Region Of Disk Research Articles

Formation of CO2 Driven by Photochemistry of Water Ice Mixed with Carbon Grains

We present results on photochemistry of carbon-grains/water-ice mixtures at temperatures from 10 to 150 K. Such a temperature range corresponds to the physical conditions found in molecular clouds, hot cores and corinos, protostellar envelopes, and planet-forming and debris disks. We demonstrate that UV irradiation of carbon-grains/water-ice mixtures leads to the formation of CO2, which, beyond the desorption temperature of CO2 partly escapes into the gas phase, and partly remains trapped on the surface of grains. Thus, we present the first direct evidence of the efficient formation of CO2 on carbon surfaces covered by water ice at high temperatures (up to 150 K) leading to a conclusion that the known low-temperature formation route of CO2 remains valid at high temperatures as long as H2O is present on carbon grains. Moreover, we demonstrate an improved capability of the dust-surface/crystalline-water-ice interface (as compared to amorphous water ice) to trap CO2 in the solid state well above the CO2 desorption temperature. The high-temperature chemical pathway to CO2 may lead to the chemical erosion of carbonaceous grains in planet-forming disks, providing an alternative explanation of the loss of solid carbon in the innermost disk regions that resulted in the formation of carbon-poor Earth and other terrestrial planets in the solar system.

Matter ejections behind the highs and lows of the transitional millisecond pulsar PSR J1023+0038

Transitional millisecond pulsars are an emerging class of sources that link low-mass X-ray binaries to millisecond radio pulsars in binary systems. These pulsars alternate between a radio pulsar state and an active low-luminosity X-ray disc state. During the active state, these sources exhibit two distinct emission modes (high and low) that alternate unpredictably, abruptly, and incessantly. X-ray to optical pulsations are observed only during the high mode. The root cause of this puzzling behaviour remains elusive. This paper presents the results of the most extensive multi-wavelength campaign ever conducted on the transitional pulsar prototype, PSR J1023+0038, covering from the radio to X-rays. The campaign was carried out over two nights in June 2021 and involved 12 different telescopes and instruments, including XMM-Newton, HST, VLT/FORS2 (in polarimetric mode), ALMA, VLA, and FAST. By modelling the broadband spectral energy distributions in both emission modes, we show that the mode switches are caused by changes in the innermost region of the accretion disc. These changes trigger the emission of discrete mass ejections, which occur on top of a compact jet, as testified by the detection of at least one short-duration millimetre flare with ALMA at the high-to-low mode switch. The pulsar is subsequently re-enshrouded, completing our picture of the mode switches.

X-Ray/UVOIR Frequency-resolved Time Lag Analysis of Mrk 335 Reveals Accretion Disk Reprocessing

UV and optical continuum reverberation mapping is a powerful tool for probing the accretion disk and inner broad-line region. However, recent reverberation mapping campaigns in the X-ray, UV, and optical have found lags consistently longer than those expected from the standard disk reprocessing picture. The largest discrepancy to date was recently reported in Mrk 335, where UV/optical lags are up to 12 times longer than expected. Here, we perform a frequency-resolved time lag analysis of Mrk 335, using Gaussian processes to account for irregular sampling. For the first time, we compare the Fourier frequency-resolved lags directly to those computed using the popular interpolated cross-correlation function method applied to both the original and detrended light curves. We show that the anticipated disk reverberation lags are recovered by the Fourier lags when zeroing in on the short-timescale variability. This suggests that a separate variability component is present on long timescales. If this separate component is modeled as reverberation from another region beyond the accretion disk, we constrain a size scale of roughly 15 lt-days from the central black hole. This is consistent with the size of the broad-line region inferred from Hβ reverberation lags. We also find tentative evidence for a soft X-ray lag, which we propose may be due to light travel time delays between the hard X-ray corona and distant photoionized gas that dominates the soft X-ray spectrum below 2 keV.

