Crossbreeding and new beef cattle breeds in Brazil.

Crossbreeding and new beef cattle breeds in Brazil.198

Clone size distributions in networks of genetic similarity

We build networks of genetic similarity in which the nodes are organisms sampled from biological populations. The procedure is illustrated by constructing networks from genetic data of a marine clonal plant. An important feature in the networks is the presence of clone subgraphs, i.e. sets of organisms with identical genotype forming clones. As a first step to understand the dynamics that has shaped these networks, we point up a relationship between a particular degree distribution and the clone size distribution in the populations. We construct a dynamical model for the population dynamics, focussing on the dynamics of the clones, and solve it for the required distributions. Scale free and exponentially decaying forms are obtained depending on parameter values, the first type being obtained when clonal growth is the dominant process. Average distributions are dominated by the power law behavior presented by the fastest replicating populations.Comment: 17 pages, 4 figures. One figure improved and other minor changes. To appear in Physica

Healthrisk assessment from exposure to trihalomethanes in drinking water

A aplicação de compostos clorados na desinfeção da água pode induzir à formação de subprodutos da desinfeção (SPD) com efeitos carcinogénicos e mutagénicos comprovados. Neste trabalho, apresenta-se uma síntese de um estudo sobre a ocorrência de trihalometanos (THM) na água de abastecimento, realizado nos catorze municípios do distrito de Braga (Portugal), visando a avaliação do risco de cancro (RC) e de efeitos não carcinogénicos (HI) com base na metodologia desenvolvida pela USEPA e IRIS. Num cenário gravoso, correspondente à prevalência da maior concentração de THM detetada no período monitorizado, o indicador RC daria valores superiores ao limite máximo definido como negligenciável, verificando-se ser a ingestão a via de exposição mais relevante. Os resultados obtidos para o indicador HI foram quase sempre inferiores à unidade, indicando um nível de risco aceitável, de acordo com os pressupostos do método utilizado. O uso de indicadores do risco para a saúde constitui uma ferramenta útil quer no apoio à decisão das entidades gestoras de sistemas de abastecimento de água, quer na definição de estratégias e políticas de saúde pública que visem a mitigação deste risco.Chlorination havebroughtenormous benefits to the preservation of public health as a low-cost disinfection method, but it cangenerate severalhalogenated organic compounds,as disinfection by-products (DBP), with potentialand proven carcinogenic and mutagenic effects. This workpresents a synthesis of the study performed in watersupply systems ofthe fourteen municipalities of Braga district (Portugal), aiming at the evaluation of lifetime cancer risk (CRindex),and the risk of non-carcinogenic effects (HI-Hazard Index) fromexposure to THMs, usingamethod proposed by USEPA and IRIS.In a severescenario, corresponding to the prevalence of maximum THMconcentrationoccurred duringthe monitored period, the CR index would achieve valueshigher than the maximum limit defined asnegligible forall these municipalities. The HI indexresultswereoftenlower than one,which is consideredas an acceptable risk level. The use of health risk indicators can be a useful tool both in supporting the decision-making of water supplyutilitiesandin the definition of public health strategies/policies forrisk mitigation in order to increasethe life quality and the wellnessof populations

Study of welding strengh in PVC profiles

Polyvinyl chloride, PVC, is one of the most widely produced and used plastic, being commonly used in civil industry due to its wide range of mechanical properties (from rigid to flexible), low cost, durability, and easy to assemble. Due to its good mechanical and thermal properties, PVC can be used to produce window and door frames, protecting the interior from the external actions, such as noise and temperature gradients. In order to achieve the final dimensions and geometry, previously extruded profiles must be cut and assembled, being the butt welding one of the most efficient techniques. This plastic welding method involves three main steps: i) pressing the parts to be joined against either side of a heated plate; ii) removing the plate when the parts are sufficiently molten and iii) pressing the components together and holding them until they are cooled. The amount of molten material, generated during the heating stage at an adequate heating time and the plate temperature, as well as the amount of material forced out from the joint during the pressing stage (joining displacement), have major influence in the final welding properties. Although the lack of information about the butt welding of PVC, previous studies with for others materials [1-3] showed that the welding strength can be optimized changing the plate temperature and/or joining displacement. The aim of this work was to study the influence of the plate temperature and the heating time in the welding strength of PVC profiles used in windows frames. The profiles were welded in an industrial butt welder machine, setting the plate temperature at 245ºC, 260ºC and 275ºC and the heating time at 15 and 20s. The mechanical properties were evaluated by mechanical bending tests, according to UNE-EN 514 standard and the welding strength was correlated with the morphology of the welded parts observed by optical microscopy. The results are showing that the increase of plate temperature and heating time increase the welding strength. However, the presence of impurities in the joint, such as trapped air or degraded material, as well as the joint alignment, can have a detrimental effect on the welding strength, as observed by the morphological analyses

