Atomic-scale grain boundary engineering to overcome hot-cracking in additively-manufactured superalloys

There are still debates regarding the mechanisms that lead to hot cracking in parts build by additive manufacturing (AM) of non-weldable Ni-based superalloys. This lack of in-depth understanding of the root causes of hot cracking is an impediment to designing engineering parts for safety-critical applications. Here, we deploy a near-atomic-scale approach to investigate the details of the compositional decoration of grain boundaries in the coarse-grained, columnar microstructure in parts built from a non-weldable Ni-based superalloy by selective electron-beam melting. The progressive enrichment in Cr, Mo and B at grain boundaries over the course of the AM-typical successive solidification and remelting events, accompanied by solid-state diffusion, causes grain boundary segregation induced liquation. This observation is consistent with thermodynamic calculations. We demonstrate that by adjusting build parameters to obtain a fine-grained equiaxed or a columnar microstructure with grain width smaller than 100 $\mu$m enables to avoid cracking, despite strong grain boundary segregation. We find that the spread of critical solutes to a higher total interfacial area, combined with lower thermal stresses, helps to suppress interfacial liquation.Comment: Accepted version at Acta Materiali

USO DE METODOLOGIA NO ENSINO DO SISTEMA DE VEIAS ÁZIGO

Anatomy is an essential tool for describing species and comparing them when they are morphologically similar, in addition to solving clinical practice problems. In addition, the azygous vein system drains the back of the thoracoabdominal walls and mediastinal viscera. It presents many variations, not only in its origin but also in its path, tributaries, anastomosis and terminations. Therefore, this research aims to carry out a study on the azygous vein system based on active teaching and learning methodology. Two groups of students were analyzed, with only one being influenced by the active methodology and, later, both were compared regarding the learning provided by each method. It was concluded that the use of active methodologies contributed satisfactorily to the student's learning, increasing his ability to fix the content and interact with the material, in addition to maintaining motivation in the active search for learning.La anatomía es un instrumento esencial para la descripción de especies y comparaciones entre ellas cuando son morfológicamente similares, además de resolver problemas de práctica clínica. Además, el sistema de venas cigotos drena la parte posterior de las paredes de las vísceras toracoabdominales y mediastínicas. Presenta muchas variaciones, no solo en su origen sino también en su trayectoria, afluentes, anastomosis y terminaciones Esta investigación tiene como objetivo realizar un estudio sobre el sistema de venas cigotos a partir de la metodología activa de enseñanza y aprendizaje. Se analizaron dos grupos de estudiantes, y solo uno fue influenciado por la metodología activa y, posteriormente, se compararon ambos para el aprendizaje proporcionado por cada método. Se concluyó que el uso de metodologías activas contribuyó satisfactoriamente al aprendizaje del estudiante, aumentando su capacidad para fijar el contenido e interactuar con el sujeto, además de mantener la motivación en la búsqueda activa del aprendizaje.A anatomia é um instrumento essencial para a descrição de espécies e comparações entre elas quando morfologicamente parecidas, além de resolução de problemas da prática clínica. Além disso, o sistema de veias ázigo drena o dorso das paredes toracoabdominais e vísceras mediastinais. Ele apresenta muitas variações, não só na sua origem mas também no seu trajeto, tributárias, anastomose e terminações Diante disso, esta pesquisa tem como objetivo realizar um estudo sobre o sistema de veias ázigo a partir de metodologia ativa de ensino e aprendizagem. Foram analisados dois grupos de estudantes, sendo que somente um recebeu influência da metodologia ativa e, posteriormente, ambos foram comparados quanto ao aprendizado proporcionado por cada método. Concluiu-se que, a utilização de metodologias ativas contribuiu de forma satisfatória para o aprendizado do aluno, aumentando sua capacidade de fixação do conteúdo e interação com a matéria, além de manter a motivação na busca ativa do aprendizado

Trick or Tweak: On the (In)security of OTR’s Tweaks

Tweakable blockcipher (TBC) is a powerful tool to design authenticated encryption schemes as illustrated by Minematsu\u27s Offset Two Rounds (OTR) construction. It considers an additional input, called tweak, to a standard blockcipher which adds some variability to this primitive. More specifically, each tweak is expected to define a different, independent pseudo-random permutation. In this work we focus on OTR\u27s way to instantiate a TBC and show that it does not achieve such a property for a large amount of parameters. We indeed describe collisions between the input masks derived from the tweaks and explain how they result in practical attacks against this scheme, breaking privacy, authenticity, or both, using a single encryption query, with advantage at least 1/4. We stress however that our results do not invalidate the OTR construction as a whole but simply prove that the TBC\u27s input masks should be designed differently

Contribuições do enfermeiro para a promoção do aleitamento materno/ Contributions of the nurse for the promotion of breastfeeding

