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Sökning: WFRF:(Clemmons J.)

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4.
  • Burch, J. L., et al. (författare)
  • Electron-scale measurements of magnetic reconnection in space
  • 2016
  • Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 352:6290, s. 1189-
  • Forskningsöversikt (refereegranskat)abstract
    • Magnetic reconnection is a fundamental physical process in plasmas whereby stored magnetic energy is converted into heat and kinetic energy of charged particles. Reconnection occurs in many astrophysical plasma environments and in laboratory plasmas. Using measurements with very high time resolution, NASA's Magnetospheric Multiscale (MMS) mission has found direct evidence for electron demagnetization and acceleration at sites along the sunward boundary of Earth's magnetosphere where the interplanetary magnetic field reconnects with the terrestrial magnetic field. We have (i) observed the conversion of magnetic energy to particle energy; (ii) measured the electric field and current, which together cause the dissipation of magnetic energy; and (iii) identified the electron population that carries the current as a result of demagnetization and acceleration within the reconnection diffusion/dissipation region.
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5.
  • Christiansen, J. S., et al. (författare)
  • Growth Hormone Research Society perspective on the development of long-acting growth hormone preparations
  • 2016
  • Ingår i: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 174:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: The Growth Hormone (GH) Research Society (GRS) convened a workshop to address important issues regarding trial design, efficacy, and safety of long-acting growth hormone preparations (LAGH). Participants: A closed meeting of 55 international scientists with expertise in GH, including pediatric and adult endocrinologists, basic scientists, regulatory scientists, and participants from the pharmaceutical industry. Evidence: Current literature was reviewed for gaps in knowledge. Expert opinion was used to suggest studies required to address potential safety and efficacy issues. Consensus process: Following plenary presentations summarizing the literature, breakout groups discussed questions framed by the planning committee. Attendees reconvened after each breakout session to share group reports. A writing team compiled the breakout session reports into a draft document that was discussed and revised in an open forum on the concluding day. This was edited further and then circulated to attendees from academic institutions for review after the meeting. Participants from pharmaceutical companies did not participate in the planning, writing, or in the discussions and text revision on the final day of the workshop. Scientists from industry and regulatory agencies reviewed the manuscript to identify any factual errors. Conclusions: LAGH compounds may represent an advance over daily GH injections because of increased convenience and differing phamacodynamic properties, providing the potential for improved adherence and outcomes. Better methods to assess adherence must be developed and validated. Long-term surveillance registries that include assessment of efficacy, cost-benefit, disease burden, quality of life, and safety are essential for understanding the impact of sustained exposure to LAGH preparations.
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6.
  • Johannsson, Gudmundur, 1960, et al. (författare)
  • Growth Hormone Research Society perspective on biomarkers of GH action in children and adults
  • 2018
  • Ingår i: Endocrine Connections. - : Bioscientifica. - 2049-3614. ; 7:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: The Growth Hormone Research Society (GRS) convened a Workshop in 2017 to evaluate clinical endpoints, surrogate endpoints and biomarkers during GH treatment of children and adults and in patients with acromegaly. Participants: GRS invited 34 international experts including clinicians, basic scientists, a regulatory scientist and physicians from the pharmaceutical industry. Evidence: Current literature was reviewed and expert opinion was utilized to establish the state of the art and identify current gaps and unmet needs. Consensus process: Following plenary presentations, breakout groups discussed questions framed by the planning committee. The attendees re-convened after each breakout session to share the group reports. A writing team compiled the breakout session reports into a document that was subsequently discussed and revised by participants. This was edited further and circulated for final review after the meeting. Participants from pharmaceutical companies were not part of the writing process. Conclusions: The clinical endpoint in paediatric GH treatment is adult height with height velocity as a surrogate endpoint. Increased life expectancy is the ideal but unfeasible clinical endpoint of GH treatment in adult GH-deficient patients (GHDA) and in patients with acromegaly. The pragmatic clinical endpoints in GHDA include normalization of body composition and quality of life, whereas symptom relief and reversal of comorbidities are used in acromegaly. Serum IGF-I is widely used as a biomarker, even though it correlates weakly with clinical endpoints in GH treatment, whereas in acromegaly, normalization of IGF-I may be related to improvement in mortality. There is an unmet need for novel biomarkers that capture the pleiotropic actions of GH in relation to GH treatment and in patients with acromegaly.
