Semiparametric estimation for accelerated failure time mixture cure model allowing non-curable competing risk

The mixture cure model is the most popular model used to analyse the major event with a potential cure fraction. But in the real world there may exist a potential risk from other non-curable competing events. In this paper, we study the accelerated failure time model with mixture cure model via kernel-based nonparametric maximum likelihood estimation allowing non-curable competing risk. An EM algorithm is developed to calculate the estimates for both the regression parameters and the unknown error densities, in which a kernel-smoothed conditional profile likelihood is maximised in the M-step, and the resulting estimates are consistent. Its performance is demonstrated through comprehensive simulation studies. Finally, the proposed method is applied to the colorectal clinical trial data

Valuation of equity-indexed annuity under stochastic mortality and interest rate

An equity-indexed annuity (EIA) contract offers a proportional participation in the return on a specified equity index, in addition to a guaranteed return on the single premium. In this paper, we discuss the valuation of equity-indexed annuities under stochastic mortality and interest rate which are assumed to be dependent on each other. Employing the method of change of measure, we present the pricing formulas in closed form for the most common product designs: the point-to-point and the annual reset. Finally, we conduct several numerical experiments, in which we analyze the relationship between some parameters and the pricing of EIAs.Equity-indexed annuity Stochastic mortality Stochastic interest rate

Constructing Narrowband Thermally Activated Delayed Fluorescence Materials with Emission Maxima Beyond 560 nm Based on Frontier Molecular Orbital Engineering

The development of purely organic materials with narrowband emission in long wavelength region beyond 560 nm still remains a great challenge. Herein, we present a modification approach of multiple resonance (MR) skeleton with electron donor based on frontier molecular orbital engineering (FMOE), resulting in significant red-shift emission of target molecules. Subsequently, the parent MR skeleton is functionalized by boron esterification reaction and changed into a universal building block, namely, the key intermediate BN-Bpin, for molecular structure optimizations. BN-Bpin has been employed to construct a series of highly efficient thermally activated delayed fluorescence (TADF) materials with high color purity through one-step Suzuki coupling reaction. The target molecule perfectly integrates the inherent advantages of MR skeleton and spatial separation typical donor–acceptor (D–A) structure. The results demonstrate that the ingenious modulation of the acceptor is an effective approach to achieve bathochromic emission and narrowband emission simultaneously.</p

Constructing Narrowband Heavy Metal Platinum (II) Complex by Integrating Multiple Resonance Molecular System

The narrowband emission required by wide color gamut display is an extremely important research topic for any luminescence mechanism, which has made significant progress in traditional fluorescence and thermally activated delayed fluorescence (TADF) based on purely organic compounds, but is far from mature in phosphorescence based on metal organic complexes. Herein, we propose a feasible molecular design paradigm for constructing the desirable narrowband-emission organic electroluminescence (EL) emitter by integrating an original multi-resonance thermally activated delayed fluorescent (MR-TADF) fragment into the classical heavy metal platinum (II) complex. The target model platinum (II) complex BNCPPt shows green emission with a single peak at 497 nm and the quite narrow full-width at half-maximum (FWHM) of 27 nm in toluene

Health Risk Assessment Based on Source Identification of Heavy Metal(loid)s: A Case Study of Surface Water in the Lijiang River, China

