Reference Frame Research Articles

I2BODIPY as a new photoswitchable spin label for light-induced pulsed EPR dipolar spectroscopy exploiting magnetophotoselection.

Electron paramagnetic resonance (EPR) pulsed dipolar spectroscopy (PDS) using triplet states of organic molecules is a growing area of research due to the favourable properties that these transient states may afford over stable spin centers, such as switchability, increased signal intensity when the triplet is formed in a non-Boltzmann distribution and the triplet signal is used for detection, and high orientation selection, when the triplet signal is probed by microwave pulses. This arises due to the large spectral width at low fields, a result of the large zero field splitting, and limited bandwidth of microwave pulses used. Here we propose the triplet state of a substituted BODIPY moiety as a spin label in light induced PDS, coupled to a nitroxide, in a model peptide with a rigid structure. Orientation selection allows information on the relative position of the centres of the two labels to be obtained with respect to the nitroxide reference frame. Additionally, magnetophotoselection effects are employed to introduce optical selection and additional constraints for the determination of the relative orientation of the spin labels considering the reference frame of the triplet state.

Exact planetary waves and jet streams

We investigate exact nonlinear waves on surfaces locally approximating the rotating sphere for two-dimensional inviscid incompressible flow. Our first system corresponds to a $\beta$ -plane approximation at the equator, and the second to a $\gamma$ approximation, with the latter describing flow near the poles. We find exact wave solutions in the Lagrangian reference frame that cannot be written down in closed form in the Eulerian reference frame. The wave particle trajectories, contours of potential vorticity and Lagrangian mean velocity take relatively simple forms. The waves possess a non-trivial Lagrangian mean flow that depends on the amplitude of the waves and on a particle label that characterizes values of constant potential vorticity. The mean flow arises due to potential vorticity conservation on fluid particles. Solutions over the entire space are generated by assuming that the flow far from the origin is zonal and there is a region of uniform potential vorticity between this zonal flow and the waves. In the $\gamma$ approximation, a class of waves is found that, based on analogous solutions on the plane, we call Ptolemaic vortex waves. The mean flow of some of these waves, which we can describe in highly nonlinear scenarios due to the exact nature of the solutions, resembles polar jet streams. Several illustrative solutions are used as initial conditions in the fully spherical rotating Navier–Stokes equations, where integration is performed via the numerical scheme presented in Salmon & Pizzo (Atmosphere, vol. 14, issue 4, 2023, 747). The potential vorticity contours found from these numerical experiments vary between stable permanent progressive form and fully turbulent flows generated by wave breaking.

FLOW AND HEAT TRANSFER IN ROTATING COMPRESSOR CAVITIES WITH INVERTED SHROUD-THROUGHFLOW TEMPERATURE DIFFERENCES

Abstract In an aero-engine compressor, co-rotating discs form cavities that interact with an axial throughflow of secondary air at low radius. In the high-pressure (HP) compressor the shroud is hotter than the throughflow (directed downstream to the turbine) and the radial temperature gradient creates buoyancy-induced flow at Grashof numbers ∼ 1013. Such flows can be unstable and typically take the form of counter-rotating vortex pairs separated by radial hot and cold plumes. However, in low pressure (LP) and intermediate pressure (IP) compressors the secondary air is directed upstream. In this inverse scenario the axial throughflow is hotter than the compressor discs, reversing the disc temperature gradient and eliminating the fundamental driver for buoyancy. Despite its practical application and importance, this inverse scenario has not been previously investigated. The University of Bath Compressor Cavity Rig has been uniquely designed to simulate such flows, measuring temperature and unsteady pressure in the frame of reference of the rotating discs. Bayesian and spectral analysis have determined the radial distribution of disc heat flux, as well as the asymmetry of the rotating vortex structures and their slip relative to the discs. Unexpectedly, the new data reveal the flow structure in cavities with positive and inverted temperature differences are fundamentally similar (albeit with reversed radial-temperature profiles). Isothermal cases identified a critical Rossby number (Ro), above which the flow structure in the cavity was dominated by a toroidal vortex. At sub-critical Ro, the flow structure for the inverted temperature gradient continued

Agroecology as a new frame of reference for French agricultural policy? Insights from a lexicometric analysis of policy documents

