On the mechanism of phase transformation in Ag2Se

A differential thermal analysis ΔT _y (T) in vacuum has been performed, and the temperature gradient ΔT _x (T) along the Ag₂Se sample during the transition α → β has been studied. It has been shown that the transitions α → α′ and β′ → β are displacive transitions and that the transition α′ → β′ is a reconstructive transition. It has been found that the temperature gradient along the sample during the transition α′ → β′ passes through a deep minimum due to a strong increase in the specific heat capacity.     

Intra- and intergroup azimuthal correlations of particles in the interaction of gold nuclei with silver and bromine nuclei of track emulsions at the projectile energy of 10.6 GeV per nucleon

Inter- and intragroup azimuthal correlations of target and projectile fragments and of shower particles in the interactions between gold nuclei of energy 10.6 GeV per nucleon and silver and bromine nuclei of a track emulsion are studied at intermediate values of the impact parameter. The asymmetry index β′₁ and the collinearity index β′₂ of groups’ asymmetry vectors are used to study azimuthal correlations between two and three groups of particles. The interplay of effects of intra- and intergroup azimuthal particle correlations is investigated.     

Rare t-quark decays t → clj+lk? and t → c?jvk induced by doublets of scalar leptoquarks within the minimal four-color-symmetry model

The rare t-quark decays t → cl _j ⁺ l _k ⁻ and t → cṽ _j k _k induced by scalar-leptoquark doublets are considered within the minimal model involving four-color quark-lepton symmetry and the Higgs mechanism of quark and lepton mass splitting. The partial widths with respect to the decays being considered and the total widths Γ(t → cl ⁺′l ⁻) = Σ_j,k Γ(t → cl _j ⁺ l _k ⁻ ) and Γ(t → cl ⁺′l ⁻) = Σ_j,kΓ(t → cṽ _j v _k ) with respect to, respectively, the charged leptonic and neutrino modes are calculated. It is shown that, at scalar-leptoquark masses higher than the t-quark mass (m _S > m _t), the branching ratios for these modes are Br(t → cl ⁺′l ⁻) ≈ (3.5−0.4) × 10⁻⁵ and Br(t → cṽ′v) ≈ (7.1−0.8) × 10⁻⁵ at m _s = 180–250 GeV and an appropriate value of the leptoquark-mixing angle (sin β ≈ 0.2) and can increase for m _S < m _t to Br(t → cl ⁺′l ⁻) ≈ 0.03−0.002 and Br(t → cl ⁺′l ⁻) ≈ 0.46−0.05 for the charged mode at m _S = 150–170 GeV for sin β ≈ 1 and sin β ≈ 0.2, respectively. In the cases being considered, t-quark decays to pairs of charged leptons can be accessible to detection at LHC. In the last case, these decays could manifest themselves (for example, in dilepton events) at the Tevatron as well. Original Russian Text ? P.Yu. Popov, A.D. Smirnov, 2006, published in Yadernaya Fizika, 2006, Vol. 69, No. 6, pp. 1006–1016.     

Determination of parameters of Cu surface mass transport on sapphire from morphological changes of beaded films caused by evaporation

s , the surface diffusion coefficient, D_s ^′, and the surface reaction rate coefficient, β_s ^′, of Cu on alumina are determined in the temperature range 1048–1198 K. Measuring simultaneously the time dependence of the effective thickness, H_eff(t), the lateral shift of the boundary, y(t) of beaded films (BF) and using vapour pressure data we concluded that the process is controlled by surface reaction at the perimeters of beads. Supposing Arrhenius-type temperature dependence for D_s ^′, β_s ^′ and λ_s the activation energies and preexponential factors have been calculated. Received: 2 October 1996/Accepted: 27 November 1996     

Quantum Gravitational Corrections to the Real Klein-Gordon Field in the Presence of a Minimal Length

The (D+1)-dimensional (β,β′)-two-parameter Lorentz-covariant deformed algebra introduced by Quesne and Tkachuk (J. Phys., A Math. Gen. 39, 10909, 2006), leads to a nonzero minimal uncertainty in position (minimal length). The Klein-Gordon equation in a (3+1)-dimensional space-time described by Quesne-Tkachuk Lorentz-covariant deformed algebra is studied in the case where β′=2β up to first order over deformation parameter β. It is shown that the modified Klein-Gordon equation which contains fourth-order derivative of the wave function describes two massive particles with different masses. We have shown that physically acceptable mass states can only exist for b < \frac18m²c²\beta<\frac{1}{8m^{2}c^{2}} which leads to an isotropic minimal length in the interval 10⁻¹⁷ m<(ΔX ⁱ )₀<10⁻¹⁵ m. Finally, we have shown that the above estimation of minimal length is in good agreement with the results obtained in previous investigations.     

