Significant Contributions of Isoprene to Summertime Secondary Organic Aerosol in Eastern United States

A modified SAPRC-11 (S11) photochemical mechanism with more detailed treatment of isoprene oxidation chemistry and additional secondary organic aerosol (SOA) formation through surface-controlled reactive uptake of dicarbonyls, isoprene epoxydiol and methacrylic acid epoxide was incorporated in the Community Multiscale Air Quality Model (CMAQ) to quantitatively determine contributions of isoprene to summertime ambient SOA concentrations in the eastern United States. The modified model utilizes a precursor-origin resolved approach to determine secondary glyoxal and methylglyoxal produced by oxidation of isoprene and other major volatile organic compounds (VOCs). Predicted OC concentrations show good agreement with field measurements without significant bias (MFB ∼ 0.07 and MFE ∼ 0.50), and predicted SOA reproduces observed day-to-day and diurnal variation of Oxygenated Organic Aerosol (OOA) determined by an aerosol mass spectrometer (AMS) at two locations in Houston, Texas. On average, isoprene SOA accounts for 55.5% of total predicted near-surface SOA in the eastern U.S., followed by aromatic compounds (13.2%), sesquiterpenes (13.0%) and monoterpenes (10.9%). Aerosol surface uptake of isoprene-generated glyoxal, methylglyoxal and epoxydiol accounts for approximately 83% of total isoprene SOA or more than 45% of total SOA. A domain wide reduction of NO_<i>x</i> emissions by 40% leads to a slight decrease of domain average SOA by 3.6% and isoprene SOA by approximately 2.6%. Although most of the isoprene SOA component concentrations are decreased, SOA from isoprene epoxydiol is increased by ∼16%

Data_Sheet_1_MLFLHMDA: predicting human microbe-disease association based on multi-view latent feature learning.ZIP

IntroductionA growing body of research indicates that microorganisms play a crucial role in human health. Imbalances in microbial communities are closely linked to human diseases, and identifying potential relationships between microbes and diseases can help elucidate the pathogenesis of diseases. However, traditional methods based on biological or clinical experiments are costly, so the use of computational models to predict potential microbe-disease associations is of great importance.MethodsIn this paper, we present a novel computational model called MLFLHMDA, which is based on a Multi-View Latent Feature Learning approach to predict Human potential Microbe-Disease Associations. Specifically, we compute Gaussian interaction profile kernel similarity between diseases and microbes based on the known microbe-disease associations from the Human Microbe-Disease Association Database and perform a preprocessing step on the resulting microbe-disease association matrix, namely, weighting K nearest known neighbors (WKNKN) to reduce the sparsity of the microbe-disease association matrix. To obtain unobserved associations in the microbe and disease views, we extract different latent features based on the geometrical structure of microbes and diseases, and project multi-modal latent features into a common subspace. Next, we introduce graph regularization to preserve the local manifold structure of Gaussian interaction profile kernel similarity and add Lp,q-norms to the projection matrix to ensure the interpretability and sparsity of the model.ResultsThe AUC values for global leave-one-out cross-validation and 5-fold cross validation implemented by MLFLHMDA are 0.9165 and 0.8942+/−0.0041, respectively, which perform better than other existing methods. In addition, case studies of different diseases have demonstrated the superiority of the predictive power of MLFLHMDA. The source code of our model and the data are available on https://github.com/LiangzheZhang/MLFLHMDA_master.</p

Thermoresponsive Dynamic Covalent Polymers with Tunable Properties

A bisaldehyde-containing trithiocarbonate chain transfer agent was prepared and mediated the synthesis of polymers with bisaldehyde-functionalized α-termini by reversible addition–fragmentation chain transfer (RAFT) radical polymerization. The α-termini of RAFT-derived thermoresponsive poly­(<i>N</i>-isopropylacrylamide) was conjugated with hydrazides via reversible acylhydrazone bonds. Introduction of hydrophilic end-groups generated a dynamic covalent polymer with “isothermal” lower critical solution temperature (LCST) response to medium pH and dynamic chain exchange character. A biofunctional dynamic covalent polymer was prepared by conjugation with biotin hydrazide. Under appropriate reaction conditions, a dynamic covalent block copolymer with an aldehyde group at the junction point was constructed through a reversible arylhydrazone linkage by coupling with acylhydrazide-terminated poly­(ethylene glycol). The dynamic covalent block copolymer exhibited pH-dependent LCST. The remaining aldehyde group was used to react with amino-containing molecules. Bioconjugated dynamic covalent block copolymers containing reversible imine and arylhydrazone linkages were constructed by conjugation of the block copolymer to glucosamine and protein

Rotation-Driven Microfluidic Disc for White Blood Cell Enumeration Using Magnetic Bead Aggregation

We recently defined a magnetic bead-based assay that exploited an agglutination-like response for DNA and applied it to DNA-containing cell enumeration using inexpensive benchtop hardware [J. Am. Chem. Soc. 2012, 134 (12), 5689−96]. Although cost-efficient, the open-well format assay required numerous manual steps, and the magnetic field actuation scheme was not readily adaptable for integration. Here, we demonstrate a low-cost (<$2 in-lab), higher-throughput “pinwheel assay” platform that relies on a combination of a disposable rotation-driven microdisc (RDM), and a simple bidirectional rotating magnetic field (bi-RMF). The assay was transformed into an integrated microfluidic system using a multilayered polyester microfluidic disc created through laser print, cut and laminate fabrication, with fluid flow controlled by rotation speed without any mechanical valves. The RDM accepts four samples that undergo on-chip dilution to five different concentrations that cover the effective concentration range needed for downstream cell counting by pinwheel assay. We show that a bi-RMF is effective for the simultaneous actuation of pinwheel assays in 20 detection chambers. The optimization of the bi-RMF frequencies allows the RDM-based pinwheel assay detect human genomic DNA down to a mass of human genomic DNA (5.5 picograms) that is roughly equal to the mass in a single cell. For proof of principle, enumeration of the white blood cells in human blood samples on the RDM provided data correlating well (C.V. of 10%) with those obtained in a clinical lab. Fusing the cost-effective RDM with a simple bi-RMF provides a promising strategy for automation and multiplexing of magnetic particle-based agglutination assays

