2,862 research outputs found
Corporate social responsibility and banks
Article discussing ethical issues and matters of social responsibility surrounding turmoil in the capital markets, bank failures and government intervention. Article by Charles Chatterjee (Global Policy Institute, London Metropolitan University) and Anna Lefcovitch (E C Harris LLP) published in Amicus Curiae - Journal of the Society for Advanced Legal Studies. The Journal is produced by the Society for Advanced Legal Studies at the Institute of Advanced Legal Studies, University of London
Electron energy probability function and L-p similarity in low pressure inductively coupled bounded plasma
Particle-In-Cell (PIC) simulations are carried out to investigate the effect of discharge length (L) and pressure (p) on Electron Energy Probability Function (EEPF) in a low pressure radio frequency (rf) inductively coupled plasma (ICP) at 13.56 MHz. It is found that for both cases of varying L (0.1â0.5 m) and p (1â10 mTorr), the EEPF is a bi-Maxwellian with a step in the bounded direction (x) and non-Maxwellian with a hot tail in the symmetric unbounded directions (y, z). The plasma space potential decreases with increase in both L and p, the trapped electrons having energies in the range 0â20 eV. In a conventional discharge bounded in all directions, we infer that L and p are similarity parameters for low energy electrons trapped in the bulk plasma that have energies below the plasma space potential (eVp). The simulation results are consistent with a particle balance model
Jigsaw percolation: What social networks can collaboratively solve a puzzle?
We introduce a new kind of percolation on finite graphs called jigsaw
percolation. This model attempts to capture networks of people who innovate by
merging ideas and who solve problems by piecing together solutions. Each person
in a social network has a unique piece of a jigsaw puzzle. Acquainted people
with compatible puzzle pieces merge their puzzle pieces. More generally, groups
of people with merged puzzle pieces merge if the groups know one another and
have a pair of compatible puzzle pieces. The social network solves the puzzle
if it eventually merges all the puzzle pieces. For an Erd\H{o}s-R\'{e}nyi
social network with vertices and edge probability , we define the
critical value for a connected puzzle graph to be the for which
the chance of solving the puzzle equals . We prove that for the -cycle
(ring) puzzle, , and for an arbitrary connected puzzle
graph with bounded maximum degree, and for
any . Surprisingly, with probability tending to 1 as the network size
increases to infinity, social networks with a power-law degree distribution
cannot solve any bounded-degree puzzle. This model suggests a mechanism for
recent empirical claims that innovation increases with social density, and it
might begin to show what social networks stifle creativity and what networks
collectively innovate.Comment: Published at http://dx.doi.org/10.1214/14-AAP1041 in the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Elliptic flow of thermal dileptons in relativistic nuclear collisions
We calculate the transverse momentum and invariant mass dependence of
elliptic flow of thermal dileptons for Au+Au collisions at the Relativistic
Heavy Ion Collider. The system is described using hydrodynamics, with the
assumption of formation of a thermalized quark-gluon plasma at some early time,
followed by cooling through expansion, hadronization and decoupling. Dileptons
are emitted throughout the expansion history: by annihilation of quarks and
anti-quarks inthe early quark-gluon plasma stage and through a set of hadronic
reactions during the late hadronic stage. The resulting differential elliptic
flow exhibits a rich structure, with different dilepton mass windows providing
access to different stages of the expansion history. Elliptic flow measurements
for dileptons,combined with those of hadrons and direct photons, are a powerful
tool for mapping the time-evolution of heavy-ion collisions.Comment: Latex 8 pages including a total of 13 postscript figures. Added 2
figures, additional references, and expanded discussions. Figures modified
for better viewing. To appear in Phys. Rev.
