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461.
Heat flow and quantity of methane deduced from a gas hydrate field in the vicinity of the Dnieper Canyon,northwestern Black Sea 总被引:1,自引:1,他引:1
Thomas?LüdmannEmail author How?Kin?Wong Philipp?Konerding Matthias?Zillmer J?rg?Petersen Ernst?Flüh 《Geo-Marine Letters》2004,24(3):182-193
Seismic reflection data document for the first time the existence of a BSR in a limited area west of the Dnieper Canyon in the northwestern Black Sea. Seismic wide-angle data suggest that gas hydrates occupy in average 15±2% of the pore space in a zone of 100 m in thickness. A conservative quantification of the amount of methane associated with this gas hydrate occurrence is about 12±3×1011 m3 (0.6±0.2 Gt of methane carbon). Conductive heat flow deduced from the BSR depth is in the range of 21±6 to 55±15 mW m–2. 相似文献
462.
Crack Coalescence in Molded Gypsum and Carrara Marble: Part 1. Macroscopic Observations and Interpretation 总被引:8,自引:5,他引:3
Cracking and coalescence behavior has been studied experimentally with prismatic laboratory-molded gypsum and Carrara marble
specimens containing two parallel pre-existing open flaws. This was done at both the macroscopic and the microscopic scales, and the results are presented in two separate papers. This paper (the first of two) summarizes the macroscopic experimental
results and investigates the influence of the different flaw geometries and material, on the cracking processes. In the companion
paper (also in this issue), most of the macroscopic deformation and cracking processes shown in this present paper will be
related to the underlying microscopic changes. In the present study, a high speed video system was used, which allowed us
to precisely observe the cracking mechanisms. Nine crack coalescence categories with different crack types and trajectories
were identified. The flaw inclination angle (β), the ligament length (L), that is, intact rock length between the flaws, and the bridging angle (α), that is, the inclination of a line linking up the inner flaw tips, between two flaws, had different effects on the coalescence
patterns. One of the pronounced differences observed between marble and gypsum during the compression loading test was the
development of macroscopic white patches prior to the initiation of macroscopic cracks in marble, but not in gypsum. Comparing
the cracking and coalescence behaviors in the two tested materials, tensile cracking generally occurred more often in marble
than in gypsum for the same flaw pair geometries.
相似文献
H. H. EinsteinEmail: |
463.
Henk Kombrink Karen A. Leever‡ Jan-Diederik van Wees† ‡ Frank van Bergen† Petra David† Theo E. Wong 《Basin Research》2008,20(3):377-395
The large thickness of Upper Carboniferous strata found in the Netherlands suggests that the area was subject to long-term subsidence. However, the mechanisms responsible for subsidence are not quantified and are poorly known. In the area north of the London Brabant Massif, onshore United Kingdom, subsidence during the Namurian–Westphalian B has been explained by Dinantian rifting, followed by thermal subsidence. In contrast, south and east of the Netherlands, along the southern margin of the Northwest European Carboniferous Basin, flexural subsidence caused the development of a foreland basin. It has been proposed that foreland flexure due to Variscan orogenic loading was also responsible for Late Carboniferous subsidence in the Netherlands. In the first part of this paper, we present a series of modelling results in which the geometry and location of the Variscan foreland basin was calculated on the basis of kinematic reconstructions of the Variscan thrust system. Although several uncertainties exist, it is concluded that most subsidence calculated from well data in the Netherlands cannot be explained by flexural subsidence alone. Therefore, we investigated whether a Dinantian rifting event could adequately explain the observed subsidence by inverse modelling. The results show that if only a Dinantian rifting event is assumed, such as is found in the United Kingdom, a very high palaeowater depth at the end of the Dinantian is required to accommodate the Namurian–Westphalian B sedimentary sequence. To better explain the observed subsidence curves, we propose (1) an additional stretching event during the Namurian and (2) a model incorporating an extra dynamic component, which might well explain the very high wavelength of the observed subsidence compared with the wavelength of the predicted flexural foreland basin. 相似文献
464.
Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L(16)(4(5))). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 degrees C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 10(6) most probable number g(-1) sediment. The phenanthrene biodegradation could be best described by the first order rate model, C=C(0)e(-kt), where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data. 相似文献
465.
By analysis of the fatty acid profiles in mussel tissues and suspended particulate matter (SPM) in water, the present study showed a significant relationship of the trophic linkage between mussels and the SPM. At seven locations from inner to outer areas along the eutrophic Tolo Harbour and Tolo Channel, Hong Kong, the composition (as percentage of total fatty acids) of both monoenoic and polyunsaturated fatty acids in the tissues of green-lipped mussels Perna viridis and SPM in water had significant correlation (p<0.01). In particular, the composition of docosahexaenoic acid (DHA, 22:6n3) (as percentage of total fatty acids) in mussel tissues was statistically correlated with that in SPM (p<0.01), implying that mussels incorporate DHA, the biomarker of dinoflagellates. Principal component analysis further demonstrated that the fatty acid profiles of SPM were different among locations in the harbour, mid and outer channel of the study area, so were the mussel tissue fatty acid profiles. Cluster analysis of phytoplankton data also revealed the dominance of diatoms in the inner harbour and channel areas, whereas dinoflagellates were abundant in the outer channel waters. The possible implications of using benthic suspension feeders such as green-lipped mussels P. viridis for controlling phytoplankton abundance in coastal waters are discussed. 相似文献
466.
Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L16(45)). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 °C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 106 most probable number g−1 sediment. The phenanthrene biodegradation could be best described by the first order rate model, C = C0e−kt, where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data. 相似文献
467.
