Lifetime Measurements in 178Hf

Lifetimes of levels from K^π = 2⁺, K^π = 4⁺ and several K^π = 0⁺ bands have been measured in the ¹⁷⁸Hf nucleus using the GRID technique. Lifetimes of the 2⁺ and 3⁺ levels were measured within the K^π = 2⁺ γ band. A lower limit was established for the lifetime of the 4⁺ level of the K^π = 4⁺ band. The resulting upper limits for the absolute B(E2) values exclude collective transitions from the K^π = 4⁺ to the ground state band but not to the K^π= 2⁺ band. Level lifetimes were also measured for several states within three separate K^π= 0⁺ bands. Evidence is presented for a previously unobserved case of two excited K^π= 0⁺ bands being connected via collective E2 transitions.     

Franck-Condon Factors to High Vibrational Quantum Numbers III: CN

Franck-Condon factor arrays have been computed numerically to high vibrational quantum numbers for the red (A²II_i–X²Σ⁺) and violet (B²Σ⁺ – X²Σ⁺) band systems of CN.     

Oxidation of U(IV) in HNO<Subscript>3</Subscript> Solutions Containing Urea and Tc(VII)

The kinetics of U(IV) oxidation with nitric acid in aqueous solutions containing urea, catalyzed with technetium ions, were studied by sampling with subsequent colorimetric determination of the U(IV) concentration. At the constant ionic strength of the solution μ = 2 in the range of the initial concentrations of U(IV) from 2 × 10⁻³ to 1.28 × 10⁻², Tc(VII) from 5 × 10⁻⁵ to 1 × 10⁻³, urea from 0.01 to 0.1, and hydrogen ions from 0.4 to 1.96 M, the reaction rate is described by the equation -d[U(IV)]/dt = k ₁[U(IV)][Tc]^0.5[CO(NH₂)₂] × {[H⁺]² + β₁[H⁺] + β₂}⁻¹ - k ₂[U(IV)]₂[H⁺]^0.4[CO(NH₂)₂]^1.6{ [H⁺]² + β₁[H⁺]+ β₂}⁻², where k ₁ = 172 ± 10 mol^0.5 l^−0.5 min⁻¹ and k ₂ = (9.4±1.2)×10² mol l⁻¹ min⁻¹ at 25°C, β₁ and β₂ are the hydrolysis constants of U⁴⁺ ions. The activation energy is 63±2 kJ mol⁻¹. A reaction mechanism is proposed, in which in the slow stages the complex ion U(OH) ₂ ²⁺ ·CO(NH₂)₂ reacts with TcO²⁺ and TcO²⁺ · CO(NH₂)₂ ions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 61–66.Original Russian Text Copyright © 2005 by Dvoeglazov, Marchenko, Koltunov.     

The effect of crystalline structure on molecular effect in ion-induced electron emission

The results of experimental and theoretical study of the molecular effect in ion-induced electron emission from single crystal and polycrystalline materials are presented. It has been found that the electron emission yield γ₂ under N₂⁺ bombardment of a single crystal shows a dependence on ion incidence angle θ, which is analogous to the anisotropy of the yield γ₁ under N⁺ impact. The ratio R₂(θ)=γ₂/2γ₁<1 exhibits, for single crystals, a drastic angular dependence, which was successfully described on the basis of electron sweeping-out mechanism by conjunction of both the sharp channeling at θ<ψ_L and the shadowing-caused bell-like pattern at θ>ψ_L, the Lindhard angle.     

