Pressure dependence of room-temperature structural properties of CaAl2Si2.

We investigated the pressure dependence of the crystal structure of CaAl2Si2 by means of ab initio calculations and room-temperature synchrotron x-ray powder diffraction. Ab initio calculations reproduce satisfactorily the experimentally observed pressure-dependent structural evolution up to 3 GPa where the title system remains in the trigonal [Formula: see text] phase. In the pressure range 3-8 GPa, pressure evolution of the calculated in-plane lattice parameters is steeper than the observed. Ab initio calculations predict a structural phase transition to a tetragonal phase ([Formula: see text] to I4/mmm) near 7.5 GPa for zero (or room) temperature. Temperature effects are included through calculation of vibrational properties (phonon spectra). These calculations confirm that both phases are either globally or locally stable (metastable) and allow for the construction of a P - T phase diagram for this system. However, our experiments show no sign of such a transition up to 12 GPa. Such a discrepancy can be explained if one considers the trigonal ([Formula: see text]) structure to be metastable above the critical pressure, but is separated from the predicted tetragonal (I4/mmm) structure by a relatively high energy barrier. The applied pressure alone may not be able to surpass the energy-barrier; rather a joint high-pressure and high-temperature (HPHT) treatment may lead to it. However, empirical verification of such a hypothetical transition may be hampered by the chemistry of CaAl2Si2 system which shows tendency to decompose peritectically into Ca2Al3Si4 and aluminum under HPHT treatment.

Escherichia coli strains from edema disease: O serogroups, and genes for Shiga toxin, enterotoxins, and F18 fimbriae.

The objectives of the research were to determine the presence of the gene sequences for Shiga Toxin 2e (Stx2e), enterotoxins (ST-I, ST-II and LT-I), and F18 fimbriae in 144 Escherichia coli strains isolated from pigs with edema disease; to assess the ability of stx2e(+) strains to produce Stx2e; and to determine the O serogroups of the E. coli strains. Presence of the genes was determined by polymerase chain reaction (PCR), production of Stx2e was assessed by cytotoxicity for Vero and Hela cells, O serogroups were identified by agglutination with specific antisera. Of the 144 strains tested, 99 were stx2e(+) by PCR, but only 45 of these were Stx2e(+) in the cell culture assays. Among the 99 stx2e(+) strains, PCR detected the genes for F18ab, ST-I, ST-II, LT-I in 76, 40, 31 and 16 strains, respectively. Forty-one of the 99 sxt2e(+) strains belonged to O group 139; the rest did not belong to the classical edema disease O serogroups. It is likely that the enterotoxins, whose genes were detected at high frequency, are responsible for diarrhea seem in pigs with edema disease in Brazil.

Colostoma - tecnica do suporte modificado. / Colostomy-modified support technic

Com o objetivo de facilitar o manuseio imediato do colostoma, os autores apresentam a tecnica do suporte subcutaneo da alca intestinal, utilizada num total de trinta pacientes.Apresenta as complicacoes precoces e tardias da tecnica, observando-se uma incidencia de oito precoces e duas tardias

Quando lesoes da boca significam cancer. / When mouth lesions mean cancer

A casuistica levantada, consta de 904 casos de lesoes de cavidade bucal e orofaringe, sendo 714 casos de lesoes ulceradas e, destes 91% tem como laudo anatomo-patologico CEC (Carcinoma Espinocelular). Outrossim, e dado importancia para comentarios sobre PAR (Pacientes de Alto Risco) e AAR (Areas de Alto Risco), confirmando certos dados da literatura com os nossos.Por fim, menciona-se a importancia da caracterizacao dos tres tipos de lesoes mais comumente encontradas neste sitio anatomico e a referida conduta diagnostica a ser tomada em consideracao