Many natural and social systems display global organization and coordination without centralized control. The origin of this global coordination is a topic of great current interest. Here we investigate a density-classification task as a model system for coordination and information processing in decentralized systems. We show that sophisticated strategies, selected under idealized conditions, are not robust to environmental changes. We also demonstrate that a simple heuristic is able to successfully complete the classification task under a broad range of environmental conditions. Our findings hint at the possibility that complex networks and ecologically efficient rules coevolve over time.

Cochannel interference occurs when two or more signals overlap in frequency and are present concurrently. Unlike in spread-spectrum multiple-access systems where the different users necessarily share the same channel, cochannel interference is a severe hindrance to frequency-and time-division multipleaccess communications, and is typically minimized by interference rejection/suppression techniques. In this paper, rather than using interference suppression, we are interested in the joint estimation of the information-bearing narrow-band cochannel signals. Novel joint estimators are proposed that employ a singleinput demodulator with oversampling to compensate for timing uncertainties. Assuming finite impulse-response channel characteristics, maximum likelihood (ML) and maximum a posteriori (MAP) criteria are used to derive cochannel detectors of varying complexities and degrees of performance. In particular, a (suboptimal) two-stage joint MAP symbol detector (JMAPSD) is introduced that has a lower complexity than the single-stage estimators while accruing only a marginal loss in error-rate performance at high signal-to-interference ratios. Assuming only reliable estimates of the primary and secondary signal powers, a blind adaptive JMAPSD algorithm for a priori unknown channels is also derived. The performance of these nonlinear joint estimation algorithms is studied through example computer simulations for two cochannel sources.

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We study the massive scalar field Sorkin-Johnston (SJ) Wightman function WSJ restricted to a flat 2D causal diamond D of linear dimension L. Our approach is two-pronged. In the first, we solve the central SJ eigenvalue problem explicitly in the small mass regime, up to order (mL) 4 . This allows us to formally construct WSJ up to this order. Using a combination of analytical and numerical methods, we obtain expressions for WSJ both in the center and the corner of D, to leading order. We find that in the center, WSJ is more like the massless Minkowski Wightman function W mink 0 than the massive one W mink m , while in the corner it corresponds to that of the massive mirror W mirror m . In the second part, in order to explore larger masses, we perform numerical simulations using a causal set approximated by a flat 2D causal diamond. We find that in the center of the diamond the causal set SJ Wightman function W c SJ resembles W mink 0 for small masses, as in the continuum, but beyond a critical value mc it resembles W mink m , as expected. Our calculations suggest that unlike W mink m , WSJ has a well-defined massless limit, which mimics the behavior of the Pauli Jordan function underlying the SJ construction. In the corner of the diamond, moreover, W c SJ agrees with W mirror m for all masses, and not, as might be expected, with the Rindler vacuum. * abhishekmathur@rri.res.in arXiv:1906.07952v2 [hep-th]

To push the 100-plex envelope of suspension array technology, we have developed fully automated methods to acquire multispectral images of multiplexed quantum-dot (QD) encoded microspheres, to segment them in the images, to classify them based on their color code, and to quantify the multiplexed assays. Instead of coding microspheres with two colors and n levels, microspheres were coded with n colors and two levels (present or absent), thus transforming the classification problem from analog to digital. Images of multiplexed microspheres, sedimented at the bottom of microwells, were acquired through a tunable filter at the peak luminescence wavelength of each QD coding species in the system and the assay label wavelength. Another image of the light scattered from microspheres was captured in the excitation bandwidth that was utilized to localize microspheres in multispectral luminescence images. Objects in the acquired images are segmented and luminescence from each identified microsphere in each channel is recorded, based on which the ''color code'' of each microsphere is determined by applying a mathematical model and a classification algorithm. Our image analysis procedures could identify and classify microspheres with more than 97% accuracy, and the assay CVs were under 20%. These proof-of-principle results demonstrate that highly multiplexed quantification of specific proteins is possible with this rapid, small-sample volume format. ' 2009 International Society for Advancement of Cytometry Key terms multiplexed assays; suspension arrays; microsphere-based arrays; quantum dots; microscopy; image analysis; imaging-based systems; imaging cytometry IN response to emerging needs to perform highly parallel quantification of specific proteins, a number of rapid, low cost, small sample volume analytical methods have been developed (1,2). Planar protein arrays have been designed that can analyze many thousands of proteins in parallel (3,4). They are printed on glass slides and each array element is identified by its location within the array's grid. However, planar arrays require immobilization of each protein on the surface with the same linking chemistry under common conditions, which limits ones ability to optimize epitope presentation and binding site density. Moreover, as each array spot is 100-200 lm in diameter, these arrays are limited to less than 10 4 assays/cm 2 that require relatively large sample volumes for highly multiplexed assays.Microsphere-based suspension arrays were developed to overcome the disadvantages of planar arrays (5-7). Microspheres offer the potential of utilizing different surfaces so each protein can be coated under optimal buffer, pH, and salt concentration conditions. They also allow assays to be performed in suspension thereby accelerating kinetics, reducing sample volumes, and allowing the reaction to proceed under homogeneous conditions. With suspension arrays, microspheres are coated in bulk, producing a large stock of immobilized proteins that can be tested for functi...