3,152 research outputs found

    Resonant inelastic x-ray scattering study of charge excitations in La2CuO4

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    We report a resonant inelastic x-ray scattering study of the dispersion relations of charge transfer excitations in insulating La2_2CuO4_4. These data reveal two peaks, both of which show two-dimensional characteristics. The lowest energy excitation has a gap energy of ∼2.2\sim 2.2 eV at the zone center, and a dispersion of ∼1\sim 1 eV. The spectral weight of this mode becomes dramatically smaller around (π\pi, π\pi). The second peak shows a smaller dispersion (∼0.5\sim 0.5 eV) with a zone-center energy of ∼3.9\sim 3.9 eV. We argue that these are both highly dispersive exciton modes damped by the presence of the electron-hole continuum.Comment: 5 pages, 3 figure

    The measurement of aircraft performance and stability and control after flight through natural icing conditions

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    The effects of airframe icing on the performance and stability and control of a twin-engine commuter-class aircraft were measured by the NASA Lewis Research Center. This work consisted of clear air tests with artificial ice shapes attached to the horizontal tail, and natural icing flight tests in measured icing clouds. The clear air tests employed static longitudinal flight test methods to determine degradation in stability margins for four simulated ice shapes. The natural icing flight tests employed a data acquisition system, which was provided under contract to NASA by Kohlman Systems Research Incorporated. This system used a performance modeling method and modified maximum likelihood estimation (MMLE) technique to determine aircraft performance degradation and stability and control. Flight test results with artificial ice shapes showed that longitudinal, stick-fixed, static margins are reduced on the order of 5 percent with flaps up. Natural icing tests with the KSR system corroborated these results and showed degradation in the elevator control derivatives on the order of 8 to 16 percent depending on wing flap configuration. Performance analyses showed the individual contributions of major airframe components to the overall degration in lift and drag

    Pembuatan dan Uji Efektivitas Chess Of Chemistry (Coc)sebagai Upaya Peningkatan Minat, Prestasi dan Kecepatan Berpikir Siswa dalam Pokok Bahasan Stoikiometri

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    Pembelajaran dibidang Kimia seringkali dianggap sulit bagi pelajar maupun mahasiswa terutama untuk bidang perhitungan kimia dan deskripsi objek yang dipelajari di kimia yang cenderung abstrak, kendala ini mesti dicari solusinya agar bidang kimia yang punya peranan penting di kehidupan dapat dipelajari dengan baik oleh pelajar ataupun mahasiswa, sehingga Sumber Daya Manusia (SDM) yang memahami kimia akan dapat termanfaatkan dengan baik demi kemajuan bangsa. Penelitian ini bertujuan untuk mengetahui pengaruh dan efektivitas Chess of Chemistry (COC) sebagai Media Pembelajaran terhadap pembelajaran siswa pada pokok bahasan Stoikiometri khususnya dan perhitungan kimia pada umumnya, penelitian ini berjenis eksperimen (Experiment Research) yang melibatkan 2 kelas yang mengambil perwakilan dari kelas-kelas IPA yang dipilih berdasarkan homogenitas sebagai sampel. Populasi dari penelitian ini adalah pelajar bidang IPA SMAN 8 Kota Bengkulu, pengujian efektivitas dari COC ini dilakukan dengan membandingkan rata-rata nilai dan kecepatan berpikir menggunakan tes yang singkat(dalam rentang waktu yang sempit), antara kelas yang menggunakan Chess of Chemistry (COC) dalam pembelajaran dan yang tidak, dengan membandingkan nilai rata-rata tes, waktu dan nilai rata-rata tes sebelumnya serta membandingkan nilai rata-rata kelas yang menggunakan COC dan kelas yang menggunakan metode konvensional, kesimpulan efektivitas positif diambil, jika nilai rata-rata kelas dengan metode menggunakan Chess of Chemistry (COC) > dari kelas yang menggunakan metode tanpa media Chess of Chemistry (COC)

    Tailoring teleportation to the quantum alphabet

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    We introduce a refinement of the standard continuous variable teleportation measurement and displacement strategies. This refinement makes use of prior knowledge about the target state and the partial information carried by the classical channel when entanglement is non-maximal. This gives an improvement in the output quality of the protocol. The strategies we introduce could be used in current continuous variable teleportation experiments.Comment: 16 pages, 6 figures, RevTeX, made changes as recommended by referee, other minor textual corrections, resubmitted to Phys. Rev.

