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The purpose of this survey is to examine the crystal packing of bent metallocenes, namely, group IV, V and VI biscyclopentadienyl dihalides and dihydrides, first synthesized in the late 1950s. This analysis is based on the present knowledge on new types of intermolecular contacts such as halogen and C–H⋯π interactions as well as dihydrogen bonds. Results are also supported by ab initio calculations that provide information on electrostatic charge distributions, in particular the effect of two V-shaped metal–halogen bonds on the molecular electron density distribution. Type I halogen interactions do not appear to be affected by this feature, specifically the geometric parameters and variation of atom polarizability, but the resultant electronic density distribution precludes the presence of Type II halogen bonds. Special attention is given to the competition among hydrogen and halogen interactions, in particular its influence on the nature and geometric orientations of the different supramolecular motifs and, ultimately, on the space groups observed for each crystal.

We discuss here a comprehensive solid state approach to the influence of diverse molecular functionalities present in a group of 1-ferrocenyl-2-(aryl)thioethanones [aryl = phenyl, 2-, 3-, and 4-chlorophenyl, 3- and 4-methoxyphenyl, 4-nitrophenyl, and 2-naphthyl] on their molecular structures, intermolecular contacts and subsequent supramolecular arrangements. Ab initio calculations provide electrostatic charge distributions and electron density isosurface maps to assist this analysis. Atomic point charges are used to evaluate the best acceptors and donors in the molecules. The absence of good hydrogen donors increases the influence of close packing factors on the crystal network for the majority of these compounds. However the characteristics of each substituent, like the donor–acceptor ability of the methoxy group, electronic anisotropy of chlorine or electronic resonance of the nitro group, also play important roles in the self-assembly processes. A systematic and detailed analysis is presented.

Two regioisomers, 3-ferrocenyl-6-methoxybenzo[b]thiophene (IV) and 3-ferrocenyl-4-methoxybenzo[b]thiophene (V), were isolated after an acid-catalysed intramolecular electrophilic cyclisation of 1-ferrocenyl-2-[3-(methoxyphenyl)thio]ethanone. This paper analyses the effect of the different positioning of the methoxy group in the benzothiophene ring on the molecular and crystal structures of both molecules. In isomer IV this group is more exposed to interactions with adjacent molecules than in V; thus, while in IV the COMe–H…OOMe intermolecular interactions determine the crystal packing, in V the overall assembly results from an interplay of the CCp–H…OOMe, CCp–H…S and CCp–H/π interactions. The supramolecular analysis provides an explanation for the spontaneous solid state separation of these regioisomers and their different physical properties, such as their melting points and their ability to interact with supports during chromatographic separations.

In the present paper it is described an analysis procedure suited for experiments where cross-sections strongly varying with energy are measured using beams having large energy dispersion. These cross-sections are typically the sub-barrier fusion excitation function of reactions induced by radioactive beams. The large beam energy dispersion, typical of these experiments, can lead to ambiguities in the association of the effective beam energy to the reaction product yields and consequently to an error in the determination of the excitation function. As a test case, the approach is applied to the experiments 6 Li+120 Sn and 7 Li+119 Sn measured in the energy range 14 MeV ≤ Ec.m. ≤28 MeV. The complete fusion cross sections are deduced from activation measurements using the stacked target technique. The results of these experiments, that employ the two weakly-bound stable Li isotopes, show that the complete fusion cross sections above the barrier are suppressed of about 70% and 85% with respect to the Universal Fusion Function, used as a standard reference, in the 6 Li and 7 Li induced reactions respectively. Moreover, the excitation functions of the two systems at energies below the barrier, do not show significant differences, despite the two systems have different n -transfer Qvalue .

Reaction between chromium and 2-trimethyl-silyl-3-methylphosphobenzene {C5PH3[Si (CH3)3](CH3)} vapours using metal vapour synthesis techniques produces an extremely air-sensitive yellow oil at room temperature; after sublimation and characterization by mass spectrometry and 1H and 31P NMR spectroscopy this oil proves to be a mixture of two isomers, which various techniques failed to separate. With the impossibility of obtaining crystal structures, we have used evidence from the NMR data that one of the isomers shows a long-distance P-P interaction, and extended Huckel calculations, to access the conformations of the two isomers. The calculations show that absolute minima occur for stereochemical reasons when both trimethylsilyl groups are pointing in opposite directions.

