Dehalorespiration bioremediation has been considered for chlorinated compound removal from two trichloroethene contaminated groundwater plumes in the OU 5 area of Hill Air Force Base, Utah. The distributions and population densities of the 16S rRNA genes of Bacteria, Dehalococcoides ethenogenes, Desulfuromonas michiganensis, Geobacter spp. and Rhodoferax ferrireducens -like bacteria, as well as the functional genes trichloroethene reductive dehalogenase ( tce A) and vinyl chloride reductase ( vcr A) were determined in contaminated aquifer material samples. The influence of aquifer physical and chemical properties, including iron availability, on these distributions was evaluated. Twenty aquifer cores were collected. DNA was extracted and analyzed using real-time quantitative polymerase chain reaction (RT-qPCR) to quantify the gene densities. Dehalococcoides population densities were low and unevenly distributed. D. michiganensis was found in 12 cores while Geobacter spp. were found in 8 cores. Rhodoferax ferrireducens -like bacteria were widely distributed. The vcr A gene distribution was relatively uniform and broad but the tce A gene was detectable in only 2 cores. Gene distribution was not related to core clusters derived from physical/chemical characteristics. 相似文献
The Virtual Observatory (VO) is becoming the de-facto standard for astronomical data publication. However, the number of radio astronomical archives is still low in general, and even lower is the number of radio astronomical data available through the VO. In order to facilitate the building of new radio astronomical archives, easing at the same time their interoperability with VO framework, we have developed a VO-compliant data model which provides interoperable data semantics for radio data. That model, which we call the Radio Astronomical DAta Model for Single-dish (RADAMS) has been built using standards of (and recommendations from) the International Virtual Observatory Alliance (IVOA). This article describes the RADAMS and its components, including archived entities and their relationships to VO metadata. We show that by using IVOA principles and concepts, the effort needed for both the development of the archives and their VO compatibility has been lowered, and the joint development of two radio astronomical archives have been possible. We plan to adapt RADAMS to be able to deal with interferometry data in the future. 相似文献
A tree-ring chronology network recently developed from the subantarctic forests provides an opportunity to study long-term
climatic variability at higher latitudes in the Southern Hemisphere. Fifty long (1911–1985), homogeneous records of monthly
mean sea-level pressure (MSLP) from the southern latitudes (15–65 °S) were intercorrelated on a seasonal basis to establish the most consistent, long-term Trans-Polar teleconnections during
this century. Variations in summer MSLP between the South America-Antarctic Peninsula and the New Zealand sectors of the Southern
Ocean are significantly correlated in a negative sense (r=−0.53, P<0.001). Climatically sensitive chronologies from Tierra del Fuego (54–55°) and New Zealand (39–47°) were used to develop verifiable reconstructions of summer (November to February) MSLP for both sectors of the Southern Ocean.
These reconstructions, which explain between 37 and 43% of the instrumentally recorded pressure variance, indicate that inverse
trends in MSLP from diametrically opposite sides of Antarctica have prevailed during the past two centuries. However, the
strength of this relationship varies over time. Differences in normalized MSLP between the New Zealand and the South America-Antarctic
Peninsula sectors were used to develop a Summer Trans-Polar Index (STPI), which represents an index of sea-level pressure
wavenumber one in the Southern Hemisphere higher latitudes. Tree-ring based reconstructions of STPI show significant differences
in large-scale atmospheric circulation between the nineteenth and the twentieth centuries. Predominantly-negative STPI values
during the nineteenth century are consistent with more cyclonic activity and lower summer temperatures in the New Zealand
sector during the 1800s. In contrast, cyclonic activity appears to have been stronger in the mid-twentieth than previously
for the South American sector of the Southern Ocean. Recent variations in MSLP in both regions are seen as part of the long-term
dynamics of the atmosphere connecting opposite sides of Antarctica. A detailed analysis of the MSLP and STPI reconstructions
in the time and frequency domains indicates that much of the interannual variability is principally confined to frequency
bands with a period around 3.3–3.6 y. Cross spectral analysis between the STPI reconstruction and the Southern Oscillation
Index suggests that teleconnections between the tropical ocean and extra-tropical MSLP variations may be influencing climate
fluctuations at southern latitudes.
Received: 18 December 1996/Accepted: 10 January 1997 相似文献
The electrical properties of opal-CT are validated at temperatures from 600 to 840 °C and frequencies from 5 Hz to 10 MHz.
