Standardising the USGS volcano alert level system: acting in the context of risk, uncertainty and complexity

A volcano alert level system (VALS) forms a key component of a volcano early warning system, which is used to communicate warning information from scientists to civil authorities managing volcanic hazards. In 2006, the United States Geological Survey (USGS) standardised its VALS, replacing all locally developed systems with a common standard. The emergence of this standardisation, and resulting implications, are charted here, in the context of managing the scientific complexities and diverse agencies involved in volcanic crises. The VALS concept embodies a linear reductionist approach to decision-making, designed around warning levels that correspond to levels of volcanic activity. Yet, complexities emerge as a consequence of the uncertain nature of the physical hazard, the contingencies of local institutional dynamics, and the plural social contexts within which each VALS is embedded, challenging its responsiveness to local knowledge and context. Research conducted at five USGS managed volcano observatories in Alaska, Cascades, Hawaii, Long Valley, and Yellowstone explores the benefits and limitations standardisation brings to each observatory. It concludes that standardisation is difficult to implement for three reasons. Firstly, conceptually, natural hazard warning systems are complex and non-linear, and the VALS intervenes in an overall system characterised by emergent properties and the interaction of many agents, for which forecasting and prediction are difficult. Secondly, pragmatically, the decision to move between alert levels is based upon more than volcanic activity and scientific information, with broader social and environmental risks playing a key role in changing alert levels. Thirdly, empirically, the geographical, social and political context to each volcano observatory results in the standardised VALS being applied in non-standard ways. It is recommended that, rather than further defining a standardised linear product, VALS should focus on developing systems based upon processes and best practice designed to facilitate communication and interaction between scientists and users in context

Charged particle multiplicity distributions for fixed number of jets in Z0 hadronic decays

The multiplicity distributions of charged particles in full phase space and in restricted rapidity intervals for events with a fixed number of jets measured by the DELPHI detector are presented. The data are well reproduced by the Lund Parton Shower model and can also be well described by fitted negative binomial distributions. The properties of these distributions in terms of the clan model are discussed. In symmetric 3-jet events the candidate gluon jet is found not to be significantly different in average multiplicity than the mean of the other two jets, thus supporting previous results of the HRS and OPAL experiments. Similar results hold for events generated according to the LUND PS and to the HERWIG models, when the jets are defined by the JADE jet finding algorithm. The method seems to be insensitive for measuring the color charge ratio between gluons and quarks. © 1992 Springer-Verlag

Bose-Einstein correlations in the hadronic decays of the Z0

Bose-Einstein correlation between pairs of like-sign charged particles produced in e+e- annihilations near the Z0 peak have been studied using data taken with the DELPHI detector at LEP. An enhancement is found in the production of pairs of identical pions of similar moments, with respect to a reference sample. Under the hypothesis that the pions are emitted by a spherically symmetrical source with gaussian density, the data indicate a radius of the source of r = 0.62±0.04(stat.)±0.20(syst.) fm. The large systematic uncertainty reflects the sensitivity of r to the choice of the reference sample0info:eu-repo/semantics/publishe

Measurement of the partial width of the Z0 into b Mathematical expression final states using their semi-leptonic decays

The spectra of prompt electrons and muons from the semi-leptonic decays of heavy hadrons produced in Z0 decays have been used to measure the coupling of the Z0 to b quarks weighted by the B hadrons mean semi-leptonic branching fraction, giving a value: {Mathematical expression}. The data has also been used to measure the value of the fragmentation parameter, defined in the context of the LUND PS Model, version 7.2, giving: {Mathematical expression}. The corresponding value of the mean fraction of the beam energy taken by a B hadron in the fragmentation of a b quark is: {Mathematical expression}. If the values of {Mathematical expression} and ΓH are taken from the Standard Model, the following value is obtained for the mean semi-leptonic braching fraction of B hadrons: BRslb=(10.1±0.7)%. Taking the value of {Mathematical expression} from an independent analysis of DELPHI data based on the use of the boosted sphericity product, a value: BRslb=(10.1±1.3)% is obtained. © 1992 Springer-Verlag

A study of the decays of tau leptons produced on the Z resonance at LEP

From the analysis of a data sample corresponding to an integrated luminosity of 4.63 pb-1 taken during the 1990 run of LEP at centre of mass energies between 88.2 GeV an 94.2 GeV, the tau decays {Mathematical expression} and their charge conjugates have been studied. The following branching ratios have been measured; {Mathematical expression}, {Mathematical expression}, Br(τ- → π- (K-)vτ)=11.9±0.7±0.7%, BR (τ- → ρ- vτ)= 22.4±0.8±1.3%, in good agreement with world averages. The measured electronic and muonic branching ratios lead to a measurement of the strong coupling constant, αs (mτ) = 0.26-0.12+0.09. Extrapolating the αs value from mτ to mZ yields αs (mZ) = 0.109-0.028+0.012. The average polarization Pτ of taus produced in Z → τs τs decays has also been measured using the above decay modes. The weighted mean of the polarizations obtained from the four decay modes is Pτ=-0.24±0.07. This value of Pτ gives, in the improved Born approximation, a ratio between the axial and vector coupling constants of the tau of υτ/aτ = 0.12 ± 0.04, and hence a value of the effective electroweak mixing parameter sin2 θW(mZ2). © 1992 Springer-Verlag

Multiplicity fluctuations in hadronic final states from the decay of the Z0

An analysis of the fluctuations in the phase space distribution of hadrons produced in the decay of 78829 Z0 has been carried out, using the method of factorial moments. The high statistics collected by the DELPHI experiment at LEP during 1990 allowed studies of the event sample both globally and in intervals of ρt and multiplicity, and for different jet topologies and for single jets. A large contribution to the factorial moments of the one-dimensional data on rapidity with respect to the event axis comes from hard gluons. Details of factorial moments in two and three dimensions are presented. Influences of resonance decays have been studied by Monte Carlo simulation: one-dimensional factorial moments at low pt, and two-, three-dimensional analyses are affected. Parton shower models describe the data reasonably well.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe