本星系群的动力学质量

本星系群的动力学质量M_（LG）可以通过多种途径来加以估测,如计时质量法、零速度面法、位力质量法等。对现有测定值的分析和讨论表明,或可取M_（LG）=（2.73±0.44）×10^（12）M_⊙作为目前所知本星系群之动力学质量的合理估值。天体的动力学质量和光度质量天文学是一门观测科学,天文学家的研究对象是各类天体,如行星、恒星、星团、星系、星系团等。

恒星初始质量分布函数对伽玛暴爆发率的影响

伽玛射线暴的产生机制比较公认的是:长暴产生于大质量恒星死亡;短暴产生于密近双星合并.因此人们很自然地推测长暴和恒星形成率直接成比例,但是最近数据分析表明这并不能很好地拟合观测.考虑到只有质量大于某一临界质量的大质量恒星才可能产生长暴,因此恒星初始质量分布函数对长暴的产生率会有较大影响.考虑用恒星初始质量分布函数来解释长暴观测个数随红移的分布,得到了比较好的结果.

世说新语

光度质量学科:天体物理光度质量是根据天体质量和光度的关系估计出的质量。通过测定某个星系的亮度与恒星平均亮度的倍数,乘以恒星的平均质量,即可得到这个星系的质量,将星系团中所有星系的质量相加得出整个星系团的质量,用这种方法得出的质量称为光度质量。

宇宙隐身人:神秘暗物质

近日,由刘烨饰演男主角——中国赴美留学生刘星的美国影片《暗物质》,正在美国盐湖城紧张地拍摄。影片中,刘星研究发现了"暗物质"这一可获诺贝尔奖的大成果。何谓"暗物质"?我们约请李啸虎教授撰写此文以飨读者。

用液相色谱-串联质谱法测定人血清中加巴喷丁的含量

目的：建立测定人血清中加巴喷丁含量的液相色谱-串联质谱（LC-MS/MS）法。方法：以磺胺二甲异嘧啶为内标,血清用乙腈直接沉淀蛋白质后进样分析。色谱条件：XBridge Phenyl（150 mm×2.1 mm,5μm）为色谱柱,流动相：0.02%甲酸的乙腈溶液-0.02%甲酸的水溶液（15∶85）。电喷雾离子源,正离子MRM扫描分析。结果：加巴喷丁和内标磺胺二甲异嘧啶离子对分别为m/z172→154.1和m/z279→124。加巴喷丁在50~5 000 ng/ml范围内线性关系良好（r=0.999 6）,检测限为50 ng/ml。批内、批间RSD均〈10%,平均提取回收率为97.7%~108.5%。结论：本方法灵敏度高、专一性好,可用于人血清中加巴喷丁的检测。

液质联用技术在环烯醚萜苷类化合物研究中的应用

液质联用技术将色谱的高分离性能和质谱强大的结构鉴别功能相结合,是较完善的现代分析技术,已广泛应用于药物定量分析、结构鉴定和代谢转化等研究。本文对液质联用技术在环烯醚萜苷类化合物定性和定量分析两方面的应用进行简要综述。

疏散星团NGC2286的研究

本文利用疏散星团NGC2286天区内25O颗恒星的相对自行及成员概率判定资料，首次对该星团的半径、光度函数以及内部运动等做较深入的研究，分析表明对NGC2286这个中等年龄的星团，正处于动力学演化的初级阶段，在空间和速度上都没有表现出象年老疏散星团M67那样较为明显的分层效应。

探寻银晕暗物质的一个可能方案

依据星系自转曲线，对银河系旋转速度曲线进行合理外推，并应用引力势理论，得到银河系质量分布及外围的密度分布．结合 Ｂａｈｃａｌｌ和 Ｓｏｎｅｉｒａ 假设的密度模型，求出银河系外围的质量，即可能的暗物质质量．同时，对密度分布曲线内推，求出可视部分可能存在的暗物质质量．用这种方法得到的暗物质晕的质量，在误差范围内与前一种结果相符。

