| 1. |
- Adolfsson, Emelie, et al.
(författare)
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A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry
- 2014
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Ingår i: Radiotherapy and Oncology. - : Elsevier. - 0167-8140 .- 1879-0887. ; 113:2, s. 279-282
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this work was to develop and test a remote end-to-end audit system using lithium formate EPR dosimeters. Four clinics were included in a pilot study, absorbed doses determined in the PTV agreed with TPS calculated doses within ±5% for 3D-CRT and ±7% (k=1) for IMRT/VMAT dose plans.
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| 2. |
- Adolfsson, Emelie, et al.
(författare)
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Investigation of signal fading in lithium formate EPR dosimeters using a new sensitive method
- 2012
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Ingår i: Physics in Medicine and Biology. - : Institute of Physics (IOP). - 0031-9155 .- 1361-6560. ; 57:8, s. 2209-2217
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to investigate signal fading in lithium formate electron paramagnetic resonance (EPR) dosimeters used for clinical applications in radiotherapy. A new experimental method for determination of signal fading, designed to resolve small changes in signal from slowly decaying unstable radicals, was used. Possible signal fading in lithium formate due to different storage temperatures was also tested. Air humidity was kept at a constant level of 33% throughout the experiments. The conclusion drawn from the investigations was that the EPR signal from lithium formate is stable during at least 1 month after irradiation and is not sensitive to variations in storage temperature andlt;40 degrees C when kept at a relative air humidity of 33%. This makes lithium formate a suitable dosimeter for transfer dosimetry in clinical audits.
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| 3. |
- Adolfsson, Emelie, 1985-
(författare)
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Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Lithium formate has shown to be a material with properties suitable for electron paramagnetic resonance (EPR) dosimetry, among them up to 7 times higher sensitivity compared to alanine, which is a well-established EPR detector material for dose determinations in radiotherapy.The aim of this thesis was to further investigate the properties of lithium formate and develop the dosimetry system towards applications in radiotherapy. The intrinsic efficiency for energies of relevance to brachytherapy and the signal stability were investigated. The dosimetry system was expanded to include a smaller dosimeter model, suitable for measurements in dose gradient regions. An individual sensitivity correction method was applied to the smaller dosimeters to be able to perform dose determinations with the same precision as for the larger ones. EPR dosimetry in general is time consuming and effort was spent to optimize the signal readout procedure regarding measurement time and measurement precision.The system was applied in two clinical applications chosen for their high demands on the dosimetry system: 1) a dosimetry audit for external photon beam therapy and 2) dose verification measurements around a low energy HDR brachytherapy source.The conclusions drawn from this thesis were: dose determinations can be performed with a standard uncertainty of 1.8-2.5% using both the original size dosimeters and the new developed smaller ones. The dosimetry system is robust and useful for applications when high measurement precision and accuracy is prioritized. It is a good candidate for dosimetry audits, both in external beam therapy and brachytherapy.
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| 4. |
- Adolfsson, Emelie, et al.
(författare)
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Measurement of absorbed dose to water around an electronic brachytherapy source : Comparison of two dosimetry systems: lithium formate EPR dosimeters and radiochromic EBT2 film
- 2015
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Ingår i: Physics in Medicine and Biology. - : Institute of Physics Publishing (IOPP). - 0031-9155 .- 1361-6560. ; 60:9, s. 3869-3882
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Tidskriftsartikel (refereegranskat)abstract
- Interest in high dose rate (HDR) electronic brachytherapy operating at 50 kV is increasing. For quality assurance it is important to identify dosimetry systems that can measure the absorbed doses in absolute terms which is difficult in this energy region. In this work a comparison is made between two dosimetry systems, EPR lithium formate dosimeters and radiochromic EBT2 film.Both types of dosimeters were irradiated simultaneously in a PMMA phantom using the Axxent EBS. Absorbed dose to water was determined at distances of 10 mm, 30 mm and 50 mm from the EBS. Results were traceable to different primary standards as regards to absorbed dose to water (EPR) and air kerma (EBT2). Monte Carlo simulations were used in absolute terms as a third estimate of absorbed dose to water.Agreement within the estimated expanded (k = 2) uncertainties (5% (EPR), 7% (EBT2)) was found between the results at 30 mm and 50 mm from the x-ray source. The same result was obtained in 4 repetitions of irradiation, indicating high precision in the measurements with both systems. At all distances, agreement between EPR and Monte Carlo simulations was shown as was also the case for the film measurements at 30mm and 50mm. At 10mm the geometry for the film measurements caused too large uncertainty in measured values depending on the exact position (within sub-mm distances) of the EBS and the 10 mm film results were exculded from comparison.This work has demonstrated good performance of the lithium formate EPR dosimetry system in accordance with earlier experiments at higher photon energies (192Ir HDR brachytherapy). It was also highlighted that there might be issues regarding the energy dependence and intrinsic efficiency of the EBT2 film that need to be considered for measurements using low energy sources.
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| 5. |
- Adolfsson, Emelie, et al.
(författare)
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Optimisation of an EPR dosimetry system for robust and high precision dosimetry
- 2014
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Ingår i: Radiation Measurements. - : Elsevier. - 1350-4487 .- 1879-0925. ; 70, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- Clinical applications of electron paramagnetic resonance (EPR) dosimetry systems demand high accuracy causing time consuming analysis. The need for high spatial resolution dose measurements in regions with steep dose gradients demands small sized dosimeters. An optimization of the analysis was therefore needed to limit the time consumption. The aim of this work was to introduce a new smaller lithium formate dosimeter model (diameter reduced from standard diameter 4.5 mm to 3 mm and height from 4.8 mm to 3 mm). To compensate for reduced homogeneity in a batch of the smaller dosimeters, a method for individual sensitivity correction suitable for EPR dosimetry was tested. Sensitivity and repeatability was also tested for a standard EPR resonator and a super high Q (SHQE) one. The aim was also to optimize the performance of the dosimetry system for better efficiency regarding measurement time and precision. A systematic investigation of the relationship between measurement uncertainty and number of readouts per dosimeter was performed. The conclusions drawn from this work were that it is possible to decrease the dosimeter size with maintained measurement precision by using the SHQE resonator and introducing individual calibration factors for dosimeter batches. It was also shown that it is possible reduce the number of readouts per dosimeter without significantly decreasing the accuracy in measurements.
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| 6. |
- Adolfsson, Emelie, 1985-, et al.
(författare)
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Response of Lithium Formate EPR Dosimeters at Photon Energies Relelvant to Brachytherapy
- 2009
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Ingår i: IFMBE Proceedings. - Heidelberg : Springer Berlin Heidelberg. - 9783642034725 - 9783642034749 ; , s. 236-239
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- After development of sensitive dosimeter materials Electron Paramagnetic Resonance EPR dosimetry has been successfully used also in radiation therapy. The intensity of the EPR-signal is a measure of the amount of free radicals created by ionizing radiation which is proportional to the absorbed dose in the dosimeter. Lithium formate monohydrate is a dosimeter material with 2-6 times higher sensitivity than alanine, a linear dose response over a wide dose range and mass-energy absorption properties similar to water. These properties make lithium formate promising for verification of absorbed doses around high dose rate brachytherapy sources where the dose gradient is steep and the photon energy distribution changing with distance from the source. Calibration of the dosimeters is performed in 60Co or MV photon beams where high dosimetric accuracy is feasible. The use in brachytherapy field relies on the assumption that the production of free radicals per mean absorbed dose in the dosimeter is similar at the lower photon energies present there. The aim of this work was to test that assumption. The response of the dosimeters as a function of photon energy was determined by irradiations with four x-ray qualities in the range 100-250 kV and 137Cs, relative to the response when irradiated with 60Co, all photon beams with well-known air kerma rates at the Swedish Secondary Standards Dosimetry Laboratory. Monte Carlo simulations were used to convert air kerma free in air to mean absorbed dose to the dosimeter. The measured response relative 60Co as a function of photon energy was below unity for all qualities. The maximum deviation from unity was 2.5% (100 kV, 135 kV) with a relative standard deviation of 1.5% (k = 1).
