The results of the irradiation experiment HELIOS

The HELIOS irradiation experiment is the latest of a series of experiments on americium transmutation, and has been carried out in the framework of EURATOM’s 6th Framework Programme (FP6) project EUROTRANS, which was completed in March 2010. The transmutation of Minor Actinide (MA) is a fundamental step in order to be able to close the cycle of the nuclear fuel. Past experimental activities in the field of transmutation and testing of innovative nuclear fuel containing Am has proved that the release or trapping of helium is a key issue for the design of such kind of fuel or targets. Therefore, the main objective of the HELIOS experiment is the study of the in-pile behaviour of U-free fuels, such as (Pu,Am,Zr,Y)O₂ or (Am,Zr,Y)O₂, CERCER (Am₂Zr₂O₇+MgO), CERMET ((Pu,Am)O₂+Mo) or ((Am,Zr,Y)O₂+Mo), to gain knowledge on the role of the fuel microstructure and of the operating temperature on gas release and fuel swelling.The HELIOS irradiation experiment started in the HFR (High Flux Reactor) in Petten (The Netherlands) on the 29th of April 2010 and finished on the 19th of February after 9 reactor cycles (∼241 full power days). Although the Post-Irradiation Examination (not performed yet) conducted on the CERCER and CERMET target fuel tested during the HELIOS irradiation experiment will determine the performance of the fuel, the behaviour of such targets during the irradiation did not show any difficulties. It is possible to conclude that from an operational point of view, these kinds of fuel targets which have been developed mainly having in mind the possibility to burn MA in a in a subcritical nuclear system, did not show significant issues. This paper summarises the main experimental data obtained during the 9 cycle irradiation of the HELIOS experiment in the HFR.     

Analysis of tin whisker growth on lead-free alloys with Ni presence under thermal shock stress

This paper presents the results of whiskers formation after thermal shocks on various tin-rich materials used in electronics: Sn100, Sn99Cu1, Sn97Cu3, Sn99.3Cu0.7Ni, Sn99.3Cu0.7AgNiGe and Sn99Ag0.3Cu0.7NiGe. Alloys plated over an Ni/Au sublayer were compared with those plated directly over a Cu layer. Scanning electron microscope (SEM) imaging was applied to determine whisker densities, lengths and types. Different degrees of susceptibility to whisker formation were found for all the investigated alloys subjected to 1500 shocks in a cyclic temperature range of −45 °C to +85 °C. Although the whisker growth rates for the alloys plated over an Ni/Au sublayer were lower than for the alloys plated directly over a Cu layer, all the materials tested were more or less prone to whisker formation.     

Alternative insight into aluminium-phosphate glass network from ab initio molecular dynamics simulations

Phosphate glasses are an important group of materials for wide applications. They have received attention as biomaterials, eco-fertilizers, in optoelectronic devices, waste immobilization, etc.The subject of the studies is binary Al₂O₃–P₂O₅ glass, seen by ab initio molecular dynamics simulations. In the paper, Mayer's Bond Order analysis was employed as a suitable tool to observe the changes in the network due to Al₂O₃ substitutions. As well as, the bonding properties across the atoms in the network, which were characterized by electron localization function. The basic structural properties of the glasses are presented.The simulations showed that oxygen atoms in [PO₄] tetrahedrons create a weak covalent bond between the atoms. The interaction spreads across the whole phosphate network via bridging oxygens. Whereas, there is no such interaction between the atoms in [AlO_x] polyhedrons. In the case of the Al₂O₃ rich glasses, there are evidence non-network oxygen atoms which influence the distribution of phosphate structural units predicted based on the O/P ratio. The possibility of estimation of the oxygens in an experiment is discussed.The atoms building the network are going to take specific values of the total bond orders and the glass network is an interplay between atoms’ affinity to saturate bond orders and the glass network neutrality.     

Rheology and processing of UV-curable textured alumina inks for additive manufacturing

A UV-curable resin containing alumina (Al₂O₃) powder and platelets was developed and characterized using a proof-of concept tape-casting system and trialed on a commercially available 3D-printing platform (Admatec Admaflex 130). The influence of solids loading and solids platelet fraction on resin viscosity and depth of cure was investigated. Resins containing up to 40 vol% solids loading at platelet fractions up to 50% were found to have sufficiently low viscosity for tape casting and cure depths ranging from 0.29 to 0.39 mm. Alumina platelets were observed to lower ink viscosity but also reduce shear thinning behavior compared to inks containing only powder. Printability of inks was assessed by layered tape casting, and verified with a trial build on an Admaflex 130. Due to the low solids loading of the resin, hot pressing at 1300°C and 66 MPa was employed to sinter specimens containing no platelets and 15% platelet fractions, yielding specimens with near theoretical densities (99.7%) and average grain sizes of 0.96 µm and 0.83 µm, respectively. Alignment before and after sintering was assessed by SEM and XRD, with lotgering factors of 0.045±0.005 and 0.114 measured in the green and sintered specimens, respectively.     

High efficient As(III) removal by self-assembled zinc oxide micro-tubes synthesized by a simple precipitation process

Zinc oxide (ZnO) micro-tubes via self-assembly of nanoparticles were synthesized by a simple precipitation process. Removal of As(III) (arsenite) from water by ZnO micro-tubes through adsorption was investigated with both lab-prepared and natural water samples. The result showed that these self-assembled ZnO micro-tubes are effective to remove As(III) from both lab-prepared and natural water samples at near neutral pH environment. These ZnO micro-tubes have a high adsorption capability on As(III) at low As(III) concentration. When the equilibrium As(III) concentration was around 0.1 mg/L, the amount of As(III) adsorbed at equilibrium was over 10 mg/g. At high equilibrium concentration, the adsorption capacity of these ZnO micro-tubes on As(III) reached over 39.4 mg/g. These ZnO micro-tubes could provide a simple single-step treatment option to treat arsenic-contaminated natural water, which requires no pre-treatment or post-treatment pH adjustment for current industrial practice.     

