13,393 research outputs found
Optimization Aspects of Carcinogenesis
Any process in which competing solutions replicate with errors and numbers of
their copies depend on their respective fitnesses is the evolutionary
optimization process. As during carcinogenesis mutated genomes replicate
according to their respective qualities, carcinogenesis obviously qualifies as
the evolutionary optimization process and conforms to common mathematical
basis. The optimization view accents statistical nature of carcinogenesis
proposing that during it the crucial role is actually played by the allocation
of trials. Optimal allocation of trials requires reliable schemas' fitnesses
estimations which necessitate appropriate, fitness landscape dependent,
statistics of population. In the spirit of the applied conceptual framework,
features which are known to decrease efficiency of any evolutionary
optimization procedure (or inhibit it completely) are anticipated as
"therapies" and reviewed. Strict adherence to the evolutionary optimization
framework leads us to some counterintuitive implications which are, however, in
agreement with recent experimental findings, such as sometimes observed more
aggressive and malignant growth of therapy surviving cancer cells
The duration distribution of Swift Gamma-Ray Bursts
Decades ago two classes of gamma-ray bursts were identified and delineated as
having durations shorter and longer than about 2 s. Subsequently indications
also supported the existence of a third class. Using maximum likelihood
estimation we analyze the duration distribution of 888 Swift BAT bursts
observed before October 2015. Fitting three log-normal functions to the
duration distribution of the bursts provides a better fit than two log-normal
distributions, with 99.9999% significance. Similarly to earlier results, we
found that a fourth component is not needed. The relative frequencies of the
distribution of the groups are 8% for short, 35% for intermediate and 57% for
long bursts which correspond to our previous results. We analyse the redshift
distribution for the 269 GRBs of the 888 GRBs with known redshift. We find no
evidence for the previously suggested difference between the long and
intermediate GRBs' redshift distribution. The observed redshift distribution of
the 20 short GRBs differs with high significance from the distributions of the
other groups.Comment: accepte
Effective Privacy Amplification for Secure Classical Communications
We study the practical effectiveness of privacy amplification for classical
key-distribution schemes. We find that in contrast to quantum key distribution
schemes, the high fidelity of the raw key generated in classical systems allow
the users to always sift a secure shorter key if they have an upper bound on
the eavesdropper probability to correctly guess the exchanged key-bits. The
number of privacy amplification iterations needed to achieve information leak
of 10^-8 in existing classical communicators is 2 or 3 resulting in a
corresponding slowdown 4 to 8. We analyze the inherent tradeoff between the
number of iterations and the security of the raw key. This property which is
unique to classical key distribution systems render them highly useful for
practical, especially for noisy channels where sufficiently low quantum bit
error ratios are difficult to achieve.Comment: 11 pages, 3 figure
Multiphoton Coincidence Spectroscopy
We extend the analysis of photon coincidence spectroscopy beyond bichromatic
excitation and two-photon coincidence detection to include multichromatic
excitation and multiphoton coincidence detection. Trichromatic excitation and
three-photon coincidence spectroscopy are studied in detail, and we identify an
observable signature of a triple resonance in an atom-cavity system.Comment: 6 page, REVTeXs, 6 Postscript figures. The abstract appeared in the
Proceedings of ACOLS9
Exact and Quasi-exact Models of Strange Stars
We construct and compare a variety of simple models for strange stars,
namely, hypothetical self-bound objects made of a cold stable version of the
quark-gluon plasma. Exact, quasi-exact and numerical models are examined to
find the most economical description for these objects. A simple and successful
parametrization of them is given in terms of the central density, and many
differences among the models are explicitly shown and discussed.Comment: 20 pp. 15 figures, to appear in IJMP
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