Time evolution of the reaction front in a subdiffusive system

Using the quasistatic approximation, we show that in a subdiffusion--reaction system the reaction front $x_{f}$ evolves in time according to the formula $x_{f} \sim t^{\alpha/2}$, with $\alpha$ being the subdiffusion parameter. The result is derived for the system where the subdiffusion coefficients of reactants differ from each other. It includes the case of one static reactant. As an application of our results, we compare the time evolution of reaction front extracted from experimental data with the theoretical formula and we find that the transport process of organic acid particles in the tooth enamel is subdiffusive.Comment: 18 pages, 3 figure

Processing of CP-Ti by high-pressure torsion and the effect of surface modification using a post-HPT laser treatment

Commercial purity titanium (CP-Ti) was processed by high-pressure torsion (HPT) with various numbers of turns (N = 1, 10 and 20). The hardness of the CP-Ti increased with an increasing number of HPT turns due to grain refinement. Tensile testing showed that the HPT-processed 10 turns sample had low ductility and high strength but the ductility may be improved through post-HPT short-term annealing at carefully selected temperatures. Some HPT-processed samples were laser surface-treated with different laser powers and scanning speeds. The surface roughness of the laser-textured samples increased with increasing laser power and led to a lower contact angle which signifies an increased hydrophilicity. After a holding time of 13 days, the samples underwent a hydrophilic-to-hydrophobic transformation as the contact angle increased to as much as 129 degree. It is concluded that laser surface texture processes are capable of controlling the hydrophilic / hydrophobic properties of ultra-fine grained CP-Ti

A Measurement of Photon Production in Electron Avalanches in CF4

This paper presents a measurement of the ratio of photon to electron production and the scintillation spectrum in a popular gas for time pro jection chambers, carbon tetrafluoride (CF4), over the range of 200 to 800 nm; the ratio is measured to be 0.34+/-0.04. This result is of particular importance for a new generation of dark matter time projection chambers with directional sensitivity which use CF4 as a fill gas.Comment: 19 pages, including appendix. 8 figure

Economic policy: genesis and changes before the period of formation of developed industrial capital

Цель статьи – исследование генезиса, содержания и специфики экономической политики от периода её зарождения в дорыночных обществах до периода ее существенных изменений в процессе формирования промышленного капитала, а также анализ особенностей и функций экономической политики через призму взглядов представителей разных направлений экономической теории. Главным в статье является эволюционный метод исследования, дополняемый методами анализируемых направлений экономической теории – описательным, аналитическим и диалектическим методами. Проведенное исследование позволяет сделать вывод о том, что экономическая политика возникает и развивается как реакция со стороны государства на развитие рынка, а выделенные нами этапы эволюции экономической политики отражают соответствующие периоды развития рынка. В процессе развития рынка и индустриализации формируется промышленный капитал и разрабатываются новые подходы к экономической политике. В данном контексте отмечается, что деиндустриализация в ходе рыночных реформ в Украине имела прямые и обратные связи с экономической политикой. Теоретические положения статьи дают возможность разрабатывать практические рекомендации по совершенствованию экономической политики и хозяйственной практики в современной Украине, в частности, это касается проблем развития промышленного капитала и реиндустриализации.The purpose of the article is to study the genesis, essence and specifics of economic policy from the period of its origination in pre-market societies to the period of its significant changes in the process of industrial capital formation, as well as to analyze the features and functions of economic policy through the prism of different schools of economic theory. The main thing in the article is the evolutionary method of research, supplemented by the methods of the analyzed schools of economic theory – descriptive, analytical and dialectical methods. The conducted research allows us to conclude that economic policy arises and develops as a reaction on the part of the state to the development of the market, and the stages of evolution of economic policy that we have identified reflect the corresponding periods of its development. In pre-market societies, the main thing was the state policy, which set the task of reproducing people in a certain class structure, by reproducing their inequality. The main features of state policy are noted, such as: orientation towards the reproduction of a certain class structure, finding new ways of subordinating some people to others. In the process of market development and industrialization, industrial capital is being formed and new approaches to economic policy are being developed. In this context, it is noted that deindustrialization in the course of market reforms in Ukraine had direct and inverse links with economic policy. The theoretical provisions of the article make it possible to develop practical recommendations for improving economic policy and economic practice in modern Ukraine, in particular, this concerns the problems of industrial capital development and reindustrialization

