Determination of the copper activity of liquid CuLa alloys

The thermodynamic activities of liquid CuLa alloys were obtained at 1549 K by Knudsen effusion experiments. The experimentally known concentration and temperature dependences of thermodynamic properties of liquid CuLa alloys are explained on the basis of an association model. These results are discussed in comparison with the enthalpy of crystallization and the crystallization temperature as well as the enthalpy of melting and the melting temperature of lanthanum-rich glassy and crystalline alloys respectively.     

Phase equilibria in the CsUO system in the temperature range from 873 to 1273 K

Portions of the cesium-uranium-oxygen system have been investigated between 873 and 1273 K and a phase diagram has been constructed using our data and the data of other workers in the field. A consistent set of measured and estimated thermodynamic data for cesium uranates has been used to calculate the equilibrium cesium partial pressure and the equilibrium oxygen partial pressure over two and three phase regions in the CsUO system. For a given temperature, the equilibrium cesium partial pressure in a two phase region decreases as the equilibrium oxygen partial pressure increases.     

Mössbauer spectroscopy of133Cs following the decay of133Xe atoms implanted in metals

Mössbauer effect measurements for the 81 keV transition in¹³³Cs have been performed with¹³³Xe-implanted sources prepared by means of an electromagnetic isotope separator. The behavior of the isomer shift of¹³³Cs impurities was studied in various metals. Some correlations were found between measured isomer shifts and electronic properties of the host materials, and they show that the host conduction electrons have an important role in the determination of the isomer shift in metals.     

An analysis of the rate of isomerization in molecules with an asymmetric double well potential

The classical theory of the rate of unimolecular isomerization developed by Gray andRice as extended by Zhao and Rice is applied to the calculation of the rate of isomerization in modelsystems which have linear asymmetric double well potentials. We are interested in this system fortwo reasons. First, we are interested in the detailed dynamical processes for the mentioned systembecause it is widely related to practical chemical reactions. Second, the present model systemhas an asymmetric double well potential, which provides a different test of the accuracy of theapproximations used in the Gray-Zhao-Rice theory than posed by previous applications. We havecalculated relaxation rates and relaxation times for the model systems on different time scales.We find that for the systems under studies the Gray-Zhao-Rice version of the classical theory ofisomerization rate yields values in good agreement with those generated from trajectory calculationsand from the Reactive Island theory of De Leon et al.     

Determination of the apparent standard potential of the Dy/Dy(Ⅲ) system in the LiCl-KCl eutectic

The apparent standard potential of Dy/Dy(III) system in the LiCl-KCl eutectic has been determined by the logarithmic analysis of the semi-integrals of voltammograms, logarithmic analysis of chronopotentiograms and the open circuit potentiometry. The dysprosium equilibrium potentiab for various concentration of dysprosium chloride in the LiCl-KCl eutectic melt between 400-500℃ were first determined experimentally, and the apparent standard potential of this system and its temperature dependance have been calculated.     

Photoionization of Xe2, Xe3 and Xe4 in the 1024–1113 Å region

The mass spectra of Xe _n ⁺ clusters (n=2–13) were recorded using a supersonic beam and an ion time-of-flight mass analyser. The yield of Xe ₂ ⁺ , Xe ₃ ⁺ and Xe ₄ ⁺ cluster ions was measured with a resolution of 0.1 Å (1 meV) in the 1024–1113 Å (11.1–12.1 eV) region. Autoionizing Rydberg series of Xe₂ converging to theC ²_3/2u state of Xe ₂ ⁺ were observed in the spectrum of Xe ₂ ⁺ . The photoionization yield of Xe ₃ ⁺ and Xe ₄ ⁺ ions each displayed similar broad features that contained no fine structure corresponding to vibrational states. The broad features were assigned to autoionizing Rydberg series by analogy with the dimer ion spectrum.     

Rényi entropy of the infinite well potential in momentum space and Dirichlet-like trigonometric functionals

The momentum entropic moments and Rényi entropies of a one-dimensional particle in an infinite well potential are found by means of explicit calculations of some Dirichlet-like trigonometric integrals. The associated spreading lengths and quantum uncertainty-like sums are also provided.     

