Showing 401 - 410 of 2039 Items
Demonstration of Dispersive Rarefaction Shocks in Hollow Elliptical Cylinder Chains
Date: 2018-05-11
Creator: H. Kim
E. Kim
C. Chong
P. G. Kevrekidis
J., Yang
Access: Open access
- We report an experimental and numerical demonstration of dispersive rarefaction shocks (DRS) in a 3D-printed soft chain of hollow elliptical cylinders. We find that, in contrast to conventional nonlinear waves, these DRS have their lower amplitude components travel faster, while the higher amplitude ones propagate slower. This results in the backward-tilted shape of the front of the wave (the rarefaction segment) and the breakage of wave tails into a modulated waveform (the dispersive shock segment). Examining the DRS under various impact conditions, we find the counterintuitive feature that the higher striker velocity causes the slower propagation of the DRS. These unique features can be useful for mitigating impact controllably and efficiently without relying on material damping or plasticity effects.
Limitations and potential of commercially available rhodamine WT as a groundwater tracer
Date: 2001-06-09
Creator: D. J. Sutton
Z. J. Kabala
A. Francisco
D. Vasudevan
Access: Open access
- We conducted chemical characterization, batch, column, and modeling studies to elucidate the sorption and transport of rhodamine WT (RWT) in the subsurface. The sand-pack material from the Lizzie field site near Greenville, North Carolina, served as our porous media. Our study confirms earlier results that RWT consists of two isomers with different sorption properties. It also shows that the two isomers have distinct emission spectra and are equally distributed in the RWT solution. The presence of the two isomers with different sorption properties and distinct emission spectra introduces an error in measuring the RWT concentration with fluorometers during porous media tracer studies. The two isomers become chromatographically separated during transport and thus arrive in a different concentration ratio than that of the RWT solutions used for fluorometer calibration and test injection. We found that this groundwater tracer chromatographic error could be as high as 7.8%. We fit six different reactive-solute transport models of varying complexity to our four column experiments. A two-solute, two-site sorption transport model that accounts for nonequilibrium sorption accurately describes the breakthrough curves of the shorter-timescale column experiments. However, possibly due to the groundwater tracer chromatographic error we discovered, this model, or a similar one that accounts for a Freundlich isotherm for one of the solutes, fails to describe the RWT transport in the longer-timescale column experiments. The presence of the two RWT isomers may complicate the interpretation of field tracer tests because a shoulder, or any two peaks in a breakthrough curve, could result from either aquifer heterogeneity or the different arrival times of the two isomers. In cases where isomer 2 sorbs to such an extent that its breakthrough is not recorded during a test, only isomer 1 is measured, and therefore only 50% of the injected mass is recorded. Isomer 1 of RWT can be accurately modeled with a one-solute, two-site, nonequilibrium sorption model. This conclusion and the results from our batch studies suggest that RWT isomer 1 is an effective groundwater tracer but that the presence of isomer 2 hampers its effectiveness.
“Mayra Santos-Febres: El lenguaje de los cuerpos”. A Body of One’s Own: Conversations with Caribbean Women Writers
Date: 2008-01-01
Creator: Nadia V. Celis Salgado
Mayra Santos Febres
Access: Open access
Dismantling the bacterial glycocalyx: Chemical tools to probe, perturb, and image bacterial glycans
Date: 2021-07-15
Creator: Phuong Luong
Danielle H. Dube
Access: Open access
- The bacterial glycocalyx is a quintessential drug target comprised of structurally distinct glycans. Bacterial glycans bear unusual monosaccharide building blocks whose proper construction is critical for bacterial fitness, survival, and colonization in the human host. Despite their appeal as therapeutic targets, bacterial glycans are difficult to study due to the presence of rare bacterial monosaccharides that are linked and modified in atypical manners. Their structural complexity ultimately hampers their analytical characterization. This review highlights recent advances in bacterial chemical glycobiology and focuses on the development of chemical tools to probe, perturb, and image bacterial glycans and their biosynthesis. Current technologies have enabled the study of bacterial glycosylation machinery even in the absence of detailed structural information.
