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Ozutok F.,Science Faculty | Demiri S.,Materials Science and Engineering | Ozbek E.,Materials Science and Engineering
AIP Conference Proceedings | Year: 2017

Recently, smart windows are very important because they are often being used in smart buildings and car glasses (windows). At this point, producing effective electrochromic materials is so necessary. In this study, we produced NiO thin films by using spin coating technique on In-doped SnO2 (ITO) substrate. Nickel proportions of these nickel oxide (NiO) films are 3, 5 and 7 %. Nickel acetate tetrahydrate is the initial solution and solvents are ethylene gl ycol and n-hexzane. Structural properties and surface images are investigated by using x-ray diffactometer (XRD) and scanning electron microscope (SEM) device, respectively. In addition, electrochemical behavior is investigated by cyclic voltammetry. A correlation between surface morphology and electrochromic performance was observed as well. © 2017 Author(s).

News Article | April 17, 2017

Aerosols are collections of fine particles, either biological or of other types, in suspension in a gaseous medium. They play a major role in cloud formation and therefore have a strong impact on climate models. They are however extremely hard to study due to the small size and immense variety of their constituent particles. But researchers from the University of Geneva (UNIGE), Switzerland, members of the PlanetSolar Deepwater expedition, have now succeeded in linking the composition of marine biological aerosols -- and therefore their influence on the climate -- to that of bodies of water under them within the Atlantic Ocean, thereby paving the way to an indirect study of these aerosols through water analysis. This study, which has been published in Scientific Reports, will contribute to making climate models more accurate. Aerosols are fine particles in suspension in the air. Over the oceans, some contain organic or biological ingredients (bacteria, degradation products of microscopic algae) which come from sea spray, others are transported in the air (mineral dust, smoke). They serve as seeds for forming clouds and also reflect light. Their role is extremely important for modelling clouds, and therefore for the climate in general. But due to the small size of the particles and their large quantity, it's difficult to accurately study them. So researchers at the University of Geneva (UNIGE) asked themselves if it would be possible to characterize biological aerosols through the composition of the water whence they come. "To answer this question, we needed two tools," explains Jérôme Kasparian, Professor in the Department of Applied Physics at the UNIGE Science Faculty. "The first is a detector of fluorescence which we designed, called Biobox, and which enables us to analyse aerosol particles one by one. The spectrum gives us information on their composition and distinguishes the organic particles, which are fluorescent, from the other particles. Then we needed PlanetSolar." Indeed this research could only be undertaken over a long time period of time without any disturbances of water and air. Only PlanetSolar, a solar boat that navigated remains at sea for three months and produces no emissions, could make it possible. During the expedition, scientists carried out analysis of the salinity, temperature, dissolved oxygen and the microalgae contained in the various bodies of water in the Atlantic, and then compared this data with that obtained by the Biobox. "And we found that they matched!" exclaims Jérôme Kasparian. The physicists discovered that biological aerosols are related to the temperature and salinity of the sea. According to previous criteria, water creates large bodies that don't inter-mix, which allows them to be differentiated. Thus, when the characteristics of a water mass were favourable for reproduction of microalgae, researchers noticed that after a certain amount of time, the aerosols detected above this same water mass contained more biological particles. The biological fraction of aerosols is therefore linked to the history of biological activity of bodies of water close to the surface. "Provided that this is also valid in oceans and seas other than the Atlantic, our research location, our results would allow us to estimate biological aerosols by directly studying the bodies of water, which would simplify aerosol caracterization and make climate models more accurate," adds Kasparian. Difficult to study directly, aerosols are now being studied via the sea, which, unlike aerosols, can easily be analysed by satellites.

