A new interpretation of the period-luminosity sequences of long-period variables

Period-luminosity (PL) sequences of long period variables (LPVs) are commonly interpreted as different pulsation modes, but there is disagreement on the modal assignment. Here, we re-examine the observed PL sequences in the Large Magellanic Cloud, including the sequence of long secondary periods (LSPs), and their associated pulsation modes. Firstly, we theoretically model the sequences using linear, radial, non-adiabatic pulsation models and a population synthesis model of the LMC red giants. Then, we use a semi-empirical approach to assign modes to the pulsation sequences by exploiting observed multi-mode pulsators. As a result of the combined approaches, we consistently find that sequences B and C$^{\prime}$ both correspond to first overtone pulsation, although there are some fundamental mode pulsators at low luminosities on both sequences. The masses of these fundamental mode pulsators are larger at a given luminosity than the mass of the first overtone pulsators. These two sequences B and C$^{\prime}$ are separated by a small period interval in which large amplitude pulsation in a long secondary period (sequence D variability) occurs, meaning that the first overtone pulsation is not seen as the primary mode of pulsation. Observationally, this leads to the splitting of the first overtone pulsation sequence into the two observed sequences B and C$^{\prime}$. Our two independent examinations also show that sequences A$^{\prime}$, A and C correspond to third overtone, second overtone and fundamental mode pulsation, respectively.Comment: 10 pages, 7 figures, accepted for publication in Ap

Reading on the right when there’s nothing left? Probabilistic tractography reveals hemispheric asymmetry in pure alexia

We present a patient with reading inexpertise and right hemianopia following left posterior cerebral artery (PCA) stroke. We examine the extent of disruption to reading performance and the extent of white matter tract damage relative to a patient with more limited PCA infarction and isolated right hemianopia. We show white matter disconnection of the temporal occipital fusiform cortex in our pure alexia patient. Connectivity-based laterality indices revealed right hemisphere laterality in the alexia patient; this was not associated with improved reading function. We speculate that the degree of premorbid laterality may be a critical factor affecting the extent of reading dysfunction in alexia

Public perceptions of U.S. earthquake early warning post-alert messages: Findings from focus groups and interviews

In May 2020, a false earthquake alert message was sent to the city of Ridgecrest, CA, in the U.S.A., an area that just 10 months prior had experienced a significant series of earthquake events. The false alert was followed by a post-alert message, indicating that the message was cancelled and under investigation. This event, the first of its kind in the U.S.A., provided an opportunity to learn about public perceptions of the post-alert message, including what individuals understood about the threat and their safety, and what actions they should take as a result. We conducted individual interviews with 40 persons in the Ridgecrest community, followed by a series of focus groups in Southern California to discuss post-alert messages, and to learn about information people most needed following false earthquake alerts. We found that individuals with and without prior earthquake experience expressed confusion about content describing the investigatory actions of the organization and had a largely negative response toward content that complimented those who took action in response to the initial earthquake early warning. While current post-alert messages are intended to reinforce the good intentions of the organization and the protective actions taken by message receivers, the message issued was perceived by members of the public to be largely ineffective in achieving either objective because it did not provide the information they desired most—an explicit statement about their safety. Instead, message receivers need information that primarily affirms their current level of safety so they can return to normal functionin

Designing Effective Tsunami Messages: Examining the Role of Short Messages and Fear in Warning Response

Although tsunamis have the potential to be extremely destructive, relatively little research on tsunami messaging has taken place. Discovering whether tsunami warning messages can be written in a way that leads to increased protective response is crucial, particularly given the increased use of mobile message services and the role they play in notifying the public of imminent threats such as tsunami and other hazards. The purpose of this study was to examine the possibility of designing warning messages for tsunamis that improve upon message style and content used by public alerting agencies to date and to gain insight that can be applied to other hazards. This study tested the impact of tsunami messages that varied in length and content on six message outcomes—understanding, believing, personalizing, deciding, milling, and fear. Relative to the short message, revised messages resulted in significantly more understanding and deciding, known precursors to taking protective action under threat. The revised message also resulted in significantly more fear, which is believed to influence behavioral intentions. Findings suggest that shorter messages may not deliver enough content to inform message receivers about the threat they face and the protective actions they should perform. Longer messages delivered with more specific information about the location of impact, threat-associated risks, and recommended protective actions were associated with better message outcomes, including quicker intended response. Recommendations for future tsunami warnings are provided

Virtual Reality and Choreographic Practice:The Potential for New Creative Methods

Virtual reality (VR) is becoming an increasingly intriguing space for dancers and choreographers. Choreographers may find new possibility emerging in using virtual reality to create movement and the WhoLoDancE: Whole-Body Interaction Learning for Dance Education project is developing tools to assist in this process. The interdisciplinary team which includes dancers, choreographers, educators, artists, coders, technologists and system architects have collaborated in engaging, discussing, analysing, testing and working with end-users to help with thinking about the issues that emerge in the creation of these tools. The paper sets out to explore the creative potential of VR in the context of WhoLoDancE and how this may offer new insights for the choreographer and dancer. We pay attention to the virtual environment, the virtual performance and the virtual dancer as some of the key components for equipping the choreographer to use in the creating process and to inform the dancing body. The cyclical process of live body to virtual, back to the dancing body as a choreographic device is an innovative way to approach practice. This approach may lead to new insights and innovations in choreographic methods that may extend beyond the project and ultimately take dance performance in a new direction

Modelling Long-Period Variables -- II. Fundamental mode pulsation in the nonlinear regime

Long-period variability in luminous red giants has several promising applications, all of which require models able to accurately predict pulsation periods. Linear pulsation models have proven successful in reproducing the observed periods of overtone modes in evolved red giants, but they fail to accurately predict their fundamental mode periods. Here, we use a 1D hydrodynamic code to investigate the long-period variability of M-type asymptotic giant branch stars in the nonlinear regime. We examine the period and stability of low-order radial pulsation modes as a function of mass and radius, and find overtone mode periods in complete agreement with predictions from linear pulsation models. In contrast, nonlinear models predict an earlier onset of dominant fundamental mode pulsation, and shorter periods at large radii. Both features lead to a substantially better agreement with observations, that we verify against OGLE and Gaia data for the Magellanic Clouds. We provide simple analytic relations describing the nonlinear fundamental mode period-mass-radius relation. Differences with respect to linear predictions originate from the readjustment of the envelope structure induced by large-amplitude pulsation. We investigate the impact of turbulent viscosity on linear and nonlinear pulsation, and probe possible effects of varying metallicity and carbon abundance.Comment: 18 pages, 17 figures; accepted for publication in MNRA

Smoothed Particle Hydrodynamics Simulations of Apsidal and Nodal Superhumps

In recent years a handful of systems have been observed to show "negative" (nodal) superhumps, with periods slightly shorter than the orbital period. It has been suggested that these modes are a consequence of the slow retrograde precession of the line of nodes in a disk tilted with respect to the orbital plane. Our simulations confirm and refine this model: they suggest a roughly axisymmetric, retrogradely-precessing, tilted disk that is driven at a period slightly less than half the orbital period as the tidal field of the orbiting secondary encounters in turn the two halves of the disk above and below the midplane. Each of these passings leads to viscous dissipation on one face of an optically-thick disk -- observers on opposite sides of the disk would each observe one brightening per orbit, but 180 degrees out of phase with each other.Comment: 11 pages. Accepted for publication in The ApJ Letter