Browsing by Subject "Water"

Now showing 1 - 18 of 18

Open Access
Bacteria encapsulated electrospun nanofibrous webs for remediation of methylene blue dye in water
(Elsevier, 2017-04) Sarioglu O.F.; Keskin, N. O. S.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials that were produced by encapsulation of bacterial cells within electrospun nanofibrous webs are described. A commercial strain of Pseudomonas aeruginosa which has methylene blue (MB) dye remediation capability was selected for encapsulation, and polyvinyl alcohol (PVA) and polyethylene oxide (PEO) were selected as the polymer matrices for the electrospinning of bacteria encapsulated nanofibrous webs. Encapsulation of bacterial cells was monitored by scanning electron microscopy (SEM) and fluorescence microscopy, and the viability of encapsulated bacteria was checked by live/dead staining and viable cell counting assay. Both bacteria/PVA and bacteria/PEO webs have shown a great potential for remediation of MB, yet bacteria/PEO web has shown higher removal performances than bacteria/PVA web, which was probably due to the differences in the initial viable bacterial cells for those two samples. The bacteria encapsulated electrospun nanofibrous webs were stored at 4 °C for three months and they were found as potentially storable for keeping encapsulated bacterial cells alive. Overall, the results suggest that electrospun nanofibrous webs are suitable platforms for preservation of living bacterial cells and they can be used directly as a starting inoculum for bioremediation of water systems.
Open Access
Bacteria immobilized electrospun polycaprolactone and polylactic acid fibrous webs for remediation of textile dyes in water
(Elsevier, 2017-10) Sarioglu O.F.; S. Keskin, N. O.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
In this study, preparation and application of novel biocomposite materials for textile dye removal which are produced by immobilization of specific bacteria onto electrospun nanofibrous webs are presented. A textile dye remediating bacterial isolate, Clavibacter michiganensis, was selected for bacterial immobilization, a commercial reactive textile dye, Setazol Blue BRF-X, was selected as the target contaminant, and electrospun polycaprolactone (PCL) and polylactic acid (PLA) nanofibrous polymeric webs were selected for bacterial integration. Bacterial adhesion onto nanofibrous webs was monitored by scanning electron microscopy (SEM) imaging and optical density (OD) measurements were performed for the detached bacteria. After achieving sufficient amounts of immobilized bacteria on electrospun nanofibrous webs, equivalent web samples were utilized for testing the dye removal capabilities. Both bacteria/PCL and bacteria/PLA webs have shown efficient remediation of Setazol Blue BRF-X dye within 48 h at each tested concentration (50, 100 and 200 mg/L), and their removal performances were very similar to the free-bacteria cells. The bacteria immobilized webs were then tested for five times of reuse at an initial dye concentration of 100 mg/L, and found as potentially reusable with higher bacterial immobilization and faster dye removal capacities at the end of the test. Overall, these findings suggest that electrospun nanofibrous webs are available platforms for bacterial integration and the bacteria immobilized webs can be used as starting inocula for use in remediation of textile dyes in wastewater systems.
Open Access
Beyond scarcity: rethinking water, climate change and conflict in the Sudans
(Elsevier, 2014) Selby, J.; Hoffmann, Clemens
This article develops a new framework for understanding environment-conflict relations, on both theoretical grounds and through a qualitative historical analysis of the links between water and conflict in the states of Sudan and South Sudan. Theoretically, the article critiques the dominant emphases on ‘scarcity’, ‘state failure’ and ‘under-development’ within discussions of environmental security, and proposes an alternative model of environment-conflict relations centring on resource abundance and globally-embedded processes of state-building and development. Empirically, it examines three claimed (or possible) linkages between water and conflict in the Sudans: over trans-boundary waters of the Nile; over the links between internal resource scarcities and civil conflict; and over the internal conflict impacts of water abundance and development. We find that there exists only limited evidence in support of the first two of these linkages, but plentiful evidence that water abundance, and state-directed processes of economic development and internal colonisation relating to water, have had violent consequences. We conclude that analysts and policymakers should pay more attention to the impacts of resource abundance, militarised state power and global political economic forces in their assessments of the potential conflict impacts of environmental and especially climate change.
