scholarly journals Chronology of sedimentation in Colesbukta, Spitsbergen (Svalbard Archipelago): the results of the 2018 expedition

2021 ◽  
Vol 937 (4) ◽  
pp. 042081
Author(s):  
N I Meshcheryakov ◽  
I S Usyagina ◽  
V V Sharin ◽  
V A Dauvalter ◽  
G N Dukhno
Keyword(s):  
Catchment Area ◽  
Temporal Dynamics ◽  
Atmospheric Precipitation ◽  
Sedimentation Rates ◽  
Climatic Fluctuations ◽  
Svalbard Archipelago ◽  
The Individual ◽  
Shallow Bay ◽  
Geomorphological Features ◽  
Sedimentation Processes

Abstract This paper presents results of a study of sedimentation in Colesbukta (Isfjorden, Spitsbergen), a typical example of sedimentation in a shallow bay of the Svalbard Archipelago. We have examined sediment samples from several cores collected in Colesbukta in May 2018. To meet the goals of this study, geomorphological features of the Colesbukta catchment area have been identified and described. The lithological characteristics of bottom sediments from the study area have been described and their spatial and temporal changes analyzed. The chronology of sedimentation has been reconstructed by 210Pb and 137Cs. We have calculated sedimentation rates in Colesbukta and their temporal dynamics over the several latest decades. According to our estimations, the sedimentation rate has increased by 2–4 times compared to the middle of the 20th century and ranges from 0.2 to 0.46 mm/year depending on the individual conditions of sedimentation in each part of the bay. Climatic fluctuations are shown to have a direct impact on sedimentation processes in Colesbukta. We have revealed that on the periphery of the studied area the rate of sedimentation better depends on the temperature regime while in its central part it is rather a result of the amount of atmospheric precipitation.

IDENTIFICAÇÃO DAS FEIÇÔES GRANÍTICAS DO MUNICÍPO DE IRAUÇUBA-CEARÁ

2019 ◽  
Vol 21 (2) ◽  
pp. 51-61
Author(s):  
Abner Monteiro Nunes Cordeiro ◽  
Rayane Barroso Araújo ◽  
Frederico De Holanda Bastos ◽  
Augusto César Praciano Sampaio
Keyword(s):  
Field Work ◽  
Granitic Rocks ◽  
Surface Erosion ◽  
Climatic Fluctuations ◽  
Geological Faults ◽  
Dry Climates ◽  
Evolution Understanding ◽  
Geomorphological Features

