Divisive Gain Modulation with Dynamic Stimuli in Integrate-and-Fire Neurons

The modulation of the sensitivity, or gain, of neural responses to input is an important component of neural computation. It has been shown that divisive gain modulation of neural responses can result from a stochastic shunting from balanced (mixed excitation and inhibition) background activity. This gain control scheme was developed and explored with static inputs, where the membrane and spike train statistics were stationary in time. However, input statistics, such as the firing rates of pre-synaptic neurons, are often dynamic, varying on timescales comparable to typical membrane time constants. Using a population density approach for integrate-and-fire neurons with dynamic and temporally rich inputs, we find that the same fluctuation-induced divisive gain modulation is operative for dynamic inputs driving nonequilibrium responses. Moreover, the degree of divisive scaling of the dynamic response is quantitatively the same as the steady-state responses—thus, gain modulation via balanced conductance fluctuations generalizes in a straight-forward way to a dynamic setting

Thin-shell wormholes from black holes with dilaton and monopole fields

We provide a new type of thin-shell wormhole from the black holes with dilaton and monopole fields. The dilaton and monopole that built the black holes may supply fuel to construct the wormholes. Several characteristics of this thin-shell wormhole have been discussed. Finally, we discuss the stability of the thin-shell wormholes with a "phantom-like" equation of state for the exotic matter at the throat.Comment: 6 pages and 3 figures, some typos are corrected and accepted in Int.J.Theor.Phy

Implementation and analysis of the TCP \u201cAdaptive-Selection\u201d Concept in ns-2 and Linux

The increasing level of heterogeneity of present and future networks poses new challenges to TCP. Wired and wireless connections (including satellite) with very different characteristics, concerning bandwidth, RTT and loss rate, will have to co-exist and to compete, possibly in a fair way, in the same network. This heterogeneity makes difficult the choice between the many TCP enhancement proposals, as they basically are focused on single impairments, resulting \u201coptimized\u201d for different network environments. To overcome this problem the authors have recently presented the TCP-Adaptive Selection (TCP-AS) concept, which challenges the very idea that one choice should actually be made. This paper aims at presenting the implementations of the TCP-AS in both Linux and ns-2. They leverage on the modular structure of the TCP Linux congestion control, which can be replicated in ns-2 by making use of the Caltech \u201cNS-2 TCP-Linux\u201d patch. As described in the paper, the implementation key is the insertion of an intermediate agent, called \u201ctcp_as\u201d, between the TCP monolithic core and the TCP congestion control modules. In the second part of the paper, results of the ns-2 implementation have been cross-checked with Linux results. The analysis of data confirms both the feasibility and the performance advantages of the TCP-AS approach

The positive effects of surgery on symptomatic stereotactic radiation-induced peritumoral brain edema: A report of three cases

Background: Peritumoral brain edema is an uncommon but life-threatening side effect of brain tumors radiosurgery. Medical therapy usually alleviates symptoms until edema spontaneously disappears. However, when peritumoral brain edema endangers the patient's life or medical therapy fails to guarantee an acceptable quality of life, surgery might be considered. Case Description: Our report focuses on three patients who developed extensive peritumoral brain edema after radiosurgery. Two were affected by vestibular schwannomas and one by a skull-base meningioma. Peritumoral brain edema worsened despite maximal medical therapy in all cases; therefore, surgical removal of the radiated lesion was carried out. In the first patient, surgery was overdue and resulted in a fatal outcome. On the other hand, in the latter two cases surgery was quickly effective. In all three cases, an unmanageable brain swelling was not found at surgery. Conclusion: Surgical removal of brain tumors previously treated with radiosurgery was safe and effective in resolving shortly peritumoral brain edema. This solution should be considered in patients who do not respond to medical therapy and before worsening of clinical conditions. Interestingly, the expected brain swelling was not confirmed intraoperatively. In our experience, this magnetic resonance finding should not be considered a criterion to delay surgery

An Integrated Testbed for Wireless Advanced Transport Protocols and Architectures

The challenges posed by data communications over both satellite and terrestrial wireless systems make the adoption of adequate countermeasures advisable. In particular, the poor performance experienced by TCP transport protocol in such environments has fed the scientific community to propose novel solutions, from both the protocols and architecture points of view. In order to perform a thorough assessment of such proposals, University of Bologna (UoB) and National Inter-University Consortium for Telecommunications (CNIT) have conceived and set-up an integrated testbed. Its characteristics and capabilities are presented and discussed in this work, focusing in particular on the advantages offered by the ubiquitous remote control of the testbed, provided by a powerful web interface specifically designed for this purpos