| 1. |
- Pastorelli, Giada, et al.
(författare)
-
Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Large Magellanic Cloud
- 2020
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 498:3, s. 3283-3301
-
Tidskriftsartikel (refereegranskat)abstract
- Reliable models of the thermally pulsing asymptotic giant branch (TP-AGB) phase are of critical importance across astrophysics, including our interpretation of the spectral energy distribution of galaxies, cosmic dust production, and enrichment of the interstellar medium. With the aim of improving sets of stellar isochrones that include a detailed description of the TP-AGB phase, we extend our recent calibration of the AGB population in the Small Magellanic Cloud (SMC) to the more metal-rich Large Magellanic Cloud (LMC). We model the LMC stellar populations with the TRILEGAL code, using the spatially resolved star formation history derived from the VISTA survey. We characterize the efficiency of the third dredge-up by matching the star counts and the K-s-band luminosity functions of the AGB stars identified in the LMC. In line with previous findings, we confirm that, compared to the SMC, the third dredge-up in AGB stars of the LMC is somewhat less efficient, as a consequence of the higher metallicity. The predicted range of initial mass of C-rich stars is between M-i approximate to 1.7 and 3 M-circle dot at Z(i) = 0.008. We show how the inclusion of new opacity data in the carbon star spectra will improve the performance of our models. We discuss the predicted lifetimes, integrated luminosities, and mass-loss rate distributions of the calibrated models. The results of our calibration are included in updated stellar isochrones publicly available.
|
|
| 2. |
- Pastorelli, Giada, et al.
(författare)
-
Constraining the thermally pulsing asymptotic giant branch phase with resolved stellar populations in the Small Magellanic Cloud
- 2019
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : OXFORD UNIV PRESS. - 0035-8711 .- 1365-2966. ; 485:4, s. 5666-5692
-
Tidskriftsartikel (refereegranskat)abstract
- The thermally pulsing asymptotic giant branch (TP-AGB) experienced by low-and intermediate-mass stars is one of the most uncertain phases of stellar evolution and the models need to be calibrated with the aid of observations. To this purpose, we couple high-quality observations of resolved stars in the Small Magellanic Cloud (SMC) with detailed stellar population synthesis simulations computed with the TRILEGAL code. The strength of our approach relies on the detailed spatially resolved star formation history of the SMC, derived from the deep near-infrared photometry of the VISTA survey of the Magellanic Clouds, as well as on the capability to quickly and accurately explore a wide variety of parameters and effects with the COLIBRI code for the TP-AGB evolution. Adopting a well-characterized set of observations - star counts and luminosity functions - we set up a calibration cycle along which we iteratively change a few key parameters of the TP-AGB models until we eventually reach a good fit to the observations. Our work leads to identify two best-fitting models that mainly differ in the efficiencies of the third dredge-up and mass-loss in TP-AGB stars with initial masses larger than about 3 M-circle dot. On the basis of these calibrated models, we provide a full characterization of the TP-AGB stellar population in the SMC in terms of stellar parameters (initial masses, C/O ratios, carbon excess, mass-loss rates). Extensive tables of isochrones including these improved models are publicly available.
|
|
| 3. |
- Roschier, L, et al.
(författare)
-
Noise performance of the radio-frequency single-electron transistor
- 2004
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:3, s. 1274-1286
-
Tidskriftsartikel (refereegranskat)abstract
- Measurements were performed on aluminum and multiwalled carbon nanotube radio-frequency single-electron transistors (RF-SETs) and analyzed the results carefully. A detailed noise model based on scattering matrix and noise wave formalisms was developed. The signal-to-noise ratios obtained from the model agree well with the measured charge sensitivities. It was found that, in the setup, the first stage HEMT amplifier was the most inadequate component contributing nearly all of the charge noise.
|
|
| 4. |
- Alheim, Katarina, et al.
(författare)
-
Identification of a functional glucocorticoid response element in the promoter of the cylcin-dependant kinase inhibitor p57(Kip2)
- 2003
-
Ingår i: Journal of Molecular Endocrinology. - : Bioscientifica. - 0952-5041 .- 1479-6813. ; 30:3, s. 359-368
-
Tidskriftsartikel (refereegranskat)abstract
- Glucocorticoids are known regulators of the cell cycle, normally exerting an anti-proliferative effect. We have previously shown that glucocorticoids stimulate expression of p57(Kip2), a member of the Cip/Kip family of cyclin-dependent kinase inhibitors which, in some cell types, may account for the anti-proliferative responses seen after glucocorticoid treatment. The induction of p57(Kip2) involves primary transcriptional effects where no de novo protein synthesis is necessary, suggesting a direct interaction of the glucocorticoid receptor with the p57(Kip2) gene. In this study we have identified a functional glucocorticoid response element (GRE), located 5 kilo bases (kb) upstream of the transcription start site in the human P57(Kip2) promoter. This GRE was functional also when isolated, suggesting a direct transcriptional effect of the glucocorticoid receptor. Furthermore, mutation of this GRE abolished glucocorticoid induction of the reporter gene, whereas mutation of a nearby Sp1 site did not. Using electrophoretic mobility shift assays, we have shown that the -5 kb p57(Kip2) promoter GRE was able to compete with a well-known GRE for glucocorticoid receptor binding. Sequence comparisons with the mouse genome showed that this GRE is highly conserved, further strengthening the biological importance of this site. All these data emphasize the involvement of this GRE in the glucocorticoid-mediated induction of p57(Kip2) expression.
|
|
| 5. |
- Andersson, I., et al.
