A Pluto-like radius and a high albedo for the dwarf planet Eris from an occultation

The dwarf planet Eris is a trans-Neptunian object with an orbital eccentricity of 0.44, an inclination of 44 degrees and a surface composition very similar to that of Pluto. It resides at present at 95.7 astronomical units (1?AU is the Earth-Sun distance) from Earth, near its aphelion and more than three times farther than Pluto. Owing to this great distance, measuring its size or detecting a putative atmosphere is difficult. Here we report the observation of a multi-chord stellar occultation by Eris on 6 November 2010 UT. The event is consistent with a spherical shape for Eris, with radius 1,163?±?6?kilometres, density 2.52?±?0.05 grams per cm(3) and a high visible geometric albedo, Pv = 0.96(+0.09)(-0.04). No nitrogen, argon or methane atmospheres are detected with surface pressure larger than ～1?nanobar, about 10,000 times more tenuous than Pluto's present atmosphere. As Pluto's radius is estimated to be between 1,150 and 1,200 kilometres, Eris appears as a Pluto twin, with a bright surface possibly caused by a collapsed atmosphere, owing to its cold environment. We anticipate that this atmosphere may periodically sublimate as Eris approaches its perihelion, at 37.8 astronomical units from the Sun.     

The evolutionary context of the first hominins

The relationships among the living apes and modern humans have effectively been resolved, but it is much more difficult to locate fossil apes on the tree of life because shared skeletal morphology does not always mean shared recent evolutionary history. Sorting fossil taxa into those that belong on the branch of the tree of life that leads to modern humans from those that belong on other closely related branches is a considerable challenge.     

A terahertz metamaterial with unnaturally high refractive index

Controlling the electromagnetic properties of materials, going beyond the limit that is attainable with naturally existing substances, has become a reality with the advent of metamaterials. The range of various structured artificial 'atoms' has promised a vast variety of otherwise unexpected physical phenomena, among which the experimental realization of a negative refractive index has been one of the main foci thus far. Expanding the refractive index into a high positive regime will complete the spectrum of achievable refractive index and provide more design flexibility for transformation optics. Naturally existing transparent materials possess small positive indices of refraction, except for a few semiconductors and insulators, such as lead sulphide or strontium titanate, that exhibit a rather high peak refractive index at mid- and far-infrared frequencies. Previous approaches using metamaterials were not successful in realizing broadband high refractive indices. A broadband high-refractive-index metamaterial structure was theoretically investigated only recently, but the proposed structure does not lend itself to easy implementation. Here we demonstrate that a broadband, extremely high index of refraction can be realized from large-area, free-standing, flexible terahertz metamaterials composed of strongly coupled unit cells. By drastically increasing the effective permittivity through strong capacitive coupling and decreasing the diamagnetic response with a thin metallic structure in the unit cell, a peak refractive index of 38.6 along with a low-frequency quasi-static value of over 20 were experimentally realized for a single-layer terahertz metamaterial, while maintaining low losses. As a natural extension of these single-layer metamaterials, we fabricated quasi-three-dimensional high-refractive-index metamaterials, and obtained a maximum bulk refractive index of 33.2 along with a value of around 8 at the quasi-static limit.     

中朝板块北缘志留纪海岛的发现

在内蒙古达尔罕茂明安联合旗北部巴特敖包地区发现了志留纪的海岸带及其底栖无脊椎动物化石（层孔虫、日射与床板珊瑚等）,证实当时该地发育一个位于中朝古板块北缘大陆棚上的小海岛,将其命名为巴特岛．该岛的基部由奥陶纪火成岩组成,长、短轴分别为６１０和２００ｍ,现今呈北东－南西向延伸．志留纪罗德洛世（距今约４２０Ｍａ）的地层围绕该岛分布,产状向四周倾状．巴特岛的南缘（背风）发育皮壳状生物,栖息在火成岩顶面并被     

