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Rajeswari M.,University of Hyderabad | Dhara S.,University of Hyderabad | Venu K.,SoCtronics Technologies Pvt. Ltd. | Sastry V.S.S.,University of Hyderabad | Dabrowski R.,Military University of Technology
Soft Matter | Year: 2012

Dispersions of proton spin-lattice relaxation rates (R1) in the nematic and smectic phases of the liquid crystal 4′-octyloxy-4- cyanobiphenyl (8OCB), embedded in a nano-porous medium formed by an aerosil matrix, are investigated over a wide frequency (ν) range (104 Hz to 5 × 107 Hz) at two average pore sizes. In the low frequency (sub-MHz) region we observe a significant increase of R1 in the confined samples, mediated by slow translational displacements (RMTD), arising from the formation of adsorption layers near the porous surface. Dispersion in this region is well accounted for by a power law behaviour (R1 ∼ ω-p), bracketed by low and high cutoff frequencies reflecting the limiting length scales of such displacements in these layers. The exponent p increases from 0.45 to 0.6 with a decrease of the temperature within the nematic phase, due to the progressive onset of longer wavelength diffusive modes within these layers. This signifies the onset of order director fluctuation (ODF) modes within the adsorption layers. Confinement is also seen to place restrictions on the long wavelength ODF modes of the bulk-like region of the liquid crystal, thus weakening considerably their dispersive effects in the low frequency region, relative to the bulk samples. In the smectic phase, p decreases appreciably signalling a depletion of such long range cooperative modes on layer formation. Analysis of the R1 data also shows that individual dynamic processes like translational diffusion and reorientations of the molecules within the voids are largely unaffected due to confinement. © 2012 The Royal Society of Chemistry. Source


Rajeswari M.,University of Hyderabad | Molugu T.R.,University of Hyderabad | Molugu T.R.,University of Arizona | Dhara S.,University of Hyderabad | And 3 more authors.
Chemical Physics Letters | Year: 2012

Nuclear spin-lattice relaxation rate dispersion study of 1H and 19F in the isotropic phase of a singly fluorinated liquid crystal 4′-butoxy-3-fluoro-4-isothiocyantotolane (4OTOLFo) points to their differing relaxation pathways and hence sensitivity to qualitatively different time modulations. In particular fluorine nuclear spins, with strong lattice coupling (larger by two orders) extending to very low frequencies, detect slowly relaxing local structures via the spin-rotation interaction. The field-cycling technique used to carry out these very low frequency measurements, provides for level crossing of the two nuclear species at low enough jump fields, facilitating an additional mechanism of cross-relaxation in the strong coupling limit. © 2012 Elsevier B.V. All rights reserved. Source


Rajeswari M.,University of Hyderabad | Molugu T.R.,University of Hyderabad | Molugu T.R.,University of Arizona | Dhara S.,University of Hyderabad | And 3 more authors.
Journal of Chemical Physics | Year: 2011

Spin-lattice relaxation rates (R 1H and R 1F) of two nuclear species ( 1H and 19F) are measured at different temperatures in the isotropic phase of a liquid crystal (4 ′- butoxy-3 ′-fluoro-4-isothiocyanatotolane-4OFTOL), over a wide range of Larmor frequency (10 kHz-50 MHz). Their dispersion profiles are found to be qualitatively very different, and the R 1F in particular shows significant dispersion (varying over two orders of magnitude) in the entire isotropic range, unlike R 1H. The proton spin-lattice relaxation, as has been established, is mediated by time modulation of magnetic dipolar interactions with other protons (case of like spins), and the discernable dispersion in the mid-frequency range, observed as the isotropic to nematic transition is approached on cooling, is indicative of the critical slowing of the time fluctuations of the nematic order. Significant dispersion seen in the R 1F extending to very low frequencies suggests a distinctly different relaxation path which is exclusively sensitive to the ultra slow modes apparently present in the system. We find that under the conditions of our experiment at low Zeeman fields, spin-rotation coupling of the fluorine with the molecular angular momentum is the dominant mechanism, and the observed dispersion is thus attributed to the presence of slow torques experienced by the molecules, arising clearly from collective modes. Following the arguments advanced to explain similar slow processes inferred from earlier detailed ESR measurements in liquid crystals, we propose that slowly relaxing local structures representing such dynamic processes could be the likely underlying mechanism providing the necessary slow molecular angular momentum correlations to manifest as the observed low frequency dispersion. We also find that the effects of the onset of cross-relaxation between the two nuclear species when their resonance lines start overlapping at very low Larmor frequencies (below ∼ 400 kHz), provide an additional relaxation contribution. © 2011 American Institute of Physics. Source


Rajeswari M.,University of Hyderabad | Dhara S.,University of Hyderabad | Venu K.,University of Hyderabad | Venu K.,SoCtronics Technologies Pvt. Ltd. | And 2 more authors.
Molecular Crystals and Liquid Crystals | Year: 2011

Frequency dispersion studies on proton spin-lattice relaxation rates of a liquid crysal (4'-octyloxy-4-cyanobiphenyl) embedded in Aerosil matrix show significant increase at low frequencies (sub-MHz regime) relative to the bulk sample, and are interpreted as primarily due to slow reorientations near the surface ordered layers mediated by translation displacements. The computed exponent in the power law behavior of the dispersion profiles at different temperatures in the isotropic phase indicates an enhanced role of the low-wavelength diffusion modes during this process. The data also show critical contribution near the isotropic-nematic transition to the length scales relevant to adsorption kinetics. Copyright © Taylor & Francis Group, LLC. Source


Kuppili M.K.,SoCtronics Technologies Pvt. Ltd. | Aryasri A.R.,Jawaharlal Nehru Technological University
IEEE International Conference on Industrial Engineering and Engineering Management | Year: 2012

This paper focuses on challenges faced in bringing two semiconductor companies under merger to a common technological platform and strategic solutions implemented to make the merger successful. A case study approach is followed to review and analyze the results. From the study, a 15% reduction was observed in the product development cycle. These savings were mainly due to efficient implementation of strategies to bring both the teams in common technology platform. From this paper one can understand better in the context of semiconductor industry the concepts of technology management its impact on product schedules & financials. The strategic solutions & benefits indicated here will help organizations just after merger, to take appropriate actions in technology management. This paper will assist future researchers to explore more ideas as there is limited research & literature available on this topic. © 2012 IEEE. Source

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