Context.
As the solar wind propagates through the heliosphere, dynamical processes irreversibly erase the signatures of the near–Sun heating and acceleration processes. The elemental fractionation of ...the solar wind should not change during transit, however, making it an ideal tracer of these processes.
Aims.
We aim to verify directly if the solar wind elemental fractionation is reflective of the coronal source region fractionation, both within and across different solar wind source regions.
Methods.
A backmapping scheme was used to predict where solar wind measured by the Advanced Composition Explorer (ACE) originated in the corona. The coronal composition measured by the Hinode Extreme ultraviolet Imaging Spectrometer (EIS) at the source regions was then compared with the in situ solar wind composition.
Results.
On hourly timescales, there is no apparent correlation between coronal and solar wind composition. In contrast, the distribution of fractionation values within individual source regions is similar in both the corona and solar wind, but distributions between different sources have a significant overlap.
Conclusions.
The matching distributions directly verify that elemental composition is conserved as the plasma travels from the corona to the solar wind, further validating it as a tracer of heating and acceleration processes. The overlap of fractionation values between sources means it is not possible to identify solar wind source regions solely by comparing solar wind and coronal composition measurements, but a comparison can be used to verify consistency with predicted spacecraft-corona connections.
Purpose
Alzheimer’s disease (AD) is associated with amyloid accumulation that takes place decades before symptoms appear. Cognitive impairment in AD is associated with reduced glucose metabolism. ...However, neuronal plasticity/compensatory mechanisms might come into play before the onset of dementia. The aim of this study was to determine whether there is evidence of cortical hypermetabolism as a compensatory mechanism before amyloid deposition takes place in subjects with amnestic mild cognitive impairment (aMCI).
Methods
Nine AD subjects and ten aMCI subjects had both
11
CPIB and
18
FFDG PET scans with arterial input in order to quantify the amyloid deposition and glucose metabolism in vivo in comparison with healthy control subjects who underwent either
11
CPIB or
18
FFDG PET scans. The
11
CPIB PET scans were quantified using
11
CPIB target region to cerebellum uptake ratio images created by integrating the activity collected from 60 to 90 min, and regional cerebral glucose metabolism was quantified using spectral analysis.
Results
In MCI subjects, cortical hypermetabolism was observed in four amyloid-negative subjects and one amyloid-positive subject, while hypometabolism was seen in five other MCI subjects with high amyloid load. Subjects with hypermetabolism and low amyloid did not convert to AD during clinical follow-up for 18 months in contrast to four amyloid-positive hypometabolic subjects who did convert to AD.
Conclusion
This preliminary study suggests that compensatory hypermetabolism can occur in aMCI subjects, particularly in those who are amyloid-negative. The increase in metabolic rate in different cortical regions with predominance in the occipital cortex may be a compensatory response to the neuronal damage occurring early in the disease process. It may also reflect recruitment of relatively minimally affected cortical regions to compensate for reduced function in the temporoparietal cortical association areas.
Activated microglia may play a role in the pathogenesis of Alzheimer disease (AD) as they cluster around beta-amyloid (Abeta) plaques. They are, therefore, a potential therapeutic target in both AD ...and its prodrome amnestic mild cognitive impairment (MCI).
To characterize in vivo with (11)C-(R)-PK11195 and (11)C-PIB PET the distribution of microglial activation and amyloid deposition in patients with amnestic MCI.
Fourteen subjects with MCI had (11)C-(R)-PK11195 and (11)C-PIB PET with psychometric tests.
Seven out of 14 (50%) patients with MCI had increased cortical (11)C-PIB retention (p < 0.001) while 5 out of 13 (38%) subjects with MCI showed increased (11)C-(R)-PK11195 uptake. The MCI subgroup with increased (11)C-PIB retention also showed increased cortical (11)C-(R)-PK11195 binding (p < 0.036) though this increase only remained significant in frontal cortex after a correction for multiple comparisons. There was no correlation between regional levels of (11)C-(R)-PK11195 and (11)C-PIB binding in individual patients with MCI: only three of the five MCI cases with increased (11)C-(R)-PK11195 binding had increased levels of (11)C-PIB retention.
Our findings indicate that, while amyloid deposition and microglial activation can be detected in vivo in around 50% of patients with mild cognitive impairment (MCI), these pathologies can occur independently. The detection of microglial activation in patients with MCI suggests that anti-inflammatory therapies may be relevant to the prevention of AD.
