A mesoscale approach to simulate residual deformations in complex laser welding processes

Laser welding can be characterized by very small radii of beam, in the order of tenths of a millimeter, and very short high power inputs (more kW in few ms), and thus, it can be certainly classified as a microscale process with a high level of physical complexity. This is clearly incompatible, due to the high computational costs, with the analysis of macroscale processes related to large geometries and non-uniform welding patterns. In order to overcome this issue, a simplified finite element method (FEM)–based thermo-elastoplastic model is presented to simulate heat transfer and residual deformations due to thermal expansion and material plasticity. The idea is to substitute the microscale analysis with a mesoscale approach that renounces to describe in detail all the physical phenomena occurring in the heated zone and focuses attention on the correct prediction of the keyhole depth and weld pool size, that are the most important para meters to describe the mechanical characteristics of the welded joint. The concept of passive element, based on the numerical adjustment of the material properties in order to take into account the orthotropic behavior during the key hole formation, is introduced. In particular, the new approach has been tested on the pulsed laser welding process of two overlapping DC04 steel plates with thickness of 0.5 mm (so-called sandwich) and validated through experimental tests involving different input parameters, such as power, pulse duration and frequency, speed, and geometrical pattern

Multifidelity Recursive Cokriging for Dynamic Systems' Response Modification

In order to perform the accurate tuning of a machine and improve its performance to the requested tasks, the knowledge of the reciprocal influence among the system\u2019s parameters is of paramount importance to achieve the sought result with minimum effort and time. Numerical simulations are an invaluable tool to carry out the system optimization, but modeling limitations restrict the capabilities of this approach. On the other side, real tests and measurements are lengthy, expensive, and not always feasible. This is the reason why a mixed approach is presented in this work. The combination, through recursive cokriging, of low-fidelity, yet extensive, numerical model results, together with a limited number of highly accurate experimental measurements, allows to understand the dynamics of the machine in an extended and accurate way. The results of a controllable experiment are presented and the advantages and drawbacks of the proposed approach are also discussed

Distributed Lagrange Multiplier Functions for Fictitious Domain Method with Spectral/hp Element Discretization

A fictitious domain approach for the solution of second-order linear differential problems is proposed; spectral/hp elements have been used for the discretization of the domain. The peculiarity of our approach is that the Lagrange multipliers are particular distributed functions, instead of classical \u3b4 Dirac (impulsive)multipliers. In this paper we present the formulation and the application of this approach to 1D and 2D Poisson problems and 2D Stokes flow (biharmonic equation)

Estudo retrospectivo de cães e gatos portadores de corpos estranhos gastrointestinais : análise de 44 casos (2013 a 2018)

Obstruções causadas por corpos estranhos no trato gastrointestinal são comumente encontradas na rotina de atendimento clínico veterinário de pequenos animais. Os objetivos deste trabalho são apresentar um estudo retrospectivo dos pacientes com ingestão de corpos estranhos encaminhados para o Serviço de Endoscopia e Gastroenterologia da Universidade Federal do Rio Grande do Sul. Foram analisados o perfil dos pacientes, os locais mais comuns de obstrução, os tipos de objetos mais encontrados, os métodos diagnósticos mais solicitados e o tipo de tratamento mais utilizado. Foram incluídos 44 pacientes de janeiro de 2013 a novembro de 2018, sendo a espécie canina a mais cometida, com 77,3 % dos casos (n = 34). Já os felinos corresponderam a 22,7% (n = 10). A representação de acordo com o sexo foi bastante homogênea (52,9% e 60% machos) para cães e gatos, a mediana das idades 4,00 (cães) e 3,00 (gatos) e o peso médio dos cães foi de 14,0 10,6 kg e dos gatos de 3,4 1,0 kg. A endoscopia foi o método diagnóstico mais solicitado e também o método de tratamento mais utilizado apresentando altas taxas de sucesso e baixas taxas de complicações. Concluímos que ambas espécies foram mais acometida por corpos estranhos não lineares. A localização mais frequente foi no estômago. O envolvimento de cães com peso superior a dez quilogramas e adultos em torno de quatro anos de idade pode sugerir doenças digestórias subjacentes; assim, a biópsia gastrointestinal pode ser uma importante ferramenta no manejo de cães e gatos portadores de corpos estranhos.Gastrointestinal foreign bodies are commonly encountered in routine clinical veterinary care of pets. The objectives of this study are to present a retrospective investigation of patients with foreign body ingestion referred to the Endoscopy and Gastroenterology Service of the Federal University of Rio Grande do Sul. Patients’ profile, the most common sites of obstruction, the types of objects found, the most requested diagnostic methods, and the type of treatment most used, were analyzed. A total of 44 patients were included from January 2013 to November 2018, with the canine species being affected in 77.3% of cases (n = 34) and the feline species in 22.7% (n = 10). According to sex, representation was quite homogeneous for dogs (52.9% males) and cats (60% males), the median age was 4.00 (dogs) and 3.00 years (cats), the mean weight of dogs was 14.0 10.6 kg and cats was 3.4 1.0 kg. Endoscopy was the most requested diagnostic method and also the most frequently used treatment method, presenting high rates of success and low complication rates. We conclude that both species were more affected by non linear foreign bodies and the most frequent location was the stomach. The involvement of dogs weighing more than ten kilograms and adult animal around the age of four years may suggest underlying digestive diseases, and gastrointestinal biopsy may be an important tool in the management of dogs and cats with foreign bodies

