Aflatoxin species: their health effects and determination methods in different foodstuffs

Carcinogenic and mutagenic properties of aflatoxin species are known in literature. Their intake over a long time period might be health-dangerous for human even at trace levels. It is well known that different foodstuffs can be contaminated by aflatoxin species through growing and storage. Due to the serious health effects, sensitive determination of aflatoxin species in any matrices related with the human being is very crucial at trace levels. In literature, there are sensitive techniques to analyze the different samples for the contents of their aflatoxin species. Each technique has some advantages and disadvantages over the other techniques. This review aims to summarize the different health effects of aflatoxin species, development of analytical techniques and applications of developed techniques in a variety of matrices.      

ITO films on glass substrate by sol–gel technique: synthesis,characterization and optical properties

The present paper extensively demonstrates synthesis, characterization and optical properties of semiconductor indium tin oxide (ITO) thin films on glass substrate using sol–gel technique for gas sensor applications. Turbidity, pH values, wettability and rheological properties of the prepared solutions were measured to determine solution characteristics by turbidimeter, pH meter, contact angle goniometer and rheometer machines prior to coating process. Thermal, structural, microstructural, mechanical and optical properties of the coatings were characterized by differential thermal analysis–thermogravimetry (DTA/TG), fourier transform infrarared, X-ray diffraction (XRD), scanning electron microscopy, scratch tester, refractometer and spectrophotometer. Four different solutions were prepared by changing solvent concentration. Turbidity, pH, contact angle and viscosity values of the solutions were convenient for coating process. Glass substrates were coated using the solutions of InCl₃, SnCl₂, methanol and glacial acetic acid. The obtained gel films were dried at 300 °C for 10 min and subsequently heat-treated at 500 °C for 10 min in air. The oxide thin films were annealed at 600 °C for 60 min in air. DTA/TG results revealed that endothermic and exothermic reactions are observed at temperature between 70 and 560 °C due to solvent removal, combustion of carbon based materials and oxidation of Sn and In. The spectrum of ITO precursor film annealed at 500–600 °C shows an absence of absorption bands corresponding to organics and hydroxyls. In₂Sn₂O_7−x phase was dominantly found as well as SnO₂ with low intensity from XRD patterns. It was found that surface morphologies of the film change from coating island with homogeneous structures to regular surface and thinner film structures with increasing solvent concentration. The films prepared from the solutions with 8 mL methanol have better adhesion strength to the glass substrate among other coatings. Refractive index, thickness and band gap of ITO thin films were determined to be 1.3171, 0.625 μm and 3.67, respectively.     

(137)Cs and (40)K activity concentration measurements and elemental analysis in lichen samples collected from the Giresun province of northeastern Turkey

About 21 years after the Chernobyl accident, (137)Cs and (40)K activity concentration measurements using gamma-ray spectroscopy and elemental analysis using energy dispersive X-ray spectroscopy were performed in five different lichen species collected from the Giresun province of northeastern Turkey. Being a symbiosis of algae and fungi, lichens are mostly used for environmental measurements since the fungal partner is responsible for the uptake of necessary nutrients or harmful substances, such as heavy metals of radionuclides. The gamma activity results showed that (137)Cs, an artificial radionuclide released from the Chernobyl power plant accident, is still eminent in the environment of the province. The mean activity concentrations of (137)Cs and (40)K ranged from 24 to 254 with the mean value of 102 Bq kg(-1) and from 345 to 2103 with the mean value of 1143 Bq kg(-1) in dry weight. The results of the elemental analyses showed potassium, calcium, titanium, iron, tin, and barium in different concentrations.     

A new high‐performance blue to transmissive electrochromic material and use of silver nanowire network electrodes as substrates

Synthesis of a novel, high‐performance blue to transmissive switching electrochromic material is described. The polymer (P1) was prepared by both electrochemical ( P1E ) and chemical ( P1C ) means from the corresponding monomer. The electrochemically synthesized polymer ( P1E ) revealed 64% optical contrast change (on ITO) in the visible region and very fast switching times of 0.32 s (coloration) and 0.90 s (bleaching). On the other hand, the chemically synthesized, solution processable polymer ( P1C ) also showed a high optical contrast value (49%, on ITO) with very fast switching times of 0.86 s for coloration and 0.57 s for bleaching. These high optical contrast values coupled with fast switching times place these materials along with high‐performance blue to transmissive electrochromic polymers. Significantly, these improved characteristics were achieved by side chain engineering of a known, inferior blue to transmissive polymer, PBEBT. Towards fabrication of flexible electrochromic devices, the performance of P1C was also tested on silver nanowire network electrodes. Even though the full potential of the material could not be demonstrated, a good optical contrast of 24% was achieved using these electrodes. Under the same potential range allowed by silver nanowire network electrodes, P1C on ITO showed an optical contrast of 30%. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 1680–1686     

The van Hemmen spin glass revisited

We simulated the van Hemmen spin glass model by multicanonical algorithm. The exact results for this mean-field model are reproduced. Physical quantities such as energy density, specific heat, susceptibility and order parameters are evaluated at all temperatures. We also studied an alternate model with short range interactions, which displays the many-valley picture in 2D for random variables having values ±1.On leave of the absence from Department of Physics Engineering, Hacettepe University, Ankara, Turkey.     

High Q-factor superconductor VHF antennae

Two versions of elementary antennae fabricated of high temperature superconductors (HTS) are presented. The ceramic YBa₂Cu₃O₇ strip as well as Bi₂Sr₂CaCu₂O₈ thick film have been used as radiators operating in the wavelength ranges of 5 cm and 8 mm respectively. Substantial gain and Q-factor enhancement if compared with similar metallic ones have been achieved for the HTS antennas.