Many Sources Asymptotics for Networks with Small Buffers

In this paper, we obtain the overflow asymptotics in a network with small buffers when the resources are accessed by a large number of stationary independent sources. Under the assumption that the network is loop-free with respect to source–destination routes, we identify the precise large deviations rate functions for the buffer overflow at each node in terms of the external input characteristics. It is assumed that each type of source requires a Quality of Service (QoS) defined by bounds on the fraction of offered work lost. We then obtain the admissible region for sources which access the network based on these QoS requirements. When all the sources require the same QoS, we show that the admissible region asymptotically corresponds to that which is obtained by assuming that flows pass through each node unchanged.     

A note on the conservation law for continuous reflected processes and its application to queues with fluid inputs

In this note we provide a new derivation of a conservation law for stationary continuous reflected processes which arise in the context of fluid queueing models. This readily gives the so-called Little's law for fluid queues as a special case. We then apply the result to compute the Laplace transform of the stationary workload distribution for a queue with fluid ON-OFF inputs in terms of the Palm distribution associated with the beginning of ON periods. This revised version was published online in June 2006 with corrections to the Cover Date.     

Energy levels of λx 2k anharmonic oscillators using the quantum normal form

The ground state and first few excited energy levels of the generalized anharmonic oscillator defined by the HamiltonianH=–d ²/dx ²+x ²+x ^2k (k=3, 4,...) have been calculated by employing the method of quantum normal form, which is the quantum mechanical analogue of the classical Birkhoff-Gustavson normal form. The present energy eigenvalues are consistent with other tabulations of the energy levels.     

Similarities in electronic properties of organic charge-transfer solids and layered cobaltates

The apparently counterintuitive carrier concentration-dependent electronic properties of layered cobaltates have attracted wide interest. Here we point out that very similar carrier-concentration dependence has previously been noted in strongly correlated quasi-one dimensional (quasi-1D) organic charge-transfer solids. The normal states of both families can be understood, over the entire range of carrier concentration of interest, within the extended Hubbard Hamiltonian with significant intersite Coulomb interaction. As with the charge-transfer solids, superconductivity in the cobaltates appears to be limited to bandfilling of one-quarter. We point out further that there exist other families of correlated superconductors, such as spinels, where too strong correlations, geometric lattice frustration and bandfilling of one-quarter seem to be the essential features of the unconventional superconductors.     

Decision tree SAR models for developmental toxicity based on an FDA/TERIS database

Humans are exposed to thousands of environmental chemicals for which no developmental toxicity information is available. Structure-activity relationships (SARs) are models that could be used to efficiently predict the biological activity of potential developmental toxicants. However, at this time, no adequate SAR models of developmental toxicity are available for risk assessment. In the present study, a new developmental database was compiled by combining toxicity information from the Teratogen Information System (TERIS) and the Food and Drug Administration (FDA) guidelines. We implemented a decision tree modeling procedure, using Classification and Regression Tree software and a model ensemble approach termed bagging. We then assessed the empirical distributions of the prediction accuracy measures of the single and ensemble-based models, achieved by repeating our modeling experiment many times by repeated random partitioning of the working database. The decision tree developmental SAR models exhibited modest prediction accuracy. Bagging tended to enhance the accuracy of prediction. Also, the model ensemble approach reduced the variability of prediction measures compared to the single model approach. Further research with data derived from animal species- and endpoint-specific components of an extended and refined FDA/TERIS database has the potential to derive SAR models that would be useful in the developmental risk assessment of the thousands of untested chemicals.     

Magnetism and transport studies in off-stoichiometric metallic perovskite compounds GdPd3Bx (x=0.25, 0.50 and 0.75)

We report the magnetic and transport properties of the off-stoichiometric metallic perovskite like compounds GdPd₃B_x (x=0.25, 0.50 and 0.75). Our results show that doping with boron in the lattice of parent binary-compound GdPd₃ leads to lattice expansion. Which in turn manifests in contrasting magnetic and transport behaviors of the doped compounds in comparison with the undoped GdPd₃. An attempt has been made to compare and correlate the results of magnetic and transport measurements of GdPd₃B_x with that of stoichiometric compositions GdPd₃B_xC_1−x. The comparative study of GdPd₃B_x and GdPd₃B_xC_1−x confirms that there is a strong correlations between the structural, magnetic and transport properties of these compounds.