A exumação de rochas graníticas do Complexo Tamboril-Santa Quitéria, especificamente, na superfície de aplainamento do município de Irauçuba, Ceará, tem revelado uma grande variedade de feições geomorfológicas que se justificam por fatores litológicos e evidentes flutuações climáticas cenozoicas, comandadas, sobretudo, por morfogênese mecânica, associada a climas secos. São relevos residuais como, maciços, cristas, inselbergs, inselguebergs, lajedos e blocos saprolitizados (boulders) em diferentes graus de desenvolvimento que se sobressaem em meio à superfície erosiva rebaixada, regionalmente conhecida como depressão sertaneja. Nesse trabalho, foram identificadas diferentes formas de relevo granítico condicionadas, sobretudo por intempéries de subsuperfície, controladas por falhas e fraturas, e por remoção do regolito através da erosão superficial, além de eventos de esfoliação. Essas formas graníticas constituem peças fundamentais na compreensão da evolução paleoclimática do município de Irauçuba. Para a realização do presente trabalho foram usadas as seguintes metodologias: revisão bibliográfica, levantamento cartográfico e trabalho de campo.Palavras-chave: Feições graníticas; Superfícies de aplainamento; Erosão diferencial. ABSTRACTThe granitic rocks exhumation of Complexo Tamboril-Santa Quitéria, specifically, on the planing surface of Irauçuba county, Ceará, has revealed a great variety of geomorphological features that are justified by lithologic factors and evident Cenozoic climatic fluctuations, mainly, headed by mechanical morphogenesis, associated with dry climates. Residual reliefs like rocky massives, residual ridges, inselbergs and inselguebergs, slab stones and boulders in different degrees of development stand out in the middle of the lowered erosive surface, regionally known by “depressão sertaneja”. In this study, different forms of granite relief were identified, specially conditioned by subsurface erosion, controlled by geological faults and fractures, but also by regolith removal through surface erosion, plus exfoliation spheroidal events. These granitic features are fundamental in paleoclimatic evolution understanding of Irauçuba municipality. For the accomplishment of the present work the following methodology was used: bibliographical revision, cartographic survey and field work. For the accomplishment of the present work the following methodology was used: bibliographical revision, cartographic survey and field work.Keywords: Granitic features; Planing surface; Differential erosion.RESUMENLa exhumación de rocas graníticas del Complejo tamboril-Santa Quitéria, específicamente en la superficie de aplanado del municipio de Irauçuba, Ceará, ha revelado una gran variedad de rasgos geomorfológicos que se justifican por factores litológicos y evidentes fluctuaciones climáticas cenozoicas, comandadas principalmente por morfogénesis mecánica, asociada a climas secos. Son relieves residuales como, macizos, crestas, Inselbergs, inselguebergs, losas y bloques saprolitizados (Boulders) en diferentes grados de desarrollo que sobresalen en medio de la superficie erosiva rebajada, regionalmente conocida como depresión sertaneja. En este trabajo, se identificaron diferentes formas de relieve granítico condicionadas, principalmente por intemperies de subsuperficie, controladas por fallas y fracturas, y por eliminación del regolito a través de la erosión superficial, además de eventos de exfoliación. Estas formas graníticas constituyen piezas fundamentales en la comprensión de la evolución paleoclimática del municipio de Irauçuba. Para la realización del presente trabajo se utilizaron las siguientes metodologías: revisión bibliográfica, levantamiento cartográfico y trabajo de campo.Palabras clave: Facciones graníticas; Superficies de aplanado; Erosión diferencial.

Effect on Sedimentation Characteristics of Bentonite Suspension at Different Conditions

2013 ◽  
Vol 333-335 ◽  
pp. 2004-2009
Author(s):  
Lin Ling Jiang ◽  
Wei Mo ◽  
Xiao Jing Yang ◽  
Tian Li Xue ◽  
Shao Jian Ma
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Sodium Pyrophosphate ◽  
Sedimentation Rates ◽  
Sedimentation Analysis ◽  
Ph Values ◽  
Bentonite Suspension ◽  
Sedimentation Time ◽  
Sedimentation Processes

To better understand the sedimentation processes of bentonite, the sedimentation characteristic of bentonite suspension was studied by using the sedimentation analysis module of Dynamic Contact Angle Meter and Tensiometer. The results indicated that sedimentation characteristics of bentonite suspension were affected by the concentration and pH values of the suspension together with the dosage of dispersants. The natural sedimentation rates of bentonite suspension declined firstly with prolonging the sedimentation time and soon stabilized after about 50s. The sedimentation weight of particles hardly changed when the concentration ranged from 0.5% to 5.0%, while it increased significantly when ranged from 5.0% to 10.0%. The sedimentation weight and rate were relatively bigger at 4.4, 11.8 than that of 6.0, 7.9, and the maximum values appeared at pH11.8. Adding sodium pyrophosphate could improve the dispersibility of bentonite suspension.

scholarly journals Levitation of non-magnetizable droplet inside ferrofluid

2018 ◽  
Vol 857 ◽  
pp. 398-448 ◽  
Author(s):  
Chamkor Singh ◽  
Arup K. Das ◽  
Prasanta K. Das
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Viscosity Ratio ◽  
Temporal Dynamics ◽  
Liquid Droplet ◽  
Droplet Surface ◽  
Two Dimensions ◽  
Projection Algorithm ◽  
The Stability ◽  
The Individual

