Texture profile analysis of bioadhesive polymeric semisolids: Mechanical characterization and investigation of interactions between formulation components

This study reports the use of texture profile analysis (TPA) to mechanically characterize polymeric, pharmaceutical semisolids containing at least one bioadhesive polymer and to determine interactions between formulation components. The hardness, adhesiveness, force per unit time required for compression (compressibility), and elasticity of polymeric, pharmaceutical semisolids containing polycarbophil (1 or 5% w/w), polyvinylpyrrolidone (3 or 5% w/w), and hydroxyethylcellulose (3, 5, or 10% w/w) in phosphate buffer (pH 6.8) were determined using a texture analyzer in the TPA mode (compression depth 15 mm, compression rate 8 mm s⁻¹, 15 s delay period). Increasing concentrations of polycarbophil, polyvinylpyrrolidone, and hydroxyethylcellulose significantly increased product hardness, adhesiveness, and compressibility but decreased product elasticity. Statistically, interactions between polymeric formulation components were observed within the experimental design and were probably due to relative differences in the physical states of polyvinylpyrrolidone and polycarbophil in the formulations, i.e., dispersed/dissolved and unswollen/swollen, respectively. Increased product hardness and compressibility were possibly due to the effects of hydroxyethylcellulose, polyvinylpyrrolidone, and polycarbophil on the viscosity of the formulations. Increased adhesiveness was related to the concentration and, more importantly, to the physical state of polycarbophil. Decreased product elasticity was due to the increased semisolid nature of the product. TPA is a rapid, straightforward analytical technique that may be applied to the mechanical characterization of polymeric, pharmaceutical semisolids. It provides a convenient means to rapidly identify physicochemical interactions between formulation components. © 1996 John Wiley & Sons, Inc.     

Does individual treatment for alcoholic fathers benefit their children? A longitudinal assessment.

Psychosocial adjustment in children of alcoholics (COAs; N = 125) was examined before and at 3 follow-ups in the 15 months after their fathers entered alcoholism treatment. Before their fathers' treatment, COAs exhibited greater overall and clinical-level symptomatology than children from the demographically matched comparison sample, but they improved significantly following their fathers' treatment. Children of stably remitted fathers were similar to their demographic counterparts from the comparison sample and had fewer adjustment problems than children of relapsed fathers, even after accounting for children's baseline adjustment. Thus, COAs' adjustment improved when their fathers received treatment for alcoholism, and fathers' recovery from alcoholism was associated with clinically significant reductions in child problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Revisiting Individual Evolutionary Learning in the Cobweb Model – An Illustration of the Virtual Spite-Effect

We examine the Cournot oligopoly model in the context of social and individual learning. In both models of learning, firms update their decisions about how much to produce via variants of the genetic algorithm updating procedure. Arifovic (1994) found that both models of social and individual learning converged to the Walrasian, competitive equilibrium. Vriend (2000) reports that the model of social learning converges to the Walrasian equilibrium outcome, while the model of individual learning converges to the Cournot–Nash equilibrium. We revisit the issue and conduct simulations varying elements of the updating algorithms, as well as of the underlying economic model. In the analysis of the outcomes of our simulations, we conclude that the convergence to the Cournot–Nash equilibrium is due to two things: the specific way in which production rules’ performance is evaluated coupled with a specific cost function specification.      

Hydrogen storage properties of MgH2 mechanically milled with α and β SiC

To understand the influence of various crystallographic phases on hydrogen storage properties, ball milling of MgH₂ with hexagonal (α) and cubic (β) SiC have been performed. Structural characterization of all samples has been done by X-ray diffraction (XRD) analysis, particle size analysis and scanning electron microscopy (SEM). Investigation of hydrogen desorption properties of prepared nanocomposites has been done using temperature programmed desorption (TPD) technique. Despite the results of structural and morphological characterization of obtained nanocomposites are very similar, TPD spectra show significant differences regarding existence of intermediate temperature peak. In the sample milled with hexagonal SiC this peak originates both from H₂ and H₂O, while in the sample milled with cubic phase it only comes from H₂O. Both samples exhibit low temperature H₂ peak at 385 K.     

Experimental design to predict process variables in the preparation of cellulose based sustained release microspheres system loaded with prednisolone-cyclodextrin complex

The purpose of this study was to evolve experimental design, to prepare the sustained release microspheres loaded with prednisolone-hydroxypropyl-β-cyclodextrin complex, and develop a successful mathematical model to predict various characteristics of microspheres. Response surface methodology (RSM) has been employed to develop model equations that correlate process variables such as ethyl cellulose (EC, mg), hydroxypropyl methyl cellulose (HPMC, mg), stirring speed (rpm) and surfactant (%) with the response variables such as entrapment efficiency (%), particle size (μm) and release rate (%) of the drug. The adequacy of model equations is confirmed by ANOVA result. Results as predicted by model equations are in good agreement with that of experimental results. In vitro drug release shows that drug (93%) is released from a check point formulation (CPF 2) over the period of 24 h with a sustained release fashion with Quasi-Fickian kinetics. Surface morphology of microspheres varies with the experimental conditions as evidenced by scanning electron microscopy.     

