232 research outputs found
APOGEE discovery of a chemically atypical star disrupted from NGC 6723 and captured by the Milky Way bulge
The central (‘bulge’) region of the Milky Way is teeming with a significant fraction of mildly metal-deficient stars with atmospheres that are strongly enriched in cyanogen (12C 14N). Some of these objects, which are also known as nitrogen-enhanced stars, are hypothesised to be relics of the ancient assembly history of the Milky Way. Although the chemical similarity of nitrogen-enhanced stars to the unique chemical patterns observed in globular clusters has been observed, a direct connection between field stars and globular clusters has not yet been proven. In this work, we report on high-resolution, near-infrared spectroscopic observations of the bulge globular cluster NGC 6723, and the serendipitous discovery of a star, 2M18594405−3651518, located outside the cluster (near the tidal radius) but moving on a similar orbit, providing the first clear piece of evidence of a star that was very likely once a cluster member and has recently been ejected. Its nitrogen abundance ratio ([N/Fe] & +0.94) is well above the typical Galactic field-star levels, and it exhibits noticeable enrichment in the heavy s-process elements (Ce, Nd, and Yb), along with moderate carbon enrichment; all characteristics are known examples in globular clusters. This result suggests that some of the nitrogen-enhanced stars in the bulge likely originated from the tidal disruption of globular clusters
Author Correction: The CaMKII/NMDA receptor complex controls hippocampal synaptic transmission by kinase-dependent and independent mechanisms.
The originally published version of this Article contained errors in Figure 5, for which we apologise. In panel c, the scatter graph was inadvertently replaced with a scatter graph comprising a subset of data points from panel d. Furthermore, the legends to Figures 5c and 5d were inverted. These errors have now been corrected in both the PDF and HTML versions of the Article, and the incorrect version of Fig. 5c is presented in the Author Correction associated with this Article
The CaMKII/NMDA receptor complex controls hippocampal synaptic transmission by kinase-dependent and independent mechanisms.
CaMKII is one of the most studied synaptic proteins, but many critical issues regarding its role in synaptic function remain unresolved. Using a CRISPR-based system to delete CaMKII and replace it with mutated forms in single neurons, we have rigorously addressed its various synaptic roles. In brief, basal AMPAR and NMDAR synaptic transmission both require CaMKIIα, but not CaMKIIβ, indicating that, even in the adult, synaptic transmission is determined by the ongoing action of CaMKIIα. While AMPAR transmission requires kinase activity, NMDAR transmission does not, implying a scaffolding role for the CaMKII protein instead. LTP is abolished in the absence of CaMKIIα and/or CaMKIIβ and with an autophosphorylation impaired CaMKIIα (T286A). With the exception of NMDAR synaptic currents, all aspects of CaMKIIα signaling examined require binding to the NMDAR, emphasizing the essential role of this receptor as a master synaptic signaling hub
In-Situ Star Formation in the Outskirts of the Large Magellanic Cloud: Gaia DR2 Confirmation
We explore the Gaia DR2 proper motions of six young, main-sequence stars,
members of the Large Magellanic Cloud (LMC) reported by Moni Bidin et al.
(2017). These stars are located in the outskirts of the disk, between 7 and 13
degrees from the LMC's center where there is very low H I content. Gaia DR2
proper motions confirm that four stars formed locally, in situ, while two are
consistent with being expelled via dynamical interactions from inner, more
gas-rich regions of the LMC. This finding establishes that recent star
formation occurred in the periphery of the LMC, where thus far only old
populations are known.Comment: Accepted for publication in Astrophysical Journal Letter
Food science and technology students self-evaluate soft and technical skills
Food Scientists and Technologists (FS&T) need diverse skills in the globalized food and drink sector:
Food-specific or scientific / technical skills and generic or intuitive soft skills. This study determined
how satisfied FS&T students were with overall improvement, and in key technical and soft skills, based
on their university work; and if satisfaction was linked to geography, degree in progress, anticipated
degree, anticipated work place or anticipated job responsibility. An on-line survey was completed
by 267 students in over 20 countries using a 5-point Likert scale to evaluate satisfaction. Responses
were analyzed by the Friedman or Kruskal Wallis tests for more than two groups, otherwise by the
Wilcoxon Signed Rank or Mann-Whitney tests. There were no differences in Overall Satisfaction
with technical and soft skills training. Among soft skills, training in Working with Others and Being
Responsible were more often rated “Excellent” and students were more satisfied with their training than
with Solving Problems, Communication and Positive Attitude. Students anticipating a job with high
responsibility were more satisfied with overall soft skill training and with 3 of the 5 specific soft skills.
