Rapid Rotation Research Articles

The Scutulum and the Pre-Auricular Aponeurosis in Bats.

The external ear in eutherian mammals is composed of the annular, auricular (pinna), and scutellar cartilages. The latter extends between the pinnae, across the top of the head, and lies at the intersection of numerous auricular muscles and is thought to be a sesamoid element. In bats, this scutulum consists of two distinct regions, (1) a thin squama that is in contact with the underlying temporalis fascia and (2) a lateral bossed portion that is lightly tethered to the medial surface of the pinna. The planar size, shape, and proportions of the squama vary by taxa, as does the relative size and thickness of the boss. The origins, insertions, and relative functions of the auricular muscles are complicated. Here, 30 muscles were tallied as to their primary attachment to the pinnae, scutula, or a pre-auricular musculo-aponeurotic plate that is derived from the epicranius. In contrast to Yangochiroptera, the origins and insertions of many auricular muscles have shifted from the scutulum to this aponeurotic plate, in both the Rhinolophidae and Hipposideridae. We propose that this functional shift is a derived character related primarily to the rapid translations and rotations of the pinna in high-duty-cycle rhinolophid and hipposiderid bats.

She’s Got Her Mother’s Hair: Unveiling the Origin of Black Hole Magnetic Fields through Stellar to Collapsar Simulations

Abstract Relativistic jets from a Kerr black hole (BH) following the core collapse of a massive star (“collapsar”) is a leading model for gamma-ray bursts (GRBs). However, the two key ingredients for a Blandford–Znajek-powered jet—rapid rotation and a strong magnetic field—seem mutually exclusive. Strong fields in the progenitor star’s core transport angular momentum outward more quickly, slowing down the core before collapse. Through innovative multidisciplinary modeling, we first use MESA stellar evolution models followed to core collapse to explicitly show that the small length scale of the instabilities—likely responsible for angular momentum transport in the core (e.g., Tayler–Spruit)—results in a low net magnetic flux fed to the BH horizon, far too small to power GRB jets. Instead, we propose a novel scenario in which collapsar BHs acquire their magnetic “hair” from their progenitor proto–neutron star (PNS), which is likely highly magnetized from an internal dynamo. We evaluate the conditions for the BH accretion disk to pin the PNS magnetosphere to its horizon immediately after the collapse. Our results show that the PNS spin-down energy released before collapse matches the kinetic energy of Type Ic-BL supernovae, while the nascent BH’s spin and magnetic flux produce jets consistent with observed GRB characteristics. We map our MESA models to 3D general-relativistic magnetohydrodynamic simulations and confirm that accretion disks confine the strong magnetic flux initiated near a rotating BH, enabling the launch of successful GRB jets, whereas a slower-spinning BH or one without a disk fails to do so.

Atmospheric Circulation on Other Planets: Venus, Mars, Jupiter

Abstract. This review provides a comparative analysis of atmospheric circulation across four planets in our solar system: Venus, Mars, Jupiter, and Earth. By examining the unique characteristics of each planet, including atmospheric composition, rotation rates, axial tilt, and solar radiation, the study explores how these factors influence the dynamics of their respective atmospheres. Venus, with its dense CO atmosphere and slow retrograde rotation, exhibits a super-rotating atmosphere leading to extreme and uniform climate conditions. Marss thin atmosphere and significant seasonal variations, combined with global dust storms, result in highly variable and dynamic atmospheric patterns. Jupiters rapid rotation and internal heat contribute to complex and powerful atmospheric dynamics, including strong jet streams and long-lasting storms like the Great Red Spot. In contrast, Earth's atmospheric circulation is driven by a combination of solar radiation, rotation, and the presence of oceans and continents, resulting in relatively stable and predictable weather patterns. The study highlights the diversity of atmospheric processes within our solar system, providing insights that are crucial for understanding planetary climates and assessing the potential habitability of exoplanets.

