A quality assessment of public water fountains and relation to human health: a case study from Yozgat,Turkey

Public fountains are very common and everyday people appreciate the benefits a water fountain can bring. However, consumption of public fountain water in some country has decreased because of growing concerns that constituents in fountain water may have adverse effects on health. A few studies have examined the safety of public fountains, proposing only limited evidence of fountain‐related health issues in Turkey. Most of these public fountains are sourced from natural springs in Turkey. In this study, a 177 fountain water and 32 rock samples were analysed for source and quality of water. The geology of the region has the direct impact on the quality of the public fountain water. The results indicate that the level of some elements exceeded the limit values determined by WHO and US.EPA. The most striking high values were observed for iron (Fe), nickel (Ni), aluminum (Al), arsenic (As) and bromine (Br) concentrations.     

MoOx/Ag/MoOx multilayers as hole transport transparent conductive electrodes for n-type crystalline silicon solar cells

Substitution of highly doped layers with conventional transparent conductive electrodes as carrier collecting and selective contacts in conventional crystalline silicon (c-Si) solar cell configurations is crucial in increasing affordability of solar cells by lowering material costs. In this study, oxide/metal/oxide (OMO) multilayers featuring molybdenum oxide (MoO_x) and silver (Ag) thin films are developed by thermal evaporation technique, as dopant-free hole transport transparent conductive electrodes (HTTCEs) for n-type c-Si solar cells. Semidopant-free asymmetric heterocontact (semi-DASH) solar cells on n-type c-Si utilizing OMO multilayers are fabricated. The effect of outer MoO_x layer thickness and Ag deposition rate on the photovoltaic characteristics of the fabricated semi-DASH solar cells are investigated. A comparison of front side pyramid textured and flat surface solar cells is performed to optimize the optical and electrical properties. Highest efficiency of 9.3% ± 0.2% is achieved in a pyramid textured semi-DASH c-Si solar cell with 15/10/30 nm of HTTCE structure.     

Improved wear properties of magnesium matrix composite with the addition of fullerene using semi powder metallurgy

The present study aims to fabricate fullerene (C60) reinforced magnesium matrix composite via semi powder metallurgy in hot press system under high purity argon atmosphere. Improvement of wear resistance of pure magnesium with the addition of fullerene is also aimed with this study. Hardness and wear tests at room temperature were performed to investigate the mechanical effect of fullerene nanoparticles. Microstructures of fabricated composites were characterized using Scanning Electron Microscope (SEM). Results clearly show that hardness performance was improved up to 0.5 wt. % fullerene addition directly. A uniform distribution was also achieved according to the mapping and line EDX analysis for the lower content of fullerene. Agglomeration of fullerene was observed for 1 wt. % reinforced composite. Wear performances of pure magnesium were also improved when harder fullerene reinforcements incorporated into the matrix. Abrasion and oxidation were main wear mechanism for unreinforced and fullerene reinforced composites. Enhancement of hardness and wear performances might be attributed to the high specific surface area of fullerene and achievement of uniform distribution of reinforcement in magnesium matrix.     

Simple lattice model with inertia for sand piles

In this article we make a critical analysis of the model proposed by Weber, present an improvement that gives the logarithmic correction on the shape of sandpiles properly, and study the normal forces on the surface supporting a pile using the improved model.     

Synthesis of positive real feedback systems: a simple derivationvia Parrott's theorem

A simple derivation of the formulas for controller rendering a closed-loop system strongly positive real is presented. The derivation is based on Parrott's theorem and the positive real lemma. When the positive real lemma is applied to the closed loop system, a bilinear matrix inequality results. The significance of Parrott's theorem in the context of a strongly positive real synthesis problem is that it allows one to convert this bilinear matrix inequality into two linear matrix inequalities     

Effects of gonadotropin and testosterone treatments on prostate volume and serum prostate specific antigen levels in male hypogonadism

