12,125 research outputs found
Study of growth parameters for refractory carbide single crystals Quarterly status report no. 6, 1 Jun. - 1 Sep. 1965
Growth parameters for refractory tantalum carbide single crystal
Study of growth parameters for refractory carbide single crystals quarterly status report no. v, mar. 1 - jun. 1, 1965
Growth parameters for refractory carbide single crystal
Study of process variables associated with manufacturing hermetically sealed nickel-cadium cells Quarterly report, 23 May - 23 Aug. 1970
Separator materials, ceramic to metal seals, cell plate polarization and impregnation processes, and plaque sintering data for study of variables in manufacture of nickel cadmium cell
Calculation of two-dimensional turbulent flow fields
Navier-Stokes equation solutions for two- dimensional turbulent flow fields of compressible viscous flui
Stringy Effects During Inflation and Reheating
We consider inflationary cosmology in the context of string compactifications
with multiple throats. In scenarios where the warping differs significantly
between throats, string and Kaluza-Klein physics can generate potentially
observable corrections to the cosmology of inflation and reheating. First we
demonstrate that a very low string scale in the ground state compactification
is incompatible with a high Hubble scale during inflation, and we propose that
the compactification geometry is altered during inflation. In this
configuration, the lowest scale is just above the Hubble scale, which is
compatible with effective field theory but still leads to potentially
observable CMB corrections. Also in the appropriate region of parameter space,
we find that reheating leads to a phase of long open strings in the Standard
Model sector (before the usual radiation-dominated phase). We sketch the
cosmology of the long string phase and we discuss possible observational
consequences.Comment: 33pp, RevTeX4, v2. minor changes, added ref
Gravitational waves from an early matter era
We investigate the generation of gravitational waves due to the gravitational
instability of primordial density perturbations in an early matter-dominated
era which could be detectable by experiments such as LIGO and LISA. We use
relativistic perturbation theory to give analytic estimates of the tensor
perturbations generated at second order by linear density perturbations. We
find that large enhancement factors with respect to the naive second-order
estimate are possible due to the growth of density perturbations on sub-Hubble
scales. However very large enhancement factors coincide with a breakdown of
linear theory for density perturbations on small scales. To produce a
primordial gravitational wave background that would be detectable with LIGO or
LISA from density perturbations in the linear regime requires primordial
comoving curvature perturbations on small scales of order 0.02 for Advanced
LIGO or 0.005 for LISA, otherwise numerical calculations of the non-linear
evolution on sub-Hubble scales are required.Comment: 23 pages, 2 figure
Magnetic cloaking by a paramagnet/superconductor cylindrical tube in the critical state
Cloaking of static magnetic fields by a finite thickness type-II
superconductor tube being in the full critical state and surrounded by a
coaxial paramagnet shell is studied. On the basis of exact solutions to the
Maxwell equations, it is shown that, additionally to previous studies assuming
the Meissner state of the superconductor constituent, perfect cloaking is still
realizable at fields higher than the field of full flux penetration into the
superconductor and for arbitrary geometrical parameters of both constituents.
It is also proven that simultaneously the structure is fully undetectable under
the cloaking conditions. Differently from the case of the Meissner state the
cloaking properties in the application relevant critical state are realized,
however, only at a certain field magnitude.Comment: 5 pages, 4 figures; to be published in Applied Physics Letters. arXiv
admin note: substantial text overlap with arXiv:1401.356
Gamma-rays from ultracompact minihalos: potential constraints on the primordial curvature perturbation
Ultracompact minihalos (UCMHs) are dense dark matter structures which can
form from large density perturbations shortly after matter-radiation equality.
If dark matter is in the form of Weakly Interacting Massive Particles (WIMPs),
then UCMHs may be detected via their gamma-ray emission. We investigate how the
{\em{Fermi}} satellite could constrain the abundance of UCMHs and place limits
on the power spectrum of the primordial curvature perturbation. Detection by
{\em Fermi} would put a lower limit on the UCMH halo fraction. The smallest
detectable halo fraction, , is for . If gamma-ray emission from UCMHs is not detected, an
upper limit can be placed on the halo fraction. The bound is tightest, , for . The
resulting upper limit on the power spectrum of the primordial curvature
perturbation in the event of non-detection is in the range on scales . This is substantially tighter than the existing constraints from
primordial black hole formation on these scales, however it assumes that dark
matter is in the form of WIMPs and UCMHs are not disrupted during the formation
of the Milky Way halo.Comment: 5 pages, 2 figures, version to appear in Phys. Rev. D, minor change
Holidaying with the family pet: No dogs allowed!
This paper assesses the extent to which dog owners located in Brisbane, Australia, wish to holiday with their pets, and whether there is a gap between this desire and reality. The paper also examines the extent to which this demand is being catered for by the tourism accommodation sector. The need for this study reflects the increasingly significant role dogs are playing in the lives of humans, and the scale
of the dog-owning population. The results suggest that, although there is a strong desire among dog owners to take holidays with their pets, the actualisation of this
desire is comparatively low. A significant obstacle to the realisation of this desire appears to be a dearth of pet-friendly accommodation. This has implications for the
ability of the tourism industry to benefit from this potentially lucrative market, that is, the dog-owning population
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