Disc Sector Research Articles

Imprint of preterm birth with very low birth weight on optic disc OCT in adulthood-A two-country birth cohort study.

To determine the pattern, degree and prevalence of optic disc optical coherence tomography (OCT) alterations in adults born preterm with very low birth weight (VLBW; birth weight < 1500 g). Optic disc OCT was assessed in 98 VLBW participants and 139 term-born controls from birth cohorts in Finland and Norway at the mean age of 36 years. The participants had not been treated for retinopathy of prematurity and had no diagnosed brain abnormality. OCT assessment included parameters for optic disc size, neural rim and peripapillary retinal nerve fibre layer thickness (pRNFLT), and for the foveal developmental stage. Background data, visual acuity, refractive error and intraocular pressure were recorded. In the VLBW group, optic disc neural rim and pRNFLT were significantly decreased, most frequently in the nasal and inferior sectors. In 40% (95% CI: 33-47) of the VLBW eyes, nerve fibre thickness of at least one optic disc sector was below the fifth percentile of the control group, including 9% (95% CI: 6-14) subgroup falling below the first percentile, that is, clinically below normal limits. VLBW participants with nerve fibre thickness below the fifth percentile did not differ by perinatal data or foveal developmental stage from the other VLBW participants. All participants had normal visual acuity. A moderate decrease of the optic disc neural rim and pRNFLT is frequently seen in clinically healthy adults born preterm with VLBW. Awareness of the VLBW-related optic disc nerve fibre shallowness especially in the inferior and nasal sectors is important while evaluating acquired optic disc pathology in adulthood.

Aero-thermodynamic responses of a novel FGM sector disks using mathematical modeling and deep neural networks

Composite sector disks have extensive applications in aerospace industries, particularly when exposed to challenging conditions such as supersonic airflow and thermal environments. These applications leverage the superior properties of composite materials, including high strength-to-weight ratios, enhanced durability, and excellent thermal resistance, to meet the stringent requirements of aerospace operations. Multi-directional functionally graded (MD-FG) materials due to high-temperature resistance and other amazing properties in each direction have gotten plenty of attention recently. So, in this research, a thermoelasticity solution has been presented to study fundamental frequency traits of an MD-FG sector disk in supersonic airflow via both mathematics simulation and deep neural networks technique. For obtaining exact displacement fields, along with defining the changes of transverse shear strains along the system's thickness, the refined zigzag hypothesis is utilized. For obtaining the temperature-dependent equations, heat conduction relation and thermal boundary conditions of the MD-FG structure are presented. A coupled quasi-3D new refined theory (Q3D-NRT) and generalized differential quadrature method (GDQM) are presented for obtaining and solving the partial differential equations in the time-displacement domain. After obtaining the mathematics results, appropriate datasets are made for testing, training, and validation of the deep neural networks technique. Finally, the results have shown that aerodynamic pressure, temperature changes, Mach number, free stream speed, and air yaw angle have a major role in the stability/instability analyses of the thermally affected MD-FG sector disk in supersonic airflow. As an amazing outcome, increasing the sector angle, FG indexes, and temperature change lead to the reduction of the critical Mach number, and aerodynamic pressure associated with the flutter phenomenon.

The structure-function relationship between multifocal pupil perimetry and retinal nerve fibre layer in glaucoma.

Multifocal pupillographic objective perimetry (mfPOP) is a novel method for assessing functional change in diseases like glaucoma. Previous research has suggested that, in contrast to the pretectally-mediated melanopsin response of intrinsically photosensitive retinal ganglion cells, mfPOP responses to transient onset stimuli involve the extrastriate cortex, and thus the main visual pathway. We therefore investigate the correlation between peripapillary retinal nerve fibre layer (pRNFL) thickness and glaucomatous visual field changes detected using mfPOP. Parallel analyses are undertaken using white on white standard automated perimetry (SAP) for comparison. Twenty-five glaucoma patients and 24 normal subjects were tested using SAP, 3 mfPOP variants, and optical coherence tomography (OCT). Arcuate clusters of the SAP and mfPOP deviations were weighted according to their contribution to published arcuate divisions of the retinal nerve fibre layer. Structure-function correlation coefficients (r) were computed between pRNFL clock-hour sector thickness measurements, and the local visual field sensitivities from both SAP and mfPOP. The strongest correlation was observed in the superior-superotemporal disc sector in patients with worst eye SAP MD < -12dB: r = 0.93 for the mfPOP LumBal test (p < 0.001). Correlations across all disc-sectors were strongest in these same patients in both SAP and mfPOP: SAP r = 0.54, mfPOP LumBal r = 0.55 (p < 0.001). In patients with SAP MD ≥ -6dB in both eyes, SAP correlations across all sectors were higher than mfPOP; mfPOP correlations however, were higher than SAP in more advanced disease, and in normal subjects. For both methods the largest correlations with pRNFL thickness corresponded to the inferior nasal field of more severely damaged eyes. Head-to-head comparison of mfPOP and SAP showed similar structure-function relationships. This agrees with our recent reports that mfPOP primarily stimulates the cortical drive to the pupils.

