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 (0.1–0.5 m) and p (1–10 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 0–20 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 $n$ vertices and edge probability $p_n$, we define the critical value $p_c(n)$ for a connected puzzle graph to be the $p_n$ for which the chance of solving the puzzle equals $1/2$. We prove that for the $n$-cycle (ring) puzzle, $p_c(n)=\Theta(1/\log n)$, and for an arbitrary connected puzzle graph with bounded maximum degree, $p_c(n)=O(1/\log n)$ and $\omega(1/n^b)$ for any $b>0$. 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 $\kappa \times$ prompt with thermal photons, where $\kappa$ 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

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 “Half and Half” 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

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 $\mu$s.Comment: 10 pages, 5 figures, plus supplementary information with 9 pages and 6 figure

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