Standard Tip Research Articles

Characterization of neonatal aortic cannula jet flow regimes for improved cardiopulmonary bypass

During pediatric and neonatal cardiopulmonary bypass (CPB), tiny aortic outflow cannulae (2–3mm inner diameter), with micro-scale blood-wetting features transport relatively large blood volumes (0.3 to 1.0L/min) resulting in high blood flow velocities (2 to 5m/s). These severe flow conditions are likely to complement platelet activation, release pro-inflammatory cytokines, and further result in vascular and blood damage. Hemodynamically efficient aortic outflow cannulae are required to provide high blood volume flow rates at low exit force. In addition, optimal aortic insertion strategies are necessary in order to alleviate hemolytic risk, post-surgical neurological complications and developmental defects, by improving cerebral perfusion in the young patient. The methodology and results presented in this study serve as a baseline for design of superior aortic outflow cannulae. In this study, direct numerical simulation (DNS) computational fluid dynamics (CFD) was employed to delineate baseline hemodynamic performance of jet wakes emanating from microCT scanned state-of-the-art pediatric cannula tips in a cuboidal test rig operating at physiologically relevant laminar and turbulent Reynolds numbers (Re: 650–2150 , steady inflow). Qualitative and quantitative validation of CFD simulated device-specific jet wakes was established using time-resolved flow visualization and particle image velocimetry (PIV). For the standard end-hole cannula tip design, blood damage indices were further numerically assessed in a subject-specific cross-clamped neonatal aorta model for different cannula insertion configurations. Based on these results, a novel diffuser type cannula tip is proposed for improved jet flow-control, decreased blood damage and exit force and increased permissible flow rates. This study also suggests that surgically relevant cannula orientation parameters such as outflow angle and insertion depth may be important for improved hemodynamic performance. The jet flow design paradigm demonstrated in this study represents a philosophical shift towards cannula flow control enabling favorable pressure-drop versus outflow rate characteristics.

Minimal modifications could decrease fistula rate during tubularized incised plate procedure in distal hypospadias repair

AimTo report outcome of technical modifications to minimize fistula after TIP procedure. Patients and methods369 boys presenting with distal hypospadias were divided into two groups. In group 1, 196 underwent the standard TIP procedure. In the 173 patients in group 2, several modifications were incorporated into the TIP repair: 1) the first proximal suture was U-shaped subepithelial, 2) dartos flap was created on ventral aspect of penis to cover the proximal suture, and 3) the midline release incision was done as a first step. Patients were monitored prospectively for fistulae, chordee, meatal position, stenosis, and evaluated postoperatively at regular intervals. Results362 patients had a good cosmetic appearance with slit-shaped meatus. Urethrocutaneous fistula was seen in 9 (4.6%) in group 1 and 4 (2.3%) in group 2. Urinary streams were of good quality and without fistula in 187 in group 1 and 169 in group 2. Glans dehiscence was seen in 7 (4 in group 1 and 3 in group 2), meatal stenosis and new urethral stricture in 15 (6 in group 1 and 9 in group 2). Glanular appearance was excellent except in those 7 patients who had glans dehiscence, and the phallus was straight in all. ConclusionThe Snodgrass repair has revolutionized the treatment of hypospadias. These technical modifications combined with careful patient selection achieved a low fistula rate.

Novel Use of the Tip of a Standard Diathermic Snare for Endoscopic Submucosal Dissection of a Large Gastric Adenomatous Polyp

This case report describes a 63-year-old man initially diagnosed as having a 2.5-cm gastric adenomatous polyp with low-grade dysplasia. In contrast to using conventional knives for endoscopic submucosal dissection, the standard diathermic snare tip was used as an alternative knife for endoscopic submucosal dissection of the lesion with successful en bloc resection. The procedure was performed without complications. The polyp was finally confirmed as a tubulovillous adenoma with focal high-grade dysplasia.

