On the meaning of the latent variables in the CT-C(M-1) model: A comment on Maydeu-Olivares and Coffman (2006).

[Correction Notice: An erratum for this article was reported in Vol 13(2) of Psychological Methods (see record 2008-06808-007). In Figures 3B and 3D, the question marks (?) should read as multiplication signs (×). That is, it should read as β×λ?, β×λ?, and β×λ?? instead of β?λ?, β?λ?, and β?λ?? in Figure 3B and as γ×λ? and γ×λ? instead of γ?λ? and γ?λ? in Figure 3D.] In a recent article, A. Maydeu-Olivares and D. L. Coffman (2006; see record 2006-22258-002) presented a random intercept factor approach for modeling idiosyncratic response styles in questionnaire data and compared this approach with competing confirmatory factor analysis models. Among the competing models was the CT-C(M-1) model (M. Eid, 2000). In an application to the Life Orientation Test (M. F. Scheier & C. S. Carver, 1985), Maydeu-Olivares and Coffman found that results obtained from the CT-C(M-1) model were difficult to interpret. In particular, Maydeu-Olivares and Coffman challenged the asymmetry of the CT-C(M-1) model. In the present article, the authors show that the difficulties faced by Maydeu-Olivares and Coffman rest upon an improper interpretation of the meaning of the latent factors. The authors' aim is to clarify the meaning of the latent variables in the CT-C(M-1) model. The authors explain how to properly interpret the results from this model and introduce an alternative restricted model that is conceptually similar to the CT-C(M-1) model and nested within it. The fit of this model is invariant across different reference methods. Finally, the authors provide guidelines as to which model should be used in which research context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparative study of the effects of 1‐MCP treatment on apple quality by instrumental and multivariate analysis

BACKGROUND: The main aim of this work was to define how 1‐methylcyclopropene (1‐MCP) treatment affects apple fruit quality by two complementary approaches. RESULTS: The results confirmed that 1‐MCP treatment maintained firmness and acidity of the fruit. Multivariate analysis distinguished treated and untreated fruits and showed that a relationship exists between 1‐MCP treatment and firmness, and also between 1‐MCP and the physiological disorder, ‘diffuse skin browning’ (DSB). Relationships for acidity were low and absent for soluble‐solids concentration (SSC). The PCA model built only with 1‐MCP treated fruit showed a positive correlation between DSB incidence and firmness, and a negative correlation between DSB and SSC or a* values. Collectively, these correlations indicated that the more immature fruits are more susceptible to DSB. This last model also characterised acidity as the best parameter to discriminate the 1‐MCP fruits. CONCLUSION: It is the first time that such a comparative study has been conducted on 1‐MCP treated fruits. The results are of interest because they (1) help to discriminate treated and untreated fruits, and (2) allow discrimination of 1‐MCP‐treated fruit during storage. Copyright © 2008 Society of Chemical Industry     

Current oscillations during chronoamperometric and cyclic voltammetric measurements in alkaline Cu(II)-citrate solutions

It is demonstrated that current oscillations can be observed during chronoamperometric and cyclic voltammetric experiments in solutions containing 0.4 M CuSO₄ and 1.2 M citrate at pH 11 and 50 °C. The oscillations, which are shown to originate from local variations in the pH, result in the deposition of nanostructured Cu and Cu₂O materials. It is concluded that the current oscillations are analogous to the previously described potential oscillations obtained under controlled current conditions in alkaline Cu(II)-lactate, -tartrate and -citrate solutions. Rotating disk electrode results clearly show that the reduction of the Cu(II)-complexes is kinetically controlled and that the rate of the reduction increases with increasing pH and temperature. It is also shown that the presence of a cathodic peak on the anodic scan in the cyclic voltammograms can be used to identify the experimental conditions leading to the spontaneous current (or potential) oscillations. Electrochemical quartz crystal microbalance results indicate that the cathodic peak stems from an increased rate of the reduction of the Cu(II)-citrate complexes due to a rapid increase in the local pH. This causes Cu₂O rather than Cu to be deposited which, however, results in a decrease in the local pH and a decreasing current. In situ ellipsometry data confirm that Cu₂O deposition replaces that of Cu in the potential region of the cathodic peak. The present findings should facilitate syntheses of nanolayered materials based on spontaneous potential or current oscillations.     

