Small Disk Research Articles

Biomechanical properties of different anterior and posterior techniques for atlantoaxial fixation: a finite element analysis

BackgroundMany techniques for atlantoaxial fixation have been developed. However, the biomechanical differences among various atlantoaxial fixation methods remain unclear. This study aimed to evaluate the biomechanical influence of anterior and posterior atlantoaxial fixation techniques on fixed and nonfixed segments.MethodsAn occiput-C7 cervical finite element model was used to construct 6 surgical models including a Harms plate, a transoral atlantoaxial reduction plate (TARP), an anterior transarticular screw (ATS), a Magerl screw, a posterior screw-plate, and a screw-rod system. Range of motion (ROM), facet joint force (FJF), disc stress, screw stress, and bone-screw interface stress were calculated.ResultsThe C1/2 ROMs were relatively small in the ATS and Magerl screw models under all loading directions except for extension (0.1°–1.0°). The posterior screw-plate system and screw-rod system generated greater stresses on the screws (77.6–1018.1 MPa) and bone-screw interfaces (58.3–499.0 MPa). The Harms plate and TARP models had relatively small ROMs (3.2°–17.6°), disc stress (1.3–7.6 MPa), and FJF (3.3–106.8 N) at the nonfixed segments. Changes in disc stress and FJF of the cervical segments were not consistent with changes in ROM.ConclusionsATS and Magerl screws may provide good atlantoaxial stability. The posterior screw-rod system and screw-plate system may have higher risks of screw loosening and breakage. The Harms plate and TARP model may more effectively relieve nonfixed segment degeneration than other techniques. The C0/1 or C2/3 segment may not be more susceptible to degeneration than other nonfixed segments after C1/2 fixation.

Perspective Study of Spontaneous Resorption of Lumbar Disc Herniation in Female Population of Telangana State, India

Background: Herniation of the disc is the one of the disadvantages human population is facing due to the erect posture. Herniation is the abnormal protrusion of nucleus pulposus from weak site in the annulus fibrosus of the intervertebral disc. It impairs the locomotion of the patients affected with herniation of the disc until the resorption occurs.Method: 30 females aged between 35 to 55 years treated with conservative treatment for low back pain were included in the study. MRI was done to confirm diagnosis and to know the degree of herniation. Routine blood investigations were done to rule out any associated diseases.Results: Out of 30 (12 (40%) were normal, 10 (33.3%) had type-II DM and 8 (26.6%) had HTN. Comparison of spontaneous resorption (in months) 7.5 (±2.4) mean value in large disc, 12.2 (±2.6) in small disc and p value was highly significant (p<0.001).Conclusion:Spontaneous resorption of herniated disc can occur by different mechanisms(retraction, dehydration, and inflammatory mediated mechanism). Early clinical recovery is usually associated with quick resorption of herniated disc.

Peripapillary Vitreous Traction Syndrome: Expanding the Spectrum of Anterior Optic Neuropathies.

Peripapillary vitreous traction (PVT) occurring without any underlying eye disease has been contemplated as a distinct entity from nonarteritic ischemic optic neuropathy (NAION) for many years and is sometimes difficult to differentiate from classical NAION. We report 6 new cases to analyze the clinical features of PVT syndrome that would expand the clinical spectrum of anterior optic neuropathies. Prospective case series. PVT syndrome seems to affect optic discs with a small area with a small cup-to-disc (C/D) ratio. The C/D ratio does not significantly increase in the chronic stage, as in NAION. Vitreous traction without detachment can either lead to mild retinal nerve fiber layer (RNFL) injury with attendant ganglion cell layer/inner plexiform layer (GCL/IPL) thinning in 29% or no injury at all in 71%. Eighty-six percent had good visual acuity (VA) and had no relative afferent pupillary defect (RAPD), whereas 14% had a transient RAPD; 71% had no color defect. Vitreous detachment after a period of severe and persistent traction can lead to more damage to the optic nerve head and RNFL that may look like NAION. Our hypothesized mechanically induced injury to the superficial optic nerve head may not lead to much visual impairment. In our study, no further therapeutic interventions were required. Based on our analysis of previously published cases and our own prospective case series of 6 patients, the PVT syndrome falls within the spectrum of anterior optic neuropathies, often affecting small optic discs with a small C/D ratio. Vitreous traction can lead to a partial or complete anterior optic neuropathy. The PVT syndrome may be a "more" anterior optic neuropathy distinct from classical NAION.

