1,077 research outputs found
The Genetic coding style of digital organisms
Recently, all the human genes were identified. But understanding the functions coded in the genes is of course a much harder problem. We are used to view DNA as some sort of a computer code, but there are striking differences. For example, by using entropy, it has been shown that the DNA code is much closer to random code than written text, which in turn is less ordered than ordinary computer code. Instead of saying that the DNA is badly written, using common programming standards, we might say that it is written in a different style − an evolutionary style. In this paper the coding style of creatures from the artificial life platform Avida has been studied. Avida creatures that have evolved under different size merit methods and mutation rates have been analysed using the notion of stylistic measures. The analysis has shown that the evolutionary coding style depends on the environment in which the code evolved, and that the choice of size merit method and mutation probabilities affect different stylistic properties of the genome. A better understanding of AvidaÂ’s coding style, might eventually lead to insights of evolutionary codes in general
Elektrochemische Korrosionsuntersuchungen an metallischen Verpackungsmaterialien fuer hochaktive Abfaelle. Verhalten von Hastelloy C4 in quinaerer Salzloesung und 1 M NaCl. Einfluss moeglicher Salzverunreinigungen und Radiolyseprodukte
Elektrochemische Untersuchung des Korrosionsverhaltens von Feinkornbaustahl 1.0566 und Weicheisen in chloridhaltigen, waessrigen Loesungen
Invisible Z-Boson Decays at e+e- Colliders
The measurement of the invisible Z-boson decay width at e+e- colliders can be
done "indirectly", by subtracting the Z-boson visible partial widths from the
Z-boson total width, or "directly", from the process e+e- -> \gamma \nu
\bar{\nu}. Both procedures are sensitive to different types of new physics and
provide information about the couplings of the neutrinos to the Z-boson. At
present, measurements at LEP and CHARM II are capable of constraining the
left-handed Z\nu\nu-coupling, 0.45 <~ g_L <~ 0.5, while the right-handed one is
only mildly bounded, |g_R| <= 0.2. We show that measurements at a future e+e-
linear collider at different center-of-mass energies, \sqrt{s} = MZ and
\sqrt{s}s ~ 170 GeV, would translate into a markedly more precise measurement
of the Z\nu\nu-couplings. A statistically significant deviation from Standard
Model predictions will point toward different new physics mechanisms, depending
on whether the discrepancy appears in the direct or the indirect measurement of
the invisible Z-width. We discuss some scenarios which illustrate the ability
of different invisible Z-boson decay measurements to constrain new physics
beyond the Standard Model
Exciton Spin Dynamics in Semiconductor Quantum Wells
In this paper we will review Exciton Spin Dynamics in Semiconductor Quantum
Wells. The spin properties of excitons in nanostructures are determined by
their fine structure. We will mainly focus in this review on GaAs and InGaAs
quantum wells which are model systems.Comment: 55 pages, 27 figure
Reef fish assemblages and fisheries in Parque Nacional del Este, Dominican Republic
Parque National del Este is the second largest protected area in the Dominican Republic, comprising 110 km2 of terrestrial habitats located in the southeastern Dominican Republic. Established in 1975, the park delineation did not include the adjacent marine area, despite its long history of commercial fisheries. Since 1994, several U.S. and Dominican partner organizations have conducted scientific investigations of the marine resources of the area. This paper provides data on the status of snapper and groupers reef assemblages and finfish fisheriescollected during 1995 1997. Methods used in the study included: 1) visual transects (20 m x 5 m) of predatory fishes in coral reef habitats and 2) fishermen interviews to obtain data on fishing methods and catch composition. Predatory fishes, particularly groupers and snappers, are rare and generally small (\u3c 30 cm TL). Larger size snappers (Lutjanus griseus, L. analis) and groupers (Mycreroperca bonaci, M. tigris and M. venenosa) were absent in the visualtransect surveys. Only two Nassau grouper (Epinephelus striatus) were