Low-energy vibrational density of states of plasticized poly(methyl methacrylate)

The low-energy vibrational density of states (VDOS)of hydrogenated or deuterated poly(methyl methacrylate)(PMMA)plasticized by dibutyl phtalate (DBP) is determined by inelastic neutron scattering.From experiment, it is equal to the sum of the ones of the PMMA and DBP components.However, a partition of the total low-energy VDOS among PMMA and DBP was observed.Contrary to Raman scattering, neutron scattering does not show enhancement of the boson peak due to plasticization.Comment: 9 pages, 2 figures (Workshop on Disordered Systems, Andalo

Parafermionic Liouville field theory and instantons on ALE spaces

In this paper we study the correspondence between the $\hat{\textrm{su}}(n)_{k}\oplus \hat{\textrm{su}}(n)_{p}/\hat{\textrm{su}}(n)_{k+p}$ coset conformal field theories and $\mathcal{N}=2$ SU(n) gauge theories on $\mathbb{R}^{4}/\mathbb{Z}_{p}$. Namely we check the correspondence between the SU(2) Nekrasov partition function on $\mathbb{R}^{4}/\mathbb{Z}_{4}$ and the conformal blocks of the $S_{3}$ parafermion algebra (in $S$ and $D$ modules). We find that they are equal up to the U(1)-factor as it was in all cases of AGT-like relations. Studying the structure of the instanton partition function on $\mathbb{R}^4/\mathbb{Z}_p$ we also find some evidence that this correspondence with arbitrary $p$ takes place up to the U(1)-factor.Comment: 21 pages, 6 figures, misprints corrected, references added, version to appear in JHE

МикроРНК: половые гормоны, гормональный канцерогенез, гормоночувствительность опухолевой ткани

