Model for Wireless Magnetoelastic Strain Sensors.

This paper describes a magnetoelastic strain sensor based on the ∆E effect and discusses some materials used in its construction. A polycrystalline Fe-Al-B alloy with good quality magnetoelastic properties was used as the transducer and glued to the test object, either brass plates or rods of SAE 1010 steel. The strain-dependent magnetic field of the transducer changes the operating point of the resonator, a strip of field-annealed Metglas 2826MB3, resulting in a modification of its resonant frequency. A model was developed to simulate the strain-dependent magnetic field acting on the resonator and thus to calculate curves of resonant frequency vs. deformation. With the help of this model, differences in the shape of the frequency vs. strain curve can be understood. For a sensor with resonant frequency of 60.5 kHz glued to a rod of SAE 1010 steel, a total resonant frequency variation ∆f ~7 kHz was observed for a deformation of 1100 ppm. The geometry of this sensor is especially favorable for the remote monitoring of a steel surface, such as the wires of the tensile armor of a marine riser.

Flow analysis of left internal thoracic artery in myocardial revascularization surgery using y graft.

In order to evaluate the left internal thoracic artery flow pattern, when the vessel is used as a graft to supply the left coronary artery system, we evaluated flow by Doppler measurement, both at rest and under dobutamine stress. There were 2 groups of 20 patients each: group A patients received only a left internal thoracic artery graft to the left anterior descending artery, and group B patients received a pedicled left internal thoracic artery graft associated with a vein graft, which together supplied the left anterior descending artery and another branch of the left coronary artery. Angiography showed patent grafts in all patients from both groups. The following characteristics were evaluated: systolic flow, diastolic flow, total flow, total flow under stress/total flow at rest ratio, systolic peak velocity, diastolic peak velocity, and systolic peak velocity/diastolic peak velocity ratio. In group A, the total flow was 45.5 +/- 21.6 mL/min at rest and 68.3 +/- 32.9 mL/min under stress. In group B, the total flow was 98.2 +/- 50.4 mL/min at rest and 175.7 +/- 79.2 mL/min under stress. Comparison between groups showed a total flow increase in group B of 115.8% (P=0.0002) at rest and 157.2% (P <0.0001) under stress. The other characteristics were also statistically significant, except systolic flow, total flow under stress/total flow at rest ratio, and systolic peak velocity. Our results showed that the left internal thoracic artery sufficiently supplies regional myocardium at rest and during exercise (stress), demonstrating its great adaptability in response to demand.

Molecular evaluation of the great vessels of patients with bicuspid aortic valve disease

OBJETIVO: A valva aórtica bicúspide (VAB) está associada a maior prevalência de ectasia anulo-aórtica, aneurisma e dissecçäo da aorta ascendente. Este estudo investigou a quantidade de fibrilina-1 e elastina nos grandes vasos de portadores de VAB. MÉTODO:Amostras de tecidos foram colhidas da aorta ascendente e tronco da artéria pulmonar de 22 portadores de VAB e 16 portadores de valva aórtica tricúspide (VAT) submetidos a cirurgia cardíaca, incluindo seis portadores de valva aórtica normal, provenientes do programa de transplante. Imunofluorescência indireta e análise computadorizada de imagens foram utilizadas para quantificaçäo das proteínas na camada média dos vasos, expressas como densidade óptica integrada média (DOI). RESULTADOS: Na aorta, a DOI específica para fibrilina-1 foi 15 ± 8 no grupo bicúspide e 24 ± 7 no grupo tricúspide (p=0,001). Na artéria pulmonar, a DOI específica para fibrilina-1 foi 18 ± 10 no grupo bicúspide e 25 ± 9 no grupo tricúspide (p=0,07). A DOI específica para elastina na aorta foi 34 ± 13 no grupo bicúspide e 36 ± 19 no grupo tricúspide (p=0,31). Na artéria pulmonar, a DOI para elastina foi 30 ± 12 no grupo bicúspide e 29 ± 14 no grupo tricúspide (p=0,34). CONCLUSÕES: Os portadores de VAB apresentaram menor quantidade de fibrilina-1, mas näo elastina, na aorta ascendente e artéria pulmonar que os portadores de VAT normal ou doente. Estes achados podem explicar a maior incidência de dilataçäo e dissecçäo da aorta ascendente em portadores desta má-formaçäo da valva aórtica.