Phase and precession evolution in the Burgers equation

We present a phenomenological study of the phase dynamics of the one-dimensional stochastically forced Burgers equation, and of the same equation under a Fourier mode reduction on a fractal set. We study the connection between coherent structures in real space and the evolution of triads in Fourier space. Concerning the one-dimensional case, we find that triad phases show alignments and synchronisations that favour energy fluxes towards small scales --a direct cascade. In addition, strongly dissipative real-space structures are associated with entangled correlations amongst the phase precession frequencies and the amplitude evolution of Fourier triads. As a result, triad precession frequencies show a non-Gaussian distribution with multiple peaks and fat tails, and there is a significant correlation between triad precession frequencies and amplitude growth. Links with dynamical systems approach are briefly discussed, such as the role of unstable critical points in state space. On the other hand, by reducing the fractal dimension $D$ of the underlying Fourier set, we observe: i) a tendency toward a more Gaussian statistics, ii) a loss of alignment of triad phases leading to a depletion of the energy flux, and iii) the simultaneous reduction of the correlation between the growth of Fourier mode amplitudes and the precession frequencies of triad phases

ACTIVITY OF RAT DORSAL STRIATAL MEDIUM SPINY NEURONS DURING ODOUR SAMPLING IN A WORKING MEMORY CAPACITY TASK

Working memory is an important cognitive function that allows us to perform everyday tasks including language comprehension and reasoning. It is, therefore, unsurprising that working memory dysfunction has been detected in many neurodegenerative and psychiatric disorders, such as schizophrenia. The striatum is an important brain region for working memory in both humans and rats, but its role remains unclear. While increased striatal activity has been shown during information updating in human working memory tasks, assessment of striatal activity during information maintenance, the retention of information for cognitive processes, have generated mixed results. No previous studies were examined striatal activity in rats completing a working memory task, although medium spiny neurons have been shown to increase activity after a reward was received in short-term memory tasks. Therefore, in the present study, I examined the activity of medium spiny neurons of the dorsomedial striatum when receiving a reward and also, when rats approached familiar and novel odours during the odour span task. Rats were then administered MK801, an N-Methyl-D-Aspartate receptor antagonist, and observed for any putative changes in neural activity during the odour span task. I observed significantly increased activity in a population of medium spiny neurons after a reward was received, while no changes of activity were detected in response to rats approaching a familiar odour. The results from the activity of medium spiny neurons in response to novel odours was inconclusive. Neural activity was recorded 30 minutes following MK801 administration. During the last 10 minutes of the recording, medium spiny neurons significantly increased activity compared to a baseline recording pre-injection. By increasing our knowledge regarding the neural activity underlying working memory and how it is affected by psychoactive drugs, our understanding of how to treat working memory dysfunction may improve

Status Report on Acrylamide in Potato Products

End of Project ReportThis status report was conducted as part of Task 1 of a research project (RMIS No. 5265) on the development and quantification of acrylamide in potatoes and potato products funded under the Food Institutional Research Measure (FIRM) of the Department of Agriculture and Food as part of the National Development Plan. Teagasc acknowledges the support of theDepartment of Agriculture and FoodAcrylamide is a toxin that can potentially occur in high concentrations in heated starchy foods especially potato products such as crisps and french fries. In model systems isotopic substitution studies have demonstrated that acrylamide is formed via the Maillard type reaction between the amino acid aspargine and a carbonyl source such as the reducing sugars glucose and fructose. Levels of acrylamide in cooked potato products are primarily influenced by the levels of reducing sugars in the product and this in turn is influenced by storage time, temperature and variety of potato used. During cooking acrylamide formation begins to occur at temperatures above 100°C and increases up to temperatures of 220°C but decreases thereafter due to thermal degradation of the compound. Risk assessment studies on acrylamide intakes have been conducted in a number of countries and mg/kg body weight daily intakes have been estimated to be between 0.2-0.8. Adequate analytical techniques exist for quantification of acrylamide in potato and are mainly based around liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) and gas chromatography mass spectrometry (GC-MS) techniquesDepartment of Agriculture, Food and the Marin

Memory for associative integrations depends on emotion and age

Thesis advisor: Elizabeth A. KensingerA key feature of human memory is the ability to remember not only discrete pieces of information but also to form novel associations between them. A special type of association, called an "integration", can be formed when the pieces are encoded as a single representation in memory (Wollen, Weber and Lowry, 1972; Murray and Kensinger, 2012). The work presented here investigates what neural mechanisms underlie the formation and subsequent retrieval of integrated mental images in younger adulthood (individuals aged 18-30), whether those mechanisms differ based on the emotional content of the integration, and whether older and younger adults generate and remember emotional integrations differently from one another. I show that younger adults utilize two different routes to form integrations, depending on their emotional content: a rapid, perceptually-supported route that allows for fast integration of emotional pairs but that leads to poor downstream memory for the associates, and a slow, conceptually-supported route for neutral pairs that takes more time but that leads to strong downstream memory. Conversely, older adults utilize slow, controlled processing of emotional integrations that leads to strong memory, but they fail to produce durable memory for non-emotional pairs due to age-related associative deficits. Together, these results highlight differences both within and between age groups in the formation and retrieval of emotional and non-emotional integrations, and suggest a circumstance - integration of emotional pairs - in which older adults can overcome previously reported age-related deficits.Thesis (PhD) — Boston College, 2013.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Psychology

Maternal immune activation during pregnancy in rats impairs working memory capacity of the offspring

Peer Reviewe