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Precisely detecting the catalysts' hot spots temperature in situ instantly during photocatalysis is a great challenge but extremely important for chemical reactions. However, no efficient method has been developed to instantly detect the hot spots temperature in situ during photocatalysis. Herein, we designed a simple and convenient method to measure the instant hot spots temperature in situ on the nanostructure surface during photocatalysis by operando Raman spectroscopy using 4-methoxyphenyl isocyanide (MI) as the probe molecule. The νN≡C frequency of MI varied linearly with temperature, which is caused by the orientation change of the MI induced by temperature, leading to the change in the frequency of the νN≡C bond that directly interacts with the nanostructure surface. Using in situ surface-enhanced Raman spectroscopy (SERS), the surface temperature of the catalysts illuminating for each time can be measured instantly. Interestingly, the catalytic activity of the hydrogen evolution reaction (HER) for the Au-Ag/Ag2S heterojunction nanorods (HJNRs) are higher than that for the Ag-Au-Ag HJNRs, although they have a lower surface temperature during photocatalysis; therefore, hot carriers and electronic structure contributed more to the catalytic activity of the Au-Ag/Ag2S HJNRs than that of the Ag-Au-Ag HJNRs. Such an instant hot spots temperature detecting method of catalysts can greatly facilitate the analysis of the mechanism of catalytic processes.

In this article, we develop a new method based on copulas to model correlated inputs in discrete-event stochastic systems. We first define a type of correlated stochastic process, called Copula Cor...

Exploring efficient catalysts for hydrogen evolution reaction (HER) is one of focus points of energy research. In this work, a series of MXene/Pt-x (wherein, x is the adding amount of 6.2 mM H2PtCl6 solution) nanomaterials were fabricated via a facile synthesis method, in which coral-like Pt nanoparticles (NPs) were deposited on Ti3C2Tx MXene. The Pt-loading amounts on the MXene could be simply controlled by varying the adding amounts of H2PtCl6, which would influence the sizes of Pt NPs on the MXene. The optimum catalytic activity was obtained on the MXene/Pt-3 with a low overpotential of 302 mV versus reversible hydrogen electrode (RHE) at 10 mA cm−2, which was about 84 mV less than MXene/Pt-2. The efficiently electrocatalytic HER activity of MXene/Pt-x nanomaterials was due to the electron transfer from MXene to Pt NPs. The HER performance of the MXene/Pt-x nanomaterials was influenced by both Pt-loading amounts and Pt particle sizes. This work expands future applications of MXene-based nanomaterials in clean energy conversion reactions.

Drug delivery nanoplatforms have been applied in bioimaging, medical diagnosis, drug delivery and medical therapy. However, insolubility, toxicity, instability, nonspecific targeting and short retention of many hydrophobic drugs limit their extensive applications. Herein, we have constructed a passive targeting and long retention therapeutic nanoplatform of core-shell gefitinib/poly (ethylene glycol)-polytyrosine nanocomplexes (Gef-PY NCs). The Gef-PY NCs have good water-solubility, non-toxicity (correspond to 1/10 dosage of effective gefitinib (hydrochloride) (Gef·HCl) (normal drug administration and slow-release) and high stability (120 days, 80% drug retention at 4 or 25 °C). The core-shell Gef-PY NCs present unexpected kidney targeting and drug slow-release capacity (ca. 72 h). The good water-solubility, non-toxicity and high stability of Gef-PY NCs effectively solve the bottleneck question that Gef-based therapy could be used only in intraperitoneal injection due to its insolubility and severe toxicity. Such excellent properties (e.g., water-solubility, non-toxicity, high stability, kidney targeting and long retention) of Gef-PY NCs create their prominent anti-fibrosis capabilities, such as decreasing approximately 40% tubulointerstitial fibrosis area and 68% expression of collagen I within 7 days. This therapeutic efficacy is well-matched with that of 10 times the dosage of toxic Gef·HCl. It is very hopeful that Gef-PY NCs could realize clinical applications and such a strategy offers an effective route to design high-efficiency treatments for kidney- and tumor-related diseases.

