3,549 research outputs found

    Model simulations of the changing distribution of Ozone and its radiative forcing of climate: past, present and future

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    A background tropospheric chemistry model that is coupled to the general circulation model ECHAM4 is used to calculate tropospheric ozone with preindustrial, present-day and future (IS92a) emission scenarios as boundary conditions. The model calculates separate contributions to tropospheric ozone levels from stratosphere-troposphere exchange (STE) and from photo- chemical production in the troposphere. In the preindustrial atmosphere, the simulated annual tropospheric ozone content is 190 Tg 03, of which about 110 Tg 03 originates from the strato- sphere. In the present-day simulation the ozone content is about 80 Tg 03 larger, mainly due to O3 precursor emissions from industrial processes in the NH and from biomass burning in trop- ical regions. In the next few decades, industrial growth is expected to occur mainly at NH (sub) tropical latitudes, leading to an additional increase of the tropospheric ozone budget by 60 Tg 03. We calculate a global and annual average radiative forcing by tropospheric ozone perturbations of 0.42 w m-2 creases in the next few decades of 0.31 W m-2 for the present-day simulation, and an additional forcing due to ozone in- The model results indicate that the amount of tropospheric ozone from stratospheric origin remains relatively unaffected by the changing pho- tochemistry

    The Development of a Sex Pheromone Lure for the American Plum Borer, \u3ci\u3eEuzophera Semifuneralis\u3c/i\u3e (Lepidoptera: Pyralidae), a Major Pest of Cherry in Michigan.

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    Pheromone components of the American plum borer, Euzophera semifuneralis, were defined by use of the electroantennogram screening technique and capillary gas chromatographic retention times of sex pheromone gland constituents. Field studies showed that greatest attraction was achieved with a 1 mg load rate of a 4-component blend in a rubber septum. This blend consisted of a 2:1 ratio of Z,E-9,12-14:ALD and Z9-14:ALD and an equal amount of the corresponding alcohols in a 2:1 ratio, respectively. Commercial lures were used to compare the flight patterns of the American plum borer, peachtree borer (Synanthedon exitiosa), and lesser peachtree borer (Synanthedon pictipes) adults in Michigan in 1988

    The AM Canum Venaticorum binary SDSS J173047.59+554518.5

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    The AM Canum Venaticorum (AM CVn) binaries are a rare group of hydrogen-deficient, ultrashort period, mass-transferring white dwarf binaries and are possible progenitors of Type Ia supernovae. We present time-resolved spectroscopy of the recently discovered AM CVn binary SDSS J173047.59+554518.5. The average spectrum shows strong double-peaked helium emission lines, as well as a variety of metal lines, including neon; this is the second detection of neon in an AM CVn binary, after the much brighter system GP Com. We detect no calcium in the accretion disc, a puzzling feature that has been noted in many of the longer period AM CVn binaries. We measure an orbital period, from the radial velocities of the emission lines, of 35.2 ± 0.2 min, confirming the ultracompact binary nature of the system. The emission lines seen in SDSS J1730 are very narrow, although double-peaked, implying a low-inclination, face-on accretion disc; using the measured velocities of the line peaks, we estimate i ≤ 11°. This low inclination makes SDSS J1730 an excellent system for the identification of emission lines

    Mesenchymal stem cells for management of rheumatoid arthritis : immune modulation, repair or both?

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    The authors are grateful for support to their research from Arthritis Research UK (grants 19271, 19429, 19667, 20050, 20775) and the Medical Research Council (grant no. MR/L020211/1)Peer reviewedPostprin

