Search

We report the influence of anisotropy and texture on elasto(ElCE)- and baro(BCE)-caloric effects in single-crystal and ceramic (NH4)2SO4. Inverse extensive and intensive ElCE in ceramics, (ΔSElCE)cer = 87 J/kg·K; ΔTAD = - 11.6 K), as well as in a single crystal along the ferroelectric axis a, (ΔSElCE)a = 115 J/kg·K; (ΔTAD)a = - 16 K, significantly exceed BCE, ΔSBCE = 75 J/kg·K; ΔTAD = - 9.8 K, even at low pressure ~ 0.3 GPa. Caloric parameters of ammonium sulphate are comparable with those for promising solid-state refrigerants.

In this study, the conventional and inverse barocaloric effects (BCE) in ferroelectric NH4HSO4 are reported. Maximum extensive and intensive BCE near order–disorder phase transition can be achieved at low pressure p ≤ 0.1 GPa. Large thermal expansion of the crystal lattice plays a very important role in the developing conventional BCE and conversation between BCE of different sign in the narrow temperature range.

Heat capacity, thermal dilatation, permittivity and sensitivity to external pressure of ( NH 4 ) 3 SiF 7 were studied. Due to the absence of cubic phases P m 3 ¯ m and P a 3 ¯ , a strong decrease in the total entropy change ∑ Δ S i = 19 J/mol K associated with four successive transformations P 4 / m b m ↔ P b a m ↔ P 2 1 / c 11 ↔ P 1 ¯ ↔ P 12 1 / c 1 was found in silicate in comparison with other double fluoride salts ( NH 4 ) 3 MeF 7 (Me: Ge, Ti, Sn) Using analysis of the excess heat capacity in the framework of the thermodynamic theory, the entropies associated with each individual phase transition were determined. In accordance with the entropic parameters, the complete ordering of the structural elements occurs in the monoclinic phase P 2 1 / c 11 . Further change in symmetry is associated with small entropy changes which prove insignificant displacement of structural units. A T − p phase diagram was constructed and good agreement was found between measured and calculated baric coefficients.

Optical and calorimetric experiments on K2TaF7 are performed in a wide temperature range. No features were found in the behavior of the birefringence Δnb(T), the angle of rotation of the indicatrix ϕ(T) and the heat capacity ΔCp(T) except for those associated with the Pnma↔P21/c phase transition. Structural transformation was characterized as strong first order “proper” ferroelastic accompanied by a huge angle ϕ ≈40° and strong pre-transition phenomena in Δnb(T). Two contributions to the anomalies of the optical properties were found associated with the photoelastic effect and the transition parameter related linearly to the spontaneous deformation. Thermal treatments cause correlated changes in temperature and enthalpy of the phase transition, which leads to the invariance of the large magnitude of the corresponding entropy ΔS = 22 J/mol·K which does not match the model with the absence of structural disorder in the Pnma phase.

We consider six-dimensional heavenly equation as a reduction in the framework of general six-dimensional linearly degenerate dispersionless hierarchy. We characterise the reduction in terms of wave functions, introduce generating relation, Lax-Sato equations and develop the dressing scheme for the reduced hierarchy. Using the dressing scheme, we construct a class of solutions for six-dimensional heavenly equation in terms of implicit functions., Comment: 10 pages

We synthesize a single-crystal Pb1-x-ySnxScyTe ingot and investigate the magnetic properties (2.0 ≤ T ≤ 300 K, B ≤ 3 T) of alloys cut from it (x = 0.045–0.175, y ≤ 0.04). At low temperatures, all samples exhibit paramagnetic contribution to the magnetization, which contradicts the generally accepted model of doping-induced rearrangement of the electronic structure of alloys and is most likely due to the paramagnetism of electrically neutral Sc2+ ions or their clusters. In p-type samples, a high-temperature ferromagnetic ordering with a Curie temperature as high as TC = 145–150 K is found, presumably due to the RKKY hole-mediated interaction of Sc2+ ions. We obtain dependences of the concentration of paramagnetic ions, of the paramagnetic Curie-Weiss temperature Θ and of the Curie temperature TC on the concentrations of scandium and tin. At temperatures T

