25,845 research outputs found

    Statistical transmutation of quantum bosonic strings coupled to general four-dimensional Chern-Simons theory

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    A bosonic string coupled to the generalized Chern-Simons theory in 3+1D acquires a magnetic field along itself, when it is closed, and a topological charge at its extremity, when it is open. We construct the creation operators for the full quantum field states associated to these strings and determine the dual algebra satisfied by them. We show that the creation operator fo the composite state of a quantum closed bosonic string, bearing a magnetic flux, and a topologically charged open bosonic string, possesses generalized statistics. The relation of our results with previous approaches to the problem is also established.Comment: 4 pages, Revtex

    Cinque Terre

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    Comparison of predation by two suburban cats in New Zealand

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    To study the effects domestic cats may have on surrounding wildlife, a complete list was made of 558 items caught in the garden or brought into the house by one cat over 17 years, from 1988 to 2005. The effect on prey populations was assessed by comparing their abundance with the previous 15 years’ population without a cat. On balance, this cat (Cat 1) was clearly beneficial to the native bird species by killing rodents and deterring mustelids. The diet of a second cat (Cat 2) was recorded in the same way from 2006 to 2016. This cat caught half the number of items 148:287, but in the same proportions: house mice (37.8:42.6); ship rats (12.8:12.1); European rabbits (all young) (8.1:6.7); weasels (0.7:0.4); dunnock (12.8:9.2); house sparrow (2.0:3.1); blackbird (2.7:2.5); song thrush (1.4:1.3); European greenfinch (0.7:5.8); chaffinch (0.7:3.3); silvereye (10.1:8.3); New Zealand fantail (2.0:1.0); lizards (8.1:1.7). Despite this, there were significant differences: Cat 2 avoided finches (2:28, P = 0.004), and took a few more lizards (12:5). For both cats, birds apparently formed about a third of their diet: 33.4% and 34.5%, but comparison of the proportion of birds and rodents brought into the house (12:92) and found dead away from the house (49:45) implies that 320 rodent kills may have been missed, being far more difficult to find. As top predators, these cats were clearly beneficial to native birds, and proposed control or elimination may precipitate mesopredator release and a rabbit problem

    Development of an inspection robot for gas distribution mains: a Mars-mission underground

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    The PIRATE project is aimed to design an energy efficient robot system, capable of autonomous navigation in low-pressure gas distribution network. A prototype of the robot structure is currently being evaluated. The prototype is able to move trough pipes of various diameters, and sharp corners can be taken (semi) autonomously. Because of the harsh conditions (temperature, gas, dust), the complex network structure and the lack of communication (no long-range transmission underground) and hence the necessary autonomy for the robot, this project can be compared to a Mars-mission underground

    Ships Observing Marine Climate: a catalogue of the VOS participating in the VSOP-NA

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    Our present knowledge of the marine climate, as represented by data sets such as COADS (Woodruff et al., 1987), is based on meteorological observations from the Voluntary Observing Ships (VOS). Because the VOS are merchant ships, rather than specially designed meteorological platforms, errors and biases exist in the data. However there is little information readily available to the climatologist either on the nature of the VOS fleet or on the observing practises which are used. This report, describing the forty-six ships that participated in the Voluntary Observing Ships' Special Observing Project - North Atlantic (VSOP-NA), therefore serves two purposes:(i) it provides a reference document to aid analysis of the VSOP-NA data set,(ii) it gives a detailed description of a subset of the VOS, which will be of value in the interpretation of marine climate data sets.This report is in two parts, Part 1 is an overall summary of the ship characteristics, Part 2 is a ship by ship description. The next section will briefly describe the VSOP-NA project, followed by a summary of the characteristics of the VSOP-NA ships (Section 3). Since these ships were specially selected (Section 2.2), the degree to which they are representative of the whole VOS fleet will be carefully considered. The meteorological instrumentation used by the VOS varies depending on which meteorological agency recruited the ships. That used on the chosen VSOP-NA ships is typical of VOS recruited by the countries bordering the North Atlantic, and will be described in Section 4. Section 5 is a summary of Part 1 of the report.Part 2 presents the VSOP-NA ship catalogue. This includes, for each ship, diagrams of the layout (indicating in particular the exposure of the sensors), a summary of the geographical positions at which observations were obtained, and details of the instrumentation used.<br/

    A CRITIQUE OF FEDERAL AGRICULTURAL PROGRAMS

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    Political Economy,

    Poverty, environment and natural resource use: introduction to the special issue

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    A growing population and growing per capita consumption threaten the environment and the natural resource base. Where natural resources are at risk, the livelihoods of many are at risk as well. In May 2006 the Environmental Economics and Natural Resources Group of Wageningen University organized a conference on `Poverty, Environment and Natural Resource Use¿ with the aim of contributing to a better understanding of the links between poverty and the natural resource base. The state of the environment affects people's living conditions ¿ and poverty affects environmental quality. Environmental policies cannot be designed and natural resources cannot be managed without appropriate consideration of local people's reactions to those policies and management decisions
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