Effect of some selective aromatic cosolutes on the main thermodynamic parameters of aqueous poly(n‐vinyl‐2‐pyrrolidone) solutions

Cloud‐point curves and theta temperatures have been determined for aqueous solutions of poly(N‐vinyl‐2‐pyrrolidone) at several concentrations for a variety of aromatic additives (benzoic acid, o‐ and p‐hydroxy benzoic acid, aniline, o‐ and p‐hydroxy aniline). The theta temperature of polymer is suppressed at lower temperatures depending on the chemical structure and the concentration of additives. The effectiveness, in decreasing order, of the cosolutes in reducing the temperature is: p‐hydroxy benzoic acid > o‐hydroxy benzoic acid > p‐hydroxy aniline > o‐hydroxy aniline ≈ benzoic acid > aniline. It is understood that changes in theta temperatures caused by the cosolute result from the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and polymer–solvent interactions from the added cosolute. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 507–510, 2000     

Thermal properties of poly(maleic anhydride‐alt‐acrylic acid) in the presence of certain metal chlorides

Polychelates were synthesized by the addition of aqueous solutions of copper(II), cadmium(II), and nickel(II) chlorides to aqueous solutions of poly(maleic anhydride‐alt‐acrylic acid) [poly(MA‐alt‐AA)] in different pH media. The thermal properties of poly(MA‐alt‐AA) and its metal complexes were investigated with thermogravimetry and differential scanning calorimetry (DSC) measurements. The polychelates showed higher thermal stability than poly(MA‐alt‐AA). The thermogravimetry of the polymer–metal complexes revealed variations of the thermal stability by complexation with metal ions. The relative thermal stabilities of the systems under investigation were as follows: poly(MA‐alt‐AA)–Cd(II) > poly(MA‐alt‐AA)–Cu(II) > poly(MA‐alt‐AA)–Ni(II) > poly(MA‐alt‐AA). The effects of pH on the complexation and gravimetric analysis of the polychelates were also studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3926–3930, 2006     

Sorption of boron by invasive marine seaweed: Caulerpa racemosa var. cylindracea

The sorption of boron from aqueous solution onto Caulerpa racemosa var. cylindracea (CRC), collected from Seferihisar/Izmir region in Turkey, was investigated as a function of pH, temperature, initial boron concentration, adsorbent dosage, contact time and ionic strength. Optimum conditions for the sorption of boron were obtained at pH 7.5, 318 K, 8 mg L⁻¹ initial boron concentration, 0.2 g of CRC, 2.5 h contact time and greater ionic strength (10⁻¹ M NaCl). As the temperature was increased the boron removal took place with higher percentages. In experiments conducted at optimum conditions, maximum boron sorption was determined to be about 63%. The experimental data were analyzed by Freundlich, Langmuir and Dubinin–Radusckevich (DR) equations. Freundlich and DR models provide best conformity with the experimental data. In order to describe kinetics of boron sorption onto CRC, first-order Lagergren equation, pseudo-second-order kinetic model and intraparticle diffusion model were used. It was seen that the first order Lagergren equation was better described than the pseudo-second-order kinetic model. Thermodynamic parameters of sorption process were also calculated. It was obtained that sorption process was not spontaneous. The characterization of CRC was carried out by Fourier transform infrared spectroscopy (FTIR) analysis.     

The effect of lemon juice on bonito (Sarda sarda,Bloch, 1793) preserved by sous vide packaging

This study examined the effect of lemon juice on sensory, biochemical and microbiological quality of sous vide (SV)‐packaged bonito. Bonitos were salted (0.2%) and divided into two groups. The first group (SV) was vacuum‐packaged in a gas barrier plastic pouch, pasteurised (70 °C, 10 min) and stored at 4 ± 1 °C. The second group [(lemon juice‐treated sous vide (LSV)] was treated with lemon juice, vacuum‐packaged, pasteurised and stored similarly. LSV samples had lower pH, mesophilic and psychrophilic aerobic counts than SV samples (P < 0.05), and they had better sensory quality. SV samples spoiled on the 35th day, while the LSV samples were acceptable until 49th day of storage. This result shows that treatment with lemon juice increased the acceptability and shelf life of SV packaged bonito for 2 weeks (40%). When compared to several other mild preservation procedures, addition of lemon juice to SV fish is inexpensive and uncomplicated method.     

Electricity consumption and economic growth: Evidence from Turkey

This study investigates the causal relationship between electricity consumption and real GDP in Turkey during the period of 1950–2000. Both of the series were found to be a stationary process around a structural break by the Zivot and Andrews test. Thus, two different methodologies have been employed to test the Granger non-causality: the Dolado–Lütkepohl test using the VARs in levels, and the standard Granger causality test using the detrended data. Both tests have yielded a strong evidence for unidirectional causality running from the electricity consumption to the income. This implies that the supply of electricity is vitally important to meet the growing electricity consumption, hence to sustain the economic growth in Turkey.     

