The Mixmaster Spacetime, Geroch's Transformation and Constants of Motion

We show that for $U(1)$-symmetric spacetimes on $S^3 \times R$ a constant of motion associated with the well known Geroch transformation, a functional $K[h_{ij},\pi^{ij}]$, quadratic in gravitational momenta, is strictly positive in an open subset of the set of all $U(1)$-symmetric initial data, and therefore not weakly zero. The Mixmaster initial data appear to be on the boundary of that set. We calculate the constant of motion perturbatively for the Mixmaster spacetime and find it to be proportional to the minisuperspace Hamiltonian to the first order in the Misner anisotropy variables, i.e. weakly zero. Assuming that $K$ is exactly zero for the Mixmaster spacetime, we show that Geroch's transformation, when applied to the Mixmaster spacetime, gives a new \mbox{$U(1)$-symmetric} solution of the vacuum Einstein equations, globally defined on \mbox{$S^2 \times S^1 \times R$},which is non-homogeneous and presumably exhibits Mixmaster-like complicated dynamical behavior.Comment: 25 pages, preprint YCTP-20-93, Revte

In vitro culture and apogamy: Alternative pathway in the life cycle of the moss Amblystegium serpens (Amblystegiaceae)

In vitro culture of the moss Amblystegium serpens (Amblystegiaceae) was established on hormone-free Murashige and Skoog (MS) medium that contained a half amount of MS micro- and macro- mineral salts and vitamins, 100 mg/l myoinositol, 30 g/l sucrose, and 0.70% (w/v) agar. Spores were germinated and primary protonema developed on the above medium at 16 h day/8 h night 25±2ºC, 60-70% air humidity, and irradiance of 47 μmol/m2s. Three months after development of primary protonema, seven sporophytes appeared directly from primary protonema without generation alternation. The phenomenon of apogamous sporophyte formation is very rare, both in nature and under in vitro conditions. This is the first report of apogamy induced by Amblystegium serpens

Efficiency zeolite and apatite in mobility harmful heavy metals in soil and plants.

