Trade and convergence : an evaluation for Turkey and EU-15

This thesis investigates the relation between trade and convergence for Turkey and EU-15 in the period 1980-2008. The countries and time period are selected because Turkey has intensive trade relation with EU-15, and these economies had experienced conversion in their economic structures and adopted liberal economic policies, as well as liberal trade policies in this period. Using panel data methods two equations are estimated; an income dispersion equation for the impact of bilateral trade on per capita income differences and a gravity model of trade for the impact of per capita income differences on bilateral trade. Overall findings of this study give strong evidence for the hypothesis that trade causes convergence, whereas weaker support for the thesis that convergence causes trade.M.S. - Master of Scienc

Improved Performance of Ceramic Solar Absorber Particles Coated with Black Oxide Pigment Deposited by Resonant Acoustic Mixing and Reaction Sintering

Spherical particles based on bauxite-type raw materials, commonly referred to as proppants, are state-of-the-art for particle receivers of concentrated solar power plants. Particles are heated in a fluidized reactor by focused sunlight and are transported to a heat-exchanger or a storage tank. Therefore, key properties for absorber particles are high solar absorptance and mechanical endurance. Due to their relatively poor content of color-giving transition-metal cations, bauxite-derived proppants show limited solar absorptance, which is even deteriorating by long-term heat exposure. A deep-black Cu, Mn, Fe- pigment with a spinel structure was employed to coat standard proppants in order to improve solar absorptance. The coating process was performed by high-energy, high-speed mixing of proppants and small quantities of spinel powders in a resonant acoustic mixer. A continuous powder coating is achieved by electrostatic attraction between the proppant surface and the coating particles. Consolidation and strong attachment of the coating is achieved by the subsequent sintering beyond the spinel melting temperature. Chemical reaction and bonding between spinel coating and proppant lead to the incorporation of Al, Mg and Ti into the spinel structure. Coated bauxite proppants exhibit a significantly improved, long-term stable solar absorption accompanied by a promising abrasion resistance. The presented coating methodology is considered to be scalable to industrial production

Processing of Rh-doped perovskite protective filters for selective gas sensing

Owing to its excellent properties, BaTiO3 is used for manufacturing of thermistors and dielectric ceramic capacitors, photocatalysis, and in gas sensing. The incorporation of precious metals into the perovskite structure enables the stabilization of BaTiO3 catalysts due to the self-healing mechanisms: the formation of well-dispersed metal nanoparticles under reducing conditions and re-incorporation of metal nanoparticles into the crystal lattice under oxidizing environments. This concept is successfully proven for gas sensing/monitoring of reformate products (CO and H2 ) and during hydrogen separation and purification. Significant decomposition of traditional SnO2 sensors under such reducing conditions necessitates the use of protective coatings to improve the performance as well as avoidance of sensing layer degradation. In this sense, the perovskite group of materials display several advantages such as: ease removal of oxygen, oxygen vacancies, electron mobility, and valence control that could improve gas sensing. This work reports on the synthesis of Rh-incorporated BaTiO3 by oxalate-assisted co-precipitation method and processing into microgranules for better application of protective filters on to gas sensors. The synthesis process was performed in two steps: (1) preparation of precursor solutions with following mixing; (2) co-precipitation by pouring an oxalic acid ethanol solution in the cationic precursor solution with subsequent precipitate filtration, drying and calcination. The micro-granulation process is carried out in a laboratory spray-dryer. Soluble organic polymers are added as processing-aids as well as sacrificial pore-formers that lead to a structural porosity that enhances gas diffusion within the Rh-incorporated BaTiO3 granulates

Identification of protein-protein interaction bridges for multiple sclerosis

Motivation: Identifying and prioritizing disease-related proteins is an important scientific problem to develop proper treatments. Network science has become an important discipline to prioritize such proteins. Multiple sclerosis, an autoimmune disease for which there is still no cure, is characterized by a damaging process called demyelination. Demyelination is the destruction of myelin, a structure facilitating fast transmission of neuron impulses, and oligodendrocytes, the cells producing myelin, by immune cells. Identifying the proteins that have special features on the network formed by the proteins of oligodendrocyte and immune cells can reveal useful information about the disease.Results: We investigated the most significant protein pairs that we define as bridges among the proteins providing the interaction between the two cells in demyelination, in the networks formed by the oligodendrocyte and each type of two immune cells (i.e. macrophage and T-cell) using network analysis techniques and integer programming. The reason, we investigated these specialized hubs was that a problem related to these proteins might impose a bigger damage in the system. We showed that 61%-100% of the proteins our model detected, depending on parameterization, have already been associated with multiple sclerosis. We further observed the mRNA expression levels of several proteins we prioritized significantly decreased in human peripheral blood mononuclear cells of multiple sclerosis patients. We therefore present a model, BriFin, which can be used for analyzing processes where interactions of two cell types play an important role

Characterization of Defined Pt Particles Prepared by Ultrasonic Spray Pyrolysis for One-Step Synthesis of Supported ORR Composite Catalysts

Polygonal Pt nanoparticles were synthesized using ultrasonic spray pyrolysis (USP) at different precursor concentrations. Physicochemical analysis of the synthesized Pt particles involved thermogravimetric, microscopic, electron diffractive, and light absorptive/refractive characteristics. Electrochemical properties and activity in the oxygen reduction reaction (ORR) of the prepared material were compared to commercial Pt black. Registered electrochemical behavior is correlated to the structural properties of synthesized powders by impedance characteristics in ORR. The reported results confirmed that Pt nanoparticles of a characteristic and uniform size and shape, suitable for incorporation on the surfaces of interactive hosts as catalyst supports, were synthesized. It is found that USP-synthesized Pt involves larger particles than Pt black, with the size being slightly dependent on precursor concentration. Among ORR-active planes, the least active (111) structurally defined the synthesized particles. These two morphological and structural characteristics caused the USP-Pt to be made of lower Pt-intrinsic capacitive and redox currents, as well as of lower ORR activity. Although being of lower activity, USP-Pt is less sensitive to the rate of ORR current perturbations at higher overpotentials. This issue is assigned to less-compact catalyst layers and uniform particle size distribution, and consequently, of activity throughout the catalyst layer with respect to Pt black. These features are considered to positively affect catalyst stability and thus promote USP synthesis for improved properties of host-supported Pt catalysts

