Cone-shaped Tips Research Articles

Fabrication of controllable porous tungsten tips for indium FEEP by dynamic reciprocating electrochemical etching combined with ultrasonic cleaning method

The porous tungsten emitter is a core component of field emission electric propulsion (FEEP). It combines the advantages of sharp tip and internal propellant transport. The emission performance of a FEEP thruster is highly depended on the emitter's tip apex radius. Traditional processing methods for solid tungsten tips are unsuitable for porous tungsten due to its unique structure and electrochemical properties. This paper introduces a novel approach combining dynamic reciprocating electrochemical etching with ultrasonic cleaning to fabricate cone-shaped porous tungsten tips with controlled apex radii. By alternating between 5 cycles of etching and an ultrasonic cleaning, a 1.9 μm apex radius is achieved after 90 repetitions. The etching current waveform reveals the material dissolution mechanism. The electrochemical characteristics of porous tungsten are investigated, with an optimal processing voltage of 2 V identified. To refine the apex radius and prevent tip collapse, a 1.9 V etching voltage is used in the final stages, maintaining the apex within 2 μm. The effectiveness of the fabricated tip is confirmed through wetting in indium and ignition tests.

Cryo-EM structure of gas vesicles for buoyancy-controlled motility.

Gas vesicles are gas-filled nanocompartments that allow a diverse group of bacteria and archaea to control their buoyancy. The molecular basis of their properties and assembly remains unclear. Here, we report the 3.2Å cryo-EM structure of the gas vesicle shell made from the structural protein GvpA that self-assembles into hollow helical cylinders closed off by cone-shaped tips. Two helical half shells connect through a characteristic arrangement of GvpA monomers, suggesting a mechanism of gas vesicle biogenesis. The fold of GvpA features a corrugated wall structure typical for force-bearing thin-walled cylinders. Small pores enable gas molecules to diffuse across the shell, while the exceptionally hydrophobic interior surface effectively repels water. Comparative structural analysis confirms the evolutionary conservation of gas vesicle assemblies and demonstrates molecular features of shell reinforcement by GvpC. Our findings will further research into gas vesicle biology and facilitate molecular engineering of gas vesicles for ultrasound imaging.

A Method to Investigate the Mechanism of Charge Transport Across Bio-Molecular Junctions with Ferritin.

To investigate the mechanisms of charge transport (CT) across biomolecular tunnel junctions, it is required to make electrical contacts by a non-invasive method that leaves the biomolecules unaltered. Although different methods to form biomolecular junctions are available, here we describe the EGaIn-method because it allows us to readily form electrical contacts to monolayers of biomolecules in ordinary laboratory settings and to probe CT as a function of voltage, temperature, or magnetic field. This method relies on a non-Newtonian liquid-metal ally of Ga and In with a few nm thin layer of GaOx floating on its surface giving this material non-Newtonian properties allowing it to be shaped in to cone-shaped tips or stabilized in microchannels. These EGaIn structures form stable contacts to monolayers making it possible to investigate CT mechanisms across biomolecules in great detail.

Array of Graphene Variable Capacitors on 100 mm Silicon Wafers for Vibration-Based Applications.

Highly flexible, electrically conductive freestanding graphene membranes hold great promise for vibration-based applications. This study focuses on their integration into mainstream semiconductor manufacturing methods. We designed a two-mask lithography process that creates an array of freestanding graphene-based variable capacitors on 100 mm silicon wafers. The first mask forms long trenches terminated by square wells featuring cone-shaped tips at their centers. The second mask fabricates metal traces from each tip to its contact pad along the trench and a second contact pad opposite the square well. A graphene membrane is then suspended over the square well to form a variable capacitor. The same capacitor structures were also built on 5 mm by 5 mm bare dies containing an integrated circuit underneath. We used atomic force microscopy, optical microscopy, and capacitance measurements in time to characterize the samples.