Open Access
Chromium(VI) biosorption and bioaccumulation by Live and acid-modified biomass of a novel morganella morganii isolate
(Taylor and Francis, 2014) Ergul-Ulger, Z.; Ozkan A.D.; Tunca E.; Atasagun, S.; Tekinay, T.
Conventional methods of chromium removal are often insufficient for the remediation of chromium-contaminated natural environments, necessitating the development of alternative strategies. In this paper, we report the isolation of a novel Morganella morganii strain capable of reducing hexavalent chromium to its less-toxic and less-soluble trivalent form. Cr(VI) reduction by this strain was evaluated in both acidic environments and conditions reflecting natural freshwater sources. The isolate achieved equilibrium within 3 h and displayed a specific uptake rate of 24.30 ± 1.67 mg Cr(VI)/g biomass following HCl treatment. Without acid treatment, a reduction of over 90% was recorded within 72 h for an initial Cr(VI) concentration 20 mg/L, corresponding to a Cr(VI) removal capacity of 19.36 ± 1.89 mg/g. Absorption data of acid-treated STB5 biomass most closely followed the Toth and Langmuir models. FTIR results indicate that hydroxyl groups and extracellular or cell membrane polysaccharides may be potential adsorption sites for hexavalent chromium. Our results suggest that the isolate may be used in situ for treatment of polluted freshwater environments. Copyright © Taylor & Francis Group, LLC.
Open Access
Conducting polymer composites of polypyrrole and a poly(arylene ether ketone)
(1998) Selampinar F.; Akbulut, U.; Toppare L.
Electrically conducting composites of polypyrrole and a poly(arylene ether ketone) were synthesized by electroinitiated polymerization of pyrrole on a poly(arylene ether ketone)-coated platinum electrode. The electrolysis medium was water and p-toluene sulfonic acid. The conductivities of the composites were in the range 1-10 S/cm. The composites were characterized by scanning electron microscopy, Fourier transform infrared, and thermal analyses. The composites were found to be composed of bilayers which can be peeled into two free-standing polymer films. The solution side of the polypyrrole layer of the alloy film contains globular structures, whereas the other side is smoother.
Open Access
Cytotoxic and bioactive properties of different color tulip flowers and degradation kinetic of tulip flower anthocyanins
(Pergamon Press, 2013) Sagdic, O.; Ekici, L.; Ozturk, I.; Tekinay, T.; Polat, B.; Tastemur, B.; Bayram, O.; Senturk, B.
This study was conducted to determine the potential use of anthocyanin-based extracts (ABEs) of wasted tulip flowers as food/drug colorants. For this aim, wasted tulip flowers were samples and analyzed for their bioactive properties and cytotoxicity. Total phenolic contents of the extracts of the claret red (126.55. mg of gallic acid equivalent (GAE)/g dry extract) and orange-red (113.76. mg GAE/g dry extract) flowers were the higher than those of the other tulip flowers. Total anthocyanin levels of the violet, orange-red, claret red and pink tulip flower extracts were determined as 265.04, 236.49, 839.08 and 404.45. mg pelargonidin 3-glucoside/kg dry extract, respectively and these levels were higher than those of the other flowers. The extracts were more effective for the inhibition of Listeria monocytogenes, Staphylococcus aureus and Yersinia enterocolitica compared to other tested bacteria. Additionally, the cytotoxic effects of five different tulip flower extracts on human breast adenocarcinoma (MCF-7) cell line were investigated. The results showed that the orange red, pink and violet extracts had no cytotoxic activity against MCF-7 cell lines while yellow and claret red extracts appeared to be toxic for the cells. Overall, the extracts of tulip flowers with different colors possess remarkable bioactive and cytotoxic properties. © 2013 Elsevier Ltd.
Open Access
Dispersion of multi-walled carbon nanotubes in an aqueous medium by water-dispersible conjugated polymer nanoparticles
(2010) Baykal, B.; Ibrahimova, V.; Er, G.; Bengü, E.; Tuncel, D.
Vertically aligned multi-walled carbon nanotubes (MWCNTs) synthesized by the alcohol catalytic CVD (ACCVD) technique are dispersed in water with the aid of water-dispersible conjugated polymer nanoparticles (CPNs). The interactions between CPNs and CNTs are studied with spectroscopy (UV-Vis, fluorescence and Raman) and electron microscopy techniques are used to confirm attachment of CPNs to the CNT sidewalls.
