A simple method for the determination of the optical constants, n and k of cadmium sulfide films from transmittance measurements

The dispersive refractive index n(λ) and extinction coefficient k(λ) of CdS thin films were evaluated from spectrophotometric transmittance characteristic in the visible region. A method is presented to determine n(λ) and k(λ) in the region k² n², using wavelength and transmittance values. This method has been used for the investigation of the effect of the deposition rate on the optical properties of cadmium sulfide films. The refractive indices are found to depend on the deposition rate with values between 2.48 and 2.60. The energy gap of the samples is found to be independent of deposition rate with the value 2.44 eV. The real and imaginary parts of the dielectric constant have also been evaluated.     

Offset dual-disk dielectric resonator antenna of very highpermittivity

An aperture-coupled offset dual-disk dielectric resonator antenna of very high permittivity is investigated experimentally. It is found that the new configuration offers an impedance bandwidth 4.6 times wider than that of the single element. The voltage standing wave ratio, radiation patterns, and antenna gain of the configuration are studied     

Prognostic factors of primary liver cancer

To investigate the prognostic factors of primary liver cancer (PLC) and improve the long-term results, 1,248 cases of PLC were analysed. Univariate analysis demonstrated that discovery approach, staging of PLC, original gamma-GPT, resection, radical resection, original AFP, tumor size, tumor number, and tumor capsule have very significant effects on prognosis of PLC (all P < 0.001); cirrhosis, HBsAg, local resection, and tumor embolus in portal vein were also significant difference (all P < 0.05); age, sex, original AFP, hepatitis, and differentiation of PLC cells were no significant difference (all P > 0.05). Multivariate analysis demonstrated that original gamma-GPT, radical resection, tumor size, and tumor number were the most significant prognostic factors (all P < 0.001). Some aspects improving long-term survival were discussed.     

Value-based transmission planning and the effects of network models

A value-based automated transmission system planning model is presented in this paper and the impact of the various network representations on the results of the model is discussed. Value-based integrated resource planning provides a “societal cost” (utility operation and investment costs plus customer outage costs) minimizing composite generation-transmission system expansion plan. The model trades-off and compares the costs and benefits of alternative generation and transmission resources using a consistent economic and engineering criterion in order to determine an “optimal” resource expansion plan. The generalized Benders decomposition algorithm with “importance sampling” used to solve the problem enables the model to estimate certain average information about scenarios or contingencies by examining only a very small fraction of all the scenarios or contingencies. The impacts of system resources upon both real and reactive power can be analyzed when using the AC power flow equations. It is concluded that for transmission system planning where reactive power flows and voltage constraints are important, it is imperative that an AC power flow model be used. The combination of AC power flow and linearized power flow models, with linearization about the solution of the AC power flow model, was found to be a promising compromise between accuracy and computation time     

Design and simulation of waveguide electrooptic beam deflectors

Numerical simulation based on the scalar beam propagation method, was used to investigate the performance of waveguide electrooptic beam deflectors. The deflectors under investigation consist of a stack of electrooptically controlled prisms in a waveguide. The results were compared to earlier simplified analysis. It was found that for given overall device dimensions, the number of interfaces between prisms in a prism-type electrooptic deflector has significant influence on the device performance when it is small. To avoid wavefront distortion, unwanted reflection from the interfaces, and asymmetry in the deflection angles caused by small number of interfaces, one should use more than about ten interfaces in a typical deflector. Additional insights of device operation and design issues are discussed     

Portosystemic shunt in Budd-Chiari syndrome: long-term survival and factors affecting shunt patency in 25 patients in Western countries

BACKGROUND: In Budd-Chiari syndrome (BCS) treated by portosystemic shunt, postoperative shunt thrombosis is associated with high morbidity and mortality rates. The aim of this study was to determine factors associated with shunt thrombosis. METHODS: From 1985 to 1991, 25 patients underwent portosystemic shunt for BCS. According to the patency of the shunt during the postoperative period and follow-up, patients were divided into two groups including 17 patients with patent shunt and 8 (32%) with shunt thrombosis. RESULTS: In patients with patent shunt, actuarial survival rate at 5 years was 87% versus 38% in patients with shunt thrombosis (p < 0.05). Duration of symptoms before operation was higher in patients with shunt thrombosis than in patients with patent shunt (315 +/- 483 vs 109 +/- 168 days, p < 0.05). In patients with patent shunt, extensive fibrosis or cirrhosis was observed in 3 of 17 (18%) versus in 5 of 8 (63%) of patients with shunt thrombosis (p < 0.05). Shunt thrombosis was observed in 3 of 3 patients (100%) with the combination of myeloproliferative disorder, duration of symptoms more than 100 days, and cirrhosis versus 0 of 6 (0%) patients without this combination (p < 0.05). CONCLUSIONS: In acute form of BCS (with short history of the disease and absence of extensive fibrosis or cirrhosis), early portal decompression is mandatory, with low risk of shunt thrombosis and good long-term results. In chronic form of BCS, the risk of shunt thrombosis is high and long-term results are bad; in these patients, orthotopic liver transplantation must be considered.     

Enamel pearls in the primary dentition: report of two cases

Concentrations of the polyamines, putrescine, spermidine and spermine were investigated in rat brains, in which chemical kindling or single convulsion had been induced by intraperitoneal injection of pentylenetetrazol (PTZ). A single injection of 60 mg/kg of PTZ produced tonic-clonic convulsion and increased the putrescine concentration 8 h after the injection. At lower doses of PTZ (10 and 30 mg/kg), neither marked behavioral seizure nor significant change in any polyamine concentration was observed. On the other hand, repeated injections of 30 mg/kg of PTZ eventually resulted in intense motor seizures (PTZ kindling) and increased the concentrations of all three polyamines. The most marked increase was detected in putrescine 1-48 h after the intense seizures. The increase in putrescine was clearly higher in PTZ kindling than in single convulsion. These results suggest that increases in polyamine concentrations are involved in neuronal excitability in the epileptic brain.     

Chemical activation of the SHS process in the Nb−C system

The phenomenon of chemical activation is investigated using combustion of the Nb–C system in the presence of an activating additive, namely, polytetrafluoroethylene, as an example. Regions of the parameters of the process are found where the interaction occurs by two different mechanisms. The characteristic features of the process are established and the role of the activating additive in each region is determined.Institute of Chemical Physics, Academy of Sciences of Armenia, Yerevan. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No.5, pp.590–593, November, 1993.