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| 7. |
- Adolfsson, Emelie, et al.
(författare)
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Response of lithium formate EPR dosimeters at photon energies relevant to the dosimetry of brachytherapy
- 2010
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Ingår i: Medical physics (Lancaster). - : American Association of Physicists in Medicine. - 0094-2405. ; 37:9, s. 4946-4959
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE:To investigate experimentally the energy dependence of the detector response of lithium formate EPR dosimeters for photon energies below 1 MeV relative to that at 60Co energies. High energy photon beams are used in calibrating dosimeters for use in brachytherapy since the absorbed dose to water can be determined with high accuracy in such beams using calibrated ion chambers and standard dosimetry protocols. In addition to any differences in mass-energy absorption properties between water and detector, variations in radiation yield (detector response) with radiation quality, caused by differences in the density of ionization in the energy imparted (LET), may exist. Knowledge of an eventual deviation in detector response with photon energy is important for attaining high accuracy in measured brachytherapy dose distributions.METHODS:Lithium formate EPR dosimeters were irradiated to known levels of air kerma in 25-250 kV x-ray beams and in 137Cs and 60Co beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free in air into values of mean absorbed dose to the detectors were made using EGSnrc MC simulations and x-ray energy spectra measured or calculated for the actual beams. The signals from the detectors were measured using EPR spectrometry. Detector response (the EPR signal per mean absorbed dose to the detector) relative to that for 60Co was determined for each beam quality.RESULTS:Significant decreases in the relative response ranging from 5% to 6% were seen for x-ray beams at tube voltages < or = 180 kV. No significant reduction in the relative response was seen for 137Cs and 250 kV x rays.CONCLUSIONS:When calibrated in 60Co or MV photon beams, corrections for the photon energy dependence of detector response are needed to achieve the highest accuracy when using lithium formate EPR dosimeters for measuring absorbed doses around brachytherapy sources emitting photons in the energy range of 20-150 keV such as 169Yb and electronic sources.
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| 8. |
- Alm Carlsson, Gudrun, et al.
(författare)
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Riskuppskattningar och strålskydds-rekommendationer : Vår strålningsmiljö
- 1991
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Människan har i alla tider varit utsatt för joniserande strålning. Kosmiskstrålning och naturligt radioaktiva nuklider i vår omgivning och i vår kropp ger ett årligtbidrag till den absorberade dosen i hela kroppen, som i genomsnitt för människorna påjorden uppgår till 1 mGy/år (1Gy = 1 J/kg). Det finns områden på jorden där stråldosenfrån naturlig strålning är 10-100 ggr större, jfr avsnittet "Vår strålningsmiljö". I slutet av 1800-talet upptäckte Röntgen röntgenstrålningen och Becquerel den naturligaradioaktiviteten. Människan fick därmed för första gången tillgång till starka källor avjoniserande strålning. Dessa togs snabbt i bruk framförallt inom medicinsk röntgendiagnostikoch radioterapi. Man gjorde snart bittra erfarenheter av den joniserandestrålningens skadliga biologiska verkningar efter höga stråldoser. Fram till år 1922 hadec:a 100 radiologer dött av strålskador. Man insåg att något måste göras för att förbättraläget för personalen och år 1928 bildades ICRP (International Commission on RadiationProtection). ICRP ger ut rekommendationer för strålskydd, som ligger till grund förnationella lagar och förordningar över hela världen. Den förhållandevis långa erfarenhet människan har av joniserande strålning och denlätthet med vilken även små stråldoser kan mätas har gett oss stränga normer vad gällerhanteringen av producerade strålkällor. Många har därför uppfattningen att joniserandestrålning är en exklusiv miljökomponent. Så är knappast fallet. Förutom att vi alltid varitnaturligt bestrålade finns det idag anledning att förmoda att den kemiska nedsmutsningenav miljön är ett långt allvarligare hot mot vårt välbefinnande än den nuvarandeanvändningen av producerade strålkällor. En rättvis bedömning av olika miljökomponenterkan endast göras den gång alla mäts med samma mått. Arbete med dennainriktning pågår med strålskydds-verksamheten som förebild.
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| 9. |
- Antonovic, Laura, et al.
(författare)
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Evaluation of a lithium formate EPR dosimetry system for dose measurements around Ir-192 brachytherapy sources
- 2009
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Ingår i: MEDICAL PHYSICS. - : Wiley. - 0094-2405. ; 36:6, s. 2236-2247
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Tidskriftsartikel (refereegranskat)abstract
- A dosimetry system using lithium formate monohydrate (HCO2Li center dot H2O) as detector material and electron paramagnetic resonance (EPR) spectroscopy for readout has been used to measure absorbed dose distributions around clinical Ir-192 sources. Cylindrical tablets with diameter of 4.5 mm, height of 4.8 mm, and density of 1.26 g/cm(3) were manufactured. Homogeneity test and calibration of the dosimeters were performed in a 6 MV photon beam. Ir-192 irradiations were performed in a PMMA phantom using two different source models, the GammaMed Plus HDR and the microSelectron PDR-v1 model. Measured absorbed doses to water in the PMMA phantom were converted to the corresponding absorbed doses to water in water phantoms of dimensions used by the treatment planning systems (TPSs) using correction factors explicitly derived for this experiment. Experimentally determined absorbed doses agreed with the absorbed doses to water calculated by the TPS to within +/- 2.9%. Relative standard uncertainties in the experimentally determined absorbed doses were estimated to be within the range of 1.7%-1.3% depending on the radial distance from the source, the type of source (HDR or PDR), and the particular absorbed doses used. This work shows that a lithium formate dosimetry system is well suited for measurements of absorbed dose to water around clinical HDR and PDR Ir-192 sources. Being less energy dependent than the commonly used thermoluminescent lithium fluoride (LiF) dosimeters, lithium formate monohydrate dosimeters are well suited to measure absorbed doses in situations where the energy dependence cannot easily be accounted for such as in multiple-source irradiations to verify treatment plans. Their wide dynamic range and linear dose response over the dose interval of 0.2-1000 Gy make them suitable for measurements on sources of the strengths used in clinical applications. The dosimeter size needs, however, to be reduced for application to single-source dosimetry.
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| 10. |
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| 11. |
- Carlsson, C.A., et al.
