1,042 research outputs found
Evaluating megaprojects: from the âiron triangleâ to network mapping
Evaluation literature has paid relatively little attention to the specific needs of evaluating large, complex industrial and infrastructure projects, often called âmegaprojectsâ. The abundant megaproject governance literature, in turn, has largely focused on the so-called âmegaproject pathologiesâ, i.e. the chronic budget overruns, and failure of such projects to keep to timetables and deliver the expected social and economic benefits. This article draws on these two strands of literature, identifies shortcomings, and suggests potential pathways towards an improved evaluation of megaprojects. To counterbalance the current overemphasis on relatively narrowly defined accountability as the main function of megaproject evaluation, and the narrow definition of project success in megaproject evaluation, the article argues that conceptualizing megaprojects as dynamic and evolving networks would provide a useful basis for the design of an evaluation approach better able to promote learning and to address the socio economic aspects of megaprojects. A modified version of ânetwork mappingâ is suggested as a possible framework for megaproject evaluation, with the exploration of the multiple accountability relationships as a central evaluation task, designed to reconcile learning and accountability as the central evaluation functions. The article highlights the role of evaluation as an âemergentâ property of spontaneous megaproject âgoverningâ, and explores the challenges that this poses to the role of the evaluator
Normal Ordering for Deformed Boson Operators and Operator-valued Deformed Stirling Numbers
The normal ordering formulae for powers of the boson number operator
are extended to deformed bosons. It is found that for the `M-type'
deformed bosons, which satisfy , the
extension involves a set of deformed Stirling numbers which replace the
Stirling numbers occurring in the conventional case. On the other hand, the
deformed Stirling numbers which have to be introduced in the case of the
`P-type' deformed bosons, which satisfy , are found to depend on the operator . This distinction
between the two types of deformed bosons is in harmony with earlier
observations made in the context of a study of the extended
Campbell-Baker-Hausdorff formula.Comment: 14 pages, Latex fil
Axial hypersensitivity is associated with aberrant nerve sprouting in a novel model of disc degeneration in female Sprague Dawley rats
Chronic low back pain is a global socioeconomic crisis and treatments are lacking in part due to inadequate models. Etiological research suggests that the predominant pathology associated with chronic low back pain is intervertebral disc degeneration. Various research teams have created rat models of disc degeneration, but the clinical translatability of these models has been limited by an absence of robust chronic painlike behavior. To address this deficit, disc degeneration was induced via an artificial annular tear in female Sprague Dawley rats. The subsequent degeneration, which was allowed to progress for 18-weeks, caused a drastic reduction in disc volume. Furthermore, from week 10 till study conclusion, injured animals exhibited significant axial hypersensitivity. At study end, intervertebral discs were assessed for important characteristics of human degenerated discs: extracellular matrix breakdown, hypocellularity, inflammation, and nerve sprouting. All these aspects were significantly increased in injured animals compared to sham controls. Also of note, 20 significant correlations were detected between selected outcomes including a moderate and highly significant correlation (R = 0.59, p \u3c 0.0004) between axial hypersensitivity and disc nerve sprouting. These data support this model as a rigorous platform to explore the pathobiology of disc-associated low back pain and to screen treatments
Sub-surface Oxygen and Surface Oxide Formation at Ag(111): A Density-functional Theory Investigation
To help provide insight into the remarkable catalytic behavior of the
oxygen/silver system for heterogeneous oxidation reactions, purely sub-surface
oxygen, and structures involving both on-surface and sub-surface oxygen, as
well as oxide-like structures at the Ag(111) surface have been studied for a
wide range of coverages and adsorption sites using density-functional theory.
