Bioclogging and biocementation can be used to improve the geotechnical properties of sand. These processes can be performed by adsorption of urease-producing bacterial cells on the sand grain surfaces, which is followed by crystallization of calcite produced from the calcium salt and urea solution due to bacterial hydrolysis of urea. In this paper, the effect of intact cell suspension of Bacillus sp. strain VS1, suspension of the washed bacterial cells, and culture liquid without bacterial cells on microbially induced calcite precipitation in sand was studied. The test results showed that adsorption/retention of urease activity on sand treated with washed cells of Bacillus sp. strain VS1 was 5–8 times higher than that treated with culture liquid. The unconfined compressive strength of sand treated with the suspension of washed cells was 1.7 times higher than that treated with culture liquid. This difference could be due to fast inactivation of urease by protease which was present in the culture liquid. The adsorption of bacterial cells on sand pretreated with calcium, aluminum, or ferric salts was 29–37 % higher as compared with that without pretreatment. The permeability of sand varied with the content of precipitated calcium. For bioclogging of sand, the content of precipitated calcium had to be 1.3 % (w/w) or higher. The shear strength of biotreated sand was also dependent on the content of precipitated calcium. To achieve an unconfined compressive strength of 1.5 MPa or higher, the content of precipitated calcium in the treated sand had to be 4.2 % (w/w) or higher. These data can be used as the reference values for geotechnical applications such as bioclogging for reducing the permeability of sand and biocementation for increasing the shear strength of soil. 相似文献
Using the observational data of the Stanford observatory on photospheric magnetic fields for 1976?C2001, we separate open and closed configurations of the magnetic field with a filter of a specified spatial scale and demonstrate that the 11-year solar cycle passes two significantly different phases. 相似文献
The present status of the nuclear reaction rates determining the solar neutrino flux is discussed. This includes the reaction
rates for the two branching ratios of the three pp-chains involving the reactions 3He(3He,2p)4He and 3He(4He,γ)7Be for the
first branching, and 7Be(e−, νe)7Li and 7Be(p, γ)8B for the second branching. Mainly we will concentrate on the basic nuclear
reaction p + p → D + e+ + νe of the pp-chains. This reaction rate can only be determined using the theoretical methods. The
present status of the application of the relativistic field theory model of the deuteron for this reaction will be discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
ABSTRACT This paper presents new geochemical data on gas-hydrate-bearing mud volcanoes discovered for the first time in the Gulf of Cadiz during cruises TTR9 and TTR10 of the R/V Professor Logachev in 1999–2000. The estimated gas hydrate content is 3–16% of sediment volume and 5–31% of pore space volume. Estimated values of the water isotopic composition for the Ginsburg mud volcano are very heavy for δ18O (up to +53‰) and light for δD (up to − 210‰). Gas released from the hydrates contains 81% of C1 and 19% of C2+. The inferred source of the gas in the hydrates is enriched in C2–C6 (≤ 5%), indicating that the gas has a thermogenic origin. Gas hydrate of cubic structure II should be formed from a gas of such composition. It is interpreted that the composition of the mud volcano fluid corresponds to deep oil basins below the Gulf of Cadiz. 相似文献
Doklady Earth Sciences - Using the remote sensing data obtained by the Sentinel-1A and Sentinel-1B satellites in the years 2016–2021, a local accumulation of oil slicks in the Barents Sea in... 相似文献
Optical fibre–based sensors have now established their place in the field of geohazard monitoring due to their sensitivity to strain and temperature changes. Progressive development in the technology leads to the availability of novel, accurate and durable sensors at a relatively limited cost. This creates room for original monitoring applications that have been, so far, impeded by the shortcomings of conventional monitoring tools. In this work, we explore the applicability of an interferometric optical fibre sensor as a vibration sensing tool at laboratory scale. We tested the ability of the sensor to identify precursors of instability in a downscaled model of a rainfall-induced landslide composed of granular material. We carried out four experimental tests which involved different sensor deployments and soil mixtures. The recorded signals were processed by means of a time–frequency analysis and we identified two frequency-domain parameters—the spectral centroid and band power—that could provide information on the development of instability. Their ratio yielded a unique parameter through which a precursory stage could be outlined by defining a threshold value based on the data collected at the beginning of the experiment. In our lab tests, precursors of instability were detected 2–3 min before a crack was observed at the surface. This may upscale to a lead time of about 20–30 min or more in the field, classifying our monitoring approach in between an alarm and a warning system. The work presented here can be considered a first promising step towards an innovative monitoring system and shows the potential of optical fibre sensing as a shallow landslide monitoring technique, encouraging further testing, especially in real-case studies.
The results of studying the temporal variability of atmospheric circulation in the Western Arctic (the Norwegian and Barents seas) are presented. The daily dataset of Girs-Vangengeim E, W, and C circulation forms for the period of 1891–2016 is used to describe atmospheric circulation. Special attention is given to the estimation of differences in weather conditions during the modern period of warming (1985–2015) and in the period of the first Arctic warming (1920–1950). For the cold (November-March) and warm (April-October) seasons, the trends in the frequency of occurrence of the circulation forms are determined. The occurrence of the number of consecutive days with the same atmospheric circulation form which can be considered as a characteristic of weather stability during the analyzed period of warming, is computed for both seasons. The prevalence of the E circulation form during the warm season is typical of both periods. The modern period of warming in the study area, as compared to the period of the first warming, is characterized by an increase in the occurrence of the C circulation form with a short duration. It is found that the current climate regime is characterized by an increase in surface air temperature against a background of less stable weather conditions. 相似文献
We reconstruct mean magnitudes of the open solar magnetic field since 1915 using α magnetic synoptic charts of the Sun. The
obtained series allows estimation of the interplanetary magnetic field. They also confirm the known conclusion about the secular
increase of the solar open magnetic flux in the first half of the 20th century. 相似文献
Astrophysics - The asymptotic results obtained above admit generalizations. First, one can take into account polarization. For an isotropic medium with arbitrary S matrix, allowance for... 相似文献