Polymer Antimicrobial Synergy Research

Recent studies have shown that certain polymers, such as branched polyethylenimine (BPEI), have the potential to be antimicrobial. We have been growing certain strains of Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli) and adding in concentrations of ampicillin to find the minimum inhibitory concentrations (MICs). This allows us to add in different concentrations of BPEI to test for synergy between our antibiotic and our polymer. To find the MIC of each antibiotic, we grew an overnight of the bacteria in Lysogeny Broth (LB) and let it inoculate for 20 hours. We then inoculated a 24 well culture cluster with LB, ampicillin, and bacteria. The volume of bacteria was 10μL to 1,000μL of LB, making a 1% concentration. The plates were checked after inoculating for 20 hours, and the results of whether there was growth or no growth would be charted. After finding the MICs of our bacteria, we began adding different amounts of BPEI, at a 1μg/mL concentration, to our bacteria and ampicillin concentrations to look for any signs of synergy. The same procedures as before were used when testing using the polymer. The results of the MIC of each bacteria are as the following: B. subtilis 1A578 was between 250μg/mL and 125μg/mL, B. subtilis 6051 was between 250μg/mL and 125μg/mL, and E. Coli ATTC11775 was between 4μg/mL and 2μg/mL. No clear synergy has been seen between BPEI and ampicillin

Far-field radiation of aft turbofan noise

Approximate expressions were developed for the noise radiation from the aft duct. The results of approximate aft radiation equation compare favorably to more exact Wiener-Hopf radiation results. Refraction as well as convective effects in the multiple flow streams is considered. The peak in the radiation pattern, which occurs nearly at engine sideline, is composed of modes with relatively large cut-off ratios. This implies that aft fan radiation will be inherently more difficult to suppress that the fan inlet noise. The theoretical multimodal radiation pattern is compared to experimental data for the first two harmonics of blade passage frequency for three full scale fans at two speeds. The agreement between theory and experiment is quite good

Spin susceptibility of underdoped cuprates: the case of Ortho-II YBa_2Cu_3O_{6.5}

Recent inelastic neutron scattering measurements found that the spin susceptibility of detwinned and highly ordered ortho-II YBa_2Cu_3O_{6.5} exhibits, in both the normal and superconducting states, one-dimensional incommensurate modulations at low energies which were interpreted as a signature of dynamic stripes. We propose an alternative model based on quasiparticle transitions between the arcs of a truncated Fermi surface. Such transitions are resonantly enhanced by scattering to the triplet spin resonance. We show that the anisotropy in the experimental spin response is consistent with this model if the gap at the saddle points is anisotropic.Comment: 5 fives, 3 postscript figure

Emulating a flexible space structure: Modeling

Control Dynamics, in conjunction with Marshall Space Flight Center, has participated in the modeling and testing of Flexible Space Structures. Through the series of configurations tested and the many techniques used for collecting, analyzing, and modeling the data, many valuable insights have been gained and important lessons learned. This paper discusses the background of the Large Space Structure program, Control Dynamics' involvement in testing and modeling of the configurations (especially the Active Control Technique Evaluation for Spacecraft (ACES) configuration), the results from these two processes, and insights gained from this work

An investigation of the compressive strength of PRD-49-3/Epoxy composites

The development of unidirectional fiber composite materials is discussed. The mechanical and physical properties of the materials are described. Emphasis is placed in analyzing the compressive behavior of composite materials and developing methods for increasing compressive strength. The test program for evaluating the various procedures for improving compressive strength are reported