为什么有些人吃过饭后身体会感到寒冷？

A：人体产热，来源于我们体内的能量代谢。我们通过消耗糖、脂肪、蛋白质这3类物质，将化学能转化为热能，通过血液送到身体各处。当身体刚开始产热时，散热机制就已经被触发，这是为了有效防止体温上升过快过高。人体有很多消耗热能的方式，比如皮肤血管扩张，还有出汗、呼吸等等。这些方式都有助于散发热量。     

Does noble metal modification improve the photocatalytic activity of BiOCl?

Noble metal-surface-deposited BiOCl photocatalysts were prepared through photo-deposition and used for photodecomposition of Rhodamine B(RhB).The received materials were characterised using X-ray photoemission spectroscopy(XPS),UV-vis diffuse reflectance spectroscopy(UV-vis DRS),and X-ray diffraction(XRD) to understand the influence of surface deposited noble metals.The results showed that the noble metal species on the surface of BiOCl are in metallic state,which also brought about enhanced light absorption in broad UV-vis region due to plasmonic effects induced by the surfacedeposited noble metal species.All the samples showed good activity in photodecomposition of RhB under UV-light irradiation,but only Ag/BiOCl was more active than bulk BiOCl.The mechanism of the different reactivity of these noble-metal modified BiOCl was tentatively proposed based on the band structure and the interactions between noble metals and the BiOCl.     

Tracking apex marine predator movements in a dynamic ocean

Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.     

Lowland-upland migration of sauropod dinosaurs during the Late Jurassic epoch

Sauropod dinosaurs were the largest vertebrates ever to walk the Earth, and as mega-herbivores they were important parts of terrestrial ecosystems. In the Late Jurassic-aged Morrison depositional basin of western North America, these animals occupied lowland river-floodplain settings characterized by a seasonally dry climate. Massive herbivores with high nutritional and water needs could periodically experience nutritional and water stress under these conditions, and thus the common occurrence of sauropods in this basin has remained a paradox. Energetic arguments and mammalian analogues have been used to suggest that migration allowed sauropods access to food and water resources over a wide region or during times of drought or both, but there has been no direct support for these hypotheses. Here we compare oxygen isotope ratios (δ(18)O) of tooth-enamel carbonate from the sauropod Camarasaurus with those of ancient soil, lake and wetland (that is, 'authigenic') carbonates that formed in lowland settings. We demonstrate that certain populations of these animals did in fact undertake seasonal migrations of several hundred kilometres from lowland to upland environments. This ability to describe patterns of sauropod movement will help to elucidate the role that migration played in the ecology and evolution of gigantism of these and associated dinosaurs.