1,630 research outputs found
Bayesian Optimisation for Safe Navigation under Localisation Uncertainty
In outdoor environments, mobile robots are required to navigate through
terrain with varying characteristics, some of which might significantly affect
the integrity of the platform. Ideally, the robot should be able to identify
areas that are safe for navigation based on its own percepts about the
environment while avoiding damage to itself. Bayesian optimisation (BO) has
been successfully applied to the task of learning a model of terrain
traversability while guiding the robot through more traversable areas. An
issue, however, is that localisation uncertainty can end up guiding the robot
to unsafe areas and distort the model being learnt. In this paper, we address
this problem and present a novel method that allows BO to consider localisation
uncertainty by applying a Gaussian process model for uncertain inputs as a
prior. We evaluate the proposed method in simulation and in experiments with a
real robot navigating over rough terrain and compare it against standard BO
methods.Comment: To appear in the proceedings of the 18th International Symposium on
Robotics Research (ISRR 2017
Fast-growing willow development on acidic mining wastes for rapid greening purposes
Metal mining generates large volumes of wastes, which can contain sulphide minerals that generate acid when exposed to atmospheric conditions, providing unfavourable conditions for plant establishment. In particular, mining waste rocks are piled on tens of meters, and remain devoid of vegetation, creating a desolated anthropogenic landscape. The use of adapted plants able to grow quickly on waste rocks can help increasing their aesthetical aspect. An experiment was conducted at the Westwood mine in Quebec to evaluate the establishment ability of a fast-growing willow (Salix miyabeana Sx64) on acid- generating waste rocks. The main objective was to identify substrate thickness and composition that maximized willow productivity while limiting water stress exposure and trace metal accumulation. A randomized complete block design was established in June 2014 with five treatments: (1) direct planting in waste rocks, (2) and (3) 20 cm or 40 cm moraine amended with 20% of organic matter (OM) (in volume), (4) 20 cm moraine at 40% of OM, and (5) 20 cm moraine at 20% of OM over 20 cm lime sludge from water treatment. Trees directly planted in waste rocks survived well (75%) but had the lowest aerial productivity, with the lowest height and diameter growth, aerial biomass, and total leaf area, while the treatment richer in OM showed the greatest aerial biomass and total leaf area, and the thicker treatment the greatest height and diameter growth. Willow root development was restricted to cover
soils the first year after planting, and foliar δ13C values decreased in thicker soil (40 cm) compared to thin soil (20 cm). Willow accumulation factors in leaves were below one for all investigated trace metals except Zn
General quasi-non-spreading linear three-dimensional wave-packets
We introduce a general approach for generation of sets of three-dimensional
quasi-non-spreading wavepackets propagating in linear media, also referred to
as linear light bullets. The spectrum of rigorously non-spreading wavepackets
in media with anomalous group velocity dispersion is localized on the surface
of a sphere, thus drastically restricting the possible wavepacket shapes.
