4,655 research outputs found
Harnessing the power of yeast to unravel the molecular basis of neurodegeneration
No full textSeveral neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), amyotrophic lateral sclerosis (ALS), or prion diseases, are known for their intimate association with protein misfolding and aggregation. These disorders are characterized by the loss of specific neuronal populations in the brain and are highly associated with aging, suggesting a decline in proteostasis capacity may contribute to pathogenesis. Nevertheless, the precise molecular mechanisms that lead to the selective demise of neurons remain poorly understood. As a consequence, appropriate therapeutic approaches and effective treatments are largely lacking. The development of cellular and animal models that faithfully reproduce central aspects of neurodegeneration has been crucial for advancing our understanding of these diseases. Approaches involving the sequential use of different model systems, starting with simpler cellular models and ending with validation in more complex animal models, resulted in the discovery of promising therapeutic targets and small molecules with therapeutic potential. Within this framework, the simple and well-characterized eukaryote Saccharomyces cerevisiae, also known as budding yeast, is being increasingly used to study the molecular basis of several neurodegenerative disorders. Yeast provides an unprecedented toolbox for the dissection of complex biological processes and pathways. Here, we summarize how yeast models are adding to our current understanding of several neurodegenerative disorders
Yeast metabolism in fresh and frozen dough : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
No full textAuthor also known as SM LovedayFresh bakery products have a very short shelf life, which limits the extent to which manufacturing can be centralised. Frozen doughs are relatively stable and can be manufactured in large volumes, distributed and baked on-demand at the point of sale or consumption. With appropriate formulation and processing a shelf life of several months can be achieved.Shelf life is limited by a decline in proofing rate after thawing, which is attributed to a) the dough losing its ability to retain gas and b) insufficient gas production, i.e. yeast activity. The loss of shelf life is accelerated by delays between mixing and freezing, which allow yeast cells the chance to ferment carbohydrates.This work examined the reasons for insufficient gas production after thawing frozen dough and the effect of pre-freezing fermentation on shelf life. Literature data on yeast metabolite dynamics in fermenting dough were incomplete. In particular there were few data on the accumulation of ethanol, a major fermentation end product which can be injurious to yeast.Doughs were prepared in a domestic breadmaker using compressed yeast from a local manufacturer and analysed for glucose, fructose, sucrose, maltose and ethanol. Gas production after thawing declined within 48 hours of frozen storage. This was accelerated by 30 or 90 minutes of fermentation at 30;C prior to freezing.Sucrose was rapidly hydrolysed and yeast consumed glucose in preference to fructose. Maltose was not consumed while other sugars remained. Ethanol, accumulated from consumption of glucose and fructose, was produced in approximately equal amounts to CO2, indicating that yeast cells metabolised reductively.Glucose uptake in fermenting dough followed simple hyperbolic kinetics and fructose uptake was competitively inhibited by glucose. Mathematical modelling indicated that diffusion of sugars and ethanol in dough occurred quickly enough to eliminate solute gradients brought about by yeast metabolism
Abyssal NE Pacific Seafloor Megafauna Dataset
No full textBenthic megafauna (animals &gt; 10 mm) observations from seabed imagery data across the NE Pacific abyss Data repository associated with the following manuscript: Simon-Lledó, E., Amon, D.J., Bribiesca‐Contreras, G., Cuvelier, D., Durden, J.M., Ramalho, S.P., Uhlenkott, K., Martinez Arbizu, P., Benoist, N., Copley, J., Dahlgren, T.G., Glover, A.G., Fleming, B., Horton, T., Ju, S-J., Mejia-Saenz, A., McQuaid, K., Pape, E., Park, C., Smith, C.R., and Jones, D.O.B. (in press). Carbonate compensation depth drives abyssal biogeography in the northeast Pacific. Nature Ecology &amp; Evolution</span
Recall of random and distorted positions: Implications for the theory of expertise.
