Density Slope Research Articles

Joint lensing–dynamics constraint on the elliptical galaxy mass profile from the largest galaxy–galaxy lens sample

AbstractFrom various lensing and non-lensing observations, the total density profile in elliptical galaxies is well approximated by a power law mass distribution. However, as neither the dark matter nor the baryons individually follow the power law, this observational result has been referred to as the “bulge–halo conspiracy”. We investigate the consistency of this conspiracy with higher precision than previous studies with the largest ever sample of galaxy–galaxy lenses assembled from archival Hubble Space Telescope (HST) data. By performing lens modelling with power law profiles and combining them with stellar dynamics using the mass-sheet transformation, we can constrain the profile’s deviation from the power law model over a redshift range of 0.1 to 0.8. To uniformly model such a large sample of lens models, we use the automated modelling pipeline dolphin. We also investigate the evolutionary trend of the total mass density slope of the lensing galaxies.

Gravitational lenses in hydrodynamical simulations

AbstractThe gravitational lensing signal produced by a galaxy or a galaxy cluster is determined by its total matter distribution, providing us with a way to directly constrain their dark matter content. State-of-the-art numerical simulations successfully reproduce many observed properties of galaxies and can be used as a source of mock observations and predictions. Many gravitational lensing studies aim at constraining the nature of dark matter, discriminating between cold dark matter and alternative models. However, many past results are based on the comparison to simulations that did not include baryonic physics. Here we show that the presence of baryons can significantly alter the predictions: we look at the structural properties (profiles and shapes) of elliptical galaxies and at the inner density slope of subhaloes. Our results demonstrate that future simulations must model the interplay between baryons and alternative dark matter, to generate realistic predictions that could significantly modify the current constraints.

Minireview: Ni–Fe and Ni–Co Metal–Organic Frameworks for Electrocatalytic Water‐Splitting Reactions

Electrolysis is one of the clean, environmentally friendly, and sustainable pathways to produce hydrogen for renewable energy storage. However, to make electrolysis a competitive technology for hydrogen production, developing nonprecious metal‐based catalysts for oxygen evolution reaction (OER) is mandatory. Several new classes of electrocatalysts are developed with outstanding OER catalytic activity, stability, and commercial viability. Owing to the structural diversity, porosity, and accessibility of catalytically active metal centers, nickel‐based metal–organic frameworks (MOFs) are intensively explored as OER catalysts. In particular, bi‐ and trimetallic Ni MOFs with Fe and Co as additional metal nodes show excellent OER activity which can be tailored through the fine tuning of the metal compositions. Herein, the current state of research in Ni‐based MOFs as OER catalyst materials for alkaline electrolysis is presented. Strategies to improve the catalytic performance like compositional variations, choice of synthetic routes, and support materials are presented. Furthermore, OER activities are compared and presented based on the performance metrics (current density, overpotential, and Tafel slopes). Finally, concluding remarks featuring the key findings in Ni‐based MOFs and the possible rooms for future developments are summarized.

The effect of heteroatoms doping for the Pt supported graphene hollow spheres on electrocatalytic properties towards oxygen reduction and hydrogen evolution reaction

Noble metal Pt is the acknowledged efficient catalyst for oxygen reduction (ORR) and hydrogen evolution reaction (HER) in commercial applications. However, due to its high price and limited reserves, its large-scale application is limited. In order to overcome this defect, the loaded Pt nanoparticles (NPs) should be small and dispersed efficiently through the design of electrode materials, so as to improve the utilization efficiency of Pt. In addition, the introduction of non-noble metal active sites can reduce the consumption of Pt efficiently. In this work, hollow graphene spheres are used as the carrier and the heteroatoms (N, Fe and Co) are introduced. The results show that the introduction of Fe and Co can form very effective heteroatom active sites (carbon encapsulated Fe/Co metals and FeCo alloy, and/or metal nitrides Fe/Co-Nx-C) in the substrate material, which improve the catalytic activity of the electrode material effectively and the utilization efficiency of Pt. In addition, the generation of Fe/Co-Nx-C active sites and the loading of Pt are also closely related to the doped N atoms. The onset potential, limiting current density (JL), half-wave potential (E1/2) and Tafel slope of sample FeCo-NxHGSs/Pt (10 wt%) can exceed or comparable to those of commercial catalysts Pt/C (20 wt%) towards ORR both in acid and alkaline electrolyte. Moreover, the values of η100 and the Tafel slope for FeCo-NxHGSs/Pt towards HER can also exceed the commercial catalysts Pt/C (20 wt%) in acid and alkaline electrolytes. The purpose of reducing the usage amount of precious metals without reducing the catalytic performance is realized. The relationship between the ORR and HER performance of the resultant electrode catalyst and the doped heteroatoms, such as nitrogen (N), iron (Fe) and cobalt (Co) atoms, was studied and discussed in detail.

