920 research outputs found
An institutional perspective on retail internationalization success: Home Depot in Chile
This study utilizes institutional theory to assess the effect of the host institutional environment on the success of internationalizing retailers. According to this framework, retailers succeed in international markets when they adapt their retail format and practices to the salient institutional norms in the host market and achieve legitimation from the relevant social actors. This framework was used in a case study of Home Depot’s entry into Chile in 1998 and its exit three years later. Findings showed that Home Depot lacked legitimacy in Chile because they failed to offer the range of merchandise and store atmosphere demanded by the traditional family shopping activity, and because their management team did not embed themselves in the broader social network. It was also apparent the competition had anticipated and responded to Home Depot’s source of competitive advantage and that Home Depot’s scale was not great enough to command any advantages in the supply chain network
Towards Baselines for Shoulder Surfing on Mobile Authentication
Given the nature of mobile devices and unlock procedures, unlock
authentication is a prime target for credential leaking via shoulder surfing, a
form of an observation attack. While the research community has investigated
solutions to minimize or prevent the threat of shoulder surfing, our
understanding of how the attack performs on current systems is less well
studied. In this paper, we describe a large online experiment (n=1173) that
works towards establishing a baseline of shoulder surfing vulnerability for
current unlock authentication systems. Using controlled video recordings of a
victim entering in a set of 4- and 6-length PINs and Android unlock patterns on
different phones from different angles, we asked participants to act as
attackers, trying to determine the authentication input based on the
observation. We find that 6-digit PINs are the most elusive attacking surface
where a single observation leads to just 10.8% successful attacks, improving to
26.5\% with multiple observations. As a comparison, 6-length Android patterns,
with one observation, suffered 64.2% attack rate and 79.9% with multiple
observations. Removing feedback lines for patterns improves security from
35.3\% and 52.1\% for single and multiple observations, respectively. This
evidence, as well as other results related to hand position, phone size, and
observation angle, suggests the best and worst case scenarios related to
shoulder surfing vulnerability which can both help inform users to improve
their security choices, as well as establish baselines for researchers.Comment: Will appear in Annual Computer Security Applications Conference
(ACSAC
Sum-max Submodular Bandits
Many online decision-making problems correspond to maximizing a sequence of
submodular functions. In this work, we introduce sum-max functions, a subclass
of monotone submodular functions capturing several interesting problems,
including best-of--bandits, combinatorial bandits, and the bandit versions
on facility location, -medians, and hitting sets. We show that all functions
in this class satisfy a key property that we call pseudo-concavity. This allows
us to prove -regret bounds for bandit feedback in
the nonstochastic setting of the order of (ignoring log factors),
where is the time horizon and is a cardinality constraint. This bound,
attained by a simple and efficient algorithm, significantly improves on the
regret bound for online monotone submodular
maximization with bandit feedback
Real-life adaptations in walking patterns in patients with established peripheral arterial disease assessed using a global positioning system in the community: A cohort study
Objective: Lower extremity peripheral arterial disease (PAD) is a chronic condition most commonly presenting with intermittent claudication (IC). IC limits walking ability and may negatively affect health-related quality of life. Treadmill assessment of maximal walking distance (MWD) is the gold standard to assess PAD symptom severity. Despite being a well-established and reproducible tool, it may be inappropriate (due to frailty or fear) for some patients and only describes maximal abilities for a single walk test. Global Positioning Systems (GPS) have been proposed as reliable and reproducible tool to measure total, mean and maximal walking distances in PAD patients, in the community setting. Using GPS our study attempted to explore what happens to the walking ability of patients with IC following no intervention under "real-life" conditions.
Design and Methods: Using the GlobalSat DG100 GPS, forty-three patients (69±9yrs; 9 female; no invasive interventions or rehabilitation) undertook two 60-minute walking assessments, 6 months apart. Assessments took place in community spaces that had even terrain, no tall trees or buildings and were free from motorised vehicles. GPS-measured maximum walking distance was the main study outcome measure.
