Hot deformation behaviour of SiCp/Al composites and their matrices and an Al-Mg-Si alloy

Isothermal hot torsion tests were performed on two metal matrix composites (15v/o SiC\sb{\rm p}/A356 Al and 15v/o SiC\sb{\rm p}/6061 Al), a casting aluminum-silicon matrix alloy (A356) and an aluminum-magnesium-silicon alloy (6201). The composites and matrix alloy were tested over the range 300 to 540\sp\circC and 0.1 to 5.0 s\sp{-1}. Flow stress ($\sigma$) and strain-to-failure (\varepsilon\sb{\rm f}) data were determined and compared with published results. The flow stresses decrease monotonically with increasing deformation temperature (T), following the same relationship as the published data. At very high temperatures, $\sigma$ is similar for all materials but as T falls to 300\sp\circC, the A356 rises more rapidly than 6061. Flow stresses for the composites rise more rapidly than the matrix alloys. The ductility of all materials increases as T increases although it did not rise nearly as much for A356 as for 6061. The decreased reduction in \varepsilon\sb{\rm f} in the A356 materials compared to the 6061 materials indicates that the SiC particles have much less effect as additional crack initiators in A356. The plot of log $\.\varepsilon$ versus log sinh $\alpha\sigma$ were approximately linear over the narrow range of strain rates tested. Testing of 6201 Al was conducted at 200 to 500\sp\circC for overaged specimens and at 300 to 600\sp\circC for the solutioned ones at rates of 0.1 to 4.0 s\sp{-1}. The activation energy for the precipitated alloy is about 192 kJ/mol which is higher than that of pure aluminum. The alloy is somewhat stronger than aluminum because of the particles at low temperatures and the increased level of solute at high ones. The solutional specimens had high peak stresses and considerable work softening at 300\sp\circC due to dynamic formation and coalescence of precipitates. The Q\sb{\rm HW} was higher but poorly defined because of variations in precipitation during heating. The ductility increased as T rose and $\.\varepsilon$ decreased and was higher for precipitated than for solutioned specimens. (Abstract shortened by UMI.

Appendix D. Elasticities of matrix elements in matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively.

Elasticities of matrix elements in matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively

Appendix B. Modified structure of transition matrices constructed for stochastically varying recruitment as a function of variable hydrologic conditions.

Modified structure of transition matrices constructed for stochastically varying recruitment as a function of variable hydrologic conditions

Appendix C. Transition matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively.

Transition matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively

Appendix A. Structure of size-classified transition matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively.

Structure of size-classified transition matrices constructed for native and introduced flathead catfish populations from the Coosa (Alabama) and Ocmulgee (Georgia) rivers, respectively

Trends in Liver and Skin Tumor Prevalence in Brown Bullhead ( Ameiurus nebulosus) from the Anacostia River, Washington, DC, and Nearby Waters.

Supplemental Material, TS2_TPX_10.11770192623318823150 for Trends in Liver and Skin Tumor Prevalence in Brown Bullhead (Ameiurus nebulosus) from the Anacostia River, Washington, DC, and Nearby Waters by Alfred E. Pinkney, John C. Harshbarger, Michael A. Rutter, and Peter C. Sakaris in Toxicologic Pathology</p

Assessment of Reading Speed and Comprehension in STEM Students at Georgia Gwinnett College

Faculty colleagues frequently assert that students have difficulty reading; students fail to read exam questions or lab instructions correctly. Additionally, students frequently report to faculty that college level texts are too hard to read. To investigate the scope of this problem, reading comprehension across the biology program was assessed. Students were asked to read a passage and mark their position when the time limit was called; students were then asked to answer a few questions and summarize the reading passage. These student reading comprehension scores are analyzed with regard to academic (e.g. GPA, college hours completed) and social metrics (e.g. English as a second language, first generation college student) to determine if correlations exist with student success and persistence. Data indicating the progress of reading comprehension through the degree program and data documenting the insufficiencies of student reading comprehension and speed will be presented. Since successful science students must understand and interpret literature that uses technical language appropriate to the field, we hope to document correlations between reading speed and comprehension and student success to better understand difficulties GGC STEM students encounter. Future studies may address remediation however this study is limited to assessing the problem