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7.
  • Trainer, P J, et al. (författare)
  • Treatment of acromegaly with the growth hormone-receptor antagonist pegvisomant.
  • 2000
  • Ingår i: The New England journal of medicine. - 0028-4793. ; 342:16, s. 1171-7
  • Tidskriftsartikel (refereegranskat)abstract
    • Patients with acromegaly are currently treated with surgery, radiation therapy, and drugs to reduce hypersecretion of growth hormone, but the treatments may be ineffective and have adverse effects. Pegvisomant is a genetically engineered growth hormone-receptor antagonist that blocks the action of growth hormone.We conducted a 12-week, randomized, double-blind study of three daily doses of pegvisomant (10 mg, 15 mg, and 20 mg) and placebo, given subcutaneously, in 112 patients with acromegaly.The mean (+/-SD) serum concentration of insulin-like growth factor I (IGF-I) decreased from base line by 4.0+/-16.8 percent in the placebo group, 26.7+/-27.9 percent in the group that received 10 mg of pegvisomant per day, 50.1+/-26.7 percent in the group that received 15 mg of pegvisomant per day, and 62.5+/-21.3 percent in the group that received 20 mg of pegvisomant per day (P<0.001 for the comparison of each pegvisomant group with placebo), and the concentrations became normal in 10 percent, 54 percent, 81 percent, and 89 percent of patients, respectively (P<0.001 for each comparison with placebo). Among patients treated with 15 mg or 20 mg of pegvisomant per day, there were significant decreases in ring size, soft-tissue swelling, the degree of excessive perspiration, and fatigue. The score fortotal symptoms and signs of acromegaly decreased significantly in all groups receiving pegvisomant (P< or =0.05). The incidence of adverse effects was similar in all groups.On the basis of these preliminary results, treatment of patients who have acromegaly with a growth hormone-receptor antagonist results in a reduction in serum IGF-I concentrations and in clinical improvement.
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8.
  • van der Lely, A J, et al. (författare)
  • Long-term treatment of acromegaly with pegvisomant, a growth hormone receptor antagonist.
  • 2001
  • Ingår i: Lancet (London, England). - 0140-6736. ; 358:9295, s. 1754-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Pegvisomant is a new growth hormone receptor antagonist that improves symptoms and normalises insulin-like growth factor-1 (IGF-1) in a high proportion of patients with acromegaly treated for up to 12 weeks. We assessed the effects of pegvisomant in 160 patients with acromegaly treated for an average of 425 days.Treatment efficacy was assessed by measuring changes in tumour volume by magnetic resonance imaging, and serum growth hormone and IGF-1 concentrations in 152 patients who received pegvisomant by daily subcutaneous injection for up to 18 months. The safety analysis included 160 patients some of whom received weekly injections and are excluded from the efficacy analysis.Mean serum IGF-1 concentrations fell by at least 50%: 467 mg/L (SE 24), 526 mg/L (29), and 523 mg/L (40) in patients treated for 6, 12 and 18 months, respectively (p<0.001), whereas growth hormone increased by 12.5 mg/L (2.1), 12.5 mg/L (3.0), and 14.2 mg/L (5.7) (p<0.001). Of the patients treated for 12 months or more, 87 of 90 (97%) achieved a normal serum IGF-1 concentration. In patients withdrawn from pegvisomant (n=45), serum growth hormone concentrations were 8.0 mg/L (2.5) at baseline, rose to 15.2 mg/L (2.4) on drug, and fell back within 30 days of withdrawal to 8.3 mg/L (2.7). Antibodies to growth hormone were detected in 27 (16.9%) of patients, but no tachyphylaxis was seen. Serum insulin and glucose concentrations were significantly decreased (p<0.05). Two patients experienced progressive growth of their pituitary tumours, and two other patients had increased alanine and asparate aminotransferase concentrations requiring withdrawal from treatment. Mean pituitary tumour volume in 131 patients followed for a mean of 11.46 months (0.70) decreased by 0.033 cm(3) (0.057; p=0.353).Pegvisomant is an effective medical treatment for acromegaly.
