共查询到20条相似文献，搜索用时 46 毫秒
1.
XIAO Zhijie LIAN Bin CHEN Jun H. Henry Teng 《中国地球化学学报》2007,26(3):252-258
A simple apparatus was designed to effectively isolate magnetotactic bacteria from soils or sediments based on their magnetotaxis. Through a series of processes including sample incubation, MTB harvesting, isolation, purification and identification, several strains of bacteria were isolated from the samples successfully. By Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray Analysis (EDXA), these bacteria were certificated to be magnetotactic bacteria. The phylogenetic relationship between the isolated magnetic strains and some known magnetotactic bacteria was inferred by the construction of phylogenetic tree based on 16SrDNA sequences. This apparatus has been proven to have the advantages of being inexpensive, simple to assemble, easy to perform and highly efficient to isolate novel magnetotactic bacteria. The research indicated that the combined approach of harvesting MTB by home-made apparatus and the method of plate colony isolation could purify and isolate magnetotactic bacteria effectively. 相似文献
2.
《Geomechanics and Geoengineering》2013,8(1):1-11
Experimental techniques of testing the mechanical properties of unsaturated soils are complex and difficult to conduct. As a consequence, complete sets of parameters that characterise the behaviour of unsaturated soils remain scarce and necessary. In this context, it has been found useful to gather the information obtained after some years of practice of the osmotic technique of controlling suction. As compared to the more documented axis-translation technique, the osmotic technique has its own advantages and drawbacks that are discussed in this paper, together with some potential future developments. The osmotic method has been developed by soil scientists in the 1960s and adapted to geotechnical testing in the early 1970s. This paper presents the osmotic technique and comments on its advantages (including suction condition close to reality and higher suctions easily attained) and drawbacks (including some concern with the membrane resistance and some membrane effects in the suction/concentration calibration). Various applications to geotechnical testing are presented such as the determination of the water retention curve, oedometer and triaxial testing procedures and the determination of the permeability of unsaturated soils. Recent developments, that include the extension of the method up to high suctions (10 MPa) are also described, together with some recent and novel applications such as data from high controlled suction oedometer compression test and the determination of the oil/water retention properties of oil reservoir chalks. 相似文献
3.
4.
In this paper, we systematically analyze the pressure projection stabilization method for the Darcy and coupled Darcy–Stokes flow problems in multiple dimensions. Stability results for this stabilization method are established. For the Darcy flow, optimal error estimates in the divergence norm for velocity and suboptimal error estimates in the $L^{2}$ -norm for pressure are obtained, and a superconvergence result for the pressure is derived; a local postprocessing scheme is constructed to generate optimal error estimates in the L 2-norm for pressure. For the coupled Darcy–Stokes flow, error estimates of optimal order are obtained in terms of the energy norm of velocity and pressure. Numerical results are presented to check the theory developed. 相似文献
5.
A dynamic, large deformation problem of fluid–solid–geomembrane interaction is analysed by the use of material point method, a variant of the finite element method stated in a Lagrangian–Eulerian format. A low-order element is used for space discretisation and the fluid is treated as a compressible liquid with a high value of bulk modulus. Therefore, two algorithms known from literature are applied to mitigate the effects related to the volumetric locking phenomenon. Moreover, a procedure of detecting the free surface is proposed. The method is applied to problems of determining the shape of geo-tubes, collapsing water column, and finally, to the problem of installation of a geo-container on the bed of a water reservoir. The obtained numerical outcomes are compared with the experimental results and the analytic ones when available. 相似文献
6.
We tested the accuracy of the chloroform fumigation–extraction method, which is commonly used to determine soil biomass C concentrations. Accurate and precise determination of total microbial biomass is important in order to characterize soil properties and to develop predictive metal transport models for soils. Two natural soils, and individual soil components, including silica sand, montmorillonite, kaolinite, a humic acid, and Bacillus subtilis bacterial cells, were fumigated for 24 h. Following the fumigation, C from fumigated and unfumigated samples was extracted using a 0.5 M K2SO4 solution. The difference between the C content in the fumigated and unfumigated samples ideally represents C due to biomass because the fumigation procedure should lyse cells and release biomass C. We observed increased C release upon fumigation for bacteria-only samples, confirming the ability of fumigation to lyse cells. There was no difference in extracted C concentration between fumigated and unfumigated samples of silica sand and of humic acid, confirming that the fumigation process does not introduce additional organic C to samples of these soil components. However, the fumigated clay samples both showed increased C release relative to the unfumigated controls, indicating that significant concentrations of the fumigant, chloroform, adsorbed onto the clay minerals studied here. Additionally, we found significant chloroform remaining in the extracts from two fumigated natural soils. Attempts to remove the chloroform from the soils or soil components prior to extraction by increasing the evacuation time, or to remove chloroform in the extracts by sparging them vigorously with nitrogen gas, both failed. This research reveals that chloroform gas may adsorb significantly to clays and the clay fraction of natural soils. Thus, the fumigation–extraction method must be corrected to account for the added chloroform C and accurately assess the concentration of biomass C in soils that contain significant concentrations of clays. 相似文献
7.
