Breakdown curves of CH2(+), CH3(+), and CH4(+) molecules

Aims. The aim of this work is to provide semi-empirical branching ratios (BRs) for the kinetic databases used in astrochemistry, such as the KInetic Database for Astrochemistry (KIDA). Our work focuses on the CHy(+) species (y = 2–4) excited by cosmic rays (CR), electrons, and photons (UV), or the intermediate excited complexes CHy(+) resulting from chemical reactions. It also intends to test the sensitivity of benchmark calculations to those new physical inputs in cold quiescent clouds and in photo-dissociation regions (PDRs). Methods. We constructed semi-empirical breakdown curves (BDCs) based on the collision of CHy+ (y = 2–4) projectiles of constant velocity (250 keV uma−1) with He atoms as explained in a previous paper, where BRs for UV, CR, and electronic processing were also derived. The same BDCs were applied to predict BRs for chemical reactions (bi-molecular neutral and ionic reactions, charge exchange). The effect of the new BRs on the chemical composition of cold dark clouds was tested using the time-dependent Nautilus gas-grain model. The same effect on the chemical composition of PDRs was tested using the Meudon PDR code. Results. Branching ratio predictions of the model are found to be in good agreement with available BR measurements for charge exchange reactions and the reaction between C and H3+. The chemistry for both cold clouds and PDRs is found to be not strongly affected by this update of BRs.

Breakdown curves of CH2(+), CH3(+), and CH4(+) molecules

Aims. The aim of this work is to furnish branching ratios (BRs) to the kinetic databases used in astrochemistry such as the KInetic Database for Astrochemistry (KIDA). This concerns CHy(+) species (y = 2–4) excited by cosmic rays, electrons and photons, or the intermediate excited complexes CHy(+) resulting from a chemical reaction. Methods. The full set of fragmentation branching ratios following CHy(+) (y = 2,4) of constant velocity (250 keV uma−1) colliding with He atoms has been measured with the multidetector AGAT. Kinetic energy distributions of neutral fragments produced in each dissociation channel have been also measured. With these experimental inputs, and theoretical dissociation energies, semiempirical breakdown curves (BDCs) have been constructed. Results. Prediction of BRs with the present BDCs is found to agree with available BR measurements for electronic dissociative recombination, collision with fast electron and photodissociation. Dependence of BRs with the various UV fields relevant to interstellar medium and planetary atmospheres is predicted.

Pre-excitation and conduction abnormalities

Ventricular pre-excitation (Wolff–Parkinson–White pattern) and conduction abnormalities may be discovered during cardiovascular pre-participation screening in athletes. Their prevalence varies between 0.1% (Wolff–Parkinson–White, left bundle branch block) and 1% (right bundle branch block). Patients with pre-excitation and paroxysmal palpitations need to be treated before considering their eligibility to participate in sport. An electrophysiological study is required in asymptomatic athletes with the Wolff–Parkinson–White pattern. Subjects are considered ineligible for participation in sport if the RR intervals between pre-excited complexes during induced atrial fibrillation are <250ms. Subjects with conduction abnormalities may or may not be affected by heart disease. In the absence of heart disease, athletes with first- or second-degree atrioventricular (AV) block which normalizes during effort are eligible to participate in sport. According to current Italian and US guidelines, athletes with right bundle branch block, left anterior hemiblock, left posterior hemiblock, and left bundle branch block can participate in all sports in the absence of heart disease (including genetic Lenègre disease) and no episodes of AV block.

PROPERTIES OF EXCITED MOLECULES IN PHOTOLYSIS OF 2,6-DIPHENYL-1,4-BENZOQUINONE WITH AMINES

To date, it is considered established that quinones with lower energy state, under the action of light tear away a hydrogen atom from a hydrocarbon or an electron donor from inorganic anion-radicals, which have a high reduction potential. However, even for the simplest quinones (1,4-benzoquinone, 1,4-naphthoquinones, 9,10-anthraquinone and their derivatives) there is no consensus in the science literature about the nature of the initial event in photoreaction with compounds which are potential donors of hydrogen atom and electron. The first step in many photochemical reactions is the formation of complexes between donors and acceptors of electrons in the excited state (exiplexes). Photoreactive quinones as elementary acts include the transfer of electron (or) hydrogen atom. The mechanism depends on the presence and strength of donor-acceptor complexes (DAC) of the quinones with the reagents. Studies of triplet exiplexes allow you to set the details of the elementary reaction acts. Only short-lived intermediate product was registered upon photoexcitation of the studied quinone Q in low-polarity solvents. The kinetic of decay of the first order with rate constant of about 2∙106 s-1 in toluene and dibutylphthalate and the introduction of oxygen leads to a decrease in the lifetime of the product in the triplet state. With the introduction of solutions of amines quenching of triplet state (QT) with rate constant close to diffusion was observed. Rate constants of quenching by dissolving in benzene and by dissolving in dibutyl phthalate were determined. It is established that formation of intermediate products is carried out from triplet state (QT). Excited complexes with charge transfer in acetonitrile were not observed. It is concluded that with decrease in electron affinity of the acceptors, when the connection of the molecules in the complex becomes weaker, the lifetime of TE increases significantly.