scholarly journals Periodicities of paleoclimate variations in the first high-resolution non-orbitally tuned grain size record of the past 1 Ma from SW Hungary and regional, global correlations

2019 ◽  
Vol 40 ◽  
pp. 74-90 ◽  
Author(s):  
Pál Sümegi ◽  
Sándor Gulyás ◽  
Dávid Molnár ◽  
Balázs P. Sümegi ◽  
Tünde Törőcsik ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
The Past

Using high-resolution portable OSL (POSL) profiling to characterize Holocene beach ridges at Lake Schweriner See, NE-Germany

2020 ◽  
Author(s):  
Marie-Luise Adolph ◽  
Reinhard Lampe ◽  
Sebatian Lorenz ◽  
Torsten Haberzettl
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Lake Level ◽  
Osl Dating ◽  
Coarse Grained ◽  
Beach Ridge ◽  
Beach Ridges ◽  
The Past ◽  
Depositional Processes ◽  
Ne Germany

<p>Beach ridges are a promising geoarchive to study lake-level variations as they indicate former lake-level maxima. Detecting paleo-shorelines and knowing their elevation, inner structure and age. This helps to quantify lake-level highstands, the duration of elevated lake levels as well as to reconstruct sedimentation processes as important indicators of either external forcing (e.g., higher precipitation/lower evaporation) or anthropogenic impacts (e.g., mill stowage) in the past. In this study, a quantitative paleohydrological reconstruction of lake Schweriner See, NE-Germany, should be achieved by a combination high-resolution multi-proxy analysis on sediment cores from both distal and littoral but also from onshore parts. This poster focuses on the onshore part of the eastern shoreline where a succession of beach ridges is located within a distance of up to 600 m away from the recent shoreline and up to 1.5 m above today’s lake level. This indicates both a greater extension and a higher water level in the past. Here we examine these beach ridges using high-resolution luminescence profiling (POSL, 5-15 cm intervals) with a SUERC portable OSL unit combined with full OSL dating (coarse grain quartz SAR protocol) and independent radiocarbon dating to obtain ages of lake-level maxima as well as a (relative) age distribution within and between individual beach ridges. We measured the water content, loss-on-ignition and grain size variation to characterize the beach ridges and their depositional processes but also to estimate the influences of these parameters on the luminescence signal.</p><p>The sandy beach ridges are deposited on peat, which overlays mainly lacustrine silty and calcareous sediment. The upper 20-40 cm are enriched in humus. This stratigraphy demonstrates a silting-up sequence and development of a wetland, which was affected by a dynamic lake-level development.The dominating grain size within the ridges is coarse grained sand with small gravel and occasionally thin organic layers in between. The initial results of full OSL dating gives a hint that all beach ridges were deposited during the Holocene. The luminescence profiles typically show an increase in photon counts with depth in the upper part, which was influenced by humus enrichment. The luminescence in the otherwise mainly organic and lime free sands below behave differently with depth in each beach ridge. The total photon count either 1) decreases perhaps influenced by a higher groundwater table in the past or reworking of older nearby beach ridges, 2) increases, offering the possibility to extract relative sedimentation rates, but sometimes has leaps to smaller values or 3) fluctuates around a mean value indicating a potential rapid sediment accumulation. Fluctuating values might also occur due to bioturbation.</p><p>In this study, high resolution POSL profiling in combination with grain-size analysis proved to be a promising tool to investigate lacustrine beach ridges and their depositional processes. The method turned out to be valuable to not only select the right sample for OSL dating but also to get a better understanding of beach ridge deposition at Schweriner See.</p>

The Contribution of Intermediate-Voltage, High-Resolution Electron Microscopy In Materials Science: An Appraisal

1990 ◽  
Vol 48 (1) ◽  
pp. 478-479
Author(s):  
John L. Hutchison
Keyword(s):  
High Resolution ◽  
Materials Science ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
The Past ◽  
Resolution Electron ◽  
Extreme Sensitivity ◽  
Electron Microscopes ◽  
New Generation ◽  
Small Metal Particles

