1,352 research outputs found
Radical learning through semantic transformation: capitalizing on novelty
YesThat organizations exist in a fluid environment of unprecedented and discontinuous change seems beyond debate. We seem
to find ourselves immersed in a world in which events have a tendency to unfold and overtake us in unforeseeable and novel
ways that defy comprehension; a crisis of meaning takes place and conventional sensemaking is disrupted. Our need to
imaginatively construct new meanings that allow us to understand what is going on and to work out how to respond becomes
ever more pressing. We do live in interesting times. The emergence of the new, however, challenges current established
ways of knowing and opens a creative space for radical learning to take place. Novelty stimulates the generative process by
which organizations and individuals learn, adapt to and cope with the exigencies they face in order to survive and progress.
Such radical learning occurs when creative linguistic interventions in dialogue opens up semantic spaces whereby new terms
are coined and old ones broken up, combined and/or redeployed in novel ways, in an effort to give expression to the fresh
circumstances experienced or new phenomena observed. We call this kind of imaginative linguistic intervention semantic
transformation. In this paper we argue that it is this semantic transformation that promotes radical transformational learning.
Such semantic transformation is predicated on the improvisatory character of dialogue as a form of communication. We
explore how, through this dialogical process of semantic transformation, we discover the resources and means to respond to
the vagueness and equivocality experienced, by exploiting language in novel ways in our attempts to make sense of and
account for such experiences
Modeling the Gas Flow in the Bar of NGC 1365
We present new observations of the strongly-barred galaxy NGC 1365, including
new photometric images and Fabry-Perot spectroscopy, as well as a detailed
re-analysis of the neutral hydrogen observations from the VLA archive. We find
the galaxy to be at once remarkably bi-symmetric in its I-band light
distribution and strongly asymmetric in the distribution of dust and in the
kinematics of the gas in the bar region. The velocity field mapped in the
H-alpha line reveals bright HII regions with velocities that differ by 60 to 80
km/s from that of the surrounding gas, which may be due to remnants of
infalling material. We have attempted hydrodynamic simulations of the bar flow
to estimate the separate disk and halo masses, using two different dark matter
halo models and covering a wide range of mass-to-light ratios (Upsilon) and bar
pattern speeds (Omega_p). None of our models provides a compelling fit to the
data, but they seem most nearly consistent with a fast bar, corotation at sim
1.2r_B, and Upsilon_I simeq 2.0 +- 1.0, implying a massive, but not fully
maximal, disk. The fitted dark halos are unusually concentrated, a requirement
driven by the declining outer rotation curve.Comment: 43 pages, 15 figures, accepted to appear in Ap
Study of the mixed state of La_{1.83}Sr_{0.17}CuO_{4} by means of muon-spin rotation and magnetization experiments in a low magnetic field
Muon-spin rotation (muSR) experiments are often used to study the magnetic
field distribution in type-II superconductors in the vortex state. Based on the
determination of the magnetic penetration depth it is frequently
speculated---also controversially---about the order-parameter symmetry of the
studied superconductors. This article reports on a combined muSR and
magnetization study of the mixed state in the cuprate high-temperature
superconductor La_{1.83}Sr_{0.17}CuO_{4} in a low magnetic field of 20 mT
applied along the c axis of a single crystal. The macroscopic magnetization
measurements reveal substantial differences for various cooling procedures.
Yet, indicated changes in the vortex dynamics between different temperature
regions as well as the results of the microscopic muSR experiments are
virtually independent of the employed cooling cycles. Additionally, it is found
that the mean magnetic flux density, locally probed by the muons, strongly
increases at low temperatures. This can possibly be explained by a non-random
sampling of the spatial field distribution of the vortex lattice in this
cuprate superconductor caused by intensified vortex pinning.Comment: 10 pages, 8 figures, accepted for publication in Physical Review
STIS Longslit Spectroscopy Of The Narrow Line Region Of NGC 4151. I. Kinematics and Emission Line Ratios
Longslit spectra of the Seyfert galaxy NGC 4151 from the UV to near infrared
have been obtained with STIS to study the kinematics and physical conditions in
the NLR. The kinematics show evidence for three components, a low velocity
system in normal disk rotation, a high velocity system in radial outflow at a
few hundred km/s relative to the systemic velocity and an additional high
velocity system also in outflow with velocities up to 1400 km/s, in agreement
with results from STIS slitless spectroscopy (Hutchings et al., 1998, Kaiser et
al., 1999, Hutchings et al., 1999) We have explored two simple kinematic models
and suggest that radial outflow in the form of a wind is the most likely
explanation. We also present evidence indicating that the wind may be
decelerating with distance from the nucleus.
We find that the emission line ratios along our slits are all entirely
consistent with photoionization from the nuclear continuum source. A decrease
in the [OIII]5007/H-beta and [OIII]5007/[OII]3727 ratios suggests that the
density decreases with distance from the nucleus. This trend is borne out by
the [SII] ratios as well. We find no strong evidence for interaction between
the radio jet and the NLR gas in either the kinematics or the emission line
ratios in agreement with the results of Kaiser et al. (1999) who find no
spatial coincidence of NLR clouds and knots in the radio jet. These results are
in contrast to other recent studies of nearby AGN which find evidence for
significant interaction between the radio source and the NLR gas.Comment: 32 pages, 13 figures, accepted for publication in The Astrophysical
Journa
Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal treatment on mesoscopic phase separation
An extended study of the superconducting and normal-state properties of
various as-grown and post-annealed RbxFe2-ySe2 single crystals is presented.
