Characteristics Of Sheath Research Articles

Novel technique and assessment of available three-dimensional delivery sheath for endomyocardial biopsy during cardiac device implantation

BackgroundEarly cardiomyopathy diagnosis allows timely treatment and may help resolve problems that occur after cardiac implantable electronic device (CIED) implantation. ObjectiveTo describe a novel technique for endomyocardial biopsy (EMB) using a three-dimensional (3D) delivery sheath during CIED implantation. Additionally, we investigated 3D delivery sheath characteristics using sheath deflection during bioptome insertion. MethodsThis study of 20 patients undergoing CIED implantation analyzed the EMB success rate and pathological findings. Fluoroscopic images assessed 3D delivery sheath characteristics before and after bioptome insertion in three sheaths. CIEDs were implanted for sick sinus syndrome (n=3), atrioventricular conduction disorder (n=16), and left ventricular dysfunction (n=1). Fluoroscopic verification was performed using right anterior oblique (RAO) and left anterior oblique (LAO) views. EMB was performed with Selectra 3D (BIOTRONIK), CSP Locator 3D (Abbott) and SSPC (Boston Scientific) (12, 4, and 4 patients, respectively). The distance moved toward the right ventricular apex (RVA) in RAO was defined as Dis-RAO (mm) and that moved toward the RVA in LAO was defined as Dis-LAO (mm). ResultsAmong the three sheaths, only the CSP Locator 3D and Selectra 3D showed significant differences in Dis-RAO (13.2±2.0mm vs. 19.8±3.8mm, p<0.01) and Dis-LAO (8.1±1.3mm vs. 15.3±3.9mm, p<0.01). A total of 77 EMB samples from 20 patients were collected without any complication, and four patients (20%) were diagnosed with cardiac amyloidosis (CA) based on pathological findings. ConclusionsAll 3D delivery sheaths were safe and effective for performing EMB from the RVS during CIED implantation, enabling early CA diagnosis in 20% of patients.

Effects of anode evaporation process on the anode sheath characteristics in vacuum arc plasma

Abstract The anode sheath of vacuum arc plasma plays a key role in the generation of anode plasma, but the effects of anode evaporation on the anode sheath remains unclear. In this paper, a theoretical model of a collisional sheath for multi-component plasma coupled with anode evaporation is developed, and the spatial evolution of the anode sheath at different anode surface temperatures is investigated. The results indicate that the distribution of charged particles density and potential in the anode sheath monotonically decreases in the absence or reduction of anode evaporation. When the anode surface temperature exceeds 1900K, a potential hump appears within the sheath. This is due to enhanced anode evaporation increasing the metal vapor density, which intensifies electron impact ionization and charge exchange collisions, resulting in a higher net space charge density. Finally, the effects of various collision reactions and electron temperatures on the potential hump are analyzed. These findings are meaningful for understanding the anode plasma generation mechanism and regulating the anode plasma parameters.&amp;#xD;

Magnetized multi-component plasmas sheath characteristics with three isothermal ion species

The dynamics of magnetized plasma sheath with three isothermal ions is studied numerically using the fluid model. The three ions ( Ar+,Kr+, and Xe+ ) are assumed to be singly charged and have the same temperature. In the beginning, the concentrations for Ar+ and Xe+ were taken in the same proportions, and then the Kr+ ion density is introduced slowly in the plasma. It is found that the presence of a third ion has changed the dynamics of ion densities inside the sheath and simultaneously their respective velocities. Ion density and electron density profiles were estimated inside the sheath region in the presence of a weak and strong magnetic field as well at different Kr+ ion concentrations. Further, the dependence of magnetic field obliqueness on the ion density profile and its velocities inside the sheath is also studied, and observed ion density bunching at different conditions. Based on the results, we have tried to introduce a concept of the derivation of system Bohm velocity by considering the ion mass as equivalent mass for the three interacting ion systems in the plasma. It is found that the system Bohm velocity with the equivalent mass effect is larger than their individual thermal velocities and close to Ar+ Bohm velocity, and higher than the system Bohm velocity with reference to the density ratio and their respective individual Bohm velocities in an isothermal multi-component plasma.