Adsorption on the surface in fcc sites is energetically favorable for low
coverages, while for higher coverage a thin surface-oxide structure is
energetically favorable. This structure has been proposed to correspond to the
experimentally observed (4x4) phase. With increasing O concentrations, thicker
oxide-like structures resembling compressed Ag2O(111) surfaces are
energetically favored. Due to the relatively low thermal stability of these
structures, and the very low sticking probability of O2 at Ag(111), their
formation and observation may require the use of atomic oxygen (or ozone, O3)
and low temperatures. We also investigate diffusion of O into the sub-surface
region at low coverage (0.11 ML), and the effect of surface Ag vacancies in the
adsorption of atomic oxygen and ozone-like species. The present studies,
together with our earlier investigations of on-surface and
surface-substitutional adsorption, provide a comprehensive picture of the
behavior and chemical nature of the interaction of oxygen and Ag(111), as well
as of the initial stages of oxide formation.Comment: 17 pages including 14 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
Quantum-well states in ultrathin Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces
Ag(111) films were deposited at room temperature onto H-passivated
Si(111)-(1x1) substrates, and subsequently annealed at 300 C. An abrupt
non-reactive Ag/Si interface is formed, and very uniform non-strained Ag(111)
films of 6-12 monolayers have been grown. Angle resolved photoemission
spectroscopy has been used to study the valence band electronic properties of
these films. Well-defined Ag sp quantum-well states (QWS) have been observed at
discrete energies between 0.5-2eV below the Fermi level, and their dispersions
have been measured along the GammaK, GammaMM'and GammaL symmetry directions.
QWS show a parabolic bidimensional dispersion, with in-plane effective mass of
0.38-0.50mo, along the GammaK and GammaMM' directions, whereas no dispersion
has been found along the GammaL direction, indicating the low-dimensional
electronic character of these states. The binding energy dependence of the QWS
as a function of Ag film thickness has been analyzed in the framework of the
phase accumulation model. According to this model, a reflectivity of 70% has
been estimated for the Ag-sp states at the Ag/H/Si(111)-(1x1) interface.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Correlates of mono- and dual-victims of cybergrooming and cyberbullying:evidence from four countries
Today's adolescents grow up using information and communication technologies as an integral part of their everyday life. This affords them with extensive opportunities, but also exposes them to online risks, such as cybergrooming and cyberbullying victimization. The aims of this study were to investigate correlates of cybergrooming and cyberbullying victimization and examine whether victims of both cybergrooming and cyberbullying (dual-cybervictims) show higher involvement in compulsive Internet use (CIU) and troubled offline behavior (TOB) compared to victims of either cybergrooming or cyberbullying (mono-cybervictims). The sample consisted of 2,042 Dutch, German, Thai, and U.S. adolescents (ageâ=â11â17 years; Mâ=â14.2; SDâ=â1.4). About every ninth adolescent (10.9 percent) reported either mono- or dual-cybervictimization. Second, both CIU and TOB were associated with all three types of cybervictimization, and finally, both CIU and TOB were more strongly linked to dual-cybervictimization than to both forms of mono-cybervictimization. These findings contribute to a better understanding of the associations between different forms of cybervictimization and psychological health and behavior problems among adolescents
Electronic properties and Fermi surface of Ag(111) films deposited onto H-passivated Si(111)-(1x1) surfaces
Silver films were deposited at room temperature onto H-passivated Si(111)
surfaces. Their electronic properties have been analyzed by angle-resolved
photoelectron spectroscopy. Submonolayer films were semiconducting and the
onset of metallization was found at a Ag coverage of 0.6 monolayers. Two
surface states were observed at -point in the metallic films,
with binding energies of 0.1 and 0.35 eV. By measurements of photoelectron
angular distribution at the Fermi level in these films, a cross-sectional cut
of the Fermi surface was obtained. The Fermi vector determined along different
symmetry directions and the photoelectron lifetime of states at the Fermi level
are quite close to those expected for Ag single crystal. In spite of this
concordance, the Fermi surface reflects a sixfold symmetry rather than the
threefold symmetry of Ag single crystal. This behavior was attributed to the
fact that these Ag films are composed by two domains rotated 60.Comment: 9 pages, 8 figures, submitted to Physical Review
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