The need to estimate a function value from sample data at a point that is itself estimated from the same data set arises in many application settings. Such applications include value-at-risk, conditional value-at-risk, and other so-called distortion risk measures. In this note, Peter W. Glynn, Lin Fan, Michael C. Fu, Jian-Qiang Hu, and Yijie Peng provide a simple proof for a central limit theorem for such estimators, and provide an accompanying batching/sectioning methodology that can be used to construct large-sample confidence intervals in the presence of such estimators.

The nano-Al2O3-promoted epoxidation of alkenes with molecular oxygen as the oxidant has been developed, providing an efficient route to a variety of epoxides in moderate to excellent yields. The environmentally friendly and efficient nano-Al2O3 catalyst could be easily recovered and reused five times without significant loss of activity.

This study develops a holistic view of the novel coronavirus (COVID-19) spread worldwide through a spatial–temporal model with network dynamics. By using a unique human mobility dataset containing 547 166 flights with a total capacity of 101 455 913 passengers from January 22 to April 24, 2020, we analyze the epidemic correlations across 22 countries in six continents and particularly the changes in such correlations before and after implementing the international travel restriction policies targeting different countries. Results show that policymakers should move away from the previous practices that focus only on restricting hotspot areas with high infection rates. Instead, they should develop a new holistic view of global human mobility to impose the international movement restriction. The study further highlights potential correlations between international human mobility and focal countries’ epidemic situations in the global network of COVID-19 pandemic. Electronic supplementary material The online version of this article (10.1007/s40305-020-00317-6) contains supplementary material, which is available to authorized users.

Background Stimuli-responsive gold nano-assemblies have attracted attention as drug delivery systems in the biomedical field. However, there are challenges achieving targeted delivery and controllable drug release for specific diseases. Materials and methods In this study, a glutathione (GSH)-modified fluorescent gold nanoparticle termed AuLA-GSH was prepared and a Co2+-induced self-assembly drug delivery platform termed AuLA-GSH-Co was constructed. Both the pH-responsive character and drug loading behavior of AuLA-GSH-Co were studied in vitro. Kidney-targeting capability was investigated in vitro and in vivo. Finally, the anti-fibrosis efficiency of AuLA-GSH-Co in a mouse model of unilateral ureteral obstruction (UUO) was explored. Results AuLA-GSH-Co was sensitive to pH changes and released Co2+ in acidic conditions, allowing it to have controllable drug release abilities. AuLA-GSH-Co was found to improve cellular uptake of Co2+ ions compared to CoCl2 in vitro. AuLA-GSH exhibited specific renal targeting and prolonged renal retention time with low non-specific accumulation in vivo. Moreover, the anti-fibrosis efficiency of AuLA-GSH-Co was higher compared to CoCl2 in a mouse model of unilateral ureteral obstruction (UUO). Conclusion AuLA-GSH-Co could greatly enhance drug delivery efficiency with renal targeting capability and obviously relieve renal fibrosis, providing a promising strategy for renal fibrosis therapy.

This paper studies the parameter estimation for Ornstein–Uhlenbeck stochastic volatility models driven by Lévy processes. We propose computationally efficient estimators based on the method of moments that are robust to model misspecification. We develop an analytical framework that enables closed-form representation of model parameters in terms of the moments and autocorrelations of observed underlying processes. Under moderate assumptions, which are typically much weaker than those for likelihood methods, we prove large-sample behaviors for our proposed estimators, including strong consistency and asymptotic normality. Our estimators obtain the canonical square-root convergence rate and are shown through numerical experiments to outperform likelihood-based methods.

