| 1. |
- Kirdyanov, Alexander V., et al.
(författare)
-
Ecological and conceptual consequences of Arctic pollution
- 2020
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 23:12, s. 1827-1837
-
Tidskriftsartikel (refereegranskat)abstract
- Although the effect of pollution on forest health and decline received much attention in the 1980s, it has not been considered to explain the 'Divergence Problem' in dendroclimatology; a decoupling of tree growth from rising air temperatures since the 1970s. Here we use physical and biogeochemical measurements of hundreds of living and dead conifers to reconstruct the impact of heavy industrialisation around Norilsk in northern Siberia. Moreover, we develop a forward model with surface irradiance forcing to quantify long-distance effects of anthropogenic emissions on the functioning and productivity of Siberia's taiga. Downwind from the world's most polluted Arctic region, tree mortality rates of up to 100% have destroyed 24,000 km(2)boreal forest since the 1960s, coincident with dramatic increases in atmospheric sulphur, copper, and nickel concentrations. In addition to regional ecosystem devastation, we demonstrate how 'Arctic Dimming' can explain the circumpolar 'Divergence Problem', and discuss implications on the terrestrial carbon cycle.
|
|
| 2. |
- Badelek, B, et al.
(författare)
-
The photon collider at TESLA
- 2004
-
Ingår i: International Journal of Modern Physics A. - 0217-751X. ; 19:30, s. 5097-5186
-
Forskningsöversikt (refereegranskat)abstract
- High energy photon colliders (gammagamma,gammae) are based on e(-)e(-) linear colliders where high energy photons are produced using Compton scattering of laser light on high energy electrons just before the interaction point. This paper is a part of the Technical Design Report of the linear collider TESLA.(1) Physics program, possible parameters and some technical aspects of the photon collider at TESLA are discussed.
|
|
| 3. |
- Mikhaylova, A. I., et al.
(författare)
-
Specific features of the current–voltage characteristics of SiO2/4H-SiC MIS structures with phosphorus implanted into silicon carbide
- 2016
-
Ingår i: Semiconductors (Woodbury, N.Y.). - 1063-7826 .- 1090-6479. ; 50:1, s. 103-105
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of phosphorus implantation into a 4H-SiC epitaxial layer immediately before the thermal growth of a gate insulator in an atmosphere of dry oxygen on the reliability of the gate insulator is studied. It is found that, together with passivating surface states, the introduction of phosphorus ions leads to insignificant weakening of the dielectric breakdown field and to a decrease in the height of the energy barrier between silicon carbide and the insulator, which is due to the presence of phosphorus atoms at the 4H-SiC/SiO2 interface and in the bulk of silicon dioxide.
|
|
| 4. |
- Giele, Walter, et al.
(författare)
-
The QCD / SM working group: Summary report
- 2002
-
Ingår i: Physics at TeV colliders. Proceedings, Euro Summer School, Les Houches, France, May 21-June 1, 2001. ; , s. 275-426, s. 275-426
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)
|
|
| 5. |
- Metcalfe, Travis S., et al.
(författare)
-
Asteroseismology and Spectropolarimetry of the Exoplanet Host Star Lambda Serpentis
- 2023
-
Ingår i: Astronomical Journal. - : Institute of Physics (IOP). - 0004-6256 .- 1538-3881. ; 166:4
-
Tidskriftsartikel (refereegranskat)abstract
- The bright star lambda Ser hosts a hot Neptune with a minimum mass of 13.6 M & OPLUS; and a 15.5 day orbit. It also appears to be a solar analog, with a mean rotation period of 25.8 days and surface differential rotation very similar to the Sun. We aim to characterize the fundamental properties of this system and constrain the evolutionary pathway that led to its present configuration. We detect solar-like oscillations in time series photometry from the Transiting Exoplanet Survey Satellite, and we derive precise asteroseismic properties from detailed modeling. We obtain new spectropolarimetric data, and we use them to reconstruct the large-scale magnetic field morphology. We reanalyze the complete time series of chromospheric activity measurements from the Mount Wilson Observatory, and we present new X-ray and ultraviolet observations from the Chandra and Hubble space telescopes. Finally, we use the updated observational constraints to assess the rotational history of the star and estimate the wind braking torque. We conclude that the remaining uncertainty on the stellar age currently prevents an unambiguous interpretation of the properties of lambda Ser, and that the rate of angular momentum loss appears to be higher than for other stars with a similar Rossby number. Future asteroseismic observations may help to improve the precision of the stellar age.
|
|
| 6. |
- Metcalfe, Travis S., et al.
