361 research outputs found

    Pilot Plant Production of Cellulase by Trichoderma Reesei QM9414 and the Effect of Dimethyl Sulfoxide on Cellulase Production by T. Reesei MCG77

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    Approximately 15-20 x 1010 tons of organic plant substance is produced on earth per annum. Half of this material is cellulose. Much of this cellulosic material is highly resistant to breakdown due to other plant components such as lignin and hemicellulose which together with the cellulose contribute to the structural integrity of the plants. Thus, these materials find relatively limited uses in comparison to their abundance. Cellulosic materials are utilized by ruminants as an energy source and in lumber and pulping applications but commercial cellulose processing to produce glucose or glucose derived products is not currently performed. The abundance of cellulosic materials make them attractive as a cheap substrate for industrial applications. However, the conversion of these materials is greatly limited by other protective constituents such as lignin and hemicellulose and by the arrangement of the cellulose molecules themselves. In the past, processes for hydrolysis of cellulose have been primarily based upon the use of acids. These processes proved to be uneconomical. More recent methods have concentrated on the use of microbial cellulases usually in conjunction with pretreatment of the cellulosic materials. The advantages of the enzymatic methods lie in the moderate temperatures for conversion, the noncorrosive nature of the process and quantitative conversion to the desired end product-glucose. The best microbial cellulase producer is the fungus Trichoderma reesei. Trichoderma reesei mutant strains hyperproduce a complete cellulase complex capable of attacking crystalline cellulose and reducing it to glucose. The T. reesei cellulase complex is composed of: S-1, 4-glucan cellobiohydrolases, endo 1, 4-Sglucan glucanohydrolases and a S-glucosidase. Production of T. reesei cellulase is conveniently accomplished in aerated, submerged culture. Trichoderma reesei fermentations on cellulose substrate go through a drop in pH with a subsequent rise at the end of the fermentation. The rise in pH can be used as a general indicator of when to harvest the enzyme. Optimum yields of enzyme require that the acidic phase of the fermentation be maintained between pH 3.0 to 3.5. Yields (in units activity/ml) of enzyme increase with an increase in the cellulose level employed in the production medium. The maximum level is approximately 8% w/v cellulose. Viscosity is a problem in media greater than 8% w/v. The cost of enzyme production is the limiting factor for an enzymatic conversion process. The system of Wilke, Yang and Von Stockar resulted in an enzyme production cost of 0.05−0 .05-0.06/lb. of glucose produced or about 60% of the cost of production. Optimization of cellulase production systems for increased yields are therefore of paramount importance to reduce the cost of enzymatic cellulose conversion. Increased yields and production rates of cellulase have been reported for the use of various additives to the production medium and from advanced culture techniques such as continuous processes. This study involves the production of T. reesei cellulase in a rudimentary production system employing used dairy equipment. The potential for enzyme stimulation by addition of dimethyl sulfoxide to the production medium is also investigated

    The amygdala: inside and out

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    Research at the interface of psychology, neuroscience, molecular biology, and genetics, focusing on the amygdala, has begun to reveal a rule book for emotional reactions. Variations in intrinsic and extrinsic factors tweak the sensitivity of the amygdala, giving rise to differences in behavior between individuals. At their most extreme, these variations may generate psychological disorders, and even our current rudimentary understanding of this brain region suggests novel strategies for the treatment of such disorders

    Neural responses to ambiguity involve domain-general and domain-specific emotion processing systems

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    Extant research has examined the process of decision making under uncertainty, specifically in situations of ambiguity. However, much of this work has been conducted in the context of semantic and low-level visual processing. An open question is whether ambiguity in social signals (e.g., emotional facial expressions) is processed similarly or whether a unique set of processors come on-line to resolve ambiguity in a social context. Our work has examined ambiguity using surprised facial expressions, as they have predicted both positive and negative outcomes in the past. Specifically, whereas some people tended to interpret surprise as negatively valenced, others tended toward a more positive interpretation. Here, we examined neural responses to social ambiguity using faces (surprise) and nonface emotional scenes (International Affective Picture System). Moreover, we examined whether these effects are specific to ambiguity resolution (i.e., judgments about the ambiguity) or whether similar effects would be demonstrated for incidental judgments (e.g., nonvalence judgments about ambiguously valenced stimuli). We found that a distinct task control (i.e., cingulo-opercular) network was more active when resolving ambiguity. We also found that activity in the ventral amygdala was greater to faces and scenes that were rated explicitly along the dimension of valence, consistent with findings that the ventral amygdala tracks valence. Taken together, there is a complex neural architecture that supports decision making in the presence of ambiguity: (a) a core set of cortical structures engaged for explicit ambiguity processing across stimulus boundaries and (b) other dedicated circuits for biologically relevant learning situations involving faces

