Variações anatômicas do tronco celíaco, artérias hepáticas e renais: Ensaio iconográfico: Anatomical variants of the celiac trunk, hepatic and renal arteries: Iconographic essay

  As variações anatômicas do tronco celíaco, artérias hepáticas e renais vêm sendo estudadas e documentadas ao longo dos anos. Representam relevância clinicocirúrgica, uma vez que podem resultar em diferentes dificuldades técnicas, sendo essencial seu relato a fim de se evitar danos vasculares e outras complicações operatórias. A angiotomografia computadorizada desempenha um papel importante, já que é um método de imagem rápido e eficaz, com menos complicações, relativamente, que a angiografia digital. Cabe ao radiologista correta avaliação diagnóstica, contribuindo com a redução de complicações e maior sucesso das intervenções terapêuticas. O presente ensaio iconográfico apresenta uma revisão de exames tomográficos de pacientes portadores de variações anatômicas do tronco celíaco, artérias hepáticas e renais, associada à descrição das imagens e classificações existentes

TIME DOMAIN RISER VIV PREDICTIONS COMPARED TO FIELD AND LABORATORY TEST DATA

ABSTRACT The time domain code ABAVIV has demonstrated the ability to reproduce basic features of riser vortex induced vibration (VIV). The VIV response of risers is a transient phenomenon. Consequently, time domain computer codes have a better basis in principle than frequency domain codes to model and predict the riser VIV response. Frequency domain codes have been used extensively by the offshore industry to calculate riser VIV response and to design risers for VIV fatigue. These codes have been successful in riser design by making conservative assumptions in modeling the VIV phenomenon and by using large safety factors. This paper shows comparisons of ABAVIV predictions to two sets of data -one from laboratory tests and the other from field tests. The laboratory tests were performed at the Imperial College with a smooth riser model. The field tests were performed as part of the DeepStar program and were carried out offshore Miami, Florida, with a riser model hanging from a moving boat. In the DeepStar tests, the current direction varied with depth, and wave flow was present along with the current. The tests included both smooth and straked riser models. The data from these tests demonstrated the transient character of the VIV response and the strong presence of higher harmonics. All available frequency domain codes lack the ability to model and predict the higher harmonic response. The paper will show that ABAVIV has the capability to model the higher harmonics of the VIV response with appropriate modifications in the lift force model

Active bialkali photocathodes on free-standing graphene substrates

The hexagonal structure of graphene gives rise to the property of gas impermeability, motivating its investigation for a new application: protection of semiconductor photocathodes in electron accelerators. These materials are extremely susceptible to degradation in efficiency through multiple mechanisms related to contamination from the local imperfect vacuum environment of the host photoinjector. Few-layer graphene has been predicted to permit a modified photoemission response of protected photocathode surfaces, and recent experiments of single-layer graphene on copper have begun to confirm these predictions for single crystal metallic photocathodes. Unlike metallic photoemitters, the integration of an ultra-thin graphene barrier film with conventional semiconductor photocathode growth processes is not straightforward. A first step toward addressing this challenge is the growth and characterization of technologically relevant, high quantum efficiency bialkali photocathodes grown on ultra-thin free-standing graphene substrates. Photocathode growth on free-standing graphene provides the opportunity to integrate these two materials and study their interaction. Specifically, spectral response features and photoemission stability of cathodes grown on graphene substrates are compared to those deposited on established substrates. In addition we observed an increase of work function for the graphene encapsulated bialkali photocathode surfaces, which is predicted by our calculations. The results provide a unique demonstration of bialkali photocathodes on free-standing substrates, and indicate promise towards our goal of fabricating high-performance graphene encapsulated photocathodes with enhanced lifetime for accelerator applications.Comment: 21 pages, 5 figures, accepted to npj 2D Materials and Application

Hospitalization Trends for Thromboembolic Events in Atrial Fibrillation: A 12-Year National Analysis

