32 research outputs found
Spectral functions, Fermi surface and pseudogap in the t-J model
Spectral functions within the generalized t-J model as relevant to cuprates
are analyzed using the method of equations of motion for projected fermion
operators. In the evaluation of the self energy the decoupling of spin and
single-particle fluctuations is performed. It is shown that in an undoped
antiferromagnet (AFM) the method reproduces the selfconsistent Born
approximation. For finite doping with short range AFM order the approximation
evolves into a paramagnon contribution which retains large incoherent
contribution in the hole part of the spectral function as well as the
hole-pocket-like Fermi surface at low doping. On the other hand, the
contribution of (longitudinal) spin fluctuations, with the coupling mostly
determined predominantly by J and next-neighbor hopping t', is essential for
the emergence of the pseudogap. The latter shows at low doping in the effective
truncation of the large Fermi surface, reduced electron density of states and
at the same time quasiparticle density of states at the Fermi level.Comment: RevTex, 13 pages, 11 figures (5 color
Spin-Charge Separation in the Model: Magnetic and Transport Anomalies
A real spin-charge separation scheme is found based on a saddle-point state
of the model. In the one-dimensional (1D) case, such a saddle-point
reproduces the correct asymptotic correlations at the strong-coupling
fixed-point of the model. In the two-dimensional (2D) case, the transverse
gauge field confining spinon and holon is shown to be gapped at {\em finite
doping} so that a spin-charge deconfinement is obtained for its first time in
2D. The gap in the gauge fluctuation disappears at half-filling limit, where a
long-range antiferromagnetic order is recovered at zero temperature and spinons
become confined. The most interesting features of spin dynamics and transport
are exhibited at finite doping where exotic {\em residual} couplings between
spin and charge degrees of freedom lead to systematic anomalies with regard to
a Fermi-liquid system. In spin dynamics, a commensurate antiferromagnetic
fluctuation with a small, doping-dependent energy scale is found, which is
characterized in momentum space by a Gaussian peak at (, ) with
a doping-dependent width (, is the doping
concentration). This commensurate magnetic fluctuation contributes a
non-Korringa behavior for the NMR spin-lattice relaxation rate. There also
exits a characteristic temperature scale below which a pseudogap behavior
appears in the spin dynamics. Furthermore, an incommensurate magnetic
fluctuation is also obtained at a {\em finite} energy regime. In transport, a
strong short-range phase interference leads to an effective holon Lagrangian
which can give rise to a series of interesting phenomena including linear-
resistivity and Hall-angle. We discuss the striking similarities of these
theoretical features with those found in the high- cuprates and give aComment: 70 pages, RevTex, hard copies of 7 figures available upon request;
minor revisions in the text and references have been made; To be published in
July 1 issue of Phys. Rev. B52, (1995
A standardised model for stool banking for faecal microbiota transplantation: a consensus report from a multidisciplinary UEG working group
Background Faecal microbiota transplantation is an emerging therapeutic option, particularly for the treatment of recurrent Clostridioides difficile infection. Stool banks that organise recruitment and screening of faeces donors are being embedded within the regulatory frameworks described in the European Union Tissue and Cells Directive and the technical guide to the quality and safety of tissue and cells for human application, published by the European Council.Objective Several European and international consensus statements concerning faecal microbiota transplantation have been issued. While these documents provide overall guidance, we aim to provide a detailed description of all processes that relate to the collection, handling and clinical application of human donor stool in this document.Methods Collaborative subgroups of experts on stool banking drafted concepts for all domains pertaining to stool banking. During a working group meeting in the United European Gastroenterology Week 2019 in Barcelona, these concepts were discussed and finalised to be included in our overall guidance document about faecal microbiota transplantation.Results A guidance document for all domains pertaining to stool banking was created. This document includes standard operating manuals for several processes involved with stool banking, such as handling of donor material, storage and donor screening.Conclusion The implementation of faecal microbiota transplantation by stool banks in concordance with our guidance document will enable quality assurance and guarantee the availability of donor faeces preparations for patients.Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc
Single-Cell RNA Sequencing of Lymph Node Stromal Cells Reveals Niche-Associated Heterogeneity.
Stromal cells (SCs) establish the compartmentalization of lymphoid tissues critical to the immune response. However, the full diversity of lymph node (LN) SCs remains undefined. Using droplet-based single-cell RNA sequencing, we identified nine peripheral LN non-endothelial SC clusters. Included are the established subsets, Ccl19 <sup>hi</sup> T-zone reticular cells (TRCs), marginal reticular cells, follicular dendritic cells (FDCs), and perivascular cells. We also identified Ccl19 <sup>lo</sup> TRCs, likely including cholesterol-25-hydroxylase <sup>+</sup> cells located at the T-zone perimeter, Cxcl9 <sup>+</sup> TRCs in the T-zone and interfollicular region, CD34 <sup>+</sup> SCs in the capsule and medullary vessel adventitia, indolethylamine N-methyltransferase <sup>+</sup> SCs in the medullary cords, and Nr4a1 <sup>+</sup> SCs in several niches. These data help define how transcriptionally distinct LN SCs support niche-restricted immune functions and provide evidence that many SCs are in an activated state
Minimising the risk of monkeypox virus transmission during faecal microbiota transplantation: recommendations from a European expert panel
Molecular basis of bacterial pathogenesis, virulence factors and antibiotic resistanc
A rare case of autoimmune haemolytic anaemia due to warm IgA autoantibodies with reticulocytopenia
Inheritance of molecular markers and sex in the Australian freshwater crayfish, Cherax destructor Clark
Inheritance of three kinds of molecular genetic markers (mtDNA, random-amplified polymorphic DNAs (RAPDs) and allozymes) and sex were investigated in crossbreeding experiments between three populations of the Australian freshwater crayfish Cherax destructor. Crossbreeding did not disrupt the ively maternally inherited, and allozyme and RAPD markers were transmitted following expected Mendelian principles for co-dominant and dominant traits respectively. Unlike these three markers, sex ratios were found to be distorted by crossbreeding in some families. Two crossbred families produced only females. The implications of these findings for freshwater crayfish population genetics, taxonomy and aquaculture are discussed.<br /