Tailoring the Refractive Indices of Thin Film Polymer Metallic Nanoparticle Nanocomposites

We demonstrate how to tailor the spatial distribution of gold nanoparticles (Au-NPs) of different sizes within polystyrene (PS) thin, supported, film hosts, thereby enabling the connection between the spatial distribution of Au-NPs within the polymer film and the optical properties to be determined. The real, <i>n</i>, and imaginary parts, <i>k</i>, of the complex refractive indices <i><i>N</i> = n</i>(λ)<i>+ik</i>(λ) of the nanocomposite films were measured as a function of wavelength, λ, using multivariable angle spectroscopic ellipsometry. The surface plasmon response of films containing nearly homogeneous Au-NP distributions were well described by predictions based on classical Mie theory and the Drude model. The optical spectra of samples containing inhomogeneous nanoparticle distributions manifest features associated with differences in the size and interparticle spacings as well as the proximity and organization of nanoparticles at the substrate and free surface

Surface Layer Dynamics in Miscible Polymer Blends

In thin film A/B polymer/polymer mixtures, the formation of a layer at the free surface, with average composition that differs from the bulk, due to the preferential segregation of the lower cohesive energy density component, is well understood. While much is also understood about this surface layer formation and growth to date, virtually nothing is known about the surface dynamics of the chains in such mixtures. Questions about the surface chain dynamics in relation to the bulk have remained unanswered. With the use of X-ray photon correlation spectroscopy (XPCS) we show that the dynamics of poly­(vinyl methyl ether) (PVME) chains at the free surface of polystyrene (PS)/PVME thin film mixtures can be orders of magnitude larger than the PVME chains in the bulk. These dynamics manifest from differences between the local compositions of the blend at the free surface and the bulk, as well as film thickness constraints

Inverse Vulcanization of Elemental Sulfur to Prepare Polymeric Electrode Materials for Li–S Batteries

Sulfur-rich copolymers based on poly­(sulfur-<i>random-</i>1,3-diisopropenylbenzene) (poly­(S-<i>r</i>-DIB)) were synthesized via inverse vulcanization to create cathode materials for lithium–sulfur battery applications. These materials exhibit enhanced capacity retention (1005 mAh/g at 100 cycles) and battery lifetimes over 500 cycles at a C/10 rate. These poly­(S-<i>r</i>-DIB) copolymers represent a new class of polymeric electrode materials that exhibit one of the highest charge capacities reported, particularly after extended charge–discharge cycling in Li–S batteries

Seropositive rates of ZIKV for selected animals in Uganda, Borneo, Pakistan, Kenya, and Brazil.

<p>Seropositive rates of ZIKV for selected animals in Uganda, Borneo, Pakistan, Kenya, and Brazil.</p

ZIKV epidemic dynamics in 2015–2016 across the Americas, in Brazil, and in an Ecuadorian province struck by an earthquake.

<p>(A) Weekly cumulative suspected and confirmed ZIKV cases (see Glossary for case definitions) across countries in the Americas, on a log scale, colored by the total size of the epidemic. (B) Weekly cumulative confirmed ZIKV-linked microcephaly cases (see Glossary for case definitions) in Brazil. (C) Weekly cumulative confirmed autochthonous cases in Manabi province, Ecuador, where a magnitude 7.8 earthquake struck on April 16, 2016 (indicated by the dashed line). Data are from weekly epidemiological reports from the Pan American Health Organization (PAHO), as compiled by the Centers for Disease Control and Prevention Epidemic Prediction Initiative (CDC EPI; <a href="https://github.com/cdcepi/zika" target="_blank">https://github.com/cdcepi/zika</a>; accessed 15 July 2016).</p

Search interest for “chikungunya” and “Zika.”

<p>Search interest, relative to the highest search volume between June 2013 and June 2016, for the terms “chikungunya” in St. Martin (A) and “Zika” in Brazil (B). A value of 100 represents the highest search volume recorded in each country within this time period, so direct comparison of relative search volume is possible without controlling for population or the number of Internet users. Gray dashed lines indicate the first cases of laboratory-confirmed CHIKV and ZIKV in the Americas. The orange bold line indicates declaration of a public health emergency of international concern (PHEIC) by WHO. Data are from Google Trends (<a href="https://www.google.com/trends/" target="_blank">https://www.google.com/trends/</a>; accessed 5 July 2016).</p

Hierarchy of factors that influence ZIKV transmission, illness, and social consequences.

<p>Climate suitability, mosquito abundance, and human–mosquito contact partly determine rates of ZIKV transmission, which causes illness in some cases. Social consequences depend on both actual and perceived risks of illness. Arrows indicate environmental (green) and social (red) changes hypothesized to contribute to the shifting ecology of vector transmission in the Americas. Figure inspired by Plowright et al. [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005135#pntd.0005135.ref022" target="_blank">22</a>].</p

Confirmed ZIKV-linked microcephaly cases in Brazilian states versus per capita GDP (in log10 US Dollars).

<p>The number of confirmed ZIKV-linked microcephaly cases per 100,000 people (as of July 15, 2016) is negatively correlated (Pearson’s correlation coefficient r = -0.64) with per capita GDP for states with one or more cases. Total GDP data were retrieved from the 2012 IBGE report (<a href="http://www.ibge.gov.br/english/estatistica/economia/contasregionais/2012/default.shtm" target="_blank">http://www.ibge.gov.br/english/estatistica/economia/contasregionais/2012/default.shtm</a>; accessed July 7, 2016). Population sizes by state were retrieved from the 2014 IBGE report. Per capita GDP = Total GDP/population size. Microcephaly data are from weekly epidemiological reports from PAHO, as compiled by the CDC EPI.</p