| 1. |
- Anoushirvani, B., et al.
(författare)
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Gamma-ray bursts from primordial quark objects in space
- 1997
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Ingår i: Proceedings of the Joint Meeting of the Networks 'The Fundamental Structure of Matter' and 'Tests of the Electroweak Symmetry Breaking', Ouranoupolis, Greece, May 1997.
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Konferensbidrag (refereegranskat)abstract
- We investigate the possibility that gamma-ray bursts originate in a concentric spherical shell with a given average redshift and find that this is indeed compatible with the data from the third BATSE (3B) catalog. It is also shown that there is enough freedom in the choice of unknown burst properties to allow even for extremely large distances to the majority of bursts. Therefore, we speculate about an early, and very energetic, origin of bursts, and suggest that they come from phase transitions in massive objects of pure quark matter, left over from the Big Bang.
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| 2. |
- Brändström, B. U. E., et al.
(författare)
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Results from the intercalibration of optical low-light calibration sources 2011
- 2012
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Ingår i: Geoscientific Instrumentation, Methods and Data Systems. - : European Geosciences Union (EGU). - 2193-0856 .- 2193-0864. ; 1, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Following the 38th Annual European Meeting on Atmospheric Studies by Optical Methods in Siuntio in Finland, an intercalibration workshop for optical low light calibration sources was held in Sodankylä, Finland. The main purpose of this workshop was to provide a comparable scale for absolute measurements of aurora and airglow. All sources brought to the intercalibration workshop were compared to the Fritz Peak reference source using the Lindau Calibration Photometer built by Wilhelm Barke and Hans Lauche in 1984. The results were compared to several earlier intercalibration workshops. It was found that most sources were fairly stable over time, with errors in the range of 5–25%. To further validate the results, two sources were also intercalibrated at UNIS, Longyearbyen, Svalbard. Preliminary analysis indicates agreement with the intercalibration in Sodankylä within about 15–25%.
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| 3. |
- Enström, Daniel, et al.
(författare)
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A Quark matter dominated universe
- 1998
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We present a new scenario for the development of the Universe after the Big Bang, built on the conjecture that a vast majority of the primordial quark matter did not undergo a phase transition to normal nuclear matter, but rather split up into massive quark objects that remained stable. Hence, such primordial quark matter would make up the so-called dark matter. We discuss, mostly in qualitative terms, the consequences for galaxy formation, the origin of normal matter, the occurrence of massive black-holes in galactic centres and the cosmic gamma-ray bursts.
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| 4. |
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| 5. |
- Fredriksson, Sverker, et al.
(författare)
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Is dark matter made up of massive quark objects?
- 1999
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Ingår i: Dark matter in astrophysics and particle physics 1998. - Bristol : IOP Publishing Ltd. - 0750306343 ; , s. 651-658
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Konferensbidrag (refereegranskat)abstract
- We suggest that dark matter is made up of massive quark objects that have survived from the Big Bang, representing the ground state of "baryonic'' matter. Hence, there was no overall phase transition of the original quark matter, but only a split-up into smaller objects. We speculate that normal hadronic matter comes about through enforced phase transitions when such objects merge or collide, which also gives rise to the cosmic gamma-ray bursts.
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| 6. |
- Hansson, T., et al.
(författare)
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High temperature fracture of a SiC whisker-reinforced alumina in air and vacuum
- 1994
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 13:5, s. 427-436
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Tidskriftsartikel (refereegranskat)abstract
- The fracture behaviour of a SiCw/alumina composite was studied between room temperature and 1320°C in vacuum by four-point bend testing of specimens pre-cracked by bridge indentation. The results are compared to those of earlier work on a similar material in air. In vacuum, the composite begins to exhibit stable crack growth (SCG) and increasing apparent toughness at about 1100°C. Between 1100 and 1320°C, the extent of SCG increases and the toughness rises to almost three times the room temperature fracture toughness. The toughness enhancement is due mainly to such processes as crack deflection, crack branching, microcrack zone formation and crack tip blunting rather than any temperature-related increase in intrinsic fracture resistance of the material. In air, the fracture processes are similar to those in vacuum but the toughness increase is delayed by about 100°C and the level of toughening is lower. These differences arise from the formation of a glass phase in air which delays microcrack formation but reduces the resistance to stable crack growth.
