Tip Contact Research Articles

Long-term safety and effectiveness of paroxysmal atrial fibrillation ablation using a porous tip contact force-sensing catheter from the SMART SF trial

PurposeThe prospective, multicenter SMART SF trial demonstrated the acute safety and effectiveness of the 56-hole porous tip irrigated contact force (CF) catheter for drug-refractory paroxysmal atrial fibrillation (PAF) ablation with a low primary adverse event rate (2.5%), leading to FDA approval of the catheter. Here, we are reporting the long-term effectiveness and safety results that have not yet been reported.MethodsAblations were performed using the 56-hole porous tip irrigated CF catheter guided by the 3D mapping system stability module. The primary effectiveness endpoint was freedom from atrial tachyarrhythmia (including atrial fibrillation, atrial tachycardia, and/or atrial flutter), based on electrocardiographic data at 12 months. Atrial tachyarrhythmia recurrence occurring 3 months post procedure, acute procedural failures such as lack of entrance block confirmation of all PVs, and undergoing repeat procedure for atrial fibrillation in the evaluation period (91 to 365 days post the initial ablation procedure) were considered to be effectiveness failures.ResultsSeventy-eight patients (age 64.8 ± 9.7 years; male 52.6%; Caucasian 96.2%) participated in the 12-month effectiveness evaluation. Mean follow-up time was 373.5 ± 45.4 days. The Kaplan-Meier estimate of freedom from 12-month atrial tachyarrhythmia was 74.9%. Two procedure-related pericardial effusion events were reported at 92 and 180 days post procedure. There were no pulmonary vein stenosis complications or deaths reported through the 12-month follow-up period.ConclusionsThe SMART SF 12-month follow-up evaluation corroborates the early safety and effectiveness success previously reported for PAF ablation with STSF.

Thermal effect of cold fluid injection on fracture integrity of host rock: a microscale analysis of single asperity

When relatively cold fluid is injected to hot host rock featured with fractures, the fluid-rock temperature difference induces cooling of the self-propping fractures and could cause the failure of the asperity. Although fracture sustainability has been extensively studied, little research has focused on thermal effects on asperity failure. A finite-element analysis is conducted to investigate the effect of fluid-rock temperature differences on the asperity failure. In the analysis, rock mechanical properties are coupled with the temperature and stress states of the host rock. The thermally-induced tensile cracks initiate at the junction of asperity and rock matrix and also start at rim of contact tip at higher temperature difference. When the temperature difference is high enough to propagate tensile cracks, two groups of tensile cracks would coalesce and lead to asperity failure. The critical threshold to initiate two groups of tensile cracks is identified in this study. This asperity failure could also result in the closure of fractures and change the fracture network distribution in the rock. Further, the comparison with fracture wall with no asperity addresses the effect of the asperity on the growth pattern of secondary thermal cracks.

Issues of constructing scanning hybrid 3D measuring heads for high-precision contact and non-contact coordinate measurements of product dimension

The article presents a model of mechanical contact of a spherical tip and a product with small forces according to elastic deformations (further – deformations) taking into account the appearance of material deformations in the gap between them along the perimeter of the contact zone in the form of so-called piles-up. Dependences are obtained that link the gap with the deformation and the piles-up size. A graph is constructed for these parameters, the general form of which is close to the function of a single jump ∼1(l-Rpile), where Rpile is the radius of the pile-up.The developed design and operating principle of the scanning hybrid fiber-optical measuring head (FOMH) based on the use of a small-sized spatial light modulator in the form of a fiber-optic piezoscanner with the formation of scanning movements of the laser beam and the measurement of gaps between the tip and the product are described. The possibilities of providing high-precision measurements of laser beam deflection angles during scanning movements by using acousto-optic heterodyne interference measurement systems are considered.

Effects of Multi-Point Contacts during Object Contour Scanning Using a Biologically-Inspired Tactile Sensor.

