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- Andersson, V., et al.
(författare)
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Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)
- 2005
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Ingår i: Proceedings of the 22nd Texas Symposium on Relativistic Astrophysics at Stanford. ; , s. 736-743
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Konferensbidrag (refereegranskat)abstract
- We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10 % polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view (~ 5 deg2) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.
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| 4. |
- Höglund, Linda, 1974-, et al.
(författare)
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Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors
- 2008
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Ingår i: Applied Physics Letters. - New York : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 93:10, s. 103501-
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Tidskriftsartikel (refereegranskat)abstract
- The performance of quantum dots-in-a-well infrared photodetectors (DWELL IPs) has been studied by means of interband and intersubband photocurrent measurements as well as dark current measurements. Using interband photocurrent measurements, substantial escape of electrons from lower lying states in the DWELL structure at large biases was revealed. Furthermore, a significant variation in the escape probability from energy states in the DWELL structure with applied bias was observed. These facts can explain the strong temperature and bias dependence of both photocurrent and dark currents in DWELL IPs.
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| 7. |
- Mårtensson, Ulrika, et al.
(författare)
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Deletion of the G protein-coupled receptor 30 impairs glucose tolerance, reduces bone growth, increases blood pressure, and eliminates estradiol-stimulated insulin release in female mice.
- 2009
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Ingår i: Endocrinology. - : The Endocrine Society. - 1945-7170 .- 0013-7227. ; 150:2, s. 687-98
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Tidskriftsartikel (refereegranskat)abstract
- In vitro studies suggest that the G protein-coupled receptor (GPR) 30 is a functional estrogen receptor. However, the physiological role of GPR30 in vivo is unknown, and it remains to be determined whether GPR30 is an estrogen receptor also in vivo. To this end, we studied the effects of disrupting the GPR30 gene in female and male mice. Female GPR30((-/-)) mice had hyperglycemia and impaired glucose tolerance, reduced body growth, increased blood pressure, and reduced serum IGF-I levels. The reduced growth correlated with a proportional decrease in skeletal development. The elevated blood pressure was associated with an increased vascular resistance manifested as an increased media to lumen ratio of the resistance arteries. The hyperglycemia and impaired glucose tolerance in vivo were associated with decreased insulin expression and release in vivo and in vitro in isolated pancreatic islets. GPR30 is expressed in islets, and GPR30 deletion abolished estradiol-stimulated insulin release both in vivo in ovariectomized adult mice and in vitro in isolated islets. Our findings show that GPR30 is important for several metabolic functions in female mice, including estradiol-stimulated insulin release.
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| 8. |
- Andersson, Maria, 1975, et al.
(författare)
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Differential global gene expression response patterns of human endothelium exposed to shear stress and intraluminal pressure
- 2005
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Ingår i: J Vasc Res. - : S. Karger AG. - 1018-1172. ; 42:5, s. 441-52
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the global gene expression response of endothelium exposed to shear stress and intraluminal pressure and tested the hypothesis that the two biomechanical forces induce a differential gene expression response pattern. Intact living human conduit vessels (umbilical veins) were exposed to normal or high intraluminal pressure, or to low or high shear stress in combination with a physiological level of the other force in a unique vascular ex vivo perfusion system. Gene expression profiling was performed by the Affymetrix microarray technology on endothelial cells isolated from stimulated vessels. Biomechanical forces were found to regulate a very large number of genes in the vascular endothelium. In this study, 1,825 genes were responsive to mechanical forces, which corresponds to 17% of the expressed genes. Among pressure-responsive genes, 647 genes were upregulated and 519 genes were down regulated, and of shear stress-responsive genes, 133 genes were upregulated and 771 down regulated. The fraction of genes that responded to both pressure and shear stimulation was surprisingly low, only 13% of the regulated genes. Our results indicate that the two different stimuli induce distinct gene expression response patterns, which can also be observed when studying functional groups. Considering the low number of overlapping genes, we suggest that the endothelial cells can distinguish between shear stress and pressure stimulation.
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