8.
Previous studies have shown that ferromanganese crusts in the Pacific Ocean commonly record paleomagnetic reversals and that the reversal patterns can be used to estimate growth rates. In order to investigate the applicability of the magnetostratigraphic method, we conducted paleomagnetic measurements of crust samples recovered from five locations in the northwest Pacific. A series of thin slices, with thicknesses of 0.5–1.0 mm, was prepared for each sample, and a paleomagnetic polarity was determined for each slice. In all five samples, we found a consistent reversal pattern of N1–R1–N2–R2–N3 from the surface to the inner part of the crust. In three samples, another polarity interval (R3) was recognized below the N3 section of the crust. These data suggest that ferromanganese crusts in the northwest Pacific recorded paleomagnetic reversals and that reversal patterns can be used for ocean-scale correlations. The magnetostratigraphic method suggests constant growth rates of 1.49, 2.54, 3.56 and 3.67 mm/Ma for four samples, three of which are consistent with those estimated using 10Be/9Be dating at the 2σ (standard deviation) level. 相似文献
9.
Natural Hazards - The evolution law for the mining-induced deformation and failure of surrounding rock is an important parameter for coal mine work safety. Accurate detection is a scientific matter... 相似文献
10.
11.
The Earth’s free oscillations are recorded for the first time in variations of the geomagnetic field measured at the Earth’s surface. The Earth’s free oscillations in the frequency range from 0.3 to 4 mHz manifest in the spectra of geomagnetic variations in the form of clearly expressed quasi-harmonic peaks. It is shown that the spectral amplitudes of the main modes of the Earth’s free oscillations are not constant and change with a periodicity corresponding to a lunar (sideral) month. The data obtained indicate the influence of oscillations in the internal geospheres on variations in the terrestrial magnetic field. The results provide new opportunities to study the Earth’s free oscillations and to specify their multiplet components. In addition, they also have certain implications for further research into the internal structure of the Earth and geodynamic processes in internal geospheres, on the basis of magnetometric data. 相似文献
12.
Two methods for obtaining information on the fractional composition of organic matter in natural waters (membrane filtration and oxythermography) are combined in this study. The method has a number of indisputable advantages, which distinguish it among the currently available methods of analytical chemistry. In earth science, the fractional composition of organic materials in natural waters is estimated by the concentration of organic carbon (Corg) in fractions. In our opinion, an indicator of chemical consumption of oxygen (CCO) for ecological estimation of water reservoir state is more informative, because this indicator carries specific ecological information on the necessary oxygen consumption for oxidation of pollutants coming into the natural water environment. Therefore, estimation of the CCO parameter in fractions provides real information on the availability of organic matter and the probable danger from its content in water. This is the principal novelty of the information obtained and our study. The method was tested in the study of variation of the fractional composition of water matter during passage of Volga water through the waterworks (upon removal of water from the storage reservoir through the dam of the Ivan’kovskaya hydro power plant in the Dubna area). Analogous results are almost absent in earth science literature. There is a lack of data on the influence of water release through the dam even with respect to the major-component chemical composition. Variation of the fractional composition of matter (both organic and inorganic) upon water release through a waterworks is not discussed in literature. Thus, this study is of fundamental character. 相似文献
13.
The method of “p–y” curves has been extensively used, in conjunction with simplified numerical methods, for the design and response evaluation of single piles. However, a straightforward application of the method to assess the response of pile groups is questionable when the group effect is disregarded. For this reason, the notion of p-multipliers has been therefore introduced to modify the “p–y” curves and account for pile group effect. The values proposed for p-multipliers result from pile group tests and are limited to the commonly applied spacing of 3.0 D and layout less than 3 × 3, restricting the applicability of the method to specific cases. With the aim of extending the applicability of the “p–y” method to pile groups, the authors have already proposed a methodology for estimating the “p G–y G” curves of soil resistance around a pile in a group for clayey soils. A complementary research allowing for the estimation of the “p G–y G” curves for sandy soils is presented in this paper. The well-known curves of soil resistance around the single pile in sandy soils are appropriately transformed to allow for the interaction effect between the piles in a group. Comparative examples validate the applicability and the effectiveness of the proposed method. In addition, the method can be straightforwardly extended to account for varying soil resistance, according to the particular location of a pile in a group. It can therefore be used in a most accurate manner in estimating the distribution of forces and bending moments along the characteristic piles of a group and therefore to design a pile foundation more accurately. 相似文献
14.
