A new dynamic renal phantom and its application to scintigraphic studies for pixel basis functional radionuclide imaging

We report the design, synthesis and antiviral evaluation of a series of lipophilic, masked phosphoramidate derivatives of the anti-human immunodeficiency virus (HIV) nucleoside analogue d4T, designed to act as membrane-soluble prodrug forms for the free nucleotide. In particular, we report a series of 12 novel compounds with systematic variation in the structure of the carboxylate ester function. In order to rationalize the changes in antiviral action with variation of this moiety we applied our recently developed 31P NMR-based assay for carboxyesterase lability to this series. However, no clear positive correlation emerged, indicating that, at least within this series, factors other than simple esterase lability may be the major determinants of antiviral potency.     

Equilibrium, thermodynamic and kinetic studies for the biosorption of aqueous lead(II), cadmium(II) and nickel(II) ions on Spirulina platensis

The biosorption of lead(II), cadmium(II) and nickel(II) ions from aqueous solution by Spirulina platensis was studied as a function of time, concentration, temperature, repetitive reactivity, and ionic competition. The kinetic results obeyed well the pseudo second-order model. Freundlich, Dubinin Radushkevich and Temkin isotherm models were applied in describing the equilibrium partition of the ions. Freundlich isotherm was applied to describe the design of a single-stage batch sorption system. According to the thermodynamic parameters such as DeltaG degrees, DeltaH degrees and DeltaS degrees calculated, the sorption process was endothermic and largely driven towards the products. Sorption activities in a three metal ion system were studied which indicated that there is a relative selectivity of the biosorbent towards Pb2+ ions. The measurements of the repetitive reusability of S. platensis indicated a large capacity towards the three metal ions.     

Evaluation of ornamental plant resources to urban biodiversity and cultural changing: A case study of residential landscapes in Trabzon city (Turkey)

The residential vegetation features in urban landscapes play an important role as indicators regarding urban biodiversity potential and cultural changing. They also include ornamental resources in the context to landscape appreciation for human environment. Therefore, this paper provides quantitative information on the distribution of plant species in urban residential landscape areas of Trabzon city (Turkey). In a total of 218 sampled areas, 274 plants species belonging to 70 families were surveyed with respect to residential use types of the city. The study results showed that among the species recorded in five residential type (traditional housing, detached housing, villa, apartment blocks and sites, mass housing for employees), non-native taxa frequency of a total species are much and dominantly represent residential landscape structure. Additionally, the species richness and diversity is positively related to new urban development areas. But, it was clearly determined that the vegetation structure has tended to ornamental purposes different from traditional residential gardens including fruit and other benefiting species. Consequently, it can be evidence that the residential vegetation is ornamental plant resources to urban biodiversity and that the distribution of the species in urban landscapes follows necessities of city and human quality.     

Characterization of the uptake of aqueous Ni ions on nanoparticles of zero-valent iron (nZVI)

This study investigates the fixation of aqueous Ni²⁺ ions by nanoparticles of zero-valent iron (nZVI) prepared using the borohydride reduction method. The uptake of Ni²⁺ was tested under various experimental conditions like initial concentration, time, pH, and repetitive application of nZVI. Part of the experiments was devoted to comparing the extent of uptake of Ni²⁺ ions with those of Cu²⁺, Cd²⁺, Zn²⁺, and Sr²⁺ ions, which belong to a wide range of standard reduction potentials. Particle size analysis of nZVI in aqueous solution indicated that the material suffered extensive aggregation, much above the extent of aggregation known for dry nZVI. Nevertheless, nZVI showed fast uptake kinetics and very high uptake capacity. The overall results demonstrated the high fixation capability of nZVI towards the studied transition metal ions in aqueous solution. The same conclusion is, however, not valid for the removal of Sr²⁺ ions.     

VULCAN-SUPPORTED Pt ELECTROCATALYSTS FOR PEMFCs PREPARED USING SUPERCRITICAL CARBON DIOXIDE DEPOSITION

In this study, supercritical carbon dioxide (scCO₂) deposition was used to prepare vulcan-supported Pt (Pt/Vulcan) electrocatalysts for proton exchange membrane fuel cells (PEMFCs), and the effects of process variables on the properties of the electrocatalysts were investigated. The two different methods used to reduce the organometallic precursor were thermal reduction in nitrogen at atmospheric pressure and thermal reduction in scCO₂. In the former method, the maximum Pt loading achieved was 9%, and this was governed by the adsorption isotherm of the Pt precursor between the scCO₂ phase and the Vulcan phase. By using the latter method, higher Pt loadings of 15% and 35% could be achieved. The Pt/Vulcan catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and cyclic voltammetry (CV). The average particle sizes for Pt/Vulcan 9%, 15%, and 35% catalysts were 1.2, 1.3, and 2 nm, respectively. Electrochemical surface areas obtained from CV data were found to vary with the Pt loading.     