Increased papillary microcirculation in inactive uveitis patients by optical coherence tomography angiography

Aim: To quantitatively analyze the vascular and structure abnormalities in the papillary areas in eyes with noninfectious uveitis during different periods using optical coherence tomography angiography (OCTA). Methods: Forty eyes of 40 uveitis patients in the acute phase, 12 eyes of 12 patients with inactive uveitis and 21 eyes of 21 healthy controls were included in this study. RPCvd% and pRNFL thickness in different regions were automatically measured and calculated by OCTA. Correlation between RPCvd% and pRNFL was assessed. Results: RPCvd% was significantly higher in uveitis-inactive eyes than in active eyes in the inferior quadrant (p = 0.036), whole image (p = 0.041) and inferior nasal (p = 0.001) sector. The RPCvd% in active uveitis eyes was lower compared to healthy eyes in the inside disc sector (p = 0.026). pRNFL was notably greater in the active group compared to the healthy group. Positive correlations were identified between pRNFL and RPCvd% both in active and inactive uveitis eyes. Conclusions: Compared with active uveitis, papillary microcirculation showed a significant improvement in inactive uveitis eyes (anterior or pan-uveitis). RPCvd% may serve as a sensitive indicator to supervising uveitis progression and treatment response using OCTA.

Simulation study on mass transfer characteristics and disk structure optimization of a rotating disk reactor with high viscosity region

AbstractDue to the excellent film‐forming specific surface area of the disk reactor, its application in the polymer devolatilization process can greatly improve the devolatilization performance of the equipment. In view of this, the fluid volume function method in computational fluid dynamics is used to simulate the film forming performance and surface renewal performance in high viscosity zone of disk reactor. In the disk window area, the liquid film thickness becomes thinner and the surface update frequency becomes faster, indicating that the disk window has a positive effect. The devolatilization performance of five new disk structures under different operating conditions is compared and analyzed. It was found that the influence of liquid level height on film area was greater than that of viscosity and rotation speed, the porous sector disk has excellent surface renewal performance and the baffle can achieve better mass transfer efficiency at a distance of 45–60 mm from the disk.

Assessment interocular symmetry of peripapillary vessel density in young myopes with optical coherence tomographic angiography

PurposeThe purpose of our study was to evaluate the interocular symmetry and distribution of peripapillary vessel density in young myopic eyes.MethodsA cross-sectional observational study was designed. A total of 174 eyes of 87 young myopic patients were recruited in this study. According to spherical equivalent (SE), 48 eyes were classified as mild myopia with a mean SE of − 2.12D (SD 0.66D), 66 as moderate myopia with a mean SE of − 4.50D (SD 0.87D), and 60 as high myopia with a mean SE of − 7.39D (SD 1.30D). Optical coherence tomography angiography (OCTA) was used to measure the vessel density. The distribution and interocular symmetry of peripapillary vessel densities were analyzed.ResultsThe vessel densities in the whole image, peripapillary, superior and inferior sectors were significantly lower in the high myopia group than in the mild or moderate myopia group (All P < 0.001), and the density in the nasal sector was significantly lower in the high myopia group than in the mild group. And most interesting, the vessel densities in the inside disc and temporal sector showed no difference among the three myopic groups (All P > 0.05). By Pearson correlation analysis, the vessel densities in the whole image, peripapillary, superior, inferior and nasal sectors were negatively correlated with axial length (AL) and SE (All P < 0.001), but vessel densities in the inside disc and temporal sector did not show this correlation (All P > 0.05). Interocular symmetry was observed in all the vascular parameters through paired-samples t-tests (All P > 0.05), intraclass correlation coefficient (ICC) and Pearson correlation analysis (All P < 0.001).ConclusionThe density of radial peripapillary capillaries decreased in the myopic eye with axial elongation, and optical vascular parameters showed significant interocular symmetry among young myopic eyes.

