REKONSTRUKCE PALEOHYDROGRAFIE NA ZÁKLADĚ DATOVÁNÍ SEDIMENTŮ HOLŠTEJNSKÉ JESKYNĚ (MORAVSKÝ KRAS)

Large sections in cave deposits are exposed in the Holštejnská Cave in the Moravian Karst. The periods of fluvial activity alternated with periods of speleothem deposition. The study of the genesis and age of these cave deposits poses a clue to the reconstruction of development of the Holštejnská Cave and of local paleohydrographic history. The time of deposition was determined by U-series dating of speleothems, 10Be and 26Al dating of quartz pebbles, radiocarbon dating of charcoal and measurement of paleomagnetic record in both clastic sediments and speleothems. The fluvial sediments were deposited during the Early, Middle and Late Pleistocene in the cave. The age of oldest cave sediment sequence deposited by a subsurface stream indicates that the local hydrographic situation has changed later than 0.8 Ma

Historical climatic record from flood sediments deposited in the interior of Spirálka Cave, Czech republic

Magnetic susceptibility (χ) was measured on more than four hundred samples collected from a 5 m high section of fine grained sediments deposited during flood events in the interior of Spirálka Cave. Spirálka Cave is located in the northeastern portion of the Moravian Karst, Czech Republic. In the upper 1.5 m of this profile, mineral magnetic (χfe, ARM/SIRM, S-ratio, χ(T)) and other non-magnetic measurements heavy mineral concentration, loss on ignition and particle grain size) indicate that χ variations are controlled by the concentration of magnetite and by magnetic grain size, i.e. increased magnetic susceptibility results from increased concentration of coarse grained magnetite. A positive correlation with Ti and Zr concentrations in this part of the profile with our magnetic susceptibility record is a detrital signal responding to changing environmental conditions in the catchment area. Furthermore, a comparison of our susceptibility record to the record of winter temperature anomalies constructed from both instrumental and historical records collected at the Klementinum Observatory in Prague shows a remarkable correlation. The most probable explanation of these correlations is that during years with warmer winters (positive winter temperature anomalies) and less snow cover the floods were less intensive but probably had access to larger tracts of cultivated land as agriculture tended to expand during these warmer periods. Cultivation of the land provided flood waters with greater access to coarser grained magnetite-like materials exposed by tilling of soils. Lower in the profile, interpreting the environmental significance of magnetic susceptibility variations is more complex as remobilization of iron has occurred. Nevertheless the magnetic susceptibility record when coupled with non-magnetic measurements can be shown to correlate to known environmental conditions present in Central Europe during the deposition of the lower portion of the profile. © 2007 Elsevier B.V. All rights reserved

Electron emission by Doppler-mediated formation of doubly excited

We present a new electron emission process which may give rise to a structure in electron energy distributions observed for grazing incidence of protons on atomically clean \chem{Al(111)}. It is conjectured that the formation of doubly excited negative hydrogen ions \chem{H^{- \ast \ast}} from the Doppler-shifted surface-density-of-states results in autodetached electrons which are scattered and diffracted at the monocrystalline surface. This scenario is a modification of a recently suggested model which assumed electron production from elastic collisions of projectiles with the free-electron gas at the surface and diffraction upon escape into vacuum. The here proposed process should be most significant for hydrogen projectiles with comparably low energy (< 10 \un{keV})

Preliminary study on the mineral magnetic properties of sediments from Kůlna Cave (Moravian Karst), Czech Republic

Magnetic property variations in marine, lacustrine and loess-paleosol sequences have proved to be useful proxies in climate change studies. However in order to correctly interpret the record of the magnetic property variations it is absolutely necessary to have a good understanding of the cause of the observed variations. Most of the ambiguity in loess-paleosol studies is in distinguishing the role of pedogenesis from other climatic factors. Studying the mineral magnetic properties of the protected cave sediments which have not undergone pedogenesis allows us to determine the degree to which detrital input is climatically driven. These results will help us better understand the variations observed in the surficial loess-paleosol sequences. This study reports mineral magnetic data collected from entrance facies sediments deposited during the early Wurmian glacial stage in the Kůlna Cave. The entrance facies sediments consist of loess-like silts with varying amount of talus. The magnetic susceptibility record from these sediments shows higher values in layers originating in colder climates which is different to that commonly observed in surficial loess deposits. Higher values of magnetic susceptibility in Kůlna sediments are probably due to higher concentrations of ferromagnetic minerals (magnetite and maghemite) and due to an increased proportion of superparamagnetic grains. The magnetic mineralogy and the grainsize distribution (grains larger than superparamagnetic) appear not to change throughout the studied profiles. Higher magnetic susceptibility accompanied by an increase in the superparamagnetic fraction observed in the sediments deposited during colder periods can be explained by an increased input from a pedogenic source when the vegetation cover was reduced and the erosion rate increased

Blind restoration of retinal images degraded by space-variant blur with adaptive blur estimation

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Plastic deformation around indentations and their effect on fatigue cycling

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Blur invariants for image recognition

Abstract Blur is an image degradation that makes object recognition challenging. Restoration approaches solve this problem via image deblurring, deep learning methods rely on the augmentation of training sets. Invariants with respect to blur offer an alternative way of describing and recognising blurred images without any deblurring and data augmentation. In this paper, we present an original theory of blur invariants. Unlike all previous attempts, the new theory requires no prior knowledge of the blur type. The invariants are constructed in the Fourier domain by means of orthogonal projection operators and moment expansion is used for efficient and stable computation. Applying a general substitution rule, combined invariants to blur and spatial transformations are easy to construct and use. Experimental comparison to Convolutional Neural Networks shows the advantages of the proposed theory

An iterative blind source separation method for convolutive mixtures of images

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