Temperature effect on (2+1) experimental Kardar-Parisi-Zhang growth

We report on the effect of substrate temperature (T) on both local structure and long-wavelength fluctuations of polycrystalline CdTe thin films deposited on Si(001). A strong T-dependent mound evolution is observed and explained in terms of the energy barrier to inter-grain diffusion at grain boundaries, as corroborated by Monte Carlo simulations. This leads to transitions from uncorrelated growth to a crossover from random-to-correlated growth and transient anomalous scaling as T increases. Due to these finite-time effects, we were not able to determine the universality class of the system through the critical exponents. Nevertheless, we demonstrate that this can be circumvented by analyzing height, roughness and maximal height distributions, which allow us to prove that CdTe grows asymptotically according to the Kardar-Parisi-Zhang (KPZ) equation in a broad range of T. More important, one finds positive (negative) velocity excess in the growth at low (high) T, indicating that it is possible to control the KPZ non-linearity by adjusting the temperature.Comment: 6 pages, 5 figure

Differential Density Statistics of Galaxy Distribution and the Luminosity Function

This paper uses data obtained from the galaxy luminosity function (LF) to calculate two types of radial number densities statistics of the galaxy distribution as discussed in Ribeiro (2005), namely the differential density $\gamma$ and the integral differential density $\gamma^\ast$. By applying the theory advanced by Ribeiro and Stoeger (2003), which connects the relativistic cosmology number counts with the astronomically derived LF, the differential number counts $dN/dz$ are extracted from the LF and used to calculate both $\gamma$ and $\gamma^\ast$ with various cosmological distance definitions, namely the area distance, luminosity distance, galaxy area distance and redshift distance. LF data are taken from the CNOC2 galaxy redshift survey and $\gamma$ and $\gamma^\ast$ are calculated for two cosmological models: Einstein-de Sitter and an $\Omega_{m_0}=0.3$, $\Omega_{\Lambda_0}=0.7$ standard cosmology. The results confirm the strong dependency of both statistics on the distance definition, as predicted in Ribeiro (2005), as well as showing that plots of $\gamma$ and $\gamma^\ast$ against the luminosity and redshift distances indicate that the CNOC2 galaxy distribution follows a power law pattern for redshifts higher than 0.1. These findings bring support to Ribeiro's (2005) theoretical proposition that using different cosmological distance measures in statistical analyses of galaxy surveys can lead to significant ambiguity in drawing conclusions about the behavior of the observed large scale distribution of galaxies.Comment: LaTeX, 37 pages, 6 tables, 10 figures. Accepted for publication in "The Astrophysical Journal

Magnetization of undoped 2-leg S = 1/2 spin ladders in La4Sr10Cu24O41

Magnetization data of single crystalline La4Sr10Cu24O41 are presented. In this compound, doped spin chains and undoped spin ladders are realized. The magnetization, at low temperatures, is governed by the chain subsystem with a finite interchain coupling which leads to short range antiferromagnetic spin correlations. At higher temperatures, the response of the chains can be estimated in terms of a Curie-Weiss law. For the ladders, we apply the low-temperature approximation for a S=1/2 2-leg spin ladder by Troyer et al.Comment: 2 pages, 2 figure

Efeito da assepsia na germinação de sementes de Caatingueira-verdadeira.

Objetivou-se com este trabalho avaliar a influência da assepsia na germinação de sementes de catingueira-verdadeira (poincianella pyramidalis (Tu!.) L.P. Queiroz).Edição dos Resumos do V Workshop de Tecnologia e Fisiologia de Sementes e Mudas, Petrolina, dez. 2014

The Apparent Fractal Conjecture: Scaling Features in Standard Cosmologies

This paper presents an analysis of the smoothness problem in cosmology by focussing on the ambiguities originated in the simplifying hypotheses aimed at observationally verifying if the large-scale distribution of galaxies is homogeneous, and conjecturing that this distribution should follow a fractal pattern in perturbed standard cosmologies. This is due to a geometrical effect, appearing when certain types of average densities are calculated along the past light cone. The paper starts reviewing the argument concerning the possibility that the galaxy distribution follows such a scaling pattern, and the premises behind the assumption that the spatial homogeneity of standard cosmology can be observable. Next, it is argued that to discuss observable homogeneity one needs to make a clear distinction between local and average relativistic densities, and showing how the different distance definitions strongly affect them, leading the various average densities to display asymptotically opposite behaviours. Then the paper revisits Ribeiro's (1995: astro-ph/9910145) results, showing that in a fully relativistic treatment some observational average densities of the flat Friedmann model are not well defined at z ~ 0.1, implying that at this range average densities behave in a fundamentally different manner as compared to the linearity of the Hubble law, well valid for z < 1. This conclusion brings into question the widespread assumption that relativistic corrections can always be neglected at low z. It is also shown how some key features of fractal cosmologies can be found in the Friedmann models. In view of those findings, it is suggested that the so-called contradiction between the cosmological principle, and the galaxy distribution forming an unlimited fractal structure, may not exist.Comment: 30 pages, 2 figures, LaTeX. This paper is a follow-up to gr-qc/9909093. Accepted for publication in "General Relativity and Gravitation

