Thin Segments Research Articles

Unstable behavior of segmental ring under various pressures and its discrete element simulation.

In February 2012, a serious accident which resulted in five fatalities happened during a TBM-tunnel construction under the seabed in Japan. The cause of the accident appeared to be due to the Key-segment slipping out of the segment ring by the thrusting tailskin (wire brushes) of the TBM into the segment ring. This resulted in the collapse of the rings, causing the seabed ground and seawater to flow into the tunnel. We investigated how thin and thick segments without any circumferential joints behave under isotropic and anisotropic pressures using small-scale physical model. In the model tests, pressures were applied to the surroundings of the segment rings and the strains at each segment were measured in order to evaluate the damage. In addition, cases where lubrication on the contact area between the K- and B-segments was present or not were investigated and their discrete element simulations were also conducted.

Fundamentals of laminar free convection in internally heated fluids at values of the Rayleigh–Roberts number up to

Motions in the solid mantle of silicate planets are predominantly driven by internal heat sources and occur in laminar regimes that have not been systematically investigated. Using high-resolution numerical simulations conducted in three dimensions for a large range of Rayleigh–Roberts numbers ($5\times 10^{3}\leqslant Ra_{H}\leqslant 10^{9}$), we have determined the characteristics of flow in internally heated fluid layers with both rigid and free slip boundaries. Superficial planforms evolve with increasing $Ra_{H}$ from a steady-state tessellation of hexagonal cells with axial downwellings to time-dependent clusters of thin linear downwellings within large areas of nearly isothermal fluid. The transition between the two types of planforms occurs as a remarkable flow polarity reversal over a small $Ra_{H}$ range, such that downwellings go from isolated cylindrical structures encircled by upwellings to thin interconnected linear segments outlining polygonal cells. In time-dependent regimes at large values of $Ra_{H}$, linear downwellings dominate the flow field at shallow depth but split and merge at intermediate depths into nearly cylindrical plume-like structures that go through the whole layer. With increasing $Ra_{H}$, the number of plumes per unit area and their velocities increase whilst the amplitude of thermal anomalies decreases. Scaling laws for the main flow characteristics are derived for $Ra_{H}$ values in a $10^{6}$–$10^{9}$ range. For given $Ra_{H}$, plumes are significantly colder, narrower and wider apart beneath free boundaries than beneath rigid ones. From the perspective of planetary studies, these results alert to the dramatic changes of convective planform that can occur along secular cooling.

Automatic liver vessel segmentation using 3D region growing and hybrid active contour model

This paper proposes a new automatic method for liver vessel segmentation by exploiting intensity and shape constraints of 3D vessels. The core of the proposed method is to apply two different strategies: 3D region growing facilitated by bi-Gaussian filter for thin vessel segmentation, and hybrid active contour model combined with K-means clustering for thick vessel segmentation. They are then integrated to generate final segmentation results. The proposed method is validated on abdominal computed tomography angiography (CTA) images, and obtains an average accuracy, sensitivity, specificity, Dice, Jaccard, and RMSD of 98.2%, 68.3%, 99.2%, 73.0%, 66.1%, and 2.56 mm, respectively. Experimental results show that our method is capable of segmenting complex liver vessels with more continuous and complete thin vessel details, and outperforms several existing 3D vessel segmentation algorithms.

Thin Limbs of Henle and Inner Medullary Collecting Ducts are the Major Points of Flow Resistance Along the Renal Tubule

