Static Friction Phenomena in Granular Materials: Coulomb Law vs. Particle Geometry

The static as well as the dynamic behaviour of granular material are determined by dynamic {\it and} static friction. There are well known methods to include static friction in molecular dynamics simulations using scarcely understood forces. We propose an Ansatz based on the geometrical shape of nonspherical particles which does not involve an explicit expression for static friction. It is shown that the simulations based on this model are close to experimental results.Comment: 11 pages, Revtex, HLRZ-33/9

The Biomphalaria glabrata DNA methylation machinery displays spatial tissue expression, is differentially active in distinct snail populations and is modulated by interactions with Schistosoma mansoni

BBSRC Grant (BB/K005448/1)Background The debilitating human disease schistosomiasis is caused by infection with schistosome parasites that maintain a complex lifecycle alternating between definitive (human) and intermediate (snail) hosts. While much is known about how the definitive host responds to schistosome infection, there is comparably less information available describing the snail?s response to infection. Methodology/Principle findings Here, using information recently revealed by sequencing of the Biomphalaria glabrata intermediate host genome, we provide evidence that the predicted core snail DNA methylation machinery components are associated with both intra-species reproduction processes and inter-species interactions. Firstly, methyl-CpG binding domain protein (Bgmbd2/3) and DNA methyltransferase 1 (Bgdnmt1) genes are transcriptionally enriched in gonadal compared to somatic tissues with 5-azacytidine (5-AzaC) treatment significantly inhibiting oviposition. Secondly, elevated levels of 5-methyl cytosine (5mC), DNA methyltransferase activity and 5mC binding in pigmented hybrid- compared to inbred (NMRI)- B. glabrata populations indicate a role for the snail?s DNA methylation machinery in maintaining hybrid vigour or heterosis. Thirdly, locus-specific detection of 5mC by bisulfite (BS)-PCR revealed 5mC within an exonic region of a housekeeping protein-coding gene (Bg14-3-3), supporting previous in silico predictions and whole genome BS-Seq analysis of this species? genome. Finally, we provide preliminary evidence for parasite-mediated host epigenetic reprogramming in the schistosome/snail system, as demonstrated by the increase in Bgdnmt1 and Bgmbd2/3 transcript abundance following Bge (B. glabrata embryonic cell line) exposure to parasite larval transformation products (LTP). Conclusions/Significance The presence of a functional DNA methylation machinery in B. glabrata as well as the modulation of these gene products in response to schistosome products, suggests a vital role for DNA methylation during snail development/oviposition and parasite interactions. Further deciphering the role of this epigenetic process during Biomphalaria/Schistosoma co-evolutionary biology may reveal key factors associated with disease transmission and, moreover, enable the discovery of novel lifecycle intervention strategiespublishersversionPeer reviewe

Flexible fibre optic vs digital ureteroscopy and enhanced vs unenhanced imaging for diagnosis and treatment of upper tract urothelial carcinoma (UTUC): results from the Clinical Research Office of the Endourology Society (CROES)‐UTUC registry

Objectives To compare the oncological outcomes of patients with upper tract urothelial carcinoma (UTUC) undergoing kidney-sparing surgery (KSS) with fibre-optic (FO) vs digital (D) ureteroscopy (URS). To evaluate the oncological impact of image-enhancement technologies such as narrow-band imaging (NBI) and Image1-S in patients with UTUC. Patients and Methods The Clinical Research Office of the Endourology Society (CROES)-UTUC registry is an international, multicentre, cohort study prospectively collecting data on patients with UTUC. Patients undergoing flexible FO- or D-URS for diagnostic or diagnostic and treatment purposes were included. Differences between groups in terms of overall survival (OS) and disease-free survival (DFS) were evaluated. Results The CROES registry included 2380 patients from 101 centres and 37 countries, of whom 401 patients underwent URS (FO-URS 186 and D-URS 215). FO-URS were performed more frequently for diagnostic purposes, while D-URS was peformed when a combined diagnostic and treatment strategy was planned. Intra- and postoperative complications did not differ between the groups. The 5-year OS and DFS rates were 91.5% and 66.4%, respectively. The mean OS was 42 months for patients receiving FO-URS and 39 months for those undergoing D-URS (P = 0.9); the mean DFS was 28 months in the FO-URS group and 21 months in the D-URS group (P < 0.001). In patients who received URS with treatment purposes, there were no differences in OS (P = 0.9) and DFS (P = 0.7). NBI and Image1-S technologies did not improve OS or DFS over D-URS. Conclusions D-URS did not provide any oncological advantage over FO-URS. Similarly, no differences in terms of OS and DFS were found when image-enhancement technologies were compared to D-URS. These findings underline the importance of surgeon skills and experience, and reinforce the need for the centralisation of UTUC care