다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

where A represents the magnetic vector potential, is an integral of the hydromagnetic equations. This -integral made it possible to formulate a variational principle for the force-free magnetic fields. The integral expresses the fact that motions cannot transform a given field in an entirely arbitrary different field, if the conductivity of the medium isconsidered infinite. In this paper we shall show that the full set of hydromagnetic equations admit five more integrals, besides the energy integral, if dissipative processes are absent. These integrals, as we shall presently verify, are I2 =fbHvdV, (2)

Proceedings of the National Academy of Sciences

The photovoltaics of organic–inorganic lead halide perovskite materials have shown rapid improvements in solar cell performance, surpassing the top efficiency of semiconductor compounds such as CdTe and CIGS (copper indium gallium selenide) used in solar cells in just about a decade. Perovskite preparation via simple and inexpensive solution processes demonstrates the immense potential of this thin-film solar cell technology to become a low-cost alternative to the presently commercially available photovoltaic technologies. Significant developments in almost all aspects of perovskite solar cells and discoveries of some fascinating properties of such hybrid perovskites have been made recently. This Review describes the fundamentals, recent research progress, present status, and our views on future prospects of perovskite-based photovoltaics, with discussions focused on strategies to improve both intrinsic and extrinsic (environmental) stabilities of high-efficiency devices. Strategies and challenges regardi...

Halide Perovskite Photovoltaics: Background, Status, and Future Prospects

Chemical methods developed over the past two decades enable preparation of colloidal nanocrystals with uniform size and shape. These Brownian objects readily order into superlattices. Recently, the range of accessible inorganic cores and tunable surface chemistries dramatically increased, expanding the set of nanocrystal arrangements experimentally attainable. In this review, we discuss efforts to create next-generation materials via bottom-up organization of nanocrystals with preprogrammed functionality and self-assembly instructions. This process is often driven by both interparticle interactions and the influence of the assembly environment. The introduction provides the reader with a practical overview of nanocrystal synthesis, self-assembly, and superlattice characterization. We then summarize the theory of nanocrystal interactions and examine fundamental principles governing nanocrystal self-assembly from hard and soft particle perspectives borrowed from the comparatively established fields of micro...

Self-Assembly of Colloidal Nanocrystals: From Intricate Structures to Functional Materials

We predict an optical curtain effect, i.e., formation of a spatially invariant light field as light emerges from a set of periodic metallic nano-objects. The underlying physical mechanism of generation of this unique optical curtain can be explained in both the spatial domain and the wave-vector domain. In particular, in each period we use one metallic nanostrip to equate the amplitudes of lights impinging on the openings of two metallic nanoslits and also shift their phases by pi difference. We elaborate the influence on the output effect from some geometrical parameters like the periodicity, the slit height and so on. By controlling the light illuminated on metallic subwavelength apertures, it is practical to generate optical curtains of arbitrary forms, which may open new routes of plasmonic nano-lithography.

Plasmon Assisted Optical Curtains

Reducing the excitation threshold to minimize the Joule heating is critical for the realization of perovskite laser diodes. Although bound excitons are promising for low threshold laser, how to generate them at room temperature for laser applications is still unclear in quasi‐2D perovskite‐based devices. In this work, via engineering quasi‐2D perovskite PEA2(CH3NH3)n‐1PbnBr3n+1 microscopic grains by the anti‐solvent method, room‐temperature multiexciton radiative recombination is successfully demonstrated at a remarkably low pump density of 0.97 µJ cm−2, which is only one‐fourth of that required in 2D CdSe nanosheets. In addition, the well‐defined translational momentum in quasi‐2D perovskite grains can restrict the Auger recombination which is detrimental to radiative emission. Furthermore, the quasi‐2D perovskite grains are favorable for increasing binding energies of excitons and biexcitons and so as the related radiative recombination. Consequently, the prepared phase quasi‐2D perovskite film renders a threshold of room‐temperature stimulated emission as low as 13.7 µJ cm−2, reduced by 58.6% relative to the amorphous counterpart with larger grains. The findings in this work are expected to facilitate the development of solution‐processable perovskite multiexcitonic laser diodes.

Localized Bound Multiexcitons in Engineered Quasi‐2D Perovskites Grains at Room Temperature for Efficient Lasers

The band alignments of high-k Er2O3 films grown on Ge substrates by molecular beam epitaxy are determined by X-ray photoelectron spectroscopy. The valence-band and the conduction-band offsets of Er2O3 to Ge are found to be \(3.16\pm0.02\) and \(2.13\pm0.02\ \mbox{eV}\), respectively. The energy gap of Er2O3 is \(5.96\pm0.02\ \mbox{eV}\) as determined by the optical spectrophotometry. From the band offset viewpoint, the above results indicate that Er2O3 could be a promising candidate for high-k gate dielectrics on Ge substrate.

Band offsets of Er2O3 films grown on Ge substrates by X-ray photoelectron spectroscopy

We propose to use a nearby metallic nano-particle to greatly enhance the transmission efficiency of a nano-slit aperture in a metallic film. The metallic nano-particle helps to form a T shape cavity which could effectively transform the propagating incident light into localized near-filed light. Harvest efficiency is enhanced by 20 times for a non-resonant 25 nm-width nano-slit.

Transmission enhancement of a metallic slit by a nearby metallic nano-particle

Narrowband‐response organic photodetectors with high responsivity are widely demanded in areas of substance detection, industry automation, smart wearable devices, etc. Photomultiplication‐type organic photodetectors (PM‐OPDs) with high responsivity usually have a broadband photoresponse due to the broadband absorption nature of the photoactive materials. In this work, effort is made to develop a high‐performance filterless narrowband PM‐OPD using the charge injection narrowing (CIN) effect. A 0.8 nm thick Al2O3 interlayer is used to mitigate the dark current density (JD) in the narrowband PM‐OPD, prepared using a 2.8 µm thick blend layer of P3HT:[6,6]‐phenyl‐C70‐butyric acid methyl ester (PC70BM), achieving a peak responsivity of 1334 A W−1 at 650 nm, with a full‐width at half‐maximum of 40 nm. The narrowband PM‐OPD also possesses an impressive high specific detectivity of 9.73 × 1013 Jones. It is shown that the use of a 0.8 nm thick Al2O3 interlayer significantly suppresses the JD, creating a high energy barrier at the anode/photoactive interface and achieving a narrowband photoresponse behavior due to the CIN effect. The results of this work provide an exciting option for a variety of applications for OPDs with low cost, flexibility, and high sensitivity.

Yanxia Cui

Papers

Plasmon Assisted Optical Curtains

Localized Bound Multiexcitons in Engineered Quasi‐2D Perovskites Grains at Room Temperature for Efficient Lasers

Band offsets of Er2O3 films grown on Ge substrates by X-ray photoelectron spectroscopy

Transmission enhancement of a metallic slit by a nearby metallic nano-particle

High Responsivity of Narrowband Photomultiplication Organic Photodetector via Interfacial Modification