Lithia porcelains as promising breeder candidates - II. Structural changes induced by fast neutron irradiation

The promise of lithia ceramics as candidate breeder materials necessitates investigations on radiation damage induced structural variations. Prepared porcelain systems consisting of β-eucryptite (Li₂O.Al₂O₃.2SiO₂), its solid-solution (Li₂O.Al₂O₃.3SiO₂) and β-spodumene (Li₂O.Al₂O₃4SiO₂), previously characterized, were irradiated by fast neutrons at room temperature. A ²⁵²Cf source (2 MeV) was used to give fluences of 1 × 10⁵, 1 × 10⁸ or 1 × 10¹⁰ n/cm². Samples of each group received fluences in a one-shot technique, i.e. new samples were used for each fluence before being subjected to structural testing. Damage was assessed by X-ray diffraction (XRD) and infrared (IR) spectral analyses. Relevance dilatation changes were followed through coefficient of change with temperature up to 1000 °C. Surface morphologies were examined using scanning electron microscopy (SEM) and selected area electron diffraction (SAED).

XRD patterns revealed various degrees of imperfections that were reflected as shifts in lattice planes. The IR spectral bands suffered shift, especially in the fingerprint region, parallel with the fluence intensity. Coefficient of contraction and/ or expansion evidenced various degree of damage, which upon intense irradiation annealed to the original values. SEM micrographs revealed that large grains comprising either β-eucryptite or β-spodumene bodies are much more affected by fast neutrons compared to smaller grains detected in the body containing the solid-solution. Additional evidence was obtained by the SAED results, where the continuous polycrystalline rings of both β-eucryptite and β-spodumene turned upon irradiation to the amorphous metamict state simulating the initial solidsolution structure. The latter acquired higher crystalline order, as well as polycrystalline habit. The degrees of induced imperfections were found to be dependent on initial crystallinity. The higher sensitivity to fast neutrons of β-eucryptite was related to its higher lithia content rather than its hexagonal spiral structure compared to the tetragonal β-spodumene. Intense irradiation caused annealing of the produced damage observed by fragmentation of the grains and various degree of amorphism.     

Atmospheric plasma‐aided biocidal finishes for nonwoven polypropylene fabrics. I. Synthesis and characterization

Novel biocidal fabrics were synthesized by the graft copolymerization of glycidyl methacrylate (GMA) onto plasma‐treated nonwoven polypropylene (PP) to produce PP/GMA grafts. Atmospheric oxygenated helium plasma was used to enhance the PP fabrics' initiation before GMA grafting. The grafted PP/GMA epoxide group was reacted with β‐cyclodextrin, monochlorotrizynyl‐β‐cyclodextrins, or a quaternary ammonium chitosan derivative [N‐(2 hydroxy propyl) 3‐trimethylammonium chitosan chloride]. Some interesting biocidal agents were complexed into the cyclodextrin (CD) cavity of PP/GMA/CD grafted fabrics. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and optical and scanning electron microscopies were used to characterize the grafted complexed fabrics. These synthesized biocidal fabrics proved to be antistatic, antimicrobial, and insect‐repelling (see part II of this study). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1900–1910, 2007     

A Review of Indoor Localization Techniques and Wireless Technologies

Wireless Personal Communications - This paper introduces a review article on indoor localization techniques and technologies. The paper starts with current localization systems and...     

Characterization of Cucumber Fermentation Spoilage Bacteria by Enrichment Culture and 16S rDNA Cloning

Commercial cucumber fermentations are typically carried out in 40000 L fermentation tanks. A secondary fermentation can occur after sugars are consumed that results in the formation of acetic, propionic, and butyric acids, concomitantly with the loss of lactic acid and an increase in pH. Spoilage fermentations can result in significant economic loss for industrial producers. The microbiota that result in spoilage remain incompletely defined. Previous studies have implicated yeasts, lactic acid bacteria, enterobacteriaceae, and Clostridia as having a role in spoilage fermentations. We report that Propionibacterium and Pectinatus isolates from cucumber fermentation spoilage converted lactic acid to propionic acid, increasing pH. The analysis of 16S rDNA cloning libraries confirmed and expanded the knowledge gained from previous studies using classical microbiological methods. Our data show that Gram‐negative anaerobic bacteria supersede Gram‐positive Fermincutes species after the pH rises from around 3.2 to pH 5, and propionic and butyric acids are produced. Characterization of the spoilage microbiota is an important first step in efforts to prevent cucumber fermentation spoilage. Practical Application An understanding of the microorganisms that cause commercial cucumber fermentation spoilage may aid in developing methods to prevent the spoilage from occurring.     

Overlapping and multi-touching text-line segmentation by Block Covering analysis

This paper presents a new approach for text-line segmentation based on Block Covering which solves the problem of overlapping and multi-touching components. Block Covering is the core of a system which processes a set of ancient Arabic documents from historical archives. The system is designed for separating text-lines even if they are overlapping and multi-touching. We exploit the Block Covering technique in three steps: a new fractal analysis (Block Counting) for document classification, a statistical analysis of block heights for block classification and a neighboring analysis for building text-lines. The Block Counting fractal analysis, associated with a fuzzy C-means scheme, is performed on document images in order to classify them according to their complexity: tightly (closely) spaced documents (TSD) or widely spaced documents (WSD). An optimal Block Covering is applied on TSD documents which include overlapping and multi-touching lines. The large blocks generated by the covering are then segmented by relying on the statistical analysis of block heights. The final labeling into text-lines is based on a block neighboring analysis. Experimental results provided on images of the Tunisian Historical Archives reveal the feasibility of the Block Covering technique for segmenting ancient Arabic documents.     

Learning with web-based interactive objects: An investigation into student perceptions of effectiveness

In its efforts to continue the modernization of its curriculum, the Faculty of Dentistry at the University of Toronto has developed a series of web-based interactive learning applications. This article presents the production cycle of these new interactive learning objects and the preliminary study conducted to measure the students’ perception of the objects’ effectiveness for learning. Three applications are described in detail in this article, namely: Panoramic Radiography: Principles and Interpretation, Gross Human Anatomy 3D Atlas and Restorative Dentistry: Virtual and Interactive Cavity Preparation. Each of these applications introduces unique elements of interactivity with the learning content, specifically designed to address hard-to-grasp concepts in their respective dental disciplines. The results of a student survey conducted post-deployment suggest that the visual and interactive features embedded in the three applications have the potential to induce positive outcomes in mediating the students’ conceptualization of difficult theoretical notions.     

A resource allocation algorithm for throughput maximization with fairness increase based on virtual PRB in MIMO-OFDMA systems

This paper deals with a new resource allocation algorithm in downlink MIMO-OFDMA systems. The objective is to maximize the system throughput with respect to fairness criteria since some users may experience bad channel conditions for a long time. Known to be NP-hard, the original optimization problem is divided into two sub-problems where radio resource allocation and power allocation are performed separately. Firstly, a recursive PRB allocation algorithm is performed aiming at maximizing the system throughput. In LTE systems, 41% of sub-carriers are considered unused which introduces spectral efficiency loss. As solution, the eNodeB aggregates the unused sub-carriers by each user to construct a “virtual” PRB to be allocated to seldom served user for fairness and throughput increase. Secondly, power allocation is performed to select a more appropriate MCS.