Improving the stability of temporal statistics in transition path theory with sparse data.

Ulam's method is a popular discretization scheme for stochastic operators that involves the construction of a transition probability matrix controlling a Markov chain on a set of cells covering some domain. We consider an application to satellite-tracked undrogued surface-ocean drifting buoy trajectories obtained from the National Oceanic and Atmospheric Administration Global Drifter Program dataset. Motivated by the motion of Sargassum in the tropical Atlantic, we apply Transition Path Theory (TPT) to drifters originating off the west coast of Africa to the Gulf of Mexico. We find that the most common case of a regular covering by equal longitude-latitude side cells can lead to a large instability in the computed transition times as a function of the number of cells used. We propose a different covering based on a clustering of the trajectory data that is stable against the number of cells in the covering. We also propose a generalization of the standard transition time statistic of TPT that can be used to construct a partition of the domain of interest into weakly dynamically connected regions.

Coherent Lagrangian swirls among submesoscale motions.

The emergence of coherent Lagrangian swirls (CLSs) among submesoscale motions in the ocean is illustrated. This is done by applying recent nonlinear dynamics tools for Lagrangian coherence detection on a surface flow realization produced by a data-assimilative submesoscale-permitting ocean general circulation model simulation of the Gulf of Mexico. Both mesoscale and submesoscale CLSs are extracted. These extractions prove the relevance of coherent Lagrangian eddies detected in satellite-altimetry-based geostrophic flow data for the arguably more realistic ageostrophic multiscale flow.

Transition paths of marine debris and the stability of the garbage patches.

We used transition path theory (TPT) to infer "reactive" pathways of floating marine debris trajectories. The TPT analysis was applied on a pollution-aware time-homogeneous Markov chain model constructed from trajectories produced by satellite-tracked undrogued buoys from the National Oceanic and Atmospheric Administration's Global Drifter Program. The latter involved coping with the openness of the system in physical space, which further required an adaptation of the standard TPT setting. Directly connecting pollution sources along coastlines with garbage patches of varied strengths, the unveiled reactive pollution routes represent alternative targets for ocean cleanup efforts. Among our specific findings we highlight: constraining a highly probable pollution source for the Great Pacific garbage patch; characterizing the weakness of the Indian Ocean gyre as a trap for plastic waste; and unveiling a tendency of the subtropical gyres to export garbage toward the coastlines rather than to other gyres in the event of anomalously intense winds.

Stability of the Malvinas Current.

Deterministic and probabilistic tools from nonlinear dynamics are used to assess enduring near-surface Lagrangian aspects of the Malvinas Current. The deterministic tools are applied to a multiyear record of velocities derived from satellite altimetry data, revealing a resilient cross-stream transport barrier. This is composed of shearless-parabolic Lagrangian coherent structures (LCSs), which, extracted over sliding time windows along the multiyear altimetry-derived velocity record, lie in near-coincidental position. The probabilistic tools are applied on a large collection of historical satellite-tracked drifter trajectories, revealing weakly communicating flow regions as basins of attraction for long-time asymptotic almost-invariant sets on either side of the altimetry-derived barrier. Shearless-parabolic LCSs are detected for the first time from altimetry data, and their significance is supported on satellite-derived ocean color data, which reveal shapes that quite closely resemble the peculiar V shapes, dubbed "chevrons," that have recently confirmed the presence of similar LCSs in the atmosphere of Jupiter. Finally, using available in situ velocity and hydrographic data, sufficient and necessary conditions for nonlinear symmetric stability are found to be satisfied, suggesting a duality between Lagrangian and Eulerian stability for the Malvinas Current.

Markov-chain-inspired search for MH370.

Markov-chain models are constructed for the probabilistic description of the drift of marine debris from Malaysian Airlines flight MH370. En route from Kuala Lumpur to Beijing, MH370 mysteriously disappeared in the southeastern Indian Ocean on 8 March 2014, somewhere along the arc of the 7th ping ring around the Inmarsat-3F1 satellite position when the airplane lost contact. The models are obtained by discretizing the motion of undrogued satellite-tracked surface drifting buoys from the global historical data bank. A spectral analysis, Bayesian estimation, and the computation of most probable paths between the Inmarsat arc and confirmed airplane debris beaching sites are shown to constrain the crash site, near 25°S on the Inmarsat arc.

Tracing the Early Development of Harmful Algal Blooms on the West Florida Shelf with the Aid of Lagrangian Coherent Structures.