On the nature of the continuum reverberation of X-ray/UV and optical emission of IRAS 09149−6206

ABSTRACT We present the results of a continuum reverberation mapping study of the radio-quiet type 1 Seyfert galaxy IRAS 09149−6206. The analysis was performed using X-ray, ultraviolet (UV), and optical observations made with the Swift telescope between 2017 January and December. The time delays between different light curves were measured using three different algorithms: PyI2CCF, PyROA, and JAVELIN. Our results show that the time delays increase with wavelength after τ ∝ λ4/3, as predicted for a geometrically thin and optically thick accretion disc, but only after accounting for significant diffuse continuum emission from the broad-line region. However, the measured size of the accretion disc can be up to five times larger than that predicted by standard theory. To our surprise, the strong increase in soft X-ray fluxes is delayed by about 15 d compared to the optical UV fluctuations, which challenges the prediction of the lamp-post model. Our analysis of the X-ray variability reveals the presence of a non-variable spectral component at 0.3–6.0 keV along with variable excess emission at 2.0–3.0 keV, which could be partly related to relativistic reflection in the inner region of the accretion disc. IRAS 09149−6206 joins the list of objects for which the traditional lamp-post model cannot explain the observed time delays. A scenario that incorporates other geometric considerations into the lamp-post model, e.g. an extended corona along a scattering source, might be better suited to explain the observed long time delays.

Avalanches and the Distribution of Reconnection Events in Magnetized Circumstellar Disks

Cosmic rays produced by young stellar objects can potentially alter the ionization structure, heating budget, chemical composition, and accretion activity in circumstellar disks. The inner edges of these disks are truncated by strong magnetic fields, which can reconnect and produce flaring activity that accelerates cosmic radiation. The resulting cosmic rays can provide a source of ionization and produce spallation reactions that alter the composition of planetesimals. These reconnection and particle acceleration processes are analogous to the physical processes that produce flaring in and the heating of stellar coronae. Flaring events on the surface of the Sun exhibit a power-law distribution of energy, reminiscent of those measured for earthquakes and avalanches. Numerical lattice reconnection models are capable of reproducing the observed power-law behavior of solar flares under the paradigm of self-organized criticality. One interpretation of these experiments is that the solar corona maintains a nonlinear attractor—or “critical”—state by balancing energy input via braided magnetic fields and output via reconnection events. Motivated by these results, we generalize the lattice reconnection formalism for applications in the truncation region of magnetized disks. Our numerical experiments demonstrate that these nonlinear dynamical systems are capable of both attaining and maintaining criticality in the presence of Keplerian shear and other complications. The resulting power-law spectrum of flare energies in the equilibrium attractor state is found to be nearly universal in magnetized disks. This finding indicates that magnetic reconnection and flaring in the inner regions of circumstellar disks occur in a manner similar to the activity on stellar surfaces. These results, in turn, have ramifications for the spallation-driven injection of radionuclides in planetesimals, disk ionization, and the subsequent planetary formation process.

Prediction of the biomechanical behaviour of the lumbar spine under multi-axis whole-body vibration using a whole-body finite element model.

Low back pain has been reported to have a high prevalence among occupational drivers. Whole-body vibration during the driving environment has been found to be a possible factor leading to low back pain. Vibration loads might lead to degeneration and herniation of the intervertebral disc, which would increase incidence of low back problems among drivers. Some previous studies have reported the effects of whole-body vibration on the human body, but studies on the internal dynamic responses of the lumbar spine under multi-axis vibration are limited. In this study, the internal biomechanical response of the intervertebral disc was extracted to investigate the biomechanical behaviour of the lumbar spine under a multi-axial vibration in a whole-body environment. A whole-body finite element model, including skin, soft tissues, the bone skeleton, internal organs and a detailed ligamentous lumbar spine, was used to provide a whole-body condition for analyses. The results showed that both vibrations close to vertical and fore-and-aft resonance frequencies would increase the transmission of vibrations in the intervertebral disc, and vertical vibration might have a greater effect on the lumbar spine than fore-and-aft vibration. The larger deformation of the posterior region of the intervertebral disc in a multi-axis vibration environment might contribute to the higher susceptibility of the posterior region of the intervertebral disc to injury. The findings of this study revealed the dynamic behaviours of the lumbar spine in multi-axis vehicle vibration conditions, and suggested that both vertical and fore-and-aft vibration should be considered for protecting the lumbar health of occupational drivers.

