A Mars orbital laser altimeter for rover trafficability: Instrument concept and science potential

Limited information on the types of geologic hazards (boulders, troughs, craters etc.) that will affect rover trafficability on Mars are available for the two Viking Lander sites, and there are no prospects for increasing this knowledge base in the near future. None of the instrument payloads on the upcoming Mars Observer or Soviet PHOBOS missions can directly measure surface obstacles on the scales of concern for rover safety (a few meters). Candidate instruments for the Soviet Mars 92 orbiter/balloon/rover mission such as balloon-borne stereo imaging, rover panoramic imaging, and orbital synthetic aperature imaging (SAR) are under discussion, but data from this mission may not be available for target areas of interest for the U.S. Mars Rover Sample Return (MRSR) mission. In an effort to determine how to directly measure the topography of surface obstacles that could affect rover trafficability on Mars, we are studying how to design a laser altimeter with extremely high spatial and vertical resolution that would be suitable for a future Mars Orbiter spacecraft (MRSR precursor or MRSR orbiter). This report discusses some of the design issues associated with such an instrument, gives examples of laser altimeter data collected for Mars analog terrains on Earth, and outlines the scientific potential of data that could be obtained with the system

Oxidized basalts on the surface of Venus: Compositional implications of measured spectral properties

Venera Lander reflectance data are compared with high temperature spectra of the same basaltic materials. The dark, flat unoxidized basalts are still inconsistent with the Venera data in the near-infrared. Basaltic material with a ferric component, however, would satisfy both the increase in reflectance beyond 0.7 microns as well as the dark, relatively colorless character in the visible. Therefore, it is concluded that besaltic surfaces of Venus represented by these measurements either contain minerals with uncommon characteristics, or, more likely, are relatively oxidized

Immunohistochemical Demonstration of IgG in Reed-Sternberg and Other Cells in Hodgkin\u27s Disease

Increased synthesis of IgG in vitro has been demonstrated in spleens from patients with Hodgkin\u27s disease, either with or without invasion of the organ by tumor (1). Interest in this laboratory has centered recently on cytochemical localization of immunoglobulins by means of an immunoglobulin-peroxidase bridge procedure (2) and a satisfactory method has been developed for selectively visualizing immunocytes with this technique. 1 As a means of assessing the basis for increased IgG biosynthesis in spleens of Hodgkin patients, this immunostaining procedure has been applied to localization of IgG-producing cells in specimens with Hodgkin\u27s disease

Geographic variation in malarial parasite lineages in the Common Yellowthroat (Geothlypis trichas)

Our current understanding of migration routes of many birds is limited and researchers have employed various methods to determine migratory patterns. Recently, parasites have been used to track migratory birds. The objective of this study was to determine whether haemosporidian parasite lineages detect significant geographic structure in common yellowthroats (Geothlypis trichas). We examined liver tissue or blood from 552 birds sampled from multiple locations throughout the continental United States, southern Canada, and the Bahamas. We found a 52.7% overall prevalence of haematozoan infection. We identified 86.1% of these infections to genus: 81% were Plasmodium; 5% were Haemoproteus; and 0.1% were Leucocytozoon. There were significant differences in the prevalence of different parasite genera among regions (χ2 = 36.82, P \u3c 0.0001) and in the proportion of Plasmodium infections versus other parasites among regions (χ2 = 35.52, P \u3c 0.0001). Sequence information identified three Haemoproteus lineages, two Leucocytozoon lineages, and thirteen Plasmodium lineages. Due to the low number of Haemoproteus and Leucocytozoon, only Plasmodium lineages were used in the geographic comparison of lineages. Six Plasmodium lineages were found in eight or more birds and the prevalence of these varied significantly among regions (χ2 = 172.33, P \u3c 0.0001). Additionally, 45 juvenile birds were sampled to determine what parasites could be obtained in the breeding grounds and we found only one lineage. In conclusion, parasite lineages show some geographic structure, with some lineages being more geographically specific than others, but are not useful for determining migratory connectivity in this species

Mars Orbiter Laser Altimeter pulse width measurements and footprint-scale roughness

The Mars Orbiter Laser Altimeter (MOLA) measured the pulse width and energy of altimetric laser returns during the course of two Mars years of operations. As secondary science objectives, MOLA obtains the footprint-scale roughness and the bidirectional reflectivity of Mars. MOLA underwent extensive preflight calibration and pulse measurements were monitored continuously in flight, but anomalous values of roughness have been inferred. A calibration of pulse widths using inflight data yields a slope-corrected roughness over ∼75-m-diameter footprints that may be used for quantitative geomorphic surface characterization, required, for example, for landing site selection. The recalibration uses a total least-squares estimation of pulse characteristics that generalizes the method of Abshire et al. [2000]. This method, utilizing the timing at voltage threshold crossings and the area between crossings, accounts for observation errors and shows that surface roughness as small as 1 m can be resolved

Microwave dielectric spectrum of rocks

A combination of several measurement techniques was used to investigate the dielectric properties of 80 rock samples in the microwave region. The real part of the dielectric constant, epsilon', was measured in 0.1 GHz steps from 0.5 to 18 GHz, and the imaginary part, epsilon'', was measured at five frequencies extending between 1.6 and 16 GHz. In addition to the dielectric measurements, the bulk density was measured for all the samples and the bulk chemical composition was determined for 56 of the samples. The study shows that epsilon' is frequency-dependent over the 0.5 to 18 GHz range for all rock samples, and that the bulk density rho accounts for about 50 percent of the observed variance of epsilon'. For individual rock types (by genesis), about 90 percent of the observed variance may be explained by the combination of density and the fractional contents of SiO2, Fe2O3, MgO, and TiO2. For the loss factor epsilon'', it was not possible to establish statistically significant relationships between it and the measured properties of the rock samples (density and chemical composition)

The effect of social media communication on consumer perceptions of brands

Researchers and brand managers have limited understanding of the effects social media communication has on how consumers perceive brands. We investigated 504 Facebook users in order to observe the impact of firm-created and user-generated social media communication on brand equity, brand attitude and purchase intention by using a standardized online survey throughout Poland. To test the conceptual model, we analyzed 60 brands across three different industries: non-alcoholic beverages, clothing and mobile network operators. When analyzing the data, we applied the structural equation modeling technique to both investigate the interplay of firm-created and user-generated social media communication and examine industry-specific differences. The results of the empirical studies showed that user-generated social media communication had a positive influence on both brand equity and brand attitude, whereas firm-created social media communication affected only brand attitude. Both brand equity and brand attitude were shown to have a positive influence on purchase intention. In addition, we assessed measurement invariance using a multi-group structural modeling equation. The findings revealed that the proposed measurement model was invariant across the researched industries. However, structural path differences were detected across the models