701 research outputs found
Approximation Algorithms for Multi-Criteria Traveling Salesman Problems
In multi-criteria optimization problems, several objective functions have to
be optimized. Since the different objective functions are usually in conflict
with each other, one cannot consider only one particular solution as the
optimal solution. Instead, the aim is to compute a so-called Pareto curve of
solutions. Since Pareto curves cannot be computed efficiently in general, we
have to be content with approximations to them.
We design a deterministic polynomial-time algorithm for multi-criteria
g-metric STSP that computes (min{1 +g, 2g^2/(2g^2 -2g +1)} + eps)-approximate
Pareto curves for all 1/2<=g<=1. In particular, we obtain a
(2+eps)-approximation for multi-criteria metric STSP. We also present two
randomized approximation algorithms for multi-criteria g-metric STSP that
achieve approximation ratios of (2g^3 +2g^2)/(3g^2 -2g +1) + eps and (1 +g)/(1
+3g -4g^2) + eps, respectively.
Moreover, we present randomized approximation algorithms for multi-criteria
g-metric ATSP (ratio 1/2 + g^3/(1 -3g^2) + eps) for g < 1/sqrt(3)), STSP with
weights 1 and 2 (ratio 4/3) and ATSP with weights 1 and 2 (ratio 3/2). To do
this, we design randomized approximation schemes for multi-criteria cycle cover
and graph factor problems.Comment: To appear in Algorithmica. A preliminary version has been presented
at the 4th Workshop on Approximation and Online Algorithms (WAOA 2006
Proceedings of the 12th Cologne-Twente Workshop on Graphs and Combinatorial Optimization (CTW 2013) - Preface
Teaching intercultural communication skills in healthcare to improve care for culturally and linguistically diverse patients
Objective: To provide recommendations for adequately training healthcare providers in intercultural communication skills. Discussion: We discuss three main recommendations concerning intercultural communication skills training. First, we give an overview of the fundamental skills in which healthcare providers should receive training, such as self-awareness and adaptability. Second, we briefly discuss how such training should be delivered, and focus on different language support methods, including those that work with different types of interpreters and digital tools. Third, we discuss how within-group differences can be taken into account to prevent stereotyping. To illustrate these recommendations, we provide certain examples of existing good practices and interventions. Conclusion: In today's superdiverse societies, delivering culturally and linguistically sensitive healthcare tailored to the needs, values, and preferences of individual patients is a prerequisite for good quality healthcare communication. To achieve this goal, there is a need for clearer recommendations for affirmative action, guidelines, policy, and support for the topic of diversity sensitivity in healthcare, such as evidence-based interventions, than is currently the case. That is, structural changes on a system level are urgently needed to support healthcare providers to implement diversity sensitivity in their daily clinical work
Efficient Certified RAT Verification
Clausal proofs have become a popular approach to validate the results of SAT
solvers. However, validating clausal proofs in the most widely supported format
(DRAT) is expensive even in highly optimized implementations. We present a new
format, called LRAT, which extends the DRAT format with hints that facilitate a
simple and fast validation algorithm. Checking validity of LRAT proofs can be
implemented using trusted systems such as the languages supported by theorem
provers. We demonstrate this by implementing two certified LRAT checkers, one
in Coq and one in ACL2
Tectonic collision and uplift of Wallacea triggered the global songbird radiation
Songbirds (oscine passerines) are the most species-rich and cosmopolitan bird group, comprising almost half of global avian diversity. Songbirds originated in Australia, but the evolutionary trajectory from a single species in an isolated continent to worldwide proliferation is poorly understood. Here, we combine the first comprehensive genome-scale DNA sequence data set for songbirds, fossil-based time calibrations, and geologically informed biogeographic reconstructions to provide a well-supported evolutionary hypothesis for the group. We show that songbird diversification began in the Oligocene, but accelerated in the early Miocene, at approximately half the age of most previous estimates. This burst of diversification occurred coincident with extensive island formation in Wallacea, which provided the first dispersal corridor out of Australia, and resulted in independent waves of songbird expansion through Asia to the rest of the globe. Our results reconcile songbird evolution with Earth history and link a major radiation of terrestrial biodiversity to early diversification within an isolated Australian continent
