Importance of pore size in high-pressure hydrogen storage by porous carbons

Development of high-capacity hydrogen-storage systems utilizing physisorption at high pressure and low temperature is hindered by poor understanding of the pore size/shape requirements for achieving the maximum hydrogen uptake. Tuning the carbon structure and pore size of carbide-derived carbons (CDCs) with high accuracy by using different starting carbides, chlorination temperatures and activation temperatures allows rational design of carbon materials with increased hydrogen-storage capacity. Systematic experimental investigation of a large number of CDCs with controlled pore size distributions and specific surface area (SSA) shows that pores larger than ∼1.5 nm contribute little to hydrogen storage. It has been experimentally demonstrated that, just as at ambient pressure, pores of 0.6–0.7 nm in diameter provide the largest H₂ uptake per unit SSA at elevated pressures and liquid nitrogen temperatures. The effect of pore size was stronger than the effect of surface chemistry on the hydrogen uptake.     

Determination of Boza's Organic Acid Composition as it is Affected by Raw Material and Fermentation

In the current study boza, a low-alcohol-content beverage, is produced from rice, maize, millet and wheat flours by spontaneous fermentation at 24 ± 1°C for 24 h. During the fermentation and storage period, changes in total titritable acidity, pH, alcohol and organic acid profiles, and sensory properties were determined. The major organic acids were found as oxalic, lactic, pyruvic, and acetic acids. Even though the ratings of sensory parameters were not within wide limits, they were significantly affected by storage time. Maize boza scored higher due to the similarity in its colour and flavour to that sold in the market.     

Role of post-sulfonation of poly(ether ether sulfone) in proton conductivity and chemical stability of its proton exchange membranes for fuel cell

Commercially available poly(ether ether sulfone), PEES, was directly sulfonated using concentrated sulfuric acid at low temperatures by minimizing degradation during sulfonation. The sulfonation reaction was performed in the temperature range of 5–25 °C. Sulfonated polymers were characterized by FTIR, ¹H NMR spectroscopy and ion exchange capacity (IEC) measurements. Degradation during sulfonation was investigated by measuring intrinsic viscosity, glass transition temperature and thermal decomposition temperature of sulfonated polymers. Sulfonated PEES, SPEES, membranes were prepared by solvent casting method and characterized in terms of IEC, proton conductivity and water uptake. The effect of sulfonation conditions on chemical stability of membranes was also investigated via Fenton test. Optimum sulfonation condition was determined to be 10 °C with conc. H₂SO₄ based on the characteristics of sulfonated polymers and also the chemical stability of their membranes. SPEES membranes exhibited proton conductivity up to 185.8 mS cm⁻¹ which is higher than that of Nafion 117 (133.3 mS cm⁻¹) measured at 80 °C and relative humidity 100%.     

Oxygen transport and surface active properties of silicone containing copolymers of methyl methacrylate II

New organofunctional siloxanes from γ-methacryloxypropyltrimethoxysilane (MPTMS) were synthesized by transesterification of methoxy groups with linear high alcohols, ether alcohols, and α-hydroxyacids. The factors affecting the substitution ratios were determined. These siloxanes were copolymerized with methyl methacrylate (MMA), crosslinked with ethylene glycol dimethacrylate (EGDM) in order to examine the effect of substituted groups to the oxygen permeability coefficient (P_d) and surface free energy properties of the resultant copolymers. The substitution of the oxygen containing polar groups decreased the oxygen permeability due to the interactions between polar groups decreasing the free volume. However, these groups increased the polar component of surface free energy (γ) and thus total surface free energy (γ_S). The hydrophilicity of the carbitol and 2-ethoxyethanol containing siloxane-MMA copolymers was found to be suitable for biomedical applications.     

