31 research outputs found
Collective filters: a new approach to analyze the gravitational-wave ringdown of binary black-hole mergers
We propose two frequency-domain filters to analyze ringdown signals of binary
black hole mergers. The first rational filter is constructed based on a set of
(arbitrary) quasi-normal modes (QNMs) of the remnant black holes, whereas the
second full filter comes from the transmissivity of the remnant black holes.
The two filters can remove corresponding QNMs from original time-domain
ringdowns, while changing early inspiral signals in a trivial way - merely a
time and phase shift. After filtering out dominant QNMs, we can visualize the
existence of various subdominant effects. For example, by applying our filters
to a GW150914-like numerical relativity (NR) waveform, we find second-order
effects in the (l = 4, m = 4), (l = 5, m = 4) and (l = 5, m = 5) harmonics; the
spherical-spheroidal mixing mode in the (l = 2,m = 2) harmonic; and a mixing
mode in the (l = 2,m = 1) harmonic due to a gravitational recoil. In another NR
simulation where two component spins are anti-aligned with the orbital angular
momentum, we also find retrograde modes. Additionally, we propose to use the
rational filter to estimate the start time of a QNM. The filters are sensitive
to the remnant properties (i.e., mass and spin) and thus have a potential
application to future data analyses and parameter estimations. We also
investigate the stability of the full filter. Its connection to the instability
of QNM spectra is discussed
Fully relativistic three-dimensional Cauchy-characteristic matching
A fully relativistic three-dimensional Cauchy-characteristic matching (CCM)
algorithm is implemented in a numerical relativity code SpECTRE. The method is
free of approximations and can be applied to any physical system. We test the
algorithm with various scenarios, including the propagation of Teukolsky waves
within a flat background, the perturbation of a Kerr black hole with a
Teukolsky wave, and the injection of a gravitational-wave pulse from the
characteristic grid. Our investigations reveal no numerical instabilities in
the simulations. In addition, the tests indicate that the CCM algorithm
effectively directs characteristic information into the inner Cauchy system,
yielding higher precision in waveforms and smaller violations of Bondi-gauge
constraints, especially when the outer boundary of the Cauchy evolution is at a
smaller radius
Worldtube excision method for intermediate-mass-ratio inspirals: scalar-field model in 3+1 dimensions
Binary black hole simulations become increasingly more computationally
expensive with smaller mass ratios, partly because of the longer evolution
time, and partly because the lengthscale disparity dictates smaller time steps.
The program initiated by Dhesi et al. (arXiv:2109.03531) explores a method for
alleviating the scale disparity in simulations with mass ratios in the
intermediate astrophysical range (), where
purely perturbative methods may not be adequate. A region ("worldtube") much
larger than the small black hole is excised from the numerical domain, and
replaced with an analytical model approximating a tidally deformed black hole.
Here we apply this idea to a toy model of a scalar charge in a fixed circular
geodesic orbit around a Schwarzschild black hole, solving for the massless
Klein-Gordon field. This is a first implementation of the worldtube excision
method in full 3+1 dimensions. We demonstrate the accuracy and efficiency of
the method, and discuss the steps towards applying it for evolving orbits and,
ultimately, in the binary black-hole scenario. Our implementation is publicly
accessible in the SpECTRE numerical relativity code.Comment: 19 pages, 10 figure
Nonlinear Effects In Black Hole Ringdown From Scattering Experiments I: spin and initial data dependence of quadratic mode coupling
We investigate quadratic quasinormal mode coupling in black hole spacetime
through numerical simulations of single perturbed black holes using both
numerical relativity and second-order black hole perturbation theory. Focusing
on the dominant quadrupolar modes, we find good agreement (within
) between these approaches, with discrepancies attributed to
truncation error and uncertainties from mode fitting. Our results align with
earlier studies extracting the coupling coefficients from select binary black
hole merger simulations, showing consistency for the same remnant spins.
Notably, the coupling coefficient is insensitive to a diverse range of initial
data, including configurations that led to a significant (up to ) increase
in the remnant black hole mass. These findings present opportunities for
testing the nonlinear dynamics of general relativity with ground-based
gravitational wave observatories. Lastly, we provide evidence of a bifurcation
in coupling coefficients between counter-rotating and co-rotating quasinormal
modes as black hole spin increases
Numerical relativity surrogate model with memory effects and post-Newtonian hybridization
Numerical relativity simulations provide the most precise templates for the
gravitational waves produced by binary black hole mergers. However, many of
these simulations use an incomplete waveform extraction technique --
extrapolation -- that fails to capture important physics, such as gravitational
memory effects. Cauchy-characteristic evolution (CCE), by contrast, is a much
more physically accurate extraction procedure that fully evolves Einstein's
equations to future null infinity and accurately captures the expected physics.
In this work, we present a new surrogate model, NRHybSur3dq8CCE, built from
CCE waveforms that have been mapped to the post-Newtonian (PN) BMS frame and
then hybridized with PN and effective one-body (EOB) waveforms. This model is
trained on 102 waveforms with mass ratios and aligned spins
. The model spans the
entire LIGO-Virgo-KAGRA (LVK) frequency band (with
) for total masses and
includes the and spin-weight spherical
harmonic modes, but not the , or modes. We find that
NRHybSur3dq8CCE can accurately reproduce the training waveforms with
mismatches for total masses and can, for a modest degree of extrapolation, capably model
outside of its training region. Most importantly, unlike previous waveform
models, the new surrogate model successfully captures memory effects.Comment: 14 pages, 11 figures. Accepted for publication in PR
Extending black-hole remnant surrogate models to extreme mass ratios
Numerical-relativity surrogate models for both black-hole merger waveforms
and remnants have emerged as important tools in gravitational-wave astronomy.
