Moscow State UniversityMoscow
Moscow State UniversityMoscow
Cabaret J.,University of Maine, France |
Bequin P.,University of Maine, France |
Theocharis G.,University of Maine, France |
Andreev V.,Moscow State UniversityMoscow |
And 2 more authors.
Physical Review Letters | Year: 2015
We theoretically study and experimentally report the propagation of nonlinear hysteretic torsional pulses in a vertical granular chain made of cm-scale, self-hanged magnetic beads. As predicted by contact mechanics, the torsional coupling between two beads is found to be nonlinear hysteretic. This results in a nonlinear pulse distortion essentially different from the distortion predicted by classical nonlinearities and in a complex dynamic response depending on the history of the wave particle angular velocity. Both are consistent with the predictions of purely hysteretic nonlinear elasticity and the Preisach-Mayergoyz hysteresis model, providing the opportunity to study the phenomenon of nonlinear dynamic hysteresis in the absence of other types of material nonlinearities. The proposed configuration reveals a plethora of interesting phenomena including giant amplitude-dependent attenuation, short-term memory, as well as dispersive properties. Thus, it could find interesting applications in nonlinear wave control devices such as strong amplitude-dependent filters. © 2015 American Physical Society.
Reznikov A.N.,Samara State Technical University |
Sibiryakova A.E.,Samara State Technical University |
Rybakov V.B.,Moscow State UniversityMoscow |
Klimochkin Y.N.,Samara State Technical University
Tetrahedron Asymmetry | Year: 2015
Transition metal catalyzed asymmetric Michael additions of dimethyl (2-oxo-2-phenylethyl)phosphonate to a variety of aromatic nitroalkenes have been developed. The effects of ligand structure, metal ions, and solvent on the reaction are described. Ni(II)-bis[(1R,2R)-N,N′-dibenzylcyclohexane-1,2-diamine]Br2 was found to be an effective catalyst for this reaction. The corresponding adducts were obtained in the presence of this complex in good yields and with excellent enantioselectivity (up to 99% ee). The absolute configurations of the reaction products were determined by X-ray diffraction. © 2015 Elsevier Ltd.
Maxwell A.D.,University of Washington |
Cunitz B.W.,University of Washington |
Kreider W.,University of Washington |
Sapozhnikov O.A.,University of Washington |
And 5 more authors.
Journal of Urology | Year: 2015
Purpose We developed a new method of lithotripsy that uses short, broadly focused bursts of ultrasound rather than shock waves to fragment stones. We investigated the characteristics of stone comminution by burst wave lithotripsy in vitro. Materials and Methods Artificial and natural stones (mean ± SD size 8.2 ± 3.0 mm, range 5 to 15) were treated with ultrasound bursts using a focused transducer in a water bath. Stones were exposed to bursts with focal pressure amplitude of 6.5 MPa or less at a 200 Hz burst repetition rate until completely fragmented. Ultrasound frequencies of 170, 285 and 800 kHz were applied using 3 transducers, respectively. Time to fragmentation for each stone type was recorded and fragment size distribution was measured by sieving. Results Stones exposed to ultrasound bursts were fragmented at focal pressure amplitudes of 2.8 MPa or greater at 170 kHz. Fractures appeared along the stone surface, resulting in fragments that separated at the surface nearest to the transducer until the stone was disintegrated. All natural and artificial stones were fragmented at the highest focal pressure of 6.5 MPa with a mean treatment duration of 36 seconds for uric acid stones to 14.7 minutes for cystine stones. At a frequency of 170 kHz the largest artificial stone fragments were less than 4 mm. Exposure at 285 and 800 kHz produced only fragments less than 2 mm and less than 1 mm, respectively. Conclusions Stone comminution with burst wave lithotripsy is feasible as a potential noninvasive treatment method for nephrolithiasis. Adjusting the fundamental ultrasound frequency allows for stone fragment size to be controlled. © 2015 American Urological Association Education and Research, Inc.
Abramovich A.I.,Moscow State UniversityMoscow |
Lanshina L.V.,Moscow State UniversityMoscow
Russian Journal of Physical Chemistry A | Year: 2015
Abstract The curve of the concentration dependence of the total molecular light scattering coefficient of xC3H7OH-(1 - x)H2O solutions showed two sharp maxima (at x = 0.04 and 0.09) and a minimum at x = 0.06 mole fractions, suggesting a considerable rearrangement of the structure of the solutions near these concentrations. The concentration dependences of excess molar volume, adiabatic compressibility, and molar refraction showed negative deviations from the ideal with a minimum in the range x = 0.18-0.3. The structure of water was assumed to undergo a rearrangement at x = 0.04 accompanied by structural fluctuations, which dispersed at 0.04 < x < 0.06. At x = 0.06, associates of isopropanol molecules started to form, whose number and size increased linearly up to x = 0.13. In the 0.13 < x < 0.35 concentration range, some kind of an aqueous alcohol emulsion containing pure alcohol "nanodrops" formed and the solutions became microheterogeneous. © 2015 Pleiades Publishing, Ltd.