Various monosialo- and disialo-gangliosides and their derivatives were examined by delayed ion extraction matrix-assisted laser desorption ionization time-of-flight mass spectrometry (DE MALDI-TOF MS) in the reflector mode with alpha-cyano-4-hydroxycinnamic acid or 2,5-dihydroxybenzoic acid used as the matrix. Native gangliosides were generally found to give good spectra in the negative ion mode. 2,5-Dihydroxybenzoic acid was a better matrix for gangliosides than alpha-cyano-4-hydroxycinnamic acid, because this matrix seemed to minimize loss of sialic acid and carbon dioxide of gangliosides. About 1 pmol of ganglioside was able to be detected with this matrix. When "A-series" gangliosides such as GD1a and GalNAc-GD1a gave undesirable extra peaks probably due to loss of sialic acid besides molecule-related ion peaks, the methyl-esterification of the gangliosides at the carboxyl groups of sialic acids was found to be necessary to obtain good DE MALDI-TOF mass spectra in the positive ion mode. In contrast, "B-series" gangliosides such as GD1b, GD2, and GD3 gave rise to major dehydrated molecule-related ion [M-H2O-H]- peaks in the negative ion mode without the pretreatment of methyl-esterification. The DE MALDI-TOF mass spectrometric analysis enabled us to distinguish between GD1a and GD1b, which have the same molecular weight. It was also found that not only a purified sample, but also a mixed sample of various gangliosides was amenable to the identification of them by DE MALDI-TOF MS.     

E-learning adoption of academicians: a proposal for an extended model

From the beginning of the e-learning technology era, many concerns arose regarding the use of e-learning in everyday academic processes. Thus, in recent years, a number of studies were conducted on e-learning acceptance, mostly with the use of Unified Theory of Acceptance and Use of Technology (UTAUT) Model. Current study investigates the determinants of acceptance of academic e-learning technologies with the use of proposed modified UTAUT model. The basic UTAUT model was supplemented by the examined new determinants: system interactivity and the area of scientific expertise. Therefore, the paper contributes to UTAUT theory, applied in e-learning, by utilising empirical research with a modified UTAUT model including these two new variables. This study confirmed the hypotheses related to the effects of performance expectancy, effort expectancy, and system interactivity on behavioural intention to use e-learning technologies, and also stated that the area of scientific expertise does not have a direct impact on the intention to use e-learning technologies. The research model has been tested in an academic environment in Turkey.     

Equilibrium studies on the adsorption of reactive azo dyes into zeolite

Zeolite was used as a low-cost adsorbent to evaluate its ability to remove color from textile effluents. The zeolit (clinoptilolite) used in this study is a natural clay mineral from the Gbrdes region of Turkey. The adsorption of reactive dyes into zeolite was investigated by a series of batch adsorption experiments. Three reactive dyes (Everzol Black, Everzol Red, Everzol Yellow) were used in laboratory studies. Adsorption test were carried out as a function of solids concentration, conditioning time and dye concentration. The degree of hydrophilicity was found to play an important role in the uptake of reactive dyes. The adsorption results indicated that natural zeolite has a limited adsorption capacity for reactive dyes but can be distinctly improved by modifying its surfaces with quaternary amines. A comparison of natural and modified zeolites at 5% solids concentration indicated that, while the adsorption densities of dyes with natural zeolite yielded negative or slightly positive values, those with modified zeolite gave adsorption densities in the range of 2.9 to 7.6 mg/g.     

OPTIMIZATION OF LEACHING OF COPPER FROM OXIDIZED COPPER ORE IN NH3-(NH4)2SO4 MEDIUM

Studies were carried out for selective leaching of Cu with simultaneous avoidance of iron dissolution during leaching of oxidized copper ore in an aqueous NH₃-(NH₄)₂SO₄ system. The effects of leaching parameters, such as ammonia concentration, ammonium sulphate concentration, leaching time, and solid-to-liquid ratio, were investigated on leaching of copper. A 2ⁿ factorial experimental design method in the dissolution experiments was used. In addition, the “Steepest Ascent” method was also applied to determine the optimum leaching conditions. It was observed that the most effective parameters on the leaching of copper were ammonia concentration and leaching time. Only 0.17% of iron in ore was dissolved in ammonia and ammonium sulphate medium. The optimum conditions established for maximum copper recovery were: ammonia concentration 2.824 mol L^-1, ammonium sulphate concentration 0.236 mol L^-1, solid-to-liquid ratio 0.167 g mL^-1, leaching time 2 h. Fixed parameters chosen in the experiments were: room temperature, average particle size 2.8 mm, stirring speed 500 rpm. Under the optimum conditions established for maximum copper recovery, the percentage of leached copper was 98.87.