Aspect ratio dependence of heat transfer and large-scale flow in turbulent convection

The heat transport and corresponding changes in the large-scale circulation (LSC) in turbulent Rayleigh-B\'{e}nard convection are studied by means of three-dimensional direct numerical simulations as a function of the aspect ratio $\Gamma$ of a closed cylindrical cell and the Rayleigh number $Ra$. For small and moderate aspect ratios, the global heat transfer law $Nu=A\times Ra^{\beta}$ shows a power law dependence of both fit coefficients $A$ and $\beta$ on the aspect ratio. A minimum Nusselt number coincides with the point where the LSC undergoes a transition from a single-roll to a double-roll pattern. With increasing aspect ratio, we detect complex multi-roll LSC configurations. The aspect ratio dependence of the turbulent heat transfer for small and moderate $\Gamma$ is in line with a varying amount of energy contained in the LSC, as quantified by the Proper Orthogonal Decomposition analysis. For $\Gamma\gtrsim 8$ the heat transfer becomes independent of the aspect ratio.Comment: 17 pages, 11 Postscript figures (in parts downscaled), accepted for J. Fluid Mec

Simulated case management of home telemonitoring to assess the impact of different alert algorithms on work-load and clinical decisions

© 2017 The Author(s). Background: Home telemonitoring (HTM) of chronic heart failure (HF) promises to improve care by timely indications when a patient's condition is worsening. Simple rules of sudden weight change have been demonstrated to generate many alerts with poor sensitivity. Trend alert algorithms and bio-impedance (a more sensitive marker of fluid change), should produce fewer false alerts and reduce workload. However, comparisons between such approaches on the decisions made and the time spent reviewing alerts has not been studied. Methods: Using HTM data from an observational trial of 91 HF patients, a simulated telemonitoring station was created and used to present virtual caseloads to clinicians experienced with HF HTM systems. Clinicians were randomised to either a simple (i.e. an increase of 2 kg in the past 3 days) or advanced alert method (either a moving average weight algorithm or bio-impedance cumulative sum algorithm). Results: In total 16 clinicians reviewed the caseloads, 8 randomised to a simple alert method and 8 to the advanced alert methods. Total time to review the caseloads was lower in the advanced arms than the simple arm (80 ± 42 vs. 149 ± 82 min) but agreements on actions between clinicians were low (Fleiss kappa 0.33 and 0.31) and despite having high sensitivity many alerts in the bio-impedance arm were not considered to need further action. Conclusion: Advanced alerting algorithms with higher specificity are likely to reduce the time spent by clinicians and increase the percentage of time spent on changes rated as most meaningful. Work is needed to present bio-impedance alerts in a manner which is intuitive for clinicians

Early indication of decompensated heart failure in patients on home-telemonitoring: a comparison of prediction algorithms based on daily weight and noninvasive transthoracic bio-impedance

Background: Heart Failure (HF) is a common reason for hospitalization. Admissions might be prevented by early detection of and intervention for decompensation. Conventionally, changes in weight, a possible measure of fluid accumulation, have been used to detect deterioration. Transthoracic impedance may be a more sensitive and accurate measure of fluid accumulation. Objective: In this study, we review previously proposed predictive algorithms using body weight and noninvasive transthoracic bio-impedance (NITTI) to predict HF decompensations. Methods: We monitored 91 patients with chronic HF for an average of 10 months using a weight scale and a wearable bio-impedance vest. Three algorithms were tested using either simple rule-of-thumb differences (RoT), moving averages (MACD), or cumulative sums (CUSUM). Results: Algorithms using NITTI in the 2 weeks preceding decompensation predicted events (P<.001); however, using weight alone did not. Cross-validation showed that NITTI improved sensitivity of all algorithms tested and that trend algorithms provided the best performance for either measurement (Weight-MACD: 33%, NITTI-CUSUM: 60%) in contrast to the simpler rules-of-thumb (Weight-RoT: 20%, NITTI-RoT: 33%) as proposed in HF guidelines. Conclusions: NITTI measurements decrease before decompensations, and combined with trend algorithms, improve the detection of HF decompensation over current guideline rules; however, many alerts are not associated with clinically overt decompensation

Bistable State Switch Enables Ultrasensitive Feedback Control in Heterogeneous Microbial Populations