    The population of AM CVn stars from the Sloan Digital Sky Survey

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    The AM Canum Venaticorum stars are rare interacting white dwarf binaries, whose formation and evolution are still poorly known. The Sloan Digital Sky Survey provides, for the first time, a sample of 6 AM CVn stars (out of a total population of 18) that is sufficiently homogeneous that we can start to study the population in some detail. We use the Sloan sample to `calibrate' theoretical population synthesis models for the space density of AM CVn stars. We consider optimistic and pessimistic models for different theoretical formation channels, which yield predictions for the local space density that are more than two orders of magnitude apart. When calibrated with the observations, all models give a local space density of 1-3x10^{-6} pc^{-3}, which is lower than expected. We discuss the implications for the formation of AM CVn stars, and conclude that at least one of the dominant formation channels (the double-degenerate channel) has to be suppressed relative to the optimistic models. In the framework of the current models this suggests that the mass transfer between white dwarfs usually cannot be stabilized. We furthermore discuss evolutionary effects that have so far not been considered in population synthesis models, but which could be of influence for the observed population. We finish by remarking that, with our lower space density, the expected number of Galactic AM CVn stars resolvable by gravitational-wave detectors like LISA should be lowered from current estimates, to about 1,000 for a mission duration of one year.Comment: Accepted to MNRA

    Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM

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    A parameterization for cloud processing is presented that calculates activation of aerosol particles to cloud drops, cloud drop size, and pH-dependent aqueous phase sulfur chemistry. The parameterization is implemented in the global aerosol-climate model ECHAM5-HAM. The cloud processing parameterization uses updraft speed, temperature, and aerosol size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum supersaturation at the cloud base, and subsequently the cloud drop number concentration (CDNC) due to activation. In-cloud sulfate production occurs through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The model simulates realistic distributions for annually averaged CDNC although it is underestimated especially in remote marine regions. On average, CDNC is dominated by cloud droplets growing on particles from the accumulation mode, with smaller contributions from the Aitken and coarse modes. The simulations indicate that in-cloud sulfate production is a potentially important source of accumulation mode sized cloud condensation nuclei, due to chemical growth of activated Aitken particles and to enhanced coalescence of processed particles. The strength of this source depends on the distribution of produced sulfate over the activated modes. This distribution is affected by uncertainties in many parameters that play a direct role in particle activation, such as the updraft velocity, the aerosol chemical composition and the organic solubility, and the simulated CDNC is found to be relatively sensitive to these uncertainties

    A Follow-up Study of the Graduating Classes of 1959, 1960, 1961, and 1962 from Belview High School, Belview, Minnesota

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    One of the primary means of evaluating the effectiveness of an organization or function is to contact the people who have been served. With this thought, a follow-up study of the graduates from Belview High School was undertaken during the 1962-1963 school year. The main intent of this study was the evaluation of the curriculum by the students whom it had served. Of additional interest was the graduates’ concepts of needed services and additional subject areas conceived from deficiencies encountered in post-high school undertaking. Answers to specific questions were sought. When did graduates marry and how many children did they have? Is graduate’s spouse from immediate Belview area? Where were graduates living? How many graduates continued their education and what schools did they attend? What reasons did graduates have for choice of further education? What type of degrees were graduates seeking? How much time elapsed between graduating and obtaining the first job? What were the most important factors which influenced graduates in getting jobs? How did occupational choice in high school compare with occupational choice at the time questionnaire was filled out? How did graduates view courses taken in high school? What type of curriculum improvements did graduates feel were essential

    The development of a prototype intelligent user interface subsystem for NASA's scientific database systems

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    The National Space Science Data Center (NSSDC) has initiated an Intelligent Data Management (IDM) research effort which has as one of its components the development of an Intelligent User Interface (IUI).The intent of the latter is to develop a friendly and intelligent user interface service that is based on expert systems and natural language processing technologies. The purpose is to support the large number of potential scientific and engineering users presently having need of space and land related research and technical data but who have little or no experience in query languages or understanding of the information content or architecture of the databases involved. This technical memorandum presents prototype Intelligent User Interface Subsystem (IUIS) using the Crustal Dynamics Project Database as a test bed for the implementation of the CRUDDES (Crustal Dynamics Expert System). The knowledge base has more than 200 rules and represents a single application view and the architectural view. Operational performance using CRUDDES has allowed nondatabase users to obtain useful information from the database previously accessible only to an expert database user or the database designer
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