804 research outputs found
Nonequilibrium phase transition in the coevolution of networks and opinions
Models of the convergence of opinion in social systems have been the subject
of a considerable amount of recent attention in the physics literature. These
models divide into two classes, those in which individuals form their beliefs
based on the opinions of their neighbors in a social network of personal
acquaintances, and those in which, conversely, network connections form between
individuals of similar beliefs. While both of these processes can give rise to
realistic levels of agreement between acquaintances, practical experience
suggests that opinion formation in the real world is not a result of one
process or the other, but a combination of the two. Here we present a simple
model of this combination, with a single parameter controlling the balance of
the two processes. We find that the model undergoes a continuous phase
transition as this parameter is varied, from a regime in which opinions are
arbitrarily diverse to one in which most individuals hold the same opinion. We
characterize the static and dynamical properties of this transition
The genetic diversity of the American oil palm, Elaeis oleifera (Kunth), Corés revealed by nuclear RFLP markers.
Amplitudes of thermal and kinetic Sunyaev-Zel'dovich signals from small-scale CMB anisotropies
While the arcminute-scale Cosmic Microwave Background (CMB) anisotropies are
due to secondary effects, point sources dominate the total anisotropy power
spectrum. At high frequencies the point sources are primarily in the form of
dusty, star-forming galaxies. Both Herschel and Planck have recently measured
the anisotropy power spectrum of cosmic infrared background (CIB) generated by
dusty, star-forming galaxies from degree to sub-arcminute angular scales,
including the non-linear clustering of these galaxies at multipoles of 3000 to
6000 relevant to CMB secondary anisotropy studies. We scale the CIB angular
power spectra to CMB frequencies and interpret the combined WMAP-7 year and
arcminute-scale Atacama Cosmology Telescope (ACT) and South Pole Telescope
(SPT) CMB power spectra measurements to constrain the Sunyaev-Zel'dovich (SZ)
effects. Allowing the CIB clustering amplitude to vary, we constrain the
amplitudes of thermal and kinetic SZ power spectra at 150 GHz.Comment: 8 pages, 3 figures, 2 table
CLC, a promising concept with challenging development issues
Chemical Looping Combustion (CLC) is a promising technique to achieve fuel combustion in a nitrogen free atmosphere, therefore giving the possibility to separate and store or use CO2. Several potential applications are considered in the field of power generation with gas, liquid and solid fuels. In the Carbon Capture, Storage and Utilization (CCSU) context, energy penalty is reduced compared to other routes. In addition, other applications of Chemical Looping are considered in the field of H2 production or gasification for instance.
In the past years, a huge effort has been conducted worldwide to investigate CLC materials and process issues. In 2008, IFPEN and Total have started an ambitious collaboration to develop CLC applications. Nowadays, the CLC concept is well demonstrated at the pilot scale. The next step is to demonstrate the technology over time at larger scale. However, for further developments, the challenges are numerous and will be discussed, both on market and technical aspects. Short term market is limited. Uncertainties around CO2 emission market and storage issues are related to CO2 policy and public acceptance of storage which still must evolve in the right direction... Financing of demonstration units in this context is challenging and other applications of CLC have to be investigated. The industrial use of synthetic metal oxides or natural ores at large scale generates a lot of issues related to availability, price, waste disposal, health and safety, additionally to chemical and mechanical stability over time, reactivity, and oxygen transfer capacity. Chemical looping reactor and process technology concepts have to be explored, developed, modeled and scaled-up in order to ensure adequate power production together with good gas solid contact and reaction requirement, controlled circulation of mixtures of particle (oxygen carrier, ash, solid fuel for instance). All these points should be considered at very large scale for CCS applications in order to minimize energy penalty and cost in severe operating conditions (temperatures above 800°C and intense solid circulation).
Technical challenges remain to be solved and proven with large demonstration over long periods of time. In this context, research in the field of fluidization technology is essential and we will address a couple of key points already investigated at IFPEN and related to control of solid circulation, oxygen carrier attrition, conceptual design of CLC reactors and process performance
Submillimetre galaxies reside in dark matter haloes with masses greater than 3 × 10^(11) solar masses
The extragalactic background light at far-infrared wavelengths comes from optically faint, dusty, star-forming galaxies in the Universe with star formation rates of a few hundred solar masses per year. These faint, submillimetre galaxies are challenging to study individually because of the relatively poor spatial resolution of far-infrared telescopes. Instead, their average properties can be studied using statistics such as the angular power spectrum of the background intensity variations. A previous attempt at measuring this power spectrum resulted in the suggestion that the clustering amplitude is below the level computed with a simple ansatz based on a halo model. Here we report excess clustering over the linear prediction at arcminute angular scales in the power spectrum
of brightness fluctuations at 250, 350 and 500 µm. From this excess, we find that submillimetre galaxies are located in darkmatter haloes with a minimum mass, M_(min), such that log_(10)[M_(min)/M_⊙] = 11.5^(+0.7)_(-0.2) at 350 µm, where M_⊙ is the solar mass. This minimum dark matter halo mass corresponds to the most efficient mass scale for star formation in the Universe, and is lower than that predicted by semi-analytical models for galaxy formation
Restoring soil functionality in degraded areas of organic vineyards - Preliminary results of the ReSolVe project in the French vineyards
Degraded soil areas in vineyards are associated with problems in vine health, grape production and quality. Different causes for soil degradation are possible such as poor organic matter content, lower plant nutrient availability, pH, water deficiency, soil compaction / lower oxygenation… The aim of this preliminary study is to assess soil functionality (OM decomposition), biodiversity through mesofauna diversity and consequences for vine growth and quality
Integrated Filterbank for DESHIMA: A Submillimeter Imaging Spectrograph Based on Superconducting Resonators
An integrated filterbank (IFB) in combination with microwave kinetic
inductance detectors (MKIDs), both based on superconducting resonators, could
be used to make broadband submillimeter imaging spectrographs that are compact
and flexible. In order to investigate the possibility of adopting an IFB
configuration for DESHIMA (Delft SRON High-redshift Mapper), we study the basic
properties of a coplanar-waveguide-based IFB using electromagnetic simulation.
We show that a coupling efficiency greater than 1/2 can be achieved if
transmission losses are negligible. We arrive at a practical design for a 9
pixel x 920 color 3 dimensional imaging device that fits on a 4 inch wafer,
which instantaneously covers multiple submillimeter telluric windows with a
dispersion of f/df = 1000.Comment: 6 pages, 4 figures, submitted to LTD-14 / Journal of Low Temperature
Physic
Two-point microrheology and the electrostatic analogy
The recent experiments of Crocker et al. suggest that microrheological
measurements obtained from the correlated fluctuations of widely-separatedprobe
particles determine the rheological properties of soft, complex materials more
accurately than do the more traditional particle autocorrelations. This
presents an interesting problem in viscoelastic dynamics. We develop an
important, simplifing analogy between the present viscoelastic problem and
classical electrostatics. Using this analogy and direct calculation we analyze
both the one and two particle correlations in a viscoelastic medium in order to
explain this observation
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