| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Backrud, M., et al.
(författare)
-
Cluster observations and theoretical explanations of broadband waves in the auroral region
- 2005
-
Ingår i: Annales Geophysicae. - : Copernicus Publications. - 1432-0576. ; 23, s. 3739-3752
-
Tidskriftsartikel (refereegranskat)abstract
- Broadband waves are common on auroral field lines. We use two different methods to study the polarization of the waves at 10 to 180 Hz observed by the Cluster spacecraft at altitudes of about 4 Earth radii in the nightside auroral region. Observations of electric and magnetic wave fields, together with electron and ion data, are used as input to the methods. We find that much of the wave emissions are consistent with linear waves in homogeneous plasma. Observed waves with a large electric field perpendicular to the geomagnetic field are more common (electrostatic ion cyclotron waves), while ion acoustic waves with a large parallel electric field appear in smaller regions without suprathermal (tens of eV) plasma. The regions void of suprathermal plasma are interpreted as parallel potential drops of a few hundred volts.
|
|
| 6. |
- Bergdahl, Jan, et al.
(författare)
-
Coping and self-image in patients with visual display terminal-related skin symptoms and perceived hypersensitivity to electricity
- 2004
-
Ingår i: International Archives of Occupational and Environmental Health. - : Springer Science and Business Media LLC. - 0340-0131 .- 1432-1246. ; 77:8, s. 538-542
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives: The aim of the present study was to measure coping resources and self-image in patients with visual display terminal (VDT)-related skin symptoms and hypersensitivity to electricity (HE).Methods: From 1980 to 1998, 350 patients with electrical sensitivity were registered. The patients were subdivided into two groups: patients with skin symptoms evoked by VDTs, television screens, and fluorescent-light tubes and patients with so-called hypersensitivity to electricity with multiple symptoms evoked by exposure to different electrical environments. A questionnaire was sent to all patients and contained the coping resources inventory (CRI) and the structural analysis of social behaviour (SASB) in order for us to measure coping resources and self-image, respectively. The CRI and SASB scores were compared with those of control groups. Two hundred and fifty respondents (73%) returned the questionnaire, 200 (78.5% women) in the VDT group and 50 (62% women) in the HE group.Results: The patient group rated high on the CRI spiritual/philosophical scale and high on the SASB spontaneous, positive and negative clusters but low on the controlled cluster. The female patients scored high on the CRI emotional scale. The VDT group rated lower than the controls on the SASB controlled cluster and higher on both the positive and negative cluster. The HE group scored higher than the control group on the SASB spontaneous and positive clusters. The women in the HE group scored higher on the CRI cognitive and CRI total scale than the VDT group and control group and higher on the CRI emotional scale than the controls. The women in the HE group rated higher than both the women in the VDT and control groups on the SASB spontaneous and positive clusters.Conclusions: The deviant self-image found in these patients, especially the female HE patients, support the view that VDT and HE symptoms can be stress related. In the clinic, a trustful alliance should be established with the patient in order for a more realistic view to be achieved of the capacity.
|
|
| 7. |
|
|
| 8. |
- Dahl, F, et al.
(författare)
-
Imaging single DNA molecules for high precision NIPT
- 2018
-
Ingår i: Scientific reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 8:1, s. 4549-
-
Tidskriftsartikel (refereegranskat)abstract
- Cell-free DNA analysis is becoming adopted for first line aneuploidy screening, however for most healthcare programs, cost and workflow complexity is limiting adoption of the test. We report a novel cost effective method, the Vanadis NIPT assay, designed for high precision digitally-enabled measurement of chromosomal aneuploidies in maternal plasma. Reducing NIPT assay complexity is achieved by using novel molecular probe technology that specifically label target chromosomes combined with a new readout format using a nanofilter to enrich single molecules for imaging and counting without DNA amplification, microarrays or sequencing. The primary objective of this study was to assess the Vanadis NIPT assay with respect to analytical precision and clinical feasibility. Analysis of reference DNA samples indicate that samples which are challenging to analyze with low fetal-fraction can be readily detected with a limit of detection determined at <2% fetal-fraction. In total of 286 clinical samples were analysed and 30 out of 30 pregnancies affected by trisomy 21 were classified correctly. This method has the potential to make cost effective NIPT more widely available with more women benefiting from superior detection and false positive rates.
|
|
| 9. |
- Edvardsson, Berit, et al.
