Tip Movement Research Articles

Unintentional Movements During the Use of Vitreoretinal Forceps.

PurposeIntraocular forceps used in vitreoretinal surgery are actuated by squeezing their handles. We studied the relationship between actuation and any accompanying unintentional movements of the instrument tip, and compared different handle designs and gauges.MethodsOptical sensors were used to measure involuntary movements of forceps tips while monitoring the extent of actuation. Mean root mean square (RMS) and ranges of signals obtained from sensors were computed before and after applying high (7–13 Hz) and low (<5 Hz) frequency filters. Four handle designs, two gauge sizes, and two users were compared to each other.ResultsIn the absence of human contact, mean RMS of noise was 6.47 μ and mean range was 21.67 μ. When the forceps were held by the surgeon but kept motionless (no actuation), mean RMS was 58.01 μ and mean range was 156.66 μ. When the forceps were actuated, mean RMS was 214.71 μ and mean range was 566.11 μ. The differences were statistically significant (P < 0.001). The process of actuation by both users was positively correlated with unintentional movements mainly at low frequencies. No statistically significant differences were found between users and between two gauges (23 and 27) at mixed and low frequencies. Pneumatic handles showed less RMS and range values at higher frequencies compared to conventional handle designs. Eliminating human error by fixing pneumatic forceps to the model did not reduce unintentional movements, but eliminated their correlation with actuation.ConclusionsActuating forceps was associated directly with increased unintentional low frequency movements at the tip of the forceps when held by hand.Translational RelevanceA novel system of measuring unintentional forceps tip movement during actuation is described which could be used to guide improved design.

Crack Propagation under the Pulsed Loads

The article deals with the dynamic 2D problem of the theory of elasticity that considers a massive body with a semi-infinite plane crack, the faces of which are subjected to a normal pulsed tensile load symmetric to the crack. When studying the stress state ahead of the crack tip, the singular and regular terms have been found. They have been used to find the pre-fracture (incubation) period under the threshold loads. It has been shown that the regular term taking into account significantly affects the stress state, in particular, the incubation period. In the case of shock impulses above the threshold (overloads), the period of the crack tip movement with a variable speed (“breakthrough” of a crack) is considered as well as the pre-fracture period. To this end, the structural-time criterion for determining the incubation period is generalized to the case of the crack movement with a variable speed. A comparison of the calculated values of increasing the length of cracks after fracture caused by three shock impulses above the threshold with experimental data is made.

Three-dimensional tracking of microbeads attached to the tip of single isolated tracheal cilia beating under external load

To study the properties of tracheal cilia beating under various conditions, we developed a method to monitor the movement of the ciliary tip. One end of a demembranated cilium was immobilized on the glass surface, while the other end was capped with a polystyrene bead and tracked in three dimensions. The cilium, when activated by ATP, stably repeated asymmetric beating as in vivo. The tip of a cilium in effective and recovery strokes moved in discrete trajectories that differed in height. The trajectory remained asymmetric in highly viscous solutions. Model calculation showed that cilia maintained a constant net flux during one beat cycle irrespective of the medium viscosity. When the bead attached to the end was trapped with optical tweezers, it came to display linear oscillation only in the longitudinal direction. Such a beating-mode transition may be an inherent nature of movement-restricted cilia.

Prevalence of mineralized elements in the rostra of bats (Mammalia: Chiroptera)

The fleshy, movable tip of the snout of most mammals is supported by cartilaginous elements that provide leverage for muscles that control movement of the nose. Mineralization or ossification of the external nasal cartilages within the snout is thought to be associated with increased loading (e.g., in the snouts of pigs) or increased structural support of the snout (e.g., in taxa with elongated noses such as solenodons). However, little is known about the distribution of such structures across most groups of mammals, in part because they are easily overlooked during specimen preparation. Bats (Order Chiroptera) exhibit a diverse array of rostral forms, but have never been surveyed for evidence of mineralization or ossification of external nasal cartilages. We examined micro-CT scans of the heads of 83 fluid-preserved bat species representing 17 families. We observed mineralization of the external nasal cartilages within the snouts of only 5 species belonging to the families Pteropodidae, Molossidae, and Vespertilionidae, suggesting these elements are rare among bats. Mineralized elements varied in size, shape, location, and number among these 5 species, suggesting differences in function related to support and movement of the fleshy tip of the snout, or a role in echolocation.

