Carbon dioxide photolysis from 150 to 210 nm: Singlet and triplet channel dynamics,UV-spectrum,and isotope effects

We present a first principles study of the carbon dioxide (CO₂) photodissociation process in the 150- to 210-nm wavelength range, with emphasis on photolysis below the carbon monoxide + singlet channel threshold at ∼167 nm. The calculations reproduce experimental absorption cross-sections at a resolution of ∼0.5 nm without scaling the intensity. The observed structure in the 150- to 210-nm range is caused by excitation of bending motion supported by the deep wells at bent geometries in the and potential energy surfaces. Predissociation below the singlet channel threshold occurs via spin-orbit coupling to nearby repulsive triplet states. Carbon monoxide vibrational and rotational state distributions in the singlet channel as well as the triplet channel for excitation at 157 nm satisfactorily reproduce experimental data. The cross-sections of individual CO₂ isotopologues (¹²C¹⁶O₂, ¹²C¹⁷O¹⁶O, ¹²C¹⁸O¹⁶O, ¹³C¹⁶O₂, and ¹³C¹⁸O¹⁶O) are calculated, demonstrating that strong isotopic fractionation will occur as a function of wavelength. The calculations provide accurate, detailed insight into CO₂ photoabsorption and dissociation dynamics, and greatly extend knowledge of the temperature dependence of the cross-section to cover the range from 0 to 400 K that is useful for calculations of propagation of stellar light in planetary atmospheres. The model is also relevant for the interpretation of laboratory experiments on mass-independent isotopic fractionation. Finally, the model shows that the mass-independent fractionation observed in a series of Hg lamp experiments is not a result of hyperfine interactions making predissociation of ¹⁷O containing CO₂ more efficient.     

A Quantum Probability Perspective on Borderline Vagueness

The term “vagueness” describes a property of natural concepts, which normally have fuzzy boundaries, admit borderline cases, and are susceptible to Zeno's sorites paradox. We will discuss the psychology of vagueness, especially experiments investigating the judgment of borderline cases and contradictions. In the theoretical part, we will propose a probabilistic model that describes the quantitative characteristics of the experimental finding and extends Alxatib's and Pelletier's ( 2011 ) theoretical analysis. The model is based on a Hopfield network for predicting truth values. Powerful as this classical perspective is, we show that it falls short of providing an adequate coverage of the relevant empirical results. In the final part, we will argue that a substantial modification of the analysis put forward by Alxatib and Pelletier and its probabilistic pendant is needed. The proposed modification replaces the standard notion of probabilities by quantum probabilities. The crucial phenomenon of borderline contradictions can be explained then as a quantum interference phenomenon.     

Successful treatment of systemic juvenile xanthogranulomatosis with cytarabine and 2‐chlorodeoxyadenosine: case report and review of the literature

The non‐Langerhans cell histiocytosis (LCH) juvenile xanthogranulomatosis (JXG) is usually a benign disease limited to the skin. Only a few cases of systemic disease with at least two affected organs and lethal outcomes have been reported to date. Treatment is controversial and no standard protocol is available. We report the rare case of a 22‐month‐old boy presenting multiple erythematous brownish papules of the head, trunk and legs, which had developed starting from his 6th month of life. Additional symptoms were delayed psychomotor development, hydrocephalus and hepatosplenomegaly. Further diagnostics revealed a systemic JXG with involvement of the skin, central nervous system, liver and spleen. The patient did not respond to initial therapy with prednisone and vinblastine according to protocol III for LCH. However, further therapy with cytarabine and 2‐chlorodeoxyadenosine followed by a consolidation phase with 2‐chlorodeoxyadenosine alone was successful and the patient is in his 4th year of remission. We provide a comprehensive review of the reported cases of systemic JXG to date.