10,157 research outputs found
Integrating Stakeholder Input into Water Policy Development and Analysis
Agricultural water use is becoming an issue in much of the South due to population growth. Results of projects evaluating the impacts of conservation strategies aimed at reallocating or extending the life of water supplies are being met with great skepticism by stakeholder groups. In order to gain acceptance of results, it is essential that stakeholder groups be involved from the beginning in the identification of potential water conservation strategies and be kept informed throughout the project. The objective of this paper is to review previous attempts at involving stakeholders and the methodology currently being employed in the Ogallala Aquifer Project.conservation, Ogallala Aquifer, stakeholder, water policy, Agribusiness, Agricultural and Food Policy, Consumer/Household Economics, Q250, Q280,
Mesoscopic and continuum modelling of angiogenesis
Angiogenesis is the formation of new blood vessels from pre-existing ones in
response to chemical signals secreted by, for example, a wound or a tumour. In
this paper, we propose a mesoscopic lattice-based model of angiogenesis, in
which processes that include proliferation and cell movement are considered as
stochastic events. By studying the dependence of the model on the lattice
spacing and the number of cells involved, we are able to derive the
deterministic continuum limit of our equations and compare it to similar
existing models of angiogenesis. We further identify conditions under which the
use of continuum models is justified, and others for which stochastic or
discrete effects dominate. We also compare different stochastic models for the
movement of endothelial tip cells which have the same macroscopic,
deterministic behaviour, but lead to markedly different behaviour in terms of
production of new vessel cells.Comment: 48 pages, 13 figure
Hybrid approaches for multiple-species stochastic reaction-diffusion models
Reaction-diffusion models are used to describe systems in fields as diverse
as physics, chemistry, ecology and biology. The fundamental quantities in such
models are individual entities such as atoms and molecules, bacteria, cells or
animals, which move and/or react in a stochastic manner. If the number of
entities is large, accounting for each individual is inefficient, and often
partial differential equation (PDE) models are used in which the stochastic
behaviour of individuals is replaced by a description of the averaged, or mean
behaviour of the system. In some situations the number of individuals is large
in certain regions and small in others. In such cases, a stochastic model may
be inefficient in one region, and a PDE model inaccurate in another. To
overcome this problem, we develop a scheme which couples a stochastic
reaction-diffusion system in one part of the domain with its mean field
analogue, i.e. a discretised PDE model, in the other part of the domain. The
interface in between the two domains occupies exactly one lattice site and is
chosen such that the mean field description is still accurate there. This way
errors due to the flux between the domains are small. Our scheme can account
for multiple dynamic interfaces separating multiple stochastic and
deterministic domains, and the coupling between the domains conserves the total
number of particles. The method preserves stochastic features such as
extinction not observable in the mean field description, and is significantly
faster to simulate on a computer than the pure stochastic model.Comment: 38 pages, 8 figure
IST Austria Thesis
Brain function is mediated by complex dynamical interactions between excitatory and inhibitory cell types. The Cholecystokinin-expressing inhibitory cells (CCK-interneurons) are one of the least studied types, despite being suspected to play important roles in cognitive processes. We studied the network effects of optogenetic silencing of CCK-interneurons in the CA1 hippocampal area during exploration and sleep states. The cell firing pattern in response to light pulses allowed us to classify the recorded neurons in 5 classes, including disinhibited and non-responsive pyramidal cell and interneurons, and the inhibited interneurons corresponding to the CCK group. The light application, which inhibited the activity of CCK interneurons triggered wider changes in the firing dynamics of cells. We observed rate changes (i.e. remapping) of pyramidal cells during the exploration session in which the light was applied relative to the previous control session that was not restricted neither in time nor space to the light delivery. Also, the disinhibited pyramidal cells had higher increase in bursting than in single spike firing rate as a result of CCK silencing. In addition, the firing activity patterns during exploratory periods were more weakly reactivated in sleep for those periods in which CCK-interneuron were