Insights into van der Waals interaction between nanotubes and planar surfaces

Advanced microscopic technology opens up the opportunity of investigating the microstructure of novel materials and devices. In particular, high-resolution Atomic Force Microscopy (AFM) allows for the atomistic observation of materials for a variety of applications. To improve the imaging capability, several tip morphologies have been proposed to be employed in the AFM field. Among such morphologies, the carbon nanotube (CNT) has drawn extensive attention in recent years due to its high resolution and mechanical strength in imaging conditions. However, the exact theoretical basis for employing the nanotube in advanced AFM remains elusive up to this point. Here, we explore the theoretical basis for employing the nanotube morphology in advanced AFM. To do so, van der Waals (vdW) interaction between the nanotube and a planar disc, a key factor for achieving high imaging sensitivity, is evaluated. The results unanimously verify that nanotube morphology has unprecedented advantages over traditional cone-shaped AFM tips.

Ecology of the Razor ClamSolen gordonisand Fishery Impact on the Population In Sasebo Bay, Kyushu, Japan

ABSTRACT In Sasebo Bay, northwestern Kyushu, Japan, the population of the razor clam Solen gordonis inhabits a coarse sandy substratum at 5- to 20-m water depths. A bundle of long metal rods with cone-shaped tips is used to vertically pierce and harvest clams from fishing boats. Knowledge of the ecological traits of this species and the fishery impact on the population is crucial for sustainable management. In April 2014 to March 2015, quadrat sampling by divers, experimental fishing surveys, and retrieval of clams detached from the fishing gear were conducted monthly. The grand mean individual density at the fishing ground was 555.7 inds/m3. New recruitment occurred in mid-November 2014, and the population excluding the recruits was divided into four cohorts by age according to shell-length-frequency distribution. Individual growth was described based on von Bertalanffy growth function, with L ∞, K, and t0 being 95.7 mm, 0.548/y, and -0.109 y, respectively. The estimated mean shell lengths at the 1+, 2+,...

Structure and enhanced field emission properties of cone-shaped Zn-doped SnO2 nanorod arrays on copper foil

Single crystal Zn-doped SnO2 (Zn–SnO2) nanorods with cone-shaped tips (~25nm) on copper foil were synthesized by an organic-free hydrothermal method. The effects of the Zn doping on the morphology, microstructure and field-emission (FE) properties of Zn–SnO2 were investigated. It is found that the Zn doping play an important role in tuning the morphology and size of the SnO2 nanorods. The turn-on fields of SnO2 and Zn–SnO2 nanorods were 3.16 and 2.37V/μm, and field enhancement factors (β) were 960 and 3352, respectively. The enhanced FE property is due to the tapered structures of nanorods with sharp tips and the weak screening effect, and the better electrical contact between conductive copper substrate and field emitters.

Graphene based electron field emitter

Graphene based electron field emitter arrays consisting of cone-shaped silicon tips, a thin Al2O3 tunnel barrier, and graphene top electrode are fabricated. Due to the monolayered graphene top electrode, the electrons are able to tunnel through the Al2O3 layer and emit into the vacuum. The temperature behavior of the tunnel leakage current as well as the emission current is characterized.

Shaping of the Root Canal Using Er:YAG Laser Irradiation

The purpose of the present study was to investigate the degree of Er:YAG laser irradiation at the apical area in vitro. Since the laser was developed, advancement of laser treatment has been seen in various fields. However, few reports exist on shaping of the root canal using Er:YAG laser irradiation. Six single-rooted human teeth were used. The working length of root canals was set at 6.5 mm, and they were enlarged to apical file size #25. An Er:YAG laser and cone-shaped irradiation tips (R135T and R200T) were used. Laser irradiation conditions were 30 m J, 20 pps, and water flow of 5 mL/min. Samples were irradiated three times for 10 sec each using each tip. To evaluate the cutting degree of horizontal area of the root canal, the laser-irradiated surfaces were observed using microfocus X-ray computed tomographic photography before and after every irradiation. The samples were observed under a scanning electron microscope. Measurement of pixels in an area was performed by image-editing software (Adobe Photoshop 7.0). Statistical analysis was performed using StatView (version 5.0). One-way ANOVA and the Tukey-Kramer tests were used; p<0.05 indicated statistical significance. When root canals were irradiated with R200T for 10 sec (p<0.05), a large amount of evaporation (0.12 ± 1.07 mm(2)) was acquired in their cut area compared with the other irradiation conditions. In scanning electron microscopic observation, there was no smear layer and the dentinal tubules were open. When the distance between the tip and root dentin was adjacent, the shaping of root dentin by Er:YAG laser irradiation was definitely observed.

