Approximating Cross-validatory Predictive P-values with Integrated IS for Disease Mapping Models

An important statistical task in disease mapping problems is to identify out- lier/divergent regions with unusually high or low residual risk of disease. Leave-one-out cross-validatory (LOOCV) model assessment is a gold standard for computing predictive p-value that can flag such outliers. However, actual LOOCV is time-consuming because one needs to re-simulate a Markov chain for each posterior distribution in which an observation is held out as a test case. This paper introduces a new method, called iIS, for approximating LOOCV with only Markov chain samples simulated from a posterior based on a full data set. iIS is based on importance sampling (IS). iIS integrates the p-value and the likelihood of the test observation with respect to the distribution of the latent variable without reference to the actual observation. The predictive p-values computed with iIS can be proved to be equivalent to the LOOCV predictive p-values, following the general theory for IS. We com- pare iIS and other three existing methods in the literature with a lip cancer dataset collected in Scotland. Our empirical results show that iIS provides predictive p-values that are al- most identical to the actual LOOCV predictive p-values and outperforms the existing three methods, including the recently proposed ghosting method by Marshall and Spiegelhalter (2007).Comment: 21 page

Association of Physical Activity and Sedentary Behaviors with the Risk of Refractive Error in Chinese Urban/Rural Boys and Girls

Background: Research shows physical activity (PA) is negatively associated with refractive error, especially outdoor activity. Our study aimed to examine the association of PA levels and sedentary time (SED) with refractive error in boys and girls living in urban and rural areas. Methods: A total of 8506 urban/rural boys and girls (13.5 ± 2.8 years old) in Shaanxi Province, China participated in this study. Questions about PA, SED, outdoor exercises, and digital screen time were asked in the study survey. Non-cycloplegic refractive error was measured by an autorefractor. The differences between sex/area groups have been analyzed by one-way ANOVA. The association of PA/SED with spherical equivalent (SE) and cylinder power was analyzed by general linear regression. The association between PA/SED and the risk of refractive error was determined using the binary logistic regression model. Results: Of the 8506 participants, the prevalence of refractive error was significantly higher in girls and urban students (p p p p < 0.05). Conclusions: PA and SED were associated with the risk of refractive error. Maintaining a healthy lifestyle can help to reduce the risk of refractive error in boys and girls

Association of Physical Activity and Sedentary Behaviors with the Risk of Refractive Error in Chinese Urban/Rural Boys and Girls

Background: Research shows physical activity (PA) is negatively associated with refractive error, especially outdoor activity. Our study aimed to examine the association of PA levels and sedentary time (SED) with refractive error in boys and girls living in urban and rural areas. Methods: A total of 8506 urban/rural boys and girls (13.5 &plusmn; 2.8 years old) in Shaanxi Province, China participated in this study. Questions about PA, SED, outdoor exercises, and digital screen time were asked in the study survey. Non-cycloplegic refractive error was measured by an autorefractor. The differences between sex/area groups have been analyzed by one-way ANOVA. The association of PA/SED with spherical equivalent (SE) and cylinder power was analyzed by general linear regression. The association between PA/SED and the risk of refractive error was determined using the binary logistic regression model. Results: Of the 8506 participants, the prevalence of refractive error was significantly higher in girls and urban students (p &lt; 0.05). Less SED and digital screen time, and more outdoor activity were significantly associated with SE (p &lt; 0.05), respectively. More PA and less SED were significantly associated with lower cylinder power (p &lt; 0.05), respectively. More PA and less SED were significantly associated with lower risks of myopia and astigmatism, respectively (p &lt; 0.05). Conclusions: PA and SED were associated with the risk of refractive error. Maintaining a healthy lifestyle can help to reduce the risk of refractive error in boys and girls

Achievement of Both Mechanical Properties and Intrinsic Self-Healing under Body Temperature in Polyurethane Elastomers: A Synthesis Strategy from Waterborne Polymers

Inspired by the growing demand for smart and environmentally friendly polymer materials, we employed 2,2&prime;-disulfanediyldianiline (22DTDA) as a chain extender to synthesize a waterborne polyurethane (WPUR). Due to the ortho-substituted structure of the aromatic disulfide, the urea moieties formed a unique microphase structure in the WPUR, its mechanical strength was enhanced more 180 times relative to that of the material prepared without 22DTDA, and excellent self-healing abilities at body temperature in air or under ultrasound in water were obtained. If the self-healing process was carried out at 37 &deg;C, 50 &deg;C or under ultrasound, the ultimate tensile strength and elongation at break of the healed film could reach 13.8 MPa and 1150%, 15.4 MPa and 1215%, or 16 MPa and 1056%, respectively. Moreover, the WPUR films could be re-healed at the same fracture location over three cutting&ndash;healing cycles, and the recovery rates of the tensile strength and elongation at break remained almost constant throughout these cycles

Synthesis of Polystyrene/Polysilsesquioxane Core/Shell Composite Particles via Emulsion Polymerization in the Existence of Poly(γ-Methacryloxypropyl trimethoxysilane) Sol

