Probe Radius Research Articles

Ultrasound-Guided Off-Plan Lumbar Seated Erector Spinae Plane Blocks : Are There Advantages?

The erector spinae plane block (ESPB) has been widely used as a treatment strategy for a variety of acute and chronic painful conditions. ESPBs are typically performed under ultrasound guidance [USG] in an in-plane long axis approach, targeting the tip of the lumbar transverse process while the patient lies prone. Off-Plane Seated Injection Technique-ESPB [OPSIT-E] represents a useful alternative in situations where a standard prone spine injection would be technically challenged by circumstances which may include morbid obesity, orthopnoea, recent upper limbs surgeries, chest pain from recent pacemaker implant, and in a subjects were in-plane approaches may be complicated by skin lesions. A seated forward flexed off-plane injection position, may also flatten the lumbar lordosis, shift adipose tissue more anteriorly, lessening skin to target distance and facilitating bony landmark identification, in high BMI and hyperlordotic subjects. The relatively larger curved transverse arc radius of the curvilinear probe [GE G1-5] in comparison to its transverse arc, also appears to offer improved central field of skin-transducer contact, earlier needle visualization, improved acute angle trajectory visualization of deep structures, which may be due to less crepuscular beam dispersion in comparison to transverse probe orientation. Even with a linear probe, the orthogonal technique facilitates a more perpendicular vector, lessening needle transit to target distance, which may in turn decrease procedure time, and improve patient comfort. The OPSITE, may also be easier to teach, learn, and master, as other studies have generally reported a higher rate of off-lane injection success among novice vascular interventionists.

Micromechanical effects of substrate hardness on graphene nano-cutting quality

In the nanocutting process of graphene, the mechanism on the atomic scale of the effect of substrate hardness on the edge quality of graphene nanoribbons has not been thoroughly investigated. In this paper, we construct a diamond probe (radius of 5 Å) to cut graphene (190 Å × 113 Å) models with different substrates (silicon/sapphire/silicon carbide), molecular dynamics simulations were used to study the effect of substrate hardness and cutting depth on the atomic structure of graphene nanoribbon edges by observing the atomic morphology, the number of C-C bonds, the radial distribution function and friction. The results show that during the nanoindentation stage, when graphene is in the critical damage state, the substrate with high hardness has high deformation strength, the substrate deformation is small, and graphene undergoes deformation is also small, but the force Fz on the probe, the critical graphene stress σz and the equivalent stress are all large, and the number of C atoms with CN=3 is large; At the nano-cutting stage, the breakage of C-C bonds and the generation of edge defects are caused by local stress concentration, and the graphene stress σxx along the x-direction has a clear directionality. With the same cutting depth (critical damage depth of silicon substrate), silicon substrate hardness is small, the graphene nanoribbon obtained has less number of circular defects generated at the edge, less total number of defective atoms, more number of CN=3 atoms, large peak of radial distribution function of graphene after cutting, and graphene integrity is better. The hardness of the silicon carbide substrate is large, and the number of C-C bond breaks in graphene during the cutting process is high. Each substrate is cut at its own critical damage depth, and the substrate hardness has no significant effect on the number of C-C bond breaks, the number of circular defects, the total number of defective atoms, and the number of CN=3 atoms in graphene. When the silicon substrate was used, the stable force of the probe is small, the edge structure of graphene has little impact, the edge effect obtained is good. The cutting depth and substrate hardness have little effect on the graphene temperature during the nano-cutting process. In this paper, the atomic structure of graphene edges after cutting is analysed and investigated on the atomic scale, and the above results are combined to provide theoretical guidance for obtaining efficient and high-quality and low-damage graphene nanoribbon cutting.

