Joint AFT random-effect modeling approach for clustered competing-risks data

Competing risks data arise when occurrence of an event hinders observation of other types of events, and they are encountered in various research areas including biomedical research. These data have been usually analyzed using the hazard-based models, not survival times themselves. In this paper, we propose a joint accelerated failure time (AFT) modeling approach to model clustered competing risks data. Times to competing events are assumed to be log-linear with normal errors and correlated through a scaled random effect that follows a zero-mean normal distribution. Inference on the model parameters is based on the h-likelihood. Performance of the proposed method is evaluated through extensive simulation studies. The simulation results show that the estimated regression parameters are robust against the violation of the assumed parametric distributions. The proposed method is illustrated with three real competing risks data sets.</p

Multifunctional Bi₂O₂(OH)(NO₃) Nanosheets with {001} Active Exposing Facets: Efficient Photocatalysis, Dye-Sensitization, and Piezoelectric-Catalysis

Exploration for multiresponsive catalytic materials and synthesis of highly active exposing crystal facets are challenging subjects for catalysis research. In this work, well-defined Bi₂O₂(OH)­(NO₃) nanosheets (BON-S) with a dominantly exposed {001} active facet were synthesized by a sodium-dodecyl-benzenesulfonate-assisted (SDBS-assisted) soft-chemical route. BON-S presents far superior photocatalytic activity compared to bulk materials as well as a universal performance for degradation of contaminants and antibiotics under UV light. The profoundly enhanced photocatalytic activity basically stems from the largely shortened diffusion pathway of photogenerated electrons (e^–) and holes (h⁺), favoring their migration from bulk to the surface of the catalyst under the internal electric field between [Bi₂O₂(OH)]⁺ and NO₃^– layers along the [001] direction. The photocatalytic active species production rates of BON-S are determined to be 3.14 μmol L^–1 min^–1 for superoxide radicals (^•O₂^–) and 0.03 μmol L^–1 min^–1 for hydroxyl radicals (^•OH). BON-S also shows an enhanced visible-light-responsive dye-sensitization degradation activity with Rhodamine B (RhB) as a sensitized medium to provide photoinduced e^–. Moreover, for the first time we unearth that Bi₂O₂(OH)­(NO₃) demonstrates an ultrasonic-assisted piezoelectric-catalytic performance for decomposition of methyl orange, bisphenol A, and tetracycline hydrochloride, and ^•OH dominates the piezoelectric-catalytic process with an evolution rate of 7.13 μmol L^–1 h^–1, which far exceeds the photocatalytically induced one. This study may cast new inspiration on developing a new microstructure-design strategy for high photocatalytic/dye-sensitization performance, and furnishes a novel piezoelectric-catalytic material for environmental applications

Membranes for Continuous Nonenergized Air Freshener Perfume Delivery

Membrane-based liquid air fresheners are attracting significant market interest because of their small size and ability to allow continuous delivery of perfume compounds without the need of external energy sources. However, the air freshener membranes that enable the nonenergized delivery are rarely reported in the literature except in patents. For the first time, we investigated a commercial air freshener membrane systematically to provide thorough characterizations of the membrane materials, morphology, and pore information. The interaction between a model perfume containing four compounds and the membrane was also studied through liquid wetting and contact angle measurements. Long-term tests to track the air freshener revealed that the perfume release rate was dependent on the perfume reservoir composition in a controlled external environment. Lastly, perfume transport through the membrane was investigated for the correlation of membrane properties and liquid flux through the membrane. This pioneering study may provide essential information for future improvement over the existing air freshener membranes to enable continuous perfume delivery without an energy provision

Asymmetric Access to the Smallest Enolate Intermediate via Organocatalytic Activation of Acetic Ester

An NHC-catalyzed activation of acetic esters to afford enolate intermediates is disclosed. The catalytically generated triazolium enolate intermediates serve as two-carbon nucleophiles that undergo highly enantioselective reactions with enones and α,β-unsaturated imines to give α-unsubstituted δ-lactones and lactams, respectively

Metal–Organic Framework Derived Magnetic Nanoporous Carbon: Novel Adsorbent for Magnetic Solid-Phase Extraction

The fabrication of a magnetic nanoporous carbon (MNPC) via one-step direct carbonization of Co-based metal–organic framework has been achieved without using any additional carbon precursors. The morphology, structure, and magnetic behavior of the as-prepared Co-MNPC were characterized by using the techniques of scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Raman spectroscopy, N₂ adsorption, and vibrating sample magnetometer. The Co-MNPC has a high specific surface area, large pore volume, and super paramagnetism. Its performance was evaluated by the magnetic solid-phase extraction of some neonicotinoid insecticides from water and fatmelon samples followed by high-performance liquid chromatographic analysis. The effects of the main experimental parameters that could affect the extraction efficiencies were investigated. The results demonstrated that the Co-MNPC had an excellent adsorption capability for the compounds

Investigation into Maximum Temperature of Synthesis Reaction and Accumulation in Isothermal Semibatch Processes

