Non-Contact Temperature Requirements (NCTM) for drop and bubble physics

Many of the materials research experiments to be conducted in the Space Processing program require a non-contaminating method of manipulating and controlling weightless molten materials. In these experiments, the melt is positioned and formed within a container without physically contacting the container's wall. An acoustic method, which was developed by Professor Taylor G. Wang before coming to Vanderbilt University from the Jet Propulsion Laboratory, has demonstrated the capability of positioning and manipulating room temperature samples. This was accomplished in an earth-based laboratory with a zero-gravity environment of short duration. However, many important facets of high temperature containerless processing technology have not been established yet, nor can they be established from the room temperature studies, because the details of the interaction between an acoustic field an a molten sample are largely unknown. Drop dynamics, bubble dynamics, coalescence behavior of drops and bubbles, electromagnetic and acoustic levitation methods applied to molten metals, and thermal streaming are among the topics discussed

Problem-Based Learning: Development Of Knowledge And Reasoning Strategies

Problem-based learning (PBL) reflects new conceptions of learning that have grown out of theory and research in cognitive science. PBL has been used in medical schools to enhance the development of clinical reasoning skills and to promote the integration of basic biomedical sciences with clinical applications. In this study, the effect of PBL on the development of clinical reasoning strategies, use of scientific knowledge, and accuracy are examined on a causal explanation task. Students in problem-based curricula were compared with students in traditional medical curricula. The results indicate that PBL plays a role in facilitating the development of expertise. In PBL, students learn through the transfer of hypothesis-driven reasoning skills that result in more coherent explanations. The PBL students are better able to apply their science knowledge than nonPBL students, leading to greater accuracy of hypotheses

Microbial interactions associated with biofilms attached to Trichodesmium spp. and detrital particles in the ocean

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2010Quorum sensing (QS) via acylated homoserine lactones (AHLs) was discovered in the ocean, yet little is known about its role in the ocean beyond its involvement in certain symbiotic interactions. The objectives of this thesis were to constrain the chemical stability of AHLs in seawater, explore the production of AHLs in marine particulate environments, and probe selected behaviors which might be controlled by AHL-QS. I established that AHLs are more stable in seawater than previously expected and are likely to accumulate within biofilms. Based on this result, I chose to study AHL-QS in the bacterial communities inhabiting biofilms attached to Trichodesmium spp. and detrital (photosynthetically-derived sinking particulate organic carbon, POC) particles. These hot spots of microbial activity are primary sites of interaction between marine primary producers and heterotrophs and crucial components of the biological pump. Biofilm communities associated with Trichodesmium thiebautii colonies in the Sargasso Sea differed considerably from seawater microbial communities. In addition, there was no overlap between the communities associated with tuft and puff colonies. These results suggest that bacterial communities associated with Trichodesmium are not random; rather, Trichodesmium selects for specific microbial flora. Novel 16S rRNA gene sequences are present both in clone libraries constructed from DNA extracted from colonies of Trichodesmium spp. and in culture collections derived from wild and laboratory cultivated Trichodesmium spp., supporting the idea that the phycosphere of Trichodesmium is a unique microenvironment. Using high performance liquid chromatography-mass spectrometry, I demonstrated that bacteria isolated from Trichodesmium synthesize AHLs. In addition, I detected AHLs in sinking particles collected from a site off of Vancouver Island, Canada. AHLs were subsequently added to laboratory cultures of non-axenic Trichodesmium colonies and sinking POC samples. This is the first time AHLs have been detected in POC and indicates that AHL-QS was occurring in POC. Further, I showed that AHLs enhanced certain organic-matter degrading hydrolytic enzyme activities. My results suggest that AHL-QS is a factor regulating biogeochemically relevant enzyme activities on sinking POC and within the biofilms attached to Trichodesmium colonies and thereby may impact the timing and magnitude of biogeochemical fluxes in the ocean.My personal funding came from an MIT Presidential Fellowship, National Science Foundation Graduate Fellowship, and the WHOI Academic Programs Office. My research was funded by grants from the National Science Foundation (Chemical Oceanography award # 0825407), the Office of Naval Research (N0014-06-1-0134) and the Ocean Life Institute (award CH12702)

