Photochemical reaction of 7-aminocoumarins. 9. [2+2]-Cycloadducts with trans,trans-1,4-diphenyl-1,3-butadiene

The photoreactions of 7-diethylaminocoumarin, 4-methyl-7-diethylaminocoumarin, 4-trifluoromethyl-7-diethylaminocoumarin, and 4-N-morpholino-7-diethylaminocoumarin with trans,trans-1,4-diphenyl-1,3-butadiene, which lead to the formation of [2+2]-cycloaddition products, were studied. It was established that photocycloaddition proceeds with the formation of adducts that have a 1-endo-styryl substituent and a 2-exo-phenyl group. The effect of the substituent in the 4-position of the 7-aminocoumarin molecule on the effectiveness of cycloaddition is discussed.See [1] for Communication 8.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1319–1325, October, 1990.     

Time-resolved X-ray powder diffractometry as a complementary thermal analysis method

The use of a conventional X-ray diffractometry together with curved position sensitive detector (PSD) allows for a complete diffraction pattern to be recorded as a function of time and temperature, so that transformations in the solid state can be traced sequentially. In this way, this technique can be regarded as complementary to the conventional thermal analysis methods, as thermogravimetry and differential scanning calorimetry. Three applications are described: the thermal decomposition of a cadmium hydroxide nitrate, the phase transformation of the dicesium cadmium tetraiodide and the investigation of microsturctural properties as a function of temperature.

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Zusammenfassung Der Einsatz konventioneller Röntgen-Diffraktometrie zusammen mit einem gebogenen positionsempfindlichen Detektor (PSD) ermöglicht die Registrierung eines vollstÄndigen Diffraktogramms als Funktion der Zeit oder Temperatur, so dass Festkörper-umwandlungen fortlaufend verfolgt werden können. Demzufolge kann diese Technik als komplementÄr zu den konventionellen thermoanalytischen Methoden wie TGA und DSC angesehen werden. Drei Anwendungen werden beschrieben:Die thermische Zersetzung eines Cadmiumhydroxidnitrats, die Phasenumwandlung des DicÄsiumcadmiumtetraiodids und die Messung mikrostruktureller Eigenschaften als Funktion der Temperatur.

     

Synthesis of 4-alkyl functionally substituted 7-dialkylaminocoumarins

7-Dialkylaminocoumarins that, depending on the reaction conditions, contain an alkyl substituent with one or two functional groups in the 4 position, were obtained in the reaction of 4-chloro-7-diethylamino-, 4-chloro-7-N-morpholino-, and 2,3,6,7-tetrahydro-9-chloro-1H,5H-quinolizino[9,9a,1-gh]coumarin with sodium derivatives of acetylacetone and acetoacetic, malonic, and cyanoacetic esters. The spectralluminescence characteristics of the synthesized compounds were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1326–1330, October, 1990.     

Synthesis and structures of 2,3,6-triaryl-1-acyl-4-acyloxypiperideines

1-Acyl-4-acyloxy-2,3,6-triaryl-³- and ⁴-piperideines were obtained by acylation of 2,3,6-triarylpiperidone and its 1-acetyl derivative with carboxylic anhydrides and chlorides. The molecular and crystal structures of 3-phenyl-2,6-bis(o-acetoxyphenyl)-1-acetyl-4-acetoxypiperidin-3-ene were established by x-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1352–1358, October, 1990.     

SHEETS IN SYMMETRIC LIE ALGEBRAS AND SLICE INDUCTION

In this paper, we study sheets of symmetric Lie algebras through their Slodowy slices. In particular, we introduce a notion of slice induction of nilpotent orbits which coincides with the parabolic induction in the Lie algebra case. We also study in more detail the sheets of the non-trivial symmetric Lie algebra of type G₂. We characterize their singular loci and provide a nice desingularization lying in so ₇.     

Acid-base characteristics of functionally 4-substituted 4-alkyl-7-aminocoumarins

The acidity and basicity of derivatives of the 7-aminocoumarin series containing a CH-acid group (ethyl acetate, acetone, acetonitrile, acetylacetone, malonic, acetoacetic, or cyanoacetic esters) at position 4 and a diethylamino group or a julolidine fragment at position 7 were investigated. It was established that the CH acidity of the functionally 4-substituted derivatives depends on steric factors.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1488–1493, November, 1991.     

REGULATION OF A FISHERY: FROM A LOCAL OPTIMAL CONTROL PROBLEM TO AN “INVARIANT DOMAIN‘ APPROACH

ABSTRACT. This study aims at regulating a fishery by reducing its catch and effort variations around a reference equilibrium point. A simple bioeconomic continuous time model is considered and the control variable acts on the rate of change of effort. Two approaches have been implemented: the first one is a local optimal approach that sets the problem in the classical linear-quadratic framework; it is extended to an “invariant domain‘ approach, whose robustness constitutes a major advantage.     

Effect of electrical conductivity of flow on current distribution in a magnetogasdynamic channel with allowance for the Hall effect

The effect of a magnetic field on the current distribution on a plane continuous anode situated opposite the cathode in a rectangular magnetogasdynamic channel with an external magnetic field was experimentally investigated. The distributions of the charged-particle density and the electron temperature near the outlet end of the electrodes were measured. The distribution of electrical conductivity in the flow was calculated. The electron density distribution along the channel is attributed to ambipolar diffusion of plasma to the walls. For an interpretation of the current distribution results, the method of integral relations in a linear approximation was used to solve the problem of a constant-velocity flow of a gas with variable electrical conductivity across a magnetic field in a plane magnetogasdynamic channel of constant cross section formed by electrodes of finite length and insulators. The Hall effect was taken into account. Experiments in which the effect of an external magnetic field on the current distribution on plane sectioned short electrodes in a magnetogasdynamic accelerator was investigated were described in [1]. In the present investigation, continuous long electrodes were used. These electrodes prevented the side effects due to coupling of the current to the ends of the electrode sections and helped to reveal some features of the current density distribution on the anode.