To capture the impact of spatial heterogeneity of environment and movement of individuals on the persistence and extinction of a disease, Allen et al. in L.J.S. Allen, B.M. Bolker, Y. Lou, A.L. ...Nevai, Asymptotic profiles of the steady states for an SIS epidemic reaction–diffusion model, Discrete Contin. Dyn. Syst. Ser. A 21 (1) (2008) 1–20 proposed a spatial SIS (susceptible-infected-susceptible) reaction–diffusion model, and studied the existence, uniqueness and particularly the asymptotic behavior of the endemic equilibrium as the diffusion rate of the susceptible individuals goes to zero in the case where a so-called low-risk subhabitat is created. In this work, we shall provide further understanding of the impacts of large and small diffusion rates of the susceptible and infected population on the persistence and extinction of the disease, which leads us to determine the asymptotic behaviors of the endemic equilibrium when the diffusion rate of either the susceptible or infected population approaches to infinity or zero in the remaining cases. Consequently, our results reveal that, in order to eliminate the infected population at least in low-risk area, it is necessary that one will have to create a low-risk subhabitat and reduce at least one of the diffusion rates to zero. In this case, our results also show that different strategies of controlling the diffusion rates of individuals may lead to very different spatial distributions of the population; moreover, once the spatial environment is modified to include a low-risk subhabitat, the optimal strategy of eradicating the epidemic disease is to restrict the diffusion rate of the susceptible individuals rather than that of the infected ones.
Origami of thick panels Chen, Yan; Peng, Rui; You, Zhong
Science (American Association for the Advancement of Science),
07/2015, Volume:
349, Issue:
6246
Journal Article
Peer reviewed
Origami patterns, including the rigid origami patterns in which flat inflexible sheets are joined by creases, are primarily created for zero-thickness sheets. In order to apply them to fold ...structures such as roofs, solar panels, and space mirrors, for which thickness cannot be disregarded, various methods have been suggested. However, they generally involve adding materials to or offsetting panels away from the idealized sheet without altering the kinematic model used to simulate folding. We develop a comprehensive kinematic synthesis for rigid origami of thick panels that differs from the existing kinematic model but is capable of reproducing motions identical to that of zero-thickness origami. The approach, proven to be effective for typical origami, can be readily applied to fold real engineering structures.
• Different phosphorus (P)-acquisition strategies may be relevant for species coexistence and plant performance in terrestrial communities on P-deficient soils. However, how interspecific P ...facilitation functions in natural systems is largely unknown.
• We investigated the root physiological activities for P mobilization across 19 coexisting plant species in steppe vegetation, and then grew plants with various abilities to mobilize sorbed P in a microcosm in a glasshouse.
• We show that P facilitation mediated by rhizosphere processes of P-mobilizing species promoted growth and increased P content of neighbors in a species-specific manner. When roots interacted with a facilitating neighbor, Cleistogenes squarrosa and Bromus inermis tended to show greater plasticity of root proliferation or rhizosheath acid phosphatase activity compared with other non-P-mobilizing species. Greater variation in these root traits was strongly correlated with increased performance in the presence of a facilitator. The results also show, for the first time, that P facilitation was an important mechanism underlying a positive complementarity effect.
• Our study highlights that interspecific P-acquisition facilitation requires that facilitated neighbors exhibit a better match of root traits with a facilitating species. It provides a better understanding of species coexistence in P-limited communities.
A therapeutic strategy that can eliminate primary tumours, inhibit metastases, and prevent tumour relapses is developed herein by combining adjuvant nanoparticle-based photothermal therapy with ...checkpoint-blockade immunotherapy. Indocyanine green (ICG), a photothermal agent, and imiquimod (R837), a Toll-like-receptor-7 agonist, are co-encapsulated by poly(lactic-co-glycolic) acid (PLGA). The formed PLGA-ICG-R837 nanoparticles composed purely by three clinically approved components can be used for near-infrared laser-triggered photothermal ablation of primary tumours, generating tumour-associated antigens, which in the presence of R837-containing nanoparticles as the adjuvant can show vaccine-like functions. In combination with the checkpoint-blockade using anti-cytotoxic T-lymphocyte antigen-4 (CTLA4), the generated immunological responses will be able to attack remaining tumour cells in mice, useful in metastasis inhibition, and may potentially be applicable for various types of tumour models. Furthermore, such strategy offers a strong immunological memory effect, which can provide protection against tumour rechallenging post elimination of their initial tumours.
1,3‐Dienes are prevalent substructures in biologically active molecules and versatile building blocks in synthetic chemistry. Herein, using Lewis acids promoted dual 1,3‐sulfur rearrangements, we ...developed an approach for the direct synthesis of 1,3‐dithianyl substituted dienes. This method enabled the synthesis of tri‐ and tetra‐substituted 1,3‐dienes with high stereoselectivity and good yield under mild reaction conditions.