Realization of Rectangular Artificial Spin Ice and Direct Observation of High Energy Topology

In this letter, we have constructed and experimentally investigated frustrated arrays of dipoles forming two-dimensional artificial spin ices with different lattice parameters (rectangular arrays with horizontal and vertical lattice spacings denoted by $a$ and $b$ respectively). Arrays with three different ratios $\gamma =a/b = \sqrt{2}$, $\sqrt{3}$ and $\sqrt{4}$ are studied. Theoretical calculations of low-energy demagnetized configurations for these same parameters are also presented. Experimental data for demagnetized samples confirm most of the theoretical results. However, the highest energy topology (doubly-charged monopoles) does not emerge in our theoretical model, while they are seen in experiments for large enough $\gamma$. Our results also insinuate that magnetic monopoles may be almost free in rectangular lattices with a critical ratio $\gamma = \gamma_{c} = \sqrt{3}$, supporting previous theoretical predictions

Silk fibroin-spider silk-like protein biomaterials for preventing microbial infections

Publicado em "Frontiers in Bioengineering and Biotechnology. Conference Abstract: 10th World Biomaterials Congress"Introduction: Microbial contamination of medical devices, such as sutures, are one of the major causes of hospital infections despite improvements in medical healthcare[1]. Thus, it is important to explore new biomaterials with antimicrobial properties in order to overcome microbial colonisation and biofilm formation. Spider silk has been considered an excellent biomaterial because of its toughness, strength and outstanding elasticity[2]. Also, through recombinant DNA technology, we can bioengineer and functionalize spider silk-based materials with antimicrobial peptides (AMP), thus evolving a new type of biomaterials[3]. Herein, the aim of this study was to develop silk-based fibers with antimicrobial properties by combining silk fibroin (SF) with recombinant spider silk proteins functionalized with AMP. Materials and Methods: Silk-based sutures were produced by combining spider silk chimeric proteins SSP (6mer and 6mer-HNP1) with different ratios of SF extracted from Bombyx mori through wet-spinning. The structure and topography of the sutures were characterized by scanning electron microscopy (SEM) and the tensile properties and knot strength of the sutures was assessed using an INSTRON 5540 Universal Machine. The formation of biofilm on the fibers was assessed and hemolytic effects of the materials were evaluated. Results and Discussion: Silk fibers containing spider silk 6mer or 6mer-HNP1 showed improved tensile behaviour when compared to silk fibers without SPP (Figure 1). The results suggest that the combination of spider silk chimeric proteins with SF increased the tensile stress of the fibers, when compared to those without spider silk chimeric proteins. No bacterial biofilm was observed on the fibers containing SSP functionalized with AMP, suggesting that the presence of the 6mer-HNP1 prevented the formation of biofilm. Conclusions: The outcomes suggest that silk-based fibers functionalized with AMP showed better mechanical properties when compared to silk fibers alone. The data also demonstrate the positive effect of the presence of AMP in preventing biofilm formation on the fibers, suggesting that the functionalized silk fibers could be used as a new strategy to produce sutures capable of preventing microbial proliferation, while retaining useful mechanical properties. Further investigation is still need in order to understand the in vivo performance of sutures and their physical changes during wound healing.Portuguese Foundation for Science and Technology under the scope of the project PTDC/BBB­BIO/0827/201

Curva de embebição de sementes Enterolobium contortisiliquum (Vell) Morong (FABACEAE).

Objetivou-se com este trabalho avaliar o padrão de embebição das sementes Enterolobium contortisiliquum submetida a diferentes concentrações polietilenoglicol.Edição dos Resumos do V Workshop de Tecnologia e Fisiologia de Sementes e Mudas, Petrolina, dez. 2014