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We present a novel approach to the portfolio selection problem for a multiperiod investor facing multiple risky assets, trading constraints, and return predictability. Our objective is to maximize mean-variance utility while addressing the computational challenges arising from the curse of dimensionality associated with dynamic programming in the presence of trading constraints. To overcome this, we employ model predictive control, a computationally efficient method for solving the problem. Additionally, we propose the use of a non-parametric Bayesian model, specifically the hierarchical Dirichlet process based Hidden Markov Model (HDP-HMM), to predict the multiperiod mean and covariance of returns. Then, we consider a time-varying maximum drawdown to adjust the risk aversion, which can effectively cope with the limit loss problems. Through extensive simulation studies and empirical analysis, we demonstrate that trading strategies based on our proposed method outperform existing approaches in out-of-sample performance. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Amines are among the most fundamental motifs in chemical synthesis, and the introduction of amine building blocks via selective C—C bond cleavage allows the construction of nitrogen compounds from simple hydrocarbons through direct skeleton modification. Herein, we report a novel method for the preparation of anilines from alkylarenes via Schmidt‐type rearrangement using redox‐active amination reagents, which are easily prepared from hydroxylamine. Primary amines and secondary amines were prepared from corresponding alkylarenes or benzyl alcohols under mild conditions. Good compatibility and valuable applications of the transformation were also displayed. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: Amines are among the most fundamental motifs in chemical synthesis, and the introduction of amine building blocks via selective C—C bond cleavage allows the construction of nitrogen compounds from simple hydrocarbons through direct skeleton modification. Herein, we report a novel method for the preparation of anilines from alkylarenes via Schmidt‐type rearrangement using redox‐active amination reagents, which are easily prepared from hydroxylamine. Primary amines and secondary amines were prepared from corresponding alkylarenes or benzyl alcohols under mild conditions. Good compatibility and valuable applications of the transformation were also displayed. [ABSTRACT FROM AUTHOR]

Abstract: Cerium-doped Lu4Si2O7N2 green phosphors were synthesized by a high-temperature solid-state reaction method under nitrogen atmosphere. Compared with Ce-doped Y4Si2O7N2 phosphors, Ce-doped Lu4Si2O7N2 phosphors showed longer wavelengths of both excitation and emission, lower Stokes shift, and much stronger emission intensity. Based on the first-principles calculations of the two phosphors, the strong emission intensity originates from the large density of states. At last, the effects of Ce3+ concentration on photoluminescence were also examined. [Copyright &y& Elsevier]

Chemical-level details such as protonation and hybridization state are critical for understanding enzyme mechanism and function. Even at high resolution, these details are difficult to determine by X-ray crystallography alone. The chemical shift in NMR spectroscopy, however, is an extremely sensitive probe of the chemical environment, making solid-state NMR spectroscopy and X-ray crystallography a powerful combination for defining chemically detailed three-dimensional structures. Here we adopted this combined approach to determine the chemically rich crystal structure of the indoline quinonoid intermediate in the pyridoxal-5'-phosphate-dependent enzyme tryptophan synthase under conditions of active catalysis. Models of the active site were developed using a synergistic approach in which the structure of this reactive substrate analogue was optimized using ab initio computational chemistry in the presence of side-chain residues fixed at their crystallographically determined coordinates. Various models of charge and protonation state for the substrate and nearby catalytic residues could be uniquely distinguished by their calculated effects on the chemical shifts measured at specifically (13)C- and (15)N-labeled positions on the substrate. Our model suggests the importance of an equilibrium between tautomeric forms of the substrate, with the protonation state of the major isomer directing the next catalytic step.