A Current Mode Detector Array for Gamma-Ray Asymmetry Measurements

We have built a CsI(Tl) gamma-ray detector array for the NPDGamma experiment to search for a small parity-violating directional asymmetry in the angular distribution of 2.2 MeV gamma-rays from the capture of polarized cold neutrons by protons with a sensitivity of several ppb. The weak pion-nucleon coupling constant can be determined from this asymmetry. The small size of the asymmetry requires a high cold neutron flux, control of systematic errors at the ppb level, and the use of current mode gamma-ray detection with vacuum photo diodes and low-noise solid-state preamplifiers. The average detector photoelectron yield was determined to be 1300 photoelectrons per MeV. The RMS width seen in the measurement is therefore dominated by the fluctuations in the number of gamma rays absorbed in the detector (counting statistics) rather than the intrinsic detector noise. The detectors were tested for noise performance, sensitivity to magnetic fields, pedestal stability and cosmic background. False asymmetries due to gain changes and electronic pickup in the detector system were measured to be consistent with zero to an accuracy of $10^{-9}$ in a few hours. We report on the design, operating criteria, and the results of measurements performed to test the detector array.Comment: 33 pages, 20 figures, 2 table

Asymptotic Expansions for Stationary Distributions of Perturbed Semi-Markov Processes

New algorithms for computing of asymptotic expansions for stationary distributions of nonlinearly perturbed semi-Markov processes are presented. The algorithms are based on special techniques of sequential phase space reduction, which can be applied to processes with asymptotically coupled and uncoupled finite phase spaces.Comment: 83 page

Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass distribution is obtained that is consistent with W decay and inconsistent with the background prediction by 3.3 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.Comment: 20 pages, 4 figures, submitted to PR

Multigene phylogeny of the Mustelidae: Resolving relationships, tempo and biogeographic history of a mammalian adaptive radiation

<p>Abstract</p> <p>Background</p> <p>Adaptive radiation, the evolution of ecological and phenotypic diversity from a common ancestor, is a central concept in evolutionary biology and characterizes the evolutionary histories of many groups of organisms. One such group is the Mustelidae, the most species-rich family within the mammalian order Carnivora, encompassing 59 species classified into 22 genera. Extant mustelids display extensive ecomorphological diversity, with different lineages having evolved into an array of adaptive zones, from fossorial badgers to semi-aquatic otters. Mustelids are also widely distributed, with multiple genera found on different continents. As with other groups that have undergone adaptive radiation, resolving the phylogenetic history of mustelids presents a number of challenges because ecomorphological convergence may potentially confound morphologically based phylogenetic inferences, and because adaptive radiations often include one or more periods of rapid cladogenesis that require a large amount of data to resolve.</p> <p>Results</p> <p>We constructed a nearly complete generic-level phylogeny of the Mustelidae using a data matrix comprising 22 gene segments (~12,000 base pairs) analyzed with maximum parsimony, maximum likelihood and Bayesian inference methods. We show that mustelids are consistently resolved with high nodal support into four major clades and three monotypic lineages. Using Bayesian dating techniques, we provide evidence that mustelids underwent two bursts of diversification that coincide with major paleoenvironmental and biotic changes that occurred during the Neogene and correspond with similar bursts of cladogenesis in other vertebrate groups. Biogeographical analyses indicate that most of the extant diversity of mustelids originated in Eurasia and mustelids have colonized Africa, North America and South America on multiple occasions.</p> <p>Conclusion</p> <p>Combined with information from the fossil record, our phylogenetic and dating analyses suggest that mustelid diversification may have been spurred by a combination of faunal turnover events and diversification at lower trophic levels, ultimately caused by climatically driven environmental changes. Our biogeographic analyses show Eurasia as the center of origin of mustelid diversity and that mustelids in Africa, North America and South America have been assembled over time largely via dispersal, which has important implications for understanding the ecology of mustelid communities.</p

The US Dollar, the Euro, and the Yen: An Evaluation of Their Present and Future Status as International Currencies

The process of European integration and especially the introduction of the euro as the single currency for up to now 12 member countries of the EU in 1999 may alter the existing clear currency hierarchy. The euro area is comparable in size to the US with respect to GDP and even exceeds the US regarding the share in world trade. Thus questions arise of whether the international monetary system turns out to be bipolar in the long run or whether the yen can also play its part. It turns out that real activity, size and sophistication of financial markets, monetary and financial stability and inertia are the most prominent characteristics making a currency to be preferred on a world-wide level. We thus conclude that the integration and the development of European financial markets are of special importance for a stronger international role of the dollar, but that the historical experience of only gradually changing supremacy of international currencies still applies

Italo Calvino and the organizational imagination: Reading social organization through urban metaphors

© 2014 Taylor & Francis. This article explores the way in which uses or abuses of urban metaphors can inform differing polities and ethics of human organization. From its earliest inception, the city has taken on a metaphorical significance for human communities; being, at one and the same time, a discursive textual product of culture and, reciprocally, a provider of artefacts and architecture that produces culture and meaning. The city can be interpreted as a trope that operates bidirectionally in cultural terms. It is a sign that can be worked to serve the principles of both metonymy and synecdoche. In metonymical or reductive form, the city has the propensity to become weighty and deadening. The work of Michael Porter on competitive strategy is invoked to illustrate this effect. In the guise of synecdoche, on the other hand, the city offers imaginative potential. Drawing inspiration from the literary works of Italo Calvino (in particular, his novel Invisible Cities), the article attempts to reveal the fecundity of the city for interpreting technologically mediated organizational life. Calvino's emphasis on the principle of ‘lightness’ provides a link to the social theoretical writing of Boltanski and Chiapello on the ‘projective city’. A synthesis of these two stylistically different literatures yields a novel way of critically approaching and understanding the reticular form and emerging ethics of contemporary human organization