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- Bridel, Claire, et al.
(author)
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Diagnostic Value of Cerebrospinal Fluid Neurofilament Light Protein in Neurology : A Systematic Review and Meta-analysis
- 2019
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In: JAMA Neurology. - : American Medical Association (AMA). - 2168-6149 .- 2168-6157. ; 76:9, s. 1035-1048
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Research review (peer-reviewed)abstract
- Importance Neurofilament light protein (NfL) is elevated in cerebrospinal fluid (CSF) of a number of neurological conditions compared with healthy controls (HC) and is a candidate biomarker for neuroaxonal damage. The influence of age and sex is largely unknown, and levels across neurological disorders have not been compared systematically to date.Objectives To assess the associations of age, sex, and diagnosis with NfL in CSF (cNfL) and to evaluate its potential in discriminating clinically similar conditions.Data Sources PubMed was searched for studies published between January 1, 2006, and January 1, 2016, reporting cNfL levels (using the search terms neurofilament light and cerebrospinal fluid) in neurological or psychiatric conditions and/or in HC.Study Selection Studies reporting NfL levels measured in lumbar CSF using a commercially available immunoassay, as well as age and sex.Data Extraction and Synthesis Individual-level data were requested from study authors. Generalized linear mixed-effects models were used to estimate the fixed effects of age, sex, and diagnosis on log-transformed NfL levels, with cohort of origin modeled as a random intercept.Main Outcome and Measure The cNfL levels adjusted for age and sex across diagnoses.Results Data were collected for 10 059 individuals (mean [SD] age, 59.7 [18.8] years; 54.1% female). Thirty-five diagnoses were identified, including inflammatory diseases of the central nervous system (n = 2795), dementias and predementia stages (n = 4284), parkinsonian disorders (n = 984), and HC (n = 1332). The cNfL was elevated compared with HC in a majority of neurological conditions studied. Highest levels were observed in cognitively impaired HIV-positive individuals (iHIV), amyotrophic lateral sclerosis, frontotemporal dementia (FTD), and Huntington disease. In 33.3% of diagnoses, including HC, multiple sclerosis, Alzheimer disease (AD), and Parkinson disease (PD), cNfL was higher in men than women. The cNfL increased with age in HC and a majority of neurological conditions, although the association was strongest in HC. The cNfL overlapped in most clinically similar diagnoses except for FTD and iHIV, which segregated from other dementias, and PD, which segregated from atypical parkinsonian syndromes.Conclusions and Relevance These data support the use of cNfL as a biomarker of neuroaxonal damage and indicate that age-specific and sex-specific (and in some cases disease-specific) reference values may be needed. The cNfL has potential to assist the differentiation of FTD from AD and PD from atypical parkinsonian syndromes.
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| 4. |
- Östberg, Gustaf, 1971, et al.
(author)
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Effect of Sigma2 grain boundaries on plastic deformation of WC-Co cemented carbides
- 2006
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In: Mat. Sci. and Eng. A.. ; 416, s. 119-
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Journal article (peer-reviewed)abstract
- Cutting inserts of WC–6 wt.% Co were investigated before and after plastic deformation. The deformation tests were performed with a turning operation under realistic, yet controlled, conditions. SEM studies showed that after deformation the WC skeleton structure had broken up and thin lamellae of binder phase had formed in less than 10% of the grain boundaries. Ab initio calculations showed that ∑2 twist WC/WC boundaries have a high work of separation and the interface energy is not lowered by forming two Co/WC boundaries. Electron backscattered diffraction (EBSD) measurements showed an apparent increase in the relative occurrence of ∑2 boundaries due to poor indexing of the deformed material. The accumulation of dislocations in general boundaries is held responsible for the difficulty in identifying them compared with ∑2 boundaries. At the ∑2 tilt boundary the grains have the glide planes {1 0 -1 0} in common and at the ∑2 twist boundary there are three glide planes intersecting, which facilitate dislocation movements across the ∑2 boundaries.