However, broadening slightly the spectrum affords the generation of a large
variety of quasi-non-spreading distributions featuring complex topologies and
shapes in space and time that are of interest in different areas, such as
biophysics or nanosurgery. Here we discuss the method and show several
illustrative examples of its potential.Comment: 3 pages, 4 figures, to appear in Optics Letter
Nanoengineered Astronomical Optics
We describe a technology for the fabrication of inexpensive and versatile
mirrors through the use of a new type of nanoengineered optical material
composed by the spreading of a self-assembling reflective colloidal film spread
at the surface of a liquid. These new reflecting liquids offer interesting
possibilities for astronomical instrumentation. For example, they can replace
mercury in conventional rotating liquid mirrors. The main advantages offered
include extremely low cost and, by coating a viscous liquid, the possibility of
tilting the mirror by a few tens of degrees. We also have coated ferromagnetic
liquids with these reflecting films. The resulting surfaces can be shaped by
the application of a magnetic field, yielding reflecting surfaces that can have
complicated shapes that can rapidly shift with time. These inexpensive and
versatile optical elements could have numerous scientific and technological
applications. Among possible astronomical applications, they could be used to
make large inexpensive adaptive mirrors exhibiting strokes ranging from
nanometers to several millimeters.Comment: Submitted to Astrophysical Journal Letters. 18 pages, 4 figure
The epidemiology of fighting in group-housed laboratory mice
Injurious home-cage aggression (fighting) in mice affects both animal welfare and scientific validity. It is arguably the most common potentially preventable morbidity in mouse facilities. Existing literature on mouse aggression almost exclusively examines territorial aggression induced by introducing a stimulus mouse into the home-cage of a singly housed mouse (i.e. the resident/intruder test). However, fighting occurring in mice living together in long-term groups under standard laboratory housing conditions has barely been studied. We performed a point-prevalence epidemiological survey of fighting at a research institution with an approximate 60,000 cage census. A subset of cages was sampled over the course of a year and factors potentially influencing home-cage fighting were recorded. Fighting was almost exclusively seen in group-housed male mice. Approximately 14% of group-housed male cages were observed with fighting animals in brief behavioral observations, but only 14% of those cages with fighting had skin injuries observable from cage-side. Thus simple cage-side checks may be missing the majority of fighting mice. Housing system (the combination of cage ventilation and bedding type), genetic background, time of year, cage location on the rack, and rack orientation in the room were significant risk factors predicting fighting. Of these predictors, only bedding type is easily manipulated to mitigate fighting. Cage ventilation and rack orientation often cannot be changed in modern vivaria, as they are baked in by cookie-cutter architectural approaches to facility design. This study emphasizes the need to invest in assessing the welfare costs of new housing and husbandry systems before implementing them
Effect of Prenatal Exposure to Polychlorinated Biphenyls on Incidence of Acute Respiratory Infections in Preschool Inuit Children
OBJECTIVE: We set out to assess whether environmental prenatal exposure to polychlorinated biphenyls (PCBs) is associated with incidence of acute respiratory infections in preschool Inuit children. STUDY DESIGN: We reviewed the medical charts of 343 children from 0 to 5 years of age and evaluated the associations between PCB-153 concentration in umbilical cord plasma and the incidence rates of acute otitis media (AOM) and of upper and lower respiratory tract infections (URTIs and LRTIs, respectively). RESULTS: The incidence rates of AOM and LRTIs were positively associated with prenatal exposure to PCBs. Compared with children in the first quartile of exposure (least exposed), children in fourth quartile (most exposed) had rate ratios of 1.25 (p < 0.001) and 1.40 (p < 0.001) for AOM and LRTIs, respectively. There was no association between prenatal PCB exposure and incidence rate of URTIs or hospitalization. CONCLUSION: Prenatal exposure to PCBs could be responsible for a significant portion of respiratory infections in children of this population
Plasma anandamide concentrations are lower in children with autism spectrum disorder
Background: Autism spectrum disorder (ASD) is a neurodevelopmentaldisorder characterized by restricted, stereotyped behaviors and impairments in social communication. Although the underlying biological mechanisms of ASD remain poorly understood, recent preclinical research has implicated the endogenous cannabinoid (or endocannabinoid), anandamide, as a significant neuromodulator in rodent models of ASD. Despite this promising preclinical evidence, no clinical studies to date have tested whether endocannabinoids are dysregulated in individuals with ASD. Here, we addressed this critical gap in knowledge by optimizing liquid chromatography-tandem mass spectrometry methodology to quantitatively analyze anandamide concentrations in banked blood samples collected from a cohort of children withand without ASD (N= 112). Findings: Anandamide concentrations significantly differentiated ASD cases (N= 59) from controls (N= 53), such that children with lower anandamide concentrations were more likely to have ASD (p= 0.041). In keeping with this notion, anandamide concentrations were also significantly lower in ASD compared to control children (p= 0.034). Conclusions: These findings are the first empirical human data to translate preclinical rodent findings to confirm a link between plasma anandamide concentrations in children with ASD. Although preliminary, these data suggest that impaired anandamide signaling may be involved in the pathophysiology of ASD
- …