Добірка наукової літератури з теми "The vestibule shaft"

The study of vestibule neurons specific firing mode of Gekko gecko under stimulus of different angles and rotating speeds has an important theoretical significance to reveal the control mechanism of Gekko geckos vestibular position as well as to the development of gecko-robots. A vari-angle rotating equipment was made to give different stimulus in study of Gekko geckos vestibular electrophysiology. The equipment mainly consisted of four parts as follows: fastening panel for stereotaxic instrument, shaft locking device, counterweight, driving system. The shaft locking device and counterweight realized tight fixation and torque equilibrium at different angles respectively. Fastening panel matched the general stereotaxic instrument. A stepper motor driver controlled the velocity and acceleration of rotation. Initial experiment verified that the equipment had superiority of easy operation, reliable positioning and accurate control of angle and speed, which indicated that it could meet the demand of the Gekko geckos vestibule research.

The pressurization of emergency or evacuation elevator shafts or duct systems during installation is used for smoke control. In this study, the performance of smoke control systems applied to emergency and evacuation elevators were compared and analyzed using the airflow network analysis program CONTAM 3.2. Under the stack effect condition (temperature difference of 30 ℃), the differential pressure formed in the vestibule was analyzed by adjusting the air volume by changing the value of the loss coefficient factor of the automatic pressure smoke damper. In the case of the duct pressurization method, the air flow in the lower floor was introduced to the elevator shaft owing to the duct pressure and the airflow in the upper floors was from the elevator shaft out to the elevator lobby. In the case of the elevator shaft pressurization method, the pressurized air passing through vestibule from the elevator shaft created a differential pressure at the fire door of vestibule. To maintain the differential pressure in the lower floor, relatively more relief dampers should be installed in the upper floors as compared to those in the duct pressurization method.

Summary Basilaphelenchus brevicaudatus n. sp., the third species of this apparently rare genus, is described and illustrated. It was recovered from wood and bark samples from a dead forest tree in the Golestan province of northern Iran. It is typologically characterised by female body length (448 (365-492) μm), three lines in the lateral fields, raised cephalic region having a sclerotised vestibule and cephalic framework, stylet thin with delicate conus and thicker shaft, both parts lacking a visible lumen, and with three elongate, backwardly directed knobs, small, spherical to spade-shaped metacorpus with small, posteriorly located valve (at 72 (58-74)% of metacorpus length), simple vulva without flap at 72.5 (69-78)% of body length, post-vulval uterine sac 32.4 (29.0-37.0) μm long, functional rectum and anus, female tail conical, short (c′ = 2.6 (1.9-3.3) in female, and 2.5 (2.3-2.8) in male), dorsally convex and ventrally concave with blunt end or having a small mucron, both forms with a hyaline-like tip. Males common, with well-curved 9.2 (9.0-10.5) μm long spicules measured along the mid-line, three pairs of small caudal papillae (lacking the single P1 ventral papilla) and no bursa at tail tip, but with hyaline region, similar to females. Basilaphelenchus brevicaudatus n. sp. is compared with the two currently known species of the genus, the type species, B. persicus, and B. grosmannae. Molecular phylogenetic inferences using partial sequences of small and large subunit ribosomal RNA genes (SSU and LSU) from different isolates of the new species revealed that it belongs to the Tylaphelenchinae clade.

