The mean value concept in mono-linear regression of multi-variables and its application to trace studies in geosciences

IEECAS SKLLQG

Molecular Dynamics Simulation of Peeling a DNA Molecule on Substrate

Molecular dynamics (MD) simulations are performed to study adhesion and peeling of a short fragment of single strand DNA (ssDNA) molecule from a graphite surface. The critical peel-off force is found to depend on both the peeling angle and the elasticity of ssDNA. For the short ssDNA strand under investigation, we show that the simulation results can be explained by a continuum model of an adhesive elastic band on substrate. The analysis suggests that it is often the peak value, rather than the mean value, of adhesion energy which determines the peeling of a nanoscale material.

An analysis on overall crack-number-density of short-fatigue-cracks

The evolution of dispersed short-fatigue-cracks is analysed based on the equilibrium of crack-number-density (CND). By separating the mean value and the stochastic fluctuation of local CND, the equilibrium equation of overall CND is derived. Comparing with the mean-field equilibrium equation, the equilibrium equation of overall CND has different forms in the expression of crack-nucleation-rate or crack-growth-rate. The simulation results are compared with experimental measurements showing the stochastic analyses provide consistent tendency with experiments. The discrepancy in simulation results between overall CND and mean-field CND is discussed.

A theoretical analysis on stochastic behaviour of short cracks and fatigue damage of metals

In this paper, the closed form of solution to the stochastic differential equation for a fatigue crack evolution system is derived. and the relationship between metal fatigue damage and crack stochastic behaviour is investigated. It is found that the damage extent of metals is independent of crack stochastic behaviour ii the stochastic deviation of the crack growth rate is directly proportional to its mean value. The evolution of stochastic deviation of metal fatigue damage in the stage close to the transition point between short and long crack regimes is also discussed.

The effect of organic matter accumulation on phosphorus release in sediment of Chinese shallow lakes

The effects of organic matter in sediment on phosphorus release were studied by field investigations in eight Chinese shallow freshwater lakes with different trophic status and a laboratory experiment. The sediment organic matter content paralleled the trophic status, ranging from 6.1 to 173.0 g kg(-1) (dry weight), with the mean value of 63.1 g kg(-1) (dry weight). It was positively proportional to Soluble reactive phosphorus concentration in the interstitial water in a form of exponential function, but inversely related to the sediment Fe/P ratio. The sediment alkaline phosphatase activity was significantly related not only to the organic matter content (r = 0.829, P < 0.01, n = 120), but also to the soluble reactive phosphorus concentration in interstitial water (r = 0.454, P < 0.01, n = 42). In the laboratory experiment, the addition of organic matter (dry materials of an aquatic macrophyte) into the sediment significantly enhanced alkaline phosphatase activity and soluble reactive phosphorus release. However, in the treatment with organic matter added and aeration, this release was generally prevented in spite of an increase in APA. Hence, sediment organic matter can effectively accelerate phosphorus release by enzymatic hydrolysis and anaerobic desorption. The latter mechanism seems to be more important.

Amplified fragment length polymorphism analysis to identify the genetic structure of the Gymnocypris przewalskii (Kessler, 1876) population from the Qinghai Basin, China

Amplified fragment length polymorphism (AFLP) was used to analyse the genetic structure of 45 individuals of Gymnocypris przewalskii (Kessler, 1876), an endangered and state-protected rare fish species, from three areas [the Heima (HM), Buha (BH) and Shaliu rivers (SL), all draining into Qinghai Lake]. A total of 563 polymorphic loci were detected. The HM, BH and SL populations have 435, 433 and 391 loci, respectively (Zhu and Wu, 1975), which account for 77.26%, 76.91% and 69.45% of the total number of polymorphic loci of each population, respectively. The Nei indices of genetic diversities (H) of the three populations were calculated to be 0.2869 (HM), 0.2884 (BH) and 0.2663 (SL), respectively. Their Shannon informative indices are 0.4244, 0.4251 and 0.3915, respectively. Research results show that the mean genetic distance between HM and BH is the smallest (0.0511), between BH and SL is the second shortest (0.0608), and between HM and SL is the largest (0.0713), with the mean genetic distance among the three populations being over 0.05. Data mentioned above indicate that the three populations have a certain genetic differentiation. The total genetic diversity (H-t = 0.3045) and the mean value of genetic diversity within the population (H-s = 0.2786) indicate that the variations have mainly come from within the population.