ABSTRACT References to agroecology have gradually started appearing in national and international public policies. We examine the extent to which agroecology is becoming a frame of reference for public action in the French national and regional context. Using textual statistics, we analyzed institutional documents concerning agroecology put out by public policy actors between 2008 and the summer of 2021, and conducted interviews with key actors of the Agroecological Project for France (PAEF, Projet Agroécologique pour la France). Our analysis shows that agroecology invoked in framing texts is reclassified in the vocabulary of triple performance, dominated by the notion of economic performance. A comparative analysis of the national and regional texts reveals mismatches, especially in terms of the level of autonomy of the actors concerned, and in the processes of knowledge transfer and support for changes in agricultural practices.

A Comparison of Thunderstorm Identification Methods

Abstract Climatological analysis of thunderstorm occurrence is important since thunderstorms have far-reaching societal impacts. Historically, the majority of thunderstorm-related climatologies have focused on Eulerian frames of reference resulting in thunderstorm day or lightning density summaries. However, a Lagrangian frame of reference is required to answer more in-depth questions such as spatial distribution and variability in thunderstorm initiation. Lagrangian approaches generally utilize object identification and tracking algorithms with tracks then classified as being a thunderstorm or not. Prior methods for thunderstorm identification have been based on classification criteria such as radar reflectivity thresholds, a combination of radar reflectivity thresholds and temporal longevity thresholds, or a combination of radar reflectivity and cloud-to-ground lightning occurrence. However, a comparison of different methods and an evaluation of their accuracy have not been documented in the peer-reviewed literature. This study examines the impact of thunderstorm identification methodology choice. Differences in three thunderstorm identification methodologies are examined over the central plains of the United States during an 11-yr study period. Results show that there is a sensitivity to methodological choice with differences in the number of candidate thunderstorms classified as thunderstorms, as well as the resulting spatial pattern of thunderstorms. Additionally, this study provides insight into the accuracy of each method via a multiyear comparison of each method to regional lightning mapping array total lightning detections where significant differences were observed between methods with the method incorporating cloud-to-ground lightning data providing the best performance metrics. Significance Statement Previous research has utilized a variety of criteria to identify thunderstorms in order to generate datasets of thunderstorm occurrence. This study directly compares commonly used criteria, demonstrating that the choice of thunderstorm identification criteria impacts the composition and accuracy of resulting datasets of thunderstorm occurrence.

Ready, Set, Modernize – ASPRS Takes on Preparing the Geospatial Industry for the Modernized National Spatial Reference System (NSRS)

The National Geodetic Survey (NGS) is modernizing the National Spatial Reference System (NSRS) in the United States. The modernization involves significant updates to the official reference frames and vertical datum used across the country, affecting the entire geospatial industry. Key benefits of the Modernized NSRS will include improved accuracies and enhanced interoperability and sustainability of geospatial data and systems. The ASPRS NSRS Modernization Working Group produced this paper to help prepare the geospatial industry for the upcoming changes. It serves as a guide for industry professionals to understand the implications of the Modernized NSRS and recommendations to begin preparing for it. It emphasizes the importance of proactive measures to ensure a smooth transition to the new reference frames and vertical datum.

Simulation Approaches for the Study of the Oil Flow Rate Distribution in Lubricating Systems with Rotating Shafts

This study addresses the issue of predicting the distribution of lubricant flow through the outlets of a rotating shaft used in vehicle power transmission. A typical geometry with closely spaced rows of holes, suitable for the lubrication of multi-disk clutches, was considered. Both lumped parameter and computational fluid dynamics approaches were applied and compared. The test rig for model validation was designed with a variable speed shaft featuring an axial oil inlet and three equally spaced pairs of radial outlet holes. The main characteristic of the experimental facility is the possibility to selectively measure the flow rates through each outlet. It was found that the three-dimensional model based on the multiple reference frame approach provides a reliable prediction of how the flow rate is distributed. Generally, the flow rate is lower through the outlet closest to the inlet and is maximum at the farthest exit. The flow distribution is minimally affected by the shaft speed. The influence of geometric parameters on making the flow distribution more uniform was studied. It was found that a better flow balance is obtained with a low ratio between the diameter of the radial holes and that of the axial channel. The results obtained offer best-practice guidelines for accurately simulating comparable systems, in order to optimize reliability of the mechanical transmission and energy efficiency of the flow generation unit.