Vibrissae are an important tactile sense organ of many mammals, in particular rodents like rats and mice. For instance, these animals use them in order to detect different object features, e.g., object-distances and -shapes. In engineering, vibrissae have long been established as a natural paragon for developing tactile sensors. So far, having object shape scanning and reconstruction in mind, almost all mechanical vibrissa models are restricted to contact scenarios with a single discrete contact force. Here, we deal with the effect of multi-point contacts in a specific scanning scenario, where an artificial vibrissa is swept along partly concave object contours. The vibrissa is modeled as a cylindrical, one-sided clamped Euler-Bernoulli bending rod undergoing large deflections. The elasticae and the support reactions during scanning are theoretically calculated and measured in experiments, using a spring steel wire, attached to a force/torque-sensor. The experiments validate the simulation results and show that the assumption of a quasi-static scanning displacement is a satisfying approach. Beyond single- and two-point contacts, a distinction is made between tip and tangential contacts. It is shown that, in theory, these contact phases can be identified solely based on the support reactions, what is new in literature. In this way, multipoint contacts are reliably detected and filtered in order to discard incorrectly reconstructed contact points.

Piezoelectric Actuators for Tactile and Elasticity Sensing

Piezoelectric actuators have achieved remarkable progress in many fields, being able to generate forces or displacements to perform scanning, tuning, manipulating, tactile sensing or delivering functions. In this work, two piezoelectric PZT (lead zirconate titanate) bimorph actuators, with different tip contact materials, were applied as tactile sensors to estimate the modulus of elasticity, or Young’s modulus, of low-stiffness materials. The actuators were chosen to work in resonance, taking advantage of a relatively low resonant frequency of the out-of-plane vibrational modes, associated with a convenient compliance, proven by optical and electrical characterization. Optical measurements performed with a scanning laser vibrometer confirmed that the displacement per applied voltage was around 437 nm/V for the resonator with the lower mass tip. In order to determine the modulus of elasticity of the sensed materials, the stiffness coefficient of the resonator was first calibrated against a force sensor, obtaining a value of 1565 ± 138 N/m. The actuators were mounted in a positioning stage to allow approximation and contact of the sensor tip with a set of target materials. Electrical measurements were performed using the resonator as part of an oscillator circuit, and the modulus of elasticity of the sample was derived from the contact resonant frequency curve of the cantilever–sample system. The resulting sensor is an effective, low-cost and non-destructive solution compared to atomic force microscopy (AFM) techniques. Materials with different modulus of elasticity were tested and the results compared to values reported in the literature.

Effect of mesoscopic structure on hydro-mechanical properties of fractures

Geothermal extraction usually requires reservoir fracturing to realize economic exploitation and fluid flow in hot-dry rock fractures has become a research hotspot. In the present study, gas flow through shear and tensile granite fractures was investigated to comparatively study effect of fracture mesoscopic structure evolution on fracture hydro-mechanical characteristics under confining stress ranging from 1 to 40 MPa and inlet pressure ranging from 0.005 to 3.6 MPa. Four major findings are reported herein. First, the conductivity of shear fractures is much higher than that of tensile fractures and the ratio of the former to the latter can be up to around 265 under the stress of 40 MPa. The second finding was that the Z2 values of tensile fractures are higher than shear fractures, indicating that the fracture surface of tensile fractures is rougher and has more mesoscopic asperities. When the two surfaces get to contact, tip contact and stress concentration happen, resulting in higher deformation in tensile fractures. The cluster coefficient characterizes fracture contact cluster property. Higher cluster coefficient indicates lower fracture deformation and lower viscous loss. Shear fractures have higher cluster coefficient than that of tensile fractures so shear fractures are weakly deformable. However, high flow velocity and Reynolds number easily occur in shear fractures, so transitional and turbulent flow dominates in shear fractures while laminar and transitional flow in tensile fractures. Third, a mechanical model relates the average imbedded depth to loading stress and lacunarity, a hydraulic aperture model based on void space and lacunarity and a friction factor model based on Reynolds number and lacunarity were built, respectively, based on the experimental data. Then a nonlinear flow model was proposed. The fourth finding was that parametric analysis on the cluster coefficient shows that the higher the cluster coefficient, the lower of fracture deformation is and the higher of hydraulic aperture is. When the cluster coefficient is high, less viscous loss occurs; however, the fluid velocity may be high, so the friction factor will be high since more inertial loss happens.

Laser-Profiled Continuum Robot with Integrated Tension Sensing for Simultaneous Shape and Tip Force Estimation.

