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Hernando, Louis, Aziz Omari i David Reungoat. "Experimental study of sedimentation of concentrated mono-disperse suspensions: Determination of sedimentation modes". Powder Technology 258 (maj 2014): 265–71. http://dx.doi.org/10.1016/j.powtec.2014.03.037.
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XIA, ZHENHUA, KEVIN W. CONNINGTON, SAIKIRAN RAPAKA, PENGTAO YUE, JAMES J. FENG i SHIYI CHEN. "Flow patterns in the sedimentation of an elliptical particle". Journal of Fluid Mechanics 625 (14.04.2009): 249–72. http://dx.doi.org/10.1017/s0022112008005521.
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We study the dynamics of a single two-dimensional elliptical particle sedimenting in a Newtonian fluid using numerical simulations. The main emphasis in this work is to study the effect of boundaries on the flow patterns observed during sedimentation. The simulations were performed using a multi-block lattice Boltzmann method as well as a finite-element technique and the results are shown to be consistent. We have conducted a detailed study on the effects of density ratio, aspect ratio and the channel blockage ratio on the flow patterns during sedimentation. As the channel blockage ratio is varied, our results show that there are five distinct modes of sedimentation: oscillating, tumbling along the wall, vertical sedimentation, horizontal sedimentation and an inclined mode where the particle sediments with a non-trivial orientation to the vertical. The inclined mode is shown to form a smooth bridge between the vertical and horizontal modes of sedimentation. For narrow channels, the mode of sedimentation is found to be sensitively dependent on the initial orientation of the particle. We present a phase diagram showing the transitions between the various modes of sedimentation with changing blockage ratio of the channel.
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Gubaidullin, Damir, Rinat Zaripov i Liudmila Tkachenko. "Dynamics of nonlinear waves in the tubes filled with aerosol". MATEC Web of Conferences 148 (2018): 01002. http://dx.doi.org/10.1051/matecconf/201814801002.
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The results of experimental investigations of nonlinear oscillations of finely dispersed aerosol in the tube with various geometry on the end in the shock-wave, the shock-free wave modes and in the mode of transition to shock waves near the resonance frequency are presented. The time dependences of the numerical concentration of the oscillating aerosol droplets are presented. The effect of the frequency and amplitude of the piston displacement and the influence of the diaphragm internal diameter on the time coagulation and sedimentation of aerosol were studied. An increase in the amplitude of the piston displacement in all modes results in acceleration of the process of coagulation and sedimentation of aerosol. The dependence of time of coagulation and sedimentation of aerosol on the excitation frequency was found to be of a nonmonotonic character with the minimum value upon the resonance frequency.
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Shen, Liang, Han Xiao, Wan Qiu Yang, De Ren Miao i Xiao Ming Li. "Study on Biological Aerated Filter as Enhanced Pretreatment Process of Coagulation and Sedimentation". Advanced Materials Research 726-731 (sierpień 2013): 1940–44. http://dx.doi.org/10.4028/www.scientific.net/amr.726-731.1940.
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Using coagulation and sedimentation process in the advanced treatment of urban secondary effluent which can be recycled to circulating cooling water system in power plant is only perform well on CODCrand turbidity removal. But the concentrations of organic matter and NH3in effluent can not meet the requirements of circulating cooling water. Therefore, in this study, the feasibility of biological aerated filter (BAF) as a pretreatment enhancing coagulation and sedimentation process was discussed. Achieved by controlling the two operating modes: (1) secondary effluentcoagulation and sedimentationeffluent; (2) secondary effluent BAFcoagulation and sedimentation effluent.The results show that the BAF pretreatment removes ammonia nitrogen effectively, and the turbidity and CODCrof effluent of BAF-coagulation sedimentation process is much lower than individual coagulation and sedimentation process. The final effluent qualities meet the requirements of circulating cooling water system in power plant.
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Minelli, Caterina, Aneta Sikora, Raul Garcia-Diez, Katia Sparnacci, Christian Gollwitzer, Michael Krumrey i Alex G. Shard. "Measuring the size and density of nanoparticles by centrifugal sedimentation and flotation". Analytical Methods 10, nr 15 (2018): 1725–32. http://dx.doi.org/10.1039/c8ay00237a.
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Dietze, E., F. Maussion, M. Ahlborn, B. Diekmann, K. Hartmann, K. Henkel, T. Kasper, G. Lockot, S. Opitz i T. Haberzettl. "Sediment transport processes across the Tibetan Plateau inferred from robust grain size end-members in lake sediments". Climate of the Past Discussions 9, nr 4 (21.08.2013): 4855–92. http://dx.doi.org/10.5194/cpd-9-4855-2013.
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Abstract. Grain size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain size end-member modelling analysis. Between three and five robust grain size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to sediment transport and depositional processes associated with certain climatic background and catchment configurations. The coarse sands and clays with grain size modes > 250 μm and < 2 μm were probably transported by fluvial processes. Aeolian sands (~ 200 μm) and coarse local dust (~ 60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ~ 25 μm may derive from near-by sources that keep in longer-term suspension. The continuous background dust is differentiated into two robust end-members (modes: 5–10 and 2–5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain size end-members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19 ± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.
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Dietze, E., F. Maussion, M. Ahlborn, B. Diekmann, K. Hartmann, K. Henkel, T. Kasper, G. Lockot, S. Opitz i T. Haberzettl. "Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments". Climate of the Past 10, nr 1 (16.01.2014): 91–106. http://dx.doi.org/10.5194/cp-10-91-2014.
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Abstract. Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly–likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes >250 μm and <2 μm were probably transported by fluvial processes. Aeolian sands (~200 μm) and coarse local dust (~60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ~25 μm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5–10 and 2–5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.
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Teťák, František. "The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)". Geologica Carpathica 61, nr 3 (1.06.2010): 201–9. http://dx.doi.org/10.2478/v10096-010-0011-6.
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The gravity flow dynamics of submarine fan sedimentation in the Magura Basin of the Western Carpathians (Magura Nappe, Slovakia)This article deals with the dynamics of the deep-water gravity flows sedimentation within the Magura Formation. This investigation is based on analysis of the Magura sandstone sedimentary structures studied on the outcrops. The final comparison of the sedimentary structures and cycles with the paleocurrent directions provided an interpretation of the gravity flows dynamics and helped to restore the migration of the sandy lobes in space and time. Three modes of sedimentation are recorded: regular cyclic sedimentation from the lobe, irregular sedimentation from the immature lobe and pelitic sedimentation on the basin plane without the lobe influence. We compared the occurrence of some sedimentary structures with the changes of the current directions and bed thickness. The following interpretations of gravity flow fan dynamics are results of this comparision: the fan consists of one or several lobes, the lobe branches out into branches with the radial current arrangement, the lobes laterally change position and the lobes suddenly die out.
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V. I. Donenko, O. M. Nazarenko, I. A. Nazarenko, M. P. Marchenko i V. P. Sulima. "Technical advantages of the city sedimentation water reconstruction system". Ways to Improve Construction Efficiency, nr 45 (16.10.2020): 26–36. http://dx.doi.org/10.32347/2707-501x.2020.45.26-36.
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The work designs a system of production components of urban infrastructure to create an energy efficient city. Hydraulic, hydrological, heat exchange processes of interaction of water structure and elements of treatment structures for centrifugal deposition of suspended matter have been investigated. Depending on the degree of contamination, devices for resource recovery are calculated. The duration of recovery operations was investigated. The technological cycle of re-water recovery and the number of cycles of cavitation generator for controlled conditioning of conditionally clean and dirty waters have been determined. Reverse osmosis devices for the recovery of conditionally pure water have been investigated. Categorized potential effluents of industrial waters as appropriate for restoration. Samples of experimental sediments for the needs of the construction industry at operating and supercritical modes of operation of the technological stream were obtained. A mathematical model of the productivity of irrigation of agro-centers in drought conditions with drip irrigation by repeated water has been developed.
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Kidwell, Susan M. "Models for fossil concentrations: paleobiologic implications". Paleobiology 12, nr 1 (1986): 6–24. http://dx.doi.org/10.1017/s0094837300002943.
