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991.
Seasonal variations and environmental controls on stalagmite calcite crystal growth in Heshang Cave,central China 总被引:1,自引:0,他引:1
Stalagmite growth rates are usually considered to reflect changes in paleoclimate and paleoenvironment. However, how exactly
growth rates are affected by climate and environment is still unclear. We launched a monitoring and modeling program that
lasted approximately 4 years on two active drip sites in Heshang Cave, central China. We collected comprehensive quantitative
data on growth rates, cave temperature, CO2 concentration, drip rate and drip-water chemistry to better understand the relationship between stalagmite growth and cave
environment. By laying out glass substrates, we successfully grew stalagmite calcite crystals with rhombic characteristics,
and quantified growth rates by measuring the long and short axes of calcite crystals under a microscope. Combined with coeval
environmental data, we explicitly examined the roles of cave temperature, drip rate and drip-water chemistry in controlling
the micro-scale growth of stalagmite calcite. Results show that growth of stalagmite calcite crystals at two drip sites exhibited
similar seasonal variations − generally faster in the summer months, at ∼3 μm d−1, and slower during the late winter to early spring, at ∼1.5 μm d−1. Variations in calcite growth rates were mainly determined by changes in cave temperature, with the growth rate increasing
by 8.1%/°C and 6.6%/°C at the two locations. This indicates the potential use of stalagmite growth rates as a seasonal-resolution
paleo-temperature proxy in some ventilated caves. On the other hand, the effect of drip rate and drip-water Ca2+ and SIC values on growth rates were not significant. 相似文献
992.
Variations in equilibrium line altitude of the Qiyi Glacier,Qilian Mountains,over the past 50 years 总被引:6,自引:0,他引:6
Based on observations of the equilibrium line altitude (ELA) of the Qiyi Glacier in the Qilian Mountain, we established a
statistical model between ELA and its major influencing factors, warm season air temperature (air temperature averages for
September, July and August) and cold season precipitation (total precipitation in the period January through March). Warm
season air temperature was the leading climatic factor influencing ELA variations. The glacier ELA ascends (descends) 172
m when warm season air temperature increases (decreases) by 1°C, and ascends (descends) 62 m when cold season precipitation
decreases (increases) by 10%. In the period 1958–2008, the glacier ELA showed a general increasing trend, ascending 230 m
and reaching its highest altitude in 2006 at 5131 m a.s.l., close to the glacier summit. If future climate is similar to that
in the period 2001–2008, the Qiyi Glacier will not stabilize until it retreats by 2.08 km. 相似文献
993.
Residue networks are constructed by defining the residues as the vertices and atom contacts between them as the edges. The residue network of a protein complex is divided into two types of networks, i.e. the hydrophobic and the hydrophilic residue networks. By analyzing the network parameters, it is found that the correct binding complex conformations are of both higher sum of the interface degree values and lower characteristic path length than those incorrect ones. These features reflect that the correct bind-ing complex conformations have better geometric and/or residue type complementarity, and the correct binding modes are very important for preserving the characteristic path lengths of native protein complexes. In addition, two scoring terms are proposed based on the network parameters, in which the characteristics of the entire complex shape and residue type complementarity are taken into account. These network-based scoring terms have also been used in conjunction with other scoring terms, and the new multi-term scoring HPNCscore is devised in this work. It can improve the discrimination of the combined scoring function of RosettaDock more than 12%. This work might enhance our knowledge of the mechanisms of protein-protein interactions and recognition. 相似文献
994.
Wettability of molten Sn-Ag-Cu alloy on Cu substrate has been determined by sessile drop method, as well as its dependence on time and temperature. It was found that the evolution of contact angle at the alloy’s melting point experienced four different stages. Especially, the contact angle was unstable and fluctuant in stage II, and gradually decreased in stage III mainly due to a chemical reaction between Sn-Ag-Cu alloy and Cu substrate. The contact angle decreased with increasing temperature, but increased slightly at 629 K, for another chemical reaction occurred. Interfacial characteristic has been further investigated by examining the sample’s cross section. Intermetallic compounds of Cu6Sn5 and β-Sn phase were found at the interface of Sn-Ag-Cu/Cu. 相似文献
995.
