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- Olsen, Martin, 1971-
(author)
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Nanomechanics – Quantum Size Effects, Contacts, and Triboelectricity
- 2019
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Doctoral thesis (other academic/artistic)abstract
- Nanomechanics is different from the mechanics that we experience in everyday life. At the nano-scale, typically defined as 1 to 100 nanometers, some phenomena are of crucial importance, while the same phenomena can be completely neglected on a larger scale. For example, the feet of a gekko are covered by nanocontacts that yield such high adhesion forces that the animal can run up on walls and even on the ceiling. At small enough distances, matter and energy become discrete, and the description of the phenomena occurring at this scale requires quantum mechanics. However, at room temperature the transitions between quantized energy levels may be concealed by the thermal vibrations of the system. As two surfaces approach each other and come into contact, electrostatic forces and van der Waals forces may cause redistribution of matter at the nano level. One effect that may occur upon contact between two surfaces is the triboelectric effect, in which charge is transferred from one surface to the other.This effect can be used to generate electricity in triboelectric nanogenerators (TENGs), where two surfaces are repeatedly brought in and out of contact, and where the charge transfer is turned into electrical energy.This thesis concerns nanomechanics addressing whether quantum mechanics play a role in elastic deformation, as well as various mechanical aspects of nanocontacts including electric charging. The objectives are to contribute to the understanding when quantum effects are of importance at the nanolevel, increase the fundamental understanding of the mechanisms responsible for triboelectric phenomena and apply the triboelectric effect to a wind harvesting device.For more insight into whether quantum effects are of importance in nanomechanics, we use a one dimensional jellium model and the standard beam theory allowing the spring constant of an oscillating nanowire cantilever to be calculated. As the nanowire bends, more electron states fit in its cross section, giving rise to an amplitude dependent resonance frequency of the nanowire oscillations.Furthermore, a model for electric field induced surface diffusion of adatoms was developed. The model takes electrostatic forces and van der Waals forces into account as a voltage is applied between a scanning tunneling microscope tip and a sample. The calculated force on the adatoms at the surface of the sample, which is stemming from the inhomogeneous electric field and the dipole moment of the adatoms, is relatively small, but due to thermal vibrations adatoms diffuse and form mounds at the sample.When bringing two different materials into contact, the difference in triboelectric potentials between the materials results in electric charging. To increase the understanding of triboelectricity, a two-level Schottky model, assuming ion transfer, was developed to describe the temperature dependence of the triboelectric effect for a TENG. The two levels correspond to the binding energy for ions on the two surfaces that are brought into contact, where the difference in binding energy enters the Boltzmanndistribution. The model describes the decreasing triboelectric effect in TENG:s with increasing temperature as described in the literature, and results in a separation energy, which is of the right order of magnitude for physically adsorbed atoms.It was recently demonstrated that TENGs can convert wind energy into electrical energy. Here, a TENG based on a plastic film fluttering between two copper electrodes was constructed. It was found that the frequency of the the fluttering film increases linearly with the wind speed. TENG:s designed in this way generate electricity already at low wind speed, and we therefore expect such TENG:s to be useful both as generators and speed sensors in the future.While quantum mechanics is of importance in a limited number of nanomechanical systems, nanocontacts have a broader meaning, and are crucial for the understanding of triboelectric phenomena. We anticipate that the findings in this thesis will contribute to a better understanding of nanomechanics, in particular the mechanism of triboelectricity.
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| 2. |
- Jönsson, Maria, 1961-
(author)
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A Gill Filament EROD Assay : Development and Application in Environmental Monitoring
- 2003
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Doctoral thesis (other academic/artistic)abstract
- A gill filament-based assay for the cytochrome P450 1A (CYP1A)-catalysed activity ethoxyresorufin O-deethylase (EROD) was developed in rainbow trout (Oncorhynchus mykiss) and applied to Atlantic salmon (Salmo salar), Arctic charr (Salvelinus alpinus), Atlantic cod (Gadus morhua), saithe (Pollachius virens), and spotted wolffish (Anarhichas minor). Exposure to waterborne β-naphthoflavone (βNF; 10-6 M) induced branchial EROD activity in all species but the spotted wolffish. In rainbow trout exposed to low concentrations of benzo[a]pyrene (BaP; 10-9 M) and the textile dye indigo (10-8 M) the gills responded more rapidly than the liver to BaP, and indigo induced branchial but not hepatic EROD activity.A CYP1A-dependent BaP adduct formation was shown in gills of fish exposed to waterborne 3H-BaP, i.e. the adduct formation was enhanced by βNF and blocked by ellipticine (CYP1A inhibitor). The predominant location for BaP adducts was the secondary lamellae (most exposed part of the gill filament), whereas the CYP1A enzyme was also present in the primary lamellae of the gill filament. Hence, in addition to the cell-specific expression of CYP1A an important determinant for the localisation of adducts seemed to be the bioavailability of BaP. This idea is supported by the fact that the CYP1A enzyme was induced only in secondary lamellae by BaP (10-7 M) and indigo (10-6 M), whereas it was induced in both primary and secondary lamellae by 3,3´,4,4´,5-pentachlorobiphenyl (10-8 M). Apparently, readily metabolised inducers (BaP and indigo) are biotransformed in the secondary lamellae.My results show that gill filament EROD activity is a sensitive biomarker of exposure to waterborne dioxin-like pollutants, and that the assay has potential for use in monitoring. Furthermore, the results suggest that readily metabolised dioxin-like compounds absorbed via the gills may undergo first-pass metabolism in the gill cells and therefore remain undetected by monitoring of EROD activity in the liver.
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| 3. |
- Olsén, K. Håkan, 1952-, et al.
(author)
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Crucian carp (Carassius carassius (L.)), an anonymous fish with great skills
- 2023
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In: Ichthyological Research. - : Springer. - 1341-8998 .- 1616-3915. ; 70, s. 313-331
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Research review (peer-reviewed)abstract
- The crucian carp (Carassius carassius) is a cyprinid fish with its natural distribution in Europe and the western part of Asia. Due to its hardiness and unique ability to survive winter anoxia, it has been translocated to small lakes and ponds, and in Northern Europe since medieval times has been used as a food source. Crucian carp was the only fish in the pond that survived anoxia. Small lakes and ponds with winter anoxia result in dense populations of stunted and slender fish. In lakes with other fish species present, the crucians' numbers and densities are low and they grow to large sizes. In the presence of piscivores such as pike, crucians are deep bodied. The presence of pike-eating crucians, or the pike odors, induce a change in the body form of crucians. The change in body form makes it more difficult for pikes to swallow crucians and the handling time increases. Closely related invasive Carassius species have become a serious threat to crucian carp populations in Central-Eastern Europe and South-Eastern England through competition for space and food resources and hybridization. The crucian carp's close relationship to goldfish (Carassius auratus), the most studied species concerning sex pheromones, has made it possible to demonstrate that sex pheromones are also present in a wild Carassius species and in their natural environment. The results indicate that two species use the same sex hormonal pheromone system. The crucian carp has become an important model for laboratory studies of olfaction and taste.
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