Lithium 2,3-dihydro-1-benzothiophene-1,1-dioxide: synthesis, characterization, DFT calculations, and reactivity toward aldehydes and azomethines

The sulfonyl carbanion derived from 2,3-dihydro-1-benzothiophene-1,1-dioxide and its lithium salt has been investigated by DFT calculations. NMR and IR spectroscopic analyses showed that the lithium sulfonyl carbanion exists in solution as a monomer in equilibrium with a dimer. The lithium carbanion was treated with aldehydes and azomethynes to give chiral hydroxy and amino derivatives. The stereochemistry of the products and the diastereoselectivity of the reaction were investigated.     

A Solution-Generating Method in Einstein-Scalar Gravity

We present a method to generate static, spherically symmetric, solutions of Einstein gravity in \(d+2\) dimensions minimally coupled to a real scalar field with a self-interacting potential. The solutions can be fully parametrised by a single function, whose behaviour encodes all the information about the local and global behaviour of the spacetime. We give several explicit applications of our solution-generating method that describe black holes, naked singularities and solitonic configurations.

     

The universal C*-algebra of the electromagnetic field II. Topological charges and spacelike linear fields

Conditions for the appearance of topological charges are studied in the framework of the universal C*-algebra of the electromagnetic field, which is represented in any theory describing electromagnetism. It is shown that non-trivial topological charges, described by pairs of fields localised in certain topologically non-trivial spacelike separated regions, can appear in regular representations of the algebra only if the fields depend non-linearly on the mollifying test functions. On the other hand, examples of regular vacuum representations with non-trivial topological charges are constructed, where the underlying field still satisfies a weakened form of “spacelike linearity”. Such representations also appear in the presence of electric currents. The status of topological charges in theories with several types of electromagnetic fields, which appear in the short distance (scaling) limit of asymptotically free non-abelian gauge theories, is also briefly discussed.     

Optimizing biological wastewater treatment

Ricerche di Matematica - In this paper we propose a non linear mathematical model describing the process of biodegradation of organic pollutants by means of fungi, and using glucose to sustain its...     

Hysteresis in $$\eta /s$$ for QFTs dual to spherical black holes

We define and compute the (analog) shear viscosity to entropy density ratio \(\tilde{\eta }/s\) for the QFTs dual to spherical AdS black holes both in Einstein and Gauss–Bonnet gravity in five spacetime dimensions. Although in this case, owing to the lack of translational symmetry of the background, \(\tilde{\eta }\) does not have the usual hydrodynamic meaning, it can be still interpreted as the rate of entropy production due to a strain. At large and small temperatures it is found that \(\tilde{\eta }/s\) is a monotonic increasing function of the temperature. In particular, at large temperatures it approaches a constant value, whereas at small temperatures, when the black hole has a regular, stable extremal limit, \(\tilde{\eta }/s\) goes to zero with scaling law behavior. Whenever the phase diagram of the black hole has a Van der Waals-like behavior, i.e. it is characterized by the presence of two stable states (small and large black holes), connected by a meta-stable region (intermediate black holes), the system evolution must occur through the meta-stable region- and temperature-dependent hysteresis of \(\tilde{\eta }/s\) is generated by non-equilibrium thermodynamics.     

Quantitative studies on free radical reactions with the scavenger 1,1,3,3-tetramethylisoindolinyl-2-oxy

Previously unobserved reaction pathways for the attack of $\text{tert}$-butoxy radicals on vinyl monomers have been found by a technique which employs the title nitroxide as radical scavenging agent.     

Bromination of single crystals of trans-1,4-polybutadiene. Thermal behavior

It is demonstrated by several methods (DSC, infrared spectroscopy, and small-angle and wideangle x-ray diffraction) that bromination of suspensions of single crystals of trans-1,4-polybutadiene is selective at the fold surface. As the thickness of the single crystals is increased, a larger number of double bonds per fold are brominated, i.e. a larger number of repeat units become accessible to bromine. This is consistent with an increase in the thickness of disordered surface layers with the crystallization temperature. A reduction of 40–60% in overall apparent enthalpies of transition and of melting and reduced ability of brominated single crystals to refold following annealing are also observed. Crystallization from the melt of trans-1,4-PBD with [ CH₂? CHB_r? CHB_r? CH₂ ] units along the chain is interpreted by assuming that some of these units are incorporated in the crystal lattice as defects.     

Reduction of mercury(II) by tropical river humic substances (Rio Negro)-Part II. Influence of structural features (molecular size, aromaticity, phenolic groups, organically bound sulfur)

The influence of structural features of tropical river humic substances (HS) on their capability to reduce mercury(II) in aqueous solutions was studied. The HS investigated were conventionally isolated from Rio Negro water-Amazonas State/Brazil by means of the collector XAD 8. In addition, the isolated HS were on-line fractionated by tangential-flow multistage ultrafiltration (nominal molecular-weight cut-offs: 100, 50, 30, 10, 5 kDa) and characterized by potentiometry and UV/VIS spectroscopy. The reduction of Hg(II) ions to elemental Hg by size-fractions of Rio Negro HS was assessed by cold-vapor AAS (CVAAS). UV/VIS spectrometry revealed that the fractions of high molecular-size (F₁>100 kDa and F₂: 50-100 kDa) have a higher aromaticity compared to the fractions of small molecular-size (F₅: 5-10 kDa, F₆: <5 kDa). In contrast, the potentiometric study showed different concentration of functional groups in the studied HS fractions. The reduction of Hg(II) by aquatic HS fractions at pH 5 proceeded in two steps (I, II) of slow first order kinetics (t_1/2 of I: 160 min, t_1/2 of II: 300 min) weakly influenced by the molecular-size, in contrast to the differing degree of Hg(II) reduction (F₅>F₂>>F₁>F₃>F₄>>F₆). Accordingly, Hg(II) ions were preferably reduced by HS molecules having a relatively high ratio of phenolic/carboxylic groups and a small concentration of sulfur. From these results a complex ‘competition’ between reduction and complexation of mercury(II) by aquatic HS occurring in tropical rivers such as the Rio Negro can be suggested.