Inhibition of polyphenol oxidase obtained from various sources by 2,3‐diaminopropionic acid

This paper reports for the first time the inhibition of the catecholase activities of mushroom, artichoke (Cynara scolymus L) and Ocimum basilicum L polyphenol oxidase by 2,3‐diaminopropionic acid. Polyphenol oxidases from artichoke and O basilicum L were purified by ammonium sulfate precipitation, dialysis and a Sepharose 4B‐L ‐tyrosine‐p‐aminobenzoic acid‐affinity column. In inhibition studies, 2,3‐diaminopropionic acid showed uncompetitive inhibition for mushroom PPO using catechol and pyrogallol as substrates, competitive inhibition for O basilicum L PPO using catechol as a substrate, and uncompetitive inhibition for artichoke PPO using catechol as a substrate. Furthermore, sodium azide, which is an inhibitor of PPO, was used as an inhibitor for comparison with the inhibition potency of 2,3‐diaminopropionic acid. The highest 2,3‐diaminopropionic acid inhibition observed with O basilicum L (K_i = 0.89 mM ), followed by artichoke (K_i = 1.42 mM ) and mushroom (K_i = 2.47 mM ), respectively. Copyright © 2005 Society of Chemical Industry     

Intrinsic factor and vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] microspheres: preparation,characterization and drug release

BACKGROUND: Vitamin B12 is an essential vitamin required by all mammals. Absorption of vitamin B12 is facilitated by binding of intrinsic factor–vitamin B₁₂ complex to specific receptors in the ileum. In humans a deficiency of this vitamin or a lack of intrinsic factor leads to pernicious anaemia. The major objective of the present study was to prepare intrinsic factor–vitamin B12 complex‐loaded poly[lactic‐co‐(glycolic acid)] (PLGA)‐based microparticles and to investigate their release kinetics. RESULTS: PLGA copolymer was synthesized by the ring‐opening polymerization method and characterized using gel permeation chromatography, Fourier transform infrared spectroscopy and ¹H NMR. The glass transition temperature measurement showed a single T_g at 40 °C. The intrinsic factor–vitamin B12 complex‐loaded PLGA microspheres were prepared by a water‐in‐oil‐in‐water double emulsion solvent extraction/evaporation technique. An environmental scanning electron microscopy investigation demonstrated that the PLGA particles had a mean particle diameter of 38 µm. Interestingly, different drug release patterns (bi‐ and triphasic ones) were observed for vitamin B12‐loaded and intrinsic factor–vitamin B12 complex‐loaded microspheres. In contrast to the rapid release of vitamin B12 by itself, in vitro release tests showed that intrinsic factor and vitamin B12 in the complex were released from PLGA microspheres in a sustained manner over 15 days. CONCLUSION: PLGA microspheres can be an effective carrier for the intrinsic factor–vitamin B12 complex. Copyright © 2007 Society of Chemical Industry     

Effect of yarn properties on thermal comfort of knitted fabrics

In this research, thermal properties of 1×1 rib fabrics knitted by using various yarns of different properties were investigated with all details. The mentioned yarn properties were yarn count, yarn twist and combing process. The thermal resistance, thermal absorptivity, thermal conductivity, water vapour permeability of samples were measured with the aid of Alambeta and Permetest devices respectively. The results of the tests were evaluated statistically and the importance levels of the relationship between the measured parameters were determined. It is observed that yarn properties like yarn count, yarn twist and combing process of cotton have affected different thermal comfort properties of 1×1 rib knitted fabrics. While the yarn twist and yarn count increase thermal resistance values decrease and water vapour permeability values increase. The combing process has the same effect on the thermal properties.     

Preparation of collagen modified photopolymers: a new type of biodegradable gel for cell growth

In this study a new branched methacrylated poly(propylene glycol-co-lactic acid) (PPG–PLA–IEM) and methacrylated cellulose acetate butyrate resin (CAB–IEM) were synthesized. Hydrogels with various amounts of PPG–PLA–IEM and CAB–IEM (25, 50 and 75 wt% IEM modified) were prepared by photopolymerization. Collagen tethered PEG–monoacrylate (PEGMA–collagen) was prepared and introduced as a bioactive moiety to modify the hydrogel in order to enhance cell affinity. In vitro attachment and growth of 3T3 mouse fibroblasts and human umbilical vein endothelial cells (HUVEC) on the hydrogels with and without collagen were also investigated. It was observed that, the collagen improves the cell adhesion onto the hydrogel surface. With the increasing amount of collagen, cell viability increased by 28% for ECV304 (P < 0.05) and 30% for 3T3 (P < 0.05).