The opals are hydrothermal, containing less than 11270 ppm total of Al, Fe, Ca, Na, and K, and from 1.17 to 17.63 wt% H2O interstitial and structural. Opal-CT shows fine crystallites, measuring from 19.4 to 22.7 μm, of an ordered tridymite-M
stratification with high-cristobalite, embedded in a non-crystalline matrix. When heated to 600 °C, the non-crystalline phase
devitrifies to the same stacked high-cristobalite-tridymite-M crystals. Opals containing less than 2070 ppm of cationic impurities
are characterized by one single high-frequency complex impedance arc corresponding to the bulk polarization of the crystalline
phase, of capacitances between 25 and 30×10−12 F and resistances from 132 to 890 ohm. Opals having over 6300 ppm of cationic impurities show two superimposed high- and
low-frequency complex impedance arcs. The high-frequency arc corresponds to the bulk polarization of the crystalline phase,
of capacitance between 8 and 15.7×10−12 F and resistance from 14 to 236 ohm, less than the capacitance of 0.25 to 0.53×10−9 F and resistance from 26 to 360 ohm of the non-crystalline minor intergranular material represented by the low-frequency
impedance arc. The electric module shows one single vertex, ascribed to the bulk polarization of the crystalline phase. The
conductivities are from 10−7 to 10−4 ohm−1cm−1, in the range of poor ionic conductors, essentially constant below 1.8 kHz, rapidly increasing at higher frequencies, due
to ionic and electronic charge carriers. The activation energy changes between 0.905 and 1.003 eV for the conduction mechanism
in the crystalline phase and from 0.924 to 1.087 eV in the non-crystaline phase. X-ray diffraction and impedance spectroscopy
confirm that opal-CT is a crystalline stacked sequence of tridymite-M and cristobalite-high, in a non-crystalline matrix.
Received October 20, 1995/Revised, accepted June 15, 1996 相似文献
The limited length and spatial coverage of instrumental climate data for many areas of the Southern Hemisphere impedes the
study of atmosphere-ocean dynamics prior to the past century. Such analyses are important for understanding interannual to
decadal variation of the Southern Hemisphere circulation and whether recent changes are related to anthropogenic effects rather
than natural variability. We use a middle- to high-latitude tree-ring width data set (from Tasmania, New Zealand and Tierra
del Fuego) to reconstruct sea-level pressure (SLP) variability spanning the Tasman Sea and vicinity since ad 1740. The variables reconstructed are austral summer (November–March) SLP for Hobart, Tasmania (43°S, 147°E) and the Chatham
Islands, New Zealand (44°S, 177°E), as well as a meridional circulation index (Hobart-Chatham Islands index) which measures
the pressure gradient between these two stations. The three reconstructions are well verified statistically and capture between
40 and 48% of the variance in the SLP data. The instrumental and estimated SLP show similar spatial patterns of correlation
with the sea surface temperature (SST) field for the Pacific. Statistically significant (above 95% level) 3–3.5 year spectral
peaks are identified in the three reconstructions using multitaper spectral analysis, and a significant 4–5 year peak is found
in both the Chatham Islands and Hobart-Chatham Islands SLP reconstructions. These two modes are within the bandwidth of the
El Nino-Southern Oscillation. Although very speculative, they may also correspond to a proposed Antarctic circumpolar wave
of SLP, SST, wind and sea-ice extent, believed to play a key role in atmosphere-ocean circulation for the Southern Hemisphere.
Received: 30 November 1998 / Accepted: 13 December 1999 相似文献
Genetic algorithms (GA) are widely used to solve engineering optimization problems. The quality and performance of the solution generated strongly depend on the selection of the GA parameter values (crossover and mutation rates and population size).
We propose an approach based on full factorial and response surface methodology experimental designs to calibrate GA parameters such that the objective function is maximized/minimized and the relative importance of the parameters is quantified. The approach was tested by applying it to stope optimization of underground mines, where profit can vary ±?7% based solely on GA parameters. Results showed that: (1) a larger population size did not always increase solution time; (2) solution time was positively related to crossover and mutation rates; and (3) simultaneous analysis of solution time and profit illustrated the trade-off between acceptable computing time and profit desirability through GA parameter selection. This approach can be used to calibrate parameters of other metaheuristics.
Spanish Port Authorities currently face a wide range of complexities in their decision-making processes, as they have to satisfy several port management objectives that may conflict with one another. This paper examines these circumstances by using decision theory methodology with multiple objectives, which, through the Promethee method, makes the design of an index possible. This index combines different decision factors that shape the competitiveness of a port to rank the Spanish Port Authorities. This ranking serves as an alternative to the traditional ranking system by easily providing more information about port traffic. 相似文献
Correlations between ecological and cultural changes occurred during a short period between the end of Subboreal and the beginning of Subatlantic in the Amblés Valley (Ávila, central Spain) are analyzed, taking into account palaeopalynological and archaeological data. Plant dynamics from pollen analyses, both from archaeological sites and peat bogs, have been interpreted in relation to human settlements and the transformation of economic practices. These provided a comprehensive hypothesis on human/climate interactions at the beginning of the 1st millennium cal BC. There was an ecological crisis in the region that lasted for a century (ca. 850–760 cal BC). This was especially sharp due to both the geographical constraints of the area and its previous agrarian history. This event implied a sudden and abrupt climatic change from xeric and warm conditions (Subboreal) to more humid and cooler ones (Subatlantic). Environmental stress derived from climatic crisis could be an important factor in the explanation of the historical process, whose main consequences were both the origin of the Iron Age peasant villages and the end of the ‘dehesa’ type landscape. 相似文献