Resolution of tonic downgaze during constant-velocity head rotation in yaw plane

2016 ◽  
Vol 37 (10) ◽  
pp. 1731-1733
Author(s):  
Ki-Tae Kim ◽  
Kwang-Dong Choi ◽  
Jae-Hwan Choi
Keyword(s):  
Constant Velocity ◽  
Head Rotation ◽  
Velocity Head

Effect of difference of cupula and endolymph densities on the dynamics of semicircular canal

2008 ◽  
Vol 18 (2-3) ◽  
pp. 69-88
Author(s):  
A.V. Kondrachuk ◽  
S.P. Sirenko ◽  
R. Boyle
Keyword(s):  
Semicircular Canal ◽  
Constant Velocity ◽  
Complex Dynamics ◽  
Semicircular Canals ◽  
Head Rotation ◽  
Gravity Vector ◽  
One Dimensional ◽  
Axis Of Rotation ◽  
Multiple Frequencies ◽  
The Difference

The effect of different densities of a cupula and endolymph on the dynamics of the semicircular canals is considered within the framework of a simplified one-dimensional mathematical model where the canal is approximated by a torus. If the densities are equal, the model is represented by Steinhausen's phenomenological equation. The difference of densities results in the complex dynamics of the cupulo-endolymphatic system, and leads to a dependence on the orientation of both the gravity vector relative to the canal plane and the axis of rotation, as well as on the distance between the axis of rotation and the center of the semicircular canal. Our analysis focused on two cases of canal stimulation: rotation with a constant velocity and a time-dependent (harmonically oscillating) angular velocity. Two types of spatial orientation of the axis of rotation, the axis of canal symmetry, and the vector of gravity were considered: i) the gravity vector and axis of rotation lie in the canal plane, and ii) the axis of rotation and gravity vector are normal to the canal plane. The difference of the cupula and endolymph densities reveals new features of cupula dynamics, for instance – a shift of the cupula to a new position of equilibrium that depends on the gravity vector and the parameters of head rotation, and the onset of cupula oscillations with multiple frequencies that results in the distortion of cupula dynamics relative to harmonic stimulation. Factors that might influence the density difference effects and the conditions under which these effects occur are discussed.

Contribution of irregular semicircular canal afferents to the horizontal vestibuloocular response during constant velocity rotation

1993 ◽  
Vol 69 (3) ◽  
pp. 996-999 ◽  
Author(s):  
D. E. Angelaki ◽  
A. A. Perachio
Keyword(s):  
Angular Velocity ◽  
Time Constant ◽  
Semicircular Canal ◽  
Constant Velocity ◽  
Head Rotation ◽  
Squirrel Monkeys ◽  
Galvanic Stimulation ◽  
Vestibular Afferents ◽  
Eye Velocity ◽  
Semicircular Canal Afferents

1. The effects of constant anodal currents (100 microA) delivered bilaterally to both labyrinths on the horizontal vestibuloocular response (VOR) were studied in squirrel monkeys during steps of angular velocity in the dark. We report that bilateral anodal currents decreased eye velocity approximately 30–50% during the period of galvanic stimulation without a change in the time constant of VOR. The decrease in eye velocity, present during steps of angular velocity, was not observed during sinusoidal head rotation at 0.2, 0.5, and 1 Hz. The results suggest that responses from irregular vestibular afferents influence VOR amplitude during constant velocity rotation.

Vestibuloocular reflex inhibition and gaze saccade control characteristics during eye-head orientation in humans

1988 ◽  
Vol 59 (3) ◽  
pp. 997-1013 ◽  
Author(s):  
D. Pelisson ◽  
C. Prablanc ◽  
C. Urquizar
Keyword(s):  
Constant Velocity ◽  
Pulse Generator ◽  
Head Rotation ◽  
Systematic Difference ◽  
Head Motion ◽  
Head Orientation ◽  
Vestibuloocular Reflex ◽  
Gaze Saccade ◽  
Gaze Saccades ◽  
Saccade Duration

