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1.
P.J. Arango A. Devia A.F. Rojas C.A. Peña J.A. Ortiz E. Restrepo 《Astrophysics and Space Science》1997,256(1-2):517-521
We have been studying direct current glow discharges aiming at the production of different paint of coatings on steel substrates. In a set of preliminary experiments, long lasting (hours) discharges performed in a Nitrogen atmosphere between a stell anode (holding the substrates) and a titanium cathode separated by a small gap (few mm) produced very thin coatings of the substrates whose colour depend on the parameter of (interelectrodes gap, gas pressure, discharge current and time duration). In some conditions, the coatings showed a golden colour, typical of the Nti compound. A discussion of the results is given. 相似文献
2.
A Nel BI Pletschke CLW Jones J Kemp G Robinson PJ Britz 《African Journal of Marine Science》2017,39(2):183-192
The effect of kelp Ecklonia maxima inclusion in formulated feeds on abalone growth and gut bacterial communities has not been previously investigated in South Africa. An eight-month on-farm growth trial was conducted with sub-adult Haliotis midae (～43 mm shell length) fed graded levels of kelp in formulated feeds. Kelp inclusion (0.44–3.54% of pellet dry mass) promoted faster growth (65.7–74.5% total mass gain), with better feed and protein conversions (apparent feed conversion ratio [FCR] 1.4–1.8, apparent protein efficiency ratio [PER] 2.3–2.7), as compared with the non-supplemented feed (52.3% total mass gain, FCR 2.1, PER 1.9; p < 0.001). Abalone-gut bacterial DNA was sequenced using 16S rRNA gene pyrosequencing and the sequences were clustered into operational taxonomic units (OTUs) at a 97% similarity level. A supplementary 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) analysis was employed. The dominant OTUs differed in terms of their relative abundances, with an autochthonous Mycoplasma strain being significantly more abundant (p = 0.03) in the gut of abalone fed a kelp-supplemented feed. The DGGE band patterns displayed higher within-group variability for abalone fed the control diet, suggesting that dietary kelp inclusion promotes gut-bacteria homeostasis. This may contribute to better feed utilisation and growth in abalone fed kelp-supplemented feeds. 相似文献
3.
Age verification of rubyfish (Plagiogeneion rubiginosum) was sought using the bomb radiocarbon chronometer procedure. Stable isotopes were investigated for life history characteristics. Radiocarbon (14C) and stable isotope (δ18O and δ13C) levels were measured in micro-samples from five otoliths that had been aged using a zone count method. All the core 14C measurements were ‘pre-bomb’ indicating ages of at least 45 years, and the 14C measurements across the otolith sections suggested that the zone-count ageing method described herein is not biased. Maximum estimated age was 100 years. There was no significant between-sex difference in the von Bertalanffy growth curves. The δ18O values indicated that rubyfish are near-surface as juveniles, and move deeper with age. Adults appear to reside in 600–1000 m; this is deeper than most trawl-capture data suggest, but not implausible, and has stock assessment implications. The δ13C values reflect fish metabolic rates, trophic feeding levels and oceanographic conditions. The stable isotopes record the environmental life history of each fish, and have value in distinguishing stocks and/or indicating vertical and latitudinal migratory patterns. 相似文献
4.
Maria C. Arango Fleur O. Strasser Julian J. Bommer Ruben Boroschek Diana Comte Hernando Tavera 《Journal of Seismology》2011,15(1):19-41
Earthquake hazard along the Peru–Chile subduction zone is amongst the highest in the world. The development of a database
of subduction-zone strong-motion recordings is, therefore, of great importance for ground-motion prediction in this region.
Accelerograms recorded by the different networks operators in Peru and Chile have been compiled and processed in a uniform
manner, and information on the source parameters of the causative earthquakes, fault-plane geometries and local site conditions
at the recording stations has been collected and reviewed to obtain high-quality metadata. The compiled database consists
of 98 triaxial ground-motion recordings from 15 subduction-type events with moment magnitudes ranging from 6.3 to 8.4, recorded
at 59 different sites in Peru and Chile, between 1966 and 2007. While the database presented in this study is not sufficient
for the derivation of a new predictive equation for ground motions from subduction events in the Peru–Chile region, it significantly
expands the global database of strong-motion data and associated metadata that can be used in the derivation of predictive
equations for subduction environments. Additionally, the compiled database will allow the assessment of existing predictive
models for subduction-type events in terms of their suitability for the Peru–Chile region, which directly influences seismic
hazard assessment in this region. 相似文献
5.