(författare)
-
Coping and Self-image in Patients With Symptoms Attributed to Indoor Environment
- 2013
-
Ingår i: Archives of Environmental & Occupational Health. - : Informa UK Limited. - 1933-8244 .- 2154-4700. ; 68:3, s. 145-152
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigated self-image and coping ability in a group of patients with symptoms from indoor environment. A follow-up questionnaire was sent to 239 patients previously referred with nonspecific building-related symptoms at University Hospital in Umeå, Sweden. One hundred seventy-four women and 14 men answered and the patient group rated their self-image as more spontaneous, more positive, and less negative than a control group. The patient group rated higher on the cognitive scale in the Coping Resources Inventory (CRI) than the control group. The female patients had an increased risk of not being able to work associated with a low score on negative self-image. The authors conclude that certain personality traits may be potential risk factors that increase the probability of encountering and experiencing stressful work situations. The resulting stress may increase workers' susceptibility to indoor environment exposure.
|
|
| 10. |
- Edvardsson, Berit, et al.
(författare)
-
Medical and social prognoses of non-specific building-related symptoms (Sick Building Syndrome) : a follow-up study of patients previously referred to hospital
- 2008
-
Ingår i: International Archives of Occupational and Environmental Health. - : Springer-Verlag New York. - 0340-0131 .- 1432-1246. ; 81:7, s. 805-812
-
Tidskriftsartikel (refereegranskat)abstract
- Objectives The aim of this study was to describe and analysethe medical and social prognoses of patients with nonspeciWcbuilding-related symptoms.Methods A follow-up questionnaire focusing on current medical and social status, care, treatment, other actions taken and personality traits was sent to 239 patients with non-speciWc building-related symptoms assessed during theperiod between1986 and 1998 at University Hospital in Umeå, Sweden. The response rate was 79%.Results Fatigue, irritation of the eyes, and facial erythemawere the most common weekly symptoms reported atfollow-up. As females constituted 92% of the respondents,statistical analyses were restricted to women. The level andseverity of symptoms decreased over time, although nearlyhalf of the patients claimed that symptoms were more or lessunchanged after 7 years or more, despite actions taken.Twenty-Wve percent of the patients were on the sick-list, and20% drew disability pension due to persistent symptoms atfollow-up. The risk of having no work capabilities at followupwas signiWcantly increased if the time from onset to Wrstvisit at the hospital clinic was more than 1 year. This riskwas also signiWcantly higher if the patient at the Wrst visithad Wve or more symptoms. All risk assessments wereadjusted for length of follow-up. Symptoms were oftenaggravated by diVerent situations in everyday life.Conclusions Long-lasting symptoms aggravated by environmentalfactors exist within this group of patients. Theresults support that early and comprehensive measures forrehabilitation are essential for the patients.
|
|
| 11. |
|
|
| 12. |
- Filiou, A, et al.
(författare)
-
Development of Sensitization to Multiple Allergen Molecules from Preschool to School Age Is Related to Asthma
- 2022
-
Ingår i: International archives of allergy and immunology. - : S. Karger AG. - 1423-0097 .- 1018-2438. ; 183:6, s. 628-639
-
Tidskriftsartikel (refereegranskat)abstract
- <b><i>Introduction:</i></b> Allergic sensitization in early life has been identified as a strong risk factor for subsequent asthma in childhood. It is still unclear why only a part of sensitized children develop asthma, and the role of specific allergen molecules in asthma pathogenesis is ambiguous [<i>Pharmacol Ther</i>. 2009 Feb;121(2):174–84]. We assessed the sensitization to multiple allergen molecules longitudinally and explored its relation to persistent asthma at 7 years. <b><i>Methods:</i></b> Seventy-two children included during an acute wheezing episode (cases) were followed prospectively from early preschool age (EPA) to age 7, and compared to 43 healthy controls at EPA. Allergen molecules were analyzed at EPA and age 7 using ImmunoCAP Solid-phase Allergen Chip (ISAC). Asthma diagnosis at 7 years was based on symptoms, medication, and spirometry. <b><i>Results:</i></b> At EPA, cases compared to controls showed a tendency toward having a higher prevalence of allergic sensitization (23.6% vs. 9.3%, <i>p</i> = 0.055). The prevalence of sensitization increased in cases from EPA to 7 years (23.6% vs. 38.9%; <i>p</i> = 0.048) as well as the median number (range) of immunoglobulin E (IgE)-reactive molecules 3 (3–14) versus 6.5 (1–21); <i>p</i> = 0.024. Sensitization to each additional molecule from EPA to the age of 7 was significantly related to asthma at 7 (OR = 1.25, 95% confidence interval [1.01, 1.54]). <b><i>Conclusion:</i></b> Polysensitization, assessed by allergen molecules, had a significant impact on persistent asthma at school age. The extent of sensitization, illustrated by molecular spreading from preschool to school age, was related to asthma diagnosis at 7 years in children with a history of wheezing at early life.
|
|
| 13. |
|
|
| 14. |
- Hagelin, N., et al.
