Inducing hardening and healability in poly(ethylene-co-acrylic acid) via blending with complementary low molecular weight additives

The design and synthesis of low molecular weight additives based on self-assembling nitroarylurea units, and their compatibility with poly(ethylene-co-acrylic acid) copolymers are reported. The self-assembly properties of the low molecular weight additives have been demonstrated in a series of gelation studies. Upon blending at low percentage weights (≤ 5%) with poly(ethylene-co-acrylic acid) the additives were capable of increasing the stress and strain to failure when compared to the parent copolymer. By varying the percentage weight of the additive as well as the type of additive the mechanical properties of poly(ethylene-co-acrylic acid) could be tailored. Finally, the healability characteristics of the blends were improved when compared to the original polymer via the introduction of a supramolecular ‘network within a network’

Synthesis and analysis of a healable, poly(propylene glycol)-based supramolecular network

An investigation into healable supramolecular networks based upon branched poly(propylene) (PPG) oligomers that feature nitroarylurea chain ends is reported. A one-pot reaction utilising bis(toluene-1,4-diisocyanate)-terminated poly(propyleneglycol) (Mn ~ 2300), a nitroarylurea recognition motif, and tris(2-aminoethyl)amine was used to synthesise several branched PPG-based oligomers. The degree of oligomerization/branching was systematically varied by changing the stoichiometry of the starting materials in this one-pot reaction. The branched oligomers thus generated self-assemble into supramolecular networks, aided by association of the nitroarylurea end groups, and from this study a material that is capable of healing at ambient temperatures was realised. The healable supramolecular material formed from these studies exhibited effective autonomous healing (80% with respect to ultimate stress) up to 6 weeks after defect formation. Furthermore, elastic recovery was observed (80% with respect to yield stress) over a period of 24 hours after the samples were elongated beyond the region of uniform strain (50%)

The environment power system analysis tool development program

The Environment Power System Analysis Tool (EPSAT) is being developed to provide space power system design engineers with an analysis tool for determining system performance of power systems in both naturally occurring and self-induced environments. The program is producing an easy to use computer aided engineering (CAE) tool general enough to provide a vehicle for technology transfer from space scientists and engineers to power system design engineers. The results of the project after two years of a three year development program are given. The EPSAT approach separates the CAE tool into three distinct functional units: a modern user interface to present information, a data dictionary interpreter to coordinate analysis; and a data base for storing system designs and results of analysis

“Show me the Data”: A Recipe for Quality Improvement Success in an Academic Surgical Department

Background Surgeons in academic medical centers have traditionally taken a siloed approach to reducing postoperative complications. We initiated a project focusing on transparency and sharing of data in order to engage surgeons in collaborative quality improvement. Its key features were the development of a comprehensive Department Quality Dashboard and the creation of a Clinical Operations Council that oversaw quality. The purpose of this study was to assess the impact of those efforts. Study Design We compared inpatient outcomes before and after our intervention, allowing one quarter as the diffusion period. The outcomes analyzed were: risk-adjusted length of stay (LOS), mortality and direct cost and unadjusted incidence of complications and 30-day all-cause readmissions, as determined by the Vizient Clinical Database. We examined the outcomes of three groups: Group 1 (Surgery), Group 2 - all other surgical departments (Other Surgery) and Group 3 - all other patients (Non-Surgery). Two-tailed Students’s t-test was used for analysis and a p value of <0.05 considered statistically significant. Results Group 1 demonstrated statistically significant improvements in mortality (p=0.01), LOS (p=0.002), cost (p=0.0001) and complications (p=0.02) while the all-cause readmission rate was unchanged, resulting in mean decrease of 0.55 LOS days and direct cost savings of $2300 per surgical admission. The comparison groups had only modest decreases in some of the analyzed outcomes and an increase in complication rates. Conclusions These data suggest that a collaborative, data-driven and transparent approach to assessing the quality of surgical care can yield significant improvements in patient outcomes

Application of the gel shift assay to study the affinity and specificity of anti-DNA autoantibodies

We have demonstrated that the gel shift assay, a powerful method to study protein [middle dot] DNA interactions under equilibrium conditions, is both an accurate and precise method to measure the affinity of anti-DNA [middle dot] DNA immune complexes. One difficulty in performing gel shift assays is disruption of protein [middle dot] DNA equilibria during the time needed for complexes to enter the gel matrix. However, we have found that highly cross-linked polyacrylamide gels, which are known to form non-restrictive matrices, do not perturb anti-DNA[middle dot]DNA complexes. Using anti-ssDNA BV04-01 as a model antibody, we find good agreement between the dissociation constants (Kd) measureed in the gel shift assay using a 5.4% polyacrylamide gel cross-linked with 0.6% (bis)acrylamide, and those obtained previously by fluorescence quenching. Because gel shift assays require only nanogram quantities of analyte and can be performed in several hours, it is well suited for a range of anti-DNA binding studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31125/1/0000022.pd

