For high-impact devices, subsequent vibrations have as much influence on the deterioration of the mechanical structure as the impact itself. To mitigate the consequences of both impacts and resulting ...vibrations, it is crucial to accurately understand the peak acceleration and vibration frequencies that originate in the structure. In this article, a radiation tolerant opto-mechanical sensor based on an absolute measurement inertial accelerometer is presented. This method of measurement is chosen due to the viability of placing the readout electronics far from the highly radioactive environment that the sensor may be installed in. The designed accelerometer consists of a fixed aluminum frame with a built-in membrane that acts as a leaf spring. In the same membrane, a retro-reflector is attached which acts as a seismic mass. The retro-reflector reflects the light beam coming from the collimator lens placed on the frame. To prove its viability, the device has been tested under different conditions. First, the device is calibrated and validated using a high-frequency exciter. Second, a high-acceleration testbench is used to compare its output signal with a commercial accelerometer and verify its proper operation as well as its expected lifetime. The experimental results showed an average sensitivity of <inline-formula> <tex-math notation="LaTeX">{9} \times {10}^{-{4}} </tex-math></inline-formula> g/pm with reading measurements of up to 5000 g and a working bandwidth located between 50 and 800 Hz.
Piezoelectric actuators are candidates for use in radioactive environments but specific radiation tests are necessary to understand the radiation effects on the whole actuator assembly. The results ...of three irradiation tests on a piezoelectric actuator used for Crystal Collimation are presented. The total ionising dose effects are studied with two Gamma ( 60 Co) Tests up to 10 MGy and 1 MGy, whereas the displacement damage effects are studied in a Proton Test up to 2 MGy and 1.14 × 10 16 p/cm 2 fluence. The main results are summarised for each test, presenting a maximum impedance increase of less than 25% (Proton Test), a maximum free stroke reduction of less than 25% (Proton Test) and a variation in the shape of the hysteresis response of the actuator.
Stepper motors are widely used in high precision positioning applications where reliability is an important factor. Field Oriented Control (FOC) can be used to damp the high-oscillatory dynamics of ...open-loop driven stepper motors and effectively reduce induced vibrations during motion. However, when it is required to hold a constant position, the induced vibrations can be higher in FOC than in open-loop control. To solve this, different techniques are proposed in this paper: i) a bump-less switch from FOC to open-loop control, ii) reducing the current reference to zero and iii) reducing the applied voltage to zero. Unlike other studies in vibration reduction techniques based on motion regimes and online feedback, the techniques presented here successfully reduce the vibrations in standstill and without the use of additional sensors. These methods are applied to a crystal collimator at CERN with good results and their performance is compared.
El carvedilol es un antagonista adrenergico con accion antioxidante y un demostrado beneficio sobre la mortalidad en insuficiencia cardiaca. El objetivo de este estudio es evaluar, en pacientes con ...insuficiencia cardiaca, diversos parametros clinicos y de la funcion ventricular izquierda, asi como el grado de estres oxidativo y el estado neurohormonal, antes y despues de 6 meses de tratamiento con carvedilol.
Se incluyo a 30 pacientes con insuficiencia cardiaca cronica estable sin tratamiento con bloqueadores beta, con capacidad funcional II-III y fraccion de eyeccion ventricular izquierda (FEVI) < 40%. Se midio el indice de Mahler, la distancia recorrida en 6 min, el consumo de oxigeno peak, la FEVI y las concentraciones circulantes de noradrenalina y estres oxidativo basales y tras 6 meses de tratamiento con carvedilol.
La edad promedio fue de 59 ± 2 anos y 23 eran varones. Se observo una mejoria clinica segun el indice de Mahler (basal de 6,8 frente a 11,0 puntos; p = 0,001) y un aumento en la distancia recorrida en 6 min (499 ± 18 a 534 ± 17 m; p = 0,032), sin cambios en el consumo de oxigeno pico. La FEVI aumento del 24 ± 1 al 31 ± 2% (p = 0,003). El malondialdehido plasmatico disminuyo a los 6 meses (2,4 ± 0,2 a 1,1 ± 0,ୖmol/l; < 0,001). No se observaron cambios significativos en los valores plasmaticos de catecolaminas ni en las actividades enzimaticas antioxidantes.
El tratamiento con carvedilol durante 6 meses en pacientes con insuficiencia cardiaca cronica se asocio a una mejoria clinica, un aumento de la funcion ventricular izquierda y una disminucion del malondialdehido plasmatico, sin cambios en los valores de catecolaminas circulantes.
Carvedilol is an antioxidant and adrenergic antagonist with demonstrated benefits in terms of mortality from heart failure (HF). The aim of the present study was to evaluate clinical parameters, left ventricular function, oxidative stress levels and neurohumoral status at baseline and after 6 months of treatment with carvedilol in patients with chronic HF.
Thirty patients with chronic HF that was stable without beta blocker treatment were included. Functional class was II or III, and left ventricular ejection fraction (LVEF) was < 40%. Mahler score, distance walked in 6 min, peak oxygen consumption, LVEF, plasma catecholamine (norepinephrine) concentration and oxidative stress parameters were evaluated at baseline and after 6 months of treatment with carvedilol.
