Oxidation of Hypophosphite and Phosphite by Anderson‐Type Hexamolybdocobaltate(III) Anion

The oxidation of hypophosphite and phosphite by the Anderson‐type hexamolybdocobaltate(III), [H₆Co^IIIMo₆O₂₄]^3?, anion was investigated at pH 2 and 1, respectively, in aqueous medium. The reaction is found to occur through an outer‐sphere mechanism with a prior weak complex formation between the reactants. Under the reaction conditions, the oxidant exists in the [H₅Co^IIIMo₅O₂₀]^2?, [H₆Co^IIIMo₆O₂₄]^3?, and [H₄Co^III₂Mo₁₀O₃₈]^6?(dimer) forms, and [H₅Co^IIIMo₅O₂₀]^2? is the active species. Inhibition of the reaction by the oxidant anion and added molybdate ion kinetically indicates existence of prior equilibria between various forms of the oxidant. Both hypophosphite and phosphite exists in their protonated forms. The reaction involves direct electron transfer from the phosphorus center to the anion‐generating free radicals in a rate‐determining step. The effect of ionic strength and change in the solvent polarity did not affect the rate of the reaction. A probable mechanism was proposed leading to a complicated rate law as a result of involvement of prior equilibria between various forms of the oxidant. The activation parameters were also determined and are in support of the proposed mechanism.     

From Chemical Gardens to Fuel Cells: Generation of Electrical Potential and Current Across Self‐Assembling Iron Mineral Membranes

We examine the electrochemical gradients that form across chemical garden membranes and investigate how self‐assembling, out‐of‐equilibrium inorganic precipitates—mimicking in some ways those generated in far‐from‐equilibrium natural systems—can generate electrochemical energy. Measurements of electrical potential and current were made across membranes precipitated both by injection and solution interface methods in iron‐sulfide and iron‐hydroxide reaction systems. The battery‐like nature of chemical gardens was demonstrated by linking multiple experiments in series which produced sufficient electrical energy to light an external light‐emitting diode (LED). This work paves the way for determining relevant properties of geological precipitates that may have played a role in hydrothermal redox chemistry at the origin of life, and materials applications that utilize the electrochemical properties of self‐organizing chemical systems.     

Surfaces et cohomologie bornée

Résumé Ce travail comprend deux parties. Dans la premiére, nous étudions le genre minimum d'une surface qui représente une classe d'homologie donnée de degré 2. La deuxième partie est consacrée à une analyse du second groupe de cohomologie bornée d'une surface.     

Electronic transition dipole moment functions and difference potentials for transitions among low-lying states of Li2 and Na2

Electronic transition dipole moment functions based on ab initio multiconfiguration self-consistent field wavefunctions are computed for the transitions ¹Σ_u⁺-¹Σ_g⁺, ³Σ_g⁺-³Σ_u⁺, ¹Π_u-¹Σ_g⁺, ³Π_g-³Σ_u⁺, ¹Σ_u⁺-¹Π_g, ³Σ_g⁺-³Π_u, ¹Π_u-¹Π_g, and ³Π_g-³Π_u in Li₂ and Na₂. (In each case the states are the lowest lying of their symmetry.) We also calculate the matrix element 〈³Σ_u⁺|i(L_x - iL_y)|³Π_u〉 for the predissociation of the ³Π_u state by the ³Σ_u⁺ state. Several unobserved spectral features are predicted.     

Kinetics of wet air oxidation of sodium sulfide over heterogeneous iron catalyst

Wet air oxidation (WAO) is an established technique for reducing the chemical oxygen demand (COD) of refinery sulfidic spent caustic waste. In the present work, the heterogeneous form of the cheap and abundant catalyst ferrous sulfate (FeSO₄) was employed for WAO of sodium sulfide. The performance of this catalyst in the oxidative destruction of this model compound is thus far unfamiliar. Kinetic data for the non-catalytic and catalytic oxidation processes was collected in a batch reactor. For the catalytic process, temperature (T), oxygen partial pressure () and catalyst concentration (ω) were varied in the ranges 80-150°C, 0.69-2.06 MPa and 0.8-2.4 g/L respectively. Around 94% COD was destroyed within 1 h when feed containing 8 g/L of sulfide was oxidized at T = 100°C, = 0.69 MPa, and ω = 0.8 g/L. First, the data on disappearance of COD were fitted to a power law model and reaction rate constants were determined. The activation energy for the non-catalytic (91 kJ/mol) and catalytic (50 kJ/mol) oxidation process was found from the temperature dependence of the rate constants. Second, hyperbolic models based on Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-L) kinetics were used for fitting kinetic data. It was found that the L-H model suggesting dissociative adsorption of oxygen provided the best fit. In this way, a deep insight into oxidation kinetics of sodium sulfide was provided.     

Microwave Irradiation in Micro‐ Meso‐Fluidic Systems; Hybrid Technology has Issued the Challenge

A combination of microwave irradiation and flow chemistry has been described as a promising smart and hyphenated technology that can fuse and synergize the benefits of the techniques. The cells and tissues of all living organisms promote a huge number of bioorganic reactions that occur as flow systems and not the batch‐type conditions typically used by chemists and biotechnologists. Microwave‐assisted chemical conversion carried out in continuous flow mode with micro‐ or meso‐channel reactors can offer significant processing advantages, including improved thermal exchange, energy efficiency, safety, mixing control, a wider range of reaction conditions, repeatability and scalability as well as dramatic reductions in side‐reactions and degradations. This review will discuss relevant examples of organic synthesis and nanoparticles production performed in continuous flow mode with integrated microwave irradiation in micro‐ or mesofluidic systems.     

Membrane trafficking and mitochondrial abnormalities precede subunit c deposition in a cerebellar cell model of juvenile neuronal ceroid lipofuscinosis

Background  

JNCL is a recessively inherited, childhood-onset neurodegenerative disease most-commonly caused by a ~1 kb CLN3 mutation. The resulting loss of battenin activity leads to deposition of mitochondrial ATP synthase, subunit c and a specific loss of CNS neurons. We previously generated Cln3 ^Δex7/8 knock-in mice, which replicate the common JNCL mutation, express mutant battenin and display JNCL-like pathology.     

An over-expression system for characterizing <Emphasis Type="Italic">Ppt1</Emphasis> function in <Emphasis Type="Italic">Drosophila</Emphasis>

Background  

The infantile onset form of Neuronal Ceroid Lipofuscinoses (INCL) is the earliest and most severe form of NCL, with neurological symptoms that reflect massive neurodegeneration in the CNS and retina. INCL is due to recessively inherited mutations at the CLN1 locus. This locus encodes the evolutionarily conserved enzyme palmitoyl-protein thioesterase 1 (PPT1), indicating an essential role for protein palmitoylation in normal neuronal function.