113,290 research outputs found
Method for precision forming of low-cost, thin-walled slotted waveguide arrays for the SPS
A method for the precision forming of thin walled, slotted waveguide arrays was devised. Models were constructed with temporary tools and evaluated. The application of the method to the solar power satellite requirements was investigated
The History of the Development of the Rectenna
The history of the development of the rectenna is reviewed through its early conceptual developmental phases. Some selective aspects of the current solar power satellite rectenna development are examined
The adapting of the crossed-field directional amplifier to the requirements of the SPS
Progress was reviewed with special emphasis upon recent developments in controlling the phase and amplitude of the microwave power output, and a perceived architecture for its placement in the subarray. Development in the critical pivotal areas of noise, potential cathode life, and efficiency are reported
NICMOS Photometry of the Unusual Dwarf Planet Haumea and its Satellites
We present here Hubble Space Telescope NICMOS F110W and F160W observations of Haumea, and its two satellites Hi'iaka and Namaka. From the measured (F110W-F160W) colors of –1.208 ± 0.004, –1.48 ± 0.06, and –1.4 ± 0.2 mag for each object, respectively, we infer that the 1.6 μm water-ice absorption feature depths on Hi'iaka and Namaka are at least as deep as that of Haumea. The light curve of Haumea is detected in both filters, and we find that the infrared color is bluer by ~2%-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family
Molecular Model of the Microvillar Cytoskeleton and Organization of the Brush Border
BACKGROUND. Brush border microvilli are ~1-µm long finger-like projections emanating from the apical surfaces of certain, specialized absorptive epithelial cells. A highly symmetric hexagonal array of thousands of these uniformly sized structures form the brush border, which in addition to aiding in nutrient absorption also defends the large surface area against pathogens. Here, we present a molecular model of the protein cytoskeleton responsible for this dramatic cellular morphology. METHODOLOGY/PRINCIPAL FINDINGS. The model is constructed from published crystallographic and microscopic structures reported by several groups over the last 30+ years. Our efforts resulted in a single, unique, self-consistent arrangement of actin, fimbrin, villin, brush border myosin (Myo1A), calmodulin, and brush border spectrin. The central actin core bundle that supports the microvillus is nearly saturated with fimbrin and villin cross-linkers and has a density similar to that found in protein crystals. The proposed model accounts for all major proteinaceous components, reproduces the experimentally determined stoichiometry, and is consistent with the size and morphology of the biological brush border membrane. CONCLUSIONS/SIGNIFICANCE. The model presented here will serve as a structural framework to explain many of the dynamic cellular processes occurring over several time scales, such as protein diffusion, association, and turnover, lipid raft sorting, membrane deformation, cytoskeletal-membrane interactions, and even effacement of the brush border by invading pathogens. In addition, this model provides a structural basis for evaluating the equilibrium processes that result in the uniform size and structure of the highly dynamic microvilli.Boston University (Graduate Student Research Fellowship); National Institutes of Health (GM62886
The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: The Compositional Classes of the Kuiper Belt
We present the first results of the Hubble Wide Field Camera 3 Test of
Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was
to measure the surface properties of a large number of Kuiper belt objects and
attempt to infer compositional and dynamical correlations. We find that the
Centaurs and the low-perihelion scattered disk and resonant objects exhibit
virtually identical bifurcated optical colour distributions and make up two
well defined groups of object. Both groups have highly correlated optical and
NIR colours which are well described by a pair of two component mixture models
that have different red components, but share a common neutral component. The
small, high-perihelion excited objects are entirely
consistent with being drawn from the two branches of the mixing model
suggesting that the colour bifurcation of the Centaurs is apparent in all small
excited objects. On the other hand, objects larger than are
not consistent with the mixing model, suggesting some evolutionary process
avoided by the smaller objects. The existence of a bifurcation amongst all
excited populations argues that the two separate classes of object existed in
the primordial disk before the excited Kuiper belt was populated. The cold
classical objects exhibit a different type of surface which has colours that
are consistent with being drawn from the red branch of the mixing model, but
with much higher albedos.Comment: Accepted to the Astrophysical Journal. 49 Pages, 15 Figure
High energy electron spikes at high latitudes
Over 750 spikes of precipitating electrons with E or = 425 KeV were observed aboard the low altitude polar orbiter OGO-D between 30 July 1967 and 31 December 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping
Summary of wind-tunnel investigations of the static longitudinal stability characteristics of the production Mercury configurations at Mach numbers from 0.05 to 20
Technique for anchoring fasteners to honeycomb panels
Two-piece fastener bushing provides mounting surface for components on a three-inch thick honeycomb structure. Specially constructed starter drill and sheet metal drill permit drilling without misalignment. Tapered knife-edge cutting tool removes honeycomb core material without tearing the adjacent material
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