The influence of wavelength in extinction measurements and beam steering in laser-induced incandescence measurements in sooting flames

The accuracy of laser-induced incandescence (LII) measurements is significantly influenced by the calibration process and the laser profile degradation due to beam steering. Additionally, the wavelength used for extinction measurements, needed for LII calibration, is critical and should be kept as high as possible in order to avoid light absorption by molecular species in the flame. The influence of beam steering on the LII measurement was studied in turbulent sooting C₂H₄/air flames at different pressures. While inhomogeneities in the laser profile become smoothed out in time-averaged measurements, especially at higher pressure, the corresponding single-shot beam profiles reveal an increasing effect of beam steering. In the current configuration it was observed that the resulting local laser fluence remains within certain limits (30% to 200%) of the original value. A sufficiently high incident laser fluence can thus prevent the local fluence from dropping below the LII threshold value of approximately 0.3 J/cm² at the cost of increased soot surface vaporization. A spatial resolution in the dimension of the sheet thickness of below 1 mm cannot be guaranteed at increased pressure of 9 bars due to beam steering. A feasibility study in a combustor at technical conditions demonstrates the influence of both effects beam steering and choice of calibration wavelength and led to the conclusion that, however, a shot-to-shot calibration of LII with simultaneously measured extinction can be realized.     

LIGHT REACTIONS OF THE CILIATE Stentor coeruleus-A THREE-DIMENSIONAL ANALYSIS

A computer-controlled three-dimensional tracking and motion analysis system was developed to study the responses of Stentor coeruleus to short light pulses and to evaluate its distribution patterns. In addition to photokinesis and phototaxis, the step-up photophobic response was analyzed, which includes a gravity-controlled component at higher fluence rates and a light direction-dependent component at lower fluence rates.     

PHOTORECEPTOR PROTEINS AND PIGMENTS IN THE PARAFLAGELLAR BODY OF THE FLAGELLATE Euglena gracilis

Abstract— –The presumed photoreceptor for phototaxis, the paraflagellar body, in the flagellate Euglena gracilis , was isolated still attached to the flagellum. After solubilization, fast protein liquid chromatography (FPLC) analysis yielded four major protein fractions with the chromophoric groups still attached. Fluorescence spectra showed that three fractions had excitation peaks at 380 nm and emission peaks around 450 nm indicative of pterins, while the fourth chromoprotein had a fluorescence emission at 520 nm and an excitation peak at 450 nm, indicative of a flavin. The separated proteins were analyzed by gel electrophoresis: the pterin binding proteins have apparent molecular masses between 27 000 and 31 600 and the flavin binding protein has an apparent molecular mass of 33 500.     

Fragment momentum distributions obtained from coupled electron-nuclear dynamics

We theoretically investigate fragmentation processes induced by femtosecond laser pulses within a model which incorporates electronic and nuclear motion. Single-pulse excitation leads to diffraction patterns in the electron momentum distribution which depend on the nature of the electronic state and also on the nuclear charge distribution. Additional structures appear in the nuclear momentum distribution if two time-delayed pulses produce fragments in the same dissociation channel. It is shown that these functions are modified by the electronic degree-of-freedom. A simultaneous excitation of two different electronic states results in further interferences which are related to electronic wave-packet dynamics on the attosecond time-scale.     

Microscopic simulation of semiconductor lasers at telecommunication wavelengths

We consider two GaAs-based laser materials emitting at telecommunication wavelengths, namely the dilute nitride (GaIn)(NAs) as well as Ga(AsSb), and model their optical properties by including scattering and dephasing on a microscopic basis. The theory shows an excellent agreement with experiment without the inclusion of fit parameters such as phenomenological scattering times. By careful comparison of measurements and computations, one can extract controversial bandstructure parameters such as the band offset.     

Universal Associative Envelopes of (n+ 1)-Dimensional n-Lie Algebras

For n even, we prove Pozhidaev's conjecture on the existence of associative enveloping algebras for simple n-Lie (Filippov) algebras. More generally, for n even and any (n + 1)-dimensional n-Lie algebra L, we construct a universal associative enveloping algebra U(L) and show that the natural map L → U(L) is injective. We use noncommutative Gröbner bases to present U(L) as a quotient of the free associative algebra on a basis of L and to obtain a monomial basis of U(L). In the last section, we provide computational evidence that the construction of U(L) is much more difficult for n odd.     

Thermal Equilibrium in Transient Forced Convection Porous Channel Flow

The validity of the local thermal equilibrium assumption in the transient forced convection channel flow is investigated numerically. Axial conduction in both fluid and solid domains is included. It is found that five dimensionless parameters control the local thermal equilibrium assumption. These parameters are the thermal diffusivity ratio _R, the volumetric Nusselt number Nu, the dimensionless channel length _max, Peclet number Pe, and the solid to fluid total thermal capacity ratio C _R. The qualitative and quantitative aspects of the effects of these five parameters on the channel thermalization time are investigated.     

Closed-loop design of a semiconductor laser

We provide what we believe is the first closed-loop prediction of a semiconductor laser performance using fully microscopic many-body models for the spontaneous emission, gain, and carrier recombination losses due to Auger processes without having to resort to phenomenological adjustable fit parameters.     

The Peirce decomposition for Jordan quadruple systems

We study the Peirce decomposition for a Jordan quadruple system with respect to a quadripotent and get the multiplication rules for the Peirce spaces.     

On Jordan quadruple systems with quadripotents

The purpose of this article is to show the link between Jordan quadruple systems with quadripotents and Jordan algebras. We also extend the notions of the orthogonality, primitivity, and minimality of tripotents in a Jordan triple system to that of quadripotents in a Jordan quadruple system. We refine the Peirce decomposition of a Jordan quadruple system with respect to a quadripotent to be with respect to a system of orthogonal quadripotents and get the multiplication rules of the Peirce spaces. We show that the notions of primitive and minimal quadripotents coincide in a Jordan quadruple system.