Rashba and Dresselhaus effects in 2D Pb-I-based perovskites

Bulk hybride halide perovskites are governed by significant Rashba and Dresselhaus splitting. This indicates that such effects will not only affect their optoelectronic properties but also those of their two dimensional layered relatives. This work aims at understanding how different ways of symmetry breaking influence these effects in those materials. For this purpose, model structures are adopted where the organic compounds are replaced by Cs atoms. Disregarding possible distortions in the inorganic layers, results in structures with composition Cs$_{n+1}$Pb$_n$I$_{3n+1}$. Using the all-electron full-potential density-functional-theory code \texttt{exciting}, the impact of atomic displacement on the band structure is systematically studied for $n=1$, 2, 3 and $\infty$. The displacement patterns that yield Rashba or Dresselhaus splitting are identified, and the amount of the splitting is determined as a function of displacement. Furthermore, the spin textures in the electronic states around the band gap are analyzed to differentiate between Rashba and Dresselhaus effects. This study reveals in-plane Pb displacements as the origin of the strongest effects.Comment: 10 pages, 8 figures, 1 tabl

Safeguarding of Fetal Growth by Mast Cells and Natural Killer Cells

Uterine natural killer cells (uNKs) and mast cells (uMCs) are of crucial importance for spiral artery (SA) remodeling and placentation. Mice deficient for both NKs and MCs including uNKs and uMCs show markedly impaired SA remodeling and their fetuses are growth-retarded. In contrast, the absence of either NKs or MCs results in only minor impairment. This suggests that uNKs can compensate for the effects of uMCs on SA remodeling and vice versa. To test this hypothesis, we assessed uNK numbers in uMC-deficient mice as well as uMC numbers in uNK-depleted mice. Notably, uMC-deficient C57BL/6J-KitW-sh/W-sh (W-sh) mice showed markedly increased numbers of uNKs in contrast to wild type, and the transfer of bone marrow-derived MCs reverted this phenotype. Vice versa, uNK-deficient C57BL/6NTac-IL15tm1ImxN5 (IL-15−/−) mice had significantly increased numbers of uMCs and MC-specific proteases. Our results suggest that uNKs and uMCs can counterbalance their effects at the feto–maternal interface and jointly promote SA remodeling and placentation

Wie Bilder «entstehen».

Wie erscheinen, «entstehen» Bilder? Welche Eigenschaften, Strukturen und Entwicklungen lassen sich in frühen graphischen Äusserungen beobachten? Sind frühe Bildmerkmale in einer bestimmten Kultur allgemein oder individuell? Worin besteht frühe bildhafte Erkenntnis und Ästhetik? Auf welche allgemeinen Bestimmungen von «Bild» oder «Bildern» verweist die Bildgenese? Auf welche allgemeinen Aspekte des frühen symbolischen Verhaltens verweisen frühe Bilder? Der vorliegende erste Band zur Bildentwicklung im frühen Kindesalter stellt die Ergebnisse einer breit angelegten empirischen Studie von Zeichnungen und Malereien europäischer Kinder (Schweiz, Frankreich und Deutschland) im Vorschulalter vor

Acquisition of clarithromycin resistance mutations in the 23S rRNA gene of Mycobacterium abscessus in the presence of inducible erm(41)

Objectives Antibiotic therapy of pulmonary Mycobacterium abscessus infection is based on a combination treatment including clarithromycin. Recent data demonstrated that M. abscessus may carry a chromosomal, inducible erm gene coding for the ribosomal methylase Erm(41). The purpose of this study was to investigate whether in patients with chronic M. abscessus infection undergoing clarithromycin therapy, M. abscessus acquires clarithromycin resistance mutations in the rrl gene in addition to the presence of an inducible Erm(41) methylase. Methods We determined clarithromycin MICs, erm(41) and rrl sequences for 29 clinical M. abscessus subsp. abscessus isolates of five different patients. The isolates were obtained between 2007 and 2011 covering a longitudinal observation period of 2-4 years for the individual patients. Results In three out of five patients with an initial rrl wild-type isolate, follow-up isolates demonstrated acquisition of resistance mutations in the rrl gene in addition to the presence of an inducible Erm methylase. Conclusions Our results show that in M. abscessus, clarithromycin resistance mutations in the 23S rRNA peptidyltransferase region provide an additional selective advantage independent of a functional erm(41) gen

Transfer of regulatory T cells into abortion-prone mice promotes the expansion of uterine mast cells and normalizes early pregnancy angiogenesis

Implantation of the fertilized egg depends on the coordinated interplay of cells and molecules that prepare the uterus for this important event. In particular, regulatory T cells (Tregs) are key regulators as their ablation hinders implantation by rendering the uterus hostile for the embryo. In addition, the adoptive transfer of Tregs can avoid early abortion in mouse models. However, it is still not defined which mechanisms underlie Treg function during this early period. Cells of the innate immune system have been reported to support implantation, in part by promoting angiogenesis. In particular, uterine mast cells (uMCs) emerge as novel players at the fetal- maternal interface. Here, we studied whether the positive action of Tregs is based on the expansion of uMCs and the promotion of angiogenesis. We observed that abortion-prone mice have insufficient numbers of uMCs that could be corrected by the adoptive transfer of Tregs. This in turn positively influenced the remodeling of spiral arteries and placenta development as well as the levels of soluble fms-like tyrosine kinase 1 (sFlt-1). Our data suggest an interplay between Tregs and uMCs that is relevant for the changes required at the feto-maternal interface for the normal development of pregnancy

Hybrid Materials: Still Challenging for Ab Initio Theory?