Quadratic Frequency Dispersion in the Oscillations of Intermediate-mass Stars

Asteroseismology, the study of stellar vibration, has met with great success, shedding light on stellar interior structure, rotation, and magnetism. Prominently known as δ Scutis, the intermediate-mass main-sequence oscillators that often exhibit rapid rotation and possess complex internal stratification are important targets of asteroseismic study. δ Scuti pulsations are driven by the κ (opacity) mechanism, resulting in a set of acoustic modes that can be challenging to interpret. Here, we apply machine learning to identify new patterns in the pulsation frequencies of δ Scuti stars, discovering resonances spaced according to quadratic functions of integer mode indices. This unusual connection between mode frequencies and indices suggests that rotational influence may play an important role in determining the frequencies of these acoustic oscillations.

The rotational disruption of porous dust aggregates from ab initio kinematic calculations

The size of dust grains in the interstellar medium follows a distribution where most of the dust mass is made up of smaller grains. However, the redistribution from larger grains towards smaller sizes, especially by means of rotational disruption, is still poorly understood. We aim to study the dynamics of porous grain aggregates undergoing an accelerated rotation, namely, a spin-up process that rapidly increases the angular velocity of the aggregate. In particular, we aim to determine the deformation of the grains and the maximal angular velocity up to the rotational disruption event by caused by centrifugal forces. We precalculated the porous grain aggregate by means of ballistic aggregation analogous to the interstellar dust as input for subsequent numerical simulations. We performed three-dimensional (3D) N-body simulations, mimicking the radiative torque spin-up process up to the point where the grain aggregates become rotationally disrupted. Our simulations results are in agreement with theoretical models predicting a characteristic angular velocity, $ disr $, on the order of $ rad\ $, where grains become rotationally disrupted. In contrast to theoretical predictions, we show that for large porous grain aggregates ($ nm $), the $ disr $ values do not strictly decline. Instead, they reach a lower asymptotic value. Hence, such grains can withstand an accelerated rotation more efficiently up to a factor of 10 because the displacement of mass by centrifugal forces and the subsequent mechanical deformation supports the buildup of new connections within the aggregate. Furthermore, we report that the rapid rotation of grains deforms an ensemble with initially 50:50 prolate and oblate shapes, respectively, preferentially into oblate shapes. Finally, we present a best-fit formula to predict the average rotational disruption of an ensemble of porous dust aggregates dependent on the internal grain structure, total number of monomers, and applied material properties.

Transient Increases in Alpha Power Relative to Healthy Reference Ranges in Awake Piglets After Repeated Rapid Head Rotations

Background/Objectives: Sports-related concussions are a main cause of cognitive dysfunction and somatic complaints, particularly in youth. While the majority of concussion symptoms resolve within one week, cognitive effects may persist. In this study, we sought to study changes to cognition within this acute time frame. Methods: In this current study, we use an established swine model of traumatic brain injury (TBI) to study the effects of single and repeated head rotations on resting-state electroencephalography (rs-EEG) in awake piglets in the acute (within 7 days) time period after injury. We studied both healthy and experimental groups to (1) establish healthy reference ranges (RRs; N = 23) for one-minute rs-EEG in awake piglets, (2) compare the effects of single (N = 12) and repeated head rotations (N = 13) on rs-EEG, and (3) examine the acute time course (pre-injury and days 1, 4, and 7 post-injury) in animals administered single and repeated head rotations. EEG data were Fourier transformed, and total (1–30 Hz) and relative power in the alpha (8–12 Hz), beta (16.5–25 Hz), delta (1–4 Hz), and theta (4–7.5 Hz) bands were analyzed. Results: Total power and relative alpha, beta, delta, and theta power were consistent measures across days in healthy animals. We found a significant and transient increase in relative alpha power after repeated injury on day 1 in all regions and a rise above the healthy RR in the frontal and left temporal regions. Conclusions: Future studies will expand the study duration to investigate and inform clinical prognoses from acute measurements of rs-EEG.

