Radioresistance studies in Methylobacterium spp.

Methylobacterium extorquen was isolated and was found as one of the most resistant microorganisms in the original bioburden of ophthalmic cotton dressings to be submitted to γ radiation sterilization. Radiation survival curves were simultaneously performed in phosphate buffer and in test-pieces on two isolates, one obtained before irradiation (wild strain) and the other after irradiation at 20 kGy (rad strain), as well as on three type strains of Methylobacterium spp. (M. extorquens^T, M. radiotolerans^T and M. fujisawaense^T). The radiation resistance was compared using D_values. To analyze the effect of non linearity on radioresistance other measures were applied, such as intercept point, fraction of surviving cells at a selected dose and area. The ranking of strains with these approaches showed to be different, pointing out the need of an integrated measure of radioresistance. Therefore, an index of relative survival (IRS) is proposed.     

A study of amino-protecting groups using the polarizable continuum model (PCM)

In order to better understand the performance of 1,2-dimethyl-5-acetyl barbituric acid (DMB) as an amino protecting group relative to 5,5-dimethylcyclohexane-1,3-dione (DMD), ab initio calculations were performed. pK_a calculations using the PCM model indicated that both molecules are more acidic in the enol form. Therefore, the protecting reaction of these molecules should involve the anions formed from the loss of a proton from the enol compounds. Contrary to what would be expected, the larger efficiency exhibited by the DMB molecule cannot be attributed to an extension of the electronic conjugation effect. In the absence of any other noticeable effect that could be responsible for the greater efficiency of the DMB molecule, we are inclined to believe that the difference could be accounted for by the presence of two independent centers of conjugation.This paper is dedicated to Jacopo Tomasi in recognition of his outstanding contribution to the field of computational chemistry in solution. The authors are honored to contribute to this volume; especially so for two of them (COS and MACN) who have the privilege of his friendship.Acknowledgements The authors would like to thank the Brazilian research agencies CNPq, CAPES and FAPERJ for the financial support. C. O. da Silva thanks the Dipartimento di Chimica e Chimica Industriale, University of Pisa, where the MCSCF calculations were performed.     

Scalar-valued dominated polynomials on Banach spaces

It is well known that 2-homogeneous polynomials on -spaces are 2-dominated. Motivated by the fact that related coincidence results are possible only for polynomials defined on symmetrically regular spaces, we investigate the situation in several classes of symmetrically regular spaces. We prove a number of non-coincidence results which makes us suspect that there is no infinite dimensional Banach space such that every scalar-valued homogeneous polynomial on is -dominated for every .

     

Theoretical and experimental analysis of ammonia ionic clusters produced by 252Cf fragment impact on an NH3 ice target

Positive and negatively charged ammonia clusters produced by the impact of (252)Cf fission fragments (FF) on an NH(3) ice target have been examined theoretical and experimentally. The ammonia clusters generated by (252)Cf FF show an exponential dependence of the cluster population on its mass, and the desorption yields for the positive (NH(3))(n)NH(4)(+) clusters are 1 order of magnitude higher than those for the negative (NH(3))(n)NH(2)(-) clusters. The experimental population analysis of (NH(3))(n)NH(4)(+) (n = 0-18) and (NH(3))(n)NH(2)(-) (n = 0-8) cluster series show a special stability at n = 4 and 16 and n = 2, 4, and 6, respectively. DFT/B3LYP calculations of the (NH(3))(0)(-)(8)NH(4)(+) clusters show that the structures of the more stable conformers follow a clear pattern: each additional NH(3) group makes a new hydrogen bond with one of the hydrogen atoms of an NH(3) unit already bound to the NH(4)(+) core. For the (NH(3))(0)(-)(8)NH(2)(-) clusters, the DFT/B3LYP calculations show that, within the calculation error, the more stable conformers follow a clear pattern for n = 1-6: each additional NH(3) group makes a new hydrogen bond to the NH(2)(-) core. For n = 7 and 8, the additional NH(3) groups bind to other NH(3) groups, probably because of the saturation of the NH(2)(-) core. Similar results were obtained at the MP2 level of calculation. A stability analysis was performed using the commonly defined stability function E(n)(-)(1) + E(n)(+1) - 2E(n), where E is the total energy of the cluster, including the zero point correction energy (E = E(t) + ZPE). The trend on the relative stability of the clusters presents an excellent agreement with the distribution of experimental cluster abundances. Moreover, the stability analysis predicts that the (NH(3))(4)NH(4)(+) and the even negative clusters [(NH(3))(n)NH(2)(-), n = 2, 4, and 6] should be the most stable ones, in perfect agreement with the experimental results.     