The effect of cosolvent on trace free water in the determination of the contamination degree of jet fuel was investigated. The interference of trace free water on the automatic particle counter can be eliminated by adding isopropanol as a cosolvent to the measured oil sample. Isopropanol can dissolve trace free water in oil. Addition of isopropanol could stabilize the pollution grade of particles with size ≥30 μm (c) at the same level, which is most obviously affected by free water without isopropanol. The standard uncertainty u(X1) is slightly reduced with the addition of isopropanol, and the repeatability and accuracy of the automatic particle counting method are obviously improved. The results show that isopropanol should be added as a cosolvent to eliminate the interference of free water when the contamination degree of jet fuel oil samples with obvious free water is determined by the automatic particle counting method.

The structure transformation between Au–Pd alloy and core–shell icosahedral nanoparticles was achieved by a one-step aqueous-phase strategy. This strategy provided a way to tune the structure and atomic distribution of Au–Pd icosahedral nanoparticles. It could modulate the electronic structure of Pd, achieving promoted electrocatalytic ability toward the hydrogen evolution reaction.

Simulation is often used to estimate the performance of alternative system designs for selecting the best. For a complex system, high-fidelity simulation is usually time-consuming and expensive. In this paper, we provide a new framework that integrates information from the multifidelity models to increase efficiency for selecting the best. A Gaussian mixture model is introduced to capture performance clustering information in the multifidelity models. Posterior information obtained by a clustering analysis incorporates both cluster-wise information and idiosyncratic information for each design. We propose a new budget allocation method to efficiently allocate high-fidelity simulation replications, utilizing posterior information. Numerical experiments show that the proposed multifidelity framework achieves a significant boost in efficiency.

Hydrophilic PEGylated porous self-assembled nanomembranes (PSANMs) with average thickness and pore diameter of ca. 10 and 20-24 nm were successfully prepared by an emulsification-induced programmable self-assembly strategy. The hydrophilicity, anti-biofouling, and anti-thrombosis properties of PEGylated PSANMs were largely improved in comparison with the nonfunctionalized PSANMs, which could transform into hydrophilic (PEGylated PSANMs, minimum water contact angle: 38.8°) from hydrophobic units (PSANMs, maximum water contact angle: 137.5°) with increasing PEG density and length. The total protein adsorption of PEGylated PSANMs was about six times lower than that of the PSANMs, while the thrombosis of the PEGylated PSANMs (maximum R-time: 5.37 min) was also greatly relieved in comparison with the PSANMs (minimum R-time: 2.93 min). Such PEG-modified PSANMs may have applications in drug delivery and tissue and organ repair in vivo.

Triptolide (TP) has been widely used in clinical medicine; however, it has created a dilemma due to its toxicity and nonspecificity. Here, we reported a biocompatible and high-efficiency renal-targeting nanoplatform for renal ischemia/reperfusion injury (IRI) therapy, in which the toxic drug of TP was encapsulated into folate (FA)-modified Pluronic F127/P123 nanoparticles (FPNPs). The TP-loaded FPNPs (TP-FPNPs) had good stability and could effectively reduce the cytotoxicity of TP. Compared with the Pluronic nanoparticles (PNPs) group, cellular uptake ability of FPNPs significantly improved because of folate receptor-mediated endocytosis effect. Ex vivo organ imaging and pharmacokinetic results indicated that FPNPs possessed high kidney selectivity and long retention time. The therapeutic effect of TP-FPNPs on renal IRI was more superior to that of free TP, such as lower acute tubular injury index (2.9-fold), renal function indexes of serum creatinine (4.3-fold), urea nitrogen (2.0-fold), and Western blotting (2.4-fold). Systemic toxicity assay suggested that TP-FPNPs had much lower nephrotoxicity, hepatotoxicity, and genital system toxicity than free TP. Thus, renal-targeting FPNPs will be a potential delivery platform of hydrophobic drugs for treatment of renal diseases.

We develop new estimators for the parameters of Ornstein-Uhlenbeck processes driven by compound Poisson processes, which can be considered as a class of stochastic hybrid systems. Our estimators are derived based on the method of moments. We also establish the central limit theorem for the proposed estimators. Numerical experiments are provided to show that our method performs better when compared with the existing methods, especially in cases when the jumps of the compound Poisson process are relatively rare.

