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Metal-halide perovskites feature very low deep-defect densities, thereby enabling high operating voltages at the solar cell level. Here, by precise extraction of their absorption spectra, we find t...

Perovskite photovoltaics have made extraordinary strides in efficiency and stability thanks to process and formulation developments like anti-solvent dripping and mixed-cation mixed-halide compositions. Solar cell fabrication through low-cost scalable methods, such as blade coating, cannot accommodate anti-solvent dripping and needs to be performed in an ambient atmosphere. Consequently, their efficiency has lagged behind that of spin-cast devices, fabricated in an inert atmosphere and with carefully timed anti-solvent dripping to control nucleation and growth. In this study, we demonstrate formamidinium (FA)-dominated mixed-halide mixed-cation perovskite solar cells fabricated by blade coating in ambient air (T = 23 °C and RH ≈ 50%) without the benefits of anti-solvent dripping or a moisture-free environment. We investigated the solidification process during blade coating of single-cation (FAPbI3) and increasingly complex mixed-cation mixed-halide (FA0.8MA0.15Cs0.05PbI2.55Br0.45, MA is methylammonium) perovskites in situ using time-resolved grazing incidence wide-angle X-ray scattering (GIWAXS). We found that the perovskite precursor composition and the blade coating temperature profoundly influence the crystallization mechanism and whether halide segregation occurs or not. The inclusion of Br− suppresses the non-perovskite 2H phase, promoting instead PbI2 together with the intermediate 6H phase and 3C phase of FAPbI2.55Br0.45. Addition of Cs+ suppresses these intermediates and promotes the direct crystallization of the perovskite 3C phase FA0.8MA0.15Cs0.05PbI2.55Br0.45 when coating at elevated temperature, unlike when anti-solvent dripping is used at room temperature. Through control of ink formulation and coating conditions, we demonstrate blade coated perovskite solar cells with a champion power conversion efficiency (PCE) of 18.20% as compared with FAPbI3 perovskites, which yield a PCE of 12.35% under similar conditions without the benefit of anti-solvent dripping. This study provides valuable insight into the crystallization pathway of mixed-cation mixed-halide formulations without anti-solvent dripping under high-temperature processing conditions that enable the translation of perovskites toward upscalable ambient manufacturing under high throughput conditions.

Summary High-performance passivating contact is a prerequisite for high-efficiency crystalline silicon (c-Si) solar cells. In this work, an electron-conductive, hole-blocking contact based on titanium nitride (TiN) deposited by reactive magnetron sputtering is presented. Quasi-metallic TiN combined with an ultrathin SiO2 passivation layer (SiO2/TiN) is demonstrated to be an effective electron-selective contact on c-Si, featuring a low-contact resistivity of 16.4 mΩ.cm2 and a tolerable recombination current parameter of ∼500 fA/cm2. By implementing the dual-function SiO2/TiN contact, which acts simultaneously as a surface passivating layer and metal electrode, an efficiency of 20% is achieved by an n-type c-Si solar cell with a simple structure. This work not only demonstrates a way to develop efficient n-type c-Si solar cells with dual-function metal nitride contacts at a low cost but also expands the pool of available carrier transport materials, from metal oxides to metal nitrides, for photovoltaic devices.

PURPOSE: Efficient compression of images while preserving image quality has the potential to be a major enabler of effective remote clinical diagnosis and treatment, since poor Internet connection conditions are often the primary constraint in such services. This paper presents a framework for organ-specific image compression for teleinterventions based on a deep learning approach and anisotropic diffusion filter. METHODS: The proposed method, DLAD, uses a CNN architecture to extract a probability map for the organ of interest; this probability map guides an anisotropic diffusion filter that smooths the image except at the location of the organ of interest. Subsequently, a compression method, such as BZ2 and HEVC-visually lossless, is applied to compress the image. We demonstrate the proposed method on 3D CT images acquired for radio frequency ablation (RFA) of liver lesions. We quantitatively evaluate the proposed method on 151 CT images using peak-signal-to-noise ratio (PSNR), structural similarity (SSIM) and compression ratio (CR) metrics. Finally, we compare the assessments of two radiologists on the liver lesion detection and the liver lesion center annotation using 33 sets of the original images and the compressed images. RESULTS: The results show that the method can significantly improve CR of most well-known compression methods. DLAD combined with HEVC-visually lossless achieves the highest average CR of 6.45, which is 36% higher than that of the original HEVC and out-performs other state-of-the-art lossless medical image compression methods. The means of PSNR and SSIM are 70 dB and 0.95, respectively. In addition, the compression effects do not statistically significantly affect the assessments of the radiologists on the liver lesion detection and the lesion center annotation. CONCLUSIONS: We thus conclude that the method has a high potential to be applied in teleintervention applications.

