GEOMETRY INDUCED MAGNETO-OPTIC EFFECTS IN LPE GROWN MAGNETIC GARNET FILMS

This dissertation addresses dimensionality-induced magneto-optic effects in liquid-phaseepitaxy magnetic garnet thin films. It is found that the Faraday rotation (FR) per unit length evinces a marked and steady enhancement as the film thickness is reduced below ~100 nm in Bi0.8Gd0.2Lu2Fe5O12, although it remains constant in the micron- and most of the submicron- regime. The reported specific FR change in such reduced dimensions is due to sizedependent modifications in diamagnetic transition processes in the garnet film. These processes correspond to the electronic transitions from the singlet 6S ground state to spinorbit split excited states of the Fe3+ ions in the garnet. A measurable reduction in the corresponding ferrimagnetic resonance linewidths is found, thus pointing to an increase in electronic relaxation times and longer lived excitations at reduced thicknesses than in the bulk. These changes together with a shift in vibrational frequency of the Bi-O bonds in the garnet at reduced thicknesses result in magneto-optical enhancement in ultra-thin garnet films. This dissertation also studies optical transmittance control through multimode elliptically birefringent waveguides achieved by one-dimensional magneto-photonic crystals (MPCs) and the tuning of longitudinal magnetic bias in such waveguides, together with the tuning of the helicity of the input elliptical beam. Magnetization reversal is found to strongly reconfigure the stop band spectrum, through hybridization of the ellipticallypolarized states due to normal mode symmetry breaking

Anti-Inflammatory Potential of Ethanolic Leaf Extract of Eupatorium adenophorum Spreng. Through Alteration in Production of TNF-α, ROS and Expression of Certain Genes

Search for a novel anti-inflammatory agent from a herbal source, such as Eupatorium adenophorum Spreng., a plant from the Eastern Himalayas, is of prime interest in the present investigation. Inflammation causes tissue destruction and development of diseases such as asthma, rheumatoid arthritis, and so forth. The ethanolic leaf extract of E. adenophorum (EEA) was administered intravenously and in other cases topically at the site of delayed type hypersensitivity (DTH) reaction in mouse foot paw induced with dinitrofluorobenzene. EEA can effectively inhibit DTH reaction and bring back normalcy to the paw much earlier than the controls. Efficacy of EEA on regulatory mechanisms for inflammation has also been considered. Intravenous administration of EEA increased the number of CD4+ T cells in spleen and tumor necrosis factor (TNF)-α in serum of DTH mice. Initially it was difficult to reconcile with the anti-inflammatory role of EEA and simultaneous induction of TNF-α, an established pro-inflammatory cytokine. EEA induces higher expression of TNF-α gene and amount of the cytokine in serum. We discussed the other role of TNF-α, its involvement in repairing tissue damage incurred in course of inflammatory reaction. EEA also induces TGF-β encoding a cytokine involved in tissue repair mechanism. EEA inhibits expression of another pro-inflammatory cytokine gene IL-1β and downregulates cycloxygenase 2 (COX2) gene responsible for metabolism of inflammatory mediators like prostaglandins. Furthermore, anti-inflammatory role of EEA is also revealed through its inhibition of hydroxyl radical generation. Notably EEA does not necessarily affect the expression of other inflammation-related genes such as IL-6, IL-10 and IKK. The present study reports and analyzes for the first time the anti-inflammatory property of the leaf extract of E. adenophorum

Activation of cell mediated immune response and apoptosis towards malignant cells with turmeric treatment in murine model