The driving force for flow along the nephron and collecting ducts is generally thought to derive from the pressure in the glomerular capsule (Bowman's space). In superficial nephrons of rats, the glomerular capsular pressure has been reported to be 12–13 mmHg under euvolemic conditions. To test the adequacy of this driving force, we calculated the theoretical pressure drop along each segment of the rat superficial renal tubule using the Hagen‐Poiseuille laminar flow equation with measured flow rates, tubule diameters, and tubule lengths. We used both a rigid tube model and an elastic tube model based on compliances from the literature. The rigid tube model predicted a net pressure drop from glomerular capsule to renal pelvis of 8.8 mmHg during antidiuresis and 15.5 mmHg during water diuresis. The latter value exceeds the measured value in the glomerular capsule. In contrast, the elastic tube model predicted a 9.5 mmHg pressure drop along the length of the renal tubule during water diuresis. In both models, the greatest flow resistance (pressure drop per unit length) was in the thin descending limb of Henle's loop and the final millimeter of the inner medullary collecting duct. We extended the elastic tube model during water diuresis to long‐looped nephrons (those with loops of Henle extending into the inner medulla). The predicted net tubular pressure drop for these nephrons was 18.3–20.3 mmHg depending on the location of the loop bend. The calculated overall flow resistance was higher in deep nephrons chiefly due to the thin descending and thin ascending limbs of Henle's loop. We do not have reliable glomerular capsular pressure values for deep nephrons. However, the glomerular capsular pressures in deep nephrons are unlikely to be substantially higher than in superficial nephrons because the single‐nephron glomerular filtration rate in deep nephrons is equal to or greater than in superficial nephrons. Thus, the calculated glomerular capsular pressure is 6–8 mmHg higher than the likely actual value with the elastic tube model. This leaves an apparent discrepancy that could be explained either by 1) an underestimate of the compliance of the thin limb segments of the long‐looped nephrons; or 2) an additional driving force for flow such as the peristaltic action of the renal pelvic contractions, which could boost the flow across the restriction points in the thin descending limbs and inner medullary collecting duct.Support or Funding InformationG.G. was a member of the 2017 NIH Summer Internship Program. V.D. was a member of the 2017 Biomedical Engineering Student Internship Program at the NIH.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Tissue factor levels and the fibrinolytic system in thin and thick intraluminal thrombus and underlying walls of abdominal aortic aneurysms

BackgroundThe hemostatic system cooperates with proteolytic degradation in processes allowing abdominal aortic aneurysm (AAA) formation. In previous studies, it has been suggested that aneurysm rupture depends on intraluminal thrombus (ILT) thickness, which varies across each individual aneurysm. We hypothesized that hemostatic components differentially accumulate in AAA tissue in relation to ILT thickness. Thick (A1) and thin (B1) segments of ILTs and aneurysm wall sections A (adjacent to A1) and B (adjacent to B1) from one aneurysm sac were taken from 35 patients undergoing elective repair. MethodsFactor levels were measured using enzyme-linked immunosorbent assay of protein extract. ResultsTissue factor (TF) activities were significantly higher in thinner segments of AAA (B1 vs A1, P = .003; B vs A, P < .001; B vs A1, P < .001; B vs B1, P = .001). Significantly higher tissue plasminogen activator was found in thick thrombus-covered wall segments (A) than in B, A1, and B1 (P = .015, P < .001, and P < .001, respectively). Plasminogen concentrations were highest in ILT. Concentrations of α2-antiplasmin in thin ILT adjacent walls (B) were higher compared with wall (A) adjacent to thick ILT (P = .021) and thick ILT (A1; P < .001). Significant correlations between levels of different factors were mostly found in thick ILT (A1). However, no correlations were found at B sites, except for a correlation between plasmin and TF activities (r = 0.55; P = .004). ConclusionsThese results suggest that higher TF activities are present in thinner AAA regions. These parameters and local fibrinolysis may be part of the processes leading to destruction of the aneurysm wall.

Deterministic figure correction of piezoelectrically adjustable slumped glass optics

Thin x-ray optics with high angular resolution (≤ 0.5 arcsec) over a wide field of view enable the study of a number of astrophysically important topics and feature prominently in Lynx, a next-generation x-ray observatory concept currently under NASA study. In an effort to address this technology need, piezoelectrically adjustable, thin mirror segments capable of figure correction after mounting and on-orbit are under development. We report on the fabrication and characterization of an adjustable cylindrical slumped glass optic. This optic has realized 100% piezoelectric cell yield and employs lithographically patterned traces and anisotropic conductive film connections to address the piezoelectric cells. In addition, the measured responses of the piezoelectric cells are found to be in good agreement with finite-element analysis models. While the optic as manufactured is outside the range of absolute figure correction, simulated corrections using the measured responses of the piezoelectric cells are found to improve 5 to 10 arcsec mirrors to 1 to 3 arcsec [half-power diameter (HPD), single reflection at 1 keV]. Moreover, a measured relative figure change which would correct the figure of a representative slumped glass piece from 6.7 to 1.2 arcsec HPD is empirically demonstrated. We employ finite-element analysis-modeled influence functions to understand the current frequency limitations of the correction algorithm employed and identify a path toward achieving subarcsecond corrections.

