177,167 research outputs found
Caroni Swamp
No full textCaroni Swamp material collected by Professor Peter R. Bacon. The collection deals with the campaign led by Professor Bacon and the Blue River Action Committee against the attempt by Shell Trinidad Limited to transport liquified propane gas by barge through the Caroni Swam
Proportional hazards models with discrete frailty
No full textWe extend proportional hazards frailty models for lifetime data to allow a negative bi-nomial, Poisson, Geometric or other discrete distribution of the frailty variable. This might represent, for example, the unknown number of flaws in an item under test. Zero frailty corresponds to a limited failure model containing a proportion of units that never fail (long- term survivors). Ways of modifying the model to avoid this are discussed. The models areapplied to a previously published set of data on failures of printed circuit boards and to new data on breaking strengths of samples of cord
Microcircuit remodeling processes underlying learning in the adult
No full textOne of the most intriguing discoveries in neuroscience of the past decades has been showing that experience is able to induce structural modifications in cortical microcircuit that might underlie the formation of memories upon learning (for a review, see Caroni, Donato and Muller 2012). Hence, learning induces phases of synapse formation and elimination that are strictly regulated by a variety of mechanisms, which impact on cortical microcircuits affecting both excitatory and inhibitory neurons. Nevertheless, the extent to which specific configurations might be implemented to support specific phases of learning, as well as the impact of experience-induced structural modifications on further learning, is still largely unknown.
Here, I explore how the remodeling of identified microcircuits in the mouse hippocampus and neocortex supports learning in the adult.
In the first part, I identifiy a microcircuit module engaging VIP and Parvalbumin (PV) positive interneurons to regulate the state of the PV+ network upon experience. This defines states of enhanced or reduced structural plasticity and learning based on the distribution of PV intensity in the network.
In the second part, I demonstrate how specific hippocampal subdivisions are exploited to learn subtasks of trial-and-errors forms of learning via the deployment of increasingly precise searching strategies, and sequential recruitment of ventral, intermediate, and dorsal hippocampus.
In the third part, I highlight the existence of genetically matched subpopulations of principal cells in the hippocampus, which achieve selective connectivity across hippocampal subdivisions via matched windows of neurogenesis and synaptogenesis during development.
In the fourth part, I investigate the maturation of microcircuits mediating feedforward inhibition in the hippocampus, and highlight windows during development for the establishment of the proper baseline configuration in the adult. Moreover, I identify a critical window for cognitive enhancement during hippocampal development.
In the fifth part, I study how ageing affects the PV network in hippocampal CA3, providing evidence for which age related neuronal loss correlates to reduced incidental learning performances in old mice. Therefore, by manipulating the PV network early during life, I provide strategies to modulate cognitive decline
Seasonal and plurennial changes of POPs repository in freshwater zooplankton: A 10-year study in the large deep subalpine Lake Maggiore (Italy)
No full textDetermining the concentration of POPs (Persistent Organic Pollutants) such as total dichlorodiphenyltrichloroethane (DDTtot) and polychlorinated biphenyls (PCBs) in the zooplankton is essential for evaluating the level of toxicity in the environment and the risk to ecosystem health. The extent to which POPs persist in the environment and affect human health depends on accumulation in the different components of the zooplankton community such as particle feeders and/or predators and their subsequent consumption by fish, which varies seasonally. We analyzed ten-years (2011–2020) of seasonal data on POPs in the crustacean zooplankton community of Lake Maggiore (Italy). The concentration of total DDTs, as sum of all congeners ranged between 23.5 and 156.9 ng/g dry weight, while sumPCB14 ranged from 24.4 and 133.6 ng/g dry weight. We traced particle feeders' vs predatory taxa within the zooplankton community using carbon and nitrogen stable isotopic values. POPs concentration was significantly related to the nitrogen isotopic values. The zooplankton biomass increase in Spring was important, both through this being a period of increased metabolism and activity of planktivorous fish and also as it was the period when the zooplankton repository of POPs was at a maximum. DDTtot stocked in zooplankton ≥450 μm was up to 275 ng/m2, while sumPCB14 was 285 ng/m2 in 2013. A decrease of DDTtot stocked in the zooplankton repository characterized the last five years examined, when mean annual values (14.8–56.9 ng/m2) were less than half those of the previous period (50.7–128.6 ng/m2)
Zooplankton taxa repository of DDTtot and sumPCB14: Seasonal and decadal variations in Lake Maggiore
