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Perturbations of Spinning Black Holes beyond General Relativity: Modified Teukolsky Equation
No full textThe detection of gravitational waves from compact binary mergers by the LIGO/Virgo Collaboration has, for the first time, allowed for tests of relativistic gravity in the strong, dynamical, and nonlinear regime. Outside Einstein’s relativity, spinning black holes may be different from their general relativistic counterparts, and their merger may then lead to a modified ringdown. We study the latter and, for the first time, derive a modified Teukolsky equation, i.e., a set of linear, decoupled differential equations that describe dynamical perturbations of non-Kerr black holes for the radiative Newman-Penrose scalars Ψ₀ and Ψ₄. We first focus on non-Ricci-flat, Petrov type-D black hole backgrounds in modified gravity and derive the modified Teukolsky equation through direct decoupling and through a new approach, proposed by Chandrasekhar, that uses certain gauge conditions. We then extend this analysis to non-Ricci-flat, Petrov type-I black hole backgrounds in modified gravity, assuming they can be treated as a linear perturbation of Petrov type-D, black hole backgrounds in general relativity by generalizing Chandrasekhar’s approach, and derive the decoupled modified Teukolsky equation. We further show that our formalism can be extended beyond linear order in both modified gravity corrections and gravitational wave perturbations. Our work lays the foundation to study the gravitational waves emitted in the ringdown phase of black hole coalescence in modified gravity for black holes of any spin. Our work can also be extended to compute gravitational waves emitted by extreme mass-ratio binary inspirals in modified gravity
Unequal exposure to heatwaves in Los Angeles: Impact of uneven green spaces
No full textCities worldwide are experiencing record-breaking summer temperatures. Urban environments exacerbate extreme heat, resulting in not only the urban heat island but also intracity variations in heat exposure. Understanding these disparities is crucial to support equitable climate mitigation and adaptation efforts. We found persistent negative correlations between daytime land surface temperature (LST) and median household income across the Los Angeles metropolitan area based on Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station observations from 2018 to 2021. Lower evapotranspiration resulting from the unequal distribution of vegetation cover is a major factor leading to higher LST in low-income neighborhoods. Disparities worsen with higher regional mean surface temperature, with a $10,000 decrease in income leading to ~0.2°C LST increase at 20°C and up to ~0.7°C at 45°C. With more frequent and intense heat waves projected in the future, equitable mitigation measures, such as increasing surface albedo and tree cover in low-income neighborhoods, are necessary to address these disparities
Immunosuppressant adherence in adult outpatient hematopoietic cell transplant recipients
No full textIntroduction. Medication nonadherence continues to be challenging for allogeneic hematopoietic cell transplant (HCT) recipients. The risk and severity of chronic graft-versus-host disease (GVHD) are associated with low immunosuppressant concentrations (which can be improved with model-informed precision dosing (MIPD)) and with immunosuppressant nonadherence (which can be improved with acceptable interventions).
Methods. With the goals of improving adherence and achieving therapeutic concentrations of immunosuppressants to eliminate GVHD, we characterized the feasibility of using the Medication Event Monitoring (MEMS®) Cap in adult HCT recipients.
Results. Of the 27 participants offered the MEMS® Cap at the time of hospital discharge, 7 (25.9%) used it, which is below our a priori threshold of 70%. These data suggest the MEMS® Cap is not feasible for HCT recipients. The MEMS® Cap data were available for a median of 35 days per participant per medication (range: 7–109 days). The average daily adherence per participant ranged from 0 to 100%; four participants had an average daily adherence of over 80%.
Conclusions. MIPD may be supported by MEMS® technology to provide the precise time of immunosuppressant self-administration. The MEMS® Cap was used by only a small percentage (25.9%) of HCT recipients in this pilot study. In accordance with larger studies using less accurate tools to evaluate adherence, immunosuppressant adherence varied from 0% to 100%. Future studies should establish the feasibility and clinical benefit of combining MIPD with newer technology, specifically the MEMS® Button, which can inform the oncology pharmacist of the time of immunosuppressant self-administration
Euclid: Testing the Copernican principle with next-generation surveys
No full textContext. The Copernican principle, the notion that we are not at a special location in the Universe, is one of the cornerstones of modern cosmology. Its violation would invalidate the Friedmann-Lemaître-Robertson-Walker metric, causing a major change in our understanding of the Universe. Thus, it is of fundamental importance to perform observational tests of this principle.