The influence of the elastic energy on L10→L12 transient ordering transformation was investigated by microscopic phase field method. It is found that there are three stages experienced in atomic ordering: solute clustering+L10 short range ordering → L10 long range ordering → L12 long range ordering. Before the formation of the high ordered L12 phase, it has firstly taken place the transformation from matrix to L10 phase, and then held the L10→L12 secondary transformation. Elastic energy is proved to take little effect on the stage of short range ordering, but as the elastic energy is multiplied, it obviously shortened the course of the solute clustering, and speeded up the proceeding of the L10 long range ordering transition. Accordingly, the increased elastic energy also strengthens the single crystalline directionality of L10 phase projecting on 2D plane and makes the ordered degree of Al and Zn atoms enhanced. With the temperature elevation, Al’s and Zn’s ordered degree decreased in L10 phase. 相似文献
996.
Built-in electric field may enhance or retard the impurity-free vacancy disordering (IFVD) during rapid thermal annealing (RTP) by imposing a drift on charged point defects. Built-in electric field is at the interface between dielectric layer and top layer of the structure. Subsequent rapid thermal annealing leads to different intermixing results due to different field directions on InP cap layers in different doping types. Experimental results also show different influences of the built-in field on the two... 相似文献
997.
We present the design of an electro-optic filter with polarization insensitivity based on a long period waveguide grating. The filter exhibits an ultra-large wavelength tuning range of exceeding 35 nm and covering the whole C band (1530 to 1565 nm) in a bias voltage range from −84 to 84 V. In the whole tuning range, the transmission coefficients for quasi TE modes are over 97% and the 3 dB bandwidths are below 0.8 nm. The wavelength sensitivity to the tunable voltage is about 0.208 nm/V. This electro-optic filter can be used in dynamic WDM networks for fast wavelength scanning/selection, communication channel reconfiguration, and optical switching. 相似文献
998.
Pyranylidene carbene complexes bearing a pyran ring carbene ligand represent a unique kind of organometallic species due to their special structures and reactivity. In this review, we present a comprehensive summary on the synthesis and reactivity of pyranylidene carbene complexes during the past four decades. 相似文献
999.
FangXiong Ruan ShunPing Zhang ZhiPeng Li ZhiLin Yang DeYin Wu Bin Ren HongXing Xu 《科学通报(英文版)》2010,55(26):2930-2936
The linear optical properties and the surface-enhanced Raman scattering (SERS) effect of spherical palladium nanoparticle dimers are analyzed theoretically using generalized Mie theory. The calculation results demonstrate that the near-field coupling effect greatly influences the absorption, scattering and extinction spectra of nanoparticle dimers. The surface plasmon resonance wavelength red-shifts dramatically as the separation between nanoparticles decreases. Because of the near-field coupling between nanoparticles and the size effect, the maximum SERS enhancement factor at the ‘hot spot’ between palladium nanoparticle dimers is as high as 107–108, while the averaged SERS enhancement factor over the entire nanoparticle surface is in the range of 105–106. The deviation between the position of the peak in the extinction spectrum and the wavelength for maximum surface-averaged enhancement for the Pd nanoparticle dimers indicates that localized surface plasmon resonance has different influences on the far and near fields. These theoretical results may help to reveal the relationship between the far and near fields, as well as understand the mechanism of electromagnetic enhancement in the surface-enhanced scattering of transition metals. 相似文献
1000.
Direct numerical simulation is employed to investigate the premixed jet flame of methane in lean, combined with a detailed chemical kinetics including 17 species and 58 elemental steps and distinct Lewis numbers. Cold methane-air mixture at 0.55 equivalence ratio is injected into the coflow area with 9500 Reynolds number. The coflow ambient gas is set to be the burnt gas of the methane-air mixture in main jet and temperature is assigned to be the corresponding adiabatic flame temperature 1515 K. The whole s... 相似文献