A Spectrophotometric Study of the Interaction of Np(VI) with Orthosilicic Acid and Polymeric Silicic Acids in Aqueous Solutions

The interaction of NpO ₂ ²⁺ ions with orthosilicic acid Si(OH)₄ and polymeric silicic acids (PSAs) in aqueous solutions was studied spectrophotometrically. The interaction at pH ≤ 4.5 is described by the equation NpO ₂ ²⁺ + Si(OH)₄ = NpO₂OSi(OH) ₃ ⁺ + H⁺ with the equilibrium constant log K = − 2.88±0.12 at the ionic strength I = 0.1–0.2 (log K ⁰ = −2.61±0.12 recalculated to I = 0); the stability constant of the complex NpO₂OSi(OH) ₃ ⁺ (I = 0) is log β⁰ = 7.20± 0.12. At pH > 5, a second complex of NpO ₂ ²⁺ with PSAs of the presumed composition NpO₂(≡ SiO)₂(≡SiOH) _{m − 2}, where (≡SiOH)_m denotes a PSA molecule with surface Si-OH groups, is formed. The absorption spectra of the complexes NpO₂OSi(OH) ₃ ⁺ and NpO₂(≡ SiO)₂(≡SiOH) _{m − 2} were obtained. In contrast to the hydroxo complexes, they have pronounced maxima at 560 – 600 nm with the molar extinction coefficients of about 25–30 l mol⁻¹ cm⁻¹, which is several times higher compared to the Np(VI) aqua ion.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 322–327.Original Russian Text Copyright © 2005 by Yusov, Shilov, Fedoseev, Astafurova, Delegard.     

Complexation of Np(V) with Silicate Ions

It was shown that Np(V) forms complexes with anions of orthosilicic acid and other silicate ions at pH higher than 8–8.5. At pH < 9.5, the reaction is mainly described by the equation NpO ₂ ⁺ + OSi(OH) ₃ ⁻ ⇄ NpO₂OSi(OH)₃; the stability constant of the NpO₂OSi(OH)₃ complex is equal to log β₁ = 2.1 ± 0.3. Thus, interaction is weak and hardly significant under real conditions. Carbonate ions in equilibrium with air at pH > 8.5 are the substantially stronger ligands for NpO ₂ ⁺ , and in their presence it is impossible to reveal Np(V) complexation with silicate ions.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 39–43.Original Russian Text Copyright © 2005 by Yusov, Fedoseev, Isakova, Delegard.     

Oxidation of Urea with Nitrous Acid in Nitric Acid Solutions

The kinetics of the reaction between urea and HNO₂ in nitric acid solution was studied spectrophotometrically. It was found that, at a constant ionic strength of the solution μ = 2, in the range of the initial concentrations of urea from 0.01 to 0.1 M, HNO₂, from 0.003 to 0.012 M, and hydrogen ions, from 0.1 to 1.5 M, the rate constant of the reaction is described by the equation -d[HNO₂]/dt = k[HNO₂][CO(NH₂)₂][H⁺] · K([H⁺]K +1)⁻¹, where the rate constant k = 15.6±0.3 l mol⁻¹ min⁻¹ and the protonation constant of urea K = 1.38 l mol⁻¹ at 15°C. From the temperature dependence of the reaction rate in the range of 15–35°C, the activation energy was determined to be 61±5 kJ mol⁻¹. The reaction mechanism involving the reaction of nondissociated HNO₂ molecules and protonated urea species NH₂CONH ₃ ⁺ was suggested.__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 57–60.Original Russian Text Copyright © 2005 by Dvoeglazov, Marchenko.     

A simple modification of the Hodgkin and Huxley equations explains type 3 excitability in squid giant axons

The Hodgkin and Huxley (HH) model predicts sustained repetitive firing of nerve action potentials for a suprathreshold depolarizing current pulse for as long as the pulse is applied (type 2 excitability). Squid giant axons, the preparation for which the model was intended, fire only once at the beginning of the pulse (type 3 behaviour). This discrepancy between the theory and experiments can be removed by modifying a single parameter in the HH equations for the K⁺ current as determined from the analysis in this paper. K⁺ currents in general have been described by I_K=g_K(V−E_K), where g_K is the membrane''s K⁺ current conductance and E_K is the K⁺ Nernst potential. However, I_K has a nonlinear dependence on (V−E_K) well described by the Goldman–Hodgkin–Katz equation that determines the voltage dependence of g_K. This experimental finding is the basis for the modification in the HH equations describing type 3 behaviour. Our analysis may have broad significance given the use of I_K=g_K(V−E_K) to describe K⁺ currents in a wide variety of biological preparations.     