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| 7. |
- Christensen, Mikael, 1973, et al.
(author)
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Morphology of WC grains in WC-Co alloys: Theoretical determination of grain shape
- 2007
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In: Acta Mater.. ; 55, s. 1515-
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Journal article (peer-reviewed)abstract
- A theoretical approach to predict grain morphology from interface energies computed using density-functional theory is presented and applied to the WC–Co system. The dependences of the WC grain shape on the geometrical misfit at the Co/WC metal–ceramic interface, and on the carbon chemical potential are investigated. The WC grains are predicted to be hexagonal when the interfaces are assumed to be coherent, and change to a truncated triangular shape where the long prism side lengths are five times longer than the short side lengths, when the interfaces are assumed to be incoherent.
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| 9. |
- Christensen, Mikael, 1973, et al.
(author)
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Strength and reinforcement of interfaces in cemented carbides
- 2006
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In: Int. J. Refract. Hard Mater.. ; 24, s. 80-
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Journal article (peer-reviewed)abstract
- The tendency for segregation of 3d-transition metals to WC/WC interfaces in cemented carbides, and resulting effect on grain boundary cohesion, have been assessed by density-functional theory calculations. The results show that the propensity for segregation increases along the 3d-series, both to free carbide surfaces and to carbide–carbide interfaces. The tendency for metal substitution in W-rich boundaries is very low while 3d atoms readily segregate to C-rich boundaries by carbon substitution. The strengthening effect on grain boundary cohesion in the latter case is largest for V, Cr, and Mn, but is substantial for all segregants in this study.
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| 10. |
- Christensen, Mikael, 1973
(author)
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Strength and Stability of Interfaces in Cemented Carbides
- 2004
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Doctoral thesis (other academic/artistic)abstract
- Cemented carbides are hard composite materials of great technological importance. They are widely used as tool materials in a large variety of applications where the demands on hardness and toughness are high, including e.g.≈mining, turning, cutting, and milling. They are powder metallurgical products produced by liquid phase sintering, with a hard carbide phase as main component embedded in a softer metal binder phase. This thesis is a theoretical study of structures and energetics of interfaces in WC-Co cemented carbides. Many properties of the material are controlled by interfacial energies, which are sensitive to chemical modifications on an atomic level. The theoretical investigations are based on the results of first-principles density-functional theory calculations for a broad selection of model interface systems, using the plane-wave pseudopotential method. The microstructural development is directly dependent on interface energies during sintering. WC grains in WC-Co develop a characteristic truncated triangular shape. The grain morphology has been reproduced by calculations in good agreement with quantitative experimental data. The known fact of better wetting in the WC-Co system than in the TiC-Co system is confirmed and explained in terms of a larger contribution of metal-metal W-Co bonding at Co/WC interfaces. It is demonstrated that Co easily infiltrate most WC/WC grain boundaries, but some special grain boundaries can remain intact. These special grain boundaries are characterized by a high density of coincidence sites. They are significantly stronger and more stable than generic boundaries, and should withstand higher load. The results are compared to, and shown consistent with, experimental observations. The results show that cobalt readily segregates to free carbide surfaces as well as to carbide-carbide grain boundaries. Interface segregation is predicted to take place in small amounts, less than a monolayer is formed in the grain boundaries, which is in agreement with experimental observations. The presence of intergranular Co atoms has a significant effect on the interface energetics. The resistance to grain decohesion and to metal infiltration is increased. It is found that there is a general trend along the 3d-series of increasing propensity for segregation, both to grain boundaries and to free carbide surfaces. The calculations show that V, Cr and Mn have the largest beneficial effect on grain boundary strength.
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| 14. |
- Norgren, Susanne, et al.
(author)
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Cemented carbide
- 2004
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Other publication (other academic/artistic)
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| 15. |
- Svensson, Henrik, 1982, et al.
