A practical approach for outdoors distributed target localization in wireless sensor networks

Wireless sensor networks are posed as the new communication paradigm where the use of small, low-complexity, and low-power devices is preferred over costly centralized systems. The spectra of potential applications of sensor networks is very wide, ranging from monitoring, surveillance, and localization, among others. Localization is a key application in sensor networks and the use of simple, efficient, and distributed algorithms is of paramount practical importance. Combining convex optimization tools with consensus algorithms we propose a distributed localization algorithm for scenarios where received signal strength indicator readings are used. We approach the localization problem by formulating an alternative problem that uses distance estimates locally computed at each node. The formulated problem is solved by a relaxed version using semidefinite relaxation technique. Conditions under which the relaxed problem yields to the same solution as the original problem are given and a distributed consensusbased implementation of the algorithm is proposed based on an augmented Lagrangian approach and primaldual decomposition methods. Although suboptimal, the proposed approach is very suitable for its implementation in real sensor networks, i.e., it is scalable, robust against node failures and requires only local communication among neighboring nodes. Simulation results show that running an additional local search around the found solution can yield performance close to the maximum likelihood estimate

Active learning of multiple source multiple destination topologies

We consider the problem of inferring the topology of a network with M sources and N receivers (an M -by-N network), by sending probes between the sources and receivers. Prior work has shown that this problem can be decomposed into two parts: first, infer smaller subnetwork components (1-by-N 's or 2-by-2's) and then merge them to identify the M -by-N topology. We focus on the second part, which had previously received less attention in the literature. We assume that a 1-by-N topology is given and that all 2-by-2 components can be queried and learned using end-to-end probes. The problem is which 2-by-2's to query and how to merge them with the given 1-by-N, so as to exactly identify the 2-by-N topology, and optimize a number of performance metrics, including the number of queries (which directly translates into measurement bandwidth), time complexity, and memory usage. We provide a lower bound, [N\2], on the number of 2-by-2's required by any active learning algorithm and propose two greedy algorithms. The first algorithm follows the framework of multiple hypothesis testing, in particular Generalized Binary Search (GBS). The second algorithm is called the Receiver Elimination Algorithm (REA) and follows a bottom-up approach. It requires exactly N-1 steps, which is much less than all N\2 possible 2-by-2's. Simulation results demonstrate that both algorithms correctly identify the 2-by-N topology and are near-optimal, but REA is more efficient in practice. © 1991-2012 IEEE

The Future of Cardiac Magnetic Resonance Clinical Trials.

Over the past 2 decades, cardiac magnetic resonance (CMR) has become an essential component of cardiovascular clinical care and contributed to imaging-guided diagnosis and management of coronary artery disease, cardiomyopathy, congenital heart disease, cardio-oncology, valvular, and vascular disease, amongst others. The widespread availability, safety, and capability of CMR to provide corresponding anatomical, physiological, and functional data in 1 imaging session can improve the design and conduct of clinical trials through both a reduction of sample size and provision of important mechanistic data that may augment clinical trial findings. Moreover, prospective imaging-guided strategies using CMR can enhance safety, efficacy, and cost-effectiveness of cardiovascular pathways in clinical practice around the world. As the future of large-scale clinical trial design evolves to integrate personalized medicine, cost-effectiveness, and mechanistic insights of novel therapies, the integration of CMR will continue to play a critical role. In this document, the attributes, limitations, and challenges of CMR's integration into the future design and conduct of clinical trials will also be covered, and recommendations for trialists will be explored. Several prominent examples of clinical trials that test the efficacy of CMR-imaging guided pathways will also be discussed

Temporal changes in FFRCT-Guided Management of Coronary Artery Disease – Lessons from the ADVANCE Registry

Background: The ADVANCE registry is a large prospective study of outcomes and resource utilization in patients undergoing coronary computed tomography angiography (CCTA) and CT-based fractional flow reserve (FFRCT). As experience with new technologies and practices develops over time, we investigated temporal changes in the use of FFRCT within the ADVANCE registry. Methods: 5083 patients with coronary artery disease (CAD) on CCTA were prospectively enrolled in the ADVANCE registry and were divided into 3 equally sized cohorts based on the temporal order of enrollment per site. Demographics, CCTA and FFRCT findings, and clinical outcomes through 1-year follow-up, were recorded and compared between tertiles. Results: The number of patients with a ≥70% stenosis on CCTA was similar over time (33.6%, 30.9%, and 33.8% for cohort 1–3). The rate of positive FFRCT ≤0.80 was higher for cohorts 2 (67.3%) and 3 (74.6%) than for cohort 1 (57.1%, p < 0.001). Invasive FFR rates decreased from 25.8% to 22.4% between cohort 1 and 3 (p = 0.023). Moreover, patients with a FFRCT ≤0.80 were less frequently referred for invasive coronary angiography (ICA) (from 62.9% to 52.9%, p < 0.001), and underwent fewer revascularizations between cohort 1 and 3 (from 41.9% to 32.0%, p < 0.001). The prevalence of major events was low (1.2%) and similar between cohorts. Conclusions: Growing experience with FFRCT improved the likelihood of identifying hemodynamically significant CAD and safely reduced the need for ICA and revascularization in patients with anatomically significant disease even in the instance of an abnormal FFRCT

Perfil epidemiológico dos pacientes em terapia renal substitutiva no Brasil, 2000-2004 Perfil epidemiológico de los pacientes en terapia renal substitutiva en Brasil, 2000-2004 Epidemiological profile of patients on renal replacement therapy in Brazil, 2000-2004

