Poly(n-vinylpyrrolidone) hydrogels: 2.Hydrogel composites as wound dressing for tropical environment

POLY(N-VINYLPYRROLIDONE) HYDROGELS: 2. HYDROGEL COMPOSITES AS WOUND DRESSING FOR TROPICAL ENVIRONMENT. The effects of irradiation on hydration and other properties of poly(vinylpyrrolidone) (PVP) hydrogel composites have been investigated. The aqueous solution of vinylpyrrolidone (VP) 10 wt % was mixed with several additives such as agar and polyethylen glycol (PEG). The solution was then irradiated with gamma rays from Cobalt-60 source at room temperature. Several parameters such as elongation at break (EB), tensile strength (TS), degree of swelling (DS), water vapor transmission rate (WVTR), equilibrium water content (EWC), microbial growth and penetration test, and water activity (Aw) were analysed at room temperature of 29 ±2°C humidity of 80 ± 10%. Results show that elongation at break of hydrogel membranes with initial composition of VP with agar, VP with agar and PEG were 240 % and 250 % kGy, the equilibrium water content of membranes were 96 to 90%, whereas degree of swelling were 55 to 10. The WVTR of hydrogel membranes with initial composition of VP with agar and PEG was 70 g m^-2h^-1, while the water activity was 0.9. Such hydrogel membranes exhibits the following properties: They are elastic, transparent, flexible, impermeable for bacteria. They absopt a high capacity of water, attached to healthy skin but not to the wound and they are easy to remove. These properties of the hydrogel membranes allow for applying as a wound dressings in tropical environment.     

Nested-ring Mach–Zehnder interferometer

We propose for the first time, a newly configured device based on nested-ring Mach-Zehnder interferometer structure (NRMZI). The device is capable of generating a box-shaped spectral response approaching an ideal filter due to the double-Fano resonances that arise from multiple interference within the nested-ring as well as that within the MZI. It may be considered as the integrated-optic analog of a reflection or diffraction grating, and as with grating, can be used efficiently as a filter, sensor, or switch at the appropriate operating wavelengths.     

Poly(N-vinylpyrrolidone) hydrogels: 1.Radiation polymerization and crosslinking of N-vinylpyrrolidone

POLY(N-VINYLPYRROLIDONE) HYDROGELS: 1 RADIATION POLYMERIZATION AND CROSSLINKING OF N-VINYLPYRROLIDONE). The effects of irradiation dose on the conversion of vinylpyrrolidone (VP) with various concentration and other characteristics such as Gelation Dose (Dg), Degree of Swelling (DS) and Equilibrium Water Content (EWC) have been investigated. Aqueous solution of vinylpyrrolidone with several concentrations such as 5, 10, 20, 40, 60, 80 and 100 Wt % were irradiated by using gamma rays of Cobalt-60 source with a dose rate of 0. 139 Gy/s. After irradiation, parameters such as conversion of vinylpyrrolidone, gelation dose, degree of swelling, and equilibrium water content were analyzed. Results show that the conversion of VP to PVP was almost 100% at a dose of 2 kGy. The gelation dose of PVP depends on initial content of monomer. Degree of swelling of gels with concentration of 10 % was 55 at the dose of 10 kGy and 30 at the dose of 40 kGy. The lowest value of degree of swelling is 15. At the range of irradiation dose of 10 to 40 kGy the EWC of gel was found to be 98 to 94 %.     

Development and Validation of an RP–LC–UV Method for the Determination of Ondansetron: Application to Pharmaceutical Dosage Forms

A new, simple, rapid, sensitive and specific isocratic RP–LC–UV method was developed and validated for the determination of ondansetron in pharmaceutical dosage forms of orally disintegrating tablets, oral solution and injection. The LC separation was achieved on a Hypersil C4 column (250 × 4.6 mm, 5 μm) using a mobile phase of 50 mM potassium dihydrogen phosphate anhydrous adjusted to pH 3.5 with orthophosphoric acid and acetonitrile (30:70, v/v) at a flow rate of 1.0 mL min^?1 and UV detection at 310 nm. The method was validated for specificity, linearity, precision, accuracy, limit of quantification, limit of detection, robustness and solution stability. The calibration curve was linear over a concentration range of 100–1,000 ng mL^?1 (r ²  = 0.9996) with limit of detection and limit of quantification 50 and 100 ng mL^?1, respectively. The intra-day and inter-day precision and accuracy were between 0.79 and 2.37% and ?0.64 and 1.65%, respectively. The method was successfully applied for analysis of ondansetron in the presence of excipients in commercially available pharmaceutical dosage forms.     

