Eccentric Position Research Articles

Eccentric position of the germinal vesicle and cortical flow during oocyte maturation specify the animal-vegetal axis of ascidian embryos

The animal-vegetal (A-V) axis is already set in unfertilized eggs. It plays crucial roles in coordinating germ-layer formation. However, how the A-V axis is set has not been well studied. In ascidians, unfertilized eggs are already polarized along the axis in terms of cellular components. This polarization occurs during oocyte maturation. Oocytes within the gonad have the germinal vesicle (GV) close to the future animal pole. When the GVs of full-grown oocytes were experimentally translocated to the opposite pole by centrifugal force, every aspect that designates A-V polarity was reversed in the eggs and embryos. This was confirmed by examining the cortical allocation of the meiotic spindle, the position of the polar body emission, the polarized distribution of mitochondria and postplasmic/PEM mRNA, the direction of the cortical flow during oocyte maturation, the cleavage pattern and germ-layer formation during embryogenesis. Therefore, the eccentric position of the GV triggers subsequent polarizing events and establishes the A-V axis in eggs and embryos. We emphasize important roles of the cortical flow. This is the first report in which the A-V axis was experimentally and completely reversed in animal oocytes before fertilization.

Custom-made mouth prop for TMJ arthrocentesis: a technical note.

TMJ arthrocentesis involves lavage of the upper joint space which forces the disc apart from the fossa and washes away the inflammatory components of the joint. To increase the joint space during arthrocentesis, the patient is usually asked to open the mouth and deviate it to the opposite side so as to distract the condyle from the glenoid fossa thereby increasing joint space. The authors describe a simple and rapid technique of preparing a custom-made mouth prop to hold the mandible in eccentric position during arthrocentesis. The custom-made mouth prop is an effective tool to help relax the patient in an eccentric position during the duration of arthrocentesis procedure.

Role of neural integrators in oculomotor systems: asystematic narrative literature review.

To evaluate the role of neural integrators (NI) in the oculomotor system. A literature search was carried out using several electronic databases during the months of June 2014 to March 2015. The following keywords were used to generate focused results: 'neural integrators', 'gaze-holding', 'oculomotor integration', 'impaired gaze-holding', 'gaze evoked nystagmus' and 'gaze dysfunction'. Further materials were found through searching relevant articles within reference lists. Seventy-one articles were sourced for this review which analysed animal and human subjects and network models; 45 were studies of humans, 16 studies of primates, three studies of felines and one study from rats and network models. The remaining articles were literature reviews. The horizontal and vertical, including torsional, NI are located logically in the brainstem, nearby their appropriate target extraocular motoneuron nuclei for stable eye position in eccentric position. The nucleus prepositus hypoglossi (NPH) and medial vestibular nuclei (MVN) are closely linked at the caudal pons and dorsal rostral medulla, integrating horizontal conjugate eye movement. The interstitial nucleus of Cajal (INC) integrates vertical and torsional eye movement at the upper midbrain. The integrator time constant is averaged to 25seconds in human horizontal and animal vertical NI to perform its function. Case reports revealed that dysfunction of horizontal NI also resulted in vertical ocular deviations, indicating some overlap of horizontal and vertical gaze control. Furthermore, pharmacological inactivation of NI exposed a population of inhibitory neurotransmitters that permits its mechanism of action; allowing for smooth conjugate movement. Neural integrators operate to integrate eye velocity and eye position information to provide signals to extraocular motoneurons to attain and maintain a new position. Therefore, NI allow image stabilization during horizontal and vertical eye movements at eccentric positions for comfortable single vision.

Analysis of the vibration attenuation of rotors supported by magnetorheological squeeze film dampers as a multiphysical finite element problem