Background: Postural stability depends on the integration of multisensory inputs to drive motor outputs. When visual and somatosensory input is available and reliable, this reduces the postural control system’s reliance on the vestibular system. Despite this, vestibular loss can still cause severe postural dysfunction (1,2). Training one or more of the three sensory systems can alter sensory weighting and change postural behavior. Vestibular activation exercises, including horizontal and vertical headshaking, influence vestibular-ocular and -motor responses and have been showed to be effective in vestibular rehabilitation (3–8). Purpose/Hypothesis: To assess sensory reweighting of postural control processing and vestibular-ocular and -motor responses after concurrent vestibular activation with postural training. It was hypothesized that the effect of this training would significantly alter the pattern of sensory weighting by changing the ratio of visual, somatosensory and vestibular dependence needed to maintain postural stability, and significantly decrease vestibular responses. Methods: Forty-two young healthy individuals (22 females; 23.0+3.9 years; 1.6+0.1 meters) were randomly assigned into four groups: 1) visual feedback weight shift training (WST) coupled with an active horizontal headshake (HHS), 2) same WST with vertical headshake (VHS), 3) WST with no headshake (NHS) and 4) no training/headshake control (CTL) groups. The headshake groups performed an intensive body WST together with horizontal or vertical rhythmic headshake at 80 to 120 beats/minute. The NHS group performed the WST with no headshake while the controls did not perform any training. Five 15-minute training sessions were performed on consecutive days for one week with the weight shift exercises involving upright limits of stability activities on a flat surface, foam or rocker board (Fig. 1). All groups performed baseline- and post-assessments including sensory organization test (SOT) and force platform ramp perturbations, coupled with electromyographic (EMG) recordings. A video head impulse test was also used to record horizontal vestibulo-ocular reflex (VOR) gain. A between- and within-group repeated measures ANOVA was used to analyze five COP sway variables, the equilibrium and composite scores and sensory ratios of the SOT as well as EMG signals and horizontal VOR gain. Similarly, COP variables, EMG, as well as vestibular reflex data (vertical VOR, vestibulo-collic reflex [VCR] and vestibulo-spinal [VSR] gains) during ramp perturbations were analyzed. Alpha level was set at p<.05. Results: The training showed a significant somatosensory downweighting (p=.050) in the headshake groups compared to the other groups. Training also showed significant decreased horizontal VOR gain (p=.040), faster automatic postural response (p=.003) (Figs. 2-4) with improved flexibility (p=.010) in the headshake groups. Muscle activation pattern in medial gastrocnemius (p=.033) was significantly decreased in the headshake. Conclusion: The concurrent vestibular activation and weight shift training modifies vestibular-dependent responses after the training intervention as evidenced in somatosensory downweighting, decreased VOR gain, better postural flexibility and faster automatic postural response. Findings suggest this is predominantly due to vestibular adaptation and habituation of VOR, VCR and VSR which induced sensory reweighting. Clinical relevance: Findings may be used to guide the development of a vestibular-postural rehabilitation intervention in impaired neurological populations, such as with vestibular disorders or sensory integration problems.

Static head roll about the naso-occipital axis is known to produce an opposite ocular counterroll with a gain of approximately 10%, but the purpose and neural mechanism of this response remain obscure. In theory counterroll could be maintained either by direct tonic vestibular inputs to motoneurons, or by a neurally integrated pulse, as observed in the saccade generator and vestibulo-ocular reflex. When simulated together with ocular drift related to torsional integrator failure, the direct tonic input model predicted that the pattern of drift would shift torsionally as in ordinary counterroll, but the integrated pulse model predicted that the equilibrium position of torsional drift would be unaffected by head roll. This was tested experimentally by measuring ocular counterroll in 2 monkeys after injection of muscimol into the mesencephalic interstitial nucleus of Cajal. Whereas 90° head roll produced a mean ocular counterroll of 8.5° (±0.7° SE) in control experiments, the torsional equilibrium position observed during integrator failure failed to counterroll, showing a torsional shift of only 0.3° (±0.6° SE). This result contradicted the direct tonic input model, but was consistent with models that implement counterroll by a neurally integrated pulse.

The oculomotor system produces eye-position signals during fixations and head movements by integrating velocity-coded saccadic and vestibular inputs. A previous analysis of nucleus prepositus hypoglossi (nph) lesions in monkeys found that the integration time constant for maintaining fixations decreased, while that for the vestibulo-ocular reflex (VOR) did not. On this basis, it was concluded that saccadic inputs are integrated by the nph, but that the vestibular inputs are integrated elsewhere. We re-analyze the data from which this conclusion was drawn by performing a linear regression of eye velocity on eye position and head velocity to derive the time constant and velocity bias of an imperfect oculomotor neural integrator. The velocity-position regression procedure reveals that the integration time constants for both VOR and saccades decrease in tandem with consecutive nph lesions, consistent with the hypothesis of a single common integrator. The previous evaluation of the integrator time constant relied upon fitting methods that are prone to error in the presence of velocity bias and saccades. The algorithm used to evaluate imperfect fixations in the dark did not account for the nonzero null position of the eyes associated with velocity bias. The phase-shift analysis used in evaluating the response to sinusoidal vestibular input neglects the effect of saccadic resets of eye position on intersaccadic eye velocity, resulting in gross underestimates of the imperfections in integration during VOR. The linear regression method presented here is valid for both fixation and low head velocity VOR data and is easy to implement.