Parity violation effects in hydrogen atom in forbidden magnetic-dipole transitions

General expressions for the probability of all strongly forbidden magnetic-dipole transitions between states njl and n′jl in the hydrogen atom and light hydrogen-like ions are derived in the lowest order in the parameter (αZ) in the form W _n′jl;njl ^(Ml) = D _n′n ^lj αm _e (αZ)¹⁰ (in relativistic units), where m _e is the electron mass, α is the fine-structure constant, Z is the nuclear charge, and the constants D _n′n ^lj are presented in an analytical form. Using these expressions, the dependence of the degree of parity violation on the principal quantum numbers n and n′ of the lower and upper states in the ns _1/2-n′s _1/2 and np _1/2-n′p _1/2 M1 transitions is systematically analyzed. The results obtained can be used in designing experiments on parity violation in the hydrogen atom.     

Piezoelectric properties of oriented Z′ cuts of PZT-type ferroelectric ceramics

The piezoelectric and dielectric properties of oriented β°Z′ cuts (β=0, 15, 30, 45, 60°) of piezoelectric crystals of TsTS-83G (lead zirconate titanate) composite are studied. A static model is proposed for the case of a maximally polarized ceramic based on the conditions of complete and partial stability of the polar axes c with allowance for their nonuniform distribution for 180° and 90° domain reorientations. It is found that the TsTS-83G piezoelectric composite does not exhibit anisotropy in the piezoelectric coefficient d ₃₃ ^′ when the axis of the Z′ cut is rotated in the ZY plane relative to the XYZ coordinate system. Zh. Tekh. Fiz. 68, 75–79 (July 1998) Deceased.     

EPR investigations of Cu(II) complexes with 5′-CMP and 5′-GMP

Electron paramagnetic resonance investigation of the Cu(II) complexes with guanosine-5′-monophosphate (5′-GMP) and cytidine-5′-monophosphate (5′-CMP) shows the affinity of the Cu(II) ion to interact with the base and the phosphate group. The different modes of the coordination of the metal ion at the nucleotide and the water molecules lead to octahedral species, distorted by dynamical Jahn-Teller effect (g₀ = 2.106) for the Cu(II)-5′-CMP complex and rhombically distorted (g₁ = 2.358, g₂ = 2.126, g₃ = 2.068) or tetragonally distorted (g_∥^′ = 2.299, g_⊥^′ = 2.126) for the Cu(II)-5′ -GMP complex. The compound with 5′-CMP presents also a more stable in time square-planar species (g_∥ = 2.265, A_∥ = 162 G, g_⊥ = 2.076). The local symmetry changes in aqueous solution by coordination of water molecules.     

