91 research outputs found
Slow dynamics near glass transitions in thin polymer films
The -process (segmental motion) of thin polystyrene films supported
on glass substrate has been investigated in a wider frequency range from
10 Hz to 10 Hz using dielectric relaxation spectroscopy and thermal
expansion spectroscopy. The relaxation rate of the -process increases
with decreasing film thickness at a given temperature above the glass
transition. This increase in the relaxation rate with decreasing film thickness
is much more enhanced near the glass transition temperature. The glass
transition temperature determined as the temperature at which the relaxation
time of the -process becomes a macroscopic time scale shows a distinct
molecular weight dependence. It is also found that the Vogel temperature has
the thickness dependence, i.e., the Vogel temperature decreases with decreasing
film thickness. The expansion coefficient of the free volume is
extracted from the temperature dependence of the relaxation time within the
free volume theory. The fragility index is also evaluated as a function of
thickness. Both and are found to decrease with decreasing film
thickness.Comment: 9 pages, 7 figures, and 2 table
Differential Expression of Rubisco in Sporophytes and Gametophytes of Some Marine Macroalgae
Rubisco (ribulose-1, 5-bisphosphate carboxylase/oxygenase), a key enzyme of photosynthetic CO2 fixation, is one of the most abundant proteins in both higher plants and algae. In this study, the differential expression of Rubisco in sporophytes and gametophytes of four seaweed species â Porphyra yezoensis, P. haitanensis, Bangia fuscopurpurea (Rhodophyte) and Laminaria japonica (Phaeophyceae) â was studied in terms of the levels of transcription, translation and enzyme activity. Results indicated that both the Rubisco content and the initial carboxylase activity were notably higher in algal gametophytes than in the sporophytes, which suggested that the Rubisco content and the initial carboxylase activity were related to the ploidy of the generations of the four algal species
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