Reticulated porous perovskite structures for thermochemical solar energy storage

The inherent capability of concentrated solar power (CSP) plants for sensible thermal energy storage ensures their continuous operation and is considered their most crucial competitive edge versus other renewable energy sources. The storage density of air-operated CSP plants can be significantly increased by hybridizing sensible with thermochemical storage of solar heat, exploiting reversible air–solid oxide reduction–oxidation reactions. Thermochemical storage-relevant-protocols testing of in-house manufactured lab-scale reticu-lated porous ceramic foams made entirely of CaMnO3 perovskite reveals fully reversible reduction-oxidation in up to 46 cycles between 300 and 1100 °C under air, without any deterioration of the foams’ structural integrity and exploitable endothermic/exothermic heat effects between 890 and 920 °C linked to an orthorhombic-to-cubic phase transition. Dilatometry experi-ments with CaMnO3 bars under identical cyclic conditions demonstrate the correlation of this phase transition to an increase in the thermal expansion coefficient but nevertheless, complete recovery of the initial specimen dimen-sions upon completion of a full heat-up/cooldown redox cycle. The possibility of shaping into sturdy reticulated porous ceramic structures which exhibit complete dimensional reversibility upon cyclic redox operation, combined with the low cost, earth abundance and environmentally benign character of the constituting elements, render such perovskite compositions extremely attractive for the manufacture of large-scale porous structured objects for exploitation in various thermochemical processes

Improved Performance of Ceramic Solar Absorber Particles Coated with Black Oxide Pigment Deposited by Resonant Acoustic Mixing and Reaction Sintering

Spherical particles based on bauxite-type raw materials, commonly referred to as proppants, are state-of-the-art for particle receivers of concentrated solar power plants. Particles are heated in a fluidized reactor by focused sunlight and are transported to a heat-exchanger or a storage tank. Therefore, key properties for absorber particles are high solar absorptance and mechanical endurance. Due to their relatively poor content of color-giving transition-metal cations, bauxite-derived proppants show limited solar absorptance, which is even deteriorating by long-term heat exposure. A deep-black Cu, Mn, Fe- pigment with a spinel structure was employed to coat standard proppants in order to improve solar absorptance. The coating process was performed by high-energy, high-speed mixing of proppants and small quantities of spinel powders in a resonant acoustic mixer. A continuous powder coating is achieved by electrostatic attraction between the proppant surface and the coating particles. Consolidation and strong attachment of the coating is achieved by the subsequent sintering beyond the spinel melting temperature. Chemical reaction and bonding between spinel coating and proppant lead to the incorporation of Al, Mg and Ti into the spinel structure. Coated bauxite proppants exhibit a significantly improved, long-term stable solar absorption accompanied by a promising abrasion resistance. The presented coating methodology is considered to be scalable to industrial production

Alfa-trikalsiyum fosfat esasli hibrit kemik benzeşikleri: çimento davranımı ve mekanik özelliklerin belirlenmesi.

The main theme of this thesis was to establish materials science and chemical issues for developing a self-hardening cement system, for potential use in bone defect filling operations. The cement comprises of a ceramic powder alpha-tricalcium phosphate (-TCP, -Ca3(PO4)2) which hardens into inorganic ceramic part of the natural bone tissue, i.e. calcium deficient hydroxyapatite (CDHAp, Ca9(HPO4)(PO4)5(OH)) upon hydration. One of the primary objectives of this study therefore was, synthesis of phase pure -TCP by solid state reactions, and investigation of its’ hydraulic reactivity at around physiological temperature (37 °C) and evaluating the microstructural and mechanical changes upon cement conversion. These were accomplished by isothermal calorimetry studies and additional analytical characterization including x-ray diffraction, electron microscopy, chemical spectroscopy and mechanical testing. Additionally, in order to improve the strength of the hydration product, -TCP based hybrid cement blends were obtained by the addition of an inorganic (calcium sulfate hemihydrate, CSH, CaSO4½H2O) or an organic (polycaprolactone, PCL, (C6H10O2)n) component. -TCP:CSH and -TCP:PCL hybrid cements were again converted into CDHAp:calcium sulfate dihydrate (CaSO42H2O, CSD) or CDHAp:PCL cement-end products by hydration at 37 °C. For both systems, comparative and parametric studies were carried out to elucidate effect of these additives on hydraulic reactivity and mechanical properties of -TCP cements. It was found that CSH dramatically suppresses -TCP→CDHAp conversion and retards setting reaction. However, CSH addition significantly improves strength of cement-end products. The fracture strength of cement end product of pure -TCP was increased from 4.5±0.1 MPa up to 9.28±0.1 MPa upon addition of 25 wt. % CSH, as evaluated by diametral compressive tests. -TCP:PCL hybrids were also investigated in terms of reaction kinetics, microstructural and mechanical properties. Isothermal calorimetry analysis revealed that PCL postpones -TCP→CDHAp conversion as also evidenced by detailed microstructural and phase analyses. Meanwhile, PCL addition improved mechanical integrity of the hardened mass leading to a maximum fracture strength value of 6.54±0.1 MPa when added in optimum amount (3 wt. %).M.S. - Master of Scienc