(författare)
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An instrument for measuring ambient dose equivalent, H*(10)
- 1996
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Ingår i: Radiation Protection Dosimetry. - 0144-8420 .- 1742-3406. ; 67:1, s. 33-39
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Tidskriftsartikel (refereegranskat)abstract
- The design and calibration of a small and simple instrument for measuring the ambient dose equivalent, H*(10), in photon fields is described. Comprising a thermoluminescence LiF dosemeter inside a 20 mm diameter PMMA sphere, it is capable of measuring the ambient dose equivalent with a nearly isotropic response. In the interval 0.1-100 mSv and for the energy range 30 keV to 1.25 MeV the energy response is within -31% and +15% relative to that of 137Cs gamma radiation (662 keV). In practical use, it is therefore sufficient to calibrate the instrument in a 137Cs gamma field using the corresponding conversion coefficient H*(10)/Kair taken from tabulations. The possibility of using the instrument to monitor the ambient dose equivalent for energies above 1.25 MeV is discussed and indicates that the range of applicability can be extended to 4.4 MeV with an energy response within -10% relative to 662 keV.
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| 12. |
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| 13. |
- Carlsson, Håkan, et al.
(författare)
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Competition Between Monovalent and Divalent Counterions in a Surfactant / Water System
- 1996
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 180:2, s. 598-604
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Tidskriftsartikel (refereegranskat)abstract
- Competition between mono- and divalent ions in the association of counterions to the headgroups of amphiphiles was studied in one surfactant system with organic counterions (piperidine+/piperazine2+octanesulfonate) and one with inorganic counterions (Na+/Ca2+octyl sulfate). By conductivity and13C NMR chemical shift measurements the critical micelle concentration (CMC) was found to decrease drastically when small amounts of divalent counterions were present in the system. Self-diffusion coefficients of surfactant ions and organic counterions were measured in the micellar phase by the Fourier transform pulsed-gradient spin-echo (FT-PGSE) NMR method. The degree of counterion binding in the micellar system with piperidine+/piperazine2+counterions was obtained from FT-PGSE NMR measurements. It was observed that the divalent counterions were more strongly bound than the monovalent counterions. The experimental results were compared with theoretical Poisson–Boltzmann calculations. The cell model was used to study the electrostatic effects. Good agreement between electrostatic theory and experiment was observed; however, an attractive force exists between the monovalent piperidine counterions and the micelle, probably because of hydrophobic interactions.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Carlsson, J, et al.
(författare)
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Kin-biased distribution in brown trout : an effect of redd location or kin recognition?
- 2004
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Ingår i: Heredity. - : Springer Science and Business Media LLC. - 0018-067X .- 1365-2540. ; 92:2, s. 53-60
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Tidskriftsartikel (refereegranskat)abstract
- A wide range of animals have been reported to show kin-biased behaviours, such as reduced aggressiveness and increased food sharing among relatives. However, less is known about whether wild animals also associate with relatives under natural conditions, which is a prerequisite to facilitate kin-biased behaviours and hence kin selection. We tested, by means of microsatellite polymorphism, correlations between pair-wise relatedness and pair-wise metric distance in wild brown trout ( Salmo trutta L.) under natural conditions in two streams. Our data show that young-of-the-year as well as older trout found close together also had a higher genetic relatedness in one of the two streams, whereas no relationship was found in the other stream. Very few half and full siblings were found in the second stream and under these conditions it is unlikely that kin-biased behaviours will receive positive selection. We discuss the underlying mechanisms for the observed structure and we specifically address the issue of whether the grouping of related individuals could reflect dispersal from the same spawning redds, or if it reflects active association with relatives, possibly conferring kin-selected advantages.
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| 20. |
- Carlsson Tedgren, Åsa, 1968-, et al.
(författare)
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Determination of absorbed dose to water around a clinical HDR 192-Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response
- 2012
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Ingår i: Medical physics (Lancaster). - USA : American Association of Physicists in Medicine. - 0094-2405. ; 39:2, s. 1133-1140
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Experimental radiation dosimetry with thermoluminescent dosimeters (TLDs), calibrated in a (60)Co or megavoltage (MV) photon beam, is recommended by AAPM TG-43U1for verification of Monte Carlo calculated absorbed doses around brachytherapy sources. However, it has been shown by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] that for TLDs of LiF:Mg,Ti, detector response was 4% higher in a (137)Cs beam than in a (60)Co one. The aim of this work was to investigate if similar over-response exists when measuring absorbed dose to water around (192)Ir sources, using LiF:Mg,Ti dosimeters calibrated in a 6 MV photon beam.Methods: LiF dosimeters were calibrated to measure absorbed dose to water in a 6 MV photon beam and used to measure absorbed dose to water at distances of 3, 5, and 7 cm from a clinical high dose rate (HDR) (192)Ir source in a polymethylmethacrylate (PMMA) phantom. Measured values were compared to values of absorbed dose to water calculated using a treatment planning system (TPS) including corrections for the difference in energy absorption properties between calibration quality and the quality in the users' (192)Ir beam and for the use of a PMMA phantom instead of the water phantom underlying dose calculations in the TPS.Results: Measured absorbed doses to water around the (192)Ir source were overestimated by 5% compared to those calculated by the TPS. Corresponding absorbed doses to water measured in a previous work with lithium formate electron paramagnetic resonance (EPR) dosimeters by Antonovic et al. [Med. Phys. 36, 2236-2247 (2009)], using the same irradiation setup and calibration procedure as in this work, were 2% lower than those calculated by the TPS. The results obtained in the measurements in this work and those obtained using the EPR lithium formate dosimeters were, within the expanded (k = 2) uncertainty, in agreement with the values derived by the TPS. The discrepancy between the results using LiF:Mg,Ti TLDs and the EPR lithium formate dosimeters was, however, statistically significant and in agreement with the difference in relative detector responses found for the two detector systems by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] and by Adolfsson et al. [Med. Phys. 37, 4946-4959 (2010)].Conclusions: When calibrated in (60)Co or MV photon beams, correction for the linear energy transfer (LET) dependence of LiF:Mg,Ti detector response will be needed as to measure absorbed doses to water in a (192)Ir beam with highest accuracy. Such corrections will depend on the manufacturing process (MTS-N Poland or Harshaw TLD-100) and details of the annealing and read-out schemes used.
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| 21. |
- Chen, Yun, 1966, et al.
(författare)
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Neonatal losartan treatment suppresses renal expression of molecules involved in cell-cell and cell-matrix interactions
- 2004
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Ingår i: Journal of the American Society of Nephrology. - : Lippincott Williams & Wilkins. - 1046-6673 .- 1533-3450. ; 15:5, s. 1232-43
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Tidskriftsartikel (refereegranskat)abstract
- Lack of neonatal angiotensin II type 1 receptor (AT(1)) stimulation produces renal abnormalities characterized by papillary atrophy and impaired urinary concentrating ability, but the mechanisms involved are still unclear. DNA microarray was used to identify genes that are differentially expressed in renal medulla in response to neonatal treatment with AT(1) receptor antagonist losartan (30 mg/kg per d), which commenced within 24 h after birth. The data showed that losartan treatment for 48 h downregulated 68 genes, approximately 30% of which encode various components of cytoskeleton and cytoskeleton-associated proteins, extracellular matrix, and enzymes involved in extracellular matrix maturation or turnover. With the use of immunohistochemistry and Western immunoblot, the microarray data were confirmed and it was demonstrated that losartan suppressed renal expression of syndecan 2, alpha-smooth muscle actin, MHC class II, and leukocyte type 12-lipoxygenase by day 4. In addition, losartan inhibited medullary expression of integrin alpha6 and caused relocalization of integrins alpha6 and alpha3. Moreover, losartan inhibited cell proliferation in medullary tubules by day 9, as detected by Ki-67 immunostaining. This study provides new data supporting the contention that a lack of AT(1) receptor stimulation results in abnormal matrix assembly, disturbed cell-cell and cell-matrix interactions, and subsequent abnormal tubular maturation. Moreover, regulation of the expression of leukocyte type 12-lipoxygenase and alpha-smooth muscle actin by the renin-angiotensin system in the immature kidney adds new knowledge toward the understanding of renal vascular development.
