333 research outputs found
Modernization of Ultrasonic Immersion Robot
This senior design project utilized an ultrasonic immersion robot to collect ultrasonic data that was then used to generate three dimensional images. Ultrasonic waves provide a means to evaluate the interior of an object without damaging it. The robot, controlled by a LinuxCNC program, is used to collect data points over a pre-programed area and resolution. The data points consist of the x and y coordinates and ultrasonic amplitudes corresponding to depths. Matlab scripts were written that process the collected data and create images and videos depicting the surfaces and features of the scanned object. During the course of two semesters the group members returned functionality to the robot system and the ultrasonic system and created the post image processing scripts. These systems were used successfully to create three dimensional images and videos of a key, a steel plate and an aluminum plate for presentation
Boom and Bust Carbon-Nitrogen Dynamics during Reforestation
Legacies of historical land use strongly shape contemporary ecosystem dynamics. In old-field secondary forests, tree growth embodies a legacy of soil changes affected by previous cultivation. Three patterns of biomass accumulation during reforestation have been hypothesized previously, including monotonic to steady state, non-monotonic with a single peak then decay to steady state, and multiple oscillations around the steady state. In this paper, the conditions leading to the emergence of these patterns is analyzed. Using observations and models, we demonstrate that divergent reforestation patterns can be explained by contrasting time-scales in ecosystem carbon-nitrogen cycles that are influenced by land use legacies. Model analyses characterize non-monotonic plant-soil trajectories as either single peaks or multiple oscillations during an initial transient phase controlled by soil carbon-nitrogen conditions at the time of planting. Oscillations in plant and soil pools appear in modeled systems with rapid tree growth and low initial soil nitrogen, which stimulate nitrogen competition between trees and decomposers and lead the forest into a state of acute nitrogen deficiency. High initial soil nitrogen dampens oscillations, but enhances the magnitude of the tree biomass peak. These model results are supported by data derived from the long-running Calhoun Long-Term Soil-Ecosystem Experiment from 1957 to 2007. Observed carbon and nitrogen pools reveal distinct tree growth and decay phases, coincident with soil nitrogen depletion and partial re-accumulation. Further, contemporary tree biomass loss decreases with the legacy soil C:N ratio. These results support the idea that non-monotonic reforestation trajectories may result from initial transients in the plant-soil system affected by initial conditions derived from soil changes associated with land-use history
Metastability, Mode Coupling and the Glass Transition
Mode coupling theory (MCT) has been successful in explaining the observed
sequence of time relaxations in dense fluids. Previous expositions of this
theory showing this sequence have required the existence of an ideal glass
transition temperature . Recent experiments show no evidence of . We
show here how the theory can be reformulated, in a fundamental way, such that
one retains this sequence of relaxation behaviors but with a smooth temperature
dependence and without any indication of . The key ingredient in the
reformulation is the inclusion of the metastable nature of the glass transition
problem through a coupling of the mass density to the defect density. A main
result of our theory is that the exponents governing the sequence of time
relaxations are weak functions of the temperature in contrast to the results
from conventional MCT.Comment: 14 pages (2 figures upon request), REVTEX
Slow dynamics, aging, and glassy rheology in soft and living matter
We explore the origins of slow dynamics, aging and glassy rheology in soft
and living matter. Non-diffusive slow dynamics and aging in materials
characterised by crowding of the constituents can be explained in terms of
structural rearrangement or remodelling events that occur within the jammed
state. In this context, we introduce the jamming phase diagram proposed by Liu
and Nagel to understand the ergodic-nonergodic transition in these systems, and
discuss recent theoretical attempts to explain the unusual,
faster-than-exponential dynamical structure factors observed in jammed soft
materials. We next focus on the anomalous rheology (flow and deformation
behaviour) ubiquitous in soft matter characterised by metastability and
structural disorder, and refer to the Soft Glassy Rheology (SGR) model that
quantifies the mechanical response of these systems and predicts aging under
suitable conditions. As part of a survey of experimental work related to these
issues, we present x-ray photon correlation spectroscopy (XPCS) results of the
aging of laponite clay suspensions following rejuvenation. We conclude by
exploring the scientific literature for recent theoretical advances in the
understanding of these models and for experimental investigations aimed at
testing their predictions.Comment: 22 pages, 5 postscript figures; invited review aricle, to appear in
special issue on soft matter in Solid State Communication
