排序方式： 共有15条查询结果，搜索用时 417 毫秒
1.
Jinghao ZhangLeonard W Lion Yarrow M Nelson Michael L ShulerWilliam C Ghiorse 《Geochimica et cosmochimica acta》2002,66(5):773-781
The kinetics of Mn(II) oxidation by the bacterium Leptothrix discophora SS1 was investigated in this research. Cells were grown in a minimal mineral salts medium in which chemical speciation was well defined. Mn(II) oxidation was observed in a bioreactor under controlled conditions with pH, O2, and temperature regulation. Mn(II) oxidation experiments were performed at cell concentrations between 24 mg/L and 35 mg/L, over a pH range from 6 to 8.5, between temperatures of 10°C and 40°C, over a dissolved oxygen range of 0 to 8.05 mg/L, and with L. discophora SS1 cells that were grown in the presence of Cu concentrations ranging from zero to 0.1 μM. Mn(II) oxidation rates were determined when the cultures grew to stationary phase and were found to be directly proportional to O2 and cell concentrations over the ranges investigated. The optimum pH for Mn(II) oxidation was approximately 7.5, and the optimum temperature was 30°C. A Cu level as low as 0.02 μM was found to inhibit the growth rate and yield of L. discophora SS1 observed in shake flasks, while Cu levels between 0.02 and 0.1 μM stimulated the Mn(II) oxidation rate observed in bioreactors. An overall rate law for Mn(II) oxidation by L. discophora as a function of pH, temperature, dissolved oxygen concentration (D.O.), and Cu concentration is proposed. At circumneutral pH, the rate of biologically mediated Mn(II) oxidation is likely to exceed homogeneous abiotic Mn(II) oxidation at relatively low (≈μg/L) concentrations of Mn oxidizing bacteria. 相似文献
2.
Tina-Simone Neset Tomasz Opach Peter Lion Anna Lilja Jimmy Johansson 《The Professional geographer》2016,68(1):103-114
This article discusses the state of the art in geovisualization supporting climate change adaptation. We reviewed twenty selected map-based Web tools, classified by their content and functionality, and assessed them by visual representations, interactive functions, information type, target audience, and how vulnerability and adaptation to climate change are addressed. Our study concludes that the tools (1) can be classified as data viewers with basic functionality and data explorers offering more sophisticated interactive functions; (2) mostly feature moderate or high richness of data content; and (3) predominantly target expert users. 相似文献
3.
The relative contributions of adsorption to particulate surfaces, complexation with surface-active organic ligands and uptake by micro-organisms were evaluated with respect to their importance in the surface microlayer enrichment (‘partitioning’) of Cd, Pb and Cu. The contributions of each process were inferred from field data in which partitioning of the dissolved and particulate forms of Cd, Pb and Cu, total and dissolved organic carbon, particles and total bacteria were observed. In the South San Francisco Bay estuary, particle enrichment appears to control trace metal partitioning. Trace metal association with the particulate phase and the levels of partitioning observed were in the order Pb > Cu > Cd and reflect the calculated equilibrium chemical speciation of these metals in computer-simulated seawater matrices. 相似文献
4.
Maxime Lion Béatrice Ledésert Frédéric Skoczylas Philippe Recourt Thierry Dubois 《地学学报》2004,16(6):351-357
Many poromechanical studies of rocks give little regard to the micropetrographic observation of their constituents. The aim of this study is to show how such a detailed study can help understand and provide more precision on the poromechanical behaviour of the material. The rock studied here is an oolitic limestone. Micropetrography reveals the nature of the constituents (calcite, mostly in the form of fine‐grained micrite), their abundance, their organization (micrite organized in ooids linked by a calcitic cement, small‐sized highly connected isotropic porosity, scarce unconnected porosity) and the structure of the rock (global isotropy, small heterogeneities due to sedimentological phenomena, no microcracks). Micropetrography completes the information obtained by poromechanics in that it allows the observation of elements deduced from macroscopical tests. The aim of this paper is to show the effect of microporosity on permeability and flow in a rock where microporous grains are in contact with each other. 相似文献
5.
南大别地体中榴辉岩的围岩──石榴黑云片麻岩具有角闪岩相变质矿物组合,其变质温度为525℃,Sm-Nd矿物等时线年龄为(229±3)Ma.黑云母的K-Ar封闭温度为300℃,相应K-Ar年龄为(231±5)Ma.因此该片麻岩在230Ma左右从525℃迅速冷却到300℃以下。然而该区榴辉岩在印支期(221Ma)变质温度为700℃左右,直到134Ma才降至400-450℃。说明该区榴辉岩与该片麻岩具有不同的冷却史。它不支持榴辉岩是原地(in situ)成因的。 相似文献
6.
