Temporal dynamics of travelling theta wave activity in infants responding to visual looming

A fundamental property of most animals is the ability to see whether an object is approaching on a direct collision course and, if so, when it will collide. Using high-density electroencephalography in 5- to 11-month-old infants and a looming stimulus approaching under three different accelerations, we investigated how the young human nervous system extracts and processes information for impending collision. Here we show that infants' looming related brain activity is characterized by theta oscillations. Source analyses reveal clear localised activity in the visual cortex. Analysing the temporal dynamics of the source waveform, we provide evidence that the temporal structure of different looming stimuli is sustained during processing in the more mature infant brain, providing infants with increasingly veridical time-to-collision information about looming danger as they grow older and become mobile

Finite dimensional representations of the quantum group GLp,q(2)GL_{p,q}(2) using the exponential map from Up,q(gl(2))U_{p,q}(gl(2))

Using the Fronsdal-Galindo formula for the exponential mapping from the quantum algebra $U_{p,q}(gl(2))$ to the quantum group $GL_{p,q}(2)$, we show how the $(2j+1)$-dimensional representations of $GL_{p,q}(2)$ can be obtained by `exponentiating' the well-known $(2j+1)$-dimensional representations of $U_{p,q}(gl(2))$ for $j$ $=$ $1,{3/2},...$; $j$ $=$ 1/2 corresponds to the defining 2-dimensional $T$-matrix. The earlier results on the finite-dimensional representations of $GL_q(2)$ and $SL_q(2)$ (or $SU_q(2)$) are obtained when $p$ $=$ $q$. Representations of $U_{\bar{q},q}(2)$ $(q$ $\in$ \C \backslash \R and $U_q(2)$ $(q$ $\in$ $\R \backslash \{0\})$ are also considered. The structure of the Clebsch-Gordan matrix for $U_{p,q}(gl(2))$ is studied. The same Clebsch-Gordan coefficients are applicable in the reduction of the direct product representations of the quantum group $GL_{p,q}(2)$.Comment: 17 pages, LaTeX (latex twice), no figures. Changes consist of more general formula (4.13) for T-matrices, explicit Clebsch-Gordan coefficients, boson realization of group parameters, and typographical correction

Led induced chlorophyll fluorescence transient imager for measurements of health and stress status of whole plants

We have developed LED (light emitting diode) induced fluorescence transient imaging instrumentation to image the plant health/stress status by calculation of two images: Fv/Fm (variable fluorescence over saturation level of fluorescence) and the time response, tTR, of the fluorescence time curve. Within a short time interval (˜580 ms) multiple images (typically 20) are captured using the LEDs in the pulsed mode. For each pixel of the fluorescence image Fv/Fm and tTR are calculated and presented as images that correlate with the quantum yield of PSII photochemistry and the time response of this process, respectively. The advantage of the technology lies in the imaging of photosynthetic parameters within a short time interval, remotely and under light conditions. This was accomplished by the development of a high intensity pulsed LED light source (total 5 kW electrical power) and using the LEDs in the pulsed mode with a pulse width of 15 ms and time between sequential pulses of 14 ms. Using this instrumentation we investigated the effect of herbicide treatment, Sencor, on black nightshade (Solanum nigrum L.) plants. Effects of the herbicide on the first fluorescence images could be detected. At the saturation level of the fluorescence this effect disappeared. The effect of the herbicide was visualized on the Fv/Fm image and the time response tTR image. Healthy and herbicide treated parts of the plant yielded average values of Fv/Fm=0.81±0.03 and 0.06±0.02, respectively. Furthermore, the effect of drought stress was investigated on saintpaulia (Saintpaulia ionantha) plants. Under dark conditions no differences in the image of Fv/Fm and tTR could be detected between the control and the plant with drought stress. Under actinic light of 90 µmol m-2 s-1 differences were observed in images of (Fm’-F’)/Fm’ and tTR’. We conclude that for the first time images of a time response of the photosynthesis of leaves are presented. Furthermore, the proposed instrumentation can be used for high throughput screening, as a sensor in sorting machines and has potential greenhouse applications

An MDP decomposition approach for traffic control at isolated signalized intersections

This article presents a novel approach for the dynamic control of a signalized intersection. At the intersection, there is a number of arrival flows of cars, each having a single queue (lane). The set of all flows is partitioned into disjoint combinations of nonconflicting flows that will receive green together. The dynamic control of the traffic lights is based on the numbers of cars waiting in the queues. The problem concerning when to switch (and which combination to serve next) is modeled as a Markovian decision process in discrete time. For large intersections (i.e., intersections with a large number of flows), the number of states becomes tremendously large, prohibiting straightforward optimization using value iteration or policy iteration. Starting from an optimal (or nearly optimal) fixed-cycle strategy, a one-step policy improvement is proposed that is easy to compute and is shown to give a close to optimal strategy for the dynamic proble

Realizations of su(1,1)su(1,1) and Uq(su(1,1))U_q(su(1,1)) and generating functions for orthogonal polynomials

Positive discrete series representations of the Lie algebra $su(1,1)$ and the quantum algebra $U_q(su(1,1))$ are considered. The diagonalization of a self-adjoint operator (the Hamiltonian) in these representations and in tensor products of such representations is determined, and the generalized eigenvectors are constructed in terms of orthogonal polynomials. Using simple realizations of $su(1,1)$, $U_q(su(1,1))$, and their representations, these generalized eigenvectors are shown to coincide with generating functions for orthogonal polynomials. The relations valid in the tensor product representations then give rise to new generating functions for orthogonal polynomials, or to Poisson kernels. In particular, a group theoretical derivation of the Poisson kernel for Meixner-Pollaczak and Al-Salam--Chihara polynomials is obtained.Comment: 20 pages, LaTeX2e, to appear in J. Math. Phy

Quantum communication through a spin chain with interaction determined by a Jacobi matrix

We obtain the time-dependent correlation function describing the evolution of a single spin excitation state in a linear spin chain with isotropic nearest-neighbour XY coupling, where the Hamiltonian is related to the Jacobi matrix of a set of orthogonal polynomials. For the Krawtchouk polynomial case an arbitrary element of the correlation function is expressed in a simple closed form. Its asymptotic limit corresponds to the Jacobi matrix of the Charlier polynomial, and may be understood as a unitary evolution resulting from a Heisenberg group element. Correlation functions for Hamiltonians corresponding to Jacobi matrices for the Hahn, dual Hahn and Racah polynomials are also studied. For the Hahn polynomials we obtain the general correlation function, some of its special cases, and the limit related to the Meixner polynomials, where the su(1,1) algebra describes the underlying symmetry. For the cases of dual Hahn and Racah polynomials the general expressions of the correlation functions contain summations which are not of hypergeometric type. Simplifications, however, occur in special cases