| 1. |
- Anchukaitis, Kevin, et al.
(författare)
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Last millennium Northern Hemisphere summer temperatures from tree rings: Part II, spatially resolved reconstructions
- 2017
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 163, s. 1-22
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Tidskriftsartikel (refereegranskat)abstract
- Climate field reconstructions from networks of tree-ring proxy data can be used to characterize regionalscale climate changes, reveal spatial anomaly patterns associated with atmospheric circulation changes, radiative forcing, and large-scale modes of ocean-atmosphere variability, and provide spatiotemporal targets for climate model comparison and evaluation. Here we use a multiproxy network of tree-ring chronologies to reconstruct spatially resolved warm season (MayeAugust) mean temperatures across the extratropical Northern Hemisphere (40-90N) using Point-by-Point Regression (PPR). The resulting annual maps of temperature anomalies (750e1988 CE) reveal a consistent imprint of volcanism, with 96% of reconstructed grid points experiencing colder conditions following eruptions. Solar influences are detected at the bicentennial (de Vries) frequency, although at other time scales the influence of insolation variability is weak. Approximately 90% of reconstructed grid points show warmer temperatures during the Medieval Climate Anomaly when compared to the Little Ice Age, although the magnitude varies spatially across the hemisphere. Estimates of field reconstruction skill through time and over space can guide future temporal extension and spatial expansion of the proxy network.
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| 2. |
- Gifford, Katherine A, et al.
(författare)
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The 12-Word Philadelphia Verbal Learning Test Performances in Older Adults: Brain MRI and Cerebrospinal Fluid Correlates and Regression-Based Normative Data.
- 2018
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Ingår i: Dementia and geriatric cognitive disorders extra. - : S. Karger AG. - 1664-5464. ; 8:3, s. 476-491
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Tidskriftsartikel (refereegranskat)abstract
- This study evaluated neuroimaging and biological correlates, psychometric properties, and regression-based normative data of the 12-word Philadelphia Verbal Learning Test (PVLT), a list-learning test.Vanderbilt Memory and Aging Project participants free of clinical dementia and stroke (n = 230, aged 73 ± 7 years) completed a neuropsychological protocol and brain MRI. A subset (n = 111) underwent lumbar puncture for analysis of Alzheimer's disease (AD) and axonal integrity cerebrospinal fluid (CSF) biomarkers. Regression models related PVLT indices to MRI and CSF biomarkers adjusting for age, sex, race/ethnicity, education, APOE-ε4 carrier status, cognitive status, and intracranial volume (MRI models). Secondary analyses were restricted to participants with normal cognition (NC; n = 127), from which regression-based normative data were generated.Lower PVLT performances were associated with smaller medial temporal lobe volumes (p < 0.05) and higher CSF tau concentrations (p < 0.04). Among NC, PVLT indices were associated with white matter hyperintensities on MRI and an axonal injury biomarker (CSF neurofilament light; p < 0.03).The PVLT appears sensitive to markers of neurodegeneration, including temporal regions affected by AD. Conversely, in cognitively normal older adults, PVLT performance seems to relate to white matter disease and axonal injury, perhaps reflecting non-AD pathways to cognitive change. Enhanced normative data enrich the clinical utility of this tool.
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| 3. |
- Green, Jonathan M. H., et al.
(författare)
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Research priorities for managing the impacts and dependencies of business upon food, energy, water and the environment
- 2017
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Ingår i: Sustainability Science. - : Springer Science and Business Media LLC. - 1862-4065 .- 1862-4057. ; 12:2, s. 319-331
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Tidskriftsartikel (refereegranskat)abstract
- Delivering access to sufficient food, energy and water resources to ensure human wellbeing is a major concern for governments worldwide. However, it is crucial to account for the 'nexus' of interactions between these natural resources and the consequent implications for human wellbeing. The private sector has a critical role in driving positive change towards more sustainable nexus management and could reap considerable benefits from collaboration with researchers to devise solutions to some of the foremost sustainability challenges of today. Yet opportunities are missed because the private sector is rarely involved in the formulation of deliverable research priorities. We convened senior research scientists and influential business leaders to collaboratively identify the top forty questions that, if answered, would best help companies understand and manage their food-energy-water-environment nexus dependencies and impacts. Codification of the top order nexus themes highlighted research priorities around development of pragmatic yet credible tools that allow businesses to incorporate nexus interactions into their decision-making; demonstration of the business case for more sustainable nexus management; identification of the most effective levers for behaviour change; and understanding incentives or circumstances that allow individuals and businesses to take a leadership stance. Greater investment in the complex but productive relations between the private sector and research community will create deeper and more meaningful collaboration and cooperation.
