Cone-shaped Tip Research Articles

Tip Effect of the Tapping Mode of Atomic Force Microscope in Viscous Fluid Environments.

Atomic force microscope with applicable types of operation in a liquid environment is widely used to scan the contours of biological specimens. The contact mode of operation allows a tip to touch a specimen directly but sometimes it damages the specimen; thus, a tapping mode of operation may replace the contact mode. The tapping mode triggers the cantilever of the microscope approximately at resonance frequencies, and so the tip periodically knocks the specimen. It is well known that the cantilever induces extra liquid pressure that leads to drift in the resonance frequency. Studies have noted that the heights of protein surfaces measured via the tapping mode of an atomic force microscope are ~25% smaller than those measured by other methods. This discrepancy may be attributable to the induced superficial hydrodynamic pressure, which is worth investigating. In this paper, we introduce a semi-analytical method to analyze the pressure distribution of various tip geometries. According to our analysis, the maximum hydrodynamic pressure on the specimen caused by a cone-shaped tip is ~0.5 Pa, which can, for example, pre-deform a cell by several nanometers in compression before the tip taps it. Moreover, the pressure calculated on the surface of the specimen is 20 times larger than the pressure without considering the tip effect; these results have not been motioned in other papers. Dominating factors, such as surface heights of protein surface, mechanical stiffness of protein increasing with loading velocity, and radius of tip affecting the local pressure of specimen, are also addressed in this study.

Designing and characterizing a multi-stepped ultrasonic horn for enhanced sonochemical performance

The commonly used ultrasonic horn generates localized cavitation below its converging tip resulting in a dense bubble cloud near the tip and limiting diffusion of reactive components into the bubble cloud or reactive radicals out of the bubble cloud. To improve contact between reactive components, a novel ultrasonic horn design was developed based on the principles of the dynamic wave equation. The horn, driven at 20kHz, has a multi-stepped design with a cone-shaped tip increasing the energy-emitting surface areas and creating multiple reactive zones. Through different physical and chemical experiments, performance of the horn was compared to a typical horn driven at 20kHz. Hydrophone measurements showed high acoustic pressure areas around the horn neck and tip. Sonochemiluminescence experiments verified multiple cavitation zones consistent with hydrophone readings. Calorimetry and dosimetry results demonstrated a higher energy efficiency (31.3%) and a larger hydroxyl radical formation rate constant (0.36μMmin−1) compared to typical horns. In addition, the new horn degraded naphthalene faster than the typical horn tested. The characterization results demonstrate that the multi-stepped horn configuration has the potential to improve the performance of ultrasound as an advanced oxidation technology by increasing the cavitation zone in the solution.

Characterization of Wear Mechanisms in Distorted Conical Picks After Coal Cutting

The interest in understanding the wear mechanisms of cemented carbide (CC) is not a new development. For a long time, there have been studies on different wear mechanisms under different coal/rock cutting conditions. These studies have helped improving the quality of CC, thereby preventing such wearing of tools. Due to highly unpredictable character of coal/rock, the wearing phenomena cannot be attributed to one single domain of conditions. However, one conclusion that can be drawn in this context is that, under similar working conditions, similar types of CC undergo similar nature of wearing process. An optimum combination of high wear resistance, strength and hardness has facilitated widespread application of CC in the field of mining engineering. The abrasive parts of the mining tools are made of CC materials. The current study is focussed on a detailed characterization of the wear mechanisms of conical picks, which are used for coal mining. Conical picks consist of a steel body with an inserted cone-shaped CC tip. After being used for a certain period of time, both, the CC tip and the steel body get distorted. In this study, selection of appropriate samples was followed by critical observation of them through field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS). In the previous study, we explained the distortion process of both, the tip as well as the body, using the SEM images. For the present study, two samples were taken from our previous investigation for further analysis. Three other samples were also included in the present study. Seven different types of wear mechanisms, such as, cracking and crushing, cavity formation, coal intermixing, chemical degradation along with abrasion, long and deep cracks, heating effect and body deformation were observed in the five tool samples.

Effect of Localized Surface-Plasmon Mode on Exciton Transport and Radiation Emission in Carbon Nanotubes

We report on a general theoretical approach to study exciton transport and emission in a single-walled carbon nanotube (SWNT) in the presence of a localized surface-plasmon (SP) mode within a metal nanoparticle interacting via near-field coupling. We derive a set of quantum mechanical equations of motion and approximate rate equations that account for the exciton, SP, and the environmental degrees of freedom. The material equations are complemented by an expression for the radiated power that depends on the exciton and SP populations and coherences, allowing for an examination of the angular distribution of the emitted radiation that would be measured in experiment. Numerical simulations for a (6,5) SWNT and cone-shaped Ag metal tip (MT) have been performed using this methodology. Comparison with physical parameters shows that the near-field interaction between the exciton-SP occurs in a weak coupling regime, with the diffusion processes being much faster than the exciton-SP population exchange. In such a case, the effect of the exciton population transfer to the MT with its subsequent dissipation (i.e., the Förster energy transfer) is to modify the exciton steady state distribution while reducing the equilibration time for excitons to reach a steady sate distribution. We find that the radiation distribution is dominated by SP emission for a SWNT-MT separation of a few tens of nanometers due to the fast SP emission rate, whereas the exciton-SP coherences can cause its rotation.

