Spinning particles in Schwarzschild-de Sitter space-time

After considering the reference case of the motion of spinning test bodies in the equatorial plane of the Schwarzschild space-time, we generalize the results to the case of the motion of a spinning particle in the equatorial plane of the Schwarzschild-de Sitter space-time. Specifically, we obtain the loci of turning points of the particle in this plane. We show that the cosmological constant affect the particle motion when the particle distance from the black hole is of the order of the inverse square root of the cosmological constant.Comment: 8 pages, 5 eps figures, submitted to Gen.Rel.Gra

Bond-forming and electron-transfer reactivity between Ar2+ and N2

Collisions between Ar2+ and N2 have been studied using a coincidence technique at a CM collision energy of 5.1 eV. Four reaction channels generating pairs of monocations are observed: Ar+ + N2+, Ar+ + N+, ArN+ + N+ and N+ + N+. The formation of Ar+ + N2+ is the most intense channel, displaying forward scattering but with a marked tail to higher scattering angles. This scattering, and other dynamics data, is indicative of direct electron transfer competing with a ‘sticky’ collision between the Ar2+ and N2 reactants. Here Ar+ is generated in its ground (2P) state and N2+ is primarily in the low vibrational levels of the C2Σu+ state. A minor channel involving the initial population of higher energy N2+ states, lying above the dissociation asymptote to N+ + N, which fluoresce to stable states of N2+ is also identified. The formation of Ar+ + N+ by dissociative single electron transfer again reveals the involvement the two different pathways for the initial electron transfer (direct or complexation). This reaction pathway predominantly involves excited states of Ar2+ (1D and 1S) populating N2+* in its dissociative C2Σu+, 22Πg and D2Πg states. Formation of ArN+ + N+ proceeds via a direct mechanism. The ArN+ is formed, with significant vibrational excitation, in its ground (X3Σ–) state. Formation of N+ + N+ is also observed as a consequence of double electron transfer. The exoergicity of the N22+ dissociation reveals the population of the A1Πu and D3Πg dication states

Bond-forming and electron-transfer reactivity between Ar2+ and O2

The reactivity, energetics and dynamics of the bimolecular reactions between Ar2+ and O2 have been studied using a position sensitive coincidence methodology at a collision energy of 4.4 eV. Four bimolecular reaction channels generating pairs of product ions are observed, forming: Ar+ + O2 +, Ar+ + O+, ArO+ + O+ and O+ + O+. The formation of Ar+ + O2 + is a minor channel, involving forward scattering, and generates O2 + in its ground electronic state. This single electron transfer process is expected to be facile by Landau–Zener arguments, but the intensity of this channel is low because the electron transfer pathways involve multi-electron processes. The formation of Ar+ + O+ + O, is the most intense channel following interactions of Ar2+ with O2, in agreement with previous experiments. Many different combinations of Ar2+ and product electronic states contribute to the product flux in this channel. Major dissociation pathways of the nascent O2 + * ion involve the ion’s first and second dissociation limits. Unusually, the experimental results clearly show the involvement of a short-lived collision complex [ArO2] 2+ in this channel. The formation of O+ and ArO+ involves direct abstraction of O from O2 by Ar2+. There is scant evidence of the involvement of a collision complex in this bond forming pathway. The ArO+ product appears to be formed in the first excited electronic state (2 P). The formation of O+ + O+ results from dissociative double electron transfer via an O2 2+ intermediate. The exoergicity of the dissociation of the nascent O2 2+ intermediate is in good agreement with previous work investigating the unimolecular dissociation of this dication

Electrophysiology Model for a Human Heart with Ischemic Scar and Realistic Purkinje Network