Kuklin S.,Moscow State UniversityMoscow |
Maximov A.,RAS Topchiev Institute of Petrochemical Synthesis |
Zolotukhina A.,Moscow State UniversityMoscow |
Karakhanov E.,Moscow State UniversityMoscow
Catalysis Communications | Year: 2016
The effect of cyclodextrins on the activity and selectivity of a catalytic system based on rhodium nanoparticles stabilized by polyacrylic acid (PAA) in the hydrogenation of phenol in aqueous solution and ionic liquid was reported. It was found that the reaction medium and the nature of the cyclodextrin (CD) essentially affect the rate of reaction and the distribution of reaction products. The use of the system based on rhodium nanoparticles stabilized by cyclodextrins makes it possible to rapidly and efficiently prepare cyclohexanone from phenol with yields up to 100% under relatively mild conditions (1 h; T = 80°°C, p(H2) = 10-40 bars). © 2015 Elsevier B.V.
Nenashev R.N.,Moscow State UniversityMoscow |
Mordvinova N.E.,Moscow State UniversityMoscow |
Zlomanov V.P.,Moscow State UniversityMoscow |
Kuznetsov V.L.,Moscow State UniversityMoscow
Inorganic Materials | Year: 2015
Abstract Using thermogravimetry, differential scanning calorimetry, X-ray diffraction, mass spectrometry, and Fourier transform IR spectroscopy, we have determined the composition of VO(acac)2 thermal decomposition products and gained insight into the bond breaking sequence in this compound. A two-step annealing procedure has been proposed to ensure control over VO(acac)2 to VO2 conversion processes without changing the oxidation state of vanadium in the preparation of VO2 films by a sol-gel process. © 2015 Pleiades Publishing, Ltd.
Rybakov A.A.,Moscow State UniversityMoscow |
Larin A.V.,Moscow State UniversityMoscow
Molecular Physics | Year: 2016
Microstructure factor (MF) is one of the most important properties of hydrogenated silicon (HS) used in industry. It is expressed via vibrational intensities of low stretching modes (LSM) of Si–H and high stretching modes (HSM) of SiH2/SiH3 bonds, i.e. MF = IHSM/(ILSM + IHSM). Mixed character of HSM due to Si–H contributions (together with SiH2/SiH3 ones) is confirmed by vibrational analysis of Si–H valence bonds in a 120Si:18H model of amorphous HS at the Perdew-Burke-Ernzerhof (PBE)/projector augmented wave (PAW)level. Comparison with precedent solutions for di- and poly-vacancies in microcrystalline HS shows that the redistribution of its Si–H modes between HSM and LSM bands depends on the extent of perturbation of the vacancies. This relation between the HSM/LSM repartition and HS distortion explains possible MF dependence from short or medium range ordering and its link with crystallisation kinetics. © 2016 Informa UK Limited, trading as Taylor & Francis Group.
Kondratiev N.M.,Moscow State UniversityMoscow |
Braginsky V.B.,Moscow State UniversityMoscow |
Vyatchanin S.P.,Moscow State UniversityMoscow |
Gorodetsky M.L.,Moscow State UniversityMoscow
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015
Core optics components for high-precision measurements are made of stable materials, having small optical and mechanical dissipation. The natural choice in many cases is glass, in particular fused silica. Glass is a solid amorphous state of material that could not become a crystal due to high viscosity. However, thermodynamically or externally activated stimulated local processes of spontaneous crystallization (known as devitrification) are still possible. Being random, these processes can produce an additional noise, and influence the performance of such experiments as laser gravitational wave detection. © 2015 American Physical Society.
Verbetsky V.N.,Moscow State UniversityMoscow |
Lushnikov S.A.,Moscow State UniversityMoscow |
Movlaev E.A.,Moscow State UniversityMoscow
Inorganic Materials | Year: 2015
The interaction of the V0.95 Cu0.05, V0.94 Co0.06 , and V0.9 W0.1 alloys with hydrogen has been studied at hydrogen pressures of up to 250 MPa. We have constructed hydrogen absorption/desorption isotherms at different temperatures and determined the thermodynamic parameters of the systems. According to X-ray diffraction data, the high-pressure hydride phases V0.94 Co0.06 H1.4 and V0.9 W0.1 H1.2 consist of a face-centered cubic phase similar in structure to the γ-phase of vanadium dihydride. In the case of the vanadium-copper alloy, the maximum composition of the hydride is V0.95Cu0.05H0.5.
Korchagina E.V.,University of Montréal |
Philippova O.E.,Moscow State UniversityMoscow
Macromolecules | Year: 2015
The effect of two monovalent salts differing in the anions (sodium acetate and sodium chloride) on intermolecular aggregation of fully protonated hydrophobically modified (HM) chitosan in dilute aqueous solutions was studied by light scattering. It was demonstrated that both salts promote the aggregation of similarly charged macromolecules. At the same time, strong ion specificity is observed: acetate ions induce the growth of the aggregates, whereas chloride ions increase the fraction of aggregated chains. The behavior observed was attributed to different mechanisms of interactions of these ions with HM chitosan. Acetate ions possessing higher affinity to chitosan involving electrostatic and hydrophobic interactions as well as hydrogen bonding screen more effectively the electrostatic repulsion between polycationic chains, which allows accommodating more macromolecules within one aggregate. On the other hand, more compact chloride ions seem to promote the formation of crystalline zones within the aggregates, thereby increasing the association energy in the system. This provides a higher fraction of associated chains, whereas keeping a small aggregation number, because large amount of macromolecules in one aggregate can hinder sterically a proper mutual arrangement of the chains necessary for the formation of crystallites. © 2015 American Chemical Society.