Abstract
There are multiple groups of comoving stars in the Solar neighbourhood, which are possible signatures of one of the fundamental resonances of non-axisymmetric structure such as the Galactic ...bar or spiral arms. One such stream, Hercules, has been proposed to result from the outer Lindblad resonance of a short-fast rotating bar as shown analytically, or the corotation resonance of a longer slower rotating bar as observed in an N-body model. We show that by including an m = 4 Fourier component in an analytical long bar model, with an amplitude that is typical for bars in N-body simulations, we can reproduce a Hercules-like feature in the stellar kinematics of the Solar neighbourhood. We describe the expected symmetry in the velocity distribution arising from such a model, which we will soon be able to test with Gaia.
ABSTRACT
Studies of the ages, abundances, and motions of individual stars in the Milky Way provide one of the best ways to study the evolution of disc galaxies over cosmic time. The formation of the ...Milky Way’s barred inner region in particular is a crucial piece of the puzzle of disc galaxy evolution. Using data from APOGEE and Gaia, we present maps of the kinematics, elemental abundances, and age of the Milky Way bulge and disc that show the barred structure of the inner Milky Way in unprecedented detail. The kinematic maps allow a direct, purely kinematic determination of the bar’s pattern speed of $41\pm 3\, \mathrm{km\, s}^{-1}\, \mathrm{kpc}^{-1}$ and of its shape and radial profile. We find the bar’s age, metallicity, and abundance ratios to be the same as those of the oldest stars in the disc that are formed in its turbulent beginnings, while stars in the bulge outside of the bar are younger and more metal-rich. This implies that the bar likely formed ${\approx}8\, \mathrm{Gyr}$ ago, when the decrease in turbulence in the gas disc allowed a thin disc to form that quickly became bar-unstable. The bar’s formation therefore stands as a crucial epoch in the evolution of the Milky Way, a picture that is in line with the evolutionary path that emerges from observations of the gas kinematics in external disc galaxies over the last ${\approx}10\, \mathrm{Gyr}$.
ABSTRACT
Action space synthesizes the orbital information of stars and is well suited to analyse the rich kinematic substructure of the disc in the second Gaia data release's radial velocity sample. ...We revisit the strong perturbation induced in the Milky Way disc by an m = 2 bar, using test particle simulations and the actions (JR, Lz, Jz) estimated in an axisymmetric potential. These make three useful diagnostics cleanly visible. (1) We use the well-known characteristic flip from outward to inward motion at the outer Lindblad resonance (OLR; l = +1, m = 2), which occurs along the axisymmetric resonance line (ARL) in (Lz, JR), to identify in the Gaia action data three candidates for the bar’s OLR and pattern speed Ωbar: 1.85Ω0, 1.20Ω0, and 1.63Ω0 (with ∼0.1Ω0 systematic uncertainty). The Gaia data is therefore consistent with both slow and fast bar models in the literature, but disagrees with recent measurements of ∼1.45Ω0. (2) For the first time, we demonstrate that bar resonances – especially the OLR – cause a gradient in vertical action 〈Jz〉 with Lz around the ARL via ‘Jz-sorting’ of stars. This could contribute to the observed coupling of 〈vR〉 and 〈|vz|〉 in the Galactic disc. (3) We confirm prior results that the behaviour of resonant orbits is well approximated by scattering and oscillation in (Lz, JR) along a slope ΔJR/ΔLz = l/m centred on the l:m ARL. Overall, we demonstrate that axisymmetrically estimated actions are a powerful diagnostic tool even in non-axisymmetric systems.
Stranger in a strange land Hunt, Joan S.
Immunological reviews,
October 2006, Letnik:
213, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Mammalian mothers and their embryos/fetuses are almost invariably genetically different, which raises the question of how the mother’s immune system is diverted so as to permit cohabitation with the ...‘foreign’ body. Several decades of research have shown that multiple cooperative systems sanction uteroplacental immune privilege. These systems include production of several varieties of soluble immunosuppressive molecules in the uterus and the placenta and strict regulation of the molecules expressed on or by placental trophoblast cells. Trophoblast, a unique lineage without counterpart in adult tissues, is in direct contact with maternal blood and tissue. The major graft rejection‐promoting molecules, human leukocyte antigens (HLAs), are tightly regulated in these cells, with none of HLA‐A, HLA‐B, or HLA class II antigens expressed. The HLA class Ib antigens, HLA‐E, HLA‐F, and HLA‐G, are detectable on some subpopulations. Our studies have focused on the expression, regulation, and functions of the soluble isoforms of HLA‐G, which circulate in maternal blood and are present at high levels in the pregnant uterus. These isoforms are derived from the single HLA‐G gene by alternative splicing and are now known to have immunosuppressive properties. Ours and other studies indicate that soluble HLA‐G proteins may comprise a unique tolerogenic system for establishing local immune privilege during pregnancy.
