Background: Cardiac and vascular involvement in Behçet disease (BD), also referred as vasculo BD, is frequent. We aimed to describe clinical characteristics, predictive factors and management of vasculo BD in the Tunisian context. Methods: We retrospectively studied 213 records of all BD patients followed between January 2004 and May 2016 in the Internal Medicine Department and who fulfilled the ISGBD criteria. We described first clinical features of BD with cardiac and vascular involvement then predictive factors were studied in univariate then multivariate analysis. Results: Among the 213 patients, 64 (30%) were diagnosed as having vasculo BD. The mean age at diagnosis was 31.5 years. About 81.25% of them were males and 18.75% females. Vascular involvement associated or not with cardiac involvement was found in 64 patients (30%). Deep venous thromboses are most common (62.5%) compared with superficial ones (23.4%), pulmonary arterial thrombosis (14.1%) or aneurysms (9.4%). Cardiac involvement is ranging from pericarditis (1.6%) to intra cardiac thrombosis (3.1%) and myocardial infarction (1.6%). Predictive factors associated with cardiac and vascular involvement in BD are male gender (OR = 3.043, 95% CI = 1.436-6.447, p = 0.004), erythema nodosum (OR = 4.134, 95% CI = 1.541-11.091, p = 0.005) and neurologic involvement (OR = 2.46, 95% CI = 1.02-5.89, p = 0.043). Conclusion: Cardiac and vascular involvement in BD is frequent in the Tunisian context with a broad spectrum of manifestations ranging from vascular involvement to cardiac one. Male gender, patients with erythema nodosum or neurologic involvement are prone to develop cardiac or vascular features of BD needing therefore a close monitoring.
Purpose The purpose of this paper is to compare the thermal effect between square and circular geometry of light emitting diode (LED) with respect of the same surface for the intent of reducing the junction temperature. Design/methodology/approach The heat equation is presented in a dimensionless form. To solve it numerically subject to the boundary conditions, the authors realized a three-dimensional code with Comsol Multiphysics. Findings The model is validated with previously published works. The authors found a good agreement. Originality/value New design of heat sink is improved for circular LED and a reduction of 18 per cent of the junction temperature is permitted. The authors study the influence of various parameters: number and length of fins and number and width of splits. New distribution of multichip LED in circular geometry permits to put 42 chips instead of 36 chips with respect of the same surface and pitch and with reduction of the junction temperature by 16 per cent.
Purpose The purpose of this paper is to optimize the configuration of a heat sink with phase change material for improving the cooling performance of light emitting diodes (LED). Design/methodology/approach A numerical three-dimensional time-dependent model is developed with COMSOL Multiphysics to simulate the phase change material melting process during both the charging and discharging period. Findings The model is validated with previously published works. It found a good agreement. The difference between filled cavities with phase change materials (PCM) and alternate cavities air-PCM is discussed. The last-mentioned showed a good ability for reducing the junction temperature during the melting time. Three cases of this configuration having the same total volume of PCM but a different number of cavities are compared. The case of ten fins with five PCM cavities is preferred because it permit a reduction of 21 per cent of the junction temperature with an enhancement ratio of 2:4. The performance of this case under different power input is verified. Originality/value The use of alternate air-PCM cavities of the heat sink. The use of PCM in LED to delay the peak temperature in the case of thermal shock (for example, damage of fan) An amount of energy is stored in the LED and it is evacuated to the ambient of the accommodation by the cycle of charging and discharging established (1,765 Joule stored and released each 13 min with 1 LED chip of 5 W).
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