The central theme of this work is that a stable levitation of a denser non-magnetizable liquid droplet, against gravity, inside a relatively lighter ferrofluid – a system barely considered in ferrohydrodynamics – is possible, and exhibits unique interfacial features; the stability of the levitation trajectory, however, is subject to an appropriate magnetic field modulation. We explore the shapes and the temporal dynamics of a plane non-magnetizable droplet levitating inside a ferrofluid against gravity due to a spatially complex, but systematically generated, magnetic field in two dimensions. The coupled set of Maxwell’s magnetostatic equations and the flow dynamic equations is integrated computationally, utilizing a conservative finite-volume-based second-order pressure projection algorithm combined with the front-tracking algorithm for the advection of the interface of the droplet. The dynamics of the droplet is studied under both the constant ferrofluid magnetic permeability assumption as well as for more realistic field-dependent permeability described by Langevin’s nonlinear magnetization model. Due to the non-homogeneous nature of the magnetic field, unique shapes of the droplet during its levitation, and at its steady state, are realized. The complete spatio-temporal response of the droplet is a function of the Laplace number $La$ , the magnetic Laplace number $La_{m}$ and the Galilei number $Ga$ ; through detailed simulations we separate out the individual roles played by these non-dimensional parameters. The effect of the viscosity ratio, the stability of the levitation path and the possibility of existence of multiple stable equilibrium states is investigated. We find, for certain conditions on the viscosity ratio, that there can be developments of cusps and singularities at the droplet surface; we also observe this phenomenon experimentally and compare with the simulations. Our simulations closely replicate the singular projection on the surface of the levitating droplet. Finally, we present a dynamical model for the vertical trajectory of the droplet. This model reveals a condition for the onset of levitation and the relation for the equilibrium levitation height. The linearization of the model around the steady state captures that the nature of the equilibrium point goes under a transition from being a spiral to a node depending upon the control parameters, which essentially means that the temporal route to the equilibrium can be either monotonic or undulating. The analytical model for the droplet trajectory is in close agreement with the detailed simulations.

scholarly journals Northern Hemisphere control of deglacial vegetation changes in the Rufiji uplands (Tanzania)

2015 ◽  
Vol 11 (5) ◽  
pp. 751-764 ◽  
Author(s):  
I. Bouimetarhan ◽  
L. Dupont ◽  
H. Kuhlmann ◽  
J. Pätzold ◽  
M. Prange ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Salt Marshes ◽  
Atmospheric Precipitation ◽  
Eastern Africa ◽  
Last Deglaciation ◽  
Sea Level Changes ◽  
Climatic Fluctuations ◽  
Coastal Dynamics ◽  
Moisture Availability ◽  
The Last Deglaciation

Abstract. In tropical eastern Africa, vegetation distribution is largely controlled by regional hydrology, which has varied over the past 20 000 years. Therefore, accurate reconstructions of past vegetation and hydrological changes are crucial for a better understanding of climate variability in the tropical southeastern African region. We present high-resolution pollen records from a marine sediment core recovered offshore of the Rufiji River delta. Our data document significant shifts in pollen assemblages during the last deglaciation, identifying, through changes in both upland and lowland vegetation, specific responses of plant communities to atmospheric (precipitation) and coastal (coastal dynamics and sea-level changes) alterations. Specifically, arid conditions reflected by a maximum pollen representation of dry and open vegetation occurred during the Northern Hemisphere cold Heinrich event 1 (H1), suggesting that the expansion of drier upland vegetation was synchronous with cold Northern Hemisphere conditions. This arid period is followed by an interval in which forest and humid woodlands expanded, indicating a hydrologic shift towards more humid conditions. Droughts during H1 and the shift to humid conditions around 14.8 kyr BP in the uplands are consistent with latitudinal shifts of the intertropical convergence zone (ITCZ) driven by high-latitude Northern Hemisphere climatic fluctuations. Additionally, our results show that the lowland vegetation, consisting of well-developed salt marshes and mangroves in a successional pattern typical for vegetation occurring in intertidal habitats, has responded mainly to local coastal dynamics related to marine inundation frequencies and soil salinity in the Rufiji Delta as well as to the local moisture availability. Lowland vegetation shows a substantial expansion of mangrove trees after ~ 14.8 kyr BP, suggesting an increased moisture availability and river runoff in the coastal area. The results of this study highlight the decoupled climatic and environmental processes to which the vegetation in the uplands and the Rufiji Delta has responded during the last deglaciation.