Measuring interdiffusion at an interface between two elastomers with tapping-mode and contact-resonance atomic force microscopy imaging

Despite the common use of tapping-mode atomic force microscopy to image composites or polymer blends, very few studies have focused on the measurement of the interdiffusion at an interface between two polymers in contact. In this study, we show how to assess the interphase between two polymers with two methods. First, stable and robust tapping conditions are established, and the problem of the phase contrast is discussed. Second, a contact-resonance method is presented: the tip in contact with the sample is electrostatically excited at its resonance frequency by a self-controlled oscillator. The gain and frequency images allow us to measure the interdiffusion width. Both methods (using high and weak mechanical solicitation) give the same assessment of the interdiffusion width. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

A review of catalytic partial oxidation of methane to synthesis gas with emphasis on reaction mechanisms over transition metal catalysts

Catalytic partial oxidation of methane has been reviewed with an emphasis on the reaction mechanisms over transition metal catalysts. The thermodynamics and aspects related to heat and mass transport is also evaluated, and an extensive table on research contributions to methane partial oxidation over transition metal catalysts in the literature is provided.Presented are both theoretical and experimental evidence pointing to inherent differences in the reaction mechanism over transition metals. These differences are related to methane dissociation, binding site preferences, the stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species.Methane dissociation requires a reduced metal surface, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H, H₂, C or CO.The comparison of elementary reaction steps on Pt and Rh illustrates that a key factor to produce hydrogen as a primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H₂ and CO as primary products is a low surface coverage of intermediates, such that the probability of O–H, OH–H and CO–O interactions are reduced.The local concentrations of reactants and products change rapidly through the catalyst bed. This influences the reaction mechanisms, but the product composition is typically close to equilibrated at the bed exit temperature.     

Bingo Voting

Wahlen bringen den Willen des Volkes zum Ausdruck und stellen damit einen fundamentalen Baustein für jede Demokratie dar. Forderungen nach einer schnelleren Ausz?hlung haben dazu geführt, dass vermehrt Wahlmaschinen Einsatz finden, trotz der massiven Kritik, die von verschiedenen Seiten ge?u?ert wird. Der Beitrag stellt ein kryptographisches Verfahren vor, das Wahlen mit Wahlmaschinen erlaubt, ohne dabei an Transparenz und Nachvollziehbarkeit einzuben. Das Verfahren wurde mit dem Deutschen IT-Sicherheitspreis 2008 ausgezeichnet.     

Species‐specific fish larvae drift in anthropogenically constructed riparian zones on the Vienna impoundment of the River Danube,Austria: Species occurrence,frequencies, and seasonal patterns based on DNA barcoding

As a result of river regulations over several centuries, followed by restoration measures in recent decades, most of the River Danube shoreline is man‐made, primarily riprap, but some reconstructed gravel banks and riparian side arms. We investigated the effects of these different structures on fish larval dispersal over a 20‐km stretch in Vienna via the use of drift nets. The habitats examined were created 18 years ago when the impoundment of the Danube hydropower station Vienna/Freudenau was constructed. About 15,000 fish larvae were trapped, and a subsample was determined to species level by DNA barcoding. In total, 26 different species were detected, including 10 species that are endangered or in danger of extinction. When species composition was considered, cyprinids become dominant at sites downstream of gravel bars, whereas in riprap sections, the majority of the larvae consist of invasive Gobiidae. Side arm habitats provide spawning and nursery grounds for additional species. Furthermore, clear species‐related seasonal patterns were observed with peak densities and multiple spawning periods of some species being recorded. The largest peak of Percidae occurred in the first half of May, followed by Cyprinidae at the end of May and Gobiidae in mid‐June.     

Factors structuring macroinvertebrate communities in a headwater stream and its springs in the Upper Austrian Limestone Alps

The Almbach, a headwater stream in the Upper Austrian foothills of the Alps bordered by mountain pastures was studied to gain insight into the benthic macroinvertebrate community and its habitat. Two springs, one of them fenced in to prevent livestock access, and two more sites of the headwater section were investigated. A discriminant analysis (DA) based on hydrochemistry and phytobenthos revealed three functions with 86% of all samples correctly classified to the four sites. The first function clearly separated the two springs with phosphorus and oxygen as the most important discriminating factors. Spring sites and headwater sites were split up by the second function mainly due to nitrate concentration, but no differences could be detected for the two stream sites. With the exception of the fenced spring, indicator taxa could be assigned to all sites by means of an Indicator Species Analysis (ISA). Polyvalent taxa groups such as Gastropoda and Ostracoda were indicators for the unfenced spring site. This is in accordance to observed low abundances of sensitive plecopteran taxa and suggests a negative impact of livestock trampling on the invertebrate community. Redundancy Analysis explained 99% of the macroinvertebrate‐environment relation. The first axis separated springs from stream sites and was correlated with nitrate, pH, water temperature and phytobenthos eveness. Phosphorus was responsible for splitting the unfenced spring and the downstream station from the fenced spring and the upstream location along the second axis. Ephemeropteran taxa like Habrophlebia sp. were related to elevated pH, increased water temperature and low nitrate concentrations. In accordance to the ISA, nitrate played an important role for tolerant Gastropoda and Ostracoda at the unfenced spring. Copyright © 2010 John Wiley & Sons, Ltd.