In this paper, we establish the theory of basic reproduction ratio
R
0
for a large class of time-delayed compartmental population models in a periodic environment. It is proved that
R
0
serves as a ...threshold value for the stability of the zero solution of the associated periodic linear systems. As an illustrative example, we also apply the developed theory to a periodic SEIR model with an incubation period and obtain a threshold result on its global dynamics in terms of
R
0
.
In this paper, we develop the theory of basic reproduction ratios
R
0
for abstract functional differential systems in a time-periodic environment. It is proved that
R
0
-
1
has the same sign as the ...exponential growth bound of an associated linear system. Then we apply it to a time-periodic Lyme disease model with time-delay and obtain a threshold type result on its global dynamics in terms of
R
0
.
Radicals are an important class of versatile and highly reactive species. Compared with the wide applications of various C-centred radicals, however, the N-radical species including N-centred ...radicals and radical ions remain largely unexplored due to the lack of convenient methods for their generation. In recent years, visible light photoredox catalysis has emerged as a powerful platform for the generation of various N-radical species and methodology development towards the synthesis of diverse N-containing compounds. In this tutorial review, we highlight recent advances in this rapidly developing area with particular emphases put on the working models and new reaction design.
Abstract
Glucose electrolysis offers a prospect of value-added glucaric acid synthesis and energy-saving hydrogen production from the biomass-based platform molecules. Here we report that ...nanostructured NiFe oxide (NiFeO
x
) and nitride (NiFeN
x
) catalysts, synthesized from NiFe layered double hydroxide nanosheet arrays on three-dimensional Ni foams, demonstrate a high activity and selectivity towards anodic glucose oxidation. The electrolytic cell assembled with these two catalysts can deliver 100 mA cm
−2
at 1.39 V. A faradaic efficiency of 87% and glucaric acid yield of 83% are obtained from the glucose electrolysis, which takes place via a guluronic acid pathway evidenced by in-situ infrared spectroscopy. A rigorous process model combined with a techno-economic analysis shows that the electrochemical reduction of glucose produces glucaric acid at a 54% lower cost than the current chemical approach. This work suggests that glucose electrolysis is an energy-saving and cost-effective approach for H
2
production and biomass valorization.
Remote control: New strategies for the activation of remote C(sp3)−H bonds by photoredox‐catalyzed (PC) radical translocation via O‐ and N‐centered radicals have recently been described. These ...methods enable the controlled and site‐selective functionalization of inert C(sp3)−H bonds and provide new opportunities for reaction design (HAT=hydrogen atom transfer).
Visible-light photocatalysis has recently received increasing attention from chemists because of its wide application in organic synthesis and its significance for sustainable chemistry. This ...catalytic strategy enables the generation of various reactive species, frequently without stoichiometric activation reagents under mild reaction conditions. Manipulation of these reactive intermediates can result in numerous synthetically useful bond formations in a controllable manner. In this Account, we describe our recent advances in the rational design and strategic application of photocatalysis in the synthesis of various synthetically and biologically important heterocycles. Our main research efforts toward this goal can be classified into four categories: formal cycloaddition and cyclization reactions, radical-mediated olefin functionalization/cyclization cascades, photocatalytic generation and cyclization of N-centered radicals, and photocatalytic functionalization of heterocycles by visible-light-induced dual catalysis. Inspired by the wide application of tertiary amines as reductive additives in photoredox catalysis, we exploited a series of readily accessible or rationally designed tertiary amines with reactive sites in a range of photocatalytic formal cycloaddition and cyclization reactions, providing efficient access to diverse nitrogen heterocycles. Employing various photogenerated radical species, we further developed a series of radical-mediated olefin functionalization/cyclization cascade reactions to successfully assemble various five- and six-membered heterocycles. We have also achieved for the first time the direct catalytic conversion of recalcitrant N–H bonds into neutral N-centered radicals through a visible-light-photocatalytic oxidative deprotonation electron transfer. Using this generic strategy, we have devised several types of radical cyclizations of unsaturated hydrazones, leading to the construction of diversely functionalized pyrazoline and pyridazine derivatives in good yields and selectivity. Moreover, we have demonstrated that this photocatalysis can serve as a mild and highly selective tool for direct functionalization of heterocycles because of its powerful capability to controllably generate diverse reactive intermediates under mild reaction conditions. Guided by the fundamental principles of photocatalysis and the redox properties of the photocatalysts, we successfully developed an array of dual-catalyst systems by combining the photocatalysts with palladium, nickel, or amine, enabling efficient and selective coupling reactions. An intriguing phototandem catalytic system using a single photocatalyst was also identified for the development of cascade reactions. Notably, some of the newly developed methodologies have also been successfully utilized for late-stage modification of biologically active natural compounds and complex molecules and as key steps for formal synthesis of natural products. This Account presents a panoramic view and the logic of our recent contributions to the design, development, and application of photocatalytic systems and reactions that provide not only methods for the efficient synthesis of heterocycles but also useful insights into the exploration of new photochemical reactions.