Nevirapine (11-cyclopropyl-5,11-dihydro-4-methyl-6H-dipyrido[3,2-b:2′,3′-e][1,4]diazepin-6-one, NVP) is a non-nucleoside HIV-1 reverse transcriptase inhibitor used to prevent mother-to-child transmission of the virus. However, severe hepatotoxicity and serious adverse cutaneous effects have raised concerns about the safety of NVP administration. NVP metabolism yields several phenol-type derivatives conceivably capable of undergoing further metabolic oxidation to electrophilic quinoid species that could react with bionucleophiles. The covalent adducts thus formed might be at the genesis of toxic responses. As an initial step to test this hypothesis, we synthesized the phenolic metabolite, 2-hydroxy-NVP, and investigated its oxidation in vitro. Using potassium nitrosodisulfonate and sodium periodate as model oxidants, we obtained evidence for fast generation of an electrophilic quinone-imine, which readily underwent hydrolytic conversion to fully characterized spiro derivatives, 1′-cyclopropyl-4-methyl-1H,1′H-spiro[pyridine-2,2′-pyrido[2,3-d]pyrimidine]-3,4′,6(3′H)-trione in aqueous media and 1′-cyclopropyl-4-methyl-1′H,2H-spiro[pyridine-3,2′-pyrido[2,3-d]pyrimidine]-2,4′,6(1H,3′H)-trione in non-aqueous media. The spiro compound generated in aqueous solution underwent subsequent hydrolytic degradation of the NVP ring system, whereas the one formed in non-aqueous media was stable to hydrolysis. The product profile observed with the chemical oxidants in aqueous solution was replicated using lactoperoxidase-mediated oxidation of 2-hydroxy-NVP. These observations suggest that metabolic activation of NVP, via Phase I oxidation to 2-hydroxy-NVP and subsequent generation of a quinone-imine, could occur in vivo and play a role in NVP-induced toxicity.

Foram caracterizadas e identificadas as frações proteicas constituintes do capim-mombaça submetido a quatro doses de nitrogênio (0, 100, 300 e 500kg.ha-1) em duas alturas de corte no período chuvoso e no seco. Utilizou-se delineamento experimental em blocos casualizados, em esquema fatorial 4 x 2, com quatro repetições. Os teores de proteína bruta (PB) e das frações A, B1, B2, B3 e C da proteína do capim-mombaça, cortado a 0,20 e 0,40m da superfície do solo foram avaliados pelo Cornell Net Carbohydrate and Protein System. Em relação ao teor de PB, ocorreu diferença significativa (P

The probability of recovering pathogenic Escherichia coli from food by the Bacteriological Analytical Manual method was determined by the effects of several factors: the number of strains per food, the ability of pathogenic strains to survive enrichment, and the frequency of plasmid loss during enrichment. Biochemical patterns indicated the presence of about six E. coli strains per food sample. About half of the strains isolated from humans did not survive enrichment. Among those which grew, plasmid loss, as determined by gel electrophoresis and DNA colony hybridization, ranged from 20 to 95%. The combined effects of failure to survive enrichment and plasmid loss decreased the relative numbers of these strains and reduced the chance of detecting pathogens. To counteract this tendency and obtain a 90 to 95% probability off recovering a given pathogenic strain, 40 to 50 colonies per food sample should be picked during the routine testing of foods.

Enteropathogenic Escherichia coli strains may produce a cholera-like, heat-labile enterotoxin (LT) as a virulence factor. The gene that codes for LT can be purified by recombinant DNA techniques and used as a genetic probe for DNA hybridization. These probes detect enterotoxigenic strains as well as strains that may not manifest toxin production but carry the genetic information to do so. In this study, 13 laboratories tested 3 known and 25 unknown (10 positive and 15 negative) cultures off. coli for the presence of the LT gene. The isolates had been tested and classified by the mouse Y-l adrenal cell test and an enzyme-linked immunosorbent assay. Cultures were spotted on nitrocellulose filters on MacConkey agar and incubated. Colonies were lysed in situ and their DNA was hybridized to 32P-labeled, purified LT gene DNA (provided to the collaborators). Positive colonies were identified by autoradiography. Of 325 samples, 315 (96.9%) were identified correctly and 10 were misclassified; there were 6 false negative and 4 false positive identifications. Chi-square values indicated that the method agreed with the previous classification and was equally efficient in distinguishing positive and negative samples (95.7 and 98.1%, respectively). The method has been adopted official first action.

Large quantities of Carbon Oxides (CO x ) Sulfide Oxides (SO x ) and Nitride Oxides (NO x ) are the main cause for acid rains, photochemical smog and Greenhouse effect. The plasma process within induced free energetic electrons discharge is one of the most effective methods of reducing SO x , NO x and CO2 from industrial flue gases. This paper for dissociation of a atmosphere pollutant gases by corona discharge. The reactor consists of two coaxial, specially designed cylindrical electrodes. An ac barrier corona discharge at atmospheric pressure is generated by application of high voltage to the inner electrode while the outer electrode is grounded. Discharge by products of air and NO x are measured by a mass spectrometer in order to investigate the effect of a surface multidipole magnetic fields on the corona discharge and on the pollutant gas reduction.