Correcting the systematic error of the density functional theory calculation: the alternate combination approach of genetic algorithm and neural network

The alternate combinational approach of genetic algorithm and neural network (AGANN) has been presented to correct the systematic error of the density functional theory (DFT) calculation. It treats the DFT as a black box and models the error through external statistical information. As a demonstration, the AGANN method has been applied in the correction of the lattice energies from the DFT calculation for 72 metal halides and hydrides. Through the AGANN correction, the mean absolute value of the relative errors of the calculated lattice energies to the experimental values decreases from 4.93% to 1.20% in the testing set. For comparison, the neural network approach reduces the mean value to 2.56%. And for the common combinational approach of genetic algorithm and neural network, the value drops to 2.15%. The multiple linear regression method almost has no correction effect here.

Uniformity Investigation in 3C-SiC Epitaxial Layers Grown on Si Substrates by Horizontal Hot-Wall CVD

50mm 3C-SiC epilayers are grown on （100） and （111） Si substrates in a newly developed horizontal lowpressure hot-wall CVD reactor under different growth pressures and flow rates of H_2 carrier gas. The structure,electrical properties, and thickness uniformity of the 3C-SiC epilayers are investigated by X-ray diffraction （XRD） ,sheet resistance measurement, and spectroscopic ellipsometry. XRD patterns show that the 3C-SiC films have excellent crystallinity. The narrowest full widths at half maximum of the SIC（200） and （111） peaks are 0.41° and 0.21°, respectively. The best electrical uniformity of the 50mm 3C-SiC films obtained by sheet resistance measurement is 2.15%. A σ/mean value of ± 5.7% in thickness uniformity is obtained.

Determination of urinary oxidative DNA damage marker 8-hydroxy-2 '-deoxyguanosine and the association with cigarette smoking

8-hydroxy-2'-deoxyguanosine (8OHdG) has been widely used as a biomarker of oxidative DNA damage in both animal models and human studies. To evaluate the effect of cigarette smoking on oxidative stress, we studied the levels of urinary 8OHdG from smokers and non-smokers and investigated the association with cigarette smoking. The urinary 8OHdG concentrations were determinated by capillary electrophoresis with end-column amprometric detection (CE-AD) after a single-step solid phase extraction (SPE), and then quantitatively expressed as a function of creatinine excretion. To increase the concentration sensitivity, a dynamic pH junction was used and the focusing effect was obvious when using 30 mM phosphate (pH 6.50) as sample matrix. The limit of detection is 4.3 nM (signal-to-noise ratio S/N = 3). The relative standard deviation (R.S.D.) was 1.1% for peak current, and 2.3% for migration time. Based on the selected CE-AD method, it was found that the mean value of urinary 8OHdG levels in the smokers significantly higher than that in non-smokers (31.4 +/- 18.9 nM versus 14.4 +/- 7.6 nM, P = 0.0004; 23.5 +/- 21.3 mug g(-1) creatinine versus 12.6 +/- 13.2 mug g(-1) creatinine, P = 0.028). (C) 2004 Elsevier B.V. All rights reserved.