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Four basic types of skeletal concentrations are modeled in terms of changes in sedimentation rate alone. The model categorizes fossil concentrations on the relatively objective basis of their bed contacts, and uses this criterion to infer directional shifts in net sedimentation. This radical simplification of accumulation histories, in which hardpart input is held constant, yields a surprisingly powerful model capable of predicting a broad spectrum of taphonomic and paleobiologic phenomena. Type I concentrations grade from less fossiliferous sediments and terminate in omission surfaces; if hardpart supply is held constant, they record a slowdown from positive to zero net sedimentation. Type II concentrations are the same as Type I but terminate in erosion surfaces (slowdown to negative net sedimentation), and Type III and IV concentrations are characterized by basal erosion or omission surfaces, respectively, grade upward into less fossiliferous sediments, and record increases in net sedimentation from negative or zero rates to positive rates. According to the model, samples collected from successive horizons within any of these shell beds will differ in the degree and type of post-mortem bias owing to differing histories of hardpart exposure at the depositional interface. Moreover, because rates of sediment accumulation govern the abundance of hardparts at the depositional interface and thus many of the physical characteristics of the benthic habitat, the dynamics of fossil accumulation have direct consequences for the structure of benthic communities (taphonomic feedback) and for ecologically controlled species morphometry.The model is highly robust to fluctuations in hardpart input, as judged by its ability to correctly infer modes of formation of concentrations in synthetic stratigraphic sections. In addition, field examples of Type I–IV concentrations show independent evidence of formation during intervals of reduced net sedimentation, and many exhibit trends in taphonomic and paleobiologic features expected from the postulated changes in net sedimentation. The model thus provides a testable working hypothesis for the accumulation of fossil material in a wide range of environments, and should be applicable to concentrations of any taxonomic composition, state of preservation, or geologic age. The power and robustness of this heuristic model in fact argue that fossil-rich and fossil-poor strata provide fundamentally different records of past conditions, and that sedimentation rather than hardpart input is the primary control on the nature of the fossil record.
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Marcou, Olivier, Bastien Chopard, Samira El Yacoubi, Boussad Hamroun, Laurent Lefèvre i Eduardo Mendes. "A Lattice Boltzmann Model to Study Sedimentation Phenomena in Irrigation Canals". Communications in Computational Physics 13, nr 3 (marzec 2013): 880–99. http://dx.doi.org/10.4208/cicp.371011.260112s.
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AbstractFresh water is one of the most significant resources for human activities and survival, and irrigation is among the most important uses of water. The sustainibility and performance of irrigation canals can be greatly affected by sediment transport and deposition. In our previous works, we proposed a Lattice Boltzmann model for simulating a free surface flow in an irrigation canal, as an alternative to more traditional models mainly based on shallow water equations. Here we introduce the sedimentation phenomenon into our model by adding a new algorithm, based on the earlier work by B. Chopard, A. Dupuis and A. Masselot [9,11,12,27]. Transport, erosion, deposition and toppling of sediments are taken into account and enable the global sedimentation algorithm to simulate different transport modes such as bed load and suspended load. In the present work, we study both the behaviour of a sediment deposit located at an underflow submerged gate (depending on the gate opening and the flow discharge) and the influence of the presence of such a deposit on the flow. Both numerical and experimental validations have been performed. The experiments were realized on the micro-canal of the LCIS laboratory at Valence, France. The comparisons between simulations and experiments give good qualitative agreement.
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Gruziel-Słomka, Magdalena, Paweł Kondratiuk, Piotr Szymczak i Maria L. Ekiel-Jeżewska. "Stokesian dynamics of sedimenting elastic rings". Soft Matter 15, nr 36 (2019): 7262–74. http://dx.doi.org/10.1039/c9sm00598f.
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We study numerically the dynamics of elastic microfilaments which form closed loops and settle under gravity in a viscous fluid. We observe diversity of periodic and stationary sedimentation modes, dependent on flexibility and initial configuration.
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Weisenstein, D. K., J. E. Penner, M. Herzog i X. Liu. "Global 2-D intercomparison of sectional and modal aerosol modules". Atmospheric Chemistry and Physics 7, nr 9 (8.05.2007): 2339–55. http://dx.doi.org/10.5194/acp-7-2339-2007.
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Abstract. We present an intercomparison of several aerosol modules, sectional and modal, in a global 2-D model in order to differentiate their behavior for tropospheric and stratospheric applications. We model only binary sulfuric acid-water aerosols in this study. Three versions of the sectional model and three versions of the modal model are used to test the sensitivity of background aerosol mass and size distribution to the number of bins or modes and to the prescribed width of the largest mode. We find modest sensitivity to the number of bins (40 vs. 150) used in the sectional model. Aerosol mass is found to be reduced in a modal model if care is not taken in selecting the width of the largest lognormal mode, reflecting differences in sedimentation in the middle stratosphere. The size distributions calculated by the sectional model can be better matched by a modal model with four modes rather than three modes in most but not all situations. A simulation of aerosol decay following the 1991 eruption of Mt. Pinatubo shows that the representation of the size distribution can have a signficant impact on model-calculated aerosol decay rates in the stratosphere. Between 1991 and 1995, aerosol extinction and surface area density calculated by two versions of the modal model adequately match results from the sectional model. Calculated effective radius for the same time period shows more intermodel variability, with a 20-bin sectional model performing much better than any of the modal models.
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Nascimento, Alexandre Ferreira do, Sheila Aparecida Correia Furquim, Eduardo Guimarães Couto, Raphael Moreira Beirigo, Jairo Calderari de Oliveira Júnior, Plínio Barbosa de Camargo i Pablo Vidal-Torrado. "Genesis of textural contrasts in subsurface soil horizons in the Northern Pantanal-Brazil". Revista Brasileira de Ciência do Solo 37, nr 5 (październik 2013): 1113–27. http://dx.doi.org/10.1590/s0100-06832013000500001.
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The Pantanal region can be characterized as a quaternary floodplain with predominant sedimentation in the form of alluvial fans. In the geomorphologic and sedimentary evolution, the avulsion process is inherent to this depositional system and its dynamics, together with surface water floods, influence soil sedimentation on this plain. The knowledge and differentiation of these two events can contribute to a better understanding of the variability of soil properties and distribution under the influence of these sedimentation processes. Therefore, this study investigated the genesis of soils in the Northern Pantanal with textural contrasts in deeper horizons and their relationship with the depositional system dynamics. We analyzed four soil profiles in the region of Barão de Melgaço, Mato Grosso State, Brazil (RPPN SESC Pantanal). Two profiles were sampled near the Rio Cuiabá (AP1 and AP4) and two near the Rio São Lourenço (AP10 and AP11). In AP11, the horizons contrast in particle size between the profile basis and the surface. In AP1, AP4 and AP10, the horizons overlaying the sand layer have similar particle size properties, mainly in terms of sand distribution. In the first case, floods (surface water) seem to have originated the horizons and layers with contrasting texture. In the second case, avulsion is the most pronounced process. Therefore, the two modes can form soils with contrasting texture that are discriminable by soil morphology, based on the distinct features associated to the specific sedimentation processes.
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Weisenstein, D. K., J. E. Penner, M. Herzog i X. Liu. "Global 2-D intercomparison of sectional and modal aerosol modules". Atmospheric Chemistry and Physics Discussions 6, nr 6 (7.12.2006): 12729–67. http://dx.doi.org/10.5194/acpd-6-12729-2006.
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Abstract. We present an intercomparison of two aerosol modules, one sectional, one modal, in a global 2-D model in order to differentiate their behavior for tropospheric and stratospheric applications. We model only binary sulfuric acid-water aerosols in this study. Two versions of the sectional model and three versions of the modal model are used to test the sensitivity of background aerosol mass and size distribution to the number of bins or modes and to the prescribed width of the largest mode. We find modest sensitivity to the number of bins (40 vs 150) used in the sectional model. Aerosol mass is found to be reduced in a modal model if care is not taken in selecting the width of the largest lognormal mode, reflecting differences in sedimentation in the middle stratosphere. The size distributions calculated by the sectional model can be better matched by a modal model with four modes rather than three modes in most but not all situations. A simulation of aerosol decay following the 1991 eruption of Mt. Pinatubo shows that the representation of the size distribution can have a signficant impact on model-calculated aerosol decay rates in the stratosphere. Between 1991 and 1995, aerosol mass and surface area density calculated by two versions of the modal model adequately match results from the sectional model. Calculated effective radius for the same time period shows more intermodel variability.
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Ksenofontov, B., E. Senik i M. Ivanov. "Analysis of hydraulic modes of operation of the divergent plates block of the flotation-sedimentation tank". IOP Conference Series: Materials Science and Engineering 492 (13.03.2019): 012024. http://dx.doi.org/10.1088/1757-899x/492/1/012024.