Experimental study on mechanism of influence of laser energy density on surface quality of Ti-6Al-4V alloy in selective laser melting

This experiment obtained different laser energy density(LED) by changing SLM molding process parameters.The surface morphology, surface quality, and microstructure of as-fabricated samples were studied. The effects of scanning speed, hatching space, and laser power on surface quality were analyzed, and the optimal LED range for surface quality was determined. The results show that pores and spherical particles appear on the sample’s surface when low LED is applied, while there are lamellar structures on the sides of the samples. Cracks appear on the sample’s surface,and the splash phenomenon increases when a high LED is taken. At the same time, a large amount of unmelted powder adhered to the side of the sample. The surface quality is the best when the LED is 150-170 J/mm^(3). The preferred hatch space is currently 0.05-0.09 mm, the laser power is 200-350 W, and the average surface roughness value is(15.1±3) μm.The average surface hardness reaches HV404±HV3, higher than the forging standard range of HV340-HV395.Increasing the LED within the experiment range can increase the surface hardness, yet an excessively high LED will not further increase the surface hardness. The microstructure is composed of needle-like α’-phases with a length of about 20μm, in a crisscross ‘N’ shape, when the LED is low. The β-phase grain boundary is not obvious, and the secondaryphase volume fraction is high;when the LED is high, the α’-phase of the microstructure is in the form of coarse slats, and the secondary-phase is composed of a small amount of secondary α’-phase, the tertiary α’-phase and the fourth α’-phase disappear, and the volume fraction of the secondary-phase becomes low.

Charge coupled devices （CCD） photometry and long-term optical variability of gamma-ray-loud BL Lacertae object Mkn 421

Evidence for the long-term optical curve variability and colour behaviour of the BL Lac object Mkn 421 is presented. Our results show that the amplitude of the optical variations of Mkn 421 is only about △B=4.7 magnitude in the B-band for its photometric history from 1899 to 2002. The results of optical photometric monitoring of the Mkn 421 from April 2000 to Jan 2002 are provided. During our observation, Mkn 421 shows significant rapid variations and exhibits short time variability of 2.42 hours in the B band. A strong correlation between the B - V colour index and the magnitude in the B band is found. Our charge coupled device （CCD） photometry of Mkn 421 shows that the measured results are in good agreement with the predicted optical variability period of about 23 years.

Effect of Fe^(3+) on the growth and lipid content of Isochrysis galbana

Inducing lipid accumulation in microalgae cells without suppressing cell growth is vital to the economical production ofbiodiesel from microalgae. In two experiments, we demonstrate that the eel1 concentration and lipid content of marine microalgae Isochrysis galbana depend upon the iron concentration in the growth media. In Experiment I, adding chelated FeC13 to the medium at the late exponential growth phase prolonged this phase and increased the lipid content in I. galbana cells. The final cell density and lipid content of I. galbana supplemented with chelated FeC13 was approximately 2 and 1.65 times higher than that of non-supplemented cultures, respectively. In Experiment II, I. galbana cells in the late exponential phase were collected and re-inoculated into new media containing Fe3＋ at various concentrations. The final cell concentration and lipid content were maximized at the highest iron concentration （38% biomass by dry weight at 1.2×10^-5 mol/L Fe3＋）. In this study, intracellular neutral lipid storage was evaluated by fluorescent spectrophotometry using fluorochrome Nile red, and the measurement conditions were optimized.

A New Method for Measurement of Local Solid Flux in Gas-Solid Two-phase Flow

Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.