Changes in Myosin Heavy Chain Isoforms Along the Length of Orbital Fibers in Rabbit Extraocular Muscle.

Extraocular muscles express 10 myosin heavy chain (MyHC) isoforms that cater for a wide range of contractile speeds. We aim to characterize the variations in MyHC expression along the length of singly (SIFs) and multiply innervated fibers (MIFs) in the orbital layer of rabbit superior rectus muscle. Monospecific antibodies to nine MyHCs, including an anti-slow-tonic antibody characterized here were used to immunohistochemically map variations in MyHC distribution in serial sections along the muscle's full length. The fastest MyHC, EO, is expressed at the endplate zone (EPZ) of SIFs, flanked proximally and distally by segments expressing the slower 2A, with or without embryonic MyHC. MIFs with constant diameter express α-cardiac MyHC at the EPZ, flanked by segments co-expressing α-cardiac/embryonic and possibly slow-tonic MyHCs. MIFs with varying diameter also express α-cardiac MyHC at the EPZ in their thin, central region, flanked by thin segments co-expressing α-cardiac/embryonic MyHCs, with long proximal and distal extensions of larger diameter that co-express embryonic/slow-tonic and α-cardiac or β/slow MyHCs. Orbital fiber types express multiple MyHCs, with faster ones in SIFs, slower ones in MIFs, but all have fast EPZs and slower end segments. We hypothesize that these unique MyHC distributions enable these fibers to relax in two kinetically distinct phases while acting in an antagonistic manner during a saccade: the fast phases facilitate acceleration of eyeball rotation during agonist contraction, while the slow phases help its deceleration toward the visual target, thereby linearizing the saccade. These properties also facilitate pulley movements to implement Listing's law.

Low-temperature synthesis of large-area graphene-based carbon films on Ni

In this work, large-area graphene-based carbon films were synthesized through a fast and low-temperature method. The processing route is illustrated on a free surface of Ni catalyst film by vacuum thermal processing of amorphous carbon. Key in the novel approach is that the synthesis is done at low temperatures, i.e. below 350°C, and within a time as short as 1min. The nucleation and growth of graphene on the free surface of nickel and along the interface between Ni film and SiO2 substrate are investigated by using a thin film Ni-C-Ni sandwiched structure on a SiO2/Si substrate. Raman spectroscopy demonstrates that the graphene-based carbon films consist of graphitic carbon rich of defects. HR-TEM observations reveal that the graphene-based carbon film grown on the top free surface is composed of thin multilayer graphene segments (3–6 atomic layers) and thick multilayer graphene segments (more than atomic 10 layers), covering the entire surface of Ni film over a large area. Growth parameters such as growth time, growth temperature and carbon/Ni ratio are reported in detail for a control of graphene growth kinetics. The results point at several attractive strategies for the facile synthesis of graphene-based carbon films for industrial applications.

Composition and diameter modulation of magnetic nanowire arrays fabricated by a novel approach

Straight magnetic nanowires composed of nickel and permalloy segments having different diameters are synthesized using a promising approach. This approach involves the controlled electrodeposition of each magnetic material into specially designed diameter-modulated porous alumina templates. Standard alumina templates are exposed to pore widening followed by a protective coating of the pore wall with ultrathin silica and further anodization. Micromagnetic simulations are employed to investigate the process of magnetization reversal in the fabricated nanowires when the magnetic materials exchange their places in the thick and thin segments. It is found that the magnetization reversal occurs by the propagation of transverse domain wall (DW) when the thick segment is composed of permalloy. However, the reversal process proceeds by the propagation of vortex DW when permalloy is located at the thin segment.

Fast occlusion processing for a polygon-based computer-generated hologram using the slice-by-slice silhouette method.