El proceso de suburbanización del cordón oeste metropolitano de Rosario. Ideas de ciudad.

Las aglomeraciones urbanas actuales han integrado espacial y funcionalmente a las ciudades próximas, mediante un proceso de transformación territorial caracterizado por la expansión urbana dispersa. La suburbanización resulta hoy uno de los principales patrones de desarrollo de las grandes ciudades. El caso de estudio se presenta como una estribación metropolitana de la ciudad de Rosario, que configura al Cordón Oeste Metropolitano, y ha experimentado un proceso de suburbanización vinculado con las expansiones urbanas de la ciudad central, que comenzó a principios de los años 60 y se intensificó en los años 90. Este cordón ofrece un área de esparcimiento, recreación y descanso debido a sus condiciones naturales y a su gran forestación. Su proceso se concretó mediante sucesivas operaciones inmobiliarias, ventas de loteos de fin de semana o viviendas permanentes y la incorporación de nuevas urbanizaciones de tipo cerrado, en donde se presentan características propias del modelo de ciudad jardín

El proceso de suburbanización del cordón oeste metropolitano de Rosario. Ideas de ciudad.

Las aglomeraciones urbanas actuales han integrado espacial y funcionalmente a las ciudades próximas, mediante un proceso de transformación territorial caracterizado por la expansión urbana dispersa. La suburbanización resulta hoy uno de los principales patrones de desarrollo de las grandes ciudades. El caso de estudio se presenta como una estribación metropolitana de la ciudad de Rosario, que configura al Cordón Oeste Metropolitano, y ha experimentado un proceso de suburbanización vinculado con las expansiones urbanas de la ciudad central, que comenzó a principios de los años 60 y se intensificó en los años 90. Este cordón ofrece un área de esparcimiento, recreación y descanso debido a sus condiciones naturales y a su gran forestación. Su proceso se concretó mediante sucesivas operaciones inmobiliarias, ventas de loteos de fin de semana o viviendas permanentes y la incorporación de nuevas urbanizaciones de tipo cerrado, en donde se presentan características propias del modelo de ciudad jardín

Multi-fidelity Gaussian process regression for prediction of random fields

We propose a new multi-fidelity Gaussian process regression (GPR) approach for prediction of random fields based on observations of surrogate models or hierarchies of surrogate models. Our method builds upon recent work on recursive Bayesian techniques, in particular recursive co-kriging, and extends it to vector-valued fields and various types of covariances, including separable and non-separable ones. The framework we propose is general and can be used to perform uncertainty propagation and quantification in model-based simulations, multi-fidelity data fusion, and surrogate-based optimization. We demonstrate the effectiveness of the proposed recursive GPR techniques through various examples. Specifically, we study the stochastic Burgers equation and the stochastic Oberbeck\u2013Boussinesq equations describing natural convection within a square enclosure. In both cases we find that the standard deviation of the Gaussian predictors as well as the absolute errors relative to benchmark stochastic solutions are very small, suggesting that the proposed multi-fidelity GPR approaches can yield highly accurate results

