44,998 research outputs found

    The Localization Hypothesis and Machines

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    In a recent article in 'Artificial Life', Chu and Ho suggested that Rosen's central result about the simulability of living systems might be flawed. This argument was later declared ''null and void'' by Louie. In this article the validity of Louie's objections are examined

    A Category Theoretical Argument Against the Possibility of Artificial Life

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    One of Robert Rosen's main contributions to the scientific community is summarized in his book 'Life itself'. There Rosen presents a theoretical framework to define living systems; given this definition, he goes on to show that living systems are not realisable in computational universes. Despite being well known and often cited, Rosen's central proof has so far not been evaluated by the scientific community. In this article we review the essence of Rosen's ideas leading up to his rejection of the possibility of real artificial life in silico. We also evaluate his arguments and point out that some of Rosen's central notions are ill- defined. The conclusion of this article is that Rosen's central proof is wrong

    Nondestructive measurement of capillary tube internal diameter

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    Technique provides nondestructive method of making quick, accurate determination by measuring electrical resistance of capillary tube when it is filled with electrolyte of known conductivity. Apparatus consists of conductivity cell and equipment for measuring resistance and for monitoring and controlling temperature

    Chemisorption on a model bcc metal

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    The system considered here is that of a single atom with one energy level chemisorbed on the (001) surface of a model bcc metal. We present the change in the density of electronic states Δn (E) due to chemisorption for two cases: one when the adatom is bound to a single substrate atom in the "on‐site" configuration and the other when it is bound to four substrate atoms in the "centered fourfold site." In principle, this change in the density of states Δn can be related to the results of photoemission measurements

    Consensus analysis of multiagent networks via aggregated and pinning approaches

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    This is the post-print version of of the Article - Copyright @ 2011 IEEEIn this paper, the consensus problem of multiagent nonlinear directed networks (MNDNs) is discussed in the case that a MNDN does not have a spanning tree to reach the consensus of all nodes. By using the Lie algebra theory, a linear node-and-node pinning method is proposed to achieve a consensus of a MNDN for all nonlinear functions satisfying a given set of conditions. Based on some optimal algorithms, large-size networks are aggregated to small-size ones. Then, by applying the principle minor theory to the small-size networks, a sufficient condition is given to reduce the number of controlled nodes. Finally, simulation results are given to illustrate the effectiveness of the developed criteria.This work was jointly supported by CityU under a research grant (7002355) and GRF funding (CityU 101109)

    The Human Right to Science and Foundational Technologies

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    Feeney et al. (2018) make a valid argument for restrictions on the exclusivity of foundational technologies such as CRISPR. The issue of balancing intellectual property right with access to scientific and technological advancements is certainly not new. In our commentary, we argue that the human right to science offers a more concrete basis for governments to balance their competing commitments in promoting scientific development on the one hand, and ensuring benefit-sharing on the other, in ways that advance social justice under non-ideal conditions

    Stellar Velocity Dispersion and Black Hole Mass in the Blazar Markarian 501

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    The recently discovered correlation between black hole mass and stellar velocity dispersion provides a new method to determine the masses of black holes in active galaxies. We have obtained optical spectra of Markarian 501, a nearby gamma-ray blazar with emission extending to TeV energies. The stellar velocity dispersion of the host galaxy, measured from the calcium triplet lines in a 2"x3.7" aperture, is 372 +/- 18 km/s. If Mrk 501 follows the M-sigma correlation defined for local galaxies, then its central black hole has a mass of (0.9-3.4)x10^9 solar masses. This is significantly larger than some previous estimates for the central mass in Mrk 501 that have been based on models for its nonthermal emission. The host galaxy luminosity implies a black hole of 6x10^8 solar masses, but this is not in severe conflict with the mass derived from the M-sigma relation because the M_BH-L_bulge correlation has a large intrinsic scatter. Using the emission-line luminosity to estimate the bolometric luminosity of the central engine, we find that Mrk 501 radiates at an extremely sub-Eddington level of L/L_Edd ~ 10^-4. Further applications of the M-sigma relation to radio-loud active galactic nuclei may be useful for interpreting unified models and understanding the relationship between radio galaxies and BL Lac objects.Comment: To appear in ApJ Letters. 5 pages, 2 figure

    Measurements of the dielectric properties of sea water at 1.43 GHz

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    Salinity and temperature of water surfaces of estuaries and bay regions are determined to accuracies of 1 ppt salinity and 0.3 kelvin surface temperature. L-band and S-band radiometers are used in combination as brightness temperature detectors. The determination of the brightness temperature versus salinity, with the water surface temperature as a parameter for 1.4 GHz, is performed with a capillary tube inserted into a resonance cavity. Detailed analysis of the results indicates that the measured values are accurate to better than 0.2 percent in the electric property epsilon' and 0.4 percent in epsilon''. The calculated brightness temperature as a function of temperature and salinity is better than 0.2 kelvin. Thus it is possible to reduce the measured data obtained with the two-frequency radiometer system with 1 ppt accuracy to values in the salinity range 5 to 40 ppt
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