Monthly sea surface temperature records reconstructed by δ<Superscript>18</Superscript>O of reef-building coral in the east of Hainan Island,South China Sea

Stable oxygen isotopic compositions of a coral colony ofPorites lutea obtained on a core allowed the reconstruction of a 56-a (1943–1998) proxy record of the sea surface temperatures. This coral δ¹⁸O data are from the east of Hainan Island water (22°20’N, 110°39’E), South China Sea. The relationship between δ¹⁸O in the skeletal aragonite carbonate and the sea surface temperature (SST) is SST = -5.36 δ¹⁸O_PDB-3.51 (r = 0.73,n = 470), dδ¹⁸O/d(SST) = -0.187?/ °C; and the thermometer was set at monthly resolution. The 56-a (1943–1998) proxy record of the sea surface temperatures reflected the same change trend in the northern part of South China Sea as the air temperature change trend in China.     

Evaluation of surface water–groundwater interaction using environmental isotopes (D, 18O and 222Rn) in Chongli Area,China

Predicting the electrical corrosion potential (ECP) of type 304 stainless steel, the structural material of recirculation pipes in fusion power plants, is important because the growth rate of intergranular stress corrosion crack (IGSCC) of 304 stainless steel is closely related to ECP. In this work, a new model has been developed, by modifying existing models, to calculate the ECP of recirculation pipes in future fusion power plant. The calculation results indicate that merely injecting hydrogen cannot reduce ECP below E_IGSCC if the dose rate exceeds a threshold, other assisted water chemistry controlling method is necessary.

     

18O(p,p′γ)18O nuclear reaction in the determination of oxygen by proton induced γ-ray emission

Journal of Radioanalytical and Nuclear Chemistry - Particle induced gamma-ray emission method was used to quantify total fluorine (F) concentrations in soil and food samples obtained from fluoride...     

The simulation of the adsorption of unsaturated cyclic hydrocarbons on the (001)-2 × 1 reconstructed silicon surface by the Monte Carlo and transfer-matrix methods

A model of the adsorption of cyclic unsaturated molecules on the Si(001)-2 × 1 reconstructed surface was developed for the example of 1,4-cyclohexadiene, which can be differently adsorbed on surface adsorption centers. Calculations were performed for a grand canonical ensemble by the Monte Carlo and transfer matrix methods. The structure of the ordered phases formed and the conditions of their appearance were studied in detail. It was shown that the suggested model reproduced all the qualitative special features of the system studied and similar systems.     

Direct-space analysis of the Si–Si bonding pattern in the π-bonded chain reconstructed Si(111)(2 × 1) surface

Atomic and bond properties of silicon atoms in the buckled π-bonded chain reconstructed Si(111)(2 × 1) system were investigated by applying the quantum theory of atoms in molecules to a number of wavefunctions from periodic ab initio calculations using a slab model for the surface and geometries from experiment. Reconstruction involves much larger surface-cell charge distortions than in the unrelaxed surface and drastic changes in the atomic polarizations of the surface layer atoms. The effect of buckling is to largely differentiate the properties (charge, energy, volume, atomic polarizations) of the two unique atoms of each surface layer. The direction of electronic charge transfer in the topmost chain (from the “up” to the “down” atom) was found to be opposite to what was claimed previously. The π conjugation is not strictly localized along the topmost layer chains (where it is also largely incomplete), but rather it extends over a 2D array of bonds between the topmost and the lower surface layers. Received: 19 July 2000 / Accepted: 2 October 2000 / Published online: 23 January 2001     

Depth profiling of oxygen in oxide films by 18O(p,α)15N nuclear reaction analysis

The paper describes the determination and depth profiling of oxygen in thin oxide films using ¹⁸O(p,??)¹⁵N nuclear reaction. The excitation function of ¹⁸O(p,??)¹⁵N nuclear reaction exhibits a resonance at 629?keV and a plateau at 730?keV with uniform cross-section. The resonance is used to determine the depth profile of oxygen in films while the plateau, to estimate its overall concentration. The resonance, characterized by a width of 2.1?keV enables high-depth resolution (~20?nm) measurements and has a probing depth of more than a micron. The paper presents depth profile measurements of oxygen in several metal oxide films (SiO₂, TiO₂ and HfO₂) using this resonance. Possible interferences arising from ¹⁵N(p,??)¹²C, ¹⁹F(p,??)¹⁶O and ¹¹B(p,??)2?? nuclear reactions are also discussed. It has been shown that it can serve as a suitable alternative to 3.05?MeV ¹⁶O(??,??)¹⁶O resonant scattering which is generally used for depth profiling oxygen. It is, in fact, more reliable and precise in materials that witness significant large angle multiple scattering. It can also be advantageously used to monitor ¹⁸O, when used as a tracer.     

