Cost assessment and evaluation of various hydrogen delivery scenarios

In this paper, performance and cost assessment studies, including the stages of hydrogen storage, transmission and distribution of three different hydrogen delivery pathways are undertaken comparatively. The produced hydrogen is stored under different temperatures and pressures and then transported to the nearby cities for distribution. In addition, three different methods for the transportation of the produced hydrogen to the distribution centers are studied, which are as transportation for hydrogen by the pressurized tanks, cryogenic liquid hydrogen tanker and the gas pipelines. Moreover, the transmission options from the distribution center to the target consumer are also examined for three different conditions. As a result, the hydrogen production capacity, the levelized cost of energy distribution (in $/kg), the infrastructure costs (truck, tanker number, gas line costs, etc.) for the selected transmission scenario are calculated. Furthermore, the environmental impact (greenhouse gas (GHG) emissions) and some application parameters of the proposed system (e.g., number of hydrogen fuel stations and the distance between the stations, length of the distribution lines, etc.) are also determined. The highest levelized cost of delivery is obtained as 8.02 $/kg H₂ for the first scenario whereas the lowest cost is obtained as 2.73 $/kg H₂ for the third scenario.     

Development of a reaction mechanism for predicting hydrogen production from homogeneous decomposition of methane

In this paper, a reaction mechanism is developed to model the kinetics of hydrogen production from decomposition of methane. The pyrolysis of hydrocarbons from several combustion mechanisms is compared with experiment to obtain the elementary reactions of this mechanism. Some modifications are then made to reduce the large errors observed at a high residence time. Sensitivity analysis is performed to find the reactions with the highest effect on hydrogen production and their rate constants are changed by using other mechanisms to obtain the lowest error in hydrogen production compared to experimental data. This study shows that modifying the rate constants of the reactions of dissociation of methane to hydrogen and methyl radicals, and the formation of benzene from propargyl radicals have the highest effect on improving the results. The new mechanism reduces the error introduced from existing models for predicting the amount of hydrogen production up to 15%, depending on residence time and temperature levels.     

Determination of Antioxidant Properties of Fruit Juice by Partial Least Squares and Principal Component Regression

The multivariate calibration methods—principal component regression and partial least squares—were employed for the prediction of antioxidant capacities of fruit juices. High-performance liquid chromatography and spectrophotometric approaches were used to determine the antioxidant capacities of fruit juices. The importance of calibration design was investigated by calculating the prediction and validation errors. The influences of using independent validation sets were emphasized. Calibration design is shown to have major effect on principal component regression and partial least squares errors. The models developed on the basis of the mean-centered data were able to predict the total antioxidant activity with a precision comparable to that of the reference [2,2-azino-di-(3-ethylbenzothialozine-sulfonic acid)] method. The partial least squares model seems preferable because of its predictive and describing abilities and good interpretability of the contribution of compounds to the antioxidant capacity. The contribution of individual phenolic compounds to the antioxidant capacity was identified by high-performance liquid chromatography.     

The effects of microalloyed steel pre-heat treatment on microstructure and machinability

An extensive study was performed in finish turning of the following microalloyed steels: as received (14.3 HRc), water-cooled (44.9 HRc), air-cooled (14.41 HRc) and furnace-cooled (9.1 HRc). The turning tests were carried out using multi-layer coated cemented carbide tools at four different cutting speeds (60, 90, 120, and 150 m/min) while feedrate and depth of cut were kept constant at 0.1 mm/rev and 1 mm, respectively. The influences of workpiece microstructure and cutting speed on cutting forces and workpiece surface roughness were investigated. The worn parts of the cutting tools were also examined under a scanning electron microscope (SEM). The results showed that cutting speed significantly affected the machined surface roughness values. However, cutting forces were not influenced significantly by workpiece microstructure and cutting speed except for water cooled specimen.     

