Classical Picture Research Articles

Tidally excited gravity waves in the cores of solar-type stars: resonances and critical-layer formation

ABSTRACT We simulate the propagation and dissipation of tidally induced non-linear gravity waves in the cores of solar-type stars. We perform hydrodynamical simulations of a previously developed Boussinesq model using a spectral-element code to study the stellar core as a wave cavity that is periodically forced at the outer boundary with a given azimuthal wavenumber and an adjustable frequency. For low-amplitude forcing, the system exhibits resonances with standing g modes at particular frequencies, corresponding to a situation in which the tidal torque is highly frequency-dependent. For high-amplitude forcing, the excited waves break promptly near the centre and spin up the core so that subsequent waves are absorbed in an expanding critical layer (CL), as found in previous work, leading to a tidal torque with a smooth frequency-dependence. For intermediate-amplitude forcing, we find that linear damping of the waves gradually spins up the core such that the resonance condition can be altered drastically. The system can evolve towards or away from g-mode resonances, depending on the difference between the forcing frequency and the closest eigenfrequency. Eventually, a CL forms and absorbs the incoming waves, leading to a situation similar to the high-amplitude case in which the waves break promptly. We study the dependence of this process on the forcing amplitude and frequency, as well as on the diffusion coefficients. We emphasize that the small Prandtl number in the centre of solar-like stars facilitates the development of a differentially rotating core owing to the non-linear feedback of waves. Our simulations and analysis reveal that this important mechanism may drastically change the phase of gravity waves and thus the classical picture of resonance locking in solar-type stars needs to be revised.

The nonlinear Benjamin–Feir instability – Hamiltonian dynamics, discrete breathers and steady solutions

We develop a general framework to describe the cubically nonlinear interaction of a degenerate quartet of deep-water gravity waves in one or two spatial dimensions. Starting from the discretised Zakharov equation, and thus without restriction on spectral bandwidth, we derive a planar Hamiltonian system in terms of the dynamic phase and a modal amplitude. This is characterised by two free parameters: the wave action and the mode separation between the carrier and the sidebands. For unidirectional waves, the mode separation serves as a bifurcation parameter, which allows us to fully classify the dynamics. Centres of our system correspond to non-trivial, steady-state nearly resonant degenerate quartets. The existence of saddle-points is connected to the instability of uniform and bichromatic wave trains, generalising the classical picture of the Benjamin–Feir instability. Moreover, heteroclinic orbits are found to correspond to discrete, three-mode breather solutions, including an analogue of the famed Akhmediev breather solution of the nonlinear Schrödinger equation.

A Review of Radio Observations of the Giant Planets: Probing the Composition, Structure, and Dynamics of Their Deep Atmospheres

Radio observations of the atmospheres of the giant planets Jupiter, Saturn, Uranus, and Neptune have provided invaluable constraints on atmospheric dynamics, physics/chemistry, and planet formation theories over the past 70 years. We provide a brief history of these observations, with a focus on recent and state-of-the-art studies. The global circulation patterns, as derived from these data, in combination with observations at UV/visible/near-IR wavelengths and in the thermal infrared, suggest a vertically-stacked pattern of circulation cells in the troposphere, with the top cell similar to the classical picture, overlying cells with the opposite circulation. Data on the planets’ bulk compositions are used to support or disfavor different planet formation scenarios. While heavy element enrichment in the planets favors the core accretion model, we discuss how the observed relative enrichments in volatile species constrain models of the outer proto-planetary disk and ice giant accretion. Radio observations of planets will remain invaluable in the next decades, and we close with some comments on the scientific gain promised by proposed and under-construction radio telescopes.

Complications of Acute Bacterial Rhinosinusitis in Contemporary Practice: Lessons Learnt and the Way Ahead.

There are variable presentations of complications of rhinosinusitis, which may be subtle especially due to use of antibiotics. Thus the classical picture as described by Chandler is rarely seen and threshold for diagnosing and treating a complication should be low. To identify possible risk factors for development of complications in acute bacterial rhinosinusitis (ABRS) and suggest a new method of reporting/classifying the complications. We conducted a retrospective study and observed the clinical presentation and risk factors of 9 patients who presented with complications of ABRS in our OPD during a period of 6years, and then tried to formulate a reporting method based on the risk factors. We identified certain risk factors which include age, gender, sinus involved, extension beyond sinus, history of trauma, anatomical variations, and duration of symptoms. There are possible risk factors for development of complications. These factors can be studied in further details to ascertain their causal relationship in causing these complications. We also suggest a new method of reporting the complications. Such a reporting system would help in accurately identifying the exact severity of the disease, prognosticating the disease and guide treatment.