OBJETIVO: Descrever o perfil epidemiológico e clínico de pacientes em terapia renal substitutiva, identificando fatores associados ao risco de morte. MÉTODOS: Estudo observacional, prospectivo não concorrente, a partir de dados de 90.356 pacientes da Base Nacional em Terapias Renais Substitutivas, no Brasil. Foi realizado relacionamento determinístico-probabilístico do Sistema de Autorização de Procedimentos de Alta Complexidade/Custo e do Sistema de Informação de Mortalidade. Foram incluídos todos os pacientes incidentes que iniciaram diálise entre 1/1/2000 e 31/12/2004, acompanhados até a morte ou final de 2004. Idade, sexo, região de residência, doença renal primária, causa do óbito foram analisados. Ajustou-se um modelo de riscos proporcionais para identificar fatores associados ao risco de morte. RESULTADOS: Ocorreu um aumento médio de 5,5% na prevalência de pacientes em terapia enquanto a incidência manteve-se estável no período. Hemodiálise foi a modalidade inicial predominante (89%). A maioria dos pacientes era do sexo masculino, com idade média de 53 anos, residente na região Sudeste, e apresentava causa indeterminada como principal causa básica da doença renal crônica, seguida da hipertensão, diabetes e glomerulonefrites. Desses pacientes, 7% realizou transplante renal e 42% evoluiu para o óbito. Os pacientes em diálise peritoneal eram mais idosos e apresentavam maior prevalência de diabetes. Entre os não transplantados, 45% foi a óbito e, entre os transplantados, 7%. No modelo final de riscos proporcionais de Cox, o risco de mortalidade foi associado com o aumento da idade, sexo feminino, ter diabetes, residir nas regiões Norte e Nordeste, diálise peritoneal como modalidade de entrada e não ter realizado transplante renal. CONCLUSÕES: Houve aumento da prevalência de pacientes em terapia renal no Brasil. Pacientes com idade avançada, diabetes, do sexo feminino, residentes nas regiões Norte e Nordeste e sem transplante renal apresentam maior risco de morte.<br>OBJETIVO: Describir el perfil epidemiológico y clínico de pacientes en terapia renal substitutiva, identificando factores asociados al riesgo de muerte. MÉTODOS: Estudio de observación, prospectivo no concurrente, a partir de datos de 90.356 pacientes de la Base Nacional en Terapias Renales Substitutivas, en Brasil. Fue realizado reracionamiento determinístico-probabilístico del Sistema de Información de Mortalidad. Fueron incluidos todos los pacientes incidentes que iniciaron diálisis entre 1/1/2000 y 31/12/2004, acompañados hasta la muerte o final de 2004. Edad, sexo, región de residencia, enfermedad renal primaria, causa del óbito fueron analizados. Se ajustó un modelo de riesgos proporcionales para identificar factores asociados al riesgo de muerte. RESULTADOS: Ocurrió un aumento promedio de 5,5% en la prevalencia de pacientes en terapia, con relación a la incidencia se mantuvo estable en el período. Hemodiálisis fue la modalidad inicial predominante (89%). La mayoría de los pacientes era del sexo masculino, con edad promedio de 53 años, residente en la región Sureste y presentaba causa indeterminada como principal causa básica de la enfermedad renal crónica, seguida de la hipertensión, diabetes y glomerulonefritis. De esos pacientes, 7% realizaron transplante renal y 42% evolucionaron a óbito. Los pacientes en diálisis peritoneal eran más ancianos y presentaban mayor prevalencia de diabetes. Entre los no transplantados, 45% fueron a óbito y, entre los transplantadas 7%. En el modelo final de riesgos proporcionales de Cox, el riesgo de mortalidad estuvo asociado con el aumento de la edad, sexo femenino, tener diabetes, residir en la región Norte y Noreste, diálisis peritoneal como modalidad de entrada y no haber realizado transplante renal. CONCLUSIONES: Hubo aumento de la prevalencia de pacientes en terapia renal en Brasil. Pacientes con edad avanzada, diabetes, del sexo femenino, residentes en la región Norte y Noreste y sin transplante renal presentan mayor riesgo de muerte.<br>OBJECTIVE: To describe the clinical and epidemiological profile of patients under renal replacement therapies, identifying risk factors for death. METHODS: This is a non-concurrent cohort study of data for 90,356 patients in the National Renal Replacement Therapies Database. A deterministic-probabilistic linkage was performed using the Authorization System for High Complexity/Cost Procedures and the Mortality Information System databases. All patients who started dialysis between 1/1/2000 and 12/31/2004 were included and followed until death or the end of 2004. Age, sex, region of residence, primary renal disease and causes of death were analyzed. A proportional hazards model was used to identify factors associated with risk of death. RESULTS: The prevalence of patients under renal replacement therapies increased an average of 5.5%, while incidence remained stable during the period. Hemodialysis was the predominant initial modality (89%). The patients were majority male with mean age 53 years, residents of the Southeast region and presented unknown causes as the main cause of chronic renal disease, followed by hypertension, diabetes and glomerulonephritis. Of these patients, 42% progressed to death and 7% underwent kidney transplantation. The patients on peritoneal dialysis were older and had higher prevalence of diabetes. The death rate varied from 7% among transplanted patients to 45% among non-transplanted patients. In the final Cox proportional hazards model, the risk of mortality was associated with increasing age, female sex, having diabetes, living in the North and Northeast region, peritoneal dialysis as a first modality and not having renal transplantation. CONCLUSIONS: There was an increased prevalence of patients on renal therapy in Brazil. Increased risk of death was associated with advanced age, diabetes, the female sex, residents of the North and Northeast region and lack of renal transplant