In a polygon-based computer-generated hologram (CGH), the three-dimensional (3D) model is represented as a polygon, which consists of numerous small facets. Lighting effect, material texture, and surface property can be included in the polygonal model, which enables polygon-based CGH to realize high-fidelity 3D display. On the other hand, the occlusion effect is an important depth cue for 3D display. In polygon-based CGH, however, occlusion processing is difficult and time-consuming work. In this paper, we proposed a simple and fast occlusion processing method, the slice-by-slice silhouette (S3) method, for generating the occlusion effect in polygon-based CGH. In the S3 method, the polygonal model is sliced into multiple thin segments. For each segment, a silhouette mask is generated and located at the backside of the segment. The incident light is first shaded by the mask and superimposes on the light emitted from the facets of the evaluated segment. In this way, every segment can be processed sequentially to get the resulting object light. Our experimental result demonstrates that the S3 method can generate a high-definition hologram with qualified occlusion effect. The computing complexity of the S3 method is lower than that of previous methods. In addition, the S3 method can be parallelized easily, and thus can be further speeded up by applying a parallel computing framework, such as multi-core CPU or GPU.

04.11: Strength enhancement in axially compressed cylinders with stepped walls

ABSTRACTMetal silos and tanks are subject to loading that increases progressively from the top to the base of the cylindrical shell. Efficient design calls for progressive increases in wall thickness, but metal sheets are made in discrete thicknesses. For silos, buckling under axial compression is the dominant design condition, whilst in tanks axial compression with internal pressure may also be critical. The step increases in wall thickness mean that the most critical point on the wall is always at the base of one strake of uniform thickness, so the location of a critical buckle is expected to be at or just above a change of thickness. Until now, design rules have always ignored the effect of the thicker lower strake in restraining the axial compression buckle above it, and the requirement for buckles to have a finite size.Whilst this effect has previously been noted [1,2], it has never been systematically studied. In this paper, a first thorough study is presented, which shows that the strength enhancement associated with a change of plate thickness can be considerable (over 40%). The presented information addresses the buckling of imperfect shells, and includes both elastic and plastic conditions. The findings are sufficient to produce a modification of the current design rules for buckling under axial compression, giving designers the freedom to extend their thin shell segments deeper in the silo or tank structure.

Delivery modes and their influencing factors of pregnant women with previous cesarean section: a retrospective study of 474 gravidas

Objective To investigate the safety of vaginal delivery in gravidas with previous cesarean section and its influencing factors. Methods Four hundred and seventy-four full-term gravidas who received cesarean section at the Department of Obstetrics and Gynecology of Peking University First Hospital from January 1, 2012 to August 31, 2014 were enrolled in this study. Among those subjects, 38 who underwent successful vaginal delivery were grouped into vaginal birth after cesarean (VBAC) group, and the other 436 accepting repeated cesarean section were grouped into cesarean group. Delivery outcomes and maternal/neonatal complications of the two groups were retrospectively analyzed with two-sample t-test and Chi-square test. Results Among the 45 patients (9.5%) who attempted VBAC, seven underwent cesarean section for suspected fetal distress and the other 38 (84.4%) succeeded in vaginal birth without uterine rupture. The amount of postpartum hemorrhage in patients of cesarean group was more than that of VBAC group [(330.8±94.8) vs (257.7±199.7) ml, t=2.021, P<0.01] after exclusion of three patients with dangerous placenta previa, and the postpartum hospital stay was shorter than that of cesarean group [(2.5±1.4) vs (4.5±1.3) d, t=7.952, P<0.01]. There were three newborns with neonatal asphyxia, twelve with neonatal infections and forty transferred to the Pediatrics Department following cesarean section. Besides, complications of headache and urinary retention occurred in 20 and 32 mothers after cesarean section, respectively. However, no complication occurred in VBAC group. Sixty-three cesarean sections were indicated as thin lower uterine segment and among them, fourteen (22.2%) had muscular rupture. Among the six patients who complained of tenderness in lower uterine segment, three were found having muscular rupture during cesarean section. Conclusion VBAC is an option for gravidas with history of cesarean section only if they meet the criteria for VBAC attempt. VBAC could lower the cesarean section rate without increase the incidence of complications. The rate of trial of labor after cesarean was low, patients education should be strengthened to increase it. Key words: Vaginal birth after cesarean; Trial of labor; Premature rupture of fetal membranes; Natural childbirth