Tell-tale Spectral Signatures of MHD-driven Ultrafast Outflows in AGNs

We aim to explore spectral signatures of the predicted multi-ion ultrafast outflows (UFOs) in the broadband X-ray spectra of active galactic nuclei by exploiting an accretion disk-wind model in the context of a simple magnetohydrodynamic (MHD) framework. We are focused primarily on examining the spectral dependences on a number of key properties: (1) ionizing luminosity ratio λ ion, (2) line-of-sight wind density slope p, (3) optical/UV-to-X-ray strength α OX, (4) inclination θ, (5) X-ray photon index Γ, and (6) wind density factor f D . With an emphasis on radio-quiet Seyferts in the sub-Eddington regime, multi-ion UFO spectra are systematically calculated as a function of these parameters to show that MHD-driven UFOs imprint a unique asymmetric absorption line profile with a pronounced blue tail structure on average. Such a characteristic line signature is generic to the simplified MHD disk-wind models presented in this work due to their specific kinematics and density structure. The properties of these absorption line profiles could be utilized as a diagnostics to distinguish between different wind-driving mechanisms or even the specific values of given MHD wind parameters. We also present high-fidelity microcalorimeter simulations in anticipation of the upcoming XRISM/Resolve and Athena/X-IFU instruments to demonstrate that such a “tell-tale” sign may be immune to a spectral contamination by the presence of additional warm absorbers and partially covering gas.

Dual-Energy Computed Tomography-Derived Iodine Density and Spectral Attenuation Analysis for Differentiation of Inverted Papilloma and Sinonasal Squamous Cell Carcinoma/Lymphoma.

This study aimed to assess the value of dual-energy computed tomography for differentiation of inverted papilloma from squamous cell carcinoma (SCC)/lymphoma. Twenty-eight patients with pathologically diagnosed inverted papilloma or SCC/lymphoma underwent contrast-enhanced dual-energy computed tomography. Qualitative features (laterality, location, enhancement pattern, border, necrosis, hemorrhage, calcification, bone destruction, pterygopalatine fossa extension, adjacent invasion, and perineural spreading) and quantitative features (iodine density and spectral attenuation curve slope) were analyzed. Optimal cutoff thresholds of diagnostic efficacy were generated. Fifteen patients had inverted papilloma, and 13 had malignancy (5 SCC and 8 lymphoma). Computed tomography findings of bilateral lesions, sphenoid sinus involvement, pterygopalatine fossa extension, and adjacent invasion were significantly associated with SCC/lymphoma. The iodine density was significantly higher in SCC/lymphoma (2.46 ± 0.22 mg/mL) than in inverted papilloma (1.42 ± 0.46 mg/mL; P = 0.001). An iodine density threshold of 1.74 mg/mL had a sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of 92.3%, 86.7%, 92.9%, 85.7%, and 90.3%, respectively. The spectral attenuation curve slope was significantly higher in SCC/lymphoma (4.35 ± 0.27 HU/keV) than in inverted papilloma (2.72 ± 0.88 HU/keV; P = 0.001). A spectral attenuation curve slope threshold of 3.34 HU/keV had a sensitivity, specificity, negative predictive value, positive predictive value, and accuracy of 92.3%, 86.7%, 92.9%, 85.7%, and 90.8%, respectively. Squamous cell carcinoma/lymphoma had a significantly higher iodine density and spectral attenuation curve slope than inverted papilloma. Using optimal quantitative measurement thresholds provides high diagnostic efficacy.

