1000 resultados para AK13-R1-10


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Studies aiming at explaining specialization along latitudinal gradients of plant-herbivore interactions have, to date, yielded inconclusive results. Here we propose the use of steep altitudinal gradients for dissecting factors driving evolution of polyphagy in insect herbivores. First, we test whether colonization of high elevation environment favours increased niche-breadth in two disparate insect groups - the wood-boring beetles and the pollinator group of bees - and show increased polyphagy at higher altitudes in both groups. We then assess classic assumptions transferred from the 'latitude-niche-breadth hypothesis', particularly the increase in environmental variability at high, compared to low, altitude. Finally, we discuss alternative mechanisms shaping the observed pattern of increased polyphagy in altitude, including variation in plant quality and predator pressure at different altitudes. We thus suggest evidence for the 'altitude niche-breadth hypothesis', in which both abiotic and biotic conditions, including increased variability and an increase of the potential feeding niche-breadth, promote evolution for increased insect polyphagy in altitude.

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Kirje 5.10.1973

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Describe las actividades realizadas en el crucero de evaluación de biomasa desovante de anchoveta y sardina, realizadas desde el 11 de agosto al 4 de octubre de 1994, con el objetivo de evaluar a las poblaciones desovantes de la anchoveta y sardina del litoral, para lo cual exploró el área comprendida entre los 10°00 'S y 17°30 'S, llegando hasta las 102 mm de la costa. Los registros acústicos mostraron que la distribución de la anchoveta fue amplia, desde las 02 hasta las 102 millas de la costa, formando grandes áreas de concentración, principalmente frente a Chimbote, Salaverry, Chicama y Pimentel y en menor densidad entre Huarmey y Pisco. La sardina en cambio se presentó en pequeñas áreas dispersas entre Pimentel y Paita, desde las 15mn hasta las 102 millas de distancia de la costa. Las concentraciones y distribución de la especie no permitieron realizar el estimado de biomasa desovante. La Biomasa desovante estimada para ala anchoveta mediante el Método de Producción de huevos es de 6,9 millones de toneladas, con una producción de 15,12 E + 13 huevos por día. La temperatura superficial del mar fluctuó entre 15.0 y 20,4° C. En general, en todo el litoral se observó una tendencia homogénea, con algunos incrementos de carácter temporal al inicio de la primavera.

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Kirje 11.10.1967

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Kirje 14.10.1969

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Purpose/Objective(s): To analyze the long-term outcome of treatment with concomitant cisplatin and hyperfractionated radiotherapy in locally advanced head and neck cancer compared with hyperfractionated radiotherapy alone.Materials/Methods: From July 1994 to July 2000 a total of 224 patients with squamous cell carcinoma of the head and neck were randomized to either hyperfractionated radiotherapy (median dose 74.4 Gy; 1.2 Gy twice daily) or the same radiotherapy combined with two cycles of concomitant cisplatin (20mg/m2 for 5 consecutive days of weeks 1 and 5). The primary endpoint was time to any treatment failure; secondary endpoints were locoregional failure, metastatic failure, overall survival, and late toxicity assessed according to RTOG criteria. The trial was registered at the National Institutes of Health (www.clinicaltrials.gov; identifier number: NCT00002654).Results: Median follow-up was 9.5 years (range, 0.1 - 15.4 years). Median time to any treatment failure was not significantly different between treatment arms (p = 0.19). Locoregional control (p\0.05), distant metastasis-free survival (p = 0.02) and cancer specific survival (p = 0.03) were significantly improved in the combined treatment arm, with no difference in late toxicity between treatment arms. However, overall survival was not significantly different (p = 0.19). Conclusions: After long-term follow-up combined treatment with cisplatin and hyperfractionated, radiotherapy maintained an improved locoregional control, distant metastasis-free survival, and cancer specific survival as compared to hyperfractionated radiotherapy alone with no difference in late toxicity.Author Disclosure: P. Ghadjar, None; M. Simcock, None; G. Studer, None; A.S. Allal, None; M. Ozsahin, None; J. Bernier, None; M. To¨ pfer, None; F. Zimmermann, None; C. Glanzmann, None; D.M. Aebersold, None.