Probing the magnetic fields of starspots with transit mapping

Starspots, regions of strong magnetic fields, serve as indicators of stellar activity and the dynamo mechanism at play in the interior of stars. The magnetic fields of main-sequence stars play a crucial role in driving stellar activity. An effective approach to better understanding stellar magnetic fields and activity lies in the detailed characterisation of starspot properties. We propose a new method for estimating the magnetic fields of starspots that employs modelling techniques of planetary transit mapping, which provides estimates of the size, intensity, and location of spots on the stellar photosphere. A starspot's maximum magnetic field was calculated using the linear relationship with the spot flux deficit, $ spot $ (the spot's brightness times its area) and the well-characterised relation for sunspots determined in this work, $B_ spot (G). Applying this relationship to previously mapped spots on the photospheres of 14 FGK and M stars yields spot maximum magnetic fields ranging from 2700 G to 4600 G, with an overall average of $3900 400$ G. We looked for correlations between starspot magnetic fields and stellar properties.\ We did not find any correlation between a spot's mean extreme magnetic field and effective temperature, nor the differential shear. However, a weak anti-correlation is seen between the spots' magnetic field and stellar age as well as between the magnetic field and the rotation period. When compared with previous results of small-scale magnetic field measurements, the B values obtained here are basically constant and near the saturation limit found for rapid rotators. This implies that it is not the intensity of the magnetic field of starspots that decreases with age but rather the filling factor. This result offers a unique window into the magnetic dynamo of stars.

Impact of proprioceptive cervical dizziness in chronic neck pain syndromes on gait and stance during active head-turn challenges.

An earlier observational study described selected patients with acute neck pain syndrome, who experienced short bursts of cervical vertigo elicited by rapid head movements. The current study on a larger cohort of 20 patients with chronic or frequently recurring neck pain syndrome and age-matched controls focused on two major questions: (1) Can head movements in subjects with exacerbations of neck pain and restrictions of neck mobility also elicit bursts of vertigo? (2) What is the impact on postural balance measured by analysis of body sway and locomotion? A detailed questionnaire was applied, posture and gait were evaluated by use of instrumented posturography-and gait analysis with and without slow or rapid horizontal head rotations in the yaw plane with and without sight/visual input. All patients reported some or frequent episodes of dizziness in the range of seconds only elicited by rapid, not by slow head movements. Postural sway in patients was unremarkable in undisturbed conditions without head movements, but specifically increased by rapid but not slow head turns. The latter is best explained by the lack of continuous control of velocity and amplitude of saccadic head movements. Gait analysis revealed a slowed and cautious gait pattern already at undisturbed condition that was even exaggerated during rapid head turns. These observations demonstrate that chronic or recurrent neck pain is associated with episodic experiences of dizziness and above results in both chronic and episodic alterations of stance and gait that resemble those described for patients with phobic postural vertigo/persistent postural perceptual dizziness, a functional gait disorder.

Rapidly Rotating Magnetohydrodynamics and the Geodynamo

The problem of the geodynamo is simple to formulate (Why does the Earth possess a magnetic field?), yet it proves surprisingly hard to address. As with most geophysical flows, the fluid flow of molten iron in the Earth's core is strongly influenced by the Coriolis effect. Because the liquid is electrically conducting, it is also strongly influenced by the Lorentz force. The balance is unusual in that, whereas each of these effects considered separately tends to impede the flow, the magnetic field in the Earth's core relaxes the effect of the rapid rotation and allows the development of a large-scale flow in the core that in turn regenerates the field. This review covers some recent developments regarding the interplay between rotation and magnetic fields and how it affects the flow in the Earth's core.

A low-complexity error-feedback lattice-equalizer with phase tracking for underwater acoustic communications.

Recursive least squares (RLS)-based equalizers are hindered by their high complexity in underwater acoustic (UWA) communications. This article proposes an adaptive equalizer with a phase tracking method for the UWA communication, named the error-feedback lattice-equalizer (EFLE). First, we derive the algorithm for recursively solving the least squares problem from EFLE, introducing a lattice structure using time and order updates, thereby reducing the complexity to be linearly related to its length. The error-feedback mechanism used in computing reflection coefficients ensures the numerical stability of the algorithm. By focusing on the rapid tap rotation in time-varying channels, we design phase tracking in EFLE to further improve equalization performance. To verify the bit error rate (BER) performance of the proposed EFLE, we study the UWA communication system and conduct UWA simulations and at-sea experiments. Comparisons include linear complexity equalizers such as least mean square (LMS), leaky LMS, least mean mixed-norm, and ϵ-normalized LMS equalizers, and quadratic complexity RLS equalizers. At-sea experiment results show that the BER performance of EFLE significantly outperforms its counterparts.

