Influence of Al concentration on structural and optical properties of Al-doped ZnO thin films

Undoped ZnO and Al-doped zinc oxide (ZnO:Al) thin films with different Al concentrations were prepared onto Si (100) substrate by pulsed filtered cathodic vacuum arc deposition system at room temperature. The influence of doping on the structural and optical properties of thin films was investigated. The preferential (002) orientation was weakened by high aluminum doping in films. Raman measurement was performed for the doping effects in the ZnO. Atomic force microscopy images revealed that the surface of undoped ZnO film grown at RT was smoother than that of the Al-doped ZnO (ZnO:Al) films. The reflectance of all films was studied as a function of wavelength using UV–Vis–NIR spectrophotometer. Average total reflectance values of about 35 % in the wavelength range of 400–800 nm were obtained. Optical band gap of the films was determined using the reflectance spectra by means of Kubelka–Munk formula. From optical properties, the band gap energy was estimated for all films.     

Synthesis and analysis of injection‐molded nanocomposites of recycled high‐density polyethylene incorporated with graphene nanoflakes

Recycled high‐density polyethylene (HDPE) was incorporated with graphene nanoflakes in a solvent at different concentrations (0, 1, 2, 4, and 8 wt%), and then the mechanical, thermal, electrical, and surface hydrophobic properties of the resultant nanocomposites were determined using universal tensile testing, thermal comparative, capacitance bridge, and goniometer techniques, respectively. The test results revealed that the mechanical, thermal, and dielectric properties of the polymer matrix nanocomposites were increased as a function of graphene concentrations, whereas the surface hydrophobic values were slightly increased at lower concentrations and then reduced at higher concentrations. These improvements occur mainly because of the excellent properties of graphene nanoflakes, such as tensile strength (150 GPa), Young's modulus (1.0 TPa), thermal conductivity (4,840–5,300 W/m K), electrical conductivity (1.3 × 10⁶ S/cm), electrical current density (10¹³ A/cm²), surface hydrophobicity (>120°), and surface smoothness/roughness (<1 nm). The worldwide consumption of polymeric products has been drastically growing, and consequently polymeric waste materials have been rising up, as well. Although the plastic recycling and reprocessing rates are considerably high, physical properties and economical values of the recycled plastics are significantly low, limiting the reuse of recycled plastics in many industrial applications. As a result, this study provides a detailed explanation of how to improve recycled plastics into highly valued new products for applications in various industries, such as transportation, energy, electronic, construction, and so forth. POLYM. COMPOS., 36:1565–1573, 2015. © 2014 Society of Plastics Engineers     

Failure analysis of woven kevlar fiber reinforced epoxy composites pinned joints

An investigation was performed to determine the failure mode and the failure load of mechanically fastened joints in woven kevlar epoxy composite plates. Two-dimensional finite element code is developed to predict damage initiation, progression and strength of joints. Hashin, Hoffman and Maximum Stress criteria were used in this failure analysis. Experiments were performed to find the failure load and to predict the failure mode. Parametric studies were also carried out to evaluate the effect of joint geometry on this analysis. The obtained results were compared each other and comparison showed good agreement between numerical and experimental methods.     

HiSQL: A Front-end Query System for Historical Relational Databases

The paper describes a prototype system called HiSQL (Historical SQL) which extends the functionality of SQL in manipulating historical data, by providing functions for spatial and temporal processing. Conceptually the paper is divided into three parts: the first part deals with the design and architecture of the system; the second part introduces a case study (the defters); and the third part describes specific functions for spatial and temporal processing of serial documents. The paper concludes with a comparison between HiSQL and SQL and suggestions for further work. This revised version was published online in August 2006 with corrections to the Cover Date.     

