Optimal and receding-horizon path planning algorithms for communications relay vehicles in complex environments

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 97-100).This thesis presents new algorithms for path planning in a communications constrained environment for teams of unmanned vehicles. This problem involves a lead vehicle that must gather information from a set of locations and relay it back to its operator. In general, these locations and the lead vehicle's position are beyond line of-sight from the operator and non-stationary, which introduces several difficulties to the problem. The proposed solution is to use several additional unmanned vehicles to create a network linkage between the operator and the lead vehicle that can be used to relay information between the two endpoints. Because the operating environment is cluttered with obstacles that block both line-of-sight and vehicle movement, the paths of the vehicles must be carefully planned to meet all constraints. The core problem of interest that is addressed in this thesis is the path planning for these link vehicles. Two solutions are presented in this thesis. The first is a centralized approach based on a numerical solution of optimal control theory. This thesis presents an optimal control problem formulation that balances the competing objectives of minimizing overall mission time and minimizing energy expenditure. Also presented is a new modification of the Rapidly-Exploring Random Tree algorithm that makes it more efficient at finding paths that are applicable to the communications chaining problem. The second solution takes a distributed, receding-horizon approach, where each vehicle solves for its own path using a local optimization that helps the system as a whole achieve the global objective.(cont.) This solution is applicable to real-time use onboard a team of vehicles. To offset the loss of optimality from this approach, a new heuristic is developed for the linking vehicles. Finally, both solutions are demonstrated in simulation and in flight tests in MIT's RAVEN testbed. These simulations and flight tests demonstrate the performance of the two solution methods as well as their viability for use in real unmanned vehicle systems.by Karl Christian Kulling.S.M

Low prevalence of Chlamydia trachomatis infection in asymptomatic young Swiss men

BACKGROUND: Prevalence and risk factors for Chlamydia trachomatis infection among young men in Switzerland is still unknown. The objective of the present study was to assess prevalence and risk factors for C. trachomatis infection in young Swiss men. METHODS: 517 young Swiss men were enrolled in this cross-sectional study during their compulsory military recruitment. Participants completed a questionnaire and gave urine samples which were screened for C. trachomatis DNA by PCR. Genotyping of positive samples was done by amplification and sequencing the ompA gene. RESULTS: The prevalence of chlamydial infection among young Swiss male was 1.2% (95% confidence interval [95%CI], 0.4-2.5%). C. trachomatis infection was only identified among the 306 men having multiple sexual partner. Although frequent, neither unprotected sex (absence of condom use), nor alcohol and drug abuse were associated with chlamydial infection. Men living in cities were more frequently infected (2.9%, 95%CI 0.8-7.4%) than men living in rural areas (0.5%, 95%CI 0.1-1.9%, p = 0.046). Moreover, naturalised Swiss citizens were more often positive (4.9%, 95%CI 1.3-12.5%) than native-born Swiss men (0.5%, 95%CI 0.1-1.7%, p = 0.003). CONCLUSION: In comparison with other countries, the prevalence of chlamydial infection in men is extremely low in Switzerland, despite a significant prevalence of risky sexual behaviour. C. trachomatis infection was especially prevalent in men with multiple sexual partners. Further research is required (i) to define which subgroup of the general population should be routinely screened, and (ii) to test whether such a targeted screening strategy will be effective to reduce the prevalence of chlamydial infection among this population

Who Drinks Most of the Total Alcohol in Young Men—Risky Single Occasion Drinking as Normative Behaviour

Aims: The objectives of this study were to analyse (a) the distribution of risky single-occasion drinking (RSOD) among 19-year-old men in Switzerland and (b) to show the percentage of all alcohol consumption in the form of RSOD. Methods: The study was based on a census of Swiss francophone 19-year-old men consecutively reporting for processing. The study was conducted at Army Recruitment Center. The participants were 4116 recruits consecutively enrolling for mandatory army recruitment procedures between 23 January and 29 August in 2007. The measures were alcohol consumption measured in drinks of ∼10 g of pure alcohol, number of drinking occasions with six or more drinks (RSOD) in the past 12 months and a retrospective 1 week drinking diary. Results: 264 recruits were never seen by the research staff, 3536 of the remaining 3852 conscripts completed a questionnaire which showed that 7.2% abstained from alcohol and 75.5% of those drinking had an RSOD day at least monthly. The typical frequency of drinking was 1-3 days per week on weekends. The average quantity on weekends was about seven drinks, 69.3% of the total weekly consumption was in the form of RSOD days, and of all the alcohol consumed, 96.2% was by drinkers who had RSOD days at least once a month. Conclusion: Among young men, RSOD constitutes the norm. Prevention consequently must address the total population and not only high-risk drinker

Implicit volatilitet och deltaneutrala optionsstrategier inför kvartalsrapporter.