Abstract P3146: Cardiac Stress-induced Arrhythmias And Myocardial Infarction Via Specific Genetically Phosphodeleted Sites In Connexin 43 Channels

Connexin 43 (Cx43) gap junction remodeling is observed in various cardiac pathologies and is linked with arrhythmogenesis, myocardial infarction, and sudden death. Here, we aim to characterize the contribution of Cx43 phosphorylation toward mislocalization at the intercalated disc. For this, we used two genetically phospho-deleted Cx43 knock-in mouse lines with serine residues replaced by alanine in the corresponding sites for phosphorylation via mitogen-activated protein kinase (MAPK) (S255/262/279/282A; Cx43MK4) or Ca 2+/ calmodulin protein kinase II (CaMKII) (S325A/S328A/S330A; Cx43S3A). Ca 2+ signaling, cardiac electrical signals, and arrhythmias were assessed via optical mapping and telemetry in wild type, Cx43MK4, and Cx43S3A mice. Upon basal conditions or isoproterenol stimulation, wild-type animals did not display arrhythmogenic behaviors. However, after isoproterenol treatment, Cx43S3A mice showed increased QTc and deadly arrhythmias compared to wild-type animals. Isoproterenol challenge only increased the number of single PVCs in Cx43MK4 mice when compared to wild-type. Isoproterenol also evoked myocardial infarction in Cx43S3A hearts, which is negligible in Cx43MK4 and wild-type mice. Interestingly, GAP19, a Cx43 hemichannel blocker, reduced lethal arrhythmias and myocardial infarction in Cx43S3A mice. Isoproterenol challenge induced an increase in arrhythmogenic Ca 2+ events in both Cx43S3A and Cx43MK4 hearts compared to wild-type mice. However, Cx43S3A also displayed prolonged Ca 2+ decay transients that were reduced in the presence of Gap19. Our results suggest that the absence of Cx43 phosphorylation by CaMKII leads to lateralization and opening of Cx43 hemichannels, and consequently severe arrhythmias and myocardial infarction. On the other hand, the absence of MAPK phosphorylation promotes mainly a reduction of Cx43 levels at the intercalated disc region that is only associated with mild arrhythmias.

Coagulation–Fragmentation Equilibrium for Charged Dust: Abundance of Submicron Grains Increases Dramatically in Protoplanetary Disks

Dust coagulation in protoplanetary disks is not straightforward and is subject to several slowdown mechanisms, such as bouncing, fragmentation, and radial drift to the star. Furthermore, dust grains in UV-shielded disk regions are negatively charged due to collisions with the surrounding electrons and ions, which leads to their electrostatic repulsion. For typical disk conditions, the relative velocities between micron-sized grains are small, and their collisions are strongly affected by the repulsion. On the other hand, collisions between pebble-sized grains can be too energetic, leading to grain fragmentation. The aim of the present paper is to study the combined effect of the electrostatic and fragmentation barriers on dust evolution. We numerically solve the Smoluchowski coagulation–fragmentation equation for grains whose charging occurs under conditions typical for the inner disk regions, where thermal ionization operates. We find that dust fragmentation efficiently resupplies the population of small grains under the electrostatic barrier. As a result, the equilibrium abundance of submicron grains is enhanced by several orders of magnitude compared to the case of neutral dust. For some conditions with fragmentation velocities of ∼1 m s−1, macroscopic grains are completely destroyed.

