Stable Light‐Emitting Diodes Using Phase‐Pure Ruddlesden–Popper Layered Perovskites

State‐of‐the‐art light‐emitting diodes (LEDs) are made from high‐purity alloys of III–V semiconductors, but high fabrication cost has limited their widespread use for large area solid‐state lighting. Here, efficient and stable LEDs processed from solution with tunable color enabled by using phase‐pure 2D Ruddlesden–Popper (RP) halide perovskites with a formula (CH₃(CH₂)₃NH₃)₂(CH₃NH₃)_n?1Pb_nI_3n+1 are reported. By using vertically oriented thin films that facilitate efficient charge injection and transport, efficient electroluminescence with a radiance of 35 W Sr^?1 cm^?2 at 744 nm with an ultralow turn‐on voltage of 1 V is obtained. Finally, operational stability tests suggest that phase purity is strongly correlated to stability. Phase‐pure 2D perovskites exhibit >14 h of stable operation at peak operating conditions with no droop at current densities of several Amperes cm^?2 in comparison to mixtures of 2D/3D or 3D perovskites, which degrade within minutes.     

Delayed renal dysfunction and flash pulmonary edema post endovascular abdominal aneurysm repair

After endovascular aortic repair (EVAR), the deterioration in long‐term renal function is probably multifactorial. Preoperative renal failure is an independent risk factor. Postoperative renal dysfunction can be associated with inadvertent renal artery occlusion, renal artery complications as stenosis, plaque dislodgement, or dissection. Ischemic nephropathy can accelerate hypertension and circulatory congestion. We report a case of coverage of the renal arteries symptomatic with flash pulmonary edema and renal failure 15 months after EVAR, suggesting a delayed endograft migration. The patient had complete resolution of symptoms and renal function after renal artery stenting with placement between endograft and aneurysm to the left renal artery.     

Microneedles for the Noninvasive Structural and Functional Assessment of Dermal Lymphatic Vessels

The medical and scientific communities' interest in the lymphatic system has been growing rapidly in recent years. It has become evident that the lymphatic system is much more than simply a homeostasis controller and that it plays key roles in several pathological conditions. This work describes the identification of the optimal combination of poly(N‐vinylpyrrolidone) and a near‐infrared dye (indocyanine green) for the manufacturing of soluble microneedles and their application to the imaging of the lymphatic system. Upon application to the skin, the microneedle‐bearing indocyanine green is delivered in the dermal layer, where the lymphatic vessels are abundant. The draining lymphatics can then be visualized and the clearance kinetics from the administration site simply determined using a near‐infrared camera. This painless functional “tattooing” procedure can be used for quantitative assessment of the dermal lymphatic function in several dermal conditions and treatment‐response evaluations. The two components of these microneedles are extensively used in routine medical care, potentially leading to rapid clinical translation. Moreover, this procedure may have a significant impact on preclinical lymphatic studies.     

Self-formation of hexagonal nanotemplates for growth of pyramidal quantum dots by metalorganic vapor phase epitaxy on patterned substrates

We demonstrate the self-formation of hexagonal nanotemplates on GaAs (111)B substrates patterned with arrays of inverted tetrahedral pyramids during metal-organic vapor phase epitaxy and its role in producing high-symmetry, site-controlled quantum dots (QDs). By combining atomic force microscopy measurements on progressively thicker GaAs epitaxial layers with kinetic Monte Carlo growth simulations, we demonstrate self-maintained symmetry elevation of the QD formation sites from three-fold to six-fold symmetry. This symmetry elevation stems from adatom fluxes directed towards the high-curvature sites of the template, resulting in the formation of a fully three-dimensional hexagonal template after the deposition of relatively thin GaAs layers. We identified the growth conditions for consistently achieving a hexagonal pyramid bottom, which are useful for producing high-symmetry QDs for efficient generation of entangled photons.

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Contribution à la modélisation de lignes hyperfréquences supraconductrices à haute température critique par la méthode FDTD

The purpose of this study is to determine the electrical behaviour of high-Tc superconductor microstrip lines. TheFdtd method is used to put into discrete terms Maxwell’s equations. The two-fluid model has been chosen to describe the behaviour of the superconductor. The variation of electrical parameters such as surface resistance as a function of frequency up to 60 GHz is presented.     

Gallium nitride MEMS resonators: how residual stress impacts design and performances

Microsystem Technologies - Starting from Gallium Nitride epitaxially grown on silicon, pre-stressed micro-resonators with integrated piezoelectric transducers have been designed, fabricated, and...     

Automated architecture synthesis for parallel programs on FPGA multiprocessor systems

This paper presents a concept for automated architecture synthesis for adaptive multiprocessors on chip, in particular for Field-Programmable Gate-Array (FPGA) devices. Given a parallel program, the intent is to simultaneously allocate processor resources and the corresponding communication network, and at the same time, to map the parallel application to get an optimum application-specific architecture. This approach builds up on a previously proposed design platform that automates system integration and FPGA synthesis for such architectures. As a result, the overall concept offers an automated design approach from application mapping to system and FPGA configuration. The automated synthesis is based on combinatorial optimization. Automation is possible because a solvable Integer Linear Programming (ILP) model that captures all necessary design trade-off parameters of such systems has been found. Experimental results to study the feasibility of the automated synthesis indicate that problems with sizes that can be encountered in the embedded domain can be readily solved. Results obtained underscore the need for an automated synthesis for design space exploration.     

Missing data mask estimation with frequency and temporal dependencies

Automatic speech recognition (ASR) has reached a very high level of performance in controlled situations. However, the performance degrades drastically when environmental noise occurs during recognition. Nowadays, the major challenge is to reach a good robustness to adverse conditions. Missing data recognition has been developed to deal with this challenge. Unlike other denoising methods, missing data recognition does not match the whole data with the acoustic models, but instead considers part of the signal as missing, i.e. corrupted by noise. The main challenge of this approach is to identify accurately missing parts (also called masks). The work reported here focuses on this issue. We start from developing Bayesian models of the masks, where every spectral feature is classified as reliable or masked, and is assumed independent of the rest of the signal. This classification strategy results in sparse and isolated masked features, like the squares of a chess-board, while oracle reliable and unreliable features tend to be clustered into consistent time–frequency blocks. We then propose to take into account frequency and temporal dependencies in order to improve the masks’ estimation accuracy. Integrating such dependencies leads to a new architecture of a missing data mask estimator. The proposed classifier has been evaluated on the noisy Aurora2 (digits recognition) and Aurora4 (continuous speech) databases. Experimental results show a significant improvement of recognition accuracy when these dependencies are considered.