Disk Thickness Research Articles

Optimisation of Permanent Magnet Eddy Current Braking System using Aluminum Discs by Taguchi Technique

In this work, an attempt has been made to understand the suitability of various positions of permanent magnets, the optimum thickness and speed of Aluminum discs, and Taguchi parameter optimisation. L9 orthogonal array was chosen for the analysis. From Signal to Noise (S/N) ratio calculations it was observed that 3000 rpm, 4mm thick disc and solo magnet with swift application situation were optimum values. SS% from ANOVA indicated that the position of magnets has the greatest influence on brake parameters. The permanent magnet used is a Neodymium – Iron – Boron (NdFeB) magnet. The brake parameters recorded are speed reduction percentage, time consumed and negative acceleration. In solo magnet condition and solo magnet with swift application, better brake parameters were observed in a 4mm thick disc. Solo magnet condition with a 4mm thick disc may be suitable for elevated-speed train applications. Solo magnet with swift application situation may be suitable for high-speed automotive applications.

Quantitative Changes in Vascular and Neural Fibers Induced by Subretinal Fluid Excluding the Peripapillary Region in Patients with Chronic Central Serous Chorioretinopathy.

Background: This study aims to evaluate the quantitative changes in retinal nerve fiber layer (RNFL) thickness and radial peripapillary capillary (RPC) vessel density in patients with chronic central serous chorioretinopathy (CSCR), specifically excluding the peripapillary region. Methods: A prospective case-control study was conducted at the Antalya Training and Research Hospital, Health Sciences University, involving 65 patients with chronic CSCR. Participants were categorized into two groups based on the presence or regression of subretinal fluid (SRF). A control group of age- and sex-matched healthy individuals was also included. Optical coherence tomography angiography (OCTA) was used to assess RNFL thickness and RPC vessel density. Statistical analyses were conducted using SPSS, with non-parametric tests employed for between-group comparisons. Results: Patients with persistent SRF exhibited significant increases in RNFL thickness in the inferior and nasal quadrants compared to healthy controls (p = 0.003 and p = 0.014, respectively). Additionally, RPC vessel density in the small vessel disc area (%) was significantly lower in the persistent SRF group compared to controls (p = 0.021). A significant negative correlation was found between nasal quadrant RNFL thickness and small vessel disc area (p = 0.014, r = -0.306). Conclusions: Chronic SRF in CSCR patients, even when not involving the peripapillary region, leads to significant structural changes in both the neural and vascular components of the retina. These findings suggest that SRF contributes to broader retinal alterations and supports the need for early detection and management of CSCR to prevent long-term visual impairment.

Intervertebral disc regeneration - Is it possible?

The aim of this study was to evaluate disc metabolism after decreasing the axial load through surgery by assessing the glycosaminoglycan content through a non-invasive method-delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC). Sixteen patients with mono-segmental disc degeneration (L4-L5 or L5-S1) who underwent posterior lumbar spine fixation with intervertebral distraction of 2 consecutive vertebrae using monoaxial transpedicular screws and lyophilized allograft to achieve segmental fusion, and who had a follow-up period of at least 2 years, were included in this study. The first lumbar disc was used as the control group. The dGEMRIC studies in degenerative and control discs, visual analogue scale (VAS), Oswestry disability index (ODI), lumbar lordosis, and disc thickness were reviewed before and after surgery. Visual analogue scale and ODI showed significant improvements (P=.003, P=.0004, respectively). The thickness of the operated discs was increased by an average of 2.41 mm (P=.0004) while maintaining lumbar lordosis (P=.35). In pre- and post-surgery dGEMRIC studies, the operated discs showed a significant di!erence (P=.0013), while the control groups remained approximately unchanged (P=.87). We have demonstrated that by restoring the disc height and reducing the associated pressure, the glycosaminoglycan content can be increased in the discs, as indicated by a decrease in gadolinium binding. Our results suggest that eliminating pressure on intervertebral discs can prevent their degeneration and initiate the regeneration process. Level IV, Therapeutic study.