Calibration of Swarm Ion Density, Drift, and Effective Mass Measurements

AbstractWe calibrate the Swarm Langmuir Probe Ion Drift, Density and Effective Mass (SLIDEM) products using the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC‐1) electron density measurements. SLIDEM combines electric current measurements from the Electric Field Instrument faceplate (situated on the ram‐facing side of the satellite) with ion admittance measurements from a spherical Langmuir probe to estimate ionospheric ion density, bulk ion drift parallel to the satellite trajectory in the polar regions, and effective ion mass at low and middle latitudes. SLIDEM processing includes an eight‐parameter empirical geometry model that expresses the corrections to the effective faceplate area and spherical probe radius arising from satellite‐plasma interactions. Validation of SLIDEM density by conjunctions with COSMIC density altitude profiles reveals systematic errors, with SLIDEM underestimating corresponding COSMIC data by around 10%. Using the same conjunctions to calibrate the SLIDEM density processor, a simple one‐parameter geometry model is obtained, which significantly reduces bias in ion density. This leads to reduced bias in the ion ram speed and in the effective mass, both of which are more consistent with empirical ionospheric models. We examined three models characterizing the variation of probe effective electrode current collection areas. Faceplate geometries are statistically indistinguishable from the physical faceplate cross section. Spherical Langmuir probe radius is effectively reduced by about 10% due to satellite‐plasma interactions. We recommend updating the SLIDEM processor to use a smaller value for the spherical probe's radius.

Effects of guard and boom on needle Langmuir probes studied with particle-in-cell simulations

We investigate the effects of different guard geometries on the currents to needle-type Langmuir probes. The results are based on particle-in-cell numerical simulations. We show that if the guard length is less than 6–8 Debye lengths there can be a significant effect on the currents to the probe. A guard radius should not be larger than the Debye length, otherwise it can also significantly affect the currents. However, since guard radii are often close to the probe radius, the second condition is usually satisfied.

Effects of probe parameters on radio-frequency ablation of localized liver cancer using a personalized patient treatment planning

This study investigates the role of different types of probes in Radiofrequency ablation based thermal therapy for tumours and surrounding healthy tissues. The findings demonstrate the significance of understanding the relationship between probe geometry, temperature distribution, and tissue response to optimize thermal therapies' design and application. By fine-tuning probe characteristics, such as radius, length, and power input, practitioners can tailor treatments for specific tissues, optimizing therapeutic outcomes while minimizing risks to healthy tissues. Additionally, the study sheds light on heat transfer mechanisms during thermal ablation, highlighting the importance of considering probe characteristics in treatment protocols. Results indicate that increasing power input leads to higher maximum temperatures, particularly in single-point probes, raising concerns about potential tissue damage at high-power settings. Furthermore, increasing the probe radius shows slight temperature reductions for both single-point and multi-point probes. Blood perfusion plays a significant role in regulating temperature, leading to temperature reductions in both probe types. This research emphasizes the importance of fine-tuning probe characteristics for improved thermal therapies and advances our understanding of thermal physics in biological systems, promising advancements in medical technology.

Mapping positron annihilation lifetime spectroscopy data of a polymer to classical molecular dynamics simulations without shifting the glass transition temperature.

Positron annihilation lifetime spectroscopy (PALS) enables the nondestructive measurement of nanoscale cavities in materials. In this study, a strategy was proposed for mapping PALS measurement data of isotactic polypropylene to classical molecular dynamics (CMD) simulations. The discrepancy between simulated and experimental glass transition temperatures was resolved by shortening the polymer chains, rather than adjusting for the temperature, using the Williams-Landel-Ferry (WLF) equation. The effective probe radii of ortho-positronium (o-Ps), determined by comparing PALS data with CMD simulations, were ∼0.8nm, which was consistent with the o-Ps size given by the solution of the Schrödinger equation. The free-volume fraction corresponding to the effective probe radius was 12.3% at the glass transition temperature, close to the value estimated using Simha-Boyer theory. The cavity number density was proportional to the effective probe radius and decreased with temperature. The o-Ps effective probe radius was proportional to both the critical probe radius and the -1/3 power of the monomer number density, and increased with increasing temperature. These findings suggest that combining PALS measurements with CMD simulations may provide insight into cavities in polymeric materials without relying on the WLF equation.

