Gordon, Jr., Darrell

Co. K. 372nd Infantry; Fort Huachuca, Arizonahttps://dh.howard.edu/prom_members/1030/thumbnail.jp

INVESTIGATIONS TOWARD THE APPLICATION OF ORGANIC PHOTOREDOX CATALYSIS TO THE SYNTHESIS OF NATURAL PRODUCTS

While chemistry proceeding through radical intermediates has been known and studied for centuries, photoredox catalysis as a means of generating these species has only entered the forefront of synthetic organic chemistry within the past few decades. This approach has gained traction due to the use of visible light and generally mild conditions, making it compatible with a range of functional groups and late-stage functionalization. Chapters 1 and 2 of this work focus on photoredox catalysis in general. The first chapter covers the basic principles of photoredox catalysis, giving special attention to acridinium ion dyes as photoredox catalysts; in addition, select applications of acridinium ion photoredox catalysis to the synthesis of natural products are discussed. The second chapter details the importance of electrochemical potentials in planning and conducting photoredox transformations. Our work on compiling a database of experimental and computational potentials, and a collaboration with Merck on the advantages of organic photoredox catalysis are presented. Chapters 3 and 4 focus on our endeavors to apply acridinium ion photoredox catalysis to the synthesis of the natural products rubriflordilactone B and stemocurtisine. This work has culminated in a diastereoselective route to the left side of rubriflordilactone B and preliminary results for an approach to stemocurtisine.Doctor of Philosoph

Can One Hear the Shape of a Graph?

We show that the spectrum of the Schrodinger operator on a finite, metric graph determines uniquely the connectivity matrix and the bond lengths, provided that the lengths are non-commensurate and the connectivity is simple (no parallel bonds between vertices and no loops connecting a vertex to itself). That is, one can hear the shape of the graph! We also consider a related inversion problem: A compact graph can be converted into a scattering system by attaching to its vertices leads to infinity. We show that the scattering phase determines uniquely the compact part of the graph, under similar conditions as above.Comment: 9 pages, 1 figur

Quantifying flow regimes in a Greenland glacial fjord using iceberg drifters

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 8411–8420, doi:10.1002/2014GL062256.Large, deep-keeled icebergs are ubiquitous in Greenland's outlet glacial fjords. Here we use the movement of these icebergs to quantify flow variability in Sermilik Fjord, southeast Greenland, from the ice mélange through the fjord to the shelf. In the ice mélange, a proglacial mixture of sea ice and icebergs, we find that icebergs consistently track the glacier speed, with slightly faster speeds near terminus and episodic increases due to calving events. In the fjord, icebergs accurately capture synoptic circulation driven by both along-fjord and along-shelf winds. Recirculation and in-/out-fjord variations occur throughout the fjord more frequently than previously reported, suggesting that across-fjord velocity gradients cannot be ignored. Once on the shelf, icebergs move southeastward in the East Greenland Coastal Current, providing wintertime observations of this freshwater pathway.Funding for this study was provided by National Science Foundation grants OCE-1130008 and ARC-0909274, and by the University of Oregon.2015-06-1

Battling the race: Stylizing language and coproducing whiteness and colouredness in a freestyle rap performance

In the last 19 years of post-apartheid South African democracy, race remains an enduring and familiar trope, a point of certainty amid the messy ambiguities of transformation. In the present article, we explore the malleable, permeable, and unstable racializations of contemporary South Arica, specifically the way in which coloured and white racializations are negotiated and interactionally accomplished in the context of Capetonian hip-hop. The analysis reveals the complex ways in which racialized bodies are figured semiotically through reference to historical time and contemporary (translocal) social space. But also the way iconic features of blackness are reindexicalized to stand for a transnational whiteness

Quantifying flow regimes in a Greenland glacial fjord using iceberg drifters

Large, deep-keeled icebergs are ubiquitous in Greenland's outlet glacial fjords. Here we use the movement of these icebergs to quantify flow variability in Sermilik Fjord, southeast Greenland, from the ice mélange through the fjord to the shelf. In the ice mélange, a proglacial mixture of sea ice and icebergs, we find that icebergs consistently track the glacier speed, with slightly faster speeds near terminus and episodic increases due to calving events. In the fjord, icebergs accurately capture synoptic circulation driven by both along-fjord and along-shelf winds. Recirculation and in-/out-fjord variations occur throughout the fjord more frequently than previously reported, suggesting that across-fjord velocity gradients cannot be ignored. Once on the shelf, icebergs move southeastward in the East Greenland Coastal Current, providing wintertime observations of this freshwater pathway.Funded by The National Science Foundation. Grant Numbers: OCE-1130008, ARC-0909274 and The University of Oregon

Evaluation of a novel autoinjector for subcutaneous self-administration of belimumab in systemic lupus erythematosus

Objective: To study self-administration and pharmacokinetics (PK) of subcutaneous (SC) belimumab in patients with systemic lupus erythematosus (SLE). Methods: Patients previously treated with belimumab self-administered belimumab 200 mg SC weekly for 8 weeks using an autoinjector. The primary endpoint was the proportion of patients able to self-administer their first and second dose (weeks 1 and 2) in the clinic. The proportion able to self-administer at weeks 4 and 8 (clinic) and weeks 3, 5, 6, and 7 (home) were secondary endpoints. Belimumab PK, safety, and injection-site pain were assessed. Results: 91/95 patients completed the study (withdrawals: adverse events (AEs): 3; lost to follow-up: 1). 93% were female, and mean (SD) age was 44.8 (12.50) years. The majority (99%, 89/90; no attempt, n = 5) successfully self-administered belimumab SC at weeks 1 and 2 (5 had clinic staff assistance), and 98% (85/87) successfully self-administered at weeks 4 and 8. Home-administration success rates were high (93%, (81/87) at weeks 3, 5, 6, and 7). Week 8 median trough concentration was 113 µg/mL. For patients with a ≤ 1.5-week interval between IV SC administration, week-1 concentrations were higher vs. week 8 (+ 51% median) but within a range observed with IV dosing; those with a ≥ 2.5-week interval had median differences close to 0. AEs and serious AEs were low, with no deaths; pain levels were low and decreased with subsequent injections. Conclusion: Patients with SLE successfully self-administered belimumab SC using a novel autoinjector; the PK profile was stable following a switch from IV with acceptable AE and pain levels. The recommended dosing interval between IV to SC dosing is 1 – 4 weeks

Seeking celestial Positronium with an OH-suppressed diffraction-limited spectrograph

Celestially, Positronium (Ps), has only been observed through gamma-ray emission produced by its annihilation. However, in its triplet state, a Ps atom has a mean lifetime long enough for electronic transitions to occur between quantum states. This produces a recombination spectrum observable in principle at near IR wavelengths, where angular resolution greatly exceeding that of the gamma-ray observations is possible. However, the background in the NIR is dominated by extremely bright atmospheric hydroxyl (OH) emission lines. In this paper we present the design of a diffraction-limited spectroscopic system using novel photonic components - a photonic lantern, OH Fiber Bragg Grating filters, and a photonic TIGER 2-dimensional pseudo-slit - to observe the Ps Balmer alpha line at 1.3122 microns for the first time.Comment: 6 pages, 9 Figures, 2 Tables. Accepted to Applied Optics feature issue on Astrophotonic