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Biomedical subjects

J Langenberg

Publications and source records attributed to J Langenberg.

4 recordsLinked to original sources
PubMed2003

Standing waves in flow between finite counterrotating cylinders.

Experimental evidence for standing waves resulting from a supercritical Hopf bifurcation that appears as the first pattern-forming instability in counterrotating Taylor-Couette flow is presented. Depending on the aspect ratio two different types of standing waves, denoted as SW0 and SW(pi), could be observed. Both modes have an azimuthal wave number m=1 but differ in symmetry. While for SW(pi), a spatiotemporal glide-reflection symmetry could be found, SW0 is purely spatial reflection symmetric. The transition between the two modes is found to be organized in a cusp bifurcation unfolded by variations of the aspect ratio. The "classical" spiral vortex flow appears in this control parameter regime only as a result of a secondary steady bifurcation from SW0. This transition is found to be either subcritical or supercritical. The experimentally observed bifurcation structure has been predicted by theory of Hopf bifurcation to spiral vortex flow in finite counterrotating Taylor-Couette systems.

Journal Article↗
PubMed1994

Clinical nutrition of exotic pets.

Successful nutritional management requires knowledge of the natural history of exotic pets, nutrient contents of foods, and roles of water, calories, and nutrients in optimal health. Unestablished dietary requirements, lack of balanced commercial diets and mismanagement by owners cause nutritional problems that affect health and recovery from illness and trauma. When presented with a sick exotic pet, veterinarians should check for provision of appropriate wholesome water and food in optimal amounts. Malnutrition and dehydration are common in exotic pets and often result from mismanagement. Starvation is common in carnivores eating whole vertebrate prey, whereas specific nutrient deficiencies are more common in herbivores and insectivores. The more common nutritional deficiencies are calcium and vitamin D3, vitamin A, thiamin, and vitamin E. When treating sick exotic pets, nutrition and fluid support may be critical to recovery.

Animal Nutritional Physiological Phenomena↗
PubMed1993

Vitamin E in cranes: reference ranges and nutrient interactions.

Fat soluble vitamins E and A (quantified as alpha-tocopherol and all-trans retinol, respectively) were measured in plasma samples from 274 captive cranes from four institutions and five free-ranging birds. Ages ranged from 4 mo to 80 yr, and all 15 crane species were represented. Captive cranes had a mean +/- standard error (SE) of 6.57 +/- 0.82 micrograms/ml alpha-tocopherol; migrating greater sandhill cranes (Grus canadenis tabida) had a plasma concentration of 3.71 +/- 0.22 micrograms/ml. Sex and age differences were not significant, but crane species that evolved in temperate habitats had higher circulating levels of alpha-tocopherol than tropical or subtropical species. Mean +/- SE retinol values were 0.69 +/- 0.05 micrograms/ml in captive cranes, and 0.66 +/- 0.08 micrograms/ml in free-ranging cranes; values did not differ significantly by sex, age, or species. Dietary vitamin E concentrations were significantly correlated with plasma alpha-tocopherol levels in a logarithmic relationship. Dietary selenium at 0.5 mg/kg was associated with decreased circulating alpha-tocopherol concentrations.

Animals↗