Time-domain dynamic opto-rheology study of polymer films using step-scan FTIR time-resolved spectroscopy (S[sup 2]FTIR TRS)

Step-scan Fourier transform infrared spectroscopy in conjunction with impulse stress on polymer films has been used to monitor dynamic rheological responses in real time. A novel piezo-electrically-driven polymer microrheometer was employed to apply repetitive impulses to the polymer sample while time-domain spectra were recorded. Recent results include the study of both semi-crystalline polymers such as isotactic polypropylene (iPP) and elastomers such as Estane polyester/polyurethane copolymer and Kraton tri-block copolymer. The spectral changes of iPP are consistent with frequency-domain results. For iPP at room temperature, large differences in the response times of different absorption bands are not seen. However, the orientation response of the CH{sub 3} rocking mode is slightly slower than the responses of the backbone modes. To the authors` knowledge, this is the first reported successful step-scan FTIR time-domain dynamic polymer opto-rheology experiment. The advantages of the time-domain experiment over the frequency-domain experiment are also discussed briefly. This technique appears to be applicable to a variety of polymer samples, and examples from additional results are illustrated

Ohio Northern Alumnus - April, 1927

https://digitalcommons.onu.edu/alumni_mag/1000/thumbnail.jp

Ohio Northern Alumnus - July, 1927

https://digitalcommons.onu.edu/alumni_mag/1001/thumbnail.jp

Multispecies reaction-diffusion systems

Multispecies reaction-diffusion systems, for which the time evolution equation of correlation functions become a closed set, are considered. A formal solution for the average densities is found. Some special interactions and the exact time dependence of the average densities in these cases are also studied. For the general case, the large time behaviour of the average densities has also been obtained.Comment: LaTeX file, 15 pages, to appear in Phys. Rev.

Nearest-neighbor distances in diffusion-controlled reactions modelled by a single mobile trap

We consider a system consisting of an infinite number of identical particles on a lattice initially uniformly distributed, which diffuese in the presence of a singke mobile trap and ask for the time-dependent behavior of the distance of the trap from the nearest particle. This quantity is a measure of the tendency of the system to self-segregate. We show, by a simulation incorporating the exact enumeration method, that in one dimension the expected distance L(t)> scales as L(t)>[approximate]t[alpha] as t-->[infinity], where the exponent [alpha] depends only on the ratio of the diffusion constant. A heuristic expression for [alpha] is suggested, analogous to a rigorous exponent found by ben-Avraham for a similar but not identical problem. The flux into the trap is found to vary as t-1/2 independent of the diffusion constants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29454/1/0000536.pd

Autonomous multispecies reaction-diffusion systems with more-than-two-site interactions

Autonomous multispecies systems with more-than-two-neighbor interactions are studied. Conditions necessary and sufficient for closedness of the evolution equations of the $n$-point functions are obtained. The average number of the particles at each site for one species and three-site interactions, and its generalization to the more-than-three-site interactions is explicitly obtained. Generalizations of the Glauber model in different directions, using generalized rates, generalized number of states at each site, and generalized number of interacting sites, are also investigated.Comment: 9 pages, LaTeX2

