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  • 1
    Publication Date: 2021-05-19
    Description: Se utiliza la información de perfiles de playa en cuatro localidades de las Playas del Este obtenidos en los últimos 27 años, para describir la tendencia de la playa a mediano plazo. A partir de datos de posición de la línea de costa y de volúmenes de arena de la playa emergida se estableció la tasa de cambio de la playa utilizando la regresión lineal simple. Los resultados confirman la tendencia erosiva de un sector de la playa de Guanabo. La tasa anual de retroceso de la línea de costa ha sido de -0.97 m/año que ha establecido un cambio total de - 26 ±7 m. La reducción de los volúmenes de arena ha sido de -28 ± 8 m3/m, a un ritmo de -1.04 m3/m/año. En la playa de Santa María, la línea de costa en algunas localidades ha experimentado retroceso y en otras ha ocurrido poco cambio, sin embargo en todos los casos se ha producido un incremento notable en los volúmenes de arena de la playa emergida debido a la formación y crecimiento de las dunas. La reactivación de los procesos eólicos que dio lugar al restablecimiento de la morfología de dunas fue posible por la eliminación del bosque de casuarinas que, durante más de 20 años, ocupó la zona posterior de la playa.
    Description: The information of beach profiles, obtained during the last 27 years in four localities of Playas del Este, is used to describe the medium-term tendency of the beach. Starting from data of the shoreline location and sand volumes of the emerged beach, the beach change rate was established applying simple linear regression. The results confirm the erosive tendency of a sector in Guanabo beach. The annual rate of shoreline retreat has been -0, 97 m/y, which has established a total change of - 26 ± 7 m. The reduction in sand volumes has been -28 ± 8 m3/m, at a rate of -1,04 m3/m/y. In Santa Maria beach, the shoreline has experienced retreat in some localities or little change in the others. However, a remarkable increase in sand volumes of the emerged beach has taken place in all the cases. The reactivation of Aeolian processes, resulting in the reestablishment of dune morphology, was possible due to the removal of the Australian pine forest that had occupied the area from the beach top landward for more than 20 years.
    Description: Published
    Description: playas, evolución a mediano plazo, regresión lineal, beach, medium- term evolution, lineal regression.
    Keywords: Dunes ; Beach morphology ; Beach erosion ; Dunes
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 2
    Publication Date: 2021-05-19
    Description: The results of the application of the formula of Kawamura (1951) to in situ meteorological data in order to forecast the sand transport rate due to wind action are described in this paper. A new episode of dune formation started in the 1980's in these beaches, and more recently they have been affected by aeolian erosion since the beginning of the destruction of foredune vegetation due to the increase in tourist activities in the area. Shear velocity (U*t) values on the surface were determined starting from wind speed vertical profiles. Critical shear velocity values to start the sand movement were also determined, taking into account the grain size variations of the beach material along the coast. And finally, transport rates are calculated in each case. A comparison is carried out between the transport rates estimated starting from wind data and those resulting from meaurements of the sand volumes accumulated in the dunes during 12 years of monitoring. The main transport directions are shown, as well as the direction of the resultant and their relation to the morphological and dynamic pattern of the dunes. Besides, it is concluded that aeolian transport is limited to those sites where grain size is higher than 0.5 mm.
    Description: Published
    Description: coastal dunes, foredunes, deflation, eolian erosion.
