| 1. |
- Brändas, Erkki J.
(författare)
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A Comment on Background Independence in Quantum Theory
- 2016
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Ingår i: Journal of the Chinese Chemical Society (Taipei). - : Wiley. - 0009-4536 .- 2192-6549. ; 63:1, s. 11-19
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Tidskriftsartikel (refereegranskat)abstract
- In this communication we take up the significance and purpose of selecting the proper coordinate system from the flat space-time of non-relativistic theories to the quantum theoretic formulation of general relativity. The universal background problem is straight forwardly framed as a momentum-energy portrait in nexus with its space-time conjugates. The description is based on operator matrix algebra, where the related analogue of the secular equation yields a Klein-Gordon type equation and the associated Minkowski eigentime element. The energy-momentum and their conjugate partners are represented by spaces that have (+,-) signatures. The general theory implicates both non-zero- and zero rest-mass entities, and it is proved that the conjugate relationship between energy and time provide a simple derivation of the Schwarzschild line element for the case of a gravitational field outside a spherical non-rotational uncharged mass. This result, indicating the appearance of a black hole as a true singularity in the energy-time formulation, and obtained as a direct consequence of their conjugate relationship, manifests background independence in concert with Einstein's equivalence principle. Inducing a reformulation of the Lorentz Transformation respecting the indefinite Minkowski metric, displays an interesting relation between complex dilations and indefinite metric spaces, validating the complex symmetric ansatz.
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| 2. |
- Tahira, Aneela, et al.
(författare)
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Role of cobalt precursors in the synthesis of Co 3 O 4 hierarchical nanostructures toward the development of cobalt‐based functional electrocatalysts for bifunctional water splitting in alkaline and acidic media
- 2022
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Ingår i: Journal of the Chinese Chemical Society (Taipei). - : John Wiley & Sons. - 0009-4536 .- 2192-6549. ; 69:4, s. 681-691
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Tidskriftsartikel (refereegranskat)abstract
- The precursors have significant influence on the catalytic activity of nonprecious electrocatalysts for effective water splitting. Herein, we report active electrocatalysts based on cobalt oxide (Co3O4) hierarchical nanostructures derived from four different precursors of cobalt (acetate, nitrate, chloride, and sulfate salts) using the low-temperature aqueous chemical growth method. It has been found that the effect of precursor on the morphology of nanostructured material depends on the synthetic method. The Co3O4 nanostructures exhibited cubic phase derived from these four precursors. The Co3O4 nanostructures obtained from chloride precursor have demonstrated improved oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) compared to other precursors due relatively higher content of Co3O4 nanostructures at the surface of material. An overpotential of 400 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2 was observed for HER. The Co3O4 nanostructures derived from the chloride precursor have shown favorable reaction kinetics via 34 mV dec−1 value of the Tafel slope for HER reaction. The Co3O4 nanostructures derived from chloride precursor have also shown an excellent HER durability for 15 hr in alkaline media. Furthermore, the OER functional characterization was carried out onto Co3O4 nanostructures derived from chloride precursor exhibited 220 mV overpotential at 10 mA cm−2 and Tafel slope of 56 mV dec−1. Importantly, the reason behind the favorable catalytic activity of Co3O4 nanostructures derived from chloride precursor was linked to one order of magnitude smaller charge transfer resistance and higher amount of Co3O4 content at the surface of nanostructures than the Co3O4 nanostructures derived from other precursors. The performance of Co3O4 nanostructures derived from chloride precursor via the wet chemical method suggests that cobalt chloride precursor could be of great interest for the development of efficient, stable, nonprecious, and environmentally friendly electrocatalysts for the chemical energy conversion and storage devices.
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| 3. |
- Dias, Rita, et al.
(författare)
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DNA-Surfactant interactions, compaction, condensation, decompaction and phase separation
- 2004
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Ingår i: Journal of the Chinese Chemical Society. - 2192-6549. ; 51:3, s. 447-469
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Forskningsöversikt (refereegranskat)abstract
- Recent investigations-of the interaction between DNA and alkyltrimethyl ammonium bromides of various chain lengths are reviewed. Several techniques have been used such as phase map determinations, fluorescence microscopy, and electron microscopy. Dissociation of the DNA-surfactant complexes, by the addition of anionic surfactant, has received special attention. Precipitation maps for DNA-cationic surfactant' systems were evaluated by turbidimetry for different salt concentrations, temperatures and surfactant chain lengths. Single-stranded DNA molecules precipitate at lower surfactant concentrations than double-helix ones. It was also observed that these systems precipitate for very low concentrations of both DNA and surfactant, and that the extension of the two-phase region increases for longer chain surfactants; these observations correlate well with fluorescence microscopy results, monitoring the system at a single molecule level. Dissociation of the DNA-cationic surfactant complexes and a concomitant release of DNA was achieved by addition of anionic surfactants. The unfolding of DNA molecules, previously compacted with cationic surfactant, was shown to be strongly dependent on the anionic surfactant chain length; lower amounts of a longer chain surfactant were needed to release DNA into solution. On the other hand, no dependence on the hydrophobicity of the compacting agent was observed. The structures of the aggregates formed by the two surfactants, after the interaction with DNA, were imaged by cryogenic transmission electron microscopy. It is possible to predict the structure of the aggregates formed by the surfactants, like vesicles, from the phase behaviour of the mixed surfactant systems. The compaction of a medium size polyanion with shorter polycations was furthermore studied by means of Monte Carlo simulations. The polyanion chain suffers a sudden collapse as a function of the condensing agent concentration and of the number of charges on the molecules. Further increase of the concentration gives an increase of the degree of compaction. The compaction was found to be associated with the polycations promoting bridging between different sites of the polyanion. When the total charge of the polycations was lower than that of the polyanion, a significant translational motion of the compacting agent along the polyanion was observed, producing only a small-degree of intrachain segregation. However, complete charge neutralization was not a prerequisite to achieve compacted forms.
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| 4. |
- Khosravi, Kaveh, et al.
(författare)
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Metal‐Free and Efficient Epoxidation of α, β‐ Unsaturated Ketones with 1, 1, 2, 2‐Tetrahydroperoxy‐1, 2‐Diphenylethane as a Powerful Solid Oxidant
- 2017
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Ingår i: Journal of the Chinese Chemical Society. - : Wiley. - 0009-4536. ; 64:6, s. 683-689
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Tidskriftsartikel (refereegranskat)abstract
- 1,1,2,2‐Tetrahydroperoxy‐1,2‐diphenylethane was used for the efficient and metal‐free epoxidation of various α,β‐unsaturated ketones, carried out under mild alkaline conditions at room temperature.
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| 5. |
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