scholarly journals Nonlinear visuoauditory integration in the mouse superior colliculus

2021 ◽  
Author(s):  
Shinya Ito ◽  
Yufei Si ◽  
Alan M. Litke ◽  
David A. Feldheim
Keyword(s):  
Superior Colliculus ◽  
Sensory Integration ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Critical Role ◽  
Sensory Information ◽  
Population Level ◽  
Object Identification ◽  
Response Properties ◽  
The Individual

AbstractSensory information from different modalities is processed in parallel, and then integrated in associative brain areas to improve object identification and the interpretation of sensory experiences. The Superior Colliculus (SC) is a midbrain structure that plays a critical role in integrating visual, auditory, and somatosensory input to assess saliency and promote action. Although the response properties of the individual SC neurons to visuoauditory stimuli have been characterized, little is known about the spatial and temporal dynamics of the integration at the population level. Here we recorded the response properties of SC neurons to spatially restricted visual and auditory stimuli using large-scale electrophysiology. We then created a general, population-level model that explains the spatial, temporal, and intensity requirements of stimuli needed for sensory integration. We found that the mouse SC contains topographically organized visual and auditory neurons that exhibit nonlinear multisensory integration. We show that nonlinear integration depends on properties of auditory but not visual stimuli. We also find that a heuristically derived nonlinear modulation function reveals conditions required for sensory integration that are consistent with previously proposed models of sensory integration such as spatial matching and the principle of inverse effectiveness.

scholarly journals Modelling the effects of bacterial cell state and spatial location on tuberculosis treatment: Insights from a hybrid multiscale cellular automaton model

2016 ◽  
Author(s):  
Ruth Bowness ◽  
Mark A. J. Chaplain ◽  
Gibin G. Powathil ◽  
Stephen H. Gillespie
Keyword(s):  
Cellular Automaton ◽  
Bacterial Cell ◽  
Temporal Dynamics ◽  
Treatment Success ◽  
Spatial Location ◽  
Multiscale Model ◽  
Host Cells ◽  
Phenotypic Switching ◽  
Cell State ◽  
The Individual

AbstractIf improvements are to be made in tuberculosis (TB) treatment, an increased understanding of disease in the lung is needed. Studies have shown that bacteria in a less metabolically active state, associated with the presence of lipid bodies, are less susceptible to antibiotics, and recent results have highlighted the disparity in concentration of different compounds into lesions. Treatment success therefore depends critically on the responses of the individual bacteria that constitute the infection.We propose a hybrid, individual-based approach that analyses spatio-temporal dynamics at the cellular level, linking the behaviour of individual bacteria and host cells with the macroscopic behaviour of the microenvironment. The individual elements (bacteria, macrophages and T cells) are modelled using cellular automaton (CA) rules, and the evolution of oxygen, drugs and chemokine dynamics are incorporated in order to study the effects of the microenvironment in the pathological lesion. We allow bacteria to switch states depending on oxygen concentration, which affects how they respond to treatment. This is the first multiscale model of its type to consider both oxygen-driven phenotypic switching of theMycobacterium tuberculosisand antibiotic treatment. Using this model, we investigate the role of bacterial cell state and of initial bacterial location on treatment outcome. We demonstrate that when bacteria are located further away from blood vessels, less favourable outcomes are more likely, i.e. longer time before infection is contained/cleared, treatment failure or later relapse. We also show that in cases where bacteria remain at the end of simulations, the organisms tend to be slower-growing and are often located within granulomas, surrounded by caseous material.