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Meldahl, Keith H. "Biogenic and Physical Modes of Stratification and Shell Bed Formation in the Recent Intertidal Environments of Bahia la Choya, Northern Gulf of California". Paleontological Society Special Publications 2 (1987): 177–88. http://dx.doi.org/10.1017/s2475262200004809.
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Fossil concentrations such as shell beds are preferred collection sites for paleontological and paleoecological data. Although ample attention has been paid to the roles and implications of physical processes in shell bed formation, the role of biogenic sediment reworking in generating shell beds has received little study.Subsurface shell beds in the Recent intertidal environment at Bahia la Choya form via three distinct processes: storm deposition, tidal channel migration, and biogenic reworking. Shell beds on the outer tidal flats are produced primarily by storm sedimentation. Lateral migration of the main tidal channel produces shell beds along the channel margins. Shell beds on the inner flats distant from the main tidal channel are generated by vertical “conveyorbelt” recycling of fine sediment by deposit feeders. Biogenic reworking concentrates shells at depth into subsurface shell beds, producing a distinct form of biogenic bedding, termed biogenic stratification.These three modes of shell bed formation leave recognizable taphonomic and sedimentologic signatures. Biogenic stratification in particular has important implications for sedimentation rates, sediment reworking, and faunal condensation in ancient strata.
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Shao, Yun-Chuan, Chen-Yen Hung i Yi-Ju Chou. "Numerical study of convective sedimentation through a sharp density interface". Journal of Fluid Mechanics 824 (6.07.2017): 513–49. http://dx.doi.org/10.1017/jfm.2017.349.
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We conduct numerical simulations using the Eulerian–Lagrangian approach to investigate the formation of the leaking, finger, and stable-settling modes in convective sedimentation when a sediment-laden fluid layer descends through a sharply stratified ambient flow. We show that the temporal evolution of the sedimentation process for the leaking mode can be divided into three stages, including (in temporal order) Rayleigh–Taylor instability, convection, and leaking stages. The presence of sheet-like descending plumes of suspended particles is an important characteristic of the leaking mode, which marks the existence of the leaking stage. For larger particles, the motion is more dominated by gravitational settling and less affected by buoyancy-induced flow motion. The resulting lack of the leaking stage for the larger-particle case leads to persistent finger-like plumes of suspended particles, known as the finger mode. The stable-settling mode occurs when the particles are large and the concentration is dilute such that flow motion due to Rayleigh–Taylor instability has no effect on the particle motion, and the convective motion of suspended particles is insignificant. For the third stage of the leaking mode, which is also the final stationary state, we derive the criterion for the occurrence of the leaking pattern from a scaling argument of the viscous boundary layer. The criterion is further confirmed by the present simulation results and previous laboratory experiments. Through analysis of the energy budget and the vertical flux, we show that although the settling of individual particles is accelerated, the presence of the sheet-like descending plumes in the leaking mode does not contribute to an efficient settling enhancement compared with the finger mode and the Rayleigh–Taylor instability, i.e., the cases with no background stratification. This implies a negative effect on the settling enhancement for small suspended particles when a stable background density stratification exists. In addition, simulations using the equilibrium Eulerian description for the suspended particles are also conducted to examine the difference between the present Lagrangian particle approach and the conventional Eulerian model.
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Doroshenko, Ya V., О. М. Karpash i B. N. Hozhaiev. "The Investigation of the Composition of Pipeline Gas-liquid Flows and the Effect of Their Harmful Impurities on the Modes of Pumping, Energy Requirements of Transportation n". Prospecting and Development of Oil and Gas Fields, nr 4(73) (30.12.2019): 35–45. http://dx.doi.org/10.31471/1993-9973-2019-4(73)-35-45.
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Based on the analysis of the composition of gas-liquid flows of various pipelines (trunk, field and gathering gas pipelines, oil pipelines, heat pipelines, water pipelines), it is established that diverse harmful impurities are contained in the interior of almost all operated metal pipelines, regardless of the purpose of pipelines use. In most cases, pipelines contain a complex multicomponent mixture of harmful impurities of various origins: gas conden-sate, water, machine oil, products of in-line corrosion, rock particles removed from the well, incrustation exfoliat-ed from the pipes, paraffins, various mineral salts, sludge deposits, sand, soil, biofilm, etc. The types and properties of distinctive harmful impurities positioned in the interior of various metal pipelines are described; the reasons for their presence in pipeline gas-liquid flows are determined. Depending on the purpose of the pipeline, harmful im-purities can be accumulated in its interior, be sedimentated on the internal walls or move in the flow of the trans-ported product. The parameters influencing significantly the accumulation in the interior of various pipelines and the sedimentation of various harmful impurities on the inner walls of pipelines are considered. Possible locations of their accumulation or sedimentation are presented. The analysis of the negative consequences that occur in the case of accumulation or sedimentation of harmful impurities in the interior of the pipelines, their movement along the pipeline and collision with the wall of shaped elements (bends, T-bends, adapters, etc.) is made. The author presents the main criteria according to which the hydraulic condition of pipelines polluted with harmful impuri-ties is evaluated, and on which energy requirements of transportation depend.
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Nowaczyk, N. R., E. M. Haltia, D. Ulbricht, V. Wennrich, M. A. Sauerbrey, P. Rosén, H. Vogel i in. "Chronology of Lake El'gygytgyn sediments". Climate of the Past Discussions 9, nr 3 (7.06.2013): 3061–102. http://dx.doi.org/10.5194/cpd-9-3061-2013.
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Abstract. A 318 m long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El'gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chrono-stratigraphic methods. The 12 km wide lake is sited in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the Earth's magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El'gygytgyn occurred in concert with global climatic cycles. The upper ~160 m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka−1, whereas the lower 160 m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka−1.
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Hyun, Sangmin, Jang Jun Bahk, Bong-Chool Suk i Byong-Kwon Park. "Alternative modes of Quaternary pelagic biosiliceous and carbonate sedimentation: A perspective from the East Sea (Japan Sea)". Palaeogeography, Palaeoclimatology, Palaeoecology 247, nr 1-2 (kwiecień 2007): 88–99. http://dx.doi.org/10.1016/j.palaeo.2006.11.023.
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Blaszczyk, Pawel, i Richard M. Ashley. "Application of new criteria to control sediment problems in combined sewers in Poland". Water Science and Technology 33, nr 9 (1.04.1996): 245–52. http://dx.doi.org/10.2166/wst.1996.0222.
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The Polish criteria for design and operation to control sediments in combined sewers may now be replaced to reflect new knowledge. A series of field investigations have been carried out to examine the occurrence and nature of sediments in sewers in Warsaw. Using the results of these studies and new UK approaches to the control of sedimentation in sewers, new simplified criteria have been defined based on different modes of sediment transport and relative sewer sizes.
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Rosemeier, Juliane, i Peter Spichtinger. "Pattern formation in clouds via Turing instabilities". Mathematics of Climate and Weather Forecasting 6, nr 1 (1.01.2020): 75–96. http://dx.doi.org/10.1515/mcwf-2020-0104.
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AbstractPattern formation in clouds is a well-known feature, which can be observed almost every day. However, the guiding processes for structure formation are mostly unknown, and also theoretical investigations of cloud patterns are quite rare. From many scientific disciplines the occurrence of patterns in non-equilibrium systems due to Turing instabilities is known, i.e. unstable modes grow and form spatial structures. In this study we investigate a generic cloud model for the possibility of Turing instabilities. For this purpose, the model is extended by diffusion terms. We can show that for some cloud models, i.e special cases of the generic model, no Turing instabilities are possible. However, we also present a general class of cloud models, where Turing instabilities can occur. A key requisite is the occurrence of (weakly) nonlinear terms for accretion. Using numerical simulations for a special case of the general class of cloud models, we show spatial patterns of clouds in one and two spatial dimensions. From the numerical simulations we can see that the competition between collision terms and sedimentation is an important issue for the existence of pattern formation.
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Krishnappan, B. G. "Modelling of settling and flocculation of fine sediments in still water". Canadian Journal of Civil Engineering 17, nr 5 (1.10.1990): 763–70. http://dx.doi.org/10.1139/l90-089.