Glass: Kohlrausch exponent,fragility, anharmonicity

The thermodynamical and mechanical properties of (fragile and strong) glass are modeled based on a generalised activation energy relationship log _τ = ΔG _β /RTn(T′) process of glass-forming liquids. This cooperative process involves 1/n(T′) elementary β motions of activation Gibbs energy ΔG _β dependent on the equivalent temperature T′, the temperature of the liquid in equilibrium having the volume of the glass, function of temperature and aging conditions. From this modified VFT law the relaxation of any properties (V , H , stress, creep) can be calculated and approximated by the Kohlrausch function. This model predicts consistency relationships for: a) the temperature (and aging time) variation of the Kohlrausch exponent; b) the temperature dependence of the stabilisation time domain of strong and fragile glass; c) the linear relation between the activation parameters (E ^* energy, S ^* entropy, V ^* volume) of the α and β transition. The Lawson and Keyes (LK) relations are recalled and it is shown that these relations (somewhat equivalant to the compensation law or Meyer-Neldel rule) are observed generally in glass. Morever the (macroscopic) ratios ΔH/ΔV observed during aging or after a temperature jump and the (microscopic) ratio E ^*/V ^* are found equal to κγ (κ compressibily, γ Grüneisen parameter), in agreement with the LK predictions. From various experiments and in agreement with predictions of this model we conclude that the Grüneisen parameter γ _B (pressure derivative of the bulk modulus) and the Mean Square Displacement (MSD) characterising the anharmonicity of solids (and liquids) are the main parameters which govern the relaxation properties of the glass state. Linear relations between the parameters γ _B , the fragility m, and the Kohlrausch exponent n _g at T _g are explained. These correlations underscore a strong relationship between the fragilty of glass formers and the extent of the anharmonicity in the interatomic interactions.     

Photophysics of bis-bipyridyl complexes of ruthenium(II) with triphenylphosphine

We studied the spectral-luminescent characteristics of the luminescence of mixed-ligand polypyridine-phosphine complexes of ruthenium(II) cis-[Ru(bpy)₂(PPh₃)X](BF₄) _n with ligands 2,2′-bipyridyl (bpy) and triphenylphosphine (PPh₃) and X = Cl⁻, Br⁻, CN⁻, NO₂⁻, NH₃, MeCN, pyridine (py), 4-aminopyridine (pyNH₂), and 4,4′-bipyridyl (4,4′-bpy) in a 4: 1 EtOH-MeOH alcoholic mixture at 77 K. The radiative and nonradiative deactivation rate constants of the lowest electronically excited state of the complexes are determined. We find that triphenylphosphine has a greater effect on the photophysical characteristics of ruthenium(II) complexes compared to π-acceptor strong-field ligands, such as MeCN, CN⁻, and NO₂⁻. At the same time, the characteristics of complexes cis-[Ru(bpy)₂(PPh₃)X] ⁿ⁺ considerably depend on the nature of the second monodentate ligand X, which is coordinated to ruthenium(II), and correlate with its position in the spectrochemical series of ligands.     

MOON for neutrino-less double beta decays

The MOON (Majorana/Mo Observatory Of Neutrinos) project aims at studies of the Majorana nature of the neutrino (ν) and the ν-mass spectrum by spectroscopic experiments of neutrino-less double beta decays (0νββ) with the ν-mass sensitivity of 〈m _ν ^m 〉 = 100−30 meV. The solid scintillator option of the MOON detector is a super ensemble of multi-layer modules, each being composed by PL scintillator plates and position-sensitive detector planes with good overall energy resolution of σ ≈ 2% at the Q _ββ ≈ 3 MeV. Thin ββ source films are interleaved between the detector planes. High localization of the two β tracks enables one to select true signals and reject BG ones. The multi-layer structure of the detector makes it realistic to build a compact ton-scale detector. MOON with detector ≠ ββ source is used for studying 0νββ decays from ¹⁰⁰Mo, ⁸²Se and other ββ isotopes with large Q _ββ . Real-time exclusive measurements of low energy solar neutrinos can be made by observing inverse β rays from solar-ν captures of ¹⁰⁰Mo in delayed coincidence with the subsequent β decay of ¹⁰⁰Tc.     

Symmetries and causes of the coincidence of the emission spectra of mirrors and charges in 1+1 and 3+1 spaces

This paper discusses the symmetry of the wave field that lies to the right and left of a two-sided accelerated mirror in 1+1 space and satisfies a single condition on it. The symmetry is embodied in the Bogolyubov matrix coefficients α and β that connect the two complete sets of solutions of the wave equations. The amplitudes of the quantum processes in the right and left half-spaces are expressed in terms of α and β and are related to each other by the transformation (12). The coefficient β _ω′ω ^* plays the role of the source amplitude of a pair of oppositely directed particles with frequencies ω and ω′ of which one is in the left half-space and the other is in the right half-space because one of them has undergone reflection. Such an interpretation makes β _ω′ω ^* observable and explains why, as shown by Eq. (1) and found earlier by Nikishov and Ritus [Zh. éksp. Teor. Fiz. 108, 1121 (1995); transl. JETP 81, 615 (1995)] and by Ritus [Zh. éksp. Teor. Fiz. 110, 526 (1996); transl. JETP 83, 282 (1996)], the emission spectra of a mirror in 1+1 space coincide with those of charges in 3+1 space. The reason is that the angular momentum of the pair emitted by the mirror coincides with the angular momentum of the single particle emitted by the charge. Zh. éksp. Teor. Fiz. 114, 46–62 (July 1998)     