Small nanofibrous disks for preconcentration of environmental contaminants followed by direct in-vial elution and chromatographic determination

A novel method for the extraction of river water contaminants as model analytes of ranging polarities, including bisphenols A, C, S, Z, fenoxycarb, kadethrin, and deltamethrin, using small compact fibrous disks has been developed and validated. Polymer nanofibers and microfibers prepared from poly(3-hydroxybutyrate), polypropylene, polyurethane, polyacrylonitrile, poly(lactic acid), and polycaprolactone doped with graphene were evaluated in terms of extraction efficiency, selectivity, and stability in organic solutions. Our novel extraction procedure comprised preconcentration of analytes from 150 mL river water to 1 mL of eluent using a compact nanofibrous disk freely vortexed in the sample. Small nanofibrous disks with a diameter of 10 mm were cut from a compact and mechanically stable 1–2 mm thick micro/nanofibrous sheet. After 60 min extraction in a magnetically stirred sample located in a beaker, the disk was removed from the liquid and washed with water. Then, the disk was inserted into a 1.5 mL HPLC vial and extracted with 1.0 ml methanol upon short intensive shaking. Our approach avoided the undesired problems related to the manual handling typical of “classical” SPE procedure since the extraction was carried out directly in the HPLC vial. No sample evaporation, reconstitution, or pipetting was required. The nanofibrous disk is affordable, needs no support or holder, and its use avoids creation of plastic waste originating from disposable materials. Recovery of compounds from the disks was 47.2–141.4% depending on the type of polymer used and the relative standard deviations calculated from 5 extractions ranged from 6.1 to 11.8% for poly(3-hydroxybutyrate), 6.3–14.8% for polyurethane, and 1.7–16.2% for polycaprolactone doped with graphene. A small enrichment factor was obtained for polar bisphenol S using all sorbents. A higher preconcentration reaching up to 40-fold was achieved for lipophilic compounds such as deltamethrin when using poly(3-hydroxybutyrate) and graphene-doped polycaprolactone.

Thin disks falling in air

We experimentally investigate the settling of millimetre-sized thin disks in quiescent air. The range of physical parameters is chosen to be relevant to plate crystals settling in the atmosphere: the diameter-to-thickness aspect ratio is$\chi =25\unicode{x2013}60$, the Reynolds numbers based on the disk diameter and fall speed are$Re=O(10^2)$and the inertia ratio is$I^*=O(1)$. Thousands of trajectories are reconstructed for each disk type by planar high-speed imaging, using the method developed by Baker & Coletti (J. Fluid Mech., vol. 943, 2022, A27). Most disks either fall straight vertically with their maximum projected area normal to gravity or tumble while drifting laterally at an angle$<20^\circ$. Two of the three disk sizes considered exhibit bimodal behaviour, with both non-tumbling and tumbling modes occurring with significant probabilities, which stresses the need for a statistical characterization of the process. The smaller disks (1 mm in diameter,$Re=96$) have a stronger tendency to tumble than the larger disks (3 mm in diameter,$Re=360$), at odds with the diffused notion that$Re=100$is a threshold below which falling disks remain horizontal. Larger fall speeds (and, thus, smaller drag coefficients) are found with respect to existing correlations based on experiments in liquids, demonstrating the role of the density ratio in setting the vertical velocity. The data supports a simple scaling of the rotational frequency based on the equilibrium between drag and gravity, which remains to be tested in further studies where disk thickness and density ratio are varied.

