Disk Axis Research Articles

X-ray spectropolarimetric characterization of GX 340+0 in the horizontal branch: A highly inclined source?

We report the first detection of X-ray polarization in the horizontal branch for as obtained by the Imaging X-ray Polarimetry Explorer ( A polarization degree of 4.3<!PCT!>pm 0.4<!PCT!> at a confidence level of 68<!PCT!> is obtained. This value agrees with the previous polarization measurements of Z-sources in the horizontal branch. The spectropolarimetric analysis, performed using a broadband spectral model obtained by and quasi-simultaneous observations, allowed us to constrain the polarization for the soft and hard spectral components that are typical of these sources. The polarization angle for the two components differs by sim This result can be explained by a misalignment of the NS rotation axis with respect to the accretion disk axis. We compared the results with the polarization that is expected in different models. Theoretical expectations for the polarization of the disk and the Comptonization components favor a higher orbital inclination for than 60 as expected for Cyg-like sources. This is in contrast with the results we report for the reflection component based on the broadband spectrum.

On the use of perforated disk inserts in a round pipe to form a gas flow of the required structure in front of an ultrasonic flow meter

Unlike conventional gas meters, ultrasonic flow meters have such advantages as contactless operation, minimal pressure loss and high accuracy. When developing ultrasonic flow meters, like any other devices, assumptions and simplifications related to the theory of ultrasonic flow meters are used. When developing such devices, researchers do not always have the necessary space to deploy such structures. Therefore, the question arises of developing devices that can replace large sections of pipelines with various turns in the role of local resistances. The paper presents some studies conducted during the development of a perforated disk capable of forming a flow profile similar to the profile after a double bend. The presented results of a study of the influence of the perforated disk geometry on the gas dynamics and flow structure. The calculations were carried out using three-dimensional computer modeling. The analysis of the influence of the hole location, their sizes and the angles of inclination of the holes relative to the disk axis on the velocity distribution and the formation of the velocity profile downstream of the disk is the purpose of this study. Scalar and vector fields of velocities downstream of the perforated disk are obtained. Velocity profiles in sections behind the disk are constructed. A comparative analysis of different designs of perforated disks is carried out. The design principles of such flow formers are indicated. The geometric factors influencing the flow structure after the former are revealed. The revealed subtleties and described design principles made it possible to develop straighteners and flow formers based on perforated disks. The final samples of disks and the results of their operation are shown

Tidal features and disc thicknesses of edge-on galaxies in the SDSS Stripe 82

ABSTRACT We examine deep optical images of edge-on galaxies selected from the Sloan Digital Sky Survey (SDSS) Stripe 82. The entire sample consists of over 800 genuine edge-on galaxies with spectroscopic redshifts out to $z\sim 0.2$. To discern the faintest details around the galaxies, we use three different data sources with a photometric depth of down to 30 mag arcsec$^{-2}$ in the r band: SDSS Stripe 82, Hyper Suprime-Cam Strategic Program, and DESI Legacy Imaging Surveys. Our analysis of the deep images reveals a variety of low surface brightness features. 49 galaxies exhibit prominent tidal structures, including tidal tails, stellar streams, bridges, and diffuse shells. Additionally, 56 galaxies demonstrate peculiar structural features such as lopsided discs, faint warps, and dim polar rings. Overall, we detect low surface brightness structures in 94 galaxies out of 838, accounting for 11 per cent of the sample. Notably, the fraction of tidal structures is only 5.8 per cent, which is significantly lower than that obtained in modern cosmological simulations and observations. Previous studies have shown that strongly interacting galaxies have stellar discs about 1.5–2 times thicker than those without apparent interactions. In an analysis where tidal features are carefully masked for precise disc axis ratio measurements, we show that discs of galaxies with tidal features are 1.33 times thicker, on average, than control galaxies that do not have visible tidal features. Furthermore, we find that edge-on galaxies with tidal structures tend to have a higher fraction of oval and boxy discs than galaxies without tidal features.

