Electronic and magnetic properties of Fe<Subscript>2</Subscript>SiC

The electronic structure and magnetic properties of Fe₂SiC compound have been studiedusing the framework of an all-electron full-potential linearized augmented-plane wave(FP-LAPW) method within the local density (LSDA) and + U corrected(LSDA + U)approximations. An antiferromagnetic spin ordering of Fe atoms is shown to be the groundstate for this compound. From the electronic band structures and density of states (DOS),Fe₂SiC has ametallic character and from the analysis of the site and momentum projected densities, itis deduced that the bonding is achieved through hybridization of Fe-3d with C-2p states andFe-3d withSi-3pstates. It is also pointed out that the Fe-C bonding is more covalent than Fe-Si. In theFM phase, the spin polarized calculations indicate that the total magnetic moment ofFe₂SiC increasesfrom 0.41 to 4.33μ _B when the Hubbard U parameter for iron isconsidered.     

Advances in new multicomponent crystal system: structure,thermal kinetic analysis,photoluminescent, and biological activity investigations

Journal of Thermal Analysis and Calorimetry - Multicomponent organic crystals based on natural metabolites or pharmaceutical active ingredients play an important role in solid state chemistry,...     

Coupled chaotic oscillators and their relation to a central pattern generator for artificial quadrupeds

Animal locomotion employs different periodic patterns known as animal gaits. In 1993, Collins and Stewart recognized that gaits possessed certain symmetries and characterized the gaits of quadrupeds and bipeds using permutation symmetry groups, which impose constraints on the locomotion center called the central pattern generator (CPG) in the animal brain. They modeled the CPG by coupling four nonlinear oscillators and found that it was possible to reproduce all symmetries of the gaits by changing the coupling strength. Here we propose to extend this idea using coupled chaotic oscillators synchronized using the Pyragas method in order to characterize the CPG symmetries. We also evaluate the time series behavior when the foot is in contact with the ground: this has potential robotic applications.     

A convenient route to chiral γ-lactones via asymmetric hydrogenation of γ-ketoesters using the RuCl3-BINAP-HCl catalytic system

A convenient one-step synthesis of chiral γ-lactones has been performed. The method is based on enantioselective hydrogenation of γ-ketoesters using the RuCl₃-BINAP-HCl catalytic system. Chiral γ-lactones (91-99% ee) have been isolated in 57-88% yield.     

Bioactive Secondary Metabolites from a New Terrestrial Streptomyces sp. TN262

During our search for Streptomyces spp. as new producers of bioactive secondary metabolites, the ethyl acetate extract of the new terrestrial Streptomyces isolate TN262 delivered eight antimicrobially active compounds. They were identified as 1-acetyl-β-carboline (1), tryptophol (2), cineromycin B (3), 2,3-dihydrocineromycin B (4), cyclo-(tyrosylprolyl) (5), 3-(hydroxyacetyl)-indole (6), brevianamide F (7), and cis-cyclo-(l-prolyl-l-leucyl) (8). Three further metabolites were detected in the unpolar fractions using GC–MS and tentatively assigned as benzophenone (9), N-butyl-benzenesulfonamide (10), and hexanedioic acid-bis-(2-ethylhexyl) ester (11). This last compound is known as plasticizer derivatives, but it has never been described from natural sources. In this article, we describe the identification of the new Streptomyces sp. isolate TN262 using its cultural characteristics, the nucleotide sequence of the corresponding 16S rRNA gene and the phylogenetic analysis, followed by optimization, large-scale fermentation, isolation of the bioactive constituents, and determination of their structures. The biological activity of compounds (2), (3), (4), and those of the unpolar fractions was addressed as well.     