Nitroarenes are stable, low‐cost, and readily available starting materials. The directly utilize nitroarenes in synthetically valuable C−N bond formation is of great significance, because the ...pre‐reduction step to corresponding amines can be avoided. Previously, phosphines and carbon monoxide (CO) are the most widely used reductants in the reductive cyclization or/and carbonylation of nitroarenes. Currently, much attention has been attracted to organosilanes as new potential reducing agents, not only because they are inexpensive, easy‐to‐handle, and mild reagents, but also various novel reaction models of nitroarenes have been explored. In this review, we mainly summarize the recent progress on the reductive coupling of nitroarenes by using organosilanes as the end reductants. We hope that a deep understanding of the reaction model and underlying working mechanism can provide a timely guideline for researchers who are interested in this fantastic area, leading to further exploration of practical and efficient reductive coupling of nitroarenes for C−N bond formation and N‐heterocycle synthesis.
Tumor hypoxia greatly suppresses the therapeutic efficacy of photodynamic therapy (PDT), mainly because the generation of toxic reactive oxygen species (ROS) in PDT is highly oxygen‐dependent. In ...contrast to ROS, the generation of oxygen‐irrelevant free radicals is oxygen‐independent. A new therapeutic strategy based on the light‐induced generation of free radicals for cancer therapy is reported. Initiator‐loaded gold nanocages (AuNCs) as the free‐radical generator were synthesized. Under near‐infrared light (NIR) irradiation, the plasmonic heating effect of AuNCs can induce the decomposition of the initiator to generate alkyl radicals (R.), which can elevate oxidative‐stress (OS) and cause DNA damages in cancer cells, and finally lead to apoptotic cell death under different oxygen tensions. As a proof of concept, this research opens up a new field to use various free radicals for cancer therapy.
A therapeutic strategy using gold nanocages loaded with initiator as a light‐induced free‐radical generator is presented. The generation of free radicals is oxygen‐independent. The therapeutic mechanism of the generated free radicals was revealed.
•The review shows building energy consumption modeling and forecasting techniques.•Eight specific data-driven forecasting methods are described.•A focus is given on the data pre-processing methods ...and forecasting algorithms.•The supervised, unsupervised, reinforcement and machine learning tasks is discussed.
Building energy consumption modeling and forecasting is essential to address buildings energy efficiency problems and take up current challenges of human comfort, urbanization growth and the consequent energy consumption increase. In a context of integrated smart infrastructures, data-driven techniques rely on data analysis and machine learning to provide flexible methods for building energy prediction. The present paper offers a review of studies developing data-driven models for building scale applications. The prevalent methods are introduced with a focus on the input data characteristics and data pre-processing methods, the building typologies considered, the targeted energy end-uses and forecasting horizons, and accuracy assessment. A special attention is also given to different machine learning approaches. Based on the results of this review, the latest technical improvements and research efforts are synthesized. The key role of occupants’ behavior integration in data-driven modeling is discussed. Limitations and research gaps are highlighted. Future research opportunities are also identified.
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