Inferring subhalo effective density slopes from strong lensing observations with neural likelihood-ratio estimation

ABSTRACT Strong gravitational lensing has emerged as a promising approach for probing dark matter (DM) models on sub-galactic scales. Recent work has proposed the subhalo effective density slope as a more reliable observable than the commonly used subhalo mass function. The subhalo effective density slope is a measurement independent of assumptions about the underlying density profile and can be inferred for individual subhaloes through traditional sampling methods. To go beyond individual subhalo measurements, we leverage recent advances in machine learning and introduce a neural likelihood-ratio estimator to infer an effective density slope for populations of subhaloes. We demonstrate that our method is capable of harnessing the statistical power of multiple subhaloes (within and across multiple images) to distinguish between characteristics of different subhalo populations. The computational efficiency warranted by the neural likelihood-ratio estimator over traditional sampling enables statistical studies of DM perturbers and is particularly useful as we expect an influx of strong lensing systems from upcoming surveys.

Electrochemical Oxygen Evolution Reaction on NixFe3-xO4 (0 ≤ x ≤ 1.0) in Alkaline Medium at 25ºC

Spinel ferrites (NixFe3-xO4; x = 0.25, 0.5, 0.75 and 1.0) have been prepared at 550ºC by egg white auto-combustion route using egg white at 550ºC and characterized by physicochemical (TGA, IR, XRD, and SEM) and electrochemical (CV and Tafel polarization) techniques. The presence of characteristic vibration peaks in FT-IR and reflection planes in XRD spectra confirmed the formation of spinel ferrites. The prepared oxides were transformed into oxide film on glassy carbon electrodes by coating oxide powder ink using the nafion solution and investigated their electrocatalytic performance for OER in an alkaline solution. The cyclic voltammograms of the oxide electrode did not show any redox peaks in oxygen overpotential regions. The iR-free Tafel polarization curves exhibited two Tafel slopes (b1 = 59–90 mV decade−1 and b2 = 92–124 mV decade−1) in lower and higher over potential regions, respectively. Ni-substitution in oxide matrix significantly improved the electrocatalytic activity for oxygen evolution reaction. Based on the current density for OER, the 0.75 mol Ni-substituted oxide electrode was found to be the most active electrode among the prepared oxides and showed the highest value of apparent current density (~9 mA cm−2 at 0.85 V) and lowest Tafel slope (59 mV decade−1). The OER on oxide electrodes occurred via the formation of chemisorbed intermediate on the active sites of the oxide electrode and follow the second-order mechanism.

Spinel structure of activated carbon supported MFe2O4 composites as an economic and efficient electrocatalyst for oxygen reduction reaction in neutral media

For more sustainability and marketing of microbial fuel cells (MFCs) in wastewater treatment, the sluggish kinetics of cathode oxygen reduction reaction (ORR) and platinum scarcity (with its high cost) should be swept away. So, this work aimed to synthesize metal ferrite (MFe2O4; M = Mn, Cu, and Ni) -based activated carbon composites as inexpensive ORR cathode catalysts. The composites were synthesized using a facile modified co-precipitation approach with low-thermal treatment and labeled as MnFe2O4/AC, CuFe2O4/AC, and NiFe2O4/AC. The as-synthesized catalysts are physicochemically characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared microscopy (FTIR), Barrett-Joyner-Halenda (BJH), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), and electron spin resonance (ESR). The electrochemical catalytic performance toward ORR was studied in a phosphate buffer solution (PBS) at neutral media via cyclic voltammetry (CV) and linear sweep voltammetry (LSV). MnFe2O4/AC has the highest onset potential (Eonset) value of − 0.223 V compared to CuFe2O4/AC (− 0.280 V) and NiFe2O4/AC (− 0.270 V). MnFe2O4/AC also has the highest kinetic current density (jK) and lowest Tafel slope (− 5 mA cm−2 and − 330 mV dec−1) compared to CuFe2O4/AC (− 3.05 mA cm−2 and − 577 mV dec−1) and NiFe2O4/AC (− 2.67 mA cm−2 and − 414 mV dec−1). The ORR catalyzed by MnFe2O4/AC at pH = 7 proceeds via a 4e− -kinetic pathway. The ESR is in good agreement with the electrochemical analysis due to the highest ∆Hppvalue for MnFe2O4/AC compared to CuFe2O4/AC and NiFe2O4/AC. Thus, MnFe2O4/AC is suggested as a promising alternative to Pt- electrocatalyst cathode for MFCs at neutral conditions.Graphical

