783 research outputs found
Implementation of Democratic Social Choice Functions
A social choice function is said to be implementable if and only if there exists a game form such that for all preference profiles an equilibrium strategy n-tuple exists and any equilibrium strategy n-tuples of the game yield outcomes in the social choice set. A social choice function is defined to be minimally democratic if and only if whenever there exists an alternative which is ranked first by n-1 voters and is no lower than second for the last voter, then the social choice must be uniquely that alternative. No constraints are placed on the social choice function for other preference profiles.
Using the usual definitions of equilibria for n-person games—namely Nash and strong equilibria—it is shown here that over unrestricted preference domains, no minimally democratic social choice function is implementable. The same result holds in certain restricted domains of the type assumed by economists over public goods spaces. We then show that a different notion of equilibrium—namely that of sophisticated equilibrium—allows for implementation of democratic social choice functions also having further appealing properties. The implication is that models of democratic political processes cannot be based on the standard equilibrium notions of Nash or strong equilibria
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Measurement of Circumsolar Radiation. Status Report
The major accomplishments of this project include the design, construction, and deployment of four complete circumsolar telescope systems. The telescopes have been maintained and data have been collected from a total of nine sites over the past two years. The data upon reaching LBL have been compiled, validated and analyzed for dissemination to DOE and other users. LBL has been collaborating with other national laboratories to quantify the impact of circumsolar radiation on specific solar collector designs. Requests for data from a wide variety of solar users have been fulfilled
How Dry is the Brown Dwarf Desert?: Quantifying the Relative Number of Planets, Brown Dwarfs and Stellar Companions around Nearby Sun-like Stars
Sun-like stars have stellar, brown dwarf and planetary companions. To help
constrain their formation and migration scenarios, we analyse the close
companions (orbital period < 5 years) of nearby Sun-like stars. By using the
same sample to extract the relative numbers of stellar, brown dwarf and
planetary companions, we verify the existence of a very dry brown dwarf desert
and describe it quantitatively. With decreasing mass, the companion mass
function drops by almost two orders of magnitude from 1 M_Sun stellar
companions to the brown dwarf desert and then rises by more than an order of
magnitude from brown dwarfs to Jupiter-mass planets. The slopes of the
planetary and stellar companion mass functions are of opposite sign and are
incompatible at the 3 sigma level, thus yielding a brown dwarf desert. The
minimum number of companions per unit interval in log mass (the driest part of
the desert) is at M = 31^{+25}_{-18} M_Jup. Approximately 16% of Sun-like stars
have close (P < 5 years) companions more massive than Jupiter: 11% +- 3% are
stellar, <1% are brown dwarf and 5% +- 2% are giant planets. The steep decline
in the number of companions in the brown dwarf regime, compared to the initial
mass function of individual stars and free-floating brown dwarfs, suggests
either a different spectrum of gravitational fragmentation in the formation
environment or post-formation migratory processes disinclined to leave brown
dwarfs in close orbits.Comment: Conforms to version accepted by ApJ. 13 pages formatted with
emulateapj.cl
Occupational Health and Safety Prevention Plan in Water Treatment Plant
The research was carried out at the "El Guarumo" drinking water plant located in Santa Ana, province of ManabĂ, Ecuador. The objective of the investigation was the proposal of a plan of prevention of occupational risks that allows the management of the labor risks in said plant. The main tools used were: survey, interview, checklist, LEST questionnaire for the diagnosis of the current situation in terms of working conditions, the risk identification matrix and the binary method of risk assessment. The main results obtained were the identification of the risks in their different categories, observing that the critical risk factors are related to the physical overexertion, the uncomfortable postures and the manual lifting of the load. Among the important risks are falling objects, skin contact with toxic substances and mental overwork, closely related to work pressures and job security? It was possible to carry out the proposal of preventive and corrective measures in order to properly manage the risks and contribute to the safety and health of the workers
Detection Of KOI-13.01 Using The Photometric Orbit
We use the KOI-13 transiting star-planet system as a test case for the
