Preparation and optimization of superabsorbent hydrogel micromatrices based on poly(acrylic acid), partly sodium salt-g-poly(ethylene oxide) for modified release of indomethacin

The purpose of this study was to prepare modified-release dosage of indomethacin (IND) in the form of micromatrices based on a superabsorbent hydrogel (SAH), poly(acrylic acid), partly sodium salt-g-poly(ethylene oxide) (PAAc-Na-g-PEO). A soaking procedure was used for the preparation of drug-loaded hydrogel micromatrices. The amount of IND, volume of drug-loading solution, and amount of PAAc-Na-g-PEO granules used for preparing micromatrices were the independent factors. The dependent factors were the measured responses from micromatrices, that is, percent recovery, percent entrapment efficiency, and the time at which 63.2% of the drug was released (T_d, minutes). A three-factor, three-level full factorial design (33) was created to optimize formulations. Nonlinear regression analysis indicated a good correlation between the measured responses and the independent factors. Optimum responses were obtained from medium levels of IND and SAH and low level of drug-loading solution. Differential scanning calorimetry, X-ray diffraction analysis, and scanning electron micrography indicated that IND crystals are physically adsorbed into the pores and irregular spaces of the hydrogel.     

Synthesis and characterization of N‐ and O‐alkylated poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline]

Poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline] was synthesized in an aqueous hydrochloric acid medium with a determined feed ratio by chemical oxidative polymerization. This polymer was used as a functional conducting polymer intermediate because of its side‐group reactivity. To synthesize the alkyl‐substituted copolymer, the initial copolymer was reacted with NaH to obtain the N‐ and O‐anionic copolymer after the reaction with octadecyl bromide to prepare the octadecyl‐substituted polymer. The microstructure of the obtained polymers was characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, and X‐ray diffraction. The thermal behavior of the polymers was investigated by thermogravimetric analysis and differential scanning calorimetry. The morphology of obtained copolymers was studied by scanning electron microscopy. The cyclic voltammetry investigation showed the electroactivity of poly [aniline‐co‐N‐(2‐hydroxyethyl) aniline] and N and O‐alkylated poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline]. The conductivities of the polymers were 5 × 10^?5 S/cm for poly[aniline‐co‐N‐(2‐hydroxyethyl) aniline] and 5 ×10^?7 S/cm for the octadecyl‐substituted copolymer. The conductivity measurements were performed with a four‐point probe method. The solubility of the initial copolymer in common organic solvents such as N‐methyl‐2‐pyrrolidone and dimethylformamide was greater than polyaniline. The alkylated copolymer was mainly soluble in nonpolar solvents such as n‐hexane and cyclohexane. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Exergy Analysis of Drying Process: An Experimental Study in Solar Greenhouse

This article examines the exergy variation during drying in solar greenhouses. Exergy efficiencies were derived as functions of drying time and temperature of the drying air. An illustrative example is considered to verify Dincer and Sahin's model and to show the applicability of the model to actual drying processes at different drying air temperatures. This work is intended not only to demonstrate the usefulness of exergy analysis in thermodynamic assessments of drying processes but to provide insights into their performances and efficiencies. In this study, the drying performance of the passively heated solar greenhouse has been investigated. Experimental results under the meteorological conditions of Izmir, Turkey (latitude 38.24 N, longitude 27.50 E), are presented.     

Monitoring of energy exergy efficiencies and exergoeconomic parameters of geothermal district heating systems (GDHSs)

In this work, the monitoring energy and exergy efficiency results of the last heating seasons of operation of the geothermal district heating systems (GDHSs) and their technical availability analysis and monitoring exergoeconomic parameters are presented. The case studies cover the actual system data taken from the systems in Afyon and Salihli GDHSs, Turkey. General energy, exergy, technical availability, and exergoeconomic analysis of the GDHSs are introduced. Furthermore, the average technical availability, real availability, capacity factor and energy and exergy efficiencies value of GDHSs have been analyzed.     

