Moving constraints as stabilizing controls in classical mechanics

The paper analyzes a Lagrangian system which is controlled by directly assigning some of the coordinates as functions of time, by means of frictionless constraints. In a natural system of coordinates, the equations of motions contain terms which are linear or quadratic w.r.t.time derivatives of the control functions. After reviewing the basic equations, we explain the significance of the quadratic terms, related to geodesics orthogonal to a given foliation. We then study the problem of stabilization of the system to a given point, by means of oscillating controls. This problem is first reduced to the weak stability for a related convex-valued differential inclusion, then studied by Lyapunov functions methods. In the last sections, we illustrate the results by means of various mechanical examples.Comment: 52 pages, 4 figure

The boundary Riemann solver coming from the real vanishing viscosity approximation

We study a family of initial boundary value problems associated to mixed hyperbolic-parabolic systems: v^{\epsilon} _t + A (v^{\epsilon}, \epsilon v^{\epsilon}_x ) v^{\epsilon}_x = \epsilon B (v^{\epsilon} ) v^{\epsilon}_{xx} The conservative case is, in particular, included in the previous formulation. We suppose that the solutions $v^{\epsilon}$ to these problems converge to a unique limit. Also, it is assumed smallness of the total variation and other technical hypotheses and it is provided a complete characterization of the limit. The most interesting points are the following two. First, the boundary characteristic case is considered, i.e. one eigenvalue of $A$ can be $0$. Second, we take into account the possibility that $B$ is not invertible. To deal with this case, we take as hypotheses conditions that were introduced by Kawashima and Shizuta relying on physically meaningful examples. We also introduce a new condition of block linear degeneracy. We prove that, if it is not satisfied, then pathological behaviours may occur.Comment: 84 pages, 6 figures. Text changes in Sections 1 and 3.2.3. Added Section 3.1.2. Minor changes in other section

On the Demand for Meat in Brazil

We used alternative specifications of the Almost Ideal Demand System to estimate the aggregate demand for beef, pork, chicken, and other consumption goods and their elasticities in Brazil. We detected the need for using time trend variables in models’ equations so that an upward trend for each meat demand and a downward trend for other consumption goods were found. The dummy variable for the prices stabilization macroeconomic Real Plan indicated it has not affected demands. According to Marshallian own-price elasticities, demands for meats are inelastic and the demand for other consumption goods is elastic. Cross-price Marshallian and Hicksian elasticities confirm beef, pork and chicken are substitutes one to each other. Expenditure elasticities showed all goods are normal, except for pork which is an inferior good. As personal consumption expenditure increases over time, ceteris paribus, meat consumption will lose importance to other consumption goods, beef consumption will lose importance to chicken, and pork consumption will lose importance to the other types of meat.Meat demand; Almost Ideal Demand System; elasticities; Brazil

Infinite reflections of shock fronts in driven diffusive systems with two species

Interaction of a domain wall with boundaries of a system is studied for a class of stochastic driven particle models. Reflection maps are introduced for the description of this process. We show that, generically, a domain wall reflects infinitely many times from the boundaries before a stationary state can be reached. This is in an evident contrast with one-species models where the stationary density is attained after just one reflection.Comment: 11 pages, 8 eps figs, to appearin JPhysA 01.200

Priorities for Cancer Research From the Viewpoints of Cancer Nurses and Cancer Patients: A Mixed-Method Systematic Review

BACKGROUND: Setting priorities in oncology is a useful way to produce a robust set of research questions that researchers can address. OBJECTIVE: The aim of this review was to describe cancer nurses and patients' main research priorities and describe their development over time. METHODS: A mixed-method systematic review was conducted for the period from 2000 to 2018 through a search of multiple databases. The methodological quality of the studies included was assessed using the Mixed-Methods Appraisal Tool, and the process of setting the health research priorities was assessed using Viergever's tool. Each study's top research priorities were extracted and summarized in categories. RESULTS: Fifteen studies were included: 13 addressed nurses' research priorities, and 2 focused on those of patients. The majority were Delphi and quantitative studies that were conducted in the United States and United Kingdom. The quality criteria score and the quality of the process were considered sufficiently good. The most important research priorities were categorized as disease control and management, patient-related issues, and professional dimensions and issues. Management of symptoms and pain, education, information, and communication were research priorities always present in the articles during the study period. CONCLUSION: Priorities change over time and depend on several factors; however, some have remained consistent for the last 18 years. Although there is increasing emphasis on including patients in establishing research priorities that inform cancer care, this involvement is still lacking. IMPLICATIONS FOR PRACTICE: Future studies should describe the primary cancer research priorities of nurses in collaboration with patients

