Complex free energy landscapes in biaxial nematics and role of repulsive interactions : A Wang - Landau study

General quadratic Hamiltonian models, describing interaction between crystal molecules (typically with $D_{2h}$ symmetry) take into account couplings between their uniaxial and biaxial tensors. While the attractive contributions arising from interactions between similar tensors of the participating molecules provide for eventual condensation of the respective orders at suitably low temperatures, the role of cross-coupling between unlike tensors is not fully appreciated. Our recent study with an advanced Monte Carlo technique (entropic sampling) showed clearly the increasing relevance of this cross term in determining the phase diagram, contravening in some regions of model parameter space, the predictions of mean field theory and standard Monte Carlo simulation results. In this context, we investigated the phase diagrams and the nature of the phases therein, on two trajectories in the parameter space: one is a line in the interior region of biaxial stability believed to be representative of the real systems, and the second is the extensively investigated parabolic path resulting from the London dispersion approximation. In both the cases, we find the destabilizing effect of increased cross-coupling interactions, which invariably result in the formation of local biaxial organizations inhomogeneously distributed. This manifests as a small, but unmistakable, contribution of biaxial order in the uniaxial phase.The free energy profiles computed in the present study as a function of the two dominant order parameters indicate complex landscapes, reflecting the difficulties in the ready realization of the biaxial phase in the laboratory.Comment: 23 pages, 12 figure

Hyponatremia induced by angiotensin converting enzyme inhibitors

Background: Hyponatraemia is commonly associated with disease conditions or as an adverse effect of certain drugs. Angiotensin converting enzyme inhibitor (ACEI) and angiotensin II receptor blockers are drugs that have been commonly prescribed for the treatment of hypertension and cardiac diseases. It has become important to evaluate and investigate the incidence of hyponatremia on consumption of these drugs. The study aims to observe the incidence of the adverse drug reaction-hyponatraemia in hypertensive patients on ACEI therapy.Methods: The patient’s data was collected using proforma following which they were randomized into three groups receiving enalapril, ramipril and captipril. Serum sodium levels were assayed by direct ISE method. Statistical analysis of data was performed using SPSS version 21.0. Chi-square test was used to compare occurrence of hyponatremia in the patients on ACEI. P<0.5 was considered as statistically significant.Results: Among all, 26 (52%) of the study population administered with ACEI developed hyponatremia. Predisposition to develop hyponatremia was high in males compared to females. The study also revealed that Enalapril had a higher association with hyponatremia compared to other drugs.Conclusions: Hyponatremia was induced in 52% of patients taking ACEI. This study revealed that monitoring of serum sodium levels in the patients with ACEI administration will help to prevent unexpected adverse reactions like hyponatremia