Mercury-rare gas van der Waals complexes: From the lightest HgHe to the heaviest HgXe

Mercury helium and mercury xenon van der Waals complexes have been observed in a supersonic free jet expansion by laser-induced fluorescence in the vicinity of the Hg(³P₁¹S₀) transition. The helium complex very weakly bonded in the ground state (D₀ = 8 ± 1 cm⁻¹) exhibited a simple rotational structure. The strongly bonded xenon complex has shown a clear example of isotopic broadening in its vibronic spectra.     

Determination of the linear expansion coefficient of CoWC η-carbides using a high temperature X-ray diffraction technique

The linear expansion coefficient of η-carbides in the CoWC system has been investigated using a high temperature X-ray technique. Four η-carbides of different compositions have been studied in the temperature range 30 –1500 °C. The coefficient of linear expansion varied between 7.0 × 10⁻⁶ and 10.2 × 10⁻⁶°C⁻¹, increasing with temperature and with the tungsten: cobalt ratio.     

New oxyborates in the MgMnBO system

Two new oxyborate compounds were synthesized during a study of the phase relationships between the pinakiolite-ludwigite series of compounds. The structural topologies of these previously unreported materials have been determined experimentally by comparing calculated with observed electron microscope images. Both of these structures are very similar to each other, and also closely related to pinakiolite which consists of flat walls of edge-sharing octahedra connected to zigzag chains of octahedra by triangular BO₃ groups. The two new structures contain similar infinite walls which are separated by slabs of octahedra that are wider than the zigzag chains found in pinakiolite. A new series of structurally related oxyborate compounds can be envisaged and are described.     

Exploring the potential of the β-thiolactones in bioorganic chemistry

A series of novel peptide-based β-thiolactones were synthesized and assayed for cytotoxicity against several human cancer cell lines, where they showed greater activity than the corresponding β-lactones and β-lactams. Several of the β-thiolactones prepared showed strong inhibitory activity in vitro against human cathepsins B and L.     

The “fine structure” of the slow micellar relaxation mode and the aggregation rates in the range between a potential hump and well in the work of aggregation

An analytical expression has been derived for the quasi-stationary size distribution of surfactant aggregates in a micellar system approaching the final equilibrium state. In contrast to previously known relations, the derived expression takes into account variations in the concentration of monomers during the slow relaxation and enables one to determine the previously unknown fine structure of the linearized mode of slow relaxation, i.e., its dependence on the aggregation numbers in the range between the maximum and minimum of the work of aggregation. This dependence has been reliably confirmed by the numerical solution of the set of linearized Becker–Döering difference equations, which describe the molecular mechanism of the kinetics of micellization and micellar relaxation. In turn, the expression found for the relaxation mode makes it possible to refine the analogous “fine structure” of aggregation rates at different points of the same range between the maximum and minimum of the work of aggregation, in which the aggregation rates appear to be low but exhibit a nonmonotonic behavior. This behavior is also confirmed by the numerical solution of the Becker–Döering difference kinetic equations.     

Determination of the leaching rate of radionuclide 134Cs from the solidified radioactive wastes in Syrian Portland cement and cement–microsilica matrixes

The suitability of Syrian Portland cement for disposal of solidified low-level radioactive waste was assessed by measuring the leaching rate of ¹³⁴Cs. In ordinary cement concrete, a leaching rate of 1.309 × 10^?3 g/cm² per day was measured. Mixing this concrete with microsilica reduced significantly the leaching rate to 3.106 × 10^?4 g/cm² per day for 1% mixing, and to 9.645 × 10^?5 g/cm² per day for 3% mixing. It was also found that the application of a latex paint reduced these leaching rates by about 10%. These results, along with mechanical strength tests (under radiation exposure, high temperature, long water immersion and freeze–thaw cycling) indicate that Syrian Portland cement is suited for the disposal of low-level radioactive waste.     

