Production and fate of the G ring arc particles due to Aegaeon (Saturn LIII)

The G ring arc hosts the smallest satellite of Saturn, Aegaeon, observed with a set of images sent by Cassini spacecraft. Along with Aegaeon, the arc particles are trapped in a 7:6 corotation eccentric resonance with the satellite Mimas. Due to this resonance, both Aegaeon and the arc material are confined to within sixty degrees of corotating longitudes. The arc particles are dust grains which can have their orbital motions severely disturbed by the solar radiation force. Our numerical simulations showed that Aegaeon is responsible for depleting the arc dust population by removing them through collisions. The solar radiation force hastens these collisions by removing most of the 10$~\mu$m sized grains in less than 40 years. Some debris released from Aegaeon's surface by meteoroid impacts can populate the arc. However, it would take 30,000 years for Aegaeon to supply the observed amount of arc material, and so it is unlikely that Aegaeon alone is the source of dust in the arc

An Improved molecular tool for distinguishing monoecious and dioedious Hydrilla

Two biotypes of hydrilla [Hydrilla verticillata(L.f.) Royle] occur in the United States, a dioecious type centered in the southeast and a monoecious type in the central Atlantic and northeastern states. Ecosystem managers need tools to distinguish the types as the ranges of each type expand and begin to overlap. A molecular tool using the randomly amplified polymorphic DNA (RAPD) procedure is available but its use is limited by a need for reference samples. We describe an alternative molecular tool which uses “universal primers” to sequence the trnL intron and trnL-F intergenic spacer of the chloroplast genome. This sequence yields three differences between the biotypes (two gaps and one single nucleotide polymorphism). A primer has been designed which ends in a gap that shows up only in the dioecious plant. A polymerase chain reaction (PCR) using this primer produces a product for the monoecious but not the dioecious plant

Teaching Laminar-flow reactors: From experimentation to CFD simulation

An integrated chemical engineering lab experiment is described in this paper. It makes use of a laminar-flow tubular reactor (LFTR) through consecutive lab sessions. In a first session (not described here), the pseudo first-order kinetic constant for the reaction between crystal violet and sodium hydroxide is determined at different temperatures in a batch reactor. Then a tracer experiment is used to characterize the flow, pattern in the LFTR, and finally the steady-state conversion of crystal violet in the reactor is measured. For computing the theoretical reactor conversion, students must use the previously collected kinetic and tracer data, in a concept-integration exercise. A computational fluid dynamics (CFD) code (Fluent) is also used to simulate both the tracer and the isothermal reaction experiments performed in the LFTR. A very good agreement is obtained between experimental and simulated results and both only differ slightly from the theoretical predictions. The use of the CFD program is particularly noteworthy. For instance, transient simulations allow a very nice visualization of the tracer concentration front evolution, while the steady-state profiles along the axial position provide a good perspective of how reactant concentration varies within the reactor

Comparative study of tributyltin toxicity on two bacteria of the genus Bacillus

Tributyltin is a potent biocide mainly used in marine antifouling paints. Owing to its widespread distribution in coast areas and its high toxicity to aquatic organisms, the use of this compound is generally restricted and under government regulation. Despite of that, it persists in the aquatic environment. Organotins used in industry have also been detected in terrestrial environments. The persistence and high lipophilicity explain bioaccumulation. The role of bacteria in recycling organic matter prompted us to study the interaction of tributyltin with two ubiquitous bacilli, B. stearothermophilus and B. subtilis, proposed as biological indicators of pollutants with ecological impact. These bacteria have been used as suitable models for the study of toxicity mechanisms of unselective lipophilic compounds (e.g., DDT and endosulfan). Drug effects on growth parameters, oxygen consumption and membrane organization were assessed. Bacteria growth in a liquid complex medium was disturbed by concentrations of TBT as low as 25 nM (8 [mu]g L-1), close to the concentration in polluted environments. The respiratory activity is affected by TBT in both microorganisms. Membrane organization, assessed by fluorescence polarization of two fluidity probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and a propionic acid derivative (DPH-PA), was also perturbed by the xenobiotic. Alterations on growth, oxygen consumption and physical properties of membrane lipids are stronger in B. stearothermophilus as compared to B. subtilis. A putative relationship between growth inhibition and respiratory activity impairment induced by TBT and its effects on the physical behaviour of bacterial membrane lipids is suggested.http://www.sciencedirect.com/science/article/B6TCP-4GSJR3R-9/1/18e0ee5c8ce4e887466d84b850ad8ec

