Re–Os geochemistry and geochronology of the Ransko gabbro–peridotite massif, Bohemian Massif

The Ransko gabbro–peridotite massif in Eastern Bohemia is a strongly differentiated intrusive complex, which hosts low-grade Ni–Cu ores mainly developed close to the contact of olivine-rich rocks with gabbros, in troctolites, and to a much lesser extent in both pyroxene and olivine gabbros and plagioclase-rich peridotites. Gabbro, troctolite, peridotite and Ni–Cu ores from the Jezírka Ni–Cu (PGE) deposit, considered to be a typical example of the liquid segregation style of mineralization, were analyzed for Re–Os concentrations and isotopic ratios. Seven barren and mineralized samples from the Jezírka deposit yielded a Re–Os regression of 341.5?±?7.9 Ma (MSWD?=?69). Strongly mineralized peridotite with mantle-like initial ¹⁸⁷Os/¹⁸⁸Os ratio of 0.125 suggests that Os as well as other PGE present in the Ni–Cu mineralization are predominantly of mantle origin. On the other hand, barren and low-mineralized samples have radiogenic initial ¹⁸⁷Os/¹⁸⁸Os ratios of 0.14–0.16 suggesting some import of Re and/or radiogenic ¹⁸⁷Os most likely through contamination by continental crust during magma emplacement. The Re–Os age of the Ransko Massif is significantly younger than the previously suggested Lower Cambrian age, but it is similar to and/or younger than the age of metamorphism of the adjacent Kutná Hora crystalline complex and the Moldanubian unit. Therefore, it is likely that the emplacement of the Ransko massif and its Ni–Cu mineralization was closely connected with the late-stage evolution of the Kutná Hora crystalline complex.     

Full‐scale Applications of Membrane Filtration in Municipal Wastewater Treatment Plants

The performance of one pilot‐scale and two full‐scale membrane bioreactors (MBR) were evaluated based on the control of main operational parameters, composition of microbial community and pathogens concentration in the treated outlet. Plants were designed for 0.75 m³/day (A), 60 m³/day (B) and 30 m³/day (C). Inlet and outlet samples were monitored for chemical oxygen demand (COD), biological oxygen demand, total suspended solids, ammonia nitrogen concentration (NH₄–N), nitrate nitrogen concentration, total Kjeldahl nitrogen, total phosphorus and phosphate phosphorus concentration concentrations. Plants showed good COD removal: 91.9% for Plant A, 97.8% for Plant B and 94.2% for Plant C. The targeted nitrogenous ion was NH₄–N due to the requirements for outlet limits. NH₄–N removal was moderate for Plant A (73.3%) and Plant B (86.1%) and excellent for Plant C (>99%). Excellent phosphorus removal was achieved by Plant A (average outlet concentration was 0.7 mg/L, efficiency 84.7%). Unsatisfactory results for phosphorus removal were achieved at the full‐scale plants due to operational problems. The dependency between the extracellular polymeric substances increase and decreasing mixed liquor volatile suspended solids for both lab and full‐scale plants was confirmed. Soluble microbial product concentrations were reduced by 65–68% after coagulant dosage for Plant A. Outlets from the MBR plants were monitored for the presence of pathogens (thermotolerant coliforms, Escherichia coli, intestinal Enterococci and culturable microorganisms at 22 and 37°C). The treated effluent from Plant A, B and C met Czech national legislation regarding reuse criteria (standards) for environment, irrigation and swimming purposes. Plants B and C were not able to achieve requirements for potable water and personal hygiene quality standards.     

Large wood load and transport in a flood-free period within an inter-dam reach: a decade of monitoring the Dyje River,Czech Republic

This study examined the large wood (LW) load and transport during the non-flood period (2009–2018) following major floods that occurred in 2002 and 2006 within the inter-dam reach of the Dyje River (Czech–Austrian border). The LW load was examined in 36 river corridor segments scattered within the reach in the 2009–2018 period. Two whole-reach surveys (2011 and 2019) on LW frequency and distribution were conducted, and the export of LW to the downstream reservoir was analysed between June 2013 and December 2018. In the period of non-flood discharges, the recruitment and depletion of LW were highly variable processes in space and time, leading to a considerable change in the total LW quantity. Whereas the total number of LW pieces decreased, the total LW volume increased because of the increasing dimensions of newly recruited pieces. The annual variability in the quantity of newly recruited pieces was better explained by the variation in the maximum annual discharges (y = 41.043ln(x) + 3.2737, R² = 0.5352) than by the variability in the number of days with wind gusts >17.2 m/s (y = 1.5004x + 82.096, R² = 0.118). The land use change with the abandonment of human settlements after World War II and the progressive expansion of forest was the major historical factor driving the increased recruitment of LW to the river corridor. While the 2006 (>100-year RI) flood brought approximately 1,250 LW pieces to the reservoir, the 2013 (1.5-year RI) flood delivered 45 pieces. The long-term average monthly input of LW to the reservoir was 7.7 pieces. The exceptional low-magnitude flood of 2013, which occurred at the beginning of the monitoring period, was shown to be a threshold above which the number of LW pieces that floated to the dam significantly increased. © 2020 John Wiley & Sons, Ltd.     

