432 research outputs found
Cell proliferation, cell shape, and microtubule and cellulose microfibril organization of tobacco BY-2 cells are not altered by exposure to near weightlessness in space
The microtubule cytoskeleton and the cell wall both play key roles in plant cell growth and division, determining the plant’s final stature. At near weightlessness, tubulin polymerizes into microtubules in vitro, but these microtubules do not self-organize in the ordered patterns observed at 1g. Likewise, at near weightlessness cortical microtubules in protoplasts have difficulty organizing into parallel arrays, which are required for proper plant cell elongation. However, intact plants do grow in space and therefore should have a normally functioning microtubule cytoskeleton. Since the main difference between protoplasts and plant cells in a tissue is the presence of a cell wall, we studied single, but walled, tobacco BY-2 suspension-cultured cells during an 8-day space-flight experiment on board of the Soyuz capsule and the International Space Station during the 12S mission (March–April 2006). We show that the cortical microtubule density, ordering and orientation in isolated walled plant cells are unaffected by near weightlessness, as are the orientation of the cellulose microfibrils, cell proliferation, and cell shape. Likely, tissue organization is not essential for the organization of these structures in space. When combined with the fact that many recovering protoplasts have an aberrant cortical microtubule cytoskeleton, the results suggest a role for the cell wall, or its production machinery, in structuring the microtubule cytoskeleto
Range-only benthic Rover localization off the central California coast
Nowadays, the use of autonomous vehicles for
ocean research has increased, since these vehicles have a better
cost/performance ratio than crewed vessels or oceanographic
ships. For example, autonomous surface vehicles can be used to
localize underwater targets. This paper describes a mission to find
a crawling robot - Benthic Rover - on the abyssal plain in the north
eastern Pacific, using single-beacon localization from onboard a
Wave Glider autonomous surface vehicle. While the Wave Glider
is moving around the surface in the target zone, it takes ranges
between the target and itself using acoustic modems. With these
ranges it can compute the target location, as a Long Baseline
(LBL) system. The benefit of this approach is the reduction of cost
and complexity relative to deployment of a traditional shipboard
LBL system. Additionally, this is a mobile system, and can cover
long distances, and can geolocate multiple targets over a large
area.Postprint (author's final draft
Range-only underwater target localization : error characterization
Locating a target from range measurements
using only one mobile transducer has been increased
over the last years. This method allows us to reduce the
high costs of deployment and maintenance of
traditional fixed systems on the seafloor such as Long
Baseline. The range-only single-beacon is one of the
new architectures developed using the new capabilities
of modern acoustic underwater modems, which can be
time synchronization, time stamp, and range
measurements.
This document presents a method to estimate the
sources of error in this type of architecture so as to
obtain a mathematical model which allows us to
develop simulations and study the best localization
algorithms. Different simulations and real field tests
have been carried out in order to verify a good
performance of the model proposed.Postprint (published version
Optimal path shape for range-only underwater target localization using a Wave Glider
Underwater localization using acoustic signals is one of the main components in a navigation system for an autonomous underwater vehicle (AUV) as a more accurate alternative to dead-reckoning techniques. Although different methods based on the idea of multiple beacons have been studied, other approaches use only one beacon, which reduces the system’s costs and deployment complexity. The inverse approach for single-beacon navigation is to use this method for target localization by an underwater or surface vehicle. In this paper, a method of range-only target localization using a Wave Glider is presented, for which simulations and sea tests have been conducted to determine optimal parameters to minimize acoustic energy use and search time, and to maximize location accuracy and precision. Finally, a field mission is presented, where a Benthic Rover (an autonomous seafloor vehicle) is localized and tracked using minimal human intervention. This mission shows, as an example, the power of using autonomous vehicles in collaboration for oceanographic research.Peer ReviewedPostprint (author's final draft
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Farmers' management of rice varietal diversity in the mid-hills of Nepal: implications for on-farm conservation and crop improvement