Among technical skills, students were more satisfied with improvement in basic sciences (Microbiology,
Chemistry, Processing, Safety), and those in Northern Europe were more satisfied with overall technical
training. These data show variations in perception and/or efficacy of technical and soft skill training
in Food Science programmes and underline the need for separate attention to the incorporation of soft
skill training into the design of FS&T coursesinfo:eu-repo/semantics/publishedVersio
Chemical Composition of Young Stars in the Leading Arm of the Magellanic System
Chemical abundances of eight O- and B-type stars are determined from
high-resolution spectra obtained with the MIKE instrument on the Magellan 6.5m
Clay telescope. The sample is selected from 42 candidates of membership in the
Leading Arm of the Magellanic System. Stellar parameters are measured by two
independent grids of model atmospheres and analysis procedures, confirming the
consistency of the stellar parameter results. Abundances of seven elements (He,
C, N, O, Mg, Si, and S) are determined for the stars, as are their radial
velocities and estimates of distances and ages.
Among the seven B-type stars analyzed, the five that have radial velocities
compatible with membership to the LA have an average [Mg/H] of ,
significantly lower than the average of the remaining two [Mg/H] =
that are kinematical members of the Galactic disk. Among the
five LA members, four have individual [Mg/H] abundance compatible with that in
the LMC. Within errors, we can not exclude the possibility that one of these
stars has a [Mg/H] consistent with the more metal-poor, SMC-like material. The
remaining fifth star has a [Mg/H] close to MW values. Distances to the LA
members indicate that they are at the edge of the Galactic disk, while ages are
of the order of Myr, lower than the dynamical age of the LA,
suggesting a single star-forming episode in the LA. V the LA
members decreases with decreasing Magellanic longitude, confirming the results
of previous LA gas studies.Comment: 61 pages, 18 figures, 5 tables. Accepted for publication in Ap
The Origins of Young Stars in the Direction of the Leading Arm of the Magellanic Stream: Abundances, Kinematics, and Orbits
We explore the origins of the young B-type stars found by Casetti-Dinescu et
al.(2014) at the outskirts of the Milky-Way disk in the sky region of Leading
Arm of the Magellanic Stream. High-resolution spectroscopic observations made
with the MIKE instrument on the Magellan Clay 6.5m telescope for nine stars are
added to the previous sample analyzed by Zhang et al. (2017). We compile a
sample of fifteen young stars with well-determined stellar types, ages,
abundances and kinematics. With proper motions from Gaia DR2 we also derive
orbits in a realistic Milky-Way potential. We find that our previous
radial-velocity selected LA candidates have substantial orbital angular
momentum. The substantial amount of rotational component for these stars is in
contrast with the near-polar Magellanic orbit, thus rendering these stars
unlikely members of the LA. There are four large orbital-energy stars in our
sample. The highest orbital-energy one has an age shorter than the time to disk
crossing, with a birthplace ~kpc and ~kpc. Therefore,
the origin of this star is uncertain. The remaining three stars have disk
runaway origin with birthplaces between 12 and 25 kpc from the Galactic center.
Also, the most energetic stars are more metal poor ([Mg/H] =) and
with larger He scatter () than the inner disk ones
([Mg/H] , ). While the former group's
abundance is compatible with that of the Large Magellanic Cloud, it could also
reflect the metallicity gradient of the MW disk and their runaway status via
different runaway mechanisms.Comment: 58 pages, 17 figures, 7 tables. Accepted for publication in Ap
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