341 research outputs found

    Substitute solders

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    Somewhat in excess of one- fifth of the tin consumed in the United States goes into the manufacture of solders ; no one type of application, with the single exception of tin plate, uses more than one-third this amount. With the growing possibility of curtailment in tin supplies to the United States, it is appropriate that an effort be made to find satisfactory substitutes in an application such as this which is vital both to peace-time industry and to the manufacture of war materials

    Cu-Au type orderings in the staggered quadrupolar region of the fcc Blume Emery Griffiths model

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    The spin-1 Ising (BEG) model has been simulated using a cellular automaton (CA) algorithm improved from the Creutz cellular automaton (CCA) for a face-centered cubic (fcc) lattice. The ground state diagram (kk, dd) of the fcc BEG model has ferromagnetic (FF), quadrupolar (QQ) and staggered quadrupolar (SQSQ) ordering regions. The simulations have been made in the staggered quadrupolar region for the parameter values in the intervals −24≤d=D/J<0 -24\leq d=D/J<0 and −3≤k=K/J≤0-3\leq k=K/J\leq 0 . The phase diagrams on the (kTC/J kT_{C}/J, dd) and the (kTC/JkT_{C}/J, kk) planes have been obtained through k=−3 k=-3 and d=−4d=-4 lines, respectively. The staggered quadrupolar ordering region separates into five ordering regions (A3B(a)A_{3}B(a), A3B(f)A_{3}B(f), ABAB (type-I), ABAB(type-II) and AB3(f)AB_{3}(f)) which have the different stoichiometric Cu-Au type structures.Comment: 24 pages, 11 figure

    Influence of Alloying upon Grain-Boundary Creep

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    Grain-boundary displacement, occurring in bicrystals during creep at elevated temperature (350 degrees c), has been measured as a function of the copper content (0.1 to 3 percent) in a series of aluminum-rich aluminum-copper solid-solution alloys. The minimums in stress and temperature, below which grain-boundary motion does not occur, increase regularly with the copper content as would be expected if recovery is necessary for movement. Otherwise, the effects, if any, of the copper solute upon grain-boundary displacement and its rate are too small for identification by the experimental technique employed. It was shown, additionally, that grain-boundary displacement appears regular and proceeds at a constant rate if observed parallel to the stress axis, whereas the motion is seen to occur in a sequence of surges and the rate to diminish with time if the observations are made perpendicular to the stress axis

    Generation and Structure of Solitary Rossby Vortices in Rotating Fluids

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    The formation of zonal flows and vortices in the generalized Charney-Hasegawa-Mima equation is studied. We focus on the regime when the size of structures is comparable to or larger than the deformation (Rossby) radius. Numerical simulations show the formation of anticyclonic vortices in unstable shear flows and ring-like vortices with quiescent cores and vorticity concentrated in a ring. Physical mechanisms that lead to these phenomena and their relevance to turbulence in planetary atmospheres are discussed.Comment: 3 pages in REVTeX, 5 postscript figures separately, submitted to Phys. Rev.

    Experimental rodent models of brainstem tumors

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    Despite recent advances in surgical technology, resection is not an option for many brainstem tumors. Experimental models have played essential roles in examining new approaches to therapy. The objective of the present study was to generate models by determining coordinates for safe inoculation into the brainstem of mice and rats, and to establish whether the implantation of heterotopic cells would create reproducible survival curves. Morbidity and survival studies were used to map stereotactic coordinates allowing successful inoculation of tumor cells. Survival studies were used to investigate the time course of tumor growth. Tumor location was examined by light microscopy and magnetic resonance imaging. Mice survived injections of 2 microL of saline at interaural, lateral, and depth coordinates of -2.5, 1.0, and 3.5 mm and -1.5, 1.0, and 3.5 mm. Rats survived injections at interaural, lateral, and depth coordinates of -2.0, 2.0, and 7.0 mm and -3.0, 0, and 7.0 mm. Median survival of mice challenged with 5 x 10(5) EMT6 and 10(4) B16 tumor cells was 11 and 10 days, respectively. Median survival for rats challenged with 10(4) 9L and F98 cells was 14 and 13 days, respectively. The present study demonstrates a feasible approach to preparing models of brainstem tumors. Limitations of these models are discussed

    C2 prosthesis: anterior upper cervical fixation device to reconstruct the second cervical vertebra

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    Destruction of the second cervical vertebra leads to a highly unstable situation. Reconstruction is difficult because the axis plays a central role in rotatory movements and has a unique function in redistributing axial loads. The axis transfers the axial load of the two lateral masses of the atlas to three surfaces on the third cervical vertebra: the two articular facets and the vertebral body. As reconstruction is difficult and the instability in this region is life threatening, pathological processes are often treated less radically compared to other areas of the cervical spine. However, this more moderate approach may result in worse outcomes and prognoses. This paper presents the development of a new implant (C2 prosthesis) and two illustrative cases describing the implementation of this new implant. The C2 prosthesis provides anterior support and therefore allows a more radical surgical approach

    Turbulent spectrum of the Earth's ozone field

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    The Total Ozone Mapping Spectrometer (TOMS) database is subjected to an analysis in terms of the Karhunen-Loeve (KL) empirical eigenfunctions. The concentration variance spectrum is transformed into a wavenumber spectrum, Ec(k)% E_c(k). In terms of wavenumber Ec(k)E_c(k) is shown to be O(k−2/3)O(k^{-2/3}) in the inverse cascade regime, O(k−2)O(k^{-2}) in the enstrophy cascade regime with the spectral {\it knee} at the wavenumber of barotropic instability.The spectrum is related to known geophysical phenomena and shown to be consistent with physical dimensional reasoning for the problem. The appropriate Reynolds number for the phenomena is Re≈1010Re\approx 10^{10}.Comment: RevTeX file, 4 pages, 4 postscript figures available upon request from Richard Everson <[email protected]

    Recent Developments in Understanding Two-dimensional Turbulence and the Nastrom-Gage Spectrum

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    Two-dimensional turbulence appears to be a more formidable problem than three-dimensional turbulence despite the numerical advantage of working with one less dimension. In the present paper we review recent numerical investigations of the phenomenology of two-dimensional turbulence as well as recent theoretical breakthroughs by various leading researchers. We also review efforts to reconcile the observed energy spectrum of the atmosphere (the spectrum) with the predictions of two-dimensional turbulence and quasi-geostrophic turbulence.Comment: Invited review; accepted by J. Low Temp. Phys.; Proceedings for Warwick Turbulence Symposium Workshop on Universal features in turbulence: from quantum to cosmological scales, 200
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