118 research outputs found
The influence of galaxy surface brightness on the mass-metallicity relation
We study the effect of surface brightness on the mass-metallicity relation
using nearby galaxies whose gas content and metallicity profiles are available.
Previous studies using fiber spectra indicated that lower surface brightness
galaxies have systematically lower metallicity for their stellar mass, but the
results were uncertain because of aperture effect. With stellar masses and
surface brightnesses measured at WISE W1 and W2 bands, we re-investigate the
surface brightness dependence with spatially-resolved metallicity profiles and
find the similar result. We further demonstrate that the systematical
difference cannot be explained by the gas content of galaxies. For two galaxies
with similar stellar and gas masses, the one with lower surface brightness
tends to have lower metallicity. Using chemical evolution models, we
investigate the inflow and outflow properties of galaxies of different masses
and surface brightnesses. We find that, on average, high mass galaxies have
lower inflow and outflow rates relative to star formation rate. On the other
hand, lower surface brightness galaxies experience stronger inflow than higher
surface brightness galaxies of similar mass. The surface brightness effect is
more significant for low mass galaxies. We discuss implications on the
different inflow properties between low and high surface brightness galaxies,
including star formation efficiency, environment and mass assembly history
Kondo QED: The Kondo effect and photon trapping in a two-impurity Anderson model ultra-strongly coupled to light
The Kondo effect is one of the most studied examples of strongly correlated
quantum many-body physics. Another type of strongly correlated physics that has
only recently been explored in detail (and become experimentally accessible) is
that of ultrastrong coupling between light and matter. Here, we study a system
which we denote as "Kondo QED") that combines both phenomena, consisting of a
two-impurity Anderson model ultra-strongly coupled to a single-mode cavity.
While presented as an abstract model, it is relevant for a range of future
hybrid cavity-QED systems. Using the hierarchical equations of motion approach
we show that the ultrastrong coupling of cavity photons to the electronic
states (impurity) noticeably suppresses the electronic Kondo resonance due to
the destruction of many-body correlations of the Kondo cloud. We observe this
transfer of correlations from the Kondo cloud to the cavity by computing the
entropy and mutual information of the impurity-cavity subsystems. In addition,
in the weak lead-coupling limit and at zero-bias, the model exhibits a
ground-state photon accumulation effect originating entirely from
counter-rotating terms in the impurity-cavity interaction. Interestingly, in
the strong lead-coupling limit, this accumulation is ``Kondo-enhanced'' by new
transition paths opening when increasing the hybridization to the leads. This
suggests a new mechanism for the generation of real photons from virtual
states. We further show that the suppression of the Kondo effect is stable
under broadening of the cavity resonance as a consequence of the interaction to
an external bosonic continuum. Our findings pave the way for the simultaneous
control of both the Kondo QED effect and a photon accumulation effect using the
ultrastrong coupling of light and matter.Comment: 23 pages, 11 figures, 2 table
Heom.jl: An efficient Julia framework for hierarchical equations of motion in open quantum systems
We introduce an open-source software package called "Heom.jl", a Julia
framework to integrate the hierarchical equations of motion (HEOM) for the
reduced dynamics of a system simultaneously coupled to multiple bosonic and
fermionic environments. Heom.jl features a collection of methods to compute
bosonic and fermionic spectra, stationary states, and the full dynamics in the
extended space of all auxiliary density operators (ADOs). The required handling
of the ADOs multi-indexes is achieved through a user-friendly interface. We
exemplify the functionalities of the package by analyzing a single impurity
interacting with two fermionic reservoirs (Anderson model), and an
ultra-strongly coupled charge-cavity system interacting with one bosonic and
two fermionic reservoirs. Heom.jl allows for an order of magnitude speedup in
the construction of the HEOM Liouvillian superoperator, solving dynamics and
stationary states for all ADOs, with respect to the corresponding method in the
Quantum Toolbox in Python (QuTiP), upon which this package is founded.Comment: 19 pages, 7 figures, 4 table
Standardizing Clinical Trials Workflow Representation in UML for International Site Comparison
