Sigma phase is commonly considered to be the most deleterious secondary phase precipitating in duplex stainless steels, as it results in an extreme reduction of corrosion resistance and toughness. ...Previous studies have mainly focused on the kinetics of sigma phase precipitation and influences on properties and only a few works have studied the morphology of sigma phase and its influences on material properties. Therefore, the influence of sigma phase morphology on the degradation of corrosion resistance and mechanical properties of 2507 super duplex stainless steel (SDSS) was studied after 10 h of arc heat treatment using optical and scanning electron microscopy, electron backscattered diffraction analysis, corrosion testing, and thermodynamic calculations. A stationary arc was applied on the 2507 SDSS disc mounted on a water-cooled chamber, producing a steady-state temperature gradient covering the entire temperature range from room temperature to the melting point. Sigma phase was the major intermetallic precipitating between 630 °C and 1010 °C and its morphology changed from blocky to fine coral-shaped with decreasing aging temperature. At the same time, the average thickness of the precipitates decreased from 2.9 µm to 0.5 µm. The chemical composition of sigma was similar to that predicted by thermodynamic calculations when formed at 800⁻900 °C, but deviated at higher and lower temperatures. The formation of blocky sigma phase introduced local strain in the bulk of the primary austenite grains. However, the local strain was most pronounced in the secondary austenite grains next to the coral-shaped sigma phase precipitating at lower temperatures. Microstructures with blocky and coral-shaped sigma phase particles were prone to develop microscale cracks and local corrosion, respectively. Local corrosion occurred primarily in ferrite and in secondary austenite, which was predicted by thermodynamic calculations to have a low pitting resistance equivalent. To conclude, the influence of sigma phase morphology on the degradation of properties was summarized in two diagrams as functions of the level of static load and the severity of the corrosive environment.
•P100-latency delay is mainly driven by pre-chiasmatic lesions but independently influenced by postchiasmatic damage.•After optic neuritis, P100-latency is associated with lateral geniculate nucleus ...atrophy, possibly indicating synaptopathy.•Better understanding of the contributors to the VEP signal may strengthen its interpretability as a biomarker.
To explore associations of the main component (P100) of visual evoked potentials (VEP) to pre- and postchiasmatic damage in multiple sclerosis (MS).
31 patients (median EDSS: 2.5), 13 with previous optic neuritis (ON), and 31 healthy controls had VEP, optical coherence tomography and magnetic resonance imaging. We tested associations of P100-latency to the peripapillary retinal nerve fiber layer (pRNFL), ganglion cell/inner plexiform layers (GCIPL), lateral geniculate nucleus volume (LGN), white matter lesions of the optic radiations (OR-WML), fractional anisotropy of non-lesional optic radiations (NAOR-FA), and to the mean thickness of primary visual cortex (V1). Effect sizes are given as marginal R2 (mR2).
P100-latency, pRNFL, GCIPL and LGN in patients differed from controls. Within patients, P100-latency was significantly associated with GCIPL (mR2 = 0.26), and less strongly with OR-WML (mR2 = 0.17), NAOR-FA (mR2 = 0.13) and pRNFL (mR2 = 0.08). In multivariate analysis, GCIPL and NAOR-FA remained significantly associated with P100-latency (mR2 = 0.41). In ON-patients, P100-latency was significantly associated with LGN volume (mR2 = −0.56).
P100-latency is affected by anterior and posterior visual pathway damage. In ON-patients, damage at the synapse-level (LGN) may additionally contribute to latency delay.
Our findings corroborate post-chiasmatic contributions to the VEP-signal, which may relate to distinct pathophysiological mechanisms in MS.
•Microstructure affected atmospheric corrosion of Al- and Mg- alloyed zinc.•Materials with finer microstructures were usually more stable.•Mg-rich phases dissolved preferentially.•Al-rich phases ...activated at cathodic sites at alkali pH.•Al and Mg reduced zinc run-off by stabilisation of protective corrosion products.
Zn-5Al and Zn-3Al-2Mg model alloys were cast and heat treated in order to obtain specimens with distinct microstructures and identical chemical compositions. The microstructure was characterised in detail to identify composition, size and distribution of present phases. Mass losses of samples with different microstructures and identical chemical compositions that were subjected to a cyclic corrosion test and a test under non-rinsing conditions differed by a factor of up to two. The mechanism is discussed based on measurements of corrosion stability of individual phases and chemical and phase compositions of corrosion products.
Background:
Optical coherence tomography (OCT) is a biomarker of neuroaxonal loss in multiple sclerosis (MS).
Objective:
The objective was to assess the relative role of OCT, next to magnetic ...resonance imaging (MRI) and serum markers of disability in MS.
Methods:
A total of 100 patients and 52 controls underwent OCT to determine peripapillary retinal nerve fiber layer (pRNFL) and ganglion cell-inner plexiform layers (GCIPL). Serum neurofilament light chain (sNfL), total lesion volume (TLV), and brain parenchymal fraction (BPF) were also assessed. The associations of OCT with disability were examined in linear regression models with correction for age, vision, and education.
Results:
In patients, pRNFL was associated with the Symbol Digit Modalities Test (SDMT; p = 0.030). In the multivariate analysis including sNfL and MRI measures, pRNFL (β = 0.19, p = 0.044) and TLV (β = −0.24, p = 0.023) were the only markers associated with the SDMT. pRNFL (p < 0.001) and GCIPL (p < 0.001) showed associations with the Expanded Disability Status Scale (EDSS). In the multivariate analysis, GCIPL showed the strongest association with the EDSS (β = −0.32, p < 0.001) followed by sNfL (β = 0.18, p = 0.024).
Conclusion:
The associations of OCT measures with cognitive and physical disability were independent of serum and brain MRI markers of neuroaxonal loss. OCT can be an important tool for stratification in MS, while longitudinal studies using combinations of biomarkers are warranted.
