15,864 research outputs found
3D environment mapping using the Kinect V2 and path planning based on RRT algorithms
This paper describes a 3D path planning system that is able to provide a solution trajectory for the automatic control of a robot. The proposed system uses a point cloud obtained from the robot workspace, with a Kinect V2 sensor to identify the interest regions and the obstacles of the environment. Our proposal includes a collision-free path planner based on the Rapidly-exploring Random Trees variant (RRT*), for a safe and optimal navigation of robots in 3D spaces. Results on RGB-D segmentation and recognition, point cloud processing, and comparisons between different RRT* algorithms, are presented.Peer ReviewedPostprint (published version
Facile syntheses of building blocks for the construction of phosphotyrosine mimetics
The copper-catalysed zinc phosphonate chemistry described by Yokomatsu and Shibuya can be used to enter the classical organometallic coupling repertoire via Stille and Suzuki–Miyaura couplings. 1,4-Diiodobenzene underwent coupling with the organozinc reagent derived from diethyl bromodifluoromethylphosphonate with copper(I) catalysis to afford diethyl (4-iodophenyl)difluoromethylphosphonate. Higher yielding couplings were run with (4-trifluoromethylsulfonyloxy)- and (4-nonafluorobutylsulfonyloxy)-iodobenzenes. The iodide and the triflate coupled under palladium-catalysed conditions with a range of stannanes and boronic acids in moderate to excellent yields. Shibuya–Yokomatsu couplings were also successful with more functionalised iodoarenes and heteroarenes presenting the important phosphate mimic on a range of scaffolds
Star formation and accretion in the circumnuclear disks of active galaxies
We explore the evolution of supermassive black holes (SMBH) centered in a
circumnuclear disk (CND) as a function of the mass supply from the host galaxy
and considering different star formation laws, which may give rise to a
self-regulation via the injection of supernova-driven turbulence. A system of
equations describing star formation, black hole accretion and angular momentum
transport was solved for an axisymmetric disk in which the gravitational
potential includes contributions from the black hole, the disk and the hosting
galaxy. Our model extends the framework provided by Kawakatu et al. (2008) by
separately considering the inner and outer part of the disk, and by introducing
a potentially non-linear dependence of the star formation rate on the gas
surface density and the turbulent velocity. The star formation recipes are
calibrated using observational data for NGC 1097, while the accretion model is
based on turbulent viscosity as a source of angular momentum transport in a
thin viscous accretion disk. We find that current data provide no strong
constraint on the star formation recipe, and can in particular not distinguish
between models entirely regulated by the surface density, and models including
a dependence on the turbulent velocity. The evolution of the black hole mass,
on the other hand, strongly depends on the applied star formation law, as well
as the mass supply from the host galaxy. We suggest to explore the star
formation process in local AGN with high-resolution ALMA observations to break
the degeneracy between different star formation models.Comment: 13 pages, 15 figures, 6 tables, accepted at A&
Offspring Sex Ratio in Double Brooding Prothonotary Warblers
Prothonotary warblers are bright, golden birds who, with their loud calls, make themselves known in wetland habitats in the spring after returning from their winter homes in the Neotropics to breed. This migratory species is important to study because of their need for these habitats and are declining in population due to the degradation of wetland environments across the western hemisphere.