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| 22. |
- Hytteborn, Håkan, et al.
(författare)
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Spatial heterogeneity ensures long-term stability in vegetation and Fritillaria meleagris flowering in Uppsala Kungsäng, a semi-natural meadow
- 2023
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 18:3
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Tidskriftsartikel (refereegranskat)abstract
- Semi-natural grasslands are becoming increasingly rare, and their vegetation may be affected by environmental changes and altered management. At Kungsängen Nature Reserve, a wet to mesic semi-natural meadow near Uppsala, Sweden, we analysed long-term changes in the vegetation using data from 1940, 1982, 1995 and 2016. We also analysed the spatial and temporal dynamics in the Fritillaria meleagris population based on countings of flowering individuals in 1938, 1981–1988 and 2016–2021. Between 1940 and 1982 the wet part of the meadow became wetter, which led to an increased cover of Carex acuta and pushed the main area of flowering of F. meleagris up towards the mesic part. Annual variation in the flowering propensity of F. meleagris (in May) was affected by temperature and precipitation in the phenological phases of growth and bud initiation (June in the previous year), shoot development (September in the previous year) and initiation of flowering (March–April). However, the response to weather was in opposite directions in the wet and mesic parts of the meadow, and the flowering population showed large year-to-year variation but no long-term trend. Variation in management (poorly documented) led to changes in different parts of the meadow, but the overall composition of the vegetation, species richness and diversity changed little after 1982. Species richness and species composition of the meadow vegetation, and the long-term stability of the F. meleagris population are maintained by the variation in wetness, highlighting the importance of spatial heterogeneity as an insurance against biodiversity loss in semi-natural grasslands and nature reserves generally.
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| 23. |
- Johnson, Magnus S.C. 1969, et al.
(författare)
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Expression of scavenger receptor class B type I in gallbladder columnar epithelium.
- 2002
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Ingår i: Journal of gastroenterology and hepatology. - 0815-9319. ; 17:6, s. 713-20
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Tidskriftsartikel (refereegranskat)abstract
- The lipid content of bile may be modified by the gallbladder epithelium. Recent studies indicate that cholesterol can be absorbed from bile and that this can be enhanced by apolipoprotein (apo) A-I. SR-BI is a multifunctional receptor capable of binding a wide array of native or modified lipoproteins, phospholipid or bile acid micelles. As apo A-I is a ligand for scavenger receptor class B type I (SR-BI) we have characterized the expression of this receptor in murine gallbladder.Reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting and immunohistochemistry were used to study SR-BI expression in murine gallbladders. SR-BI expression was also used to examine gallbladders from high-fat-fed wild-type and apo B-100 transgenic mice.SR-BI and SR-BII mRNA are expressed in gallbladder. SR-BI immunoreactivity was localized to the columnar epithelium of the gallbladder. Immunoreactive SR-BI in gallbladder had an estimated molecular weight of 57 kDa, in contrast to the expected 82 kDa. Deglycosylation experiments indicated that the size difference between the two forms of the receptor is due to post-translational modification. Fat feeding of apo B transgenic mice resulted in gallstone formation but had no effect on the abundance of SR-BI.Gallbladder epithelial cells express SR-BI. This opens the possibility that SR-BI may influence the modification of bile in the gallbladder.
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| 24. |
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| 25. |
- Ling, Charlotte, et al.
(författare)
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Prolactin (PRL) receptor gene expression in mouse adipose tissue: increases during lactation and in PRL-transgenic mice
- 2000
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Ingår i: Endocrinology. - 0013-7227 .- 1945-7170. ; 141:10, s. 3564-3572
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Tidskriftsartikel (refereegranskat)abstract
- There are indications that PRL may exert important metabolic actions on adipose tissue in different species. However, with the exception of birds, the receptor has not been identified in white adipose tissue. The present study was designed to examine the possible expression and regulation of the PRL receptor (PRLR) in mouse adipose tissue. The long PRLR messenger RNA (mRNA) splice form (L-PRLR) and two short splice forms (S2- and S3-PRLR) were detected in mouse adipose tissue by RT-PCR. Furthermore, L-PRLR mRNA was detected by ribonuclease protection assay. Immunoreactive PRLR with a relative molecular mass of 95,000 was revealed by immunoblotting. Furthermore, L-PRLR mRNA expression was demonstrated in primary isolated adipocytes. In mouse adipose tissue, the level of L-PRLR mRNA expression increased 2.3-fold during lactation compared with those in virgin and pregnant mice. In contrast, in the liver the expression of L-PRLR increased 3.4-fold during pregnancy compared with those in virgin and lactating mice. When comparing the levels of L-PRLR expression in virgin female and male mice, no difference was detected in adipose tissue. However, in virgin female liver the expression was 4.5-fold higher than that in male liver. As PRL up-regulates its own receptor in some tissues, we analyzed L-PRLR expression in PRL-transgenic female and male mice. In PRL-transgenic mice L-PRLR expression was significantly increased in both adipose tissue (1.4-fold in females and 2.4-fold in males) and liver (1.9-fold in females and 2.7-fold in males) compared with that in control mice. Furthermore, in female PRL-transgenic mice retroperitoneal adipose tissue was decreased in weight compared with that in control mice. However, no difference was detected when comparing the masses of parametrial adipose tissue. Our results suggest a direct role for PRL, mediated by PRLR, in modulating physiological events in adipose tissue.
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| 26. |
- Noren, Håkan, 1948, et al.
(författare)
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STAN in clinical practice--the outcome of 2 years of regular use in the city of Gothenburg
- 2006
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Ingår i: Am J Obstet Gynecol. ; 195:1, s. 7-15
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The purpose of this study was to monitor the introduction of the STAN-methodology (Noventa Medical, Moelndal, Sweden). STUDY DESIGN: This was a prospective observational study covering the total population of deliveries at term during 2 years. Four thousand eight hundred and thirty out of 14,687 term pregnancies were monitored using the STAN S 21 fetal heart monitor and the associated clinical guidelines. Cord artery metabolic acidosis, neonatal outcome, and rates of operative deliveries for fetal distress were assessed. RESULTS: The annual rate of STAN usage increased from 28.1% to 37.7% and was associated with a significant reduction in metabolic acidosis rate in the total population from 0.76% to 0.44% (P < .05). The compliance with the clinical guidelines increased in cases requiring intervention. The rates for moderate/severe hypoxic neonatal encephalopathy were consistently low, 0.55 and 0.68 per 1000 deliveries, respectively, and corresponding to previous findings. The rate of operative delivery did not change during the 2 years in the total population. CONCLUSION: Increasing STAN usage provided consistent improvements in fetal outcome equalling those noted in the Swedish randomized controlled trial (RCT) without increasing operative interventions for fetal distress.
