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- Rise, H. H., et al.
(författare)
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Brain disconnectome mapping derived from white matter lesions and serum neurofilament light levels in multiple sclerosis: A longitudinal multicenter study
- 2022
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Ingår i: Neuroimage-Clinical. - : Elsevier BV. - 2213-1582. ; 35
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Tidskriftsartikel (refereegranskat)abstract
- Background and Objectives: Connectivity-based approaches incorporating the distribution and magnitude of the extended brain network aberrations caused by lesions may offer higher sensitivity for axonal damage in patients with multiple sclerosis (MS) than conventional lesion characteristics. Using individual brain disconnectome mapping, we tested the longitudinal associations between putative imaging-based brain network aberrations and levels of serum neurofilament light chain (NfL) as a neuroaxonal injury biomarker. Methods: MS patients (n = 312, mean age 42.9 years, 71 % female) and healthy controls (HC) (n = 59, mean age 39.9 years, 78 % female) were prospectively enrolled at four European MS centres, and reassessed after two years (MS, n = 242; HC, n = 30). Post-processing of 3 Tesla (3 T) MRI data was performed at one centre using a harmonized pipeline, and disconnectome maps were calculated using BCBtoolkit based on individual lesion maps. Global disconnectivity (GD) was defined as the average disconnectome probability in each patient's white matter. Serum NfL concentrations were measured by single molecule array (Simoa). Robust linear mixed models (rLMM) with GD or T2-lesion volume (T2LV) as dependent variables, patient as a random factor, serum NfL, age, sex, timepoint for visit, diagnosis, treatment, and center as fixed factors were run. Results: rLMM revealed significant associations between GD and serum NfL (t = 2.94, p = 0.003), age (t = 4.21, p = 2.5 x 10(-5)), and longitudinal changes in NfL (t =-2.29, p = 0.02), but not for sex (t = 0.63, p = 0.53) or treatments (t = 0.80-0.83, p = 0.41-0.42). Voxel-wise analyses revealed significant associations between dysconnectivity in cerebellar and brainstem regions and serum NfL (t = 7.03, p < 0.001). Discussion: In our prospective multi-site MS cohort, rLMMs demonstrated that the extent of global and regional brain disconnectivity is sensitive to a systemic biomarker of axonal damage, serum NfL, in patients with MS. These findings provide a neuroaxonal correlate of advanced disconnectome mapping and provide a platform for further investigations of the functional and potential clinical relevance of brain disconnectome mapping in patients with brain disorders.
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- Zhang, Haofei, et al.
(författare)
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Monoterpenes are the largest source of summertime organic aerosol in the southeastern United States
- 2018
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 115:9, s. 2038-2043
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Tidskriftsartikel (refereegranskat)abstract
- The chemical complexity of atmospheric organic aerosol (OA) has caused substantial uncertainties in understanding its origins and environmental impacts. Here, we provide constraints on OA origins through compositional characterization with molecular-level details. Our results suggest that secondary OA (SOA) from monoterpene oxidation accounts for approximately half of summertime fine OA in Centreville, AL, a forested area in the southeastern United States influenced by anthropogenic pollution. We find that different chemical processes involving nitrogen oxides, during days and nights, play a central role in determining the mass of monoterpene SOA produced. These findings elucidate the strong anthropogenic–biogenic interaction affecting ambient aerosol in the southeastern United States and point out the importance of reducing anthropogenic emissions, especially under a changing climate, where biogenic emissions will likely keep increasing.
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- Lee, Ben H, et al.
(författare)
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Highly functionalized organic nitrates in the southeast United States: Contribution to secondary organic aerosol and reactive nitrogen budgets.
- 2016
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 113:6, s. 1516-21
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Tidskriftsartikel (refereegranskat)abstract
- Speciated particle-phase organic nitrates (pONs) were quantified using online chemical ionization MS during June and July of 2013 in rural Alabama as part of the Southern Oxidant and Aerosol Study. A large fraction of pONs is highly functionalized, possessing between six and eight oxygen atoms within each carbon number group, and is not the common first generation alkyl nitrates previously reported. Using calibrations for isoprene hydroxynitrates and the measured molecular compositions, we estimate that pONs account for 3% and 8% of total submicrometer organic aerosol mass, on average, during the day and night, respectively. Each of the isoprene- and monoterpenes-derived groups exhibited a strong diel trend consistent with the emission patterns of likely biogenic hydrocarbon precursors. An observationally constrained diel box model can replicate the observed pON assuming that pONs (i) are produced in the gas phase and rapidly establish gas-particle equilibrium and (ii) have a short particle-phase lifetime (∼2-4 h). Such dynamic behavior has significant implications for the production and phase partitioning of pONs, organic aerosol mass, and reactive nitrogen speciation in a forested environment.
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- Ahlberg, Erik, et al.
(författare)
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Effect of salt seed particle surface area, composition and phase on secondary organic aerosol mass yields in oxidation flow reactors
- 2019
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 19:4, s. 2701-2712
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric particulate water is ubiquitous, affecting particle transport and uptake of gases. Yet, research on the effect of water on secondary organic aerosol (SOA) mass yields is not consistent. In this study, the SOA mass yields of an α-pinene and m-xylene mixture, at a concentration of 60 μgm-3, were examined using an oxidation flow reactor operated at a relative humidity (RH) of 60% and a residence time of 160 s. Wet or dried ammonium sulfate and ammonium nitrate seed particles were used. By varying the amount of seed particle surface area, the underestimation of SOA formation induced by the short residence time in flow reactors was confirmed. Starting at a SOA mass concentration of 5 μgm-3, the maximum yield increased by a factor of 2 with dry seed particles and on average a factor of 3.2 with wet seed particles. Hence, wet particles increased the SOA mass yield by 60% compared to the dry experiment. Maximum yield in the reactor was achieved using a surface area concentration of 1600 μm2 cm-3. This corresponded to a condensational lifetime of 20 s for low-volatility organics. The O V C ratio of SOA on wet ammonium sulfate was significantly higher than when using ammonium nitrate or dry ammonium sulfate seed particles, probably due to differences in heterogeneous chemistry.
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