Minitips in Frequency-Modulation Atomic Force Microscopy at Liquid–Solid Interfaces

A frequency-modulation atomic force microscope was operated in liquid using sharpened and cone-shaped tips. The topography of mica and alkanethiol monolayers was obtained with subnanometer resolution, regardless of nominal tip radius, which was either 10 or 250 nm. Force–distance curves determined over a hexadecane–thiol interface showed force modulations caused by liquid layers structured at the interface. The amplitude of force modulation and the layer-to-layer distance were completely insensitive to the nominal tip radius. These results are evidence that minitips smaller than the nominal radius are present on the tip body and function as a force probe.

Carbon Nanohorn Sensitized Electrochemical Immunosensor for Rapid Detection of Microcystin-LR

A sensitive electrochemical immunosensor was proposed by functionalizing single-walled carbon nanohorns (SWNHs) with analyte for microcystin-LR (MC-LR) detection. The functionalization of SWNHs was performed by covalently binding MC-LR to the abundant carboxylic groups on the cone-shaped tips of SWNHs in the presence of linkage reagents and characterized with Raman spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and a transmission electron micrograph. Compared with single-walled carbon nanotubes, SWNHs as immobilization matrixes showed a better sensitizing effect. Using home-prepared horseradish peroxidase-labeled MC-LR antibody for the competitive immunoassay, under optimal conditions, the immunosensor exhibited a wide linear response to MC-LR ranging from 0.05 to 20 microg/L with a detection limit of 0.03 microg/L at a signal-to-noise of 3. This method showed good accuracy, acceptable precision, and reproducibility. The assay results of MC-LR in polluted water were in a good agreement with the reference values. The proposed strategy provided a biocompatible immobilization and sensitized recognition platform for analytes as small antigens and possessed promising application in food and environmental monitoring.

Material and temperature dependent behaviour of single macro-asperity tip when crushed against flat platen

Thermo-mechanical forming of metals is of special concern due to its complex nature which involves temperature, load and particularly tribological parameters at elevated temperatures. Previous studies have given much emphasis to the deformation behaviour of surface asperities at micro level which in turn determines quality and surface finish of a component produced by thermo-mechanical forming. In this work, special attention is given to the deformation behaviour in the case when a single macro-asperity tip is crushed by a flat platen, dependent on the constitutive behaviour of the asperity material and the asperity temperature. Different cone-shaped single asperity tips with two different cone angles, as well as with top-flat facets, were studied bearing in mind that a surface may contain these forms of asperities. Experiments were conducted on the Al-alloy AA6082 at room temperature (RT) and FEM analyses were run to study the behaviour at high temperature (450°C). This work gives deep insight into the deformation behaviour of the macro-asperity tips, with regard to for instance lateral spread of the tip, and its ability to provide contact pressure against the crushing platen. The analysis also reveals how high and low friction against the platen affects the deformation behaviour of the asperity tips.