An effective method and its modifications for isolation of high-quality total RNA from fruit pulps

An effective method for isolation of total RNA from pulps of mainly deciduous fruit trees was discussed in this paper. Here we shown that total RNA was successfully isolated from pulps of apple, peach and strawberry, but not grape berry via the effective CTAB method modified by ZENG, et al. However, total RNA was isolated from grape berry according to ZENG＇s protocols with a modification including 16% of β-Mercatoethanol and 3% of PVP in extraction buffer, 1/3 （V/V） of 5mol/L potassium acetate （KAC PH4.8） in supernatant. The detection of the isolated total RNA above using ultraviolet spectrophoto-metry, electrophoresis, reverse transcription and RT-PCR shown that the CTAB and its modifications is a preferred method for isolation of high-quality total RNA from fruit pulps.

Development of RAMS-CMAQ to Simulate Aerosol Optical Depth and Aerosol Direct Radiative Forcing and Its Application to East Asia

The air quality modeling system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) is developed to simulate the aerosol optical depth (AOD) and aerosol direct forcing (DF). The aerosol-specific extinction, single scattering albedo, and asymmetry factor are parameterized based on Mie theory taking into account the aerosol size distribution, composition, refractive index, and water uptake of solution particles. A two-stream solar radiative model considers all gaseous molecular absorption, Rayleigh scattering, and aerosols and clouds. RAMSCMAQ is applied to simulate all major aerosol concentrations (e.g., sulfate, nitrate, ammonium, organic carbon, black carbon, fine soil, and sea salt) and AOD and DF over East Asia in 2005. To evaluate its performance, the simulated AOD values were compared with ground-based in situ measurements. The comparison shows that RAMSCMAQ performed well in most of the model domain and generally captured the observed variations. High AOD values (0.2 1.0) mainly appear in the Sichuan Basin as well as in central and southeastern China. The geographic distribution of DF generally follows the AOD distribution patterns, and the DF at the top-of-the-atmosphere is less than 25 and 20 W m 2 in clear-sky and all-sky over the Sichuan Basin. Both AOD and DF exhibit seasonal variations with lower values in July and higher ones in January The DF could obviously be impacted by high cloud fractions.

Using Support Vector Regression to Analyze Urban Atmosphere Pollution with Optical Remote Sensing Data

The concentration of absorbable particulate matter less than 10 μm termed as PM10 is the most important urban air pollution index for air quality monitoring. This paper presents a space based PM10 monitoring algorithm based on QUAC （QUick atmosphere correction） for optical remote sensing data and SVR （support vector regression）. PM 10 concentration measurements from nine ground based stations in Hangzhou, China and the MODIS （moderate-resolution imaging spectroradiometer） images were analyzed. Experimental result indicates that the correlation between CD （correction differences） with actual measured data is better than correlation between AOD （aerosol optical depth） with measured data. In addition, the fitting performance of the SVR model established with CD and measured data is better than traditional regression models.

Plant size,environmental factors and functional traits jointly shape the stem radius growth rate in an evergreen coniferous species across ontogenetic stages

Aims Plant size,environmental conditions and functional traits are important for plant growth;however,it is less clear which combination of these factors is the most effective for predicting tree growth across ontogenetic stages.Methods We selected 65 individuals of an evergreen coniferous species,Pinus koraiensis,with diameters at breast height(DBH)from 0.3 to 100 cm in Northeast China.For each individual,we measured the stem radius growth rate(SRGR,µm/year)for the current year,environmental factors(light,soil nutrient and soil water)and functional traits(leaf,branch and root traits).Important Findings SRGR increased with DBH when the DBH was lower than 58 cm,whereas it decreased with DBH when the DBH was larger than 58 cm.Structural equation modeling analysis suggested that,when the DBH was 0–15 cm,plant size had a direct negative influence on SRGR and an indirect positive influence on SRGR due to the light intensity above the plant.Plant size had direct positive and negative effects when the DBH was 16–58 cm and 59–100 cm,respectively.When the DBH was larger than 15 cm,soil parameters were more important than light intensity for SRGR.The functional traits selected for use in the best model were changed from the specific leaf area and wood density to the root nitrogen concentration with increasing tree size.In summary,plant size,environmental factors and functional traits jointly shaped tree growth,and their relative influence varied with size,suggesting that the resources limiting tree growth may change from light to soil nutrient with increasing tree size.