The development of miniaturized continuum robots has a wide range of applications in minimally invasive endoluminal interventions. To navigate inside tortuous lumens without impinging on the vessel wall and causing tissue damage or the risk of perforation, it is necessary to have simultaneous shape sensing of the continuum robot and its tip contact force sensing with the surrounding environment. Miniaturization and size constraint of the device have precluded the use of conventional sensing hardware and embodiment schemes. In this study, we propose the use of optical fibers for both actuation and tension/shape/force sensing. It uses a model-based method with structural compensation, allowing direct measurement of the cable tension near the base of the manipulator without increasing the dimensions. It further structurally filters out disturbances from the flexible shaft. In addition, a model is built by considering segment differences, cable interactions/cross talks, and external forces. The proposed model-based method can simultaneously estimate the shape of the manipulator and external force applied onto the robot tip. Detailed modeling and validation results demonstrate the accuracy and reliability of the proposed method for the miniaturized continuum robot for endoluminal intervention.

The Overlapped Electron‐Cloud Model for Electron Transfer in Contact Electrification

AbstractContact electrification (CE) is one of the oldest topics in physics, which has been discussed for more than 2600 years. Recently, an overlapped electron‐cloud (OEC) model was proposed by Wang to explain all types of CE phenomena for general materials in which a deep overlapping of electron clouds belonging to two atoms results in a lowered potential barrier for electron transfer from one to the other by applying a compressive force, which is simply referred to as Wang transition for CE. Here, the degree of electron‐cloud overlap between two atoms is controlled by using tapping mode atomic force microscopy. A temperature difference and electric field are applied between atoms of two surfaces. It is found that electron transfer only occurs when the contact tip and sample interact in the repulsive‐force region, which corresponds to a strong overlap of the electron clouds. Such a fact even preserves if the tip is at a higher temperature than the sample for 120 K. Alternatively, by applying a bias, electron tunneling would occur when the tip is in the attractive‐force region within which normal electron transfer would not occur. These studies solidify the overlapped electron‐cloud model first proposed by Wang. Further, the temperature and bias effects on the CE are explained based on a modified OEC model.

A study on MOORA-based taguchi method for optimization in automated GMA welding process

Abstract Generally, welding is an essential technique, which widely used in industries such as automobile, aerospace, shipbuilding, transportation, nuclear and offshore wind energy. The automatic GMA(Gas Metal Arc) welding process is a welding process that yields coalescence of metals by heating with a welding arc between a continuous filler metal electrode and the workpiece. A controller is used to control wire feed rate, arc current and welding voltage such as welding parameters. The welding processalso is a multi-objective, multi-factor metal fabrication technique. Several welding parameters interact in a complicated way, which could lead to direct or indirect effect on the bead geometry as welding quality. Therefore, welding parameters are required to be optimized for their responses or welding characteristics. Multi-Objective Optimization Method by Ratio Analysis (MOORA) has been used with great success in experimental designs for problems with multiple parameters due to its practicality. This paper proposed an intelligent algorithm with entropy measurement method for optimizing GMA welding process with multiple performance characteristics. The weights of the quality characteristics are determined by employing the entropy measurement method. Welding parameters are selected welding current, arc voltage, welding speed and CTWD (Contact Tip to Work Distance) and analyzed their effect on the three quality characteristics such as bead width, bead height and hardness of the weldments. Based on the Taguchi quality design theory, a L9 orthogonal array was chosen for the experiments. The S/N (signal-to-noise) ratio was employed to predict the optimal parameter setting. The confirmation experiment verifies the proposed the developed MOORA with entropy measurement technology has the ability to predict the optimal welding parameters with multiple quality characteristics

Computational model of electrode-induced microenvironmental effects on pH measurements near a cell membrane.

The mechanism of gas transport across cell membranes remains a topic of considerable interest, particularly regarding the extent to which lipids vs. specific membrane proteins provide conduction pathways. Studies of transmembrane (CO2) transport often rely on data collected under controlled conditions, using pH-sensitive microelectrodes at the extracellular surface to record changes due to extracellular CO2 diffusion and reactions. Although recent detailed computational models can predict a qualitatively correct behavior, a mismatch between the dynamical ranges of the predicted and observed pH curves raises the question whether the discrepancy may be due to a bias introduced by the pH electrode itself. More specifically, it is reasonable to ask whether bringing the electrode tip near or in contact with the membrane creates a local microenvironment between the electrode tip and the membrane, so that the measured data refer to the microenvironment rather than to the free surface. Here, we introduce a detailed computational model, designed to address this question. We find that, as long as a zone of free diffusion exists between the tip and the membrane, the microenvironment behaves effectively as the free membrane. However, according to our model, when the tip contacts the membrane, partial quenching of extracellular diffusion by the electrode rim leads to a significant increase in the pH dynamics under the electrode, matching values measured in physiological experiments. The computational schemes for the model predictions are based on semi-discretization by a finite-element method, and an implicit-explicit time integration scheme to capture the different time scales of the system.