Materials and Manufacturing Methods for EWOD Devices: Current Status and Sustainability Challenges

Electrowetting-on-dielectric (EWOD) devices have proven to be effective tools for precise microfluidic manipulation or in liquid lenses that surpass conventional solid lenses in versatility. However, the fabrication of these devices presents many challenges, such as their scalability or the growing concern on their environmental impact due to materials used in their fabrication. This review provides a comprehensive analysis of the materials currently used in the fabrication of EWOD devices and the characteristics they must meet. In addition, a discussion of future challenges in the fabrication of EWOD devices is presented, in particular the environmental problems presented by some of the materials currently in use.     

Heteronuclear 19F-1H statistical total correlation spectroscopy as a tool in drug metabolism: study of flucloxacillin biotransformation

We present a novel application of the heteronuclear statistical total correlation spectroscopy (HET-STOCSY) approach utilizing statistical correlation between one-dimensional 19F/1H NMR spectroscopic data sets collected in parallel to study drug metabolism. Parallel one-dimensional (1D) 800 MHz 1H and 753 MHz 19F{1H} spectra (n = 21) were obtained on urine samples collected from volunteers (n = 6) at various intervals up to 24 h after oral dosing with 500 mg of flucloxacillin. A variety of statistical relationships between and within the spectroscopic datasets were explored without significant loss of the typically high 1D spectral resolution, generating 1H-1H STOCSY plots, and novel 19F-1H HET-STOCSY, 19F-19F STOCSY, and 19F-edited 1H-1H STOCSY (X-STOCSY) spectroscopic maps, with a resolution of approximately 0.8 Hz/pt for both nuclei. The efficient statistical editing provided by these methods readily allowed the collection of drug metabolic data and assisted structure elucidation. This approach is of general applicability for studying the metabolism of other fluorine-containing drugs, including important anticancer agents such as 5-fluorouracil and flutamide, and is extendable to any drug metabolism study where there is a spin-active X-nucleus (e.g., 13C, 15N, 31P) label present.     

Hydrogen desorption properties of MgH2/LiAlH4 composites

The hydrogen desorption properties of MgH₂–LiAlH₄ composites obtained by mechanical milling for different milling times have been investigated by Thermal Desorption Spectroscopy (TDS) and correlated to the sample microstructure and morphology analysed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The MgH₂–LiAlH₄ composites show improved hydrogen desorption properties in comparison with both as-received and ball-milled MgH₂. Mixing of MgH₂ with small amount of LiAlH₄ (5 wt.%) using short mechanical milling (15 min) shifts, in fact, the hydrogen desorption peak to lower temperature than those observed with both as-received and milled MgH₂ samples. Longer mixing times of the MgH₂–LiAlH₄ composites (30 and 60 min) reduce the catalytic activity of the LiAlH₄ additive as revealed by the shift of the hydrogen desorption peak to higher temperatures.     

Hydrogen desorption properties of MgH2 catalysed with NaNH2

To improve hydrogen desorption properties of MgH₂, mechanical milling of MgH₂ with low concentration (2 and 5%) of NaNH₂ has been performed. Pre-milling of MgH₂ for 10 h has been done and then six samples have been synthesised with different milling times from 15 to 60 min. Microstructural characterisation has been performed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering measurements (PSD), and correlated to desorption properties examined using Differential Scanning Calorimetry (DSC) and Hydrogen Sorption Analyser (HSA). Thermal analysis shows that desorption temperatures are shifted towards lower values. It also highlights the significance of milling time and additive concentration on desorption behaviour.     

Changes in kinetic parameters of decomposition of MgH2 destabilized by irradiation with C ions

In attempt to improve desorption behaviour of MgH₂, the influence of well-defined structural changes induced within a thin surface layer of MgH₂ have been investigated. The defects were induced by 30 keV C²⁺ ions irradiation using different fluencies ranging from 10¹²–10¹⁶ ions/cm². The hydrogen desorption properties were investigated by thermal desorption spectroscopy analysis (TDS), while kinetics parameters were deduced using non-isothermal kinetic approach. The existence of multiple TDS peaks and different curve shapes indicate difference in desorption mechanism. To understand changes in the rate limiting step, shapes of all desorption peaks have been analyzed using different kinetic models. Regarding the irradiated sample, the function based on Avrami–Erofeev model with n=4$n=4$ gives the best fit over θ   range from 0.3 to 0.8 while for untreated sample the best fit is obtained for Avrami–Erofeev model with n=3$n=3$. The change in mechanism can be attributed to the different way of nuclei growth.