Excitons and their Fine Structure in Lead Halide Perovskite Nanocrystals from Atomistic GW/BSE Calculations

Atomistically detailed computational studies of nanocrystals, such as those derived from the promising lead-halide perovskites, are challenging due to the large number of atoms and lack of symmetries to exploit. Here, focusing on methylammonium lead iodide nanocrystals, we combine a real-space tight binding model with the GW approximation to the self-energy and obtain exciton wavefunctions and absorption spectra via solutions of the associated Bethe-Salpeter equation. We find that the size dependence of carrier confinement, dielectric contrast, electron-hole exchange, and exciton binding energies has a strong impact on the lowest excitation energy, which can be tuned by almost 1 eV over the diameter range of 2-6 nm. Our calculated excitation energies are about 0.2 eV higher than experimentally measured photoluminescence, and they display the same qualitative size dependence. Focusing on the fine structure of the band-edge excitons, we find that the lowest-lying exciton is spectroscopically dark and about 20-30 meV lower in energy than the higher-lying triplet of bright states, whose degeneracy is slightly broken by crystal field effects.Comment: 8 pages, 4 figure

Cardiac resynchronization therapy in persistent left superior vena cava: Can you do it two-leads-only?

Cardiac resynchronization therapy in persistent left superior vena cava: Can you do it two-leads-only

Dual binding of an antibody and a small molecule increases the stability of TERRA G-quadruplex.

In investigating the binding interactions between the human telomeric RNA (TERRA) G-quadruplex (GQ) and its ligands, it was found that the small molecule carboxypyridostatin (cPDS) and the GQ-selective antibody BG4 simultaneously bind the TERRA GQ. We previously showed that the overall binding affinity of BG4 for RNA GQs is not significantly affected in the presence of cPDS. However, single-molecule mechanical unfolding experiments revealed a population (48%) with substantially increased mechanical and thermodynamic stability. Force-jump kinetic investigations suggested competitive binding of cPDS and BG4 to the TERRA GQ. Following this, the two bound ligands slowly rearrange, thereby leading to the minor population with increased stability. Given the relevance of G-quadruplexes in the regulation of biological processes, we anticipate that the unprecedented conformational rearrangement observed in the TERRA-GQ-ligand complex may inspire new strategies for the selective stabilization of G-quadruplexes in cells.H.M. acknowledges support from NSF CHE-1026532. The Balasubramanian lab is supported by programme funding from Cancer Research UK.This is the final published version. It first appeared at http://onlinelibrary.wiley.com/doi/10.1002/anie.201408113/abstract;jsessionid=BB18FC03F2AF0C3EB95EC57CCBDB3DB9.f01t01

A Historical Perspective of Cardiac Implantable Electronic Device Infection: How a Menace Can Drive Technological and Clinical Improvement

In recent decades there has been a relevant increase in the implantation rate of cardiac implantable electronic devices (CIEDs), albeit with relevant geographical inhomogeneities. Despite the positive impact on clinical outcomes, the possibility of major complications is not negligible, particularly with respect to CIED infections. CIED infections significantly affect morbidity and mortality, especially in instances of delayed diagnosis and appropriate treatment. In the present review, we will start to depict the factors underlying the development of CIED infection as well as the difficulties related to its diagnosis and treatment. We will explain the reasons underlying the need to focus on prophylaxis rather than treatment, in view of the poor outcomes despite improvements in lead extraction procedures. This will lead to the consideration of management of this complication in a hub-spoke manner, and to our analysis of the several technological and procedural improvements developed to minimize this complication. These include prolongation of CIED longevity, the development of leadless devices, and integrated prophylactic approaches. We will conclude with a discussion regarding new devices and strategies under development. This complete excursus will provide the reader with a new perspective on how a major complication can drive technological improvements

A framework for the comparative assessment of neuronal spike sorting algorithms towards more accurate off-line and on-line microelectrode arrays data analysis

Neuronal spike sorting algorithms are designed to retrieve neuronal network activity on a single-cell level from extracellular multiunit recordings with Microelectrode Arrays (MEAs). In typical analysis of MEA data, one spike sorting algorithm is applied indiscriminately to all electrode signals. However, this approach neglects the dependency of algorithms' performances on the neuronal signals properties at each channel, which require data-centric methods. Moreover, sorting is commonly performed off-line, which is time and memory consuming and prevents researchers from having an immediate glance at ongoing experiments. The aim of this work is to provide a versatile framework to support the evaluation and comparison of different spike classification algorithms suitable for both off-line and on-line analysis. We incorporated different spike sorting "building blocks" into a Matlab-based software, including 4 feature extraction methods, 3 feature clustering methods, and 1 template matching classifier. The framework was validated by applying different algorithms on simulated and real signals from neuronal cultures coupled to MEAs. Moreover, the system has been proven effective in running on-line analysis on a standard desktop computer, after the selection of the most suitable sorting methods. This work provides a useful and versatile instrument for a supported comparison of different options for spike sorting towards more accurate off-line and on-line MEA data analysis

Maternal and fetal outcomes of intraplacental choriocarcinoma complicated by fetomaternal hemorrhage: a systematic review

Introduction: Intraplacental choriocarcinoma is a gestational trophoblastic neoplasia located within the placenta. Due to the usual silent presentation, more than half of the cases are diagnosed incidentally. It has been demonstrated that this pathology is linked to feto-maternal hemorrhage (FMH), stillbirth, and intrauterine growth restriction. The aim of our review was to establish if there are recurrent signs that might lead to an early diagnosis and better management in cases complicated by FMH. Materials and methods: We performed a systematic review of the literature from 2000 up to March 2023. The adopted research strategy included the following terms: (gestational choriocarcinoma obstetrics outcome) AND (intraplacental choriocarcinoma) AND (gestational choriocarcinoma). The MEDLINE (PubMed), Google Scholar, and Scopus databases were searched. Results: The research strategy identified 19 cases of FMH coexisting with intraplacental choriocarcinoma (IC), as described in 17 studies. The perinatal mortality rate was 36.8%. In eight cases, histological diagnosis of IC was made post-delivery. Metastatic lesions were found in 75% (6/8) of described cases. One case of maternal death has been described. Chemotherapy was necessary in seven cases. Sporadical prenatal ultrasound signs were described. Discussion: The diagnosis of IC is usually delayed, mostly due to aspecific symptoms and signs. Histological analysis of the placenta, when not routinely performed, should be performed when warning symptoms are encountered. The maternal prognosis was good, with a mortality rate of 5.5%. A fertility-sparing approach is always possible even in the presence of metastasis. Chemotherapy seems to be useful in cases of maternal and neonatal metastasis