Novel statistical approach for primary high-throughput screening hit selection

The standard activity threshold-based method (the "top X" approach), currently widely used in the high-throughput screening (HTS) data analysis, is ineffective at identifying good-quality hits. We have proposed a novel knowledge-based statistical approach, driven by the hidden structure-activity relationship (SAR) within a screening library, for primary hit selection. Application to an in-house ultrahigh-throughput screening (uHTS) campaign has demonstrated it can directly identify active scaffolds containing valuable SAR information with a greatly improved confirmation rate compared to the standard "top X" method (from 55% to 85%). This approach may help produce high-quality leads and expedite the hit-to-lead process in drug discovery.     

Method of calculating the contours of aerodynamic nozzles with transition through the velocity of sound

The existing methods of constructing an “ideal” contour (i.e., a contour without taking account of viscosity) for aerodynamic nozzles has a number of drawbacks: they are extremely unwieldly and are not versatile and, moreover, they give in practice an impairment of the flow uniformity, caused by nonconformity of the true flow in the transonic region assumed in the solution, as only the hypersonic flow region is usually calculated. In this paper, a method is proposed for calculating the ideal contours of aerodynamic nozzles with transition through the velocity of sound, which is free from these drawbacks. Cauchy's problem is solved numerically by the method in [1]. A specially corrected pressure distribution, obtained experimentally [2], is used as the initial distribution. Examples of the calculation are given for the ideal contours of plane, axisymmetrical and annular aerodynamic nozzles.     

Numerical modeling of carbon monoxide neutralization by metered water injection into a high-temperature mixture of combustion products

A closed mathematical model of the flow of a two-phase mixture consisting of evaporating water droplets and a chemically reacting multicomponent gas is described. The effect of the real droplet heating and evaporationkinetics on the gas-phase chemical reactions in a mixture of combustion products is studied within the framework of this model.Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No.6, pp. 96–106, November–December, 1993.     

Laval nozzle flow calculation

The inverse problem of the theory of the Laval nozzle is considered, which leads to the Cauchy problem for the gasdynamic equations; the streamlines and the flow parameters are found from the known velocity distribution on the axis of symmetry.The inverse problem of Laval nozzle theory was considered in 1908 by Meyer [1], who expanded the velocity potential into a series in powers of the Cartesian coordinates and constructed the subsonic and supersonic solutions in the vicinity of the center of the nozzle. Taylor [2] used a similar method to construct a flowfield which is subsonic but has local supersonic zones in the vicinity of the minimal section. Frankl [3] and Fal'kovich [4] studied the flow in the vicinity of the nozzle center in the hodograph plane. Their solution, just as the Meyer solution, made it possible to obtain an idea of the structure of the transonic flow in the vicinity of the center of the nozzle.A large number of studies on transonic flow in the vicinity of the center of the nozzle have been made using the method of small perturbations. The approximate equation for the transonic velocity potential in the physical plane, obtained in [3–6], has been studied in detail for the plane and axisymmetric cases. In [7] Ryzhov used this equation to study the question of the formation of shock waves in the vicinity of the center of the nozzle, and conditions were formulated for the plane and axisymmetric cases under which the flow will not contain shock waves. However, none of the solutions listed above for the inverse problem of Laval nozzle theory makes it possible to calculate the flow in the subsonic and transonic parts of the nozzles with large gradients of the gasdynamic parameters along the normal to the axis of symmetry.Among the studies devoted to the numerical calculation of the flow in the subsonic portion of the Laval nozzle we should note the study of Alikhashkin et al., and the work of Favorskii [9], in which the method of integral relations was used to solve the direct problem for the plane and axisymmetric cases.The present paper provides a numerical solution of the inverse problem of Laval nozzle theory. A stable difference scheme is presented which permits analysis with a high degree of accuracy of the subsonic, transonic, and supersonic flow regions. The result of the calculations is a series of nozzles with rectilinear and curvilinear transition surfaces in which the flow is significantly different from the one-dimensional flow. The flowfield in the subsonic and transonic portions of the nozzles is studied. Several asymptotic solutions are obtained and a comparison is made of these solutions with the numerical solution.The author wishes to thank G. D. Vladimirov for compiling the large number of programs and carrying out the calculations on the M-20 computer.     