Transitions in nutation trajectory geometry in peppermint (Mentha x piperita L.) with respect to lunisolar acceleration.

Nutations of plant organs are significantly affected by the circatidal modulation in the gravitational force exerted by the Moon and Sun (lunisolar tidal acceleration, Etide). In a previous study on nutational rotations of stem apices, we observed abrupt alterations in their direction and irregularities of the recorded trajectories. Such transitions have not yet been analysed in detail. Peppermint plants were continuously recorded with time-lapse photography and aligned with contemporaneous time courses of the Etide estimates. Each nutational stem tip movement path was assigned to one of two groups, depending on its geometry, as: (i) regular elliptical movements and (ii) irregular movements (with a random type of trajectory). Analyses of the correlation between the plant nutation trajectory parameters and Etide, as well as of the trajectory geometry of the individual plants were performed. The trajectory geometry of young mint stem apices was related to the velocity of the apex rotation and significantly affected by the gravitational force estimated from the Etide. A low velocity of nutational movement, associated with the random character of the trajectory, usually occurred simultaneously with local minima or maxima of Etide. As the mint plant ages, the transitions in the stem tip trajectory were limited; no correspondence with Etide dynamics was observed. The results indicate that the plant tip geometry path transitions with respect to the changing gradient of lunisolar tidal acceleration could be interpreted as manifestation of a continuous accommodation of the shoot apical part to the state of minimum energy dissipation.

Investigation of the Turbulent Near Wall Flame Behavior for a Sidewall Quenching Burner by Means of a Large Eddy Simulation and Tabulated Chemistry

Combustion will play a major part in fulfilling the world’s energy demand in the next 20 years. Therefore, it is necessary to understand the fundamentals of the flame–wall interaction (FWI), which takes place in internal combustion engines or gas turbines. The FWI can increase heat losses, increase pollutant formations and lowers efficiencies. In this work, a Large Eddy Simulation combined with a tabulated chemistry approach is used to investigate the transient near wall behavior of a turbulent premixed stoichiometric methane flame. This sidewall quenching configuration is based on an experimental burner with non-homogeneous turbulence and an actively cooled wall. The burner was used in a previous study for validation purposes. The transient behavior of the movement of the flame tip is analyzed by categorizing it into three different scenarios: an upstream, a downstream and a jump-like upstream movement. The distributions of the wall heat flux, the quenching distance or the detachment of the maximum heat flux and the quenching point are strongly dependent on this movement. The highest heat fluxes appear mostly at the jump-like movement because the flame behaves locally like a head-on quenching flame.

A Prospective Assessment of Optimal Mechanical Ventilation Parameters for Pediatric Catheter Ablation.

Catheter stability, an important factor in ablation success, is affected by ventilation. Optimal ventilation strategies for pediatric catheter ablation are not known. We hypothesized that small tidal volume and positive end-expiratory pressure are associated with reduced ablation catheter movement at annular positions. Subjects aged 5-25years undergoing ablation for supraventricular tachycardia (SVT) or WPW at two centers from March 2015 to September 2016 were prospectively enrolled and randomized to receive mechanical ventilation with either positive end-expiratory pressure of 5cm H2O (PEEP) or 0cm H2O (ZEEP). Movement of the ablation catheter tip at standard annular positions was measured using 3D electroanatomic mapping systems under two conditions: small tidal volume (STV) (3-5mL/kg) or large TV (LTV) (6-8mL/kg). 58 subjects (mean age 13.8years) were enrolled for a total of 266 separate observations of catheter movement. STV ventilation was associated with significantly reduced catheter movement, compared to LTV at all positions (right posteroseptal: 2.5 ± 1.4 vs. 5.2 ± 3.1mm, p < 0.0001; right lateral: 2.7 ± 1.6 vs. 6.3 ± 3.5mm, p < 0.0001; left lateral: 1.8 ± 1.0 vs. 4.3 ± 1.9mm, p < 0.0001). The presence or absence of PEEP had no effect on catheter movement. In multivariable analysis, STV was associated with a 3.1-mm reduction in movement (95% CI 2.6-3.5, p < 0.0001), adjusting for end-expiratory pressure, annular location, and patient size. We conclude that STV ventilation is associated with reduced ablation catheter movement compared to a LTV strategy, independent of PEEP and annular position.