Imitation from 12 to 24 months in autism and typical development: A longitudinal Rasch analysis.

The development of imitation during the second year of life plays an important role in domains of sociocognitive development such as language and social learning. Deficits in imitation ability in persons with autism spectrum disorder (ASD) from toddlerhood into adulthood have also been repeatedly documented, raising the possibility that early disruptions in imitation contribute to the onset of ASD and the deficits in language and social interaction that define the disorder. This study prospectively examined the development of imitation between 12 and 24 months of age in 154 infants at familial risk for ASD and 78 typically developing infants who were all later assessed at 36 months for ASD or other developmental delays. The study established a developmental measure of imitation ability and examined group differences over time, using an analytic Rasch measurement model. Results revealed a unidimensional latent construct of imitation and verified a reliable sequence of imitation skills that was invariant over time for all outcome groups. Results also showed that all groups displayed similar significant linear increases in imitation ability between 12 and 24 months and that these increases were related to individual growth in both expressive language and ratings of social engagement but not in fine motor development. The group of children who developed ASD by age 3 years exhibited delayed imitation development compared with the low-risk typical outcome group across all time-points, but were indistinguishable from other high-risk infants who showed other cognitive delays not related to ASD. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Alterations in Tau Protein Level and Phosphorylation State in the Brain of the Autistic-Like Rats Induced by Prenatal Exposure to Valproic Acid

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by deficient social interaction and communication besides repetitive, stereotyped behaviours. A characteristic feature of ASD is altered dendritic spine density and morphology associated with synaptic plasticity disturbances. Since microtubules (MTs) regulate dendritic spine morphology and play an important role in spine development and plasticity the aim of the present study was to investigate the alterations in the content of neuronal α/β-tubulin and Tau protein level as well as phosphorylation state in the valproic acid (VPA)-induced rat model of autism. Our results indicated that maternal exposure to VPA induces: (1) decrease the level of α/β-tubulin along with Tau accumulation in the hippocampus and cerebral cortex; (2) excessive Tau phosphorylation and activation of Tau-kinases: CDK5, ERK1/2, and p70S6K in the cerebral cortex; (3) up-regulation of mTOR kinase-dependent signalling in the hippocampus and cerebral cortex of adolescent rat offspring. Moreover, immunohistochemical staining showed histopathological changes in neurons (chromatolysis) in both analysed brain structures of rats prenatally exposed to VPA. The observed changes in Tau protein together with an excessive decrease in α/β-tubulin level may suggest destabilization and thus dysfunction of the MT cytoskeleton network, which in consequence may lead to the disturbance in synaptic plasticity and the development of autistic-like behaviours.     

Mīmāṃsā deontic reasoning using specificity: a proof theoretic approach

Artificial Intelligence and Law - Over the course of more than two millennia the philosophical school of Mīmā?sā has thoroughly analyzed normative statements. In this paper we...     

EPIP-Evoked Modifications of Redox,Lipid, and Pectin Homeostasis in the Abscission Zone of Lupine Flowers

Yellow lupine is a great model for abscission-related research given that excessive flower abortion reduces its yield. It has been previously shown that the EPIP peptide, a fragment of LlIDL (INFLORESCENCE DEFICIENT IN ABSCISSION) amino-acid sequence, is a sufficient molecule to induce flower abortion, however, the question remains: What are the exact changes evoked by this peptide locally in abscission zone (AZ) cells? Therefore, we used EPIP peptide to monitor specific modifications accompanied by early steps of flower abscission directly in the AZ. EPIP stimulates the downstream elements of the pathway—HAESA and MITOGEN-ACTIVATED PROTEIN KINASE6 and induces cellular symptoms indicating AZ activation. The EPIP treatment disrupts redox homeostasis, involving the accumulation of H₂O₂ and upregulation of the enzymatic antioxidant system including superoxide dismutase, catalase, and ascorbate peroxidase. A weakening of the cell wall structure in response to EPIP is reflected by pectin demethylation, while a changing pattern of fatty acids and acyl lipids composition suggests a modification of lipid metabolism. Notably, the formation of a signaling molecule—phosphatidic acid is induced locally in EPIP-treated AZ. Collectively, all these changes indicate the switching of several metabolic and signaling pathways directly in the AZ in response to EPIP, which inevitably leads to flower abscission.     

Influence of nanostructure on titanium corrosion resistance in fluoridated medium

ABSTRACT

Nanocrystalline titanium, mainly owing to its high corrosion resistance, mechanical strength to density ratio and biocompatibility, has a great application potential in dental implantology. However, fluoridated agents commonly used for oral hygiene could have a destructive influence on the titanium protective passive films and lead to the formation of local corrosion damages. In this work, the effect of nanostructuring on titanium corrosion resistance in the concentration of F^? which is typical for toothpastes, was evaluated by different electrochemical and surface characterisation techniques. It was found that nanostructure influences beneficially on titanium corrosion resistance in fluoride solution. Furthermore, the lower increase in nanocrystalline titanium surface roughness in corrosion solutions indicates better stability of passive film formed on its surface.

This paper is part of a thematic issue on Titanium.