On the representation ring of the polynomial algebra over a perfect field

We consider the tensor product of modules over the polynomial algebra corresponding to the usual tensor product of linear operators. We present a general description of the representation ring in case the ground field k is perfect. It is made explicit in the special cases when k is real closed respectively algebraically closed. Furthermore, we discuss the generalisation of this problem to representations of quivers. In particular the representation ring of quivers of extended Dynkin type A is provided.Comment: 17 page

The landscape of a Swedish boat-grave cemetery

This is the published PDF version of an article published in Landscapes© 2010. The definitive version is available at http://www.maneyonline.com/toc/lan/11/1The paper integrates topographical and experiential approaches to the mortuary landscape of a Viking period inhumation-grave excavated in 2005 within the cemetery at Skamby, Kuddy parish, Östergötland province, Sweden. We argue that the landscape context was integral to the performance of the funerary ceremonies and the subsequent monumental presence of the dead in the landscape. We offer a way to move beyond monocausal explanations for burial location based on single-scale analyses. Instead, we suggest that boat-inhumation at Skamby was a commemorative strategy that operated on multiple scales and drew its significance from multiple landscape attributes.British Academ

Typing Late Prehistoric Cows and Bulls—Osteology and Genetics of Cattle at the Eketorp Ringfort on the Öland Island in Sweden

Human management of livestock and the presence of different breeds have been discussed in archaeozoology and animal breeding. Traditionally osteometrics has been the main tool in addressing these questions. We combine osteometrics with molecular sex identifications of 104 of 340 morphometrically analysed bones in order to investigate the use of cattle at the Eketorp ringfort on the Öland island in Sweden. The fort is dated to 300–1220/50 A.D., revealing three different building phases. In order to investigate specific patterns and shifts through time in the use of cattle the genetic data is evaluated in relation to osteometric patterns and occurrence of pathologies on cattle metapodia. Males were genotyped for a Y-chromosomal SNP in UTY19 that separates the two major haplogroups, Y1 and Y2, in taurine cattle. A subset of the samples were also genotyped for one SNP involved in coat coloration (MC1R), one SNP putatively involved in resistance to cattle plague (TLR4), and one SNP in intron 5 of the IGF-1 gene that has been associated to size and reproduction

In vitro community synergy between bacterial soil isolates can be facilitated by pH stabilization of the environment

© 2018 American Society for Microbiology. The composition and development of naturally occurring microbial communities are defined by a complex interplay between the community and the surrounding environment and by interactions between community members. Intriguingly, these interactions can in some cases cause synergies, where the community is able to outperform its single-species constituents. However, the underlying mechanisms driving community interactions are often unknown and difficult to identify due to high community complexity. Here, we show how opposite pH drift induced by specific community members leads to pH stabilization of the microenvironment, acting as a positive interspecies interaction, driving in vitro community synergy in a model consortium of four coisolated soil bacteria, Microbacterium oxydans, Xanthomonas retroflexus, Stenotrophomonas rhizophila, and Paenibacillus amylolyticus. We use microsensor pH measurements to show how individual species change the local pH microenvironment and how cocultivation leads to a stabilized pH regime over time. Specifically, in vitro acid production from P. amylolyticus and alkali production primarily from X. retroflexus led to an overall pH stabilization of the local environment over time, which in turn resulted in enhanced community growth. This specific type of interspecies interaction was found to be highly dependent on medium type and concentration; however, similar pH drift from the individual species could be observed across medium variants

Characterization of the metal-ceramic bonding in the Ag/MgO(001) interface from ab initio calculations

The nature of the metal-ceramic interaction in the Ag/MgO(001) interface is studied using periodic Hartree-Fock calculations with density functional theory a posteriori correlation corrections. Different aspects of the Ag-MgO interaction have been studied by analysis of the electronic properties: total and projected density of states, multipole moments, bond population, and the difference electron density. By linking these properties to the adsorption energy and making a comparative analysis for interfaces with different degrees of coverage and different adsorption models (one- and two-sided adsorption), a detailed description of the Ag-MgO has been acquired

The adhesion properties of the Ag/α-Al2O3(0001) interface: an ab initio study

Ab initio computer simulations of the atomic and electronic structure of the Ag/alpha-Al2O3(0 0 0 1) (corundum) interface have been performed for a periodic two-dimensional slab model using the Hartree-Fock method and a posteriori electron correlation corrections. We have considered both Al- and O- terminated corundum substrate surfaces. The dependence of the adhesion energy on the interfacial distance has been analyzed for the two most favorable Ag adsorption positions over corundum and for two different metal coverages (a 1/3 monolayer (NIL) of the Ag(l 1 1) crystallographic plane and a full Ag(I 1 1) monolayer). The two different terminations (Al- and O-) give rise to qualitatively different results. The former case corresponds to the most stable termination of the pure corundum (0 0 0 1) substrate where small adhesion energies per Ag atom (0.15-0.25 eV for I ML and 0.40-0.55 eV for 1/3 NIL) are accompanied by minor interfacial charge transfer, indicating physisorption, which may be explained by a weak atomic polarization. In contrast, for O-terminated corundum, substantial adhesion energies (3-5 eV per Ag atom at I ML coverage and 6-11 eV for 1/3 ML) combined with noticeable charge transfer from silver atoms towards the substrate (0.5e to 0.9e) are clear indications of a strong interfacial ion bonding. For both terminations, the observed difference in Ag adhesion energies for 1/3 NIL and I NIL coverages arises from a transition from directed Ag-O bonding towards a more delocalized electron density distribution in the complete monolayer. The results of our calculations are compared with available experimental studies and theoretical simulations for various Me/Al2O3 interfaces. (C) 2002 Elsevier Science B.V. All rights reserved