Here we present the consecutive study of colloid systems formed by novel isatin derivative as compound with high pharmacological potential and series of carboxyresorcinarenes. The azo-modified isatin derivative bearing ammonium moiety (I-3) was synthesized and its antimicrobial activity was investigated. To increase its solubility the solubilization experiment using amphiphilic carboxyresorcinarenes, characterized by low hemolytic activity, was carried out. The I-3 – macrocycles systems were studied by NMR, UV–vis, DLS and TEM. The FT PGSE and 2D NOESY NMR methods demonstrated, that solubilization of I-3 is caused by the incorporation of its molecules in the hydrophobic part of the macrocycles associates. Herewith the loading efficiency of I-3 into the macrocycles associates was reached of 20–30% due to the change of the volume of hydrophobic part of associates by varying the length and structure of hydrophobic substituents of macrocyclic amphiphiles.

Photochemical stability and possible routes for photodegradation of twisted diarylnitroxides were determined. It was shown that quantum yields for twisted diarylnitroxides fall in the range typical for the best representatives of alkylnitroxides providing an additional support that twisting of the phenyl ring from the N-O conjugation plane constitutes an efficient route for increasing thermo and photo stability of the nitroxides.

The necessity of measuring the radioactivity of the 230Тh nuclide arises when attempting to solve a number of geochemical or geochronological problems based on the effects of radioactive disequilibrium in the 238U series. It is the authors' opinion that the use of the traditional α- and β-emitters of thorium as a radiotracer in order to determine the activity of 230Тh leads to various inconveniences and difficulties of a technical nature. The authors recommend using the 234Тh isotope contained in the study sample as the simplest and most natural way of measuring the chemical yield of the targeted nuclide (230Тh). A sequence of radio-analytical procedures is proposed that will provide a correct assessment of the radioactivity of 230Тh. In addition, a specific example and an evaluation of the accuracy of the proposed methodology are presented, using actual experimental data.

Single crystals of (NH 4 ) 3 HfF 7 were grown. Polarising optical observations as well as measurement of the heat capacity and birefringence Δn(Т) were performed in the temperature range of 200–310 K. Reversible phase transitions at temperatures T 0 = 290 K, Т 1 = 280.5 K, Т 2 ≈ 273 K, Т 3 = 266 K, Т 4 = 259 K, Т 5 = 231 K, Т 6 = 229 K were found. Observations in polarised light make it possible to suggest a sequence of changes in the symmetry groups for these transitions: F m 3 ¯ m ⟵Т 0 → cub. ⟵Т 1 → mmm (1) ⟵Т 2 → mmm (2) ⟵Т 3 → mmm (3) ⟵Т 5 → 2/c. The T-p phase diagram was studied and the temperature boundaries of the stability of the distorted crystalline phases were determined. A significant change of the entropy at successive phase transitions ΣΔS = 10.6 J/mol K indicates a disordering of the initial cubic phase.

Heat capacity, thermal dilatation, susceptibility to hydrostatic pressure and dielectric properties associated with succession of three phase transitions below room temperature in double fluoride salt (NH 4 ) 3 GeF 7 were studied. A possible transformation into the parent Pm -3 m cubic phase was not observed up to the decomposition of compound. Nonferroelectric nature of structural distortions was confirmed. The DTA under pressure studies revealed a high temperature stability of two phases: P 4 /mbm and Pbam . The entropies of the phase transitions agree well with the model of structural distortions. Analysis of the thermal properties associated with the individual phase transitions in the framework of thermodynamic equations has shown a high reliability of the data obtained.