Stress analysis of a hyperbolic elastic-plastic disk under thermomechanical loading

A general solution is constructed for the distribution of stresses within a thin, hyperbolic elastic-plastic disk subjected to external and internal pressures while in a steady-state temperature field and under plane stress conditions. The pressures applied to the disk are assumed not to induce any plastic flow at the initial, uniformly distributed temperature. The disk is loaded by increasing the temperature of its inner radius. The temperature of the outer radius is kept constant. Elastic and temperature strains are related to stresses by the Duhamel–Neumann law. In the plastic region, the von Mises yield criterion is valid. The tensile yield stress is taken as constant. The boundary value problem is statically determinate. Therefore, the plastic flow rule is not required to determine the stress field. The final part of the general solution depends on the parameters classifying the boundary value problem, including whether the plastic flow initiates at the inner or outer radius of the disk. The solution is presented in dimensionless form. The loading parameter comprises the inner surface temperature of the disk, the coefficient of linear thermal expansion, the initial temperature of the disk, the dimensionless inner radius of the disk, the yield stress under uniaxial tension, and Young’s modulus. The general solution is obtained for both cases (for a plastic region appearing at the inner or outer radius of the disk). A specific numerical solution is constructed for a disk subjected to external pressure and a steady-state temperature field. The temperature of the inner radius at which the plastic region first appears is calculated. As it increases, the plastic region extends. At a certain temperature value, another plastic region appears near the outer radius of the disk. This value is determined as part of solving the boundary value problem. The influence of the parameters classifying the boundary value problem on the development of the plastic region and the stress distribution along the radius of the disk is shown. The qualitative differences between the new and existing solutions for a disk of constant thickness under the action of a uniform temperature field are discussed.

Influence of the turbulent magnetic pressure on isothermal jet emitting disks

Context. The theory of jet emitting disks (JEDs) provides a mathematical framework for a self-consistent treatment of steady-state accretion and ejection. A large-scale vertical magnetic field threads the accretion disk where magnetic turbulence occurs in a strongly magnetized plasma. A fraction of mass leaves the disk and feeds the two laminar super-Alfvénic jets. In previous treatments of JEDs, the disk turbulence has been considered to provide only anomalous transport coefficients, namely magnetic diffusivities and viscosity. However, 3D numerical experiments show that turbulent magnetic pressure also sets in. Aims. We analyze how this turbulent magnetic pressure modifies the classical picture of JEDs and their parameter space. Methods. We included this additional pressure term using a prescription that is consistent with the latest 3D global (and local) simulations. We then solved the complete system of self-similar magnetohydrodynamic (MHD) equations, accounting for all dynamical terms. The magnetic surfaces are assumed to be isothermal, limiting the validity of our results to cold outflows. We explored the effects of the disk thickness and the level of magnetic diffusivities on the JED response to turbulent magnetic pressure. Results. The disk becomes puffier and less electrically conductive, causing radial and toroidal electric currents to flow at the disk surface. Field lines within the disk become straighter, with their bending and shearing occurring mainly at the surface. Accretion remains supersonic, but becomes faster at the disk surface. Large values of both turbulent pressure and magnetic diffusivities allow powerful jets to be driven, and their combined effects have a constructive influence. Nevertheless, cold outflows do not seem to be able to reproduce mass-loss rates as large as those observed in numerical simulations. Conclusions. Our results are a major upgrade of the JED theory, allowing a direct comparison with full 3D global numerical simulations. We argue that JEDs provide a state-of-the-art mathematical description of the disk configurations observed in numerical simulations, commonly referred to as magnetically arrested disks (MADs). However, further efforts from both theoretical and numerical perspectives are needed to firmly establish this point.

