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Sökning: WFRF:(Kurth T)

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51.
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52.
  • Menietti, J. D., et al. (författare)
  • Analysis of Intense Z-Mode Emission Observed During the Cassini Proximal Orbits
  • 2018
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 45:14, s. 6766-6772
  • Tidskriftsartikel (refereegranskat)abstract
    • The role of Z-mode emission in the diffusive scattering and resonant acceleration of electrons is believed to be important at Saturn. A survey of the 5kHz component of this emission at Saturn earlier reported strong intensity in the lower density regions where the ratio of plasma frequency to cyclotron frequency, f(p)/f(c)<1. At Saturn this occurs along the inner edge of the Enceladus torus near the equator and at higher latitudes. Using the Cassini Radio and Plasma Wave Science instrument observations during the Cassini proximal orbits, we have now identified these emissions extending down to and within the ionosphere. Wave polarization measurements and unique frequency cutoffs are used to positively identify the wave mode. Analogous to the role of whistler mode chorus at Earth, Saturn Z-mode emissions may interact with electrons contributing to the filling or depleting of Saturn's inner radiation belts.
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53.
  • Menietti, J. D., et al. (författare)
  • Extended Survey of Saturn Z-Mode Wave Intensity Through Cassini's Final Orbits
  • 2018
  • Ingår i: Geophysical Research Letters. - : AMER GEOPHYSICAL UNION. - 0094-8276 .- 1944-8007. ; 45:15, s. 7330-7336
  • Tidskriftsartikel (refereegranskat)abstract
    • Similar to whistler mode chorus, Z-mode emission is an efficient diffusive scatterer of electrons possibly resulting in resonant acceleration. We present results of a survey of both the low-band (5 kHz) and for the first time the high-band (20 kHz) intensity of these emissions, based on over 11 years of Cassini Radio and Plasma Wave Science instrument data including nine ring-grazing orbits and two proximal orbits, which occurred at the end of the mission. We distinguish these emissions using density and polarization measurements and calculate the mean intensity as a function of frequency and spatial coordinates. We find that the average low-band Z-mode intensity peak is P-0 similar to 7 x 10(-8) nT(2), while the high-band peak is much lower at P-0 similar to 10(-9) nT(2). The spatial distribution of intensity differs for each emission band implying different source regions and perhaps different source mechanisms.Plain Language SummaryIntense narrow band waves (Z-mode) are observed at Saturn when the spacecraft is located in regions of relatively low density and high magnetic field. These waves are of special importance because they are not seen at such high intensity or over as large a spatial range at Earth. In addition, these waves are known to be very efficient at accelerating electrons under certain conditions and could be responsible for a portion of the observed radiation belts at Saturn. We present an extensive survey of the observations of Z-mode extending over more than 11 years. The survey includes for the first time both the low and high-frequency emissions and orbits from the Cassini final mission, where these waves were seen at a high rate of occurrence. Contour plots and graphs of wave intensity as a function of radius, latitude, and longitude are shown, which will be of value to scientists who model the dynamic processes controlling the electron population at Saturn.
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54.
  • Morooka, Michiko, et al. (författare)
  • Saturn's Dusty Ionosphere
  • 2019
  • Ingår i: Journal of Geophysical Research - Space Physics. - : American Geophysical Union (AGU). - 2169-9380 .- 2169-9402. ; 124:3, s. 1679-1697
  • Tidskriftsartikel (refereegranskat)abstract
    • Measurements of electrons and ions in Saturn's ionosphere down to 1,500-km altitudes as well as the ring crossing region above the ionosphere obtained by the Langmuir probe onboard the Cassini spacecraft are presented. Five nearly identical deep ionosphere flybys during the Grand Finale orbits and the Final plunge orbit revealed a rapid increase in the plasma densities and discrepancies between the electrons and ions densities (N-e and N-i) near the closest approach. The small N-e/N-i ratio indicates the presence of a dusty plasma, a plasma which charge carrier is dominated by negatively charged heavy particles. Comparison of the Langmuir probe obtained density with the light ion density obtained by the Ion and Neutral Mass Spectrometer confirmed the presence of heavy ions. An unexpected positive floating potential of the probe was also observed when N-e/N-i << 1. This suggests that Saturn's ionosphere near the density peak is in a dusty plasma state consisting of negatively and positively charged heavy cluster ions. The electron temperature (T-e) characteristics in the ionosphere are also investigated and unexpectedly high electron temperature value, up to 5000 K, has been observed below 2,500-km altitude in a region where electron-neutral collisions should be prominent. A well-defined relationship between T-e and N-e/N-i ratio was found, implying that the electron heating at low altitudes is related to the dusty plasma state of the ionosphere.