    Seismic and geodetic constraints on Cascadia slow slip

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    Automatically detected and located tremor epicenters from episodic tremor and slip (ETS) episodes in northern Cascadia provide a high-resolution map of Washington’s slow slip region. Thousands of epicenters from the past four ETS events from 2004 to 2008 provide detailed map-view constraints that correlate with geodetic estimates of the simultaneous slow slip. Each of these ETS events exhibits remarkable similarity in the timing and geographic distribution of tremor density and geodetically inferred slip. Analysis of the latest 15-month inter-ETS period also reveals ageodetic tremor activity similar both in duration and extent to ETS tremor. Epicenters from both ETS and inter- ETS tremor are bounded between the 30- and 45-km plate interface depth contours and locate approximately 75 km east of previous estimates of the locked portion of the subducting Juan de Fuca plate. Inter-ETS tremor overlaps but is generally downdip of ETS tremor and does not yet correlate with geodetically observed slip, but this is likely because the slip is below current GPS detection levels. Based on the tremor and slip correlation and the tremor-duration and slip magnitude relationship, we suggest that the well-resolved, sharp updip edge of tremor epicenters reflects a change in plate interface coupling properties. The region updip of this boundary may accumulate stress with the potential for coseismic shear failure during a megathrust earthquake. Alternatively, plate convergence in this region could be accommodated by continuous slow slip with no detectable tremor or by slow slip events with sufficiently long recurrence intervals that none have been detected during the past 10 years of GPS observations

    The vertebrate fauna of the Upper Permian of Niger—III, morphology and ontogeny of the hindlimb of Moradisaurus grandis (Reptilia, Captorhinidae)

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    We describe hindlimb elements of the large captorhinid Moradisaurus grandis (Reptilia: Captorhinidae) recently collected from the Upper Permian Moradi Formation of north-central Niger. This description is based primarily on an associated partial skeleton comprising a hemimandible, vertebral column, and partial left and nearly complete right hindlimb. Additionally, we report on a well-preserved, articulated, and essentially complete juvenile pes that provides important information on the ontogeny of the captorhinid tarsus. The hindlimb of Moradisaurus is stout and more massively built than in any other known captorhinid. The femur displays several features interpreted as adaptations to the demands of large body size, and the tibia and fibula have short, wide shafts and hypertrophied condyles and epicondyles. The astragalus is very derived, possessing two accessory ossifications and a relatively horizontal tibial articulation, indicating that the tibia was held more vertically than in other captorhinids. The calcaneum is co-ossified with distal tarsal five. The juvenile pes indicates that the captorhinid centrale arose from the fusion of two ossification centers, and that the captorhinid astragalus arose from the fusion of at least three ossification centers

    Crystal growth of ice Ih by revapor-deposition and diffusion suppression of monomolecular water in a polymer solid: spectroscopic observation of phase transition of water sorbed into solid polystyrene.

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    Monomolecular water in a solid polymer, which has no effective hydrogen bonding sites, was revealed by temperature-variable Fourier transform infrared spectroscopy to be condensable and crystallizable. Ice Ih formed in the polymer matrix was grown by vapor deposition and was reduced by sublimation. Moreover, rapid cooling induced crystal growth by vapor deposition during heating (revapor-deposition). These results indicate the requirement of a change in the generally accepted understanding of the thermal responses of water in a polymer matrix and give rise to a problem for general interpretation of the category of water in a polymer matrix based on calorimetrical analysis at very low water contents
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