The effect of wrapping of light-cure tips on the cure of composite resin

Abstract Aim: Dental curing lights are vulnerable to contamination during routine intra-oral use. The purpose of this study was to evaluate the effect of wrapping light-cure tips on the hardness of cured composite resin. Settings and Design: Two types of barriers were used, which are the commercially available cellophane wraps and the disposable light-cure sleeves. A new light-cure unit used with a standard light-cure tip fixed at distance of 0.5 mm from the specimens. Materials and Methods: Sixty molds of 8 mm diameter and 2 mm depth filled with same type and shade of composite resin; 20 specimens cured without wrapping the tips, and 20 used for each wrapping method with new barrier was placed for each. The light-cure intensity and the Knoop hardness value were recorded. Statistical Analysis: Kruskal-Wallis test was used to analyze the statistical differences between the groups. Pearson′s correlation analysis was used to determine the correlation between light intensity and Knoop hardness values. Results: The results of this study showed that there were significant differences in the light intensity among the groups. However, there were no significant differences in the Knoop hardness values among the 3 groups. The cellophane-wrapped around the light-cure tips is appeared to cause the least reduction of hardness from the non-wrapped tip. Conclusions: The effect of the barriers on the hardness of composite resin was small and probably clinically insignificant. The light intensity output was above the acceptable curing levels using any of the two barriers. The use of non-opaque barriers with the light-cure tips is recommended to prevent cross contamination.

Micro- and Nano-scale Measurement of the Thermophysical Properties of Polymeric Materials Using Atomic Force Microscopy

To realize the benefits and optimize the performance of micro- and nano-structured materials and thin films, designers need to understand and thus be able to characterize their thermal, thermophysical, and thermomechanical properties on appropriate length scales. This paper describes the determination of glass-transition temperatures of polymers on the micro-scale, obtained from contact force–distance curves for poly(methyl methacrylate) and poly(vinyl acetate) measured using an atomic force microscope (AFM). Measurements were made using a standard AFM tip where thin films were heated using a temperature controlled hot stage and by using a scanning thermal microscopy (SThM) probe. The latter was used either with the hot stage or with the SThM probe providing a localized heating source via Joule heating. Differences in the glass-transition temperature measured using the hot stage and Joule heating were apparent and considered to be due to heat transfer effects between the probe, specimen, and surroundings. Gradients of force–distance curves, pull-off and snap-in forces, and adhesion energy were obtained. The results suggest that the onset of changes in the material’s mechanical properties at the glass transition was found to be dependent on the mechanical property measured, with pull-off force values changing at lower temperatures than the snap-in force and adhesion energy.

An Evaluation Testbed for Wind Turbine Blade Tip Designs — Winglet Results

A 3.3 m diameter variable speed wind turbine and rotor has been designed, fabricated and tested with exchangeable blade tip capability. This rotor was custom designed utilizing the National Renewable Energy Laboratory's S83X series airfoils for the University of Waterloo Wind Energy research facility with blades that allow the outer 10% of the blade to be exchanged.Turbine power production measurements were completed in the controlled wind facility covering a range of mean wind speeds, 3.6 m/s to 11 m/s, and turbine rotor shaft rotational rates, 100 rpm to 240 rpm. Power produced by the blades was determined as a function of input wind speed. The coefficient of power, CP, was determined as a function of the tip speed ratio λ and peak CPwas found to approach 0.42 at the design λ of 6.7. At the design shaft speed of 200 rpm, the maximum power produced was 1.45 kW at 11 m/s.Prior winglet designs are discussed and two winglet designs are evaluated. The effects of two different winglets, the Maniaci and Gertz designs, were evaluated with surface oil flow visualization and quantified by repeating the test that was executed with the standard tip for each winglet. Both winglets were found to have a bell-shaped power augmentation profile, with a broad peak between 6.5 m/s and 9.5 m/s where power was increased by 5% to 7%. These power augmentation figures matched closely with the findings in the literature that suggested increases of 2% to 8% are possible. It is noted, however, that these designs are certainly not optimal and it is possible that an optimized winglet design through further modeling and testing could be attained.

Recanalization of Femoropopliteal Chronic Total Occlusions Using the ENABLER-P Balloon Catheter System

To evaluate the safety and effectiveness of a new system to facilitate intraluminal advancement of conventional guidewires through chronic total occlusions (CTO) of the superficial femoral artery (SFA) and popliteal artery. The ENABLER-P Balloon Catheter System uses a unique balloon-anchoring mechanism and an automated balloon inflation device for steady, controlled advancement of a standard non-hydrophilic guidewire. The system was evaluated in 37 patients (22 men; mean age 67 years (range 41-87) with femoropopliteal CTOs averaging 86 mm in length (range 10-340). The device was used in a variety of occlusions, including heavily calcified, long, and fibrotic lesions. After successful guidewire recanalization facilitated by the system, occluded arterial segments were treated conventionally with balloon angioplasty, atherectomy, and stents as appropriate. The primary endpoint of successful crossing was achieved in 86% (32/37) of the overall study population. The average activation time for successful crossing was 5.3 minutes (range 0.4-22). Of the 32 cases successfully crossed with the ENABLER-P System, all but 1 was successfully recanalized. One (3%) device-related complication occurred when the wire was advanced into a side branch when treating a 300-mm-long flush ostial SFA occlusion; the resulting perforation was managed with a covered stent without further sequelae. This novel system, which provides enhanced force to a standard guidewire tip for controlled intraluminal advancement, is a promising device for the treatment of peripheral CTOs.

