Simulation of ion behavior in an open three-dimensional Paul trap using a power series method

Simulations of the dynamics of ions trapped in a Paul trap with terms in the potential up to the order 10 have been carried out. The power series method is used to solve numerically the equations of motion of the ions. The stability diagram has been studied and the buffer gas cooling has been implemented by a Monte Carlo method. The dipole excitation was also included. The method has been applied to an existing trap and it has shown good agreement with the experimental results and previous simulations using other methods

Misinformation on Misinformation: Conceptual and Methodological Challenges

Copyright © 2021 The Author(s). Alarmist narratives about online misinformation continue to gain traction despite evidence that its prevalence and impact are overstated. Drawing on research questioning the use of big data in social science and reception studies, we identify six misconceptions about misinformation and examine the conceptual and methodological challenges they raise. The first three misconceptions concern the prevalence and circulation of misinformation. First, the internet is not rife with misinformation or news, but with memes and entertaining content. Second, scientists focus on social media because it is methodologically convenient, but misinformation is not just a social media problem. Third, falsehoods do not spread faster than the truth; how we define (mis)information influences our results and their practical implications. The second three misconceptions concern the impact and the reception of misinformation. First, people do not believe everything they see on the internet: sheer volume of engagement should not be conflated with belief. Second, the influence of misinformation on people’s behavior is overblown since it often ‘preaches to the choir’. Third, people are more likely to be uninformed than misinformed; surveys overestimate misperceptions and say little about the causal influence of misinformation. To appropriately understand and fight misinformation, future research needs to address these challenges

On inelastic hydrogen atom collisions in stellar atmospheres

The influence of inelastic hydrogen atom collisions on non-LTE spectral line formation has been, and remains to be, a significant source of uncertainty for stellar abundance analyses, due to the difficulty in obtaining accurate data for low-energy atomic collisions either experimentally or theoretically. For lack of a better alternative, the classical "Drawin formula" is often used. Over recent decades, our understanding of these collisions has improved markedly, predominantly through a number of detailed quantum mechanical calculations. In this paper, the Drawin formula is compared with the quantum mechanical calculations both in terms of the underlying physics and the resulting rate coefficients. It is shown that the Drawin formula does not contain the essential physics behind direct excitation by H atom collisions, the important physical mechanism being quantum mechanical in character. Quantitatively, the Drawin formula compares poorly with the results of the available quantum mechanical calculations, usually significantly overestimating the collision rates by amounts that vary markedly between transitions.Comment: 9 pages, 6 figures, accepted for A&

High Pressure Line Shapes of the Rb \u3ci\u3eD\u3csub\u3e1\u3c/sub\u3e\u3c/i\u3e and \u3ci\u3eD\u3csub\u3e2\u3c/sub\u3e\u3c/i\u3e lines for \u3csup\u3e4\u3c/sup\u3eHe and \u3csup\u3e3\u3c/sup\u3eHe Collisions

Line shapes for the Rb D1 (52S1/2 ↔ 52P1/2) and D2 (52S1/2 ↔ 52P3/2) transitions with 4He and 3He collisions at pressures of 500–15,000 Torr and temperatures of 333–533 K have been experimentally observed and compared to predictions from the Anderson–Talman theory. The ground X2Σ+1/2 and excited A2Π1/2, A2Π3/2, and B2Σ+1/2 potential energy surfaces required for the line shape predictions have been calculated using a one-electron pseudo-potential technique. The observed collision induced shift rates for 4He are dramatically higher for the D1 line, 4.60±0.12 MHz/Torr, than the D2 line, 0.20±0.14 MHz/Torr. The asymmetry is somewhat larger for the D1 line and has the same sign as the shifting rate. The 3He broadening rate for the D2 line is 4% larger than the 4He rate, and 14% higher for the D1 line, reflecting the higher relative speed. The calculated broadening rates are systematically larger than the observed rates by 1.1–3.2 MHz/Torr and agree within 14%. The primary focus of the current work is to characterize the high pressure line shapes, focusing on the non-Lorentzian features far from line center. In the far wing, the cross-section decreases by more than 4 orders of magnitude, with a broad, secondary maximum in the D2 line near 735 nm. The potentials do not require empirical modification to provide excellent quantitative agreement with the observations. The dipole moment variation and absorption Boltzmann factor is critical to obtaining strong agreement in the wings

Evaluation of Fibre-Matrix Interfacial Strength in a SiC Fibre-Reinforced Ti6A14V Composite

NRC publication: Ye

Aider les consommateurs a changer de comportement financier : Les apports d\textquotesingleun modele de changement multiphases

National audienceDe nombreux acteurs sont de plus en plus attentifs aux comportements budgétaires et financiers problématiques des consommateurs. Les modèles de changement de comportement peuvent aider à la mise en œuvre d’actions de marketing social dans ce domaine. Cette recherche montre que les stratégies de changement utilisées par le consommateur sont fondamentalement des stratégies d’approche et d’évitement et propose un modèle définissant le rôle de la balance décisionnelle dans l’utilisation de ces stratégies. Ce modèle est appliqué à des groupes constitués de consommateurs en situations similaires sur la trajectoire du changement. Les dimensions de changement du modèle transthéorique (précontemplation, contemplation, action, maintien) ont servi de base à la construction de ces groupes, dans la lignée des recherches qui adoptent cette orientation plutôt que celle de la succession d’une série de phases distinctes dans le processus de changement. Les résultats ont des implications directes pour la connaissance des modifications des comportements et pour les actions de marketing social dans le domaine étudié

On the relationship between the mechanical properties of interfacial reaction products and the shear strength of diffusion bonded SiC-Mo joints

NRC publication: Ye

Computed distributions of rotovibrational transitions in

Accurate potential energy curves for the ground electronic states of LiH and $\rm LiH^{+}$ are employed to generate vibrational and rotational levels over a broad range of J values for both systems. The corresponding dipole functions are computed and used to obtain the frequency and intensity distributions of all relevant transitions between bound states for pure vibrational excitations, pure rotational excitations and for dipole allowed rovibrational processes. This extensive set of absorption data for both molecules is employed to locate the most likely region in the infrared spectrum where characteristic lines could be observed. Such data should be useful in experimental attempts to search for LiH and $\rm LiH^{+}$ lines at high redshifts. We found that transitions between ionic levels will be markedly less intense than those for the neutral system and that transitions between rotationally `hot' levels will be markedly more intense than those between low-J levels