420 research outputs found
Fuzzy Simultaneous Congruences
We introduce a very natural generalization of the well-known problem of
simultaneous congruences. Instead of searching for a positive integer that
is specified by fixed remainders modulo integer divisors we
consider remainder intervals such that is feasible if and
only if is congruent to modulo for some remainder in
interval for all .
This problem is a special case of a 2-stage integer program with only two
variables per constraint which is is closely related to directed Diophantine
approximation as well as the mixing set problem. We give a hardness result
showing that the problem is NP-hard in general.
By investigating the case of harmonic divisors, i.e. is an
integer for all , which was heavily studied for the mixing set problem as
well, we also answer a recent algorithmic question from the field of real-time
systems. We present an algorithm to decide the feasibility of an instance in
time and we show that if it exists even the smallest
feasible solution can be computed in strongly polynomial time
Scheduling with Many Shared Resources
Consider the many shared resource scheduling problem where jobs have to be
scheduled on identical parallel machines with the goal of minimizing the
makespan. However, each job needs exactly one additional shared resource in
order to be executed and hence prevents the execution of jobs that need the
same resource while being processed. Previously a -approximation
was the best known result for this problem. Furthermore, a -approximation
for the case with only two machines was known as well as a PTAS for the case
with a constant number of machines. We present a simple and fast
5/3-approximation and a much more involved but still reasonable
1.5-approximation. Furthermore, we provide a PTAS for the case with only a
constant number of machines, which is arguably simpler and faster than the
previously known one, as well as a PTAS with resource augmentation for the
general case. The approximation schemes make use of the N-fold integer
programming machinery, which has found more and more applications in the field
of scheduling recently. It is plausible that the latter results can be improved
and extended to more general cases. Lastly, we give a
inapproximability result for the natural problem extension where each job may
need up to a constant number (in particular ) of different resources
A practical approach to the sensitivity analysis for kinetic Monte Carlo simulation of heterogeneous catalysis
Lattice kinetic Monte Carlo simulations have become a vital tool for
predictive quality atomistic understanding of complex surface chemical
reaction kinetics over a wide range of reaction conditions. In order to expand
their practical value in terms of giving guidelines for the atomic level
design of catalytic systems, it is very desirable to readily evaluate a
sensitivity analysis for a given model. The result of such a sensitivity
analysis quantitatively expresses the dependency of the turnover frequency,
being the main output variable, on the rate constants entering the model. In
the past, the application of sensitivity analysis, such as degree of rate
control, has been hampered by its exuberant computational effort required to
accurately sample numerical derivatives of a property that is obtained from a
stochastic simulation method. In this study, we present an efficient and
robust three-stage approach that is capable of reliably evaluating the
sensitivity measures for stiff microkinetic models as we demonstrate using the
CO oxidation on RuO2(110) as a prototypical reaction. In the first step, we
utilize the Fisher information matrix for filtering out elementary processes
which only yield negligible sensitivity. Then we employ an estimator based on
the linear response theory for calculating the sensitivity measure for non-
critical conditions which covers the majority of cases. Finally, we adapt a
method for sampling coupled finite differences for evaluating the sensitivity
measure for lattice based models. This allows for an efficient evaluation even
in critical regions near a second order phase transition that are hitherto
difficult to control. The combined approach leads to significant computational
savings over straightforward numerical derivatives and should aid in
accelerating the nano-scale design of heterogeneous catalysts
"A Tool Doesn't Add Anything" Physicians' Perceptions and Use of Pain Assessment Tools with People with Advanced Dementia Approaching the End of Life
Evaluation of the impact of telementoring using ECHO© technology on healthcare professionals' knowledge and self-efficacy in assessing and managing pain for people with advanced dementia nearing the end of life
