Towards Contextual Action Recognition and Target Localization with Active Allocation of Attention

Exploratory gaze movements are fundamental for gathering the most relevant information regarding the partner during social interactions. We have designed and implemented a system for dynamic attention allocation which is able to actively control gaze movements during a visual action recognition task. During the observation of a partners reaching movement, the robot is able to contextually estimate the goal position of the partner hand and the location in space of the candidate targets, while moving its gaze around with the purpose of optimizing the gathering of information relevant for the task. Experimental results on a simulated environment show that active gaze control provides a relevant advantage with respect to typical passive observation, both in term of estimation precision and of time required for action recognition. © 2012 Springer-Verlag

Nuclear Dependence in Direct Photon Production

We calculate the nuclear dependence of direct photon production in hadron-nucleus collisions. In terms of a multiple scattering picture, we factorize the cross section for direct photon production into calculable short-distance partonic parts times multiparton correlation functions in nuclei. We present the hadron-nucleus cross section as $A^{\alpha}$ times the hadron-nucleon cross section. Using information on the multiparton correlation functions extracted from photon-nucleus experiments, we compute the value of $\alpha$ as a function of transverse momentum of the direct photon. We also compare our results with recent data from Fermilab experiment E706.Comment: 24 pages text in RevTex, 9 Postscript figure

The AC Impedance of Frog Skin and Its Relation to Active Transport

The AC electrical impedance of frog skin was measured in the range 1 cycle/second to 50 kc/second by injecting current sinusoidally at low current density. The behavior of the skin was found to be linear so the usual concepts of impedance could be validly employed. In the range 1 cycle/second to 5 kc/second, the impedance traces out a circular arc locus with its center off the real axis; thus the skin could be represented by a series resistance and a parallel combination of a conductance and a phase shift element. The phase shift element has an impedance angle of about 80°, current leading voltage, with an equivalent capacitance of about 2 μf/cm(2). The phase shift and the equivalent capacitance were independent of the experimental conditions. The parallel conductance, which was responsible for most of the low frequency impedance, could be subdivided into two approximately equal conductances, one associated with sodium ion current and the other associated with chloride ion current. Both currents were determined mainly by the concentrations of the respective ions bathing the outside of the skin. The response to changes in concentration and the response to CO(2) indicated that the chloride current was passive, but the sodium current appeared to be associated with the active transport mechanism; little sodium could pass through the skin unless associated with active transport

The Dynamic Response of Brain Temperature to Localized Heating

Several mathematical descriptions of heat transport in perfused tissues have been proposed but have not been thoroughly tested under conditions of time-varying temperatures. Data was obtained by measuring the response of brain temperature to step changes in temperature of chronically implanted thermodes in conscious baboons. These responses were compared to numerical solutions of an equation expressing heat transport in terms of conduction in the tissue and convection due to capillary blood flow. Good agreement between experimental and theoretical curves was obtained for values of k (thermal diffusivity) of 0.0017-0.0021 cm(2)/sec and ø (blood flow per unit volume of tissue) of 0.3-0.7 cm(3)/cm(3)-min. The predicted temperature response at a given tissue location was not greatly affected either by changes in k and ø over the physiological range, or by small errors in describing experimental geometry. However, inaccuracies in describing boundary locations or failing to account for the relatively avascular scar tissue around the thermode changed the value of ø needed to fit the data by as much as 50%. Thus, we conclude that the model described in this paper can be used for a description of thermal gradients surrounding a thermode but extreme caution should be exercised if such a model is used to quantitatively evaluate blood flow