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Feedforward inhibition and synaptic scaling are important adaptive processes that control the total input a neuron can receive from its afferents. While often studied in isolation, the two have been reported to co-occur in various brain regions. The functional implications of their interactions remain unclear, however. Based on a probabilistic modeling approach, we show here that fast feedforward inhibition and synaptic scaling interact synergistically during unsupervised learning. In technical terms, we model the input to a neural circuit using a normalized mixture model with Poisson noise. We demonstrate analytically and numerically that, in the presence of lateral inhibition introducing competition between different neurons, Hebbian plasticity and synaptic scaling approximate the optimal maximum likelihood solutions for this model. Our results suggest that, beyond its conventional use as a mechanism to remove undesired pattern variations, input normalization can make typical neural interaction and learning rules optimal on the stimulus subspace defined through feedforward inhibition. Furthermore, learning within this subspace is more efficient in practice, as it helps avoid locally optimal solutions. Our results suggest a close connection between feedforward inhibition and synaptic scaling which may have important functional implications for general cortical processing.
The vegetation of the Mount Murchison and Wilga areas, Paroo Darling National Park (latitude 31o00’-32o 40’S and longitude 142o10’-144o25’E) in north western New South Wales was assessed using intensive quadrat sampling and mapped using extensive ground truthing and interpretation of aerial photograph and Landsat Thematic Mapper satellite images. In the survey 237 vascular plant species including 37 (15.6%) exotic species, from 46 families were recorded. Seventeen vegetation communities were identified and mapped, 15 for Mount Murchison area and 13 for the Wilga area. The most widespread for Mount Murchison being Maireana pyramidata low open shrubland, Flindersia maculosa low open woodland, Muehlenbeckia florulenta open shrubland and Eucalyptus coolabah / Eucalyptus largiflorens open woodland. The most widespread for Wilga being Muehlenbeckia florulenta open shrubland and Eucalyptus coolabah / Eucalyptus largiflorens open woodland. Many of these communities have been impacted by a history of 150 years of pastoral use.
The listed threatened plant taxa within the South Coast Region of New South Wales (Helensburgh to Batemans Bay, as designated by the NSW National Parks and Wildlife Service) are documented. Of the 100 NSW listed taxa, 69 are also listed by the Commonwealth, while two additional taxa are only listed by the Commonwealth. An analysis of the individual taxa and the 62 conservation reserves in the region, found that 30 taxa can with confidence be said to be adequately reserved, while 50 are assessed as inadequately reserved; for the remaining 22 taxa, reservation status is unknown. Examples of challenges for the conservation of threatened plants in the region are examined; these challenges have relevance well beyond the South Coast Region. Managing for individual plant species may be hampered by a lack of basic ecological information; this is particularly so for the rarer species such as orchids. One of the main areas where information is lacking is the response of most species to bushfire. Conservation on private land is becoming an increasingly important and challenging area for plant species conservation as the last large areas of public land are dedicated for one purpose or another. A more co-ordinated approach to conservation on private land may produce improved outcomes for many inadequately reserved taxa.
Species may become vulnerable because of a reduction of habitat, leading to reduction of population sizes and an increase in geographic isolation between populations, leading to genetic drift that may result in reduced reproductive fitness. The restricted sedge Gahnia insignis S.T. Blake (family Cyperaceae), occurring in isolated pockets in north-east New South Wales and Queensland, was compared to a closely related, sympatric, common and widespread Gahnia clarkei Benl for flowering phenology and reproductive success. Flowering patterns, examination of pollen, fertilisation and embryo development and seed-ovule ratios show Gahnia clarkei has every indication of successful sexual reproduction, but that Gahnia insignis appears to reproduce mostly by vegetative means, with an occasional sexual event. This was due to the rarity of pollination opportunities, and to poor pollen viability and pollen quantity, resulting in a much lower seed-ovule ratio than Gahnia clarkei. The additional high level of vegetative reproduction in Gahnia insignis suggests it may be largely clonal in Nightcap National Park. A genetic study of the whole distribution would add knowledge of the species genetic diversity and differentiation between populations.
Free riders play fair
(2012)
After the demise of the social contract theory, the argument from fair play, which employs the principle of fair play, has been widely acknowledged as one of the most promising ways of justifying political obligation. First, I articulate the most promising version of the principle of fair play. Then, I show that free riders play fair, that is, that their moral fault lies not in unfairness but in the violation of a rule by appealing to the example of three-in-a-boat. Finally, I conclude that even the most promising version is false because those who have accepted benefits from a social cooperative scheme do not owe an obligation of fair play.
When judges are authorised to invalidate legal acts for being unconstitutional, the competence of the legislator is directly concerned. The question raises, if thus judges do not usurp legislative power. In the traditional doctrine of the separation of powers the parliament is the first power, based on its direct democratic legitimacy. Yet cancelling legal acts completely or partially does evoke more irritations in the public that could be expected. The people seem to have more confidence to the assumed impartiality of the judges than to the results of the parliamentary work which seems to be dominated by the struggles of the parties. The necessity of judicial review mainly is based on the consideration that individual rights even in an authentic democratic system may be violated by a legal act of the parliament. In this case constitutional courts have the very task to defend individual rights, principles of liberty and authentic equality. Therefore it is justified to speak of the “jurisdiction of liberty”, as the Italian constitutional expert Cappelletti has said. But also without such legitimacy in many countries the Courts intervene in the field of the legislator. The courts themselves discuss the limits of judicial interventions, emphasising themselves, that they have to respect the legislative decisions principally, but do not abide always by their own proclaimed principles. In Spanish recent publications it is spoken of the principle “in dubio pro legislatore”, (in case of doubt in favour the legislator), reminding of “in dubio pro reo”, in order to treat the legislative power not worse than the defendant in a criminal process..
This paper reconstructs the argument of Axel Honneth's recent book Das Recht der Freiheit as a theory of the institutionalization of freedom in modern society. In particular, it looks at Honneth's argument for the realization of freedom in law and morality that is proposed as a contemporary re-interpretation of Hegel's Philosophy of Right. Then I discuss Honneth's argument for the reality of freedom in the ethical spheres of civil society, in particular in the family, the market and in democracy. Finally, the paper proposes some critical remarks to Honneth's theory.
We provide a mathematical framework to model continuous time trading in limit order markets of a small investor whose transactions have no impact on order book dynamics. The investor can continuously place market and limit orders. A market order is executed immediately at the best currently available price, whereas a limit order is stored until it is executed at its limit price or canceled. The limit orders can be chosen from a continuum of limit prices.
In this framework we show how elementary strategies (hold limit orders with only finitely many different limit prices and rebalance at most finitely often) can be extended in a suitable
way to general continuous time strategies containing orders with infinitely many different limit prices. The general limit buy order strategies are predictable processes with values in the set of nonincreasing demand functions (not necessarily left- or right-continuous in the price variable). It turns out that this family of strategies is closed and any element can be approximated by a sequence of elementary strategies.
Furthermore, we study Merton’s portfolio optimization problem in a specific instance of this framework. Assuming that the risky asset evolves according to a geometric Brownian
motion, a proportional bid-ask spread, and Poisson execution times for the limit orders of the small investor, we show that the optimal strategy consists in using market orders to keep the
proportion of wealth invested in the risky asset within certain boundaries, similar to the result for proportional transaction costs, while within these boundaries limit orders are used to profit from the bid-ask spread.