The unit for improvement of degenerated mountainside sections

BACKGROUND: The results of RD works on the laboratory prototype of a small disk harrow aimed for operation at mountainsides and capable to improve labor capacity and yield capacity of highland forage lands by 1520% are presented.
 AIMS: The developed laboratory prototype of a module of a mountain tractor-drawn small disk harrow for operation at sections of highland and piedmont areas capable to eliminate weed infestation of soil; to increase fertility and yield capacity of forage lands, to ensure stability of grass areas against deflation and erosion.
 METHODS: The technical examination of the laboratory prototype of the machine was carried out at the highland station of North Caucasian Research Institute of Highland and Piedmont Agriculture in Dargvas village, Republic of North Ossetia-Alania at the altitude of 1540 meters above the sea level and at the slope angle of up to 12. The properties of the testing conditions and the functional properties of unit operation were determined. The technical examination of the scientific documentation of the laboratory prototype of a module of a mountain tractor-drawn small disk harrow for cultivation of soil of highland grass areas was carried out in compliance with the GOST 33687-2015 standard. The subject of the study includes operating tools (the disks), distance between neighboring disks, disk curvature radius, disk diameter as well as the design of operating tools mounting at the frame of a small disk harrow.
 RESULTS: The laboratory prototype of a small disk harrow for soil cultivation at sections of highland and piedmont areas was developed and produced on the basis of a minitractor. The small disk harrow is represented as a tractor-drawn unit with inline arrangement of 9 spherical disks mounted to individual struts. The design of the mountain small disk harrow is provided with the capability of the unit to switch from the right-to-left mountainside operation mode to the left-to-right mountainside operation mode when turning and with the optional mounting of press wheels.
 CONCLUSIONS: Practical use of the module of a small disk harrow ensures reduction of generating processes ofmountainside sections, increases yield capacity of forage lands, ensures stability against water erosion and wind erosion as well as increases environmental stability and efficiency of grassland farming.

Evaluation of Retinal Nerve Fiber Layer and Macular Ganglion Cell Layer Thickness in Relation to Optic Disc Size.

To investigate whether optic nerve ganglion cell amount is dependent on optic disc size, this trial analyzes the correlation between Bruch's membrane opening area (BMOA) and retinal nerve fiber layer (RNFL) thickness as well as macular ganglion cell layer thickness (mGCLT). Additionally, differences in RNFL and mGCLT regarding various optic disc cohorts are evaluated. This retrospective, monocentric study included 501 healthy eyes of 287 patients from the University Hospital Münster, Germany, who received macular and optic disc optical coherence tomography (OCT) scans. Rank correlation coefficients for clustered data were calculated to investigate the relationship between BMOA and thickness values of respective retinal layers. Furthermore, these values were compared between different optic disc groups based on BMOA. Statistical analysis did not reveal a significant correlation between BMOA and RNFL thickness, nor between BMOA and mGCLT. However, groupwise analysis showed global RNFL to be significantly decreased in small and large discs in comparison to medium discs. This was not observed for global mGCLT. This study extends existing normative data for mGCLT taking optic disc size into account. While the ganglion cell amount represented by the RNFL and mGCLT seemed independent of BMOA, mGCLT was superior to global RNFL in displaying optic nerve integrity in very small and very large optic discs.

Kazakhstan Study of the influence of large shear deformations and vortex flow of metal on the formation of an equiaxed ultrafine‑grained structure of the E110 zirconium alloy by the method of RSP

In this work, the task was to investigate the processes of microstructure change occurring in relatively large bulk bars under the action of large plastic deformations. Such large levels of deformation are usually achievable in high pressure twisting of small flat disks, but are difficult to achieve in large bulk bars. The method of radial shear rolling makes it possible to achieve comparable ultrahigh degrees of deformation (~45 mm/mm) in combination with the vortex flow of the metal. Sequential rolling of the E110 zirconium alloy was carried out under extreme conditions on 2 radial shear rolling mills with a total diameter reduction ε = 185 % and a maximum accumulated strain = 46 mm/mm. To assess the level of deformation and its distribution over the section, FEM modeling was carried out in Deform‑3D. The resulting structure was studied by electron microscopy (TEM/SEM). A detailed cross‑sectional study of the EBSD structure was performed with a resolution of 1 mm. A gradient structure with a predominance of an equiaxed ultrafine‑grained structure was found, which was not very pronounced compared to the use of smaller deformations.