Visualization of Irrigant Flow and Cavitation Induced by Er:YAG Laser within a Root Canal Model

Introduction Laser-activated irrigation (LAI) has recently been introduced as an innovative method for root canal irrigation. However, there is limited information about the cleaning mechanism of an Er:YAG laser. In this study, we visualized the action of laser-induced bubbles and fluid flow in vitro to better understand the physical mechanisms underlying LAI. Methods An Er:YAG laser was equipped with a novel cone-shaped tip with a lateral emission rate of approximately 80%. Laser light was emitted at a pulse energy of 30, 50, or 70 mJ (output energy: 11, 18, or 26 mJ) and a repetition rate of 1 or 20 pulses per second, without air or water spray. Fluid flow dynamics in a root canal model were observed by using glass-bead tracers under a high-speed camera. Moreover, laser-induced bubble patterns were visualized in both free water and the root canal model. Results Tracers revealed high-speed motion of the fluid. A full cycle of expansion and implosion of vapor and secondary cavitation bubbles were clearly observed. In free water, the vapor bubble expanded for 220 microseconds, and its shape resembled that of an apple. In the root canal model, the vapor bubble expanded in a vertical direction along the canal wall, and bubble expansion continued for ≥700 microseconds. Furthermore, cavitation bubbles were created much more frequently in the canal model than in free water. Conclusions These results suggest that the cleaning mechanism of an Er:YAG laser within the root canal might depend on rapid fluid motion caused by expansion and implosion of laser-induced bubbles.

Synthesis and field emission property of carbon nanotubes with sharp tips

Carbon nanotubes (CNTs) with sharp tips were synthesized by a hydrogen arc discharge method. Three unusual morpholo- gies, i.e., a cone-shaped tip, a suddenly-shrinking tip, and a pencil point-like tip were observed. These novel tip structures are considered to be related to the addition of a small amount of silicon powder in the raw material, which may introduce structural defects in the CNTs. The field emission property of the sharp-tip CNTs was investigated, and a low threshold electric field of 3.75 V/m, a high field emission current density of ~1.6×10 5 A/cm 2 , and a good emission stability were demonstrated. The superior field emission performance of the CNTs can be attributed to their good crystallinity and unique tip structures.

DETERMINATION OF TRACE CADMIUM BY FLOW INJECTION ON-LINE MICROCOLUMN PRECONCENTRATION COUPLED WITH FLAME ATOMIC ABSORPTION SPECTROMETRY USING HUMAN HAIR AS A SORBENT

A novel method using a cone-shaped pipette tip packed with human hair as an adsorption material has been developed for the on-line flow injection preconcentration of trace Cd(II) ions based on its complex formation with the ammonium pyrrolidine dithiocarbamate (APDC) prior to flame atomic absorption spectrometric (FAAS) determination. Cd-PDC complex sorbed on the human hair was eluted by 4.0 mol L−1 HNO3. The enhancement factor is 19, and the detection limit (3σ) is 0.77 μg L−1. The proposed method was successfully applied to the determination of trace cadmium in drinking water, beverage samples, and the certified reference materials.

Synthesis and field emission property of carbon nanotubes with sharp tips

Carbon nanotubes (CNTs) with sharp tips were synthesized by a hydrogen arc discharge method. Three unusual morphologies, i.e., a cone-shaped tip, a suddenly-shrinking tip, and a pencil point-like tip were observed. These novel tip structures are considered to be related to the addition of a small amount of silicon powder in the raw material, which may introduce structural defects in the CNTs. The field emission property of the sharp-tip CNTs was investigated, and a low threshold electric field of 3.75 V/m, a high field emission current density of ∼1.6×10 5 A/cm 2, and a good emission stability were demonstrated. The superior field emission performance of the CNTs can be attributed to their good crystallinity and unique tip structures.

