The poverty of journal publishing

The article opens with a critical analysis of the dominant business model of for-profit, academic publishing, arguing that the extraordinarily high profits of the big publishers are dependent upon a double appropriation that exploits both academic labour and universities’ financial resources. Against this model, we outline four possible responses: the further development of open access repositories, a fair trade model of publishing regulation, a renaissance of the university presses, and, finally, a move away from private, for-profit publishing companies toward autonomous journal publishing by editorial boards and academic associations. </jats:p

Desempenho de bovinos Nelore e cruzados Bos taurus x Nelore recriados em pastagem e terminados em confinamento.

Foram utilizados dados de desempenho de 32 animais de quatro grupos genéticos (GG) recriados em pastagem e terminados em confinamento. Os animais eram oriundos do mesmo lote de fêmeas Nelore acasaladas com touros Angus, Canchim, Nelore e Simental, produzindo animais Nelore, 'h Canchim + 'h Nelore, 'h Angus + 'h Nelore (AN) e 'h Simental + 'h Nelore. Do nascimento aos 22 meses de idade, os bovinos permaneceram em pastagens, com suplementação mineral à vontade. AP.óS esse período, os animais foram distribuídos em baias individuais, recebendo dieta com 13,3% de proteína bruta e 68,7% de nutrientes digestíveis totais, à base de silagem de milho e concentrados, sem período de adaptação, durante 101 dias. Por meio da metodologia de modelos mistos, com a opção de medidas repetidas, criaram-se curvas de crescimento (CC) para comparar diferenças na inclinação das curvas de cada GG. Os efeitos fixos de GG e o efeito linear, quadrático e cúbico da idade em dias na expressão da variável "peso vivo" foram significativos (P<0,01). Houve interação (P<0,05) do efeito linear da idade com GG, na variável peso vivo. Isso evidencia que as maiores diferenças na inclinação das CC entre genótipos ocorreram entre o nascimento e os 12 meses de idade, sobretudo em razão da superioridade do AN sobre os demais GG. Não havendo interação com o efeito quadrático e o cúbico, concluiu-se que, mesmo apresentando ganho compensatório, estes efeitos se comportaram de forma semelhante nos quatro GG

Desempenho e características de carcaça de bovinos Nelore e cruzados Bos taurus x Nelore terminados em confinamento.

Trinta e dois novilhos castrados, com média de idade de 22 meses +- 23 dias e média de peso corporal de 310 +- 30 kg, foram confinados durante 101 dias, com o objetivo de avaliar o desempenho e as características de carcaça. Utilizou-se delineamento inteíramente ao acaso, com quatro tratamentos: Y2 Angus + Y2 Nelore (AN), Y2 Canchim + Y2 Nelore (CN), Nelore (NE) e Y2 Simental + Y2 Nelore (SN). Todos os cruzamentos foram conduzidos no mesmo rebanho de fêmeas Nelore com múltiplos touros de cada raça. Os animais foram mantidos em pastos de "Brachiaria decumbens" até a entrada no confinamento. A única dieta utilizada em todo o período experimental continha 13,34% de proteína bruta e 68,69% de nutrientes digestíveis totais. Comparados na mesma idade, os novilhos AN apresentavam maior peso no início do confinamento e maior peso ao abate, em relação aos animais CN, NE e SN (P0,05) rendimento de carcaça. Animais AN apresentaram maior espessura de gordura (P<0,05), em relação aos demais grupos avaliados

Formal analogies between gravitation and electrodynamics

We develop a theoretical framework that allows us to compare electromagnetism and gravitation in a fully covariant way. This new scenario does not rely on any kind of approximation nor associate objects with different operational meaning as it's sometime done in the literature. We construct the electromagnetic analogue to the Riemann and Weyl tensors and develop the equations of motion for these objects. In particular, we are able to identify precisely how and in what conditions gravity can be mapped to electrodynamics. As a consequence, many of the gemometrical tools of General Relativity can be applied to Electromagnetism and vice-versa. We hope our results would shed new light in the nature of electromagnetic and gravitational theories.Comment: 9pages, submitted to General Relativity and Gravitatio

