17,782 research outputs found
The Forecasting Capacity of Housing Price Expectations
This study captures the essential elements of the price expectations of market participants in a rising market. Adopting a forward-looking approach, this paper explores the effectiveness of expectations as an indicator of forthcoming housing price changes in Hong Kong. Examination of the quarterly survey data from December 2003 to September 2007 indicates that both homeowners and non-homeowners tend to overestimate the probability of future housing price increases yet underestimate its volatility. This adds weight to the argument that market participants are generally not rational in the prediction of price movement. Homeowners, investors and potential home buyers have more or less the same level of confidence about the future market outlook. Like non-owners, they expect higher prices. The number of correct forecasts exceeds incorrect forecasts, suggesting that overall price expectations are fairly close to realization. It can be broadly concluded that the aggregate price expectations in the long run can be an appropriate forecasting tool for future market performance.Price expectations; Forecastability; Housing market; Hong Kong
Presumed choroidal metastasis from soft tissue myoepithelial carcinoma
Purpose: To report a case of presumed choroidal metastasis from soft tissue myoepithelial carcinoma and highlight challenges in its diagnosis.
Observations: A 52-year-old man was referred with a two-week history of photopsia in his left eye. His background medical history included known soft tissue myoepithelial carcinoma metastatic to his bone, lung, liver and chest wall. A large, raised, yellow choroidal lesion was identified nasal to and abutting the optic disc. This lesion demonstrated growth 1 month after presentation. The patient died with widespread metastatic disease 5 months after initial presentation.
Conclusion and importance: Soft tissue myoepithelial carcinoma can rarely metastasise to the choroid and present as a rapidly-growing, yellow, echodense tumour with serous retinal detachment. MRI brain can assist in tumour evaluation and monitoring progression, while immunoperoxidase stains and molecular testing can assist with diagnosis. The condition has an aggressive natural history and poor prognosi
Anisotropic Galactic Outflows and Enrichment of the Intergalactic Medium. I: Monte Carlo Simulations
We have developed an analytical model to describe the evolution of
anisotropic galactic outflows. With it, we investigate the impact of varying
opening angle on galaxy formation and the evolution of the IGM. We have
implemented this model in a Monte Carlo algorithm to simulate galaxy formation
and outflows in a cosmological context. Using this algorithm, we have simulated
the evolution of a comoving volume of size [12h^(-1)Mpc]^3 in the LCDM
universe. Starting from a Gaussian density field at redshift z=24, we follow
the formation of ~20,000 galaxies, and simulate the galactic outflows produced
by these galaxies. When these outflows collide with density peaks, ram pressure
stripping of the gas inside the peak may result. This occurs in around half the
cases and prevents the formation of galaxies. Anisotropic outflows follow the
path of least resistance, and thus travel preferentially into low-density
regions, away from cosmological structures (filaments and pancakes) where
galaxies form. As a result, the number of collisions is reduced, leading to the
formation of a larger number of galaxies. Anisotropic outflows can
significantly enrich low-density systems with metals. Conversely, the
cross-pollution in metals of objects located in a common cosmological
structure, like a filament, is significantly reduced. Highly anisotropic
outflows can travel across cosmological voids and deposit metals in other,
unrelated cosmological structures.Comment: 32 pages, 9 figures (2 color). Revised version accepted in Ap
The Variability of Sagittarius A* at Centimeter Wavelengths
We present the results of a 3.3-year project to monitor the flux density of
Sagittarius A* at 2.0, 1.3, and 0.7 cm with the VLA. The fully calibrated light
curves for Sgr A* at all three wavelengths are presented. Typical errors in the
flux density are 6.1%, 6.2%, and 9.2% at 2.0, 1.3, and 0.7 cm, respectively.
There is preliminary evidence for a bimodal distribution of flux densities,
which may indicate the existence of two distinct states of accretion onto the
supermassive black hole. At 1.3 and 0.7 cm, there is a tail in the distribution
towards high flux densities. Significant variability is detected at all three
wavelengths, with the largest amplitude variations occurring at 0.7 cm. The rms
deviation of the flux density of Sgr A* is 0.13, 0.16, and 0.21 Jy at 2.0, 1.3,
and 0.7 cm, respectively. During much of this monitoring campaign, Sgr A*
appeared to be relatively quiescent compared to results from previous
campaigns. At no point during the monitoring campaign did the flux density of
Sgr A* more than double its mean value. The mean spectral index of Sgr A* is
alpha=0.20+/-0.01, with a standard deviation of 0.14. The spectral index
appears to depend linearly on the observed flux density at 0.7 cm with a
steeper index observed during outbursts. This correlation is consistent with
the expectation for outbursts that are self-absorbed at wavelengths of 0.7 cm
or longer and inconsistent with the effects of simple models for interstellar
scintillation. Much of the variability of Sgr A*, including possible time lags
between flux density changes at the different wavelengths, appears to occur on
time scales less than the time resolution of our observations (8 days). Future
observations should focus on the evolution of the flux density on these time
scales.Comment: 16 pages, 10 figures, accepted for publication in A
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