A strongly inhomogeneous superfluid in an iron-based superconductor

Among the mysteries surrounding unconventional, strongly correlated superconductors is the possibility of spatial variations in their superfluid density. We use atomic-resolution Josephson scanning tunneling microscopy to reveal a strongly inhomogeneous superfluid in the iron-based superconductor FeTe0.55Se0.45. By simultaneously measuring the topographic and electronic properties, we find that this inhomogeneity in the superfluid density is not caused by structural disorder or strong inter-pocket scattering, and does not correlate with variations in Cooper pair-breaking gap. Instead, we see a clear spatial correlation between superfluid density and quasiparticle strength, putting the iron-based superconductors on equal footing with the cuprates and demonstrating that locally, the quasiparticles are sharpest when the superconductivity is strongest. When repeated at different temperatures, our technique could further help elucidate what local and global mechanisms limit the critical temperature in unconventional superconductors

Amplifier for scanning tunneling microscopy at MHz frequencies

Conventional scanning tunneling microscopy (STM) is limited to a bandwidth of circa 1kHz around DC. Here, we develop, build and test a novel amplifier circuit capable of measuring the tunneling current in the MHz regime while simultaneously performing conventional STM measurements. This is achieved with an amplifier circuit including a LC tank with a quality factor exceeding 600 and a home-built, low-noise high electron mobility transistor (HEMT). The amplifier circuit functions while simultaneously scanning with atomic resolution in the tunneling regime, i.e. at junction resistances in the range of giga-ohms, and down towards point contact spectroscopy. To enable high signal-to-noise and meet all technical requirements for the inclusion in a commercial low temperature, ultra-high vacuum STM, we use superconducting cross-wound inductors and choose materials and circuit elements with low heat load. We demonstrate the high performance of the amplifier by spatially mapping the Poissonian noise of tunneling electrons on an atomically clean Au(111) surface. We also show differential conductance spectroscopy measurements at 3MHz, demonstrating superior performance over conventional spectroscopy techniques. Further, our technology could be used to perform impedance matched spin resonance and distinguish Majorana modes from more conventional edge states

Nanofabricated tips for device-based scanning tunneling microscopy

We report on the fabrication and performance of a new kind of tip for scanning tunneling microscopy. By fully incorporating a metallic tip on a silicon chip using modern micromachining and nanofabrication techniques, we realize so-called smart tips and show the possibility of device-based STM tips. Contrary to conventional etched metal wire tips, these can be integrated into lithographically defined electrical circuits. We describe a new fabrication method to create a defined apex on a silicon chip and experimentally demonstrate the high performance of the smart tips, both in stability and resolution. In situ tip preparation methods are possible and we verify that they can resolve the herringbone reconstruction and Friedel oscillations on Au(111) surfaces. We further present an overview of possible applications

Changes in the Library Landscape Regarding Visible Minority Librarians in Canada

As a follow-up to the first 2013 survey, the Visible Minority Librarians of Canada (ViMLoC) network conducted its second comprehensive survey in 2021. The 2021 survey gathered detailed information about the demography, education, and employment of visible minority librarians (VMLs) working in Canadian institutions. 162 VMLs responded to the 2021 survey, 35% up from the 2013 survey. Changes occurred in ethnic identity, generation, where VMLs earned a Master of Library and Information Science (MLIS) or equivalent degree, library type, geographic location, and job responsibilities. The 2021 survey also explored other aspects of the VMLs not covered in the 2013 survey, such as librarian experience, salary, management positions, and mentorship experience. The research findings will help us better understand the current library landscape and help professional associations and library administrators to develop initiatives to support VMLs

Single-electron charge transfer into putative Majorana and trivial modes in individual vortices

Majorana bound states are putative collective excitations in solids that exhibit the self-conjugate property of Majorana fermions - they are their own antiparticles. In iron-based superconductors, zero-energy states in vortices have been reported as potential Majorana bound states, but the evidence remains controversial. Here, we use scanning tunneling noise spectroscopy to study the tunneling process into vortex bound states in the conventional superconductor NbSe2, and in the putative Majorana platform FeTe0.55Se0.45. We find that tunneling into vortex bound states in both cases exhibits charge transfer of a single electron charge. Our data for the zero-energy bound states in FeTe0.55Se0.45 exclude the possibility of Yu-Shiba-Rusinov states and are consistent with both Majorana bound states and trivial vortex bound states. Our results open an avenue for investigating the exotic states in vortex cores and for future Majorana devices, although further theoretical investigations involving charge dynamics and superconducting tips are necessary.Comment: 15 pages, 4 figures, and 16 pages for supplementary informatio

Sequence divergence of Mus spretus and Mus musculus across a skin cancer susceptibility locus