Synthesis of Aligned Carbon Nanofibers on Electrochemically Preroughened Silicon

Aligned carbon nanofibers (CNFs) with a population density of about 3 × 108 cm−2 are synthesized on electrochemically roughened silicon using the bias-assisted chemical vapor deposition system. Isolated CNFs with much lower population density (∼3 × 106 cm−2) are formed on polished silicon wafer at the same growth conditions. The morphologies, microstructures, and components of the CNFs are accordingly characterized using scanning electron microscopy, Raman spectroscopy, transmission electron microscopy, and energy dispersive analysis of X-rays. On the basis of the surface barrier limited diffusion model, it is shown that electrochemical roughening of silicon surface can increase the population density of energetic carbon species that act as self-catalysts for the vertical growth of CNFs. The formation of CNFs with cone-shaped tips simultaneously involves the vertical growth and a continuous thinning of fiber tips by the bombarding of CH4+ and H+ ions in CH4/H2 plasma.

Synthesis and photoluminescence of aligned straight silica nanowires on Si substrate

Aligned straight silica nanowires (NWs) have been synthesized on Si wafer by thermal evaporation of mixed powders of zinc carbonate hydroxide and graphite at 1100 °C and condensation on Si substrate without using any catalyst. The straight silica NWs have diameters ranging from 50 to 100 nm, and lengths of several micrometers, with cone-shaped tips at their ends. High deposition temperature and relatively high SiO x vapor concentration near the growth substrate would be beneficial to the formation of the aligned straight silica NWs. Different morphologies of silica nanostructures have also been obtained by varying the deposition temperature and the vapor concentration of the SiO x molecules. Room temperature photoluminescence measurements on the oriented silica NWs show that two green emission bands at 510 and 560 nm, respectively, revealing that the aligned straight silica NWs might have potential applications in the future optoelectronic devices.

Atmospheric molded poly(methylmethacrylate) microchip emitters for sheathless electrospray.

Disposable poly(methylmethacrylate) (PMMA) sheathless electrospray microchip emitters were prepared for the first time using the atmospheric molding fabrication protocol. A sheathless electrospray from uncoated channel outlets, machined to cone-shaped three-dimensional tips, is demonstrated utilizing a simple cross design with an on-chip liquid junction to obviate the need for external unions to voltage electrodes, thus reducing the dead volume effects as well as the complexity of fabrication. The fast replication of microchip emitters was performed by molding prepolymeric methylmethacrylate solutions into silicon-master/aluminum-spacer/glass-plate molds followed by UV-initiated free radical polymerization. The performance of the new microchip emitters was demonstrated for mass spectral measurements of methionine enkephalin, adrenocorticotropic hormone and insulin peptide/protein mixtures. The samples were infused through capillary connections using hydrodynamic pumping. The polymeric emitters prepared by this flexible fabrication route offer an easy way of operation and high stability, without a need for attachment of external voltage unions or metallizing the emitter tips. The new approach should provide a useful low-cost tool for widespread coupling of mass spectrometry to chip systems.

Pressure polishing: a method for re-shaping patch pipettes during fire polishing

The resolution of patch-clamp recordings is limited by the geometrical and electrical properties of patch pipettes. The ideal whole-cell patch pipette has a blunt, cone-shaped tip and a low resistance. The best glasses for making patch pipettes are low noise, low capacitance glasses such as borosilicate and aluminasilicate glasses. Regrettably, nearly all borosilicate glasses form pipettes with sharp, cone-shaped tips and relatively high resistance. It is possible, however, to reshape the tip during fire polishing by pressurizing the pipette lumen during fire polishing, a technique we call ‘pressure polishing.’ We find that this technique works with pipettes made from virtually any type of glass, including thick-walled aluminasilicate glass. We routinely use this technique to make pipettes suitable for whole-cell patch-clamp recording of tiny neurons (1–3 μm in diameter). Our pipettes are made from thick-walled, borosilicate glass and have submicron tip openings and resistances <10 MΩ. Similar pipettes could be used to record from subcellular neuronal structures such as axons, dendrites and dendritic spines. Pressure polishing should also be useful in patch-clamp applications that benefit from using pipettes with blunt tips, such as perforated-patch whole-cell recordings, low-noise single channel recordings and experiments that require internal perfusion of the pipette.

