1,948 research outputs found

    Literacy Instruction and the Learning Disabled High School Student : Ideas and Applications for a Mindful Classroom

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    This thesis suggests that the emergent field of mindfulness and contemplative pedagogy can be a uniquely effective tool for use in the English classroom for learning disabled (LD) high school students. By first exploring definitions of difference and initiating a conversation about how we, as a society, conceptualize difference and how we provide literacy instruction for students who learn differently, this thesis advocates for a more complex and meaningful understanding of the difficult issues surrounding teaching literature and writing to LD high school students. The discussion then introduces some of the central tenets of mindfulness and contemplative practice and explores, first, some of its historical underpinnings and then, secondly, looks to some of its current applications in educational settings. An argument is made that the specific benefits of this type of approach—improved attention, awareness and empathy—are exactly the issues that seem to be most problematic for LD high school students. Because of this, mindulness and contemplative pedagogy has unique potential as an effective strategy with LD students. Finally, this thesis explores how the high school English classroom, in its attention to both literature and student writing is an ideal site for such an endeavor. By teaching LD students to use reflection and other contemplative strategies while reading literary texts and doing writing assignments, educators can help students make meaningful connections between themselves and what they learn. Ultimately, this kind of attention and awareness fosters confidence and curiosity in students and helps them to engage more meaningfully not only with what they read and write, but also with the world they live in

    Physical Mechanism of the d->d+is Transition

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    We discuss the basic physical mechanism of the d->d+is transition, which is the currently accepted explanation for the results of tunneling experiments into abab planes. Using the first-order perturbation theory, we show that the zero-bias states drive the transition. We present various order-of-magnitude estimates and consistency checks that support this picture.Comment: 7 pages, 2 figure

    Different regimes of Forster energy transfer between an epitaxial quantum well and a proximal monolayer of semiconductor nanocrystals

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    We calculate the rate of non-radiative, Forster-type energy transfer (ET) from an excited epitaxial quantum well (QW) to a proximal monolayer of semiconductor nanocrystal quantum dots (QDs). Different electron-hole configurations in the QW are considered as a function of temperature and excited electron-hole density. A comparison of the theoretically determined ET rate and QW radiative recombination rate shows that, depending on the specific conditions, the ET rate is comparable to or even greater than the radiative recombination rate. Such efficient Forster ET is promising for the implementation of ET-pumped, nanocrystal QD-based light emitting devices.Comment: 14 pages, 4 figure

    Spin noise of itinerant fermions

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    We develop a theory of spin noise spectroscopy of itinerant, noninteracting, spin-carrying fermions in different regimes of temperature and disorder. We use kinetic equations for the density matrix in spin variables. We find a general result with a clear physical interpretation, and discuss its dependence on temperature, the size of the system, and applied magnetic field. We consider two classes of experimental probes: 1. electron-spin-resonance (ESR)-type measurements, in which the probe response to a uniform magnetization increases linearly with the volume sampled, and 2. optical Kerr/Faraday rotation-type measurements, in which the probe response to a uniform magnetization increases linearly with the length of the light propagation in the sample, but is independent of the cross section of the light beam. Our theory provides a framework for interpreting recent experiments on atomic gases and conduction electrons in semiconductors and provides a baseline for identifying the effects of interactions on spin noise spectroscopy

    Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy

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    Positive and negative streamers are studied in ambient air at 1 bar; they emerge from a needle electrode placed 40 mm above a planar electrode. The amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses have rise times of 30 ns or shorter. Diameters, velocities and energies of the streamers are measured. Two regimes are identified; a low voltage regime where only positive streamers appear and a high voltage regime where both positive and negative streamers exist. Below 5 kV, no streamers emerge. In the range from 5 to 40 kV, positive streamers form, while the negative discharges only form a glowing cloud at the electrode tip, but no streamers. For 5 to 20 kV, diameters and velocities of the positive streamers have the minimal values of d=0.2 mm and v \approx 10^5 m/s. For 20 to 40 kV, their diameters increase by a factor 6 while the voltage increases only by a factor 2. Above the transition value of 40 kV, streamers of both polarities form; they strongly resemble each other, though the positive ones propagate further; their diameters continue to increase with applied voltage. For 96 kV, positive streamers attain diameters of 3 mm and velocities of 4*10^6 m/s, negative streamers are about 20 % slower and thinner. An empirical fit formula for the relation between velocity v and diameter d is v=0.5 d^2/(mm ns) for both polarities. Streamers of both polarities dissipate energies of the order of several mJ per streamer while crossing the gap.Comment: 20 pages, 9 figures, accepted for J. Phys.