Application of antimicrobial ice for extending shelf life of fish

In this study, we investigated whether wild-thyme (Thymus serpyllum) hydrosol had a preserving effect against spoilage of freshwater fish. Sensorial characteristics, chemical freshness indicator contents, and microbial counts (total aerobes, psychrotrophics, Enterobacteriaceae, fecal coliform bacteria, Aeromonas spp., and Pseudomonas spp.) of whole ungutted and gutted Transcaucasian barb (Capoeta capoeta capoeta Guldenstaedt, 1772) stored on ice produced from wild-thyme hydrosol and tap water at 4 degrees C for 20 days were compared. The results did not reveal any significant (P > 0.05) differences in the microbial counts, sensorial characteristics, pH, and total volatile basic nitrogen values between gutted and ungutted groups. Sensory evaluation and microbiological and chemical analyses indicated that the storage of the fish on ice produced from wild-thyme hydrosol had a significant increase in shelf life by at least 15 to 20 days.     

Transport of sodium chloride,urea, and creatinine through membranes derived from methylmethacrylate-co-methacrylic acid and its ionomers

Permeabilities of cast films of methylmethacrylate-co-methacrylic acid (MMA—MAA) and its 5% neutralized Na¹⁺, CS¹⁺, Zn²⁺, Ba²⁺, and Al³⁺ ionomers for urea, sodium chloride, and creatinine were determined using a double (donor and acceptor) compartment cell. Film permeability was increased as the ionic potential decreased and it was more marked with urea as compared with sodium chloride and creatinine. Tensile properties of the above samples were also tested and variations in Young's Moduli were based on the effect of type of aggregates produced by the cations in the matrix of the copolymer. © 1993 John Wiley & Sons, Inc.     

Thioethyl‐Porphyrazine/Nanocarbon Hybrids for Photoinduced Electron Transfer

A novel pyrene‐substituted thioethyl‐porphyrazine ( PzPy ) and the formation of supramolecular assembly with nanocarbons demonstrating photoinduced electron transfer ability are designed. As revealed by spectroscopic and electrochemical studies, PzPy displays wide spectral absorption in the visible range, charge separation upon photoexcitation, as well as bandgap and highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) energy values, matching the key requirements of organic optoelectronic. Moreover, the presence of a pyrene moiety promotes attractive interactions with π‐conjugated systems. In particular, theoretical calculations show that in the PzPy the HOMO and LUMO are localized on different positions of the molecule, i.e., the HOMO on the pyrene moiety and the LUMO on the macrocycle. Therefore, HOMO–LUMO excitation gives rise to a charge separation, preventing excitons recombination. Two kinds of noncovalent hybrid composites are prepared by mixing the PzPy with single‐wall carbon nanotubes (SWNTs) and graphene nanoflakes (GNFs), respectively, and used for photocurrent generation through charge transfer processes between PzPy and nanocarbons. Photoconduction experiments show photocurrent generation upon visible light irradiation of both PzPy /SWNT and PzPy /GNF composites (0.78 and 0.71 mA W^?1 at 500 nm, respectively), demonstrating their suitability for optoelectronic applications and light harvesting systems.     

Synthesis and characterization of water‐dispersed flame‐retardant polyurethane resin using phosphorus‐containing chain extender

In this research, a flame‐retardant water‐dispersed polyurethane resin was synthesized through incorporating phosphonate groups into the polyurethane structure in the chain‐extension step. A phosphorus‐containing reactive flame‐retardant compound was synthesized for this purpose. First, bis(4‐nitrophenyl)phenyl phosphine oxide was synthesized and then converted to bis(4‐amino phenyl)phenyl phosphine oxide (BAPPO) by reducing its nitro groups into amines. The obtained products were characterized by IR, ¹H‐NMR, and ³¹P‐NMR, and the thermal properties of the polymers were determined by DSC analysis. The BAPPO‐containing polyurethane showed physical properties that were almost similar to those of phosphorus‐free polyurethane and exhibited good flame resistance with a limiting oxygen index value of 27. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1314–1321, 2004     

Comparison of new activation functions in neural network for forecasting financial time series

In artificial neural networks (ANNs), the activation function most used in practice are the logistic sigmoid function and the hyperbolic tangent function. The activation functions used in ANNs have been said to play an important role in the convergence of the learning algorithms. In this paper, we evaluate the use of different activation functions and suggest the use of three new simple functions, complementary log-log, probit and log-log, as activation functions in order to improve the performance of neural networks. Financial time series were used to evaluate the performance of ANNs models using these new activation functions and to compare their performance with some activation functions existing in the literature. This evaluation is performed through two learning algorithms: conjugate gradient backpropagation with Fletcher–Reeves updates and Levenberg–Marquardt.