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

This paper reviews recent experimental and theoretical progress concerning many-body phenomena in dilute, ultracold gases. It focuses on effects beyond standard weak-coupling descriptions, such as the Mott-Hubbard transition in optical lattices, strongly interacting gases in one and two dimensions, or lowest-Landau-level physics in quasi-two-dimensional gases in fast rotation. Strong correlations in fermionic gases are discussed in optical lattices or near-Feshbach resonances in the BCS-BEC crossover.

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Many-Body Physics with Ultracold Gases

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

Summary form only given. We report on an experiment performed with a gaseous Bose-Einstein condensate, which is analogous to the rotating bucket experiment performed with liquid He. The atoms are confined in a static, cylindrically symmetric Ioffe-Pritchard magnetic trap upon which we superimpose a nonaxisymmetric, attractive dipole potential created by a stirring laser beam. The combined potential leads to a cigar-shaped harmonic trap with a slightly anisotropic transverse profile. The transverse anisotropy is rotated as the gas is evaporatively cooled to Bose-Einstein condensation, and it plays the role of the bucket wall roughness. Pictures taken at various rotation frequencies, after a ballistic expansion of the condensate, clearly show that for fast enough rotation frequencies, we can generate one or several "holes" in the transverse density distribution corresponding to vortices. We discuss our determination of the critical frequency for the single and multiple vortex formation, and we report measurements of the nucleation time and the lifetime of the vortex state.

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Vortex formation in a stirred Bose-Einstein condensate

Coherent light sources have been widely used in control schemes that exploit quantum interference effects to direct the outcome of photochemical processes. The adaptive shaping of laser pulses is a particularly powerful tool in this context: experimental output as feedback in an iterative learning loop refines the applied laser field to render it best suited to constraints set by the experimenter. This approach has been experimentally implemented to control a variety of processes, but the extent to which coherent excitation can also be used to direct the dynamics of complex molecular systems in a condensed-phase environment remains unclear. Here we report feedback-optimized coherent control over the energy-flow pathways in the light-harvesting antenna complex LH2 from Rhodopseudomonas acidophila, a photosynthetic purple bacterium. We show that phases imprinted by the light field mediate the branching ratio of energy transfer between intra- and intermolecular channels in the complex's donor acceptor system. This result illustrates that molecular complexity need not prevent coherent control, which can thus be extended to probe and affect biological functions.

Quantum control of energy flow in light harvesting.

Research efforts in the past two decades have resulted in thousands of potential application areas for nanoparticles - which materials have become industrially relevant? Where are sustainable applications of nanoparticles replacing traditional processing and materials? This tutorial review starts with a brief analysis on what makes nanoparticles attractive to chemical product design. The article highlights established industrial applications of nanoparticles and then moves to rapidly emerging applications in the chemical industry and discusses future research directions. Contributions from large companies, academia and high-tech start-ups are used to elucidate where academic nanoparticle research has revolutionized industry practice. A nanomaterial-focused analysis discusses new trends, such as particles with an identity, and the influence of modern instrument advances in the development of novel industrial products.

Industrial applications of nanoparticles

The tissue distribution and toxicity of intravenously administered nanoparticles of titanium dioxide (TiO2) (>10 wt.% at <100 nm size) were investigated because of the fundamental importance to obtain information on the kinetics of this widely used nanoparticle in a situation of 100% bioavailability. Male Wistar rats were treated with single intravenous injections of a suspension of TiO2 in serum (5 mg/kg body weight), and the tissue content of TiO2 was determined 1, 14, and 28 days later. Biochemical parameters and antigens in serum were also assessed to determine potential pathological changes. The health and behavior of the animals were normal throughout the study. There were no detectable levels of TiO2 in blood cells, plasma, brain, or lymph nodes. The TiO2 levels were highest in the liver, followed in decreasing order by the levels in the spleen, lung, and kidney, and highest on day 1 in all organs. TiO2 levels were retained in the liver for 28 days, there was a slight decrease in TiO2 levels from day 1 to days 14 and 28 in the spleen, and a return to control levels by day 14 in the lung and kidney. There were no changes in the cytokines and enzymes measured in blood samples, indicating that there was no detectable inflammatory response or organ toxicity. Overall, rats exposed to TiO2 nanoparticles by a route that allows immediate systemic availability showed expected tissue distribution, no obvious toxic health effects, no immune response, and no change in organ function. Therefore, even with 100% bioavailability of the 5 mg/kg TiO2 dose afforded by the intravenous route of administration, there were no remarkable toxic effects evident in the experimental animals. These results indicate that TiO2 nanoparticles could be used safely in low doses.

Tissue distribution and toxicity of intravenously administered titanium dioxide nanoparticles in rats.

Nanomaterials can display distinct biological effects compared with bulk materials of the same chemical composition. The physico-chemical characterization of nanomaterials and their interaction with biological media are essential for reliable studies and are reviewed here with a focus on widely used metal oxide and carbon nanomaterials. Available rat inhalation and cell culture studies compared to original results suggest that hazard potential is not determined by a single physico-chemical property but instead depends on a combination of material properties. Reactive oxygen species generation, fiber shape, size, solubility and crystalline phase are known indicators of nanomaterials biological impact. According to these properties the summarized hazard potential decreases in the order multi-walled carbon nanotubes >> CeO(2), ZnO > TiO(2) > functionalized SiO(2) > SiO(2), ZrO(2), carbon black. Enhanced understanding of biophysical properties and cellular effects results in improved testing strategies and enables the selection and production of safe materials.

Wendel Wohlleben

Papers

Vortex formation in a stirred Bose-Einstein condensate

Quantum control of energy flow in light harvesting.

Industrial applications of nanoparticles

Tissue distribution and toxicity of intravenously administered titanium dioxide nanoparticles in rats.

Testing metal-oxide nanomaterials for human safety.