Experimental study of the formation and propagation of three-dimensional (3D) faults is of great sig- nificance in the understanding of the propagation process developing from initial natural faults. In the study described in this paper, experimental investigations of 3D propagation processes of a type of surface fault are carried out under biaxial compression. The strain field near the surface fault is dy- namically measured and fully analyzed with a high-density Multi-Channel Digital Strain Gauge (MCDSG) and Digital Speckle Correlation Method (DSCM) based on the white-light image analysis. Simultane- ously the micro-fracture process involved in fault formation is observed by a 3D acoustic emission (AE) location system with a set of multi-channel whole-wave record equipment. The experimental results show that the 3D propagation process of surface fault differs greatly from that of the two-dimensional (2D) state and that a new more complicated type of 3D morphological characters and deformation mechanisms are produced. The 3D propagation process of surface faults may be divided into three stages: 1) the first stage of crack propagation initiated by wing cracks; 2) the conversion stage propa- gated by petal cracks; and 3) the second stage of crack propagation formed by shell-shaped fracture surface. The primary propagation patterns of the three stages are different. The corresponding defor- mation fields and micro-fracture distributions are likewise different. The fracture activities from petal cracks especially are of vital importance during surface fault propagation. This is also a key conversion state and marks an intrinsic difference between 2D-like and the 3D state in fault development. 相似文献
468.
Summary A completely new nonhydrostatic model system known as the Advanced Regional Prediction System (ARPS) has been developed in
recent years at the Center for Analysis and Prediction of Storms (CAPS) at the University of Oklahoma. The ARPS is designed
from the beginning to serve as an effective tool for basic and applied research and as a system suitable for explicit prediction
of convective storms as well as weather systems at other scales. The ARPS includes its own data ingest, quality control and
objective analysis packages, a data assimilation system which includes single-Doppler velocity and thermodynamic retrieval
algorithms, the forward prediction component, and a self-contained post-processing, diagnostic and verification package.
The forward prediction component of the ARPS is a three-dimensional, nonhydrostatic compressible model formulated in generalized
terrain-following coordinates. Minimum approximations are made to the original governing equations. The split-explicit scheme
is used to integrate the sound-wave containing equations, which allows the horizontal domain-decomposition strategy to be
efficiently implemented for distributed-memory massively parallel computers. The model performs equally well on conventional
shared-memory scalar and vector processors. The model employs advanced numerical techniques, including monotonic advection
schemes for scalar transport and variance-conserving fourth-order advection for other variables. The model also includes state-of-the-art
physics parameterization schemes that are important for explicit prediction of convective storms as well as the prediction
of flows at larger scales.
Unique to this system are the consistent code styling maintained for the entire model system and thorough internal documentation.
Modern software engineering practices are employed to ensure that the system is modular, extensible and easy to use.
The system has been undergoing real-time prediction tests at the synoptic through storm scales in the past several years over
the continental United States as well as in part of Asia, some of which included retrieved Doppler radar data and hydrometeor
types in the initial condition.
As the first of a two-part paper series, we describe herein the dynamic and numerical framework of the model, together with
the subgrid-scale turbulence and the PBL parameterization. The model dynamic and numerical framework is then verified using
idealized and realistic mountain flow cases and an idealized density current. Other physics parameterization schemes will
be described in Part II, which is followed by verification against observational data of the coupled soil-vegetation model,
surface layer fluxes and the PBL parameterization. Applications of the model to the simulation of an observed supercell storm
and to the prediction of a real case are also found in Part II. In the latter case, a long-lasting squall line developed and
propagated across the eastern part of the United States following a historical number of tornado outbreak in the state of
Arkansas.
Received April 14, 2000 Revised July 17, 2000 相似文献
469.
Changing population density is often ignored in studies of population growth and population transfer in the United States. We show that there is a complex relationship between patterns of population growth and density increase by state. The largest gains in density are in the states of the northeastern megalopolis, California, and Florida. Analysis of the 150 counties with the greatest increases in density between 1980 and 1990 shows that they are well distributed across the United States including the larger metropolitan areas of the “Rustbelt.” In general, the most densely populated states and places are becoming more densely populated, a concept we refer to as densification. 相似文献
470.
β-mannanase is an enzyme that is commonly expressed in environmental bacteria. It degrades hemicellulose found in plant material and recycles nutrients back into the environment. Because this enzyme significantly contributes to biodegradation and has recently been applied in industry, we conducted a comparative analysis of bacterial isolates found in soil samples from Schirmacher Oasis, Antarctica, and Sabah, Malaysia that were capable of degrading mannan. A total of 9 bacterial isolates from Antarctica and 30 bacterial isolates from Malaysia exhibited β-mannanase activity. These bacteria were differentiated and clustered using their random amplified polymorphic DNA (RAPD) profiles, and the β-mannanase activity of these isolates was tested at different temperatures and pH. Five out of 9 Antarctica isolates and seven out of 30 Malaysian isolates were identified based on their 16S rDNA sequences. Identified bacterial isolates from Antarctica were: MP1 (Bacillus amyloliquefaciens), MP2 (Bacillus pumilus), MP5 (Bacilluspumilus), A40 (Arthrobacter sp.), and C27 (Arthrobacter oxydans). Identified bacterial isolates from Ma- laysia were: Y1 (Paenibacillus sp.), Y2 (Bacillus sp.), Y16 (Paenibacillus sp.), Y18 (Paenibacillus sp.), A7 (Paenibacillus sp.), B26 (Streptomyces sp.), and D4 (Paenibacillus amylolyticus). β-mannanases produced by the Antarctica bacterial isolates MP1 (Bacillus amyloliquefaciens) and A40 (Arthrobacter sp.) were active at 5℃ and 20℃, respectively, while the β-mannanase pro- duced by the bacterial isolate from Malaysia, A7 (Paenibacillus sp.), was active at 35 ℃. 相似文献