Sex hormones, regulating normal physiological processes of most tissues and organs, are considered to be one of the key factors in the development and progression of the reproductive system cancer. Recently, the importance of the system for post-transcriptional control of gene expression mediated by short single-stranded RNA molecules (microRNA) became evident. This system is involved in regulation of normal physiological processes and in the pathogenesis of many diseases, including cancer. In review we discuss the relationship between the two regulatory systems – sex hormones and microRNAs. The relationship of these systems is considered in the context of two tumors – breast and prostate cancer. In particular, the history of research on the role of sex hormones in the pathogenesis of breast cancer and prostate cancer is briefly covered. Additionally, modern scientific data on the biogenesis and biological role of microRNAs are presented in more detail. In the cells of the hormone-sensitive tissues, sex hormones regulate the microRNA-mediated machinery of gene expression control by two known ways: specifically, affecting the activity of individual microRNA molecules and non-specifically by altering the efficiency of microRNA biogenesis and activity of RNA-induced silencing complex. This downstream regulatory network substantially enhances biological effects of sex hormones at physiological conditions. Malignant transformation leads to a distortion of the regulatory effects of sex hormones that crucially influence the system of microRNA-regulated post-transcriptional control of gene expression. The most established and clinically significant example of such phenomenon is the loss of sensitivity of cells to the regulatory action of these hormones. As a consequence, cancer cells acquire the ability to active proliferation without stimulation with sex hormones. This effect is partly mediated by microRNAs. Also, relevant experimental data indicating the involvement of microRNAs in the phenomenon of breast cancer and prostate cancer cells hormone resistance are discussed in the review.Conception of the possible primary role of microRNAs in the process of malignant transformation and distortion of hormonal regulation is based on a smaller number of scientific reports. In general, in accordance with the main biological role of microRNAs, latter may affect sex hormones function via interaction with the mRNAs of hormone receptors and inhibition of their synthesis. As a result, the effect of many microRNA is converging on the single mRNA, results in suppression of corresponding protein function and, in the end, leads to inhibition of regulatory cascade downstream of sex steroids.Finally, the analysis of the fundamental aspects of sex hormones – microRNA interplay is supplemented by brief overview of clinically significant problems. The prospects for development and introduction into clinical practice innovative methods of diagnosis, prediction and optimization of therapy of breast and prostate cancers are discussed as well.Половые гормоны, регулируя нормальные физиологические процессы большинства тканей и органов, традиционно считаются одним из ключевых факторов развития и прогрессии опухолей органов репродуктивной системы. В течение последних лет стала очевидной значимость системы посттранскрипционного контроля генной экспрессии, опосредуемой короткими одноцепочечными молекулами РНК, так называемыми микроРНК, в регуляции нормальных физиологических процессов и в патогенезе многих заболеваний, включая онкологические. В представленном обзоре обсуждается взаимосвязь между двумя в определенном смысле самостоятельными регуляторными системами – половыми гормонами и микроРНК. Взаимоотношения этих систем рассматриваются в контексте двух онкологических заболеваний – рака молочной железы (РМЖ) и рака предстательной железы (РПЖ).Кратко освещается история исследований роли половых гормонов в патогенезе РМЖ и РПЖ, более подробно представлены современные данные о биогенезе и биологической роли микроРНК. В клетках гормоночувствительных тканей половые гормоны регулируют работу микроРНК-аппарата регуляции генной экспрессии двумя известными путями: специфично, влияя на активность отдельных молекул микроРНК, и неспецифично, изменяя эффективность биогенеза микроРНК и активность цитоплазматического РНК-белкового комплекса. С учетом работы такой регуляторной сети существенно расширяются представления о биологических эффектах половых гормонов в физиологических условиях. Злокачественная трансформация приводит к искажению регуляторных эффектов половых гормонов, что отражается и усиливается регулируемой ими системой посттранскрипционного контроля генной экспрессии, опосредуемой микроРНК. К числу наиболее исследованных и клинически значимых примеров этого феномена относится утрата чувствительности к влиянию половых гормонов, на фоне чего клетки приобретают способность к активной пролиферации безгормональной стимуляции за счет подключения коллатеральных сигнальных путей и ростовых факторов. Этот феномен отчасти опосредуется микроРНК, и как следствие, к обсуждению привлекаются современные экспериментальные данные, указывающие на причастность микроРНК к формированию феномена гормональной резистентности клеток РМЖ и РПЖ. Представления о возможной первичной роли нарушений функций микроРНК в процессе опухолевой трансформации и искажения механизмов гормональной регуляции основаны на меньшем количестве проведенных и опубликованных исследований. В целом, в соответствии с основной биологической ролью микроРНК, их таргетное воздействие на функции половых гормонов в основном опосредуется взаимодействием с различными участками матричной РНК (мРНК) соответствующих гормональных рецепторов и ведет к угнетению синтеза последних. В итоге действие многих микроРНК конвергируется на одной молекуле мРНК, что в большинстве случаев приводит к подавлению сигнальных каскадов, индуцируемых половыми гормонами.Анализ фундаментальных аспектов дополнен обзором клинически значимых проблем, в решении которых должна учитываться взаимосвязь половых гормонов и микроРНК. Коротко обсуждаются перспективы развития и внедрения в клиническую практику методов диагностики, прогнозирования и оптимизации терапии опухолевых заболеваний гормоночувствительных тканей на основе сведений о микроРНК и их связях с обсуждаемыми проблемами

Instanton moduli spaces and bases in coset conformal field theory

Recently proposed relation between conformal field theories in two dimensions and supersymmetric gauge theories in four dimensions predicts the existence of the distinguished basis in the space of local fields in CFT. This basis has a number of remarkable properties, one of them is the complete factorization of the coefficients of the operator product expansion. We consider a particular case of the U(r) gauge theory on C^2/Z_p which corresponds to a certain coset conformal field theory and describe the properties of this basis. We argue that in the case p=2, r=2 there exist different bases. We give an explicit construction of one of them. For another basis we propose the formula for matrix elements.Comment: 31 pages, 3 figure

Polyurethane–poly(2-hydroxyethyl methacrylate) semi- IPN–nanooxide composites

Two sets of hybrid polyurethane–poly(2-hydroxyethyl methacrylate) semi-interpenetrating polymer network–nanooxide composites with 0.25 or 3 wt% nanosilica or nanoalumina functionalised with OH, NH2 or CHLCH2 groups were prepared. A combination of atomic force microscopy, infrared spectroscopy, thermally stimulated depolarisation current measurement, differential scanning calorimetry and creep rate spectroscopy analysis of the nanostructure and properties of the composites was performed. The pronounced dynamic heterogeneity and the strong impact of oxide additives, basically suppression of the dynamics and temperature-dependent increasing modulus of elasticity, were observed. The effects correlated with either interfacial interactions (for silica) or the nanostructure (for alumina). A low oxide content strongly affected the matrix due to the formation of an unusual cross-linked, via double covalent hybridisation of three components, structure of the nanocomposites