Solar flare hard X-rays from the anchor points of an eruptive filament

Context.We present an analysis of a GOES M1.8 flare with excellent observational coverage in UV, extreme-UV (EUV), and X-ray, including observations from the Interface Region Imaging Spectrograph (IRIS), from the Solar Dynamics Observatory (SDO) with the Atmospheric Imaging Assembly (AIA), from the Hinode/EUV Imaging Spectrometer (EIS), from the Hinode/X-ray Telescope (XRT), and from Solar Orbiter with the Spectrometer/Telescope for Imaging X-rays (STIX). Hard X-ray emission is often observed at the footpoints of flare loops and is occasionally observed in the corona. In this flare, four nonthermal hard X-ray sources are seen.Aims.Our aim is to understand why we can observe four individual nonthermal sources in this flare and how we can characterize the physical properties of these four sources.Methods.We used the multiwavelength approach to analyze the flare and characterize the four sources. To do this, we combined imaging at different wavelengths and spectroscopic fitting in the EUV and X-ray range.Results.The flare is eruptive with an associated coronal mass ejection, and it shows the classical flare picture of a heated flare loop seen in EUV and X-rays, and two nonthermal hard X-ray footpoints at the loop ends. In addition to the main flare sources, we observed two outer sources in the UV, EUV, and nonthermal X-ray range located away from the main flare loop to the east and west. The two outer sources are clearly correlated in time, and they are only seen during the first two minutes of the impulsive phase, which lasts a total of about four minutes.Conclusions.Based on the analysis, we determine that the outer sources are the anchor points of an erupting filament. The hard X-ray emission is interpreted as flare-accelerated electrons that are injected upward into the filament and then precipitate along the filament toward the chromosphere, producing Bremsstrahlung. While sources like this have been speculated to exist, this is the first report of their detection.

Double Paddle‐Wheel Enhanced Sodium Ion Conduction in an Antiperovskite Solid Electrolyte (Adv. Energy Mater. 7/2023)

Solid State Electrolytes Solid-state conductors utilizing the rotation of atomic clusters to facilitate fast-ion transport provide an alternative mechanism to the classical picture of ion hopping through a fixed lattice. The antiperovskite compound Na2NH2BH4, described in article number 2203284 by Yet-Ming Chiang and co-workers, is an example where two such clusters work in concert to increase Na+ conduction.

Identifying the energy release site in a solar microflare with a jet

Context. One of the main science questions of the Solar Orbiter and Parker Solar Probe missions deals with understanding how electrons in the lower solar corona are accelerated and how they subsequently access interplanetary space. Aims. We aim to investigate the electron acceleration and energy release sites as well as the manner in which accelerated electrons access the interplanetary space in the case of the SOL2021-02-18T18:05 event, a GOES A8 class microflare associated with a coronal jet. Methods. This study takes advantage of three different vantage points, Solar Orbiter, STEREO-A, and Earth, with observations drawn from eight different instruments, ranging from radio to X-ray. Multi-wavelength timing analysis combined with UV/EUV imagery and X-ray spectroscopy by Solar Orbiter/STIX (Spectrometer/Telescope for Imaging X-rays) is used to investigate the origin of the observed emission during different flare phases. Results. The event under investigation satisfies the classical picture of the onset time of the acceleration of electrons coinciding with the jet and the radio type III bursts. This microflare features prominent hard X-ray (HXR) nonthermal emission down to at least 10 keV and a spectrum that is much harder than usual for a microflare with γ = 2.9 ± 0.3. From Earth’s vantage point, the microflare is seen near the limb, revealing the coronal energy release site above the flare loop in EUV, which, from STIX spectroscopic analysis, turns out to be hot (i.e., at roughly the same temperature of the flare). Moreover, this region is moving toward higher altitudes over time (∼30 km s−1). During the flare, the same region spatially coincides with the origin of the coronal jet. Three-dimensional (3D) stereoscopic reconstructions of the propagating jet highlight that the ejected plasma moves along a curved trajectory. Conclusions. Within the framework of the interchange reconnection model, we conclude that the energy release site observed above-the-loop corresponds to the electron acceleration site, corroborating that interchange reconnection is a viable candidate for particle acceleration in the low corona on field lines open to interplanetary space.

