676 research outputs found
Development of silicon nitride and cermet resistors for use in a binary counter, metal insulator field effect transistor circuit Final report, 1 Dec. 1966 - 31 Mar. 1968
Silicon nitride and cermet resistors for binary counter metal insulator field effect transistor circui
Baryon Resonance Analysis from SAID
We discuss the analysis of data from piN elastic scattering and single pion
photo- and electroproduction. The main focus is a study of low-lying
non-strange baryon resonances. Here we concentrate on some difficulties
associated with resonance identification, in particular the Roper and higher
P11 states.Comment: 4 pages, 6 figures; Nstar2009 Conf Proceedings; small revisio
The de Rham homotopy theory and differential graded category
This paper is a generalization of arXiv:0810.0808. We develop the de Rham
homotopy theory of not necessarily nilpotent spaces, using closed dg-categories
and equivariant dg-algebras. We see these two algebraic objects correspond in a
certain way. We prove an equivalence between the homotopy category of schematic
homotopy types and a homotopy category of closed dg-categories. We give a
description of homotopy invariants of spaces in terms of minimal models. The
minimal model in this context behaves much like the Sullivan's minimal model.
We also provide some examples. We prove an equivalence between fiberwise
rationalizations and closed dg-categories with subsidiary data.Comment: 47 pages. final version. The final publication is available at
http://www.springerlink.co
Constraints on Decaying Dark Matter from Fermi Observations of Nearby Galaxies and Clusters
We analyze the impact of Fermi gamma-ray observations (primarily
non-detections) of selected nearby galaxies, including dwarf spheroidals, and
of clusters of galaxies on decaying dark matter models. We show that the fact
that galaxy clusters do not shine in gamma rays puts the most stringent limits
available to-date on the lifetime of dark matter particles for a wide range of
particle masses and decay final states. In particular, our results put strong
constraints on the possibility of ascribing to decaying dark matter both the
increasing positron fraction reported by PAMELA and the high-energy feature in
the electron-positron spectrum measured by Fermi. Observations of nearby dwarf
galaxies and of the Andromeda Galaxy (M31) do not provide as strong limits as
those from galaxy clusters, while still improving on previous constraints in
some cases.Comment: 27 pages, 5 figures, submitted to JCAP, revised version with some
additions and correction
Variation in inbreeding rates across the range of Northern Spotted Owls (\u3ci\u3eStrix occidentalis caurina\u3c/i\u3e): Insights from over 30 years of monitoring data
Inbreeding has been difficult to quantify in wild populations because of incomplete parentage information. We applied and extended a recently developed framework for addressing this problem to infer inbreeding rates in Northern Spotted Owls (Strix occidentalis caurina) across the Pacific Northwest, USA. Using pedigrees from 14,187 Northern Spotted Owls, we inferred inbreeding rates for 14 types of matings among relatives that produce pedigree inbreeding coefficients of F=0.25 or F=0.125. Inbreeding was most common in the Washington Cascades, where an estimated 15% of individuals are inbred. Inbreeding was lowest in western Oregon (3.5%) and northern California (2.7%), and intermediate for the Olympic Peninsula of Washington (6.1%). Estimates from the Olympic Peninsula were likely underestimates because of small sample sizes and the presence of few pedigrees capable of resolving inbreeding events. Most inbreeding resulted from matings between full siblings or half siblings, although a high rate of inbreeding from mother–son pairs was identified in the Olympic Peninsula. Geographic variation in inbreeding rates may reflect population declines and bottlenecks that have been detected in prior investigations. We show that there is strong selection against inbred birds. Only 3 of 44 inbred birds were later identified as parents (6.8%), whereas 2,823 of 10,380 birds that represented a comparable cross section of the data were later seen as reproducing parents (27.2%). Habitat loss and competition with Barred Owls (S. varia) remain primary threats to Northern Spotted Owls. However, given the negative consequences of inbreeding, Spotted Owl populations in Washington with suitable habitat and manageable numbers of Barred Owls may benefit from translocations of individuals from Oregon and California to introduce new genetic variation and reduce future inbreeding events.