Turbulent jet mixing of supersonic flows in profiled flow-equalization channels

A numerical model for the calculation of gas dynamic systems with turbulent mixing of supersonic jets is proposed. The problem of designing a transitional flow-equalization channel of minimum length is solved for the viscous turbulent mixing of two parallel or mutually inclined supersonic flows. The problem is solved in two stages. In the first stage the flow-equalization channel is designed by solving the inverse problem in the ideal gas approximation. In the second stage the basic problem is solved for the channel thus obtained on the basis of the parabolized Navier-Stokes equations. Investigations have demonstrated the validity of this approach to the equalization of nonuniform flows.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 175–178, July–August, 1987.The authors are grateful to V. I. Kopchenov for supplying the program for solving the basic problem by a first-order Godunov method and to A. I. Kraiko and Yu. V. Kurochkin for their interest and advice.     

Impurity optical absorption in parabolic quantum well

Optical absorption in GaAs parabolic quantum well in the presence of hydrogenic impurity is considered. The absorption coefficient associated with the transitions between the upper valence subband and donor ground state is calculated. The impurity ground state wave function and energy are obtained using the variational method. Dependence of the absorption spectra on impurity position in quantum well was investigated. It is shown, that along with quantum well width decrease the absorption threshold shifts to higher frequencies. Results obtained within frames of parabolic approximation are compared with results for rectangular infinite-barrier quantum well case. The acceptor state → conduction band transitions considered as well.     

Stabilization of the 2D incompressible Euler system in an infinite strip

The paper is devoted to the study of a stabilization problem for the 2D incompressible Euler system in an infinite strip with boundary controls. We show that for any stationary solution (c,0)$(c,0)$ of the Euler system there is a control which is supported in a given bounded part of the boundary of the strip and stabilizes the system to (c,0)$(c,0)$.     

Numerical solution of an inverse problem of nozzle theory for a two-phase gas-particle mixture

In the present paper gas flows with monodisperse and polydisperse particles in plane and axisymmetric nozzles are calculated by the inverse method [1, 2]. The gas velocity distribution is specified on the axis of symmetry of the nozzle, while the gas and particle parameters are specified in the entrance section. As a result of the numerical integration of a system of equations describing a flow of gas with condensate particles in it we determine the gas and particle parameters, the gas streamlines, and the particle trajectories with allowance for the mutual influence of the gas and particles. One of the gas streamlines is taken as the nozzle contour and the limiting trajectories and pure gas zone are found. A difference method is described which makes it possible to calculate the subsonic, transonic, and supersonic flow regions using a single algorithm, its features are noted, and the results of the calculation for monodisperse mixtures with particle diameters 1 and 5 m and fractions by weight 0.3 are given. A comparison is made with the results of calculations by other methods.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 106–114, July–August, 1986.The authors express their gratitude to N. B. Ponomarev and G. E. Dumnov for their useful discussions and help in carrying out the calculations.     

Two-layer flows of gas in supersonic axisymmetric nozzles

This article describes two methods for calculating two-layer flows. The first is a generalization of a numerical method for solving the inverse problem [1] for the case of two-layer flows, without taking mixing into account. The second is a method of characteristics, for calculating a two-layer flow in a supersonic nozzle. In this case, the usual method of characteristics is changed in such a way that it is possible to calculate a point on the interface between two layers having different adiabatic indices, and different total pressures and temperatures. This article also gives the results of calculation of two-layer flows in nozzles with different adiabatic indices and different ratios of the mass flow rates of the gas in the layers.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 76–81, July–August, 1970.The calculations were programmed and carried out by G. D. Vladimirova and M. F. Tamarovskii, to whom the author expresses his thanks.