Dislocation Content Measured Via 3D HR-EBSD Near a Grain Boundary in an AlCu Oligocrystal

Interactions between dislocations and grain boundaries are poorly understood and crucial to mesoscale plasticity modeling. Much of our understanding of dislocation-grain boundary interaction comes from atomistic simulations and TEM studies, both of which are extremely limited in scale. High angular resolution EBSD-based continuum dislocation microscopy provides a way of measuring dislocation activity at length scales and accuracies relevant to crystal plasticity, but it is limited as a two-dimensional technique, meaning the character of the grain boundary and the complete dislocation activity is difficult to recover. However, the commercialization of plasma FIB dual-beam microscopes have made 3D EBSD studies all the more feasible. The objective of this work is to apply high angular resolution cross correlation EBSD to a 3D EBSD data set collected by serial sectioning in a FIB to characterize dislocation interaction with a grain boundary. Three dimensional high angular resolution cross correlation EBSD analysis was applied to an AlCu oligocrystal to measure dislocation densities around a grain boundary. Distortion derivatives associated with the plasma FIB serial sectioning were higher than expected, possibly due to geometric uncertainty between layers. Future work will focus on mitigating the geometric uncertainty and examining more regions of interest along the grain boundary to glean information on dislocation-grain boundary interaction

B780: A Cost Analysis of Pruning Procedures in Lowbush Blueberry Production

Burning fields with fuel oil is currently the most practical method of pruning blueberries but is costly and destructive to the organic material on the surface of the soil. Fuel oil is a nonrenewable resource that is rapidly increasing in cost and, in the future, may become less readily available for this use. The need to develop alternative means of pruning lowbush bleuberries is evident. This bulletin compares the economics of six pruning procedures on operations of three sizes. The budgets are based on certain assumptions and costs which will change over time. The results will allow blueberry growers to compare procedures to determine which one is most economically feasible for their particular operation and its resources.https://digitalcommons.library.umaine.edu/aes_bulletin/1066/thumbnail.jp

XMM-Newton and Optical Observations of Cataclysmic Variables from SDSS

We report on XMM-Newton and optical results for 6 cataclysmic variables that were selected from Sloan Digital Sky Survey spectra because they showed strong HeII emission lines, indicative of being candidates for containing white dwarfs with strong magnetic fields. While high X-ray background rates prevented optimum results, we are able to confirm SDSSJ233325.92+152222.1 as an intermediate polar from its strong pulse signature at 21 min and its obscured hard X-ray spectrum. Ground-based circular polarization and photometric observations were also able to confirm SDSSJ142256.31-022108.1 as a polar with a period near 4 hr. Photometry of SDSSJ083751.00+383012.5 and SDSSJ093214.82+495054.7 solidifies the orbital period of the former as 3.18 hrs and confirms the latter as a high inclination system with deep eclipses.Comment: 31 pages, 14 figures. Accepted for publication in the Astronomical Journa

Vermonters’ Opinions on Low-Dose CT Lung Cancer Screening

Introduction: Lung cancer is the number one cause of cancer death among men and women in Vermont and the United States. Smoking increases the risk of lung cancer—nearly 90% of lung cancer is due to smoking. Frequently, lung cancers do not present clinically until they are advanced stage and therefore prognosis is poor. However, if detected early lung cancers are more operable and patients have better outcomes. In December 2013 the US Preventive Services Task Force released new guidelines for lung cancer screening among current and former smokers ages 55 to 80. It is recommended that current and former (within 15 years of quitting) smokers of 30 pack years receive an annual low-dose CT scan. The objective of this project was to assess the level of knowledge and attitudes towards lung cancer screening with low-dose CT scanning among Vermonters in the Burlington area.https://scholarworks.uvm.edu/comphp_gallery/1205/thumbnail.jp

Ultracompact X-ray Binaries in Globular Clusters: Variability of the Optical Counterpart of X1832-330 in NGC 6652