Interference with Non-Interacting Free Particles and a Special Type of Detector

This paper demonstrates how a classical detector that collects non-interacting individual classical massive free particles can generate a quantum interference pattern. The proposed classical picture requires that particles carry the information of a phase equal to an action integral along their trajectory. At the point of their detection, a special type of detector collects the phases from all individual particles reaching it, adds them up over time as complex numbers, and divides them by the square root of their number. The detector announces a number of detections equal to the square of the amplitude of the resulting complex number. An interference pattern is gradually built from the collection of particle phases in the detection bins of the detector after several repetitions of the experiment. We obtain perfect agreement with three solutions of the Schrödinger equation for free particles: a Gaussian wavepacket, two Gaussian wavepackets approaching each other, and a Gaussian wavepacket reflecting off a wall. The main conclusion of the present work is that the interference of quantum mechanics is basically due to the detectors that collect the particles when there are macroscopic detectors operating as proposed. Finally, a simple physical experiment with a single-photon detector is proposed that will be able to test our theory.

Carcinosarcomas and epithelial to mesenchymal transition (EMT)

Carcinosarcomas are rare, extremely aggressive malignant neoplasms, combining two cellular epithelial and sarcomatous components. Epithelial to mesenchymal transition (EMT) is a biological process that occurs in malignant tumors. Sarcomatous component in carcinosarcomas is derived from the carcinomatous component as a result of metaplasia/transdifferentiation (ЕМТ). We present the pathohistological characteristics and immunohistochemical analysis of four clinicalcarcinosarcoma cases with a different primary localization. Our main goal is to present the classic pathohistological picture of EMT and the role of intermediate filament (IF) proteins in cell and tissue structural integrity, as well as their importance for local invasion and distant hematogenous metastases in carcinosarcomas.

Polarity-extended 8 - Neff rule for semiconducting main-group compounds with the TiNiSi-type of crystal structure.

Application of chemical bonding analysis in position-space techniques based on combined topological analysis of the electron density and electron-localizability indicator distributions has recently led to the formulation of a polarity-extended 8 - Neff rule for consistent inclusion of quantum chemically obtained polar-covalent bonding data into the classical 8 - N scheme for main-group compounds. Previous application of this scheme to semiconducting main-group compounds of the cubic MgAgAs type of structure with 8 valence electrons per formula unit (8 ve per f.u.) has shown a covalent bonding tendency preferring one zinc blende type partial structure over the other one, which seems to corroborate the classical Lewis picture of maximally four covalent bonds per main-group element. In contrast to the MgAgAs type, the orthorhombic TiNiSi type of structure displays a much higher geometrical flexibility to incorporate different kinds of metal atoms. The analysis of polar-covalent bonding in semiconducting 8 ve per f.u. containing main-group compounds AA'E of this structure type reveals a transition to non-Lewis type bonding scenarios of species E with up to ten polar-covalently bonded metal atoms. This kind of situation is consistently included into the extended 8 - Neff type bonding scheme. A systematic increase of partially covalent bonding from chalcogenides E16 to the tetrelides E14 is found, summing up to as much as 2 covalent bonds E14-A and E14-A', and correspondingly remaining 4 lone pair type electrons on species E14. The familiar notion of this structure type consisting of a '[NiSi]'-type framework with 'Ti'-type atoms filling the voids cannot be supported for the compounds investigated.