found in 142 transects among 7 reef areas. Among groupers, red hind (E. guttatus), coney (E. fulvus) and graysby (E. cr ue nt atu s) dominated the grouper assemblage in visual transect surveys, as well as in fishermen’s catch. Yellowtail snapper (Ocyurus chrysurus) was the most abundant snapper species in reefs and in fishermen’s catch. Fishermen interviews (n = 120) showed that hook-and-line, traps, and spears were the most commonly used methods. The catch composition reflects the artisanal nature of the fishery. A significant alteration of the park’s fish assemblages due to overfishing is apparent. The designation of zones with different degree of protection (including a no-take zone) is recommended. This plan includes specific regulations on the use of fishing gears, and others regarding minimum size, closed season. These measures should be included in the oncoming Coastal Management Plan, and will allow to: i) evaluate the potential for fisheries recovery ii) protect what little spawning stock biomass remains in the area, and iii) protect nursery grounds important for juvenile stages. There are few data on the potential contribution of up-current areas (Eastern Caribbean) to reef fish recruitment in the park. A research program addressed to this subject is also recommended
Global Search for New Physics with 2.0/fb at CDF
Data collected in Run II of the Fermilab Tevatron are searched for
indications of new electroweak-scale physics. Rather than focusing on
particular new physics scenarios, CDF data are analyzed for discrepancies with
the standard model prediction. A model-independent approach (Vista) considers
gross features of the data, and is sensitive to new large cross-section
physics. Further sensitivity to new physics is provided by two additional
algorithms: a Bump Hunter searches invariant mass distributions for "bumps"
that could indicate resonant production of new particles; and the Sleuth
procedure scans for data excesses at large summed transverse momentum. This
combined global search for new physics in 2.0/fb of ppbar collisions at
sqrt(s)=1.96 TeV reveals no indication of physics beyond the standard model.Comment: 8 pages, 7 figures. Final version which appeared in Physical Review D
Rapid Communication
Observation of Orbitally Excited B_s Mesons
We report the first observation of two narrow resonances consistent with
states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar
collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the
Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed
as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+,
\bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1})
= 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let
Measurement of the p-pbar -> Wgamma + X cross section at sqrt(s) = 1.96 TeV and WWgamma anomalous coupling limits
The WWgamma triple gauge boson coupling parameters are studied using p-pbar
-> l nu gamma + X (l = e,mu) events at sqrt(s) = 1.96 TeV. The data were
collected with the DO detector from an integrated luminosity of 162 pb^{-1}
delivered by the Fermilab Tevatron Collider. The cross section times branching
fraction for p-pbar -> W(gamma) + X -> l nu gamma + X with E_T^{gamma} > 8 GeV
and Delta R_{l gamma} > 0.7 is 14.8 +/- 1.6 (stat) +/- 1.0 (syst) +/- 1.0 (lum)
pb. The one-dimensional 95% confidence level limits on anomalous couplings are
-0.88 < Delta kappa_{gamma} < 0.96 and -0.20 < lambda_{gamma} < 0.20.Comment: Submitted to Phys. Rev. D Rapid Communication
Measurement of the ttbar Production Cross Section in ppbar Collisions at sqrt{s} = 1.96 TeV using Kinematic Characteristics of Lepton + Jets Events
We present a measurement of the top quark pair ttbar production cross section
in ppbar collisions at a center-of-mass energy of 1.96 TeV using 230 pb**{-1}
of data collected by the DO detector at the Fermilab Tevatron Collider. We
select events with one charged lepton (electron or muon), large missing
transverse energy, and at least four jets, and extract the ttbar content of the
sample based on the kinematic characteristics of the events. For a top quark
mass of 175 GeV, we measure sigma(ttbar) = 6.7 {+1.4-1.3} (stat) {+1.6- 1.1}
(syst) +/-0.4 (lumi) pb, in good agreement with the standard model prediction.Comment: submitted to Phys.Rev.Let
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