Comparisons of Speech Anxiety in Basic Public Speaking Courses: Are Intensive or Traditional Semester Courses Better?

Students of public speaking are often asked if a basic public speaking course helped them deal with their fear of public speaking. Comparisons of anxiety levels between students enrolled in traditional 15-week semester courses and those enrolled in intensive courses has received little attention. The purpose of this exploratory, quasi-experimental study was to determine whether students enrolled in intensive public speaking courses reported higher levels of communication apprehension, i.e., speech anxiety. Participants were 722 undergraduate students who completed the Personal Report of Public Speaking Anxiety instrument. The findings indicated that students enrolled in intensive public speaking courses had significant moderate communication apprehension scores compared to students enrolled in 15-week semester courses. It is argued that the study indicates that there are factors that should be explored in further research on intensive public speaking courses

Metallurgical Structures of As-Cast and Heat-Treated High-Palladium Dental Alloys

Scanning electron microscope observations and energy-dispersive spectroscopic analyses have been performed on two first-generation and two second-generation high-palladium dental casting alloys. A specimen design simulating a maxillary central incisor coping was employed to conserve metal, while providing thin and thick sections to yield a range of solidification rates. The alloys were centrifugally cast in air, following standard dental laboratory techniques; three castings were prepared for each alloy. Each casting was sectioned to produce two mirror-image specimens, and one specimen received the appropriate oxidation heat treatment, followed by a simulated full porcelain firing sequence. After metallographic polishing, specimens were examined with a scanning electron microscope. The as-cast alloys displayed multi-phase microstructures which could be explained by the rapid solidification conditions and the relevant phase diagrams. The simulated porcelain firing heat treatment caused a variety of bulk microstructural changes in the coping sections, along with formation of complex subsurface oxidation regions which were less thick for the second-generation alloys. Elemental compositions of the palladium solid solution matrix in the heat-treated alloys were in good agreement with nominal alloy compositions provided by the manufacturers. Ruthenium-rich particles found in the microstructures of three alloys are consistent with a proposed mechanism for grain refinement

Metallurgical Structures of As-Cast and Heat-Treated High-Palladium Dental Alloys

Scanning electron microscope observations and energy-dispersive spectroscopic analyses have been performed on two first-generation and two second-generation high-palladium dental casting alloys. A specimen design simulating a maxillary central incisor coping was employed to conserve metal, while providing thin and thick sections to yield a range of solidification rates. The alloys were centrifugally cast in air, following standard dental laboratory techniques; three castings were prepared for each alloy. Each casting was sectioned to produce two mirror-image specimens, and one specimen received the appropriate oxidation heat treatment, followed by a simulated full porcelain firing sequence. After metallographic polishing, specimens were examined with a scanning electron microscope. The as-cast alloys displayed multi-phase microstructures which could be explained by the rapid solidification conditions and the relevant phase diagrams. The simulated porcelain firing heat treatment caused a variety of bulk microstructural changes in the coping sections, along with formation of complex subsurface oxidation regions which were less thick for the second-generation alloys. Elemental compositions of the palladium solid solution matrix in the heat-treated alloys were in good agreement with nominal alloy compositions provided by the manufacturers. Ruthenium-rich particles found in the microstructures of three alloys are consistent with a proposed mechanism for grain refinement

Landscape heterogeneity drives contrasting concentration–discharge relationships in shale headwater catchments