Massive pre-main-sequence stars in M17

Context. Recently much progress has been made in probing the embedded stages of massive star formation, pointing to formation scenarios that are reminiscent of a scaled-up version of low-mass star formation. However, the latest stages of massive-star formation have rarely been observed, as young massive stars are assumed to reveal their photospheres only when they are fully formed. Aims. Using first and second overtone CO bandhead emission and near- to mid-infrared photometry, we aim to characterize the remnant formation disks around five unique pre-main-sequence (PMS) stars with masses 6–12 M⊙ that have constrained stellar parameters thanks to their detectable photospheres. We seek to understand this emission and the disks from which it originates in the context of the evolutionary stage of the studied sources. Methods. We used an analytic disk model, and adopted local thermodynamical equilibrium, to fit the CO bandhead and the dust emission, assumed to originate in different disk regions. For the first time, we modeled the second overtone emission, which helped us to put tighter constraints on the density of the CO gas. Furthermore, we fit continuum normalized bandheads, using models for stellar and dust continuum, and show the importance of this in constraining the emission region. We also included 13CO in our models as an additional probe of the young nature of the studied objects. Results. We find that the CO emission originates in a narrow region close to the star (<1 AU) and under very similar disk conditions (temperatures and densities) for the different objects. This is consistent with previous modeling of this emission in a diverse range of young stellar objects and identifies CO emission as an indicator of the presence of a gaseous inner disk reaching close to the stellar surface. From constraining the location of the inner edge of the dust emission, we find that all but one of the objects have undisrupted inner dust disks. Conclusions. We discuss these results in the context of the positions of these PMS stars in the Hertzsprung-Russel diagram and the CO emission’s association with an early age and high accretion rates in (massive) young stellar objects. We conclude, considering their mass range and the fact that their photospheres are detected, that the M17 PMS stars are observed in a relatively early formation stage. They are therefore excellent candidates for longer wavelength studies to further constrain the end stages of massive star formation.

X-ray photodesorption of complex organic molecules in protoplanetary disks

Context. X-rays emitted from pre-main-sequence stars at the center of protoplanetary disks can induce nonthermal desorption from interstellar ices populating the cold regions of the disk. This process, known as X-ray photodesorption, needs to be quantified for complex organic molecules (COMs), including acetonitrile CH3CN, which has been detected in several disks. Aims. The purpose of this work is to experimentally estimate the X-ray photodesorption yields of neutral species from pure CH3CN ices and from interstellar ice analogs for which CH3CN is mixed either in a CO-dominated ice or in a H2O-dominated ice. Methods. The ices, grown in an ultrahigh vacuum chamber, were irradiated at 15 K by soft X-rays from synchrotron light (SOLEIL synchrotron) in the N K edge region (395–420 eV) and in the O K edge region (530–555 eV). X-ray photodesorption was probed in the gas phase via quadrupole mass spectrometry by monitoring the changes in the mass signals due to the X-ray irradiation of the ices. X-ray photodesorption yields were derived from the mass signals and were extrapolated to higher X-ray energies in order to provide astrophysical yields adapted to astrochemical models. Results. X-ray photodesorption of the intact CH3CN is detected from pure CH3CN ices and from mixed 13CO:CH3CN ices, with an experimental yield of about 5 × 10−4 molecules photon−1 at 560 eV. When mixed in H2O-dominated ices, X-ray photodesorption of the intact CH3CN at 560 eV is below its detection limit, which is 10−4 molecules photon−1. Yields associated with the desorption of HCN, CH4, and CH3 are also provided. The derived astrophysical yields significantly depend on the local conditions expected in protoplanetary disks, that is, on the ice composition and on the local X-ray irradiation spectrum. They vary from ~10−4 to ~10−6 molecules photon−1 for the X-ray photodesorption of intact CH3CN from CO-dominated ices. Only upper limits varying from ~5 × 10−5 to ~5 × 10−7 molecules photon−1 could be derived for the X-ray photodesorption of intact CH3CN from H2O-dominated ices. Conclusions. X-ray photodesorption of intact CH3CN from interstellar ices might in part explain the abundances of CH3CN observed in protoplanetary disks. The desorption efficiency is expected to vary with the local physical conditions, hence with the disk region considered.

