Observations of H2S toward OMC-1

Interstellar hydrogen sulfide (H2S) and its isotopic variant (H2(34)S) have been observed toward several positions in OMC-1 via their 1(10)-1(01) transitions near 168 GHz using the FCRAO 14 m telescope. We derive total column densities toward Orion(KL) for the extended ridge, for the plateau, and for the hot core, in addition to values for other positions in OMC-1. The fractional abundance of H2S (approximately 10(-9)) in the quiescent regions of OMC-1 seems to be difficult to explain by currently known ion-molecule reactions. The fractional abundance of H2S relative to H2 is enhanced by a factor of 1000 in the hot core and the plateau relative to the quiescent clouds. This enhancement may be a result of grain surface chemistry and/or of high-temperature gas-phase chemistry. From the nondetection of HDS in its 2(11)-2(12) transition, we estimate the abundance ratio [HDS]/H2S] < or = 0.02 in the hot core.     

Trace metals in sediment cores from Deception and Penguin Islands (South Shetland Islands, Antarctica)

This paper presents information on the levels of trace elements in sediments collected at Deception and Penguin Islands and tracks the sources of natural and anthropogenic inputs of metals into this sub-Antarctic region. The results suggest that natural processes, such as volcanic activity, hydrothermal processes and sediment transport, are more important than anthropogenic inputs in accounting for the metal concentrations measured in sediments at Deception Island. The higher levels of trace metals recorded in sediments at Penguin Island seem to reflect the composition of the source rocks of the island, which are dominated by the olivine-basalt group. Our findings show that human activities in the study areas may contribute to negligible levels of trace metals associated with anthropogenic inputs (e.g., Cr and Zn) in sediments, and these results can be used in the future as background levels related to low anthropogenic impacts.     

威布尔分布函数在南非采矿诱发地震分析中的应用

岩石爆破与堕落为南非金矿开采巾生命安全的最大危害,在所有灾害事件中占55％。Gay与Wainwright(1984)全面综述了对致力于理解采矿诱发地震的广泛研究。里氏(Richter)强度为二级及其以上为大约1000次采矿绣发地震事件已被检测了,每年都由南非地质调查局的国家地震网所定位。Slapra(1987)已说明,对于1971年以来的18年中,对于强度为3.3级以上的事件,这些数据是完整的。这些地震历史可为不同采矿地区期望地震发生的频度和强度提出有效的预见。本文研究了在事件发     

Cyanide Chemistry in Comet Hale-Bopp (C/1995 O1)

Observations of comet Hale-Bopp (C/1995 O1) have been carried out near perihelion (1997 March) at millimeter wavelengths using the NRAO 12 m telescope. The J=1-->0, 2-->1, and 3-->2 lines of HCN at 88, 177, and 265 GHz were measured in the comet as well as the J=3-->2 lines of H13CN, HC15N, and HNC. The N=2-->1 transition of CN near 226 GHz was also detected, and an upper limit was obtained for the J=2-->1 line of HCNH+. From the measurements, column densities and production rates have been estimated. A column density ratio of [HCN]/[HNC] = 7+/-1 was observed near perihelion, while it was found that [HCN]/[HCNH+] greater, similar 1. The production rates at perihelion for HCN and CN were estimated to be Q(HCN) approximately 1x1028 s-1 and Q(CN) approximately 2.6x1027 s-1, respectively, resulting in a ratio of [HCN]/[CN] approximately 3. Consequently, HCN is sufficiently abundant to be the parent molecule of CN in Hale-Bopp, and HCNH+ could be a source of HNC. Finally, carbon and nitrogen isotope ratios of 12C/13C = 109+/-22 and 14N/15N = 330+/-98 were obtained from HCN measurements, in agreement with previous values obtained from J=4-->3 data. Such ratios suggest that comet Hale-Bopp formed coevally with the solar system.     

Effect of linear alkylbenzene sulfonate (LAS) and atrazine on marine microalgae

Five marine microalgae (Tetraselmis chuii, Rhodomonas salina, Chaetoceros sp., Isochrysis galbana (T-iso) and Nannochloropsis gaditana), in the same biovolume quantity, were exposed to 72h growth-inhibition tests with atrazine and LAS. In all cases, the inhibition effect of atrazine was higher than that of LAS up to two orders of magnitude higher in the case of T. chuii. In a second part of the study, initial cellular densities for each microalga strain and fixed organic compound concentration were varied, and results show density has a clear influence in growth inhibition tests. Finally, the sum of all data obtained in the study was expressed in terms of "toxic cellular quota" (mass of chemical substance per cell). The result was a sigmoid curve with a good fit, including the two main factors in toxicity tests, initial cellular density and contaminant concentration. This toxic cellular quota exhibits a general tendency to increase with cell volume/size.     

Effects of Elevated Atmospheric CO(2) on Rhizosphere Soil Microbial Communities in a Mojave Desert Ecosystem

The effects of elevated atmospheric carbon dioxide [CO₂] on microbial communities in arid rhizosphere soils beneath Larrea tridentata were examined. Roots of Larrea were harvested from plots fumigated with elevated or ambient levels of [CO₂] using Free-Air CO₂ Enrichment (FACE) technology. Twelve bacterial and fungal rRNA gene libraries were constructed, sequenced and categorized into operational taxonomical units (OTUs). There was a significant decrease in OTUs within the Firmicutes (bacteria) in elevated [CO₂], and increase in Basiomycota (fungi) in rhizosphere soils of plots exposed to ambient [CO₂]. Phylogenetic analyses indicated that OTUs belonged to a wide range of bacterial and fungal taxa. To further study changes in bacterial communities, Quantitative Polymerase Chain Reaction (QPCR) was used to quantify populations of bacteria in rhizosphere soil. The concentration of total bacteria 16S rDNA was similar in conditions of enriched and ambient [CO₂]. However, QPCR of Gram-positive microorganisms showed a 43% decrease in the population in elevated [CO₂]. The decrease in representation of Gram positives and the similar values for total bacterial DNA suggest that the representation of other bacterial taxa was promoted by elevated [CO₂]. These results indicate that elevated [CO₂] changes structure and representation of microorganisms associated with roots of desert plants.     

SHORT COMMUNICATION USE OF A LINEAR FUNCTION OF SEVERAL VARIABLES IN SIMPLEX OPTIMIZATION AS A PROCEDURE FOR ASSESSING ANALYTICAL VERSATILITY IN FIA

A linear response function RF=C_H R_H+C_T(1-R_T)(R_H=peak height,used as a measure of‘sensitivity’,and R_T=analysis time,1-R_T,used as a measure of sampling rate)was used to optimize aFIA system for the determination of nitrite in water with respect to four experimental parameters(twotube lengths and two flow rates)by a Simplex procedure.The weights C_H and C_T placed on R_H and R_Twere systematically varied to cover their allowed range and the system obtained in each optimizationexperiment was implemented and evaluated by determining the following analytical parameters:reproducibility,limit of detection and sampling rate,It was found that these depend very markedly onthe weights used in the response function.Hence the use of a linear function for optimization provides auseful procedure for assessing the versatility of the experimental technique and for choosing the systemsfor its implementation in different practical situations.