Results: Over the 6-month period, patients demonstrated significantly shorter GPS-measured, mean (552m vs 334m; p=0.02) and maximum (714m vs 545m; p=0.04) walking distances, stopping also more frequently (9 v 5 times; p=0.03).
Conclusions: Given the reported symptom progression we advocate early intervention (e.g. exercise interventions) combined with frequent patient monitoring in attempts to maintain or improve walking ability.
Key Words: peripheral arterial disease; Global Position System; maximum walking distance; intermittent claudication; community assessments
STIS UV spectroscopy of early B supergiants in M31
We analyze STIS spectra in the 1150-1700 Angstrom wavelength range obtained
for six early B supergiants in the neighboring galaxy M31. Because of their
likely high (nearly solar) abundance, these stars were originally chosen to be
directly comparable to their Galactic counterparts, and represent a much-needed
addition to our current sample of B-type supergiants, in our efforts to study
the dependence of the Wind Momentum-Luminosity Relationship on spectral type
and metallicity. As a first step to determine wind momenta we fit the P-Cygni
profiles of the resonance lines of N V, Si IV and C IV with standard methods,
and derive terminal velocities for all of the STIS targets. From these lines we
also derive ionic stellar wind column densities. Our results are compared with
those obtained previously in Galactic supergiants, and confirm earlier claims
of `normal' wind line intensities and terminal velocities in M31. For half of
the sample we find evidence for an enhanced maximum turbulent velocity when
compared to Galactic counterparts.Comment: 15 pages, 9 figures, 2 tables. Accepted for publication in The
Astrophysical Journa
The twelve dimensional super (2+2)-brane
We discuss supersymmetry in twelve dimensions and present a covariant
supersymmetric action for a brane with worldsheet signature (2,2), called a
super (2+2)-brane, propagating in the osp(64,12) superspace. This superspace is
explicitly constructed, and is trivial in the sense that the spinorial part is
a trivial bundle over spacetime, unlike the twisted superspace of usual
Poincare supersymmetry. For consistency, it is necessary to take a projection
of the superspace. This is the same as the projection required for worldvolume
supersymmetry. Upon compactification of this superspace, a torsion is naturally
introduced and we produce the membrane and type IIB string actions in 11 and 10
dimensional Minkowski spacetimes. In addition, the compactification of the
twelve dimensional supersymmetry algebra produces the correct algebras for
these theories, including central charges. These considerations thus give the
type IIB string and M-theory a single twelve dimensional origin.Comment: 32 pages LaTex, no figures, minor comments and address(!) adde
Effects of a pragmatic lifestyle intervention for reducing body mass in obese adults with obstructive sleep apnoea: a randomised controlled trial
This study investigated the effects of a pragmatic lifestyle intervention in obese adults with continuous positive airway pressure-treated obstructive sleep apnoea hypopnoea syndrome (OSAHS). Sixty patients were randomised 1 : 1 to either a 12-week lifestyle intervention or an advice-only control group. The intervention involved supervised exercise sessions, dietary advice, and the promotion of lifestyle behaviour change using cognitive-behavioural techniques. Outcomes were assessed at baseline (week 0), intervention end-point (week 13), and follow-up (week 26). The primary outcome was 13-week change in body mass. Secondary outcomes included anthropometry, blood-borne biomarkers, exercise capacity, and health-related quality of life. At end-point, the intervention group exhibited small reductions in body mass (−1.8 [−3.0, −0.5] kg; P = 0.007) and body fat percentage (−1 [−2, 0]%; P = 0.044) and moderate improvements in C-reactive protein (−1.3 [−2.4, −0.2] mg·L−1; P = 0.028) and exercise capacity (95 [50, 139] m; P <0.001 ). At follow-up, changes in body mass (−2.0 [−3.5, −0.5] kg; P = 0.010), body fat percentage (−1 [−2, 0]%; P = 0.033), and C-reactive protein (−1.3 [−2.5, −0.1] mg·L−1; P = 0.037 ) were maintained and exercise capacity was further improved (132 [90, 175] m; P <0.001). This trial is registered with ClinicalTrials.gov NCT01546792
The TIGA technique for detecting gravitational waves with a spherical antenna
