There is considerable current interest in neural modeling of the attentional blink phenomenon. Two prominent models of this task are the Simultaneous Type Serial Token (ST(2)) model and the Locus ...Coeruleus-Norepinephrine (LC-NE) model. The former of these generates a broad spectrum of behavioral data, while the latter provides a neurophysiologically detailed account. This paper explores the relationship between these two approaches. Specifically, we consider the spectrum of empirical phenomena that the two models generate, particularly emphasizing the need to generate a reciprocal relationship between bottom-up trace strength and the blink bottleneck. Then we discuss the implications of using ST(2) token mechanisms in the LC-NE setting.
Abstract There is considerable current interest in neural modeling of the attentional blink phenomenon. Two prominent models of this task are the Simultaneous Type Serial Token (ST2 ) model and the ...Locus Coeruleus–Norepinephrine (LC–NE) model. The former of these generates a broad spectrum of behavioral data, while the latter provides a neurophysiologically detailed account. This paper explores the relationship between these two approaches. Specifically, we consider the spectrum of empirical phenomena that the two models generate, particularly emphasizing the need to generate a reciprocal relationship between bottom-up trace strength and the blink bottleneck. Then we discuss the implications of using ST2 token mechanisms in the LC–NE setting.
Observers often miss a second target (T2) if it follows an identified first target item (T1) within half a second in rapid serial visual presentation (RSVP), a finding termed the attentional blink. ...If two targets are presented in immediate succession, however, accuracy is excellent (Lag 1 sparing). The resource sharing hypothesis proposes a dynamic distribution of resources over a time span of up to 600 msec during the attentional blink. In contrast, the ST
model argues that working memory encoding is serial during the attentional blink and that, due to joint consolidation, Lag 1 is the only case where resources are shared. Experiment 1 investigates the P3 ERP component evoked by targets in RSVP. The results suggest that, in this context, P3 amplitude is an indication of bottom–up strength rather than a measure of cognitive resource allocation. Experiment 2, employing a two-target paradigm, suggests that T1 consolidation is not affected by the presentation of T2 during the attentional blink. However, if targets are presented in immediate succession (Lag 1 sparing), they are jointly encoded into working memory. We use the ST
model's neural network implementation, which replicates a range of behavioral results related to the attentional blink, to generate “virtual ERPs” by summing across activation traces. We compare virtual to human ERPs and show how the results suggest a serial nature of working memory encoding as implied by the ST
model.
There is considerable current interest in neural modeling of the attentional blink phenomenon. Two prominent models of this task are the Simultaneous Type Serial Token (ST super(2)) model and the ...Locus Coeruleus-Norepinephrine (LC-NE) model. The former of these generates a broad spectrum of behavioral data, while the latter provides a neurophysiologically detailed account. This paper explores the relationship between these two approaches. Specifically, we consider the spectrum of empirical phenomena that the two models generate, particularly emphasizing the need to generate a reciprocal relationship between bottom-up trace strength and the blink bottleneck. Then we discuss the implications of using ST super(2) token mechanisms in the LC-NE setting.
There is considerable current interest in neural modeling of the attentional blink phenomenon. Two prominent models of this task are the Simultaneous Type Serial Token (ST
2) model and the Locus ...Coeruleus–Norepinephrine (LC–NE) model. The former of these generates a broad spectrum of behavioral data, while the latter provides a neurophysiologically detailed account. This paper explores the relationship between these two approaches. Specifically, we consider the spectrum of empirical phenomena that the two models generate, particularly emphasizing the need to generate a reciprocal relationship between bottom-up trace strength and the blink bottleneck. Then we discuss the implications of using ST
2 token mechanisms in the LC–NE setting.
Intact gellan gum (0.1% m/v) was detectable by capillary electrophoresis (CE) with UV detection. Characteristic tetrasaccharide fragments, prepared with a newly characterised gellan-degrading enzyme, ...provided a clearer signal that was detectable in complex food products containing other polysaccharides. Food products spiked with gellan gum could be analysed reproducibly with high accuracy and specificity by CE–ESI–MS, which is recommended as the technique of choice. Gellan gum declared as a fruit flavour drink ingredient could not be identified by CE–ESI–MS. When added to the product at the start of sample preparation, before enzyme treatment, the gum was readily detectable, demonstrating that the method was compatible with this sample type. Possible explanations for the negative results are that gellan gum was used as a trace component, with other texturing agents; that its declaration was precautionary only; or that the product contained a chemically modified form. Further work will establish whether modified gellan gums can be similarly analysed.
An approach to rapid soil testing which involved the use of simple solvent extraction methods was developed. The analytes of interest were priority pollutants of low water solubility which could not ...be readily removed from the soil using water. Direct toxicity testing of the soil samples by Microtox
® showed a high background toxicity which prevented realistic toxicity data from being obtained for the contaminants present. A range of different extraction solutions was used in an attempt to extract the contaminants while eliminating the matrix effects of the soil. It was necessary that the solvents selected for extraction of the soil samples were not of significant toxicity, as this could potentially mask the toxic effects of any compounds extracted from the soil. The extraction efficiencies of solvent systems were evaluated using pentachlorophenol (PCP) as a model compound of known toxicity in the Microtox
® assay. A rapid and cost-effective method was developed in order to determine the amount of PCP recovered from the soil by the extraction solvents employed. This method consisted of a solid phase extraction (SPE) step followed by quantification using capillary electrochromatography (CEC). Recoveries were greater when a higher proportion of organic solvent (methanol) was used in the extraction process, and lowest when water was used. An extraction based on water could provide information on the potential for leaching of contaminants from the soil into nearby water bodies in an environmental setting. An organic solvent extraction method could indicate how much toxicity soil-dependent organisms might be exposed to through ingestion. Extraction based on 50% (v/v) methanol in water was considered to be the most suitable overall extraction solution for soil screening, given that this permitted extraction of the water-insoluble compound PCP at a level which was clearly toxic in the Microtox
® assay while also retaining the capability to extract water-soluble contaminants.
There have been several instances worldwide of children and elderly people choking to death on soft slippery dome-shaped jellies that are designed to be placed in the mouth in one bite. This problem ...was addressed in the European Union by the provisions of Directive 2006/52/EC of the European Parliament and of the Council prohibiting the use of a range of gel-forming additives in jelly mini-cups. Unfortunately, the definition given in the Directive of what exactly constitutes a ‘jelly mini-cup’ remains open to interpretation. We present a case study illustrating a recommended analytical strategy, including characteristics such as size, weight and insolubility in artificial saliva to determine if such a product falls within the Directive’s definition and thus represents a potential choking risk.
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