Magmatic zircon in high-grade metamorphic rocks is often characterized by complex textures as revealed by cathodoluminenscence （CL） that result from multiple episodes of recrystallization, over- growth, Pb-loss and modifications through fluid-induced disturbances of the crystal structure and the original U-Th-Pb isotopic systematics. Many of these features can be recognized in 2-dimensional CL images, and isotopic analysis of such domains using a high resolution ion-microprobe with only shallow penetration of the zircon surface may be able to reconstruct much of the magmatic and complex post- magmatic history of such grains. In particular it is generally possible to find original magmatic domains yielding concordant ages. In contrast, destructive techniques such as LA-ICP-MS consume a large volume, leave a deep crater in the target grain, and often sample heterogeneous domains that are not visible and thus often yield discordant results which are difficult to interpret. We provide examples of complex magmatic zircon from a southern Indian granulite terrane where SHRIMP lI and LA-ICP-MS analyses are compared. The SHRIMP data are shown to be more precise and reliable, and we caution against the use of LA-ICP-MS in deciphering the chronology of complex zircons from high-grade terranes. 相似文献
15.
Tatsuhide Hamasaki Yoko Fujikawa Daisuke Yoneda Masataka Sugahara 《中国地球化学学报》2006,25(B08):114-115
The purpose of this study is to do an experiment in finding conditions of search purification materials and the way of their proper processing for the rapid infiltration method. It seems that this result makes an index of further selection of a purification material. This experiment is to conduct sorption tests of fulvic acid and phosphoric acid regarding Kanuma-soil （volcanic ash soil） with iron oxide and aluminum oxide, to fred relationship between sorption coefficients and heating temperature, concentrations of iron and aluminum. The sorption experiment on heated and unheated materials was conducted at 25℃ in a dark place at the solid to liquid ratio of 1 ： 2.5. The liquid is simulated river water. According to the result of the study, a deference was found of the best heating temperature between sorption coefficients of fulvic acid and phosphoric acid. The peak of a sorption coefficient of fulvic acid is 800℃, however the peak of a sorption coefficient of phosphoric acid is 400℃. In the case of fulvic acid, it is high sorption coefficients when Kanuma-soil with aluminum oxide is unheated and heated as 400℃. However, sorption coefficients when Kanuma-soil with iron oxide is not conspicuously different when heated, and coefficients are descended gradually more than 600℃. Sorption coefficients of unheated Kanuma-soil are descended when adding iron oxide. When heating temperature is higher, pH of water is higher. High pH causes to descend sorption coefficient, however it is remarkable result that sorption coefficient is ascended at 800℃. In the case of phosphoric acid, it is high sorption coefficient when Kanuma-soil is heated at 400℃, and Kanuma-soil with aluminum oxide is heated between 200℃ and 400℃. Sorption coefficients of Kanuma-soil with iron oxide are the highest when unheated, but sorption coefficients of Kanuma-soil with iron oxide are the highest when heated. 相似文献
16.
Although simplified numerical methods are reliable for evaluating the response of a single pile under horizontal load, their application is questionable for assessing the response of pile groups. The notion of “p–y” curves has been considered with the aim of establishing a transformation relationship able to provide the “pG–yG” curves of soil resistance around a pile in a group from the well-known curves of soil resistance around the single pile.This transformation extends the applicability of the “p–y” method to pile groups, without the need for time consuming numerical computations, rendering the proposed method efficient and attractive. Comparative examples demonstrated the applicability and the effectiveness of the proposed method. In addition, the method can be straightforwardly extended to account for varying soil resistance, according to the particular location of a pile in a group. It can therefore be used to estimate accurately force and bending moment distributions along the characteristic piles of a group, which are required for the efficient design of foundations. 相似文献
17.
