91 research outputs found
Asteroseismology of KIC 8263801:Is it a member of NGC 6866 and a red clump star?
We present an asteroseismic analysis of the Kepler light curve of KIC
8263801, a red-giant star in the open cluster NGC 6866 that has previously been
reported to be a helium-burning red-clump star. We extracted the frequencies of
the radial and quadrupole modes from its frequency power spectrum and
determined its properties using a grid of evolutionary models constructed with
MESA. The oscillation frequencies were calculated using the GYRE code and the
surface term was corrected using the Ball & Gizon(2014) prescription. We find
that the star has a mass of , age Gyr and radius . By analyzing the internal
structure of the best-fitting model, we infer the evolutionary status of the
star KIC 8263801 as being on the ascending part of the red giant branch, and
not on the red clump. This result is verified using a purely asteroseismic
diagnostic, the diagram which can distinguish red
giant branch stars from red clump stars. Finally, by comparing its age with NGC
6866 ( Gyr) we conclude that KIC 8263801 is not a member of
this open cluster
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
Real-time Monitoring for the Next Core-Collapse Supernova in JUNO
Core-collapse supernova (CCSN) is one of the most energetic astrophysical
events in the Universe. The early and prompt detection of neutrinos before
(pre-SN) and during the SN burst is a unique opportunity to realize the
multi-messenger observation of the CCSN events. In this work, we describe the
monitoring concept and present the sensitivity of the system to the pre-SN and
SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is
a 20 kton liquid scintillator detector under construction in South China. The
real-time monitoring system is designed with both the prompt monitors on the
electronic board and online monitors at the data acquisition stage, in order to
ensure both the alert speed and alert coverage of progenitor stars. By assuming
a false alert rate of 1 per year, this monitoring system can be sensitive to
the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos
up to about 370 (360) kpc for a progenitor mass of 30 for the case
of normal (inverted) mass ordering. The pointing ability of the CCSN is
evaluated by using the accumulated event anisotropy of the inverse beta decay
interactions from pre-SN or SN neutrinos, which, along with the early alert,
can play important roles for the followup multi-messenger observations of the
next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure
Robust Reconstruction of Electrocardiogram Using Photoplethysmography: A Subject-Based Model
Electrocardiography and photoplethysmography are non-invasive techniques that measure signals from the cardiovascular system. While the cycles of the two measurements are highly correlated, the correlation between the waveforms has rarely been studied. Measuring the photoplethysmogram (PPG) is much easier and more convenient than the electrocardiogram (ECG). Recent research has shown that PPG can be used to reconstruct the ECG, indicating that practitioners can gain a deep understanding of the patients' cardiovascular health using two physiological signals (PPG and ECG) while measuring only PPG. This study proposes a subject-based deep learning model that reconstructs an ECG using a PPG and is based on the bidirectional long short-term memory model. Because the ECG waveform may vary from subject to subject, this model is subject-specific. The model was tested using 100 records from the MIMIC III database. Of these records, 50 had a circulatory disease. The results show that a long ECG signal could be effectively reconstructed from PPG, which is, to our knowledge, the first attempt in this field. A length of 228 s of ECG was constructed by the model, which was trained and validated using 60 s of PPG and ECG signals. To segment the data, a different approach that segments the data into short time segments of equal length (and that do not rely on beats and beat detection) was investigated. Segmenting the PPG and ECG time series data into equal segments of 1-min width gave the optimal results. This resulted in a high Pearson's correlation coefficient between the reconstructed 228 s of ECG and referenced ECG of 0.818, while the root mean square error was only 0.083 mV, and the dynamic time warping distance was 2.12 mV per second on average.ISSN:1664-042
Solid-State NMR Shows That Dynamically Different Domains of Membrane Proteins Have Different Hydration Dependence
Hydration has a profound influence
on the structure, dynamics,
and functions of membrane and membrane-embedded proteins. So far the
hydration response of molecular dynamics of membrane proteins in lipid
bilayers is poorly understood. Here, we reveal different hydration
dependence of the dynamics in dynamically different domains of membrane
proteins by multidimensional magic angle spinning (MAS) solid-state
NMR (ssNMR) spectroscopy using 121-residue integral diacylglycerol
kinase (DAGK) in 1,2-dimyristoyl-<i>sn</i>-glycero-3-phosphocholine
(DMPC)/1,2-dimyristoyl-<i>sn</i>-glycero-3-phospho-(1′-<i>rac</i>-glycerol) (DMPG) lipid bilayers as a model system. The
highly mobile and immobile domains of DAGK and their water accessibilities
are identified site-specifically by scalar- and dipolar-coupling based
MAS ssNMR experiments, respectively. Our experiments reveal different
hydration dependence of the dynamics in highly mobile and immobile
domains of membrane proteins. We demonstrate that the fast, large-amplitude
motions in highly mobile domains are not triggered until 20% hydration,
enhanced at 20–50% hydration and unchanged at above 50% hydration.
In contrast, motions on submicrosecond time scale of immobile residues
are observed to be independent of the hydration levels in gel phase
of lipids, and at the temperature near gel–liquid crystalline
phase transition, amplitude of whole-molecule rotations around the
bilayer normal is dominated by the fluidity of lipid bilayers, which
is strongly hydration dependent. The hydration dependence of the dynamics
of DAGK revealed by this study provides new insights into the correlations
of hydration to dynamics and function of membrane proteins in lipid
bilayers
Nanocoiled Assembly of Asymmetric Perylene Diimides: Formulation of Structural Factors
Nanocoiled
assemblies of organic π-conjugated molecules have attracted
intense attention because of their various practical applications.
Herein, the assembly of highly fluorescent monolayer and bilayer nanocoils
from asymmetric perylene diimide (PDI) molecules is reported. Through
systematic investigation of 21 asymmetric PDI derivatives, some critical
molecular structural parameters for the formation of nanocoils, involving
the position of methoxy substituents at the phenyl moiety on one side
and the appropriate linker that attaches the phenyl moiety to the
PDI core, are formulated. The J-aggregate nature of the helical π-stacking
geometry within the nanocoil is demonstrated by optical characterization.
All of the nanocoils are highly emissive, with a fluorescence quantum
yield greater than 25%. Furthermore, all of the nanocoils exhibited
a NIR emission with a band maximum greater than 710 nm. This new class
of highly NIR fluorescent nanostructures offers promising applications
in areas such as optoelectronics, fluorescent sensors, and biological
imaging
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