Critical neural networks with short and long term plasticity

In recent years self organised critical neuronal models have provided insights regarding the origin of the experimentally observed avalanching behaviour of neuronal systems. It has been shown that dynamical synapses, as a form of short-term plasticity, can cause critical neuronal dynamics. Whereas long-term plasticity, such as hebbian or activity dependent plasticity, have a crucial role in shaping the network structure and endowing neural systems with learning abilities. In this work we provide a model which combines both plasticity mechanisms, acting on two different time-scales. The measured avalanche statistics are compatible with experimental results for both the avalanche size and duration distribution with biologically observed percentages of inhibitory neurons. The time-series of neuronal activity exhibits temporal bursts leading to 1/f decay in the power spectrum. The presence of long-term plasticity gives the system the ability to learn binary rules such as XOR, providing the foundation of future research on more complicated tasks such as pattern recognition.Comment: 8 pages, 7 figure

Perturbing the Shortest Path on a Critical Directed Square Lattice

We investigate the behaviour of the shortest path on a directed two-dimensional square lattice for bond percolation at the critical probability $p_c$ . We observe that flipping an edge lying on the shortest path has a non-local effect in the form of power-law distributions for both the differences in shortest path lengths and for the minimal enclosed areas. Using maximum likelihood estimation and extrapolation we find the exponents $\alpha = 1.36 \pm 0.01$ for the path length differences and $\beta = 1.186 \pm 0.001$ for the enclosed areas

Recent trends in daily temperature extremes over southern Montenegro (1951–2010)

Montenegro so far has been poorly investigated in terms of climate extremes. The aim of this paper was to analyse the extreme ETCCDI (Expert Team on Climate Change Detection and Indices) temperature indices in the Mediterranean region of Montenegro for the period of 1951–2010. Four stations in the coastal area of Montenegro have been analysed: Herceg Novi, Ulcinj, Budva and Bar. Two periods (before 1980 and after 1980) were separately investigated in this study due to a well-known climate shift that occurred in the late 1970s. Seven indices of temperature extremes have been chosen. The trend was analysed using a Mann–Kendall non-parametric test, while the slope was estimated using Sen's slope estimator. A negative trend has been calculated for cold nights and cold days at almost all stations. The most significant positive trends were obtained for warm conditions. The two separately investigated periods have shown contrasting temperature trends

High resolution grid of potential incoming solar radiation for Serbia

Solar radiation is a key driving force for many natural processes. At the Earth's surface solar radiation is the result of complex interactions between the atmosphere and Earth's surface. Our study highlights the development and evaluation of a data base of potential solar radiation that is based on a digital elevation model with a resolution of 90 m over Serbia. The main aim of this paper is to map solar radiation in Serbia using digital elevation model. This is so far the finest resolution being applied and presented using this model. The final results of the potential direct, diffuse and total solar radiation as well as duration of insolation databases of Serbia are portrayed as thematic maps that can be communicated and shared easily through the cartographic web map-based service

Precipitation extremes in the wettest Mediterranean region (Krivošije) and associated atmospheric circulation types

The aim of this paper is to analyse indices of extreme precipitation in Krivošije, Montenegro, the wettest Mediterranean region, from the period 1951–2007 and their relationships with atmospheric circulation using "SynopVis Grosswetterlagen" (SVG) series. Data from two stations were analysed, namely Crkvice (42°34'N and 18°39'E) and Herceg Novi (42°27'N and 18°31'E). Four indices of precipitation extremes (SDII, R75p, R95p, R95pTOT) were assessed including number of dry days. The results suggest that the number of days with precipitation decreased. To analyse the relationship between extreme precipitation events and circulation types we have used an efficiency coefficient (<i>E</i><sub>c</sub>). Regarding relation to atmospheric circulation, westerly, southwesterly and northwesterly circulation types with anticyclonic features over Central Europe are more frequent for dry days (days with <i>R</i><1.0 mm) and northerly, easterly and southerly types for wet and very wet days (R75p and R95p indices). The types with cyclonic condition over Central Europe show a large proportion of wet and very wet days. Also, activity of Genoa cyclogenesis and orographic influence over a small area are the main reasons for the high precipitation amounts recorded in the Krivošije region (Crkvice)

Do brain networks evolve by maximizing their information flow capacity?

We propose a working hypothesis supported by numerical simulations that brain networks evolve based on the principle of the maximization of their internal information flow capacity. We find that synchronous behavior and capacity of information flow of the evolved networks reproduce well the same behaviors observed in the brain dynamical networks of Caenorhabditis elegans and humans, networks of Hindmarsh-Rose neurons with graphs given by these brain networks. We make a strong case to verify our hypothesis by showing that the neural networks with the closest graph distance to the brain networks of Caenorhabditis elegans and humans are the Hindmarsh-Rose neural networks evolved with coupling strengths that maximize information flow capacity. Surprisingly, we find that global neural synchronization levels decrease during brain evolution, reflecting on an underlying global no Hebbian-like evolution process, which is driven by no Hebbian-like learning behaviors for some of the clusters during evolution, and Hebbian-like learning rules for clusters where neurons increase their synchronization

The politics of performance: transnationalism and its limits in former Yugoslav popular music, 1999–2004

This paper examines transnational relations between the Yugoslav successor states from the point of view of popular music, and demonstrates how transnational musical figures (such as Djordje Balaševi?, Mom?ilo Bajagi?-Bajaga and Ceca Ražnatovi?) are interpreted as symbolic reference points in national ethnopolitical discourse in the process of identity construction. Another symbolic function is served by Serbian turbofolk artists, who in Croatia serve as a cultural resource to distance oneself from a musical genre associated by many urban Croats with the ruralization (and Herzegovinization) of Croatian city space. In addition, value judgements associated with both Serbian and Croatian newly composed folk music provide an insight into the transnational negotiation of conflicting identities in the ex-Yugoslav context. Ultimately the paper shows how the ethnonational boundaries established by nationalizing ideologies created separate cultural spaces which themselves have been transnationalized after Yugoslavia's disintegration

Influence of humidity on complex impedance and dielectric properties of iron manganite (FeMnO3)

Bulk samples of iron manganite with a cubic Ia3 lt mml:mo stretchy="false"> lt overbar> lt /mml:mover> crystal structure were obtained by solid state synthesis (combination of milling and calcination) of starting hematite (Fe2O3) and manganese carbonate (MnCO3) powders followed by sintering green samples at 1000 degrees C for 4h. Structural characterization performed by XRD and SEM analysis confirmed the formation of iron manganite in the form of a porous network of grains and pores with average particle size of 530 and 430nm, respectively. The influence of humidity on complex impedance and dielectric properties was monitored in the relative humidity range 30-90% in a climatic chamber in the frequency range 42Hz-1MHz at working temperatures of 25 and 50 degrees C. At the lowest frequency of 42Hz the impedance reduced with relative humidity from 57.9 (RH 30%) to 3.21M ohm (RH 90%) at 25 degrees C, and from 23.3 (RH 30%) to 1.3M ohm (RH 90%) at 50 degrees C that is approximately 20 times. Analysis of complex impedance using an equivalent circuit showed the dominant influence of grain boundaries. The influence of grains (bulk) was taken into account for higher relative humidity values (70% at 25 degrees C and 60% at 50 degrees C) that is related to the mechanism of water interaction with the sample surface. The dielectric constant and loss tangent decreased with increase in frequency in accordance with the Maxwell-Wagner type interfacial polarization mechanism and also increased with increase in relative humidity