Mechanical behavior and cement sheath damage characteristics of casing pullout based on peridynamics

In petroleum exploration and production, the recovery and replacement of casing are crucial. However, difficulties often arise during casing pullout operations due to the strong bonding strength between the casing and the cement sheath. Currently, there are few researches on casing pullout process, which leads to the fact that casing pullout operations often relies on experience and lacks theoretical support. To comprehend the mechanical behavior, interface shear failure mechanisms of casing pullout process, and to propose rational solutions for practical engineering applications, this study establishes a Peridynamics (PD) numerical model for casing pullout to conduct research and analysis on its process. Based on the characteristics of the cement sheath, a damage model for the cement sheath is proposed in this paper. Additionally, a kernel function is introduced to reflect the variation of long-range forces with the distance between material points, aiming to characterize the changes in the stiffness of bond constant within the horizon of material points. The mechanical responses of the cement sheath and casing at different phases of the casing pullout process are analyzed and characterized. The research results indicate that an increase in the casing-cement sheath thickness ratio promotes the damage at the casing-cement sheath interface, reducing the time required for casing pullout but inhibiting the expansion of cement sheath cracks. As the thickness ratio increases from 0.1 to 0.18, the degree of cement sheath damage decreases from 6.904% to 6.453%. The increase in Young's modulus of the cement sheath is negatively correlated with the time required for casing pullout, positively correlated with the interface failure rate, and it does not exhibit a linear relationship with the degree of cement sheath damage. Within the range of Young's modulus from 4 to 20 GPa, the maximum difference in cement sheath damage degree is 3.715%. In engineering practice, the Young's modulus of well cement and the thickness ratio of casing-cement sheath can be appropriately increased to enhance pullout efficiency.

Modified Bohm Criterion and Sheath Characteristics in Nonextensive Electronegative Collisional Warm Plasma With Electron Emitting Surfaces

Modified Bohm Criterion and Sheath Characteristics in Nonextensive Electronegative Collisional Warm Plasma With Electron Emitting Surfaces

Nucleation and growth of plasma sputtered silver nanoparticles under acoustic wave activation

Early results on the plasma deposition of dielectric thin films on acoustic wave (AW) activated substrates revealed a densification pattern arisen from the focusing of plasma ions and their impact on specific areas of the piezoelectric substrate. Herein, we extend this methodology to tailor the plasma deposition of metals onto AW-activated LiNbO3 piezoelectric substrates. Our investigation reveals the tracking of the initial stages of nanoparticle (NP) formation and growth during the submonolayer deposition of silver. We elucidate the specific role of AW activation in reducing particle size, enhancing particle circularity, and retarding NP agglomeration and account for the physical phenomena making these processes differ from those occurring on non-activated substrates. We provide a comparative analysis of the results obtained under two representative plasma conditions: diode DC sputtering and magnetron sputtering. In the latter case, the AW activation gives rise to a 2D pattern of domains with different amounts of silver and a distinct size and circularity for the silver NPs. This difference was attributed to the specific characteristics of the plasma sheath formed onto the substrate in each case. The possibilities of tuning the plasmon resonance absorption of silver NPs by AW activation of the sputtering deposition process are discussed.

Secondary electron emission reduction from boron nitride composite ceramic surfaces by the artificial microstructures and functional coating

Boron nitride-silicon dioxide (BN–SiO2) composite ceramic is a typical Hall thruster wall material, and its secondary electron emission (SEE) property dominates the sheath characteristics inside the thrusters. Lowering the SEE yield (SEY) of the wall surface can remarkably improve the sheath stability of Hall thrusters. To accomplish the SEY reduction for BN–SiO2, artificial surface microstructure and surface coating technologies are employed. The morphology analysis demonstrated the shape and feature sizes of the microstructure could be largely controlled by adjusting the laser etching parameters. Then we realized an increasingly significant SEY reduction for BN–SiO2 as the average aspect ratio of the microhole increases. The microstructures showed a remarkable SEY reduction when the laser power was 10 W and the scanning cycle was 50. In this case, the SEY peak values (δ m) of the two BN–SiO2 samples with mass ratios of 7:3 and 6:4 decrease from 2.62 and 2.38 to 1.55 and 1.46 respectively. For a further SEY reduction, a sputtering process was employed to deposit TiN film on the microstructures. The results showed that the TiN coating of 246 nm thickness reduced the δ m values of the two samples from 1.55 and 1.46 to 0.82 and 0.76, which achieved a notable SEY reduction compared to the original surface. Via simulation work, the SEY reduction achieved by microstructures was theoretically interpreted. Besides, by considering the effect of surface charging, the results of SEY converged to 1 with the irradiation pulse increasing presented. The research demonstrated a remarkable SEY reduction for BN–SiO2 ceramic by constructing surface microstructure and depositing TiN coating, which has application sense for low SEY engineering in specific working scenarios.