On the supersonic vibrations of the advanced composite quasi-3D hyperbolic refined high-order sector annular/circular structure in thermal environment

Functionally graded materials (FGMs) have been used in many high-tech engineering fields because they could improve material properties. Some well-known applications of these materials are over different geometrical shapes like shells and plates. Multi-directional FGMs have the main role in the improvement of multi-functional materials by introducing modern materials. A detailed study of sector annular/circular disks with different thickness directions has been carried out. In practice, the material properties need to be categorized in other directions as well. Sector annular/circular disks made of multi-dimensional FGM (MD-FGM) are vulnerable to high-temperature gradients and enormous deflections. Using the discrete singular convolution method (DSCM), we investigated asymmetric deformations of MD-FG sector annular/circular disk tolerating thermo-aerodynamics loads. What makes this research unique is using thickness classification for the material properties of the disk while radial and circumferential directions follow an exponential trend. In practical conditions, this assumption would result in a more accurate simulation. Having developed equations based on quasi-3D new refined theory (Q3D-NRT) considering the effect of thickness stretching, we solved the equations based on our conditions. With the aid of COMSOL multi-physics finite element simulation, the results are verified and new recommendations for improving the stability of presented MD-FG sector disks are reported. This research might be helpful for scientists working in the field of thermoelastic theory of disks. Since it is very important to have small and uniform thermal stresses in every direction of the materials, the study’s results could be used as a trustworthy database to determine a material property function.

Flutter analysis of multi-directional functionally graded sector poroelastic disks

For the first time, in this article, stable/unstable zones of multi-directional functionally graded (MD-FG) sector disks under aerodynamic pressures are sought. Also, because of porous media, the system is modeled as a poroelastic system. The damping matrix, together with the aerodynamic stiffness matrix, is modeled upon Krumhaar's modified supersonic piston hypothesis. For more accuracy of the results, the Series-Fourier expansion of displacement fields in two-dimension is considered. To solve the partial differential equations, the singular convolution integration method with a singular convolution, as a numerical solver, is used. The precision of the outcomes is verified with those available in the other published research. It is demonstrated that the 3D model has great accuracy in predicting the flutter phenomenon and supersonic vibrations of the MD-FG sector disks. Finally, it has been shown that MD-FG power indices, radius ratio, boundary condition, poroelastic media, geometry, Mach number, aerodynamic pressure, and air yaw angle, in addition to Biot's coefficient, have a crucial role in the stable/unstable zones of the MD-FG sector disks under various conditions. One of the most important results of the current report is that the alteration in material properties of the MD-FG sector disk does not alter the yaw angle in which maximum frequency occurs.

Design and prediction of PIT devices through deep learning.

Graphene material has excellent performance and unique variable carrier density characteristics, making it an excellent mid-infrared material. And deep learning makes it possible to quickly design mid-infrared band devices with good performance. A graphene nano-ring-symmetric sector-shaped disk array structure based on the PIT principle is proposed here for sensing. The influence of structural parameters and Fermi energy changes are studied. And its FOM (Figure Of Merit) can reach 28.7; the sensitivity is 574 cm-1 / RIU (Refractive Index Unit). At the same time, we designed a six-layer deep learning network that can predict structural parameters and curve predictions. When predicting structural parameters, its MAPE (Mean Absolute Percentage Error) converges to 0.5. In curve prediction, MSE (Mean Square Error) converges to 1.2. It shows that predictions can be made very well. This paper proposes a symmetrical sector disk array structure and a 6-layer deep learning network. And the deep neural network designed based on the device data has good prediction accuracy under the premise of ensuring the network is simple. This will lay a good foundation for future sensor design and device acceleration optimization design.

