The Heisenberg ferromagnet in spin coherent state representation

A new approach to Heisenberg ferromagnet using the spin coherent state representation is developed. The differential operator representation of spin angular momentum operators is used to derive thec-number analogs of the basic quantum mechanical equations, viz., the Schrödinger, Bloch and Liouville equations for the Heisenberg ferromagnet. As an important illustration of our formulation, which has noad hoc assumptions and does not use any boson representation, the excitation spectrum for one, two and three spin waves is obtained. In these cases it is also shown that eigenvalue spectrum can be obtained by completely ignoring the kinematical interactions.     

Projection-speckle digital-correlation method for surface-displacement measurement

A whole-field projection-speckle technique to measure out of plane displacements of initially flat structures has been presented. The method is based on digital correlation of images obtained from a TV camera. An improved digital-correlation function has been derived and described along with the analysis scheme. An instrumentation system based on a desktop computer has been set up to implement the method. Experimental results from simple static tests have been used to validate the technique.     

Nonlinear chiral models: Soliton solutions and spatio-temporal chaos

Nonlinear effective Lagrangian models with a chiral symmetry have been used to describe strong interactions at low energy, for a long time. The Skyrme model and the chiral quark-meson model are two such models, which have soliton solutions which can be identified with the baryons. We describe the various kinds of soliton states in these nonlinear models and discuss their physical significance and uses in this review. We also study these models from the view point of classical nonlinar dynamical systems. We consider fluctuations around theB=1 soliton solutions of these models (B, being the baryon number) and solve the spherically symmetric, time-dependent systems. Numerical studies indicate that the phase space around the Skyrme soliton solution exhibits spatio-temporal chaos. It is remarkable that topological solitons signifying stability/order and spatio-temporal chaos coexist in this model. In contrast with this, the soliton of the quark-meson model is stable even for large perturbations.     

Cyclic chlorophosphites as scaffolds for the one-pot synthesis of α-aminophosphonates under solvent-free conditions

New α-aminophosphonates of the type (OCH₂CMe₂CH₂O)P(O)CH(NHCO₂R)(R′) [6a-i, 7a-e, and 8a-c] have been synthesized in high yields by a three-component reaction using (OCH₂CMe₂CH₂O)PCl (3), benzamide (or urethane or benzyl carbamate), and an aldehyde without using any catalyst under solvent-free conditions. This route can be readily adapted for bis-aminophosphonates as well as optically active binaphthoxy α-aminophosphonates; it also tolerates the phenolic -OH group as shown by the synthesis of hydroxy functionalized aminophosphonates. Partial hydrolysis of compounds 7a-d leads to products in which the phosphorinane ring is cleaved first. Compounds (OCH₂CMe₂CH₂O)P(O)CH[NHC(O)Ph](9-anthryl) (6f) and optically pure (R,S)-(−)-(C₂₀H₁₂O₂)P(O)CH(NHCO₂Et)(Ph) (14a) were characterized by X-ray crystallography.     

One-electron oxidation of DNA: the effect of replacement of cytosine with 5-methylcytosine on long-distance radical cation transport and reaction

One-electron oxidation of duplex DNA generates a radical cation that migrates through the nucleobases until it is trapped by an irreversible reaction with water or oxygen. The trapping site is often a GG step, because this site has a relatively low ionization potential and this causes the radical cation to pause there momentarily. Modifications to guanine that lower its ionization potential convert it to a better trap for the radical cation. One such modification is the formation of the Watson-Crick base pair with cytosine, which is reported to very significantly decrease its ionization potential. Methylation of cytosine to form 5-methylcytosine (5-MeC) is a naturally occurring reaction in genomic DNA that may be associated with regions of enhanced oxidative damage. The G.5-MeC base pair is reported to be more rapidly oxidized than normal G.C base pairs. We examined the oxidation of DNA oligomers that were substituted in part with 5-MeC. Irradiation of a covalently linked anthraquinone group injects a radical cation into the DNA and results in strand cleavage after piperidine treatment. For the sequences examined, substitution of 5-MeC for C has no measurable effect on the reactions. Cytosine methylation is not a general cause of enhanced oxidative damage in DNA.     

Stereoselective synthesis of belactosin C and its derivatives using a catalytic proline catalyzed crossed-aldol reaction

A highly practical and concise stereoselective total synthesis of belactosin C and synthetic variants was achieved using an S-proline catalyzed crossed-aldol reaction as the key step.     

Phytochemical analysis of flower from Pandanus odorifer (Forssk.) Kuntze for industrial application

Pandanus odorifer (Forssk.) Kuntze is an economically important aromatic plant. The essential oil from male flowers is widely used in aromatherapy, cosmetics and as food flavouring agent. Phenylethyl methyl ether (PEME), the major constituent of essential oil, gives the chief characteristic fragrance to the oil. In the present study, 180 samples from 12 different regions were collected and hydrodistilled for essential oil isolation. The oil was then subjected to GC and GC-MS analysis to find out the percentage of the constituents. The results revealed PEME as the major constituent ranging from 58.03 to 81.86% and terpinen-4-ol, the second major constituent ranging from 7.81 to 21.46%. Soil nitrogen was found to be the most influential factor for oil yield and PEME content. The flowers containing high essential oil yield and PEME content could be used as elite chemotypes with enough potential for large-scale commercial cultivation to meet the demand of kewda industries.