2,836 research outputs found
Cumulative prospect theory and gambling
Whilst Cumulative Prospect theory (CPT) provides an explanation of gambling on longshots at actuarially unfair odds, it cannot explain why people might bet on more favoured outcomes. This paper shows that this is explicable if the degree of loss aversion experienced by the agent is reduced for small-stake gambles (as a proportion of wealth), and probability distortions are greater over losses than gains. If the utility or value function is assumed to be bounded, the degree of loss aversion assumed by Kahneman and Tversky leads to absurd predictions, reminiscent of those pointed out by Rabin (2000), of refusal to accept infinite gain bets at low probabilities. Boundedness of the value function in CPT implies that the indifference curve between expected-return and win-probability will typically exhibit both an asymptote (implying rejection of an infinite gain bet) and a minimum at low probabilities, as the shape of the value function dominates the probability weighting function. Also the high probability section of the indifference curve will exhibit a maximum. These implications are consistent with outcomes observed in gambling markets.
Dark Matter Constraints from the Sagittarius Dwarf and Tail System
2MASS has provided a three-dimensional map of the >360 degree, wrapped tidal
tails of the Sagittarius (Sgr) dwarf spheroidal galaxy, as traced by M giant
stars. With the inclusion of radial velocity data for stars along these tails,
strong constraints exist for dynamical models of the Milky Way-Sgr interaction.
N-body simulations of Sgr disruption with model parameters spanning a range of
initial conditions (e.g., Sgr mass and orbit, Galactic rotation curve, halo
flattening) are used to find parameterizations that match almost every extant
observational constraint of the Sgr system. We discuss the implications of the
Sgr data and models for the orbit, mass and M/L of the Sgr bound core as well
as the strength, flattening, and lumpiness of the Milky Way potential.Comment: 6 pages, 0 figures. Contribution to proceedings of ``IAU Symposium
220: Dark Matter in Galaxies'', eds. S. Ryder, D.J. Pisano, M. Walker, and K.
Freema
Student Success: A Literature Review of Faculty to Student Mentoring
This review summarizes the literature on university faculty to student mentoring programs. There has been a proliferation of mentoring programs because of the perceived benefit to student persistence and retention. While mentoring programs have become common, the research on these programs has not kept pace. Shortcomings identified thirty years ago such as lack of theoretical guidance, lack of operational definition of mentoring, and poor design continue to plague mentoring research. Recommendations to address these shortcomings and improve internal and external validity are examined. As universities continue to have increasingly constrained resources, and pressure to demonstrate strategies to help students be successful, evidence-based research will be increasingly desired. If shortcomings in mentoring research can be addressed, mentoring programs hold the potential to be part of a university’s strategic plan to help students be successful
The kinematics of ionized gas in lyman-break analogs at z ~ 0.2
We present results for 19 “Lyman-break analogs” observed with Keck/OSIRIS with an adaptive-optics-assisted
spatial resolution of less than 200 pc. We detect satellites/companions, diffuse emission, and velocity shear, all
with high signal-to-noise ratios. These galaxies present remarkably high velocity dispersion along the line of sight
(~70 km s^(−1)), much higher than standard star-forming spirals in the low-redshift universe. We artificially redshift
our data to z ~ 2.2 to allow for a direct comparison with observations of high-z Lyman-break galaxies and find
striking similarities between both samples. This suggests that either similar physical processes are responsible
for their observed properties, or, alternatively, that it is very difficult to distinguish between different mechanisms
operating in the low- versus high-redshift starburst galaxies based on the available data. The comparison between
morphologies in the UV/optical continuum and our kinemetry analysis often shows that neither is by itself sufficient
to confirm or completely rule out the contribution from recent merger events. We find a correlation between the
kinematic properties and stellar mass, in that more massive galaxies show stronger evidence for a disk-like structure.
This suggests a co-evolutionary process between the stellar mass buildup and the formation of morphological and
dynamical substructure within the galaxy
Skin Blood Perfusion and Oxygenation Colour Affect Perceived Human Health
Skin blood perfusion and oxygenation depends upon cardiovascular, hormonal and circulatory health in humans and provides socio-sexual signals of underlying physiology, dominance and reproductive status in some primates. We allowed participants to manipulate colour calibrated facial photographs along empirically-measured oxygenated and deoxygenated blood colour axes both separately and simultaneously, to optimise healthy appearance. Participants increased skin blood colour, particularly oxygenated, above basal levels to optimise healthy appearance. We show, therefore, that skin blood perfusion and oxygenation influence perceived health in a way that may be important to mate choice
Learn, Apply, Share: Combining Student Learning and Community Engagement
This paper describes how an upper division Family Life Education course was redesigned using the personal teaching philosophy of Learn, Apply, Share. This philosophy provides the framework for meaningful learning to occur at three levels. The Learn portion of the philosophy focuses on an experiential learning project based on andragogy principles that prepare students enrolled in the course to be family life educators. The Apply portion describes how student research assistants have used their research experiences to prepare them for professional positions in academia or other helping professions. This paper concludes by describing how students and the research assistants Share and evaluate what they have learned by offering a marriage enrichment workshop to couples from the community who are seeking to improve or strengthen their own relationship
An isoform of ZBP-89 predisposes the colon to colitis
Alternative splicing enables expression of functionally diverse protein isoforms. The structural and functional complexity of zinc-finger transcription factor ZBP-89 suggests that it may be among the class of alternatively spliced genes. We identified a human ZBP-89 splice isoform (ZBP-89(ΔN)), which lacks amino terminal residues 1–127 of the full-length protein (ZBP-89(FL)). ZBP-89(ΔN) mRNA was co-expressed with its ZBP-89(FL) cognate in gastrointestinal cell lines and tissues. Similarly, ZBP-89(ΔN) protein was expressed. To define its function in vivo, we generated ZBP-89(ΔN) knock-in mice by targeting exon 4 that encodes the amino terminus. Homozygous ZBP-89(ΔN) mice, expressing only ZBP-89(ΔN) protein, experienced growth delay, reduced viability and increased susceptibility to dextran sodium sulfate colitis. We conclude that ZBP-89(ΔN) antagonizes ZBP-89(FL) function and that over-expression of the truncated isoform disrupts gastrointestinal homeostasis
Exploring Halo Substructure with Giant Stars: Spectroscopy of Stars in the Galactic Anticenter Stellar Structure
To determine the nature of the recently discovered, ring-like stellar
structure at the Galactic anticenter, we have collected spectra of a set of
presumed constituent M giants selected from the 2MASS point source catalog.