Analytical Methods for Determination of Non-Nutritive Sweeteners in Foodstuffs

Sweeteners have been used in food for centuries to increase both taste and appearance. However, the consumption of sweeteners, mainly sugars, has an adverse effect on human health when consumed in excessive doses for a certain period, including alteration in gut microbiota, obesity, and diabetes. Therefore, the application of non-nutritive sweeteners in foodstuffs has risen dramatically in the last decade to substitute sugars. These sweeteners are commonly recognized as high-intensity sweeteners because, in a lower amount, they could achieve the same sweetness of sugar. Regulatory authorities and supervisory agencies around the globe have established the maximum amount of these high-intensity sweeteners used in food products. While the regulation is getting tighter on the market to ensure food safety, reliable analytical methods are required to assist the surveillance in monitoring the use of high-intensity sweeteners. Hence, it is also necessary to comprehend the most appropriate method for rapid and effective analyses applied for quality control in food industries, surveillance and monitoring on the market, etc. Apart from various analytical methods discussed here, extraction techniques, as an essential step of sample preparation, are also highlighted. The proper procedure, efficiency, and the use of solvents are discussed in this review to assist in selecting a suitable extraction method for a food matrix. Single- and multianalyte analyses of sweeteners are also described, employing various regular techniques, such as HPLC, and advanced techniques. Furthermore, to support on-site surveillance of sweeteners’ usage in food products on the market, non-destructive analytical methods that provide practical, fast, and relatively low-cost analysis are widely implemented.     

Trap-controlled behavior in ultrathin Lu2O3 high-k gate dielectrics

Amorphous Lu₂O₃ high-k gate dielectrics were grown directly on n-type (100) Si substrates by the pulsed laser deposition (PLD) technique. High-resolution transmission electron microscope (HRTEM) observation illustrated that the Lu₂O₃ film has amorphous structure and the interface with Si substrate is free from amorphous SiO₂. An equivalent oxide thickness (EOT) of 1.1 nm with a leakage current density of 2.6×10⁻⁵ A/cm² at 1 V accumulation bias was obtained for 4.5 nm thick Lu₂O₃ thin film deposited at room temperature followed by post-deposition anneal (PDA) at 600 °C in oxygen ambient. The effects of PDA process and light illumination were studied by capacitance-voltage (C-V) and current density-voltage (J-V) measurements. It was proposed that the net fixed charge density and leakage current density could be altered significantly depending on the post-annealing conditions and the capability of traps to trap and release charges.     

Characterization of poly(vinyl alcohol) hydrogel for prosthetic intervertebral disc nucleus

In the recent years, development of intervertebral disc prosthesis has been of great concern to the world of medicine and science. Substitution of the spinal disc or its part being displaced or damaged due to trauma or a disease process for the artificial structure well imitating high tensile properties and elasticity of the real disc would highly improve the existing treatment techniques. In this work, the attempt to develop the PVA-based hydrogel material for artificial spinal disc has been made. The polymer was initially processed with the use of formaldehyde solution as a crosslinking agent and sulfuric acid as a catalyst. Then properties of the material have been altered by saturating the already existing PVA hydrogel with a mixture of hydrophilic and hydrophobic monomers (2-hydroxyethyl methacrylate and methyl methacrylate) and a subsequent exposure to ionizing radiation (⁶⁰Co source). In this way, interpenetrating polymer network has been built on the crosslinked PVA scaffold. Resulting structures were tested for their mechanical behavior at different loads. Series of measurements leading to the determination of the physicochemical properties of created gels including crosslink density and swelling abilities were also performed.