1,877 research outputs found

    Time-Resolved Ultrafast Transient Polarization Spectroscopy to Investigate Nonlinear Processes and Dynamics in Electronically Excited Molecules on the Femtosecond Time Scale

    Get PDF
    We report a novel experimental technique to investigate ultrafast dynamics in photoexcited molecules by probing the third-order nonlinear optical susceptibility. A non-colinear 3-pulse scheme is developed to probe the ultrafast dynamics of excited electronic states using the optical Kerr effect by time-resolved polarization spectroscopy. Optical heterodyne and optical homodyne detection are demonstrated to measure the third-order nonlinear optical response for the S1 excited state of liquid nitrobenzene, which is populated by 2-photon absorption of a 780 nm 35 fs excitation pulse.Comment: 12 pages, 4 figures. Changes from previous version: added panel labels to figures 3-

    Sliver® modules - a crystalline silicon technology of the future

    Get PDF
    A new technique has been devised for the manufacture of thin (<60µm) highly efficient single crystalline solar cells. Novel methods of encapsulating these Sliver® solar cells have also been devised. Narrow grooves are formed through a 1-2mm thick wafer. Device processing (diffusion, oxidation, deposition) is performed on the wafer, so that each of the narrow strips becomes a solar cell. The strips are then detached from the wafer and laid on their sides, which greatly increases the surface area of solar cell that can be obtained from the wafer. Further gains of a factor of two can be obtained by utilising a simple method of static concentration. Large decreases in processing effort (up to 30-fold) and silicon usage (up to 10-fold) per m2 of module are possible. The size, thickness and bifacial nature of the cells create the opportunity for a wide variety of module architectures and applications

    Ultrafast Dynamics of Excited Electronic States in Nitrobenzene Measured by Ultrafast Transient Polarization Spectroscopy.

    Get PDF
    We investigate ultrafast dynamics of the lowest singlet excited electronic state in liquid nitrobenzene using ultrafast transient polarization spectroscopy, extending the well-known technique of optical Kerr effect spectroscopy to excited electronic states. The third-order nonlinear response of the excited molecular ensemble is measured using a pair of femtosecond pulses following a third femtosecond pulse that populates the S1 excited state. By measuring this response, which is highly sensitive to details of the excited state character and structure, as a function of time delays between the three pulses involved, we extract the dephasing time of the wave packet on the excited state. The dephasing time, measured as a function of time delay after pump excitation, shows oscillations indicating oscillatory wave packet dynamics on the excited state. From the experimental measurements and supporting theoretical calculations, we deduce that the wave packet completely leaves the S1 state potential energy surface after three traversals of the intersystem crossing between the singlet S1 and triplet T2 states

    2-[4-(Methyl­sulfan­yl)phen­yl]naphtho[1,8-de][1,3,2]diaza­borinane

    Get PDF
    The title compound, C17H15BN2S, is one member in a series of diaza­borinanes featuring substitution at the 1-, 2- and 3-positions in the nitro­gen–boron heterocycle. The dihedral angle between the mean planes of the naphthalene and phenyl ring systems is 19.86 (6)°. In the crystal structure, two C—H⋯π inter­actions link the mol­ecules into sheets which lie parallel to the bc plane. There is a π–π inter­action between each pair of centrosymmetrically related sheets [centroid–centroid distance = 3.5922 (8) Å]

    Building Community and Tools for Analyzing Web Archives through Datathons

    Get PDF
    Starting in March 2016, the Archives Unleashed team and our collaborators have brought together social scientists, humanists, archivists, librarians, computer scientists, and other stakeholders to explore web archives as research objects. Three objectives motivated our team to develop and organize these events: facilitating scholarly access, community building, and skills training. We believe that we have been successful on all three fronts. For each event, over the course of two to three days, participants formed interdisciplinary teams and explored web archives using a variety of methods and tools. This paper details our experiences in designing these "datathons", with an intent to share lessons learned, highlight interdisciplinary approaches to research and education on web archives, and describe future opportunities.This research was supported by the Andrew W. Mellon Foundation, the Social Sciences and Humanities Research Council, the National Science Foundation (Grants #1624067, #1723430), Start Smart Labs, Rutgers University, Compute Canada, University of Waterloo, and York University. Additional support came from University of Toronto Libraries, Library of Congress, Internet Archive, British Library, the International Internet Preservation Consortium, Simon Fraser University Libraries, SFU Key, and Université du Québec en Outaouais

    T cell epitope: Friend or Foe? Immunogenicity of biologics in context

    Get PDF
    Like vaccines, biologic proteins can be very immunogenic for reasons including route of administration, dose frequency and the underlying antigenicity of the therapeutic protein. Because the impact of immunogenicity can be quite severe, regulatory agencies are developing risk-based guidelines for immunogenicity screening. T cell epitopes are at the root of the immunogenicity issue. Through their presentation to T cells, they activate the process of anti-drug antibody development. Preclinical screening for T cell epitopes can be performed in silico, followed by in vitro and in vivo validation. Importantly, screening for immunogenicity is complicated by the discovery of regulatory T cell epitopes, which suggests that immunogenicity testing must now take regulatory T cells into consideration. In this review, we address the application of computational tools for preclinical immunogenicity assessment, the implication of the discovery of regulatory T cell epitopes, and experimental validation of those assessments

    Long-Range Exciton Diffusion in Two-Dimensional Assemblies of Cesium Lead Bromide Perovskite Nanocrystals

    Get PDF
    F\"orster Resonant Energy Transfer (FRET)-mediated exciton diffusion through artificial nanoscale building block assemblies could be used as a new optoelectronic design element to transport energy. However, so far nanocrystal (NC) systems supported only diffusion length of 30 nm, which are too small to be useful in devices. Here, we demonstrate a FRET-mediated exciton diffusion length of 200 nm with 0.5 cm2/s diffusivity through an ordered, two-dimensional assembly of cesium lead bromide perovskite nanocrystals (PNC). Exciton diffusion was directly measured via steady-state and time-resolved photoluminescence (PL) microscopy, with physical modeling providing deeper insight into the transport process. This exceptionally efficient exciton transport is facilitated by PNCs high PL quantum yield, large absorption cross-section, and high polarizability, together with minimal energetic and geometric disorder of the assembly. This FRET-mediated exciton diffusion length matches perovskites optical absorption depth, opening the possibility to design new optoelectronic device architectures with improved performances, and providing insight into the high conversion efficiencies of PNC-based optoelectronic devices
    • …
    corecore