Evidence from Opportunity's Microscopic Imager for water on Meridiani Planum.

The Microscopic Imager on the Opportunity rover analyzed textures of soils and rocks at Meridiani Planum at a scale of 31 micrometers per pixel. The uppermost millimeter of some soils is weakly cemented, whereas other soils show little evidence of cohesion. Rock outcrops are laminated on a millimeter scale; image mosaics of cross-stratification suggest that some sediments were deposited by flowing water. Vugs in some outcrop faces are probably molds formed by dissolution of relatively soluble minerals during diagenesis. Microscopic images support the hypothesis that hematite-rich spherules observed in outcrops and soils also formed diagenetically as concretions.

Textures of the soils and rocks at Gusev Crater from Spirit's Microscopic Imager.

The Microscopic Imager on the Spirit rover analyzed the textures of the soil and rocks at Gusev crater on Mars at a resolution of 100 micrometers. Weakly bound agglomerates of dust are present in the soil near the Columbia Memorial Station. Some of the brushed or abraded rock surfaces show igneous textures and evidence for alteration rinds, coatings, and veins consistent with secondary mineralization. The rock textures are consistent with a volcanic origin and subsequent alteration and/or weathering by impact events, wind, and possibly water.

Results from the Mars Pathfinder camera.

Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.

Helping students understand the value of the professional association.

Baccalaureate nursing students were involved in a unique learning activity that facilitated their understanding of the value of the professional association, The American Nurses Association (ANA). By participating actively in group dialogue, the learners identified critical issues that affect professional nursing practice and appreciated the worth of a committed, organized body of professionals dedicated to improving health care. As an instructional strategy, the activity incorporated numerous teaching and learning principles that supported the learners' decision-making, analytical, and interpersonal process skill development. The technique may be used with a variety of topics that concern nursing students.

Effects of viral exposure of the two-cell mouse embryo on cleavage and blastocyst formation in vitro.

The effect of viral exposure of two-cell mouse embryos on their capacity to undergo subsequent cleavage and blastocyst formation in vitro was determined. Exposure to Coxsackie viruses B-4 and B-6, reovirus type 2, influenza virus type A, mouse cytomegalovirus, adenovirus type 5, and mouse adenovirus resulted in statistically significant inhibition of blastocyst formation. Development in vitro was unaffected by exposure to ECHO virus type 11, attenuated poliomyelitis virus type 2, parainfluenza virus type 1, mumps, rubella, and herpes simplex viruses types 1 and 2. Blastocyst formation was also unaffected by exposure of embryos to mouse interferon in a concentration 24 units/ml of culture fluid. Coxsackie virus B-4 was recovered from exposed embryos.

Virological and immunological studies in experimental SSPE.

Subacute sclerosing panencephalitis (SSPE) is a progressive, fatal inclusion cell encephalitis of children and adolescents caused by persistent measles virus within the central nervous system (CNS). Because studies in man have failed to elucidate the pathogenesis of this condition, animal studies are necessary. Persistent infection of the hamster CNS can be achieved with a hamster adapted SSPE agent. Animals inoculated intracerebrally with this virus raise antibodies to all known antigens of measles virus and some display clinical signs and pathological changes similar to those noted in human SSPE. Persistent CNS infection occurs only if the hamster is inoculated at a critical age (18 to 25 days of life) or if adults are given transient immunosuppression during acute infection. The biological behavior of the virus isolated from hamster CNS appears to change from a complete to a defective state coincidents with the appearance of serum antibodies to measles virus. Adult hamsters from whom the thymus was removed in the newborn period develop a subacute, uniformly fatal infection when exposed to the SSPE agent. These studies suggest that SSPE may develop in man when measles virus invades the immature CNS at a critical age or when the immune system is uncompletely developed or is inhibited. The finding that transient immunosuppression allows development of persistent CNS infection in adults suggest that immunological malfunction is the significant factor. Of interest, antibody appears to alter viral behavior to a defective, intracellular state thus enhancing viral survival in the host. Once a defective, CNS infection is achieved, lack of, or inhibition of the host cellular immunes response allows it to persist. Methods of therapy in light of these findings will be discussed.

Miniculture plaquing technique for mouse cytomegalovirus.

A method for plaquing mouse cytomegalovirus under agar in miniature cultures is described. Maximal virus adsorption was found to take approximately 5 hr.