2,198 research outputs found
Predicting the extinction of Ebola spreading in Liberia due to mitigation strategies
The Ebola virus is spreading throughout West Africa and is causing thousands of deaths. In order to quantify the effectiveness of different strategies for controlling the spread, we develop a mathematical model in which the propagation of the Ebola virus through Liberia is caused by travel between counties. For the initial months in which the Ebola virus spreads, we find that the arrival times of the disease into the counties predicted by our model are compatible with World Health Organization data, but we also find that reducing mobility is insufficient to contain the epidemic because it delays the arrival of Ebola virus in each county by only a few weeks. We study the effect of a strategy in which safe burials are increased and effective hospitalisation instituted under two scenarios: (i) one implemented in mid-July 2014 and (ii) one in mid-August—which was the actual time that strong interventions began in Liberia. We find that if scenario (i) had been pursued the lifetime of the epidemic would have been three months shorter and the total number of infected individuals 80% less than in scenario (ii). Our projection under scenario (ii) is that the spreading will stop by mid-spring 2015.H.E.S. thanks the NSF (grants CMMI 1125290 and CHE-1213217) and the Keck Foundation for financial support. L.D.V. and L.A.B. wish to thank to UNMdP and FONCyT (Pict 0429/2013) for financial support. (CMMI 1125290 - NSF; CHE-1213217 - NSF; Keck Foundation; UNMdP; Pict 0429/2013 - FONCyT)Published versio
Some boundary effects in quantum field theory
We have constructed a quantum field theory in a finite box, with periodic
boundary conditions, using the hypothesis that particles living in a finite box
are created and/or annihilated by the creation and/or annihilation operators,
respectively, of a quantum harmonic oscillator on a circle. An expression for
the effective coupling constant is obtained showing explicitly its dependence
on the dimension of the box.Comment: 12 pages, Late
Generalized quantum field theory: perturbative computation and perspectives
We analyze some consequences of two possible interpretations of the action of
the ladder operators emerging from generalized Heisenberg algebras in the
framework of the second quantized formalism. Within the first interpretation we
construct a quantum field theory that creates at any space-time point particles
described by a q-deformed Heisenberg algebra and we compute the propagator and
a specific first order scattering process. Concerning the second one, we draw
attention to the possibility of constructing this theory where each state of a
generalized Heisenberg algebra is interpreted as a particle with different
mass.Comment: 19 page
Perfil de competências éticas para gerir Unidades de Saúde
A presente investigação decorre de um estudo em curso, no âmbito do doutoramento em Bioética, no qual auscultamos a opinião de 421 profissionais de saúde que exercem a gestão em hospitais da zona Norte. Provocar a reflexão ética nos hospitais bem como contribuir para a identificação de um “Perfil de competências éticas para gerir Unidades de Saúde” revelam-se simultaneamente necessárias e atuais no sentido de recolocar o primado da Pessoa no centro de todas as decisões
Effect of phonon scattering by surface roughness on the universal thermal conductance
The effect of phonon scattering by surface roughness on the thermal
conductance in mesoscopic systems at low temperatures is calculated using full
elasticity theory. The low frequency behavior of the scattering shows novel
power law dependences arising from the unusual properties of the elastic modes.
This leads to new predictions for the low temperature depression of the thermal
conductance below the ideal universal value. Comparison with the data of Schwab
et al. [Nature 404, 974 (2000)] suggests that surface roughness on a scale of
the width of the thermal pathway is important in the experiment.Comment: 6 pages, 3 figure
Positive leadership action framework: Simply doing good and doing well
This article presents the Positive Leadership Action Framework (PLAF) to structure Positive Leadership (PL). The novelty of the PLAF is that it incorporates the connections of PL to positive outcomes (financial and economic performance and social well-being) and organizational virtuousness. Also, it acknowledges its conditional nature on the virtues to achieve flourishing within the organization and society at large. We argue that the leader’s actions function as the engine for positive change within the organization, bridging the gap between individual virtues and organizational virtuousness and creating a feedback loop among both. To develop a positive organization, a leader needs to create positive assumptions among (and about) coworkers, positively impact the personal and professional development of employees, and balance positive formal and informal conditions at work. To do so, it is a sine qua non condition that the positive leader fosters his/her personal development by exercising the virtues and developing practical wisdom. In this way, the positive leader automatically provides followers with a vision of the final end towards the common good and achieves to set his/her organization on a pathway towards excellence
Nonlinear regression and plot size to estimate green beans production
The objectives of this work were to adjust nonlinear regression models for the green beans production and to identify the plot size which provides the best explanation and adjustment to the models. The authors used two field and two protected environment (plastic tunnel) trials in the autumn-winter and spring-summer seasons. The logistic and von Bertalanffy models were adjusted for average weight of green beans accumulated after multiple harvests and with different plot sizes. The models presented similar estimates and the same parameters estimates in all the plot sizes. The logistic model provided estimates closest to the reality, showing the best description performance for the average weight of pods during the productive cycle. In the autumn-winter season, plot size of 14 basic units (28 plants in the cultivation line direction) in the field and of two basic units (four plants in the cultivation line direction) under the plastic tunnel provide a good quality in the models adjustment. In the springsummer season, the plot sizes are made of six basic units (12 plants in the cultivation line) in the field and seven basic units (14 plants in the cultivation line) under the plastic tunnel.Os objetivos do trabalho foram ajustar modelos de regressão não-
-linear para a produção de feijão-de-vagem e identificar o tamanho da
parcela com melhor poder de explicação e ajuste dos modelos. Foram
utilizados dois ensaios a campo e dois em túnel plástico, realizados
nas estações outono-inverno e primavera-verão. Os modelos ajustados
foram o logístico e o de von Bertalanffy, para peso médio de vagens
acumulado nas múltiplas colheitas e com diferentes tamanhos de
parcela. Os modelos apresentaram estimativas semelhantes entre sí e
as mesmas estimativas dos parâmetros em todas os casos de tamanho
de parcela. O modelo logístico proporcionou estimativas mais próximas
da realidade, apresentando melhor desempenho na descrição
do comportamento do peso médio de vagens no decorrer do ciclo
produtivo da cultura. Na estação sazonal outono-inverno parcelas de
14 UBs (28 plantas no sentido da linha de cultivo) a campo e de duas
UBs (quatro plantas no sentido da linha de cultivo) em túnel plástico
proporcionam uma boa qualidade no ajuste dos modelos. Na estação
sazonal primavera-verão os tamanhos de parcela são de seis UBs (12
plantas no sentido da linha de cultivo) a campo e de sete UBs (14
plantas no sentido da linha de cultivo) em túnel plástico.The authors thank CAPES
(Coordination of Improvement of
Higher Education Personnel) for PhD
scholarship, abroad, granted, process no
BEX 1457/14-4.info:eu-repo/semantics/publishedVersio
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