(författare)
-
Gains from Adding Funds of Hedge Funds to Portfolios of Traditional Assets: An International Perspective
- 2005
-
Ingår i: FUNDS OF HEDGE FUNDS. - : BUTTERWORTH HEINEMANN. - 9780750679848 ; , s. 171-187
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We investigate the certainty-equivalent wealth gain from adding funds of hedge funds to portfolios of traditional assets for investors in G7 countries. The allows us to incorporate the effect of currency exposure and different proxies of equity performance. We find that for many investors, access to funds of hedge funds is as valuable as access to international equity markets. Difference between investors in different countries are documented. These differences are due to the relative performance of the different equity markets as well as the fact that hedge fund exposure contains currency exposure that vigilant investors should take care in hedging to reduce unnecessary volatility.
|
|
| 15. |
- Hagelin, N, et al.
(författare)
-
Hedge Fund Allocation under Higher Moments and Illiquidity
- 2005
-
Ingår i: HEDGE FUNDS. - : John Wiley & Sons. - 0471737437
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- We use the discrete-time dynamic investment model to evaluate the gains from including hedge funds in the investment opportunity set. In this multi-period framework, an investor's utility is affected by all moments of the return distribution. We assume that investors rebalance their portfolios on a monthly basis, and we compare the performance of portfolios which may include hedge funds versus portfolios consisting of stocks and bonds only. Our findings show that: (1) investors will allocate wealth to hedge funds even when they take into account deviations from normality in hedge fund returns. Those ex ante optimal allocations result in portfolios that ex post have higher geometric returns compared to the case in which hedge fund investing is not permitted; (2) investors that form portfolios taking all moments of the return distribution into account construct portfolios that are very similar to the portfolios being constructed by investors who care only about expected return and standard deviation, suggesting that the two first moments of the return distribution dominate higher moments; (3) the positive effect on capital growth from including hedge funds into the portfolios remains, although smaller, when the so-called "stale-pricing effect" is considered; and (4) lock-up periods and advance notice periods may force investors to have portfolios that deviate from their targeted ex ante optimal portfolios. Through a simple experiment we show that this inability to rebalance hedge fund allocations may seriously impact the benefits that hedge fund allocations appear to offer.
|
|
| 16. |
- Ivarsson, Ylva, 1976-
(författare)
-
Evolutionary Analysis and Posttranslational Chemical Modifications in Protein Redesign : A Study on Mu Class Glutathione Transferases
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glutathione transferases (GSTs) constitute a family of multifarious enzymes that conjugate glutathione (GSH) with a wide range of electrophiles. GSTs are grouped into different classes based on protein sequence similarities. Despite high sequence identities between GSTs of the same class they often display different substrate specificites. Human GST M1-1 is efficiently catalyzing the conjugation of GSH and various epoxide substrates, whereas the 84% sequence-identical GST M2-2 has low activities with the same substrates.Evolutionary rate analysis was used to identify hypervariable amino acid positions among GST Mu class sequences. A Thr to Ser conversion of the variable residue 210 in GST M2-2 elicited a drastic increase in catalytic activity with epoxides, which is the characteristic activity of GST M1-1. This provides support for the usefulness of evolutionary analysis in identifying functionally important residues, although the additional mutations of two other variable residues did not confer any noteworthy changes in activity.To further investigate the functional importance of residue T210 in GST M2-2 it was replaced by all other commonly occurring amino acids. The replacements caused marked changes in substrate specificity, stability, and expressivity, indicating how functionalities of a duplicated Mu class GST may easily be altered by point mutations. The stereo- and regioselectivity in epoxide-conjugation catalyzed by GSTs M1-1 and M2-2 was investigated. The results show that a serine in position 210 is beneficial for high enantioselectivity with trans-stilbene oxide. However, an alanine in position 210 is more favorable for stereo- and regioselectivity with the smaller epoxide substrate styrene-7,8-oxide. The low enantioselectivity of GST M1-1 was improved 10- and 9- fold with styrene-7,8-oxide and 1-phenylpropylene oxide, respectively, through different combination of site-specific mutations and posttranslational chemical modifications. The approach can be employed in more extensive screening experiments where a large variety of modifications easily can be tested.
|
|
| 17. |
|
|
| 18. |
- Jivegård, Lennart, 1950, et al.
