| 1. |
- Limburg, Karin E., et al.
(författare)
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In search of the dead zone : Use of otoliths for tracking fish exposure to hypoxia
- 2015
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Ingår i: Journal of Marine Systems. - : Elsevier BV. - 0924-7963 .- 1879-1573. ; 141, s. 167-178
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Tidskriftsartikel (refereegranskat)abstract
- Otolith chemistry is often useful for tracking provenance of fishes, as well as examining migration histories. Whereas elements such as strontium and barium correlate well with salinity and temperature, experiments that examine manganese uptake as a function of these parameters have found no such correlation. Instead, dissolved manganese is available as a redox product, and as such, is indicative of low-oxygen conditions. Here we present evidence for that mechanism in a range of habitats from marine to freshwater, across species, and also present ancillary proxies that support the mechanism as well. For example, iodine is redox-sensitive and varies inversely with Mn; and sulfur stable isotope ratios provide evidence of anoxic sulfate reduction in some circumstances. Further, S may be incorporated trophically whereas other elements appear to be taken up directly from water. This research suggests a potential means to identify individual fish exposure to hypoxia, over entire lifetimes. With further testing and understanding, in the future fish may be able to be used as "mobile monitors" of hypoxic conditions. (C) 2014 The Authors. Published by Elsevier B.V.
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| 2. |
- Busby, CJ, et al.
(författare)
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The missing half of the subduction factory : shipboard results from the Izu rear arc, IODP expedition 350
- 2017
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Ingår i: International Geology Review. - : Informa UK Limited. - 0020-6814 .- 1938-2839. ; 59:13, s. 1677-1708
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- IODP Expedition 350 was the first to be drilled in the rear part of the Izu-Bonin, although severalsites had been drilled in the arc axis to fore-arc region; the scientific objective was to understand theevolution of the Izu rear arc, by drilling a deep-water volcaniclastic section with a long temporalrecord (Site U1437). The Izu rear arc is dominated by a series of basaltic to dacitic seamount chainsup to ~100-km long roughly perpendicular to the arc front. Dredge samples from these aregeochemically distinct from arc front rocks, and drilling was undertaken to understand this arcasymmetry. Site U1437 lies in an ~20-km-wide basin between two rear arc seamount chains, ~90-kmwest of the arc front, and was drilled to 1804 m below the sea floor (mbsf) with excellent recovery.We expected to drill a volcaniclastic apron, but the section is much more mud-rich than expected(~60%), and the remaining fraction of the section is much finer-grained than predicted from itsposition within the Izu arc, composed half of ashes/tuffs, and half of lapilli tuffs of fine grain size(clasts <3 cm). Volcanic blocks (>6.4 cm) are only sparsely scattered through the lowermost 25% ofthe section, and only one igneous unit was encountered, a rhyolite peperite intrusion at~1390 mbsf. The lowest biostratigaphic datum is at 867 mbsf (~6.5 Ma), the lowest palaeomagneticdatum is at ~1300 mbsf (~9 Ma), and the rhyolite peperite at ~1390 mbsf has yielded a U–Pb zirconconcordia intercept age of (13.6 + 1.6/−1.7) Ma. Both arc front and rear arc sources contributed tothe fine-grained (distal) tephras of the upper 1320 m, but the coarse-grained (proximal) volcani-clastics in the lowest 25% of the section are geochemically similar to the arc front, suggesting arcasymmetry is not recorded in rocks older than ~13 Ma.
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| 3. |
- McWhinney, Sean R, et al.
(författare)
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Association between body mass index and subcortical brain volumes in bipolar disorders-ENIGMA study in 2735 individuals.
- 2021
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Ingår i: Molecular psychiatry. - : Springer Science and Business Media LLC. - 1476-5578 .- 1359-4184. ; 26:11, s. 6806-6819
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Tidskriftsartikel (refereegranskat)abstract
- Individuals with bipolar disorders (BD) frequently suffer from obesity, which is often associated with neurostructural alterations. Yet, the effects of obesity on brain structure in BD are under-researched. We obtained MRI-derived brain subcortical volumes and body mass index (BMI) from 1134 BD and 1601 control individuals from 17 independent research sites within the ENIGMA-BD Working Group. We jointly modeled the effects of BD and BMI on subcortical volumes using mixed-effects modeling and tested for mediation of group differences by obesity using nonparametric bootstrapping. All models controlled for age, sex, hemisphere, total intracranial volume, and data collection site. Relative to controls, individuals with BD had significantly higher BMI, larger lateral ventricular volume, and smaller volumes of amygdala, hippocampus, pallidum, caudate, and thalamus. BMI was positively associated with ventricular and amygdala and negatively with pallidal volumes. When analyzed jointly, both BD and BMI remained associated with volumes of lateral ventricles and amygdala. Adjusting for BMI decreased the BD vs control differences in ventricular volume. Specifically, 18.41% of the association between BD and ventricular volume was mediatedby BMI (Z=2.73, p=0.006). BMI was associated with similar regional brain volumes as BD, including lateral ventricles, amygdala, and pallidum. Higher BMI may in part account for larger ventricles, one of the most replicated findings in BD. Comorbidity with obesity could explain why neurostructural alterations are more pronounced in some individuals with BD. Future prospective brain imaging studies should investigate whether obesity could be a modifiable risk factor for neuroprogression.
