Interfacial waves with free-surface boundary conditions: an approach via a model equation

In a two-fluid system where the lower fluid is bounded below by a rigid bottom and the upper fluid is bounded above by a free surface, two kinds of solitary waves can propagate along the interface and the free surface: classical solitary waves characterized by a solitary pulse or generalized solitary waves with nondecaying oscillations in their tails in addition to the solitary pulse. The classical solitary waves move faster than the generalized solitary waves. The origin of the nonlocal solitary waves can be understood from a physical point of view. The dispersion relation for the above system shows that short waves can propagate at the same speed as a “slow” solitary wave. The interaction between the solitary wave and the short waves creates a nonlocal solitary wave. In this paper, the interfacial-wave problem is reduced to a system of ordinary differential equations by using a classical perturbation method, which takes into consideration the possible resonance between short waves and “slow” solitary waves. In the past, classical Korteweg–de Vries type models have been derived but cannot deal with the resonance. All solutions of the new system of model equations, including classical as well as generalized solitary waves, are constructed. The domain of validity of the model is discussed as well. It is also shown that fronts connecting two conjugate states cannot occur for “fast” waves. For “slow” waves, fronts exist but they have ripples in their tails.     

Theory of electron transfer reactions in blue-copper proteins

The rates of electron transfer reactions in azurin and plastocyanin are calculated with the Intersecting-State Model and compared with experimental data. The calculated distance, free-energy and temperature dependencies of the intraprotein rates in Ru-modified azurins are in good agreement with the experiment. These calculations do not require the fitting of any parameters. Significant tunneling contributions to the room temperature rate are found in some systems. In some cases the symmetry or the orientation of the donor and acceptor orbitals are not favorable and the ET rates are reduced by factors exceeding 4 orders of magnitude.     

Factorial analysis of a chemiluminescence system for bromate detection in water

A chemiluminescent flow system for bromate detection, based on the reaction of bromate with sulphite in acid medium and using the steroid hydrocortisone as sensitiser, was studied. A factorial analysis strategy for the study of the effect on the system response of the experimental factors, flow rates of two pumps (Q₁ — acid sulphite plus hydrocortisone aqueous solution; Q₂ — carrier, water), sample injection volume (V_L), reactor volume (V_R), sulphite concentration (C_S), hydrocortisone concentration (C_H) and acid concentration (C_A), was used. Screening analysis of the system performance was made using Plackett Burman designs. The system optimisation procedure was achieved by three levels three factors full factorial designs. V_L and C_H are the most significant factors — a quadratic C_H term was also observed to be significant. The optimised system responded linearly (logarithm of the detector signal as function of the logarithm of the bromate concentration) in the concentration range between 3.6×10⁻⁷ and 5.0×10⁻⁴ M with a limit of detection of about 8.0×10⁻⁸ M (about 10 microg/l). An analysis of some interfering ions was made and it was suggested that bromide and chloride begin to quench chemiluminescence when they are in a 10-fold excess relatively to bromate concentration.     

Synthesis of 4‐hydroxyquinolin‐2(1H)‐one analogues and 2‐substituted quinolone derivatives

A versatile synthetic method for preparing 4‐hydroxyquinolone and 2‐substituted quinolone compounds from simple benzoic acid derivatives was demonstrated. The synthetic strategies involve the use of well known ethyl acetoacetate synthesis, malonic ester synthesis and reductive cyclization. The key intermediates were keto esters 4a‐e , which could be transformed to 4‐hydroxyquinolones 5a,b or 2‐substituted quinolone ethyl esters 6a‐c depending on the reaction conditions. 4‐Hydroxyquinolone analogues were prepared and investigated for N‐methyl‐D‐aspartate (NMDA) activity in vitro. Among these derivatives, 6,7‐difluoro‐3‐nitro‐4‐hydroxyquinolin‐2(1H)‐one ( 9 ) exhibited moderate activity.     

Computation, Properties and Resonance Topology of Benzenoid Monoradicals and Polyradicals and the Eigenvectors Belonging to Their Zero Eigenvalues

Radical benzenoid structures, i.e., those which cannot have all electrons paired, are known to possess much larger structure counts than closed-shell benzenoids of similar size. Building on our previous work, we report methods for calculating eigenvectors, eigenvalues, and structure counts for benzenoid radicals, diradicals, and radicals of higher multiplicity. When a series of such species is constructed by repeated addition of an aufbau unit, structure counts can usually be expressed as a polynomial in one or two variables. Structure counts for radical series generated by repeated circumscribing, however, cannot.     

Radiometrie study of the adsorption of TcO 4 - on hematite

The adsorption of TCO ₄ ^- on hematite powder is studied as a model system to demonstrate usefulness of the application of the so called radiotracer foil method for the investigation of sorption phenomena occurring at powdered oxides. It is shown that the character of the pH dependence of the adsorption and the role of the nature and concentration of supporting electrolyte in the sorption can be easily demonstrated and the problems connected with the reversibility of the processes can be easily solved. It is demonstrated that the addition of acids to the TCO ₄ ^- (H₂O)/hematite system results in two opposite tendencies: an increase in the adsorption owing to the surface protonation and a decrease due to the adsorption competition of anions. The sign of the result depends on the absolute and relative concentration of the supporting electrolyte and the species added to the solution phase. Dedicated to the ninetieth anniversary of Ya.M. Kolotyrkin’s birth. Submitted in English.     

[13C]Dynamic NMR and Molecular Modeling of 2,4-Bis(N-Pyrrolidinyl)-6-chloro-s-triazine

The room temperature [¹³C]NMR spectrum of 2,4-bis(N-pyrrolidinyl)-6-chloro-s-triazine shows doubled signals for the pyrrolidine rings, which suggests restricted rotation about the Ar-C—N bond. The rotational barrier around this bond was determined by [¹³C]dynamic NMR (DNMR) spectra run at different increasing temperatures and also by the PM3 Hamiltonian contained in the MOPAC package. The values thus obtained, 16.6 and 13.6 kcal mol^–1, respectively, are in good agreement.     

catena‐Poly­[fac‐tri­chloro­methyl­tin(IV)‐μ‐[meso‐1,2‐bis­(phenyl­sulfinyl)­ethane‐O:O′]]

In the title compound, [SnCl₃(CH₃)(C₆H₅SOCH₂)₂]_n, the octahedral Sn^IV centres are bridged by meso‐1,2‐bis­(phenyl­sulfinyl)­ethane ligands forming infinite chains along the [100] direction.     

Use of the hole-drilling method for measuring residual stresses in highly stressed shot-peened surfaces

The same shot-peening treatment was applied to five steels with different mechanical properties. The induced residual stress profiles were analyzed using X-ray diffraction and incremental hole drilling (IHD). The results of both techniques showed that IHD can still be successfully used for measuring shot-peening residual stresses, even if these exceed the yield strength of the bulk material. Expected errors due to the plasticity effect are reduced by the strain hardening of the surface. For an assessment of the reliability of IHD data, strain-hardening variation was quantified by microhardness measurements to estimate the yield strength of the plastified layer. All the main calculation methods for IHD were applied. The results were compared and discussed with respect to the characteristics of each method.     

N-demethylation of methylene blue by lignin peroxidase from Phanerochaete chrysosporium

Applied Biochemistry and Biotechnology - Phanerochaete chrysosporium lignin peroxidase (LiP) can degrade synthetic dyes such as heterocyclic, azo, and triphenylmethane on its activation by H2O2....