D. A. Stone

Sham device v inert pill: randomised controlled trial of two placebo treatments

Abstract Objective To investigate whether a sham device (a validated sham acupuncture needle) has a greater placebo effect than an inert pill in patients with persistent arm pain. Design A single blind randomised controlled trial created from the two week placebo run-in periods for two nested trials that compared acupuncture and amitriptyline with their respective placebo controls. Comparison of participants who remained on placebo continued beyond the run-in period to the end of the study. Setting Academic medical centre. Participants 270 adults with arm pain due to repetitive use that had lasted at least three months despite treatment and who scored ≥3 on a 10 point pain scale. Interventions Acupuncture with sham device twice a week for six weeks or placebo pill once a day for eight weeks. Main outcomemeasures Arm pain measured on a 10 point pain scale. Secondary outcomes were symptoms measured by the Levine symptom severity scale, function measured by Pranskys upper extremity function scale, and grip strength. Results Pain decreased during the two week placebo run-in period in both the sham device and placebo pill groups, but changes were not different between the groups (−0.14, 95% confidence interval −0.52 to 0.25, P = 0.49). Changes in severity scores for arm symptoms and grip strength were similar between groups, but arm function improved more in the placebo pill group (2.0, 0.06 to 3.92, P = 0.04). Longitudinal regression analyses that followed participants throughout the treatment period showed significantly greater downward slopes per week on the 10 point arm pain scale in the sham device group than in the placebo pill group (−0.33 (−0.40 to −0.26) v −0.15 (−0.21 to −0.09), P = 0.0001) and on the symptom severity scale (−0.07 (−0.09 to −0.05) v −0.05 (−0.06 to −0.03), P = 0.02). Differences were not significant, however, on the function scale or for grip strength. Reported adverse effects were different in the two groups. Conclusions The sham device had greater effects than the placebo pill on self reported pain and severity of symptoms over the entire course of treatment but not during the two week placebo run in. Placebo effects seem to be malleable and depend on the behaviours embedded in medical rituals.

Nonlinear observers for predicting state-of-charge and state-of-health of lead-acid batteries for hybrid-electric vehicles

This paper describes the application of state-estimation techniques for the real-time prediction of the state-of-charge (SoC) and state-of-health (SoH) of lead-acid cells. Specifically, approaches based on the well-known Kalman Filter (KF) and Extended Kalman Filter (EKF), are presented, using a generic cell model, to provide correction for offset, drift, and long-term state divergence-an unfortunate feature of more traditional coulomb-counting techniques. The underlying dynamic behavior of each cell is modeled using two capacitors (bulk and surface) and three resistors (terminal, surface, and end), from which the SoC is determined from the voltage present on the bulk capacitor. Although the structure of the model has been previously reported for describing the characteristics of lithium-ion cells, here it is shown to also provide an alternative to commonly employed models of lead-acid cells when used in conjunction with a KF to estimate SoC and an EKF to predict state-of-health (SoH). Measurements using real-time road data are used to compare the performance of conventional integration-based methods for estimating SoC with those predicted from the presented state estimation schemes. Results show that the proposed methodologies are superior to more traditional techniques, with accuracy in determining the SoC within 2% being demonstrated. Moreover, by accounting for the nonlinearities present within the dynamic cell model, the application of an EKF is shown to provide verifiable indications of SoH of the cell pack.

Rotor loss in permanent-magnet brushless AC machines

The eddy-current loss in the permanent magnets of brushless AC machines is usually neglected, since the fundamental air-gap field usually rotates in synchronism with the rotor, and time harmonics in the current waveform and space harmonics in the winding distribution are generally small. However, an important category of brushless AC machine design is emerging in which the fundamental component of the stator MMF has fewer poles than the rotor, the torque being developed by a higher order MMF harmonic. The fundamental and lower order MMF harmonics can then give rise to significant rotor eddy currents. An analytical model is developed to predict rotor-induced eddy currents in such machines, and to quantify the effectiveness of circumferentially segmenting the permanent magnets in reducing the rotor loss.