A Comparison of Flat and Shallow Conical Tips for Cervical Cryotherapy

J Am Board Fam Pract 1999;12:360–6 Both flat and shallow cone-shaped cryoprobe tips are used for cryotherapy of the cervix. Some controversy exists regarding which is more effective in eradicating CIN and more likely to cause the posttreatment squamocolumnar junction (SCJ) to be positioned within the endocervical canal. These two outcomes were assessed after 84 women returned for post-therapy evaluation following nitrous oxide cryotherapy using a flat or cone-shaped probe tip. Cure rates for CIN were equivalent, 76% and 77%, for the flat and cone-shaped tips, respectively. All posttreatment colposcopy exams were considered satisfactory. The flat tip was more apt to prevent posttreatment SCJ positioning within the endocervical canal when compared with the cone-shaped tip only when the pretreatment SCJ was located entirely on the ectocervix (p = .04). Editorial Comment: It is no surprise that the cone-shaped tip was more likely to force the posttreatment SCJ into the endocervical canal. Furthermore, since all posttreatment colposcopy exams were considered satisfactory, the tendency for more proximal SCJ positioning should not be considered clinically significant. Observation of the posttreatment location of the SCJ on the ectocervix or at the os helps to assess cure clinically, but a cytologic sampling of the endocervical canal is mandatory to evaluate outcome. Regardless, effective treatment always takes precedence over the location of the SCJ. Maximal tissue/probe contact is preferred to ablate the majority of CIN lesions that are located within the central or inner curve area of the cervix. Because the cone-shaped tip conforms better to the epithelium and extends further towards the os, more effective ablation occurs. Other researchers have documented that the cone-shaped probe is better able to destroy neoplastic epithelium. However, the assumption that both tips are equally effective in eradicating CIN should not be considered proven by this study. The sample was extremely small and of insufficient size to detect a clinically significant difference in outcomes. The abbreviated follow-up interval may have also influenced these data. Finally, the cryotherapy technique used was very likely inadequate based on the facts that rather poorer than average cure rates were reported, large cervical lesions greater than two quadrants in size not typically conducive to cryotherapy were treated, and no single postcryotherapy colposcopy examination was considered unsatisfactory (an extremely unlikely probability if effective cryotherapy is implemented). Therefore, cone-shaped probe tips are indicated for treating centrally positioned lesions and the transformation zone, and flat-tips are used when overlapping treatment beyond the central area is necessary. (DGF)

Diamond tip fabrication by air-plasma etching of diamond with an oxide mask

We have fabricated an array of cone-shaped diamond tips for use as a field electron emitter by air-plasma etching a polycrystalline diamond film with a silicon oxide mask. The difference in etching speed between the mask and the diamond resulted in the formation of cone-shaped diamond tips. Post-treatment with hydrogen plasma was effective in cleaning the diamond tips and increasing the surface conductivity. The emission from the diamond tips was measured with a diode configuration. The threshold field was 3 V μm −1 , and the emission current was 0.8 nA tip −1 when the field was raised to 10 V μm −1 .

Atrioventricular valves of the mouse: III. Collagenous skeleton and myotendinous junction

The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves. The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction. The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone-shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected. The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagen-muscle junction in the mitral valve is more similar to the structure of a pennate muscle. The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed.

Vinyl Augerlike Picker Tips for Berry Detachment in a Strawberry Harvester1

Abstract An experimental model strawberry harvester with a series of counter-rotating coneshaped vinyl tips for fruit pickup and removal showed potential for rapid harvesting with reduced injury. Flexible auger-like tips on steel shafts were fabricated by molding and heat curing liquid vinyl around the shafts. Tips were molded in pairs with oppositely twisted ribs to provide upward and backward lift to the fruit. Fruit detachment was achieved with a pinching and snapping action of the screw-like ribbed tips counter-rotating in an upward pattern. A soft nylon bristle brush mounted above the picker tips was found unsatisfactory for pushing detached fruit backward onto a transport belt