Magnetization experiments evidence that annealing of RbxFe2-ySe2 at 413 K, well
below the onset of phase separation Tp=489 K, neither changes the magnetic nor
the superconducting properties of the crystals. In addition, annealing at 563
K, well above Tp, suppresses the superconducting transition temperature Tc and
leads to an increase of the antiferromagnetic susceptibility accompanied by the
creation of ferromagnetic impurity phases, which are developing with annealing
time. However, annealing at T=488K=Tp increases Tc up to 33.3 K, sharpens the
superconducting transition, increases the lower critical field, and strengthens
the screening efficiency of the applied magnetic field. Resistivity
measurements of the as-grown and optimally annealed samples reveal an increase
of the upper critical field along both crystallographic directions as well as
its anisotropy. Muon spin rotation and scanning transmission electron
microscopy experiments suggest the coexistence of two phases below Tp: a
magnetic majority phase of Rb2Fe4Se5 and a non-magnetic minority phase of
Rb0.5Fe2Se2. Both microscopic techniques indicate that annealing the specimens
just at Tp does not affect the volume fraction of the two phases, although the
magnetic field distribution in the samples changes substantially. This suggests
that the microstructure of the sample, caused by mesoscopic phase separation,
is modified by annealing just at Tp, leading to an improvement of the
superconducting properties of RbxFe2-ySe2 and an enhancement of Tc.Comment: 13 pages, 12 figure
A Practical Cryptanalysis of the Algebraic Eraser
Anshel, Anshel, Goldfeld and Lemieaux introduced the Colored Burau Key
Agreement Protocol (CBKAP) as the concrete instantiation of their Algebraic
Eraser scheme. This scheme, based on techniques from permutation groups, matrix
groups and braid groups, is designed for lightweight environments such as RFID
tags and other IoT applications. It is proposed as an underlying technology for
ISO/IEC 29167-20. SecureRF, the company owning the trademark Algebraic Eraser,
has presented the scheme to the IRTF with a view towards standardisation.
We present a novel cryptanalysis of this scheme. For parameter sizes
corresponding to claimed 128-bit security, our implementation recovers the
shared key using less than 8 CPU hours, and less than 64MB of memory.Comment: 15 pages. Updated references, with brief comments added. Minor typos
corrected. Final version, accepted for CRYPTO 201
Star Formation Thresholds in Galactic Disks
We report the first results of a detailed study of the star formation law in
a sample of 32 nearby spiral galaxies with well-measured rotation curves, HI
and H (as traced by CO) surface density profiles, and new \Ha CCD
photometry. Our results strongly support the view that the formation of
gravitationally bound interstellar clouds regulates the onset of widespread
star formation -- at least in the outer regions of galactic disks.Comment: Will appear in July 1 ApJ. Abbreviated abstract. Postscript version
available at http://www.astro.caltech.edu/~clm
Evidence For Recent Accretion in Nearby Galaxies
I discuss observations of magnitude residuals from the B-band Tully-Fisher
relationship, B-V color, chemical abundance gradients, and asymmetries in the H
I and stellar disks of nearby spiral galaxies within the context of a model in
which small satellites or H I clouds are accreted onto the outer disks of
spiral galaxies. Correlations between the various observables support the
hypothesis that accretion dilutes the gas phase abundances in the outer disk,
steepens the abundance gradient across the disk, increases the star formation
rate, and creates asymmetries in the outer disk. By estimating the duration of
steep abundance gradients, elevated rates of star formation, or outer disk
asymmetries, constraints can be placed on the rate of accretion events. The
data suggest that accretion events at the current time are common.Comment: 4 pages (one Table and one Figure included). Accepted for Publication
in ApJ Letter
Local governance and business performance in Vietnam:the transaction costs’ perspective
Local governance and business performance in Vietnam: the transaction costs’ perspective. Regional Studies. This paper adopts a transaction costs’ perspective to explain why the growth of small and medium-sized enterprises (SMEs) may vary across regions of an emerging economy. Furthermore, it is argued that young and small firms gain more from the improvement of local governance than do old and large firms. In addition, depending on the institutional history, SMEs will respond differently to the incentives provided by local governance. Analysing more than 300,000 SMEs in Vietnam during 2006–12, it is shown that higher-quality local governance positively influences local SME revenue growth; this effect is stronger for young and small firms, and matters more where institutional history suggests there is less support for entrepreneurship
The Metallicity-Luminosity Relation, Effective Yields, and Metal Loss in Spiral and Irregular Galaxies
I present results on the correlation between galaxy mass, luminosity, and
metallicity for a sample of spiral and irregular galaxies having well-measured
abundance profiles, distances, and rotation speeds. Additional data for low
surface brightness galaxies from the literature are also included for
comparison. These data are combined to study the metallicity-luminosity and
metallicity-rotation speed correlations for spiral and irregular galaxies. The
metallicity luminosity correlation shows its familiar form for these galaxies,
a roughly uniform change in the average present-day O/H abundance of about a
factor 100 over 11 magnitudes in B luminosity. However, the O/H - V(rot)
relation shows a change in slope at a rotation speed of about 125 km/sec. At
faster V(rot), there appears to be no relation between average metallicity and
rotation speed. At lower V(rot), the metallicity correlates with rotation
speed. This change in behavior could be the result of increasing loss of metals
from the smaller galaxies in supernova-driven winds. This idea is tested by
looking at the variation in effective yield, derived from observed abundances
and gas fractions assuming closed box chemical evolution. The effective yields
derived for spiral and irregular galaxies increase by a factor of 10-20 from
V(rot) approximately 5 km/sec to V(rot) approximately 300 km/sec, asympotically
increasing to approximately constant y(eff) for V(rot) > 150 km/sec. The trend
suggests that galaxies with V(rot) < 100-150 km/sec may lose a large fraction
of their SN ejecta, while galaxies above this value tend to retain metals.Comment: 40 pages total, including 7 encapsulated postscript figures. Accepted
for publication in 20 Dec 2002 Ap
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