A Reanalysis of Single Photon Data at CERN SPS
We reanalyze the WA98 single photon data at CERN SPS by incorporating several
recent developments in the study of prompt and thermal photon production from
relativistic heavy ion collisions. Isospin and shadowing corrected NLO pQCD,
along with an optimized scale for factorization, fragmentation and
renormalization are considered for prompt photon production. Photons from
thermal medium are estimated by considering a boost invariant azimuthally
anisotropic hydrodynamic expansion of the plasma along with a well tested
equation of state and initial conditions. A quantitative explanation of the
data is obtained by combining prompt with thermal photons,
where is an overall scaling factor. We show that, elliptic flow of
thermal photons can play a crucial role to distinguish between the `with' and
`without' phase transition scenarios at SPS energy.Comment: 4 pages, 3 figures - To appear in the conference proceedings for
Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee, v2: minor
correction
Fast charge sensing of Si/SiGe quantum dots via a high-frequency accumulation gate
Quantum dot arrays are a versatile platform for the implementation of spin
qubits, as high-bandwidth sensor dots can be integrated with single-, double-
and triple-dot qubits yielding fast and high-fidelity qubit readout. However,
for undoped silicon devices, reflectometry off sensor ohmics suffers from the
finite resistivity of the two-dimensional electron gas (2DEG), and alternative
readout methods are limited to measuring qubit capacitance, rather than qubit
charge. By coupling a surface-mount resonant circuit to the plunger gate of a
high-impedance sensor, we realized a fast charge sensing technique that is
compatible with resistive 2DEGs. We demonstrate this by acquiring at high speed
charge stability diagrams of double- and triple-dot arrays in Si/SiGe
heterostructures as well as pulsed-gate single-shot charge and spin readout
with integration times as low as 2.4 s.Comment: 10 pages, 5 figures, plus supplementary information with 9 pages and
6 figure
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Combinatorial Recruitment of CREB, C/EBPβ and c-Jun Determines Activation of Promoters upon Keratinocyte Differentiation
Background: Transcription factors CREB, C/EBPβ and Jun regulate genes involved in keratinocyte proliferation and differentiation. We questioned if specific combinations of CREB, C/EBPβ and c-Jun bound to promoters correlate with RNA polymerase II binding, mRNA transcript levels and methylation of promoters in proliferating and differentiating keratinocytes. Results: Induction of mRNA and RNA polymerase II by differentiation is highest when promoters are bound by C/EBP β alone, C/EBPβ together with c-Jun, or by CREB, C/EBPβ and c-Jun, although in this case CREB binds with low affinity. In contrast, RNA polymerase II binding and mRNA levels change the least upon differentiation when promoters are bound by CREB either alone or in combination with C/EBPβ or c-Jun. Notably, promoters bound by CREB have relatively high levels of RNA polymerase II binding irrespective of differentiation. Inhibition of C/EBPβ or c-Jun preferentially represses mRNA when gene promoters are bound by corresponding transcription factors and not CREB. Methylated promoters have relatively low CREB binding and, accordingly, those which are bound by C/EBPβ are induced by differentiation irrespective of CREB. Composite âHalf and Halfâ consensus motifs and co localizing consensus DNA binding motifs are overrepresented in promoters bound by the combination of corresponding transcription factors. Conclusion: Correlational and functional data describes combinatorial mechanisms regulating the activation of promoters. Colocalization of C/EBPβ and c-Jun on promoters without strong CREB binding determines high probability of activation upon keratinocyte differentiation
Magnetic Field Amplification and Flat Spectrum Radio Quasars
We perform time-dependent, spatially-resolved simulations of blazar emission
to evaluate several flaring scenarios related to magnetic-field amplification
and enhanced particle acceleration. The code explicitly accounts for
light-travel-time effects and is applied to flares observed in the flat
spectrum radio quasar (FSRQ) PKS 0208-512, which show optical/{\gamma}-ray
correlation at some times, but orphan optical flares at other times. Changes in
both the magnetic field and the particle acceleration efficiency are explored
as causes of flares. Generally, external Compton emission appears to describe
the available data better than a synchrotron self-Compton scenario, and in
particular orphan optical flares are difficult to produce in the SSC framework.
X-ray soft-excesses, {\gamma}-ray spectral hardening, and the detections at
very high energies of certain FSRQs during flares find natural explanations in
the EC scenario with particle acceleration change. Likewise, optical flares
with/without {\gamma}-ray counterparts can be explained by different
allocations of energy between the magnetization and particle acceleration,
which may be related to the orientation of the magnetic field relative to the
jet flow. We also calculate the degree of linear polarization and polarization
angle as a function of time for a jet with helical magnetic field. Tightening
of the magnetic helix immediately downstream of the jet perturbations, where
flares occur, can be sufficient to explain the increases in the degree of
polarization and a rotation by >= 180 degree of the observed polarization
angle, if light-travel-time effects are properly considered.Comment: 12 pages, 9 figures. Accepted for publication in MNRA
The thermal nature of high p_T photons in high energy nuclear collisions
We discuss the recent status of some penetrating electromagnetic probes of
relativistic nuclear collisions, and the information contained in their
measurement. We concentrate in turn on sources that produce high p_T photons:
those of purely thermal origin, those producing direct photons, those related
to jet fragmentation, and those associated with the interaction of jets with
the colored plasma. Whenever possible, we compare with RHIC data and in some
cases we make predictions for the LHC.Comment: 8 page
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