Placing damping devices between the rotor and its frame is a frequently used engineering solution for reducing excessive vibrations of rotating machines. Their damping effect must be controllable to achieve their optimum performance in a wide range of operating speeds. This is enabled by magnetorheological squeeze film dampers, the damping force of which can be controlled by changing magnetic flux passing through the lubricating layer. The magnetorheological oil is represented in the developed mathematical model by Bingham material. The magnetic induction in the damper gap is a significant parameter that directly influences resistance against the flow of the magnetorheological oil and generates the additional magnetic force acting on the rotor journal. Therefore, three approaches (1D, 2D, and 3D) to determination of the semi-analytical relations describing its distribution in the lubricating film were proposed, tested, and compared. The appropriate coefficients were determined by repeatedly solving 2D or 3D magnetostatic problems for the specified damper dimensions, design, and rising magnitude of the journal eccentricity utilizing the finite element and least square methods. In the developed computational model of the rotating machine, the rotor shaft is represented by a beam like-body that is discretised into finite elements. The magnetorheological dampers are implemented by springs and force couplings. The principal contribution of this article consists in the development of a methodology, based on three approaches, for the derivation of closed form formulas describing the distribution of magnetic induction in the damper gap as a function of the rotor journal eccentricity and angular position. The individual approaches give some differences in the results that are consequent upon the distinguishing level used for modelling the damping device. The extent of their applicability is discussed in the article. The developed computational models are intended for the investigation of the vibration attenuation of rotor systems in a wide range of rotational speeds.

Disk displacement, eccentric condylar position, osteoarthrosis - misnomers for variations of normality? Results and interpretations from an MRI study in two age cohorts.

BackgroundClinical decision-making and prognostic statements in individuals with manifest or suspected temporomandibular disorders (TMDs) may involve assessment of (a) the position of articular disc relative to the mandibular condyle, (b) the location of the condyle relative to the temporal joint surfaces, and (c) the depth of the glenoid fossa of the temporomandibular joints (TMJs). The aim of this study was twofold: (1) Determination of the prevalence of these variables in two representative population-based birth cohorts. (2) Reinterpretation of the clinical significance of the findings.MethodsFrom existing magnetic resonance imaging (MRI) scans of the TMJs that had been taken in 2005 and 2006 from 72 subjects born between 1930 and 1932 and between 1950 and 1952, respectively, the condylar position at closed jaw was calculated as percentage displacement of the condyle from absolute centricity. By using the criteria introduced by Orsini et al. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 86:489-97, 1998), a textbook-like disc position at closed jaw was distinguished from an anterior location. TMJ morphology of the temporal joint surfaces was assessed at open jaw by measuring the depth of the glenoid fossa, using the method proposed by Muto et al. (J Oral Maxillofac Surg 52:1269-72, 1994).Frequency distributions were recorded for the condylar and disc positions at closed jaw.Student’s t-test with independent samples was used as test of significance to detect differences of condylar positions between the age cohorts (1930 vs. 1950) and the sexes. The significance levels were set at 5%. First, the results from the measurement of the age cohorts were compared without differentiation of sexes, i.e., age cohort 1930–1932 versus age cohort 1950–1952. Subsequently, the age cohorts were compared by sex, i.e., men in cohort 1930–1932 versus men in cohort 1950–1952, and women in cohort 1930–1932 women men in cohort 1950–1952.ResultsIn both cohorts, condylar position was characterized by great variability. About 50% of the condyles were located centrically, while the other half was either in an anterior or in a posterior position. In both female cohorts, a posterior position predominated, whereas a centric position prevailed among men. Around 75% of the discs were positioned textbook-like, while the remaining forth was located anteriorly. Age had no statistically significant influence on condylar or on disc position. Conversely, comparison between the age groups revealed a statistically significant decrease of the depth of the glenoid fossa in both older cohorts. This age-dependent changes may be interpreted as flattening of the temporal joint surfaces.ConclusionsWe call for a re-interpretation of imaging findings because they may insinuate pathology which usually is not present. Instead, anterior or posterior positions of the mandibular condyle as well as an anterior location of the articular disc should be construed as a variation of normalcy. Likewise, flattening of articular surfaces of the TMJs may be considered as normal adaptive responses to increased loading, rather than pathological degenerative changes.Trial registrationNot applicable.

