Mechanisms of Porphyrinoid and Carotenoid Spectral Tuning Revealed with Quantum Chemistry

Continued advances in a myriad of biomedical and technological fields require the rational design of molecules or supramolecular architectures with specific photophysical properties. Central to this endeavor is a mechanistic understanding of optical property modulation as a function of molecular structure, conformation, and environment. Natural pigments and protein-pigment complexes constitute a ‘solutions manual’ to challenges in electronic (optical) engineering that has been refined over a few billion years of evolution, and from which design principles can be deduced. In this thesis, unique mechanisms for modulating the optical properties of natural or synthetic porphyrinoid and carotenoid pigments are elucidated with quantum chemical methods. Our investigations add a new conformational mechanism, as well as design principles for regioisomer-dependent electronic substituent effects to the cannon of structural tools for regulating the optical properties of pyrrole-modified porphyrins. The lessons learned provide insight into analogous spectral tuning mechanisms found in nature. We also delineate the molecular factors optimally regulating light harvesting in a natural photosynthetic antenna complex. These discoveries have advanced the fundamental understanding and practical utilization of structure-optical property modulation mechanisms, and may aid the design of next-generation photonic-based technologies

Light-Trap: A SiPM Upgrade for Very High Energy Astronomy and Beyond

With the development of the Imaging Atmospheric Cherenkov Technique (IACT), Gamma-ray astronomy has become one of the most interesting and productive fields of astrophysics. Current IACT telescope arrays (MAGIC, H.E.S.S, VERITAS) use photomultiplier tubes (PMTs) to detect the optical/near-UV Cherenkov radiation emitted due to the interaction of gamma rays with the atmosphere. For the next generation of IACT experiments, the possibility of replacing the PMTs with Silicon photomultipliers (SiPMs) is being studied. Among the main drawbacks of SiPMs are their limited active area (leading to an increase in the cost and complexity of the camera readout) and their sensitivity to unwanted wavelengths. Here we propose a novel method to build a relatively low-cost pixel consisting of a SiPM attached to a PMMA disc doped with a wavelength shifter. This pixel collects light over a much larger area than a single standard SiPM and improves sensitivity to near-UV light while simultaneously rejecting background. We describe the design of a detector that could also have applications in other fields where detection area and cost are crucial. We present results of simulations and laboratory measurements of a pixel prototype and from field tests performed with a 7-pixel cluster installed in a MAGIC telescope camera.Comment: Proceedings of the 35th International Cosmic Ray Conference (ICRC 2017), Bexco, Busan, Korea. Id:81

Dissociative Autoionization in (1+2)-photon Above Threshold Excitation of H2 Molecules

We have theoretically studied the effect of dissociative autoionization on the photoelectron energy spectrum in (1+2)-photon above threshold ionization(ATI) of H2 molecules. We have considered excitation from the ground state X-singlet-Sigma-g+(v=0,j) to the doubly excited autoionizing states of singlet-Sigma-u+ and singlet-Pi-u+ symmetry, via the intermediate resonant B-singlet-Sigma-u+(v=5,j) states. We have shown that the photoelectron energy spectrum is oscillatory in nature and shows three distinct peaks above the photoelectron energy 0.7 eV. This feature has been observed in a recent experiment by Rottke et al, J. Phys. B, Vol. 30, p-4049 (1997).Comment: 11 pages and 4 figure

Adapting Advanced Inorganic Chemistry Lecture and Laboratory Instruction for a Legally Blind Student

In this article, the strategies and techniques used to successfully teach advanced inorganic chemistry, in the lecture and laboratory, to a legally blind student are described. At Fairfield University, these separate courses, which have a physical chemistry corequisite or a prerequisite, are taught for junior and senior chemistry and biochemistry majors. A student earns a separate grade in each the lecture (three credits) and the laboratory course (two credits). An overview of the course topics is given, followed by general accommodations and specific approaches that were used. Student assistants were very helpful and provided extra support for the blind student. Student assistants were utilized for the laboratory course, problem sets, and exams. Specific examples and detailed explanations of approaches that were helpful to the legally blind student throughout the entire course are provided. The legally blind student benefited from extensive, verbal description of complexes, figures, and diagrams. In addition, the student benefited from tactile description of figures and models. The student assistants and extra office hours were essential for the blind student to succeed and excel in advanced inorganic chemistry. The approaches discussed in this paper are the product of immediate and continual feedback from the student over the course of the semester. The student would frequently comment after class that he followed the lesson or was confused, and the latter comment elicited experimentation with different approaches

Bioinformatics advances in saliva diagnostics

There is a need recognized by the National Institute of Dental & Craniofacial Research and the National Cancer Institute to advance basic, translational and clinical saliva research. The goal of the Salivaomics Knowledge Base (SKB) is to create a data management system and web resource constructed to support human salivaomics research. To maximize the utility of the SKB for retrieval, integration and analysis of data, we have developed the Saliva Ontology and SDxMart. This article reviews the informatics advances in saliva diagnostics made possible by the Saliva Ontology and SDxMart