    Nuclear Cryogenic Propulsion Stage Conceptual Design and Mission Analysis

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    The Nuclear Cryogenic Propulsion Stage (NCPS) is an in-space transportation vehicle, comprised of three main elements, designed to support a long-stay human Mars mission architecture beginning in 2035. The stage conceptual design and the mission analysis discussed here support the current nuclear thermal propulsion going on within partnership activity of NASA and the Department of Energy (DOE). The transportation system consists of three elements: 1) the Core Stage, 2) the In-line Tank, and 3) the Drop Tank. The driving mission case is the piloted flight to Mars in 2037 and will be the main point design shown and discussed. The corresponding Space Launch System (SLS) launch vehicle (LV) is also presented due to it being a very critical aspect of the NCPS Human Mars Mission architecture due to the strong relationship between LV lift capability and LV volume capacity

    Interplanetary Mission Design Handbook: Earth-to-Mars Mission Opportunities and Mars-to-Earth Return Opportunities 2009-2024

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    This paper provides information for trajectory designers and mission planners to determine Earth-Mars and Mars-Earth mission opportunities for the years 2009-2024. These studies were performed in support of a human Mars mission scenario that will consist of two cargo launches followed by a piloted mission during the next opportunity approximately 2 years later. "Porkchop" plots defining all of these mission opportunities are provided which include departure energy, departure excess speed, departure declination arrival excess speed, and arrival declinations for the mission space surrounding each opportunity. These plots are intended to be directly applicable for the human Mars mission scenario described briefly herein. In addition, specific trajectories and several alternate trajectories are recommended for each cargo and piloted opportunity. Finally, additional studies were performed to evaluate the effect of various thrust-to-weight ratios on gravity losses and total time-of-flight tradeoff, and the resultant propellant savings and are briefly summarized

    Advanced Lithography Simulation Tools for Development and Analysis of Wide-Field High Numerical Aperture Projection Optical Systems

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    Industrial demands for integrated circuits of higher speed and complexity have required the development of advanced lithographic exposure tools capable of sub-half micron resolution over increasingly larger fields. To this end, i-line and deep-uv tools employing Variable, high numerical aperture (NA) objectives are being aggressively developed. The design and manufacture of these advanced optical systems has also grown in complexity, since tighter tolerances on resolution and image placement must be maintained over the larger lens field. At the same time, usable focus and exposure latitude must be retained. The influence of lens aberrations on image formation under different illumination conditions, along with their non-intuitive nature has required the development of simulation tools that allow both the designer and the user of these systems to better understand their implications. These tools can be used to investigate and optimize the lithography process, including the effects of emerging technologies such as phase-shift masking, oblique illumination and frequency plane filtering./super 1,2,3/ This paper presents a method for determining the effects and interactions of various aberrations and illumination conditions using a statistically designed experhnent./super 4/ Fundamental differences in the way the aerial image is formed when varying the pupil energy distribution in the presence of aberrations are presented, as are examples of some of the more interesting effects

    Strain control of superlattice implies weak charge-lattice coupling in La0.5_{0.5}Ca0.5_{0.5}MnO3_3

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    We have recently argued that manganites do not possess stripes of charge order, implying that the electron-lattice coupling is weak [Phys Rev Lett \textbf{94} (2005) 097202]. Here we independently argue the same conclusion based on transmission electron microscopy measurements of a nanopatterned epitaxial film of La0.5_{0.5}Ca0.5_{0.5}MnO3_3. In strain relaxed regions, the superlattice period is modified by 2-3% with respect to the parent lattice, suggesting that the two are not strongly tied.Comment: 4 pages, 4 figures It is now explained why the work provides evidence to support weak-coupling, and rule out charge orde
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