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9.
  • Allen, D. B., et al. (författare)
  • GH safety workshop position paper: a critical appraisal of recombinant human GH therapy in children and adults
  • 2016
  • Ingår i: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 174:2
  • Tidskriftsartikel (refereegranskat)abstract
    • Recombinant human GH (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-term safety, including cancer risk, impact on glucose homeostasis, and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk, and the need for long-term surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS, and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement.
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10.
  • Allen, David B, et al. (författare)
  • GH Safety Workshop Position Paper: a critical appraisal of recombinant human growth hormone therapy in children and adults.
  • 2016
  • Ingår i: European Journal of Endocrinology. - 1479-683X. ; 174:2, s. 1-9
  • Tidskriftsartikel (refereegranskat)abstract
    • Recombinant human growth hormone (rhGH) has been in use for 30 years, and over that time its safety and efficacy in children and adults has been subject to considerable scrutiny. In 2001, a statement from the GH Research Society (GRS) concluded that 'for approved indications, GH is safe'; however, the statement highlighted a number of areas for on-going surveillance of long-term safety including; cancer risk, impact on glucose homeostasis and use of high dose pharmacological rhGH treatment. Over the intervening years, there have been a number of publications addressing the safety of rhGH with regard to mortality, cancer and cardiovascular risk and the need for longterm surveillance of the increasing number of adults who were treated with rhGH in childhood. Against this backdrop of interest in safety, the European Society of Paediatric Endocrinology (ESPE), the GRS and the Pediatric Endocrine Society (PES) convened a meeting to reappraise the safety of rhGH. The ouput of the meeting is a concise position statement.
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11.
  • Knudsen, D. J., et al. (författare)
  • Sub-kilometer thermal plasma structure near 1750 km altitude in the polar cusp/cleft
  • 1994
  • Ingår i: Geophysical Research Letters. - 0094-8276. ; 21:17, s. 1907-1910
  • Tidskriftsartikel (refereegranskat)abstract
    • We present Freja Cold Plasma Analyzer (CPA) measurements from an encounter with the low altitude (approx.1750 km) polar cusp during which the CPA measured 2-D images of the thermal (0-16 eV) particle distributions at 1.2 s time resolution, and simultaneously made rapid estimates (600/s) of integrated thermal particle flux into the instrument. The high resolution data show bursty ion flux enhancements of the order of tens of percent on time scales of tens of ms, or alternatively, hundreds of m spatial scales. The flux of electrons from 0-16 eV also varied by tens of percent and on temporal/spatial scales comparable to those in the ion cases. There is some evidence that the thermal particle flux variations are associated with intense low-frequency electromagnetic fluctuations with temporal/spatial scales identical to those seen by the CPA (tens of ms. hundreds of m).
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  • Andersson, L., Wahlund, J.E., Clemmons, J., Gustavsson, B. and Eliasson, L. (författare)
  • Electromagnetic waves and bursty electron acceleration: implications from Freja.