Rapid Interpretation of Protein Backbone Rotation Dynamics Directly from Spin Relaxation Data.

Besides their structure, dynamics is pivotal for protein functions, particularly for intrinsically disordered proteins (IDPs) that do not fold into a fixed 3D structure. However, the detection of protein dynamics is difficult for IDPs and other disordered biomolecules. NMR spin relaxation rates are sensitive to the rapid rotations of chemical bonds, but their interpretation is arduous for IDPs or molecular assemblies with a complex dynamic landscape. Here we demonstrate numerically that the dynamics of a wide range of proteins, from short peptides to partially disordered proteins and peptides in micelles, can be characterized by calculating the total effective correlation times of protein backbone N-H bond rotations, τeff, from experimentally measured transverse 15N spin relaxation rates, R2, using a linear relation. Our results enable the determination of magnetic-field-independent and intuitively understandable parameters describing protein dynamics at different regions of the sequence directly from experiments. A practical advance of the approach is demonstrated by analyzing partially disordered proteins in which rotations of disordered regions occur with timescales of 1-2 ns, independent of their size, suggesting that rotations of disordered and folded regions are uncoupled in these proteins.

The δ Scuti stars of the Cep–Her Complex – I. Pulsator fraction, rotation, asteroseismic large spacings, and the νmax relation

ABSTRACT We identify delta Scuti ($\delta$ Sct) pulsators amongst members of the recently discovered Cep–Her Complex using light curves from the Transiting Exoplanet Survey Satellite (TESS). We use Gaia colours and magnitudes to isolate a subsample of provisional Cep–Her members that are located in a narrow band on the colour–magnitude diagram compatible with the zero-age main sequence. The $\delta$ Sct pulsator fraction amongst these stars peaks at 100 per cent and we describe a trend of higher pulsator fractions for younger stellar associations. We use four methods to measure the frequency of maximum amplitude or power, $\nu _{\rm max}$, to minimize methodological bias, and we demonstrate their sound performance. The $\nu _{\rm max}$ measurements display a correlation with effective temperature, but with a scatter that is too large for the relation to be useful. We find two ridges in the $\nu _{\rm max}$–$T_{\rm eff}$ diagram, one of which appears to be the result of rapid rotation causing stars to pulsate in low-order modes. We measure the $\nu _{\rm max}$ values of $\delta$ Sct stars in four other clusters or associations of similar age (Trumpler 10, the Pleiades, NGC 2516, and Praesepe) and find similar behaviour with $T_{\rm eff}$. Using échelle diagrams, we measure the asteroseismic large spacing, $\Delta \nu$, for 70 stars, and find a correlation between $\Delta \nu$, rotation, and luminosity that allows rapid rotators seen at low inclinations to be distinguished from slow rotators. We find that rapid rotators are more likely than slow rotators to pulsate, but they do so with less regular pulsation patterns. We also investigate the reliability of Gaia’s vbroad measurement for A-type stars, finding that it is mostly accurate but underestimates $v\sin i$ for slow rotators ($v\sin i \lt 50$ km s−1) by 10–15 per cent.

