Integral equation approach to tropical ocean dynamics: Part II-Rossby wave scattering from the equatorial Atlantic western boundary

We develop a linear theory for the scattering of equatorial waves of a fixed frequency ω by islands and continental margins of arbitrary geometry by use of the boundary integral equation (BIE) method of Vianna and Holvorcem (Part I of this work). All the solutions of the equatorial β-plane dispersion relations at frequency ω are treated explicitly through the extensive use of exact Green\u27s functions, so that the approach is more general and more rigorous than previous attempts to solve equatorial scattering problems, many of which employ the low-frequency and long-wave approximations. The numerical solution of the HIE is obtained through application of the boundary element method. A numerical study of the scattering of Rossby waves with periods between 50 and 90 days from the equatorial Atlantic western boundary is presented. Some of the resulting interference patterns exhibit a sharp amplitude maximum, whose center lies between 3-9N, 35-47W. The position, width and intensity of this maximum all depend on wave period. We find evidences that this maximum arises from the superposition of zonally damped equatorial modes (evanescent waves) excited at the western boundary. The largest pressure amplitudes along the boundary are found in the southern hemisphere between the Equator and 5S. The phase propagation along the boundary is generally northwestward, except at a few positions where the phase is stationary. We discuss similarities and differences between the calculated responses and observations of intraseasonal oscillations in the tropical Atlantic Ocean

Integral equation approach to tropical ocean dynamics: Part I-Theory and computational methods

In linear, three-dimensional, continuously stratified equatorial β-plane ocean models with arbitrary eastern and western boundaries the shallow water equations for each vertical mode must be solved numerically in the horizontal variables. This paper introduces a new numerical method of solution for the time-Fourier transformed shallow water equations with slip boundary conditions at boundaries of arbitrary geometry. The method is based on a boundary integral equation (BIE) for the pressure perturbation response to the specified wind-stress forcing field. All other dependent variables are expressed as boundary functionals of the pressure perturbation. The kernels of all functionals are constructed from the Green\u27s function for the Laplace Tidal Equation on the β-plane and its derivatives. The efficient computation of these kernels from their exact meridional mode representations may be performed by use of asymptotic methods especially developed for the numerical evaluation of functions expressed as slowly converging series of Hermite functions. The solution of the basic BIE and the computation of the boundary functionals involve the discretization of the ocean boundaries into a number of boundary segments (boundary elements). It is shown that the terms of the BIE involving the wind-stress field over the ocean may be reduced to a boundary integral, which effectively reduces the simulation problem to the solution of a one-dimensional BIE. The method incorporates the ocean physics through the relationship between the coastal pressure field and the basin-wide variables, pointing out to the possibility that the dynamic topography of the ocean may be estimated directly from the wind-stress field and coastal sea-level data

Interannual variability of the South Indian Countercurrent

Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 121 (2016): 3465–3487, doi:10.1002/2015JC011417.In the present work, we investigate the interannual variability of the South Indian Countercurrent (SICC), a major and still understudied current of the Indian Ocean circulation. To characterize the interannual variability of the SICC, four different data sets (altimetry, GLORYS, OFAM3, and SODA) are analyzed using multiple tools, which include Singular Spectrum Analysis and wavelet methods. The quasi-biennial band dominates the SICC low-frequency variance, with the main peak in the 1.5–1.8 year interval. A secondary peak (2.1–2.5 year) is only found in the western basin. Interannual and decadal-type modulations of the quasi-biennial signal are also identified. In addition, limitations of SODA before the 1960s in the SICC region are revealed. Within the quasi-biennial band, the SICC system presents two main patterns with a multiple jet structure. One pattern is characterized by a robust northern jet, while in the other the central jet is well developed and northern jet is weaker. In both patterns, the southern jet has always a strong signature. When the northern SICC jet is stronger, the northern cell of the subtropical gyre has a triangular shape, with its southern limb having a strong equatorward slant. The quasi-biennial variability of the SICC is probably related to the Indian Ocean tropical climate modes that are known to have a strong biennial characteristic.ARC Discovery Project Grant Number: DP130102088; NSF Grant Number: OCE-091716; Ocean Science Division of VM Oceanica2016-11-2

Plasma Dynamics

Contains reports on four research projects.National Science Foundation (Grant GK-37979X)U.S. Atomic Energy Commission (Contract AT(11-1)-3070

Plasmas and Controlled Nuclear Fusion

Contains research objectives and reports on six research projects.U. S. Atomic Energy Commission (Contract AT(30-1)-3980

Plasma Dynamics

Contains research objectives and summary of research on eighteen research projects split into seven sections and reports on four research projects.U.S. Atomic Energy Commission (Contract AT(l1-1)-3070)National Science Foundation (Grant GK-37979X1

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

A High Resolution Satellite-only GRACE-based Mean Dynamic Topography of the South Atlantic Ocean

A new filtering method based on Singular Spectrum Analysis has been devised to extract high resolution (0.25° × 0.25° grid) satellite-only Mean Dynamic Ocean Topography(MDT) constructed by differencing of the GGM02 GRACE Gravity Model from the GSFCMSS00 Mean Sea Surface. This data-adaptive interpolation-type filter is adequate for the finite domain MDT processing since it minimizes smoothing and does not lose boundary points. It is applied to the computation of two new MDTs and MDT-derived mean geostrophic circulation maps of the South Atlantic region from 15°N to 50°S. Advantages of these new maps are clarified when contrasted with the Rio-2005, Chambers-Zlotnicki-2004 and ADCP cruise transect data

Síndrome do impacto do tornozelo na ressonância magnética: ensaio iconográfico Magnetic resonance imaging of ankle impingement syndrome: iconographic essay

A síndrome do impacto do tornozelo é uma condição dolorosa causada por atrito de tecidos articulares, que é tanto causa quanto consequência de uma biomecânica alterada desta articulação. A sua principal causa são as lesões pós-traumáticas, principalmente lesões ligamentares, resultando em dor crônica no tornozelo. Do ponto de vista anatômico e clínico, estas síndromes são classificadas em: ântero-lateral, anterior, ântero-medial, póstero-medial e posterior. A ressonância magnética é um ótimo método diagnóstico para demonstrar as alterações ósseas e as partes moles dos vários tipos de impacto do tornozelo, fornecendo dados que auxiliam não só na comprovação desse diagnóstico, como na diferenciação com outras causas de dor articular. Os autores objetivam ilustrar os principais achados de ressonância magnética na síndrome do impacto do tornozelo.<br>Ankle impingement syndrome is a painful condition resulting from friction of joint tissues that is both cause and effect of an altered joint biomechanics. The leading causes of such condition are post-traumatic lesions, particularly the ligamentous ones, resulting in chronic ankle pain. From an anatomic and clinical point of view, these syndromes may be classified as anterolateral, anterior, anteromedial, posteromedial, and posterior. Magnetic resonance imaging is an excellent diagnostic method for demonstrating bone and soft tissue abnormalities resulting from different types of ankle impingement, providing useful data to confirm the diagnosis as well as to rule out other possible causes of joint pain. The present essay is aimed at illustrating the main magnetic resonance imaging findings in ankle impingement syndrome