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| 4. |
- Juckes, Martin N., et al.
(författare)
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Millennial temperature reconstruction intercomparison and evaluation
- 2007
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Ingår i: Climate of the Past. - 1814-9324. ; 3, s. 591-609
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Tidskriftsartikel (refereegranskat)abstract
- There has been considerable recent interest in paleoclimate reconstructions of the temperature history of the last millennium. A wide variety of techniques have been used. The interrelation among the techniques is sometimes unclear, as different studies often use distinct data sources as well as distinct methodologies. Here recent work is reviewed and some new calculations performed with an aim to clarifying the consequences of the different approaches used. A range of proxy data collections introduced by different authors is used to estimate Northern Hemispheric annual mean temperatures with two reconstruction algorithms: (1) inverse regression and, (2) compositing followed by variance matching (CVM). It is found that inverse regression tends to give large weighting to a small number of proxies and that the second approach (CVM) is more robust to varying proxy input. The choice of proxy records is one reason why different reconstructions show different ranges. A reconstruction using 13 proxy records extending back to AD 1000 shows a maximum pre-industrial temperature of 0.25 K (relative to the 1866 to 1970 mean). The standard error on this estimate, based on the residual in the calibration period, is 0.14 K. Instrumental temperatures for two recent years (1998 and 2005) have exceeded the pre-industrial estimated maximum by more than 4 standard deviations of the calibration period residual.
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| 5. |
- Kresge, Hailey A, et al.
(författare)
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Lower Left Ventricular Ejection Fraction Relates to Cerebrospinal Fluid Biomarker Evidence of Neurodegeneration in Older Adults.
- 2020
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Ingår i: Journal of Alzheimer's disease : JAD. - 1875-8908. ; 74:3, s. 965-974
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Tidskriftsartikel (refereegranskat)abstract
- Subclinical cardiac dysfunction is associated with decreased cerebral blood flow, placing the aging brain at risk for Alzheimer's disease (AD) pathology and neurodegeneration.This study investigates the association between subclinical cardiac dysfunction, measured by left ventricular ejection fraction (LVEF), and cerebrospinal fluid (CSF) biomarkers of AD and neurodegeneration.Vanderbilt Memory & Aging Project participants free of dementia, stroke, and heart failure (n=152, 72±6 years, 68% male) underwent echocardiogram to quantify LVEF and lumbar puncture to measure CSF levels of amyloid-β42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau). Linear regressions related LVEF to CSF biomarkers, adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, cognitive diagnosis, and apolipoprotein E ɛ4 status. Secondary models tested an LVEF x cognitive diagnosis interaction and then stratified by diagnosis (normal cognitive (NC), mild cognitive impairment (MCI)).Higher LVEF related to decreased CSF Aβ42 levels (β=-6.50, p=0.04) reflecting greater cerebral amyloid accumulation, but this counterintuitive result was attenuated after excluding participants with cardiovascular disease and atrial fibrillation (p=0.07). We observed an interaction between LVEF and cognitive diagnosis on CSF t-tau (p=0.004) and p-tau levels (p=0.002), whereas lower LVEF was associated with increased CSF t-tau (β=-9.74, p=0.01) and p-tau in the NC (β=-1.41, p=0.003) but not MCI participants (p-values>0.13).Among cognitively normal older adults, subclinically lower LVEF relates to greater molecular evidence of tau phosphorylation and neurodegeneration. Modest age-related changes in cardiovascular function may have implications for pathophysiological changes in the brain later in life.