The option for surface forcing correction, recently developed in the 4D-variational (4DVAR) data assimilation systems of the Regional Ocean Model System (ROMS), is presented. Assimilation of remotely-sensed (satellite sea surface height anomaly and sea surface temperature) and in situ (from mechanical and expendable bathythermographs, Argo floats and CTD profiles) oceanic observations has been applied in a realistic, high resolution configuration of the California Current System (CCS) to sequentially correct model initial conditions and surface forcing, using the Incremental Strong constraint version of ROMS-4DVAR (ROMS-IS4DVAR). Results from both twin and real data experiments are presented where it is demonstrated that ROMS-IS4DVAR always reduces the difference between the model and the observations that are assimilated. However, without corrections to the surface forcing, the assimilation of surface data can degrade the temperature structure at depth. When using surface forcing adjustment in ROMS-IS4DVAR the system does not degrade the temperature structure at depth, because differences between the model and surface observations can be reduced through corrections to surface forcing rather than to temperature at depth. However, corrections to surface forcing can generate abnormal spatial and temporal variability in the structure of the wind stress or surface heat flux fields if not properly constrained. This behavior can be partially controlled via the choice of decorrelation length scales that are assumed for the forcing errors. Abnormal forcing corrections may also arise due to the effects of model error which are not accounted for in IS4DVAR. In particular, data assimilation tends to weaken the alongshore wind stress in an attempt to reduce the rate of coastal upwelling, which seems to be too strong due to other sources of error. However, corrections to wind stress and surface heat flux improve systematically the ocean state analyses. Trends in the correction of surface heat fluxes indicate that, given the ocean model used and its potential limitations, the heat flux data from the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) used to impose surface conditions in the model are generally too low except in spring-summer, in the upwelling region, where they are too high. Comparisons with independent data provide confidence in the resulting forecast ocean circulation on timescales ～14 days, with less than 1.5 °C, 0.3 psu, and 9 cm RMS error in temperature, salinity and sea surface height anomaly, respectively, compared to observations. 相似文献
6.
The ability to utilise carbohydrates is limited for many predatory marine fishes. Graded levels of dietary carbohydrate (4.1–24.6%) were formulated using pregelatinised maize starch, to determine optimal levels for dusky kob Argyrosomus japonicus, an emerging mariculture finfish for which pelleted feeds are being developed. Specific growth rate increased with an increase in the carbohydrate level up to 16.72%, after which it declined. Feed utilisation followed a similar trend, with the best feed conversion ratio (1.28) and protein efficiency ratio (1.76) recorded at 16.4% carbohydrate. Lipid vacuolisation of the hepatocytes was evident in all livers examined, with melano-macrophage aggregates in those of fish fed 24.6% carbohydrate suggesting starvation. Gut bacterial community profiles were variable but were not influenced by dietary carbohydrate level and differed mostly between fish fed trout feed prior to the trial and those fed experimental diets containing starch. The dusky kob were able to clear glucose from their blood when fed up to 16.4% carbohydrate, but glucose removal was not achieved at 24.6% carbohydrate. In conclusion, dusky kob has a limited ability to utilise cooked starch as a carbohydrate source, which may be included in pelleted feed at 16.4% without adverse effects. For this species, levels of dietary carbohydrate above this may result in symptoms consistent with physiological breakdown, including reduced growth, reduced feed intake and feed conversion efficiency, prolonged hyperglycaemia, liver pathology and altered microbial communities in the foregut. 相似文献
7.
One hundred and three samples of granitic rock taken systematically from the Andean part of Colombia reveal that the observed variation in phosphorus content reflects the variation observed for the wholerock chemical composition. This relationship was established using a form of trend analysis termed COMTRENA and information-theory statistics. 相似文献
8.