Morphological Evidence of Telocytes in Canine Inferior Vena Cava

Telocytes (TCs) are a distinctive population of stromal cells extending special long prolongations with thin segments (podomers) and dilations (podoms). They have been identified in various organs and tissues of multispecies organisms. TCs have been identified in large arteries. The present study aimed to explore whether TCs also exists in large veins by Transmission Electron Microscope (TEM). The results indicated that TCs indeed exist in inferior vena cava, which are a newly recognized compartment distinct from other interstitial cells in large veins. The TCs in inferior vena cava are mainly located in subendothelium and apparently different from the TCs in large artery, which exist in the tunica adventitia and adjacent to the outer elastic lamina. The characteristic morphological features of Tps in inferior vena cava were identified: the presence of secondary lysosomes and endoplasmic reticulum.

New Description of Telocyte Sheaths in the Bovine Uterine Tube: An Immunohistochemical and Scanning Microscopic Study

Telocytes are a special type of interstitial cells characterized by distinctive cellular extensions with alternating thin segments (podomers) and dilations (podoms). Telocytes establish contact with various cells and structures, but their role in the regulation of the function of many cell types is still obscure. The aim of the current study was to investigate the morphology, histochemistry, and immunohistochemistry of telocytes, and their distribution, organization, and morphometric measurements in different layers of the adult bovine uterine tube. Telocytes showed positive immunostaining for CD117, S-100 protein, vimentin, desmin, α-smooth muscle actin, tubulin, laminin, estrogen receptor-α, and progesterone receptor. They were organized in different types of sheaths: subepithelial, inner/outer perimuscular, and intramuscular sheaths. Telocytes were scattered in the lamina propria, in the muscular layer, and the serosa. According to their size, they were grouped into different types of telocytes: small, large, and giant telocytes. Small telocytes were the most common type and located in all layers; large telocytes were observed in the epithelium, lamina propria, and inner/outer perimuscular and intramuscular sheaths, and giant telocytes were found in the external layer of the outer perimuscular sheath. Telocytes were connected by thin and thick telopodes (fenestrated membranes). Fenestrated membranes enabled connections between telocytes along the entire muscular wall of the uterine tube. Telocytes established an extensive biological network of different types of cells and structures, including epithelial, muscular, and mast cells, blood vessels, glomus, and nerve fibers. We hypothesize that telocytes help to organize the functional coordination between different types of cells in the uterine tube.

Ultrastructural evidence for impaired mitochondrial fission in the aged rhesus monkey dorsolateral prefrontal cortex

Dorsolateral prefrontal cortex mediates high-order cognitive functions that are impaired early in the aging process in monkeys and humans. Here, we report pronounced changes in mitochondrial morphology in dendrites of dorsolateral prefrontal cortex neurons from aged rhesus macaques. Electron microscopy paired with 3D reconstruction from serial sections revealed an age-related increase in mitochondria with thin segments that intermingled with enlarged ones, the ‘mitochondria-on-a-string’ phenotype, similar to those recently reported in patients with Alzheimer's disease. The thin mitochondrial segments were associated with endoplasmic reticulum cisterns, and the mitochondrial proteins Fis1 and Drp1, all of which initiate mitochondrial fission. These data suggest that the ‘mitochondria-on-a-string’ phenotype may reflect malfunction in mitochondrial dynamics, whereby fission is initiated, but the process is incomplete due to malfunction of subsequent step(s). Thus, aged rhesus monkeys may be particularly helpful in exploring the age-related changes that render higher cortical circuits so vulnerable to degeneration.

Coupled, Simultaneous Displacement and Dealloying Reactions into Fe-Ni-Co Nanowires for Thinning Nanowire Segments.

A new methodology is reported to shape template-assisted electrodeposition of Fe-rich, Fe-Ni-Co nanowires to have a thin nanowire segment using a coupled displacement reaction with a more noble elemental ion, Cu(II), and at the same time dealloying predominantly Fe from Fe-Ni-Co by the reduction of protons (H+), followed by a subsequent etching step. The displacement/dealloyed layer was sandwiched between two trilayers of Fe-Ni-Co to facilitate the characterization of the reaction front, or penetration length. The penetration length region was found to be a function of the ratio of proton and Cu(II) concentration, and a ratio of 0.5 was found to provide the largest penetration rate, and hence the larger thinned length of the nanowire. Altering the etching time affected the diameter of the thinned region. This methodology presents a new way to thin nanowire segments connected to larger nanowire sections and also introduces a way to study the propagation of a reaction front into a nanowire.

