Envelope of mid-planes of a surface and some classical notions of affine differential geometry

For a pair of points in a smooth locally convex surface in 3-space, its mid-plane is the plane containing its mid-point and the intersection line of the corresponding pair of tangent planes. In this paper we show that the limit of mid-planes when one point tends to the other along a direction is the Transon plane of the direction. Moreover, the limit of the envelope of mid-planes is non-empty for at most six directions, and, in this case, it coincides with the center of the Moutard's quadric. These results establish an unexpected connection between these classical notions of affine differential geometry and the apparently unrelated concept of envelope of mid-planes. We call the limit of envelope of mid-planes the affine mid-planes evolute and prove that, under some generic conditions, it is a regular surface in 3-space.Comment: 15 pages, 1 figur

Faecal carriage of extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella spp. in Mozambican students.

Masters Degree. University of KwaZulu-Natal, Durban.In recent years, the world has seen a surge in extended-spectrum β-lactamase (ESBL)-producing bacteria. Among antibiotic resistance mechanisms, the production of β-lactamase is the most rapidly developing and clinically significant in Gram-negative bacteria. In the present study, a total of 275 stool samples were collected from students of both sexes in three student residencies of Eduardo Mondlane UniversityMozambique from January to February 2016. All samples were cultured on MacConkey agar with ceftriaxone (1mg/L) and without ceftriaxone. The isolates were biochemically identified with API20E test. Confirmed E. coli and Klebsiella spp. isolates were subjected to antimicrobial susceptibility testing by the disc diffusion method and ESBL strains were confirmed with the disc approximation method. From these samples, 56 ESBL positive E. coli(n=35) and Klebsiella spp. (n=21) strains were isolated. Among the ESBL-positive isolates, 39.3% (22/56) were cefoxitin resistant and none were confirmed as carbapenemase producers. The frequency of ESBL colonization in both sex were similar for E. coli and Klebsiella spp. Among the ESBL-positive isolates, 50% (28/56) of the isolates only contained class A ESBLs, 5.4% (3/56) only class C ESBLs, and 44.6% (25/56) both class A and C ESBLs. Among the E. coli strains, 100% were resistance to ampicillin, and both E. coli and Klebsiella spp. demonstrated69.6% resistance to tetracycline and cotrimoxazole, 62.5% to ceftazidime, 33.9% to ciprofloxacin, and 34.8% to cefoxitin. None of the isolates showed resistance to meropenem. In total, 78.6 % of ESBL strains were defined as multi-resistant. The ERIC-PCR demonstrated low similarity among the strains. This study demonstrated that the carriage rates and the diversity of ESBL genes among the students are high

Applied structure from motion photogrammetry: habitat complexity and sponge distribution in natural rocky reefs adjacent to Ria Formosa (Southern Portugal)

