Perpendicular Junctions Research Articles

The perpendicular gyroscope: modal analysis of plate, beam and gyroscope multistructures.

This paper presents a study of the perpendicular gyroscope, which is formed of two orthogonal beams, a flexural plate and a gyroscope. Two sets of chiral-torsional boundary conditions are derived to analytically model the dynamic effects of the gyroscope while taking into account the broken symmetries of the system. The perpendicular junction causes the coupling of the compressional, flexural and torsional displacements in the system. This complex behaviour is accounted for with a comprehensive set of kinematic and dynamic junction conditions. Modal analysis demonstrates the fully coupled system and reveals how the spinning gyroscope induces dynamic chiral Chladni patterns in the plate.This article is part of the theme issue 'Current developments in elastic and acoustic metamaterials science (Part 2)'.

#2795 In-silico assessment of arteriovenous fistula maturation with patient-specific computational hemodynamic models

Abstract Background and Aims Native arteriovenous fistula (nAVF) is the preferred access for haemodialysis (HD) treatment. Both the quality and complications of the haemodialysis technique are closely related to vascular access. nAVF maturation process includes several morphological changes affecting haemodynamics, with previous studies suggesting that it is highly related to AVF failure. Computational Fluid Dynamics (CFD) simulations by using idealized morphologies or the analysis of one patient-specific geometry have been proposed to understand the pathophysiology of maturation failure. However, it is difficult to correlate with clinical practice and therefore limits its use. The aim is to develop a patient-specific modelling time pipeline, incorporating the haemodynamics of the blood flow to real anatomical and morphological characteristics. Method Design: prospective computational simulation analysis of nAVF in 3 patients at 3 different stages: after fistula creation, (1 week), maturation (1 month) and post-maturation (6 months). Analysis: morphological and haemodynamic. Inclusion criteria: >18 years and end-stage chronic kidney disease. Variables and data: Once morphology was extracted from nAVF magnetic resonance imaging, generated meshes were refined and compiled to obtain a volumetric mesh. The boundary conditions of the model were defined and extracted using ultrasound nAFV data. Data were analyzed at the 3 stages. Models: A 3-element Windkessel model was used to simulate the pressure waveform to feed the vein of the system. In this model, clinical data were also considered to classify the patient as normotensive or hypertensive to estimate waveform parameters. The Windkessel model estimates wall shear stress (WSS), velocity and flow for all the points located in the mesh by making an analogy from an electric circuit resistance model. As validation, the flow obtained from the Windkessel model was compared with the one obtained from the ultrasound scan of the patient. Results Different temporal points were analyzed for each nAVF. Results from the simulations in Fig. 1, illustrating the evolution over time and development. The geometrical characteristics were found to significantly impact on flow dynamics. The area most affected by flow was the juxta-anastomotic section which showed higher magnitude distribution of WSS and velocity for all time-points. According to the analysis of the simulations, a perpendicular junction between the vein and the artery potentially resulted in less damage in this area (in WSS terms), being important to mitigate the AVF failure. At maturation stage (1 month) the analysis shows WSS distribution mainly located in the juxta-anastomotic section and decreased in magnitude regarding one week; therefore, this can be marked as the stabilization point for nAFV maturation. Conclusion

Connecting effect on the charge transport and nonlinear optical properties of heteronanotubes

Carbon/boron nitride heteronanotubes are now at the centre of experimental and theoretical studies because of their tunable properties and diverse applications. Herein, we investigate the charge transport and optical properties of carbon/boron nitride hybrid single- and double-walled nanotubes on the basis of first-principles calculations. Our results reveal that the C/BN heterojunctions with radial junctions parallel (horizontal) to the tube axis have more effects than the perpendicular (vertical) junctions on the charge transport properties of heteronanotubes. Furthermore, we find that the nonlinear optical response can be meaningfully controlled by altering the C/BN content and junction arrangement. In double-walled coaxial heteronanotubes, the interwall interaction is also found to increase the electron and hole transport rates noticeably and to have a major effect on the first hyperpolarizabilities of C/BN heteronanotubes. In contrast with coaxial carbon nanotubes, where the inner constituent is totally shielded by the outer tube, in our studied C/BN coaxial heteronanotubes, the inner shell is only partially shielded by the outer constituent. This study suggests a strategy to high-efficient design heteronanotubes with high charge transport properties and tunable nonlinear optical responses. Moreover, the designed C/BN heteronanotubes can discrete electrons and holes, suggesting their application in solar cell materials.

