147 research outputs found
MARGIN: Uncovering Deep Neural Networks using Graph Signal Analysis
Interpretability has emerged as a crucial aspect of machine learning, aimed
at providing insights into the working of complex neural networks. However,
existing solutions vary vastly based on the nature of the interpretability
task, with each use case requiring substantial time and effort. This paper
introduces MARGIN, a simple yet general approach to address a large set of
interpretability tasks ranging from identifying prototypes to explaining image
predictions. MARGIN exploits ideas rooted in graph signal analysis to determine
influential nodes in a graph, which are defined as those nodes that maximally
describe a function defined on the graph. By carefully defining task-specific
graphs and functions, we demonstrate that MARGIN outperforms existing
approaches in a number of disparate interpretability challenges.Comment: Technical Repor
Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Inorganic Non-Aqueous Electrolytes
Multi-valent (MV) battery architectures based on pairing a Mg metal anode
with a high-voltage ( 3 V) intercalation cathode offer a realistic design
pathway toward significantly surpassing the energy storage performance of
traditional Li-ion based batteries, but there are currently only few
electrolyte systems that support reversible Mg deposition. Using both static
first-principles calculations and molecular dynamics, we perform
a comprehensive adsorption study of several salt and solvent species at the
interface of Mg metal with an electrolyte of Mg and Cl dissolved in
liquid tetrahydrofuran (THF). Our findings not only provide a picture of the
stable species at the interface, but also explain how this system can support
reversible Mg deposition and as such we provide insights in how to design other
electrolytes for Mg plating and stripping. The active depositing species are
identified to be (MgCl) monomers coordinated by THF, which exhibit
preferential adsorption on Mg compared to possible passivating species (such as
THF solvent or neutral MgCl complexes). Upon deposition, the energy to
desolvate these adsorbed complexes and facilitate charge-transfer is shown to
be small ( 61 46.2 kJ mol to remove 3 THF from the strongest
adsorbing complex), and the stable orientations of the adsorbed but desolvated
(MgCl) complexes appear favorable for charge-transfer. Finally,
observations of Mg-Cl dissociation at the Mg surface at very low THF
coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode
may occur upon plating. In the stripping process, this is beneficial by further
facilitating the Mg removal reaction
Glycan receptor specificity as a useful tool for characterization and surveillance of influenza A virus
Influenza A viruses are rapidly evolving pathogens with the potential for novel strains to emerge and result in pandemic outbreaks in humans. Some avian-adapted subtypes have acquired the ability to bind to human glycan receptors and cause severe infections in humans but have yet to adapt to and transmit between humans. The emergence of new avian strains and their ability to infect humans has confounded their distinction from circulating human virus strains through linking receptor specificity to human adaptation. Herein we review the various structural and biochemical analyses of influenza hemagglutinin–glycan receptor interactions. We provide our perspectives on how receptor specificity can be used to monitor evolution of the virus to adapt to human hosts so as to facilitate improved surveillance and pandemic preparedness.National Institutes of Health (U.S.) (Merit Award R37 GM057073-13)Singapore. National Research Foundation (Singapore-MIT Alliance for Research and Technology)Skolkovo Institute of Science and Technolog
Searching for Gravitational-Wave Counterparts using the Transiting Exoplanet Survey Satellite
In 2017, the LIGO and Virgo gravitational wave (GW) detectors, in conjunction
with electromagnetic (EM) astronomers, observed the first GW multi-messenger
astrophysical event, the binary neutron star (BNS) merger GW170817. This marked
the beginning of a new era in multi-messenger astrophysics. To discover further
GW multi-messenger events, we explore the synergies between the Transiting
Exoplanet Survey Satellite (TESS) and GW observations triggered by the
LIGO-Virgo-KAGRA Collaboration (LVK) detector network. TESS's extremely wide
field of view of ~2300 deg^2 means that it could overlap with large swaths of
GW localizations, which can often span hundreds of deg^2 or more. In this work,
we use a recently developed transient detection pipeline to search TESS data
collected during the LVK's third observing run, O3, for any EM counterparts. We
find no obvious counterparts brighter than about 17th magnitude in the TESS
bandpass. Additionally, we present end-to-end simulations of BNS mergers,
including their detection in GWs and simulations of light curves, to identify
TESS's kilonova discovery potential for the LVK's next observing run (O4). In
the most optimistic case, TESS will observe up to one GW-found BNS merger
counterpart per year. However, TESS may also find up to five kilonovae which
did not trigger the LVK network, emphasizing that EM-triggered GW searches may
play a key role in future kilonova detections. We also discuss how TESS can
help place limits on EM emission from binary black hole mergers, and rapidly
exclude large sky areas for poorly localized GW events.Comment: 16 pages, 7 figures, 2 tables. Submitted to AAS Journal
Radon in Underground Mines
Radon, a radioactive noble gas, is a decay product of uranium found in varying concentrations in all soils and rocks in the earth crust. It is colorless, odorless, tasteless, and a leading cause of lung cancer death in the USA. A study of underground miners shows that 40% of lung cancer deaths may be due to radon progeny exposure. In underground mines, radon monitoring and exposure standards help in limiting miners’ exposure to radioactivity. Radon mitigation techniques play an important role in keeping its concentration levels under permissible limits. This chapter presents a review of the radon sources and monitoring standards followed for underground mines in the USA. Also, the different radon prediction and measurement techniques employed in the underground mines and potential mitigation techniques for underground mining operations are discussed
Multi-messenger astrophysics in the gravitational-wave era
The observation of GW170817, the first binary neutron star merger observed in
both gravitational waves (GW) and electromagnetic (EM) waves, kickstarted the
age of multi-messenger GW astronomy. This new technique presents an
observationally rich way to probe extreme astrophysical processes. With the
onset of the LIGO-Virgo-KAGRA Collaboration's O4 observing run and wide-field
EM instruments well-suited for transient searches, multi-messenger astrophysics
has never been so promising. We review recent searches and results for
multi-messenger counterparts to GW events, and describe existing and upcoming
EM follow-up facilities, with a particular focus on WINTER, a new near-infrared
survey telescope, and TESS, an exoplanet survey space telescope.Comment: 5 pages, 1 figure, proceedings from TAUP 202
TIC 184743498: The First Tri-Axial Stellar Pulsator
We have discovered a Scuti pulsator in a tight binary (P = 1.053 d)
with nine pulsation modes whose frequencies are between 38 and 56 d.
