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Processing Demands (processing + demand)
Selected AbstractsBiodiesel fuel production via transesterification of oils using lipase biocatalystGCB BIOENERGY, Issue 2 2009MAN XIAO Abstract Biodiesel has gained widespread importance in recent years as an alternative, renewable liquid transportation fuel. It is derived from natural triglycerides in the presence of an alcohol and an alkali catalyst via a transesterification reaction. To date, transesterification based on the use of chemical catalysts has been predominant for biodiesel production at the industrial scale due to its high conversion efficiency at reasonable cost. Recently, biocatalytic transesterification has received considerable attention due to its favorable conversion rate and relatively simple downstream processing demands for the recovery of by-products and purification of biodiesel. Biocatalysis of the transesterification reaction using commercially purified lipase represents a major cost constraint. However, more cost-effective techniques based on the immobilization of both extracellular and intracellular lipases on support materials facilitate the reusability of the catalyst. Other variables, including the presence of alcohol, glycerol and the activity of water can profoundly affect lipase activity and stability during the reaction. This review evaluates the current status for lipase biocatalyst-mediated production of biodiesel, and identifies the key parameters affecting lipase activity and stability. Pioneer studies on reactor-based lipase conversion of triglycerides are presented. [source] A locus for an auditory processing deficit and language impairment in an extended pedigree maps to 12p13.31-q14.3GENES, BRAIN AND BEHAVIOR, Issue 6 2010L. Addis Despite the apparent robustness of language learning in humans, a large number of children still fail to develop appropriate language skills despite adequate means and opportunity. Most cases of language impairment have a complex etiology, with genetic and environmental influences. In contrast, we describe a three-generation German family who present with an apparently simple segregation of language impairment. Investigations of the family indicate auditory processing difficulties as a core deficit. Affected members performed poorly on a nonword repetition task and present with communication impairments. The brain activation pattern for syllable duration as measured by event-related brain potentials showed clear differences between affected family members and controls, with only affected members displaying a late discrimination negativity. In conjunction with psychoacoustic data showing deficiencies in auditory duration discrimination, the present results indicate increased processing demands in discriminating syllables of different duration. This, we argue, forms the cognitive basis of the observed language impairment in this family. Genome-wide linkage analysis showed a haplotype in the central region of chromosome 12 which reaches the maximum possible logarithm of odds ratio (LOD) score and fully co-segregates with the language impairment, consistent with an autosomal dominant, fully penetrant mode of inheritance. Whole genome analysis yielded no novel inherited copy number variants strengthening the case for a simple inheritance pattern. Several genes in this region of chromosome 12 which are potentially implicated in language impairment did not contain polymorphisms likely to be the causative mutation, which is as yet unknown. [source] The neural response to changing semantic and perceptual complexity during language processingHUMAN BRAIN MAPPING, Issue 3 2010David J. Sharp Abstract Speech comprehension involves processing at different levels of analysis, such as acoustic, phonetic, and lexical. We investigated neural responses to manipulating the difficulty of processing at two of these levels. Twelve subjects underwent positron emission tomographic scanning while making decisions based upon the semantic relatedness between heard nouns. We manipulated perceptual difficulty by presenting either clear or acoustically degraded speech, and semantic difficulty by varying the degree of semantic relatedness between words. Increasing perceptual difficulty was associated with greater activation of the left superior temporal gyrus, an auditory-perceptual region involved in speech processing. Increasing semantic difficulty was associated with reduced activity in both superior temporal gyri and increased activity within the left angular gyrus, a heteromodal region involved in accessing word meaning. Comparing across all the conditions, we also observed increased activation within the left inferior prefrontal cortex as the complexity of language processing increased. These results demonstrate a flexible system for language processing, where activity within distinct parts of the network is modulated as processing demands change. Hum Brain Mapp, 2010. © 2009 Wiley-Liss, Inc. [source] Spelling as a self-teaching mechanism in orthographic learningJOURNAL OF RESEARCH IN READING, Issue 1 2008Daphna Shahar-Yames The present study examined the possibility that spelling fulfils a self-teaching function in the acquisition of orthographic knowledge because, like decoding, it requires close attention to letter order and identity as well as to word-specific spelling,sound mapping. We hypothesised that: (i) spelling would lead to significant (i.e. above-chance) levels of orthographic learning; (ii) spelling would actually result in superior learning relative to reading owing to the additional processing demands invoked when spelling; (iii) there would be stronger outcomes for post-test spelling production compared with spelling recognition; and (iv) relative to reading, spelling would produce superior orthographic learning in the case of later-occurring orthographic detail compared with information appearing earlier in the letter string. In a fully within-subjects design, third grade Hebrew readers were exposed to novel letter strings presented in three conditions: spelling, reading and an unseen control condition. With the exception of the position by condition interaction (our fourth hypothesis), which, although in the expected direction, failed to attain significance, all hypotheses were supported. These data highlight yet another dimension of reading,writing reciprocity by suggesting that spelling offers a powerful self-teaching tool in the compilation of word-specific orthographic representations. [source] Prepulse inhibition of the acoustic startle reflex and oculomotor controlPSYCHOPHYSIOLOGY, Issue 4 2005Ulrich Ettinger Abstract Prepulse inhibition and the suppression of reflexive saccades on the antisaccade task are thought to tap inhibitory function. Reports of a lack of association between these measures suggest that they reflect different facets of inhibition. This study aimed to reexamine this relationship in a large sample and investigate the association of prepulse inhibition with oculomotor tasks that require inhibition of a reflexive saccade with lower concurrent processing demands than antisaccades, namely the oculomotor delayed response and fixation with distractors tasks. One hundred and seven healthy volunteers took part. Prepulse inhibition was uncorrelated with oculomotor performance. The error rate was highest for antisaccades, intermediate for the delayed response task, and lowest for fixation with distractors, and was correlated across tasks. These findings provide no evidence of a relationship between prepulse inhibition and oculomotor inhibition. Failure in suppressing reflexive saccades toward a peripheral target may represent a common inhibitory component underlying these oculomotor tasks. [source] | ||||||||||