Life safety assessment in multi-storey building fires

Life safety is one of the most important objectives of Performance Based Fire-Design and is commonly considered to be achieved if building occupants escape the effects of the fire unharmed. Numerical simulations are often used to predict fire dynamics and factors affecting the evacuation capabilities of occupants. The main scope of this research is to assess life safety in a multi-storey building fire. Statistics based fire risk assessment is used to choose the scenario to be simulated taking into consideration the damage severity and likelihood of occurrence. In the fire simulations, particular attention is given to the fuel modelling to consider the toxicity of combustion products and thus, its effects on the building occupants. Fire simulations results are then integrated with evacuation simulations. The fire risk assessment and fire/evacuation simulations are performed for a multi-storey hotel building located in Lecce, Italy

Chemical chaperone treatment reduces intracellular accumulation of mutant collagen IV and ameliorates the cellular phenotype of a COL4A2 mutation that causes haemorrhagic stroke

Haemorrhagic stroke accounts for approximately 20% of stroke cases and porencephaly is a clinical consequence of perinatal cerebral haemorrhaging. Here we report the identification of a novel dominant G702D mutation in the collagen domain of COL4A2 (collagen IV alpha chain 2) in a family displaying porencephaly with reduced penetrance. COL4A2 is the obligatory protein partner of COL4A1 but in contrast to most COL4A1 mutations, the COL4A2 mutation does not lead to eye or kidney disease. Analysis of dermal biopsies from patient and his unaffected father, who also carries the mutation, revealed that both display basement membrane (BM) defects. Intriguingly, defective collagen IV incorporation into the dermal BM was only observed in the patient and was associated with endoplasmic reticulum (ER) retention of COL4A2 in primary dermal fibroblasts. This intracellular accumulation led to ER-stress, unfolded protein response activation, reduced cell proliferation and increased apoptosis. Interestingly, absence of ER retention of COL4A2 and ER-stress in cells from the unaffected father indicate that accumulation and/or clearance of mutant COL4A2 from the ER may be a critical modifier for disease development. Our analysis also revealed that mutant collagen IV is degraded via the proteasome. Importantly, treatment of patient cells with a chemical chaperone decreased intracellular COL4A2, ER-stress and apoptosis, demonstrating that reducing intracellular collagen accumulation can ameliorate the cellular phenotype of COL4A2 mutations. Importantly, these data highlight that manipulation of chaperone levels, intracellular collagen accumulation and ER-stress are potential therapeutic options for collagen IV diseases including haemorrhagic stroke

Hox10 Genes Function in Kidney Development in the Differentiation and Integration of the Cortical Stroma

Organogenesis requires the differentiation and integration of distinct populations of cells to form a functional organ. In the kidney, reciprocal interactions between the ureter and the nephrogenic mesenchyme are required for organ formation. Additionally, the differentiation and integration of stromal cells are also necessary for the proper development of this organ. Much remains to be understood regarding the origin of cortical stromal cells and the pathways involved in their formation and function. By generating triple mutants in the Hox10 paralogous group genes, we demonstrate that Hox10 genes play a critical role in the developing kidney. Careful examination of control kidneys show that Foxd1-expressing stromal precursor cells are first observed in a cap-like pattern anterior to the metanephric mesenchyme and these cells subsequently integrate posteriorly into the kidney periphery as development proceeds. While the initial cap-like pattern of Foxd1-expressing cortical stromal cells is unaffected in Hox10 mutants, these cells fail to become properly integrated into the kidney, and do not differentiate to form the kidney capsule. Consistent with loss of cortical stromal cell function, Hox10 mutant kidneys display reduced and aberrant ureter branching, decreased nephrogenesis. These data therefore provide critical novel insights into the cellular and genetic mechanisms governing cortical cell development during kidney organogenesis. These results, combined with previous evidence demonstrating that Hox11 genes are necessary for patterning the metanephric mesenchyme, support a model whereby distinct populations in the nephrogenic cord are regulated by unique Hox codes, and that differential Hox function along the AP axis of the nephrogenic cord is critical for the differentiation and integration of these cell types during kidney organogenesis

