In this paper we consider the design of minimum mean square error (MMSE) transceivers for non-regenerative multiuser multiple-input multiple-output (MIMO) relay systems, where the main challenge ...resides in the joint optimal design of the precoder to be used at the base station and the relaying algorithms. We propose the use of non-linear precoding techniques, such as Tomlinson-Harashima pre-coding (THP) and vector precoding (VP), at the downlink relayed transmission scenario with the aim of outperforming the more common linear strategies. In order to reduce the computational cost of the proposed schemes, we propose a novel suboptimal matrix design approach for VP transmission. Provided simulation results show that the proposed non-linear precoding schemes outperform the best MIMO-AF relaying architectures in the literature, even when a reduced-complexity suboptimal strategy is adopted, considering both BER performance and mean square error minimization.
A two-hop non-regenerative multiuser multiple input multiple output (MIMO) relaying scenario is analysed in this paper, where the main design challenge resides in the selection of the interdependent ...precoding and relaying matrices. Several linear and non-linear approaches have been proposed for amplify-and-forward (AF) relaying, the best performance being achieved when an iterative joint design approach is followed. We propose the use of non-linear precoding techniques such as Tomlinson-Harashima precoding (THP) and vector precoding (VP) at the downlink transmission with the aim of outperforming the more common linear strategies. Provided simulation results show that the proposed optimum iterative nonlinear precoding schemes outperform the best MIMO-AF relaying architectures in the literature, considering both BER performance and error minimization speed.
Resumen Objetivo El objetivo de la I Conferencia Española de Consenso sobre el Injerto Óseo Sinusal era intentar llegar a puntos de acuerdo sobre las principales controversias de esta técnica, ...aplicada de forma muy variada y con el empleo de materiales muy diversos, y conseguir plasmar los mismos en un documento resumen consensuado por todos los autores. Material y método Durante los días 17 y 18 de octubre de 2008 se celebró en Oviedo la citada conferencia, auspiciada por la Sociedad Española de Cirugía Oral y Maxilofacial. En ella se dieron cita un total de 50 ponentes de reconocido prestigio nacional e internacional que repasaron en 6 mesas de trabajo las principales controversias sobre los injertos óseos sinusales. Tras las conferencias de los ponentes, los moderadores establecían las principales conclusiones de cada mesa y se abría un turno de debate donde participaban todos los asistentes. Resultado Este documento y sus conclusiones emanan de las presentaciones realizadas por los ponentes y de las deliberaciones y acuerdos de cada mesa de trabajo. Ambos han sido aprobados tras varias correcciones por todos los autores antes de ser enviados para su publicación. Además, han obtenido el reconocimiento científico oficial de la Sociedad Española de Cirugía Oral y Maxilofacial y deben servir como base para futuros estudios y reuniones científicas. Conclusiones El objetivo fundamental cuando se realiza un injerto óseo sinusal es la formación de hueso vital en el seno maxilar, para conseguir la supervivencia a largo plazo de los implantes tras su carga protésica. Para ello, la técnica y la secuencia de tratamiento deben orientarse a conseguir resultados predecibles y estables en el tiempo, aunque esto suponga un mayor tiempo de espera hasta la colocación de la prótesis. La estabilidad inicial del implante es el factor clave para la osteointegración y debe ser el principal criterio para indicar implantes simultáneos o diferidos en el seno maxilar.
A study was made of 45 patients with arterial hypertension, no prior angina or myocardial infarction, mean age 64 +/- 5 years, and ejection fraction > 50%. Twenty (group I) had congestive heart ...failure while 25 (group II) were asymptomatic. Testing following remission of symptoms revealed impaired exercise tolerance (VO2 max < 20 ml/kg/min) in 22 (subgroup A-80% from group I), and normal tolerance in 23 (subgroup B). Of ventricular function indexes, only peak filling rate correlated significantly with VO2 max (r = 0.65). Of 32 patients with thallium-201 negative in ergometric tests, the 12 in subgroup A had a higher degree of hypertrophy (p > 0.01). Nine thallium-positive patients had lower VO2 max (p > 0.05) than did 17 thallium-negative patients with a similar degree of hypertrophy. Thus, in hypertensive patients, exercise tolerance depends on prior congestive heart failure, diastolic dysfunction, degree of hypertrophy and silent regional ischemia.
We have studied the distribution of the coronary reserve, evaluated by serial effort tests, in patients with proved coronaropathy, determining the correlation between clinic (effort and mixed angina) ...and coronary reserve (fixed and variable), assessing angiographic findings in function to that reserve. We took 120 patients with stable angina to whom 2 effort tests were performed, basal and after vasodilator drugs. It was considered variable reserve if in the second test the S-T descend improved greater than or equal to 1 mm for a similar of greater double product and fixed when it didn't improve. In all patients coronarography was performed. Seventy two patients (60%) showed fixed reserve, 58 with effort angina (80%) and 14 (20%) with mixed. Forty eight showed variable reserve, 40 (80%) with mixed angina and 8 (17%) with effort. The group with fixed reserve had a greater S-T max. descent (2.9 +/- 0.9 vs 2.2 +/- 0.4) (p less than 0.001), a lower double product max. (221 +/- 44 vs 284 +/- 37) (p less than 0.001) and a lower maximal oxygen consumption (MVO2 7 +/- 2 vs 11 +/- 2) (p less than 0.001) than the variable reserve group. Considering the angiography, the fixed reserve group had more number of vessels affected (1.9 +/- 0.7 vs 1.4 +/- 0.5) (p less than 0.01), a higher angiographic score (4.88 +/- 2.4 vs 2.2 +/- 1.2) (p less than 0.001), a lower ejection fraction (59 +/- 8.5 vs 65 +/- 7.5) (p less than 0.001), more multivessel and descending anterior artery lesion than the variable reserve group.
Emergency surgery and ulcerative colitis Otero Ramírez, A; Del Cazo Cativiela, J; Ortega Arruti, J A ...
Revista espanola de las enfermedades del aparato digestivo
61, Številka:
6
Journal Article
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