Current cosmological data exhibit a tension between inferences of the Hubble constant, H0, derived from early and late-Universe measurements. One proposed solution is to introduce a new component in ...the early Universe, which initially acts as "early dark energy" (EDE), thus decreasing the physical size of the sound horizon imprinted in the cosmic microwave background (CMB) and increasing the inferred H0. Previous EDE analyses have shown this model can relax the H0 tension, but the CMB-preferred value of the density fluctuation amplitude, σ8, increases in EDE as compared to Λ cold dark matter (Λ CDM ), increasing tension with large-scale structure (LSS) data. We show that the EDE model fit to CMB and SH0ES data yields scale-dependent changes in the matter power spectrum compared to Λ CDM, including 10% more power at k = 1h/Mpc. Motivated by this observation, we reanalyze the EDE scenario, considering LSS data in detail. We also update previous analyses by including Planck 2018 CMB likelihoods, and perform the first search for EDE in Planck data alone, which yields no evidence for EDE. We consider several data set combinations involving the primary CMB, CMB lensing, supernovae, baryon acoustic oscillations, redshift-space distortions, weak lensing, galaxy clustering, and local distance-ladder data (SH0ES). While the EDE component is weakly detected (3σ) when including the SH0ES data and excluding most LSS data, this drops below 2σ when further LSS data are included. Further, this result is in tension with strong constraints imposed on EDE by CMB and LSS data without SH0ES, which show no evidence for this model. We also show that physical priors on the fundamental scalar field parameters further weaken evidence for EDE. We conclude that the EDE scenario is, at best, no more likely to be concordant with all current cosmological data sets than Λ CDM , and appears unlikely to resolve the H0 tension.
Charting and comparing Tunisia's, Algeria's, Morocco's and Mauritania's political development over the past 10 years, this book offers fresh and original insight into their contrasting experiences as ...well as extending Levitsky and Way's model.
The cosmic microwave background temperature bispectrum is currently the most precise tool for constraining non-Gaussianity (NG) in the primordial curvature perturbations. The Planck temperature data ...tightly constrain the amplitude of local-type NG: fNLloc=2.5±5.7. In this paper, we compute previously neglected foreground biases in temperature-based fNLloc measurements. We consider signals from the integrated Sachs-Wolfe (ISW) effect, gravitational lensing, the thermal and kinematic Sunyaev-Zel’dovich effects, and the cosmic infrared background. In standard analyses, a significant foreground bias arising from the ISW-lensing bispectrum is subtracted from the fNLloc measurement. However, a number of other terms sourced by the ISW, lensing, thermal and kinematic Sunyaev-Zel’dovich effects, and cosmic infrared background fields are also present in the temperature bispectrum. We compute the dominant biases on fNLloc arising from these signals, focusing on “squeezed” bispectrum shapes. Most of the biases are nonblackbody in nature, and are thus reduced by multifrequency component separation methods; however, recent analyses have found that extragalactic foregrounds are present at non-negligible levels in the Planck component-separated maps. Moreover, the Planck FFP8 simulations do not include the correlations amongst components that are responsible for these biases. We compute the biases for individual Planck frequencies, finding that some are comparable to the statistical error bar on fNLloc, even for the main cosmic microwave background channels (100, 143, and 217 GHz). For future experiments, they can greatly exceed the statistical error bar (considering temperature data only). Alternatively, the foreground contributions can be marginalized over, but without strong priors this leads to a non-negligible increase in the error bar on fNLloc. A full assessment for Planck and other experiments will require calculations in tandem with component separation, ideally using simulations. We also compute these biases for equilateral and orthogonal NG, finding large effects for the latter. Similar calculations must be performed for trispectrum NG. We conclude that the search for primordial NG using Planck data may not yet be over.
