Preparation of chitosan‐coated magnetite nanoparticles and application for immobilization of laccase

In this study, immobilization of laccase (L) enzyme on magnetite (Fe₃O₄) nanoparticles was achieved, so that the immobilized enzyme could be used repeatedly. For this purpose, Fe₃O₄ nanoparticles were coated and functionalized with chitosan (CS) and laccase from Trametes versicolor was immobilized onto chitosan‐coated magnetic nanoparticles (Fe₃O₄‐CS) by adsorption or covalent binding after activating the hydroxyl groups of chitosan with carbodiimide (EDAC) or cyanuric chloride (CC). For chitosan‐coated magnetic nanoparticles, the thickness of CS layer was estimated as 1.0–4.8 nm by TEM, isoelectric point was detected as 6.86 by zeta (ζ)‐potential measurements, and the saturation magnetization was determined as 25.2 emu g^?1 by VSM, indicating that these nanoparticles were almost superparamagnetic. For free laccase and immobilized laccase systems, the optimum pH, temperature, and kinetic parameters were investigated; and the change of the activity against repeated use of the immobilized systems were examined. The results indicated that all immobilized systems retained more than 71% of their initial activity at the end of 30 batch uses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rapid Transmutation of High-Level Nuclear Wastes in a Catalyzed Fusion-Driven System

The aim of this study is to investigate the high-level waste (HLW) transmutation potential of fusion-driven transmuter (FDT) based on catalyzed D–D fusion plasma for various fuel fractions. The Minor actinide (MA) (²³⁷Np, ²⁴¹Am, ²⁴³Am and ²⁴⁴Cm) and long-lived fission product (LLFP) (⁹⁹Tc, ¹²⁹I and ¹³⁵Cs) nuclides discharged from high burn-up pressured water reactor-mixed oxide spent fuel are considered as the HLW. The volume fractions of the MA and LLFP are raised from 10 to 20% stepped by 2% and 10 to 80% stepped by 5%, respectively. The transmutation analyses have been performed for an operation period (OP) of up to 6 years by 75% plant factor (η) under a first-wall neutron load (P) of 5 MW/m² by using two different computer codes, the XSDRNPM/SCALE4.4a neutron transport code and the MCNP4B Monte Carlo code. The numerical results bring out that the considered FDT has a high neutronic performance for an effective and rapid transmutation of MA and LLFP as well as the energy generation along the OP.     

Numerical study of effect of oxygen fraction on local entropy generation in a methane-air burner

This study considers numerical simulation of the combustion of methane with air, including oxygen and nitrogen, in a burner and the numerical solution of local entropy generation rate due to high temperature and velocity gradients in the combustion chamber. The effects of equivalence ratio (Φ) and oxygen percentage (γ ) on combustion and entropy generation rates are investigated for different Φ (from 0.5 to 1.0) andγ values (from 10 to 30%). Combustion is simulated for the fuel mass flow rate resulting in the same heat transfer rate (Q)y to the combustion chamber in each case. Numerical calculation of combustion is performed individually for all cases with the use of the Fluent CFD code. Furthermore, a computer program has been developed to calculate the volumetric entropy generation rate and the other thermodynamic parameters numerically by using the results of the calculations performed with the FLUENT code. The predictions show that the increase of Φ (or the decrease of λ) significantly reduces the reaction rate levels. Average temperature in the combustion chamber increases by about 70 and 35% with increase ofγ (from 10 to 30%) and Φ (from 0.5 to 1.0) respectively. With increase ofγ from 10 to 30%, volumetric local entropy generation rate decreases by about 9 and 4% for Φ = 0.5 and 1.0 respectively, while total entropy generation rate decreases exponentially and the merit numbers increase. The ratio of the rates useful energy transfer to irreversibility therefore improves as the oxygen percentage increases     

Views on Turkey's impending ESCO market: Is it promising?

Turkey's Energy Efficiency Law (EEL) came into force in May 2007. The EEL will transform energy policies implemented in the government and private sectors. The law and upcoming regulations will offer opportunities for the impending Energy Service Company (ESCO) market in Turkey. In this work, we briefly review the ESCO literature and its financing mechanisms in the world, and present our views with regard to the funding and related risks that are likely to be associated with the forthcoming Turkish ESCO market. These views are backed up with Turkish credit and banking market performance and the lessons learned from implementation of some EU-related projects involving the banking sector and small-and-medium-sized firms. We conclude that in order to create a promising competitive ESCO market, Turkey's policy must be to sustain its average 5% growth rate achieved lately for the coming decade, finish the structural reforms which will invite necessary capital inflows to ensure an economic stability and financing.     

