Spin-Hall effect and circular birefringence of a uniaxial crystal plate

The linear birefringence of uniaxial crystal plates is known since the 17th century, and it is widely used in numerous optical setups and devices. Here we demonstrate, both theoretically and experimentally, a fine lateral circular birefringence of such crystal plates. This effect is a novel example of the spin-Hall effect of light, i.e., a transverse spin-dependent shift of the paraxial light beam transmitted through the plate. The well-known linear birefringence and the new circular birefringence form an interesting analogy with the Goos-H\"anchen and Imbert-Fedorov beam shifts that appear in the light reflection at a dielectric interface. We report the experimental observation of the effect in a remarkably simple system of a tilted half-wave plate and polarizers using polarimetric and quantum-weak-measurement techniques for the beam-shift measurements. In view of great recent interest in spin-orbit interaction phenomena, our results could find applications in modern polarization optics and nano-photonics.Comment: 16 pages, 8 figures, to appear in Optic

Formulation and Evaluation of Controlled-Release Tablet of Zolpidem Tartrate by Melt Granulation Technique

The present investigation describes the influence of the concentration of PEG 6000 as a melt binder and ratio of HPMC K4M : PVP on Zolpidem tartrate controlled-release tablet formulations using 32 full factorial design. The ratio of HPMC K4M and PVP K30 (X1) and the concentration of melt binder (X2) were selected as independent variables, and drug release at 1 hr (Q1), 4 hr (Q4), 8 hr (Q8), diffusion coefficient (n), and release rate constant (K) were selected as a dependent variable. Tablets were prepared by melt granulation technique and evaluated for various evaluation parameters. It was observed that concentration of melt binder had significant effect on Q1, Q4, n, and K Binder concentration 25% w/w was found optimum. Optimized formulation (F7) showed good similarity with theoretical profile of drug. The X2 variable had a significant effect on dependent variables, and the X1 variable had no significant effect on dependent variables

Formulation and Evaluation of Transdermal Patch of Repaglinide

Repaglinide has the half life of 1 hour, and bioavailability in the body is 56% due to first-pass metabolism. The total daily dose of Repaglinide is 16 mg (e.g., 4 mg four times daily depending on meal patterns); hence, it required frequent dosing. Transdermal patch of Repaglinide was prepared to sustain the release and improve bioavailability of drug and patient compliance. Different formulations were prepared by varying the grades of HPMC and concentration of PVP K30 by solvent casting method. The prepared formulations were evaluated for various parameters like thickness, tensile strength, folding endurance, % elongation, % moisture content, % moisture uptake, % drug content, in vitro drug release, in vitro permeation, and drug excipient compatibility. A 32 full factorial design was applied to check the effect of varying the grades of HPMC (X1) and PVP concentration (X2) on the responses, that is, tensile strength, percentage drug released in 1 hr (Q1), 9 hr (Q9), and diffusion coefficient as a dependent variables. In vitro release data were fitted to various models to ascertain kinetic of drug release. Regression analysis and analysis of variance were performed for dependent variables. The results of the F2 statistics between factorial design batches and theoretical profile were used to select optimized batch. Batch F6 was considered optimum batch which contained HPMC K100 and PVP (1.5%), showed release 92.343% up to 12 hr, and was more similar to the theoretical predicted dissolution profile (f2 = 69.187)

A Comparative Evaluation of Mono-, Di- and Triglyceride of Medium Chain Fatty Acids by Lipid/Surfactant/Water Phase Diagram, Solubility Determination and Dispersion Testing for Application in Pharmaceutical Dosage Form Development

Purpose To compare physiochemical properties of mono-, diand triglycerides of medium chain fatty acids for development of oral pharmaceutical dosage forms of poorly water-soluble drugs using phase diagrams, drug solubility, and drug dispersion experiments. Methods Phase diagrams were prepared using a monoglyceride (glycerol monocaprylocaprate: Capmul MCM ® EP), a diglyceride (glycerol dicaprylate) and two triglycerides (glycerol tricaprylate