Analysis of signal fluctuations of Cortical Spreading Depression: Preliminary findings

In this work, we apply Detrended Fluctuation Analysis (DFA) to study the dynamics of electrical cortical activity in rats during the phenomenon of Cortical Spreading Depression (CSD), as well as the periods before and after this phenomenon. The characteristic of CSD is reduced electrical activity that occurs and spreads in the cerebral cortex after the application of electrical, chemical or mechanical stimulus. Our results show that the electrocorticogram signal shows long range temporal correlations and scaling behavior, except during the pre-CSD burst phase (significant increase of amplitude provoked by stimulus).     

Algebraic reflexivity of sets of bounded operators on vector valued Lipschitz functions

In this paper we establish algebraic reflexivity properties of subsets of bounded linear operators acting on spaces of vector valued Lipschitz functions. We also derive a representation for the generalized bi-circular projections on these spaces.     

A unified Pietsch domination theorem

In this paper we prove an abstract version of Pietsch's domination theorem which unify a number of known Pietsch-type domination theorems for classes of mappings that generalize the ideal of absolutely p-summing linear operators. A final result shows that Pietsch-type dominations are totally free from algebraic conditions, such as linearity, multilinearity, etc.     

Differential equations in Schatten classes of operators

We study a system of differential equations in Schatten classes of operators, ${\mathcal{C}_p(\mathcal{H})\,(1 \leq p < \infty}$ ), with ${\mathcal{H}}$ a separable complex Hilbert space. The systems considered are infinite dimensional generalizations of mathematical models of unsupervised learning. In this new setting, we address the usual questions of existence and uniqueness of solutions. Under some restrictions on the spectral properties of the initial conditions, we explicitly solve the system. We also discuss the long-term behavior of solutions.     

Requirements for Efficient Raman Amplification and Dispersion Compensation Using Microstructured Optical Fibers

Abstract

The design and performance of microstructured optical fibers (MOFs) for simultaneous dispersion compensation and Raman amplification is numerically investigated. We studied a lumped Raman amplifier designed to compensate the signal loss and dispersion introduced by a 100-km, 16-channel C-band WDM link. The impairments induced by the nonlinearities caused by the small mode area of the designed MOF are investigated and the analysis is extended to include non-ideal factors such as excess background losses, splice loss, and the geometry variations during the fabrication process. The results are discussed and compared to those obtained for conventional dispersion compensating fibers (DCFs).     

Evaluation of the concentration of chemical elements in suspended particulate matter inside a small bronze and iron foundry industry,using a streaker sampler and EDXRF

The aim of this study was to determine and evaluate the temporal profiles of the concentration of chemical elements in the suspended particulate matter present inside a small bronze and an iron foundry industry. To collect the samples, we used a streaker sampler that separates particles with aerodynamic diameters smaller than 10 µm (PM₁₀) in two fractions: fine (particles with aerodynamic diameters less than 2.5 µm; PM_2.5) and coarse (between 2.5 µm and less than 10 µm; PM_10–2.5). The collection of samples was taken every 20 min during a total time of 8 and 5 h of molding and casting of bronze and iron, respectively. The samples collected in the form of strips on a filter (fine fraction) and an impactor (coarse fraction) were analyzed by the energy dispersive X‐ray fluorescence technique. In the excitation, an X‐ray tube with Mo target and Zr filter was used, operated at 30 mA/30 kV. For detecting the characteristic of X‐rays, a semiconductor Si(Li) detector was used, coupled to a multi‐channel spectrometer, with a 300 s excitation/detection time. The results of the temporal profiles of chemical element concentrations in coarse and fine fractions were discussed and compared with the maximum levels set by the Brazilian and international environmental agencies. Copyright © 2013 John Wiley & Sons, Ltd.