| 1. |
- Mattsson, Niklas, 1979, et al.
(författare)
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The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers.
- 2011
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Ingår i: Alzheimer's & dementia : the journal of the Alzheimer's Association. - : Wiley. - 1552-5279. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer's disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer's Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.
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| 2. |
- Chapman, I. T., et al.
(författare)
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Power requirements for electron cyclotron current drive and ion cyclotron resonance heating for sawtooth control in ITER
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 53:6, s. 066001-
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Tidskriftsartikel (refereegranskat)abstract
- 13MW of electron cyclotron current drive (ECCD) power deposited inside the q = 1 surface is likely to reduce the sawtooth period in ITER baseline scenario below the level empirically predicted to trigger neoclassical tearing modes (NTMs). However, since the ECCD control scheme is solely predicated upon changing the local magnetic shear, it is prudent to plan to use a complementary scheme which directly decreases the potential energy of the kink mode in order to reduce the sawtooth period. In the event that the natural sawtooth period is longer than expected, due to enhanced a particle stabilization for instance, this ancillary sawtooth control can be provided from >10MW of ion cyclotron resonance heating (ICRH) power with a resonance just inside the q = 1 surface. Both ECCD and ICRH control schemes would benefit greatly from active feedback of the deposition with respect to the rational surface. If the q = 1 surface can be maintained closer to the magnetic axis, the efficacy of ECCD and ICRH schemes significantly increases, the negative effect on the fusion gain is reduced, and off-axis negative-ion neutral beam injection (NNBI) can also be considered for sawtooth control. Consequently, schemes to reduce the q = 1 radius are highly desirable, such as early heating to delay the current penetration and, of course, active sawtooth destabilization to mediate small frequent sawteeth and retain a small q = 1 radius. Finally, there remains a residual risk that the ECCD + ICRH control actuators cannot keep the sawtooth period below the threshold for triggering NTMs (since this is derived only from empirical scaling and the control modelling has numerous caveats). If this is the case, a secondary control scheme of sawtooth stabilization via ECCD + ICRH + NNBI, interspersed with deliberate triggering of a crash through auxiliary power reduction and simultaneous pre-emptive NTM control by off-axis ECCD has been considered, permitting long transient periods with high fusion gain. The power requirements for the necessary degree of sawtooth control using either destabilization or stabilization schemes are expected to be within the specification of anticipated ICRH and ECRH heating in ITER, provided the requisite power can be dedicated to sawtooth control.
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| 3. |
- Chapman, I. T., et al.
(författare)
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Sawtooth control in ITER using ion cyclotron resonance heating
- 2011
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 53:12, s. 124003-
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Tidskriftsartikel (refereegranskat)abstract
- Numerical modelling of the effects of ion cyclotron resonance heating (ICRH) on the stability of the internal kink mode suggests that ICRH should be considered as an essential sawtooth control tool in ITER. Sawtooth control using ICRH is achieved by directly affecting the energy of the internal kink mode rather than through modification of the magnetic shear by driving localized currents. Consequently, ICRH can be seen as complementary to the planned electron cyclotron current drive actuator, and indeed will improve the efficacy of current drive schemes. Simulations of the ICRH distribution using independent RF codes give confidence in numerical predictions that the stabilizing influence of the fusion-born alphas can be negated by appropriately tailored minority (3)He ICRH heating in ITER. Finally, the effectiveness of all sawtooth actuators is shown to increase as the q = 1 surface moves towards the manetic axis, whilst the passive stabilization arising from the alpha and NBI particles decreases.
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| 4. |
- Nyström, Sofie, et al.
(författare)
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Evidence for Age-Dependent in Vivo Conformational Rearrangement within A beta Amyloid Deposits
- 2013
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Ingår i: ACS Chemical Biology. - : American Chemical Society. - 1554-8929 .- 1554-8937. ; 8:6, s. 1128-1133
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Tidskriftsartikel (refereegranskat)abstract
- Deposition of aggregated A beta peptide in the brain is one of the major hallmarks of Alzheimers disease. Using a combination of two structurally different, but related, hypersensitive fluorescent amyloid markers, LCOs, reporting on separate ultrastructural elements, we show that conformational rearrangement occurs within A beta plaques of transgenic mouse models as the animals age. This important mechanistic insight should aid the design and evaluation of experiments currently using plaque load as readout.
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| 5. |
- Chapman, I. T., et al.
(författare)
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Kinetic damping of resistive wall modes in ITER
- 2012
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 19:5, s. 052502-
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Tidskriftsartikel (refereegranskat)abstract
- Full drift kinetic modelling including finite orbit width effects has been used to assess the passive stabilisation of the resistive wall mode (RWM) that can be expected in the ITER advanced scenario. At realistic plasma rotation frequency, the thermal ions have a stabilising effect on the RWM, but the stability limit remains below the target plasma pressure to achieve Q = 5. However, the inclusion of damping arising from the fusion-born alpha particles, the NBI ions, and ICRH fast ions extends the RWM stability limit above the target beta for the advanced scenario. The fast ion damping arises primarily from finite orbit width effects and is not due to resonance between the particle frequencies and the instability.