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| 27. |
- Rung, Emilia, 1974, et al.
(författare)
-
Progesterone-receptor antagonists and statins decrease de novo cholesterol synthesis and increase apoptosis in rat and human periovulatory granulosa cells in vitro
- 2005
-
Ingår i: Biology of reproduction. - : Oxford University Press (OUP). - 0006-3363 .- 1529-7268. ; 72:3, s. 538-45
-
Tidskriftsartikel (refereegranskat)abstract
- Progesterone-receptor (PR) stimulation promotes survival in rat and human periovulatory granulosa cells. To investigate the mechanisms involved, periovulatory rat granulosa cells were incubated in vitro with or without the PR-antagonist Org 31710. Org 31710 caused the expected increase in apoptosis, and expression profiling using cDNA microarray analysis revealed regulation of several groups of genes with functional and/or metabolic connections. This regulation included decreased expression of genes involved in follicular rupture, increased stress responses, decreased angiogenesis, and decreased cholesterol synthesis. A decreased cholesterol synthesis was verified in experiments with both rat and human periovulatory granulosa cells treated with the PR-antagonists Org 31710 or RU 486 by measuring incorporation of [14C]acetate into cholesterol, cholesterol ester, and progesterone. Correspondingly, specific inhibition of cholesterol synthesis in periovulatory rat granulosa cells using 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors (lovastatin, mevastatin, or simvastatin) increased apoptosis, measured as DNA fragmentation and caspase-3/7 activity. The increase in apoptosis caused by simvastatin was reversed by addition of the cholesterol synthesis-intermediary mevalonic acid. These results show that PR antagonists reduce cholesterol synthesis in periovulatory granulosa cells and that cholesterol synthesis is important for granulosa cell survival.
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| 28. |
- Sundín, Anders, et al.
(författare)
-
Radioimmunolocalization of hepatic metastases and subcutaneous xenografts from a human colonic cancer in the nude rat : Aspects of tumour implantation site and mode of antibody administration
- 1993
-
Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 32:7-8, s. 877-885
-
Tidskriftsartikel (refereegranskat)abstract
- Antibody localization was analyzed following intraperitoneal (i.p.) or intravenous (i.v.) injection of the 125I-labelled anti-CEA-MAb I-38S1 in 44 nude rats, in order to evaluate the influence of tumour implantation site and the route of MAb administration. The animals were xenografted with a human colonic cancer (LS 174 T), either in the form of hepatic metastases, subcutaneous (s.c.) tumours or both. Tissue measurements, 4 days after MAb injection, showed better uptake for hepatic than for s.c. tumours, irrespective of the route of antibody administration. Antibody accumulation per g liver metastases was not size dependent for noduli weighing between 4 and 1,110 mg. MAb excretion evaluated in 20 animals and blood activity studied in 11 rats were equivalent 24-96 h following i.p. and i.v. injection. Dissimilar autoradiographic patterns were seen in hepatic metastases with predominantly peripherally located clusters following i.p. and more homogeneously distributed grains after i.v. MAb administration. The results indicate that tumour implantation site has a quantitative, and the route of administration at least a qualitative impact on the tumour accretion of anti-CEA MAb I-38S1 in the present xenograft model.
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| 29. |
- Svensson, Per-Arne, 1969, et al.
(författare)
-
Copper induces the expression of cholesterogenic genes in human macrophages.
- 2003
-
Ingår i: Atherosclerosis. - 0021-9150. ; 169:1, s. 71-6
-
Tidskriftsartikel (refereegranskat)abstract
- Accumulation of lipids and cholesterol by macrophages and subsequent transformation into foam cells are key features in development of atherosclerosis. Serum copper concentrations have been shown to be associated with cardiovascular disease. However, the mechanism behind the proatherogenic effect of copper is not clear. We used DNA microarrays to define the changes in gene expression profile in response to copper exposure of human macrophages. Expression monitoring by DNA microarray revealed 91 genes that were regulated. Copper increased the expression of seven cholesterogenic genes (3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) synthase, IPP isomerase, squalene synthase, squalene epoxidase, methyl sterol oxidase, H105e3 mRNA and sterol-C5-desaturase) and low-density lipoprotein receptor (LDL-R), and decreased the expression of CD36 and lipid binding proteins. The expression of LDL-R and HMG CoA reductase was also investigated using real time PCR. The expression of both of these genes was increased after copper treatment of macrophages (P<0.01 and P<0.01, respectively). We conclude that copper activates cholesterogenic genes in macrophages, which may provide a mechanism for the association between copper and atherosclerosis. The effect of copper on cholesterogenic genes may also have implications for liver steatosis in early stages of Wilson's disease.
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| 30. |
- Söderqvist, Emil, et al.
(författare)
-
Design of a single segment conductance catheter for measurement of left ventricular volume
- 2001
-
Ingår i: Annual Reports of the Research Reactor Institute, Kyoto University. ; , s. 151-154
-
Konferensbidrag (refereegranskat)abstract
- The objective of this paper is to investigate how to best position the sensing electrodes on a single segment conductance catheter, and to calculate the expected performance. Using electrode potential data, obtained with the present five segment conductance catheter in pig experiments, we have interpolated the electrical field at any given point of time, and calculated what volume curve to expect with only two sensing electrodes. Comparison shows that the deviation between our calculated method and the present one is stable and small. Mean deviation with optimized electrode positions was 0.05% per sample, and the maximum deviation found for a single time sample was 2.57%. This indicates that it is possible to build a thin single segment catheter with as good performance as for the present five segment conductance catheter.
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| 31. |
- Stjernberg, Helena, et al.
(författare)
-
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Open Access (OA) is defined as the free, online, immediate, permanent access to scientific and scholarly material in full-text. Open Access practices have reached the universities and now nearly all university researchers report knowledge of OA. Statistics Sweden (SCB) has estimated that 75% of all money invested in research activities in Sweden is done by private companies. In spite of this, the private sector has been relatively absent from the Open Access discussion and development, in contrast to the universities. The goal of this project was to study the advance of OA practices in the private sector. The method was to visit a number of Swedish companies and present the OA concept. After the presentations web-based surveys were distributed to measure previous knowledge of OA, publishing and readership practices, and views of the matter. Knowledge and awareness of Open Access is less within companies than at universities, although it seems to increase with publishing practices and higher educational degree. The publishing practices, and to lesser extent the reading practices, of scientific articles is less within companies, which could lead to a skewed funding situation for a future Open Access-economy based on an “author-pays” model. In discussions regarding how companies might pay for Open Access we therefore suggest that the flow of information needs to be guarded so that the benefit of access to scientific data does not become limited for companies and industry in a new way, as is already seen by some Open Access journals. The researchers’ access to information should be the same irrespective of whether they work at a company or at the university.
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| 32. |
- Stjernberg, Helena, et al.
