3,025 research outputs found
Letter from P. A. Doran to John Muir, 1903 Apr 21
San Francisco April 21st 1903 Professor John Muir. Martinez My Dear Professor Leaving here Thursday morning next with the Columbia will be my last trip for some time, and I go east from Portland, and possibly heave to in Europe/ Mrs. Doran will be accompanying me. I intended calling on you last month, but the annual drydocking and overhauling threw us so far behind thime that it looks nearly like the whole month to catch our old schedule. And this month Mrs. Doran has been busy preparing for our journey. I am sorry I canÎĂĂt see Helen before I leave, as I have some huge stories of our friends the ÎĂÂŁHuge Levithians of the deep.ÎĂ„ But I will expect to see some on the Atlantic and will tell her all about them when I return. Mrs. Doran joins me in kindest regards to yourself and your family. Wishing you a successful voyage and that you may discover several new ÎĂÂŁHuge LeviathasrsÎĂ„ I am Sincerely yours P. A. Doran S.S. Columbi
Letter from P. A. Doran to John Muir, 1901 Dec 21.
San Francisco Dec 21st, 1901.Professor John Muir,Martinez,My dear Professor,I beg to acknowledge receipt of you new book for which I thank you. I shall take it with me this voyage, and have the pleasure of a stroll through the forests while on the dark blue. Trusting you are all well, and with kindest regards to Wanda and Helen, and best wishes for a Happy New Year I amRespectfully yoursP. A. Doran.2110 Union St.0290
Letter from P. A. Doran to John Muir, 1905 Sep 28.
[letterhead]S. S. Columbia Sept. 28, 1905My dear Professor Muir,I am very much pleased to know that Helen is improving and hope, for your sake as well as her own, she will continue so and grow entirely well.I wish I could prescribe for her with the same success as in your case. However, when she is again well and strong, I would recommend a trip on the Columbia, and I shall arrange matters with old ocean, and ours esteemed friends the huge leviathans, for a pleasant voyage.Trusting this will find you in good health and confidence regarding Helen\u27s speedy recover I amYours very truly, P. A. Dorans. S. ColumbiaSpear St. WharfS. F.0363
Letter from P. A. Doran to John Muir, 1899 Sep 8.
san Francisco Sept 8th, 99.Professor John Muir,Martinez, Cal.My Dear Professor; I received your book and many thanks to you. I can see your many characteristics throughout the work, and every page reminds me of the pleasant hours spent together during our voyage to Alaska. To say the least it is a noble and interesting work, and we are all delighted with it. I forward you a copy of the H.A.E. poems. I would have send them before but I was called to Portland unexpectedly, to take command of S.S. Columbia . Should you contemplate a trip to Portland, I would be very pleased to have you come on the Columbia , and I promise you our morning coffee shall be the best.Hoping we will be shipmates again in the near future and commemorate the 02619 H.A.E. by sliding over a few glaciers Slivers I am Yours very respectfullyP.A. DoranS.S. ColumbiaSan Francisco0261
Women's mountaineering tourism::an empirical investigation of its theoretical constraint dimensions
The purpose of this study is to investigate the perceived constraints on participating in mountaineering tourism faced by women, and to empirically verify the dimensionality of those constraints. Survey responses from 314 female mountaineers were collected and four constraint dimensions were identified using confirmatory factor analysis. Three of these dimensions: 'intra-personal', 'inter-personal' and 'structural' constraints support earlier findings in the extant literature, both in general and in the adventure literature more specifically. The identification of a fourth dimension relating to 'family' constraints represents a theoretical contribution to the literature and an additional barrier to women's participation in mountaineering tourism. In previous studies, âfamilyâ constraints have typically been subsumed within âinter-personalâ or 'intra-personal' constraints, but have emerged as a distinctly separate constraint category for women in relation to this particular tourist activity. The findings also have important implications for adventure tourism management practice
Fermion absorption cross section of a Schwarzschild black hole
We study the absorption of massive spin-half particles by a small
Schwarzschild black hole by numerically solving the single-particle Dirac
equation in Painleve-Gullstrand coordinates. We calculate the absorption cross
section for a range of gravitational couplings Mm/m_P^2 and incident particle
energies E. At high couplings, where the Schwarzschild radius R_S is much