Filtering on the Go: Effect of Filters on Gaze Pointing Accuracy During Physical Locomotion in Extended Reality.

Eye tracking filters have been shown to improve accuracy of gaze estimation and input for stationary settings. However, their effectiveness during physical movement remains underexplored. In this work, we compare common online filters in the context of physical locomotion in extended reality and propose alterations to improve them for on-the-go settings. We conducted a computational experiment where we simulate performance of the online filters using data on participants attending visual targets located in world-, path-, and two head-based reference frames while standing, walking, and jogging. Our results provide insights into the filters' effectiveness and factors that affect it, such as the amount of noise caused by locomotion and differences in compensatory eye movements, and demonstrate that filters with saccade detection prove most useful for on-the-go settings. We discuss the implications of our findings and conclude with guidance on gaze data filtering for interaction in extended reality.

Envy and Ressentiment

Abstract This article is about the connection between envy and ressentiment. Both are understood as emotional strategies for dealing with desire. Ressentiment is understood as the perpetuation and radicalization of a strong form of envy. Lacan’s mirror stage as well as Nietzsche’s and Scheler’s theories of ressentiment serve as a frame of reference for the development of this thesis.

The Discovery of Accelerating Expansion of Universe 8.8 Billion Years after the Big Bang Vindicates M1 World One Out of the Six Solutions of Einstein’s General Theory of Relativity

This paper gives the mathematical methodology (Tensor mathematics) of describing the surfaces of our Universe in General Theory of Relativity. It expresses the mass energy equivalence formula. It introduces the concept of time dilation, length contraction and mass increment in high speed frame of reference. Minowski space time 4D manifold is illustrated for representing the flat spacetime fabric Reimannian Metric is enumerated. Schwarzschild metric and how mass is accounted for is given.

Experimental Simulation Studies on Non-Uniform Fluidization Characteristics of Two-Component Particles in a Bubbling Fluidized Bed

Taking the fluidized pre-reduction process of iron ore powder bubbling fluidized bed as the background, for the problem of non-uniform structure in the bed of gas-solid fluidization process, the non-uniform fluidization characteristics of bicomponent particles are investigated in a cold two-dimensional bubbling fluidized bed by using a combination of physical experiments and mathematical simulations. Fluidization experiments were carried out under typical working conditions by using glass beads to study the effects of apparent gas velocity, mass ratio, and other factors on the non-uniform structure in the bed. Through the experimental observation of the bubble behavior, the effect of the cyclic change in bubble formation, rise and growth to rupture on the bed uniformity were analyzed. The experiments showed that the fluidized bed of two-component particles would be stratified, and the non-uniformity was strong in the upper part and weak in the lower part, and the apparent gas velocity and particle size were the main influencing factors. Based on the Euler-Lagrange reference frame modeling, the fluidization process of the two-dimensional bubble bed was simulated by the CFD-DEM method. The simulations of typical experimental conditions were carried out to further analyze the velocity distribution and the volume ratio of each phase in the bed from the gas-solid interaction level, revealing that the velocity distribution in the upper part of the bed is not uniform, and the gas flow is strongly perturbed, with intense bubble aggregation. The results reveal the reasons for the non-uniform phenomenon of gas-solid fluidization, which can provide a theoretical basis for the regulation of the non-uniform structure of the fluidization process.

Comparison between shear-driven and pressure-driven oscillatory flows over ripples

Direct numerical simulations of oscillatory flow over a bed made of ripples have been performed. Two oscillatory flow forcing mechanisms have been compared: (i) a sinusoidal external pressure gradient (pressure-driven flow); and (ii) a sinusoidal velocity boundary conditions on the rippled bed (shear-driven flow). In the second case, the oscillations of the bed are such that when observed from a reference frame fixed with the bed, the free stream follows the same harmonic oscillation as in the pressure-driven case. While the outer layers have the same dynamics in the two cases, close to the bed differences are observed during the cycle, mostly because the large form drag across the ripples cannot be reproduced in the shear-driven case. A comparison against experimental data from an oscillating tray apparatus provides a relatively good agreement for the phase-averaged flow when the same forcing is considered (i.e. a shear-driven flow). The pressure-driven case has a comparable error to the shear-driven numerical results over the crest of the ripples, whereas the discrepancy is larger at the troughs. The discrepancies between the two cases are more limited for time-averaged flow quantities, such as the mean flow pattern and the time-averaged Reynolds stress distribution. This suggests that numerical or experimental shear-driven configurations may capture well the net effects of coastal transport processes (which occur in pressure-driven oscillatory flow), but care should be exercised in interpreting phase-dependent dynamics near the troughs. More work is needed to fully assess the sensitivity to the forcing mechanisms in different flow regimes.