Difference of articulatory movement between native and non-native consonant clusters

We investigated the difference of articulatory movement between native and non-native consonant clusters. English has consonant clusters, but Japanese does not. Therefore, speakers chosen for comparison were native English and native Japanese speakers. Speech samples consisted of 4 words, “blat,” “bnat,” “plat,” “pnat.” In these words, /bl/ and /pl/ are English clusters, but /bn/ and /pn/ are not. We measured the movement of the tongue tip, the mandible and the lower lip by WAVE system (NDI corp.). There were remarkable differences in the mandible and the lower lip movement between native (/bl/, /pl/) and non-native (/bn/, /pn/) clusters in English speakers. Namely, with the non-native clusters the difference of the articulatory movement in the mandible and the lower lip of every utterance was quite large; however, in native clusters, the difference was quite small. For Japanese speakers it was large for all clusters. Thus, it was revealed that the articulatory movement of the mandible and the lower lip in non-native clusters was not stable in native English speakers, even though English has consonant clusters. (This study was supported by KAKENHI 15K02524, 17K02707.)

Cyclic movement primitives underlying two-handed alternating signs in signed language

Biomechanical constraints have been described as underlying patterns in speech production: e.g., cyclic neural central pattern generators (CPGs) in the jaw that evolved for chewing have been claimed to affect syllabic patterns [MacNeilage 1998, Behav. Brain Sci. 21: 4] and cyclic patterns in tongue tip movement may span sequences of segments [Derrick &amp; al. 2015, JASA-EL 137:3]. Similarly, we propose that otherwise unexplained universal aspects of sign languages may result from a preference for repeated alternating arm movements developed in human ancestors for quadrupedal locomotion. For example, in ASL-LEX corpus of 1000 ASL signs, 159 are balanced (not including signs without movement or articulated in the transverse plane, which has alternative properties we will address in the talk). Of those, 60% are alternating, and the alternating group had fewer iconic signs (30.5% vs 41%) and more repeated signs (61% vs 30%) than symmetrical signs. While both groups had a large proportion of signs realized on coronal plane, which makes them more visible in face-to-face communication (33% for alternating vs 52% for symmetrical), the former have more signs in midsagittal and coronal/transverse planes (63% vs 44%), as predicted. Supporting data from additional sign languages will be presented.

A 3D measuring endoscope for hand-guided operation

Optical measuring devices are widely used in industrial production and maintenance processes. With increasing integration, the accessibility of functional elements inside machines is limited for measuring devices. In order to provide a new measurement tool for these applications, the design of an endoscopic 3D sensor based on the structured light principle is presented. Application specific sensor heads are introduced, with diameters down to 8 mm attached to endoscopes with a length of 1 m. The sensor features a flexible pattern generator and a camera, allowing for dynamic reconfiguration of structured illumination patterns. Based on a brief comparison of existing light coding approaches, two different measuring modes for the sensor are described. The first measuring mode uses conventional phase-shift sequences in order to achieve highly accurate measurements under controlled conditions. The second measuring mode uses a new interleaved encoding approach for phase-shift patterns, which enables robust measurements even in the presence of relative motion between object and sensor. An example for this type of motion is the movement of the endoscope tip by hand. Using the proposed sequence design, the 3D acquisition rate is identical to the capture rate of the camera, which amounts to a maximum of 180 Hz in the current hardware configuration of the measuring endoscope. In combination with a registration and merging algorithm, consecutive measurements are automatically combined, enabling the measurement of large surfaces. Moreover, the approach is capable of estimating the relative location and orientation of the endoscope tip using odometry based on depth data. The performance of the sensor in both measuring modes is evaluated on the basis of measurements of reference objects. Furthermore, the results of a hand-held measurement of a reference standard are shown.

