There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

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

Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems.

Issues and challenges facing rechargeable lithium batteries

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This review describes a new paradigm of electronics based on the spin degree of freedom of the electron. Either adding the spin degree of freedom to conventional charge-based electronic devices or using the spin alone has the potential advantages of nonvolatility, increased data processing speed, decreased electric power consumption, and increased integration densities compared with conventional semiconductor devices. To successfully incorporate spins into existing semiconductor technology, one has to resolve technical issues such as efficient injection, transport, control and manipulation, and detection of spin polarization as well as spin-polarized currents. Recent advances in new materials engineering hold the promise of realizing spintronic devices in the near future. We review the current state of the spin-based devices, efforts in new materials fabrication, issues in spin transport, and optical spin manipulation.

http://science.sciencemag.org/content/sci/294/5546/1488.full.pdf

Spintronics: a spin-based electronics vision for the future.

The complex conductivity has been measured in $n$-type silicon with various kinds of impurities at frequencies between ${10}^{2}$ and ${10}^{5}$ cps and temperatures between 1 and 20\ifmmode^\circ\else\textdegree\fi{}K. In most cases it is orders of magnitude larger than the measured dc conductivity and is attributed to polarization caused by hopping processes. The observed frequency dependence in the measured range can be expressed as $A{\ensuremath{\omega}}^{0.8}$, where $A$ is a complex constant. At the low-temperature end the conductivity is roughly proportional to minority impurity concentration and is almost independent of the majority impurity concentration and At higher temperatures the conductivity becomes approximately proportional to the product of both concentrations. A simple theory, based on the currently accepted model of impurity conduction, is given for the higher temperature range. It accounts well for the observed frequency and concentration dependences. However, only order-of-magnitude absolute agreement is obtained.

Low-Frequency Conductivity Due to Hopping Processes in Silicon

As discovered by Ohtomo and Hwang, a large sheet charge density with high mobility exists at the interface between SrTiO3 and LaAlO3. Based on transport, spectroscopic, and oxygen-annealing experiments, we conclude that extrinsic defects in the form of oxygen vacancies introduced by the pulsed laser deposition process used by all researchers to date to make these samples is the source of the large carrier densities. Annealing experiments show a limiting carrier density. We also present a model that explains the high mobility based on carrier redistribution due to an increased dielectric constant.

/pdf/origin-of-charge-density-at-laalo3-on-srtio3-1kkpmwsk4o.pdf

Origin of Charge Density at LaAlO3 on SrTiO3 Heterointerfaces: Possibility of Intrinsic Doping

We describe a new calorimeter for measuring heat capacity in the range 1–35 K, using a silicon chip bolometer as sample holder, temperature sensor, and sample heater. The apparatus is capable of measuring very small samples (1–500 mg), and may be used with a number of different experimental methods.

Heat Capacity Measurements on Small Samples at Low Temperatures

Superconductivity in Graphitic Compounds

The Seebeck effect has been measured from liquid hydrogen temperatures into the intrinsic range for a series of single-crystal silicon samples in which varying concentrations of donor and acceptor atoms have been incorporated. Large values of Seebeck voltage believed to be caused by the type of phonon-electron coupling previously postulated as occurring in germanium have been found. This effect is found to be dependent upon charge carrier concentration, and upon sample dimension below 100\ifmmode^\circ\else\textdegree\fi{}K. A low-temperature reversal of the sign of the Seebeck voltage is observed for large carrier concentrations. It is understandable in terms of impurity band conduction. The behavior above room temperature into the intrinsic range is found to be consistent with electrical conductivity data.

Theodore H. Geballe

Papers

Low-Frequency Conductivity Due to Hopping Processes in Silicon

Origin of Charge Density at LaAlO3 on SrTiO3 Heterointerfaces: Possibility of Intrinsic Doping

Heat Capacity Measurements on Small Samples at Low Temperatures

Superconductivity in Graphitic Compounds

Seebeck Effect in Silicon