Influence of gaze rotation on the visual response of primate MSTd neurons. When we move forward, the visual image on our retina expands. Humans rely on the focus, or center, of this expansion to estimate their direction of heading and, as long as the eyes are still, the retinal focus corresponds to the heading. However, smooth rotation of the eyes adds nearly uniform visual motion to the expanding retinal image and causes a displacement of the retinal focus. In spite of this, humans accurately judge their heading during pursuit eye movements and during active, smooth head rotations even though the retinal focus no longer corresponds to the heading. Recent studies in macaque suggest that correction for pursuit may occur in the dorsal aspect of the medial superior temporal area (MSTd) because these neurons are tuned to the retinal position of the focus and they modify their tuning during pursuit to compensate partially for the focus shift. However, the question remains whether these neurons also shift focus tuning to compensate for smooth head rotations that commonly occur during gaze tracking. To investigate this question, we recorded from 80 MSTd neurons while monkeys tracked a visual target either by pursuing with their eyes or by vestibulo-ocular reflex cancellation (VORC; whole-body rotation with eyes fixed in head and head fixed on body). VORC is a passive, smooth head rotation condition that selectively activates the vestibular canals. We found that neurons shift their focus tuning in a similar way whether focus displacement is caused by pursuit or by VORC. Across the population, compensation averaged 88 and 77% during pursuit and VORC, respectively (tuning shift divided by the retinal focus to true heading difference). Moreover the degree of compensation during pursuit and VORC was correlated in individual cells ( P< 0.001). Finally neurons that did not compensate appreciably tended to be gain-modulated during pursuit and VORC and may constitute an intermediate stage in the compensation process. These results indicate that many MSTd cells compensate for general gaze rotation, whether produced by eye-in-head or head-in-world rotation, and further implicate MSTd as a critical stage in the computation of heading. Interestingly vestibular cues present during VORC allow many cells to compensate even though humans do not accurately judge their heading in this condition. This suggests that MSTd may use vestibular information to create a compensated heading representation within at least a subpopulation of cells, which is accessed perceptually only when additional cues related to active head rotations are also present.

Spatial transformations of the vestibular-optokinetic system must account for changes in head position with respect to gravity in order to produce compensatory oculomotor responses. The purpose of this experiment was to study the influence of gravity on the vestibulo-ocular reflex (VOR) in darkness and on visual-vestibular interaction in the pitch plane in human subjects using two different comparisons: (1) Earth-horizontal axis (EHA) rotation about an upright versus a supine body orientation, and (2) Earth-horizontal versus Earth-vertical (EVA) rotation axes. Visual-vestibular responses (VVR) were evaluated by measuring the slow phase velocity of nystagmus induced during sinusoidal motion of the body in the pitch plane (at 0.2 Hz and 0.8 Hz) combined with a constant-velocity vertical optokinetic stimulation (at ±36°/s). The results showed no significant effect on the gain or phase of the VOR in darkness or on the VVR responses at 0.8 Hz between EHA upright and EHA supine body orientations. However, there was a downward shift in the VOR bias in darkness in the supine orientation. There were systematic changes in VOR and VVR between EHA and EVA for 0.2 Hz, including a reduced modulation gain, increased phase lead, and decreased bias during EVA rotation. The same trend was also observed at 0.8 Hz, but at a lesser extent, presumably due to the effects of eccentric rotation in our EVA condition and/or to the different canal input across frequencies. The change in the bias at 0.2 Hz between rotation in darkness and rotation with an optokinetic stimulus was greater than the optokinetic responses without rotation. During EHA, changes in head position relative to gravity preserve graviceptor input to the VVR regardless of body orientation. However, the modifications in VVR gain and phase when the rotation axis is aligned with gravity indicate that this graviceptive information is important for providing compensatory eye movements during visual-vestibular interaction in the pitch plane.

