Hong Kong Baptist University

About: Hong Kong Baptist University is a education organization based out in Hong Kong, China. It is known for research contribution in the topics: Population & China. The organization has 7811 authors who have published 18919 publications receiving 555274 citations. The organization is also known as: Hong Kong Baptist College & HKBU.

A Multifunctional Iridium‐Carbazolyl Orange Phosphor for High‐Performance Two‐Element WOLED Exploiting Exciton‐Managed Fluorescence/Phosphorescence

Abstract: By attaching a bulky, inductively electron-withdrawing trifluoromethyl (CF3) group on the pyridyl ring of the rigid 2-[3- (N-phenylcarbazolyl)]pyridine cyclometalated ligand, we successfully synthesized a new heteroleptic orange-emitting phosphorescent iridium(III) complex [Ir(L1)2(acac)] 1 (HL1 = 5-trifluoromethyl-2-[3-(N-phenylcarbazolyl)]pyridine, Hacac = acetylacetone) in good yield. The structural and electronic properties of 1 were examined by X-ray crystallography and time-dependent DFT calculations. The influence of CF3 substituents on the optical, electrochemical and electroluminescence (EL) properties of 1 were studied. We note that incorporation of the carbazolyl unit facilitates the hole-transporting ability of the complex, and more importantly, attachment of CF3 group provides an access to a highly efficient electrophosphor for the fabrication of orange phosphorescent organic light-emitting diodes (OLEDs) with outstanding device performance. These orange OLEDs can produce a maximum current efficiency of ∼40 cd A−1, corresponding to an external quantum efficiency of ∼12% ph/el (photons per electron) and a power efficiency of ∼24 lm W−1. Remarkably, high-performance simple two-element white OLEDs (WOLEDs) with excellent color stability can be fabricated using an orange triplet-harvesting emitter 1 in conjunction with a blue singlet-harvesting emitter. By using such a new system where the host singlet is resonant with the blue fluorophore singlet state and the host triplet is resonant with the orange phosphor triplet level, this white light-emitting structure can achieve peak EL efficiencies of 26.6 cd A−1 and 13.5 lm W−1 that are generally superior to other two-element all-fluorophore or all-phosphor OLED counterparts in terms of both color stability and emission efficiency.

Involvement of polyamines in the drought resistance of rice

Abstract: This study investigated whether and how polyamines (PAs) in rice (Oryza sativa L.) plants are involved in drought resistance. Six rice cultivars differing in drought resistance were used and subjected to well-watered and water-stressed treatments during their reproductive period. The activities of arginine decarboxylase, S-adenosyl-L-methionine decarboxylase, and spermidine (Spd) synthase in the leaves were significantly enhanced by water stress, in good agreement with the increase in putrescine (Put), Spd, and spermine (Spm) contents there. The increased contents of free Spd, free Spm, and insoluble-conjugated Put under water stress were significantly correlated with the yield maintenance ratio (the ratio of grain yield under water-stressed conditions to grain yield under well-watered conditions) of the cultivars. Free Put at an early stage of water stress positively, whereas at a later stage negatively, correlated with the yield maintenance ratio. No significant differences were observed in soluble-conjugated PAs and insoluble-conjugated Spd and Spm among the cultivars. Free PAs showed significant accumulation when leaf water potentials reached -0.51 MPa to -0.62 MPa for the drought-resistant cultivars and -0.70 MPa to -0.84 MPa for the drought-susceptible ones. The results suggest that rice has a large capacity to enhance PA biosynthesis in leaves in response to water stress. The role of PAs in plant defence to water stress varies with PA forms and stress stages. In adapting to drought it would be good for rice to have the physiological traits of higher levels of free Spd/free Spm and insoluble-conjugated Put, as well as early accumulation of free PAs, under water stress.

Omnidirectional gap and defect mode of one-dimensional photonic crystals with single-negative materials

Abstract: A new type of omnidirectional gaps is theoretically found in one-dimensional photonic crystals (1DPCs) composed of two kinds of single-negative (SNG) (permittivity- or permeability-negative) materials. In contrast to the Bragg gaps, the properties (the central frequency and width of the gap) of such omnidirectional gaps are insensitive to the incident angles and the light polarizations, and are invariant upon the change of scale length. Such omnidirectional gaps result from the interaction of evanescent waves. When a defect layer is introduced, a defect mode appears inside the omnidirectional gap, and the spectral position of the defect mode is almost independent of incident angles and nearly invariant with the scaling.

Tunneling and Propping Up: An Analysis of Related Party Transactions by Chinese Listed Companies

Abstract: We examine a sample of related party transactions between Chinese publicly listed firms and their controlling shareholders during 2001-2002. Minority shareholders in these firms seem to be subject to expropriation through tunneling but also gain from propping up. On balance, there is more tunneling than propping. Both types of firms have larger state ownership compared to the rest of the Chinese market but firms that are propped up are larger and have larger state ownership than firms subject to tunneling. Propped up firms are more likely to have foreign shareholders and to be cross-listed abroad compared to firms that are subject to tunneling. Propped up firms also tend to have worse operating performance in the fiscal year preceding the announcement of the related party transaction. Finally, we find that related party transactions representing tunneling are accompanied by significantly less information disclosure compared to related party transactions representing propping.