Mass and heat transfer control in the GMAW process utilizing feedback linearization and sliding mode observer

Controlling the gas metal arc welding (GMAW) process is investigated utilizing feedback linearization with heat input, detaching droplet diameter and melting rate as controlled variables while accounting for actuator saturation. The control algorithm is employed using a state space model with eight dynamic states. Stability and internal dynamics of the process are studied thoroughly. Sliding mode state observers are implemented to determine the arc current and contact tip to work piece distance as well as the stick out length (which constitute the internal states of the system). Several simulation reports are provided to demonstrate successful regulation and tracking of detaching droplet diameter, heat input rate and melting rate. Finally, simulations indicate that the method is capable of overcoming parametric uncertainty.

Evaluation of Intensity of LED Curing Light on the Depth of Cure of Composite- An in Vitro Study

Aim: To evaluate the effect of intensity of curing light on depth of cure of resin based composite material and also to bring about the awareness to the dentists community regarding the maintenance of intensity of curing light unit. Materials and Method: The resin based composite material of A2 shade was tightly packed into a plastic mould (fig1D) of diameter 6mm and depth 5mm. The sample size for each group was 10 in numbers, which was irradiated from the top, for each varying intensity, with light tip in nearest contact. An LED Light Curing unit was used throughout this study; the input voltage to the curing light was controlled by a regulated dc power supply. Four different settings of voltage 2.9V, 3.0V, 3.1V and 3.2V which yielded the light intensity as 200mW/cm 2 , 250mW/cm 2 , 300 mW/cm 2 and 375 mW/cm 2 , the power supply to the curing light then was set to this voltage level i.e. 5V and the intensity was verified according to the ISO test method to determine the depth of cure of the resin-based composites. Results: Statistical difference between the groups and among the groups were calculated using Students ‘t’ test. Results clearly shows a statistically significant difference in depth of cure with varying intensity of light used. Conclusion: Depth of cure is comparatively low when intensity of curing light is low. These measurements provide valuable baseline information about the specific depth of cure for different intensities of curing light on resin-based composite materials used by dentists.

Investigations on weld bead geometry and microstructure in CMT, MIG pulse synergic and MIG welding of AA6061-T6

This research paper focuses on a comparative study on weld bead geometries of three different welding techniques: Cold Metal Transfer (CMT), Metal Inert Gas Pulse Synergic (MIG P) and MIG Manual Standard (MIG M). Bead-on-plate tests were performed using ER4043 (AlSi5%) as a filler material on the 3.18 mm thick plates of AA6061-T6. Current (80 A, 100 A and 120 A) and welding speed (7.5, 10.5 and 13.5 mm sec−1) were used as input process parameters while shielding gas flow rate and contact tip to workpiece distance (CTWD) were maintained constant as 15 l min−1 and 10 mm respectively. The weld beads processed by all the three techniques are compared by analysing the weld bead geometry. Microstructural characterization is carried out using optical microscopy and Field Emission Scanning Electron Microscope (FESEM). CMT has high dilution and penetration with low heat input. Compared to MIG Pulse Synergic and MIG Manual, CMT shows a drastic reduction in residual stresses. A good amount of penetration and dilution with low heat input is necessitated for better joint efficiency.