Molecular feedback control circuits can improve robustness of gene expression at the single cell level. This achievement can be offset by requirements of rapid protein expression, that may induce cellular stress, known as burden, that reduces colony growth. To begin to address this challenge we take inspiration by 'division-of-labor' in heterogeneous cell populations: we propose to combine bistable switches and quorum sensing systems to coordinate gene expression at the population level. We show that bistable switches in individual cells operating in parallel yield an ultrasensitive response, while cells maintain heterogeneous levels of gene expression to avoid burden across all cells. Within a feedback loop, these switches can achieve robust reference tracking and adaptation to disturbances at the population-level. We also demonstrate that molecular sequestration enables tunable hysteresis in individual switches, making it possible to obtain a wide range of stable population-level expressions

MORPHOMETRIC DISTINCTION OF DOMESTIC AND SYLVATIC POPULATIONS OF Rhodnius ecuadoriensis FROM DIFFERENT GEOGRAPHICAL ORIGINS

ABSTRACTRhodnius ecuadoriensis (Hemiptera, Reduviidae) is an important vector of both Trypanosoma hemoflagellates, Trypanosoma cruzi and Trypanosoma rangeli, in Ecuador and Peru. Ecotopes of sylvatic and domestic/peridomestic habitats have been reported in Ecuador. Meanwhile in Peru, to the best of our knowledge, findings of sylvatic populations in their different ecosystem regions have not yet been documented. Could this be the product of a lack of appropriate studies on wild populations of triatominae in Peruvian environments? In order to elucidate this topic, we take advantage of new insights in geometric morphometry as a tool to help differentiate between wild populations and the corresponding domestic/peridomestic ones, collected in their respective environments. When analyzing our results, we confirmed the efficacy of this technique in our study, and furthermore, we believe that it could be a proper tool for rangeliosis and Chagas disease vector control surveillance in Ecuador and Peru.Keywords: Morphometric geometry, sylvatic, domestic/peridomiestic populations distinction, Rhodnius ecuadoriensis. RESUMENRhodnius ecuadoriensis (Hemiptera, Reduviidae) es un importante vector de los tripanosomas Trypanosoma cruzi y Trypanosoma rangeli en el Ecuador y Perú. Se han reportado ecotopos de hábitats silvestres y domésticos/peridomésticos en Ecuador. Sin embargo, en Perú, hasta donde sabemos, no se ha documentado hallazgos de dichas poblaciones silvestres. ¿Podría este ser el caso de una falta de estudios focalizados en la búsqueda de poblaciones silvestres de triatominos dentro de los diferentes ecosistemas del Perú? Para elucidar este tema, aplicamos nuevas perspectivas en morfometría geométrica, como una herramienta que podría auxiliar en la diferenciación de poblaciones silvestres de aquellas domésticas/peridomésticas, colectadas en sus respectivos ambientes naturales. Al analizar nuestros resultados, se confirmó la utilidad de esta técnica dentro de nuestro estudio, y esto nos llevó a creer asimismo que serviría como un elemento apropiado en el control vectorial de la enfermedad de Chagas y de la rangeliosis, en Ecuador y Perú.Palabras claves: Geometría morfométrica, silvestre, diferenciación de poblaciones domesticas/peridomesticas, Rhodnius ecuadoriensis

A Mathematical Framework for Agent Based Models of Complex Biological Networks

Agent-based modeling and simulation is a useful method to study biological phenomena in a wide range of fields, from molecular biology to ecology. Since there is currently no agreed-upon standard way to specify such models it is not always easy to use published models. Also, since model descriptions are not usually given in mathematical terms, it is difficult to bring mathematical analysis tools to bear, so that models are typically studied through simulation. In order to address this issue, Grimm et al. proposed a protocol for model specification, the so-called ODD protocol, which provides a standard way to describe models. This paper proposes an addition to the ODD protocol which allows the description of an agent-based model as a dynamical system, which provides access to computational and theoretical tools for its analysis. The mathematical framework is that of algebraic models, that is, time-discrete dynamical systems with algebraic structure. It is shown by way of several examples how this mathematical specification can help with model analysis.Comment: To appear in Bulletin of Mathematical Biolog

Comparative analysis of the role of cytokinin in feeding site formation induced by cyst and root-knot nematodes