Geochemistry of the upper Han River basin, China: 2: Seasonal variations in major ion compositions and contribution of precipitation chemistry to the dissolved load

A total of 252 water samples were collected from 42 sites across the upper Han River basin during the time period from 2005–2006. Major ions (Cl⁻, NO₃⁻, SO₄²⁻, HCO₃⁻, Na⁺, K⁺, Ca²⁺ and Mg²⁺), Si, water temperature, pH, EC and TDS were determined and consequently correlation matrix, analysis of variance, factor analysis and principal component analysis were performed in order to identify their seasonal variations and atmospheric inputs into river solutes. The results reveal that pH, EC, TDS, Cl⁻, SO₄²⁻, HCO₃⁻, Ca²⁺ and Mg²⁺, K⁺ and Si generally tend to show the minimum compositions in months belong to the rainy season, while the dry season for NO₃⁻ and Na⁺. NO₃⁻, Mg²⁺ and Si have the maximum concentrations in months belong to the rainy season. By comparing the major ions relating to hydrological regime, NO₃⁻, contrary to other elements, has higher concentration in the rainy season. The overall water quality is non-polluted, while there are indications of enrichment of inorganic anions including NO₃⁻ causing water entrophication in the near future. The atmospheric inputs contribute to river solutes is limited with a mean inputs of approximate 1% in the basin. The understanding of the major ion dynamics would help water quality conservation in the basin for China's interbasin water transfer project.     

Kinetics and Mechanism of Np(IV) Oxidation with Nitric Acid

Neptunium (IV) is oxidized to Np(V) with nitric acid in the presence of U(VI) under conditions of low acidity (<∼0.1 M). The reaction rate is described by the equation d[Np(V)]/dt = k ₁[Np(IV)]/[H⁺]² + k ₂[Np(IV)]²[U(VI)]/[H⁺]³, in which k ₁ = (2.0±0.3) × 10⁻⁵ mol² l⁻² min⁻¹ and k ₂ = (5.50±0.47) × 10⁻² mol l⁻¹ min⁻¹ at 50°C and solution ionic strength μ = 0.5. The activation energies of the two pathways are 148±31 and 122±12 kJ mol⁻¹. The reaction along the main pathway (with the rate constant k ₂) is limited by disproportionation of Np(IV) involving NpOH³⁺ and Np(OH)₂UO ₂ ⁴⁺ complex ions.__________Translated from Radiokhimiya, Vol. 47, No. 3, 2005, pp. 228–233.Original Russian Text Copyright © 2005 by Koltunov, Taylor, Marchenko, Savilova, Dvoeglazov, Zhuravleva.     

Measurement of the heat capacity of molybdenum (Standard Reference Material) in the range 1500–2800 K

Measurement of the heat capacity of molybdenum (Standard Reference Material 781 of the National Bureau of Standards) in the temperature range 1500–2800 K by a subsecond-duration, pulse-heating technique is described. The results of the measurements on three specimens are in agreement within 0.6%. The heat capacity of molybdenum in the temperature range 1500–2800 K based on the present results is expressed by the following function (standard deviation =0.5%): C _p =–3.0429+4.7215×10^–2 T–2.3139×10^–5 T ²+4.7090× 10^–9 T ³ where T is in K and C _p is in J · mol^–1 · K^–1. The inaccuracy of the reported results is estimated to be not more than 3%.     