SYFTE: Huvudsyftet med denna studie är att undersöka om det är möjligt att utnyttja marknadens osäkerhet inför kvartalsrapporter. METOD: Metodmässigt bygger vår studie på sekundärdata, med fokus på Ericssons historiska slutkurser på aktier och optioner. Vi har prognostiserat den implicita volatiliteten inför kvartalsrapporter för att sedan utforma lämpliga deltaneutrala optionsstrategier som vi testar på nästkommande år. TEORI: Vi utgår från tidigare studier om att den implicita volatiliteten stiger inför kvartalsrapporter vilket vi vill testa. Dessutom testas teorin om svag marknadseffektivitet. EMPIRI: Våra resultat visar att den implicita volatiliteten generellt stiger inför kvartalsrapporter. De deltaneutrala optionsstrategierna genererade positiv avkastning som var högre än den riskfria räntan, men när transaktionskostnader medräknades blev avkastningen negativ. SLUTSATSER: Den implicita volatiliteten stiger innan kvartalsrapporter, men marknaden är redan uppmärksam på detta. När den implicita volatiliteten inte stiger lika mycket som marknaden förväntar sig medför det en negativ avkastning. Det är därför viktigt att alltid ha rätt tro och kunskap om volatiliteten. Då våra strategier inte genererade överavkastning kan vi dra slutsatsen att den del av marknaden som vi har studerat varit minst svagt effektiv

Microbial Metabolism of the Soy Isoflavones Daidzein and Genistein in Postmenopausal Women: Human Intervention Study Reveals New Metabotypes

Background: Soy isoflavones belong to the group of phytoestrogens and are associated with beneficial health effects but are also discussed to have adverse effects. Isoflavones are intensively metabolized by the gut microbiota leading to metabolites with altered estrogenic potency. The population is classified into different isoflavone metabotypes based on individual metabolite profiles. So far, this classification was based on the capacity to metabolize daidzein and did not reflect genistein metabolism. We investigated the microbial metabolite profile of isoflavones considering daidzein and genistein. Methods: Isoflavones and metabolites were quantified in the urine of postmenopausal women receiving a soy isoflavone extract for 12 weeks. Based on these data, women were clustered in different isoflavone metabotypes. Further, the estrogenic potency of these metabotypes was estimated. Results: Based on the excreted urinary amounts of isoflavones and metabolites, the metabolite profiles could be calculated, resulting in 5 metabotypes applying a hierarchical cluster analysis. The metabotypes differed in part strongly regarding their metabolite profile and their estimated estrogenic potency

Glyphosate and AMPA levels in human urine samples and their correlation with food consumption: results of the cross-sectional KarMeN study in Germany

Glyphosate (N-[phosphonomethyl]-glycine) is the most widely used herbicide worldwide. Due to health concerns about glyphosate exposure, its continued use is controversially discussed. Biomonitoring is an important tool in safety evaluation and this study aimed to determine exposure to glyphosate and its metabolite AMPA, in association with food consumption data, in participants of the cross-sectional KarMeN study (Germany). Glyphosate and AMPA levels were measured in 24-h urine samples from study participants (n = 301). For safety evaluation, the intake of glyphosate and AMPA was calculated based on urinary concentrations and checked against the EU acceptable daily intake (ADI) value for glyphosate. Urinary excretion of glyphosate and/or AMPA was correlated with food consumption data. 8.3% of the participants (n = 25) exhibited quantifiable concentrations (> 0.2 μg/L) of glyphosate and/or AMPA in their urine. In 66.5% of the samples, neither glyphosate (< 0.05 μg/L) nor AMPA (< 0.09 μg/L) was detected. The remaining subjects (n = 76) showed traces of glyphosate and/or AMPA. The calculated glyphosate and/or AMPA intake was far below the ADI of glyphosate. Significant, positive associations between urinary glyphosate excretion and consumption of pulses, or urinary AMPA excretion and mushroom intake were observed. Despite the widespread use of glyphosate, the exposure of the KarMeN population to glyphosate and AMPA was found to be very low. Based on the current risk assessment of glyphosate by EFSA, such exposure levels are not expected to pose any risk to human health. The detected associations with consuming certain foods are in line with reports on glyphosate and AMPA residues in food

Quantification of Urinary Phenyl-γ-Valerolactones and Related Valeric Acids in Human Urine on Consumption of Apples

Flavan-3-ols are dietary bioactive molecules that have beneficial effects on human health and reduce the risk of various diseases. Monomeric flavan-3-ols are rapidly absorbed in the small intestine and released in the blood stream as phase II conjugates. Polymeric flavan-3-ols are extensively metabolized by colonic gut microbiota into phenyl-γ-valerolactones and their related phenylvaleric acids. These molecules are the main circulating metabolites in humans after the ingestion of flavan-3-ol rich-products; nevertheless, they have received less attention and their role is not understood yet. Here, we describe the quantification of 8 phenyl-γ-valerolactones and 3 phenylvaleric acids in the urine of 11 subjects on consumption of apples by using UHPLC-ESI-Triple Quad-MS with pure reference compounds. Phenyl-γ-valerolactones, mainly as sulfate and glucuronic acid conjugates, reached maximum excretion between 6 and 12 after apple consumption, with a decline thereafter. Significant differences were detected in the cumulative excretion rates within subjects and in the ratio of dihydroxyphenyl-γ-valerolactone sulfate to glucuronide conjugates. This work observed for the first time the presence of two distinct metabotypes with regards to the excretion of phenyl-γ-valerolactone phase II conjugates