Clinical trial for development of a steerable microcatheter

Purpose: A steerable microcatheter provided with a mechanism on the handle for changing the direction of the catheter tip was developed by Sumitomo Bakelite and evaluated in a clinical trial before introduction into clinical use.Material and methods: The steerable microcatheter has a 2.4F/2.9-F external diameter (distal/proximal portion) and a 0.021-inch internal diameter with a dial on the proximal portion for moving the tip. In patients scheduled to undergo selective transarterial procedures, selective arteriography of target arterial branches chosen by the evaluator was performed using the steerable microcatheter during the procedure. Efficacy was evaluated based on operability (technical success, procedure time, use of guidewire, usefulness of tip mobility), and safety was evaluated based on defects and adverse events.Results: Between September 2013 and October 2013, 20 patients were enrolled at four institutions. The success rate for guidewireless insertion of the steerable microcatheter into the target vessels was 96.7%, and operability was judged as good in all 20 patients. Poor tip movement was identified as a defect of the steerable microcatheter in one patient. There were no adverse events associated with the use of the steerable microcatheter.Conclusion: This trial confirmed that the steerable microcatheter had the utility required for medical device approval. Thereafter, it obtained marketing approval.

Involuntary Neuromuscular Coupling between the Thumb and Finger of Stroke Survivors during Dynamic Movement.

Finger–thumb coordination is crucial to manual dexterity but remains incompletely understood, particularly following neurological injury such as stroke. While being controlled independently, the index finger and thumb especially must work in concert to perform a variety of tasks requiring lateral or palmar pinch. The impact of stroke on this functionally critical sensorimotor control during dynamic tasks has been largely unexplored. In this study, we explored finger–thumb coupling during close–open pinching motions in stroke survivors with chronic hemiparesis. Two types of perturbations were applied randomly to the index with a novel Cable-Actuated Finger Exoskeleton: a sudden joint acceleration stretching muscle groups of the index finger and a sudden increase in impedance in selected index finger joint(s). Electromyographic signals for specific thumb and index finger muscles, thumb tip trajectory, and index finger joint angles were recorded during each trial. Joint angle perturbations invoked reflex responses in the flexor digitorum superficialis (FDS), first dorsal interossei (FDI), and extensor digitorum communis muscles of the index finger and heteronymous reflex responses in flexor pollicis brevis of the thumb (p < 0.017). Phase of movement played a role as a faster peak reflex response was observed in FDI during opening than during closing (p < 0.002) and direction of perturbations resulted in shorter reflex times for FDS and FDI (p < 0.012) for extension perturbations. Surprisingly, when index finger joint impedance was suddenly increased, thumb tip movement was substantially increased, from 2 to 10 cm (p < 0.001). A greater effect was seen during the opening phase (p < 0.044). Thus, involuntary finger–thumb coupling was present during dynamic movement, with perturbation of the index finger impacting thumb activity. The degree of coupling modulated with the phase of motion. These findings reveal a potential mechanism for direct intervention to improve poststroke hand mobility and provide insight on prospective neurologically oriented therapies.

Influence of adequate pelvic floor muscle contraction on the movement of the coccyx during pelvic floor muscle training.

[Purpose] Pelvic floor muscle training is a first-line therapy for female stress urinary incontinence. Previous studies have suggested that the coccyx tip moves ventrally and cranially during pelvic floor muscle contraction. The study aimed to elucidate the influence of adequate pelvic floor muscle contraction on coccyx movement. [Subjects and Methods] Sixty-three females (57 patients with stress urinary incontinence and additional 6 healthy volunteers) were enrolled. Using magnetic resonance imaging, coccyx movement was evaluated during pelvic floor muscle contraction and strain. An adequate contraction was defined as a contraction with good Oxford grading scale [≥3] and without inadequate muscle substitution patterns. [Results] Inadequate muscle substitution patterns were observed in 33 participants (52.4%). No significant difference was observed in the movement of the coccyx tip in the ventrodorsal direction between females with and without inadequate muscle substitution patterns. However, a significant increase in the movement of the coccyx tip in the cranial direction was detected in the group without inadequate muscle substitution patterns. Compared to participants with inadequate pelvic floor muscle contraction, those who had adequate pelvic floor muscle contraction exhibited significantly increased cranial movement of the coccyx. [Conclusion] Adequate pelvic floor muscle contraction can produce cranial movement of the coccyx tip.

Reaching and grasping with the tongue: Shared motor planning between hand actions and articulatory gestures.

