8,949 research outputs found
Contexts for ‘pure’ mathematics: a framework for analysing A-level mathematics papers
No full textThe use of context in mathematics test items is now accepted practice in many forms of national assessment in the UK. Yet research suggests that such use of context is not straightforward and that children may apply a variety of interpretations to contextual mathematics problems. Our analysis focuses on the use of context in post-16 ‘pure’ mathematics questions set by two UK Examination Boards. From our analysis, a framework for analysing the use of context is proposed that encompasses issues such as accessibility, realism and authenticity
Synthesis optimization and charge carrier transfer mechanism in LiLuSiO<sub>4</sub>:Ce, Tm storage phosphor
No full textLiLuSiO4:Ce and LiLuSiO4:Ce, Tm show very efficient charge carrier storage properties upon beta irradiation after samples have received treatment in vacuum. They outperform the commercial storage phosphor BaFBr(I):Eu2+ in many aspects. The influence of the synthesis conditions, Ce and Tm concentration, nonstoichiometry and codoping with Ca, Hf, Al and Ge are reported. Based on the results of the synthesis optimization, thermoluminescence (TL) emission and TL excitation spectra a mechanism of charge carrier transfer, storage, and recombination during irradiation and thermal or optical readout is proposed.Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material
Realization of analog-to-digital coders
No full textMicrofiche copy available in Barker.Bibliography: p. leaf 19.Also available on microfiche. AFOSR Grant 77-3281.by Steven N. Jones
Seismoelectric Modelling of the Flux-Normalized P-SV-TM Propagation Mode
No full textElastodynamic and electromagnetic processes are coupled together in saturated, porous media, by a phenomenon known as the electrokinetic effect. In horizontally layered media, the seismoelectric system, which contains the coupled elastodynamic and electromagnetic systems, can be separated into two independent modes of propagation: SH-TE and P-SV-TM. The SH-TE mode contains horizontally polarized shear waves coupled with transverse electric polarized electromagnetic waves. In the P-SV-TM mode, both fast and slow compressional waves are coupled with vertically polarized shear waves and transverse magnetic polarized electromagnetic waves. In this thesis, the P-SV-TM mode of the two-dimensional seismoelectric system was expressed in the form of both the two-way and one-way wave equations. The principle of normalizing energy flux across boundaries was applied, improving the matrix amplitude balance of the system and allowing for the implementation of one-way reciprocity theorems. We carried out full-waveform modelling of the flux-normalized P-SV-TM seismoelectric system in a 2-D fluid-saturated, horizontally-stratified, porous media. Both one-way and two-way wavefields were modelled, allowing the composition of one-way wavefields into two-way wavefields to be clearly observed. We investigated both the generation of electromagnetic fields due to the propagation of a seismic pertubation and the generation of seismic waves due to the propagation of a diffusive electromagnetic wave. Reciprocity of the wavefields was verified by applying reciprocity theorems to both one-way and two-way wave vectors. The electromagnetic field that is created when a seismic wave traverses a contrast in medium parameters is rapidly attenuated during propagation. To mitigate the decay in the amplitude of the signal with distance, we modelled a Vertical ElectroSeismic Profiling (VESP) survey, in which receivers could be placed in near proximity to the target layer. In another model, the sensitivity of the seismoelectric method to pore fluid contrasts was tested by simulating the influx of contaminants into an aquifer. It was observed that a small change in the conductivity of the aquifer led to a significant change in the strength of the electromagnetic signal that was generated at the top of the aquifer.Applied Geophysics and PetrophysicsGeotechnologyCivil Engineering and Geoscience
Tangle-bearing neurons survive despite disruption of membrane integrity in a mouse model of tauopathy
No full textNeurofibrillary tangles (NFTs) are associated with neuronal loss and correlate with cognitive impairment in Alzheimer disease, but how NFTs relate to neuronal death is not clear. We studied cell death in Tg4510 mice that reversibly express P301L mutant human tau and accumulate NFTs using in vivo multiphoton imaging of neurofibrillary pathology, propidium iodide (PI) incorporation into cells, caspase activation, and DNA labeling. We first observed that in live mice, a minority of neurons were labeled with the caspase probe or with PI fluorescence. These markers of cell stress were localized in the same cells and appeared specifically within NFT-bearing neurons. Contrary to expectations, the PI-stained neurons did not die during a day of observation; the presence of Hoechst-positive nuclei in them on the subsequent day indicated that the NFT-associated membrane disruption, as suggested by PI staining, and caspase activation do not lead to immediate death of neurons in this tauopathy model. This unique combination of in vivo multiphoton imaging with markers of cell death and pathological alteration is a powerful tool for investigating neuronal damage associated with neurofibrillary pathology
TM Steers Ready for the Trail. June 1909
No full textRecto: [inscribed] 1678 TM Steers Ready for the Trail. June 1909; Verso: [handwritten] near Wellington, Texas ca. 190
TM-score of the final (lowest energy) model against mean pair-wise TM-score within the model's ensemble.
