Diagnostic imaging in the diagnosis of acute complications of bariatric surgery

Purpose: The aim of study is to identify the frequency of acute complications and imaging findings at gastro-intestinal transit (GI) and computerised tomography (CT) in a group of obese patients who developed clinical suspicion of acute complications (painful and meteoric abdomen, nausea, vomiting, fever, intestinal blockage) in post bariatric surgery. Material and methods: We retrospectively review 954 obese patients who underwent bariatric surgery between 2013 and 2019. The study included 72 patients who developed clinical suspicion of acute complications (painful and meteoric abdomen, nausea, vomiting, fever, intestinal blockage) within 6 days of bariatric surgery of sleeve gastrectomy, gastric banding, gastric bypass with Roux loop confirmed by CT, and who underwent a gastrointestinal transit before the CT examination. Results: GI exam allowed visualisation of 58% of complications. Analysing the data for each surgical technique, 46 post-operative complications were found involve gastric banding. The most frequent was bandage migration (26 cases, 56 %), identified in all cases at GI transit and then confirmed on CT. Conclusions: The study suggests that CT should be used to clarify all doubtful or clinically discordant GI transit exam results. The participation of a radiologist in qualification and post-operative evaluation is important for bariatric surgery patients

Graded vertical phase separation of donor/acceptor species for polymer solar cells

The donor/acceptor inter-mixing in bulk heterojunction (BHJ) solar cells is a critical parameter, often leading to irreproducible performance of the finished device. An alternative solution-processed device fabrication strategy towards a better control of the micro/nano-structured morphology consists of a sequential coating of the donor (e.g., poly-(3-hexylthiophene), P3HT) and the acceptor (e.g., [6,6]-phenyl-C61-butyric acid methyl ester, PCBM) from orthogonal solvents. We demonstrate that, in spite of the solvent orthogonality, this technique does not lead to a well-defined bilayer with a sharp interface, but it rather results in a graded vertical phase-separated junction, resulting from the diffusion of the PCBM in the P3HT bottom layer. We are able to control the diffusion of PCBM, which occurs preferentially in the amorphous P3HT domains, by easily varying the ratio between crystalline/amorphous domains in the P3HT. Such a ratio can be simply modified by changing the solvent for P3HT. We show that the donor–acceptor diffused bilayer (DB) junction is an intermediate structure which combines both advantages of the well-defined bilayer and conventional BHJ configurations. Indeed, the DB device geometry ensures the good reproducibility and charge percolation, like the well-defined bilayer, while preserving the interpenetration of the donor and acceptor species, resulting in an efficient charge separation, characteristic of the BHJ. Overall the annealed DB device geometry can be assimilated to a graded BHJ with an improved reproducibility and mean power conversion efficiency (PCE) of 3.45%, higher than that of the standard BHJ devices of 3.07%. Furthermore, we demonstrate the highest performance for the as-cast DB device with a PCE of 2.58%. It is worthy to note that our DB device exhibits improved open circuit voltage, fill factor, series and shunt resistances, which denote that the vertically phase separated DB junction ensures improved charge percolation

Pulsed laser deposition of a dense and uniform Au nanoparticles layer for surface plasmon enhanced efficiency hybrid solar cells

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CsPbBr3 QD/AlOx inorganic nanocomposites with exceptional stability in water, light and heat

Herein, the assembly of CsPbBr3 QD/AlOx inorganic nanocomposites, by using atomic layer deposition (ALD) for the growth of the amorphous alumina matrix (AlOx), is described as a novel protection scheme for such QDs. The nucleation and growth of AlOx on the QD surface was thoroughly investigated by miscellaneous techniques, which highlighted the importance of the interaction between the ALD precursors and the QD surface to uniformly coat the QDs while preserving the optoelectronic properties. These nanocomposites show exceptional stability towards exposure to air (for at least 45 days), irradiation under simulated solar spectrum conditions (for at least 8 h), and heat (up to 200 degrees C in air), and finally upon immersion in water. This method was extended to the assembly of CsPbBrxI3-x QD/AlOx and CsPbI3 QD/AlOx nanocomposites, which were more stable than the pristine QD films

Long-Range Exciton Diffusion in Two-Dimensional Assemblies of Cesium Lead Bromide Perovskite Nanocrystals

F\"orster Resonant Energy Transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as a new optoelectronic design element to transport energy. However, so far nanocrystal (NC) systems supported only diffusion length of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm2/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (PNC). Exciton diffusion was directly measured via steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs high PL quantum yield, large absorption cross-section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites optical absorption depth, opening the possibility to design new optoelectronic device architectures with improved performances, and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices

Synthesis and Photovoltaic Properties of Regioregular Head-to-Head Substituted Thiophene Hexadecamers

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Assembly and photocarrier dynamics of heterostructured nanocomposite photoanodes from multicomponent colloidal nanocrystals

Multicomponent oxides and their heterostructures are rapidly emerging as promising light absorbers to drive oxidative chem. To fully exploit their functionality, precise tuning of their compn. and structure is crucial. Here, we report a novel soln.-based route to nanostructured bismuth vanadate (BiVO4) that facilitates the assembly of BiVO4/metal oxide (TiO2, WO3, and Al2O3) nanocomposites in which the morphol. of the metal oxide building blocks is finely tailored. The combination of transient absorption spectroscopy-spanning from picoseconds to second time scales-and photoelectrochem. measurements reveals that the achieved structural tunability is key to understanding and directing charge sepn., transport, and efficiency in these complex oxide heterostructured films

Photoluminescence Emission Induced by Localized States in Halide Passivated Colloidal Two-Dimensional WS2 Nanoflakes

Engineering physicochemical properties of two-dimensional transition metal dichalcogenide (2D-TMD) materials by surface manipulation is essential for their practical and large-scale application especially for colloidal 2D-TMDs that are plagued by the unintentional formation of structural defects during the synthetic procedure. However, the available methods to manage surface states of 2D-TMDs in solution-phase are still limited hampering the production of high quality colloidal 2D-TMD inks to be straightforwardly assembled into actual devices. Here, we demonstrate an efficient solution-phase strategy to passivate surface defect states of colloidally synthetized WS2 nanoflakes with halide ligands, resulting in the activation of the photoluminescence emission. Photophysical investigation and density functional theory calculations suggest that halide atoms enable the suppression of non-radiative recombination through the elimination deep gap trap states, and introduce localized states in the energy band structure from which excitons efficiently recombine. Halide passivated WS2 nanoflakes importantly preserve colloidal stability and photoluminescence emission after several weeks of storing in ambient atmosphere, corroborating the potential of our developed 2D-TMD inks

Bandgap Tunability in Sb-Alloyed BiVO4 Quaternary Oxides as Visible Light Absorbers for Solar Fuel Applications

One approach to reducing the bandgap is the utilization of ternary and quaternary oxides, which have been receiving increased attention as light absorbers that, critically, also supply the potential needed to drive multi-electron oxidn. reactions. In this work, we report the discovery of antimony-alloyed bismuth vanadate (Sb-BiVO4). Through a combination of theor. predication and exptl. validation, we show that this novel photoanode material possesses a bandgap that linearly decreases below 2.4 eV with increasing Sb content. This work is enabled by the development of a novel two-step synthesis process that will broadly aid new materials discovery by providing synthetic access to a wide range of compositionally complex oxides