23-29The effect of ethanolic turmeric extract (ETE) on murine lymphocytes vis-à-vis tumor cells was studied, in terms of its ability to activate lymphocytes and to induce apoptosis in tumor cells. Degree of activation and proliferation of lymphocytes treated with ETE was analyzed in terms of blastogenesis, DNA synthesis through ³H-thymidine incorporation and cell cycle analysis by flourescence activated cell sorter (FACS). FACS analysis was also carried out to observe the proliferation as well as apoptosis of tumor cells. Morphological condition of both the cell types in presence of ETE was examined by scanning electron microscopy (SEM). Cytotoxic capability of ETE-treated effector T lymphocytes towards tumor cells was judged in vitro by ⁵¹Cr-release assay and the growth of tumor in situ. ETE stimulated murine lymphocytes towards blastogenesis and synthesis of DNA, as revealed by increased incorporation of ³H-thymidine. FACS indicated that the lymphocytes were driven towards mitotic cycle by activating G₂-M transition. In the same count, the tumor cells mostly remained accumulated in the G₂-M phase, and thus mitotically arrested. Scanning electron photomicrographs revealed the blastoid transformation of lymphocytes and ETE-induced apoptotic condition of tumor cells. Furthermore, ETE-treated T cells were cytotoxic towards tumor cells in vitro, as shown by ⁵¹Cr- release assay. ETE administered intravenously or orally could delay the onset and growth of tumor, and thus prolonged the life span of the tumor-bearing host. The present investigation suggests potential of turmeric both to destroy the malignant cells directly and via activation of the host’s cellular immunit

Benzaldehyde-induced developmental genotoxicity triggers both neural and non-neuronal cells including the cells of immunity in Drosophila melanogaster

Although benzaldehyde, an aromatic aldehyde, has been declared safe for uses in food, conflicting reports exist regarding its genotoxic and cytotoxic potentials in organisms. Our present study is the first attempt to evaluate the effects of exposure of benzaldehyde on the entire course of development of a eukaryote model organism, Drosophila melanogaster. Total time required for the initial appearance of the third instar larvae, pupae and adults increased dose dependently with the increasing dietary concentration of benzaldehyde. Exposure of flies to each concentration of benzaldehyde caused dose-dependent and significant reductions in the population of pupae and young adults of the fly. Developmental inhibition was associated with dose dependent and significant structural aberrations of larval polytene chromosomes like ectopic pairing, inversion, fusion, etc., and deformities of hemocytes and neuroblasts and death of hemocytes. As much as 34% (SD ± 1.76)-52% (SD ± 1.7) and 18% (SD ± 2.5)-40% (SD ± 3.38) hemocytes and neuroblasts, respectively, underwent nuclear deformations in response to dietary exposures of flies to BA 100–1000 mg/l. Moreover, 16% (SD ± 0.52)-31% (SD ± 1.97) and 19% (SD ± 0.3)-33% (SD ± 1.78) hemocyte mortalities in response to BA 100–1000 mg/l were determined by two cell viability assays. Thus our study revealed that benzaldehyde was genotoxic to Drosophila melanogaster larvae that might be responsible for larval cell death and their subsequent developmental retardation. As this fly possesses substantial genetic homology with human, possibility of developmental inhibition of the later due to exposure of this chemical during pregnancy may not be ruled out

Elliptical normal modes and stop band reconfiguration in multimode birefringent one-dimensional magnetophotonic crystals

This study examines photonic stop band reconfiguration upon magnetization reversal in multimode elliptically birefringent Bragg filter waveguides. Magnetization reversal in longitudinally magnetized magneto-optic waveguides affects the character of the local orthogonal elliptically polarized normal modes, impacting the filter\u27s stop band configuration. Unlike the standard case of circular birefringence in magneto-optic media, opposite helicity states do not transform into each other upon magnetization reversal for a given propagation direction. Rather, helicity reversals yield new and different normal modes with perpendicularly oriented semimajor axes, corresponding to a north-south mirror reflection through the equatorial plane of the Poincaré sphere. For asymmetric contradirectional coupling between different-order waveguide modes in multimode magnetophotonic crystals, this symmetry breaking, namely, the obliteration of normal modes upon magnetization reversal, allows for strongly reconfigured stop bands, through the hybridization of the elliptically polarized states. The effect of Bloch mode reconfiguration on the stop band spectral profile contributes to the magnetic response of the filter. In such elliptically birefringent media, input polarization helicity reversal also becomes a powerful tool for optical transmittance control. Both magnetization and helicity reversals can thus serve as useful tools for the fabrication of on-chip magnetophotonic crystal switches. © 2011 American Physical Society

Enhancement of the magneto-optical response in ultra-thin ferromagnetic films and Its registration using the transverse magneto-optical kerr effect

Enhancement of the magneto-optical response in ultra-thin ferromagnetic films (less than 100 nm thick) is studied using the transverse magneto-optical Kerr effect. The gyration of the material increases as the film grows thinner, though the Kerr effect itself may wane