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| 2. |
- Mikkola, T. M., et al.
(författare)
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Influence of long-term postmenopausal hormone-replacement therapy on estimated structural bone strength: A study in discordant monozygotic twins
- 2011
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Ingår i: Journal of Bone and Mineral Research. - : Wiley. - 0884-0431. ; 26:3, s. 546-52
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Tidskriftsartikel (refereegranskat)abstract
- Although postmenopausal hormone-replacement therapy (HRT) is known to prevent fractures, knowledge on the influence of long-term HRT on bone strength and its determinants other than areal bone mineral density is scarce. This study used a genetically controlled design with 24 monozygotic female twin pairs aged 54 to 72 years in which one cotwin was using HRT (mean duration 8 years) and the other had never used HRT. Estimated bone strength, cross-sectional area, volumetric bone mineral density, bone mineral mass, and cross-sectional density and mass distributions were assessed in the tibial shaft, distal tibia, and distal radius with peripheral computed tomography (pQCT). In the tibial shaft, HRT users had 9% [95% confidence interval (CI) 3%-15%] higher estimated bending strength than their nonusing cotwins. Larger cortical area and higher cortical bone mineral density accounted for this difference. The cortex was larger in the HRT users in the endocortical region. In the distal tibia, estimated compressive strength was 24% (95% CI 9%-40%) higher and in the distal radius 26% (95% CI 11%-41%) higher in the HRT users than in their nonusing cotwins owing to higher volumetric bone mineral density. No difference between users and nonusers was observed in total bone cross-sectional area in any measured bone site. The added mineral mass in the HRT users was distributed evenly within and between bone sites. In postmenopausal women, long-term HRT preserves estimated bone strength systemically by preventing bone mineral loss similarly in body weight-loaded and non-weight-loaded bone. (c) 2011 American Society for Bone and Mineral Research.
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| 3. |
- Bilato, A., et al.
(författare)
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Impact of ICRF fast-ions on core turbulence and MHD activity in ASDEX upgrade
- 2023
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Ingår i: 24th Topical Conference On Radio-Frequency Power In Plasmas. - : AIP Publishing.
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Konferensbidrag (refereegranskat)abstract
- Experiments in various tokamaks and their analysis identify the fast ions (FI) generated by NBI and/or ICRF heating as one of the main causes of the observed improvement in core confinement: fast ions can reduce core microturbulence (mainly Ion-Temperature-Gradient (ITG) driven modes) either electrostatically or electromagnetically, or they can resonate with fishbones and high-frequency Alfvén modes, which in turn contribute in stabilizing ITG. In this perspective, we discuss recent experiments done on ASDEX Upgrade (AUG) where ICRF is the main actuator for FI generation for energies above 100 keV. Additionally, ICRF-FIs can substantially impact the MHD activity and its consequent effects on fast ion losses (FILs) and ion-cyclotron emission (ICE). We present dedicated AUG experiments with NBI-D further accelerated by ICRF.
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| 4. |
- Lehtipalo, Katrianne, et al.
(författare)
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The effect of acid-base clustering and ions on the growth of atmospheric nano-particles
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
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| 5. |
- Tröstl, Jasmin, et al.
(författare)
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The role of low-volatility organic compounds in initial particle growth in the atmosphere
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531
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Tidskriftsartikel (refereegranskat)abstract
- About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday(1). Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres(2,3). In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles(4), thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth(5,6), leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer(7-10). Although recent studies(11-13) predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon(2), and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory)(2,14), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown(15) that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
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| 6. |
- Wang, Mingyi, et al.
(författare)
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Synergistic HNO3–H2SO4–NH3 upper tropospheric particle formation
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 605:7910, s. 483-489
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Tidskriftsartikel (refereegranskat)abstract
- New particle formation in the upper free troposphere is a major global source of cloud condensation nuclei (CCN). However, the precursor vapours that drive the process are not well understood. With experiments performed under upper tropospheric conditions in the CERN CLOUD chamber, we show that nitric acid, sulfuric acid and ammonia form particles synergistically, at rates that are orders of magnitude faster than those from any two of the three components. The importance of this mechanism depends on the availability of ammonia, which was previously thought to be efficiently scavenged by cloud droplets during convection. However, surprisingly high concentrations of ammonia and ammonium nitrate have recently been observed in the upper troposphere over the Asian monsoon region. Once particles have formed, co-condensation of ammonia and abundant nitric acid alone is sufficient to drive rapid growth to CCN sizes with only trace sulfate. Moreover, our measurements show that these CCN are also highly efficient ice nucleating particles—comparable to desert dust. Our model simulations confirm that ammonia is efficiently convected aloft during the Asian monsoon, driving rapid, multi-acid HNO3–H2SO4–NH3 nucleation in the upper troposphere and producing ice nucleating particles that spread across the mid-latitude Northern Hemisphere.
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| 7. |
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| 8. |
- Huhtaniemi, R., et al.
(författare)
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Adrenals Contribute to Growth of Castration-Resistant VCaP Prostate Cancer Xenografts
- 2018
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Ingår i: American Journal of Pathology. - : Elsevier BV. - 0002-9440. ; 188:12, s. 2890-2901
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Tidskriftsartikel (refereegranskat)abstract
- The role of adrenal androgens as drivers for castration-resistant prostate cancer (CRPC) growth in humans is generally accepted; however, the value of preclinical mouse models of CRPC is debatable, because mouse adrenals do not produce steroids activating the androgen receptor. In this study, we confirmed the expression of enzymes essential for de novo synthesis of androgens in mouse adrenals, with high intratissue concentration of progesterone (P4) and moderate levels of androgens, such as androstenedione, testosterone, and dihydrotestosterone, in the adrenal glands of both intact and orchectomized (ORX) mice. ORX alone had no effect on serum P4 concentration, whereas orchectomized and adrenalectomized (ORX + ADX) resulted in a significant decrease in serum P4 and in a further reduction in the low levels of serum androgens (androstenedione, testosterone, and dihydrotestosterone), measured by mass spectrometry. In line with this, the serum prostate-specific antigen and growth of VCaP xenografts in mice after ORX + ADX were markedly reduced compared with ORX alone, and the growth difference was not abolished by a glucocorticoid treatment. Moreover, ORX + ADX altered the androgen-dependent gene expression in the tumors, similar to that recently shown for the enzalutamide treatment. These data indicate that in contrast to the current view, and similar to humans, mouse adrenals synthesize significant amounts of steroids that contribute to the androgen receptor–dependent growth of CRPC. © 2018 American Society for Investigative Pathology
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| 9. |
- Kirkby, Jasper, et al.
(författare)
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Ion-induced nucleation of pure biogenic particles
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood(1). Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours(2). It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere(3,4), and that ions have a relatively minor role(5). Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded(6,7). Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of a-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
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| 10. |
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