Dendritic to globular morphology transition in ternary alloy solidification

The evolution of solidification microstructures in ternary metallic alloys is investigated by adaptive finite element simulations of a general multicomponent phase-field model. A morphological transition from dendritic to globular growth is found by varying the alloy composition at a fixed undercooling. The dependence of the growth velocity and of the impurity segregation in the solid phase on the composition is analyzed and indicates a smooth type of transition between the dendritic and globular growth structures.Comment: 4 pages, 2 figure

Mopra CO Observations of the Bubble HII Region RCW120

We use the Mopra radio telescope to test for expansion of the molecular gas associated with the bubble HII region RCW120. A ring, or bubble, morphology is common for Galactic HII regions, but the three-dimensional geometry of such objects is still unclear. Detected near- and far-side expansion of the associated molecular material would be consistent with a three-dimensional spherical object. We map the $J = 1\rightarrow 0$ transitions of $^{12}$CO, $^{13}$CO, C$^{18}$O, and C$^{17}$O, and detect emission from all isotopologues. We do not detect the $0_0\rightarrow 1_{-1} E$ masing lines of CH$_3$OH at 108.8939 GHz. The strongest CO emission is from the photodissociation region (PDR), and there is a deficit of emission toward the bubble interior. We find no evidence for expansion of the molecular material associated with RCW120 and therefore can make no claims about its geometry. The lack of detected expansion is roughly in agreement with models for the time-evolution of an HII region like RCW120, and is consistent with an expansion speed of $< 1.5\, {\rm km\, s^{-1}}$. Single-position CO spectra show signatures of expansion, which underscores the importance of mapped spectra for such work. Dust temperature enhancements outside the PDR of RCW120 coincide with a deficit of emission in CO, confirming that these temperature enhancements are due to holes in the RCW120 PDR. H$\alpha$ emission shows that RCW120 is leaking $\sim5\%$ of the ionizing photons into the interstellar medium (ISM) through PDR holes at the locations of the temperature enhancements. H-alpha emission also shows a diffuse "halo" from leaked photons not associated with discrete holes in the PDR. Overall $25\pm10\%$ of all ionizing photons are leaking into the nearby ISM.Comment: 35 pages, 14 figures. Accepted to Ap

Low temperature shape relaxation of 2-d islands by edge diffusion

We present a precise microscopic description of the limiting step for low temperature shape relaxation of two dimensional islands in which activated diffusion of particles along the boundary is the only mechanism of transport allowed. In particular, we are able to explain why the system is driven irreversibly towards equilibrium. Based on this description, we present a scheme for calculating the duration of the limiting step at each stage of the relaxation process. Finally, we calculate numerically the total relaxation time as predicted by our results and compare it with simulations of the relaxation process.Comment: 11 pages, 5 figures, to appear in Phys. Rev.

Acute liver failure of unclear cause? Acetaminophen-protein adducts make the diagnosis

Acetaminophen poisoning remains a leading cause of acute liver failure. Some cases may be difficult to diagnose when clinical findings are equivocal, the patient\u27s history is misleading or incomplete, or the acetaminophen concentration is low or undetectable at arrival to care. We describe a case of a medically complicated young child whose acute liver failure had two of these features. Measurement of acetaminophen-protein adducts confirmed acetaminophen as the primary cause of her liver failure

Applying knowledge management strategies to economic development in sub-Saharan Africa

Sustainability looks to achieve best outcomes for human and natural environments both now and in the indefinite future. It relates to the continuity of economic, social, institutional and environmental aspects of human society, as well as the non-human environment. This paper examines economic development as one aspect of sustainability, with a focus on knowledge management as an economic development strategy. Using Grey&rsquo;s categories of knowledge management, the authors address sustainable economic development in the context of sub-Saharan Africa. Production capability is no longer completely dependent on capital and equipment; information and knowledge assets are increasingly important. In this information economy, success comes from harnessing the information and knowledge of a community. Such &ldquo;indigenous knowledge,&rdquo; local and often tacit, exists in every community, every region and every country. This knowledge is useful in identifying new entrepreneurial opportunities, as well as for sustaining and advancing local businesses. Sub-Saharan Africa provides an excellent case study. No other region of the world is in more dire need of development. The 700 million people in this area face tremendous challenges, including the world&rsquo;s highest incidence of HIV/AIDS, deep poverty, unemployment, political instability, and a host of related problems. Key factors for using knowledge management as an economic development strategy in the region will include ICT (Information and Communication Technologies) literacy; uncovering and developing local intellectual assets; capturing tacit knowledge; internal and external knowledge sharing; and managing political, social and technological barriers. Other specific recommendations include promoting ICT literacy through training programs; leveraging internet and email technologies for community building; investing financial resources in R &amp; D; and developing metrics for outcome assessment.Keywords: Knowledge management, economic development, sub-Saharan Africa

Pursuing a Common Goal: Measuring the Comfort Level of Educational Diagnosticians to Manage a Caseload of Students with Visual Impairments

This study was conducted to measure the level of comfort and knowledge that educational diagnosticians possess regarding the unique learning needs, assistive technology, special accommodations, agencies, required visual impairment related Individual Educational Plan documents, and special evaluation considerations appropriate for students with a vision loss. Teachers of students with visual impairments were surveyed to gauge their perception of educational diagnosticians’ knowledge of the field of visual impairment and diagnosticians were also surveyed to determine their comfort level in the management of a caseload of students with visual impairments. Research question were based on how TVIs rated the comfort level and knowledge of educational diagnosticians to effectively manage a caseload of students with visual impairments, how diagnosticians rated their own comfort level and knowledge to manage a caseload of students with visual impairments, where TVIs and diagnosticians agreed that there is a lack of knowledge or awareness on the part of the diagnostician when it comes to managing a caseload of students with visual impairments, and what TVIs and diagnosticians believe can be done to better prepare diagnosticians to work with students who are visually impaired. Data collected for this study found that collaboration among a team of professionals, including TVIs and diagnosticians, provided benefit to students who are visually impaired. Survey responses from diagnosticians indicated they would like more training in low-incidence disabilities such as visual impairment to prepare them to manage a caseload of students with visual impairments

Numerical study of domain coarsening in anisotropic stripe patterns

We study the coarsening of two-dimensional smectic polycrystals characterized by grains of oblique stripes with only two possible orientations. For this purpose, an anisotropic Swift-Hohenberg equation is solved. For quenches close enough to the onset of stripe formation, the average domain size increases with time as $t^{1/2}$. Further from onset, anisotropic pinning forces similar to Peierls stresses in solid crystals slow down defects, and growth becomes anisotropic. In a wide range of quench depths, dislocation arrays remain mobile and dislocation density roughly decays as $t^{-1/3}$, while chevron boundaries are totally pinned. We discuss some agreements and disagreements found with recent experimental results on the coarsening of anisotropic electroconvection patterns.Comment: 8 pages, 11 figures. Phys. Rev E, to appea

Self-Organized Ordering of Nanostructures Produced by Ion-Beam Sputtering

We study the self-organized ordering of nanostructures produced by ion-beam sputtering (IBS) of targets amorphizing under irradiation. By introducing a model akin to models of pattern formation in aeolian sand dunes, we extend consistently the current continuum theory of erosion by IBS. We obtain new non-linear effects responsible for the in-plane ordering of the structures, whose strength correlates with the degree of ordering found in experiments. Our results highlight the importance of redeposition and surface viscous flow to this nanopattern formation process.Comment: 4 pages, 2 figure