APPLICATION OF GENETIC ALGORITHM IN PARTICLE SIZE ANALYSIS BY MULTISPECTRAL EXTINCTION MEASUREMENTS

Both dependent and independent model algorithms are designed with genetic algorithm (GA) to retrieve aerosol size data from multispectral extinction measurements. Compared with the traditional dependent model algorithm, e.g., simplex, GA can locate the global optimized solution instead of local ones. As an independent model algonthm, when combined with B-splines, GA gives consistent results with Chahine and Phillip-Twomey-NNLS algorithms. Numerical simulations also show that GA has high stability and good resistance to relatively higher error levels. For a population size of 50 in the present paper, the feasible ranges for genetic operators Pc and pm are found to be [0.01, 0.5] and [0.01, 0.15], respectively, and the generation number Gen_Max should be larger than 250.     

Hopf Bifurcation from Rotating Waves and Patterns in Physical Space

Summary. Hopf bifurcations from time periodic rotating waves to two frequency tori have been studied for a number of years by a variety of authors including Rand and Renardy. Rotating waves are solutions to partial differential equations where time evolution is the same as spatial rotation. Thus rotating waves can exist mathematically only in problems that have at least \bf SO (2) symmetry. In this paper we study the effect on this Hopf bifurcation when the problem has more than \bf SO (2) symmetry. These effects manifest themselves in physical space and not in phase space. We use as motivating examples the experiments of Gorman et al . on porous plug burner flames, of Swinney et al . on the Taylor-Couette system, and of a variety of people on meandering spiral waves in the Belousov-Zhabotinsky reaction. In our analysis we recover and complete Rand's classification of modulated wavy vortices in the Taylor-Couette system. It is both curious and intriguing that the spatial manifestations of the two frequency motions in each of these experiments is different, and it is these differences that we seek to explain. In particular, we give a mathematical explanation of the differences between the nonuniform rotation of cellular flames in Gorman's experiments and the meandering of spiral waves in the Belousov-Zhabotinsky reaction. Our approach is based on the center bundle construction of Krupa with compact group actions and its extension to noncompact group actions by Sandstede, Scheel, and Wulff. Received January 20, 1998; revised December 1, 1998     

Efficient synthesis of an adenosine A2a agonist: glycosylation of 2-haloadenines and an N2-alkyl-6-chloroguanine

A convergent synthesis of adenosine A2a agonist 1 in the form of its maleate salt 2 was achieved. The key step in this approach was the highly selective 9beta-glycosylation reaction between 2-haloadenines or an N(2)-alkyl-6-chloroguanine and a D-ribose derivative containing a 2-ethyltetrazolyl moiety. Glycosylations of other purine derivatives were also examined, and the methods developed provide efficient access to a variety of adenosine analogues such as 2-alkylaminoadenosines, an attractive class of compounds with antiinflammatory activity.     

Density gradient stabilization of electron temperature gradient driven turbulence in a spherical tokamak

In this Letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k(⊥)ρ(s) ? 10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of 2 decrease in the plasma effective thermal diffusivity.     

Zero-Hopf bifurcation in the Van der Pol oscillator with delayed position and velocity feedback

In this paper, we consider the traditional Van der Pol oscillator with a forcing dependent on a delay in feedback. The delay is taken to be a nonlinear function of both position and velocity, which gives rise to many different types of bifurcations. In particular, we study the Zero-Hopf bifurcation that takes place at certain parameter values using methods of center manifold reduction of DDEs and normal form theory. We present numerical simulations that have been accurately predicted by the phase portraits in the Zero-Hopf bifurcation to confirm our numerical results and provide a physical understanding of the oscillator with the delay in feedback.     

Acoustic trapping as a generic non-contact incubation site for multiplex bead-based assays

In this study, we show a significantly reduced assay time and a greatly increased bead recovery for a commercial Luminex-based multiplex diagnostic immunoassay by performing all liquid handling steps of the assay protocol in a non-contact acoustic trapping platform.     

Mathematical efficiency calibration methods for high quality laboratory based gamma spectrometry systems

The efficiency calibration of laboratory based gamma spectrometry systems typically involves the purchase or construction of calibration samples that are supposed to represent the geometries of the unknown samples to be measured. For complete and correct calibrations, these sample containers must span the operational range of the system, which at times can include difficult configurations of size, density, matrix, and source distribution. The efficiency calibration of a system is dependent not only on the detector, but on the radiation attenuation factors in the detector–source configuration, and therefore is invalid unless all parameters of the sample assay condition are identical to the calibration condition. An alternative to source-based calibrations is to mathematically model the efficiency response of a given detector–sample configuration. In this approach, the measurement system is calibrated using physically accurate models whose parameters can generally be easily measured. Using modeled efficiencies, systems can be quickly adapted to changing sample containers and detector configurations. This paper explores the advantages of using mathematically computed efficiencies in place of traditional source-based measured efficiencies for laboratory samples, focusing specifically on the possibility of sample optimization for a given detector, uncertainty estimation, and cascade summing corrections.