Response of braiding channel morphodynamics to peak discharge changes in the Upper Yellow River

The braiding intensity and dynamics in large braiding rivers are well known to depend on peak discharges, but the response in braiding and channel–floodplain transformations to changes in discharge regime are poorly known. This modelling study addresses the morphodynamic effects of increasing annual peak discharges in braiding rivers. The study site is a braiding reach of the Upper Yellow River. We estimated the effects on the larger‐scale channel pattern, and on the smaller‐scale bars, channel branches and floodplains. Furthermore, we determined the sensitivity of the channel pattern to model input parameters. The results showed that the dominant effect of a higher peak discharge is the development of chute channels on the floodplains, formed by connecting head‐cut channels and avulsive channels. Widening of the main channel by bank erosion was found to be less dominant. In addition, sedimentation on the bars and floodplains increased with increasing peak discharge. The model results also showed that the modelled channel pattern is especially sensitive to parametrization of the bed slope effect, whereas the effect of median grain size was found to be relatively small. Copyright © 2018 John Wiley & Sons, Ltd.     

The Košice meteorite fall: Recovery and strewn field

We provide the circumstances and details of the fireball observation, search expeditions, recovery, strewn field, and physical characteristics of the Ko?ice meteorite that fell in Slovakia on February 28, 2010. The meteorite was only the 15th case of an observed bolide with a recovered mass and subsequent orbit determination. Despite multiple eyewitness reports of the bolide, only three videos from security cameras in Hungary were used for the strewn field determination and orbit computation. Multiple expeditions of professionals and individual searchers found 218 fragments with total weight of 11.3 kg. The strewn field with the size of 5 × 3 km is characterized with respect to the space distribution of the fragments, their mass and size‐frequency distribution. This work describes a catalog of 78 fragments, mass, size, volume, fusion crust, names of discoverers, geographic location, and time of discovery, which represents the most complex study of a fresh meteorite fall. From the analytical results, we classified the Ko?ice meteorite as an ordinary H5 chondrite.     

Population genetic structure of the endangered limpet Cymbula nigra in a temperate Northern hemisphere region: influence of palaeoclimatic events?

Cymbula nigra (da Costa L, 1771) is the largest limpet in Europe and it is at present considered an endangered species. Nevertheless, its biology is poorly understood and there is a lack of knowledge about population genetic structure. A total of 61 C. nigra specimens were sampled and studied for a fragment of the mitochondrial gene cytochrome c oxidase subunit I. The low genetic diversity, the absence of geographic structure, the significant values reported by measures to test for a recent population expansion and a star‐shaped phylogeny pattern are here interpreted as forming a hypothesis concerning the influence of palaeoclimatic events in the genetic pool of limpets, considering also the information available on different limpet species.     

Marine artificial micro‐reserves: a possibility for the conservation of endangered species living on artificial substrata

The installation of urban and commercial infrastructures on the coast has a severe impact on the marine environment. This impact is mostly negative but, simultaneously, some of the species that colonize artificial substrata (sometimes rare or threatened) find refuge in man‐made structures. The protection of endangered species is usually provided by marine protected areas or by laws that punish their damage or collection, but effective enclosure and custody must be achieved in the case of easily accessible intertidal species. We used the ferruginous limpet, Patella ferruginea, as a case study because it is the most endangered invertebrate in the Mediterranean. This species, which lives in the intertidal zone and is very accessible to people, is a free‐spawning, protandric hermaphrodite, highly dependent on population density and individual size for its reproductive success. Previous work by the authors found the species is especially abundant on artificial substrates on both shores of the Strait of Gibraltar, where people collect fewer of them. Spanish laws of coastal management do not allow the enclosure of the natural coastline, but artificial installations like harbour breakwaters may be closed or guarded, and visits for educational purposes may be carried out under control. The possibility of declaring some kind of environmental protection for these artificial areas would be a very helpful tool for conservation and management purposes. Protected individuals would grow larger and eventually produce exponentially more offspring, which could be transported by currents to adjacent habitats. Here we propose a protection concept for artificial sites termed Artificial Marine Micro‐Reserve (AMMR), where some endangered species experience a refuge from human disturbance. This concept is a modification of the land micro‐reserves that have been recently declared in small natural sites that keep rare plant species. A network of AMMRs would be the final objective, allowing the creation of a great metapopulation of P. ferruginea and also giving refuge to other endangered species that have been found to grow in this type of substratum. Critically, the declaration of a micro‐reserve cannot be used as a reason in favour of new construction because of the negative influence of such structures on the marine environment, together with the fact that there is no certainty that valuable species will settle on them.     