(författare)
-
Constraints on Magnetic Braking from the G8 Dwarf Stars 61 UMa and tau Cet
- 2023
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 948:1
-
Tidskriftsartikel (refereegranskat)abstract
- During the first half of their main-sequence lifetimes, stars rapidly lose angular momentum to their magnetized winds, a process known as magnetic braking. Recent observations suggest a substantial decrease in the magnetic braking efficiency when stars reach a critical value of the Rossby number, the stellar rotation period normalized by the convective overturn timescale. Cooler stars have deeper convection zones with longer overturn times, reaching this critical Rossby number at slower rotation rates. The nature and timing of the transition to weakened magnetic braking have previously been constrained by several solar analogs and two slightly hotter stars. In this Letter, we derive the first direct constraints from stars cooler than the Sun. We present new spectropolarimetry of the old G8 dwarf tau Cet from the Large Binocular Telescope, and we reanalyze a published Zeeman Doppler image of the younger G8 star 61 UMa, yielding the large-scale magnetic field strengths and morphologies. We estimate mass-loss rates using archival X-ray observations and inferences from Ly alpha measurements, and we adopt other stellar properties from asteroseismology and spectral energy distribution fitting. The resulting calculations of the wind braking torque demonstrate that the rate of angular momentum loss drops by a factor of 300 between the ages of these two stars (1.4-9 Gyr), well above theoretical expectations. We summarize the available data to help constrain the value of the critical Rossby number, and we identify a new signature of the long-period detection edge in recent measurements from the Kepler mission.
|
|
| 7. |
- Mikhaylov, Aleksey I., et al.
(författare)
-
On the ion implantation of phosphorus as a method for the passivation of states at the interface between 4H-SiC and SiO2 produced by thermal oxidation in dry oxygen
- 2014
-
Ingår i: Semiconductors (Woodbury, N.Y.). - : Maik Nauka-Interperiodica Publishing. - 1063-7826 .- 1090-6479. ; 48:12, s. 1581-1585
-
Tidskriftsartikel (refereegranskat)abstract
- A method is suggested for reducing the density of surface states at the 4H-SiC/SiO2 interface by the implantation of phosphorus ions into a 4H-SiC epitaxial layer immediately before the growth of a gate insulator in an atmosphere of dry oxygen. A significant decrease in the density of surface states is observed at a phosphor-ion concentration at the SiO2/SiC interface exceeding 1018 cm−3. However, together with the passivation of surface states, the introduction of phosphorus ions leads to an increase in the built-in charge in the insulator and also slightly deteriorates the reliability of the gate insulator fabricated by this technique.
|
|
| 8. |
- Accomando, E., et al.
(författare)
-
Physics with e + e - linear colliders
- 1998
-
Ingår i: Physics Reports. - 0370-1573. ; 299:1, s. 1-78
-
Tidskriftsartikel (refereegranskat)abstract
- The physics potential of e + e - linear colliders is summarized in this report. These machines are planned to operate in the first phase at a center-of-mass energy of 500 GeV, before being scaled up to about 1 TeV. In the second phase of the operation, a final energy of about 2 TeV is expected. The machines will allow us to perform precision tests of the heavy particles in the Standard Model, the top quark and the electroweak bosons. They are ideal facilities for exploring the properties of Higgs particles, in particular in the intermediate mass range. New vector bosons and novel matter particles in extended gauge theories can be searched for and studied thoroughly. The machines provide unique opportunities for the discovery of particles in supersymmetric extensions of the Standard Model, the spectrum of Higgs particles, the supersymmetric partners of the electroweak gauge and Higgs bosons, and of the matter particles. High precision analyses of their properties and interactions will allow for extrapolations to energy scales close to the Planck scale where gravity becomes significant. In alternative scenarios, i.e. compositeness models, novel matter particles and interactions can be discovered and investigated in the energy range above the existing colliders up to the TeV scale. Whatever scenario is realized in Nature, the discovery potential of e + e - linear colliders and the high precision with which the properties of particles and their interactions can be analyzed, define an exciting physics program complementary to hadron machines.
|
|
| 9. |
|
|
| 10. |
- Cole-Kodikara, Elizabeth M., et al.
(författare)
-
Spot evolution on LQ Hya from 2006-2017 : temperature maps based on SOFIN and FIES data
- 2019
-
Ingår i: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 629:Sept
-
Tidskriftsartikel (refereegranskat)abstract
- Context. LQ Hya is one of the most frequently studied young solar analogue stars. Recently, it has been observed to show intriguing behaviour when analysing long-term photometry. For instance, from 2003-2009, a coherent spot structure migrating in the rotational frame was reported by various authors. However, ever since, the star has entered a chaotic state where coherent structures seem to have disappeared and rapid phase jumps of the photometric minima occur irregularly over time. Aims. LQ Hya is one of the stars included in the SOFIN/FIES long-term monitoring campaign extending over 25 yr. Here, we publish new temperature maps for the star during 2006-2017, covering the chaotic state of the star. Methods. We used a Doppler imaging technique to derive surface temperature maps from high-resolution spectra. Results. From the mean temperatures of the Doppler maps, we see a weak but systematic increase in the surface temperature of the star. This is consistent with the simultaneously increasing photometric magnitude. During nearly all observing seasons, we see a high-latitude spot structure which is clearly non-axisymmetric. The phase behaviour of this structure is very chaotic but agrees reasonably well with the photometry. Equatorial spots are also frequently seen, but we interpret many of them to be artefacts due to the poor to moderate phase coverage. Conclusions. Even during the chaotic phase of the star, the spot topology has remained very similar to the higher activity epochs with more coherent and long-lived spot structures. In particular, we see high-latitude and equatorial spot activity, the mid latitude range still being most often void of spots. We interpret the erratic jumps and drifts in phase of the photometric minima to be caused by changes in the high-latitude spot structure rather than the equatorial spots.
|
|