© 2017 Elsevier Ltd In this study, a new and efficient computational approach based on isogeometric analysis (IGA) and refined plate theory (RPT) is proposed for the geometrically nonlinear analysis of functionally graded (FG) microplates. While the microplates’ size-dependent effects are efficiently captured by a simple modified couple stress theory (MCST) with only one length scale parameter, the four-unknown RPT is employed to establish the displacement fields which are eventually used to derive the nonlinear von Kámán strains. The NURBS-based isogeometric analysis is used to construct high-continuity elements, which is essentially required in the modified couple stress and refined plate theories, before the iterative Newton-Raphson algorithm is employed to solve the nonlinear problems. The successful convergence and comparison studies as well as benchmark results of the nonlinear analysis of FG microplates ascertain the validity and reliability of the proposed approach. In addition, a number of studies have been carried out to investigate the effects of material length scale, material and geometrical parameters on the nonlinear bending behaviours of microplates.

To investigate the effectiveness of nutritional supplement Bao Khi Khang as an adjuvant therapy in acute exacerbations of chronic obstructive pulmonary disease (COPD) compared to conventional therapy alone. This was a prospective, randomized, open-label controlled trial in 60 patients presenting with acute exacerbation of COPD. Patients were randomized into two groups, the control and the experimental groups. The control group was treated with the standard therapeutic protocol (Antimicrobial+Corticosteroids+Bronchodilator+Mucolytic drugs). The experimental group was treated with Bao Khi Khang tablets combined with the standard therapeutic protocol. The treatment outcomes, including clinical and paraclinical parameters of exacerbation of COPD, were compared between the experimental group and the control group at day 15 and 30. This study was conducted according to protocol: 01.2014-HTNCKH. The results showed a significant reduction of major COPD exacerbation symptoms in experimental group. The favorable progresses in mMRC scale and COPD Assessment Test score before and after treatment, between experimental group and control group, were statistically different. Symptom control such as cough, copious sputum secretion, and bacterial infection was 90% effective (very good 50.0%, good 40.0%) in experimental group compared to 50% (very good 20%, good 30.0%) in control group. No adverse side effects were observed in experimental group. Bao Khi Khang nutritional supplement could be an effective and safe adjuvant therapy in acute exacerbations of COPD. Further interventional studies are required to confirm these findings.

Introduction: Current management guidelines for pit viper envenomations recommend against the use of nonsteroidal anti-inflammatory drugs (NSAIDs) for pain control due to concern for platelet dysfu...

Hybrid energy storage devices face the challenges of pairing suitable redox chemistries with stable electrodes to simultaneously realize the energy storage mechanisms of batteries and supercapacitors. Functionalization of electrodes enables improved catalytic activity and long-term cycling stability by introducing desired functional groups. Herein, we demonstrate novel hybrids using reversible vanadium (V) redox couples along with functionalized graphene electrodes. Redox couples of V(III)/V(IV) and V(IV)/V(V) are formed upon initial charging of the V(IV) electrolyte present in both half-cells, leading to a Galvani potential difference during operation. Moreover, functionalized electrodes with high surface area facilitate both facile redox reactions and electric double layer formation. The unique chemistry offers a straightforward device regeneration step which significantly enhances the cycling stability. Optimized hybrids exhibit a battery-like specific capacity of 700 mAh g−1 at 0.5 A g−1, a supercapacitor-like capacitance of 850 F g−1 over 10,000 cycles at 10 A g−1, and a very low self-discharge rate. This corresponds to power densities of 0.3 kW kg−1 and 9.2 kW kg−1 and energy densities of 363.8 Wh kg−1 and 24.9 Wh kg−1, respectively, outperforming similar aqueous redox hybrid systems.

No abstract available.

