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[en] A discussion is made of existing theories of Ps inhibition in the presence of Cl- ions. Our favoured interpretation of the data uses the thermalised pre-solvated positron as a common precursor of Ps and e+Cl-. Consideration is given to the prevention of solvation by the strong electric fields in the vicinity of Cl- ions, assuming best estimates for the solvation time, positron mobility and intermolecular spacing. An expression for the Ps inhibition constant K is derived on the basis of diffusive capture. The observed enhancement of Ps yield at higher Cl- concentrations is attributed to the scavenging by the Cl- ion of highly mobile species such as H2+O within times approx.=10-14 s. Dissociation between e+Cl- and the solvated state esub(s)+ is suggested as the cause of the ''missing fraction''. (orig.)
[en] Hollow-structured nanomaterials generally showed enhanced catalytic abilities due to their high utilization. In this work, a general method for the synthesis of PtCu3 nanoframes was reported with the employment of hexadecyltrimethylammonium chloride (CTAC), copper(I) chloride, and various kinds of platinum precursors such as K2PtCl6, H2PtCl6, and Pt(acac)2. It was revealed that the presence of CTAC was crucial for the formation of frame structures. On the one hand, CTAC could act as a structure director, and on the other hand, the galvanic replacement and etching effect of the chloride ions together with oxygen was also responsible for the formation of the frame structure. A similar effect was also evidenced in the case of hexadecyltrimethylammonium bromide. Finally, the as-obtained PtCu3 nanoframes demonstrated high catalytic abilities in the oxidation of methanol as a model reaction. .
[en] The negative ion resonances in molecular chlorine are probed using velocity slice imaging of the Cl− fragment produced in dissociative electron attachment (DEA). The capability of the velocity slice imaging to cover the entire 360° allows us to obtain clear evidence for the presence of the resonance in the 2.5 eV DEA peak along with the presence of The resonance is expected to be the contributor only to the 0 eV DEA peak. Its presence in the 2.5 eV DEA peak calls for a relook at the theoretical calculations which have not identified any resonance in the 2.5 eV peak. We also identify the presence of the and resonances in the 5.6 eV peak. The momentum images indicate no signature of a resonant contribution in the dipolar dissociation region up to 80 eV. (paper)
[en] Three tetrazole derivatives (TDs), 1-(3-Acetamide) phenyl-5-mercaptotetrazole (ACET), 1-Phenyl-5-mercaptotetrazole (PMT) and 1-Methyl-5-mercaptotetrazole (MMT), have been studied as novel levelers for filling electroplated Cu microvia. It is found that the Cu deposition potential decreases with the addition of TDs into the Cu plating solutions, with the lowest deposition potential observed for MMT and the largest deposition potential change (Δη) observed for ACET. The ACET exhibits the strongest convection-dependent adsorption behavior with SPS, Cl"−, and OP/OE, and the thickness of copper surface layer can be thinned to ∼15 μm in the ACET concentration range of 1.0 ∼ 10.0 ppm. The electrochemical impedance spectroscopy studies suggest that both the charge transfer resistance (R_c_t) and the adsorbed layer resistance (R_a_d) increase with the addition of TDs. Quantum chemical calculations indicate that the energy gaps (ΔE) of TDs correlate negatively with Δη, and the most active reaction sites for surface adsorption are the N3 in the thiol forms and the N4 in the thione forms of the TDs through Fukui functions.
