Diatoms are unicellular
algae of enormous biodiversity that occur in all water habitats on
earth. Their cell walls are composed of amorphous biosilica and exhibit
species-specific nanoporous to microporous and macroporous patterning.
Therefore, diatom biosilica is a promising renewable material for
various applications, such as in catalysis, drug-delivery systems,
and biophotonics. In this study, diatom biosilica of three different
species (
Stephanopyxis turris
,
Eucampia zodiacus
, and
Thalassiosira
pseudonana
) was used as support material for gold
nanoparticles using a covalent coupling method. The resulting catalysts
were applied for the oxidation of
d
-glucose to
d
-gluconic acid. Because of its high specific surface area, well-established
transport pores, and the presence of small, homogeneously distributed
gold nanoparticles on the surface, diatom biosilica provides a highly
catalytically active surface and advanced accessibility to the active
sites. In comparison to those of the used reference supports, higher
catalytic activities (up to 3.28 × 10
–4
mmol
Glc
s
–1
mg
Au
–1
for
T. pseudonana
biosilica) and
slower deactivation were observed for two of the diatom biosilica
materials. In addition, diatom biosilica showed very high gold-loading
capacities (up to 45 wt %), with a homogeneous nanoparticle distribution.
If we are to change the pedagogy of teacher education, then teacher educators need to listen carefully to the students they teach. Drawing on a longitudinal study where prospective teachers talk about their learning across a 2-year teacher education program, this article seeks to illustrate and to interpret interview comments from five prospective teachers about their learning experiences. Data analysis highlights the diversity of needs expressed by prospective teachers and how a teacher educator adapts his or her teaching practices in response to their comments. The relationship between student-teacher voices and the reflecting practitioner's voice is at the center of this article. A hermeneutic stance is used to examine the circular nature of learning to teach and the role of a teacher educator in it. Teacher education is continuous, and to change it, teacher educators need to change the ways in which they guide new professionals as they begin to feel and adapt to the unsteady beat of learning to teach.
What conceptions do student teachers hold about good primary science teaching? Do these conceptions change during preservice education? To determine answers to these questions, 12 Canadian preservice primary teachers were interviewed on four occasions as they completed their postgraduate 2-year education degree. The findings from these interviews are compared with a similar longitudinal Australian study, in which the nine preservice teachers were completing an undergraduate education award. Entry conceptions of good science teaching dominated and learning frameworks did not appear to change. Issues for teacher educators are raised about extending and changing student teachers' conceptions of effective practice.
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