ACKNOWLEDGMENTS I would like to give many thanks to Dr. Shengli Fu and Dr. Yan Huang as my advi-

Responses of soil biological processes to elevated atmospheric [CO2] and nitrogen addition in a poplar plantation

We explore two fundamental questions at the intersection of sampling theory and information theory: how is channel capacity affected by sampling below the channel’s Nyquist rate, and what sub-Nyquist sampling strategy should be employed to maximize capacity. In particular, we first derive the capacity of sampled analog channels for two prevalent sampling mechanisms: filtering followed by sampling and sampling following filter banks. Connections between sampling and MIMO Gaussian channels are illuminated based on this analysis. Optimal prefilters that maximize capacity are identified for both cases, as well as several kinds of channels for which these sampling mechanisms are optimal to maximize capacity at sub-Nyquist rates. We also highlight connections between sampled analog channel capacity and minimum mean squared error estimation from sampled data. In particular, it is shown that for both filtering and filter-bank sampling strategies, the filters maximizing capacity and minimizing mean squared error are equivalent. We also investigate a more general sampling strategy by adding modulation banks to filter-bank sampling. This general sampling method subsumes most nonuniform sampling techniques applied in both theory and practice. We also show a connection between this general sampling method and MIMO Gaussian channels. We then identify the optimal sampling strategy for piece-wise flat sampled

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et a ̀ la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Abstract. We review theoretical models of individual motility as well as collective dynamics and pattern formation of active particles. We focus on simple models of active dynamics with a particular emphasis on nonlinear and stochastic dynamics of such self-propelled entities in the framework

measurements. This paper begins by unifying two front-end architectures proposed for MUD by showing that both lead to the same discrete signal model. Algorithms are presented for coherent and noncoherent detection that are based on iterative matching pursuit. Noncoherent detection is all that is needed

Abstract-The ion microprobe has been used to determine the concentrations of a number oftrace elements (including all 14 stable rare earth elements) and the isotopic compositions of Ca and Mg in seven hibonite-rich refractory inclusions. Hibonite in every inclusion analyzed shows the effect of RAZE partitioning with other solid or liquid phases, in which hibonite is enriched in light over heavy REE compared to other existing phases. This partitioning causes Cl chondrite-normalized enrichments to drop by factors of 4 to 22 from lanthanum to lutetium. Fractionations due to gas-solid partitioning of REE are sometimes uperimposed on the pattern produced by partitioning between condensed phases. Two inclusions, HAL and DH-H 1, show evidence for formation in extremely oxidizing environments and their Ca is mass fm~ionat ~ in favor of the heavy isotopes by 7 and 12~/~u, reape&vely. Two ~~ndurn-hi~nite inclu~ons show evidence of extremely high temperature gas-solid fractionation, such that the more volatile tight REE are depleted as a group relative to the more refractory heavy REE. These inciusions both have Ca that is mass fractionated in favor of the light isotopes. Hibonite preserves the largest nuclear isotope anomalies inTi found to date (FAHEY ef al., 198Sa; HINTON et al., 1987b), but there does not seem to be a simple relationship between chemical composition, isotopic mass fractionation and the sign and magnitude of nuclear isotopic anomalies in hibonite-rich inclusions. One possibility for producing a variety of chemical compositions and degrem of mass fractionation while preserving nuclear isotope anomalies is by multiple cycles of condensation and evaporation in a turbulent protoplanetary accretion disk (MORL~LL,

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of the spectrum by legacy sys-tems. Cognitive radio exhibits a tremendous promise for increasing the spectral efficiency for future wireless systems. Ideally, new secondary users would have a perfect panorama of the spectrum usage, and would opportunistically communicate over the available re-sources without