A cosmological model in Weyl-Cartan spacetime

We present a cosmological model for early stages of the universe on the basis of a Weyl-Cartan spacetime. In this model, torsion $T^{\alpha}$ and nonmetricity $Q_{\alpha \beta}$ are proportional to the vacuum polarization. Extending earlier work of one of us (RT), we discuss the behavior of the cosmic scale factor and the Weyl 1-form in detail. We show how our model fits into the more general framework of metric-affine gravity (MAG).Comment: 19 pages, 5 figures, typos corrected, uses IOP style fil

Epidemic dynamics in finite size scale-free networks

Many real networks present a bounded scale-free behavior with a connectivity cut-off due to physical constraints or a finite network size. We study epidemic dynamics in bounded scale-free networks with soft and hard connectivity cut-offs. The finite size effects introduced by the cut-off induce an epidemic threshold that approaches zero at increasing sizes. The induced epidemic threshold is very small even at a relatively small cut-off, showing that the neglection of connectivity fluctuations in bounded scale-free networks leads to a strong over-estimation of the epidemic threshold. We provide the expression for the infection prevalence and discuss its finite size corrections. The present work shows that the highly heterogeneous nature of scale-free networks does not allow the use of homogeneous approximations even for systems of a relatively small number of nodes.Comment: 4 pages, 2 eps figure

Self-organization of collaboration networks

We study collaboration networks in terms of evolving, self-organizing bipartite graph models. We propose a model of a growing network, which combines preferential edge attachment with the bipartite structure, generic for collaboration networks. The model depends exclusively on basic properties of the network, such as the total number of collaborators and acts of collaboration, the mean size of collaborations, etc. The simplest model defined within this framework already allows us to describe many of the main topological characteristics (degree distribution, clustering coefficient, etc.) of one-mode projections of several real collaboration networks, without parameter fitting. We explain the observed dependence of the local clustering on degree and the degree--degree correlations in terms of the ``aging'' of collaborators and their physical impossibility to participate in an unlimited number of collaborations.Comment: 10 pages, 8 figure

The effects of anthocyanin-rich Myrtaceae fruits peel powder on fibrosis-associated hepatocarcinogenesisin mice.

Fruits from Myrtaceae family, as jabuticaba (Myrciaria jaboticaba (Vell) O. Berg), jamelão (Syzygium cumini (L.) Skeels) and jambo (Syzygium malaccense), raise interest due to their high levels of anthocyanins, antioxidant compounds, and, thus, potential for chronic disease risk reduction¹. Therefore, the study evaluated whether the ingestion of jabuticaba, jamelão or jambo peel powder attenuates fibrosis-associated hepatocarcinogenesis. Neonatal female C3H/Hej mice were submitted to a diethylnitrosamine (DEN)/carbon tetrachloride (CCl4)-induced fibrosis-associated hepatocarcinogenesis model. Mice also received basal diet or basal diet containing 2% of jabuticaba, jamelão or jambo dehydrated peels for 10 weeks. HPLC analysis of dehydrated fruit peels revealed high levels of anthocyanins in jabuticaba (802.89±22.88 mg/100g), jamelão (575.95±9.42 mg/100g) and jambo (156.05±10.39 mg/100g). These fruits displayed different types of anthocyanins (Figures 1-3). Interestingly, only the ingestion of basal diet containing jamelão peel powder attenuated liver fibrosis compared to DEN/CCl4 (Figure 4). Mechanisms will be evaluated, as well as the effects of these fruits on the development of preneoplasic/neoplastic liver lesions.WTPC. 21 a 26 de abril

Diffusion-annihilation processes in complex networks

We present a detailed analytical study of the $A+A\to\emptyset$ diffusion-annihilation process in complex networks. By means of microscopic arguments, we derive a set of rate equations for the density of $A$ particles in vertices of a given degree, valid for any generic degree distribution, and which we solve for uncorrelated networks. For homogeneous networks (with bounded fluctuations), we recover the standard mean-field solution, i.e. a particle density decreasing as the inverse of time. For heterogeneous (scale-free networks) in the infinite network size limit, we obtain instead a density decreasing as a power-law, with an exponent depending on the degree distribution. We also analyze the role of finite size effects, showing that any finite scale-free network leads to the mean-field behavior, with a prefactor depending on the network size. We check our analytical predictions with extensive numerical simulations on homogeneous networks with Poisson degree distribution and scale-free networks with different degree exponents.Comment: 9 pages, 5 EPS figure