Can Lava Flow Like Water? Assessing Applications of Critical Flow Theory to Channelized Basaltic Lava Flows

AbstractFlowing lava and water have dramatically different physical properties but can form similar hydraulic structures, including undular hydraulic jumps, or standing wave trains. In water flows, undular hydraulic jumps are evidence of critical flow (Froude number ∼1) and open‐channel hydraulic theory provides a powerful tool for estimating flow depth and velocity. Monitoring these parameters in an active lava channel is inherently challenging, but essential for calculating lava discharge (effusion rate), a primary control on the rate of flow front advance and ultimate flow runout distance. We analyze undular hydraulic jumps in both water and lava flows to assess the conditions under which they form and, by extension, the potential use of critical flow theory to estimate, in real time, lava flow velocity, depth, and discharge. Experimental data for water flows show that these structures mark the transition from supercritical to subcritical flow. Undular hydraulic jumps in the near‐vent lava channel of the 2018 lower East Rift Zone eruption of Kīlauea, Hawaiʻi also reflect critical flow conditions; their wavelengths scale with flow depth and velocity, consistent with hydraulic theory. Calculated lava effusion rates are similar to estimates made using more traditional approaches (Jeffreys', 1925, https://doi.org/10.1080/14786442508634662, equation based on lava viscosity, density, and channel slope) and with lava volumes derived from topographic‐change mapping. From this we conclude that critical flow phenomena show great potential to track flow dynamics and inform hazard assessment for a wide range of geophysical fluids.

Incorporating baryon-driven contraction of dark matter halos in rotation curve fits

The condensation of baryons within a dark matter (DM) halo during galaxy formation should result in some contraction of the halo as the combined system settles into equilibrium. We quantify this effect on the cuspy primordial halos predicted by DM-only simulations for the baryon distributions observed in the galaxies of the SPARC database. We find that the DM halos of high surface brightness galaxies (with Σeff ≳ 100 L⊙ pc−2 at 3.6 μm) experience strong contraction. Halos become more cuspy as a result of compression: the inner DM density slope increases with the baryonic surface mass density. We iteratively fit rotation curves to find the balance between initial halo parameters (constrained by abundance matching), compression, and stellar mass-to-light ratio. The resulting fits often require lower stellar masses than expected for stellar populations, particularly in galaxies with bulges: stellar mass must be reduced to make room for the DM it compresses. This trade off between dark and luminous mass is reminiscent of the cusp-core problem in dwarf galaxies, but occurs in more massive systems: the present-epoch DM halos cannot follow from cuspy primordial halos unless (1) the stellar mass-to-light ratios are systematically smaller than expected from standard stellar population synthesis models, and/or (2) there is a net outward mass redistribution from the initial cusp, even in massive galaxies widely considered to be immune from such effects.

Variations and Factors Characterizing Ecological Niches of Understory Herbaceous Species in Plantation Forests

Plant ecological niche characteristics are powerful representations of plant survival status. Understory herbaceous species in plantation forests are sensitive to local ecological environment changes; patterns of ecological niche changes of herbaceous plants under plantation forests are of great significance for maintaining the stability and sustainable development of plantation forest ecosystems. This study aims to explore the ecological niche characteristics of understory herbaceous species in plantation forests and their influencing factors. Six different site types of Pinus tabulaeformis plantations were selected from a stable plantation community in the feldspathic sandstone area of the Loess Plateau (China). The relative importance value and niche breadth were used as comprehensive quantitative indices to characterize the status, role, and degree of dominance of understory herbaceous species in plantation forests. We found few dominant species of understory herbaceous species in plantation forests, mostly companion species. The niche characteristics of understory herbaceous species in plantation forests varied significantly. For understory herbaceous species, the niche width was positively correlated with slopes and the niche overlap of the sunny slopes was positively relevant with slopes, while that of the shady slopes was negatively correlated. A canonical correspondence analysis indicated that several major factors influencing the niche breadth and niche overlap of understory herbaceous species in plantation forests were different. The canopy density and slope of plantation played a major role in the niche breadth and niche overlap of understory herbaceous species in plantation forests. In summary, the species distribution of understory herbaceous species in plantation forests was determined by site type. The canopy density and geographical slope were the dominant environmental factors for different ecological niche characteristics of understory herbaceous species. The ecological niche variation of different herbaceous species was the consequence of the integrated effects of the plantation and geographical environment.

Modelling the host galaxies of binary compact object mergers with observational scaling relations

ABSTRACT The merger rate density evolution of binary compact objects and the properties of their host galaxies carry crucial information to understand the sources of gravitational waves. Here, we present galaxy$\mathcal {R}$ate, a new code that estimates the merger rate density of binary compact objects and the properties of their host galaxies, based on observational scaling relations. We generate our synthetic galaxies according to the galaxy stellar mass function. We estimate the metallicity according to both the mass–metallicity relation (MZR) and the fundamental metallicity relation (FMR). Also, we take into account galaxy–galaxy mergers and the evolution of the galaxy properties from the formation to the merger of the binary compact object. We find that the merger rate density changes dramatically depending on the choice of the star-forming galaxy main sequence, especially in the case of binary black holes (BBHs) and black hole neutron star systems (BHNSs). The slope of the merger rate density of BBHs and BHNSs is steeper if we assume the MZR with respect to the FMR, because the latter predicts a shallower decrease of metallicity with redshift. In contrast, binary neutron stars (BNSs) are only mildly affected by both the galaxy main sequence and metallicity relation. Overall, BBHs and BHNSs tend to form in low-mass metal-poor galaxies and merge in high-mass metal-rich galaxies, while BNSs form and merge in massive galaxies. We predict that passive galaxies host at least ∼5–10 per cent, ∼15–25 per cent, and ∼15–35 per cent of all BNS, BHNS, and BBH mergers in the local Universe.

The feasibility study of XACT imaging for characterizing osteoporosis.

Osteoporosis is a progressive bone disease that is characterized by a decrease in bone mass and the deterioration in bone microarchitecture, which might be related to age and space travel. An unmet need exists for the development of novel imaging technologies to characterize osteoporosis. The purpose of our study is to investigate the feasibility of X-ray-induced acoustic computed tomography (XACT) imaging for osteoporosis detection. An in-house simulation workflow was developed to assess the ability of XACT for osteoporosis detection. To evaluate this simulation workflow, a three-dimensional digital bone phantom for XACT imaging was created by a series of two-dimensional micro-computed tomography (micro-CT) slices of normal and osteoporotic bones in mice. In XACT imaging, the initial acoustic pressure rise caused by the X-ray induce acoustic (XA) effect is proportional to bone density. First, region growing was deployed for image segmentation of different materials inside the bone. Then k-wave simulations were deployed to model XA wave propagation, attenuation, and detection. Finally, the time-varying pressure signals detected at each transducer location were used to reconstruct the XACT image with a time-reversal reconstruction algorithm. Through the simulated XACT images, cortical porosity has been calculated, and XA signal spectra slopes have been analyzed for the detection of osteoporosis. The results have demonstrated that osteoporotic bones have lower bone mineral density and higher spectra slopes. These findings from XACT images were in good agreement with porosity calculation from micro-CT images. This work explores the feasibility of using XACT imaging as a new imaging tool for Osteoporosis detection. Considering that acoustic signals are generated by X-ray absorption, XACT imaging can be combined with traditional X-ray imaging that holds potential for clinical management of osteoporosis and other bone diseases.

Influence of Low-Coercive-Force Magnet Property on Electromagnetic Performance of Variable Flux Memory Machine

The magnetization properties of low-coercive-force (LCF) permanent magnets (PMs), i.e., remanent flux density, coercivity, and hysteresis curve slopes, are closely related to the magnetization characteristics of variable flux memory machine (VFMM). Therefore, this article investigates the inherent relationship between the properties of LCF PMs and electromagnetic characteristics of VFMM using a combined solution integrated with magnetic equivalent circuit (MEC) and graphical methods. First, the hysteresis curve of the LCF PM is analytically modeled by a simplified piecewise linear hysteresis model to characterize the mathematical relationships among the key parameters of the hysteresis model. Then, a simplified MEC method is used to obtain the permeability curves of VFMM, thereby further determining the intrinsic relationship between the dimensional parameters of the LCF PM and the electromagnetic characteristics of VFMM. Afterward, the flux regulation characteristics and on-load magnetization state (MS) stabilization capability of VFMM are qualitatively analyzed using a newly developed coupled approach. Furthermore, the electromagnetic characteristics of three VFMMs equipped with different version LCF PM materials are comprehensively compared using the finite-element (FE) method. Finally, a VFMM prototype using the selected AlNiCo magnet is manufactured and tested to verify the correctness of the theoretical and FE analyses.

Time Lag Modeling in Modification of Nakayasu Synthetic Unit Hydrograph

In the development of the synthetic unit hydrograph method, the empirical formula expresses the relation between the watershed morphometry characteristic and the constituent elements of hydrographs that are peak discharge (Qp), time to peak (tp), time lag (TL), and time base (Tb). This research intends to build a model of time lag in order to modify the Nakayasu SUH modeling. The Nakayasu synthetic unit hydrograph (SUH) model, seen as very popular and widely used by practitioners, needs to be adjusted for the main parameters that form the hydrograph to be able to be directly used based on the watershed morphometry characteristic. Based on the specific characteristic of the Nakayasu SUH formulation, this research will focus on developing the Nakayasu SUH model by the modification with adding the watershed characteristic parameter to the time lag parameter (tL). This research was conducted in 23 watersheds in Indonesia. The previous research in the same watersheds indicates five morphometry parameters with a positive effect on the time lag with the ranking due to the strongest effect as follows: watershed area (A), the river length from outlet to the weight point of the watershed (Lc), H = L.Lc, and the main river length (L). However, the two other parameters negatively affect the time lag with the ranking due to the strongest effect as follows: river network density (D) and river slope (K). Then, the modeling of time lag is carried out based on the research result, and the result of the time lag model is as follows: tL=Lc0.1809H-0.00159A0.003459

Influence of optical transmissivity on signal characteristics of photoacoustic guided waves in long cortical bone

Long cortical bone allows axial transmission of ultrasonic guided waves, which has been utilized for osteoporosis evaluation. Benefiting structural and molecular sensitivity, photoacoustic has been used for tissue composition characterization. However, photoacoustic guided waves (PAGWs) in long cortical bone as well as the influence of optical transmissivity on PAGWs have not been thoroughly investigated. In the study, the influence of optical transmissivity on the signal characteristics of PAGWs was experimentally studied with a 1064 nm pulsed laser ultrasonic system and a tunable laser system (wavelength range: 650–2600 nm). Results show that dispersion curves of PAGWs are not significantly affected by the optical transmissivity; while photoacoustic guided modes and signal spectrum are sensitive to the optical transmissivity in cortical bone. In experiments, the lasers with high transmissivity can emit pure A0 mode PAGWs at the low frequency, around 22 kHz, in the relatively thick 6.2 mm bone plate; on the contrary, both A0 and S0 modes are generated. The slope of power spectrum density (PSD) of PAGWs decreases with the increase of transmissivity, and the decline rate is around −0.229. The study proves the correlation between the signal characteristics of PAGWs and the optical transmissivity, it is helpful for the development of PAGWs in long cortical bone towards the osteoporosis evaluation.

Probing dark matter with strong gravitational lensing through an effective density slope

ABSTRACT Many dark matter (DM) models that are consistent with current cosmological data show differences in the predicted (sub)halo mass function, especially at sub-galactic scales, where observations are challenging due to the inefficiency of star formation. Strong gravitational lensing has been shown to be a useful tool for detecting dark low-mass (sub)haloes through perturbations in lensing arcs, therefore allowing the testing of different DM scenarios. However, measuring the total mass of a perturber from strong lensing data is challenging. Overestimating or underestimating perturber masses can lead to incorrect inferences about the nature of DM. In this paper, we argue that inferring an effective slope of the DM density profile, which is the power-law slope of perturbers at intermediate radii, where we expect the perturber to have the largest observable effect, is a promising way to circumvent these challenges. Using N-body simulations, we show that (sub)halo populations under different DM scenarios differ in their effective density slope distributions. Using realistic mocks of Hubble Space Telescope observations of strong lensing images, we show that the effective density slope of perturbers can be robustly measured with high enough accuracy to discern between different models. We also present our measurement of the effective density slope $\gamma =1.96\substack{+0.12 \\ -0.12}$ for the perturber in JVAS B1938+666, which is a 2σ outlier of the cold DM scenario. More measurements of this kind are needed to draw robust conclusions about the nature of DM.

