Stability of the hard-sphere icosahedral quasilattice

The stability of the hard-sphere icosahedral quasilattice is analyzed using the differential formulation of the generalized effective liquid approximation. We find that the icosahedral quasilattice is metastable with respect to the hard-sphere crystal structures. Our results agree with recent findings by McCarley and Ashcroft [Phys. Rev. B {\bf 49}, 15600 (1994)] carried out using the modified weighted density approximation.Comment: 15 pages, 2 figures available from authors upon request, (revtex), submitted to Phys. Rev.

VARIATIONS IN SOLAR ACTIVITY AND CHANGES IN THE LEVEL OF KHAKASSIA SALT LAKES IN THE LAST MILLENNIUM

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Propargylated Novolac Resins for Solvent-Free Technology for High-Performance Composites

Propargyl substituted novolac phenolic resin diluted with unsaturated bisphenol-A ethers was used for glass fiber solvent-free impregnation for the formation of high-performance composites. The addition of 20% mass of diallyl (DAEBA) or dipropargyl (DPEBA) bisphenol-A to propargyl substituted novolac phenolic resin resulted in viscosity drop from 2000 mPa∙s to 400‒500 mPa∙s at 140 °C. This proved to be enough to achieve complete impregnation of the twisted glass fibers, as illustrated by SEM analysis. This  improvement in impregnation was shown to result in increasing both flexural strength and modulus of the unidirectional glass fiber composite material approximately with a factor of two compared to the composite impregnated with resin without bisphenol-A ethers. DPEBA was shown to be more suitable for high-temperate applications since its addition does not seem to result in a decrease of the heat deflection temperature (HDT)

Preparation and study of growth stimulating activity of 1-propyl-4-(3’-amino-1’, 2’, 4’-triazolo-3’-thiopropinyl) piperidin-4-ol

Results on the obtaining and the study of a plant growth stimulator based on 1-propyl-4-(3'-amino-1’,2’,4'-triazolo-3'-thiopropinyl) piperidin-4-ol are presented in the article. 1-propylpiperidin-4-on and 3-mercaptopropinyl-5-amin-1,2,4-triazolo were obtained with the basic parameters of the synthesis for synthesizing of 1-propyl-4-(3'-amino-1', 2', 4'-triazolo-3'-thiopropinyl) piperidin-4-ol. The structures of the obtained organic compounds were proved using IR spectroscopy and1H and13C NMR spectrometry. The obtained 1-propyl-4-(3’-amino-1’2’4’-triazolo-3’-thiopropynyl)-piperidine-4-ol was tested for growth-stimulating activity on spring wheat grains compared with control (water) and has proved to be a domestic growth regulator «Akpinol-alpha» (KN-2). © 2019, Universitatea Babes-Bolyai, Catedra de Filosofie Sistematica. All rights reserved

Rules for Computing Symmetry, Density and Stoichiometry in a Quasi-Unit-Cell Model of Quasicrystals

The quasi-unit cell picture describes the atomic structure of quasicrystals in terms of a single, repeating cluster which overlaps neighbors according to specific overlap rules. In this paper, we discuss the precise relationship between a general atomic decoration in the quasi-unit cell picture atomic decorations in the Penrose tiling and in related tiling pictures. Using these relations, we obtain a simple, practical method for determining the density, stoichiometry and symmetry of a quasicrystal based on the atomic decoration of the quasi-unit cell taking proper account of the sharing of atoms between clusters.Comment: 14 pages, 8 figure

Phonon Localization in One-Dimensional Quasiperiodic Chains

Quasiperiodic long range order is intermediate between spatial periodicity and disorder, and the excitations in 1D quasiperiodic systems are believed to be transitional between extended and localized. These ideas are tested with a numerical analysis of two incommensurate 1D elastic chains: Frenkel-Kontorova (FK) and Lennard-Jones (LJ). The ground state configurations and the eigenfrequencies and eigenfunctions for harmonic excitations are determined. Aubry's "transition by breaking the analyticity" is observed in the ground state of each model, but the behavior of the excitations is qualitatively different. Phonon localization is observed for some modes in the LJ chain on both sides of the transition. The localization phenomenon apparently is decoupled from the distribution of eigenfrequencies since the spectrum changes from continuous to Cantor-set-like when the interaction parameters are varied to cross the analyticity--breaking transition. The eigenfunctions of the FK chain satisfy the "quasi-Bloch" theorem below the transition, but not above it, while only a subset of the eigenfunctions of the LJ chain satisfy the theorem.Comment: This is a revised version to appear in Physical Review B; includes additional and necessary clarifications and comments. 7 pages; requires revtex.sty v3.0, epsf.sty; includes 6 EPS figures. Postscript version also available at http://lifshitz.physics.wisc.edu/www/koltenbah/koltenbah_homepage.htm

Random Tilings: Concepts and Examples

We introduce a concept for random tilings which, comprising the conventional one, is also applicable to tiling ensembles without height representation. In particular, we focus on the random tiling entropy as a function of the tile densities. In this context, and under rather mild assumptions, we prove a generalization of the first random tiling hypothesis which connects the maximum of the entropy with the symmetry of the ensemble. Explicit examples are obtained through the re-interpretation of several exactly solvable models. This also leads to a counterexample to the analogue of the second random tiling hypothesis about the form of the entropy function near its maximum.Comment: 32 pages, 42 eps-figures, Latex2e updated version, minor grammatical change

Intelligence within BAOR and NATO's Northern Army Group

During the Cold War the UK's principal military role was its commitment to the North Atlantic Treaty Organisation (NATO) through the British Army of the Rhine (BAOR), together with wartime command of NATO's Northern Army Group. The possibility of a surprise attack by the numerically superior Warsaw Pact forces ensured that great importance was attached to intelligence, warning and rapid mobilisation. As yet we know very little about the intelligence dimension of BAOR and its interface with NATO allies. This article attempts to address these neglected issues, ending with the impact of the 1973 Yom Kippur War upon NATO thinking about warning and surprise in the mid-1970s. It concludes that the arrangements made by Whitehall for support to BAOR from national assets during crisis or transition to war were - at best - improbable. Accordingly, over the years, BAOR developed its own unique assets in the realm of both intelligence collection and special operations in order to prepare for the possible outbreak of conflict

А не пора ли вернуться к Tg Таммана?

Based on the analysis of numerous experimental data shows that the generally accepted today, the glass transition temperature Tg is not. It was the result of borrowing from tammana symbol Tg, is meant the temperature of viscous flow liquid transformation into solid brittle glassy state, and use it together symbol Tw, means the temperature tammana bend on the dependence of the «property-temperature» glass-forming substances above Tg of tammana. On the basis of the application of polymer-polymorphing representations of the structure of glass-forming substances are disclosed physico-chemical nature of the temperature curve Tw (conventional Segodnya), which is the temperature of the reverse direction interconversion of nanofragments patterns (polymorphical) high and low temperature polymorphs that coexist in the vitreous substance. The discovery in recent decades prezentatsionnogo effect located as tammana Tg, is below the standard Tg, Tg confirms the truth of tammana characterized by increasedspecific heat of the heated glass.На основе анализа многочисленных экспериментальных данных показано, что общепринятая сегодня температура стеклования Tg таковой не является. Она возникла в результате заимствования у Г. Таммана обозначения Tg, соответствующего температуре превращения вязкотекучей жидкостив твердое хрупкое стеклообразное состояние, и использования его вместо обозначения Tw. Последнее соответствовало у Г. Таммана температуре изгиба на зависимости «свойство— температура» для стеклообразующего вещества, расположенной выше TgТаммана. На основании применения полимерно-полиморфоидных представлений о строении стеклообразующего вещества раскрыта физико-химическая сущность температуры изгиба Tw (общепринятой сегодня Tg), являющейся температурой реверса направления взаимопревращения нанофрагментов структуры (полиморфоидов) высоко- и низкотемпературной полиморфных модификаций, сосуществующих в стеклообразующем веществе. Открытие в последние десятилетия предэндотермического эффекта, расположенного, как и Tg Таммана, ниже общепринятой Tg, подтверждает истинность Tg Таммана, характеризуемой увеличением удельной теплоемкости нагреваемого стекла

ПОЛИМЕРНО–ПОЛИМОРФОИДНАЯ ПРИРОДА СТАРЕНИЯ СТЕКЛА

Based on the concept of polymeric−polymorphous structure of glass and glassforming liquid (Minaev, 1987) experimental data have been analyzed revealing the nature of glass aging. We show that the glass forming substance is a copolymer consisting of structural nano-fragments (polymorphoids) in different polymorphous modifications (PM) of the material having no translational symmetry (long-range order). The study revealed that the process and degree of glass aging influences the properties of glasses, including a change in enthalpy, manifested in the exothermic and endothermic effects observed in thermograms of differential scanning calorimetry of heated and cooled glasses. We have shown that the physicochemical essence of aging is the transformation of polymorphoids from high−temperature PM (HTPM) into low−temperature PM (LTPM) which results, under certain conditions, in LTPM crystallization.На основе концепции полимерно-полиморфоидного строения стекла и стеклообразующей жидкости (В. С. Минаев, 1987 г.) проведен анализ экспериментальных данных, раскрывающих природу старения стекла. Показано, что стеклообразующее вещество представляет собой сополимер, состоящий из нанофрагментов структуры (полиморфоидов) различных полиморфных модификаций (ПМ) данного вещества, не имеющих трансляционной симметрии (дальнего порядка). Выявлено, что процесс и степень старения стекла влияют на свойства стекла, включая изменение энтальпии, проявляющееся в экзо- и эндотермических эффектах, наблюдаемых на термограммах дифференциальной сканирующей калориметрии, нагреваемого и охлаждаемого стекла. Установлено, что физико-химической сущностью процесса старения стекла является процесс превращения полиморфоидов высокотемпературной ПМ (ВТПМ) в полиморфоиды низкотемпературной ПМ (НТПМ), заканчивающийся при определенных условиях кристаллизацией НТПМ