Label-free detection and identification of single bacteria via terahertz near-field imaging.

In recent years, terahertz (THz) imaging has attracted much attention because of its ability to obtain physical and chemical information in a label-free, noninvasive and nonionizing manner. However, the low spatial resolution of traditional THz imaging systems and the weak dielectric response of biological samples hinder the application of this technology in the biomedical field. In this paper, we report a new THz near-field imaging method for a single bacteria, through the coupling effect of nanoscale radius of probe and platinum gold substrate, which greatly enhances THz near-field signal of biological samples. A THz super-resolution image of bacteria has been successfully obtained by strictly controlling the relevant test parameters such as tip parameters and driving amplitude. By analyzing and processing the THz spectral image, the morphology and inner structure of bacteria have been observed. The method has been used to detect and identify Escherichia coli represented by Gram-negative bacteria and Staphylococcus aureus represented by Gram-positive bacteria. This application provides a new label-free, noninvasive and nonionizing testing protocol for the detection of single bacteria.

Analysis of the virtual cathode and floating potential of a thermionic emissive probe operating in the space-charge-limited regime

This paper analyses by this and characterizes a thermionic emissive probe operating in both the temperature-limited current regime (T-region) and the space-charge-limited current regime (S-region) characterized by the formation of a virtual cathode. For this last case, we obtain the potential profile, the emitted current that overcomes the virtual cathode, as well as the thickness and depth of the potential well in front of the probe for different probe temperatures, plasma electron temperatures and neutral gas pressures. From these results, we obtain the I–V curves and the floating potential. Depending on the probe radius, when the floating potential is reached in the S-region, its value saturates, becoming almost independent of the probe temperature and the electron temperature.

Reference-free self-calibrating tip-based scattering-type THz near-field microscopy

In this work, we present a quantitative analysis model based on reference-free self-calibration to analyze scattered fields and approach curves on a dielectric substrate for terahertz scattering-type scanning near-field optical microscopy. The results of our model are compared with experimentally measured data and a fully numerical analysis based on a line dipole image method and a quasi-electrostatic approximation. The model is used to extract the effective radius of the tip and the relative permittivity of the silicon substrate to the near-field scattering signal. The measured approach curves on Au and silicon substrates show good agreement with the calculated approach curves, and the refractive index for silicon is precisely determined to be 3.42. For a tip-based THz scattering-type scanning near-field optical microscope, the proposed analysis model allows for the extraction of the effective probe radius and dielectric functions, thereby enabling conclusive measurements of geometric parameters and optical constants.

Experimental Investigation of Tip Wear of AFM Monocrystalline Silicon Probes.

AFM has a wide range of applications in nanostructure scanning imaging and fabrication. The wear of AFM probes has a significant impact on the accuracy of nanostructure measurement and fabrication, which is particularly significant in the process of nanomachining. Therefore, this paper focuses on the study of the wear state of monocrystalline silicon probes during nanomachination, in order to achieve rapid detection and accurate control of the probe wear state. In this paper, the wear tip radius, the wear volume, and the probe wear rate are used as the evaluation indexes of the probe wear state. The tip radius of the worn probe is detected by the nanoindentation Hertz model characterization method. The influence of single machining parameters, such as scratching distance, normal load, scratching speed, and initial tip radius, on probe wear is explored using the single factor experiment method, and the probe wear process is clearly divided according to the probe wear degree and the machining quality of the groove. Through response surface analysis, the comprehensive effect of various machining parameters on probe wear is determined, and the theoretical models of the probe wear state are established.

