3,253 research outputs found
Improving Monte Carlo radiative transfer in the regime of high optical depths: The minimum scattering order
Radiative transfer (RT) simulations are a powerful tool that enables the
calculation of synthetic images of a wide range of astrophysical objects. These
simulations are often based on the Monte Carlo (MC) method, as it provides the
needed versatility that allows the consideration of the diverse and often
complex conditions found in those objects. However, this method faces
fundamental problems in the regime of high optical depths which may result in
noisy images and underestimated flux values. In this study, we propose an
advanced MCRT method, i.e., an enforced minimum scattering order that is aimed
at providing a minimum quality of determined flux estimates. For that purpose,
we extended our investigations of the scattering order problem and derived an
analytic expression for the minimum number of interactions that depends on the
albedo and optical depth of the system, which needs to be considered to achieve
a certain coverage of the scattering order distribution. The method is based on
the utilization of this estimated minimum scattering order and enforces the
consideration of a sufficient number of interactions during a simulation.
Moreover, we identified two notably distinct cases that shape the kind of
complexity that arises in MCRT simulations: the albedo-dominated and the
optical depth-dominated case. Based on that, we analyzed implications regarding
the best usage of a stretching method as a means to alleviate the scattering
order problem. We find that its most suitable application requires taking into
account the albedo and the optical depth. Then, we argue that the derived
minimum scattering order can be used to assess the performance of a stretching
method with regard to the scattering orders its usage promotes. Finally, we
stress the need for developing advanced pathfinding techniques to fully solve
the problem of MCRT simulations in the regime of high optical depths.Comment: Accepted for publication in A&A, 10 pages, 5 figure
Cold-water coral <em>Lophelia pertusa</em> as a high-resolution archive of paleo-environmental conditions in the central Mediterranean
Comparison of the scientific performance in hip and knee arthroplasty between the leading continents
Background: Scientific progress in the field of knee and hip arthroplasty has
enabled the preservation of mobility and quality of life in the case of patients
with many primary degenerative and (post-) traumatic joint diseases. This
comparative study aims to investigate differences in scientific performance
between the leading continents in the field of hip and knee arthroplasty.
Methods: Using specific search terms all studies published by the scientific leading
continents Europe, North America, Asia and Oceania listed in the Web of Science
databases were included. All identified publications were analysed and
comparative conclusions were drawn regarding the qualitative and quantitative
scientific merit of each continent.
Results: Europe, followed by North America, Asia, and Oceania, had the highest
overall number of publications in the field of arthroplasty. Since 2000, there has
been a strong increase in knee arthroplasty publication rate, particular pronounced
in Asia. Studies performed and published in North America and those on knee
arthroplasty received the highest number of fundings. Publications regarding hip
arthroplasty achieved the highest average citation rate. In contradistinction to the
others, in North America most funding was provided by private agencies.
Conclusion: Although Europe showed the highest total number of publications,
authors and institutions, arthroplasty research from North America received greater
scientific attention and financial support. Measured by citations, publications on hip
arthroplasty attained higher scientific interest and studies on knee arthroplasty
received higher economic affection
Myelodysplastic syndromes: Aspects of current medical care and economic considerations in Germany
Myelodysplastic syndromes (MDS) are a heterogeneous group of diseases mainly affecting older people. The use of an increasing number of therapeutic options depends on a systematic risk stratification of the patients. A high percentage of MDS patients need blood transfusions as supportive care, which influence quality of life and cause a great part of the costs generated by MDS therapy. In this article which is based on a workshop about the burden of MDS held in October 2006 in Munich, MDS is discussed with regard to different aspects: current therapies, transfusion medicine, geriatrics, quality of life, and health economic aspects
The Software Value Chain as an Analytical Framework for the Software Industry and Its Exemplary Application for Vertical Integration Measurement
The value chain concept disaggregates a firm into the various activities it performs. Abstracting from the firm-level thisconcept has also been applied to industries as a whole. In this paper we conceptualize a software specific value chain andprovide a first proof of concept. Our approach aggregates and unifies findings from a literature review on industry-level valuechains, software value chains, and related concepts. The resulting unified software value chain comprises eleven activities:product research, component procurement, product development, user documentation, production and packaging, marketing,implementation, training and certification, maintenance and support, operations, and replacement. A first proof of concept isprovided through expert interviews with software firms. Furthermore, we present an example that shows how the softwarevalue chain can be applied to measure the degree of vertical integration in the software industry
Subgroup analysis of scientific performance in the field of arthroplasty
Introduction: Arthroplasty is the final treatment option for maintaining mobility and
quality of life in many primary degenerative and (post-) traumatic joint diseases.