Chromatically modeling the parsec-scale dusty structure in the center of NGC 1068

Context. The Very Large Telescope Interferometer (VLTI) has been providing breakthrough images of the dust in the central parsecs of active galactic nuclei (AGNs), which is thought to be a key component of the AGN unification scheme and AGN host galaxy interaction. In single infrared bands, these images can enjoin multiple interpretations, some of which could challenge the unification scheme. This is the case for the archetypal type 2 AGN of NGC 1068, whereby the degeneracy is reduced by multi-band temperature maps that are hindered by an ambiguity in the alignment between different single-band images. Aims. We aim to solve this problem by creating a chromatic model capable of simultaneously explaining the VLTI GRAVITY+MATISSE 2 μm–13 μm observations of AGNs hosted by NGC 1068. Methods. We employed a simple disk and wind geometry populated by spherical black-body emitters and dust obscuration to create a versatile multi-wavelength modelling method for chromatic IR interferometric data of dusty objects. Results. This simple geometry is capable of reproducing the spectro-interferometric data of NGC 1068 from the K through N bands. It explains the complex single band images with obscuration and inclination effects, and it solves the alignment problem between bands. We find that the resulting model disk and wind geometry is consistent with previous studies of comparable and larger scales. For example, compared to molecular gas emission, our model wind position angle (PA) of 2322° is close to the mas-scale outflowing CO(6–5) PA of ∼33° seen with ALMA. The equivalent 90° offset model disk PA is also consistent with the CO(6–5) disk axis of 112° as well as the mas-scale disk axis from CO(2–1), CO(3–2), and HCO+(4–3) of 115 ± 5°. Furthermore, the resulting model images visually resemble the multiple achromatic image reconstructions of the same data when evaluated at the same wavelengths. We conclude that the IR emitting structure surrounding the AGN within NGC 1068 can indeed be explained by the clumpy disk+wind iteration of the AGN unification scheme. Within the scheme, we find that it is best explained as a type 2 AGN and the obscuring dust chemistry can be explained by a mix of olivine silicates and 16 ± 1% amorphous carbon.

Association between periodontitis and disc structural failures in patients with cervical degenerative disorders

ObjectiveRecent studies have shown that the mouth–gut–disc axis may play a key role in the process of disc structural failures (including intervertebral disc degeneration (IDD) and endplate change) in the cervical spine and neck pain. However, the potential mechanisms underlying the mouth–gut–disc axis remain elusive. Therefore, we explored whether periodontal disease is associated with disc structural failures in patients with cervical degeneration disorders and clinical outcomes.MethodsAdults (aged > 18 years) who met open surgery criteria for cervical spine were enrolled in this prospective cohort study. Participants were allocated into two groups based on periodontal examinations before surgery: no/mild periodontitis group and moderate/severe periodontitis group. Data were evaluated using an independent t test and Pearson’s correlation analysis.ResultsA total of 108 patients were enrolled, including 68 patients in the no/mild periodontitis group and 40 patients in the moderate/severe periodontitis group. The number of common causes of missing teeth (P = 0.005), plaque index (PLI) (P = 0.003), bleeding index (BI) (P = 0.000), and probing depth (PD) (P = 0.000) significantly differed between the two groups. The incidence rate of endplate change (P = 0.005) was higher in the moderate/severe periodontitis group than in the no/mild periodontitis group. A moderate negative association was found between the neck disability index (NDI) score and periodontal parameters (PLI: r = − 0.337, P = 0.013; BI: r = − 0.426, P = 0.001; PD: r = − 0.346, r = − 0.010).ConclusionsThis is the first study to provide evidence that severe periodontitis is associated with a higher occurrence rate of disc structural failures and poor clinical outcomes in patients with cervical degenerative disorders.

The geometry of the hot corona in MCG-05-23-16 constrained by X-ray polarimetry

ABSTRACT We report on the second observation of the radio-quiet active galactic nucleus MCG-05-23-16 performed with the Imaging X-ray Polarimetry Explorer (IXPE). The observation started on 2022 November 6 for a net observing time of 640 ks, and was partly simultaneous with NuSTAR (86 ks). After combining these data with those obtained in the first IXPE pointing on 2022 May (simultaneous with XMM–Newton and NuSTAR) we find a 2–8 keV polarization degree Π = 1.6 ± 0.7 (at 68 per cent confidence level), which corresponds to an upper limit Π = 3.2 per cent (at 99 per cent confidence level). We then compare the polarization results with Monte Carlo simulations obtained with the monk code, with which different coronal geometries have been explored (spherical lamppost, conical, slab, and wedge). Furthermore, the allowed range of inclination angles is found for each geometry. If the best-fitting inclination value from a spectroscopic analysis is considered, a cone-shaped corona along the disc axis is disfavoured.

