Delayed effects of sudden ionospheric disturbances on 164 Kc/s transmission between Tashkent and Ahmedabad

Continuous recording of the field strength of 164 Kc/s CW transmission from Tashkent (42° N, 69° E) has been going on at Ahmedabad (23° 01′ N, 72° 36′ E) since March 1960. The present communication deals with a delayed effect of S.I.D.’s which has been observed on the 164 Kc/s transmissions.     

Field strengths of 164 kHz radio-waves received at Ahmedabad from Tashkent in 1960–65 and effect of solar X-ray emissions

The paper summarises the results of observations on the field strength of 164 kHz radio-waves received at Ahmedabad from Tashkent during the period 1960–65. There is a general increase in field strength with decrease in solar activity. From the end of 1965 when we began to receive X-ray data from N.R.L. satellites, it has been noticed that increases in the intensity of 0–8 Å at satellite level, are associated with daytime decreases in the field strength of 164 kHz waves received at Ahmedabad. As may be expected, the enhancement of 0–8 Å X-rays is also associated in a general way with an increased emission from the sun of 10·7 cm. radio-waves. Examples are given.     

Simulations of information transport in spin chains

Transport of quantum information in linear spin chains has been the subject of much theoretical work. Experimental studies by NMR in solid state spin systems (a natural implementation of such models) is complicated since the dipolar Hamiltonian is not solely comprised of nearest-neighbor XY-Heisenberg couplings. We present here a similarity transformation between the XY Hamiltonian and the double-quantum Hamiltonian, an interaction which is achievable with the collective control provided by radio-frequency pulses. Not only can this second Hamiltonian simulate the information transport in a spin chain, but it also creates coherent states, whose intensities give an experimental signature of the transport. This scheme makes it possible to study experimentally the transport of polarization beyond exactly solvable models and explore the appearance of quantum coherence and interference effects.     

Analyses of the complex proton NMR spectra: determination of anisotropic proton chemical shifts of oriented molecules by a two dimensional experiment

NMR spectra of molecules oriented in the liquid crystalline media provide information on the molecular structure and order parameter. However, the numerical iterative analysis of the proton spectra of strongly coupled spins is difficult and time consuming. Such analysis is simplified if nearly accurate starting parameters are available. One such parameter is the chemical shift which in the oriented media is very different from the isotropic values due to anisotropic contributions. In this study, we have explored the possibility of obtaining chemical shifts in the oriented phase to aid the analysis of the spectra. A two dimensional experiment in which FSLG decoupling employed during the t1 period eliminates the homonuclear dipolar couplings and retains only the chemical shifts has been implemented. Experiments on the molecule cis,cis-mucononitrile demonstrate that the chemical shifts obtained by this procedure are nearly the same as the chemical shifts derived by iterative analysis of the one dimensional spectrum of the molecule following the standard procedure. The method has also been used to analyse the spectrum of 1-iodopropane using the chemical shifts obtained from the proposed experiment as the starting parameters.     

Synthesis, mechanism of formation, and dynamics of a highly fluorinated methylenecyclobutene

Treatment of the hydrazone of 2H-perfluoro-2-methyl-3-pentanone with triethylamine at elevated temperatures yields a methylenecyclobutene via degradation to an acetylene followed by dimerization. The dimerization occurs even at -78 degrees C, and details of the reaction pathway have been elucidated. Both the acidity and the conformational dynamics of the methylenecyclobutene are influenced by buttressing effects in this crowded molecule.