Brine-driven destruction of clay minerals in Gale crater, Mars.

Mars' sedimentary rock record preserves information on geological (and potential astrobiological) processes that occurred on the planet billions of years ago. The Curiosity rover is exploring the lower reaches of Mount Sharp, in Gale crater on Mars. A traverse from Vera Rubin ridge to Glen Torridon has allowed Curiosity to examine a lateral transect of rock strata laid down in a martian lake ~3.5 billion years ago. We report spatial differences in the mineralogy of time-equivalent sedimentary rocks <400 meters apart. These differences indicate localized infiltration of silica-poor brines, generated during deposition of overlying magnesium sulfate-bearing strata. We propose that destabilization of silicate minerals driven by silica-poor brines (rarely observed on Earth) was widespread on ancient Mars, because sulfate deposits are globally distributed.

Evidence for Multiple Diagenetic Episodes in Ancient Fluvial-Lacustrine Sedimentary Rocks in Gale Crater, Mars.

The Curiosity rover's exploration of rocks and soils in Gale crater has provided diverse geochemical and mineralogical data sets, underscoring the complex geological history of the region. We report the crystalline, clay mineral, and amorphous phase distributions of four Gale crater rocks from an 80-m stratigraphic interval. The mineralogy of the four samples is strongly influenced by aqueous alteration processes, including variations in water chemistries, redox, pH, and temperature. Localized hydrothermal events are evidenced by gray hematite and maturation of amorphous SiO2 to opal-CT. Low-temperature diagenetic events are associated with fluctuating lake levels, evaporative events, and groundwater infiltration. Among all mudstones analyzed in Gale crater, the diversity in diagenetic processes is primarily captured by the mineralogy and X-ray amorphous chemistry of the drilled rocks. Variations indicate a transition from magnetite to hematite and an increase in matrix-associated sulfates suggesting intensifying influence from oxic, diagenetic fluids upsection. Furthermore, diagenetic fluid pathways are shown to be strongly affected by unconformities and sedimentary transitions, as evidenced by the intensity of alteration inferred from the mineralogy of sediments sampled adjacent to stratigraphic contacts.

Mineralogy of a mudstone at Yellowknife Bay, Gale crater, Mars.

Sedimentary rocks at Yellowknife Bay (Gale crater) on Mars include mudstone sampled by the Curiosity rover. The samples, John Klein and Cumberland, contain detrital basaltic minerals, calcium sulfates, iron oxide or hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The John Klein smectite has basal spacing of ~10 angstroms, indicating little interlayer hydration. The Cumberland smectite has basal spacing at both ~13.2 and ~10 angstroms. The larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating H2O retention. Basaltic minerals in the mudstone are similar to those in nearby eolian deposits. However, the mudstone has far less Fe-forsterite, possibly lost with formation of smectite plus magnetite. Late Noachian/Early Hesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time.

X-ray diffraction results from Mars Science Laboratory: mineralogy of Rocknest at Gale crater.

The Mars Science Laboratory rover Curiosity scooped samples of soil from the Rocknest aeolian bedform in Gale crater. Analysis of the soil with the Chemistry and Mineralogy (CheMin) x-ray diffraction (XRD) instrument revealed plagioclase (~An57), forsteritic olivine (~Fo62), augite, and pigeonite, with minor K-feldspar, magnetite, quartz, anhydrite, hematite, and ilmenite. The minor phases are present at, or near, detection limits. The soil also contains 27 ± 14 weight percent x-ray amorphous material, likely containing multiple Fe(3+)- and volatile-bearing phases, including possibly a substance resembling hisingerite. The crystalline component is similar to the normative mineralogy of certain basaltic rocks from Gusev crater on Mars and of martian basaltic meteorites. The amorphous component is similar to that found on Earth in places such as soils on the Mauna Kea volcano, Hawaii.

Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow.

The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand <150 micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the Sample Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.

Falls and physical activity in persons with multiple sclerosis.

Objectives. To examine the association between fall history and physical activity using an objective measure of physical activity (i.e., accelerometry) in persons with multiple sclerosis. Design. A community-based sample of 75 ambulatory persons with multiple sclerosis volunteered for the investigation. Participants self-reported fall history in the last year, underwent a neurological exam to determine Expanded Disability Status Scale (EDSS) score, and wore an accelerometer around the waist for 7 consecutive days to determine physical activity. Results. Overall, 37 persons (49.3% of the sample) reported falling in the last year with 28 of the 37 falling more than once. Persons who fell in the last year had a significantly lower number of steps/day than nonfallers (3510 versus 4940 steps/day; P < .05). However, when controlling for disability status there was no statistically significant difference between fallers and nonfallers (4092 versus 4373 steps/day; P > .05). Conclusions. Collectively, the findings suggest that fall history may have little impact on current physical activity levels in persons with multiple sclerosis.

Immunomorphologic studies of mast cell heterogeneity, location, and distribution in the rat conjunctiva.

