Observation of crack microstructure in oxides and its correlation to oxidation and hydrogen-uptake by 3D FIB Tomography – case of Zr-ZrO2 in reactor

Abstract

Zirconium based alloys are used as fuel claddings in Light Water Reactors due to their good resistance to degradation and low neutron absorption cross section. However, life limiting processes occur during the service of the cladding such as oxidation and hydrogen-uptake. During the oxidation of the material, hydrogen enters the metal and it precipitates as brittle hydrides. In this study the 3D microstructure of a high burn-up and a low-burnup LK3/L Zircaloy-2 cladding is characterized and compared using FIB Tomography. 3D reconstruction of the oxides of the claddings shows that the crack volume fraction increases with the number of cycles in the reactor, reducing its protectiveness against further corrosion and H-uptake. The visualization of the metal-oxide interface revealed that the oxidation of the hydrides in the metal could induce crack formation in the oxide and therefore it could be one of the causes of the increasing oxidation and H-uptake in this material.     

Anatomical connectivity changes in bipolar disorder and schizophrenia investigated using whole-brain tract-based spatial statistics and machine learning approaches

Neural Computing and Applications - Schizophrenia and bipolar disorder have similar clinical features. Their differential diagnosis is crucial because each has different prognostic and therapeutic...     

Designing an electronic performance support system for technology-rich environments

This study aims to design and validate an electronic performance support system that enables educators to use instructional technologies effectively and efficiently. The study was designed and conducted using developmental research methods and with the participation, at different stages, of educators and educational technology and software experts. The tangible product of the designed system is a session plan independent of the content. The system’s activity database contains 44 activities. The system works as follows. Based on the learning outcome, student, educator, and environment characteristics, activities not deemed suitable are eliminated, the most suitable activities are presented for the educator to select, and the educator makes a selection. The educator then accesses a session plan produced by the system and can edit this plan as desired. The system has additional features that were created based on the opinions of educators and educational technology experts. These features are tools for supporting academic, technical, administrative, and professional cooperation. To validate the designed system, the views and recommendations of educators and software and educational technology experts were collected. All three groups confirmed the validity of the design. Nevertheless, based on the feedback received, improvements were made before giving the design its final shape.     

Biosynthesis of gold nanoparticles using marine bacteria and Box–Behnken design optimization

Gold nanoparticles are exciting materials because of their potential applications in optics, electronics, biomedical, and pharmaceutical fields. In recent years, environmentally friendly, low-cost biosynthesis methods with bio-applicable features have continued to be developed for the synthesis of gold nanoparticles. In the present study, an actinobacterial strain was isolated from the Petrosia ficiformis (Poiret 1798) sponge, which was collected from a marine environment, and the gold nanoparticle synthesis was performed for the first time from the bacteria type belonging to the Citricoccus genus. The synthesis conditions were optimized using the Box–Behnken experimental design, with a statistical method that included three independent variables (temperature, time, and mixture ratio) to affect the synthesis at three levels (+1, 0, and ?1). Accordingly, the conditions proposed for the biosynthesis of gold nanoparticles at the maximum optical density values that are specific for the Citricoccus sp. K1D109 strain were estimated as 35°C temperature, 24?h, and 1/5 mixture ratio (cell-free extract/HAuCl₄?·?3H₂O). When recommended conditions were applied, it was determined that the maximum absorbance of the synthesized gold nanoparticles is 1.258 at 545?nm, and their sizes are in the range of 25–65?nm, according to transmission electron microscopy (TEM) data.     

Electroluminescence properties of a PIN structure made by nearly stoichiometric a-SiCx:H active layer

a-SiC_x:H PIN diode has been fabricated within a single pump-down process under the same deposition conditions used for doped and undoped PECVD grown thin films, whose optical and electrical properties are determined and compared with a-Si:H. Current-voltage characteristics of PIN diode are evaluated and concluded to be limited by tunnelling of holes at p-i interface into valence band tail states. Electroluminescence measurements revealed radiative monomolecular recombinations. Deconvolution of the luminescence spectra is utilized to analyse recombination mechanism to be dominated by the transitions between band tails and deep states, which are created by the large density of both silicon and carbon dangling bonds, probable in the stoichiometric a-SiC_x:H film. Finally, a small luminescence peak around 1.9 eV would be an evidence of reduced probability of tail to tail transitions, than that of the transitions between tail and deep states.     

A numerical simulation study for the human passive thermal system

The objective of this study is to create a dynamic model representing a transient three-dimensional passive thermal model of the human body. The model is a multi-segmental, multi-layered representation of the human body with spatial subdivisions which simulates the heat transfer phenomena within the body and at its surface. In order to represent the mechanisms of heat transfer within the body, energy balance equations including conduction with adjacent tissue, heat storage, metabolic heat generation, and convective heat transfer due to the blood flow in the capillaries are taken into consideration for each tissue. The present model of the passive system accounts for the geometric and anatomic characteristics of the human body and considers the thermo-physical and the basal physiological properties of tissue materials. It is assumed that the body is exposed to combination of the convection, evaporation and radiation which are taken into account as boundary conditions when solving the passive thermal system equation. The model is capable of predicting human body temperature in any given environmental conditions. Finite difference solution scheme is used to find out the temperature distribution of human body. The results are compared with the experimental data of previous studies present in the literature. Consequently, the numerical results of present model show good agreement with the experimental data.     

Poly(benzoxazine‐co‐sulfur): An efficient sorbent for mercury removal from aqueous solution

A novel sulfur‐rich adsorbent, poly(BA‐ala‐co ‐sulfur), was synthesized by reacting allyl functional benzoxazine (BA‐ala) and elemental sulfur. Simultaneous inverse vulcanization and ring‐opening reactions of benzoxazine generated copolymers in several feed ratios. The adsorption behavior of these copolymers was investigated in aqueous solutions containing Hg²⁺. A three level Box–Behnken design with four factors was applied in order to examine the interactive effect of Hg²⁺ concentration (ppm), S % in adsorbent, temperature, and pH. The optimum adsorption conditions were determined as: 10.33 ppm Hg²⁺, 68% S content, 329 K, and pH 6.3. Common isotherm and kinetic models were applied to the experimental data, where the Langmuir isotherm provided the better fit (q _max = 79.36 mg g^?1) and the pseudo‐second order fit indicated chemisorption as the process‐controlling step. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45306.