| 45041. |
- Fedorets, Dmytro, 1976, et al.
(författare)
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Quantum shuttle phenomena in a nanoelectromechanical single-electron transistor
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92
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Tidskriftsartikel (refereegranskat)abstract
- An analytical analysis of quantum shuttle phenomena in a nanoelectromechanical single-electron transistor has been performed in the realistic case, when the electron tunneling length is much greater than the amplitude of the zero point oscillations of the central island. It is shown that when the dissipation is below a certain threshold value, the vibrational ground state of the central island is unstable. The steady state into which this instability develops is studied. It is found that if the electric field E between the leads is much greater than a characteristic value E-q, the quasiclassical shuttle picture is recovered, while if E0) shuttle vibrations.
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| 45042. |
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| 45043. |
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| 45044. |
- Fedorov, A., et al.
(författare)
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Segmented diffusion-weighted imaging of the prostate: Application to transperineal in-bore 3 T MR image-guided targeted biopsy
- 2016
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Ingår i: Magnetic Resonance Imaging. - : Elsevier BV. - 0730-725X. ; 34:8, s. 1146-1154
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study aims to evaluate the applicability of using single-shot and multi-shot segmented diffusion-weighted imaging (DWI) techniques to support biopsy target localization in a cohort of targeted MRI-guided prostate biopsy patients. Materials and methods: Single-shot echo-planar diffusion-weighted imaging (SS-DWI) and multi-shot segmented (MS-DWI) were performed intra-procedurally on a 3 Tesla system in a total of 35 men, who underwent in-bore prostate biopsy inside the scanner bore. Comparisons between SS-DWI and MS-DWI were performed with (in 16 men) and without (in 19 men) parallel coil acceleration (iPAT) for SS-DWI. Overall image quality and artifacts were scored by a radiologist and scores were compared with the Wilcoxon-Mann-Whitney rank test. Correlation between the presence of air and image quality scores was evaluated with Spearman statistics. To quantify distortion, the anteroposterior prostate dimension was measured in SS and MS b = 0 diffusion- and T-2-weighted images. Signal-to-noise ratio was estimated in a phantom experiment. Agreement and accuracy of targeting based on retrospective localization of restricted diffusion areas in DWI was evaluated with respect to the targets identified using multi-parametric MRI (mpMRI). Results: Compared to SS-DWI without iPAT, the average image quality score in MS-DWI improved from 2.0 to 33 (p < 0.005) and the artifact score improved from 23 to 1.4 (p < 0.005). When iPAT was used in SS-DWI, the average image quality score in MS-DWI improved from 2.6 to 33 (p < 0.05) and the artifact score improved from 2.1 to 1.4 (p < 0.01). Image quality (rho = 0.74, p < 0.0005) and artifact scores (rho = 0.77, p < 0.0005) both showed strong correlation with the presence of air in the rectum for the SS-DWI sequence without iPAT. These correlations remained significant when iPAT was enabled (rho = 052, p < 0.05 and rho = 0.64, p < 0.01). For the comparison MS-DWI vs SS-DWI without iPAT, median differences between diffusion- and T2-weighted image gland measurements were 1.1 (0.03-10.4) mm and 4.4 (0.5-22.7) mm, respectively. In the SS-DWI-iPAT cohort, median gland dimension differences were 2.7 (0.4-5.9) mm and 42 (0.7-8.9) mm, respectively. Out of the total of 89 targets identified in mpMRI, 20 had corresponding restricted diffusion areas in SS-DWI and 28 in MS-DWI. No statistically significant difference was observed between the distances for the targets in the target-concordant SS- and MS-DWI restricted diffusion areas (5.5 mm in SS-DWI vs 45 mm in MS-DWI, p > 0.05). Conclusions: MS-DWI applied to prostate imaging leads to a significant reduction of image distortion in comparison with SS-DWI. There is no sufficient evidence however to suggest that intra-procedural DWI can serve as a replacement for tracking of the targets identified in mpMRI for the purposes of targeted MRI-guided prostate biopsy. (C) 2016 Elsevier Inc. All rights reserved.
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| 45045. |
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| 45046. |
- Fedorowski, Artur, et al.
(författare)
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Cardiorespiratory dysautonomia in post-COVID-19 condition: Manifestations, mechanisms and management
- 2023
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Ingår i: Journal of Internal Medicine. - : John Wiley & Sons. - 0954-6820 .- 1365-2796. ; 294:5, s. 548-562
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Forskningsöversikt (refereegranskat)abstract
- A significant proportion of COVID-19 patients experience debilitating symptoms for months after the acute infection. According to recent estimates, approximately 1 out of 10 COVID-19 convalescents reports persistent health issues more than 3 months after initial recovery. This 'post-COVID-19 condition' may include a large variety of symptoms from almost all domains and organs, and for some patients it may mean prolonged sick-leave, homestay and strongly limited activities of daily life. In this narrative review, we focus on the symptoms and signs of post-COVID-19 condition in adults - particularly those associated with cardiovascular and respiratory systems, such as postural orthostatic tachycardia syndrome or airway disorders - and explore the evidence for chronic autonomic dysfunction as a potential underlying mechanism. The most plausible hypotheses regarding cellular and molecular mechanisms behind the wide spectrum of observed symptoms - such as lingering viruses, persistent inflammation, impairment in oxygen sensing systems and circulating antibodies directed to blood pressure regulatory components - are discussed. In addition, an overview of currently available pharmacological and non-pharmacological treatment options is presented.