M. Fulchignoni A. Aboudan M. Antonello C. Bettanini G. Colombatti E. Flamini N. Ghafoor A.-M. Harri P.F. Lion Stoppato J.C. Zarnecki 《Planetary and Space Science》2004,52(9):867-880
We developed a series of balloon experiments parachuting a 1:1 scale mock-up of the Huygens probe from an altitude just over to simulate at planetary scale the final part of the descent of the probe through Titan's lower atmosphere. The terrestrial atmosphere represents a natural laboratory where most of the physical parameters meet quite well the bulk condition of Titan's environment, in terms of atmosphere composition, pressure and mean density ranges, though the temperature range will be far higher.The probe mock-up consists of spares of the HASI sensor packages, housekeeping sensors and other dedicated sensors, and also incorporates the Huygens Surface Science Package (SSP) Tilt sensor and a modified version of the Beagle 2 UV sensor, for a total of 77 acquired sensor channels, sampled during ascent, drift and descent phase.An integrated data acquisition and instrument control system, simulating the HASI data-processing unit (DPU), has been developed, based on PC architecture and soft-real-time application. Sensor channels were sampled at the nominal HASI data rates, with a maximum rate of . Software has been developed for data acquisition, onboard storage and telemetry transmission satisfying all requests for real-time monitoring, diagnostic and redundancy.The mock-up of the Huygens probe mission was successfully launched for the second time (first launch in summer 2001, see Gaborit et al., 2001) with a stratospheric balloon from the Italian Space Agency Base “Luigi Broglio” in Sicily on May 30, 2002, and recovered with all sensors still operational. The probe was lifted to an altitude of and released to perform a parachuted descent lasting , to simulate the Huygens mission at Titan. Preliminary aerodynamic study of the probe has focused upon the achievement of a descent velocity profile reproducing the expected profile of Huygens probe descent into Titan.We present here the results of this experiment discussing their relevance in the analysis of the data which will be obtained during the Huygens mission at Titan. 相似文献
7.
Transport and distribution of bacteria and diatoms in the aqueous surface microlayer of a salt marsh
Ronald W. Harvey Leonard W. Lion Lily Y. Young 《Estuarine, Coastal and Shelf Science》1983,16(5):543-547
The effects of tide and wind upon the distribution and transport of bacteria and diatoms in the aqueous surface microlayers of a Massachusetts and San Francisco Bay salt marsh were examined. The compression of the surface films by both tide and wind resulted in significant enrichments of bacterioneuston. At the San Francisco Bay site, significant numbers of diatoms were transported within the microlayer over a tidal cycle. 相似文献
8.
Air-sea interfacial solutions have characteristically high concentrations of trace metals, microorganisms, organic compounds,
and solids relative to bulk solutions. The potential for the chemical interaction of an array of trace metals in the interfacial
regions with complexing organic ligands and adsorbing solid surfaces has been evaluated through the use of an equilibrium
computer model. Computations suggest that higher interfacial accumulations of copper and lead may occur relative to cadmium
and mercury. These results are found to be generally compatible with available field data describing trace metal interfacial
accumulation. The forms of metals found to be partitioned between bulk and interfacial solutions are consistent with the hypothesis
that solid surface adsorption and dissolved organic complexation reactions bring about metal enrichment at the surface microlayer. 相似文献
9.
The minimum-propellant deterministic guidance law for bounded-thrust, constant jetexhaust velocity, spacecrafts is developed using the neighboring extremal theory. Minimization of the first-order variation in cost between a multi-burn nominal extremal and the perturbed trajectory eliminates all correction strategies except small changes in the nominal thrust-on, thrust-off times and small rotations of the thrust vector. Optimal values of these corrective controls for fixed values of initial state deviations, x
0, are found by minimizing the second variation in cost subject to the variational state and adjoint equations — an accessory minimum problem. The solution takes the linear feedback form u=A
–1
22
A
21x
0, where the matricesA
22 andA
21 are functions only of transition matrices calculated along the nominal trajectory. The solution is applied to a three-burn Earth-Mars transfer. 相似文献
10.
“Grand Paris” is a study carried out by ten teams of researchers and city planners in the aim of putting forward general guidelines for Paris urban area’s evolution by 2030. All the teams suggest making the area “greener” in some way, to combat climate warming by CO2 sequestration. Our team also shows that extending the nearby forests by 30 %, favouring short farm-to-consumer circuits and using lighter coloured building materials will decrease the urban heat island, reducing the mortality during heat waves as well as the need for air-conditioning. These results lead us to reverse the way of thinking urban planning: the geographic and natural aspects should replace the urban infrastructure as a driver for planning urban development. This new strategy allows city changes on quite a large scale, that will have a favourable impact in terms of economics, leisure activities, greenhouse gas emissions and the local microclimate. 相似文献