内蒙古岱海古盐度定量复原初探

通过分析湖泊表层沉积物中活体介形类（Ｌｉｍｎｏｃｙｔｈｅｒｅ ｃｆ。ｉｎｏｐｉｎａｔａ）壳体的Ｓｒ,Ｃａ比值以及湖水的Ｓｒ＾２＋,Ｃａ＾２＋比值,获取岱海介形类壳体的Ｓｒ分配系数Ｋｄ（Ｓｒ）。利用湖水Ｓｒ＾２＋／Ｃａ＾２＋值与盐度的相关关系,建立岱海湖水盐度与水介质离子比函数方程。结合岱海沉积钻孔中同种介形类壳体的 Ｓｒ,Ｃａ比值,定量恢复湖水的古盐度。     

Thirty new loci for age at menarche identified by a meta-analysis of genome-wide association studies

To identify loci for age at menarche, we performed a meta-analysis of 32 genome-wide association studies in 87,802 women of European descent, with replication in up to 14,731 women. In addition to the known loci at LIN28B (P = 5.4 × 10???) and 9q31.2 (P = 2.2 × 10?33), we identified 30 new menarche loci (all P < 5 × 10??) and found suggestive evidence for a further 10 loci (P < 1.9 × 10??). The new loci included four previously associated with body mass index (in or near FTO, SEC16B, TRA2B and TMEM18), three in or near other genes implicated in energy homeostasis (BSX, CRTC1 and MCHR2) and three in or near genes implicated in hormonal regulation (INHBA, PCSK2 and RXRG). Ingenuity and gene-set enrichment pathway analyses identified coenzyme A and fatty acid biosynthesis as biological processes related to menarche timing.     

Quantifying social group evolution

The rich set of interactions between individuals in society results in complex community structure, capturing highly connected circles of friends, families or professional cliques in a social network. Thanks to frequent changes in the activity and communication patterns of individuals, the associated social and communication network is subject to constant evolution. Our knowledge of the mechanisms governing the underlying community dynamics is limited, but is essential for a deeper understanding of the development and self-optimization of society as a whole. We have developed an algorithm based on clique percolation that allows us to investigate the time dependence of overlapping communities on a large scale, and thus uncover basic relationships characterizing community evolution. Our focus is on networks capturing the collaboration between scientists and the calls between mobile phone users. We find that large groups persist for longer if they are capable of dynamically altering their membership, suggesting that an ability to change the group composition results in better adaptability. The behaviour of small groups displays the opposite tendency-the condition for stability is that their composition remains unchanged. We also show that knowledge of the time commitment of members to a given community can be used for estimating the community's lifetime. These findings offer insight into the fundamental differences between the dynamics of small groups and large institutions.     

LI-cadherin cis-dimerizes in the plasma membrane Ca2+ independently and forms highly dynamic trans-contacts

LI-cadherin belongs to the family of 7D-cadherins that is characterized by a low sequence similarity to classical cadherins, seven extracellular cadherin repeats (ECs), and a short cytoplasmic domain. Nevertheless, LI-cadherins mediates Ca²⁺-dependent cell–cell adhesion and induces an epitheloid cellular phenotype in non-polarized CHO cells. Whereas several studies suggest that classical cadherins cis-dimerize in a Ca²⁺-dependent manner and interact in trans by strand-swapping tryptophan 2 of EC1, little is known about the molecular interactions of LI-cadherin, which lacks tryptophan 2. We thus expressed fluorescent LI-cadherin fusion proteins in HEK293 and CHO cells, analyzed their cell–cell adhesive properties and studied their cellular distribution, cis-interaction, and lateral diffusion in the presence and absence of Ca²⁺. LI-cadherin highly concentrates in cell contact areas but rapidly leaves those sites upon Ca²⁺ depletion and redistributes evenly on the cell surface, indicating that it is only kept in the contact areas by trans-interactions. Fluorescence resonance energy transfer analysis of LI-cadherin-CFP and -YFP revealed that LI-cadherin forms cis-dimers that resist Ca²⁺ depletion. As determined by fluorescence redistribution after photobleaching, LI-cadherin freely diffuses in the plasma membrane as a cis-dimer (D?=?0.42?±?0.03?μm²/s). When trapped by trans-binding in cell contact areas, its diffusion coefficient decreases only threefold to D?=?0.12?±?0.01?μm²/s, revealing that, in contrast to classical and desmosomal cadherins, trans-contacts formed by LI-cadherin are highly dynamic.     

