Field experience with momentary fast turbine valving and otherspecial stability controls employed at AEP's Rockport plant

Several special stability controls, including fast turbine valving are in service at AEP's Rockport generating plant to enhance the plant's transient and voltage stability performance. An account of how these supplementary controls evolved over time to meet changing system needs is provided. An overview of field tests, maintenance practices and operating history of the fast turbine valving equipment is presented. Finally, one of the successful Rockport fast valving events is analyzed in detail, with respect to valve stroke characteristics and electrical response of the Rockport units. This paper emphasizes the lessons learned from the operating experience, which include a need to constantly monitor the adequacy of the special stability control equipment, through regular maintenance and analysis of actual operations     

Emulsifying Properties of the Total Fraction and the Hydrophobic Fraction of Bovine Milk Proteose-peptones

Since proteose-peptone is a mixture of heterogeneous proteins and peptides, its functional properties have not yet been fully understood. The present study was undertaken to elucidate the emulsifying properties of proteose-peptones and a parallel evaluation was performed of the emulsifying activity of the total fraction prepared from bulk skimmed milk by precipitation with ammonium sulphate and of the most hydrophobic fraction purified by hydrophobic interaction fast protein liquid chromatography. A turbidimetric technique was used and the absorbance value at 500 nm was then directly used as the emulsifying activity index. The results obtained confirmed the good emulsifying activity of this protein fraction of the whey and demonstrated the considerable influence of the concentration on the capacity of the proteose-peptones to stabilize a model oil-in-water emulsion. Moreover, at all the concentrations examined, the purified component 3 showed a higher emulsifying activity than the total unpurified fraction.     

Early induction of alterations in cancellous and cortical bone histology after orchiectomy in mature rats

Androgen deficiency is associated with low bone mass in humans and animals, but the remodeling alterations that lead to bone loss are unclear. Our objective was to define early responses in both cancellous and cortical bone to orchiectomy (ORX) using histomorphometry in sexually mature (4-month-old) rats. A total of 62 male rats, 4 months of age, were divided into six groups, sham operated (SH) or orchiectomized (ORX), and sacrificed 1, 2, or 4 weeks after ORX. Calcein was given 5 and 2 days before sacrifice to label mineralizing surfaces. Bone mineral density (BMD) was measured in excised femurs by dual energy X-ray absorptiometry (DEXA). Static and dynamic histomorphometry was evaluated in the cancellous bone of the proximal tibial metaphysis and lumbar vertebral bodies, and in the cortical bone of the tibial diaphysis. Osteopenia began to develop by 2 weeks after ORX, though weight gain and femur length did not change. Femoral BMD was significantly reduced and BMC decreased (NS) by 4 weeks after ORX (p < 0.05). Tibial and vertebral cancellous bone volume decreased 19% and 13%, respectively, while osteoblast and osteoclast surfaces, and numbers of osteoclasts, increased after ORX. At 2 weeks post-ORX, an increase in cancellous bone formation rate was attributable primarily to an increase in mineralizing surfaces and a smaller rise in mineral apposition rate. In contrast, cortical bone periosteal, but not endosteal, bone formation rate and mineralizing surfaces decreased. We conclude that ORX stimulates cancellous and diminishes periosteal bone turnover rapidly after ORX, with subsequent decreases in bone volume and mineral density. The clear divergence in cortical and cancellous bone responses to hypogonadism raises important questions regarding the control of bone formation and its role in defining the skeletal phenotype.     

Quantitative molecular monitoring of HIV-1 RNA during antiretroviral therapy

Plasma HIV-1 RNA testing was used to monitor 43 HIV-1 infected patients newly placed on antiretroviral therapy or whose therapy had been recently changed. A polymerase chain reaction kit was used to measure HIV-1 RNA in clinical samples or frozen plasma. The cutoff of this test was 200 RNA copies/ml. The first group (11 patients) was stable on long-term zidovudine monotherapy when switched to stavudine. The HIV-1 RNA of three patients who had a regular decline in CD4+ T cell count did not change despite this switch, with a mean follow-up of 630 days. The HIV-1 RNA copy numbers of eight patients whose CD4+ T cell counts were stable declined an average of 0.53 log10 between days 90 and 650. The second group (14 patients) was on long-term zidovudine monotherapy and had declining CD4+ T cell counts over the past 6 months. Lamivudine was added to this regimen on day 0. HIV-1 RNA copy number decreased rapidly within 30 d, reaching -0.86 log10 on day 90, and this effect was maintained thereafter, with a mean follow-up of 161 days. There was a concomitant mean gain of +33 CD4+ T cells on day 90. The third group (nine patients) had never received anti-retroviral therapy and was given zidovudine+didanosine. HIV-1 RNA copy number decreased in all cases but one, reaching -1.31 log10 on day 150. This decrease was transient in three cases. The last group (nine patients) had also not had previous anti-retroviral therapy and was given zidovudine + didanosine + lamivudine in combination. HIV-1 RNA copy numbers declined rapidly in all cases, to below the cutoff in eight cases within a mean period of 50.5 days. The CD4+ cell counts increased by 164 cells/microliter on day 14 and by 201 cells/microliter on day 180. The response to therapy of the total population of 43 patients varied according to cases. The relative changes in p24 antigen compared to HIV-1 RNA also differed between patients. Measurement of HIV-1 viremia appears to be a valuable tool in current practice for individualizing therapy.