Spectroscopic studies into the influence of UV radiation on elastin hydrolysates in water solution

An investigation into the influence of UV irradiation on elastin hydrolysates dissolved in water was carried out using UV-Vis spectroscopy and spectrofluorometry. It was found that the absorption of elastin hydrolysates in solution increased during irradiation of the sample. For fluorescence of elastin hydrolysates we observed both, a decrease and increase of this value during irradiation of the sample. After UV irradiation of the elastin solution we observed a minor increase of overall absorption, most notably between 250 nm and 280 nm. Moreover, after UV irradiation a wide peak emerged between 290 nm and 310 nm with maximum at about 305 nm. The new peak suggests that new photoproducts are formed during UV irradiation of elastin hydrolysates. The fluorescence of elastin hydrolysates was observed at 305 nm and at 380 nm after excitation at 270 nm. UV irradiation caused fluorescence fading at 305 nm and 380 nm. After 30 min of irradiation a new broad weak band of fluorescence, attributable to new photoproducts, emerged in the UV wavelength region with emission maximum between 400 nm and 500 nm.     

Application of the genetic algorithms to data modeling in the case of fluorescence spectroscopy

The genetic algorithms (GAs) are applied to extract the values of parameters that describe the behavior of the asymmetric rotorlike fluorescence probes embedded in the uniaxially ordered system. The capabilities of the GA are enhanced by an application of a simple first order derivative search for the values of the multiplicative factors at each stage of the evolutionary run. The convergence is improved by the help of a gradient-expansion search performed after the GA is done. The potentiality of this approach demonstrates an example concerning the synthetic data set. The text was submitted by the authors in English.     

The NMR reciprocity theorem for arbitrary probe geometry

It is shown that the NMR reciprocity theorem is a variant of a problem considered by Lorentz in 1895. This formulation is quite general and applies to electric-dipole-based as well as coil-based or resonator-based magnetic resonance probes. The reasoning is related to, but different from, the proof of the reciprocity theorem for radiofrequency networks and for transmit/receive antenna systems in telecommunications. The signal-to-noise ratio of the NMR experiment is also discussed in very general terms.     

Another look at magic-angle-detected fluorescence and emission anisotropy decays in fluorescence microscopy

It is shown that in contrast to a traditional fluorescence spectroscopy with the parallel beams of light, in which the kinetic fluorescence decays are collected at the so-called magic-angle of thetamag=54.7 degrees, in the fluorescence microscopy, the value of the magic-angle depends on the numerical aperture (NA) of a microscope objective and on the refractive index (n) of an immersion liquid used. Two methods enabling the determination of the magic-angle values corresponding to different values of NA/n, are discussed. It is shown that thetamag changes from a value of 54.7 degrees at the NA/n-->0, to a value of 45 degrees with NA/n-->1. Also in contrast to a traditional fluorescence spectroscopy, in the fluorescence microscopy the term I parallel(t)+2I perpendicular (t) does not represent the total fluorescence intensity Itot(t), because the resulting fluorescence decay I parallel(t)+2I perpendicular (t) is contributed by the dynamic evolution of excited fluorophores. A correctly defined total fluorescence intensity solely represents the kinetic evolution of excited fluorophores, and in the fluorescence microscopy it equals Itot(t)=3Imag(t), where Imag(t) represents the fluorescence intensity detected at thetamag corresponding to a particular NA/n value. If the correct (true) decay of Itot(t) is substituted into the denominator in the expression for the emission anisotropy r(t), r(t) is a (multi)exponential function of time and it accounts for the high-aperture excitation-detection conditions.     

Fluorescence of N,N′-dimethylaminobenzonitrile in polyvinyl alcohol stretched films

We have demonstrated that the conditions of the charge-transfer (CT) reaction in the N,N′-dimethylaminobenzonitrile (DMABN) molecule in polyvinyl alcohol (PVA) polymer matrices can be considerably changed upon their stretching deformation. The fluorescence spectrum of DMABN in PVA has two characteristic bands in the ultraviolet (UV) and visible spectral ranges, which indicates that a CT reaction proceeds in the excited state. Stretching leads to a strong decrease in the intensity of the UV band, the contribution of which in undeformed samples is comparable with the emission in the violet range. Even single stretching PVA films strongly reduces the emission intensity of the UV band, with this effect being dramatically enhanced upon sixfold stretching. In the latter case, The fluorescence spectrum is characterized by a strong CT band, the relative intensity of which is 3.5 times higher than even in a strongly polar aprotic solvent, such as acetonitrile. The obtained data indicate that, as a result of mechanical stretching, it becomes possible to change basic intermolecular factors that affect the CT rate in PVA samples.     

A condition for absolute continuity of infinitely divisible distribution functions

Summary Throughout this paper the symbols r.v., d.f., ch.f., and i.d. will stand, respectively, for random variable, distribution function, characteristic function, and infinitely divisible.Let F(x) be an i.d.d.f. Hartman and Wintner [5] and Blum and Rosenblatt [1] have given a condition, necessary and sufficient, for F(x) to be a continuous d.f. In this note a sufficient condition for F(x) to be an absolutely continuous d.f. is given.Research supported by ONR Contract No. NONR-285(46).Research supported in part by a National Science Foundation fellowship.