We report the conventional and inverse barocaloric effect (BCE) in ferroelastics (NH4)3NbOF6 and (NH4)3TiOF5. We found a rich set of the structural phase transitions and triple points on the T − p phase diagrams. Extensive and intensive BCE near some transformations and around triple points in both crystals are outstanding (|∆ SBCEmax | = 30–100 J/kg·K; |∆ TADmax | = 4–22 K) and can be achieved at low pressure 0.01–0.60 GPa. PACS 62.50.-p 65.40.-b 81.30.-t

A study of heat capacity, thermal dilatation, permittivity, dielectric loops and susceptibility to hydrostatic pressure was carried out on quasi-ceramic samples of NH 4 HSO 4 obtained from an aqueous solution as well as the melt. The main parameters of the successive P 2 1 / c ( T 1 ) ↔ Pc ( T 2 ) ↔ P 1 phase transitions did not depend on the method of preparation of the samples, and were close to those determined in previous studies of single crystal and powder, except for the sign and magnitude of the baric coefficient for T 2 . Direct measurements of the pressure effect on the permittivity and thermal properties showed d T 2 /d p = −123 K·GPa −1 , which is consistent in terms of magnitude and sign with the baric coefficient evaluated using dilatometric and calorimetric data in the framework of the Clausius-Clapeyron equation. Thus, the temperature region of the ferroelectric Pc phase existence is extended under pressure. A strong decrease in the entropy jump at the Pc ↔ P 1 transformation with an increase in pressure, and the linear dependence of T 2 on pressure, indicate that an increase in pressure shifts this phase transition towards the tricritical point on the T – p phase diagram. A significant barocaloric effect was found in the region of the Pc ↔ P 1 phase transition.

A radiochemical analysis of the valence state of uranium isotopes in minerals involves isolation of the U(IV) and U(VI) valence forms and determination of the radioactivity of the 234U and 238U isotopes in each fraction. If the nuclear decay of the uranium in the minerals is accompanied by a redox process, the distribution of the 234U isotope in the U(IV) and U(VI) forms will differ from that of the 238U isotope: oxidation leads to enrichment of the U(VI) fraction with the radiogenic 234U isotope; reduction facilitates enrichment of the U(IV) fraction with 234U. If the mineral is heated to 600–700 °C before the radiochemical analysis, then an equilibrium activity ratio (AR) for both valences. The question arises: What are the processes that bring this about? The authors of this research studied changes of the AR in the U(IV) and U(VI) fractions after isochronous thermal annealing.

The first examples of phosphorus-containing analogues of natural alkaloids, convolutamydines, have been obtained by aldol condensation of 4-[dialkyl(diphenyl)phosphoryl]-4-methylpentan-2-one with isatin. An unusually facile reversible process of dehydration–hydration of these phosphorus-containing hydroxy indoles has been discovered.

X-ray, calorimetric and dilatometric studies of RbCdZrF7 revealed the existence of the second order phase transition Cmcm ↔ P21/m at T0 = 200 K. The structure of the initial and distorted phases is ordered. The phase transition is associated with displacements of fluorine atoms, which leads to minor rotations of the CdF7 and ZrF7 pentagonal bipyramids. A small change in entropy, 0.1R, is characteristic of displacive-type transformations. An anomalously high susceptibility of the transition temperature to hydrostatic pressure was found.

Experimental study of temperature-pressure phase diagrams revealed a slight difference in the sensitivity to hydrostatic pressure of triglycine sulfate (TGS) as a bulk (single crystal, ceramics), and nanoparticles embedded in porous glass (TGS + PG). An analysis of the pressure sensitivity, dT0/p and dT0/dσ, and entropies of the P21 ↔ P21/m phase transition showed the closeness of the barocaloric parameters in various materials under study. Due to the strong anisotropy of thermal expansion, the piezocaloric effect under pressure along the axis c exceeds the barocaloric effect in single-crystal TGS. The reasons for the strong reduction in the electrocaloric effect in the ferroelectric component of nanocomposites compared with a single-crystal are discussed.

Single crystals of (ND4)2MoO2F4 containing 95% deuterium were produced by repeated recrystallization of (NH4)2MoO2F4 in heavy water. The effect of deuteration on the parameters of successive phase transitions was investigated by differential scanning microcalorimetry and polarization optics. X-ray analysis of the original and distorted phases was performed. It was found that deuteration does not change the sequence of crystal phases typical for (NH4)2MoO2F4, but leads to a shift in the phase transition Cmcm → Pnma towards the tricritical point. The mechanism of phase transitions in (ND4)2MoO2F4 was associated with both the ordering and the displacement of atoms.