Relentless workloads are birthing unprecedented levels of burnout, mental ill health, substance misuse, and suicide amongst clinical staff working in the NHS. The consequent epidemic of sickness ...absence, early retirement, and poor staff retention means the workforce gap is widening at an alarming rate within the caring professions. The clarion call rings out loud, clear, and with urgency for organisational engagement in preventative measures to invest in its human capital. Interventions for increasing clinician wellbeing and resilience must encompass strategies at the personal level, at peer groups and teams, right through to the level of the culture and practices — the “operating system” — of the whole organisation. In hospitals across the nation, where the pervading environment is one of “lack” — time, space, thanks, morale — significant casualties are a sense of “community at work” and sanctioned time for reflective practice. Relaxed, reflective group debrief cultivates relational connection, enables off-loading of the burdens associated with caring and guides reflective “work on work”. Clinicians attending reflective groups appreciate the opportunity for a “space to breathe”, for self-reflection, mindfulness, and self-care, whilst gaining professional robustness and a sense of value and team. Could the low-cost model of monthly, facilitated “clinician wellbeing and debrief” gatherings and the provision of “pop-up” departmental café spaces, as pioneered in Cambridge, UK, significantly enrich our healthcare system's culture of “lack”?
•Burnout, mental ill-health, substance misuse and suicide are on the increase amongst the NHS clinical workforce.•Sickness absence, poor staff retention and a widening workforce gap are inevitable consequences, if no action is taken.•Moves to promote clinician wellbeing and resilience should target all levels from the individual to the whole organisation.•Regular facilitated reflective debrief groups draw clinicians together, enable catharsis and guided reflection on work issues.•Clinicians appreciate a sanctioned break from work, a time for mindfulness and self-care, professional reflection and team.
Antiepileptic drug (AED) exposure during pregnancy increases the risk of major congenital malformations (MCMs). The magnitude of this risk varies by AED exposure. Here we provide updated results from ...the UK Epilepsy and Pregnancy Register of the risk of MCMs after monotherapy exposure to valproate, carbamazepine and lamotrigine.
Fifteen-year prospective observational study from 1996 until 2012. The main outcome measure is the MCM rate.
Informative outcomes were available for 5206 cases. 1290 women were exposed to valproate monotherapy, 1718 to carbamazepine monotherapy and 2198 to lamotrigine monotherapy. The MCM risk with valproate monotherapy exposure in utero was 6.7% (95% CI 5.5% to 8.3%) compared with 2.6% with carbamazepine (95% CI 1.9% to 3.5%) and 2.3% with lamotrigine (95% CI 1.8% to 3.1%). A significant dose effect was seen with valproate (p=0.0006) and carbamazepine (p=0.03) exposed pregnancies. A non-significant trend towards higher MCM rate with increasing dose was found with lamotrigine. MCM rate for high-dose lamotrigine (>400 mg daily) was lower than the MCM rate for pregnancies exposed to <600 mg daily of valproate, but this was not significant (3.4% vs 5.0%, p=0.31).
In utero exposure to valproate carries a significantly higher MCM risk than lamotrigine (p=0.0001) and carbamazepine (p=0.0001) monotherapy. In contrast to prior findings, high-dose lamotrigine was associated with fewer MCMs than all doses of valproate. While lamotrigine has a favourable profile compared with valproate for adverse pregnancy outcomes, the requirements for seizure control should not be overlooked.
Angiogenesis is crucial to many physiological and pathological processes including development and cancer cell survival. Vascular endothelial growth factor-A (VEGFA) is the predominant mediator of ...angiogenesis in the VEGF family. During development, adverse environmental conditions like nutrient deprivation, hypoxia and increased protein secretion occur. IRE1alpha, PERK, and ATF6alpha, master regulators of the unfolded protein response (UPR), are activated under these conditions and are proposed to have a role in mediating angiogenesis.
Here we show that IRE1alpha, PERK, and ATF6alpha powerfully regulate VEGFA mRNA expression under various stress conditions. In Ire1alpha(-/-) and Perk(-/-) mouse embryonic fibroblasts and ATF6alpha-knockdown HepG2 cells, induction of VEGFA mRNA by endoplasmic reticulum stress is attenuated as compared to control cells. Embryonic lethality of Ire1alpha-/- mice is due to the lack of VEGFA induction in labyrinthine trophoblast cells of the developing placenta. Rescue of IRE1alpha and PERK in Ire1alpha(-/-) and Perk(-/-) cells respectively, prevents VEGFA mRNA attenuation. We further report that the induction of VEGFA by IRE1alpha, PERK and ATF6 involves activation of transcription factors, spliced-XBP-1, ATF4 and cleaved ATF6 respectively.
