Waveguide probe structures for a multilayer magnetodielectric: An inverse problem

Direct and inverse problems are considered for diffraction by an open end of a rectangular waveguide (RW) with a flange that adjoins a piecewise inhomogeneous planar layered lossy medium. Also considered are similar diffraction problems for a junction of an RW and a rectangular resonator filled with a multilayer medium and a junction of two RWs, one of which contains a multilayer plate. Such open and shielded waveguide probe structures (WPSs) are used for determination and nondestructive testing of parameters of multilayer samples. The direct problem is formulated on the basis of admittance and impedance algorithms with consideration for losses existing in the medium, flange, and screens. In this case, the approximation of the given aperture field allows obtainment of explicit solutions for open and shielded WPSs in the form of integrals. Solution of the inverse problem that lies in determining thicknesses, permittivities, and permeabilities of the layers from measured values of the magnitude of the reflection coefficient is obtained by minimizing the corresponding least-squares error and by constructing artificial neural networks. In order to increase the accuracy, it is proposed to use a two-port of errors and perform measurements for several positions of the sample with respect to the flange and different impedance conditions behind the sample.     

Antitubercular activity of lomefloxacin in an experiment

The effect of lomefloxacin was studied on mice with experimental infection due to Mycobacterium tuberculosis. The antibiotic was administered in doses of 100 and 200 mg/kg. It was shown that the use of lomefloxacin for a month provided a lower death rate of the animals with progressing acute generalized tuberculosis, a lower level of the lesions in the internal organs and a lower number of the Mycobacterium isolates from them. The efficacy of the treatment depended on the drug dose. When lomefloxacin was used in a dose of 200 mg/kg, the survival rate was much higher and the number of the epithelial unicellular granulomas in the tissue of the lung and spleen was markedly decreased while with the lower dose the indices did not differ from those in the control.     

Quenching of chlorophyll fluorescence by quinones

Obese (Lepr(fa)/Lepr(fa)) Zucker rats have a missense mutation in the leptin receptor gene. One amino acid substitution in the extracellular domain common to all known leptin receptor proteins results from this mutation. Obese Zucker rats are unable to respond behaviorally to leptin which is peripherally administered. However, conflicting reports exist on whether obese Zucker rats can respond to centrally administered leptin. The purpose of this study was to determine whether obese Zucker rats responded behaviorally and metabolically to intracerebroventricularly (i.c.v.) administered leptin and to compare the responses of lean and obese Zucker rats. We found that both lean and obese Zucker rats had similar body weight and food intake responses when administered a single i.c.v. leptin injection in a range of doses (1.25, 2.5, 5, and 10 microg), as well as daily i.c.v. administered leptin for five consecutive days. Both single and daily leptin administration also decreased respiratory quotient (RQ) similarly in lean and obese Zucker rats, indicating mobilization of fat as an energy source for leptin-treated rats. After withdrawal of daily leptin treatment, lean and obese Zucker rats exhibited different recovery responses. It is concluded that obese Zucker rats can respond to exogenous leptin when leptin is delivered into the brain ventricles.     

Requirement of major histocompatibility complex-compatible microenvironment for spleen colony formation (CFU-S on day 12 but not on day 8)

The objectives of this study were 1) to evaluate interleukin-8 concentrations in cervical secretions in predicting preterm delivery, microbial invasion of the amniotic cavity and histologic chorioamnionitis in patients with preterm labor and intact membranes and 2) to compare the diagnostic value of interleukin-8 with fetal fibronectin determinations in predicting preterm delivery, microbial invasion of the amniotic cavity and histologic chorioamnionitis in patients with preterm labor and intact membranes. Interleukin-8 and fetal fibronectin were assayed in cervical secretions in 106 patients with singleton pregnancies and intact membranes admitted for preterm labor. Amniotic fluid obtained by amniocentesis was cultured and placentas (No = 43) analyzed for the presence of chorioamnionitis. The prevalence of pregnancies delivered preterm was 46.2% (49/106) and 15.09% (16/106) of amniotic fluid cultures were positive. Interleukin-8 levels in cervical secretions were significantly increased in patients who delivered preterm (p < or = 0.0001), in presence of positive amniotic fluid culture (p = 0.0016) and histological chorioamnionitis (p = 0.008) than in patients with negative findings. Receiver-operator characteristics curve analysis showed that an interleukin-8 value > 450 pg/ml is comparable to that of a fetal fibronectin value > 50 ng/ml in predicting preterm delivery (p = 0.247). Among patients who delivered preterm interleukin-8 concentrations > 860 pg/ml predicted a positive amniotic fluid culture with a sensitivity of 81.2% and a specificity 66.6%. Further, in patients who delivered preterm and had a negative amniotic fluid culture, IL-8 concentrations > 480 pg/ml predicted histological chorioamnionitis with a sensitivity 78.5% and specificity 61.5%. A positive fetal fibronectin > 50 ng/ml was not predictve of either a positive amniotic fluid culture or the presence of histological chorioamnionitis. In conclusion, increased concentrations of interleukin-8 and fetal fibronectin are associated with impending delivery and their diagnostic value seems comparable. However, interleukin-8 concentrations identify patients at risk of a positive amniotic fluid culture and the presence of histological chorioamnionitis. Measurement of interleukin-8 in cervical secretion is a non-invasive method to identify patients at risk for both preterm delivery and intrauterine infection.     

A contribution to the theory of parametric excitation of thermomechanical oscillations

The conditions for a rather fast increase in parametric thermomechanical oscillations have been revealed by using numerical solutions of some types of Hill's equation. It is shown that the occurrence of a real parametric resonance is essentially determined by the character of thermal modulations. It is hypothesized that the indicated trends are observed in oscillations of any physical nature.Stavropol State Pedagogical Institute, Stavropol. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 3, pp. 294–298, September, 1992.