Structural dynamic eutrophication models

This article discusses problems of modelling the seasonal succession of algal species in lakes and reservoirs, and the adaptive selection of certain groups of algae in response to changes in the inputs and relative concentrations of nutrients and other environmental variables. A new generation of quantitative models is being developed which attempts to translate some important biological properties of species (survival, variation, inheritance, reproductive rates and population growth) into predictions about the survival of the fittest, where ”fitness” is measured or estimated in thermodynamic terms. The concept of ”exergy” and its calculation is explored to examine maximal exergy as a measure of fitness in ecosystems, and its use for calculating changes in species composition by means of structural dynamic models. These models accomodate short-term changes in parameters that affect the adaptive responses (species selection) of algae

Hydrophysical and Ecological Modelling of Deep Lakes and Reservoirs: Summary Report of an IIASA Workshop, December 1977

A series of questions related to the geophysical and ecological modelling of deep lakes and reservoirs were formulated and distributed in advance of the workshop. This workshop report summarizes the discussion of each of the questions relating to the following topics: element cycles, nutrient uptake and grazing rates by phytoplankton and zooplankton, single versus multi-layer models, vertical mixing and diffusion, lake circulation and methods of parameter estimation

Recent Trends in the Development of Ecological Models Applied on Aquatic Ecosystems

This paper presents an overview of the application of models on aquatic ecosystems. More than 17% of the models published in the focal journal in the field, Ecological Modelling, are aquatic ecosystem models. An increasing number of papers are dealing with the theoretical aspects of modeling – new modeling approaches and techniques, how models can be used to reveal ecosystem properties, and how models can better reflect the properties of ecosystems. This development implies that today we have more types of models. The characteristics, the advantages, and the disadvantages of these model types are presented briefly. The selection criteria for the presented model types are discussed, and the application of these types to models for aquatic ecosystems is reviewed. A recent improvement in model calibration of particular interest for aquatic ecosystems is presented, and the perspectives resulting from this new calibration procedure and from possible hybrids of the presented model types are discussed

Hydrophysical and Ecological Models of Shallow Lakes and Reservoirs: A Summary Report of an IIASA Workshop

An important subtask within the Resources and Environment Area (REN) of the International Institute for Applied Systems Analysis (IIASA) is the development and application of models for environmental quality control and management. The initial objectives of this task are to assess existing models, to develop improved hydrophysical and ecological models as tools for the analysis of water quality problems, and to apply these models to lakes, reservoirs, and river systems. On September 13-16, 1977, a workshop on the general aspects of water quality modeling (IIASA CP-78-10) was held at IIASA. The most recent theoretical developments in the field of Water Quality were discussed at this meeting. At the same time the application of hydrophysical and ecological models to various water bodies was considered. As a result of this workshop it was decided that attention should be focussed on the water quality problems of natural lakes and man-made impoundments (reservoirs). In addition, it was felt that IIASA could make an important contribution to the use of models for water quality control and management purposes by attempting to bridge the gap between the hydrophysical and ecological modeling disciplines. Accordingly, it was decided to convene two specialized workshops. The first of these was on Hydrophysical and Ecological Modelling of Deep Lakes and Reservoirs (IIASA CP-78-7) held on December 12-15, 1977, in Laxenburg. The second of these was on hydrological and ecological modeling of shallow lakes and reservoirs, and was held on April 11-14, 1978, in Laxenburg. The subject of deep lakes and reservoirs chosen for the December workshop implies a basic concern with stratification and interactions at the free surface boundary rather than with conditions of full vertical mixing and bottom sediment interactions. The subject of shallow lakes and reservoirs chosen for the April workshop implies a basic concern with the condition of full vertical mixing and bottom sediment interactions. This report summarizes the results of this second workshop, which was attended by 28 people representing 14 countries and by 13 IIASA staff members from 5 countries. Prior to the workshop, a set of questions related to ecological and hydrophysical modeling problems were formulated by the IIASA staff and sent to the participants with the request to indicate on which questions they would like to give a short presentation as a start to the discussion of the questions. Topics discussed at the workshop included: -- Characteristic Features of Shallow Lakes and Reservoirs: influence of wind and wave action, longitudinal and vertical mass transport processes, exchange of nutrients between the water body and the sediments, influence of sediment types on the transformation processes of chemical compounds -- Hydrophysical Models: horizontal and vertical transport and diffusion processes, interaction across the water/sediment interface -- Ecological Models: evaluation of available data by simple models, sensitivity analysis, improvement in the quantity of data, further development of ecological models of shallow lakes taking into account the binding and mobilization of nutrients in the sediments -- Water Quality Models: limiting nutrients/carbon, nitrogen, phosphorus, element-cycle models/simple and complex models -- Field Data Collection and Model Verification Techniques: coordination of chemical and biological field measurements with water quality models, choice of parameters -- Possible Case Studies These discussions are summarized in the Introduction. In addition, some of the participants presented original papers at the discussion of the ecological and hydrophysical questions. These papers are included in the second part of this Proceedings following the Discussion. It should be noted that a paper by H.A. Tsvetova on Numerical Modeling of the Dynamics of Lake Baikal was presented at the workshop. It is not included in these proceedings but will be published separately in IIASA's Professional Paper Series. The paper was originally intended for presentation at the workshop on Hydrophysical and Ecological Modelling of Deep Lakes and Reservoirs. This workshop was an excellent opportunity for experienced modelers from both the ecological and hydrophysical areas to come together for a discussion of problems of mutual interest and to exchange ideas and viewpoints