BACKGROUND: Direct oral anticoagulants and percutaneous left atrial appendage occlusion (LAAO) devices were approved for use in 2010 and 2015, respectively. It is unknown to what extent, if any, these new stroke preventive therapies have impacted hospitalizations for thromboembolic (TE) events. OBJECTIVES: To evaluate temporal trends in AF-related hospitalizations for acute ischemic stroke (AIS), transient ischemic attack (TIA), and systemic embolism (SEE) in the U.S. from 2010 to 2021. METHODS: Using the National Inpatient Sample, we identified hospitalizations for TE events with comorbid AF. Data were grouped into two periods (2010-2015 and 2016-2021). Linear regression assessed trends in TE frequency. We also examined anticoagulation (AC) use and LAAO procedures among inpatients with AF. RESULTS: A total of 1,692,373 AF-related TE hospitalizations were identified: 798,413 (2010-2015) and 893,960 (2016-2021). The frequency of hospitalizations for any AF-TE event, as a fraction of total hospitalizations in patients with AF, declined from 3.69 % to 3.35 % (P \u3c 0.001). AF-related AIS hospitalizations rose from 2.71 % to 2.89 % in 2010-2015 (P \u3c 0.001) but declined from 3.02 % to 2.89 % in 2016-2021 (P \u3c 0.001). TIA (0.75 % to 0.35 %) and SEE (0.22 % to 0.10 %) hospitalizations also decreased (P \u3c 0.001). AC use increased from 21.2 % in 2010 to 42.4 % in 2021 (P \u3c 0.001), while LAAO procedures rose sharply from 5129 in 2016 to 46,080 in 2021 (P \u3c 0.001). CONCLUSION: TE hospitalizations among inpatients with comorbid AF declined from 2010 to 2021, primarily driven by a decrease in TIAs and SEE. Acute ischemic stroke hospitalizations declined after 2016, coinciding with increased AC use and LAAO adoption

Bright triplet excitons in lead halide perovskites

Nanostructured semiconductors emit light from electronic states known as excitons[1]. According to Hund's rules[2], the lowest energy exciton in organic materials should be a poorly emitting triplet state. Analogously, the lowest exciton level in all known inorganic semiconductors is believed to be optically inactive. These 'dark' excitons (into which the system can relax) hinder light-emitting devices based on semiconductor nanostructures. While strategies to diminish their influence have been developed[3-5], no materials have been identified in which the lowest exciton is bright. Here we show that the lowest exciton in quasi-cubic lead halide perovskites is optically active. We first use the effective-mass model and group theory to explore this possibility, which can occur when the strong spin-orbit coupling in the perovskite conduction band is combined with the Rashba effect [6-10]. We then apply our model to CsPbX3 (X=Cl,Br,I) nanocrystals[11], for which we measure size- and composition-dependent fluorescence at the single-nanocrystal level. The bright character of the lowest exciton immediately explains the anomalous photon-emission rates of these materials, which emit 20 and 1,000 times faster[12] than any other semiconductor nanocrystal at room[13-16] and cryogenic[17] temperatures, respectively. The bright exciton is further confirmed by detailed analysis of the fine structure in low-temperature fluorescence spectra. For semiconductor nanocrystals[18], which are already used in lighting[19,20], lasers[21,22], and displays[23], these optically active excitons can lead to materials with brighter emission and enhanced absorption. More generally, our results provide criteria for identifying other semiconductors exhibiting bright excitons with potentially broad implications for optoelectronic devices.Comment: 14 pages and 3 figures in the main text, Methods and extended data 16 pages which include 11 figures, and supporting information 28 page

Bright triplet excitons in caesium lead halide perovskites

Nanostructured semiconductors emit light from electronic states known as excitons. For organic materials, Hund’s rules state that the lowest-energy exciton is a poorly emitting triplet state. For inorganic semiconductors, similar rules predict an analogue of this triplet state known as the ‘dark exciton’. Because dark excitons release photons slowly, hindering emission from inorganic nanostructures, materials that disobey these rules have been sought. However, despite considerable experimental and theoretical efforts, no inorganic semiconductors have been identified in which the lowest exciton is bright. Here we show that the lowest exciton in caesium lead halide perovskites (CsPbX_3, with X = Cl, Br or I) involves a highly emissive triplet state. We first use an effective-mass model and group theory to demonstrate the possibility of such a state existing, which can occur when the strong spin–orbit coupling in the conduction band of a perovskite is combined with the Rashba effect. We then apply our model to CsPbX_3 nanocrystals, and measure size- and composition-dependent fluorescence at the single-nanocrystal level. The bright triplet character of the lowest exciton explains the anomalous photon-emission rates of these materials, which emit about 20 and 1,000 times faster than any other semiconductor nanocrystal at room and cryogenic temperatures, respectively. The existence of this bright triplet exciton is further confirmed by analysis of the fine structure in low-temperature fluorescence spectra. For semiconductor nanocrystals, which are already used in lighting, lasers and displays, these excitons could lead to materials with brighter emission. More generally, our results provide criteria for identifying other semiconductors that exhibit bright excitons, with potential implications for optoelectronic devices

Cardiac Resynchronization Therapy Selection in a Patient with Non Left Bundle Branch Block

A patient with heart failure with reduced ejection fraction and a wide QRS complex is evaluated for cardiac resynchronization therapy