Contact on-machine measurement probe error correction method for optical aspheric surface ultraprecision machining

Optical aspheric ultraprecision machining requires nanometer-scale on-machine measurement (OMM) techniques, and small probe errors in the contact OMM process can seriously affect the OMM accuracy, thereby reducing machining accuracy. Thus, a master ball-based probe radius error and probe profile error correction method is proposed to analyze the effects of probe radius error and probe profile error on OMM results while ensuring accurate probe alignment to establish an identification and correction model for probe radius error and probe profile error. OMM probe error correction measurement and error compensation machining experiments were conducted to verify the effectiveness of the probe error correction method. After the probe profile error correction measurement, the probe measurement error was changed from 0.436 μm to 0.023 μm. Compared with the uncorrected probe error and the probe radius error correction compensation machining results, the accuracy of the compensation machining after the probe profile error correction compensation was improved by 43 % and 41 %, respectively. Results show that this OMM system probe error correction method is effective in improving OMM accuracy.

Rate effects in detachment of a spherical probe from fibrillar adhesive surfaces

Rate effects in fibrillar adhesive surfaces have received increasing attention recently. However, the requirement for taking into account the viscoelastic behavior of the material, combined with the backing layer coupling, complicates the theoretical treatment. As a result, the role of rate effects, particularly on the array level, remains unclear. This work focuses on a general problem: a rigid spherical probe is detached from a viscoelastic fibrillar adhesive surface at a certain velocity. A theoretical framework is proposed based on the Lee & Radok corresponding principle and the Schapery approximation for crack initiation in viscoelastic solids. The fibril force across the array is explicitly determined during the dynamic detaching process. Simulation results reveal the influence of rate effects on the adhesion response, the preload dependence, and the effective work of adhesion of the fibrillar surface. As expected, the adhesion force monotonically increases with the retraction velocity. An interesting phenomenon is observed at intermediate velocities that modest preload is favorable to the pull-off force while an overlarge one would have an adverse effect. The pull-off force would finally approach a lower steady-state constant at a sufficiently high preload value. Most significantly, it is found that the dependence of the effective work of adhesion on the crack velocity is almost independent of the basic properties of the fibrillar surface when traversing typical parameter space. This indicates that the contribution of the viscoelastic-induced adhesion enhancement can be approximately decoupled as a multiplicative term in the overall effective work of adhesion. For a sufficiently large probe radius, this rate-dependent characteristic can be well captured by the continuum theory of viscoelastic crack propagation.

Flexoelectric vibration control of parabolic shells

The presented work focuses on the spatially distributed actuation behavior of flexoelectric actuators on a parabolic cylindrical shell panel with simply supported boundary conditions. A flexoelectric actuator with significant electric field gradients could generate actuation forces and control moments to drive or control system oscillations. For an engineering structure with initial excitations, flexoelectric actuators could be employed to achieve vibration control with designed electric inputs. The dynamic equations of the parabolic cylindrical panel laminated with an arbitrary flexoelectric actuator are defined first. The transverse displacement excited by an external mechanical loading and flexoelectric actuators is calculated. Actuation effects and vibration control efficiency contributed by various design parameters including flexoelectric patch thickness and atomic force microscopy (AFM) probe radius are studied. As the purpose of this study is to accelerate the vibration attenuation, the open-loop control usually causes insufficient control or over-actuation effects. Using displacement feedback, velocity feedback, and acceleration feedback, the effectiveness of these three closed-loop control methods is analyzed and evaluated by the modal response. Analyses suggest that the velocity feedback could effectively attenuate oscillations with the lowest voltage input than in the other two cases. Specifically, the system damping ratio can be adjusted with velocity feedback. Lower voltage input could benefit system design and release stress concentrations caused by high electric field gradients. This research provides a basis for vibration control based on flexoelectric parabolic shell structures and provides an optimal choice for the design of flexoelectric drive closed-loop control for parabolic shell structures.