Inelastic light, neutron, and X-ray scatterings related to the heterogeneous elasticity of glasses

The effects of plasticization of poly(methyl methacrylate) glass on the boson peaks observed by Raman and neutron scattering are compared. In plasticized glass the cohesion heterogeneities are responsible for the neutron boson peak and partially for the Raman one, which is enhanced by the composition heterogeneities. Because the composition heterogeneities have a size similar to that of the cohesion ones and form quasiperiodic clusters, as observed by small angle X-ray scattering, it is inferred that the cohesion heterogeneities in a normal glass form nearly periodic arrangements too. Such structure at the nanometric scale explains the linear dispersion of the vibrational frequency versus the transfer momentum observed by inelastic X-ray scattering.Comment: 9 pages, 2 figures, to be published in J. Non-Cryst. Solids (Proceedings of the 4th IDMRCS

Challenges of beta-deformation

A brief review of problems, arising in the study of the beta-deformation, also known as "refinement", which appears as a central difficult element in a number of related modern subjects: beta \neq 1 is responsible for deviation from free fermions in 2d conformal theories, from symmetric omega-backgrounds with epsilon_2 = - epsilon_1 in instanton sums in 4d SYM theories, from eigenvalue matrix models to beta-ensembles, from HOMFLY to super-polynomials in Chern-Simons theory, from quantum groups to elliptic and hyperbolic algebras etc. The main attention is paid to the context of AGT relation and its possible generalizations.Comment: 20 page

Instantons and 2d Superconformal field theory

A recently proposed correspondence between 4-dimensional N=2 SUSY SU(k) gauge theories on R^4/Z_m and SU(k) Toda-like theories with Z_m parafermionic symmetry is used to construct four-point N=1 super Liouville conformal block, which corresponds to the particular case k=m=2. The construction is based on the conjectural relation between moduli spaces of SU(2) instantons on R^4/Z_2 and algebras like \hat{gl}(2)_2\times NSR. This conjecture is confirmed by checking the coincidence of number of fixed points on such instanton moduli space with given instanton number N and dimension of subspace degree N in the representation of such algebra.Comment: 13 pages, exposition improved, references adde

Exact results for N = 2 supersymmetric gauge theories on compact toric manifolds and equivariant Donaldson invariants

We provide a contour integral formula for the exact partition function of N = 2 supersymmetric U(N) gauge theories on compact toric four-manifolds by means of supersymmetric localisation. We perform the explicit evaluation of the contour integral for U(2) N = 2 17 theory on CP2 for all instanton numbers. In the zero mass case, corresponding to the N = 4 supersymmetric gauge theory, we obtain the generating function of the Euler characteristics of instanton moduli spaces in terms of mock-modular forms. In the decoupling limit of infinite mass we find that the generating function of local and surface observables computes equivariant Donaldson invariants, thus proving in this case a longstanding conjecture by N. Nekrasov. In the case of vanishing first Chern class the resulting equivariant Donaldson polynomials are new. \ua9 2016, The Author(s)

Predictability of evolutionary trajectories in fitness landscapes

Experimental studies on enzyme evolution show that only a small fraction of all possible mutation trajectories are accessible to evolution. However, these experiments deal with individual enzymes and explore a tiny part of the fitness landscape. We report an exhaustive analysis of fitness landscapes constructed with an off-lattice model of protein folding where fitness is equated with robustness to misfolding. This model mimics the essential features of the interactions between amino acids, is consistent with the key paradigms of protein folding and reproduces the universal distribution of evolutionary rates among orthologous proteins. We introduce mean path divergence as a quantitative measure of the degree to which the starting and ending points determine the path of evolution in fitness landscapes. Global measures of landscape roughness are good predictors of path divergence in all studied landscapes: the mean path divergence is greater in smooth landscapes than in rough ones. The model-derived and experimental landscapes are significantly smoother than random landscapes and resemble additive landscapes perturbed with moderate amounts of noise; thus, these landscapes are substantially robust to mutation. The model landscapes show a deficit of suboptimal peaks even compared with noisy additive landscapes with similar overall roughness. We suggest that smoothness and the substantial deficit of peaks in the fitness landscapes of protein evolution are fundamental consequences of the physics of protein folding.Comment: 14 pages, 7 figure