The multilevel measurement model: introduction to the special issue

An introduction to the special issue on the multilevel measurement model (MMM) is provided. The two- and three-level multilevel models for continuous outcomes are reviewed. The extension to the hierarchical generalized linear model and its use as a multilevel measurement model for dichotomous measurement indicators is demonstrated. The six articles in the special issue are described.     

Rapid Absorption of Dietary 1,8-Cineole Results in Critical Blood Concentration of Cineole and Immediate Cessation of Eating in the Common Brushtail Possum (<Emphasis Type="Italic">Trichosurus vulpecula</Emphasis>)

The blood concentration of 1,8-cineole and its metabolites was measured in six male brushtail possums while they voluntarily fed on diets laced with varying concentrations of cineole for 3 d. On the third day, blood samples were collected during and after each bout of feeding for 3 hr. Blood cineole was measured by using headspace solid-phase microextraction (SPME), while cineole metabolites were measured by liquid–liquid extraction followed by gas chromatography-mass spectroscopy. Feeding patterns were measured by continual recording of residual food weight and time. Cineole absorption was rapid, resulting in a peak blood concentration at the end of each feeding bout. The blood concentration of cineole did not exceed a critical value (51.8 ± 14.1 μmol/l) regardless of the concentration in the diet. Food and, therefore, cineole intake was regulated. The amount of food ingested in the first feeding bout decreased from 236 ± 52 g on the control diet to 36 ± 20 g on the 4% cineole diet. The amount of cineole ingested in the first bout (1.18 ± 1.10 g) was the same regardless of the dietary concentration and was controlled by the size of the meal. Total food eaten during the 7-hr feeding session decreased by 64% from 368 ± 94 g (control diet) to 131 ± 52 g (4% diet). Total cineole intake increased from 2.47 ± 0.60 g (1% diet) to 5.05 ± 2.41 g (4% diet). Cineole metabolites accumulated throughout the sampling period and were generally still rising at the end of blood sampling period. Blood levels of metabolites were at least 10-fold higher than cineole levels. The immediate control of feeding seems to be regulated by blood levels of cineole, whereas metabolites are likely to be more important in regulating the chronic ingestion of cineole.     

Developing markets for forest environmental services: an opportunity for promoting equity while securing efficiency?

Market-based approaches to environmental management are all the rage. Claims that market mechanisms can encourage environmental protection and promote greater economic efficiency while saving taxpayers' money are tantalizing. In the forestry sector, policy makers are widely heeding this advice and shrinking command-and-control systems in favour of incentive mechanisms that seek to align private enthusiasm with the public good. In some cases, governments are even promoting the creation of markets where none existed before. In others, markets are evolving of their own accord. In such times of change, it is difficult to stand back and take stock. Yet, it is during such times that guidance is most needed. In the rush to introduce market-based solutions to environmental problems, a particular concern is how markets are impacting on the poor. In this paper an effort is made to draw on a recent review of markets for four forest environmental services (biodiversity conservation, carbon sequestration, watershed protection and landscape beauty) to draw out preliminary insights into how markets are performing with respect to their impacts on the poor. The evidence suggests a need for caution. While the potential benefits are significant, the poor face an uphill battle in realizing them. Key constraints facing the poor include a lack of property rights over forest resources and their environmental services; inadequate skills and education; poor market information; lack of market contacts; inadequate communication infrastructure; inappropriate contract design; and lack of access to financial resources. To tackle these, four potential ways forward are highlighted: (1) assign property rights to forest assets and their related environmental services in ways that respect customary arrangements and poor people's tenure; (2) strengthen capacity for market participation, e.g. through training and education; (3) invest in the provision of market information, advice and, essentially, a contact point for buyers and sellers, perhaps through the establishment of a 'market support centre'; and (4) improve access to finance so that poor individuals can make necessary up-front investments in market participation.     

Moving the cut score on Rasch scored tests

Empirically based item selection guidelines are presented for moving the cut score on equated tests consisting of n dichotomous items calibrated assuming the Rasch model. The cut score on a test form B, c(B), may be made higher than test form A's cut score, c(A), in the following ways: (1) select items for test form B such that the variance of test form B's item difficulties, sigma(2)(B), will be equal to test form A's sigma(2)(A), but test form B's mean item difficulty, mu(B), will be less that of test form A, mu(A); (2) given c(A) > n/2, select items for test form B such that mu(B) s(2)(A). To make c(B) lower than c(A), the direction of the changes listed above for the two tests item difficulties sigma(2) and mu should be reversed. Derivations of lemmas that underlie the guidelines are provided as well as a simulated example.     

