Publications by authors named "Sathyaprakash"

Nucleic acid nanostructures offer unique opportunities for biomedical applications due to their sequence-programmable structures and functions, which enable the design of complex responses to molecular cues. Control of the biological activity of therapeutic cargoes based on endogenous molecular signatures holds the potential to overcome major hurdles in translational research: cell specificity and off-target effects. Endogenous microRNAs (miRNAs) can be used to profile cell type and cell state, and are ideal inputs for RNA nanodevices.

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Antisense oligonucleotide (ASO)-based exon skipping therapy is thought to be promising for Duchenne muscular dystrophy (DMD). For the screening or assessing patient eligibility before administering ASO to patients, in vitro testing using myoblasts derived from each DMD patient is considered crucial. We previously reported state-of-the-art technology to obtain patient primary myoblasts from MYOD1-induced urine-derived cells (UDCs) as a model of DMD.

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Article Synopsis
  • The study investigates compact binary coalescences with at least one component mass between 0.2 and 1.0 solar masses using data from Advanced LIGO and Advanced Virgo detectors over six months in 2019, but they found no significant gravitational wave candidates.
  • The analysis leads to an upper limit on the merger rate of subsolar binaries ranging from 220 to 24,200 Gpc⁻³ yr⁻¹, based on the detected signals’ false alarm rate.
  • The researchers use these limits to set new constraints on two models for subsolar-mass compact objects: primordial black holes (suggesting they make up less than 6% of dark matter) and
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Synapse loss is associated with cognitive decline in Alzheimer's disease, and owing to their plastic nature, synapses are an ideal target for therapeutic intervention. Oligomeric amyloid beta around amyloid plaques is known to contribute to synapse loss in mouse models and is associated with synapse loss in human Alzheimer's disease brain tissue, but the mechanisms leading from Aβ to synapse loss remain unclear. Recent data suggest that the fast-activating and -inactivating voltage-gated potassium channel subtype 3.

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Splice-switching antisense oligonucleotide- (SSO-) mediated correction of framedisrupting mutation-containing premessenger RNA (mRNA) transcripts using exon skipping is a highly promising treatment method for muscular diseases such as Duchenne muscular dystrophy (DMD). Phosphorothioate (PS) chemistry, a commonly used oligonucleotide modification, has been shown to increase the stability of and improve the pharmacokinetics of SSOs. However, the effect of PS inclusion in 2'-O-methyl SSOs (2OMe) on cellular uptake and splice switching is less well-understood.

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Third generation (3G) gravitational-wave detectors will observe thousands of coalescing neutron star binaries with unprecedented fidelity. Extracting the highest precision science from these signals is expected to be challenging owing to both high signal-to-noise ratios and long-duration signals. We demonstrate that current Bayesian inference paradigms can be extended to the analysis of binary neutron star signals without breaking the computational bank.

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In this Letter, we show that multiband observations of stellar-mass binary black holes by the next generation of ground-based observatories (3G) and the space-based Laser Interferometer Space Antenna (LISA) would facilitate a comprehensive test of general relativity by simultaneously measuring all the post-Newtonian coefficients. Multiband observations would measure most of the known post-Newtonian phasing coefficients to an accuracy below a few percent-2 orders-of-magnitude better than the best bounds achievable from even "golden" binaries in the 3G or LISA bands. Such multiparameter bounds would play a pivotal role in constraining the parameter space of modified theories of gravity beyond general relativity.

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We present our current best estimate of the plausible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next several years, with the intention of providing information to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals for the third (O3), fourth (O4) and fifth observing (O5) runs, including the planned upgrades of the Advanced LIGO and Advanced Virgo detectors. We study the capability of the network to determine the sky location of the source for gravitational-wave signals from the inspiral of binary systems of compact objects, that is binary neutron star, neutron star-black hole, and binary black hole systems.

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Article Synopsis
  • On May 21, 2019, Advanced LIGO and Virgo detected a significant gravitational-wave signal known as GW190521, indicating a high probability event with a low chance of false alarms.
  • The signal suggests it resulted from the merger of two black holes, one around 85 solar masses and the other about 66 solar masses, with the primary black hole likely being an intermediate mass black hole.
  • The source of the merger is estimated to be about 5.3 billion light-years away, and the rate of similar black hole mergers is estimated to be about 0.13 mergers per billion cubic parsecs per year.
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Several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), have a complex genetic background, in addition to cases where the disease appears to manifest sporadically. The recent discovery of the hexanucleotide repeat expansion in the C9orf72 gene as the causative agent of ALS (C9ALS) gives rise to the opportunity to develop new therapies directed at this mutation , which is responsible for a large proportion of ALS and/or frontotemporal dementia cases. Mammalian models conscientiously replicating the late-onset motor defects and cellular pathologies seen in human patients do not exist.