Resonance Raman studies of Rieske-type proteins

Resonance Raman (RR) spectra are reported for the [2Fe-2S] Rieske protein from Thermus thermophilus (TRP) and phthalate dioxygenase from Pseudomonas cepacia (PDO) as a function of pH and excitation wavelength. Depolarization ratio measurements are presented for the RR spectra of spinach ferredoxin (SFD), TRP, and PDO at 74 K. By comparison with previously published RR spectra of SFD, we suggest reasonable assignments for the spectra of TRP and PDO. The spectra of PDO exhibit virtually no pH dependence, while significant changes are observed in TRP spectra upon raising the pH from 7.3 to 10.1. One band near 270 cm-1, which consists of components at 266 cm-1 and 274 cm-1, is attributed to Fe(III)-N(His) stretching motions. We suggest that these two components arise from conformers having a protonated-hydrogen-bonded imidazole (266 cm-1) and deprotonated-hydrogen-bonded imidazolate (274 cm-1) coordinated to the Fe/S cluster and that the relative populations of the two species are pH-dependent; a simple structural model is proposed to account for this behavior in the respiratory-type Rieske proteins. In addition, we have identified RR peaks associated with the bridging and terminal sulfur atoms of the Fe-S-N cluster. The RR excitation profiles of peaks associated with these atoms are indistinguishable from each other in TRP (pH 7.3) and PDO and differ greatly from those of [2Fe-2S] ferredoxins. The profiles are bimodal with maxima near 490 nm and > approx. 550 nm. By contrast, bands associated with the Fe-N stretch show a somewhat different enhancement profile. Upon reduction, RR peaks assigned to Fe-N vibrations are no longer observed, with the resulting spectrum being remarkably similar to that reported for reduced adrenodoxin. This indicates that only modes associated with Fe-S bonds are observed and supports the idea that the reducing electron resides on the iron atom coordinated to the two histidine residues. Taken as a whole, the data are consistent with an St2FeSb2Fe[N(His)]t2 structure for the Rieske-type cluster.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29687/1/0000014.pd

Inkjet Metrology: High-Accuracy Mass Measurements of Microdroplets Produced by a Drop-on-Demand Dispenser

We describe gravimetric methods for measuring the mass of droplets generated by a drop-on-demand (DOD) microdispenser. Droplets are deposited, either continuously at a known frequency or as a burst of known number, into a cylinder positioned on a submicrogram balance. Mass measurements are acquired precisely by computer, and results are corrected for evaporation. Capabilities are demonstrated using isobutyl alcohol droplets. For ejection rates greater than 100 Hz, the repeatability of droplet mass measurements was 0.2%, while the combined relative standard uncertainty (uc) was 0.9%. When bursts of droplets were dispensed, the limit of quantitation was 72 μg (1490 droplets) with uc = 1.0%. Individual droplet size in a burst was evaluated by high-speed videography. Diameters were consistent from the tenth droplet onward, and the mass of an individual droplet was best estimated by the average droplet mass with a combined uncertainty of about 1%. Diameters of the first several droplets were anomalous, but their contribution was accounted for when dispensing bursts. Above the limits of quantitation, the gravimetric methods provided statistically equivalent results and permit detailed study of operational factors that influence droplet mass during dispensing, including the development of reliable microassays and standard materials using DOD technologies

Framing the Real: Lefèbvre and NeoRealist Cinematic Space as Practice

In 1945 Roberto Rossellini's Neo-realist Rome, Open City set in motion an approach to cinema and its representation of real life – and by extension real spaces – that was to have international significance in film theory and practice. However, the re-use of the real spaces of the city, and elsewhere, as film sets in Neo-realist film offered (and offers) more than an influential aesthetic and set of cinematic theories. Through Neo-realism, it can be argued that we gain access to a cinematic relational and multidimensional space that is not made from built sets, but by filming the built environment. On the one hand, this space allows us to "notice" the contradictions around us in our cities and, by extension, the societies that have produced those cities, while on the other, allows us to see the spatial practices operative in the production and maintenance of those contradictions. In setting out a template for understanding the spatial practices of Neo-realism through the work of Henri Lefèbvre, this paper opens its films, and those produced today in its wake, to a spatio-political reading of contemporary relevance. We will suggest that the rupturing of divisions between real spaces and the spaces of film locations, as well the blurring of the difference between real life and performed actions for the camera that underlies much of the central importance of Neo-realism, echoes the arguments of Lefèbvre with regard the social production of space. In doing so, we will suggest that film potentially had, and still has, a vital role to play in a critique of contemporary capitalist spatial practices

MATERIALS IN RESTORATIVE DENTISTRY

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73465/1/j.1749-6632.1968.tb20274.x.pd