Study of the evolution of CaCO3-V2O5 (1∶1) mixture at room temperature by thermal analysis

Reactivity of solid mixtures of crystalline V₂O₅ and basic compounds strongly increases at room temperature by means of water molecules adsorption process from a saturated atmosphere (100% RH). This is due, firstly, to a crystalline-amorphous V₂O₅ transformation and secondly to the formation of strongly acid V₂O₅ gels. In the present paper the evolution with time of the CaCO₃-V₂O₅ (11) mixture in the aforementioned conditions was studied by thermal analysis (TG, DTG and DSC), X-ray diffraction (XRD) and infrared spectroscopy (IR). The results confirmed the V₂O₅ gels formation which decomposed the basic CaCC₃ at room temperature through an acid-base mechanism reaction. A new crystalline compound was obtained which corresponded to a hydrated calcium metavanadate.This paper is a part of the L. Sobrados's PhD.     

Structural and dynamical studies of δ-Bi2O3 oxide ion conductors: III. Phase relationships in the system (Bi2O3)1−x(M2O3)x as a function of pressure and temperature (M = Y,Er, or Yb)

We report the results of a structural investigation of the nonstoichiometric solid solutions (Bi₂O₃)_1−x(M₂O₃)_x (M = Y, Er, or Yb) treated at temperatures of between 298 and 1023 K and at pressures of up to 4 GPa. For x = 0.25 and M = Er or Y, 4 GPa pressure at 873 K causes the fluorite-related phase stable under ambient conditions to transform to a monoclinic phase which on subsequent annealing transforms to a rhombohedral phase isostructural with that adopted by the solid solution (Bi₂O₃)_1−x(Sm₂O₃)_x under ambient conditions. For x = 0.4 and M = Er or Y, application of 4 GPa at 1073 K causes the fluorite phase to undergo a distortion to another rhombohedral structure with a smaller unit cell. No transitions were found in the Yb³⁺-doped system.     

Theoretical investigation of inhibition of the corrosion of A106 steel in NaCl solution by di-n-butyl bis(thiophene-2-carboxylato-O,O′)tin(IV)

This work reports results from potentiodynamic polarisation and impedance investigation, with a rotating disc electrode, of inhibition of corrosion of A106 steel in aerated, unstirred 3.0 % NaCl solutions using di-n-butyl bis(thiophene-2-carboxylato-O,O′)tin(IV) as inhibitor. These studies showed that it is a mixed-type inhibitor. Inhibition efficiency increased with increasing di-n-butyl bis(thiophene-2-carboxylato-O,O′)tin(IV) concentration and decreases with increasing solution temperature. Maximum efficiency of inhibition of the inhibitor of approximately 78 % is observed at a concentration at 10^?2 M. The inhibition process was attributed to formation of an adsorbed film on the metal surface that protects the metal against corrosive agents. The adsorption isotherm confirms the applicability of Langmuir equation to describe the adsorption process. Thermodynamic functions for the adsorption process were determined. The efficiency of corrosion inhibitors and global chemical reactivity depend on such properties as energy of the highest occupied molecular orbital (E _HOMO), energy of the lowest unoccupied molecular orbital (E _LUMO), energy gap (ΔE), which were calculated. All calculation was been performed by density functional theory (DFT) using the Gaussian03W suite of software. Calculated results were usually in agreement with the experimental data.     

Crystal Structure of the Bis(Picrato-O,O")Tetraaquacalcium Complex with 18-Crown-6, [Ca(Pic)2(H2O)4] · 18C6

The crystal structure of the bis(picrato-O,O")tetraaquacalcium complex with 18-crown-6, [Ca(Pic)₂(H₂O)₄] · 18C6 (I), was studied using X-ray diffraction analysis: space group C2/c, a= 20.446 Å, b= 14.985 Å, c= 16.163 Å, = 135. 41°, Z= 4. The structure of Iwas solved by the direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R= 0.047 over all 3044 measured independent reflections (CAD4 automated diffractometer, MoK radiation). In the crystal, Iis not a guest–host complex but exists as individual [Ca(Pic)₂(H₂O)₄] and 18C6 molecules joined by intermolecular hydrogen bonds and van der Waals interactions. The Ca²⁺cation (CN 8) is located on a twofold crystallographic axis, its coordination polyhedron being a distorted square antiprism. The centrosymmetrical 18C6 molecule has a crown conformation with approximate D _3d symmetry and has six neighboring water molecules (three on each side of its mean plane), which form eight hydrogen bonds involving all six O atoms of 18C6.     

Encapsulation of anion/cation in the central cavity of tetrameric polyoxometalate, composed of four trititanium(IV)-substituted α-Dawson subunits, initiated by protonation/deprotonation of the bridging oxygen atoms on the intramolecular surface