Each of these modes exhibits amplitude modulations and -rad phase shifts
twice per orbital cycle. Five of these modes exhibit amplitude and phase shifts
that are readily explained by dipole pulsations along an axis that is aligned
with the binary's tidal axis. The novelty of the system lies in the remaining
four pulsation modes, which we show are dipole pulsations along an axis that is
perpendicular to both the tidal axis and the binary's orbital angular momentum
axis. There are additionally two pulsation modes whose amplitudes and phases do
not change significantly with orbital phase; they are explained as dipole modes
along an axis aligned with the orbital/rotation axis. Hence, we propose that
TIC 184743498 is a tri-axial pulsator, the first of its kind.Comment: Submitted to MNRAS, 12 figures, 4 table
Decoding the Distribution of Glycan Receptors for Human-Adapted Influenza A Viruses in Ferret Respiratory Tract
Ferrets are widely used as animal models for studying influenza A viral pathogenesis and transmissibility. Human-adapted influenza A viruses primarily target the upper respiratory tract in humans (infection of the lower respiratory tract is observed less frequently), while in ferrets, upon intranasal inoculation both upper and lower respiratory tract are targeted. Viral tropism is governed by distribution of complex sialylated glycan receptors in various cells/tissues of the host that are specifically recognized by influenza A virus hemagglutinin (HA), a glycoprotein on viral surface. It is generally known that upper respiratory tract of humans and ferrets predominantly express α2→6 sialylated glycan receptors. However much less is known about the fine structure of these glycan receptors and their distribution in different regions of the ferret respiratory tract. In this study, we characterize distribution of glycan receptors going beyond terminal sialic acid linkage in the cranial and caudal regions of the ferret trachea (upper respiratory tract) and lung hilar region (lower respiratory tract) by multiplexing use of various plant lectins and human-adapted HAs to stain these tissue sections. Our findings show that the sialylated glycan receptors recognized by human-adapted HAs are predominantly distributed in submucosal gland of lung hilar region as a part of O-linked glycans. Our study has implications in understanding influenza A viral pathogenesis in ferrets and also in employing ferrets as animal models for developing therapeutic strategies against influenza.Singapore-MIT Alliance for Research and Technolog
A Single Base-Pair Change in 2009 H1N1 Hemagglutinin Increases Human Receptor Affinity and Leads to Efficient Airborne Viral Transmission in Ferrets
The 2009 H1N1 influenza A virus continues to circulate among the human population as the predominant H1N1 subtype. Epidemiological studies and airborne transmission studies using the ferret model have shown that the transmission efficiency of 2009 H1N1 viruses is lower than that of previous seasonal strains and the 1918 pandemic H1N1 strain. We recently correlated this reduced transmission efficiency to the lower binding affinity of the 2009 H1N1 hemagglutinin (HA) to α2→6 sialylated glycan receptors (human receptors). Here we report that a single point mutation (Ile219→Lys; a base pair change) in the glycan receptor-binding site (RBS) of a representative 2009 H1N1 influenza A virus, A/California/04/09 or CA04/09, quantitatively increases its human receptor-binding affinity. The increased human receptor-affinity is in the same range as that of the HA from highly transmissible seasonal and 1918 pandemic H1N1 viruses. Moreover, a 2009 H1N1 virus carrying this mutation in the RBS (generated using reverse genetics) transmits efficiently in ferrets by respiratory droplets thereby reestablishing our previously observed correlation between human receptor-binding affinity and transmission efficiency. These findings are significant in the context of monitoring the evolution of the currently circulating 2009 H1N1 viruses
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