MgGa2O4 as alternative barrier for perpendicular MRAM junctions and VCMA

The CoFeB/MgO/CoFeB magnetic tunnel junction (MTJ) is the central element of any high performance perpendicular Magnetoresistive Random Access Memory (MRAM) device. The MgO tunnel barrier, in contact with CoFeB films at both sides in the magnetic tunnel junction, provides a high tunnel magneto resistance (TMR) and perpendicular magnetic anisotropy (PMA) thanks to the high crystalline quality of the MgO/CoFeB interface achieved upon post-deposition annealing. We study MgGa2O4 as an alternative barrier material due to its lower bandgap and show how to introduce it into state-of-the-art perpendicular MRAM stacks. We demonstrate that thin MgO films at both sides of the barrier are key to ensure a proper crystallization and induce reference layer and free layer perpendicular magnetic anisotropy. Consequently, a stack incorporating a MgGaxOy barrier with full PMA and TMR > 100% can be fabricated with a resistance-area (RA) product as low as 50 Ω μm2, which is of strong interest as a potential barrier in the field of voltage control magnetic anisotropy MRAM.

Biofilm distribution on tympanostomy tubes: An ex vivo descriptive study

BackgroundTympanostomy tube (TT) insertion is a common procedure in children with otitis media with effusion. Post-TT otorrhea (PTTO) is a frequent post-operative complication. Biofilms are involved in chronic PTTO cases. ObjectiveTo describe and qualitatively analyze the geometry and sites prone to biofilms on removed TTs, relatively to their position in the ear, past medical/surgical history and PTTO presence. MethodsBiofilms presence and topographic distribution on TTs were ex vivo evaluated by using scanning electron microscope, confocal microscope and stereo-microscope. ResultsForty-eight TTs from 30 children were analyzed. Indications for removal were: 71% due to retained TTs (average time from insertion: 24.4 ± 15.1 months), 23% due to chronic PTTO, and 6% due to TT obstruction/dysfunction. Different types of bacterial biofilms were detected on all TTs, regardless the time from their insertion nor their types. Biofilms were observed more on the perpendicular junction and on the internal lumen, and more biofilm colonies were detected on the medial part, facing the middle ear mucosa. TTs removed from children with PTTO exhibited more biofilm colonies when compared to their peers. Of the 16 children who underwent adenoidectomy concomitantly with TT insertion, 10 (62%) children were sent for TT removal due to retained TTs, and 6 (38%) children due to chronic PTTO (p = 0.03). ConclusionDescriptive analysis of biofilm topographic distribution demonstrated adhesions on specific TT areas: perpendicular junctions and the internal lumen. Such “prone zones” may be the future target areas for changes in TT geometry or can be specifically coated with anti-biofilm materials.

Role of Biofilms in Post-Tympanostomy Tube Otorrhea.