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A numerical model to predict settling behaviour of fine sediment mixtures in a stagnant water column is described. Both single-grain settling mode and the floc settling mode are considered. The single-grain settling mode is analyzed by solving the unsteady, one-dimensional diffusion–advection equation numerically and the floc settling mode is examined by solving a coagulation equation expressed as a discrete equation in logarithmic radius space considering the differential settling as the only collision mechanism. The model results are compared with the laboratory experimental data of K. Kranck for both modes of sediment settling. The agreement between the model predictions and the experimental data is good. The model can be used as a basis for such practical applications as predicting sedimentation rates in reservoirs and settling basins. Key words: sediment mixtures, settling, flocculation, advection, diffusion, floc size distribution, primary particles.
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Nowaczyk, N. R., E. M. Haltia, D. Ulbricht, V. Wennrich, M. A. Sauerbrey, P. Rosén, H. Vogel i in. "Chronology of Lake El'gygytgyn sediments – a combined magnetostratigraphic, palaeoclimatic and orbital tuning study based on multi-parameter analyses". Climate of the Past 9, nr 6 (1.11.2013): 2413–32. http://dx.doi.org/10.5194/cp-9-2413-2013.
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Abstract. A 318-metre-long sedimentary profile drilled by the International Continental Scientific Drilling Program (ICDP) at Site 5011-1 in Lake El'gygytgyn, Far East Russian Arctic, has been analysed for its sedimentologic response to global climate modes by chronostratigraphic methods. The 12 km wide lake is sited off-centre in an 18 km large crater that was created by the impact of a meteorite 3.58 Ma ago. Since then sediments have been continuously deposited. For establishing their chronology, major reversals of the earth's magnetic field provided initial tie points for the age model, confirming that the impact occurred in the earliest geomagnetic Gauss chron. Various stratigraphic parameters, reflecting redox conditions at the lake floor and climatic conditions in the catchment were tuned synchronously to Northern Hemisphere insolation variations and the marine oxygen isotope stack, respectively. Thus, a robust age model comprising more than 600 tie points could be defined. It could be shown that deposition of sediments in Lake El'gygytgyn occurred in concert with global climatic cycles. The upper ~160 m of sediments represent the past 3.3 Ma, equivalent to sedimentation rates of 4 to 5 cm ka−1, whereas the lower 160 m represent just the first 0.3 Ma after the impact, equivalent to sedimentation rates in the order of 45 cm ka−1. This study also provides orbitally tuned ages for a total of 8 tephras deposited in Lake El'gygytgyn.
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BLIGNAULT, H. J., i J. N. THERON. "MODES OF SEDIMENTATION AND GLACIOLOGICAL ASPECTS OF THE PERMO-CARBONIFEROUS DWYKA GROUP IN THE ELANDSVLEI - ELANDSDRIF AREA, SOUTH AFRICA". South African Journal of Geology 115, nr 2 (1.06.2012): 211–24. http://dx.doi.org/10.2113/gssajg.115.2.211.
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MEIER, J. A., J. S. JEWELL, C. E. BRENNEN i J. IMBERGER. "Bubbles emerging from a submerged granular bed". Journal of Fluid Mechanics 666 (6.01.2011): 189–203. http://dx.doi.org/10.1017/s002211201000443x.
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This paper explores the phenomena associated with the emergence of gas bubbles from a submerged granular bed. While there are many natural and industrial applications, we focus on the particular circumstances and consequences associated with the emergence of methane bubbles from the beds of lakes and reservoirs since there are significant implications for the dynamics of lakes and reservoirs and for global warming. This paper describes an experimental study of the processes of bubble emergence from a granular bed. Two distinct emergence modes are identified, mode 1 being simply the percolation of small bubbles through the interstices of the bed, while mode 2 involves the cumulative growth of a larger bubble until its buoyancy overcomes the surface tension effects. We demonstrate the conditions dividing the two modes (primarily the grain size) and show that this accords with simple analytical evaluations. These observations are consistent with previous studies of the dynamics of bubbles within porous beds. The two emergence modes also induce quite different particle fluidization levels. The latter are measured and correlated with a diffusion model similar to that originally employed in river sedimentation models by Vanoni and others. Both the particle diffusivity and the particle flux at the surface of the granular bed are measured and compared with a simple analytical model. These mixing processes can be consider applicable not only to the grains themselves, but also to the nutrients and/or contaminants within the bed. In this respect they are shown to be much more powerful than other mixing processes (such as the turbulence in the benthic boundary layer) and could, therefore, play a dominant role in the dynamics of lakes and reservoirs.
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Pang, Xiongqi, Ian Lerche, Haiyan Zhou i Zhengxue Jiang. "Hydrocarbon Accumulation Control by Predominant Migration Pathways". Energy Exploration & Exploitation 21, nr 3 (czerwiec 2003): 167–86. http://dx.doi.org/10.1260/014459803769520034.
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Geological analysis and physical analogy experiments indicate that, under geological conditions, hydrocarbon tends to migrate along a path of least resistance and attempt to follow the largest buoyancy component. There are four generalized modes of possible transport. First, hydrocarbons tends to migrate along the pathways with high porosity and permeability, and with a large grade difference relative to surrounding rocks (grade difference predominance); second, hydrocarbons tends to migrate in the opposite direction in overlying formations to the nadir of the sedimentation centre (divided syncline predominance); third, hydrocarbons tends to migrate in the direction of lower fluid pressure (fluid pressure predominance); fourth, hydrocarbons tends to migrate in the direction vertical to buoyancy (flow direction predominance). This paper reports on field observations in the Daqing oilfield area of China and also on physical analog experiments used to illuminate the four basic modes of transport. Under geological conditions, the hydrocarbon migration pathways are controlled by these four basic modes, which can be used to predict the directions of hydrocarbons migration and select favourable exploration locations.
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Сеник, E. Senik, Виноградов, M. Vinogradov, Таранов, R. Taranov, Козодаев i in. "Rare Earth Metals Leaching from Coal Ash and Theirs Concentration". Safety in Technosphere 5, nr 1 (25.02.2016): 48–55. http://dx.doi.org/10.12737/19023.
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Problems related to rare earth metals leaching from coal ash and theirs ion-exchange concentration from sulfuric solutions, in particular the characteristics of scandium, yttrium and lanthanum sorption by different ion exchange resins have been considered in this work. It has been shown that the best way to leach rare earth metals from coal ash is a complex acid and biological treatment of ash waste. Kinetics related to the process of scandium, yttrium and lanthanum acid leaching from ash and slag waste of CHPP in Kumertau has been investigated. Subsequent metal solutions concentration was achieved using ion exchange resins. The results of experimental studies related to the processes of rare-earth metals (in particularly scandium) ion exchange concentration by cation exchange resin in the Naform PC-100 have been presented, as well as the results of experimental studies related to rare earth metals (scandium including) sedimentation process, using special sedimentators. Dependences of rare earth metals (in particular scandium) sedimentation efficiency against pH value have been constructed, and recommendations for pH values, that are optimal for rare earth metals sedimentation, have been given. Based on obtained experimental results it was created and tested an experimental laboratory prototype of plant for rare earth metals (scandium, yttrium and lanthanum including) extraction from located near Moscow brown coal basin’s slag heaps, and from ash dumps of Russian Federation’s energy enterprises. This plant’s process flow diagram as well as its operation description has been presented. The created plant was tested in modes previously fulfilled in laboratory conditions. At the same time, carried out integrated exploration have showed the prospects for implementation of developed technical solutions for processing of ash dumps of Russian Federation’s various energy enterprises.
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PEDERNERA, TOMÁS E., ADRIANA C. MANCUSO, CECILIA A. BENAVENTE i EDUARDO G. OTTONE. "PLANT TAPHONOMY IN A LAKE AFFECTED BY VOLCANISM (AGUA DE LA ZORRA FORMATION, UPPER TRIASSIC) MENDOZA, ARGENTINA". PALAIOS 35, nr 6 (26.06.2020): 245–61. http://dx.doi.org/10.2110/palo.2019.104.