Ion‐driven instabilities in the solar wind: Wind observations of 19 March 2005

Intervals of enhanced magnetic fluctuations have been frequently observed in the solar wind. But it remains an open question as to whether these waves are generated at the Sun and then transported outward by the solar wind or generated locally in the interplanetary medium. Magnetic field and plasma measurements from the Wind spacecraft under slow solar wind conditions on 19 March 2005 demonstrate seven events of enhanced magnetic fluctuations at spacecraft‐frame frequencies somewhat above the proton cyclotron frequency and propagation approximately parallel or antiparallel to the background magnetic field Bo. The proton velocity distributions during these events are characterized by two components: a more dense, slower core and a less dense, faster beam. Observed plasma parameters are used in a kinetic linear dispersion equation analysis for electromagnetic fluctuations at k x Bo = 0; for two events the most unstable mode is the Alfvén‐cyclotron instability driven by a proton component temperature anisotropy T⊥/T|| > 1 (where the subscripts denote directions relative to Bo), and for three events the most unstable mode is the right‐hand polarized magnetosonic instability driven primarily by ion component relative flows. Thus, both types of ion anisotropies and both types of instabilities are likely to be local sources of these enhanced fluctuation events in the solar wind.Key PointsIon temperature anisotropies and proton beam/core flows are sources of enhanced field observationsFor two events Alfven‐cyclotron modes are most unstableFor three events magnetosonic modes are most unstablePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137412/1/jgra52322.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/137412/2/jgra52322_am.pd

Nitroarylurea-terminated supramolecular polymers that exhibit facile thermal repair and aqueous swelling-induced sealing of defects

Bi- and tri-armed polyethylene glycol units endcapped with nitroaryl urea units have been synthesised. These endcapped polymers are able to self-assemble via complementary supramolecular interactions, specifically urea-urea and nitro-urea hydrogen bonding, to afford materials with dramatically increased mechanical and thermal properties when compared to those of the uncapped polyethylene glycol precursors. Thin films of the capped polymeric systems are able to self-repair following defect creation. Control over the mechanical and thermal characteristics (in terms of bulk viscosity) of the self-assembled networks was achieved by varying the proportion of tri-armed to bi-armed self-assembly units included in the polymer. These systems demonstrate water absorption and swelling capabilities that are also controllable by varying the ratio of the two types of unit. These physical properties have been optimised to realise a secondary pathway to puncture-repair as a result of swelling on water contact

Phase Coexistence of a Stockmayer Fluid in an Applied Field

We examine two aspects of Stockmayer fluids which consists of point dipoles that additionally interact via an attractive Lennard-Jones potential. We perform Monte Carlo simulations to examine the effect of an applied field on the liquid-gas phase coexistence and show that a magnetic fluid phase does exist in the absence of an applied field. As part of the search for the magnetic fluid phase, we perform Gibbs ensemble simulations to determine phase coexistence curves at large dipole moments, $\mu$. The critical temperature is found to depend linearly on $\mu^2$ for intermediate values of $\mu$ beyond the initial nonlinear behavior near $\mu=0$ and less than the $\mu$ where no liquid-gas phase coexistence has been found. For phase coexistence in an applied field, the critical temperatures as a function of the applied field for two different $\mu$ are mapped onto a single curve. The critical densities hardly change as a function of applied field. We also verify that in an applied field the liquid droplets within the two phase coexistence region become elongated in the direction of the field.Comment: 23 pages, ReVTeX, 7 figure

Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations

Parker Solar Probe (PSP) achieved its first orbit perihelion on November 6, 2018, reaching a heliocentric distance of about 0.165 au (35.55 R$_\odot$). Here, we study the evolution of fully developed turbulence associated with the slow solar wind along the PSP trajectory between 35.55 R$_\odot$ and 131.64 R$_\odot$ in the outbound direction, comparing observations to a theoretical turbulence transport model. Several turbulent quantities, such as the fluctuating kinetic energy and the corresponding correlation length, the variance of density fluctuations, and the solar wind proton temperature are determined from the PSP SWEAP plasma data along its trajectory between 35.55 R$_\odot$ and 131.64 R$_\odot$. The evolution of the PSP derived turbulent quantities are compared to the numerical solutions of the nearly incompressible magnetohydrodynamic (NI MHD) turbulence transport model recently developed by Zank et al. (2017). We find reasonable agreement between the theoretical and observed results. On the basis of these comparisons, we derive other theoretical turbulent quantities, such as the energy in forward and backward propagating modes, the total turbulent energy, the normalized residual energy and cross-helicity, the fluctuating magnetic energy, and the correlation lengths corresponding to forward and backward propagating modes, the residual energy, and the fluctuating magnetic energy