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From the origins of hydrology, the time of concentration, tc, has conventionally been tackled as a constant quantity. However, theoretical proof and empirical evidence imply that tc exhibits significant variability against rainfall, making its definition and estimation a hydrological paradox. Adopting the assumptions of the Rational method and the kinematic approach, an effective procedure in a GIS environment for estimating the travel time across a catchment’s longest flow path is provided. By application in 30 Mediterranean basins, it is illustrated that tc is a negative power function of excess rainfall intensity. Regional formulas are established to infer its multiplier (unit time of concentration) and exponent from abstract geomorphological information, which are validated against observed data and theoretical literature outcomes. Besides offering a fast and easy solution to the paradox, we highlight the necessity of implementing the varying tc concept within hydrological modelling, signalling a major shift from current engineering practices. [ABSTRACT FROM AUTHOR]

Cervical lymphadenopathy (CL) is common in childhood. The aim of this study is to evaluate the etiology, follow-up, and treatment of persistent CL. The authors studied retrospectively 50 children with CL, hospitalized at the Department of Pediatrics and Pediatrics Surgery. Patients underwent ultrasonography. Thirty-six percent presented abnormal ultrasonographic image and underwent excisional biopsy. Biopsies revealed 4 thyroglossal cysts, 3 branchial cysts, 1 hemangioma, 2 sebaceous cysts, 1 dermoid cyst, 5 occurrences of tuberculosis lymphadenitis, 1 occurrence of Bartonella henselae lymphadenopathy, and 1 case of non-Hodgkin lymphoma. In conclusion, CL is usually a benign finding; bacterial and viral infections are the most common causes. Ultrasonography help in etiology and follow-up of CL. [ABSTRACT FROM AUTHOR]