Study of curved and planar frequency-selective surfaces withnonplanar illumination

A locally planar technique (LPT) is investigated for determining the forward scattered field from a generally shaped inductive frequency-selective surface (FSS) with nonplanar illumination. The results of an experimental study are presented to assess the LPT accuracy. The effects of a nonplanar incident field are determined by comparing the LPT numerical results with a series of experiments with the feed source placed at varying distances from the planar FSS. The limitations of the LPT model due to surface curvature are investigated in an experimental study of the scattered fields from a set of hyperbolic cylinders of different curvatures. From these comparisons, guidelines for applying the locally planar technique are developed     

Full-wafer technology-A new approach to large-scale laserfabrication and integration

A concept for full-wafer processing (FWP) and full-wafer testing (FWT) for semiconductor laser fabrication in the AlGaAs-GaAs material system is presented. The approach is based on chemically assisted ion beam etching for the laser-mirror formation. Record values for mirror scattering, optimum mirror reflectivity, and equivalence to cleaved mirrors in terms of laser threshold and efficiency have been achieved. Promising results for uniformity and reproducibility for major laser diode characteristics on processed 2-in wafers have been found. The FWP technology has been extensively used for designing test sites to determine various materials, process, and laser parameters, such as sheet resistance, ridge dimensions, lithographic alignment errors, mirror surface leakage, etc     

Treatment of insomnia. Getting to the root of sleeping problems

Insomnia may be periodic and transient, as caused by situational stress, or persistent, as caused by a chronic sleep disorder. Physicians can gain much information concerning the type, probable cause, onset, and duration of insomnia through history taking. A sleep diary may reveal helpful information, and input from the patient's sleeping partner can also be valuable. Complicating disorders, such as heart failure, prostatism, or depression, should be sought and specific treatment prescribed. Chemical dependency, too, requires appropriate treatment. These measures, institution of good sleep-hygiene practices, and behavior modification may resolve sleeplessness. The primary indication for use of hypnotic agents is transient sleep disruption caused by acute stress. When an agent is chosen, onset of action, metabolism, and side effects should be considered, especially in elderly patients. Addictive agents should not be given to patients with substance abuse problems. If insomnia persists, evaluation at a sleep-disorder center is recommended to facilitate design of an appropriate therapeutic regimen.     

Enantioselective, mechanism-based inactivation of guinea pig hepatic cytochrome P450 by N-(alpha-methylbenzyl)-1-aminobenzotriazole

N-Aralkylated derivatives of 1-aminobenzotriazole are well-established, mechanism-based inhibitors of cytochrome P450 (CYP or P450). In this study, the kinetics of inactivation of CYP2B-dependent 7-pentoxyresorufin O-depentylation (PROD) and CYP1A-dependent 7-ethoxyresorufin O-deethylation (EROD) activities by enantiomers of N-(alpha-methylbenzyl)-1-aminobenzotriazole (alphaMB) were compared. The racemic mixture (+/-)-alphaMB, as well as the enantiomers (-)-alphaMB and (+)-alphaMB, produced a time-, concentration-, and NADPH-dependent loss of PROD and EROD activity in hepatic microsomes from phenobarbital-treated guinea pigs. The rates of PROD inactivation by (-)-alphaMB were significantly faster than for (+)-alphaMB. Consistent with this, the derived maximal kinact was also significantly greater for (-)-alphaMB than for (+)-alphaMB (0.49 vs. 0.35 min-1). In contrast, the concentrations required for the half-maximal rate of inactivation (Ki) were equivalent for (-)-alphaMB and (+)-alphaMB, whereas the degree of competitive inhibition of PROD activity was greater for (+)-alphaMB. No significant differences were found among (-)-alphaMB, (+)-alphaMB, and (+/-)-alphaMB with respect to mechanism-based inactivation (kinact = 0.18, 0.16, and 0.17 min-1, respectively) or competitive inhibition of EROD activity. No differences were found for the maximal extent of PROD or EROD inhibition or the loss of spectral P450 after an extended 30-min incubation with the inhibitors. We conclude that mechanism-based inactivation of guinea pig CYP2B, but not CYP1A, isozymes by alphaMB occurs in a stereoselective manner, most likely as a result of a difference in the balance between metabolic activation and deactivation for the alphaMB enantiomers.     