Pyrolysis Model for Predicting the Heat Release Rate of Birch Wood

The numerical modeling of solid pyrolysis for fire simulations consists of three stages: specifying the reaction scheme and physical models, estimating the kinetic and thermal parameters from experimental data, and then solving the system using a computer. The interpretation of the experimental input parameters must be verified by reproducing the experimental conditions with the same model for which the parameters are being sought. In this work, the performance of three previously proposed reaction schemes of wood pyrolysis in reproducing thermogravimetric experiments of birch wood was evaluated, and the remaining model parameters from small and bench scale calorimetric experiments were determined. The predictive capability was tested by cone calorimeter experiments at different heat fluxes. The results indicate that the first-order single-step reaction scheme can provide equally good predictions for the heat release rate as the more complex schemes. The source of the thermal parameters-direct measurement or inverse modeling-did not have a great influence on the predictive capability.Peer reviewe

Predictive Computational Fluid Dynamics Simulation of Fire Spread on Wood Cribs

Presently, there is a need for a robust numerical simulation approach to investigate the influence of various parameters on fire spread in large open framed structures. CFD-based methods can already be used for analyzing the fire conditions but they are difficult to apply for large calculations where the geometrical details of the fuel are sub-grid scale. In this paper we present a CFD-based fire spread simulation method that makes use of the ignition temperature model for pyrolysis and introduce a correction for the mesh dependency of the fuel surface area. Wood sticks, with an ignition temperature of 300°C and a specified heat release rate per unit area of 260 kW/m 2 , were used as fire load. The method was validated using laboratory scale tunnel (10 m×0.6 m×0.396 m) fire tests with a longitudinal velocity of 0.6 m/s, demonstrating a 3% bias for the peak heat release rates and less than 33% biases for the fire growth rate. The method was then applied to room-scale fire spread simulations with uniformly distributed wood cribs at 600MJ/m2. The results show that, with the help of the surface area correction, the fine-mesh predictions of the heat release rate and thermal environment can be reproduced with coarser meshes and one order of magnitude lower computational costs. Due to the inherent inability of the large-scale CFD to resolve the flame temperature, there is a minimum size of the initial, prescribed fire area which is required for consistent fire spread predictions. Through this study, the authors attempt to build a reliable CFD modelling approach for fire spread and traveling fires.Peer reviewe

MODELING THE THERMAL RADIATION PENETRATION INTO THE LIQUID FUELS FOR FIRE SIMULATIONS

Funding Information: The authors greatly acknowledge the support of the Academy of Finland under grant no. 314487 and the Finnish Fire Protection Fund (Palosuojelurahasto). Publisher Copyright: © 2023 Begell House Inc.. All rights reserved.In-depth radiation absorption is one of the main mechanisms for liquid fuels evaporation in fires. The common approach in modeling of thermal radiation for liquids is applying the constant absorption coefficient (i.e., gray method) in solving the radiative transfer equation (RTE) and same reflectivity values at different sides of the interfaces. This approach neglects the spectral nature of the absorption coefficient and redistribution of the penetrated thermal radiation at the interfaces. To consider the spectral nature, we previously presented a novel gray modeling that accounts the absorption spectra. This physics-based gray method applies different values for the absorption coefficient based on the flame temperature and depth from the sample surface. For the interface effect, equivalent reflectivity is introduced at different sides of the interface applying the Fresnel relation. The new method was implemented into Fire Dynamics Simulator (FDS) that is an open-source CFD software for fire-driven flows. Simulations were done using 1040 cores on a supercomputer applying around 5.8 million grids for a 10×7×5 m3 room with two sizes of the heptane pools. Results showed that new approach could predict the measured burning rates for heptane pools. At the initial stage of the burning, the common approach underestimates the burning rate, while at the last stage it overestimates the burning rate compared to the new approach. The new approach brings the detailed radiation physics into the account and solves the issue of applying unrealistic values for the absorption coefficient and reflectivity in fire simulations.Peer reviewe