Surge Limiters for Vacuum Circuit Breaker Switchgear

The use of vacuum circult breakers In motor feeder applications (where motor terminal surge protection is not normally used) may require overvoltage surge protection within the switchgear to properly protect the motors. This need can be fulfilled by surge limiters designed for installation within the switchgear connected to the load side of the vacuum circuit breaker. This paper reviews the basic phenomena which cause vacuum switchgear related surges and dtscusses the need for surge limiters. This paper also describes the design of these surge limiters and provides information and performance data for their application.     

Impaired lymphokine secretion in anergic CD4+ T cells leads to defective help for B cell growth and differentiation

The ability of anergic helper T cells to interact with resting B cells was examined in vitro. B cell growth and differentiation in cocultures were found to be dependent on the expression of CD40 ligand (CD40L) on the cloned T cells, and the expression of this molecule was only marginally blocked by the induction of anergy. In contrast, secretion of IL-3, IL-4, IL-5, and IL-6 within the cocultures was found to be significantly reduced following the induction of anergy, and this correlated with the development of a 3- to 10-fold decrease in the ability of the T cells to induce B cell proliferation and IgG secretion. In contrast to the B cells, the activation of the T cells in these cocultures did not result in proliferation; thus, the effects of T cell anergy observed on the B cell responses were independent of an ability of clonal anergy to block T cell clonal expansion. In one T cell clone (E6), lymphokine production was reduced in part because of an increased propensity to undergo apoptosis; nevertheless, two other clones (A.E7 and 16B.2) showed no reduced viability after anergy induction. Finally, the addition of rIL-2 to the anergic T cells significantly improved their helper activity relative to control cells; this was associated with a partial reversal of the IL-3, - 4, and -5 production defects. Therefore, clonal anergy can interfere with the delivery of helper lymphokines by T cells, resulting in a decreased capacity to stimulate the growth and differentiation of B cells.     

Total colectomy with rectal mucosectomy and ileoanal anastomosis for chronic ulcerative colitis in children and young adults

Total colectomy with rectal mucosectomy and ileoanal anastomosis has been utilized as a sphincter-saving operation in young people with chronic ulcerative colitis. From 1977 to 1979, our section of pediatric surgery performed this procedure on 12 children and young adults with chronic ulcerative colitis, with encouraging results. All patients are alive and well, and all have had excellent rectal continence. Follow-up ranges from 7 to 27 months. Eight patients describe an excellent result, two have had a fair result, and two have required a temporary ileostomy. Numerous loose stools have been observed early, but stools become formed by diet and medical management, and early return to school and work has been possible. The number of stools continues to decrease for at least 1 year.     

Evidence for repression of IL-2 gene activation in anergic T cells

The induction of clonal anergy in a T cell inhibits IL-2 secretion because of the development of a proximal signal transduction defect. Fusion of anergic murine T cells to human Jurkat T leukemia cells and formation of heterokaryons failed to result in a complementation of this signaling defect and restoration of murine IL-2 mRNA inducibility. Instead, signal transduction to the human IL-2 gene became disrupted. Heterokaryons formed by the fusion of anergic murine T cells to normal murine T cells also failed to accumulate intracellular IL-2 protein in response to stimulation either with the combination of CD3 and CD28 mAbs or with ionomycin plus a protein kinase C-activating phorbol ester. The results argue against a loss-of-function signaling defect as the sole basis for clonal anergy induction and document the presence of a dominant-acting repressor molecule that inhibits signal transduction to the IL-2 gene within viable anergic T cells.     

Surge limiters for vacuum circuit breakers

Computer modeling was used to confirm the applications which require surge protection and to verify that surge limiters installed within the switchgear will provide this protection. The basic phenomena which cause vacuum-switchgear-related surges are reviewed, and the need for surge limiters is discussed. Also described is the design of these surge limiters. Information and performance data for their applications are provided. The potential sources of switching overvoltages are reviewed and the basic requirements of surge limiters are described