The regulation of ion channels and transporters by glycolytically derived ATP

Glycolysis is an evolutionary conserved metabolic pathway that provides small amounts of energy in the form of ATP when compared to other pathways such as oxidative phosphorylation or fatty acid oxidation. The ATP levels inside metabolically active cells are not constant and the local ATP level will depend on the site of production as well as the respective rates of ATP production, diffusion and consumption. Membrane ion transporters (pumps, exchangers and channels) are located at sites distal to the major sources of ATP formation (the mitochondria). We review evidence that the glycolytic complex is associated with membranes; both at the plasmalemma and with membranes of the endo/sarcoplasmic reticular network. We examine the evidence for the concept that many of the ion transporters are regulated preferentially by the glycolytic process. These include the Na⁺/K⁺-ATPase, the H⁺-ATPase, various types of Ca²⁺-ATPases, the Na⁺/H⁺ exchanger, the ATP-sensitive K⁺ channel, cation channels, Na⁺ channels, Ca²⁺ channels and other channels involved in intracellular Ca²⁺ homeostasis. Regulation of these pumps, exchangers and ion channels by the glycolytic process has important consequences in a variety of physiological and pathophysiological processes, and a better understanding of this mode of regulation may have important consequences for developing future strategies in combating disease and developing novel therapeutic approaches. Received 20 July 2007; received after revision 30 July 2007; accepted 17 August 2007     

How do Shp2 mutations that oppositely influence its biochemical activity result in syndromes with overlapping symptoms?

Activating and inactivating mutations of SHP-2 are responsible, respectively, for the Noonan (NS) and the LEOPARD (LS) syndromes. Clinically, these developmental disorders overlap greatly, resulting in the apparent paradox of similar diseases caused by mutations that oppositely influence SHP-2 phosphatase activity. While the mechanisms remain unclear, recent functional analysis of SHP-2, along with the identification of other genes involved in NS and in other related syndromes (neurofibromatosis-1, Costello and cardio-facio-cutaneous syndromes), strongly suggest that Ras/MAPK represents the major signaling pathway deregulated by SHP-2 mutants. We discuss the idea that, with the exception of LS mutations that have been shown to exert a dominant negative effect, all disease-causing mutations involved in Ras/MAPK-mediated signaling, including SHP-2, might lead to enhanced MAPK activation. This suggests that a narrow range of MAPK signaling is required for appropriate development. We also discuss the possibility that LS mutations may not simply exhibit dominant negative activity. Received 30 November 2006; received after revision 8 February 2007; accepted 13 March 2007     

Variation in FTO contributes to childhood obesity and severe adult obesity

We identified a set of SNPs in the first intron of the FTO (fat mass and obesity associated) gene on chromosome 16q12.2 that is consistently strongly associated with early-onset and severe obesity in both adults and children of European ancestry with an experiment-wise P value of 1.67 x 10(-26) in 2,900 affected individuals and 5,100 controls. The at-risk haplotype yields a proportion of attributable risk of 22% for common obesity. We conclude that FTO contributes to human obesity and hence may be a target for subsequent functional analyses.     

The Shwachman-Bodian-Diamond syndrome protein mediates translational activation of ribosomes in yeast

The autosomal recessive disorder Shwachman-Diamond syndrome, characterized by bone marrow failure and leukemia predisposition, is caused by deficiency of the highly conserved Shwachman-Bodian-Diamond syndrome (SBDS) protein. Here, we identify the function of the yeast SBDS ortholog Sdo1, showing that it is critical for the release and recycling of the nucleolar shuttling factor Tif6 from pre-60S ribosomes, a key step in 60S maturation and translational activation of ribosomes. Using genome-wide synthetic genetic array mapping, we identified multiple TIF6 gain-of-function alleles that suppressed the pre-60S nuclear export defects and cytoplasmic mislocalization of Tif6 observed in sdo1Delta cells. Sdo1 appears to function within a pathway containing elongation factor-like 1, and together they control translational activation of ribosomes. Thus, our data link defective late 60S ribosomal subunit maturation to an inherited bone marrow failure syndrome associated with leukemia predisposition.