Phase transitions in liquid crystals

Alzheimer's disease is an age-associated, irreversible, progressive neurodegenerative disease that is characterized by severe memory loss, unusual behavior, personality changes, and a decline in cognitive function. No cure for Alzheimer's exists, and the drugs currently available to treat the disease have limited effectiveness. It is believed that therapeutic intervention that could postpone the onset or progression of Alzheimer's disease would dramatically reduce the number of cases in the next 50 years. Ayurvedic medicinal plants have been the single most productive source of leads for the development of drugs, and over a hundred new products are already in clinical development. Indeed, several scientific studies have described the use of various Ayurvedic medicinal plants and their constituents for treatment of Alzheimer's disease. Although the exact mechanism of their action is still not clear, phytochemical studies of the different parts of the plants have shown the presence of many valuable compounds, such as lignans, flavonoids, tannins, polyphenols, triterpenes, sterols, and alkaloids, that show a wide spectrum of pharmacological activities, including anti-inflammatory, anti-amyloidogenic, anti-cholinesterase, hypolipidemic, and antioxidant effects. This review gathers research on various medicinal plants that have shown promise in reversing the Alzheimer's disease pathology. The report summarizes information concerning the phytochemistry, biological, and cellular activities and clinical applications of these various plants in order to provide sufficient baseline information that could be used in drug discovery campaigns and development process, thereby providing new functional leads for Alzheimer's disease.

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Ayurvedic medicinal plants for Alzheimer's disease: a review

Anticonvulsant and neurotoxicity profile of Nardostachys jatamansi in rats.

Cognitive deficits that present with many of neuropsychiatric conditions and/or alone as developmental deficit demand use of nootropics to boost cognitive abilities. Recently there is a tremendous urge to explore medicinal plants globally for improving cognitive function owing to their less adverse effects. Ayurveda provides a list of herbs known for nootropic activity as well as their multi-dimensional utility in various conditions. Present paper is a review to update knowledge on pharmacological properties, major chemical constituents, therapeutic actions, preclinical studies, safety and possible mode of action of the selected herbs from ayurvedic pharmacopoeia. Concurrently, it opens up for further research and standardization on nootropic herbs

Nootropic Herbs (Medhya Rasayana) in Ayurveda: An Update

Critical behavior of dielectric permittivity in the isotropic phase of nematogens

The structure and stereochemistry of a new terpenoid ester, nardostachysin (1), isolated from the rhizomes of Nardostachys jatamansi, were established as the 7‘,8‘-dihydroxy-4‘-methylene hexahydrocyclopenta[c]pyran-1‘-one-8‘-methyl ester of 7,9-guaiadien-14-oic acid, by spectral and chemical studies.

Structure and stereochemistry of nardostachysin, a new terpenoid ester constituent of the rhizomes of Nardostachys jatamansi.

Critical behavior of the nematic-isotropic phase transition.

An earlier Monte-Carlo simulation of a cholesteric configuration of molecules is generalised in the present work allowing for full rotational degrees of freedom. The effect of temperature on pitch has been studied and the results are compared with the results obtained from mean field and plane rotator model simulation studies.

A lattice model Monte Carlo simulation of cholesteric liquid crystal with freely rotating molecules

Direct smectic-A to isotropic phase transition is studied by means of Landau theory. The theory predicts the first order behaviour of the smectic-A to isotropic phase transition. The temperature difference TAI-T* is also calculated from the scaling equation of state and compared with the nematic to isotropic phase transition

Landau Theory of the Direct Smectic-A to Isotropic Phase Transition

In this paper we report the application of Wilson's recursion relations to the numerical calculation of critical indices for the d = 3 Landau-de Gennes model near the isolated critical point on the nematic-isotropic phase transition line. We find that the calculated critical exponents namely y = 1.277 and v = 0.638 in fair agreement with the best epsilon expansion results.

M. Saha

Papers

Structure and stereochemistry of nardostachysin, a new terpenoid ester constituent of the rhizomes of Nardostachys jatamansi.

Critical behavior of the nematic-isotropic phase transition.

A lattice model Monte Carlo simulation of cholesteric liquid crystal with freely rotating molecules

Landau Theory of the Direct Smectic-A to Isotropic Phase Transition

Critical exponents for the Landau-De Gennes model of the nematic-isotropic phase transition