12,727 research outputs found

    Observation of the stray field of thin film magnetic tips using electron holography

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    The stray field around thin film ferromagnetic tips employed for magnetic force microscopy has been revealed using electron holography. The experimental phase difference maps are in good agreement with simulations. Quantitative flux measurements of the leakage field are obtained

    Electromagnetic containerless processing requirements and recommended facility concept and capabilities for space lab

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    Containerless melting, reaction, and solidification experiments and processes which potentially can lead to new understanding of material science and production of new or improved materials in the weightless space environment are reviewed in terms of planning for spacelab. Most of the experiments and processes discussed are amenable to the employment of electromagnetic position control and electromagnetic induction or electron beam heating and melting. The spectrum of relevant properties of materials, which determine requirements for a space laboratory electromagnetic containerless processing facility are reviewed. Appropriate distributions and associated coil structures are analyzed and compared on the basis of efficiency, for providing the functions of position sensing, control, and induction heating. Several coil systems are found capable of providing these functions. Exchangeable modular coils in appropriate sizes are recommended to achieve the maximum power efficiencies, for a wide range of specimen sizes and resistivities, in order to conserve total facility power

    From Instantons to Sphalerons: Time-Dependent Periodic Solutions of SU(2)-Higgs Theory

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    We solve numerically for periodic, spherically symmetric, classical solutions of SU(2)-Higgs theory in four-dimensional Euclidean space. In the limit of short periods the solutions approach tiny instanton-anti-instanton superpositions while, for longer periods, the solutions merge with the static sphaleron. A previously predicted bifurcation point, where two branches of periodic solutions meet, appears for Higgs boson masses larger than 3.091MW3.091 M_W.Comment: 14 pages, RevTeX with eps figure

    Structural Collapse Behavior of Sands in Undrained Shear

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    Results from undrained torsional shear tests are presented and used to further examine the concepts of steady state and structural collapse in sands, with emphasis on the influence of the collapse mechanism on soil behavior at steady state. It is shown that the degree to which the material collapses is dependent on the loading conditions and the initial fabric of the sand. Consequently, the steady state position in the state diagram is also function of these parameters

    Observations of celestial X-ray sources above 20 keV with the high-energy scintillation spectrometer on board OSO 8

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    High-energy X-ray spectra of the Crab Nebula, Cyg- XR-1, and Cen A were determined from observations with the scintillation spectrometer on board the OSO-8 satellite, launched in June, 1975. Each of these sources was observed over two periods of 8 days or more, enabling a search for day-to-day and year to year variations in the spectral and temporal characteristics of the X-ray emission. No variation in the light curve of the Crab pulsar was found from observations which span a 15-day period in March 1976, with demonstrable phase stability. Transitions associated with the binary phase of Cyg XR-1 and a large change in the emission from Con A are reported

    Detection of high energy X-rays from the galactic center region

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    Observations of the galactic center region made with the high energy X-ray detector on OSO-8 are discussed. A strong hard X-ray which was detected during these observations from the vicinity of the galactic center are examined. The counting rate spectrum and the photon number spectrum of the flux are determined. Comparisons with the high energy X-ray fluxes observed from sources in the region by others are discussed

    The High Energy X-ray Spectrum of 4U1700-37 Observed from OSO-8

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    The most intense hard X-ray source in the confused region in Scorpius is identified as 4U1700-37. The 3.4-day modulation is seen above 20 keV with the intensity during eclipse being consistent with zero flux. The photon-number spectrum from 20 to 150 keV is well represented by a single power law with a photo-number spectral index of -2.77 + or - 0.35 or by a thermal bremsstrahlung spectrum with kT = 27 96.8-min X-ray modulation previously reported at lower energies. Despite the difficulties in reconciling both the lack of periodic modulation in the emitted X-radiation and the orbital dynamics of the system with theories of the evolution and physical properties of neutron stars, the observed properties of 4U1700-37 are all consistent with the source being a spherically accreting neutron star rather than a black hole
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