recently developed BEER algorithm (Faigler & Mazeh 2011), aimed at identifying
non-transiting low-mass companions by detecting the photometric variability
induced by the companion along its orbit. Such photometric variability is
generated by three mechanisms, including the beaming effect, tidal ellipsoidal
distortion, and reflection/heating. We use data from three Kepler quarters,
from the first year of the mission, while ignoring measurements within the
transit and occultation, and show that the planet's ephemeris is clearly
detected. We fit for the amplitude of each of the three effects and use the
beaming effect amplitude to estimate the planet's minimum mass, which results
in M_p sin i = 9.2 +/- 1.1 M_J (assuming the host star parameters derived by
Szabo et al. 2011). Our results show that non-transiting star-planet systems
similar to KOI-13.01 can be detected in Kepler data, including a measurement of
the orbital ephemeris and the planet's minimum mass. Moreover, we derive a
realistic estimate of the amplitudes uncertainties, and use it to show that
data obtained during the entire lifetime of the Kepler mission, of 3.5 years,
will allow detecting non-transiting close-in low-mass companions orbiting
bright stars, down to the few Jupiter mass level. Data from the Kepler Extended
Mission, if funded by NASA, will further improve the detection capabilities.Comment: Accepted to AJ on October 4, 2011. Kepler Q5 Long Cadence data will
become publicly available on MAST by October 23. Comments welcome (V2: minor
changes, to reflect proof corrections
PHL 5038: a spatially resolved white dwarf + brown dwarf binary
A near-infrared excess is detected at the white dwarf PHL 5038 in UKIDSS photometry, consistent with the presence of a cool, substellar companion. We have obtained H- and K-grism spectra and images of PHL 5038 using NIRI on Gemini North. The target is spatially and spectrally resolved into two components: an 8000 K DA white dwarf, and a likely L8 brown dwarf companion, separated by 0.94\arcsec. The spectral type of the secondary was determined using standard spectral indices for late L and T dwarfs. The projected orbital separation of the binary is 55 AU, so it becomes only the second known wide WD+dL binary to be found after GD 165AB. This object could potentially be used as a benchmark for testing substellar evolutionary models at intermediate to older ages
Clues to the nature of the Delta^*(1700) resonance from pion- and photon-induced reactions
We make a study of the (pi^- p --> K^0 pi^0 Lambda), (pi^+ p --> K^+ pi^+
Lambda), (K^+\bar{K}^0 p), (K^+ pi^+ Sigma^0), (K^+ pi^0 Sigma^+), and (eta
pi^+ p) reactions, in which the basic dynamics is given by the excitation of
the Delta^*(1700) resonance which subsequently decays into (K Sigma^*(1385)) or
(Delta(1232) eta). In a similar way we also study the (gamma p --> K^0 pi^+
Lambda), (K^+ pi^- Sigma^+), (K^+ pi^+ Sigma^-), (K^0 pi^0 Sigma^+), and (eta
pi^0 p) related reactions. The cross sections are proportional to the square of
the coupling of Delta^*(1700) to (Sigma^*K), (Delta eta) for which there is no
experimental information but which is provided in the context of coupled
channels chiral unitary theory where the Delta^*(1700) is dynamically
generated. Within present theoretical and experimental uncertainties one can
claim a global qualitative agreement between theory and experiment. We provide
a list of items which need to be improved in order to make further progress
along these lines.Comment: 11 pages, 5 figure
Modeling the variability of shapes of a human placenta
While it is well-understood what a normal human placenta should look like, a
deviation from the norm can take many possible shapes. In this paper we propose
a mechanism for this variability based on the change in the structure of the
vascular tree
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I owe you: age-related similarities and differences in associative memory for gains and losses
Older adults often experience associative memory impairments but can sometimes remember important information. The current experiments investigate potential age-related similarities and differences associate memory for gains and losses. Younger and older participants were presented with faces and associated dollar amounts, which indicated how much money the person “owed” the participant, and were later given a cued recall test for the dollar amount. Experiment 1 examined face-dollar amount pairs while Experiment 2 included negative dollar amounts to examine both gains and losses. While younger adults recalled more information relative to older adults, both groups were more accurate in recalling the correct value associated with high value faces compared to lower value faces and remembered gist-information about the values. However, negative values (losses) did not have a strong impact on recall among older adults versus younger adults, illustrating important associative memory differences between younger and older adults
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