Differences and Commonalities in the Gas‐Phase Reactions of Closed‐Shell Metal Dioxide Clusters [MO2]+ (M=V,Nb, and Ta) with Methane

High‐level electronic structure calculations, in combination with Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometric studies, permit the mechanism by which closed‐shell, “naked” [TaO₂]⁺ brings about C?H bond activation of methane to be revealed. These studies also help to understand why the lighter congeners of [MO₂]⁺ (M=V, Nb) are unreactive under ambient conditions.     

Terpenoids from Loxocalyx urticifolius

Two new diterpenoids, loxocalyxin A ( 1 ) and 13‐epiloxocalyxin A ( 2 ), and two new sesquiterpenoids, loxocalyxins B and C ( 3 and 4 , resp.), together with three known compounds, were isolated from the MeOH extract of the whole plant of Loxocalyx urticifolius Hemsl . The structures of the new compounds were established by means of spectroscopic analysis including one‐ and two‐dimensional NMR spectroscopy. All new structures were confirmed by X‐ray crystallographic analysis. Their absolute configurations were established.     

Modified low temperature solid state synthesis and photoluminescent properties of Y0.48Li1.5V1 ? x P x O4:Eu3+ (x = 0.2, 0.4, 0.6) nanophosphors

A modified low temperature solid state process has been proposed to systematically synthesize europium-doped yttrium phosphate-vanadates with general formula Y_0.48Li_1.5V_{1 ? x} P _x O₄:Eu³⁺ (x = 0.2, 0.4, 0.6). All the Y_0.48Li_1.5V_{1 ? x} P _x O₄:Eu³⁺ products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The excitation and emission spectra were measured at room temperature. Y_0.48Li_1.5V_{1 ? x} P _x O₄:Eu³⁺ show the characteristic missions of Eu³⁺ (⁵ D ₀?⁷ F _{1, 2, 3, 4} transitions dominated by ⁵ D ₀?⁷ F ₂), intensities of the products were sensitive to the x value, and the x value had an obvious influence on the (⁵ D ₀?⁷ F ₂)/(⁵ D)₀?⁷ F ₁) intensity ratio of Eu³⁺. In addition, incorporation of Li⁺ ions in the phosphors reduce the amount of Y₂O₃, lower the cost of production, and cause a new phase Li₃VO₄.     

Joint decision and Naive Bayes learning for detection of space multi-target

In the photoelectric tracking system, the detection of space multi-target is crucial for target localization and tracking. The difficulties include the interferences from CCD smear and strong noise, the few characteristics of spot-like targets and the challenge of multiple targets. In this paper, we propose a hybrid algorithm of joint decision and Naive Bayes (JD-NB) learning, and present the duty ratio feature to discriminate the target and smear blocks. Firstly, we extract the proper features and train the parameters of the Naive Bayes classifier. Secondly, target blocks are preliminarily estimated with the Naive Bayes. Lastly, the 4-adjacent blocks of the candidate target blocks are jointed to analyze the distribution pattern and the true target blocks are secondarily extracted by the method of pattern matching. Experimental results indicate that the proposed JD-NB algorithm not only possesses a high recognition rate of better than 90% for the target block, but also effectively overcomes the disturbance of the smear block. Moreover, it performs well in the detection of small and faint targets when the SNR of the block is higher than about 0.014.     

Hyperchaos,chaos, and horseshoe in a 4D nonlinear system with an infinite number of equilibrium points

Based on three-dimensional (3D) Lü chaotic system, we introduce a four-dimensional (4D) nonlinear system with infinitely many equilibrium points. The Lyapunov-exponent spectrum is obtained for the 4D chaotic system. A hyperchaotic attractor and a chaotic attractor are emerged in this 4D nonlinear system. Furthermore, to verify the existence of hyperchaos, the chaotic dynamics of this 4D nonlinear system is also studied by means of topological horseshoe theory and numerical computation.     

A new electronically deficient atropisomeric diphosphine ligand (S)-CF3O-BiPhep and its application in asymmetric hydrogenation

A new electronically deficient atropisomeric diphosphine ligand (S)-CF₃O-BiPhep was synthesized from 1-bromo-3-(trifluoromethoxy)benzene in high yield. The key steps included oxidative coupling with anhydrous ferric chloride and optical resolution by (+)-DMTA. The ligand afforded high performance for Ir-catalyzed asymmetric hydrogenation of quinolines with ee up to 92% and TON up to 25,000. It was also successfully applied to the Pd-catalyzed asymmetric hydrogenation of simple indoles with ee up to 87% and Rh-catalyzed asymmetric 1,4-addition of phenylboronic acid to 2-cyclohexenone with 97% ee.