Fractal geometry of aggregate snowflakes revealed by triple wavelength radar measurements

Radar reflectivity measurements from three different wavelengths are used to retrieve information about the shape of aggregate snowflakes in deep stratiform ice clouds. Dual-wavelength ratios are calculated for different shape models and compared to observations at 3, 35 and 94 GHz. It is demonstrated that many scattering models, including spherical and spheroidal models, do not adequately describe the aggregate snowflakes that are observed. The observations are consistent with fractal aggregate geometries generated by a physically-based aggregation model. It is demonstrated that the fractal dimension of large aggregates can be inferred directly from the radar data. Fractal dimensions close to 2 are retrieved, consistent with previous theoretical models and in-situ observations.

Understanding the link between single cell and population scale responses of Escherichia coli in differing ligand gradients

We formulate an agent-based population model of Escherichia coli cells which incorporates a description of the chemotaxis signalling cascade at the single cell scale. The model is used to gain insight into the link between the signalling cascade dynamics and the overall population response to differing chemoattractant gradients. Firstly, we consider how the observed variation in total (phosphorylated and unphosphorylated) signalling protein concentration affects the ability of cells to accumulate in differing chemoattractant gradients. Results reveal that a variation in total cell protein concentration between cells may be a mechanism for the survival of cell colonies across a wide range of differing environments. We then study the response of cells in the presence of two different chemoattractants.In doing so we demonstrate that the population scale response depends not on the absolute concentration of each chemoattractant but on the sensitivity of the chemoreceptors to their respective concentrations. Our results show the clear link between single cell features and the overall environment in which cells reside.

Metallicity effects on the modified wind momentum of CSPN

Recent investigations on the central stars of planetary nebulae (CSPN) indicate that the masses based on model atmospheres can be much larger than the masses derived from theoretical mass-luminosity relations. Also, the dispersion in the relation between the modified wind momentum and the luminosity depends on the mass spread of the CSPN, and is larger than observed in massive hot stars. Since the wind characteristics probably depend on the metallicity, we analyze the effects on the modified wind momentum by considering the dispersion in this quantity caused by the stellar metallicity. Our CSPN masses are based on a relation between the core mass and the nebular abundances. We conclude that these masses agree with the known mass distribution both for CSPN and white dwarfs, and that the spread in the modified wind momentum can be explained by the observed metallicity variations.

Multi-agent simulation of sawmill yard operations

This paper reports the findings of using multi-agent based simulation model to evaluate the sawmill yard operations within a large privately owned sawmill in Sweden, Bergkvist Insjön AB in the current case. Conventional working routines within sawmill yard threaten the overall efficiency and thereby limit the profit margin of sawmill. Deploying dynamic work routines within the sawmill yard is not readily feasible in real time, so discrete event simulation model has been investigated to be able to report optimal work order depending on the situations. Preliminary investigations indicate that the results achieved by simulation model are promising. It is expected that the results achieved in the current case will support Bergkvist-Insjön AB in making optimal decisions by deploying efficient work order in sawmill yard.

A tecnologia de informação e o indivíduo: propondo um modelo de adoção de tecnologia para a inclusão digital

A presente pesquisa sugeriu um novo modelo de Adoção de Tecnologia com o foco na inclusão digital, levando em consideração três dimensões: o acesso à tecnologia, a capacitação para utilizá-la e a atitude do usuário em relação a ela. Foi proposto um modelo cúbico, onde o volume do cubo representaria a tendência à adoção de tecnologia de um determinado sujeito ou grupo. Foram criados, para tanto, um conjunto de quatro instrumentos de pesquisa, a saber, um questionário, duas lâminas relacionadas à capacitação e uma lâmina projetiva para o estudo da atitude. Como resultado, foi possível observar que o volume do cubo de adoção realmente aumenta quanto mais freqüente é a utilização de tecnologia. Apesar disso, houve uma inversão interessante em relação à atitude. Viu-se que ela tende a diminuir quando o usuário está sendo inserido numa determinada tecnologia, nova para ele.

