RESUMEN
A 3D printing system able to print circuits of conductive epoxy resin doped with carbon nanotubes (CNTs) is proposed. Different simple circuits, more specifically lines and strain gauge patterns, made of resins reinforced with 0.3, 0.5, 0.8 and 1 wt% of CNTs were printed on the surface of glass fiber laminates. It was observed that increasing the CNT content reduced the wettability of the printed circuits on the glass fiber substrate. In every case the contact angle was far below 90°. Furthermore, the strain sensing capabilities were analyzed under a flexural load. The results showed that the sensitivity increased with CNT content (with gauge factor values from 1.5 to 2.5) as a result of the prevalent effect of well-dispersed areas due to a reduction in the tunneling distance. On the other hand, the strain gauges showed a lower sensitivity (around 20%-40% less, depending on the condition) compared with line circuits due to localized compressive effects. Furthermore, good repeatability of the strain sensors was proved during cycling tests, with similar baseline and peak values for the electrical resistance in each cycle. Therefore, the proposed materials have a high potential for applications in structural health monitoring.
RESUMEN
This research studied the influence of the chloride ion concentration on the corrosion behaviour of high-purity magnesium (Mg) and two Mg alloys in Hank's solution, using hydrogen evolution and weight loss. A buffer based on CO2 and NaHCO3 was used to maintain the pH constant. The corrosion behaviour was governed by a partially protective surface film, and film breakdown by the chloride ions. The carbonated calcium phosphate layer that formed in Hank's solution was important in determining the protective properties of the surface film.
Asunto(s)
Aleaciones , Cloruros/análisis , Corrosión , Concentración de Iones de Hidrógeno , SolucionesRESUMEN
Embolic events, particularly involving the central nervous system, represent one of the important hazards associated with the implantation of mechanical valves. The use of the transcranial Doppler to insonate the middle cerebral artery has allowed us to detect microembolic events in some of these patients. Patients with long term implantation and frequent microemboli appear to be more prone to transient ischemic attacks or stroke. Evaluation of 26 patients with mechanical valves revealed 14 with detectable microemboli, four of whom experienced central nervous system symptoms. Modifications in the medical or anticoagulant regimes have not been successful in decreasing or eliminating these microemboli. As the transcranial Doppler is a non-invasive means of quantifying these microemboli, it may become a useful tool in identifying those patients in need of a new type of antithrombotic regimen, or even a valve replacement. Transcranial Doppler could thus provide advance warning before a catastrophic cerebral embolism occurs.
Asunto(s)
Prótesis Valvulares Cardíacas/efectos adversos , Embolia y Trombosis Intracraneal/diagnóstico por imagen , Embolia y Trombosis Intracraneal/etiología , Válvula Aórtica , Trastornos Cerebrovasculares/diagnóstico por imagen , Trastornos Cerebrovasculares/etiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Diseño de Prótesis , Ultrasonografía Doppler TranscranealAsunto(s)
Infarto Cerebral/diagnóstico por imagen , Embolia/diagnóstico por imagen , Cardiopatías/diagnóstico por imagen , Infarto Cerebral/etiología , Embolia/complicaciones , Femenino , Cardiopatías/complicaciones , Prótesis Valvulares Cardíacas , Humanos , Válvula Mitral , Embarazo , Complicaciones Hematológicas del Embarazo , UltrasonografíaAsunto(s)
Insuficiencia de la Válvula Aórtica/cirugía , Espondilitis Anquilosante/complicaciones , Adulto , Insuficiencia de la Válvula Aórtica/etiología , Insuficiencia de la Válvula Aórtica/fisiopatología , Calcinosis/complicaciones , Humanos , Pulmón/fisiopatología , Masculino , Persona de Mediana Edad , Cuidados Posoperatorios , Cuidados PreoperatoriosAsunto(s)
Enfermedades Pulmonares/cirugía , Pulmón/fisiopatología , Insuficiencia Respiratoria/etiología , Cirugía Torácica , Tórax/cirugía , Adulto , Humanos , Neoplasias Pulmonares/cirugía , Persona de Mediana Edad , Neumonectomía , Neumonía/cirugía , Cuidados Posoperatorios , Complicaciones Posoperatorias , Enfisema Pulmonar/cirugía , Insuficiencia Respiratoria/fisiopatología , Espirometría , Estadística como AsuntoAsunto(s)
Determinación de la Presión Sanguínea/instrumentación , Cateterismo , Adolescente , Adulto , Anciano , Niño , Preescolar , Humanos , Persona de Mediana Edad , Venas , Vena Cava SuperiorAsunto(s)
Pulmón/inervación , Degeneración Nerviosa , Sistema Nervioso Parasimpático/fisiología , Reimplantación , Sistema Nervioso Simpático/fisiología , Nervio Vago/fisiología , Animales , Gatos , Perros , Pulmón/patología , Vaina de Mielina/anatomía & histología , Neuronas/citología , Células Receptoras Sensoriales/fisiología , Simpatectomía , VagotomíaAsunto(s)
Embolia Pulmonar/cirugía , Adulto , Angiografía , Cateterismo Cardíaco , Pruebas Enzimáticas Clínicas , Heparina/uso terapéutico , Humanos , Pulmón/diagnóstico por imagen , Masculino , Arteria Pulmonar/cirugía , Embolia Pulmonar/complicaciones , Embolia Pulmonar/diagnóstico , Cintigrafía , Choque/etiologíaAsunto(s)
Embolia Pulmonar/cirugía , Adulto , Angiocardiografía , Angiografía , Máquina Corazón-Pulmón , Humanos , Cuidados PosoperatoriosRESUMEN
The effect of deferring immediate coronary artery bypass was evaluated in two groups of similar patients having successful direct coronary artery thrombolysis with streptokinase in the treatment of evolving myocardial infarction. Within 6 hours of onset of myocardial infarction, 140 patients underwent immediate cardiac catheterization and infusion of intracoronary streptokinase up to 500,000 units. Of those patients having restoration of orthograde coronary blood flow coupled with immediate evidence of myocardial salvage, 31 patients (group I) had immediate coronary artery bypass and 34 patients (group II) had coronary artery bypass deferred. Group I had no hemorrhagic, hemodynamic, or new cardiac complications. There were no deaths, reinfarction, recurrence of angina, or loss of salvaged myocardium at restudy. In group II, 11 of 34 patients had early reinfarction (p less than 0.01 vs. group I), 16 of 34 patients had recurrent angina (p less than 0.01 vs. group I) and two deaths occurred from cardiac causes. Subsequent coronary bypass was needed in 16 patients. All restudied reinfarction patients lost restored myocardium. We concluded that immediate coronary artery bypass is safe after acute myocardial infarction and coronary artery thrombolysis with streptokinase, delay of coronary artery bypass leads to an unacceptable incidence of reinfarction and recurrent severe angina, and early coronary artery bypass is needed to ensure success of thrombolysis.