Cathodic electrodeposition of mixed molybdenum tungsten oxides from peroxo-polymolybdotungstate solutions

Mixed molybdenum tungsten trioxide films of varying stoichiometry (MoxW1 - xO3, 0 < x < 1) were prepared by cathodic electrodeposition on indium tin oxide (ITO)-coated glass substrates from aqueous peroxo-polymolybdotungstate solutions. Electrochemical quartz crystal microbalance (EQCM), cyclic voltammetry, and chronocoulometry were used to gain insight into the electrodeposition mechanism. The compositional and structural properties were characterized for MoxW1 - xO3 films deposited at intermediate potentials (-0.35 V vs Ag/AgCl) and sintered at 250 degrees C using energy-dispersive spectroscopy, X-ray diffraction, and Raman spectroscopy. These studies reveal that films consist of homogeneously mixed MoxW1 - xO3, with an enriched Mo content ranging in composition from 0.4 < x < 0.7 depending upon the mol % Mo present in the deposition solution. Chronoamperometry and spectroelectrochemical measurements were conducted to estimate lithium ion diffusion coefficients and coloration efficiencies for the mixed metal oxide films in 1 M LiClO4/propylene carbonate. The subtle interplay between structural and compositional properties due to the uniform mixing of Mo and W oxide components shows that electrochromic and lithium ion transport properties are moderately enhanced relative to those of single-component WO3 and MoO3 and demonstrate improved structural stability over pure MoO3 polymorphs during electrochemical cycling.     

DNA fingerprinting of Vibrio cholerae and Aeromonas species by pulsed-field minigel electrophoresis

DNA molecules of Vibrio cholerae and Aeromonas species were prepared by incubating immobilized cells for 4 and 2 h, respectively, with a nonenzymatic solution that contains chemical reagents only (NDSUPlus). This method gave results as reproducible as the enzymatic one that uses proteinase K, and rendered DNA molecules suitable for fingerprinting by mini-CHEF electrophoresis. As rapid DNA separations at high electric field are achieved in mini-CHEF chamber with low heat evolution, DNA restriction fragments were separated in 5 h at 10 V/cm in a single resolution window. Then, fragment separations in three resolution windows were done in 15 h. This time is shorter than the one needed by the large CHEF chamber for resolving fragments in a single resolution window. Three windows permitted to include larger numbers of restriction fragments in the calculation of isolate similarities. Both sample preparation and mini-CHEF electrophoresis may represent an alternative for performing massive epidemiological studies of V. cholerae and Aeromonas species.     

Assessment of a pioneer metabolic information service in Brazil

The Information Service on Inborn Errors of Metabolism (SIEM), a pioneer toll-free service in both Brazil and South America, is based in Porto Alegre, Southern Brazil. SIEM has been operating since October 2001 providing support to health care professionals involved in the diagnosis and management of suspected metabolic diseases. We analyzed the demographic and clinical characteristics of the 376 consults received and followed in the first two and half years of SIEM. Our results show that the suspicion of a metabolic disease was most often associated with neurological symptoms. Among the consults, 24.4% were eventually confirmed as inborn errors of metabolism (IEM), with organic acidurias and amino acid disorders being the two most frequent diagnostic groups. Our conclusion shows this kind of service to provide helpful support to the diagnosis and acute management of IEM, especially to health professionals working in developing countries who are often far from reference centers.     

The modular systems biology approach to investigate the control of apoptosis in Alzheimer's disease neurodegeneration

Apoptosis is a programmed cell death that plays a critical role during the development of the nervous system and in many chronic neurodegenerative diseases, including Alzheimer's disease (AD). This pathology, characterized by a progressive degeneration of cholinergic function resulting in a remarkable cognitive decline, is the most common form of dementia with high social and economic impact. Current therapies of AD are only symptomatic, therefore the need to elucidate the mechanisms underlying the onset and progression of the disease is surely needed in order to develop effective pharmacological therapies. Because of its pivotal role in neuronal cell death, apoptosis has been considered one of the most appealing therapeutic targets, however, due to the complexity of the molecular mechanisms involving the various triggering events and the many signaling cascades leading to cell death, a comprehensive understanding of this process is still lacking. Modular systems biology is a very effective strategy in organizing information about complex biological processes and deriving modular and mathematical models that greatly simplify the identification of key steps of a given process. This review aims at describing the main steps underlying the strategy of modular systems biology and briefly summarizes how this approach has been successfully applied for cell cycle studies. Moreover, after giving an overview of the many molecular mechanisms underlying apoptosis in AD, we present both a modular and a molecular model of neuronal apoptosis that suggest new insights on neuroprotection for this disease.