Background:
Clinical and radiological signs of recurring disease activity (RDA) have been described in patients with multiple sclerosis (pwMS) after discontinuation of fingolimod (FGL).
Objective:
To ...describe frequency, severity and potential risk factors for RDA after FGL discontinuation in a large real-world cohort of pwMS.
Methods:
Post-FGL RDA was defined as evidence of clinical and/or radiological activity within 6 months after FGL discontinuation. Relapses with Expanded Disability Status Scale increase ⩾2 points and/or magnetic resonance imaging (MRI) activity with at least five cerebral gadolinium-enhancing lesions and/or ⩾6 cerebral new T2 lesions were defined as severe recurring disease activity (sRDA). Using a multivariate logistic model, we explored the influence of age, disease duration, sex, clinical, and MRI activity under FGL on the occurrence of RDA.
Results:
We identified 110 pwMS who discontinued FGL. Thirty-seven (33.6%) developed post-FGL RDA and 13 (11.8%) also fulfilled criteria for sRDA. Younger age at diagnosis odds ratio (OR) = 1.10, p < 0.01, shorter disease duration (OR = 1.17, p < 0.01), and MRI activity under FGL (OR = 2.92, p = 0.046) were independent risk factors for the occurrence of post-FGL RDA.
Conclusion:
Individual risk assessment and optimal treatment sequencing can help to minimize the risk of post-FGL RDA. Early switch to highly effective disease-modifying therapy might reduce occurrence of post-FGL RDA.
Background
Retinal degeneration leading to optical coherence tomography (OCT) changes is frequent in patients with multiple sclerosis (PwMS).
Objective
To investigate associations among OCT changes, ...MRI measurements of global and regional brain volume loss, and physical and cognitive impairment in PwMS.
Methods
95 PwMS and 52 healthy controls underwent OCT and MRI examinations. Mean peripapillary retinal nerve fiber layer (pRNFL) thickness and ganglion cell/inner plexiform layer (GCIPL) volume were measured. In PwMS disability was quantified with the Expanded Disability Status Scale (EDSS) and Symbol Digit Modalities Test (SDMT). Associations between OCT, MRI, and clinical measures were investigated with multivariable regression models.
Results
In PwMS, pRNFL and GCIPL were associated with the volume of whole brain (
p
< 0.04), total gray matter (
p
< 0.002), thalamus (
p
≤ 0.04), and cerebral cortex (
p
≤ 0.003) –both globally and regionally–, but not white matter. pRNFL and GCIPL were also inversely associated with T2-lesion volume (T2LV), especially in the optic radiations (
p
< 0.0001). The brain volumes associated with EDSS and SDMT significantly overlapped with those correlating with pRNFL and GCIPL.
Conclusions
In PwMS, pRNFL and GCIPL reflect the integrity of clinically-relevant gray matter structures, underling the value of OCT measures as markers of neurodegeneration and disability in multiple sclerosis.
Background:
The Neurostatus-eEDSS is an electronic tool providing automated real-time feedback on inconsistencies of Neurostatus-EDSS calculations.
Objective:
To analyze the performance of the ...Neurostatus-eEDSS in two multicenter phase 3 multiple sclerosis (MS) trials.
Methods:
All assessments captured with the Neurostatus-eEDSS web service during a period of 2.5 years were analyzed.
Results:
Of the total 10,789 assessments, 40.1% had inconsistencies after first entry, reduced to 22.1% due to the real-time feedback. The entire checking process resulted in a change of the expanded disability status scale (EDSS) score in 14.8% of the assessments.
Conclusion:
The Neurostatus-eEDSS can increase consistency and reliability of EDSS assessments in clinical MS trials.
Duplex stainless steels generally solidify with a ferritic microstructure, followed by a partial transformation to austenite during cooling. Rapid cooling may render the transformation incomplete. ...The too-low or too-high cooling rate can also result in the formation of intermetallic phases and precipitates which can have a detrimental effect on the pitting corrosion resistance. The possibilities of achieving a microstructure with 30–70% ferrite in duplex stainless steel (1.4462, DX 2205) autogenously welded with a novel plasma welding equipment were investigated. Welding was performed as a square butt joint, with a 0-mm nominal gap size, on a 6-mm plate thickness, without the use of filler metal. The plasma torch uses a focus gas that allows it to constrict the arc in addition to the conventional constriction by the plasma nozzle. The three separated gas flows (plasma, focus and shielding gas) allow the gas composition to be tailored in the different gas flows. The effect of argon, nitrogen and helium content on the phase balance related to the gas flow channels was studied. The presence of nitrides as well as the sigma phase was investigated, and the joint quality was evaluated. The microstructure of the welded samples, investigated by image analysis, was correlated to pitting corrosion resistance. It was shown that high joint quality, quality level B, with favourable ferrite/austenite phase balance can be achieved through autogenous single-pass welding of duplex stainless steel 1.4462, DX 2205 (6.0 mm) using the novel plasma torch. With N
2
additions in, most notably, the plasma gas and the shielding gas, it was possible to get a ferrite phase fraction in the weld metal close to 50%.
The aim of the present work was to study the influence of the stress on the electrode potential of the austenitic stainless steel 301LN using Scanning Kelvin Probe (SKP). It was found that elastic ...deformation reversibly ennobles the potential whereas plastic deformation decreases the potential in both tensile and compressive deformation mode and this decrease is retained even 24 h after removal of the load. To interpret the stress effects, different surface preparations were used and the composition and thickness of the passive film were determined by GDOES. Slip steps formed due to plastic deformation were observed using AFM. The effect of plastic strain on the potential is explained by the formation of dislocations, which creates more a defective passive film.
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