Changes in alcohol use during the COVID-19 pandemic in Europe: a meta-analysis of observational studies
Modeling Spanish anxiolytic consumption: Economic, demographic and behavioral influences
Anxiolytics (AX) are the psychotropic drugs prescribed for the treatment of anxiety and
insomnia for 2–4 weeks, for longer periods of consumption (>1 month) may lead to
the development of tolerance or addiction. In fact, its prescription was 16% of the total
pharmaceutical expenditure in Spain in 2007. This paper deals with the development of a
mathematical model describing the dynamic of the addiction to AX for the case study of
the Spanish region of Castellón. The reasons believed to cause the development of addicts
to AX are the economic situation, the marriage termination and the social contact. The
simulations performed to forecast the addicts rate for the period 2010–2014 showed an
increase from 6% in 2010 to 14% in 2014 with a fluctuation of about 2% between the
possible economic scenarios. Finally, the analysis of sensitivity of the rate of addicts to the
fluctuation of the social contact parameters was performed, letting us estimate its impact
on the pharmaceutical expenditure.De La Poza, E.; Guadalajara Olmeda, MN.; Jódar Sánchez, LA.; Merello Giménez, P. (2013). Modeling Spanish anxiolytic consumption: Economic, demographic and behavioral influences. Mathematical and Computer Modelling. 57(7):1619-1624. https://doi.org/10.1016/j.mcm.2011.10.020S1619162457
BEENCHIME SALAATINSKY CRATER IN NORTHERN YAKUTIA - ORIGIN AND ENVIRONMENTAL DYNAMICS IN THE 8-KM CIRCULAR STRUCTURE
106-10
Electronic properties of LaOFFeAs in the normal state probed by NMR/NQR
We report 139La, 57Fe and 75As nuclear magnetic resonance (NMR) and nuclear
quadrupole resonance (NQR) measurements on powders of the new LaO1-xFxFeAs
superconductor for x = 0 and x = 0.1 at temperatures up to 480 K, and compare
our measured NQR spectra with local density approximation (LDA) calculations.
For all three nuclei in the x = 0.1 material, it is found that the local Knight
shift increases monotonically with an increase in temperature, and scales with
the macroscopic susceptibility, suggesting a single magnetic degree of freedom.
Surprisingly, the spin lattice relaxation rates for all nuclei also scale with
one another, despite the fact that the form factors for each site sample
different regions of q-space. This result suggests a lack of any q-space
structure in the dynamical spin susceptibility that might be expected in the
presence of antiferromagnetic correlations. Rather, our results are more
compatible with simple quasi-particle scattering. Furthermore, we find that the
increase in the electric field gradient at the As cannot be accounted for by
LDA calculations, suggesting that structural changes, in particular the
position of the As in the unit cell, dominate the NQR response.Comment: 17 pages, 6 figure
Comprehensive analysis of chemical and biological problems associated with browning agents used in aquatic studies
Inland waters receive and process large amounts of colored organic matter from the terrestrial surroundings. These inputs dramatically affect the chemical, physical, and biological properties of water bodies, as well as their roles as global carbon sinks and sources. However, manipulative studies, especially at ecosystem scale, require large amounts of dissolved organic matter with optical and chemical properties resembling indigenous organic matter. Here, we compared the impacts of two leonardite products (HuminFeed and SuperHume) and a freshly derived reverse osmosis concentrate of organic matter in a set of comprehensive mesocosm- and laboratory-scale experiments and analyses. The chemical properties of the reverse osmosis concentrate and the leonardite products were very different, with leonardite products being low and the reverse osmosis concentrate being high in carboxylic functional groups. Light had a strong impact on the properties of leonardite products, including loss of color and increased particle formation. HuminFeed presented a substantial impact on microbial communities under light conditions, where bacterial production was stimulated and community composition modified, while in dark potential inhibition of bacterial processes was detected. While none of the browning agents inhibited the growth of the tested phytoplankton Gonyostomum semen, HuminFeed had detrimental effects on zooplankton abundance and Daphnia reproduction. We conclude that the effects of browning agents extracted from leonardite, particularly HuminFeed, are in sharp contrast to those originating from terrestrially derived dissolved organic matter. Hence, they should be used with great caution in experimental studies on the consequences of terrestrial carbon for aquatic systems
- …