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| 4. |
- McWhinney, Sean R, et al.
(författare)
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Diagnosis of bipolar disorders and body mass index predict clustering based on similarities in cortical thickness-ENIGMA study in 2436 individuals.
- 2022
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Ingår i: Bipolar disorders. - : Wiley. - 1399-5618 .- 1398-5647. ; 24:5, s. 509-520
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Tidskriftsartikel (refereegranskat)abstract
- Rates of obesity have reached epidemic proportions, especially among people with psychiatric disorders. While the effects of obesity on the brain are of major interest in medicine, they remain markedly under-researched in psychiatry.We obtained body mass index (BMI) and magnetic resonance imaging-derived regional cortical thickness, surface area from 836 bipolar disorders (BD) and 1600 control individuals from 14sites within the ENIGMA-BD Working Group. We identified regionally specific profiles of cortical thickness using K-means clustering and studied clinical characteristics associated with individual cortical profiles.We detected two clusters based on similarities among participants in cortical thickness. The lower thickness cluster (46.8% of the sample) showed thinner cortex, especially in the frontal and temporal lobes and was associated with diagnosis of BD, higher BMI, and older age. BD individuals in the low thickness cluster were more likely to have the diagnosis of bipolar disorder I and less likely to be treated with lithium. In contrast, clustering based on similarities in the cortical surface area was unrelated to BD or BMI and only tracked age and sex.We provide evidence that both BD and obesity are associated with similar alterations in cortical thickness, but not surface area. The fact that obesity increased the chance of having low cortical thickness could explain differences in cortical measures among people with BD. The thinner cortex in individuals with higher BMI, which was additive and similar to the BD-associated alterations, may suggest that treating obesity could lower the extent of cortical thinning in BD.
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| 5. |
- McWhinney, Sean R, et al.
(författare)
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Mega-analysis of association between obesity and cortical morphology in bipolar disorders: ENIGMA study in 2832 participants.
- 2023
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Ingår i: Psychological medicine. - 1469-8978. ; 53:14, s. 6743-6753
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Tidskriftsartikel (refereegranskat)abstract
- Obesity is highly prevalent and disabling, especially in individuals with severe mental illness including bipolar disorders (BD). The brain is a target organ for both obesity and BD. Yet, we do not understand how cortical brain alterations in BD and obesity interact.We obtained body mass index (BMI) and MRI-derived regional cortical thickness, surface area from 1231 BD and 1601 control individuals from 13 countries within the ENIGMA-BD Working Group. We jointly modeled the statistical effects of BD and BMI on brain structure using mixed effects and tested for interaction and mediation. We also investigated the impact of medications on the BMI-related associations.BMI and BD additively impacted the structure of many of the same brain regions. Both BMI and BD were negatively associated with cortical thickness, but not surface area. In most regions the number of jointly used psychiatric medication classes remained associated with lower cortical thickness when controlling for BMI. In a single region, fusiform gyrus, about a third of the negative association between number of jointly used psychiatric medications and cortical thickness was mediated by association between the number of medications and higher BMI.We confirmed consistent associations between higher BMI and lower cortical thickness, but not surface area, across the cerebral mantle, in regions which were also associated with BD. Higher BMI in people with BD indicated more pronounced brain alterations. BMI is important for understanding the neuroanatomical changes in BD and the effects of psychiatric medications on the brain.
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| 6. |
- Schmitt, Axel K., et al.