Cyclic mechanical stretching of human tendon fibroblasts increases the production of prostaglandin E2 and levels of cyclooxygenase expression: a novel in vitro model study.

Prostaglandin E 2 (PGE 2 ) is a known inflammatory mediator of tendinitis, for which mechanical loading on tendons is believed to be one of the most prominent causation factors. Previous in vitro studies have shown that cyclic mechanical stretching of cells can cause changes in cell morphology and alteration of both DNA and protein syntheses. In our study, a novel system was used whereby tendon fibroblasts are cultured on microgrooved silicone surfaces and are subjected to cyclic uniaxial stretching along their long axes to mimic in vivo conditions. Using this unique model system, the cell shape and alignment can be controlled. Further, this study was designed to test the hypotheses that PGE 2 production increases in a stretching magnitude-dependent manner and that cyclooxygenase (COX) is responsible for the increased PGE 2 production in tendon fibroblasts. Human patellar tendon fibroblasts were cultured on the microgrooved silicone membranes and cyclically stretched at 4%, 8%, or 12% of nominal dish length for 24 hr. PGE 2 production was found to be increased 1.7-fold at 8% cyclic stretching and 2.2-fold at 12% cyclic stretching compared with nonstretched controls. In addition, human tendon fibroblasts had increased expression of both COX-1 and COX-2 for all three applied stretching magnitudes, with the exception of COX-1 at 4% cyclic stretching. Also, cellular PGE 2 production, after 8% cyclic stretching, was significantly decreased with the addition of indomethacin (25 w M), a COX competitive inhibitor, compared with stretched cells without indomethacin treatment. These findings suggest that the increase in PGE 2 production by the human tendon fibroblasts is stretching magnitude-dependent, and that the increase in COX expression contributes to the increased production of PGE 2 after cyclic stretching. As PGE 2 is a known inflammatory mediator of tendinitis, the contribution of COX-1 and COX-2 to PGE 2 production and their roles in tendon inflammation are clearly indicated.

Inflammatory response of human tendon fibroblasts to cyclic mechanical stretching.

Background The cellular and molecular mechanisms for the development of tendinopathy are not clear, but inflammatory mediators produced by tendon fibroblasts in response to repetitive mechanical loading may be an important factor. Hypotheses (1) Cyclic stretching of tendon fibroblasts affects the production of leukotriene B4 and the expression of 5-lipoxygenase; and (2) the production level of leukotriene B4 is inversely related to that of prostaglandin E2. Study Design Controlled laboratory study. Methods Human patellar tendon fibroblasts were uniaxially stretched in the presence of indomethacin (25 μM) or MK-886 (10 μM). After stretching for 4 hours, followed by 4 hours rest, levels of prostaglandin E2, leukotriene B4, and expression of 5-lipoxygenase were measured. Results Stretched tendon fibroblasts increased the levels of leukotriene B4 but did not appreciably change the expression of 5-lipoxygenase. Indomethacin decreased the cellular production of prostaglandin E2 but caused increased leukotriene B4 levels. MK-886 caused decreased production of leukotriene B4 but increased production of prostaglandin E2. Conclusions Cyclic stretching of human tendon fibroblasts increases the production of prostaglandin E2 and leukotriene B4. Blocking prostaglandin E2 production leads to increased leukotriene B4 levels and vice versa. Clinical Relevance The use of nonsteroidal anti-inflammatory drugs for the treatment of tendon inflammation might increase the levels of leukotriene B4 within the tendon, potentially contributing to the development of tendinopathy.

Rotor loss in permanent magnet brushless AC machines

The eddy current loss in the permanent magnets of brushless AC machines is usually neglected, since the fundamental airgap field rotates in synchronism with the rotor and time harmonics in the current waveform and space harmonics in the winding distribution are generally small. However, machine designs are emerging for which the fundamental component of the stator MMF has fewer poles than the rotor, the torque being developed by a higher order MMF harmonic. The fundamental and lower order MMF harmonics can then give rise to significant rotor eddy currents. An analytical model is developed to predict rotor induced eddy currents in such machines, and to quantify the effectiveness of circumferentially segmenting the permanent magnets in reducing the rotor loss.