Uncovering the geometry of the hot X-ray corona in the Seyfert galaxy NGC 4151 with IXPE

ABSTRACT We present an X-ray spectropolarimetric analysis of the bright Seyfert galaxy NGC 4151. The source has been observed with the Imaging X-ray Polarimetry Explorer (IXPE) for 700 ks, complemented with simultaneous XMM–Newton (50 ks) and NuSTAR (100 ks) pointings. A polarization degree Π = 4.9 ± 1.1 per cent and angle Ψ = 86° ± 7° east of north (68 per cent confidence level) are measured in the 2–8 keV energy range. The spectropolarimetric analysis shows that the polarization could be entirely due to reflection. Given the low reflection flux in the IXPE band, this requires, however, a reflection with a very large (>38 per cent) polarization degree. Assuming more reasonable values, a polarization degree of the hot corona ranging from ∼4 to ∼8 per cent is found. The observed polarization degree excludes a ‘spherical’ lamppost geometry for the corona, suggesting instead a slab-like geometry, possibly a wedge, as determined via Monte Carlo simulations. This is further confirmed by the X-ray polarization angle, which coincides with the direction of the extended radio emission in this source, supposed to match the disc axis. NGC 4151 is the first active galactic nucleus with an X-ray polarization measure for the corona, illustrating the capabilities of X-ray polarimetry and IXPE in unveiling its geometry.

Very long baseline interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261

Abstract We report dual-frequency very long baseline interferometry (VLBI) observations at 22 and 43 GHz toward the nucleus of a nearby radio galaxy NGC 4261. In particular, we present a VLBI image of the 22 GHz H2O maser line and its location in the circumnuclear region of NGC 4261. H2O maser emission is marginally detected above the three times the image rms level at channels within a velocity range of approximately 2250–2450 km s−1, slightly red-shifted with respect to the systemic velocity. H2O maser emission is located approximately 1 milliarcsecond east of the brightest continuum component at 22 GHz, where the continuum spectrum is optically thick, that is, at the free–free absorbed receding jet by ionized gas. A positional coincidence between H2O maser emission and an ionized gas disk implies that the H2O maser emission arises from the near side of the disk, amplifying continuum emission from the background receding jet. If the disk axis is oriented 64° relative to the line of sight, the H2O maser emission is expected to be at a mean radius of 0.3 pc in the disk. The broad line width of the H2O maser emission can be attributed to complex kinematics in the immediate vicinity of the supermassive black hole (SMBH), including ongoing gas infall on to the SMBH, turbulence, and outflow. This is analogous to the multi-phase circumnuclear torus model in the nearest radio-loud H2O megamaser source NGC 1052. An alternative explanation for H2O maser association is the shock region between the jet and ambient molecular clouds. However, this explanation fails to describe the explicit association of H2O maser emission only with the free–free absorbed receding jet.

Misalignment of the outer disk of DK Tau and a first look at its magnetic field using spectropolarimetry

Context. Misalignments between a forming star’s rotation axis and its outer disk axis, although not predicted by standard theories of stellar formation, have been observed in several classical T Tauri stars (cTTs). The low-mass cTTs DK Tau is suspected of being among them. In addition, it is an excellent subject to investigate the interaction between stellar magnetic fields and material accreting from the circumstellar disk, as it presents clear signatures of accretion. Aims. The goal of this paper is to study DK Tau’s average line-of-sight magnetic field in both photospheric absorption lines and emission lines linked to accretion, using spectropolarimetric observations, as well as to examine inconsistencies regarding its rotation axis. Methods. We used data collected with the ESPaDOnS spectropolarimeter, at the Canada-France-Hawaii Telescope, and the NARVAL spectropolarimeter, at the Télescope Bernard Lyot, probing two distinct epochs (December 2010 to January 2011 and November to December 2012), each set spanning a few stellar rotation cycles. We first determined the stellar parameters of DK Tau, such as effective temperature and vsini. Next, we removed the effect of veiling from the spectra, then obtained least-squares deconvolution (LSD) profiles of the photospheric absorption lines for each observation, before determining the average line-of-sight magnetic field from them. We also investigated accretion-powered emission lines, namely the 587.6 nm HeI line and the CaII infrared triplet (at 849.8 nm, 854.2 nm and 866.2 nm), as tracers of the magnetic fields present in the accretion shocks. Results. We find that DK Tau experiences accretion onto a magnetic pole at an angle of ∼30° from the pole of its rotation axis, with a positive field at the base of the accretion funnels. In 2010 we find a magnetic field of up to 0.95 kG (from the CaII infrared triplet) and 1.77 kG (from the HeI line) and in 2012 we find up to 1.15 kG (from the CaII infrared triplet) and 1.99 kG (from the HeI line). Additionally, using our derived values of period, vsini and stellar radius, we find a value of 58° (+18)(−11) for the inclination of the stellar rotation axis, which is significantly different from the outer disk axis inclination of 21° given in the literature. Conclusion. We find that DK Tau’s outer disk axis is likely misaligned compared to its rotation axis by 37°.