Nearly half of children who undergo tympanostomy tube (TT) insertion may experience otorrhea following surgery. We sought to review the evidence for the role of bacterial biofilms in post-tympanostomy tube otorrhea (PTTO) and the accumulated experience regarding the preventive measures for biofilm formation/adhesion on TTs. English literature search for relevant MeSH keywords was conducted in the following databases: MEDLINE (via PubMed), Ovid Medline, Google Scholar, and Clinical Evidence (BMJ Publishing) between January 1, 1995, and December 31, 2019. Subsequently, articles were reviewed and included if biofilm was evident in PTTO. There is an increased evidence supporting the role of biofilms in PTTO. Studies on TT design and material suggest that nitinol and/or silicone TTs had a lower risk for PTTO and that biofilms appeared in specific areas, such as the perpendicular junction of the T-tubes and the round rims of the Paparella-type tubes. Biofilm-component DNAB-II protein family was present in half of children with PTTO, and targeting this protein may lead to biofilm collapse and serve as a potential strategy for PTTO treatment. Novel approaches for the prevention of biofilm-associated PTTO include changing the inherent tube composition; tube coating with antibiotics, polymers, plant extracts, or other biofilm-resistant materials; impregnation with antimicrobial compounds; and surface alterations by ion-bombardment or surface ionization, which are still under laboratory investigation. Currently, there is no type of TT on which bacteria will not adhere. The challenges of treating PTTO indicate the need for further research in optimization of TT design, composition, and coating.

Quantitatively relating brain endothelial cell\u2013cell junction phenotype to global and local barrier properties under varied culture conditions via the Junction Analyzer Program

BackgroundThe endothelial cell–cell junctions of the blood–brain barrier (BBB) play a pivotal role in the barrier’s function. Altered cell–cell junctions can lead to barrier dysfunction and have been implicated in several diseases. Despite this, the driving forces regulating junctional protein presentation remain relatively understudied, largely due to the lack of efficient techniques to quantify their presentation at sites of cell–cell adhesion. Here, we used our novel Junction Analyzer Program (JAnaP) to quantify junction phenotype (i.e., continuous, punctate, or perpendicular) in response to various substrate compositions, cell culture times, and cAMP treatments in human brain microvascular endothelial cells (HBMECs). We then quantitatively correlated junction presentation with barrier permeability on both a “global” and “local” scale.MethodsWe cultured HBMECs on collagen I, fibronectin, collagen IV, laminin, fibronectin/collagen IV/laminin, or hyaluronic acid/gelatin for 2, 4, and 7 days with varying cAMP treatment schedules. Images of immunostained ZO-1, VE-cadherin, and claudin-5 were analyzed using the JAnaP to calculate the percent of the cell perimeter presenting continuous, punctate, or perpendicular junctions. Transwell permeability assays and resistance measurements were used to measure bulk (“global”) barrier properties, and a “local” permeability assay was used to correlate junction presentation proximal to permeable monolayer regions.ResultsSubstrate composition was found to play little role in junction presentation, while cAMP supplements significantly increased the continuous junction architecture. Increased culture time required increased cAMP treatment time to reach similar ZO-1 and VE-cadherin coverage observed with shorter culture, though longer cultures were required for claudin-5 presentation. Prolonged cAMP treatment (6 days) disrupted junction integrity for all three junction proteins. Transwell permeability and TEER assays showed no correlation with junction phenotype, but a local permeability assay revealed a correlation between the number of discontinuous and no junction regions with barrier penetration.ConclusionsThese results suggest that cAMP signaling influences HBMEC junction architecture more than matrix composition. Our studies emphasized the need for local barrier measurement to mechanistically understand the role of junction phenotype and supported previous results that continuous junctions are indicative of a more mature/stable endothelial barrier. Understanding what conditions influence junction presentations, and how they, in turn, affect barrier integrity, could lead to the development of therapeutics for diseases associated with BBB dysfunction.

Photodynamic Priming Modulates Endothelial Cell-Cell Junction Phenotype for Light-activated Remote Control of Drug Delivery.

The blood-brain barrier (BBB) remains a major obstacle for drug delivery to the central nervous system. In particular, the tight and adherens junctions that join the brain capillary endothelial cells limit the diffusion of various molecules from the bloodstream into the brain. Photodynamic priming (PDP) is a non-cytotoxic modality that involves light activation of photosensitizers to photochemically modulate nearby molecules without killing the cells. Here we investigate the effects of sub-lethal photochemistry on junction phenotype (i.e., continuous, punctate, or perpendicular), as well as the BBB permeability in a transwell model of human brain microvascular endothelial cells (HBMECs). We showed that PDP decreases the continuous junction architecture by ~20%, increases the perpendicular junction architecture by ~40%, and has minimal impact on cell morphology in HBMECs. Furthermore, transwell permeability assay revealed that PDP improves the HBMEC permeability to dextran or nanoliposomes by up to 30-fold for 6-9 days. These results suggest that PDP could safely reverse the mature brain endothelial junctions without killing the HBMECs. This study not only emphasizes the critical roles of PDP in the modulation junction phenotype, but also highlights the opportunity to further develop PDP-based combinations that opens the cerebrum endothelium for enhanced drug transporter across the BBB.

