Latent structure and factorial invariance of a neuropsychological test battery for the study of preclinical Alzheimer's disease.

Objective: To examine the latent structure of a test battery currently being used in a longitudinal study of asymptomatic middle-aged adults with a parental history of Alzheimer's disease (AD) and test the invariance of the factor solution across subgroups defined by selected demographic variables and known genetic risk factors for AD. Method: An exploratory factor analysis (EFA) and a sequence of confirmatory factor analyses (CFA) were conducted on 24 neuropsychological measures selected to provide a comprehensive estimate of cognitive abilities most likely to be affected in preclinical AD. Once the underlying latent model was defined and the structural validity established through model comparisons, a multigroup confirmatory factor analysis model was used to test for factorial invariance across groups. Results: The EFA solution revealed a factor structure consisting of five constructs: verbal ability, visuospatial ability, speed & executive function, working memory, and verbal learning & memory. The CFA models provided support for the hypothesized 5-factor structure. Results indicated factorial invariance of the model across all groups examined. Conclusions: Collectively, the results suggested a relatively strong psychometric basis for using the factor structure in clinical samples that match the characteristics of this cohort. This confirmed an invariant factor structure should prove useful in research aimed to detect the earliest cognitive signature of preclinical AD in similar middle aged cohorts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Optimizing substrate surface and catalyst conditions for high yield chemical vapor deposition grown epitaxially aligned single-walled carbon nanotubes

Single-crystal stable-temperature (ST)-cut quartz substrates, which have a (0 1 1 1) crystallographic plane with their surface normal lying close to 38° from the y axis ([0 1 0]), were annealed in air prior to use as a support for aligned carbon nanotube growth by chemical vapor deposition. Very smooth substrate surfaces were obtained with annealing times in the vicinity of 15 h at a temperature of 750 °C. These smooth surfaces are ideal for the growth of horizontally aligned SWCNTs with high spatial density, while less dense SWCNTs were obtained with less smooth surfaces. Under optimized growth conditions, only SWCNT are observed and they can grow to lengths in excess of 100 μm. Our findings suggest structural defects interfere with the growth process. A binary Fe/Co catalyst was employed to grow the nanotubes. No obvious dependence on the Fe:Co ratio is observed.     

Syngas fermentation in a 100-L pilot scale fermentor: Design and process considerations

Fermentation of syngas offers several advantages compared to chemical catalysts such as higher specificity of biocatalysts, lower energy costs, and higher carbon efficiency. Scale-up of syngas fermentation from a bench scale to a pilot scale fermentor is a critical step leading to commercialization. The primary objective of this research was to install and commission a pilot scale fermentor, and subsequently scale-up the Clostridium strain P11 fermentation from a 7.5-L fermentor to a pilot scale 100-L fermentor. Initial preparation and fermentations were conducted in strictly anaerobic conditions. The fermentation system was maintained in a batch mode with continuous syngas supply. The effect of anaerobic fermentation in a pilot scale fermentor was evaluated. In addition, the impact of improving the syngas mass transfer coefficient on the utilization and product formation was studied. Results indicate a six fold improvement in ethanol concentration compared to serum bottle fermentation, and formation of other compounds such as isopropyl alcohol, acetic acid and butanol, which are of commercial importance.     

Automated generation of program translation and verification tools using annotated grammars

Automatically generating program translators from source and target language specifications is a non-trivial problem. In this paper we focus on the problem of automating the process of building translators between operations languages, a family of DSLs used to program satellite operations procedures. We exploit their similarities to semi-automatically build transformation tools between these DSLs. The input to our method is a collection of annotated context-free grammars. To simplify the overall translation process even more, we also propose an intermediate representation common to all operations languages. Finally, we discuss how to enrich our annotated grammars model with more advanced semantic annotations to provide a verification system for the translation process. We validate our approach by semi-automatically deriving translators between some real world operations languages, using the prototype tool which we implemented for that purpose.     

Revisiting and Extending Interface Penalties for Multi-domain Summation-by-Parts Operators

A general interface procedure is presented for multi-domain collocation methods satisfying the summation-by-parts (SBP) spatial discretization convention. Unlike more traditional operators (e.g. FEM) applied to the advection-diffusion equation, the new procedure penalizes the solution and the first p derivatives across the interface. The combined interior/interface operators are proven to be pointwise stable, and conservative, although accuracy deteriorates for p≥2. Penalties between two different sets of variables are compared (motivated by FEM primal and flux formulations), and are shown to be equivalent for certain choices of penalty parameters. Extensive validation studies are presented using two classes of high-order SBP operators: (1) central finite difference, and (2) Legendre spectral collocation.     

Clinical practice as natural laboratory for psychotherapy research: A guide to case-based time-series analysis.

Both researchers and practitioners need to know more about how laboratory treatment protocols translate to real-world practice settings and how clinical innovations can be systematically tested and communicated to a skeptical scientific community. The single-case time-series study is well suited to opening a productive discourse between practice and laboratory. The appeal of case-based time-series studies, with multiple observations both before and after treatment, is that they enrich our design palette by providing the discipline another way to expand its empirical reach to practice settings and its subject matter to the contingencies of individual change. This article is a user's guide to conducting empirically respectable case-based time-series studies in a clinical practice or laboratory setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What is false memory development the development of? Comment on Brainerd, Reyna, and Ceci (2008).

In this commentary, assumptions about the nature and development of children's false memories as described in a recent article by C. J. Brainerd, V. F. Reyna, and S. J. Ceci (2008; see record 2008-04614-001) are reviewed. Specifically, questions are raised about what drives the development of false memories in fuzzy-trace theory (FTT). Recent studies that challenge a core assumption of FTT, that false memory illusions increase across development as children learn to establish meaningful connections across items (i.e., establish gist), are discussed. An alternative conceptualization of the development of false memory illusions, associative-activation theory (AAT), is presented. AAT provides as viable an account of the development of false memory illusions as does FTT and anticipates a unique set of outcomes that have recently appeared in the developmental literature on false memory illusions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identification of new epidemiological molecular markers by comparative proteomics of serogroup A meningococcal isolates from three pandemic waves

We previously described the first reference map for the proteome of one strain of serogroup A Neisseria meningitidis (MenA), a major cause of epidemic meningitis in humans. As a preliminary finding, in that work we noted that 2‐DE protein maps of closely related MenA isolates from different epidemics spreads could be easily compared to detect minor differences and that 2‐DE phenotypes attributable to the well‐known epidemiological marker tbpB agreed with the genoclouds model of MenA epidemiological variation during pandemic waves. We explored here the possibility that an extended comparative study of 2‐DE maps of isolates representative of the nine genoclouds described by Achtman and collaborators could be used to discriminate between strains otherwise undistinguishable. We showed the example of 14 proteins with different 2‐DE spot patterns in different genoclouds that could be considered as putative tracers for alike‐strains discrimination. We introduce the novel concept that comparative proteomics can be useful in identifying new epidemiological markers for N. meningitidis.