Research has shown connections between articulatory mouth actions and manual actions. This study investigates whether forward-backward hand movements could be associated with vowel production processes that programme tongue fronting/backing, lip rounding/spreading (Experiment 1), and/or consonant production processes that programme tongue tip and tongue dorsum actions (Experiment 2). The participants had to perform either forward or backward hand movement and simultaneously pronounce different vowels or consonants. The results revealed a response benefit, measured in vocal and manual reaction times, when the responses consisted of front vowels and forward hand movements. Conversely, back vowels were associated with backward hand movements. Articulation of rounded versus unrounded vowels or coronal versus dorsal consonants did not produce the effect. In contrast, when the manual responses of forward-backward hand movements were replaced by precision and power grip responses, the coronal consonants [t] and [r] were associated with the precision grip, whereas the dorsal consonant [k] was associated with the power grip. We propose that the movements of the tongue body, operating mainly for vowel production, share the directional action planning processes with the hand movements. Conversely, the tongue articulators related to tongue tip and dorsum movements, operating mainly for consonant production, share the action planning processes with the precision and power grip, respectively.

Effects of force magnitude on torque control in the correction of bimaxillary protrusion with mass retraction.

OBJECTIVES:This study was designed to explore whether force magnitude would influence incisor torque control and the overall outcome in patients with bimaxillary protrusion who need mass incisor retraction.MATERIALS AND METHODS:Forty-one female patients (aged > 15 years) with bimaxillary protrusion requiring mass incisor retraction were selected. Two sliding mechanics were utilized, with the elastic group receiving a light force of ~100 g by wearing elastics and the power chain group receiving a moderate force of ~250 g by power chain. Lateral cephalograms obtained before and after treatment were traced and measured.RESULTS:Patients in both groups displayed maxillary protrusion with a similar skeletal class II tendency. A longer treatment time was found in the elastic group. No difference in the distance of incisor tip movement was observed between the two groups; however, a larger inclination of upper incisors was found in the elastic group, indicating less loss of torque. In addition, larger reduction in Sella-Nasion-A and A-Nasion-B angle was observed in the elastic group, which was accompanied by a larger ratio of upper lip retraction to upper incisor retraction as well as more upper lip retraction.CONCLUSIONS:Sliding mechanics with elastics to generate light forces can achieve better torque control with more reduction in skeletal and soft tissue protrusion.

Manually Steerable Catheter With Improved Agility.

Purpose:A prototype steerable catheter was designed for endovascular procedures. This technical pilot study reports the initial experience using the catheter for cannulation of visceral arteries.Technique:The 7F catheter was manually steerable with operator control handle for bending and rotation of the tip. The maximum bending angle was approximately 90° and full 360° rotation of the tip was supported. The study involved 1 pig with 4 designated target arteries: the left and right renal arteries, the superior mesenteric artery, and the celiac trunk. Fluoroscopy with 3-dimensional (3D) overlay showing the ostia from preoperative computed tomography angiography was used for image guidance. The cannulation was considered successful if the guidewire was placed well inside the target artery. In addition to evaluating cannulation success, procedure time and associated radiation doses were recorded. The procedure was performed twice with 2 different operators.Conclusions:Both operators successfully reached all 4 target arteries, demonstrating the feasibility of the steerable catheter for endovascular cannulation of visceral arteries. No contrast medium was used, and median radiation dose was 4.5 mGy per cannulation. An average of approximately 2 minutes was used per cannulation. This study motivates further testing in a more comprehensive study to evaluate reproducibility in several animals and with inclusion of more operators. Further development by integrating the new catheter tool in a navigation system is also an interesting next step, combining fine control of catheter tip movements and 3D image guidance without ionizing radiation.

An experimental investigation into surface roughness of a hydraulic fracture

The fracture surface roughness is an essential characteristic of the hydraulic fracturing process and has not been fully explored. The surface asperities play a significant role in proppant flow and settlement, fluid leak-off and fracture tip movement. In this study, we performed an experimental investigation to evaluate the fracture surface roughness of a hydraulic fracture generated in the lab tests. The experiments were conducted using a polyaxial cell and a cuboid siltstone block with dimensions of 20 cm × 20 cm × 16.5 cm. The fracturing fluid was injected into a drilled hole in the specimen to initiate and propagate the hydraulic fracture in nearly homogeneous siltstone material. Low injection rates were applied to all lab tests to maintain slow and stable fracture propagation as in the field. The fracture surfaces were digitised by surface mapping techniques utilising high-resolution laser scanning method and analysed using a standard statistical way. Our results showed that the surface topography and roughness parameters are different in various selected segments. However, they follow an increasing trend in radial directions from the initiation point at the wellbore wall toward the specimen borders.

