Determining the storage, availability and reactivity of NH3 within Cu-Chabazite-based Ammonia Selective Catalytic Reduction systems.

Three different types of NH3 species can be simultaneously present on Cu(2+)-exchanged CHA-type zeolites, commonly used in Ammonia Selective Catalytic Reduction (NH3-SCR) systems. These include ammonium ions (NH4(+)), formed on the Brønsted acid sites, [Cu(NH3)4](2+) complexes, resulting from NH3 coordination with the Cu(2+) Lewis sites, and NH3 adsorbed on extra-framework Al (EFAl) species, in contrast to the only two reacting NH3 species recently reported on Cu-SSZ-13 zeolite. The NH4(+) ions react very slowly in comparison to NH3 coordinated to Cu(2+) ions and are likely to contribute little to the standard NH3-SCR process, with the Brønsted groups acting primarily as NH3 storage sites. The availability/reactivity of NH4(+) ions can be however, notably improved by submitting the zeolite to repeated exchanges with Cu(2+), accompanied by a remarkable enhancement in the low temperature activity. Moreover, the presence of EFAl species could also have a positive influence on the reaction rate of the available NH4(+) ions. These results have important implications for NH3 storage and availability in Cu-Chabazite-based NH3-SCR systems.

The neurological illness of Friedrich Nietzsche.

BACKGROUND: Friedrich Nietzsche (1844-1900), one of the most profound and influential modern philosophers, suffered since his very childhood from severe migraine. At 44 he had a mental breakdown ending in a dementia with total physical dependence due to stroke. From the very beginning, Nietzsche's dementia was attributed to a neurosyphilitic infection. Recently, this tentative diagnosis has become controversial. OBJECTIVE: To use historical accounts and original materials including correspondence, biographical data and medical papers to document the clinical characteristics of Nietzsche's illness and, by using this pathography, to discuss formerly proposed diagnoses and to provide and support a new diagnostic hypothesis. MATERIALS: Original letters from Friedrich Nietzsche, descriptions by relatives and friends, and medical descriptions. Original German sources were investigated. Biographical papers published in medical journals were also consulted. RESULTS: Nietzsche suffered from migraine without aura which started in his childhood. In the second half of his life he suffered from a psychiatric illness with depression. During his last years, a progressive cognitive decline evolved and ended in a profound dementia with stroke. He died from pneumonia in 1900. The family history includes a possible vascular-related mental illness in his father who died from stroke at 36. CONCLUSIONS: Friedrich Nietzsche's disease consisted of migraine, psychiatric disturbances, cognitive decline with dementia, and stroke. Despite the prevalent opinion that neurosyphilis caused Nietzsche's illness, there is lack of evidence to support this diagnosis. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) accounts for all the signs and symptoms of Nietzsche's illness. This study adds new elements to the debate and controversy about Nietzsche's illness. We discuss former diagnoses, comment on the history of a diagnostic mistake, and integrate for the first time Nietzsche's medical problems.

Spin-polarized conceptual density functional theory study of the regioselectivity in ring closures of radicals.

The regioselectivity of ring-forming radical reactions is investigated within the framework of the so-called spin-polarized conceptual density functional theory. Two different types of cyclizations were studied. First, a series of model reactions of alkyl- and acyl-substituted radicals were investigated. Next, attention was focused on the radical cascade cyclizations of N-alkenyl-2-aziridinylmethyl radicals (a three-step mechanism). In both of these reactions, the approaching radical (carbon or nitrogen centered) adds to a carbon-carbon double bond within the same molecule to form a radical ring compound. In this process, the number of electrons is changing from a local point of view (a charge transfer occurs from one part of the molecule to another one) at constant global spin number Ns (both the reactant and the product ring compound are in the doublet state). It is shown that the experimentally observed regioselectivities for these ring-closure steps can be predicted using the spin-polarized Fukui functions for radical attack, f0NN(r).