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[en] A model of two interacting self-attracting, self-avoiding walks is proposed to study the critical behavior of two interacting chemically different linear polymers in a solution that may have different qualities for different chains. We solve the model exactly on truncated n-simplex lattices for 4≤n≤6 using the real-space renormalization-group transformation. Depending upon the solvent quality, the temperature, and the attractive interactions between interchain and intrachain monomers, the configuration of either segregation or interpenetration or zipping of chains may arise. It is shown that these configurations correspond to different fixed points of the renormalized-group transformation. The value of the contact exponent is calculated exactly at the tricritical points corresponding to the segregation-interpenetration and the interpenetration--zipped-state chain transitions. The phase boundaries of these states are shown on a plane of fugacity weight attached with a zipped step (i.e., a step in which both walks move side by side) and the Boltzmann factor associated with the attraction between unlike monomers. The phase diagram is shown to have different universality domains of critical behavior
[en] Measurements of the average thermal contractions (294→72 K) of 26 different cryosolutions are presented and discussed in conjunction with other recent advances in the rational design of protocols for cryogenic cooling in macromolecular crystallography. Cryogenic cooling of macromolecular crystals is commonly used for X-ray data collection both to reduce crystal damage from radiation and to gather functional information by cryogenically trapping intermediates. However, the cooling process can damage the crystals. Limiting cooling-induced crystal damage often requires cryoprotection strategies, which can involve substantial screening of solution conditions and cooling protocols. Here, recent developments directed towards rational methods for cryoprotection are described. Crystal damage is described in the context of the temperature response of the crystal as a thermodynamic system. As such, the internal and external parts of the crystal typically have different cryoprotection requirements. A key physical parameter, the thermal contraction, of 26 different cryoprotective solutions was measured between 294 and 72 K. The range of contractions was 2–13%, with the more polar cryosolutions contracting less. The potential uses of these results in the development of cryocooling conditions, as well as recent developments in determining minimum cryosolution soaking times, are discussed
[en] Although reductions in the tax of injuries and accidents have been observed in recent years, Mining is still one of the highest risks industries. The basic causes for occurrence of fatalities can be attributed to unsafe conditions and unsafe acts. In this scene is necessary to identify safety problems and to aim the effective solutions. On the other hand, the developing countries dependence on primary industries as mining is evident. In the Peruvian economy, approximately 16% of the GNP and more than 50% of the exportations are due to the mining sector, detaching its competitive position in the worldwide mining. This paper presents fatal accidents analysis in the Peruvian mining industry, having as basis the register of occurred fatal accidents since year 2000 until 2007, identifying the main types of accidents occurred. The source of primary information is the General Mining Direction (DGM) of the Peruvian Mining and Energy Ministry (MEM). The majority of victims belongs to tertiary contractor companies that render services for mine companies. The results of the analysis show also that the majority of accidents happened in the underground mines, and that it is necessary to propose effective solutions to manage risks, aiming at reducing the fatal accidents taxes. (Author)
[en] Ethical and societal issues concerning justice, safety, risks, and benefits are well-established topics in the discourses of nanotechnology innovation and development. That nanotechnology innovation should be socially and ethically responsible is generally accepted by scientists, policymakers, regulators, and industry, and the idea of public involvement and communication is part and parcel of the conceptualization of responsible technology development. This paper systematically reviews the social science research literature accumulated between 2002 and 2018 on the communication of nanotechnology. A critical and constructivist perspective on policy problems guides the analysis. Two questions are asked of this literature: what problems are identified regarding the communication of nanotechnology to the public? How can these problems be managed and/or resolved? Three different problem themes are identified: the public, societal institutions, and nanotechnology itself. While for some identified problems, there are corresponding solutions; in other instances, there is little alignment between problems and solutions. In conclusion, the paper recommends that in communicating nanotechnology to the public: (i) the objectives of communication should be defined; (ii) previous research should be used responsibly; (iii) communication strategies should be adapted to the context; and (iv) effort should not be spent trying to develop a generic framework for communication.
