Simultaneous Determination and Drug Dissolution Testing of Combined Amlodipine Tablet Formulations Using RP-LC

In the proposed work, the simultaneous analysis of amlodipine–rosuvastatin and amlodipine–atorvastatin in their dosage forms was achieved. Simultaneous dissolution profiles of the amlodipine–rosuvastatin and amlodipine–atorvastatin tablets are realized using Apparatus II with a simple, accurate and precise RP-LC method. The mobile phase consisting of 0.2 % H₃PO₄ and pH 5:methanol:acetonitrile (46:27:27) was used. The samples of 10 µL were injected onto a Zorbax SB C18 (100 mm, 4.6 mm, 3.5 µm particle size) column with 1.2 µL min⁻¹ flow rate. The samples were detected at 236 nm. By plotting peak area ratios vs. concentration, the linearity for amlodipine–rosuvastatin and amlodipine–atorvastatin was determined. With the developed RP-LC method, AML, ROS and ATOR were detected within the range of 0.25–10, 0.5–10 and 0.25–25 µg mL⁻¹, respectively. LOD and LOQ values were also calculated as 0.028, 0.058, 0.021 and 0.095 µg mL⁻¹, 0.195 µg mL⁻¹, 0.070 µg mL⁻¹ for AML, ROS and ATOR, respectively. System suitability tests parameters, such as capacity factor, selectivity to previous peak, selectivity to next peak, resolution to previous peak, resolution to next peak, tailing factor, theoretical number of plates, were performed and found coherent with the ICH guideline parameters. The proposed method has been extensively validated in terms of recovery, and recovery results were between 99 and 101 %. For proving the precision, between-day and within-day repeatability results of the method were proposed. The method can be used for the simultaneous determination of amlodipine–rosuvastatin and amlodipine–atorvastatin.

     

Fully Developed Forced Convection Heat Transfer in a Porous Channel with Asymmetric Heat Flux Boundary Conditions

An analytical study is performed on steady, laminar, and fully developed forced convection heat transfer in a parallel plate channel with asymmetric uniform heat flux boundary conditions. The channel is filled with a saturated porous medium, and the lower and upper walls are subjected to different uniform heat fluxes. The dimensionless form of the Darcy–Brinkman momentum equation is solved to determine the dimensionless velocity profile, while the dimensionless energy equation is solved to obtain temperature profile for a hydrodynamically and thermally fully developed flow in the channel. Nusselt numbers for the lower and upper walls and an overall Nusselt number are defined. Analytical expressions for determination of the Nusselt numbers and critical heat flux ratio, at which singularities are observed for individual Nusselt numbers, are obtained. Based on the values of critical heat flux ratio and Darcy number, a diagram is provided to determine the direction of heat transfer between the lower or upper walls while the fluid is flowing in the channel.     

Surface Propensity of Anions in a Binary Ionic-Liquid Mixture Assessed by Full-Range Angle-Resolved X-ray Photoelectron Spectroscopy and Surface-Tension Measurements

Angle-resolved X-ray photoelectron spectroscopy and contact-angle measurements guided by a signal attenuation model are utilized to extract molar composition and anion enrichment in the vacuum interface of a binary ionic liquid mixture, having a common quaternary ammonium cation and two different anions. By using the intensity ratio of the F1s peaks belonging to the two different anions recorded at the full electron take-off angle range, from 0° to 80°, we have determined that only a fractionally covered and anion enriched surface layer can predict the AR-XPS data, which is also consistent with surface tension measurements. Moreover, the more bulky and non-spherical anion enrichment is evident even at the conventional and the so assumed bulk sensitive take-off angle of 0°. This methodology provides a surface enrichment factor of the molecular ions and clearly serves as an experimental evidence for recently debated surface layering and/or island structure in ionic liquid systems.     

Proton conducting polymers containing 1H‐1,2,3‐triazole moieties

Polyacrylates containing a different number of 1H‐1,2,3‐triazole groups per repeat unit have been synthesized via conventional free radical polymerization. These polymers were characterized by nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Proton conductivity measurements were made using impedance spectroscopy. Introduction of more than one triazole per repeat unit did not result in an increase in conductivity as there was an accompanying increase in glass transition temperature (T_g). A maximum conductivity of 17.5 μS/cm was obtained at 200 °C under anhydrous condition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 188–196, 2009     

Complexation of Titanium n-butoxide Ti(OBu n )4 and Zirconium n-butoxide Zr(OBu n )4 with Some Oxime Ligands and Structural Analysis of the Complexes

Titanium tetra-n-butoxide, Ti(OBuⁿ)₄, and zirconium tetra-n-butoxide, Zr(OBuⁿ)₄, were reacted with some well-known dioxime and monoxime ligands such as dimethylglyoxime (DMG), salicylaldoxime (SO) and acetone oxime (AO). The structures of the resulting complexes have been determined by elemental analysis, i.r. and ¹H-n.m.r. spectroscopy. The complexation ratio of both Ti(OBuⁿ)₄ and Zr(OBuⁿ)₄ was found to be 1:2 with DMG and SO. On the other hand, both 1:1 and 1:2 complexation ratios of the same metal alkoxides were observed with the ligand AO.     

