Quantum correlations and entanglement shared among multiple quantum modes are important for both fundamental science and the future development of quantum technologies. This development will also ...require an efficient quantum interface between multimode quantum light sources and atomic ensembles, which makes it necessary to implement multimode quantum light sources that match the atomic transitions. Here, we report on such a source that provides a method for generating quantum correlated beams that can be extended to a large number of modes by using multiple four-wave mixing (FWM) processes in hot rubidium vapor. Experimentally, we show that two cascaded FWM processes produce strong quantum correlations between three bright beams but not between any two of them. In addition, the intensity-difference squeezing is enhanced with the cascaded system to -7.0±0.1 dB from the -5.5±0.1/-4.5±0.1 dB squeezing obtained with only one FWM process. One of the main advantages of our system is that as the number of quantum modes increases, so does the total degree of quantum correlations. The proposed method is also immune to phase instabilities due to its phase insensitive nature, can easily be extended to multiple modes, and has potential applications in the production of multiple quantum correlated images.
Food insecurity is defined as "a household-level economic and social condition of limited or uncertain access to adequate food." While, levels of food insecurity in the United States have fluctuated ...over the past 20 years; disparities in food insecurity rates between people of color and whites have continued to persist. There is growing recognition that discrimination and structural racism are key contributors to disparities in health behaviors and outcomes. Although several promising practices to reduce food insecurity have emerged, approaches that address structural racism and discrimination may have important implications for alleviating racial/ethnic disparities in food insecurity and promoting health equity overall.
In this volume, authors draw from theoretical and methodological frameworks in the health, social and behavioral sciences to illustrate how poor outcomes among individuals and communities can be ...linked to the interplay of multiple factors operating at various levels.
Asteroseismic constraints on K giants make it possible to infer radii, masses and ages of tens of thousands of field stars. Tests against independent estimates of these properties are however scarce, ...especially in the metal-poor regime. Here, we report the detection of solar-like oscillations in eight stars belonging to the red-giant branch (RGB) and red-horizontal branch (RHB) of the globular cluster M4. The detections were made in photometric observations from the K2 Mission during its Campaign 2. Making use of independent constraints on the distance, we estimate masses of the eight stars by utilizing different combinations of seismic and non-seismic inputs. When introducing a correction to the Δν scaling relation as suggested by stellar models, for RGB stars we find excellent agreement with the expected masses from isochrone fitting, and with a distance modulus derived using independent methods. The offset with respect to independent masses is lower, or comparable with, the uncertainties on the average RGB mass (4–10 per cent, depending on the combination of constraints used). Our results lend confidence to asteroseismic masses in the metal-poor regime. We note that a larger sample will be needed to allow more stringent tests to be made of systematic uncertainties in all the observables (both seismic and non-seismic), and to explore the properties of RHB stars, and of different populations in the cluster.
We explain the multiple populations recently found in the ‘prototype’ globular cluster (GC) NGC 2808 in the framework of the asymptotic giant branch (AGB) scenario. The chemistry of the five – or ...more – populations is approximately consistent with a sequence of star formation events, starting after the Type II supernova epoch, lasting approximately until the time when the third dredge-up affects the AGB evolution (age ∼90–120 Myr), and ending when the Type Ia supernovae begin exploding in the cluster, eventually clearing it from the gas. The formation of the different populations requires episodes of star formation in AGB gas diluted with different amounts of pristine gas. In the nitrogen-rich, helium-normal population identified in NGC 2808 by the UV Legacy Survey of GCs, the nitrogen increase is due to the third dredge-up in the smallest mass AGB ejecta involved in the star formation of this population. The possibly iron-rich small population in NGC 2808 may be a result of contamination by a single Type Ia supernova. The NGC 2808 case is used to build a general framework to understand the variety of ‘second-generation’ stars observed in GCs. Cluster-to-cluster variations are ascribed to differences in the effects of the many processes and gas sources which may be involved in the formation of the second generation. We discuss an evolutionary scheme, based on pollution by delayed Type II supernovae, which accounts for the properties of s-Fe-anomalous clusters.
Omega-3 polyunsaturated fatty acids (PUFA) are essential unsaturated fatty acids with a double bond (C=C) starting after the third carbon atom from the end of the carbon chain. They are important ...nutrients but, unfortunately, mammals cannot synthesize them, whereby they must be obtained from food sources or from supplements. Amongst nutritionally important polyunsaturated n-3 fatty acids, α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are highly concentrated in the brain and have anti-oxidative stress, anti-inflammatory and antiapoptotic effects. They are involved in many bodily processes and may reportedly lead to neuron protection in neurological diseases. aged or damaged neurons and in Alzheimer's disease. Their effect in cognitive and behavioral functions and in several neurological and psychiatric disorders has been also proven. The dentate gyrus (DG), a sub-region of hippocampus, is implicated in cognition and mood regulation. The hippocampus represents one of the two areas in the mammalian brain in which adult neurogenesis occurs. This process is associated with beneficial effects on cognition, mood and chronic pharmacological treatment. The exposure to n-3 fatty acids enhances adult hippocampal neurogenesis associated with cognitive and behavioral processes, promotes synaptic plasticity by increasing long-term potentiation and modulates synaptic protein expression to stimulate the dendritic arborization and new spines formation. On this basis we review the effect of n-3 fatty acids on adult hippocampal neurogenesis and neuroplasticity. Moreover their possible use as a new therapeutic approach for neurodegenerative diseases is pointed out.