In this study, 24 surface water samples were collected from the main trunk/tributary of the Lijiang River during the wet season (April) and the dry season (December) in 2021. The total concentration of 11 heavy metal(loid)s (Al, Cu, Pb, Zn, Cr, Ni, Co, Cd, Mn, As, and Hg) was determined to investigate their physicochemical properties and spatial-temporal distribution characteristics. The heavy metal evaluation index (HEI) and the positive matrix factorization (PMF) model were employed to evaluate water quality and to reveal quantitatively identified pollution sources for further investigation to obtain a health risk assessment using the hazard index (HI) and carcinogenic risk (CR) of various pollution sources. The mean concentrations of heavy metal(loid)s in surface water in the wet and dry seasons were ranked as: Al > Mn > Zn > Ni > Cd > Cr > Cu > As >Hg = Pb > Co, with the mean concentration of Hg being higher than the national Class II surface water environmental quality standard (GB3838-2002). In terms of time scale, the concentration of most heavy metal(loid)s was higher in the wet season; most heavy metal(loid)s were distributed mainly in the midstream area. HEI index indicated that the main water quality status was “slightly affected” in the study area. Five potential sources of pollution were obtained from the PMF model, including industrial activities, traffic sources, agricultural activities, domestic waste emissions, and natural resources. The source-oriented risk assessment indicated that the largest contributions of HI and CR were agricultural sources in the Lijiang River. This study provides a “target” for the precise control of pollution sources, which has a broad impact on improving the fine management of the water environment in the basin

Attaching Strong Auxiliary Acceptor onto B-N-Containing Multiple Resonance Framework and Achieving Highly Efficient Electroluminescence with Ultrahigh Color Purity

The development and enrichment of organic materials with narrowband emission in longer wavelength region beyond 515 nm still remains a great challenge. Herein, a series of unique narrowband green thermally activated delayed fluorescence (TADF) emitters has been constructed based on a synthetic strategy by localized attachment of acceptor onto B-N-containing multiple resonance (MR) framework. The precise modulation of acceptor is an ingenious approach for achieving bathochromic shift and narrowband emission, simultaneously. Furthermore, an important synthetic methodology has been proposed to functionalize MR skeleton and generate a universal building block, which can be utilized to construct multifarious TADF materials with ultrahigh color purity through a simple one-step Suzuki coupling reaction. The DtCzB-TPTRZ-based organic light-emitting diode (OLED) exhibits pure green emission with Commission Internationale de L’Eclairage (CIE) coordinates of (0.23, 0.68), and achieves remarkable maximum external quantum efficiency (EQE) of 30.6% with low efficiency roll-off.</p

Purely Organic Phosphor Sensitization Based Highly Efficient Electrofluorescence Material

Pure organic room temperature phosphorescence (RTP) materials are considered as potential candidates for replacing precious metal-based complexes to fabricate highly efficient organic light emitting devices (OLEDs). However, for reported RTP materials, low photoluminescence quantum yields (PLQYs) in thin film state seriously impede their applications in OLEDs. On the other hand, how using normal organic fluorescence materials to fabricate OLEDs with an internal quantum efficiency (IQE) over 25% remains a great unaddressed issue beyond the thermally activated delayed fluorescence (TADF) sensitization approach. Here, we establish a strategy to construct highly efficient OLEDs based on pure organic RTP material sensitized fluorescence emitter. The key point for our strategy is that benzimidazole-triazine molecules (PIM-TRZ), 2,6-di(phenothiazinyl)naphthalene (β-DPTZN) and 5,6,11,12-tetraphenylnaphthacene (rubrene) were screened as host, phosphor sensitizer and fluorescent emitter, respectively. Detail photophysical characterizations demonstrate that the host material PIMTRZ with unique RTP nature is critical for achieving phosphor sensitizing process. As an organic RTP compound, the singlet and triplet state energy levels of β-DPTZN perfectly match with those of PIMTRZ, resulting in the formation and lasting existence of phosphor’s excitons in emitting layer. The large overlap between the absorption spectrum of rubrene and PL spectrum of PIM-TRZ:10% β-DPTZN film can facilitate the Förster energy transfer from the triplet β-DPTZN to the singlet rubrene and the finally displayed fluorescence is derived from singlet excited states of rubrene. The perfect collocation of host, phosphorescent sensitizer and fluorescent emitter in the emitting layer promise the predominant performance of the devices with external quantum efficiency (EQE) of 15.7%. The PLQY of emitting layer is 60.3%, and therefore about 90% carrier injection induced excitons are harvested for light emission. We present a new strategy to fabricate efficient fluorescent devices by employing ingenious combination of host, phosphorescent sensitizer and fluorescent emitter, which is significant to the development of OLEDs.<br /