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

Vulnerability of horticultural crop production to extreme weather events

The potential impact of future extreme weather events on horticultural crops was evaluated. A review was carried out of the sensitivities of a representative set of crops to environmental challenges. It confirmed that a range of environmental factors are capable of causing a significant impact on production, either as yield or quality loss. The most important of these were un-seasonal temperature, water shortage or excess,and storms. Future scenarios were produced by the LARS-WG1, a stochastic weather generator linked with UKCIP02 projections of future climate. For the analyses, 150 years of synthetic weather data were generated for baseline, 2020HI and 2050HI scenarios at defined locations. The output from the weather generator was used in case studies, either to estimate the frequency of a defined set of circumstances known to have impact on cropping, or as inputs to models of crop scheduling or pest phenology or survival. The analyses indicated that episodes of summer drought severe enough to interrupt the continuity of supply of salads and other vegetables will increase while the frequency of autumns with sufficient rainfall to restrict potato lifting will decrease. They also indicated that the scheduling of winter cauliflowers for continuity of supply will require the deployment of varieties with different temperature sensitivities from those in use currently. In the pest insect studies, the number of batches of Agrotis segetum (cutworm) larvae surviving to third instar increased with time, as did the potential number of generations of Plutella xylostella (diamond-back moth) in the growing season, across a range of locations. The study demonstrated the utility of high resolution scenarios in predicting the likelihood of specific weather patterns and their potential effect on horticultural production. Several limitations of the current scenarios and biological models were also identified

Weak localization, Aharonov-Bohm oscillations and decoherence in arrays of quantum dots

Combining scattering matrix theory with non-linear $\sigma$-model and Keldysh technique we develop a unified theoretical approach enabling one to non-perturbatively study the effect of electron-electron interactions on weak localization and Aharonov-Bohm oscillations in arbitrary arrays of quantum dots. Our model embraces (i) weakly disordered conductors (ii) strongly disordered conductors and (iii) metallic quantum dots. In all these cases at $T \to 0$ the electron decoherence time is found to saturate to a finite value determined by the universal formula which agrees quantitatively with numerous experimental results. Our analysis provides overwhelming evidence in favor of electron-electron interactions as a universal mechanism for zero temperature electron decoherence in disordered conductors.Comment: 19 pages, 13 figures, invited paper, published in a special issue of Fiz. Nizk. Temp. (Kharkov) dedicated to Prof. Igor Kuli

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

On the methanol emission detection in the TW Hya disc: the role of grain surface chemistry and non-LTE excitation

The recent detection of gas-phase methanol (CH$_3$OH) lines in the disc of TW Hya by Walsh et al. provided the first observational constraints on the complex O-bearing organic content in protoplanetary discs. The emission has a ring-like morphology, with a peak at $\sim 30-50$ au and an inferred column density of $\sim 3-6\times10^{12}$ cm$^{-2}$. A low CH$_3$OH fractional abundance of $\sim 0.3-4\times 10^{-11}$ (with respect to H$_2$) is derived, depending on the assumed vertical location of the CH$_3$OH molecular layer. In this study, we use a thermo-chemical model of the TW Hya disc, coupled with the ALCHEMIC gas-grain chemical model, assuming laboratory-motivated, fast diffusivities of the surface molecules to interpret the CH$_3$OH detection. Based on this disc model, we performed radiative transfer calculations with the LIME code and simulations of the observations with the CASA simulator. We found that our model allows to reproduce the observations well. The CH$_3$OH emission in our model appears as a ring with radius of $\sim60$ au. Synthetic and observed line flux densities are equal within the rms noise level of observations. The synthetic CH$_3$OH spectra calculated assuming local thermodynamic equilibrium (LTE) can differ by up to a factor of 3.5 from the non-LTE spectra. For the strongest lines, the differences between LTE and non-LTE flux densities are very small and practically negligible. Variations in the diffusivity of the surface molecules can lead to variations of the CH$_3$OH abundance and, therefore, line flux densities by an order of magnitude.Comment: Accepted for publication in MNRAS, 8 pages, 8 figure

Less-structured time in children's daily lives predicts self-directed executive functioning.

Executive functions (EFs) in childhood predict important life outcomes. Thus, there is great interest in attempts to improve EFs early in life. Many interventions are led by trained adults, including structured training activities in the lab, and less-structured activities implemented in schools. Such programs have yielded gains in children's externally-driven executive functioning, where they are instructed on what goal-directed actions to carry out and when. However, it is less clear how children's experiences relate to their development of self-directed executive functioning, where they must determine on their own what goal-directed actions to carry out and when. We hypothesized that time spent in less-structured activities would give children opportunities to practice self-directed executive functioning, and lead to benefits. To investigate this possibility, we collected information from parents about their 6-7 year-old children's daily, annual, and typical schedules. We categorized children's activities as "structured" or "less-structured" based on categorization schemes from prior studies on child leisure time use. We assessed children's self-directed executive functioning using a well-established verbal fluency task, in which children generate members of a category and can decide on their own when to switch from one subcategory to another. The more time that children spent in less-structured activities, the better their self-directed executive functioning. The opposite was true of structured activities, which predicted poorer self-directed executive functioning. These relationships were robust (holding across increasingly strict classifications of structured and less-structured time) and specific (time use did not predict externally-driven executive functioning). We discuss implications, caveats, and ways in which potential interpretations can be distinguished in future work, to advance an understanding of this fundamental aspect of growing up

Relic density of dark matter in the NMSSM

We present a code to compute the relic density of dark matter in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). Dominant corrections to the Higgs masses are calculated with NMHDECAY as well as theoretical and collider constraints. All neutralino annihilation and coannihilation processes are then computed with an extended version of micrOMEGAs, taking into acount higher order corrections to Higgs vertices. We explore the parameter space of the NMSSM and consider in particular the case of a bino LSP, of a mixed bino-higgsino LSP and of a singlino LSP. As compared to the MSSM, neutralino annihilation is often more efficient as it can take place via (additional) Higgs resonances as well as annihilation into light Higgs states. Models with a large singlino component can be compatible with WMAP constraints.Comment: 25 pages, 8 figures; one reference added and minor change in acknowledgement

CID: Chemistry In Disks VII. First detection of HC3N in protoplanetary disks

Molecular line emission from protoplanetary disks is a powerful tool to constrain their physical and chemical structure. Nevertheless, only a few molecules have been detected in disks so far. We take advantage of the enhanced capabilities of the IRAM 30m telescope by using the new broad band correlator (FTS) to search for so far undetected molecules in the protoplanetary disks surrounding the TTauri stars DM Tau, GO Tau, LkCa 15 and the Herbig Ae star MWC 480. We report the first detection of HC3N at 5 sigma in the GO Tau and MWC 480 disks with the IRAM 30-m, and in the LkCa 15 disk (5 sigma), using the IRAM array, with derived column densities of the order of 10^{12}cm^{-2}. We also obtain stringent upper limits on CCS (N < 1.5 x 10^{12} cm^{-3}). We discuss the observational results by comparing them to column densities derived from existing chemical disk models (computed using the chemical code Nautilus) and based on previous nitrogen and sulfur-bearing molecule observations. The observed column densities of HC3N are typically two orders of magnitude lower than the existing predictions and appear to be lower in the presence of strong UV flux, suggesting that the molecular chemistry is sensitive to the UV penetration through the disk. The CCS upper limits reinforce our model with low elemental abundance of sulfur derived from other sulfur-bearing molecules (CS, H2S and SO).Comment: 8 pages, 4 figures, 3 tables, Accepted for publication in Ap