O ambiente marinho, e as propriedades da água como fluido, expõem os organismos que nele habitam a uma força de arrasto muito maior do que o ambiente terrestre. Essa condição aumenta a necessidade dos organismos de procurarem por abrigos e refúgios. No caso dos organismos invertebrados sésseis, como as esponjas, que têm na fase planctônica larval o seu principal, ou único, modo de dispersão, a busca por um local ideal para o desenvolvimento é ainda mais importante, já que não podem se deslocar posteriormente. Portanto, o assentamento larval é um processo de vital importância para esses organismos, e leva em conta uma série de fatores, como luminosidade, presença de outros organismos e a topografia do fundo. Dessa forma, o estudo das estruturas que fornecem substrato para o assentamento larval, assim como de seus diferentes componentes, tanto bióticos como abióticos, é necessário para entender sua influência na distribuição dos organismos. Uma propriedade dos habitats, muito utilizada atualmente nesse tipo de estudo, é a complexidade do habitat. Ecossistemas marinhos recifais em todo o mundo estão registrando perda de complexidade do habitat, uma característica ambiental que, de uma forma mais qualitativa, está relacionada com a variedade de elementos que constituem o habitat, como rochas, troncos de árvores ou algas. De uma forma mais quantitativa, pode ser descrita por variáveis que quantificam o arranjo espacial desses elementos, seus tamanhos, abundâncias, entre outras propriedades. Assim, a complexidade do habitat é gerada tanto por elementos abióticos, como bióticos, e é uma característica ambiental essencial, não só para o assentamento larval, mas também para as relações ecológicas. A complexidade apresentou uma correlação positiva com a biodiversidade na maioria dos estudos já realizados. Apesar de os mecanismos por trás dessa relação não estarem totalmente claros, diferentes explicações foram propostas, como uma maior exploração de microhabitats, que geram mais nichos, uma maior produtividade gerada por uma maior área superficial, e uma maior riqueza de espécies devido à disponibilidade de refúgios de diferentes tamanhos. Este trabalho, realizado no âmbito do projeto de investigação MaréFormosa, que decorre na Faculdade de Ciência e Tecnologia (FCT) da Universidade do Algarve, estuda a relação entre a complexidade do habitat, e a abundância e distribuição de esponjas em dois recifes rochosos no Sul de Portugal, ambos situados a aproximadamente 12 m de profundidade. Distribuição essa, que está fortemente relacionada com o assentamento das larvas das espécies encontradas, que são o principal mecanismo de dispersão para invertebrados bentônicos. A fim de analisar essa relação e testar a hipótese de uma correlação positiva, foram construidos modelos 3D, com escala, das áreas de estudo com a utilização de fotogrametria (Structure from Motion photogrammetry - SfM), uma técnica que utiliza um conjunto de fotografias com um grau mínimo de sobreposição para a construção dos modelos. No lugar das fotografias, foram utilizados frames individuais retirados de vídeos gravados com uma GoPro Hero 3 nos dois recifes escolhidos. Os vídeos foram feitos por um mergulhador, que percorreu uma longa extensão dos recifes ao longo de um transecto, mantendo uma distância de aproximadamente 1 m acima do fundo. Após a construção dos modelos, foram calculadas variáveis relacionadas com a complexidade do habitat. Valores de dimensão fractal (fractal dimension - FD) em três diferentes escalas (0.15 - 0.30, 0.30 - 0.60, 0.60 - 1.80 m), rugosidade e inclinação foram calculados para áreas de 2 x 2 m aleatoriamente amostradas a partir dos modelos gerados para os diferentes segmentos dos recifes, juntamente com a abundância de cada uma das espécies de esponja presentes em cada área.(…)Marine ecosystems all over the world are registering loss of habitat complexity, a key environmental feature for ecological relations, that presented a positive correlation with biodiversity in most previous studies. This work investigates the relationship between habitat complexity, and the abundance and distribution of sponges in two rocky reefs in Southern Portugal. To assess this relationship and test the hypothesis of a positive correlation, 3D models of the study areas were built using Structure from Motion photogrammetry (SfM), and habitat complexity related variables were calculated. Fractal dimension (FD) in three scales (0.15 - 0.30, 0.30 - 0.60, 0.60 - 1.80 m), rugosity and slope values were calculated for 2 x 2mareas randomly sampled from models of different segments of the reefs, together with the abundance of each species of sponge present in each area. The results showed an affinity of Phorbas sp., one of the two most abundant sponges, for higher values of FD in the 0.15 - 0.30 m interval, related to algal cover, and of rugosity and slope, indicating an influence of the terrain on this species distribution. An aggregating behaviour was also noticed for this species. Spongia sp., the other abundant sponge, together with Phorbas sp., presented high abundances in exposed areas, suggesting that the low light environments not only make them avoid the typical sponge behaviour of settling in areas protected from light, but also might favour them in relation to algae. SfM generated high resolution models, with enough detail for the smaller scales and a wide area cover for the greater ones, proving to be an adequate technique for complexity analysis and, as a new application, for organisms localisation. Although there was not a clear positive correlation between habitat complexity and sponge abundance, there were indications of an influence of the terrain characteristics on the sponge distribution, with differences between species

Fund of hedge funds: implementation and operation

Hedge funds are an interesting investment alternative for those seeking international diversification. However, the task of analyzing and selecting a hedge fund to invest in is a very demanding one for the average investor. A fund of hedge funds is also an interesting alternative for those seeking international diversification through hedge funds. It is a specialized product of fered by some investment companies. Its objective is to maximize the expected return-risk ratio by diversifying the clients' investments in a portfolio of hedge funds. Our objective in this article is to discuss implementation and operational details related to funds of hedge funds. Our discussion will address important practical questions for both investors and investment companies

