Vlasov simulation of laser-driven shock acceleration and ion turbulence

We present a Vlasov, i.e. a kinetic Eulerian simulation study of nonlinear collisionless ion-acoustic shocks and solitons excited by an intense laser interacting with an overdense plasma. The use of the Vlasov code avoids problems with low particle statistics and allows a validation of particle-in-cell results. A simple original correction to the splitting method for the numerical integration of the Vlasov equation has been implemented in order to ensure the charge conservation in the relativistic regime. We show that the ion distribution is affected by the development of a turbulence driven by the relativistic "fast" electron bunches generated at the laser-plasma interaction surface. This leads to the onset of ion reflection at the shock front in an initially cold plasma where only soliton solutions without ion reflection are expected to propagate. We give a simple analytic model to describe the onset of the turbulence as a nonlinear coupling of the ion density with the fast electron currents, taking the pulsed nature of the relativistic electron bunches into account

Horizontal and vertical growth of S. cerevisiae metabolic network

<p>Abstract</p> <p>Background</p> <p>The growth and development of a biological organism is reflected by its metabolic network, the evolution of which relies on the essential gene duplication mechanism. There are two current views about the evolution of metabolic networks. The retrograde model hypothesizes that a pathway evolves by recruiting novel enzymes in a direction opposite to the metabolic flow. The patchwork model is instead based on the assumption that the evolution is based on the exploitation of broad-specificity enzymes capable of catalysing a variety of metabolic reactions.</p> <p>Results</p> <p>We analysed a well-studied unicellular eukaryotic organism, <it>S. cerevisiae</it>, and studied the effect of the removal of paralogous gene products on its metabolic network. Our results, obtained using different paralog and network definitions, show that, after an initial period when gene duplication was indeed instrumental in expanding the metabolic space, the latter reached an equilibrium and subsequent gene duplications were used as a source of more specialized enzymes rather than as a source of novel reactions. We also show that the switch between the two evolutionary strategies in <it>S. cerevisiae </it>can be dated to about 350 million years ago.</p> <p>Conclusions</p> <p>Our data, obtained through a novel analysis methodology, strongly supports the hypothesis that the patchwork model better explains the more recent evolution of the <it>S. cerevisiae </it>metabolic network. Interestingly, the effects of a patchwork strategy acting before the Euascomycete-Hemiascomycete divergence are still detectable today.</p

Cardiovascular and hepatic toxicity of cocaine: potential beneficial effects of modulators of oxidative stress

Oxidative stress (OS) is thought to play an important role in the pharmacological and toxic effects of various drugs of abuse. Herein we review the literature on the mechanisms responsible for the cardiovascular and hepatic toxicity of cocaine with special focus on OS-related mechanisms. We also review the preclinical and clinical literature concerning the putative therapeutic effects of OS modulators (such as N-acetylcysteine, superoxide dismutase mimetics, nitroxides and nitrones, NADPH oxidase inhibitors, xanthine oxidase inhibitors, and mitochondriotropic antioxidants) for the treatment of cocaine toxicity. We conclude that available OS modulators do not appear to have clinical efficacy

Vlasov simulations of nonlinear wave dynamics and particle acceleration in laser-plasma interaction.

We have developed a numerical Vlasov code to study high intensity laser-plasma interaction. Our analysis began by focusing on the study of laser wakefield acceleration, a mechanism to generate high energy electrons.we concentrated our attention on the wavebreak in a thermal plasma, in order to inves- tigate the role of the velocity distribution in the dynamics of the accelerated particles. The detailed phase space representation provided by our code, have showed novel features directly related to the relativistic particle kinematics. Subsequently we focused on the collisionless dynamics of nonlinear electrostatic waves, such as shocks and solitons, and the related ion acceleration, in condition of interest for laboratory experiments. The energy spectrum of the ions accelerated by reflection at the shock front appears to be strongly dependent on the initial ion distribution. In a cold plasma the reflection is related to a turbulence in the ion density, whose origin is explained with a simple analytic model. By increasing the initial ion temperature, our simulations suggest the existence of an optimal temperature to obtain monoenergetic ion beams

Antioxidant activity of different cheese-honey combinations before and after in vitro gastrointestinal digestion

This study aimed to evaluate the effect of different cheese-honey combinations on antioxidant activity before and after in vitro gastrointestinal digestion, using the 2,2′-azino-bis-3-ethylbenzothiazoline- 6-sulfonic acid (ABTS), and ferric-reducing antioxidant power (FRAP) assays. Honey addition significantly enhanced the antioxidant activity of cheese samples (P &lt; 0.05). The antioxidant activity of in vitro digested samples was significantly lower than the undigested ones. However, digested cheese-honey combination showed a percentage decrease of antioxidant activity lower than plain cheese. The cheese and honey types affected the percentage decrease of antioxidant activity in the digested samples, this is mainly due to the bioaccessibility of the honey polyphenols after digestion. Sensory analysis showed that all cheese-honey combinations were well accepted by the consumers, the health information on higher antioxidant capacity of dark honeys has not influenced the degree of acceptability of consumers, who preferred the cheese - clear honey combination

Effect of species on the distribution and oxidative stability of milk added of lead and cadmium

The aim of this study was to evaluate the effect of species on added lead (Pb) and cadmium (Cd) content in cow, buffalo, and goat milk and their distribution in fat, casein, and whey fractions. In addition, the oxidative stability of the milk was evaluated. Most of the Pb and Cd were recovered in the skimmed milk (96.74 and 94.21%, respectively). The distribution of Cd and Pb in casein and whey fractions, obtained by enzymatic coagulation, highlighted that they were mainly associated with casein (on average 94.77 and 90.54% of Pb and Cd, respectively). The species significantly affected the distribution of Cd and Pb in the casein and fat fractions (p &lt; 0.01). In particular, Cd and Pb levels in fat fraction were the highest in the buffalo milk, whereas casein fraction was the highest in bovine milk. Furthermore, the presence of metals negatively influenced the oxidative stability of the milk and the species influenced its response. The results showed that in the presence of Cd and Pb, bovine milk increased the content of Malondialdehyde (MDA), advanced oxidation protein products (AOPP) and dithyrosines compared to other species. In addition, there was a significant decrease in the thiol content, highlighting a reduction in the antioxidant capacity of the contaminated milk

Minerals content in Basilicata region (southern Italy) honeys from areas with different anthropic impact

SummaryThe aim of this study was to examine the minerals content (toxic elements, macro‐elements and trace elements) of Basilicata region (southern Italy) honeys and compare the mineral profile of honeys classified as rural, industrial and urban according to anthropic characteristics of geographical origin. Overall, Ca, Na, Mg, Fe, Al, Zn and Mn were the most abundant elements detected in honeys, with average contents exceeding 1 ppm, whereas heavy metals content was lower than the maximum limit established for honey. Statistical analysis revealed significant differences (P < 0.05) among honeys as function of anthropic characteristics of geographical origin, with the exception for Se, Co and Ag content. Industrial honeys were characterised by the highest Zn, Cr, Sn, Cd and Pb content, urban honeys showed the highest As, Fe, Ni, Mn, Na, Mg and Ca content, whereas rural honeys showed the highest Cu, Al and Ba content (P < 0.05). The findings of this study highlighted that honeys mineral profile is closely related to different content of elements in environment, which is affected by anthropogenic activities