New carbon cone nanotip for use in a highly coherent cold field emission electron microscope

A new cathode for cold-field emission gun using a pyrolytic carbon-cone supported onto a carbon nanotube as the electron emitting tip has been developed. This tip was mounted in a TEM using a FIB based method, and the brightness measured under real operating conditions is five times better than obtained with a standard tungsten tip. Its use overcomes the many technical difficulties which have dogged the use of carbon nanotube-based tips as proposed replacements for tungsten tips. The resulting properties of the final CFEG exhibit a very good energy spread of 0.32eV, a reduced brightness of 1.6×109Am−2sr−1V−1 and a very good long-term stability with a current damping less than 16% per hour.

Measuring the Adhesion Force on Natural Fibre Surface Using Scanning Probe Microscopy

This work has focused on measuring the adhesion forces on both untreated and atmospheric helium plasma treated single jute fibre surfaces using scanning probe microscopy (SPM). The measurements were conducted on three differently aged surfaces for one week, three weeks and six weeks using a standard silicon nitride tip in force-volume (f-v) mode. Up to 256 adhesion data points were collected from various locations on the surface of the studied fibres using in-house developed software and the resulting data were statistically analysed by the histogram method. Results obtained from this analysis method were found to be very consistent with a small statistical variation. The work of adhesion, W a, was calculated from measured adhesion force using the Johnson–Kendall–Roberts (JKR) and Derjaguin–Muller–Toporov (DMT) models. Increases in both adhesion force and work of adhesion were observed on jute fibre with certain levels of atmospheric plasma treatment and ageing time.

Theory and Experiment for Capillary Condensation of Water on Metal Oxide Films in a Humid Environment Studied by Atomic Force Microscope

This article critically discusses van der Waals and capillary forces as a function of relative humidity (RH) measured by atomic force microscope (AFM), which, as recently reported, show a discontinuous behavior at a low and high RH. We measure adhesion forces systematically on hydrophilic aluminum and copper oxide sample surfaces in a controlled humid environment using three different AFM probes, an AFM cantilever with a standard probe tip, super sharp probe tip, and an AFM tipless cantilever. In addition, we estimate the van der Walls and capillary forces by a prolate spheroid-plane, oblate spheroid-plane, or tilted plane-plane geometry in view of the actual AFM probe shapes, and compare with the experimental data in adhesion force measurements. Our studies indicate that a discontinuous behavior of capillary force on the hydrophilic surface at low RH is due to the influence of the sample surface roughness, and that at high RH is due to the effect of shape of the AFM probe. The modified formulations predict adhesion force better than conventional ones between the AFM probe and sample surface in the RH range of 10-85%.

Radiological evaluation of intertrochanteric fracture fixation by the proximal femoral nail

BackgroundSuccessful treatment of intertrochanteric femoral fractures was reportedly influenced by the position of the fixation devices, by reduction quality and by fracture type. MethodsThe records of 227 patients with intertrochanteric fractures treated by intramedullary hip screws were analysed retrospectively. The angle and distance from the femur head apex were transformed into Cartesian coordinates. Comparisons were performed between patients with no mechanical failure (207 patients, 90.7%), with cutouts (15 patients, 6.6%) and with secondary loss of reduction (5 patients, 2.2%). ResultsThe standard tip apex distance (TAD) measurement above 25mm did not predict failure (p=0.62). Mechanical failure rates increased from 4.8% to 34.4% when the centre of lag screw was not in the second quarter of the head–neck interface line (the so-called “safe zone”) (p=0.001). Lag screw insertion lower or higher than 11mm of the head apex line were associated with failure rates of 5.5% and 18.6%, respectively (p=0.004). Multivariate logistic regression showed that lag screw insertion not within the “safe-zone” was associated an Odds Ratio of 13.4 (95% CI 2.24–81) for mechanical failure (p=0.004). ConclusionsThe TAD scale focuses on length measurement and lacks the vector properties of multidirectional measurements. Vector analysis revealed that the caudal-cranial correct lag screw position is the most important factor in preventing mechanical failure.