Analysis of electromagnetic wave characteristics of heterogeneous plasma sheath based on the ZT-DGTD

Analysis of electromagnetic wave characteristics of heterogeneous plasma sheath based on the ZT-DGTD

Ion flow and dust charging at the sheath boundary in dusty plasma with an electron-emitting surface: applications to laboratory and lunar dusty plasmas

In laboratory and space plasmas, the emission of electrons from the surface significantly affects the characteristics of the plasma sheath that forms at that surface, which is crucial to understanding the overall plasma-wall interaction mechanism. In this work, the collisional fluid model is used for laboratory dusty plasma, whereas the collisionless model is used for lunar dusty plasma. We have extended the Bohm sheath criterion for the formation of the stable plasma sheath due to electron emission from the surface, loss of ion flux, and the gas pressure of the collisional laboratory dusty plasmas. It is found that ion flow at the sheath boundary is considerably influenced by the concentration of electron emission, the ion loss term, and gas pressure. The evolution of the dust charge explicitly determines the magnitude of the ion flow at the sheath boundary. The plasma parameters adopted in the present case are reliable in laboratory and space dusty plasmas, especially the dusty plasma environment on the lunar surface. The lunar surface and dust grains on the Moon become electrically charged as a result of the interaction between solar wind plasma and photoemission electrons emitted from the lunar surface. In addition, the lunar plasma sheath characteristics, dust-charging process, and stable dust levitation in the sheath region have been studied.

Distinctiveness, Uniformity and Stability (DUS) Characterization in Twenty Five Landraces of Rice (Oryza sativa L.)

For the establishment of Distinctiveness, Uniformity and Stability (DUS) characterization, Twenty five landraces of rice (Oryza sativa L.), collected from different parts of Tamil Nadu, were characterized according to the DUS guidelines of the Plant Varieties Protection and Farmers’ Rights Authority, using thirty agro-morphological traits. Rice accessions were planted with three replications using the randomized block design (RBD) in 2021 at the Plant Breeding Farm, Department of Genetics and plant Breeding, Faculty of Agriculture, Annamalai University. Observations were recorded on various agro-morphological traits such as Leaf sheath, flag leaf, leaf blade, awns, panicle, ligure and clum characteristics. The results obtained revealed a wide range of variability for twenty five landraces, essential characters of the thirty DUS characters studied. The results of this study will be useful for restoration and conservation of beneficial genes. Contemporary research work will be advantageous for breeders to choose the right parent for crop improvement and the researchers for genetic diversity among landraces.

Deposition processes of superhard diamond-like carbon films co-adjusted by ion energy and ion flux in arc discharges

As a kind of protective material, Diamond-Like Carbon (DLC) film can effectively improve the mechanical and tribological properties of the substrate surface. In DLC family, tetrahedral amorphous carbon (ta-C) with ultra-high hardness and excellent protective properties has been widely concerned in the field of hard protective materials. It is well known that the structure and properties of ta-C are strongly dependent on carbon plasma characteristics in the plasma environment. Therefore, it is extremely crucial to obtain the optimal process window of ta-C described by plasma micro-parameters with general significance. This paper proposed the Langmuir probe was used to diagnose the carbon plasma of the afterglow generated by arc evaporation, aiming to investigate the characteristics of carbon plasma and sheath. The effect of ion energy and ion flux adjusted by the pulse bias voltage and arc current on the sp3 hybrid bonds and hardness of DLC films was studied, aiming to find out which conditions satisfied the formation of ta-C. The results showed the microstructure and properties of DLC films were co-adjusted by ion energy and ion flux. When the carbon ions met the appropriate ion energy range (50–300 eV) and low ion flux (<8.99 × 1010 cm−2 s−1), the films tended to form ta-C structures with high sp3 bonds. However, under the condition of high ion energy and high ion flux, the structure of the films changed from sp3 bonds to sp2 bonds, resulting in the graphitization and formation of DLC films with high sp2 bonds. This work will provide new solutions to guide the design and acquisition of high-performance DLC films.