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ABSTRACT Volcanic eruptions have an impact on the paleoecology of plant communities and their preservation in the fossil record. The aim of this contribution is to evaluate the influence of volcanism on plant preservation in lacustrine settings via systematic sampling and chemical analyses of fossil plants in the Upper Triassic Agua de la Zorra Formation, of the Argentinian Cuyana Basin. Plant remains are not uniformly preserved throughout the Agua de la Zorra Formation and their stratigraphic distribution reflects the original spatial pattern of the plant communities. SEM-EDX analyses was used to demonstrate how volcanism affected diagenesis of the plant remains. Eight taphonomic modes were determined from biostratinomic analysis, and three preservational modes from the chemical features observed in the SEM-EDX spectra. The three preservation modes recognized by SEM-EDX analysis are more likely linked to diagenesis and are not equivalent to the taphonomic modes described based on the biostratinomic features. The Agua de la Zorra paleolake preferentially preserved plant material because of anoxic conditions in deeper parts of the lake, and a high sedimentation rate in proximal near-shore facies. The plant remains are most abundant in sandy facies deposited by high-energy flows but there is no evidence that these flows were pyroclastic nor that the plant remains were generated by volcanic trauma.
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KHALIL, HANY, i RICARDO VILLOTA. "The Effect of Microwave Sublethal Heating on the Ribonucleic Acids of Staphylococcus aureus". Journal of Food Protection 52, nr 8 (1.08.1989): 544–48. http://dx.doi.org/10.4315/0362-028x-52.8.544.
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The effect of microwave sublethal heat injury on the integrity of S. aureus FRI-100 RNA was examined. The extent of damage to RNA during sublethal microwave heat injury was greater than that occurring as a result of conventional sublethal heating. Although both heating modes resulted in the destruction of the 16S RNA, only those cells heated with microwave energy suffered lesions in their 23S RNA. When cells were allowed to recover, the conventionally heated cells regained normal profiles of the 16S and the 23S RNA after 180 min on the recovery medium. Microwave heated cells restored their 16S RNA after 180 min of recovery. Microwave-injured cells required 270 min to have 23S RNA with sedimentation properties similar to those found in the unheated cells.
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Schwamborn, Georg, Kai Hartmann, Bernd Wünnemann, Wolfgang Rösler, Annette Wefer-Roehl, Jörg Pross, Marlen Schlöffel i in. "Sediment history mirrors Pleistocene aridification in the Gobi Desert (Ejina Basin, NW China)". Solid Earth 11, nr 4 (23.07.2020): 1375–98. http://dx.doi.org/10.5194/se-11-1375-2020.
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Abstract. Central Asia is a large-scale source of dust transport, but it also held a prominent changing hydrological system during the Quaternary. A 223 m long sediment core (GN200) was recovered from the Ejina Basin (synonymously Gaxun Nur Basin) in NW China to reconstruct the main modes of water availability in the area during the Quaternary. The core was drilled from the Heihe alluvial fan, one of the world's largest alluvial fans, which covers a part of the Gobi Desert. Grain-size distributions supported by endmember modelling analyses, geochemical–mineralogical compositions (based on XRF and XRD measurements), and bioindicator data (ostracods, gastropods, pollen and non-pollen palynomorphs, and n-alkanes with leaf-wax δD) are used to infer the main transport processes and related environmental changes during the Pleistocene. Magnetostratigraphy supported by radionuclide dating provides the age model. Grain-size endmembers indicate that lake, playa (sheetflood), fluvial, and aeolian dynamics are the major factors influencing sedimentation in the Ejina Basin. Core GN200 reached the pre-Quaternary quartz- and plagioclase-rich “Red Clay” formation and reworked material derived from it in the core bottom. This part is overlain by silt-dominated sediments between 217 and 110 m core depth, which represent a period of lacustrine and playa-lacustrine sedimentation that presumably formed within an endorheic basin. The upper core half between 110 and 0 m is composed of mainly silty to sandy sediments derived from the Heihe that have accumulated in a giant sediment fan until modern time. Apart from the transition from a siltier to a sandier environment with frequent switches between sediment types upcore, the clay mineral fraction is indicative of different environments. Mixed-layer clay minerals (chlorite/smectite) are increased in the basal Red Clay and reworked sediments, smectite is indicative of lacustrine-playa deposits, and increased chlorite content is characteristic of the Heihe river deposits. The sediment succession in core GN200 based on the detrital proxy interpretation demonstrates that lake-playa sedimentation in the Ejina Basin has been disrupted likely due to tectonic events in the southern part of the catchment around 1 Ma. At this time Heihe broke through from the Hexi Corridor through the Heli Shan ridge into the northern Ejina Basin. This initiated the alluvial fan progradation into the Ejina Basin. Presently the sediment bulge repels the diminishing lacustrine environment further north. In this sense, the uplift of the hinterland served as a tipping element that triggered landscape transformation in the northern Tibetan foreland (i.e. the Hexi Corridor) and further on in the adjacent northern intracontinental Ejina Basin. The onset of alluvial fan formation coincides with increased sedimentation rates on the Chinese Loess Plateau, suggesting that the Heihe alluvial fan may have served as a prominent upwind sediment source for it.
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Lee, Dong-Jin, i Robert J. Elias. "Mode of growth and life-history strategies of a Late Ordovician halysitid coral". Journal of Paleontology 65, nr 2 (marzec 1991): 191–99. http://dx.doi.org/10.1017/s0022336000020424.
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The upper surface of the corallum ofCatenipora rubrawas often at or just above the sediment-water interface during life. The vertical growth rate was barely sufficient to keep pace with background sedimentation and possible subsidence of the corallum. Therefore, the colonies were in constant danger of being covered by influxes of sediment, especially during storms. This was compensated by the ability of polyps to respond to sedimentation events and by certain aspects of colony growth. Rapid regeneration following partial mortality involved budding of uninjured polyps and rejuvenation of damaged individuals, in some cases accompanied by a type of axial increase not previously known in tabulate corals. Rapid lateral expansion was possible because small, “immature” polyps could bud and grow in a reptant manner.Interconnected ranks of the cateniform corallum served to dam shifting sediment at the periphery of the colony. Lacunae within the colony were reservoirs for material that breached peripheral ranks and for sediment that settled on the ranks and was rejected by polyps or removed by passive flow. Polyps comprising the colony were distributed over a large area of the substrate surface, thereby decreasing the probability of complete mortality during sedimentation events and increasing the probability that a sufficient number of individuals would survive to ensure optimum regeneration. The corallum, anchored in the substrate and with sediment filling the lacunae, provided a broad, stable base during high-energy events.It remains to be established how widespread these growth patterns and strategies were among other corals with cateniform colonies, a form that appeared in many unrelated stocks. Most previous workers emphasized physical strength when considering functional morphology, following a tacit assumption that the corallum rose high above the substrate and was therefore susceptible to breakage during high-energy events. An understanding of the origin of cateniform patterns and the phylogeny of these corals requires knowledge of their modes of growth and life-history strategies, which were genetically as well as environmentally controlled.
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Varga, G., J. Kovács i G. Újvári. "Late Pleistocene variations of the background aeolian dust concentration in the Carpathian Basin: an estimate using decomposition of grain-size distribution curves of loess deposits". Netherlands Journal of Geosciences - Geologie en Mijnbouw 91, nr 1-2 (wrzesień 2013): 159–71. http://dx.doi.org/10.1017/s0016774600001566.
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AbstractAeolian dust deposits can be considered as one of the most important archives of past climatic changes. Alternating loess and paleosol strata display variations of the dust load in the Pleistocene atmosphere. By using the observations of recent dust storms, we are able to employ Late Pleistocene stratigraphic datasets (with accurate chronological framework) and detailed granulometric data for making conclusions on the atmospheric dust load in the past. Age-depths models, created from the absolute age data and stratigraphic interpretation, allow us to calculate sedimentation rates and dust fluxes, while grain-size specifies the dry-deposition velocity, i.e. the atmospheric residence time of mineral particles. Thus, the dust concentration can be expressed as the quotient of the dust flux and gravitational settling velocity. Recent observations helped to clarify the mechanisms behind aeolian sedimentation and the physical background of this process has nowadays been well established. Based on these two, main contrasting sedimentary modes of dust transport and deposition can be recognised: the short suspension episodes of the coarse (silt and very fine sand) fraction and the long-range transport of a fine (clay and fine silt) component. Using parametric curve fitting the basic statistical properties of these two sediment populations can be revealed for Pleistocene aeolian dust deposits, as it has been done for loess in Hungary. As we do not have adequate information on the magnitude and frequency of the Pleistocene dust storms, conclusions could only be made on the magnitude of continuous background dust load. The dust concentration can be set in the range between 1100 and 2750 μg/m3. These values are mostly higher than modern dust concentrations, even in arid regions. Another interesting proxy of past atmospheric conditions could be the visibility, being proportional to the dust concentration. According to the known empirical dust concentration – visibility equations, its value is around 6.5 to 26 kilometres.