A novel hybrid PU-alumina flexible foam with superior hydrophilicity and adsorption of carcinogenic compounds from tobacco smoke

A novel porous polyurethane (PU) hybrid foam was designed to improve the hydrophilicity of a conventional open pore PU foam, and to enhance the adsorption of carcinogenic compounds from tobacco smoke. The hybrid foam was prepared by interdispersing ultramilled alumina particles within PU precursors to realize a PU/Al 2O 3 hybrid porous material with well controlled microstructural properties and improved hydrophilicity. The capability of the as obtained hybrid foam to adsorb toxic compounds from the mainstream of tobacco smoke was investigated by using a cellulose-active carbon-cellulose triple filter model, and the results were compared to those obtained for neat PU foam and the standard cigarette filter tip. The results of this study showed that the ultramilled alumina particles enhanced both thermal stability and hydrophilicity of the neat PU foam. Furthermore, the as-obtained hybrid PU/Al 2O 3 foam was able to improve the adsorption of nitrosamines, acetamide, idroquinone, cresol and small aminic and aldehydic molecules, if compared to neat PU foam and standard cigarette filter tip, evidencing potential as tobacco smoke filter.

Tribochemical wear of single crystal aluminum in NaCl solution studied by atomic force microscopy

We report a systematic study of chemically enhanced wear of single crystal aluminum surfaces in aqueous solutions using an environmentally equipped atomic force microscope (AFM). The experiments were conducted by using a standard Si3N4 AFM tip to apply a localized force on a polished, single crystal aluminum (110) surface. Most measurements were performed in 0.5 M NaCl solution. We show the effect of applied force, number of scans, chemical solution, and temperature on the chemical−mechanical wear of aluminum on the nanometer scale. Aggressive chemical environments significantly enhance the wear of aluminum relative to scanning in dry air. Quantitative measurements show that the wear volume increases in proportion to the square root of force and the number of scans (or time). Arrhenius plots of wear volume versus temperature are consistent with an activation energy of 31 kJ/mol for scanning in 0.5 M NaCl. The wear of the AFM tip and the aluminum substrate is explained in terms of the synergistic surface chemical reactions and mechanical action of the tip. We compare these results to previous studies of AFM wear of silicate glass.

In Vivo Evaluation of Virtual Electrode Mapping and Ablation Utilizing a Direct Endocardial Visualization Ablation Catheter

Radiofrequency (RF) ablation utilizing direct endocardial visualization (DEV) requires a "virtual electrode" to deliver RF energy while preserving visualization. This study aimed to: (1) examine the virtual electrode RF ablation efficacy; (2) determine the optimal power and duration settings; and (3) evaluate the utility of virtual electrode unipolar electrograms. The DEV catheter lesions were compared to lesions formed using a 3.5 mm open irrigated tip catheter within the right atria of 12 sheep. Generator power settings for DEV were titrated from 12W, 14W and 16W for 20, 30 and 40 seconds duration with 25 mL/min saline irrigation. Standard irrigated tip catheter settings of 30W, 50°C for 30 seconds and 30 mL/min were used. The DEV lesions were significantly greater in surface area and both major and minor axes compared to irrigated tip lesions (surface area 19.43 ± 9.09 vs 10.88 ± 4.72 mm, P<0.01) with no difference in transmurality (93/94 vs 46/47) or depth (1.86 ± 0.75 vs 1.85 ± 0.57 mm). Absolute electrogram amplitude reduction was greater for DEV lesions (1.89 ± 1.31 vs 1.49 ± 0.78 mV, P = 0.04), but no difference in percentage reduction. Pre-ablation pacing thresholds were not different between DEV (0.79 ± 0.36 mA) and irrigated tip (0.73 ± 0.25 mA) lesions. There were no complications noted during ablation with either catheter. Virtual electrode ablation consistently created wider lesions at lower power compared to irrigated tip ablation. Virtual electrode electrograms showed a comparable pacing and sensing efficacy in detecting local myocardial electrophysiological changes.

The Use of Hydrophobic and Hydrophilic Tensiometers in the Measurement of Water and NAPL Suctions and Determination of SLRC

This technical note presents some preliminary results obtained with the use of hydrophobic and hydrophilic tensiometers to measure liquid pressures in three-phase systems (air-NAPL-water). The porous tips of the hydrophobic tensiometers underwent a surface treatment known as silanization. The silanized tensiometers demonstrated little influence of the interstitial water in the measured values of NAPL suctions, the contrary occurring in the case of the standard ones. Due to water preferential wetability, the water tensiometers with standard porous stone tips presented adequate hydrophilic behavior, measuring water suctions satisfactorily. These tensiometers were also used to determine the soil-liquid retention curves (SLRC) of an eolian sand by vaporization. Water and diesel were used in the performed tests. The performance of the vaporization technique was satisfactory, reducing the time required for test accomplishment and presenting repeatable results. In the case of diesel, due its low vapor pressure and the selective nature of its vaporization process, the use of this technique was shown to be limited. Sample heating was used to accelerate the vaporization process.

