A two-step approach for relating tapered element oscillating microbalance and dichotomous air sampler PM_2.5 measurements

<div><p>A method for transforming continuous monitoring (CM) fine particulate matter (aerodynamic diameter <2.5 μm; PM_2.5) data (i.e., by tapered element oscillating microbalance [TEOM]) obtained from the Canadian National Air Pollution Surveillance (NAPS) program to meet the data quality objective (DQO) of <i>R</i>² > 0.8 against the co-located federal reference method (i.e., dichotomous air sampler) is described. By using a two-step linear regression to account for the effect of the ambient temperature, 16 out of the 23 examined sites met the common model adequacy threshold of <i>R</i>² > 0.8. After the transformation, 20 out of the 23 examined sites met the DQO of <i>R</i>² > 0.7, as recommended by the U.S. Environmental Protection Agency (EPA). A combined two-step statistical approach was also examined and revealed similar results. The methods described herein show that the CM data can be successfully transformed to meet DQOs for representative sites across Canada using year-round (both summer and winter) data. </p><p></p><p>Implications:</p><p>This study provides a transformation approach to correct ambient TEOM data against the federal reference method without dividing the ambient data according to warm and cold seasons. This transformation approach will significantly improve the correlation coefficient between TEOM and dichotomous air sampler data. It is possible that TEOM data at many Canadian locations can be transformed to meet the EPA data quality objective, thus making this transformation approach useful for comparisons of ambient PM data across jurisdictions.</p><p></p><p></p></div

Study Viscoelasticity of Ultrathin Poly(oligo(ethylene glycol) methacrylate) Brushes by a Quartz Crystal Microbalance with Dissipation

Ultrathin polymer brushes play important roles in natural and artificial systems. To better understand and utilize their unique behaviors, characterization is a fundamental, but not trivial, task. In this paper, we demonstrated that the quartz crystal microbalance with dissipation (QCM-D) could be applied to study ultrathin poly(oligo(ethylene glycol) methacrylate) brushes. First, we identified four linear relations between dissipation/frequency changes and thickness changes, which were measured by QCM-D and ellipsometry, respectively. Next, we derived a set of equations starting from the Voigt model to further extract viscoelasticity of poly(OEGMA) brushes (≤30 nm) under high-frequency vibration in contact with water. The viscosity was ∼10−3 N s m−2 and the elasticity was ∼105 N m−2. Both were frequency dependent. Also discussed were other quantities such as the density (both the dry and wet film) and the working range of linear relations. These equations and quantitative information are important in advancing our understanding of ultrathin polymer brushes, which consequently promote our ability in designing functional surface coatings (i.e., in biosensor applications) and studying related interfacial phenomena

Surface-Imprinted Nanostructured Layer-by-Layer Film for Molecular Recognition of Theophylline Derivatives

In this article we report the introduction of the cooperativity of various specific interactions combined with photo-cross-linking of the interlayers to yield binding sites that can realize better selectivity and imprinting efficiency of a surface molecularly imprinted LbL film (SMILbL), thus providing a new approach toward fabrication of nanostructured molecularly imprinted thin films. It involves preassembly of poly(acrylic acid) (PAA) conjugated of the theophylline residue template via a disulfide bridge, denoted as PAAtheo15, in solution, and layer-by-layer (LbL) assembly of PAAtheo15 and a positively charged photoreactive diazo resin (DAR) to form multilayer thin film with designed architecture. After photo-cross-linking of the film and template removal, binding sites specific to 7-(β-hydroxyethyl)theophylline (Theo-ol) molecules are introduced within the film. Binding assay demonstrates that the SMILbL has a high selectivity of SMILbL to Theo-ol over caffeine. A control experiment demonstrates that the selectivity of SMILbL derives from nanostructured recognition sites among the layers. The imprinting amount per unit mass of the film can be 1 order of magnitude larger than that of the conventional bulk molecular imprinting systems. As this concept of construction SMILbL can be easily extended to the other molecules by the following similar protocol: its applications in building many other different molecular recognition systems are greatly anticipated

Effects of Erythromycin on <i>Nereis succinea</i> and the Intestinal Microbiome across Different Salinity Levels

The exposure of aquatic organisms to pollutants often occurs concomitantly with salinity fluctuations. Here, we reported the effects of erythromycin (0.250, 7.21, and 1030 μg/L) on marine invertebrate N. succinea and its intestinal microbiome under varying salinity levels (5‰, 15‰, and 30‰). The salinity elicited significant effects on the growth and intestinal microbiome of N. succinea. The susceptibility of the intestinal microbiome to erythromycin increased by 8.7- and 6.2-fold at salinities of 15‰ and 30‰, respectively, compared with that at 5‰ salinity. Erythromycin caused oxidative stress and histological changes in N. succinea intestines, and inhibited N. succinea growth in a concentration-dependent manner under 30‰ salinity with a maximum inhibition of 25%. At the intestinal microbial level, erythromycin enhanced the total cell counts at 5‰ salinity but reduced them at 15‰ salinity. Under all tested salinities, erythromycin diminished the antibiotic susceptibility of the intestinal microbiome. Two-way ANOVA revealed significant interactive effects (p < 0.05) between salinity and erythromycin on various parameters, including antibiotic susceptibility and intestinal microbial diversity. The present findings demonstrated the significant role of salinity in modulating the impacts of erythromycin, emphasizing the necessity to incorporate salinity fluctuations into environmental risk assessments

Integrated Poly(dimethysiloxane) with an Intrinsic Nonfouling Property Approaching “Absolute” Zero Background in Immunoassays

The key to achieve a highly sensitive and specific protein microarray assay is to prevent nonspecific protein adsorption to an “absolute” zero level because any signal amplification method will simultaneously amplify signal and noise. Here, we develop a novel solid supporting material, namely, polymer coated initiator integrated poly(dimethysiloxane) (iPDMS), which was able to achieve such “absolute” zero (i.e., below the detection limit of instrument). The implementation of this iPDMS enables practical and high-quality multiplexed enzyme-linked immunosorbent assay (ELISA) of 11 tumor markers. This iPDMS does not need any blocking steps and only require mild washing conditions. It also uses on an average 8-fold less capture antibodies compared with the mainstream nitrocellulose (NC) film. Besides saving time and materials, iPDMS achieved a limit-of-detection (LOD) as low as 19 pg mL−1, which is sufficiently low for most current clinical diagnostic applications. We expect to see an immediate impact of this iPDMS on the realization of the great potential of protein microarray in research and practical uses such as large scale and high-throughput screening, clinical diagnosis, inspection, and quarantine