Open Access
Effect of temperature and wavelength on the refractive index of water : a fiber-optic sensor application
(Springer (India) Private Ltd., 2021-03-25) Kendir, Esra; Yaltkaya, Ş.
The refractive index n(λ,T) is a basic optical property of materials. The refractive index and the thermo-optic coefficient (dn/dT) are significant parameters of liquids for optically controlled systems, such as the direct measurement of liquid solution concentrations and optical paths. In this study, the variation in the refractive index of water in the liquid phase with temperature was measured with our self-designed fiber optic-based refractive index sensor and dn/dT values were obtained with a full-width half-maximum method at wavelengths of 980, 1426, and 1550 nm, respectively. Water is the most abundant and life-critical substance in the world, and its optical properties pose challenging scientific problems that require knowledge of the refractive index to be resolved. The results indicate that the experimental refractive index values are compatible with both the theoretical and experimental data in the literature. We also tested the refraction index results with two theoretical models and obtained good agreement between the calculated and experimental values. The resolution of the fiber optic-based refractive index sensor was 10−5. Our designed sensor could measure the refractive index of liquids with temperature with accuracy.
Open Access
Encapsulation of gallic acid/cyclodextrin inclusion complex in electrospun polylactic acid nanofibers: release behavior and antioxidant activity of gallic acid
(Elsevier, 2016-06) Aytac Z.; Kusku S. I.; Durgun, Engin; Uyar, Tamer
Cyclodextrin-inclusion complexes (CD-ICs) possess great prominence in food and pharmaceutical industries due to their enhanced ability for stabilization of active compounds during processing, storage and usage. Here, CD-IC of gallic acid (GA) with hydroxypropyl-beta-cyclodextrin (GA/HPβCD-IC) was prepared and then incorporated into polylactic acid (PLA) nanofibers (PLA/GA/HPβCD-IC-NF) using electrospinning technique to observe the effect of CD-ICs in the release behavior of GA into three different mediums (water, 10% ethanol and 95% ethanol). The GA incorporated PLA nanofibers (PLA/GA-NFs) were served as control. Phase solubility studies showed an enhanced solubility of GA with increasing amount of HPβCD. The detailed characterization techniques (XRD, TGA and 1H-NMR) confirmed the formation of inclusion complex between GA and HPβCD. Computational modeling studies indicated that the GA made an efficient complex with HPβCD at 1:1 either in vacuum or aqueous system. SEM images revealed the bead-free and uniform morphology of PLA/GA/HPβCD-IC-NF. The release studies of GA from PLA/GA/HPβCD-IC-NF and PLA/GA-NF were carried out in water, 10% ethanol and 95% ethanol, and the findings revealed that PLA/GA/HPβCD-IC-NF has released much more amount of GA in water and 10% ethanol system when compared to PLA/GA-NF. In addition, GA was released slowly from PLA/GA/HPβCD-IC-NF into 95% ethanol when compared to PLA/GA-NF. It was also observed that electrospinning process had no negative effect on the antioxidant activity of GA when GA was incorporated in PLA nanofibers.
Open Access
H-O for H2O: can the Heckscher-Ohlin framework explain the role of free trade in distributing scarce water resources around the Middle East?
(Walter de Gruyter GmbH, 2003) Sayan, S.
This paper aims to test econometrically the validity of Heckscher–Ohlin (H–O) theory within the context of export patterns of 11 relatively waterabundant and relatively water-scarce countries located in the Eastern Mediterranean and Middle East and North Africa (MENA) regions. For this purpose, the paper calculates the revealed comparative advantage (RCA) and net trade indices (NTI) for 13 sectors in each country and estimates the relationship between RCA values and water requirements of production in each sector. The results are then used to test whether parameter values estimated from this exercise can be linked to water endowments of the countries considered. By helping determine whether the countries in the sample act according to their comparative advantages, econometric results from this innovative application of H–O theory yield interesting policy conclusions.
Open Access
Highly sensitive determination of 2, 4, 6-trinitrotoluene and related byproducts using a diol functionalized column for high performance liquid chromatography
(Public Library of Science, 2014) Gumuscu, B.; Erdogan, Z.; Güler, Mustafa O.; Tekinay, T.
