The angular pattern in the hyperfine structure of Xe I and Kr I atoms

Recent reviews of the hyperfine structure of xenon and krypton have highlighted the variety of the values taken by the hyperfine coefficients A and B of these atoms. These variations, as functions of the atomic angular momenta, were however not explained quantitatively. This article shows the simple picture and angular momentum algebra that make it possible to account for the observed trend. The only necessary approximations are to consider the interaction of the outer electron negligible with respect to the coupling of the p5 core with the nucleus, and to assume that the Racah ||(p5)j l[K]J F〉basis, conventionally used for the atomic states of noble gases, makes a fitting description of the hierarchy of their angular momentum couplings. The way the calculation corroborates the apparently erratic values of hyperfine coefficients A and B in Xe I and Kr I shows up as a confirmation of the validity of these approximations.

From half-metallic to magnetic semiconducting triazine g-C4N3: computational designs and insight

A simple picture of charge transfer has been given, for the first time, as physicochemical insight into the electronic structure routes from half-metallic to magnetic semiconducting triazine g-C4N3.

MnBi2Te4-family intrinsic magnetic topological materials

MnBi2Te4 and its derivative compounds have received focused research interests recently for their inherent magnetic order and the rich, robust and tunable topological phases hosted in them. Here, I briefly introduce MnBi2Te4-family intrinsic magnetic topological materials—the electronic and magnetic properties, the topological phase diagrams and the research progress made on them in the past years. I try to present a simple picture to understand their rich electronic, magnetic and topological properties, and a concise guide to engineer them for intended topological phases and the quantum anomalous Hall effect at higher temperature.

From reflex to reflection: Moving from the space of causes to the space of reasons and back

This article proposes to narrow the gap between the space of reasons and the space of causes. By articulating the standard phenomenology of reasons and causes, we investigate the cases in which the clear-cut divide between reasons and causes starts to break down. Thus, substituting the simple picture of the relationship between the space of reasons and the space of causes with an inverted and complex one, in which reasons can have a causal-like phenomenology and causes can have a reason-like phenomenology. This is attained by focusing on “swift reasoned actions” on the one hand, and on “causal noisy brain mechanisms” on the other hand. In the final part of the article, I show how an analogous move, that of narrowing the gap between one’s normative framework and the space of reasons, can be seen as an extension of narrowing the gap between the space of causes and the space of reasons.

Marginal Instability and the Efficiency of Ocean Mixing

The mixing efficiency of stratified turbulence in geophysical fluids has been the subject of considerable controversy. A simple parameterization, devised decades ago when empirical knowledge was scarce, has held up remarkably well. The parameterization rests on the assumption that the flux coefficient Γ has the uniform value 0.2. This note provides a physical explanation for Γ = 0.2 in terms of the “marginal instability” property of forced stratified shear flows, and also sketches a path toward improving on that simple picture by examining cases where it fails.

Improving the communication with stakeholders: the infrastructure degradation index and the infrastructure histogram

Water infrastructures are rapidly ageing without being properly replaced. Communicating the state of the network and the sector’s needs to stakeholders is key for guaranteeing the sustainability of water and sewage systems. The infrastructure value index (IVI) is becoming a standard in the water industry as a communication tool; however, as a single value metric, it can mask key information. The complementary use of the infrastructure degradation index (IDI) and the infrastructure histogram (Hi) can provide a better understanding of the network's state while maintaining the simplicity of the analysis needed for public dissemination. The IVI is focused on the value of the infrastructure, the IDI on its median remaining life. The HI provides a detailed but simple picture of the network's remaining life, providing a clear idea of the magnitude of the investments needed in the future for maintaining the infrastructure.

Framing Temptations in Relation to the Self

Self-control concerns the successful management of the conflicting desires or emotions toward which the self is in some sense invested. The prospects for self-control are affected by how these desires and emotions are represented, and this chapter argues for giving special attention to how people frame temptations with respect to their sense of self. Drawing on philosopher Harry Frankfurt’s concept of identification, which is supposed to establish the boundaries for what is internal and external to the self, the authors distinguish two attitudes that a person can take toward her temptations: acceptance and alienation. They describe their descriptive and laboratory studies testing, among other things, whether those who accept their temptations as part of the self fare better at self-control than do those who alienate their temptations as external to the self. The results show significant differences, but they do not paint a simple picture of the relationship.

A general model of population dynamics accounting for multiple kinds of interaction

ABSTRACTPopulation dynamics has been modelled using differential equations almost since Malthus times, more than two centuries ago. Basic ingredients of population dynamics models are typically a growth rate, a saturation term in the form of Verhulst’s logistic brake, and a functional response accounting for interspecific interactions. However intraspecific interactions are not usually included in the equations. The simplest models use linear terms to represent a simple picture of the nature, meanwhile to represent more complex landscapes, it is necessary to include more terms with higher order or analytically more complex. The problem to use a simpler or more complex model depends on many factors: mathematical, ecological, or computational. To address it, here we discuss a new model based on a previous logistic-mutualistic model. We have generalised the interspecific terms (for antagonistic and competitive relationships) and we have also included new polynomial terms to explain any intraspecific interaction. We show that by adding simple intraspecific terms, new free-equilibrium solutions appear driving a much richer dynamics. These new solutions could represent more realistic ecological landscapes by including a new high order term.

Where did the globular clusters of the Milky Way form? Insights from the E-MOSAICS simulations

ABSTRACT Globular clusters (GCs) are typically old, with most having formed at z ≳ 2. This makes understanding their birth environments difficult, as they are typically too distant to observe with sufficient angular resolution to resolve GC birth sites. Using 25 cosmological zoom-in simulations of Milky Way-like galaxies from the E-MOSAICS project, with physically motivated models for star formation, feedback, and the formation, evolution, and disruption of GCs, we identify the birth environments of present-day GCs. We find roughly half of GCs in these galaxies formed in situ (52.0 ± 1.0 per cent) between z ≈ 2–4, in turbulent, high-pressure discs fed by gas that was accreted without ever being strongly heated through a virial shock or feedback. A minority of GCs form during mergers (12.6 ± 0.6 per cent in major mergers, and 7.2 ± 0.5 per cent in minor mergers), but we find that mergers are important for preserving the GCs seen today by ejecting them from their natal, high density interstellar medium (ISM), where proto-GCs are rapidly destroyed due to tidal shocks from ISM substructure. This chaotic history of hierarchical galaxy assembly acts to mix the spatial and kinematic distribution of GCs formed through different channels, making it difficult to use observable GC properties to distinguish GCs formed in mergers from ones formed by smooth accretion, and similarly GCs formed in situ from those formed ex situ. These results suggest a simple picture of GC formation, in which GCs are a natural outcome of normal star formation in the typical, gas-rich galaxies that are the progenitors of present-day galaxies.