Ancillary PanoMap OCT shows the progression of glaucomatous papillomacular bundle defect with disc haemorrhage on the fovea–disc axis

Background/aimsTo identify the spatial relationship between disc haemorrhage (DH) on the fovea–disc axis and retinal nerve fibre layer (RNFL) defect in the papillomacular bundle (PMB) using ancillary PanoMap optical coherence...

Precession and Jitter in FRB 180916B

ABSTRACT Recent CHIME/FRB observations of the periodic repeating fast radio bursts (FRB) 180916B have produced a homogeneous sample of 44 bursts. These permit a redetermination of the modulation period and phase window, in agreement with earlier results. If the periodicity results from the precession of an accretion disc, in analogy with those of Her X-1, SS 433, and many other superorbital periods, the width of the observable phase window indicates that the disc axis jitters by an angle of about 0.14 of the inclination angle, similar to the ratio of 0.14 in the well-observed jittering jet source SS 433.

A model grid for the reflected light from transition disks

Context. The dust in protoplanetary disks is an important ingredient in planet formation and can be investigated with model simulations and quantitative imaging polarimetry of the scattered stellar light. Aims. This study explores circumstellar disks with calculations for the intensity and polarization of the reflected light. We aim to describe the observable radiation dependencies on parameters in order to constrain the dust scattering properties and the disk geometry. Methods. The photon scattering and absorption by the disk are calculated with a Monte Carlo method for a grid of simple, rotationally symmetric models approximated at each point by a plane–parallel dusty atmosphere. The adopted geometry is described by a strongly illuminated inner wall of a transition disk with inclination i, a constant wall slope χ, and an angular wall height a. Dust scattering parameters are the single scattering albedo ω, the Henyey–Greenstein scattering phase function with the asymmetry parameter ɡ, and the maximal fractional polarization pmax induced by the scattering. First, the results for the reflectivity, the polarized reflectivity, and the fractional polarization of a plane–parallel surface element are calculated as functions of the incidence angle and the escape direction of the photons and as functions of the scattering parameters. Integration over all escape directions yields the surface albedo and the fraction of radiation absorbed by the dust. Second, disk images of the reflected intensity and polarization are calculated, and the appearance of the disk is described for various parameter combinations. The images provide many quantitative radiation parameters for a large range of model calculations, which can be compared to observations. These include the disk integrated intensity I¯/I★, azimuthal polarization Q¯φ/I★, the polarization aligned with the apparent disk axes Q¯/I★, the quadrant polarization parameters Qxxx and Uxxx, the disk-averaged fractional polarization 〈pφ〉 or 〈pQ〉, but also the front-to-back intensity ratio I180/I000 or the maximum fractional scattering polarization тах(pφ). Results. The results of our simple disk models reproduce well the measurements for I/I⋆,Qφ/I⋆, and 〈pφ〉 reported for well-observed transition disks. They describe the dependencies of the scattered radiation on the disk geometry and the dust scattering parameters in detail. Particularly strong constraints on disk properties can be obtained from certain diagnostic quantities: for example the fractional polarization 〈pφ〉 or тах(pφ) depend predominantly on the dust-scattering parameters ω and pmax; for disks with well-defined inclination, ratios of the quadrant polarization parameter depend mainly on the scattering asymmetry ɡ and the wall slope χ; wavelength dependencies of I/I✶ and Qφ/I✶ can mostly be attributed to the wavelength dependence of the dust scattering parameters ω(λ), ɡ(λ), and pmmах(λ); and the ratio between the scattered and thermal light of the disk roughly constrains the disk reflectivity R and the single scattering albedo of the dust ω. Conclusions. This computational investigation of the scattered radiation from transition disks shows well-defined dependencies on model parameters and the results can therefore be used as a diagnostic tool for the analysis of quantitative measurements, specifically in constraining or even determining the scattering properties of the dust particles in disks. Collecting and comparing such information for many systems is required to understand the nature of the scattering dust in planet-forming disks.