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter

Measurement of the inclusive isolated prompt photon cross-section in pp collisions at sqrt(s)= 7 TeV using 35 pb-1 of ATLAS data

A measurement of the differential cross-section for the inclusive production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The measurement covers the pseudorapidity ranges |eta|<1.37 and 1.52<=|eta|<2.37 in the transverse energy range 45<=E_T<400GeV. The results are based on an integrated luminosity of 35 pb-1, collected with the ATLAS detector at the LHC. The yields of the signal photons are measured using a data-driven technique, based on the observed distribution of the hadronic energy in a narrow cone around the photon candidate and the photon selection criteria. The results are compared with next-to-leading order perturbative QCD calculations and found to be in good agreement over four orders of magnitude in cross-section.Comment: 7 pages plus author list (18 pages total), 2 figures, 4 tables, final version published in Physics Letters

Reducing heterotic M-theory to five dimensional supergravity on a manifold with boundary

This paper constructs the reduction of heterotic $M$-theory in eleven dimensions to a supergravity model on a manifold with boundary in five dimensions using a Calabi-Yau three-fold. New results are presented for the boundary terms in the action and for the boundary conditions on the bulk fields. Some general features of dualisation on a manifold with boundary are used to explain the origin of some topological terms in the action. The effect of gaugino condensation on the fermion boundary conditions leads to a `twist' in the chirality of the gravitino which can provide an uplifting mechanism in the vacuum energy to cancel the cosmological constant after moduli stabilisation.Comment: 16 pages, RevTe

Measurement of D*+/- meson production in jets from pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

This paper reports a measurement of D*+/- meson production in jets from proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV at the CERN Large Hadron Collider. The measurement is based on a data sample recorded with the ATLAS detector with an integrated luminosity of 0.30 pb^-1 for jets with transverse momentum between 25 and 70 GeV in the pseudorapidity range |eta| < 2.5. D*+/- mesons found in jets are fully reconstructed in the decay chain: D*+ -> D0pi+, D0 -> K-pi+, and its charge conjugate. The production rate is found to be N(D*+/-)/N(jet) = 0.025 +/- 0.001(stat.) +/- 0.004(syst.) for D*+/- mesons that carry a fraction z of the jet momentum in the range 0.3 < z < 1. Monte Carlo predictions fail to describe the data at small values of z, and this is most marked at low jet transverse momentum.Comment: 10 pages plus author list (22 pages total), 5 figures, 1 table, matches published version in Physical Review