Gravitational lensing of the cosmic microwave background (CMB) is expected to be amongst the most powerful cosmological tools for ongoing and upcoming CMB experiments. In this work, we investigate a ...bias to CMB lensing reconstruction from temperature anisotropies due to the kinematic Sunyaev-Zel’dovich (kSZ) effect, that is, the Doppler shift of CMB photons induced by Compton scattering off moving electrons. The kSZ signal yields biases due to both its own intrinsic non-Gaussianity and its nonzero cross-correlation with the CMB lensing field (and other fields that trace the large-scale structure). This kSZ-induced bias affects both the CMB lensing autopower spectrum and its cross-correlation with low-redshift tracers. Furthermore, it cannot be removed by multifrequency foreground separation techniques because the kSZ effect preserves the blackbody spectrum of the CMB. While statistically negligible for current data sets, we show that it will be important for upcoming surveys, and failure to account for it can lead to large biases in constraints on neutrino masses or the properties of dark energy. For a stage 4 CMB experiment, the bias can be as large as ≈15% or 12% in cross-correlation with LSST galaxy lensing convergence or galaxy overdensity maps, respectively, when the maximum temperature multipole used in the reconstruction is ℓmax=4000, and about half of that when ℓmax=3000. Similarly, we find that the CMB lensing autopower spectrum can be biased by up to several percent. These biases are many times larger than the expected statistical errors. We validate our analytical predictions with cosmological simulations and present the first complete estimate of secondary-induced CMB lensing biases. The predicted bias is sensitive to the small-scale gas distribution, which is affected by pressure and feedback mechanisms, thus making removal via “bias-hardened” estimators challenging. Reducing ℓmax can significantly mitigate the bias at the cost of a decrease in the overall lensing reconstruction signal-to-noise. A bias ≲1% on large scales requires ℓmax≲2000, which leads to a reduction in signal-to-noise by a factor of ≈3–5 for a stage 4 CMB experiment. Polarization-only reconstruction may be the most robust mitigation strategy.
Mammalian organogenesis is a remarkable process. Within a short timeframe, the cells of the three germ layers transform into an embryo that includes most of the major internal and external organs. ...Here we investigate the transcriptional dynamics of mouse organogenesis at single-cell resolution. Using single-cell combinatorial indexing, we profiled the transcriptomes of around 2 million cells derived from 61 embryos staged between 9.5 and 13.5 days of gestation, in a single experiment. The resulting 'mouse organogenesis cell atlas' (MOCA) provides a global view of developmental processes during this critical window. We use Monocle 3 to identify hundreds of cell types and 56 trajectories, many of which are detected only because of the depth of cellular coverage, and collectively define thousands of corresponding marker genes. We explore the dynamics of gene expression within cell types and trajectories over time, including focused analyses of the apical ectodermal ridge, limb mesenchyme and skeletal muscle.
Ending Aging in Super Glassy Polymer Membranes Lau, Cher Hon; Nguyen, Phuc Tien; Hill, Matthew R. ...
Angewandte Chemie (International ed.),
May 19, 2014, Letnik:
53, Številka:
21
Journal Article
Recenzirano
Odprti dostop
Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4‐methyl‐2‐pentyne) (PMP), and polymers with intrinsic microporosity (PIM‐1) reduces gas permeabilities and limits ...their application as gas‐separation membranes. While super glassy polymers are initially very porous, and ultra‐permeable, they quickly pack into a denser phase becoming less porous and permeable. This age‐old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.
Forever young: Like stringed beads, polymer chains of a permeable membrane are intercalated within the pores of PAF‐1 particles thus inhibiting polymer chain relaxation and stopping aging. PAF‐1 incorporation also drastically enhanced gas permeabilities (see picture).
The fabrication of oriented, crystalline films of metal-organic frameworks (MOFs) is a critical step toward their application to advanced technologies such as optics, microelectronics, microfluidics ...and sensing. However, the direct synthesis of MOF films with controlled crystalline orientation remains a significant challenge. Here we report a one-step approach, carried out under mild conditions, that exploits heteroepitaxial growth for the rapid fabrication of oriented polycrystalline MOF films on the centimetre scale. Our methodology employs crystalline copper hydroxide as a substrate and yields MOF films with oriented pore channels on scales that primarily depend on the dimensions of the substrate. To demonstrate that an anisotropic crystalline morphology can translate to a functional property, we assembled a centimetre-scale MOF film in the presence of a dye and showed that the optical response could be switched 'ON' or 'OFF' by simply rotating the film.
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