The characterisation of the polyethylene-polystyrene-divinylbenzene interpolymer cation-exchange membranes in the electrolysis of borax solutions

The synthesis and the characterization of the PE-PS-DVB interpolymer cationexchange membranes in the electrolysis of borax solutions to produce boric acid and sodium hydroxide simultaneously was carried out. The characterization of the teflon based “Nafion 324” and polystyrene-DVB based “Permaplex C-20” membranes was also performed in the same system for comparison. The DVB contents were varied between 3 – 12% (by wt. in total monomers) and the increase of the cross-links resulted in the decrease of the water contents and ionexchange capacities of the membranes. The PE present in the membrane acted as a barrier for electroosmotic water transport. The membranes with high DVB contents showed better electrolysis performance due to their low water contents and low electroosmotic water transport properties. The use of the interpolymer membrane containing 11.6% DVB resulted in high current efficiency and high sodium cation dynamic transport number and worked satisfactorily at the process conditions of borax electrolysis.     

Identification of metabolic correlates of mild cognitive impairment in Parkinson's disease using magnetic resonance spectroscopic imaging and machine learning

Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate metabolic changes of mild cognitive impairment in Parkinson’s disease (PD-MCI) using proton magnetic resonance...     

Determination of acceptable operating cost level of nuclear energy for Turkey's power system

Generally, it is very difficult to assess the true operating cost of an electrical power unit in the countries where there is little or no operational experience. Since Turkey has no experience on operating a nuclear unit, operating costs of a nuclear unit is uncertain for use in generation expansion planning (GEP). Furthermore, there is a disagreement of whether it is cheap or not. In this study, an acceptable level of operating cost of nuclear units is determined for Turkey's power system. It is aimed to find a numerical value for nuclear operating cost at which nuclear is able to compete with other energy sources. Seven types of units are chosen as candidate units to the power system. Mixed-integer programming (MIP) is used as a mathematical model of generation expansion planning. The model consists of the cost function that minimizes the construction and operating costs and the reliability constraints. Adaptive simulated annealing genetic algorithm (ASAGA) is used for optimization algorithm to determine the types, times, and number of candidate units which meet forecasted demand within a pre-specified reliability criterion over the planning horizon from 2006 to 2025. In the case studies, a high level of nuclear energy operating cost is taken and then the cost is gradually lowered. Optimizations are made for each level of nuclear operating costs within four different scenarios and the quantities of nuclear capacity selected by optimizations are recorded. It is determined that, nuclear energy is able to compete with other energy sources when the operating cost is less than 210$/kWh yr or 2.4cent/kWh.     

Incidence of Listeria monocytogenes and Escherichia coli O157:H7 in two Kasar Cheese processing environments

This study was designed to determine the presences of two environmental pathogens in two dairy factories in Sakarya, Turkey. A total of 264 environmental samples, raw milk and cheese samples were taken at four different seasons. According to the results, Listeria monocytogenes or Escherichia coli O157:H7 was isolated from 26 or 2.7% of the samples collected from both factories, respectively. None of the cheese or curd samples were found to be positive for Listeria or E. coli O157:H7. However, 50% of raw milk samples contained Listeria innocua. Listeria was mostly isolated from the swap samples taken from the drains or the floors in processing or packaging areas. However, E. coli was also isolated from the swap samples taken from the workers’ hands and gloves as well as the drains and the floor. Only one raw milk sample contained E. coli O157:H7. A higher prevalence of both pathogens was observed in the summer months than in the other months.     

Surface Waves Due to Geometrical Discontinuities over Ground

The “ground wave” measured with the receiving antenna is actually inhomogeneous lateral wave, guided by the homogeneous plane wave which propagates along the surface of the ground and they have strong effect in communication systems. In this study, we examine surface waves due to geometrical discontinuities over the ground. This is done by simulating the problem as a diffraction phenomena. The boundary value problem leads to vector Wiener-Hopf equation which is reduced to scalar form and solved by standard techniques. The asymptotic expressions for the diffraction are obtained by evaluating the field integrals asymptotically. Surface waves and related currents are analyzed by using Wiener-Hopf technique in detail. Some numerical examples are also presented.