Synthesis and characterization of degradable hyperbranched poly(2‐ethyl‐2‐oxazoline)

Hyperbranched poly(2‐ethyl‐2‐oxazoline) was synthesized by a combination of cationic ring‐opening polymerization and the oxidation of thiol to disulfide groups. A three‐arm star poly(2‐ethyl‐2‐oxazoline) (PEtOx) was first synthesized using 1,3,5‐tris(bromomethyl) benzene as an initiator. The star PEtOx was end‐capped with potassium ethyl xanthate. Similarly, a linear PEtOx was synthesized and end‐capped with potassium ethyl xanthate using benzyl bromide as an initiator. Hyperbranched PEtOx was then obtained by in situ cleaving and subsequent oxidation of the star PEtOx and linear PEtOx mixture with n‐butylamine as both a cleaving agent and a base in tetrahydrofuran. The linear PEtOx was used to prevent the formation of gel. The hyperbranched PEtOx can be cleaved with dithiothreitol to trithiol and monothiol polymer. The hyperbranched PEtOx shows no remaining thiols using Ellman's assay. The resulting hyperbranched PEtOx was hydrolyzed to a novel hyperbranched polyethyleneimine with degradable disulfide linkages. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2030–2037     

Stable isotope dilution assay for the accurate determination of tricaine in fish samples by HPLC–MS–MS

Tricaine methanesulfonate is one of most commonly used anesthetics in fish during blood sampling, artificial propagation and long‐distance transportation. In this study, an accurate method for the quantitative determination of tricaine in fish samples by a stable isotope dilution assay coupled with high‐performance liquid chromatography–triple quadrupole mass spectrometry was developed. Tricaine‐D₅ was synthesized and used as an isotopically labeled internal standard for the determination of tricaine. The analytical performance of the method was validated for tricaine determination in marine fish and freshwater fish. The determination of tricaine was linear in the range of 2.0–200.0 μg L^?1. The limit of detection and limit of quantitation for fish muscle tissues were 1.0 and 4.0 μg kg^?1, respectively. Good recoveries were obtained in the range of 92.08–97.50%. The inter‐ and intra‐assay relative standard deviations (RSD values) were investigated, and the values were 0.39–3.01 and 0.85–2.77%, respectively. The values of CCα and CCβ were 10.21–10.43 and 10.42–10.87 μg kg^?1, respectively. The clearance of MS‐222 from grass carp was further studied using our method. The results demonstrate that MS‐222 could be well absorbed and rapidly eliminated after bath administration.     

Convergence of the Best Linear Predictor of a Weakly Stationary Random Field

Journal of Fourier Analysis and Applications - Suppose that $$\{X_{m,n}\}_{(m,n)\in \mathbb {Z}^2}$$ is a centered, weakly stationary random field with spectral density function W. Let $$X'$$...     

Multi-criteria decision analysis for emergency medical service assessment

In emergency management, it is important to arrange the medical resources according to emergency needs. This paper proposes a multi-criteria decision analysis model that combines grey theory and multi-criteria decision making theory to assess the current medical resource situation, find satisfactory solutions, and help the emergency decision makers to take appropriate responses in a timely manner. In addition, the best alternative is identified by the global optimal solution which can provide a theoretical guidance for decision makers to optimize the allocation of medical resources. To validate the proposed model, this paper conducts a case study of medical service assessment in provinces of East China. The results demonstrate that the proposed model can provide objective and comprehensive assessment of medical resources.     

Gold-surface binding of molecular switches studied by M?ssbauer spectroscopy

The nonanuclear coordination compound [Mo^IV{(CN)Fe^III(3-methyl-saldptn)}₈]Cl₄ exhibits multiple spin transitions (3-methyl-saldptn = N,N′-bis(3′′-methyl-2′′-hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. M?ssbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid.     

Low-temperature combustion synthesis of CuCr2O4 spinel powder for spectrally selective paints

CuCr₂O₄ spinel powder with high quality black hue, investigated as solar-absorbing pigment for spectrally selective paint, was synthesized by an environmental friendly sol–gel combustion process using citric acid as the fuel and metal nitrates as oxidizers. Single-phase CuCr₂O₄ spinel crystals were obtained after heat treatment of the as-burnt powder at a low temperature (600 °C) and the average crystallite size of the CuCr₂O₄ powders increased with the calcining temperature. Morphological analysis of powders calcined at various temperatures was done by field emission scanning electron microscopy. CuCr₂O₄ powder calcined at 700 °C was chosen as pigment to fabricate thickness sensitive spectrally selective paint coatings by simple spray-coating technique. For the sake of comparison, the as-burnt powder composed of mixed metal oxides (i.e., CuO and Cr₂O₃) was also used as pigment. The results reveal that the spinel CuCr₂O₄ based paint coatings exhibit much higher spectral selectivity (α _s = 0.88–0.91, ε ₁₀₀ = 0.27–0.35) which is depending on the coating thicknesses than that of coatings using as-burnt powder as pigment (α _s = 0.83–0.88, ε ₁₀₀ = 0.60–0.66). The CuCr₂O₄-based paint coatings showed no visible degradation after 600 h of condensation test and the performance criterion value is 0.04, indicating that the coatings have excellent long term stability.     

A vectorial algorithm with finite element method for prediction of powder segregation in metal injection molding

The design of the mold and the choice of the injection parameters for metal injection molding (MIM) is required to maintain homogeneity of the filled mixture. However, powder segregation is unavoidable in MIM because of the significant difference in densities of the metallic powder and the polymer binder. To achieve an effective prediction of segregation effect, a biphasic model based on mixture theory is employed. The viscous behaviors of each phase and the interaction coefficient between the flows of the two phases should be determined. The solution of two coupled Navier–Stokes equations results in a tremendous computation effort. The previous development of an explicit algorithm makes the biphasic simulation much faster than that of the classic methods. However, it is strongly desired to reduce or even eliminate the numerous global solutions for pressure fields at each time step. Hence, a new vectorial algorithm is proposed and developed to perform the simulation only by vectorial operations. It provides the anticipated efficiency in the simulation of biphasic modeling, and the advantage to use the classic elements of equal‐order interpolations. Some results produced by the two algorithms are compared with the experimental values to validate the new vectorial algorithm. Copyright © 2012 John Wiley & Sons, Ltd.