2,422 research outputs found
The South African King IV Report on corporate governance: is the crown shiny enough?
No abstract available
Low-energy electronic properties of clean CaRuO: elusive Landau quasiparticles
We have prepared high-quality epitaxial thin films of CaRuO with residual
resistivity ratios up to 55. Shubnikov-de Haas oscillations in the
magnetoresistance and a temperature dependence in the electrical
resistivity only below 1.5 K, whose coefficient is substantially suppressed in
large magnetic fields, establish CaRuO as a Fermi liquid (FL) with
anomalously low coherence scale. Non-Fermi liquid (NFL) dependence is
found between 2 and 25 K. The high sample quality allows access to the
intrinsic electronic properties via THz spectroscopy. For frequencies below 0.6
THz, the conductivity is Drude-like and can be modeled by FL concepts, while
for higher frequencies non-Drude behavior, inconsistent with FL predictions, is
found. This establishes CaRuO as a prime example of optical NFL behavior in
the THz range.Comment: 12 pages, 21 figures including supplemental materia
Engaging stakeholders in corporate decision-making through strategic reporting: an empirical study of FTSE 100 companies (Part 2)
Non-financial reporting has risen in significance in recent years as the role of stakeholders who are not shareholders has been recognised in corporate governance frameworks. In the UK the ‘strategic reporting’ provisions of the Companies Act 2006 give effect to this policy. In Part 1 we examined the strategic reports of the FTSE 100 companies from 2015 and 2016 and focused on compliance by companies with nonfinancial reporting requirements. We found that compliance with those requirements was very high, amounting even to super or over-compliance. This article (Part 2 of the project) assesses the quality of non-financial reporting through a series of interviews. It evaluates whether the current regulatory framework on non-financial reporting in the UK informs stakeholders adequately so as to facilitate effective engagement in corporate decision-making
Surface Alfven Wave Damping in a 3D Simulation of the Solar Wind
Here we investigate the contribution of surface Alfven wave damping to the
heating of the solar wind in minima conditions. These waves are present in
regions of strong inhomogeneities in density or magnetic field (e. g., the
border between open and closed magnetic field lines). Using a 3-dimensional
Magnetohydrodynamics (MHD) model, we calculate the surface Alfven wave damping
contribution between 1-4 solar radii, the region of interest for both
acceleration and coronal heating. We consider waves with frequencies lower than
those that are damped in the chromosphere and on the order of those dominating
the heliosphere. In the region between open and closed field lines, within a
few solar radii of the surface, no other major source of damping has been
suggested for the low frequency waves we consider here. This work is the first
to study surface Alfven waves in a 3D environment without assuming a priori a
geometry of field lines or magnetic and density profiles. We determine that
waves with frequencies >2.8x10^-4 Hz are damped between 1-4 solar radii. In
quiet sun regions, surface Alfven waves are damped at further distances
compared to active regions, thus carrying additional wave energy into the
corona. We compare the surface Alfven wave contribution to the heating by a
variable polytropic index and find that it an order of magnitude larger than
needed for quiet sun regions. For active regions the contribution to the
heating is twenty percent. As it has been argued that a variable gamma acts as
turbulence, our results indicate that surface Alfven wave damping is comparable
to turbulence in the lower corona. This damping mechanism should be included
self consistently as an energy driver for the wind in global MHD models.Comment: Accepted to ApJ (scheduled September '09), 22 pages, 8 figure
Measurement of polarization-transfer to bound protons in carbon and its virtuality dependence
We measured the ratio of the transverse to longitudinal
components of polarization transferred from electrons to bound protons in
by the process at the
Mainz Microtron (MAMI). We observed consistent deviations from unity of this
ratio normalized to the free-proton ratio,
, for both -
and -shell knocked out protons, even though they are embedded in averaged
local densities that differ by about a factor of two. The dependence of the
double ratio on proton virtuality is similar to the one for knocked out protons
from and , suggesting a universal behavior.
