On the Feasibility of Monitoring Power Transformer's Winding Vibration and Temperature along with Moisture in Oil Using Optical Sensors.

Despite major progress in the design of power transformers, the Achilles' heel remains the insulation system, which is affected by various parameters including moisture, heat, and vibrations. These important machines require extreme reliability to guarantee electricity distribution to end users. In this contribution, a fiber optic sensor (FOS), consisting of a Fabry-Perot cavity made up of two identical fiber Bragg gratings (FBGs), is proposed, to monitor the temperature and vibration of power transformer windings. A phase shifted gratings recoated sensor, with multilayers of polyimide films, is used to monitor the moisture content in oil. The feasibility is investigated using an experimental laboratory transformer model, especially fabricated for this application. The moisture contents are well correlated with those measured by a Karl Fisher titrator, while the values of temperature compare well with those recorded from thermocouples. It is also shown that the sensors can be used to concurrently detect vibration, as assessed by sensitivity to the loading current. The possibility of dynamically measuring humidity, vibrations, and temperatures right next to the winding, appears to be a new insight that was previously unavailable. This approach, with its triple ability, can help to reduce the required number of sensors and therefore simplify the wiring layout.

Microwave photonic filter-based interrogation system for multiple fiber Bragg grating sensors.

Fiber optic sensors based on fiber Bragg gratings (FBGs) find potential use in condition monitoring because their spectral properties change according to external environmental and/or physical factors. We propose and demonstrate a technique for interrogating multiple FBG-based sensors based on microwave photonic (MWP) filtering. In particular, we exploit the spectrum-slicing properties of two different FBG Fabry-Perot cavities to implement a double passband MWP filter. Each sensor spectrum results in a unique MWP filter passband. As temperature is applied to a sensor, the corresponding MWP filter passband will shift in frequency; we track such shifts by monitoring the detected power at a fixed radio frequency. We discuss the use of a ratiometric approach for enhancing the sensitivity and the impact of cross-talk from the MWP filter responses in terms of simultaneous multi-sensor operation. Results show that we can monitor local temperatures at two (or multiple) different locations simultaneously and independently using a single measurement system.

Musical instrument recordings made with a fiber Fabry-Perot cavity: photonic guitar pickup.

A 1 cm long, low-finesse fiber-optic cavity was used as a transducer for the vibrations of the soundboard of an acoustic guitar and of a violin. The reflected light is detected and then amplified and recorded using conventional audio instrumentation. The fiber-optic pickup is found to have a high response range in both amplitude (up to 100 microm displacement) and audio frequency (DC to 20 kHz) and good linearity up to a displacement of 225 microm. The audio noise is found to arise from the fiber-optic cables and, to a lesser extent, from the laser and laser driver.

Oral intake of rosiglitazone promotes a central antihypertensive effect via upregulation of peroxisome proliferator-activated receptor-gamma and alleviation of oxidative stress in rostral ventrolateral medulla of spontaneously hypertensive rats.

Rosiglitazone, a synthetic ligand of transcription factor peroxisome proliferator-activated receptor-gamma (PPAR-gamma), possesses a blood pressure-lowering effect beyond insulin sensitizing and glucose lowering. Oxidative stress in rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons for the maintenance of neurogenic vasomotor tone are located, contributes to neural mechanisms of hypertension. Activation of PPAR-gamma protects against oxidative stress in RVLM by upregulation of mitochondrial uncoupling protein 2 (UCP2). We tested the hypothesis that oral intake of rosiglitazone exerts a central antihypertensive effect by ameliorating oxidative stress in RVLM via transcriptional upregulation of UCP2 after PPAR-gamma activation. In adult spontaneously hypertensive rats but not normotensive Wistar-Kyoto rats, oral intake of rosiglitazone for 1 week resulted in vasodepression and a reduction in the vasomotor components of the systemic arterial pressure spectrum, our experimental index for sympathetic vasomotor tone. These antihypertensive effects of rosiglitazone in spontaneously hypertensive rats were abrogated by microinjection bilaterally into RVLM of PPAR-gamma small interfering RNA. Oral intake of rosiglitazone also upregulated UCP2 and ameliorated the heightened superoxide anion level in RVLM of spontaneously hypertensive rats. Protection against oxidative stress in RVLM by rosiglitazone was abrogated by PPAR-gamma small interfering RNA or by antisense oligonucleotide against ucp2 mRNA. Gene knockdown of ucp2 in RVLM also reversed the antihypertensive effect of rosiglitazone. These results suggest that oral intake of rosiglitazone promotes a central antihypertensive effect by decreasing sympathetic vasomotor activity through a PPAR-gamma-dependent protection against oxidative stress in RVLM via transcriptional upregulation of the mitochondrial UCP2.

Distal clavicle fracture as a complication of arthroscopic distal clavicle resection.

Arthroscopic resection of the distal clavicle has been advocated as a surgical treatment option for acromioclavicular (AC) joint pathology. To our knowledge, iatrogenic fracture of the distal clavicle during distal clavicle resection has never been reported. This report describes distal clavicle fracture as a complication of misidentification of the AC joint and subsequent aggressive burring of the distal clavicle during shoulder arthroscopy. This case is further complicated by the development of symptomatic delayed union and adhesive capsulitis. Ultimately, a revision distal clavicle resection was performed, underscoring the fact that special care must be taken to properly identify the AC joint and rule out pre-existing distal clavicle stress fracture or osteolysis before performing the arthroscopic Mumford procedure.

Shoulder biomechanics.

The biomechanics of the glenohumeral joint depend on the interaction of both static and dynamic-stabilizing structures. Static stabilizers include the bony anatomy, negative intra-articular pressure, the glenoid labrum, and the glenohumeral ligaments along with the joint capsule. The dynamic-stabilizing structures include the rotator cuff muscles and the other muscular structures surrounding the shoulder joint. The combined effect of these stabilizers is to support the multiple degrees of motion within the glenohumeral joint. The goal of this article is to review how these structures interact to provide optimal stability and how failure of some of these mechanisms can lead to shoulder joint pathology.

Effect of femoral head size and abductors on dislocation after revision THA.

Dislocation is a common complication after revision total hip arthroplasty, particularly if the abductor mechanism is deficient. Use of a large femoral head may reduce the incidence of dislocation. However, it is not clear if the large femoral head is effective in controlling dislocation when the abductor mechanism is deficient. We separated 230 patients who underwent revision total hip arthroplasty into four groups: Group 1 (159 patients) had an intact abductor mechanism and a 28-mm femoral head, Group 2 (20 patients) had an absent abductor mechanism (trochanteric nonunion or complete segmental proximal femoral bone loss) and a 28-mm femoral head, Group 3 (42 patients) had an intact abductor mechanism and a 36-mm femoral head, and Group 4 (nine patients) had an absent abductor mechanism and a 36-mm femoral head. The minimum followup was 6 months (mean, 27 months; range, 6 months to 7 years). A 36-mm head was associated with a lower dislocation rate after revision total hip arthroplasty than a 28-mm head with an intact abductor mechanism; the rate of dislocation was 12.7% for Group 1, 40.0% for Group 2, 0% for Group 3, and 33.3% for Group 4. However, the use of a large-diameter head does not reduce the rate of dislocation if the abductor mechanism is absent.