Investigation of Betel Palm Sheath during Punch/Die Shear Cutting

This research was carried out to study punch/die shear cutting of betel palm sheath. In a shear cutting experiment, shearing process parameters i.e., the moisture content of the palm sheath and the punch/die clearance were varied and investigated. Experimental results showed that both of the process parameters played an important role on the surface cracking of the palm sheath. In order to discuss the cutting characteristics of the palm sheath, a finite element method (FEM) analysis of the shear cutting was conducted. Based on simulation results with the surface cracking observed in the experiment, it was confirmed that the position of the peak maximum principal stress on the palm sheath surface varied with the punch/die clearance. Also, the position of the surface cracking was relevant to the position of the peak maximum principal stress.

Influence analysis of uncertainty of chemical reaction rate under different reentry heights on the plasma sheath and terahertz transmission characteristics

Plasma sheath prediction of hypersonic vehicle is critical to radio frequency (RF) blackout solutions as well as vehicle design and development. In this paper, an optimized chemical reaction (OCR) model by considering the difference in reaction rate coefficient under different re-entry heights is proposed to obtain more accurate plasma sheath distribution. In the OCR model, the correction coefficient of chemical reaction rate at different heights is obtained by deriving the relationship between vehicle surface temperature and reaction rate. Further, through the coupling with hypersonic plasma flow model and co-simulation with terahertz transmission model, the influence of reaction rate uncertainty on the plasma sheath and terahertz transmission characteristics under different heights is studied. The reaction rate uncertainty has little effect on the collision frequency and sheath thickness, but has a significant effect on the electron density. Numerical simulations and comparisons with flight data validate the electron density prediction accuracy of OCR model was improved by more than 13.1% compared with the traditional chemical reaction (TCR) model, which causes prediction accuracy of signal attenuation at 0.05 THz improves about 25%, and it gradually decreases with the increasing terahertz frequency. The above conclusions are of great significance for the communication attenuation prediction and RF blackout schemes.

Are the oscillations found in magnetized collisional electronegative warm plasma artifact during plasma-surface interaction?

The formation of the sheath and its characteristics are investigated in an electronegative plasma under the impact of an oblique and constant magnetic field. Specifically, the role of the magnetic field and initial conditions of positive ion velocity on the sheath characteristics are uncovered by adopting the Sagdeev potential approach for the determination of the modified Bohm’s criterion. At the sheath edge, the upper and lower components of the positive ion velocity perpendicular to the probe/wall are determined and examined in greater detail. The sheath structure is found to be modified considerably by the initial conditions. If the magnetic field is strong near the sheath edge, then the profile of the positive ion density shows a pulse-like structure for the case when we neglect the x-component (parallel to the wall) of positive ion velocity at the sheath edge. This pulse-like structure disappears when all the components of the positive ion velocity at the sheath edge are included, i.e. the ions are considered to move in any direction but towards the probe. The occurrence or disappearance of pulse-like structures or oscillations completely depend upon the initial conditions. Since in real situations the ions are expected to move in any direction (carrying all their velocity components) and are not aligned only in the direction perpendicular to the wall, these oscillations are artifact in nature. The sheath thickness is observed to be reduced with increasing magnetic field strength and its inclination. In order to better understand the phenomenon, isothermal and adiabatic cases are also discussed.