Solar PV (photovoltaic) technology has gained considerable attention worldwide, as it can help reduce the adverse effects of CO2 emissions. Though the government of Pakistan is adopting solar PV ...technology due to its environmental friendliness nature, studies focusing on consumer’s acceptance of solar PV are limited in the country. This research aims to close this knowledge gap by looking into the various considerations that may influence consumers’ willingness to adopt (WTA) solar PV for household purposes. The study further contributes by expanding the conceptual framework of the theory of planned behavior by including three novel factors (perceived risk, perception of self-efficacy, and openness to technology). The analysis is based on questionnaire data collected from 683 households in Pakistan’s provincial capitals, including Lahore, Peshawar, Quetta, Gilgit, and Karachi. The proposed hypotheses are investigated using the state-of-the-art structural equation modeling approach. The empirical results reveal that social norms, perception of self-efficacy, and belief about solar PV benefits positively influence consumers’ WTA solar PV. On the contrary, the perceived risk and solar PV cost have negative effects. Notably, the openness to technology has an insignificant effect. This study can help government officials and policymakers explore cost-effective, risk-free technologies to lessen the environmental burden and make the country more sustainable. Based on research results, study limitations, as well as prospective research directions, are also addressed.
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•Polypyrrole coated graphene foam is used as stretchable electrode.•High areal capacitance and energy density can be obtained.•Structure design improves the stability of conductivity ...during deformation.•The supercapacitor also shows excellent flexibility and stretchability.
Flexible and stretchable all-solid-state supercapacitors are of considerable interest as promising energy storage devices for wearable electronics. Although considerable effort has been devoted to investigate flexible and stretchable supercapacitors, challenges remain in developing supercapacitors with the combination of flexibility, high stretchability and excellent electrochemical performance. In this study, we fabricate highly stretchable electrodes based on a graphene foam/polypyrrole composite through the chemical vapor deposition method and chemical interfacial polymerization method. Because the tensile strain applied to the polypyrrole network is shared by the structural deformation of the graphene foam, the graphene/polypyrrole composite can effectively accommodate the stretching deformation without a significant decay in conductivity. Benefiting from these superior features, an all-solid-state supercapacitor assembled with graphene/polypyrrole compact film electrodes shows a high areal specific capacitance of 258 mF cm−2, energy density of 22.9 μWh cm−2 at a power density of 0.56 mW cm−2 and excellent flexibility (180°) and stretchability (50% strain).
This article reviews the latest progresses regarding the applications of carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), as ...multifunctional nano-probes for biomedical imaging. Utilizing the intrinsic band-gap fluorescence of semi-conducting single-walled carbon nanotubes (SWNTs), fluorescence imaging in the near infrared II (NIR-II) region with enhanced tissue penetration and spatial resolution has shown great promise in recent years. Raman imaging based on the resonance Raman scattering of SWNTs has also been explored by a number of groups for in vitro and in vivo imaging of biological samples. The strong absorbance of CNTs in the NIR region can be used for photoacoustic imaging, and their photoacoustic signals can be dramatically enhanced by adding organic dyes, or coating with gold shells. Taking advantages of metal nanoparticle impurities attached to nanotubes, CNTs can also serve as a T2-contrast agent in magnetic resonance (MR) imaging. In addition, when labeled with radioactive isotopes, many groups have developed nuclear imaging with functionalized CNTs. Therefore CNTs are unique imaging probes with great potential in biomedical multimodal imaging.
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•GF@CNT@MoS2 hybrid foam was synthesized for flexible anode of lithium-ion battery.•Rational structural design offers several merits for lithium storage.•The negligible resistance ...change allows it to be used in flexible battery.•The flexible GF@CNT@MoS2 electrode showed excellent electrochemical performance.
A three-dimensional (3D) flexible hybrid foam composed of graphene foam@carbon nanotubes decorated with MoS2 nanoparticles is synthesized for flexible anode applications in lithium-ion battery. The inner layer of graphene foam (GF), serving as a 3D skeleton of the hybrid foam, enlarges the electrode/electrolyte contact, shortens the diffusion distance of Li+ ions and provides enough internal void space to accommodate the large volume change of MoS2 nanoparticles. The middle carbon nanotubes (CNT) layer wrapped on the graphene foam is more conductive to facilitate electron/ion transport within the hybrid foam and can further enhance the flexibility of the hybrid foam. The outer layer of active MoS2 nanoparticles can provide high specific capacity. Owing to these advantages, the flexible GF@CNT@MoS2 electrodes delivers a specific capacity of 935 mAh g−1 at a current density of 0.1 A g−1, high reversible capacity of 606 mAh g−1 after 200 cycles at 0.2 A g−1.
Graphene aerogel with three-dimensional (3D) interconnected porous structure and good hydrophobicity has been extensively investigated for sorbent materials for oils and demonstrated to be effective. ...Herein, a 3D polyimide–graphene aerogel (PI-GA) nanocomposite has been prepared by introducing water-soluble polyimide (PI). Benefiting from the synergetic effect of PI and GA, the PI-GA nanocomposite exhibits ultralow density, excellent compressibility and hydrophobicity. When evaluated as a sorbent material for oils and organic solvent, PI-GA nanocomposite has high absorption capacity and can separate oil from water rapidly and efficiently. Furthermore, the mechanical squeezing process can be used for the recycling of the PI-GA due to its excellent compressibility. The excellent absorption performance and robust mechanical properties make the PI-GA suitable for oil cleanup and chemical leakage.
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