742 research outputs found
Commuting homotopy limits and smash products
In general the processes of taking a homotopy inverse limit of a diagram of
spectra and smashing spectra with a fixed space do not commute. In this paper
we investigate under what additional assumptions these two processes do
commute. In fact we deal with an equivariant generalization which involves
spectra and smash products over the orbit category of a discrete group. Such a
situation naturally occurs if one studies the equivariant homology theory
associated to topological cyclic homology. The main theorem of this paper will
play a role in the generalization of the results obtained by Boekstedt, Hsiang
and Madsen about the algebraic K-theory Novikov Conjecture to the assembly map
for the family of virtually cyclic subgroups.Comment: 23 page
Algebraic K-theory of group rings and the cyclotomic trace map
We prove that the Farrell-Jones assembly map for connective algebraic
K-theory is rationally injective, under mild homological finiteness conditions
on the group and assuming that a weak version of the Leopoldt-Schneider
conjecture holds for cyclotomic fields. This generalizes a result of
B\"okstedt, Hsiang, and Madsen, and leads to a concrete description of a large
direct summand of in terms
of group homology. In many cases the number theoretic conjectures are true, so
we obtain rational injectivity results about assembly maps, in particular for
Whitehead groups, under homological finiteness assumptions on the group only.
The proof uses the cyclotomic trace map to topological cyclic homology,
B\"okstedt-Hsiang-Madsen's functor C, and new general isomorphism and
injectivity results about the assembly maps for topological Hochschild homology
and C.Comment: To appear in Advances in Mathematics. 77 page
Modification of the Lipid Profile of the Initial Oral Biofilm In Situ Using Linseed Oil as Mouthwash
Lipids are of interest for the targeted modification of oral bioadhesion processes. Therefore,
the sustainable effects of linseed oil on the composition and ultrastructure of the in situ pellicle
were investigated. Unlike saliva, linseed oil contains linolenic acid (18:3), which served as a marker
for lipid accumulation. Individual splints with bovine enamel slabs were worn by five subjects.
After 1 min of pellicle formation, rinses were performed with linseed oil for 10 min, and the slabs’
oral exposure was continued for up to 2 or 8 h. Gas chromatography coupled with electron impact
ionization mass spectrometry (GC-EI/MS) was used to characterize the fatty acid composition of
the pellicle samples. Transmission electron microscopy was performed to analyze the ultrastructure.
Extensive accumulation of linolenic acid was recorded in the samples of all subjects 2 h after the
rinse and considerable amounts persisted after 8 h. The ultrastructure of the 2 h pellicle was less
electron-dense and contained lipid vesicles when compared with controls. After 8 h, no apparent
ultrastructural effects were visible. Linolenic acid is an excellent marker for the investigation of fatty
acid accumulation in the pellicle. New preventive strategies could benefit from the accumulation of
lipid components in the pellicle
Integrating all Dimensions: 3D-Applications from Excavation to Research to Dissemination
3D-technologies are increasingly shaping the way archaeologists work and think. The fact that 3D recording techniques are becoming part of the standard toolkit in archaeological fieldwork opens up enormous opportunities for research and public outreach. As archaeological excavations are seen to be destructive, conventional documentation techniques have been shaped over decades if not centuries to mitigate as much information loss as possible. This includes the development of fitting tools and workflows as well as best practices in archaeological data collection, long-term archiving, research and dissemination.
As new tools, 3D-Technologies need to be implemented into these existing best practices and workflows. In order to take full advantage of the new possibilities, we consider an integrated approach from the beginning of a project to be essential. This enables the successful implementation of 3D-technologies in all stages: it is not only important during fieldwork, but also later during research or public outreach. There, for instance, challenges concerning interoperability or quality may arise and have to be coped with. Also, the irreversibility of archaeological excavations has to be met with the functioning of long-term archiving of mostly large and complex datasets.
Despite the increasing implementation of 3D-technologies in everyday archaeological practice, the overall experience of knowing what decisions to make and how they will affect the later possibilities and limitations is still developing. Nevertheless, there are ever more successful projects showing how 3D-techniques can be fully integrated into archaeological practice.
This session aims to bring these examples of integrated research projects to a broader archaeological audience. As these potent documentation techniques have found their way into everyday practice, a broad dissemination and discussion of their possibilities and arising challenges is urgently needed
Galactic Magnetic Turbulence from Radio data
Fluctuations in the Galactic synchrotron emission can be traced by the
angular power spectrum of radio maps at low multipoles. At frequencies below
few GHz, large-scale anisotropies are mainly induced by magnetic field
turbulence. By performing an analysis of five radio maps, we extract
constraints on turbulence spectral index and halo scale. Results favour a power
spectrum significantly flatter than for 3D Kolmogorov-like turbulence, and a
thin halo. This can be interpreted as an indication supporting non-conventional
models of propagation of cosmic-ray particles in the Galaxy, or as a suggestion
of a spectral-index break in the observed magnetic turbulence power spectrum.Comment: 15 pages, 3 figures. v2: discussions and references improved, to
appear in Astropart.Phys.
A new Approach for Structure from Motion Underwater Pile-Field Documentation
For a pilot study carried out by the University of Bern together with local partners in Summer 2018 at the pile-dwelling site Bay of Bones (Rep. of Macedonia), a new workflow for underwater pile-field documentation was developed.
The site lies in shallow water of 3–5 meters depth and the most obvious constructive remains of the prehistoric settlement are thousands of wooden piles. The piles, mainly of oak and juniper, are excellently preserved in the lake sediments. The aim of the project was to document and sample 40 m2 surface area of the pile-field and the dendrochronological analysis of the samples.
