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1.
  • Advances in Thermal Imaging
  • 2021
  • Ingår i: Journal of Thermal Biology. - : Elsevier. - 0306-4565.
  • Annan publikation (refereegranskat)abstract
    • Thermal imaging, or more correctly infrared thermography, has been widely applied to studies of animal and human biology (see Burnay et al. 1988; McCafferty 2007; Soerensen and Pedersen 2015; Fernandez-Cuevas et al., 2015; Tattersall 2016). This technique provides non-contact measurement of surface temperature, allowing real-time recording of the spatial temperature distribution of a body region, physical structure or habitat of interest. Thermal imaging technology has advanced rapidly in the last decade and is now becoming a key tool in thermal biology. Technological advances include greater spatial and temporal resolution, increased capacity to record and store high resolution radiometric video, as well as reduced device size and portability. In addition, high-quality thermal imaging devices are quickly becoming more affordable, meaning thermal imaging is an increasingly common item of the research tool-kit in many pure and applied fields. The aim of this Special Issue was to highlight how advances in thermal imaging can be used to answer important questions in biology, and to demonstrate how the combination of this technology with novel analytical methods can further advance our conceptual understanding of thermal biology.
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2.
  • Lewden, Agnès, et al. (författare)
  • Body temperature responses to handling stress in wintering Black-capped Chickadees (Poecile atricapillus L.)
  • 2017
  • Ingår i: Physiology & Behavior. - : Elsevier. - 1873-507X. ; 179, s. 49-54
  • Tidskriftsartikel (refereegranskat)abstract
    • Body temperature variation in response to acute stress is typically characterized by peripheral vasoconstriction and a concomitant increase in core body temperature (stress-induced hyperthermia). It is poorly understood how this response differs between species and within individuals of the same species, and how it is affected by the environment. We therefore investigated stress-induced body temperature changes in a non-model species, the Black-capped Chickadee, in two environmental conditions: outdoors in low ambient temperature (mean: − 6.6 °C), and indoors, in milder ambient temperature close to thermoneutrality (mean: 18.7 °C). Our results show that the change in body temperature in response to the same handling stressor differs in these conditions. In cold environments, we noted a significant decrease in core body temperature (− 2.9 °C), whereas the response in mild indoor conditions was weak and non-significant (− 0.6 °C). Heat loss in outdoor birds was exacerbated when birds were handled for longer time. This may highlight the role of behavioral thermoregulation and heat substitution from activity to body temperature maintenance in harsh condition. Importantly, our work also indicates that changes in the physical properties of the bird during handling (conductive cooling from cold hands, decreased insulation from compression of plumage and prevention of ptiloerection) may have large consequences for thermoregulation. This might explain why females, the smaller sex, lost more heat than males in the experiment. Because physiological and physical changes during handling may carry over to affect predation risk and maintenance of energy balance during short winter days, we advice caution when designing experimental protocols entailing prolonged handling of small birds in cold conditions.
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3.
  • Evenäs, Johan, et al. (författare)
  • NMR studies of the E140Q mutant of the carboxy-terminal domain of calmodulin reveal global conformational exchange in the Ca2+-saturated state
  • 1997
  • Ingår i: Biochemistry. - : The American Chemical Society (ACS). - 0006-2960. ; 36:12, s. 3448-3457
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present investigation, the Ca2+ activation of the C-terminal domain of bovine calmodulin and the effects of replacing the bidentate Ca2+-coordinating glutamic acid residue in the 12th and last position of loop IV with a glutamine are studied by NMR spectroscopy. The mutation E140Q results in sequential Ca2+ binding in this domain and has far-reaching effects on the structure of (Ca2+)2 TR2C, thereby providing further evidence for the critical role of this glutamic acid residue for the Ca2+- induced conformational change of regulatory EF-hand proteins. Analyses of the NOESY spectra of the mutant under Ca2+-saturated conditions, such that 97% of the protein is in the (Ca2+)2 form, revealed two sets of mutually exclusive NOEs. One set of NOEs is found to be consistent with the closed structure observed in the apo state of the C-terminal domain of the wild- type protein, while the other set supports the open structure observed in the Ca2+-saturated state. In addition, several residues in the hydrophobic core exhibit broadened resonances. We conclude that the (Ca2+)2 form of the mutant experiences a global conformational exchange between states similar to the closed and open conformations of the C-terminal domain of wild-type calmodulin. A population of 65 ± 15% of the open conformation and an exchange rate of (1-7) x 104 s-1 were estimated from the NMR data and the chemical shifts of the wild-type protein. From a Ca2- titration of the 15N-labeled mutant, the macroscopic binding constants (log(K1) = 4.9 ± 0.3 and log(K2) = 3.15 ± 0.10] and the inherent chemical shifts of the intermediate (Ca2+)1 form of the mutant were determined using NMR. Valuable information was also provided on the mechanism of the Ca2+ activation and the roles of the structural elements in the two Ca2+- binding events. Comparison with the wild-type protein indicates that the (Ca2+)1 conformation of the mutant is essentially closed but that some rearrangement of the empty loop IV toward the Ca2+-bound form has occurred.
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4.
  • Gagnon, Yakir, et al. (författare)
  • Adjusting a light dispersion model to fit measurements from vertebrate ocular media as well as ray-tracing in fish lenses.
  • 2010
  • Ingår i: Vision Research. - : Elsevier. - 1878-5646. ; 50:9, s. 850-853
  • Tidskriftsartikel (refereegranskat)abstract
    • Color dispersion, i.e., the dependency of refractive index of any transparent material on the wavelength of light, has important consequences for the function of optical instruments and animal eyes. Using a multi-objective goal attainment optimization algorithm, a dispersion model was successfully fitted to measured refractive indices of various ocular media and the longitudinal chromatic aberration determined by laser-scanning in the crystalline lens of the African cichlid fish, Astatotilapia burtoni. The model describes the effects of color dispersion in fish lenses and may be applicable to the eyes of other vertebrates as well.
