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The assumption that EMG biofeedback cultivates an antistress response was tested under stress conditions while investigating the comparative efficacy of low versus high arousal treatment strategies. Biofeedback-assisted, cue-controlled relaxation training was used as the low arousal treatment strategy for half of the 20 normal subjects used in the study. The other half received a high arousal treatment strategy which used the same training in combination with an avoidance conditioning procedure. In this procedure mild electric shock was used as contingent aversive stimulation designed to reinforce relaxation responses. Both groups received four in-lab training sessions with a 4-day interim of home practice of cuecontrolled relaxation prior to the last in-lab training session. Pretraining assessment consisted of four 10-minute periods of alternating no-stress and stress conditions. Mild electric shock and loud tones were used as stressors. Posttraining assessment was identical to pre training except subjects employed self-directed, cue-controlled relaxation rather than self-directed relaxation based on instructions without training. Frontal EMG, subjective mental and muscle tension ratings, and behavioral observations of relaxation behavior served as dependent measures during pre- and posttraining assessment. EMG readings were used during in-lab training and the two subjective rating scales were used during home practice.

Conducting and semiconducting polymers, consisting of delocalized π-electrons, have been studied for the past three decades. These materials have shown novel physical properties with interesting applications in batteries, detectors, light emitting diodes, field effect transistors, solar cells, biosensors etc. Nevertheless the charge transport properties are yet to be understood in detail due to the complexity of the system, especially due to the interplay of quasi-one dimensionality (q-1D), disorder, localization and electron-electron interactions(EEI). A combined investigation of both conductivity and spin lattice relaxation time, especially at very low temperatures and high magnetic fields, is really lacking in conducting polymers. In this thesis a set of experiments – dc conductivity, magnetoresistance (MR), Nuclear Magnetic Resonance (NMR) spin lattice relaxation time (T1) measurements, magnetic susceptibility amd ac conductivity have been carried out in conducting polymers. NMR being a local probe it is possible to get the nanoscopic scale charge transport mechanism. Further, this helps to develop a consistent understanding among a wide range of the physical properties in conducting polymers. In this thesis author has reported the results of experiments at ultra low temperature (mk) and ultra high magnetic field which give more insight about the roles of electron-electron interaction(EEI) and disorderin charge transport properties. This thesis describes a detailed study of charge transport and NMR relaxation in three representative conducting polymers namely polypyrrole(PPy)., poly-3-methylthiophene(P3MT) and poly3-hexylthiophene(P3HT). The emphasis is to understand the charge transport phenomena and NMR relaxation, especially at ultra low temperatures (down to 20 mk) and high magnetic field (up to 23.4 T). The NMR T1 relaxation mechanisms are discussed in terms of (i) Korringa relaxation, (ii) relaxation due to spin diffusion to paramagnetic centers (SDPC) amd (iii) reorientation of symmetric groups, depending upon the temperature range.