Surface pigments,algal biomass profiles,and potential production of the euphotic layer:Relationships reinvestigated in view of remote-sensing applications

Maps of surface chlorophyllous pigment (Chl a + Pheo a) are currently produced from ocean color sensors. Transforming such maps into maps of primary production can be reliably done only by using light-production models in conjuction with additional information about the column-integrated pigment content and its vertical distribution. As a preliminary effort in this direction. $\ticksim 4,000$ vertical profiles pigment (Chl a + Pheo a) determined only in oceanic Case 1 waters have been statistically analyzed. They were scaled according to dimensionless depths (actual depth divided by the depth of the euphotic layer, $Z_e$) and expressed as dimensionless concentrations (actual concentration divided by the mean concentration within the euphotic layer). The depth $Z_e$ generally unknown, was computed with a previously develop bio-optical model. Highly sifnificant relationships were found allowing $\langle C \rangle_tot$, the pigment content of the euphotic layer, to be inferred from the surface concentration, $\bar C_pd$, observed within the layer of one penetration depth. According to their $\bar C_pd$ values (ranging from $0.01 to > 10 mg m^-3$), we categorized the profiles into seven trophic situations and computed a mean vertical profile for each. Between a quasi-uniform profile in eutrophic waters and a profile with a strong deep maximum in oligotrophic waters, the shape evolves rather regularly. The wellmixed cold waters, essentially in the Antarctic zone, have been separately examined. On average, their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values their profiles are featureless, without deep maxima, whatever their trophic state. Averaged values of $ρ$, the ratio of Chl a tp (Chl a + Pheo a), have also been obtained for each trophic category. The energy stored by photosynthesizing algae, once normalized with respect to the integrated chlorophyll biomass $\langle C \rangle _tot $ is proportional to the available photosythetic energy at the surface via a parameter $ψ∗$ which is the cross-section for photosynthesis per unit of areal chlorophyll. By tanking advantage of the relative stability of $ψ∗.$ we can compute primary production from ocean color data acquired from space. For such a computation, inputs are the irradiance field at the ocean surface, the "surface" pigment from which $\langle C \rangle _tot$ can be derived, the mean $ρ value pertinent to the trophic situation as depicted by the $\bar C_pd or $\langle C \rangle _tot$ values, and the cross-section $ψ∗$. Instead of a contant $ψ∗.$ value, the mean profiles can be used; they allow the climatological field of the $ψ∗.$ parameter to be adjusted through the parallel use of a spectral light-production model.

区域尺度地貌参数及其与水土流失的关系

基于坡度均一和坡面连续2个假定,提出了综合反映区域地貌特征的区域地貌参数计算方法。由于计算区域地貌参数所采用的地面坡度可以自动提取,而且对研究单元大小没有明确要求,因此可用于地形、地貌指标相关研究的尺度转换。黄河中游多沙粗沙区区域地貌参数平均值为10.89,其中:黄土丘陵沟壑区第一副区最大,黄土丘陵沟壑区第二副区与土石山区次之,风沙区最小。区域地貌参数与沟壑密度、林草覆盖率、水土流失面积比例均呈极显著正相关,其与坡耕地面积比例、年降水量和垦殖率等参数组合,可以很好地反映水土流失特征。

颅颌运动仿真系统(牙合)接触精度初探

目的 探讨颅颌运动仿真系统的骀接触模拟精度,为该仿真系统的应用提供依据.方法 制作10副石膏模型并上(牙合)架.用(牙合)架模拟侧方运动,三维扫描侧方运动终点(牙合)架上的上下颌模型,重建数字化上下颌模型作为对照组.运用仿真系统模拟耠架的侧方运动,以仿真系统输出的侧方运动终点的数字化上下颌模型为试验组.通过比较试验组与对照组下颌牙列之间的位置差异评价仿真系统的(牙合)接触模拟精度.结果 仿真系统模拟的下颌牙列与对照组下颌牙列之间的绝对平均距离为(0.18±0.05)mm;在前后左右四个分区中,两组右后牙区之间的绝对平均距离最大,为(0.19±0.07)mm.结论 该仿真系统的体外胎接触模拟精度为0.19mm.