Comparison of vibration values of rotating discs with variable parameters obtained by finite element analysis modeling with different machine learning algorithms

PurposeRotating functionally graded (FG) disks of variable thickness generates vibration. This study aims to analyze the vibration generated by the rotating disks using a finite element program and compare the results obtained with the regression methods.Design/methodology/approachTransverse vibration values of rotating FG disks with variable thickness were modeled using different regression methods. The accuracies of the obtained models are compared. In the context of comparing regression methods, multiple linear regression (MLR), extreme learning machine (ELM), artificial neural networks (ANNs) and radial basis function (RBF) were used in this study. The error graph between the observed value and the predicted value of each regression method was obtained. The error values of the regression methods used with scientific error measures were calculated.FindingsThe analysis of the transverse vibration of rotating FG disks with the finite element program is consistent with the studies in the literature. When the variables and vibration value determined on the disk are modeled with ELM, MLR, ANN and RBF regression methods, it is concluded that the most accurate model order is RBF, ANN, MLR and ELM.Originality/valueThere are studies on the vibration value of rotating discs in the literature, but there are very few studies on modeling. This study shows that ELM, MLR, ANN and RBF, which are machine learning methods, can be used in modeling the vibration value of rotating discs.

Therapeutic potential of hyaluronic acid hydrogel combined with bone marrow stem cells-conditioned medium on arthritic rats’ TMJs

Conditioned media (CM) is derived from mesenchymal stem cells (MSC) culture and contains biologically active components. CM is easy to handle and reduces inflammation while repairing injured joints. Combination therapy of the CM with cross-linked hyaluronic acid (HA) could ameliorate the beneficial effect of HA in treating degenerative changes of articulating surfaces associated with arthritic rats’ temporomandibular joints (TMJs). This study aimed to evaluate the therapeutic potential of HA hydrogel combined with bone marrow stem cells-conditioned medium (BMSCs-CM) on the articulating surfaces of TMJs associated with complete Freund’s adjuvant (CFA)-induced arthritis. Fifty female Sprague-Dawley rats were divided randomly into five equal groups. Rats of group I served as the negative controls and received intra-articular (IA) injections of 50 µl saline solution, whereas rats of group II were subjected to twice IA injections of 50 µg CFA in 50 µl; on day 1 of the experiment to induce persistent inflammation and on day 14 to induce arthritis. Rats of group III and IV were handled as group II and instead, they received an IA injection of 50 µl HA hydrogel and 50 µl of BMSCs-CM, respectively. Rats of group V were given combined IA injections of 50 µl HA hydrogel and BMSCs-CM. All rats were euthanized after the 4th week of inducing arthritis. The joints were processed for sectioning and histological staining using hematoxylin and eosin, Masson’s trichrome and toluidine blue special staining, and immunohistochemical staining for nuclear factor-kappa B (NF-κB). SPSS software was used to analyze the data and one-way analysis of variance followed by post-hoc Tukey statistical tests were used to test the statistical significance at 0.05 for alpha and 0.2 for beta. In the pooled BMSC-CM, 197.14 pg/ml of platelet-derived growth factor and 112.22 pg/ml of interleukin-10 were detected. Compared to TMJs of groups III and IV, TMJs of group V showed significant improvements (P = 0.001) in all parameters tested as the disc thickness was decreased (331.79 ± 0.73), the fibrocartilaginous layer was broadened (0.96 ± 0.04), and the amount of the trabecular bone was distinctive (19.35 ± 1.07). The mean values for the collagen amount were increased (12.29 ± 1.38) whereas the mean values for the NF-κB expression were decreased (0.62 ± 0.15). Combination therapy of HA hydrogel and BMSCs-CM is better than using HA hydrogel or BMSCs-CM, separately to repair degenerative changes in rats’ TMJs associated with CFA-induced arthritis.

