Construction and Calibration of a Low-Cost 3D Laser Scanner with 360◦ Field of View for Mobile Robots

Navigation of many mobile robots relies on environmental information obtained from three-dimensional (3D) laser scanners. This paper presents a new 360◦ field-of-view 3D laser scanner for mobile robots that avoids the high cost of commercial devices. The 3D scanner is based on spinning a Hokuyo UTM- 30LX-EX two-dimensional (2D) rangefinder around its optical center. The proposed design profits from lessons learned with the development of a previous 3D scanner with pitching motion. Intrinsic calibration of the new device has been performed to obtain both temporal and geometric parameters. The paper also shows the integration of the 3D device in the outdoor mobile robot Andabata.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Barrier Graphs and Extremal Questions on Line, Ray, Segment, and Hyperplane Sensor Networks

A sensor network is typically modeled as a collection of spatially distributed objects with the same shape, generally for the purpose of surveilling or protecting areas and locations. In this dissertation we address several questions relating to sensors with linear shapes: line, line segment, and rays in the plane, and hyperplanes in higher dimensions. First we explore ray sensor networks in the plane, whose resilience is the number of sensors that must be crossed by an agent traveling between two known locations. The coverage of such a network is described by a particular tripartite graph, the barrier graph of the network. We show that barrier graphs are perfect (Berge) graphs and have a rigid neighborhood structure due to the rays\u27 geometry. We introduce two extremal problems for networks in the plane made of line sensors, line segment sensors, or ray sensors, which informally ask how well it is possible to simultaneously protect k locations with n (line/ray/segment)-shaped sensors from intruders. The first question allows any number of intruders, while the second assumes there is a lone intruder. We show these are questions to be answered separately, and provide complete answers for k = 2 in both cases. We provide asymptotically tight answers for question (1) when k = 3, 4 and the locations are in convex position. We also provide asymptotic lower bounds for question (1) for any k. Finally, we generalize these extremal problems to d dimensions. For the d-dimensional version of question (1) we provide asymptotic lower and upper bounds for any combination of k and d, though these bounds do not meet

On Barrier Graphs of Sensor Networks

The study of sensor networks begins with a model, which usually has a geometric component. This thesis focuses on networks of sensors modeled as collections of rays in the plane whose use is to detect intruders, and in particular a graph derived from this geometry, called the barrier graph of the network, which captures information about the network\u27s coverage. Every such ray-barrier sensor network corresponds to a barrier graph, but not every graph is the barrier graph of some network. We show that any barrier graph is not just tripartite, but perfect. We describe how to find networks which have certain designated graphs as their barrier graphs. We show that the size of a minimum vertex cover (in this context called the resilience) of a given graph can yield information about whether and how one can find a sensor network whose barrier graph is the given graph. Finally, we demonstrate that barrier graphs have certain strong structural properties, as a result of the geometry of ray-barrier networks, which represent progress towards a full characterization of barrier graphs

In vivo manipulation of the extracellular matrix induces vascular regression in a basal chordate.

We investigated the physical role of the extracellular matrix (ECM) in vascular homeostasis in the basal chordate Botryllus schlosseri, which has a large, transparent, extracorporeal vascular network encompassing an area >100 cm2 We found that the collagen cross-linking enzyme lysyl oxidase is expressed in all vascular cells and that in vivo inhibition using β-aminopropionitrile (BAPN) caused a rapid, global regression of the entire network, with some vessels regressing >10 mm within 16 h. BAPN treatment changed the ultrastructure of collagen fibers in the vessel basement membrane, and the kinetics of regression were dose dependent. Pharmacological inhibition of both focal adhesion kinase (FAK) and Raf also induced regression, and levels of phosphorylated FAK in vascular cells decreased during BAPN treatment and FAK inhibition but not Raf inhibition, suggesting that physical changes in the vessel ECM are detected via canonical integrin signaling pathways. Regression is driven by apoptosis and extrusion of cells through the basal lamina, which are then engulfed by blood-borne phagocytes. Extrusion and regression occurred in a coordinated manner that maintained vessel integrity, with no loss of barrier function. This suggests the presence of regulatory mechanisms linking physical changes to a homeostatic, tissue-level response