(författare)
-
Effects of three months of low molecular weight heparin (dalteparin) treatment after bypass surgery for lower limb ischemia--a randomised placebo-controlled double blind multicentre trial.
- 2005
-
Ingår i: European journal of vascular and endovascular surgery : the official journal of the European Society for Vascular Surgery. - : Elsevier BV. - 1078-5884. ; 29:2, s. 190-8
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To test the hypothesis that long-term postoperative dalteparin (Fragmin), Pharmacia Corp) treatment improves primary patency of peripheral arterial bypass grafts (PABG) in lower limb ischemia patients on acetylsalicylic acid (ASA) treatment. DESIGN: Prospective randomised double blind multicenter study. MATERIALS AND METHODS: Using a computer algorithm 284 patients with lower limb ischemia, most with pre-operative ischemic ulceration or partial gangrene, from 12 hospitals were randomised, after PABG, to 5000 IU dalteparin or placebo injections once daily for 3 months. All patients received 75 mg of ASA daily for 12 months. Graft patency was assessed at 1, 3 and 12 months. RESULTS: At 1 year, 42 patients had died or were lost to follow-up. Compliance with the injection schedule was 80%. Primary patency rate, in the dalteparin versus the control group, respectively, was 83 versus 80% (n.s.) at 3 months and 59% for both groups at 12 months. Major complication rates and cardiovascular morbidity were not different between the two groups. CONCLUSIONS: In patients on ASA treatment, long-term postoperative dalteparin treatment did not improve patency after peripheral artery bypass grafting. Therefore, low molecular weight heparin treatment cannot be recommended for routine use after bypass surgery for critical lower limb ischemia.
|
|
| 19. |
- Johansson, Fredrik, et al.
(författare)
-
Plasma densities, flow, and solar EUV flux at comet 67P : A cross-calibration approach
- 2021
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 653
-
Tidskriftsartikel (refereegranskat)abstract
- Context. During its two-year mission at comet 67P, Rosetta nearly continuously monitored the inner coma plasma environment for gas production rates varying over three orders of magnitude, at distances to the nucleus ranging from a few to a few hundred kilometres. To achieve the best possible measurements, cross-calibration of the plasma instruments is needed. Aims. Our goal is to provide a consistent plasma density dataset for the full mission, while in the process providing a statistical characterisation of the plasma in the inner coma and its evolution.Methods. We constructed physical models for two different methods to cross-calibrate the spacecraft potential and the ion current as measured by the Rosetta Langmuir probes (LAP) to the electron density as measured by the Mutual Impedance Probe (MIP). We also described the methods used to estimate spacecraft potential, and validated the results with the Ion Composition Analyser (ICA).Results. We retrieve a continuous plasma density dataset for the entire cometary mission with a much improved dynamical range compared to any plasma instrument alone and, at times, improve the temporal resolution from 0.24-0.74 Hz to 57.8 Hz. The physical model also yields, at a three-hour time resolution, ion flow speeds and a proxy for the solar EUV flux from the photoemission from the Langmuir probes.Conclusions. We report on two independent mission-wide estimates of the ion flow speed that are consistent with the bulk H2O+ ion velocities as measured by the ICA. We find the ion flow to consistently be much faster than the neutral gas over the entire mission, lending further evidence that the ions are collisionally decoupled from the neutrals in the coma. Measurements of ion speeds from Rosetta are therefore not consistent with the assumptions made in previously published plasma density models of the comet 67P's ionosphere at the start and end of the mission. Also, the measured EUV flux is perfectly consistent with independently derived values previously published from LAP and lends support for the conclusions drawn regarding an attenuation of solar EUV from a distant nanograin dust population, when the comet activity was high. The new density dataset is consistent with the existing MIP density dataset, but it facilitates plasma analysis on much shorter timescales, and it also covers long time periods where densities were too low to be measured by MIP.
|
|
| 20. |
|
|
| 21. |
|
|
| 22. |
|
|
| 23. |
|
|
| 24. |
- Mandt, K. E., et al.
