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Temperature and biodiversity changes occur in concert, but their joint effects on ecological stability of natural food webs are unknown. Here, we assess these relationships in 19 planktonic food webs. We estimate stability as structural stability (using the volume contraction rate) and temporal stability (using the temporal variation of species abundances). Warmer temperatures were associated with lower structural and temporal stability, while biodiversity had no consistent effects on either stability property. While species richness was associated with lower structural stability and higher temporal stability, Simpson diversity was associated with higher temporal stability. The responses of structural stability were linked to disproportionate contributions from two trophic groups (predators and consumers), while the responses of temporal stability were linked both to synchrony of all species within the food web and distinctive contributions from three trophic groups (predators, consumers, and producers). Our results suggest that, in natural ecosystems, warmer temperatures can erode ecosystem stability, while biodiversity changes may not have consistent effects.

 

Realization of ferromagnetic (FM) interlayer coupling in magnetic topological insulators (TIs) of the MnBi 2 Te 4 family of materials (MBTs) may pave the way for realizing the high-temperature quantum anomalous Hall effect (high- T QAHE). Here we propose a generic dual d-band (DDB) model to elucidate the energy difference (Δ E = E AFM − E FM ) between the AFM and FM coupling in transition-metal (TM)-doped MBTs, where the valence of TMs splits into d-t 2g and d-e g sub-bands. Remarkably, the DDB shows that Δ E is universally determined by the relative position of the dopant (X) and Mn d-e g / t 2g bands, . If Δ E d > 0, then Δ E > 0 and the desired FM coupling is favored. This surprisingly simple rule is confirmed by first-principles calculations of hole-type 3d and 4d TM dopants. Significantly, by applying the DDB model, we predict the high- T QAHE in the V-doped Mn 2 Bi 2 Te 5 , where the Curie temperature is enhanced by doubling of the MnTe layer, while the topological order mitigated by doping can be restored by strain. 

We study coherent anti-Stokes Raman spectroscopy in air-filled anti-resonance hollow-core photonic crystal fiber, otherwise known as “revolver” fiber. We compare the vibrational coherent anti-Stokes Raman signal of N 2 , at ∼2331 cm −1 , generated in ambient air (no fiber present), with the one generated in a 2.96 cm of a revolver fiber. We show a ∼170 times enhancement for the signal produced in the fiber, due to an increased interaction path. Remarkably, the N 2 signal obtained in the revolver fiber shows near-zero non-resonant background, due to near-zero overlap between the laser field and the fiber cladding. Through our study, we find that the revolver fiber properties make it an ideal candidate for the coherent Raman spectroscopy signal enhancement.