Disordered Topography Mediates Filopodial Extension and Morphology of Cells on Stiff Materials

In cell–material interactions, cells use filopodia to sense external biochemical and mechanical cues, and subsequently dictate their survival. In an effort toward understanding how disordered topography of stiff materials influences filopodial recognition, diamond films with grain sizes varying from nano‐ to micrometers are fabricated for the investigation of osteoblast filopodial extension. Interestingly, straight filopodia with pronounced cell–substrate adhesion are observed on a nanocrystalline diamond (NCD) region, whereas filopodia on a microcrystalline diamond (MCD) surface only adhere to, and get deflected by, large diamond grains. More importantly, filopodia on NCD keep propagating with a constant velocity, whereas the same process takes place in a slow and intermittent manner on MCD. A theoretical model is also developed and it suggests that the contact between the disordered topography and the filopodial tip plays a key role in altering filopodial growth dynamics. In particular, it is predicted that large surface asperities can block the movement of the filopodial tip, delay its extension, and cause bending of the structure, in quantitative agreement with experimental observations. These findings reveal previously underappreciated effects of random, stiff topographies on the response of cells, and hence can provide new insights for the design of future implant biomaterials.

Assessing colonoscopic inspection skill using a virtual withdrawal simulation: a preliminary validation of performance metrics

BackgroundThe effectiveness of colonoscopy for diagnosing and preventing colon cancer is largely dependent on the ability of endoscopists to fully inspect the colonic mucosa, which they achieve primarily through skilled manipulation of the colonoscope during withdrawal. Performance assessment during live procedures is problematic. However, a virtual withdrawal simulation can help identify and parameterise actions linked to successful inspection, and offer standardised assessments for trainees.MethodsEleven experienced endoscopists and 18 endoscopy novices (medical students) completed a mucosal inspection task during three simulated colonoscopic withdrawals. The two groups were compared on 10 performance metrics to preliminarily assess the validity of these measures to describe inspection quality. Four metrics were related to aspects of polyp detection: percentage of polyp markers found; number of polyp markers found per minute; percentage of the mucosal surface illuminated by the colonoscope (≥0.5 s); and percentage of polyp markers illuminated (≥2.5 s) but not identified. A further six metrics described the movement of the colonoscope: withdrawal time; linear distance travelled by the colonoscope tip; total distance travelled by the colonoscope tip; and distance travelled by the colonoscope tip due to movement of the up/down angulation control, movement of the left/right angulation control, and axial shaft rotation.ResultsStatistically significant experienced-novice differences were found for 8 of the 10 performance metrics (p’s < .005). Compared with novices, experienced endoscopists inspected more of the mucosa and detected more polyp markers, at a faster rate. Despite completing the withdrawals more quickly than the novices, the experienced endoscopists also moved the colonoscope more in terms of linear distance travelled and overall tip movement, with greater use of both the up/down angulation control and axial shaft rotation. However, the groups did not differ in the number of polyp markers visible on the monitor but not identified, or movement of the left/right angulation control. All metrics that yielded significant group differences had adequate to excellent internal consistency reliability (α = .79 to .90).ConclusionsThese systematic differences confirm the potential of the simulated withdrawal task for evaluating inspection skills and strategies. It may be useful for training, and assessment of trainee competence.

Intravascular catheters-an ultrasound imaging based observational study of position and function.

Peripheral intravenous and intra-arterial catheters often block with movement of the limb in which they are inserted. Although the cause of this blockage is commonly attributed to a valve or other structure within the vein, evidence for this is lacking. We used ultrasound to assess the cause of blockage on movement, and degree of tip movement, of 62 venous and 21 radial arterial catheters. In both venous and arterial catheters, blockage was predominantly caused by impingement of the catheter on the vessel wall, with catheter kinking and spasm of the vessel also seen. Mean potential tip movement was 12.3 mm and 5.7 mm in hand and forearm venous catheters respectively and 9.5 mm in radial artery catheters. There was a significantly lower rate of blockage for forearm (20%) compared to dorsal hand venous catheters (83%, P <0.001) and 52% of radial artery catheters showed damping and blockage on wrist flexion. This study emphasises the advantages of placement of venous catheters in the straight veins of the forearm.