Cytomegalovirus-positive Posner-Schlossman syndrome: to compare differences in retinal vessel area density between the affected and non-affected eye using optical coherence tomography angiography

PurposeTo analyse differences in the retinal microvasculature in eyes with cytomegalovirus (CMV)-positive Posner-Schlossman syndrome (PSS) compared to the non-affected eyes using optical coherence tomography angiography (OCTA).MethodsIn this monocentric, observational prospective case series, 25 patients with unilateral CMV-positive PSS were included. We compared the vessel area densities (VAD) in the macula, optic disc, and peripapillary region in PSS-affected and non-affected eyes using OCTA. We compared the visual fields (VF) of the affected and healthy eyes of each patient. The mean deviation (MD) of the VF was analysed together with the retinal nerve fibre layer (RNFL) thickness to evaluate the strength of correlation with the VAD parameters.ResultsThe VAD of the peripapillary superficial vascular complex (SVC) is significantly reduced in CMV-positive PSS-affected eyes (46.1 ± 9.3% versus 50.1 ± 6.3%, p = 0.008, adjusted p = 0.048). The VAD of the deeper macular, papillary, and peripapillary layers showed no differences between the affected and non-affected eyes. The mean deviation and the retinal nerve fibre layer thickness had correlations with the VAD of the macula (r = 0.451, p = 0.001, r = 0.553, p < 0.001), the peripapillary SCV (r = 0.430, p = 0.002, r = 0.723, p < 0.001), and the papillary region (r = 0.512, p < 0.001, r = 0.292, p = 0.039). Patients receiving systemic antiviral therapy (SAT) showed better VAD of the peripapillary choriocapillary layer (p = 0.001, no therapy: 31.4 ± 1.9%, SAT: 35.0 ± 1.6%), and choroidal layer (p = 0.009, no therapy: 34.2 ± 0.3%, SAT: 36.3 ± 1.8%) compared to those with no SAT.ConclusionA lower peripapillary VAD in the SVC might indicate vascular dysfunction as a sign of glaucomatous damage. SAT might have positive effects on the microcirculation in the deep retinal and choroidal layers.Trial registrationTRN: DRKS00028266, https://www.drks.de/drks_web/.

Performance in a Simulated Virtual Reality Anterior Cervical Discectomy and Fusion Task: Disc Residual, Rate of Removal, and Efficiency Analyses.

Anterior cervical discectomy and fusion (ACDF) is among the most common spine procedures. The Sim-Ortho virtual reality simulator platform contains a validated ACDF simulated task for performance assessment. This study aims to develop a methodology to extract three-dimensional data and reconstruct and quantitate specific simulated disc tissues to generate novel metrics to analyze performance metrics of skilled and less skilled participants. We used open-source platforms to develop a methodology to extract three-dimensional information from ACDF simulation data. Metrics generated included, efficiency index, disc volumes removed from defined regions, and rate of tissue removal from superficial, central, and deep disc regions. A pilot study was performed to assess the utility of this methodology to assess expertise during the ACDF simulated procedure. The system outlined, extracts data allowing the development of a methodology which accurately reconstructs and quantitates 3-dimensional disc volumes. In the pilot study, data sets from 27 participants, divided into postresident, resident, and medical student groups, allowed assessment of multiple novel metrics, including efficiency index (surgical time spent in actively removing disc), where the postresident group spent 61.8% of their time compared with 53% and 30.2% for the resident and medical student groups, respectively ( P = .01). During the annulotomy component, the postresident group removed 47.4% more disc than the resident groups and 102% more than the medical student groups ( P = .03). The methodology developed in this study generates novel surgical procedural metrics from 3-dimensional data generated by virtual reality simulators and can be used to assess surgical performance.

Unravelling the structure of magnetized molecular clouds with SILCC-Zoom: sheets, filaments, and fragmentation