  • 2001
  • Ingår i: Annales Geophysicae. ; 20:2, s. 139-150
  • Tidskriftsartikel (refereegranskat)abstract
    • Dispersive Alfven wave activity is identified in four dayside auroral oval events measured by the Freja satellite. The events are characterized by ion injection, bursty electron precipitation below about 1 keV, transverse ion heating and broadband extreme
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  • Frey, H U, et al. (författare)
  • Freja and ground-based analysis of inverted-V events
  • 1998
  • Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - 0148-0227. ; 103:A3, s. 4303-4314
  • Tidskriftsartikel (refereegranskat)abstract
    • During two campaigns, ground-based auroral observations were performed in coordination with Freja. The high temporal and spatial resolution of the satellite instruments as well as the real-time recording with a stereoscopic camera system from the ground enabled detailed comparison of small- and large-scale optical phenomena with particle and field data measured by the satellite. Three passes of the satellite over inverted-V auroral arcs and over precipitation regions with strong field-aligned electron spectra are investigated. Brightness modulations within auroral arcs coincide with modulations of primary electron fluxes. The dynamics of small-scale structures within arcs as well as the proper motion of arcs are analyzed and compared with electric fields measured by the satellite and with BARS radar measurements. Energy fluxes independently determined from the ground and from the satellite are used to calculate the field-aligned conductance. The results agree with predictions of the kinetic theory of the mirror force, if we allow for variations of the density and thermal energy of the electrons in the source region of the magnetosphere. Detailed comparison of electron spectra and electric and magnetic field perturbations provide evidence of different acceleration mechanisms for the electrons, electrostatic acceleration inside inverted-V's, and wave acceleration in transient regions.
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  • Yamauchi, M., et al. (författare)
  • Acceleration signatures in the dayside boundary layer and the cusp
  • 2001
  • Ingår i: Physics and Chemistry of the Earth, Part C. - 1464-1917 .- 1873-4685. ; 26:03-jan, s. 195-200
  • Tidskriftsartikel (refereegranskat)abstract
    • Freja data show various electron acceleration signatures in the cusp and the dayside boundary layer: (1) time dispersive super-Alfvénic electrons followed by strong wave activity which accompanies transient downward super-thermal electron burst in both the boundary layer and the cusp; (2) quasi-stationary bidirectional electron burst coinciding with localized intense field-aligned current in the boundary layer; (3) downgoing electron burst without visible time dispersion in the cusp; and (4) thermal electrons accelerated by electrostatic potential in both the boundary layer and the cusp. The first and last signatures are different between two regions for typical energies and fluxes, and these differences probably reflect the different auroral emission in the cusp proper (red) and the boundary layer (green). Contributions of these electrons to the large-scale field-aligned currents are also different between two regions. The dispersed electron burst is probably accelerated within 1 Re above the ionosphere. From this result we believe that the cusp red aurora is caused mainly by accelerated electrons, but not by the smoothly entering magnetosheath electrons without acceleration. This also requires revisions of flux transfer event models for the structured cusp red aurora.
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17.
  • Andersson, L, et al. (författare)
  • Electron signatures and Alfven waves
  • 2002
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 107:A9
  • Tidskriftsartikel (refereegranskat)abstract
    • [1] We identify two distinct electron populations associated with Alfven waves in the Freja data set using the high time resolution state of the art electron detector. One of the populations, detected together with an Alfven wave, is field-aligned and can be seen as trapped within the wave. The other electron population is detected before the wave and consists of electrons which have left the wave at a point with a velocity higher than the local Alfven speed. In the paper, the electrons leaving wave are modeled for different density profiles and are compared with the observed data. Depending on the density profile, the model can produce the same energy-time and pitch angle-time dispersion that is observed in the Freja data. The conclusion of the paper is that the Alfven wave can explain the observed particle signatures. It is shown that the Alfven wave acceleration can create electron signatures similar to inverted-V structures. The density distribution along a flux tube has an important role in the type of particle signatures that can be detected at low altitudes.
