Switching dynamics of surface stabilized ferroelectric liquid crystal cells: effects of anchoring energy asymmetry

We study both theoretically and experimentally switching dynamics in surface stabilized ferroelectric liquid crystal cells with asymmetric boundary conditions. In these cells the bounding surfaces are treated differently to produce asymmetry in their anchoring properties. Our electro-optic measurements of the switching voltage thresholds that are determined by the peaks of the reversal polarization current reveal the frequency dependent shift of the hysteresis loop. We examine the predictions of the uniform dynamical model with the anchoring energy taken into account. It is found that the asymmetry effects are dominated by the polar contribution to the anchoring energy. Frequency dependence of the voltage thresholds is studied by analyzing the properties of time-periodic solutions to the dynamical equation (cycles). For this purpose, we apply the method that uses the parameterized half-period mappings for the approximate model and relate the cycles to the fixed points of the composition of two half-period mappings. The cycles are found to be unstable and can only be formed when the driving frequency is lower than its critical value. The polar anchoring parameter is estimated by making a comparison between the results of modelling and the experimental data for the shift vs frequency curve. For a double-well potential considered as a deformation of the Rapini-Papoular potential, the branch of stable cycles emerges in the low frequency region separated by the gap from the high frequency interval for unstable cycles.Comment: 35 pages, 15 figure

Optical properties of nematic liquid crystals doped with gold nanorods

Composites consisting of nematic liquid crystal (5-CB) and gold nanorods have been elaborated and investigated with a polarizing microscope. It was detected that the nanorods form inside the oriented liquid crystal matrix their own self-assembling well-ordered structures. Nanorods ordered structures appear as a result of aligning layers action and provides defects corresponding to the spatial distortion of the nematic liquid crystal director field

Ferroelectric C* phase induced in a nematic liquid crystal matrix by a chiral non-mesogenic dopant

We report on a ferroelectric chiral smectic C (C*) phase obtained in a mixture of a nematic liquid crystal (NLC) and a chiral nonmesogenic dopant. The existence of C* phase was proven by calorimetric, dielectric and optical measurements, and also by X-rays analysis. The smectic C* which is obtained in such a way can flow, allowing to restore the ferroelectric liquid crystal layer structure in the electro-optical cells after action of the mechanical stress, as it happens with the cells filled with NLC. The proposed method of obtaining smectic C* material allows us to create innovative electro-optical cell combining the advantages of NLC (mechanical resilience) and smectic C* (high switching speed

Limited Associations Between 5-HT Receptor Gene Polymorphisms and Treatment Response in Antidepressant Treatment-Free Patients With Depression

Major depressive disorder has become a prominent cause of disability, as lifetime prevalence has increased to similar to 15% in the Western world. Pharmacological effects of serotonin (5-hydroxytryptamine, 5-HT) are mediated through 5-hydroxytryptamine receptor (5-HTR) binding. Serotonin regulation of amygdala activity is attained through activation of three 5-HT2 family receptor subtypes, 5-HT2A, 5-HT2B, and 5-HT2C. Specifically, HT2A and the HT2C receptors have similar gross cerebral distribution and function, with higher constitutive activity found in HT2C than in HT2A. We investigated the possible association of 5-HTR gene polymorphisms to specific and non-specific antidepressant treatment responses in treatment-free patients in Siberia. 156 patients, aged between 18-70 years and clinically diagnosed with depressive disorders, were treated with antidepressants for 4 weeks. Patients were genotyped for a subset of 29 SNPs from the following 5-HT Receptor genes: HTR1A, HTR1B, HTR2A, HTR2C, HTR3A, HTR3B and HTR6. Primary outcome was measured by differences in Hamilton Depression Rating Scale (Delta HAM-D 17) scores between baseline/week two, week two/week four and baseline/week four. Univariate linear regression was initially conducted to determine the 5-HTR SNPs to be studied within the multiple linear regression. Multiple linear regression analyses over the three time periods were conducted for Delta HAM-D 17 with independent factors including: age, gender, depression diagnosis, antidepressant treatment and selected 5-HTR SNPs. We found improved increment HAM-D 17 in patients taking tricyclic antidepressants (0-4 weeks: B = 4.85, p = 0.0002; 0-2 weeks: B = 3.58, p = 0.002) compared to patients taking SSRIs. Over the course of study, significant associations between 5-HT receptors SNPs and antidepressant response were not identified

