High-resolution record of Northern Hemisphere climate extending into the last interglacial period

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5 degrees C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time.     

Sleep inspires insight

Insight denotes a mental restructuring that leads to a sudden gain of explicit knowledge allowing qualitatively changed behaviour. Anecdotal reports on scientific discovery suggest that pivotal insights can be gained through sleep. Sleep consolidates recent memories and, concomitantly, could allow insight by changing their representational structure. Here we show a facilitating role of sleep in a process of insight. Subjects performed a cognitive task requiring the learning of stimulus-response sequences, in which they improved gradually by increasing response speed across task blocks. However, they could also improve abruptly after gaining insight into a hidden abstract rule underlying all sequences. Initial training establishing a task representation was followed by 8 h of nocturnal sleep, nocturnal wakefulness, or daytime wakefulness. At subsequent retesting, more than twice as many subjects gained insight into the hidden rule after sleep as after wakefulness, regardless of time of day. Sleep did not enhance insight in the absence of initial training. A characteristic antecedent of sleep-related insight was revealed in a slowing of reaction times across sleep. We conclude that sleep, by restructuring new memory representations, facilitates extraction of explicit knowledge and insightful behaviour.     

Stereocilia defects in the sensory hair cells of the inner ear in mice deficient in integrin alpha8beta1

The mammalian inner ear contains organs for the detection of sound and acceleration, the cochlea and the vestibule, respectively. Mechanosensory hair cells within the neuroepithelia of these organs transduce mechanical force generated by sound waves or head movements into neuronal signals. Defects in hair cells lead to deafness and balance defects. Hair cells have stereocilia that are indispensable for mechanosensation, but the molecular mechanisms regulating stereocilia formation are poorly understood. We show here that integrin alpha8beta1, its ligand fibronectin and the integrin-regulated focal adhesion kinase (FAK) co-localize to the apical hair-cell surface where stereocilia are forming. In mice homozygous for a targeted mutation of Itga8 (encoding the alphabeta8 subunit), this co-localization is perturbed and hair cells in the utricle, a vestibular subcompartment, lack stereocilia or contain malformed stereocilia. Most integrin alpha-8beta1-deficient mice die soon after birth due to kidney defects. Many of the survivors have difficulty balancing, consistent with the structural defects of the inner ear. Our data suggest that integrin alpha8beta1, and potentially other integrins, regulates hair-cell differentiation and stereocilia maturation. Mutations affecting matrix molecules cause inherited forms of inner ear disease and integrins may mediate some effects of matrix molecules in the ear; thus, mutations in integrin genes may lead to inner-ear diseases as well.     

Mutations in the gene encoding the serine protease inhibitor, Kazal type 1 are associated with chronic pancreatitis

Chronic pancreatitis (CP) is a continuing or relapsing inflammatory disease of the pancreas. In approximately one-third of all cases, no aetiological factor can be found, and these patients are classified as having idiopathic disease. Pathophysiologically, autodigestion and inflammation may be caused by either increased proteolytic activity or decreased protease inhibition. Several studies have demonstrated mutations in the cationic trypsinogen gene (PRSS1) in patients with hereditary or idiopathic CP. It is thought that these mutations result in increased trypsin activity within the pancreatic parenchyma. Most patients with idiopathic or hereditary CP, however, do not have mutations in PRSS1 (ref. 4). Here we analysed 96 unrelated children and adolescents with CP for mutations in the gene encoding the serine protease inhibitor, Kazal type 1 (SPINK1), a pancreatic trypsin inhibitor. We found mutations in 23% of the patients. In 18 patients, 6 of whom were homozygous, we detected a missense mutation of codon 34 (N34S). We also found four other sequence variants. Our results indicate that mutations in SPINK1 are associated with chronic pancreatitis.     

Loss-of-function mutations in the EGF-CFC gene CFC1 are associated with human left-right laterality defects

All vertebrates display a characteristic asymmetry of internal organs with the cardiac apex, stomach and spleen towards the left, and the liver and gall bladder on the right. Left-right (L-R) axis abnormalities or laterality defects are common in humans (1 in 8,500 live births). Several genes (such as Nodal, Ebaf and Pitx2) have been implicated in L-R organ positioning in model organisms. In humans, relatively few genes have been associated with a small percentage of human situs defects. These include ZIC3 (ref. 5), LEFTB (formerly LEFTY2; ref. 6) and ACVR2B (encoding activin receptor IIB; ref. 7). The EGF-CFC genes, mouse Cfc1 (encoding the Cryptic protein; ref. 9) and zebrafish one-eyed pinhead (oep; refs 10, 11) are essential for the establishment of the L-R axis. EGF-CFC proteins act as co-factors for Nodal-related signals, which have also been implicated in L-R axis development. Here we identify loss-of-function mutations in human CFC1 (encoding the CRYPTIC protein) in patients with heterotaxic phenotypes (randomized organ positioning). The mutant proteins have aberrant cellular localization in transfected cells and are functionally defective in a zebrafish oep-mutant rescue assay. Our findings indicate that the essential role of EGF-CFC genes and Nodal signalling in left-right axis formation is conserved from fish to humans. Moreover, our results support a role for environmental and/or genetic modifiers in determining the ultimate phenotype in humans.     

福建省筑坝与泄洪技术发展报告

文章总结和回顾了福建在筑坝和泄洪技术方面的研究、实践与进展,着重介绍了高掺粉煤灰碾压混凝土、碾压混凝土坝的防渗结构和层面抗剪强度研究,混凝土面板堆石坝的防裂技术、新型止水结构、挤压式混凝土边墙和新近建成的胶凝砂砾石围堰等坝工技术,以及具有福建特色,拥有自主知识产权的拱坝大差动齿坎泄洪结构,宽尾墩一阶梯式坝面一戽池联合消能结构和宽带低真空实用堰的设计方法等大坝泄洪技术、旁侧溢洪道扩散泄洪技术和未完建面板堆石坝过洪技术.     

中国热点论文榜

"热点论文"在科学界已经是耳熟能详的名词。顾名思义,热点论文即为众人所关注的论文。这种关注度在科学计量学领域可以用论文被引用的次数来量化和测试。美国汤姆森科技信息集团(Thomson