(författare)
-
Human MxA Protein Inhibits the Replication of Crimean-Congo Hemorrhagic Fever Virus
- 2004
-
Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 78:8, s. 4323-4329
-
Tidskriftsartikel (refereegranskat)abstract
- Crimean-Congo hemorrhagic fever virus (CCHFV) belongs to the genus Nairovirus within the family Bunyaviridae and is the causative agent of severe hemorrhagic fever. Despite increasing knowledge about hemorrhagic fever viruses, the factors determining their pathogenicity are still poorly understood. The interferon-induced MxA protein has been shown to have an inhibitory effect on several members of the Bunyaviridae family, but the effect of MxA against CCHFV has not previously been studied. Here, we report that human MxA has antiviral activity against CCHFV. The yield of progeny virus in cells constitutively expressing MxA was reduced up to 1,000-fold compared with control cells, and accumulation of viral genomes was blocked. Confocal microscopy revealed that MxA colocalizes with the nucleocapsid protein (NP) of CCHFV in the perinuclear regions of infected cells. Furthermore, we found that MxA interacted with NP by using a coimmunoprecipitation assay. We also found that an amino acid substitution (E645R) within the C-terminal domain of MxA resulted in a loss of MxA antiviral activity and, concomitantly, in the capacity to interact with CCHFV NP. These results suggest that MxA, by interacting with a component of the nucleocapsid, prevents replication of CCHFV viral RNA and thereby inhibits the production of new infectious virus particles.
|
|
| 6. |
- Brackmann, Christian, et al.
(författare)
-
Laser-induced fluorescence of formaldehyde in combustion using third harmonic Nd : YAG laser excitation
- 2003
-
Ingår i: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. - 1386-1425. ; 59:14, s. 3347-3356
-
Tidskriftsartikel (refereegranskat)abstract
- Formaldehyde (CH2O) is an important intermediate species in combustion processes and it can through laser-induced fluorescence measurements be used for instantaneous flame front detection. The present study has focussed on the use of the third harmonic of a Nd:YAG laser at 355 nm as excitation wavelength for formaldehyde, and different dimethyl ether (C2H6O) flames were used as sources of formaldehyde in the experiments. The investigations included studies of the overlap between the laser profile and the absorption lines of formaldehyde, saturation effects and the potential occurrence of laser-induced photochemistry. The technique was applied for detection of formaldehyde in an internal combustion engine operated both as a spark ignition engine and as a homogenous charge compression ignition engine. (C) 2003 Elsevier B.V. All rights reserved.
|
|
| 7. |
|
|
| 8. |
- Erlandsson, A C, et al.
(författare)
-
Herpes simplex virus type 1 infection and glucocorticoid treatment regulate viral yield, glucocorticoid receptor and NF-kappaB levels.
- 2002
-
Ingår i: The Journal of endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 175:1, s. 165-76
-
Tidskriftsartikel (refereegranskat)abstract
- The interplay between the endocrine and immune systems has come into focus in recent years with the insight that endocrine parameters may affect susceptibility to both auto-immune and infectious diseases. Our interest in immunoendocrine regulation led us to investigate the effects of glucocorticoids on Herpes simplex virus type 1 (HSV-1) infections. Glucocorticoids used to treat inflammatory conditions are not yet recommended for HSV-1 therapy, since they have been reported to prolong viral shedding both in vivo and in vitro. Here we report that glucocorticoids did not alter the viral yield in human gingival fibroblast (HGF) cell culture when glucocorticoid treatment and viral infection occured simultaneously, but the viral yield increased when cells were treated with the glucocorticoid dexamethasone (dex) prior to viral infection. We found that viral infection in our primary cell system increased NF-kappaB levels and DNA binding. In addition, the amount of glucocorticoid receptor (GR) increased following viral infection, and HSV-1 infection as such could induce glucocorticoid-driven transcription of a reporter gene in human embryo kidney (HEK) 293 cells stably transfected with GR. Dex treatment did not affect HSV-1-induced binding of p65 to an NF-kappaB element in an electrophoretic mobility shift assay, and acyclovir was still efficient as an anti-viral drug in the presence of dex. Further studies of the observed effects of HSV-1 infection and glucocorticoid treatment on GR and NF-kappaB regulation could give insights into the immunoendocrine mechanisms important for defence and therapy against viral infections.
|
|
| 9. |
|
|
| 10. |
|
|