    Remembering People: Neuroimaging Takes On the Real World

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    Interpreting Ambiguous Social Cues in Unpredictable Contexts

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    Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to aversive stimuli. Even neutral stimuli, when presented in an unpredictable fashion, prime anxiety-like behavior and elicit heightened amygdala activity. The amygdala plays a key role in initiating responses to biologically relevant information, such as facial expressions of emotion. While some expressions clearly signal negative (anger) or positive (happy) events, other expressions (e.g. surprise) are more ambiguous in that they can predict either valence, depending on the context. Here, we sought to determine whether unpredictable presentations of ambiguous facial expressions would bias participants to interpret them more negatively. We used functional magnetic resonance imaging and facial electromyography (EMG) to characterize responses to predictable vs unpredictable presentations of surprised faces. We observed moderate but sustained increases in amygdala reactivity to predictable presentations of surprised faces, and relatively increased amygdala responses to unpredictable faces that then habituated, similar to previously observed responses to clearly negative (e.g. fearful) faces. We also observed decreased corrugator EMG responses to predictable surprised face presentations, similar to happy faces, and increased responses to unpredictable surprised face presentations, similar to angry faces. Taken together, these data suggest that unpredictability biases people to interpret ambiguous social cues negatively

    Parcellation of Human Amygdala Subfields Using Orientation Distribution Function and Spectral K-means Clustering

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    Amygdala plays an important role in fear and emotional learning, which are critical for human survival. Despite the functional relevance and unique circuitry of each human amygdaloid subnuclei, there has yet to be an efficient imaging method for identifying these regions in vivo. A data-driven approach without prior knowledge provides advantages of efficient and objective assessments. The present study uses high angular and high spatial resolution diffusion magnetic resonance imaging to generate orientation distribution function, which bears distinctive microstructural features. The features were extracted using spherical harmonic decomposition to assess microstructural similarity within amygdala subfields are identified via similarity matrices using spectral k-mean clustering. The approach was tested on 32 healthy volunteers and three distinct amygdala subfields were identified including medial, posterior-superior lateral, and anterior-inferior lateral

    Physiographic Controls on Landfast Ice Variability from 20 Years of Maximum Extents across the Northwest Canadian Arctic

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    Landfast ice is a defining feature among Arctic coasts, providing a critical transport route for communities and exerting control over the exposure of Arctic coasts to marine erosion processes. Despite its significance, there remains a paucity of data on the spatial variability of landfast ice and limited understanding of the environmental processes’ controls since the beginning of the 21st century. We present a new high spatiotemporal record (2000–2019) across the Northwest Canadian Arctic, using MODIS Terra satellite imagery to determine maximum landfast ice extent (MLIE) at the start of each melt season. Average MLIE across the Northwest Canadian Arctic declined by 73% in a direct comparison between the first and last year of the study period, but this was highly variable across regional to community scales, ranging from 14% around North Banks Island to 81% in the Amundsen Gulf. The variability was largely a reflection of 5–8-year cycles between landfast ice rich and poor periods with no discernible trend in MLIE. Interannual variability over the 20-year record of MLIE extent was more constrained across open, relatively uniform, and shallower sloping coastlines such as West Banks Island, in contrast with a more varied pattern across the numerous bays, headlands, and straits enclosed within the deep Amundsen Gulf. Static physiographic controls (namely, topography and bathymetry) were found to influence MLIE change across regional sites, but no association was found with dynamic environmental controls (storm duration, mean air temperature, and freezing and thawing degree day occurrence). For example, despite an exponential increase in storm duration from 2014 to 2019 (from 30 h to 140 h or a 350% increase) across the Mackenzie Delta, MLIE extents remained relatively consistent. Mean air temperatures and freezing and thawing degree day occurrences (over 1, 3, and 12-month periods) also reflected progressive northwards warming influences over the last two decades, but none showed a statistically significant relationship with MLIE interannual variability. These results indicate inferences of landfast ice variations commonly taken from wider sea ice trends may misrepresent more complex and variable sensitivity to process controls. The influences of different physiographic coastal settings need to be considered at process level scales to adequately account for community impacts and decision making or coastal erosion exposure
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