Computation of a three-dimensional flow in a square microchannel: a comparison between a particle method and a finite volume method

Traditional grid-based numerical methods, such as finite volume method (FVM), are not suitable to simulate multiphase biofluids (such as blood) at the microscale level. Alternatively, meshfree Lagrangian methods can deal with two or more finely dispersed phases moving relatively to each other. The Moving Particle Semi-Implicit Method (MPS), used in this study, is a deterministic particle method based on a Lagrangian technique to simulate incompressible flows. The advantages of particle methods over traditional grid-based numerical methods have motivated several researchers to implement them into a wide range of studies in computational biomicrofluidics. The main aim of this paper is to evaluate the accuracy of the MPS method by comparing it with numerical simulations performed by an FVM. Hence, simulations of a Newtonian fluid flowing through a constriction were performed for both methods. For the MPS, a section of the channel of 3011.511.5 m was simulated using periodic boundary conditions. The obtained results have provided indications that, if the initial particle distance is sufficiently small, the MPS method can calculate accurately velocity profiles in the proposed channel.The authors acknowledge the financial support provided by PTDC/SAU-ENB/116929/2010 and EXPL/EMSSIS/2215/2013 from FCT (Science and Technology Foundation), COMPETE, QREN and European Union (FEDER). D. Bento acknowledge the financial support provided by SFRH/BD/91192/2012 from FCT (Science and Technology Foundation), COMPETE, QREN and European Union (FEDER). The authors are also very grateful to Dr. Alberto Gambaruto (Bristol University) for helpful explanations and suggestions regarding the MPS method.info:eu-repo/semantics/publishedVersio

Cultivo de abóbora do tipo japonesa por semeio direto e por transplante de mudas em diferentes sistemas de plantio.

Esse trabalho teve por objetivo avaliar duas cultivares de abóbora tipo japonesa (Jabras e Fortuna) em três sistemas de plantio (sistema de plantio direto - SPD, Sistema de plantio convencional com preparo do solo SPC e dois métodos de plantio (semeio direto no local definitivo e transplante de mudas produzidas em bandeijas.Suplemento. Trabalho apresentado no 52. Congresso Brasileiro de Olericultura, Salvador, 2012

Social Innovation by Tourism Strategy in the Western Amazon

This work concerns the strategies of social innovation focused on the concept of inbound tourism and hospitality in Rondônia State, Brazil. The general objective is to study the main strategies for qualifying as a tourist attraction. The specific objectives are to: point out the strategic elements to (1) qualify the facilities for inbound tourism and hospitality in the scenario;(2)examine the perspective on the implementation of the strategic elements in practice; and (3)indicate the elements of social innovation in support of the strategy of qualification to the concepts of inbound tourism and hospitality. This study is supported by the Theory of Planned Behaviour and concepts of inbound tourism, hospitality, creativity and innovation. It adopts the method of a case study which is both qualitative and quantitative in nature. As part of the methodological procedure, workshops were held for 28 stakeholders in Rondônia’s tourism, during which questionnaire data were collected from answers using the Likert Scale, participant observation was conducted and documents were analysed to enable the causal relationship to be critically assessed. A SWOT matrix was imposed upon the survey report. The tourist potential in the scenario has consequently been acknowledged, together with a need for the strategic planning of its attributes; valid elements for social innovation which use qualifying strategies for inbound tourism and hospitality are indicated; Possible public-private partnerships with the third sector and society could together create an ideal form of intervention. This study is of interest to both the public and the private sector, to academia and the community. It can contribute suggestions for the planning and management required for tourism to develop as well as outline strategies for social innovation

Relações entre atributos de fertilidade e matéria orgânica em solo cultivado com hortaliças em sistemas conservacionistas.

O presente trabalho teve como objetivo identificar possíveis relações entre os atributos de fertilidade e de matéria orgânica em um Latossolo Vermelho Distrófico cultivado com hortaliças em sistemas conservacionistas há seis anos

Seleção de clones de mandioquinha-salsa em áreas naturalmente infestadas pelo nematoide-das-galhas por meio de escala de notas.

Realizou-se este trabalho com o objetivo de avaliar clones de mandioquinha-salsa quanto à reação a Meloidogyne spp. por meio da elaboração de uma escala de notas.bitstream/item/85035/1/bpd-93.pd