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| 7. |
- Huber, Johannes A. J., 1989-, et al.
(författare)
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A method for generating finite element models of wood boards from X-ray computed tomography scans
- 2022
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Ingår i: Computers & structures. - : Elsevier. - 0045-7949 .- 1879-2243. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- A method is presented for reconstructing the geometry, the pith, the knots and the local fibre orientations in timber boards, based on X-ray computed tomography scans. The local fibre deviations around knots were found by a new algorithm, based on image analysis. The experimental data comprised tomography scans, eigenfrequency measurements and four-point bending tests of 20 Norway spruce boards. 3D and 1D finite element models of the pure bending zone of the bending tests were created, accounting for the exact board geometry and the reconstructed fibre deviations. A purely density based, a purely eigenfrequency based, and a mixed constitutive law were compared. Model estimations showed a high coefficient of determination (R2) for global modulus of elasticity (MoE) (R2⩽0.93), local MoE (R2⩽0.87), bending strength (R2⩽0.83), and the location of initial failure. Constitutive laws accounting for eigenfrequency showed the most accurate results. In the future, adapting the method for logs could enable analyses of boards before sawing.
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| 8. |
- Nicolaidis, A., et al.
(författare)
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TeV neutrinos in a dense medium
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The dispersion relation of energetic (few TeV) neutrinos traversing a medium is studied. We use the real time formalism of thermal field theory and we include the effects from the propagator of the W gauge boson. We consider then the MSW oscillations for cosmic neutrinos traversing the Earth, adopting for the neutrino parameters values suggested by the LSND results. It is found that the $\nu_\mu$ flux, for neutrinos passing through the center of the Earth, will appear reduced by 15% for energies around 10 TeV.
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| 9. |
- Sellgren, Anders, et al.
(författare)
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Hydraulic hoisting : An economic alternative in the deepening of underground mines
- 1989
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Ingår i: Mining engineering. - 0026-5187. ; 41:8, s. 857-859
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to demonstrate the feasibility of hydraulic hoisting in hypothetical examples of mine deepening. Underground grinding to a maximum particle size of about 700 μm (about 25 mesh) is considered. The pumping of ground ore products with positive displacement plunger or membrane type of pumps at working pressures of up to 15 MPa (2200 psi) is a tested technique. The chief advantage of hydraulic hoisting is that the hoisting capacity can be increased at comparatively low total cost without necessitating the sinking of new shafts. Alternative examples include deepening of the existing mechanical hoisting system, truck, or conveyor belts transport in ramps to the present level.
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| 10. |
- Ström, Kristoffer, et al.
(författare)
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N1-methylnicotinamide is a signalling molecule produced in skeletal muscle coordinating energy metabolism
- 2018
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is a major health problem, and although caloric restriction and exercise are successful strategies to lose adipose tissue in obese individuals, a simultaneous decrease in skeletal muscle mass, negatively effects metabolism and muscle function. To deeper understand molecular events occurring in muscle during weight-loss, we measured the expressional change in human skeletal muscle following a combination of severe caloric restriction and exercise over 4 days in 15 Swedish men. Key metabolic genes were regulated after the intervention, indicating a shift from carbohydrate to fat metabolism. Nicotinamide N-methyltransferase (NNMT) was the most consistently upregulated gene following the energy-deficit exercise. Circulating levels of N1-methylnicotinamide (MNA), the product of NNMT activity, were doubled after the intervention. The fasting-fed state was an important determinant of plasma MNA levels, peaking at ~18 h of fasting and being lowest ~3 h after a meal. In culture, MNA was secreted by isolated human myotubes and stimulated lipolysis directly, with no effect on glucagon or insulin secretion. We propose that MNA is a novel myokine that enhances the utilization of energy stores in response to low muscle energy availability. Future research should focus on applying MNA as a biomarker to identify individuals with metabolic disturbances at an early stage.
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