The prediction of stellar ( γ , α ) reaction rates for heavy nuclei is based on the calculation of ( α , γ ) cross sections at sub-Coulomb energies. These rates are essential for modeling the ...nucleosynthesis of so-called p nuclei. The standard calculations in the statistical model show a dramatic sensitivity to the chosen α -nucleus potential. The present study explains the reason for this dramatic sensitivity which results from the tail of the imaginary α -nucleus potential in the underlying optical model calculation of the total reaction cross section. As an alternative to the optical model, a simple barrier transmission model is suggested. It is shown that this simple model in combination with a well-chosen α -nucleus potential is able to predict total α -induced reaction cross sections for a wide range of heavy target nuclei above A ≳ 150 with uncertainties below a factor of 2. The new predictions from the simple model do not require any adjustment of parameters to experimental reaction cross sections whereas in previous statistical model calculations all predictions remained very uncertain because the parameters of the α -nucleus potential had to be adjusted to experimental data. The new model allows us to predict the reaction rate of the astrophysically important 176W (α , γ)180 Os reaction with reduced uncertainties, leading to a significantly lower reaction rate at low temperatures. The new approach could also be validated for a broad range of target nuclei from A ≈ 60 up to A ≳ 200 .
Research gaps in understanding flood changes at the catchment scale caused by changes in forest management, agricultural practices, artificial drainage, and terracing are identified. Potential ...strategies in addressing these gaps are proposed, such as complex systems approaches to link processes across time scales, long‐term experiments on physical‐chemical‐biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology.
Plain Language Summary
This commentary explores research gaps in the field of land use change impacts on floods at the catchment scale and proposes possible ways forward for addressing these gaps. Specifically the impacts of forest management, agricultural practices, artificial drainage, and terracing on flood generation at the catchment scale are explored. Potential strategies in addressing research gaps in these fields are complex systems approaches to link processes across time scales, long‐term experiments on physical‐chemical‐biological process interactions, and a focus on connectivity and patterns across spatial scales. It is suggested that these strategies will stimulate new research that coherently addresses the issues across hydrology, soil and agricultural sciences, forest engineering, forest ecology, and geomorphology.
Key Points
Land use change impacts on floods are poorly understood at the catchment scale
Numerous synergies are identified in exploring the effects of changed agricultural practices, artif. drainage, terracing, and forest cover
A cross‐disciplinary systems approach aided by long‐term field studies and a focus on flow connectivity are needed to make major advances
Sleep is integral to life
. Although insufficient or disrupted sleep increases the risk of multiple pathological conditions, including cardiovascular disease
, we know little about the cellular and ...molecular mechanisms by which sleep maintains cardiovascular health. Here we report that sleep regulates haematopoiesis and protects against atherosclerosis in mice. We show that mice subjected to sleep fragmentation produce more Ly-6C
monocytes, develop larger atherosclerotic lesions and produce less hypocretin-a stimulatory and wake-promoting neuropeptide-in the lateral hypothalamus. Hypocretin controls myelopoiesis by restricting the production of CSF1 by hypocretin-receptor-expressing pre-neutrophils in the bone marrow. Whereas hypocretin-null and haematopoietic hypocretin-receptor-null mice develop monocytosis and accelerated atherosclerosis, sleep-fragmented mice with either haematopoietic CSF1 deficiency or hypocretin supplementation have reduced numbers of circulating monocytes and smaller atherosclerotic lesions. Together, these results identify a neuro-immune axis that links sleep to haematopoiesis and atherosclerosis.