Effect of Melatonin on Telocytes in the Seminal Vesicle of the Soay Ram: An Immunohistochemical, Ultrastructural and Morphometrical Study

Telocytes (TCs) are a special type of interstitial cell with characteristic cellular processes that are described in many organs. The current study aimed to investigate TCs in seminal vesicles of the Soay ram responding to melatonin treatment during the nonbreeding season by conventional immunohistochemical stains, and to detect the ultrastructural and morphometrical changes of TCs. TCs in the control group showed a broad range of staining affinity and also reacted positively to CD117/c-kit, CD34, desmin, S-100 protein, and progesterone and estrogen receptors alpha, while after melatonin treatment a strong reaction against these 6 antibodies was recorded. Electron microscopically, TCs in the control group were characterized by a small cell body with distinct long cytoplasmic extensions called telopodes (Tps). Tps had alternation of the thin segment (podomers) and dilated segments (podoms), in which the latter accommodate mitochondria, rough endoplasmic reticulum and caveolae. TCs and their Tps were interconnected by homo- and heterocellular junctions and form a wide network to communicate between different cell types. Tps showed close contact with immune cells, progenitor stem cells, smooth muscle cells and other interstitial cells. Melatonin caused a significant increase in the number of TCs, length of Tps, and number and diameter of secretory vesicles. Also, the melatonin-treated group showed exaggerated secretory activity in the form of a massive release of secretory vesicles from Tps. Moreover, Tps showed an increase in their contact with blood and lymphatic capillaries, nerve endings and Schwann cells. In addition, the shedding of secretory structures (exosomes, ectosomes, and multivesicular bodies) was greater from Tps, which were involved in paracrine signaling in the melatonin-treated group. The length and ramifications of Tps together with the intercellular junctions and the releasing of shed vesicles or exosomes assumed an essential role of TCs in intercellular signaling and coordination. On the basis of their distribution and morphology, we investigated whether the different locations of TCs could be associated with different roles.

Magnetic field created by a conducting cylindrical shell of finite length

A conceptually simple result, which was recently derived for the circulation of the magnetic field created by a finite portion of wire carrying a slowly varying current, is used with the superposition principle and symmetry considerations to obtain an expression for the magnetic field of a thin cylindrical shell of finite length. This expression is combined with a new formula for an oblique solid angle, to obtain closed form solutions for the magnetic field created by the thin cylindrical shell segment in all regions of space. The solutions derived herein are applied in the limiting situations where the cylindrical shell’s length or radius is very large and compared to the known results for the magnetic field of a long conducting tube, and of an infinite plane, respectively. In addition, the use of physical principles of superposition and symmetry in this study is instructive from an educational perspective.

Electron-hole interactions in coupled InAs-GaSb quantum dots based on nanowire crystal phase templates

We report growth and characterization of a coupled quantum dot structure that utilizes nanowire templates for selective epitaxy of radial heterostructures. The starting point is a zinc blende InAs nanowire with thin segments of wurtzite structure. These segments have dual roles: they act as tunnel barriers for electron transport in the InAs core, and they also locally suppress growth of a GaSb shell, resulting in coaxial InAs-GaSb quantum dots with integrated electrical probes. The parallel quantum dot structure hosts spatially separated electrons and holes that interact due to the type-II broken gap of InAs-GaSb heterojunctions. The Coulomb blockade in the electron and hole transport is studied, and periodic interactions of electrons and holes are observed and can be reproduced by modeling. Distorted Coulomb diamonds indicate voltage-induced ground-state transitions, possibly a result of changes in the spatial distribution of holes in the thin GaSb shell.

EP19.08: Clinical outcome of pregnant women with a previous Caesarean section and an extremely thin lower uterine segment

EP19.08: Clinical outcome of pregnant women with a previous Caesarean section and an extremely thin lower uterine segment