A de novo Diels-Alder strategy toward the novel pentacyclic natural product fluostatin C: a concise synthesis of 6-deoxyfluostatin C

A conceptually new Diels-Alder approach, involving a diene moiety grafted on a preformed epoxyquinone platform and a 4-hydroxy-indenone as the dienophile, delivers the pentacyclic framework of fluostatin C in one key step.     

Temperature dependent small-angle neutron scattering of CTABr—magnetic fluid emulsion

Small-angle neutron scattering studies have been carried out to check the structural integrity of citryltrimethylammonium bromide (CTABr) micelles in a magnetic fluid for different magnetic fluid concentrations at two different temperatures 303 and 333 K. It is found that the CTABr micelles grow with increasing magnetic fluid concentration and there is a decrease in the micellar size with increase in temperature.     

High spin states in120Xe

High spin states in ¹²⁰Xe, populated via¹⁰⁷Ag(¹⁶O, p2n) and¹⁰⁸Pd(¹⁶O, 4n)reactions have been studied using γ-ray spectroscopic techniques. 21 new transitions have been added to extend the level scheme. Two S-bands are extended upto 26⁺ and 22⁺;these bands are found to cross the g. s band at hΩ=0. 39 and 0. 47 MeV. The band structures have been discussed within the framework of CSM.     

Weakly analytic sets for function spaces

We define and study weakly analytic sets for function spaces. This concept generalizes the concept of weak analyticity for function algebras. We also define weak analyticity for the space of affine functions using the ideas of convexity. We show that it coincides with the same concept regarding it as a function space. We give several examples to illustrate the concepts.     

Numerical analysis of pressure oscillations over axisymmetric spiked blunt bodies at Mach 6.80

The pressure oscillations over a forward facing spike attached to an axisymmetric blunt body are simulated by solving time-dependent compressible Navier–Stokes equations. The governing fluid flow equations are discretized in spatial coordinates employing a finite volume approach which reduces the equations to semidiscretized ordinary differential equations. Temporal integration is performed using the two-stage Runge–Kutta time stepping scheme. A global time step is used to obtain a time-accurate numerical solution. The numerical computation is carried out for a freestream Mach number of 6.80 and for spike length to hemispherical diameter ratios of 0.5, 1.0 and 2.0. The flow features around the spiked blunt body are characterized by a conical shock wave emanating from the spike tip, a region of separated flow in front of the hemispherical cap, and the resulting reattachment shock wave. Comparisons of the numerical results are made with the available experimental results, such as schlieren pictures and the surface pressure distribution along the spiked blunt body. They are found to be in good agreement. Spectral analysis of the computed pressure oscillations are performed employing fast Fourier transforms. The surface pressure oscillations over the spike and phase plots exhibit a behaviour analogous to that of the Van der Pol equation for a self-sustained oscillatory flow. Received 28 February 2001 / Accepted 17 January 2002     

Numerical investigation of the impingement of an oblique shock on a flat plate

Summary The unsteady, compressible Navier-Stokes equations in Reynolds-averaged variables are solved for a shock wave turbulent boundary layer interaction. For the free stream Mach number 3.7 and Reynolds number 8.202×10⁶ computation is performed using MacCormack's explicit-implicit finite difference scheme with 42×42 grid points. It is found that the peak heating amplification correlation agrees well with computational results.

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Numerische Untersuchung des Auftreffens einer schiefen Stoßwelle auf eine ebene Platte

Zusammenfassung Die Navier-Stokes-Gleichungen in instationärer, kompressibler Form mit Reynolds-gemittelten Variablen werden für die gegenseitige Beeinflussing einer Stoßwelle mit einer turbulenten Grenzschicht gelöst. Die Berechnung wird anhand des MacCormack's explizit-impliziten Finite-Differenzen-Verfahrens mit 42×42 Gitterpunkten für eine Freistrahl-Machzahl von 3,7 und einer Reynoldszahl von 8,202·10⁶ durchgeführt. Die Rechenergebnisse stimmen mit den Experimenten gut überein.

     

Pd-catalyzed amination as an alternative to nucleophilic aromatic substitution for the synthesis of N-alkyltacrines and analogues

A reliable Pd-catalyzed amination protocol is described for the synthesis of N-alkyltacrines and analogs. The Josiphos ligand CyPFtBu was found to provide optimum yields: 16 examples are given. Compared to the typical high-temperature nucleophilic aromatic substitution (NAS) routes, Pd-catalyzed aminations proceed at significantly lower reaction temperatures, and enable the synthesis of otherwise inaccessible products.