Текст статьи не публикуется в открытом доступе в соответствии с политикой журнала. Calorimetric, dilatometric and differential thermal analysis studies were performed on (NH4)3SnF7 for a wide range of temperatures and pressures. Large entropy (δS0 = 22 J/mol•K) and elastic deformation (δ(ΔV/V) 0 = 0.89%) jumps have proven that the Pa-3 ↔ Pm-3m phase transition is a strong first order structural transformation. A total entropy change of ΔS0 = 32.5 J/mol•K agrees well with the model associated with the complete ordering of structural units in the Pa-3 phase, which are disordered in the Pm-3m phase, and is equal to the sum of entropy changes in the related material, (NH4)3TiF7, undergoing transformation between the two cubic phases through the intermediate phases. Hydrostatic pressure decreases the stability of the high temperature Pm-3m phase in (NH4)3SnF7, contrary to (NH4)3TiF7, characterised by a negative baric coefficient. The effect of experimental conditions on the chemical stability of (NH4)3SnF7 was observed.

Heat capacity, thermal expansion, and sensitivity to the hydrostatic pressure of (NH4)2KZrF7 elpasolite are studied in a wide temperature range. The changes in deformation and entropy during successive phase transitions are determined: Δ(ΔV/V) = 3·10−4; ΔS = 8 J/mol K The temperatures and entropies of phase transitions turned out to be slightly sensitive to pressure changes. An analysis of the entropy of phase transformations was performed in the framework of the model of the cubic phase structure Fm-3 m. In the low temperature phase, an anomalous behavior of thermodynamic properties, which is not characteristic of phase transitions, was observed, accompanied by a significant change in the crystal lattice entropy.

Using the group method, single crystals of NdSc3(BO3)4 are grown from a melt solution and X-ray structural studies are performed. It is shown that at room temperature the NdSc3(BO3)4 crystal has a huntite-type structure with space group P3121. The temperature dependence of the heat capacity shows anomalous behaviour at Т = 504 ± 1 K. This anomaly corresponds to a structural phase transition from R32 to P3121. It is known that a similar transition occurs in RFe3(BO3)4 crystals; an anomaly in the specific heat is also observed. Theoretical calculations are carried out from the first principles of the lattice dynamics of the crystal under study in a high-symmetry phase with the R32 space group. An unstable (soft) mode in the boundary point of Brillouin zone was found. It was determined that this structural instability is responsible for the structural displacement-type phase transition R32 → P3121.

High sensitivity of electron paramagnetic resonance spectra of spiro-fused dinitroxide probe to dynamical and structural characteristics of the matrix was experimentally demonstrated. Geometrical parameters describing the relative position and orientation of nitroxide fragments of the biradical, as well as characteristics of dipolar and exchange interaction between the nitroxide moieties were determined from experimental spectra. Orientation order parameters of biradical dissolved in aligned smectic and supercooled smectic media determined by numerical simulation of the angular dependence of electron paramagnetic resonance spectrum show very high degree of orientation of the probe in the liquid-crystalline matrix.

A series of isatin derivatives were synthesized and studied by XRD. For the first time the peculiarities of the molecule structure and crystal packing effects were analyzed. Indoline heterocycles are planar in all the investigated structures. The molecules bearing the sterically hindered substituents at nitrogen atom of indoline heterocycle have the maximum deviations of two oxygen atoms from the indoline plane. The substituent nature at nitrogen atom does not effect on the bond lengths of indoline moiety. The value of endocyclic bond angle at nitrogen not so strongly depends on the substituent and is almost equal to the one in unsubstituted isatin. In contrast to the unsubstituted isatin, where the system of classical hydrogen N H⋯O-bonds is realized, in crystals of investigated compounds there is no opportunity to reveal ones, and the crystal structure is stabilized by C H⋯O- and π–π-interactions.

The reaction of diverse symmetrically-substituted isoindigo derivatives with 80% aqueous hydrazine hydrate is described. The influence of the structure of the substituent on either oxindole or isatin-3-hydrazone formation is discussed.

