Quasilinear rate-type constitutive equations and incremental stress waves

The requirement that the leading edge of an incremental loading pulse superimposed on a preloading that has reached a constant state will propagate at the elastic wave speed imposes some restrictions on the material functions describing a quasilinear rate-type material. These restrictions are discussed, and it is shown that the incremental wave behavior implies the existence of at least one relaxation boundary, and that a natural continuous transition from the quasilinear equation to a semilinear equation occurs in the neighborhood of the relaxation boundary.How the knowledge of a relaxation boundary can be used in determining the material functions is also discussed.     

Quantum cascade laser-based sensor for detection of exhaled and biogenic nitric oxide

A real-time, in situ CO sensor using 2.3 μm DFB diode laser absorption, with calibration-free wavelength-modulation-spectroscopy, was demonstrated for continuous monitoring in the boiler exhaust of a pulverized-coal-fired power plant up to temperatures of 700 K. The sensor was similar to a design demonstrated earlier in laboratory conditions, now refined to accommodate the harsh conditions of utility boilers. Measurements were performed across a 3 m path in the particulate-laden economizer exhaust of the coal-fired boiler. A 0.6 ppm detection limit with 1 s averaging was estimated from the results of a continuous 7-h-long measurement with varied excess air levels. The measured CO concentration exhibited expected inverse trends with the excess O₂ concentration, which was varied between 1 and 3 %. Measured CO concentrations ranged between 6 and 200 ppm; evaluation of the data suggested a dynamic range from 6 to 10,000 ppm based on a minimum signal-to-noise ratio of ten and maximum absorbance of one. This field demonstration of a 2.3 μm laser absorption sensor for CO showed great potential for real-time combustion exhaust monitoring and control of practical combustion systems.     

Parameter motivated mutual correlation analysis: Application to the study of currency exchange rates based on intermittency parameter and Hurst exponent

We present a novel method for the parameter oriented analysis of mutual correlation between independent time series or between equivalent structures such as ordered data sets. The proposed method is based on the sliding window technique, defines a new type of correlation measure and can be applied to time series from all domains of science and technology, experimental or simulated. A specific parameter that can characterize the time series is computed for each window and a cross correlation analysis is carried out on the set of values obtained for the time series under investigation. We apply this method to the study of some currency daily exchange rates from the point of view of the Hurst exponent and the intermittency parameter. Interesting correlation relationships are revealed and a tentative crisis prediction is presented.     

Thin films of polymer mimics of cross-linking mussel adhesive proteins deposited by matrix assisted pulsed laser evaporation

Mussels secrete specialized adhesives known as mussel adhesive proteins, which allow attachment of the organisms to underwater marine environments. Obtaining large quantities of naturally derived mussel adhesive proteins adhesives has proven to date rather problematic, thus, synthetic analogs of mussel adhesive proteins have recently been developed. We report deposition of 1:100 and 1:1000 poly[(3,4-dihydroxystyrene)-co-styrene)] mussel adhesive protein analogs by matrix assisted pulsed laser evaporation (MAPLE) using an ArF* excimer laser source. The deposited films have been evaluated for their antifouling behavior. The MAPLE-deposited synthetic mussel adhesive protein analog thin films are homogenous and adhesive, making the use of these materials in thin film form a viable option.     

The dynamics of exchange rate time series and the chaos game

This work presents a novel method of reconstructing some relevant characteristics of exchange rate time series by the superposition of two components: a mostly deterministic one, the chaos game as expressed by the Yuan/USD exchange rate and a purely stochastic one, Gaussian white noise. We analyzed 20 economic systems with the average Index of Economic Freedom above 50. The considered characteristics (the Lempel-Ziv complexity index, the slimness of the distribution and the Iterated Function Systems clumpiness test) are well reproduced by the reconstruction process. Additional confirmation is obtained by an analysis of the exchange rate of the Romanian national currency as an example of an application of the method to a transition economy, and by an analysis of the time series of the Euro-zone as an example of an application to a multinational system using a shorter time series.     

Transform-Limited Pulses Are Not Optimal for Resonant Multiphoton Transitions

Maximizing nonlinear light-matter interactions is a primary motive for compressing laser pulses to achieve ultrashort transform limited pulses. Here we show how, by appropriately shaping the pulses, resonant multiphoton transitions can be enhanced significantly beyond the level achieved by maximizing the pulse's peak intensity. We demonstrate the counterintuitive nature of this effect with an experiment in a resonant two-photon absorption, in which, by selectively removing certain spectral bands, the peak intensity of the pulse is reduced by a factor of 40, yet the absorption rate is doubled. Furthermore, by suitably designing the spectral phase of the pulse, we increase the absorption rate by a factor of 7.