The fabrication and performance of an Ag/AgCl reference electrode in human serum

A simple set of electric circuits was used to assemble a pulse generator. With pulse potentials and under galvanostatical control, a clean silver wire was anodized electrochemically for 0.2-0.5 min in 1.0 moll(-1) HCl with a pulse current density of 20 mA cm(-2), and the pulse wave parameters of t(a)/t(c) = 1 and a cycle of 4 s forming an Ag/AgCl reference electrode. Even though the AgCl layer was consumed during the working period when the Ag/AgCl electrode was used as a cathode, the AgCl layer could be in situ recovered electrochemically in serum used when a reversed potential was applied to the electrode system immediately after the measuring program was finished. The current response curve of the anode indicated that an AgCl layer in high density was basically accomplished during the first 6 pulse cycles in human serum. In order to keep a stable and uniform AgCl layer on the reference electrode after each measuring cycle, the ratio of the recovery time (t(r)) to the working time (t(w)) was measured and the smallest value was obtained at 0.03. The open-circuit potential of the Ag/AgCl electrode with respect to a SCE in 0.1 moll(-1) KCl was monitored over a period of 14 days and the mean value was 40.09 mV vs SCE with a standard deviation of 2.55 mV. The potential of the Ag/AgCl reference electrode did remain constant when the measurements were repeated more than 600 times in undiluted human serum with a standard deviation of 1.89 mV. This study indicated that the Ag/AgCl reference electrode could been rapidly fabricated with a pulse potential and could be used as a reference electrode with long-term stable properties in human serum samples.

SYNTHESIS AND PROPERTIES OF ALPHA-MOLYBDOTUNGSTONIOBIC DIPHOSPHATES

Four kinds of new molybdotungstoniobic diphosphates with the Dawson structure, formulated as alpha-P2W15Mo2Nb62(7-), are prepared and characterized by IR, UV spectra, polarography and W-183 NMR which show that the same ''polar'' W atoms in the Dawson frames-are substituted. The mean value of W-183 chemical shifts of the ''polar'' group varies linearly with the number of substituted atoms in the opposite polar group.

Geochemical properties of the variolitic andesite from Susong in the Dabie orogenic belt, China

The variolitic andesite from the Susong County in the Dabie Mountains implies that it was erupted in water. The mineralogy of the varioles is primarily radiate plagioclase (albite sind oligoclase), with little pyroxene, hornblende and quartz (derived from alteration). The pyroxene, hornblende and quartz are in the interstices between plagiocalse. The matrix consists of glass, hornblende, chlorite, epidote and zoisite. It is clearly subjected an extensive alteration. The andesite has an uncommon chemical composition. The SiO2 content is about 56.8%, TiO2 = 0.9%, MgO = 6.4%, Fe2O3 (tot) = 6.7%similar to 7.6%, 100Mg/(Mg + Fe) = 64.1 similar to 66.2. Mg-# is significantly high. The andesite has high abundances of large-lithophile trace elements (e.g. K, Ba. Sr, LREE), e.g. La/Nb = 5.56 similar to 6.07, low abundances of high-strength-field elements (HFSE e.g. Ta, Nb, P, Ti), particularly Ta and Nb strongly depleted. These are consistent with the characteristics of subduction-related magmas. In the spider diagram of trace elements, from Ce to right hand, the abundances of elements decrease quickly, showing a character of the continental margins. There has a strong punishment of light-rare-earth elements, with a significant diffraction of REEs (the mean value of (La/Yb)(N) is 32.84). No Eu anomaly, but there are anomaly high (La/Yb)(N) = 28.63 similar to 36.74, (La/Y)(N) = 70.33 similar to 82.4. The elements Y and Yb are depleted greatly, Y<20 g/g, Y-N = 2.74 similar to 2.84, Yb-N = 2.18 similar to 2.35. From the La-(La/Sm) diagram, the andesite is derived from partial melting. But the epsilone value of Nd is - 18.7 similar to -19.2, so that the material source may be the mantle materials affected by the crustal materials. The Nd model age is 1.9 Ga indicating that the variolitic basaltic andesite was resulted from the mantle wedge of North China block, which had the Nd model age of 2.5Ga, when the Yangze block which had the Nd model age of 1.7Ga subducted beneath it. So the variolitic andesite has characteristics of the island-are volconic rocks oil a continental basement in the vicinity of the destructive continental margin.