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The probationary period as a screening device: competitive markets
Seminal papers about asymmetry of information in a competitive insurance market, and the monetary deductible as a screening device show that any existing equilibrium is of a separating type. High risks buy complete insurance whilst low risks buy partial insurance. Rothschild and Stiglitz (1976) deal with insurance companies showing Nash behaviour, while Miyazaki (1977) and Spence (1978) consider firms with Wilson foresight. In this paper, we analyze the strength of the probationary period as a screening device. We show that in such a case a) under Nash behavior, low risks may prefer not to purchase any insurance at all in equilibrium and b)under Wilson foresight, a pooling equilibrium may exist
Quantum measurement of the degree of polarization of a light beam
We demonstrate a coherent quantum measurement for the determination of the
degree of polarization (DOP). This method allows to measure the DOP in the
presence of fast polarization state fluctuations, difficult to achieve with the
typically used polarimetric technique. A good precision of the DOP measurements
is obtained using 8 type II nonlinear crystals assembled for spatial walk-off
compensation.Comment: 4 pages, 3 figure
Contour calculus for many-particle functions
In non-equilibrium many-body perturbation theory, Langreth rules are an
efficient way to extract real-time equations from contour ones. However, the
standard rules are not applicable in cases that do not reduce to simple
convolutions and multiplications. We introduce a procedure for extracting
real-time equations from general multi-argument contour functions with an
arbitrary number of arguments. This is done for both the standard Keldysh
contour, as well as the extended contour with a vertical track that allows for
general initial states. This amounts to the generalization of the standard
Langreth rules to much more general situations. These rules involve
multi-argument retarded functions as key ingredients, for which we derive
intuitive graphical rules. We apply our diagrammatic recipe to derive Langreth
rules for the so-called double triangle structure and the general vertex
function, relevant for the study of vertex corrections beyond the
approximation
Real-time image streaming over a low-bandwidth wireless camera network
In this paper we describe the recent development of a low-bandwidth wireless camera sensor network. We propose a simple, yet effective, network architecture which allows multiple cameras to be connected to the network and synchronize their communication schedules. Image compression of greater than 90% is performed at each node running on a local DSP coprocessor, resulting in nodes using 1/8th the energy compared to streaming uncompressed images. We briefly introduce the Fleck wireless node and the DSP/camera sensor, and then outline the network architecture and compression algorithm. The system is able to stream color QVGA images over the network to a base station at up to 2 frames per second. © 2007 IEEE
An O(1) Solution to the Prefix Sum Problem on a Specialized Memory Architecture
In this paper we study the Prefix Sum problem introduced by Fredman.
We show that it is possible to perform both update and retrieval in O(1) time
simultaneously under a memory model in which individual bits may be shared by
several words.
We also show that two variants (generalizations) of the problem can be solved
optimally in time under the comparison based model of
computation.Comment: 12 page
Mn induced modifications of Ga 3d photoemission from (Ga, Mn)As: evidence for long range effects
Using synchrotron based photoemission, we have investigated the Mn-induced
changes in Ga 3d core level spectra from as-grown . Although Mn is located in Ga substitutional sites, and does
therefore not have any Ga nearest neighbours, the impact of Mn on the Ga core
level spectra is pronounced even at Mn concentrations in the range of 0.5%. The
analysis shows that each Mn atom affects a volume corresponding to a sphere
with around 1.4 nm diameter.Comment: Submitted to Physical Review B, Brief Repor
Joining Forces of Bayesian and Frequentist Methodology: A Study for Inference in the Presence of Non-Identifiability
Increasingly complex applications involve large datasets in combination with
non-linear and high dimensional mathematical models. In this context,
statistical inference is a challenging issue that calls for pragmatic
approaches that take advantage of both Bayesian and frequentist methods. The
elegance of Bayesian methodology is founded in the propagation of information
content provided by experimental data and prior assumptions to the posterior
probability distribution of model predictions. However, for complex
applications experimental data and prior assumptions potentially constrain the
posterior probability distribution insufficiently. In these situations Bayesian
Markov chain Monte Carlo sampling can be infeasible. From a frequentist point
of view insufficient experimental data and prior assumptions can be interpreted
as non-identifiability. The profile likelihood approach offers to detect and to
resolve non-identifiability by experimental design iteratively. Therefore, it
allows one to better constrain the posterior probability distribution until
Markov chain Monte Carlo sampling can be used securely. Using an application
from cell biology we compare both methods and show that a successive
application of both methods facilitates a realistic assessment of uncertainty
in model predictions.Comment: Article to appear in Phil. Trans. Roy. Soc.
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