A New Ultrasonic Thermostatic-Assisted Cloud Point Extraction/Spectrophotometric Method for the Preconcentration and Determination of Bisphenol A in Food,Milk, and Water Samples in Contact with Plastic Products

Bisphenol A (BPA) contamination in foods and beverages usually occurs as a result of migration from the packages that contain it. In this context, a simple, easy-to-use, and efficient method was developed for the spectrophotometric determination of BPA in food, milk, and water samples in contact with plastic products after preconcentration by ultrasonic-thermostatic-assisted cloud point extraction (UTA-CPE). The method is based on the charge transfer-sensitive complexation of BPA with 3-methylamino-7-dimethylaminophenothiazin-5-ium chloride (AzB) in the presence of cetyltrimethylammonium bromide (CTAB) at pH 8.5 and then extraction of the formed complex into the micellar phase of polyethylene glycol dodecyl ether (Brij 35). The effects of the analytical variables affecting complex formation and extraction efficiency were systematically studied and optimized. Under optimized conditions, a good linear relationship was obtained in the range of 1.2–160 μg L^?1 with a detection limit of 0.35 μg L^?1. After preconcentration of a sample of 20 mL, a sensitivity enhancement factor was found to be 180. The accuracy and reliability of the method were evaluated by recovery studies from the spiked quality control samples and intraday and interday precision studies. From the studies conducted, the extraction efficiency (E%) was in the range of 94–103% with a relative standard deviation lower than 5.2% (as RSD%, n = 5). The method was successfully applied to the preconcentration and determination of BPA from the selected sample matrices.

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Graphical Abstract Migration of bisphenol A into the foodstuffs

     

Effects of physical growth conditions on the structural and optical properties of sputtered grown thin HfO2 films

HfO₂ thin films were prepared by reactive DC magnetron sputtering technique on (100) p-Si substrate. The effects of O₂/Ar ratio, substrate temperature, sputtering power on the structural properties of HfO₂ grown films were studied by Spectroscopic Ellipsometer (SE), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, and X-ray photoelectron spectroscopy (XPS) depth profiling techniques. The results show that the formation of a SiO_x suboxide layer at the HfO₂/Si interface is unavoidable. The HfO₂ thickness and suboxide formation are highly affected by the growth parameters such as sputtering power, O₂/Ar gas ratio during sputtering, and substrate temperature. XRD spectra show that the deposited films have (111) monoclinic phase of HfO₂, which is also supported by FTIR spectra. XPS depth profiling spectra shows that highly reactive sputtered Hf atoms consume some of the oxygen atoms from the underlying SiO₂ to form HfO₂, leaving Si-Si bonds behind.     

Transition from the Steady to the Oscillatory Thermocapillary Convection in a Rectangular Container Under Various Cold Wall Temperature Effects

The transition from the steady to the oscillatory thermocapillary flow of high Prandtl number fluid in the rectangular container configuration under various cold wall temperatures effects have been studied experimentally. The fluid is heated by a thin wire placed along the free surface. The effects of buoyancy on the transport phenomenon are carefully assessed. The thermocapillary flow field is described based on a flow visualization and temperature measurement. The critical temperature difference for the onset of oscillations varies when the cold wall temperature is varied. The heat loss at the liquid free surface is identified to be responsible for this effect.     

Inhibitory effect of pollen and propolis extracts

Bee pollen and propolis were collected from Apis mellifera colonies in five regions of Turkey. The antifungal properties of methanol extracts of pollen and propolis (2% and 5% concentrations) were determined on Alternaria alternata and Fusarium oxysporium f. sp. melonis. The least active concentration towards the tested fungi was 2% concentration of both extracts. The inhibitory effect of all propolis extracts on growth of F. oxysporium and A. alternata were generally higher when compared with pollen extracts. The growth of A. alternata and F. oxysporium were not affected at both concentrations of pollens. However, F. oxysporium against propolis extracts was more sensitive than A. alternata (P < 0.01). None of the pollen extracts tested completely inhibited mycelial growth of fungi used in our experiment. Percent inhibition of both pollen concentrations against A. alternata and F. oxysporium was lower than 50%. However, both concentrations of Alanya and Bey?ehir propolis extracts were 100% effective on mycelial growth of F. oxysporium until the 7th day of incubation (P < 0.01). 2% Alanya and Bey?ehir pollen extracts completely stimulated mycelial growth of F. oxysporium on the 7th day of incubation. Both concentrations of propolis extract showed more than 50% inhibition against E. oxysporium. It is suggested that high concentrations ofpropolis extract could be used as an antifungal agent against tested fungi.     

