Picosecond emission anisotropy decays of dimethyl aminobenzonitrile

Picosecond polarized fluorescence experiments on DMABN (4-(dimethyl amino) benzonitrile) in polar solvents and toluene are reported. From the detected polarized fluorescence components emission anisotropy histograms are constructed and compared with the synthetic data simulated for the energy levels scheme in DMABN. For the short-wavelength emission of DMABN vibronic coupling between the close-lying S₁ and S₂ energy levels occurs and leads to a vibronically mixed polarization of the S₁ (F_B) fluorescence. Low initial values of the emission anisotropy decays for the long-wavelength (F_A) emission are observed. This observation can be explained by an assumption that the internal twisting of the amino group in DMABN changes the angular orientation of DMABN and by an assumption that the emission dipole moment in the F_A emission band is not parallel to the absorption dipole moment in the S₂ (¹L_a) absorption band.     

Asset Pricing Using Finite State Markov Chain Stochastic Discount Functions

This article fuses two pieces of theory to make a tractable model for asset pricing. The first is the theory of asset pricing using a stochastic discounting function (SDF). This will be reviewed. The second is to model uncertainty in an economy using a Markov chain. Using the semi-martingale dynamics for the chain these models can be calibrated and asset valuations derived. Interest rate models, stock price models, futures pricing, exchange rates can all be introduced endogenously in this framework.     

Nonlinear Filter Estimation of Volatility

A discrete time nonlinear filter is used to estimate the volatility in a financial model. New filters are derived for sums of unobserved quantities and the EM algorithm applied to determine the parameters of the model.     

On the direct determination of metals in lubricating oils by ICP

New equipment and procedures are evaluated for the direct analysis of metals in lubricating oils without the need for sample pretreatment or dilution. A modified Babington principle nebulizer equipped with a sample heater is shown to be capable of producing aerosols from undiluted oils, which are suitable for introduction into an inductively coupled plasma atomic emission spectrophotometer. Heating the samples immediately prior to nebulization greatly increases the output of aerosol and reduces output variations in emission intensity due to differences in oil manufacture and viscosity. The type of organometallic complex used in the preparation of standards is shown to be unimportant if the plasma observation region is properly chosen. Performance of a conventional plasma geometry and an inverted torch geometry on analysis of field collected oil samples is presented.     

The effect of signal duration on the underwater detection thresholds of a harbor porpoise (Phocoena phocoena) for single frequency-modulated tonal signals between 0.25 and 160 kHz

The underwater hearing sensitivity of a young male harbor porpoise for tonal signals of various signal durations was quantified by using a behavioral psychophysical technique. The animal was trained to respond only when it detected an acoustic signal. Fifty percent detection thresholds were obtained for tonal signals (15 frequencies between 0.25-160 kHz, durations 0.5-5000 ms depending on the frequency; 134 frequency-duration combinations in total). Detection thresholds were quantified by varying signal amplitude by the 1-up 1-down staircase method. The hearing thresholds increased when the signal duration fell below the time constant of integration. The time constants, derived from an exponential model of integration [Plomp and Bouman, J. Acoust. Soc. Am. 31, 749-758 (1959)], varied from 629 ms at 2 kHz to 39 ms at 64 kHz. The integration times of the porpoises were similar to those of other mammals including humans, even though the porpoise is a marine mammal and a hearing specialist. The results enable more accurate estimations of the distances at which porpoises can detect short-duration environmental tonal signals. The audiogram thresholds presented by Kastelein et al. [J. Acoust. Soc. Am. 112, 334-344 (2002)], after correction for the frequency bandwidth of the FM signals, are similar to the results of the present study for signals of 1500 ms duration. Harbor porpoise hearing is more sensitive between 2 and 10 kHz, and less sensitive above 10 kHz, than formerly believed.     

The hearing threshold of a harbor porpoise (Phocoena phocoena) for impulsive sounds (L)

The distance at which harbor porpoises can hear underwater detonation sounds is unknown, but depends, among other factors, on the hearing threshold of the species for impulsive sounds. Therefore, the underwater hearing threshold of a young harbor porpoise for an impulsive sound, designed to mimic a detonation pulse, was quantified by using a psychophysical technique. The synthetic exponential pulse with a 5?ms time constant was produced and transmitted by an underwater projector in a pool. The resulting underwater sound, though modified by the response of the projection system and by the pool, exhibited the characteristic features of detonation sounds: A zero to peak sound pressure level of at least 30?dB (re 1?s(-1)) higher than the sound exposure level, and a short duration (34?ms). The animal's 50% detection threshold for this impulsive sound occurred at a received unweighted broadband sound exposure level of 60?dB re 1?μPa(2)s. It is shown that the porpoise's audiogram for short-duration tonal signals [Kastelein et al., J. Acoust. Soc. Am. 128, 3211-3222 (2010)] can be used to estimate its hearing threshold for impulsive sounds.     

Standardisation of a European measurement method for the determination of mercury in deposition: results of the field trial campaign and determination of a measurement uncertainty and working range

A standard method for the measurement of mercury in deposition is currently being finalised by Working Group 25 of the European Committee for Standardisation’s Technical Committee 264 ‘Air Quality’, in response to the requirements of the European Union’s Fourth Air Quality Daughter Directive. This paper reports the results of a field measurement programme which was undertaken to assess the uncertainty of the proposed standard method, define its working range and determine its compliance with the required data quality objectives of the Fourth Air Quality Daughter Directive.     

Electronic Spectra and Fluorescence Polarization Kinetics of Thin Zn-Porphyrin Films

The photophysical properties of thin films of Zn-monopyridyltriphenylporphyrin (Zn(4-Py)TrPP) obtained by the method of centrifugation on a quartz film substrate have been investigated. The results of the analysis of the measured excitation and luminescence spectra and also of the kinetic curves of fluorescence depolarization, as they decay, of the Zn(4-Py)TrPP films permit the conclusion that Zn-meso-monopyridylporphyrins self-organize into aggregates. The symmetric closed tetramer ([Zn(4-Py)TrPP]₄) seems to be the most probable aggregate of Zn-meso-monopyridylporphyrins.