Diffusion of a passive scalar by convective flows under parametric disorder

We study transport of a weakly diffusive pollutant (a passive scalar) by thermoconvective flow in a fluid-saturated horizontal porous layer heated from below under frozen parametric disorder. In the presence of disorder (random frozen inhomogeneities of the heating or of macroscopic properties of the porous matrix), spatially localized flow patterns appear below the convective instability threshold of the system without disorder. Thermoconvective flows crucially effect the transport of a pollutant along the layer, especially when its molecular diffusion is weak. The effective (or eddy) diffusivity also allows to observe the transition from a set of localized currents to an almost everywhere intense "global" flow. We present results of numerical calculation of the effective diffusivity and discuss them in the context of localization of fluid currents and the transition to a "global" flow. Our numerical findings are in a good agreement with the analytical theory we develop for the limit of a small molecular diffusivity and sparse domains of localized currents. Though the results are obtained for a specific physical system, they are relevant for a broad variety of fluid dynamical systems.Comment: 12 pages, 4 figures, the revised version of the paper for J. Stat. Mech. (Special issue for proceedings of 5th Intl. Conf. on Unsolved Problems on Noise and Fluctuations in Physics, Biology & High Technology, Lyon (France), June 2-6, 2008

Bird Images on Ceramics Produced in South-Eastern Crimea from the Excavations of Azak

The paper considers the 14th century Crimean glazed ceramics with ornithomorphic design made in “sgraffito”, “sgraffito with polychrome coloring” techniques, or a combination of “sgraffito” and “engobe scraping” techniques discovered in the territory of the town of Azov. On the basies of the most preserved items, the following compositions were subdivided, according to the main or key characters, which is a bird: a long-legged bird in tall grass with wings decorated with stylized floral ornament and folded on its back; a large short-legged bird in brushwood with a large expanding tail and plumage designed with rows of scalloped lines; a bird with its wings spread over its back set against the background of spiral-shaped, wavy lines; a procession of birds in a circle, schematically arranged; a small bird widely opening its beak with spread wings over its back with a large elongated object in front of it; a feeding bird arranged inside a hexagon formed by double lines with an ornament between them; a small bird in round medallion with a floral ornament; a bird and a fish with their beak and mouth touching each other. Moreover, the variants of painting of different body parts of the bird, their ornaments, and the elements emphasized by the craftsman: drawn pupils, nasal bone, crest, additional ornaments on the neck, protuberant breast, folded or spread ornamented wings, and other features were also investigated in detail

Properties of impact-related pseudotachylite and associated shocked zircon and monazite in the upper levels of a large impact basin : a case study from the Vredefort impact structure

The Vredefort impact structure in South Africa is deeply eroded to its lowermost levels. However, granophyre (impact melt) dykes in such structures preserve clasts of supracrustal rocks, transported down from the uppermost levels of the initial structure. Studying these clasts is the only way to understand the properties of already eroded impactites. One such lithic clast from the Vredefort impact structure contains a thin pseudotachylite vein and is shown to be derived from the near-surface environment of the impact crater. Traditionally, impact pseudotachylites are referred to as in situ melt rocks with the same chemical and isotopic composition as their host rocks. The composition of the sampled pseudotachylite vein is not identical to its host rock, as shown by the micro-X-ray fluorescence ( XRF) and energy-dispersive X-ray (EDX) spectrometry mapping. Mapping shows that the melt transfer and material mixing within pseudotachylites may have commonly occurred at the upper levels of the structure. The vein is spatially related to shocked zircon and monazite crystals in the sample. Granular zircons with small granules are concentrated within and around the vein (not farther than 6–7 mm from the vein). Zircons with planar fractures and shock microtwins occur farther from the vein (6–12 mm). Zircons with microtwins (65 /{112}) are also found inside the vein, and twinned monazite (180 /[101]) is found very close to the vein. These spatial relationships point to elevated shock pressure and shear stress, concentrated along the vein’s plane during impact.The National Research Foundation (NRF) and the Directorate for Research Development, University of the Free State, 2019–2020.http://www.mdpi.com/journal/mineralsam2021Geolog

Comparison of neuromuscular development in two dinophilid species (Annelida) suggests progenetic origin of <i>Dinophilus gyrociliatus</i>

BACKGROUND: Several independent meiofaunal lineages are suggested to have originated through progenesis, however, morphological support for this heterochronous process is still lacking. Progenesis is defined as an arrest of somatic development (synchronously in various organ systems) due to early maturation, resulting in adults resembling larvae or juveniles of the ancestors. Accordingly, we established a detailed neuromuscular developmental atlas of two closely related Dinophilidae using immunohistochemistry and CLSM. This allows us to test for progenesis, questioning whether i) the adult smaller, dimorphic Dinophilus gyrociliatus resembles a younger developmental stage of the larger, monomorphic D. taeniatus and whether ii) dwarf males of D. gyrociliatus resemble an early developmental stage of D. gyrociliatus females. RESULTS: Both species form longitudinal muscle bundles first, followed by circular muscles, creating a grid of body wall musculature, which is the densest in adult D. taeniatus, while the architecture in adult female D. gyrociliatus resembles that of prehatching D. taeniatus. Both species display a subepidermal ganglionated nervous system with an anterior dorsal brain and five longitudinal ventral nerve bundles with six sets of segmental commissures (associated with paired ganglia). Neural differentiation of D. taeniatus and female D. gyrociliatus commissures occurs before hatching: both species start out forming one transverse neurite bundle per segment, which are thereafter joined by additional thin bundles. Whereas D. gyrociliatus arrests its development at this stage, adult D. taeniatus condenses the thin commissures again into one thick commissural bundle per segment. Generally, D. taeniatus adults demonstrate a seemingly more organized (= segmental) pattern of serotonin-like and FMRFamide-like immunoreactive elements. The dwarf male of D. gyrociliatus displays a highly aberrant neuromuscular system, showing no close resemblance to any early developmental stage of female Dinophilus, although the onset of muscular development mirrors the early myogenesis in females. CONCLUSION: The apparent synchronous arrest of nervous and muscular development in adult female D. gyrociliatus, resembling the prehatching stage of D. taeniatus, suggests that D. gyrociliatus have originated through progenesis. The synchrony in arrest of three organ systems, which show opposing reduction and addition of elements, presents one of the morphologically best-argued cases of progenesis within Spiralia