Tumor Cell Mechanosensing During Incorporation into the Brain Microvascular Endothelium.

Tumor metastasis to the brain occurs in approximately 20% of all cancer cases and often occurs due to tumor cells crossing the blood-brain barrier (BBB). The brain microenvironment is comprised of a soft hyaluronic acid (HA)-rich extracellular matrix with an elastic modulus of 0.1-1kPa, whose crosslinking is often altered in disease states. To explore the effects of HA crosslinking on breast tumor cell migration, we developed a biomimetic model of the human brain endothelium, consisting of brain microvascular endothelial cell (HBMEC) monolayers on HA and gelatin (HA/gelatin) films with different degrees of crosslinking, as established by varying the concentration of the crosslinker Extralink. Metastatic breast tumor cell migration speed, diffusion coefficient, spreading area, and aspect ratio increased with decreasing HA crosslinking, a mechanosensing trend that correlated with tumor cell actin organization but not CD44 expression. Meanwhile, breast tumor cell incorporation into endothelial monolayers was independent of HA crosslinking density, suggesting that alterations in HA crosslinking density affect tumor cells only after they exit the vasculature. Tumor cells appeared to exploit both the paracellular and transcellular routes of trans-endothelial migration. Quantitative phenotyping of HBMEC junctions via a novel Python software revealed a VEGF-dependent decrease in punctate VE-cadherin junctions and an increase in continuous and perpendicular junctions when HBMECs were treated with tumor cell-secreted factors. Overall, our quantitative results suggest that a combination of biochemical and physical factors promote tumor cell migration through the BBB.

Correlation of tunnel magnetoresistance with the magnetic properties in perpendicular CoFeB-based junctions with exchange bias

We investigate the dependence of magnetic properties on the post-annealing temperature/time, the thickness of the soft ferromagnetic electrode, and the Ta dusting layer in the pinned electrode as well as their correlation with the tunnel magnetoresistance ratio, in a series of perpendicular magnetic tunnel junctions of materials sequence Ta/Pd/IrMn/CoFe/Ta(x)/CoFeB/MgO(y)/CoFeB(z)/Ta/Pd. We obtain a large perpendicular exchange bias of 79.6 kA/m for x=0.3nm. For stacks with z=1.05nm, the magnetic properties of the soft electrode resemble the characteristics of superparamagnetism. For stacks with x=0.4nm, y=2nm, and z=1.20nm, the exchange bias presents a significant decrease at post-annealing temperature Tann=330°C for 60 min, while the interlayer exchange coupling and the saturation magnetization per unit area sharply decay at Tann=340°C for 60 min. Simultaneously, the tunnel magnetoresistance ratio shows a peak of 65.5% after being annealed at Tann=300°C for 60 min, with a significant reduction down to 10% for higher annealing temperatures (Tann≥330°C) and down to 14% for longer annealing times (Tann=300°C for 90 min). We attribute the large decrease of tunnel magnetoresistance ratio to the loss of exchange bias in the pinned electrode.

Post Treatment of Guided Wave by using Wavelet Transform in the Presence of a Defect on Surface

This article presents a Lamb wave processing by using two methods: Fast Fourier Transform (FFT2D) and Continuous Wavelet Transform (CWT) using Morlet wavelet. This treatment is done for a structure of two aluminum-copper plates, which are in contact edge to edge of a perpendicular junction with a thickness “e” in the presence of a rectangular and symmetrical defect located on the surface of the junction with a depth “d”. The aim under this study is to calculate the transmission and reflection energy coefficients by the two methods. The results of simulation obtained by Comsol software of an incident wave S0 at F = 800 kHz indicate us a good coherence between the two methods (FFT2D and CWT).