Radial velocities have been obtained for stars spanning ~100 degrees,
exhibiting a trend in velocity with Galactic longitude and an estimated
dispersion of 20 +/- 4 km/sec. A mean metallicity [Fe/H] = -0.4 +/- 0.3
measured for these stars combines with previous evidence from the literature to
suggest a population with a significant metallicity spread. In addition, a
curious alignment of at least four globular clusters of lower mean metallicity
is noted to be spatially and kinematically consistent with this stellar
distribution. We interpret the M giant sample position and velocity variation
with Galactic longitude as suggestive of a satellite galaxy currently
undergoing tidal disruption in a non-circular, prograde orbit about the Milky
Way.Comment: (1) University of Virginia, 4 pages, 3 figures, accepted for
publication in The Astrophysical Journal Letter
A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: IV. Modeling the Sagittarius Tidal Tails
M giants recovered from the Two Micron All-Sky Survey (2MASS) have recently
been used to map the position and velocity distributions of tidal debris from
the Sagittarius (Sgr) dwarf spheroidal galaxy entirely around the Galaxy. We
compare this data set to both test particle orbits and N-body simulations of
satellite destruction run within a variety of rigid Milky Way potentials and
find that the mass of the Milky Way within 50 kpc of its center should be
3.8-5.6 x 10^11 Msun in order for any Sgr orbit to simultaneously fit the
velocity gradient in the Sgr trailing debris and the apocenter of the Sgr
leading debris. Orbital pole precession of young debris and leading debris
velocities in regions corresponding to older debris provide contradictory
evidence in favor of oblate/prolate Galactic halo potentials respectively,
leading us to conclude that the orbit of Sgr has evolved over the past few Gyr.
Based upon the velocity dispersion and width along the trailing tidal stream
we estimate the current bound mass of Sgr to be M_Sgr = 2 - 5 x 10^8 Msun
independant of the form of the Galactic potential; this corresponds to a range
of mass to light ratios (M/L)_Sgr = 14 - 36 (M/L)_Sun for the Sgr core. Models
with masses in this range best fit the apocenter of leading Sgr tidal debris
when they orbit with a radial period of roughly 0.85 Gyr and have periGalactica
and apoGalactica of about 15 kpc and 60 kpc respectively. These distances will
scale with the assumed distance to the Sgr dwarf and the assumed depth of the
Galactic potential. The density distribution of debris along the orbit in these
models is consistent with the M giant observations, and debris at all orbital
phases where M giants are obviously present is younger (i.e. was lost more
recently from the satellite) than the typical age of a Sgr M giant star.Comment: 42 pages, 13 figures; Accepted for publication by ApJ (October 08,
2004; originally submitted May 10, 2004). Fixed typos and added references.
PDF file with high resolution figures may be downloaded from
http://www.astro.caltech.edu/~drlaw/Papers/Sgr_paper4.pd
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Design Attributes and Scale Up Testing of Annular Centrifugal Contactors
Annular centrifugal contactors are being used for rapid yet efficient liquid- liquid processing in numerous industrial and government applications. Commercialization of this technology began eleven years ago and now units with throughputs ranging from 0.25 to 700 liters per minute are readily available. Separation, washing, and extraction processes all benefit from the use of this relatively new commercial tool. Processing advantages of this technology include: low in-process volume per stage, rapid mixing and separation in a single unit, connection-in-series for multi-stage use, and a wide operating range of input flow rates and phase ratios without adjustment. Recent design enhancements have been added to simplify maintenance, improve inspection ability, and provide increased reliability. Cartridge-style bearing and mechanical rotary seal assemblies that can include liquid-leak sensors are employed to enhance remote operations, minimize maintenance downtime, prevent equipment damage, and extend service life. Clean-in-place capability eliminates the need for disassembly, facilitates the use of contactors for feed clarification, and can be automated for continuous operation. In nuclear fuel cycle studies, aqueous based separations are being developed that efficiently partition uranium, actinides, and fission products via liquid-liquid solvent extraction. Thus, annular centrifugal contactors are destined to play a significant role in the design of such new processes. Laboratory scale studies using mini-contactors have demonstrated feasibility for many such separation processes but validation at an engineering scale is needed to support actual process design
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