Steep-front short-duration voltage surge tests of power linefilters and transient voltage suppressors

Steep-front short-duration voltage surge tests were conducted on commercially available power-line filters and two types of transient voltage suppressors to determine their effectiveness for protection against nuclear electromagnetic pulse (EMP) induced power-line transients. The tested power line filters were single-phase industrial-type units in the 120/208 V and 277/480 V class rated at 100 or 200 A. It was found that the tested power-line filters provide from 38 to 54 dB of attenuation for steep front surges (20 to 40 ns rise time and 150 to 400 ns fall time to half-value waves for 2 to 20 kV peak voltage), and transient voltage suppressors add an additional 2 to 8 dB of attenuation. It was also found that while the tested power line filters provide good protection against EMP induced surges, degradation of the filter characteristics may occur and delayed failures of filter components are possible. Transient voltage suppressors reduce the EMP induced surge by 40% and thus provide some protection for the filter     

Preliminary,space focused,reliability tests on European GaN HEMTs

ESA is investing significant efforts towards developing a European, space qualified, GaN supply chain for microwave components. Numerous R&D projects have been completed, or are ongoing, that focus on areas such as epitaxial growth, transistor electrical performance and reliability enhancement, e.g. in projects such as GREAT². In order to perform independent verification and validation, ESA has also begun to modernise and re-equip its microwave component laboratory to augment the well established materials and component test capabilities. This paper describes the laboratory capabilities and provides some preliminary results and lessons learned from performing high temperature storage, hydrogen poisoning and DC step stress tests on European sourced GaN samples.     

The non-linear viscoelastic behaviour of human hair at moderate extensions

We report the results of experiments carried out on the stress relaxation of slightly stretched human hair. The results show that human hair is viscoelastic, and that when quickly extended to a moderate degree (0.5-6.5%) and held, the force generated will fall to half its original value in about 15 h. However, the relaxation process is also dependent on extension, so that iso-chronous (constant time) data is non-Hookean. We show that the iso-chronous stress/strain behaviour departs from linearity at about 1% extension and the modulus progressively decreases thereafter according to a power-law relationship with strain.     

High resolution MR imaging of joint degeneration in the knee of the STR/ORT mouse

MR imaging of the knee joints of the mouse at 2.35 T produces an in-plane resolution of 35 x 70 microns and a slice thickness of 600 microns from the sagittal and coronal planes, in less than 60 min. In normal, live DBA mice, which have no known pathology, the images clearly resolve many joint structures, such as the cruciate ligaments, menisci, and articulating surfaces of the femur and tibia. Gross pathological changes were identified first in excised knees from cadaver mice of the STR/ORT strain. Males of this strain spontaneously exhibit rapid joint degeneration with increasing age compared to females, in which much milder symptoms develop more slowly. Thickening of the patellar tendon, displacement of the patella, deformity, and sclerosis were clearly distinguishable in males compared with females older than 7 mo of age. The same degenerative features were evident in MR images of the knees of the live male but not female STR/ORT mice of this age, indicating that it would be possible to monitor longitudinally by MR imaging progressive development of joint changes in this osteoarthritic model.     

The influence of grain size on the creep of uranium dioxide

The creep of uranium dioxide has been investigated as a function of grain size. At high stresses, when creep is controlled by dislocation movement, grain boundaries exert a strengthening effect and this strengthening is correlated with the Hall-Petch equation. The degree of strengthening diminishes with increases in temperature. At lower stresses, when creep is controlled by mass transport, grain boundaries exert a weakening effect owing to the reduction in diffusion path length as grain size is reduced. In this range behaviour is correlated with the Nabarro-Herring equation with stress replaced by an effective stress _E=–₀ where ₀ is a threshold stress for diffusional creep associated with the limitation of the ability of boundaries to emit and absorb vacancies. ₀ appears to decrease as grain size is increased.     

Life-Style Monitoring for Supported Independence

As the proportion of older people continues to increase there will be a greater need to provide support and care more efficiently. CAREnet proactively supports older people in their own homes by recording patterns of behaviour using distributed sensors. Telephone help messages can be sent to a carer should an unusual activity pattern be detected.     

Hydroxylamine blocks adenosine A1 receptor-mediated inhibition of synaptic transmission in rat hippocampus

BACKGROUND AND PURPOSE: Stroke-induced hemiparesis involving the arm and hand results in regular, repeated overuse of the opposite hand and wrist. Because repetitive hand and wrist movement is a common cause of carpal tunnel syndrome (CTS), we examined the nonparetic upper limb in stroke patients for evidence of CTS. METHODS: We measured bilaterally sensory nerve conduction velocity (SNCV), motor nerve conduction velocity (MNCV), sensory nerve action potentials (SNAP) at the wrist, palm-to-wrist distal sensory latency (DSL), palm-to-wrist SNAP, compound motor action potentials (CMAP), and distal motor latency (DML) in stroke patients and control subjects. Controls were right-handed, >/=65 years old, lucid, independent in their activities of daily living, and had no disease known to cause CTS. Stroke patients were divided into a functioning hand group (n=61) and a disused hand group (n=71). All patients had hemiplegia. RESULTS: Tinel's sign was observed on the nonparetic side in 57.7% of patients with a disused hand and in 31.1% of those with a functioning hand. All electrophysiological indices were significantly more abnormal on the nonparetic side than on the hemiparetic side or in controls. Patients with a disused hand showed greater abnormality on the nonparetic side in SNCV, SNAP, palm-to-wrist DSL, DML, and CMAP than patients with a functioning hand. CONCLUSIONS: Overuse of the nonparetic hand and wrist of the nonparetic side may result in CTS in stroke patients, especially when the paretic hand is not functional. Wrist splinting or other prophylactic treatments beginning soon after stroke might help to prevent CTS.     

Aberrant methylation of p16INK4a and deletion of p15INK4b are frequent events in human esophageal cancer in Linxian, China

Esophageal transit scintigraphy seems to be a valid methodology to assess impaired esophageal motility in early stages of disease. The purpose of this study was to discriminate patients with primary Raynaud's phenomenon (RP) and patients with systemic sclerosis (SSc) from healthy subjects by esophageal scintigraphy with a semisolid meal. METHODS: We studied 32 patients with primary RP, 18 with SSc and 13 healthy subjects. Dysphagia, acid regurgitation and heartburn were scored. After an overnight fast, all subjects underwent esophageal scintigraphy, using a semisolid orally ingested bolus (10 mL apple puree) labeled with 99mTc-sulfur colloid. Esophageal transit and emptying time and integral value were evaluated with the subjects in the upright (sitting) and supine positions. Transit time was defined as the time from the entry of 50% of radioactivity into the upper esophagus until the clearance of 50% of the bolus from the whole esophagus. Emptying time was defined as the time from the entry of 50% of radioactivity into the upper esophagus, until the clearance of 100% of the bolus from the whole esophagus. Integral value was defined as the total counts under the time-activity curve normalized to the maximum. RESULTS: Esophageal transit and emptying time and integral value, evaluated in both positions, were significantly higher in patients with SSc than in healthy subjects and than in patients with RP. Moreover, patients with RP had all three parameters, assessed in supine position, significantly longer compared to healthy subjects. Clinical scores regarding dysphagia, acid regurgitation and heartburn were not significantly different between patients with RP and SSc. CONCLUSION: Esophageal transit and emptying time and integral value appear to be able to discriminate patients with primary RP from patients with SSc and patients with RP from healthy subjects, suggesting an early mild esophageal dysfunction in RP.