Carretero M.I.,Crystallography | Pozo M.,Science Faculty | Martin-Rubi J.A.,Geological Survey of Spain | Pozo E.,Geological Survey of Spain | Maraver F.,Complutense University of Madrid
Applied Clay Science | Year: 2010

All four peloids currently used in Spanish spas and from Lo Pagán lagoon sediment have been characterized mineralogically and chemically. They range in composition from smectites-rich to complex mixtures or even peat-clay mixtures. The peloids were mixed with artificial sweat and stirred for 1h (EN 1811:1998. +. A1: 2008) at 45°C (±2°C), simulating the thermal-therapy action commonly utilized in the spas. Later the leached extract was analyzed chemically after centrifugation and separation. In the leached sweat extract the concentration of 31 elements, including essential and/or potentially toxic elements, was determined by means of ICP-MS, ICP-AES and AAS.The principal leached elements are Na, Ca, Mg and K (between 29,000μg/g and 50μg/g). The quantity of Na, Mg and K after leaching is related to the composition of the mineral-medicinal water and the mineralogical composition (smectite content) of the raw material. However the leaching of Ca is related more to the presence of calcite and aragonite in the peloid used than to the composition of the mineral-medicinal water.Other elements are also leached in smaller proportions: Si and Sr (<45μg/g, except Sr: 197.5μg/g in Lo Pagán peloid); Ba and B (<6μg/g, except B: 42.9μg/g in Lo Pagán peloid); Al and Li (<2μg/g); Fe, Mn, Mo and V (<0.4μg/g, except Fe and Mo: 1.5μg/g in Lo Pagán peloid); and As, Sb and U (<0.1μg/g). Heavy metals such as Cu, Ni, Pb and Zn are ab/adsorbed from the sweat to the peloid leading in most cases to their removal from the leached extract. The other trace elements (Ag, Be, Cd, Co, Cr, Hg, Rb, Se, Th and Tl) are not leached by the Spanish spas peloids or leached at a concentration below 0.05μg/g in the case of the natural lagoon peloid.Of all the peloids studied, the highest quantities of elements were leached from the Lo Pagán peloid due to the hypermarine, sodium-chloride-type of lagoon water where the peloids originate.It is noteworthy that the content of potentially toxic elements (Ag, As, Be, Cd, Hg, Pb, Sb, Se, Tl and Zn) in the leached extracts is negligible (less than 0.05μg/g). © 2010 Elsevier B.V.

Kebede S.,Science Faculty | Travi Y.,University of Strasbourg
Quaternary International | Year: 2012

Understanding the origin of the δ 18O and δ 2H content of meteoric waters is the initial step in using these isotopes in water resources, hydrological and hydro-climatic investigations. Specifically, isotopes of water are proven tools in a) constraining rate and mechanism of groundwater recharge, b) tracing movement of groundwaters, c) reconstructing past climate (rainfall amount, humidity and temperature) at various time scales, d) quantifying water flux across boundaries (e.g. evaporation rates, mixing), and e) complementing regional and global climate models. The δ 18O and δ 2H values in rainfall waters of Ethiopia have long been recognised as a 'regional anomaly'. Regardless of the station's high altitude (2360 m asl) and the region's low mean annual temperature (16 °C), two conditions that would otherwise lead to relative isotope depletion, the rains show the highest 18O composition with no sign of effect of evaporative enrichment (as revealed by d-excess). This enrichment is also reflected in other local meteoric waters (shallow groundwaters, lakes, ambient vapour and rivers). Here, the δ 18O and δ 2H of 600 lake water samples, 3000 groundwater samples, and rainfall isotope data base from IAEA/WMO stations at Addis Ababa have been used to show the linkage between rainfall derivation processes and isotope signals. The major sources of moisture in Ethiopia are recycled moisture from continental sources for western and northern Ethiopia, and direct moisture from the Southern Indian Ocean for eastern lowlands of Ethiopia. Southern Ethiopia is influenced by South Indian Ocean moisture, which is characterised by relatively depleted 18O and 2H. Spatial variation (altitude and latitude) in 18O and 2H is weak, with altitude effect accounting for 0.1‰/100 m depletion in δ 18O. Detailed investigation of the relation between isotope pattern and isotope effects (amount, seasonality, temperature, etc.) shows that these effects are not pronounced. The -4.5‰ δ 18O shift recorded in deeper groundwaters and other paleo-climate achieves (from the current wt. mean rainfall value of -0.5‰) can only be explained by a shift in source of moisture, such as the northward penetration of the South Indian Ocean moisture into the Ethiopian highlands, or changes in evaporation conditions at the source. © 2011 Elsevier Ltd and INQUA.

