Ferroelectric characterization and growth optimization of thermally evaporated vinylidene fluoride thin films

Organic thin films have numerous advantages over inorganics in device processing and price. The large polarization of the organic ferroelectric oligomer vinylidene fluoride (VDF) could prove useful for both device applications and the investigation of fundamental physical phenomena. A VDF oligomer thin film vacuum deposition process, such as thermal evaporation, preserves film and interface cleanliness, but is challenging, with successful deposition occurring only within a narrow parameter space. We report on the optimal deposition parameters for VDF oligomer thin films, refining the parameter space for successful deposition, resulting in a high yield of robust ferroelectric films. In particular, we investigate the influence of deposition parameters on surface roughness, and the role that roughness plays in sample yield. The reliable production of ferroelectric films allowed us to perform detailed measurements of previously unreported properties, including the Curie temperature, the temperature and thickness dependence of the coercive field, the melting temperature, and the index of refraction. The ability to successfully grow robust, switchable, well-characterized films makes VDF oligomer a viable candidate in the field of organic ferroelectrics

Seismic Mapping of Subglacial Hydrology Reveals Previously Undetected Pressurization Event

Understanding the dynamic response of glaciers to climate change is vital for assessing water resources and hazards, and subglacial hydrology is a key player in glacier systems. Traditional observations of subglacial hydrology are spatially and temporally limited, but recent seismic deployments on and around glaciers show the potential for comprehensive observation of glacial hydrologic systems. We present results from a high-density seismic deployment spanning the surface of Lemon Creek Glacier, Alaska. Our study coincided with a marginal lake drainage event, which served as a natural experiment for seismic detection of changes in subglacial hydrology. We observed glaciohydraulic tremor across the surface of the glacier that was generated by the subglacial hydrologic system. During the lake drainage, the relative changes in seismic tremor power and water flux are consistent with pressurization of the subglacial system of only the upper part of the glacier. This event was not accompanied by a significant increase in glacier velocity; either some threshold necessary for rapid basal motion was not attained, or, plausibly, the geometry of Lemon Creek Glacier inhibited speedup. This pressurization event would have likely gone undetected without seismic observations, demonstrating the power of cryoseismology in testing assumptions about and mapping the spatial extent of subglacial pressurization.This work was made possible in part by hard work in the field by Margot Vore, Daniel Bowden, Galen Kaip, and the students and staff of the 2017 Juneau Icefield Research Program. We especially thank Matt Beedle for provision of the photogrammetrically-produced DEM of Lake Linda, following lake drainage. This work was also aided by the advice of Mike Gurnis and Rob Clayton. We thank Paul Winberry and two anonymous reviewers for their helpful feedback, which improved this paper greatly. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1745301. This work was made possible in part by a University of Idaho seed grant, #FY18-01. DEM provided by the Polar Geospatial Center under NSF-OPP awards 1043681, 1559691, and 1542736.Ye

Organic ferroelectric evaporator with substrate cooling and \u3ci\u3ein situ\u3c/i\u3e transport capabilities

We report on the design, operation, and performance of a thermal evaporation chamber capable of evaporating organic thin films. Organic thin films are employed in a diverse range of devices and can provide insight into fundamental physical phenomena. However, growing organic thin films is often challenging and requires very specific deposition parameters. The chamber presented here is capable of cooling sample substrates to temperatures below 130 K and allows for the detachment of the sample from the cooling stage and in situ transport. This permits the use of multiple deposition techniques in separate, but connected, deposition chambers without breaking vacuum and therefore provides clean, well characterized interfaces between the organic thin film and any adjoining layers. We also demonstrate a successful thin film deposition of an organic material with a demanding set of deposition parameters, showcasing the success of this design

New and unusual butterfly records from Kansas

Volume: 37Start Page: 256End Page: 25

Science at Engineer Cantonment

Conclusions It is our contention that Thomas Say, Titian Peale, Edwin James, and their colleagues of the Stephen Long Expedition of 1819–1820 were heavily engaged in scientific research, which took the form of the first biodiversity inventory undertaken in the United States. This accomplishment has been overlooked both by biologists and historians, but it should rank among the most significant accomplishments of the expedition. The results of this inventory continue to inform us today about environmental, faunal, and floral changes along the Missouri River in an area that is known to be an ecotone between the deciduous forests of the eastern United States and the prairies of the Great Plains. This inventory was completed at a time when the impact of Euroamericans was just beginning. A modern archeological excavation of the Engineer Cantonment dwellings has added significantly to our knowledge of the environment and species present at the site in 1819–1820. The archeological investigation has added 7 percent more species for the species richness estimate for Engineer Cantonment. These additions to the biota of Engineer Cantonment were not made uniformly across the groups surveyed. The species added to the inventory are primarily plants, mollusks, and fish. The flora at Engineer Cantonment was not heavily surveyed by James because he was at the site only a little over two weeks. The survey party\u27s interest in fish appears to have been only as food items, so we learn the most about them from their skeletal remains in the camp\u27s trash. The mollusks are difficult to survey because they are small, secretive animals. The written documents, collections, and drawings left to us, along with the archeological inventory, form an image of a dynamic riverine system with a highly meandering river having a wide valley filled with oxbows, palustrine wetlands, and scattered groves of trees. This has now been modified to an area that has a channelized river with the surrounding wetlands being drained and converted to agricultural and municipal purposes. Construction of upriver dams has controlled flooding, especially in the spring, so that the river valley is not renewed and changed. Irrigation of farmlands has promoted the growth of riparian forests composed primarily of cottonwood. Suppression of prairie fires, which were prevalent during the fall of 1819, also has promoted the growth of trees and other woody vegetation. The city of Omaha and its suburbs are expanding and encroaching on the site from the south and west, converting once open grasslands and scattered trees to housing tracts with well-manicured lawns and non-native Nebraska shade trees. The impacts of these landscape and environmental changes are clearly reflected in the plants and animals of the area. Although the U.S. Fish and Wildlife Service has done some habitat restoration in the Boyer Chute National Wildlife Refuge and continues fish and wildlife habitat restoration in associated upland and wetland areas along the Missouri River, their efforts will never be totally successful, because many of the plants and animals no longer occur in the area. Among mammals, three of the top herbivores are gone as are four of the top carnivores. We are not advocating reintroduction of bison or wolves, but without these species interacting with the plant and animal communities, no restoration will truly re-establish what once was. Secondary herbivores and carnivores have now filled these top niches and make a vastly different impact. The gray squirrel and eastern chipmunk appear to indicate that it is not just trees that make a forest, because the forest established along the Missouri River and its former floodplain is dominated by cottonwoods that do not provide the necessary habitat for these species. We believe our examination of the Engineer Cantonment area in eastern Nebraska demonstrates the value of biodiversity inventories, both historical and modem. Although it is beyond our power to undertake historical inventories, we urge efforts be directed toward the reconstruction of other historical biodiversity inventories, including phytoarcheological and zooarcheological surveys. This may be feasible in areas such as historical forts, which were visited by traveling biologists on a recurring basis. The results of these explorations, especially when combining the work of a number of parties and scientists, may result in useful historical biodiversity inventories. Other places on the Great Plains where this may be possible would include Fort Union in North Dakota, Fort Sisseton in South Dakota, Fort Hays in Kansas, and Fort Sill in Oklahoma. Today\u27s modem inventory is tomorrow\u27s historical inventory, and so there is still an ongoing need for biodiversity inventories. They provide the baseline information for dynamic biological systems that will change over time and with environmental shifts