Biomechanical Strategies for Obstacle Crossing in Patients with Anterior Cruciate Ligament Deficiency

The current study aimed to investigate the biomechanical control strategies in patients with anterior cruciate ligament deficiency (ACLD) when crossing obstacles of different heights. Eighteen patients with unilateral ACLD and sixteen age-matched healthy controls were recruited. They crossed obstacles of heights of 10%, 20% and 30% of their leg lengths at a self-selected pace while the kinematic and kinetic data were measured and analyzed using inverse dynamics analysis. Patients with ACLD were found to avoid using the quadriceps on both affected and unaffected sides during stance phase. Training programs on both quadriceps are needed for more efficient rehabilitation of the patients with unilateral ACLD

VALIDITY OF A MAKER-BASED LOCATOR FOR MEASURING IN VIVO THREEDIMENSIONAL SCAPULAR STATIC POSES USING STEREOPHOTOGRAMMETRY

The study aimed to (1) develop a marker-based scapular locator for measuring scapular poses and (2) to design an in vivo experimental procedure for this static marker-based measurement method to decrease measurement errors, and (3) to validate this scapular locator and the experimental procedure. Six young male adults were implanted into the spine of the scapula with two bone-pins that were attached with a cluster of four retroreflective markers (bone markers). The scapular poses were measured simultaneously using the developed scapular locator and the bone markers. The results showed that very high validity for scapular rotations and for the acromial angle (AA), the root of spine (RS) and the inferior angle (IA) of the scapular translation were achieved. Two main reasons contributed to the results: (1) the adjustable scapular locator and (2) careful palpation of the bony landmarks over the scapula

IDENTIFICATION OF BEARING COEFFICIENTS OF FLEXIBLE ROTOR-BEARING SYSTEMS

ABSTRACT The accuracy of stiffness and damping coefficients of bearings is critical for the rotordynamic analysis of rotating machinery. However, the influence of bearings depends on the design, manufacturing, assembly, and operating conditions of the bearings. Uncertainties occur quite often in manufacturing and assembly, which causes the inaccuracy of bearing predictions. An accurate and reliable in-situ identification method for the bearing coefficients is valuable to both analyses and industrial applications. The identification method developed in this research used the receptance matrices of flexible shafts from FEM modeling and the unbalance forces of trial masses to derive the displacements and reaction forces at bearing locations. Eight bearing coefficients are identified through a Total Least Square (TLS) procedure, which can handle noise effectively. A special feature of this method is that it can identify bearing coefficients at a specific operating speed, which make it suitable for the measurement of speed-dependent bearings, like hydrodynamic bearings. Numerical validation of this method is presented. The configurations of unbalance mass arrangements are discussed. INTRODUCTION The rotor-bearing system is a critical dynamic subsystem in rotating machinery. As the technology advances, the demands of the design of rotor-bearing systems become increasingly stringent. Excess vibrations of the rotors during operation not only degrade the performance of the machines, but also cause wear and damage of the bearing, failure of the machines, or even serious disasters. Therefore the analysis of the dynamic behavior of rotor-bearing systems is vital to the successful design of the machines. The common problems occur in industrial applications is the discrepancy between the predictive results of mathematical analysis and the actual vibration measurements of the rotating machines. The reason for this is the inaccuracy of the mathematic modeling. One way to improve these analyses is to increase the precision of the parameter values in the modeling to accurately represent the element conditions during real operations. For the modeling of rotor-bearing systems, shafts and disks can be modeled pretty accurately (Vance, 1988). However, the predictions of the bearing characteristics are not accurate enough for the rotordynamic analyses of industrial machine

A comparison of intraocular pressure measurement using SUOER SW-500 rebound tonometer and conventional reusable Goldmann prisms

