Remote sensing of life: Polarimetric signatures of photosynthetic pigments as sensitive biomarkers

We develop a polarimetry-based remote-sensing method for detecting and identifying life forms in distant worlds and distinguishing them from non-biological species. To achieve this we have designed and built a bio-polarimetric laboratory experiment BioPol for measuring optical polarized spectra of various biological and non-biological samples. Here we focus on biological pigments, which are common in plants and bacteria that employ them either for photosynthesis or for protection against reactive oxygen species. Photosynthesis, which provides organisms with the ability to use light as a source of energy, emerged early in the evolution of life on Earth. The ability to harvest such a significant energy resource could likely also develop on habited exoplanets. Thus, we investigate the detectability of biomolecules that can capture photons of particular wavelengths and contribute to storing their energy in chemical bonds. We have carried out laboratory spectropolarimetric measurements of a representative sample of plants containing various amounts of pigments such as chlorophyll, carotenoids and others. We have also measured a variety of non-biological samples (sands, rocks). Using our lab measurements, we have modelled intensity and polarized spectra of Earth-like planets having different surface coverage by photosynthetic organisms, deserted land and ocean, as well as clouds. Our results demonstrate that linearly polarized spectra provide very sensitive and rather unambiguous detection of photosynthetic pigments of various kinds. Our work paves the path towards analogous measurements of microorganisms and remote sensing of microbial ecology on the Earth and of extraterrestrial life on other planets and moons

EXPLAINING THE RELATIONSHIP BETWEEN EMPLOYMENT AND JUVENILE DELINQUENCY*

Most criminological theories predict an inverse relationship between employment and crime, but teenagers' involvement in paid work during the school year is positively correlated with delinquency and substance use. Whether the work-delinquency association is causal or spurious has long been debated. This study estimates the effect of paid work on juvenile delinquency using longitudinal data from the national Monitoring the Future project. We address issues of spuriousness by using a two-level hierarchical model to estimate the relationships of within-individual changes in juvenile delinquency and substance use to those in paid work and other explanatory variables. We also disentangle effects of actual employment from preferences for employment to provide insight about the likely role of time-varying selection factors tied to employment, delinquency, school engagement, and leisure activities. Whereas causal effects of employment would produce differences based on whether and how many hours respondents worked, we found significantly higher rates of crime and substance use among non-employed youth who preferred intensive versus moderate work. Our findings suggest the relationship between high-intensity work and delinquency results from preexisting factors that lead youth to desire varying levels of employment

Polymer Directed Self-Assembly of pH-Responsive Antioxidant Nanoparticles

We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using flash nanoprecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e., stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. In vitro, the nanoparticles have low cytotoxicity and show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants

Aromaticity Competition in Differentially Fused Borepin-Containing Polycyclic Aromatics

This report describes the synthesis and characterization of a series of borepin-based polycyclic aromatics bearing two different arene fusions. The borepin synthesis features streamlined Ti-mediated alkyne reduction, leading to <i>Z</i>-olefins, followed by direct lithiation and borepin formation. These molecules allow for an assessment of aromatic competition between the fused rings and the central borepin core. Crystallographic, magnetic, and computational studies yielded insights about the aromaticity of novel, differentially fused [<i>b</i>,<i>f</i>]­borepins and allowed for comparison to literature compounds. Multiple borepin motifs were also incorporated into polycyclic aromatics with five or six rings in the main backbone, and their properties were also evaluated

Aromaticity Competition in Differentially Fused Borepin-Containing Polycyclic Aromatics

This report describes the synthesis and characterization of a series of borepin-based polycyclic aromatics bearing two different arene fusions. The borepin synthesis features streamlined Ti-mediated alkyne reduction, leading to <i>Z</i>-olefins, followed by direct lithiation and borepin formation. These molecules allow for an assessment of aromatic competition between the fused rings and the central borepin core. Crystallographic, magnetic, and computational studies yielded insights about the aromaticity of novel, differentially fused [<i>b</i>,<i>f</i>]­borepins and allowed for comparison to literature compounds. Multiple borepin motifs were also incorporated into polycyclic aromatics with five or six rings in the main backbone, and their properties were also evaluated

Polymer Directed Self-Assembly of pH-Responsive Antioxidant Nanoparticles

We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using flash nanoprecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e., stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. <i>In vitro</i>, the nanoparticles have low cytotoxicity and show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants

Benzo[<i>b</i>]thiophene Fusion Enhances Local Borepin Aromaticity in Polycyclic Heteroaromatic Compounds

This report documents the synthesis, characterization, and computational evaluation of two isomeric borepin-containing polycyclic aromatics. The syntheses of these two isomers involved symmetrical disubstituted alkynes that were reduced to <i>Z</i>-olefins followed by borepin formation either through an isolable stannocycle intermediate or directly from the alkene via the trapping of a transient dilithio intermediate. Comparisons of their magnetic, crystallographic, and computational characterization to literature compounds gave valuable insights about the aromaticity of these symmetrically fused [<i>b</i>,<i>f</i>]­borepins. The fusion of benzo­[<i>b</i>]­thiophene units to the central borepin cores forced a high degree of local aromaticity within the borepin moieties relative to other known borepin-based polycyclic aromatics. Each isomer had unique electronic responses in the presence of fluoride anions. The experimental data demonstrate that the local borepin rings in these two compounds have a relatively high amount of aromatic character. Results from quantum chemical calculations provide a more comprehensive understanding of local and global aromatic characters of various rings in fused ring systems built upon boron heterocycles