Study on the Serial Design of Chain Wheel of the Roller Chain Based on Pro/E

The roller chain is a kind of flexible transmission with high transmission efficiency, low precision requirement for the manufacture and mount of the base machine. Therefore, the roller chain is widely used in machinery manufacturing. In this paper, we use the man-machine interactive input to set a different parameters to create a different number of chain wheels with different standard pitch diameter and tip diameter by the Pro/Programme and we use the Family table that allows for rapid modeling of chain wheel to improve the design efficiency and quality of parts.

New phacoemulsification tip with a grooved, threaded-tip construction

To visually compare ultrasonic tip vibrations between a phaco tip with internal grooves (threaded tip) and a standard phaco tip during continuous-mode ultrasound (US) using ultra-high-speed digital video imaging. Watanabe Eye Clinic, Hyogo, Japan. Experimental study. The threaded tip was constructed by creating grooves inside a standard phaco tip using a screw. An ultra-high-speed digital video camera was used to record the image during continuous-mode US. Samples used in the test chamber during phacoemulsification included a piece of chestnut as a representative human lens sample and actual human lens fragments. Ultra-high-speed digital images showed that the threaded tip created a larger amount of cavitation than the standard phaco tip during US oscillation. Phacoemulsification of the sample using the standard phaco tip produced a chattering motion, making it difficult to maintain a steady tip position. The threaded tip produced little chattering motion, making it relatively easy to maintain a steady tip position. Once a piece of sample was gripped by the threaded tip, it was shaved and aspirated into the threaded tip without chattering motion. The mean effective phacoemulsification time (EPT) of the threaded tip was significantly shorter than that of the normal phaco tip (6.0 seconds ± 1.9 [SD] versus 15.4 ± 1.3 seconds; P=.002). The threaded tip created larger amounts of cavitation and had strong destructive and holding power. This threaded construction is simple to produce and appears to be very effective for phacoemulsification.

Diamond-Modified AFM Probes: From Diamond Nanowires to Atomic Force Microscopy-Integrated Boron-Doped Diamond Electrodes

In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are suitable for probing, manipulating, sculpting, and sensing at single digit nanoscale.

Field Investigation into Effectiveness of Compaction Grouting

AbstractThe common design approach of compaction grouting for ground improvement works is oversimplified and does not account for the effects of soil properties and grouting variables. The obtained improvements therefore appear inconsistent with the predicted ones. This paper presents the results of a field test conducted at Tokyo International Airport to evaluate the effectiveness of compaction grouting under well-controlled conditions. The test consisted of 87 compaction grout piles injected in three cases of different pile diameters and spacings. The paper also discusses the effects of soil properties, replacement ratio, and injection sequence on the effectiveness that is evaluated in terms of the standard penetration test N-value and cone penetration test tip resistance, and the variation of effectiveness with depth. A new design procedure that accounts for the effects of initial soil properties is introduced. It has been found that the injection sequence has a significant effect on the grouting mecha...

Diamond tips for automated electrical probing inside a scanning electron microscopy system

Pyramidal tips made from boron doped diamond have become the ultimate choice for electrically measuring semiconductor device structures in electrical atomic force microscopy (AFM). An advanced measurement setup with diamond probing units directly integrated inside a scanning electron microscopy (SEM) system is highly wanted as this allows for accurate tip positioning compared to the optical microscope of a standard AFM and enables also multiple tip measurements. Therefore, we have developed highly conductive in-plane diamond tips with a triangular shape and attached them to Ni cantilevers. We have established a LabVIEW-based setup enabling automated electrical measurements inside a SEM system using stick-and-slip motion nanomanipulators and a parameter analyzer system. To our best knowledge, this paper presents first 1- and 2-tip electrical measurements of microfabricated diamond probes inside a SEM system. Measurements of Si staircase and Ge structures are shown and compared to scanning spreading resistance (SSRM) results. Our work demonstrates that doped diamond tips clearly outperform common tungsten probe needles enabling nanoprobing experiments which were impossible so far. Based on our results, we predict that doped diamond is going to be the standard tip material not only for electrical AFM but also for nanoprobing of semiconductor materials.