Methods of elimination of rails increased damage in the area of weld joints

Rail weld joints from electric-contact welding in stationary and fi eld conditions, as well as those from aluminothermic welding are weak points on tracks that are easily damaged compared with rails outside the weld joints. Currently, these weak points are the defects connected with lack of penetration in the welding area, burns at the points of poor contact of the rail foot with the current-carrying contact tips, or with defects of the weld joint machining after welding, as well as the local hardness reduction in areas affected by heat after welding, and local heat treatment after welding. Elimination of wide areas of reduced hardness at the weld joint points producing saddles, cracks, and chipping, and promoting rails damage next to such joints is a major challenge for increasing the serviceability of weld joints. This study introduces three avenues for elimination of increased damage of rails at weld joints including:• Improvement of technology and equipment for electriccontact welding and local heat treatment after welding in the stationary and fi eld conditions.• Development of technology and equipment for induction welding in the stationary and fi eld conditions.• Development of technology and equipment for differentiated induction tempering of rails preliminary welded in strings 800 m long.

StopBlues: a French e-health device to prevent suicide in the general population

Abstract Background France is one of the Western European countries most affected by suicide, an epidemiological burden and high societal cost of several million euros/year. Several European projects have either implemented web-based interventions for care of mental disorders or recommended online actions which have demonstrated their effectiveness for suicide prevention. The objective of the project was the construction of an application and website to prevent suicide in the general population, with its promotion being supported at the local authority level. Methods The detailed content of the devices and promotional tools available to local authorities was determined through literature reviews and expert groups (psychiatrists, local authorities’ workers and potential users). Results An application and website were constructed with two parts: a public interface with videos (psychological suffering, coping strategies and help available), an emergency button, a map with local resources and contact information (psychiatrists, psychologists, associations...), tips and videos to overcome a period of psychological suffering; and a private interface requiring registration giving access to self-assessment questionnaires and a safety plan to fill in case of crisis. 40 local authorities are involved in StopBlues promotion, with a referent each, responsible of contact with our team, and local organization of promotion. Conclusions Since 04-2018, StopBlues is available at www.stopblues.fr and can be downloaded on iOs and Android. Its promotion is part of a cluster randomized trial with 3 arms: a control group with no promotion, a group with promotion by local authorities, and a group with promotion by local authorities and general practitioner’s waiting room. As promotion could have different intensities depending on budgets and referent’s involvement, we decided to extend it for another year, with local authorities of group control receiving additional financial and organizational support. Key messages As the first e-health program for suicide primary prevention in the French general population, StopBlues’ main goal is to help people find solutions that suit them and direct them to the right help. Local authorities are a key level to promote primary health prevention programs.

Size-dependent random vibration analysis of AFM probe with tip mass considering surface viscoelastic effect

In the present paper, the random vibration response of an atomic force microscope (AFM) cantilever with a tip mass which is excited by a white-noise random displacement at the tip has been studied based on the nonlocal theory of Eringen for the first time. The Laplace transform method has been utilized to find the frequency response function of the beam and effect of various parameters such as tip mass, contact stiffness, contact damping and nonlocal parameter on the mean square value of vibrations has been analyzed numerically and illustrated graphically. It has been revealed through numerical examples that the amount of the tip mass has a powerful effect on the random vibration response of the beam, and the effect of the tip mass must be taken into account to perform a viable and realistic random vibration analysis in the field of Atomic Force Microscopy. Also, it has been shown that the contact damping, on the one hand, reduces the amplitude and mean value of vibrations and, on the other hand, when this coefficient increases the input force increases and the mean value of vibration increases as well.

Effect of material removal state on the selection of theoretical models when scratching single-crystal copper using the load modulation approach

This article presents a constant force–controlled cutting approach with two different geometries of cutting tools. The methodologies for establishing two theoretical models were proposed to quantitatively predict the required applied normal forces at the expected machined depths, which were obtained with a solution to the horizontal projection of the sample–tip contact area and the multi-edge form tip based on a generalized cutting approach, respectively. The selection of the proposed theoretical models is dependent on the two material removal states, respectively, in which one is plowing for a regular triangular pyramid and the other one is cutting chips for a single-point diamond tip. To verify the feasibility and effectiveness of the proposed theoretical models and cutting strategy, a constant normal force cutting of microgrooves was implemented on a single-crystal copper substrate, while realizing constant cutting depths. The difference between the setting normal forces and the theoretical normal forces was analyzed by comparing the experimental results and the model prediction results. The aim of the present study was to investigate the effect of the geometry of the cutting tools on the material removal state and on the selection of the theoretical models.