Isolation and characterization of a novel bacterium that promotes the degradation of poly(glycolic acid) by its extracellular esterase under thermophilic conditions

Poly(glycolic acid) (PGA) is widely utilized in the shale oil and gas industry owing to its biodegradable nature, as well as superior mechanical and barrier properties. However, PGA degradability is limited by environmental conditions such as temperature and pH, and using acids to optimize the degradation can have adverse environmental impact. Thus, it is essential to identify methods that can effectively promote the degradation of PGA under mild conditions, such as microbial degradation. In the present study, strain DB14, a bacterium that promotes PGA degradation, was isolated from drain water of a steam pipeline. Sequence analysis of the 16S rRNA gene of the bacterium revealed that it is mostly closely related to Geobacillus icigianus; however, it also differed from Geobacillus icigianus in several physiological properties. To investigate PGA degradation by strain DB14, a PGA film and disc were incubated with the strain. The residual weight of the PGA film (thickness: 170 μm) significantly reduced after incubation, whereas the decrease in the thickness of the PGA disc (thickness: 3 mm) was relatively small. The penetration of water, the bacterium, and the extracellular enzymes into the interior from the reaction-erosion front of the PGA disc may be inhibited by the high barrier performance of PGA. Strain DB14 was also found to change the pH of the surrounding environment to approximately 8–9. To investigate the effect of pH on PGA degradability, degradation tests with crude extracellular enzymes derived from strain DB14 were conducted in various buffers. The results showed that the degradation activity was highest at pH 8, which implied that DB14 efficiently maximized the hydrolytic capacity of its enzyme for degrading PGA. Thus, this study provides a basis for developing environmentally friendly technologies that can promote the degradation of PGA molding articles, especially those used in wellbores for oil and gas recovery.

Analysis of fiber post–resin cement interfacial adaptation at different post regions using field emission scanning electron microscopy

Abstract Introduction: An ideal interfacial adaptation between fiber posts and resin cement is critical for optimum retention and good scenario. Therefore, this research was designed to estimate the interfacial adaptation at fiber post–resin cement interfaces using field emission scanning electron microscopy (FESEM) investigation. Materials and Methods: Forty-five extracted human lower premolars with sole and round canal were classified into three groups (n = 15) following the fiber post types. Each tooth was decoronated and implanted in acrylic resin-filled polyvinyl chloride mold. Roots were undergone endodontic management and post space preparations. Then, each group was classified into three subdivisions (n = 5) according to the resin cement types. After cementation, each post space was marked into apical, middle, and coronal thirds and sectioned horizontally into three 2 mm disc thickness for each third. After that, each disc in each sub-group was then subjected to FESEM analysis to evaluate the gaps width at fiber post–resin cement interface in µm. The data were recorded and statistically evaluated and compared using two-way analysis of variance and Duncan’s multiple range tests at P ≤ 0.05. Results: The everStick post with the RelyX U-200 cement group showed significantly the least gap width mean, while the glass fiber post with the TOTAL C-RAM cement has statistically the greatest gap width mean along the coronal, middle, and apical thirds of fiber post at P ≤ 0.05. The apical third of fiber post showed significantly the greatest mean of gap width, while the middle third showed the least gap width mean at P ≤ 0.05. Conclusion: Different brands of fiber post and resin cement can influence the interfacial adaptation at post–cement interface.

Correction for partial volume averaging in the quantification of radiopaque nanomaterial-embedded resorbable polymers