Neurophysiological confirmation of phrenic nerve affection in a patient with dyspnea and herpes zoster

Introduction. Herpetic lesion of the phrenic nerve is quite uncommon. These lesions are usually unilateral, and for most clinicians, the clinical manifestation of herpes zoster in the cervical or thoracic region and diaphragmatic paralysis on the same side is sufficient for making a diagnosis of segmental herpes zoster phrenic nerve palsy. We report a patient with a classic clinical picture, in which we confirmed phrenic nerve affection on nerve conduction study. Case report. A 58-year-old female patient came for an examination due to shortness of breath. The patient had a herpetic rash on her right shoulder two and a half months earlier. The elevation of the right hemidiaphragm was seen on chest X-ray imaging. Asymmetry was evident in the nerve conduction study of the phrenic nerve: prolonged latency and reduced amplitude of her right phrenic nerve. The patient was treated with acyclovir, pregabalin, and B complex vitamins. After six months, the motor deficit was reduced completely. Conclusion. A nerve conduction study of the phrenic nerve is useful in making the definitive diagnosis. Good outcome, as in this patient, is rare in patients with this diagnosis and may be linked to timely treatment with acyclovir.

Phantom Tooth pain, is it Often a Trigeminal Neuralgia?

Toothache, buccal pain, facial pains are common presentations in dental clinics. Among them, phantom tooth pain always hits as a trigeminal neuralgia. Though classical picture of trigeminal neuralgia usually does not present with solo toothache, which may sometime masks the whole scenario.

A Rare Case of Vulvar Dermatofibrosarcoma Protuberans: A Case Report

Background Dermatofibrosarcoma protuberans (DFSP) is a low-to-intermediate grade sarcoma of dermal origin with high local recurrence rate that rarely presents in the vulva. It affects adults between the second and fifth decade of life and the involved areas are most frequently the trunk, proximal extremities, head and neck. Case Presentation A 45-years-old Para 4 women presented with two raised masses on the right part of vulva for the last 17-month duration which increase in size for the last 6-month. First, incisional biopsy was taken from the mass and diagnosed as “Suggestive of leiomyoma”. Following to this, excision of the whole mass was done and sent for histopathologic examination. The final histopathologic diagnosis became DFSP with the classic microscopic picture of a storiform and honeycomb pattern of monomorphic bland spindle cells. Conclusion Dermatofibrosarcoma protuberans infrequently involves the vulva and should be considered in the differential diagnosis of other spindle cell lesions presenting in this unusual site.

Classical Nuclear Motion: Comparison to Approaches with Quantum Mechanical Nuclear Motion

Ab initio molecular dynamics combines a classical description of nuclear motion with a density-functional description of the electronic cloud. This approach nicely describes chemical reactions. A possible conclusion is that a quantum mechanical description of nuclear motion is not needed. Using Occam’s razor, this means that, being the simpler approach, classical nuclear motion is preferable. In this paper, it is claimed that nuclear motion is classical, and this hypothesis will be tested in comparison to methods with quantum mechanical nuclear motion. In particular, we apply ab initio molecular dynamics to two photoreactions involving hydrogen. Hydrogen, as the lightest element, is often assumed to show quantum mechanical tunneling. We will see that the classical picture is fully sufficient. The quantum mechanical view leads to phenomena that are difficult to understand, such as the entanglement of nuclear motion. In contrast, it is easy to understand the simple classical picture which assumes that nuclear motion is steady and uniform unless a force is acting. Of course, such a hypothesis must be verified for many systems and phenomena, and this paper is one more step in this direction.

Skeletal Dysplasia: Approach to Simplify Diagnosis, Looking for Radiographic Clue Signs

Skeletal dysplasia is a heterogeneous group of disorders affecting the growth of bones and cartilage. Diagnosis can be difficult for many reasons; they are over 400 diseases, and some are rare and might have atypical presentation when clinical manifestations and radiological findings might not match the classical picture of the specific disorder. The final diagnosis of a skeletal dysplasia is a combined workup that includes clinical examination, family history, radiological assessment (skeletal survey and other investigations), and finally the laboratory, molecular and genetic assessment. These all steps require tertiary centers, therefore, the primary clinical practice would require a tool-kit to help identify the most common skeletal dysplasia easily and identify the most important features of uncommon or rare disorders. The combined clinical assessment and radiological assessment can together reach this goal.
 The aim of this article is to spotlight on few important checkpoints to help the clinician and radiologist to narrow the differential diagnosis in the primary evaluation before the referral, if available, for molecular and genetic study. This article will focus on essential initial steps in diagnosis and some clue diagnostic features in the skeletal survey images that are classic for the most common disorders.

