Collapse of Primordial Clouds

We present here studies of collapse of purely baryonic Population III objects with masses ranging from $10M_\odot$ to $10^6M_\odot$. A spherical Lagrangian hydrodynamic code has been written to study the formation and evolution of the primordial clouds, from the beginning of the recombination era ($z_{rec} \sim 1500$) until the redshift when the collapse occurs. All the relevant processes are included in the calculations, as well as, the expansion of the Universe. As initial condition we take different values for the Hubble constant and for the baryonic density parameter (considering however a purely baryonic Universe), as well as different density perturbation spectra, in order to see their influence on the behavior of the Population III objects evolution. We find, for example, that the first mass that collapses is $8.5\times10^4M_\odot$ for $h=1$, $\Omega=0.1$ and $\delta_i={\delta\rho / \rho}=(M / M_o)^{-1/3}(1+z_{rec})^{-1}$ with the mass scale $M_o=10^{15}M_\odot$. For $M_o=4\times10^{17}M_\odot$ we obtain $4.4\times10^{4}M_\odot$ for the first mass that collapses. The cooling-heating and photon drag processes have a key role in the collapse of the clouds and in their thermal history. Our results show, for example, that when we disregard the Compton cooling-heating, the collapse of the objects with masses $>8.5\times10^4M_\odot$ occurs earlier. On the other hand, disregarding the photon drag process, the collapse occurs at a higher redshift.Comment: 10 pages, MN plain TeX macros v1.6 file, 9 PS figures. Also available at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS" and then "ARTICLES"). MNRAS in pres

Collapse of Primordial Clouds II. The Role of Dark Matter

In this article we extend the study performed in our previous article on the collapse of primordial objects. We here analyze the behavior of the physical parameters for clouds ranging from $10^7M_\odot$ to $10^{15}M_\odot$. We studied the dynamical evolution of these clouds in two ways: purely baryonic clouds and clouds with non-baryonic dark matter included. We start the calculations at the beginning of the recombination era, following the evolution of the structure until the collapse (that we defined as the time when the density contrast of the baryonic matter is greater than $10^4$). We analyze the behavior of the several physical parameters of the clouds (as, e.g., the density contrast and the velocities of the baryonic matter and the dark matter) as a function of time and radial position in the cloud. In this study all physical processes that are relevant to the dynamical evolution of the primordial clouds, as for example photon-drag (due to the cosmic background radiation), hydrogen molecular production, besides the expansion of the Universe, are included in the calculations. In particular we find that the clouds, with dark matter, collapse at higher redshift when we compare the results with the purely baryonic models. As a general result we find that the distribution of the non-baryonic dark matter is more concentrated than the baryonic one. It is important to stress that we do not take into account the putative virialization of the non-baryonic dark matter, we just follow the time and spatial evolution of the cloud solving its hydrodynamical equations. We studied also the role of the cooling-heating processes in the purely baryonic clouds.Comment: 8 pages, MN plain TeX macros v1.6 file, 13 PS figures. Also available at http://www.iagusp.usp.br/~oswaldo (click "OPTIONS" and then "ARTICLES"). MNRAS in pres

Model Reduction on the Wnt Pathway Leads to Biological Adaptation

Complex systems are an unavoidable problem in the field of biology. One of the ways that scientists have tried to overcome this problem is by building mathematical models—manageable representations designed to look at specific physical phenomena. The Wnt Signaling Pathway is a complex system known to regulate cell-to-cell interactions, play a crucial role in Embryonic Development, and has been implicated in the study of cancer. Typically, the Wnt signal is observed through the behavior of a protein called beta-Catenin (β-Catenin). In 2003, Lee et al. built a model of the Wnt pathway which caused β-Catenin to increase over time. However, in 2010, Jensen et al. built a different model of the Wnt pathway which caused β-Catenin to oscillate over time. This project called for model reduction on the Jensen et al. model to identify the phenomenological parameter combinations that determined features of the Wnt oscillations. The method used to reduce the model is called the Manifold Boundary Approximation Method, which is a geometric, parameter-independent method of reducing the model one parameter at a time. Reduction of the model showed that there were 5 variables and 8 parameters which drove the oscillating behavior of the system. After comparing our results to the Lee et al. reduced model of the Wnt pathway done by student Dane Bjork, a minimal model was constructed which predicted a novel class behavior of the Wnt system: biological adaptation

