| 1. |
- Avlund, M., et al.
(författare)
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Observation of Periodic Orbits on Curved Two-Dimensional Geometries
- 2010
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Ingår i: Physical Review Letters. - 1079-7114. ; 104:16
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Tidskriftsartikel (refereegranskat)abstract
- We measure elastomechanical spectra for a family of thin shells. We show that these spectra can be described by a "semiclassical'' trace formula comprising periodic orbits on geodesics, with the periods of these orbits consistent with those extracted from experiment. The influence of periodic orbits on spectra in the case of two-dimensional curved geometries is thereby demonstrated, where the parameter corresponding to Planck's constant in quantum systems involves the wave number and the curvature radius. We use these findings to explain the marked clustering of levels when the shell is hemispherical.
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| 2. |
- Bomholt, Tobias, et al.
(författare)
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The Accuracy of Hemoglobin A1c and Fructosamine Evaluated by Long-Term Continuous Glucose Monitoring in Patients with Type 2 Diabetes Undergoing Hemodialysis
- 2022
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Ingår i: Blood Purification. - : S. Karger. - 0253-5068 .- 1421-9735. ; 51:7, s. 608-616
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: The accuracy of hemoglobin A1c (HbA1c) as a glycemic marker in patients with type 2 diabetes (T2D) receiving hemodialysis (HD) remains unknown. To assess accuracy, we compared HbA1c and fructosamine levels with interstitial glucose measured by continuous glucose monitoring (CGM) in patients with T2D receiving HD.METHODS: Thirty patients in the HD group and 36 patients in the control group (T2D and an estimated glomerular filtration rate >60 mL/min/1.73 m2) completed the study period of 17 weeks. CGM (Ipro2®, Medtronic) was performed 5 times for periods of up to 7 days (with 4-week intervals) during a 16-week period. HbA1c (mmol/mol), the estimated mean plasma glucose from HbA1c (eMPGA1c [mmol/L]) and fructosamine (μmol/L) was measured at week 17 and compared with mean sensor glucose levels from CGM.FINDINGS: In the HD group, mean sensor glucose was 1.4 mmol/L (95% confidence interval [CI]: 1.0-1.8) higher than the eMPGA1c, whereas the difference for controls was 0.1 mmol/L (95% CI: -0.1-[0.4]; p < 0.001). Adjusted for mean sensor glucose, HbA1c was lower in the HD group (-7.3 mmol/mol, 95% CI: -10.0-[-4.7]) than in the control group (p < 0.001), with no difference detected for fructosamine (p = 0.64).DISCUSSION: HbA1c evaluated by CGM underestimates plasma glucose levels in patients receiving HD. The underestimation represents a clinical challenge in optimizing glycemic control in the HD population. Fructosamine is unaffected by the factors affecting HbA1c and appears to be more accurate for glycemic monitoring. CGM or fructosamine could thus complement HbA1c in obtaining more accurate glycemic control in this patient group.
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| 3. |
- Boxberg, Fredrik, et al.
(författare)
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Elastic and Piezoelectric Properties of Zincblende and Wurtzite Crystalline Nanowire Heterostructures.
- 2012
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Ingår i: Advanced Materials. - : Wiley. - 1521-4095 .- 0935-9648. ; 24:34, s. 4692-4706
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Tidskriftsartikel (refereegranskat)abstract
- The elastic and piezoelectric properties of zincblende and wurtzite crystalline InAs/InP nanowire heterostructures have been studied using electro-elastically coupled continuum elasticity theory. A comprehensive comparison of strains, piezoelectric potentials and piezoelectric fields in the two crystal types of nanowire heterostructures is presented. For each crystal type, three different forms of heterostructures-core-shell, axial superlattice, and quantum dot nanowire heterostructures-are considered. In the studied nanowire heterostructures, the principal strains are found to be insensitive to the change in the crystal structure. However, the shear strains in the zincblende and wurtzite nanowire heterostructures can be very different. All the studied nanowire heterostructures are found to exhibit a piezoelectric field along the nanowire axis. The piezoelectric field is in general much stronger in a wurtzite nanowire heterostructure than in its corresponding zincblende heterostructure. Our results are expected to be particularly important for analyzing and understanding the properties of epitaxially grown nanowire heterostructures and for applications in nanowire electronics, optoelectronics, and biochemical sensing.
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| 4. |
- Boxberg, Fredrik, et al.
(författare)
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Photovoltaics with Piezoelectric Core-Shell Nanowires
- 2010
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6992 .- 1530-6984. ; 10:4, s. 1108-1112
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Tidskriftsartikel (refereegranskat)abstract
- We report on a theoretical discovery of a generic piezoelectric held in strained core shell compound semiconductor nanowires. We show, using both an analytical model and numerical simulations based on fully electroelastically coupled continuum elasticity theory, that lattice-mismatch-induced strain in an epiraxial core shell nanowire gives rise to an internal electric held along the axis of the nanowire. This piezoelectric field results predominantly from atomic layer displacements along the nanowire axis within both the core and shell materials and can appear in both zinc blende and wurtzite crystalline core-shell nanowires. The effect can be employed to separate photon-generated electron hole pairs in the core shell nanowires and thus offers a new device concept for solar energy conversion.
