Methanolysis of cerebrosides with boron trifluoride-methanol

A time study was carried out to determine conditions under which BF₃-methanol could be used reliably for methanolysis of cerebrosides. Results indicate that heating at 100 C in a sealed tube with 14% w/v BF₃-methanol for 60 min yields satisfactory cleavage of cerebrosides to fatty acid methyl esters without significant destruction of normal or hydroxy fatty acids.     

An agent-based multilayer architecture for bioinformatics grids

Due to the huge volume and complexity of biological data available today, a fundamental component of biomedical research is now in silico analysis. This includes modelling and simulation of biological systems and processes, as well as automated bioinformatics analysis of high-throughput data. The quest for bioinformatics resources (including databases, tools, and knowledge) becomes therefore of extreme importance. Bioinformatics itself is in rapid evolution and dedicated Grid cyberinfrastructures already offer easier access and sharing of resources. Furthermore, the concept of the Grid is progressively interleaving with those of Web Services, semantics, and software agents. Agent-based systems can play a key role in learning, planning, interaction, and coordination. Agents constitute also a natural paradigm to engineer simulations of complex systems like the molecular ones. We present here an agent-based, multilayer architecture for bioinformatics Grids. It is intended to support both the execution of complex in silico experiments and the simulation of biological systems. In the architecture a pivotal role is assigned to an "alive" semantic index of resources, which is also expected to facilitate users' awareness of the bioinformatics domain.     

Strain-Rate Sensitivity of a Pultruded E-Glass/Polyester Composite

Structural analysis of composite structures subjected to dynamic loads requires detailed knowledge of the mechanical behavior of component materials under high strain-rates. This paper presents the results of tests to investigate the tensile dynamic behavior of a pultruded E-glass/polyester composite used in a steel-less blast protection barrier. The described activity is part of the Security of Airport Structures research project, focusing on structural protection of airport infrastructures against disruptive action. Modified Hopkinson bars and hydropneumatic machine devices were used to conduct strain-rate controlled tensile failure tests on glass fiber-reinforced polymer specimens. The results are discussed and then implemented within a viscoplasticity constitutive model and a strain-rate-dependent failure criterion in order to simulate the exhibited mechanical behavior.     

On the construction of group block codes

We consider the construction of group block codes, i.e., subgroups of Gⁿ, the n-fold direct product of a group G. Two concepts are introduced that make this construction similar to that of codes over gf(2). The first concept is that of an indecomposable code. The second is that of a parity-check matrix. As a result, group block codes over a decomposable Abelian group of exponent d_m can be seen as block codes over the ring of residues modulo d_m, and their minimum Hamming distance can be easily determined. We also prove that, under certain technical conditions, (n, k) systematic group block codes over non-Abelian groups are asymptotically bad, in the sense that their minimum Hamming distance cannot exceed [n/k].     

Chain transfer activity of some activated allylic compounds

Summary Various olefins that are activated towards free radical addition and contain a homolytic leaving group in the allylic position are effective chain transfer agents in free radical polymerizations of methyl methacrylate and other monomers. These allylic compounds include bromides, phosphonates, stannanes, thioethers, sulfoxides, and sulfones. Allylic silanes and chlorides, however, do not posess significant chain transfer activity. Suitable activating substituents towards radical addition are phenyl, ethoxycarbonyl, cyano, and acetoxy. Several of the compounds have an advantage over thiols in that they do not contain sulfur.     

Atrial Fibrillation and Aortic Ectasia as Complications of Primary Aldosteronism: Focus on Pathophysiological Aspects

Primary aldosteronism (PA) is the most common cause of secondary hypertension. A growing body of evidence has suggested that, beyond its well-known effects on blood pressure and electrolyte balance, aldosterone excess can exert pro-inflammatory, pro-oxidant and pro-fibrotic effects on the kidney, blood vessels and heart, leading to potentially harmful pathophysiological consequences. In clinical studies, PA has been associated with an increased risk of cardiovascular, cerebrovascular, renal and metabolic complication compared to essential hypertension, including atrial fibrillation (AF) and aortic ectasia. An increased prevalence of AF in patients with PA has been demonstrated in several clinical studies. Aldosterone excess seems to be involved in the pathogenesis of AF by inducing cardiac structural and electrical remodeling that in turn predisposes to arrhythmogenicity. The association between PA and aortic ectasia is less established, but several studies have demonstrated an effect of aldosterone on aortic stiffness, vascular smooth muscle cells and media composition that, in turn, might lead to an increased risk of aortic dilation and dissection. In this review, we focus on the current evidence regarding the potential role of aldosterone excess in the pathogenesis of AF and aortic ectasia.     

Aqueous atmospheric chemistry: formation of 2,4-dinitrophenol upon nitration of 2-nitrophenol and 4-nitrophenol in solution

Field studies have shown that the powerful phytotoxic agent 2,4-dinitrophenol is very likely to form in the atmospheric aqueous phase upon nitration of 2-nitrophenol or 4-nitrophenol. However, until now, the nitration pathway and the relative importance of the two mononitrophenols as sources of 2,4-dinitrophenol were not known. The present study shows that 2,4-dinitrophenol formation from mononitrophenols can take place upon photolysis and photooxidation of nitrite/nitrous acid (NO2-/HONO) and that nitrogen dioxide plays a key role in the process. A possible pathway might be the reaction between light-excited mononitrophenols (both 2- and 4-isomers) and nitrogen dioxide, in the presence of oxygen. As an alternative, nitration might involve *NO3 + *NO2. Possible sources of nitrogen dioxide in the atmospheric aqueous phase are dissolution from the gas phase and oxidation of NO2-. In the latter case, however, it is necessary that NO2- oxidation is faster than the oxidation of mononitrophenols. This would happen, for instance, in the presence of hematite under irradiation. Radiation absorption and scattering by hematite would also inhibit the direct photolysis of nitrophenols. The formation rate and the yield of 2,4-dinitrophenol are slightly higher when starting from 2-nitrophenol than those from 4-nitrophenol, but they are compensated by the higher concentration of 4-nitrophenol in the atmospheric aqueous phase.     

Day-by-day maturation of the long-term expression of cocaine sensitization acquired before weaning in the rat.

This study aimed to identify the ontogenetic period during which long-term expression of behavioral sensitization to cocaine begins to emerge. Rat pups aged 4, 8, 12, or 16 days received a pretreatment of 4 daily injections of 15 mg/kg sc: cocaine paired with the test chamber for 45 min. Pups were then tested for sensitization in that context after abstinence intervals ranging from 2 to 10 days. On test days, pups were videotaped, and their behavior was scored later. Sensitization was detected after intervals of 2, 4, 5, or 9 days in pups aged 4–7, 8–11, 12–15, or 16–19 days during pretreatment, respectively. These results suggest that the mechanisms for long-term retention of sensitization mature incrementally in the rat, starting to emerge gradually after the 1st week of age, whereas those relevant to short-term retention and initiation of sensitization are present earlier. (PsycINFO Database Record (c) 2010 APA, all rights reserved)