393 research outputs found
The Information Commons: a public policy report
This report describes the history of the information commons, presents examples of online commons that provide new ways to store and deliver information, and concludes with policy recommendations. Available in PDF and HTML versions.BRENNAN CENTER FOR JUSTICE at NYU SCHOOL OF LAW
Democracy Program, Free Expression Policy Project
161 Avenue of the Americas, 12th floor New York NY 10013
Phone: (212) 998-6730 Web site: www.brennancenter.org
Free Expression Policy Project: www.fepproject.or
The Information Commons: a public policy report
This report describes the history of the information commons, presents examples of online commons that provide new ways to store and deliver information, and concludes with policy recommendations. Available in PDF and HTML versions.BRENNAN CENTER FOR JUSTICE at NYU SCHOOL OF LAW
Democracy Program, Free Expression Policy Project
161 Avenue of the Americas, 12th floor New York NY 10013
Phone: (212) 998-6730 Web site: www.brennancenter.org
Free Expression Policy Project: www.fepproject.or
Axiomatic Bargaining Theory on Opportunity Assignments
This paper discusses issues of axiomatic bargaining problems over opportunity assignments. The fair arbitrator uses the principle of "equal opportunity" for all players to make the recommendation on re- source allocations. A framework in such a context is developed and several classical solutions to standard bargaining problems are reformulated and axiomatically characterized. Working Paper 06-4
Helical motion and the origin of QPO in blazar-type sources
Recent observations and analysis of blazar sources provide strong evidence
for (i) the presence of significant periodicities in their lightcurves and (ii)
the occurrence of helical trajectories in their radio jets. In scenarios, where
the periodicity is caused by differential Doppler boosting effects along a
helical jet path, both of these facts may be naturally tied together. Here we
discuss four possible driving mechanisms for the occurrence of helical
trajectories: orbital motion in a binary system, Newtonian-driven jet
precession, internal jet rotation and motion along a global helical magnetic
field. We point out that for non-ballistic helical motion the observed period
may appear strongly shortened due to classical travel time effects. Finally,
the possible relevance of the above mentioned driving mechanisms is discussed
for Mkn~501, OJ 287 and AO 0235+16.Comment: 6 pages, 1 figure; presented at the 5th Microquasar Workshop,
Beijing, June 2004. Accepted for publication in the Chinese Journal of
Astronomy and Astrophysic
Alternative splicing of MALT1 controls signalling and activation of CD4+ T cells
MALT1 channels proximal T-cell receptor (TCR) signalling to downstream
signalling pathways. With MALT1A and MALT1B two conserved splice variants
exist and we demonstrate here that MALT1 alternative splicing supports optimal
T-cell activation. Inclusion of exon7 in MALT1A facilitates the recruitment of
TRAF6, which augments MALT1 scaffolding function, but not protease activity.
Naive CD4+ T cells express almost exclusively MALT1B and MALT1A expression is
induced by TCR stimulation. We identify hnRNP U as a suppressor of exon7
inclusion. Whereas selective depletion of MALT1A impairs T-cell signalling and
activation, downregulation of hnRNP U enhances MALT1A expression and T-cell
activation. Thus, TCR-induced alternative splicing augments MALT1 scaffolding
to enhance downstream signalling and to promote optimal T-cell activation
The Energy Spectrum of TeV Gamma-Rays from the Crab Nebula as measured by the HEGRA system of imaging air Cherenkov telescopes
The Crab Nebula has been observed by the HEGRA (High-Energy Gamma-Ray
Astronomy) stereoscopic system of imaging air Cherenkov telescopes (IACTs) for
a total of about 200 hrs during two observational campaigns: from September
1997 to March 1998 and from August 1998 to April 1999. The recent detailed
studies of system performance give an energy threshold and an energy resolution
for gamma-rays of 500 GeV and ~ 18%, respectively. The Crab energy spectrum was
measured with the HEGRA IACT system in a very broad energy range up to 20 TeV,
using observations at zenith angles up to 65 degrees. The Crab data can be
fitted in the energy range from 1 to 20 TeV by a simple power-law, which yields
dJg/dE = (2.79+/-0.02 +/- 0.5) 10^{-7} E^{-2.59 +/- 0.03 +/- 0.05}, ph m^{-2}
s^{-1} TeV^{-1} The Crab Nebula energy spectrum, as measured with the HEGRA
IACT system, agrees within 15% in the absolute scale and within 0.1 units in
the power law index with the latest measurements by the Whipple, CANGAROO and
CAT groups, consistent within the statistical and systematic errors quoted by
the experiments. The pure power-law spectrum of TeV gamma-rays from the Crab
Nebula constrains the physics parameters of the nebula environment as well as
the models of photon emission.Comment: to appear in ApJ, 29 pages, 6 figure
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