Experimental study of the adaptive gain feature for improved position-sensitive ion spectroscopy with Timepix2

In the present work, we study the Timepix2 pixels’ high energy response in the so-called adaptive gain mode. Therefore, Timepix2 with a 500 μm thick silicon sensor was irradiated with protons of energies in the range from 400 keV to 2 MeV and α-particles of 5.5 MeV from 241Am. A novel method was developed to determine the energy deposit in single pixels of particle imprints, which are spread out over a set of neighbor pixels (cluster). We show that each pixel is capable of measuring the deposited energy from 4 keV up to ∼3.2 MeV. Reconstructing the full energy content of the clusters, we found relative energy resolutions ( σ E ) better than 2.7% and better than 4% for proton and α-particle data, respectively. In a simple experiment with a 5.5 MeV α-particle source, we demonstrate that energy losses in thin (organic) specimen can be spatially resolved, mapping out sample thickness variations, with a resolution around 1–2 μm, across the sensor area. The inherent spatial resolution of the device was determined to be 350 nm in the best case.

OmpF Downregulation Mediated by Sigma E or OmpR Activation Confers Cefalexin Resistance in Escherichia coli in the Absence of Acquired β-Lactamases.

Cefalexin is a widely used 1 st generation cephalosporin, and resistance in Escherichia coli is caused by Extended-Spectrum (e.g., CTX-M) and AmpC β-lactamase production and therefore frequently coincides with 3 rd generation cephalosporin resistance. However, we have recently identified large numbers of E. coli isolates from human infections, and from cattle, where cefalexin resistance is not β-lactamase mediated. Here we show, by studying laboratory selected mutants, clinical isolates, and isolates from cattle, that OmpF porin disruption or downregulation is a major cause of cefalexin resistance in E. coli . Importantly, we identify multiple regulatory mutations that cause OmpF downregulation. In addition to mutation of ompR , already known to downregulate OmpF and OmpC porin production, we find that rseA mutation, which strongly activates the Sigma E regulon, greatly increasing DegP production, which degrades OmpF, OmpC and OmpA. Furthermore, we reveal that mutations affecting lipopolysaccharide structure, exemplified by the loss of GmhB, essential for lipopolysaccharide heptosylation, also modestly activate DegP production, resulting in OmpF degradation. Remarkably, given the critical importance attached to such systems for normal E. coli physiology, we find evidence for DegP-mediated OmpF downregulation, gmhB and rseA loss of function mutation in E. coli isolates derived from human infections. Finally, we show that these regulatory mutations enhance the ability of group 1 CTX-M β-lactamase to confer reduced carbapenem susceptibility, particularly those mutations that cause OmpC in addition to OmpF downregulation.

LEAN SIX SIGMA E INDUSTRIA 4.0, UNA REVISIÓN DESDE LA ADMINISTRACIÓN DE OPERACIONES PARA LA MEJORA CONTINUA DE LAS ORGANIZACIONES

La administración de operaciones es un área de estudio de la administración que se centra en la gestión estratégica de las organizaciones. En un contexto mundial marcado por la globalización, la Industria 4.0 e impactado por la pandemia Covid-19, que ha generado mayor incertidumbre y complejidad para las empresas, la adopción de metodologías, métodos y herramientas de administración de operaciones constituye una necesidad para mejorar el desempeño empresarial. El objetivo de la investigación es discutir la contribución actual que tiene la metodología Lean Six Sigma en la mejora continua de las organizaciones, el aumento de la productividad y la competitividad. Se realiza la discusión a partir del análisis de las principales aseveraciones realizadas por académicos, investigadores y empresarios de reconocido prestigio en la temática a nivel mundial. La investigación tiene un enfoque cualitativo, el alcance es exploratorio y el diseño es no experimental. El análisis documental realizado por medio de la plataforma de la Web of Sciences de Clarivate Analytics arrojó 1015 resultados, los cuales fueron procesados por medio de la implementación de la metodología PRISMA. Los resultados obtenidos permiten afirmar que la implementación de la metodología Lean Six Sigma en las organizaciones contribuye a aumentar los niveles de productividad y competitividad. Los trabajos futuros deben dirigirse a evaluar cuantitativamente el impacto real y los beneficios que aporta a las empresas su adopción en el logro de una mayor eficiencia, productividad y obtención de ventajas competitivas sostenidas.

Circular Chromatic Number of Signed Graphs

A signed graph is a pair $(G, \sigma)$, where $G$ is a graph (loops and multi edges allowed) and $\sigma: E(G) \to \{+, -\}$ is a signature which assigns to each edge of $G$ a sign. Various notions of coloring of signed graphs have been studied. In this paper, we extend circular coloring of graphs to signed graphs. Given a signed graph $(G, \sigma)$ with no positive loop, a circular $r$-coloring of $(G, \sigma)$ is an assignment $\psi$ of points of a circle of circumference $r$ to the vertices of $G$ such that for every edge $e=uv$ of $G$, if $\sigma(e)=+$, then $\psi(u)$ and $\psi(v)$ have distance at least $1$, and if $\sigma(e)=-$, then $\psi(v)$ and the antipodal of $\psi(u)$ have distance at least $1$. The circular chromatic number $\chi_c(G, \sigma)$ of a signed graph $(G, \sigma)$ is the infimum of those $r$ for which $(G, \sigma)$ admits a circular $r$-coloring. For a graph $G$, we define the signed circular chromatic number of $G$ to be $\max\{\chi_c(G, \sigma): \sigma \text{ is a signature of $G$}\}$. We study basic properties of circular coloring of signed graphs and develop tools for calculating $\chi_c(G, \sigma)$. We explore the relation between the circular chromatic number and the signed circular chromatic number of graphs, and present bounds for the signed circular chromatic number of some families of graphs. In particular, we determine the supremum of the signed circular chromatic number of $k$-chromatic graphs of large girth, of simple bipartite planar graphs, $d$-degenerate graphs, simple outerplanar graphs and series-parallel graphs. We construct a signed planar simple graph whose circular chromatic number is $4+\frac{2}{3}$. This is based and improves on a signed graph built by Kardos and Narboni as a counterexample to a conjecture of Máčajová, Raspaud, and Škoviera.

