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1.
Analysis of the Pampa, Texas, multicell storms showed prestorm environmental conditions of a strong horizontal convergence
of moisture, mixing ratio 12 g/kg at the 850 mb level in the Texas Panhandle areas and strong winds with shear veering with
height. Rapid-scan satellite imagery showed that the clouds penetrated above the tropopause and cloud-top temperatures were
at least 4 to 9° C colder than the temperature of the tropopause. This formation and collapsing of high-mass-density overshooting
cloud tops above the tropopause is characteristic of tornadoes in the middle portion of the United States. 相似文献
2.
Auger electron spectroscopy has been used to study K-feldspar that has been reacted with both aqueous 10% HF and a 50% mixture of a 10% HF/0.1 N H2SO4 solution. In the feldspar/HF system, the resulting feldspar surface was shown to have been fluorinated; depth profiling, using argon ion sputtering, showed the fluorination to have occurred substantially into the mineral bulk. In the feldspar/ system, the resulting surface contained both fluorine and sulfur. The fluorination had again penetrated into the bulk, but the sulfur could be removed with mild argon ion sputtering. The signal ratio was much lower on the feldspar surface treated with the 10% HF/0.1 N H2SO4 solution than the feldspar surface treated with the weaker 10% HF acid solution. 相似文献
3.
Both laboratory experiments and numerical modelling were conducted to study the biodegradation and transport of benzene–toluene–xylenes (BTX) in a simulated semi‐confined aquifer. The factors incorporated into the numerical model include advection, hydrodynamic dispersion, adsorption, and biodegradation. The various physico‐chemical parameters required by the numerical model were measured experimentally. In the experimental portion of the study, BTX compounds were introduced into the aquifer sand. After the contaminants had been transported through the system, BTX concentrations were measured at 12 equally spaced wells. Subsequently, microorganisms obtained from the activated sludge of a sewage treatment plant and cultured in BTX mixtures were introduced into the aquifer through the 12 sampling wells. The distribution data for BTX adsorption by the aquifer sand form a nonlinear isotherm. The degree of adsorption by the sand varies, depending on the composition of the solute. The degradation time, measured from the time since the bacteria were added to the aquifer until a specific contaminant was no longer detectable, was 35–42 h for BTX. The dissolved oxygen, after degradation by BTX compounds and bacteria, was consumed by about 40–60% in the entire simulated aquifer; thus the aerobic conditions were maintained. This study provides insights for the biodegradation and transport of BTX in aquifers by numerical modelling and laboratory experiments. Experimental and numerical comparisons indicate that the results by Monod degradation kinetics are more accurate than those by the first‐order degradation kinetics. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
4.
Solar Physics - Although the method of superposed epochs (Chree analysis) has been utilized for seven decades, a procedure to determine the statistical significance of the results has not been... 相似文献
5.
Evaluation of proxy-based millennial reconstruction methods 总被引：2，自引：1，他引：1
A range of existing statistical approaches for reconstructing historical temperature variations from proxy data are compared using both climate model data and real-world paleoclimate proxy data. We also propose a new method for reconstruction that is based on a state-space time series model and Kalman filter algorithm. The state-space modelling approach and the recently developed RegEM method generally perform better than their competitors when reconstructing interannual variations in Northern Hemispheric mean surface air temperature. On the other hand, a variety of methods are seen to perform well when reconstructing surface air temperature variability on decadal time scales. An advantage of the new method is that it can incorporate additional, non-temperature, information into the reconstruction, such as the estimated response to external forcing, thereby permitting a simultaneous reconstruction and detection analysis as well as future projection. An application of these extensions is also demonstrated in the paper. 相似文献
6.
John R. Letaw J. H. Adams Jr. Rein Silberberg C. H. Tsao 《Astrophysics and Space Science》1985,114(2):365-379
Cosmic-ray nuclei are close to fully ionized during their passage through the Galaxy. Electron capture decay is rare among these nuclides because most do not have bound electrons. Under certain conditions, specifically low energies and/or high charges, electron capture becomes an essential factor in determining cosmic-ray composition. In this paper we discuss the general nature of electron capture decay in cosmic rays and describe specific measurements which can reveal the existence of electron capture decay, and energy and density-dependent processes in the interstellar medium. 相似文献
7.
