On the wavelength dependence of picosecond relaxation in crystal violet

The depopulation-repopulation kinetics of ground-state crystal violet in glycerol at room temperature has been investigated. A D₂O generated picosecond continuum served as a probe source and a 530 nm single pulse as an excitation source. The repopulation rate varies with probe wavelength; this dependence is ascribed to the presence of two rotamers of crystal violet.     

Use of a Luenberger observer to control the numerator and denominator of a transfer function

It is shown that a Luenberger observer may be used to convert a transfer function having a numerator of degree m and a denominator of degree n (with m?n?1) into one having a numerator of degree n+m?1 and a denominator of degree 2n?1, with the denominator polynomial and n?1 of the numerator coefficients assignable arbitrarily.     

Uniqueness of the “nonsingular core” for Hermitian and other matrix pencils

Every pencil of hermitian matrices is conjunctive with a pencil of the form L ⊕ M, where L (the "minimal-indices" part) has no elementary divisors and M (the "nonsingular core") is a nonsingular pencil. Here it is shown that the conjunctivity type ofM is determined by that of L ⊕ M. The same method of proof applies to many other types of pencils, e.g. to congruence of pencils based on (1) a pair of symmetric matrices, (2) a pair of alternating matrices, or (3) a symmetric and an alternating matrix.     

UV photopatterning of a highly metallized, cluster-containing poly(ferrocenylsilane)

Thin films of a cobalt-clusterized poly(ferrocenylsilane) have been shown to behave as a negative-tone resist for UV photolithography, allowing access to feature sizes between 20 and 300 microm. Pyrolysis of the patterned polymer at 900 degrees C under a N(2) atmosphere afforded patterned ferromagnetic ceramics with excellent shape retention.     

Atomistic study of dislocation loop emission from a crack tip

We report the first atomistic calculation of the saddle-point configuration and activation energy for the nucleation of a 3D dislocation loop from a stressed crack tip in single crystal Cu. The transition state is found using reaction pathway sampling schemes, the nudged elastic band, and dimer methods. For the (111)[110] crack, loaded typically at 75% of the athermal critical strain energy release rate for spontaneous dislocation nucleation, the calculated activation energy is 1.1 eV, significantly higher than the continuum estimate. Implications concerning homogeneous dislocation nucleation in the presence of a crack-tip stress field are discussed.     

Blind identification of multichannel FIR systems based on linearprediction

A blind identification algorithm for multichannel FIR systems is proposed. In the approach, the identification of each channel is decoupled, and channel responses are estimated separately without having to solve for the augmented channel responses. The algorithm can be implemented using linear prediction techniques. It is computationally efficient and suitable for real-time applications. Computer simulations are used to demonstrate the effectiveness of the proposed algorithm     

Likelihood Inferences for High-Dimensional Factor Analysis of Time Series With Applications in Finance

This article investigates likelihood inferences for high-dimensional factor analysis of time series data. We develop a matrix decomposition technique to obtain expressions of the likelihood functions and its derivatives. With such expressions, the traditional delta method that relies heavily on score function and Hessian matrix can be extended to high-dimensional cases. We establish asymptotic theories, including consistency and asymptotic normality. Moreover, fast computational algorithms are developed for estimation. Applications to high-dimensional stock price data and portfolio analysis are discussed. The technical proofs of the asymptotic results and the computer codes are available online.     

Tunable light‐harvesting polymers containing embedded dipolar chromophores for polymer solar cell applications

A series of light‐harvesting conjugated polymers were designed and synthesized for polymer solar cells. These newly designed polymers comprise an unusual two‐dimensional conjugated structure with an electron‐rich thiophene–triphenylamine backbone and stable planar indacenodithiophene π‐bridges terminated with tunable electron acceptors. It was found that the electron‐withdrawing strength of the acceptor could be used to manipulate the energy level of the lowest unoccupied molecular orbital and bandgap (as much as 0.3 eV), generating derivatives with complementary absorbance in the visible spectrum. This approach provides great flexibility in fine tuning the electronic and optical properties of the resultant polymers and facilitates the investigation of how these chemical modifications alter the subsequent photovoltaic properties of these materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Sensitized phosphorescence: a gas phase molecular mixing diagnostic

The use of sensitized phosphorescence for visualization of gas phase fluid mixing and the requirements for quantitative imaging measurements are discussed. A model for estimating the molecular-mixing signal's dependence on fluid composition is developed and candidate molecular reactants are considered within the framework of the model. Experiments based on sensitized phosphorescence from both an acetonebiacetyl system and a toluene-biacetyl system show good qualitative agreement with modeled results. It is concluded that quantitative measurements using sensitized phosphorescence are feasible.