Model evaluation experiments in the North Atlantic Basin: simulations in nonlinear terrain-following coordinates 总被引：7，自引：0，他引：7
Dale B. Haidvogel Hernan G. Arango Kate Hedstrom Aike Beckmann Paola Malanotte-Rizzoli Alexander F. Shchepetkin 《Dynamics of Atmospheres and Oceans》2000,32(3-4)
A primitive equation ocean circulation model in nonlinear terrain-following coordinates is applied to a decadal-length simulation of the circulation in the North Atlantic Ocean. In addition to the stretched sigma coordinate, novel features of the model include the utilization of a weakly dissipative, third-order scheme for tracer advection, and a conservative and constancy-preserving time-stepping algorithm. The objectives of the study are to assess the quality of the new terrain-following model in the limit of realistic basin-scale simulations, and to compare the results obtained with it against those of other North Atlantic models used in recent multi-model comparison studies.The new model is able to reproduce many features of both the wind-driven and thermohaline circulation, and to do so within error bounds comparable with prior model simulations (e.g., CME and DYNAMO). Quantitative comparison with comparable results obtained with the Miami Isopycnic Coordinate Model (MICOM) show our terrain-following solutions are of similar overall quality when viewed against known measures of merit including meridional overturning and heat flux, Florida Straits and Gulf Stream transport, seasonal cycling of temperature and salinity, and upper ocean currents and tracer fields in the eastern North Atlantic Basin. Sensitivity studies confirm that the nonlinear vertical coordinate contributes significantly to model fidelity, and that the global inventories and spatial structure of the tracer fields are affected in important ways by the choice of lateral advection scheme. 相似文献
9.
Ignacio Arango 《Soil Dynamics and Earthquake Engineering》2002,22(9-12):1067-1073
Analyses of damage data from earthquakes in the last 35 years show that very high financial losses have resulted from cases where liquefaction of soils was associated with ground lateral displacements towards a free boundary such as a shoreline, a river channel, or an open trench. Lateral displacements in excess of 10 m have been documented in the literature [Bartlett and Youd, J. Geotech. Engng, ASCE 121 (1995) 316]. In fact, in many cases, displacements amounting to only a fraction of this number are capable of causing considerable disruption to man-made works. Several factors contribute to the extent of lateral spreading: surface and subsurface geometry, soil characteristics, and intensity of ground motion.
Ground displacements can be minimized or even arrested in practice with an underground structure properly designed to counter the driving forces, gravity and inertia combined. Mitchell et al. suggested practical guidance for the design of such structures, or barriers, in 1998 [Geotech. Spec. Publ. 75 (1998) 580]. However, to date there is no standard procedure to carry out the analysis of such barriers. The paper describes several recent designs of underground barriers that have been constructed in highly seismic environments. Three types of underground barriers are described: clay fill, a grid of structural piles, and a grid of cement-treated soil. The design of the cement-treated cell barrier is discussed in detail as it accounts for the most unfavorable combination of all forces acting on the structure: lateral stresses induced by liquefied soil, hydrodynamic effects, inertia forces, and loss of ground. 相似文献
10.
Spatial and temporal distribution and characteristics of three eukaryotic biofilms were monitored for an 18-month period in an acid mine drainage environment at the Green Valley coalmine in Indiana, USA. Each biofilm is dominated (>90 %) by a single eukaryotic microorganism based on enumeration: Euglena mutabilis, the diatom species Nitzschia tubicola, and a filamentous alga belonging to the genus Klebsormidium sp. The E. mutabilis-dominated biofilm occurs year round, covering up to 100 % of the channel bottom in spring and fall. The N. tubicola-dominated biofilm is less abundant, exists as small patches in spring and fall, expands from these patches to cover up to 50 % of the channel bottom in June, and is absent in winter. The Klebsormidium-dominated biofilm is restricted to small patches covering <5 % of the channel bottom from spring through fall and is absent in winter. Also present are floating microbial scum layers. The eukaryotic biofilms and scum layers contribute to the attenuation of precipitates and to the formation of organosedimentary structures, or stromatolites, by trapping and binding chemical precipitates via aerotaxis and phototaxis and by serving as a medium for passive accumulation of precipitates. Each stromatolite layer represents the morphological characteristics of each eukaryotic biofilm that served as the architect of the layer and the time of year the biofilm populated the channel. Processes involved in stromatolite formation also attenuate chemical sediments by binding them to the channel bottom and prior stromatolite surface rather than allowing them to be carried to the adjacent drainage system where they may become bioavailable to other forms of life. 相似文献