ABSTRACT
We present results from our on-going MusE GAs FLOw and Wind (MEGAFLOW) survey, which consists of 22 quasar lines of sight, each observed with the integral field unit MUSE and the UVES ...spectrograph at the ESO Very Large Telescopes (VLT). The goals of this survey are to study the properties of the circumgalactic medium around z ∼ 1 star-forming galaxies. The absorption-line selected survey consists of 79 strong Mg ii absorbers (with rest-frame equivalent width ≳0.3 Å) and, currently, 86 associated galaxies within 100 projected kpc of the quasar with stellar masses (M⋆) from 109 to 1011 M⊙. We find that the cool halo gas traced by Mg ii is not isotropically distributed around these galaxies from the strong bi-modal distribution in the azimuthal angle of the apparent location of the quasar with respect to the galaxy major axis. This supports a scenario in which outflows are bi-conical in nature and co-exist with a co-planar gaseous structure extending at least up to 60–80 kpc. Assuming that absorbers near the minor axis probe outflows, the current MEGAFLOW sample allowed us to select 26 galaxy–quasar pairs suitable for studying winds. From this sample, using a simple geometrical model, we find that the outflow velocity only exceeds the escape velocity when M⋆ ≲ 4 × 109 M⊙, implying the cool material is likely to fall back except in the smallest haloes. Finally, we find that the mass loading factor η, the ratio between the ejected mass rate and the star formation rate, appears to be roughly constant with respect to the galaxy mass.
M dwarfs are the most numerous stars in the Galaxy. They are characterized by strong magnetic activity. The ensuing high-energy emission is crucial for the evolution of their planets and the eventual ...presence of life on them. We systematically study the X-ray and ultraviolet emission of a subsample of M dwarfs from a recent proper-motion survey, selecting all M dwarfs within 10 pc to obtain a nearly volume-limited sample (∼90 per cent completeness). Archival ROSAT, XMM-Newton and GALEX data are combined with published spectroscopic studies of Hα emission and rotation to obtain a broad picture of stellar activity on M dwarfs. We make use of synthetic model spectra to determine the relative contributions of photospheric and chromospheric emission to the ultraviolet flux. We also analyse the same diagnostics for a comparison sample of young M dwarfs in the TW Hya association (∼10 Myr). We find that generally the emission in the GALEX bands is dominated by the chromosphere but the photospheric component is not negligible in early-M field dwarfs. The surface fluxes for the Hα, near-ultraviolet, far-ultraviolet and X-ray emission are connected via a power-law dependence. We present here for the first time such flux-flux relations involving broad-band ultraviolet emission for M dwarfs. Activity indices are defined as flux ratio between the activity diagnostic and the bolometric flux of the star in analogy to the Ca ii
R′HK index. For given spectral type, these indices display a spread of 2-3 dex which is largest for M4 stars. Strikingly, at mid-M spectral types, the spread of rotation rates is also at its highest level. The mean activity index for fast rotators, likely representing the saturation level, decreases from X-rays over the FUV to the NUV band and Hα, i.e. the fractional radiation output increases with atmospheric height. The comparison to the ultraviolet and X-ray properties of TW Hya members shows a drop of nearly three orders of magnitude for the luminosity in these bands between ∼10 Myr and few Gyr age. A few young field dwarfs (<1 Gyr) in the 10-pc sample bridge the gap indicating that the drop in magnetic activity with age is a continuous process. The slope of the age decay is steeper for the X-ray than for the UV luminosity.
Abstract
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters (GCs) has investigated GCs and their stellar populations. In previous papers of this series we have introduced a ...pseudo two-colour diagram, or ‘chromosome map’ (ChM) that maximizes the separation between the multiple populations. We have identified two main classes of GCs: Type I, including ∼83 per cent of the objects, and Type II clusters. Both classes host two main groups of stars, referred to in this series as first (1G) and second generation (2G). Type II clusters host more complex ChMs, exhibiting two or more parallel sequences of 1G and 2G stars. We exploit spectroscopic elemental abundances from the literature to assign the chemical composition to the distinct populations as identified on the ChMs of 29 GCs. We find that stars in different regions of the ChM have different compositions: 1G stars share the same light-element content as field stars, while 2G stars are enhanced in N and Na and depleted in O. Stars with enhanced Al, as well as stars with depleted Mg, populate the extreme regions of the ChM. We investigate the intriguing colour spread among 1G stars observed in many Type I GCs, and find no evidence for internal variations in light elements among these stars, whereas either a ∼0.1 dex iron spread or a variation in He among 1G stars remains to be verified. In the attempt of analysing the global properties of the multiple-population phenomenon, we have constructed a universal ChM, which highlights that, though very variegate, the phenomenon has some common pattern among all the analysed GCs. The universal ChM reveals a tight connection with Na abundances, for which we have provided an empirical relation. The additional ChM sequences observed in Type II GCs are enhanced in metallicity and, in some cases, s-process elements. Omega Centauri can be classified as an extreme Type II GC, with a ChM displaying three main extended ‘streams’, each with its own variations in chemical abundances. One of the most noticeable differences is found between the lower and upper streams, with the latter, associated with higher He, being also shifted towards higher Fe and lower Li abundances. We publicly release the ChMs.
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