| 1. |
- Frøbert, Anne Mette, et al.
(författare)
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Differential Changes in Circulating Steroid Hormones in Hibernating Brown Bears : Preliminary Conclusions and Caveats
- 2022
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Ingår i: Physiological and Biochemical Zoology. - : University of Chicago Press. - 1522-2152 .- 1537-5293. ; 95:5, s. 365-378
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Tidskriftsartikel (refereegranskat)abstract
- Brown bears are obese when they enter the den, and after 6 mo of hibernation and physical inactivity, bears show none of the adverse consequences of a sedentary lifestyle in humans, such as cardiovascular disease, type 2 diabetes, and kidney failure. The metabolic mechanisms that drive hibernation physiology in bears are poorly defined, but systemic endocrine regulators are likely involved. To investigate the potential role of steroid hormones, we quantified the total levels of 12 steroid hormones, the precursor cholesterol, sex hormone-binding globulin (SHBG), and corticosterone-binding globulin (CBG) in paired serum samples from subadult free-ranging Scandinavian brown bears during the active and hibernation states. During hibernation, androstenedione and testosterone were significantly decreased in subadult female bears (n=13), whereas they increased in all males but one (n=6) and therefore did not reach a significant difference. Despite this difference, SHBG increased more than 20-fold during hibernation for all bears. Compared with SHBG concentrations in humans, bear levels were very low in the active state, but during hibernation, levels equaled high levels in humans. The increased SHBG levels likely maintain a state of relative quiescence of the reproductive hormones in hibernating bears. Interestingly, the combination of SHBG and testosterone levels results in similar free bioavailable testosterone levels of 70-80 pM in both subadult and adult sexually active male bears, suggesting a role for SHBG in controlling androgen action during hibernation in males. Dehydroepiandrosterone sulfate, dihydrotestosterone, and estradiol levels were below the detection limit in all but one animal. The metabolically active glucocorticoids were significantly higher in both sexes during hibernation, whereas the inactive metabolite cortisone was reduced and CBG was low approaching the detection limit. A potential caveat is that the glucocorticoid levels might be affected by the ketamine applied in the anesthetic mixture for hibernating bears. However, increased hibernating cortisol levels have consistently been reported in both black bears and brown bears. Thus, we suggest that high glucocorticoid activity may support the hibernation state, likely serving to promote lipolysis and gluconeogenesis while limiting tissue glucose uptake to maintain a continuous glucose supply to the brain.
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| 2. |
- Fundana, Ketut, et al.
(författare)
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Variational Segmentation of Image Sequences Using Region-Based Active Contours and Deformable Shape Priors
- 2008
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Ingår i: International Journal of Computer Vision. - : Kluwer Academic Publishers. - 0920-5691 .- 1573-1405. ; 80:3, s. 289-299
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we address the problem of segmentation in image sequences using region-based active contours and level set methods. We propose a novel method for variational segmentation of image sequences containing nonrigid, moving objects. The method is based on the classical Chan-Vese model augmented with a novel frame-to-frame interaction term, which allow us to update the segmentation result from one image frame to the next using the previous segmentation result as a shape prior. The interaction term is constructed to be pose-invariant and to allow moderate deformations in shape. It is expected to handle the appearance of occlusions which otherwise can make segmentation fail. The performance of the model is illustrated with experiments on synthetic and real image sequences.
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| 3. |
- Gummeson, Anna, et al.
(författare)
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Automatic Gleason grading of H&E stained microscopic prostate images using deep convolutional neural networks
- 2017
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Ingår i: Medical Imaging 2017: Digital Pathology. - : SPIE. - 9781510607255 ; 10140
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Konferensbidrag (refereegranskat)abstract
- Prostate cancer is the most diagnosed cancer in men. The diagnosis is confirmed by pathologists based on ocular inspection of prostate biopsies in order to classify them according to Gleason score. The main goal of this paper is to automate the classification using convolutional neural networks (CNNs). The introduction of CNNs has broadened the field of pattern recognition. It replaces the classical way of designing and extracting hand-made features used for classification with the substantially different strategy of letting the computer itself decide which features are of importance. For automated prostate cancer classification into the classes: Benign, Gleason grade 3, 4 and 5 we propose a CNN with small convolutional filters that has been trained from scratch using stochastic gradient descent with momentum. The input consists of microscopic images of haematoxylin and eosin stained tissue, the output is a coarse segmentation into regions of the four different classes. The dataset used consists of 213 images, each considered to be of one class only. Using four-fold cross-validation we obtained an error rate of 7.3%, which is significantly better than previous state of the art using the same dataset. Although the dataset was rather small, good results were obtained. From this we conclude that CNN is a promising method for this problem. Future work includes obtaining a larger dataset, which potentially could diminish the error margin.
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| 4. |
- Masic, Alma, et al.
(författare)
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Determination of the oxygen profile in a nitrifying Moving Bed Biofilm Reactor by microelectrodes and a mathematical model
- 2009
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we determine the oxygen profile in a biofilm on suspended carriers in two ways: firstly by microelectrode measurements and secondly by a simple mathematical model. The Moving Bed Biofilm Reactor is well-established for wastewater treatment where bacteria grow as a biofilm on the protective surfaces of suspended carriers. The flat shaped BiofilmChipTM P was developed to allow good conditions for transport of substrates into the biofilm. Firstly, the oxygen profile was measured in situ the nitrifying biofilm with a microelectrode and secondly, the profile was simulated with a one-dimensional mathematical model. We refined a classical model by adding a dynamical tank equation, to connect the tank to the biofilm through the boundary conditions. This proved to be an important key in achieving relevant simulations. We also estimated the erosion parameter λ to increase the concordance between the measured and simulated profiles. Promising results have been obtained from our mathematical model. The accordance improved when simulating profiles without the boundary layer. Microelectrode measurements are a valuable tool in design of new suspended carriers.
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| 5. |
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| 6. |
- Preger, Calle, et al.
(författare)
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Predicting the deposition spot radius and the nanoparticle concentration distribution in an electrostatic precipitator
- 2020
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 54:6, s. 718-728
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of aerosol nanoparticles using an electrostatic precipitator is widely used in the aerosol community. Despite this, basic knowledge regarding what governs the deposition has been missing. This concerns the prediction of the size of the particle collection zone, but also, perhaps more importantly, prediction of the nanoparticle concentration distribution on the substrate, both of which are necessary to achieve faster and more precise deposition. In this article, we have used COMSOL Multiphysics simulations, experimental depositions, and two analytical models to describe the deposition. Based on that, we propose a simple equation that can be used to predict the size of the deposition spot as well as the particle concentration on the substrate. The equation we derive concludes that the size of the deposition spot only depends on the gas flow rate into the precipitator, and on the constant drift velocity of a particle in an electric field. The equation also displays that the deposited particle concentration is independent of the gas flow rate. Our general mathematical analysis has great applicability, as it can be used to model different geometries and different types of deposition methods than the one described in this article. We can therefore also propose that the drift velocity in this model easily could be replaced by another velocity acting on the particles at other deposition conditions, for instance, the thermophoretic velocity during thermophoretic deposition. This would result in the same dependence as presented in this article. Finally, we demonstrate analytically and through experiment that the particle distribution inside the spot will be homogenous and follows a top hat profile.
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