The title compound, first example of a stable diarylnitroxyl with vacant para-position, was best synthesized by CuCl-assisted coupling of o-tert-butylnitrosobenzene and p-tert-butylphenylboronic acid followed by N-xidation of the thus obtained unsymmetrical diarylamine. ESR investigation showed that ortho-substituted aromatic ring is removed from the conjugation plane providing unusual stability of this radical.

A mild, catalyst-free and simple synthesis of 1,1′-di(n-alkyl)-isoindigo via the reaction of substituted isatins with tris(diethylamino)phosphine is reported. Their self-assembly in water–DMF (50% v/v) solution was investigated. Unexpectedly, no surface activity was observed for compound 2h. Spectrophotometry and fluorimetry allowed determining critical micelle concentration (0.1 mM and 0.8 mM respectively). Aggregation numbers of 8 and sizes of aggregates were determined.

A series of 1-fluorobenzylated isatins and water-soluble pyridinium isatin-3-acylhydrazones on their base were obtained. The biological evaluation of novel hydrazones showed a significant dependence of their antimicrobial activity on the position of fluorine atom in benzyl substituent. The best activity showed compounds containing a 2-fluoro-6-chlorobenzyl fragment with selective action against S. aureus. The absence of hemotoxicity of both fluorine-containing products and their some non-fluorinated analogues was shown.

This work deals with polyfunctional biocompatible amphiphilic isatin derivatives. Isatin-3-acylhydrazones containing a quaternary ammonium moiety (Is-Q-n) with varying hydrophobicity (R = CnH2n+1, where n = 10, 12, 14, 16, 18, 20) were synthesized. Tunable self-assembly behavior, morphology of nanostructures, and their biological activity were modulated by hydrophilic-lipophilic balance of π-amphiphiles and solvent polarity. Self-assembly of Is-Q-n was investigated by tensiometry, conductometry, IR and UV–Vis spectroscopy, fluorimetry and dynamic light scattering. The unexpected values of the physicochemical parameters at long alkyl chain length have been interpreted. The CAC of Is-Q-16 is lower than CMC of classical surfactant CTAB. Solvent-induced self-assembly for Is-Q-16 was observed. The hydrophobic dye Orange OT was solubilized in Is-Q-10 solutions twice better than in CTAB solutions. Is-Q-n self-assembled structures with size 50 nm and 100 nm in a concentration range from 0.01 mM (below CAC) to 10 mM were found. Is-Q-10 forms small associates with size 3 nm. Selective antimicrobial activity of low toxic ammonium salts against Gram-positive bacteria (S. aureus 209p and B. cereus 8035) and fungus Candida albiсans 855–653 was shown. Newly synthesized 1-dodecylisatin derivatives containing a quaternary ammonium moiety may be recommended as antimicrobial agents and for drug solubilization, in particular for drugs capable for π-π stacking interactions.

The heat capacity, thermal dilatation, permittivity, and T - p phase diagram of (NH 4 ) 3 ZrF 7 have been studied in wide temperature and pressure ranges. Two phase transitions were found in addition to previously known structural transformations. The stability of crystal phases to temperature and pressure has been examined and a possibility of transition between two cubic phases has been discussed. The total excess entropy change ΣΔ S i = Rln6 is characteristic for the order–disorder processes, but its stepwise increase is not consistent with the structural model associated with the strong disorder assumed in the initial cubic phase.

Lipid transfer protein, designated as Lc-LTP2, was isolated from seeds of the lentil Lens culinaris. The protein has molecular mass 9282.7 Da, consists of 93 amino acid residues including 8 cysteines forming 4 disulfide bonds. Lc-LTP2 and its stable isotope labeled analogues were overexpressed in Escherichia coli and purified. Antimicrobial activity of the recombinant protein was examined, and its spatial structure was studied by NMR spectroscopy. The polypeptide chain of Lc-LTP2 forms four α-helices (Cys4-Leu18, Pro26-Ala37, Thr42-Ala56, Thr64-Lys73) and a long C-terminal tail without regular secondary structure. Side chains of the hydrophobic residues form a relatively large internal tunnel-like lipid-binding cavity (van der Waals volume comes up to ∼600 A3). The side-chains of Arg45, Pro79, and Tyr80 are located near an assumed mouth of the cavity. Titration with dimyristoyl phosphatidylglycerol (DMPG) revealed formation of the Lc-LTP2/lipid non-covalent complex accompanied by rearrangements in the protein spatial structure and expansion of the internal cavity. The resultant Lc-LTP2/DMPG complex demonstrates limited lifetime and dissociates within tens of hours.