The effect of a phase change on the temperature evolution during the deposition stage in fused filament fabrication

Additive Manufacturing Techniques such as Fused Filament Fabrication (FFF) produce 3D parts with complex geometries directly from a computer model without the need of using molds and tools, by gradually depositing material(s), usually in layers. Due to the rapid growth of these techniques, researchers have been increasingly interested in the availability of strategies, models or data that may assist process optimization. In fact, 3D printed parts often exhibit limited mechanical performance, which is usually the result of poor bonding between adjacent filaments. In turn, the latter is influenced by the temperature field history during deposition. This study aims at evaluating the influence of the phase change from the melt to the solid state undergone by semi-crystalline polymers such as Polylactic Acid (PLA), on the heat transfer during the deposition stage. The energy equation considering solidification is solved analytically and then inserted into a MatLab® code to model cooling in FFF. The deposition and cooling of simple geometries is studied first, in order to assess the differences in cooling of amorphous and semi-crystalline polymers. Acrylonitrile Butadiene Styrene (ABS) was taken as representing an amorphous material. Then, the deposition and cooling of a realistic 3D part is investigated, and the influence of the build orientation is discussed.This work has been partially supported by national funds through FCT- Fundação para a Ciência e Tecnologia through project UIDB/04728/2020. Partial support for this research has been provided by the Search-ON2: Revitalization of HPC infrastructure of Uminho, (NORTE-07-0162- FEDER-000086), co-funded by the North Portugal Regional Operational Programme (ON.2-O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Defaults in bank loans to SMEs during the financial crisis

We investigate the role of (business) collateral and (personal) guarantees alongside small and medium enterprise (SME), lending bank and loan characteristics, macroeconomic conditions, sectors, and geographic locations while controlling for unobserved time effects in predicting default at the peak of the financial crisis. First, we find a positive relation between collateral and default, and a negative relation between guarantees and default. Second, we find a negative relation between the joint influence of collateral and high credit score, and a positive relation between the joint influence of collateral and low credit score and default. We also find a negative relation between the joint influence of guarantees and high credit score. These findings are relevant for SME policies aimed at facilitating access to credit, reducing the cost of borrowing, and decreasing default; risk management of banks; and the application of theories of financial economics in the context of a financial crisis.info:eu-repo/semantics/publishedVersio

Credit risk, owner liability and bank loan maturities during the global financial crisis

We relate credit risk and owners’ personal guarantees to bank loan maturities during the global financial crisis. The findings, which remain robust to reverse causality, show that firms rated as low risk, with a strong relationship with the bank, whose owners provided personal guarantees and with large loan sizes obtained longer maturities. Banks with larger nonperforming loans provided loans with shorter maturities. Firms with low and high risk ratings that provided owners’ personal guarantees obtained longer maturities. These findings shed additional light on the relationship between risk and loan maturities and the role of personal guarantees in reducing information asymmetries.info:eu-repo/semantics/acceptedVersio

Studying the cooling stage in fused filament fabrication

Fused Filament Fabrication (FFF) is one of the available techniques that is capable of producing parts by additive manufacturing, i.e., by depositing thin filaments of thermoplastic polymers or composites onto a support as a vertical series of horizontal 2D slices of a 3D part. This chapter approaches FFF from a phenomenological point of view, and then focus on the deposition and cooling stage. A code capable of predicting the evolution of temperature during deposition and until cooling is completed, as well as of the final bonding between filaments is presented. The tool is then used to enlighten the effect of major processing parameters on the quality of parts

Computer aided definition of the printing conditions of parts made by FFF

The growing worldwide use of 3D printing techniques requires the support of scientific research to improve the process and the quality of 3D printed parts. In a previous work, the authors developed a computer code that predicts the temperature evolution and the adhesion at any location of a 3D part produced by Fused Filament Fabrication (FFF). Here, a 3D printed scalpel handle is used as a case study to evaluate the usefulness of the simulation tool in the definition of the printing conditions. Considering a printer with a convection oven, the best built orientation is selected. The results demonstrate the complexity of the heat transfer mechanisms that develop during the deposition stage. For this particular case study, the importance of using a 3D printer fitted with a convection oven is demonstrated, as its positive effect on adhesion cannot be compensated by tuning other process parametersThis work has been partially supported by national funds through FCT – Fundação para a Ciência e Tecnologia through project UIDB/04728/2020. Partial support for this research has been provided by the Search-ON2: Revitalization of HPC infrastructure of Uminho, (NORTE-07-0162-FEDER-000086), co-funded by the North Portugal Regional Operational Programme (ON.2-O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), at the University of Minho, Portugal

Using matlab to compute heat transfer In free form extrusion

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