Record of mid-Archaean subduction from metamorphism in the Barberton terrain, South Africa

Although plate tectonics is the central geological process of the modern Earth, its form and existence during the Archaean era (4.0-2.5 Gyr ago) are disputed. The existence of subduction during this time is particularly controversial because characteristic subduction-related mineral assemblages, typically documenting apparent geothermal gradients of 15 degrees C km(-1) or less, have not yet been recorded from in situ Archaean rocks (the lowest recorded apparent geothermal gradients are greater than 25 degrees C km(-1)). Despite this absence from the rock record, low Archaean geothermal gradients are suggested by eclogitic nodules in kimberlites and circumstantial evidence for subduction processes, including possible accretion-related structures, has been reported in Archaean terrains. The lack of spatially and temporally well-constrained high-pressure, low-temperature metamorphism continues, however, to cast doubt on the relevance of subduction-driven tectonics during the first 1.5 Gyr of the Earth's history. Here we report garnet-albite-bearing mineral assemblages that record pressures of 1.2-1.5 GPa at temperatures of 600-650 degrees C from supracrustal amphibolites from the mid-Archaean Barberton granitoid-greenstone terrain. These conditions point to apparent geothermal gradients of 12-15 degrees C-similar to those found in recent subduction zones-that coincided with the main phase of terrane accretion in the structurally overlying Barberton greenstone belt. These high-pressure, low-temperature conditions represent metamorphic evidence for cold and strong lithosphere, as well as subduction-driven tectonic processes, during the evolution of the early Earth.     

Defective acidification of intracellular organelles in cystic fibrosis.

The phenotype of cystic fibrosis (CF) includes abnormalities in transepithelial transport of Cl- (refs 1-5), decreased sialylation and increased sulphation and fucosylation of glycoproteins, and lung colonization with Pseudomonas. It is not apparent how these abnormalities are interrelated, nor how they result from loss of function of the CF gene-encoded transmembrane regulator (CFTR). We have previously shown that that the pH of a secretory granule is regulated by the vesicular conductance for Cl- (ref. 11). Here we find defective acidification in CF cells of the trans-Golgi/trans-Golgi network, of prelysosomes and of endosomes as a result of diminished Cl- conductance. Sialytation of proteins and lipids is reduced and ligand traffic altered. These abnormalities can result from defective acidification because vacuolar pH regulates glycoprotein processing and ligand transport. The CF phenotype is similar to that of alkalinized cells and acidification-defective mutatants.     

Developmental defects of the ear, cranial nerves and hindbrain resulting from targeted disruption of the mouse homeobox gene Hox-1.6.

Gene targeting in mouse embryo-derived stem cells has been used to generate mice with a disruption in the homeobox gene Hox-1.6. Mice heterozygous at the Hox-1.6 locus appear normal, whereas Hox-1.6-/Hox-1.6- mice die at or shortly after birth. These homozygotes exhibit profound defects in the formation of the external, middle and inner ears as well as in specific hindbrain nuclei, and in cranial nerves and ganglia. The affected tissues lie within a narrow region along the anteroposterior axis of the mouse but are of diverse embryonic origin. The set of defects associated with the disruption of Hox-1.6 is distinct from and nonoverlapping with that of the closely linked Hox-1.5 gene. But both mutations cause loss, rather than homeotic transformation, of tissues and structures.     

磁性多层膜Ta/NiO/NiFe/Ta角分辨XPS

磁性多层膜Ta/NiO/NiFe/Ta由磁控溅射方法制备.采用角分辨X射线光电子能谱(XPS)研究了反铁磁(NiO)/铁磁(NiFe)界面.结果表明,在NiO/NiFe界面发生了化学反应: NiO+Fe = Ni+FeO和3NiO+2Fe =3Ni+Fe2O3,此反应深度约为1～1.5 nm.反应产物将影响NiO对NiFe的交换耦合.     

凝胶-浇注法制备LaxSr1-1.5xTiO3阳极材料及其性能的研究

采用凝胶-浇注法合成钙钛矿复合系的阳极材料LaxSr1-1.5xTiO3(x=0.1～0.4),探究La掺杂量对相组成、烧结性能、力学性能及高温电导率等的影响.LaxSr1-1.5xTiO3粉体在1 100℃下预烧可得到典型的钙钛矿结构.在1 400℃下煅烧得到的烧结体的电导率数据显示:当x=0.3时电导率最高,在测试温度为800℃时高达180 S.cm-1,与传统固相法相比,其烧结温度降低了约200℃.     

