Expression of structure-specific recognition protein mRNA in fetal kidney and Fe-nitrilotriacetate-induced renal carcinoma in the rat

Specific expression of the structure-specific recognition protein (SSRP) gene was investigated in rat fetal, adult, and tumor tissues using a 2.0-kb partial sequence of rat SSRP cDNA isolated from a cDNA library of rat renal cell carcinoma. The results revealed that it was rather specifically expressed in rat fetal kidney and renal cell carcinoma induced by Fenitrilotriacetate, but not in adult kidney, when various organs were tested by Northern blot analysis. In situ hybridization further demonstrated that it was located in the neoplastic cells of renal cell carcinoma and in the epithelial cells of fetal kidney but undetectable in any cells of normal adult kidney. These observations seem to imply the involvement of SSRP gene, which is believed to recognize structural alterations of DNA, in kidney development and carcinogenesis of certain types of kidney cancer.     

Extension of the boundary element method to systems with conductorsand piece-wise constant dielectrics

Accurate modeling of electric fields is necessary to study the dynamics of microelectromechanical systems (MEMS). Typical microelectromechanical systems use high dielectric-constant materials, however, which significantly affect the electric field. Many numerical packages use the finite element method (FEM) to deal with systems with dielectrics. The FEM is not, however, very efficient in modeling microelectromechanical systems. There exist numerical packages that use the boundary element method (BEM), which is more desirable due to its low computational cost. But the BEM as it exists cannot model the effects of the dielectrics. This paper extends the BEM to systems with piece-wise constant dielectrics as well as conductors     

An effective heuristic method for generalized job shop scheduling with due dates

This paper is concerned with the generalized job shop scheduling problem with due dates wherein the objective is to minimize total job tardiness. An efficient heuristic algorithm called the revised exchange heuristic algorithm (REHA) is presented for solving this problem. It has been shown that the algorithm can be completed in polynomial time. Results, generated over a range of shop sizes with different due date tightness levels, indicate that the proposed technique is capable of yielding notable reductions in total tardiness (over initial schedules) for practical size problems. This suggests that this approach is an efficient scheduling option for this class of complex optimization problems.     

Thermodynamic criterion of separated eutectic phenomena

About 26 kinds of simple and complex binary eutectics were frozen directionally under the condition of electromagnetic stirring. It was found that anomalous eutectics including most metals/non-metals and some metal/intermetallic eutectics, can be separated on macroscopic scale by flow caused by electromagnetic stirring. Moreover, the eutectics in which one of their component phases possess an entropy of solution over 23 J mol-1K-1 showed notable separation. In addition, process factors also affect the formation of a separated eutectic. © 1998 Chapman & Hall     

Feldkamp and circle-and-line cone-beam reconstruction for 3D micro-CT of vascular networks

Detailed morphometric knowledge of the microvascular network is needed for studies relating structure to haemodynamic function in organs like the lung. Clinical volumetric CT is limited to millimetre-order spatial resolution. Since evidence suggests that small arterioles (50 to 300 micrometres) dominate pulmonary haemodynamics, we built a micro-CT scanner, capable of imaging excised lungs in 3D with 100 microm resolution, for basic physiology research. The scanner incorporates a micro-focal (3 microm) x-ray source, an xyz theta stage and a CCD-coupled image intensifier detector. We imaged phantoms and contrast-enhanced rat lungs, reconstructing the data with either the Feldkamp or the circle-and-line cone-beam reconstruction algorithm. We present reconstructions using 180 views over 360 degrees for the circular trajectory, augmented with views from a linear scan for the circle-and-line algorithm. Especially for platelike features perpendicular to the rotation axis and remote from the midplane, the circle-and-line algorithm produces superior reconstructions compared with Feldkamp's algorithm. We conclude that the use of nonplanar source trajectories to perform micro-CT on contrast-enhanced, excised lungs can provide data useful for morphometric analysis of vascular trees, currently down to the 130 microm level.     

Aged-rodent models of long-term growth hormone therapy: lack of deleterious effect on longevity

Studies were carried out to examine the effects of long-term recombinant human growth hormone (GH) therapy on longevity in rodents. In the first study, 150 18-month-old female F344 rats were divided into three groups of 50 rats per group: Group 1, solvent vehicle; Group 2, 10 microg GH/kg body weight three times per week; Group 3, 50 microg GH/kg body weight three times per week. GH and solvent vehicle therapies were started at 18 months of age and continued until all the animals died spontaneously. Serum insulin-like growth factor (IGF)-I was measured at 18 and 29 months of age and on 3-month-old rats. Serum IGF-I level decreased between 3 and 29 months of age. GH therapy reversed the decrease in a dose-dependent manner, with the 50 microg GH dose returning the serum IGF-I level to that of 3-month-old animals. However, statistical analysis revealed no significant effect of GH therapy on median life span, 10th percentile life span, or maximum life span. Similar observations on longevity were made on aged F344 male rats and on aged Balb/c mice, even when the dose of GH was increased to 1.0 mg/kg body weight two times per week. The main pathologic lesions in control animals were nephropathy, cardiomyopathy, leukemia, and testicular interstitial cell tumor; the prevalence of these lesions was not significantly altered by GH therapy. We conclude that long-term low-dose GH therapy that includes doses in the range that is given to humans in clinical trials in GH deficiency and to revert age-related physiologic declines has no overt deleterious effects on longevity and pathology in aged rodents.     

Modeling, analysis, and design of the quasi-charge control

A current-mode control technique, quasi-charge control (QCC), is studied. A small-signal model is developed for QCC. The model is derived for converters operating in the continuous conduction mode. The model is accurate up to half of the switching frequency. The proposed small-signal model is used to assess the dynamics of pulse-width-modulated (PWM) power converters with QCC, and to compare their performance to the current-injected control (CIC) and charge control (CC) schemes. As in CC, the QCC converges to CIC at light loads close to the boundary between continuous and discontinuous conduction modes. The dynamics of power converters with QCC or CC are more sensitive to load change and less sensitive to line change than those of power converters with CIC, especially the current loop dynamics. However, unlike in the case of CC, the dependency on the load/line can be controlled when the QCC is designed. Control design guidelines for DC-DC power converters and power factor correction rectifiers are presented, and experimental measurements are performed to verify the proposed model     

Field effect semiconductor lasers

A new semiconductor laser, the field-effect semiconductor (FES) laser, in which the both sides of the active region are surrounded by the burying layers with the reverse-biased p-n junctions is proposed. The proposed FES laser is aQ-switching device based on the direct control of laser beam intensity by the internal loss modulation through the field effect. The structure design and the operating principles of the device are discussed. Numerical solution shows that a pulsewidth shorter than 30 ps can be obtained.