Detection of a Chirp Ionosonde Signal under Conditions of a Priori Non-Parametric Uncertainty

Radiophysics and Quantum Electronics - We consider the model of a mixture of probability distributions for background and target samples in the problem of extracting a signal from radiophysical...     

Ozonides of N-acyl-4-phenyl-3a,4,5,9b-tetrahydro-3H-cyclopenta [c]quinoline

Ozonation of N-acyl-4-phenyl-3a,4,5,9b-tetrahydro-3 H-cyclopenta[ c]quinoline gave stable ozonides: a conformationally mobile isomer with the pseudoequatorial N-acyl group and a conformationally stable isomer with the pseudoaxial N-trifluoroacetyl group.     

New Derivatives of 20-Hydroxyecdyzone. Viticosterone E Synthesis

New 20,22-mono- and 2,3:20,22-diacetals of 20-hydroxyecdyzone were synthesized, and some thereof were applied to the synthesis of 25-O-acetyl-20-hydroxyecdyzone (viticosterone E).     

Synthesis of 4‐Aryl‐8‐fluoro‐3a,4,5,9b‐tetrahydro‐3H‐cyclopenta[c]quinolines and Their Ozonides

4‐Aryl‐8‐fluoro‐3a,4,5,9b‐tetrahydro‐3H‐cyclopenta[c]quinolines are synthesized by acid‐catalyzed (CF₃CO₂H) three‐component cyclocondensation of 4‐fluoroaniline with aromatic aldehydes and cyclopentadiene. Stable ozonides with (1R*,4S*,5aR*,6S*,11bS*)‐configurations are obtained by ozonolysis of corresponding trifluoroacetyl derivatives.     

Evaluation of the time of prompt-fission-neutron emission from 252Cf by measuring a two-particle correlation function

The time of prompt-fission-neutron emission from ²⁵²Cf is evaluated at τ₀≥(1?2)×10^?19 s by measuring a two-neutron correlation function. The final-state interaction of identical neutrons emitted by moving fission fragments is taken into account.     

Magnetooptical method of measuring the characteristics of the reservoir of spin-spin interactions in paramagnets

Based on the phenomenon of coherent spin Raman scattering a magnetooptical method of measuring the characteristics of the reservoir of electronic spin-spin interactions in paramagnets was implemented. A formula relating the intensity of the inelastically scattered light to the temperature of the spin-spin reservoirs under conditions of saturation of the EPR of paramagnetic ions has been derived. For the Ce³⁺ ions in the (Ce_xLa_1−x)₂Mg₃(NO₃)₁₂·24H₂O crystal values of the time of spin-lattice relaxation of the spin-spin reservoir and the local magnetic field have been measured, and a relation between the spin-spin reservoir temperature and the external magnetic field strength under conditions of stationary saturation of the EPR of the Ce³⁺ ions has been obtained. V. I. Ul’yanov-Lenin Kazan State University,18, Lenin St., Kazan, 420008, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 76–81, January–February, 1997.     

Transformation of 20-Hydroxyecdysone Acetonides into Podecdysone B

Hydrogenation of 20-hydroxyecdysone 2,3:20,22-diacetonide and 20,22-acetonide over palladium catalyst yields podecdysone B 20,22-acetonide. Acid hydrolysis of the latter affords podecdysone B which is a natural phytoecdysteroid.     

Specific features of resonance electron capture mass spectra of ecdysteroid molecules

Specificity of the dissociative attachment of low-energy electrons to ecdysteroid molecules (viz., 20-hydroxyecdysone 2,3:20,22-diacetonide, 20-hydroxyecdysone 20,22-acetonide, and poststerone 2-acetate) was found, which is manifested as the formation of long-lived pseudo-molecular negative ions that appeared due to the elimination of the H₂ and H₂O molecules. These rearrangements are resulted from the formation of the system of conjugated double bonds in the ecdysteroid skeleton, stabilizing the lowest vacant molecular orbital.     

Validation of MRI-Based Fiber-Tracking Results

A new approach to estimating the probability of the fiber-track existence has been developed and validated on the basis of digital phantoms and diffusion-weighted magnetic resonance imaging measurements on human brain. The proposed approach includes two parameters—the local probability of the tract direction and the Shannon entropy. The local probability of the tract direction characterizes how well tracts “fit” the direction information in a voxel. The Shannon entropy characterizes the shape of diffusivity in the voxel. Calculations on digital phantoms and in vivo data showed that the combination of these parameters makes it possible to verify fiber-tracking results.