Geochemical evidence for evolving Proterozoic crustal thickness and orogenic styles in southwestern Laurentia

It has long been challenging for researchers to track the crustal thickness and mode(s) of crustal modification in ancient convergent margins, limiting evaluation of the tectonic styles and processes that modify continental crust during orogenesis. We present trace element igneous geochemical crustal thickness proxies that quantitatively track the crustal thickness evolution of the long-lived Proterozoic active margin in the southwestern U.S.A. We integrate these results with geobarometric data to constrain the mode of crustal modification. The data indicate a complex record of crustal thickness change in space and time and evolving orogenic styles. Geochemical proxies at 1.84–1.72 Ga are consistent with 20–40 km thick magmatic arcs that were locally thickened to ∼50 km during ∼1.75 Ga tectonism. During the Yavapai orogeny, 1.72–1.69 Ga, a ∼200-km-wide belt of 50-60 km thick crust extended from southern California to northern Colorado and was rapidly thinned and exhumed by ∼1.68 Ga. Crustal thickening and thinning during the Yavapai orogeny largely occurred by shortening and exhumation, respectively, in the upper 25 km of the crust. Subsequent 1.68–1.60 Ga tectonism involved crustal growth, local crustal thickening, and low-P, high-T metamorphism, consistent with extensional accretionary orogenesis. The 1.47–1.37 Ga Picuris orogeny was associated with 50–60 km thick crust across much of the Southwest and involved crustal shortening with ∼10 km of magmatic underplating. Advective heat from the emplacement of ferroan granites in the mid-crust likely contributed to elevated geothermal gradients and rheologically weakened the crust. Our results suggest evolving orogenic styles in the Southwest from 1.75–1.69 Ga short-lived crustal thickening associated with terrane accretion to 1.69–1.60 Ga largely extensional accretionary orogenesis, and regional, long-lived crustal thickening at 1.47–1.37 Ga involving extensive basaltic underplating. Contrasting with some recent hypotheses, our data document a complex middle Proterozoic record for the Southwest that was not orogenically quiescent or tectonically stagnant but involved complex mountain building styles

Melding Information Systems Evaluation with the Information Systems Development Lifecycle

In this paper we consider the synergy between two areas of IS literature: that concerned with the evaluation of information systems and that concerned with explaining the phenomenon of IS failure. On the basis of an analysis of both such areas a model is developed which attempts to integrate IS evaluation into the life-cycle of information systems development. The model clearly links the issue of failure assessment with the evaluation process and constitutes a strategy for stimulating organisational learning in relation to information systems development. The paper concludes with a brief description of our attempts to validate aspects of the model and plans for further empirical work in this area

The Millenium Problem as a Form of Information Systems Failure

In this paper we wish to examine the phenomenon of Y2K as an instance of information systems failure. Taking this particular stance on the issue leads we feel to a number of interesting areas that demand further investigation. We first review the current phenomenon of Y2K and discuss some of the relevant work in the area of IS failure. The topic of IS failure has tended to concentrate on issues of success or failure in relation to one specific IS project. We highlight a number of ways in which Y2K can be characterised as a particularly unique and interesting instance of IS failure. In one sense Y2K can be characterised merely as a technological failure and the responses to it merely of a technical kind. However Y2K, and the responses taken to it are of interest also on the organisational, societal, and economic level. It is therefore a phenomenon of primary concern to the IS academic. We raise a number of issues posed by our examination of Y2K that demand further investigation by IS academics. Y2K and the panic that it has generated can be seen as a clear demonstration of the degree to which IS/IT is closely embedded within modern organisations. However, there is preliminary evidence that Y2K has had an effect on the relationship between the IS/IT function and organisations. We particularly raise questions of its effect on IS strategy and planning, outsourcing and the IS development portfolio of organisations

Measurement of ψ(2S) polarisation in pp collisions at √s = 7 TeV

The polarisation of prompt ψ(2S) mesons is measured by performing an angular analysis of ψ(2S) → μ[superscript +]μ[superscript −] decays using proton-proton collision data, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected by the LHCb detector at a centre-of-mass energy of 7 TeV. The polarisation is measured in bins of transverse momentum p[subscript T] and rapidity y in the kinematic region 3.5 < p[subscript T] < 15 GeV/c and \(2.0 , and is compared to theoretical models. No significant polarisation is observed.National Science Foundation (U.S.

Search for long-lived particles decaying to jet pairs

A search is presented for long-lived particles with a mass between 25 and 50 GeV/c[superscript 2] and a lifetime between 1 and 200 ps in a sample of proton–proton collisions at a centre-of-mass energy of √s = 7 TeV, corresponding to an integrated luminosity of 0.62 fb[superscript −1], collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a standard model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets. No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.National Science Foundation (U.S.

