| 1. |
|
|
| 2. |
- Shamrai, K P, et al.
(author)
-
Discharge disruptions in a helicon plasma source
- 1997
-
In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. - : American Vacuum Society. - 0734-2101 .- 1520-8559. ; 15:6, s. 2864-2874
-
Journal article (peer-reviewed)abstract
- We study experimentally and theoretically stable regimes and dischargedisruptions in a helicon plasma source. At fixed input power and gas pressure, stable operation of the source is possible below some critical value of magnetic field Bcr." role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">Bcr.Bcr. The plasma density increases with the magnetic field and reaches a maximum value nmax" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">nmaxnmax at Bcr;" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">Bcr;Bcr; after which the discharge disruption occurs. Both Bcr" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">BcrBcr and nmax" role="presentation" style="display: inline; line-height: normal; word-spacing: normal; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative;">nmaxnmax increase almost linearly with the input power and the rate of increase is increasing with the pressure. Matching of the plasma load to the rf power source improves when approaching the disruption point, and becomes perfect at the critical field. The theory of discharge disruptions assumes the power absorption in a helicon source to arise from the linear conversion of helicon waves into electrostatic waves at the plasma edge. The calculated dependence of the absorbed power on the plasma density turns out to be nonmonotonic with minima at antiresonances of the electrostatic waveexcitation. This explains qualitatively principal peculiarities of dischargedisruptions. The calculated plasma impedance is in agreement with experimental value within a factor of 2.
|
|
| 3. |
|
|
| 4. |
- Fraver, Shawn, et al.
(author)
-
Demographics and disturbance history of a boreal old-growth Picea abies forest
- 2008
-
In: Journal of Vegetation Science. - : Wiley. - 1100-9233 .- 1654-1103. ; 19:6, s. 789-798
-
Journal article (peer-reviewed)abstract
- Question: To what extent do tree growth, mortality, and long-term disturbance patterns affect stand structure and composition of an old-growth Picea abies forest?Location: Boreal Sweden.Methods: We linked data from three 50 m × 50 m permanent plots established in 1986 with dendrochronology data to evaluate tree growth and mortality over an 18-year period and to describe a several-hundred-year disturbance history for this forest type.Results: Averaged over all diameters, P. abies trees had an annual mortality rate of 0.60%; however, diameter had a striking effect on both growth and mortality, with trees of intermediate diameters (ca. 20–30 cm) showing faster growth and lower mortality. Their increased vigor gave rise to a diameter distribution resembling the ‘rotated sigmoid’ (not reverse-J) proposed for such conditions, and it led to a deficit of snags of intermediate diameters. Slow-growing trees had an increased likelihood of dying. Although recruitment occurred in most decades over the past 400 years, two prominent recruitment peaks occurred (mid 1700s and 1800s), neither of which appeared to cause a shift in tree species composition. The lack of fire evidence suggests that fire was not responsible for these recruitment peaks.Conclusions: Taken together, these results depict a rather impassive system, where canopy trees die slowly over decades. Field observations suggest that fungal infections, mediated by wind, account for much of the mortality during these periods of relative quiescence. However, these periods are at times punctuated by moderate-severity disturbances that foster abundant recruitment.
|
|
| 5. |
- Halme, P., et al.
(author)
-
Challenges of ecological restoration : Lessons from forests in northern Europe
- 2013
-
In: Biological Conservation. - : Elsevier BV. - 0006-3207 .- 1873-2917. ; 167, s. 248-256
-
Research review (peer-reviewed)abstract
- The alarming rate of ecosystem degradation has raised the need for ecological restoration throughout different biomes and continents. North European forests may appear as one of the least vulnerable ecosystems from a global perspective, since forest cover is not rapidly decreasing and many ecosystem services remain at high level. However, extensive areas of northern forests are heavily exploited and have lost a major part of their biodiversity value. There is a strong requirement to restore these areas towards a more natural condition in order to meet the targets of the Convention on Biological Diversity. Several northern countries are now taking up this challenge by restoring forest biodiversity with increasing intensity. The ecology and biodiversity of boreal forests are relatively well understood making them a good model for restoration activities in many other forest ecosystems. Here we introduce northern forests as an ecosystem, discuss the historical and recent human impact and provide a brief status report on the ecological restoration projects and research already conducted there. Based on this discussion, we argue that before any restoration actions commence, the ecology of the target ecosystem should be established with the need for restoration carefully assessed and the outcome properly monitored. Finally, we identify the most important challenges that need to be solved in order to carry out efficient restoration with powerful and long-term positive impacts on biodiversity: coping with unpredictability, maintaining connectivity in time and space, assessment of functionality, management of conflicting interests and social restrictions and ensuring adequate funding. © 2013 Elsevier Ltd.
|
|
| 6. |
- Jonsson, Anders P, 1954-
(author)
-
Entropy, Free Energy and the Creation of Order out of Chaos
- 2016
-
In: Society’s steering systems – a Friend book to Inga Carlman<em> </em>. - Östersund : Avdelingen för Ekoteknik och Hålbart Byggande. - 9789188025975 ; , s. 57-73
-
Book chapter (other academic/artistic)
|
|
| 7. |
|
|
| 8. |
- Östberg, Tomas L., et al.
(author)
-
Accelerated biodegradation of n-alkanes in aqueous solution by the addition of fermented whey
- 2006
-
In: International Biodeterioration & Biodegradation. - : Elsevier BV. - 0964-8305 .- 1879-0208. ; 57:3, s. 190-194
-
Journal article (peer-reviewed)abstract
- The effect of fermented whey on the aerobic degradation of n-alkanes by a microbial consortium was investigated in an aqueous system. Microbial degradation of 100 mg n-alkanes (C12, C14, C16 and C18) in mineral nutrient medium was assessed by measuring the decrease in n-alkanes, production of CO2 and increase in biomass. The addition of fermented whey at a concentration of 5 mg dry weight to a nutrient medium receiving a small-sized inoculum (103.4 CFU ml-1)shortened the lag phase from 8 to 3 days, but the degradation rate during the degradation phase was not enhanced. The shortened lag phase at low initial concentration of microorganisms indicates that the fermented whey stimulates growth in the initial phase, without reducing the consortium's capacity for n-alkane degradation.
|
|
| 9. |
|
|