A phase field crystal model for real-time grain boundary formation and motion in complex concentration alloy

The complex concentration alloys exhibit the excellent mechanical property due to the dual roles of their heterogeneous compositions and microstructures. However, the formation and motion of grain boundaries to significantly regulate the mechanical properties remain unknown at several microsecond and nanoscale in the complex concentration alloys. Here, we utilize a phase field crystal model to investigate the real-time grain boundary formation and motion in complex concentration alloys, specifically, in comparison to traditional alloys, using the example of AlCu alloys. Our findings reveal that the low concentration alloys exhibit segregation primarily at grain boundaries with minimal compositional fluctuations over a long period of grain growth, and the complex concentration alloys display a high concentration gradient within the grains to cause rapid grain rotation and merging in a short time frame. In the complex concentration alloys, the large component fluctuations not only cause the local lattice distortion to hinder dislocation movement during the deformation process, but also lead to the occurrence from dislocation locking to self-unlocking, which is beneficial to improve the strength and ductility. The present work provides a real-time atomic-scale understanding of grain boundary evolution using in situ atomic-resolution simulations.

Favorable Conditions for Heavy Element Nucleosynthesis in Rotating Protomagnetar Winds

The neutrino-driven wind cooling phase of proto-neutron stars (PNSs) follows successful supernovae. Wind models without magnetic fields or rotation fail to achieve the necessary conditions for production of the third r-process peak, but robustly produce a weak r-process in neutron-rich winds. Using 2D magnetohydrodynamic simulations with magnetar-strength magnetic fields and rotation, we show that the PNS rotation rate significantly affects the thermodynamic conditions of the wind. We show that high-entropy material is quasiperiodically ejected from the closed zone of the PNS magnetosphere with the required thermodynamic conditions to produce heavy elements. We show that maximum entropy S of the material ejected depends systematically on the magnetar spin period P ⋆ and scales as S∝P⋆−5/6 for sufficiently rapid rotation. We present results from simulations at a constant neutrino luminosity representative of ∼1–2 s after the onset of cooling for P ⋆ ranging from 5–200 ms and a few simulations with evolving neutrino luminosity where we follow the evolution of the magnetar wind until 10–14 s after the onset of cooling. We estimate at magnetar polar magnetic field strength B 0 = 3 × 1015 G and 1015 G that neutron-rich magnetar winds can, respectively, produce at least ∼1–5 × 10−5 M ⊙ and ∼1–4 × 10−7 M ⊙ of material with the required parameters for synthesis of the third r-process peak, within 1–2 s and 10 s, respectively, in that order after the onset of cooling. We show that proton-rich magnetar winds can have favorable conditions for production of p-nuclei, even at a modest B 0 = 5 × 1014 G.

Fabrication of Patterned Magnetic Particles in Microchannels and Their Application in Micromixers.

Due to the extremely low Reynolds number, the mixing of substances in laminar flow within microfluidic channels primarily relies on slow intermolecular diffusion, whereas various rapid reaction and detection requirements in lab-on-a-chip applications often necessitate the efficient mixing of fluids within short distances. This paper presents a magnetic pillar-shaped particle fabrication device capable of producing particles with planar shapes, which are then utilized to achieve the rapid mixing of multiple fluids within microchannels. During the particle fabrication process, a degassed PDMS chip provides self-priming capabilities, drawing in a UV-curable adhesive-containing magnetic powder and distributing it into distinct microwell structures. Subsequently, an external magnetic field is applied, and the chip is exposed to UV light, enabling the mass production of particles with specific magnetic properties through photo-curing. Without the need for external pumping, this chip-based device can fabricate hundreds of magnetic particles in less than 10 min. In contrast to most particle fabrication methods, the degassed PDMS approach enables self-priming and precise dispensing, allowing for precise control over particle shape and size. The fabricated dual-layer magnetic particles, featuring fan-shaped blades and disk-like structures, are placed within micromixing channels. By manipulating the magnetic field, the particles are driven into motion, altering the flow patterns to achieve fluid mixing. Under conditions where the Reynolds number in the chip ranges from 0.1 to 0.9, the mixing index for substances in aqueous solutions exceeds 0.9. In addition, experimental analyses of mixing efficiency for fluids with different viscosities, including 25 wt% and 50 wt% glycerol, reveal mixing indices exceeding 0.85, demonstrating the broad applicability of micromixers based on the rapid rotation of magnetic particles.