Resorbable inferior vena cava (IVC) filters require embedded contrast for image-guided placement and integrity monitoring. We calculated correction factors to account for partial volume averaging of thin nanoparticle (NP)-embedded materials, accounting for object and slice thicknesses, background signal, and nanoparticle concentration. We used phantoms containing polycaprolactone disks embedded with bismuth (Bi) or ytterbium (Yb): 0.4- to 1.2-mm-thick disks of 20 mg ml−1 NPs (thickness phantom), 0.4-mm-thick disks of 0–20 mg ml−1 NPs in 2 mg ml−1 iodine (concentration phantom), and 20 mg ml−1 NPs in 0.4-mm-thick disks in 0–10 mg ml−1 iodine (background phantom). Phantoms were scanned on a dual-source CT with 80, 90, 100, and 150 kVp with tin filtration and reconstructed at 1.0- to 1.5-mm slice thickness with a 0.1-mm interval. Following scanning, disks were processed for inductively coupled plasma optical emission spectrometry (ICP-OES) to determine NP concentration. Mean and maximum CT numbers (HU) of all disks were measured over a 0.5-cm2 area for each kVp. HU was converted to concentration using previously measured calibrations. Concentration measurements were corrected for partial volume averaging by subtracting residual slice background and extrapolating disk thickness to both nominal and measured slice sensitivity profiles (SSP, mm). Slice thickness to agreement (STTA, mm) was calculated by replacing the CT-derived concentrations with ICP-OES measurements and solving for thickness. Slice thickness correction factors improved agreement with ICP-OES for all measured data. Yb corrections resulted in lower STTA than Bi corrections in the concentration phantom (1.01 versus 1.31 STTA/SSP, where 1.0 is perfect agreement), phantoms with varying thickness (1.30 versus 1.87 STTA/SSP), and similar ratio in phantoms with varying background iodine concentration (1.34 versus 1.35 STTA/SSP). All measured concentrations correlated strongly with ICP-OES and all corrections for partial volume averaging increased agreement with ICP-OES concentration, demonstrating potential for monitoring the integrity of thin IVC resorbable filters with CT.

An SEM study on the effect of 9.3-µm CO2 laser on dentinal tubules for hypersensitivity treatment.

In-vitro studies were performed on dentin of extracted human molars to investigate the effectiveness of 9.3μm CO2 laser irradiation to occlude dentinal tubules. The observed occlusion of dentinal tubules with the irradiation was compared with application of three reagents: 2% Sodium Fluoride gel, an aqueous solution of hydroxyapatite nanoparticles and an equal mix of the two. We show that 9.3μm CO2 laser irradiation occludes dentinal tubules, and the use of laser irradiation produces better occlusion of the opened tubules compared to the use of topical reagents. Nine extracted and cleaned human molars were cut to obtain dentin disks of thickness of 3-5mm. Each disc was divided into four quarters, and each quarter served as two samples corresponding to irradiated and non-irradiated group counterparts. Five disks were used to study the effect of various laser irradiation energies on the dentinal tubules to find a good pulse fluence for occlusion of the dentinal tubules, and four disks were used for studying the effects of reagents and irradiation at the pulse fluences found in the first part of the study. The samples were irradiated with a beam diameter of 1mm (1/e2) at 15Hz pulse repetition rate, scanned automatically using a set of scanning mirrors. Samples were imaged using Scanning Electron Microscope (SEM) which were processed to determine tubule diameter. Safety of the irradiation treatment was investigated on 6 samples by measuring pulpal temperature rise. The effect of three topical reagents corresponding to 2% Sodium Fluoride gel (F), Hydroxyapatite nanoparticles (HA) and an equal mix of F and HA (HAF) on dentinal tubule occlusion was evaluated and compared with the laser irradiation. In all examined cases, laser irradiation at a fluence of 0.81J/cm2 resulted in a temperature increase less than 3°C which is safe, and no surface cracking was observed. There is a threshold pulse fluence of 0.27J/cm2 above which, laser produced surface melting. At a pulse fluence of 0.81J/cm2 a layer of recast of melted dentin was formed. Under this layer, peritubular dentin melting and occluding of the dentinal tubules was observed. Application of either F or HA or HAF did not produce visible occlusion effect on open tubules after washing and microbrushing with excess distilled water. 9.3μm CO2 laser irradiation on extracted human molar dentin at pulse fluence of 0.81J./cm2 resulted in tubule area reduction by 97% without rising pulpal temperatures to unsafe levels.