(författare)
-
- 2008
-
Rapport (populärvet., debatt m.m.)abstract
- Open Access (OA) is defined as the free, online, immediate, permanent access to scientific and scholarly material in full-text. Open Access practices have reached the universities and now nearly all university researchers report knowledge of OA. Statistics Sweden (SCB) has estimated that 75% of all money invested in research activities in Sweden is done by private companies. In spite of this, the private sector has been relatively absent from the Open Access discussion and development, in contrast to the universities. The goal of this project was to study the advance of OA practices in the private sector. The method was to visit a number of Swedish companies and present the OA concept. After the presentations web-based surveys were distributed to measure previous knowledge of OA, publishing and readership practices, and views of the matter. Knowledge and awareness of Open Access is less within companies than at universities, although it seems to increase with publishing practices and higher educational degree. The publishing practices, and to lesser extent the reading practices, of scientific articles is less within companies, which could lead to a skewed funding situation for a future Open Access-economy based on an “author-pays” model. In discussions regarding how companies might pay for Open Access we therefore suggest that the flow of information needs to be guarded so that the benefit of access to scientific data does not become limited for companies and industry in a new way, as is already seen by some Open Access journals. The researchers’ access to information should be the same irrespective of whether they work at a company or at the university.
|
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| 33. |
- Stjernberg, Helena, et al.
(författare)
-
- 2008
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Open Access (OA) is defined as the free, online, immediate, permanent access to scientific and scholarly material in full-text. Open Access practices have reached the universities and now nearly all university researchers report knowledge of OA. Statistics Sweden (SCB) has estimated that 75% of all money invested in research activities in Sweden is done by private companies. In spite of this, the private sector has been relatively absent from the Open Access discussion and development, in contrast to the universities. The goal of this project was to study the advance of OA practices in the private sector. The method was to visit a number of Swedish companies and present the OA concept. After the presentations web-based surveys were distributed to measure previous knowledge of OA, publishing and readership practices, and views of the matter. Knowledge and awareness of Open Access is less within companies than at universities, although it seems to increase with publishing practices and higher educational degree. The publishing practices, and to lesser extent the reading practices, of scientific articles is less within companies, which could lead to a skewed funding situation for a future Open Access-economy based on an “author-pays” model. In discussions regarding how companies might pay for Open Access we therefore suggest that the flow of information needs to be guarded so that the benefit of access to scientific data does not become limited for companies and industry in a new way, as is already seen by some Open Access journals. The researchers’ access to information should be the same irrespective of whether they work at a company or at the university.
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| 34. |
|
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| 35. |
-
Accounting, Innovation and Inter-Organisational Relationships
- 2018
-
Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Successful innovation is a true challenge and especially when today's companies are intertwined in close inter-organisational relationships and networks with e.g. customers and suppliers. Research has indicated that accounting can play important roles in such innovation processes, but there is little in-depth systematic knowledge about this issue. ã Accounting, Innovation and Inter-Organisational Relationships gathers leading researchers from all around the world to argue for the importance of more systematic knowledge about accounting, innovation and inter-organisational relationships. ã Accounting, Innovation and Inter-Organisational Relationships thus becomes an important source for researchers and practitioners interested in accounting and inter-organisational relationships as well as the related disciplines of management, marketing, innovation and strategy.
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| 36. |
- Ackerley, Rochelle, 1980, et al.
(författare)
-
Touch perceptions across skin sites: Differences between sensitivity, direction discrimination and pleasantness
- 2014
-
Ingår i: Frontiers in Behavioral Neuroscience. - : Frontiers Media SA. - 1662-5153. ; 8:54
-
Tidskriftsartikel (refereegranskat)abstract
- Human skin is innervated with different tactile afferents, which are found at varying densities over the body. We investigate how the relationships between tactile pleasantness, sensitivity and discrimination differ across the skin. Tactile pleasantness was assessed by stroking a soft brush over the skin, using five velocities (0.3, 1, 3, 10, 30 cm s-1), known to differentiate hedonic touch, and pleasantness ratings were gained. The ratings velocity-profile is known to correlate with firing in unmyelinated C-tactile (CT) afferents. Tactile sensitivity thresholds were determined using monofilament force detection and the tactile discrimination level was obtained in the direction discrimination of a moving probe; both tasks readily activate myelinated touch receptors. Perceptions were measured over five skin sites: forehead, arm, palm, thigh and shin. The assessment of tactile pleasantness over the skin resulted in a preference for the middle velocities (1-10 cm s-1), where higher ratings were gained compared to the slowest and fastest velocities. This preference in tactile pleasantness was found across all the skin sites, apart from at the palm, where no decrease in pleasantness for the faster stroking velocities was seen. We find that tactile sensitivity and discrimination vary across the skin, where the forehead and palm show increased acuity. Tactile sensitivity and discrimination levels also correlated significantly, although the tactile acuity did not relate to the perceived pleasantness of touch. Tactile pleasantness varied in a subtle way across skin sites, where the middle velocities were always rated as the most pleasant, but the ratings at hairy skin sites were more receptive to changes in stroking velocity. We postulate that although the mechanoreceptive afferent physiology may be different over the skin, the perception of pleasant touch can be interpreted using all of the available incoming somatosensory information in combination with central processing. © 2014 Ackerley, Carlsson, Wester, Olausson and Backlund Wasling.
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| 37. |
- Ahlberg, Erik, et al.
(författare)
-
"Vi klimatforskare stödjer Greta och skolungdomarna"
- 2019
-
Ingår i: Dagens nyheter (DN debatt). - 1101-2447.
-
Tidskriftsartikel (populärvet., debatt m.m.)abstract
- DN DEBATT 15/3. Sedan industrialiseringens början har vi använt omkring fyra femtedelar av den mängd fossilt kol som får förbrännas för att vi ska klara Parisavtalet. Vi har bara en femtedel kvar och det är bråttom att kraftigt reducera utsläppen. Det har Greta Thunberg och de strejkande ungdomarna förstått. Därför stödjer vi deras krav, skriver 270 klimatforskare.
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| 38. |
- Ahlström, Håkan, et al.
(författare)
-
An experimental model for pharmacokinetic studies of monoclonal antibodies in human colonic cancer
- 1987
-
Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 26:6, s. 447-451
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental model consisting of athymic rats carrying human colonic tumours from cell line LS 174T in both hind legs was used. 125I-labelled anti-carcinoembryonic antigen (anti-CEA) monoclonal antibodies were injected intra-arterially (i.a.), either alone (21 rats) or together with degradable starch microspheres (6 rats). As a control, an irrelevant antibody was injected i.a., alone (6 rats) or together with microspheres (3 rats). An intra-arterial injection was given on the side bearing one tumour in each rat, while the contralateral tumour served as an 'intravenous' control. The rats were submitted to external gamma measurements daily for four days. On the fourth day they were killed and pieces from the tumours and from various organs were examined by in vitro measurements. The results indicate strong expression of CEA in LS 174T cells grafted to athymic rats. No lasting enhancement of the tumour uptake was achieved by intra-arterial injection of antibodies as compared with the control tumours.
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| 39. |
- Ahlström, Håkan, et al.
(författare)
-
Enhanced uptake of intra-arterially injected anti-CEA monoclonal antibodies in human colonic cancer after mannitol infusion in an experimental model
- 1987
-
Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 26:6, s. 453-458
-
Tidskriftsartikel (refereegranskat)abstract
- In a previous report athymic rats carrying transplanted human colonic tumours from cell line LS 174T in both hind legs were injected intra-arterially (i.a.) with 125I-labelled anti-carcinoembryonic (anti-CEA) monoclonal antibodies. The i.a. injection was given on one side bearing a tumour in each rat, while the contralateral tumour served as an 'intravenous' control. In the same experimental model and treated in the same way, 10 rats were injected i.a. with anti-CEA monoclonal antibodies after an i.a. mannitol infusion. In both groups of rats external gamma measurements were performed daily for four days. On the fourth day the rats were killed and pieces of the tumours and of various organs were weighed and the activity was determined with a gamma-counter. The tumour uptake of antibodies was significantly enhanced after mannitol infusion.
