Widespread local house-sparrow extinctions

House-sparrow populations have declined sharply in Western Europe in recent decades, but the reasons for this decline have yet to be identified, despite intense public interest in the matter. Here we use a combination of field experimentation, genetic analysis and demographic data to show that a reduction in winter food supply caused by agricultural intensification is probably the principal explanation for the widespread local extinctions of rural house-sparrow populations in southern England. We show that farmland populations exhibit fine-level genetic structuring and that some populations are unable to sustain themselves (sinks), whereas others act as sources.     

Interdecadal variation in the extent of South Pacific tropical waters during the Younger Dryas event

During the Younger Dryas event, about 12,000 years ago, the Northern Hemisphere cooled by between 2 and 10 degrees C (refs 1, 2) whereas East Antarctica experienced warming. But the spatial signature of the event in the southern mid-latitudes and tropics is less well known, as records are sparse and inconclusive. Here we present high-resolution analyses of skeletal Sr/Ca and 18O/16O ratios for a giant fossil Diploastrea heliopora coral that was preserved in growth position on the raised reef terraces of Espiritu Santo Island, Vanuatu, in the southwestern tropical Pacific Ocean. Our data indicate that sea surface temperatures in Vanuatu were on average 4.5 +/- 1.3 degrees C cooler during the Younger Dryas event than today, with a significant interdecadal modulation. The amplified annual cycle of sea surface temperatures, relative to today, indicates that cooling was caused by the compression of tropical waters towards the Equator. The positive correlation in our record between the oxygen isotope ratios of sea water and sea surface temperatures suggests that the South Pacific convergence zone, which brings 18O-depleted precipitation to the area today, was not active during the Younger Dryas period.     

Extinction risk from climate change

Climate change over the past approximately 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15-37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction ( approximately 18%) than mid-range ( approximately 24%) and maximum-change ( approximately 35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.     

Geology and palaeontology of the Upper Miocene Toros-Menalla hominid locality,Chad

All six known specimens of the early hominid Sahelanthropus tchadensis come from Toros-Menalla site 266 (TM 266), a single locality in the Djurab Desert, northern Chad, central Africa. Here we present a preliminary analysis of the palaeontological and palaeoecological context of these finds. The rich fauna from TM 266 includes a significant aquatic component such as fish, crocodiles and amphibious mammals, alongside animals associated with gallery forest and savannah, such as primates, rodents, elephants, equids and bovids. The fauna suggests a biochronological age between 6 and 7 million years. Taken together with the sedimentological evidence, the fauna suggests that S. tchadensis lived close to a lake, but not far from a sandy desert, perhaps the oldest record of desert conditions in the Neogene of northern central Africa.     

水分和热胁迫对5种苗木生长及生物量的影响

以杉木、马尾松、花旗松、北美乔柏和扭叶松为对象，研究了水分和热胁迫对苗木生长期间生长和生物量的影响。结果表明：(1)水分胁迫对杉木、马尾松、花旗松、北美乔柏和扭叶松5个树种的苗高增长量和增长率均有显影响，但影响的程度因树种而异；(2)热胁迫对苗高增长量和增长率也有一定影响，但不如水分胁迫的影响大。热胁迫对北美乔柏和花旗松的苗高增长量及增长率有显影响，对其它树种的影响较小；(3)水分胁迫对杉苗生物量的影响不大，热胁迫对杉苗生物量指标的各部分干重有显影响；热和水分胁迫对马尾松苗木3个生物量指标均有显影响；热胁迫对花旗松、北美乔柏和扭叶松苗木生物量指标的影响均大于水分胁迫；(4)5个受试树种的根茎比受热和水分胁迫的影响都不大。     

Observation of random-phase lattice solitons

The coherence of waves in periodic systems (lattices) is crucial to their dynamics, as interference effects, such as Bragg reflections, largely determine their propagation. Whereas linear systems allow superposition, nonlinearity introduces a non-trivial interplay between localization effects, coupling between lattice sites, and incoherence. Until recently, all research on solitary waves (solitons) in nonlinear lattices has involved only coherent waves. In such cases, linear dispersion or diffraction of wave packets can be balanced by nonlinear effects, resulting in coherent lattice (or 'discrete') solitons; these have been studied in many branches of science. However, in most natural systems, waves with only partial coherence are more common, because fluctuations (thermal, quantum or some other) can reduce the correlation length to a distance comparable to the lattice spacing. Such systems should support random-phase lattice solitons displaying distinct features. Here we report the experimental observation of random-phase lattice solitons, demonstrating their self-trapping and local periodicity in real space, in addition to their multi-peaked power spectrum in momentum space. We discuss the relevance of such solitons to other nonlinear periodic systems in which fluctuating waves propagate, such as atomic systems, plasmas and molecular chains.     

La dualité des « Prolans » urinaires

Conclusions La préhypophyse sécrète deux hormones, l'auxogène et la crinogène. On peut, en détruisant ou éliminant le crinogène, obtenir des extraits à effet auxogène pur. L'urine de femme castrée ne contient que le principe auxogène: la lutéinisation, observée dans certains cas, est un effet secondaire dû à l'intervention de l'hypophyse de l'animal traité.L'urine de femme enceinte contient deux prolans: un principe crinogène identique à celui de l'hypophyse et agissant, comme ce dernier, directement sur l'ovaire; un principe hypophysotrope, stimulant l'hypophyse de l'animal — dans la mesure où elle est présente ou capable de réponse — et se traduisant dans l'ovaire par un effet auxogène de type physiologique.Les deux principes de l'UFE peuvent être séparés ou l'un peut être détruit avec conservation partielle de l'autre. Les taux des deux prolans varient d'une urine à l'autre, pour une même urine au cours de la gestation ou au cours du chauffage.L'existence de ces deux principes est importante à considérer lorsqu'on utilise, dans la pratique médicale, des extraits d'UFE qui sont, en réalité, des mélanges variables de deux hormones, dont les effets physiologiques et, par suite, les indications thérapentiques ne sont certainement pas les mémes.     

颈椎前路单节段融合中加压钉和限制型固定板的力学特性

研究了一款颈椎前路加压钉在颈椎前路融合手术中临近椎体的应力。分别采用传统结构的固定板和新结构加压钉,对12具人体颈椎标本实施C4-C5节段椎间盘切除术后的前路融合固定,利用生物力学试验机和高精度三维运动测试系统进行试验,比较了两种不同结构固定板(钉)植入颈椎后在前屈15°或后伸20°运动条件下的融合性能,以及在50N及100N的轴向载荷条件下二者的静态载荷分布。结果表明:在固定效果上,前路加压钉和限制型前路固定板两者功能相仿,不存在显著差异;针对C4-C5椎间植入体上所承受的压力,选用前路加压钉较选用限制型前路固定板为佳。     

Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy

Although many genes that predispose for epilepsy in humans have been determined, those that underlie the classical syndromes of idiopathic generalized epilepsy (IGE) have yet to be identified. We report that an Ala322Asp mutation in GABRA1, encoding the alpha1 subunit of the gamma-aminobutyric acid receptor subtype A (GABA(A)), is found in affected individuals of a large French Canadian family with juvenile myoclonic epilepsy. Compared with wildtype receptors, GABA(A) receptors that contain the mutant subunit show a lesser amplitude of GABA-activated currents in vitro, indicating that seizures may result from loss of function of this inhibitory ligand-gated channel. Our results confirm that mutation of GABRA1 predisposes towards a common idiopathic generalized epilepsy syndrome in humans.