Globular cluster orbital decay in dwarf galaxies with MOND and CDM: Impact of supernova feedback

Dynamical friction works very differently for Newtonian gravity with dark matter and in modified Newtonian dynamics (MOND). While the absence of dark matter considerably reduces the friction in major galaxy mergers, analytic calculations indicate the opposite for very small perturbations, such as globular clusters (GCs) sinking in dwarf galaxies. Here, we study the decay of GCs in isolated gas-rich dwarf galaxies using simulations with the Phantom of Ramses code, which enables both the Newtonian and the QUMOND MOND gravity. We modeled the GCs as point masses, and we simulated the full hydrodynamics, with star formation and supernovae feedback. We explored whether the fluctuations in gravitational potential caused by the supernovae can prevent GCs from sinking toward the nucleus. For GCs of typical mass or lighter, we find that this indeed works in both Newtonian and MOND simulations. The GC can even make a random walk . However, we find that supernovae cannot prevent massive GCs ($M from sinking in MOND. The resulting object looks similar to a galaxy with an offset core, which embeds the sunk GC. The problem is much milder in the Newtonian simulations. This result thus favors Newtonian over QUMOND gravity, but we note that it relies on the correctness of the difficult modeling of baryonic feedback. We propose that the fluctuations in the gravitational potential could be responsible for the thickness of the stellar disks of dwarf galaxies and that strong supernova winds in modified gravity can transform dwarf galaxies into ultra-diffuse galaxies.

Choroidal Vascularity Index and Subfoveal Choroidal Thickness in Rheumatoid Arthritis Assessed with Enhanced-Depth Imaging Optical Coherence Tomography

ABSTRACT Purpose To evaluate the effects of rheumatoid arthritis (RA) on choroidal vascularity index (CVI) and subfoveal choroidal thickness (SFCT). Methods The study included 56 eyes of 56 rheumatoid arthritis patients and 65 eyes of 65 age- and sex-matched healthy normal participants. CVIs of all participants were measured by transferring enhanced depth imaging optical coherence tomography (EDI-OCT) images to the image J program that is software used for image binarization and compared between the 2 groups. SFCT, central macular thickness (CMT) and optic disc parameters of all participants were measured with spectral domain OCT and compared. Results The mean CVI values of the RA and control groups were 65.9 ± 1.52 and 68.56 ± 1.62, respectively, and were significantly lower in the RA group (p = 0.001). Mean SFCT values of the RA and control groups were 290.11 ± 15.18 and 332.88 ± 11.04, respectively, and SFCT was significantly lower in the RA group (p = 0.001). RA patients have thin SFCT and low CVI. There was no significant difference between the two groups in terms of CMT and optic disc parameters. Conclusion RA patients have lower CVI and thinner SFCT than healthy participants.

Fate of a remnant solid disk around an eccentric giant planet

The composition of giant planets' atmospheres is an important tracer of their formation history. While many theoretical studies investigate the heavy-element accretion within a gaseous protoplanetary disk, the possibility of solid accretion after disk dissipation has not been explored. Here, we focus on the case of a gas giant planet excited to an eccentric orbit and assess the likelihood of solid accretion after disk dissipation. We follow the orbital evolution of the surrounding solid materials and investigate the scattering and accretion of heavy elements in the remnant solid disks. We perform N-body simulations of planetesimals and embryos around an eccentric giant planet. We consider various sizes and orbits for the eccentric planet and determine the fate of planetesimals and embryos. We find that the orbital evolution of solids, such as planetesimals and embryos, is regulated by weak encounters with the eccentric planet rather than strong close encounters. Even in the region where the Safronov number is smaller than unity, most solid materials fall onto the central star or are ejected from the planetary system. We also develop an analytical model of the solid accretion along the orbital evolution of a giant planet, where the accretion probability is obtained as a function of the planetary mass, radius, semi-major axis, eccentricity, inclination, and solid disk thickness. Our model predicts that sim 0.01-0.1 $M_ of solids is accreted onto an eccentric planet orbiting in the outer disk ($ The accreted heavy-element mass increases (decreases) with the eccentricity (inclination) of the planet. We also discuss the possibility of collisions of terrestrial planets and find that $ of the hot Jupiters formed via high-eccentric migration collide with a planet of $10M_ However, we find that solid accretion and collisions with terrestrial planets are minor events for planets in the inner orbit, and a different accretion process is required to enrich eccentric giant planets with heavy elements.