(författare)
-
RPC observation of the development and evolution of plasma interaction boundaries at 67P/Churyumov-Gerasimenko
- 2016
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 462, s. S9-S22
-
Tidskriftsartikel (refereegranskat)abstract
- One of the primary objectives of the Rosetta Plasma Consortium, a suite of five plasma instruments on-board the Rosetta spacecraft, is to observe the formation and evolution of plasma interaction regions at the comet 67P/Churyumov-Gerasimenko (67P/CG). Observations made between 2015 April and 2016 February show that solar wind-cometary plasma interaction boundaries and regions formed around 2015 mid-April and lasted through early 2016 January. At least two regions were observed, separated by an ion-neutral collisionopause boundary. The inner region was located on the nucleus side of the boundary and was characterized by low-energy water-group ions, reduced magnetic field pileup and enhanced electron densities. The outer region was located outside of the boundary and was characterized by reduced electron densities, water-group ions that are accelerated to energies above 100 eV and enhanced magnetic field pileup compared to the inner region. The boundary discussed here is outside of the diamagnetic cavity and shows characteristics similar to observations made on-board the Giotto spacecraft in the ion pileup region at 1P/Halley. We find that the boundary is likely to be related to ion-neutral collisions and that its location is influenced by variability in the neutral density and the solar wind dynamic pressure.
|
|
| 25. |
|
|
| 26. |
|
|
| 27. |
- Mozzachiodi, S., et al.
(författare)
-
Aborting meiosis allows recombination in sterile diploid yeast hybrids
- 2021
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
-
Tidskriftsartikel (refereegranskat)abstract
- Hybrids are often considered evolutionary dead ends because they do not generate viable offspring. Here, the authors show that sterile yeast hybrids generate genetic diversity through meiotic-like recombination by aborting meiosis and return to asexual growth. Hybrids between diverged lineages contain novel genetic combinations but an impaired meiosis often makes them evolutionary dead ends. Here, we explore to what extent an aborted meiosis followed by a return-to-growth (RTG) promotes recombination across a panel of 20 Saccharomyces cerevisiae and S. paradoxus diploid hybrids with different genomic structures and levels of sterility. Genome analyses of 275 clones reveal that RTG promotes recombination and generates extensive regions of loss-of-heterozygosity in sterile hybrids with either a defective meiosis or a heavily rearranged karyotype, whereas RTG recombination is reduced by high sequence divergence between parental subgenomes. The RTG recombination preferentially arises in regions with low local heterozygosity and near meiotic recombination hotspots. The loss-of-heterozygosity has a profound impact on sexual and asexual fitness, and enables genetic mapping of phenotypic differences in sterile lineages where linkage analysis would fail. We propose that RTG gives sterile yeast hybrids access to a natural route for genome recombination and adaptation.
|
|
| 28. |
- Möslinger, Anja, et al.
(författare)
-
Solar Wind Protons Forming Partial Ring Distributions at Comet 67P
- 2023
-
Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 128:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present partial ring distributions of solar wind protons observed by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. The formation of ring distributions is usually associated with high activity comets, where the spatial scales are larger than multiple ion gyroradii. Our observations are made at a low-activity comet at a heliocentric distance of 2.8 AU on 19 April 2016, and the partial rings occur at a spatial scale comparable to the ion gyroradius. We use a new visualization method to simultaneously show the angular distribution of median energy and differential flux. A fitting procedure extracts the bulk speed of the solar wind protons, separated into components parallel and perpendicular to the gyration plane, as well as the gyration velocity. The results are compared with models and put into context of the global comet environment. We find that the formation mechanism of these partial rings of solar wind protons is entirely different from the well-known partial rings of cometary pickup ions at high-activity comets. A density enhancement layer of solar wind protons around the comet is a focal point for proton trajectories originating from different regions of the upstream solar wind. If the spacecraft location coincides with this density enhancement layer, the different trajectories are observed as an energy-angle dispersion and manifest as partial rings in velocity space.
|
|
| 29. |
- Nilsson, Hans, et al.
