Electrical properties of crystalline boron

The boron crystals used in this study were prepared by reducing boron tribromide with hydrogen upon contact with a hot (1500°C) tantalum filament. The largest single crystals weighed less than ten micrograms and were a few hundred microns in length. The high purity of the specimens was verified spectrographically and their crystalline nature was verified by means of Laue photographs

Thermal excitation of Trivelpiece-Gould modes in a pure electron plasma

Thermally excited plasma modes are observed in trapped, near-thermal-equilibrium pure electron plasmas over a temperature range of 0.05<T<5 eV. The measured thermal emission spectra together with a separate measurement of the wave absorption coefficient uniquely determines the temperature. Alternately, kinetic theory including the antenna geometry and the measured mode damping (i.e. spectral width) gives the plasma impedance, obviating the reflection measurement. This non-destructive temperature diagnostic agrees well with standard diagnostics, and may be useful for expensive species such as anti-matter

The Mars observer camera

A camera designed to operate under the extreme constraints of the Mars Observer Mission was selected by NASA in April, 1986. Contingent upon final confirmation in mid-November, the Mars Observer Camera (MOC) will begin acquiring images of the surface and atmosphere of Mars in September-October 1991. The MOC incorporates both a wide angle system for low resolution global monitoring and intermediate resolution regional targeting, and a narrow angle system for high resolution selective surveys. Camera electronics provide control of image clocking and on-board, internal editing and buffering to match whatever spacecraft data system capabilities are allocated to the experiment. The objectives of the MOC experiment follow

Library Design in Combinatorial Chemistry by Monte Carlo Methods

Strategies for searching the space of variables in combinatorial chemistry experiments are presented, and a random energy model of combinatorial chemistry experiments is introduced. The search strategies, derived by analogy with the computer modeling technique of Monte Carlo, effectively search the variable space even in combinatorial chemistry experiments of modest size. Efficient implementations of the library design and redesign strategies are feasible with current experimental capabilities.Comment: 5 pages, 3 figure

Cross-Resistance and Resistance Longevity as Induced by Bean Leaf Beetle, Cerotoma trifurcata and Soybean Looper, Pseudoplusia includens herbivory on Soybean

Cross-resistance, and longevity of resistance, induced by the bean leaf beetle, Cerotoma trifurcata, was studied IN the soybean PI 227687 that exhibited induced response in earlier studies. Bean leaf beetle adults and soybean looper, Pseudoplusia includens, larvae were used to induce resistance and to determine beetle feeding preference. Beetles were collected from soybean fields 2 to 5 days prior to the feeding preference test. The level of cross-resistance induced by soybean looper herbivory to subsequent bean leaf beetle feeding was higher when compared to cross-resistance induced by bean leaf beetle herbivory against subsequent feeding by soybean looper. Further, herbivory by the bean leaf beetle also induced resistance against soybean looper feeding. In the longevity study, leaflets from treated plants were collected 5, 10, 12, 14, 16, 20 and 25 days after initiation of feeding. Pairwise comparisons of leaflets from plants treated by bean leaf beetle herbivory with untreated plants revealed that induced responses were highest 14 and lowest 25 days after initiation of feeding. On other sampling days, levels of induced response varied with the sampling day

Visual and infrared observations of the distant Comets P/Stephan-Oterma (1980g), Panther (1980u), and Bowell (1980b)

Broadband observations of comets P/Stephan-Oterma (1980g), Bowell (1980b), and Panther (1980u) in the visual [0.5≾ λ(µm)≾0.9] and infrared [1.2≾λ(µm)≾20] wavelength regions are reported together with measurements in the 1.5-2.4-µm wavelength range having 5% spectral resolution. The visual data indicate the existence of solid grains in extended halos around the nuclei of the three comets. The visual photometric profiles of comets P/Stephan- Oterma and Panther are interpreted as evidence that grains around Panther and those close to the nucleus of P/Stephan-Oterma are sublimating. Broadband near-infrared and thermal infrared measurements of comet Panther suggest the presence of 2—4-µm radius particles in the coma. The particles within a 5.8X 10^6-m diameter region centered on the comet have a total cross section of 10^8 m^2 and a near-infrared geometric albedo of about 14%. Comet Bowell presents a total cross section of 3 X 10^8 m^2 within a 1.2 X 10^7-m region centered on the comet and its coma grains also have an albedo of 14%. The near-infrared spectrum of P/Stephan-Oterma is a featureless solar-reflection continuum. The near-infrared spectra of Bowell and Panther exhibit features which are similar in the two comets. The spectral features are not due to H_2O, CH_4, or CO_2 ices nor to emissions from gases released from the nuclei nor to reflection from mineral grains of known composition in the comae. The spectrum of solid ammonia provides the best match to the near infrared; it is nevertheless significantly different from the comet spectra. The synthesis of the visual data with the infrared data is attempted in terms of a model involving a mantle of volatile material on the nuclei of Bowell and Panther, but not on P/Stephan-Oterma. The composition of the mantle cannot be exactly specified from the existing data but a complex molecule incorporating the N-H bond may be present