Polarization dependence of the optical response in SnO2 and the effects from heavily F doping

The optical properties of intrinsic SnO₂ (TO) and fluorine doped (FTO) are characterized in terms of the dielectric function ε(ħω) = ε₁(ħω) + iε₂(ħω) by electronic structure calculations. The intrinsic TO shows intriguing absorption characteristics in the 3.0–8.0 eV region: (i) the low energy region of the fundamental band gap (3.2 < ħω < 3.9 eV), the optical transitions Г₃⁺ → Г₁⁺ (valence-band maximum to conduction-band minimum) is symmetry forbidden, and the band-edge absorption is therefore extremely weak. (ii) In the higher energy region (3.9 < ħω < 5.1 eV) the Г₅⁻ → Г₁⁺ transitions (from the second uppermost valence band) is strongly polarized perpendicular to the main c axis. (iii) Transitions with polarization axis parallel to c axis are generated from Г₂⁻ → Г₁⁺ transitions (from the third uppermost valence bands), and dominates at high energies (5.1 < ħω eV). Heavily F doped TO (FTO) with doping concentrations n_F = 4 × 10²⁰ cm^− 3 changes the absorption significantly: (iv) Substitutional F_O generates strong inter-conduction band absorption at 0.8, 2.2, and 3.8 eV which affects also the high frequency dielectric constant ε_∞. (v) Interstitial F_i is inactive as a single dopant, but act as a compensating acceptor in highly n-type FTO. This explains the measured non-linear dependence of the resistivity with respect to F concentration.     

Performance of the ALEPH detector at LEP

The performance of the ALEPH detector at the LEP e⁺e⁻ collider is reviewed. The accuracy of the tracking detectors to measure the impact parameter and momentum of charged tracks is specified. Calorimeters are used to measure photons and neutral hadrons, and the accuracy obtained in energy and angle is given. An essential property of the detector is its ability to identify particles; the performance in identification of electrons, muons, neutrinos (from missing energy), charged hadrons, π⁰'s and V⁰'s is described.     

Cesium leaching from gamma-irradiated CsA and CsX zeolites

The present study discusses the effect of γ-irradiation on Cs⁺-exchanged X and A zeolites. The incorporation of Cs⁺ ions into A and X zeolites was performed using three different cesium salts (chloride, nitrate or acetate). Cs⁺ ions immobilized into the vitrified zeolites by thermal treatment are located in different sites of the zeolite networks. It is found that γ-irradiation favors cesium retention depending on the cesium precursor salt used in the cationic exchange step.     

From three-dimensional weavings to swollen corneocytes

A novel technique to generate three-dimensional Euclidean weavings, composed of close-packed, periodic arrays of one-dimensional fibres, is described. Some of these weavings are shown to dilate by simple shape changes of the constituent fibres (such as fibre straightening). The free volume within a chiral cubic example of a dilatant weaving, the ideal conformation of the G₁₂₉ weaving related to the Σ⁺ rod packing, expands more than fivefold on filament straightening. This remarkable three-dimensional weaving, therefore, allows an unprecedented variation of packing density without loss of structural rigidity and is an attractive design target for materials. We propose that the G₁₂₉ weaving (ideal Σ⁺ weaving) is formed by keratin fibres in the outermost layer of mammalian skin, probably templated by a folded membrane.     

Ion exchange of ammonium in natural and synthesized zeolites

In this study, zeolite Na–P and Na–Y was prepared by hydrothermal treatment of the Chinese natural clinoptilolite with NaOH. The ion exchange of NH₄⁺ into the three zeolites in the temperature range of 288–333 K was also investigated, and the thermodynamic parameters were calculated. The selectivity sequence for NH₄⁺ entering the sodium form of the three materials was Na–clinoptilolite > Na–Y > Na–P, as indicated by values of ΔG°. The results demonstrated that the Si/Al molar ratio of zeolites determined the selectivity for NH₄⁺.     