This work deals with the reduction–oxidation processes that occur in natural britholite Ca5(PO4)3(OH,Cl,F) when it is subjected to temperatures between 20 °C and 900 °C. Uranium and cerium, present in britholite as isomorphic impurities, served as chemical “sensing elements”. Several stages of redox processes were identified, alternating back and forth within the temperature range that was examined. Assumptions were made about the types of radiation-induced defects responsible for the thermochemical transformations of uranium and cerium that were observed. Activation energy values for the corresponding redox processes were estimated.

Calorimetric, X-ray, dielectric and DTA under pressure measurements have been performed on oxyfluoride (NH 4 ) 3 Ta(O 2 ) 2 F 4 . The succession of nonferroelectric phase transitions was found associated with the order-disorder processes. The comparative analysis tantalate with related niobate has revealed the important role of the central atom in the physical properties behavior, mechanism of structural distortions and barocaloric effect in oxyfluorides with the eight-coordinated anionic polyhedra.

The rate of photochemical isomerization of azobenzene derivatives dispersed in glassy polystyrene has been measured along with rotational mobility of reacting molecules. For this purpose bifunctional probe molecules carrying a paramagnetic nitroxide fragment and a photochromic azobenzene moiety were used. The kinetics of photoisomerization was followed by monitoring the change in the UV–Vis absorbance spectra. Rotational mobility was determined by numerical simulation of the ESR spectra. It has been shown that in the matrix of glassy polystyrene amplitudes of high-frequency angular displacements (quasi-librations) correlate with the rate of photochemical trans–cis isomerization.

A detailed study of the normal state photoemission lineshapes and quasiparticle dispersion for the single layer Bi 2 Sr 2− x La x CuO 6+ δ (Bi2201) superconductor is presented. We report the first experimental evidence of a double peak structure and a dip of spectral intensity in the energy distribution curves (EDCs) along the nodal direction. The double peak structure is well identified in the normal state, up to 10 times the critical temperature. As a result of the same self-energy effect, a strong mass renormalization of the quasiparticle dispersion, i.e. kink, and an increase of the quasiparticle lifetime in the normal state are also observed. Our results provide unambiguous evidence on the existence of bosonic excitation in the normal state, and support a picture where nodal quasiparticles are strongly coupled to the lattice.

The $\dbar$-dressing scheme based on local nonlinear vector $\dbar$-problem is developed. It is applicable to multidimensional nonlinear equations for vector fields, and, after Hamiltonian reduction, to heavenly equation. Hamiltonian reduction is described explicitely in terms of the $\dbar$-data. An analogue of Hirota bilinear identity for heavenly equation hierarchy is introduced, $\tau$-function for the hierarchy is defined. Addition formulae (generating equations) for the $\tau$-function are found. It is demonstrated that $\tau$-function for heavenly equation hierarchy is given by the action for $\dbar$-problem evaluated on the solution of this problem., Comment: 11 pages

Evaporation of metallic silver was performed in Ar, N 2 and He using the ELV-6 electron accelerator. The obtained ultra-dispersed powders with a particle size of 70–80 nm were investigated by XRD, HREM and UV–Vis spectroscopy. The structure of Ag(Ar) powder was shown to differ substantially from that of Ag(N 2 ) by the presence of small oxide-like species of 10–20 nm on the particle surface. Catalytic activity of the powders in the reaction of ethylene epoxidation was also studied.