Solute concentrations in stream water vary with discharge in patterns that record complex feedbacks between hydrologic and biogeochemical processes. In a comparison of three shale-underlain headwater catchments located in Pennsylvania, USA (the forested Shale Hills Critical Zone Observatory), and Wales, UK (the peatland-dominated Upper Hafren and forest-dominated Upper Hore catchments in the Plynlimon forest), dissimilar concentration–discharge (C–Q) behaviors are best explained by contrasting landscape distributions of soil solution chemistry – especially dissolved organic carbon (DOC) – that have been established by patterns of vegetation and soil organic matter (SOM). Specifically, elements that are concentrated in organic-rich soils due to biotic cycling (Mn, Ca, K) or that form strong complexes with DOC (Fe, Al) are spatially heterogeneous in pore waters because organic matter is heterogeneously distributed across the catchments. These solutes exhibit non-chemostatic behavior in the streams, and solute concentrations either decrease (Shale Hills) or increase (Plynlimon) with increasing discharge. In contrast, solutes that are concentrated in soil minerals and form only weak complexes with DOC (Na, Mg, Si) are spatially homogeneous in pore waters across each catchment. These solutes are chemostatic in that their stream concentrations vary little with stream discharge, likely because these solutes are released quickly from exchange sites in the soils during rainfall events. Furthermore, concentration–discharge relationships of non-chemostatic solutes changed following tree harvest in the Upper Hore catchment in Plynlimon, while no changes were observed for chemostatic solutes, underscoring the role of vegetation in regulating the concentrations of certain elements in the stream. These results indicate that differences in the hydrologic connectivity of organic-rich soils to the stream drive differences in concentration behavior between catchments. As such, in catchments where SOM is dominantly in lowlands (e.g., Shale Hills), we infer that non-chemostatic elements associated with organic matter are released to the stream early during rainfall events, whereas in catchments where SOM is dominantly in uplands (e.g., Plynlimon), these non-chemostatic elements are released later during rainfall events. The distribution of SOM across the landscape is thus a key component for predictive models of solute transport in headwater catchments

Room Temperature Aging of Pd-Cu-Ga Dental Alloys

Specimens of three Pd-Cu-Ga dental alloys cast five years ago and subsequently stored at room temperature were reexamined and observed to have lower amounts of the eutectic constituents in the near-surface region than originally present, along with other microstructural changes. This previously unreported room temperature aging behavior of these alloys is attributed to the presence of high-diffusivity paths in the non-equilibrium ascast eutectic structures and to the essential role of the surface for the vacancy diffusion mechanism. These results may have important clinical significance for the ill vivo corrosion resistance and long-term biocompatibility of the Pd-Cu-Ga alloys

Biotic controls on solute distribution and transport in headwater catchments

Solute concentrations in stream water vary with discharge in patterns that record complex feedbacks between hydrologic and biogeochemical processes. In a comparison of headwater catchments underlain by shale in Pennsylvania, USA (Shale Hills) 5 and Wales, UK (Plynlimon), dissimilar concentration-discharge behaviors are best explained by contrasting landscape distributions of soil solution chemistry – especially dissolved organic carbon (DOC) – that have been established by patterns of vegetation. Specifically, elements that are concentrated in organic-rich soils due to biotic cycling (Mn, Ca, K) or that form strong complexes with DOC (Fe, Al) are spatially heteroge- 10 neous in pore waters because organic matter is heterogeneously distributed across the catchments. These solutes exhibit non-chemostatic “bioactive” behavior in the streams, and solute concentrations either decrease (Shale Hills) or increase (Plynlimon) with increasing discharge. In contrast, solutes that are concentrated in soil minerals and form only weak complexes with DOC (Na, Mg, Si) are spatially homogeneous in pore waters 15 across each catchment. These solutes are chemostatic in that their stream concentrations vary little with stream discharge, likely because these solutes are released quickly from exchange sites in the soils during rainfall events. Differences in the hydrologic connectivity of organic-rich soils to the stream drive differences in concentration behavior between catchments. As such, in catchments where soil organic matter (SOM) is dom- 20 inantly in lowlands (e.g., Shale Hills), bioactive elements are released to the stream early during rainfall events, whereas in catchments where SOM is dominantly in uplands (e.g., Plynlimon), bioactive elements are released later during rainfall events. The distribution of vegetation and SOM across the landscape is thus a key component for predictive models of solute transport in headwater catchments