光学电流互感器的关键技术

通过对光学电流互感器(OCT)的2种主要类型磁光电流互感器(MOCT)和光纤电流互感器(FOCT)的原理介绍和详细分析,指出MOCT的光学传感头加工、测量受光功率波动的影响,分析了FOCT光纤器件的非理想偏振特性,以及光纤材料的Verdet常数的补偿等关键技术和存在问题.MOCT、FOCT共同存在小电流测量时信噪比较低的问题.     

Crystal structure of the extracellular domain from P0, the major structural protein of peripheral nerve myelin

P0, the major protein of peripheral nerve myelin, mediates membrane adhesion in the spiral wraps of the myelin sheath. We have determined the crystal structure of the extracellular domain from P0 (P0ex) at 1.9 A resolution. P0ex is folded like a typical immunoglobulin variable-like domain; five residues at the C-terminus are disordered, suggesting a flexible linkage to the membrane. The requirements for crystallization of P0ex are similar to those for maintaining the native extracellular spacing of adjacent myelin lamellae; thus, given the self-adhesive character of P0ex, the crystal itself may reveal some of the natural interactions that occur between P0 molecules in myelin. The structure leads to the suggestion that P0 extracellular domains may emanate from the membrane surface as tetramers that link to tetramers on the opposing membrane surface, to result in the formation of networks of molecules. We report analytical ultracentrifugation data for P0ex that support this idea.     

Effect of infants on adult social relations in the squirrel monkey (Saimiri Sciureus)

7 groups of squirrel monkeys were observed to assess the effect of infants on social interactions and interanimal distances among adult members of their natal groups. Each group contained one or two infants, 5 to 7 months of age at the start of the study. Infants initiated affiliative and playful interactions with all adults, whereas adults directed few mostly antagonistic, interactions toward infants. Following the removal of infants from groups, distances between adults decreased and adult affiliative interactions increased more than 100%. The results indicate that infants within the age range examined can have a pervasive, primarily inhibitory, influence on adult social relationships.     

The use of tertiary collimation for spinal irradiation with extended SSD electron fields

PURPOSE: The spine can be treated with an electron beam when its maximum posterior depth is within the therapeutic range of electrons. Electron fields treated at extended source-to-surface distances (SSDs), however, have larger penumbras and narrower therapeutic isodose widths relative to those at the standard SSD of 100 cm. We investigated the use of tertiary collimation close to the patient surface for these fields to sharpen the penumbra, minimizing dose to normal tissue and maximizing target coverage. METHODS AND MATERIALS: Using film dosimetry in a polystyrene phantom, we measured the dose distribution for electron fields at extended SSD under varying collimation conditions. Beam penumbra and therapeutic width as a function of depth, SSD, applicator insert size, and tertiary collimator opening were determined. We also measured the dose distributions in the junction region for various gaps between x-ray fields and an electron field as used for craniospinal irradiation. RESULTS: Measurements show that tertiary collimation close to the skin surface reduces penumbra width (lateral distance between the 90 and 20% isodose lines) by 56% and increases therapeutic isodose width (lateral width of the 90% isodose curve) by 25% at a depth of dmax relative to standard collimation. These numbers change to 23 and 13%, respectively, at an average depth of the spine. When lateral brain and posterior spine fields are used to irradiate the entire craniospinal axis, tertiary collimation aids in reducing the volume of the hot spot in the junction region by as much as 10% without compromising target coverage. CONCLUSIONS: Tertiary collimation for extended SSD electron fields is preferable to standard collimation in order to minimize dose to normal tissue and increase target coverage. This technique can be applied to both spinal and craniospinal irradiation. Support structures for the tertiary blocking are needed because the weight of the lead is usually too great for placement on the skin.     

Role of angiotensin II and vasopressin receptors within the supraoptic nucleus in water and sodium intake induced by the injection of angiotensin II into the medial septal area

In this study we investigated the effects of the injection into the supraoptic nucleus (SON) of non-peptide AT1- and AT2-angiotensin II (ANG II) receptor antagonists, DuP753 and PD123319, as well as of the arginine-vasopressin (AVP) receptor antagonist d(CH2)5-Tyr(Me)-AVP, on water and 3% NaCl intake induced by the injection of ANG II into the medial septal area (MSA). The effects on water or 3% NaCl intake were assessed in 30-h water-deprived or in 20-h water-deprived furosemide-treated adult male rats, respectively. The drugs were injected in 0.5 microliter over 30-60 s. Controls were injected with a similar volume of 0.15 M NaCl. Antagonists were injected at doses of 20, 80 and 180 nmol. Water and sodium intake was measured over a 2-h period. Previous administration of the AT1 receptor antagonist DuP753 into the SON decreased water (65%, N = 10, P < 0.01) and sodium intake (81%, N = 8, P < 0.01) induced by the injection of ANG II (10 nmol) into the MSA. Neither of these responses was significantly changed by injection of the AT2-receptor antagonist PD123319 into the SON. On the other hand, while there was a decrease in water intake (45%, N = 9, P < 0.01), ANG II-induced sodium intake was significantly increased (70%, N = 8, P < 0.01) following injection of the V1-type vasopressin antagonist d(CH2)5-Tyr(Me)-AVP into the SON. These results suggest that both AT1 and V1 receptors within the SON may be involved in water and sodium intake induced by the activation of ANG II receptors within the MSA. Furthermore, they do not support the involvement of MSA AT2 receptors in the mediation of these responses.