silenced than in the unaffected periods. Furthermore, light pulses during sleep disrupted the reactivation of recent waking patterns. Hence, silencing CCK neurons during exploration suppressed the reactivation of waking firing patterns in sleep and CCK interneuron activity was also required during sleep for the normal reactivation of waking patterns. These findings demonstrate the involvement of CCK cells in reactivation-related memory consolidation. An important part of our analysis was to test the relationship of the identified CCKinterneurons to brain oscillations. Our findings showed that these cells exhibited different oscillatory behaviour during anaesthesia and natural waking and sleep conditions. We showed that: 1) Contrary to the past studies performed under anaesthesia, the identified CCKinterneurons fired on the descending portion of the theta phase in waking exploration. 2) CCKinterneuron preferred phases around the trough of gamma oscillations. 3) Contrary to anaesthesia conditions, the average firing rate of the CCK-interneurons increased around the peak activity of the sharp-wave ripple (SWR) events in natural sleep, which is congruent with new reports about their functional connectivity. We also found that light driven CCK-interneuron silencing altered the dynamics on the CA1 network oscillatory activity: 1) Pyramidal cells negatively shifted their preferred theta phases when the light was applied, while interneurons responses were less consistent. 2) As a population, pyramidal cells negatively shifted their preferred activity during gamma oscillations, albeit we did not find gamma modulation differences related to the light application when pyramidal cells were subdivided into the disinhibited and unaffected groups. 3) During the peak of SWR events, all but the CCK-interneurons had a reduction in their relative firing rate change during the light application as compared to the change observed at SWR initiation. Finally, regarding to the place field activity of the recorded pyramidal neurons, we showed that the disinhibited pyramidal cells had reduced place field similarity, coherence and spatial information, but only during the light application. The mechanisms behind such observed behaviours might involve eCB signalling and plastic changes in CCK-interneuron synapses. In conclusion, the observed changes related to the light-mediated silencing of CCKinterneurons have unravelled characteristics of this interneuron subpopulation that might change the understanding not only of their particular network interactions, but also of the current theories about the emergence of certain cognitive processes such as place coding needed for navigation or hippocampus-dependent memory consolidation
Variational Mote Carlo Study of Flat Band Ferromagnetism -- Application to CeRh_3 B_2
A new mechanism for ferromagnetism in CeRh_3B_2 is proposed on the basis of
variational Monte Carlo results. In a one-dimensional Anderson lattice where
each 4f electron hybridizes with a ligand orbital between neighboring Ce sites,
ferromagnetism is stabilized due to a nearly flat band which is a mixture of
conduction and 4f electron states. Because of the strong spin-orbit interaction
in 4f electron states, and of considerable amount of hybridization in the
nearly flat band, the magnetic moments from 4f and conduction electrons tend to
cancel each other. The resultant ferromagnetic moment becomes smaller as
compared with the local 4f moment, and the Fermi surface in the ferromagnetic
ground state is hardly affected by the presence of 4f electrons. These
theoretical results are consistent with experimental observations in CeRh_3B_2
by neutron scattering and dHvA effects.Comment: to be published in J.Phys.Soc.Jp
Building a Sentiment Corpus of Tweets in Brazilian Portuguese
The large amount of data available in social media, forums and websites
motivates researches in several areas of Natural Language Processing, such as
sentiment analysis. The popularity of the area due to its subjective and
semantic characteristics motivates research on novel methods and approaches for
classification. Hence, there is a high demand for datasets on different domains
and different languages. This paper introduces TweetSentBR, a sentiment corpora
for Brazilian Portuguese manually annotated with 15.000 sentences on TV show
domain. The sentences were labeled in three classes (positive, neutral and
negative) by seven annotators, following literature guidelines for ensuring
reliability on the annotation. We also ran baseline experiments on polarity
classification using three machine learning methods, reaching 80.99% on
F-Measure and 82.06% on accuracy in binary classification, and 59.85% F-Measure
and 64.62% on accuracy on three point classification.Comment: Accepted for publication in 11th International Conference on Language
Resources and Evaluation (LREC 2018
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