Cosmological models with interacting components and mass-varying neutrinos

A model for a homogeneous and isotropic spatially flat Universe, composed of baryons, radiation, neutrinos, dark matter and dark energy is analyzed. We infer that dark energy (considered to behave as a scalar field) interacts with dark matter (either by the Wetterich model, or by the Anderson and Carroll model) and with neutrinos by a model proposed by Brookfield et al.. The latter is understood to have a mass-varying behavior. We show that for a very-softly varying field, both interacting models for dark matter give the same results. The models reproduce the expected red-shift performances of the present behavior of the Universe.Comment: 8 pages, 5 figures, to be published in Gravitation and Cosmolog

Diseño de plataforma rotativa para medición de dispositivos acústicos

La medición de diversas características de un dispositivo acústico requiere la utilización de equipos, instrumentos, instalaciones y operadores que conforman el sistema de medición. Para medir la directividad de una fuente o receptor sonoro se necesita caracterizar la radiación o sensibilidad en el espacio respectivamente. Por lo cual, la precisión y exactitud del posicionamiento del dispositivo ensayado son factores significativos para obtener resultados plausibles y de calidad. Por lo general, los sistemas automáticos de medición de dispositivos acústicos son complejos y costosos. En este trabajo, se presenta el diseño de una plataforma rotativa de alta precisión angular y bajo costo, implementada con un motor paso a paso, un reductor mecánico y un circuito electrónico de control y excitación, la cual forma parte de un sistema automático de medición de dispositivos acústicos.Publicado en: Mecánica Computacional, vol. XXXV, no. 2Facultad de Ingenierí

Diseño de plataforma rotativa para medición de dispositivos acústicos

La medición de diversas características de un dispositivo acústico requiere la utilización de equipos, instrumentos, instalaciones y operadores que conforman el sistema de medición. Para medir la directividad de una fuente o receptor sonoro se necesita caracterizar la radiación o sensibilidad en el espacio respectivamente. Por lo cual, la precisión y exactitud del posicionamiento del dispositivo ensayado son factores significativos para obtener resultados plausibles y de calidad. Por lo general, los sistemas automáticos de medición de dispositivos acústicos son complejos y costosos. En este trabajo, se presenta el diseño de una plataforma rotativa de alta precisión angular y bajo costo, implementada con un motor paso a paso, un reductor mecánico y un circuito electrónico de control y excitación, la cual forma parte de un sistema automático de medición de dispositivos acústicos.Publicado en: Mecánica Computacional, vol. XXXV, no. 2Facultad de Ingenierí

Diseño de plataforma rotativa para medición de dispositivos acústicos

La medición de diversas características de un dispositivo acústico requiere la utilización de equipos, instrumentos, instalaciones y operadores que conforman el sistema de medición. Para medir la directividad de una fuente o receptor sonoro se necesita caracterizar la radiación o sensibilidad en el espacio respectivamente. Por lo cual, la precisión y exactitud del posicionamiento del dispositivo ensayado son factores significativos para obtener resultados plausibles y de calidad. Por lo general, los sistemas automáticos de medición de dispositivos acústicos son complejos y costosos. En este trabajo, se presenta el diseño de una plataforma rotativa de alta precisión angular y bajo costo, implementada con un motor paso a paso, un reductor mecánico y un circuito electrónico de control y excitación, la cual forma parte de un sistema automático de medición de dispositivos acústicos.Publicado en: Mecánica Computacional, vol. XXXV, no. 2Facultad de Ingenierí

Consistent patterns of common species across tropical tree communities

Trees structure the Earth’s most biodiverse ecosystem, tropical forests. The vast number of tree species presents a formidable challenge to understanding these forests, including their response to environmental change, as very little is known about most tropical tree species. A focus on the common species may circumvent this challenge. Here we investigate abundance patterns of common tree species using inventory data on 1,003,805 trees with trunk diameters of at least 10 cm across 1,568 locations1,2,3,4,5,6 in closed-canopy, structurally intact old-growth tropical forests in Africa, Amazonia and Southeast Asia. We estimate that 2.2%, 2.2% and 2.3% of species comprise 50% of the tropical trees in these regions, respectively. Extrapolating across all closed-canopy tropical forests, we estimate that just 1,053 species comprise half of Earth’s 800 billion tropical trees with trunk diameters of at least 10 cm. Despite differing biogeographic, climatic and anthropogenic histories7, we find notably consistent patterns of common species and species abundance distributions across the continents. This suggests that fundamental mechanisms of tree community assembly may apply to all tropical forests. Resampling analyses show that the most common species are likely to belong to a manageable list of known species, enabling targeted efforts to understand their ecology. Although they do not detract from the importance of rare species, our results open new opportunities to understand the world’s most diverse forests, including modelling their response to environmental change, by focusing on the common species that constitute the majority of their trees.Publisher PDFPeer reviewe

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

Pratos e mais pratos: louças domésticas, divisões culturais e limites sociais no Rio de Janeiro, século XIX

Reply to ten comments on a paper published in the last issue of this journal. The discussion follows along six main lines: History museums, identity, ideology and the category of nation; the need of material collections and their modalities: patrimonial, operational, virtual; theater versus laboratory; visitors and their ambiguities; Public History: the museum and the academy.Resposta aos comentários de dez especialistas que contribuíram no debate de texto publicado no último número desta revista. A discussão orientou-se segundo seis tópicos principais: museus históricos, identidade, ideologia e a categoria de nação; a necessidade de acervos materiais e suas modalidades: acervo patrimonial, operacional, virtual; teatro versus laboratório; o público e suas ambigüidades; História Pública: o museu e a Academia