Perianal Psoriasis as the First Manifestation of the Disease

Abstract Introduction Inverse psoriasis affects the skin of flexural areas, such as the groin, axillae, umbilicus, intergluteal fold, and external genitalia. Clinical Case We herein report the case of a man who presented with anal pruritus and, upon physical examination, a perianal dermatosis was found, which was characterized by erythematous plaques, with fine scaling. The case was initially managed with zinc oxide, and when no improvement was observed, we decided to take an incisional biopsy, which indicated histological changes suggestive of psoriasiform dermatitis. Discussion Inverse psoriasis affects 3% to 7% of patients with psoriasis, and it manifests with erythematous plaques without the classic scaling appearance. The skin in these areas is susceptible to maceration, irritation, and ulceration, which alter the classic clinical picture. It may present with typical lesions or, less frequently, in isolation in the anogenital region. In the anogenital presentation only, the diagnosis should be made by biopsy, looking for the classic histopathological features of psoriasis. As for the first-line treatment, low- or medium-potency topical steroids are used for short periods of time; the second-line treatment is with emollients and tar-based products; and the third-line treatment uses an immunomodulator. Conclusion This presentation is infrequent, and it requires a high index of suspicion for the diagnosis, always supported by biopsies, in search of the classic histopathological features of psoriasis.

Anomalous resonance between low-energy particles and electromagnetic plasma waves

Cyclotron resonance between plasma waves and charged particles is a fundamental and ubiquitous process in the plasma universe, during which the particle’s gyromotion has a constant phase in the wave field to enable a sustained energy exchange. In this classical picture, however, the particle’s angular velocity is determined only by the background magnetic field. Here, we show that the classical condition of cyclotron resonance fails to describe the observations of low-energy particles in resonance with large-amplitude waves, which highlights the roles of the wave field in nonlinearly modifying the resonant picture. The revised scenario of anomalous resonance is then validated by the agreement between test-particle simulations and ultrafast spacecraft measurements, which present in-phase and/or antiphase relationships between the wave magnetic field and ion flux oscillations at energy and pitch-angle ranges incompatible with the classical resonance condition. This revision could significantly affect the wave-particle energy exchange and wave evolution processes.

Concepts towards Functional Eukaryotic Microbial Biogeography in the Ocean

High-throughput sequencing technologies have revolutionized microbial diversity studies, shedding light on the oceans’ plankton evolution, distribution, and biological activity. Whereas marine prokaryotes have been more extensively studied and specific methods developed, the research on microbial eukaryotes (protists) is falling behind, with major groups still largely unknown regarding their ecology and function. Because of numerous anthropogenic pressures, it is increasingly important to highlight the functional roles of protists in marine ecosystems. This review outlines the practices, challenges, and opportunities of high-throughput sequencing approaches (i.e., metabarcoding, metagenomics, and metatranscriptomics) to disentangle evolutionary, ecological, and functional aspects of protists in the ocean. These multidimensional approaches allow us to move from the classic picture of microbial biogeography towards functional microbial biogeography, explicitly highlighting the role of protists therein. We provide resources for functional classification and reflect on the current and future potential. We outline aspects of detecting and describing ecosystem changes at the species, population, and community levels, advancing methodological approaches for studying taxonomic diversity towards functional and evolutionary biodiversity concepts, seeking a more complete understanding and monitoring of ocean ecosystems.

Congenital pyloric atresia with epidermolysis bullosa: A case series

Background: Carmi syndrome is the name given to the association of congenital pyloric atresia and epidermolysis bullosa. It has a high mortality. Case series: We report 3 neonates with features of multiple skin blisters and a classical X-ray picture of a single bubble appearance. Two of them underwent surgery while 1 succumbed to sepsis in the pre-operative period. One baby had delayed mortality and the other is doing well in follow-up. Conclusions: Carmi syndrome should be kept as a differential diagnosis in neonates with skin blisters and feed intolerance. Early recognition with prompt medical and surgical management may contribute to a successful outcome.

Non-equilibrium dissipation scaling in atmospheric turbulence

This work is devoted to the detection of non-equilibrium turbulence states in atmospheric turbulence. The non-equilibrium scaling contradicts the classical Richardson-Kolmogorov cascade picture and many turbulence models do not account for it. The existence of such scaling has been discovered in various laboratory experiments. We show here that non-equilibrium states are also present in the stratocumulus-topped boundary layers, which indicates the presence rapidly changing external conditions.