The metrology of spherical shells using synchrotron x ray microtomography

With recent advances in solid state imaging technology and the increasing availability of synchrotron x-ray radiation sources, synchrotron x-ray microtomography is emerging as a nondestructive technique for the evaluation of the structure and composition of small specimens with spatial resolution in the micron range. Synchrotron radiation offers the following advantages over conventional x-ray sources: high brightness, continuous emission which is tunable over a large energy range, faster data collection rates, and a highly collimated beam of large cross section permitting the illumination of large specimens. Synchrotron x-ray microtomography enables the structure of individual spheres to be evaluated in order to reveal the concentricity and sphericity of the internal void and the uniformity of the shell wall in the case of high quality spherical shells for Sandia National Laboratories' Inertial Confinement Fusion project

Creating a Learning Space in Problem-based Learning

An important aspect of PBL problems is the affordances that they hold for engaging students in discussion of important content knowledge. In this paper, I argue that one can analyze a problem in terms of a deep problem space and a broader learning space to identify the conceptual ideas for potential engagement. The problem space refers to the specific ideas and concepts that are part of the goals of the problem at hand. The learning space includes those aspects of the problem space and also includes the broader space of related conceptual ideas such as the anatomy and physiology related to a particular disorder or the pathology and clinical medicine of other disorders that might be considered as part of a differential diagnosis. This idea is tested in an exploratory analysis of a PBL tutorial conducted by Howard Barrows. The results demonstrate that much of students’ talk is focused in these related conceptual spaces and a substantial amount of the overall learning space is engaged in the group discussion. These results have implications for understanding the affordances of problems and providing another lens on how learning unfolds in a PBL problem. It also provides another means for evaluation of learning and assessment of discursive productivity in PBL groups

JOVE: Program Accomplishments and Research Continuation Plans

We designed and constructed a centrifuge for high gravity materials science research. One Master's theses project on the directional solidification of Pb-Sn alloys demonstrated effects of high gravity on the fluid flow at the solid-liquid interface during processing. These results were published. Another investigation applied flow visualization techniques to image flow patterns in a water cell. This activity supported our research proposal for aqueous growth of L-Anginin Phosphate Single Crystals in a high gravity environment. This proposal was well reviewed but ultimately denied funding

Methodological challenges for collaborative learning research

Research on collaborative learning, both face-to-face and computer-supported, has thrived in the past 10 years. The studies range from outcome-oriented (individual and group learning) to process-oriented (impact of interaction on learning processes, motivation and organisation of collaboration) to mixed studies. Collaborative learning research is multi-disciplinary. This introduces a multitude of theoretical accounts for collaborative learning, accompanied by a broad spectrum of methods to study processes and outcomes of collaboration. This special issue will provide an overview of methods that are at the core of current research effort, but also identifies opportunities and problems to sensibly combine methods into mixed method approaches

Anchors, Cases, Problems, and Scenarios as Contexts for Learning

The constructivist paradigm, which views learning as an active process in which students participate by engaging in activities that facilitate the construction of internal representations, is fast gaining currency as an innovative and effective way to overhaul classroom instruction. One way to promote constructivist learning is to firmly embed the acquisition of knowledge in realistic and stimulating contexts that challenge students to explore a variety of issues and employ a variety of their skills. This symposium will focus on four approaches (anchored instruction, casebased reasoning, goal-based scenarios, and problembased learning) designed to contextualize learning in this fashion. They do so in different, yet related ways. Examples of these approaches, ways in which they are similar and different, and important concerns regarding their effects on student learning and performance will be some of the issues that panelists will address. The panelists in this symposium are: Ray Bareiss, Institute for the Learning Sciences, Northwestern University; Cindy Hmelo, Janet Kolodner, and Hari Narayanan, EduTech Institute, Georgia Institute of Technology; Vimla Patel, Center for Cognitive Science, McGill University; and Susan Williams. School of Education and Social Policy, Northwestern University