<p>Abstract</p> <p>Background</p> <p><it>Mus spretus </it>diverged from <it>Mus musculus </it>over one million years ago. These mice are genetically and phenotypically divergent. Despite the value of utilizing <it>M. musculus </it>and <it>M. spretus </it>for quantitative trait locus (QTL) mapping, relatively little genomic information on <it>M. spretus </it>exists, and most of the available sequence and polymorphic data is for one strain of <it>M. spretus</it>, Spret/Ei. In previous work, we mapped fifteen loci for skin cancer susceptibility using four different <it>M. spretus </it>by <it>M. musculus </it>F1 backcrosses. One locus, <it>skin tumor susceptibility 5 </it>(<it>Skts5</it>) on chromosome 12, shows strong linkage in one cross.</p> <p>Results</p> <p>To identify potential candidate genes for <it>Skts5</it>, we sequenced 65 named and unnamed genes and coding elements mapping to the peak linkage area in outbred <it>spretus</it>, Spret/EiJ, FVB/NJ, and NIH/Ola. We identified polymorphisms in 62 of 65 genes including 122 amino acid substitutions. To look for polymorphisms consistent with the linkage data, we sequenced exons with amino acid polymorphisms in two additional <it>M. spretus </it>strains and one additional <it>M. musculus </it>strain generating 40.1 kb of sequence data. Eight candidate variants were identified that fit with the linkage data. To determine the degree of variation across <it>M. spretus</it>, we conducted phylogenetic analyses. The relatedness of the <it>M. spretus </it>strains at this locus is consistent with the proximity of region of ascertainment of the ancestral mice.</p> <p>Conclusion</p> <p>Our analyses suggest that, if <it>Skts5 </it>on chromosome 12 is representative of other regions in the genome, then published genomic data for Spret/EiJ are likely to be of high utility for genomic studies in other <it>M. spretus </it>strains.</p

Differential effects of Radix Paeoniae Rubra (Chishao) on cytokine and chemokine expression inducible by mycobacteria

<p>Abstract</p> <p>Background</p> <p>Upon initial infection with mycobacteria, macrophages secrete multiple cytokines and chemokines, including interleukin-6 (IL-6), IL-8 and tumor necrosis factor-α (TNF-α), to mediate host immune responses against the pathogen. Mycobacteria also induce the production of IL-10 <it>via </it>PKR activation in primary human monocytes and macrophages. As an anti-inflammatory cytokine, over-expression of IL-10 may contribute to mycobacterial evasion of the host immunity. <it>Radix Paeoniae Rubra </it>(RPR, <it>Chishao</it>), a Chinese medicinal herb with potentials of anti-inflammatory, hepatoprotective and neuroprotective effects, is used to treat tuberculosis. This study investigates the immunoregulatory effects of RPR on primary human blood macrophages (PBMac) during mycobacterial infection.</p> <p>Methods</p> <p>The interaction of Bacillus Calmette-Guerin (BCG) with PBMac was used as an experimental model. A series of procedures involving solvent extraction and fractionation were used to isolate bioactive constituents in RPR. RPR-EA-S1, a fraction with potent immunoregulatory effects was obtained with a bioactivity guided fractionation scheme. PBMac were treated with crude RPR extracts or RPR-EA-S1 before BCG stimulation. The expression levels of IL-6, IL-8, IL-10 and TNF-α were measured by qPCR and ELISA. Western blotting was used to determine the effects of RPR-EA-S1 on signaling kinases and transcriptional factors in the BCG-activated PBMac.</p> <p>Results</p> <p>In BCG-stimulated macrophages, crude RPR extracts and fraction RPR-EA-S1 specifically inhibited IL-10 production while enhanced IL-8 expression at both mRNA and protein levels without affecting the expressions of IL-6 and TNF-α. Inhibition of BCG-induced IL-10 expression by RPR-EA-S1 occurred in a dose- and time-dependent manner. RPR-EA-S1 did not affect the phosphorylation of cellular protein kinases including MAPK, Akt and GSK3β. Instead, it suppressed the degradation of IκBα in the cytoplasm and inhibited the translocation of transcription factor NF-κB1 p50 to the nucleus.</p> <p>Conclusion</p> <p>RPR crude extracts and its fraction RPR-EA-S1 inhibited anti-inflammatory cytokine IL-10 and enhanced pro-inflammatory chemokine IL-8 expression in BCG-activated PBMac. The inhibitory effects of RPR-EA-S1 on IL-10 expression in BCG-activated PBMac may be due to the reduced nuclear translocation of NF-κB1 p50.</p

Publishing and sharing multi-dimensional image data with OMERO

Imaging data are used in the life and biomedical sciences to measure the molecular and structural composition and dynamics of cells, tissues, and organisms. Datasets range in size from megabytes to terabytes and usually contain a combination of binary pixel data and metadata that describe the acquisition process and any derived results. The OMERO image data management platform allows users to securely share image datasets according to specific permissions levels: data can be held privately, shared with a set of colleagues, or made available via a public URL. Users control access by assigning data to specific Groups with defined membership and access rights. OMERO’s Permission system supports simple data sharing in a lab, collaborative data analysis, and even teaching environments. OMERO software is open source and released by the OME Consortium at www.openmicroscopy.org