Discovery of a magma chamber and faults beneath a Mid-Atlantic Ridge hydrothermal field

Crust at slow-spreading ridges is formed by a combination of magmatic and tectonic processes, with magmatic accretion possibly involving short-lived crustal magma chambers. The reflections of seismic waves from crustal magma chambers have been observed beneath intermediate and fast-spreading centres, but it has been difficult to image such magma chambers beneath slow-spreading centres, owing to rough seafloor topography and associated seafloor scattering. In the absence of any images of magma chambers or of subsurface near-axis faults, it has been difficult to characterize the interplay of magmatic and tectonic processes in crustal accretion and hydrothermal circulation at slow-spreading ridges. Here we report the presence of a crustal magma chamber beneath the slow-spreading Lucky Strike segment of the Mid-Atlantic Ridge. The reflection from the top of the magma chamber, centred beneath the Lucky Strike volcano and hydrothermal field, is approximately 3 km beneath the sea floor, 3-4 km wide and extends up to 7 km along-axis. We suggest that this magma chamber provides the heat for the active hydrothermal vent field above it. We also observe axial valley bounding faults that seem to penetrate down to the magma chamber depth as well as a set of inward-dipping faults cutting through the volcanic edifice, suggesting continuous interactions between tectonic and magmatic processes.     

Fast neurotransmitter release triggered by Ca influx through AMPA-type glutamate receptors

Feedback inhibition at reciprocal synapses between A17 amacrine cells and rod bipolar cells (RBCs) shapes light-evoked responses in the retina. Glutamate-mediated excitation of A17 cells elicits GABA (gamma-aminobutyric acid)-mediated inhibitory feedback onto RBCs, but the mechanisms that underlie GABA release from the dendrites of A17 cells are unknown. If, as observed at all other synapses studied, voltage-gated calcium channels (VGCCs) couple membrane depolarization to neurotransmitter release, feedforward excitatory postsynaptic potentials could spread through A17 dendrites to elicit 'surround' feedback inhibitory transmission at neighbouring synapses. Here we show, however, that GABA release from A17 cells in the rat retina does not depend on VGCCs or membrane depolarization. Instead, calcium-permeable AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors (AMPARs), activated by glutamate released from RBCs, provide the calcium influx necessary to trigger GABA release from A17 cells. The AMPAR-mediated calcium signal is amplified by calcium-induced calcium release (CICR) from intracellular calcium stores. These results describe a fast synapse that operates independently of VGCCs and membrane depolarization and reveal a previously unknown form of feedback inhibition within a neural circuit.     

Widespread amphibian extinctions from epidemic disease driven by global warming

As the Earth warms, many species are likely to disappear, often because of changing disease dynamics. Here we show that a recent mass extinction associated with pathogen outbreaks is tied to global warming. Seventeen years ago, in the mountains of Costa Rica, the Monteverde harlequin frog (Atelopus sp.) vanished along with the golden toad (Bufo periglenes). An estimated 67% of the 110 or so species of Atelopus, which are endemic to the American tropics, have met the same fate, and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis) is implicated. Analysing the timing of losses in relation to changes in sea surface and air temperatures, we conclude with 'very high confidence' (> 99%, following the Intergovernmental Panel on Climate Change, IPCC) that large-scale warming is a key factor in the disappearances. We propose that temperatures at many highland localities are shifting towards the growth optimum of Batrachochytrium, thus encouraging outbreaks. With climate change promoting infectious disease and eroding biodiversity, the urgency of reducing greenhouse-gas concentrations is now undeniable.