ABSTRACT To what extent magnetic fields affect how molecular clouds (MCs) fragment and create dense structures is an open question. We present a numerical study of cloud fragmentation using the SILCC-Zoom simulations. These simulations follow the self-consistent formation of MCs in a few hundred parsec-sized region of a stratified galactic disc; and include magnetic fields, self-gravity, supernova-driven turbulence, as well as a non-equilibrium chemical network. To discern the role of magnetic fields in the evolution of MCs, we study seven simulated clouds, five with magnetic fields, and two without, with a maximum resolution of 0.1 parsec. Using a dendrogram, we identify hierarchical structures, which form within the clouds. Overall, the magnetized clouds have more mass in a diffuse envelope with a number density between 1 and 100 cm−3. We find that six out of seven clouds are sheet-like on the largest scales, as also found in recent observations, and with filamentary structures embedded within, consistent with the bubble-driven MC formation mechanism. Hydrodynamic simulations tend to produce more sheet-like structures also on smaller scales, while the presence of magnetic fields promotes filament formation. Analysing cloud energetics, we find that magnetic fields are dynamically important for less dense, mostly but not exclusively atomic structures (typically up to ∼100−1000 cm−3), while the denser, potentially star-forming structures are energetically dominated by self-gravity and turbulence. In addition, we compute the magnetic surface term and demonstrate that it is generally confining, and some atomic structures are even magnetically held together. In general, magnetic fields delay the cloud evolution and fragmentation by ∼ 1 Myr.

Probing Neutrino Production in Blazars by Millimeter VLBI

The advancement of neutrino observatories has sparked a surge in multi-messenger astronomy. Multiple neutrino associations among blazars are reported while neutrino production sites are located within their central (sub)parsecs. Yet, many questions remain on the nature of those processes. The next generation Event Horizon Telescope (ngEHT) is uniquely positioned for these studies, as its high frequency and resolution can probe both the accretion disk region and the parsec-scale jet. This opens up new opportunities for connecting the two regions and unraveling the proton acceleration and neutrino production in blazars. We outline observational strategies for ngEHT and highlight what it can contribute to the multi-messenger study of blazars.

Recommendations for intervertebral disc notochordal cell investigation: From isolation to characterization.

Lineage-tracing experiments have established that the central region of the mature intervertebral disc, the nucleus pulposus (NP), develops from the embryonic structure called "the notochord". However, changes in the cells derived from the notochord which form the NP (i.e., notochordal cells [NCs]), in terms of their phenotype and functional identity from early developmental stages to skeletal maturation are less understood. These key issues require further investigation to better comprehend the role of NCs in homeostasis and degeneration as well as their potential for regeneration. Progress in utilizing NCs is currently hampered due to poor consistency and lack of consensus methodology for in vitro NC extraction, manipulation, and characterization. Here, an international group has come together to provide key recommendations and methodologies for NC isolation within key species,numeration, in vitro manipulation and culture, and characterization. Recommeded protocols are provided for isolation and culture of NCs. Experimental testing provided recommended methodology for numeration of NCs. The issues of cryopreservation are demonstrated, and a pannel of immunohistochemical markers are provided to inform NC characterization. Together we hope this article provides a road map for in vitro studies of NCs to support advances in research into NC physiology and their potential in regenerative therapies.

Segmentation of retinal blood vessels by a novel hybrid technique- Principal Component Analysis (PCA) and Contrast Limited Adaptive Histogram Equalization (CLAHE).

