5,648 research outputs found
The Galactic Centre - A Laboratory for Starburst Galaxies (?)
The Galactic centre - as the closest galactic nucleus - holds both intrinsic
interest and possibly represents a useful analogue to star-burst nuclei which
we can observe with orders of magnitude finer detail than these external
systems. The environmental conditions in the GC - here taken to mean the inner
200 pc in diameter of the Milky Way - are extreme with respect to those
typically encountered in the Galactic disk. The energy densities of the various
GC ISM components are typically ~two orders of magnitude larger than those
found locally and the star-formation rate density ~three orders of magnitude
larger. Unusually within the Galaxy, the Galactic centre exhibits
hard-spectrum, diffuse TeV (=10^12 eV) gamma-ray emission spatially coincident
with the region's molecular gas. Recently the nuclei of local star-burst
galaxies NGC 253 and M82 have also been detected in gamma-rays of such
energies. We have embarked on an extended campaign of modelling the broadband
(radio continuum to TeV gamma-ray), non- thermal signals received from the
inner 200 pc of the Galaxy. On the basis of this modelling we find that
star-formation and associated supernova activity is the ultimate driver of the
region's non-thermal activity. This activity drives a large-scale wind of hot
plasma and cosmic rays out of the GC. The wind advects the locally-accelerated
cosmic rays quickly, before they can lose much energy in situ or penetrate into
the densest molecular gas cores where star-formation occurs. The cosmic rays
can, however, heat/ionize the lower density/warm H2 phase enveloping the cores.
On very large scales (~10 kpc) the non-thermal signature of the escaping GC
cosmic rays has probably been detected recently as the spectacular 'Fermi
bubbles' and corresponding 'WMAP haze'.Comment: Invited talk to appear in Proceedings of IAU Symposium No. 284, 2011
(R.J. Tuffs & C.C. Popescu, eds.) `The Spectral Energy Distribution of
Galaxies
sPlot: a statistical tool to unfold data distributions
The paper advocates the use of a statistical tool dedicated to the
exploration of data samples populated by several sources of events. This new
technique, called sPlot, is able to unfold the contributions of the different
sources to the distribution of a data sample in a given variable. The sPlot
tool applies in the context of a Likelihood fit which is performed on the data
sample to determine the yields of the various sources.Comment: 27 pages, 8 figures, Accepted for publication in Nucl. Instr. Method
A new simulation technique for RF oscillators
The study of phase-noise in oscillators and the design of new circuit topologies necessitates an efficient technique for the simulation of oscillators. While numerous approaches have been developed over the years e.g. [1-3], each has its own merits and demerits. In this contribution, an asymptotic numeric method developed in e.g. [4-5] is applied to the simulation of RF oscillators. The method is closely related to the stroboscopic and high-order averaging method in [6] and the Heterogeneous Multiscale Methods in [7]. The method is advantageous in that the same methodology can be applied for the simulation of general circuit problems involving highly oscillatory ordinary differential equations, partial differential equations and delay differential equations. Furthermore and counter-intuitively, its efficacy improves with increasing frequency, a feature that is very favourable in modern communications systems where operating frequencies are ever rising. Results for a CMOS oscillator will confirm the validity and efficiency of the proposed method
Causal and stable reduced-order model for linear high-frequency systems
With the ever-growing complexity of high-frequency systems in the electronic industry, formation of reduced-order models of these systems is paramount. In this reported work, two different techniques are combined to generate a stable and causal representation of the system. In particular, balanced truncation is combined with a Fourier series expansion approach. The efficacy of the proposed combined method is shown with an example
Symmetries and collective excitations in large superconducting circuits
The intriguing appeal of circuits lies in their modularity and ease of
fabrication. Based on a toolbox of simple building blocks, circuits present a
powerful framework for achieving new functionality by combining circuit
elements into larger networks. It is an open question to what degree modularity
also holds for quantum circuits -- circuits made of superconducting material,
in which electric voltages and currents are governed by the laws of quantum
physics. If realizable, quantum coherence in larger circuit networks has great
potential for advances in quantum information processing including topological
protection from decoherence. Here, we present theory suitable for quantitative
modeling of such large circuits and discuss its application to the fluxonium
device. Our approach makes use of approximate symmetries exhibited by the
circuit, and enables us to obtain new predictions for the energy spectrum of
the fluxonium device which can be tested with current experimental technology
THE OLD AND NEW DIVIDES OF PATENT LAW: FROM THE THEORY OF ANTEDATION TO DEFINING IMMEDIATELY ENVISAGEABLE LIMITED CLASSES
Recently, the United States Court of Appeals for the Federal Circuit (âFederal Circuitâ) ruled on a patent case involving the application of pre-America Invents Act (âAIAâ) antedation and the issue of when a genus of compounds is narrowly limited enough to anticipate an individual compound found within the genus.1 On appeal, this case generally discussed why the claimantâs anticipation and obviousness claims failed.2
While the entire Federal Circuit decision will be discussed, this Comment will discuss in greater depth the reasons why antedation is no longer applicable under the AIA, and the implications of the Federal Circuitâs decision to not set a standard for what defines a âlimited classâ under In re Petering
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