O aleitamento materno é o meio mais eficaz para garantir o crescimento saudável do bebê, sendo fundamental para a saúde do binômio mãe e filho. O presente estudo foi realizado com o objetivo de evidenciar a atuação do Enfermeiro em ações educativas, para promoção ao aleitamento materno, e os benefícios desta prática efetiva, elucidando as dificuldades encontradas pelas mães durante a lactação, bem como descrever os riscos inerentes, desencadeados pelo desmame precoce para o binômio mãe e filho. Trata-se de uma revisão integrativa, adotando os descritores aleitamento materno, saúde materno-infantil, cuidados de enfermagem. As buscas ocorreram nas bases de dados na Biblioteca Virtual em Saúde (BVS), Scientific Electronic Library (SciELO), e PubMed com seleção entre 2013 a 2018, artigos completos, gratuitos, em português e inglês. Como resultado, foram selecionados vinte e quatro artigos que atenderam aos critérios de inclusão. Nas pesquisas foram evidenciadas as altas taxas de desmame precoce, visto que muitas mães deixam de amamentar exclusivamente até os seis meses de vida, a prematuridade do recém-nascido, a ansiedade, medo e insegurança das nutrizes contribuíram para este fator. Verificou-se a necessidade das ações do enfermeiro em apoiar as nutrizes e estimular o aleitamento materno junto com o apoio dos pais e familiares. Conclui-se que a prática de amamentar deve ser um ato de prazer e dedicação garantindo os benefícios oriundos desta prática para mãe e filho, onde o enfermeiro deverá estimular a amamentação e oferecer apoio emocional frente às dificuldades que podem surgir

eXtraembryonic ENdoderm (XEN) Stem Cells Produce Factors that Activate Heart Formation

Initial specification of cardiomyocytes in the mouse results from interactions between the extraembryonic anterior visceral endoderm (AVE) and the nascent mesoderm. However the mechanism by which AVE activates cardiogenesis is not well understood, and the identity of specific cardiogenic factors in the endoderm remains elusive. Most mammalian studies of the cardiogenic potential of the endoderm have relied on the use of cell lines that are similar to the heart-inducing AVE. These include the embryonal-carcinoma-derived cell lines, END2 and PYS2. The recent development of protocols to isolate eXtraembryonic ENdoderm (XEN) stem cells, representing the extraembryonic endoderm lineage, from blastocyst stage mouse embryos offers new tools for the genetic dissection of cardiogenesis.Here, we demonstrate that XEN cell-conditioned media (CM) enhances cardiogenesis during Embryoid Body (EB) differentiation of mouse embryonic stem (ES) cells in a manner comparable to PYS2-CM and END2-CM. Addition of CM from each of these three cell lines enhanced the percentage of EBs that formed beating areas, but ultimately, only XEN-CM and PYS2-CM increased the total number of cardiomyocytes that formed. Furthermore, our observations revealed that both contact-independent and contact-dependent factors are required to mediate the full cardiogenic potential of the endoderm. Finally, we used gene array comparison to identify factors in these cell lines that could mediate their cardiogenic potential.These studies represent the first step in the use of XEN cells as a molecular genetic tool to study cardiomyocyte differentiation. Not only are XEN cells functionally similar to the heart-inducing AVE, but also can be used for the genetic dissection of the cardiogenic potential of AVE, since they can be isolated from both wild type and mutant blastocysts. These studies further demonstrate the importance of both contact-dependent and contact-independent factors in cardiogenesis and identify potential heart-inducing proteins in the endoderm

Utilisation of an operative difficulty grading scale for laparoscopic cholecystectomy

Background A reliable system for grading operative difficulty of laparoscopic cholecystectomy would standardise description of findings and reporting of outcomes. The aim of this study was to validate a difficulty grading system (Nassar scale), testing its applicability and consistency in two large prospective datasets. Methods Patient and disease-related variables and 30-day outcomes were identified in two prospective cholecystectomy databases: the multi-centre prospective cohort of 8820 patients from the recent CholeS Study and the single-surgeon series containing 4089 patients. Operative data and patient outcomes were correlated with Nassar operative difficultly scale, using Kendall’s tau for dichotomous variables, or Jonckheere–Terpstra tests for continuous variables. A ROC curve analysis was performed, to quantify the predictive accuracy of the scale for each outcome, with continuous outcomes dichotomised, prior to analysis. Results A higher operative difficulty grade was consistently associated with worse outcomes for the patients in both the reference and CholeS cohorts. The median length of stay increased from 0 to 4 days, and the 30-day complication rate from 7.6 to 24.4% as the difficulty grade increased from 1 to 4/5 (both p < 0.001). In the CholeS cohort, a higher difficulty grade was found to be most strongly associated with conversion to open and 30-day mortality (AUROC = 0.903, 0.822, respectively). On multivariable analysis, the Nassar operative difficultly scale was found to be a significant independent predictor of operative duration, conversion to open surgery, 30-day complications and 30-day reintervention (all p < 0.001). Conclusion We have shown that an operative difficulty scale can standardise the description of operative findings by multiple grades of surgeons to facilitate audit, training assessment and research. It provides a tool for reporting operative findings, disease severity and technical difficulty and can be utilised in future research to reliably compare outcomes according to case mix and intra-operative difficulty

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Search for direct stau production in events with two hadronic tau-leptons in root s=13 TeV pp collisions with the ATLAS detector

A search for the direct production of the supersymmetric partners ofτ-leptons (staus) in final stateswith two hadronically decayingτ-leptons is presented. The analysis uses a dataset of pp collisions corresponding to an integrated luminosity of139fb−1, recorded with the ATLAS detector at the LargeHadron Collider at a center-of-mass energy of 13 TeV. No significant deviation from the expected StandardModel background is observed. Limits are derived in scenarios of direct production of stau pairs with eachstau decaying into the stable lightest neutralino and oneτ-lepton in simplified models where the two staumass eigenstates are degenerate. Stau masses from 120 GeV to 390 GeV are excluded at 95% confidencelevel for a massless lightest neutralino

Search for chargino-neutralino production with mass splittings near the electroweak scale in three-lepton final states in √s=13 TeV pp collisions with the ATLAS detector

A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton final state. The analyzed proton-proton collision data taken at a center-of-mass energy of √s=13  TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139  fb−1. A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015–2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV