Sampling-based Algorithms for Optimal Motion Planning

During the last decade, sampling-based path planning algorithms, such as Probabilistic RoadMaps (PRM) and Rapidly-exploring Random Trees (RRT), have been shown to work well in practice and possess theoretical guarantees such as probabilistic completeness. However, little effort has been devoted to the formal analysis of the quality of the solution returned by such algorithms, e.g., as a function of the number of samples. The purpose of this paper is to fill this gap, by rigorously analyzing the asymptotic behavior of the cost of the solution returned by stochastic sampling-based algorithms as the number of samples increases. A number of negative results are provided, characterizing existing algorithms, e.g., showing that, under mild technical conditions, the cost of the solution returned by broadly used sampling-based algorithms converges almost surely to a non-optimal value. The main contribution of the paper is the introduction of new algorithms, namely, PRM* and RRT*, which are provably asymptotically optimal, i.e., such that the cost of the returned solution converges almost surely to the optimum. Moreover, it is shown that the computational complexity of the new algorithms is within a constant factor of that of their probabilistically complete (but not asymptotically optimal) counterparts. The analysis in this paper hinges on novel connections between stochastic sampling-based path planning algorithms and the theory of random geometric graphs.Comment: 76 pages, 26 figures, to appear in International Journal of Robotics Researc

Removal of imidacloprid from polluted water using adsorption and membrane separation technologies

In this work, the stability of imidacloprid in fresh water and sludge was studied. The results revealed that the pesticide is unstable in both media. In freshwater, it underwent hydrolysis whereas a degradation to several metabolites has been observed in sludge. The rate constants for the hydrolysis and degradation at 25°C were 0.0.0067 and 0.0.0099 d–1, respectively. Monitoring the degradation of imidacloprid in sludge by high-pressure liquid chromatography-mass spectrometry (HPLC-MS) revealed that five metabolites have emerged during the study. These metabolites include imidacloprid urea, imidacloprid-guanidine, 6-hydroxynicotinic acid, an olefin, and 5-hydroxy, 1-(6-chloro-3-pyridylmethyl)-2-(nitroimino)-imidazolidin-5-ol. The efficiency of Al-Quds University Wastewater Treatment Plant towards the removal of imidacloprid indicates that the ultrafiltration-hollow fiber unit was insufficient, whereas the ultrafiltration-spiral wound, activated carbon, and reverse osmosis units were efficient for complete removal of the pesticide. Adsorption experiments of imidacloprid using either activated charcoal or micelle-clay complex were found to fit Langmuir isotherms better than Freundlich isotherm. The data demonstrate a higher Langmuir Qmax value for the activated charcoal (126.6 mg g–1) when compared to the micelle-clay complex (11.76 mg g–1). Filtration column experiments, conducted with mixed micelle-clay complex and sand (using a ratio of 1/50 by mass) at a flow rate of 2 mL min–1 and influent concentration of 50 mg L–1, revealed that a sufficient removal of imidacloprid was achieved in the first fraction of 100 mL elution. These findings indicate that the adsorption technology using the micelle-clay complex provides efficient removal of imidacloprid in continuous flow mode

The effect of long-term feeding of conjugated linoleic acid on fertility in Japanese quail

The objective of this study was to determine the effects of the long-term feeding of conjugated linoleic acid (CLA) on laying hen performance, egg fertility and hatchability of fertile eggs of Japanese quail (Coturnix coturnix japonica). One hundred and sixty 7-day old Japanese quail chicks were randomly assigned to four groups (40 birds per group) and fed for five weeks on a commercial diet supplemented with either 0.5% hazelnut (Group A), 0.5% sunflower oil (Group B), 0.25% CLA (Group C) or 0.5% CLA (Group D). The birds received water and feed ad libitum during the study. At the end of the five weeks the birds were sexed, and 21 females and seven males from each group were selected. For a further six weeks these selected birds were fed a layer diet supplemented with their respective sources of oil. Eggs were collected daily and incubated weekly. The fertility rate was determined by visual inspection at the end of the incubation period. Dietary CLA at the inclusion level of 0.5%, but not at 0.25%, caused a significant decrease in percentage hatchability of the fertile eggs compared to Groups A and B. Hatchability of fertile eggs from Groups A, B, C and D was 74, 80, 72 and 70, respectively. Fertility rates between Groups A, B, C and D did not differ significantly, and were 64.4, 56.4, 66.0 and 62.8%, respectively. Hen-day egg production of Groups A, C and D were similar, but in weeks 3, 4, 5 and 6, hens in Group B had a significantly lower hen-day egg production (%) compared to Group A. Also, in weeks 3, 4, 5 and 6, egg size in Group B was significantly lower than that in the other groups. From this study it is concluded that dietary CLA at inclusion levels of 0.25% or 0.5% did not influence egg fertility, egg weight and egg production in Japanese quail. South African Journal of Animal Science Vol. 36(2) 2006: 99-10

The water we would like

Water is needed for our health: it maintains the health and integrity of every cell in the body, keeps the bloodstream liquid enough to flow through blood vessels, helps eliminate the by-products of the body’s metabolism, aids digestion, and other exceptional properties. High-quality water is needed to preserve health. Unfortunately, the environment and all its sectors are differently contaminated. This dangerous state is closely linked to increased anthropic activities (industrial and agricultural) and the use of harmful substances released without control. Old contaminants (pesticides and substances deriving from industrial activities) and new contaminants, called "emerging" (drugs, phytotoxins, body care products), can arrive in rivers, in surface and deep water, and the sea if they are not removed from the wastewater. These substances are harmful to human health because they enter the environment in quantities exceeding the natural self capacity purification of the ecosystems. We can be exposed to water-derived contaminants in different ways. For example, people can ingest small amounts of pollutants by drinking water; they can absorb pollutants through the skin while bathing or showering and during recreational activities, such as swimming, windsurfing, and water skiing; they can inhale droplets suspended in the air or vapors while taking a shower. They can also ingest foods that have been contaminated with water-borne pollutants.Wastewater treatment plants (WWTPs) cannot altogether remove most of these substances, which can easily reach the drinking water supplies, causing health problems for adults and children. Although drinking water quality is regulated and monitored in many countries, today’s increased knowledge suggests reviewing standards and guidelines on a near-permanent basis for both held and newly identified contaminants and adopting technologies as tertiary treatment processes, which could promote the easy degradation of recalcitrant compounds. It will be necessary to verify that the degradation products are less dangerous than the original molecules and that no dangerous aggregation products are formed. This communication reports some of the degradation studies carried out by our Research Teams in collaboration with foreign researchers using Advanced Oxidation Processes (AOPs) on pesticides and pharmaceuticals present in actual water samples. Photolysis and heterogeneous photocatalysis under simulated solar irradiation using two forms of TiO2 (suspended or immobilized on the surface of thin glass plates) have been investigated to assess the suitability of different oxidation processes to promote mineralization of recalcitrant substances. Transformation products (TPs) have been identified by an LC system coupled to a hybrid LTQ-FTICR (7-T) mass spectrometer (MS). To evaluate the treatment methods' effectiveness, the treated solutions' measurements have been performed using the “Microtox® Toxicity Test” that reports the luminescence inhibition of the marine bacteria Vibrio fischeri. During the degradation process, the temporary formation of toxic fragments was observed, which rapidly degraded to complete mineralization. Samples collected during the degradation process showed the temporary toxicity of the water. The rate of decomposition was highly dependent on the method used. Advanced oxidation processes such as TiO2/Xe-arc system, lead to a rapid decrease of the biorecalcitrant chemical concentrations in aqueous solutions, while photolysis and TiO2-coated glass are less effective. These promising results push us to continue and improver experimental trials. What is the future prospect? The creation of prototypes to be used by farmers and artisans to start with the virtuous path of water recycle

Glassy phonon heralds a strain glass state in a shape memory alloy

Shape memory strain glasses are frustrated ferroelastic materials with glasslike slow relaxation an

Project-based, collaborative, algorithmic robotics for high school students: Programming self-driving race cars at MIT

We describe the pedagogy behind the MIT Beaver Works Summer Institute Robotics Program, a new high-school STEM program in robotics. The program utilizes state-of-the-art sensors and embedded computers for mobile robotics. These components are carried on an exciting 1/10-scale race-car platform. The program has three salient, distinguishing features: (i) it focuses on robotics software systems: the students design and build robotics software towards real-world applications, without being distracted by hardware issues; (ii) it champions project-based learning: the students learn through weekly project assignments and a final course challenge; (iii) the learning is implemented in a collaborative fashion: the students learn the basics of collaboration and technical communication in lectures, and they work in teams to design and implement their software systems. The program was offered as a four-week residential program at MIT in the summer of 2016. In this paper, we provide the details of this new program, its teaching objectives, and its results. We also briefly discuss future directions and opportunities

Reactive synthesis from signal temporal logic specifications

We present a counterexample-guided inductive synthesis approach to controller synthesis for cyber-physical systems subject to signal temporal logic (STL) specifications, operating in potentially adversarial nondeterministic environments. We encode STL specifications as mixed integer-linear constraints on the variables of a discrete-time model of the system and environment dynamics, and solve a series of optimization problems to yield a satisfying control sequence. We demonstrate how the scheme can be used in a receding horizon fashion to fulfill properties over unbounded horizons, and present experimental results for reactive controller synthesis for case studies in building climate control and autonomous driving

Finding Correspondence between Metabolomic Features in Untargeted Liquid Chromatography-Mass Spectrometry Metabolomics Datasets

Integration of multiple datasets can greatly enhance bioanalytical studies, for example, by increasing power to discover and validate biomarkers. In liquid chromatography-mass spectrometry (LC-MS) metabolomics, it is especially hard to combine untargeted datasets since the majority of metabolomic features are not annotated and thus cannot be matched by chemical identity. Typically, the information available for each feature is retention time (RT), mass-to-charge ratio (m/z), and feature intensity (FI). Pairs of features from the same metabolite in separate datasets can exhibit small but significant differences, making matching very challenging. Current methods to address this issue are too simple or rely on assumptions that cannot be met in all cases. We present a method to find feature correspondence between two similar LC-MS metabolomics experiments or batches using only the features' RT, m/z, and FI. We demonstrate the method on both real and synthetic datasets, using six orthogonal validation strategies to gauge the matching quality. In our main example, 4953 features were uniquely matched, of which 585 (96.8%) of 604 manually annotated features were correct. In a second example, 2324 features could be uniquely matched, with 79 (90.8%) out of 87 annotated features correctly matched. Most of the missed annotated matches are between features that behave very differently from modeled inter-dataset shifts of RT, MZ, and FI. In a third example with simulated data with 4755 features per dataset, 99.6% of the matches were correct. Finally, the results of matching three other dataset pairs using our method are compared with a published alternative method, metabCombiner, showing the advantages of our approach. The method can be applied using M2S (Match 2 Sets), a free, open-source MATLAB toolbox, available at https://github.com/rjdossan/M2S

High-throughput identification of genotype-specific cancer vulnerabilities in mixtures of barcoded tumor cell lines.

Hundreds of genetically characterized cell lines are available for the discovery of genotype-specific cancer vulnerabilities. However, screening large numbers of compounds against large numbers of cell lines is currently impractical, and such experiments are often difficult to control. Here we report a method called PRISM that allows pooled screening of mixtures of cancer cell lines by labeling each cell line with 24-nucleotide barcodes. PRISM revealed the expected patterns of cell killing seen in conventional (unpooled) assays. In a screen of 102 cell lines across 8,400 compounds, PRISM led to the identification of BRD-7880 as a potent and highly specific inhibitor of aurora kinases B and C. Cell line pools also efficiently formed tumors as xenografts, and PRISM recapitulated the expected pattern of erlotinib sensitivity in vivo