Electro-fenton and photoelectro-fenton degradation of sulfanilic acid using a boron-doped diamond anode and an air diffusion cathode

The mineralization of sulfanilic acid has been studied by electro-Fenton (EF) and photoelectro-Fenton (PEF) reaction with UVA light using an undivided electrochemical cell with a boron-doped diamond (BDD) anode and an air diffusion cathode able to generate H(2)O(2). Organics were then oxidized by hydroxyl radicals formed at the anode surface from water oxidation and in the bulk from Fenton's reaction between generated H(2)O(2) and added Fe(2+). The UVA irradiation in PEF enhanced the production of hydroxyl radicals in the bulk, accelerating the removal of organics and photodecomposed intermediates like Fe(III)-carboxylate complexes. Partial decontamination of 1.39 mM sulfanilic acid solutions was achieved by EF until 100 mA cm(-2) at optimum conditions of 0.4 mM Fe(2+) and pH 3.0. The increase in current density and substrate content led to an almost total mineralization. In contrast, the PEF process was more powerful, yielding almost complete mineralization in less electrolysis time under comparable conditions. The kinetics for sulfanilic acid decay always followed a pseudo-first-order reaction. Hydroquinone and p-benzoquinone were detected as aromatic intermediates, whereas acetic, maleic, formic, oxalic, and oxamic acids were identified as generated carboxylic acids. NH(4)(+) ion was preferentially released in both treatments, along with NO(3)(-) ion in smaller proportion.     

All bipartite entangled states are useful for information processing

The question of whether all entangled states can be used as a nonclassical resource has remained open so far. Here we provide a conclusive answer to this problem for the case of systems shared by two parties. We show that any entangled state can enhance the teleportation power of some other state. This holds even if the state is bound entangled.     

Structural insights for the design of new PPARgamma partial agonists with high binding affinity and low transactivation activity

Peroxisome Proliferator-Activated Receptor γ (PPARγ) full agonists are molecules with powerful insulin-sensitizing action that are used as antidiabetic drugs. Unfortunately, these compounds also present various side effects. Recent results suggest that effective PPARγ agonists should show a low transactivation activity but a high binding affinity to inhibit phosphorylation at Ser273. We use several structure activity relationship studies of synthetic PPARγ agonists to explore the different binding features of full and partial PPARγ agonists with the aim of differentiating the features needed for binding and those needed for the transactivation activity of PPARγ. Our results suggest that effective partial agonists should have a hydrophobic moiety and an acceptor site with an appropriate conformation to interact with arm II and establish a hydrogen bond with Ser342 or an equivalent residue at arm III. Despite the fact that interactions with arm I increase the binding affinity, this region should be avoided in order to not increase the transactivation activity of potential PPARγ partial agonists.     

Principal mappings of 3-dimensional Riemannian spaces into spaces of constant curvature

As is well-known, the Gauss theorem, according to which any 2-dimensional Riemannian metric can be mapped locally conformally into an euclidean space, does not hold in three dimensions. We define in this paper transformations of a new type, that we call principal. They map 3-dimensional spaces into spaces of constant curvature. We give a few explicit examples of principal transformations and we prove, at the linear approximation, that any metric deviating not too much from the euclidean metric can be mapped by a principal transformation into the euclidean metric.     

Mechanistic studies on the conversion of dicobalt octacarbonyl into colloidal cobalt nanoparticles

In situ ATR-FTIR monitoring has allowed the direct study of the effect of additives (trioctylphosphine oxide [TOPO] and oleic acid) on the kinetics and rate of the thermal decomposition of dicobalt octacarbonyl leading to the formation of colloidal cobalt nanoparticles (CoCNPs). The study has shown that additives usually considered as simple surfactants influence the rate and kinetics of the decomposition of dicobalt octacarbonyl. Several of the initial intermediates connecting Co2(CO)8 with CoCNPs have been identified, and a tentative mechanism for the formation of the colloidal nanoparticles has been proposed.     

A valence-bond-based complete-active-space self-consistent-field method for the evaluation of bonding in organic molecules

We present the complete-active-space self-consistent-field (CASSCF) implementation of a valence-bond (VB) based method for the analysis of bonding in organic molecules. The method uses the spin-exchange density matrix P with a localized orbital basis, where the determinants of the CASSCF wavefunction become VB-like determinants with different spin coupling patterns. The index P_ij evaluates the contributions of the determinants to the CASSCF wavefunction and is used to generate resonance formulas. We use the bonding contributions in the original VB formulation of the method ( terms). The method is applied in studies of excited-state reactivity, as shown here for indole. Its first excited state is covalent and is characterized by a decrease in the bond orders in the benzene moiety, similar to the B_2u excited state of benzene. In contrast, the ionic excited state has an inversion in the bonds of the pyrrole moiety induced by charge transfer to the benzene ring.     

Transmitting information along oligo-para-phenylenes: 1,12-stereochemical control in a terphenyl tetracarboxamide

Amide-substituted terphenyls adopt a well-defined conformation that allows the transmission of stereochemical information from a controlling centre to a reaction site 11 bond lengths away, providing a model of how extended polymeric systems might be used to communicate binary information.     

MS-CASPT2 calculation of excess electron transfer in stacked DNA nucleobases

Calculations using the complete active space self-consistent field (CASSCF) and complete active space second-order perturbation (CASPT2) methods, and the multistate formulation of CASPT2 (MS-CASPT2), are performed for the ground and excited states of radical anions consisting of two pi-stacked nucleobases. The electronic couplings for excess electron transfer (EET) in the pi-stacks are estimated by using the generalized Mulliken-Hush approach. We compare results obtained within the different methods with data derived using Koopmans' theorem approximation at the Hartree-Fock level. The results suggest that although the one-electron scheme cannot be applied to calculate electron affinities of nucleobases, it provides reasonable estimates for EET energies. The electronic couplings calculated with KTA lie between the CASPT2 and the MS-CASPT2 based values in almost all cases.