Improved Calculation of Hydraulic Conductivity for Small Disk Tension Infiltrometers

AbstractBecause tension infiltrometers apply water through a disk of finite size, the infiltrated water moves laterally as well as downward. Only the vertical component of this flow is indicative of the hydraulic conductivity K, so the algorithm for computing K must include a way of isolating that component from the total flow. Some commonly used formulas correct for the multidimensional effects by subtracting an estimate of the laterally spreading flow. For disks smaller than about 200 mm in diameter, however, lateral spreading constitutes so much of the total flow that these subtractive formulas lose considerable accuracy, and sometimes overcorrect so severely as to produce a negative number for K. Other methods rely on empiricisms that are not completely consistent with unsaturated‐flow theory and that require prior knowledge of certain soil properties. We developed a new formula that uses a multiplicative factor instead of a subtracted term to achieve the needed correction. For testing we conducted numerical experiments with synthetic data produced by solving the Richardson‐Richards equation using the code VS2DRTI, for diverse media and a range of disk sizes, including the widely used 45‐mm diameter. We compared K values calculated from our formula to the actual K used to generate the simulated data, as well as to results from other published formulas. This comparison shows that our method provides an algorithm based in unsaturated‐flow theory that produces more reliable values for small disks without requiring prior knowledge of soil properties.

Sensorium

Sensorium

Models of Rotating Infall for the B335 Protostar

Models of the protostellar source, B335, are developed using axisymmetric three-dimensional models to resolve conflicts found in one-dimensional models. The models are constrained by a large number of observations, including ALMA, Herschel, and Spitzer data. Observations of the protostellar source B335 with ALMA show redshifted absorption against a central continuum source indicative of infall in the HCO+ and HCN J = 4 → 3 transitions. The data are combined with a new estimate of the distance to provide strong constraints to three-dimensional radiative transfer models including a rotating, infalling envelope, outflow cavities, and a very small disk. The models favor ages since the initiation of collapse between 3 × 104 and 4 × 104 yr for both the continuum and the lines, resolving a conflict found in one-dimensional models. The models underpredict the continuum emission seen by ALMA, suggesting an additional component such as a pseudo-disk. The best-fitting model is used to convert variations in the 4.5 μm flux in recent years into a model for a variation of a factor of 5–7 in luminosity over the last 8 yr.

A mixed stirring mechanism for debris discs with giant and dwarf planetary perturbations

ABSTRACT Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and structure. Two key stirring mechanisms – self-stirring by planetesimals and secular perturbation by an external giant planet – have been identified to explain the dynamics of planetesimal belts; their relative importance has been studied independently, but are yet to be considered in combination. In this work, we perform a suite of 286 N-body simulations exploring the evolution of debris discs over 1 Gyr, combining the gravitational perturbations of both dwarf planets embedded in the discs, and an interior giant planet. Our systems were somewhat modelled after the architecture of the outer Solar system: a Solar mass star, a single massive giant planet at 30 au (MGP = 10 to 316 M⊕), and a debris disc formed by 100 massive dwarf planets and 1000 massless particles (MDD = 3.16 to 31.6 M⊕). We present the evolution of both the disc and the giant planet after 1 Gyr. The time evolution of the average eccentricity and inclination of the disc is strongly dependent on the giant planet mass as well as on the remaining disc mass. We also found that efficient stirring is achieved even with small disc masses. In general, we find that a mixed mechanism is more efficient in the stirring of cold debris discs than either mechanism acting in isolation.

Fully soluble polymeric foams for in-vial dried blood spot collection and analysis of acidic drugs by capillary electrophoresis

Polymeric foams tailor-made of polyvinylpyrrolidone (PVP) and carboxymethylcellulose/oxidized 6-carboxycellulose (CMC07/OC) composite were proposed as suitable sorbents for the collection and analysis of dried blood spots (DBSs). The PVP and CMC07/OC foams were easy to prepare, enabled collection of minute volumes of capillary blood, and blood drying at ambient temperature. The resulting foams were prepared as small porous discs with uniform dimensions (approx. 6 × 3 mm) and were fully soluble in aqueous solutions. The DBSs were formed in standard capillary electrophoresis (CE) vials fitted with the soluble foam discs and enabled the direct in-vial DBS processing and at-line analysis by CE. The DBSs were pretreated with a simple process, which involved a complete dissolution of the foam disc in an acidic solution and a simultaneous hollow fiber liquid-phase microextraction (HF-LPME) in one step. The complete solubility of the foam disc with the DBS served for a quantitative transfer of all blood components into the eluate and a nearly exhaustive HF-LPME of target analytes, whereas the blood matrix and the polymeric foam components were efficiently retained by the organic solvent impregnated in the walls of the HF. The suitability of the PVP and CMC07/OC foams for the collection and the direct analysis of DBSs was demonstrated by the HF-LPME/CE determination of model acidic drugs (warfarin, ibuprofen, naproxen, ketoprofen, and diclofenac) at therapeutically relevant concentrations. Repeatability of the analytical method was better than 8.1% (RSD), extraction recoveries ranged from 70 to 99% (for PVP foam), calibration curves were linear over two orders of magnitude (R2 higher than 0.9991), and limits of detection were less than 44 μg/L (for concentrations in undiluted capillary blood). The soluble polymeric foams exhibited non-significant variations in analyte concentrations for DBSs prepared from blood samples with different hematocrit levels and for aged DBSs (less than 9.2%), moreover, they outperformed standard DBS sampling devices in terms of sample pretreatment time and extraction recovery.

