Microstructural analysis of deformation-induced hypoxic damage in skeletal muscle

Deep pressure ulcers are caused by sustained mechanical loading and involve skeletal muscle tissue injury. The exact underlying mechanisms are unclear, and the prevalence is high. Our hypothesis is that the aetiology is dominated by cellular deformation (Bouten et al. in Ann Biomed Eng 29:153–63, 2001; Breuls et al. in Ann Biomed Eng 31:1357–364, 2003; Stekelenburg et al. in J App Physiol 100(6):1946–954, 2006) and deformation-induced ischaemia. The experimental observation that mechanical compression induced a pattern of interspersed healthy and dead cells in skeletal muscle (Stekelenburg et al. in J App Physiol 100(6):1946–954, 2006) strongly suggests to take into account the muscle microstructure in studying damage development. The present paper describes a computational model for deformation-induced hypoxic damage in skeletal muscle tissue. Dead cells stop consuming oxygen and are assumed to decrease in stiffness due to loss of structure. The questions addressed are if these two consequences of cell death influence the development of cell injury in the remaining cells. The results show that weakening of dead cells indeed affects the damage accumulation in other cells. Further, the fact that cells stop consuming oxygen after they have died, delays cell death of other cells

Intermediate species detection in a morpholine flame: contributions to fuel-bound nitrogen conversion from a model biofuel

Nau P, Seipel A, Lucassen A, Brockhinke A, Kohse-Höinghaus K. Intermediate species detection in a morpholine flame: contributions to fuel-bound nitrogen conversion from a model biofuel. EXPERIMENTS IN FLUIDS. 2010;49(4):761-773.A slightly fuel-rich (I broken vertical bar = 1.3) premixed laminar flat morpholine/oxygen/argon flame at 40 mbar was studied with cavity ring-down spectroscopy (CRDS). Morpholine as a secondary amine was considered as a prototypical nitrogenated biofuel. To contribute to the investigation of fuel-nitrogen conversion chemistry in this flame, absolute mole fraction profiles of CH, CN, and NH2 were determined. To our knowledge, this is the first study reporting quantitative mole fractions of these radicals from CRDS in a low-pressure flame of a model biofuel. The species profiles are discussed in combination with some relevant intermediates from molecular beam mass spectrometry, determined in this flame very recently (Lucassen et al., Proc Combust Inst 32(1):1269-1276, 2009). Some relative species profiles were also determined in flames of further amines to facilitate comparison. The results demonstrate that NH3- and HCN-related chemistry occurs in different regions of this flame. HCN production is considerable, and NO is found in the exhaust gases in percent-level concentrations. To monitor the combustion status, chemiluminescence is increasingly being applied as an intrinsic low-cost sensor. We believe to present the first chemiluminescence measurements in a flame of a prototypical nitrogenated biofuel, reporting relative emission intensities for five excited-state species. The shapes and maximum positions of the ground- and excited-state profiles show interesting differences, especially for the CN radical, which must be the consequence of different reaction pathways