We investigate reductions of the two-dimensional Dirac equation imposed by the requirement of the existence of a differential operator D n of order n mapping its eigenfunctions to adjoint eigenfunctions. For first order operators these reductions (and multicomponent analogs thereof) lead to the Lame equations descriptive of orthogonal coordinate systems. Our main observation is that n th order reductions coincide with the projective-geometric ‘Gauss–Codazzi’ equations governing special classes of line congruences in the projective space P 2 n −1 , which is the projectivised kernel of D n . In the second order case this leads to the theory of W -congruences in P 3 which belong to a linear complex, while the third order case corresponds to isotropic congruences in P 5 . Higher reductions are compatible with odd order flows of the Davey–Stewartson hierarchy. All these flows preserve the kernel D n , thus defining nontrivial geometric evolutions of line congruences. Multicomponent generalizations are also discussed. The correspondence between geometric picture and the theory of integrable systems is established; the definition of the class of reductions and all geometric objects in terms of the multicomponent KP hierarchy is presented. Generating forms for reductions of arbitrary order are constructed.

A detailed study of the quasiparticle excitations by angle resolved photoemission spectroscopy is reported in three different families of high temperature superconductors. The data show the coupling of quasiparticles to phonons in the range of 50–80 meV. The effect persists above the critical temperature and shows a slight decrease as we increase doping.

The continuous spectrum and soliton solutions for the Boussinesq equation are investigated using the ∂-dressing method. Solitons demonstrate quite extraordinary behavior; they may decay or form a singularity in a finite time. Formation of singularity (collapse of solitons) for the Boussinesq equation was discovered several years ago. Systematic study of the solitonic sector is presented.

1,4-Bis(diphenylphosphino)butane and 1,5-bis(diphenylphosphino)pentane add two molecules of 6-bromo-1,2-naphthoquinone to afford bis-ylides which on treatment with protic acids are converted into the corresponding P,P’-bis(7-bromo-3,4-dihydroxy-1-naphthyl)-substituted bis-phosphonium salts.

Analytic-bilinear approach is used to study continuous and discrete non-isospectral symmetries of the generalized KP hierarchy. It is shown that Mobius symmetry transformation for the singular manifold equation leads to continuous or discrete non-isospectral symmetry of the basic (scalar or multicomponent KP) hierarchy connected with binary Backlund transformation. A more general class of multicomponent Mobius-type symmetries is studied. It is demonstrated that symmetry constraints of KP hierarchy defined using multicomponent Mobius-type symmetries give rise to Calogero–Moser system.

We report high-resolution ARPES data from Bi 2 Sr 2 CaCu 2 O 8 superconductors as a function of doping and temperature. A clear break in the quasiparticle dispersion near 50±10 meV binding energy has been observed, resulting in a change of the quasiparticle velocity up to a factor of two or more. This break is present at various points of the momentum space, and the magnitude of the dispersion change decreases with temperature and with doping.

The three-component reaction of acenaphthenequinone, fullerene C 60 and hexaethyltriaminophosphine leads to the formation of the new methanofullerene – 2-{3’-cyclopropa[1,9](C 60 -I h )[5,6]fulleren-3’-yl}-1-acenaphthenone.

The reaction of 6-bromo-1,2-naphthoquinone with tri(2-cyanoethyl)phosphine or tricyclohexylphosphine leads to the unusual formation of 6,6’-dibromo-1,1’,2,2’-tetrahydroxy-4,4’-binaphthyl; its structure was confirmed by NMR spectroscopy and single crystal X-ray diffraction analysis.

A pronounced nonlinearity of the current–voltage characteristics (CVC) accompanied by a high photosensitivity to IR-illumination was observed in In contact–[p-PbTe(Ga)]–Pt contact structures. The experimental data are discussed in terms of energy-band distortion near the Schottky barrier taking into account that at high-ohmic state formation the Fermi level (FL) is pinned by an impurity level within the energy gap. The possible influence of the crystal imperfections is also considered.

This paper reports the measurements of high electric field transport and the persistent photoconductivity in delta-doped by Sn on vicinal and singular substrate GaAs structures. Transport properties of the hot electron gas were measured in the temperature range 4.2 K

The reaction of chrysenequinone with phenylacetylene in the presence of phosphorus trichloride leads to the formation of a new phosphorus heterocycle, 2,7-dichloro-2-oxo-4-phenylbenzoo-1,2-oxaphosphatriphenylene, whose structure was established by NMR spectroscopy and single crystal X-ray diffraction.