Acquisition efficiency of Flavescence dorée phytoplasma by Scaphoideus titanus Ball from infected tolerant or susceptible grapevine cultivars or experimental host plants

The rate of Flavescence dorée phytoplasma (FDP) acquisition by the leafhopper vector Scaphoideus titanus Ball was tested under field and glass house conditions confining healthy reared nymphs on canes of FDP-infected grapevines or on FDP-infected cuttings collected in the field during the dormant season. Acquisition tests were performed using FD-tolerant (Merlot) or highly susceptible (Pinot blanc) grapevine cultivars, or alternatively using experimentally infected broadbean plants. Frequency of FDP acquisition by leafhoppers was evaluated using a polymerase chain reaction (PCR) assay. Different batches of insects were confined on the same infected source plants in the vineyard for acquisition access periods (AAP) of 7 d at a time at intervals of 15-20 d during spring and summer. When diseased Pinot blanc grapevines were used as source plants, acquisition by leafhoppers and transmission to healthy grapevines increased over summer, while almost no acquisition or transmission was observed when diseased Merlot grapevines were used as source plants. Tests conducted under controlled conditions confirmed that Merlot is a poorer source of FDP than Pinot blanc; the optimum FDP source for S. titanus was broadbean although this plant is not a natural host of the leafhopper. It is assumed that grapevine cultivars play an important role in influencing the proportion of FDP-infected leafhoppers in the vineyards and therefore influencing the rate of disease progress.

El Congreso Nacional y los proyectos para la construcción de los Ferrocarriles en el Litoral. Corrientes y Entre Ríos, 1862-1880.

El presente artículo aborda el desarrollo de los proyectos ferroviarios para las provincias de Corrientes y Entre Ríos durante la etapa de construcción del Estado-Nación. El análisis se centra en los debates parlamentarios que tuvieron lugar durante las décadas de 1860 y 1870 e indaga cuál fue el rol desempeñado por los legisladores y por diversos actores, a nivel nacional y provincial, en la promoción de los ferrocarriles diseñados para estas provincias. A partir del examen de fuentes como los diarios de sesiones de la cámara de diputados y senadores, correspondencia particular y oficial de los funcionarios públicos y artículos periodísticos, se busca repensar los vínculos establecidos entre el Estado nacional y las elites provinciales -planteados por estudios ya clásicos como relaciones de cooptación- y mostrar las interacciones y conflictos entre las instituciones nacionales y provinciales que arbitraron la dirección de las políticas públicas en las provincias del litoral

Sistema de classificação fuzzy para o risco de infestação por plantas daninhas considerando a sua variabilidade espacial.

Este artigo trata do problema de classificação do risco de infestação por plantas daninhas usando técnicas geoestatísticas, análise de imagens e modelos de classificação fuzzy. Os principais atributos utilizados para descrever a infestação incluem a densidade de sementes, bem como a sua extensão, a cobertura foliar e a agressividade das plantas daninhas em cada região. A densidade de sementes reflete a produção de sementes por unidade de área, e a sua extensão, a influência das sementes vizinhas; a cobertura foliar indica a extensão dos agrupamentos das plantas daninhas emergentes; e a agressividade descreve a porcentagem de ocupação de espécies com alta capacidade de produção de sementes. Os dados da densidade de sementes, da cobertura foliar e da agressividade para as diferentes regiões são obtidos a partir de simulação com modelos matemáticos de populações. Neste artigo propõe-se um sistema de classificação fuzzy utilizando os atributos descritos para inferir os riscos de infestação de regiões da cultura por plantas daninhas. Resultados de simulação são apresentados para ilustrar o uso desse sistema na aplicação localizada de herbicida