TbGT8 is a bifunctional glycosyltransferase that elaborates<em> N</em>-linked glycans on a protein phosphatase AcP115 and a GPI-anchor modifying glycan in <em>Trypanosoma brucei</em>

AbstractThe procyclic form of Trypanosoma brucei expresses procyclin surface glycoproteins with unusual glycosylphosphatidylinositol-anchor side chain structures that contain branched N-acetyllactosamine and lacto-N-biose units. The glycosyltransferase TbGT8 is involved in the synthesis of the branched side chain through its UDP-GlcNAc: βGal β1-3N-acetylglucosaminyltransferase activity. Here, we explored the role of TbGT8 in the mammalian bloodstream form of the parasite with a tetracycline-inducible conditional null T. brucei mutant for TbGT8. Under non-permissive conditions, the mutant showed significantly reduced binding to tomato lectin, which recognizes poly-N-acetyllactosamine-containing glycans. Lectin pull-down assays revealed differences between the wild type and TbGT8 null-mutant T. brucei, notably the absence of a broad protein band with an approximate molecular weight of 110kDa in the mutant lysate. Proteomic analysis revealed that the band contained several glycoproteins, including the acidic ecto-protein phosphatase AcP115, a stage-specific glycoprotein in the bloodstream form of T. brucei. Western blotting with an anti-AcP115 antibody revealed that AcP115 was approximately 10kDa smaller in the mutant. Enzymatic de-N-glycosylation demonstrated that the underlying protein cores were the same, suggesting that the 10-kDa difference was due to differences in N-linked glycans. Immunofluorescence microscopy revealed the colocalization of hemagglutinin epitope-tagged TbGT8 and the Golgi-associated protein GRASP. These data suggest that TbGT8 is involved in the construction of complex poly-N-acetyllactosamine-containing type N-linked and GPI-linked glycans in the Golgi of the bloodstream and procyclic parasite forms, respectively

Toxoplasma gondii Syntaxin 6 is required for vesicular transport between endosomal-like compartments and the Golgi Complex

Apicomplexans are obligate intracellular parasites that invade the host cell in an active process that relies on unique secretory organelles (micronemes, rhoptries and dense granules) localized at the apical tip of these highly polarized eukaryotes. In order for the contents of these specialized organelles to reach their final destination, these proteins are sorted post-Golgi and it has been speculated that they pass through endosomal-like compartments (ELCs), where they undergo maturation. Here, we characterize a Toxoplasma gondii homologue of Syntaxin 6 (TgStx6), a well-established marker for the early endosomes and trans Golgi network (TGN) in diverse eukaryotes. Indeed, TgStx6 appears to have a role in the retrograde transport between ELCs, the TGN and the Golgi, because overexpression of TgStx6 results in the development of abnormally shaped parasites with expanded ELCs, a fragmented Golgi and a defect in inner membrane complex maturation. Interestingly, other organelles such as the micronemes, rhoptries and the apicoplast are not affected, establishing the TGN as a major sorting compartment where several transport pathways intersect. It therefore appears thatToxoplasma has retained a plant-like secretory pathway

Protein trafficking through the endosomal system prepares intracellular parasites for a home invasion

Toxoplasma (toxoplasmosis) and Plasmodium (malaria) use unique secretory organelles for migration, cell invasion, manipulation of host cell functions, and cell egress. In particular, the apical secretory micronemes and rhoptries of apicomplexan parasites are essential for successful host infection. New findings reveal that the contents of these organelles, which are transported through the endoplasmic reticulum (ER) and Golgi, also require the parasite endosome-like system to access their respective organelles. In this review, we discuss recent findings that demonstrate that these parasites reduced their endosomal system and modified classical regulators of this pathway for the biogenesis of apical organelles