Unbalanced Tension Research Articles

Effects of polar cortical cytoskeleton and unbalanced cortical surface tension on intercellular bridge thinning during cytokinesis

To probe the contributions of polar cortical cytoskeleton and the surface tension of daughter cells to intercellular bridge thinning dynamics during cytokinesis, we applied cytochalasin D (CD) or colchicine (COLC) in a highly localized manner to polar regions of dividing normal rat kidney (NRK) cells. We observed cellular morphological changes and analyzed the intercellular bridge thinning trajectories of dividing cells with different polar cortical characteristics. Global blebbistatin (BS) application was used to obtain cells losing active contractile force groups. Our results show that locally released CD or colchicine at the polar region caused inhibition of cytokinesis before ingression. Similar treatment at phases after ingression allowed completion of cytokinesis but dramatically influenced the trajectories of intercellular bridge thinning. Disturbing single polar cortical actin induced transformation of the intercellular bridge thinning process, and polar cortical tension controlled deformation time of intercellular bridges. Our study provides a feasible framework to induce and analyze the effects of local changes in mechanical properties of cellular components on single cellular cytokinesis.

Unbalanced tension analysis for UHV transmission towers in heavy icing areas

Unbalanced tension is one of the most important controlling loads for the design of transmission towers in cold regions. It can be caused in some cases including non-uniform accreted ice, broken wires, ice shedding and galloping. Firstly, for the comparison of the unbalanced tensions and the inclinations of the suspension strings, the FEA method and the constant conductor length method were applied. The results by two methods are approximately well agreed. With the consideration of some design parameters of the transmission line, a seven continuous span FEA model of conductors and insulators was established. Secondly, under different load cases, the tensions and the unbalanced tensions of conductors were analyzed for the UHV suspension tower and tension tower in heavy icing areas. It shows that the load modes and the eccentricity of the accreted ice, as well as the wind velocity only have little effect on the unbalanced tensions. The transforming density method and 10 m/s of wind velocity are proposed for the analysis of the unbalanced tensions. When there are no elevation difference and span difference, the unbalanced tension of the UHV suspension tower increases with the ice thickness, the span length and the icing rate, and the calculated values for different ice thickness are lower than those of regulations. With the increasing of the elevation difference and the span difference, the ratios of the unbalanced tensions with and without elevation difference as well as span difference increase. However, the ratios of the unbalanced tensions with and without elevation difference as well as span difference decrease with the ice thickness. For tension towers, variations of the elevation difference and the span difference have little effect on the unbalanced tensions. Lastly, the calculated values of the unbalanced tension percentages of UHV transmission towers were compared with those of applicable regulations, some suggestions on the unbalanced tension values were proposed.

Dynamic Response of Conductor Breakage for Oxytropis Transmission Tower-Line System

Dynamic response of conductor breakage is analyzed on guyed oxytropis transmission tower-line system of 500KV 5291 JinJiang-Zhenjiang lines. Considering unbalanced tension, finite element method is presented. Result of the transient analysis shows that the vibration of tower-line system happens after conductor breakage. With the damping affect，the system vibration becomes gentle. For the tension of lines, the peak value of dynamic tension of conductor can be times of the initial tension. It is shown that the proposed method is of efficiency and practicality.

DYNAMIC RESPONSES OF TRANSMISSION TOWER-LINE SYSTEM UNDER ICE SHEDDING

Ice shedding from conductors may easily induce electrical and mechanical accidents, which cause a serious threat to the safe operation of transmission lines. In this paper, a 3D finite element model of tower-conductor-ground wire-insulator system was established in ANSYS, and the dynamic responses of ice shedding under different cases were analyzed for a transmission tower-line system. The computed jumping heights are in excellent agreement with the experimental values of a two span conductors model. Many variables were considered in the ice-shedding simulations that include tower-line coupled effect, phase combination of the ice-shedding conductors, thickness of the accreted ice, length of the ice-shedding span as well as elevation difference. Influences of all the variables on the dynamic responses of jumping heights, loads at the end of insulators and the forces of transmission tower were studied. Ice-shedding simulations of an actual 500 kV transmission line section which experience failure under ice shedding in 2008 were performed. The results show that stress ratios of members at the tower head under design ice thickness exceed the limiting values when the amount of shedding ice is large. For ice shedding at the top phase conductors, the jumping height and unbalanced tension at the end of insulator can be reduced by applying interphase spacers in triangular arrangement. The tower is in a safe state under the load of the design ice thickness. In order to prevent ice-shedding accidents, interphase spacers should be used, and the weak members at the tower head should be strengthened according to the calculated load values at the end of insulators.

Simulation of Lubricant Behavior by Using the Particle Method

Lubricant behavior within a head-disk clearance in recent hard disk drives was simulated by using a particle method, which is based on continuum dynamics. The lubricant was simulated as a group of particles. The surface tension and the wall-adhesion models used in the particle method were verified before applying the particle method to the lubricant behavior simulation first. That is, simple benchmark problems like liquid-droplet deformations under unbalanced surface tension and wall adhesion force were used to confirm the accuracy of the models. In the lubricant simulation, the effects of viscous stress and surface tension on the lubricant behavior were studied. The study found that viscous stress is the dominant factor in comparison with surface tension on bulk condition of viscosity; that is, the lubricant bridge is deformed by the viscous stress, not by the surface tension.

A Technique of Staged Lateral Release to Correct Patellar Tracking in Total Knee Arthroplasty

Optimal patellar tracking and component alignment are important in achieving a well-functioning total knee arthroplasty (TKA). The patella is constrained partly by design of the prosthetic trochlear groove, and patellar tracking is governed by a combination of static and dynamic factors. Maltracking may result from excessive or unbalanced tension in the surrounding soft tissues. This article describes a staged progressive lateral release of the patellar retinaculum in TKA, which is classified into 6 stages. Stage 1 transects the deep lateral patellofemoral ligament; stages 2 to 6 extend the lateral patellar incision distally from vastus lateralis to the tibial tubercle. This technique was used in a series of 96 primary TKAs. We report the rates of the various stages of lateral release and the variables that might affect the decision to perform such a release.

A method for evaluating skeletal relapsing force during maxillomandibular fixation after orthognathic surgery: A preliminary report

Although skeletal relapse after orthognathic surgery can be considered primarily the result of unbalanced tension in the surgically modified stomatognathic system (i.e., skeletal relapsing force [SRF] acting on the mandibular segment), no study of SRF has been reported and its nature still remains unclarified. This article presents a practicable method for evaluating SRF during the fixation period with the use of a foil strain gauge fixed to the upper arch wire between the central incisors, with a preliminary result after mandibular advancement by sagittal split ramus osteotomy to demonstrate the value of this method for studying SRF. The pattern and degree of SRF were shown to vary during the postoperative period and in accordance with experimental situations, including the mandibular resting posture, swallowing, clenching, and speaking. On day 3, a constant SRF of 550 gm existed even in the resting posture and was increased by 450 gm to a maximum of about 1 kg on swallowing; clenching and speaking also produced an increase. Thus it was inferred that SRF arose not only from surgically stretched perimandibular connective tissues but also from intermittent physiologic muscle actions. The constant SRF subsided gradually with time, and after day 33, swallowing as well as clenching no longer increased the SRF, which indicates that the critical period for postoperative skeletal stability was the first few weeks, during which muscle readaptation and primary bone healing occurred. It was concluded that this method of evaluating SRF, which is capable of immediately revealing any tendency to relapse or the progress of soft tissue adaptation and bone healing, could be used as an effective research tool. (A M J O RTHOD D ENTOFAC O RTHOP 1991;100:38-46.)