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Rai, Bijendra Kumar, SU Kafle i A. Sundas. "A case of abdominal tuberculosis diagnosed by fine needle aspiration cytology (FNAC) of mesenteric lymph node". Health Renaissance 13, nr 3 (7.08.2017): 177–80. http://dx.doi.org/10.3126/hren.v13i3.17966.
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Background: The modes of presentation of abdominal tuberculosis can be vague resulting in diagnostic dilemma.Objective: To report a case of abdominal tuberculosis diagnosed by FNAC of a mesenteric lymphnode.Case: A 17-year-old boy presented in General out Patient department complaining of abdominal pain, abdominal distension, and low grade fever, anorexia and weight loss for 2 months. The examination revealed pallor, low body weight, doughing of abdomen and multiple palpable painless, slightly mobile abdominal lymph nodes. The ultrasonography (USG) guided fine needle aspiration cytology (FNAC) of a mesenteric lymphnode showed caseating necrosis suggestive of tuberculosis. The erythrocytes sedimentation rate (ESR) was raised.Conclusion: The abdominal tuberculosis can present with abdominal pain and abdominal distension associated with low grade fever, anorexia and weight loss. The diagnosis of abdominal tuberculosis can be confirmed by FNAC of the lymphnodes. Health Renaissance 2015;13(3): 177-180
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Inoue, Hidenari. "SPECTROSCOPIC AND PHYSICOCHEMICAL METHODS FOR STUDYING THE INTERACTION OF METALLOPORPHYRIN WITH DNA". Indonesian Journal of Chemistry 2, nr 3 (9.06.2010): 131–34. http://dx.doi.org/10.22146/ijc.21907.
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In recent years studies on the interaction of porphyrin with DNA have received much attention because of the importance in DNA-probing and photodynamic therapy of cancer. A variety of spectroscopic methods, e.g. NMR, ESR, Mössbauer, UV-visible absorption, circular dichroism (CD), magnetic circular dichroism (MCD), IR and Raman spectroscopy, have been employed for studying interactions between porphyrin and DNA. Of these spectroscopic methods, only a few instrumental analytical techniques applicable to an aqueous buffer solution of DNA have been particularly developed to investigate porphyrin-DNA interactions. On the other hand, a number of physicochemical methods, e.g. gel electrophoresis, melting temperature measurements and hydrodynamic methods such as viscosity and sedimentation measurements, have been also used for determining the binding modes of porphyrin to DNA. The present lecture will focus on the application of visible absorption, CD and MCD spectroscopy as well as melting temperature and viscosity measurements to studies of porphyrin-DNA interactions.
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Titorova, Valentina, Konstantin Sabbatovskiy, Veronika Sarapulova, Evgeniy Kirichenko, Vladimir Sobolev i Ksenia Kirichenko. "Characterization of MK-40 Membrane Modified by Layers of Cation Exchange and Anion Exchange Polyelectrolytes". Membranes 10, nr 2 (27.01.2020): 20. http://dx.doi.org/10.3390/membranes10020020.
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Coating of ion exchange membranes used in electrodialysis with layers of polyelectrolytes is a proven approach that allows for the increasing of the limiting current, the suppressing of sedimentation, the controlling of the intensity of generation of H+ and OH− ions, and also the improving of monovalent selectivity. However, in the case when two materials with the opposite sign of the charge of fixed groups come in contact, a bipolar boundary is created that can cause undesirable changes in the membrane properties. In this work, we used a MK-40 heterogeneous membrane on the surface of which a layer of polyethyleneimine was applied by adsorption from a solution as a model of heterogeneous membranes modified with oppositely charged polyelectrolyte. It was found that, on one hand, the properties of modified membrane were beneficial for electrodialysis, its limiting current did not decrease and the membrane even acquired a barrier to non-selective electrolyte transport. At the same time, the generation of H+ and OH− ions of low intensity arose, even in underlimiting current modes. It was also shown that despite the presence of a layer of polyethyleneimine, the surface charge of the modified membrane remained negative, which we associate with low protonation of polyethyleneimine at neutral pH.
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Su, L., i O. B. Toon. "Saharan and asian dust: similarities and differences determined by CALIPSO, AERONET and a coupled climate-aerosol microphysical model". Atmospheric Chemistry and Physics Discussions 10, nr 12 (2.12.2010): 29513–67. http://dx.doi.org/10.5194/acpd-10-29513-2010.
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Abstract. This study compares the properties of atmospheric dust from the Saharan deserts and the Asian deserts using data from CALIPSO and AERONET during 2006 and 2007 along with simulations using a coupled climate-microphysical sectional model. Saharan deserts are largely south of 30° N, while Asian ones are primarily north of 30° N, hence they experience different meteorological regimes. Saharan dust lifting occurs all year long, primarily due to subtropical weather systems. However, Asian dust is lifted mostly in spring when mid-latitude frontal systems lead to high winds. Rainfall is more abundant over Asia during the dust lifting events, leading to greater local dust removal than over the Sahara. However, most dust removal is due to sedimentation. Despite the different meteorological regimes, the same dust lifting schemes work in models for Asian and Saharan dust. The magnitudes of dust lifted in Africa and Asia differ significantly over the year. In our model the yearly horizontal dust flux just downwind of the African dust source is about 1446 Tg (10° S–40° N, 10° E) and from the Asian dust source it is about 355 Tg (25° N–55° N, 105° E) in 2007, which is comparable to previous studies. We find the difference in dust flux is mainly due to the larger area over which dust is lifted in Africa than Asia. However, Africa also has stronger winds in some seasons. Once lifted, the Saharan dust layers generally move toward the west and descend in altitude from about 7 km to the surface over several days in the cases studied. Asian dust often has multiple layers (two layers in the cases studied) during transport largely to the east. One layer stays well above boundary layer during transport and shows little descent, while the other, lower, layer descends with time. This observation contrasts with studies suggesting the descent of Saharan dust is due to sedimentation of the particles, and suggests instead it is dominated by meteorology. We find the size distributions of Asian and African dust are similar when the dust is lifted, but the mode size can differ and secondary size modes can develop due to differences in vertical wind velocities during transport. The single scattering albedo of African and Asian dust does differ, due primarily to the imaginary parts of the refractive indexes being different, which in turn is likely due to different dust composition. This study is a step towards a global understanding of dust and its properties.
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Su, L., i O. B. Toon. "Saharan and Asian dust: similarities and differences determined by CALIPSO, AERONET, and a coupled climate-aerosol microphysical model". Atmospheric Chemistry and Physics 11, nr 7 (5.04.2011): 3263–80. http://dx.doi.org/10.5194/acp-11-3263-2011.
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Abstract. This study compares the properties of atmospheric dust from the Saharan deserts and the Asian deserts using data from CALIPSO and AERONET during 2006 and 2007 along with simulations using a coupled climate-microphysical sectional model. Saharan deserts are largely south of 30° N, while Asian ones are primarily north of 30° N, hence they experience different meteorological regimes. Saharan dust lifting occurs all year long, primarily due to subtropical weather systems. However, Asian dust is lifted mostly in spring when mid-latitude frontal systems lead to high winds. Rainfall is more abundant over Asia during the dust lifting events, leading to greater local dust removal than over the Sahara. However, most dust removal is due to sedimentation. Despite the different meteorological regimes, the same dust lifting schemes work in models for Asian and Saharan dust. The magnitudes of dust lifted in Africa and Asia differ significantly over the year. In our model the yearly horizontal dust flux just downwind of the African dust source is about 1088 Tg (10° S–40° N, 10° W) and from the Asian dust source it is about 355 Tg (25° N–55° N, 105° E) in 2007, which is comparable to previous studies. We find the difference in dust flux is mainly due to the larger area over which dust is lifted in Africa than Asia. However, Africa also has stronger winds in some seasons. Once lifted, the Saharan dust layers generally move toward the west and descend in altitude from about 7 km to the surface over several days in the cases studied. Asian dust often has multiple layers (two layers in the cases studied) during transport largely to the east. One layer stays well above boundary layer during transport and shows little descent, while the other, lower, layer descends with time. This observation contrasts with studies suggesting the descent of Saharan dust is due to sedimentation of the particles, and suggests instead it is dominated by meteorology. We find the size distributions of Asian and African dust are similar when the dust is lifted, but the mode size can differ and secondary size modes can develop probably due to differences in vertical wind velocities during transport. The single scattering albedo of African and Asian dust does differ, due primarily to the imaginary parts of the refractive indexes being different, which in turn is likely due to different dust composition. This study is a step towards a global understanding of dust and its properties.