Ascenção e queda do provimento de acesso gratuito à Internet no Brasil: o papel dos modelos de negócio

This research was commenced with the idea to promote an strategic evaluation of the sustentability of the free Internet access, analysing its process of value creation, its sources of revenue generation, its business models development as well as its capacity to generate adequated returns to the investors. It was concluded that the free Internet access is not dead. Indeed, what has occoured was a migration from a model completely based on delivering a single service, generally dependent of publicity sells revenues, to a hibrid based business model with different types of services and with revenues been generated from multiple sources. Nevertheless, not all players were capable to evolute their business models and survive, what occasioned a huge number of fails, mergers and acquisitions, resulting in a concentration all over the segment.

Análise e proposta de aprimoramento para a gestão da Sabina Escola Parque do Conhecimento

Este trabalho teve como objetivo principal buscar, por meio de benchmarking, um modelo mais apropriado de gestão para o equipamento público Sabina Escola Parque do Conhecimento – localizado na cidade de Santo André-São Paulo –, cuja finalidade é ser uma extensão lúdica e prática do ambiente escolar. Para isso, avaliaram-se os modelos de gestão aplicados em equipamentos públicos similares, isto é, que também fornecem serviços educacionais e ambientais inovadores. Os equipamentos públicos escolhidos para compor a análise foram: Museu Catavento, Plug Minas e Aquário Municipal de Santos, situados, respectivamente, nas cidades de São Paulo, Belo Horizonte e Santos. Para alcançar esse objetivo, recorreu-se a um estudo investigativo, que compreendeu pesquisa bibliográfica e documental, visitas técnicas, coleta de dados quantitativos sobre os equipamentos e suas respectivas localidades, bem como entrevistas com os gestores desses atrativos e com responsáveis por órgãos governamentais relacionados. A partir disso, e com auxílio da análise SWOT, foram elaboradas algumas propostas para melhorar a gestão da Sabina Escola Parque: implantar um modelo de gestão por resultados, implementar parcerias formalizadas por meio de contrato de gestão com entidade qualificada, como as Organizações Sociais, incrementar as receitas, melhorar a eficiência das despesas, dentre outras.

Brazilian competitiveness on international trade

In recent years, Brazil benefited from foreign trade expansion and its exports of goods grew by 16.5%. If this strong growth trend keeps up for the next years, today’s bottlenecks may have a negative impact on the competitiveness of the country’s products in the global market. This is especially critical for one of the main “green fuels” producers in a scenario where the demand for this energy source grows due to rising oil prices and environmental concerns. Based on a survey that collected data from 250 Brazilian exporters, this study focuses on the constraints that reduce the competitiveness of exports. This study differs from previous ones in that it considers the professionals directly involved with export activities and evaluates different aspects, including logistics, operations, taxes, legal, bureaucratic and informational ones. Results show that the most important constraints strongly affect costs and delivery reliability

Uma abordagem comportamental para inserção de robôs em ambientes culturais

In this work, we propose methodologies and computer tools to insert robots in cultural environments. The basic idea is to have a robot in a real context (a cultural space) that can represent an user connected to the system through Internet (visitor avatar in the real space) and that the robot also have its representation in a Mixed Reality space (robot avatar in the virtual space). In this way, robot and avatar are not simply real and virtual objects. They play a more important role in the scenery, interfering in the process and taking decisions. In order to have this service running, we developed a module composed by a robot, communication tools and ways to provide integration of these with the virtual environment. As welI we implemented a set of behaviors with the purpose of controlling the robot in the real space. We studied available software and hardware tools for the robotics platform used in the experiments, as welI we developed test routines to determine their potentialities. Finally, we studied the behavior-based control model, we planned and implemented alI the necessary behaviors for the robot integration to the real and virtual cultural spaces. Several experiments were conducted, in order to validate the developed methodologies and tools