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| 5. |
- De Backer, Ole, et al.
(författare)
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Efficacy and safety of the Lotus Valve System for treatment of patients with severe aortic valve stenosis and intermediate surgical risk: Results from the Nordic Lotus-TAVR registry
- 2016
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Ingår i: International Journal of Cardiology. - : Elsevier. - 0167-5273 .- 1874-1754. ; 219, s. 92-97
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Tidskriftsartikel (refereegranskat)abstract
- Background: Transcatheter aortic valve replacement (TAVR) has becomean established therapeutic option for patients with symptomatic, severe aortic valve stenosis (AS) who are ineligible or at high risk for conventional valvular surgery. In Northwestern Europe, the TAVR technology is also increasingly used to treat patients with an intermediate risk profile. Methods and results: The study was designed as an independent Nordic multicenter registry of intermediate risk patients treated with the Lotus Valve System (Boston Scientific, MA, USA; N = 154). Valve Academic Research Consortium (VARC)-defined device success was obtained in 97.4%. A Lotus Valve was successfully implanted in all patients. There was no valve migration, embolization, ectopic valve deployment, or TAV-in-TAV deployment. The VARC-defined combined safety rate at 30 days was 92.2%, with a mortality rate of 1.9% and stroke rate of 3.2%. The clinical efficacy rate after 30 days was 91.6% - only one patient had moderate aortic regurgitation. When considering only those patients in the late experience group (N=79), the combined safety and clinical efficacy rates were 93.7% and 92.4%, respectively. The pacemaker implantation rate was 27.9% - this rate was 12.8% in case of a combined implantation depth amp;lt;4 mm and a device/annulus ratio amp;lt; 1.05. Conclusions: The present study demonstrates the efficacy and safety of the repositionable, retrievable Lotus Valve System in intermediate risk patients with AS. The VARC-defined device success rate was 97.4% with a 30-day patient safety and clinical efficacy rate of more than 90%. Less than moderate aortic regurgitation was obtained in 99.4% of patients. (C) 2016 Elsevier Ireland Ltd. All rights reserved.
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| 6. |
- Gnutzmann, S, et al.
(författare)
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Resolving isospectral 'drums' by counting nodal domains
- 2005
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Ingår i: Journal of Physics A: Mathematical and General. - : IOP Publishing. - 0305-4470 .- 1361-6447. ; 38:41, s. 8921-8933
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Tidskriftsartikel (refereegranskat)abstract
- Several types of systems have been put forward during the past few decades to show that there exist isospectral systems which are metrically different. One important class consists of Laplace-Beltrami operators for pairs of flat tori in R-n with n >= 4. We propose that the spectral ambiguity can be resolved by comparing the nodal sequences (the numbers of nodal domains of eigenfunctions, arranged by increasing eigenvalues). In the case of isospectral flat tori in four dimensions-where a four-parameter family of isospectral pairs is known-we provide heuristic arguments supported by numerical simulations to support the conjecture that the isospectrality is resolved by the nodal count. Thus one can count the shape of a drum (if it is designed as a flat torus in four dimensions).
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| 7. |
- Grönqvist, Johan, et al.
(författare)
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Strain in semiconductor core-shell nanowires
- 2009
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Ingår i: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 106:5
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Tidskriftsartikel (refereegranskat)abstract
- We compute strain distributions in core-shell nanowires of zinc blende structure. We use both continuum elasticity theory and an atomistic model, and consider both finite and infinite wires. The atomistic valence force-field (VFF) model has only few assumptions. But it is less computationally efficient than the finite-element (FE) continuum elasticity model. The generic properties of the strain distributions in core-shell nanowires obtained based on the two models agree well. This agreement indicates that although the calculations based on the VFF model are computationally feasible in many cases, the continuum elasticity theory suffices to describe the strain distributions in large core-shell nanowire structures. We find that the obtained strain distributions for infinite wires are excellent approximations to the strain distributions in finite wires, except in the regions close to the ends. Thus, our most computationally efficient model, the FE continuum elasticity model developed for infinite wires, is sufficient, unless edge effects are important. We give a comprehensive discussion of strain profiles. We find that the hydrostatic strain in the core is dominated by the axial strain-component, epsilon(ZZ). We also find that although the individual strain components have a complex structure, the hydrostatic strain shows a much simpler structure. All in-plane strain components are of similar magnitude. The nonplanar off-diagonal strain components (epsilon(XZ) and epsilon(YZ)) are small but nonvanishing. Thus the material is not only stretched and compressed but also warped. The models used can be extended for the study of wurtzite nanowire structures, as well as nanowires with multiple shells.
