Compensation of the laser diode smile by the use of micro-optics.

The smile of a laser diode bar has a dramatic impact on the beam quality in the fast axis and significantly degrades the beam parameter product. We present an optical design that allows for a compensation of the laser diode smile by the use of micro-optics. The possibility to compensate the smile of an arbitrary laser diode bar by using a given set of optical modules is evaluated. This technique potentially increases the yield of suitable diode bars in the production process and the efficiency for fiber coupling applications.

Analysis of the modal evolution in fused-type mode-selective fiber couplers.

Fused-type mode-selective fiber couplers exciting the LP(11) mode are fabricated by well-defined fiber cladding reduction, pretapering and fusion. At a wavelength of 905 nm 80 % of the injected power in the single-mode fiber was transmitted in the few-mode fiber selectively exciting the LP(11) mode. The coupling behavior was experimentally investigated for the case of strong as well as weak fusion. Numerical simulations based on the super-mode coupling approach were used to estimate fabrication parameters and to discuss the modal evolution in arbitrarily fused couplers. The influence of changes in the coupler geometry on the super-modes and their modal weighting are analyzed by calculations of the effective refractive index and by modal decomposition.

Matching of the propagation constants in an asymmetric single-mode fused fiber coupler for core pumping thulium-doped fiber at 795 nm.

We developed a fused fiber coupler (FFC) capable of multiplexing wavelengths in the range of 795 nm and 2 µm. A simple 2D simulation model to calculate the pretaper length for matching the propagation constants in the coupling region was established. Based on the numerical data, we fabricated an asymmetric FFC consisting of two different fibers with single-mode guidance for the respective wavelength, achieving a transmission of 90% in the signal fiber for both wavelengths. In order to demonstrate the application, we integrated the FFC into a core pumped thulium-doped fiber amplifier.

An Evaluation of modified case definitions for the detection of dengue hemorrhagic fever

The case definition for dengue hemorrhagic fever (DHF) requires fever, platelets < or = 100,000/mm3, any hemorrhagic manifestation, and plasma leakage evidenced by hemoconcentration > or = 20 percent, pleural or abdominal effusions, hypoproteinemia or hypoalbuminemia. We evaluated the specificity and yield of modified DHF case definitions and the recently proposed World Health Organization criteria for a provisional diagnosis of DHF, using a data base of laboratory-positive and laboratory-negative reports of hospitalizations for suspected dengue in Puerto Rico, 1994 to 1996. By design, all modifications had 100 percent sensitivity. More liberal criteria for plasma leakage were examined: 1) adding as evidence a single hematocrit > or = 50 percent (specificity 97.4 percent); 2) accepting hemoconcentration > or = 10 percent (specificity 90.1 percent); and 3) accepting either hematocrit > or = 50 percent or hemoconcentration > or = 10 percent (specificity 88.8 percent). The new DHF cases identified by these definitions (and percent laboratory positive) were 25 (100.0 percent), 95 (90.5 percent), and 107 (91.6 percent), respectively. In contrast, the provisional diagnosis of DHF (fever and hemorrhage, and one or more of platelets < or = 100,000/mm3, or hemoconcentration > or = 20 percent, or at least a rising hematocrit [redefined quantitatively as a 5 percent or greater relative change]) showed a specificity of 66.8 percent, and identified 318 new DHF cases, of which 282 (88.7 percent) were laboratory-positive. Very small changes in the criteria may result in a large number of new cases. The modification that accepted either hematocrit > or = 50 percent or hemoconcentration > or = 10 percent had acceptable specificity, while doubling the detection of DHF-compatible, laboratory-positive severe cases, but ®provisional diagnosis® showed even lower specificity, and may produce inflated DHF incidence figures. Modified case definitions should be prospectively evaluated with patients in a health-care facility before they are recommended for widespread use.

Síndrome de Papillon-Lefevre: Estudio genético-clínico de dos familias

Dentro del grupo de la queratodermias palmo-plantares, con padrón hereditario autosómico recesivo, se describe el síndrome de Papillon-lefevre, asociado entre otras anomalias con alteraciones dentales y calcificaciones intracraneales. Reportamos el caso de dos familias afectadas con el sindrome, hacemos una breve revisón de la literatura, estudio genético-clínico de las familias, y se recalca la importancia del consejo genético, como forma de prevención.

Fracturas del cuello del femur en los ninos / Fractures of the neck of the femur in children

Se revisa la experiencia obtenida en el tratamiento de las fracturas del extremo proximal del femur en los ninos. Se analizaron las historias clinicas y los estudios radiologicos de 43 casos tratados en el Hospital Universitario Pediatrico de La Misericordia de Bogota, en los ultimos 20 anos y 5 casos, tratados y controlados personalmente por el autor desde julio de 1982 hasta julio de 1987. Se siguio la clasificacion establecida por Delbet, en 4 grupos: Tipo I transepifisiarias: 3 casos (6.25%); Tipo II Transcervicales: 17 casos (35.41%); Tipo III cervico-trocantericas: 18 casos (37.5%); Tipo IV Intertrocantericas: 10 casos (20.83%). Los resultados obtenidos se analizaron, siguiendo los criterios establecidos por Ratliff y en general, se consideran similares a los encontrados por la mayoria de los autores que se han ocupado de este tema. La frecuencia con que se presentan estas fracturas, continua siendo baja (aproximadamente 2.5 por ano) lo cual aun hace valida la premisa establecida por Blount en 1955, segun la cual "las verdaderas fracturas del extremo proximal del femur son tan raras que nadie tiene suficiente experiencia con ellas". Los metodos de tratamiento no se han modificado significativamente con el transcurso de los anos y la aparicion de la necrosis osea avascular, la gran responsable de los malos resultados, se encuentra relacionada principalmente con el grado de desplazamiento inicial de las fracturas.