$ mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a $3.43$ $\mu$m-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time $T_1=0.39\pm0.08$ ms and spin density $\sigma=0.14\pm0.01$ spins per nm$^2$. Our analysis shows that at temperatures $\leq500$ mK magnetic dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure

THE USE AS BIO-INDICATORS SPONGE Callispongia sp. HEAVY METALS CD METAL CONTAMINATION IN THE WATERS OF THE AMBON BAY

The deposition of heavy metals in Ambon Bay was investigated by using sponge species (Callispongia sp.) as bioindicator. Two different sampling schemes are discussed in this paper: a random sampling scheme with 8 sampling sites distributed over the whole territory of Ambon Bay. Unwashed, dried samples were totally the concentrations of metal elements were determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Heavy metal Cd. The median concentrations and statistical parameters of elements were discussed by comparing two sampling schemes. The results of both sampling schemes are compared with the results of other the location of the net. Different levels of the contamination valuated by the respective contamination factor (CF) of each element are obtained for both sampling schemes, while the local contamination&nbsp; identified like cadmium metallurgy and cement industry, oil refinery, mining industry, and transport have been the same for both sampling schemes. In addition, the natural sources, from the accumulation of these metals in sponge caused by metal-enriched soil, associated with activity in the land were pointed as another possibility of local factors

The increased susceptibility to hydrogen peroxide of the (post)-ischemic rat heart is associated with the magnitude of the low molecular weight iron pool

Recently we have shown that intracellular low molecular weight (LMW) iron increases during ischemia. It is hypothesized that this increase in LMW iron during ischemia underlies the reported hydrogen peroxide toxicity toward ischemic hearts. To investigate this hypothesis, rat hearts were subjected to 15 min of no-flow ischemia and reperfused with buffer saturated against 95% N2 and 5% CO2 (anoxic reperfusuion) for 7 min. Hearts were then swithched to buffer saturated against 95% O2 and 5% CO2 (reoxygenation) to assess functional recovery. The cardiac function recovered to 80 ± 7% of the preischemic value. When the anoxic reperfusion was applied in the presence of 10 μM hydrogen peroxide, functional recovery after reoxygenation was 47 ± 7%. Hearts that were perfused with deferoxamine before ischemia and then subjected to ischemia and anoxic reperfusion in the presence of 10 μM hydrogen peroxide recovered to 78 ± 8%. Immediate reoxygenation after ischemia led to only 45 ± 6% recovery of function. During ischemia, LMW iron increased from 49 ± 45 to 183 ± 45 pmol/mg protein (p < .05) and decreasedto 58 ± 38 pmol/mg protein (p < .05) during the subsequent anoxic perfusion. Rat hearts preloaded with deferoxamine showed a slightly higher LMW iron content than normal (85 ± 23 and 49 ± 45 pmol/mg protein, respectively; n.s.), which showed a small, nonsignificant increase up to 136 ± 42 pmol/mg protein after 15 min of ischemia. No significant changes were found in reduced and oxidized glutathione content and glutathione peroxidase or catalase activities under those conditions. Our results indicate that hydrogen peroxide toxicity is determined by the amount of catalytic iron in the LMW pool and not by a decrease in antioxidant defense capacity to hydrogen peroxide

Symbolic Semantics for Probabilistic Programs

We present a new symbolic execution semantics of probabilistic programs that include observe statements and sampling from continuous distributions. Building on Kozen’s seminal work, this symbolic semantics consists of a countable collection of measurable functions, along with a partition of the state space. We use the new semantics to provide a full correctness proof of symbolic execution for probabilistic programs. We also implement this semantics in the tool symProb, and illustrate its use on examples

Effective Use of Simulation Means in Collective Mission Simulation

Mission training and rehearsal are vital to successful operations. Advances in modeling and simulation (M&S) technology now allow for Collective Mission Simulation (CMS). The Royal Netherlands Armed Forces have exploited CMS through participation in a number of virtual exercises. The potential of collective mission simulation has been recognized and the requirement for a CMS capability was formalized. Such a capability is characterized by effective realism, interoperable systems across domains, and seamless information flow. Within the next few years the Royal Netherlands Armed Forces want to establish a validated, reusable, interoperable mission simulation environment that will support the distributed simulation of tactical and operational missions at varying degrees of security classification

Iron and the oxygen paradox in ischemic hearts

Reintroduction of oxygen into ischemic tissue causes the formation of reactive oxygen species among which the oxygen radicals. This contributes to the tissue injwy that becomes apparent upon reperfusion. The phenomenon is known as the oxygen paradox. It is known that iron enhances the toxicity of oxygen radicals and that iron is important in the pathology of reperfusion after ischemia. Although this had been shown extensively, it was left unexplained when and how the catalytic iron becomes available. The research described in this thesis addresses the interplay between reduced metabolites of oxygen, reactive oxygen species. and iron in the isolated rat heart. In chapter two it is shov.rn that superoxide dismutase, the enzyme that speeds up the conversion of superoxide to hydrogen peroxide, is not always beneficial in ischerrria/reperfusion experiments showing that this is not the primary toxic species. In chapter three it was shown in hearts from iron loaded rats the iron is localised mainly in the endothelial cells and pericytes. However, no relation was found between functional deterioration and morphological abberations. Chapter four describes a new method to determine the amount of catalytic iron in ischemic hearts. It was shown that ischemia causes a dramatic rise in the amount of catalytic iron and hence predisposes the hearts to oxygen damage. Indeed, in chapter five it was shown that after ischemia rat hearts are more susceptible to hydrogen peroxide through an iron dependent mechanism. This enhanced toxicity could not be induced by anoxic perfusion, in which the hearts were perfused with nitrogen saturated buffer. During anoxia the amount of catalytic iron did not increase suggesting that the accumulation of glycolytic metabolites is essential for ischemic iron release. Subsequently. in chapter six it was shown that interventions that limit the accumulation of reducing equivalents during ischemia, did indeed attenuate the release of iron during ischemia and caused an improved post ischemic recovery. These results of these studies lead to the conclusion that it is the reductive release of iron during ischemia that causes the toxicity of oxygen radicals upon reperfusion. Tne ferrous iron reacts with hydrogen peroxide to form the more toxic ox-ygen radicals that induce tissue injury