Comparison of the magnetic properties of MmFeband NdFeB compounds

NdFeB and corresponding MmFeB compounds were studied, the high field magnetization at 4.2 K, the a.c. susceptibility (4.2 < T < 300 K) and the anisotropy field were measured using the singular point detection technique (77 < T < 570 K). At room temperature the anisotropy field of the MmFeB is about 3T, whereas that of NdFeB compounds is about 7T. The MmFeB compounds showed effects due to the cerium (lowering the Curie temperature) as well as due to the neodymium (spin reorientation at low temperatures).     

Thermodynamics of the URuC system

Thermodynamic measurements by the electromotive force method were made on the binary intermetallic phases URu₃ and U₃Ru₅ and on the ternary carbides URu₃C_0.7 and U₂RuC₂ of the URu and the URuC systems between 950 and 1200 K using galvanic cells with CaF₂ single crystal electrolytes: U, UF₃¦CaF₂¦UF₃, URu₃, Ru; U, UF₃¦CaF₂¦UF₃, U₃Ru₅, URu₃; Ru, URu₃, UF₃¦CaF₂¦UF₃, URu₃C_0.7, Ru, C; U, UF₃¦CaF₂¦UF₃, URu₃C_0.7, U₂RuC₂, C. The Gibbs energies of formation of URu₃, U₃Ru₅, URu₃C_0.7 and U₂RuC₂ were evaluated from the measured electromotive force which give ^fΔG^o〈URu₃〉 = −199 100 + 35.9 T J mol^−1fΔG^o〈U₃Ru₅〉 = −398 600 + 43.6 T J mol^−1fΔG^o〈URu₃C_0.7〉 = −192 600 + 2.5 T J mol^−1fΔG^o〈U₂RuC₂〉 = −380 200 + 52.5 T J mol⁻¹ The implications of these thermodynamic data for the behaviour of the fission product ruthenium in irradiated carbide fuels are discussed.     

The frequency of the HOH bending fundamental in solids and liquids

A survey has been made of HOH bending frequencies in water-containing solids and liquids, using data from the literature and from the author's laboratory. After the effects of hydrogen bonding and dynamic coupling have been allowed for, HOH bending frequencies are found to be lowered by cation—water interactions. This frequency lowering increases statistically with increasing cation charge and with decreasing cation size.     

Hydrolysis of POAl bonds in AlPO4 and SAPO molecular sieves

It is shown for three AlPO₄ and SAPO molecular sieves (structures SAPO-5, AlPO₄-17, SAPO-17, and SAPO-44) that the framework is attacked by water in the temperature range between ca. 323 and 473 K. The structural damage is more severe in the presence of ions such as NH⁺₄ or Na⁺, probably due to a shift in POAl hydrolysis equilibrium.     

Determination of the solubility product of plutonium sesquioxide in the NaCl+CaCl2 eutectic and calculation of a potential–pO2− diagram

Reactions between plutonium trichloride and oxide ions were studied in the fused NaCl+CaCl₂ equimolar mixture at 823 K, by potentiometry with an yttria-stabilised zirconia membrane electrode. Titration curve demonstrated the existence of a precipitated plutonium oxide (Pu₂O₃) with dissociation constant 10^−17.5 (molality scale). The combination of this data with the standard potentials allowed to set up the potential–pO²⁻ diagram of plutonium which summarises the properties of plutonium species in the melt.     

Determination of Melatonin in the Mian Erkang Capsules by HPLC

IntroductionTheMianErkangmadebyusisahighpotencycalciumpreparation.ItfindswideapplicationinmanysymPtomswherethereisalackofcalcium.Atthesametime,itcanhypnotizeandactasananti-decrepitude.Melatoninisoneofthemaineffectivecomponents.ItschendcalnameisN-acetyl-5-methoxytryptamine,andcanhypnotize,calm,relievepain',increasethebody'sinununity,beusedincancertherapyanddelaydecrepitude"'.ForqualitycontrolofMianErkangcapsules,arapid,sensitiveandaccurateHPLCmethodforthedeterminationofmelatonininMianErka…