27 research outputs found
Structure, Photophysics and the Order-Disorder Transition to the Beta Phase in Poly(9,9-(di -n,n-octyl)fluorene)
X-ray diffraction, UV-vis absorption and photoluminescence (PL) spectroscopy
have been used to study the well-known order-disorder transition (ODT) to the
beta phase in poly(9,9-(di n,n-octyl)fluorene)) (PF8) thin film samples through
combination of time-dependent and temperature-dependent measurements. The ODT
is well described by a simple Avrami picture of one-dimensional nucleation and
growth but crystallization, on cooling, proceeds only after molecular-level
conformational relaxation to the so called beta phase. Rapid thermal quenching
is employed for PF8 studies of pure alpha phase samples while extended
low-temperature annealing is used for improved beta phase formation. Low
temperature PL studies reveal sharp Franck-Condon type emission bands and, in
the beta phase, two distinguishable vibronic sub-bands with energies of
approximately 199 and 158 meV at 25 K. This improved molecular level structural
order leads to a more complete analysis of the higher-order vibronic bands. A
net Huang-Rhys coupling parameter of just under 0.7 is typically observed but
the relative contributions by the two distinguishable vibronic sub-bands
exhibit an anomalous temperature dependence. The PL studies also identify
strongly correlated behavior between the relative beta phase 0-0 PL peak
position and peak width. This relationship is modeled under the assumption that
emission represents excitons in thermodynamic equilibrium from states at the
bottom of a quasi-one-dimensional exciton band. The crystalline phase, as
observed in annealed thin-film samples, has scattering peaks which are
incompatible with a simple hexagonal packing of the PF8 chains.Comment: Submitted to PRB, 12 files; 1 tex, 1 bbl, 10 eps figure
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Herbicide-Resistance in Turf Systems: Insights and Options for Managing Complexity
Due to complex interactions between social and ecological systems, herbicide resistance has classic features of a “wicked problem.” Herbicide-resistant (HR) Poa annua poses a risk to sustainably managing U.S. turfgrass systems, but there is scant knowledge to guide its management. Six focus groups were conducted throughout the United States to gain understanding of socio-economic barriers to adopting herbicide-resistance management practices. Professionals from major turfgrass sectors (golf courses, sports fields, lawn care, and seed/sod production) were recruited as focus-group participants. Discussions emphasized challenges of the weed management of turfgrass systems as compared to agronomic crops. This included greater time constraints for managing weeds and more limited chemical control options. Lack of understanding about the proper use of compounds with different modes of action was identified as a threat to sustainable weed management. There were significant regional differences in perceptions of the existence, geographic scope, and social and ecological causes of HR in managing Poa annua. Effective resistance management will require tailoring chemical and non-chemical practices to the specific conditions of different turfgrass sectors and regions. Some participants thought it would be helpful to have multi-year resistance management programs that are both sector- and species-specific. © 2022 by the authors.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
PowerPoint Slides for: Renal Function and Scaled Troponin in Patients Presenting to the Emergency Department with Symptoms of Myocardial Infarction
<p><b><i>Background:</i></b> Cardiac troponins are often found to be
elevated in patients with renal dysfunction, even in the absence of
acute myocardial injury. The objective of this report was to
characterize the scaled troponin values and proportion of adjudicated
acute myocardial infarction (AMI) among patients with and without renal
dysfunction. <b><i>Methods:</i></b> The data was from a multicenter
prospective study including patients presenting to the emergency
department with symptoms of AMI. Troponin measurements were standardized
across various assays by calculating the observed results as multiples
of the assay-specific 99th percentile upper limit of normal. Patients
with an estimated glomerular filtration rate (eGFR; calculated by the
Chronic Kidney Disease Epidemiology Collaboration formula) <60
mL/min/1.73 m<sup>2</sup> were considered to have renal dysfunction. <b><i>Results:</i></b>
Of 430 included patients, 249 (58%) were male and 181 (42%) were
female, with a mean age of 55.9 ± 12.3 and 57.3 ± 12.8 years,
respectively. Eighty-seven (20.2%) had renal dysfunction. The
proportions of patients with at least one scaled troponin value above
the 99th percentile cut-off point among patients with and without renal
dysfunction were 40 (45.9%) and 81 (23.6%) respectively (<i>p</i> <
0.001). The proportions of patients with an adjudicated diagnosis of AMI
among those with and without renal dysfunction were 20.7 and 18.7%,
respectively (<i>p</i> = 0.67). Using scaled troponins, by the second
test there was >5X and by the third test >15X separation in the
excursion of troponin among those with AMI compared to those without. <b><i>Conclusions:</i></b>
One or more elevated troponin values are common in those with renal
dysfunction. Scaled troponins for eGFR groups were similar, indicating
that the use of this interpretative technique is applicable in
discerning AMI for those with and without renal dysfunction.</p