Since its publication in 2010, the paper by Schmid (J. Fluid Mech., vol. 656, 2010, pp. 5–28) has wielded considerable influence, an impact we examine here. That seminal work introduced dynamic mode decomposition, a method for performing flow-field spectral analysis of snapshot sequences of data. As a data-driven approach aimed at uncovering spatial and temporal patterns or modes within datasets, its applicability has extended far beyond fluid mechanics, reaching into a wide array of fields.

This article examines three high-profile House ethics cases involving former Speakers James Wright (1988–1989) and Newt Gingrich (1994–1997) and former House Majority Leader Tom DeLay (1997–2004). The analysis of the filing and disposition of charges in the three cases provides some evidence for the “politics-by-other-means” or “partisan-ethics-wars” framework that is sometimes used to evaluate ethics enforcement in Congress. However, the analysis also provides evidence of bipartisan agreement both in the ethics committee and on the floor. The article highlights the areas of bipartisan consensus and the principles behind that consensus. In paying attention to the content of the cases, it also highlights an important change in ethics investigations over time, specifically an increase in “political gain” cases. The article thus calls attention to aspects of House ethics investigations that are undervalued and inadequately addressed by the partisan-ethics-wars framework.

Due to the F2 ionospheric layer’s ability to reflect radio waves, the foF2 critical frequency is essential since sudden irregularities can disrupt communication and navigation systems, affecting the weather forecast’s accuracy. This paper aims to develop accurate foF2 critical frequency prediction up to 24 hours ahead, focusing on mid and high latitudes, using the long short-term memory (LSTM) model covering the 24th solar cycle from 2008 to 2019. To evaluate the effectiveness of the proposed model, a comparative analysis is conducted with commonly referenced machine learning techniques, including linear regression, decision tree algorithms, and multilayer perceptron (MLP) using the Taylor diagram and error plots. The study involved five monitoring stations, different years with minimum and maximum solar activity, and prediction timeframes. Through extensive experimentation, a comprehensive set of outcomes is evaluated across diverse metrics. The findings conclusively established that the LSTM model has demonstrated superior performance compared to the other models across all stations and years. On average, LSTM is 1.2 times better than the second-best model (DT), 1.6 times as effective as the multilayer perceptron MLP, and three times more accurate than linear regression. The results of this research hold promise for increasing the precision of foF2-prediction, with potential implications for enhancing communication systems and weather forecasting capabilities.

Can the best arguments for a privation theory of evil be parodied, with equal plausibility, as arguments for a privation theory of good? The privation theory of evil claims that evil has no positive existence, and it is but a privation of good. The privation theory of good claims the opposite. I approach this topic as one element in the so-called evil-God Challenge. Stephen Law has argued that the epistemic support for belief in an omniscient, omnipotent, and morally perfect God (theism) is on a par with the epistemic support for belief in an omniscient, omnipotent, but completely evil-God (maltheism). In fact, he concludes, the arguments for an evil God are symmetrical with, and isomorphic to, those for a good God. The privation theory of evil has often been used to defend theism against the argument from evil. Thus, part of the evil-God Challenge is to evaluate arguments for the privation theory of evil for their vulnerability to maltheist parody. I consider a broad range of arguments for the privation theory of evil, and I argue that most of them are vulnerable to parodic neutralization. Furthermore, I argue that although the thesis of the convertibility of being and goodness is often held to entail the privation theory of evil, or to be entailed by it (or to be equivalent to it), it is independent of the privation theory. I do find that David Oderberg’s recent argument for the privation theory of evil resists any easy maltheist parody, but I argue that it has a defect. I sketch an argument according to which his good-as-fulfillment account is compatible with a perfectly evil god. My tentative conclusion is that the privation theory of evil enjoys little more plausibility than does the privation theory of good.

Boundary layers are present in many natural and industrial fluid flows. The concept of boundary layers can be traced back to Leonardo da Vinci's paintings of pipe flow, where he was aware of a higher velocity away from the walls. During the 19th century, the physics of boundary conditions had been extensively debated, and the well-known Maxwell–Navier slip length was proposed in 1823. In most cases, the no-slip boundary condition is valid at a fluid–solid interface. However, with the advancement of measurement techniques, slip lengths ranging from nanometre to micrometre scales were experimentally measured, raising questions regarding the applicability of the no-slip condition. In 2003, Lauga & Stone (J. Fluid Mech., vol. 489, 2003, pp. 55–77) proposed a simple model to elucidate the effect of surface heterogeneities on the slip length, elegantly bridging the microscopic structure of the wall-boundary conditions to the macroscopic effective slip length.

The entrainment hypothesis states that the mean inflow velocity across the boundary of a turbulent flow is proportional to a characteristic velocity of the flow. Proposed by G. I. Taylor approximately 80 years ago, it is still a common model of turbulence closure widely used in environmental engineering and geophysical fluid mechanics. Although it is a very simple concept and mathematical model, it has proven to be able to predict the entrainment in a variety of geophysical flows, e.g. convective clouds and plumes from erupting volcanoes in the atmosphere; dense water overflows and turbidity currents in the ocean; magma injection in a magma chamber in the interior of the Earth, to name just a few. In a seminal paper, Turner (J. Fluid Mech., vol. 173, 1986, pp. 431–471) presents a variety of laboratory and geophysical flows to illustrate the success of the entrainment hypothesis and discusses why such a simple hypothesis works so well even when the original assumptions are no longer valid.