Post-translational modification directs nuclear and hyphal tip localization of Candida albicans mRNA-binding protein Slr1
Date: 2017-05-01
Creator: Chaiyaboot Ariyachet
Christian Beißel
Xiang Li
Selena Lorrey
Olivia, Mackenzie
Patrick M. Martin
Katharine O'Brien
Tossapol Pholcharee
Sue Sim
Heike Krebber
Anne E. McBride
Access: Open access
- The morphological transition of the opportunistic fungal pathogen Candida albicans from budding to hyphal growth has been implicated in its ability to cause disease in animal models. Absence of SR-like RNA-binding protein Slr1 slows hyphal formation and decreases virulence in a systemic candidiasis model, suggesting a role for post-transcriptional regulation in these processes. SR (serine–arginine)-rich proteins influence multiple steps in mRNA metabolism and their localization and function are frequently controlled by modification. We now demonstrate that Slr1 binds to polyadenylated RNA and that its intracellular localization is modulated by phosphorylation and methylation. Wildtype Slr1-GFP is predominantly nuclear, but also co-fractionates with translating ribosomes. The non-phosphorylatable slr1-6SA-GFP protein, in which six serines in SR/RS clusters are substituted with alanines, primarily localizes to the cytoplasm in budding cells. Intriguingly, hyphal cells display a slr1-6SA-GFP focus at the tip near the Spitzenkörper, a vesicular structure involved in molecular trafficking to the tip. The presence of slr1-6SA-GFP hyphal tip foci is reduced in the absence of the mRNA-transport protein She3, suggesting that unphosphorylated Slr1 associates with mRNA–protein complexes transported to the tip. The impact of SLR1 deletion on hyphal formation and function thus may be partially due to a role in hyphal mRNA transport.
Data Set for North American Colleges and Universities with Italian and Digital Humanities Programs
Date: 2016-09-13
Creator: Crystal Hall
Access: Open access
- This data set represents a first attempt to identify the North American colleges and universities that offer Italian courses at any level and also have support for digital humanities (DH) pedagogy or scholarship at any level. The list of schools with Italian programs was developed using the American Association of Teachers of Italian (AATI) list of undergraduate and graduate programs and College Source as of July 2016. The list was supplemented by checking if institutions listed with CenterNet (for Digital Humanities Centers) also have Italian programs. Overall, 10% of the Italian programs identified were not included in the AATI list, from the level of service courses through Masters degree. A search of each institution’s website was then performed to determine the level of DH resources available. Based on this collected data, 70% of North American colleges and universities that offer Italian also offer support for digital humanities courses or research through a center/lab, courses, major or minor programs, certificates, or graduate programs. A supplemental code sheet is available. Further analysis is provided in the author’s working paper “Digital Humanities & Italian Studies: Intersections and Oppositions” that is part of the State of the Discipline symposium organized by Wellesley College, October 1, 2016. (The data has been updated since the circulation of that paper, so numbers may not match.) The topic will be addressed in more detail based on the related survey and presentation at MLA 2017.
Magni, isabella, lia markey, and maddalena signorini, eds. Italian paleography. other.
Date: 2020-01-01
Creator: Crystal Hall
Access: Open access
Implementing the Optimal Provision of Ecosystem Services
Date: 2013-08-01
Creator: Stephen Polasky
David Lewis
Andrew Plantinga
Erik Nelson
Access: Open access
- Many ecosystem services are public goods whose provision depends on the spatial pattern of land use. The pattern of land use is often determined by the decisions of multiple private landowners. Increasing the provision of ecosystem services, while beneficial for society as a whole, may be costly to private landowners. A regulator interested in providing incentives to landowners for increased provision of ecosystem services often lacks complete information on landowners’ costs. The combination of spatially-dependent benefits and asymmetric cost information means that the optimal provision of ecosystem services cannot be achieved using standard regulatory or payment for ecosystem services (PES) approaches. Here we show that an auction that pays a landowner for the increased value of ecosystem services generated by the landowner’s actions provides incentives for landowners to truthfully reveal cost information, and allows the regulator to implement the optimal provision of ecosystem services, even in the case with spatially-dependent benefits and asymmetric information.
Measuring the Relative Importance of Different Agricultural Inputs to Global and Regional Crop Yield Growth Since 1975
Date: 2016-09-01
Creator: Erik Nelson
Clare Bates Congdon
Access: Open access
- We identify the agricultural inputs that drove the growth in global and regional crop yields from 1975 to the mid-2000s. We find that improvements in agricultural technology, increased fertilizer use, and changes in crop mix around the world explained most of the gain in global crop yields, although impacts varied across the latitude gradient. Climate change over this time period caused yields to be only slightly lower than they would have been otherwise. In some cases cropland extensification had as much of a negative impact on global and regional yields as climate change. To maintain the momentum in yield growth across the globe 1) use of agricultural chemicals and investment in agricultural technology in the tropics must increase rapidly and 2) international trade in agricultural products must expand significantly.
State of the Arg: Protein methylation at arginine comes of age
Date: 2001-07-13
Creator: Anne E. McBride
Pamela A. Silver
Access: Open access