(författare)
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U–Pb ages of rare rutile inclusions in diamond indicate entrapment synchronous with kimberlite formation
- 2019
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Ingår i: Lithos. - : Elsevier BV. - 0024-4937 .- 1872-6143. ; 350-351
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Tidskriftsartikel (refereegranskat)abstract
- The timing of diamond crystallization is generally inferred from radiometric dating of individual or multiple mineral inclusions in diamond, where ages are derived from isochrons or isotopic evolution models. Resulting ages often significantly predate the emplacement ages of host kimberlites, but age information from both approaches can be ambiguous due to long-lived mantle heterogeneities where mixing can mimic isochrons or in-situ aging. Direct dating of accessory mineral inclusions in diamonds, by contrast, has rarely been attempted because of the scarcity of such inclusions, requiring careful high grading of large amounts of diamond concentrates. Here, we report secondary ionization mass spectrometry (SIMS) U–Pb ages from a suite of rare rutile inclusions which were extracted from diamond in an eclogitic paragenesis from the Mir kimberlite pipe, Siberia. One population of rutile inclusions shows diamond crystal-shapes and was petrographically identified as completely enclosed in diamond prior to host burning for inclusion extraction. These rutile inclusions were screened for U abundances (0.24–23 μg/g U) and those with the highest U contents were dated, yielding a uniform U–Pb concordia age of 375.5 ± 7.0 Ma (error 95% confidence; mean square of weighted deviates MSWD = 0.74; number of spots n = 19). This age is nearly coeval with, but significantly (at the 95% confidence level) older than combined U–Pb rutile ages for rutile intergrown with polycrystalline fibrous diamond (362.9 ± 9.5 Ma; MSWD = 0.96; n = 7) and rutile from the eclogitic xenolith matrix (369 ± 16 Ma; MSWD = 0.30; n = 5). Rutile ages are consistent with published ages for kimberlite emplacement (ca. 360 Ma), but much younger than Re–Os sulfide isochron ages between ca. 913 Ma and 2.1 Ga for groups of individual inclusions in diamond from the same location. When assuming the oldest Re–Os sulfide age as the timing of rutile entrapment, diffusive Pb-loss from rutile inclusions over ca. 2 Ga would require diffusivities of Pb in diamond of >10−22 m2/s, as well as Pb partitioning coefficients between diamond and rutile at near or greater unity. Alternatively, if Pb is immobile in diamond, ancient rutile ages could have been reset due to processes other than volume diffusion through diamond (e.g., due to fluid migration along cracks). However, in this scenario it remains difficult to explain why all rutile inclusions dated here would have been located along cracks, whereas sulfide inclusions investigated in other studies were not. Another explanation is that rutile inclusions were entrapped at the time of diamond formation, and that this event is recorded by U–Pb rutile ages, whereas sulfides predate diamond crystallization and their Re–Os systematics were incompletely reset. Trace element heterogeneity in rutile suggests that they originated in chemically different environments, and thus rutile likely predates diamond formation. However, due to rapid diffusion of Pb in rutile, radiogenic Pb accumulated only after entrapment in diamond (for inclusions) or eruptive quenching (for intergrown or matrix rutile). Overall, rutile geochronology indicates that at least some diamond from the Mir pipe formed briefly (within the ca. 20 Ma age difference between U–Pb rutile ages for inclusions and intergrown/matrix rutile) before kimberlite eruption, supporting models that link diamond formation with carbon-rich precursors of kimberlite magmas.
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| 7. |
- Topuz, Gültekin, et al.
(författare)
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Jurassic accretionary complex and ophiolite from northeast Turkey: No evidence for the Cimmerian continental ribbon
- 2013
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Ingår i: Geology. - : Geological Society of America. - 0091-7613 .- 1943-2682. ; 41:2, s. 255-258
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Tidskriftsartikel (refereegranskat)abstract
- Permian-Triassic and Late Cretaceous accretionary complexes, ascribed to the consumption of two distinct oceans, the Paleo- and Neo-Tethys, are exposed over extensive areas in the Eastern Mediterranean region. However, a separating continental ribbon, the so-called Cimmeride continent, between the Paleo- and Neo-Tethys during early Mesozoic time cannot be defined. Here we report a previously unknown Early Jurassic metamorphic oceanic accretionary complex and ophiolite from northeast Turkey, bounded by oceanic accretionary complexes of Permian-Triassic and Late Cretaceous age to the north and the south, respectively, without a continental domain in between. This special tectonic position and widespread coexistence of Permian-Triassic and Late Cretaceous accretionary complexes alongside the Izmir-Ankara-Erzincan suture imply that (1) the southern margin of Laurasia in the eastern Mediterranean region grew by episodic accretionary processes from late Paleozoic to end-Mesozoic time without involvement of a Cimmerian continental ribbon, and (2) the Paleo-Tethys and northern branch of the Neo-Tethys were not distinct oceans in the Eastern Mediterranean region.
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