2,073 research outputs found
Carbon monoxide in an extremely metal-poor galaxy
Extremely metal-poor galaxies with metallicity below 10% of the solar value
in the local universe are the best analogues to investigating the interstellar
medium at a quasi-primitive environment in the early universe. In spite of the
ongoing formation of stars in these galaxies, the presence of molecular gas
(which is known to provide the material reservoir for star formation in
galaxies, such as our Milky Way) remains unclear. Here, we report the detection
of carbon monoxide (CO), the primary tracer of molecular gas, in a galaxy with
7% solar metallicity, with additional detections in two galaxies at higher
metallicities. Such detections offer direct evidence for the existence of
molecular gas in these galaxies that contain few metals. Using archived
infrared data, it is shown that the molecular gas mass per CO luminosity at
extremely low metallicity is approximately one-thousand times the Milky Way
value.Comment: 12 pages, 3 figures, 1 table. Supplementary data at
http://www.nature.com/article-assets/npg/ncomms/2016/161209/ncomms13789/extref/ncomms13789-s1.pd
Inefficient Star Formation In Extremely Metal Poor Galaxies
The first galaxies contain stars born out of gas with little or no metals.
The lack of metals is expected to inhibit efficient gas cooling and star
formation but this effect has yet to be observed in galaxies with oxygen
abundance relative to hydrogen below a tenth of that of the Sun. Extremely
metal poor nearby galaxies may be our best local laboratories for studying in
detail the conditions that prevailed in low metallicity galaxies at early
epochs. Carbon Monoxide (CO) emission is unreliable as tracers of gas at low
metallicities, and while dust has been used to trace gas in low-metallicity
galaxies, low-spatial resolution in the far-infrared has typically led to large
uncertainties. Here we report spatially-resolved infrared observations of two
galaxies with oxygen abundances below 10 per cent solar, and show that stars
form very inefficiently in seven star-forming clumps of these galaxies. The
star formation efficiencies are more than ten times lower than found in normal,
metal rich galaxies today, suggesting that star formation may have been very
inefficient in the early Universe.Comment: Author's version (10 pages, 4 figures). Published in Natur
The Weak Carbon Monoxide Emission In An Extremely Metal Poor Galaxy, Sextans A
Carbon monoxide (CO) is one of the primary coolants of gas and an easily
accessible tracer of molecular gas in spiral galaxies but it is unclear if CO
plays a similar role in metal poor dwarfs. We carried out a deep observation
with IRAM 30 m to search for CO emission by targeting the brightest far-IR peak
in a nearby extremely metal poor galaxy, Sextans A, with 7% Solar metallicity.
A weak CO J=1-0 emission is seen, which is already faint enough to place a
strong constraint on the conversion factor (a_CO) from the CO luminosity to the
molecular gas mass that is derived from the spatially resolved dust mass map.
The a_CO is at least seven hundred times the Milky Way value. This indicates
that CO emission is exceedingly weak in extremely metal poor galaxies,
challenging its role as a coolant in these galaxies.Comment: 4 pages, 1 table, 4 figures. ApJL in pres
Development of a Simple Multiplex Electrochemiluminescence (ECL) Assay for Screening Pre-Type 1 Diabetes and Multiple Relevant Autoimmune Diseases
The presence of islet autoantibodies (iAbs) is currently the most reliable biomarker for type 1 diabetes (T1D). The current “gold” standard radio-binding assays that measure four major iAbs to insulin, IAA, GAD65, IA-2A and ZnT8, are laborious and do not fit for large-scale screenings. Around 40% of patients with T1D develop other autoimmune diseases like celiac disease, autoimmune thyroid disease, and so on. It is highly recommended to screen these closely related autoimmune diseases during T1D screening; however, there is no method available. Recently, on the platform of extensively validated high-sensitive and high-specific electrochemiluminescence (ECL) assay, we developed a multiplex ECL assay to combine up to 10 autoantibody assays into one single well with 5 μl of blood sample. It not only allows us to combine multiple iAbs into one but also makes it possible to simultaneously screen T1D and other multiple autoimmune diseases, which in turn facilitates large-scale screenings in the general population
Mechanical Force-Triggered Drug Delivery
Advanced drug delivery systems (DDS) enhance treatment efficacy of different therapeutics in a dosage, spatial, and/or temporal controlled manner. To date, numerous chemical- or physical-based stimuli-responsive formulations or devices for controlled drug release have been developed. Among them, the emerging mechanical force-based stimulus offers a convenient and robust controlled drug release platform and has attracted increasing attention. The relevant DDS can be activated to promote drug release by different types of mechanical stimuli, including compressive force, tensile force, and shear force as well as indirect formats, remotely triggered by ultrasound and magnetic field. In this review, we provide an overview of recent advances in mechanically activated DDS. The opportunities and challenges regarding clinical translations are also discussed
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