Maximum temperature of synthesis reaction (MTSR), which is a function of the process temperature (<i>T</i>_p) and the maximum accumulation (<i>X</i>_ac,max), is an important criterion for process hazard assessment and reactor design. For isothermal reactions, <i>X</i>_ac,max is influenced by kinetics, thermodynamics and operating conditions. To analyze the behaviors of MTSR and <i>X</i>_ac,max, a mathematical model for isothermal homogeneous semibatch reactors is proposed. The influence of several dimensionless parameters (ν_ADa<i>R</i>_E, γ, Δτ) and reaction orders on MTSR and <i>X</i>_ac,max are also studied. It is found that the MTSR curves for slow and highly exothermic reactions tend to present a “S” shape. On the basis of the above analysis, a semiempirical criterion is suggested to quantificationally decide whether the MTSR curves are monotonously increasing or not. A typical esterification reaction is conducted to validate the proposed model and the semiempirical criterion. Applications using the mathematical model and the criterion in hazard assessment and process optimization are also discussed

Investigation into Maximum Temperature of Synthesis Reaction and Accumulation in Isothermal Semibatch Processes

Maximum temperature of synthesis reaction (MTSR), which is a function of the process temperature (<i>T</i>_p) and the maximum accumulation (<i>X</i>_ac,max), is an important criterion for process hazard assessment and reactor design. For isothermal reactions, <i>X</i>_ac,max is influenced by kinetics, thermodynamics and operating conditions. To analyze the behaviors of MTSR and <i>X</i>_ac,max, a mathematical model for isothermal homogeneous semibatch reactors is proposed. The influence of several dimensionless parameters (ν_ADa<i>R</i>_E, γ, Δτ) and reaction orders on MTSR and <i>X</i>_ac,max are also studied. It is found that the MTSR curves for slow and highly exothermic reactions tend to present a “S” shape. On the basis of the above analysis, a semiempirical criterion is suggested to quantificationally decide whether the MTSR curves are monotonously increasing or not. A typical esterification reaction is conducted to validate the proposed model and the semiempirical criterion. Applications using the mathematical model and the criterion in hazard assessment and process optimization are also discussed

Image_4_Interaction between seawater carbon dioxide dynamics and stratification in shallow coastal waters: A preliminary study based on a weekly validated three-dimensional ecological model.tif

Shallow coastal waters (SCWs) have attracted wide attention in recent years due to their strong carbon sequestration capacity. However, the complex carbon dioxide (CO2) dynamics in the water column makes it difficult to estimate the air–water CO2 fluxes (FCO2) accurately. We developed a numerical model of CO2 dynamics in water based on field measurements for a typical stratified semi-enclosed shallow bay: the Yatsushiro Sea, Japan. The developed model showed an excellent ability to reproduce the stratification and CO2 dynamics of the Yatsushiro Sea. Through numerical model simulations, we analyzed the annual CO2 dynamics in the Yatsushiro Sea in 2018. The results show that the effect of stratification on the CO2 dynamics in seawater varies greatly depending on the distance from the estuary and the period. In the estuarine region, stratification manifests itself throughout the year by promoting the maintenance of a high partial pressure of CO2 (pCO2) in surface waters, resulting in surface pCO2 being higher than atmospheric pCO2 for up to 40 days during the flood period (average surface pCO2 of 539.94 µatm). In contrast, in areas farther from the estuary, stratification mainly acts to promote the maintenance of high pCO2 in surface waters during periods of high freshwater influence. Then changes to a lower surface pCO2 before the freshwater influence leads towards complete dissipation. Finally, we estimated the FCO2 of the Yatsushiro Sea in 2018, and the results showed that the Yatsushiro Sea was a sink area for atmospheric CO2 in 2018 (−1.70 mmol/m2/day).</p

Table_1_Interaction between seawater carbon dioxide dynamics and stratification in shallow coastal waters: A preliminary study based on a weekly validated three-dimensional ecological model.xlsx

Shallow coastal waters (SCWs) have attracted wide attention in recent years due to their strong carbon sequestration capacity. However, the complex carbon dioxide (CO2) dynamics in the water column makes it difficult to estimate the air–water CO2 fluxes (FCO2) accurately. We developed a numerical model of CO2 dynamics in water based on field measurements for a typical stratified semi-enclosed shallow bay: the Yatsushiro Sea, Japan. The developed model showed an excellent ability to reproduce the stratification and CO2 dynamics of the Yatsushiro Sea. Through numerical model simulations, we analyzed the annual CO2 dynamics in the Yatsushiro Sea in 2018. The results show that the effect of stratification on the CO2 dynamics in seawater varies greatly depending on the distance from the estuary and the period. In the estuarine region, stratification manifests itself throughout the year by promoting the maintenance of a high partial pressure of CO2 (pCO2) in surface waters, resulting in surface pCO2 being higher than atmospheric pCO2 for up to 40 days during the flood period (average surface pCO2 of 539.94 µatm). In contrast, in areas farther from the estuary, stratification mainly acts to promote the maintenance of high pCO2 in surface waters during periods of high freshwater influence. Then changes to a lower surface pCO2 before the freshwater influence leads towards complete dissipation. Finally, we estimated the FCO2 of the Yatsushiro Sea in 2018, and the results showed that the Yatsushiro Sea was a sink area for atmospheric CO2 in 2018 (−1.70 mmol/m2/day).</p

Enantioselective Activation of Stable Carboxylate Esters as Enolate Equivalents <i>via</i> N-Heterocyclic Carbene Catalysts

The first N-Heterocyclic Carbene (NHC) mediated activation of stable carboxylate esters to generate enolate intermediates is disclosed. The catalytically generated arylacetic ester enolates undergo enantioselective reactions with α,β-unsaturated imines