Tympanostomy tube otorrhea in children: prevention and treatment.

One in two children treated with tympanostomy tubes, experience episodes of otorrhea whilst their tubes are in place. In this review, we present the results of the most recent publications on prevention and treatment of tympanostomy tube otorrhea (TTO). Recent systematic reviews on water precautions for children with tympanostomy tubes support the American Academy of Otolaryngology - Head and Neck Surgery guideline recommendation against such preventive measures as there is no evidence that it protects against TTO. Studies on tympanostomy tube design and material suggest that silicone tubes have a lower TTO risk and that biofilms appear to be mainly located in the perpendicular junction of the T-tubes and the round rims of the Paparella-type tubes. Another study shows that the biofilm-component DNAB-II protein is present in otorrhea of half of children with TTO. Targeting this protein could lead to a collapse of the biofilm structure and as such a potential new treatment for chronic TTO. New systematic reviews show that antibiotic eardrops are the most effective first-line treatment of acute TTO and suggest that an antibiotic-corticosteroid combination is more effective than antibiotic only. Although in many countries, quinolone eardrops are the preferred choice because of being non-ototoxic, one study found a higher risk of persistent perforation after tube extrusion in children treated with quinolone eardrops as compared with children treated with aminoglycoside eardrops. Recent evidence confirms that water precautions for children with tympanostomy tubes are not effective in preventing TTO. Antibiotic-corticosteroid eardrops are the most effective treatment of acute TTO.

Perceiving perpendicular and parallel contours in the frontoparallel plane

The perception of a pair of contours in a retinal image cannot be understood simply by adding up the perceptions of the individual contours, especially when they form a perpendicular junction, or are parallel to one another. It is the relationship among the contours that determines what is perceived. Note that it is hard to actually compare the perception of such configurations quantitatively. We managed to do this by testing the perception of such configurations in three psychophysical experiments in which the perception was characterized by measuring the orientation threshold of a single contour. This threshold was estimated by using a modified Method of Constant Stimuli based on the assumption that contours forming a configuration are perceived individually, and that they are integrated linearly. This assumption made the quantitative comparison of the perceived configurations possible. We found that changes of the estimated threshold depended on the type of the configuration, specifically thresholds estimated from a perpendicular junction were substantially lower than thresholds estimated from a single contour or from a non-perpendicular junction. The lowest thresholds were observed when the threshold was estimated from a pair of parallel contours. These results suggest that the visual system is sensitive to perpendicular junctions and parallel contours in a retinal image.

Tunneling Anisotropic Magnetoresistance in L10-MnGa Based Antiferromagnetic Perpendicular Tunnel Junction**Supported by the National Basic Research Program of China under Grant No 2015CB921500, the National Natural Science Foundation of China under Grant Nos 61334006 and 11774339, the Key Research Project of Frontier Science of the Chinese Academy of Sciences under Grant No QYZDY-SSW-JSC015, and the Key Research Program of the Chinese

We report on the tunneling anisotropic magnetoresistance in antiferromagnetic perpendicular tunnel junction consisting of L10-MnGa/FeMn/AlOx/Pt grown on GaAs (001) substrates by molecular-beam epitaxy. The temperature-dependent perpendicular exchange bias effect reveals an exchange coupling between ferromagnetic L10-MnGa and antiferromagnetic FeMn. The rotation of antiferromagnetic spins in FeMn can be driven by perpendicularly magnetized L10-MnGa due to the exchange-spring effect at the interface and leads to room-temperature tunneling anisotropic magnetoresistance ratio of 0.86%. We also find that the tunneling anisotropic magnetoresistance strongly depends on temperature and angle. These results have broadened the material selection range for high performance antiferromagnetic spintronic devices.