(author)
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Influence of Pt on the metal-oxide interface during high temperature oxidation of NiAl bulk materials
- 2009
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In: Corrosion Science. - : Elsevier BV. - 0010-938X. ; 51:3, s. 539-546
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Journal article (peer-reviewed)abstract
- The purpose of the investigation was to study the mechanisms improving oxide scale adherence in Pt-free and Pt-rich beta-NiAl materials during high temperature oxidation. Theoretical density-functional theory (DFT) calculations were used to calculate the work of separation of the beta-NiAl(111)/alpha-Al(2)O(3)(0001) metal-oxide interfaces, in pure NiAl and Pt-rich NiAl materials. The experimental work was focused on the studies of the metal-oxide interface, its development and morphology. Based on the theoretical and experimental results a complementary picture is presented for a better understanding of the Pt effect on the oxidation and oxide adhesion. It is shown that the interfacial bonding is decreased with addition of Pt to beta-NiAl. The beneficial effect of Pt on the adhesion energy is attributed to the enhancement of contact areas between the oxide and the metal. The influence of Pt on the diffusion of Al and the formation of interfacial voids is also discussed.
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| 16. |
- Östberg, Gustaf, 1971, et al.
(author)
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Effect of TaC on plastic deformation of WC-Co and Ti(C,N)-WC-Co
- 2006
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In: International Journal of Refractory Metals and Hard Materials. - : Elsevier BV. - 0263-4368. ; 24:1-2, s. 145-154
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Journal article (peer-reviewed)abstract
- The plastic deformation resistance of metal cutting inserts made from a WC–Co cemented carbide, a Ti(C, N)–WC–Co cermet and corresponding materials with additions of TaC has been studied. The cermets were produced with both high and low carbon activity, resulting in a total of six materials. Ab initio calculations of some WC/WC grain boundary geometries suggest that both Co and Ta segregate substitutionally to the boundary and improve the grain boundary strength when substituting carbon. However, only Co segregation was found experimentally, probably due to (Ta, W)C formation. Plastic deformation tests were performed with a turning operation under controlled conditions. For the WC–Co, the addition of Ta had a positive effect for lower cutting speeds but at higher speeds the effect was negative. Three-point bending tests indicated a beneficial effect of Ta in WC–Co, which was also confirmed by internal friction (IF) measurements. However, after thermal cycling, the effect of Ta could be smaller, or even negative. The Ta cermet produced with low carbon activity exhibited a better plastic deformation resistance during cutting but no apparent effects of Ta could be seen either in IF measurements or in three-point bending tests of the cermets. However, a correlation was found between plastic deformation during turning and IF spectra. In the cermet materials, binder phase lamella formation promotes grain boundary sliding at high temperatures.
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| 17. |
- Östberg, Gustaf, 1971, et al.
(author)
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Mechanisms of plastic deformation of WC-Co and Ti(C,N)-WC-Co
- 2006
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In: Int. J. Refract. Hard Mater.. - : Elsevier BV. - 0263-4368. ; 24:1-2, s. 135-144
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Journal article (peer-reviewed)abstract
- The deformation of the cutting edge of inserts made from WC–Co and Ti(C, N)–19%WC–Co upon radial turning was measured as a function of the cutting speed. Ab initio calculations of some grain boundary geometries in WC–Co indicated that Co segregates to WC/WC grain boundaries in submonolayer proportions and increases their strength and resistance to Co infiltration. This was also confirmed with TEM-EDX. SEM studies showed that during plastic deformation the hard phase skeletons in both materials were partly broken up and infiltrated by binder phase. TEM observations showed a considerable deformation of the WC grains and some infiltrated grain boundaries were facetted along low energy planes. In the cermet, no deformation of the hard phase grains could be seen. The plastic deformation at high temperatures observed by three-point bending corresponds to a number of relaxation processes, detected by internal friction, related to grain boundary sliding. Both materials deform by grain boundary sliding, accommodated in the cermet by Co diffusion and in the WC–Co by deformation of the hard phase and diffusion of Co.
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