Constraining primordial black holes with relativistic degrees of freedom

Scalar perturbations in the early Universe create over-dense regions that can collapse into primordial black holes (PBH). This process emits scalar-induced gravitational waves (SIGW) that behaves like an extra radiation component and contributes to the relativistic degrees of freedom ($N_{\rm{eff}}$). We show that $N_{\rm{eff}}$ limits from cosmic microwave background (CMB) give promising sensitivities on both the abundance of PBHs and the primordial curvature perturbation ($\mathcal{P}_{\mathcal{R}}(k)$) at small scales. We show that {\it Planck} and ACTPol data can exclude supermassive PBHs with peak mass $M_{\bullet} \in [3 \times 10^{5}, 5 \times 10^{10}] {\rm{M}}_{\odot}$ as the major component of dark matter, depending on the shape of the PBHs mass distribution. Future CMB-S4 mission is capable of broadening this limit to a vast PBH mass window of $M_{\bullet} \in [8 \times 10^{-5}, 5 \times 10^{10}] {\rm{M}}_{\odot}$, covering sub-stellar masses. These limits correspond to the enhanced sensitivity of $\mathcal{P}_{\mathcal{R}}(k)$ on scales of $k \in [10^1, 10^{22}]\ \rm{Mpc^{-1}}$, which is much smaller than those scales probed by direct perturbation power spectra (CMB and large-scale structure).Comment: 7 pages, 3 figure

Survival saplings

Survival sapling

Data from: Shrubs facilitate recruitment of Caragana stenophylla Pojark: microhabitat amelioration and protection against herbivory

Key message: Mature Caragana stenophylla shrubs facilitated intraspecific sapling establishment by two mechanisms: microhabitat amelioration and protection against herbivory. Facilitation was mediated by climate, grazing and sapling age. Context: Pre-existing shrubs could facilitate sapling establishment of woody plants, however, how these facilitation vary across abiotic and biotic stress gradients and the underlying mechanisms remain unclear. Aims: The aim of this study is understanding the facilitation of shrub on sapling establishment, and how the two underlying mechanisms, microhabitat amelioration and protection against herbivory, vary across climatic aridity gradients, grazing gradients and sapling age. Methods: We conducted field sowing experiments to examine the facilitation of mature Caragana stenophylla Pojark on intraspecific sapling establishment. Results: Facilitation of C. stenophylla on sapling survival increased as drought stress, grazing intensity and sapling age increased. Microhabitat amelioration increased as drought stress and sapling age increased. Similarly, protection against herbivory increased as drought stress, grazing intensity and sapling age increased. Relative importance of microhabitat amelioration increased as drought stress increased, and relative importance of protection against herbivory increased as grazing intensity and sapling age increased. Conclusions: Facilitation of shrub on sapling establishment involves both microhabitat amelioration and protection against herbivory. Facilitation, the two mechanisms and relative importance between the two mechanisms would all be affected by climatic aridity, grazing intensity and sapling age. Shrub establishment has a positive feedback effect

Plasma-treated Ce/TiO₂–SiO₂ catalyst for the NH₃-SCR of NO<i>_x</i>

<p>Ce/TiO₂–SiO₂ catalysts with different Ti/Si molar ratios are prepared by the incipient impregnation method and their NH₃-SCR activities are evaluated at 100–500°C on a fixed reactor. The Ce/TiO₂–SiO₂ (3/1) catalyst, modified by non-thermal plasma (NTP) treatment and then activated by thermal treatment at 500°C for 4 h, exhibits best performance. Comprehensive deNO<i>_x</i> performance of the catalyst is evidently improved and its efficiency reaches up to 99.21% at 350°C. NO conversion efficiency of the treated catalyst doped with K remains about 90.23% at 300°C and the catalyst also shows improved activity at lower temperatures. Various characterization methods show that the activity enhancement is correlated only with NTP treatment, as it increases the number of Ce³⁺ species, which generates more chemisorbed oxygen, leads to improved dispersion of Brønsted and Lewis acidic sites and finally has an inherent etching effect.</p

Proportion of MA versus PAH

data of Table 3 and Table

Survival seedlings

Survival seedling

PFE

data of Fig.1 and Table

MA and PAH

data of Fig.2, Fig.3 and Table