Ion-beam erosion of carbon fibers of the composites

The results of experimental studies of the structural and morphological changes of the surface of carbon PAN fibers of a carbon-carbon KUP-VM (1D) composite as a result of high-dose irradiation (10¹⁸–10¹⁹ ion/cm²) with Ne⁺ and Ar⁺ ions with an energy of 10–30 keV are presented. The threshold values of radiation damage, resulting in an amorphization of the PAN carbon fibers at room temperature and ion-induced crimping at temperatures greater than the annealing temperature of the radiation damage, are determined.     

Modified Eulerian–Lagrangian formulation for hydrodynamic modeling

We present the modified Eulerian–Lagrangian (MEL) formulation, based on non-divergent forms of partial differential balance equations, for simulating transport of extensive quantities in a porous medium. Hydrodynamic derivatives are written in terms of modified velocities for particles propagating phase and component quantities along their respective paths. The particles physically interpreted velocities also address the heterogeneity of the matrix and fluid properties. The MEL formulation is also implemented to parabolic Partial Differential Equations (PDE’s) as these are shown to be interchangeable with equivalent PDE’s having hyperbolic – parabolic characteristics, without violating the same physical concepts. We prove that the MEL schemes provide a convergent and monotone approximation also to PDE’s with discontinuous coefficients. An extension to the Peclet number is presented that also accounts for advective dominant PDE’s with no reference to the fluid velocity or even when this velocity is not introduced.In Sorek et al. [27], a mathematical analysis for a linear system of coupled PDE’s and an example of nonlinear PDE’s, proved that the finite difference MEL, unlike an Eulerian scheme, guaranties the absence of spurious oscillations. Currently, we present notions of monotone interpolation associated with the MEL particle tracking procedure and prove the convergence of the MEL schemes to the original balance equation also for discontinuous coefficients on the basis of difference schemes approximating PDE’s. We provide numerical examples, also with highly random fields of permeabilities and/or dispersivities, suggesting that the MEL scheme produces resolutions that are more consistent with the physical phenomenon in comparison to the Eulerian and the Eulerian–Lagrangian (EL) schemes.     

Substantiation of the mechanism of biphoton nonresonance excitation of molecules of bacteriochlorophyll of purple bacteria by femtosecond pulses

In a series of published experimental works, there has been observed nonresonance biphoton excitation, by femtosecond IR pulses (1250–1500 nm) of molecules of bacteriochlorophyll-a and the pigment in the composition of light-absorbing natural “antenna” complexes of photosynthesizing purple bacteria. The authors of these works believe that IR quanta excite hypothetical forbidden levels of pigments of these bacteria in the dual frequency range of 625–750 nm. In this study, an alternative mechanism of intramolecular electron transport apparently responsible for this phenomenon is suggested and substantiated. The mechanism should manifest itself in powerful electric fields, which are achieved in the pulses of picofemtosecond lasers.     

Electret-thermal and dielectric analyses of electrically active colloids

The nature and mechanism of interfacial electrical interaction in organic colloids containing an active solid phase and a polar liquid phase are studied. Such systems are shown to offer specific properties. Specifically, high electrical forces producing gradients of the potential of the self-electric internal field arise at the liquid-solid interface. In the presence of free charges and ionic conductivity channels, this field can induce currents in such systems. When investigating the colloid system of the human venous blood, it is found that the internal field causes mesoscopic inhomogeneity in the structure of the aqueous components of the plasma and cytoplasm. It is shown that the concentration of free water molecules in the liquid phase of the system is maximal in group I blood and the physically nonuniform properties of combined water show up to the greatest extent in group IV blood. This finding is corroborated by the dispersion of the dielectric polarization in blood of different groups.     

Polar cycloaddition of 2-pyridinetellurium trichloride to multiple bonds

A reaction of 2-pyridinetellurium trichloride with unsaturated hydrocarbons leads to [1,3]tellurazolo[3,2-a]pyridinium-4 derivatives — the products of polar cycloaddition of tellurium-containing electrophile at the multiple bond.     

Synthesis of oligoorganosilsesquioxanes via acidohydrolytic polycondensation

Methyl acrylate oligosilsesquioxanes based on γ-methacryloxypropyltrimethoxysilane and its mixtures with phenyltrimethoxysilane have been synthesized through acidohydrolytic polycondensation and studied via NMR spectroscopy and MALDI-TOF mass spectrometry. It is shown that the addition of the aforementioned oligosilsesquioxanes to a dental composition based on 2,2-bis[p-(3-metacryloyloxy-2-hydroxypropoxy)phenyl]propane and triethylene glycol dimethacrylate improves the mechanical characteristics of cured polymer composites.     

The well-defined bootstrap effect in the macroinitiator-mediated pseudoliving radical copolymerization of styrene and acrylic acid

The bootstrap effect is observed in the pseudoliving radical copolymerization of styrene and acrylic acid mediated by a macroinitiator: the adduct of poly(acrylic acid) with a nitroxide radical. In this case, the macroinitiator serves as a peculiar “microreactor” with an increased local concentration of acrylic acid; as a result, the apparent activity of acrylic acid is higher than that in copolymerization mediated by low-molecular-mass initiators.     

Physicochemical and adsorption properties of hypercross‐linked polystyrene with ultimate cross‐linking density

The paper describes unexpected properties of hypercross‐linked polystyrenes with ultimate cross‐linking degrees of 300, 400, and 500%, where three, four, or five methylene links, respectively, could bind each polystyrene phenyl ring to its spacious neighbors. The polymers exhibit a strong electron spin resonance signal, unusual spectra in IR, UV, and visible ranges, and they are not typical dielectrics. The nonfunctionalized hypercross‐linked polymers absorb significant amounts of inorganic acids, salts, and bases due to interactions of protons or other cations with electron‐donating fragments of the aromatic network with the high extent of mutual connectivity and also due to dispersion interactions of anions with the polymer matrix.     

Temperature dependences of the ion-electron emission of glassy carbons under 30-keV argon ion irradiation

The temperature dependences (?200°C < T ≤ 350°C) of the ion-induced electron emission yield γ and the structures of modified surface layers have been studied experimentally for SU-850, SU-1000, SU-1300, SU-2000, and SU-2500 glassy carbons under high-dose 30-keV Ar⁺ and N ₂ ⁺ ion irradiation. Glassy carbons manufactured using a relatively high heat-treatment temperature T _ht exhibit a stepwise increase in the electron yield at certain annealing temperatures T _a. The same behavior is observed for graphitized carbon materials. For low-temperature glassy carbons, the electron yield exhibits a monotonic increase with increasing irradiation temperature. The observed differences are related to the occurrence of different structural types of fullerene-like nanoparticles in the low-and high-temperature glassy carbons.