The Impact of Isotopic Composition of Lead on the Neutron-Physical Characteristics of Fast Reactor with Liquid Metal Coolant

It is well known, that lead coolant, highly enriched by 208Pb, has some advantages over other coolants. It is predicted that the use of 208Pb in the reactor core will lead to an increase in the production of plutonium and transmutation of long-lived decay products. The main objective of this paper was to investigate the influence of the isotopic composition on the fast reactor neutron-physical characteristics. For this purpose we used the RBETS-M benchmark - a fast energy reactor that includes 12 zones with different sizes and temperatures of the materials. Calculations were performed for homogeneous and heterogeneous models. Our calculations show that the replacement of the coolant with the natural lead to 208Pb and 208Pb together with Bi can substantially improve the neutron-physical characteristics of the fast reactor, in particular by reducing the initial reactivity margin. Studies of the heterogeneity effect in the reactor model showed an increase in the effective multiplication factor of about 1.5% at the end of the campaign

Adaptive strategy of halophytic plants Polygonum maritimum and Euphorbia paralias

The leaf surface microstructure, pigments spectrum, phytohormones content, and lipids composition of halophytes with various metabolic and physiological strategies of adaptation to salinity of Polygonum maritimum L. and Euphorbia paralias L. grown under natural conditions on dunes of the Pomorie Lake (Bulgaria) are compared. P. maritimum stomata are located on the leaf both sides below the cuticle level, whereas, in E. рaralias, stomata are present only on the abaxial side, and they are surrounded with hump-shaped cuticle constructions. A high amount of carotenoids (as compared with chlorophylls) in P. maritimum leaves indicates that these pigments have a light-collecting function and could transfer an additional energy to chlorophylls. In leaves of E. paralias and P. maritimum, free abscisic acid and conjugated indole-3-acetic acid prevailed. The inactive cytokinins (cis-zeatin and zeatin-O-glucoside) dominated in E. paralias leaves, whereas P. maritimum leaves contained a significant quantity of isopentenyl-type cytokinins. The presence of a large amount of saturated fatty acids provides a decrease of membrane permeability and better resistance against soil salinity. It is concluded that the ecological strategy of halophytes involves the complex of structural and functional adaptations and determines a successful existence under salinity conditions.Проведено порівняння мікроструктури листкової поверхні, пігментного спектра, вмісту фітогормонів і складу ліпідів у галофітів з різною метаболічною і фізіологічною стратегіями адаптації до засолення Polygonum maritimum L. та Euphorbia paralias L., які зростали у природних умовах на дюнах Поморійського озера (Болгарія). У P. maritimum продихи знаходяться по обидва боки листка нижче рівня кутикули, тоді як у E. paralias — лише на абаксіальному боці й оточені складками кутикули. Значна кількість каротиноїдів (порівняно з хлорофілами) у листках P. maritimum указує на те, що ці пігменти виконують світлозбиральну функцію і можуть передавати додаткову енергію на хлорофіли. У листках E. paralias і P. maritimum переважають вільна абсцизова кислота і кон'югована індоліл-3-оцтова кислота. Неактивні цитокініни (цисзеатин і зеатин-О-глюкозид) домінують у листках E. paralias, тоді як у листках P. maritimum міститься значна кількість ізопентенільних форм цитокінінів. Наявність великої концентрації насичених жирних кислот забезпечує зменшення проникності мембран і кращу солестійкість. Зроблено висновок, що екологічна стратегія галофітів поєднує комплекс структурних та функціональних пристосувань і визначає успішне існування в умовах засолення.Проведено сравнение микроструктуры листовой поверхности, пигментного спектра, содержания фитогормонов и состава липидов у галофитов с различной метаболической и физиологической стратегиями адаптации к засолению Polygonum maritimum L. и Euphorbia paralias L., произраставших в естественных условиях на дюнах Поморийского озера (Болгария). У P. maritimum устьица находятся по обе стороны листа ниже уровня кутикулы, тогда как у E. paralias — только на абаксиальной стороне и окружены складками кутикулы. Значительное количество каротиноидов (относительно хлорофиллов) в листьях P. maritimum указывает на то, что эти пигменты выполняют светособирающую функцию и могут передавать дополнительную энергию на хлорофиллы. В листьях E. paralias и P. maritimum преобладают свободная абсцизовая кислота и конъюгированная индолил-3-уксусная кислота. Неактивные цитокинины (цис-зеатин и зеатин-О-глюкозид) доминируют в листьях E. paralias, в то время как в листьях P. maritimum содержится значительное количество изопентенильных форм цитокининов. Наличие высокой концентрации насыщенных жирных кислот обеспечивает уменьшение проницаемости мембран и улучшает солеустойчивость. Сделан вывод, что экологическая стратегия галофитов объединяет комплекс структурных и функциональных приспособлений и определяет успешное существование в условиях засоления