Structural analysis of the Γ phase in cholesterol-distearoylphosphatidylcholine multilamellar vesicles

Summary The interaction of cholesterol with membranes is particularly interesting as the cholesterol concentration influences membrane stability and permeability by inducing changes in the structure and dynamics of the constituent lipid molecules. On the other hand, cholesterol is present in the atherosclerotic plaques and in some skin diseases, like xanthomas and xantelasmas. An investigation was performed on the Γ phase in a cholesterol-distearoyl phosphatidyl choline (DSPC) mixture by using X-ray diffraction and differential scanning calorimetry. The cholesterol/DSPC molar ratio was 35/65 and DSPC-to-water weight ratio was 1/3. The Γ phase appears at sufficiently high concentration of cholesterol and it is characterized by interchain positional order considerably lower than in theL _β′ andP _β′ phases but higher than in theL _∝ liquid crystalline phase of pure lecithin in excess water. The results suggest that a lateral phase separation exists in the temperature range of existence of the Γ phase. The other phase Γ′ appears to be richer in cholesterol. The (Γ+Γ′) toL _∝ phase transition was investigated and the temperature dependence of the in-plane correlation length in the Γ phase was determined. A very weak enthalpy peak was observed at the chain melting transition, confirming the highly disordered nature of phases Γ and Γ′. Work presented at the First USSR-Italy Bilateral Meeting on Liquid Crystals held in Portonovo, Ancona (Italy), September 30–October 2, 1987.     

A Measurement of the ψ′ to J/ψ production ratio in 920?GeV proton-nucleus interactions

Ratios of the ψ^′ over the J/ψ production cross sections in the dilepton channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus interactions with the HERA-B detector at the HERA storage ring. The ψ^′ and J/ψ states were reconstructed in both the μ⁺μ^- and the e⁺e^- decay modes. The measurements covered the kinematic range -0.35≤x_F≤0.1 with transverse momentum p_T≤4.5 GeV/c. The angular dependence of the ratio has been used to measure the difference of the ψ^′ and J/ψ polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is R_ψ′(μ)/R_ψ′(e)=1.00±0.08±0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B^′(μ)B(e))/(B(μ)B^′(e)), of ψ^′ and J/ψ in the two channels. The ψ^′ to J/ψ production ratio is almost constant in the covered x_F range and shows a slow increase with p_T.     

Molecular oxygen detection in low pressure flames using cavity ring-down spectroscopy

Cavity ring down spectroscopy is used for measurement of the concentration profiles of oxygen in the low pressure (30 Torr) methane/nitrogen/oxygen flames. Three different equivalence ratios are used: 0.8, 1.0 and 1.17. Molecular oxygen concentration is monitored via rotational spectrum of b¹ Σ _g ⁺←X³ Σ _g ^- (v^′=0-v^′′=0) transition, also known as atmospheric A band, located near 750 nm. The P(15)P(15) line is used for concentration measurements. The sensitivity reached is 2.2×10^-8 cm^-1. The concentration profiles are in a good agreement with the ones calculated using GRI-3.0 mechanism. PACS 33.20.Kf; 33.70.Fd; 42.60.Da     

Measurement of the τ lepton mass at the KEDR detector

A precise τ lepton mass measurement performed at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the τ⁺τ⁻ cross section behavior around the production threshold. The result based on 6.7 pb⁻¹ of data is m _τ = 1776.81 _−0.23 ^+0.25 ± 0.15 MeV. Using 0.8 pb⁻¹ of data collected at the ψ′ peak, we have also determined that Γ _ee B _ττ(ψ′) = 9.0 ± 2.6 eV. The text was submitted by the authors in English.     

