A systematic crystallization kinetic study using thermal microscopy and diOE erential scanning calorimetry has been carried out on two novel liquid crystalline compounds, DBA : MHB and DBA : ACP. These involve intermolecular hydrogen bonding between 4-n -decyloxybenzoic acid (DBA) and methyl 4-hydroxybenzoate (MHB); and between DBA and 2-amino-5-chloropyridine (ACP). The kinetics experiments were performed from the crystal G phase, which is a common induced kinetophase in both the compounds. Further, the proton donor and acceptor capabilities of the COOH group of DBA towards the OH group of MHB and N atom of ACP were studied in the light of mesomorphism and rate of crystallization. The dimensionality in the crystal growth and the sporadic nucleation were estimated from the Avrami exponent, n . A similar type of crystallization mechanism is predicted to operate for all the crystallization temperatures. The characteristic crystallization time ( t *) at each crystallization temperature is deduced from the individual plots of log t vs. D H (change in enthalpy).

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Human studies of substance use disorder show that psychological stress and drug availability interact following rehabilitation, contributing to the high relapse potential. Social stressors trigger particularly strong motivation for drug, but how this affects neuronal function to increase relapse is unknown. Animal models, which allow for the dissection of neural mechanisms, primarily utilize physical stressors to trigger relapse. To recapitulate psychosocial post-rehabilitation challenges in animals, we developed a model of social stress-potentiated methamphetamine (METH) seeking. Rats receive a single social defeat (SD) session after completion of self-administration and extinction of lever pressing. While a reminder of the SD was insufficient to reinstate METH seeking on its own, rats that received a reminder of SD followed by a METH-priming injection displayed potentiated reinstatement over METH-priming alone. Examination of neuronal activation patterns of the METH-primed reinstatement session identified c-Fos-immunoreactivity in the basolateral amygdala (BLA) as correlated with SD score, a measure of defeat latency. Rapidly defeated rats showed potentiated METH-primed reinstatement and elevated BLA c-Fos compared with controls. Conversely, rats that were undefeated during the social stress did not show potentiated METH-primed reinstatement or elevated BLA c-Fos. Interestingly, inactivation of the BLA with baclofen/muscimol prior to the stress reminder and METH-priming generated a potentiation of METH seeking in the undefeated rats, suggesting the BLA may mediate resilience to the stressor. This model provides a tool for the further dissection of neural mechanisms mediating social stress-potentiated relapse and for the development of relapse-reducing therapeutics.

A systematic kinetic study leading to the crystallization process from the kinetophases (which occur prior to crystal phase) smectic B, crystal G and smectic F is performed on representative compounds of the homologous series p-phenylbenzylidene-p¾ -alkylanilines (PBnA) and p-n-alkoxybenzylidene-p¾ -alkylanilines (nO.m) these compounds are p-phenylbenzylidene-p¾ -nonylaniline ( PB9A), p-phenylbenzylidene-p¾ -tetradecylaniline ( PB14A), p-n-pentadecyloxybenzylidenep¾ -tetradecylaniline (15O.14) and p-n-octadecyloxybenzylidene-p¾ -nonylaniline (18O.9). The molecular mechanism and dimensionality in crystal growth from the kineto phases are computed from the Avrami equation, while the characteristic crystalline time (t*) at each crystallization temperature is deduced from the individual plots of log t vs. DH. The low magnitudes of the dimensionality parameter n infers the occurrence of diVusion-controlled transformations leading to the formation of plates or needles of nite size possessing impinged edges. The degree of variation in the value of n at each crystallization temperature also reveals the existence of an independent nucleation mechanism for any individual member of the series. The in uence of the terminal alkyl chain lengths on the rate of crystallization is determined from a comparative study with the reported analogous compounds.

A comparative systematic crystallization kinetics study has been carried out on two distinct novel liquid crystalline isomers, DBA : R : DBA and DBA : H : DBA (where DBA 5 p-n-decyloxybenzoic acid, R 5 resorcinol and H 5 hydroquinone) using diVerential scanning calorimetry. The kinetics experiment is performed from the crystal G phase ( kinetophase), which is a common induced phase in both compounds. The molecular mechanism and dimensionality of crystal growth are studied from the Avrami exponent n while the characteristic crystallization time (t*) at each crystallization temperature is deduced from the individual plots of log t vs. DH.