658 research outputs found
Clearing price distributions in call auctions
We propose a model for price formation in financial markets based on clearing
of a standard call auction with random orders, and verify its validity for
prediction of the daily closing price distribution statistically. The model
considers random buy and sell orders, placed following demand- and supply-side
valuation distributions; an equilibrium equation then leads to a distribution
for clearing price and transacted volume. Bid and ask volumes are left as free
parameters, permitting possibly heavy-tailed or very skewed order flow
conditions. In highly liquid auctions, the clearing price distribution
converges to an asymptotically normal central limit, with mean and variance in
terms of supply/demand-valuation distributions and order flow imbalance. By
means of simulations, we illustrate the influence of variations in order flow
and valuation distributions on price/volume, noting a distinction between high-
and low-volume auction price variance. To verify the validity of the model
statistically, we predict a year's worth of daily closing price distributions
for 5 constituents of the Eurostoxx 50 index; Kolmogorov-Smirnov statistics and
QQ-plots demonstrate with ample statistical significance that the model
predicts closing price distributions accurately, and compares favourably with
alternative methods of prediction
Event Weighted Tests for Detecting Periodicity in Photon Arrival Times
This paper treats the problem of detecting periodicity in a sequence of
photon arrival times, which occurs, for example, in attempting to detect
gamma-ray pulsars. A particular focus is on how auxiliary information,
typically source intensity, background intensity, and incidence angles and
energies associated with each photon arrival should be used to maximize the
detection power. We construct a class of likelihood-based tests, score tests,
which give rise to event weighting in a principled and natural way, and derive
expressions quantifying the power of the tests. These results can be used to
compare the efficacies of different weight functions, including cuts in energy
and incidence angle. The test is targeted toward a template for the periodic
lightcurve, and we quantify how deviation from that template affects the power
of detection
Permutation entropy as a universal disorder criterion: how disorders at different scale levels are manifestations of the same underlying principle
Action Contro
On the newsboy model with a cutoff transaction size
In this paper we analyse the effect of satisfying in a different way customers with an order larger than a prespecified cutoff transaction size, in a simple newsboy setting. For compound Poisson demand with discrete order sizes, we show how to determine the expected costs and the optimal cutoff transaction size. Moreover, by approximating the distribution of the total demand during a period by the normal distribution one can determine an expression for the average cost function that depends on the cutoff transaction size only. A main advantage of this approximation is that the computational effort is much less. The quality of using the normal approximation is evaluated through a number of numerical experiments, which show that the approximative results are satisfactory
Neurotransmitters as food supplements: the effects of GABA on brain and behavior
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the human cortex. The food supplement version of GABA is widely available online. Although many consumers claim that they experience benefits from the use of these products, it is unclear whether these supplements confer benefits beyond a placebo effect. Currently, the mechanism of action behind these products is unknown. It has long been thought that GABA is unable to cross the blood–brain barrier (BBB), but the studies that have assessed this issue are often contradictory and range widely in their employed methods. Accordingly, future research needs to establish the effects of oral GABA administration on GABA levels in the human brain, for example using magnetic resonance spectroscopy. There is some evidence in favor of a calming effect of GABA food supplements, but most of this evidence was reported by researchers with a potential conflict of interest. We suggest that any veridical effects of GABA food supplements on brain and cognition might be exerted through BBB passage or, more indirectly, via an effect on the enteric nervous system. We conclude that the mechanism of action of GABA food supplements is far from clear, and that further work is needed to establish the behavioral effects of GABA
Methodieken voor de prioritering van milieumaatregelen bij Zeeuwse bedrijven
VakpublicatieInstitute of Environmental Science
The impact of human-robot synchronization on anthropomorphization
To elucidate the working mechanism behind anthropomorphism, this study investigated whether human participants would anthropomorphize a robot more if they move synchronously versus non-synchronously with it, and whether this is affected by which of the two initiates the movements. We tested two competing hypotheses. The feature-overlap hypothesis predicts that moving in synchrony would increase perceived self-other feature overlap, which in turn might spread activation to codes of features related to humans—which should increase anthropomorphization. In contrast, the autonomy hypothesis predicts that unpredictability increases anthropomorphization, and thus that whenever the robot initiates movements, or when the human initiates movements to which the robot moves non-synchronously, there is an increased perception of the robot as a more human-like, intentionally acting creature, which in turn should increase anthropomorphization. We performed a study with synchrony as within-subjects factor, and initiator (robot or human) as between-subjects factor. To study the impact of synchrony on self-other overlap and perception of human likeness, participants completed two tasks that served as implicit measures of state anthropomorphization, and two questionnaires that served as explicit measures of state anthropomorphization toward the robot. The two implicit measures were the joint Simon task and one-shot Dictator Game. Additionally, participants filled in a trait anthropomorphization questionnaire, to enable correction for baseline tendencies to anthropomorphize. The synchrony manipulation did not affect the joint Simon effect, although there was an effect on average reaction time (RT), where in the group in which the robot initiated the movement, RTs were slower when the human and robot moved non-synchronously. The Dictator Game offer and the state anthropomorphization questionnaires were not affected by the synchrony manipulation. There was, however, a positive correlation between current anthropomorphization of the robot and amount of money offered to it. Given that most measures were not systematically affected by our manipulation, it appears that either our design was suboptimal, or that synchronization does not affect the anthropomorphization of a robot.Action Contro
The core fundamental plane of B2 radio galaxies
The photometric, structural and kinematical properties of the centers of
elliptical galaxies, harbor important information of the formation history of
the galaxies. In the case of non active elliptical galaxies these properties
are linked in a way that surface brightness, break radius and velocity
dispersion of the core lie on a fundamental plane similar to that found for
their global properties. We construct the Core Fundamental Plane (CFP) for a
sizeable sample of low redshift radio galaxies and compare it with that of non
radio ellipticals. To pursue this aim we combine data obtained from high
resolution HST images with medium resolution optical spectroscopy to derive the
photometric and kinematic properties of ~40 low redshift radio galaxies. We
find that the CFPs of radio galaxies is indistinguishable from that defined by
non radio elliptical galaxies of similar luminosity. The characteristics of the
CFP of radio galaxies are also consistent (same slope) with those of the
Fundamental Plane (FP) derived from the global properties of radio (and non
radio) elliptical galaxies. The similarity of CFP and FP for radio and non
radio ellipticals suggests that the active phase of these galaxies has minimal
effects for the structure of the galaxies.Comment: 8 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
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