Field of study: Plant insect & microbial sciences.Dr. Melissa G. Mitchum, Doctoral Supervisor.Includes vita."May 2017."Cyst and root-knot nematodes are obligate plant parasites of global economic importance with a remarkable ability to reprogram root cells into unique feeding sites. Previous studies have suggested a role for cytokinin in feeding site formation induced by these two types of nematodes, but the mechanistic details have not yet been described. Using Arabidopsis as a host plant species, this study shows a comparative analysis of cytokinin genes in response to the beet cyst nematode (BCN), Heterodera schachtii, and the root-knot nematode (RKN), Meloidogyne incognita. Distinct differences in the regulation of cytokinin biosynthesis, catabolism and signaling genes in response to BCN and RKN infection were found, suggesting differential manipulation of the cytokinin pathway by these two nematode species. Furthermore, key cytokinin genes contributing to BCN and RKN disease susceptibility were identified. This study also evaluated ARABIDOPSIS HISTIDINE KINASE (AHK), ahk2/3, ahk2/4 and ahk3/4 receptor mutant lines in response to BCN and RKN infection and found a decrease in susceptibility compared to the wild type control, Col-0. An analysis of ahk double mutants using CYCB1:GUS/ahk introgressed lines revealed contrasting differences in the cytokinin receptors controlling cell cycle activation in feeding sites caused by RKN and BCN. Results from these studies could be used in the future to engineer novel forms of nematode resistance in crops of economic importance.Includes bibliographical references

Planificación de cultivos y rentabilidad de las Micro y Pequeños Empresarios Agrícolas de la Cooperativa Agraria de Usuarios San José – Miraflores del Valle de Huaral 2017.

Nuestra tesis: Planificación de Cultivos y Rentabilidad de las Micro y Pequeños Empresarios Agrícolas de la Cooperativa Agraria de Usuarios San José – Miraflores del Valle de Huaral 2017, nace de la identificación del problema consistente en una baja o nula rentabilidad de la inversión realizada, lo que genera una paulatina descapitalización, incumplimiento de pagos a proveedores, planillas, entidades financieras, etc. Frente a esto nos planteamos la siguiente interrogante: ¿De qué manera la Planificación de Cultivos influye en la Rentabilidad de las micro y pequeños empresarios agrícolas? Ante esta situación proponemos la solución formulando la siguiente hipótesis: La Planificación de cultivos influye en la rentabilidad de los micro y pequeños empresarios agrícolas de la Cooperativa Agraria de Usuarios San José – Miraflores del Valle de Huaral 2017. El desarrollo de esta investigación tiene el siguiente objetivo: determinar cómo la planificación de cultivos podrá influir en la rentabilidad de las micro y pequeños empresarios agrícolas de la referida cooperativa. La población estuvo conformada por 105 socios de la cooperativa y la muestra por 50 personas. Se empleó la técnica de las encuestas para el recojo de datos y el cuestionario Likert como instrumento para aplicarlas. El resultado de mayor importancia es que el 50 % de las personas encuestadas acepta estar de acuerdo y el otro 50% acepta estar totalmente de acuerdo que la planificación de cultivos influye en la rentabilidad de las micro y pequeños empresarios agrícolas de la Cooperativa Agraria San José – Miraflores del Valle de Huaral.Tesi

Depression symptoms and mortality in elderly peruvian navy veterans: a retrospective cohort study

Abstract: Our study was design to determine the association between depressive symptoms and mortality in adults over 60 years old Navy Peruvian Veterans. We performed a retrospective cohort study based on a previous cohort study. A total of 1681 patients over 60 years old were included between 2010–2015. Demographic information, self-reported information about falls, physical frailty assessment, tobacco consumption, hypertension, Type 2 Diabetes Mellitus, Chronic Obstructive Pulmonary Disease and was collected. Depression was assessed by the short form of the Geriatric Depression Scale. We found that depressive symptoms were present in 24.9% of the participants and 40.5% of them died. Mortality risk in patients with depressive symptoms, physical frailty, and male sex was: RR of 23.1 (95% CI: 11.7–45.7), 3.84 (95% CI: 2.16–6.82), and 1.37 (95% CI: 1.07–1.75) respectively. We concluded that depressive symptoms in Peruvian retired military personnel and their immediate relatives are high and are significatively associated with mortality. Also, being male and frail was associated with an increased risk of death. This reinforces that early detection and assessment of depressive symptoms could be an opportunity to improve the health status of older adults