Global gene expression under nitrogen starvation in Xylella fastidiosa: contribution of the sigma(54) regulon

Background: Xylella fastidiosa, a Gram-negative fastidious bacterium, grows in the xylem of several plants causing diseases such as citrus variegated chlorosis. As the xylem sap contains low concentrations of amino acids and other compounds, X. fastidiosa needs to cope with nitrogen limitation in its natural habitat. Results: In this work, we performed a whole-genome microarray analysis of the X. fastidiosa nitrogen starvation response. A time course experiment (2, 8 and 12 hours) of cultures grown in defined medium under nitrogen starvation revealed many differentially expressed genes, such as those related to transport, nitrogen assimilation, amino acid biosynthesis, transcriptional regulation, and many genes encoding hypothetical proteins. In addition, a decrease in the expression levels of many genes involved in carbon metabolism and energy generation pathways was also observed. Comparison of gene expression profiles between the wild type strain and the rpoN null mutant allowed the identification of genes directly or indirectly induced by nitrogen starvation in a sigma(54)-dependent manner. A more complete picture of the sigma(54) regulon was achieved by combining the transcriptome data with an in silico search for potential sigma(54)-dependent promoters, using a position weight matrix approach. One of these sigma(54)-predicted binding sites, located upstream of the glnA gene (encoding glutamine synthetase), was validated by primer extension assays, confirming that this gene has a sigma(54)-dependent promoter. Conclusions: Together, these results show that nitrogen starvation causes intense changes in the X. fastidiosa transcriptome and some of these differentially expressed genes belong to the sigma(54) regulon.

Sublattice magnetism in sigma-phase Fe(100-x)Vx (x=34.4, 39.9, and 47.9) studied via zero-field (51)V NMR

The successful measurements of a sublattice magnetism with (51)V NMR techniques in the sigma-phase Fe(100-x)V(x) alloys with x=34.4, 39.9, and 47.9 are reported. Vanadium atoms, which were revealed to be present on all five crystallographic sites, are found to be under the action of the hyperfine magnetic fields produced by the neighboring Fe atoms, which allow the observation of (51)V NMR signals. Their nuclear magnetic properties are characteristic of a given site, which strongly depend on the composition. Site A exhibits the strongest magnetism while site D is the weakest. The estimated average magnetic moment per V atom decreases from 0.36 mu(B) for x=34.4 to 0.20 mu(B) for x=47.9. The magnetism revealed at V atoms is linearly correlated with the magnetic moment of Fe atoms, which implies that the former is induced by the latter.

Sigma phase morphologies in cast and aged super duplex stainless steel

Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material`s impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 degrees C and 980 degrees C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 degrees C and block-shaped when heat treated at 980 degrees C. (C) 2009 Elsevier Inc. All rights reserved.

Ultrasound, eddy current and magnetic Barkhausen noise as tools for sigma phase detection on a UNS S31803 duplex stainless steel

Sigma phase is a deleterious one which can be formed in duplex stainless steels during heat treatment or welding. Aiming to accompany this transformation, ferrite and sigma percentage and hardness were measured on samples of a UNS S31803 duplex stainless steel submitted to heat treatment. These results were compared to measurements obtained from ultrasound and eddy current techniques, i.e., velocity and impedance, respectively. Additionally, backscattered signals produced by wave propagation were acquired during ultrasonic inspection as well as magnetic Barkhausen noise during magnetic inspection. Both signal types were processed via a combination of detrended-fluctuation analysis (DFA) and principal component analysis (PCA). The techniques used were proven to be sensitive to changes in samples related to sigma phase formation due to heat treatment. Furthermore, there is an advantage using these methods since they are nondestructive. (C) 2010 Elsevier B.V. All rights reserved.

Short-term spatial diffusion in sigma o+ o- optical molasses

We have measured the spatial diffusion of atoms in a three-dimensional sigma(+)-sigma(-) optical molasses over twenty milliseconds timescale, starting from the initial interaction of the atoms with the molasses. We find that the diffusion constants agree well with a linear model for these short time scales and also compare favourably to other studies of diffusion made over longer time scales. These measurements enable us to quantify the detection method known as freezing molasses. We discuss this method, for detecting and measuring the momentum distribution of cold atoms, which relies on the slow diffusion of atoms in optical molasses to produce a freeze-frame of the spatial distribution of the atoms. This method enables a longer interrogation interval, providing a greatly increased signal-to-noise ratio. (C) 1998 Elsevier Science B.V.

The impact of Six Sigma in the performance of a Pollution Prevention program

The diffusion of Pollution Prevention faces organizational barriers as for instance resistance to change, insufficient support from decision-makers, unclear project leadership, insufficient employee accountability and inflexible organizational structures. To understand how to overcome such barriers, the performance of a Pollution Prevention program of a multinational corporation is analyzed. The quantitative analyses of 2096 Pollution Prevention projects conducted between 1995 and 2007 support the conclusion that the performance of the Pollution Prevention program increased after the implementation of the Six Sigma program. Moreover, the analyses of 1906 Pollution Prevention projects and 31,133 Six Sigma projects for cost reduction in 27 countries indicate that in countries where the implementation of Six Sigma is more expressive, pollution is prevented more than in countries with less expressive Six Sigma implementation. In fact, the Six Sigma implementation improved the organizational capability for data based project management. Therefore, comparing six years before and six years after the Six Sigma implementation, the total number of Pollution Prevention projects recognized increased 6.9 times and the total amount of pollution prevented increased by 62%. The qualitative analysis describes how the Six Sigma program interacts with the Pollution Prevention program in the studied company. (C) 2009 Elsevier Ltd. All rights reserved.