Machine learning method for extracting elastic modulus of cells

The Hertz contact mechanics model is commonly used to extract the elastic modulus of the cell, but the basic assumptions of the model are often not met in cell indentation experiments, which can lead to errors in the obtained elastic modulus of cell. The establishment of theoretical formulas or modification of the Hertz formulas has been proposed to reduce the errors introduced by indentation depth and cell thickness, but errors from cell radius and probe radius are largely neglected. Herein, we build a neural network model in machine learning to extract the elastic modulus of cell, which takes into account of four variables: indentation depth, cell thickness, cell radius, and probe radius. The validity of the model is demonstrated by the indentation experiment. The introduction of machine learning methods provides an alternative solution for extracting the elastic modulus of the cell and has potential for application.

Effect on the measurement for gear involute profile caused by the error of probe position

Gear involute artefact (GIA) is a kind of measurement standard used to calibrate involute measuring instruments. To measure the profile deviation of GIA more accurately, the effect on the measurement of a gear involute profile caused by the error of the probe position is considered, the value of profile deviations would be affected and the measurement curve of profile deviations would be compressed or stretched along the roll path length, caused by the error of the probe position. Moreover, about 60% of the measurement errors are concentrated within the involute root of roll path length ρ= 0–5 mm. Based on the above research, an adjustment method for the probe position with a double roller-guide involute measuring instrument is proposed and measurement experiments are carried out using probes with probe radius ro = 0.5 mm, 1.5 mm and 2.5 mm. As the error of probe position e > 0, the curve of profile deviations at the root of the involute is biased towards the body. As the error of probe position e < 0, the profile deviation curve at the root of the involute except for the vicinity of base circle is biased towards the body, while the profile deviation curve near the base circle is biased out of the body caused by the interference of the transition surface, and the measurement curve of profile deviations at the root of the involute is significantly compressed. These errors decrease as the probe radius increases and the error of the probe position decreases. The difference of profile slope deviations and profile form deviations measured by the three probes after adjustment is 0.11 μm and 0.04 μm respectively, which indicates the feasibility of the probe adjustment method described above. The research supports the machining and measurement of a high-precision gear involute artefact.

Partial Discharge Detection and Sensitivity Improvement for Bushing Based on Optical Interference Technique

Bushing plays a significant role in insulation and mechanical support for power transformers. Its working state is closely related to the reliable operation of power transformers. To overcome the electromagnetic interference and security risks during sensor installation, a Sagnac interference optical technique for partial discharge (PD) detection is proposed in this paper. By establishing a simulation model of the sensing structure, it is verified that output signal amplitude varies periodically with the length of sensing and delay fibers. Moreover, the output value decreases with increasing probe radius. The results show that a delay fiber of 1.5 km, a sensing fiber of 3 m, and a bending radius of 5 mm are optimal parameter combinations to detect PD in a 72.5 kV defective bushing. In addition, consistent detection waveforms induced by both internal and external defects are obtained by the optical sensor and high frequency current transformer (HFCT) simultaneously, then the effectiveness of the optical sensor on detecting PD signals for bushing is verified. It is of great help to carry out online monitoring of bushing insulation defects through optical non-destructive installation.

High precision measurement of blade profile curve using iterative normal vector approximation

The precision measurement of blades has always been a complex problem in free-form surface inspection. For contact inspection of blades by coordinate measuring machine (CMM), the probe radius compensation has a critical influence on the measurement accuracy. In this study, an iterative approach based on the normal vector approximation is proposed to measure the blade profile curve, which aims to reduce the measurement error caused by the conventional method relying on a computer aided design model for compensation. The proposed method combines the local reconstruction of blade surface and CMM measurement software. It first takes the measured results of conventional method as a base, then the resulting corrected points of several sectional profiles are fitted to a B-spline surface to provide an alternative nominal model for CMM software, leading to the next same measurement task. Thus, the measurement-fitting process iterates, in which the current nominal model in CMM software is updated by the reconstructed model of foregoing iteration, until a preset condition is reached. Consequently, the proposed method is implemented on a four-axis CMM, and two blade samples are designed to verify the approach’s effectiveness. Experiments show that our approach is superior to the conventional one in blade profile measurement accuracy.