Uma plataforma de integração de middleware para computação ubíqua

One of the current challenges of Ubiquitous Computing is the development of complex applications, those are more than simple alarms triggered by sensors or simple systems to configure the environment according to user preferences. Those applications are hard to develop since they are composed by services provided by different middleware and it is needed to know the peculiarities of each of them, mainly the communication and context models. This thesis presents OpenCOPI, a platform which integrates various services providers, including context provision middleware. It provides an unified ontology-based context model, as well as an environment that enable easy development of ubiquitous applications via the definition of semantic workflows that contains the abstract description of the application. Those semantic workflows are converted into concrete workflows, called execution plans. An execution plan consists of a workflow instance containing activities that are automated by a set of Web services. OpenCOPI supports the automatic Web service selection and composition, enabling the use of services provided by distinct middleware in an independent and transparent way. Moreover, this platform also supports execution adaptation in case of service failures, user mobility and degradation of services quality. The validation of OpenCOPI is performed through the development of case studies, specifically applications of the oil industry. In addition, this work evaluates the overhead introduced by OpenCOPI and compares it with the provided benefits, and the efficiency of OpenCOPI s selection and adaptation mechanism

The small x behavior of the gluon strucutre function from total cross-sections

Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q(2) is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small x gluon distribtuion function exhibits the power law xg(x, Q(2)) = h(Q(2))x(-epsilon). Assuming that the Q(2) scale is proportional to the dynamical gluon mass one, we show that the values of h(Q(2)) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales.

Desenvolvimento de uma proposta de educação sexual para adolescentes

O objetivo geral do presente estudo foi descrever a experiência de construção e aplicação de uma proposta pedagógica no campo da educação sexual, fundamentada em algumas premissas contidas na concepção de Paulo Freire, visando atender adolescentes de uma comunidade carente do interior paulista. A partir dos questionamentos iniciais levantados pelos jovens foram realizados quatro encontros focando questões sobre sexualidade, anatomia e fisiologia humana, métodos anticoncepcionais e DST/Aids. Com a realização desse trabalho, os jovens tiveram oportunidade de participar de um processo educativo que possibilitou, pelo resgate de suas próprias experiências e crenças, a reflexão sobre sua autonomia na vivência de uma sexualidade saudável, respeitando a si próprio e ao outro.

Rural-urban migration in D-dimensional lattices

The rural-urban migration phenomenon is analyzed by using an agent-based computational model. Agents are placed on lattices which dimensions varying from d = 2 up to d = 7. The localization of the agents in the lattice defines that their social neighborhood (rural or urban) is not related to their spatial distribution. The effect of the dimension of lattice is studied by analyzing the variation of the main parameters that characterizes the migratory process. The dynamics displays strong effects even for around one million of sites, in higher dimensions (d = 6, 7).

A comparative evaluation of open loop and closed loop drug administration strategies in the treatment of AIDS.

In recent years, many researchers in the field of biomedical sciences have made successful use of mathematical models to study, in a quantitative way, a multitude of phenomena such as those found in disease dynamics, control of physiological systems, optimization of drug therapy, economics of the preventive medicine and many other applications. The availability of good dynamic models have been providing means for simulation and design of novel control strategies in the context of biological events. This work concerns a particular model related to HIV infection dynamics which is used to allow a comparative evaluation of schemes for treatment of AIDS patients. The mathematical model adopted in this work was proposed by Nowak & Bangham, 1996 and describes the dynamics of viral concentration in terms of interaction with CD4 cells and the cytotoxic T lymphocytes, which are responsible for the defense of the organism. Two conceptually distinct techniques for drug therapy are analyzed: Open Loop Treatment, where a priori fixed dosage is prescribed and Closed Loop Treatment, where the doses are adjusted according to results obtained by laboratory analysis. Simulation results show that the Closed Loop Scheme can achieve improved quality of the treatment in terms of reduction in the viral load and quantity of administered drugs, but with the inconvenience related to the necessity of frequent and periodic laboratory analysis.

The small x behavior of the gluon structure function from total cross-sections

Within a QCD-based eikonal model with a dynamical infrared gluon mass scale we discuss how the small x behavior of the gluon distribution function at moderate Q 2 is directly related to the rise of total hadronic cross-sections. In this model the rise of total cross-sections is driven by gluon-gluon semihard scattering processes, where the behavior of the small x gluon distribution function exhibits the power law xg(x, Q 2) = h(Q 2)x( -∈). Assuming that the Q 2 scale is proportional to the dynamical gluon mass one, we show that the values of h(Q 2) obtained in this model are compatible with an earlier result based on a specific nonperturbative Pomeron model. We discuss the implications of this picture for the behavior of input valence-like gluon distributions at low resolution scales. © 2008 World Scientific Publishing Company.