2,860 research outputs found
The Illinois State University Civic Chorale Spring Concert: Music of ISU Composers Past and Present, April 14, 2023
Center for the Performing Arts Concert HallFridayApril 14, 20237:00 p.m
Bark Beetle (Coleoptera: Curculionidae: Scolytinae) Community Structure in Northeastern and Central Minnesota
Large-scale surveys of forest insects provide two distinct benefits: the detection of invasive and exotic species that cause millions of dollars of damage annually to forest and ornamental industries, and the addition of a wealth of species distribution and diversity information to the scientific community. We intensively surveyed the Northeast and East-central regions of Minnesota from 2006-2008 for invasive/exotic and native Scolytinae using Lindgren funnel traps baited with one of four lures (a/β-pinene, ultra-high-release ethanol [EtOH], EtOH+a-pinene, and Ips 3-part). We captured 16,841 scolytines (representing 25 genera) of which over 40% were Ips pini (Say) and Ips grandicollis (Eichhoff). We found two exotic Scolytinae, Scolytus multistriatus (Marsham) and Scolytus schevyrewi Semenov, both of which had previously been recorded in Minnesota. Two native species, Conophthorus coniperda (Schwarz) and Crypturgus pusillus (Gyllenhal), were reported for the first time in Minnesota. Non-metric multi- dimensional scaling and analysis of similarities indicate that lure types capture different Scolytinae communities, while year, weather pattern and region factors were not significant. We also report the seasonal phenology of the seven most abundantly captured species; Dendroctonus valens LeConte, Hylastes porculus Erichson, Hylurgops rugipennis pinifex (Fitch),I. grandicollis, I. pini, Orthotomicus caelatus (Eichhoff) and Pityophthorus spp. Eichhoff
Pion photoproduction on nucleons in a covariant hadron-exchange model
We present a relativistic dynamical model of pion photoproduction on the
nucleon in the resonance region. It offers several advances over the existing
approaches. The model is obtained by extending our -scattering
description to the electromagnetic channels. The resulting photopion amplitude
is thus unitary in the , \ga N channel space, Watson's theorem is
exactly satisfied. At this stage we have included the pion, nucleon,
\De(1232)-resonance degrees of freedom. The and meson
exchanges are also included, but play a minor role in the considered energy
domain (up to GeV). In this energy range the model provides a
good description of all the important multipoles. We have allowed for only two
free parameters -- the photocouplings of the -resonance. These
couplings are adjusted to reproduce the strength of corresponding
resonant-multipoles and at the resonance position.Comment: 17 pages, 4 figs, version to appear in Phys. Rev. C 70 (2004
Further Evidence for a Merger Origin for the Thick Disk: Galactic Stars Along Lines-of-sight to Dwarf Spheroidal Galaxies
The history of the Milky Way Galaxy is written in the properties of its
stellar populations. Here we analyse stars observed as part of surveys of local
dwarf spheroidal galaxies, but which from their kinematics are highly probable
to be non-members. The selection function -- designed to target metal-poor
giants in the dwarf galaxies, at distances of ~100kpc -- includes F-M dwarfs in
the Milky Way, at distances of up to several kpc. Thestars whose motions are
analysed here lie in the cardinal directions of Galactic longitude l ~ 270 and
l ~ 90, where the radial velocity is sensitive to the orbital rotational
velocity. We demonstrate that the faint F/G stars contain a significant
population with V_phi ~ 100km/s, similar to that found by a targeted, but
limited in areal coverage, survey of thick-disk/halo stars by Gilmore, Wyse &
Norris (2002). This value of mean orbital rotation does not match either the
canonical thick disk or the stellar halo. We argue that this population,
detected at both l ~ 270 and l ~ 90, has the expected properties of `satellite
debris' in the thick-disk/halo interface, which we interpret as remnants of the
merger that heated a pre-existing thin disk to form the thick disk.Comment: Accepted, Astrophysical Journal Letter
Stereoscopic electron spectroscopy of solar hard X-ray flares with a single spacecraft
Hard X-ray (HXR) spectroscopy is the most direct method of diagnosing
energetic electrons in solar flares. Here we present a technique which allows
us to use a single HXR spectrum to determine an effectively stereoscopic
electron energy distribution. Considering the Sun's surface to act as a
'Compton mirror' allows us to look at emitting electrons also from behind the
source, providing vital information on downward-propagating particles. Using
this technique we determine simultaneously the electron spectra of downward and
upward directed electrons for two solar flares observed by the Ramaty High
Energy Solar Spectroscopic Imager (RHESSI). The results reveal surprisingly
near-isotropic electron distributions, which contrast strongly with the
expectations from the standard model which invokes strong downward beaming,
including collisional thick-target model.Comment: 7 pages, 3 figures, accepted to Astrophysical Journal Letter
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