Evidence is emerging that the luminous X-ray sources in the cores of globular clusters may often consist of, or perhaps even as a class be dominated by, ultracompact (P < 1 hr) binary stars. To the two such systems already known, in NGC 6624 and NGC 6712, we now add evidence for two more. We detect large amplitude variability in the candidate optical counterpart for the X-ray source in the core of NGC 6652. Although the available observations are relatively brief, the existing Hubble Space Telescope data indicate a strong 43.6 min periodic modulation of the visible flux of semi-amplitude 30%. Further, although the orbital period of the source in NGC 1851 is not yet explicitly measured, we demonstrate that previous correlations of optical luminosity with X-ray luminosity and accretion disk size, strengthened by recent data, strongly imply that the period of that system is also less than 1 hr. Thus currently there is evidence that 4 of the 7 globular cluster X-ray sources with constrained periods are ultracompact, a fraction far greater than that found in X-ray binaries the field.Comment: 10 pages including 2 figures and 1 table. Accepted for publication in The Astrophysical Journal Letter

Modeling the mechanical behavior of amorphous metals by shear transformation zone dynamics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 105-110).A new mesoscale modeling technique for the thermo-mechanical behavior of amorphous metals is proposed. The modeling framework considers the shear transformation zone (STZ) as the fundamental unit of deformation, and coarse-grains an amorphous collection of atoms into an ensemble of STZs on a mesh. By employing finite element analysis and a kinetic Monte Carlo algorithm, the modeling technique is capable of simulating processing and deformation on time and length scales relevant to those used for experimental testing of an amorphous metal. The framework is developed in two and three dimensions and validated in both cases over a range of temperatures and stresses. The model is shown to capture the basic behaviors of amorphous metals, including high-temperature homogeneous flow following the expected constitutive law, and low-temperature strain localization into shear bands. Construction of deformation maps from the response of models, in both two and three dimensions, match well with the experimental behaviors of amorphous metals. Examination of the trends between STZ activations elucidates some important spatio-temporal correlations which are shown to be the cause of the different macroscopic modes of deformation. The value of the mesoscale modeling framework is also shown in two specific applications to investigate phenomena observed in amorphous metals. First, simulated nanoindentation is used to explore the recently revealed phenomenon of nanoscale cyclic strengthening, in order to provide insight into the mechanisms behind the strengthening. Second, a detailed investigation of shear localization provides insight into the nucleation and propagation of a shear band in an amorphous metal. Given these applications and the broad range of conditions over which the model captures the expected behaviors, this modeling framework is anticipated to be a valuable tool in the study of amorphous metals.by Eric R. Homer.Ph.D

Fernald restoration: ecologists and engineers integrate restoration and cleanup

As cleanup workers excavate pits and tear down buildings at the Fernald site in southwest Ohio, site ecologists are working side-by-side to create thriving wetlands and develop the early stages of forest, prairie, and savanna ecosystems to restore natural resources that were impacted by years of site operations. In 1998, the U.S. Department of Energy-Fernald Office (DOE-FN) and its cleanup contractor, Fluor Fernald, Inc., initiated several ecological restoration projects in perimeter areas of the site (e.g., areas not used for or impacted by uranium processing or waste management). The projects are part of Fernald's final land use plan to restore natural resources over 904 acres of the 1,050-acre site. Pete Yerace, the DOE-FN Natural Resource Trustee representative is working with the Fernald Natural Resource Trustees in an oversight role to resolve the state of Ohio's 1986 claim against DOE for injuries to natural resources. Fluor Fernald, Inc., and DOE-FN developed the ''Natural Resource Restoration Plan'', which outlines 15 major restoration projects for the site and will restore injured natural resources at the site. In general, Fernald's plan includes grading to maximize the formation of wetlands or expanded floodplain, amending soil where topsoil has been removed during excavation, and establishing native vegetation throughout the site. Today, with cleanup over 35 percent complete and site closure targeted for 2006, Fernald is entering a new phase of restoration that involves heavily remediated areas. By working closely with engineers and cleanup crews, site ecologists can take advantage of remediation fieldwork (e.g., convert an excavated depression into a wetland) and avoid unnecessary costs and duplication. This collaboration has also created opportunities for relatively simple and inexpensive restoration of areas that were discovered during ongoing remediation. To ensure the survival of the plant material in heavily disturbed soils, Fernald will use techniques such as large-scale soil amendment, drainage modifications, and specially designed plant mixes during restoration. While these techniques have helped ecologists manage the early phases of restoration at Fernald, they will be critical to the long-term success of restoring heavily remediated areas of the site