Islet-1 is required for ventral neuron survival in Xenopus

Islet-1 is a LIM domain transcription factor involved in several processes of embryonic development. Xenopus Islet-1 (Xisl-1) has been shown to be crucial for proper heart development. Here we show that Xisl-1 and Xisl-2 are differentially expressed in th

利用MC-ICP-MS测定硼同位素及其在西藏地热和盐湖中的初步应用

Based on previous studies, boron can be separated from aqueous samples with Amberlite IRA-743 resin. Experiments on the elute temperature, elute volume and the dynamic resin exchange capacity have been performed in this study. Results show that the dynamic exchange capacity of the resin is 4.2mg B/g and at room temperature, boron fixed on the resin within this capacity level can be extracted quantitatively by using 5ml 2%HNO3. A new procedure has been developed for the measurement of boron isotope ratios in water samples using a Neptune MC-ICP-MS, after resolving the memory effect, which is a key problem, and investigating the impacts of mass bias and Si matrix effect. Using this method, it usually takes 20 min to perform one measurement on 0.1ppm boron solution with a precision of 0.23‰ (SD). If the relative deviation between a sample and the standard is large, the washout time needs to be doubled to achieve a higher precision. δ11B values of water samples from Yangbajing geothermal field vary from -10.53 to -9.13‰. Owing to the large difference B concentration and the small B isotope difference between deep geothermal water and surface water, B isotope ratios of the shallow geothermal fluids are dominated by the deep end member rather than the shallower one in the mixing process. As a consequence, δ11B-B relation is indicative basically of a dilution process. Vapor-liquid separation and calcite scaling also greatly influence B isotope fractionation. δ11B values of water samples from Dagejia geothermal field are from -15.98‰ to -11.67‰. Boron in Changma River near the field has two sources, freshwater lakes (Dajiamang Lake and Canke Lake) and geothermal waters. Finally, a preliminary discussion is included on boron geochemical characteristics of the salt lakes in Shuanghu area and other geothermal fields, to provide information for future studies on boron isotope geochemistry of geothermal systems and salt lakes in Tibet.

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。