scholarly journals 14C Dated Chronology of the Thickest and Best Resolved Loess/Paleosol Record of the LGM from SE Hungary Based on Comparing Precision and Accuracy of Age-Depth Models

Radiocarbon ◽  
2020 ◽  
Vol 62 (2) ◽  
pp. 403-417
Author(s):  
Pál Sümegi ◽  
Sándor Gulyás ◽  
Dávid Molnár ◽  
Gábor Szilágyi ◽  
Balázs P Sümegi ◽  
...  
Keyword(s):  
Computer Program ◽  
Central Europe ◽  
North Atlantic ◽  
Small Scale ◽  
Sedimentation Rates ◽  
Accumulation Rates ◽  
Climatic Fluctuations ◽  
Precision And Accuracy ◽  
Calculated Average ◽  
Sedimentation Time

ABSTRACTThe Madaras profile found at the northernmost fringe of Bácska loess plateau is one of the thickest and best-developed last glacial loess sequences of Central Europe. The 10-m profile corresponds to a period between 29 and 12 b2k. To unravel feedback to small-scale centennial climatic fluctuations at our site, recorded in the Greenland ice and North Atlantic marine cores, construction of a reliable chronology is needed. Reliability is expressed in terms of best achievable chronological precision. Accuracy however is based on choosing the model best describing the sedimentological features of our profile. Five different age-depth models had constructed and compared relying on 15 14C dates using various statistical, probabilistic approaches to choose the model with the highest achievable precision. Accuracy was also evaluated using accumulation rates against stratigraphy. Models constructed using the computer program Bacon performed best in terms of achieving the best possible stratigraphic accuracy. Seven meters of the profile represents the period of the LGM. The average sedimentation time was 16.8 yr/cm with the highest confined to the period of the LGM. Calculated average sedimentation rates were 4 times higher than previously reported. The peak accumulation periods are dated to the nadir of the LGM.

Recent Paleolimnology of Three Lakes in Northwestern Minnesota

1976 ◽  
Vol 6 (2) ◽  
pp. 249-272 ◽  
Author(s):  
Hilary H. Birks ◽  
M.C. Whiteside ◽  
Donna M. Stark ◽  
R.C. Bright
Keyword(s):  
Catchment Area ◽  
Plant Macrofossils ◽  
Agricultural Runoff ◽  
Water Volume ◽  
Sedimentation Rates ◽  
Minnesota Lakes ◽  
Types Of Information ◽  
The City ◽  
Integrated Study ◽  
Elk Lake

A paleolimnological study was undertaken to investigate changes in three Minnesota lakes over the last 100 years and to demonstrate the stratigraphic effects of cultural eutrophication in two of them. The study combined the analysis of the lake sediment from short cores with stratigraphic analyses of pollen, plant macrofossils, mollusks, diatoms and certain other algae, chydorid Cladocera, and Daphnia ephippia.The rise of Ambrosia type pollen (ragweed) marks the onset of interference with the landscape by European man, which can be closely dated. Calculations of sedimentation rates from this base gave reasonable correlations of other stratigraphic events with historical events.Elk Lake is considered “unpolluted” today and was chosen as a control. Man's effects are limited to logging some of the surrounding forest and to the construction of a dam. Small changes in the lake's fauna and flora are demonstrated, showing the sensitivity of the lake to changes in its catchment area.Lake Sallie and St. Clair Lake, in the same watershed as the city of Detroit Lakes, have been affected not only by logging but also by addition of nutrients from agricultural runoff and sewage effluent. Considerable responses by the lake organisms are apparent. In Lake Sallie the changes were gradual, but in St. Clair Lake they were very abrupt because the lake was partially drained at the same time and the water volume was thereby reduced.The merits of such an integrated study, the types of information gained from the analyses of the various fossils, and the wider application of the results are discussed.

