| 11. |
- Houshang, A., et al.
(författare)
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Effect of Excitation Fatigue on the Synchronization of Multiple Nanocontact Spin-Torque Oscillators
- 2014
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Ingår i: IEEE Magnetics Letters. - 1949-307X .- 1949-3088. ; 5, s. 3000404-
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Tidskriftsartikel (refereegranskat)abstract
- Nanocontact spin-torque oscillators (NC-STOs) act as intrinsically nanoscale and highly current and magnetic field tunable, ultrawide band microwave signal generators. However, their low output power and high phase noise remain critical obstacles toward actual applications. Mutual synchronization of multiple NCs is one possibility to overcome these shortcomings. This letter presents a detailed study of the mutual synchronization in a NC-STO with two NCs. In particular, the effect of repeated measurements on the synchronization behavior is explored. Repeated measurements at high drive currents are shown to significantly degrade the performance of the devices with the most striking consequence being that the devices can no longer be synchronized. Ferromagnetic resonance measurements reveal a decrease in the saturation magnetization and an increase in the damping coefficient in annealed NiFe films, consistent with Cu diffusion into the NiFe from the adjacent Cu layers. This increase in damping will act to sever the spin wave-mediated communication channel between the NCs necessary for synchronization. These results highlight an important consideration when studying the synchronization behavior of multi-NC devices where Joule heating is expected to scale unfavorably with the number of NCs.
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| 12. |
- Jolkkonen, Mikael, et al.
(författare)
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Kinetic evidence for different mechanisms of interaction of black mamba toxins MT alpha and MT beta with muscarinic receptors
- 2001
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Ingår i: Toxicon. - 0041-0101 .- 1879-3150. ; 39:2-3, s. 377-382
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Tidskriftsartikel (refereegranskat)abstract
- By studying the influence of two toxins from the black mamba Dendroaspis polylepis on the kinetics of [H-3]-N-methylscopolamine binding to muscarinic acetylcholine receptors from rat cerebral cortex, it was revealed that these toxins, MT alpha and MT beta, interact with the receptors via kinetically distinct mechanisms. MT beta bound to receptors in a one-step, readily reversible process with the dissociation constant K-d = 5.3 mu M. The binding mechanism of MT alpha was more complex, involving at least two consecutive steps. A fast receptor-toxin complex formation (K-T = 3.8 mu M) was followed by a slow process of isomerisation of this complex (k(i) = 1.8 x 10(-2) s(-1), half-time 39 s). A similar two-step interaction mechanism has been established for a related toxin, MT2 from the green mamba D. angusticeps (K-T = 1.4 mu M, k(i) = 8.3 x 10(-4) s(-1), half-time 840 s). The slow isomerisation process delays the effect of MT alpha and MT2, but increases their apparent potency compared to toxins unable to induce the isomerisation process.
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| 13. |
- Lund, P E, et al.
(författare)
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The orexin OX1 receptor activates a novel Ca2+ influx pathway necessary for coupling to phospholipase C.
- 2000
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 275:40, s. 30806-12
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Tidskriftsartikel (refereegranskat)abstract
- Ca(2+) elevations in Chinese hamster ovary cells stably expressing OX(1) receptors were measured using fluorescent Ca(2+) indicators fura-2 and fluo-3. Stimulation with orexin-A led to pronounced Ca(2+) elevations with an EC(50) around 1 nm. When the extracellular [Ca(2+)] was reduced to a submicromolar concentration, the EC(50) was increased 100-fold. Similarly, the inositol 1,4,5-trisphosphate production in the presence of 1 mm external Ca(2+) was about 2 orders of magnitude more sensitive to orexin-A stimulation than in low extracellular Ca(2+). The shift in the potency was not caused by depletion of intracellular Ca(2+) but by a requirement of extracellular Ca(2+) for production of inositol 1,4,5-trisphosphate. Fura-2 experiments with the "Mn(2+)-quench technique" indicated a direct activation of a cation influx pathway by OX(1) receptor independent of Ca(2+) release or pool depletion. Furthermore, depolarization of the cells to +60 mV, which almost nullifies the driving force for Ca(2+) entry, abolished the Ca(2+) response to low concentrations of orexin-A. The results thus suggest that OX(1) receptor activation leads to two responses, (i) a Ca(2+) influx and (ii) a direct stimulation of phospholipase C, and that these two responses converge at the level of phospholipase C where the former markedly enhances the potency of the latter.
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| 14. |
- Oster, S., et al.
(författare)
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Self-management and hospitalization in 615 Swedish patients with Addison's disease during the coronavirus disease 2019 pandemic: a retrospective study
- 2023
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Ingår i: European Journal of Endocrinology. - : Oxford University Press (OUP). - 0804-4643 .- 1479-683X. ; 188:2
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Tidskriftsartikel (refereegranskat)abstract
- Objective Autoimmune Addison's disease (AAD) entails a chronic adrenal insufficiency and is associated with an increased risk of severe infections. It is, however, unknown how patients with AAD were affected by the coronavirus disease 2019 (COVID-19) pandemic of 2020-2021. This study was aimed at investigating the incidence of COVID-19 in patients with AAD in Sweden, the self-adjustment of medications during the disease, impact on social aspects, and treatment during hospitalization. Additionally, we investigated if there were any possible risk factors for infection and hospitalization. Design and methods Questionnaires were sent out from April to October 2021 to 813 adult patients with AAD in the Swedish Addison Registry. The questionnaires included 55 questions inquiring about COVID-19 sickness, hospital care, medications, and comorbidities, focusing on the pre-vaccine phase. Results Among the 615 included patients with AAD, COVID-19 was reported in 17% of which 8.5% required hospital care. Glucocorticoid treatment in hospitalized patients varied. For outpatients, 85% increased their glucocorticoid dosage during sickness. Older age (P = .002) and hypertension (P = .014) were associated with an increased risk of hospital care, while younger age (P < .001) and less worry about infection (P = .030) were correlated with a higher risk of COVID-19. Conclusions In the largest study to date examining AAD during the COVID-19 pandemic, we observed that although one-fifth of the cohort contracted COVID-19, few patients required hospital care. A majority of the patients applied general recommended sick rules despite reporting limited communication with healthcare during the pandemic.
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