Exoplanet Research with NASA\u27s EXOTIC

The investigation of exoplanets is a relatively recent field with abundant potential. The launch of the Transiting Exoplanet Survey Satellite (TESS) in 2018 marks an exponential increase in the amount of exoplanets we can study. 420 planets have been confirmed as of Feb 21st 2024, and as of Feb. 16th 2024, 7,071 exoplanet candidates are actively being researched. While TESS has been pivotal in expanding the field of exoplanet research, it has become equally important for ground-based observations to determine whether or not the transits detected by TESS are exoplanet systems. The National Aeronautics and Space Administration (NASA) exoplanetary community offers both access to their MicroObservatory telescope and data reduction pipeline, Exoplanet Transit Interpretation Code (EXOTIC), for undergraduate, graduate and civilian scientific researchers to work with. Through the EXOTIC program, we perform multi-aperture photometry with the data given from NASA’s MicroObservatory to obtain light curves for target stars with potential exoplanets. These light curves are then analyzed to find incremental and repetitive dips in the flux that represent a system with a transiting exoplanet. As an ongoing project, we are currently working exclusively with the MicroObservatory data. However, this project has the potential of growing to analyze personal data taken by undergraduate students through EXOTIC to detect or confirm exoplanet candidates. As the field of exoplanetary astrophysics grows, this project stands out as a unique student-led, unfunded team with NASA

WholeTree Substrate and Fertilizer Rate in Production of Greenhouse-grown Petunia (Petunia ×hybrida Vilm.) and Marigold (Tagetes patula L.)

A substrate component (WholeTree) made from loblolly pine (Pinus taeda L.) was evaluated along with starter fertilizer rate in the production of greenhouse-grown petunia (Petunia ×hybrida Vilm. ‘Dreams Purple’) and marigold (Tagetes patula L. ‘Hero Spry’). Loblolly pine from a 12-year-old plantation were harvested at ground level, chipped, and further processed through a hammer mill to pass a 0.64-cm screen. The resulting WholeTree (WT) substrate was used alone or combined with 20% (WTP2) or 50% (WTP5) (by volume) Canadian sphagnum peatmoss and compared with an industry standard peat-lite (PL) mix of 8 peatmoss : 1 vermiculite : 1 perlite (by volume). Substrates were amended with 1.78 kg·m−3 dolomitic lime, 0.59 kg·m−3 gypsum [CaSO4-2(H2O)], 0.44 kg·m−3 Micromax, 1.78 kg·m−3 16N–2.6P–9.9K (3- to 4-month release), and 1.78 kg·m−3 16N–2.6P–10.8K (5- to 6-month release). A 7N–1.3P–8.3K starter fertilizer (SF) was added to each substrate at 0.0, 1.19, 2.37, or 3.56 kg·m−3. Container capacity (CC) was greatest for PL and decreased as the percentage of peatmoss in the substrate decreased with WT having 35% less CC than PL. Conversely, air space (AS) was greatest for the WT and decreased as percentage of peatmoss increased with PL containing 33% less AS than WT. In general, petunia dry weight was greatest for any substrate containing peatmoss with a SF rate of 2.37 kg·m−3 or greater. The exception was that petunia grown in WT at 3.56 kg·m−3 SF had similar dry weight as all other treatments. Marigold dry weight was similar for all substrates where at least 2.37 kg·m−3 SF was used

Use of artificial nutrition near the end of life: Results from a French national population-based study of hospitalized cancer patients

International audienceBackgroundThe use of artificial nutrition, defined as a medical treatment that allows a non‐oral mechanical feeding, for cancer patients with limited life expectancy is deemed nonbeneficial. High‐quality evidence about the use of artificial nutrition near the end of life is lacking. This study aimed (a) to quantify the use of artificial nutrition near the end‐of‐life, and (b) to identify the factors associated with the use of artificial nutrition.MethodsThis was a retrospective cohort study of decedents based on data from the French national hospital database. The study population included adult cancer patients who died in hospitals in France between 2013 and 2016 and defined to be in a palliative condition. Use of artificial nutrition during the last 7 days before death was the primary endpoint.ResultsA total of 398 822 patients were included. The median duration of the last hospital stay was 10 (interquartile range, 4‐21) days. The artificial nutrition was used for 11 723 (2.9%) during the last 7 days before death. Being a man, younger, having digestive cancers, metastasis, comorbidities, malnutrition, absence of dementia, and palliative care use were the main factors associated to the use of artificial nutrition.ConclusionThis study indicates that the use of artificial nutrition near the end of life is in keeping with current clinical guidelines. The identification of factors associated with the use of artificial nutrition, such as cancer localization, presence of comorbidities or specific symptoms, may help to better manage its use