Study on channeling-leakage pressure of casing-cement sheath-stratum assembly in thermal recovery wells

The main purpose of the article is to study the critical leakage pressure of the casing cement sheath stratum assembly for cyclic alternating thermal effect in the thermal recovery wells, to provide technical measures for sealing integrity of thermal recovery wells. To achieve those objectives, a device for evaluating the sealing integrity of casing-cement sheath-stratum assembly in a high-temperature, high-pressure cyclic alternating environment is established in this paper due to wellbore safety risks of offshore thermal recovery directional wells, such as wellbore fluid channeling-leakage and sustained annular pressure caused by the alternating thermal effect of multi-round steam huff and puff. The device is adopted to simulate two working conditions: low-temperature production at 50 ℃ and ultra-high temperature curing at 350℃. The channeling-leakage curves of different gas-sealing pressures at cementing interfaces I and II are measured to obtain the critical channeling leakage pressure of the assembly. The influence rules of cyclic alternating thermal effect on the microstructure and pore characteristics of cement sheath are analyzed using industrial CT scanning technology. The study clarifies the equivalent diameter of pores inside the cement sheath and the dimensional variation of cracks. Moreover, the mechanism of cementing interface damage is revealed, and the wellbore’s sealing integrity failure under cyclic alternating thermal effect acting on thermal recovery wells is investigated. Technical measures are proposed to improve the wellbore’s sealing integrity of thermal recovery wells from three aspects: elastic-plastic parameters design of cement sheath, elastic-specific work optimization, and control of wellbore critical temperature and pressure. Thus, theoretical basis and technical support are provided for ensuring the wellbore’s entire-life sealing integrity of offshore thermal recovery wells.

Experimental study on the channeling leakage properties of compact-size casing-cement sheath-stratum assembly in deep and ultra-deep wells

Within deep and ultra-deep wells, the casing-cement sheath-stratum rock assembly(CCS) bears thermal, mechanical, and chemical multi-field coupling, causing some damage or creating micro-annular gaps at the interface between the casing and the cement sheath as well as the interface between the cement sheath and the stratum. Radial and axial cracks in the cement sheath occur, and even channeling-leakage channels form due to shear failure. These are critical reasons for sustained annular pressure and the risk of wellbore sealing integrity. This paper establishes an evaluation device for channeling-leakage properties of a compact-size CCS assembly. It observes the microstructure and morphology characteristics of cement sheath integrity, tests the channeling-leakage pressure and paths of two cement slurries, and explores the relationships between the channeling-leakage properties of the assembly and the damage to the cementing interfaces as well as the cracking characteristics of cement sheath. Results showed that the proposed method was suitable for evaluating unpredictable security risks of CCS assembly caused by a complex load in deep and ultra-deep wells, such as overload-induced cracking, cementing interface unsealing, and channeling-leakage of the cement sheath. The findings revealed the evolution law from deformation points to cracks and channeling-leakage channels inside the cement sheath under the action of load and proposed technical measures to avoid channeling-leakage of the cement sheath. This research provides a theoretical basis and testing method for evaluating the wellbore sealing integrity and formulating technical safety measures for deep and ultra-deep wells.

The kraft lignin characteristics of areca leaf sheath isolated by phosphoric acid

This study reported on lignin extraction from the Areca leaf sheath (ALS) by boiling treatment before kraft pulping. OFAT (one factor, one time) was designed to determine the optimal pulping condition for the highest delignification selectivity (DS). On that optimum condition, lignin was precipitated from black liquor by 20 % phosphoric acid. The 22 % active alkali and 22 % sulfidity were the optimal conditions. The lignin was then characterized by the morphological, chemical, and thermal properties and particle size. Isolated lignin has similar functional groups to reference lignin with purity and yield of 62.7 % and 12.27 %. The thermal analysis of lignin resulted in a char residue of 30.2 % with a glass transition temperature (Tg) of 117.34 °C. The lignin has an irregular or non-uniform form in micron size. A low equivalent weight of lignin indicates its prospect as an adhesive or an adhesive filler for panels.