Abstract
From 2022 March 18 to 21, NOAA Active Region (AR) 12967 was tracked simultaneously by Solar Orbiter at 0.35 au and Hinode/EIS at Earth. During this period, strong blueshifted plasma upflows ...were observed along a thin, dark corridor of open magnetic field originating at the AR’s leading polarity and continuing toward the southern extension of the northern polar coronal hole. A potential field source surface model shows large lateral expansion of the open magnetic field along the corridor. Squashing factor
Q
-maps of the large-scale topology further confirm super-radial expansion in support of the S-web theory for the slow wind. The thin corridor of upflows is identified as the source region of a slow solar wind stream characterized by ∼300 km s
−1
velocities, low proton temperatures of ∼5 eV, extremely high density >100 cm
−3
, and a short interval of moderate Alfvénicity accompanied by switchback events. When the connectivity changes from the corridor to the eastern side of the AR, the in situ plasma parameters of the slow solar wind indicate a distinctly different source region. These observations provide strong evidence that the narrow open-field corridors, forming part of the S-web, produce some extreme properties in their associated solar wind streams.
Recent, large-scale outbreaks of bark beetle infestations have affected millions of hectares of forest in western North America, covering an area similar in size to that impacted by fire. Bark ...beetles kill host trees in affected areas, thereby altering water supply, carbon storage, and nutrient cycling in forests; for example, the timing and amount of snow melt may be substantially modified following bark beetle infestation, which impacts water resources for many western US states. The quality of water from infested forests may also be diminished as a result of increased nutrient export. Understanding the impacts of bark beetle outbreaks on forest ecosystems is therefore important for resource management. Here, we develop a conceptual framework of the impacts on coupled biogeophysical and biogeochemical processes following a mountain pine beetle (
Dendroctonus ponderosae
) outbreak in lodgepole pine (
Pinus contorta
Douglas var
latifolia
) forests in the weeks to decades after an infestation, and highlight future research needs and management implications of this widespread disturbance event.
Spinal cord injury and neurogenic bowel dysfunction (NBD) are life-changing events for affected patients. The clinical manifestations of NBD vary depending on the level and severity of the spinal ...cord lesion. Managing patients with NBD can be complicated by comorbidities, such as immobility, bladder dysfunction, progressive neurologic decline, psychological factors, loss of independence, and social withdrawal, and ideally involves a multimodal, multidisciplinary approach. Evaluation and management should be individualized, depending on the residual neurologic capabilities of the patient and their predominant gastrointestinal symptoms, and commonly involves lifestyle modifications, physical therapy, laxative medications, and surgical interventions.
Hydrology is an integrative discipline linking the broad array of water‐related research with physical, ecological, and social sciences. The increasing breadth of hydrological research, often where ...subdisciplines of hydrology partner with related sciences, reflects the central importance of water to environmental science, while highlighting the fractured nature of the discipline itself. This lack of coordination among hydrologic subdisciplines has hindered the development of hydrologic theory and integrated models capable of predicting hydrologic partitioning across time and space. The recent development of the concept of the critical zone (CZ), an open system extending from the top of the canopy to the base of groundwater, brings together multiple hydrological subdisciplines with related physical and ecological sciences. Observations obtained by CZ researchers provide a diverse range of complementary process and structural data to evaluate both conceptual and numerical models. Consequently, a cross‐site focus on “critical zone hydrology” has potential to advance the discipline of hydrology and to facilitate the transition of CZ observatories into a research network with immediate societal relevance. Here we review recent work in catchment hydrology and hydrochemistry, hydrogeology, and ecohydrology that highlights a common knowledge gap in how precipitation is partitioned in the critical zone: “how is the amount, routing, and residence time of water in the subsurface related to the biogeophysical structure of the CZ?” Addressing this question will require coordination among hydrologic subdisciplines and interfacing sciences, and catalyze rapid progress in understanding current CZ structure and predicting how climate and land cover changes will affect hydrologic partitioning.
Key Points:
The disparate nature of hydrologic research hinders theoretical advancement
Coordinated research on subsurface hydrologic partitioning to ET or streamflow can address this gap
Multiple areas of research identify extensive groundwater interaction with streamflow and atmosphere
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