Causes of gelation in solutions of acrylonitrile copolymers

The effect of aluminum and some other metals on gelation in spinning solutions in production of the polyacrylonitrile fiber nitron-S was investigated. It was found that gelation in industrial spinning solutions is caused by the aluminum—iron electric pair contained in the filter press so that the aluminum lons formed cross-link the macromolecules of the acrylonitrile copolymers. It was shown that separation of the electric pair reduces gelation and consequently increases the stability of formation and improves the quality of the fiber.All-Russian Scientific-Research Institute of Synthetic Fibers, Tver'. Translated from Khimicheskie Volokna, No. 4, pp. 26–28, July–August, 1992.     

Tissue ablation with radiofrequency using multiprobe arrays

RATIONALE AND OBJECTIVES: We studied the feasibility of increasing the volume of tissue destroyed by radiofrequency tissue coagulation using multiprobe arrays and defined parameters that determine lesion size and shape. METHODS: Radiofrequency was applied to ex vivo calf liver using arrays of two to five 18-gauge probes for 6 min at 70-90 degrees C. Probe spacing (1-3 cm) and arrangement, as well as the method of radiofrequency application (simultaneous or sequential), were varied. The resulting areas of tissue coagulation were measured and compared. RESULTS: Uniform tissue necrosis was observed with simultaneous radiofrequency application for probes 1.5 cm or less apart. At 1.5 cm, arrays of three equidistant probes produced spheroid lesions approximately 3.0 +/- 0.2 cm in diameter. Arrays of four equidistant probes produced cuboid lesions of 3.2 +/- 0.1 cm per side. However, probes placed 2 cm or more apart produced independent lesions 1.4 cm in diameter, with incomplete necrosis between probes. In the trials using five-probe arrays, a central region 4mm in diameter showed no visible evidence of tissue necrosis. With each array, lesion size varied less than 3 mm in any direction. Greater necrosis was accomplished when radiofrequency was applied simultaneously rather than sequentially. CONCLUSION: Multiprobe radiofrequency arrays permit the destruction of more tissue in a single treatment session than is possible with multiple individual probes operating alone. Probes spaced 1.5 cm or less apart act synergistically, producing a total volume of coagulated tissue that is greater than when the individual probes are operated sequentially.     

Effects of salt depletion on the kidney: changes in medullary oxygenation and thick ascending limb size

Previous studies have shown that salt depletion enhances the susceptibility of the kidney to nephrotoxins (amphotericin, cyclosporine, and contrast). To study the renal response to salt depletion, Sprague-Dawley rats were fed a sodium-deficient diet (N = 12) with pair-fed controls (N = 13) for 4 wk. In addition, rats from each group underwent 24-h water deprivation studies (N = 9; four salt deprived, five normal). Plastic 1-micron horizontal sections of mid-inner stripe were examined, and cross-sectional areas of the medullary thick ascending limb (mTAL) were analyzed. The mTAL of the salt-deprived rats were smaller (P = 0.04) and showed greater variance in size (P = 0.02) than control (618 +/- 106 versus 693 +/- 50 microns2). However, mean glomerular and collecting duct cross-sectional areas were unaffected by salt intake. Cross-sectional areas of long- and short-loop mTAL were significantly different, regardless of group (518 +/- 78 versus 732 +/- 92 microns2). Maximal urinary concentrating ability was found to correlate with mTAL cross-sectional area (r = 0.85; P = 0.004) and with long-loop mTAL size (r = 0.77; P = 0.016). However, it did not significantly correlate with short loop mTAL size (r = 0.53; P = 0.14).(ABSTRACT TRUNCATED AT 250 WORDS)