12,457 research outputs found
Exact asymptotic distribution of change-point mle for change in the mean of Gaussian sequences
We derive exact computable expressions for the asymptotic distribution of the
change-point mle when a change in the mean occurred at an unknown point of a
sequence of time-ordered independent Gaussian random variables. The derivation,
which assumes that nuisance parameters such as the amount of change and
variance are known, is based on ladder heights of Gaussian random walks hitting
the half-line. We then show that the exact distribution easily extends to the
distribution of the change-point mle when a change occurs in the mean vector of
a multivariate Gaussian process. We perform simulations to examine the accuracy
of the derived distribution when nuisance parameters have to be estimated as
well as robustness of the derived distribution to deviations from Gaussianity.
Through simulations, we also compare it with the well-known conditional
distribution of the mle, which may be interpreted as a Bayesian solution to the
change-point problem. Finally, we apply the derived methodology to monthly
averages of water discharges of the Nacetinsky creek, Germany.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS294 the Annals of
Applied Statistics (http://www.imstat.org/aoas/) by the Institute of
Mathematical Statistics (http://www.imstat.org
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Cytoplasmic Flow and Mixing Due to Deformation of Motile Cells.
The cytoplasm of a living cell is a dynamic environment through which intracellular components must move and mix. In motile, rapidly deforming cells such as human neutrophils, bulk cytoplasmic flow couples cell deformation to the transport and dispersion of cytoplasmic particles. Using particle-tracking measurements in live neutrophil-like cells, we demonstrate that fluid flow associated with the cell deformation contributes to the motion of small acidic organelles, dominating over diffusion on timescales above a few seconds. We then use a general physical model of particle dispersion in a deforming fluid domain to show that transport of organelle-sized particles between the cell periphery and the bulk can be enhanced by dynamic deformation comparable to that observed in neutrophils. Our results implicate an important mechanism contributing to organelle transport in these motile cells: cytoplasmic flow driven by cell shape deformation
The role of simulations in consumer experiences and behavior: insights from the grounded cognition theory of desire
What are the mechanisms by which extrinsic and environmental cues affect consumer experiences, desires, and choices? Based on the recent grounded cognition theory of desire, we argue that consumption and reward simulations constitute a central mechanism in these phenomena. Specifically, we argue that appetitive stimuli, such as specific product cues, can activate simulations of consuming and enjoying the respective products, based on previous learning experiences. These consumption and reward simulations can lead to motivated behavior, and can be modulated by state and trait individual differences, situational factors, and product-extrinsic cues. We outline the role of simulations within the grounded theory of desire, offering a theoretical framework for understanding motivational processes in consumer behavior. Then we illustrate the theory with behavioral, physiological, and neuroimaging findings on simulations in appetitive behavior and sensory marketing. Finally, we outline important issues for further research and applications for stimulating healthy, prosocial, and sustainable consumer choices
Deriving AGN properties from radio CP and LP
We report multi-frequency circular polarization measurements for the radio
source 0056-00 taken at the Effelsberg 100-m radiotelescope. The data reduction
is based on a new calibration procedure that allows the contemporary
measurement of the four Stokes parameters with single-dish radiotelescopesComment: 2 pages, Proceeding of "IAU Symposium No.259. Cosmic Magnetic Fields
from planets, to stars and galaxies
Selection bias in the M_BH-sigma and M_BH-L correlations and its consequences
It is common to estimate black hole abundances by using a measured
correlation between black hole mass and another more easily measured observable
such as the velocity dispersion or luminosity of the surrounding bulge. The
correlation is used to transform the distribution of the observable into an
estimate of the distribution of black hole masses. However, different
observables provide different estimates: the Mbh-sigma relation predicts fewer
massive black holes than does the Mbh-L relation. This is because the sigma-L
relation in black hole samples currently available is inconsistent with that in
the SDSS sample, from which the distributions of L or sigma are based: the
black hole samples have smaller L for a given sigma or have larger sigma for a
given L. This is true whether L is estimated in the optical or in the NIR. If
this is a selection rather than physical effect, then the Mbh-sigma and Mbh-L
relations currently in the literature are also biased from their true values.