We report the results of a theoretical and experimental study of a spherical
gravitational wave antenna. We show that it is possible to understand the data
from a spherical antenna with 6 radial resonant transducers attached to the
surface in the truncated icosahedral arrangement. We find that the errors
associated with small deviations from the ideal case are small compared to
other sources of error, such as a finite signal-to-noise ratio. An in situ
measurement technique is developed along with a general algorithm that
describes a procedure for determining the direction of an external force acting
on the antenna, including the force from a gravitational wave, using a
combination of the transducer responses. The practicality of these techniques
was verified on a room-temperature prototype antenna.Comment: 15 pages, 14 figures, submitted to Physical Review
Unveiling the nature of INTEGRAL objects through optical spectroscopy. VIII. Identification of 44 newly detected hard X-ray sources
(abridged) Hard X-ray surveys performed by the INTEGRAL satellite have
discovered a conspicuous fraction (up to 30%) of unidentified objects among the
detected sources. Here we continue our identification program by selecting
probable optical candidates using positional cross-correlation with soft X-ray,
radio, and/or optical archives, and performing optical spectroscopy on them. As
a result, we identified or more accurately characterized 44 counterparts of
INTEGRAL sources: 32 active galactic nuclei, with redshift 0.019 < z < 0.6058,
6 cataclysmic variables (CVs), 5 high-mass X-ray binaries (2 of which in the
Small Magellanic Cloud), and 1 low-mass X-ray binary. This was achieved by
using 7 telescopes of various sizes and archival data from two online
spectroscopic surveys. The main physical parameters of these hard X-ray sources
were also determined using the available multiwavelength information. AGNs are
the most abundant population among hard X-ray objects, and our results confirm
this tendency when optical spectroscopy is used as an identification tool. The
deeper sensitivity of recent INTEGRAL surveys enables one to begin detecting
hard X-ray emission above 20 keV from sources such as LINER-type AGNs and
non-magnetic CVs.Comment: 22 pages, 14 figures, 6 tables, accepted for publication on A&A, main
journa
Unveiling the nature of INTEGRAL objects through optical spectroscopy. IX. 22 more identifications, and a glance into the far hard X-ray Universe
(Abridged) Since its launch in October 2002, the INTEGRAL satellite has
revolutionized our knowledge of the hard X-ray sky thanks to its unprecedented
imaging capabilities and source detection positional accuracy above 20 keV.
Nevertheless, many of the newly-detected sources in the INTEGRAL sky surveys
are of unknown nature. The combined use of available information at longer
wavelengths (mainly soft X-rays and radio) and of optical spectroscopy on the
putative counterparts of these new hard X-ray objects allows us to pinpoint
their exact nature. Continuing our long-standing program that has been running
since 2004, and using 6 different telescopes of various sizes, we report the
classification through optical spectroscopy of 22 more unidentified or poorly
studied high-energy sources detected with the IBIS instrument onboard INTEGRAL.
We found that 16 of them are active galactic nuclei (AGNs), while the remaining
6 objects are within our Galaxy. Among the identified extragalactic sources, 14
are Type 1 AGNs; of these, 6 lie at redshift larger than 0.5 and one has z =
3.12, which makes it the second farthest object detected in the INTEGRAL
surveys up to now. The remaining AGNs are of type 2, and one of them is a pair
of interacting Seyfert 2 galaxies. The Galactic objects are identified as two
cataclysmic variables, one high-mass X-ray binary, one symbiotic binary and two
chromospherically active stars. We thus still find that AGNs are the most
abundant population among hard X-ray objects identified through optical
spectroscopy. Moreover, we note that the higher sensitivity of the more recent
INTEGRAL surveys is now enabling the detection of high-redshift AGNs, thus
allowing the exploration of the most distant hard X-ray emitting sources and
possibly of the most extreme blazars.Comment: 18 pages, 9 figures, 8 tables, accepted for publication on Astronomy
& Astrophysics, main journa
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