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5.
  • Gagnon, Yakir, et al. (författare)
  • Effects of the peripheral layers on the optical properties of spherical fish lenses
  • 2008
  • Ingår i: Journal of the Optical Society of America A. - : Optical Society of America. - 1084-7529. ; 25:10, s. 2468-2475
  • Tidskriftsartikel (refereegranskat)abstract
    • We created a computational optical model of spherical fish lenses that takes into account the effects of the peripheral layers that differ in cellular composition from the bulk of the lens. A constant refractive index, except for the lens capsule, in the outer about 6 % of lens radius made it possible to uniquely infer the refractive index gradient in more central layers from a known or desired longitudinal spherical aberration curve using the inverse Abel transform. Since the zone of constant refractive index is wider than necessary to make the solution unique and for optimal optical performance of the lens, we propose that its width is set by the metabolic needs of the lens.
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6.
  • Gagnon, Yakir, et al. (författare)
  • Optical advantages and function of multifocal spherical fish lenses
  • 2012
  • Ingår i: Journal of the Optical Society of America A. - : Optical Society of America. - 1084-7529. ; 29:9, s. 1786-1793
  • Tidskriftsartikel (refereegranskat)abstract
    • The spherical crystalline lenses in the eyes of many fish species are well-suited models for studies on how natural selection has influenced the evolution of the optical system. Many of these lenses exhibit multiple focal lengths when illuminated with monochromatic light. Similar multifocality is present in a majority of vertebrate eyes, and it is assumed to compensate for the defocusing effect of longitudinal chromatic aberration. In order to identify potential optical advantages of multifocal lenses, we studied their information transfer capacity by computer modeling. We investigated four lens types: the lens of Astatotilapia burtoni, an African cichlid fish species, an equivalent monofocal lens, and two artificial multifocal lenses. These lenses were combined with three detector arrays of different spectral properties: the cone photoreceptor system of A. burtoni and two artificial arrays. The optical properties compared between the lenses were longitudinal spherical aberration curves, point spread functions, modulation transfer functions, and imaging characteristics. The multifocal lenses had a better balance between spatial and spectral information than the monofocal lenses. Additionally, the lens and detector array had to be matched to each other for optimal function. (C) 2012 Optical Society of America
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7.
  • Kauffman, S, et al. (författare)
  • Genetic networks with canalyzing Boolean rules are always stable
  • 2004
  • Ingår i: Proceedings of the National Academy of Sciences. - : National Acad Sciences. - 1091-6490. ; 101:49, s. 17102-17107
  • Tidskriftsartikel (refereegranskat)abstract
    • We determine stability and attractor properties of random Boolean genetic network models with canalyzing rules for a variety of architectures. For all power law, exponential, and flat in-degree distributions, we find that the networks are dynamically stable. Furthermore, for architectures with few inputs per node, the dynamics of the networks is close to critical. In addition, the fraction of genes that are active decreases with the number of inputs per node. These results are based upon investigating ensembles of networks using analytical methods. Also, for different in-degree distributions, the numbers of fixed points and cycles are calculated, with results intuitively consistent with stability analysis; fewer inputs per node implies more cycles, and vice versa. There are hints that genetic networks acquire broader degree distributions with evolution, and hence our results indicate that for single cells, the dynamics should become more stable with evolution. However, such an effect is very likely compensated for by multicellular dynamics, because one expects less stability when interactions among cells are included. We verify this by simulations of a simple model for interactions among cells.
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8.
  • Kauffman, Stuart, et al. (författare)
  • Random Boolean network models and the yeast transcriptional network
  • 2003
  • Ingår i: Proceedings of the National Academy of Sciences. - : National Acad Sciences. - 1091-6490. ; 100:25, s. 14796-14799
  • Tidskriftsartikel (refereegranskat)abstract
    • The recently measured yeast transcriptional network is analyzed in terms of simplified Boolean network models, with the aim of determining feasible rule structures, given the requirement of stable solutions of the generated Boolean networks. We find that, for ensembles of generated models, those with canalyzing Boolean rules are remarkably stable, whereas those with random Boolean rules are only marginally stable. Furthermore, substantial parts of the generated networks are frozen, in the sense that they reach the same state, regardless of initial state. Thus, our ensemble approach suggests that the yeast network shows highly ordered dynamics.
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9.
  • KleinHeerenbrink, Marco, et al. (författare)
  • Wake analysis of drag components in gliding flight of a jackdaw (Corvus monedula) during moult
  • 2017
  • Ingår i: Interface Focus. - : Royal Society Publishing. - 2042-8898. ; 7:1
  • Tidskriftsartikel (refereegranskat)abstract
    • To maintain the quality of the feathers, birds regularly undergo moult. It is widely accepted that moult affects flight performance, but the specific aerodynamic consequences have received relatively little attention. Here we measured the components of aerodynamic drag from the wake behind a gliding jackdaw (Corvus monedula) at different stages of its natural wing moult. We found that span efficiency was reduced (lift induced drag increased) and the wing profile drag coefficient was increased. Both effects best correlated with the corresponding reduction in spanwise camber. The negative effects are partially mitigated by adjustments of wing posture to minimize gaps in the wing, and by weight loss to reduce wing loading. By studying the aerodynamic consequences of moult, we can refine our understanding of the emergence of various moulting strategies found among birds.
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10.
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