Manufacturing flow line systems: a review of models and analytical results

The most important models and results of the manufacturing flow line literature are described. These include the major classes of models (asynchronous, synchronous, and continuous); the major features (blocking, processing times, failures and repairs); the major properties (conservation of flow, flow rate-idle time, reversibility, and others); and the relationships among different models. Exact and approximate methods for obtaining quantitative measures of performance are also reviewed. The exact methods are appropriate for small systems. The approximate methods, which are the only means available for large systems, are generally based on decomposition, and make use of the exact methods for small systems. Extensions are briefly discussed. Directions for future research are suggested.National Science Foundation (U.S.) (Grant DDM-8914277

The values of urinary NTx in postmenopausal women undergoing HRT; the role of additional alendronate therapy.

Objective: To determine the changes in levels of urinary NTx at the end of the 6th month of oral and transdermal hormone replacement therapy (HRT) and the effects of additional alendronate therapy for osteoporotic women. Method: Of 66 postmenopausal women 23 were treated with oral estradiol + norethisterone acetate (E + P), and 22 were treated with transdermal estradiol+norethisterone acetate. The third group consisted of 21 women with osteoporosis (bone mineral density 0.05). There was no additional decrease in the levels of NTx with alendronate therapy (P > 0.05) but NTx excretion diminished more in patients with high baseline levels. Conclusion: The decline of NTx at the end of the 6th month of HRT reflects the decrease of bone resorption and it is not related to the route of administration. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved

Effect of anticoagulants on plasma homocysteine determination

Background: Waiting temperature before centrifugation and anticoagulants used, markedly effect total homocysteine concentrations. The aim of this study was to investigate the effect of different anticoagulants and temperature on plasma homocysteine levels. Methods: We studied total homocysteine concentrations in 23 healthy subjects. Blood was drawn in K(3)EDTA, sodium citrate- or sodium fluoride-containing tubes, and kept at 0 degreesC or 22 degreesC for 3 h. Total homocysteine measurements were performed with fluorescence polarization immunoassay (FPIA) method. We compared all results with baseline EDTA values (samples put on crushed ice and centrifuged immediately) recommended in literature for reference handling. Results: At 22 degreesC, the tubes: containing sodium citrate and sodium fluoride showed significantly higher total homocysteine concentrations than their respective baseline values (p = 0.000). However, sodium fluoride tubes were not significantly different than baseline EDTA levels. Waiting 3 h at 0 degreesC did not effect sodium citrate and EDTA plasma total homocysteine concentrations when compared to baseline EDTA, but sodium fluoride-containing plasma levels were significantly decreased( p = 0.000). Conclusions: According to our results, the most available and practical temperature and anticoagulant for total homocysteine determination is sodium fluoride at room temperature up to 3 h. (C) 2001 Elsevier Science B.V. All rights reserved

Cadmium exposure in tobacco workers: possible renal effects

Cadmium is a nephrotoxic metal widely used in industry and the main source of Cd in general population is smoking. Considering that the source of Cd in cigarettes is the tobacco Leaf, the exposure to Cd was evaluated in workers employed at a tobacco leaf processing factory. Blood and urinary Cd Levels were measured by flameless atomic absorption spectrometry in 87 workers and 35 controls. Urinary enzymes, total protein, albumin and uric acid were also determined to investigate the possible nephrotoxic effects of Cd

Effect of simvastatin therapy on blood and tissue ATP levels and erythrocyte membrane lipid composition

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors decrease mevalonate and subsequently cholesterol synthesis competitively. Mevalonate is also the precursor of ubiquinone. Ubiquinone is an important component of electron transport chain. We therefore investigated the effect of simvastatin on rat blood and tissue ATP concentrations and the lipid composition of red blood cell membranes after 4 weeks of therapy. Significant reductions in rat plasma cholesterol, triglyceride, and blood ATP concentrations were detected. Tissue ATP levels were not affected. Membrane phospholipids increased, while cholesterol and the cholesterol to phospholipid ratio decreased (P<0.05). A positive correlation between the plasma cholesterol concentration and the cholesterol to phospholipid ratio was noted (P<0.05, r=0.851). Our results show that HMG-CoA reductase inhibitors change the composition and probably also the functions of cell membrane lipids and blood ATP concentration