No full text<p>Good correlation (Spearman's ρ = 0.73) emerges from the results. Inter-residue TM-score >0.26 is likely to produce a model with TM-score >0.5.</p
A FORMAL PROOF OF THE FACTOR PRICE EQUALIZATION THEOREM
No full textThis paper provides a formal proof of the Factor Price Equalization Theorem within the Heckscher Ohlin model derived by Ronald W. Jones in The Structure of Simple General Equilibrium Models" (1965), where formal proof is provided for the Heckscher Ohlin, Stolper Samuelson and Rybczynski Theorems."International Trade
GA Landsat 5 TM Analysis Ready Data Collection 3
No full textMaintenance and Update Frequency: asNeededStatement: This product is derived from the USGS Landsat Collection 1 archive.
The Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A1 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameters dataset was provided by the National Aeronautics and Space Administration (NASA). It was produced daily using 16 days of Terra and Aqua MODIS data at 500 m resolution.
The ozone data was provided by Environment Canada.
The Aerosol Optical Thickness data was provided by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).
The Precipitable Water for Entire Atmosphere data was provided by the National Oceanic and Atmospheric Administration (NOAA) / Earth System Research Laboratory (ESRL) / Physical Sciences Division (PSD).
The baseline Digital Surface Model (DSM) data produced from the Shuttle Radar Topography Mission (SRTM) was provided by the National Geospatial-Intelligence Agency (NGA).
Level 1 Collection 1 data was provided by the United States Geological Survey (USGS)'s Earth Resources Observation and Science (EROS) Center.<b>BACKGROUND</b><br/><p><br/><p>The United States Geological Survey's (USGS) Landsat satellite program has been capturing images of the Australian continent for more than 30 years. This data is highly useful for land and coastal mapping studies. <br/><p>In particular, the light reflected from the Earth’s surface (surface reflectance) is important for monitoring environmental resources – such as agricultural production and mining activities – over time. <br/><p>We need to make accurate comparisons of imagery acquired at different times, seasons and geographic locations. However, inconsistencies can arise due to variations in atmospheric conditions, sun position, sensor view angle, surface slope and surface aspect. These need to be reduced or removed to ensure the data is consistent and can be compared over time. <br/><p> </p><br/><b>WHAT THIS PRODUCT OFFERS</b><br/><p><br/><p>GA Landsat 5 TM Analysis Ready Data Collection 3 takes Landsat 5 Thematic Mapper (TM) imagery captured over the Australian continent and corrects for inconsistencies across land and coastal fringes. The result is accurate and standardised surface reflectance data, which is instrumental in identifying and quantifying environmental change. <br/><p><br/><p>The TM instrument is an advanced, multispectral scanning, Earth resources sensor which is designed to categorise the Earth's surface. It is particularly useful for agricultural applications and identification of land use. <br/><p><br/><p>This product is a single, cohesive Analysis Ready Data (ARD) package, which allows you to analyse surface reflectance data as is, without the need to apply additional corrections. <br/><p><br/><p>It contains three sub-products that provide corrections or attribution information:<br/><p><br/><p> 1) GA Landsat 5 TM NBAR Collection 3 <br/><p> 2) GA Landsat 5 TM NBART Collection 3<br/><p> 3) GA Landsat 5 TM OA Collection 3<br/><p><br/><p>The resolution is a 30 m grid based on the USGS Landsat Collection 1 archive
The dependence of light extraction improvement on optimized surface microstructure for AlGaN-based UVC-LEDs considering TM-polarized emission
No full textIn order to improve the light extraction of AlGaN-based short wavelength ultraviolet light emitting diodes (DUC-LEDs), a type of microstructure with high aspect ratio is introduced and optimized on the AlN substrate surface. And, particle swarm optimization (PSO) algorithm is used to inverse design of the surface microstructure to maximize the light extraction efficiency (LEE). Considering that the propagation characteristics of TM-polarized light are different from that of TE-polarized light, the optical field distribution and LEE is analyzed for the UVC-LEDs with different TE-polarized component when the optimized surface microstructure is applied. Furthermore, the preparation process tolerance of the high aspect ratio structure is discussed by calculating the LED's LEE when the structural deviation occurs or morphology changes. Simulation results show that, by using the optimized surface microstructure based on parabola cone array, the LEDs' LEE is increased from 4.4% to 8.7% and from 0.4% to 3.7% for TE-polarized and TM-polarized emission, respectively. In addition, it is demonstrated that the light extraction improvement by the surface microstructure has a good tolerance to the structural deviation and morphology. The results are significant for improving light extraction and realizing high efficient short wavelength AlGaN-based UVC-LEDs by designing surface microstructures.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Esmaeil Zadeh grou
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