Zinc oxide–silver/water hybrid nanofluid flow toward an off‐centered rotating disk using temperature‐dependent experimental‐based thermal conductivity

AbstractHerein, the off‐centered stagnation flow and heat transfer of zinc oxide–silver/water hybrid nanofluid over a rotating disk according to the mass‐based algorithm is studied. It is assumed that the nanoparticles have a spherical shape. Also, the velocity slip between the base fluid and nanoparticles is negligible. The Prandtl number is kept constant at 6.2. In addition, it has been used an experimental relation for effective thermal conductivity which is a function of volume fraction and temperature. The governing partial differential equations are converted to dimensionless ordinary differential equation (ODE)s by the similarity transformation method. The simplified ODEs are solved numerically by the bvp4c function from MATLAB which is an efficient and reliable code according to the three‐stage Lobatto IIIa formula. The influence of rotational parameters and both nanoparticles masses on the profiles and quantities of engineering interest are presented and discussed in detail. It is shown that the flow becomes complicated when there is a distance between the flow axis and the disk axis. Under determined conditions for a hybrid nanofluid with 30‐g mass for both nanoparticles and 100‐g mass for pure water, adding 30 g of the second nanoparticle's mass into the base fluid leads to enhance all hydrodynamic quantities of engineering interest by about 4.3%, while dispersing 30 g of the first nanoparticle's mass inside water results in decreasing the similarity temperature gradient at the surface about 3.6%. Also, when the disk rotates faster, the maximum radial velocity near the disk, s′(0) and f″(0) increases.

Numerical Solutions of the External Field Effect on the Radial Acceleration in Disk Galaxies

Abstract In modified Newtonian dynamics (MOND)-based theories, the strong equivalence principle is generically broken in an idiosyncratic manner, manifested in the action of an “external field effect” (EFE). The internal dynamics in a self-gravitating system is affected even by a constant external field. In disk galaxies, the EFE can induce warps and modify the rotational speeds. Due to the nonlinearity of MOND, it is difficult to derive analytic expressions of this important effect in a disk. Here we study numerically the EFE in two nonrelativistic Lagrangian theories of MOND: the “Aquadratic–Lagrangian” theory (AQUAL) and “Quasilinear MOND” (QUMOND). For AQUAL, we consider only the axisymmetric field configurations with the external field along the disk axis, or a spherical galaxy with test-particle orbits inclined to the external field. For the more manageable QUMOND, we also calculate the three-dimensional field configurations, with the external field inclined to the disk axis. We investigate in particular to what degree an external field modifies the quasi-flat part of rotation curves. While our QUMOND results agree well with published numerical results in QUMOND, we find that AQUAL predicts weaker EFE than published AQUAL results. However, AQUAL still predicts stronger EFE than QUMOND, which demonstrates current theoretical uncertainties. We also illustrate how the MOND prediction on the rising part of the rotation curve, in the inner parts, depends largely on disk thickness but only weakly on a plausible external field for a fixed galaxy model. Finally, we summarize our results for the outer parts as an improved, approximate analytic expression.

Detections of inflowing gas from narrow absorption lines at parsec scales

The detection of inflows at the scale of the dusty torus and smaller is crucial for investigating the process of supermassive black hole (SMBH) accretion. However, only a few cases of inflowing gas at small scales have been reported through redshifted broad absorption lines so far. Here we report nine redshifted narrow absorption lines (NALs) of Mg+ions with inflowing speeds of 1071–1979 km s−1, which are likely along the directions close to the axes of accretion disks. The quasars showing inflowing Mg IINALs have, on average, slightly smaller Eddington ratios than the sources with outflowing Mg IINALs. The upper limits on the locations of the detected NALs are at parsec scale, that is, the distance from dusty tori to their central SMBHs. One possible origin of these infalling NALs is from dusty tori. However, these infalling NALs could also be naturally explained by chaotic cold accretion resulting from the nonlinear interaction of active galactic nucleus (AGN) jets with the interstellar medium (ISM), and these cold gaseous blobs may originally precipitate in metal-rich trailing outflows uplifted by AGN jet ejecta. The infalling NALs may therefore provide direct evidence for cold gas precipitation and accretion in AGN feedback processes, and provide direct evidence of inflowing gas along the directions close to quasar jets and at parsec scale. Regardless of whether these infalling NALs are from the dusty tori or the interaction of AGN jets with the ISM, the infalling NALs cannot provide sufficient fuel to power the quasars.