Association of ANKK1 polymorphism with antipsychotic-induced hyperprolactinemia

Objective: Schizophrenia is a severe highly heritable mental disorder. Genetic polymorphisms of dopaminergic pathways are related to pathogenesis of drug response. Hyperprolactinemia (HPRL), a common adverse effect of antipsychotics, is attributed to blockade of dopamine D2 receptors. Ankyrin Repeat and Kinase Domain containing 1 (ANKK1) gene is closely related to Dopamine Receptor D2 type (DRD2) gene functioning. We examined whether the functional polymorphism rs2734849 in the ANKK1 gene is associated with antipsychotic-induced HPRL. Methods: We recruited 446 patients with schizophrenia from among the Russian population of the Siberian region. The polymorphism rs2734849 in the ANKK1 gene was genotyped with The MassARRAY® Analyzer 4 by Agena Bioscience™, using the kit SEQUENOM Consumables iPLEXGold 384. Genotype and allele frequencies were compared between groups of schizophrenia patients with and without HPRL using the χ2 test. Results: A comparison between schizophrenia patients with and without HPRL revealed significantly higher frequency of the C allele of the polymorphic variant rs2734849 in the ANKK1 gene in patients with HPRL as compared to the patients without it (χ2 = 3.70; p =.05; odds ratio [OR] = 1.30 [0.99–1.69]). Conclusion: The functional polymorphism rs2734849 in the ANKK1 gene was associated with HPRL in patients with schizophrenia

Preliminary pharmacogenetic study to explore putative dopaminergic mechanisms of antidepressant action

Background: There is sufficient evidence that interference of dopaminergic neurotransmission contributes to the therapeutic effects of antidepressants in unipolar and bipolar depression. Methods: Hamilton depression rating scale (HAMD 17) scores of 163 at least moderately ill patients with major depressive disorders were used to establish treatment response. HAMD 17 score status was measured before initiation, after two weeks, and after four weeks of treatment with various antidepressants. The possible association between response and genotype in a total of 14 variants of dopamine neurotransmission-related proteins was investigated. Results: DRD4 rs11246226 CA heterozygous patients were found with a greater improvement of HAMD 17 score when compared to homozygous C patients during 0–2 weeks and 0–4 weeks. Patients with MAOB rs1799836 heterozygous GA and homozygous A also demonstrated improved scores during 2–4 weeks and 0–4 weeks. Conclusions: The results are preliminary due to the limited population size and the small number of variants. Further research into the involvement of habenular dopamine D4 receptors in the antidepressant response is desirable

Polymorphisms in the adrenergic neurotransmission pathway impact antidepressant response in depressed patients

Mood disorders are a prevalent mental health disorder. The adrenergic neurotransmission pathway presents an opportunity to determine whether genetic mutations impact antidepressant response. For this study, 163 patients with major depressive disorders were enrolled to measure treatment response using the Hamilton Depression Rating Scale (HAMD-17). More than half of the patients had never been treated with antidepressants previously. Patients were genotyped for 14 SNPs within ADRA1A, SLC6A2, ADRβ1, MAOA and COMT to determine the impact of adrenergic neurotransmission polymorphisms related in antidepressant response. Patients were treated mainly with SSRIs and TCAs. The difference in HAMD-17 scores between the measurement periods were defined as the outcome measure. Multiple linear regression was conducted to determine the association between the genotypes and difference in HAMD-17 across the study period. Covariates of age, sex, antidepressant medication and depression diagnoses were included in the regression. Throughout the study HAMD-17 scores were measured at initiation, at two weeks and at four weeks for each patient. The difference in HAMD-17 scores was found to be 11.2 ​± ​4.4 between initiation and two weeks, 7.8 ​± ​5.3 between two week and four week, and 19.0 ​± ​5.3 throughout the entire study. SLC6A2 rs1532701 homozygous G/G Patients were associated with improved ΔHAMD-17 across week 2–4 and the entire study (B ​= ​7.1, p ​= ​0.002; B ​= ​6.7, p ​= ​0.013) compared to homozygous A/A patients. SLC6A2 rs1532701 homozygous A/G patients were further associated with improved ΔHAMD-17 compared to homozygous A/A patients at week 2–4 (B ​= ​2.8, p ​= ​0.023). Through our investigation, we were able to determine the genes within the adrenergic pathway to investigate further. To further elucidate these findings, replication and combination with other neurotransmitter pathways to better map the mechanism of actions of antidepressant for tailored treatment would be suggested