Hypotheses Concerning Global Magnetospheric Convection, Magnetosphere‐Ionosphere Coupling, and Auroral Activity at Uranus

AbstractWe investigate the unique magnetosphere of Uranus and its interaction with the solar wind. Following the work of Masters (2014), https://doi.org/10.1002/2014ja020077 and others, we developed and validated a simple yet valuable and illustrative model of Uranus' offset, tilted, and rapidly‐spinning magnetic field and magnetopause (nominal and fit to the Voyager‐2 inbound crossing point) in three‐dimensional space. With this model, we investigated details of the seasonal and interplanetary magnetic field (IMF) orientation dependencies of dayside and flank reconnection along the Uranian magnetopause. We found that anti‐parallel (magnetic field shear angle greater than 170°) reconnection occurs nearly continuously along the Uranian dayside and/or flank magnetopause under all seasons of the 84 (Earth) year Uranian orbit and the most likely IMF orientations. Such active and continuous driving of the Uranian magnetosphere should result in constant loading and unloading of the Uranian magnetotail, which may be further complicated and destabilized by sudden changes in the IMF orientation and solar wind conditions plus the reconfigurations from the rotation of Uranus itself. We demonstrate that unlike the other magnetospheric systems that are Dungey‐cycle driven (i.e., Mercury and Earth) or rotationally driven (Jupiter and Saturn), global magnetospheric convection of plasma, magnetic flux, and energy flow may occur via three distinct cycles, two of which are unique to Uranus (and possibly also Neptune). Our simple model is also used to map signatures of dayside and flank reconnection down to the Uranian ionosphere, as a function of planetary latitude and longitude. Such mapping demonstrates that “spot‐like” auroral features should be very common on the Uranian dayside, consistent with observations from Hubble Space Telescope. We further detail how the combination of Uranus' rapid rotation and unique and very active global magnetospheric convection should be consistent with fueling of the surprisingly intense trapped radiation environment observed by Voyager‐2 during its single flyby. Summarizing, Uranus is a very interesting magnetosphere that offers new insights on the nature, complexity, and diversity of planetary magnetospheric systems and the acceleration of particles in space plasmas, which might have important analogs to exoplanetary magnetospheric systems. Our hypotheses can be tested with further work involving more advanced models, new auroral observations, and unprecedented missions to explore the in situ environment from orbit around Uranus, which should include a complement of magnetospheric instruments in the payload.

Magnetic Fields in M-dwarf Members of the Pleiades Open Cluster Using APOGEE Spectra

Average magnetic field measurements are presented for 62 M-dwarf members of the Pleiades open cluster, derived from Zeeman-enhanced Fe i lines in the H band. A Markov Chain Monte Carlo methodology was employed to model magnetic filling factors using Sloan Digital Sky Survey (SDSS) IV APOGEE high-resolution spectra, along with the radiative transfer code Synmast, MARCS stellar atmosphere models, and the APOGEE Data Release 17 spectral line list. There is a positive correlation between mean magnetic fields and stellar rotation, with slow-rotator stars (Rossby number, Ro > 0.13) exhibiting a steeper slope than rapid rotators (Ro < 0.13). However, the latter sample still shows a positive trend between Ro and magnetic fields, which is given by 〈B〉 = 1604 × Ro−0.20. The derived stellar radii when compared with physical isochrones show that, on average, our sample shows radius inflation, with median enhanced radii ranging from +3.0% to +7.0%, depending on the model. There is a positive correlation between magnetic field strength and radius inflation, as well as with stellar spot coverage, correlations which together indicate that stellar spot-filling factors generated by strong magnetic fields might be the mechanism that drives radius inflation in these stars. We also compare our derived magnetic fields with chromospheric emission lines (Hα, Hβ, and Ca ii K), as well as with X-ray and Hα to bolometric luminosity ratios, and find that stars with higher chromospheric and coronal activity tend to be more magnetic.