We provide a framework for describing the effect of this bias. We then combine
it with a model of the bias to make an estimate of the true intrinsic
relations. While we do not claim to have understood the source of the bias, our
simple model is able to reproduce the observed trends. If we have correctly
modeled the selection effect, then our analysis suggests that the bias in the
relation is likely to be small, whereas the relation is
biased towards predicting more massive black holes for a given luminosity. In
addition, it is likely that the Mbh-L relation is entirely a consequence of
more fundamental relations between Mbh and sigma, and between sigma and L. The
intrinsic relation we find suggests that at fixed luminosity, older galaxies
tend to host more massive black holes.Comment: 12 pages, 7 figures. Accepted by ApJ. We have added a figure showing
that a similar bias is also seen in the K-band. A new appendix describes the
BH samples as well as the fits used in the main tex
The Importance of the Study of the Hemodynamics of the Uterine Tumors by the Method of Dopplerometry in the Two- and Three-dimensional Echography Modes for Differential Diagnostics of Simple, Proliferating Leiomyomas and Uterine Sarcomas (Review of Litera
The article analyzes modern literature data on the importance of studying the hemodynamics of uterine tumors with dopplerometry in two - and three - dimensional regimens of echography for differential diagnosis of simple proliferating leiomyomas and sarcomas of the uterus. It is shown that the differential diagnosis of benign and Malignant tumors using the dopplerometry is based on various features of the blood supply of these tumors. On the basis of the analysis of literature data, it was concluded that in the dopplerometry evaluation of benign, borderline and Malignant tumors of myometrium in the two-dimensional regime, there were differences in the localization of the detected vessels in the CDM regimen, in the rates of vascular blood flow and vascular resistance in pulse dopplerometry. For a simple leiomyoma, the absence of a central intra-node localization of blood vessels in the CDM regimen, a low rate of arterial and venous blood flow, as well as an average resistance of arterial blood flow in the regime of impulsive dopplerometry are most typical; in a leiomyoma with eating disorders, the absence of a central intra-node localization of blood vessels, a low rate of arterial and venous blood flow in combination with high arterial resistance were more often observed. For the proliferating leiomyoma, the central intra-node localization of the vessels and the average blood flow velocities with low and medium resistance are characteristic. For sarcoma of the uterus, there is abundant vascularization both around the periphery and in the center, high blood flow rates and low resistance. The authors emphasize that there is information about the low specificity of this gradation, since the detection of a central type of vascularization and low resistance values can be in simple myomatous nodes with edema, eating disorders and destruction, and leads to diagnostic errors and suspicion of Malignancy. In the three-dimensional dopplerometry mode for simple leiomyomas, low indices of volume perfusion indices were characteristic, and for proliferating leiomyomas and sarcomas of the uterus – high indices of volume perfusion indices exceeding those in the uterus as a whole.Based on the review of the literature, the authors concluded that the presently available echographic and dopplerometric two- and three-dimensional markers are characterized by high sensitivity, but very low specificity. The low specificity of the known ultrasonic and dopplerometric criteria combined with the rarity of cases of sarcoma in the uterus against the background of a large number of similar echographically and dopplerometrically leiomyomas lead to low diagnostic accuracy of ultrasound diagnostics. This situation requires a further continuation of the scientific search for differential diagnostic ultrasound criteria by leiomyomas and sarcomas of the uterus using modern technologies, including three-dimensional echography
The Costs of Ecosystem Adaptation: Methodology and Estimates for Indian Forests
This paper presents a detailed methodology for estimating the cost of adaptation to climate change impacts on ecosystems. Up to date estimates are built-up following national investments in measures such as protected areas, with inaccurate estimates of the adaptation level needed. Here we propose a new methodology which identifies vulnerable areas due to climate impacts and the specific adaptation options feasible for these regions. An illustration of the methodology for shifts in forest ecosystems in India is presented. Advantages and future requirements for this methodology are finally discussed.Climate change, adaptation costs, forest ecosystems, India
ON SOLVING AN ENHANCED EVASION PROBLEM FOR LINEAR DISCRETE–TIME SYSTEMS
We consider the problem of an enhanced evasion for linear discrete-time systems, where there are two conflicting bounded controls and the aim of one of them is to be guaranteed to avoid the trajectory hitting a given target set at a given final time and also at intermediate instants. First we outline a common solution scheme based on the construction of so called solvability tubes or repulsive tubes. Then a much more quick and simple for realization method based on the construction of the tubes with parallelepiped-valued cross-sections is presented under assumptions that the target set is a parallelepiped and parallelotope-valued constraints on controls are imposed. An example illustrating this method is considered
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