In this work, a new detection method for complete separation of 2,4,6-trinitrotoluene (TNT); 2,4-dinitrotoluene (2,4-DNT); 2,6-dinitrotoluene (2,6-DNT); 2-aminodinitrotoluene (2-ADNT) and 4-aminodinitrotoluene (4-ADNT) molecules in high-performance liquid-chromatography (HPLC) with UV sensor has been developed using diol column. This approach improves on cost, time, and sensitivity over the existing methods, providing a simple and effective alternative. Total analysis time was less than 13 minutes including column re-equilibration between runs, in which water and acetonitrile were used as gradient elution solvents. Under optimized conditions, the minimum resolution between 2,4-DNT and 2,6-DNT peaks was 2.06. The recovery rates for spiked environmental samples were between 95-98%. The detection limits for diol column ranged from 0.78 to 1.17 μg/L for TNT and its byproducts. While the solvent consumption was 26.4 mL/min for two-phase EPA and 30 mL/min for EPA 8330 methods, it was only 8.8 mL/min for diol column. The resolution was improved up to 49% respect to two-phase EPA and EPA 8330 methods. When compared to C-18 and phenyl-3 columns, solvent usage was reduced up to 64% using diol column and resolution was enhanced approximately two-fold. The sensitivity of diol column was afforded by the hydroxyl groups on polyol layer, joining the formation of charge-transfer complexes with nitroaromatic compounds according to acceptor-donor interactions. Having compliance with current requirements, the proposed method demonstrates sensitive and robust separation. © 2014 Gumuscu et al.
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Köy Hizmetleri Genel Müdürlüğü ve kırsal kalkınma faaliyetleri
(Bilkent University, 2021) Ayaz, Eda İrem; Budak, Yağmur; Özbay, Ece; Özdemir, Aslı Zeynep; Özlü, Arda
Köy Hizmetleri Genel Müdürlüğü 1984 yılında kırsal kalkınmayı desteklemesi, köy yollarının onarımı ve geliştirilmesi ve köylere elektrik ve içme suyu sağlanması gibi birçok hizmeti vermesi amacıyla kurulmuştur. Bu kurum, kırsal kalkınma bağlamında birçok proje ve çalışmaya imza atmıştır ve aktif olduğu seneler içerisinde sürekli olarak gelişimini sürdürmüştür. Hizmetlerini ülke genelinde sürdüren genel müdürlük 2005 yılında yerel çalışmalara ağırlık verilebilmesi için kapatılmıştır ve yetkileri il özel idarelerine devredilmiştir.
Open Access
Morphology-tailored synthesis of tungsten trioxide (Hydrate) thin films and their photocatalytic properties
(ACS Publications, 2011-01-10) Jiao, Z. H.; Wang, J. M.; Ke, L.; Sun, X. W.; Demir, Hilmi Volkan
Tungsten trioxide hydrate (3WO(3)center dot H(2)O) films with different morphologies were directly grown on fluorine doped tin oxide (FTO) subsi:rate via a facile crystal-seed-assisted hydrothermal method. Scanning electron microscopy (SEM) analysis showed that 3WO(3)center dot H(2)O thin films composed of platelike, wedgelike, and sheetlike nanostructures could be selectively synthesized by adding Na(2)SO(4), (NH(4))(2)SO(4), and CH(3)COONH(4) as capping agents, respectively. X-ray diffraction (XRD) studies indicated that these films were of orthorhombic structure. The as-prepared thin films after dehydration showed obvious photcicatalytic activities. The best film grown using CH(3)COONH(4) as a capping agent generated anodic photocurrents of 1.16 mA/cm(2) fork oxidization of methanol and 0.5 mA/cm(2) for water splitting with the highest photoconversion efficiency of about 0.3% under simulated solar illumination.