greater than the wavelength lambda, we find that the cross section approaches
the classical result for a point particle. At intermediate couplings we find
oscillations around the classical limit whose precise form depends on the
particle mass. These oscillations give quantum violations of the equivalence
principle. At high energies the cross section converges on the geometric-optics
value of 27 \pi R_S^2/4, and at low energies we find agreement with an
approximation derived by Unruh. When the hole is much smaller than the particle
wavelength we confirm that the minimum possible cross section approaches \pi
R_S^2/2.Comment: 11 pages, 3 figure
Varying Alpha Monopoles
We study static magnetic monopoles in the context of varying alpha theories
and show that there is a group of models for which the t'Hooft-Polyakov
solution is still valid. Nevertheless, in general static magnetic monopole
solutions in varying alpha theories depart from the classical t'Hooft-Polyakov
solution with the electromagnetic energy concentrated inside the core seeding
spatial variations of the fine structure constant. We show that Equivalence
Principle constraints impose tight limits on the allowed variations of alpha
induced by magnetic monopoles which confirms the difficulty to generate
significant large-scale spatial variation of the fine structure constant found
in previous works. This is true even in the most favorable case where magnetic
monopoles are the source for these variations.Comment: 8 pages, 10 figures; Version to be published in Phys. Rev.
Early Dark Energy Cosmologies
We propose a novel parameterization of the dark energy density. It is
particularly well suited to describe a non-negligible contribution of dark
energy at early times and contains only three parameters, which are all
physically meaningful: the fractional dark energy density today, the equation
of state today and the fractional dark energy density at early times. As we
parameterize Omega_d(a) directly instead of the equation of state, we can give
analytic expressions for the Hubble parameter, the conformal horizon today and
at last scattering, the sound horizon at last scattering, the acoustic scale as
well as the luminosity distance. For an equation of state today w_0 < -1, our
model crosses the cosmological constant boundary. We perform numerical studies
to constrain the parameters of our model by using Cosmic Microwave Background,
Large Scale Structure and Supernovae Ia data. At 95% confidence, we find that
the fractional dark energy density at early times Omega_early < 0.06. This
bound tightens considerably to Omega_early < 0.04 when the latest Boomerang
data is included. We find that both the gold sample of Riess et. al. and the
SNLS data by Astier et. al. when combined with CMB and LSS data mildly prefer
w_0 < -1, but are well compatible with a cosmological constant.Comment: 6 pages, 3 figures; references added, matches published versio
Painleve-Gullstrand Coordinates for the Kerr Solution
We construct a coordinate system for the Kerr solution, based on the zero
angular momentum observers dropped from infinity, which generalizes the
Painleve-Gullstrand coordinate system for the Schwarzschild solution. The Kerr
metric can then be interpreted as describing space flowing on a (curved)
Riemannian 3-manifold. The stationary limit arises as the set of points on this
manifold where the speed of the flow equals the speed of light, and the
horizons as the set of points where the radial speed equals the speed of light.
A deeper analysis of what is meant by the flow of space reveals that the
acceleration of free-falling objects is generally not in the direction of this
flow. Finally, we compare the new coordinate system with the closely related
Doran coordinate system.Comment: 6 pages; v2: new section, matches final published version; v3: sign
error in the expression of the function delta correcte
New Techniques for Analysing Axisymmetric Gravitational Systems. 1. Vacuum Fields
A new framework for analysing the gravitational fields in a stationary,
axisymmetric configuration is introduced. The method is used to construct a
complete set of field equations for the vacuum region outside a rotating
source. These equations are under-determined. Restricting the Weyl tensor to
type D produces a set of equations which can be solved, and a range of new
techniques are introduced to simplify the problem. Imposing the further
condition that the solution is asymptotically flat yields the Kerr solution
uniquely. The implications of this result for the no-hair theorem are
discussed. The techniques developed here have many other applications, which
are described in the conclusions.Comment: 30 pages, no figure
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