1,340 research outputs found
Bank runs, deposit insurance, and liquidity
This article develops a model which shows that bank deposit contracts can provide allocations superior to those of exchange markets, offering an explanation of how banks subject to runs can attract deposits. Investors face privately observed risks which lead to a demand for liquidity. Traditional demand deposit contracts which provide liquidity have multiple equilibria, one of which is a bank run. Bank runs in the model cause real economic damage, rather than simply reflecting other problems. Contracts which can prevent runs are studied, and the analysis shows that there are circumstances when government provision of deposit insurance can produce superior contracts.Deposit insurance ; Liquidity (Economics)
The Application of Ranging Techniques to Navigation and Traffic Control
During the last decade a variety of ground- and airbased radio aids have been implemented in efforts to solve major military problems in navigation and guidance, and command, control and communications. Because of significant advances in space technology and avionics, satellite-based systems to provide position-fixing data by means of ranging and range-differencing techniques, and to provide communications capability, have been shown to be feasible and attractive, and to have unique technical and operational advantages. World-wide coverage, essentially instantaneously availability, and threedimensional position-fixing accuracy of a few tens of feet seem feasible. In the civil area, demand for improved communications over the oceans, and for improved air traffic control over both the U.S. and the oceans, may be met by space-based systems. Indeed, the Office of Telecommunications Policy has recently called for a satellite telecommunications service for over-ocean aeronautical operations. A developing view supports the use of satellite-ranging techniques and satellite communications to provide for certain fundamental air traffic control functions over the U. S. in the period through the 1990s. From a satellite and data processing point of view, it appears feasible to implement in the early 1980s a system which could provide surveillance data to the order of 100 feet in three dimensions; an emergency communications capability corresponding to the operational notion of intermittent positive control; data for accurate autonomous navigation and for terminal approach and blind landing. These capabilities would be available to aircraft to an extent depending on its investment in avionics. To accomplish the implied objectives requires the establishment of organized and systematic R&D programs, including a well conceived evaluation methodology
The spatiokinematical structure of H_2O and OH masers in the "water fountain" source IRAS 18460-0151
Using the Very Long Baseline Array and the European VLBI Network, we have
observed 22.2 GHz H_2O and 1612 MHz OH masers in the "water fountain" source
IRAS 18460-0151. The H_2O maser spectrum has a very wide line-of-sight velocity
range (~310 km/s) and consists of three groups of emission features at the
blue-shifted (-68 km/s <~ V_LSR <~ -17 km/s) and red-shifted (V_LSR ~= 240
km/s) edges as well as around the systemic velocity (112 km/s <~ V_LSR <~ 133
km/s). The first two H_2O spectral components exhibit a highly-collimated
high-velocity bipolar jet on the sky, with an angular separation of ~120
milliarcseconds (mas) (240 AU in linear length) and a three-dimensional flow
velocity of ~160 km/s. The flow dynamical age is estimated to be only ~6 yr (at
the time of the observation epochs of 2006--2007). Interestingly, the systemic
velocity component clearly exhibits a spherically-expanding outflow with a
radius of ~36 AU and a flow velocity of ~9 km/s. On the other hand, the OH
maser spectrum shows double peaks with a velocity separation of ~25 km/s
(V_LSR=$111--116 and 138--141 km/s), as typically seen in circumstellar
envelopes of OH/IR stars. The angular offset between the velocity-integrated
brightness peaks of the two high-velocity H_2O components is ~25 mas (50 AU).
The offset direction and the alignment of the red-shifted maser spots are
roughly perpendicular to the axis of the H_2O maser flow. High-accuracy
astrometry for the H_2O and OH masers demonstrates that the collimated fast jet
and the slowly expanding outflow originate from a single or multiple sources
which are located within 15 mas (30 AU). On the other hand, the estimated
systemic velocity of the collimated jet (V_sys ~87--113 km/s) has a large
uncertainty. This makes it difficult to provide strong constraints on models of
the central stellar system of IRAS 18460-0151.Comment: 25 pages, 5 figures, 8 tables, accepted for publication in Ap
High Velocity Precessing Jets from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations
We report the results of multi-epoch VLBA observations of the 22.2GHz water
maser emission associated with the "water fountain" IRAS 18286-0959. We suggest
that this object is the second example of a highly collimated bipolar
precessing outflow traced by water maser emission, the other is W43A. The
detected water emission peaks are distributed over a velocity range from
-50km/s to 150km/s. The spatial distribution of over 70% of the identified
maser features is found to be highly collimated along a spiral jet (jet 1)
extended southeast to northwest, the remaining features appear to trace another
spiral jet (jet 2) with a different orientation. The two jets form a
"double-helix" pattern which lies across ~200 milliarcseconds. The maser
distribution is reasonably fit by a model consisting of two bipolar precessing
jets. The 3D velocities of jet 1 and jet 2 are derived to be 138km/s and
99km/s, respectively. The precession period of jet 1 is about 56 years. For jet
2, three possible models are tested and they give different values for the
kinematic parameters. We propose that the appearance of two jets is the result
of a single driving source with significant proper motion.Comment: 84 pages, 16 figures, accepted for publication in Ap
Interstellar Scattering Towards the Galactic Center as Probed by OH/IR Stars
Angular broadening measurements are reported of 20 OH/IR stars near the galactic center. This class of sources is known to have bright, intrinsically compact (less than or equal to 20 mas) maser components within their circumstellar shells. VLBA antennas and the VLA were used to perform a MKII spectral line VLBI experiment. The rapid drop in correlated flux with increasing baseline, especially for sources closest to the galactic center, is attributed to interstellar scattering. Angular diameters were measured for 13 of our sources. Lower limits were obtained for the remaining seven. With the data, together with additional data taken from the literature, the distribution was determined of interstellar scattering toward the galactic center. A region was found of pronounced scattering nearly centered on SgrA*. Two interpretations are considered for the enhanced scattering. One hypothesis is that the scattering is due to a clump of enhanced turbulence, such as those that lie along lines of sight to other known objects, that has no physical relationship to the galactic center. The other model considers the location of the enhanced scattering to arise in the galactic center itself. The physical implications of the models yield information on the nature of interstellar scattering
ENDING THE EPIDEMIC OF ACCIDENTAL PERSONALITY DISORDER DISCRIMINATION BY WELL-MEANING MEDIATORS
People who have or appear to have mental disorders encounter rampant bias and stigma, including from mediators. This article focuses on some of the most heavily stigmatized mental health problems - personality disorders - and how some mediators discriminate against parties based on their guesses and assumptions that those parties may have these conditions
Vitamin D in Australia : issues and recommendations
BACKGROUND A significant number of Australians and people from specific groups within the community are suffering from vitamin D deficiency. It is no longer acceptable to assume that all people in Australia receive adequate vitamin D from casual exposure to sunlight.OBJECTIVE This article provides information on causes, consequences, treatment and prevention of vitamin D deficiency in Australia. DISCUSSION People at high risk of vitamin D deficiency include the elderly, those with skin conditions where avoidance of sunlight is required, dark skinned people (particularly women during pregnancy or if veiled) and patients with malabsorption, eg. coeliac disease. For most people, deficiency can be prevented by 5–15 minutes exposure of face and upper limbs to sunlight 4–6 times per week. If this is not possible then a vitamin D supplement of at least 400 IU* per day is recommended. In cases of established vitamin D deficiency, supplementation with 3000-5000 IU per day for at least 1 month is required to replete body stores. Increased availability of larger dose preparations of cholecalciferol would be a useful therapy in the case of severe deficiencies. * 40 IU (international units) = 1 µg<br /
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