Over the past five years or so the development of a new generation of high resolution electron microscopes operating routinely in the 300-400 kilovolt range has produced a dramatic increase in resolution, to around 1.6 Å for “structure resolution” and approaching 1.2 Å for information limits. With a large number of such instruments now in operation it is timely to assess their impact in the various areas of materials science where they are now being used. Are they falling short of the early expectations? Generally, the manufacturers’ claims regarding resolution are being met, but one unexpected factor which has emerged is the extreme sensitivity of these instruments to both floor-borne and acoustic vibrations. Successful measures to counteract these disturbances may require the use of special anti-vibration blocks, or even simple oil-filled dampers together with springs, with heavy curtaining around the microscope room to reduce noise levels. In assessing performance levels, optical diffraction analysis is becoming the accepted method, with rotational averaging useful for obtaining a good measure of information limits. It is worth noting here that microscope alignment becomes very critical for the highest resolution.In attempting an appraisal of the contributions of intermediate voltage HREMs to materials science we will outline a few of the areas where they are most widely used. These include semiconductors, oxides, and small metal particles, in addition to metals and minerals.

The Contribution of Phonon-Scattered Electrons to High-Resolution Electron Micrographs of Crystals

1990 ◽  
Vol 48 (1) ◽  
pp. 62-63
Author(s):  
H. Kohl
Keyword(s):  
High Resolution ◽  
Spherical Aberration ◽  
High Resolution Electron Microscopy ◽  
Static Potential ◽  
Qualitative Comparison ◽  
The Past ◽  
Resolution Electron ◽  
High Resolution Images ◽  
High Resolution Electron Micrographs ◽  
Extract Information

High-Resolution Electron Microscopy is able to determine structures of crystals and interfaces with a spatial resolution of somewhat less than 2 Å. As the image is strongly dependent on instrumental parameters, notably the defocus and the spherical aberration, the interpretation of micrographs necessitates a comparison with calculated images. Whereas one has often been content with a qualitative comparison of theory with experiment in the past, one is currently striving for quantitative procedures to extract information from the images [1,2]. For the calculations one starts by assuming a static potential, thus neglecting inelastic scattering processes.We shall confine the discussion to periodic specimens. All electrons, which have only been elastically scattered, are confined to very few directions, the Bragg spots. In-elastically scattered electrons, however, can be found in any direction. Therefore the influence of inelastic processes on the elastically (= Bragg) scattered electrons can be described as an attenuation [3]. For the calculation of high-resolution images this procedure would be correct only if we had an imaging energy filter capable of removing all phonon-scattered electrons. This is not realizable in practice. We are therefore forced to include the contribution of the phonon-scattered electrons.

scholarly journals d4PDF: large-ensemble and high-resolution climate simulations for global warming risk assessment

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Masayoshi Ishii ◽  
Nobuhito Mori
Keyword(s):  
Risk Assessment ◽  
Global Warming ◽  
High Resolution ◽  
Climate Changes ◽  
Future Climate ◽  
Atmospheric Models ◽  
Large Ensemble ◽  
Past Climate ◽  
The Past ◽  
Climate Simulations

Abstract A large-ensemble climate simulation database, which is known as the database for policy decision-making for future climate changes (d4PDF), was designed for climate change risk assessments. Since the completion of the first set of climate simulations in 2015, the database has been growing continuously. It contains the results of ensemble simulations conducted over a total of thousands years respectively for past and future climates using high-resolution global (60 km horizontal mesh) and regional (20 km mesh) atmospheric models. Several sets of future climate simulations are available, in which global mean surface air temperatures are forced to be higher by 4 K, 2 K, and 1.5 K relative to preindustrial levels. Nonwarming past climate simulations are incorporated in d4PDF along with the past climate simulations. The total data volume is approximately 2 petabytes. The atmospheric models satisfactorily simulate the past climate in terms of climatology, natural variations, and extreme events such as heavy precipitation and tropical cyclones. In addition, data users can obtain statistically significant changes in mean states or weather and climate extremes of interest between the past and future climates via a simple arithmetic computation without any statistical assumptions. The database is helpful in understanding future changes in climate states and in attributing past climate events to global warming. Impact assessment studies for climate changes have concurrently been performed in various research areas such as natural hazard, hydrology, civil engineering, agriculture, health, and insurance. The database has now become essential for promoting climate and risk assessment studies and for devising climate adaptation policies. Moreover, it has helped in establishing an interdisciplinary research community on global warming across Japan.

