This article extends current discussion of how to disaggregate between-person and within-person effects with longitudinal data using multilevel models. Our main focus is on the 2 issues of centering ...and detrending. Conceptual and analytical work demonstrates the similarities and differences among 3 centering approaches (no centering, grand-mean centering, and person-mean centering) and the relations and differences among various detrending approaches (no detrending, detrending X only, detrending Y only, and detrending both X and Y). Two real data analysis examples in psychology are provided to illustrate the differences in the results of using different centering and detrending methods for the disaggregation of between- and within-person effects. Simulation studies were conducted to further compare the various centering and detrending approaches under a wider span of conditions. Recommendations of how to perform centering, whether detrending is needed or not, and how to perform detrending if needed are made and discussed.
Antibacterial property of packaging is needed to improve the microbiological safety of foods. The aim of this work was to incorporate various amounts of carboxymethyl cellulose (CMC) into films based ...on quaternized chitosan (2-N-Hydroxypropyl-3-trimethylammonium chloride chitosan, HTCC) to develop coating for preserving food. The HTCC film and blend films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction measurements, scanning electron microscopy, and thermogravimetric analysis. The effects of CMC content on the physical properties and antibacterial activities of the blend films were investigated. The effect of coating bananas with the films on their preservation was also determined. The results revealed that HTCC and CMC in the blend films interacted by hydrogen bonding. Both of them could be partly miscible. Compared with HTCC100 film, CMC incorporation improved tensile strength, thermostability, and water resistance, however, increased oxygen permeability, and decreased light transmittance and antibacterial activity against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. Bananas coated with the HTCC/CMC blend films had longer shelf life than uncoated bananas. CMC incorporation thus evidently reinforced the HTCC film and lowered its WVP. These results suggest that HTCC/CMC blend films can be used as food packaging materials.
•HTCC/CMC blend films were prepared through a simple mixing method.•The films had low water permeability, high tensile strength and thermostability.•The films had good activity against Escherichia coli and Staphylococcus aureus.•Bananas coated with the blend films exhibited extended shelf life.
Conventionally, moderated mediation analysis is conducted through adding relevant interaction terms into a mediation model of interest. In this study, we illustrate how to conduct moderated mediation ...analysis by directly modeling the relation between the indirect effect components including a and b and the moderators, to permit easier specification and interpretation of moderated mediation. With this idea, we introduce a general moderated mediation model that can be used to model many different moderated mediation scenarios including the scenarios described in Preacher, Rucker, and Hayes (2007). Then we discuss how to estimate and test the conditional indirect effects and to test whether a mediation effect is moderated using Bayesian approaches. How to implement the estimation in both BUGS and Mplus is also discussed. Performance of Bayesian methods is evaluated and compared to that of frequentist methods including maximum likelihood (ML) with 1st-order and 2nd-order delta method standard errors and mL with bootstrap (percentile or bias-corrected confidence intervals) via a simulation study. The results show that Bayesian methods with diffuse (vague) priors implemented in both BUGS and Mplus yielded unbiased estimates, higher power than the ML methods with delta method standard errors, and the ML method with bootstrap percentile confidence intervals, and comparable power to the ML method with bootstrap bias-corrected confidence intervals. We also illustrate the application of these methods with the real data example used in Preacher et al. (2007). Advantages and limitations of applying Bayesian methods to moderated mediation analysis are also discussed.
Protein hydration is essential to its structure, dynamics, and function, but water–protein interactions have not been directly observed in real time at physiological temperature to our awareness. By ...using a tryptophan scan with femtosecond spectroscopy, we simultaneously measured the hydration water dynamics and protein side-chain motions with temperature dependence. We observed the heterogeneous hydration dynamics around the global protein surface with two types of coupled motions, collective water/side-chain reorientation in a few picoseconds and cooperative water/side-chain restructuring in tens of picoseconds. The ultrafast dynamics in hundreds of femtoseconds is from the outer-layer, bulk-type mobile water molecules in the hydration shell. We also found that the hydration water dynamics are always faster than protein side-chain relaxations but with the same energy barriers, indicating hydration shell fluctuations driving protein side-chain motions on the picosecond time scales and thus elucidating their ultimate relationship.
Intra-individual variability over a short period of time may contain important information about how individuals differ from each other. In this article we begin by discussing diverse indicators for ...quantifying intra-individual variability and indicate their advantages and disadvantages. Then we propose an alternative method that models inter-individual differences in intra-individual variability by separately considering both the amplitude of fluctuations and temporal dependency in the data. In the proposed model, temporal dependency and amplitude of fluctuations are both included as random effects. Parameter estimation is done with a multiple-step approach using maximum likelihood, or with a recommended 1-step approach using a Bayesian method. The similarities and differences between the proposed method and some existing methods are discussed and investigated using diary study data from older adults. The results from empirical data analysis revealed that temporal dependency and amplitude of fluctuations have different predictability of health outcomes and thus should be modeled and considered separately.
The enhancement of g-C3N4 photocatalytic degradation of bisphenol A (BPA) via persulfate (PS) addition was investigated under visible light irradiation. The effects of various parameters on the BPA ...degradation were investigated, such as catalysts dosage, PS concentrations, initial pH value and BPA concentration. The results showed that g-C3N4 nanosheets exhibited superior photocatalytic activity toward BPA degradation as compared with bulk g-C3N4. The addition of PS can further improve the g-C3N4 photocatalytic performance for BPA degradation. With 5 mM PS, the degradation rate of BPA was increased from 72.5% to 100% at 90 min, and the corresponding first-order kinetic constants were increased from 0.0028 to 0.0140 min−1. The removal efficiency of BPA increased with the decrease of solution pH value. The active radicals in the reaction system were tested by electron spin resonance (ESR) and radicals quenching experiments. Instead of persulfate radicals’ oxidation, it was proposed that the main active radicals for BPA degradation were superoxide radicals and the photogenerated holes.
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•The g-C3N4 nanosheets presents better photocatalytic activity than bulk g-C3N4.•Persulfate improved BPA degradation in g-C3N4 visible light photocatalysis system.•Superoxide radicals are the dominant oxidizing species for bisphenol A degradation.
The metastatic potential of cells is an important parameter in the design of optimal strategies for the personalized treatment of cancer. Using atomic force microscopy (AFM), we show, consistent with ...previous studies conducted in other types of epithelial cancer, that ovarian cancer cells are generally softer and display lower intrinsic variability in cell stiffness than non-malignant ovarian epithelial cells. A detailed examination of highly invasive ovarian cancer cells (HEY A8) relative to their less invasive parental cells (HEY), demonstrates that deformability is also an accurate biomarker of metastatic potential. Comparative gene expression analyses indicate that the reduced stiffness of highly metastatic HEY A8 cells is associated with actin cytoskeleton remodeling and microscopic examination of actin fiber structure in these cell lines is consistent with this prediction. Our results indicate that cell stiffness may be a useful biomarker to evaluate the relative metastatic potential of ovarian and perhaps other types of cancer cells.
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