1. In natural conditions, gaze (i.e., eye + head) orientation is a complex behavior involving simultaneously the eye and head motor systems. Thus one of the key problems of gaze control is whether or not the vestibuloocular reflex (VOR) elicited by head rotation and saccadic eye movement linearly add. 2. Kinematics of human gaze saccades within the oculomotor range (OMR) were quantified under different conditions of head motion. Saccades were visually triggered while the head was fixed or passively moving at a constant velocity (200 deg/s) either in the same direction as, or opposite to, the saccade. Active eye-head coordination was also studied in a session in which subjects were trained to actively rotate their head at a nearly constant velocity during the saccade and, in another session, during natural gaze responses. 3. When the head was passively rotated toward the visual target, both maximum and mean gaze velocities increased with respect to control responses with the head fixed; these effects increased with gaze saccade amplitude. In addition, saccade duration was reduced so that corresponding gaze accuracy, although poorer than for control responses, was not dramatically affected by head motion. 4. The same effects on gaze velocity were present during active head motion when a constant head velocity was maintained throughout saccade duration, and gaze saccades were as accurate as with the head fixed. 5. During natural gaze responses, an increased gaze velocity and a decreased saccade duration with respect to control responses became significant only for gaze displacement larger than 30 degrees, due to the negligible contribution of head motion for smaller responses. 6. When the head was passively rotated in the opposite direction to target step, gaze saccades were slower than those obtained with the head fixed; but their average accuracy was still maintained. 7. These results confirm a VOR inhibition during saccadic eye movements within the OMR. This inhibition, present in all 16 subjects studied, ranged from 40 to 96% (for a 40 degree target step) between subjects and increased almost linearly with target step amplitude. Furthermore, the systematic difference between instantaneous VOR gain estimated at the time of maximum gaze velocity and mean VOR gain estimated over the whole saccadic duration indicates a decay of VOR inhibition during the ongoing saccade. 8. A simplified model is proposed with a varying VOR inhibition during the saccade. It suggests that VOR inhibition is not directly controlled by the saccadic pulse generator.(ABSTRACT TRUNCATED AT 400 WORDS)

Record Wear Studies by Scanning Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 364-365
Author(s):  
M.D. Coutts ◽  
E.R. Levin ◽  
J.G. Woodward
Keyword(s):  
Electron Microscopy ◽  
Constant Velocity ◽  
Peak Velocity ◽  
Great Depth ◽  
Depth Of Focus ◽  
Sweep Frequency ◽  
Transmission Electron ◽  
Test Record ◽  
Lateral Mode ◽  
Scanning Electron

While record grooves have been studied by transmission electron microscopy with replica techniques, and by optical microscopy, the former are cumbersome and restricted and the latter limited by lack of depth of focus and resolution at higher magnification. With its great depth of focus and ease in specimen manipulation, the scanning electron microscope is admirably suited for record wear studies.A special RCA sweep frequency test record was used with both lateral and vertical modulation bands. The signal is a repetitive, constant-velocity sweep from 2 to 20 kHz having a duration and repetitive rate of approximately 0.1 sec. and a peak velocity of 5.5 cm/s.A series of different pickups and numbers of plays were used on vinyl records. One centimeter discs were then cut out, mounted and coated with 200 Å of gold to prevent charging during examination. Wear studies were made by taking micrographs of record grooves having 1, 10 and 50 plays with each stylus and comparing with typical “no-play” grooves. Fig. 1 shows unplayed grooves in a vinyl pressing with sweep-frequency modulation in the lateral mode.

Developing an inkjet printer IV: printer mechanism control for best print quality

2020 ◽  
Vol 2020 (15) ◽  
pp. 349-1-349-9
Author(s):  
Daulet Kenzhebalin ◽  
Baekdu Choi ◽  
Sige Hu ◽  
Yin Wang ◽  
Davi He ◽  
...  
Keyword(s):  
Motor Control ◽  
Constant Velocity ◽  
Control Problems ◽  
Print Quality ◽  
Control Parameters ◽  
Test Page ◽  
Mechanism Control ◽  
Testing Accuracy ◽  
Inkjet Printer

Inkjet printer motor control consists of moving the printhead in the scan direction and in the process direction. Both movements have different objectives. Scan direction movement needs to have constant velocity and process direction movement needs to have accurate movement. In this paper, we discuss a method for controlling the velocity of the printhead and how to tune the motor control parameters. We also design six test pages for testing accuracy of the printhead movement and cartridge properties. For each test page, we discuss expected prints, common printer control problems that could alter the print quality, and how to identify them.