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| 6. |
- Chapman, I. T., et al.
(författare)
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Sawtooth Control in ITER using Ion Cyclotron Resonance Heating
- 2011
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Ingår i: Proceedings of the EPS Conference on Plasma Physics.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Numerical modelling of the effects of ion cyclotron resonance heating (ICRH) on the stability of the internal kink mode suggests that ICRH should be considered as an essential sawtooth control tool in ITER. Sawtooth control using ICRH is achieved by directly affecting the energy of the kink mode rather than through modification of the magnetic shear by driving localised currents. Consequently, ICRH can be seen as complementary to the planned electron cyclotron current drive actuator. Simulations of the ICRH distribution using independent RF codes give confidence in numerical predictions that the stabilising influence of the fusion-born alphas can be negated by appropriately tailored minority 3He ICRH heating in ITER.
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| 7. |
- Jucker, M., et al.
(författare)
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Integrated modeling for ion cyclotron resonant heating in toroidal systems
- 2011
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Ingår i: Computer Physics Communications. - : Elsevier BV. - 0010-4655 .- 1879-2944. ; 182:4, s. 912-925
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Tidskriftsartikel (refereegranskat)abstract
- An integrated model capable of self-consistent Ion Cyclotron Resonant Heating (ICRH) simulations has been developed. This model includes both full shaping and pressure effects, warm contributions to the dielectric tensor, pressure anisotropy and finite orbit width. It evolves the equilibrium, wave field and full hot particle distribution function until a self-consistent solution is found. This article describes the workings of the three codes VMEC, LEMan and VENUS and how they are linked for iterated computations in a code package we have named SCENIC. The package is thoroughly tested and it is demonstrated that a number of iterations have to be performed in order to find a consistent solution. Since the formulation of the problem can treat general 3D systems, we show a quasi-axisymmetric stellarator low power test case, and then concentrate on experimentally relevant Joint European Torus (JET) 2D configurations.
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| 8. |
- Jucker, M., et al.
(författare)
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Ion cyclotron resonance heating with consistent finite orbit widths and anisotropic equilibria
- 2011
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Ingår i: PLASMA PHYS CONTROL FUSION. - : IOP Publishing. ; , s. 054010-
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Konferensbidrag (refereegranskat)abstract
- Minority ion cyclotron resonance heating is studied using the self-consistent numerical model SCENIC. This model includes 3D geometries with full shaping and anisotropic pressure effects, warm contributions to the dielectric tensor and full orbit effects. It evolves the equilibrium, wave field and hot particle distribution function iteratively until a self-consistent solution is found. We will show applications to JET-like two-dimensional equilibria with minority heating scenarios. The effects due to different heating locations on the hot particle distribution function, the hot dielectric tensor and the equilibrium will be studied for symmetric wave injection. Finally, the RF-induced particle pinch is investigated using asymmetric wave injection.
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| 9. |
- Wegenast-Braun, Bettina M., et al.
(författare)
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Spectral Discrimination of Cerebral Amyloid Lesions after Peripheral Application of Luminescent Conjugated Oligothiophenes
- 2012
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Ingår i: American Journal of Pathology. - : Elsevier. - 0002-9440 .- 1525-2191. ; 181:6, s. 1953-1960
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Tidskriftsartikel (refereegranskat)abstract
- In vivo imaging of pathological protein aggregates provides essential knowledge of the kinetics and implications of these lesions in the progression of proteopathies, such as Alzheimer disease. Luminescent conjugated oligothiophenes are amyloid-specific ligands that bind and spectrally distinguish different types of amyloid aggregates. Herein, we report that heptamer formyl thiophene acetic acid (hFTAA) passes the blood-brain barrier after systemic administration and specifically binds to extracellular beta-amyloid deposits in the brain parenchyma (A beta plaques) and in the vasculature (cerebral beta-amyloid angiopathy) of beta-amyloid precursor protein transgenic APP23 mice. Moreover, peripheral application of hFIAA also stained intracellular lesions of hyperphosphorylated Tau protein in P301S Tau transgenic mice. Spectral profiling of all three amyloid types was acquired ex vivo using two-photon excitation. hFTAA revealed a distinct shift in its emission spectra when bound to A beta plaques versus Tau lesions. Furthermore, a spectral shift was observed for A beta plaques versus cerebral beta-amyloid angiopathy, indicating that different amyloid types and structural variances of a specific amyloid type can be distinguished. In conclusion, by adding spectral signatures to amyloid lesions, our results pave the way for a new area of in vivo amyloid imaging, allowing in vivo differentiation of amyloid (sub)types and monitoring changes of their structure/composition over time. (Am J Pathol 2012, 181: 1953-1960 http://dx.doi.org/10.1016/j.ajpath.2012.08.031)
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