Mast cells are crucial components of immediate and some delayed-type hypersensitivity reactions. They play a pivotal role in allergic conjunctivitis and other immunoinflammatory disorders of the ocular surface, yet little is known of their distribution and heterogeneity in the conjunctiva of potential animal models, such as the rat. In this study, mast cell types were investigated in histologic sections and corneal-conjunctival-lid whole mounts by using toluidine blue, alcian blue-safranin, and immunohistochemical staining methods (anti-rat mast cell proteinase [RMCP] antibodies). Quantitative analyses were performed on corneal-conjunctival-lid whole mounts by using the optical dissector procedure to obtain the density of mast cells per unit volume in different regions of the conjunctiva. Single and double immunohistochemical analyses revealed that the mast cells in the conjunctiva of the limbus, fornices, and lid margin were strongly RMCP I+, suggesting that they were of the connective tissue phenotype. Mast cells containing the mucosal mast cell proteinase RMCP II were not present in the normal conjunctiva. Histochemical analysis revealed that the maturity of the connective tissue mast cells, as assessed by the presence or absence of safranin (heparin)-positive granules in their cytoplasm varied in different regions. In the lid margin 60% to 78% of the mast cells were solely alcian blue-positive, whereas in the fornices 68% to 78% were safranin-positive. In the limbus the predominant type of mast cell was either safranin-positive or contained mixed granules. Mast cell densities were greatest close to the lid margin (10,000 to 12,000 cells/mm3), followed by the limbus (3400 to 4800 cells/mm3) and were rare in the remainder of the conjunctiva (500 to 1000 cells/mm3), with the exception of the region around the nictitating membrane. This study of rat conjunctival mast cells provides essential baseline data for future studies of the role of mast cells in models of allergic conjunctivitis.

Mycobacterium tuberculosis pneumonia in two HIV antibody positive patients.

The acquired immunodeficiency syndrome is associated with the development of opportunistic infections. We report the cases of two HIV antibody positive male partners who developed pneumonia responding to antituberculous therapy.

Effect of cigarette smoking on the specific antibody response in pigeon fanciers.

Titres of circulating IgG antibodies to pigeon gammaglobulin and end expired carbon monoxide concentrations were measured in 86 pigeon fanciers attending the "Show of the Year." Antibody levels were significantly higher in non-smokers and in those with end expired carbon monoxide concentrations below 10 parts per million.

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa.

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.

Membrane filter technique for the isolation of Yersinia enterocolitica.

A membrane filter procedure was developed for the isolation of Yersinia enterocolitica from aquatic environments. Primary differentiation was based on the fermentation of sorbitol, the absence of lysine decarboxylase and arginine decarboxylase-dihydrolase activities, and the production of urease. Sodium deoxycholate was incorporated as an inhibitor of background organisms. The presumptive identification of Y. enterocolitica was accomplished in 50 h, and the rate of identity confirmation of typical colonies was 88%. The mean recovery rate of 15 strains from phosphate buffer suspensions was 91%, and quantitative recovery was demonstrated for low populations of the organism in both laboratory-prepared and naturally occurring mixed cultures. The technique was used to isolate 33 strains of Y. enterocolitica from 15 of 27 river water samples and from prechlorinated sewage effluent. Nine (27%) of the isolates were rhamnose positive, and only five (15%) were serotypable. Two isolates were identified as serotype O:4 (or O:4,32), two were O:17, and the fifth was O:40.

Microbiology Standards for Waters.

This is a discussion of the kinds of microbial standards that apply to various kinds of water and the circumstances under which the standards might be used. Standards are universal language. Appropriate standards depend upon proper personnel, materials and procedures to be effective. Comments are made on some possible situations where the concept of standards may restrain good scientific and technical development. Historically, there is circumstantial evidence enforcement of microbial standards has aided our great advances in water hygiene.

Bacterial bioconcentration of chlorinated hydrocarbon insecticides from aqueous systems.

The prevalence of chlorinated hydrocarbon insecticide uptake by chemoorganotrophic bacteria has been investigated. Thirteen bacterial species were observed to sorb and concentrate (bioconcentratc)α-chlordane,ß-chlordane, dieldrin, heptachlor epoxide, and lindane from aqueous systems. Bioconcentration, as expressed by the ratio of cellular insecticide in ng/mg (dry wt) to supernatant insecticide in ng/µl, ranged from 10 for lindane byEnterobacter aerogenes to a high of 55,900 forß-chlordane byCaulobacter vibrioides var.limonus. Amounts of cellular chlorinated hydrocarbon insecticides (CHI) detected and the bioconcentration ratios were observed to have the following order in magnitude:α- orß-chlordane > dieldrin > heptachlor epoxide > lindane. This decreasing order was the inverse of reported water solubilities for the CHI and the inverse relationship was mathematically defined. The CHI were not easily removed from cells by washing (desorbing) and desorption was directly proportional to insecticide water solubility. Uptake of the CHI was rapid, near-maximum amounts being sorbed within 15 min, and pH 7 appeared optimal for bioconcentration as examined over the range pH 6 to 8. Implications of this investigation are that bioconcentration of CHI by bacteria might serve as a means of introducing these toxic compounds into aquatic food chains and that the bioconcentration phenomenon might lend itself as a treatment procedure for the intentional removal of residual CHI from water supplies and wastewater.

Synergistic false-positive coliform reaction on M-Endo MF medium.

The reported occurrence of synergistic false-positive coliform reactions on M-Endo MF medium was investigated. The objectives of the study were (i) to isolate populations of bacteria which produced such false-positive reactions, (ii) to determine whether false-positive sheen reactions are a result of synergistic interaction, and (iii) to determine the metabolic intermediates involved in false-positive sheen production. Samples of river water were subjected to coliform analysis by the membrane filter technique with M-Endo MF medium. Suspect sheen-forming colonies were analyzed to determine purity and identity of cultures. Mixed cultures were separated, and individual isolates were examined for sheen production. The isolates not producing a sheen were recombined and tested further for sheen production. Those mixtures reproducing the sheen were characterized biochemically and tested to determine the metabolic intermediates involved. Chromatographic analysis of the metabolites showed that individual isolates produced an assortment of neutral organic compounds including 2-butanone, 2,3-butanedione, formaldehyde, and butyraldehyde, whereas acetaldehyde or propionaldehyde was produced only by the mixed cultures. Tests showed that both propionaldehyde and acetaldehyde could react to produce a sheen on M-Endo medium. The conclusion was reached that synergistic false-positive coliform reactions do indeed occur on M-Endo MF medium.