Signaling pathways in Ras-mediated tumorigenicity and metastasis

The effector domain mutants of oncogenic Ras, V12S35 Ras, V12G37 Ras, and V12C40 Ras were tested for their abilities to mediate tumorigenic and metastatic phenotypes in athymic nude mice when expressed in NIH 3T3 fibroblasts. All mutants displayed comparable tumorigenic properties, but only the mutant that activates the Raf-mitogen-activated protein kinase kinase (MEK)-extracellular regulated kinase (ERK) 1/2 pathway, V12S35 Ras, induced tumors in the experimental metastasis assay. Furthermore, direct activation of the MEK-ERK1/2 pathway in NIH 3T3 cells by mos or a constitutively active form of MEK was sufficient to induce metastasis whereas R-Ras, which fails to activate the ERK1/2 pathway, is tumorigenic but nonmetastatic. The subcutaneous tumors and lung metastases derived from V12S35 Ras-transformed NIH 3T3 cells expressed higher levels of activated ERK1/2 in culture when compared with the parental cellular pool before injection, indicating that selection for cells with higher levels of activated ERK1/2 occurred during tumor growth and metastasis. By contrast, cells explanted from V12G37-Ras or V12C40-Ras-induced tumors did not show changes in the level of ERK1/2 activation when compared with the parental cells. When tumor-explanted cell lines derived from each of the effector domain mutants were passaged one additional time in vivo, all mediated rapid tumor growth, but, again, only cells derived from V12S35 Ras-tumors formed numerous metastatic lesions within the lung. These results show that the metastatic properties of the Ras effector domain mutants segregate, and that, whereas Ras-mediated tumorigenicity can arise independently of ERK1/2 activation, experimental metastasis appears to require constitutive activation of the ERK1/2 pathway.     

High-current characteristics of the continuous-wave hollow-cathode He-I2laser

Output power versus current characteristics of a multiple-anode hollow-cathode He-I2laser have been studied using quasi-continuous excitation. Oscillation has been obtained on a total of 25 transitions of I⁺ranging in wavelength from the blue to near infrared and including 9 new CW transitions. For all transitions, upper level excitation is attributed to thermal-energy charge-transfer reactions. No saturation in laser output power has been detected for increasing discharge current up to 20 A in the 75-cm-long 2.5-mm-bore device. CW power levels up to 100 mW each for strong transitions and approaching 1 W total over all transitions have been achieved.     

An Overview of Progress in the Design And Implementation of Landsat-D Systems

Landsat-D will be launched in late 1981 or early 1982 into a Sun-synchronous orbit near 700 km. Landsat-D systems and the principal observing instrument, the Thematic Mapper, are being designed and implemented to provide a significantly improved Earth-resources monitoring capability. The Thematic Mapper will have seven spectral bands (0.45-0.52, 0.52-0.60, 0.63-0.69, 0.76-0.90, 1.55-1.75, 2.08-2.35, and 10.5-12.5 ?m), with an instantaneous field of view at nadir of 30 m except for the thermal band (120 m). The data from the Thematic Mapper and other Landsat-D flight segment systems will be relayed to the Landsat-D ground data processing system using a direct readout capability or the Tracking and Data Relay Satellite System and communications satellites. The ground systems will process the data as it arrives at rates up to 100 Mbit/s and a total volume of 2.6 × 1011 bit/day into standard digital and photographic products within 48 hours of data acquisition. This includes 200 Multispectral Scanner Subsystem and 100 Thematic Mapper scenes per day. The Thematic Mapper increased spatial, spectral, and radiometric resolution should be of primary benefit in agricultural and vegetation surveys, but substantial improvements in resource and land cover observations for geology, land use, and water resources applications are also to be anticipated.     

A note on the stability of CSDT methods for solving parabolic equations

In this note we study the stability aspects of CSDT methods for solving parabolic partial differential equations. We define two types of stability and discuss the stability of various CSDT methods.