527 research outputs found
Autonomous Apple Fruitlet Sizing and Growth Rate Tracking using Computer Vision
In this paper, we present a computer vision-based approach to measure the
sizes and growth rates of apple fruitlets. Measuring the growth rates of apple
fruitlets is important because it allows apple growers to determine when to
apply chemical thinners to their crops in order to optimize yield. The current
practice of obtaining growth rates involves using calipers to record sizes of
fruitlets across multiple days. Due to the number of fruitlets needed to be
sized, this method is laborious, time-consuming, and prone to human error. With
images collected by a hand-held stereo camera, our system, segments, clusters,
and fits ellipses to fruitlets to measure their diameters. The growth rates are
then calculated by temporally associating clustered fruitlets across days. We
provide quantitative results on data collected in an apple orchard, and
demonstrate that our system is able to predict abscise rates within 3.5% of the
current method with a 6 times improvement in speed, while requiring
significantly less manual effort. Moreover, we provide results on images
captured by a robotic system in the field, and discuss the next steps required
to make the process fully autonomous
Cyclic Di-GMP-Regulated Periplasmic Proteolysis of a Pseudomonas aeruginosa Type Vb Secretion System Substrate
We previously identified a second-messenger-regulated signaling system in the environmental bacterium Pseudomonas fluorescens which controls biofilm formation in response to levels of environmental inorganic phosphate. This system contains the transmembrane cyclic di-GMP (c-di-GMP) receptor LapD and the periplasmic protease LapG. LapD regulates LapG and controls the ability of this protease to process a large cell surface adhesin protein, LapA. While LapDG orthologs can be identified in divers
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The discovery and maturation of peptide biologics targeting the small G protein Cdc42: a bioblockade for Ras-driven signalling
Aberrant Ras signalling drives 30% of cancers and inhibition of Rho family small-GTPase signalling has been shown to combat Ras-driven cancers. Here we present the discovery of a 16mer cyclic peptide that binds to Cdc42 with nanomolar affinity. Affinity maturation of this sequence has produced a panel of derived candidates with increased affinity and modulated specificity for other closely related small-GTPases. The structure of the tightest binding peptide was solved by NMR and its binding site on Cdc42 determined. Addition of a cell penetrating sequence allowed the peptides to access the cell interior and engage with their target(s), modulating signalling pathways. In Ras-driven cancer cell models, the peptides have an inhibitory effect on proliferation and show suppression of both invasion and motility. As such they represent promising candidates for Rho-family small GTPase inhibitors and therapeutics targeting Ras-driven cancers. Our data adds to the growing literature demonstrating that peptides are establishing their place in the biologics arm of drug discovery.This research was supported by an MRC CASE Studentship (MR/K017101/1) to DO and RNC, a BBSRC DTP iCASE Studentship (BB/M011194/1) to DO and JR and a short-term Glover Research Fund Fellowship to GJNT
Swimming in circles: Motion of bacteria near solid boundaries
Near a solid boundary, E. coli swims in clockwise circular motion. We provide
a hydrodynamic model for this behavior. We show that circular trajectories are
natural consequences of force-free and torque-free swimming, and the
hydrodynamic interactions with the boundary, which also leads to a hydrodynamic
trapping of the cells close to the surface. We compare the results of the model
with experimental data and obtain reasonable agreement. In particular, we show
that the radius of curvature of the trajectory increases with the length of the
bacterium body.Comment: Also available at http://people.deas.harvard.edu/~lauga
An initial spatial conflict analysis for potential deep-sea mining of marine minerals in U.S. Federal Waters
Demand for critical minerals is projected to double or even triple by 2030 as the global energy and transportation sectors transition away from fossil fuels toward renewable energy. This anticipated demand raises interest in new critical mineral resources, including marine minerals, to supplement future supplies. While the environmental benefits of transitioning to green energy are many, there are inherent environmental costs. In this study, we compiled broad-scale datasets of prominent environmental features and human uses within four deep ocean regions of the U.S. Exclusive Economic Zone where marine minerals are predicted to occur, called prospective regions: they are the Blake Plateau, the Hawaiian Islands, Offshore California, and the Gulf of Alaska. We generated a normalized metric to score regions based on the co-occurrence of either environmental or human use variables within hexagonal grid cells, allowing us to assess the occurrence intensity and spatial patterns of environmental and/or human use variables within each region. Driven by the presence of threatened species and total species richness, the Blake Plateau and the Hawaiian Islands have the highest environmental occurrence scores, followed by Offshore California and the Gulf of Alaska. Offshore California is the busiest shipping region, followed by the Blake Plateau, the Gulf of Alaska and Hawaiian Islands, and subsea cables are densest in Offshore California, followed by Gulf of Alaska and Hawaiian Islands. The Gulf of Alaska has the largest reported fisheries landings. The sensitivities of biota and human uses to mining are highest for benthic or sessile species and infrastructure on or near ferromanganese crusts or manganese nodules that would be directly and physically altered through crust extraction or nodule removal. This study illustrates the usefulness of comprehensive, spatially explicit risk assessments to inform deep sea mining management and minimize ecological harm and human use conflicts. We assert that the relatively straightforward GIS-based methodology tested here can be applied and iterated upon elsewhere
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Mechanistic insight into the conserved allosteric regulation of periplasmic proteolysis by the signaling molecule cyclic-di-GMP
Stable surface adhesion of cells is one of the early pivotal steps in bacterial biofilm
formation, a prevalent adaptation strategy in response to changing environments. In Pseudomonas
fluorescens, this process is regulated by the Lap system and the second messenger cyclic-di-GMP.