SIMULATION AND PERFORMANCE ANALYSIS OF A HYBRID ROCKET ENGINE WITH SELF-PRESSURIZING OXIDIZER

There are many challenges to simulate and design a hybrid engine, such as the dimensioning of the feed lines and tanks, propulsive performance calculations, and simulations of the expected behavior in the combustion chamber and the oxidizer tank during the engine operation. In this work, methods are assembled in a concise and complete analysis of the Gluon hybrid rocket engine, developed by PION Labs, with a blowdown pressurization system, using N2O as oxidizer and a paraffin-based fuel. For that, a study will be presented on the peculiar characteristics of the oxidizer and its behavior during the phases of operation of the rocket engine. Then, the main equations that describe the operation of the rocket engine, including the combustion chamber, injection plate, feed lines, and the oxidizer tank are presented, and the performance indicators calculations of the engine are shown and discussed. Finally, simulation results of the combustion chamber and the oxidizer tank during engine firing will be presented, leading to the concluding remarks on the data obtained

Substrate-mediated regulation of the arginine transporter of Toxoplasma gondii

Intracellular parasites, such as the apicomplexan Toxoplasma gondii, are adept at scavenging nutrients from their host. However, there is little understanding of how parasites sense and respond to the changing nutrient environments they encounter during an infection. TgApiAT1, a member of the apicomplexan ApiAT family of amino acid transporters, is the major uptake route for the essential amino acid L-arginine (Arg) in T. gondii. Here, we show that the abundance of TgApiAT1, and hence the rate of uptake of Arg, is regulated by the availability of Arg in the parasite's external environment, increasing in response to decreased [Arg]. Using a luciferase-based 'biosensor' strain of T. gondii, we demonstrate that the expression of TgApiAT1 varies between different organs within the host, indicating that parasites are able to modulate TgApiAT1-dependent uptake of Arg as they encounter different nutrient environments in vivo. Finally, we show that Arg-dependent regulation of TgApiAT1 expression is post-transcriptional, mediated by an upstream open reading frame (uORF) in the TgApiAT1 transcript, and we provide evidence that the peptide encoded by this uORF is critical for mediating regulation. Together, our data reveal the mechanism by which an apicomplexan parasite responds to changes in the availability of a key nutrient

CONSTRUCTAL DESIGN APPLIED TO A FINNED CHANNEL UNDER FORCED CONVECTION FLOWS WITH DIFFERENT IMPOSED PRESSURE DROPS

This paper aims to numerically study the heat transfer in a two dimensional finned channel under laminar, incompressible and forced convective flow with adiabatic walls. The main purpose is to maximize the convection heat transfer by changing the fin’s dimensions by means of Constructal Design. Numerical computations are performed for different Bejan numbers ranging from 0.182 up to 18.2. For all simulations the Prandlt number is kept constant, Pr = 0.71. The fluid motion throughout the channel is caused by imposition of pressure difference between inlet/outlet surfaces. Concerning heat transfer, it is caused by the difference of temperature between the inlet stream of fluid and the heated fins placed at the channel surfaces. The first fin is positioned in the lower surface of the channel while the second one is placed in the upper one. The problem is submitted to three constraints, the channel area (H × L), area of two fins and occupancy areas for the fins. It is considered here that both fins have the same fraction area (ratio between the fins and occupancy areas) f = 0.2. The problem is submitted to three degrees of freedom: H/L (ratio between height and length of channel), H3/L3 and H4/L4 which represent the ratio between the height and length of the first and second fin, respectively. Here, the second fin remains unchanged, being its dimensions H4/L4 = 2.0, whereas the first one is free to modify its dimensions, H3/L3. The channel dimensions are also constant. The solutions are sought using the conservation equations of mass, momentum and energy being these ones discretized through the Finite Volume Method (FVM). Results showed the importance of Constructal Design application for thermal improvement of the problem. Thermal efficiency differences of 5 times where achieved when comparing the best and worst cases. Other important observation is concerned with the effect of ratio H3/L3 over heat transfer ratio (q) which varied significantly from a case where a pressure drop is imposed in the channel to other case where the driven force is caused by imposition of velocity field at the channel inlet