The Chemical Puzzle of Weak G-Band Stars: A Comprehensive Study of HD 54627, HD 105783, HD 198718, and HD 201557

Weak G-band stars (WGBs) are a unique class of objects characterized by weak CH molecular lines in the Fraunhofer G band, indicative of a deficiency in 12C. This peculiar spectral feature is often accompanied by significant enrichments in N and, occasionally, Li and Na abundances. Despite their rarity and recent discoveries of new WGB candidates, the underlying formation mechanism of these stars remains unknown. In this study, we present a comprehensive chemical analysis of four neglected WGBs: HD 54627, HD 105783, HD 198718, and HD 201557. These stars, though identified as WGBs, have been poorly studied to date. Our analysis utilizes high-resolution échelle spectra with a power resolution of R ≈ 48,000, complemented by photometric and astrometric data from the literature. Applying the local thermodynamic equilibrium (LTE) approximation we determine the chemical abundance and then we conduct posterior non-LTE (NLTE) corrections for specific chemical abundances, including Li, O, Na, and Mg. Additionally, we provide details on the projected rotational velocities ( vsini ) and conduct a thorough investigation of the kinematics and orbits of our sample, comparing them with other well-studied WGBs reported in the literature. Our findings indicate that these stars originate from the thin disk, as evidenced by the absence of alpha-element enrichment and kinematics. Notably, half of the WGBs in our sample exhibit Li-rich characteristics, and we identify no rapid rotators ( vsini> 8.0 km s−1) or infrared excess among our studied stars.

Investigation of structural, electronic, and optical properties of halide perovskites with different amide cations: A first-principles approach

Hybrid halide perovskites (CH3NH3PbI3) have emerged as an appealing candidate in photovoltaic devices due to their low-cost fabrication and remarkable optical and electronic properties. However, the commercial applications of these perovskites are limited by their instability due to the rapid rotation and orientation of methylammonium cation (CH3NH3+), and interaction with PbI2 lattice at high temperatures. Since CH3NH3+ can deteriorate structural stability of MAPbI3 perovskites, it is possible to use molecular cation design and substitution as a mechanism to enhance the stability and remove this limitation. We here investigate the effect of replacing this cation with other organic cations (HCOHNH2PbI3 (FPbI3), CH3COHNH2PbI3 (AcPbI3), and NH2COHNH2PbI3 (UPbI3)) in order to enhance the performance of the perovskites, while also keeping the band gap energy (Eg) in an appropriate range for solar cell applications. The calculations are performed using the full potential linearized augmented plane wave method, providing lattice parameters and the formation energy of the proposed perovskites. Our results indicate that AcPbI3 perovskite outperforms the other structures in terms of various optical parameters, such as the absorption coefficient, optical conductivity, and reflectance. The optical and electronic band gaps of the AcPbI3 structure and its resonance form (Ac'PbI3) are found to be in agreement with each other, proposing them as optically tunable hybrid perovskites in emerging solar cells.

Modeling the Progenitor Stars of Observed Type IIP Supernovae

Type IIP supernovae (SNe IIP) are thought to originate from the explosion of massive stars >10 M ⊙. Their luminosity is primarily powered by the explosion energy and the radioactive decay energy of 56Co, with the photosphere location regulated by hydrogen recombination. However, the physical connections between SNe IIP and their progenitor stars remain unclear. This paper presents a comprehensive study of SNe IIP and their progenitor stars by using the one-dimensional stellar evolution code, MESA. Our model grids consider the effects of stellar metallicity, mass, and rotation in the evolution of massive stars, as well as the explosion energy and 56Ni production in modeling supernovae. To elucidate the observed SNe IIP and their origins, we compare their light curves (LCs) with our models. Furthermore, we investigate the impact of stellar parameters on LCs by considering stellar mass, metallicity, rotation, explosion energy, and 56Ni production. We find that more massive stars exhibit longer plateaus due to increased photon diffusion time caused by massive ejecta. Higher metallicity leads to increased opacity and mass loss of progenitor stars. Rapid rotation affects internal stellar structures, enhancing convective mixing and mass loss, potentially affecting the plateau’s brightness and duration. Higher explosion energy results in brighter but shorter plateaus due to faster-moving ejecta. 56Ni mass affects late-time luminosity and plateau duration, with larger masses leading to slower declines.