3,043 research outputs found

    Cosmic String Loop Microlensing

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    Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.Comment: 20 pages, 19 figure

    Magnetism and Magnetic Isomers in Free Chromium Clusters

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    We have used the Stern-Gerlach deflection technique to study magnetism in chromium clusters of 20-133 atoms. Between 60 K and 100 K, we observe that these clusters have large magnetic moments and respond superparamagnetically to applied magnetic fields. Using superparamagnetic theory, we have determined the moment per atom for each cluster size and find that it often far exceeds the moment per atom present anywhere in the bulk antiferromagnetic lattice. Remarkably, our cluster beam contains two magnetically distinguishable forms of each cluster size with >= 34 atoms. We attribute this observation to structural isomers

    Importance of disinfection as a means of prevention in our changing world hygiene and the home

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    Contrary to expectation, the risks of infection are growing rather than declining, even in everyday life. After all, who is able to make a distinction between cleanliness and hygiene? This situation is further compounded by the growing number of persons who are susceptible to infections. If one wants to combat infectious diseases in an economically feasible and consistent manner, public support must be sought. In turn, the public have a right to be informed in a proper and responsible manner. The difference between “dirt” and “contamination” must be highlighted once again

    Work-rate of substitutes in elite soccer: A preliminary study

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    The aim of this study was to investigate the work-rate of substitutes in professional soccer. A computerised player tracking system was used to assess the work-rates of second-half substitutes (11 midfielders and 14 forwards) in a French Ligue 1 club. Total distance, distance covered in five categories of movement intensity and recovery time between high-intensity efforts were evaluated. First- and second-half work-rates of the replaced players were compared. The performance of substitutes was compared to that of the players they replaced, to team-mates in the same position who remained on the pitch after the substitution and in relation to their habitual performances when starting games. No differences in work-rate between first- and second-halves were observed in all players who were substituted. In the second-half, a non-significant trend was observed in midfield substitutes who covered greater distances than the player they replaced whereas no differences were observed in forwards. Midfield substitutes covered a greater overall distance and distance at high-intensities (p<0.01) and had a lower recovery time between high-intensity efforts (p<0.01) compared to other midfield team-mates who remained on the pitch. Forwards covered less distance (p<0.01) in their first 10-minutes as a substitute compared to their habitual work-rate profile in the opening 10-minutes when starting matches while this finding was not observed in midfielders. These findings suggest that compared to midfield substitutes, forward substitutes did not utilise their full physical potential. Further investigation is warranted into the reasons behind this finding in order to optimise the work-rate contributions of forward substitutes

    Wintertime losses of ozone in high northern latitudes

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    Total column ozone data over the past 22 to 30 years from ground-based Dobson and filter ozonometer stations between 30 N and 80 N are analyzed for residual trends remaining after allowance for the known geophysical variations corresponding to: (1) the change of seasons; (2) the quasi-biennial oscillation; and (3) the 11-year solar sunspot cycle. Examination of the data from several ground stations between 45 and 55 N indicated a seasonal difference in the long-term ozone series, with statistically significant losses in several winter months. Accordingly, the data from individual stations were analyzed with multiple regression analysis, seeking trends on a monthly basis after allowance for the known geophysical cycles. Previous statistical analyses were conducted as tests of 1-D model calculations which do not show any differences with the seasons, and any trend toward change in ozone concentrations is expressed in a yearly trend without seasonal variation. Such a model is inappropriate for calculations with a data set which exhibits a pronounced tendency toward seasonal differences in the trends. Comparisons with model calculations then require 2-D models into which seasonal and latitudinal differences can easily be programmed

    Coupled quintessence and vacuum decay

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    We discuss observational consequences of a class of cosmological models characterized by the dilution of pressureless matter attenuated with respect to the usual a3a^{-3} scaling due to the decay of vacuum energy. We carry out a joint statistical analysis of observational data from the new \emph{gold} sample of 182 SNe Ia, recent estimates of the CMB shift parameter, and BAO measurements from the SDSS to show that such models favor the decay of vacuum only into the dark matter sector, and that the separately conserved baryons cannot be neglected. In order to explore ways to more fundamentally motivated models, we also derive a coupled scalar field version for this general class of vacuum decay scenarios.Comment: 6 pages, 3 figures, LaTe

    A guide to the harvesting of plums for export - Part - 2

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    The Santa Rosa is an important export plum variety. It is the earliest of the main varieties shipped to Singapore and under proper conditions of harvesting and handling it carries well. It is, however, necessary to give close attention to harvest maturity to ensure that the fruit will arrive in the best possible condition

    The handling, presentation and storage of stone fruits

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    The stone fruit industry in Western Australia produces up to 250,000 bushels of fruit per annum. The crop is disposed of mainly as fresh fruit on the local market, but during the last few years a useful outlet for certain varieties of plums has developed in Singapore which imports about 12,000 bushels each year. Stone fruits are not dried commercially and processing is confined mainly to the use of surplus fruit for jam making

    A guide to the harvesting of plums for export

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    Western Australia is well situated geographically to supply the demand for plums on the Singapore market and over the past 10 years, a substantial export trade has been developed. Growers have found this outlet profitable, and increased plantings of suitable varieties have been made. During the 1957 season—a record export year—almost 40,000 boxes were shipped
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