Dendrochronological sampling requires cutting the top-ends of the piles and thus changes the preserved situation. Therefore beforehand documentation must ensure the localization of each pile on a map.
This calls for a method that ensures a) that every pile is distinctly labeled and b) the location of each pile is accurately captured. While on land, this can easily be achieved, underwater working conditions complicate common procedures. E.g. by measuring with a folding ruler from a local grid, there is later no way to evaluate measuring mistakes or the internal error of the local grid. In addition, for unpracticed divers measuring by hand underwater is not only time-consuming but also tends a lot more to erroneous results than on land.
The goal was therefore to find a time-saving, accurate and easy to carry out way to locate the positions of several hundred piles in shallow water. The best solution for us to achieve these goals was a new standardized and reproducible workflow with Structure from Motion (SfM). The applied approach for underwater SfM-documentation includes on-site workflow and post-processing.
The on-site workflow covers all steps from the preparation of the archaeological structures to the photographic data acquisition, the calculation of a preliminary 3D-model and its on-site verification. The crucial step was to ensure the suitability for modeling of the data before the situation underwater was irreversibly changed through sampling.
Post-processing was carried out in Adobe Photoshop, Agisoft PhotoScan and QGIS where the data was optimized in quality and standardized from digital image processing to the construction of a georeferenced orthomosaic. Applying these results, we can later visualize patterns in the spatial distribution of the piles concerning e.g. their age, their size or their wood species. This will lead to answers regarding architecture, internal chronology, and in-site settlement dynamics.
With this newly standardized two-step-workflow for underwater structure documentation, we are able to asses and compare the quality of each orthomosaic in a reproducible way. The presented method is highly promising for underwater-documentation of prehistoric pile-fields, yielding accurate digital plans in an efficient and cost-saving way.</p
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Barriers to Treatment Access for Chagas Disease in Mexico
Background: According to World Health Organization (WHO) prevalence estimates, 1.1 million people in Mexico are infected with Trypanosoma cruzi, the etiologic agent of Chagas disease (CD). However, limited information is available about access to antitrypanosomal treatment. This study assesses the extent of access in Mexico, analyzes the barriers to access, and suggests strategies to overcome them. Methods and Findings: Semi-structured in-depth interviews were conducted with 18 key informants and policymakers at the national level in Mexico. Data on CD cases, relevant policy documents and interview data were analyzed using the Flagship Framework for Pharmaceutical Policy Reform policy interventions: regulation, financing, payment, organization, and persuasion. Data showed that 3,013 cases were registered nationally from 2007–2011, representing 0.41% of total expected cases based on Mexico's national prevalence estimate. In four of five years, new registered cases were below national targets by 11–36%. Of 1,329 cases registered nationally in 2010–2011, 834 received treatment, 120 were pending treatment as of January 2012, and the treatment status of 375 was unknown. The analysis revealed that the national program mainly coordinated donation of nifurtimox and that important obstacles to access include the exclusion of antitrypanosomal medicines from the national formulary (regulation), historical exclusion of CD from the social insurance package (organization), absence of national clinical guidelines (organization), and limited provider awareness (persuasion). Conclusions: Efforts to treat CD in Mexico indicate an increased commitment to addressing this disease. Access to treatment could be advanced by improving the importation process for antitrypanosomal medicines and adding them to the national formulary, increasing education for healthcare providers, and strengthening clinical guidelines. These recommendations have important implications for other countries in the region with similar problems in access to treatment for CD
Virtual Reality applications for visualization of 6000-year-old Neolithic graves from Lenzburg (Switzerland)
The last decade has seen a steady increase in the application of virtual 3D approaches in cultural heritage research. Although a large literature exists about the advantages of 3D methods in this field, here we go one step further and elucidate a) how image-based 3D reconstructions can be displayed in virtual reality (VR) space using freeware game engine software and low-cost VR hardware and b) highlight the relative benefits and advantages with a focus on interactive museum displays of relatively large archaeological objects. Specifically, we present three 3D models of different stone grave structures from the Neolithic necropolis of Lenzburg (Northern Switzerland, 4450-3500 BCE). The site has been excavated in 1959/60 and certain graves were subsequently preserved for museum display. By means of VR applications, it is now possible to experience these approximately 6000-year-old tombs with an innovative approach circumventing various barriers or constraints and offering interactive display options
Dendroarchaeology at Lake Ohrid: 5th and 2nd millennia BCE tree-ring chronologies from the waterlogged site of PloÄŤa MiÄŤov Grad, North Macedonia
On the prehistoric site of PloÄŤa MiÄŤov Grad (Ohrid, North Macedonia) on the eastern shore of Lake Ohrid a total of 799 wooden elements were recorded from a systematically excavated area of nearly 100 square meters. Most of them are pile remains of round wood with diameters up to almost 40 cm. A comprehensive dendrochronological analysis allowed the construction of numerous well-replicated chronologies for different species. High agreements between the chronologies prove that oak, pine, juniper, ash and hop-hornbeam can be cross-dated. The chronologies were dated by means of radiocarbon dating and modelling using wiggle matching. An intensive settlement phase is attested for the middle of the 5th millennium BCE. Further phases follow towards the end of the 5th millennium BCE and in the 2nd millennium around 1800, 1400 and 1300 BCE. Furthermore, the exact, relative felling dates allow first insights into the minimum duration of the settlement phases, which lie between 17 and 87 years. The multi-centennial chronologies presented in this study represent a first robust dating basis for future research in the numerous not yet dated prehistoric lake shore settlements in the southwestern Balkans with excellently preserved wooden remains
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