A Spectrophotometric Study of the Interaction of Uranyl Ions with Orthosilicic Acid and Polymeric Silicic Acids in Aqueous Solutions

The interaction of UO ₂ ²⁺ ions with orthosilicic acid Si(OH)₄ and polymeric silicic acids (PSAs) was studied spectrophotometrically. The equilibrium constant of the reaction UO ₂ ²⁺ + Si(OH)₄ = UO₂OSi(OH) ₃ ⁺ + H⁺ in solutions with the ionic strength I = 0.1–0.2 is log K = −2.56±0.09 (log K ⁰ = −2.29±0.09 recalculated to I = 0); the stability constant of the complex UO₂OSi(OH) ₃ ⁺ (I = 0) is log β⁰ = 7.52±0.09. Formation of small oligomers (degree of polymerization n ≤ 4) has virtually no effect on the apparent constant K. When high polymers are formed (n > 100), the apparent equilibrium constant decreases by a factor of 2–3, and the “true” equilibrium constant recalculated to the actual concentration of silanol groups increases by a factor of 3–4. The absorption spectrum of the complex UO₂OSi(OH) ₃ ⁺ was obtained by treatment of the experimental spectra; it has an absorption maximum in the visible range at 422.5 nm, ɛ_422.5 = 35±2 l mol⁻¹ cm^{− 1}. At pH higher than 5–6, complexes of UO ₂ ²⁺ with PSAs of the composition UO₂(≡SiO)₂(≡ SiOH) _{m − 2} are formed. The absorption spectrum of such a complex was obtained.__________Translated from Radiokhimiya, Vol. 47, No. 4, 2005, pp. 315–321.Original Russian Text Copyright © 2005 by Yusov, Fedoseev.     

Investigation of Electric Discharge in Gas of Superhigh Density with Preliminary Adiabatic Compression

A powerful electric discharge in high-density hydrogen is investigated in a two-stage facility. The initial experimental conditions are as follows: the energy stored in a capacitive storage, 140–300 kJ; the discharge current, 90–220 kA; the current rise rate dI/dt 10⁸ A/s; the charging voltage, 4.0–6.0 kV. The maximal concentration of hydrogen molecules n, achieved after adiabatic compression of gas (immediately before the discharge), is 3.3 × 10²² cm^–3. The electrical parameters of the discharge and the gas pressure are measured in the experiments. The temperature, the concentration of charged particles, and the discharge channel radius are calculated using the results of these measurements. The estimates reveal that, under the given initial conditions, the arc channel temperature is (1.3–1.8) × 10⁵ K, the concentration of charged particles is (0.7–1.2) × 10²⁰ cm^–3, and the channel radius is 0.14–0.20 cm.     

Composition and Properties of Crystals Growing in the Ca2+–Mg2+–HPO2- 4–HCO- 3 System in the Presence of Na+, K+, Cl–, and SO2- 4 Ions

Data are presented on crystallization processes in aqueous solutions in the Ca²⁺–Mg²⁺–HPO^2- ₄–HCO^- ₃ system in the presence of Na⁺, K⁺, Cl^–, and SO^2- ₄ ions for molar ratios of the ions similar to those in human blood plasma. The solution concentration is shown to have a significant effect on the chemical composition and physicochemical properties of the forming precipitates.     

Electronic structure of the filled tetrahedral compound LiCdP and zinc–blende InP: Application of the interstitial insertion rule

We report on first principles studies of the electronic properties of the filled tetrahedral compound LiCdP and zinc–blende InP, using the full potential linearized augmented plane wave method within the local density approximation. The total energy calculations show that the α phase (Li⁺ near the anion) to be more stable than the β one (Li⁺ near the cation) for the LiCdP. The conduction band valleys follow the Γ–L–X ordering of increasing energy for β-LiCdP and InP, and the Γ–X–L one for α–LiCdP. The conduction band modifications are discussed and found to obey the interstitial insertion rule except for the Γ state of β-LiCdP. The valence charge density analysis shows that the Cd–P bond is covalent whereas the Li–P and the Li–Cd ones in α and β phases, respectively, are ionic.