The rise of multiple births in Brazil

Aim: The aim of this study was to assess the rise in multiple births and its influence on trends of low birth weight (LBW) rates in Porto Alegre, Brazil. Methods: This is a registry-based study of live births from 1994 to 2005 obtained from the national live birth information system. Chi-square tests for trends were assessed for LBW and multiple birth rates. The impact of multiple births on LBW trends was assessed by sequential modelling, including year and further adjustment for multiple births. Risk factors for multiple births were assessed using the Poisson regression. Results: A total of 263 252 live births were studied. The LBW rate increased from 9.70% to 9.88% (p < 0.001) and the multiple birth rate rose from 1.95% to 2.53% (p < 0.001). LBW rate increased among twins, from 57.14% to 63.46% (p = 0.001). The twin birth rate rose by 24.7%, while the rate of triplets or higher-order increased by 150%. Multiple births may be responsible for 23.9% of the increase in the LBW rate over the period. Mothers with higher levels of schooling, older mothers and mothers delivering in private hospitals were more likely to deliver multiple births. Conclusions: It seems that both the increase in multiple births and in the LBW among multiple births contributed to this rise in overall LBW rate.

Effect of Multiple Cranial Burr Hole Surgery on Prevention of Recurrent Ischemic Attacks in Children with Moyamoya Disease

Moyamoya disease (MMD) is an uncommon cerebrovascular disorder characterized by progressive stenosis of the terminal portion of the internal carotid artery and its main branches. Direct and indirect bypass techniques have been devised with the aim of promoting neoangiogenesis. The current study aimed to investigate the role of multiple cranial burr hole (MCBH) operations in the prevention of cerebral ischemic attacks in children with MMD. Seven children suffering from progressive MMD were submitted to the MCBH and arachnoid opening technique. Ten to 20 burr holes were drilled in the fronto-temporo-parieto-occipital area of each hemisphere in each patient, depending on the site and extent of the disease. All patients were evaluated pre- and postoperatively by means of Barthel index (BI), CT, MR, angio-MR, and angiography. Patients had no recurrence of ischemic attacks postoperatively. Neoangiogenesis was observed in both hemispheres. One patient developed a persistent subdural collection after surgery, thus requiring placement of a subdural-peritoneal shunt. Postoperative BI was statistically significantly improved (P = 0.02). This report suggests that MCBH for revascularization in MMD is a simple procedure with a relatively low risk of complications and effective for preventing cerebral ischemic attacks in children. In addition, MCBH may be placed as an adjunct to other treatments for MMD.

Resonant Wave Interactions in the Equatorial Waveguide

Weakly nonlinear interactions among equatorial waves have been explored in this paper using the adiabatic version of the equatorial beta-plane primitive equations in isobaric coordinates. Assuming rigid lid vertical boundary conditions, the conditions imposed at the surface and at the top of the troposphere were expanded in a Taylor series around two isobaric surfaces in an approach similar to that used in the theory of surface-gravity waves in deep water and capillary-gravity waves. By adopting the asymptotic method of multiple time scales, the equatorial Rossby, mixed Rossby-gravity, inertio-gravity, and Kelvin waves, as well as their vertical structures, were obtained as leading-order solutions. These waves were shown to interact resonantly in a triad configuration at the O(epsilon) approximation. The resonant triads whose wave components satisfy a resonance condition for their vertical structures were found to have the most significant interactions, although this condition is not excluding, unlike the resonant conditions for the zonal wavenumbers and meridional modes. Thus, the analysis has focused on such resonant triads. In general, it was found that for these resonant triads satisfying the resonance condition in the vertical direction, the wave with the highest absolute frequency always acts as an energy source (or sink) for the remaining triad components, as usually occurs in several other physical problems in fluid dynamics. In addition, the zonally symmetric geostrophic modes act as catalyst modes for the energy exchanges between two dispersive waves in a resonant triad. The integration of the reduced asymptotic equations for a single resonant triad shows that, for the initial mode amplitudes characterizing realistic magnitudes of atmospheric flow perturbations, the modes in general exchange energy on low-frequency (intraseasonal and/or even longer) time scales, with the interaction period being dependent upon the initial mode amplitudes. Potential future applications of the present theory to the real atmosphere with the inclusion of diabatic forcing, dissipation, and a more realistic background state are also discussed.