Autistic-like behaviours and hyperactivity in mice lacking ProSAP1/Shank2

Autism spectrum disorders comprise a range of neurodevelopmental disorders characterized by deficits in social interaction and communication, and by repetitive behaviour. Mutations in synaptic proteins such as neuroligins, neurexins, GKAPs/SAPAPs and ProSAPs/Shanks were identified in patients with autism spectrum disorder, but the causative mechanisms remain largely unknown. ProSAPs/Shanks build large homo- and heteromeric protein complexes at excitatory synapses and organize the complex protein machinery of the postsynaptic density in a laminar fashion. Here we demonstrate that genetic deletion of ProSAP1/Shank2 results in an early, brain-region-specific upregulation of ionotropic glutamate receptors at the synapse and increased levels of ProSAP2/Shank3. Moreover, ProSAP1/Shank2(-/-) mutants exhibit fewer dendritic spines and show reduced basal synaptic transmission, a reduced frequency of miniature excitatory postsynaptic currents and enhanced N-methyl-d-aspartate receptor-mediated excitatory currents at the physiological level. Mutants are extremely hyperactive and display profound autistic-like behavioural alterations including repetitive grooming as well as abnormalities in vocal and social behaviours. By comparing the data on ProSAP1/Shank2(-/-) mutants with ProSAP2/Shank3αβ(-/-) mice, we show that different abnormalities in synaptic glutamate receptor expression can cause alterations in social interactions and communication. Accordingly, we propose that appropriate therapies for autism spectrum disorders are to be carefully matched to the underlying synaptopathic phenotype.     

一种新型金属表面抛光剂

研究了用于金属表面的液体抛光剂,含有1%~3%二甘醇丁醚,0.5%~1.0%烷基苯磺酸钠,1%~1.5?TA,2%~3%苯甲醇及少量助剂等,广泛用于金属表面的抛光与洗涤,各项性能指标优于传统型金属表面抛光剂.     

Facile synthesis of polypyrrole nanowires for high-performance supercapacitor electrode materials

Polypyrrole nanowires are facile synthesized under a mild condition with FeCl_3 as an oxidant. Polypyrrole nanowires with the width of 120 nm form many nanogaps or pores due to the intertwined nanostructures. More importantly, PPy nanowires were further applied for supercapacitor electrode materials.After electrochemical testing, it was observed that the PPy nanowire based electrode showed a large specific capacitance(420 Fg~(-1), 1.5 Ag~(-1)) and good rate capability(272 Fg~(-1), 18.0 Ag~(-1)), which is larger than that of most of published results. The as-prepared electrode can work well even after 8000 cycles at 1.5 Ag~(-1).     

NMDA spikes in basal dendrites of cortical pyramidal neurons

Basal dendrites are a major target for synaptic inputs innervating cortical pyramidal neurons. At present little is known about signal processing in these fine dendrites. Here we show that coactivation of clustered neighbouring basal inputs initiated local dendritic spikes, which resulted in a 5.9 +/- 1.5 mV (peak) and 64.4 +/- 19.8 ms (half-width) cable-filtered voltage change at the soma that amplified the somatic voltage response by 226 +/- 46%. These spikes were accompanied by large calcium transients restricted to the activated dendritic segment. In contrast to conventional sodium or calcium spikes, these spikes were mediated mostly by NMDA (N-methyl-D-aspartate) receptor channels, which contributed at least 80% of the total charge. The ionic mechanism of these NMDA spikes may allow 'dynamic spike-initiation zones', set by the spatial distribution of glutamate pre-bound to NMDA receptors, which in turn would depend on recent and ongoing activity in the cortical network. In addition, NMDA spikes may serve as a powerful mechanism for modification of the cortical network by inducing long-term strengthening of co-activated neighbouring inputs.     