East Asian winter monsoon variation during the last 3000 years as recorded in a subtropical mountain lake, northeastern Taiwan

The Holocene ◽  
2021 ◽  
pp. 095968362110190
Author(s):  
Tsai-Wen Lin ◽  
Stefanie Kaboth-Bahr ◽  
Kweku Afrifa Yamoah ◽  
André Bahr ◽  
George Burr ◽  
...  
Keyword(s):  
Grain Size ◽  
East Asian Winter Monsoon ◽  
East Asian ◽  
Winter Monsoon ◽  
Mountain Lake ◽  
Sediment Grain Size ◽  
Global Monsoon ◽  
Asian Winter Monsoon ◽  
The Past ◽  
Monsoon System

The East Asian Winter Monsoon (EAWM) is a fundamental part of the global monsoon system that affects nearly one-quarter of the world’s population. Robust paleoclimate reconstructions in East Asia are complicated by multiple sources of precipitation. These sources, such as the EAWM and typhoons, need to be disentangled in order to understand the dominant source of precipitation influencing the past and current climate. Taiwan, situated within the subtropical East Asian monsoon system, provides a unique opportunity to study monsoon and typhoon variability through time. Here we combine sediment trap data with down-core records from Cueifong Lake in northeastern Taiwan to reconstruct monsoonal rainfall fluctuations over the past 3000 years. The monthly collected grain-size data indicate that a decrease in sediment grain size reflects the strength of the EAWM. End member modelling analysis (EMMA) on sediment core and trap data reveals two dominant grain-size end-members (EMs), with the coarse EM 2 representing a robust indicator of EAWM strength. The downcore variations of EM 2 show a gradual decrease over the past 3000 years indicating a gradual strengthening of the EAWM, in agreement with other published EAWM records. This enhanced late-Holocene EAWM can be linked to the expansion of sea-ice cover in the western Arctic Ocean caused by decreased summer insolation.

scholarly journals Paleoenvironments from robust loess stratigraphy using high-resolution color and grain-size data of the last glacial Krems-Wachtberg record (NE Austria)

2020 ◽  
Vol 248 ◽  
pp. 106602
Author(s):  
Tobias Sprafke ◽  
Philipp Schulte ◽  
Simon Meyer-Heintze ◽  
Marc Händel ◽  
Thomas Einwögerer ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Last Glacial ◽  
Size Data ◽  
The Last Glacial

scholarly journals Rip current evidence by hydrodynamic simulations, bathymetric surveys and UAV observation

2017 ◽  
Author(s):  
Guido Benassai ◽  
Pietro Aucelli ◽  
Giorgio Budillon ◽  
Massimo De Stefano ◽  
Diana Di Luccio ◽  
...  
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Numerical Simulations ◽  
Current System ◽  
Current Evidence ◽  
Rip Current ◽  
Rip Currents ◽  
Transport Pathways ◽  
Fine Sediments ◽  
Scientific Challenge

Abstract. The prediction of the formation, spacing and location of rip currents is a scientific challenge that can be achieved by means of different complementary methods. In this paper the analysis of numerical and experimental data, including UAV observation, allowed to detect the presence of rip currents and rip channels at the mouth of Sele river, in the Gulf of Salerno, southern Italy. The dataset used to analyze these phenomena consisted of two different bathymetric surveys, a detailed sediment 5 analysis and a set of high-resolution wave numerical simulations, completed with satellite and UAV observation. The grain size trend analysis and the numerical simulations allowed to identify the rip current system, forced by topographically constrained channels incised on the seabed, which were detected by high resolution bathymetric surveys. The study evidenced that on the coastal area of the Sele mouth grain-size trends are controlled by the contribution of fine sediments, which exhibit suspended transport pathways due to rip currents and longshore currents. The results obtained were confirmed by satellite and UAV 10 observations in different years.

A high-resolution hydrogen isotope record of behenic acid for the past 16 kyr in the northeastern United States

2017 ◽  
Vol 449 ◽  
pp. 1-11 ◽  
Author(s):  
Li Gao ◽  
Yongsong Huang ◽  
Bryan Shuman ◽  
W. Wyatt Oswald ◽  
David Foster
Keyword(s):  
United States ◽  
High Resolution ◽  
Hydrogen Isotope ◽  
Behenic Acid ◽  
Northeastern United States ◽  
The Past ◽  
Isotope Record
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