Noise impact on working woodchip board

High noise level in the production of particle is one of the main occupational hazards at the Joint-Stock Company “Ivatsevichidrev”. Studies have shown that the maximum excess of permissible levels observed at mid and high frequencies, the most harmful to humans. In the workplace, levels from 1 to 14 dB were measured at workplace of shaving machine operator and the operator of the sorting chips machine PESSA, from 3 to 17 dB at machinist cutting board, from 1 to 4 dB at separator operators workplace. To reduce the harmful effects of noise, new sound insulating cab design was developed for the operators of these jobs

Realistic protein-protein association rates from a simple diffusional model neglecting long-range interactions, free energy barriers, and landscape ruggedness

We develop a simple but rigorous model of protein-protein association kinetics based on diffusional association on free energy landscapes obtained by sampling configurations within and surrounding the native complex binding funnels. Guided by results obtained on exactly solvable model problems, we transform the problem of diffusion in a potential into free diffusion in the presence of an absorbing zone spanning the entrance to the binding funnel. The free diffusion problem is solved using a recently derived analytic expression for the rate of association of asymmetrically oriented molecules. Despite the required high steric specificity and the absence of long-range attractive interactions, the computed rates are typically on the order of 10^4-10^6 M-1 s-1, several orders of magnitude higher than rates obtained using a purely probabilistic model in which the association rate for free diffusion of uniformly reactive molecules is multiplied by the probability of a correct alignment of the two partners in a random collision. As the association rates of many protein-protein complexes are also in the 10^5-10^6 M-1 s-1, our results suggest that free energy barriers arising from desolvation and/or side-chain freezing during complex formation or increased ruggedness within the binding funnel, which are completely neglected in our simple diffusional model, do not contribute significantly to the dynamics of protein-protein association. The transparent physical interpretation of our approach that computes association rates directly from the size and geometry of protein-protein binding funnels makes it a useful complement to Brownian dynamics simulations.Comment: 9 pages, 5 figures, 1 table. One figure and a few comments added for clarificatio

A Langevin canonical approach to the dynamics of two level systems. I. Populations and coherences

A canonical framework for chiral two--level systems coupled to a bath of harmonic oscillators is developed to extract, from a stochastic dynamics, the thermodynamic equilibrium values of both the population difference and coherences. The incoherent and coherent tunneling regimes are analyzed for an Ohmic environment in terms of a critical temperature defined by the maximum of the heat capacity. The corresponding numerical results issued from solving a non-linear coupled system are fitted to approximate path--integral analytical expressions beyond the so-called non-interacting blip approximation in order to determine the different time scales governing both regimes.Comment: 8 pages, 4 figures, 1 tabl

State-dependent diffusion: thermodynamic consistency and its path integral formulation

The friction coefficient of a particle can depend on its position as it does when the particle is near a wall. We formulate the dynamics of particles with such state-dependent friction coefficients in terms of a general Langevin equation with multiplicative noise, whose evaluation requires the introduction of specific rules. Two common conventions, the Ito and the Stratonovich, provide alternative rules for evaluation of the noise, but other conventions are possible. We show the requirement that a particle's distribution function approach the Boltzmann distribution at long times dictates that a drift term must be added to the Langevin equation. This drift term is proportional to the derivative of the diffusion coefficient times a factor that depends on the convention used to define the multiplicative noise. We explore the consequences of this result in a number examples with spatially varying diffusion coefficients. We also derive path integral representations for arbitrary interpretation of the noise, and use it in a perturbative study of correlations in a simple system.Comment: 18 pages, 8 figures, Accepted to PR

Viscosity Dependence of the Folding Rates of Proteins

The viscosity dependence of the folding rates for four sequences (the native state of three sequences is a beta-sheet, while the fourth forms an alpha-helix) is calculated for off-lattice models of proteins. Assuming that the dynamics is given by the Langevin equation we show that the folding rates increase linearly at low viscosities \eta, decrease as 1/\eta at large \eta and have a maximum at intermediate values. The Kramers theory of barrier crossing provides a quantitative fit of the numerical results. By mapping the simulation results to real proteins we estimate that for optimized sequences the time scale for forming a four turn \alpha-helix topology is about 500 nanoseconds, whereas the time scale for forming a beta-sheet topology is about 10 microseconds.Comment: 14 pages, Latex, 3 figures. One figure is also available at http://www.glue.umd.edu/~klimov/seq_I_H.html, to be published in Physical Review Letter

Like-charge attraction through hydrodynamic interaction

We demonstrate that the attractive interaction measured between like-charged colloidal spheres near a wall can be accounted for by a nonequilibrium hydrodynamic effect. We present both analytical results and Brownian dynamics simulations which quantitatively capture the one-wall experiments of Larsen and Grier (Nature 385, p. 230, 1997).Comment: 10 pages, 4 figure

Down syndrome-recent progress and future prospects

Down syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and is associated with a number of deleterious phenotypes, including learning disability, heart defects, early-onset Alzheimer's disease and childhood leukaemia. Individuals with DS are affected by these phenotypes to a variable extent; understanding the cause of this variation is a key challenge. Here, we review recent research progress in DS, both in patients and relevant animal models. In particular, we highlight exciting advances in therapy to improve cognitive function in people with DS and the significant developments in understanding the gene content of Hsa21. Moreover, we discuss future research directions in light of new technologies. In particular, the use of chromosome engineering to generate new trisomic mouse models and large-scale studies of genotype-phenotype relationships in patients are likely to significantly contribute to the future understanding of DS

Partition-Induced Vector Chromatography in Microfluidic Devices

The transport of Brownian particles in a slit geometry in the presence of an arbitrary two-dimensional periodic energy landscape and driven by an external force or convected by a flow field is investigated by means of macrotransport theory. Analytical expressions for the probability distribution and the average migration angle of the particles are obtained under the Fick-Jackobs approximation. The migration angle is shown to differ from the orientation angle of the driving field and to strongly depend on the physical properties of the suspended species, thus providing the basis for vector chormatography, in which different species move in different directions and can be continuously fractionated. The potential of microfluidic devices as a platform for partition-induced vector chromatography is demonstrated by considering the particular case of a piece-wise constant, periodic potential that, in equilibrium, induces the spontaneous partition of different species into high and low concentration stripes, and which can be easily fabricated by patterning physically or chemically one of the surfaces of a channel. The feasibility to separate different particles of the same and different size is shown for systems in which partition is induced via 1g-gravity and Van der Waals interactions in physically and chemically patterned channels, respectively

INTERDISCIPLINARY INTEGRATION ON THE BASIS OF THE GEOMETRICAL CONSTITUENT OF THE NATURAL SCIENTIFIC PICTURE OF THE WORLD

Fragmentariness of the picture of the world in majority modern students is a significant obstacle in the development of their scientific worldview. The lack of integrity of the image of the universe is aggravated by the prevalence of the clip-on thinking among students, which prevents the students from fully acquiring fundamental classical education. The formation of an integral scientific picture of the world is necessary for the realization of an in-dependent productive research activity. In whatever field this activity is carried out, it is closely related to the creation of spatial representations and the mental manipulation of them in the process of solving various problems. Spatial representations are ordered in the mind of the learner on the basis of the geometric component of the natural science picture of the world. Integrated content courses such as "Introduction to the Modern Geometry of the Universe" while teaching of students should be combined with the implementation of the principle of interdisciplinary integration in the development of the educational program, carried out on the basis of the geometric component of the natural-science picture of the world.