Nori-Shargh D.,Islamic Azad University at Tehran | Hassanzadeh N.,Islamic Azad University at Ahvāz | Kosari M.,Science Faculty | Sharifi S.,Science Faculty
Journal of Molecular Structure: THEOCHEM | Year: 2010

NBO analysis, hybrid-density functional theory (hybrid-DFT: B3LYP/6-311+G**//HF/6-311+G**) and ab initio molecular orbital (MO: MP2/6-311+G**//HF/6-311+G**) based methods were used to study the anomeric effects (AE) on the stability of the cis- and trans-stereoisomers of 1,4,5,8-tetraoxadecalin (1), 1,4,5,8-tetrathiadecalin (2) and 1,4,5,8-tetraselenadecalin (3). The B3LYP/6-311+G**//HF/6-311+G** results revealed that the cis-stereoisomers of compounds 1-3 are more stable than their trans-stereoisomers by about 4.26, 1.03 and 0.70 kcal mol-1, respectively. Also, the cis-stereoisomers of compounds 1-3 are more stable than their trans-stereoisomers by about 4.18, 2.11 and 01.18 kcal mol-1, respectively, as calculated at the MP2/6-311+G**//HF/6-311+G** level of theory. In addition, HF/6-311+G**//HF/6-311+G** results revealed that the Gibbs free energy difference (Gcis - Gtrans) values (e.g. GFEDcis-trans) between the cis- and trans-stereoisomers decrease from compound 1 to compound 3. On the other hand, the NBO analysis of donor-acceptor (bond-antibond) interactions revealed that the anomeric effects (AE) for compounds 1-3 are -22.08, -17.84 and -13.22 kcal mol-1, respectively. The decrease of the AE could fairly explain the decrease of the GFEDcis-trans from compound 1 to compound 3. On the other hand, the decrease of the donor-acceptor interactions associated with LPaxM1 → σ*C9-O8 electronic delocalizations could fairly explain the increase of occupancies of LPaxM1 non-bonding orbitals and the decrease of occupancies of σ*C9-O8 anti-bonding orbitals from the cis-stereoisomers of compound 1 to compound 3. © 2009 Elsevier B.V. All rights reserved.

Sadeghi M.,Science Faculty | Heidari B.,Engineer Faculty
Oriental Journal of Chemistry | Year: 2011

The present work focused on the design of drug delivery system (DDS) based on a pH-, salt-and temperature sensitive superabsorbent hydrogel. The novel biopolymer-based superabsorbent hydrogels were prepared by grafting crosslinked poly(AA-co-BuMC) chains onto CMC backbones through a free radical polymerization method, the hydrogel.s structure was confirmed using FTIR spectroscopy. Results from scanning electron microscopy (SEM) observation also showed a porous structure with smooth surface morphology of the hydrogel. Due to the reversible swelling behavior of the hydrogels, the synthesized networks can sense the environmental pH,lonic strength and temperature change, respectively, and achieve an oscillatory release pattern. Swelling profiles obtained clearly indicated that these hydrogels swell slightly in a simulated gastric fluid (SGF) and strongly in a simulated intestinal fluid (SIF). Using drug metronidazole(MZ) as a model molecule, the in vitro controlled drug-release behaviors of these hydrogels were investigated. The release proûles of MZ from the hydrogel were determined by UV-Vis absorption measurement at λ max 278 nm. The metronidazole drug, was successfully loaded into the hydrogels and in vitro release studies were performed in SGF for the initial 70 min, followed by SIF until complete dissolution. The release of metronidazole was continued up to 150 min. The release mechanism of the hydrogels was also studied using the Ritger-Peppas model.

