Estimating unconscious processes: Implications of a general class of models.

Jacoby and his colleagues (e.g., L.L. Jacoby, J.P. Toth, & A.P. Yonelinas, see record 1993-36166-001) have shown how the mnemonic contributions of conscious recollection and unconscious familiarity can be separated using a process-dissociation procedure based on a comparison of tasks in which consciously recollected material is to be included in vs. excluded from the responses. However, the estimate of unconscious familiarity depends on the assumptions of the model. This article describes a more general class of models in which the ratio of overlap between conscious and unconscious processes remains fixed and shows that this class of models (which includes the redundancy and exclusivity models as extreme cases) yields improbable results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On learning complex procedural knowledge.

P. Lewicki et al (see record 1988-03338-001) demonstrated learning without awareness in a visual search task. Rules determined target location on every seventh trial on the basis of target locations in the preceding six trials. Learning was demonstrated by negative transfer effects when the rules were changed. When questioned afterwards, the subjects could not describe the rules and denied awareness of them. This experiment was designed to replicate that of Lewicki et al and to test several hypotheses about this apparent learning without awareness. Transfer conditions were included to determine whether rule learning was primarily perceptual or motor. The present assessment of awareness was based on an objective definition of awareness, rather than a subjective definition as in Lewicki et al's study. Their effect was replicated, and the transfer conditions revealed that learning relied on perceptual aspects of the task. The objective measure of awareness provided further evidence that subjects were unaware of the rules. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On Discriminative Bayesian Network Classifiers and Logistic Regression

Discriminative learning of the parameters in the naive Bayes model is known to be equivalent to a logistic regression problem. Here we show that the same fact holds for much more general Bayesian network models, as long as the corresponding network structure satisfies a certain graph-theoretic property. The property holds for naive Bayes but also for more complex structures such as tree-augmented naive Bayes (TAN) as well as for mixed diagnostic-discriminative structures. Our results imply that for networks satisfying our property, the conditional likelihood cannot have local maxima so that the global maximum can be found by simple local optimization methods. We also show that if this property does not hold, then in general the conditional likelihood can have local, non-global maxima. We illustrate our theoretical results by empirical experiments with local optimization in a conditional naive Bayes model. Furthermore, we provide a heuristic strategy for pruning the number of parameters and relevant features in such models. For many data sets, we obtain good results with heavily pruned submodels containing many fewer parameters than the original naive Bayes model.Editors: Pedro Larrañaga, Jose A. Lozano, Jose M. Peña and Iñaki Inza     

Halogen bonding based recognition processes: a world parallel to hydrogen bonding

Halogen bonding is the noncovalent interaction between halogen atoms (Lewis acids) and neutral or anionic Lewis bases. The main features of the interaction are given, and the close similarity with the hydrogen bonding will become apparent. Some heuristic principles are presented to develop a rational crystal engineering based on halogen bonding. The focus is on halogen-bonded supramolecular architectures given by halocarbons. The potential of the interaction is shown by useful applications in the field of synthetic chemistry, material science, and bioorganic chemistry.     

Lachnumon and lachnumol a, new metabolites with nematicidal and antimicrobial activities from the ascomycete Lachnum papyraceum (Karst.) Karst. II. Structural elucidation

The structures of two new biologically active chlorinated metabolites isolated from submerged cultures of the ascomycete Lachnum papyraceum have been elucidated by NMR and mass spectroscopy. The compounds, lachnumon (1) and lachnumol A (2), which structurally are related with mycorrhizin A that also is produced by the fungus, contain an unusual chlorinated epoxide group.     

Tannin assays in ecological studies Precipitation of ribulose-1,5-bisphosphate carboxylase/oxygenase by tannic acid,quebracho, and oak foliage extracts

Tannic acid and quebracho precipitate many times their weight of the abundant leaf protein, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBPC). The use of this protein in protein precipitation assays for tannin content is described. Extracts of mature foliage of pin, bur, and black oak precipitate 2.01, 0.69, and 0.09 mg RuBPC/ mg (dry wt) of leaf powder extracted, respectively, at pH 6.1. From these measurements it can be calculated that all three of these oak species have sufficient tannins to precipitate all of the RuBPC present in their foliage. At mildly alkaline pHs, however (pH ? 7.5), RuBPC is not precipitated by tannins. Since RuBPCis the most abundant protein present in photosynthetic tissues, often constituting as much as 50% of the soluble proteins and 25% of the total proteins in leaf tissue, the interactions of this protein with tannins are highly relevant to an evaluation of the role of tannins as antiherbivore, digestibility-reducing substances. Our measurements provide no basis for arguing that differences in tannin levels in different species reflect differences in the digestibility of leaf proteins or that tannins have any effect whatsoever upon the digestibility of leaf protein under conditions which normally prevail in most insects' guts. These findings emphasize the need to test more of the assumptions underlying contemporary interpretations of the importance of tannins in plant herbivore interactions.     

Process control of lightly salted wild and farmed Atlantic cod (Gadus morhua) by brine injection, brining, and freezing--a low field NMR study

The aim of this study was to use low-field nuclear magnetic resonance (NMR) and traditional chemical methods to investigate the physical and chemical differences in wild and farmed cod processed pre- and postrigor, and how these properties were affected by brine injection, brining, and freezing. In prerigor processed farmed or wild cod, brine injections followed by brining for 2 d, with brine concentrations up to 5.5% and 4%, respectively, were not sufficient to reach a muscle salt concentration of 2% as aimed for, while wild cod processed postrigor had sufficient salt uptake after the same processing. Low-field NMR gave valuable information about the differences in the muscle structure between wild and farmed cod as well as the state of the water in the muscle during brine injection, brining, and during rigor tension. Low-field NMR is, therefore, a valuable tool that can be used to optimize the salting and storing processes of lightly salted cod products from both wild and farmed cod. For farmed cod to be used in the production of lightly salted products further research is needed. Practical Application: Optimal processing of lightly salted cod products is important to the fish industry, due to an increasing market for this product in southern Europe. Farmed cod, which is seen as a potential steady raw material source for this production, differs considerably from its wild counterparts by having other chemical and physical muscle properties, such as lower water content and lower pH. With the processing procedures used today the farmed cod can, therefore, only be used in some of the products, where wild cod is currently used as raw material. It is, therefore, important that the processing of these products is optimized with regard to these differences in the raw material. This study gives a valuable contribution to further studies about optimal combinations of brine injections, brining, and freezing of pre- and postrigor processed farmed compared to wild cod.