Fractional Order Transient Thermoelastic Stress Analysis of a Thin Circular Sector Disk

Analysis of transient thermoelastic stress distribution of a thin circular sector disk with a time-fractional derivative of order α is proposed. The Neumann types of boundary conditions are used and the integral transform method and Caputo fractional derivative are used to obtain the analytical solutions of the temperature, displacement, and stresses. Numerical values of temperature, displacement, and stresses are computed for an Aluminum (pure) material and presented graphically with help of Mathcad software.

Thermoelastic Modeling of Time Fractional Heat conduction in Circular Disk with Internal Heat Generation

In this paper, thermoelastic modeling of a circular sector disk is done under the influence of fractional time theory of thermoelasticity to evaluate the changes in temperature flow, displacement and stress behavior subjected to internal heat generation within it. At the fixed edge a time dependent heat flux is applied while thermally insulation type boundary are maintained at upper part of surface as well as the lower part surface is kept at zero temperature. Also certain boundary surfaces at 0 are fixed as a function of temperatures field , 1 f 2 f which is function of respectively. Furthermore, method of Integral transformations is employed to determine the required solution of equation of heat conduction. The obtained expressions areof Bessel’s type and in form of series. For numerical analysis the pure aluminum circular sector disk considered and obtained results are plotted as shown in figures.

Partial MDS Codes With Regeneration

Partial MDS (PMDS) and sector-disk (SD) codes are classes of erasure correcting codes that combine locality with strong erasure correction capabilities. We construct PMDS and SD codes with local regeneration where each local code is a bandwidth-optimal regenerating MDS code. In the event of a node failure, these codes reduce both, the number of servers that have to be contacted as well as the amount of network traffic required for the repair process. The constructions require significantly smaller field size than the only other construction known in literature. Further, we present a construction of PMDS codes with global regeneration which allow to efficiently repair patterns of node failures that exceed the local erasure correction capability of the code and thereby invoke repair across different local groups.

Bruch Membrane Opening Minimum Rim Width and Retinal Nerve Fiber Layer Helps Differentiate Compressive Optic Neuropathy From Glaucoma

To compare optical coherence tomography-measured Bruch membrane opening minimum rim width (MRW), peripapillary retinal nerve fiber layer (pRNFL) measurements, and MRW:pRNFL ratios in eyes with compressive optic neuropathy (CON) and glaucoma and controls, and evaluate the ability of these parameters to differentiate CON from glaucoma. Prospective, cross-sectional study. Setting: Single-center tertiary hospital and outpatient clinic. One hundred fifteen eyes of 77 participants, 34 with CON from chiasmal lesions, 21 with glaucoma, and 22 healthy controls. Optical coherence tomography-measured MRW, pRNFL, and MRW:pRNFL ratios for each optic disc sector and global average. MRW, pRNFL, and MRW:pRNFL ratios compared using generalized estimated equations. Area under the receiver operating characteristic curve and positive and negative likelihood ratios were calculated. MRW and pRNFL measurements were significantly reduced in CON and glaucoma compared with controls. In glaucoma, MRW was thinner than in CON in the global, inferotemporal, superonasal, inferonasal, and vertical average measurements, but a significant overlap was observed in many parameters. MRW:pRNFL ratios increased the ability to discriminate between CON and glaucoma, as shown by the high area under the receiver operating characteristic curve, high positive likelihood ratios, and low negative likelihood ratios, especially in the nasal disc sector and the nasal and temporal average. MRW measurements alone cannot reliably distinguish CON from glaucoma, but the combination of MRW, pRNFL, and MRW:pRNFL ratios significantly improves accuracy. When comparing the 2 conditions, MRW:pRNFL ratios yielded higher area under the receiver operating characteristic curve and positive and negative likelihood ratios, suggesting this parameter may be helpful in clinical practice.

