Chemistry of Ayurvedic Crude Drugs — VII guggulu (Resin From Commiphora Mukul) —6 : Absolute stereochemistry of guggultetrols

With a view to elucidating the stereochemistry of quqqultetrols, components of saponified Commiphora mukul resin, D-lyxo-, L-ribo-, and L-xylo-octadecane-1,2,3,4-tetrols have been synthesised by two different routes. One method starts with D-glyceraldehyde, while the second route is based on the appropriate pentose. The absolute configuration of the natural product guggultetrol-18, has been deduced as D-xylo (2S, 3S, 4R-configuration) by direct comparison with synthetic compounds. This work also serves to establish the chirality of guggultetrol-20.     

Majorana neutrino transition magnetic moment in a variant of Zee model with horizontal symmetry

A SU(2) _H symmetric variant of Zee model of lepton flavor violation is presented and is shown to lead to neutrino transition magnetic moment of the order required to explain the solar neutrino deficit and the possible anticorrelation of solar neutrino flux with sunspot activity via VVO mechanism. The use of horizontal symmetry leads to totally degenerate neutrino states which may be combined to form a ZKM Dirac neutrino with naturally small mass.     

Higher isoprenoids-IX : Diterpenoids from the oleoresin of Hardwickia pinnata Part 2: Kolavic,kolavenic, kolavenolic and kolavonic acids

Structure determination of four new diterpene acids from the oleoresin of Hardwickia pinnata Roxb. is described. All four acids belong to ent-clerodane type and have been chemically correlated with (?)-hardwickiic acid of proven absolute stereochemistry. One of these acids, kolavonic acid, is shown to be a bisnor diterpenoid.     

Higher isoprenoids—V: Partial syntheses from cycloartenol,cyclolaudenol part 1: mangiferolic acid,ambolic acid

Conversion of cycloartenol into mangiferolic acid and of cyclolaudenol into ambolic acid is described.     

On linear codes correcting random and low-density burst errors

This paper presents lower and upper bounds on the number of parity-check digits required for a linear code that corrects random errors and errors which are in the form of low-density bursts.     

Products active on arthropod—III: Insect juvenile hormone mimics (part 3): cyclononane analogue of cecropia juvenile hormone

Synthesis of cyclononane analogue of Cecropia juvenile hormone-I is described. The analogue is only moderately active against Dysdercus cingulatus.     

Partial state feedback control of chaotic neural network and its application

The chaos control in the chaotic neural network is studied using the partial state feedback with a control signal from a few control neurons. The controlled CNN converges to one of the stored patterns with a period which depends on the initial conditions, i.e., the set of control neurons and other control parameters. We show that the controlled CNN can distinguish between two initial patterns even if they have a small difference. This implies that such a controlled CNN can be feasibly applied to information processing such as pattern recognition.     

Radiative lifetimes,branching ratios and absolute transition probabilities of atomic uranium by delayed photoionization measurements

Radiative lifetimes of ten even-parity energy levels of atomic uranium in the 15,500–19,000 cm^?1 region and branching ratios of six transitions originating either from ground level (⁵L ₆ ^o ) or from lowest metastable level (⁵K ₅ ^o ) at 620.32 cm^?1 are measured employing three-step delayed photoionization technique. The lifetimes of five energy levels and branching ratios of five transitions are measured for the first time. By combining the experimentally measured values of radiative lifetimes and branching ratios, we have determined the absolute transition probabilities of six transitions of uranium and compared with those previously reported in the literature.     

Dynamic Jahn-Teller effect in the NV(-) center in diamond

The negatively charged nitrogen-vacancy (NV(-)) center in diamond is considered to be one of the most promising solid state systems for quantum information applications. Excited states of the NV(-) center play a center role in the proposed applications. Using a combination of first-principles calculations and vibronic interaction model analysis, we establish the presence of a dynamic Jahn-Teller effect in the (3)E excited state. The calculated temperature-dependent dephasing rate for the zero phonon line as well as the splitting of the first two vibronic states are in good agreement with experiment.