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55.
  • Nyberg, Jenny, 1976, et al. (författare)
  • Cardiovascular fitness and risk of migraine: A large, prospective population-based study of Swedish young adult men
  • 2019
  • Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 9:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Objectives To examine the longitudinal relationship between cardiovascular fitness in young adult men and future risk of migraine and to estimate eventual differential effects among categories of body mass index (BMI) and blood pressure. Design National, prospective, population-based cohort study. Setting Sweden 1968-2014. Participants 18-year-old Swedish men (n=1 819 828) who underwent mandatory military conscription examinations during the years 1968-2005. Primary and secondary outcomes The primary outcome was the first dispensation of prescribed migraine-specific medication, identified using the Swedish Prescribed Drug Register. The secondary outcome was documented migraine diagnosis from the Swedish National Hospital Register. Results During follow-up, 22 533 men filled a prescription for migraine-specific medication. After confounding adjustment, compared with high cardiovascular fitness, low and medium fitness increased the risk of migraine-specific medication (risk ratio (RR) low: 1.29, 95% CI 1.24 to 1.35; population attributable fraction: 3.6%, 95% CI 1.7% to 5.3% and RR medium: 1.15, 95% CI 1.12 to 1.19; population attributable fraction: 8.0%, 95% CI 4.0% to 11.7%). To assess potential effect measure modification, stratified analyses of these association by levels of BMI and blood pressure showed that lower fitness levels increased risk of migraine across all groups except among underweight men or men with high diastolic blood pressure. Conclusions Young men with a lower cardiovascular fitness had a higher long-term risk of developing pharmacological prescription-requiring migraine. This study contributes with information regarding risk factors for migraine in men, an understudied population in migraine research. © 2019 Author(s) (or their employer(s)).
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56.
  • Persoon, A. M., et al. (författare)
  • Evidence of Electron Density Enhancements in the Post-Apoapsis Sector of Enceladus' Orbit
  • 2020
  • Ingår i: Journal of Geophysical Research - Space Physics. - : AMER GEOPHYSICAL UNION. - 2169-9380 .- 2169-9402. ; 125:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Enceladus' plume is the dominant source of neutrals and plasma in Saturn's magnetosphere. The plasma results from the ionization of icy particles and water vapor, which are vented into Saturn's inner magnetosphere through fissures in Enceladus' southern polar region. These fissures are subjected to tidal stresses that can vary as Enceladus moves in a slightly eccentric orbit around Saturn. Plume activity and brightness have also been shown to vary with the moon's orbital position, reaching a maximum when Enceladus is farthest away from Saturn in its orbit (the Enceladus orbital apoapsis). In this paper we will show that temporal variations in the thermal electron density distribution correlate with the position of Enceladus in its orbit around Saturn, with the strongest density enhancements in the vicinity of Enceladus when the moon is in the post-apoapsis sector of its orbit.
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57.
  • Petimar, J, et al. (författare)
  • Coffee, tea, and caffeine intake and amyotrophic lateral sclerosis mortality in a pooled analysis of eight prospective cohort studies.
  • 2019
  • Ingår i: European Journal of Neurology. - : Wiley. - 1351-5101 .- 1468-1331. ; 26:3, s. 468-475
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND AND PURPOSE: Caffeine is associated with a lower risk of some neurological diseases, but few prospective studies have investigated caffeine intake and risk of amyotrophic lateral sclerosis (ALS) mortality. We therefore determined associations between coffee, tea and caffeine intake, and risk of ALS mortality.METHODS: We conducted pooled analyses of eight international, prospective cohort studies, including 351 565 individuals (120 688 men and 230 877 women). We assessed coffee, tea and caffeine intake using validated food-frequency questionnaires administered at baseline. We used Cox regression to estimate study- and sex-specific risk ratios and 95% confidence intervals (CI) for ALS mortality, which were then pooled using a random-effects model. We conducted analyses using cohort-specific tertiles, absolute common cut-points and continuous measures of all exposures.RESULTS: During follow-up, 545 ALS deaths were documented. We did not observe statistically significant associations between coffee, tea or caffeine intake and risk of ALS mortality. The pooled multivariable risk ratio (MVRR) for ≥3 cups per day vs. >0 to <1 cup per day was 1.04 (95% CI, 0.74-1.47) for coffee and 1.17 (95% CI, 0.77-1.79) for tea. The pooled MVRR comparing the highest with the lowest tertile of caffeine intake (mg/day) was 0.99 (95% CI, 0.80-1.23). No statistically significant results were observed when exposures were modeled as tertiles or continuously.CONCLUSIONS: Our results do not support associations between coffee, tea or total caffeine intake and risk of ALS mortality.