The discovery that a common polymorphism (5-HTTLPR, short variant) in the human serotonin transporter gene (SLC6A4) can influence personality traits and increase the risk for depression in adulthood ...has led to the hypothesis that a relative increase in the extracellular levels of serotonin (5-HT) during development could be critical for the establishment of brain circuits. Consistent with this idea, a large body of data demonstrate that 5-HT is a strong neurodevelopmental signal that can modulate a wide variety of cellular processes. In humans, serotonergic fibers appear in the developing cortex as early as the 10th gestational week, a period of intense neuronal migration. In this study we hypothesized that an excess of 5-HT could affect embryonic cortical interneuron migration. Using time-lapse videometry to monitor the migration of interneurons in embryonic mouse cortical slices, we discovered that the application of 5-HT decreased interneuron migration in a reversible and dose-dependent manner. We next found that 5-HT6 receptors were expressed in cortical interneurons and that 5-HT6 receptor activation decreased interneuron migration, whereas 5-HT6 receptor blockade prevented the migratory effects induced by 5-HT. Finally, we observed that interneurons were abnormally distributed in the cerebral cortex of serotonin transporter gene (Slc6a4) knockout mice that have high levels of extracellular 5-HT. These results shed new light on the neurodevelopmental alterations caused by an excess of 5-HT during the embryonic period and contribute to a better understanding of the cellular processes that could be modulated by genetically controlled differences in human 5-HT homeostasis.
As one of the cornerstones of innate immunity, the complement system has long been implicated in the pathogenesis of atherosclerosis. Growing evidence demonstrates the presence of complement ...activation products in human atherosclerotic plaques, where they can exhibit both protective and proatherogenic properties as supported by numerous experimental findings. While complement initiation resulting in the cleavage of the central complement component C3 appears to have a crucial role in tempering lesion progression by aiding the clearance of apoptotic cells, cascade propagation to the terminal pathway characterized by C5 cleavage and membrane attack complex formation may promote plaque vulnerability. Nevertheless, these assumptions are made based on studies focusing predominantly on systemic, liver-derived complement, whereas it is now evident that almost every cell type can produce complement proteins and the site of synthesis can dictate the function of complement. However, the role of local complement activation in lesion formation remains largely understudied. Here, we review the current literature on complement activation in human atherosclerotic plaques, discuss clinical and genetic associations between complement and cardiovascular disease susceptibility and summarize experimental evidence gained from animal studies. Furthermore, by highlighting recent findings with respect to extrahepatic complement production in the artery wall, we illustrate the necessity to uncover the contribution of local (paracrine, autocrine as well as intracellular) vis-à-vis systemic complement activation to atherosclerotic lesion formation.
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•The complement system is involved in atherogenesis.•Depending on the stage of complement activation, complement can mitigate or promote lesion formation.•There is increasing evidence that local complement expression is key to the understanding of complement in atherosclerosis.•The understanding of the role of endogenous or pharmacological regulators of complement is limited.
Communication within the glial cell ecosystem is essential for neuronal and brain health
. The influence of glial cells on the accumulation and clearance of β-amyloid (Aβ) and neurofibrillary tau in ...the brains of individuals with Alzheimer's disease (AD) is poorly understood, despite growing awareness that these are therapeutically important interactions
. Here we show, in humans and mice, that astrocyte-sourced interleukin-3 (IL-3) programs microglia to ameliorate the pathology of AD. Upon recognition of Aβ deposits, microglia increase their expression of IL-3Rα-the specific receptor for IL-3 (also known as CD123)-making them responsive to IL-3. Astrocytes constitutively produce IL-3, which elicits transcriptional, morphological, and functional programming of microglia to endow them with an acute immune response program, enhanced motility, and the capacity to cluster and clear aggregates of Aβ and tau. These changes restrict AD pathology and cognitive decline. Our findings identify IL-3 as a key mediator of astrocyte-microglia cross-talk and a node for therapeutic intervention in AD.
In this paper, we present an analysis of K2 mission Campaign 3 observations of the irregular Neptune satellite, Nereid. We determined a rotation period of P = 11.594±0.017 h and amplitude of Δm = 0
...$.\!\!\!^{{\mathrm{m}}}$
0328±0
$.\!\!\!^{{\mathrm{m}}}$
0018, confirming previous short rotation periods obtained in ground-based observations. The similarities of light-curve amplitudes between 2001 and 2015 show that Nereid is in a low-amplitude rotation state nowadays and it could have been in a high-amplitude rotation state in the mid-1960s. Another high-amplitude period is expected in about 30 yr. Based on the light-curve amplitudes observed in the last 15 yr, we could constrain the shape of Nereid and obtained a maximum a:c axis ratio of 1.3:1. This excludes the previously suggested very elongated shape of a:c ≈ 1.9:1 and clearly shows that Nereid's spin axis cannot be in forced precession due to tidal forces. Thermal emission data from the Spitzer Space Telescope and the Herschel Space Observatory indicate that Nereid's shape is actually close to the a:c axis ratio limit of 1.3:1 we obtained, and it has a very rough, highly cratered surface.
