Electrical properties of Bi-implanted amorphous chalcogenide films

The impact of Bi implantation on the conductivity and the thermopower of amorphous chalcogenide films is investigated. Incorporation of Bi in Ge-Sb-Te and GeTe results in enhanced conductivity. The negative Seebeck coefficient confirms onset of the electron conductivity in GeTe implanted with Bi at a dose of 2x1016 cm-2. The enhanced conductivity is accompanied by defect accumulation in the films upon implantation as is inferred by using analysis of the space-charge limited current. The results indicate that native coordination defects in lone-pair semiconductors can be deactivated by means of ion implantation, and higher conductivity of the films stems from additional electrically active defects created by implantation of bismuth.Comment: This is an extended version of the results presented in Proc. SPIE 8982, 898213 (2014

Total carotenoid content, α-carotene and β-carotene, of landrace pumpkins (Cucurbita moschata Duch): A preliminary study

AbstractLandrace pumpkins occur in nature and their potential as source of pro-vitamin A may be investigated in order to be used in conventional plant breeding or biofortification programs, aiming to increase the total carotenoids and β-carotene contents. The objective of the study was to determine the total carotenoid, α-carotene, β-carotene and its isomers and contents in two landrace samples (A and B) of raw pumpkins (Cucurbita moschata) to verify its seed production potential. High Performance Liquid Chromatography and UV/Visible spectrophotometry were used to determine α-carotene, β-carotene and its isomers, and total carotenoid contents, respectively. All analyses were carried out in triplicate. The results showed mean total carotenoid contents of 404.98 in sample A, and 234.21μg/g in sample B. The α-carotene contents varied from 67.06 to 72.99μg/g in samples A and B, respectively. All E-β-carotene was the most abundant isomer found varying from 244.22 to 141.95μg/g in samples A and B, respectively. The 9 and 13-Z-β-carotene isomers were still found in low concentrations in both analyzed landrace samples. The content of β-carotene in raw sample A showed to be promising for the production of seeds for cultivation and consumption

Stability problem for the torque-free gyrostat by using algebraic methods

We apply an algebraic method for studying the stability with respect to a set of conserved quantities for the problem of torque-free gyrostat. If the conditions of this algebraic method are not fulfilled then the Lyapunov stability cannot be decided using the specified set of conserved quantities

Modifying Polyester Surfaces with Incompatible Polymer Additives

Surface modification of amorphous PET in incompatible blends is demonstrated using fluorocarbon end-functional polystyrenes. Contact angles with water and decane were consistent with high levels of surface fluorocarbon, even for spin-cast films with no further processing required. Hydrophobicity and lipophobicity were further increased by annealing above the glass transition temperature. High resolution depth profiling using complementary ion beam analysis and specular neutron reflectometry has enabled accurate characterisation of the composition profile of the additive including the minimum in additive concentration found just below the surface enriched layer. This analysis quantified the very low compatibility between the modifying polymer and the amorphous PET and was consistent with the highly segregated nature of the adsorbing species and its sharp interface with the subphase. For these incompatible polymer blends, surfaces enriched with the surface active polymer could coexist at equilibrium with extremely low (∼0.4%) bulk loadings of the additive. This suggests that for thicker films at even lower additive concentrations than the minimum 1% that we studied, it may be possible to achieve efficient surface modification. However, at this concentration, the efficiency of surface modification is limited by the processing conditions. Finally we note that in higher loadings of surface active additive there is clear evidence for lateral phase separation into patterned domains of differing composition. The enhancement in surface properties is due to local reorganisation rather than bulk redistribution of the components within the film, as the composition versus depth distributions of the polymer blend components was observed to be relatively unaffected by annealing

Krypton irradiation damage in Nd-doped zirconolite and perovskite as potential ceramics for inert matrix fuel and plutonium disposition

ABSTRACT Understanding the effect of radiation damage and noble gas accommodation in potential ceramic hosts for plutonium disposition is necessary to evaluate the long-term behaviour during geological disposal. Polycrystalline samples of Nd-doped zirconolite and Nd-doped perovskite were irradiated ex-situ with 2 MeV Kr + at a dose of 5x10 15 ions.cm -2 to simulate plutonium nuclei recoil during alpha decay. The feasibility of thin section preparation of both pristine and irradiated samples by Focussed Ion Beam sectioning was demonstrated. After irradiation, the Nd-doped zirconolite revealed a well defined amorphous region separated from the pristine material by a thin (40-60 nm) damaged interface. The Nd-doped perovskite contained a defined irradiated region composed of an amorphous region surrounded by damaged regions. In both samples, as revealed by electron diffraction, the damaged regions and interface have a structure in which the fluorite sublattice is present while the pristine lattice is absent. In addition in Nddoped perovskite, the amorphisation dose depended on crystallographic orientation and possibly sample configuration (thin section and bulk). In Nd-doped perovskite, Electron Energy Loss Spectroscopy study revealed a change in Ti coordination associated with the crystal to amorphous transition

Science lives: School choices and ‘natural tendencies’

An analysis of 12 semi-structured interviews with university-based scientists and non-scientists illustrates their life journeys towards, or away from, science and the strengths and impact of life occurrences leading them to choose science or non-science professions. We have adopted narrative approaches and used Mezirow's transformative learning theory framework. The areas of discussion from the result have stressed on three main categories that include ‘smooth transition’, ‘incremental wavering transition' and ‘transformative transition’. The article concludes by discussing the key influences that shaped initial attitudes and direction in these people through natural inclination, environmental inspirations and perceptions of science

Sampling and Analysis of Impact Crater Residues Found on the Wide Field Planetary Camera-2 Radiator

After nearly 16 years in low Earth orbit (LEO), the Wide Field Planetary Camera-2 (WFPC2) was recovered from the Hubble Space Telescope (HST) in May 2009, during the 12 day shuttle mission designated STS-125. The WFPC-2 radiator had been struck by approximately 700 impactors producing crater features 300 microns and larger in size. Following optical inspection in 2009, agreement was reached for joint NASA-ESA study of crater residues, in 2011. Over 480 impact features were extracted at NASA Johnson Space Center's (JSC) Space Exposed Hardware clean-room and curation facility during 2012, and were shared between NASA and ESA. We describe analyses conducted using scanning electron microscopy (SEM) - energy dispersive X-ray spectrometry (EDX): by NASA at JSC's Astromaterials Research and Exploration Science (ARES) Division; and for ESA at the Natural History Museum (NHM), with Ion beam analysis (IBA) using a scanned proton microbeam at the University of Surrey Ion Beam Centre (IBC)

Slogging and Stumbling Toward Social Justice in a Private Elementary School: The Complicated Case of St. Malachy

This case study examines St. Malachy, an urban Catholic elementary school primarily serving children traditionally marginalized by race, class, linguistic heritage, and disability. As a private school, St. Malachy serves the public good by recruiting and retaining such traditionally marginalized students. As empirical studies involving Catholic schools frequently juxtapose them with public schools, the author presents this examination from a different tack. Neither vilifying nor glorifying Catholic schooling, this study critically examines the pursuit of social justice in this school context. Data gathered through a 1-year study show that formal and informal leaders in St. Malachy adapted their governance, aggressively sought community resources, and focused their professional development to build the capacity to serve their increasingly pluralistic student population. The analysis confirms the deepening realization that striving toward social justice is a messy, contradictory, and complicated pursuit, and that schools in both public and private sectors are allies in this pursuit