Manifestation of pseudogap in ab-plane optical characteristics

A model in which a gap forms in the renormalized electronic density of state (DOS) with missing states recovered just above the pseudogap $\Delta_{pg}$, is able to give a robust description of the striking, triangular like, peak seen in the real part of the optical self-energy of underdoped cuprates. We use this model to explore the effect of the pseudogap on the real part of the optical conductivity and on the partial sum rule associated with it. An important result is that the optical spectral weight redistributes over a much larger frequency window than it does in the DOS.Comment: 12 pages, 3 figures. Submitted to Journal of Physics: Condensed Matte

Study of single-phase convection and condensation in thermoplate heat exchanger (part I)

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The heat transfer and pressure drop in a thermoplate heat exchanger operated as condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, first the single phase forced convection in the thermoplate using distilled water and Marlotherm oil has been studied and correlation for the Nusselt number and friction factor developed. For the condensation experiments an apparatus has been conceived comprising two identical condensers made of the same thermoplate type as employed in the single phase experiments. Isopropanol was used as test fluid at pressures below the atmospheric pressure. With the aid of the results obtained in the single phase studies the heat transfer resistances in the condensation experiments were separated and expressions for the condensation heat transfer and pressure drop developed.cs201

Numerical simulation of fluid flow, heat transfer and pressure drop in thermoplates

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The objective of our investigations is to numerically investigate the optimal geometry of the thermoplate with respect to heat transfer of the inside fluid that passes through the channel as a single phase. In order to achieve this, the geometrical and process parameters such as the pattern of welding spots, the distance between the sheets, and the Reynolds number have been varied. For the simulation, the commercial software StarCD was used. The numerical experiments show that the heat transfer potential of the thermoplate having a staggered arrangement of welding spots is markedly higher than the one of a common flat channel, particularly at larger Reynolds numbers. The variations of the geometrical parameters indicate the welding spot pitch in a streamwise direction to be a pivotal quantity regarding the heat transfer optimisation.cs201

How much support is necessary for self-regulated learning?

Self-regulated learning is crucial for learning success, and is even of greater importance for online learning as there is less support and feedback available to students. We describe a simple intervention designed to support self-regulated learning in the context of SQL-Tutor, a mature intelligent tutoring system. SQL-Tutor logged data about all interactions students performed, including interactions with the SRL support. Frequency-based analyses did not identify any differences in behaviors of low or high scoring students. However, epistemic network analysis identified significant differences in how students use help available from SQL-Tutor. Students who scored low on the SQL test asked for high-level help (in the form of partial or full solution), copied the provided solutions and submitted them as their own. We conclude that additional support is necessary for students with weak self-regulation skills

Study of single-phase convection and condensation in thermoplate heat exchanger (part II)

Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The heat transfer and pressure drop in a thermoplate heat exchanger operated as condenser have been investigated experimentally. In order to separate the heat transfer resistances in the condensation process, first the single phase forced convection in the thermoplate using distilled water and Marlotherm oil has been studied and correlation for the Nusselt number and friction factor developed. For the condensation experiments an apparatus has been conceived comprising two identical condensers made of the same thermoplate type as employed in the single phase experiments. Isopropanol was used as test fluid at pressures below the atmospheric pressure. With the aid of the results obtained in the single phase studies the heat transfer resistances in the condensation experiments were separated and expressions for the condensation heat transfer and pressure drop developed.cs201

NMR Studies of Field Induced Magnetism in CeCoIn5_5

Recent Nuclear Magnetic Resonance and elastic neutron scattering experiments have revealed conclusively the presence of static incommensurate magnetism in the field-induced B phase of CeCoIn5. We analyze the NMR data assuming the hyperfine coupling to the In(2) nuclei is anisotropic and simulate the spectra for several different magnetic structures. The NMR data are consistent with ordered Ce moments along the [001] direction, but are relatively insensitive to the direction of the incommensurate wavevector.Comment: 4 pages, 3 figure

Combined Catalysis and Optical Screening for High Throughput Discovery of Solar Fuels Catalysts

Considerable research and development efforts are being devoted to the efficient generation of solar fuels. A solar fuels device couples a solar photoabsorber with catalysts to convert solar energy to chemical energy via reactions such as oxygen evolution (water splitting). Widespread deployment of this technology hinges upon discovery of new materials through efforts such as the high throughput screening of oxygen evolution catalysts, as discussed in this manuscript. We derive an expression for the efficiency of the oxygen evolution catalyst that combines catalytic and optical properties. Using this hybrid efficiency, we screen 5456 samples in a (Fe-Co-Ni-Ti)O_x pseudo-quaternary catalyst library using automated, high throughput electrochemical and optical experiments. The observed compositional trends in this catalyst efficiency lead to the discovery of a new high performance composition region

Leaf litter breakdown along an elevational gradient in Australian alpine streams

The breakdown of allochthonous organic matter, is a central step in nutrient cycling in stream ecosystems. There is concern that increased temperatures from climate change will alter the breakdown rate of organic matter, with important consequences for the ecosystem functioning of alpine streams. This study investigated the rate of leaf litter breakdown and how temperature and other factors such as microbial and invertebrate activities influenced this over elevational and temporal gradients. Dried leaves of Snow Gum (Eucalyptus pauciflora) and cotton strips were deployed in coarse (6 mm), and fine (50 mu m) mesh size bags along an 820 m elevation gradient. Loss of mass in leaf litter and cotton tensile strength per day (k per day), fungal biomass measured as ergosterol concentration, invertebrate colonization of leaf litter, and benthic organic matter (mass and composition) were determined. Both microbial and macroinvertebrate activities were equally important in leaf litter breakdown with the abundance of shredder invertebrate taxa. The overall leaf litter breakdown rate and loss of tensile strength in cotton strips (both k per day) were greater during warmer deployment periods and at lower elevations, with significant positive relationships between mean water temperature and leaf breakdown and loss of tensile strength rate, but no differences between sites, after accounting for the effects of temperature. Despite considerably lower amounts of benthic organic matter in streams above the tree line relative to those below, shredders were present in coarse mesh bags at all sites. Ergosterol concentration was greater on leaves in coarse mesh bags than in fine mesh bags, implying differences in the microbial communities. The importance of water temperatures on the rate of leaf litter breakdown suggests the potential effects of climate change-induced temperature increases on ecological processes in such streams

Composition and field tuned magnetism and superconductivity in Nd1-xCexCoIn5

The Nd1-xCexCoIn5 alloys evolve from local moment magnetism (x = 0) to heavy fermion superconductivity (x =1). Magnetic order is observed over a broad range of x. For a substantial range of x (0.83 <= x <= 0.95) in the temperature - composition phase diagram we find that superconductivity may coexist with spin - density wave magnetic order at the Fermi surface. We show that a delicate balance betwen superconducting and magnetic instabilities can be reversibly tuned by both the Ce/Nd ratio and magnetic field, offering a new and unique model electronic system.Comment: 7 pages, 7 figures. Physical Review B in pres