High cytoplasmic levels of cyclic-di-GMP activate the transmembrane receptor LapD that in turn
recruits the periplasmic protease LapG, preventing it from cleaving a cell surface-bound adhesin,
thereby promoting cell adhesion. In this study, we elucidate the molecular basis of LapG regulation
by LapD and reveal a remarkably sensitive switching mechanism that is controlled by LapD's HAMP
domain. LapD appears to act as a coincidence detector, whereby a weak interaction of LapG with
LapD transmits a transient outside-in signal that is reinforced only when cyclic-di-GMP levels increase.
Given the conservation of key elements of this receptor system in many bacterial species, the results
are broadly relevant for cyclic-di-GMP- and HAMP domain-regulated transmembrane signaling.This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by eLife Sciences Publications Ltd. The published article can be found at: http://elifesciences.org/
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Measurement and simulation of jet mass caused by a high-aspect ratio pertubation
Inertial confinement fusion (ICF) capsule performance can be negatively impacted by the presence of hydrodynamic instabilities. To perform a gas fill on an ICF capsule current plans involve drilling a small hole and inserting a fill tube to inject the gas mixture into the capsule. This introduces a perturbation on the capsule, which can seed hydrodynamic instabilities. The small hole can cause jetting of the shell material into the gas, which might adversely affect the capsule performance. We have performed simulations and experiments to study the hydrodynamic evolution of jets from high-aspect ratio holes, such as the fill tube hole. Although simulations using cold materials over predict the amount of mass in the jet, when a reasonable amount of preheat (< 1 eV) is introduced, the simulations are in better agreement with the experiment
Oscillatory Exchange Coupling and Positive Magnetoresistance in Epitaxial Oxide Heterostructures
Oscillations in the exchange coupling between ferromagnetic
layers with paramagnetic spacer layer
thickness has been observed in epitaxial heterostructures of the two oxides.
This behavior is explained within the RKKY model employing an {\it ab initio}
calculated band structure of , taking into account strong electron
scattering in the spacer. Antiferromagnetically coupled superlattices exhibit a
positive current-in-plane magnetoresistance.Comment: 4 pages (RevTeX), 5 figures (EPS
Second Line of Defense Spares Program
During Fiscal Year 2012, a team from the Pacific Northwest National Laboratory (PNNL) conducted an assessment and analysis of the Second Line of Defense (SLD) Sustainability spare parts program. Spare parts management touches many aspects of the SLD Sustainability Program including contracting and integration of Local Maintenance Providers (LMP), equipment vendors, analyses and metrics on program performance, system state of health, and maintenance practices. Standardized spares management will provide better data for decisions during site transition phase and will facilitate transition to host country sustainability ownership. The effort was coordinated with related SLD Sustainability Program initiatives, including a configuration items baselining initiative, a metrics initiative, and a maintenance initiative. The spares study has also led to pilot programs for sourcing alternatives that include regional intermediate inventories and partnering agreements that leverage existing supply chains. Many partners from the SLD Sustainability program contributed to and were consulted in the course of the study. This document provides a description of the findings, recommendations, and implemented solutions that have resulted from the study
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