Measurement of the inelastic pp cross-section at a centre-of-mass energy of √s = 7 TeV

The cross-section for inelastic proton-proton collisions, with at least one prompt long-lived charged particle of transverse momentum p [subscript T] > 0.2GeV/c in the pseudorapidity range 2.0 < η < 4.5, is measured by the LHCb experiment at a centre-of-mass energy of √s = 7 TeV. The cross-section in this kinematic range is determined to be σ [acc over inel] = 55.0 ± 2.4 mb with an experimental uncertainty that is dominated by systematic contributions. Extrapolation to the full phase space, using Pythia 6, yields σ [subscript inel] = 66.9 ± 2.9 ± 4.4 mb, where the first uncertainty is experimental and the second is due to the extrapolation.National Science Foundation (U.S.

Measurement of Υ production in pp collisions at √s = 2.76 TeV

The production of Υ(1S), Υ(2S) and Υ(3S) mesons decaying into the dimuon final state is studied with the LHCb detector using a data sample corresponding to an integrated luminosity of 3.3 pb[superscript −1] collected in proton–proton collisions at a centre-of-mass energy of √s = 2.76 TeV. The differential production cross-sections times dimuon branching fractions are measured as functions of the Υ transverse momentum and rapidity, over the ranges p[subscript T] < 15 GeV/c and 2.0 < y < 4.5. The total cross-sections in this kinematic region, assuming unpolarised production, are measured to be σ(pp → Υ(1S)X) × B(Υ(1S) → μ[superscript +]μ[superscript −]) = 1.111 ± 0.043 ± 0.044 nb, σ(pp → Υ(2S)X) × B(Υ(2S) → μ[superscript +]μ[superscript −]) = 0.264 ± 0.023 ± 0.011 nb, σ(pp → Υ(3S)X) × B(Υ(3S) → μ[superscript +]μ[superscript −]) = 0.159 ± 0.020 ± 0.007 nb, where the first uncertainty is statistical and the second systematic.National Science Foundation (U.S.

Measurement of charged particle multiplicities and densities in pp collisions at √s = 7 TeV in the forward region

Charged particle multiplicities are studied in proton–proton collisions in the forward region at a centre-of-mass energy of √s = 7 TeV with data collected by the LHCb detector. The forward spectrometer allows access to a kinematic range of 2.0 < η < 4.8 in pseudorapidity, momenta greater than 2 GeV/ c and transverse momenta greater than 0.2 GeV/ c. The measurements are performed using events with at least one charged particle in the kinematic acceptance. The results are presented as functions of pseudorapidity and transverse momentum and are compared to predictions from several Monte Carlo event generators.National Science Foundation (U.S.

First Measurement of the Charge Asymmetry in Beauty-Quark Pair Production

The difference in the angular distributions between beauty quarks and antiquarks, referred to as the charge asymmetry, is measured for the first time in b[bar over b] pair production at a hadron collider. The data used correspond to an integrated luminosity of 1.0  fb[superscript −1] collected at 7 TeV center-of-mass energy in proton-proton collisions with the LHCb detector. The measurement is performed in three regions of the invariant mass of the b[bar over b] system. The results obtained are A[b[bar over b] over C](40 105  GeV/c[superscript 2]) = 1.6 ± 1.7 ± 0.6%, where A[b[bar over b] over C] is defined as the asymmetry in the difference in rapidity between jets formed from the beauty quark and antiquark, where in each case the first uncertainty is statistical and the second systematic. The beauty jets are required to satisfy 2 20  GeV, and have an opening angle in the transverse plane Δϕ > 2.6  rad. These measurements are consistent with the predictions of the standard model.National Science Foundation (U.S.

Electronic Consultation at the National Assembly for Wales

Significant developments are occurring in the domain of electronic government within the UK – the use of ICT to enable re-structuring of governmental processes. In this paper we look at that subset of e-Government known as electronic democracy. In particular, we describe how electronic consultation, an important facet of electronic democracy, is being used to procure ideas from partnership organisations and citizenry in relation to the policy formulation processes at a devolved regional assembly in the UK – the National Assembly for Wales (NAfW). We utilise a process model of governance focused around the concept of the policy cycle. This process is currently being enabled at the NAfW through the development of a series of bespoke ICT systems. Such forms of ICT innovation are seen by many to be significant ways in which government may re-engage with its populace, address issues of social exclusion in the area of democratic participation and generally re-energise the democratic process