Aims. We determine the precision with which future surveys will be able to test the Copernican principle and their ability to detect any possible violations.
Methods. We forecast constraints on the inhomogeneous Lemaître-Tolman-Bondi (LTB) model with a cosmological constant Λ, basically a cosmological constant Λ and cold dark matter (CDM) model but endowed with a spherical inhomogeneity. We consider combinations of currently available data and simulated Euclid data, together with external data products, based on both ΛCDM and ΛLTB fiducial models. These constraints are compared to the expectations from the Copernican principle.
Results. When considering the ΛCDM fiducial model, we find that Euclid data, in combination with other current and forthcoming surveys, will improve the constraints on the Copernican principle by about 30%, with ±10% variations depending on the observables and scales considered. On the other hand, when considering a ΛLTB fiducial model, we find that future Euclid data, combined with other current and forthcoming datasets, will be able to detect gigaparsec-scale inhomogeneities of contrast −0.1.
Conclusions. Next-generation surveys, such as Euclid, will thoroughly test homogeneity at large scales, tightening the constraints on possible violations of the Copernican principle
Microwave-to-optical transduction with erbium ions coupled to planar photonic and superconducting resonators
No full textOptical quantum networks can connect distant quantum processors to enable secure quantum communication and distributed quantum computing. Superconducting qubits are a leading technology for quantum information processing but cannot couple to long-distance optical networks without an efficient, coherent, and low noise interface between microwave and optical photons. Here, we demonstrate a microwave-to-optical transducer using an ensemble of erbium ions that is simultaneously coupled to a superconducting microwave resonator and a nanophotonic optical resonator. The coherent atomic transitions of the ions mediate the frequency conversion from microwave photons to optical photons and using photon counting we observed device conversion efficiency approaching 10⁻⁷. With pulsed operation at a low duty cycle, the device maintained a spin temperature below 100 mK and microwave resonator heating of less than 0.15 quanta
The influence of frailty on perioperative outcomes in patients undergoing surgical resection of liver metastases: a nationwide readmissions database study
No full textBackground: Liver metastases arise frequently from primary colorectal, pancreatic, and breast cancers. Research has highlighted the patient's frailty status as an important predictor of outcomes, but the literature evaluating the role of frailty in patients with secondary metastatic disease of the liver remains limited. Using predictive analytics, we evaluated the role of frailty in patients who underwent hepatectomy for liver metastases.
Methods: We used the Nationwide Readmissions Database from 2016-2017 to identify patients who underwent resection of a secondary malignant neoplasm of the liver. Patient frailty was evaluated using the Johns Hopkins Adjusted Clinical Groups (JHACG) frailty-defining diagnosis indicator. Propensity score matching was performed and Mann-Whitney U testing was used to analyze complication rates. Receiver operating characteristic (ROC) curves were created following creation of logistic regression models for predicting discharge disposition.
Results: Frail patients reported significantly higher rates of nonroutine discharges, longer inpatient stays, greater costs, higher rates of acute infection, posthemorrhagic anemia, urinary tract infection (UTI), deep vein thrombosis (DVT), wound dehiscence and readmission, and greater mortality (P<0.05). Predictive models for patient discharge disposition, DVT and UTI demonstrated that the use of frailty status and age improved the area under the ROC curves significantly compared to models using age alone.
