1,720,999 research outputs found
MaPBI3 and 2D hybrid organic-inorganic perovskite based microcavities employing periodic, aperiodic, and disordered photonic structures with light-induced tuning possibility
Full text linkInorganic-organic perovskites semiconductors are becoming increasingly interesting due to their remarkable optical properties, such as a high photoluminescence quantum yield and the possibility to show optical gain in a broad range of wavelengths. We have here simulated microcavities that embed MaPBI3 and 2D hybrid organic-inorganic perovskite semiconductors by sandwiching such active layers between periodic, aperiodic and disordered photonic structures. The complex refractive index dispersions of MaPBI3 and 2D hybrid organic-inorganic perovskite have been recently reported in literature. Thus, we have carefully considered the refractive index dispersion of all the materials employed, such as silicon dioxide, titanium dioxide, and the aforementioned perovskite layers. Moreover, by employing a photochromatic polymer, namely the diarylethene-based polyester pDTE, we have designed a microcavity with light-induced tuning of the cavity modes is possible
Light transmission behaviour as a function of the homogeneity in one dimensional photonic crystals
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Threshold extinction in food webs
No full textFood web response to species loss has been investigated in several ways in the last years. In binary food webs species go secondarily extinct if no resource item remains to exploit. We considered that species can go extinct well before their remain without energy intake and we explore this issue by introducing thresholds of minimum energy requirement for species survival. According to this approach extinction would occur whenever an initial extinction event eliminates links so that certain nodes are left with an overall energy intake lower than the threshold value. We tested 18 real food webs by removing species from most to least connected and considering different scenarios defined by a progressively increasing extinction threshold. Increasing energy requirement threshold negatively affect food web robustness. We found that a very low increase of the energy requirement induces a significative increase in system fragility. In addition, above a certain value of energy requirement threshold we found no relationship between the robustness and the connectance of the web. Further, networks with more species showed higher level of fragility when energy threshold is more severe. Such discovery indicates that the shape of the robustnesscomplexity
relationship of a web depends on the sensitivity of consumers to loss of prey
The influence of a power law distribution of cluster size on the light transmission of disordered 1-D photonic structures
No full textAn energy window study of light transmission-disorder relationship in 1D photonic structures
No full textWhile the light transmission of photonic crystals is characterized by the photonic band gap, the one of disordered photonic structures is typified by a multiplicity of transmission depths. The total transmission over a range of wavelengths is related to the width of such range, but also to the type of disorder. Less homogeneous disordered structures transmit more light than the ordered counterpart regardless of the wavelengths range width. More homogeneous disordered structures transmit more light than the ordered counterpart only above a certain value of the width. We studied this behaviour with a statistical analysis over 5000 permutations of structures for six wavelength widths and for two different homogeneity degrees (Shannon-Wiener index)
The heterogeneity in link weights may decrease the robustness of real-world complex weighted networks
Full text linkHere we report a comprehensive analysis of the robustness of seven high-quality real-world complex weighted networks to errors and attacks toward nodes and links. We use measures of the network damage conceived for a binary (e.g. largest connected cluster LCC, and binary efficiency Effbin) or a weighted network structure (e.g. the efficiency Eff, and the total flow TF). We find that removing a very small fraction of nodes and links with respectively higher strength and weight triggers an abrupt collapse of the weighted functioning measures while measures that evaluate the binary-topological connectedness are almost unaffected. These findings unveil a problematic response-state where the attack toward a small fraction of nodes-links returns the real-world complex networks in a connected but inefficient state. Our findings unveil how the robustness may be overestimated when focusing on the connectedness of the components only. Last, to understand how the networks robustness is affected by link weights heterogeneity, we randomly assign link weights over the topological structure of the real-world networks and we find that highly heterogeneous networks show a faster efficiency decrease under nodes-links removal: i.e. the robustness of the real-world complex networks against nodes-links removal is negatively correlated with link weights heterogeneity
Inhomogeneous two-dimensional photonic media: A statistical study
No full textPhotonic media, in which disorder is introduced, are interesting materials for light management. In this paper, we have performed a statistical study of the average light transmission, over the range of wavelengths 450–1400 nm, for two-dimensional photonic structures with different homogeneity (quantified by the Shannon index). The photonic structure is a square lattice of circular pillars and the homogeneity is varied by clustering pillars in the crystal unit cells. We have calculated the light transmission for 50 different crystal realizations (permutating cluster position in the crystal) for each Shannon index value. Such Monte Carlo Markov Chain method produced the “a posteriori” distribution of the light transmission. We have observed a linear trend of the average transmission as a function of the crystal homogeneity. Furthermore, we have found a linear dependence of the average light transmission on the mean distance between pillars in the photonic structures
Using dominator trees to catch secondary extinction in action
No full textIn ecosystems a single extinction event could eventually precipitate in a mass extinction, involving species that may be several connections away from the target of the perturbation. To forecast the effects of a species removal one can use an algorithm that unfolds a complex food web into a topologically simpler scheme, called dominator tree. This structure has revealed simple. elegant, and highly informative. Aim of this research is to test the dominator tree model in cases where secondary extinction has been observed
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