Improving the characteristics of a transducer using multiple piezoelectric layers

A type of transducer composed of several active piezoelectric layers is described. These layers are independently stimulated electrically to achieve performance, in terms of sensitivity and bandwidth, not available in conventional, single active layer designs. A straightforward modeling technique is employed for predicting the performance of these transducers and for determining the optimal excitation characteristics. The technique is initially developed for transmission, but its extension to reception and pulse-echo conditions is discussed. A selection of experimental results demonstrates the feasibility of the technique.     

Audit of colorectal cancer surgery by non-specialist surgeons

BACKGROUND: Some authorities recommend that colorectal cancer should be treated in specialist units but evidence that non-specialist units demonstrate comparatively poor results may be lacking. METHODS: Between 1987 and 1991, 267 patients were operated on by four general surgeons, none of whom was a specialist in colorectal surgery. Procedure-related complications, postoperative mortality and disease-related survival rates were analysed. RESULTS: There were four cases of intraperitoneal sepsis (1 per cent) and five of 189 patients (3 per cent) had clinical anastomotic dehiscence; there was no case of wound dehiscence. The postoperative mortality rate after elective and emergency surgery was 2 and 13 per cent respectively. The 5-year disease-related survival rate for curative and palliative surgery was 67 and 9 per cent respectively. There were no significant differences between the surgeons. CONCLUSION: Disease-related variables such as early-stage disease and fewer patients presenting as emergencies may have a greater favourable influence on ultimate survival than surgeon-related variables.     

Single-mode operation of coplanar waveguides

A grounded coplanar waveguide structure with finite-size ground planes is analysed as three coupled microstrip lines. The three normal propagation modes of this structure are examined for various geometries, and some physical layout guidelines are established.     

Effects of subependymal and mild intraventricular lesions on visual attention and memory in premature infants.

Evaluated 10-mo-old infants to determine if subependymal or mild intraventricular hemorrhage (S/IVH) affects visual attention, visual memory, or memory for location. 30 premature infants with normal ultrasound scans, 30 premature infants with S/IVH, and 30 full-term infants were evaluated on a habituation/novelty preference task, the AB? object permanence task, and the Bayley Scales of Infant Development. Premature infants with S/IVH took longer to habituate than premature infants without S/IVH or full-term infants. Although the Bayley Mental Scales were significantly higher for both full-term and premature infants without S/IVH than those with S/IVH, number of trials to habituation better distinguished infants with S/IVH from those with no hemorrhage. (PsycINFO Database Record (c) 2010 APA, all rights reserved)