3,880 research outputs found

    Designing and Implementing effective autonomous vehicle regulation in Toronto, Ontario

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    Thesis: M.C.P., Massachusetts Institute of Technology, Department of Urban Studies and Planning, 2018.Cataloged from PDF version of thesis.Includes bibliographical references (pages 162-169).Studies suggest autonomous vehicles can enable a more equitable, efficient, and sustainable transportation network. Yet, experts point out this outcome is not guaranteed, and that without outside policy intervention autonomous vehicle (AV) use might actually exacerbate congestion, sprawl, and inequitable access to travel. These challenges will be most acutely felt in areas under the purview of local governments-such as transportation congestion, land use, and impacts on public transit. As such, the goal of this thesis is to assist municipal policymakers with mitigating these impacts by answering the question: How can local governments effectively regulate autonomous vehicles? Looking at Toronto, Canada, specifically, this thesis addresses the following issues: - When is a contract, and when is a regulation, the most appropriate tool to encourage AV companies to act in ways that help foster a sustainable and equitable transportation network? - What does the City of Toronto require to develop effective AV regulation? - How can the City of Toronto codify broad AV policies into specific, enforceable regulations? This thesis employs three research methods: a literature review, a document analysis, and qualitative interviews with relevant experts. The primary literature review looks at the possible benefits and harms that might come from AV development and the policies local governments can enact to correct for these externalities. Interviews were conducted with 23 experts from the public and private sectors and academia, with responses analysed and themes drawn out to develop answers to the above research questions. Finally, analysis of Toronto's Official Plan and Municipal Code helped inform the creation of a proposed Article 10-A of the code to regulate AV rideshare companies. Chapters three to five of this thesis develop a framework (laid out in Figure 0.1) for thinking about how best to design effective AV regulation. Firstly, the government needs legal capacity to regulate in a given area. Toronto, for example, is responsible for overseeing local rideshare company activity. The remaining four elements all relate to human resources. Interviews show Toronto's bureaucrats believe they have a responsibility and ability to craft effective and ambitious regulations that advance the city's goals. These willing civil servants need the time and the expertise to design good policy, and the Toronto government has an AV working group that provides a forum for such a discussion. To see regulations enacted effectively, however, the mayor and council must not only support rules eventually proposed by the working group; they may also need to approach the provincial government to convince them to craft their own complementary AV legislation. Figure 0.1. The five elements to effective regulation [illustration] Chapter six explores how broad AV policy can be applied concretely. Along with Article 10-A (Appendix C), it offers an example of the specific legal language for AV regulation. Divided into two broad categories--'Equity' and 'Urban Form and Street Space'-the article addresses some of the anticipated issues that might arise with AV rideshare operations including a need to allow citizens without a smartphone are able to use the service, limit AV rideshare travel on local roads, and ensure all neighbourhoods enjoy a relatively similar level of service (accounting for geography and density). Beyond the proposed article itself, chapter six provides feedback from Toronto officials as to the challenges the provisions in the article might face were the government to attempt their ratification. Positively, none of the regulations were unanimously viewed as infeasible, with staff seemingly eager to act boldly when it comes to addressing the challenges of AV activity. As such, this thesis can be used both by Toronto policymakers and their counterparts elsewhere as the basis for discussion in designing the specific rules for AV operations that will be incorporated into a future version of the Municipal Code.by Benjamin M. Gillies-Podgorecki.M.C.P

    The Size Distribution of Kuiper Belt Objects

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    We describe analytical and numerical collisional evolution calculations for the size distribution of icy bodies in the Kuiper Belt. For a wide range of bulk properties, initial masses, and orbital parameters, our results yield power-law cumulative size distributions, N_C propto r^{-q}, with q_L = 3.5 for large bodies with radii of 10-100 km, and q_s = 2.5-3 for small bodies with radii lesss than 0.1-1 km. The transition between the two power laws occurs at a break radius of 1-30 km. The break radius is more sensitive to the initial mass in the Kuiper Belt and the amount of stirring by Neptune than the bulk properties of individual Kuiper Belt objects (KBOs). Comparisons with observations indicate that most models can explain the observed sky surface density of KBOs for red magnitudes, R = 22-27. For R 28, the model surface density is sensitive to the amount of stirring by Neptune, suggesting that the size distribution of icy planets in the outer solar system provides independent constraints on the formation of Neptune.Comment: 24 pages of text, 12 figures; to appear in the Astronomical Journal, October 200

