南苏鲁超高压榴辉岩中罕见的原生高密度盐水溶液包裹体

在南苏鲁超高压变质带发现了原生高密度流体包裹体. 这种包裹体在超高压榴辉岩的石榴石中呈孤立和小群分布, 冷冻法确定包裹体的低共熔温度≤–52℃, 在重复冷冻-升温的特定阶段, 液相包裹体中出现气泡, 测得液-气均一温度≤–12.5℃, 由此得到流体成分属CaCl₂-NaCl-H₂O体系, 流体密度为1.27 g/cm³, 在相当于榴辉岩相峰期温度下的压力约为2.4 GPa, 接近超高压变质条件. 这类包裹体在榴辉岩的折返过程中与寄主矿物发生反应, 形成含水硅酸盐矿物, 并使其密度降低, 转变成气液多相包裹体.     

Somatic mutations in PTPN11 in juvenile myelomonocytic leukemia,myelodysplastic syndromes and acute myeloid leukemia

We report here that individuals with Noonan syndrome and juvenile myelomonocytic leukemia (JMML) have germline mutations in PTPN11 and that somatic mutations in PTPN11 account for 34% of non-syndromic JMML. Furthermore, we found mutations in PTPN11 in a small percentage of individuals with myelodysplastic syndrome (MDS) and de novo acute myeloid leukemia (AML). Functional analyses documented that the two most common mutations in PTPN11 associated with JMML caused a gain of function.     

Robust judgement of inter-object distance by an arthropod

Animals use several strategies for depth vision, reflecting the constraints imposed by body size, the structure of the visual system and the visual geometry of the environment. Arthropods in particular have restricted depth perception, because they are small and possess closely set, low-resolution compound eyes. Yet, here we show that fiddler crabs defending their burrows from conspecifics can judge how close other crabs are to their burrow. When confronted with small dummy crabs, the burrow owners assess the dummy's position and motion relative to their burrow and not relative to themselves--in other words, by using an allocentric rather than an egocentric frame of reference. Irrespective of their own distance from the dummy, the likelihood that the crabs rush back to defend their burrow increases strongly as the dummy approaches the burrow. In addition, the mean dummy-burrow distance at which the crabs respond is constant and independent of the dummy's direction of approach. We propose that to solve this sophisticated task of relative distance judgement, the crabs combine visual information on dummy position and direction with information on burrow location acquired during path integration. In doing so, the crabs, like humans, make clever use of the visual geometry of their environment.     

A very energetic supernova associated with the gamma-ray burst of 29 March 2003

Over the past five years evidence has mounted that long-duration (>2 s) gamma-ray bursts (GRBs)-the most luminous of all astronomical explosions-signal the collapse of massive stars in our Universe. This evidence was originally based on the probable association of one unusual GRB with a supernova, but now includes the association of GRBs with regions of massive star formation in distant galaxies, the appearance of supernova-like 'bumps' in the optical afterglow light curves of several bursts and lines of freshly synthesized elements in the spectra of a few X-ray afterglows. These observations support, but do not yet conclusively demonstrate, the idea that long-duration GRBs are associated with the deaths of massive stars, presumably arising from core collapse. Here we report evidence that a very energetic supernova (a hypernova) was temporally and spatially coincident with a GRB at redshift z = 0.1685. The timing of the supernova indicates that it exploded within a few days of the GRB, strongly suggesting that core-collapse events can give rise to GRBs, thereby favouring the 'collapsar' model.     

Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB030329

The association of a supernova with GRB030329 strongly supports the 'collapsar' model of gamma-ray bursts, where a relativistic jet forms after the progenitor star collapses. Such jets cannot be spatially resolved because gamma-ray bursts lie at cosmological distances; their existence is instead inferred from 'breaks' in the light curves of the afterglows, and from the theoretical desire to reduce the estimated total energy of the burst by proposing that most of it comes out in narrow beams. Temporal evolution of the polarization of the afterglows may provide independent evidence for the jet structure of the relativistic outflow. Small-level polarization ( approximately 1-3 per cent) has been reported for a few bursts, but its temporal evolution has yet to be established. Here we report polarimetric observations of the afterglow of GRB030329. We establish the polarization light curve, detect sustained polarization at the per cent level, and find significant variability. The data imply that the afterglow magnetic field has a small coherence length and is mostly random, probably generated by turbulence, in contrast with the picture arising from the high polarization detected in the prompt gamma-rays from GRB021206 (ref. 18).