Proteomic analysis reveals that 14-3-3 sigma in downregulated in human breast cancer cells

The class of molecular chaperones known as 14-3-3 is involved in the control of cellular growth by virtue of its apparent regulation of various signaling pathways, including the Raf/mitogen-activated protein kinase pathway. In breast cancer cells, the sigma form of 14-3-3 has been shown to interact with cyclin-dependent kinases and to control the rate of entry into mitosis. To test for a direct role for 14-3-3 in breast epithelial cell neoplasia, me have quantitated 14-3-3 protein levels using a proteomic approach based on two-dimensional electrophoresis and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF). We show here that 14-3-3 sigma protein is strongly down-regulated in the prototypic breast cancer cell lines MCF-7 and MDA-MB-231 and in primary breast carcinomas as compared with normal breast epithelial cells. In contrast, levels of the alpha, beta, delta, or zeta isoforms of 14-3-3 mere the same in both normal and transformed cells. The data support the idea that 14-3-3 sigma is involved in the neoplastic transition of breast epithelial cells by virtue of its role as a tumor suppressor; as such, it may constitute a robust marker with clinical efficacy for this pathology.

"Seis sigma": uma nova cultura empresarial

Existe uma miríade de ferramentas para a gestão da qualidade. A grande maioria apareceu no meio industrial, e algumas ultrapassaram barreiras, chegando a todas as áreas de negócio. O processo Seis Sigma é uma ferramenta que se destacou pela sua versatilidade e eficácia, e alcançou uma grande notoriedade na indústria fabril. O discente teve a oportunidade de contactar com o processo Seis Sigma, que evidenciou a sua validade, como ferramenta poderosa em qualquer área de negócio. Baseado nesse trabalho, pretende-se demonstrar a mais-valia que esta ferramenta apresenta, e que, com empenho e dedicação, todos podem usar. Os objectivos deste trabalho são: • Identificar o valor superior numa empresa do ramo automóvel na implementação de um processo Seis Sigma numa área de BackOffice; • Verificar se após o fim do projecto Seis Sigma, as medidas implementadas continuam a produzir efeitos. Metodologia usada para a execução deste trabalho • O discente, com a função de Green Belt, foi o responsável pela implementação de um projecto Seis Sigma. No seguimento do que já havia sido efectuado no projecto Seis Sigma, este trabalho usou a ferramenta DMAIC (ver p.5) como metodologia para a sua execução. Conclusões Ficou demonstrado com este projecto, em que o discente teve um profundo envolvimento, que a metodologia Seis Sigma ao ser aplicada num qualquer processo repetitivo de trabalho vai: • Obrigar a repensar todos os procedimentos instalados procurando todas as oportunidades demelhoria; • Criar novas ferramentas para dar solução às oportunidades encontradas; • Verificar a validade e mais-valia nas novas ferramentas e procedimentos; • Em função da constante verificação, melhorar as ferramentas e procedimentos instalados, ou criar novos procedimentos ou ferramentas; • De uma forma permanente, continuar a analisar o processo, monitorizando a qualidade e a procura de novas oportunidades de melhoria. O facto de o processo Seis Sigma obrigar a uma introspecção ao trabalho realizado, e, tornar todo o processo de melhoria sistemático, faz com que seja sempre uma mais-valia a sua aplicação, num ambiente fabril, ou de BackOffice. Ainda que o processo Seis Sigma seja terminado a dada altura, as melhorias que trouxe e as ferramentas que foram desenvolvidas para a sua execução ficam, deixando um legado de melhoria de processos, que, por si só, justificam a sua implementação.

A prova dos 9 : "valores sigma"

Neste artigo abordam-se as provas dos nove para quatro operações aritméticas elementar, bem como o valor sigma que é a soma dos algarismos de um numeral retirados os noves.

Sistema de transmissão rádio UWB para amplificação digital de áudio com modulação sigma-delta

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Electrotécnica e de Computadores

Multi-bit sigma-delta modulators with enhanced dynamic-range using non-linear DAC for hearing aids

15th IEEE International Conference on Electronics, Circuits and Systems, Malta

Implementação da metodologia 6 sigma no processo de facturação

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Industrial

Six sigma methodologies: implementation and impacts on Portuguese small and medium companies (SMES)

Artigo elaborador no âmbito dos trabalhos decorrentes à dissertação de Mestrado do Aluno David Leite, no Mestrado em Gestão Integrada Qualidade, Ambiente e Segurança, ESTGF-IPP, Oreintados pelos Professores Luís Fonseca (ISEP-IPP) e Vanda Lima (ESTGF-IPP).

Evolução das freguesias da cidade de Lisboa ao longo do século XIX – SIGMA, SIG e Modelação de Dados Aplicados à História de Portugal

As freguesias de Lisboa sofreram profundas alterações ao longo dos séculos XIX e XX. Não só foram alteradas em número, mas também na sua dimensão geográfica. A última grande reforma, datada de 1959, modificou de tal forma os contornos das freguesias lisboetas que inviabiliza a utilização dos contornos actuais para a realização de estudos no passado. Procurando dar resposta a esta problemática e com base em cartografia histórica, foram desenhadas as freguesias em três períodos (1826, 1852 e 1909) sendo incluídas num sistema de informação geográfica, o que possibilita não só a análise da evolução administrativa da capital, mas também o estudo de muitas variáveis históricas, de base paroquial, para todo o século XIX e início do século XX.

Metodologia Seis Sigma: Implementação e Impacto nas PMEs Portuguesas

Dissertação de Mestrado em Gestão Integrada da Qualidade, Ambiente e Segurança