X-ray powder diffraction of high-absorption materials at the XRD1 beamline off the best conditions: Application to (Gd,Nd)5Si4 compounds

Representative compounds of the new family of magnetic materials Gd5-xNdxSi4 were analyzed by X-ray diffraction at the XRD1 beamline at LNLS. To reduce X-ray absorption, thin layers of the powder samples were mounted outside the capillaries and measured in Debye-Scherrer geometry as usual. The X-ray diffraction analyses and the magnetometry results indicate that the behavior of the magnetic transition temperature as a function of Nd content may be directly related to the average of the four smallest interatomic distances between different rare earth sites of the majority phase of each compound. The quality and consistency of the results show that the XRD1 beamline is able to perform satisfactory X-ray diffraction experiments on high-absorption materials even off the best conditions.Comment: 12 pages, 3 figures, 3 table

DNA-psoralen: single-molecule experiments and first principles calculations

The authors measure the persistence and contour lengths of DNA-psoralen complexes, as a function of psoralen concentration, for intercalated and crosslinked complexes. In both cases, the persistence length monotonically increases until a certain critical concentration is reached, above which it abruptly decreases and remains approximately constant. The contour length of the complexes exhibits no such discontinuous behavior. By fitting the relative increase of the contour length to the neighbor exclusion model, we obtain the exclusion number and the intrinsic intercalating constant of the psoralen-DNA interaction. Ab initio calculations are employed in order to provide an atomistic picture of these experimental findings.Comment: 9 pages, 4 figures in re-print format 3 pages, 4 figures in the published versio

Economic crisis and the firms´ innovation process

The economic and financial crisis has brought firms, territories and countries before a set of restrictions to a greater or lesser extent, function as the conditioners of economic activity for several agents, also affecting their activities associated with the development of its innovation process. Innovation is a highly complex process, very contingent and onerously demanding. With innovation as a key source of high economic performance, it is important to understand to what extent the current economic crisis is to constrain the innovation of firms and thus, the process of wealth creation. The main objective of this paper is to show that the economic crisis has a different effect on firms, depending on the type of innovation strategies adopted. For this, we identify some relevant relations between the economic crisis and the critical factors of the innovation process, namely knowledge networks and context costs, special dimensions that we associate with the efficiency of institutional and relational capital. These objectives will be achieved using several statistical and econometric techniques, with information found in a database obtained through a business survey. Our main results show some interesting findings: first we find evidence that the most dynamic firms recognize less impact of the economic crisis. Second, we find empirical evidence that the knowledge networks can be taken as a resilient mechanism of firms to manage the negative impacts of the crisis. Finally, firms that recognize more importance to the reduction of context cost seems more resilient to economic crisis. We finish with some recommendations for regional policy.FC

Reduction and construction of Poisson quasi-Nijenhuis manifolds with background

We extend the Falceto-Zambon version of Marsden-Ratiu Poisson reduction to Poisson quasi-Nijenhuis structures with background on manifolds. We define gauge transformations of Poisson quasi-Nijenhuis structures with background, study some of their properties and show that they are compatible with reduction procedure. We use gauge transformations to construct Poisson quasi-Nijenhuis structures with background.Comment: to appear in IJGMM