"Ekscentrična pozicionalnost" u filozofskoj antropologiji Helmutha Plessnera

The paper outlines the category of eccentric positionality of the man in philosophical thought of Helmuth Plessner. Using the term positionality, Plessner determined the existence of living beings towards not living beings, and using the category eccentric positionality he tried to precise the specificity of human survival. In the background of these concepts is the idea of possibilities of characterization of specific modes of living bodies and overcoming of ambiguity of human existence as natural and unnatural, in other words physical and not physical. In discussions about the man, starting from Descartes, precisely that was happening. In order to get the concept of man, of imagined from the position of experience, and trying to clarify the aforementioned duality of his description, Plessner started from the phenomenon of life, which cannot be understood through Cartesian alternative of spirit or physical thing. Starting from this principle, he was able to reconcile the two philosophical traditions of understanding men, in what is mostly consist significance of his thought. The fact that Plessner is not the first author who has been using the concept of eccentricity does not diminish the merit of detailed elaboration of this concept as well as its high-quality application in an attempt to understand the human being. "Eccentric positionality", which will eventually infuse all his analysis in the sphere of man, shows the height of Plessner’s philosophical power. Therefore, this paper shows the historical and scientific context of development of this category in thought of this German philosopher.

Saccadic and Postsaccadic Disconjugacy in Zebrafish Larvae Suggests Independent Eye Movement Control.

Spontaneous eye movements of zebrafish larvae in the dark consist of centrifugal saccades that move the eyes from a central to an eccentric position and postsaccadic centripetal drifts. In a previous study, we showed that the fitted single-exponential time constants of the postsaccadic drifts are longer in the temporal-to-nasal (T->N) direction than in the nasal-to-temporal (N->T) direction. In the present study, we further report that saccadic peak velocities are higher and saccadic amplitudes are larger in the N->T direction than in the T->N direction. We investigated the underlying mechanism of this ocular disconjugacy in the dark with a top-down approach. A mathematic ocular motor model, including an eye plant, a set of burst neurons and a velocity-to-position neural integrator (VPNI), was built to simulate the typical larval eye movements in the dark. The modeling parameters, such as VPNI time constants, neural impulse signals generated by the burst neurons and time constants of the eye plant, were iteratively adjusted to fit the average saccadic eye movement. These simulations suggest that four pools of burst neurons and four pools of VPNIs are needed to explain the disconjugate eye movements in our results. A premotor mechanism controls the synchronous timing of binocular saccades, but the pools of burst and integrator neurons in zebrafish larvae seem to be different (and maybe separate) for both eyes and horizontal directions, which leads to the observed ocular disconjugacies during saccades and postsaccadic drifts in the dark.

Inhibition of Rac1 GTPase activity affects porcine oocyte maturation and early embryo development

Mammalian oocyte asymmetric division relies on the eccentric positioning of the spindle, resulting in the polar body formation. Small signaling G protein Rac1 is a member of GTPases, which regulates a diverse array of cellular events, including the control of cell growth, cytoskeletal reorganization, and the activation of protein kinases. However, effects of Rac1 on the porcine oocyte maturation and early embryo development are not fully understood. In present study we investigated the role of Rac1 in oocyte maturation and embryo cleavage. We first found that Rac1 localized at the cortex of the porcine oocytes, and disrupting the Rac1 activities by treating with NSC 23766 led to the failure of polar body emission. In addition, a majority of treated oocytes exhibited abnormal spindle morphology, indicating that Rac1 may involve into porcine oocyte spindle formation. This might be due to the regulation of Rac1 on MAPK, since p-MAPK expression decreased after NSC 23766 treatments. Moreover, we found that the position of most meiotic spindles in treated oocytes were away from the cortex, indicating the roles of Rac1 on meiotic spindle positioning. Our results also showed that inhibition of Rac1 activity caused the failure of early embryo development. Therefore, our study showed the critical roles of Rac1 GTPase on porcine oocyte maturation and early embryo cleavage.

Identification of embryo-fetal cells in celomic fluid using morphological and short-tandem repeats analysis.

The main problem to wide acceptability of celocentesis as earlier prenatal diagnosis is contamination of the sample by maternal cells. The objective of this study was to investigate the cellular composition of celomic fluid for morphological discrimination between maternal and embryo-fetal cells. Celomic fluids were aspired by ultrasound-guided transcervical celocentesis at 7-9 weeks' gestation from singleton pregnancies before surgical termination for psychological reasons. DNA extracted from celomic fluid cells showed the same morphology, and quantitative fluorescent polymerase chain reaction (PCR) assay was performed to evaluate their fetal or maternal origin. Six different types of non-hematological maternal and four different types of embryo-fetal cells were detected. The most common maternal cells were of epithelial origin. The majority of embryo-fetal cells were roundish with a nucleus located in an eccentric position near the wall. These cells were considered to be erythroblasts, probably derived from the yolk sac that serves as the initial site of erythropoiesis. The combined use of morphology and DNA analysis makes it possible to select and isolate embryo-fetal cells, even when maternal contamination is high. This development provides the opportunity for the use of celocentesis for early prenatal diagnosis of genetic diseases and application of array comparative genomic hybridization. © 2016 John Wiley & Sons, Ltd.