ESR determination of the thermal stability of Mn<Superscript>2+</Superscript> ion binding sites in different legume lectins

The legume lectins are a large family of homologous carbohydrate-binding proteins. Their carbohydrate specificity and quaternary structure vary widely. The carbohydrate binding activity of legume lectins depends on the simultaneous presence of calcium and transition-metal ions, especially the Mn²⁺ ion. In the present work, thermal stabilities of Mn²⁺ binding sites in pea, lentil, soybean and kidney-bean lectins have been studied by electron spin resonance spectroscopy in the temperature range of 120–400 K in different atmospheres. The evolution of parameters, such as the line width, peak-to-peak intensity associated with the hyperfine transition [m _I (+5/2) → m′ _I (−5/2)] at the lowest magnetic field side of the central electron transition [m _S (+1/2) → m′ _S (−1/2)] of the Mn⁺² ion, g-factor and hyperfine splitting was evaluated. Annealing was also performed at high temperatures (353, 373, 383, 403 and 443 K) and the oxidation activation energy of Mn²⁺ ions in the indicated legumes was determined.     

Baryon magnetic moments in a quark model

The magnetic moments of uncharmed and charmed baryons are considered to arise through single-quark and two-quark transitions in a quark model. The magnetic moment operator is taken to transform as:T _β ^α ˜aT ₁ ¹ , +bT ₂ ² +cT ₃ ³ +dT ₄ ⁴ , whereT _β ^α are members of SU(4)20′-plet. The assumption, that the magnetic moment operator obtains contribution from the single and two-quark transitions, yields good results for the magnetic moment values of uncharmed baryons. Magnetic moments of charmed baryons can be expressed in terms of one parameter.     

New CUORICINO results and status of CUORE

CUORICINO is an array of 62 TeO₂ bolometers with a total mass of 40.7 kg (11.2 kg of ¹³⁰Te), operated at about 10 mK to search for ββ(0ν) of ¹³⁰Te. The detectors are organized as a 14-story tower and intended as a slightly modified version of one of the 19 towers of the CUORE project, a proposed tightly packed array of 988 TeO₂ bolometers (741 kg of total mass of TeO₂) for ultralow-background searches on neutrinoless double-beta decay, cold dark matter, solar axions, and rare nuclear decays. Started in April 2003 at the Laboratori Nazionali del Gran Sasso (LNGS), CUORICINO data taking was stopped in November 2003 to repair the readout wiring system of the 62 bolometers. Restarted in spring 2004, CUORICINO is presently the most sensitive running experiment on neutrinoless double-beta decay. No evidence for ββ(0ν) decay has been found so far and a new lower limit, T ₁ ^2/0ν ≥ 1.8 × 10²⁴ yr (90% C.L.), is set, corresponding to 〈m _ν〉 ≤ 0.2–1.1 eV, depending on the theoretical nuclear matrix elements used in the analysis. Detector performance, operational procedures, and background analysis results are reviewed. The expected performance and sensitivity of CUORE is also discussed. CUORE Collaboration The text was submitted by the authors in English.     

Pressure-induced amorphization of Gd2(MoO4)3: A high pressure Raman investigation

High pressure Raman spectroscopic studies on Gd₂(MoO₄)₃(GMO) have been carried out at ambient temperature in the diamond cell to 10 GPa hydrostatic pressure. These experiments have revealed pressure-induced phase transitions in GMO near 2 GPa and 6.0 GPa. The first transition is from Pba2(β′) phase to another undetermined crystalline phase, designated as phase II, and the second transition is to an amorphized state. On releasing pressure there is a partial reversion to the crystalline state. The Raman data indicate that the amorphization is due to disordering of the MoO₄ tetrahedral units. Further, it is inferred from the nature of the Raman bands in the amorphized material that the Mo-O bond lengths and bond angles have a range of values, instead of a few set values. The results of the present study as well as previous high pressure-high temperature quenching experiments strongly support that pressure-induced amorphization in GMO is a consequence of the kinetically impededβ toα phase transition. The system in frustration becomes disordered. The rare earth trimolybdates crystallizing in theβ′ structure are all expected to undergo similar pressure-induced amorphization.