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| 40. |
- Ahmed, Abubeker, 1981-, et al.
(författare)
-
Utvärdering av gummiasfalt : provväg E22 Mönsterås : etapp 1
- 2019
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Laboratorieundersökningar och vägytemätningar utfördes på referens- och gummimodifierade asfaltbeläggningar på E22 Mönsterås.Laboratorieundersökningarna visar inte några tydliga skillnader i styvhet och skjuvmodul mellan massorna. Gummiasfalt har dock lägre fasvinkel jämfört med referens vilket betyder att gummiasfalten är mer elastisk. Gummiasfalten visar också lite lägre modul i låga temperaturer och lite högre modul i höga temperaturer vilket är bra för sprickbildning vid låga temperaturer respektive deformationsstabilitet. Utmattningsprovningen visar att gummiasfalt har något bättre utmattningsegenskaper men skillnaderna är inte signifikanta.De initiala fältmätningarna visar inte på några framträdande skillnader mellan sträckorna utan mätresultaten är väldigt likvärdiga. Det är dock för tidigt att dra slutsatser efter mindre än ett års trafik och fortsatta tillståndutvecklingen bör följas ytterligare innan slutsatser kan dras. Någon skillnad i spårbildning mellan sträckorna kan inte fastställas p.g.a. systematiska variationer inom provsträckan.
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| 41. |
- Ahmed, Abubeker W, 1981-, et al.
(författare)
-
Pavement performance follow-up and evaluation of polymer-modified test sections
- 2019
-
Ingår i: The international journal of pavement engineering. - : Taylor and Francis Ltd.. - 1029-8436 .- 1477-268X. ; 20:12, s. 1474-1487
-
Tidskriftsartikel (refereegranskat)abstract
- Between 2003 and 2006, a test road consisting of several conventional and polymer-modified structures was built on a motorway. Different combinations of styrene–butadiene–styrene (SBS) and ethyl vinyl acetate (EVA) polymer-modified binders were used. The test structures have been in service since then and have been monitored for over 9 years. The resistance of the different types of asphalt concrete mixes to rutting and cracking was measured and predicted. The impact of ageing on the mixes was also evaluated. Although all the sections are in good condition after 9 years of traffic, the predicted differences between the test sections based on the PEDRO (Permanent Deformation of asphalt concrete layers for Roads) approach and laboratory evaluations are noticeable. Lateral wander and transverse profile measurements indicated that studded winter tyre wear contributed to most of the rutting compared to permanent deformation due to heavy traffic. The unmodified mixes exhibited considerable ageing and the SBS-modified mixes were least affected by ageing. Furthermore, the SBS-modified base mix produced significantly better fatigue resistance than the conventional base mix. However, further investigations of the relationships between bitumen and mix properties and further follow-ups of the test sections are recommended to validate the findings.
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| 42. |
- Akil, Shahnaz, et al.
(författare)
-
Appropriate coronary revascularization can be accomplished if myocardial perfusion is quantified by positron emission tomography prior to treatment decision
- 2021
-
Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 28:4, s. 1664-1672
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Many patients undergo percutaneous coronary intervention (PCI) without the use of non-invasive stress testing prior to treatment. The aim of this study was to determine the potential added value of guiding revascularization by quantitative assessment of myocardial perfusion prior to intervention. Methods and Results: Thirty-three patients (10 females) with suspected or established CAD who had been referred for a clinical coronary angiography (CA) with possibility for PCI were included. Adenosine stress and rest 13N-NH3 PET, cardiac magnetic resonance (CMR), and cardiopulmonary exercise test were performed 4 ± 3 weeks before and 5 ± 1 months after CA. The angiographer was blinded to the PET and CMR results. Myocardial flow reserve (MFR) < 2.0 by PET was considered abnormal. A PCI was performed in 19/33 patients. In 41% (11/27) of the revascularized vessel territories, a normal regional MFR was found prior to the PCI and no improvement in MFR was found at follow-up (P = 0.9). However, vessel territories with regional MFR < 2.0 at baseline improved significantly after PCI (P = 0.003). Of the 14 patients not undergoing PCI, four had MFR < 2.0 in one or more coronary territories. Conclusion: Assessment of quantitative myocardial perfusion prior to revascularization could lead to more appropriate use of CA when managing patients with stable CAD.
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| 43. |
- Akil, Shahnaz, et al.
(författare)
-
Gender aspects on exercise-induced ECG changes in relation to scintigraphic evidence of myocardial ischaemia
- 2018
-
Ingår i: Clinical Physiology and Functional Imaging. - : Wiley. - 1475-0961. ; 38:5, s. 798-807
-
Tidskriftsartikel (refereegranskat)abstract
- Background: This retrospective study aimed to determine the diagnostic performance of exercise-induced ST response in relation to findings by myocardial perfusion single photon emission computed tomography (MPS), with focus on gender differences, in patients with suspected or established stable ischemic heart disease. Methods: MPS findings of 1 021 patients (518 females) were related to the exercise-induced ST response alone (blinded and unblinded to gender) and ST response together with additional exercise stress test (EST) variables (exercise capacity, blood pressure and heart rate response). Results: Exercise-induced ischaemia by MPS was found in 9% of females and 23% of males. Diagnostic performance of exercise-induced ST response in relation to MPS findings in females versus males was: sensitivity = 48%,70%; specificity = 67%, 64%; PPV = 13%, 38%; NPV = 93%, 87%. Adding more EST variables to the ST response interpretation yielded in females vs males: sensitivity = 44%, 51%; specificity = 84%, 83%; PPV = 22%, 48% and NPV = 93%, 85%. Conclusions: In patients who have performed EST in conjunction with MPS, there is a gender difference in the diagnostic performance of ST response at stress, with a significantly lower PPV in females compared to males. For both genders, specificity can be significantly improved, and a higher PPV can be obtained, while the sensitivity might be compromised by considering more EST variables, in addition to the ST response.
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| 44. |
- Akil, Shahnaz, et al.
(författare)
-
Qualitative assessments of myocardial ischemia by cardiac MRI and coronary stenosis by invasive coronary angiography in relation to quantitative perfusion by positron emission tomography in patients with known or suspected stable coronary artery disease
- 2020
-
Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 27:6, s. 2351-2359
-
Tidskriftsartikel (refereegranskat)abstract
- Background: To relate findings of qualitative evaluation of first-pass perfusion-CMR and anatomical evaluation on coronary angiography (CA) to the reference standard of quantitative perfusion, cardiac PET, in patients with suspected or known stable coronary artery disease (CAD). Methods and Results: Forty-one patients referred for CA due to suspected stable CAD, prospectively performed adenosine stress/rest first-pass perfusion-CMR as well as 13N-NH3 PET on the same day, 4 ± 3 weeks before CA. Angiographers were blinded to PET and CMR results. Regional myocardial flow reserve (MFR) < 2.0 on PET was considered pathological. Vessel territories with stress-induced ischemia by CMR or vessels with stenosis needing revascularization had a significantly lower MFR compared to those with no regional stress-induced ischemia or vessels not needing revascularization (P < 0.001). In 4 of 123 vessel territories with stress-induced ischemia by CMR, PET showed a normal MFR. In addition, 12 of 123 vessels that underwent intervention showed normal MFR assessed by PET. Conclusion: The limited performance of qualitative assessment of presence of stable CAD with CMR and CA, when related to quantitative 13N-NH3 cardiac PET, shows the need for fully quantitative assessment of myocardial perfusion and the use of invasive flow reserve measurements for CA, to confirm the need of elective revascularization.