Effect of the eccentricity of normal resistivity borehole tools on the current field and resistivity measurement

Three-dimensional finite element numerical model calculations have been carried out to investigate the quantitative effect of the eccentric position of a normal resistivity borehole probe used in practice. Detailed calculations were done between the point-wise analytical solution and numerical solution to verify the results obtained from the finite element method for a normal probe with finite-length cylindrical electrodes. In the borehole the pattern of the current flowing out from current electrode A is efficiently influenced by the eccentricity. For high-resistivity rock the current density is decreased, while for low-resistivity rock it is increased toward the wall side. On the other hand, the eccentricity does not affect considerably the apparent resistivity calculated from electrode potentials. In most geological situations the deviation is less than 2%. However, in infrequent cases when the true resistivity of the rock is extremely low and/or the distance between the potential and current electrodes is very small the effect of the eccentricity can exceed even 10%.

CFD simulation of interfacial instability from the nozzle in the formation of viscous core‐annular flow

AbstractThe interfacial instability in the development of core‐annular flow by the influence of the inlet nozzle in a horizontal pipe was investigated by computational fluid dynamics (CFD). The two‐phase flow has been simulated using Volume‐Of‐Fluid model (VOF) and k‐ϵ turbulence model for the core (viscous oil) and the annular phase (water). The simulation results showed that by increasing the water input fraction, the interfacial instability appeared when the eccentricity of the core with an upward position and an oscillating position were generated by the input pressure, turbulent kinetic, and buoyancy force. In the development of the perfect core‐annular flow an input concentric core changes to eccentric position with negligible turbulence. The onset of entrainment is formed by a reverse flow at the junction of the two‐phase at the nozzle exit. The interfacial formation was analyzed using a proposed two‐phase Froude number and modified Eötvos number involving the water input fraction.

Transient Response of a Short-Length (L/D = 0.2) Open-Ends Elastically Supported Squeeze Film Damper: Centered and Largely Off-Centered Whirl Motions

Commonly employed in air breathing (gas turbine) engines, squeeze film dampers (SFDs) reduce the amplitude of rotor vibration while traversing system critical speeds or in transient events such as during a maneuver load, a hard landing, a blade loss, or an engine startup/shutdown sequence that could instantaneously shift a damper journal eccentricity (es) to near its clearance (c). Experiments investigate the dynamic force performance of an open ends, short-length (L/D = 0.2) SFD test rig with radial clearance c = 267 μm and undergoing centered (es/c = 0) to largely off-centered (es/c → 1) whirl orbit motions induced by both a large static load plus a dynamic load. Four rods, symmetrically arranged to resemble a squirrel cage, elastically support the SFD test rig. A hydraulic load system displaces the test damper structure into static eccentricity (es/c). One of two types of dynamic load with amplitude FX = FY excite the SFD: a single-frequency, stepping from low frequency to high frequency discretely; or a sine-sweep frequency growing linearly with time at 6 Hz/s, 33 Hz/s, 40 Hz/s, or 55 Hz/s. For motions departing from es/c = 0.0, 0.95, and 0.99, the dynamic load uses a sine-sweep frequency varying from 5 Hz to 245 Hz and evolving rapidly at ∼33 Hz/s. Measurements of SFD displacements characterize the behavior of the SFD rig during its transient response which crosses two system natural frequencies. For motions departing from a largely off-centered condition (es → c), the dynamic load forces the damper to whirl with highly elliptical orbits, in particular while crossing a resonance (damped natural frequency). Moreover, the dynamic motions departing from es ∼ c are smaller in amplitude than those arising from a centered condition (es/c = 0). The larger damping produced by a very small squeeze film thickness explains the difference in response amplitude. At a largely off-centered condition (es/c = 0.99) and a low excitation frequency (f < 40 Hz), intermittent contact between the damper journal and its housing occurs as evidenced by a large magnitude recorded dynamic pressure (on the order of MPa). For whirl motions around various static eccentricity positions, es/c = 0.0–0.75, the dynamic load covers a frequency range from 10 Hz to 100 Hz using either a single-frequency excitation or a sine-sweep frequency excitation with a slow growth rate ∼6.5 Hz/s to induce a quasi-steady-state response. The experimental procedure builds complex stiffness in the frequency domain for identification of SFD stiffness, damping, and added mass force coefficients, (K, C, M)SFD. For motions centered around small to large static eccentricities, es/c = 0–0.75, the identified (K, C, M)SFD coefficients from sine-sweep frequency dynamic loads coincide with those extracted from single-frequency dynamic load tests over the same frequency range. Short-length SFD theory predictions for damping coefficients agree with the experimental results. Predicted added mass or inertia coefficients, like the model, fall short of the target experimental magnitudes. The test results give practitioners the credence to certify the ability of a SFD to control rotor response amplitude during typical transient events.