Influence of microstructure on the electrochemical performance of tin-doped indium oxide film electrodes

The effect of the microstructure of tin-doped indium oxide (ITO) films on their electrochemical performance was studied using three redox probes, tris(2,2'-bipyridyl ruthenium(II) chloride (Ru(bpy)3(2+/3+)), ferrocyanide (Fe(CN)6(4-/3-)), and ferrocenemethanol (FcCH2H(0/+)). ITO films were deposited using dc magnetron sputtering under a variety of conditions that resulted in films having different degrees of crystallinity, crystallographic texture, sheet resistance, surface roughness, and percent tin. It was found that the electron transfer for all three redox probes used in this study was more efficient at polycrystalline films than at amorphous ITO films. This effect is more pronounced at faster scan rates. The crystallographic texture of the ITO films, surface roughness, and a change in sheet resistance from 7.9 to 13.7 ohms/square did not have an effect on electron-transfer kinetics. ITO films deposited using a 1 wt % SnO2 target and having sheet resistance comparable to films deposited using a 10 wt % SnO2 target had dramatically different microstructure from the films with higher weight percent Sn and were shown to perform poorly when used as electrode materials. We believe that the dramatic differences in electron-transfer kinetics observed at the various ITO films can be attributed to either the different density of defect sites along the grain boundaries or defect sites caused by substitutional Sn in the film.     

Physiologic responses to loud tones in Vietnam veterans with posttraumatic stress disorder.

The authors evaluated eyeblink and autonomic components of the acoustic startle response in combat-related posttraumatic stress disorder (PTSD). Thirty-seven Vietnam combat veterans with current PTSD and 19 combat veterans without PTSD were exposed to 15 consecutive 95-dB, 500-ms, 1000-Hz tones with 0-ms rise and fall times, while orbicularis oculi electromyogram, skin conductance, and heart rate responses were measured. PTSD veterans produced larger averaged electromyographic and heart rate responses, and a slower decline in skin conductance responses, across the 15 tone presentations compared to non-PTSD veterans. Results of this study provide laboratory support for an exaggerated startle response in PTSD and replicate and extend previous findings of increased autonomic responses to loud tone stimuli in this disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Loop summarization using state and transition invariants

This paper presents algorithms for program abstraction based on the principle of loop summarization, which, unlike traditional program approximation approaches (e.g., abstract interpretation), does not employ iterative fixpoint computation, but instead computes symbolic abstract transformers with respect to a set of abstract domains. This allows for an effective exploitation of problem-specific abstract domains for summarization and, as a consequence, the precision of an abstract model may be tailored to specific verification needs. Furthermore, we extend the concept of loop summarization to incorporate relational abstract domains to enable the discovery of transition invariants, which are subsequently used to prove termination of programs. Well-foundedness of the discovered transition invariants is ensured either by a separate decision procedure call or by using abstract domains that are well-founded by construction. We experimentally evaluate several abstract domains related to memory operations to detect buffer overflow problems. Also, our light-weight termination analysis is demonstrated to be effective on a wide range of benchmarks, including OS device drivers.     

„Deal of the Day“-Plattformen: Was treibt die Kundenloyalität?

“Deal of the Day” (DoD) platforms have quickly become popular by offering savings on local services, products and vacations. For merchants, these platforms represent a new marketing channel to advertise their products and services and attract new customers. DoD platform providers, however, struggle to maintaining a stable market share and profitability, because entry and switching costs are low. To sustain a competitive market position, DoD providers are looking for ways to build a loyal customer base. However, research examining the determinants of user loyalty in this novel context is scarce. To fill this gap, this study employs Grounded Theory methodology to develop a conceptual model of customer loyalty to a DoD provider. In the next step, qualitative insights are enriched and validated using quantitative data obtained in a survey with 202 DoD users. We find that customer loyalty is in large part driven by monetary incentives, but can be eroded if impressions from merchant encounter are below expectations. In addition, enhancing the share of deals relevant for consumers, i.e. signal-to-noise ratio, and mitigating perceived risks of a transaction emerge as challenges. Beyond theoretical value, our results offer practical insights into how customer loyalty to a DoD provider can be promoted.