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WILSON, BRONWEN. "Venice, print, and the early modern icon". Urban History 33, nr 1 (maj 2006): 39–64. http://dx.doi.org/10.1017/s0963926806003518.
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Venetian printmakers in the sixteenth century were enthusiastic participants in what became a project of civic self-promotion as they looked beyond the local market to an international one. In response to the fascination of foreigners who marvelled at the city's singular topography and its reputation for liberty and licentiousness, the bird's-eye view and images of local social types – such as the doge and courtesan – became transmuted into icons of the city's urban identity. The medium and modes of representation used to reproduce the republic's social and physical organization on paper are crucial here, for it was the repetition and sedimentation of visual conventions that forged iconicity. Venice was redefined as a centre in which all the world could be seen. And the mechanisms for this redefinition, as this article argues, emerged, in part, out of print, for it was because the city could be seen from the eye of a bird, on paper as an image, by foreigners – that it could be re-envisioned from the outside in.
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Berger, G. W., J. J. Clague i D. J. Huntley. "Thermoluminescence dating applied to glaciolacustrine sediments from central British Columbia". Canadian Journal of Earth Sciences 24, nr 3 (1.03.1987): 425–34. http://dx.doi.org/10.1139/e87-044.
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Glaciolacustrine and lacustrine sediments are important indicators of deglacial, interglacial, and nonglacial intervals within the Quaternary of Canada, yet there are no techniques for measuring their absolute deposition ages beyond the last ~ 50 000 years. In an attempt to develop an absolute dating tool for such sediments, we applied the partial bleach thermoluminescence (TL) dating technique to glaciolacustrine sediments of known age from central British Columbia. Samples were selected to represent both ice-proximal and ice-distal deposition and different modes of sedimentation.The results show clearly that both TL procedures and sedimentation processes, as reflected in the particle size and sedimentary structures of the samples, critically affected the accuracy of TL apparent ages. Specifically, care was required to isolate the effects of laboratory overbleaching, apparent glow-curve shifts, and inappropriate regression analysis. Clay-dominant layers lacking silt or sand interlayers produced expected ages, whereas sand- and silt-rich samples (with one exception) yielded excessive TL apparent ages. The single exception was a thin (9 mm), ice-distal, silt-rich layer.
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Tempel, Karlheinz, Hannelore Kortenbeutel i Christina von Zallinger. "Bleomycin - Induced DNA Damage and DNA Repair in Chicken Embryo Cells as Compared to X-Irradiation". Zeitschrift für Naturforschung C 54, nr 12 (1.12.1999): 1068–74. http://dx.doi.org/10.1515/znc-1999-1211.
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Following in vitro- and in ovo-exposure of chicken embryo cells, the level of bleomycin (BM) - induced damage was evaluated by using DNA synthesis, nucleoid sedimentation (SED), and viscometry of alkaline cell lysates (VISC). This damage was compared to Xirradiation, using 5.9-378 nM BM in vitro, 1.5-116 μg BM/egg in ovo, and 2-32 Gy, respectively, in vitro as well as in ovo. With respect to BM. the most notable result is the increase in DNA synthesis and VISC at the lowest concentrations of the drug. A decrease in both parameters was observed at high BM concentrations and following exposure to X-rays, concomitantly with an increase in SED. Regarding the radiomimetic drug BM and X-rays, different modes of DNA damage and DNA repair are suggested by previous investigations and the present results. Therefore, further evidence is presented, that the chicken embryo can act as a simple, rapid and inexpensive test system to characterize the biological effects of many nucleo- and/or cytotoxic agents.
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Guensburg, Thomas E., i James Sprinkle. "Environmental controls of rapidly diversifying echinoderms during the Early Paleozoic". Paleontological Society Special Publications 6 (1992): 114. http://dx.doi.org/10.1017/s2475262200006742.
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Echinoderms were among the earliest phyla to exploit global environmental shifts leading to the rise of the Paleozoic Evolutionary Fauna during the Ordovician. Echinoderms including crinoids and rhombiferans diversified more rapidly and actually precede other groups such as bryozoans, corals, and many articulate brachiopods in the record. We argue that preadaptive morphologic strategies among the echinoderms coupled with newly available and widespread living space led to this success.Sessile attached echinoderms, especially crinoids and some blastozoans, dominate echinoderm faunas generally throughout the Paleozoic. These organisms were rheophilic suspension feeders with elongate stalked morphologies capable of attaining high feeding levels above competitors. However, this morphology required firm attachment. Suitable sites were relatively rare in Early and especially Middle Cambrian time when shelf and slope sedimentation was dominated by fine siliciclastics and nonbiogenic carbonates resulting in extensive soft substrates. Sea level was relatively low during the Middle Cambrian, restricting shallow shelf living space. Stalked echinoderms then lived attached to scattered bioclastic fragments but had low diversity and were a relatively minor component of the faunal record. Mode of occurrence and morphologic features suggest they were generally unable to cope with soft and unstable substrates. Nearshore shelf sedimentation styles changed during the Late Cambrian and Early Ordovician to bioclastic-dominated carbonates and organic buildups. These were often subject to intermittent storm events and rapid submarine cementation of the seafloor because of changes in global atmospheric and seawater chemistry. This resulted in formation of hardgrounds on intraformational conglomerates, grainstones, and buildups. Gradual sea level rise beginning in the Late Cambrian and continuing through the Early Ordovician was a major contributing cause for these changes. The widespread lithified substrates provided ideal attachment sites for the preadapted echinoderms and greatly expanded the total habitable area, resulting in rapidly increasing diversity.Among crinoids, disparid inadunates were the first to extensively exploit this situation and they dominated throughout the Early Ordovician. Attached blastozoans were also common both in the Late Cambrian and Early Ordovician. Later, many camerate and cladid inadunate crinoids and a few blastozoans developed attachment styles suitable to soft substrates, continuing and expanding this diversification. Some previous authors have misidentified life modes of these Cambro-Ordovician echinoderms because they used forced senarios based on phylogenetic analysis alone. In contrast, we argue that life modes and paleoecologic settings are basic field-derived data that should be used along with morphologic character analysis to determine phylogenetic relationships. Both the fossils and their environmental settings must be studied together to reconstruct the adaptive history and phylogeny of a rapidly-radiating group.
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Dong, Yingdi, Hongliang Li, Yuping Fan, Xiaomin Ma, Dong Sun, Yanhong Wang, Zhiyong Gao i Xianshu Dong. "Tunable Dewatering Behavior of Montmorillonite Suspension by Adjusting Solution pH and Electrolyte Concentration". Minerals 10, nr 4 (25.03.2020): 293. http://dx.doi.org/10.3390/min10040293.
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Montmorillonite is always a troublemaker for the dewatering in coal processing since its existence can decrease the rates of sedimentation and filtration of coal slurry. To eliminate the adverse effect of montmorillonite, adjusting the slurry pH and adding electrolytes are always the key methods. However, the underlying mechanism still needs to be further studied. The dewatering of Na-montmorillonite (Na-Mt) suspensions has been studied as a function of NaCl concentration (10−3, 10−2, and 10−1 M) at different pH values (6.0, 7.7, 8.1, 9.2). The point of zero charge of edge surface of Na-Mt (pHPZC,edge) appeared at the pH value of 6.8. The sedimentation and rheology experiments described the coagulation and flow behaviors of Na-Mt suspensions, respectively. The Na-Mt suspension coagulated spontaneously at low salt concentration with the pH ~ 6.0. For the pH > pHPZC,edge, the height of the sediment bed reduced and apparent viscosity increased with the increase of the electrolyte concentration. The filtration properties were evaluated on the basis of Darcy’s law. The obtained result clearly demonstrated that the filtration rate was accelerated with the increase of pH and electrolyte concentration. The modes of particle association and its effect on filtration performance were discussed. Moreover, a comparison with related results from the literature was performed. At pH ~ 6 and low electrolyte concentration, the positively charged Edge surfaces and negatively charged Face surfaces coagulate rapidly to form a sealed structure by electrostatic attraction. Furthermore, inside this sealed structure, the water molecules cannot be removed in the filtration process easily. However, by increasing the electrolyte concentration at pH > pHPZC,edge, the gradually formed Face/Face structure increases the filtration rate sharply because of the inhibiting effect of the electric double layer (EDL) and the osmotic expansion. Therefore, adjusting solution conditions of the aqueous suspension to tune the particle coagulation behavior is one of the effective methods to solve the problem of montmorillonite dewatering.