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  • Blomberg, Lars G., et al. (författare)
  • Solar windmagnetosphere-ionosphere coupling : an event study based on Freja data
  • 2004
  • Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 66:5, s. 375-380
  • Tidskriftsartikel (refereegranskat)abstract
    • Freja data are used to study the relative contributions from the high-latitude (reconnection/direct entry) and low-latitude (viscous interaction) dynamos to the cross-polar potential drop. Convection streamlines which are connected to the high-latitude dynamo may be identified from dispersed magnetosheath ions not only in the cusp/cleft region itself but also several degrees poleward of it. This fact, together with Freja's orbital geometry allows us to infer the potential drop from the high-latitude dynamo as well as to obtain a lower limit to the potential drop from the low-latitude dynamo for dayside Freja passes. All cases studied here are for active magnetospheric conditions. The Freja data suggest that under these conditions at least one third of the potential is generated in the low-latitude dynamo. These observations are consistent with earlier observations of the potential across the low-latitude boundary layer if we assume that the low-latitude dynamo region extends over several tens of Earth radii in the antisunward direction along the tail flanks, and that the majority of the potential drop derives from the sun-aligned component of the electric field rather than from its cross-boundary component, or equivalently, that the centre of the dynamo region is located quite far down tail. A possible dynamo geometry is illustrated.
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21.
  • Boehm, M. H., et al. (författare)
  • Observations of an  upward-directed electron beam with the perpendicular temperature of the cold ionosphere
  • 1995
  • Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 22, s. 2103-2106
  • Tidskriftsartikel (refereegranskat)abstract
    • The Freja TESP electron spectrometer has repeatedly observed similar to 100 eV - 1 keV upward-directed, anti-field-aligned electron beams near 1700 km altitude in the auroral zone. A particularly intense event, at energies up to 2 keV, is described. The beam perpendicular temperature T perpendicular to(e)), was as low as 0.1-0.2 eV at 100-200 eV parallel energy. The 10-15 s period of upward fluxes was coincident with a low density (similar to 10 cm(-3)) period and a similar to 5 keV ion conic. Strong low frequency waves and the lack of any downward motion in the simultaneously observed ion conic suggest a strong element of wave acceleration, while electric field and ion loss cone measurements provide limited evidence of potential acceleration to a fraction of the observed energies.
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  • Hamrin, Maria, et al. (författare)
  • Inhomogeneous transverse electric fields and wave generation in the auroral region : A statistical study
  • 2001
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 106:A6, s. 10803-10816
  • Tidskriftsartikel (refereegranskat)abstract
    • We use data from the Freja satellite to investigate the importance of localized transverse DC electric fields for the generation of broadband waves responsible for ion heating in the auroral region. Theoretical models indicate that shear in the plasma Row perpendicular to the geomagnetic field can generate waves in a broad range around the ion gyrofrequency for parallel currents significantly below the threshold of the current-driven electrostatic ion cyclotron instability. We compare in situ data with laboratory measurements and theoretical predictions, and we find that inhomogeneous electric fields might well be important for the generation of waves in the auroral region.
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24.
  • Ho, Ken, et al. (författare)
  • Pituitary Neoplasm Nomenclature Workshop: Does Adenoma Stand the Test of Time?
  • 2021
  • Ingår i: Journal of the Endocrine Society. - : The Endocrine Society. - 2472-1972. ; 5:3
  • Forskningsöversikt (refereegranskat)abstract
    • The WHO Classification of Endocrine Tumours designates pituitary neoplasms as adenomas. A proposed nomenclature change to pituitary neuroendocrine tumors (PitNETs) has been met with concern by some stakeholder groups. The Pituitary Society coordinated the Pituitary Neoplasm Nomenclature (PANOMEN) workshop to address the topic. Experts in pituitary developmental biology, pathology, neurosurgery, endocrinology, and oncology, including representatives nominated by the Endocrine Society, European Society of Endocrinology, European Neuroendocrine Association, Growth Hormone Research Society, and International Society of Pituitary Surgeons. Clinical epidemiology, disease phenotype, management, and prognosis of pituitary adenomas differ from that of most NETs. The vast majority of pituitary adenomas are benign and do not adversely impact life expectancy. A nomenclature change to PitNET does not address the main challenge of prognostic prediction, assigns an uncertain malignancy designation to benign pituitary adenomas, and may adversely affect patients. Due to pandemic restrictions, the workshop was conducted virtually, with audiovisual lectures and written précis on each topic provided to all participants. Feedback was collated and summarized by Content Chairs and discussed during a virtual writing meeting moderated by Session Chairs, which yielded an evidence-based draft document sent to all participants for review and approval. There is not yet a case for adopting the PitNET nomenclature. The PANOMEN Workshop recommends that the term adenoma be retained and that the topic be revisited as new evidence on pituitary neoplasm biology emerges.