Experiments on eccentric granular discharge from a quasi-two-dimensional silo

A comprehensive experimental investigation has been made to study the flow behavior during the discharge of granular material through an orifice at the bottom of a two-dimensional rectangular silo with an emphasis on eccentric orifice position. Two different methods, the deformation of colored bands and digital particle image velocimetry have been used to investigate the flow field. Based on the dynamics during the discharge, the entire granular matrix can be divided into different regimes. The evolution of free surface exhibits a self-similarity of its contour. Though the dynamics of granular flow for any position of the orifice exhibits some general trends, eccentricity of the orifice position induces unique complexity in the flow behavior. The proximity of the orifice with the wall induces a noticeable slip on it. This wall slip has a profound effect on the velocity distribution of the vertical flowing region. The rate of discharge has been observed to increase with eccentricity of the orifice position. Further, a detailed analysis of the inclined flow region reveals a unique velocity distribution with three distinct zones and helps to understand the flow physics.

Magnetic Actuator with Multiple Vibration Components Arranged at Eccentric Positions for Use in Complex Piping

This paper proposes a magnetic actuator using multiple vibration components to perform locomotion in a complex pipe with a 25 mm inner diameter. Due to the desire to increase the turning moment in a T-junction pipe, two vibration components were attached off-center to an acrylic plate with an eccentricity of 2 mm. The experimental results show that the magnetic actuator was able to move at 40.6 mm/s while pulling a load mass of 20 g in a pipe with an inner diameter of 25 mm. In addition, this magnetic actuator was able to move stably in U-junction and T-junction pipes. If a micro-camera is implemented in the future, the inspection of small complex pipes can be enabled. The possibility of inspection in pipes with a 25 mm inner diameter was shown by equipping the pipe with a micro-camera.

Cervical dystonia: a neural integrator disorder

Ocular motor neural integrators ensure that eyes are held steady in straight-ahead and eccentric positions of gaze. Abnormal function of the ocular motor neural integrator leads to centripetal drifts of the eyes with consequent gaze-evoked nystagmus. In 2002 a neural integrator, analogous to that in the ocular motor system, was proposed for the control of head movements. Recently, a counterpart of gaze-evoked eye nystagmus was identified for head movements; in which the head could not be held steady in eccentric positions on the trunk. These findings lead to a novel pathophysiological explanation in cervical dystonia, which proposed that the abnormalities of head movements stem from a malfunctioning head neural integrator, either intrinsically or as a result of impaired cerebellar, basal ganglia, or peripheral feedback. Here we briefly recapitulate the history of the neural integrator for eye movements, then further develop the idea of a neural integrator for head movements, and finally discuss its putative role in cervical dystonia. We hypothesize that changing the activity in an impaired head neural integrator, by modulating feedback, could treat dystonia.

Influence of conductor eccentricity on Faraday phase shift errors of portable fiber-optic current transformer

A portable fiber-optic current transformer (P-FOCT) with flexible sensing coil was proposed in this paper. The model has been established to describe the Faraday phase shift errors, which are influenced by the non-closed error of flexible sensing coil and eccentric position of current conductor. It has been obtained that the Faraday phase shift relative error is mainly influenced by the non-closed angle of sensing coil and can be decreased by increasing number of turns, the matching installation region of current conductor was found, the theoretical model was verified by the finite element method (FEM). It provides an important reference for the installation of P-FOCT to satisfy the accuracy requirement.