Davor Stanko Snježana Markušić Stjepan Strelec Mario Gazdek 《Environmental Earth Sciences》2017,76(18):642
This paper presents a major extension of seismic vulnerability research project on the site of Trako??an Castle based on the initial horizontal-to-vertical-spectral-ratio (HVSR) results from Stanko et al. (2016). The estimated HVSR site frequencies and HV amplification at Trako??an Castle can only be used as an indication of the initial soil site frequency and amplification, so-called natural soil model, corresponding to the subsoil profile without the influence of an earthquake. The equivalent-linear (EQL) site response analysis has been carried out for different earthquake scenarios for a maximum input rock peak ground acceleration (PGAROCK) that corresponds to return periods of 95 (0.08 g), 475 (0.18 g) and 1000 years (0.31 g). The aim of the research is to evaluate structural seismic design responses and to determine type and degree of damage caused by local site effect, which is the result of an alluvial basin and topographic influences. The main objective of this research is the formation of local microseismic zones based on an EQL analysis: surface spectral acceleration and amplification maps at the predominant frequency. Based on the HVSR frequency response of the core structure of Trako??an Castle and the Tower itself (fundamental and higher frequency modes), maps of surface spectral acceleration and soil amplification at different frequencies (3, 5 and 10 Hz) are developed for different input PGAROCK levels (0.08, 0.18 and 0.31 g) to evaluate seismic response of the Castle. Observed amplifications are correlated with ground motion polarization and directionality of the ground motion from the alluvial basin to the hilltop. Shortening of predominant frequencies (lengthening of the period), particularly in the alluvial basin, has been observed with higher input PGAROCK in the EQL analysis. This effect is not manifested in the Trako??an hill, and predominant frequencies match HVSR frequencies. The use of certain geophysical survey methods at historical sites is a big problem, because terrain features (e.g. steep hills, mountains, ridges, slopes, cliffs) create lack of space and make it impossible to carry out geophysical investigation. Microtremor measurements at historical sites can overcome this limitation and provide local seismic response and vulnerability behaviour of historical monuments without destroying their authenticity. Also, computational modelling can greatly improve the results. The EQL site response analysis on the site of Trako??an Castle has confirmed and improved the results of seismic response and vulnerability based on HVSR method. 相似文献
18.
V.P. Gubatenko 《Russian Geology and Geophysics》2013,54(1):102-109
We propose a heuristic method for the analytical solution of electrical-prospecting problems for direct currents and 3D isotropic media. The corresponding parameters of the medium (conductivity, magnetic permeability) are determined from Maxwell’s equations by the assignment of electric- or magnetic-field intensity in the analytical form. The application of this method is illustrated with examples. 相似文献
19.
Landslide susceptibility assessment forms the basis of any hazard mapping, which is one of the essential parts of quantitative
risk mapping. For the same study area, different susceptibility maps can be achieved depending on the type of susceptibility
mapping methods, mapping unit, and scale. Although there are various methods of obtaining susceptibility maps, the efficiency
and performance of each method should be evaluated. In this study the effect of mapping unit and susceptibility mapping method
on landslide susceptibility assessment is investigated. When analyzing the effect of susceptibility mapping method, logistic
regression (LR) which is widely used in landslide susceptibility mapping and, spatial regression (SR), which have not been
used for landslide susceptibility mapping, are selected. The susceptibility maps with logistic and spatial regression models
are obtained using two different mapping units namely slope unit-based and grid-based mapping units. The procedure for investigation
of effect of mapping unit on different susceptibility mapping methods is applied to Kumluca watershed, in Bartin Province
of Western Black Sea Region, Turkey. 18 factor maps are prepared for landslide susceptibility assessment in the study region.
Geographic information systems and remote sensing techniques are used to create the landslide factor maps, to obtain susceptibility
maps and to compare the results. The relative operating characteristics (ROC) curve is used to compare the predictive abilities
of each model and mapping unit and also the accuracy is evaluated depending on the observations made during field surveys.
By analyzing the area under the ROC curve for grid-based and slope unit-based mapping units, it can be concluded that SR model
provide better predictive performance (0.774 in grids and 0.898 in slope units) as compared to the LR model (0.744 in grids
and 0.820 in slope units). This result is also supported by the accuracy analysis. For both mapping units, the SR model provides
more accurate result (0.55 for grids and 0.57 for slope units) than the LR model (0.50 for grids and 0.48 for slopes). The
main reason for this better performance is that the spatial correlations between the mapping units are incorporated into the
model in SR while this fact is not considered in LR model. 相似文献
20.
Anil Kumar Mishra Masami Ohtsubo Loretta Y. Li Takahiro Higashi 《Environmental Earth Sciences》2012,65(1):21-27
As there are many correlations linking the liquid limit directly or indirectly with various engineering properties of the
soil, the accurate determination of the liquid limit is quite essential. Generally, two methods, i.e. Casagrande’s and fall
cone are adopted to determine the liquid limit of soil. Research was carried out to study the influence of the properties
of bentonite and the presence of the salt solution on the liquid limit values of soil-bentonite mixtures determined by the
Casagrande’s and fall cone methods. The results showed that irrespective of the presence of the type of bentonite or salt
solution, a higher value of the liquid limit was obtained by the Casagrande’s method as compared to the fall cone method.
However, the difference between the two methods decreased with the decrease in the liquid limit, clay fraction, specific surface
area and free swelling capacity of the bentonite present in the mixture. Similarly, the difference in the liquid limit values
obtained by both these methods is reduced with an increase in the salt concentration. 相似文献