Multidisciplinary design and manufacturing of a Tesla pump prototype

To widen the range of hydraulic efficiencies of boundary layer pumps, a full design methodology has been proposed in order to identify critical issues for their performance and manufacturing. The methodology integrated a 2D numerical code, CFD and FEM analyses, coupled with manufacturing assessments as feedback mechanism. Considering budget constraints and in-house machining capabilities, a quick first prototype was produced. Analyses of the design are pointing out that the volute design initially chosen will not help to achieve an increase in the overall efficiency. The curves of head achieved with 2D and CFD are in agreement, but the latter determines the losses with larger accuracy, thus achieving lower values of head. The 2D model shows limits in the determination of the efficiency, effectively corrected by the CFD analysis. Critical parameters as disc thickness and gap between discs will require a more sophisticated assembly process and materials outsource. The proposed methodology could be used as a reference for the design and performance evaluation of this kind of turbomachinery in the future. The procedure lead to a prototype design, whose optimal efficiency slightly lower than 30 % was achieved at 5000 rpm with 0.3 mm disks gap.

Peripapillary and subfoveal choroidal vascular index in patients with tension-type headache and migraine.

This study aimed to evaluate the choroidal vascular characteristics of patients followed up with different headache diagnoses. Prospective comparative study. This study included 21 patients with migraine with visual aura (MwA), 20 with migraine without aura, 29 patients experiencing episodic tension-type headache, and 30 healthy participants. The participants was performed refraction values, axial length, and intraocular pressure were examined. Choroidal thickness was determined in all participants with HD-line optical coherence tomography (OCT) in the subfoveal, nasal, and temporal quadrants 500 µm from the fovea. Using special image processing software, luminal area (LA), stromal area, total choroidal area, and choroidal vascular index (CVI) values were calculated in both macular and peripapillary regions. OCT was also used to perform peripapillary retinal nerve fiber layer (pRNFL) thickness and optic disc head measurements. Spherical refraction, axial length, and intraocular pressure values did not significantly differ among the four groups with similar gender and age distributions ( P > 0.05). The LA values in both macular and peripapillary regions were found to be statistically significantly lower in the MwA group ( P = 0.007 and P = 0.005, respectively). There was no statistically significant difference among the groups in terms of the remaining choroidal area parameters or CVI values ( P > 0.05). The groups also did not show any significant difference in the pRNFL or optic disc head measurements performed in different quadrants ( P > 0.05). While LA, one of the choroidal vascular parameters, was found to be lower in the MwA group in both the macular and peripapillary regions, there were no statistically significant differences between the groups in terms of the peripapillary or macular CVI values.

MRI study on the influence of lumbosacral vertebral body and disc factors on lumbar lordosis in children

PurposeTo evaluate the influence of vertebral and disc wedging on the contribution of lumbar lordosis and the change of disc thickness before and after walking based on MRI.MethodsCross-sectional study. A total of 96 normally developing children, aged 5.7 ± 3.0 years old, 55 boys and 41 girls. They were divided into 3 groups: Pre-walking group, Walking group, and Post-walking group. Parameters: lumbar lordosis Angle (LLA), the sum of the lumbar disc wedge Angle (∑D), the sum of the lumbar vertebral body wedge Angle (∑B), disc height (DH).Results(1) LLA, ∑D, ∑B, and DHL1-S1 were 33.2 ± 8.7°, 14.1 ± 8.6°, 11.9 ± 8.6°, and 6.9 ± 1.2 mm, 7.6 ± 1.4 mm, 8.2 ± 1.6 mm, 8.9 ± 1.7 mm, 8.5 ± 1.8 mm. (2) The difference in LLA values between the Pre-walking and the Post-walking group was statistically significant. DH were significantly different among the three groups. (3) In the Post-walking group, LLA value of girls was significantly higher than that of boys, and DHL3 − 4 and DHL4 − 5 values of girls were significantly lower than that of boys. (4) Age had a low positive correlation with LLA and ∑D and a moderate to strong positive correlation with DH; LLA showed a moderate positive correlation with ∑D, and a low positive correlation with ∑B and DH.ConclusionAge and walking activity are the influencing factors of lumbar lordosis and disc thickening. Walking activity can significantly increase lumbar lordosis, and age is the main factor promoting lumbar disc thickening. DHL4-5 was the thickest lumbar intervertebral disc with the fastest intergroup thickening. Disc wedging contributes more to lumbar lordosis than vertebral wedging.