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25.
  • Norqvist, P, et al. (författare)
  • Ion cyclotron heating in the dayside magnetosphere
  • 1996
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 101:A6, s. 13179-13193
  • Tidskriftsartikel (refereegranskat)abstract
    • Observations of waves and particles obtained by the Freja satellite at altitudes around 1700 km in the dayside high-latitude magnetosphere are used to study ion energization. We find that ions, including O+, during several events of intense ion energization can be heated perpendicularly to the geomagnetic field to mean energies df up to about 20 eV via the process of cyclotron resonance by broadband waves around the ion gyrofrequencies. There is a good correlation between such broadband waves and the ion energization. The waves show no spectral features at the O+ gyrofrequency. The observed wave amplitudes are used as an input to a Monte Carlo simulation to obtain the observed ion energies. The waves around the ion gyrofrequencies may be generated either by field-aligned electrons or by nonlinear processes transferring energy from waves with lower frequencies. Not only the mean energy but also the shape of the particle distribution agrees with the cyclotron resonance heating mechanism. Other mechanisms, such as heating by lower hybrid waves or by a slowly varying electric field, are investigated but are found to be less important than cyclotron heating in this region of space.
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26.
  • Olsson, A, et al. (författare)
  • Freja studies of the current-voltage relation in substorm-related events
  • 1998
  • Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - : AMER GEOPHYSICAL UNION. ; 103:A3, s. 4285-4301
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Field-aligned currents and electrostatic potentials play important roles in the coupling between the magnetosphere and the ionosphere. If one assumes that the ionosphere-magnetosphere potential difference is mainly due to the mirror force, one can use the
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27.
  • Sarris, Theodoros, et al. (författare)
  • Plasma-neutral interactions in the lower thermosphere-ionosphere : The need for in situ measurements to address focused questions
  • 2023
  • Ingår i: Frontiers in Astronomy and Space Sciences. - : Frontiers Media SA. - 2296-987X. ; 9
  • Forskningsöversikt (refereegranskat)abstract
    • The lower thermosphere-ionosphere (LTI) is a key transition region between Earth's atmosphere and space. Interactions between ions and neutrals maximize within the LTI and in particular at altitudes from 100 to 200 km, which is the least visited region of the near-Earth environment. The lack of in situ co-temporal and co-spatial measurements of all relevant parameters and their elusiveness to most remote-sensing methods means that the complex interactions between its neutral and charged constituents remain poorly characterized to this date. This lack of measurements, together with the ambiguity in the quantification of key processes in the 100-200 km altitude range affect current modeling efforts to expand atmospheric models upward to include the LTI and limit current space weather prediction capabilities. We present focused questions in the LTI that are related to the complex interactions between its neutral and charged constituents. These questions concern core physical processes that govern the energetics, dynamics, and chemistry of the LTI and need to be addressed as fundamental and long-standing questions in this critically unexplored boundary region. We also outline the range of in situ measurements that are needed to unambiguously quantify key LTI processes within this region, and present elements of an in situ concept based on past proposed mission concepts.
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28.