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| 6. |
- Moore, Elizabeth E, et al.
(författare)
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Neurofilament relates to white matter microstructure in older adults.
- 2018
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Ingår i: Neurobiology of aging. - : Elsevier BV. - 1558-1497 .- 0197-4580. ; 70, s. 233-241
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Tidskriftsartikel (refereegranskat)abstract
- Cerebrospinal fluid (CSF) neurofilament light (NFL) is a protein biomarker of axonal injury. To study whether NFL is associated with diffusion tensor imaging (DTI) measurements of white matter (WM) microstructure, Vanderbilt Memory & Aging Project participants with normal cognition (n= 77), early mild cognitive impairment (n= 15), and MCI (n= 55) underwent lumbar puncture to obtain CSF and 3T brain MRI. Voxel-wise analyses cross-sectionally related NFL to DTI metrics, adjusting for demographic and vascular risk factors. Increased NFL correlated with multiple DTI metrics (p-values < 0.05). An NFL× diagnosis interaction (excluding early mild cognitive impairment) on WM microstructure (p-values < 0.05) was detected, with associations strongest among MCI. Multiple NFL× CSF biomarker interactions were detected. Associations between NFL and worse WM metrics were strongest among amyloid-β42-negative, tau-positive, and suspected nonamyloid pathology participants. Findings suggest increased NFL, a biomarker of axonal injury, is correlated with compromised WM microstructure. Results highlight the role of elevated NFL in predicting WM damage in cognitively impaired older adults who are amyloid-negative, tau-positive, or meet suspected nonamyloid pathology criteria.
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| 7. |
- Osborn, Katie E, et al.
(författare)
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Cerebrospinal fluid and plasma neurofilament light relate to abnormal cognition.
- 2019
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Ingår i: Alzheimer's & dementia. - : Wiley. - 2352-8729. ; 11:C, s. 700-709
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Tidskriftsartikel (refereegranskat)abstract
- Neuroaxonal damage may contribute to cognitive changes preceding clinical dementia. Accessible biomarkers are critical for detecting such damage.Plasma and cerebrospinal fluid (CSF) neurofilament light (NFL) were related to neuropsychological performance among Vanderbilt Memory & Aging Project participants (plasma n=333, 73±7years; CSF n=149, 72±6years) ranging from normal cognition (NC) to mild cognitive impairment (MCI). Models adjusted for age, sex, race/ethnicity, education, apolipoprotein E ε4 carriership,and Framingham Stroke Risk Profile.Plasma NFL was related to all domains (P values ≤ .008) except processing speed (P values ≥ .09). CSF NFL was related to memory and language (P values ≤ .04). Interactions with cognitive diagnosis revealed widespread plasma associations, particularly in MCI participants, which were further supported in head-to-head comparison models.Plasma and CSF NFL (reflecting neuroaxonal injury) relate to cognition among non-demented older adults albeit with small to medium effects. Plasma NFL shows particular promise as an accessible biomarker with relevance to cognition in MCI.
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| 8. |
- Schneider, Lea, et al.
(författare)
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The impact of proxy selection strategies on a millennium-long ensemble of hydroclimatic records in Monsoon Asia
- 2019
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 223
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale palaeoclimate reconstructions can be very sensitive to the proxy records they are based on, and hence to the criteria used to select proxy records. Data selection rarely follows objective criteria that are applicable to all types of proxies, including both low- and high-resolution records. Thus, there is a need for a uniform and transparent approach to assess the suitability of input proxy data for a reconstruction. Here, we develop classification criteria that are applicable to multiple proxy types and evaluate different selection strategies using a network of 62 millennium-long terrestrial hydroclimate proxy records from Monsoon Asia. Our results reveal that robust evidence for a coherent climate signal and high dating accuracy are important criteria for benchmarking the suitability of each proxy record. We determine these criteria by reviewing the literature for each record (rather than screening against instrumental data). We show that the proposed selection approach can yield a network with a stronger common signal. By evaluating the uncertainty and centennial variability of composite reconstructions, from differently selected subsets of the proxy network, it appears beneficial to use suitable proxies stemming from different archives, as well as having a dense network of proxy sites. We suggest that future large-scale palaeoclimate reconstructions might be improved by evaluating proxy networks according to the universal categories presented here and, if indicated, removing less suitable records. This will strengthen the climate signal in the final reconstruction, allowing more precise inferences about past climate variability and more robust comparisons with climate model simulations.