A COMPARATIVE STUDY FOR PROPELLER BLADE DESIGN

This work presents a comparative study between two propeller design methods for aeronautical application, with emphasis on its main element, the blade. The first method is an empirical approach based on graphical distribution of design parameters of a propeller and consists on a sequence of steps which starts from defined value for parameters like flight speed, propeller RPM, etc; with a view to obtain others dimensional parameters (diameter, twisting angle, etc) for a propeller to be used on a general aviation aircraft, with the goal to achieve certain performance target. According to the author of this method, the design of a propeller should be seen more as an art rather than exact science. The second method is well known by the aeronautical industry and called “method or theory of blade element”. This theory consider a propeller blade as a twisted wing, for which the quantities of interest to be obtained are the aerodynamics reactions, lift and drag, which are a function of the airfoil characteristics (treated as aerodynamic coefficients, cl for lift and cd for drag) for each section along blades length, twist angle, Mach, etc. For obtaining the propeller value of interest, the number of blades must also be considered. As an application for the study it was used a tri-blade propeller which equips an airplane for general aviation, that can carry 4 occupants flying at 170 Knots. The first aim of this study was to compare the results provided by the empirical method against the BET (Blade Element Theory). A secondary objective was to extend the empirical method in the design of a propeller for use on a closed circuit wind tunnel, once verified the consistency of obtained results as aimed on the first part of this study. Although the results were favorable, showing that both methods provide similar results, the study showed that the empirical method is not valid for operating and constructive conditions set for conditions like the defined for this wind tunnel, once for this type of application, the design parameters extrapolates the minimum and maximum limits established in the empirical method, providing extremely inconsistent results

Germinação e comportamento das espécies Bagassa guianensis, Copaifera multijuga, Hymenaea courbaril, Dipteryx odorata e Tabebuia serratifolia, em Floresta plantada na Amazônia Oriental brasileira.

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Obtenção de plântulas de híbridos de dendezeiro por cultivo in vitro.

Este trabalho teve como objetivo aplicar técnicas de cultura de tecidos em diferentes híbridos de dendezeiro (Elaeis guineensis Jacq.) para a conversão in vitro de embriões zigóticos em plântulas para produção de mudasviáveis para serem disponibilizadas no Estado do Pará. O experimento foi realizado na Embrapa Amazônia Oriental, Belém-PA. A metodologia foi a aplicação de práticas assépticas de isolamento embrionário, cultura de embriões, conversão em plântulas e aclimatação destas. Dezessete híbridos foram submetidos a desinfestação e assepsia, com posterior inoculação nos meios de cultura MS, ½ MS, Y3 e ½ Y3. Os frascos inoculados foram dispostos em sala de cultivo sob fotoperíodo de 16 h luz dia-1, com intensidade luminosa de 25 μmol s-1 e temperatura de 25±3 °C. O delineamento experimental foi o inteiramente casualizado em fatorial 3 x 4. Após avaliação da germinação e crescimento dos embriões, quanto à oxidação os genótipos CN 470, nos tratamentos MS e 1/2 Y3 não apresentaram oxidação, e esta apresentou-se mais adequada para o desenvolvimento do comprimento de raiz. Quanto ao genótipo indicado para a conversão de embriões zigóticos de híbridos de dendezeiro em plântulas viáveis à aclimatização, em extrato de vermiculita e solução nutritiva, o CN 514 em meio Y3 foi o mais viável. Aos três meses foi possível a conversão de embriões de híbridos de dendezeiro até a formação de plântulas