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| 45047. |
- Fedorowski, Artur, et al.
(författare)
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Systolic and diastolic component of orthostatic hypotension and cardiovascular events in hypertensive patients: the Captopril Prevention Project
- 2014
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Ingår i: Journal of Hypertension. - 0263-6352 .- 1473-5598. ; 32:1, s. 75-81
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Tidskriftsartikel (refereegranskat)abstract
- Objective:Impact of SBP vs. DBP decrement during orthostasis on cardiovascular events in hypertension is not clear.Methods:We assessed prospective association of orthostatic hypotension with mortality and major cardiovascular events [myocardial infarction (MI) and stroke] among 8788 treated hypertensive patients (52.2% men; mean age 52 years, mean BP 161/99mmHg) without history of MI or stroke at baseline. Orthostatic hypotension was defined according to combined international consensus criteria, and as either systolic (decrease 20mmHg) or diastolic orthostatic hypotension (decrease 10mmHg). Final Cox regression model was adjusted for age, sex, supine SBP and DBP, diabetes, smoking, and total cholesterol.Results:A total of 1060 (12.1%) study participants fulfilled combined orthostatic hypotension criteria, of these 886 (10.1%) met systolic and 290 (3.3%) diastolic criterion. In the crude analysis, combined orthostatic hypotension criteria were predictive of the composite endpoint, major cardiovascular event, total mortality, and stroke but not MI. After full adjustment, combined orthostatic hypotension criteria and systolic orthostatic hypotension were independently associated with stroke only (hazard ratio: 1.48, 1.07-2.05, P=0.019, and 1.53, 1.08-2.15, P=0.015, respectively), whereas the composite endpoint tended in the same direction (hazard ratio: 1.21, 0.98-1.51, P=0.075, and 1.24, 0.99-1.55, P=0.066, respectively). In contrast, diastolic orthostatic hypotension was associated with increased risk of MI (hazard ratio: 2.04, 1.20-3.46, P=0.008).Conclusion:Orthostatic hypotension has a dual role in cardiovascular events among hypertensive patients: SBP fall indicates higher risk of stroke, whereas DBP fall confers higher risk of MI.
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| 45048. |
- Fedosova, Ksenia, et al.
(författare)
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Fourier expansions of vector-valued automorphic functions with non-unitary twists
- 2023
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Ingår i: Communications in Number Theory and Physics. - 1931-4531 .- 1931-4523. ; 17:1, s. 173-248
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Tidskriftsartikel (refereegranskat)abstract
- We provide Fourier expansions of vector-valued eigenfunctions of the hyperbolic Laplacian that are twist-periodic in a horocycle direction. The twist may be given by any endomorphism of a finite-dimensional vector space; no assumptions on invertibility or unitarity are made. Examples of such eigenfunctions include vector-valued twisted automorphic forms of Fuchsian groups. We further provide a detailed description of the Fourier coefficients and explicitly identify each of their constituents, which intimately depend on the eigenvalues of the twisting endomorphism and the size of its Jordan blocks. In addition, we determine the growth properties of the Fourier coefficients.
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| 45049. |
- Fedosova, K., et al.
(författare)
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High energy asymptotics for the perturbed anharmonic oscillator
- 2021
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Ingår i: Complex Variables and Elliptic Equations. - : Informa UK Limited. - 1747-6933 .- 1747-6941.
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we study the spectral properties of the perturbation of the generalized anharmonic oscillator. We consider a piecewise Holder continuous perturbation and investigate how the Holder constant can affect the eigenvalues. More precisely, we derive several first terms in the asymptotic expansion for the eigenvalues.
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| 45050. |
- Fedosova, Ksenia, et al.
(författare)
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Second variation of Selberg zeta functions and curvature asymptotics
- 2020
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Ingår i: Annals of Global Analysis and Geometry. - : Springer Science and Business Media LLC. - 1572-9060 .- 0232-704X. ; 57:1, s. 23-60
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Tidskriftsartikel (refereegranskat)abstract
- We give an explicit formula for the second variation of the logarithm of the Selberg zeta function, Z(s), on Teichmüller space. We then use this formula to determine the asymptotic behavior as Rs→ ∞ of the second variation. As a consequence, for m∈ N, we obtain the complete expansion in m of the curvature of the vector bundle H(Xt, Kt) → t∈ T of holomorphic m-differentials over the Teichmüller space T, for m large. Moreover, we show that this curvature agrees with the Quillen curvature up to a term of exponential decay, O(m2e-l0m), where l is the length of the shortest closed hyperbolic geodesic.
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