Understanding the interactions of cellulose fibres and deep eutectic solvent of choline chloride and urea

This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.A deep eutectic solvent composed of choline chloride (ChCl) and urea has been recently introduced as a promising cellulose compatible medium that enables e.g. fibre spinning. This paper clarifies the influence of such a solvent system on the structure and chemical composition of the cellulosic pulp fibres. Special emphasis was placed on the probable alterations of the chemical composition due to the dissolution of the fibre components and/or due to the chemical derivatisation taking place during the DES treatment. Possible changes in fibre morphology were studied with atomic force microscopy and scanning electron microscopy. Chemical compositions of pulp fibres were determined from the carbohydrate content, and by analysing the elemental content. Detailed structural characterisation of the fibres was carried out using spectroscopic methods; namely X-Ray Photoelectron Spectroscopy, solid state Nuclear Magnetic Resonance and Raman Spectroscopy. No changes with respect to fibre morphology were revealed and negligible changes in the carbohydrate composition were noted. The most significant change was related to the nitrogen content of the pulp after the DES treatment. Comprehensive examination using spectroscopic methods revealed that the nitrogen originated from strongly bound ChCl residuals that could not be removed with a mild ethanol washing procedure. According to Raman spectroscopic data and methylene blue adsorption tests, the cationic groups of ChCl seems to be attached to the anionic groups of pulp by electrostatic forces. These findings will facilitate the efficient utilisation of DES as a cellulose compatible medium without significantly affecting the native fibre structure.The authors acknowledge the Finnish Funding Agency for Innovation (TEKES) for funding the work via Design Driven Value Chains in the World of Cellulose 2.0 project. The Academy of Finland (Project ID 300367) is acknowledged for enabling the research mobility of T.T. to the University of Exeter, UK. Unto Tapper (VTT) is thanked for the SEM imaging, Atte Mikkelson, Ritva Heinonen and Marita Ikonen (VTT) for the chemical analysis and Robertus Nugroho (Aalto University) for the AFM imaging

Dynamics and Critical Behaviour of the q-model

The $q$-model, a random walk model rich in behaviour and applications, is investigated. We introduce and motivate the $q$-model via its application proposed by Coppersmith {\em et al.} to the flow of stress through granular matter at rest. For a special value of its parameters the $q$-model has a critical point that we analyse. To characterise the critical point we imagine that a uniform load has been applied to the top of the granular medium and we study the evolution with depth of fluctuations in the distribution of load. Close to the critical point explicit calculation reveals that the evolution of load exhibits scaling behaviour analogous to thermodynamic critical phenomena. The critical behaviour is remarkably tractable: the harvest of analytic results includes scaling functions that describe the evolution of the variance of the load distribution close to the critical point and of the entire load distribution right at the critical point, values of the associated critical exponents, and determination of the upper critical dimension. These results are of intrinsic interest as a tractable example of a random critical point. Of the many applications of the q-model, the critical behaviour is particularly relevant to network models of river basins, as we briefly discuss. Finally we discuss circumstances under which quantum network models that describe the surface electronic states of a quantum Hall multilayer can be mapped onto the classical $q$-model. For mesoscopic multilayers of finite circumference the mapping fails; instead a mapping to a ferromagnetic supersymmetric spin chain has proved fruitful. We discuss aspects of the superspin mapping and give a new elementary derivation of it making use of operator rather than functional methods.Comment: 34 pages, Revtex, typo correcte