463 research outputs found
Winter activity of a population of greater horseshoe bats (Rhinolophus ferrumequinum)
Activity patterns of a greater horseshoe bats Rhinolophus ferrumequinum were investigated at caves in Cheddar (south-west England) during the hibernation season. An ultrasound detector and datalogger were used to monitor and record the number of echolocation calls in a single cave. Activity of R. ferrumequinum remained largely nocturnal throughout winter, and the mean time of activity over 24 hours was 88 to 369 minutes (1.47 to 6.15 hours) after sunset. There was an increase in diurnal activity from late May to early June, probably because bats remained active after foraging at dawn towards the end of the hibernation season. Visits to the cave did not increase bat activity. Cave air temperature reflected external climatic temperature, although there was variation in cave temperature and its range within and across caves. Individual R. ferrumequinum are usually dispersed in caves in regions where temperature fluctuations correlate with climatic variations in temperature. There was a positive correlation between the number of daily bat passes monitored by the bat detector and datalogger (= daily activity) and cave temperature. Nocturnal activity may sometimes be associated with winter feeding. Neither date nor barometric pressure had a significant effect on daily activity. Activity patterns largely reflected the findings from individual R. ferrumequinum studied by telemetry (Park, 1998), in that bat activity increased with cave and climatic temperatures, and the temporal pattern of activity remained consistently nocturnal throughout winter, starting at dusk
Phenomenology of the Deuteron Electromagnetic Form Factors
A rigorous extraction of the deuteron charge form factors from tensor
polarization data in elastic electron-deuteron scattering, at given values of
the 4-momentum transfer, is presented. Then the world data for elastic
electron-deuteron scattering is used to parameterize, in three different ways,
the three electromagnetic form factors of the deuteron in the 4-momentum
transfer range 0-7 fm^-1. This procedure is made possible with the advent of
recent polarization measurements. The parameterizations allow a
phenomenological characterization of the deuteron electromagnetic structure.
They can be used to remove ambiguities in the form factors extraction from
future polarization data.Comment: 18 pages (LaTeX), 2 figures Feb. 25: minor changes of content and in
Table
Organization theory and military metaphor: time for a reappraisal?
A ‘conventional’ use of military metaphor would use it to convey attributes such as hierarchical organization, vertical communication and limited autonomy. This is often used in contrast to a looser form of organization based on the metaphor of the network. However, this article argues that military practice is more complex, with examples of considerable autonomy within the constraints of central direction. It is suggested that not only might this be a more useful metaphor for many contemporary organizations, but also that simplistic uses of military metaphor divert our attention away from the functions that management hierarchies play. The discussion is embedded within a critical realist account of metaphor, arguing for both its value and the need for its further development
The MINERA Data Acquisition System and Infrastructure
MINERA (Main INjector ExpeRiment -A) is a new few-GeV neutrino
cross section experiment that began taking data in the FNAL NuMI (Fermi
National Accelerator Laboratory Neutrinos at the Main Injector) beam-line in
March of 2010. MINERA employs a fine-grained scintillator detector capable
of complete kinematic characterization of neutrino interactions. This paper
describes the MINERA data acquisition system (DAQ) including the read-out
electronics, software, and computing architecture.Comment: 34 pages, 16 figure
A precise measurement of the deuteron elastic structure function A(Q^2)
The A(Q^2) structure function in elastic electron-deuteron scattering was
measured at six momentum transfers Q^2 between 0.66 and 1.80 (GeV/c)^2 in Hall
C at Jefferson Laboratory. The scattered electrons and recoil deuterons were
detected in coincidence, at a fixed deuteron angle of 60.5 degrees. These new
precise measurements resolve discrepancies between older sets of data. They put
significant constraints on existing models of the deuteron electromagnetic
structure, and on the strength of isoscalar meson exchange currents.Comment: 3 LaTeX pages plus 2 PS figure
The Quasielastic 3He(e,e'p)d Reaction at Q^2 = 1.5 GeV^2 for Recoil Momenta up to 1 GeV/c
We have studied the quasielastic 3He(e,e'p)d reaction in perpendicular
coplanar kinematics, with the energy and momentum transferred by the electron
fixed at 840 MeV and 1502 MeV/c, respectively. The 3He(e,e'p)d cross section
was measured for missing momenta up to 1000 MeV/c, while the A_TL asymmetry was
extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150
MeV/c, the measured cross section is described well by calculations that use a
variational ground-state wave function of the 3He nucleus derived from a
potential that includes three-body forces. For missing momenta from 150 to 750
MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c,
the experimental cross section is more than an order of magnitude larger than
predicted by available theories. The A_TL asymmetry displays characteristic
features of broken factorization, and is described reasonably well by available
models.Comment: 5 pages, 3 figures, submitted to Physical Review Letters, v3: changed
conten
Measurement of the 3He(e,e'p)pn reaction at high missing energies and momenta
Results of the Jefferson Lab Hall A quasielastic 3He(e,e'p)pn measurements
are presented. These measurements were performed at fixed transferred momentum
and energy, q = 1502 MeV/c and omega = 840 MeV, respectively, for missing
momenta p_m up to 1 GeV/c and missing energies in the continuum region, up to
pion threshold; this kinematic coverage is much more extensive than that of any
previous experiment. The cross section data are presented along with the
effective momentum density distribution and compared to theoretical models.Comment: 5 pages, 3 figures, updated to reflect published paper: minor text
changes from previous version along with updated and added reference
Measurement of Tensor Polarization in Elastic Electron-Deuteron Scattering at Large Momentum Transfer
Tensor polarization observables (t20, t21 and t22) have been measured in
elastic electron-deuteron scattering for six values of momentum transfer
between 0.66 and 1.7 (GeV/c)^2. The experiment was performed at the Jefferson
Laboratory in Hall C using the electron HMS Spectrometer, a specially designed
deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new
data determine to much larger Q^2 the deuteron charge form factors G_C and G_Q.
They are in good agreement with relativistic calculations and disagree with
pQCD predictions.Comment: 5 pages, 4 figures, for associated informations, see
http://isnwww.in2p3.fr/hadrons/t20/t20_ang.html clarification about several
topics, one figure has been had, extraction of form factors use AQ
interpolation in our Q2 range onl
Cross Section Measurement of Charged Pion Photoproduction from Hydrogen and Deuterium
We have measured the differential cross section for the gamma n --> pi- p and
gamma p --> pi+ n reactions at center of mass angle of 90 degree in the photon
energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at photon
energies greater than 3.3 GeV exhibit a global scaling behavior for both pi-
and pi+ photoproduction, consistent with the constituent counting rule and the
existing pi+ photoproduction data. Possible oscillations around the scaling
value are suggested by these new data The data show enhancement in the scaled
cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio
of exclusive pi- to pi+ photoproduction at high energy is consistent with the
prediction based on one-hard-gluon-exchange diagrams
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