Rezime: Poznavanja mobilnosti teških metala Pb, Cd, Zn i radionuklida U predstvalja jedan od ciljeva zaštite, uređenja i racionalnog korišćenja poljoprivrednog zemljišta sa aspekta proizvodnje zadravstveno bezbedne hrane. Cilj istraživanja disertacije je proučavanje efikasnosti prirodnih mineralnih sirovina na bazi zeolita i apatita sa domaćih nalazišta u mobilnosti teških metala i radionuklida u zemljištima različitih fizičko- hemijskih karakteristika (pseudoglej i černozem) koristeći test kulture slačicu (Sinapis Alba L.) i suncokret (Hellianthus annuus L.). Afinitet, efikasnost, mehanizmi adsorpcije zeolita i precipitacije apatita utvrđeni su u sistemu kolona sa konstantnim pritiskom, pri različitim pH vrednostima (5.00, 7.00) osnovnog kontaminiranog rastvora (Pb, Cd, Zn, U) 300 mg l -1 u vremenskim intervalima 30, 60, 90, 120, 180 minuta. U svim varijantama došlo je do značajnih promena pH vrednosti filtrata. Najviše promene pH vrednosti filtrata, minimalna kolebanja u vremenskom intervalu, pri pH=5.00, zabeležili su osnovni rastvori Pb (7.69-7.87) i U (7.77-7.93) kroz kolonu sa apatitom i nešto nižim promenama za Cd i Zn. Promene pH vrednosti osnovnih kontaminiranih rastvora, pH =5.00, zabeležene su i nakon propuštanja kroz kolone sa zeolitom ali znatno manjeg intenziteta sa trendom promena U>Pb>Cd>Zn. Trend promena između apatita i zeolita nastupile su i kod osnovnog kontaminiranog rastvora pH =7.00. Zeolit i apatit procesima adsorpcije/precipitacije uspešno su imobilisali Pb, pri pH vrednosti osnovnog rastvora 5.00 i 7.00. U kolonama apatit je bolje imobilisao U, zeolit je bolji za imobilizaciju Cd, dok su za Zn pokazali veoma sličan afinitet. Zeolit i apatit dodati u količini od 20 g kg-1 zemljišta smanjuju sadržaj vodnorastvorljivih i lakopristupačnih oblika Pb, Cd i Zn u nekontaminiranom i kontaminiranom zemljištu. Kontaminacija pseudogleja i černozema sa Pb i U je negativno uticala na morfofiziološke osobine suncokreta, dok je uticaj za Cd i Zn zavisio od tipa zemljišta. Povećano prisustvo Pb i U na černozemu negativno je uticalo na slačicu, Cd i U u pseudogleju su uticali stimulativno, dok je uticaj ostalih teških metala i radionuklida na masu korena i nadzemnu masu različit i zavisi od tipa zemljišta. Dostupnost Pb i Cd biljkama je veća u pseudoglejnom zemljištu, najvećim delom se akumulira u korenu, sa malom translokacijom u nadzemne delove za Pb i dobrom za Cd i većim afinitetom kod slačice. Cink je veoma mobilan u pseudoglejnom zemljištu, sadržaj Zn u korenu je niži od sadržaja u nadzemnim delovima i kod suncokreta i slačice. Mobilnost urana je veća u černozemu, pri čemu najveći deo ostaje u korenu biljke. Upotrebom zeolita, posebno apatita smanjen je sadržaj mobilnih formi toksičnih metala i radionuklida u zemljištu, dostupnost biljkama, kao i sadržaj u korenu i nadzemnoj masi suncokreta i slačice.SUMMARY: Knowledge of the mobility of heavy metals Pb, Cd, Zn and radionuclides U represents one of the goals of protection, regulation and rational use of agricultural soils from the aspect of production of safe food. The aim of the research thesis is the study of the efficiency of natural mineral materials based on zeolite and apatite from domestic deposits in the mobility of heavy metals and radionuclides in the soils of the different physicochemical characteristics (pseudogley and chernozem) using a test culture mustard (Sinapis alba L.) and sunflower (Hellianthus annuus L.). Affinity, efficiency, zeolite adsorption mechanisms and apatite adsorption precipitation were determined in a constant-pressure column system at 300 mg l-1 for different pH values (5.00, 7.00) of the basic contaminated solution (Pb, Cd, Zn, U) at time intervals 30, 60, 90, 120, 180 minutes. In all variants, significant changes in the pH of the filtrate occurred. The most significant changes in the pH of the filtrate, minimal fluctuations in the time interval, at pH = 5.00, recorded the basic solutions of Pb (7.69-7.87) and U (7.77-7.93) through the column with apatite and somewhat lower changes for Cd and Zn. Changes in the pH of the basic contaminated solutions, pH=5.00, were also recorded after leaking through the zeolite columns but with significantly lower intensity with the trend of changes U> Pb> Cd> Zn. The trend of changes between apatite and zeolite also occurred in the basic contaminated solution pH=7.00. Zeolite and apatite adsorption/precipitation processes successfully immobilized Pb at pH of the basic solution 5.00 and 7.00. In colonies, apatite better immobilized U, zeolite is better for immobilisation of Cd, while for Zn, they showed a very similar affinity. Zeolite and apatite are added in an amount of 20 g kg-1 soil to reduce the content of watersoluble and easily accessible forms of Pb, Cd and Zn in uncontaminated and contaminated soil. Contamination of pseudogley and chernozems with Pb and U negatively influenced the morpho-physiological characteristics of sunflower, while the influence of Cd and Zn was dependent on the soil type. The increased presence of Pb and U in chernozems had a negative impact on the mustard, Cd and U in pseudogley were influenced by stimulus, while the influence of other heavy metals and radionuclides on the root mass and above ground mass varies and depends on the type of soil. The availability of Pb and Cd plants is higher in pseudogley soil, mostly accumulating at the root, with a small translocation into the above-ground parts for Pb and good for Cd and greater affinity in the mustard. Zinc is very mobile in pseudogley soil, the content of Zn at the root is lower than the content in the above-ground parts and sunflower and mushrooms. Uranium mobility is higher in chernozem, with most of it remaining at the root of the plant. The use of zeolite, especially apatite, reduced the content of mobile forms of toxic metals and radionuclides in soil, availability to plants, as well as the content at the root and above ground mass of sunflower and mustard