Our results reveal that the IRE1alpha-XBP-1, PERK-ATF4, and ATF6alpha pathways constitute novel upstream regulatory pathways of angiogenesis by modulating VEGF transcription. Activation of these pathways helps the rapidly growing cells to obtain sufficient nutrients and growth factors for their survival under the prevailing hostile environmental conditions. These results establish an important role of the UPR in angiogenesis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
New neurons are continually generated from the resident populations of precursor cells in selective niches of the adult mammalian brain such as the hippocampal dentate gyrus and the olfactory bulb. ...However, whether such cells are present in the adult amygdala, and their neurogenic capacity, is not known. Using the neurosphere assay, we demonstrate that a small number of precursor cells, the majority of which express Achaete-scute complex homolog 1 (Ascl1), are present in the basolateral amygdala (BLA) of the adult mouse. Using neuron-specific Thy1-YFP transgenic mice, we show that YFP+ cells in BLA-derived neurospheres have a neuronal morphology, co-express the neuronal marker βIII-tubulin, and generate action potentials, confirming their neuronal phenotype. In vivo, we demonstrate the presence of newly generated BrdU-labeled cells in the adult BLA, and show that a proportion of these cells co-express the immature neuronal marker doublecortin (DCX). Furthermore, we reveal that a significant proportion of GFP+ neurons (~23%) in the BLA are newly generated (BrdU+) in DCX-GFP mice, and using whole-cell recordings in acute slices we demonstrate that the GFP+ cells display electrophysiological properties that are characteristic of interneurons. Using retrovirus-GFP labeling as well as the Ascl1
mouse line, we further confirm that the precursor cells within the BLA give rise to mature and functional interneurons that persist in the BLA for at least 8 weeks after their birth. Contextual fear conditioning has no effect on the number of neurospheres or BrdU-labeled cells in the BLA, but produces an increase in hippocampal cell proliferation. These results demonstrate that neurogenic precursor cells are present in the adult BLA, and generate functional interneurons, but also show that their activity is not regulated by an amygdala-dependent learning paradigm.
Seismology records the presence of various heterogeneities throughout the lower mantle1,2, but the origins of these signals- whether thermal or chemical-remain uncertain, and therefore much of the ...information that they hold about the nature of the deep Earth is obscured. Accurate interpretation of observed seismic velocities requires knowledge of the seismic properties of all of Earth's possible mineral components. Calcium silicate (CaSiO3) perovskite is believed to be the third most abundant mineral throughout the lower mantle. Here we simultaneously measure the crystal structure and the shear-wave and compressional-wave velocities of samples of CaSiO3 perovskite, and provide direct constraints on the adiabatic bulk and shear moduli of this material. We observe that incorporation of titanium into CaSiO3 perovskite stabilizes the tetragonal structure at higher temperatures, and that the material's shear modulus is substantially lower than is predicted by computations3-5 or thermodynamic datasets6. When combined with literature data and extrapolated, our results suggest that subducted oceanic crust will be visible as low-seismic-velocity anomalies throughout the lower mantle. In particular, we show that large low-shear-velocity provinces (LLSVPs) are consistent with moderate enrichment of recycled oceanic crust, and mid-mantle discontinuities can be explained by a tetragonal-cubic phase transition in Ti-bearing CaSiO3 perovskite.
ABSTRACT
Using a numerical simulation of an isolated barred disc galaxy, we first demonstrate that the resonances of the inner bar structure induce more prominent features in the action space ...distribution for the kinematically hotter stars, which are less sensitive to the local perturbation, such as the transient spiral arms. Then, we analyse the action distribution for the kinematically hotter stars selected from the Gaia EDR3 data as the stars with higher values of radial and vertical actions. We find several resonance features, including two new features, in the angular momentum distribution similar to what are seen in our numerical simulations. We show that the bar pattern speeds of about Ωbar ∼ 34 and 42 km s−1 kpc−1 explain all these features equally well. The resonance features we find correspond to the inner 4:1, co-rotation (CR), outer 4:1, outer Lindblad, and outer 4:3 (CR, outer 4:1, outer Lindblad, outer 4:3, and outer 1:1) resonances, when Ωbar ∼ 34 (42) km s−1 kpc−1 is assumed.
PDF