Comb-forming roller with elastic rods

A design diagram of comb formation roller in resilient stems is given. Comb-forming roller consists of support and small discs, as well as elastic rods. Elastic rods are installed along the perimeter of the diameter of the disks through their holes. Analytical dependences and mathematical models are obtained for determining the distance between disks, the diameter of disks, the diameter, length and number of elastic rods. One-factor experiments were carried out to substantiate the diameter of the disks and the number of rods. It was found that with the length of the elastic rods of the comb-forming roller 65-75 cm, the diameters of large, medium and small discs, respectively, at least 600mm, 550 mm and 200 mm, the angle of sharpening of the discs within 55-650, the issue of stems within 64 - 69 trimming and diameter bars 3 mm, intensive defeat of chunk and high- quality creation of ridges is ensured.

The link between infall location, early disc size, and the fraction of self-gravitationally fragmenting discs

Context. Many protoplanetary discs are self-gravitating early in their lives. If they fragment under their own gravity, they form bound gaseous clumps that can evolve to become giant planets. Today, the fraction of discs that undergo fragmentation, and therefore also the frequency of conditions that may lead to giant planet formation via gravitational instability, is still unknown. Aims. We study the formation and evolution of a large number of star-disc systems, focusing on the early sizes of the discs and their likelihood to fragment. We investigate how the fraction of discs that fragments depends on the disc-size distribution at early times. Methods. We performed a population synthesis of discs from formation to dispersal. Whilst varying the infall radius, we study the relationship between early disc size and fragmentation. Furthermore, we investigate how stellar accretion heating affects the fragmentation fraction. Results. We find that discs fragment only if they become sufficiently large early in their lives. This size depends sensitively on where mass is added to the discs during the collapse of their parent molecular cloud core. Infall locations derived from pure hydrodynamic and non-ideal magnetised collapse simulations lead to large and small discs, respectively, and 22 and 0% fragmentation fractions, respectively, in populations representative of the initial mass function; however, the resulting synthetic disc size distribution is larger and smaller, respectively, than the observed Class 0 disc size distribution. By choosing intermediate infall locations, leading to a synthetic disc size distribution that is in agreement with the observed one, we find a fragmentation fraction of between 0.1 and 11%, depending on the efficiency of stellar accretion heating of the discs. Conclusions. We conclude that the frequency of fragmentation is strongly affected by the early formation process of the disc and its interaction with the star. The early disc size is mainly determined by the infall location during the collapse of the molecular cloud core and controls the population-wide frequency of fragmentation. Stellar accretion heating also plays an important role in fragmentation and must be studied further. Our work is an observationally informed step towards a prediction of the frequency of giant planet formation by gravitational instability. Upcoming observations and theoretical studies will further our understanding of the formation and early evolution of discs in the near future. This will eventually allow us to understand how infall, disc morphology, giant planet formation via gravitational instability, and the observed extrasolar planet population are linked.

