992 research outputs found
Multiplicity distributions inside parton cascades developing in a medium
The explanation of the suppression of high-pT hadron yields at RHIC in terms
of jet-quenching implies that the multiplicity distributions of particles
inside a jet and jet-like particle correlations differ strongly in
nucleus-nucleus collisions at RHIC or at the LHC from those observed at e+e- or
hadron colliders. We present a framework for describing the medium-induced
modification, which has a direct interpretation in terms of a probabilistic
medium-modified parton cascade, and which treats leading and subleading partons
on an equal footing. We show that our approach can account for the strong
suppression of single inclusive hadron spectra measured in Au-Au collisions at
RHIC, and that this implies a characteristic distortion of the single inclusive
distribution of soft partons inside the jet. We determine, as a function of the
jet energy, to what extent the soft fragments within a jet can be measured
above some momentum cut.Comment: 5 pages, 4 eps-figures; talk given at Hot Quarks 2006, Villasimius
(Sardinia, Italy), May 15-20, 200
Dimensions of professional competences for interventions towards sustainability
This paper investigates sustainability competences through the eyes of professional practitioners in the field of sustainability and presents empirical data that have been created using an action research approach. The design of the study consists of two workshops, in which professional practitioners in interaction with each other and the facilitators are invited to explore and reflect on the specific knowledge, skills, attitudes and behaviours necessary to conduct change processes successfully towards sustainability in a variety of business and professional contexts. The research focuses on the competences associated with these change processes to devise, propose and conduct appropriate interventions that address sustainability issues. Labelled ‘intervention competence’, this ability comprises an interlocking set of knowledge, skills, attitudes and behaviours that include: appreciating the importance of (trying to) reaching decisions or interventions; being able to learn from lived experience of practice and to connect such learning to one’s own scientific knowledge; being able to engage in political-strategic thinking, deliberations and actions, related to different perspectives; the ability for showing goal-oriented, adequate action; adopting and communicating ethical practices during the intervention process; being able to cope with the degree of complexity, and finally being able to translate stakeholder diversity into collectively produced interventions (actions) towards sustainability. Moreover, this competence has to be practised in contexts of competing values, non-technical interests and power relations. The article concludes with recommendations for future research and practice
Spectroscopic and Mechanistic Studies of Heterodimetallic Forms of Metallo-β-lactamase NDM-1
In an effort to characterize the roles of each metal ion in metallo-β-lactamase NDM-1, heterodimetallic analogues (CoCo-, ZnCo-, and CoCd-) of the enzyme were generated and characterized. UV–vis, 1H NMR, EPR, and EXAFS spectroscopies were used to confirm the fidelity of the metal substitutions, including the presence of a homogeneous, heterodimetallic cluster, with a single-atom bridge. This marks the first preparation of a metallo-β-lactamase selectively substituted with a paramagnetic metal ion, Co(II), either in the Zn1 (CoCd-NDM-1) or in the Zn2 site (ZnCo-NDM-1), as well as both (CoCo-NDM-1). We then used these metal-substituted forms of the enzyme to probe the reaction mechanism, using steady-state and stopped-flow kinetics, stopped-flow fluorescence, and rapid-freeze-quench EPR. Both metal sites show significant effects on the kinetic constants, and both paramagnetic variants (CoCd- and ZnCo-NDM-1) showed significant structural changes on reaction with substrate. These changes are discussed in terms of a minimal kinetic mechanism that incorporates all of the data
Counteracting gradients of light and soil nutrients in the understorey of Mediterranean oak forests.
The forest canopy modifies the availability of resources (light, water, and soil nutrients)
in the understorey. In this paper we analyze the relationships between woody canopy
density, litter accumulation, and topsoil N and P availability in the understorey of two
oak forests: one in southern Portugal and the other in southern Spain. Both forests
persist on low-nutrient soils, particularly poor in P. We hypothesize that direct and
indirect effects of the canopy overstorey cause opposite gradients in the availability of
essential resources (light and key soil nutrients) in the understorey. In both studied
forests we found significant relationships between the overall canopy density, light availability,
topsoil litter accumulation, and the availability of N and P, which frequently
limit plant growth. Path analysis (by Shipley’s d-sep method) showed that the available
data were consistent with the proposed causal model. The average values of soil variables
at the end quartiles of the light-availability gradient were compared. Results showed
large differences in litter accumulation (~30×) and available-N and -P topsoil concentrations
(~3×) in the Spanish forest (with the wider environmental gradient). Furthermore,
P increased from the ‘very low’ range to the ‘low’ or even the ‘optimum’ range of
availability (according to standard plant growth criteria), which suggests potential effects
on the growth of the understorey plant species. We conclude that the counteracting
gradients of the essential resources -light and nutrients- in the forest understorey
resulted from direct and indirect effects of the canopy overstorey, respectively. We suggest
that these counteracting effects of the woody canopy on essential resources of different
nature must be considered when interpreting the patterns of understorey plant populations
and communities.The spanish MEC (CGL2005-05830-C03-01-BOS, DINAMED project) and the Portuguese FCT(SFRH/BD/8322/2002 grant to SMM)supported the research.Peer reviewe
Parton fragmentation in the vacuum and in the medium
We present the mini-proceedings of the workshop on ``Parton fragmentation in
the vacuum and in the medium'' held at the European Centre for Theoretical
Studies in Nuclear Physics and Related Areas (ECT*, Trento) in February 2008.
The workshop gathered both theorists and experimentalists to discuss the
current status of investigations of quark and gluon fragmentation into hadrons
at different accelerator facilities (LEP, B-factories, JLab, HERA, RHIC, and
Tevatron) as well as preparations for extension of these studies at the LHC.
The main physics topics covered were: (i) light-quark and gluon fragmentation
in the vacuum including theoretical (global fits analyses and MLLA) and
experimental (data from e+e-, p-p, e-p collisions) aspects, (ii) strange and
heavy-quark fragmentation, (iii) parton fragmentation in cold QCD matter
(nuclear DIS), and (iv) medium-modified fragmentation in hot and dense QCD
matter (high-energy nucleus-nucleus collisions). These mini-proceedings consist
of an introduction and short summaries of the talks presented at the meeting.Comment: 43 pages, mini-proceedings Workshop ECT*, Trento, Feb. 25 - 29, 200
A Large Hadron Electron Collider at CERN
This document provides a brief overview of the recently published report on
the design of the Large Hadron Electron Collider (LHeC), which comprises its
physics programme, accelerator physics, technology and main detector concepts.
The LHeC exploits and develops challenging, though principally existing,
accelerator and detector technologies. This summary is complemented by brief
illustrations of some of the highlights of the physics programme, which relies
on a vastly extended kinematic range, luminosity and unprecedented precision in
deep inelastic scattering. Illustrations are provided regarding high precision
QCD, new physics (Higgs, SUSY) and electron-ion physics. The LHeC is designed
to run synchronously with the LHC in the twenties and to achieve an integrated
luminosity of O(100) fb. It will become the cleanest high resolution
microscope of mankind and will substantially extend as well as complement the
investigation of the physics of the TeV energy scale, which has been enabled by
the LHC
Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC
The uncertainty on the calorimeter energy response to jets of particles is
derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the
calorimeter response to single isolated charged hadrons is measured and
compared to the Monte Carlo simulation using proton-proton collisions at
centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009
and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter
response to specific types of particles (positively and negatively charged
pions, protons, and anti-protons) is measured and compared to the Monte Carlo
predictions. Finally, the jet energy scale uncertainty is determined by
propagating the response uncertainty for single charged and neutral particles
to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3%
for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table,
submitted to European Physical Journal
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