Analysis of CLL Voltage-Output ResonantConverters Using Describing Functions

A new AC equivalent circuit for the CLL voltage-output resonant converter is presented, that offers improved accuracy compared with traditional FMA-based techniques. By employing describing function techniques, the nonlinear interaction of the parallel inductor, rectifier and load is replaced by a complex impedance, thereby facilitating the use of AC equivalent circuit analysis methodologies. Moreover, both continuous and discontinuous rectifier-current operating conditions are addressed. A generic normalized analysis of the converter is also presented. To further aid the designer, error maps are used to demonstrate the boundaries for providing accurate behavioral predictions. A comparison of theoretical results with those from simulation studies and experimental measurements from a prototype converter, are also included as a means of clarifying the benefits of the proposed techniques.

Parameter Estimation for Condition Monitoring of PMSM Stator Winding and Rotor Permanent Magnets

Winding resistance and rotor flux linkage are important to controller design and condition monitoring of a surface-mounted permanent-magnet synchronous machine (PMSM) system. In this paper, an online method for simultaneously estimating the winding resistance and rotor flux linkage of a PMSM is proposed, which is suitable for application under constant load torque. It is based on a proposed full-rank reference/variable model. Under constant load torque, a short pulse of id ≠ 0 is transiently injected into the d-axis current, and two sets of machine rotor speeds, currents, and voltages corresponding to id = 0 and id ≠ 0 are then measured for estimation. Since the torque is kept almost constant during the transient injection, owing to the moment of system inertia and negligible reluctance torque, the variation of rotor flux linkage due to injected id ≠ 0 can be taken into account by using the equation of constant torque without measuring the load torque and is then associated with the two sets of machine equations for simultaneously estimating the winding resistance and rotor flux linkage. Furthermore, the proposed method does not need the values of the dq-axis inductances, while the influence from the nonideal voltage measurement, which will cause an ill-conditioned problem in the estimation, has been taken into account and solved by error analysis. This method is finally verified on two prototype PMSMs and shows good performance.

State-of-the-art Piezoelectric Transformer technology

To date, piezoelectric transformers (PTs) have been extensively commercialised in step-up applications, such as cold cathode fluorescent lamp backlighting for LCDs. As step-down PT technology matures, PT-based converters are set to replace conventional transformers and power converters in a wide variety of applications that require relatively low power levels, low cost, high efficiency, high power density, small size and weight, low EMI, and high reliability. This paper examines the various types of piezoelectric transformer and provides an overview of the materials technology, converter designs, and control methods involved with their use.

Effect of lateral ankle ligament anesthesia on single-leg stance stability

PURPOSE This study was designed to determine, in isolation, the contribution of lateral ankle ligament mechanoreceptors to postural stability during single leg static (eyes open, eyes closed) and landing tasks. METHODS Fourteen healthy subjects (nine males, five females) underwent two different treatment conditions (control, anesthesia) in a counterbalanced order (48-h interval). During the anesthetic treatment, lidocaine was injected into the anterior talofibular and calcaneofibular ligament (1.5 cc each) regions. Postural stability was measured using forceplate and kinematic variables. The average of each variable across multiple trials under each treatment for the three tasks was analyzed statistically. RESULTS Results of all statistical analyses failed to demonstrate significant alterations (P > 0.05) in postural control attributable to the treatment condition. CONCLUSION These results suggest that lateral ankle ligament mechanoreceptors either do not make a significant contribution to single leg stance stability, do not have a unique, irreplaceable role, or have a role that is too subtle to be detected given the measurement techniques used. Thus, the idea that single leg stability becomes altered after ankle joint injury because of proprioceptive disruption was not supported. This would suggest that reported postural control alterations in persons after repetitive ankle injury more likely occur as a result of alterations in mechanical stability, motor components, and/or central motor programming.