Reassessing the proper motions of M31/M33 with Gaia DR3. Unravelling systematic uncertainties

We provide an updated inference of the proper motion of M31 using the Gaia DR3 proper motions of bright stars from the disc of M31. By refining the motion of the quasar reference frame, and statistically accounting for the variations in the inferred proper motions obtained across different regions of M31, we demonstrate that these inconsistencies most likely arise from systematic uncertainties. Our updated favoured values for the proper motion of M31 are $46.9 stat sys in the right ascension direction and $-29.1 stat sys in the declination direction, the systematics being determined at a 90<!PCT!> confidence level (the values for M33 are given in the paper). This clearly highlights that the systematics are the dominant source of uncertainty, their magnitudes being comparable to the proper motion of M31 itself. The analysis conducted using Gaia DR2 instead of DR3 revealed that a net reduction in these systematic uncertainties occurred between the two data releases. If similar progress is made with the upcoming DR4, the future Gaia -based estimates could match the uncertainty level of HST, and could be used to refine the dynamics and history of M31 and M33.

Economical, Innovative, or Ecological? What Are the Green Energy Users?

Green energy sources play a vital role in mitigating environmental impacts and reducing dependence on energy imports. Growing concerns over climate change, coupled with public policies promoting the expansion of green energy, have notably shaped consumer attitudes and behaviours. This study aims to address the knowledge gap by examining the impact of a sustainable lifestyle, consumer innovativeness, and economic attitudes on the intention to adopt green energy sources. The research was conducted on 580 Polish consumers using an online survey. The results of structural equation modelling revealed that pro-environmental self-identity (PESI) and consumer innovativeness (CI) have a positive impact on consumer behaviour toward green energy sources. Pro-environmental self-identity (PESI) is the strongest determinant of consumer behaviour toward green energy sources. Our research on Polish consumer behaviour could serve as a frame of reference for other countries, particularly in Central and Eastern Europe. From a theoretical standpoint, this research enhances the understanding of pro-environmental self-identity (PESI) and its link to consumer innovativeness while also offering insights into consumer behaviour related to green energy sources, based on the experiences from the Polish market. The conclusions derived from this study may provide valuable guidance for managers and policymakers in formulating strategies to promote the adoption of green energy sources across Europe effectively.

Why the standard definition of creativity fails to capture the creative act

The “standard definition” of creativity holds that a creative idea is one that is novel and useful. This judgement is customarily based on an external frame of reference as it is passed by people who are receiving the idea (the recipient). The internal frame of reference of the person who has generated the idea (the creator) is usually ignored. I make two cases in this paper. First, that employing external frames of reference in assessing creative products has been erroneously applied to understand the creative mind. Second, that any definition of creativity needs to be one that can be reasonably applied whether following an internal frame of reference of the creative experience or an external frame of reference of the creative product. With these aims in mind, I propose the following amendment to the definition of creativity: a creative idea is one that is both novel and satisfying.

Leadership in a social dilemma: Does it matter if the leader is pro‐social or just says they are pro‐social?

AbstractPrevious studies have shown that pro‐social leaders cooperate, on average, more than pro‐self leaders in social dilemmas. It can, thus, be beneficial for the group to have a pro‐social leader. In this paper we analyze the consequences of a leader informing followers that they are pro‐social (or pro‐self). In doing so, we compare a setting in which the leader's type is truthfully revealed to settings where the leader can ‘hide’ or ‘lie’ about their pro‐sociality. We find that a leader saying they are pro‐social boosts efficiency, even if the signal is not fully credible. Cooperation is highest in a truth setting with a pro‐social leader. We demonstrate that these results are consistent with a belief‐based model of social preference in which the stated type of the leader changes the frame of reference for followers.