No full textThis paper explores the question, important to the theory of expert performance, of the nature and number of chunks that chess experts hold in memory. It examines how memory contents determine players' abilities to reconstruct (a) positions from games, (b) positions distorted in various ways and (c) and random positions. Comparison of a computer simulation with a human experiment supports the usual estimate that chess Masters store some 50,000 chunks in memory. The observed impairment of recall when positions are modified by mirror image reflection, implies that each chunk represents a specific pattern of pieces in a specific location. A good account of the results of the experiments is given by the template theory proposed by Gobet and Simon (in press) as an extension of Chase and Simon's (1973a) initial chunking proposal, and in agreement with other recent proposals for modification of the chunking theory (Richman, Staszewski & Simon, 1995) as applied to various recall tasks
Stochastic Optimal Control, International Finance and Debt
No full textWe use stochastic optimal control-dynamic programming (DP) to derive the optimal foreign debt/net worth, consumption/net worth, current account/net worth, and endogenous growth rate in an open economy. Unlike the literature that uses an Intertemporal Budget Constraint (IBC) or the Maximum Principle, the DP approach does not require perfect foresight or certainty equivalence. Errors of measurement and the effects of unanticipated shocks are corrected in an optimal manner. We contrast the DP and IBC approaches, show how the results of the dynamic programming approach can be interpreted in a traditional simple mean-variance/Tobin-Markowitz context, and explain why our results are generalizations of the Merton model.stochastic optimal control, foreign debt, international finance, vulnerability to external shocks, sustainable current account deficits
The beginnings of behavioral economics : Katona, Simon, and Leibenstein's X-efficiency theory /
No full text1. Introduction2. Two beginnings3. The "Big 3.#x94; Simon, Katona, Leibenstein4. It didn't just happen overnight5. Leibenstein before X-efficiency theory6. X-efficiency. An intervening variable7. Empirical research on XE: c.1967-19908. XE among US financial institutions9. XE among financial firms in Asia10. XE among Asian non-financial institutions11. XE in Europe12. XE in Australia and New Zealand, Latin America, the Middle East, Africa, and the world13. ConclusionsDescription based on CIP data; resource not viewed.Elsevie
A born-digital author lexicon for 17th c. French: Sévigné’s case
No full textPreparing an edition of Madame de Sévigné’s correspondance encoded in TEI, we are currently facing two problems. First, while French medievalists have a long experience of establishing lexicons, specialists of 17th c. French literature traditionally do not provide such a study in their editions. Second, we are not aware of any born-digital author lexicon in TEI for (17th c.) French language. We therefore have to tackle two problems at the same time, and create both a scientific methodology, a..
A born-digital author lexicon for 17th c. French: Sévigné’s case
No full textPreparing an edition of Madame de Sévigné’s correspondance encoded in TEI, we are currently facing two problems. First, while French medievalists have a long experience of establishing lexicons, specialists of 17th c. French literature traditionally do not provide such a study in their editions. Second, we are not aware of any born-digital author lexicon in TEI for (17th c.) French language. We therefore have to tackle two problems at the same time, and create both a scientific methodology, a..
Partial errors, confidence and detection task
No full textHuman beings have the ability to express confidence judgements on their own decisions. In case of perceptual decisions, confidence has been thought to depend upon the quality of the sensory input. In a recent article, Steve Fleming and colleagues questioned this view (Fleming, S.M., Maniscalco, B., Ko, Y., Amendi, N., Ro, T. & Lau, H. (2015) Action-specific disruption of perceptual confidence. Psychological Science). They manipulated response-specific representations in the premotor cortex with transcranial magnetic stimulation (TMS) in a perceptive task. They show that stimulating the motor representation associated with the unchosen response reduced confidence in correct answer, thereby demonstrating that « action-specific information in the premotor cortex contributes to perceptual confidence ».
It has been shown that in conflict tasks (like Simon or Eriksen flankers tasks) subjects make «partial errors»: these trials correspond to sub-threshold (yet detectable by electromyographic recording) motor responses that are successfully inhibited before they turn into an overt error (Hasbroucq, T., Possamaï, C. A., Bonnet, M., & Vidal, F. (1999). Effect of the irrelevant location of the response signal on choice reaction time: An electromyographic study in humans. Psychophysiology). Interestingly, it has been found that the supplementary motor area (either the SMA or pre-SMA) provides cognitive control signals to the primary motor cortex to exert online inhibition and in turn rectify the course of initial (incorrect) action (partial errors) (Roger, C., Núñez Castellar, E., Pourtois, G., & Fias, W. (2014). Changing your mind before it is too late: The electrophysiological correlates of online error correction during response selection. Psychophysiology). Similar EMG patterns (partial errors) have been observed for discrimination. Crucially, the link between confidence and partial error has not been studied yet. The reason is probably that partial errors have mainly been studied in conflict tasks (Simon or Eriksen) for which there is no post-decision ambiguity about the correctness of the provided answers.
This leads us to the question we aim to study: does the presence of partial errors modulate confidence in a detection task
Metamaterial fibres for subdiffraction imaging and focusing at terahertz frequencies over optically long distances
No full textUsing conventional materials, the resolution of focusing and imaging devices is limited by diffraction to about half the wavelength of light, as high spatial frequencies do not propagate in isotropic materials. Wire array metamaterials, because of their extreme anisotropy, can beat this limit; however, focusing with these has only been demonstrated up to microwave frequencies and using propagation over a few wavelengths only. Here we show that the principle can be scaled to frequencies orders of magnitudes higher and to considerably longer propagation lengths. We demonstrate imaging through straight and tapered wire arrays operating in the terahertz spectrum, with unprecedented propagation of near field information over hundreds of wavelengths and focusing down to 1/28 of the wavelength with a net increase in power density. Applications could include in vivo terahertz-endoscopes with resolution compatible with imaging individual cells.Alessandro Tuniz, Korbinian J. Kaltenecker, Bernd M. Fischer, Markus Walther, Simon C. Fleming, Alexander Argyros and Boris T. Kuhlme
- …