Perceiving Perpendicular and Parallel Contours in the Frontoparallel Plane

The perception of a pair of contours in a retinal image cannot be understood simply by adding up the perceptions of the individual contours. We compared the perception of configurations of contours in three psychophysical experiments. The results of the experiments were analyzed so that the quantitative comparison of the perceived configurations was possible. Thresholds estimated were substantially lower from a perpendicular junction than from a single contour or from a non-perpendicular junction. The lowest thresholds were observed from a pair of parallel contours. The results suggest that the visual system is sensitive to perpendicular junctions and parallel contours in a retinal image.

Tunneling magnetoresistance of perpendicular CoFeB-based junctions with exchange bias

Recently, magnetic tunnel junctions with perpendicular magnetized electrodes combined with exchange bias films have attracted great interest. In this paper, we examine the tunnel magnetoresistance of Ta/Pd/IrMn/Co-Fe/Ta/Co-Fe-B/MgO/Co-Fe-B/capping/Pd magnetic tunnel junctions dependent on the capping layer, i.e., Hf or Ta. In these stacks, perpendicular exchange bias fields of −500 Oe along with perpendicular magnetic anisotropy are combined. A tunnel magnetoresistance of (47.2 ± 1.4)% for the Hf-capped sample was determined compared to the Ta one (42.6 ± 0.7)% at room temperature. Interestingly, this observation is correlated with the higher boron absorption of Hf compared to Ta, which prevents the suppression of the Δ1 channel and leads to higher tunnel magnetoresistance values. Furthermore, the temperature dependent coercivities of the soft electrodes of both samples are mainly described by the Stoner-Wohlfarth model including thermal fluctuations. Slight deviations at low temperatures can be attributed to a torque on the soft electrode which is generated by the pinned magnetic layer system.

Perpendicular magnetic tunnel junction with W seed and capping layers

We present a study on perpendicular magnetic tunnel junctions with W as buffer and capping layers. A tunneling magnetoresistance of 138% and an interfacial magnetic anisotropy of 1.67 erg/cm2 were obtained in optimally annealed samples. However, after extended annealing at 420 °C, junctions with W layers showed extremely small resistance due to interdiffusion of W into the MgO barrier. In contrast, in Ta-based junctions, the MgO barrier remained structurally stable despite disappearance of magnetoresistance after extended annealing due to loss of perpendicular magnetic anisotropy. Compared with conventional tunnel junctions with in-plane magnetic anisotropy, the evolution of tunneling conductance suggests that the relatively low magnetoresistance in perpendicular tunnel junctions is related to the lack of highly polarized Δ1 conducting channel developed in the initial stage of annealing.

Enhanced tunnel magnetoresistance and electric-field effect in CoFeB/MgO/CoFeB perpendicular tunnel junctions with W underlayer

We investigated the dependence of tunnel magnetoresistance (TMR) and its electric-field effect in CoFeB/MgO/CoFeB magnetic tunnel junctions (MTJ) on different underlayer (UL) materials. We observed enhancements in the TMR ratio and its temperature dependence as well as electric-field effect in MTJs with W UL, as compared to those in MTJs with a conventional Ta UL. This is attributed to better thermal stability of perpendicular magnetic anisotropy (PMA) in W/CoFeB/MgO, which sustains up to 380 °C, compared to that of Ta/CoFeB/MgO which starts to degrade at 270 °C. This demonstrates that the PMA in a CoFeB/MgO structure and its electric-field dependence can be enhanced by the careful selection of underlayer, opening the way for the realization of electric-field effect-driven spintronic devices.

Pseudomonal Biofilm Topographic Distribution on Tympanostomy Tubes: An In Vitro Model.

In vitro growth of Pseudomonas aeruginosa biofilm on tympanostomy tubes showed that in Armstrong T-tubes, biofilm colonies were mainly located in the perpendicular junction between the body and the flanges, but in Paparella-type tube, they concentrated on the round rims. These "weakness" zones can be the future target areas for geometry changes, and can be specifically coated with antibiofilm materials.

A high-power microwave circular polarizer and its application on phase shifter.

A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.