Towards an understanding of hole superconductivity

From the very beginning K. Alex M\"uller emphasized that the materials he and George Bednorz discovered in 1986 were $hole$ superconductors. Here I would like to share with him and others what I believe to be $the$ key reason for why high $T_c$ cuprates as well as all other superconductors are hole superconductors, which I only came to understand a few months ago. This paper is dedicated to Alex M\"uller on the occasion of his 90th birthday.Comment: Dedicated to Alex M\"uller on the Occasion of his 90th Birthday. arXiv admin note: text overlap with arXiv:1703.0977

pep2pro: the high-throughput proteomics data processing, analysis, and visualization tool

The pep2pro database was built to support effective high-throughput proteome data analysis. Its database schema allows the coherent integration of search results from different database-dependent search algorithms and filtering of the data including control for unambiguous assignment of peptides to proteins. The capacity of the pep2pro database has been exploited in data analysis of various Arabidopsis proteome datasets. The diversity of the datasets and the associated scientific questions required thorough querying of the data. This was supported by the relational format structure of the data that links all information on the sample, spectrum, search database, and algorithm to peptide and protein identifications and their post-translational modifications. After publication of datasets they are made available on the pep2pro website at www.pep2pro.ethz.ch. Further, the pep2pro data analysis pipeline also handles data export do the PRIDE database (http://www.ebi.ac.uk/pride) and data retrieval by the MASCP Gator (http://gator.masc-proteomics.org/). The utility of pep2pro will continue to be used for analysis of additional datasets and as a data warehouse. The capacity of the pep2pro database for proteome data analysis has now also been made publicly available through the release of pep2pro4all, which consists of a database schema and a script that will populate the database with mass spectrometry data provided in mzIdentML format

PlantDB – a versatile database for managing plant research

Background Research in plant science laboratories often involves usage of many different species, cultivars, ecotypes, mutants, alleles or transgenic lines. This creates a great challenge to keep track of the identity of experimental plants and stored samples or seeds. Results Here, we describe PlantDB – a Microsoft® Office Access database – with a user-friendly front-end for managing information relevant for experimental plants. PlantDB can hold information about plants of different species, cultivars or genetic composition. Introduction of a concise identifier system allows easy generation of pedigree trees. In addition, all information about any experimental plant – from growth conditions and dates over extracted samples such as RNA to files containing images of the plants – can be linked unequivocally. Conclusion We have been using PlantDB for several years in our laboratory and found that it greatly facilitates access to relevant information.ISSN:1746-481

Perimeter of sublevel sets in infinite dimensional spaces

We compare the perimeter measure with the Airault-Malliavin surface measure and we prove that all open convex subsets of abstract Wiener spaces have finite perimeter. By an explicit counter-example, we show that in general this is not true for compact convex domains

Slope of the superconducting gap function in Bi2Sr2CaCu2O8+δBi_2Sr_2CaCu_2O_{8+\delta} measured by vacuum tunneling spectroscopy

Reproducible scanning tunneling microscope (STM) spectra of $Bi_2Sr_2CaCu_2O_{8+\delta}$ consistently exhibit asymmetric tunneling characteristics, with the higher peak conductance corresponding to a negatively biased sample. We consider various possible sources of this asymmetry that are not intrinsic to the superconducting state, including energy dependence of the normal state densities of states of sample and/or tip, existence of bandwidth cutoffs, unequal work functions of tip and sample, and energy-dependent transmission probability. None of these effects can explain the sign and temperature dependence of the observed asymmetry. This indicates that the observed asymmetry reflects an intrinsic property of the superconducting state: an energy-dependent superconducting gap function with non-zero slope at the Fermi energy. Such a sloped gap function will also give rise to a thermoelectric effect in STM experiments, resulting in a $positive$ thermopower. We discuss the feasibility of observing this thermoelectric effect with an STM and conclude that it is easily observable. An analysis of thermoelectric currents and voltages together with the tunneling spectra as function of temperature and tip- sample distance would allow for accurate determination of the slope of the gap function. It is suggested that it would be very worthwhile to perform these experiments, because the slope of the gap function reflects a fundamental property of the superconducting state. The theory of hole superconductivity has predicted the existence of such a slope, of universal sign, in all superconductors. It is furthermore argued that recent experimental results on vortex lattice imaging provide further strong evidence for the existence of the gap slope discussed here.Comment: Changes from original version: the discussion on Ref. 13 is modified. Publication info: to be published in Phys.Rev.B (May 99) Author's e-mail: [email protected]

Aging of poled ferroelectric ceramics due to relaxation of random depolarization fields by space-charge accumulation near grain boundaries

Migration of charged point defects triggered by the local random depolarization field is shown to plausibly explain aging of poled ferroelectric ceramics providing reasonable time and acceptor concentration dependences of the emerging internal bias field. The theory is based on the evaluation of the energy of the local depolarization field caused by mismatch of the polarizations of neighbor grains. The kinetics of charge migration assumes presence of mobile oxygen vacancies in the material due to the intentional or unintentional acceptor doping. Satisfactory agreement of the theory with experiment on the Fe-doped lead zirconate titanate is demonstrated.Comment: theory and experiment, 22 pages, 3 figure

Structural determinants of Rab11 activation by the guanine nucleotide exchange factor SH3BP5

Rab11 GTPases are involved in various cellular processes but their activation by guanine nucleotide exchange factors (GEFs) is not fully understood. Here, the authors present a structural and biochemical analysis of Rab11 bound to the GEF SH3BP5, providing insights how Rab-GEF specificity is achieved