Open Access
Polymer-free electrospun nanofibers from sulfobutyl ether7-beta-cyclodextrin (SBE7-β-CD) inclusion complex with sulfisoxazole: fast-dissolving and enhanced water-solubility of sulfisoxazole
(Elsevier, 2017-10) Yildiz, Z. I.; Celebioglu A.; Uyar, Tamer
In this study, our aim was to develop solid drug-cyclodextrin inclusion complex system having nanofibrous morphology in order to have fast-dissolving property and enhanced water-solubility of poorly water-soluble drug. Here, we prepared a highly concentrated aqueous solution of inclusion complex between sulfisoxazole and sulfobutyl ether7-beta-cyclodextrin (SBE7-β-CD, Captisol®), and then, without using any polymeric matrix, the electrospinning of sulfisoxazole/SBE7-β-CD-IC nanofibers was performed in order to obtain free-standing and handy nanofibrous web. As a control sample, nanofibers from pure SBE7-β-CD was also electrospun and free-standing nanofibrous web was obtained. The SEM imaging revealed that the bead-free and uniform nanofiber morphology with the average fiber diameter (AFD) of 650 ± 290 nm for sulfisoxazole/SBE7-β-CD-IC NF and 890 ± 415 nm for pure SBE7-β-CD NF was obtained. The inclusion complex formation between sulfisoxazole and SBE7-β-CD in sulfisoxazole/SBE7-β-CD-IC NF sample was confirmed by 1H NMR, TGA, DSC, XRD and FTIR analyses. Due to the combined advantage of cyclodextrin inclusion complexation and high surface area of electrospun nanofibers, fast-dissolving property with enhanced water-solubility was successfully achieved for sulfisoxazole/SBE7-β-CD-IC NF. Our findings suggest that electrospun nanofibers/nanowebs from CD-IC of poorly water-soluble drugs may offer applicable approaches for high water-solubility and fast-dissolving tablet formulations for drug delivery systems.
Open Access
Profiling turkish honeys to determine authenticity using physical and chemical characteristics
(2009) Senyuva H.Z.; Gilbert J.; Silici, S.; Charlton, A.; Dal, C.; Gürel, N.; Cimen, D.
Seventy authentic honey samples of 9 different floral types (rhododendron, chestnut, honeydew, Anzer (thymus spp.), eucalyptus, gossypium, citrus, sunflower, and multifloral) from 15 different geographical regions of Turkey were analyzed for their chemical composition and for indicators of botanical and geographical origin. The profiles of free amino acids, oligosaccharides, and volatile components together with water activity were determined to characterize chemical composition. The microscopic analysis of honey sediment (mellissopalynology) was carried out to identify and count the pollen to provide qualitative indicators to confirm botanical origin. Statistical analysis was undertaken using a bespoke toolbox for Matlab called Metabolab. Discriminant analysis was undertaken using partial least-squares (PLS) regression followed by linear discriminant analysis (LDA). Four data models were constructed and validated. Model 1 used 51 variables to predict the floral origin of the honey samples. This model was also used to identify the top 5 variable important of projection (VIP) scores, selecting those variables that most significantly affected the PLS-LDA calculation. These data related to the phthalic acid, 2-methylheptanoic acid, raffinose, maltose, and sucrose. Data from these compounds were remodeled using PLS-LDA. Model 2 used only the volatiles data, model 3 the sugars data, and model 4 the amino acids data. The combined data set allowed the floral origin of Turkish honey to be accurately predicted and thus provides a useful tool for authentication purposes. However, using variable selection techniques a smaller subset of analytes have been identified that have the capability of classifying Turkish honey according to floral type with a similar level of accuracy. © 2009 American Chemical Society.
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Su üzerine
(1996) Oktay, Ahmet
Open Access
Water scarcity, conflict, and migration: a comparative analysis and reappraisal
(Sage Publications, 2012) Selby, J.; Hoffmann, Clemens
How should we characterise the relations between environmental scarcity, conflict, and migration? Most academic and policy analyses conclude that scarcities of environmental resources can have significant impacts upon conflict and migration, and claim or imply that within the context of accelerating global environmental changes these impacts are likely to become more significant still. Many analyses admittedly recognise that these impacts are often indirect rather than direct and that there exist multiple ‘drivers’ of conflict and migration, of which environmental stresses are but one. We argue that even these qualifications do not go far enough, however: they still overstate the current and likely future significance of environmental changes and stresses in contributing to conflict and migration and underemphasise a far more important causal pathway-from conflict and migration to environmental vulnerabilities. These arguments are advanced via a comparative analysis of water-migration-conflict linkages in Cyprus and Israel and the West Bank and Gaza.
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Yaşam suyu yolunda İvan Illich
(1991) Ayvaz, Sezer Ateş