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

Anyone who ever took an electronics laboratory class will be familiar with the fundamental passive circuit elements: the resistor, the capacitor and the inductor. However, in 1971 Leon Chua reasoned from symmetry arguments that there should be a fourth fundamental element, which he called a memristor (short for memory resistor). Although he showed that such an element has many interesting and valuable circuit properties, until now no one has presented either a useful physical model or an example of a memristor. Here we show, using a simple analytical example, that memristance arises naturally in nanoscale systems in which solid-state electronic and ionic transport are coupled under an external bias voltage. These results serve as the foundation for understanding a wide range of hysteretic current-voltage behaviour observed in many nanoscale electronic devices that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches.

/pdf/the-missing-memristor-found-55upit5xe7.pdf

The missing memristor found

Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field.

Carbon quantum dots and their applications

Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

A bipyridinium bisthiol adsorbs spontaneously on the surface of optically-transparent platinum electrodes to form electrochromic multilayers.

Self-assembling and electrochromic films of bipyridinium building blocks

From supramolecular complexes to interlocked molecular compounds

Visible-light excitation of the surface plasmon band of silver nanoplates can effectively localize and concentrate the incident electromagnetic field enhancing the photochemical performance of organic molecules. Herein, the first single-molecule study of the plasmon-assisted isomerization of a photochrome-fluorophore dyad, designed to switch between a nonfluorescent and a fluorescent state in response to the photochromic transformation, is reported. The photochemistry of the switchable assembly, consisting of a photochromic benzooxazine chemically conjugated to a coumarin moiety, is examined in real time with total internal reflection fluorescence microscopy in the presence of silver nanoplates excited with a 633 nm laser. The metallic nanostructures significantly enhance the visible light-induced performance of the photoconversion, which normally requires ultraviolet excitation. The resulting ring-open isomer is strongly fluorescent and can also be excited at 633 nm. These stochastic emission events are used to monitor photochromic activation and show quadratic dependence on incident power. The utilization of a single laser wavelength for both photochromic activation and excitation effectively mimics a pseudo two-colours system.

/pdf/two-photon-excitation-of-a-plasmonic-nanoswitch-monitored-by-t70zt8h75w.pdf

Two‐Photon Excitation of a Plasmonic Nanoswitch Monitored by Single‐Molecule Fluorescence Microscopy

The borondipyrromethene (BODIPY) chromophore is a versatile platform for the construction of photoresponsive dyes with unique properties. Specifically, its covalent connection to a photocleavable group can be exploited to engineer compounds with photoswitchable fluorescence. The resulting photoactivatable fluorophores can increase their emission intensity or shift their emission wavelengths in response to switching. Such changes permit the spatiotemporal control of fluorescence with optical stimulations and the implementation of imaging strategies that would be impossible to replicate with conventional fluorophores. Indeed, BODIPYs with photoactivatable fluorescence enable the selective highlighting of intracellular targets, the nanoscaled visualization of sub-cellular components, the real-time monitoring of dynamic events and the photochemical writing of optical barcodes.

BODIPYs with Photoactivatable Fluorescence

Bipyridinium dications are versatile building blocks for the assembly of functional materials. In particular, their reliable electrochemical response has encouraged the design of electroactive films. Diverse and elegant experimental strategies to coat metallic and semiconducting electrodes with bipyridinium compounds have, in fact, emerged over the past two decades. The resulting interfacial assemblies span from a few nanometers to several micrometers in thickness. They incorporate from a single molecular layer to large collections of entangled polymer chains. They transport electrons efficiently from the electrode surface to the film/solution interface and vice versa. Electron self-exchange between and the physical diffusion of the bipyridinium building blocks conspire in defining the charge transport properties of these fascinating electroactive assemblies. Often, the matrix of electron-deficient bipyridinium dications can be exploited to entrap electron-rich analytes. Electrostatic interactions promote the supramolecular association of the guests with the surface-confined host matrix. Furthermore, chromophoric sites can be coupled to the bipyridinium dications to produce photosensitive arrays capable of harvesting light and generating current. Thus, thorough investigations on the fundamental properties of these functional molecule-based materials can lead to promising applications in electroanalysis and solar energy conversion, while contributing to advances in the basic understanding of electron transport in interfacial assemblies. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 204–218; 2004: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20013

Françisco M. Raymo

Papers

Self-assembling and electrochromic films of bipyridinium building blocks

From supramolecular complexes to interlocked molecular compounds

Two‐Photon Excitation of a Plasmonic Nanoswitch Monitored by Single‐Molecule Fluorescence Microscopy

BODIPYs with Photoactivatable Fluorescence

Electron transport in bipyridinium films