VCU started a project in 1987 to study prothonotary warblers including population genetics, breeding biology, and migration ecology. Since then, with the help of Richmond Audubon Society, the project has erected over 600 nesting boxes along the James River contributing to a database going back 30 years. This makes them an accessible bird to study and, with the collected information, help to better understand the causes of their declin
Xenopus Drf1, a Regulator of Cdc7, Displays Checkpoint-dependent Accumulation on Chromatin during an S-phase Arrest
We have cloned a Xenopus Dbf4-related factor named Drf1 and characterized this protein by using Xenopus egg extracts. Drf1 forms an active complex with the kinase Cdc7. However, most of the Cdc7 in egg extracts is not associated with Drf1, which raises the possibility that some or all of the remaining Cdc7 is bound to another Dbf4-related protein. Immunodepletion of Drf1 does not prevent DNA replication in egg extracts. Consistent with this observation, Cdc45 can still associate with chromatin in Drf1-depleted extracts, albeit at significantly reduced levels. Nonetheless, Drf1 displays highly regulated binding to replicating chromatin. Treatment of egg extracts with aphidicolin results in a substantial accumulation of Drf1 on chromatin. This accumulation is blocked by addition of caffeine and by immunodepletion of either ATR or Claspin. These observations suggest that the increased binding of Drf1 to aphidicolin-treated chromatin is an active process that is mediated by a caffeine-sensitive checkpoint pathway containing ATR and Claspin. Abrogation of this pathway also leads to a large increase in the binding of Cdc45 to chromatin. This increase is substantially reduced in the absence of Drf1, which suggests that regulation of Drf1 might be involved in the suppression of Cdc45 loading during replication arrest. We also provide evidence that elimination of this checkpoint causes resumed initiation of DNA replication in both Xenopus tissue culture cells and egg extracts. Taken together, these observations argue that Drf1 is regulated by an intra-S-phase checkpoint mechanism that down-regulates the loading of Cdc45 onto chromatin containing DNA replication blocks
Developing priorities to achieve health equity through diabetes translation research: A concept mapping study
Introduction: The goal of diabetes translation research is to advance research into practice and ensure equitable benefit from scientific evidence. This study uses concept mapping to inform and refine future directions of diabetes translation research with the goal of achieving health equity in diabetes prevention and control.
Research design and methods: This study used concept mapping and input from a national network of diabetes researchers and public health practitioners. Concept mapping is a mixed-method, participant-based process. First, participants generated statements by responding to a focus prompt (
Results: Ten clusters were identified containing between 6 and 12 statements from 95 total generated statements. The ranges of average importance and feasibility ratings for clusters were fairly high and narrow (3.62-4.09; 3.10-3.93, respectively). Clusters with the most statements in the go-zone quadrant (above average importance/feasibility) were
Conclusions: This study created a framework of 10 priority areas to guide current and future efforts in diabetes translation research to achieve health equity. Themes rated as highly important and feasible provide the basis to evaluate current research support. Future efforts should explore how to best support innovative-targets, those rated highly important but less feasible
Review: emerging concepts in the pathogenesis of tendinopathy
Tendinopathy is a common clinical problem and has a significant disease burden attached, not only in terms of health care costs, but also for patients directly in terms of time off work and impact upon quality of life. Controversy surrounds the pathogenesis of tendinopathy, however the recent systematic analysis of the evidence has demonstrated that many of the claims of an absence of inflammation in tendinopathy were more based around belief than robust scientific data. This review is a summary of the emerging research in this topical area, with a particular focus on the role of neuronal regulation and inflammation in tendinopathy
Kinematics of Circumgalactic Gas: Feeding Galaxies and Feedback
We present observations of 50 pairs of redshift z ~ 0.2 star-forming galaxies
and background quasars. These sightlines probe the circumgalactic medium (CGM)
out to half the virial radius, and we describe the circumgalactic gas
kinematics relative to the reference frame defined by the galactic disks. We
detect halo gas in MgII absorption, measure the equivalent-width-weighted
Doppler shifts relative to each galaxy, and find that the CGM has a component
of angular momentum that is aligned with the galactic disk. No net
counter-rotation of the CGM is detected within 45 degrees of the major axis at
any impact parameter. The velocity offset of the circumgalactic gas correlates
with the projected rotation speed in the disk plane out to disk radii of
roughly 70 kpc. We confirm previous claims that the MgII absorption becomes
stronger near the galactic minor axis and show that the equivalent width
correlates with the velocity range of the absorption. We cannot directly
measure the location of any absorber along the sightline, but we explore the
hypothesis that individual velocity components can be associated with gas
orbiting in the disk plane or flowing radially outward in a conical outflow. We
conclude that centrifugal forces partially support the low-ionization gas and
galactic outflows kinematically disturb the CGM producing excess absorption.
Our results firmly rule out schema for the inner CGM that lack rotation and
suggest that angular momentum as well as galactic winds should be included in
any viable model for the low-redshift CGM.Comment: Accepted for publication in the Astrophysical Journa
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