Efficient power extraction at TRAPATT harmonics

Using silicon planar diodes in a coaxial cavity that closely approximates to- Evans's TRAPATT circuit, microwave power up to the fourth harmonic has been extracted efficiently with a very low subharmonic content. The efficiency at the fundamental (1 GHz) and the third harmonic (3 GHz) were almost identical at 35% and 34%, respectively.     

Characterization of a 34-kDa soybean binding protein for the syringolide elicitors

Syringolides are water-soluble, low-molecular-weight elicitors that trigger defense responses in soybean cultivars carrying the Rpg4 disease-resistance gene but not in rpg4 cultivars. 125I-syringolide 1 previously was shown to bind to a soluble protein(s) in extracts from soybean leaves. A 34-kDa protein that accounted for 125I-syringolide 1 binding activity was isolated with a syringolide affinity-gel column. Partial sequences of internal peptides of the 34-kDa protein were identical to P34, a previously described soybean seed allergen. In soybean seeds, P34 is processed from a 46-kDa precursor protein and was shown to have homology with thiol proteases. P34 is a moderately abundant protein in soybean seeds and cotyledons but its level in leaves is low. cDNAs encoding 46-, 34-, and 32-kDa forms of the soybean protein were cloned into the baculovirus vector, pVL1392, and expressed in insect cells. The resulting 32- and 34-kDa proteins, but not the 46-kDa protein, exhibited ligand-specific 125I-syringolide binding activity. These results suggest that P34 may be the receptor that mediates syringolide signaling.     

Intracavity spatial filtering in unstable ring resonator geometries: Part I--Passive cavity mode theory

The general theory of attaining enhanced transverse mode discrimination in an unstable ring resonator by employing an intracavity spatial fiber is developed. The theory presented is for the passive cavity mode structures of both the forward and reverse traveling wave fields supported by the optical cavity. Of particular interest here is the transverse mode behavior in the presence of strong spatial filtering wherein the spatial filter aperture completely dominates the diffractive mode structure formation processes. Both a circular focal point aperture and a pair of orthogonal focal line apertures are considered. The succeeding parts to this first paper describes the numerical and experimental results obtained for several unstable ring laser geometries with intracavity spatial filtering. The analysis presented here provides the fundamental understanding of these results.     

Formation of CuIn1 − xAlxSe2 thin films studied by Raman scattering

CuIn_1 − xAl_xSe₂ (CIAS) thin films (x = 0.06, 0.18, 0.39, 0.64, 0.80 and 1) with thicknesses of approximately 1 μm were formed by the selenization of sputtered Cu―In―Al precursors and studied via X-ray diffraction, inductively coupled plasma mass spectrometry and micro-Raman spectroscopy at room temperature. Precursor films selenized at 300, 350, 400, 450, 500 and 550 °C were examined via Raman spectroscopy in the range 50-500 cm^− 1 with resolution of 0.3 cm^− 1. Sequential formation of In_xSe_y, Cu_2 − xSe, CuInSe₂ (CIS) and CIAS phases was observed as the selenization temperature was increased. Conversion of CIS to CIAS was initiated at 500 °C. For all CuIn_1 − xAl_xSe₂ products, the A₁ phonon frequency varied nonlinearly with respect to the aluminum composition parameter x in the range 172 cm^− 1 to 186 cm^− 1.     

Noninvasive assessment of collateral blood flow of the cerebral hemisphere by Doppler ultrasound

Directional flow in the frontal artery, a terminal branch of the ophthalmic artery, was assessed nonivasively by Doppler ultrasound druing brief digital compression of the ipsilateral common carotid artery in 62 patients. Directional frontal artery flow during carotid compression was compared with mean distal internal carotid back pressure measured at subsequent carotid endarterectomy. Mean carotid back pressure in 28 patients with normal frontal artery flow direction during carotid compression, 68 +/- 14 millimeters of mercury, was significantly higher than that observed in 24 patients in whom frontal artery flow was completely obliterated and ten in whom frontal artery flow was reversed. Distal internal carotid back pressure exceeded 48 millimeters of mercury in all patients with normal frontal artery flow direction during carotid compression. Conversely, carotid back pressure was below 41 millimeters of mercury in all but one patient in whom frontal artery flow was obliterated or bliterated or reversed during carotid compression. The results of this study indicate that Doppler ultrasound assessment of frontal artery flow direction during simultaneous carotid compression provides a rapid, sale noninvasive estimate of the adequacy of collateral hemispheric circulation.     