Asymptotic Behavior of the T3×RT^3 \times R Gowdy Spacetimes

We present new evidence in support of the Penrose's strong cosmic censorship conjecture in the class of Gowdy spacetimes with $T^3$ spatial topology. Solving Einstein's equations perturbatively to all orders we show that asymptotically close to the boundary of the maximal Cauchy development the dominant term in the expansion gives rise to curvature singularity for almost all initial data. The dominant term, which we call the ``geodesic loop solution'', is a solution of the Einstein's equations with all space derivatives dropped. We also describe the extent to which our perturbative results can be rigorously justified.Comment: 30 page

Derivation of a new set of force field parameters for ammine complexes of chromium(III) containing halogenido ligands: modeling of the trans-influence of halogenido ligands

An approach to model the trans-influence using partial atomic charges derived from the molecular electrostatic potential by means of the restrained electrostatic potential (RESP) fitting method is exemplified on a series of halogenido-ammine octahedral chromium(III) complexes. RESP charges incorporated in the present vibrationally optimized consistent force field account for second-order phenomena, improve the modeling and assignment of skeletal vibrations, and reproduce the trends in frequency shifts along the F, Cl, Br, I series. In addition, a supplementary statistical analysis is given for the Cr-halogen bonds in the crystal structures from the CSD

Supplementary data for article: Filipović, N. R.; Elshaflu, H.; Grubišić, S.; Jovanović, L. S.; Rodić, M.; Novaković, I.; Malešević, A.; Djordjević, I. S.; Li, H.; Šojić, N.; et al. Co(III) Complexes of (1,3-Selenazol-2-Yl)Hydrazones and Their Sulphur Analogues. Dalton Transactions 2017, 46 (9), 2910–2924. https://doi.org/10.1039/c6dt04785h

Supplementary material for: [https://doi.org/10.1039/c6dt04785h]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2430

Effect of NaCl on seed germination in some Centaurium Hill. Species (Gentianaceae)

The influence of high NaCl concentrations on seed germination in both light and darkness was examined in the species Centaurium pulchellum, C. erythraea, C. littorale, C. spicatum, and C. tenuiflorum. Salt tolerance was found to depend on the life history of the seeds. To be specific, seeds of all five species failed to complete germination when exposed to continuous white light if kept all the time in the presence of 100-200 mM and greater NaCl concentrations. However, when after two weeks NaCl was rinsed from the seeds and the seeds were left in distilled water under white light for an additional two weeks, all species completed germination to a certain extent. The percent of germination not only depended on NaCl concentration in the prior medium, but was also species specific. Thus, seeds of C. pulchellum, C. erythraea, and C. littorale completed germination well almost irrespective of the salt concentration previously experienced. On the other hand, seeds of C. tenuiflorum completed germination poorly if NaCl concentrations in the prior media were greater than 200 mM. When seeds after washing were transferred to darkness for an additional 14 days, they failed to complete germination if previously imbibed on media containing NaCl concentrations greater than 400 mM. However, the seeds of all species, even if previously imbibed at 800 mM NaCl, could be induced to complete germination in darkness by 1 mM gibberellic acid. .Uticaj visokih koncentracija NaCl na klijanje semena, kako na svetlosti tako i u tami, ispitivano je kod vrsta Centaurium pulchellum, C. erythraea, C. littorale, C. spicatum i C. tenuiflorum. Tolerantnost ovih biljaka na natrijum-hlorid zavisi od životnog ciklusa semena. Zapravo, semena svih pet ispitivanih vrsta nisu završavala klijanje kada su bila izložena kontinuelnoj beloj svetlosti u prisustvu 100-200 mM i pri većim koncentracijama. Pored toga, semena svih ovih vrsta, izložena imbibiciji na 800 mM NaCl, mogla su biti indukovana da završe klijanje u mraku uz dodatak 1 mM giberelinske kiseline. .nul

Wake response to an ocean-feedback mechanism: Madeira Island case study

This discussion focused on the numerical study of a wake episode. The Weather Research and Forecasting model was used in a downscale mode. The current literature focuses the discussion on the adiabatic dynamics of atmospheric wakes. Changes in mountain height and consequently on its relation to the atmospheric inversion layer should explain the shift in wake regimes: from a 'strong-wake' to a 'weak-wake' scenario. Nevertheless, changes in SST variability can also induce similar regime shifts. Increase in evaporation, contributes to increase convection and thus to an uplift of the stratified atmospheric layer, above the critical height, with subsequent internal gravity wave activity.Comment: Under review proces