Mean age was 59 (2) years, and 23 patients were men. After 6 months of treatment there were clinical improvements as measured by the Mahler score (from 6.8 to 11.0 points; P=.001) and the 6-min walk distance (from 499 18 to 534 17 m; P =.032), but no changes in peak oxygen consumption. The LVEF increased from 24 (1) to 31 (2)% (P=.003). In patients with chronic HF, plasma malondialdehyde concentration was significantly lower after 6 months (decrease from 2.4 0.2 to 1.1 0.2 ìmol/l; P <.001). No significant changes were observed in plasma catecholamine levels or antioxidant enzyme activities.
In patients with chronic HF, carvedilol treatment for 6 months was associated with clinical improvements, increased left ventricular function and decreased plasma concentrations of malondialdehyde, with no changes in plasma catecholamine levels.
La angioplastia primaria ha resultado ser el tratamiento más eficaz para pacientes con infarto agudo de miocardio (IAM). Tanto la obtención de un flujo coronario óptimo, grado TIMI 3, como la ...asociación de indicadores no invasivos de reperfusión coronaria han demostrado ser métodos útiles para predecir el pronóstico inmediato y a medio plazo de pacientes con IAM tratados con trombólisis o angioplastia primaria. El objetivo es comparar el valor pronóstico del flujo TIMI 3 con la asociación de indicadores no invasivos de reperfusión coronaria (disminución del supradesnivel del segmento ST > 50% a los 90 min, inversión de la onda T dentro de las 24 h y elevación máxima de la creatincinasa CK < 12 h postangioplastia primaria) en la evolución intrahospitalaria y a medio plazo en pacientes con un infarto de miocardio reciente tratados con angioplastia primaria.
Se analizó a 172 pacientes consecutivos con IAM y supradesnivel del ST tratados con angioplastia primaria durante las primeras 12 h de evolución e ingresados en el Hospital de la Universidad Católica entre enero de 1997 y diciembre de 2002. La edad promedio fue 61 ± 13 años, el 77% eran hombres y el 56% presentó un IAM anterior.
La mortalidad intrahospitalaria de esta serie fue de 3,6%; el 16,6% desarrolló insuficiencia cardíaca y el 11,1% de la población analizada presentó arritmias complejas durante la hospitalización.
Se consideró como criterio de reperfusión exitosa la presencia de 2 o más indicadores de reperfusión y para los criterios angiográficos de recanalización se utilizó la clasificación de TIMI. En el 87,7% se obtuvo una reperfusión exitosa y en el 87% se obtuvo un flujo TIMI 3. No hubo concordancia significativa entre ambos métodos (índice kappa = 0,012). El análisis multivariado (ajustado por edad, sexo, factores de riesgo, localización y tiempo de evolución del infarto, frecuencia cardíaca y presión arterial de ingreso, CK al ingreso, número de vasos con estenosis > 70%, valor máximo de CK) demostró que tanto la reperfusión exitosa como el flujo TIMI 3 resultaron ser protectores frente a la mortalidad intrahospitalaria (odds ratio OR = 0,028; intervalo de confianza IC del 95%, 0,003–0,268, y OR = 0,104; IC del 95%, 0,019–0,563, respectivamente). Sin embargo, sólo la reperfusión exitosa resultó ser protectora frente a la insuficiencia cardíaca y las arritmias complejas en la evolución intrahospitalaria y en la mortalidad a medio plazo al ajustar por ambos criterios en el análisis multivariado.
Se confirma que tanto el flujo TIMI 3 como la reperfusión coronaria exitosa evaluada a través de indicadores no invasivos tienen un valor pronóstico independiente en pacientes con IAM tratados con angioplastia primaria. Sin embargo, la reperfusión coronaria exitosa resultó ser un indicador de pronóstico independiente para la mortalidad intrahospitalaria y a medio plazo, el desarrollo de insuficiencia cardíaca y arritmias complejas. Los indicadores no invasivos de reperfusión coronaria debieran emplearse en forma complementaria a la angiografía en estos pacientes.
The aim of this study was to compare the prognostic value of TIMI 3 flow versus noninvasive markers of coronary artery reperfusion on the outcome of patients with a recent acute myocardial infarction (AMI) treated with primary angioplasty.
We analyzed 172 consecutive patients with AMI and ST-segment elevation, who were treated with primary angioplasty within 12 hours of admission. Mean age was 61±13 years, 77% were men, and 56% had a history of previous AMI.
In-hospital mortality was 3.6%; 16.6% developed heart failure, and 11.1% had complex arrhythmias during their hospital stay. The noninvasive criterion for successful reperfusion was the presence of two or moremarkers of reperfusion based on ECG changes or CK levels after angioplasty. Reperfusion was successful in 87.7% of the patients, and TIMI 3 flow was achieved in 87%. There was no significant concordance between the two methods (kappa index = 0.012). Multivariate analysis showed that both successful reperfusion (OR=0.028; 95% CI, 0.003–0.268) and TIMI 3 flow (OR=0.104; 95% CI, 0.019–0.563) were protective for in-hospital mortality. However, in the multivariate analysis only successful reperfusion was a protective factor for heart failure and complex arrhythmias.
Our findings confirm that both TIMI 3 flow and successful coronary reperfusion evaluated noninvasively show independent prognostic value in patients with AMI treated with primary angioplasty. Noninvasive markers of coronary reperfusion should be used as complementary to angiography in these patients.
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