The Redox Chemistry of Dirhodium Carboxamidates: From Fundamental Structures to Catalytic Functions.

Redox chemistry is the study of molecular structure and function associated with changes in oxidation state. In this manuscript, the structures and functions of dinuclear rhodium complexes in various oxidation states are investigated. In Chapter 1, probing the structural chemistry of dirhodium(II) carboxamidates reveals that an unprecedented, stable, dirhodium(III) complex can be synthesized and characterized. Bis(σ-phenyl)-tetrakis(μ-caprolactamato)dirhodium(III) [Rh2(cap)4Ph2] was prepared from Rh2(cap)4 by a copper catalyzed, aerobic oxidation with aryl transfer from sodium tetraphenylborate. Structural data was obtained by single crystal X-ray diffraction (XRD) of Rh2(cap)4Ph2 and related structures with systematic changes in oxidation state. X-ray photoelectron spectroscopy (XPS) was used to determine binding energies for the rhodium electrons in the complexes. The structural data and XPS binding energies indicate that the Rh-Rh bonding interaction does not exist in Rh2(cap)4Ph2. In Chapter 2, the synthesis of Rh2(cap)4Ph2 was made general by using aryl-boronic acids as the aryl transfer agent. The synthesis provided access to an array of bis(σ-aryl)-Rh2L4 complexes with varying substitution of the aryl ligands. X-ray structures, electrochemical, and computational analysis of complexes with substituents of varying electron-deficiency confirm the Rh Rh bond cleavage. A second-order Jahn-Teller effect is proposed as the basis for the observed Rh-Rh-C bond angle distortions in the X-ray crystal structures. The delocalization of the aromatic π-system through the Rh2-core was investigated and found to be absent, consistent with the calculated electronic structure. The final chapter explores the catalytic redox chemistry of Rh2(cap)4. The mechanism for the oxidative Mannich reaction catalyzed by Rh2(cap)4 in conjunction with tert-butyl hydroperoxide was investigated. This study revealed that iminium ions were formed by the oxidation of N,N-dialkylanilines with the Rh2(cap)4/TBHP system. Rh2(cap)4 was found to be a catalyst for the homolytic decomposition of TBHP to yield the tert-butylperoxyl radical (t BuOO) in a one-electron redox couple. Iminium ions were formed in a stepwise process from N,N-dialkylaniline via rate-limiting, hydrogen atom transfer to t-BuOO followed by rapid electron transfer to excess oxidant in situ. The net hydrogen atom transfer was found to be a step-wise electron transfer/proton transfer between the N,N-dialkylaniline and t BuOO providing evidence for a novel reactivity mode for peroxyl radicals. Nucleophilic capture of the iminium ion to complete the Mannich process was found to occur without association to Rh2(cap)4 under thermodynamic control

Shoreline armoring disrupts marine-terrestrial connectivity in the Salish Sea, with consequences for invertebrates, fish, and birds

Within the marine-terrestrial ecotone, upper intertidal “wrack zones” accumulate organic debris from algae, seagrass, and terrestrial plant sources and provide food and shelter for many organisms. We conducted detailed surveys of wrack and log accumulations and supralittoral invertebrates in spring and fall over 3 years at 29 armored-unarmored beach pairs in Puget Sound, WA, USA. Additionally, behavioral observations of juvenile salmon (Oncorhynchus spp.) and birds were conducted at 6 pairs. Armored beaches had substantially less wrack overall, a lower proportion of terrestrial plant material in the wrack, and far fewer logs. Armored beaches had significantly fewer invertebrates and differed from unarmored beaches in their taxonomic composition. Unarmored invertebrate assemblages were dominated by talitrid amphipods and insects, and were correlated with the amount of beach wrack and logs, the proportion of terrestrial material in wrack, and the maximum elevation of the beach. Shoreline armoring influenced juvenile salmon distribution, with fewer overall observations and fish in deeper water at armored beaches, but their feeding rates were relatively high at all sites. Terrestrial birds were commonly observed foraging among beach wrack and logs at unarmored beaches, but were largely absent from armored beaches. This study demonstrates that shoreline armoring disrupts marine-terrestrial connectivity, affecting the amount and type of organic material delivered to the nearshore ecotone in the form of wrack and logs, the abundance and taxonomic composition of supralittoral invertebrates, and the distribution and behavior of secondary consumers (juvenile salmon and birds)

Conductance-Based Profiling of Nanopores: Accommodating Fabrication Irregularities

Solid-state nanopores are nanoscale channels through otherwise impermeable membranes. Single molecules or particles can be passed through electrolyte-filled nanopores by, e.g. electrophoresis, and then detected through the resulting physical displacement of ions within the nanopore. Nanopore size, shape, and surface chemistry must be carefully controlled, and on extremely challengingwork, confirmed the suitability of the basic conductance equation using the results of a time-dependent experimental conductance measurement during nanopore fabrication by Yanagi et al., and then deliberately relaxed the model constraints to allow for (1) the presence of defects; and (2) the formation of two small pores instead of one larger one. Our simulations demonstrated that the time-dependent conductance formalism supports the detection and characterization of defects, as well as the determination of pore number, but with implementation performance depending on the measurement context and results. In some cases, the ability to discriminate numerically between the correct and incorrect nanopore profiles was slight, but with accompanying differences in candidate nanopore dimensions that could yield to post-fabrication conductance profiling, or be used as convenient uncertainty bounds. Time-dependent nanopore conductance thus offers insight into nanopore structure and function, even in the presence of fabrication defects