It further implies no dependence on average local nuclear density
Transition from the Couette-Taylor system to the plane Couette system
We discuss the flow between concentric rotating cylinders in the limit of
large radii where the system approaches plane Couette flow. We discuss how in
this limit the linear instability that leads to the formation of Taylor
vortices is lost and how the character of the transition approaches that of
planar shear flows. In particular, a parameter regime is identified where
fractal distributions of life times and spatiotemporal intermittency occur.
Experiments in this regime should allow to study the characteristics of shear
flow turbulence in a closed flow geometry.Comment: 5 pages, 5 figure
A Large-Scale FPGA-Based Trigger and Dead-Time Free DAQ System for the Kaos Spectrometer at MAMI
The Kaos spectrometer is maintained by the A1 collaboration at the Mainz
Microtron MAMI with a focus on the study of (e,e'K^+) coincidence reactions.
For its electron-arm two vertical planes of fiber arrays, each comprising
approximately 10 000 fibers, are operated close to zero degree scattering angle
and in close proximity to the electron beam. A nearly dead-time free DAQ system
to acquire timing and tracking information has been installed for this
spectrometer arm. The signals of 144 multi-anode photomultipliers are collected
by 96-channel front-end boards, digitized by double-threshold discriminators
and the signal time is picked up by state-of-the-art F1 time-to-digital
converter chips. In order to minimize background rates a sophisticated trigger
logic was implemented in newly developed Vuprom modules. The trigger performs
noise suppression, signal cluster finding, particle tracking, and coincidence
timing, and can be expanded for kinematical matching (e'K^+) coincidences. The
full system was designed to process more than 4 000 read-out channels and to
cope with the high electron flux in the spectrometer and the high count rate
requirement of the detectors. It was successfully in-beam tested at MAMI in
2009.Comment: Contributed to 17th IEEE Real Time Conference (RT10), Lisbon, 24-28
May 201
Mapping the Distribution of Electron Temperature and Fe Charge States in the Corona with Total Solar Eclipse Observations
The inference of electron temperature from the ratio of the intensities of emission lines in the solar corona is valid only when the plasma is collisional. Once collisionless, thermodynamic ionization equilibrium no longer holds, and the inference of an electron temperature and its gradient from such measurements is no longer valid. At the heliocentric distance where the transition from a collision-dominated to a collisionless plasma occurs, the charge states of different elements are established, or frozen-in. These are the charge states which are subsequently measured in interplanetary space. We show in this study how the 2006 March 29 and 2008 August 1 eclipse observations of a number of Fe emission lines yield an empirical value for a distance, which we call Rt , where the emission changes from being collisionally to radiatively dominated. Rt ranges from 1.1 to 2.0 R ☉, depending on the charge state and the underlying coronal density structures. Beyond that distance, the intensity of the emission reflects the distribution of the corresponding Fe ion charge states. These observations thus yield the two-dimensional distribution of electron temperature and charge state measurements in the corona for the first time. The presence of the Fe X 637.4 nm and Fe XI 789.2 nm emission in open magnetic field regions below Rt , such as in coronal holes and the boundaries of streamers, and the absence of Fe XIII 1074.7 nm and Fe XIV 530.3 nm emission there indicate that the sources of the solar wind lie in regions where the electron temperature is less than 1.2 × 106 K. Beyond Rt , the extent of the Fe X [Fe9+] and Fe XI emission [Fe10+], in comparison with Fe XIII [Fe12+] and Fe XIV [Fe13+], matches the dominance of the Fe10+ charge states measured by the Solar Wind Ion Composition Spectrometer, SWICS, on Ulysses, at –43° latitude at 4 AU, in March-April 2006, and Fe9+ and Fe10+ charge states measured by SWICS on the Advanced Composition Explorer, ACE, in the ecliptic plane at 1 AU, at the time of both eclipses. The remarkable correspondence between these two measurements establishes the first direct link between the distribution of charge states in the corona and in interplanetary space
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