Predictive modelling of heat and mass transfer in hamburger patties

This study concerns fundamental analysis and predictive modelling of heat and mass transfer in frozen hamburger patties cooked in a double-sided contact fryer. Mathematical and physical models are formulated and further developed to enable improved understanding of the transport processes and reveal the influence of essential parameters. Prediction and analysis of practical situations with heating are investigated. The coupled governing partial differential equations are solved by a finite difference technique. In particular, the boundary conditions are treated carefully. The mathematical and physical models, the governing equations and the boundary conditions are presented in detail and special care is taken in the frozen region. The numerical method is briefly described. Results from a few simulations are reported. Parametric studies were carried out by changing the contact heat transfer coefficient, effective thermal conductivity for the core, effective specific heat in the core, the initial freezing temperature, diffusion coefficient and the mass fraction of ice. The calculated cooking time was found to be most influenced by the effective thermal conductivity and effective specific heat. in the core and the heat transfer coefficient, in descending order of importanc

Maternal use of thyroid hormones in pregnancy and neonatal outcome

Objective. To describe neonatal outcome including the presence of congenital malformations in infants born to women substituted with thyroid hormones, and the maternal characteristics of these women. Design. Register study based on prospectively collected data in relation to delivery. Setting. Swedish Health Registers. Population. All pregnant women (n = 848,468) and all infants born (n = 861,989) in Sweden from 1 July 1995 to 31 December 2004. Methods. Women who reported the use of thyroid hormones in early pregnancy or obtained a prescription for thyroid hormones later in pregnancy (n = 9,866), as well as their infants (n = 10,055) were identified from the Swedish Medical Birth Register. The reference population consisted of all women giving birth and their offspring during the same time interval. Main outcome measures. Neonatal outcome, malformations and maternal characteristics. Data were analyzed with adjustments for identified confounders. Results. Women using thyroxine had an increased rate of pre-eclampsia, diabetes (pre-existing or gestational), cesarean sections and inductions of labour compared to women in the reference population. The risk for preterm birth was marginally increased (OR 1.13, 95% CI 1.03-1.25). Neonatal thyroid disease was found in eight infants (seven with thyreotoxicosis and one unspecified), the expected number was 0.2. No further anomalies in neonatal diagnoses were found. A small but statistically significant risk for congenital malformations (OR = 1.14, 95% CI 1.05-1.26) was found. Conclusion. Women on thyroid substitution during pregnancy had an increased risk for some pregnancy complications, but their infants were only slightly affected