The interplay of sediment characteristics,depth, water temperature,and ocean currents shaping the biogeography of lancelets (Subphylum Cephalochordata) in the NW Pacific waters 
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下载免费PDF全文 Lancelets (or amphioxus) are often found within the soft bottom of shallow tropical and temperate seas. The present study is the first to provide a fine‐scale biogeography of five species of lancelets (Asymmetron lucayanum, Branchiostoma belcheri, Branchiostoma japonicum, Epigonichthys cultellus, and Epigonichthys maldivensis) in the NW Pacific and examine the effects of multiple environmental parameters. From multivariate analyses, the distribution and abundance patterns of lancelets were explained by a combination of factors comprising depth, temperature of the collecting month, mean temperature of the coldest month in the year, medium particle size and silt/clay ratio of the sediments. In addition, ocean currents also affect their distribution range. The major occurrence of A. lucayanum and E. maldivensis was associated with the warm Kuroshio current, but E. maldivensis exhibited higher tolerance to low salinity and low temperature, and preferred substrata of slightly larger grain size, a lower ratio of suspended sediments, and deeper water. The closely related B. belcheri and B. japonicum exhibited fine‐scale habitat differentiation, and B. japonicum was abundant along the southern coast of China, where the salinity is lower in winter because of the China Coastal Current and the substratum is composed of very coarse sand with suspended sediments. Branchiostoma belcheri occurred in low abundance and was only recorded in Northern Taiwan and the Taiwan Banks. Epigonichthys cultellus was found only at the Taiwan Banks, which had deep water, coarse sand, and a negligible amount of suspended sediments. 相似文献
8.
Xiaolong Geng Michel C. Boufadel Yves R. Personna Ken Lee David Tsao Erik D. Demicco 《Marine pollution bulletin》2014
Modeling oil biodegradation is an important step in predicting the long term fate of oil on beaches. Unfortunately, existing models do not account mechanistically for environmental factors, such as pore water nutrient concentration, affecting oil biodegradation, rather in an empirical way. We present herein a numerical model, BIOB, to simulate the biodegradation of insoluble attached hydrocarbon. The model was used to simulate an experimental oil spill on a sand beach. The biodegradation kinetic parameters were estimated by fitting the model to the experimental data of alkanes and aromatics. It was found that parameter values are comparable to their counterparts for the biodegradation of dissolved organic matter. The biodegradation of aromatics was highly affected by the decay of aromatic biomass, probably due to its low growth rate. Numerical simulations revealed that the biodegradation rate increases by 3–4 folds when the nutrient concentration is increased from 0.2 to 2.0 mg N/L. 相似文献
9.
In quantitative risk analyses for natural hazards, vulnerability can be expressed as the ratio of reconstruction, replacement or reproduction expenses due to a damage caused by a certain process intensity and the original value of the element at risk exposed. To discuss the building vulnerability under debris flow events, the ratio is mostly related to debris flow inundation height, building materials and building values. Different types of buildings would resist to the impact of debris flows differently, resulting in different damage levels even under the same inundation height. After debris flow events, the damages to a building include the content loss and the structure loss, which is also variable due to the individual building conditions. This study proposes a flowchart to establish building vulnerability curves through estimating the damages to buildings after debris flow hazards. The losses of content and structure are firstly calculated separately to obtain the loss ratios with respect to original buildings. Secondly, by combining the content and structure loss ratio, the building vulnerability function is derived. In this paper, the original building content value was obtained from governmental statistic records and was based on the market price, and the structure value was received from a regional architecture office. The losses resulting from debris flow impacts were synthetically derived following field surveys. To combine the content and structure losses, a unit building with a floor area of 60?m2 was assumed. The result shows that due to a higher percentage of content value compared with the total building value, the loss ratio resulting from debris flows in Taiwan is higher compared with European studies, in particular with respect to high-frequency but low-magnitude events. The concept of obtaining building vulnerability is particularly suitable for regions where well-documented building loss records are unavailable. 相似文献
10.
Claudio CocozzaCalvin C.G. Tsao Sing-Foong CheahStephan M. Kraemer Kenneth N. RaymondTeodoro M. Miano Garrison Sposito 《Geochimica et cosmochimica acta》2002,66(3):431-438
This article reports an investigation of the temperature dependence of goethite dissolution kinetics in the presence of desferrioxamine B (DFO-B), a trihydroxamate siderophore, and its acetyl derivative, desferrioxamine D1 (DFO-D1). At 25 and 40°C, DFO-D1 dissolved goethite at twice the rate of DFO-B, whereas at 55°C, the behavior of the two ligands was almost the same. Increasing the temperature from 25 to 55°C caused little or no significant change in DFO-B or DFO-D1 adsorption by goethite. A pseudo-first-order rate coefficient for dissolution, calculated as the ratio of the mass-normalized dissolution rate coefficient to the surface excess of siderophore, was approximately the same at 25 and 40°C for both siderophores. At 55°C, however, this rate coefficient for DFO-D1 was about half that for DFO-B. Analysis of the temperature dependence of the mass-normalized dissolution rate coefficient via the Arrhenius equation led to an apparent activation energy that was larger for DFO-B than for DFO-D1, but much smaller than that reported for the proton-promoted dissolution of goethite. A compensation law was found to relate the pre-exponential factor to the apparent activation energy in the Arrhenius equation, in agreement with what has been noted for the proton-promoted dissolution of oxide minerals and for the complexation of Fe3+ by DFO-B and simple hydroxamate ligands in aqueous solution. Analysis of these results suggested that the siderophores adsorb on goethite with a only single hydroxamate group in bidentate ligation with an Fe(III) center. 相似文献