Diode-pumped Yb : YAG ceramic laser

Transparent polycrystalline Yb:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Yb2O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1730 degrees C in vacuum. Transparent fully dense samples with grain sizes of several micrometers were obtained. The phase from 1500 degrees to 1700 degrees C was important for the grain growth, in which the grains grew quickly and a mass of pores were eliminated from the body of the sample. Annealing was an important step to remove the vacancies of oxygen and transform Yb2+ to Yb3+. The 1 at.% Yb:YAG ceramic sample was pumped by a diode laser to study the laser properties. The maximum output power of 1.02 W was obtained with a slope efficiency of 25% at 1030 nm. The size of the lasering sample was 4 mm x 4 mm x 3 mm.

尼卡地平血药浓度测定及其人体药代动力学

目的　建立人血浆中尼卡地平 (Nic)浓度测定的毛细管柱气相色谱法 ,并以此法研究健康受试者 poNic缓释胶囊后的药代动力学。方法　样品经甲苯提取 ,过无水硫酸钠小柱后 ,用HP 12 5m× 0 32mmID毛细管柱分离 ,采用无分流进样方式 ,以巴尼地平作为内标 ,63 Ni电子捕获检测器检测。结果　该法在 0 5～ 10 0ng·mL-1浓度范围内呈线性关系 ,最低定量浓度为 0 5ng·mL-1,日内、日间RSD分别小于 4%和 7% ,低、中、高浓度 (0 5 ,10 ,5 0ng·mL-1)

Kinetic Model Study on Enzymatic Hydrolysis of Cellulose Using Artificial Neural Networks

Enzymatic hydrolysis of cellulose was highly complex because of the unclear enzymatic mechanism and many factors that affect the heterogeneous system. Therefore, it is difficult to build a theoretical model to study cellulose hydrolysis by cellulase. Artificial neural network (ANN) was used to simulate and predict this enzymatic reaction and compared with the response surface model (RSM). The independent variables were cellulase amount X-1, substrate concentration X-2, and reaction time X-3, and the response variables were reducing sugar concentration Y-1 and transformation rate of the raw material Y-2. The experimental results showed that ANN was much more suitable for studying the kinetics of the enzymatic hydrolysis than RSM. During the simulation process, relative errors produced by the ANN model were apparently smaller than that by RSM except one and the central experimental points. During the prediction process, values produced by the ANN model were much closer to the experimental values than that produced by RSM. These showed that ANN is a persuasive tool that can be used for studying the kinetics of cellulose hydrolysis catalyzed by cellulase.

Environmental Kuznets Curve for SO_2 Emissions in China

This study examines the link between the economic growth and the environmental quality. Based on a panel data set, a N-shaped Environmental Kuzents Curve has been found for the sample period: a cubic relationship between per capita GDP and emissions of sulphur dioxide (SO2). We also find that energy consumption is an important determinant of environmental degradation. The empirical results suggest that we should promote environmental protection as soon as possible.

The Impact of Environmental Non-Tariff Measures on China's Agricultural Exports

This article assesses the impact of environmental non-tariff measures on China's agricultural exports. It uses two measures to show which countries make most intensive use of environmental non-tariff measures and which agricultural products exported by China are the most affected. Environmental non-tariff measures were most prevalence in Malaysia, Vietnam, Philippines, Mexico, Japan, Russian, USA, Germany, and Netherland. Labor-intensive agricultural products, such as fish, vegetables, and fruit were most seriously affected.

Nonenzymatic glucose sensor based on renewable electrospun Ni nanoparticle-loaded carbon nanofiber paste electrode

A novel nonenzymatic glucose sensor was developed based on the renewable Ni nanoparticle-loaded carbon nanofiber paste (NiCFP) electrode. The NiCF nanocomposite was prepared by combination of electrospinning technique with thermal treatment method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that large amounts of spherical nanoparticles were well dispersed on the surface or embedded in the carbon nanofibers. And the nanoparticles were composed of Ni and NiO, as revealed by energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). In application to nonenzymatic glucose determination, the renewable NiCFP electrodes, which were constructed by simply mixing the electrospun nanocomposite with mineral oil, exhibited strong and fast amperometric response without being poisoned by chloride ions. Low detection limit of 1 mu M with wide linear range from 2 mu M to 2.5 mM (R = 0.9997) could be obtained.

运用硼同位素示踪贵阳市地下水污染

由于硼化合物的可溶性使水系中的硼污染日趋严重，我们运用选取了贵阳市地下水19个点，分别测定了12个月的硼浓度和硼同位素组成来指示贵阳市地下水的污染程度和污染来源。运用87Sr/86Sr及水化学特征辅助判断地层的岩性和地层的连通情况。通过本项研究，我们得到以下认识： 1.在国内首先用MC-ICP-MS测定低含量硼同位素组成； 2.提出硼浓度和硼同位素组成分别指示地下水的污染程度和污染来源； 3.87Sr/86Sr表明地下水受以碳酸盐岩为主的储水层岩性控制，局部有少量硅酸盐影响； 4. 水化学指标研究显示本地区岩溶作用发育，地下水与地表水的连通条件好，大多数地下水系统已经受到地表水的混合影响，部分水质已经受到较严重的污染； 5. 根据硼同位素研究结果并与水化学等指标相结合，可以将研究区地下水的主要污染源划分为农业污染和城市综合排放污染两大类； 6.本区岩石以碳酸盐岩为主，也有部分硅酸盐组分，二者明显不同的成因及化学组成导致不同的硼含量及硼同位素组成背景，水/岩作用后进入水体的硼同位素组成也不同。 在研究过程中，有以下思考，需要通过实验来验证： 1.改变树脂的粒度和用量会有何效果？ 2. 肖应凯等(1997)详细研究了溶液pH对Amberlite IRA-743树脂吸附硼的影响，结果表明pH在2~13的范围内，小体积(10ml)交换溶液中硼的回收率没有明显变化。pH的改变对大体积交换溶液中硼的回收率是否会有明显变化？ 3.地表水和地下水混合模型能否通过模拟实验来建立？ 4.对于文中的关于岩性影响硼的浓度和硼同位素组成的假想和推测需要通过实验验证。