Facial expression differences indicate pain improvement at the emergency department

2020 ◽  
Keyword(s):  
Emergency Department ◽  
Aspect Ratio ◽  
Facial Expressions ◽  
Pain Measurement ◽  
Rating Scale ◽  
Head Rotation ◽  
Numeric Rating Scale ◽  
Nasolabial Fold ◽  
Measurement Strategy ◽  
Pain Improvement

Purpose: Pain is a major symptom for patients to seek medical services, but limited evidence supports the applicability and usage of facial expressions as a pain measurement strategy in the emergency department (ED). In this study, we explored possible differences in facial expressions before and after pain management and compared these differences with those in a self-reported pain scale. Methods: In this observational study, convenience sampling of patients admitted to the ED was conducted. Two video sessions of facial expressions were recorded for each participant, and participants rated their painon a self-reported numeric rating scale (NRS). A total of 25 facial parameters were extracted per frame. The main outcome measurements were the differences in facial parameters, and their correlation with changes in NRS scores was examined. Results: This study included 163 participants. A stronger reduction in NRS scores was associated with differences in systolic blood pressure (sBPr = 0.247, P = 0.011) and the following changes in facial features: eye opening (left: r = -0.210, P = 0.007; right: r = -0.206, P = 0.008), eye aspect ratio (left: r = -0.382, P < 0.001; right: r = -0.305, P < 0.001), and head rotation angle (r = 0.218, P = 0.005). Pain improvement (a difference of ≥ 4 in NRS scores) was associated with differences in BP (sBP, odds ratio [OR] = 0.973, 95%confidence interval [CI]: 0.949-0.998, P = 0.034; dBP, OR = 1.078, 95% CI: 1.026-1.113, P = 0.003), eye aspect ratio (Left: β = 5.613, 95% CI: 2.234-14.104, P < 0.001; Right: β = 2.743, 95% CI: 1.395-5.391, P = 0.003), and nasolabial fold variation (β = 0.548, 95% CI: 0.306-0.982, P = 0.043), after adjustment for variables Conclusions: Intraindividual changes in facial expressions can be used to track clinically relevant differences in pain. Facial expressions alone cannot be used as a pain measurement strategy in the ED.

scholarly journals Does Head Orientation Influence 3D Facial Imaging? A Study on Accuracy and Precision of Stereophotogrammetric Acquisition

2021 ◽  
Vol 18 (8) ◽  
pp. 4276
Author(s):  
Giuditta Battistoni ◽  
Diana Cassi ◽  
Marisabel Magnifico ◽  
Giuseppe Pedrazzi ◽  
Marco Di Blasio ◽  
...  
Keyword(s):  
Head Rotation ◽  
Anthropometric Measurements ◽  
Head Orientation ◽  
3D Images ◽  
Face Shape ◽  
Operator Error ◽  
Accuracy And Precision ◽  
Error Magnitude ◽  
Repeatability And Reproducibility ◽  
Head Positions

This study investigates the reliability and precision of anthropometric measurements collected from 3D images and acquired under different conditions of head rotation. Various sources of error were examined, and the equivalence between craniofacial data generated from alternative head positions was assessed. 3D captures of a mannequin head were obtained with a stereophotogrammetric system (Face Shape 3D MaxiLine). Image acquisition was performed with no rotations and with various pitch, roll, and yaw angulations. On 3D images, 14 linear distances were measured. Various indices were used to quantify error magnitude, among them the acquisition error, the mean and the maximum intra- and inter-operator measurement error, repeatability and reproducibility error, the standard deviation, and the standard error of errors. Two one-sided tests (TOST) were performed to assess the equivalence between measurements recorded in different head angulations. The maximum intra-operator error was very low (0.336 mm), closely followed by the acquisition error (0.496 mm). The maximum inter-operator error was 0.532 mm, and the highest degree of error was found in reproducibility (0.890 mm). Anthropometric measurements from alternative acquisition conditions resulted in significantly equivalent TOST, with the exception of Zygion (l)–Tragion (l) and Cheek (l)–Tragion (l) distances measured with pitch angulation compared to no rotation position. Face Shape 3D Maxiline has sufficient accuracy for orthodontic and surgical use. Precision was not altered by head orientation, making the acquisition simpler and not constrained to a critical precision as in 2D photographs.

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