TRANSACTION COSTS: AN EMPIRICAL ANALYSIS OF THEIR RELATIONSHIP WITH INVESTMENT AND FOREIGN DIRECT INVESTMENT

As stated by the New Institutional Economics theory, transaction costs play a relevant role in economics and, according to the extent of such costs, agents make investment decisions. Actually,transaction costs may represent a disincentive to entrepreneurship.This work aims to verify whether transaction costs are related to investment rate and foreign direct investment rate (FDI) in different business environments. The results suggest that foreign investors do not have precise information about other countries as domestic investors do; as it is observed, only the relation between ransaction costs and investment rate is significant. Furthermore, there is evidence that the business environments of BRIC countries are less developed when compared to business environments of other countries in the stud

Soil management in Brazilian states: comparative analyzes of Physical and Monetary Soil Nutrient Balance in 2005 and 2015

Intensive agricultural production tends to stimulate the outflow of nutrients from the soil, requiring producers to properly manage the soil to avoid reducing fertility in the following crops. Thus, the objective was to estimate the annual monetary balance of nutrients in the soil of six Brazilian states that present the highest consumption of inorganic fertilizers in the years 2005 and 2015. The Annual Balance of Nutrients in Soil was used to calculate the physical and monetary balance of nutrients, in the main crops of these States, by quantifying the export of N, P, K from the soil by plants and the insertion of nutrients, through the application of fertilizers, fertigation, and biological fixation. The monetary balance of N, P and K added for the six states was positive and increased by 114% between 2005 and 2015, however, the balance of P for the state of Paraná was negative in 2015 reaching R$ 1,769.17. The balances and Mato Grosso, Rio Grande do Sul, and Paraná were higher concerning Goiás, São Paulo, and Minas Gerais. Except for Paraná, related to P, there was no positive depreciation of the associated NPK nutrients. The different flows, in the comparison among states, are caused by the different dynamics of land use, mainly in the size of the corn and soybean cultivation area

Operational Practices of Lean Manufacturing: Potentiating Environmental Improvements

Purpose: The objective of this paper is to investigate how environmental improvements can be achieved through operational practices of Lean Manufacturing. Design/methodology/approach: A literature review was conducted to analyze the relationship between operational practices of Lean and reduction of environmental impact in organizational contexts. Verified theoretically, this relationship was observed in a company of the electronics industry, through an exploratory research which contemplated a mixed approach. The adopted research method consisted of a single case study, by providing greater depth and detail of the study. Utilized a research protocol, validated pilot test. The instruments for data collection were semi-structured interviews, direct observation and document analysis. The information was examined qualitatively considering the technique for content analysis. Findings: As a result of the study, it was found that there is evidence for the existence of relationship between the practices of Lean, for example, Kaizen, PDCA (plan, do, check, act), Ishikawa Diagram, Poka-Yoke, and Standardized Work, with the reduction of environmental impacts of an organization. This reduction was observed after application of these practices that resulted in the reduction of energy consumption and water consumption. These results were accounted for financially, contributing to a reduction of annual costs by about US$ 17,900. Originality/value: The study presents in detail, the application of operational practices of Lean Manufacturing, with an effective view to reducing the environmental impact and cost reduction. The literature review, a detailed description of the application process and financial results are important information that contributes to the scientific studies that address traditional operating practices and the search for better environmental performance.Peer Reviewe

Towards a Generic Trace for Rule Based Constraint Reasoning

CHR is a very versatile programming language that allows programmers to declaratively specify constraint solvers. An important part of the development of such solvers is in their testing and debugging phases. Current CHR implementations support those phases by offering tracing facilities with limited information. In this report, we propose a new trace for CHR which contains enough information to analyze any aspects of \CHRv\ execution at some useful abstract level, common to several implementations. %a large family of rule based solvers. This approach is based on the idea of generic trace. Such a trace is formally defined as an extension of the $\omega_r^\lor$ semantics of CHR. We show that it can be derived form the SWI Prolog CHR trace