This paper presents objective priors for robust Bayesian estimation against outliers based on divergences. The minimum -divergence estimator is well-known to work well in estimation against heavy contamination. The robust Bayesian methods by using quasi-posterior distributions based on divergences have been also proposed in recent years. In the objective Bayesian framework, the selection of default prior distributions under such quasi-posterior distributions is an important problem. In this study, we provide some properties of reference and moment matching priors under the quasi-posterior distribution based on the -divergence. In particular, we show that the proposed priors are approximately robust under the condition on the contamination distribution without assuming any conditions on the contamination ratio. Some simulation studies are also presented. 相似文献
A reversible optical transition has been found in thin films of Se---Ge and P---Se---Ge glasses. This optical transition is similar to that found in As---Se---Ge and As---Se---S---Ge glass films; heating causes the shift of the absorption edge to shorter wavelengths, and illumination moves it to longer wavelengths without crystallization. It was found that the presence of arsenic is not always necessary. Fundamental optical properties of these glasses, i.e. absorption constant, optical energy gap, change of the optical energy gap, and the refractive index by heating and illumination are reported. Change of the optical energy gap and the refractive index is small in Se---Ge and P---Se---Ge glasses, compared with that in As---Se---Ge and As---Se---S---Ge glasses. 相似文献
Aliphatic dicarboxylic acid/aliphatic diol‐derived polyesters, poly(butylene succinate) and poly(butylene succinate/adipate), have been hydrolytically degraded in the melt in high‐temperature and high‐pressure water over a wide temperature range of 180–300 °C for periods of up to 30 min. The formation/decomposition of succinic acid (SA), adipic acid (AA), and butane‐1,4‐diol (BD), plus the molecular weight change of PBS and PBSA were then investigated. SA and AA were recovered at maximum yields of 65–80%, whereas BD was recovered at a maximum yield of only 30%, probably because of its decomposition. The obtained results were compared with those reported for aliphatic hydroxycarboxylic acid‐derived polyesters and aromatic dicarboxylic acid/aliphatic diol‐derived polyesters.
A homochiral rare-earth metal Tb complex that exhibited a very large dielectric anisotropic property with a temperature-independent feature is obtained. Our findings on high-dielectric anisotropy will provide a new impetus in this field of materials science. 相似文献
Oxidative cyclization-carbonylation of 2-alkyl-2-propargylcyclohexane-1,3-diones mediated by Pd(TFA)2/2,2′-isopropylidenebis[(4R)-4-(3,4-dimethoxyphenyl)-2-oxazoline] 28 afforded bicyclic-β-alkoxyacrylates in 51-74% yields with 72-82% ee. The products containing quaternary carbon were converted to optically active hydrindanes 33. 相似文献
Fully π-conjugated ladder polymers with a spiral geometry represent a new class of helical polymers with great potential for organic nanodevices, but there is no precedent for an optically active helical ladder polymer totally composed of achiral units. We now report the defect-free synthesis and resolution of a fully π-conjugated helical ladder polymer with a rigid helical cavity, which has been achieved by quantitative and chemoselective acid-promoted alkyne benzannulations of a rationally designed, random-coil achiral polymer followed by chromatographic enantioseparation. Because of a sufficiently high helix-inversion barrier, the isolated excess one-handed helical ladder polymer with a degree of polymerization of more than 15 showed a strong circular dichroism with a dissymmetry factor of up to 1.7×10−2 and is thermally stable, maintaining its optical activity in solution even at 100 °C, as well-supported by molecular dynamics simulation. 相似文献
Reduction of dibenzo[a,e]pentalene 3 (denoted as dibenzopentalene hereafter) with excess lithium gave dilithium dibenzopentalenide 1. Since oxidation of 1 with iodine gave 3, redox behavior between 1 and 3 is controllable and reversible. Reaction of 3 with methyllithium gave lithium 5-methyldibenzopentalenide 5, the formation of which was evidenced by some trapping experiments and X-ray crystallographic analysis. Reactions of 3 with halogens gave 5,10-dihalodibenzopentalenes, 8 and 9. Some optical properties of novel dibenzopentalene derivatives are also demonstrated. 相似文献
Unsymmetrical gold(III)-dithiolene complexes are potential candidates for molecular materials that exhibit thermal structural phase transitions. In this study, unsymmetrical ppy-gold(III) (ppy−=C-deprotonated-2-phenylpyridine(−)) complexes [AuC5] and [AuC6] coordinated by dithiolene ligands containing tetrathiafulvalene (TTF) skeletons with pentylthio (2-{bis(pentylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate(2−)) and hexylthio groups (2-{bis(hexylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate(2−)) were synthesized. Both complexes exhibited a large absorption band at approximately 508 nm, owing to intramolecular ligand-to-ligand charge transfer. One-dimensional columnar structures with head-to-tail molecular arrangements around the metal ions were constructed in the crystals. The flexible alkylthio groups were intercalated into crystalline spaces between dithiolene ligands in the columns. [AuC5] exhibits a simple phase transition at 198 °C between crystalline and isotropic phases irreversibly. The crystalline phase of [AuC6] observed at 25 °C melted at 148 °C. Another crystalline phase grew above 148 °C with a very slow crystallization rate from the liquid phase and was completely transformed into an isotropic phase at 200 °C. 相似文献