A laboratory investigation of the production and properties of molecular and radical species pertinent to planetary atmospheres

Vinylidene (H2C=C) is shown to be the largest photodecomposition channel in the direct photolysis of both C2H2 and C2H4. The chemistry of H2C=C as it relates to planetary atmospheres is discussed. The vinyl radical (C2H3), important in the acetylene chemistry cycle, has been directly observed spectroscopically and the kinetics of several key reactions of this species measured

The Magnetic Susceptibility of Manganese Pyrophosphate as a Function of Temperature

The Magnetic Susceptibility of manganese pyrophosphate has been measured as a function of temperature from 300 to 1165 °K. The Curie and Weiss constants for the substance have been found to be 4.57 and -14 ° respectively. The Curie constant is larger than the value predicted from theoretical considerations

Benthic fluxes and nitrogen cycling in sediments of the continental margin of the eastern North Pacific

The exchange of O2, N2, NO3−, NH4+, Si(OH)4, and PO4−3 between the sediments and the overlying water (benthic flux) was determined at 18 locations on the Washington State continental margin using an in situ benthic tripod. Oxygen consumption by the sediments ranged from 21.2 pmole cm−2 s−1 on the shelf to 2.85 pmole cm−2 s−1 on the slope. Nitrogen gas fluxes were from the sediments to the overlying water. They varied 5.5 to 1.2 pmole-N cm−2 s−1 and were always greater than the corresponding NO3− flux into the sediments. A nitrogen mass balance indicated that the difference between the N2 flux out and the NO3− flux in could be accounted for by oxidation of NH4+ produced during aerobic and anaerobic carbon remineralization to NO3− and subsequent denitrification to N2. Comparison of the benthic fluxes of O2, NO3− and Si(OH)4 with the fluxes predicted from molecular diffusion across the sediment water interface showed that for all three solutes the benthic fluxes were up to three times greater than the molecular fluxes and indicated the importance of macrobenthic irrigation in these sediments. However, several existing empirical irrigation models were not able to describe all three solutes. The overall carbon oxidation rate, as estimated from the sum of the O2 flux, the N2 flux and the measured SO4= reduction rate, could be fit with a normalized power function; i.e., carbon oxidation rate (gC m−2 y−1) = 110 · (z/100)−0.91. The exponent describing the rate of attenuation with depth (−0.91) was similar to the carbon rain rate attenuation coefficient determined from sediment traps in the pelagic, eastern North Pacific

Reproduction of Spanish Mackerel, Scomberomorus maculatus, from the Southeastern United States

Spanish mackerel, Scomberomorus maculatus, were collected during 1977-80 in the Gulf of Mexico and from North Carolina to south Florida during 1980-81 to describe their reproductive biology. The major spawning period extended from May to September in all areas and peaked during the spring and early summer. Most fish were mature at about 350 mm FL, but size at maturity varied between sexes and sampling areas. Males matured at a smaller size than females. Fecundity was estimated from 52 fish from all areas and ranged from about 100,000 eggs for a 328 mm (295 g) fish to 2,113,000 eggs for a 626 mm (2,415 g) fish. Fork length and total weight were equally good predictors of fecundity

Case-control study of arsenic in drinking water and lung cancer in California and Nevada.

Millions of people are exposed to arsenic in drinking water, which at high concentrations is known to cause lung cancer in humans. At lower concentrations, the risks are unknown. We enrolled 196 lung cancer cases and 359 controls matched on age and gender from western Nevada and Kings County, California in 2002-2005. After adjusting for age, sex, education, smoking and occupational exposures, odds ratios for arsenic concentrations ≥85 µg/L (median = 110 µg/L, mean = 173 µg/L, maximum = 1,460 µg/L) more than 40 years before enrollment were 1.39 (95% CI = 0.55-3.53) in all subjects and 1.61 (95% CI = 0.59-4.38) in smokers. Although odds ratios were greater than 1.0, these increases may have been due to chance given the small number of subjects exposed more than 40 years before enrollment. This study, designed before research in Chile suggested arsenic-related cancer latencies of 40 years or more, illustrates the enormous sample sizes needed to identify arsenic-related health effects in low-exposure countries with mobile populations like the U.S. Nonetheless, our findings suggest that concentrations near 100 µg/L are not associated with markedly high relative risks

The PAS domain-containing histidine kinase RpfS is a second sensor for the diffusible signal factor of <em>Xanthomonas campestris</em>

Summary: A cell-cell signalling system mediated by the fatty acid signal DSF controls the virulence of Xanthomonas campestris pv. campestris (Xcc) to plants. The synthesis and recognition of the DSF signal depends upon different Rpf proteins. DSF signal generation requires RpfF whereas signal perception and transduction depends upon the sensor RpfC and regulator RpfG. Detailed analyses of the regulatory roles of different Rpf proteins have suggested the occurrence of further sensors for DSF. Here we have used a mutagenesis approach coupled with high-resolution transcriptional analysis to identify XC_2579 (RpfS) as a second sensor for DSF in Xcc. RpfS is a complex sensor kinase predicted to have multiple Per/Arnt/Sim (PAS) domains, a histidine kinase domain and a C-terminal receiver (REC) domain. Isothermal calorimetry showed that DSF bound to the isolated N-terminal PAS domain with a Kd of 1.4μM. RpfS controlled expression of a sub-set of genes distinct from those controlled by RpfC to include genes involved in type IV secretion and chemotaxis. Mutation of XC_2579 was associated with a reduction in virulence of Xcc to Chinese Radish when assayed by leaf spraying but not by leaf inoculation, suggesting a role for RpfS-controlled factors in the epiphytic phase of the disease cycle.</p