Experimental investigation of the influence of laser intensity on the quality of Einstein-Podolsky-Rosen entangled photons

Using spontaneous parametric down conversion,polarization post selection and coincidence counting technique,the polarization Einstein-Podolsky-Rosen(EPR) entangled states are prepared.Experimental studies on the efficiency,contrast and fidelity with different pump laser intensities are performed systematically.The results show that the pump laser intensity distinctly influences the quality of entangled photons,especially the contrast and the fidelity.On the other hand,the pump efficiency of entangled photons is almost invariable,namely the entangled source brightness increases linearly with the increase of pump laser power.

Inter-comparison of seasonal variability and nonlinear trend between AERONET aerosol optical depth and PM10 mass concentrations in Hong Kong

Here we used Empirical Mode Decomposition （EMD） method to study seasonal variability and nonlinear trend of corrected AERONET Aerosol Optical Depth （AOD/Hi） and corrected PM10 mass concentrations （PMmxf（RH）） in Hong Kong during 2005-2011. AODPrli is highly correlated with PMI0xf（RH） in semi-annual and annual time scales （with correlation coefficient 0.67 for semi-annual and 0.79 for annual components, 95% confidence interval）. On the semi-annual scale, both AOD/Hi and PM10xf（RH） can capture the two maxima in March and October, respectively, with much stronger amplitude in March proba- bly due to the long-range transport of dust storm. On the annual cycle, the AOD/Hi and PMI0xf（RH）, which are negatively correlated with the precipitation and solar radiation, vary coherently with the maxima in February. This annual peak occurs about one month earlier than the first peak of the semi-annual variability in March, but with only half amplitude. During 2005-2011, both AOD/Hi and PM10xf（RH） exhibit the pronounced decreasing trend with the mean rate of 14 gg m-3 per year for PM10xf（RH）, which reflects the significant effects of the air pollution control policy in Hong Kong during the past decade. The nonlinear trend analysis indicates that the decreasing of PM10xf（RH） is slower than that of AOD/Hi when the AOD/Hi is less than 0.44 but becomes faster when the AOD/Hi exceeds 0.44. These results illustrate that the AERONET AOD can be used quantitatively to estimate local air-quality variability on the semi-annual, annual, and long-term trend time scales.

Donor Binding Energy in GaAs/Ga_(1-x) Al_xAs Quantum Well:the Laser Field and Temperature Effects

Based on the effective-mass approximation theory and variational method, the laser field and temperature effects on the ground-state donor binding energy in the GaAsflGa1-x AlxAs quantum well （QW） are investigated. Numerical results show that the donor binding energy depends on the impurity position, laser parameter, temperature, Al composition, and well width. The donor binding energy is decreased when the laser field and temperature are increased in the QW for any impurity position and QW parameter case. Moreover, the laser field has an obvious influence on the donor binding energy of impurity located at the vicinity of the QW center. In addition, our results also show that the donor binding energy decreases （or increases） as the well width （or AI composition x） increases in the QW.

DFT Investigation of Structural,Electronic,Elastic and Optical Properties of SrMO_4(M=Mo and W)

A planes waves pseudo-potential calculations are performed for the SrMO4 （M=Mo and W） compound in order to investigate the structural, electronic, elastic and optical properties. The calculated lattice constants are in good agreement with experiment ones. The electronic structures show that SrMO4 has a direct band gap situated at F point. The calculated elastic constants indicate that both structures are mechanically stable. The bulk modulus, shear modulus, Young＇s modulus and Poisson ratio are investigated from the elastic constants, in the same time the anisotropy of the elastic properties is discussed. The imaginary part of the dielectric functions is calculated and the contributions of various transitions peaks are analyzed. Furthermore, the other optical properties such as absorption coefficient I（w）, optical reflectivity R（w）, energy-loss spectrum L（w）, and the refractive index n（w） have been investigated.