1,773 research outputs found
Gas content and evolution of a sample of YSO associations at 3.5 kpc from the Sun
Young Stellar Objects (YSO) are newly formed stars from molecular clouds.
They stay close to where they were born and serve as good tracers to study gas
and star formation. During cloud evolution, young massive stars can disrupt the
surrounding gas through stellar feedback, changing the gas distribution. We
study the distribution of the gas around a sample of YSO associations located
at from the Sun by comparing the location and
morphology between CO (J = 10) emission, Planck 870 m maps and
YSO associations. Based on the spatial distribution of the gas compared to that
of the YSOs, we classify the YSO associations into six types: direct, close,
bubble, complex, diffuse, and clean associations. The complex associations are
large structures consisting of both gas-rich and gas-poor segments. We study
the velocity dispersion-size relation toward different association types. From
the ratio between different types, we estimate a feedback time of 1.7
Myr in the solar neighborhood. The sample sets a solid foundation to explore
the relationship between interstellar medium evolution, star formation, and
Galaxy structure.Comment: accepted by MNRA
Weather Forecast of the Milky Way: Shear and Stellar feedback determine the lives of Galactic-scale filaments
The interstellar medium (ISM) is an inseparable part of the Milky Way
ecosystem whose evolutionary history remains a challenging question. We trace
the evolution of the molecular ISM using a sample of Young Stellar Objects
(YSO) association --molecular cloud complex (YSO-MC complex). We derive their
three-dimensional (3D) velocities by combining the Gaia astrometric
measurements of the YSO associations and the CO observations of the associated
molecular clouds. Based on the 3D velocities, we simulate the motions of the
YSO-MC complexes in the Galactic potential and forecast the ISM evolution by
tracing the motions of the individual complexes, and reveal the roles of shear
and stellar feedback in determining ISM evolution: Galactic shear stretches
Galactic-scale molecular cloud complexes, such as the G120 Complex, into
Galactic-scale filaments, and it also contributes to the destruction of the
filaments; while stellar feedback creates interconnected superbubbles whose
expansion injects peculiar velocities into the ISM. The Galactic-scale
molecular gas clumps are often precursors of the filaments and the
Galactic-scale filaments are transient structures under a constant stretch by
shear. This evolutionary sequence sets a foundation to interpret other gas
structures. Animations are available at
https://gxli.github.io/ISM-6D/movie.html.Comment: Accepted by MNRAS letter
Transport experiments in semiconductor-superconductor hybrid Majorana devices
As the condensed matter analog of Majorana fermion, Majorana zero-mode is
well known as a building block of fault-tolerant topological quantum computing.
In this review, we focus on the recent progress of Majorana experiments,
especially experiments about semiconductor-superconductor hybrid devices. We
first sketch Majorana zero-mode formation from a bottom-up view, which is more
suitable for beginners and experimentalist. Then, we survey the status of
zero-energy state signatures reported recently, from zero-energy conductance
peaks, the oscillations, the quantization, and the interactions with
extra-degrees of freedom. This paper also gives prospects on future experiments
for advancing one-dimensional semiconductor nanowire-superconductor hybrid
materials and devices.Comment: 14 pages, 8 figure
(meso-5,7,7,12,14,14-Hexamethyl-1,4,8,11-tetraÂazacycloÂtetraÂdeca-4,11-diene)nickel(II) bisÂ[O,O′-bis(4-methylÂphenÂyl) dithioÂphosphate]
In the title compound, [Ni(C16H32N4)](C14H14O2PS2)2 or [Ni(trans[14]dien)][S2P(OC6H4Me-4)2]2, where trans[14]dien is meso-5,7,7,12,14,14-hexaÂmethyl-1,4,8,11-tetraÂazacycloÂtetraÂdeca-4,11-diene, the NiII ion lies across a centre of inversion and is four-coordinated in a relatively undistorted square-planar arrangement by the four N atoms of the macrocyclic ligand trans[14]dien. The two O,O′-di(4-methylÂphenÂyl)dithioÂphosÂphates act as counter-ions to balance the charge. Important geometric data include Ni—N = 1.9135 (16) and 1.9364 (15) Å
IMass time: The future, in future!
Joseph John Thomson discovered and proved the existence of electrons through a series of experiments. His work earned him a Nobel Prize in 1906 and initiated the era of mass spectrometry (MS). In the intervening time, other researchers have also been awarded the Nobel Prize for significant advances in MS technology. The development of soft ionization techniques was central to the application of MS to large biological molecules and led to an unprecedented interest in the study of biomolecules such as proteins (proteomics), metabolites (metabolomics), carbohydrates (glycomics), and lipids (lipidomics), allowing a better understanding of the molecular underpinnings of health and disease. The interest in large molecules drove improvements in MS resolution and now the challenge is in data deconvolution, intelligent exploitation of heterogeneous data, and interpretation, all of which can be ameliorated with a proposed IMass technology. We define IMass as a combination of MS and artificial intelligence, with each performing a specific role. IMass will offer advantages such as improving speed, sensitivity, and analyses of large data that are presently not possible with MS alone. In this study, we present an overview of the MS considering historical perspectives and applications, challenges, as well as insightful highlights of IMass
Video Event Extraction via Tracking Visual States of Arguments
Video event extraction aims to detect salient events from a video and
identify the arguments for each event as well as their semantic roles. Existing
methods focus on capturing the overall visual scene of each frame, ignoring
fine-grained argument-level information. Inspired by the definition of events
as changes of states, we propose a novel framework to detect video events by
tracking the changes in the visual states of all involved arguments, which are
expected to provide the most informative evidence for the extraction of video
events. In order to capture the visual state changes of arguments, we decompose
them into changes in pixels within objects, displacements of objects, and
interactions among multiple arguments. We further propose Object State
Embedding, Object Motion-aware Embedding and Argument Interaction Embedding to
encode and track these changes respectively. Experiments on various video event
extraction tasks demonstrate significant improvements compared to
state-of-the-art models. In particular, on verb classification, we achieve
3.49% absolute gains (19.53% relative gains) in F1@5 on Video Situation
Recognition
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