Non-Abelian Vortices, Super-Yang-Mills Theory and Spin(7)-Instantons

We consider a complex vector bundle E endowed with a connection A over the eight-dimensional manifold R^2 x G/H, where G/H = SU(3)/U(1)xU(1) is a homogeneous space provided with a never integrable almost complex structure and a family of SU(3)-structures. We establish an equivalence between G-invariant solutions A of the Spin(7)-instanton equations on R^2 x G/H and general solutions of non-Abelian coupled vortex equations on R^2. These vortices are BPS solitons in a d=4 gauge theory obtained from N=1 supersymmetric Yang-Mills theory in ten dimensions compactified on the coset space G/H with an SU(3)-structure. The novelty of the obtained vortex equations lies in the fact that Higgs fields, defining morphisms of vector bundles over R^2, are not holomorphic in the generic case. Finally, we introduce BPS vortex equations in N=4 super Yang-Mills theory and show that they have the same feature.Comment: 14 pages; v2: typos fixed, published versio

The Microstructure Organization and Functional Peculiarities of Euphorbia paralias L. and Polygonum maritimum L. – Halophytic Plants from Dunes of Pomorie Lake (Bulgaria)

The aim of this research was to investigate the leaf surface microstructure, pigments spectrum, hormones status and lipids composition of halophytes Polygonum maritimum L. and Euphorbia paralias L. that grow under natural conditions on the dunes of Pomorie Lake, (Bulgaria). It was shown that the existence in saline and dry soils provided among others adaptive mechanisms by specific microstructure of leaf. The adaxial and abaxial surfaces of P. maritimum leaves are covered with a dense layer of cuticle wax, stomata are located on the leaf both sides below the cuticle level. In E. paralias the cuticle is also well developed on the adaxial surface of leaf laminas. The epidermis of the leaf lower side is covered with a less dense cuticle layer formed by large wax crystals. This plant has stoma pores only on the abaxial side of small leaves below the cuticle level and they are surrounded with hump-shaped cuticle constructions. A high amount of carotenoids (as compared with that of chlorophylls) in P. maritimum leaves indicates that these pigments have a light-collecting function and could transfer an additional energy to chlorophylls. The high performance liquid chromatography method has been used to provide a qualitative and quantitative analysis of hormones. It was shown that in leaves of E. paralias and P. maritimum free abscisic (ABA) and conjugated indole-3-acetic (IAA) acids prevailed. A high level of active ABA is correlated with the salt tolerance and ability to survive and grow in stress conditions. A high level of conjugated form of IAA demonstrated that activity of this hormone is limited. The cytokinins qualitative and quantitative analyses demonstrated that in E. paralias leaves zeatin forms dominated, and the level of inactive cytokinins (cis-zeatin and zeatin-O-glucoside) was much higher than that of active ones (trans-zeatin and zeatin riboside). P. maritinum leaves contained a significant quantity of isopentenyl forms – isopentenyladenine and isopentenyladenosine, and among zeatin forms, zeatin-O-glucoside prevailed. Studies on the fatty acids content showed that in halophytes the salt resistance mechanism is based on the regulation of plasmatic membrane transport function that involves non-saturated fatty acids. The presence of a large amount of saturated fatty acids provides a decrease of membrane permeability and better resistance against soil salinity

Common Scaling Patterns in Intertrade Times of U. S. Stocks

We analyze the sequence of time intervals between consecutive stock trades of thirty companies representing eight sectors of the U. S. economy over a period of four years. For all companies we find that: (i) the probability density function of intertrade times may be fit by a Weibull distribution; (ii) when appropriately rescaled the probability densities of all companies collapse onto a single curve implying a universal functional form; (iii) the intertrade times exhibit power-law correlated behavior within a trading day and a consistently greater degree of correlation over larger time scales, in agreement with the correlation behavior of the absolute price returns for the corresponding company, and (iv) the magnitude series of intertrade time increments is characterized by long-range power-law correlations suggesting the presence of nonlinear features in the trading dynamics, while the sign series is anti-correlated at small scales. Our results suggest that independent of industry sector, market capitalization and average level of trading activity, the series of intertrade times exhibit possibly universal scaling patterns, which may relate to a common mechanism underlying the trading dynamics of diverse companies. Further, our observation of long-range power-law correlations and a parallel with the crossover in the scaling of absolute price returns for each individual stock, support the hypothesis that the dynamics of transaction times may play a role in the process of price formation.Comment: 8 pages, 5 figures. Presented at The Second Nikkei Econophysics Workshop, Tokyo, 11-14 Nov. 2002. A subset appears in "The Application of Econophysics: Proceedings of the Second Nikkei Econophysics Symposium", editor H. Takayasu (Springer-Verlag, Tokyo, 2003) pp.51-57. Submitted to Phys. Rev. E on 25 June 200

Astronomical Distance Determination in the Space Age: Secondary Distance Indicators

The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Geographical and temporal distribution of SARS-CoV-2 clades in the WHO European Region, January to June 2020

We show the distribution of SARS-CoV-2 genetic clades over time and between countries and outline potential genomic surveillance objectives. We applied three available genomic nomenclature systems for SARS-CoV-2 to all sequence data from the WHO European Region available during the COVID-19 pandemic until 10 July 2020. We highlight the importance of real-time sequencing and data dissemination in a pandemic situation. We provide a comparison of the nomenclatures and lay a foundation for future European genomic surveillance of SARS-CoV-2.Peer reviewe

TRY plant trait database – enhanced coverage and open access

Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives