Quantifying the redshift space distortion of the bispectrum III : Detection prospects of the multipole moments

The redshift space anisotropy of the bispectrum is generally quantified using multipole moments. The possibility of measuring these multipoles in any survey depends on the level of statistical fluctuations. We present a formalism to compute the statistical fluctuations in the measurement of bispectrum multipoles for galaxy surveys. We consider specifications of a {\it Euclid} like galaxy survey and present two quantities: the signal-to-noise ratio (SNR) which quantifies the detectability of a multipole, and the rank correlation which quantifies the correlation in measurement errors between any two multipoles. Based on SNR values, we find that {\it Euclid} can potentially measure the bispectrum multipoles up to $\ell=4$ across various triangle shapes, formed by the three {\bf k} vectors in Fourier space. In general, SNR is maximum for the linear triangles. SNR values also depend on the scales and redshifts of observation. While, $\ell \leq 2$ multipoles can be measured with ${\rm SNR}>5$ even at linear/quasi-linear ($k \lesssim 0.1 \,{\rm Mpc}^{-1}$) scales, for $\ell>2$ multipoles, we require to go to small scales or need to increase bin sizes. For most multipole pairs, the errors are only weakly correlated across much of the triangle shapes barring a few in the vicinity of squeezed and stretched triangles. This makes it possible to combine the measurements of different multipoles to increase the effective SNR.Comment: Submitted to MNRAS main journal, 14 Pages, 8 Figure

HERA bound on X-ray luminosity weakens when accounting for Population III stars

Recent upper bounds from the Hydrogen Epoch of Reionization Array (HERA) on the cosmological 21-cm power spectrum at redshifts $z \approx 8, 10$, have been used to constrain $L_{\rm X<2 \, keV}/{\rm SFR}$, the soft-band X-ray luminosity measured per unit star formation rate (SFR), strongly disfavoring values lower than $\approx 10^{39.5} \, {\rm erg} \;{\rm s}^{-1} \;{\rm M}_{\odot}^{-1} \;{\rm yr}$ . In this work, we first reproduce the bounds on $L_{\rm X<2 \, keV}/{\rm SFR}$ and other parameters using a pipeline that combines machine learning emulators for the power spectra and the intergalactic medium characteristics, together with a standard Markov chain Monte Carlo parameter fit. We then use this approach when including molecular cooling galaxies that host PopIII stars in the cosmic dawn 21-cm signal, and show that lower values of $L_{\rm X<2 \, keV}/{\rm SFR}$ are hence no longer strongly disfavored. The revised HERA bound does not require high-redshift X-ray sources to be significantly more luminous than high-mass X-ray binaries observed at low redshift.Comment: 20 pages, 13 figures, 2 table

Engineered mesenchymal stem cells with self-assembled vesicles for systemic cell targeting

Cell therapy has the potential to impact the quality of life of suffering patients. Systemic infusion is a convenient method of cell delivery; however, the efficiency of engraftment presents a major challenge. It has been shown that modification of the cell surface with adhesion ligands is a viable approach to improve cell homing, yet current methods including genetic modification suffer potential safety concerns, are practically complex and are unable to accommodate a wide variety of homing ligands or are not amendable to multiple cell types. We report herein a facile and generic approach to transiently engineer the cell surface using lipid vesicles to present biomolecular ligands that promote cell rolling, one of the first steps in the homing process. Specifically, we demonstrated that lipid vesicles rapidly fuse with the cell membrane to introduce biotin moieties on the cell surface that can subsequently conjugate streptavidin and potentially any biotinylated homing ligand. Given that cell rolling is a pre-requisite to firm adhesion for systemic cell homing, we examined the potential of immobilizing sialyl Lewis X (SLeX) on mesenchymal stem cells (MSCs) to induce cell rolling on a P-selectin surface, under dynamic flow conditions. MSCs modified with SLeX exhibit significantly improved rolling interactions with a velocity of 8 μm/s as compared to 61 μm/s for unmodified MSCs at a shear stress of 0.5 dyn/cm[superscript 2]. The cell surface modification does not impact the phenotype of the MSCs including their viability and multi-lineage differentiation potential. These results show that the transitory modification of cell surfaces with lipid vesicles can be used to efficiently immobilize adhesion ligands and potentially target systemically administered cells to the site of inflammation.American Heart Association (Grant 0970178N)National Institutes of Health (U.S.) (Grant DE019191