Transport of sulfur dioxide from the Asian Pacific Rim to the North Pacific troposphere

The NASA Pacific Exploratory Mission over the Western Pacific Ocean (PEM-West B) field experiment provided an opportunity to study sulfur dioxide (SO2) in the troposphere over the western Pacific Ocean from the tropics to 60°N during February–March 1993. The large suite of chemical and physical measurements yielded a complex matrix in which to understand the distribution of sulfur dioxide over the western Pacific region. In contrast to the late summer period of Pacific Exploratory Mission-West A (PEM-West A) (1991) over this same area, SO2showed little increase with altitude, and concentrations were much lower in the free troposphere than during the PEM-West B period. Volcanic impacts on the upper troposphere were again found as a result of deep convection in the tropics. Extensive emission of SO2 from the Pacific Rim land masses were primarily observed in the lower well-mixed part of the boundary layer but also in the upper part of the boundary layer. Analyses of the SO2 data with aerosol sulfate, beryllium-7, and lead-210 indicated that SO2 contributed to half or more of the observed total oxidized sulfur (SO2 plus aerosol sulfate) in free tropospheric air. The combined data set suggests that SO2 above 8.5 km is transported from the surface but with aerosol sulfate being removed more effectively than SO2. Cloud processing and rain appeared to be responsible for lower SO2 levels between 3 and 8.5 km than above or below this region

Mars Observer Camera

The Mars Observer camera (MOC) is a three-component system (one narrow-angle and two wide-angle cameras) designed to take high spatial resolution pictures of the surface of Mars and to obtain lower spatial resolution, synoptic coverage of the planet's surface and atmosphere. The cameras are based on the “push broom” technique; that is, they do not take “frames” but rather build pictures, one line at a time, as the spacecraft moves around the planet in its orbit. MOC is primarily a telescope for taking extremely high resolution pictures of selected locations on Mars. Using the narrow-angle camera, areas ranging from 2.8 km × 2.8 km to 2.8 km × 25.2 km (depending on available internal digital buffer memory) can be photographed at about 1.4 m/pixel. Additionally, lower-resolution pictures (to a lowest resolution of about 11 m/pixel) can be acquired by pixel averaging; these images can be much longer, ranging up to 2.8 × 500 km at 11 m/pixel. High-resolution data will be used to study sediments and sedimentary processes, polar processes and deposits, volcanism, and other geologic/geomorphic processes. The MOC wide-angle cameras are capable of viewing Mars from horizon to horizon and are designed for low-resolution global and intermediate resolution regional studies. Low-resolution observations can be made every orbit, so that in a single 24-hour period a complete global picture of the planet can be assembled at a resolution of at least 7.5 km/pixel. Regional areas (covering hundreds of kilometers on a side) may be photographed at a resolution of better than 250 m/pixel at the nadir. Such images will be particularly useful in studying time-variable features such as lee clouds, the polar cap edge, and wind streaks, as well as acquiring stereoscopic coverage of areas of geological interest. The limb can be imaged at a vertical and along-track resolution of better than 1.5 km. Different color filters within the two wide-angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition

Mars Observer Camera

The Mars Observer camera (MOC) is a three-component system (one narrow-angle and two wide-angle cameras) designed to take high spatial resolution pictures of the surface of Mars and to obtain lower spatial resolution, synoptic coverage of the planet's surface and atmosphere. The cameras are based on the “push broom” technique; that is, they do not take “frames” but rather build pictures, one line at a time, as the spacecraft moves around the planet in its orbit. MOC is primarily a telescope for taking extremely high resolution pictures of selected locations on Mars. Using the narrow-angle camera, areas ranging from 2.8 km × 2.8 km to 2.8 km × 25.2 km (depending on available internal digital buffer memory) can be photographed at about 1.4 m/pixel. Additionally, lower-resolution pictures (to a lowest resolution of about 11 m/pixel) can be acquired by pixel averaging; these images can be much longer, ranging up to 2.8 × 500 km at 11 m/pixel. High-resolution data will be used to study sediments and sedimentary processes, polar processes and deposits, volcanism, and other geologic/geomorphic processes. The MOC wide-angle cameras are capable of viewing Mars from horizon to horizon and are designed for low-resolution global and intermediate resolution regional studies. Low-resolution observations can be made every orbit, so that in a single 24-hour period a complete global picture of the planet can be assembled at a resolution of at least 7.5 km/pixel. Regional areas (covering hundreds of kilometers on a side) may be photographed at a resolution of better than 250 m/pixel at the nadir. Such images will be particularly useful in studying time-variable features such as lee clouds, the polar cap edge, and wind streaks, as well as acquiring stereoscopic coverage of areas of geological interest. The limb can be imaged at a vertical and along-track resolution of better than 1.5 km. Different color filters within the two wide-angle cameras permit color images of the surface and atmosphere to be made to distinguish between clouds and the ground and between clouds of different composition