    INVESTIGATING CATALYST DESIGN STRATEGIES FOR SELECTIVE REACTION OF CYCLIC C4 OXYGENATES FROM BIOMASS

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    Numerous studies have shown that the properties of metal catalysts can in principle be fine-tuned by controlling the composition of the metal surface with high precision. The ability to design catalysts capable of high selectivity towards the conversion of a single functional group in a multifunctional molecule is a major objective for heterogeneous catalysis research. This need for high selectivity toward a single functional group is of growing importance in efforts to improve biorefining operations, where biomass-derived multifunctional carbohydrates are key building block intermediates that must be converted to a vast range of commodity chemical products such as fuels, pharmaceuticals, food products, and more. This work focuses on results from high resolution electron energy loss spectroscopy (HREELS) and temperature programmed desorption (TPD) experiments combined with selective use of density functional theory (DFT) calculations on single-crystal surfaces under ultrahigh vacuum conditions to study structure-property relations for a series of C4 cyclic oxygenates on catalytic metal surfaces. The objective of this work is to identify methods to tailor surfaces that are able to selectively catalyze conversions of one functional group in the multifunctional molecule. Two types of cyclic probe molecules have been studied in particular: 3-membered epoxide rings (in which ring-strain is high and the character of the oxygenate function is therefore more reactive) and 5-membered furanone rings (in which the ring is relatively stable). Both the epoxides and furanones contain an unsaturated C=C bond; for many biorefining applications it is desirable to selectively hydrogenate the olefin while keeping the oxygenate functionality intact. In this contribution, we explore the role of surface structure and composition in dictating the reaction pathways for multifunctional C4 cyclic oxygenates on key transition metal and bimetallic surfaces. Results for the epoxide probe molecule studies indicate differing modes of interaction with different metal surfaces. On a platinum or palladium surface, the epoxide ring opens irreversibly while the C=C functional group has a strong interaction with the surface. However, on a silver surface, the epoxide ring also opens, but can be made to close reversibly. An effective catalyst design strategy, then, is to combine silver on a predominantly platinum or palladium surface in order to create a bimetallic catalyst with high selectivity toward reaction of the olefin while keeping the epoxide ring intact. Recent studies of the chemistry of furanone species indicate that the olefin group interacts strongly with a platinum or palladium metal surface, and therefore is very likely to also determine how the molecule reacts. In this presentation, relationships between catalyst design strategies for epoxides versus furanones will be discussed, as will the likely biorefining reactions that such strategies can impact

    Searching the web builds fuller picture of arachnid trade

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    Trade in arachnids includes millions of individuals and over 1264 species, with over 70% of individuals coming from the wild. Wildlife trade is a major driver of biodiversity loss, yet whilst the impacts of trade in some species are relatively well-known, some taxa, such as many invertebrates are often overlooked. Here we explore global patterns of trade in the arachnids, and detected 1,264 species from 66 families and 371 genera in trade. Trade in these groups exceeds millions of individuals, with 67% coming directly from the wild, and up to 99% of individuals in some genera. For popular taxa, such as tarantulas up to 50% are in trade, including 25% of species described since 2000. CITES only covers 30 (2%) of the species potentially traded. We mapped the percentage and number of species native to each country in trade. To enable sustainable trade, better data on species distributions and better conservation status assessments are needed. The disparity between trade data sources highlights the need to expand monitoring if impacts on wild populations are to be accurately gauged and the impacts of trade minimised.Peer reviewe

    Stellar populations in a standard ISOGAL field in the Galactic disk

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    We aim to identify the stellar populations (mostly red giants and young stars) detected in the ISOGAL survey at 7 and 15micron towards a field (LN45) in the direction l=-45, b=0.0. The sources detected in the survey of the Galactic plane by the Infrared Space Observatory are characterized based on colour-colour and colour-magnitude diagrams. We combine the ISOGAL catalog with the data from surveys such as 2MASS and GLIMPSE. Interstellar extinction and distance are estimated using the red clump stars detected by 2MASS in combination with the isochrones for the AGB/RGB branch. Absolute magnitudes are thus derived and the stellar populations are identified based on their absolute magnitudes and their infrared excess. A standard approach to the analysis of ISOGAL disk observations has been established. We identify several hundred RGB/AGB stars and 22 candidate young stellar objects in the direction of this field in an area of 0.16 deg^2. An over-density of stellar sources is found at distances corresponding to the distance of the Scutum-Crux spiral arm. In addition, we determine mass-loss rates of AGB-stars using dust radiative transfer models from the literature.Comment: 48pages, 38 figures, accepted for publication in A &