OmpF Downregulation Mediated by Sigma E or OmpR Activation Confers Cefalexin Resistance in Escherichia coli in the Absence of Acquired β-Lactamases.

Cefalexin is a widely used 1st generation cephalosporin, and resistance in Escherichia coli is caused by Extended-Spectrum (e.g. CTX-M) and AmpC β-lactamase production and therefore frequently coincides with 3rd generation cephalosporin resistance. However, we have recently identified large numbers of E. coli isolates from human infections, and from cattle, where cefalexin resistance is not β-lactamase mediated. Here we show, by studying laboratory selected mutants, clinical isolates, and isolates from cattle, that OmpF porin disruption or downregulation is a major cause of cefalexin resistance in E. coli. Importantly, we identify multiple regulatory mutations that cause OmpF downregulation. In addition to mutation of ompR, already known to downregulate OmpF and OmpC porin production, we find that rseA mutation, which strongly activates the Sigma E regulon, greatly increasing DegP production, which degrades OmpF, OmpC and OmpA porins. Furthermore, we reveal that mutations affecting lipopolysaccharide structure, exemplified by the loss of GmhB, essential for lipopolysaccharide heptosylation, also modestly activate DegP production, resulting in OmpF degradation. Remarkably, given the critical importance attached to such systems for normal E. coli physiology, we find evidence for DegP-mediated OmpF downregulation, gmhB and rseA loss of function mutation in E. coli isolates derived from human infections. Finally, we show that these regulatory mutations enhance the ability of group 1 CTX-M β-lactamase to confer reduced carbapenem susceptibility, particularly those mutations that cause OmpC in addition to OmpF downregulation.

Influência da Fase Sigma na Resistência à Cavitação em Solda de Reparo de Aço Inoxidável Austenítico AISI 309L

Resumo: O reparo por soldagem de regiões erodidas por cavitação em rotores de turbinas hidráulicas é muitas vezes realizado utilizando como metal de adição o aço inoxidável austenítico AISI 309L. Ciclos térmicos provenientes dos sobrepasses, bem como a realização de tratamento térmico de alívio de tensão após a soldagem, induzem a formação de fase sigma na microestrutura do material depositado. Neste trabalho são apresentados resultados de ensaios de cavitação realizados conforme a norma ASTM G32-10 obtidos em depósitos de soldas do aço AISI 309L, com e sem fase sigma resultante de tratamentos térmicos. Os resultados do ensaio de cavitação revelaram que a fase sigma ocasionou a redução de 78% do período de incubação e o aumento de 30% da taxa de erosão máxima em comparação ao material sem esta fase. Infere-se que a redução do período de incubação estaria, a princípio, relacionada a diferenças de propriedades mecânicas entre a fase sigma e a matriz austenítica. Por outro lado, constatou-se que a taxa de erosão máxima seria resultante da presença da fase sigma a qual promoveu a redução da tenacidade do material

UM ESTUDO SOBRE A METODOLOGIA SEIS SIGMA

O atual cenário está cada vez mais competitivo e os clientes mais exigentes, pensando nisso iniciou-se a busca pela qualidade total e alta competitividade com o menor custo possível. O Seis Sigma, metodologia criada na década de 80 vem com esse objetivo, ele utiliza do embasamento estatístico para conquistar as metas estabelecidas. Tem como objetivo atingir a excelência na competitividade com a melhoria contínua dos processos, sendo uma estratégia gerencial para acelerar o aperfeiçoamento em processos, produtos e serviços. A expressão Sigma mensura a capacidade do processo a trabalhar isento de falhas. A contenção da oscilação no resultado cedido aos clientes em uma taxa de 3,4 imperfeições por milhão ou 99,99966% de perfeição define o Seis Sigma. O método se torna único e extremamente eficaz pela sua estruturação e foco na redução da variabilidade do processo. O estudo tem como objetivo apresentar os conceitos, definições e ferramentas do Seis Sigma e entender sua eficácia. A metodologia garantiu a empresa estudada uma economia de milhões de dólares além de maior produção, conquistaram a satisfação dos clientes e um maior desempenho dos colaboradores. A ferramenta DMAIC possibilitou maior comunicação e participação em equipe se tornando parte da cultura da empresa, garantindo assim que os colaboradores tivessem o mesmo nível de conhecimento da metodologia e ferramenta auxiliando na comunicação e tomada de decisões da empresa em conjunto com seus funcionários. Utilizando como metodologia de estudo revisão bibliográfica e estudo de caso.