Novel submicroscopic extrachromosomal elements containing amplified genes in human cells

In previous work, several methotrexate (MTX)-resistant variants were isolated frm the human cell line HeLa BU25, which exhibited a high degree of dihydrofolate (DHFR) gene amplification (estimated to be 250- to 300-fold). These variants did not contain any chromosome with a homogeneously staining region (HSR) and exhibited only a small average number of minute chromosomes per cell: these two types of karyotypic abnormalities generally accompany selective gene amplification. We now report that structures containing amplified DHFR genes in one of these variants (HeLa BU25-10B3) can be isolated by pulsed-field gradient or field-inversion gel electrophoresis as homogeneous DNA molecules of approximately 650 kilobases (kb). Electron microscopy of metaphase spreads from these cells reveals chromatin fibres with a similar DNA content, which are probably related to the above elements. These represent a novel type of extrachromosomal structures in mammalian cells.     

阿尔茨海默病DT-MRI脑图像的识别

利用脑部的扩散张量磁共振图像(d iffus ion tensorm agnetic resonance im ag ing,DT-M R I),探索对阿尔茨海默病计算机辅助诊断方法,提出了一种线性识别方法。对9例阿尔茨海默病患者和9例正常人脑部在1.5 T磁共振成像系统上作DT-M R I扫描。测量胼胝体膝部、胼胝体压部和海马的表观扩散系数和各向异性分数。对这些参数进行了统计,以训练识别器。用留一法估算,得到识别正确率为83.33%。结果表明,DT-M R I图像可以反映阿尔茨海默患者脑部的受损情况,该识别方法能为阿尔茨海默病的临床诊断提供帮助。     

A highly basic histone H4 domain bound to the sharply bent region of nucleosomal DNA

A nucleosomal core particle is composed of two each of histones H2A, H2B, H3 and H4 located inside the particle with approximately 47 base pairs (bp) of DNA wrapped around the octamer in about 1.8 turns of a left-handed superhelix. The path of the superhelix is not smooth; the DNA is sharply bent, or kinked, at positions symmetrically disposed at a distance of about one and four double-helical turns in both directions from the nucleosomal dyad axis (designated as sites +/- 1 and +/- 4 respectively). This non-uniform bending is considered archetypal to other DNA-protein complexes, but its mechanism is not clear (reviewed in ref. 4). DNA-histone chemical cross-linking within the core particle has revealed strong binding of each of the two histone H4 molecules to DNA at a distance of 1.5 helical turns either side of the nucleosomal dyad axis (sites +/- 1.5). In each of these sites, a single flexible domain of H4 was previously shown to contact three points, at about nucleotides 55 and 65 on one strand and nucleotide 88 on the complementary strand, numbering from the 5' terminus of each 147-base strand; these three locations are closely juxtaposed across the highly compressed minor and major grooves (Fig. 1). Here we report that the amino-acid residue of histone H4 cross-linked at the 1.5 site is histidine-18, embedded in a highly basic cluster Lys-Arg-His-Arg-Lys-Val-Leu-Arg which is probably involved in the sharp bending of the DNA double helix at the +/- 1 sites.     

Rapid appearance and local toxicity of amyloid-beta plaques in a mouse model of Alzheimer's disease

Senile plaques accumulate over the course of decades in the brains of patients with Alzheimer's disease. A fundamental tenet of the amyloid hypothesis of Alzheimer's disease is that the deposition of amyloid-beta precedes and induces the neuronal abnormalities that underlie dementia. This idea has been challenged, however, by the suggestion that alterations in axonal trafficking and morphological abnormalities precede and lead to senile plaques. The role of microglia in accelerating or retarding these processes has been uncertain. To investigate the temporal relation between plaque formation and the changes in local neuritic architecture, we used longitudinal in vivo multiphoton microscopy to sequentially image young APPswe/PS1d9xYFP (B6C3-YFP) transgenic mice. Here we show that plaques form extraordinarily quickly, over 24 h. Within 1-2 days of a new plaque's appearance, microglia are activated and recruited to the site. Progressive neuritic changes ensue, leading to increasingly dysmorphic neurites over the next days to weeks. These data establish plaques as a critical mediator of neuritic pathology.     