Hydrodynamical simulations of Galactic fountains - II. Evolution of multiple fountains

The ejection of gas out of the disc in late-type galaxies is related to star formation and is mainly due to the explosion of Type II supernovae (SN II). In a previous paper, we considered the evolution of a single Galactic fountain, that is, a fountain powered by a single SN cluster. Using three-dimensional hydrodynamical simulations, we studied in detail the fountain flow and its dependence with several factors, such as the Galactic rotation, the distance to the Galactic centre and the presence of a hot gaseous halo. As a natural followup, this paper investigates the dynamical evolution of multiple generations of fountains generated by similar to 100 OB associations. We have considered the observed size-frequency distribution of young stellar clusters within the Galaxy in order to appropriately fuel the multiple fountains in our simulations. Most of the results of the previous paper have been confirmed, like for example the formation of intermediate velocity clouds above the disc by the multiple fountains. Also, this work confirms the localized nature of the fountain flows: the freshly ejected metals tend to fall back close to the same Galactocentric region where they are delivered. Therefore, the fountains do not change significantly the radial profile of the disc chemical abundance. The multiple fountain simulations also allowed us to consistently calculate the feedback of the star formation on the halo gas. We found that the hot gas gains about 10 per cent of all the SN II energy produced in the disc. Thus, the SN feedback more than compensate for the halo radiative losses and allow for a quasi steady-state disc-halo circulation to exist. Finally, we have also considered the possibility of mass infall from the intergalactic medium and its interaction with the clouds that are formed by the fountains. Though our simulations are not suitable to reproduce the slow rotational pattern that is typically observed in the haloes around the disc galaxies, they indicate that the presence of an external gas infall may help to slow down the rotation of the gas in the clouds and thus the amount of angular momentum that they transfer to the coronal gas, as previously suggested in the literature.

Plasmodium vivax: Microsatellite analysis of multiple-clone infections

We used mixtures of genomic DNA from two genetically distinct isolates from Brazil, 42M and 312M, to investigate how accurately 12-locus microsatellite typing describes the overall genetic diversity and characterizes multilocus haplotypes in multiple-clone Plasmodium vivax infections. We found varying PCR amplification efficiencies of microsatellite alleles; for example, from the same 1:1 mixture of 42M and 312M DNA we amplified predominantly 312M-type alleles at 10 loci and 42M-type alleles at 2 loci. All microsatellite alleles were accurately scored in 1:0.5 and 1:0.25 312M:42M DNA mixtures, even when minor peak heights did not meet previously suggested criteria for minor allele detection in multiple-clone infections. Relative proportions of major and minor alleles were unaffected by multiple displacement amplification of template DNA prior to PCR-based microsatellite typing. Although microsatellite typing may detect minor alleles in clone mixtures, amplification biases may lead to inaccurate assignment of predominant haplotypes in multiple-clone P. vivax infections. (C) 2008 Elsevier Inc. All rights reserved.

A new processing method of CaZn(2)(OH)(6)center dot 2H(2)O powders: Photoluminescence and growth mechanism

In this communication, we report on the formation of calcium hexahydroxodizincate dehydrate, CaZn(2)(OH)(6)center dot 2H(2)O (CZO) powders under microwave-hydrothermal (MH) conditions. These powders were analyzed by X-ray diffraction (XRD), Field-emission gum scanning electron microscopy (FEG-SEM), ultraviolet-visible (UV-vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns confirmed that the pure CZO phase was obtained after MH processing performed at 130 degrees C for 2 h. FEG-SEM micrographs indicated that the morphological modifications as well as the growth of CZO microparticles are governed by Ostwald-ripening and coalescence mechanisms. UV-vis spectra showed that this material have an indirect optical band gap. The pure CZO powders exhibited an yellow PL emission when excited by 350 nm wavelength at room temperature. (C) 2009 Elsevier Masson SAS. All rights reserved.

Tellurium tetrachloride: an improved method of preparation

An efficient and practical synthesis of tellurium tetrachloride from elemental tellurium and sulfuryl chloride is described. (C) 2008 Elsevier Ltd. All rights reserved.