EFFECT OF GAS DIFFUSION LAYER CHARACTERISTICS AND ADDITION OF PORE-FORMING AGENTS ON THE PERFORMANCE OF POLYMER ELECTROLYTE MEMBRANE FUEL CELLS

The performance of five layer membrane electrode assemblies having different characteristics of gas diffusion layers was determined at 70°C cell temperature and ambient pressure. The maximum power density at 0.6 V was 0.36 W/cm² for the membrane electrode assembly prepared with the gas diffusion layer having minimum thickness (SGL BC 30 type). On the other hand, the maximum power density at 0.5 V was 0.44 W/cm² for the membrane electrode assembly prepared with SGL BC 34 type gas diffusion layer. It was found that resistance of a membrane electrode assembly is strongly dependent on gas diffusion layer thickness. Moreover, membrane electrode assemblies prepared with carbon paper gas diffusion layers resulted in higher performance than the assembly prepared with carbon cloth gas diffusion layer. Addition of pore-forming agents, which were ammonium carbonate, ammonium bicarbonate, ammonium sulfonate, and ammonium oxalate, to the catalyst ink lowered the performance.     

Visual perception of tree forms

This study, made in the cities of Adapazar?, Duzce, and Bolu, has three fundamental goals. The first one is the evaluation of visual quality and strength of each tree form, second is the determination of visual quality and strength of different tree forms next to each other, and the third goal of this study is determining the effects of personal characteristics to the perception of tree forms. To reach these three goals the semantic differential method was used to evaluate graphical visions of tree forms. According to the findings, trees with pyramid forms have the most effective visual quality and strength. Pyramid-formed tree combinations have higher visual quality and strength than mixed combinations do. At the same time personal characteristics are effective on the visual perception of tree forms. A strong relationship between the amount of area per person in the cities the participants live in and their visual perception of tree forms has been found.     

Comparison of physicochemical characteristics and photofermentative hydrogen production potential of wastewaters produced from different olive oil mills in Western-Anatolia,Turkey

Olive oil extraction produces a dark-colored wastewater that contains nutrients that can be further processed using biotechnology, in parallel with treatment for disposal. For instance, olive mill wastewater (OMW) can be used as a substrate for photofermentative hydrogen production by purple bacteria. A comparative study was investigated with several OMW samples from different olive oil mills in Western-Anatolia, Turkey. The composition of OMW varies significantly for each mill; thus, a detailed physicochemical analysis of each sample has been carried out. Subsequently, samples were assessed for their functioning in anaerobic photofermentative hydrogen production by Rhodobacter sphaeroides O.U.001. The highest hydrogen production potential (19.9 m³ m^?3) was obtained by the OMW sample with the highest organic content (mainly acetic acid, 9.71 kg m^?3) and the highest carbon-to-nitrogen (C/N) molar ratio (73.8 M M^?1). The organic content was found to be composed of primarily acetic, aspartic, and glutamic acids. There was a linear relationship between C/N ratio and hydrogen production potential across the different OMW samples. This study is unique due to the wide range of analyses of OMW samples and the comparison of many parameters for hydrogen production from wastewater. The results obtained throughout this study can aid in the design of systems using wastewater for biohydrogen production. Particularly, the C/N ratio was found to be the best parameter for choosing a proper substrate.     

Effects of sulfonated polyether-etherketone (SPEEK) and composite membranes on the proton exchange membrane fuel cell (PEMFC) performance

Sulfonated polyether-etherketone (SPEEK) has a potential for proton exchange fuel cell applications. However, its conductivity and thermohydrolytic stability should be improved. In this study the proton conductivity was improved by addition of an aluminosilicate, zeolite beta. Moreover, thermohydrolytic stability was improved by blending poly-ether-sulfone (PES). Sulfonated polymers were characterized by H-NMR. Composite membranes prepared were characterized by Electrochemical Impedance Spectroscopy (EIS) for their proton conductivity. Degree of sulfonation (DS) values calculated from H-NMR results, and both proton conductivity and thermohydrolytic stability was found to strongly depend on DS. Therefore, DS values were controlled time in the range of 55–75% by controlling the reaction time. Zeolite beta fillers at different SiO₂/Al₂O₃ ratios (20, 30, 40, 50) were synthesized and characterized by XRD, EDX, TGA, and SEM. The proton conductivity of plain SPEEK membrane (DS = 68%) was 0.06 S/cm at 60 °C and the conductivity of the composite membrane containing of zeolite beta filled SPEEK was found to increase to 0.13 S/cm. Among the zeolite Beta/SPEEK composite membranes the best conductivity results were achieved with zeolite beta having a SiO₂/Al₂O₃ ratio of 50 at 10 wt% loading.