On the fretting fatigue behavior of quenched and tempered steel in smooth point contact

Fretting fatigue can lead to a rapid decrease in the life of machine components when their contact surfaces have to transfer high tractions. Fretting fatigue was studied in partial, mixed and gross slip conditions made on quenched and tempered steel 34CrNiMo6. Measurements were made with sphere-on-plane contact geometry for smooth surfaces to detect macroscopic cracks. The fretting map type test series outlined a certain zone in partial and mixed slip conditions, where cracking occurred. The parameters affecting cracking threshold values and crack initiation are discussed

On the violation of a local form of the Lieb-Oxford bound

In the framework of density-functional theory, several popular density functionals for exchange and correlation have been constructed to satisfy a local form of the Lieb-Oxford bound. In its original global expression, the bound represents a rigorous lower limit for the indirect Coulomb interaction energy. Here we employ exact-exchange calculations for the G2 test set to show that the local form of the bound is violated in an extensive range of both the dimensionless gradient and the average electron density. Hence, the results demonstrate the severity in the usage of the local form of the bound in functional development. On the other hand, our results suggest alternative ways to construct accurate density functionals for the exchange energy.Comment: (Submitted on 27 April 2012

FEAST fundamental framework for electronic structure calculations: Reformulation and solution of the muffin-tin problem

In a recent article [1], the FEAST algorithm has been presented as a general purpose eigenvalue solver which is ideally suited for addressing the numerical challenges in electronic structure calculations. Here, FEAST is presented beyond the "black-box" solver as a fundamental modeling framework which can naturally address the original numerical complexity of the electronic structure problem as formulated by Slater in 1937 [2]. The non-linear eigenvalue problem arising from the muffin-tin decomposition of the real-space domain is first derived and then reformulated to be solved exactly within the FEAST framework. This new framework is presented as a fundamental and practical solution for performing both accurate and scalable electronic structure calculations, bypassing the various issues of using traditional approaches such as linearization and pseudopotential techniques. A finite element implementation of this FEAST framework along with simulation results for various molecular systems are also presented and discussed.Comment: 20 pages, 7 figure

Fossiliferous boulders of Lower Cambrian phosphoritic sandstone in southwestern Finland

The paper deals with fossiliferous sandstone boulders from three localities in southwestern Finland. The largest of the boulders was found on the west coast west of Olkiluoto. It is conglomeratic with an abundance of worn remains of lingulid and obolellid brachiopod valves. Its rock type is made up of a relatively coarse, bimodal quartz sandstone containing a few phosphoritic siltstone fragments. The main part is sandy and practically free of glauconite, which is more common in the phosphoritic fragments. A few of the phosphoritic pieces are tubular in form having phosphorite enriched in an outer ring and a one-grain-thick outermost crust of quartz. They may be worn remains of Hyolithellus micans. Some of the brachiopod shells contain small calcitic globules in a carbonaceous phosphorite matrix. Tasmanites sp. is one of the few preserved forms of the Acritarch genera. According to the fossils, the sandstone dates to the upper part of the Lower Cambrian, corresponding to the Lingulid sandstone facies in Västergötland, which in turn corresponds to the Holmia kjerulfi-group Zone in southern Scandinavia. Mineralogically and petrologically, too, the rock could be derived from such lithostratigraphical units. Sandstones of the same age have not been reported previously from Finland. The present boulders would seem to derive from the bottom of the Bothnian Sea. Although smaller and not so conglomeratic the boulders from Säkylä and Uusikaupunki are fossiliferous. The fossil fragments in the boulder from Pyhäjärvi, Säkylä, are probably remains of the brachiopod Mickwitzia, and thus refer to a Lower Cambrian stratum still older than the former. The worn brachiopod fragments in the boulder from North Viisastenkari, Uusikaupunki, did not allow the boulder to be dated more accurately within the Lower Cambrian

Structural complexity of defective-interfering RNAs of Semliki Forest virus as revealed by analysis of complementary DNA.

The 18S defective interfering RNA of Semliki Forest virus has been reverse transcribed to cDNA, which was shown to be heterogeneous by restriction enzyme analysis. After transformation to E.coli, using pBR322 as a vector, two clones, pKTH301 and pKTH309 with inserts of 1.7 kb and 2 kb, were characterized, respectively. The restriction maps of the two clones were different but suggested that both contained repeating units. At the 3' terminus, pKTH301 had preserved 106 nucleotides and pKTH309 102 nucleotides from the 3' end of the viral 42S genome. The conserved 3' terminal sequence was joined to a different sequence in the two clones, and these sequences were not derived from the region coding for the viral structural proteins. The DI RNAs represented by the two clones are generated from the viral 42S RNA by several noncontinuous internal deletions, since the largest colinear regions with 42S RNA are 320 nucleotides in pKTH301, and 430 and 340 nucleotides in pKTH309. All these fragments had unique RNase T1 oligonucleotide fingerprints, suggesting that they were derived from different regions of 42S RNA

Combining resource use assessment techniques reveals trade-offs in trophic specialization of polymorphic perch

Trophic polymorphism has found to be common in many taxa and is a suggested mechanism of ecological speciation. To characterize the trophic linkages of specific morphotypes of organisms as well as a time-integrated niche use, several methods are available. In this study, we present data of multiple techniques to investigate the trophic divergence of Eurasian perch (Perca fluviatilis) that displays well-studied trophic polymorphism associated with littoral and pelagic habitats in lakes. We combined bulk stable isotope and fatty acid analyses on the muscle tissue of perch from three different lakes in Sweden with analyses of stomach content. By comparing the three methods, we aimed at providing a broad and highly resolved picture on the trophic divergence in freshwater fish. The degree in morphological divergence varied between perch caught in the three different lakes. Generally, perch caught in the pelagic zone were more streamlined compared to the ones caught in the littoral zone that had a deeper body, as shown by geometric morphometrics. The three diet assessment methods revealed different levels of information. Data on stomach content showed some preferences for specific dietary items in littoral and pelagic perch, but general trophic specialization could not be concluded due to the small sample size. Analyses of delta C-13 and delta N-15, however, confirmed these results as a long-term pattern connected to specific habitat use in two of the three lakes. Fatty acid signatures of perch reflected partly those of the prey items of the specific habitats. Although the proportions of the essential fatty acid 22:6n-3 were lower in littoral resources, the proportions in littoral fish were similar to the ones caught in the pelagic zone. We concluded that although a fundamental contribution from littoral resources exists in littoral phenotypes, a minor reliance on pelagic prey items is obviously needed to provide essential compounds. Thus, by combining the methods to characterize direct resource use (i.e., stomach analyses) with others that utilize trophic biomarkers (i.e., analyses of stable isotopes and fatty acids), we were able to illustrate the degree of variation in trophic divergence of perch but also shed some light on potential trade-offs that are related to resource specialization in freshwater fish