Residence time distribution and flow field study of aero-shielded solar cyclone reactor for emission-free generation of hydrogen

This paper provides a thorough analysis on the flow field and Residence Time Distribution (RTD) of our “aero-shielded cyclone solar reactor” designed to generate hydrogen from solar thermal methane cracking process. The analysis has been carried out based on the results from flow dynamics, and residence time distribution by using Computational Fluid Dynamics (CFD). Kinetics is taken from the literature and the reactor volume is estimated based on a plug flow reactor assumption. Residence time distribution characteristics are obtained by gas tracer injection method, and particle tracking method. Based on the results of our flow studies, “reactors in series model” is adopted to model the aero-shielded cyclone reactor. Path lines show that operating variables have significant effect on the flow behavior inside the reactor. Results show that thermo chemical properties of the gases have effect on the flow behavior which significantly affect the mean residence time in the reactor. Results also show that the residence time, spread of the tracer by variance, and the number of reactors in series are observed to be changed by change in the flow rate, type of screening gas, and methane mole fraction in the feed.     

Preparation and characterization of Chitosan and PLGA‐based scaffolds for tissue engineering applications

Three dimensional (3D) biodegradable porous scaffolds play a crucial role in bone tissue repair. In this study, four types of 3D polymer/hydroxyapatite (HAp) composite scaffolds were prepared by freeze drying technique in order to mimic the organic/inorganic nature of the bone. Chitosan (CH) and poly(lactic acid‐co‐glycolic acid) (PLGA) were used as the polymeric part and HAp as the inorganic component. Properties of the resultant scaffolds, such as morphology, porosity, degradation, water uptake, mechanical and thermal stabilities were examined. 3D scaffolds having interconnected macroporous structure and 77–89% porosity were produced. The pore diameters were in the range of 6 and 200 µm. PLGA and HAp containing scaffolds had the highest compressive modulus. PLGA maintained the strength by decreasing water uptake but increased the degradation rate. Scaffolds seeded with SaOs‐2 osteoblast cells showed that all scaffolds were capable of encouraging cell adhesion and proliferation. The presence of HAp particles caused an increase in cell number on CH‐HAp scaffolds compared to CH scaffolds, while cell number decreased when PLGA was incorporated in the structure. CH‐PLGA scaffolds showed highest cell number on days 7 and 14 compared to others. Based on the properties such as interconnected porosity, high mechanical strength, and in vitro cell proliferation, blend scaffolds have the potential to be applied in hard tissue treatments. POLYM. COMPOS., 36:1917–1930, 2015. © 2014 Society of Plastics Engineers     

Gamification for enhancing Web 2.0 based educational activities: The case of pre-service grade school teachers using educational Wiki pages

This study seeks to uncover the effects of using gamification elements in courses that make use of a Wiki environment on the participation rates of undergraduate students in Wiki-based course activities as well as on student academic success in the course. Owing to the fact that the group of students chosen for the study consisted of pre-service grade school teachers, their opinions on the use of the Wiki environment along with its embedded gamification elements in their future careers have been sought. Of particular interest were the considerations of pre-service teachers concerning the age levels of a target audience that they believed would benefit from instruction with this particular educational tool. Following a mixed-research methodological pattern, the study was conducted in two consecutive stages. The first stage involved a quasi-experiment and the second was handled as a case study. In order to examine the long-term effects of Wiki activities supported by gamification elements on student academic success, a repeated measures analysis of variance (ANOVA) statistical test was conducted based on scores from an initial pre-knowledge test, an applied interim examination, and a final examination. In order to determine the opinions of teacher candidates regarding Wiki activities and the process of gamification, results from an open-ended questionnaire were consulted. It was eventually discovered that students in both the Wiki-only (p = 0.02) and gamified-Wiki (p = 0.00) activity groups displayed significantly greater academic success compared to a control group. Although gamification elements also caused a significant difference between the two Wiki groups in terms of the number of times content is displayed (1670 > 637) and edited (38 > 18), it was observed that participation rates fell over time in both groups. As for academic success, there was no difference between the two Wiki groups (p = 0.92). It was found that teacher candidates regard Wiki and gamification activities positively. Also, it was noted that they did not possess an adequate level of consciousness of the fact that student capabilities are an important factor in making effective use of technology.     

Developments of Multi-nanostitched 3D Carbon/epoxy Nanocomposites: Tensile/shear and Interlaminar Properties

Applied Composite Materials - Mechanical properties such as tensile, shear and interlaminar shear of multi-nanostitched three dimensional (3D) carbon/epoxy composites were studied. Introducing the...