40,962 research outputs found
Texas Watershed Planning Training Project Final Report 2013
Watershed planning remains a high priority to address the more than 568 impaired water body segments in Texas. To ensure that watershed protection efforts are adequately planned, coordinated and implemented, proper training of watershed coordinators and water professionals is necessary. The Texas Watershed Planning Short Course project, funded by the U.S. Environmental Protection Agency (EPA) through the Texas Commission on Environmental Quality (TCEQ), provides this training.
Through a coordinated effort led by the Texas Water Resources Institute, the institute partnered with the Texas A&M AgriLife Extension Service, Texas A&M AgriLife Research, Texas State Soil and Water Conservation Board (TSSWB), TCEQ, EPA, Texas State University-River Systems Institute and the Texas Institute for Applied Environmental Research (TIAER) to develop and conduct the watershed planning training project
Identifying "communities" within energy landscapes
Potential energy landscapes can be represented as a network of minima linked
by transition states. The community structure of such networks has been
obtained for a series of small Lennard-Jones clusters. This community structure
is compared to the concept of funnels in the potential energy landscape. Two
existing algorithms have been used to find community structure, one involving
removing edges with high betweenness, the other involving optimization of the
modularity. The definition of the modularity has been refined, making it more
appropriate for networks such as these where multiple edges and
self-connections are not included. The optimization algorithm has also been
improved, using Monte Carlo methods with simulated annealing and basin hopping,
both often used successfully in other optimization problems. In addition to the
small clusters, two examples with known heterogeneous landscapes, LJ_13 with
one labelled atom and LJ_38, were studied with this approach. The network
methods found communities that are comparable to those expected from landscape
analyses. This is particularly interesting since the network model does not
take any barrier heights or energies of minima into account. For comparison,
the network associated with a two-dimensional hexagonal lattice is also studied
and is found to have high modularity, thus raising some questions about the
interpretation of the community structure associated with such partitions.Comment: 13 pages, 11 figure
Attoyac Bayou GIS Inventory, Source Survey and Land Use Cover Report
The Attoyac Bayou watershed is one of many rural watersheds included in the Texas Water Quality Inventory and 303(d) List as an impaired water body due to excessive E. coli levels. In many cases the assessed data in these waterbodies is limited and information regarding potential sources of pollution or other factors that may influence the presence of pollutant sources is not readily available.
To address this need, a comprehensive geographic information system (GIS) inventory of the watershed will be developed and will integrate numerous existing information resources into a single location. Generally, the GIS will illustrate waterbodies, roadways, permitted point-source dischargers, and other points of concern. Additionally, current land use/land cover (LULC) maps for the watershed will be updated. Existing LULC layers will be utilized as a starting point and will be re-delineated utilizing groundtruthed data points collected for the GIS inventory to verify the accuracy of the LULC map. Through the development of the GIS and update of the LULC maps, a physical source survey will also be conducted across the watershed to document the primary sources of bacteria in the watershed
Stick-slip instability for viscous fingering in a gel
The growth dynamics of an air finger injected in a visco-elastic gel (a
PVA/borax aqueous solution) is studied in a linear Hele-Shaw cell. Besides the
standard Saffmann-Taylor instability, we observe - with increasing finger
velocities - the existence of two new regimes: (a) a stick-slip regime for
which the finger tip velocity oscillates between 2 different values, producing
local pinching of the finger at regular intervals, (b) a ``tadpole'' regime
where a fracture-type propagation is observed. A scaling argument is proposed
to interpret the dependence of the stick-slip frequency with the measured
rheological properties of the gel.Comment: 7 pages, 4 figures. Submitted to Europhysics Letter
A new approach to quantum backflow
We derive some rigorous results concerning the backflow operator introduced
by Bracken and Melloy. We show that it is linear bounded, self adjoint, and not
compact. Thus the question is underlined whether the backflow constant is an
eigenvalue of the backflow operator. From the position representation of the
backflow operator we obtain a more efficient method to determine the backflow
constant. Finally, detailed position probability flow properties of a numerical
approximation to the (perhaps improper) wave function of maximal backflow are
displayed.Comment: 12 pages, 8 figure
Acid-Labile Traceless Click Linker for Protein Transduction
Intracellular delivery of active proteins presents an interesting approach in research and therapy. We created a protein transduction shuttle based on a new traceless click linker that combines the advantages of click reactions with implementation of reversible pH-sensitive bonds. The azidomethyl-methylmaleic anhydride (AzMMMan) linker was found compatible with different click chemistries, demonstrated in bioreversible protein modification with dyes, polyethylene glycol, or a transduction carrier. Linkages were stable at physiological pH but reversible at the mild acidic pH of endosomes or lysosomes. We show that pH-reversible attachment of a defined endosome-destabilizing three-arm oligo(ethane amino)amide carrier generates an effective shuttle for protein delivery. The cargo protein nlsEGFP, when coupled via the traceless AzMMMan linker, experiences efficient cellular uptake and endosomal escape into the cytosol, followed by import into the nucleus. In contrast, irreversible linkage to the same shuttle hampers nuclear delivery of nlsEGFP which after uptake remains trapped in the cytosol. Successful intracellular delivery of bioactive ß-galactosidase as a model enzyme was also demonstrated using the pH-controlled shuttle system
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