While producing very accurate predictions, their applicability is limited to
the region of the parameter space where numerical-relativity simulations are
available and computationally feasible. Notably, this excludes extreme mass
ratios. We present a machine-learning approach to extend the validity of
existing and future numerical-relativity surrogate models toward the
test-particle limit, targeting in particular the mass and spin of post-merger
black-hole remnants. Our model is trained on both numerical-relativity
simulations at comparable masses and analytical predictions at extreme mass
ratios. We extend the gaussian-process-regression model NRSur7dq4Remnant,
validate its performance via cross validation, and test its accuracy against
additional numerical-relativity runs. Our fit, which we dub
NRSur7dq4EmriRemnant, reaches an accuracy that is comparable to or higher than
that of existing remnant models while providing robust predictions for
arbitrary mass ratios.Comment: 10 pages, 3 figures. Model publicly available at
https://pypi.org/project/surfinB
Spatial Organization and Molecular Correlation of Tumor-Infiltrating Lymphocytes Using Deep Learning on Pathology Images
Beyond sample curation and basic pathologic characterization, the digitized H&E-stained images
of TCGA samples remain underutilized. To highlight this resource, we present mappings of tumorinfiltrating lymphocytes (TILs) based on H&E images from 13 TCGA tumor types. These TIL
maps are derived through computational staining using a convolutional neural network trained to
classify patches of images. Affinity propagation revealed local spatial structure in TIL patterns and
correlation with overall survival. TIL map structural patterns were grouped using standard
histopathological parameters. These patterns are enriched in particular T cell subpopulations
derived from molecular measures. TIL densities and spatial structure were differentially enriched
among tumor types, immune subtypes, and tumor molecular subtypes, implying that spatial
infiltrate state could reflect particular tumor cell aberration states. Obtaining spatial lymphocytic
patterns linked to the rich genomic characterization of TCGA samples demonstrates one use for
the TCGA image archives with insights into the tumor-immune microenvironment
Cabbage and fermented vegetables : From death rate heterogeneity in countries to candidates for mitigation strategies of severe COVID-19
Large differences in COVID-19 death rates exist between countries and between regions of the same country. Some very low death rate countries such as Eastern Asia, Central Europe, or the Balkans have a common feature of eating large quantities of fermented foods. Although biases exist when examining ecological studies, fermented vegetables or cabbage have been associated with low death rates in European countries. SARS-CoV-2 binds to its receptor, the angiotensin-converting enzyme 2 (ACE2). As a result of SARS-CoV-2 binding, ACE2 downregulation enhances the angiotensin II receptor type 1 (AT(1)R) axis associated with oxidative stress. This leads to insulin resistance as well as lung and endothelial damage, two severe outcomes of COVID-19. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is the most potent antioxidant in humans and can block in particular the AT(1)R axis. Cabbage contains precursors of sulforaphane, the most active natural activator of Nrf2. Fermented vegetables contain many lactobacilli, which are also potent Nrf2 activators. Three examples are: kimchi in Korea, westernized foods, and the slum paradox. It is proposed that fermented cabbage is a proof-of-concept of dietary manipulations that may enhance Nrf2-associated antioxidant effects, helpful in mitigating COVID-19 severity.Peer reviewe
Nrf2-interacting nutrients and COVID-19 : time for research to develop adaptation strategies
There are large between- and within-country variations in COVID-19 death rates. Some very low death rate settings such as Eastern Asia, Central Europe, the Balkans and Africa have a common feature of eating large quantities of fermented foods whose intake is associated with the activation of the Nrf2 (Nuclear factor (erythroid-derived 2)-like 2) anti-oxidant transcription factor. There are many Nrf2-interacting nutrients (berberine, curcumin, epigallocatechin gallate, genistein, quercetin, resveratrol, sulforaphane) that all act similarly to reduce insulin resistance, endothelial damage, lung injury and cytokine storm. They also act on the same mechanisms (mTOR: Mammalian target of rapamycin, PPAR gamma:Peroxisome proliferator-activated receptor, NF kappa B: Nuclear factor kappa B, ERK: Extracellular signal-regulated kinases and eIF2 alpha:Elongation initiation factor 2 alpha). They may as a result be important in mitigating the severity of COVID-19, acting through the endoplasmic reticulum stress or ACE-Angiotensin-II-AT(1)R axis (AT(1)R) pathway. Many Nrf2-interacting nutrients are also interacting with TRPA1 and/or TRPV1. Interestingly, geographical areas with very low COVID-19 mortality are those with the lowest prevalence of obesity (Sub-Saharan Africa and Asia). It is tempting to propose that Nrf2-interacting foods and nutrients can re-balance insulin resistance and have a significant effect on COVID-19 severity. It is therefore possible that the intake of these foods may restore an optimal natural balance for the Nrf2 pathway and may be of interest in the mitigation of COVID-19 severity
Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021
BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed