SHRIMP U-Pb zircon age of tuff at the bottom of the Lower Cambrian Niutitang Formation,Zunyi, South China

A SHRIMP U-Pb zircon geochronology study of the tuff at the bottom of the Lower Cambrian Niutitang Formation at Songlin, Zunyi, South China yielded a mean ^206Pb/^238U age of 518±5 Ma. It is significantly younger than the Re-Os ages of 537--542 Ma for the overlying polymetallic Ni-Mo-PGE-rich layer in the basal Niutitang Formation at Songlin, suggesting that the Re-Os ages might represent that of the original magma chamber for the Ni-Mo-PGE-rich layer rather than the formation age of the strata. The intra-basinal stratigraphic correlation also implies that the absolute age of the Chengjiang biota should be younger than 518±5 Ma. Our new result, together with the SHRIMP U-Pb zircon age for the K-bentonite in the Zhongyicun member of the Zhujiaqing Formation at the Meishucun section, Yunnan Province, provides a temporal constraint for the Lower Cambrian of the Yangtze Platform in South China.     

Electromagnetic behavior of two-dimensional quasi-crystal left-handed materials with dendritic unit

We demonstrated a two-dimensional quasi-crystal dendritic structure model with negative permeability. The microwave transmission and reflection properties of periodic and quasi-crystal dendritic structure mediums with varied angle incidence were measured. The results showed that the resonant peaks of quasi-crystal negative permeability samples and left-handed samples had tiny shift with the altering of incident angle. Because of the influence of coupling between quasi-crystal dendritic cells, the resonance of the entire material was enhanced or weakened. The quasi-crystal dendritic structure model will provide an easy method to design isotropic left-handed materials （LHMs）.     

Rearrangements of microtubule cytoskeleton in stomatal closure of <Emphasis Type="Italic">Arabidopsis</Emphasis> induced by nitric oxide

NO （nitric oxide）, known as a key signal molecule in plant, plays important roles in regulation of stomatal movement. In this study, microtubule dynamics and its possible mechanism in the NO signal pathway were investigated. The results were as follows： （i） In vivo stomatsl aperture assays revealed that both vinblastine （microtubule-disrupUng drug） and SNP （exogenous NO donor） prevented stomatsl opening in the light, and vinblastine even could enhance the inhibitory effect of SNP, whereas tsxol （a microtubule-stsbilizing agent） was able to reduce this effect; （ii） microtubules in the opening Arabi-dopsis guard cells expressing GFP：a-tubulin-6 （AtGFP：a-tubulin-6） were organized in parallel, straight and dense bundles, radiating from the ventral side to the dorsal side, and most of them were localized perpendicularly to the ventral wall; （iii） under the same environmental conditions, treated with SNP for 30 min, the radial arrays of microtubules in guard cells began to break down, twisted partially and be- came oblique or exhibited a random pattern; （iv） furthermore, the involvement of cytosolic Ca^2＋ in this event was tested. Stomatal aperture assays revealed that BAPTA-AM （a chelator of Ca^2＋） greatly suppressed the effect of NO on stomatal closure; however, it did not show the same function on stomatal closure induced by vinblastine. When BAPTA-AM was added to the SNP-pretreated solution, the SNP-induced disordered microtubulue cytoskeleton in guard cells underwent rearrangement in a time-dependent manner. After 30 min of treatment with BAPTA-AM, the cortical microtubules resumed the original radial distribution, almost the same as the control. All this indicates that NO may promote rearrangement of microtubule cytoskeleton via elevation of [Ca^2＋]cyt （free Ca^2＋ concentration in the cytoplasm）, finally leading to stomatsl closure.     

The optical afterglow of the short gamma-ray burst GRB 050709

It has long been known that there are two classes of gamma-ray bursts (GRBs), mainly distinguished by their durations. The breakthrough in our understanding of long-duration GRBs (those lasting more than approximately 2 s), which ultimately linked them with energetic type Ic supernovae, came from the discovery of their long-lived X-ray and optical 'afterglows', when precise and rapid localizations of the sources could finally be obtained. X-ray localizations have recently become available for short (duration <2 s) GRBs, which have evaded optical detection for more than 30 years. Here we report the first discovery of transient optical emission (R-band magnitude approximately 23) associated with a short burst: GRB 050709. The optical afterglow was localized with subarcsecond accuracy, and lies in the outskirts of a blue dwarf galaxy. The optical and X-ray afterglow properties 34 h after the GRB are reminiscent of the afterglows of long GRBs, which are attributable to synchrotron emission from ultrarelativistic ejecta. We did not, however, detect a supernova, as found in most nearby long GRB afterglows, which suggests a different origin for the short GRBs.     

Improved verifiability scheme for data storage in cloud computing

In Cloud computing,data and service requests are responded by remote processes calls on huge data server clusters that are not totally trusted.The new computing pattern may cause many potential security threats.This paper explores how to ensure the integrity and correctness of data storage in cloud computing with user’s key pair.In this paper,we aim mainly at constructing of a quick data chunk verifying scheme to maintain data in data center by implementing a balance strategy of cloud computing costs,removing the heavy computing load of clients,and applying an automatic data integrity maintenance method.In our scheme,third party auditor (TPA) is kept in the scheme,for the sake of the client,to periodically check the integrity of data blocks stored in data center.Our scheme supports quick public data integrity verification and chunk redundancy strategy.Compared with the existing scheme,it takes the advantage of ocean data support and high performance.     

Thermal detection of surface plasmons on gold nanohole arrays

We used a thin-film thermocouple to detect the thermal effect of surface plasmons excited in Au nanohole array structures.We found that the thermal electromotive force of Au film with periodic nanohole structures is three times greater than that of a bare Au film for 785-nm laser excitation at a given power.This effect is caused by the resonant excitation of localized surface plas- mons in the nanoholes.In addition,we found that the thermal electromotive force(EMF)of the Au film with dumbbell-like na- nohole arrays depends strongly on the incident polarization.The thermal EMF is the greatest when the excitation light is polarized perpendicular to the long axis of the dumbbell.     

Driving the cell cycle with a minimal CDK control network

Control of eukaryotic cell proliferation involves an extended regulatory network, the complexity of which has made it difficult to understand the basic principles of the cell cycle. To investigate the core engine of the mitotic cycle we have generated a minimal control network in fission yeast that efficiently sustains cellular reproduction. Here we demonstrate that orderly progression through the major events of the cell cycle can be driven by oscillation of an engineered monomolecular cyclin-dependent protein kinase (CDK) module lacking much of the canonical regulation. We show further that the CDK oscillator acts as the primary organizer of the cell cycle, imposing timing and directionality to a system of two CDK activity thresholds that define independent cell cycle phases. We propose that this simple core architecture forms the basic control of the eukaryotic cell cycle.     

Electrochemical performance of high purity zinc and Zn-Al-Cd alloy as reference electrodes

The effects of Cl-concentration,temperature,pH,flow velocity,soluble oxygen content of seawater and anodic current on the potential of high purity zinc and Zn-Al-Cd reference electrodes were investigated. The results show that the investigated metal materials are liable to establish stable potential and act as reference electrodes in seawater,diluted seawater and urban tap water. Cl-concentration,temperature,seawater flow velocity and anodic current have an obvious effect on zinc potentials. However,seawate...     

Kinetics and formation mechanisms of intragranular ferrite in V-N microalloyed 600 MPa high strength rebar steel

To systematically investigate the kinetics and formation mechanisms of intragranular ferrite (IGF), isothermal heat treatment in the temperature range of 450℃ to 600℃ with holding for 30 s to 300 s, analysis of the corresponding microstructures, and observation of the precipitated particles were conducted in V-N microalloyed 600 MPa high strength rebar steel. The potency of V(C,N) for IGF nucleation was also analyzed statistically. The results show that the dominant microstructure transforms from bainite (B) and acicular ferrite (AF) to grain boundary ferrite (GBF), intragranular polygonal ferrite (IPF), and pearlite (P) as the isothermal temperature increases from 450℃ to 600℃. When the holding time at 600℃ is extended from 30 s to 60 s, 120 s, and 300 s, the GBF content ranges from 6.0vol% to 6.5vol% and the IPF content increases from 0.5vol% to 2.8vol%, 13.1vol%, and 13.5vol%, respectively, because the ferrite transformation preferentially occurs at the grain boundaries and then occurs at the austenite grains. Notably, V(C,N) particles are the most effective nucleation site for the formation of IPF, accounting for 51% of the said formation.