1,031 research outputs found

    Fairbairn’s Eastern Orthodoxy through Western Eyes - Book Review

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    Ram booster

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    The present invention is a space launch system and method to propel a payload bearing craft into earth orbit. The invention has two, or preferably, three stages. The upper stage has rocket engines capable of carrying a payload to orbit and provides the capability of releasably attaching to the lower, or preferably, middle stage. Similar to the lower stage, the middle stage is a reusable booster stage that employs all air breathing engines, is recoverable, and can be turned-around in a short time between missions

    Bostonia: The Boston University Alumni Magazine. Volume 20

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    Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

    Entire solutions of hydrodynamical equations with exponential dissipation

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    We consider a modification of the three-dimensional Navier--Stokes equations and other hydrodynamical evolution equations with space-periodic initial conditions in which the usual Laplacian of the dissipation operator is replaced by an operator whose Fourier symbol grows exponentially as \ue ^{|k|/\kd} at high wavenumbers k|k|. Using estimates in suitable classes of analytic functions, we show that the solutions with initially finite energy become immediately entire in the space variables and that the Fourier coefficients decay faster than \ue ^{-C(k/\kd) \ln (|k|/\kd)} for any C<1/(2ln2)C<1/(2\ln 2). The same result holds for the one-dimensional Burgers equation with exponential dissipation but can be improved: heuristic arguments and very precise simulations, analyzed by the method of asymptotic extrapolation of van der Hoeven, indicate that the leading-order asymptotics is precisely of the above form with C=C=1/ln2C= C_\star =1/\ln2. The same behavior with a universal constant CC_\star is conjectured for the Navier--Stokes equations with exponential dissipation in any space dimension. This universality prevents the strong growth of intermittency in the far dissipation range which is obtained for ordinary Navier--Stokes turbulence. Possible applications to improved spectral simulations are briefly discussed.Comment: 29 pages, 3 figures, Comm. Math. Phys., in pres

    Type IIP Supernova SN 2004et: A Multi-Wavelength Study in X-Ray, Optical and Radio

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    We present X-ray, broad band optical and low frequency radio observations of the bright type IIP supernova SN 2004et. The \cxo observed the supernova at three epochs, and the optical coverage spans a period of \sim 470 days since explosion. The X-ray emission softens with time, and we characterise the X-ray luminosity evolution as \Lx \propto t^{-0.4}. We use the observed X-ray luminosity to estimate a mass-loss rate for the progenitor star of \sim \ee{2}{-6} M_\odot \mathrm{yr}^{-1}. The optical light curve shows a pronounced plateau lasting for about 110 days. Temporal evolution of photospheric radius and color temperature during the plateau phase is determined by making black body fits. We estimate the ejected mass of 56^{56}Ni to be 0.06 ±\pm 0.03 M_\odot. Using the expressions of Litvinova & Nad\"{e}zhin (1985) we estimate an explosion energy of (0.98 ±\pm 0.25) ×1051\times 10^{51} erg. We also present a single epoch radio observation of SN 2004et. We compare this with the predictions of the model proposed by Chevalier et al. (2006). These multi-wavelength studies suggest a main sequence progenitor mass of \sim 20 M_\odot for SN 2004et.Comment: 13 Figures, Accepted for Publication in MNRA

    EDITOR : an interactive interface to ILLIAC IV - ARPA network multispectral image processing systems / CAC No. 114

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    Includes bibliographic references (p. 15-16)

    Hyperviscosity, Galerkin truncation and bottlenecks in turbulence

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    It is shown that the use of a high power α\alpha of the Laplacian in the dissipative term of hydrodynamical equations leads asymptotically to truncated inviscid \textit{conservative} dynamics with a finite range of spatial Fourier modes. Those at large wavenumbers thermalize, whereas modes at small wavenumbers obey ordinary viscous dynamics [C. Cichowlas et al. Phys. Rev. Lett. 95, 264502 (2005)]. The energy bottleneck observed for finite α\alpha may be interpreted as incomplete thermalization. Artifacts arising from models with α>1\alpha > 1 are discussed.Comment: 4 pages, 2 figures, Phys. Rev. Lett. in pres

    Identification and purification of a recombinant Treponema pallidum basic membrane protein antigen expressed in Escherichia coli.

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    A recombinant plasmid designated pLVS3 previously was described that harbored a 14-kilobase insert of Treponema pallidum genomic DNA. Escherichia coli maxicells programmed with this plasmid synthesized three treponemal protein antigens of molecular weights 39,000, 35,000, and 25,000 (39K, 35K, and 25K proteins, respectively). In this study, a detailed deletion analysis of pLVS3 demonstrated that the genetic information for all three protein antigens is contained within a 1.5-kilobase EcoRI-HpaI restriction fragment. The DNA sequence of this fragment revealed a single open reading frame of 361 codons that most likely encodes a signal peptide-bearing precursor to the 39K protein that can be transiently detected in E. coli maxicells. Evidence indicated that the 35K and 25K protein antigens are derivatives of the larger protein and are only produced in maxicells. A significant elevation in expression of the 39K treponemal protein antigen in E. coli was obtained by using the E. coli lpp and lac promoters and a genetic construction in which the signal peptide and first four residues of the "mature" 39K protein were replaced by six amino acids encoded by the vector. This hybrid protein exhibited an unusually high pI, which greatly facilitated its purification to homogeneity. By using antibody prepared against the hybrid protein, the native treponemal protein counterpart, also of molecular weight 39,000, was identified as a membrane component of T. pallidum. Since the native protein also exhibited a net positive charge, it has been designated the T. pallidum basic membrane protein

    Astrometry and geodesy with radio interferometry: experiments, models, results

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    Summarizes current status of radio interferometry at radio frequencies between Earth-based receivers, for astrometric and geodetic applications. Emphasizes theoretical models of VLBI observables that are required to extract results at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the achievements of VLBI during the past two decades in reference frames, Earth orientation, atmospheric effects on microwave propagation, and relativity.Comment: 83 pages, 19 Postscript figures. To be published in Rev. Mod. Phys., Vol. 70, Oct. 199
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