Kinetic Alfvén wave cascade in sub-ion range plasma turbulence

Kinetic Alfvén waves (KAWs) are simulated with a 3D particle-in-cell (PIC) code by using the eigenvector relations of density, velocity, electric, and magnetic field fluctuations derived from a two-fluid KAW model. Similar simulations are also performed with a whistler waves setup. The 2D two-fluid eigenvector relations are converted into 3D by using rotation of the reference frame. The initial condition for the simulations is a superposition of several waves at scales slightly larger than the ion skin depth. The nonlinear interactions produce a transfer of energy to smaller scales. The magnetic field perturbation ratios, velocity perturbation, and density perturbation ratios are calculated from the simulation at higher wavenumbers and compared with the analytically expected ratios for KAWs and whistler waves. We find that in both types of simulations, initialized either with an ensemble of KAWs or with whistlers, the observed polarization relations at later times match better with the KAW relations compared to whistlers. This indicates a preference for excitation of KAW fluctuations at smaller scales. The power spectrum in the perpendicular direction is calculated, and it shows similar indices as measured in the solar wind power spectrum in the transition (sub-ion) region. The power law extends to smaller scales when a higher ion-to-electron mass ratio is taken. The 2D magnetic power spectrum in magnetic field parallel and perpendicular directions shows typical anisotropy where the power spreads more in the perpendicular direction than in the parallel direction. This study shows that KAWs can explain features of the sub-ion range plasma turbulence in the solar wind.

A reassessment of ice cliff dynamics upon debris-covered glaciers

Abstract We present a new model for understanding ice cliff dynamics within a debris-covered glacier ablation zone. This simple energy-balance model incorporates a moving frame of reference, made necessary by the melt of the surrounding debris-covered ice. In so doing, this also formalises how different types of field measurements can be utilised and compared. Our predictions include showing: ice cliffs can endogenously select their own slope angles; that there should be an indifference between illuminated north- and south-facing ice cliff slopes; that ice cliffs grow steeper with thicker debris layers; that ice cliffs cannot stably exist below a certain critical debris thickness and that some modelling of ice cliffs (when not incorporating the moving frame) may incorrectly estimate ice mass losses. All of our results are produced using parametrisations from Baltoro Glacier, Karakoram.

A Non-Stochastic Special Model of Risk Based on Radon Transform

The concept of risk is fundamental in various scientific fields, including physics, biology and engineering, and is crucial for the study of complex systems, especially financial markets. In our research, we introduce a novel risk model that has a natural transactional–financial interpretation. In our approach, the risk of holding a financial instrument is related to the measure of the possibility of its loss. In this context, a financial instrument is riskier the more opportunities there are to dispose of it, i.e., to sell it. We present a model of risk understood in this way, introducing, in particular, the concept of financial time and a financial frame of reference, which allows for associating risk with the subjective perception of the observer. The presented approach does not rely on statistical assumptions and is based on the transactional interpretation of models. To measure risk, we propose using the Radon transform. The financial concept of risk is closely related to the concepts of uncertainty, entropy, information, and error in physics. Therefore, the well-established algorithmic aspects of the computed tomography method can be effectively applied to the broader field of uncertainty analysis, which is one of the foundational elements of experimental physics.

China as data coloniser? rethinking cultural production, cultural mediation, and consumer agency on Kenyan and Chinese e-commerce platforms

Has China become a neo-colonizer, exporting its cultural and economic power to the world based on its agenda of building soft power? Existing scholarship on neocolonialism and data colonialism largely focuses on how China's infrastructural expansion and increasingly platformised cultural sectors can achieve its ambitious platformised cultural sectors overseas. Yet, how China's cultural power is manifested, negotiated, or resisted in people's daily lives in a South–South setting remains under-researched and under-theorised. This article uses everyday fashion in Kenya as a case study to investigate China's cultural and economic power expansion in the Global South. We examined how cultural differences are negotiated and mediated on two Chinese(-invested) e-commerce platforms. Through focus groups and platform walkthrough method, our findings serve to enrich existing theories of cultural production–platform relationships applicable in the study of various cultural and creative sectors, to offer new understandings of how symbolic, sociopolitical and cultural meanings of fashion are constructed through divergent platform affordances, and to reveal the various forms of cultural negotiations and resistance in different contexts, multiplying our frames of reference.