New conserved quantities of Noether--Mei symmetry of mechanical system in phase space

This paper studies two new types of conserved quantities deduced by Noether Mei symmetry of mechanical system in phase space. The definition and criterion of Noether Mei symmetry for the system are given. A coordination function is introduced, and the conditions under which the Noether- Mei symmetry leads to the two types of conserved quantities and the forms of the two types of conserved quantities are obtained. An illustrative example is given. The coordination function can be selected according to the demand for finding the gauge function, and the choice of the coordination function has multiformity, so more conserved quantities deduced from Noether Mei symmetry of mechanical system can be obtained.     

A new type of conserved quantity of Mei symmetry for relativistic nonholonomic mechanical system in phase space

In this paper, a new type of conserved quantity induced directly from the Mei symmetry for a relativistic nonholonomic mechanical system in phase space is studied. The definition and the criterion of the Mei symmetry for the system are given. The conditions for the existence and form of the new conserved quantity are obtained. Finally, an example is given to illustrate the application of the result.     

Enhanced cooling of a V-type three-level atom in an optical cavity

We have studied theoretically and numerically the enhanced cooling of a V-type three-level atom in a high-finesse optical cavity and shown that the cooling rate can be increased by one order of magnitude over that of a two-level atom, and the momentum amplitude tends to a stationary state much smaller than that of a two-level atom. We have further shown that the cooling rate can be significantly improved by using feedback and a time-dependent pump.     

Relations between compositional modulation and atomic ordering degree in thin films of ternary III—V semiconductor alloys

This paper derives the expressions for the ordering degree and the modulation factor of A and B atoms in A_xB_1-xC epilayers of ternary III--V semiconductor alloys. Using these expressions, it identifies quantitatively the alternating atom-enhanced planes, compositional modulations, atomic ordering degree on the group-III sublattices and the fine structure of NMR spectra.     

Application of multi-phase particle swarm optimization technique to retrieve the particle size distribution

The multi-phase particle swarm optimization (MPPSO) technique is applied to retrieve the particle size distribution (PSD) under dependent model.Based on the Mie theory and the Lambert-Beer theory, three PSDs, i.e., the Rosin-Rammer (R-R) distribution, the normal distribution, and the logarithmic normal distribution, are estimated by MPPSO algorithm.The results confirm the potential of the proposed approach and show its effectiveness.It may provide a new technique to improve the accuracy and reliability of the PSD inverse calculation.     

Electrically induced microflows probed by Fluorescence Correlation Spectroscopy

We report on the experimental characterisation of electrically induced flows at the micrometer scale through Fluorescence Correlation Spectroscopy (FCS) measurements. We stress the potential of FCS as a useful characterisation technique in microfluidics devices for transport properties cartography. The experimental results obtained in a model situation are in agreement with previous calculations (F. Nadal, F. Argoul, P. Kestener, B. Pouligny, C. Ybert, A. Ajdari, Eur. Phys. J. E 9, 387 (2002)) predicting the structure and electric-field dependency of the induced flow. Additionally, the present study evidences a complex behaviour of the probe nanobeads under electric field whose precise understanding might prove relevant for situations where nano-objects interact with an external electric field.     

Transport and recombination in organic light-emitting diodes studied by electrically detected magnetic resonance

We have used electrically detected magnetic resonance (EDMR) to study a series of multilayer organic devices based on aluminum (III) 8-hydroxyquinoline (Alq₃). These devices were designed to identify the microscopic origin of different spin-dependent processes, i.e. hopping and exciton formation. The EDMR signal in organic light-emitting diodes (OLEDs) based on Alq₃ is only observed when the device is electroluminescent and is assigned to spin-dependent exciton formation. It can be decomposed in at least two Gaussians: one with peak-to-peak line ( ΔH_PP) of 1.6 mT and another with ΔH_PP of 2.0 to 3.4 mT, depending on bias and temperature. The g-factors of the two components are barely distinguishable and close to 2.003. The broad line is attributed to the resonance in Alq₃ anions, while the other line is attributed to cationic states. These attributions are supported by line shape and its electrical-field dependence of unipolar Alq₃-based diodes, where hopping process related to dication and dianion formation is observed. In these unipolar devices, it is shown that the signal coming from spin-dependent hopping occurs close to organic semiconductor/metal interfaces. The sign of the magnetic-resonance-induced conductivity change is dominated by charge injection rather than charge mobility. Our results indicate that the probability of singlet exciton formation in our OLEDs is smaller than 25%.     

A new method of discovering new meteor showers from the IMO single-station video meteor database

It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization (IMO) by assuming the geocentric velocity and adjusting it within the dynamically permitted range. The mean geocentric velocities of new meteor showers can be obtained, as well as the coordinates of the radiants. The activity period and maximum time can also be obtained if there are sufficient shower meteors. All single station video meteor observations between February 13 and 17 (from 2000 to 2005) in IMO’s database are processed with this method. As a result, two new meteor showers, one near RA=245.10°, Dec=41.82° in Hercules and the other near RA=233.03°, Dec=17.04° in Serpenids, are discovered. Some dynamical characteristics of the new meteor showers are also determined. Considering the random nature on the selection of period in this work, it is expected that there are some more potential new meteor showers in IMO’s video database. Supported by the National Natural Science Foundation of China (Grant No. 10373004)     

Optically-Pumped Far-Infrared Laser Lines of Methanol Isotopomers: 12CH3OH, 12CH3OD, and 12CH2DOH

Twenty-seven new far-infrared laser lines from the isotopomers of methanol: ¹²CD₃OH, ¹²CH₃OD, and ¹²CH₂DOH, were obtained by optically-pumping the molecules with an efficient cw CO₂ laser. The CO₂ laser provided pumping from regular, sequence, and hot-band CO₂ laser transitions. The 2-m long far-infrared cavity was a metal-dielectric waveguide closed by two, flat end mirrors. Several short-wavelength (below 100 m) lines were observed. The frequencies of 28 laser lines observed in this cavity (including new lines and already known lines) were measured with a fractional uncertainty limited by the fractional resetability of the far-infrared laser cavity, of 2 parts in 10⁷.     

Lasing action of active-particles dispersed in microdroplets and its enhanced characteristics by highly scattering intralipid-10% mixture

The first laser action of active-particles of 1–2 m in diameter, red fluorescent-powder (FP), dispersed in nonactive (nonlasing) 100 m-sized liquid microdroplets is reported. Lasing characteristics of FP-containing microdroplets by mixing Intralipid-10% as highly scattering turbid media are also described. Well-defined lasing thresholds can be confirmed from the FP-dispersed pure microdroplets, and lowered lasing threshold along with enhanced lasing emission is achieved by appropriately mixing the Intralipid-10% solution. Lasing threshold in these microdroplets can be determined not through the spectral narrowing features but through the input–output data. We believe that these new microdroplet configurations offer one of the new categories of lasing media and they seem also to simulate to some biological pigments or organelles contained in cells and small tissues.