Motility fractionation of bacteria by centrifugation

Centrifugation is a widespread laboratory technique used to separate mixtures into fractions characterized by a specific size, weight or density. We demonstrate that centrifugation can be also used to separate swimming cells having different motility. To do this we study self-propelled bacteria under the influence of an external centrifugal field. Using dynamic image correlation spectroscopy we measure the spatially resolved motility of bacteria after centrifugation. A significant gradient in swimming-speeds is observed for increasing centrifugal speeds. Our results can be reproduced by a model that treats bacteria as "hot" colloidal particles having a diffusion coefficient that depends on the swimming speed.Comment: 7 pages, 5 figures (in press

Sensitivity analysis of agent-based models: a new protocol

Agent-based models (ABMs) are increasingly used in the management sciences. Though useful, ABMs are often critiqued: it is hard to discern why they produce the results they do and whether other assumptions would yield similar results. To help researchers address such critiques, we propose a systematic approach to conducting sensitivity analyses of ABMs. Our approach deals with a feature that can complicate sensitivity analyses: most ABMs include important non-parametric elements, while most sensitivity analysis methods are designed for parametric elements only. The approach moves from charting out the elements of an ABM through identifying the goal of the sensitivity analysis to specifying a method for the analysis. We focus on four common goals of sensitivity analysis: determining whether results are robust, which elements have the greatest impact on outcomes, how elements interact to shape outcomes, and which direction outcomes move when elements change. For the first three goals, we suggest a combination of randomized finite change indices calculation through a factorial design. For direction of change, we propose a modification of individual conditional expectation (ICE) plots to account for the stochastic nature of the ABM response. We illustrate our approach using the Garbage Can Model, a classic ABM that examines how organizations make decisions

Sensitivity analysis of agent-based models: a new protocol

Agent-based models (ABMs) are increasingly used in the management sciences. Though useful, ABMs are often critiqued: it is hard to discern why they produce the results they do and whether other assumptions would yield similar results. To help researchers address such critiques, we propose a systematic approach to conducting sensitivity analyses of ABMs. Our approach deals with a feature that can complicate sensitivity analyses: most ABMs include important non-parametric elements, while most sensitivity analysis methods are designed for parametric elements only. The approach moves from charting out the elements of an ABM through identifying the goal of the sensitivity analysis to specifying a method for the analysis. We focus on four common goals of sensitivity analysis: determining whether results are robust, which elements have the greatest impact on outcomes, how elements interact to shape outcomes, and which direction outcomes move when elements change. For the first three goals, we suggest a combination of randomized finite change indices calculation through a factorial design. For direction of change, we propose a modification of individual conditional expectation (ICE) plots to account for the stochastic nature of the ABM response. We illustrate our approach using the Garbage Can Model, a classic ABM that examines how organizations make decisions

Régimen jurídico básico de la función pública : análisis de la Ley 22.140 y su relación con la normativa laboral

Fil: Rizzo, Gabriel Leonardo. Universidad de Buenos Aires. Facultad de Derecho. Cátedra Teoría del Estado. Buenos Aires, Argentin

Honeycomb Seal Effect on Rotor Response to Unbalance

LectureHigh pressure centrifugal compressors are often equipped with honeycomb seal on balance drum in order to optimize rotordynamic stability. In very high pressures applications (>200 bar) the direct stiffness and damping of the honeycomb seal may reach the same order of magnitude of the journal bearings, thus altering the peak frequency and amplification factor of rotor critical speeds as well as their mode shapes. This phenomenon is ultimately due to the density and viscosity of the gas leakage flowing through the seal, and it has a substantial effect on the rotordynamic behavior of the compressor. According to current standards, aerodynamic seal effects are not necessarily included in the calculation of rotor response to unbalance. For high pressure compressors equipped with a honeycomb seal, the associated aerodynamic effects may have major impacts on rotor critical speeds in terms of frequency, amplitude and amplification factor. A procedure for the calculation of rotor response in loaded condition is here proposed, aiming to improve the predictability of the rotordynamic analysis and to provide practical criteria for the evaluation of the outcome. A back-to-back compressor with final discharge pressure of 386 bar is presented as case study; it was tested at full pressure at Authors’ Company facilities in 2013. In this case the stiffening effect of the honeycomb seal is particularly relevant, since it is positioned close to rotor midspan. Test measures show that in loaded condition the 1st critical speed shifts upwards by several thousand rpm, eventually exceeding the Maximum Critical Speed and even the Trip Speed of the compressor

