1,501 research outputs found
Investigations of a novel pile and anchorage concept
Imperial Users onl
The 1998 November 14 Occultation of GSC 0622-00345 by Saturn. I. Techniques for Ground-Based Stellar Occultations
On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345.
We observed atmospheric immersion with NSFCAM at the National Aeronautics and
Space Administration's Infrared Telescope Facility on Mauna Kea, Hawaii.
Immersion occurred at 55.5\circ S planetocentric latitude. A 2.3 {\mu}m,
methane-band filter suppressed reflected sunlight. Atmospheric emersion and
ring data were not successfully obtained. We describe our observation,
light-curve production, and timing techniques, including improvements in
aperture positioning, removal of telluric scintillation effects, and timing.
Many of these techniques are known within the occultation community, but have
not been described in the reviewed literature. We present a light curve whose
signal-to-noise ratio per scale height is 267, among the best ground-based
signals yet achieved, despite a disadvantage of up to 8 mag in the stellar flux
compared to prior work.Comment: LaTeX/emulateapj, 6 pages, 3 figures. Online items: The FITS-format
light curve and the IDL code for the timing model are available from ApJ or
the lead autho
The 1998 November 14 Occultation of GSC 0622-00345 by Saturn. II. Stratospheric Thermal Profile, Power Spectrum, and Gravity Waves
On 1998 November 14, Saturn and its rings occulted the star GSC 0622-00345.
The occultation latitude was 55.5 degrees S. This paper analyzes the 2.3 {\mu}m
light curve derived by Harrington & French. A fixed-baseline isothermal fit to
the light curve has a temperature of 140 +/- 3 K, assuming a mean molecular
mass of 2.35 AMU. The thermal profile obtained by numerical inversion is valid
between 1 and 60 {\mu}bar. The vertical temperature gradient is >0.2 K/km more
stable than the adiabatic lapse rate, but it still shows the
alternating-rounded-spiked features seen in many temperature gradient profiles
from other atmospheric occultations and usually attributed to breaking gravity
(buoyancy) waves. We conduct a wavelet analysis of the thermal profile, and
show that, even with our low level of noise, scintillation due to turbulence in
Earth's atmosphere can produce large temperature swings in light-curve
inversions. Spurious periodic features in the "reliable" region of a wavelet
amplitude spectrum can exceed 0.3 K in our data. We also show that gravity-wave
model fits to noisy isothermal light curves can lead to convincing wave
"detections". We provide new significance tests for localized wavelet
amplitudes, wave model fits, and global power spectra of inverted occultation
light curves by assessing the effects of pre- and post-occultation noise on
these parameters. Based on these tests, we detect several significant ridges
and isolated peaks in wavelet amplitude, to which we fit a gravity wave model.
We also strongly detect the global power spectrum of thermal fluctuations in
Saturn's atmosphere, which resembles the "universal" (modified Desaubies) curve
associated with saturated spectra of propagating gravity waves on Earth and
Jupiter.Comment: LaTeX/emulateapj, 13 pages, 7 figure
Linkages between U.S Cross-border Portfolio Equity Flows and Equity Markets
There is an ongoing debate over the role that equity markets play in determining and influencing international equity flows. The first chapter of this dissertation describes the large portfolio equity flows into China and India, in order to understand the buying behavior of US investors. The rapid growth of the Chinese and Indian economies, coupled with the recent development and liberalization of their financial markets has attracted significant portfolio investment from U.S. investors. It is commonly assumed that domestic investors have an informational advantage over foreign investors; however, some recent empirical literature has questioned this assumption. Essay one dissects the nature of the relationship between foreign equity flows, equity returns, and related variables. The results of my empirical investigation provides evidence that U.S. institutional investors are making investment decisions based on long-run determinants of value rather than responding to price signals or ‘chasing returns\u27. I anticipate that the strong relationship between equity flows and fundamentals will strengthen as information asymmetries decline and US investors continue to develop more sophisticated methods of assessing underlying value in China and India. The second essay of this dissertation explores a new panel data set based on US gross cross-border equity flows to 20 industrialized nations combined with measures of market valuation for the period of 1977-2005. Empirical evidence of imperfect integration across world equity markets indicates that valuation matters. Consistent with relative value trading as a determinant of equity flow patterns, I find that equity flows decrease sharply with host-country market valuations—in particular the component of valuation that is forecasted to revert the following year. I also find that equity flows increase sharply with US equity market valuations. These results suggest the existence of a valuation channel for cross-border equity flows. The findings of this chapter show that US investors are informed about both domestic markets and foreign markets. Peripheral findings of this essay confirm the findings of other researches, but with a longer sample period. Consistent with existing literature, I find a negative influence of interest rates spreads, and information asymmetries on cross-border trade in equities
Relation of economics to higher accounting
I have always had, as most men seem to have, a rather hazy idea of what is called the science of accounting, and of the exact difference between the work of the accountant and the work of the bookkeeper. There is a difference, however, and in my remarks I shall endeavor to make clear the distinction as well as the relation of each to political economy
U(3) and Pseudo-U(3) Symmetry of the Relativistic Harmonic Oscillator
We show that a Dirac Hamiltonian with equal scalar and vector harmonic
oscillator potentials has not only a spin symmetry but an U(3) symmetry and
that a Dirac Hamiltonian with scalar and vector harmonic oscillator potentials
equal in magnitude but opposite in sign has not only a pseudospin symmetry but
a pseudo-U(3) symmetry. We derive the generators of the symmetry for each case.Comment: 8 pages, 0 figures, pusblished in Physical Review Letters 95, 252501
(2005
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