Perceived Ontological Weaknesses of Process Modeling Techniques: Further Evidence

The Architecture of Integrated Information Systems (ARIS) is a popular framework for integrated process modeling. Previous research analysed ARIS using an ontology developed by Bunge, Wand and Weber. The results of this study have been summarized in six propositions. This paper reports on insights gained from an empirical study testing these evaluative propositions. The study is conducted with post-graduate students as well as with experienced users of ARIS. Even when considering all five views of ARIS, modelers have problems representing business rules and the scope and boundary of systems. Surprisingly, even though it is completely ontologically redundant, users still find the function view useful in modeling

Scanning Quantum Dot Microscopy

Interactions between atomic and molecular objects are to a large extent defined by the nanoscale electrostatic potentials which these objects produce. We introduce a scanning probe technique that enables three-dimensional imaging of local electrostatic potential fields with sub-nanometer resolution. Registering single electron charging events of a molecular quantum dot attached to the tip of a (qPlus tuning fork) atomic force microscope operated at 5 K, we quantitatively measure the quadrupole field of a single molecule and the dipole field of a single metal adatom, both adsorbed on a clean metal surface. Because of its high sensitivity, the technique can record electrostatic potentials at large distances from their sources, which above all will help to image complex samples with increased surface roughness.Comment: main text: 5 pages, 4 figures, supplementary information file: 4 pages, 2 figure

Core Values and the Road to Change

Higher education draws much of the vocabulary and many of the concepts about change from the corporate sector. Corporations downsized and restructured in the early 1990s in response to competitive and financial pressures; higher education currently is experiencing similar pressures. Yet change and renewal in higher education are not just about money and becoming more cost-effective. Although these are important objectives, higher education must incorporate changes that improve student learning, foster closer connections with their communities, and adapt to the demands of an increasingly technological society. Reorganizing and cutting costs alone do not suggest how colleges and universities might become more agile as institutions, nor do efficiency measures usually address the core issues of the higher education enterprise

Magnetic-crystallographic phase diagram of superconducting parent compound Fe1+x_{1+x}Te

hrough neutron diffraction experiments, including spin-polarized measurements, we find a collinear incommensurate spin-density wave with propagation vector $\mathbf k =$ ($0.4481(4) \, \,0 \, \, \frac1 2$) at base temperature in the superconducting parent compound Fe$_{1+x}$Te. This critical concentration of interstitial iron corresponds to $x \approx 12$ and leads crystallographic phase separation at base temperature. The spin-density wave is short-range ordered with a correlation length of 22(3) \AA, and as the ordering temperature is approached its propagation vector decreases linearly in the H-direction and becomes long-range ordered. Upon further populating the interstitial iron site, the spin-density wave gives way to an incommensurate helical ordering with propagation vector $\mathbf k =$ ($0.3855(2) \, \,0 \, \, \frac1 2$) at base temperature. For a sample with $x \approx 9(1)$, we also find an incommensurate spin-density wave that competes with the bicollinear commensurate ordering close to the N\'eel point. The shifting of spectral weight between competing magnetic orderings observed in several samples is supporting evidence for the phase separation being electronic in nature, and hence leads to crystallographic phase separation around the critical interstitial iron concentration of 12%. With results from both powder and single crystal samples, we construct a magnetic-crystallographic phase diagram of Fe$_{1+x}$Te for $ 5% < x <17%

Regarding the Correlation of Nuclear Spin Relaxation and Electrical Conductivity Relaxation in Ionic Glasses

Much attention has been focused recently on the apparent differences between ion dynamics in ion-containing glasses as probed by electrical conductivity relaxation (ECR) and by nuclear spin relaxation (NSR) techniques. In both relaxation processes, a power law frequency dependence is observed. Based upon fluctuation-dissipation arguments, the power law exponents should be equivalent. However, experimentally, it appears that the conductivity exponent is generally smaller than the NSR exponent. While an explanation for this discrepancy based upon fundamental differences in the correlation functions probed by the two techniques has been proffered, we show how this discrepancy may simply arise from differing analyses of the ac conductivity. We review several cases taken from the literature in which the conductivity exponent was obtained from analysis of the electrical modulus. We demonstrate how this analysis approach generally underestimates the conductivity exponent. When we instead determine the exponent directly from the ac conductivity, we find near equivalence between the NSR and ECR exponents

