Binary orbits as the driver of γ-ray emission and mass ejection in classical novae

Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel �10,000 solar masses of material at velocities exceeding 1,000 km/s. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of the thermonuclear runaway, prolonged optically thick winds, or binary interaction with the nova envelope. Classical novae are now routinely detected in GeV gamma-rays, suggesting that relativistic particles are accelerated by strong shocks in nova ejecta. Here we present high-resolution imaging of the gamma-ray-emitting nova V959 Mon at radio wavelengths, showing that its ejecta were shaped by binary motion: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are gamma-ray emitters

Os Restaurantes por peso no contexto de alimentação saudável fora de casa Pay-per-kilo restaurants in the context of healthy eating away from home

O consumo de refeições fora de casa é uma tendência em diferentes regiões do mundo, mas há indícios de que essa prática possa apresentar riscos à saúde. É reconhecido que os comportamentos e as escolhas alimentares dos indivíduos são complexos e estão condicionados a diversos fatores. O fator ambiental vem recebendo crescente atenção dentre as variáveis que envolvem as escolhas alimentares. Nesse contexto, este artigo discute a possibilidade de os restaurantes por peso, modalidade de serviço muito utilizada na realidade brasileira, representarem uma alternativa saudável de alimentação fora de casa. Os dados científicos disponíveis relativos aos restaurantes por peso ainda são escassos, não permitindo uma avaliação sistematizada sobre o tema. Assim, com base em pesquisa bibliográfica, discutem-se os modelos praticados e alguns estudos que comparam a possibilidade de escolhas saudáveis em restaurantes com diferentes modalidades de distribuição. Sugere-se que, devido às suas características - que incluem a diversidade, a possibilidade da prática de preços acessíveis, a rapidez e a conveniência -, os restaurantes por peso possam estimular a escolha de alimentos saudáveis nas refeições realizadas fora de casa. Ressalta-se, também, a importância de intervenções nutricionais tanto na disponibilização dos alimentos quanto na orientação à população para escolhas saudáveis nesse contexto.<br>Consumption of food away from home is a trend in different regions of the world, with indications that this practice may pose a health risk. It is recognized that eating behaviors and food choices are complex and conditioned to several factors. The environmental factor has been receiving increasing attention among the variables that involve food choices. In this context, this article discusses the possibility of pay-per-kilo restaurants, a typical Brazilian service, being a healthy alternative when eating out. Scientific facts related to pay-per-kilo restaurants are scarce, making it unfeasible to perform a systematic assessment of the subject. Hence, this review discusses restaurant modalities and some studies that compare the possibility of healthy choices in restaurants with different distribution modalities. Given its characteristics, which include diversity, reasonable prices, speed and convenience, pay-per-weight restaurants can encourage healthy food choices away from home. Also, there is emphasis on the importance of nutrition interventions that make healthy foods available and educate the population to make healthier food choices