© 2019 Elsevier Ltd In this study, the vibration behaviours of functionally graded microplates with cracks are investigated by means of a simple yet rigorous version of Mindlin's generialised continuum and the extended isogeometric analysis (XIGA). The simplified strain gradient theory which includes one material length parameter and an additional micro-inertia term is employed to capture the size effects. Meanwhile, the displacement field of the plates is described using the refined plate theory with four unknowns and the XIGA in which enrichment functions are involved to effectively predict the responses of microplates with cracks. In addition, the IGA approach with highly smooth basis functions of non-uniform rational B-spline (NURBS) ensures a clean and efficient treatment of higher continuity requirements in the strain gradient theory. The benchmark numerical results show significant departure from those analysed by the classical continuum elasticity. Indeed, they reveal strong influences of microstructural characteristics on the vibration responses of microplates which are not shown in the platform of the classical theory and the influences are more pronounced as the size of the plates becomes comparable with the material length parameter.

Mixed halide, mixed cation lead perovskite films have been demonstrated to benefit tremendously from the addition of Cs and Rb into the perovskite formulation, resulting in high performance, enhanced reproducibility and stability. However, the root cause of these effects in these complicated systems is not well understood. We address the above challenge by tracking in situ the solidification of perovskite precursors during solution-casting using time-resolved grazing incidence wide-angle X-ray scattering (GIWAXS). In doing so, we can directly link the formation or suppression of different crystalline phases to the presence of Cs and/or Rb. In the absence of these elements, the multi-component perovskite film is inherently unstable, phase segregating into a solvated MAI-rich phase and a FABr-rich phase. Adding even one of the two (Cs or Rb) is shown to alter the solidification quite dramatically, promoting different solidification pathways. Importantly, the addition of both components in the optimal ratio can drastically suppress phase segregation and promotes the spontaneous formation of the desired perovskite phase. This result is also confirmed by elemental mapping of organic cations (FA+, MA+) and halide anions (I-, Br-) via time-of-flight secondary ion mass spectroscopy (ToF-SIMS). Perovskite precursors with an optimal combination of additives (7% Cs, 3% Rb) result in solar cells with 20.1% power conversion efficiency (PCE), outperforming formulation excluding Cs and Rb (PCE=14.6%). We propose that the synergistic effect is due to the collective benefits of Cs and Rb on the formation kinetics of the perovskite phase, and on the halides redistribution throughout the film. Importantly, our study points to new design rules for tuning the crystallization pathway of multi-component hybrid perovskites.

In this article, we present for the first time a research analysis for the size-dependent effects on thermal buckling and post-buckling behaviors of functionally graded material micro-plates with porosities (imperfect FGM) using isogeometric analysis. A seventh-order shear deformation plate theory associated with the modified couple stress theory (MCST) is particularly imposed to capture the size-dependent phenomenon within imperfect FGM micro-plates. The material properties of imperfect FGM micro-plates with three different distributions of porosities including even, uneven and logarithmic-uneven varying across the plate thickness are derived from the modified rule-of-mixture assumption. The nonlinear governing equation for size-dependent imperfect FGM micro-plate under uniform, linear and nonlinear temperature rise is derived using the Von-Karman assumption and Hamilton’s principle. Through numerical example, the effect of temperature rise, boundary conditions, power index, porosity volume fraction, porosity distribution pattern and material length scale parameter on thermal buckling and post-buckling behaviors of FGP micro-plates are investigated.

Tumor necrosis factor-alpha (TNF-α) is a cytokine that plays an important role in inflammatory process and tumor development. Recent studies demonstrate that triterpene saponins from Vietnamese ginseng are efficient inhibitors of TNF-α. But the interactions between TNF-α and the saponins are still unclear. In this study, molecular docking and molecular dynamics simulations of TNF-α with three different triterpene saponins (majonoside R2, vina-ginsenoside R1 and vina-ginsenoside R2) were performed to evaluate their binding ability. Our results showed that the triterpene saponins have a good binding affinity with protein TNF-α. The saponins were docked to the pore at the top of the “bell” or “cone” shaped TNF-α trimer and the complexes were structurally stable during 100 ns molecular dynamics simulation. The predicted binding sites would help to subsequently investigate the inhibitory mechanism of triterpene saponins.