Kinetic features of the low-temperature oxidation of propane

The results from recording the chemiluminescence in the infrared part of the spectrum that emerges during the oxidation of propane in air under the effect of monotonically increasing pressure within the range 2666 Pa ?? P ?? 16000 Pa, both under isothermal conditions and in the 593?C600 K temperature range, are presented. It is established that no pulsed chemiluminescence is observed at constant values of pressure within the range 2666 Pa ?? P ?? 16000 Pa and temperature within the range of 593?C600 K in the reaction mixture.     

Sequence and linker dependent chiral dimerization of DNA–porphyrin conjugates

Circular dichroism (CD), UV–vis absorption, fluorescence, and resonance light scattering (RLS) spectroscopies were used to elucidate the role of the DNA sequence, linkers between DNA and porphyrin, and metal in the porphyrin coordination center on the self-assembly of DNA–porphyrin conjugates. A series of eight non-self-complementary DNA–porphyrin conjugates have been synthesized with zinc and free-base porphyrins covalently attached to the short ODNs (A₈ or T₈) via amide or phosphate linker. A small structural modification (e.g., amide linker replaced by the phosphate linker) showed a dramatic effect on the aggregation properties of DNA–porphyrin conjugates and greatly altered their spectroscopic properties. At low ionic strength, porphyrin aggregation was not observed for any conjugate. An increase in the ionic strength caused two out of eight conjugates to form chiral porphyrin dimers.     

Identifying and reducing error in cluster‐expansion approximations of protein energies

Protein design involves searching a vast space for sequences that are compatible with a defined structure. This can pose significant computational challenges. Cluster expansion is a technique that can accelerate the evaluation of protein energies by generating a simple functional relationship between sequence and energy. The method consists of several steps. First, for a given protein structure, a training set of sequences with known energies is generated. Next, this training set is used to expand energy as a function of clusters consisting of single residues, residue pairs, and higher order terms, if required. The accuracy of the sequence‐based expansion is monitored and improved using cross‐validation testing and iterative inclusion of additional clusters. As a trade‐off for evaluation speed, the cluster‐expansion approximation causes prediction errors, which can be reduced by including more training sequences, including higher order terms in the expansion, and/or reducing the sequence space described by thecluster expansion. This article analyzes the sources of error and introduces a method whereby accuracy can be improved by judiciously reducing the described sequence space. The method is applied to describe the sequence–stability relationship for several protein structures: coiled‐coil dimers and trimers, a PDZ domain, and T4 lysozyme as examples with computationally derived energies, and SH3 domains in amphiphysin‐1 and endophilin‐1 as examples where the expanded pseudo‐energies are obtained from experiments. Our open‐source software package Cluster Expansion Version 1.0 allows users to expand their own energy function of interest and thereby apply cluster expansion to custom problems in protein design. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010     

Hyperfine Paschen-Back regime realized in Rb nanocell

A simple and efficient scheme based on a one-dimensional nanometric-thin cell filled with Rb and strong permanent ring magnets allows direct observation of the hyperfine Paschen-Back regime on the D(1) line in the 0.5-0.7 T magnetic field. Experimental results are perfectly consistent with the theory. In particular, with σ(+) laser excitation, the slopes of the B-field dependence of frequency shifts for all 10 individual transitions of (85,87)Rb are the same and equal to 18.6 MHz/mT. Possible applications for magnetometry with submicron spatial resolution and tunable atomic frequency references are discussed.     

Cooperative Lamb shift in an atomic vapor layer of nanometer thickness

We present an experimental measurement of the cooperative Lamb shift and the Lorentz shift using a nanothickness atomic vapor layer with tunable thickness and atomic density. The cooperative Lamb shift arises due to the exchange of virtual photons between identical atoms. The interference between the forward and backward propagating virtual fields is confirmed by the thickness dependence of the shift, which has a spatial frequency equal to twice that of the optical field. The demonstration of cooperative interactions in an easily scalable system opens the door to a new domain for nonlinear optics.     

Quantum statistical effects in nuclear reactions,fission, and open quantum systems

Quantum diffusion equations with time-dependent transport coefficients are derived from generalized non-Markovian Langevin equations. Generalized fluctuation-dissipation relations and analytical formulas for calculating friction and diffusion coefficients in nuclear processes are obtained. The asymptotics of the transport coefficients and of the correlation functions are investigated. The problem of correlation decay in quantum dissipative systems is studied. A comparative analysis of diffusion coefficients for the harmonic and inverted oscillators is performed. The role of quantum statistical effects during passage through a parabolic potential barrier is investigated. Sets of diffusion coefficient assuring the purity of states at any time instant are found in cases of non-Markovian dynamics. The influence of different sets of transport coefficients on the rate of decay from a metastable state is studied in the framework of the master equation for reduced density matrices describing open quantum systems. The approach developed is applied to investigation of fission processes and the processes of projectile-nuclei capture by target nuclei for bombarding energies in the vicinity of the Coulomb barrier. The influence of dissipation and fluctuation on these processes is taken into account in a self-consistent way. The evaporation residue cross sections for asymmetric fusion reactions are calculated from the derived capture probabilities averaged over all orientations of the deformed projectile and target nuclei.     

Covering with universally Baire operators

We introduce a covering conjecture and show that it holds below A_DR+“Θ is regular”$A{D}_{\mathbb{R}}+\text{“}\Theta \text{is regular”}$. We then use it to show that in the presence of mild large cardinal axioms, PFA   implies that there is a transitive model containing the reals and ordinals and satisfying A_DR+“Θ is regular”$A{D}_{\mathbb{R}}+\text{“}\Theta \text{is regular”}$. The method used to prove the Main Theorem of this paper is the core model induction. The paper contains the first application of the core model induction that goes significantly beyond the region of AD⁺+_θ0<Θ$A{D}^{+}+{\theta }_0<\Theta$.     

Metal-containing polymer coatings based on poly(2-aminothiazole)

Polymer film based on 2-aminothiazole has been prepared at the surface of glassy carbon electrode via electropolymerization. The film has been modified via electrodeposition of rhodium particles. Hydrogen reduction has been observed at the so prepared composite films. Rhodium nanoparticles have been found uniformly distributed within the polymer matrix. Amount of the deposited metal depends on time of the electrode keeping in the rhodium salt solution. The prepared composite metal-polymers are highly heatresistant.     

Features of faraday rotation in cs atomic vapor in a cell thinner than the wavelength of light

Features of the effect of Faraday rotation (the rotation of the radiation polarization plane) in a magnetic field of the D ₁ line in Cs atomic vapor in a nanocell with the thickness L varying in the range of 80–900 nm have been analyzed. The key parameter is the ratio L/λ, where λ = 895 nm is the wavelength of laser radiation resonant with the D ₁ line. The comparison of the parameters for two selected thicknesses L = λ and λ/2 has revealed an unusual behavior of the Faraday rotation signal: the spectrum of the Faraday rotation signal at L = λ/2 = 448 nm is several times narrower than the spectrum of the signal at L = λ, whereas its amplitude is larger by a factor of about 3. These differences become more dramatic with an increase in the power of the laser: the amplitude of the Faraday rotation signal at L = λ/2 increases, whereas the amplitude of the signal at L = λ almost vanishes. Such dependences on L are absent in centimeter-length cells. They are inherent only in nanocells. In spite of a small thickness, L = 448 nm, the Faraday rotation signal is certainly detected at magnetic fields ≥0.4 G, which ensures its application. At thicknesses L < 150 nm, the Faraday rotation signal exhibits “redshift,” which is manifestation of the van der Waals effect. The developed theoretical model describes the experiment well.