FORMULATION AND EVALUATION OF MUCOADHESIVE BUCCAL TABLETS OF CARVEDILOL

Objective: The aim of the study was to formulate and evaluate mucoadhesive buccal tablets of carvedilol to avoid the first-pass metabolism. Methods: Mucoadhesive Buccal tablets of carvedilol were prepared by direct compression techniques using a combination of bioadhesive polymers such as hydroxypropyl cellulose (HPC) and polyethlyelne oxide WSR-1105 (PEO WSR-1105). In order to improve solubility of carvedilol, solid dispersion was prepared using poloxamer 188. A 32 Full factorial design was applied to investigate the combined effect of the two independent variables i.e. concentration of HPC (X1) and concentration of PEO WSR-1105(X2) on the dependent variables, % in vitro drug release at 1 h (Y1), % in vitro drug release at 4 h (Y2), mucoadhesive strength (Y3) and mucoadhesion time (Y4). Results: Optimized mucoadhesive buccal tablets shows in vitro drug release of 96.23±2.45 in 8 h, mucoadhesive strength of 18.20±1.44 g, mucoadhesion time 420±2.6 min and surface pH 6.75±0.015. Drug excipients compatibility study by FTIR showed no interaction between drug and excipients. Conclusion: From all parameters and experimental design evaluation, it was concluded that the drug release rate decreased with an increase the concentration of HPC and PEO WSR-1105 and mucoadhesion property increased with increase the concentration of PEO WSR-1105. The in vitro release kinetics revealed the Korsmeyer-Peppas model is followed and drug release is by anomalous diffusion

Geological stratigraphy and spatial distribution of microfractures over the Costa Rica convergent margin, Central America – a wavelet-fractal analysis

Identification of spatial distribution of lithology as a function of position and scale is a very critical job for lithology modelling in industry. Wavelet transform (WT) is an efficacious and powerful mathematical tool for time (position) and frequency (scale) localization. It has numerous advantages over Fourier transform (FT) to obtain frequency and time information of a signal. Initially continuous wavelet transform (CWT) was applied on gamma ray logs for identification of lithofacies distribution, and later discrete wavelet transform (DWT) was applied on density logs to identify the fracture zones. In this study the data were taken from two different well sites (well 1039 and well 1043) of the Costa Rica convergent margin, Central America. The CWT analysis provides four major sedimentary layers terminated with a concordant igneous intrusion passing through both the wells. In addition, the wavelet-based fractal analysis (WBFA) technique was applied on identified sedimentary successions, and fractal-dimension (FD) values were calculated for every succession to know the presence and distribution of fractures. We found that the second and third successions have a high FD value, whereas the first and fourth successions have a low FD value. These high values may be due to the presence of abundant shale content and low-energy environments in the sedimentary successions

Pregnancy outcomes following different types of bariatric surgery: A national cohort study

OBJECTIVE: To assess the impact of type of bariatric surgery on pregnancy outcomes. STUDY DESIGN: This is a national prospective observational study using the UK Obstetric Surveillance System (UKOSS). Data collection was undertaken in 200 consultant-led NHS maternity units between November 2011 and October 2012 (gastric banding), and April 2014 and March 2016 (gastric bypass and sleeve gastrectomy). Participants were pregnant women following gastric banding (n = 127), gastric bypass (n = 134) and sleeve gastrectomy (n = 29). Maternal and perinatal outcomes were compared using generalised linear and linear mixed models. Maternal outcomes included gestational weight gain, pre-eclampsia, gestational diabetes, anaemia, surgical complications. Perinatal outcomes included birthweight, small/large for gestational age (SGA/LGA), preterm birth, stillbirth. RESULTS: Maternal: Women pregnant after gastric banding and sleeve gastrectomy had a lower risk of anaemia compared with gastric bypass (banding (16 %) vs bypass (39 %): p = 0.002, sleeve (21 %) vs bypass: p = 0.04). Gestational diabetes risk was lower after gastric banding compared with gastric bypass (7 % vs 16 %, p = 0.03) despite women with banding having significantly greater weight at booking as well as gestational weight gain. Women pregnant after gastric banding and sleeve gastrectomy had a lower risk of surgical complications than after gastric bypass (banding (0.9 %) vs bypass (11.4 %): p = 0.03, sleeve (0.0 %) vs bypass: p = 0.06). Perinatal: Infants born to mothers after gastric banding had a higher birthweight than those born to mothers after gastric bypass (mean difference = 260 g (125-395), p < 0.001). Infants were more likely to be LGA if their mothers had gastric banding compared with gastric bypass or sleeve gastrectomy (banding (21 %) vs bypass (5 %): p = 0.006; banding vs sleeve (3 %): p = 0.03). Risk of preterm birth was higher in women with gastric banding compared with gastric bypass (13 % vs 8 %, p = 0.04). CONCLUSIONS: Women planning bariatric surgery should be counselled regarding the differing impacts of different types of procedure on any future pregnancy. Pre-existing gastric bypass is associated with higher rates of potentially serious surgical complications during pregnancy