Free-form surface form error evaluation based on smaller-scale sampling points in touch-trigger probing

Surface reconstruction is an essential operation in the evaluation of free-form surface form error. As a feasible technology in free-form surface sampling, touch-trigger probing has been widely used in on-machine measurement and coordinate measurement machine. However, surface reconstruction quality is influenced by limited sampling point size. This study proposes a surface reconstruction method based on surface position error and deformation error model. Surface form error is decomposed into surface position error and deformation error. Then, the design surface is taken as a rigid body, and a point-to-surface function-based iterative algorithm is conducted to adjust surface location and orientation to best match the sampling points. The advantage of this algorithm is that it considers the probe dimension, so further compensation of probe radius is not required. The geometry of the adjusted design surface is modified based on thin plate energy minimization and point-to-surface function. Due to the inherent feature of the proposed method, geometric features of the design surface are kept. Experiments are conducted to verify the effectiveness of the proposed method, and results show that the proposed method can achieve lower error compared with existing methods.

Two-point diameter calibration of a sphere using a micro-coordinate measuring machine at NMIJ

The National Metrology Institute of Japan (NMIJ) has developed a highly accurate two-point diameter measurement method of a sphere using a micro-coordinate measuring machine (µ-CMM) with a low-force two-dimensional touch probe. The measured sphere is used as a reference to calibrate the probe of other µ-CMM in industry. Our strategy for measuring sphere’s diameter is that the probe radius of NMIJ’s µ-CMM is calibrated using a reference gauge block, and the NMIJ’s µ-CMM using the calibrated probe measures the mean two-point diameter of a sphere. To achieve the highly accurate calibration of the reference gauge block, we have adopted a double-sided interferometer (DSI) and an atomic force microscopy (AFM). The DSI measures the length of gauge block without wringing. The phase correction value of the gauge block is evaluated by measuring the surface roughness using the AFM. Using the DSI and AFM, the mechanical length of reference gauge block was obtained with the expanded uncertainty of 13 nm (k = 2). Then, the probe radius of NMIJ’s µ-CMM was also calibrated using the reference gauge block calibrated by the DSI and the AFM. The µ-CMM’s probe radius was obtained with the expanded uncertainty of 10 nm (k = 2). Finally, the µ-CMM measured the mean two-point diameter of a sphere with the expanded uncertainty 21 nm (k = 2) was demonstrated.

Benchmark experiments of the power law parametrization of the effective ion collecting area of a planar Langmuir probe in low temperature plasmas

For unmagnetized low temperature Ar plasmas with plasma density ranging from 3 × 108 to 1010 cm−3 and an electron temperature of ∼1 eV, the expansion of the ion collecting area of a double-sided planar Langmuir probe with respect to probe bias is experimentally investigated, through a systematic scan of plasma parameters. In accordance with many existing numerical studies, the ion collecting area is found to follow a power law for a sufficiently negative probe bias. Within our experimental conditions, the power law coefficient and exponent have been parameterized as a function of the normalized probe radius and compared with numerical results where qualitatively comparable features are identified. However, numerical results underestimate the power law coefficient while the exponent is overestimated. Our experimental measurements also confirm that ion–neutral collisions play a role in determining the expanded ion collecting area, thus changing values of the power law coefficient and exponent. This work suggests that a power law fit to the ion collecting area must be performed solely based on experimentally obtained data rather than using empirical formulae from simulation results since material and cleanness of the probe, type of working gas, and neutral pressure may also affect the expansion of the ion collecting area, factors which are difficult to model in a numerical simulation. A proper scheme of analyzing an I–V characteristic of a Langmuir probe based on a power law fit is also presented.