Diffusion-annihilation processes in complex networks

We present a detailed analytical study of the $A+A\to\emptyset$ diffusion-annihilation process in complex networks. By means of microscopic arguments, we derive a set of rate equations for the density of $A$ particles in vertices of a given degree, valid for any generic degree distribution, and which we solve for uncorrelated networks. For homogeneous networks (with bounded fluctuations), we recover the standard mean-field solution, i.e. a particle density decreasing as the inverse of time. For heterogeneous (scale-free networks) in the infinite network size limit, we obtain instead a density decreasing as a power-law, with an exponent depending on the degree distribution. We also analyze the role of finite size effects, showing that any finite scale-free network leads to the mean-field behavior, with a prefactor depending on the network size. We check our analytical predictions with extensive numerical simulations on homogeneous networks with Poisson degree distribution and scale-free networks with different degree exponents.Comment: 9 pages, 5 EPS figure

Produção de mudas de caramboleiras 'B-10' e 'Golden Star': II. Marcha de absorção e acúmulo de nutrientes.

A participação do Brasil no mercado externo de frutas tem aumentado consideravelmente e com potencial para crescer ainda mais. A constante ascensão dos dados de exportação brasileira é resultado da combinação de avanços tecnológicos do setor produtivo e de acesso a novos mercados consumidores. A caramboleira apresenta-se como uma excelente opção de cultivo de frutas exóticas, com grande potencial para atender ao mercado interno e às exportações. Assim, objetivou-se avaliar a marcha de absorção e de acúmulo de nutrientes em mudas de caramboleiras cultivadas em solução nutritiva. O experimento foi realizado em parcelas subdivididas, sendo utilizadas como parcela as duas cultivares de caramboleira (?B-10? e ?Golden Star?) e, como subparcelas, cinco épocas de coleta de plantas, realizadas aos 208; 233; 258; 283 e 308 dias após o transplantio para a solução nutritiva. O delineamento foi inteiramente casualizado, com três repetições. As mudas foram cultivadas em vasos (8L) com solução nutritiva (pH=5,5 ± 0,5), com aeração. O experimento iniciou-se em 24-08-2005. Nos diferentes órgãos das mudas (folhas, caule e raízes), determinaram-se a marcha de absorção, o acúmulo de nutrientes e os índices nutricionais. Não houve diferenças no acúmulo de nutrientes entre as mudas de caramboleira de ambas as cultivares, sendo a ordem decrescente dos nutrientes em cada muda de ?B-10?, no final do período experimental: N > K > Ca > Mg > S > P > Fe > Mn > B > Cu > Zn. Para a ?Golden Star?, a ordem foi: N > K > Ca > Mg > P > S > Fe > Mn > B > Cu > Zn. Para as duas cultivares, o acúmulo médio foi maior nas folhas > caule > raízes. O período de maior exigência para ?B-10? foi entre 208 ? 233 e, para ?Golden Star?, entre 233 ? 283 dias após o transplantio. As diferentes taxas de acumulação líquida dos nutrientes, nos diferentes órgãos da caramboleira, nem sempre acompanharam a taxa de acumulação de nutrientes do respectivo órgão. Production of star fruit ?B-10? and ?Golden Star? seedlings: II ? Absorption rate and acumulation of nutrients. Abstract ? Brazil?s participation in the external market of fruits has increased considerably with the potential to grow further. The constant rise of the Brazilian exportation data is the result of a combination of technological advances in the productive sector and access to new markets. The star fruit is presented as an excellent option for cultivation of exotic fruits, with great potential to attend the domestic market and exportation. Thus, the objective was to assess absorption rate and accumulation of nutrients in star fruit seedlings, grown in nutrient solution. The experiment was conducted in split plots being used as part of the two cultivars of star fruit (?B-10? and ?Golden Star?) and as subplots, five plant collecting periods, realized at 208, 233, 258, 283 and 308 days after transplanting to the nutrient solution. The experimental design was completely randomized with three replications. The seedlings were grown in pots (8L) with nutrient solution (pH = 5.5 ± 0.5) with aeration. The experiment started on 08.24.2005. In different plant organs (leaves, stems and roots), absorption rate, accumulation of nutrients and nutritional indices were determined. It did not have differences in the accumulation of nutrients in the star fruit seedlings for both cultivars, the decreasing order of the nutrients in each ?B-10?seedlings, in the end of the experimental period, was: N > K > Ca > Mg > S > P > Fe > Mn > B > Cu > Zn. For ?Golden Star? the decreasing order was: N > K > Ca > Mg > P > S > Fe > Mn > B > Cu > Zn. For the two cultivars, the average accumulation was bigger in leaves > stem > roots. The period of bigger requirement for ?B-10? was between 208 - 233 and, for ?Golden Star?, between 233 - 283 days after the transplantation. The different rates of nutrient liquid accumulation, in the different organs of star fruit trees, not always followed the nutrient accumulation rate of the respective organ