Here, we synthesized the polystyrene/polysilsesquioxane (PS/PSQ) core/shell latex particles via emulsion polymerization, which behave as an amusing morphology. First, the nanosized PSQ particles were prepared by the hydrolysis–condensation reaction of γ-methacryloxypropyl trimethoxysilane (MPTS) in ethanol medium. Subsequently, the as-obtained methacryloxypropylene functionalized PSQ (PMPTS) sol was directly added into the emulsion system of styrene (St) monomer, and PS/PSQ composite particles with core/shell structure were obtained through emulsion polymerization. We found that the structure of the composite particles can be affected by the synthesis parameters such as reaction time, content of PMPTS added in the reaction, amount of coemulsifier, and the pH value of emulsion system, which were systemically explored by transmission electron microscopy (TEM), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy, dynamic light scattering (DLS), and thermogravimetric analysis (TGA) in this work. These results indicate that the PMPTS particles in the size of about 5 nm could first absorb onto the surface of PS latex particles so as to assemble in a strawberry-like morphology. The further coalescence among the PMPTS particles would result in a continuous PMPTS shell around the PS core. Moreover, the hollow PSQ capsules were prepared after extraction of the PS core by organic solvent, further confirming the core/shell structure of the as-synthesized PS/PMPTS particles. Meanwhile, we also explored the application of the PS/PSQ core/shell particles as a new kind of Pickering emulsifier in the emulsion polymerization of St, and composite particles with complex patchy morphologies have been obtained finally under different ratios of styrene monomer to PS/PMPTS colloidal emulsifier

Self-Assembly of Poly(methacrylic acid)‑<i>b</i>‑poly(butyl acrylate) Amphiphilic Block Copolymers in Methanol via RAFT Polymerization and during Film Formation for Wrinkly Surface Pattern

Reversible addition–fragmentation chain transfer (RAFT) dispersion polymerization was utilized to synthesize poly­(methacrylic acid)-<i>b</i>-poly­(butyl acrylate) (PMAA-<i>b</i>-PBA) amphiphilic block copolymer dispersions in methanol by using the PMAA homopolymer with dithiobenzoate end-group as macro-RAFT agent. And the PMAA macro-RAFT agent was synthesized first by using 4-cyanopentanoic acid dithiobenzoate (CADB) as RAFT agent, where the intermolecular hydrogen bondings can be formed between the MAA units. With the formation of solvophobic PBA block by propagating BA monomer on the PMAA homopolymer chain, the PMAA-<i>b</i>-PBA block copolymer <i>in situ</i> self-assembled into core/shell sphere with PBA and PMAA blocks as core and shell matrix, respectively. The repulsive steric interaction within the PMAA block on shell matrix stabilized the copolymer particles in methanol dispersion, which further resulted in the formation of wrinkly surface pattern on the PMAA-<i>b</i>-PBA copolymer film. During the film formation process, the core/shell copolymer particles were concentrated and then anisotropically aggregated with the evaporation of methanol. The aggregated copolymer particles further assembled into the fibrous structure, so that the film with wrinkly surface pattern was obtained. And the fibrous width and the amplitude of fluctuant film surface can be controlled by copolymer molecular structure and film casting temperature, which are synergetically governed by both the self-assembly of core/shell copolymer particles and the hydrogen-bonding network within the PMAA blocks

Reduction–Coagulation Preparation of Hybrid Nanoparticles of Graphene and Halloysite Nanotubes for Use in Anticorrosive Waterborne Polymer Coatings

Graphene has been extensively concerned as an ideal modifier in the exploration on mordern polymer coatings with high performance. However, the poor dispersibility of graphene in water strongly limits the application in waterborne systems. Here, we demonstrate a simple but effective reduction–coagulation method for the preparation of hybrid nanoparticles of halloysite nanotubes (HNTs) and reduced graphene oxide (rGO). The work was started from the simple mixture of the aqueous dispersion of graphene oxide­(GO) and HNTs. As the subtle introduction of the reducing agent, GO was reduced into rGO and co<b>-</b>coagulated with HNTs. Tailored by the residual hydrophilic groups inside the nanotube of HNTs, the phase separation was controlled in colloidal scale, and stable aqueous dispersion of HNTs–rGO hybrid nanoparticles was thereafter obtained conveniently. We directly blended the product into the polymer latex for the formation of coating films. The tests reveal that the composite coating system with the addition of 0.5 wt % of HNTs–rGO can provide excellent corrosion protection for more than 90 days in all the testing mediums except 10 wt % H₂SO₄, which is much superior to the blank polymer coating

Rational Design of Core-Shell ZnTe@N-Doped Carbon Nanowires for High Gravimetric and Volumetric Alkali Metal Ion Storage

© 2020 Wiley-VCH GmbH Among the various semiconductor materials, zinc telluride possesses the lowest electron affinity and ultrafast charge separation capability, facilitating improved charge transfer kinetics. In addition, ZnTe has a relatively high density, contributing to high volumetric capacity. Here, 1D N-doped carbon-coated ZnTe core-shell nanowires (ZnTe@C) are designed and prepared via a facile ion-exchange and carbonization technique. When evaluated as anode for metal ion batteries, it demonstrates superior electrochemical performance in both Li and Na ion storage, including high gravimetric and volumetric capacities (1119 mA h g−1 and 906 mA h cm−3, respectively, at 100 mA g−1 for Li ion storage), excellent high-rate capability, and long-term cycling stability. This remarkable electrochemical performance is attributed to the low electron affinity and high density of ZnTe, and the amorphous nature of the N-doped carbon layer in the heterostructured ZnTe@C nanowires, which not only provide fast charge transfer paths, but also effectively maintain the structural and electrical integrity of the ZnTe. The strategy of embedding high density and high-performance active materials in highly conductive nanostructures represents an effective way of achieving electrode materials with excellent gravimetric and volumetric capacities towards superior energy storage systems