No full textLake Maggiore has been the subject of a monitoring program on persistent organic pollutants (DDTs and PCBs) since 1996 when DDT contamination was first detected. In this context, in 2009 we started to estimate the concentration of DDTtot (Dichlorodiphenyltrichloroethane, sum of p,p’-DDT, o,p’-DDT, p,p’-DDD, o,p-DDD, p,p-DDE, o,p-DDE) and sumPCB14 (polychlorinated biphenyls 18, 28, 31, 44, 52, 101, 118, 149, 138, 153, 170, 180, 194 and 209) in zooplankton pelagic organisms preyed on by zooplanktivorous fish (size fraction ≥450 μm). We evaluated taxa specific repositories of DDTtot and sumPCB14, their seasonal variation, their changes over the period 2009–2021 and the potential contribution of different taxa in transferring toxicants to whitefish, based on the Ivlev's Electivity Index. The repository of both POPs was generally higher in spring. A decrease in the zooplankton Standing Stock Biomass (SSB) drove a decline in the zooplankton DDTtot repository over the last six years (2016–2021 SSBmean = 12.5 mg m−3; 2009–2015; SSBmean = 30 mg m−3), despite the concentration being broadly constant during this period. The sumPCB14 repository was generally characterized by lower values during the last six years, but the difference with the previous period was not so marked. Daphnia and cyclopoids were the major contributors to the repository; however, when the whitefish selectivity index was applied, the role of carnivorous Bythotrephes was more important to the detriment of cyclopoids, particularly in summer and winter. Our results are useful to elaborate predictive models on the transfer of POPs along the food chain and highlight not only the importance of freshwater zooplankton in toto, but also that different taxa can have different roles. The increasing importance of microphagous zooplankton, driven by water warming and extended thermal stratification, underlines the need for future studies on the role of small zooplankton as carriers of POPs in freshwater lakes
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Regional and subpopulation rules for plasticity in the adult mouse hippocampus
No full textThe aim of my thesis was to elucidate regional and subpopulation rules for structural plasticity in the adult mouse hippocampus, which can provide insights to information processing and memory formation within the hippocampal circuitry.
Previous studies have shown that dorsal, intermediate and ventral hippocampus have distinct coding and behavioural roles, consistent with the distinct afferent and efferent connectivities along the longitudinal (dorsoventral) axis of the hippocampus. In addition, evidence for distinct hippocampal regions has been provided in the form of discrete molecular domains of gene expression across the hippocampus. However, none of these studies has investigated the anatomy and connectivity at the level of individual identified neurons. Also, it still remains unknown whether structural plasticity upon experience and learning may differ along the dorsoventral axis of the hippocampus and across distinct mossy fibre subpopulations.
To address these questions, I mapped granule cell mossy fibre anatomy and connectivity throughout the hippocampus in three “sparse” Thy1 transgenic reporter mice (Lsi1, Lsi2 and Lsi3) that express membrane-targeted GFP in a subset of principal neurons. By combining behavioural and lesion experiments, as well as high-resolution confocal microscopy and gene expression analysis, I provide evidence that distinct regions of the hippocampus (dorsal, intermediate and ventral) and distinct subpopulations of granule cells exhibit different anatomy and connectivity under baseline conditions and upon learning. Using the growth of filopodial synapses that mediate feed-forward inhibition to the network in CA3 as a specific readout for learning, I show that the dorsal hippocampus encodes spatial information and is specifically recruited for spatial learning, while the ventral hippocampus encodes goal-oriented information and is specifically recruited for goal-oriented learning. Moreover, the results reveal objective distinctions at the circuit level between hippocampal-dependent memory and hippocampal-dependent learning. In addition, I provide evidence that distinct granule cell subpopulations respond in unique ways to experience and learning, suggesting that principal neuron subpopulations may have distinct functional roles in hippocampal-dependent learning and memory
Investigation of Pollution from Land Based Sources and Activities and their Impacts on the Marine Environment: the Caroni River Basin
No full text"The Institute of Marine Affairs (IMA) is investigating the impacts of pollution from land-based sources and
activities of the Caroni River Basin (CRB) on the marine environment...
The project will investigate the types, sources, levels of pollution, fate of pollutants, and potential impacts on the marine environment. In addition, the
project will investigate the impacts of physical alterations of habitats caused by land uses in the Caroni River Basin."This poster was created for World Wetlands Day
Stable isotope analysis and persistent organic pollutants in crustacean zooplankton: The role of size and seasonality(Article)(Open Access) Piscia,
No full text"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
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