Local and Global Properties of the World

The essence of the method of physics is inseparably connected with the problem of interplay between local and global properties of the universe. In the present paper we discuss this interplay as it is present in three major departments of contemporary physics: general relativity, quantum mechanics and some attempts at quantizing gravity (especially geometrodynamics and its recent successors in the form of various pregeometry conceptions). It turns out that all big interpretative issues involved in this problem point towards the necessity of changing from the standard space-time geometry to some radically new, most probably non-local, generalization. We argue that the recent noncommutative geometry offers attractive possibilities, and gives us a conceptual insight into its algebraic foundations. Noncommutative spaces are, in general, non-local, and their applications to physics, known at present, seem very promising. One would expect that beneath the Planck threshold there reigns a "noncommutative pregeometry", and only when crossing this threshold does the usual space-time geometry emerges.     

高压下MgO-ZnO-SiO2体系的亚固相相关系

在１．０ＧＰａ和１２００℃条件下,利用活塞圆筒高压装置实验确定了ＭｇＯ－ＺｎＯ－ＳｉＯ２体系的亚固相相关系,结果显示该体系具有不同于其他类似的三元体系的相组合特征,无法形成Ｍｇ２ＳｉＯ４－Ｚｎ２ＳｉＯ４橄榄石和Ｍｇ２ＳｉＯ６－Ｚｎ２Ｓｉ２Ｏ６辉石续固溶体,这种相组合特征是由Ｚｎ＾２＋具有（Ａｒ）３ｄ＾１０外层电子结构,不同于其他过渡金属离子,如Ｆｅ＾２＋,Ｎｉ＾２＋和Ｃｏ＾２＋的性质所制约。     

Orbital forcing of the martian polar layered deposits

Since the first images of polar regions on Mars revealed alternating bright and dark layers, there has been speculation that their formation might be tied to the planet's orbital climate forcing. But uncertainties in the deposition timescale exceed two orders of magnitude: estimates based on assumptions of dust deposition, ice formation and sublimation, and their variations with orbital forcing suggest a deposition rate of 10(-3) to 10(-2) cm yr(-1) (refs 5, 6), whereas estimates based on cratering rate result in values as high as 0.1 to 0.2 cm yr(-1) (ref. 7). Here we use a combination of high-resolution images of the polar layered terrains, high-resolution topography and revised calculations of the orbital and rotational parameters of Mars to show that a correlation exists between ice-layer radiance as a function of depth (obtained from photometric data of the images of the layered terrains) and the insolation variations in summer at the martian north pole, similar to what has been shown for palaeoclimate studies of the Earth. For the best fit between the radiance profile and the simulated insolation parameters, we obtain an average deposition rate of 0.05 cm yr(-1) for the top 250 m of deposits on the ice cap of the north pole of Mars.     

Determinants of woody cover in African savannas

Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than approximately 650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of approximately 650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation may considerably affect their distribution and dynamics.     

Variants of ENPP1 are associated with childhood and adult obesity and increase the risk of glucose intolerance and type 2 diabetes

We identified a locus on chromosome 6q16.3-q24.2 (ref. 1) associated with childhood obesity that includes 2.4 Mb common to eight genome scans for type 2 diabetes (T2D) or obesity. Analysis of the gene ENPP1 (also called PC-1), a candidate for insulin resistance, in 6,147 subjects showed association between a three-allele risk haplotype (K121Q, IVS20delT-11 and A-->G+1044TGA; QdelTG) and childhood obesity (odds ratio (OR) = 1.69, P = 0.0006), morbid or moderate obesity in adults (OR = 1.50, P = 0.006 or OR = 1.37, P = 0.02, respectively) and T2D (OR = 1.56, P = 0.00002). The Genotype IBD Sharing Test suggested that this obesity-associated ENPP1 risk haplotype contributes to the observed chromosome 6q linkage with childhood obesity. The haplotype confers a higher risk of glucose intolerance and T2D to obese children and their parents and associates with increased serum levels of soluble ENPP1 protein in children. Expression of a long ENPP1 mRNA isoform, which includes the obesity-associated A-->G+1044TGA SNP, was specific for pancreatic islet beta cells, adipocytes and liver. These findings suggest that several variants of ENPP1 have a primary role in mediating insulin resistance and in the development of both obesity and T2D, suggesting that an underlying molecular mechanism is common to both conditions.     

Recent ice-rich deposits formed at high latitudes on Mars by sublimation of unstable equatorial ice during low obliquity

Observations from the gamma-ray spectrometer instrument suite on the Mars Odyssey spacecraft have been interpreted as indicating the presence of vast reservoirs of near-surface ice in high latitudes of both martian hemispheres. Ice concentrations are estimated to range from 70 per cent at 60 degrees latitude to 100 per cent near the poles, possibly overlain by a few centimetres of ice-free material in most places. This result is supported by morphological evidence of metres-thick layered deposits that are rich in water-ice and periglacial-like features found only at high latitudes. Diffusive exchange of water between the pore space of the regolith and the atmosphere has been proposed to explain this distribution, but such a degree of concentration is difficult to accommodate with such processes. Alternatively, there are suggestions that ice-rich deposits form by transport of ice from polar reservoirs and direct redeposition in high latitudes during periods of higher obliquity, but these results have been difficult to reproduce with other models. Here we propose instead that, during periods of low obliquity (less than 25 degrees), high-latitude ice deposits form in both hemispheres by direct deposition of ice, as a result of sublimation from an equatorial ice reservoir that formed earlier, during a prolonged high-obliquity excursion. Using the ice accumulation rates estimated from global climate model simulations we show that, over the past ten million years, large variations of Mars' obliquity have allowed the formation of such metres-thick, sedimentary layered deposits in high latitude and polar regions.