Micelle-Mediated Extraction and Flame Atomic Absorption Spectrometric Method for Determination of Trace Cobalt Ions in Beverage Samples

A new method has been developed for preconcentration of cobalt at trace levels in beverage samples using calcon carboxylic acid as chelating agent and cetyl pyridinium chloride as an auxiliary ligand and entrapped into Triton X-114 prior to its determination by flame atomic absorption spectrometry (FAAS). The main parameters affecting cloud point extraction (CPE) efficiency such as pH, concentration of the complexing agent, cationic and nonionic surfactant concentration, salt effect, the equilibrium time, and temperature were investigated and optimized. After optimization of the CPE conditions, a preconcentration factor of 60, an enhancement factor of 106, and a detection limit of 0.20 μg L⁻¹ by (R ² = 0.9978) were obtained from a calibration curve constructed in the range of 0.7–100 μg L⁻¹. The proposed preconcentration procedure was successfully applied to the determination of cobalt ions in some real samples including natural drinking water, tap water, and beer and wine samples. The accuracy and validity of the proposed CPE/FAAS method was tested by means of five repeated analysis of reference standard materials (TM-253, a low level fortified water standard for trace elements). A good agreement between analytical results (28.8 and 28.5 μg L⁻¹ with calibration curve and standard addition curve method, respectively) and certified value (27.9 μg L⁻¹) for Co (p < 0.05) were obtained and verified by means of calibration curve and standard addition curve method using CPE procedure.     

Morphology-tailored synthesis of tungsten trioxide (hydrate) thin films and their photocatalytic properties

Tungsten trioxide hydrate (3WO(3)·H(2)O) films with different morphologies were directly grown on fluorine doped tin oxide (FTO) substrate via a facile crystal-seed-assisted hydrothermal method. Scanning electron microscopy (SEM) analysis showed that 3WO(3)·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 photocatalytic activities. The best film grown using CH(3)COONH(4) as a capping agent generated anodic photocurrents of 1.16 mA/cm(2) for 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.     

Conductivity Study of Polyaniline-Cobalt Ferrite (PANI-CoFe2O4) Nanocomposite

Nano-Micro Letters - In this investigation, the structural and electrical properties of nanocomposites of polyaniline (PANI) and cobalt ferrite synthesized by hydrothermal route are reported for...     

Oxidative DNA damage correlates with carotid artery atherosclerosis in hemodialysis patients

Oxidative stress is accepted as a nonclassical cardiovascular risk factor in chronic renal failure patients. The aim of this study was to evaluate the relation between oxidative DNA damage (8‐hydroxy‐2′‐deoxyguanosine/deoxyguanosine [8‐OHdG/dG] ratio), oxidative stress biomarkers, antioxidant enzymes, and carotid artery intima‐media thickness (CIMT) in hemodialysis (HD) patients. Forty chronic HD patients without known atherosclerotic disease and 48 age‐ and sex‐matched healthy individuals were included in the study. Plasma malondialdehyde (MDA) levels and 8‐OHdG/dG ratio were determined as oxidative stress markers. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities were measured as antioxidants. CIMT was assessed by carotid artery ultrasonography. 8‐OHdG/dG ratios and MDA levels were higher; SOD and GPx activities were lower in HD patients compared to controls. HD patients had significantly higher CIMT compared to controls (0.61 ± 0.08 vs. 0.42 ± 0.05, p < 0.001). There was a significant positive correlation between CIMT and 8‐OHdG/dG ratio (r = 0.57, p < 0.01) and MDA levels (r = 0.41, p < 0.01), while there was a significant negative correlation between CIMT and SOD (r = ?0.47, p < 0.01) and GPx levels (r = ?0.62, p < 0.01). It is firstly demonstrated that CIMT is positively correlated with oxidative DNA damage in HD patients without known atherosclerotic disease.     

Tailoring insoluble nanobelts into soluble anti-UV nanopotpourris

Soluble, transparent and anti-UV nanopotpourris have been prepared by tailoring long nanobelts. The strains and layered structures facilitate the breaking of the as-synthesized nanobelts under an applied mechanical action. The developed tailoring process of nanobelts is a general top-down secondary processing of layered nanostructures at the nanoscale level, which can be expended to the modifications of layered nanowires, nanotubes and hierarchical nanostructures. By tailoring, the size, morphology and solubility are modified, which may open up an area of advanced processing of nanomaterials and hint at some potential applications. Because of the excellent solubility of the tailored nanopotpourris, they are easily dispersed in cosmetics or polymer films, which are quite useful for some anti-UV protection applications, such as anti-UV sunscreen creams and anti-UV window films for vehicles and buildings.