MS scheduler: New, scalable, and high-performance sparse AVX-2 parity encoding and decoding technique for erasure-coded cloud storage systems

In cloud storage scenarios, each chunk with multiple symbols of a coding strip resides in a different node and, hence, on a different disk. Existing STAIR and sector-disk (SD) scheduling techniques are not scalable because the performance of existing STAIR and SD encoding and decoding schedulers decreases sharply as the number of parity disks increases. This paper proposes a new, scalable, multisector (MS) scheduler that provides three-level fault tolerance for multiple sectors, disks, and nodes. In addition, the MS scheduler is extendable to multilevel failure recovery. MS schedulers are aware of the inner structure of each node, such as the number of disks and sectors for each node. Compared with SD and STAIR schedulers, an MS scheduler improves the average encoding and decoding performance by 198.34%, on average (ranging from 170.46% to 228.54%). However, STAIR and SD schedulers are bound to a specific number of parity disks and sectors. This is because the MS scheduler uses streaming SIMD extensions (SSE) for the dense matrix-based parity computation software implementation. In contrast, an MS scheduler can perform parity calculations for a large number of parity disks and sectors using advanced vector extensions (AVX)-2, OpenMP thread parallelism, and sparse parity computation software implementation. As a result, fewer XOR operations are performed to calculate parity chunks owing to the diagonal structure of the MS scheduler. The sparse AVX-2/-512 diagonal erasure coding implementation of the MS scheduler enables the proposed scheduler to be compatible with recovery from multilevel failures by skipping a large number of XOR and multiplication operations. This proves that the MS scheduler is suitable for use in a scalable cloud storage environment.

On Optimal Locally Repairable Codes and Generalized Sector-Disk Codes

Optimal locally repairable codes with information locality are considered. Optimal codes are constructed, whose length is also order-optimal with respect to a new bound on the code length derived in this article. The length of the constructed codes is super-linear in the alphabet size, which improves upon the well known pyramid codes, whose length is only linear in the alphabet size. The recoverable erasure patterns are also analyzed for the new codes. Based on the recoverable erasure patterns, we construct generalized sector-disk (GSD) codes, which can recover from disk erasures mixed with sector erasures in a more general setting than known sector-disk (SD) codes. Additionally, the number of sectors in the constructed GSD codes is super-linear in the alphabet size, compared with known SD codes, whose number of sectors is only linear in the alphabet size.

Expression of degenerative markers in intervertebral discs of young and elderly asymptomatic individuals.

Intervertebral disc (IVD) degeneration is a remodeling process mediated by several growth factors and cytokines. This process has been extensively studied in vitro and with pathologic specimens obtained during surgery for scoliosis or back pain. However, the occurrence and temporal evolution of these molecules during normal aging, particularly in the cervical segment, is not known. Our objective was to study and compare the presence of putative mediators in the IVD of young (<35 years, G1) and elderly (>65 years, G2) presumably asymptomatic individuals. Thirty C4-5 and C5-6 discs and thirty L4-5 and L5-S1 discs per group were collected during the autopsy of individuals whose family members denied a history of neck or back pain. Discs were divided into anterior, central (lumbar only) and posterior sectors for analysis. Immunohistochemistry for TNF-α, IL-1β, VEGF, NGF-β, BDNF, TIMP-1, MMP-1, -2 and -3 was performed and reactivity compared between groups and sectors. All of these molecules were detected in every disc sector of both G1 and G2. Most statistical comparisons (25/45, 55.6%) revealed an increase in mediator expression in G2 in relation to G1. Regional differences in the expression of remodeling enzymes were rare; NGF-β and BDNF had slightly higher expression in the cervical segment of elderly individuals. A senescent profile with elevated VEGF, MMP-2 and MMP-3 was observed across most G2 disc regions and were generally elevated from G1. In conclusion, the mere presence of any of the studied molecules inside the IVD cannot be considered pathologic. Expression of remodeling enzymes and inflammatory mediators is relatively similar across different vertebral segments and disc regions leading to a common degenerated pattern, while neurotrophins have slightly higher expression in cervical discs. These findings support the concept that disc remodeling in different segments follows a similar pathway that can be potentially mediated to avoid structural failure.