Abstract Background Pain assessment and management in advanced and end-stage dementia are challenging; patients are at risk of under-diagnosis, under-assessment and under-treatment. Previous research has highlighted the importance of needs-driven training and development in this area for physicians, nurses and healthcare assistants (HCAs) across specialties, disciplines and care settings. This study used teleconferencing technology to connect healthcare professionals across multiple settings and disciplines in real-time clinics, based on the Project ECHO© model. This paper reports the evaluation of the clinics by physicians, nurses and HCAs, including their knowledge and self-efficacy in pain assessment and management for patients with advanced and end-stage dementia. Methods A mixed method evaluation comprising quantitative survey of self-reported knowledge and self-efficacy pre- and post-ECHO clinic participation, and qualitative exploration of experiences of the clinics using focus group interviews. A census approach to sampling was undertaken. Pre- and post-ECHO evaluations were administered electronically using Survey Monkey software. Mann-Whitney U tests were used to explore differences in knowledge and self-efficacy scores pre- and post-ECHO clinic participation. Statistical significance was set a-priori at p = 0.05. Focus groups were video- and audio-recorded, transcribed verbatim and analysed using Braun & Clarke’s model of thematic analysis. Results Eighteen healthcare professionals [HCPs] (physicians [n = 7], nurses [n = 10], HCA [n = 1]) and twenty HCPs (physicians [n = 10], nurses [n = 10]) completed pre- and post-ECHO evaluations respectively, reporting improvements in knowledge and self-efficacy on participation in ECHO clinics and perceived utility of the clinics. Seven HCPs (physicians [n = 2], nurses [n = 5]) participated in two focus groups. Four themes emerged: knowledge and skills development and dissemination; protected time; areas for improvement; and the future of ECHO. Conclusions Telementoring clinics for HCP education and training in pain assessment and management in advanced and end-stage dementia demonstrate a positive impact on knowledge and self-efficacy of HCPs and highlight the value of a cross-specialty network of practice which spans across disciplines/HCP types, care settings and geographical areas. Further development of ECHO services in this and in other clinical areas, shows significant potential to support delivery of high-quality care to complex patient populations
No added value for Computer-Assisted surgery to improve femoral component positioning and Patient Reported Outcomes in Hip Resurfacing Arthroplasty; a multi-center randomized controlled trial
“There’s a Catch-22”. The complexities of pain management for people with advanced dementia nearing the end of life: a qualitative exploration of physicians’ perspectives
Rest-Frame Optical Spectra of Three Strongly Lensed Galaxies at z~2
We present Keck II NIRSPEC rest-frame optical spectra for three recently
discovered lensed galaxies: the Cosmic Horseshoe (z = 2.38), the Clone (z =
2.00), and SDSS J090122.37+181432.3 (z = 2.26). The boost in signal-to-noise
ratio (S/N) from gravitational lensing provides an unusually detailed view of
the physical conditions in these objects. A full complement of high S/N
rest-frame optical emission lines is measured, spanning from rest-frame 3600 to
6800AA, including robust detections of fainter lines such as H-gamma,
[SII]6717,6732, and in one instance [NeII]3869. SDSS J090122.37+181432.3 shows
evidence for AGN activity, and therefore we focus our analysis on star-forming
regions in the Cosmic Horseshoe and the Clone. For these two objects, we
estimate a wide range of physical properties, including star-formation rate
(SFR), metallicity, dynamical mass, and dust extinction. In all respects, the
lensed objects appear fairly typical of UV-selected star-forming galaxies at
z~2. The Clone occupies a position on the emission-line diagnostic diagram of
[OIII]/H-beta vs. [NII]/H-alpha that is offset from the locations of z~0
galaxies. Our new NIRSPEC measurements may provide quantitative insights into
why high-redshift objects display such properties. From the [SII] line ratio,
high electron densities (~1000 cm^(-3)) are inferred compared to local
galaxies, and [OIII]/[OII] line ratios indicate higher ionization parameters
compared to the local population. Building on previous similar results at z~2,
these measurements provide further evidence (at high S/N) that star-forming
regions are significantly different in high-redshift galaxies, compared to
their local counterparts (abridged).Comment: 16 pages, 8 figures. Accepted for publication in the Astrophysical
Journa
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