Direct modulation of d.h. GaAlAs lasers with GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s are used to directly modulate d.h. GaAlAs lasers with a 200 Mbit/s pseudorandom, return-to-zero bit stream. The detected light pulses have 100% modulation depth, no significant intersymbol interference, 40 mW of peak power and risetimes and falltimes of 240 ps for a halfpower width of 280 ps.     

Geocoded digital videography for validation of land cover mapping in the Amazon basin

Four Validation Overflights for Amazon Mosaics (VOAM) aerial video surveys have been carried out in the Brazilian Amazon to provide ground verification for mapping of wetland cover with the Global Rain Forest Mapping (GRFM) Project JERS-1 (Japanese Earth Remote Sensing Satellite) mosaics of the Amazon basin. Surveys in 1995 and 1996, acquired with handheld analog camcorders from small aircraft, were timed to imaging of the GRFM low- and high-water mosaics, and limited to within 600 km of Manaus. For the 1997 and 1999 flights, digital camcorder systems were installed in the Bandeirante survey plane operated by Brazil's National Institute for Space Research. The VOAM97 and VOAM99 surveys circumscribed the Brazilian Amazon, documenting ground conditions at resolutions on the order of 1 m (wide-angle format) and 10 cm (zoom format) for wetlands, forests, savannas, and human-impacted areas. Global Positioning System (GPS) information encoded on the video audio track was extracted by mosaicking software that automatically generates geocoded digital mosaics from video clips. On the 1999 survey, a laser altimeter recorded profiles of terrain and vegetation canopy heights. A validation dataset was compiled from the videography for a portion of the GRFM mosaics extending 6° by 4° in longitude and latitude, using randomly selected points along flight lines. Other applications of the VOAM videography include acquisition of ground control points for image geolocation, creation of a high-resolution geocoded mosaic of a forest study area, forest biomass estimation, and rapid assessment of fire damage. Geocoded digital videography provides a cost-effective means of compiling high-resolution validation datasets for land cover mapping in remote, cloud-covered regions.     

Estimation of phosphorus flux in a regulated channel

During a nutrient loading study in the Okanagan River Basin, British Columbia, the regression relationship between phosphorus concentration and the Okanagan River discharge was shown to be not statistically significant. Phosphorus flux could, therefore, not be determined by conventional methods which rely on the concentration-discharge relationship. The reason for failure of conventional methods is the regulated nature of the Okanagan River flow. Two sampling strategies for chemical analysis of water samples were applied: (a) simultaneous, based on manual collection of sample replicates; and (b) sequential, using an automatic device to obtain a series of point concentration measurements. These sampling strategies provided a basis for nutrient flux estimation by the following methods: (a) partial load method, resulting from simultaneous sampling; and (b) flow interval method, based on sequential sampling. Load estimates and their confidence limits derived from the partial load method were compared with loads obtained by the flow interval method. There was a high level of correlation between the load estimates. Annual trends are more appropriately investigated by the flow interval method, cross-sectional load variability and confidence limits should be assessed by the partial load method.     

Value of segmental limb blood pressures in predicting results of aortofemoral bypass

The efficacy of segmental limb blood pressure measurements, assessed noninvasively by Doppler ultrasound, in predicting the result of aortofemoral reconstruction was evaluated in fifty-two extremities with varying extent of aortoiliac and more distal arterial occlusive disease. Three prognostic correlates were analyzed: (1) preoperative proximal thigh/arm pressure index (TPI); (2) preoperative pressure gradient between adjacent leg segments (proximal thigh, above-knee, below-knee, and ankle), normally less than 30 mm Hg; and (3) early postoperative increase in the ankle/arm pressure index (API). After aortofemoral bypass, forty-one limbs (79 per cent) were asymptomatic or improved and eleven were unimproved. The mean TPI in extremities benefiting from aortofemoral bypass, 0.82 +/- 0.17 (+/-1SD) was significantly less than that of unimproved limbs, 1.01 +/- 0.09 (p less than 0.01). Aortofemoral bypass was beneficial in all twenty limbs with normal leg pressure gradients. Conversely, six of twenty-five legs with one abnormal gradient and five of seven with two abnormal gradients failed to improve. The postoperative increase in API was 0.1 or more in all forty-one improved extremities and was less than 0.1 in all eleven failures. Although eleven of thirty-two limbs (34 per cent) with arteriographic evidence of combined aortoiliac and subinguinal occlusive disease were not improved after proximal bypass, the result of operation could not be predicted from the angiographic pattern or severity of distal disease. Segmental limb blood pressures provide useful predictive indices of the efficacy of aortofemoral bypass and the potential need for more distal reconstruction in multisegmental disease.