Algae is an informal term used to describe a broad group of simple organisms from the plant kingdom. The organisms included within this grouping are aquatic photosynthetic biota with an extensive range of life habits and forms. These organisms range from micron-sized unicellular forms to giant seaweeds and kelps, which can grow to several metres long. Both benthic and planktonic modes of life are known and display a wide variety of life cycles. 相似文献
Geotectonics - Study of morphometric parameters such as stream length (Lu) and stream length ratios (Rl), bifurcation ratio (Rb), drainage density (D), form factor (Rf), circularity ratio (Rc),... 相似文献
Exhumed basin margin‐scale clinothems provide important archives for understanding process interactions and reconstructing the physiography of sedimentary basins. However, studies of coeval shelf through slope to basin‐floor deposits are rarely documented, mainly due to outcrop or subsurface dataset limitations. Unit G from the Laingsburg depocentre (Karoo Basin, South Africa) is a rare example of a complete basin margin scale clinothem (>60 km long, 200 m‐high), with >10 km of depositional strike control, which allows a quasi‐3D study of a preserved shelf‐slope‐basin floor transition over a ca. 1,200 km2 area. Sand‐prone, wave‐influenced topset deposits close to the shelf‐edge rollover zone can be physically mapped down dip for ca. 10 km as they thicken and transition into heterolithic foreset/slope deposits. These deposits progressively fine and thin over tens of km farther down dip into sand‐starved bottomset/basin‐floor deposits. Only a few km along strike, the coeval foreset/slope deposits are bypass‐dominated with incisional features interpreted as minor slope conduits/gullies. The margin here is steeper, more channelized and records a stepped profile with evidence of sand‐filled intraslope topography, a preserved base‐of‐slope transition zone and sand‐rich bottomset/basin‐floor deposits. Unit G is interpreted as part of a composite depositional sequence that records a change in basin margin style from an underlying incised slope with large sand‐rich basin‐floor fans to an overlying accretion‐dominated shelf with limited sand supply to the slope and basin floor. The change in margin style is accompanied with decreased clinoform height/slope and increased shelf width. This is interpreted to reflect a transition in subsidence style from regional sag, driven by dynamic topography/inherited basement configuration, to early foreland basin flexural loading. Results of this study caution against reconstructing basin margin successions from partial datasets without accounting for temporal and spatial physiographic changes, with potential implications on predictive basin evolution models. 相似文献
Natural Resources Research - This study tested and compared the mineral potential mapping capabilities of the random forest (RF) and maximum entropy (MaxEnt) algorithms using gold deposit... 相似文献
Natural Resources Research - Machine learning (ML) schemes can enhance success in geochemical prospectivity mapping. This study has examined the effectiveness of several feature extraction or... 相似文献
Natural Resources Research - High-volatile bituminous coal samples were reacted in deionized water with supercritical CO2 (ScCO2–water) under simulated in situ pressure and temperature... 相似文献
Oceanology - New data are presented on sedimentary matter fluxes and its main components along a meridional transect (59°30′ N) in the North Atlantic under the effect of multidirectional... 相似文献
Izvestiya, Atmospheric and Oceanic Physics - An investigation into mesoscale roll circulation and its transport characteristics in the atmospheric boundary layer (ABL) is carried out. The case... 相似文献
It has been shown that the model of a scattering medium composed of clusters located in the far zones of each other allows some properties of regolith-like surfaces to be quantitatively estimated from the phase dependences of intensity and polarization measured in the backscattering domain. From the polarization profiles, the sizes of particles, the structure and porosity of the medium, and a portion of the surface area covered with a disperse material can be determined. At the same time, the intensity profiles of the scattered light weakly depend on the sizes and structure of particles; they are mainly controlled by the concentration of scatterers in the medium and the shadow-hiding contribution at small phase angles. Since the latter effect is beyond the considered model, a good agreement between the model and the measured intensity cannot be achieved. Nevertheless, if a portion of the surface that participates in coherent backscattering has been found from the phase profile of polarization, the present model makes it possible to determine the relative contribution of the shadow-hiding effect to the brightness surge measured at zero phase angle. This, in turn, may allow the roughness of the scattering surface to be estimated. The model contains no free parameters, but there is currently no possibility to verify it comprehensively by the data obtained in laboratory measurements of the samples with thoroughly controlled characteristics, because such measurements are rare for a wide range of the properties of particles in a medium, their packing density, and phase angles.
Oued Awlitis 001 is a highly feldspathic, moderately equilibrated, clast‐rich, poikilitic impact melt rock lunar meteorite that was recovered in 2014. Its poikilitic texture formed due to moderately slow cooling, which judging from textures of rocks in melt sheets of terrestrial impact structures, is observed in impact melt volumes at least 100 m thick. Such coherent impact melt volumes occur in lunar craters larger than ~50 km in diameter. The composition of Oued Awlitis 001 points toward a crustal origin distant from incompatible‐element‐rich regions. Comparison of the bulk composition of Oued Awlitis 001 with Lunar Prospector 5° γ‐ray spectrometer data indicates a limited region of matches on the lunar farside. After its initial formation in an impact crater larger than ~50 km in diameter, Oued Awlitis 001 was excavated from a depth greater than ~50 m. The cosmogenic nuclide inventory of Oued Awlitis 001 records ejection from the Moon 0.3 Ma ago from a depth of at least 4 m and little mass loss due to ablation during its passage through Earth's atmosphere. The terrestrial residence time must have been very short, probably less than a few hundred years; its exact determination was precluded by a high concentration of solar cosmic ray‐produced 14C. If the impact that excavated Oued Awlitis 001 also launched it, this event likely produced an impact crater >10 km in diameter. Using petrologic constraints and Lunar Reconnaissance Orbiter Camera and Diviner data, we test Giordano Bruno and Pierazzo as possible launch craters for Oued Awlitis 001. 相似文献