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| 9. |
- Wang, Jianglin, et al.
(författare)
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Causes of East Asian Temperature Multidecadal Variability Since 850 CE
- 2018
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 45:24, s. 13485-13494
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Tidskriftsartikel (refereegranskat)abstract
- The drivers of multidecadal- to centennial-scale variability in East Asian temperature, apparent in temperature reconstructions, are poorly understood. Here we apply a multivariate regression analysis to distinguish the influences of large-scale modes of internal variability (Atlantic Multidecadal Oscillation and Pacific Multidecadal Oscillation) and external natural (orbital, solar, and volcanic) and anthropogenic (greenhouse gas concentrations, aerosols, and land use changes) forcings on East Asian warm-season temperature over the period 850-1999 CE (Common Era). We find that similar to 80% of the temperature change on time scales longer than 30 years can be explained including all drivers over the full-length period. The Pacific Multidecadal Oscillation was the most important driver of multidecadal temperature variability during the Medieval Climate Anomaly (here 950-1250), while solar contribution was important during the Little Ice Age (here 1350-1850). Since 1850, two thirds of temperature change can be explained with anthropogenic forcing, whereas one third was related mainly to the Atlantic Multidecadal Oscillation and volcanic forcing. Plain Language Summary The Atlantic Multidecadal Oscillation (AMO) and Pacific Multidecadal Oscillation (PMO) are suggested to be key components of internal temperature variability globally and in the Northern Hemisphere. However, the contribution of the AMO and PMO to temperature at regional/continental scales in preindustrial times is still unclear. Here we use a multivariate regression analysis to distinguish the AMO and PMO contributions to the East Asian temperature multidecadal (> 30 years) changes from the influence of external (orbital solar, volcanic, and anthropogenic) forcings. We find that the contribution of the AMO and PMO is of similar magnitude as solar and volcanic forcing during the period 850-1999 CE (Common Era). We apply the same approach to three subperiods and find that the PMO, solar forcing, and anthropogenic forcing contributed most during the periods 950-1250, 1350-1850, and 1850-1999, respectively.
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| 10. |
- Wang, Jianglin, et al.
(författare)
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Internal and external forcing of multidecadal Atlantic climate variability over the past 1,200 years
- 2017
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Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 10:7, s. 512-517
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Tidskriftsartikel (refereegranskat)abstract
- The North Atlantic experiences climate variability on multidecadal scales, which is sometimes referred to as Atlantic multidecadal variability. However, the relative contributions of external forcing such as changes in solar irradiance or volcanic activity and internal dynamics to these variations are unclear. Here we provide evidence for persistent summer Atlantic multidecadal variability from AD 800 to 2010 using a network of annually resolved terrestrial proxy records from the circum-North Atlantic region. We find that large volcanic eruptions and solar irradiance minima induce cool phases of Atlantic multidecadal variability and collectively explain about 30% of the variance in the reconstruction on timescales greater than 30 years. We are then able to isolate the internally generated component of Atlantic multidecadal variability, which we define as the Atlantic multidecadal oscillation. We find that the Atlantic multidecadal oscillation is the largest contributor to Atlantic multidecadal variability over the past 1,200 years. We also identify coherence between the Atlantic multidecadal oscillation and Northern Hemisphere temperature variations, leading us to conclude that the apparent link between Atlantic multidecadal variability and regional to hemispheric climate does not arise solely from a common response to external drivers, and may instead reflect dynamic processes.
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