    Errors in Sounding of the Atmosphere Using Broadband Emission Radiometry (SABER) Kinetic Temperature Caused by Non-Local Thermodynamic Equilibrium Model Parameters

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    The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions. The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude. The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 1.5 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions. For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to +/- 3 K

    Highly purified human-derived follicle-stimulating hormone (Bravelle®) has equivalent efficacy to follitropin-beta (Follistim ®) in infertile women undergoing in vitro fertilization

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    BACKGROUND: These data compare the efficacy and safety of highly purified human-derived follicle-stimulating hormone (Bravelle(R)) and recombinant follitropin-β (Follistim(R)) in women undergoing in vitro fertilization. METHODS: This report describes the pooled data from two, nearly identical, randomized, controlled, parallel-group, multicenter studies conducted in a total of 19 academic and private IVF-ET centers in the United States. Infertile premenopausal women underwent pituitary down-regulation using leuprolide acetate followed by a maximum of 12 days of subcutaneous Bravelle(R) (n = 120) or Follistim(R) (n = 118), followed by administration of human chorionic gonadotropin, oocyte retrieval and embryo transfer. The primary efficacy measure was the mean number of oocytes retrieved; secondary efficacy measures included the total dose and duration of gonadotropin treatment; peak serum estradion levels; embryo transfer and implantation rates; chemical, clinical and continuing pregnancies; and live birth rates. All adverse events were recorded and injection site pain was recorded daily using a patient, self-assessment diary. RESULTS: Similar efficacy responses were observed for all outcome parameters in the two treatment groups. Although patients receiving Bravelle(R) consistently reported a greater number of chemical, clinical and continuing pregnancies, as well as an increased rate of live birth, the data did not attain statistical significance (P > 0.05). The overall incidence of adverse events was similar in both groups, but compared to Follistim(R), injections of Bravelle(R) were reported by patients to be significantly less painful (P < 0.001). CONCLUSIONS: Bravelle(R) and Follistim(R) had comparable efficacy in controlled ovarian hyperstimulation in women undergoing IVF-ET. There were no differences in the nature or number of adverse events between the treatment groups although Bravelle(R) injections were reported to be significantly less painful

    A new model for magnetoreception

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    Certain migratory birds can sense the earth's magnetic field. The nature of this process is not yet properly understood. Here we offer a simple explanation according to which birds literally `see' the local magnetic field: Our model relates the well-established radical pair hypothesis to the phenomenon of Haidinger's brush, a capacity to see the polarisation of light. This new picture explains recent surprising experimental data indicating long lifetimes for the radical pair. Moreover there is a clear evolutionary path toward this field sensing mechanism: it is an enhancement of a weak effect that may be present in many species.Comment: 8 pages, 5 figures, version of final published pape

    Survey of Constellation-Era LOX/Methane Development Activities and Future Development Needs

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    NASA formed the Constellation Program in 2005 to achieve the objectives of maintaining American presence in low-Earth orbit, returning to the moon for purposes of establishing an outpost, and laying the foundation to explore Mars and beyond in the first half of the 21st century. The Exploration Technology Development Program (ETDP) was formulated to address the technology needs to address Constellation architecture decisions. The Propellants and Cryogenic Advanced Development (PCAD) project was tasked with risk mitigation of specific propulsion related technologies to support ETDP. Propulsion systems were identified as critical technologies owing to the high gear-ratio of lunar Mars landers Cryogenic propellants offer performance advantage over storables (NTOMMH) Mass savings translate to greater payload capacity In-situ production of propellant an attractive feature; methane and oxygen identified as possible Martian in-situ propellants New technologies were required to meet more difficult missions High performance LOX/LH2 deep throttle descent engines High performance LOX/LCH4 ascent main and reaction control system (RCS) engines The PCAD project sought to provide those technologies through Reliable ignition pulse RCS Fast start High efficiency engines Stable deep throttling
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