Economic modeling of international water use (the case of the aral sea basin)

Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 61–66, July–August 1994.     

System optimization and multitest linear programming problems for preference assigned as intervals

Cybernetics and Systems Analysis -     

Modeling the heat transfer when a chemically reacting flow passes a rib by means of the finite-element method

The finite-element method is used to solve the conjugate problem of heat transfer between a ribbed wall and a chemically reacting flow. The distribution of the velocities, temperatures, and concentrations, as well as the local heat-transfer coefficients and efficiency of the rib, is obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 2, pp. 202–208, August, 1988.     

Absorption of various actinomycins by Staphylococcus aureus cells

The absorption of actinomycin D by the cell suspension of Staphylococcus aureus via diffusion linearly depended on the antibiotic concentration in the suspension within the ranges of 2 to 15 micrograms/ml. The absorption of active actinomycins C2, C3 and Au6 was the same as that of actinomycin D. The Staphylococcus intact membranes limited the inlet of the actinomycins to the cells since the membranotropic substances such as gramicidin S and its derivatives and thyrocidin increased their absorption by 30-70 per cent. The absorption of a low active actinomycin D0 and inactive actinomycinic acid even after the exposure to the membranotropic substances was not detectable. These compounds did not form any complexes with DNA. The level of the absorption of the actinomycins by the cells was likely defined by their ability to complex with DNA.     

Autoactivation in cell populations

A mathematical model of cell population with cooperatively controlled mitotic activity is analysed. The mitotic activity of stem cells is activated by the cells themselves and is inhibited by differentiated cells. Analysis of the model shows that steady-state oscillations in the mitotic activity are possible in such populations. The appearance of self oscillations is due to a delay in the negative feedback loop. The oscillation period, determined to a linear approximation, is greater than a quadruplicate delay.     

Contents of alpha-fetoprotein in the blood of pregnant women as a criterion of the presence of congenital heart defects in the fetus

alpha-Fetoprotein (AFP) was measured in the blood of 16 women pregnant with twins at various terms of gestation and 24 pregnant women whose fetuses were found to have anencephaly, patent spina bifida, gastroschisis, renal polycystosis, or Down's disease. In Down's disease AFP level was 7 ng/ml (0.17 multiple of medians, MoM) at 17 weeks gestation and 6 ng/ml (0.12 MoM) at 19 weeks. In the fetal abnormalities studied AFP level was 372 ng/ml on average (6.8 MoM) at 16 to 18 weeks gestation, this being about 10 times higher than the normal level. AFP level in twin pregnancy at the same period was 2.3 MoM. AFP measurements are important for the prenatal diagnosis of fetal status in order to plan follow-up of pregnancy and labor management.     

Dosimetric basis of mean fractionation in the irradiation of bone metastases in breast cancer

Proceeding from the drawing of maps with biologically isoeffective percentage doses the authors provide a dosimetric substantiation of gamma-beam irradiation of different parts of the bony skeleton using the following irradiation scheme: a single dose of 4 Gy, 5-6 fractions daily. It has been shown that to choose a therapeutic plan in the utilization of a nonstandard scheme of fractionation, the calculation of the TDF factor by Orton's tables is safe and illustrative. By way of example are given maps of isoeffective doses used in the irradiation of bone metastases in breast cancer patients with metastases to different parts of the skeleton.     

Multiplane transesophageal echocardiographic doppler imaging accurately determines cardiac output measurements in critically ill patients

OBJECTIVES: To compare cardiac output and stroke volume measured by multiplane transesophageal Doppler echocardiography with that measured by the thermodilution technique. DESIGN: Prospective direct comparison of paired measurements by both techniques in each patient. SETTING: Cardiac surgery and myocardial infarction intensive care units. PATIENTS: Twenty-nine patients, mean age (+/- SD) 67 +/- 8 years. Nineteen had undergone open heart surgery and 10 had suffered acute myocardial infarction. METHODS: Cardiac output and stroke volume were measured simultaneously by the thermodilution technique and multiplane transesophageal Doppler echocardiography via the transgastric view (119 +/- 8 degrees) with the sample volume positioned at the level of the left ventricular outflow tract. RESULTS: Stroke volume and cardiac output measurements were obtained in 29 of 33 patients (88%). Mean values were 50 +/- 13 mL and 4.8 +/- 1.3 L/min by Doppler and 51 +/- 14 mL and 4.9 +/- 1.4 L/min by thermodilution (r = 0.90, r = 0.91, p < 0.001). The mean differences in values obtained with the two techniques were 1 +/- 6 mL (2 +/- 12%) and 0.1 +/- 0.7 L/min (2 +/- 12%). CONCLUSIONS: Multiplane transesophageal echocardiography enhances the ability to estimate accurately cardiac output and stroke volume by providing new access to left ventricular outflow tract in critically ill patients.