Specific Heat and Transport “Anomalies” in Mixed Alkali Glasses

We show that changes in the relative mole fractions of Li2O and Na2O in alkali metaphosphate glasses lead to “anomalies” in the specific heat and structural relaxations. The heat capacity change between the liquid and glassy states, Δcp(Tg), at the calorimetric glass transition temperature, Tg, exhibits a minimum when the mole fractions of Li2O and Na2O are comparable. Moreover, systematic changes in the temperature dependence of the viscosity, η, i.e., changes in the “fragility” of the system, accompany these changes in mole fraction. This observed dependence of the “fragility” on the mixed alkali ion composition occurs in the absence of apparent changes in the covalent network connectivity which normally accounts for this behavior in glasses

Anomalous-diffusion Model of Ionic Transport in Oxide Glasses

The power-law frequency dependence of both the conductivity, (), and permittivity, (), of ion-conducting materials suggests that self-similar or scale-invariant behavior influences the transport of ions at high frequencies. Using an anomalous-diffusion model, we derive relevant power-law expressions for () and () and compare these with measurements performed on LiPO3 glass. Superior fits to the measured data are obtained compared to the commonly used Kohlrausch-Williams-Watts (KWW) description of the electrical modulus, most particularly in the notorious high-frequency regime. Evaluation of our results in terms of an anomalous-diffusion model suggests the dominance of interaction-based constraints to diffusion. © 1995 The American Physical Society

Two Contributions to the Ac Conductivity of Alkali Oxide Glasses

Although the frequency dependent conductivity of ion-containing glasses often displays scale invariant power law dispersion at high temperatures, the exponent increases to unity at lower temperatures. We report measurements of the conductivity of a series of alkali metaphosphate glasses including a mixed alkali composition and demonstrate that this temperature dependence results from the superposition of two power law dispersions originating from separate mechanism, and does not indicate any intrinsic change in scaling of the process which dominates at high temperatures. © 1995 The American Physical Society

Scaling Parallels in the Non-Debye Dielectric Relaxation of Ionic Glasses and Dipolar Supercooled Liquids

We compare the dielectric response of ionic glasses and dipolar liquids near the glass transition. Our work is divided into two parts. In the first section we examine ionic glasses and the two prominent approaches to analyzing the dielectric response. The conductivity of ion-conducting glasses displays a power law dispersion σ(ω)∞ωn, where n≈0.67, but frequently the dielectric response is analyzed using the electrical modulus M*(ω) = 1/ε*(ω), where ε*(ω) = ε(ω) - iσ(ω)/ω is the complex permittivity. We reexamine two specific examples where the shape of M*(ω) changes in response to changes in (a) temperature and (b) ion concentration, to suggest fundamental changes in ion dynamics are occurring. We show, however, that these changes in the shape of M*(ω) occur in the absence of changes in the scaling properties of σ(ω), for which n remains constant. In the second part, we examine the dielectric relaxation found in dipolar liquids, for which ε*(ω) likewise exhibits changes in shape on approach to the glass transition. Guided by similarities of M*(ω) in ionic glasses and ε*(ω) in dipolar liquids, we demonstrate that a recent scaling approach proposed by Dixon and co-workers for ε*(ω) of dipolar relaxation also appears valid for M*(ω) in the ionic case. While this suggests that the Dixon scaling approach is more universal than previously recognized, we demonstrate how the dielectric response can be scaled in a linear manner using an alternative data representation

Higher derivative type II string effective actions, automorphic forms and E11

By dimensionally reducing the ten-dimensional higher derivative type IIA string theory effective action we place constraints on the automorphic forms that appear in the effective action in lower dimensions. We propose a number of properties of such automorphic forms and consider the prospects that E11 can play a role in the formulation of the higher derivative string theory effective action.Comment: 34 page