(författare)
-
Upstream solar wind speed at comet 67P : reconstruction method, model comparison, and results
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 659
-
Tidskriftsartikel (refereegranskat)abstract
- Context: Rosetta followed comet 67P at heliocentric distances from 1.25 to 3.6 au. The solar wind was observed for much of this time, but was significantly deflected and to some extent slowed down by the interaction with the coma.Aims: We use the different changes in the speed of H+ and He2+ when they interact with the coma to estimate the upstream speed of the solar wind. The different changes in the speed are due to the different mass per charge of the particles, while the electric force per charge due to the interaction is the same. A major assumption is that the speeds of H+ and He2+ were the same in the upstream region. This is investigated.Methods: We derived a method for reconstructing the upstream solar wind from H+ and He2+ observations. The method is based on the assumption that the interaction of the comet with the solar wind can be described by an electric potential that is the same for both H+ and He2+. This is compared to estimates from the Tao model and to OMNI and Mars Express data that we propagated to the observation point.Results: The reconstruction agrees well with the Tao model for most of the observations, in particular for the statistical distribution of the solar wind speed. The electrostatic potential relative to the upstream solar wind is derived and shows values from a few dozen volts at large heliocentric distances to about 1 kV during solar events and close to perihelion. The reconstructed values of the solar wind for periods of high electrostatic potential also agree well with propagated observations and model results.Conclusions: The reconstructed upstream solar wind speed during the Rosetta mission agrees well with the Tao model. The Tao model captures some slowing down of high-speed streams as compared to observations at Earth or Mars. At low solar wind speeds, below 400 km s-1, the agreement is better between our reconstruction and Mars observations than with the Tao model. The magnitude of the reconstructed electrostatic potential is a good measure of the slowing-down of the solar wind at the observation point.
|
|
| 30. |
- Rees, R. M., et al.
(författare)
-
Nitrous oxide emissions from European agriculture; an analysis of variability and drivers of emissions from field experiments
- 2012
-
Ingår i: Biogeosciences Discussions. - : Copernicus GmbH. - 1810-6277. ; 9:7, s. 9259-9288
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrous oxide emissions from a network of agricultural experiments in Europe and Zimbabwe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared 5 within replicated experimental designs in plot based experiments. Arable experiments were conducted at Beano in Italy, El Encin in Spain, Foulum in Denmark, Logården in Sweden, Maulde in Belgium, Paulinenaue in Germany, Harare in Zimbabwe and Tulloch in the UK. Grassland experiments were conducted at Crichton, Nafferton and Peaknaze in the UK, Gödöllö in Hungary, Rzecin in Poland, Zarnekow in Germany and 10 Theix in France. Nitrous oxide emissions were measured at each site over a period of at least two years using static chambers. Emissions varied widely between sites and as a result of manipulation treatments. Average site emissions (throughout the study period) varied between 0.04 and 21.21 kg N2O-N ha−1 yr−1, with the largest fluxes and variability associated with the grassland sites. Total nitrogen addition was found to be 15 the single most important determinant of emissions, accounting for 15% of the variance (using linear regression) in the data from the arable sites (p < 0.0001), and 77% in the grassland sites. The annual emissions from arable sites were significantly greater than those that would be predicted by IPCC default emission factors. Variability in N2O within sites that occurred as a result of manipulation treatments was greater than that 20 resulting from site to site and year to year variation, highlighting the importance of management interventions in contributing to greenhouse gas mitigation.
|
|
| 31. |
- Rees, R. M., et al.
(författare)
-
Nitrous oxide emissions from European agriculture - an analysis of variability and drivers of emissions from field experiments
- 2013
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 10:4, s. 2671-2682
-
Tidskriftsartikel (refereegranskat)abstract
- Nitrous oxide emissions from a network of agricultural experiments in Europe and Zimbabwe were used to explore the relative importance of site and management controls of emissions. At each site, a selection of management interventions were compared within replicated experimental designs in plot based experiments. Arable experiments were conducted at Beano in Italy, El Encin in Spain, Foulum in Denmark, Logården in Sweden, Maulde in Belgium, Paulinenaue in Germany, Harare in Zimbabwe and Tulloch in the UK. Grassland experiments were conducted at Crichton, Nafferton and Peaknaze in the UK, Gödöllö in Hungary, Rzecin in Poland, Zarnekow in Germany and Theix in France. Nitrous oxide emissions were measured at each site over a period of at least two years using static chambers. Emissions varied widely between sites and as a result of manipulation treatments. Average site emissions (throughout the study period) varied between 0.04 and 21.21 kg N2O-N ha−1 yr−1, with the largest fluxes and variability associated with the grassland sites. Total nitrogen addition was found to be the single most important determinant of emissions, accounting for 15% of the variance (using linear regression) in the data from the arable sites (p < 0.0001), and 77% in the grassland sites. The annual emissions from arable sites were significantly greater than those that would be predicted by IPCC default emission factors. Variability in N2O within sites that occurred as a result of manipulation treatments was greater than that resulting from site to site and year to year variation, highlighting the importance of management interventions in contributing to greenhouse gas mitigation.
|
|
| 32. |
|
|
| 33. |
|
|
| 34. |
|
|
| 35. |
|
|
| 36. |
- Stenberg, Gabriella, et al.
