Mathematical modelling of shallow flows: closure models drawn from grain-scale mechanics of sediment transport and flow hydrodynamics

Canadian Journal of Civil Engineering 36(10) 1605–16Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data

Motivos que influenciam a não-realização do exame de papanicolaou segundo a percepção de mulheres

O objetivo deste estudo foi analisar os motivos que influenciaram um grupo de mulheres a nunca ter realizado o exame de Papanicolaou mesmo após iniciarem a atividade sexual. É uma pesquisa qualitativa. Utilizou-se a entrevista a partir da questão norteadora: Por que você nunca tinha realizado o exame preventivo anteriormente? A técnica da análise de conteúdo proposta por Bardin foi utilizada para a análise das descrições. As mulheres demonstraram desconhecimento do câncer, da técnica e da importância do preventivo. Revelaram ainda medo na realização e resultado do exame. A vergonha e o constrangimento foram sentimentos expressados por elas pela exposição da intimidade a que se submetem. Expressaram ainda possuírem valores culturais que dificultam mudança de atitude. O acesso ao serviço, ter emprego e filhos também foram relatados como impedimento. Os resultados mostram a importância de ações educativas sobre a necessidade do preventivo ao iniciar as atividades sexuais e desmistificar a técnica e resultado.El objetivo de este estudio fue analizar las razones que influenciaron un grupo de mujeres que nunca realizaron la prueba de Papanicolaou mismo después de que iniciaron la actividad sexual. Es una investigación cualitativa, se utilizó la entrevista con la cuestión guía: ¿Por que nunca había usted realizado el examen preventivo anteriormente? La técnica del análisis de contenido propuesta por Bardin fue utilizada para el análisis de las descripciones. Las mujeres demostraron desconocimiento del cáncer, de la técnica y de la importancia del preventivo. Revelaron aun miedo en la realización y resultado del examen. La vergüenza y reparo fueron sentimientos que expresaron por la exposición de la intimidad a la que se someten. También dijeron poseer valores culturales que dificultan un cambio de actitud. El acceso al servicio, tener trabajo e hijos también fueron relatados como impedimento. Los resultados muestran la importancia de acciones educativas sobre la necesidad del preventivo al iniciar las actividades sexuales y desmitificar la técnica y resultado.The aim of this study was to analyze reasons which influenced a group of women on never having done the Papanicolaou test, even after they started their sexual life. It was a qualitative research and the question "Why have you never done the preventive exam before?" was asked during the approach. The descriptions were analyzed through Bardin´s content analysis technique. Women showed not to know much about cancer and the importance and techniques for prevention. They also revealed to be afraid of doing the exam and knowing the result. Shame and embarrassment were feelings expressed by women, due to the intimacy exposition they're submitted to. They also expressed cultural values which make attitude changing difficult. Having a job, children and the access to this kind of service were related as impediment factors too. The results showed the importance of educational actions on the necessity of prevention in the beginning of sexual activities, as well as the demystification of techniques and results

Turbulence in Rivers

The study of turbulence has always been a challenge for scientists working on geophysical flows. Turbulent flows are common in nature and have an important role in geophysical disciplines such as river morphology, landscape modeling, atmospheric dynamics and ocean currents. At present, new measurement and observation techniques suitable for fieldwork can be combined with laboratory and theoretical work to advance the understanding of river processes. Nevertheless, despite more than a century of attempts to correctly formalize turbulent flows, much still remains to be done by researchers and engineers working in hydraulics and fluid mechanics. In this contribution we introduce a general framework for the analysis of river turbulence. We revisit some findings and theoretical frameworks and provide a critical analysis of where the study of turbulence is important and how to include detailed information of this in the analysis of fluvial processes. We also provide a perspective of some general aspects that are essential for researchers/ practitioners addressing the subject for the first time. Furthermore, we show some results of interest to scientists and engineers working on river flows

Geomorphic dam-break flows. Part I: conceptual model

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM6This paper presents a one-dimensional conceptual model for simulating geomorphic dam-break flows. The model is based on conservation laws drawn from continuum mixture theory that are integrated over the flow depth,assuming that the f10w is composed of two transport layers. Closure equations were derived from the review and reanalysis of previous studies on granular flow,debris f10w and sheet flow. The sediment transport is modelled assuming capacity regime. The c10sure equation coefficients are estimated based on a large set of experiments available in the literature. The validity of the model is discussed by computing the most relevant dimensionless parameters. The model is expected to simulate adequately the friction at the wave front and the sheet flow throughout the wave profile. Ultimately, although the problem incorporates complex phenomena,the model can be easily implemented by practising engineers for simulating one- dimensional geomorphic dam-break flows. The implementation and the verification of the adequacy of the model for simulating these flows are presented in a 'companion paper

Geomorphic dam-break flows. Part I: conceptual model

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM6This paper presents a one-dimensional conceptual model for simulating geomorphic dam-break flows. The model is based on conservation laws drawn from continuum mixture theory that are integrated over the flow depth,assuming that the f10w is composed of two transport layers. Closure equations were derived from the review and reanalysis of previous studies on granular flow,debris f10w and sheet flow. The sediment transport is modelled assuming capacity regime. The c10sure equation coefficients are estimated based on a large set of experiments available in the literature. The validity of the model is discussed by computing the most relevant dimensionless parameters. The model is expected to simulate adequately the friction at the wave front and the sheet flow throughout the wave profile. Ultimately, although the problem incorporates complex phenomena,the model can be easily implemented by practising engineers for simulating one- dimensional geomorphic dam-break flows. The implementation and the verification of the adequacy of the model for simulating these flows are presented in a 'companion paper

Geomorphic dam-break flows. Part II: numerical simulation

Proceedings of the Institution of Civil Engineers - Water Management 163 Issue WM

X-ray Free Electron Laser Determination of Crystal Structures of Dark and Light States of a Reversibly Photoswitching Fluorescent Protein at Room Temperature.

The photochromic fluorescent protein Skylan-NS (Nonlinear Structured illumination variant mEos3.1H62L) is a reversibly photoswitchable fluorescent protein which has an unilluminated/ground state with an anionic and cis chromophore conformation and high fluorescence quantum yield. Photo-conversion with illumination at 515 nm generates a meta-stable intermediate with neutral trans-chromophore structure that has a 4 h lifetime. We present X-ray crystal structures of the cis (on) state at 1.9 Angstrom resolution and the trans (off) state at a limiting resolution of 1.55 Angstrom from serial femtosecond crystallography experiments conducted at SPring-8 Angstrom Compact Free Electron Laser (SACLA) at 7.0 keV and 10.5 keV, and at Linac Coherent Light Source (LCLS) at 9.5 keV. We present a comparison of the data reduction and structure determination statistics for the two facilities which differ in flux, beam characteristics and detector technologies. Furthermore, a comparison of droplet on demand, grease injection and Gas Dynamic Virtual Nozzle (GDVN) injection shows no significant differences in limiting resolution. The photoconversion of the on- to the off-state includes both internal and surface exposed protein structural changes, occurring in regions that lack crystal contacts in the orthorhombic crystal form