Several theories have been proposed to explain the development of harmful algal blooms (HABs) produced by the toxic dinoflagellate Karenia brevis on the West Florida Shelf. However, because the early stages of HAB development are usually not detected, these theories have been so far very difficult to verify. In this paper we employ simulated Lagrangian coherent structures (LCSs) to trace potential early locations of the development of a HAB in late 2004 before it was transported to a region where it could be detected by satellite imagery. The LCSs, which are extracted from surface ocean currents produced by a data-assimilative HYCOM (HYbrid-Coordinate Ocean Model) simulation, constitute material fluid barriers that demarcate potential pathways for HAB evolution. Using a simplified population dynamics model we infer the factors that could possibly lead to the development of the HAB in question. The population dynamics model determines nitrogen in two components, nutrients and phytoplankton, which are assumed to be passively advected by surface ocean currents produced by the above HYCOM simulation. Two nutrient sources are inferred for the HAB whose evolution is found to be strongly tied to the simulated LCSs. These nutrient sources are found to be located nearshore and possibly due to land runoff.

Extracting quasi-steady Lagrangian transport patterns from the ocean circulation: An application to the Gulf of Mexico.

We construct a climatology of Lagrangian coherent structures (LCSs)-the concealed skeleton that shapes transport-with a twelve-year-long data-assimilative simulation of the sea-surface circulation in the Gulf of Mexico (GoM). Computed as time-mean Cauchy-Green strain tensorlines of the climatological velocity, the climatological LCSs (cLCSs) unveil recurrent Lagrangian circulation patterns. The cLCSs strongly constrain the ensemble-mean Lagrangian circulation of the instantaneous model velocity, showing that a climatological velocity can preserve meaningful transport information. The quasi-steady transport patterns revealed by the cLCSs agree well with aspects of the GoM circulation described in several previous observational and numerical studies. For example, the cLCSs identify regions of persistent isolation, and suggest that coastal regions previously identified as high-risk for pollution impact are regions of maximal attraction. We also show that cLCSs are remarkably accurate at identifying transport patterns observed during the Deepwater Horizon and Ixtoc oil spills, and during the Grand LAgrangian Deployment (GLAD) experiment. Thus it is shown that computing cLCSs is an efficient and meaningful way of synthesizing vast amounts of Lagrangian information. The cLCS method confirms previous GoM studies, and contributes to our understanding by revealing the persistent nature of the dynamics and kinematics treated therein.

Lagrangian dynamical geography of the Gulf of Mexico.

We construct a Markov-chain representation of the surface-ocean Lagrangian dynamics in a region occupied by the Gulf of Mexico (GoM) and adjacent portions of the Caribbean Sea and North Atlantic using satellite-tracked drifter trajectory data, the largest collection so far considered. From the analysis of the eigenvectors of the transition matrix associated with the chain, we identify almost-invariant attracting sets and their basins of attraction. With this information we decompose the GoM's geography into weakly dynamically interacting provinces, which constrain the connectivity between distant locations within the GoM. Offshore oil exploration, oil spill contingency planning, and fish larval connectivity assessment are among the many activities that can benefit from the dynamical information carried in the geography constructed here.

Persistent transport barrier on the West Florida Shelf.

Analysis of drifter trajectories in the Gulf of Mexico has revealed the existence of a region on the southern portion of the West Florida Shelf (WFS) that is not visited by drifters that are released outside of the region. This so-called "forbidden zone" (FZ) suggests the existence of a persistent cross-shelf transport barrier on the southern portion of the WFS. In this letter a year-long record of surface currents produced by a Hybrid-Coordinate Ocean Model simulation of the WFS is used to compute Lagrangian coherent structures (LCSs), which reveal the presence of a persistent cross-shelf transport barrier in approximately the same location as the boundary of the FZ. The location of the cross-shelf transport barrier undergoes a seasonal oscillation, being closer to the coast in the summer than in the winter. A month-long record of surface currents inferred from high-frequency (HF) radar measurements in a roughly 60 km × 80 km region on the WFS off Tampa Bay is also used to compute LCSs, and these also reveal the presence of transient transport barriers. While the HF-radar-derived transport barriers cannot be unambiguously linked to the boundary of the FZ, this analysis does demonstrate the feasibility of monitoring transport barriers on the WFS using a HF-radar-based measurement system. The implications of a persistent cross-shelf transport barrier on the WFS for the development of harmful algal blooms on the shoreward side of the barrier are considered.

[Benign atheroembolic syndrome secondary to systemic fibrinolysis with streptokinase]. / Síndrome ateroembólico de curso benigno secundario a fibrinólisis sistémica con estreptoquinasa.

