Fiber propagation of vector modes

Here we employ both dynamic and geometric phase control of light to produce radially modulated vector-vortex modes, the natural modes of optical fibers. We then measure these modes using a vector modal decomposition set-up as well as a tomography measurement, the latter providing a degree of the non-separability of the vector states, akin to an entanglement measure for quantum states. We demonstrate the versatility of the approach by creating the natural modes of a step-index fiber, which are known to exhibit strong mode coupling, and measure the modal cross-talk and non-separability decay during propagation. Our approach will be useful in mode division multiplexing schemes for transport of classical and quantum states.Comment: 6 pages, 4 figures, 1 tabl

Bacterially derived non-ribosomally synthesized peptides : isolation, structural elucidation, total synthesis and biological investigation

PhD ThesisSiderophores are non-ribosomally derived peptides, and are key components in bacterial virulence and in the bacterial endogenous secondary metabolome. Therefore, they provide a unique insight into bacterial infection and potential treatments. As such, we have isolated two bacterial siderophores, the first being produced by a novel Actinomadura species. We carried out a de novo structural determination, utilising NMR, HMRS and Marfey’s analysis, allowing us to identify the isolated siderophore as madurastatin C1. This work also allowed us to determine the absolute stereochemistry of madurastatin C1 and ultimately reassigned the structures of the madurastatin family of siderophores. This culminated in a publication in the ACS Journal of Natural Products in early 2017. As a continuation of this work, the total synthesis of madurastatin C1 has been completed. A second novel bacterial strain yielded a novel siderophore like peptide, with structural similarities to the known siderophores; chlorocatechelins. Once again the structure was elucidated via NMR and HRMS with the stereochemistry assigned through Marfey’s analysis. The total synthesis of this novel siderophore was completed, and the synthetic material used in biological studies, confirming the efficacy of the originally isolated natural product

A General Analysis of the Convergence of ADMM

We provide a new proof of the linear convergence of the alternating direction method of multipliers (ADMM) when one of the objective terms is strongly convex. Our proof is based on a framework for analyzing optimization algorithms introduced in Lessard et al. (2014), reducing algorithm convergence to verifying the stability of a dynamical system. This approach generalizes a number of existing results and obviates any assumptions about specific choices of algorithm parameters. On a numerical example, we demonstrate that minimizing the derived bound on the convergence rate provides a practical approach to selecting algorithm parameters for particular ADMM instances. We complement our upper bound by constructing a nearly-matching lower bound on the worst-case rate of convergence.Comment: 10 pages, 6 figure

Rapid and Accurate Pressure Sensing Device for Direct Measurement of Intraocular Pressure.

PurposeIntraocular pressure (IOP) is the primary modifiable risk factor for glaucoma. Current devices measure IOP via the dynamic response of the healthy cornea and do not provide the accurate IOP measurements for patients with altered corneal biomechanics. We seek to develop and test an accurate needle-based IOP measurement device that is not cornea dependent.MethodsOur device combines a high-resolution pressure microsensor with 30- and 33-gauge Luer lock needles to provide IOP measurements via a microcontroller and USB interface to a computer. The device was calibrated in a membrane chamber and then tested and validated in the anterior chamber and post-vitrectomy vitreous chamber of rabbit eyes. The results were compared to Tonopen readings across a pressure range of 0 to 100 mm Hg, imposed in increments of 10 mm Hg.ResultsBoth the needle based sensor device and the Tonopen demonstrated a linear relationship with changes in imposed pressure. The Tonopen was found to consistently underestimate the IOP both in the anterior and vitreous chambers. The Tonopen exhibited a significantly greater error than our needle-based sensor device. With increased pressure (>30 mm Hg), the error of the Tonopen increased, whereas the error of our device did not. The 30-gauge needle produces an insignificant improvement in accuracy over the 33-gauge needle.ConclusionsA needle-based sensor device enables accurate IOP measurements over a broad range of induced IOP.Translational relevanceDirect measurement of IOP in the anterior chamber circumvents the influence of corneal parameters on IOP measurement

Terminal ruthenium carbido complexes as σ-donor ligands

The terminal carbido ligand of (Pcy_3)_2(Cl)_2RuC coordinates to other metal centers in a σ-donor fashion, as in (Pcy_3)_2(Cl)_2Ru≡C–Pd(Cl)_2(Sme_2) and (Pcy_3)_2(Cl)_2Ru≡C–Mo(CO)_5

Spectral radiometry and tropospheric aerosols: Report of panel

The term aerosols, as used here, refers to the haze, smoke, and dust that appear in the troposphere. The term does not refer to the hydrometeors in cumulus and stratus clouds but does include the sulfuric acid-water droplets which are assumed to predominate in the stratospheric aerosol layer. The aerosol properties that were measured from satellites and those which can be made in the near term (up to 1992) will be reviewed. The capabilities that will exist in the years 1992 to 2000, with implementation of EOS, are then discussed. Finally, a few words will be said concerning the potential for aerosol measurements for the decade after 2000