Freshwater Cyanobacterial Toxins, Cyanopeptides and Neurodegenerative Diseases.

Cyanobacteria produce a wide range of structurally diverse cyanotoxins and bioactive cyanopeptides in freshwater, marine, and terrestrial ecosystems. The health significance of these metabolites, which include genotoxic- and neurotoxic agents, is confirmed by continued associations between the occurrence of animal and human acute toxic events and, in the long term, by associations between cyanobacteria and neurodegenerative diseases. Major mechanisms related to the neurotoxicity of cyanobacteria compounds include (1) blocking of key proteins and channels; (2) inhibition of essential enzymes in mammalian cells such as protein phosphatases and phosphoprotein phosphatases as well as new molecular targets such as toll-like receptors 4 and 8. One of the widely discussed implicated mechanisms includes a misincorporation of cyanobacterial non-proteogenic amino acids. Recent research provides evidence that non-proteinogenic amino acid BMAA produced by cyanobacteria have multiple effects on translation process and bypasses the proof-reading ability of the aminoacyl-tRNA-synthetase. Aberrant proteins generated by non-canonical translation may be a factor in neuronal death and neurodegeneration. We hypothesize that the production of cyanopeptides and non-canonical amino acids is a more general mechanism, leading to mistranslation, affecting protein homeostasis, and targeting mitochondria in eukaryotic cells. It can be evolutionarily ancient and initially developed to control phytoplankton communities during algal blooms. Outcompeting gut symbiotic microorganisms may lead to dysbiosis, increased gut permeability, a shift in blood-brain-barrier functionality, and eventually, mitochondrial dysfunction in high-energy demanding neurons. A better understanding of the interaction between cyanopeptides metabolism and the nervous system will be crucial to target or to prevent neurodegenerative diseases

Phytoliths from some grasses (Poaceae) in arid lands of Xinjiang, China

Opal phytoliths, as silicon dioxide inclusions, are abundant in different parts of a plant. It is known that grasses are the most representative in this respect. The research of phytoliths, removed from 25 most common grass species in the arid and semiarid lands of the Junggar Basin and adjacent areas, has been undertaken. The visual estimation of diversity and variability of silica cells and identification of their morphological types (patterns) were also the aim of our research. Since the work is preliminary, we have emphasized on the visual estimation of silica cell variability and involved only the leaf blades in the analysis. Drawings of the revealed silica cells, characteristic of 25 species, are provided. The sig-nificant morphological diversity of phytoliths has been revealed, as well as their taxonomic similarity at the level of subfamilies. These data can be used for the identification of phytoliths from sediments

Lithologic-petrographic features and conditions of regional cyclite J15 rock formation, revealed by parametrical well 1st Western-Tomsk area

The implemented lithologic-petrographic researches have shown that formation of regional cyclitis U15 rocks, revealed by the parametrical well 1 of the Western-Tomsk area (Tomsk region), occurred during two alternating transgressive cycles, features of which are reflected in lithological structure of lower and upper zonal cyclitis. Inclusions of glauconite and chlorite, organic fossils, faunae, various stratification, washout and redeposition traces of underlaying sediments indicates the formation of the studied strata in shallow marine basin with an active hydrodynamic mode

Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals

The work of V. Pankratova was supported by the financial support of Scientific Research Project for Students and Young Researchers (SJZ/2020/05) realized at Institute of Solid State Physics, University of Latvia. The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.Luminescence properties of nominally pure and doped with Eu3+ and Pr3+ ions SrMoO4 single crystals grown by the Czochralski method have been studied. Thermal quenching of intrinsic emission of pure and doped SrMoO4 single crystals has been observed, as well as a correlation of thermal quenching activation energies with rare-earth ion concentration has been observed. Tunable laser was used to study time-resolved luminescence in a range from 10 K to room temperature. The effect of dopant nature and concentration on intrinsic emission and decay kinetics has been elucidated. --//-- Viktorija Pankratova, Elizaveta E. Dunaeva, Irina S. Voronina, Anna P. Kozlova, Roman Shendrik, Vladimir Pankratov, Luminescence properties and time-resolved spectroscopy of rare-earth doped SrMoO4 single crystals, Optical Materials: X, Volume 15, 2022, 100169, ISSN 2590-1478, https://doi.org/10.1016/j.omx.2022.100169. Article published under the CC BY-NC-ND licence.Scientific Research Project for Students and Young Researchers (SJZ/2020/05); the Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2