Effect of the shaft eccentricity and rotational direction on the mixing characteristics in cylindrical tank reactors

Strategy of the shaft eccentricity is introduced to enhance the mixing characteristics in a flat bottomed cylindrical vessel without baffles. The mixing is ensured by a six-curved blade impeller. Three solutions which are models of food emulsions are used as working fluids. These solutions have a shear thinning behavior modeled by the power-law. The effects of fluid properties, stirring rates, impeller rotational direction and impeller eccentricity on the 3D flow fields and power consumption are investigated. Three values of impeller eccentricity are considered, namely 0%, 24% and 48% of the vessel diameter. It is found that the opposite clockwise rotational direction reduces the power consumption, compared with the clockwise rotational direction. Also, the obtained results show that an impeller placed at an eccentric position between 24% and 48% of the vessel diameter and at the third of the vessel height may ensure the best mixing characteristics.

Predicting bias in perceived position using attention field models.

Attention is the mechanism through which we select relevant information from our visual environment. We have recently demonstrated that attention attracts receptive fields across the visual hierarchy (Klein, Harvey, & Dumoulin, 2014). We captured this receptive field attraction using an attention field model. Here, we apply this model to human perception: We predict that receptive field attraction results in a bias in perceived position, which depends on the size of the underlying receptive fields. We instructed participants to compare the relative position of Gabor stimuli, while we manipulated the focus of attention using exogenous cueing. We varied the eccentric position and spatial frequency of the Gabor stimuli to vary underlying receptive field size. The positional biases as a function of eccentricity matched the predictions by an attention field model, whereas the bias as a function of spatial frequency did not. As spatial frequency and eccentricity are encoded differently across the visual hierarchy, we speculate that they might interact differently with the attention field that is spatially defined.

Optimizing compression: Comparing eccentric plate holes and external tensioning devices

ObjectiveElimination of interfragmentary motion in fracture fixation using plates to impart compression and promote primary bone healing through absolute stability has been well described as a reliable and successful method to treat simple transverse and short oblique fracture morphologies. Our hypothesis is that dynamic compression plating augmented by external compression techniques would produce and maintain a significantly greater amount of compression than using the plate alone. MethodsSimple transverse diayphyseal fractures were simulated in nine 4th generation composite bone models. A load cell was placed within the transverse fracture osteotomy and stabilized and compressed using either eccentric screw placement in a dynamic compression plate alone or augmented with an opposite segment Verbrugge clamp or articulated tensioning device (ATD) compressing using a screw outside of the plate. Dynamic plate compression was evaluated independently and in conjunction with the external compression techniques. Statistical analyses were carried out using a linear mixed effects model and pairwise comparisons between conditions with a significance set at a P-value <0.05. ResultsBoth of the external compression techniques (Verbrugge and ATD) achieved significantly higher compression than the plate compression technique alone with 78% (P<0.001) and 134% (P<0.001) more compression respectively. The measured compression across the osteotomy after screw application and removal of external compression decreases by 17% for the Verbrugge device (P=0.215) and by 22%, after removal of the ATD device (P=0.038). For both techniques, adding additional screws in eccentric (load) position further increases compression. ConclusionPlate compression is a reliable method for inducing compression across transverse and short oblique fractures. Augmenting plate compression technique with external compression techniques (Verbrugge clamp or ATD) allows for a significantly greater compressive load to be achieved. Compression lost after removal of the external compression device indicates that the maximal compression attainable across a fracture may not be reliably maintained with standard dynamic compression plating techniques.

Propagation law of shock waves in single layer spherical lattice shell under internal explosion

Using software of finite element analysis LS-DYNA, in this paper we performed numerical simulation on the propagation law of shock waves in single layer spherical lattice shell under the effect of internal explosion, obtained the laws of propagation, reflection, convergence and peak appeared of shock waves, concluded that the damage of enclosed structure is closely related to, initial overpressure peak, and partial secondary overpressure peak, analyzed the influences of explosive quantity, explosion center height, and explosive eccentric position on the propagation law of shock waves. Based on the results of numerical simulation, we concluded joint area between lattice shell top and wall shell is the key location for explosion venting and pointed out the calculation formula of overpressure peak on structure surface of higher fitting precision is feasible.