The styrenated sulfur- and phosphorus-free organic titanate (STAE) was synthesized via an in situ method with soybean oil, diethanolamine, and isopropyl titanate. The tribological and antioxidant behavior of the as-synthesized STAE as an additive in PAO was evaluated by a four-ball test, a rotary oxygen bomb test (ROBT), and differential scanning calorimetry (DSC), and its oxidative stability was estimated through thermogravimetric analysis (TGA). The as-synthesized STAE exhibits excellent antiwear and load-carrying capacities as well as good antiwear synergism with zinc dialkyldithiophosphate (ZDDP) in poly-α-olefin (PAO). STAE in PAO also showed good synergistic antioxidation effects with the traditional additive p,p-(dioctyldiphenylamine (DODPA). This is because STAE can effectively reduce the oxidation rate of DODPA, which was confirmed by the results of Fourier transform infrared spectroscopy (FTIR) and gas chromatography-tandem mass spectrometry (GC/MS).

Distortion risk measure, defined by an integral of a distorted tail probability, has been widely used in behavioral economics and risk management as an alternative to expected utility. The sensitivity of the distortion risk measure is a functional of certain distribution sensitivities. We propose a new sensitivity estimator for the distortion risk measure that uses generalized likelihood ratio estimators for distribution sensitivities as input and establish a central limit theorem for the new estimator. The proposed estimator can handle discontinuous sample paths and distortion functions.

Segmented metal-metal heterostructure nanorods/nanowires are very promising for development in photoelectric devices, wearable electronics, biomedicine, and energy storage due to unique surface and interface and adjustable electronic and optical properties. Regretfully, most of the segmented heterojunctions are presently synthesized in organic solvent, and its electronic dynamics is still rarely studied and poorly understood. Here, we reported a pressure-assisted one-step aqueous-phase strategy to successfully synthesize segmented Ag-Au-Ag heterojunction nanorods (HJNRs), the aspect ratios and heterojunction contents of which can be well controlled by varying pressure value. The heterojunction-induced femtosecond-to-nanosecond dynamics in 1D direction of the Ag-Au-Ag HJNRs were for the first time acquired and presented a unique regularity tendency (e.g., electron-phonon scattering time). The unprecedented aqueous-phase strategy opens up horizons of synthesis of other segmented metal-metal HJNRs, and the fascinating Ag-Au-Ag HJNRs are hopeful for the development of a new class devices in photothermal and photoelectronic fields.

We study a decentralized admission control problem with capacity borrowing. In this problem, the admission decision is made by each server who is assigned dedicated capacity. However, a server can borrow capacity from other servers if his dedicated capacity is exhausted. The borrower compensates the lender by a payment equal to the ‘‘borrowing cost’’. Hence, the servers share their capacities via borrowing, but they also compete against each other for their pooled capacities. We formulate this problem as a stochastic dynamic game and characterize the equilibrium strategic admission behavior of servers. We show that the critical factors that affect the equilibrium behavior and the system revenue are the magnitude of the borrowing cost, the arrival rate of customers and the revenue difference between different classes of customers. We have identified conditions under which servers maximizing their own payoffs end up making decisions that benefit the system. Our study highlights the important roles that the borrowing cost plays in shaping servers' behavior in service systems and provides concrete guidance for practitioners to design a decentralized admission control system.

We propose a simulation-based value iteration algorithm for approximately solving infinite horizon discounted MDPs with continuous state spaces and finite actions. At each time step, the algorithm employs the shrinking ball method to estimate the value function at sampled states and uses historical estimates in an interpolation-based fitting strategy to build an approximator of the optimal value function. Under moderate conditions, we prove that the sequence of approximators generated by the algorithm converges uniformly to the optimal value function with probability one. Simple numerical examples are provided to compare our algorithm with two other existing methods.