Rectal Perforation After Procedure for Prolapse and Hemorrhoids: Possible Causes

Our aim was to explore possible causes of rectal perforation occurring in patients who undergo the procedure for prolapse and hemorrhoids. We evaluated data from cases of rectal perforation that occurred after the procedure for prolapse and hemorrhoids in China in conjunction with case reports from the international medical literature. We identified 7 patients from 5 hospitals in 2 provinces of China who had rectal perforation after the procedure despite having received prophylactic antibiotic treatment. Two patients had a disrupted staple line and 5 had perforations on the rectum wall above the intact staple line. Six patients presented with symptoms in the first 3 days after the procedure. Three patients had concomitant disease: 1 had concomitant constipation and internal rectal prolapse, 1 had concomitant constipation, and 1 had concomitant liver cirrhosis ascites that was not diagnosed preoperatively. Of the 15 cases of rectal perforation found in the literature, 3 patients had an intact staple line and 5 patients had a ruptured staple line. The cone-shaped tip of the anvil, concomitant rectal prolapse and pelvic floor descent, and concomitant ascites are possible causes of rectal perforation after the procedure for prolapse and hemorrhoids.

A Chandelier-Illuminated Anterior Chamber Maintainer for Use During Descemet Stripping Automated Endothelial Keratoplasty in Patients With Advanced Bullous Keratopathy

A new 25-gauge illuminated anterior chamber maintainer composed of a 25-gauge infusion cannula through which a 29-gauge chandelier fiber probe passes was developed for use during Descemet stripping automated endothelial keratoplasty to treat patients with advanced bullous keratopathy. This device, which is compatible with a xenon or mercury vapor illuminator to generate powerful wide-angle illumination from the cone-shaped chandelier fiber tip, is self-retained at the corneal limbus after insertion of the infusion cannula through a corneal side port. Because of its bifunctionality, that is, bright illumination and adequate irrigation flow, excellent visibility with stable anterior chamber maintenance can be concurrently obtained for Descemet stripping, endothelial graft insertion, and subsequent intraocular manipulations without the need for use of a biologic staining technique or ophthalmic viscosurgical products even in patients with severe corneal haze. This new device facilitates safe and simple intraocular manipulation during Descemet stripping automated endothelial keratoplasty.

Er:YAGレーザーを用いた根管内洗浄効果に関する研究

The aim of this study was to clarify the working mechanism of intra-canal irrigation by pulsed lasers. Using a high-speed camera, vapor and cavitation bubbles induced by Er:YAG laser were visualized in a water environment and in a glass root canal model. In addition, the motion of glass-bead tracers was captured in the root canal model. The vapor bubbles produced by a cone-shaped tip and flat one were different in shape and lifetime. In the root canal model, the vapor bubbles grew up and down along the canal wall, followed by the repeated formation and collapse of many smaller cavitation bubbles. The analysis using tracers showed rapid agitation caused by laser irradiation. These results suggest that the mechanism of Er:YAG laser in root canal irrigation might be attributed to high-speed fluid motion due to bubble formation and collapse. An Er:YAG laser with a cone-shaped tip may be promising for intra-canal irrigation.

The influence of surface topography on Kelvin probe force microscopy

Long-range electrostatic forces govern the imaging mechanism in electrostatic forcemicroscopy as well as in Kelvin probe force microscopy. To improve the analysis of suchimages, simulations of the electrostatic field distribution have been performed in the pastusing a flat surface and a cone-shaped tip. However, the electrostatic field distributionbetween a tip and a sample depends strongly on the surface topography, which has beenneglected in previous studies. It is therefore of general importance to study the influence ofsample topography features on Kelvin probe force microscopy images, which we addresshere by performing finite element simulations. We show how the surface potentialmeasurement is influenced by surface steps and surface grooves, considering potentialvariations in the form of a potential peak and a potential step. The influence of thetopography on the measurement of the surface potential is found to be rathersmall compared to a typical experimental resolution. Surprisingly, in the caseof a coinciding topography and potential step an improvement of the potentialprofile due to the inclusion of the topography is observed. Finally, based on theobtained results, suggestions for the realization of KPFM measurement are given.

Observation of particles manipulated by ultrasound in close proximity to a cone-shaped infrared spectroscopy probe

The presented investigations aimed to enhance surface sensitive infrared spectroscopy for chemical analysis by ultrasonic particle manipulation. The combination of these techniques has the potential for new measurement concepts for use in the chemical analysis of suspensions. Local increases of particle concentration brought about by ultrasound could facilitate measurements of molecular-specific infrared spectra of the suspending phase and particles independently. By changing the frequency of an ultrasonic standing wave around 2 MHz it was possible to control the position of particles in respect to the optically sensitive region of the infrared spectroscope. Results obtained with a set-up that enabled us to explore the application of an ultrasonic standing wave to push suspended particles at or into μm distances of the sensing element of an in-line fiber optic probe and subsequently retract them from there are presented. Light micrographs suggested, that the task was successfully accomplished with polystyrene beads suspended in methanol, aggregates were manipulated to and from the cut surface of the truncated, cone-shaped fibre probe tip by changes of the ultrasonic frequency between 1.85 and 1.87 MHz. Feasibility was confirmed by infrared absorption spectra recorded when PTFE particles suspended in tetrahydrofuran were used.

