11,414 research outputs found
In Favor of Rigor and Relevance. A Reply to Mark Blaug
The paper discusses Mark Blaugâs recent criticisms of âSraffian economicsâ. It is shown that none of the criticisms stand up to close examination. Blaug commits a number of elementary blunders and mistakes the mathematical form of an argument for its content. He variously contradicts himself and puts forward bold contentions that cannot be sustained. The paper concludes with an obvious plea for rigor and relevance.Piero Sraffa;Mark Blaug; General Equilibrium
High-resolution [C II] imaging of HDF850.1 reveals a merging galaxy at z=5.185
New high-resolution maps with the IRAM Interferometer of the redshifted [C
II] 158 micron line and the 0.98mm dust continuum of HDF850.1 at z = 5.185 show
the source to have a blueshifted northern component and a redshifted southern
component, with a projected separation of 0.3 arcsec, or 2 kpc. We interpret
these components as primordial galaxies that are merging to form a larger
galaxy. We think it is the resulting merger-driven starburst that makes
HDF850.1 an ultraluminous infrared galaxy, with an L(IR) of 1E13 Lsun. The
observed line and continuum brightness temperatures and the constant
line-to-continuum ratio across the source imply (1) high [C II] line optical
depth, (2) a [C II] excitation temperature of the same order as the dust
temperature, and (3) dust continuum emission that is nearly optically thick at
158 microns. These conclusions for HDF850.1 probably also apply to other
high-redshift submillimeter galaxies and quasar hosts in which the [C II] 158
micron line has been detected, as indicated by their roughly constant [C
II]-to-158 micron continuum ratios, in sharp contrast to the large dispersion
in their [C II]-to-FIR luminosity ratios. In brightness temperature units, the
[C II] line luminosity is about the same as the predicted CO(1-0) luminosity,
implying that the [C II] line can also be used to estimate the molecular gas
mass, with the same assumptions as for CO.Comment: Accepted by Astronomy and Astrophysic
Autocatalytic reaction-diffusion processes in restricted geometries
We study the dynamics of a system made up of particles of two different
species undergoing irreversible quadratic autocatalytic reactions: . We especially focus on the reaction velocity and on the average time at
which the system achieves its inert state. By means of both analytical and
numerical methods, we are also able to highlight the role of topology in the
temporal evolution of the system
Reset and switch protocols at Landauer limit in a graphene buckled ribbon
Heat produced during a reset operation is meant to show a fundamental bound
known as Landauer limit, while simple switch operations have an expected
minimum amount of produced heat equal to zero. However, in both cases,
present-day technology realizations dissipate far beyond these theoretical
limits. In this paper we present a study based on molecular dynamics
simulations, where reset and switch protocols are applied on a graphene buckled
ribbon, employed here as a nano electromechanical switch working at the
thermodynamic limit
Universal features of information spreading efficiency on -dimensional lattices
A model for information spreading in a population of mobile agents is
extended to -dimensional regular lattices. This model, already studied on
two-dimensional lattices, also takes into account the degeneration of
information as it passes from one agent to the other. Here, we find that the
structure of the underlying lattice strongly affects the time at which
the whole population has been reached by information. By comparing numerical
simulations with mean-field calculations, we show that dimension is
marginal for this problem and mean-field calculations become exact for .
Nevertheless, the striking nonmonotonic behavior exhibited by the final degree
of information with respect to and the lattice size appears to be
geometry independent.Comment: 8 pages, 9 figure
Autocatalytic reaction-diffusion processes in restricted geometries
We study the dynamics of a system made up of particles of two different
species undergoing irreversible quadratic autocatalytic reactions: . We especially focus on the reaction velocity and on the average time at
which the system achieves its inert state. By means of both analytical and
numerical methods, we are also able to highlight the role of topology in the
temporal evolution of the system
Discovery of Water Vapor in the High-redshift Quasar APM 08279+5255 at z = 3.91
We report a detection of the excited 2_(20)-2_(11) rotational transition of para-H_2O in APM 08279+5255 using the IRAM Plateau de Bure Interferometer. At z = 3.91, this is the highest-redshift detection of interstellar water to date. From large velocity gradient modeling, we conclude that this transition is predominantly radiatively pumped and on its own does not provide a good estimate of the water abundance. However, additional water transitions are predicted to be detectable in this source, which would lead to an improved excitation model. We also present a sensitive upper limit for the hydrogen fluoride (HF) J = 1-0 absorption toward APM 08279+5255. While the face-on geometry of this source is not favorable for absorption studies, the lack of HF absorption is still puzzling and may be indicative of a lower fluorine abundance at z = 3.91 compared with the Galactic interstellar medium
Scalable Layer-2/Layer-3 Multistage Switching Architectures for Software Routers
Software routers are becoming an important alternative to proprietary and expensive network devices, because they exploit the economy of scale of the PC market and open-source software. When considering maximum performance in terms of throughput, PC-based routers suffer from limitations stemming from the single PC architecture, e.g., limited bus bandwidth, and high memory access latency. To overcome these limitations, in this paper we present a multistage architecture that combines a layer-2 load-balancer front-end and a layer-3 routing back-end, interconnected by standard Ethernet switches. Both the front-end and the back-end are implemented using standard PCs and open- source software. After describing the architecture, evaluation is performed on a lab test-bed, to show its scalability. While the proposed solution allows to increase performance of PC- based routers, it also allows to distribute packet manipulation functionalities, and to automatically recover from component failures
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