IntroductionTo determine the agreement between intraocular pressure (IOP) measurements using conventional Goldmann applanation tonometry (GA1,2T) and SUOER SW-500 Rebound Tonometer.MethodsThis was a retrospective observational study where 205 eyes of 106 glaucoma patients had their IOPs measured by 2 fellowship trained ophthalmologists. Data were analyzed using the Bland–Altman method of differences. Correlation was measured using the Pearson coefficient.ResultsMost of our patients were Chinese (88.7%) and female (51.9%). The average age was 66.9 years. The range of IOPs as measured by GAT was 2 to 58 mm Hg. Using the Bland–Altman method to compare GAT and SUOER SW-500 Rebound Tonometer. The tonometer overestimated the IOP by 0.5 mm Hg in the right eye and underestimated it by 0.1 mm Hg in the left eye. Overall, the tonometer overestimated the IOP by 0.2 mmHg. The Tonometer IOP correlated well with GAT, with a Pearson coefficient of correlation(r) of 0.89 (p < 0.001) for the right eye and 0.86 (p < 0.001) for the left eye, respectively. In patients with GAT IOP ≥ 21 mm Hg (n = 25), the Tonometer underestimated the IOP by 2.96 mm Hg.DiscussionThe IOP measurements from the SUOER SW-500 Rebound Tonometer correlates well with the conventional GAT in measuring the IOP within normal ranges of IOP. SUOER SW-500 Rebound Tonometer may be of use, especially if the risk of transmission of infection is high considering that the probes are disposable. It is easy to use and its small size and portability makes it useful in situations where the patient is unable to be examined at the slit lamp

Observation of Magnetic Flux Generated Spontaneously During a Rapid Quench of Superconducting Films

We report observations of spontaneous formation of magnetic flux lines during a rapid quench of YBa$_{2}$Cu$_{3}$O$_{7-\delta}$ films through T$_{c}$. This effect is predicted according to the Kibble-Zurek mechanism of creation of topological defects of the order parameter during a symmetry-breaking phase transition. Our previous experiment, at a quench rate of 20K/sec, gave null results. In the present experiment, the quench rate was increased to \TEXTsymbol{>} 10$^{8}$ K/sec. Within experimental resolution, the dependence of the measured flux on the cooling rate is consistent with the prediction

AMP-activated protein kinase activation mediates CCL3-induced cell migration and matrix metalloproteinase-2 expression in human chondrosarcoma

Chemokine (C-C motif) ligand 3 (CCL3), also known as macrophage inflammatory protein-1α, is a cytokine involved in inflammation and activation of polymorphonuclear leukocytes. CCL3 has been detected in infiltrating cells and tumor cells. Chondrosarcoma is a highly malignant tumor that causes distant metastasis. However, the effect of CCL3 on human chondrosarcoma metastasis is still unknown. Here, we found that CCL3 increased cellular migration and expression of matrix metalloproteinase (MMP)-2 in human chondrosarcoma cells. Pre-treatment of cells with the MMP-2 inhibitor or transfection with MMP-2 specific siRNA abolished CCL3-induced cell migration. CCL3 has been reported to exert its effects through activation of its specific receptor, CC chemokine receptor 5 (CCR5). The CCR5 and AMP-activated protein kinase (AMPK) inhibitor or siRNA also attenuated CCL3-upregulated cell motility and MMP-2 expression. CCL3-induced expression of MMP-2 and migration were also inhibited by specific inhibitors, and inactive mutants of AMPK, p38 mitogen activated protein kinase (p38 or p38-MAPK), and nuclear factor κB (NF-κB) cascades. On the other hand, CCL3 treatment demonstrably activated AMPK, p38, and NF-κB signaling pathways. Furthermore, the expression levels of CCL3, CCR5, and MMP-2 were correlated in human chondrosarcoma specimens. Taken together, our results indicate that CCL3 enhances the migratory ability of human chondrosarcoma cells by increasing MMP-2 expression via the CCR5, AMPK, p38, and NF-κB pathways

Modelling radiation-induced cell cycle delays

Ionizing radiation is known to delay the cell cycle progression. In particular after particle exposure significant delays have been observed and it has been shown that the extent of delay affects the expression of damage such as chromosome aberrations. Thus, to predict how cells respond to ionizing radiation and to derive reliable estimates of radiation risks, information about radiation-induced cell cycle perturbations is required. In the present study we describe and apply a method for retrieval of information about the time-course of all cell cycle phases from experimental data on the mitotic index only. We study the progression of mammalian cells through the cell cycle after exposure. The analysis reveals a prolonged block of damaged cells in the G2 phase. Furthermore, by performing an error analysis on simulated data valuable information for the design of experimental studies has been obtained. The analysis showed that the number of cells analyzed in an experimental sample should be at least 100 to obtain a relative error less than 20%.Comment: 19 pages, 11 figures, accepted for publication in Radiation and Environmental Biophysic