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58.
  • van der Kaay, D. C. M., et al. (författare)
  • Comprehensive genetic testing approaches as the basis for personalized management of growth disturbances: current status and perspectives
  • 2022
  • Ingår i: Endocrine Connections. - : Bioscientifica. - 2049-3614. ; 11:11
  • Forskningsöversikt (refereegranskat)abstract
    • The implementation of high-throughput and deep sequencing methods in routine genetic diagnostics has significantly improved the diagnostic yield in patient cohorts with growth disturbances and becomes increasingly important as the prerequisite of personalized medicine. They provide considerable chances to identify even rare and unexpected situations; nevertheless, we must be aware of their limitations. A simple genetic test in the beginning of a testing cascade might also help to identify the genetic cause of specific growth disorders. However, the clinical picture of genetically caused growth disturbance phenotypes can vary widely, and there is a broad clinical overlap between different growth disturbance disorders. As a consequence, the clinical diagnosis and therewith connected the decision on the appropriate genetic test is often a challenge. In fact, the clinician asking for genetic testing has to weigh different aspects in this decision process, including appropriateness (single gene test, stepwise procedure, comprehensive testing), turnaround time as the basis for rapid intervention, and economic considerations. Therefore, a frequent question in that context is 'what to test when'. In this review, we aim to review genetic testing strategies and their strengths and limitations and to raise awareness for the future implementation of interdisciplinary genome medicine in diagnoses, treatment, and counselling of growth disturbances.
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59.
  • van Rheenen, Wouter, et al. (författare)
  • Genome-wide association analyses identify new risk variants and the genetic architecture of amyotrophic lateral sclerosis
  • 2016
  • Ingår i: Nature Genetics. - : Springer Science and Business Media LLC. - 1061-4036 .- 1546-1718. ; 48:9, s. 1043-1048
  • Tidskriftsartikel (refereegranskat)abstract
    • To elucidate the genetic architecture of amyotrophic lateral sclerosis (ALS) and find associated loci, we assembled a custom imputation reference panel from whole-genome-sequenced patients with ALS and matched controls (n = 1,861). Through imputation and mixed-model association analysis in 12,577 cases and 23,475 controls, combined with 2,579 cases and 2,767 controls in an independent replication cohort, we fine-mapped a new risk locus on chromosome 21 and identified C21orf2 as a gene associated with ALS risk. In addition, we identified MOBP and SCFD1 as new associated risk loci. We established evidence of ALS being a complex genetic trait with a polygenic architecture. Furthermore, we estimated the SNP-based heritability at 8.5%, with a distinct and important role for low-frequency variants (frequency 1-10%). This study motivates the interrogation of larger samples with full genome coverage to identify rare causal variants that underpin ALS risk.
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60.
  • Visscher, Pieter T., et al. (författare)
  • Modern arsenotrophic microbial mats provide an analogue for life in the anoxic Archean
  • 2020
  • Ingår i: Communications Earth & Environment. - : Springer Science and Business Media LLC. - 2662-4435. ; 1:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Arsenic-consuming microbes of the hypersaline Laguna La Brava in Chile may be an analogue for early life during the anoxic conditions of the Archean, according to geochemical and metagenomic analyses of the extant microbial mats The earliest evidence of life captured in lithified microbial mats (microbialites) predates the onset of oxygen production and yet, modern oxygenic mats are often studied as analogs based on their morphological similarity and their sedimentological and biogeochemical context. Despite their structural similarity to fossil microbialites, the presence of oxygen in most modern microbial mats disqualifies them as appropriate models for understanding early Earth conditions. Here we describe the geochemistry, element cycling and lithification potential of microbial mats that thrive under permanently anoxic conditions in arsenic laden, sulfidic waters feeding Laguna La Brava, a hypersaline lake in the Salar de Atacama of northern Chile. We propose that these anoxygenic, arsenosulfidic, phototrophic mats are a link to the Archean because of their distinctive metabolic adaptations to a reducing environment with extreme conditions of high UV, vast temperature fluctuations, and alkaline water inputs from combined meteoric and volcanic origin, reminiscent of early Earth.
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