Difference analysis in terahertz wave propagation in thermochemical nonequilibrium plasma sheath under different hypersonic vehicle shapes

Research on terahertz communication under different vehicles has important guiding significance for the design of future hypersonic vehicle and Radio Frequency (RF) blackout. In this paper, a joint simulation model of plasma flow under thermochemical nonequilibrium state and terahertz transmission is developed to investigate the differences in terahertz wave transmission characteristics under different vehicle shapes and the related mechanisms. By comparing the plasma sheath characteristics and terahertz transmission among HIFIRE-5b (Hypersonic International Flight Research Experimentation-5b), RAM C(Radio Attenuation Measurement C) and ARD (Atmospheric Reentry Demonstrator) vehicles, it is found that the sheath thickness and electron density of ARD vehicles is significantly larger than that of HIFIRE-5b and RAM C vehicles, resulting in greater terahertz wave attenuation. Collision absorption plays a major role in the terahertz attenuation of vehicles, and the contribution of reflection effects is only observed in the ARD vehicle due to its larger plasma sheath thickness and spatial structure variation. Based on the above comparison results, a shape design scheme of reducing the vehicle head and tail for mitigating RF blackout is proposed, and the scheme is proved by further analyzing the effects of different vehicle heads and tails on the terahertz communication. With the decrease of the head radius and tail width of hypersonic vehicle, the wave attenuation at the same terahertz frequency decreases, and the contribution of reflection effect to wave attenuation gradually disappears. Therefore, the shape design scheme of reducing the vehicle head and tail can effectively alleviate the RF blackout problem, which provides an important reference value for future hypersonic vehicle design.

Analysis of the Electrically Large Target in Isotropic Medium by the Physical Optics Method With Adaptive Mesh Technique

In this work, the physical optics (PO) method based on multilayered medium theory is used to analyze high-frequency scattering characteristics of plasma sheath covering an aircraft. The ray intersection method is taken for occlusion judgment, but some errors occur on the edge between illuminated and shadowed regions of a target. Therefore, the iterative edge patch segmentation based on adaptive mesh technique is proposed to reduce this error, which is significant to enhance computational accuracy of the PO method. Furthermore, to simplify the computational process and validate effectiveness of adaptive mesh technique, the plasma sheath covering a RAM-C II aircraft is modeled with a five-layered isotropic medium. Compared with uniform fine segmentation, the proposed adaptive mesh technique markedly reduces the computational cost by an order of magnitude while maintaining accuracy of the PO method. Moreover, high-frequency scattering characteristics of plasma sheath covering a RAM-C II aircraft under different flight conditions are presented via the bistatic radar cross section (RCS) with observable attenuation effects. Hence, the PO method for multilayered media combined with the proposed lit region judgment method is suitable to analyze scattering features of electrically large coated target.

Use of steerable sheaths for complex aortic procedures.

To demonstrate the ease with which steerable sheaths, designed for cardiac electrophysiological applications, can be used to aid endovascular treatment of a wide range of non-cardiac vascular disease and to assist with target vessel cannulation in branched and fenestrated aortic grafts. A retrospective medical chart review was carried out to identify cases from a single vascular surgery unit (2019-2022) where the HeartSpan Steerable Sheath (HSS) (Merit Medical, South Jordan, UT, USA) was utilised to enable endovascular management of complex vascular pathology. A case presentation of branch graft insertion performed entirely via distal access is described and used to help identify pertinent sheath characteristics and technical considerations, and to illustrate the advantages and disadvantages of the design for modified use in target vessel cannulation. The HSS was used in the endovascular treatment of different vascular pathologies in 15 patients (23 target vessels) where access to the vessels using standard catheters and approaches was not possible. Cannulation and subsequent stenting were successful for 21 of the 23 target vessels in total. Of these cases, the HSS was used as an adjunct for deployment of fenestrated endovascular graft systems when conventional techniques for canulation of target vessels had failed on five occasions. On another four occasions, the HSS enabled full deployment of the entire Zenith® t-Branch™ Thoracoabdominal Endovascular Graft system from an exclusively femoral approach. An additional three cases involved use of the HSS for superior mesenteric artery cannulation in patients with mesenteric ischaemia. The device was also used once in each of the following cases: contralateral common iliac cannulation, cannulation of contralateral internal iliac artery for coil embolisation, and access of a contralateral iliac branched device. There were no stent dislocations and all aortic branches that were patent at the completion of each case remained so 1-year post procedure. Steerable sheaths designed for cardiac electrophysical applications, like the HSS Introducer, can be successfully utilised for cannulation of challenging target vessels in a wide range of aortic endovascular procedures. This modified approach may salvage cases that would otherwise be considered inoperable in regions of the world where steerable sheaths designed for aortic use are not readily available.