MAPPING THE RISK OF FOREST FIRES IN THE RIO PRETO NATIONAL FOREST IN THE ATLANTIC FOREST

The Atlantic Forest biome is annually exposed to forest fires that damage thousands of hectares of forest, promote the formation of forest fragments, the destruction of biodiversity, soil compaction, runoff and silting of water bodies. Thus, the prediction and suppression of fire outbreaks are important to minimize the damage caused by fire. In this sense, this study aimed to analyze and model the risk of forest fires occurring in the Rio Preto National Forest and its buffer zone using the Fuzzy artificial intelligence technique. To do so, the land use and occupation, proximity to roads, slope and relief orientation variables were used to compose the model. Thus, the influence of each variable on burning episodes was determined with the aid of geographic information systems (GIS), as well as the spatial distribution of each of the risk classes (very low, low, moderate and high). a historical series of fires between the years 2010 and 2020 was used to perform a comparative analysis of the model. The results showed that the study area does not present worrisome risks regarding the occurrence of fires, since it is mostly covered by very low and low risk classes. Thus, it can be concluded that the application of Fuzzy modeling enables evaluating the spatial distribution of fire risk classes for the protected area areas, for which the proposed comparative analysis indicated the model’s effectiveness

Plan operativo anual para la Asociación Jimbitono 26 de Agosto del cantón Morona, de la provincia de Morona Santiago, período 2014-2015

El presente trabajo está orientado al diseño y elaboración de Un Plan Operativo Anual para La Asociación Jimbitono 26 de Agosto del Cantón Morona, de la Provincia de Morona Santiago, periodo 2014-2015; siendo el principal problema, no contar con un direccionamiento planificado, se realiza una administración empírica de los recursos perjudicando el desarrollo del sector. Se definió que el Plan Operativo Anual es una herramienta de gestión que parte de la planificación estratégica, se estableció la respectiva misión, visión y objetivos, de donde parte los objetivos operativos, enfocados a la atención en salud, educación, distracción, proyectos productivos y la creación de una caja de ahorros comunal. Se definieron actividades dirigidas al mejoramiento de los recursos económicos de los habitantes del sector como: producción de tilapias, criaderos de cerdos e impulsando un proyecto turístico, que implicará la creación de una página web para la comunicación con los turistas extranjeros quienes son potenciales clientes. Se recomienda la aplicación del Plan Operativo Anual, para alcanzar los resultados proyectados, de modo que, los miembros de la Asociación Jimbitono 26 de Agosto tengan el sentimiento de crecimiento personal y bienestar social, cumpliendo así, con el objetivo para el cual fue fundada dicha asociación

Black holes in an ultraviolet complete quantum gravity

In this Letter we derive the gravity field equations by varying the action for an ultraviolet complete quantum gravity. Then we consider the case of a static source term and we determine an exact black hole solution. As a result we find a regular spacetime geometry: in place of the conventional curvature singularity extreme energy fluctuations of the gravitational field at small length scales provide an effective cosmological constant in a region locally described in terms of a de Sitter space. We show that the new metric coincides with the noncommutative geometry inspired Schwarzschild black hole. Indeed, we show that the ultraviolet complete quantum gravity, generated by ordinary matter is the dual theory of ordinary Einstein gravity coupled to a noncommutative smeared matter. In other words we obtain further insights about that quantum gravity mechanism which improves Einstein gravity in the vicinity of curvature singularities. This corroborates all the existing literature in the physics and phenomenology of noncommutative black holes.Comment: 5 pages, 2 figures, minor corrections, version matching that published by Physics Letters

Axial Thrust in High Pressure Centrifugal Compressors: Description of a Calculation Model Validated by Experimental Data from Full Load Test

LectureThe residual axial thrust acting on the rotor of a centrifugal compressor is the result of the non-uniform pressure distribution on the surfaces in contact with the process gas, plus the differential pressure acting on the faces of the balance piston(s) and the contribution due to the momentum variation of the process gas. During the design phase the axial load shall be verified to remain safely lower than the thrust bearing capacity, under all possible operating conditions; this requires a high degree of accuracy in the calculation model used to evaluate each thrust component. Errors in this calculation may lead to high bearing pad temperature during operation, to early wearing of the pad surfaces and ultimately to the damage or failure of the thrust bearing (Moll and Postill, 2011), thus jeopardizing the integrity of the whole compressor. The main difficulty of axial thrust calculation lies in the correct prediction of the static pressure distribution over the external surface of the impeller hub and shroud. This distribution depends on a large set of parameters, including rotor geometry, operating conditions, properties of the process gas, leakages flows across the rotor-stator seals. A detailed fluid-dynamic model of the gas in the cavities between impeller and diaphragm was developed and applied first to stage model tests and then to high-pressure centrifugal compressors, and its predictability was assessed by direct comparison with experimental data. The compressors were tested in full load conditions, with thrust bearing pads equipped with load cells, and the thrust values were recorded for several points across the operating envelope