General statement of the problem of substance analysis by the products of photochemical reactions

The aim of this study was to formulate the problem and develop a formal procedure for structure determination and substance quantification by the products of its photochemical reaction. This problem appears in studies of rapid photochemical processes, when the lifetime of the initial substance is shorter than the time to the moment of its registration (ecology, toxic substances, etc.). Algorithms of solving corresponding inverse problems are considered, and procedure including several steps is proposed. It includes the determination of the composition and concentrations of mixture components by the spectra of a test substance using the theory of molecular spectra; the recovery of the quantitative composition of the initial substance by the structural formulae of the products of a chemical reaction; and the determination of the initial concentrations of substances and the kinetics of the process on the basis of the developed theory of chemical transformations using information on the reactants and their concentrations. The application of the proposed approach is demonstrated on examples.     

Low‐Temperature FT‐NIR Spectroscopy of Strain‐Induced Orientation and Crystallization in a Poly(dimethylsiloxane) Network

Summary: The mechanical properties, morphology, and orientation of a poly(dimethylsiloxane) (PDMS) network have been studied during cyclic elongation and recovery by simultaneous Fourier‐transform near‐infrared polarization spectroscopy at temperatures ranging from room temperature to −40 °C. Completely different orientation/recovery mechanisms and changes in the state of order of PDMS were detected as a consequence of cyclic loading/unloading with decreasing temperature. The differences observed at −20 °C compared to room temperature are explained in terms of conformationally regular chain segments, whereas the cooling to −40 °C leads to the formation of lamellar crystals.

Stress/strain diagrams of the elongation/recovery‐cycles of the PDMS films.     

Hemicarceplexes That Release Guests upon Irradiation

Cleavage of one of the four bridging units in the two new types of hemicarceplexes presented here is sufficient to effect immediate guest release into the chloroform solvent (shown schematically on the right). The thermal stability and photoactivity of these hemicarceplexes indicate that incarceration is potentially useful for the controlled delivery of drugs.     

IR Spectra of Carbynoid Films Prepared by Dehydrofluorination of Polyvinylidene Fluoride

IR and X-ray photoelectron spectra of the products of chemical carbonization of polyvinylidene fluoride were recorded and discussed.     

Effectiveness of Space-Division Multiple-Access in MIMO Communication Systems with Parallel Data Transmission

We consider multiple-input multiple-output (MIMO) cellular communication systems with antenna arrays at both link ends and data transmission via parallel eigenchannels matched with a random spatial channel. We analyze the effectiveness of the space-division multiple-access (SDMA) method, which does not require estimation of signal-arrival directions and is based on orthogonalization of the parallel channels of all users. We obtained approximate analytical expressions for the mean ratio of the signal power to the noise power and the MIMO system capacity, which are derived for the case of Rayleigh fading of signals. Although the obtained formulas are much simpler than the exact ones, they ensure high accuracy for an arbitrary number of transmitting and receiving antennas and an arbitrary power of transmitter. Our results demonstrate the high effectiveness of the proposed SDMA method.