P2835Feasibility and safety of same day discharge after radiofrequency catheter ablation for paroxysmal atrial fibrillation

Abstract Background Atrial fibrillation catheter ablation (CA) is the most frequent arrhythmia ablation and accounts for a significant proportion of treatment cost. Same day discharge (SDD) after paroxysmal atrial fibrillation (PAF) ablation is an attractive strategy for both patients and hospitals. Objective To understand the eligibility criteria and outcomes for PAF patients who can safely undergo same day discharge after radiofrequency catheter ablation. Methods Patients undergoing CA for PAF were evaluated for SDD at a pre-procedure visit to assess the risk of groin, respiratory, cardiac or bleeding complications. Eligibility criteria for SDD were stable anticoagulation and absence of bleeding history, systolic/diastolic heart failure, or interventional procedures within 60 days, with recommended BMI <35. Patient proximity to the hospital was also considered. Anesthesia included propofol with endotracheal intubation and all patients were ablated with a porous tip contact force catheter (STSF). Patients were on bed rest for 6 hours post-procedure, then ambulated intermittently for 1–2 hours. Discharge followed if they were stable with no evidence of vascular access complications or bleeding. A dedicated RN telephoned patients the following morning to ask a series of standard questions designed to elicit evidence of any complications. Results 52 procedures were identified for SDD, with 7 patients declining. 45 planned SDD procedures for 43 patients occurred 4/17–6/18. Average age was 57±11 years and CHA2DS2-VASc was 1.5±1.1 at procedure. Procedure time was 69±26 min (IQR: 49 - 84 min) with maximum fluoroscopy usage of 0.2 min and 508±149 mL of fluid infused through the catheter. Two patients stayed overnight due a groin bleed and atelectasis with fever, and one chose to stay for comfort. The remaining 42 discharges occurred after 7.2±1.0 hours in recovery, with no SDD-related complications and no required return visits after the follow-up call. There were 3 AF recurrences (6.7%) as of the 10 week visit. Conclusion Appropriate low risk patients identified by simple clinical criteria can be safely discharged the same day after CA of PAF. Further evaluation is required for higher risk patients. Acknowledgement/Funding The study was funded by Biosense Webster Inc.

Load-displacement response of drilled shaft tip in soft rocks of sedimentary origin

A database of in situ drilled shaft and plate load tests in soft rock mass is developed. Analyses of the in situ load tests suggest that (i) the development of tip contact pressures is related to the rock mass shear strength, rock mass deformation modulus, and the vertical displacement of the drilled shaft tip, (ii) embedding the drilled shaft tip contributes to the development of punching shear failure mechanism in the underlying rock mass, however, the mobilized tip contact pressures do not significantly increase as the embedment depth increases unless the rock mass shear strength and deformational properties drastically increase with embedment depth, and (iii) the drilled shaft diameter does not significantly influence the development of the contact pressures, especially in large diameter drilled shafts. A framework for the analysis of the load-displacement response of the drilled shaft tip in soft rock mass is proposed using the in situ load tests. The proposed framework accounts for the observed nonlinear load-displacement response of soft rock mass and is a function of the initial normal stiffness and the initial yield pressure of the rock mass under the drilled shaft tip. Simple equations are developed for the initial normal stiffness and the initial yield pressure of soft sedimentary rocks. Additionally, in situ and laboratory test results are used to provide recommendations for the prediction of the parameters that are required in the proposed models for the initial normal stiffness and the initial yield pressure, namely the unconfined compressive strength and deformation modulus for the rock mass.

A Cost-Effective Solution to Improving the Electrical Performance of Metal Contacting Interfaces in IC System under Temperature-Humidity Environment

Temperature-humidity (TH) induced failure mechanism (FM) of metal contacting interfaces in integrated circuit (IC) systems has played a significant role in system reliability issues. This paper focuses on central processing unit (CPU)/motherboard interfaces and studies several factors that are believed to have a great impact on TH performance. They include: Enabling load, surface finish quality, and contacting area. Test vehicles (TVs) of Clarkdale package and of Ibex peak motherboard were designed to measure low level contact resistance (LLCR) for catching any failure. Several sets of design of experiments (DOE) were conducted on 85°C/85% relative humidity and test results were analyzed. A proposal that correlates asperity spots and contact tip design with contact resistance was proposed and thus a cost-effective solution for improving electrical performance under TH was deduced. The proposal has proven to be reasonably effective in practice.