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- Persson, Ninni, et al.
(författare)
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Regional brain shrinkage over two years : Individual differences and effects of pro-inflammatory genetic polymorphisms
- 2014
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 103, s. 334-348
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Tidskriftsartikel (refereegranskat)abstract
- We examined regional changes in brain volume in healthy adults (N = 167, age 19–79 years at baseline; N = 90 at follow-up) over approximately two years. With latent change score models, we evaluated mean change and individual differences in rates of change in 10 anatomically-defined and manually-traced regions of interest (ROIs): lateral prefrontal cortex (LPFC), orbital frontal cortex (OF), prefrontal white matter (PFw), hippocampus (Hc), parahippocampal gyrus (PhG), caudate nucleus (Cd), putamen (Pt), insula (In), cerebellar hemispheres (CbH), and primary visual cortex (VC). Significant mean shrinkage was observed in the Hc, CbH, In, OF, and PhG, and individual differences in change were noted in all regions, except the OF. Pro-inflammatory genetic variants modified shrinkage in PhG and CbH. Carriers of two T alleles of interleukin-1β (IL-1β C-511T, rs16944) and a T allele of methylenetetrahydrofolate reductase (MTHFR C677T, rs1801133) polymorphisms showed increased PhG shrinkage. No effects of a pro-inflammatory polymorphism for C-reactive protein (CRP-286C>A>T, rs3091244) or apolipoprotein (APOE) ε4 allele were noted. These results replicate the pattern of brain shrinkage observed in previous studies, with a notable exception of the LPFC, thus casting doubt on the unique importance of prefrontal cortex in aging. Larger baseline volumes of CbH and In were associated with increased shrinkage, in conflict with the brain reserve hypothesis. Contrary to previous reports, we observed no significant linear effects of age and hypertension on regional brain shrinkage. Our findings warrant further investigation of the effects of neuroinflammation on structural brain change throughout the lifespan.
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| 3. |
- Ben David, O., et al.
(författare)
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Evaluation of the Mechanical Properties of PMMA Reinforced with Carbon Nanotubes - Experiments and Modeling
- 2014
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Ingår i: Experimental Mechanics. - : Springer Science and Business Media LLC. - 1741-2765 .- 0014-4851. ; 54:2, s. 175-186
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Tidskriftsartikel (refereegranskat)abstract
- The effective mechanical properties of polymethyl-methacrylate (PMMA) reinforced with carbon nanotubes (CNTs) were evaluated by means of two approaches: experiments and a micromechanical model. With various concentrations of CNTs, two specimen fabrication processes were examined: hot pressing (HP) and injection molding (IM). Experiments included a series of uniaxial tensile tests guided by an ASTM standard. Using displacement control, tests were carried out while images were taken of the gage area. The in-plane displacement fields were evaluated by means of Digital Image Correlation (DIC). A MATLAB program was then used to calculate strains, create stress-strain and strain-force curves and determine Young's modulus E, Poisson's ratio , the ultimate tensile stress and the strain to failure . In addition, simulations were carried out using a micromechanical model (High-Fidelity Generalized Method of Cells or HFGMC). A Repeating Unit Cell (RUC) consisting of one CNT and PMMA surrounding it was modeled and analyzed in order to determine the effective mechanical properties of the composite. This method allows for imperfect bonding between the phases which is controlled by two parameters. These damage parameters decrease the stress-strain response of the material. However, the increase of the volume fraction increases the composite response. These two conflicting effects appear to provide the observed decrease in Young's modulus for low volume fractions as discussed. The effects of CNT concentration, geometry and orientation, as well as the interface between the phases, were examined. It was seen from the experimental results, for HP specimens, that for low concentrations of CNTs, E initially decreases and then increases significantly as the weight fraction increases. This behavior of E was quantitatively predicted by the HFGMC model. For IM specimens, Young's modulus is nearly constant for low weight fractions of CNTs and then increases with weight fraction.
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| 4. |
- Wetmore, Stephen J., et al.
(författare)
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Challenges and Opportunities in Managing the Dizzy Older Adult
- 2011
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Ingår i: Otolaryngology: Head and Neck Surgery. - : Wiley. - 0194-5998 .- 1097-6817. ; 144:5, s. 651-656
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Konferensbidrag (refereegranskat)abstract
- Balance disorders are common in elderly people, not only resulting in distressing sensations but also leading to reduced activity levels and quality of life. It has been estimated that 30% of elderly patients experience a balance disorder. Managing these disorders is a substantial challenge for patients and their caregivers and physicians. Moreover, abnormalities in balance are associated with falls, a major cause of morbidity and mortality for elderly people. Management is complicated by the inherent difficulties in assessing the generic complaint of dizziness, as well as the likelihood of multiple, often nonvestibular causes. The authors of this mini-seminar review both vestibular and nonvestibular causes of balance disorders in elderly people, emphasizing practical therapeutic maneuvers that can be used.
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