Diabetic Retinopathy is a persistent disease of eyes that may lead to permanent loss of sight. In this paper, methodology is proposed to segment region of interest (ROI) i.e. new blood vessels in fundus images of retina of Diabetic Retinopathy (DR). The database of 50 fundus retinal images of healthy subjects and DR patients is fetched from Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. The experimental set up consists of three set of experiments for the disease. For DR, in the first stage of automated blood vessel segmentation, gray-scale image is produced from the colored image using Principal Component Analysis (PCA) in the preprocessing step. The contrast enhancement by the Contrast Limited Adaptive Histogram Equalization (CLAHE) highlights the retinal blood vessels in the gray-scale image i.e. it unsheathed newly formed retinal blood vessels whereas PCA preserved their texture and color discrimination in DR images. The expert ophthalmologist(s) scrutiny on both internet repository and real time data acted as the gold standard for further analysis and formation of the proposed method. Further, ophthalmologists ascertained the forming of new blood vessels only on the disc region and divulging them, which were impossible with the naked eye. These operations help in extracting retinal blood vessels present on the disc and non-disc region of the image. The comparison of the results are done with the state of art methods like watershed transform. It is observed from the results that the new blood vessels are better segmented by the proposed methodology and are marked by the experienced ophthalmologist for validation. Further, for quantitative analysis, the features are extracted from new blood vessels as they are crucial for scientific interpretation. The results of the features lie in permissible limits such as no. of segments vary from 2 to 5 and length of segments varies from 49 to 164 pixels. Similarly, other features such as gray level of new blood vessels lie in 0.296-0.935 normalized range, coefficient with variations in gray level in the range of 0.658-10.10 and distance from vessel origin lie in the range of 56-82 pixels respectively. Both quantitative and qualitative results show that the methodologies proposed boosted the ophthalmic and clinical diagnosis. The developed method further handled the false detection of vessels near the optic disk boundary, under-segmentation of thin vessels, detection of pathological anomalies such as exudates, micro-aneurysms and cotton wool spots. From the numerical analysis, ophthalmologist extracted the information of number of vessels formed, length of the new vessels, observation that the new vessels appearing are less homogenous than the normal vessels. Also about the new vessels, whether they lie on the centre of disc region or towards its edges. These parameters lie as per the findings of the ophthalmologists on retinal images and automated detection helped in monitoring and comprehensive patient assessment. The experimental results show case that the proposed method has higher sensitivity, specificity and accuracy as compared to state of art methods i.e. 0.9023, 0.9610 and 0.9921, respectively. Similar results are obtained on retinal fundus images of PGIMER Chandigarh with sensitivity-0.9234, specificity-0.9955 and accuracy-0.9682.

Probing the temperature structure of the inner region of a protoplanetary disk

Context. Disk temperature structure is crucial for the formation of planets. Midplane heating induced by disk accretion plays a key role in determining the disk temperature, particularly at the inner disk midplane where planets are formed. However, the efficiency of accretion heating has been not well constrained by observations. Aims. Our aim is to observationally constrain the physical properties of the inner region of the CW Tau disk, where the midplane heating potentially takes place. Methods. We constructed two-dimensional physical models of the CW Tau disk that take the midplane heating into account. We compared the models with the ALMA dust continuum observations at Bands 4, 6, 7, and 8, with an angular resolution of 0″. 1. The observed brightness temperatures are almost wavelength-independent at ≲10 au. Results. We find that if the maximum dust size is amax ≲100 µm, the brightness temperatures predicted by the model exceed the observed values, regardless of the efficiency of accretion heating. The low observed brightness temperatures can be explained if millimeter scattering reduces the intensity. If the disk is passive, amax needs to be either ~150 µm or more than a few cm. The accretion heating significantly increases the brightness temperature, particularly when amax ≲ 300 µm; thus, the value of amax must be either ~300 µm or over a few cm. The midplane temperature is expected to be ~1.5–3 times higher than the observed brightness temperatures, depending on the models. The dust settling effectively increases the temperature of the dust responsible for the millimeter emission in the active disk, which leads to the model with 300 µm-sized dust overpredicting the brightness temperatures when strong turbulence is absent. Porous dust (porosity of 0.9) makes the accretion heating more efficient, so that some sort of reduction in accretion heating is required. Conclusions. The brightness temperature is not a simple function of the dust temperature because of the effect of scattering and midplane heating – even when the disk is optically thick. The current data of the CW Tau disk are not sufficient to allow us to discriminate between the passive and active disk models. Future observations at longer wavelengths and higher angular resolution will help to constrain the heating mechanisms of the inner regions of protoplanetary disks.

Segmentation of Optic Disc and Optic Cup Based on Two-Layer Level Set with Sparse Shape Prior Constraint in Fundus Images

Glaucoma is a common high-incidence eye disease. The detection of the optic cup and optic disc in fundus images is one of the important steps in the clinical diagnosis of glaucoma. However, the fundus images are generally intensity inhomogeneity, and complex organizational structure, and are disturbed by blood vessels and lesions. In order to extract the optic disc and optic cup regions more accurately, we propose a segmentation method of the optic disc and optic cup in fundus image based on distance regularized two-layer level with sparse shape prior constraint. The experimental results show that our method can segment the optic disc and optic cup region more accurately and obtain satisfactory results.