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| 8. |
- Guhr, Thomas, et al.
(författare)
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A certain localization effect in coupled systems and messages from the crystal sphere
- 2005
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Ingår i: AIP Conference Proceedings. - : AIP. - 0094-243X .- 1551-7616. ; 777, s. 160-170
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Konferensbidrag (refereegranskat)abstract
- Two theoretical studies are presented, both prompted by recent experiments. First, we investigate the time evolution of excitations in two chaotically coupled systems. There is a certain localization effect, because equipartition of the probability density or the energy is typically not reached. We use a random matrix model to give a generic explanation for this effect. Second, we derive a leading order Weyl formula for the elastic vibration spectrum of anisotropic quartz. This is non-trivial due to the presence of different modes. We discuss a duality between one spherical billiard with anisotropy in configuration space and three non-spherical billiards without anisotropy in slowness space
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| 9. |
- Kopic, S., et al.
(författare)
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Isolated pulmonary regurgitation causes decreased right ventricular longitudinal function and compensatory increased septal pumping in a porcine model
- 2017
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Ingår i: Acta Physiologica. - : Wiley. - 1748-1716 .- 1748-1708. ; 221:3, s. 163-173
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Longitudinal ventricular contraction is a parameter of cardiac performance with predictive power. Right ventricular (RV) longitudinal function is impaired in patients with free pulmonary regurgitation (PR) following corrective surgery for Tetralogy of Fallot (TOF). It remains unclear whether this is a consequence of the surgical repair, or whether it is inherent to PR. The aim of this study was to assess the relationship between longitudinal, lateral and septal pumping in a porcine model of isolated PR. Methods: Piglets were divided into a control (n = 8) group and a treatment (n = 12) group, which received a stent in the pulmonary valve orifice, inducing PR. After 2-3 months, animals were subjected to cardiac magnetic resonance imaging. A subset of animals (n = 6) then underwent percutaneous pulmonary valve replacement (PPVR) with follow-up 1 month later. Longitudinal, lateral and septal contributions to stroke volume (SV) were quantified by measuring volumetric displacements from end-diastole to end-systole in the cardiac short axis and long axis. Results: PR resulted in a lower longitudinal contribution to RV stroke volume, compared to controls (60.0 ± 2.6% vs. 73.6 ± 3.8%; P = 0.012). Furthermore, a compensatory increase in septal contribution to RVSV was observed (11.0 ± 1.6% vs. -3.1 ± 1.5%; P < 0.0001). The left ventricle (LV) showed counter-regulation with an increased longitudinal LVSV. Changes in RV longitudinal function were reversed by PPVR. Conclusion: These findings suggest that PR contributes to decreased RV longitudinal function in the absence of scarring from cardiac surgery. Measurement of longitudinal RVSV may aid risk stratification and timing for interventional correction of PR in TOF patients.
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| 10. |
- Schophuus Jensen, Annette, et al.
(författare)
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Cause-Specific Mortality in Patients During Long-Term Follow-Up After Atrial Switch for Transposition of the Great Arteries
- 2022
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Ingår i: Journal of the American Heart Association. - : American Heart Association. - 2047-9980. ; 11:14
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Little is known about the cause of death (CoD) in patients with transposition of the great arteries palliated with a Mustard or Senning procedure. The aim was to describe the CoD for patients with the Mustard and Senning procedure during short-(<10 years), mid-(10–20 years), and long-term (>20 years) follow-up after the operation.METHODS AND RESULTS: This is a retrospective, descriptive multicenter cohort study including all Nordic patients (Denmark, Finland, Norway, and Sweden) who underwent a Mustard or Senning procedure between 1967 and 2003. Patients who died within 30 days after the index operation were excluded. Among 968 patients with Mustard/Senning palliated transposition of the great arteries, 814 patients were eligible for the study, with a mean follow-up of 33.6 years. The estimated risk of all-cause mortality reached 36.0% after 43 years of follow-up, and the risk of death was highest among male patients as compared with female patients (P=0.004). The most common CoD was sudden cardiac death (SCD), followed by heart failure/heart transplantation accounting for 29% and 27%, respectively. During short-, mid-, and long-term follow-up, there was a change in CoD with SCD accounting for 23.7%, 46.6%, and 19.0% (P=0.002) and heart failure/heart transplantation 18.6%, 22.4%, and 46.6% (P=0.0005), respectively.CONCLUSIONS: Among patients corrected with Mustard or Senning transposition of the great arteries, the most common CoD is SCD followed by heart failure/heart transplantation. The CoD changes as the patients age, with SCD as the most common cause in adolescence and heart failure as the dominant cause in adulthood. Furthermore, the risk of all-cause mortality, SCD, and death attributable to heart failure or heart transplantation was increased in men >10 years after the Mustard/Senning operation.
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