Harmonic Green functions for the Almaty apple

The parqueting reflection principle is suitable for constructing harmonic Green functions for certain plane domains with boundaries consisting of sub-arcs from circles and straight lines. The (continued) reflection at the boundary parts has to provide a parqueting of the complex plane. Occasionally, however, a parqueting of is not sufficient and multiple parqueting is required, e.g. for the disc sector with opening angle , where a double parqueting is needed, then compensated by applying the square root mapping. The parqueting-reflection principle is more convenient to apply than basing on the conformal invariance of the harmonic Green functions, see e.g., but sometimes the latter is applicable where the first is not. Here the situation is studied for the Almaty apple, a modified half disc. While the bigger of this cut disc is also requiring a double parqueting, for the smaller part a simple one suffices. However, for the bigger part a proper square root reduction to a simple parqueting is still to be determined in order to find the harmonic Green (and Neumann) function. The idea to use this disc cap for a parqueting of the complex plane has occured while two of the authors were visiting a monument of an apple in Almaty, the centre of an area full of wild apple trees considered as the locus of origin of the apple fruit.

Normal aging in human lumbar discs: An ultrastructural comparison.

The normal aging of the extracellular matrix and collagen content of the human lumbar intervertebral disc (IVD) remains relatively unknown despite vast amounts of basic science research, partly because of the use of inadequate surrogates for a truly normal, human IVD. Our objective in this study was to describe and compare the morphology and ultrastructure of lumbar IVDs in 2 groups of young (G1—<35 years) and elderly (G2—>65 years). Thirty L4-5 and L5-S1 discs per group were obtained during autopsies of presumably-asymptomatic individuals and analyzed with magnetic resonance imaging (MRI), a morphological grading scale, light microscopy, scanning electron microscopy (SEM) and immunohistochemistry (IHC) for collagen types I, II, III, IV, V, VI, IX and X. As expected, a mild to moderate degree of degeneration was present in G1 discs and significantly more advanced in G2. The extracellular matrix of G2 discs was significantly more compact with an increase of cartilaginous features such as large chondrocyte clusters. Elastic fibers were abundant in G1 specimens and their presence correlated more with age than with degeneration grade, being very rare in G2. SEM demonstrated persistence of basic structural characteristics such as denser lamellae with Sharpey-type insertions into the endplates despite advanced age or degeneration grades. Immunohistochemistry revealed type II collagen to be the most abundant type followed by collagen IV. All collagen types were detected in every disc sector except for type X collagen. Statistical analysis demonstrated a general decrease in collagen expression from G1 to G2 with an annular- and another nuclear-specific pattern. These results suggest modifications of IVD morphology do not differ between the anterior or posterior annulus but are more advanced or happen earlier in the posterior areas of the disc. This study finally describes the process of extracellular matrix modification during disc degeneration in an unselected, general population and demonstrates it is similar to the same process in the cervical spine as published previously.

Cilioretinal Arteries and Cilioretinal Veins in Eyes with Pathologic Myopia

We investigated the clinical characteristics of cilioretinal arteries (CAs) and cilioretinal veins (CVs) in eyes with pathologic myopia. Ninety-five eyes with pathologic myopia and CAs were studied. The retrobulbar vessels from which the CAs originated were identified by indocyanine green angiography (ICGA). The results showed that 114 CAs were identified in the 95 eyes. ICGA showed that 60% of the CAs branched directly off the short posterior ciliary arteries (SPCAs) and 40% originated from the Zinn-Haller arterial circle (ZHAC). The SPCA-derived CAs tended to be located superiorly and served a large retinal area whereas the ZHAC-associated CAs tended to be located temporally and served mainly the macular area. In 15% of the 95 eyes, the CVs were observed to run parallel to the CAs. The CVs exited the eye at the same point where the CAs entered the eye. This study showed that CAs in eyes with pathologic myopia can be divided into those that are SPCA-derived and tend to emerge in the superior optic disc sector, and those that are ZHAC-associated and usually emerge temporally. An elongating peripapillary scleral flange in eyes with progressive axial myopia may lead to a change of chorioretinal vascular system.

Neumann boundary value problems in fan-shaped domains

n this article we give the solvability conditions and the integral representations of the solutions of the Neumann boundary value problem for the Cauchy-Riemann operator and the Beltrami operator with constant coefficient in a disc sector with angle $\vartheta=\frac{\pi}{n},\,n\in\mathbb N$. Moreover, the Neumann problem for second-order operators with the Bitsadze/Laplace operator as the main part is studied. Classical results of complex analysis are used to obtain the expressions of the solvability conditions and the integral representations for the solutions explicitly.