La endogamia ha sido dif´ıcil de cuantificar en las poblaciones silvestres debido a la falta de informaci ´on sobre los parentescos. Aplicamos y extendimos un marco conceptual recientemente desarrollado para encarar el problema de inferir las tasas de endogamia en Strix occidentalis caurina a trav´es del noroeste del Pac´ıfico, EEUU. Usando los pedigr´ıes provenientes de 14187 individuos, inferimos las tasas de endogamia para 14 tipos de apareamiento entre parientes que producen coeficientes de endogamia de pedigr´ı de F=0.25 o F=0.125. La endogamia fue ma´s com´un en las Cascadas de Washington, donde se estima que 15% de los individuos son endoga´micos. La endogamia fue menor en el oeste de Oreg´on (3.5%) y el norte de California (2.7%), e intermedia en la Pen´ınsula Ol´ımpica de Washington (6.1%). Las estimaciones de la Pen´ınsula Ol´ımpica fueron probablemente subestimadas debido a los peque ˜nos tama ˜nos de muestreo y a la presencia de pocos pedigr´ıes capaces de resolver los eventos de endogamia. La mayor´ıa de la endogamia result ´o de los apareamientos entre hermanos completos o medios hermanos, aunque se identific ´o una alta tasa de endogamia en parejas madre/hijo en la Pen´ınsula Ol´ımpica. La variaci ´on geogra´ fica en las tasas de endogamia puede reflejar disminuciones poblacionales y cuellos de botella que han sido detectados en investigaciones previas. Mostramos que hay una fuerte selecci ´on contra las aves endoga´micas. Solo tres de 44 aves endoga´micas fueron ma´s tarde identificadas como progenitores (6.8%), mientras que 2823 de 10380 aves que representaron una secci ´on transversal comparable de datos fueron vistas ma´s tarde como progenitores reproductivos (27.2%). La p´erdida de ha´bitat y la competencia con Strix varia sigue siendo la principal amenaza para S. o. caurina. Sin embargo, dadas las consecuencias negativas de la endogamia, las poblaciones de S. occidentalis en Washington con ha´bitat adecuado y n´umeros manejables de Strix varia pueden beneficiarse de traslocaciones de individuos de Oreg´on y California para introducir nueva variaci ´on gen´etica y reducir futuros eventos de endogamia
Measurement of eta photoproduction on the proton from threshold to 1500 MeV
Beam asymmetry and differential cross section for the reaction gamma+p->eta+p
were measured from production threshold to 1500 MeV photon laboratory energy.
The two dominant neutral decay modes of the eta meson, eta->2g and eta->3pi0,
were analyzed. The full set of measurements is in good agreement with
previously published results. Our data were compared with three models. They
all fit satisfactorily the results but their respective resonance contributions
are quite different. The possible photoexcitation of a narrow state N(1670) was
investigated and no evidence was found.Comment: 18 pages, 14 figures, 4 tables Submitted to EPJ
Comment on the narrow structure reported by Amaryan et al
The CLAS Collaboration provides a comment on the physics interpretation of
the results presented in a paper published by M. Amaryan et al. regarding the
possible observation of a narrow structure in the mass spectrum of a
photoproduction experiment.Comment: to be published in Physical Review
Photoproduction of K+K− meson pairs on the proton
The exclusive reaction γp→pK+K− was studied in the photon energy range 3.0–3.8 GeV and momentum transfer range 0.6<−t<1.3 GeV2. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately 20 pb−1. The reaction was isolated by detecting the K+ and the proton in CLAS, and reconstructing the K− via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the ϕ meson in the P wave, evidence for S−P interference was found. The differential production cross sections dσ/dt for individual waves in the mass range of the ϕ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the t-dependent cross section of the S-wave contribution to the elastic K+K− photoproduction has been measured
Light Vector Mesons in the Nuclear Medium
The light vector mesons (, , and ) were produced in
deuterium, carbon, titanium, and iron targets in a search for possible
in-medium modifications to the properties of the meson at normal nuclear
densities and zero temperature. The vector mesons were detected with the CEBAF
Large Acceptance Spectrometer (CLAS) via their decays to . The rare
leptonic decay was chosen to reduce final-state interactions. A combinatorial
background was subtracted from the invariant mass spectra using a
well-established event-mixing technique. The meson mass spectrum was
extracted after the and signals were removed in a nearly
model-independent way. Comparisons were made between the mass spectra
from the heavy targets () with the mass spectrum extracted from the
deuterium target. With respect to the -meson mass, we obtain a small
shift compatible with zero. Also, we measure widths consistent with standard
nuclear many-body effects such as collisional broadening and Fermi motion.Comment: 15 pages, 18 figures, 3 table
Measurement of Inclusive Spin Structure Functions of the Deuteron
We report the results of a new measurement of spin structure functions of the
deuteron in the region of moderate momentum transfer ( = 0.27 -- 1.3
(GeV/c)) and final hadronic state mass in the nucleon resonance region (
= 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam
at Jefferson Lab off a dynamically polarized cryogenic solid state target
(ND) and detected the scattered electrons with the CEBAF Large
Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal
double spin asymmetry and the spin structure function . Our
data are generally in reasonable agreement with existing data from SLAC where
they overlap, and they represent a substantial improvement in statistical
precision. We compare our results with expectations for resonance asymmetries
and extrapolated deep inelastic scaling results. Finally, we evaluate the first
moment of the structure function and study its approach to both the
deep inelastic limit at large and to the Gerasimov-Drell-Hearn sum rule
at the real photon limit (). We find that the first moment varies
rapidly in the range of our experiment and crosses zero at between
0.5 and 0.8 (GeV/c), indicating the importance of the resonance at
these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys.
Rev.
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