How does flow in a pipe become turbulent?

The transition to turbulence in pipe flow does not follow the scenario familiar from Rayleigh-Benard or Taylor-Couette flow since the laminar profile is stable against infinitesimal perturbations for all Reynolds numbers. Moreover, even when the flow speed is high enough and the perturbation sufficiently strong such that turbulent flow is established, it can return to the laminar state without any indication of the imminent decay. In this parameter range, the lifetimes of perturbations show a sensitive dependence on initial conditions and an exponential distribution. The turbulence seems to be supported by three-dimensional travelling waves which appear transiently in the flow field. The boundary between laminar and turbulent dynamics is formed by the stable manifold of an invariant chaotic state. We will also discuss the relation between observations in short, periodically continued domains, and the dynamics in fully extended puffs.Comment: for the proceedings of statphys 2

Travelling waves in pipe flow

A family of three-dimensional travelling waves for flow through a pipe of circular cross section is identified. The travelling waves are dominated by pairs of downstream vortices and streaks. They originate in saddle-node bifurcations at Reynolds numbers as low as 1250. All states are immediately unstable. Their dynamical significance is that they provide a skeleton for the formation of a chaotic saddle that can explain the intermittent transition to turbulence and the sensitive dependence on initial conditions in this shear flow.Comment: 4 pages, 5 figure

The effective electroweak mixing angle sin⁡2θeff\sin^2\theta_{eff} with two-loop fermionic contributions

We present the results from a calculation of the full electroweak two-loop fermionic contributions to the effective leptonic mixing angle of the $Z$ boson, $\sin^2\theta_{eff}$, in the Standard Model. On-shell renormalization and analytic calculations are performed for the three-point vertex functions at zero external momenta, whereas irreducible three-point integrals for non-vanishing external momenta are evaluated semi-analytically applying two different methods. Comparisons with a previous calculation show complete agreement.Comment: 15 pages, 5 figures, reference added, few typos correcte

The effective electroweak mixing angle sin⁡2θeff\sin^2\theta_{eff} with two-loop bosonic contributions

We present the results for the full electroweak two-loop bosonic contributions to the effective leptonic mixing angle of the $Z$ boson, $\sin^2\theta_{\rm eff}$, in the Standard Model. A method applied to extract collinear divergences from two-loop vertex-functions is described. Comparisons of our results with those from a recent previous calculation show complete agreement.Comment: 14 pages, 3 figures, 4 table

Calidad de servicio y su relación con la satisfacción del cliente en la empresa comercial y eventos Dibu E.I.R.L Juliaca, durante el año 2019

El objetivo de la presente investigación es determinar la calidad del servicio y su relación con la satisfacción del cliente de Comercial y eventos Dibu E.I.R.L Juliaca durante el año 2019, el tipo de investigación es descriptiva correlacional, de diseño no experimental de corte transversal. La muestra estuvo conformada por los clientes de la empresa, habiendo un total de 118 personas de manera aleatoria, la técnica que se utilizó fue la encuesta, a través de un cuestionario de 28 ítems correspondientes a las dimensiones de las variables, cuyas respuestas se midieron con la escala Likert de cinco alternativas. El procesamiento y generación de las tablas y figuras de los datos recolectados en este trabajo de investigación, fueron obtenidos con el programa SPSS. Los resultados de la investigación demuestran una correlación de Pearson R= 0.572 la cual nos indica que las variables calidad de servicio y satisfacción del cliente hay una correlación positiva moderada. Por lo que se concluye que los colaboradores de la empresa dan a sus clientes tangibilidad, fiabilidad y sobre todo la capacidad de respuesta eficiente logrando así una satisfacción grata en el cliente.Trabajo de investigaciónJULIACAEscuela Profesional de AdministraciónMarketin

The -786T>C promoter polymorphism of the NOS3 gene is associated with prostate cancer progression

<p>Abstract</p> <p>Background</p> <p>There is no biological or epidemiological data on the association between <it>NOS3 </it>promoter polymorphisms and prostate cancer. The polymorphisms in the promoter region of <it>NOS3 </it>gene may be responsible for variations in the plasma NO, which may promote cancer progression by providing a selective growth advantage to tumor cells by angiogenic stimulus and by direct DNA damage.</p> <p>Methods</p> <p>This study aimed evaluating the <it>NOS3 </it>promoter polymorphisms by PCR-SSCP and sequencing, associating genotypes and haplotypes with <it>NOS3 </it>expression levels through semi-quantitative RT-PCR, and with <it>PCA</it>3 mRNA detection, a specific tumor biomarker, in the peripheral blood of pre-surgical samples from 177 patients; 83 PCa and 94 BPH.</p> <p>Results</p> <p>Three novel SNPs were identified -764A>G, -714G>T and -649G>A in the <it>NOS3 </it>gene promoter region, which together with the -786T>C generated four haplotypes (N, T, C, A). <it>NOS3 </it>gene expression levels were affected by the -786T>C polymorphism, and there was a 2-fold increase in <it>NOS3 </it>levels favored by the incorporation of each C allele. <it>NOS3 </it>levels higher than 80% of the constitutive gene expression level (<it>B2M</it>) presented a 4-fold increase in PCa occurrence.</p> <p>Conclusion</p> <p>The -786T>C polymorphism was the most important promoter alteration of the <it>NOS3 </it>gene that may affect the PCa progression, but not its occurrence, and the incorporation of the C allele is associated with increased levels of <it>NOS3 </it>transcripts. The <it>NOS3 </it>transcript levels presented a bimodal behavior in tumor development and may be used as a biomarker together with the <it>PCA3 </it>marker for molecular staging of the prostate cancer.</p

W mass and Leptonic Z-decays in the NMSSM

We study a subset of electroweak-precision observables consisting of $M_W$, $\sin^2\theta_{{\tiny eff}}^{\tau}$, $BR(Z\to\tau^+\tau^-)$ and $\Gamma(Z\to\tau^+\tau^-)/\Gamma(Z\to e^+e^-)-1$ (characterizing leptonic $Z$-decays) in the context of the NMSSM. After a brief review of common MSSM-NMSSM effects, e.g. for $\Gamma(Z\to\tau^+\tau^-)/\Gamma(Z\to e^+e^-)-1$, which has been little discussed, even in the MSSM), specific NMSSM scenarios are studied, with the result that the NMSSM, considering existing constraints on its spectrum, is essentially consistent with available measurements, given the current accuracy.Comment: 25 pages, 12 figure

Economic Valuation for Information Security Investment: A Systematic Literature Review

Research on technological aspects of information security risk is a well-established area and familiar territory for most information security professionals. The same cannot be said about the economic value of information security investments in organisations. While there is an emerging research base investigating suitable approaches measuring the value of investments in information security, it remains difficult for practitioners to identify key approaches in current research. To address this issue, we conducted a systematic literature review on approaches used to evaluate investments in information security. Following a defined review protocol, we searched several databases for relevant primary studies and extracted key details from the identified studies to answer our research questions. The contributions of this work include: a comparison framework and a catalogue of existing approaches and trends that would help researchers and practitioners navigate existing work; categorisation and mapping of approaches according to their key elements and components; and a summary of key challenges and benefits of existing work, which should help focus future research efforts