179 research outputs found
TlCaBa<SUB>2</SUB>Cu<SUB>2</SUB>O<SUB>7</SUB>: the 1122 (90 K) superconductor in the new Tl(Ca,Ba)<SUB>n+1</SUB>Cu<SUB>n</SUB>O<SUB>2n+3</SUB> series
No full textThe 1122 (n=2) member of the Tl(Ca,Ba)n+1CunO2n+3 series containing a single Tl-O layer is shown to be associated with a Tc of 90 K. This value of Tc is significantly lower than that of the 2122 phase (Tc~110 K) with two Tl-O layers
TlCaBa2Cu2O7: The 1122 (90 K) superconductor in the new Tl(Ca,Ba)n+1CunO2n+3 seriesstar, open
No full textThe 1122 (n=2) member of the Tl(Ca,Ba)n+1CunO2n+3 series containing a single Tl-O layer is shown to be associated with a Tc of 90 K. This value of Tc is significantly lower than that of the 2122 phase (Tcnot, vert, similar110 K) with two Tl-O layers
Theory of the electronic states of semiconductor heterostructures
No full textThis thesis is concerned with theoretical calculations of the properties of electronic bound states in semiconductor heterostructures. The complex band structure empirical pseudopotential method (EPM) is used as the foundation of the work. Spin orbit coupling and strain effects (due to lattice mismatch) are included in familiar ways, as is the transfer matrix method, allowing the study of arbitrarily configured heterostructures. These techniques are used to investigate the unusually deep InAs/AlSb conduction band well. The strong possibility of intraband transitions at electro magnetic wavelengths around 1.55µm is predicted, with corresponding enhanced momentum matrix elements and joint density of states over interband transitions. An InAs/GaSb/AlSb asymmetric well is investigated, paying particular attention to the bound states in the vicinity of the InAs/GaSb band overlap. The electron-like states are found to cross with heavy hole and anti-cross with light hole-like states, as a function of heterostructure dimension or applied electrostatic field. This is analogous to the hybridisation of states in the in-plane band structure, except that for zero in-plane wave vector there can be no appreciable hybridisation of electron and heavy hole states. A technique is described that has been developed to extract envelope functions from heterostructure wavefunctions calculated using the realistic complex band structure EPM approach. These envelope functions conform to Burt’s theory (M. G. Burt, J. Phys.: Condens. Matt. 4, 6651 (1992)) in that they are uniquely defined, continuous and smooth over all space. Comparisons with traditional effective mass envelope functions are made. The extracted envelope functions are used to demonstrate conclusively Burt's predictions (M. G. Burt, Superlatt. Mi- crostruct. 17, 335 (1995)) concerning the inadequacy of certain approximations for the calculation of interband dipole matrix elements and charge oscillation. Finally, the issue of k • p operator ordering is convincingly settled, in favour of 'ordered' over 'symmetrised' Hamiltonians, by comparison to EPM calculations, and using EPM derived k • p parameters
Emerg Infect Dis
No full textBecause of the broadened acute flacid paralysis (AFP) definition and enhanced surveillance, many nonpolio AFP (NP-AFP) cases have been reported in India since 2005. To determine the spectrum of nonpolio enterovirus (NPEV) serotypes associated with NP-AFP from polio-endemic and -free regions, we studied antigenic diversity of AFP-associated NPEVs. Of fecal specimens from 2,786 children with NP-AFP in 1 polio-endemic and 2 polio-free states, 823 (29.5%) were positive for NPEVs in RD cells, of which 532 (64.6%) were positive by viral protein 1 reverse transcription PCR. We identified 66 serotypes among 581 isolates, with enterovirus 71 most frequently (8.43%) detected, followed by enterovirus 13 (7.1%) and coxsackievirus B5 (5.0%). Most strains within a serotype represented new genogropups or subgenogroups. Agents for 4835.0% and 70.0% of culture-positive and -negative cases, respectively, need to be identified. Association of human enterovirus with NP-AFP requires better assessment and understanding of health risks of NPEV infections after polio elimination
Superconductivity in the 100-120 K region in oxides of the Tl-Ca-Ba-Cu-O system
No full textOxides with different cation ratios 2122, 2212, 2213 and 2223 in the Ti-Ca-Ba-Cu-O system exhibit onset of superconductivity in the 110-125 K range with zero-resistance in the 95-105 K range. Electron microscopic studies show dislocations, layered morphology and other interesting features. These oxides absorb electromagnetic radiation (9.11 GHz) in the superconducting phase
Superconductivity in the 100–120 K region in oxides of the Tl-Ca-Ba-Cu-O system
No full textOxides with different cation ratios 2122, 2212, 2213 and 2223 in the Ti-Ca-Ba-Cu-O system exhibit onset of superconductivity in the 110–125 K range with zero-resistance in the 95–105 K range. Electron microscopic studies show dislocations, layered morphology and other interesting features. These oxides absorb electromagnetic radiation (9.11 GHz) in the superconducting phase
Nature and stability of the "60-K superconducting phase" in the system
No full textBased on electron microscopy, nonresonant microwave absorption, electron paramagnetic resonance, and other studies, it is shown that in the system, compositions with , 0.25, and 0.5 are stable and monophasic, the last two being associated with ordered-oxygen-vacancy structures. The region is not associated with an ordered-vacancy structure. More importantly, compositions in this region undergo structural changes on annealing at relatively low tempertures, eventually decomposing to the more stable phases. It appears that compositions such as are not thermodynamically stable, casting thereby some doubt on the belief that the 60-K regime represents a genuine single-phase superconducting material
Addressing Mental Health Needs in a Rural K-8 School
No full textAfter the COVID-19 pandemic, a rural K-8 school faced unique challenges due to its isolated location. Faculty members reported increased use of social media and other online communication by students. In addition, the staff noticed an increase in bullying, stress, and a greater need for mental health resources. In partnership with Quillen College of Medicine, a group of 5 medical students implemented lessons from the Alberta Health Services Junior High Mental Health Kit curriculum. Overall, the mission was to improve student attitudes and skills related to healthy relationships, stress, mental illness, cyber bullying, substance abuse, and hope. Analysis of research survey data showed that there was a significant change in students’ overall wellness (p=0.04108) and knowledge of healthy strategies to cope with stress (p=0.03709) after the intervention
Nature and stability of the "60-K superconducting phase''in the YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB> system
No full textBased on electron microscopy, nonresonant microwave absorption, electron paramagnetic resonance, and other studies, it is shown that in the YBa2Cu3O7-δ system, compositions with δ=0.0- 0.20, 0.25, and 0.5 are stable and monophasic, the last two being associated with ordered-oxygen-vacancy structures. The δ=0.3-0.4 region (Tc~60 K) is not associated with an ordered-vacancy structure. More importantly, compositions in this region undergo structural changes on annealing at relatively low tempertures, eventually decomposing to the more stable phases. It appears that compositions such as YBa2Cu3O6.7 are not thermodynamically stable, casting thereby some doubt on the belief that the 60-K regime represents a genuine single-phase superconducting material
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