光磁共振实验中干扰峰的辨别方法

简要介绍了光磁共振实验原理及采用扫场法测量铷原子朗德因子的实验方法.通过对磁共振原理的研究与分析,发现实验中正常磁共振信号的产生受到有关实验条件的限制,并且实验条件改变时会遵循一定的规律,而干扰信号则不具备这些特征.提出了辨别干扰峰的3种方法,即去射频场法、变频法和差值法,并对这3种方法的原理与应用作了介绍.     

原子吸收光谱法测定火电厂水汽中钾钠钙

采用空气-乙炔火焰原子吸收光谱法对火电厂水汽中钾、钠、钙元素进行了测定。对测定介质、释放剂的影响进行了探讨,结果表明:以体积分数为1%的盐酸作为测定介质,选择质量浓度为100 g/L的SrCl_2溶液作为释放剂。方法测定的线性范围分别是钾:0.01～2.00μg/mL,钠:0.01～1.00μg/mL,钙:0.01～10.0μg/mL,线性相关系数均大于0.999 0;检出限分别是0.003μg/mL,0.002μg/mL,0.006μg/mL。用于火电厂水汽中钾、钠、钙的测定,回收率分别为95.7%～1     

Desensitization of the GABAA receptor shifts the dynamic range of retinal horizontal cells due to light and dark adaptation

The effects of the GABAergic pathway on the dynamic range of the light response of cone-driven horizontal cells (HCs) in the carp retina were investigated using conventional intracellular recordings and computer simulations. The amplitude of the HC responses to repetitive test flashes was altered by background illumination in control Ringer's solution, but was not changed following the application of picrotoxin or bicuculline, which suggests that GABAA receptors mediate the subsequent change in light response. This phenomenon was simulated by introducing the desensitization mechanism of the GABAA receptor into a cone-HC network model. These results suggest that desensitization of the GABAA receptor shifts the dynamic range of the HCs due to light and dark adaptation.     

The modeling of pool profiles,temperature profiles and velocity fields in ESR systems

Through the simultaneous statement of Maxwell’s equations, the turbulent Navier-Stokes equations and the differential thermal energy balance equations a mathematical model has been developed to represent the pool profiles, the velocity fields and the temperature profiles in an ESR system. The major advance over earlier modeling efforts is the fact that the model is capable of predicting the pool profiles from first principles. The theoretically predicted pool profiles and temperature fields were found to be in reasonable agreement with experimental measurements reported by Mellberg for a laboratory scale system. The model is used to investigate the interdependence of key process parameters, with the power input, fill ratio, amount of slag used and the position of the electrode as the independent variables and the casting rate, pool depth, velocity and temperature fields as the dependent variables.     

Determination of power absorption in man exposed to high frequency electromagnetic fields by thermographic measurements on scale models

Ultrafiltrable serum uric acid (u.a.) was determined by ultrafiltration under in vivo conditions in humans using a reliable technique described in detail. It could be demonstrated that u.a. binding to macromolecules occurs in healthy humans (controls) and in patients with renal calcium stones. The percentage of free u.a. in controls (n=60) averages 86.2 +/- 0.9 SEM. With increasing age, bound u.a. rises slightly. On the other hand, younger (less than 40 years) stone patients have significantly more bound u.a. than matched controls (80.7 +/- 1.0 SEM; p less than 0.001), whereas this is not found in elderly patients. The degree of binding is not related to concentration of plasma proteins but inversely related to free fatty acid concentration in healthy controls (r= -0.52; p less than 0.01). It is suggested that no augmentation of tubular u.a. filtered by the glomeruli could have occurred. The origin of fasting hyperuricosuria shown earlier to be a prominent feature of young renal calcium stone formers is yet unknown.     

Adapting to phase shifts, II. Effects of melatonin and conflicting light treatment

The effects of melatonin (MT) and placebo (P) on adaptation to a rapid 9-h advance phase shift, in the presence and absence of inappropriate bright light (BL) exposure were examined. Volunteers were initially subjected to a gradual 9-h delay phase shift over 5 days (D1-D5) using a combination of bright light and darkness/sleep. Readaptation to a subsequent rapid 9-h advance phase shift was studied using: 1) MT, 5 mg, 2300 h, D6-D8, 2) BL, 2,000 lx, 0800-1200 h, D7-D8, 3) MT+BL and 4) P, 2300 h, D6-D8. MT treatment was timed to phase advance and BL to phase delay. BL delayed the 6-sulphatoxymelatonin rhythm in five out of seven subjects. Two subjects delayed and five phase advanced with both MT and MT+BL. MT consistently improved subjective sleep, alertness, and performance even in the presence of inappropriate BL and before phase readaptation had occurred. BL improved alertness and performance transiently. The beneficial effects of MT are not wholly mediated through an effect on the biological clock.