Gaia Early Data Release 3 Hodgkin, S. T.; Harrison, D. L.; Breedt, E. ...
Astronomy and astrophysics (Berlin),
08/2021, Letnik:
652
Journal Article
Recenzirano
Odprti dostop
Context.
Since July 2014, the
Gaia
mission has been engaged in a high-spatial-resolution, time-resolved, precise, accurate astrometric, and photometric survey of the entire sky.
Aims.
We present the
...Gaia
Science Alerts project, which has been in operation since 1 June 2016. We describe the system which has been developed to enable the discovery and publication of transient photometric events as seen by
Gaia
.
Methods.
We outline the data handling, timings, and performances, and we describe the transient detection algorithms and filtering procedures needed to manage the high false alarm rate. We identify two classes of events: (1) sources which are new to
Gaia
and (2)
Gaia
sources which have undergone a significant brightening or fading. Validation of the
Gaia
transit astrometry and photometry was performed, followed by testing of the source environment to minimise contamination from Solar System objects, bright stars, and fainter near-neighbours.
Results.
We show that the
Gaia
Science Alerts project suffers from very low contamination, that is there are very few false-positives. We find that the external completeness for supernovae,
C
E
= 0.46, is dominated by the
Gaia
scanning law and the requirement of detections from both fields-of-view. Where we have two or more scans the internal completeness is
C
I
= 0.79 at 3 arcsec or larger from the centres of galaxies, but it drops closer in, especially within 1 arcsec.
Conclusions.
The per-transit photometry for
Gaia
transients is precise to 1% at
G
= 13, and 3% at
G
= 19. The per-transit astrometry is accurate to 55 mas when compared to
Gaia
DR2. The
Gaia
Science Alerts project is one of the most homogeneous and productive transient surveys in operation, and it is the only survey which covers the whole sky at high spatial resolution (subarcsecond), including the Galactic plane and bulge.
The bare nucleus S(E) factors for the H2(d,p)H3 and H2(d,n)He3 reactions have been measured for the first time via the Trojan Horse Method off the proton in 3He from 1.5 MeV down to 2 keV. This range ...overlaps with the relevant region for Standard Big Bang Nucleosynthesis as well as with the thermal energies of future fusion reactors and deuterium burning in the Pre-Main-Sequence phase of stellar evolution. This is the first pioneering experiment in quasi free regime where the charged spectator is detected. Both the energy dependence and the absolute value of the S(E) factors deviate by more than 15% from available direct data with new S(0) values of 57.4±1.8 MeVb for H3+p and 60.1±1.9 MeVb for He3+n. None of the existing fitting curves is able to provide the correct slope of the new data in the full range, thus calling for a revision of the theoretical description. This has consequences in the calculation of the reaction rates with more than a 25% increase at the temperatures of future fusion reactors.
The M protein of coronavirus plays a central role in virus assembly, turning cellular membranes into workshops where virus and host factors come together to make new virus particles. We investigated ...how M structure and organization is related to virus shape and size using cryo-electron microscopy, tomography and statistical analysis. We present evidence that suggests M can adopt two conformations and that membrane curvature is regulated by one M conformer. Elongated M protein is associated with rigidity, clusters of spikes and a relatively narrow range of membrane curvature. In contrast, compact M protein is associated with flexibility and low spike density. Analysis of several types of virus-like particles and virions revealed that S protein, N protein and genomic RNA each help to regulate virion size and variation, presumably through interactions with M. These findings provide insight into how M protein functions to promote virus assembly.
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