Identification of research output and potential deficits for specific subspecialties
may be an important measure to achieve long-term improvement of patient care
in this field.
Methods: Using specific search terms and Boolean operators, all studies published
since 1945 to the subgroups of arthroplasty listed in the Web of Science Core
Collection were included. All identified publications were analysed according to
bibliometric standards, and comparative conclusions were drawn regarding the
scientific merit of each subgroup.
Results: Most publications investigated the subgroups of septic surgery and materials
followed by approach, navigation, aseptic loosening, robotic and enhanced recovery
after surgery (ERAS). In the last 5 years, research in the fields of robotic and ERAS
achieved the highest relative increase in publications In contrast, research on
aseptic loosening has continued to lose interest over the last 5 years. Publications
on robotics and materials received the most funding on average while those on
aseptic loosening received the least. Most publications originated from USA,
Germany, and England, except for research on ERAS in which Denmark stood out.
Relatively, publications on aseptic loosening received the most citations, whereas
the absolute scientific interest was highest for the topic infection.
Discussion: In this bibliometric subgroup analysis, the primary scientific outputs
focused on septic complications and materials research in the field of arthroplasty.
With decreasing publication output and the least financial support, intensification
of research on aseptic loosening is urgently recommended
Complex effects of environment and Wolbachia infections on the life history of Drosophila melanogaster hosts
Wolbachia bacteria are common endosymbionts of many arthropods found in gonads and various somatic tissues. They manipulate host reproduction to enhance their transmission and confer complex effects on fitness-related traits. Some of these effects can serve to increase the survival and transmission efficiency of Wolbachia in the host population. The Wolbachia–Drosophila melanogaster system represents a powerful model to study the evolutionary dynamics of host–microbe interactions and infections. Over the past decades, there has been a replacement of the ancestral wMelCS Wolbachia variant by the more recent wMel variant in worldwide D. melanogaster populations, but the reasons remain unknown. To investigate how environmental change and genetic variation of the symbiont affect host developmental and adult life-history traits, we compared effects of both Wolbachia variants and uninfected controls in wild-caught D. melanogaster strains at three developmental temperatures. While Wolbachia did not influence any developmental life-history traits, we found that both lifespan and fecundity of host females were increased without apparent fitness trade-offs. Interestingly, wMelCS-infected flies were more fecund than uninfected and wMel-infected flies. By contrast, males infected with wMel died sooner, indicating sex-specific effects of infection that are specific to the Wolbachia variant. Our study uncovered complex temperature-specific effects of Wolbachia infections, which suggests that symbiont–host interactions in nature are strongly dependent on the genotypes of both partners and the thermal environment
Effects of Two Energy Scales in Weakly Dimerized Antiferromagnetic Quantum Spin Chains
By means of thermal expansion and specific heat measurements on the
high-pressure phase of (VO)PO, the effects of two energy scales of
the weakly dimerized antiferromagnetic = 1/2 Heisenberg chain are explored.
The low energy scale, given by the spin gap , is found to manifest
itself in a pronounced thermal expansion anomaly. A quantitative analysis,
employing T-DMRG calculations, shows that this feature originates from changes
in the magnetic entropy with respect to , . This term, inaccessible by specific heat, is visible only in the
weak-dimerization limit where it reflects peculiarities of the excitation
spectrum and its sensitivity to variations in .Comment: 4 pages, 4 figures now identical with finally published versio
Does a specific MR imaging protocol with a supine-lying subject replicate tarsal kinematics seen during upright standing?
Magnetic resonance (MR) imaging is becoming increasingly important in the study of foot biomechanics. Specific devices have been constructed to load and position the foot while the subject is lying supine in the scanner. The present study examines the efficacy of such a newly developed device in replicating tarsal kinematics seen during the more commonly studied standing loading conditions. The results showed that although knee flexion and the externally applied load were carefully controlled, subtalar and talo-navicular joint rotations while lying during MR imaging and when standing (measured opto-electrically with markers attached to intracortical pins) did not match, nor were they systematically shifted. Thus, the proposed MR protocol cannot replicate tarsal kinematics seen during upright standing. It is concluded that specific foot loading conditions have to be considered when tarsal kinematics are evaluated. Improved replication of tarsal kinematics in different postures should comprehensively consider muscle activity, a fixed hip position, and a well-defined point of load applicatio
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