(författare)
-
Electron-scale sheets of whistlers close to the magnetopause
- 2005
-
Ingår i: Annales Geophysicae. - Göttingen : Copernicus gesellschaft. - 0992-7689 .- 1432-0576. ; 23:12, s. 3715-3725
-
Tidskriftsartikel (refereegranskat)abstract
- Whistler emissions close to the magnetopause on the magnetospheric side are investigated using the four Cluster spacecraft. The waves are found to be generated in thin (electron-scale) sheets moving with the plasma drift velocity. A feature in the electron data coincides with the waves; hot magnetospheric electrons disappear for a few satellite spins. This produces or enhances a temperature anisotropy, which is found to be responsible for the generation of the whistler mode waves. The high energy electrons are thought to be lost through the magnetopause and we suggest that the field lines, on which the waves are generated, are directly connected to a reconnection diffusion region at the magnetopause.
|
|
| 37. |
|
|
| 38. |
- Stenberg, Gabriella, et al.
(författare)
-
Internal structure and spatial dimensions of whistler wave regions in the magnetopause boundary layer
- 2007
-
Ingår i: Annales Geophysicae. - : European Geosciences Union (EGU). - 0992-7689 .- 1432-0576. ; 25:11, s. 2439-2451
-
Tidskriftsartikel (refereegranskat)abstract
- We use whistler waves observed close to the magnetopause as an instrument to investigate the internal structure of the magnetopause-magnetosheath boundary layer. We find that this region is characterized by tube-like structures with dimensions less than or comparable with an ion inertial length in the direction perpendicular to the ambient magnetic field. The tubes are revealed as they constitute regions where whistler waves are generated and propagate. We believe that the region containing tube-like structures extend several Earth radii along the magnetopause in the boundary layer. Within the presumed wave generating regions we find current structures moving at the whistler wave group velocity in the same direction as the waves.
|
|
| 39. |
|
|
| 40. |
- Stenberg, N., et al.
(författare)
-
Measuring the stress-strain properties of paperboard in the thickness direction
- 2001
-
Ingår i: Journal of Pulp and Paper Science (JPPS). - 0826-6220. ; 27:6, s. 213-221
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a device for measuring stress-strain properties in the thickness direction of paperboard is presented. The device is used for out-of-plane tensile, compression and shear loading. In order to measure stress and strain accurately: the deformation of the test piece is restricted to two directions in the desired plane of deformation by means of an attached fixture. The paperboard is first glued io metal blocks with a high-viscosity adhesive and these blocks are then attached ro the device using a fast-curing epoxy adhesive. To find the true strain in the material, knowledge of the penetration nf the adhesive into the surface of the paper structure is important. A method for determining the penetration of the adhesive, based on a comparison of stress-deformation curves for glued and non-glued rest pieces, is presented, Finally: true stress-strain curves in tension, compression, and shear are presented together with an analysis of the accuracy of the method.
|
|
| 41. |
- Stenberg, N., et al.
(författare)
-
Plasticity in the thickness direction of paperboard under combined shear and normal loading
- 2001
-
Ingår i: Journal of engineering materials and technology. - : ASME International. - 0094-4289 .- 1528-8889. ; 123:2, s. 184-190
-
Tidskriftsartikel (refereegranskat)abstract
- Creasing and offset printing are both examples of paperboard converting operations where the stress state is multiaxial. and where elastic-plastic deformation occurs in the thickness direction. Optimization of paperboard for such operations requires both advanced modeling and a better understanding of the mechanical behavior of the material. Today, our understanding and modeling of the our-of-plane properties are nor as well established as our knowledge of the in-plane behavior. In order to bridge this gap, a modification of the Arcan device, which is well known in other fields, was developed for the experimental characterization of the out-of-plane mechanical behavior of paperboard. A fixture attached to the Arcan device was used to control the deformation in the test piece during loading. The test piece was glued to the device with a high viscosity adhesive and left stress-free during curing to achieve an initial state free of stresses, The apparatus proved to work well and to produce reliable results. Measurements of the mechanical behavior in combined normal and shear loading generated data points for the determination of the yield surface in the stress space. The elastic-plastic behavior in the thickness direction of paperboard was modeled assuming small-strain orthotropic linear elasticity and a quadratic yield function. Simulations using this yield function and an associative flow law showed good agreement with the rest results.
|
|
| 42. |
|
|
| 43. |
- Williamson, H.N., et al.