Preparation and structural characterization of a novel polyoxometalate (POM), [(P(2)W(15)Ti(3)O(60.5))(4)(NH(4))](35-) 1, i.e., an encapsulated NH(4)(+) cation species in the central cavity of a tetramer (called the Dawson tetramer) constituted by trititanium(IV)-substituted α-Dawson POM substructure, are described. POM 1 was synthesized by several different methods and unequivocally characterized by complete elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR spectroscopy, solution ((15)N{(1)H}, (31)P, (183)W) NMR spectroscopy, and X-ray crystallography. First, POM 1 was synthesized by a reaction of NH(4)Cl in aqueous solution with a precursor, which was derived by thermal treatment of a monomeric triperoxotitanium(IV)-substituted Dawson POM, [α-1,2,3-P(2)W(15)(TiO(2))(3)O(56)(OH)(3)](9-) 2, for 3 h in an electric furnace at 200 °C. The encapsulated NH(4)(+) cation in 1 was confirmed by (15)N{(1)H} NMR measurement and X-ray crystallography. As another synthesis of 1, a direct exchange of the Cl(-) anion encapsulated in [{α-1,2,3-P(2)W(15)Ti(3)O(57.5)(OH)(3)}(4)Cl](25-) 3 with the NH(4)(+) cation was attained by neutralizing an aqueous solution containing 3 with the addition of aqueous NH(3) (the initial pH of ca. 2-2.5 was changed to 6.4), followed by adding NH(4)Cl. It has been clarified that the conditions as to whether the anion or the cation is encapsulated in the central cavity of the Dawson tetramer were significantly related to the protonation/deprotonation of the bridging oxygen atoms on the intramolecular surface, Ti-O-Ti/Ti-OH-Ti sites constituting the Dawson subunits.     

Tuning the thermal properties of poly(ethylene)-like poly(esters) by copolymerization of ε-caprolactone with macrolactones,in the presence of a pyridylamidozinc(II) complex

Linear aliphatic poly(ester)s, as thermoplastic materials, are more and more envisaged as the potential “green” alternative to traditional plastics. Aliphatic polyesters having long methylene chain behave as “polyethylene-like” materials and can be prepared by ring-opening polymerization (ROP) of macrolactones. A pyridylamidozinc(II) complex was used for the ROP of ε-caprolactone (CL) and of two large ring size lactones, the ω-6-hexadecenlactone (6HDL) and the ω-pentadecalactone (PDL). High turnover frequencies were observed for the CL polymerization, while for the macrolactones, an entropy-driven behavior was recognized. Random copolymerizations of the PDL with 6HDL and of the macrolactones with CL were successfully achieved, and the copolymer microstructure was ascertained by NMR and MALDI analyses. The copolymer melting temperatures, measured by DSC, and the thermal degradation behavior, studied by TGA in nitrogen and air atmosphere, were dependent on the copolymer's composition. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 528–539     

Study of the oxygen distribution in YBa2Cu3O7−x ceramics by (n, α) radiography technique

A technique to determine the oxygen distribution in high T_c superconducting YBa₂Cu₃O_7–x ceramics has been developed which is based on the (n, ) radiography method. The technique enables the non-destructive study of superconducting ceramics as well as monocrystal samples with spatial resolution not worse than 1 m at a relative standard deviation of 1.5%. This technique is used to study the influence of radiation-stimulated diffussion of oxygen on the formation of the superconducting phase in an yttrium ceramic. The oxygen distribution in the samples with a narrow transition (T1 K) and with a transition widened (T10 K) by thermal and thermo-radiative treatment is compared in the experiment. The oxygen distribution radiographs of irradiated and unirradiated samples provide strong evidence for the influence of irradiation on the ordering of superconducting ceramics structure.     

Heavy element contamination of surface waters in the region Banská Štiavnica (SR) measured by radionuclide X-ray fluorescence analysis

Heavy metals (Pb, Cd, Mn, Cu, Zn, Fe) were determined in surface waters in the surroundings of the depositories of the mining shrubs in the region of Banská tiavnica (SR) by radionuclide X-ray fluorescence analysis. Allowed concentrations of the determined metals are exceeded numerously (multiplicity in some cases was 10³–10⁶).     

9Mg(OH)(2)·MgCl(2)·4H(2)O, a high temperature phase of the magnesia binder system

The metastable phase 9Mg(OH)(2)·MgCl(2)·4H(2)O (9-1-4 phase) was found at the extended metastable isotherm of Mg(OH)(2) in the system MgO-MgCl(2)-H(2)O at 120 °C and occurs as intermediate binder phase during setting of magnesia cement due to temperature development of the setting reaction. The crystal structure of the 9-1-4 phase was solved from high resolution laboratory X-ray powder diffraction data in space group I2/m (C2/m) (a = 22.2832(3) ?, b = 3.13501(4) ?, c = 8.1316(2) ?, β = 97.753(1)°, V = 562.86(2) ?(3), and Z = 1). Structural and characteristical relations of the phases in the system MgO-MgCl(2)-H(2)O can be derived, with which the development of the cement or concrete qualities becomes explainable.     

Source Rocks of the Caledonian-Age Granitoid Rocks in Wanyanshan-Zhuguangshan, Southeast China (Ⅱ)——Topological Analysis in Isotopic Multispace

Topological analysis in Sr-Nd-O-Pb_3 six-dimensional isotopic space suggests that the source rocks of the Caledonian-age granitoid rocks in Wanyangshan-Zhuguangshan, southeast China, comprise three end-member components. Isotopic mixing model discrimination indicates that the granitoid rocks were produced through mixing of the three componentsin varying proportions. Comprehensive study of multiple isotopic systems and geochemistry of the granitoid rocks suggests that the three end-member components were crustal rocks which are continent-derived sediments, geosycline sediments and altered basic volcanic rocks.