  • Stasiewicz, K, et al. (författare)
  • Cavity resonators and Alfven resonance cones observed on Freja
  • 1997
  • Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 102:A2, s. 2565-2575
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiresolution wavelet analysis of magnetic field, electric field, and plasma density records taken on Freja during strong auroral events shows evidence for cavity Alfven resonators in the topside ionosphere. The cavity (or transverse) resonators consist of standing perpendicular wave modes which are trapped inside plasma cavities of different perpendicular scales. The smallest size cavities have perpendicular widths comparable to the electron skin depth, lambda(s) = 2 pi c/omega(pe), and are presumably associated with the resonance cones of Alfven waves launched by a magnetospheric source. The Alfven resonance cones (ARCs) carry intense field-aligned currents, support strong parallel electric fields and represent discharge and heating channels for auroral particles. We have made a detailed analysis of the electromagnetic properties of two singular auroral structures associated with ARCs. Field-aligned currents at the resonance structures reach intensities of 100-300 rho Am-2 in the upward and downward directions and are carried mainly by cold ionospheric plasma in both directions. The parallel electric field of ARCs is observed at amplitudes up to 100 mV/m, which is 2 orders of magnitude larger than expected for the unbounded Alfven waves. Field-aligned electron beams accelerated inside ARCs are observed to drive Langmuir waves with parallel electric field occasionally exceeding 1 V/m. One of the analyzed ARC structures has electromagnetic and particle properties characteristic of ''black aurora'' with electric field diverging from the center of the cavity; the other has converging electric field.
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29.
  • Stasiewicz, K, et al. (författare)
  • Cavity resonators and Alfven resonance cones observed on Freja
  • 1997
  • Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - : AMER GEOPHYSICAL UNION. ; 102:A2, s. 2565-2575
  • Tidskriftsartikel (refereegranskat)abstract
    • Multiresolution wavelet analysis of magnetic field, electric field, and plasma density records taken on Freja during strong auroral events shows evidence for cavity Alfven resonators in the topside ionosphere. The cavity (or transverse) resonators consist
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30.
  • Vaivads, A, et al. (författare)
  • Energy transport during O+ energization by ELF waves observed by the Freja satellite
  • 1999
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 104:A2, s. 2563-2572
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a study of strong ELF waves correlated with Of ion heating. We investigate the kinetic energy flux of oxygen ions and electrons parallel to the ambient magnetic field and the Poynting flux along the magnetic field of waves in different frequency regions. We show that the Poynting flux of lower hybrid waves and waves with frequencies below the oxygen gyrofrequency is downward but much less than the upgoing oxygen ion energy flux. The Poynting flux of ELF waves with frequencies at about half the local proton gyrofrequency is also downward, and it is comparable to, or larger, than the upward oxygen energy flux. Our results are consistent with a scenario where ELF waves with frequencies around half the proton gyrofrequency are generated above the satellite and transfer energy to oxygen ions in a region below the satellite.
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31.
  • van der Lely, Aart Jan, et al. (författare)
  • Development of ACRODAT®, a new software medical device to assess disease activity in patients with acromegaly
  • 2017
  • Ingår i: Pituitary. - : Springer Science and Business Media LLC. - 1386-341X .- 1573-7403. ; 20:6, s. 692-701
  • Tidskriftsartikel (refereegranskat)abstract
    • Purpose: Despite availability of multimodal treatment options for acromegaly, achievement of long-term disease control is suboptimal in a significant number of patients. Furthermore, disease control as defined by biochemical normalization may not always show concordance with disease-related symptoms or patient’s perceived quality of life. We developed and validated a tool to measure disease activity in acromegaly to support decision-making in clinical practice. Methods: An international expert panel (n = 10) convened to define the most critical indicators of disease activity. Patient scenarios were constructed based on these chosen parameters. Subsequently, a panel of 21 renowned endocrinologists at pituitary centers (Europe and Canada) categorized each scenario as stable, mild, or significant disease activity in an online validation study. Results: From expert opinion, five parameters emerged as the best overall indicators to evaluate disease activity: insulin-like growth factor I (IGF-I) level, tumor status, presence of comorbidities (cardiovascular disease, diabetes, sleep apnea), symptoms, and health-related quality of life. In the validation study, IGF-I and tumor status became the predominant parameters selected for classification of patients with moderate or severe disease activity. If IGF-I level was ≤1.2x upper limit of normal and tumor size not significantly increased, the remaining three parameters contributed to the decision in a compensatory manner. Conclusion: The validation study underlined IGF-I and tumor status for routine clinical decision-making, whereas patient-oriented outcome measures received less medical attention. An Acromegaly Disease Activity Tool (ACRODAT) is in development that might assist clinicians towards a more holistic approach to patient management in acromegaly.