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Kacan, Kevin G., i Zachary J. Lebo. "Microphysical and Dynamical Effects of Mixed-Phase Hydrometeors in Convective Storms Using a Bin Microphysics Model: Melting". Monthly Weather Review 147, nr 12 (12.11.2019): 4437–60. http://dx.doi.org/10.1175/mwr-d-18-0032.1.
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Abstract The dynamics of convective systems are inherently linked to microphysical processes through phase changes that result in warming or cooling. This is especially true of near-surface cooling via evaporation and melting of falling hydrometeors. In most numerical simulations, the melting of frozen hydrometeors (e.g., hail, graupel, snow) is computed within parameterized bulk microphysics schemes, many of which lack the ability to accurately represent mixed-phase hydrometeors (i.e., partially melted ice), which can affect hydrometeor sedimentation, melting, and evaporation of shed drops. To better understand the microphysical and dynamical effects of melting in convective storms, a bin microphysics scheme was used in the Weather Research and Forecasting Model for two idealized cases: a supercell storm and a squall line. Physically based predicted liquid fraction, instantaneous melting, and instantaneous shedding schemes were used to examine the role and importance of melting hydrometeors for these two storm modes. The results suggest that the amount of precipitation is dependent on the representation of melting. Moreover, the dynamic and thermodynamic characteristics of the simulated storms are found to differ substantially between the melting scenarios, resulting in varied storm system evolution; these differences are found to be dependent on the ambient aerosol concentration, although the differences induced by changing the representation of melting generally outweigh those of changing the aerosol loading. The results highlight the large role of melting in convective storm characteristics and suggest that further model improvements are needed in the near future.
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Yang, C. B., Y. L. Cheng, J. C. Liu i D. J. Lee. "Treatment and reuse of backwash water in Taipei water treatment plant, Taiwan". Water Supply 6, nr 6 (1.12.2006): 89–98. http://dx.doi.org/10.2166/ws.2006.961.
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A case study on the treatment and reuse of backwash water from Chang-Hsing Water Treatment Plant (CHWTP) and Swan-Sea Water Treatment Plant (SSWTP) of Taipei Water Department was conducted. Both backwash waters showed different properties. However, the characteristics of each backwash water did not vary considerably among samples taken during different time. Results from jar tests indicated that both polyaluminium chloride (PACl) and alum could result in effective removal of turbidity. Both DOC and absorbance of UV254 decreased slightly with increasing coagulant dosage. In continuous operation of backwash water recycle in pilot study in CHWTP, it was found that treated water quality was not affected by two different modes of recycle: intermittent recycle at ratio of 1:7 (backwash water:raw water) and continuous recycle at ratio of 1:42. In the pilot study in SSWTP, no impact was found on the introduction of backwash water at recycle ratio of 4, 6 and 8%, regardless of whether the backwash water was recycled directly or went through 3 min pre-sedimentation before it is recycled. Further study on the impact of typhoon on treatment and recycle of backwash water was recommended.
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Mahler, Bryon P., Paul J. Bujalowski, Huzhang Mao, Erik A. Dill, Paul J. Jardine, Kyung H. Choi i Marc C. Morais. "NMR structure of a vestigial nuclease provides insight into the evolution of functional transitions in viral dsDNA packaging motors". Nucleic Acids Research 48, nr 20 (21.10.2020): 11737–49. http://dx.doi.org/10.1093/nar/gkaa874.
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Abstract Double-stranded DNA viruses use ATP-powered molecular motors to package their genomic DNA. To ensure efficient genome encapsidation, these motors regulate functional transitions between initiation, translocation, and termination modes. Here, we report structural and biophysical analyses of the C-terminal domain of the bacteriophage phi29 ATPase (CTD) that suggest a structural basis for these functional transitions. Sedimentation experiments show that the inter-domain linker in the full-length protein promotes oligomerization and thus may play a role in assembly of the functional motor. The NMR solution structure of the CTD indicates it is a vestigial nuclease domain that likely evolved from conserved nuclease domains in phage terminases. Despite the loss of nuclease activity, fluorescence binding assays confirm the CTD retains its DNA binding capabilities and fitting the CTD into cryoEM density of the phi29 motor shows that the CTD directly binds DNA. However, the interacting residues differ from those identified by NMR titration in solution, suggesting that packaging motors undergo conformational changes to transition between initiation, translocation, and termination. Taken together, these results provide insight into the evolution of functional transitions in viral dsDNA packaging motors.
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Jeong, J. O., C. W. Kwon i Y. K. Sohn. "Lithofacies and architecture of a basinwide tuff unit in the Miocene Eoil Basin, SE Korea: Modes of pyroclastic sedimentation, changes in eruption style, and implications for basin configuration". Geological Society of America Bulletin 120, nr 9-10 (1.09.2008): 1263–79. http://dx.doi.org/10.1130/b26077.1.
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Baimanov, Kenesbay, Kadirbek Nazarbekov, Ruslan Baimanov i Sharap Tazhibayev. "Hydraulic calculation of irrigation settling tanks of Amu Darya irrigation systems". E3S Web of Conferences 264 (2021): 03027. http://dx.doi.org/10.1051/e3sconf/202126403027.
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The Amu Darya river carries a large amount of up to 15 kg/m3 of suspended matter containing up to 85-90% suspended and 10-15% bottom sediments, which pose a serious threat to the hydroelectric power station and irrigation systems operating in its basin. In case of dam water intake, head sump tanks are provided in the composition of waterworks. So, in the composition of Right-Bank and Left-Bank, sedimentation tanks with mechanical cleaning to protect the channels were built at the Takhiatash hydroelectric complex Kaskelenskaya and Selinsky irrigation system. It is established that the hydraulic and alluvial modes of operation of these settling tanks depend on the water, alluvial, and backwater modes of operation Takhiatash waterworks. It is noted that due to low water conditions, this hydroelectric power plant operated for a significant part of the year with fully closed gates in all spans, producing intensive siltation of the upper stream. These processes led to a change in the alluvial mode of operation of the settling tanks. At the same time, due to low water and excessive design dimensions, in the first years of operation, these settling tanks were heavily silted up, the bottom mark rose to 17.2 m (above the design 165 m). Properly designed settling tanks should prevent siltation of main and distribution channels while respecting the transport capacity of the channels located below. It is proved that some well-known methods for calculating settling tanks, due to their complexity and bulkiness, cannot be used in calculating siltation modes of settling tanks under operational conditions that require simplification or finding a simpler relationship. A simple method is developed for calculating the dynamics of sediment deposition in irrigation sump tanks based on the probability of turbulent pulsation motion. Recommended: for normal operation of irrigation septic tanks, it is necessary to carry out systematic monitoring of the output turbidity and intensity of treatment, as well as water supply according to the water consumption schedule.
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Cati, Alice. "The vulnerable gaze of the migrant". Alphaville: Journal of Film and Screen Media, nr 18 (1.12.2019): 54–69. http://dx.doi.org/10.33178/alpha.18.05.
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In the current media system, we are observing the increasing sedimentation of symbolic forms, discourses and imagery regarding contemporary migrations. With the reuse of videos filmed by migrants, the documentary form represents the best “yielding field” where intercultural modes of representation and visual self-inscriptions can be constantly reinvented. In particular, videos made with nonprofessional devices have drawn viewers’ attention to the capacity of moving images to bear witness to reality “from below” and, in some respects, to reproduce aesthetically the opacity and the contingency of events, even the most tragic ones. This paper examines how such a gaze, when it is embodied by the migrant subject, raises questions about the representation of a first-person experience, an experience which paradoxically constitutes a denial of all identity and subjectivity in a deeper sense. To do this, two interesting experiments recently hosted by the website of the Italian newspaper La Repubblica will be analysed: the web series Com’è profondo il mare and Un unico destino—Tre padri e il naufragio che ha cambiato la nostra storia. These web series not only represent traumatic events, but the images show clashes within the depictions themselves and a collision or negotiation between conflicting points of view.