Produção de mudas de caramboleiras 'B-10' e 'Golden Star': I. Parâmetros biológicos.

O Brasil é um dos maiores produtores de carambola do mundo, entretanto há poucas informações científicas, especialmente estudos de nutrição mineral com mudas dessa frutífera. Objetivando contribuir com o conhecimento desse importante aspecto, desenvolveu-se estudo que permitisse avaliar o crescimento e o acúmulo de nutrientes em mudas de caramboleiras, cultivadas em solução nutritiva. O experimento foi realizado em parcelas subdivididas, sendo utilizadas como parcela as duas cultivares de caramboleira ('B-10' e 'Golden Star') e, como subparcelas, as cinco épocas de coleta de plantas, realizadas aos 208; 233; 258; 283 e 308 dias após o transplantio para a solução nutritiva. O delineamento foi inteiramente casualizado, com três repetições. As mudas foram cultivadas em vasos (8L) com solução nutritiva (pH=5,5 ± 0,5), com aeração. O experimento iniciou-se em 24-08-2005. Nos diferentes órgãos das mudas (folhas, caule e raízes), avaliaram-se o crescimento e o acúmulo de nutrientes, e os índices nutricionais. Não houve diferenças no crescimento e, em geral, no acúmulo da massa da matéria seca entre as duas cultivares. Houve acúmulo linear da massa da matéria seca das mudas de caramboleira com o tempo de cultivo, sendo maior nas folhas > caule > raízes. O período de maior acúmulo da massa de matéria seca e da taxa de crescimento relativo na planta inteira esteve compreendido entre 208 ? 233 e 233 258 dias após o transplantio para a 'B-10' e a 'Golden Star', respectivamente. Production of seedlings of star fruit 'B-10' and 'Golden Star': I biological parameters. Abstract ? Brazil is one of the greatest producer of star fruit in the world, however, there are few scientific information, especially studies of mineral nutrition with seedlings of this fruitful. In order to contribute with the knowledge of this important aspect, it was developed a study that allowed evaluating the growth and the accumulation of nutrients in seedlings of star fruits trees, cultivated in nutritional solution. The experiment was realize in split plot, with two cultivars ('B-10' and 'Golden Star') and as subplots, five collecting periods of plants, realized in 208, 233, 258, 283 and 308 days after the transplantation to nutritional solution, with 3 repetitions. The seedlings had been cultivated in pots (8L) with nutritional solution (pH=5.5 ± 0.5), with aeration. The experiment started on 08-24-2005. In the different parts of the seedlings (leaves, stem and roots), it was evaluated the growth and the accumulation of nutrients and nutritional ratios. It did not have differences in the growth and, in general, in the accumulation of the dry matter between the two cultivars. There was linear accumulation of the dry matter of the seedlings of star fruit trees with the cultivation period, it was bigger in leaves > stem > roots. The period of greater accumulation of dry matter and the tax of relative growth in the entire plant was between 208 - 233 and 233 - 258 days after the transplantation for 'B-10' and 'Golden Star' respectively

Class of correlated random networks with hidden variables

We study a class models of correlated random networks in which vertices are characterized by \textit{hidden variables} controlling the establishment of edges between pairs of vertices. We find analytical expressions for the main topological properties of these models as a function of the distribution of hidden variables and the probability of connecting vertices. The expressions obtained are checked by means of numerical simulations in a particular example. The general model is extended to describe a practical algorithm to generate random networks with an \textit{a priori} specified correlation structure. We also present an extension of the class, to map non-equilibrium growing networks to networks with hidden variables that represent the time at which each vertex was introduced in the system