[en] This essay is based on a talk at Advances in Atomic, Molecular, and Optical Sciences 2020 (AAMOS20) in a symposium honoring Prof. S. T. Manson’s decades-long contribution to photoabsorption studies. Quantum physics introduced into physics pairs of conjugate quantities bearing a specific complementary relationship, energy and time being one such pair. This gives rise to two alternative representations, a time-dependent and a time-independent one, seemingly very different but both capable of embracing the same physics. They give complementary descriptions and insight, with technical questions, theoretical and experimental, determining which may be the more convenient and practicable at any juncture. Two recent topics, Cooper minima in photoabsorption in Cl− and Ar, and angular-momentum barrier tunneling of f photoelectrons from Se in WSe2, provide illustrative examples, also of the role that technological developments over the past five decades played in our approach to and understanding of phenomena. (paper)
[en] Densities of ionic liquids at different temperature and pressure were collected from 84 references. The collection contains 7381 data points derived from 123 pure ionic liquids and 13 kinds of binary ionic liquids mixtures. In terms of the collected database, a group contribution method based on 51 groups was used to predict the densities of ionic liquids. In group partition, the effect of interaction among several substitutes on the same center was considered. The same structure in different substitutes may have different group values. According to the estimation of pure ionic liquids' densities, the results show that the average relative error is 0.88% and the standard deviation (S) is 0.0181. Using the set of group values three pure ionic liquids densities were predicted, the average relative error is 0.27% and the S is 0.0048. For ionic liquid mixtures, they are thought considered as idea mixtures, so the group contribution method was used to estimate their densities and the average relative error is 1.22% with S is 0.0607. And the method can also be used to estimate the densities of MClx type ionic liquids which are produced by mixing an ionic liquid with a Cl- anion and a kind of metal chloride.
[en] To find the suitable conditions under which nano-SiO2 can exhibit a significant impermeability enhancement effect and the mechanism underlying this effect, comparisons between the permeability-related properties of a nano-SiO2-filled cement paste and those of a reference cement paste composed of different water/cement (W/C) ratios were carried out in this research. Permeability-related properties of cement paste, such as the chloride-ion penetration coefficient (Dnssm), water permeability coefficient (Kp), and initial water sorptivity coefficient (Si), were tested. Furthermore, Power’s model, mercury intrusion porosimetry data, and the general effective media theory were also applied to analyse the evolution mechanism. The results indicate that the effect of nano-SiO2 on the enhancement of the impermeability becomes more remarkable at a lower W/C ratio. The decreasing rates of Dnssm, Kp, and Si increase as the W/C ratio decreases. Furthermore, it can be concluded that the effects of nano-SiO2 on promoting the hydration, refining the pore structure, narrowing the width of microcrack and thus enhancing the impermeability of cement paste become much clearer as the W/C ratio decreases.
[en] In search for solution to the challenges posed by the degradation of roofing steel sheet in an aggressive environment, galvanization of steel sheet for roofing of buildings and manufacture of other Engineering structures has been a valuable remedy. Galvanization of steel in recent years has emerged as a physical barrier which minimizes the penetration of contamination of sulphide and chloride ion. Zinc coating of steel top surface is a strategy that has been found to be effective for wide range applications. Galvanized steel sheets have been widely used by various manufacturing company. Occasional switching from steel to other metal like aluminum have not been cost effective because of the present economically situation. This makes substituting galvanized steel difficult. This mini review provides insight to the production process, stages and properties of galvanized roofing steel sheet use in Nigeria and most part of Africa. (paper)
[en] Electron beam was used for degradation of aqueous solutions of 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP) in this research. The effect of absorbed dose on substrate degradation, dechlorination and pH of solutions with an initial concentration of 200 mg/L each and another solution containing 50 mg/L each of the three solutes mixed together were investigated. The results show that increased dose leads to increased degradation of the chlorophenols, increased Cl- yield and decreasing pH value of the solutions. For the individual solutions containing 200 mg/L of solutes, the rate of degradation and chloride ion yield was in the order of 2,4-DCP>4-CP>2-CP, while for the mixed 50 mg/L solution, while 2,4-DCP still has the highest degradation rate, the degradation of 4-CP and 2-CP proceeded almost at the same rate. At a dose of 21 kGy, the rate of degradation were 93.0% for 2-CP, 98.5% for 4-CP and 99.4% for 2,4-DCP (200 mg/L individual solutions), and the chloride yield was 55.4%, 71.3% and 69.0% for 2-CP, 4-CP and 2,4-DCP respectively. The calculated dose required for 90% degradation of the original solute (D90) are 18.0 kGy (2-CP), 11.4 kGy(4-CP) and 6.1 kGy (2,4-DCP) for the 200 mg/L solutions and 16.1 kGy(2-CP), 15.6 kGy(4-CP) and 12.8 kGy (2,4-DCP) for the 50 mg/L mixed solution. (authors)