Sofia University

About: Sofia University is a education organization based out in Sofia, Bulgaria. It is known for research contribution in the topics: Large Hadron Collider & Standard Model. The organization has 8533 authors who have published 15730 publications receiving 306320 citations. The organization is also known as: University of Sofia & BFUS.

Single-cell transcriptome analysis of human skin identifies novel fibroblast subpopulation and enrichment of immune subsets in atopic dermatitis.

Abstract: Background Atopic dermatitis (AD) is a prevalent inflammatory skin disease with a complex pathogenesis involving immune cell and epidermal abnormalities. Despite whole tissue biopsy studies that have advanced the mechanistic understanding of AD, single cell–based molecular alterations are largely unknown. Objective Our aims were to construct a detailed, high-resolution atlas of cell populations and assess variability in cell composition and cell-specific gene expression in the skin of patients with AD versus in controls. Methods We performed single-cell RNA sequencing on skin biopsy specimens from 5 patients with AD (4 lesional samples and 5 nonlesional samples) and 7 healthy control subjects, using 10× Genomics. Results We created transcriptomic profiles for 39,042 AD (lesional and nonlesional) and healthy skin cells. Fibroblasts demonstrated a novel COL6A5+COL18A1+ subpopulation that was unique to lesional AD and expressed CCL2 and CCL19 cytokines. A corresponding LAMP3+ dendritic cell (DC) population that expressed the CCL19 receptor CCR7 was also unique to AD lesions, illustrating a potential role for fibroblast signaling to immune cells. The lesional AD samples were characterized by expansion of inflammatory DCs (CD1A+FCER1A+) and tissue-resident memory T cells (CD69+CD103+). The frequencies of type 2 (IL13+)/type 22 (IL22+) T cells were higher than those of type 1 (IFNG+) in lesional AD, whereas this ratio was slightly diminished in nonlesional AD and further diminished in controls. Conclusion AD lesions were characterized by expanded type 2/type 22 T cells and inflammatory DCs, and by a unique inflammatory fibroblast that may interact with immune cells to regulate lymphoid cell organization and type 2 inflammation.

Elementary Micromechanics of Heterogeneous Media

Abstract: The introductory and more elementary ideas and results of micromechanics of heterogeneous media are collected in the survey. The central problem under discussion is “homogenization.” It replaces such media by homogeneous ones, which behave macroscopically in the same way and possess certain gross effective properties. These properties are related in a complicated manner to the prescribed internal structure of the medium and their evaluation, in general, represents a profound challenge in any specific situation. A brief historical survey is given, underlying the reappearance of essentially the same “homogenization” quest in numerous guises and contexts over the last two centuries. Within the framework of the volume-averaging approach the basic notions are introduced and some of the central, now classical, results are then derived and discussed such as perturbation expansions, Hashin-Shtrikman’s bounds, variational estimates and Levin’s cross-property relation. A general “one-particle” scheme for approximate evaluation of the effective properties (in the static case) is detailed in its various implementations like selfconsistency, iterated limits and effective field. Illustrations concern conductivity, elasticity, and absorption phenomena in heterogeneous particulate media, as well as a simple self-consistent model for polycrystals’ homogenization.

Distortion-dependent Raman spectra and mode mixing in R MnO 3 perovskites ( R = La , Pr , Nd , Sm , Eu , Gd , Tb , Dy , Ho , Y )

Abstract: The polarized Raman spectra of orthorhombic $R{\mathrm{MnO}}_{3}$ series $(R=\mathrm{La},\mathrm{Pr},\mathrm{Nd},\mathrm{Sm},\mathrm{Eu},\mathrm{Gd},\mathrm{Tb},\mathrm{Dy},\mathrm{Ho},\mathrm{Y})$ were studied at room temperature. The variation of phonon frequencies with $R$ ionic radius ${r}_{R}$ as a whole confirms the commonly accepted Raman line assignments with two noticeable exceptions: (1) with decreasing ${r}_{R}$ the stretching ${A}_{g}(1)$ and bending ${A}_{g}(3)$ modes strongly mix for $R=\mathrm{Sm}$ to Tb, while for further decrease or ${r}_{R}$ $(R=\mathrm{Dy},\mathrm{Ho},\mathrm{Y})$ the ${A}_{g}(3)$ mode is observed at higher frequency than ${A}_{g}(1)$ mode; (2) similar distortion-dependent mode mixing takes place for the rotational ${A}_{g}(2)$ and $\mathrm{O}1(x)$ $[{A}_{g}(7)]$ modes. The mode mixing is particularly strong for the $R{\mathrm{MnO}}_{3}$ compounds with ${r}_{R}$ values close to the transition from $A$ type to incommensurate sinusoidal antiferromagnetic ordering at low temperatures. The frequency of rotational ${A}_{g}(2)$ and ${A}_{g}(4)$ modes scales to the angles of ${\mathrm{MnO}}_{6}$ $[101]$ and $[010]$ rotations, respectively, and could be used as a measure of their value.