JWST’s PEARLS: A JWST/NIRCam View of ALMA Sources

We report the results of James Webb Space Telescope/NIRCam observations of 19 (sub)millimeter sources detected by the Atacama Large Millimeter Array (ALMA). The accurate ALMA positions allowed unambiguous identifications of their NIRCam counterparts. Taking gravitational lensing into account, these represent 16 distinct galaxies in three fields and constitute the largest sample of its kind to date. The counterparts’ spectral energy distributions cover from rest-frame ultraviolet to near-IR and provide photometric redshifts (1 < z < 4.5) and stellar masses (M * > 1010.5 M ⊙), which are similar to submillimeter galaxies (SMGs) studied previously. However, our sample is fainter in (sub)millimeter than the classic SMG samples are, and our sources exhibit a wider range of properties. They have dust-embedded star formation rates as low as 10 M ⊙ yr−1, and the sources populate both the star-forming main sequence and the quiescent categories. The deep NIRCam data allow us to study the rest-frame near-IR morphologies. Excluding two multiply imaged systems and one quasar, the majority of the remaining sources are disk-like and show either little or no disturbance. This suggests that secular growth is a potential route for the assembly of high-mass disk galaxies. While a few objects have large disks, the majority have small disks (median half-mass radius of 1.6 kpc). At this time, it is unclear whether this is due to the prevalence of small disks at these redshifts or some unknown selection effects of deep ALMA observations. A larger sample of ALMA sources with NIRCam observations will be able to address this question.

Deterministic Modeling for Radiation Attenuation-integrated Radon Transform in Emission Computed Tomography: Algorithm, Curve Fitting Analysis, and Introduction of Attenuation Hadamard Matrix.

The purpose of the study is to propose an algorithm to implement and visualize radiation attenuation-integrated Radon transform based on Beer-Lambert law during emission computed tomography simulation using a deterministic model and also to perform image analysis on resulting images. Two types of phantoms are designed: plain-disk phantom and patterned-disk phantom. The large disk is filled with an activity of 5 units and the smaller disks have 10 units of activity of 99mTc isotope as an emission map. Three transmission maps for patterned-disk phantom are created with uniform linear attenuation coefficient. Phantoms are scanned with 360° and 180° acquisition arcs. Then, using the algorithm designed, the exponential Radon transform is implemented. After that, the projections are back-projected and filtered to generate tomographic slices. Finally, all slices are analyzed using profile plotting and curve fitting. Moreover, an attenuation Hadamard matrix is provided to facilitate attenuation modeling. The uniform intensity of activity in the phantoms is converted to a disk with progressively decreasing intensity from the periphery to the center in the tomographic slices. Similarly, the circles positioned more centrally appear less intense than those positioned in the periphery, despite all circles having equal activity. When the phantom is scanned in 180° arc, the circles closest to the camera are visualized more intensely. The profile curves of the slices generated by exponential Radon transformation are depicted as U-shaped in profile plotting and are fitted to a bi-exponential function with a near-perfect precision. The incorporation of radiation attenuation results in the development of more realistic models for quantification purposes.

The Plastic Bag Store (Excerpt)

The Plastic Bag Store (Excerpt)

Blockage coefficient of cylindrical blocker and diffusion resistance of membrane channels.

This study deals with potential flow of ideal fluid in an infinite cylindrical tube in the presence of a blocking object. The blockage effect of the object on the flow can be characterized by a lump parameter, blockage coefficient, which accounts for the object shape and size. For a cylindrical blocking object, analytical results for the blockage coefficient are known only in three limiting cases: for a long thin cylinder and for small and large blocking disks. We propose a simple analytical expression for the blockage coefficient of a cylindrical blocker of arbitrary length and radius that reduces to the known asymptotic results in the corresponding limits.

Stripline Y-Junction Circulators: Accurate Model and Electromagnetic Analysis Based on Gaussian Field Distribution Boundary Conditions

The conventional analysis of the circulator usually ignores ferrite disk thickness by assuming no axial variation, where the outcomes are limited to the case of small thickness ferrite disks. However, a typical scenario of a stripline Y-junction circulator has a ferrite disk thickness equal to that of the substrate. As a result, the assumption of a constant field along the feed-linewidth does not account for a realistic boundary condition. Increasing the ferrite thickness results in a significant variation in the field along the perimeter of the ferrite disk, which must be considered for accurate modeling and analysis. In this article, modeling of the Y-junction stripline circulator is proposed and investigated using Gaussian field distribution (GFD) boundary conditions. The proposed analysis takes into account the effects of ferrite thickness that controls both the field distribution and the demagnetization factor. The proposed analysis is applied to the case of a single ferrite disk and validated through a comparison between the analytical and simulation results conducted using a 3-D electromagnetic solver in different frequency bands. An excellent agreement is observed between the simulated and analytical results, highlighting the limitations of the conventional analysis methodology.