Season-long monitoring of on-farm rice (Oryza sativa, L.) plots in Nepal explored farmers' decision-making process on the deployment of varieties to agroecosystems, application of production inputs to varieties, agronomic practices and relationship between economic return and area planted per variety. Farmers deploy varieties [landraces (LRs) and modern varieties (MVs)] to agroecosystems based on their understanding of characteristics of varieties and agroecosystems, and the interaction between them. In marginal growing conditions, LRs can compete with MVs. Within an agroecosystem, economic return and area planted to varieties have positive relationship, but this is not so between agroecosystems. LRs are very diverse on agronomic and economic traits; therefore, they cannot be rejected a priori as inferior materials without proper evaluation. LRs have to be evaluated for useful traits and utilized in breeding programmes to generate farmer-preferred materials for marginal environments and for their conservation on-farm
Acoustic tag tracking: first experiments
Nowadays, the use of autonomous vehicles for ocean research has increased, since these vehicles have a better cost/performance ratio than crewed vessels or oceanographic ships. For example, autonomous surface vehicles can be used to localize underwater targets. Whereas different research works are focused in target tracking using acoustic modems (or USBL), in this paper a new method called Area-Only target tracking is presented, which uses the signal generated by acoustic TAGs. This document, the first tests are presented and their results discussed, which were conducted in the Monterey Bay.Peer Reviewe
Acoustic TAG tracking: First experiments
Nowadays, the use of autonomous vehicles for
ocean research has increased, since these vehicles have a better
cost/performance ratio than crewed vessels or oceanographic
ships. For example, autonomous surface vehicles can be used to
localize underwater targets. Whereas different research works are
focused in target tracking using acoustic modems (or USBL), in
this paper a new method called Area-Only target tracking is
presented, which uses the signal generated by acoustic TAGs. This
document, the first tests are presented and their results discussed,
which were conducted in the Monterey Bay.Peer ReviewedPostprint (published version
Prokaryotic responses to a warm temperature anomaly in northeast subarctic Pacific waters
Recent studies on marine heat waves describe water temperature anomalies causing changes in food web structure, bloom dynamics, biodiversity loss, and increased plant and animal mortality. However, little information is available on how water temperature anomalies impact prokaryotes (bacteria and archaea) inhabiting ocean waters. This is a nontrivial omission given their integral roles in driving major biogeochemical fluxes that influence ocean productivity and the climate system. Here we present a time-resolved study on the impact of a large-scale warm water surface anomaly in the northeast subarctic Pacific Ocean, colloquially known as the Blob, on prokaryotic community compositions. Multivariate statistical analyses identified significant depth- and season-dependent trends that were accentuated during the Blob. Moreover, network and indicator analyses identified shifts in specific prokaryotic assemblages from typically particle-associated before the Blob to taxa considered free-living and chemoautotrophic during the Blob, with potential implications for primary production and organic carbon conversion and export. Traving et al. use small subunit ribosomal RNA gene sequencing to examine spatial and temporal trends in bacterial and archaeal community structure during a large marine warm water surface anomaly, the Blob. Their findings suggest that community structure shifted during the Blob, with taxa considered free-living and chemoautotrophic prevailing under these unusual conditions
Tackling Healthcare Inequities: Development & Implementation of a Virtual Platform to Improve Global Access to Oncology Education
View full abstracthttps://openworks.mdanderson.org/leading-edge/1006/thumbnail.jp
The TgsGP gene is essential for resistance to human serum in Trypanosoma brucei gambiense
Trypanosoma brucei gambiense causes 97% of all cases of African sleeping sickness, a fatal disease of sub-Saharan Africa. Most species of trypanosome, such as T. b. brucei, are unable to infect humans due to the trypanolytic serum protein apolipoprotein-L1 (APOL1) delivered via two trypanosome lytic factors (TLF-1 and TLF-2). Understanding how T. b. gambiense overcomes these factors and infects humans is of major importance in the fight against this disease. Previous work indicated that a failure to take up TLF-1 in T. b. gambiense contributes to resistance to TLF-1, although another mechanism is required to overcome TLF-2. Here, we have examined a T. b. gambiense specific gene, TgsGP, which had previously been suggested, but not shown, to be involved in serum resistance. We show that TgsGP is essential for resistance to lysis as deletion of TgsGP in T. b. gambiense renders the parasites sensitive to human serum and recombinant APOL1. Deletion of TgsGP in T. b. gambiense modified to uptake TLF-1 showed sensitivity to TLF-1, APOL1 and human serum. Reintroducing TgsGP into knockout parasite lines restored resistance. We conclude that TgsGP is essential for human serum resistance in T. b. gambiense
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