Modeling and control of a nonlinear half-vehicle suspension system: a hybrid fuzzy logic approach

Modeling and control of vehicle suspension system are high noteworthy from safety to comfort. In this paper, an analytical nonlinear half-vehicle model which is included quadratic tire stiffness, cubic suspension stiffness, and coulomb friction is derived based on fundamental physics. A hybrid fuzzy logic approach which combines fuzzy logic and PID controllers is designed for reducing the vibration levels of passenger seat and vehicle body. Performances of designed controllers have been evaluated by numerical simulations. Comparisons with classical PID control, Fuzzy Logic Control (FLC) and Hybrid Fuzzy-PID control (HFPID) have also been provided. Results of numerical simulations are evaluated in terms of time histories of displacement and acceleration responses and ride index comparison. A good performance for the Hybrid Fuzzy-PID controller with coupled rules (HFPIDCR) is achieved in simulation studies despite the nonlinearities.     

A probe into the chaotic nature of daily streamflow time series by correlation dimension and largest Lyapunov methods

Two chaotic indicators namely the correlation dimension and the Lyapunov exponent methods are investigated for the daily river flow of Kizilirmak River. A delay time of 60 days used for the reconstruction is chosen after examining the first minimum of the average mutual information of the data. The sufficient embedding dimension is estimated using the false nearest neighbor algorithm, which has a value of 11. Based on these embedding parameters the correlation dimension of the resulting attractor is calculated, as well as the average divergence rate of nearby orbits given by the largest Lyapunov exponent. The presence of chaos in the examined river flow time series is evident with the low correlation dimension (2.4) and the positive value of the largest Lyapunov exponent (0.0061).     

Effect of benzyladenine on recovery of cryopreserved shoot tips of grapevine and citrus cultured in vitro

The effect of N6-benzyladenine (BA) on the recovery of cryopreserved shoot tips of the LN33 hybrid (Vitis L.) and Troyer citrange [Poncirus trifoliata (L.) Raf. x Citrus sinensis [L.] Osbeck.] cultured in vitro was examined. For the LN33 hybrid, the presence of BA in the recovery medium was essential for survival of control and cryopreserved shoot tips, although the BA concentration did not influence the survival percentage. BA at 5, 2, and 5 microM or higher induced callus formation in control, and shoot tips cryopreserved by vitrification, and by encapsulation-dehydration, respectively. While a BA concentration of 4 microM was found optimal for recovery of control shoot tips, 1 and 2-4 microM produced the best recovery of shoot tips cryopreserved by vitrification and encapsulation-dehydration, respectively. A similar pattern of effect of BA on recovery was found for 'Troyer' citrange. Low survival of control and cryopreserved shoot tips was observed with a BA-free recovery medium. The addition of BA to the recovery medium significantly increased survival. The BA concentration that induced callus formation in shoot tips cryopreserved by encapsulation-vitrification was higher than that which induced it in those cryopreserved by encapsulation-dehydration. Recovery of control shoot tips was best with an addition of 6-10 microM BA to the medium. Optimal recovery of shoot tips cryopreserved by encapsulation-vitrification and encapsulation-dehydration was achieved with 3-4 and 2 microM BA, respectively. Results from the present study suggest that an optimal BA concentration for recovery of control shoot tips may be different from that for cryopreserved shoot tips; furthermore, the optimal BA concentration for recovery of cryopreserved shoot tips may also differ among different cryogenic procedures.     

Coordination-Induced Band Gap Reduction in a Metal–Organic Framework

Herein, we report on the synthesis of a microporous, three-dimensional phosphonate metal–organic framework (MOF) with the composition Cu₃(H₅-MTPPA)₂ ⋅ 2 NMP (H₈-MTPPA=methane tetra-p-phenylphosphonic acid and NMP=N-methyl-2-pyrrolidone). This MOF, termed TUB1, has a unique one-dimensional inorganic building unit composed of square planar and distorted trigonal bipyramidal copper atoms. It possesses a (calculated) BET surface area of 766.2 m²/g after removal of the solvents from the voids. The Tauc plot for TUB1 yields indirect and direct band gaps of 2.4 eV and 2.7 eV, respectively. DFT calculations reveal the existence of two spin-dependent gaps of 2.60 eV and 0.48 eV for the alpha and beta spins, respectively, with the lowest unoccupied crystal orbital for both gaps predominantly residing on the square planar copper atoms. The projected density of states suggests that the presence of the square planar copper atoms reduces the overall band gap of TUB1, as the beta-gap for the trigonal bipyramidal copper atoms is 3.72 eV.