Quantification of an oval optic disc in relation to myopic foveoschisis using swept-source optical coherence tomography

BackgroundTo investigate the relationship between an oval optic disc and the occurrence of myopic foveoschisis (MF) using swept-source optic coherence tomography (SS-OCT).MethodsFifty eyes of 25 patients with unilateral MF were included in this retrospective observational study. The biometric features of the optic disc and peripapillary structures were evaluated using SS-OCT.ResultsThe ovality index (OI) of the optic disc was significantly smaller (P = 0.003) and the optic disc tilt angle was greater (P = 0.023) in the eyes with MF than in the contralateral eyes. The optic disc tilt angle was significantly correlated with the OI (P = 0.000). Generalized estimating equation (GEE) model (linear regression) demonstrated that spherical equivalent refraction (P = 0.001), narrow macular staphyloma (P = 0.001) and the occurrence of MF (P = 0.026) were the independent factors associated with the OI. Narrow macular staphyloma was more frequent (P = 0.020) and the staphyloma was deeper (P = 0.006) in eyes with MF. GEE model (logistic regression) revealed that narrow macular staphyloma was the only independent factor related to the occurrence of MF (P = 0.013).ConclusionsAn oval optic disc in eyes with MF resulted from the increased tilt around the vertical disc axis. The optic disc tilt was related to narrow macular staphyloma, which was the only independent factor associated with the occurrence of MF. The clinical relevance needs further exploration through longitudinal analysis.

Off-centered stagnation point flow of an experimental-based hybrid nanofluid impinging to a spinning disk with low to high non-alignments

PurposeThe purpose of this study is to model and solve numerically the three-dimensional off-centered stagnation point flow and heat transfer of magnesium oxide–silver/water hybrid nanofluid impinging to a spinning disk.Design/methodology/approachThe applied effective thermophysical properties of hybrid nanofluid including thermal conductivity and dynamics viscosity are according to the reported experimental relations that would be expanded by a mass-based algorithm. The single phase formulations coupled with experimental-based hybrid nanofluid model is implemented to derive the governing partial differential equations which are then transferred to a set of dimensionless ordinary differential equations (ODEs) with the use of the similarity transformation method. Afterward, the reduced ODEs are solved numerically by bvp4c function from MATLAB that is a trustworthy and efficient code according to three-stage Lobatto IIIa formula.FindingsThe effect of spinning parameter and nanoparticles masses (mMgO, mAg) on the hydrodynamics and thermal boundary layers behavior and also the quantities of engineering interest are presented in tabular and graphical forms. The recent work demonstrates that the analysis of flow and heat transfer becomes more complicated when there is a non-alignment between the impinging flow and the disk axes. From computational results demonstrate that, the radial and azimuthal velocities are, respectively, the increasing and decreasing functions of the disk spinning parameter. Further, for the greater values of the spinning parameter, an overshoot of the radial velocity owing to the centrifugal forces of the spinning disk is observed. Besides, the quantities of engineering interest gently enhance with first and second nanoparticle masses, while comparing their absolute values illustrates the fact that the effect of second nanoparticle mass (mAg) is greater. Further, it is inferred that the second nanoparticle’s mass enhancement results in the amplification of the heat transfer; although, the high skin friction and the relevant shear stress should be controlled.Originality/valueThe combination of experimental thermophysical properties with theoretical modeling of the problem can be the novelty of the present work. It is evident that the experimental relations of effective thermophysical properties can be trustable and flexible in the theoretical/mathematical modeling of hybrid nanofluids flows. Besides, to the best of the authors’ knowledge, no one has ever attempted to study the present problem through a mass-based model for hybrid nanofluid.