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TDP-43 dysfunction is common to 97% of amyotrophic lateral sclerosis (ALS) cases, including those with mutations in C9orf72. To investigate how C9ORF72 mutations drive cellular pathology in ALS and to identify convergent mechanisms between C9ORF72 and TARDBP mutations, we analyzed motor neurons (MNs) derived from induced pluripotent stem cells (iPSCs) from patients with ALS. C9ORF72 iPSC-MNs have higher Ca release after depolarization, delayed recovery to baseline after glutamate stimulation, and lower levels of calbindin compared with CRISPR/Cas9 genome-edited controls.

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  • The study investigates the existence of subsolar mass ultracompact objects by analyzing data from Advanced LIGO's second observing run and includes the impact of spin on gravitational waves.
  • No suitable gravitational-wave candidates were found for binaries with at least one component between 0.2 and 1.0 solar masses, leading to significant constraints on their binary merger rates.
  • The findings suggest that such ultracompact objects likely do not form through conventional stellar evolution, and they outline how these constraints on merger rates can be applied to different black hole population models that predict subsolar mass binaries.
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The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in the presence of matter. In this Letter, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime.

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We present the first Advanced LIGO and Advanced Virgo search for ultracompact binary systems with component masses between 0.2  M_{⊙}-1.0  M_{⊙} using data taken between September 12, 2015 and January 19, 2016.

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On 17 August 2017, the LIGO and Virgo observatories made the first direct detection of gravitational waves from the coalescence of a neutron star binary system. The detection of this gravitational-wave signal, GW170817, offers a novel opportunity to directly probe the properties of matter at the extreme conditions found in the interior of these stars. The initial, minimal-assumption analysis of the LIGO and Virgo data placed constraints on the tidal effects of the coalescing bodies, which were then translated to constraints on neutron star radii.

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We present possible observing scenarios for the Advanced LIGO, Advanced Virgo and KAGRA gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We estimate the sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron star systems, which are the most promising targets for multi-messenger astronomy.

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The LIGO Scientific and Virgo Collaborations have announced the event GW170817, the first detection of gravitational waves from the coalescence of two neutron stars. The merger rate of binary neutron stars estimated from this event suggests that distant, unresolvable binary neutron stars create a significant astrophysical stochastic gravitational-wave background. The binary neutron star component will add to the contribution from binary black holes, increasing the amplitude of the total astrophysical background relative to previous expectations.

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We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies, we utilize analytical fits to postmerger numerical relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass.

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Article Synopsis
  • * The analysis focused on detecting continuous signals from pulsars and did not depend on any specific gravity theory.
  • * After examining data from advanced LIGO, we found no signs of these gravitational waves, but established upper limits for scalar and vector strains that are similar to existing limits for tensor strain.
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On August 17, 2017 at 12∶41:04 UTC the Advanced LIGO and Advanced Virgo gravitational-wave detectors made their first observation of a binary neutron star inspiral. The signal, GW170817, was detected with a combined signal-to-noise ratio of 32.4 and a false-alarm-rate estimate of less than one per 8.

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On August 14, 2017 at 10∶30:43 UTC, the Advanced Virgo detector and the two Advanced LIGO detectors coherently observed a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes, with a false-alarm rate of ≲1 in 27 000 years. The signal was observed with a three-detector network matched-filter signal-to-noise ratio of 18. The inferred masses of the initial black holes are 30.

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Article Synopsis
  • GW170104 was observed on January 4, 2017, as a gravitational-wave signal from two stellar-mass black holes merging, detected by LIGO with a high signal-to-noise ratio and a very low false alarm rate.
  • The black hole masses were found to be approximately 31.2 and 19.4 solar masses, with spin parameters suggesting that their spins are not aligned with their orbital motion.
  • The event supports general relativity and sets an upper limit on the graviton mass, indicating that modifications to gravitational-wave behavior in vacuum are minimal.
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