[en] The mean dimensions of multichain polymer systems are predicted to follow a scaling relation with scaling variable X = l/sup d/ν-1 rho, where l is the number of statistical segments on the chain, rho is the segment density, d is the dimension, and ν is the critical exponent for the mean dimensions of an isolated polymer chain. The scaling laws are < R2>roughly-equalA(X) l/sup 2nu/ for l→ infinity with X bounded, and < R2>roughly-equalB(rho) l for l→ infinity with X → infinity. Moreover, the critical amplitudes behave as A(X)approx.X/sup()( -2nu-1/d/ν-1) as X → infinity and B(rho)approx.rho/sup()( -2nu-1/d/ν-1) as rho → 0. Simulations of both continuum and lattice systems are reanalyzed and found to be consistent with these scaling relations. Previous naive use of short-chain data has led to misleading results
[en] Thermo-dependence of electrodiffusional measurements of wall velocity gradient has been studied in a fully developed turbulent channel flow. In isothermal conditions, the direct thermo-compensation can be provided using the measurements of thermo-dependence of molecular diffusivity and viscosity. The simultaneous transient and steady-state limiting diffusion current measurements open the possibility for in situ compensation of thermal effects in electrodiffusional flow diagnostics at non-isothermal conditions where the local temperature gradients are presented. The feasibility of the proposed method of thermo-compensation has been confirmed experimentally for the case of local heating of the solution by means of pulse hot-wire technique
[en] The structure of RT room is consist of concrete. Because of low cost and shielding efficiency, the concrete is used widely for building of RT room. But in fortunately, gamma radiation is scattered so much with the concrete and back scattering also very strong. The secondary radiation by back scattering will be big affected in making film image quality in case of heavy wall casting, it is needed long exposure time. The long exposure time means increasing of scattered radiation to the film. In the topic, the interaction of gamma radiation and materials by scattered radiation will discussed and also the attenuation of scattered radiation with concrete. It is the main object to find the method of minimizing the effects by the scattered radiation for each materials and its application.
[en] The aim of this essay is to address some of the aspects of the Bridge alternative and to examine the conclusions reached back in 1995 over the feasibility of such a solution. Although having been left aside for decades, the Bridge Solution of the Strait of Gibraltar Crossing Project has been brought back to life as an available alternative to close the gap between the two continents, being the reason to have recently detected some impediment down into the lower layers of the site laying grounds. All of which has revealed further geotechnical issues to tackle. Given the current level of development the Tunnel solution has reached, the 20-year-old Bridge solution needs to be fully updated in order to catch up with the former: As well as taking into consideration the new trends present in the state of the art on design of structures, the Bridge solution would also entail updating construction procedures if it is to incorporate all the potentialities offered by: (1) related tools (2) machinery, and (3), many new ideas which, coming from distinct industrial sectors others than the public works, have worked their way through the construction field. Furthermore, it would be necessary to bear in mind the ceaseless development materials science is going through, which involves constant increases in both levels of resilience and number of characteristics such materials present. (Author)
[en] The shear viscosity expressions for a polydisperse hard-sphere fluid in both the dilute and dense fluid regions have been obtained as the solution of a set of linear integral equations in the Enskog transport theory. In the monodisperse limit we recover the known Enskog result. Explicit analytical solutions have been obtained for the special case of equal-mass particles. For general mass-size distributions, a simple numerical method has been proposed. Computations have been performed for a mass-size relation of power-law form. The two size distributions we have looked at are the Schulz distribution and the log-normal distribution. It is found that both distributions show similar effects on the shear viscosity. In the dilute-gas region, for each given fractal dimension, there exists a critical variance of the size distribution at which the shear viscosity attains a maximum. In the dense-gas region, the shear viscosity increases as the variance and the density increase except for the low density and the high fractal-dimension region where the shear viscosity attains a minimum at some particular variance. The shear viscosity diverges at a close-packing density that decreases with increasing variance
[en] The fundamentals of the theory of formation of surface complexes (or the surface complexation theory, SCT), which is used in processing the results of studies on the equilibria in multicomponent ion exchange sorption systems, are outlined. The advantage of the theory is the use of the sorption characteristics of binary ion exchange systems for the description and calculation of multicomponent equilibria with allowance for the medium pH value. The solutions to some problems of nonlinear sorption dynamics theory obtained using the description of multicomponent equilibria in the framework of the SCT model are considered. Experimental data on the concentration distributions of components in frontal and displacement chromatograms are compared with the results of corresponding numerical calculations using various sets of parameters of the SCT model (including versions with allowance for the effect of complexation reactions in the mobile phase).