Infrared Dielectric Functions and Brillouin Zone Center Phonons of \u3cem\u3eÎą\u3c/em\u3e-Ga\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e compared to \u3cem\u3eÎą\u3c/em\u3e-Al\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e3\u3c/sub\u3e
We determine the anisotropic dielectric functions of rhombohedral Îą-Ga2O3 by far-infrared and infrared generalized spectroscopic ellipsometry and derive all transverse optical and longitudinal optical phonon mode frequencies and broadening parameters. We also determine the high-frequency and static dielectric constants. We perform density functional theory computations and determine the phonon dispersion for all branches in the Brillouin zone, and we derive all phonon mode parameters at the Brillouin zone center including Raman-active, infrared-active, and silent modes. Excellent agreement is obtained between our experimental and computation results as well as among all previously reported partial information from experiment and theory. We also compute the same information for Îą-Al2O3, the binary parent compound for the emerging alloy of Îą-(AlxGa1âx)2O3, and use results from previous investigations [Schubert, Tiwald, and Herzinger, Phys. Rev. B 61, 8187 (2000)] to compare all properties among the two isostructural compounds. From both experimental and theoretical investigations, we compute the frequency shifts of all modes between the two compounds. Additionally, we calculate overlap parameters between phonon mode eigenvectors and discuss the possible evolution of all phonon modes into the ternary alloy system and whether modes may form single-mode or more complex mode behaviors
The Grizzly, September 22, 1989
Kane Claiming Greeks Shall Survive ⢠Olin Noise Annoys All ⢠Letters: Boot Booze Begs Senior; Rovers Rotten ⢠DiFeliciantonio: A Mouthful ⢠McNulty Directs Residents ⢠Surprise, surprise! UC Stomps Swarthmore ⢠Ursinus Closes Gap with F&M Diplomats ⢠Commentary; Why Bush War Can\u27t be Won; HPER Lab a Strong Addition ⢠Intramurals: Full Steam Ahead! ⢠One Giant Step ⢠Sports Summary ⢠Pledging: End of an Era? ⢠BWC Causes Electrical Overloadhttps://digitalcommons.ursinus.edu/grizzlynews/1241/thumbnail.jp
The Grizzly, December 6, 1994
Beetlemania Hits Ursinus ⢠Strassburger Appointed President ⢠Unrest in the Baltics Continues ⢠Ursinus Birthday Card Unveiled ⢠Jeffrey Dahmer Dead ⢠Philadelphia Teen Slain as Result of Inner City Rivalries ⢠Lectures, Friendships, and Giving Up Shop ⢠The Holidays Mean More Than Just Christmas ⢠Alumna Spotlight: The Life of a Doctor ⢠The Java Trench: More Than Just Coffee ⢠Indigo Girls Delight Philly Fans ⢠Intramural Updatehttps://digitalcommons.ursinus.edu/grizzlynews/1349/thumbnail.jp
Cellular iron governs the host response to malaria
Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor (TfrcY20H/Y20H), which limits the ability of cells to internalise iron from plasma. At homeostasis TfrcY20H/Y20H mice appear healthy and are not anaemic. However, TfrcY20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that TfrcY20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected TfrcY20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4+ T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, TfrcY20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria
The Grizzly, December 8, 1992
Gomez Speaks on Gildah Stories ⢠Wellness Center Confusion ⢠Greek Service Projects ⢠How To Handle Holiday Dysfunction ⢠Senior Profile: Tina Moukoulis ⢠Wismer\u27s Christmas Dinner ⢠Russian Rock With Yuri ⢠Exam Schedule ⢠Standards ⢠A Lack of Preventive Aid ⢠Letters: Greetings from France; Response to Disabled Accessibility ⢠UC Snaps Losing Steak; Picks Up Three Wins ⢠Lady Bears Recaphttps://digitalcommons.ursinus.edu/grizzlynews/1307/thumbnail.jp
Significant Surface-Water Connectivity of Geographically Isolated Wetlands
We evaluated the current literature, coupled with our collective research expertise, on surface-water connectivity of wetlands considered to be geographically isolated (sensu Tiner Wetlands 23:494â516, 2003a) to critically assess the scientific foundation of grouping wetlands based on the singular condition of being surrounded by uplands. The most recent research on wetlands considered to be geographically isolated shows the difficulties in grouping an ecological resource that does not reliably indicate lack of surface water connectivity in order to meet legal, regulatory, or scientific needs. Additionally, the practice of identifying geographically isolated wetlands based on distance from a stream can result in gross overestimates of the number of wetlands lacking ecologically important surface-water connections. Our findings do not support use of the overly simplistic label of geographically isolated wetlands . Wetlands surrounded by uplands vary in function and surface water connections based on wetland landscape setting, context, climate, and geographic region and should be evaluated as such. We found that the geographically isolated grouping does not reflect our understanding of the hydrologic variability of these wetlands and hence does not benefit conservation of the Nationâs diverse wetland resources. Therefore, we strongly discourage use of categorizations that provide overly simplistic views of surface water connectivity of wetlands fully embedded in upland landscapes
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