An Exact Inequality of Jackson-Chernykh Type for Spline Approximations of Periodic Functions

Siberian Mathematical Journal - We establish the inequality with exact constant for spline approximations of periodic functions which is similar to the Jackson-Chernykh inequality for...     

Total synthesis and biochemical characterization of mirror image barnase

In this study we synthesized and characterized mirror image barnase (B. amyloliquefaciens ribonuclease). d-Barnase was identical to l-barnase, when analyzed by liquid chromatography and mass-spectrometry. Proteolysis of the mirror image enzyme revealed that in contrast to its native counterpart, d-barnase was completely stable to digestive proteases. In enzymatic assays, d-barnase had the reciprocal chiral specificity and was fully active towards mirror image substrates. Interestingly, d-barnase also hydrolyzed the substrate of the native chirality, albeit 4000 times less efficiently. This effect was further confirmed by digesting a native 112-mer RNA with the enzyme. Additional studies revealed that barnase accommodates a range of substrates with various chiralities, but the prime requirement for guanosine remains. These studies point toward using mirror image enzymes as modern agents in biotechnology.     

物理化学混合式教学设计与实践——以“单组分系统相变热力学”为例*

以“单组分系统相变热力学”为例介绍了物理化学混合式教学设计与教学实践。围绕课程教学目标,在课前、课中、课后的每一个教学环节中践行课程教学理念,通过“问题+案例”方式突出物理化学基本方法的应用性、普适性与前沿性,让学生在教学过程中获取原理、体验探究、发展思维、生成智慧。教学评价结果显示,绝大部分学生对混合式教学模式给予了积极的评价。     

Determination of the shape of the shocks ahead of a transverse jet injected into a supersonic flow

The three-dimensional shape of the shock wave formed ahead of a sonic jet flowing out into a supersonic flow through the surface of a sharp cone is determined. The shape of the wave in the longitudinal and transverse cross-sections of the model is constructed using schlieren photographs taken for various angles of rotation and freestream Mach numbers M=1.75–3. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 2, pp. 41–44, March–April, 1998. This research was carried out with financial support from the Russian Foundation for Basic Research (project No. 95-01-00709a).     

The laminar flow of plastic disperse systems in circular tubes

Summary The present work offers an analysis of the regularities of the flow of plastic disperse systems (PDS) as applied to the Bulkley-Herschel three-constant rheological equation. Theoretical data on the velocity profile distribution have been confirmed by experiments on the device, in which the flow structure was studied by the method of the frozen flow. By introducing expressions for the generalized Bingham and Reynolds numbers for non-linear viscoplastic bodies, formulas have been obtained for the calculation of the resistance coefficient of a hydrodynamically stabilized flow; the formulas for power law liquids and the Schwedoff-Bingham model follow from it as special cases. The results of the calculations are in good accord with experimental data for various PDS. A nomogram is given for the determination of the resistance coefficient in engineering calculations.Finally the present work considers the flow in the initial hydrodynamic zone of the tube. An analysis is given of the existing methods used for the solution of the problems and it is shown that the method used in this work for numerical calculation of simplified equations of continuity and motion provides sufficient accuracy. The results of numerical calculations are compared with the literature data, and these results are used for the analysis of the development of the flow of nonlinearly viscoplastic bodies in the initial zone. Relations are given for the determination of the length of the initial zone and of the increase of the resistance to flow due to the formation of the velocity profile. With account taken of this resistance, formulas have been derived for the calculation of pressure losses during the flow of PDS in tubes, including the initial zone.

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Zusammenfassung Es wird die Rohrströmung plastischer disperser Systeme (PDS), welche mittels einer drei-konstantigen Stoffgleichung nachBulkley undHerschel beschrieben werden können, untersucht. Das theoretisch berechnete Strömungsprofil wird durch Experimente unter Verwendung von Strömungs-Sichtbarmachungs-Methoden bestätigt. Durch Einführung geeignet definierter verallgemeinerter Bingham- und Reynolds-Zahlen für nicht-linear viskoplastische Stoffe werden Formeln zur Berechnung des Widerstandsbeiwerts einer hydrodynamisch stabilisierten Strömung erhalten; die Formeln für Ostwald-de Waele-Flüssigkeiten und Schwedoff-Bingham-Körper sind als Spezialfälle darin enthalten. Die berechneten Ergebnisse stimmen gut mit den bei verschiedenen PDS erhaltenen experimentellen Daten überein. Für ingenieurmäßige Rechnungen wird ein Nomogramm zur Bestimmung des Widerstandsbeiwerts mitgeteilt.Schließlich wird noch die Strömung im Einlaufbereich des Rohrs betrachtet. Die für die Lösung dieses Problems bekannten Methoden werden analysiert, und es wird gezeigt, daß die hier verwendete numerische Methode unter Zugrundelegung von vereinfachten Gleichungen für Kontinuität und Bewegung eine hinreichende Genauigkeit liefert. Die Ergebnisse der numerischen Rechnung werden mit aus der Literatur bekannten Daten verglichen, und diese werden dann zur Analyse der Entwicklung der Strömung von nichtlinear-viskoplastischen Stoffen in der Einlaufzone herangezogen. Es werden Beziehungen zur Bestimmung der Länge der Einlaufzone und der Vergrößerung des Widerstands infolge der Abweichung des Profils von der stationären Form angegeben. Durch Einbeziehung des erhöhten Einlaufwiderstands werden Formeln abgeleitet, mit denen sich der Druckverlust beim Fließen von PDS in Rohren unter Berücksichtigung der Einlaufzone berechnen lassen.

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With 11 figures and 2 tables     

Electric fields in the rheology of disperse systems

In the present survey, the influence of electric fields on the structure and rheological properties of disperse systems as well as the effect of deformations on their electrical characteristics are discussed. The properties of these systems are considered in terms of the dielectric permittivity and electrification potential. The considerable thickness of the double electric layer around the disperse phase particles, which is characteristic of disperse systems with nonpolar hydrocarbon dispersion media, provides the possibility for strong electric fields to produce an electric nonuniformity on the surface of the disperse phase particles. The formation of hydrate layers on the particles creates the possibility of polarization of the disperse phase. In plastic disperse systems such as greases, a strong orientation effect is observed, which contributes to the creation of frozen flow patterns when the flow is suddenly stopped. The survey is concluded with a consideration of the process of formation of chain structures in the direction of the lines of force of the electric field whose orientation is normal to the direction of flow, which can lead to complete stoppage of the flow.     

Investigation of flow beyond a supersonic nozzle by an electron-beam technique

The results of an experimental study of a flow of rarefied gas of density 10^–5 g/cm³ beyond the cutoff of a hypersonic nozzle (M11) by means of an electron beam with energy up to 43 keV are presented. The density and velocity fields at different distances from the nozzle and various receiver pressures were measured using this method and the static and total pressure fields were also measured with the help of a Pitot tube. The flow parameters beyond the nozzle were calculated for two limiting cases: with equilibrium condensation and without condensation. This calculation is compared with the experimental results.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 111–117, January–February, 1976.The authors thank S. N. Romanenko for help with the electron-beam experiments.     

Mechanical Properties of Diamond-Like Silicon–Carbon Films Doped with Vanadium

Crystallography Reports - The influence of doping with vanadium on the mechanical properties of nanocomposite films deposited on silicon substrates has been investigated. It is found that the...