A 3D view on the local gravitational instability of cold gas discs in star-forming galaxies at 0 ≲ z ≲ 5

Local gravitational instability (LGI) is considered crucial for regulating star formation and gas turbulence in galaxy discs, especially at high redshift. Instability criteria usually assume infinitesimally thin discs or rely on approximations to include the stabilising effect of the gas disc thickness. We test a new 3D instability criterion for rotating gas discs that are vertically stratified in an external potential. This criterion reads Q3D < 1, where Q3D is the 3D analogue of the Toomre parameter Q. The advantage of Q3D is that it allows us to study LGI in and above the galaxy midplane in a rigorous and self-consistent way. We apply the criterion to a sample of 44 star-forming galaxies at 0 ≲ z ≲ 5 hosting rotating discs of cold gas. The sample is representative of galaxies on the main sequence at z ≈ 0 and includes massive star-forming and starburst galaxies at 1 ≲ z ≲ 5. For each galaxy, we first apply the Toomre criterion for infinitesimally thin discs, finding ten unstable systems. We then obtain maps of Q3D from a 3D model of the gas disc derived in the combined potential of dark matter, stars and the gas itself. According to the 3D criterion, two galaxies with Q < 1 show no evidence of instability and the unstable regions that are 20% smaller than those where Q < 1. No unstable disc is found at 0 ≲ z ≲ 1, while ≈60% of the systems at 2 ≲ z ≲ 5 are locally unstable. In these latter, a relatively small fraction of the total gas (≈30%) is potentially affected by the instability. Our results disfavour LGI as the main regulator of star formation and turbulence in moderately star-forming galaxies in the present-day Universe. LGI likely becomes important at high redshift, but the input by other mechanisms seems required in a significant portion of the disc. We also estimate the expected mass of clumps in the unstable regions, offering testable predictions for observations.

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.

Peripapillary Microvascular and Structural Parameters in Atrophic Nonarteritic Anterior Ischemic Optic Neuropathy, Unaffected Fellow Eyes and Controls in an Indian Population

ABSTRACT Nonarteritic ischemic optic neuropathy (NAION) is believed to be an ischemic insult to the optic nerve head and is one of the most common acute optic neuropathies of adulthood. Prevention of NAION in the fellow eye has not yet been accomplished. Optical coherence tomography angiography (OCTA) is a new and emerging non-invasive technology that provides microvascular information that complements the structural data. This prospective study is aimed to fill the lacunae in data that is available in the Indian population. We included 36 patients with NAION, their 36 fellow eyes and 37 healthy controls. The peripapillary perfusion index, peripapillary flux, peripapillary retinal nerve fibre layer (RNFL) thickness values and disc volumes of eyes were evaluated. The NAION eyes had lower peripapillary perfusion index, flux and RNFL thickness values in all sectors compared with both the fellow and the healthy control eyes (p = < .05). A statistically significant difference was found in disc volume between control eyes and fellow eyes, which included eyes with disc at risk configuration as well as normal disc configuration. Eyes with disc at risk configuration had a numerically lower disc volume than eyes with normal disc configuration. Fellow eyes overall had numerically lower perfusion index, higher RNFL thickness, and similar flux which was statistically non-significant compared with the healthy eyes. Correlation between the localization of visual field defects and the quadrants showing impairments of perfusion index and peripapillary RNFL were also assessed. These findings may indicate the potential vascular risk factors for the development of NAION in fellow eyes.