Morpho-kinematics of the wind of asymptotic giant branch star L2 Pup

ABSTRACT Single-dish observations of asymptotic giant branch star L2 Pup have revealed exceptionally low mass-loss rate and expansion velocity, challenging interpretations in terms of standard wind models. Recent VLT and ALMA observations have drawn a detailed picture of the circumstellar envelope within ∼20 au from the centre of the star: a nearly edge-on rotating disc of gas and dust, probably hosting a planetary companion near the star. However, these observations provide no direct information on the wind escaping the gravity of the star. This article uses ALMA observations of the 12, 13CO(3-2), 29SiO(8-7), 12CO(2-1), and 28SiO(5-4) line emissions to shed new light on this issue. It shows the apparent normality of L2 Pup in terms of the formation of the nascent wind, with important line broadening within 4 au from the centre of the star, but no evidence for a wind flowing along the disc axis. At larger distances, up to some 200 au from the centre of the star, the wind morpho-kinematics is dominated by a disc, or equatorial enhancement, expanding isotropically and radially with a velocity not exceeding some 5 km s−1, inclined in the north-west/south-east direction with respect to the plane of the sky. In addition, outflows of lower density are observed on both sides of the disc, covering large solid angles about the disc axis, contributing about half the flux of the disc. Such morphology is at strong variance with the expectation of a pair of back-to-back outflows collimated by the central gas-and-dust disc.

Comparison of Dorsal-to-Ventral Ratios of the Cervical Paraspinal Musculature in French Bulldogs With and Without Cervical Intervertebral Disk Disease and Two Other Breeds Based on CT Scan Measurements

Objective: To objectively assess the cervical paraspinal musculature of French bulldogs (FBs) using computed tomography (CT) scan-based measurements, outline differences in other breeds published in the literature, and investigate the potential influence of its cervical paraspinal musculature on predisposed sites for intervertebral disk disease.Animals: Thirty FBs that underwent CT scans of the cervical spine from the skull to C7/T1 were enrolled. Fifteen dogs were patients suffering from intervertebral disk herniation (IVDH group), and 15 dogs underwent CT scans due to brachycephalic obstructive airway syndrome (BOAS group).Methods: At the level of each cervical intervertebral disk from C2/C3 to C7/T1, measurements were performed and statistically analyzed. On the sagittal CT scan reconstruction, the height ratio of the dorsal to ventral paraspinal musculature and the angle of the disk axis to vertebral body length were assessed. On the transverse plane, the area ratio of the dorsal and ventral paraspinal musculature and the ratio of force moments were determined at each intervertebral disk level. Finally, ratios were compared to the values of Labrador retrievers and dachshunds published by Hartmann et al. (1).Results: Comparing the two FB groups, one significant difference was detected in the mean height ratio of the dorsal to ventral paraspinal musculature at the level of C5/C6 (P = 0.0092) and C6/C7 (P = 0.0076), with IVDH FBs having the more prominent dorsal paraspinal musculature. At the level of C3/C4, a significantly less prominent dorsal paraspinal musculature in FBs than in dachshunds (P = 0.0058) and a significantly steeper disk to vertebral body angulation were observed (P = 0.0005).Conclusion: Although some incidental differences were found, most parameters did not significantly differ between the BOAS and IVDH FBs. Significant conformational differences in the cervical paraspinal musculature and disk to vertebral body length angulation were found between FBs and two other breeds (chondrodystrophic and non-chondrodystrophic). This study's findings suggest that the paraspinal musculature is an additional biomechanical influencing factor on the preferential sites of IVDH in the cervical spine and that other major factors exist in IVDH development, especially in FBs.

Residual velocities of Small Magellanic Cloud star clusters

ABSTRACT We analysed the largest Small Magellanic Cloud (SMC) cluster sample (32) with proper motions and radial velocity measurements, from which we obtained their space velocity components. By adopting as a reference, the recent best-fitting rotating disc of SMC star clusters as a function of the position angle, we computed their residual velocity vectors, and compared their magnitudes ($\Delta \, V$) with that of a cluster with residual velocity components equal to the velocity dispersions along the three independent SMC rotating disc axes of motion ($\Delta \, V$ = 60 km s−1). We found that clusters that belong to SMC tidally induced structures have $\Delta \, V\, \gt $ 50 km s−1, which suggests that space velocities of clusters in the process of escaping the rotating disc kinematics are measurably different. Studied clusters pertaining to a northern branch of the Magellanic Bridge, the main Magellanic Bridge, the Counter-Bridge, and the West Halo give support these findings. NGC 121, the oldest known SMC cluster, does not belong to any SMC tidal feature, and has $\Delta \, V$ = 64 km s−1, slightly above the boundary between bound and kinematically perturbed clusters.