The present work focused on the design of a drug delivery system (DDS) based on pH-sensitive hydrogel. The hydrogels were prepared via graft copolymerization of mixtures of acrylic acid (AA) and 2-hydroxy ethyl methacrylate (HEMA) onto starch backbones by a free radical polymerization technique. Sodium bicarbonate (NaHCO 3) was added to function as a foaming agent under acidic conditions, rendering the hydrogels to be porous. The porous structure of the hydrogel was essential in this system to yield a large surface area so that 5-fluorouracil (5-FU) release could be facilitated. The hydrogel, thus prepared, possessed a porous structure as determined by scanning electron microscopy. The water absorbency of the hydrogels was measured in solutions with pH levels ranging from 1 to 13. The starch-based hydrogel exhibited a pH-responsiveness character such that a swelling-deswelling pulsatile behavior was recorded at pH levels of 2 and 7. Using the drug 5-FU as a model molecule, the in vitro controlled drug-release behaviors of these hydrogels were investigated. The results indicate that the main parameter affecting the drug-release behavior of hydrogels is the pH of the solution. The release rate of 5-FU from hydrogel at pH 7.4 was faster than that at pH 1.2 due to the shrinkage of the hydrogel at pH 1.2. These results suggest that a porous hydrogel could potentially be a useful local delivery system to release drugs, primarily at a specific site of body.

In this article, we synthesized of a novel graft copolymer of gelatin-based via radical polymerization mixtures of Acrylamide (AAm) and 2-Acrylamido-2-methyl propan solfonic acid (AMPS) onto gelatin backbones. The polymerization reaction was carried out in an aqueous medium and in the presence of ammonium persulfate (APS) as an initiator. The graft copolymer structures were confirmed by FTIB spectroscopy Gelatin and the graft copolymer as well as solubility characteristics of the products. The effect of grafting variables, i.e. AAm/AMPS weight ratio and concentration of APS, and Gelatin and temperature was systematically optimized to achieve a highest percent grafting possible.

A novel superabsorbent hydrogel was synthesized via crosslinking graft copolymerization of acrylacid (AA) abd buthylmethacrylate (BuMC) onto Carboxymethyl cellulose (CMC) backbones in a homogeneous solution. The methylenebisacrylamide (MBA) and Ceric amounium sulfate (CAN) were used as water-soluble crosslinker and initiator, respectively. Evidence of grafting was obtained by comparing FTIR. SEM spectra of CMC and the graft copolymer as well as solubility characteristics of the products. A mechanism for the superabsorbent hydrogel formation was also suggested. The affecting parameters onto swelling capacity of the synthesized hydrogel, i.e., concentration of AA/BuMC waight ratio, MBA as well as reaction temperature were systematically optimized for obtaining maximum absorbency as possible as. The swelling capacity of hydrogels was also measured in various salt solutions (LiCI, NaCI, KCl, MgCI 2, CaCI 2, SrCI 2, BaCI 2, and AICI 3). Due to high swelling ability in salt solutions, the hydrogel may be referred as "anti-salt superabsorbent" polymers. The overall activation energy for the graft copolymerization reaction was found to be 374 kJ/mol. The swelling kinetics of the hydrogels in distilled water was preliminary investigated.

Sadeghp M.,Science Faculty | Yarahmadi M.,Humaniti Faculty
Oriental Journal of Chemistry | Year: 2011

In this work, a novel family of pH-responsive polymeric hydrogel based on collagen was prepared. Acrylic monomers, acrylic acid (AA) and itaconic acid (IA) were simultaneously graft copolymerized onto collagen backbones by a free radical polymerization technique using ammonium persulfate (APS) as initiator and methylene bisacrylamide (MBA) as a crosslinker. A mechanism for the superabsorbent hydrogel formation was also suggested. Hydrogel formation was confirmed by FTIR spectroscopy. Results from scanning electron microscopy (SEM) observation also showed a porous structure with smooth surface morphology of the hydrogel. The swelling capacity of hydrogels was also measured in various salt solutions (LiCI, NaCI, KCl, CaCI2 and AICI3). Due to high swelling ability in salt solutions, the hydrogel may be referred as "anti-salt superabsorbent" polymers. Furthermore, the water absorbency of hydrogels was measured in solutions with pH ranged 1 to 13. The collagen-based hydrogel exhibited a pH-responsiveness character so that a swelling-deswelling pulsatile behavior was recorded at pHs 2 and 8.

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