    Keywords: Dunes ; Dunes ; Beach morphology ; Sand structures ; Eolian transport
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 3
    Publication Date: 2011-08-24
    Description: BACKGROUND: The effective orifice area (EOA) of a prosthetic valve is superior to transvalvular gradients as a measure of valve function, but measurement of mitral prosthesis EOA has not been reliable. METHODS AND RESULTS: In vitro flow across St Jude valves was calculated by hemispheric proximal isovelocity surface area (PISA) and segment-of-spheroid (SOS) methods. For steady and pulsatile conditions, PISA and SOS flows correlated with true flow, but SOS and not PISA underestimated flow. These principles were then used intraoperatively to calculate cardiac output and EOA of newly implanted St Jude mitral valves in 36 patients. Cardiac output by PISA agreed closely with thermodilution (r=0.91, Delta=-0.05+/-0.55 L/min), but SOS underestimated it (r=0.82, Delta=-1.33+/-0.73 L/min). Doppler EOAs correlated with Gorlin equation estimates (r=0.75 for PISA and r=0.68 for SOS, P〈0.001) but were smaller than corresponding in vitro EOA estimates. CONCLUSIONS: Proximal flow convergence methods can calculate forward flow and estimate EOA of St Jude mitral valves, which may improve noninvasive assessment of prosthetic mitral valve obstruction.
    Keywords: Life Sciences (General)
    Type: Circulation (ISSN 0009-7322); Volume 98; 12; 1205-11
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  • 4
    Publication Date: 2011-08-24
    Description: This study evaluates a new device that uses color Doppler ultrasonography to enable real-time image guidance of the aspirating needle, which has not been possible until now. The ColorMark device (EchoCath Inc, Princeton, NJ) induces high-frequency, low-amplitude vibrations in the needle to enable localization with color Doppler. We studied this technique in 25 consecutive patients undergoing pericardiocentesis, and in vitro, in a urethane phantom with which the accuracy of color Doppler localization of the needle tip was compared with that obtained by direct measurement. Tip localization was excellent in vitro; errors axial to the ultrasound beam (velocity Doppler -0.13 +/- 0.90 mm, power Doppler -0.05 +/- 1.7 mm) were less than lateral errors (velocity -0.36 +/- 1.8 mm, power -0.02 +/- 2.8 mm). In 18 of 25 patients, the needle was identified and guided into the pericardial space with the ColorMark technique, and it allowed successful, uncomplicated drainage of fluid. Initial failures were the result of incorrect settings on the echocardiographic machine and inappropriate combinations of the needle puncture site and imaging window. This study demonstrates a novel color Doppler technique that is highly accurate at localizing a needle tip. The technique is feasible for guiding pericardiocentesis. Further clinical validation of this technique is required.
    Keywords: Life Sciences (General)
    Type: Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography (ISSN 0894-7317); Volume 14; 1; 29-37
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  • 5
    Publication Date: 2019-07-13
    Description: BACKGROUND: Myocardial fiber strain is directly related to left ventricular (LV) contractility. Strain rate can be estimated as the spatial derivative of velocities (dV/ds) obtained by tissue Doppler echocardiography (TDE). The purposes of the study were (1) to determine whether TDE-derived strain rate may be used as a noninvasive, quantitative index of contractility and (2) to compare the relative accuracy of systolic strain rate against TDE velocities alone. METHODS AND RESULTS: TDE color M-mode images of the interventricular septum were recorded from the apical 4-chamber view in 7 closed-chest anesthetized mongrel dogs during 5 different inotropic stages. Simultaneous LV volume and pressure were obtained with a combined conductance-high-fidelity pressure catheter. Peak elastance (Emax) was determined as the slope of end-systolic pressure-volume relationships during caval occlusion and was used as the gold standard of LV contractility. Peak systolic TDE myocardial velocities (Sm) and peak (epsilon'(p)) and mean (epsilon'(m)) strain rates obtained at the basal septum were compared against Emax by linear regression. Emax as well as TDE systolic indices increased during inotropic stimulation with dobutamine and decreased with the infusion of esmolol. A stronger association was found between Emax and epsilon'(p) (r=0.94, P〈0.01, y=0.29x+0.46) and epsilon'(m) (r=0.88, P〈0.01) than for Sm (r=0.75, P〈0.01). CONCLUSIONS: TDE-derived epsilon'(p) and epsilon'(m) are strong noninvasive indices of LV contractility. These indices appear to be more reliable than S(m), perhaps by eliminating translational artifact.