Abstract 3241: IC50-Seeding Density Slope (ISDS)-measurement as a standardized methodology for assessing anti-cancer therapeutic activity in vitro

Abstract The 50% inhibitory concentration (IC50) is a widely used measure of how effective a given anti-cancer therapeutic is at reducing cancer cell viability in vitro. It is known that IC50 of a given therapeutic agent is dependent on the seeding density of the treated cells (in that more densely-seeded cells tend to be more resistant to therapeutic agents). We performed experiments using the CellTiter Glo cell viability assay to assess the cytotoxicity of various chemotherapeutic drugs towards various cancer cell lines. To elucidate the role the extracellular environment of densely-seeded cells plays in cancer cell chemoresistance, we tested conditioned media from cells cultured at high density on cells seeded at low densities. The resulting impact on the IC50 of the low-density cells was determined. The IC50 of the various therapeutic agents tested was cell density-dependent in each cancer cell line examined. Based on this analysis, we propose the IC50-seeding density slope (ISDS), which relates seeding density to the effectiveness of a drug and that we believe could be a standardized quantitative measurement of how a given cancer cell line responds to a given therapeutic treatment. Our results from the conditioned media experiments consistently indicated that the environment of densely-seeded tumor cells conferred chemoresistance to sparsely-seeded cells, suggesting that extracellular cytokines and growth factors may be involved in density-dependent chemoresistance mechanisms. We are currently exploring the effect of serum deprivation on in vitro chemoresistance, in order to further understand how the presence of extracellular nutrients impacts observed IC50 trends. In addition, we are examining the role that cell-cell contact, integrin and FGF signaling pathways play in giving rise to density-dependent chemoresistance. Moreover, to analyze the manner in which conditioned media gives rise to chemoresistance and how this effect relates to intracellular survival pathways, we are performing cytokine profiling experiments. Overall, we describe density-dependent IC50 variations as a hallmark of cancer cells and propose that ISDS may serve as a standardized method of assessing chemosensitivity. Citation Format: Ujwal Punyamurtula, Shengliang Zhang, Thomas Brown, Arielle De La Cruz, Alexander Raufi, Jillian Strandberg, Lindsey Carlsen, Lanlan Zhou, Wafik El-Deiry. IC50-Seeding Density Slope (ISDS)-measurement as a standardized methodology for assessing anti-cancer therapeutic activity in vitro [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3241.

Constraints on the symmetry energy from PREX-II in the multimessenger era

The neutron skin thickness $\Delta r_{\rm{np}}$ of heavy nuclei is essentially determined by the symmetry energy density slope $L({\rho })$ at $\rho_c = 0.11~{\rm {fm}^{-3}}\approx 2/3\rho_0$ ($\rho_0$ is nuclear saturation density), roughly corresponding to the average density of finite nuclei. The PREX collaboration recently reported a model-independent extraction of $\Delta r^{208}_{\rm{np}} = 0.283 \pm 0.071$ fm for the $\Delta r_{\rm{np}}$ of $^{208}$Pb, suggesting a rather stiff symmetry energy $E_{\rm{sym}}({\rho })$ with $L({\rho_c }) \ge 52$ MeV. We show that the $E_{\rm{sym}}({\rho })$ cannot be too stiff and $L({\rho_c }) \le 73$ MeV is necessary to be compatible with (1) the ground-state properties and giant monopole resonances of finite nuclei, (2) the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities from flow data in heavy-ion collisions, (3) the largest neutron star (NS) mass reported so far for PSR J0740+6620, (4) the NS tidal deformability extracted from gravitational wave signal GW170817 and (5) the mass-radius of PSR J0030+045 measured simultaneously by NICER. This allows us to obtain $52 \le L({\rho_c }) \le 73$ MeV and $0.212 \le \Delta r^{208}_{\rm{np}} \le 0.271$ fm, and further $E_{\rm{sym}}({\rho_0 }) = 34.3 \pm 1.7$ MeV, $L({\rho_0 }) = 83.1 \pm 24.7$ MeV, and $E_{\rm{sym}}({2\rho_0 }) = 62.8 \pm 15.9$ MeV. A number of critical implications on nuclear physics and astrophysics are discussed.