Breast milk lead and cadmium levels from suburban areas of Ankara

The objectives of this study were (1) to evaluate levels of lead (Pb) and cadmium (Cd) in the breast milk at 2 months postpartum, (2) to investigate the relationship between Pb and Cd levels in breast milk and some sociodemographic parameters and (3) to detect whether these levels have any influence on the infant's physical status or on postpartum depression in the mothers. Pb and Cd levels in breast milk were determined by Inductively Coupled Plasma Mass Spectroscopy (ICP-MS). The median breast milk concentrations of Pb and Cd were 20.59 and 0.67 μg/l, respectively. In 125 (87%) of 144 samples, Pb levels were higher than the limit in breast milk reported by the World Health Organization (WHO) (> 5 μg/l). Breast milk Cd levels were > 1 μg/l in 52 (36%) mothers. The mothers with a history of anemia at any time had higher breast milk Pb levels than those without a history of anemia (21.1 versus 17.9 μg/l; p = 0.0052). The median breast milk Cd levels in active and passive smokers during pregnancy were significantly higher than in non-smokers (0.89, 0.00 μg/l, respectively; p = 0.023). The breast milk Cd levels of the mothers who did not use iron and vitamin supplements for 2 months postpartum were found to be higher than in those who did use the supplements (iron: 0.73, 0.00 μg/l, p = 0.023; vitamin: 0.78, 0.00 μg/l, p = 0.004, respectively). Breast milk Cd levels at the 2nd month were correlated negatively with the z scores of head circumference and the weight for age at birth (r = − 0.257, p = 0.041 and r = − 0.251, p = 0.026, respectively) in girls. We found no correlation between the breast milk Pb and Cd levels and the Edinburgh Postpartum Depression Scale scores. Breast milk monitoring programs should be conducted that have tested considerable numbers of women over time in view of the high levels of Pb in breast milk in this study.     

Pomological features, nutritional quality, polyphenol content analysis, and antioxidant properties of domesticated and 3 wild ecotype forms of raspberries (Rubus idaeus L.)

Abstract: The raspberry (Rubus idaeus L.) is an economically important berry crop that contains many phenolic compounds with potential health benefits. In this study, important pomological features, including nutrient content and antioxidant properties, of a domesticated and 3 wild (Yayla, Yavuzlar, and Yedigöl) raspberry fruits were evaluated. Also, the amount of total phenolics and flavonoids in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were calculated as gallic acid equivalents (GAEs) and quercetin equivalents (QE). The highest phenolic compounds were found in wild Yayla ecotype (26.66 ± 3.26 GAE/mg extract). Whilst, the highest flavonoids were determined in wild Yedigöl ecotype (6.09 ± 1.21 QA/mg extract). The antioxidant activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were investigated as trolox equivalents using different in vitro assays including DPPH^?, ABTS^?+, DMPD^?+, and O^??₂ radical scavenging activities, H₂O₂ scavenging activity, ferric (Fe³⁺) and cupric ions (Cu²⁺) reducing abilities, ferrous ions (Fe²⁺) chelating activity. In addition, quantitative amounts of caffeic acid, ferulic acid, syringic acid, ellagic acid, quercetin, α‐tocopherol, pyrogallol, p‐hydroxybenzoic acid, vanillin, p‐coumaric acid, gallic acid, and ascorbic acid in lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits were detected by high‐performance liquid chromatography and tandem mass spectrometry (LC‐MS‐MS). The results clearly show that p‐coumaric acid is the main phenolic acid responsible for the antioxidant and radical scavenging activity of lyophilized aqueous extracts of domesticated and wild ecotypes of raspberry fruits.