(författare)
-
Development of a cometosheath at comet 67P/Churyumov-Gerasimenko : a case study comparison of Rosetta observations
- 2022
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 660
-
Tidskriftsartikel (refereegranskat)abstract
- Context: The ionosphere of a comet is known to deflect the solar wind through mass loading, but the interaction is dependent on cometary activity. We investigate the details of this process at comet 67P using the Rosetta Ion Composition Analyzer.Aims: This study aims to compare the interaction of the solar wind and cometary ions during two different time periods in the Rosetta mission.Methods: We compared both the integrated ion moments (density, velocity, and momentum flux) and the velocity distribution functions for two days, four months apart. The velocity distribution functions were projected into a coordinate system dependent on the magnetic field direction and averaged over three hours.Results: The first case shows highly scattered H+ in both ion moments and velocity distribution function. The He2+ ions are somewhat scattered, but less so, and appear more like those of H2O+ pickup ions. The second case shows characteristic evidence of mass-loading, where the solar wind species are deflected, but the velocity distribution function is not significantly changed.Conclusions. The distributions of H+ in the first case, when compared to He2+ and H2O+ pickup ions, are indicative of a narrow cometosheath on the scale of the H+ gyroradius. Thus, He2+ and H2O+, with larger gyroradii, are largely able to pass through this cometosheath. An examination of the momentum flux tensor suggests that all species in the first case have a significant non-gyrotropic momentum flux component that is higher than that of the second mass-loaded case. Mass loading is not a sufficient explanation for the distribution functions and momentum flux tensor in the first case, and so we assume this is evidence of bow shock formation.
|
|
| 44. |
- Williamson, H. N., et al.
(författare)
-
Momentum and Pressure Balance of a Comet Ionosphere
- 2020
-
Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 47:15
-
Tidskriftsartikel (refereegranskat)abstract
- We calculate the momentum flux and pressure of ions measured by the Ion Composition Analyzer (ICA) on the Rosetta mission at comet 67P/Churyumov-Gerasimenko. The total momentum flux stays roughly constant over the mission, but the contributions of different ion populations change depending on heliocentric distance. The magnetic pressure, calculated from Rosetta magnetometer measurements, roughly corresponds with the cometary ion momentum flux. When the spacecraft enters the solar wind ion cavity, the solar wind fluxes drop drastically, while the cometary momentum flux becomes roughly 10 times the solar wind fluxes outside of the ion cavity, indicating that pickup ions behave similarly to the solar wind ions in this region. We use electron density from the Langmuir probe to calculate the electron pressure, which is particularly important close to the comet nucleus where flow changes from antisunward to radially outward.
|
|
| 45. |
|
|
| 46. |
|
|
| 47. |
|
|
| 48. |
|
|
| 49. |
- Zhao, Xiaoyu, 1990-, et al.
(författare)
-
Role of Superficial Defects and Machining Depth in Tensile Properties of Electron Beam Melting (EBM) Made Inconel 718
- 2021
-
Ingår i: Journal of materials engineering and performance (Print). - : Springer. - 1059-9495 .- 1544-1024. ; 30:3, s. 2091-2101
-
Tidskriftsartikel (refereegranskat)abstract
- Since there is no report on the influence of machining depth on electron beam melting (EBM) parts, this paper investigated the role of superficial defects and machining depth in the performance of EBM made Inconel 718 (IN718) samples. Therefore, as-built EBM samples were analyzed against the shallow-machined (i.e., only removal of outer surfaces) and deep-machined (i.e., deep surface removal into the material) parts. It was shown that both as-built and shallow-machined samples had a drastically lower yield strength (970 ± 50 MPa), ultimate tensile stress (1200 ± 40 MPa), and ductility (28 ± 2%) compared to the deep-machined samples. This was since premature failure occurred due to various superficial defects. The superficial defects appeared in two levels, as (1) notches and pores on the surface and (2) irregular pores and cracks within the subsurface. Since the latter occurred down to 2 mm underneath the surface, shallow machining only exposed the subsurface defects to outer surfaces. Thus, the shallow-machined parts achieved only 68% and 8% of UTS and elongation of the deep-machined parts, respectively. This low performance occurred to be comparable to the as-built parts, which failed prematurely due to the high fraction surface voids and notches as well as the subsurface defects.
|
|