    Keywords: Life Sciences (General)
    Type: Circulation (ISSN 0009-7322); 105; 1; 99-105
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  • 6
    Publication Date: 2019-07-13
    Description: The objective of this study was to determine the utility of Doppler tissue echocardiography in the evaluation of diastolic filling and in discriminating between normal subjects and those with various stages of diastolic dysfunction. We measured myocardial velocities in 51 patients with various stages of diastolic dysfunction and in 27 normal volunteers. The discriminating power of each of the standard Doppler indexes of left ventricular filling, pulmonary venous flow, and myocardial velocities was determined with the use of Spearman rank correlation and analysis of variance F statistics. Early diastolic myocardial velocity (E(m)) was higher in normal subjects (16.0 +/- 3.8 cm/s) than in patients with either delayed relaxation (n = 15, 7.5 +/- 2.2 cm/s), pseudonormal filling (n = 26, 7.6 +/- 2.3 cm/s), or restrictive filling (n = 10, 7.4 +/- 2.4 cm/s, P 〈.0001). E(m ) was the best single discriminator between control subjects and patients with diastolic dysfunction (P =.7, F = 64.5). Myocardial velocities assessed by Doppler tissue echocardiography are useful in differentiating patients with normal from those with abnormal diastolic function. Myocardial velocity remains reduced even in those stages of diastolic dysfunction characterized by increased preload compensation.
    Keywords: Life Sciences (General)
    Type: Journal of the American Society of Echocardiography : official publication of the American Society of Echocardiography (ISSN 0894-7317); 12; 8; 609-17
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  • 7
    Publication Date: 2019-07-13
    Description: OBJECTIVES: The study assessed whether hemodynamic parameters of left atrial (LA) systolic function could be estimated noninvasively using Doppler echocardiography. BACKGROUND: Left atrial systolic function is an important aspect of cardiac function. Doppler echocardiography can measure changes in LA volume, but has not been shown to relate to hemodynamic parameters such as the maximal value of the first derivative of the pressure (LA dP/dt(max)). METHODS: Eighteen patients in sinus rhythm were studied immediately before and after open heart surgery using simultaneous LA pressure measurements and intraoperative transesophageal echocardiography. Left atrial pressure was measured with a micromanometer catheter, and LA dP/dt(max) during atrial contraction was obtained. Transmitral and pulmonary venous flow were recorded by pulsed Doppler echocardiography. Peak velocity, and mean acceleration and deceleration, and the time-velocity integral of each flow during atrial contraction was measured. The initial eight patients served as the study group to derive a multilinear regression equation to estimate LA dP/dt(max) from Doppler parameters, and the latter 10 patients served as the test group to validate the equation. A previously validated numeric model was used to confirm these results. RESULTS: In the study group, LA dP/dt(max) showed a linear relation with LA pressure before atrial contraction (r = 0.80, p 〈 0.005), confirming the presence of the Frank-Starling mechanism in the LA. Among transmitral flow parameters, mean acceleration showed the strongest correlation with LA dP/dt(max) (r = 0.78, p 〈 0.001). Among pulmonary venous flow parameters, no single parameter was sufficient to estimate LA dP/dt(max) with an r2 〉 0.30. By stepwise and multiple linear regression analysis, LA dP/dt(max) was best described as follows: LA dP/dt(max) = 0.1 M-AC +/- 1.8 P-V - 4.1; r = 0.88, p 〈 0.0001, where M-AC is the mean acceleration of transmitral flow and P-V is the peak velocity of pulmonary venous flow during atrial contraction. This equation was tested in the latter 10 patients of the test group. Predicted and measured LA dP/dt(max) correlated well (r = 0.90, p 〈 0.0001). Numerical simulation verified that this relationship held across a wide range of atrial elastance, ventricular relaxation and systolic function, with LA dP/dt(max) predicted by the above equation with r = 0.94. CONCLUSIONS: A combination of transmitral and pulmonary venous flow parameters can provide a hemodynamic assessment of LA systolic function.