We present the case of an 60-year-old male patient that after a acute myocardial infarction inferior diagnostic was subjected to a fibrinolysis with streptokinase. The evolution from the cardiologic point of view was favourable, but at fourth day postacute myocardial infartion he starts with peripherics vasculars symptoms, pain and livedo reticularis in lower part of the body. A symptomatic treatment was made requiring amputation of his fifth right toe. The evolution was towards healing without any organic afectation at another level.

[Gastrointestinal alterations in a female patient with common variable immunodeficiency]. / Alteraciones gastrointestinales en una paciente con inmunodeficiencia variable común.

We present the case of a 33-year-old woman who complained of intermittent diarrhea over the previous 8 years and who was diagnosed with common variable immunodeficiency. The woman presented antral atrophic gastritis, partial atrophy of the duodenal villi, nodular lymphoid hyperplasia of the small intestine and lymphocytic colitis. We also review the literature.

Tamponade as the clinical onset of a cardiac angiosarcoma.

Primary tumors of the heart are usually benign, with the malignant forms being rare. In this article we report the case of an angiosarcoma with the only manifestation being a cardiac tamponade. When the patient being admitted to the hospital, an important differential diagnosis was pulmonary tumor. A mass in the right atrium was later detected in the echocardiogram. Further image studies, such as MRI, showed spectacular images of this mass suggestive of neoplasm. An intra-operatory biopsy diagnosed the mass as an angiosarcoma. Since there was no evidence of primary neoplasm in other studies carried out, the neoformation was diagnosed as a primary angiosarcoma. Surgery was carried out with a survival of only 13 months after the procedure. We also use this case to make a brief review of the primary tumors of the heart, especially angiosarcomas.

Subaortic stenosis diagnosed in the course of a twins pregnancy: a controversial management.

Fixed subaortic stenosis, commonly associated with other congenital cardiac defects, is the cause of 10 per cent of cases of congenital obstruction of the left ventricular outflow. Corrective surgery is frequently a successful treatment, recommendations being based on the transaortic gradient in Europe while in the USA the most prevalent opinion is surgical repair independently of the gradient. We present a case of adult clinical onset of a fixed subaortic stenosis during pregnancy, in which hemodynamic changes are significant, that was medically treated and followed in the outpatient clinic of our hospital, and review the state of the art of the management and surgical indications of this condition.

[Appropriateness of the admissions and stays in an internal medicine department of a secondary hospital using the current version of the AEP ( Appropriateness Evaluation Protocol)]. / Adecuación de los ingresos y estancias en un Servicio de Medicina Interna de un hospital de segundo nivel utilizando la versión concurrente del AEP (Appropriateness Evaluation Protocol).

AIMS: To Study the inappropriateness of the admissions and stays in an Internal Medicine Department using the concurrent version of the AEP (Appropriateness Evaluation Protocol). METHOD: Aplication of the concurrent version of the AEP to all the patients internated in an Internal Medicine Department. 257 RESULTS: 59 patients and 485 stays fulfilled the inclusion criteria. A 15.3/ of the admissions and a 33/ of the stays did not acomplish the criteria of appropriateness of the AEP. The most frequent cause of innappropriate admision was to avoid the delay of the ambulatory studies. The most common cause of innappropriate stay was the wait for results of complementary tests and consultancy between different specialities. CONCLUSIONS: Using the concurrent version of the AEP allows to obtain information about the overuse of the hospitalization resources in an easy and rapid way. The results obtained in our study are similar to other made in Spain using the retrospective version of the AEP.

[Appropriateness of admissions to an internal medicine department of a second level hospital]. / Adecuación de los ingresos en un servicio de Medicina Interna de un hospital de segundo nivel.

BACKGROUND: Study about the admissions appropriateness in the Internal Medicine ward of Hospital Juan Ramón Jiménez. MATERIAL AND METHODS: Retrospective review of the admissions in the first three months of 1997 not coming from any other ward. Two physicians not responsible of the admission evaluated separately the medical records by using the Appropriateness Evaluation Protocol. 201 patients were selected randomly from the 518 admissions which accomplished the criteria formerly exposed. RESULTS: 13.4% of the admissions did not fulfill any criteria of the Appropriateness Evaluation Protocol. The most frequent inadequate admission cause was for diagnostic purposes (66%). No significative difference was found in the percentage of inappropriate admissions with respect to age, gender, days of stay and number of previous admissions. CONCLUSIONS: The percentage of inappropriate admissions was slightly lower than that of similar studies carried out in similar conditions, probably because of the possibility of moving the patient to lower levels of care units according their needs.