Genetic relationships of solar system bodies based on their nucleosynthetic Ti isotope compositions and sub-structures of the solar protoplanetary disk

Nucleosynthetic isotope variations are powerful tools to investigate genetic relationships between meteorite groups and planets. They are instrumental to assess the early evolution of the solar system, including mixing and reservoir formation in the protoplanetary disk, as well as planet formation. To address these questions, we report high-precision nucleosynthetic Ti isotope compositions of a wide range of bulk meteorites, partially complemented with new Cr isotope data. New Ti isotope data confirm the first order dichotomy observed between carbonaceous chondrites (CC), representing outer solar system compositions, and non-carbonaceous (NC) meteorites from the inner solar system. The data in combination with nucleosynthetic isotope data of other elements (e.g., Cr, Ca) indicate that isotopically heterogeneous reservoirs were also present as sub-reservoirs in the inner disk (NC reservoir), generating two or more clusters i.e., (i) the Vesta-like howardites-eucrites-diogenites (HEDs), mesosiderites, angrites, acapulcoites, lodranites, and brachinites and (ii) the Earth-Mars-like ordinary chondrites (OC), aubrites, enstatite chondrites (EC), winonaites, IAB silicates, rumuruti chondrites (R), Martian and terrestrial samples. These reservoirs likely represent disk substructures such as secondary gaps and ring-structures, created by spiral arms, which were emitted from the growing Jupiter and/or Saturn. The distinct isotopic compositions of these reservoirs may reflect thermal processing of material within the disk in combination with temporal isotopic variations either due to isotopically variable infalling material from a heterogeneous molecular cloud and/or thermal processing during the infall that induced such heterogeneities. Such effects were likely reinforced by thermal processing of the material within the disk itself and by physical size- and density sorting of dust caused by the giant planets, creating gaps and pressure bumps in the disk.Genetic relationships of meteorite groups and their implications on parent body formation are evaluated. New high precision Ti isotope data are consistent with that (i) CH and CB meteorites derive from a common parent body, which most likely accreted material from the same isotopic reservoir as the parent body of CR chondrites, (ii) silicates of IAB irons and winonaites originate from the same parent body, and (iii) mesosiderites and HED meteorites have a common origin on Vesta. The indistinguishable Ti and Cr isotope compositions of HEDs/mesosiderites to acapulcoites are not attributed to a common parent body, because of petrologic and chemical differences in addition to their distinct O isotope compositions. Their parent bodies likely accreted in the same disk region, which showed a higher level of O isotope heterogeneity compared to that of Ti, Cr and other refractory nucleosynthetic tracers. The similarity in Ti isotope compositions of Martian meteorites and OCs indicates that OC-like material belongs to the main building blocks of Mars.

Analysis of accretion disc structure and stability using open code for vertical structure

ABSTRACT Radial structure of accretion discs around compact objects is often described using analytic approximations which are derived from averaging or integrating vertical structure equations. For non-solar chemical composition, partial ionization, or for supermassive black holes, this approach is not accurate. Additionally, radial extension of ‘analytically-described’ disc zones is not evident in many cases. We calculate vertical structure of accretion discs around compact objects, with and without external irradiation, with radiative and convective energy transport taken into account. For this, we introduce a new open Python code, allowing different equations of state and opacity laws, including tabular values. As a result, radial structure and stability ‘S-curves’ are calculated for specific disc parameters and chemical composition. In particular, based on more accurate power-law approximations for opacity in the disc, we supply new analytic formulas for the farthest regions of the hot disc around stellar-mass object. On calculating vertical structure of a self-irradiated disc, we calculate a self-consistent value of the irradiation parameter Cirr for stationary α-disc. We find that, for a fixed shape of the X-ray spectrum, Cirr depends weakly on the accretion rate but changes with radius, and the dependence is driven by the conditions in the photosphere and disc opening angle. The hot zone extent depends on the ratio between irradiating and intrinsic flux: corresponding relation for $T_{\rm irr,\, crit}$ is obtained.