Modelling the penumbra in computed tomography

Background: In computed tomography (CT), the spot geometry is one of the main sources of error in CT images. Since X-rays do not arise from a point source, artefacts are produced. In particular there is a penumbra effect, leading to poorly defined edges within a reconstructed volume. Penumbra models can be simulated given a fixed spot geometry and the known experimental setup. Objective: This paper proposes to use a penumbra model, derived from Beer’s law, both to confirm spot geometry from penumbra data, and to quantify blurring in the image. Methods: Two models for the spot geometry are considered; one consists of a single Gaussian spot, the other is a mixture model consisting of a Gaussian spot together with a larger uniform spot. Results: The model consisting of a single Gaussian spot has a poor fit at the boundary. The mixture model (which adds a larger uniform spot) exhibits a much improved fit. The parameters corresponding to the uniform spot are similar across all powers, and further experiments suggest that the uniform spot produces only soft X-rays of relatively low-energy. Conclusions: Thus, the precision of radiographs can be estimated from the penumbra effect in the image. The use of a thin copper filter reduces the size of the effective penumbra

Public Scholarship at Indiana University-Purdue University

Community engagement is a defining attribute of the campus, and the current Strategic Plan identifies a number of strategic actions to “Deepen our Commitment to Community Engagement.” In May 2015, A Faculty Learning Community (FLC) on Public Scholarship was established in May, 2015 to address the campus strategic goals to “recognize and reward contributions to community engagement” and “define community engagement work…in Faculty Annual Reports and promotion and tenure guidelines.” At IUPUI, scholarly work occurs in research and creative activity, teaching, and/or service. In terms of promotion and tenure, faculty members must declare an area of excellence in one of these three domains. The FLC on Public Scholarship is a 3-year initiative co-sponsored by Academic Affairs and the Center for Service and Learning (CSL). Seven faculty members from across campus were selected to be part of the 2015-2016 FLC, and two co-chairs worked closely with CSL staff to plan and facilitate the ongoing work. The FLC is charged with defining public scholarship, identifying criteria to evaluate this type of scholarship, assist faculty in documenting their community-engaged work, and working with department Chairs and Deans in adapting criteria into promotion and tenure materials. The intended audiences for this work includes faculty, community-engaged scholars, public scholars, promotion and tenure committees, external reviewers, and department Chairs and Deans. The following provides background to the campus context and a brief summary of work to date, including definition and proposed criteria to evaluate public scholarship.IUPUI Center for Service and Learning; IUPUI Office of Academic Affair

ESA-listed Puget Sound rockfish: How did we get here and how do we assess progress towards recovery planning goals?

In Puget Sound, WA, rockfish abundance declined significantly over the last 50+ years as a result of fishing pressure, life-history characteristics and the isolated geography of Puget Sound. In 2010, three species of rockfish were listed under the Endangered Species Act (ESA): yelloweye rockfish, canary rockfish and bocaccio. Due to a general lack of data specific to these three species, data from other rockfish species were used to support the listings. Since the listings, targeted research and recovery planning has begun to address major data gaps for these three species. First, cooperative research with the recreational fishing community has revealed that yelloweye rockfish are genetically distinct from coastal populations, whereas canary rockfish are not distinct - which has led to canary rockfish being delisted, the first delisting of a marine fish. Second, an ROV survey has been designed specifically to provide a path forward to estimate changes in abundance of listed rockfish in Puget Sound. Third, the Rockfish Recovery Plan for yelloweye rockfish and bocaccio has been published. This plan provides, and we have begun to address, a list of research activities related to environmental conditions and human activities that might constrain rockfish recovery. Two ongoing studies examine whether specific environmental covariates (e.g. dissolved oxygen) alter the movement and foraging behavior of yelloweye rockfish and whether rockfish bycatch can be reduced in the recreational lingcod fishery by using specific bait types. Finally, we will discuss the criteria to be used for delisting these species under the ESA, including statistical methods and operational challenges

TFOS DEWS II Report Executive Summary

This article presents an Executive Summary of the conclusions and recommendations of the 10-chapter TFOS DEWS II report. The entire TFOS DEWS II report was published in the July 2017 issue of The Ocular Surface. A downloadable version of the document and additional material, including videos of diagnostic and management techniques, are available on the TFOS website: www.TearFilm.org

The Liberation of Embryonic Stem Cells

Mouse embryonic stem (ES) cells are defined by their capacity to self-renew and their ability to differentiate into all adult tissues including the germ line. Along with efficient clonal propagation, these properties have made them an unparalleled tool for manipulation of the mouse genome. Traditionally, mouse ES (mES) cells have been isolated and cultured in complex, poorly defined conditions that only permit efficient derivation from the 129 mouse strain; genuine ES cells have not been isolated from another species in these conditions. Recently, use of small molecule inhibitors of glycogen synthase kinase 3 (Gsk3) and the Fgf-MAPK signaling cascade has permitted efficient derivation of ES cells from all tested mouse strains. Subsequently, the first verified ES cells were established from a non-mouse species, Rattus norvegicus. Here, we summarize the advances in our understanding of the signaling pathways regulating mES cell self-renewal that led to the first derivation of rat ES cells and highlight the new opportunities presented for transgenic modeling on diverse genetic backgrounds. We also comment on the implications of this work for our understanding of pluripotent stem cells across mammalian species

Addressing Risks of Lead in Water and Soil: Using Citizen Science and a Unique Partnership with Faith Organizations

One of the most widespread environmental health hazards in the United States remains exposure to the harmful neurotoxin lead. So much lead remains in the urban environment that it is not unusual to find neighborhoods where more than 10% of children exhibit harmful levels of lead, compared to the national average of about 1%. To overcome this challenge, a partnership between IUPUI researchers and faith organizations in Indianapolis is taking aim at the risk of household lead contamination by providing residents the tools they need to protect against it. The community-driven science aspect of this project is intentional—not only will the individuals who participate benefit directly, but the resulting data will also play a role in keeping communities safer more broadly