The role of Purkinje fibres in the onset of arrhythmias is controversial and computer simulations may shed light on possible arrhythmic mechanisms involving the Purkinje fibres. However, few computational modelling studies currently include a detailed Purkinje network as part of the model. We present a coupled Purkinje-myocardium electrophysiology model that includes an explicit model for the ischemic scar plus a detailed Purkinje network, and compare simulated activation times to those obtained by electro-anatomical mapping in vivo during sinus rhythm pacing. The results illustrate the importance of using sufficiently dense Purkinje networks in patient-specific studies to capture correctly the myocardial early activation that may be influenced by surviving Purkinje fibres in the infarct region

Screening of antioxidant properties of the apple juice using the front-face synchronous fluorescence and chemometrics

Fluorescence spectroscopy is gaining increasing attention in food analysis due to its higher sensitivity and selectivity as compared to other spectroscopic techniques. Synchronous scanning fluorescence technique is particularly useful in studies of multi-fluorophoric food samples, providing a further improvement of selectivity by reduction in the spectral overlapping and suppressing light-scattering interferences. Presently, we study the feasibility of the prediction of the total phenolics, flavonoids, and antioxidant capacity using front-face synchronous fluorescence spectra of apple juices. Commercial apple juices from different product ranges were studied. Principal component analysis (PCA) applied to the unfolded synchronous fluorescence spectra was used to compare the fluorescence of the entire sample set. The regression analysis was performed using partial least squares (PLS1 and PLS2) methods on the unfolded total synchronous and on the single-offset synchronous fluorescence spectra. The best calibration models for all of the studied parameters were obtained using the PLS1 method for the single-offset synchronous spectra. The models for the prediction of the total flavonoid content had the best performance; the optimal model was obtained for the analysis of the synchronous fluorescence spectra at Delta lambda = 110 nm (R (2) = 0.870, residual predictive deviation (RPD) = 2.7). The optimal calibration models for the prediction of the total phenolic content (Delta lambda = 80 nm, R (2) = 0.766, RPD = 2.0) and the total antioxidant capacity (Delta lambda = 70 nm, R (2) = 0.787, RPD = 2.1) had only an approximate predictive ability. These results demonstrate that synchronous fluorescence could be a useful tool in fast semi-quantitative screening for the antioxidant properties of the apple juices.info:eu-repo/semantics/publishedVersio

CAFE-AMR: A computational MHD Solar Physics simulation tool that uses AMR

The study of our Sun holds significant importance in Space Weather research, encompassing a diverse range of phenomena characterized by distinct temporal and spatial scales. To address these complexities, we developed CAFE-AMR, an implementation of an Adaptive Mesh Refinement (AMR) strategy coupled with a Magnetohydrodynamics (MHD) equation solver, aiming to tackle Solar Physics-related problems. CAFE-AMR employs standard fluid dynamics methods, including Finite Volume discretization, HLL and Roe class flux formulas, linear order reconstructors, second-order Runge-Kutta, and Corner Transport Upwind time stepping. In this paper, we present the core structure of CAFE-AMR, discuss and evaluate mesh refinement criteria strategies, and conduct various tests, including simulations of idealized Solar Wind models, relevant for Space Weather applications.Comment: 17 pages, 23 figures. Accepted for publication in MNRA

The Utility of the Prototype/Willingness Model in Predicting Alcohol Use Among North American Indigenous Adolescents

In the present study, we considered the utility of the prototype/willingness model in predicting alcohol use among North-American Indigenous adolescents. Specifically, using longitudinal data, we examined the associations among subjective drinking norms, positive drinker prototypes, drinking expectations (as a proxy of drinking willingness), and drinking behavior among a sample of Indigenous adolescents from ages 12 to 14 years. Using an autoregressive cross-lagged analysis, our results showed that subjective drinking norms and positive drinker prototypes at 12 years of age were associated with increased drinking expectations at 13 years of age, and that greater drinking expectations at 13 years of age were associated with increased drinking behavior at 14 years of age. Our results provide initial evidence that the prototype/willingness model may generalize to Indigenous adolescents, a population that has received little attention within the psychological sciences. Our results also highlight some potential ways in which existing prevention efforts aimed at reducing substance use among Indigenous adolescents may be enhanced