Surfaces of zero kinetic energy in a general three-body problem

We generalize the concept of zero-velocity surface and construct zero-kinetic-energy surfaces. In the space of three mutual distances, we determine the regions where motion is possible; these regions are in the shape of an infinitely long tripod. Motions in the three-body problem are shown to be unstable according to Hill.     

Towards monitoring groundwater‐dependent ecosystems using synthetic aperture radar imagery

Mapping of groundwater‐dependent ecosystems (GDEs) relies largely on assumption‐laden evaporation models, and few global, direct, and real‐time monitoring techniques exist. We propose a new synthetic aperture radar imagery‐derived index, SARGDE, to identify and monitor these ecosystems across Australia. The index captures vegetation reliance on groundwater during dry periods by estimating the relative stability of foliage and branch structure from the vertical/horizontal cross‐polarized band and InSAR coherence. SARGDE is tested over two contrasting study sites in Australia. To build and verify the index, a total of 90 Sentinel‐1 interferometric wide images are processed and stacked in two data‐cubes. GDE response to the SAR signal is explored using a non‐linear dimension reduction algorithm. Relevant statistical parameters are derived from data‐cubes and combined to form the index. As the index relies on a 1‐year time series of globally, freely available, and cloud‐insensitive SAR imagery, SARGDE offers unprecedented capabilities for large‐scale, annual monitoring of GDEs. Such monitoring will aid reconciliation of human and ecosystem groundwater needs by acting as a systematic monitoring tool, helping policy makers to assure ecosystem sustainability where impacts related to mining, agriculture, or climate change may occur.     

The Lagrange-Jacobi equation in the finite-size many-body problem

We determine the values of the barycentric energy constant that necessarily result in collisions between bodies. The standard Hill stability regions in the problem of four or more bodies are shown to be located inside the regions where collisions are inevitable. Only in the problem of three finite bodies is part of the Hill stability region preserved where the bodies can move without colliding with one another. We point out possible astronomical applications of our results.     

Elliptical motions of stars in close binary systems

The motion of stars in close binary systems with conservative mass transfer is considered. It is shown that the Paczynski-Huang model that is currently used to determine the variations of the semimajor axis of the relative orbit of the stars is not correct, and leads to large errors in the derived semi-major axis. A new model is proposed, suitable for elliptical stellar orbits. The reaction forces and gravitational forces between the stars and the stream of overflowing matter are taken into account. The possibility of mass transfer in the presence of an accretion disk is considered.     

The geological-geomorphological structure of the Baltic (Vistula) spit

A model of Holocene evolution for the coastal zone is discussed using the example of the geological-geomorphological structure of the Vistula spit. The conclusion is drawn that there is a significant role played by the aeolian factor in the formation of the studied area. The entire spit, excluding beaches, the near-gulf terrace, and several remnants of the ancient deltaic plain, is mostly composed by aeolian sands. One of these remnants is found in the near-gulf part of the spit near Cape Vysokii.     

Inflation and compactification from Galaxy redshifts?

The distribution of galaxies in the pencil-beam surveys of Broadhurstet al. which proved periodical across 8–10 consecutive steps in a flat dust model withq ₀=0.5 is found to reveal extended periodicity up to 16–17 phase-coherent steps, covering the total sample, in a flat, moderately inflationary model withq ₀=–0.5 (vacuum/dust ratio 2/1). In the latter model the vacuum component helps to reach the critical density and lengthens the expansion time-scale. It is shown that the explanation of the found periodicity as a consequence of space compactification as suggested by G. Paál twenty years ago in connection with apparent quasar periodicities is still possible.     

On the Hill stability in the general problem of three finite bodies

We construct zero-kinetic-energy surfaces and determine the regions where motion is possible. We show that for bodies with finite sizes, there are bounded regions of space within which a three-body system never breaks up. The Hill stability criterion is established.