Spatial imaging of modifications to fluorescence lifetime and intensity by individual Ag nanoparticles

Highly ordered periodic arrays of silver nanoparticles have been fabricated which exhibit surface plasmon resonances in the visible spectrum. We demonstrate the ability of these structures to alter the fluorescence properties of vicinal dye molecules by providing an additional radiative decay channel. Using fluorescence lifetime imaging microscopy (FLIM), we have created high resolution spatial maps of the molecular lifetime components; these show an order of magnitude increase in decay rate from a localized volume around the nanoparticles, resulting in a commensurate enhancement in the fluorescence emission intensity.Comment: 3 pages, 2 figures, submitted Applied Physics Letter

Plasmonic engineering of metal nanoparticles for enhanced fluorescence and Raman scattering

We have investigated the effects of tuning the localized surface plasmon resonances (LSPRs) of silver nanoparticles on the fluorescence intensity, lifetime, and Raman signal from nearby fluorophores. The presence of a metallic structure can alter the optical properties of a molecule by increasing the excitation field, and by modifying radiative and non-radiative decay mechanisms. By careful choice of experimental parameters we have been able to decouple these effects. We observe a four-fold increase in fluorescence enhancement and an almost 30-fold increase in decay rate from arrays of Ag nanoparticles, when the LSPR is tuned to the emission wavelength of a locally situated fluorophore. This is consistent with a greatly increased efficiency for energy transfer from fluorescence to surface plasmons. Additionally, surface enhanced Raman scattering (SERS) measurements show a maximum enhancement occurs when both the incident laser light and the Raman signal are near resonance with the plasmon energy. Spatial mapping of the SERS signal from a nanoparticle array reveals highly localized differences in the excitation field resulting from small differences in the LSPR energy.Comment: Submitted to Plasmonics (Springer

Doctor of Philosophy

dissertationThe different negative events that people experience may threaten distinct forms of adaptive functioning. A growing literature on the narrative study of self and well-being suggests that one way people may resolve adaptive functioning threats is through narrative meaning-making. However, past research shows that meaning-making is not always linked to salutary effects. Meaning-making may be most likely to restore adaptive functioning when people's narratives address specific threats associated with specific types of negative event. However, we know little about the types of threats that may be tied to different negative events. The current studies used an online, experimental, repeated measures design to test which types of adaptive functioning threats are linked to what types of negative events. Understanding whether particular adaptive functioning threats are tied to specific negative events may provide a framework for theorizing about the most beneficial types of meanings to be made when narrating specific negative events. Participants spent 2 minutes recalling four negative events: actor/competence, target/competence, actor/relatedness, target/relatedness (event order was randomized). Afterwards, each participant responded to a battery of adaptive functioning measures. Study 1 examined these topics in an undergraduate student sample. Study 2 examined these topics using a community sample of MTurk workers who ranged from 20 to 69 years of age. In addition to testing the extent to which different types of threats arise in different types of events, we also tested the extent to which individual differences mitigated threat-level perceived. In Study 1, we examined the impact of psychological well-being and emotional stability on levels of threat. In Study 2, we also examined age as an individual difference. Different negative events led to distinct adaptive functioning threats when individual differences were not accounted for. However, the majority of the variance in levels of perceived threat was explained by individual differences in well-being, emotional stability, and age. Overall, this pattern of findings suggests the importance of idiographic methods for understanding how people perceive negative events. Furthermore, the pattern suggests that beneficial meaning-making is likely a person-specific, as opposed to event-specific, process

Investor behavior and the benefits of direct stock ownership

Whereas prior research emphasizes the monitoring benefits of concentrated stock ownership, we examine a variety of potential benefits of dispersed ownership for public companies. Using a field experiment to rule out reverse causality, we examine whether a small investment in a company’s stock leads investors to purchase more of the company’s products and adopt other views and preferences that benefit the company. We find little evidence consistent with our hypotheses using frequentist statistics, and Bayesian parameter estimation shows substantial downward belief revision for more optimistic ex ante expectations of the treatment effects for the average investor. However, we do find that the effects of ownership on product purchase behavior and on regulatory preferences are intuitively stronger for certain subgroups of investors—namely, for investors who are most likely to consume the types of products offered by the company and for investors who are most likely to be politically active, respectively. The results contribute to our understanding of the benefits of dispersed stock ownership and are informative to public company managers and directors

A Follow-Up Study of the Graduates of an Orphans\u27 Home

This study was made of the graduates of a semi-public school located on the grounds at the Indiana Masonic Home at Franklin, Indiana. Almost all of the graduates are obliged to work for their living immediately after graduation and the present curriculum was arranged to meet this need. This study was made to determine if the program has been functioning and, if not, to find out what changes should be made to make it fulfill the needed requirements

Mechanisms of Mouse Hepatitis Virus Entry into Cells

Background: Viruses can enter cells through several mechanisms, two common ones being clathrin-mediated and caveolin-mediated endocytosis. The clathrin pathway delivers viral particles to endosomes, with subsequent acidification of the endosome and endosome/lysosome fusion often a prerequisite for release of the viral genome into the cytoplasm. The caveolin-mediated pathway delivers virus initially into vesicles called caveosomes, which have a neutral pH, before viral uncoating occurs. Viral entry pathways can be examined by using various drugs to inhibit the different endocytosis pathways, as well as by siRNA technology to down-regulate expression of clathrin or caveolin proteins on the surface of host cells