Pancreatic duct holder for facilitating duct-to-mucosa pancreatojejunostomy after pancreatoduodenectomy

Duct-to-mucosa pancreatojejunostomy after pancreatoduodenectomy may be technically difficult, particularly in cases in which the remnant pancreas is soft with a small main pancreatic duct. We devised a pancreatic duct holder for duct-to-mucosa pancreatojejunostomy. The holder has a cone-shaped tip. A one-third circle of the tip is cut away, which makes a slit. As the tip is inserted gently into the pancreatic duct, the duct can be adequately expanded. The holder provides a good surgical field for anastomosis. A slit of the tip allows needle insertion. The holder facilitates stitches of the jejunum also. Twelve patients underwent pancreatoduodenectomy, followed by duct-to-mucosa pancreatojejunostomy using the holder. The holder allowed 8 or more stitches in duct-to-mucosa anastomosis, even in patients with a small pancreatic duct. No patients developed prolonged pancreatic leakage or pancreatic fistula postoperatively. In conclusion, the pancreatic duct holder is a simple and useful tool for facilitating duct-to-mucosa pancreatojejunostomy.

Bactericidal effects of Er:YAG laser with a cone-shaped tip within root canal dentin

Bactericidal effects of Er:YAG laser with a cone-shaped tip within root canal dentin

Removal of the Smear Layer Using Er: YAG Laser with a Cone-shaped Tip

Removal of the Smear Layer Using Er: YAG Laser with a Cone-shaped Tip

Fabrication of CdSe–ZnS nanocrystal-based local fluorescent aperture probes by active polymerization of photosensitive epoxy

We report the fabrication of a nanocrystal (NC) doped polymer tip at the end of a single-mode optical fiber with active polymerization technique. The tip is created by immersing the fiber in a photosensitive epoxy precursor containing colloidal CdSe–ZnS NCs and polymerizing the epoxy using laser light introduced through the fiber. The laser power was found to have a strong influence on the tip height and shape. As the laser beam progressed from the fiber end, the power was reduced by conversion and absorption, resulting in a cone-shaped tip. The shape of the extreme end of the tip was sensitive to the transmitted beam pattern, indicating that the shape of the tip is independent of the substrate fiber. A blue shift and reduction in decay time suggest that the emission properties of the NCs are affected by immobilization in the epoxy, possibly because of oxidation at the NC surface.

A simple facet-based method for single crystal electrochemical study

In this paper, we demonstrate a simple facet-based method for single crystal electrochemical study. Based on the design of a simple and proper electrochemical cell using a cone-shaped pipette tip, one of the natural (1 1 1) facets of a Au single crystal bead has been directly used for electrochemical measurements. Since the processes of orientating, cutting and mechanical polishing are avoided, misorientation and mechanical damage to single crystal surface can be eliminated and reliable data are expected. The advantages of the method have been proved by the nice cyclic voltammogram of Ag underpotential deposition (UPD), a system that has shown large discrepancy in cyclic voltammograms reported by different laboratories due to the dissimilarity of the surface state. The sharp and reversible UPD peaks from the facet-based measurements resemble the best of the reported data in the literature. The method can be extended to (1 1 1) surfaces of some other metals.

Field emission patterns from multiwall carbon nanotubes with a cone-shaped tip

Electron emission from multiwall carbon nanotubes (CNTs) with a cone-shaped tip, on the apex of which five pentagons are present, has been studied by field emission microscopy (FEM). Two types of FEM patterns were observed: one is a well-defined “pentagon” pattern that is typically observed for ordinal multiwall CNTs though the number of pentagons is five in the case of cone-shaped CNTs, and the other is a “dim” pattern that is usually observed for single-wall CNTs. Appearance voltages of the respective patterns and transmission electron microscopy study of the cone-shaped CNTs suggest that the pentagon patterns originate from CNTs with apex radii larger than approximately 2nm while the dim patterns originate from those with the smaller apex radii.

Mechanical sensing of the penetration of various nanoneedles into a living cell using atomic force microscopy

Mechanical responses during insertion of a silicon nanoneedle into a living melanocyte were observed by using an atomic force microscope (AFM). In order to study the dependence of the mechanical response on the shape of the nanoneedle, we prepared various shapes of silicon AFM tips by focused-ion beam (FIB) etching. The force curves showed increases up to 0.65–1.9 nN after contact on the cell surface, and then the force dropped corresponding with the penetration of the needle through the cell membrane. The force required for penetration was significantly smaller than that using a normal pyramidal tip. The force curves with a cylindrical tip showed a shorter indenting distance before penetration than that with the cone-shaped tip. It is considered that the information about the geometry of penetrating material leads to the development of more suitable micro- and nano-materials to insert into a living cell for cell surgery.