Laboratory measurements of electrical conductivity of biotites

Summary For the sake of helping to clarify the anisotropic behaviour of KTB borehole rock samples, AC (10³ Hz) and DC electrical conductivities of powdered biotites and flogopites (sheet silicates) were investigated in various atmospheres (air, argon) at temperatures of 20–1200°C.Contribution No. 106/90, Geophysical Institute, Czechosl. Acad. Sci., Prague.     

Automation of measuring the temperature dependence of electrical conductivity of rocks using a PMD-85-1 microcomputer

Summary The new for measuring the electrical conductivity of rocks and minerals developed in the Geophysical Institute is briefly discussed. Unlike the earlier method it uses a PMD-85-1 microcomputer and related equipment (all of CMEA production), which enable the automatic control of the experiment, collection, evaluation, graphic display and storage of the results. This method is verified by measuring the electrical conductivities of granitoids.

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Diatom-based reconstruction of Holocene hydrological changes along the Colorado River floodplain (northern Patagonia,Argentina)

Diatom assemblages recovered from a Colorado River delta core in northern Patagonia, Argentina were analyzed in order to assess past environmental conditions. A total of 35 samples were selected from a 172-cm core extracted 37 km from the mouth (39°36′19.6″S; 62°29′26.1″W). One-hundred and thirty-eight taxa were recognized and grouped according to life forms. Two diatom zones were identified by cluster analysis. At the base of the sequence, the Diatom Zone I (DZI; 4132 ± 35 ??2919?±?27 ¹⁴C yr BP), consisted of clays, and was characterized by assemblages dominated by aerophilous and benthic taxa and chrysophyte stomatocysts, which led to inferences of a sedimentary environment corresponding to a pond experiencing dry periods. The upper section (DZII) was dominated by fine sands and silts encompassing the last ~?150 yr with abundant planktonic and tychoplanktonic diatoms. Benthic diatoms were abruptly replaced by planktonic forms in this zone indicating a shift to deeper waters. These results characterize the meandering dynamics of a deltaic system. During the Mid-Holocene, more arid periods would have favored the deactivation of meanders and the formation of riverine and oxbow wetlands. In Late-Holocene and historical times, more humid conditions and the hydrological system across the floodplain reactivated the paleochannel. Today, the dominant diatom species are brackish/freshwater fragilaroids. A non-multidimensional scaling analysis showed a lack of analogy between fossil and modern samples. The change in diatom floras in recent historical times was attributed to anthropogenic disturbances, a consequence of the regulation of the river flow. This regulation is evidenced by less discharge, morphological modifications in the floodplain and increased salinity in the last decade.     

The effect of estrogen on cadmium distribution in rainbow trout (Oncorhynchus mykiss)

The effects of injections of 17β-estradiol (E2) and Cd, on the distribution of Cd and the induction of metallothionein (MT) mRNA and vitellogenin mRNA was investigated. Bone and liver were the main organs accumulating Cd. However, E2 redirected the metal accumulation from the bone and liver to the gill, gut and muscle upon exposure to E2. Cd did not induce the hepatic MT mRNA levels in animals treated with E2. The VTG mRNA levels were also reduced following co-injection of E2 and Cd. However, the kidney responded to Cd exposure by upregulating MT mRNA even in the presence of E2 treatment. In the liver the reduced MT mRNA induction led to a redistribution of CD from MT to non-MT proteins. The toxicological significance of these alterations in Cd handling remains to be determined.     

НЕКОТОРЫЕ СВЯЗЫ ЭЛЕКТРИЧЕСКИХ ПАРАМЕТРоВ ГОРНЫХ ПОРоД И ИХ ХИМИЧЕСКОГО СОСТАВА

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Summary Analysis of the data set describing the chemical composition of the rocks and their electrical parameters was performed by the principal component method. Some relations between chemical composition and electrical parameters were established.

     

Time patterns of polarization currents generated in measuring the electrical conductivity of rocks

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