Al2 O3掺杂对Ce0.8 Gd0.15 Y0.05 O2-δ固体电解质的微结构与电性能的影响

采用溶胶-凝胶法制备了AlO1.5掺杂浓度为0.5%,1.0%,2.0%的AlO1.5/Ce0.8Gd0.15Y0.05O2-δ固体电解质材料,利用X射线衍射（XRD）、扫描电子显微镜（SEM）和交流阻抗谱研究了Al2O3掺杂对Ce0.8Gd0.15Y0.05O2-δ微观结构及电性能的影响,结果表明：800℃焙烧的所有粉末样品均为单相立方萤石结构,在所有样品中,AlO1.5掺杂量为0.5%的样品晶粒均匀,较致密,交流阻抗谱测试表明掺杂AlO1.5（x=0.5%）使Ce0.8Gd0.15Y0.05O2-δ晶界电阻减小,晶界电导率增高;当AlO1.5掺杂量x≥1%时,Al2O3对晶界的阻塞作用使晶界电导率降低,在所有样品中Ce0.8Gd0.15Y0.05O2-δ/0.5%AlO1.5晶界电导率最高（σ700℃=8.12×10-3S/cm）,说明在Ce0.8Gd0.15Y0.05O2-δ少量掺杂AlO1.5（x=0.5%）具有烧结助剂和晶界清除剂的作用.     

铝-锌合金在氯化物-醋酸介质中的电化学活化机理

目的 研究商用Al-Zn(Zn 4%)合金在氯化物-乙酸介质中的电化学行为.方法 用传统电化学方法获得其电化学数据.通过利用扫描电镜(SEM)和定量能量色散X-射线分析(EDX),测试了金电极的表面特征.结果 研究发现,在氯化物溶液中,活性分解发生在一个非常负的电位上(-1.5V).这显著增加了该合金的电化学行为.其目的在于解释该合金给出的工作电位(-1.1V)、高效率、观察到的准均衡侵蚀和增强的电化学行为(-1.5V)之间的关系.提出了一个用来解释这一发现和利用铟离子来活化纯铝的标准模型.结论 研究发现铝的活化机制有2个:(ⅰ)当在表面上有足够的以准液体状态存在铟时,In-Al汞合金是造成活化作用过程(-1.5 V)的原因.这一过程是通过置换反应促进了Zn的表面富集.(ⅱ)在更高阳极电位处(接近-1.2 V),表面上铟的存在促进了氯化物的吸附过程,该过程使阳极反应去极化.     

Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge

Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr(-1)). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth's slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (approximately 1.0 cm yr(-1)) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought.     

一种新的环金属化钌配合物的合成与表征

合成了一种新的C,N-配位型环金属化钌染料敏化剂Ru-1,通过核磁共振氢谱以及红外光谱对该配合物进行了表征．由紫外-可见吸收光谱表明：该配合物的金属到配体的电荷转移跃迁（MLCT）吸收最大可达546nm,比传统的明星染料N3（[Ru（dcbpy）2（NCS）2],dcbpy=2,2＇-二联吡啶-4,4’-二羧酸）红移约10nm,且摩尔消光系数提高了约1．5倍．由此说明该配合物在长波方向表现出比N3更为优良的吸收性能,这对提高染料敏化纳米晶太阳能电池的光电转化效率十分有利．     

利用大孔树脂吸附法分离儿茶素EGCG和咖啡因

考察了S-8、X-5、XAD-200等树脂对绿茶水提液中儿茶素EGCG和咖啡因的吸附性能,结果显示,具有高比表面积的弱极性吸附树脂XAD-200对EGCG和咖啡因的吸附差异较大,动态吸附过程中发生层析分离,儿茶素EGCG在1.5 BV后即开始泄漏,而咖啡因在6 BV后才开始泄漏.收集1.5～6 BV处的流出液可得w（咖啡因）＜0.30％的儿茶素,EGCG的质量分数由48.65％提高至66.37％.在最佳上样量下,EGCG的收率可达65.21％.     

高压凝固Al—17Zn-1．5Mg合金组织与显微硬度

利用扫描电镜、X射线衍射仪和显微硬度计对常压及6GPa高压下凝固的Al-17Zn-1．5Mg合金的组织和显微硬度进行了研究。结果表明,Al-17Zn-1．5Mg合金在常压凝固条件下,由α-A1相和MgZn2相组成,其中α—Al相长成粗大的枝晶,大量针状第二相位于枝晶间位置,相互连接形成网络状。当该合金在6GPa高压下凝固时,枝晶组织显著细化,第二相尺寸减小、数量减少,形态变成点粒状。合金高压凝固后,显微硬度增加了21％。