Commercial microwave links in urban rainfall-runoff modelling: Two different approaches to removing the bias

2020 ◽  
Author(s):  
Jaroslav Pastorek ◽  
Martin Fencl ◽  
Jörg Rieckermann ◽  
Vojtěch Bareš
Keyword(s):  
Wave Attenuation ◽  
Temporal Dynamics ◽  
Estimation Methods ◽  
Rainfall Runoff ◽  
Geophysical Research ◽  
Urban Catchment ◽  
Individual Level ◽  
The Individual ◽  
Commercial Microwave Links ◽  
Heavy Rainfalls

<p>Commercial microwave links (CMLs) are point-to-point radio connections widely used as cellular backhaul and thus very well covering urbanized areas. They can provide path-integrated quantitative precipitation estimates (QPEs) as they operate at frequencies where radio wave attenuation caused by raindrops is almost proportional to rainfall intensity. Pastorek et al. (2019b) demonstrated the feasibility of using CML QPEs to predict rainfall-runoff in a small urban catchment. Unfortunately, runoff volumes were highly biased, mostly for QPEs from short CMLs, although the temporal runoff dynamics were predicted very well, especially during heavy rainfall events. It was also shown that, for the heavy rainfalls, reducing the bias by adjusting the CML QPEs to traditional rainfall measurements (Fencl et al., 2017) leads to less accurate reproduction of the runoff temporal dynamics.</p><p>Current understanding is that the bias in CML QPEs is often caused by imprecise estimation of wet antenna attenuation (WAA), which is a complex process influenced by many physical phenomena, including radome hardware or positioning of the outdoor unit. However, traditional WAA estimation methods are typically unable to take into account all the individual-level factors. We proposed (Pastorek et al., 2019a) to estimate WAA separately for each of the examined CMLs by using discharge measurements at the outlet of a small urban catchment and showed that this approach can reduce the bias in CML QPEs, leading to generally satisfying performance of rainfall-runoff models, mainly for heavy rainfalls.</p><p>In the presented study, we evaluate the effect of the method proposed in Pastorek et al. (2019a) (method i) on rainfall-runoff modelling in more detail and compare it to the method of Fencl et al. (2017) (method ii). For a case study in Prague-Letňany, Czech Rep., a calibrated rainfall-runoff model is used to predict discharges at the outlet of the small urban catchment (1.3 km<sup>2</sup>) using QPEs from 16 CMLs. First results confirm that minimizing the bias in CML QPEs using method i is convenient mainly for heavy rainfalls, as Nash-Sutcliffe efficiency is considerably higher in this case for all but one CML (on average 0.65; only 0.40 for method ii). Moreover, method i preserves the information about the rainfall temporal dynamics during heavy rainfalls better than method ii for most of the individual CMLs (correlation coefficient with observed runoffs on average 0.83 for method i and 0.78 for method ii). Next steps should include generalization for other case studies, including an exploratory analysis of the potential mismatches.</p><p> </p><p>References</p><p>Fencl, M., Dohnal, M., Rieckermann, J., Bareš, V., 2017. Gauge-adjusted rainfall estimates from commercial microwave links. Hydrol. Earth Syst. Sci. 21, 617–634.</p><p>Pastorek, J., Fencl, M., Rieckermann, J. and Bareš, V., 2019b. Commercial microwave links for urban drainage modelling: The effect of link characteristics and their position on runoff simulations. Journal of environmental management 251, 109522.</p><p>Pastorek, J., Fencl, M., and Bareš, V., 2019a. Calibrating microwave link rainfall retrieval model using runoff observations. Geophysical Research Abstracts 21, EGU2019-10072.</p><p> </p><p>This study was supported by the project no. 20-14151J of the Czech Science Foundation and by the project of the Czech Technical University in Prague no. SGS19/045/OHK1/1T/11.</p>

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