Showing papers by "Wolfgang Wagner published in 1996"

A New Equation of State for Carbon Dioxide Covering the Fluid Region from the Triple‐Point Temperature to 1100 K at Pressures up to 800 MPa

Abstract: This work reviews the available data on thermodynamic properties of carbon dioxide and presents a new equation of state in the form of a fundamental equation explicit in the Helmholtz free energy. The function for the residual part of the Helmholtz free energy was fitted to selected data of the following properties: (a) thermal properties of the single‐phase region (pρT) and (b) of the liquid‐vapor saturation curve (p s, ρ′, ρ″) including the Maxwell criterion, (c) speed of soundw and (d) specific isobaric heat capacityc p of the single phase region and of the saturation curve, (e) specific isochoric heat capacityc v , (f) specific enthalpyh, (g) specific internal energyu, and (h) Joule–Thomson coefficient μ. By applying modern strategies for the optimization of the mathematical form of the equation of state and for the simultaneous nonlinear fit to the data of all these properties, the resulting formulation is able to represent even the most accurate data to within their experimental uncertainty. In the technically most important region up to pressures of 30 MPa and up to temperatures of 523 K, the estimated uncertainty of the equation ranges from ±0.03% to ±0.05% in the density, ±0.03% to ±1% in the speed of sound, and ±0.15% to ±1.5% in the isobaric heat capacity. Special interest has been focused on the description of the critical region and the extrapolation behavior of the formulation. Without a complex coupling to a scaled equation of state, the new formulation yields a reasonable description even of the caloric properties in the immediate vicinity of the critical point. At least for the basic properties such as pressure, fugacity, and enthalpy, the equation can be extrapolated up to the limits of the chemical stability of carbon dioxide. Independent equations for the vapor pressure and for the pressure on the sublimation and melting curve, for the saturated liquid and vapor densities, and for the isobaric ideal gas heat capacity are also included. Property tables calculated from the equation of state are given in the appendix.

Relevance, discourse and the ‘hot’ stable core social representations—A structural analysis of word associations

Abstract: This paper presents an investigation of the structure of word associations dependent on the context in which they are assessed. Respondents from Spain and Nicaragua produced free associations about war and peace. Word associations about each of the two stimulus words were produced either spontaneously or within the context of a distracting priming condition in contrast to the association task. The semantic space for each stimulus word (war, peace) is analysed to find substructures of words which remain stable across contexts. These substructures or stable cores are taken to indicate a well-structured social representation as opposed to a loosely organized knowledge domain. Such cores were found for associations about war in both countries, but for peace in the Nicaraguan sample only. This finding is interpreted as a consequence of public discourse and symbolic coping with relevant or threatening objects or phenomena. Stable cores were found to consist primarily of ‘hot’ words, i.e. words which are proximal to an individual's experience. More intellectual and distant (‘cold’) words did not enter the stable core. Results are discussed in terms of the central core theory of social representations and of numerical consensus being an insufficient criterion for social representations.

An accurate Van der Waals-type equation of state for the Lennard-Jones fluid

Abstract: A new equation of state (EOS) is proposed for the Helmholtz energyF of the Lennard Jones fluid which represents the thermodynamic properties over a wide range of temperatures and densities. The EOS is written in the form of a generalized van der Waals equation.F =Fu +Fv. WhereFu is a hard body contribution andFA an anttractive dispersion force contribution. The expression forFH is closely related to the hybrid Barker Henderson pertubation theory. The construction ofFA is accomplished with the Setzmann Wagner optimization procedure on the basis of virial coefficients and critically assessed computer simulation data. A comparison with the EOS of Johnson et al. shows improvement in the description of the vapor liquid coexistence properties, thepvT data. and in peculiar, of the calorie properties. A comparison with the EOS of Kolafa and Nezbeda which appeared after the bulk of this work was finished shows still by about 30%.

Queries about social representation and construction

Abstract: L'A. porte son attention sur l'analyse des representations sociales. Ce type de perspective permet d'etudier aussi bien la connaissance scientifique que les conceptions communes. Il se demande en quoi une telle approche des representations sociales peut affecter la construction sociale de ces memes phenomenes. Il montre que le langage scientifique peut s'averer trompeur en ce domaine. Il s'efforce de savoir si les representations sociales constituent un objet veritable, si elle peuvent etre vraies ou fausses, si elles servent a la construction sociale de l'action

Scalp, earlobe and nasopharyngeal recordings of the median nerve somatosensory evoked P14 potential in coma and brain death Detailed latency and amplitude analysis in 181 patients

Abstract: Summary Median nerve somatosensory evoked potentials (SEPs) were recorded in a total of 181 patients in coma and brain death. Special attention was paid to the derivation of P14 (the positive potential occurring ~14 ms after median nerve stimulation) with different electrode montages, using midfrontal scalp (Fz), linked earlobe (A ia), median nasopharyngeal (Pgz) and non-cephalic reference (NC) electrodes. The P14 amplitude (and, to a lesser extent, latency) were invariably lower in brain death than in coma. The potential was preserved in coma in all patients, but lost in brain death in 9.8% in Fz-NC and Pgz-NC recordings, in 23.2% in Fz-A l/2, and in 100% in Fz-Pgz. Thus, Fz-Pgz was the derivation yielding the most reliable results with respect to the distinction between coma and brain death and is therefore recommended as a confirmatory test, when other diseases interrupting the lemniscal pathway (isolated brainstem death, high cervical transverse cord lesion and focal bilateral lemniscal lesion) are excluded. Theoretical considerations lead to the hypothesis of different (rostral and caudal) segments of the P14 generator dipole being recorded by the different electrode montages. It is assumed that Fz-Pgz picks up the most rostral part of P14 (rP14) that is invariably lost in brain death and preserved in coma.

A functional law of large numbers for Boltzmann type stochastic particle systems

Abstract: A large system of particles is studied. Its time evolution is determined as the superposition of two components. The first component is the independent motion of each particle. The second component is the random interaction mechanism between pairs of particles. The intensity of the interaction depends on the state of the system and is assumed to be bounded Convergence of the empirical measures is proved as the number of particles tends to infinity. The limiting deterministic measure-valued function is characterized as the unique solution of a nonlinear equation of the Boltzmann type

The Social Representation Paradigm

Abstract: This paper presents a brief overview of the social representation approach Relevant content-oriented as well as theory-driven research and their implications are presented Some critical topics in the ongoing debate among scholars are presented and important future foci of research are discussed The paper includes an extensive bibliography

Search for chargino-neutralino production in pp̄ collisions at s=1.96TeV

Abstract: The authors present a search for the associated production of charginos and neutralinos in p{bar p} collisions at {radical}s = 1.96 TeV. The data were collected at the Collider Detector at Fermilab (CDF II) and correspond to integrated luminosities between 0.7 and 1.0 fb{sup -1}. They look for final states with one high-p{sub T} electron or muon, and two additional leptons. The results are consistent with the standard model expectations, and they set limits on the cross section as a function of the chargino mass in three different supersymmetric scenarios. For a specific MSSM scenario with no slepton mixing they set a 95% C.L. limit at 151 GeV/c{sup 2}.