2,334 research outputs found

    "Pricing of Non-ferrous Metals Futures on the London Metal Exchange"

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    The London Metal Exchange (LME) is the most important centre for spot and futures trading in the main industrially-used non-ferrous metals. In this paper, data on 3-month futures contracts for aluminium, aluminium alloy, copper, lead, nickel, tin and zinc are analysed. The risk premium hypothesis and the cost-of-carry model are the standard theoretical models for pricing futures contracts, but these two models have rarely been estimated within a unified framework for metals futures. Single equation versions of the risk premium hypothesis and the cost-of-carry model are nested within a more general model. If the spot price, futures price, interest rate and stock level variables contain stochastic trends, long run versions of the general model can be estimated within a cointegration framework. Various long run pricing models are estimated using daily LME price data for the period 1 February 1986 to 30 September 1998. Likelihood ratio tests are used to test restrictions on the general model to examine the validity of alternative nested specifications.

    Becoming a Novice Smoker: Initial Smoking Behaviours among Jor danian Psychiatric Nurses

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    A better understanding of how male Jordanian psychiatric nurses become smokers and continue the habit mainly at work is necessary if smoking reduction and cessation programs are to help them better manage their smoking behaviours. Here we use a grounded theory approach to describe the factors that influenced the eight nurses in our sample to take up smoking. We use five categories derived from open coding to explain the initial stage in the smoking histories of the nurses. We situate our account of becoming a novice smoker within the contextualizing smoking behaviours over time theory we developed from our study. Finally, we relate the substantive findings we report here to the theoretical perspectives of symbolic interactionism and transtheoretical theory

    The benchmark aeroelastic models program: Description and highlights of initial results

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    An experimental effort was implemented in aeroelasticity called the Benchmark Models Program. The primary purpose of this program is to provide the necessary data to evaluate computational fluid dynamic codes for aeroelastic analysis. It also focuses on increasing the understanding of the physics of unsteady flows and providing data for empirical design. An overview is given of this program and some results obtained in the initial tests are highlighted. The tests that were completed include measurement of unsteady pressures during flutter of rigid wing with a NACA 0012 airfoil section and dynamic response measurements of a flexible rectangular wing with a thick circular arc airfoil undergoing shock boundary layer oscillations

    Variability in supply and cross-shelf transport of pink shrimp (Farfantepenaeus duorarum) postlarvae into western Florida Bay

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    The variability in the supply of pink shrimp (Farfantepenaeus duorarum) postlarvae and the transport mechanisms of planktonic stages were investigated with field data and simulations of transport. Postlarvae entering the nursery grounds of Florida Bay were collected for three consecutive years at channels that connect the Bay with the Gulf of Mexico, and in channels of the Middle Florida Keys that connect the southeastern margin of the Bay with the Atlantic Ocean. The influx of postlarvae in the Middle Florida Keys was low in magnitude and varied seasonally and among years. In contrast, the greater postlarval influx occurred at the northwestern border of the Bay, where there was a strong seasonal pattern with peaks in influx from July through September each year. Planktonic stages need to travel up to 150 km eastward between spawning grounds (northeast of Dry Tortugas) and nursery grounds (western Florida Bay) in about 30 days, the estimated time of planktonic development for this species. A Lagrangian trajectory model was developed to estimate the drift of planktonic stages across the SW Florida shelf. The model simulated the maximal distance traveled by planktonic stages under various assumptions of behavior. Simulation results indicated that larvae traveling with the instantaneous current and exhibiting a diel behavior travel up to 65 km and 75% of the larvae travel only 30 km. However, the eastward distance traveled increased substantially when a larval response to tides was added to the behavioral variable (distance increased to 200 km and 85% of larvae traveled 150 km). The question is, when during larval development, and where on the shallow SW Florida shelf, does the tidal response become incorporated into the behavior of pink shrimp

    Gonadotropin-releasing hormone regulates expression of the DNA damage repair gene, Fanconi anemia A, in pituitary gonadotroph cells