Relationship between Polyelectrolyte Bulk Complexation and Kinetics of Their Layer-by-Layer Assembly

The effects of pH and salinity on both the bulk phase behavior and the layer-by-layer (LbL) growth kinetics are investigated for polyanion poly­(acrylic acid) or PAA with two polycations, namely poly­(<i>N</i>,<i>N</i>-dimethylaminoethyl methacrylate) or PDMAEMA and poly­(diallyldimethylammonium chloride) or PDADMAC, with the goal of relating the phase behavior to the LbL growth kinetics. Depending on salinity, pH, and mixing ratio, the complex formed in the bulk is either a powdery precipitate or a gel-like coacervate, and the multilayers grow either linearly or exponentially with deposition time. In addition to primary Coulombic interactions, we observe that polymer-specific interactions have a profound effect on both bulk complexation and LbL growth of the three PE pairs studied here. The overall strength of interaction between polyelectrolytes, as indicated by their phase behavior, has a nonmonotonic effect on LbL growth rate, apparently because stronger interactions not only increase the driving force for diffusion but also reduce the effective diffusion coefficient of a polyelectrolyte molecule through the LbL multilayer. As a result, there is little correspondence between coacervation and exponential growth on one hand and precipitation and linear growth on the other. Salt concentration has a nonmonotonic effect on LbL growth kinetics at pH 7, with exponential growth found over the range 15–60% of the critical salt concentration (<i>C</i>_S^c) needed to transition from coacervation to a clear solution in the bulk, regardless of the physical chemistry of polyelectrolytes employed, whereas salt concentrations both below and above this range result in linearly growing films. Finally, for our polyelectrolyte pairs at pH 7, we report a “universal curve” for the dependence of LbL growth rate, normalized by its maximum value, against the salt concentration, normalized by <i>C</i>_S^c. If it proves to be robust, this correlation could be used to estimate optimal salinity for LbL growth from bulk measurements of the critical salt concentration needed to suppress complexation

ABC Triblock Copolymer Particles with Tunable Shape and Internal Structure through 3D Confined Assembly

Here we present 3D confined assembly of polystyrene-<i>b</i>-polyisoprene-<i>b</i>-poly­(2-vinylpyridine) (PS-<i>b</i>-PI-<i>b</i>-P2VP) ABC triblock copolymers into particles with tunable shape and internal structures. Under weak confinement (i.e., ratio of the particle size to the periodicity dimension of the block copolymer <i>D</i>/<i>L</i>₀ > 4), surfactants in the suspension show significant influence on the morphology of the particles. Unique structures, such as onion-, bud-, and pupa-like particles, can be obtained by tailoring properties of the surfactants. Both particle shape and internal structure can be reversibly tuned through pathway independent solvent vapor absorption annealing. While under strong confinement (e.g., <i>D</i>/<i>L</i>₀ < 2), commensurability between <i>D</i> and <i>L</i>₀ will dominate the structure of the particles. Moreover, these structured particles with cross-linkable PI domain can be selectively cross-linked and disassembled into isolated nano-objects. Janus nanodiscs with PS and P2VP chains at different sides can be obtained from pupa-like particles. Such nanodiscs can act as surfactants to stabilize oil/water emulsion droplets. This strategy, combining 3D confinement, selective cross-linking, and disassembly, is believed to be a promising approach for constructing structured particles and unique nano-objects

Spectroscopic Observation of Reversible Surface Reconstruction of Copper Electrodes under CO₂ Reduction

The ability of copper to catalyze the electrochemical reduction of CO₂ has been shown to greatly depend on its nanoscale surface morphology. While previous studies found evidence of irreversible changes of copper nanoparticle and thin film electrodes following electrolysis, we present here the first observation of the <i>reversible</i> reconstruction of electrocatalytic copper surfaces induced by the adsorbed CO intermediate. Using attenuated total internal reflection infrared and surface-enhanced Raman spectroscopies, the reversible formation of nanoscale metal clusters on the electrode is revealed by the appearance of a new CO absorption band characteristic of CO bound to undercoordinated copper atoms and by the strong enhancement of the surface-enhanced Raman effect. Our study shows that the morphology of the catalytic copper surface is not static but dynamically adapts with changing reaction conditions

EDS (left column) and XRD (right column) figures of the as-received TiO₂ NPs.

<p>EDS (left column) and XRD (right column) figures of the as-received TiO₂ NPs.</p

Relative contents of intracellular ROS (A) and MDA (B) in the bacterial cells after 3 h exposure to the TiO₂ NPs (50 mg L⁻¹).

<p>a–e stand for TiO₂-NP 10A, TiO₂-NP 25A, TiO₂-NP 25AR, TiO₂-NP 50A, and TiO₂-NP 50R, respectively. Asterisk indicates a significant difference relative to the control (*, <i>p</i><0.05; **, <i>p</i><0.01) based on the Student’s <i>t</i> test. Error bars represent standard deviation (n = 3).</p

TEM images of the as-received TiO₂ NPs.

<p>TEM images of the as-received TiO₂ NPs.</p