Hybrid inorganic/organic systems (HIOS) open new avenues for tailoring them with respect to desired features and functions by exploiting the respective advantages of their components. Therefore, these materials are actively explored in many experimental studies and devices. On the theory side, similar investigations are rather scarce as such interfaces, in addition to exhibiting large unit cells, require highest-level theories to be described reliably. Consequently, hybrid materials pose a challenge for electronic structure theory, starting from density-functional theory to methods beyond, particularly many-body perturbation theory. This concerns both conceptual aspects and computational bottlenecks. In this perspective, the performance of state-of-the-art theoretical approaches applied to HIOS is summarized, mainly focusing on optoelectronic properties. Recent achievements, open challenges, and urgent needs are addressed.Peer Reviewe

Disentangling Quantum and Classical Contributions in Hybrid Quantum Machine Learning Architectures

Quantum computing offers the potential for superior computational capabilities, particularly for data-intensive tasks. However, the current state of quantum hardware puts heavy restrictions on input size. To address this, hybrid transfer learning solutions have been developed, merging pre-trained classical models, capable of handling extensive inputs, with variational quantum circuits. Yet, it remains unclear how much each component -- classical and quantum -- contributes to the model's results. We propose a novel hybrid architecture: instead of utilizing a pre-trained network for compression, we employ an autoencoder to derive a compressed version of the input data. This compressed data is then channeled through the encoder part of the autoencoder to the quantum component. We assess our model's classification capabilities against two state-of-the-art hybrid transfer learning architectures, two purely classical architectures and one quantum architecture. Their accuracy is compared across four datasets: Banknote Authentication, Breast Cancer Wisconsin, MNIST digits, and AudioMNIST. Our research suggests that classical components significantly influence classification in hybrid transfer learning, a contribution often mistakenly ascribed to the quantum element. The performance of our model aligns with that of a variational quantum circuit using amplitude embedding, positioning it as a feasible alternative

Batch anaerobic digestion of banana waste - energy potential and modelling of methane production kinetics

Different fractions of banana (stalk, peel, and flesh) as well as the whole unpeeled banana were studied in a laboratory Biochemical Methane Potential (BMP) assay. After completion of 35-day digestion at 37°C in 2L-reactors, specific methane yields reached 0.256, 0.322, 0.367 and 0.349 m³/kg VS (volatile solids) for stalk, peel, flesh, and unpeeled banana respectively. Considering the country of Uganda, East Africa, the collection of peels and stalks from banana production would yield a theoretical potential of about 60 GWh of electrical energy per year in biogas plants. In order to verify the suitability of banana fractions to the biogas process, their chemical composition was analyzed, and their methane production kinetics was estimated with exponential and logistic models. Banana peel was found to be easily degradable, and well suited for biogas production. Banana flesh had the fastest degradation rate of all banana fractions, and banana stalk had the slowest degradation rate, respectively. Methane production kinetics was fitted with first order and logistic models. The kinetics of methane production from banana flesh correlated well with a logistic model, but did not with exponential models. Alternately, methane production kinetics from banana stalk correlated well with exponential models, but did not with the logistic model. Methane production kinetics from banana peel did not correlate well with any model. Hence, the biochemistry of anaerobic processes may follow different patterns depending on substrate degradability, explaining the difficulty of finding a universal explanatory model of methane production kinetics in batch mode

Aminoglycoside-modifying enzymes determine the innate susceptibility to aminoglycoside antibiotics in rapidly growing mycobacteria

Objectives Infections caused by the rapidly growing mycobacterium (RGM) Mycobacterium abscessus are notoriously difficult to treat due to the innate resistance of M. abscessus to most clinically available antimicrobials. Aminoglycoside antibiotics (AGA) are a cornerstone of antimicrobial chemotherapy against M. abscessus infections, although little is known about intrinsic drug resistance mechanisms. We investigated the role of chromosomally encoded putative aminoglycoside-modifying enzymes (AME) in AGA susceptibility in M. abscessus. Methods Clinical isolates of M. abscessus were tested for susceptibility to a series of AGA with different substituents at positions 2′, 3′ and 4′ of ring 1 in MIC assays. Cell-free extracts of M. abscessus type strain ATCC 19977 and Mycobacterium smegmatis strains SZ380 [aac(2′)-Id+], EP10 [aac(2′)-Id−] and SZ461 [aac(2′)-Id+, rrs A1408G] were investigated for AGA acetylation activity using thin-layer chromatography (TLC). Cell-free ribosome translation assays were performed to directly study drug-target interaction. Results Cell-free translation assays demonstrated that ribosomes of M. abscessus and M. smegmatis show comparable susceptibility to all tested AGA. MIC assays for M. abscessus and M. smegmatis, however, consistently showed the lowest MIC values for 2′-hydroxy-AGA as compared with 2′-amino-AGA, indicating that an aminoglycoside-2′-acetyltransferase, Aac(2′), contributes to innate AGA susceptibility. TLC experiments confirmed enzymatic activity consistent with Aac(2′). Using M. smegmatis as a model for RGM, acetyltransferase activity was shown to be up-regulated in response to AGA-induced inhibition of protein synthesis. Conclusions Our findings point to AME as important determinants of AGA susceptibility in M. abscessu