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    Gonadal function is critically dependant on regulated secretion of the gonadotropin hormones from anterior pituitary gonadotroph cells. Gonadotropin biosynthesis and release is triggered by the binding of hypothalamic GnRH to GnRH receptor expressed on the gonadotroph cell surface. The repertoire of regulatory molecules involved in this process are still being defined. We used the mouse LβT2 gonadotroph cell line, which expresses both gonadotropin hormones, as a model to investigate GnRH regulation of gene expression and differential display reverse transcription-polymerase chain reaction (RT-PCR) to identify and isolate hormonally induced changes. This approach identified Fanconi anemia a (Fanca), a gene implicated in DNA damage repair, as a differentially expressed transcript. Mutations in Fanca account for the majority of cases of Fanconi anemia (FA), a recessively inherited disease identified by congenital defects, bone marrow failure, infertility, and cancer susceptibility. We confirmed expression and hormonal regulation of Fanca mRNA by quantitative RT-PCR, which showed that GnRH induced a rapid, transient increase in Fanca mRNA. Fanca protein was also acutely upregulated after GnRH treatment of LβT2 cells. In addition, Fanca gene expression was confined to mature pituitary gonadotrophs and adult mouse pituitary and was not expressed in the immature αT3-1 gonadotroph cell line. Thus, this study extends the expression profile of Fanca into a highly specialized endocrine cell and demonstrates hormonal regulation of expression of the Fanca locus. We suggest that this regulatory mechanism may have a crucial role in the GnRH-response mechanism of mature gonadotrophs and perhaps the etiology of FA

    Flight Test Results of an Axisymmetric Channeled Center Body Supersonic Inlet at Off-Design Conditions

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    Flight-testing of a channeled center-body axisymmetric supersonic inlet design concept was conducted at the National Aeronautics and Space Administration (NASA) Dryden Flight Research Center in collaboration with the NASA Glenn Research Center (Cleveland, Ohio) and TechLand Research, Inc. (North Olmsted, Ohio). This testing utilized the Propulsion Flight Test Fixture, flown on the NASA F-15B research test bed airplane (NASA tail number 836) at local experiment Mach numbers up to 1.50. The translating channeled center-body inlet was designed by TechLand Research, Inc. (U.S. Patent No. 6,276,632 B1) to allow for a novel method of off-design flow matching, with original test planning conducted under a NASA Small Business Innovative Research study. Data were collected in flight at various off-design Mach numbers for fixed-geometry representations of both the channeled center-body design and an equivalent area smooth center-body design for direct comparison of total pressure recovery and limited distortion measurements

    Exchanging demands: Weaknesses in SSL implementations for mobile platforms

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    The ActiveSync protocol’s implementation on some embedded devices leaves clients vulnerable to unauthorised remote policy enforcement. This paper discusses a proof of concept attack against the implementation of ActiveSync in common Smart phones including Android devices and iOS devices. A two‐phase approach to exploiting the ActiveSync protocol is introduced. Phase 1 details the usage of a man‐in‐the‐middle attack to gain a vantage point over the client device, whilst Phase 2 involves spoofing the server‐side ActiveSync responses to initiate the unauthorised policy enforcement. These vulnerabilities are demonstrated by experiment, highlighting how the system can be exploited to perform a remote factory reset upon an Exchange‐integrated Smart phone

    Thermodynamic Limits on Magnetodynamos in Rocky Exoplanets

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    To ascertain whether magnetic dynamos operate in rocky exoplanets more massive or hotter than the Earth, we developed a parametric model of a differentiated rocky planet and its thermal evolution. Our model reproduces the established properties of Earth's interior and magnetic field at the present time. When applied to Venus, assuming that planet lacks plate tectonics and has a dehydrated mantle with an elevated viscosity, the model shows that the dynamo shuts down or never operated. Our model predicts that at a fixed planet mass, dynamo history is sensitive to core size, but not to the initial inventory of long-lived, heat-producing radionuclides. It predicts that rocky planets larger than 2.5 Earth masses will not develop inner cores because the temperature-pressure slope of the iron solidus becomes flatter than that of the core adiabat. Instead, iron "snow" will condense near or at the top of these cores, and the net transfer of latent heat upwards will suppress convection and a dynamo. More massive planets can have anemic dynamos due to core cooling, but only if they have mobile lids (plate tectonics). The lifetime of these dynamos is shorter with increasing planet mass but longer with higher surface temperature. Massive Venus-like planets with stagnant lids and more viscous mantles will lack dynamos altogether. We identify two alternative sources of magnetic fields on rocky planets: eddy currents induced in the hot or molten upper layers of planets on very short period orbits, and dynamos in the ionic conducting layers of "ocean" planets with ~10% mass in an upper mantle of water (ice).Comment: Accepted to The Astrophysical Journa
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