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| 45. |
- Akil, Shahnaz, et al.
(författare)
-
Stress-induced ST elevation with or without concomitant ST depression is predictive of presence, location and amount of myocardial ischemia assessed by myocardial perfusion SPECT, whereas isolated stress-induced ST depression is not
- 2016
-
Ingår i: Journal of Electrocardiology. - : Elsevier BV. - 1532-8430 .- 0022-0736. ; 49:3, s. 15-307
-
Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Evaluation of stress-induced ST deviations constitutes a central part when interpreting the findings from an exercise test. The aim of this analysis was to assess the pathophysiologic correlate of stress-induced ST elevation and ST depression with regard to presence, amount and location of myocardial ischemia as assessed by myocardial perfusion SPECT (MPS) in patients with suspected coronary artery disease.METHODS AND RESULTS: 226 patients who had undergone bicycle stress test in conjunction with MPS were included. Of these, 198 were consecutive patients while 28 patients were included on the basis of having stress-induced ST elevation mentioned in their clinical report. The amount and location of ST changes were related to MPS findings. Summed stress scores (SSS) from MPS images were used to measure the amount of stress-induced ischemia. The positive predictive values for detecting stress-induced ischemia were 28% for the consecutive patients with ST depression and 75% for patients with ST elevation. The maximum and sum of stress-induced ST elevations correlated with SSS (r(2)=0.58, p<0.001 and r(2)=0.73, p<0.001), whereas the maximum and sum of significant ST depressions did not (r(2)=0.022, p=0.08 and r(2)=0.024, p=0.10). The location of ST elevation corresponded to the location of ischemia by MPS (kappa=1.0), whereas the location of ST depression did not (kappa=0.20).CONCLUSIONS: Stress-induced ST elevation, with or without concomitant ST depression, is predictive of the presence, amount and location of myocardial ischemia assessed by MPS, whereas stress-induced ST depression without concomitant ST elevation is not.
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| 46. |
- Al-Mashat, Mariam, et al.
(författare)
-
Pulmonary perfusion and NYHA classification improve after cardiac resynchronization therapy
- 2022
-
Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 29:6, s. 2974-2983
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Evaluation of cardiac resynchronization therapy (CRT) often includes New York Heart Association (NYHA) classification, and echocardiography. However, these measures have limitations. Perfusion gradients from ventilation/perfusion single-photon emission computed tomography (V/P SPECT) are related to left-heart filling pressures and have been validated against invasive right-heart catheterization. The aim was to assess if changes in perfusion gradients are associated with improvements in heart failure (HF) symptoms after CRT, and if they correlate with currently used diagnostic methods in the follow-up of patients with HF after receiving CRT. Methods and results: Nineteen patients underwent V/P SPECT, echocardiography, NYHA classification, and the quality-of-life scoring system “Minnesota living with HF” (MLWHF), before and after CRT. CRT caused improvement in perfusion gradients from V/P SPECT which were associated with improvements in NYHA classification (P =.0456), whereas improvements in end-systolic volume (LVESV) from echocardiography were not. After receiving CRT, the proportion of patients who improved was lower using LVESV (n = 7/19, 37%) than perfusion gradients (n = 13/19, 68%). Neither change in perfusion gradients nor LVESV was associated with changes in MLWHF (P = 1.0, respectively). Conclusions: Measurement of perfusion gradients from V/P SPECT is a promising quantitative user-independent surrogate measure of left-sided filling pressure in the assessment of CRT response in patients with HF.
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| 47. |
- Alm Carlsson, Gudrun, et al.
(författare)
-
Monte Carlo metoden : ett verktyg inom strålningsfysiken
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Detta kompendium är tänkt att användas som ett propedeutiskt kursmaterial för kursdeltagare i kursen "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter". Först följer en kort repetition av den grundläggande statistik som utnyt1jas i beräkningarna. Därefter följer en beskrivning av slumptal. det fundament som metoden bygger på. Vidare beskrivs val ur olika frekvensfunktioner. Valet kan även göras ur så kallade falska fördelningar för att reducera variansen i den skattade storheten. Metoderna belyses i ett avsnitt om problemlösningsmetodik. först i allmänna termer för att sen gå in på ett specifikt problem (Buffons nålproblem) där en analys och strukturering av problemet görs varefter flödesschema och kodning exemplifieras. Så följer två moment där en beskrivning görs av färderna av fotoner respektive elektroner genom materia. För elektronfärderna gör man en indelning i klass 1- och klass II-färder. Vad detta innebär och hur deltapartiklar tas om hand beskrivs i ett kapitel. Till sist kommer en kort introduktion till de tre laborationerna med laborationshandledningar. Speciell vikt har lagts vid att initiera laboranten att fundera på fysiken i de simulerade experimenten. Detta kompendium har tillkommit som examinationsarbete vid en kurs i "Monte Carlo simulering av foton- och elektrontransport vid diagnostiska och radioterapeutiska strålkvaliteter", med andra ord den kurs du själv nu ämnar studera. Författarna önskar dig lycka till med kursen och hoppas att du kommer att få glädje av den. Speciellt hoppas vi att denna skrift ska underlätta för dig att tillgodogöra dig informationen vid föreläsningarna och under laborationerna.
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- Arvidsson, Per M, et al.
(författare)
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Hemodynamic force analysis is not ready for clinical trials on HFpEF
- 2022
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Hemodynamic force analysis has been proposed as a novel tool for early detection of subclinical systolic dysfunction in heart failure with preserved ejection fraction (HFpEF). Here we investigated the ability of hemodynamic forces to discriminate between healthy subjects and heart failure patients with varying degrees of systolic dysfunction. We studied 34 controls, 16 HFpEF patients, and 25 heart failure patients with mid-range (HFmrEF) or reduced ejection fraction (HFrEF) using cardiac magnetic resonance with acquisition of cine images and 4D flow at 1.5 T. The Navier-Stokes equation was used to compute global left ventricular hemodynamic forces over the entire cardiac cycle. Forces were analyzed for systole, diastole, and the entire heartbeat, with and without normalization to left ventricular volume. Volume-normalized hemodynamic forces demonstrated significant positive correlation with EF (r2 = 0.47, p < 0.0001) and were found significantly lower in heart failure with reduced ejection fraction compared to controls (p < 0.0001 for systole and diastole). No difference was seen between controls and HFpEF (p > 0.34). Non-normalized forces displayed no differences between controls and HFpEF (p > 0.24 for all analyses) and did not correlate with EF (p = 0.36). Left ventricular hemodynamic force analysis, whether indexed to LV volumes or not, is not ready for clinical trials on HFpEF assessment.
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