During gaze shifts, the eyes and head collaborate to rapidly capture a target (saccade) and fixate it. Accordingly, models of gaze shift control should embed both saccadic and fixation modes and a mechanism for switching between them. We demonstrate a model in which the eye and head platforms are driven by a shared gaze error signal. To limit the number of free parameters, we implement a model reduction approach in which steady-state cerebellar effects at each of their projection sites are lumped with the parameter of that site. The model topology is consistent with anatomy and neurophysiology, and can replicate eye-head responses observed in multiple experimental contexts: 1) observed gaze characteristics across species and subjects can emerge from this structure with minor parametric changes; 2) gaze can move to a goal while in the fixation mode; 3) ocular compensation for head perturbations during saccades could rely on vestibular-only cells in the vestibular nuclei with postulated projections to burst neurons; 4) two nonlinearities suffice, i.e., the experimentally-determined mapping of tectoreticular cells onto brain stem targets and the increased recruitment of the head for larger target eccentricities; 5) the effects of initial conditions on eye/head trajectories are due to neural circuit dynamics, not planning; and 6) “compensatory” ocular slow phases exist even after semicircular canal plugging, because of interconnections linking eye-head circuits. Our model structure also simulates classical vestibulo-ocular reflex and pursuit nystagmus, and provides novel neural circuit and behavioral predictions, notably that both eye-head coordination and segmental limb coordination are possible without trajectory planning.

Пояснювальна записка складається із вступу, 8 розділів, висновків, переліку посилань із 20 найменувань. Загальний обсяг роботи становить 120 с. основного тексту, 20 рисунків, 12 таблиць і 4 додатків. Метою проекту є проектування і модернізація конструкції периферичного накату, призначеного для намотування санітарно-гігієнічного паперу в рулони. Поставлена задача досягається шляхом дослідження літературних джерел, виконанням розрахунків тамбурного валу, циліндра накату та розрахунків на міцність основних вузлів і деталей конструкції. Виконано аналіз результатів та зроблено висновки. Наведено список використаної літератури. Розрахунково-пояснювальна записка містить схему отримання санітарно-гігієнічного паперу, її опис та місце периферичного накату в ній. Графічна частина проекту включає креслення формату А1х3, А1, А2 і А2х3, що містять: складальний кресленик накату, складальний кресленик тамбурного валу, складальний кресленик циліндра та кресленик патрону.
Explanatory note consists of an introduction, eight chapters, conclusions, list of references of 20 items. The total work contains 120 p. of the main text, 20 drawings, 12 tables and 4 appendices. The explanatory note consists of an introduction, 8 chapters, conclusions, a list of references from 20 titles. Total work is 92 seconds. main text, 20 drawings, 6 tables and 3 appendices. The purpose of the project is to design and modernize the peripheral rolling design designed to wrap sanitary paper in rolls. The task is achieved by studying literary sources, performing calculations of the tambour shaft, rolling cylinder and calculating the strength of the main units and design details. The analysis of the results and conclusions are made. The list of used literature is given. The settlement and explanatory note contains the scheme of obtaining sanitary-hygienic paper, its description and the place of peripheral rolling in it. The graphic part of the project includes drawings of the format A1х3, А1, А2 and А2х3, which contain: an assembly drawing roller, an assembly drawing of a tambourine shaft, an assembly drawing of a cylinder and a cartridge.
Пояснительная записка состоит из введения, 8 глав, заключения, списка ссылок из 20 наименований. Общий объем работы составляет 120 с. основного текста, 20 рисунков, 12 таблиц и 4 приложений. Целью проекта является проектирование и модернизация конструкции периферического наката, предназначенного для намотки санитарно-гигиенической бумаги в рулоны. Поставленная задача достигается путем исследования литературных источников, выполнением расчетов тамбурного вала, цилиндра наката и расчетов на прочность основных узлов и деталей конструкции. Выполнен анализ результатов и сделаны выводы. Приведен список использованной литературы. Расчетно-пояснительная записка содержит схему получения санитарно-гигиенической бумаги, ее описание и место периферического наката в ней. Графическая часть проекта включает чертежи формата А1х3, А1, А2 и А2х3, содержащие: сборочный чертеж наката, сборочный чертеж тамбурного вала, сборочный чертеж цилиндра и чертеж патрона.