Conclusions: Frailty was found to be significantly correlated with higher rates of medical complications during inpatient stay following hepatectomy in patients with liver metastasis. The inclusion of patient frailty status in predictive models improved their predictive capacity compared to those using age alone
Price’s Law and Precise Late-Time Asymptotics for Subextremal Reissner-Nordström Black Holes
No full textIn this paper, we prove precise late-time asymptotics for solutions to the wave equation supported on angular frequencies greater or equal to ℓ on the domain of outer communications of subextremal Reissner–Nordström spacetimes up to and including the event horizon. Our asymptotics yield, in particular, sharp upper and lower decay rates which are consistent with Price’s law on such backgrounds. We present a theory for inverting the time operator and derive an explicit representation of the leading-order asymptotic coefficient in terms of the Newman–Penrose charges at null infinity associated with the time integrals. Our method is based on purely physical space techniques. For each angular frequency ℓ, we establish a sharp hierarchy of r-weighted radially commuted estimates with length 2ℓ+5. We complement this hierarchy with a novel hierarchy of weighted elliptic estimates of length ℓ+1
Visualizing Protein Localizations in Fixed Cells: Caveats and the Underlying Mechanisms
No full textFluorescence microscopy techniques have been widely adopted in biology for their ability to visualize the structure and dynamics of a wide range of cellular and subcellular processes. The specificity and sensitivity that these techniques afford have made them primary tools in the characterization of protein localizations within cells. Many of the fluorescence microscopy techniques require cells to be fixed via chemical or alternative methods before being imaged. However, some fixation methods have been found to induce the redistribution of particular proteins in the cell, resulting in artifacts in the characterization of protein localizations and functions under physiological conditions. Here, we review the ability of commonly used cell fixation methods to faithfully preserve the localizations of proteins that bind to chromatin, undergo liquid–liquid phase separation (LLPS), and are involved in the formation of various membrane-bound organelles. We also review the mechanisms underlying various fixation artifacts and discuss potential alternative fixation methods to minimize the artifacts while investigating different proteins and cellular structures. Overall, fixed-cell fluorescence microscopy is a very powerful tool in biomedical research; however, each experiment demands the careful selection of an appropriate fixation method to avoid potential artifacts and may benefit from live-cell imaging validation
β2 nAChR Activation on VTA DA Neurons Is Sufficient for Nicotine Reinforcement in Rats
No full textMesolimbic nicotinic acetylcholine receptor (nAChRs) activation is necessary for nicotine reinforcement behavior, but it is unknown whether selective activation of nAChRs in the dopamine (DA) reward pathway is sufficient to support nicotine reinforcement. In this study, we tested the hypothesis that activation of β2-containing (β2*) nAChRs on VTA neurons is sufficient for intravenous nicotine self-administration (SA). We expressed β2 nAChR subunits with enhanced sensitivity to nicotine (referred to as β2Leu9′Ser) in the VTA of male Sprague Dawley (SD) rats, enabling very low concentrations of nicotine to selectively activate β2* nAChRs on transduced neurons. Rats expressing β2Leu9′Ser subunits acquired nicotine SA at 1.5 μg/kg/infusion, a dose too low to support acquisition in control rats. Saline substitution extinguished responding for 1.5 μg/kg/inf, verifying that this dose was reinforcing. β2Leu9′Ser nAChRs also supported acquisition at the typical training dose in rats (30 μg/kg/inf) and reducing the dose to 1.5 μg/kg/inf caused a significant increase in the rate of nicotine SA. Viral expression of β2Leu9′Ser subunits only in VTA DA neurons (via TH-Cre rats) also enabled acquisition of nicotine SA at 1.5 μg/kg/inf, and saline substitution significantly attenuated responding. Next, we examined electrically-evoked DA release in slices from β2Leu9′Ser rats with a history of nicotine SA. Single-pulse evoked DA release and DA uptake rate were reduced in β2Leu9′Ser NAc slices, but relative increases in DA following a train of stimuli were preserved. These results are the first to report that β2* nAChR activation on VTA neurons is sufficient for nicotine reinforcement in rats
A Simple Cosmology in G4v
No full textThere has been a great deal of debate as to the role, if any, of Mach’s Principle in cosmology. We propose that these questions have meaning only in the context of a cosmic gravitational potential. G4v operates with such a four-potential, which imposes a different symmetry on its treatment of light propagation than that employed by GR. That combination enables a simple cosmic solution that is Lorentz-invariant in free-fall frames of reference. The solution is compared with supernovae data, which, together with an internal self-consistency condition, fixes the parameters of the solution. The resulting Hubble trajectory is, in broad brush, consistent with many cosmic observations