Entropy-induced Microphase Separation in Hard Diblock Copolymers

Whereas entropy can induce phase behavior that is as rich as seen in energetic systems, microphase separation remains a very rare phenomenon in entropic systems. In this paper, we present a density functional approach to study the possibility of entropy-driven microphase separation in diblock copolymers. Our model system consists of copolymers composed of freely-jointed slender hard rods. The two types of monomeric segments have comparable lengths, but a significantly different diameter, the latter difference providing the driving force for the phase separation. At the same time these systems can also exhibit liquid crystalline phases. We treat this system in the appropriate generalization of the Onsager approximation to chain-like particles. Using a linear stability (bifurcation) analysis, we analytically determine the onset of the microseparated and the nematic phases for long chains. We find that for very long chains the microseparated phase always preempts the nematic. In the limit of infinitely long chains, the correlations within the chain become Gaussian and the approach becomes exact. This allows us to define a Gaussian limit in which the theory strongly simplifies and the competition between microphase separation and liquid crystal formation can be studied essentially analytically. Our main results are phase diagrams as a function of the effective diameter difference, the segment composition and the length ratio of the segments. We also determine the amplitude of the positional order as a function of position along the chain at the onset of the microphase separation instability. Finally, we give suggestions as to how this type of entropy-induced microphase separation could be observed experimentally.Comment: 16 pages, 7 figure

Построение информационных отношений в сфере майнинга, криптовалюты и криптоактивов на примере Кыргызской Республики

The subject of the research is the study of mining, cryptocurrency, crypto assets in the legislation of the Kyrgyz Republic. Relevance. The relevance of the article is due to the presence of gaps in the field of mining, cryptocurrency, crypto assets in the legislation of the Kyrgyz Republic. The objectives of the article are to analyze the areas of mining, cryptocurrency, crypto assets and identify legal problems, as well as make proposals for improving the national legislation of the Kyrgyz Republic. Methodology. The authors use scientific methods: general methods (analysis, synthesis, induction, deduction, comparison); special methods (legal, comparative legal).Main results. Problems were identified, such as: lack of legal status of crypto assets, cryptocurrencies; lack of legal status of a cryptocurrency exchange operator; the system of risk management in the field of cryptocurrency is not indicated; lack of detailed study of the legal status of mining; subjects of mining, mining objects, classification of mining, standards for conducting financial transactions are not defined; lack of understanding of the nature of cryptocurrencies, crypto assets and virtual assets; lack of licensing and permitting activities in the field of mining, cryptocurrency, crypto assets; the absence of the category of mining, cryptocurrencies, crypto assets in the State Classifier of Economic Activities; lack of legal status of blockchain in the format of a regulatory legal act and etc. Relevant proposals were given: to finalize and adopt a single regulatory legal act (in the form of a law) in the field of crypto assets, cryptocurrencies, since they are interconnected; establish the legal status of a cryptocurrency exchange operator and introduce licensing and permitting activities (obtaining a license from the National Bank of the Kyrgyz Republic); develop and adopt a regulatory legal act (in the form of a law) on mining, with a detailed designation of what mining is, its classification, mining object, mining subjects; understand the nature of cryptocurrencies, crypto assets, virtual assets and understand what they can be attributed to, in particular, to money, a product, a medium of exchange, a universal service or other activity; Enshrine in civil law the concepts of cryptocurrency, crypto assets, virtual assets, including the rights and obligations arising from them; add to the Law of the Kyrgyz Republic "On licensing and permitting activities of the system in the Kyrgyz Republic" paragraph 61 of Article 15 - the activity of mining, cryptocurrency, crypto assets; add a category to the State Classifier of Economic Activities - mining, cryptocurrencies, crypto assets; form a working group at the level of the Cabinet of Ministers of the Kyrgyz Republic to study blockchain technology with areas of application, both in the private sector and in the public sector, including smart contracts and etc.Conclusion. Introduce legal regulators in the field of mining, cryptocurrency, crypto assets in the Kyrgyz Republic in order to avoid possible legal gaps that can lead to negative consequences in relation to the state, ranging from various shadow schemes in the economy that can slow down the digital transformation of the country.Вопросы развития майнинга, криптовалюты, криптоактивов рассматриваются на примере Кыргызской Республики. Актуальность статьи обусловлена существованием пробелов в законодательстве Кыргызской Республики по данным направлениям. Цели статьи – провести анализ сфер майнинга, криптовалюты, криптоактивов и выявить правовые проблемы, а также дать предложения по совершенствованию национального законодательства Кыргызской Республики. Сделан вывод о необходимости правового регулирования отношений в области майнинга, криптовалюты, криптоактивов в Кыргызской Республике для преодоления правовых пробелов, способствующих развитию теневых схем в экономике и препятствующих общей цифровой трансформации

Mixed Quantum/Classical Approach for Description of Molecular Collisions in Astrophysical Environments

An efficient and accurate mixed quantum/classical theory approach for computational treatment of inelastic scattering is extended to describe collision of an atom with a general asymmetric-top rotor polyatomic molecule. Quantum mechanics, employed to describe transitions between the internal states of the molecule, and classical mechanics, employed for description of scattering of the atom, are used in a self-consistent manner. Such calculations for rotational excitation of HCOOCH3 in collisions with He produce accurate results at scattering energies above 15 cm–1, although resonances near threshold, below 5 cm–1, cannot be reproduced. Importantly, the method remains computationally affordable at high scattering energies (here up to 1000 cm–1), which enables calculations for larger molecules and at higher collision energies than was possible previously with the standard full-quantum approach. Theoretical prediction of inelastic cross sections for a number of complex organic molecules observed in space becomes feasible using this new computational tool

Search for solar axions produced by Compton process and bremsstrahlung using the resonant absorption and axioelectric effect

The search for resonant absorption of Compton and bremsstrahlung solar axions by $^{169}$Tm nuclei have been performed. Such an absorption should lead to the excitation of low-lying nuclear energy level: $A+^{169}$Tm $\rightarrow ^{169}$Tm$^*$ $\rightarrow ^{169}$Tm $+ \gamma$ (8.41 keV). Additionally the axio-electric effect in silicon atoms is sought. The axions are detected using a Si(Li) detectors placed in a low-background setup. As a result, a new model independent restrictions on the axion-electron and the axion-nucleon coupling: $g_{Ae}\times|g^0_{AN}+ g^3_{AN}|\leq 2.1\times10^{-14}$ and the axion-electron coupling constant: $|g_{Ae}| \leq 2.2\times 10^{-10}$ has been obtained. The limits leads to the bounds $m_{A}\leq$ 7.9 eV and $m_{A}\leq$ 1.3 keV for the mass of the axion in the DFSZ and KSVZ models, respectively ($90\%$ C.L.).Comment: 6 pages, 3 figures, contributed to the 9th Patras Workshop on Axions, WIMPs and WISPs, Mainz, June 24-28, 201

Spreading of Block Copolymer Films and Domain Alignment at Moving Terrace Steps

We investigate spreading of phase separated copolymer films, where domain walls and thickness steps influence polymer flow. We show that at early stages of spreading its rate is determined by slow activated flow at terrace steps (i.e. thickness steps). At late stages of spreading, on the other hand, the rate is determined by the flow along terraces, with diffusion-like time dependence $t^{-1/2}$. This dependence is similar to de Gennes and Cazabat's prediction for generic layered liquids, as opposed to the classical Tanner's law of drop spreading. We also argue that chain hopping at the spreading terrace steps should lead to the formation of aligned, defect-free domain patterns on the growing terraces.Comment: 11 pages, 7 figures, submitted to J. Chem. Phy