146 research outputs found
Prepubertal melanoma
No full textThe incidence of prepubertal melanoma is not raising in children, unlike adolescent and adult (24). Its incidence therefore remains so low that no center is able to do statistics only based on its cases. Over the past 40 years in five Italian Pediatric Dermatology centers 15 cases of melanoma in children aged under 12 years were observed, 4 of which associated with large or multiple congenital melanocytic nevi. The latter, including two cutaneous melanomas arising on congenital melanocytic nevi and 2 meningoencephalic melanomas, started early - average age at diagnosis 18 months - and had poor prognosis quoad vitam. The 11 melanomas arising on normal skin - 8 cases - or associated with small congenital - 1 case - or acquired - 2 cases - melanocytic nevi started at a later age - average age 9.2 years - and had a good prognosis despite average thickness of 2 mm and lymph node involvement in 3/11 cases. These two categories of prepubertal melanoma, though so different from each other, shared the same nodular or ulcerative non specific, often amelanotic clinical appearance. Therefore, they were different and more difficult to be diagnosed as compared with pigmented and usually initially superficial spreading adult melanoma
Orange-brown chromonychia and Kawasaki disease: A possible novel association?
No full textA 4-year-old girl with clinical and laboratory signs of Kawasaki disease (KD) was hospitalized and given intravenous immunoglobulin plus aspirin therapy, with rapid defervescence and clinical improvement, and was discharged 48 hours after admission. At the time of her follow-up echocardiography on day 14, orange-brown pigmentation of the nail beds was noticed and confirmed with dermoscopy. No clear association between KD and orange-brown chromonychia has been demonstrated, although reports and case series suggest a possible link between these two entities. We suggest that this particular finding might be encompassed in late (subacute) changes of extremities as part of KD diagnostic criteria
A flamelet/progress-variable approach for the simulation of turbulent combustion of real gas mixtures
No full textThe industrial and scientific communities are devoting major research efforts to identify and assess critical technologies for new advanced propulsive concepts: combustion at high pressure has been assumed as a key issue to achieve better propulsive performance and lower environmental impact, as long as the replacement of hydrogen with a hydrocarbon, to reduce the costs related to ground operations (propellant handling, infrastructure and procedures) and increase flexibility. For the class of engines of interest in this work, namely liquid-propellant rocket engines, the pressure is always supercritical, whereas the temperature could be either sub- or super-critical; however, propellants are typically injected into an environment that exceeds the critical temperature and pressure for both fuel and oxidizer, therefore a fast transition to a supercritical state is observed. In such a condition, it is possible to neglect the liquid phase and treat the liquid as a "dense" gaseous jet. However, the ideal gas equation of state is not suitable for computing the correct p-v-T relationship for oxygen and fuel at the operating pressure and temperature typical of LOx/HC rocket combustion chambers. Therefore, a suitable equation of state together with adequate model equations for the transport properties are employed. Starting from this background, the current work provides a model for the numerical simulation of high-pressure turbulent combustion employing detailed chemistry description, embedded in a Reynolds averaged Navier-Stokes equations solver with a Low Reynolds number k-ε turbulence model
A RANS flamelet-progress-variable method for computing reacting flows of real-gas mixtures
No full textThis paper provides an efficient numerical method for solving reacting flows of industrial interest in the presence of significant real-gas effects. The method combines a state-of-the-art solver of the Reynolds-averaged Navier-Stokes equations - equipped with the low-Reynolds number k - ω turbulence closure - with a combustion flamelet-progress-variable approach. A real-gas model as well as a detailed kinetic scheme are used to generate the flamelet library. The method is tested versus several applications chosen to demonstrate the importance of the real-gas effects and of the kinetic scheme for computing high-pressure combustion. The major contribution of the paper is to provide a single-phase approach which solves turbulent reacting real-gas flows at a computational cost comparable with that of the simulation of a non-reacting flow thanks to the use of the flamelet library
Numerical Investigation of High Enthalpy Flows
No full textThis work deals with fluid dynamic simulations of high enthalpy flows. Thermochemical non-equilibrium, typical of such flows, was modelled by using the well known multi-temperature model developed by Park. The non-equilibrium model was implemented in a 2D finite volume solver of the Euler equations and was assessed by comparing the results with available experimental measurements. Several test cases concerning 2D and axisymmetric expansion nozzles were performed by varying gas composition and stagnation temperature
Nose-to-tail analysis of an airbreathing hypersonic vehicle using an in-house simplified tool
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