    Keywords: Life Sciences (General)
    Type: Journal of the American College of Cardiology (ISSN 0735-1097); 34; 3; 795-801
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  • 8
    Publication Date: 2019-07-13
    Description: Shortened early transmitral deceleration times (E(DT)) have been qualitatively associated with increased filling pressure and reduced survival in patients with cardiac disease and increased left ventricular operating stiffness (K(LV)). An equation relating K(LV) quantitatively to E(DT) has previously been described in a canine model but not in humans. During several varying hemodynamic conditions, we studied 18 patients undergoing open-heart surgery. Transesophageal echocardiographic two-dimensional volumes and Doppler flows were combined with high-fidelity left atrial (LA) and left ventricular (LV) pressures to determine K(LV). From digitized Doppler recordings, E(DT) was measured and compared against changes in LV and LA diastolic volumes and pressures. E(DT) (180 +/- 39 ms) was inversely associated with LV end-diastolic pressures (r = -0.56, P = 0.004) and net atrioventricular stiffness (r = -0.55, P = 0.006) but had its strongest association with K(LV) (r = -0.81, P 〈 0.001). K(LV) was predicted assuming a nonrestrictive orifice (K(nonrest)) from E(DT) as K(nonrest) = (0.07/E(DT))(2) with K(LV) = 1.01 K(nonrest) - 0.02; r = 0.86, P 〈 0.001, DeltaK (K(nonrest) - K(LV)) = 0.02 +/- 0.06 mm Hg/ml. In adults with cardiac disease, E(DT) provides an accurate estimate of LV operating stiffness and supports its application as a practical noninvasive index in the evaluation of diastolic function.
    Keywords: Life Sciences (General)
    Type: American journal of physiology. Heart and circulatory physiology (ISSN 0363-6135); 280; 2; H554-61
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  • 9
    Publication Date: 2019-07-13
    Description: OBJECTIVES: We sought to validate direct planimetry of mitral regurgitant orifice area from three-dimensional echocardiographic reconstructions. BACKGROUND: Regurgitant orifice area (ROA) is an important measure of the severity of mitral regurgitation (MR) that up to now has been calculated from hemodynamic data rather than measured directly. We hypothesized that improved spatial resolution of the mitral valve (MV) with three-dimensional (3D) echo might allow accurate planimetry of ROA. METHODS: We reconstructed the MV using 3D echo with 3 degrees rotational acquisitions (TomTec) using a transesophageal (TEE) multiplane probe in 15 patients undergoing MV repair (age 59 +/- 11 years). One observer reconstructed the prolapsing mitral leaflet in a left atrial plane parallel to the ROA and planimetered the two-dimensional (2D) projection of the maximal ROA. A second observer, blinded to the results of the first, calculated maximal ROA using the proximal convergence method defined as maximal flow rate (2pi(r2)va, where r is the radius of a color alias contour with velocity va) divided by regurgitant peak velocity (obtained by continuous wave [CW] Doppler) and corrected as necessary for proximal flow constraint. RESULTS: Maximal ROA was 0.79 +/- 0.39 (mean +/- SD) cm2 by 3D and 0.86 +/- 0.42 cm2 by proximal convergence (p = NS). Maximal ROA by 3D echo (y) was highly correlated with the corresponding flow measurement (x) (y = 0.87x + 0.03, r = 0.95, p 〈 0.001) with close agreement seen (AROA (y - x) = 0.07 +/- 0.12 cm2). CONCLUSIONS: 3D echo imaging of the MV allows direct visualization and planimetry of the ROA in patients with severe MR with good agreement to flow-based proximal convergence measurements.
    Keywords: Life Sciences (General)
    Type: Journal of the American College of Cardiology (ISSN 0735-1097); 32; 2; 432-7
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