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32.
  • Wahlund, JE, et al. (författare)
  • Broadband ELF plasma emission during auroral energization 1. Slow ion acoustic waves
  • 1998
  • Ingår i: JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS. - : AMER GEOPHYSICAL UNION. ; 103:A3, s. 4343-4375
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • High-resolution measurements by the Freja spacecraft of broadband extremely low frequency (BB-ELF) emission from de up to the lower hybrid frequency (a few kHz) are reported from regions of transverse ion acceleration (TAI) and broad-energy suprathermal e
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33.
  • Yamauchi, M, et al. (författare)
  • Acceleration signatures in the dayside boundary layer and the cusp
  • 2001
  • Ingår i: PHYSICS AND CHEMISTRY OF THE EARTH PART C-SOLAR-TERRESTIAL AND PLANETARY SCIENCE. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1464-1917. ; 26:1-3, s. 195-200 Language: English
  • Tidskriftsartikel (refereegranskat)abstract
    • Freja data show various electron acceleration signatures in the cusp and the dayside boundary layer: (1) time dispersive suger-Alfvenic electrons followed by strong wave activity which accompanies transient downward super-thermal electron burst in both th
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34.
  • Yamauchi, M, et al. (författare)
  • Dynamic response of the cusp morphology to the solar wind : A case study during passage of the solar wind plasma cloud on February 21, 1994
  • 1996
  • Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 101:A11, s. 24675-24687
  • Tidskriftsartikel (refereegranskat)abstract
    • On February 21, 1994, both Geotail and LMP 8 satellites detected an interplanetary plasma cloud with intense interplanetary magnetic field (IMF>50 nT) and high dynamic pressure (> 50 nPa). During this interval the Freja satellite detected intense cusp-like plasma injections in four out of six dayside traversals. The first two traversals are carefully studied, During the first traversal the overall morphology of the ion injection is characterized by a ''multiple-injection'' signature over a wide magnetic local time (MLT) range, whereas it is characterized by a ''single-injection'' signature with narrow injection region at 8 MLT in the second traversal, The solar wind conditions were also quite different between these two periods: while both dynamic and magnetic pressures stayed high during entire period, the dynamic beta was much higher during the first Freja traversal than during the second traversal. Between these two traversals, the cusp plasma injection is detected by the Sondre Stromfjord radar. The radar signature of the plasma injection is identified using the satellite particle data when the satellite and the radar were conjugate (the satellite's footprint was in the radar's field of view.) The cusp position and dynamics observed by the Sondre Stromfjord radar again show a very good correlation to the solar wind condition, especially to the dynamic pressure. The result indicates the following. (1) During southward IMF the cusp morphology differs for conditions of high or low solar wind dynamic pressure. High dynamic pressure widens the cusp (with multiple injections), whereas high magnetic pressure narrows it (with single injection), The effect of the IMF on the cusp locations and morphology becomes dominant only when the dynamic pressure is not very high, (2) Such a morphological difference reflects dynamic pressure more than dynamic beta during southward IMF at least during times of high solar wind dynamic pressure. (3) The cusp morphology responds very quickly to the changes in the solar wind conditions.
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