BACKGROUND: With the globalization of clinical trials, a growing emphasis has been placed on the standardization of the workflow in order to ensure the reproducibility and reliability of the overall trial. Despite the importance of workflow evaluation, to our knowledge no previous studies have attempted to adapt existing modeling languages to standardize the representation of clinical trials. Unified Modeling Language (UML) is a computational language that can be used to model operational workflow, and a UML profile can be developed to standardize UML models within a given domain. This paper's objective is to develop a UML profile to extend the UML Activity Diagram schema into the clinical trials domain, defining a standard representation for clinical trial workflow diagrams in UML. METHODS: Two Brazilian clinical trial sites in rheumatology and oncology were examined to model their workflow and collect time-motion data. UML modeling was conducted in Eclipse, and a UML profile was developed to incorporate information used in discrete event simulation software. RESULTS: Ethnographic observation revealed bottlenecks in workflow: these included tasks requiring full commitment of CRCs, transferring notes from paper to computers, deviations from standard operating procedures, and conflicts between different IT systems. Time-motion analysis revealed that nurses' activities took up the most time in the workflow and contained a high frequency of shorter duration activities. Administrative assistants performed more activities near the beginning and end of the workflow. Overall, clinical trial tasks had a greater frequency than clinic routines or other general activities. CONCLUSIONS: This paper describes a method for modeling clinical trial workflow in UML and standardizing these workflow diagrams through a UML profile. In the increasingly global environment of clinical trials, the standardization of workflow modeling is a necessary precursor to conducting a comparative analysis of international clinical trials workflows
The Fast, Luminous Ultraviolet Transient AT2018cow: Extreme Supernova, or Disruption of a Star by an Intermediate-Mass Black Hole?
Wide-field optical surveys have begun to uncover large samples of fast
(t_rise < 5d), luminous (M_peak < -18), blue transients. While commonly
attributed to the breakout of a supernova shock into a dense wind, the great
distances to the transients of this class found so far have hampered detailed
investigation of their properties. We present photometry and spectroscopy from
a comprehensive worldwide campaign to observe AT2018cow (ATLAS18qqn), the first
fast-luminous optical transient to be found in real time at low redshift. Our
first spectra (<2 days after discovery) are entirely featureless. A very broad
absorption feature suggestive of near-relativistic velocities develops between
3-8 days, then disappears. Broad emission features of H and He develop after
>10 days. The spectrum remains extremely hot throughout its evolution, and the
photospheric radius contracts with time (receding below R<10^14 cm after 1
month). This behaviour does not match that of any known supernova, although a
relativistic jet within a fallback supernova could explain some of the observed
features. Alternatively, the transient could originate from the disruption of a
star by an intermediate-mass black hole, although this would require
long-lasting emission of highly super-Eddington thermal radiation. In either
case, AT2018cow suggests that the population of fast luminous transients
represents a new class of astrophysical event. Intensive follow-up of this
event in its late phases, and of any future events found at comparable
distance, will be essential to better constrain their origins.Comment: Corrected Figure 8 / Table 4 to use final fits. Includes
machine-readable photometry table (hopefully for real this time
Potential of Core-Collapse Supernova Neutrino Detection at JUNO
JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve
Detection of the Diffuse Supernova Neutrino Background with JUNO
As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO
The genetic architecture of the human cerebral cortex
The cerebral cortex underlies our complex cognitive capabilities, yet little is known about the specific genetic loci that influence human cortical structure. To identify genetic variants that affect cortical structure, we conducted a genome-wide association meta-analysis of brain magnetic resonance imaging data from 51,665 individuals. We analyzed the surface area and average thickness of the whole cortex and 34 regions with known functional specializations. We identified 199 significant loci and found significant enrichment for loci influencing total surface area within regulatory elements that are active during prenatal cortical development, supporting the radial unit hypothesis. Loci that affect regional surface area cluster near genes in Wnt signaling pathways, which influence progenitor expansion and areal identity. Variation in cortical structure is genetically correlated with cognitive function, Parkinson's disease, insomnia, depression, neuroticism, and attention deficit hyperactivity disorder
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