78 research outputs found
Extended dividend, cash flow and residual income valuation models: Accounting for deviations from ideal conditions
Standard equity valuation approaches (i.e., DDM, RIM, and DCF model) are derived under the assumption of ideal conditions, such as infinite payoffs and clean surplus accounting. Because these conditions are hardly ever met, we extend the standard approaches, based on the fundamental principle of financial statement articulation. The extended models are then tested empirically by employing two sets of forecasts: (1) analyst forecasts provided by Value Line and (2) forecasts generated by cross-sectional regression models. The main result is that our extended models yield considerably smaller valuation errors. Moreover, by construction, identical value estimates are obtained across the extended models. By reestablishing empirical equivalence under non-ideal conditions, our approach provides a benchmark that enables us to quantify the errors resulting from individual deviations from ideal conditions, and thus, to analyze the robustness of the standard approaches. Finally, by providing a level playing field for the different valuation approaches, our findings have implications for other empirical settings, for example, estimating the implied cost of capital. --Dirty Surplus,Terminal Value,Steady-State,Valuation Error
Kinetic phenomena in mechanochemical depolymerization of poly(styrene
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Is the Lecompte technique the last word on transposition of the great arteries repair for all patients? A magnetic resonance imaging study including a spiral technique two decades postoperatively.
ObjectivesTo compare the Lecompte technique and the spiral anastomosis (complete anatomic correction) two decades after arterial switch operation (ASO).MethodsNine patients after primary ASO with Lecompte and 6 selected patients after spiral anastomosis were evaluated 20.8 ± 2.1 years after ASO versus matched controls. Blood flow dynamics and flow profiles (e.g. vorticity, helicity) in the great arteries were quantified from time-resolved 3D magnetic resonance imaging (MRI) phase contrast flow measurements (4D flow MR) in addition to a comprehensive anatomical and functional cardiovascular MRI analysis.ResultsCompared with spiral reconstruction, patients with Lecompte showed more vortex formation, supranatural helical blood flow (relative helicity in aorta: 0.036 vs 0.089; P < 0.01), a reduced indexed cross-sectional area of the left pulmonary artery (155 vs 85 mm²/m²; P < 0.001) and more semilunar valve dysfunctions (n = 5 vs 1). There was no difference in elastic aortic wall properties, ventricular function, myocardial perfusion and myocardial fibrosis between the two groups. Cross-sectional area of the aortic sinus was larger in patients than in controls (669 vs 411 mm²/m²; P < 0.01). In the spiral group, the pulmonary root was rotated after ASO more towards the normal left position (P < 0.01).ConclusionsIn this study, selected patients with spiral anastomoses showed, two decades after ASO, better physiologically adapted blood flow dynamics, and attained a closer to normal anatomical position of their great arteries, as well as less valve dysfunction. Considering the limitations related to the small number of patients and the novel MRI imaging techniques, these data may provoke reconsidering the optimal surgical approaches to transposition of the great arteries repair
Investigation into the role of an extracellular loop in mediating proton-evoked inhibition of voltage-gated sodium channels
Proton-evoked activation of sensory neurons is counteracted by inhibition of voltage-gated Na+ channels, and the low acid-sensitivity of sensory neuron of the African naked mole-rat (ANMr) was reported to be due to a strong proton-evoked block of ANMrNav1.7. Here we aimed to reevaluate the role of the suggested negatively-charged motif in the ANMrNav1.7 domain IV P-loop for inhibition by protons. Patch clamp recordings were performed on the recombinant α-subunits Nav1.2–1.8. The insertion of the negatively charged motif (EKE) of ANMrNav1.7 into human Nav1.7 results in an increased proton-evoked tonic inhibition, but also in a reduced channel function. While the voltage-dependency of fast inactivation is changed in hNav1.7-EKE, pH 6.4 fails to induce a significant shift in both constructs. Proton-evoked inhibition of other channel α-subunits reveals a discrete differential inhibition among α-subunits with hNav1.7 displaying the lowest proton-sensitivity. The mutant hNav1.7-EKE displays a similar proton-sensitivity as Nav1.2, Nav1.3, Nav1.6 and Nav1.8. Overall, a correlation between proton-evoked inhibition and motif charge was not evident. Accordingly, a homology model of hNav1.7 shows that the EKE motif residues do not contribute to the pore lumen. Our data confirms that a negative charge of a postulated proton-motif encodes for a high proton-sensitivity when inserted into hNav1.7. However, a negatively charged motif is not a reliable predictor for a high proton-sensitivity in other α-subunits. Given the distance of the proton-motif from the pore mouth it seems unlikely that a blocking mechanism involving direct obstruction of the pore underlies the observed proton-evoked channel inhibition
COLD GASS, an IRAM legacy survey of molecular gas in massive galaxies: I. Relations between H2, HI, stellar content and structural properties
We are conducting COLD GASS, a legacy survey for molecular gas in nearby
galaxies. Using the IRAM 30m telescope, we measure the CO(1-0) line in a sample
of ~350 nearby (D=100-200 Mpc), massive galaxies (log(M*/Msun)>10.0). The
sample is selected purely according to stellar mass, and therefore provides an
unbiased view of molecular gas in these systems. By combining the IRAM data
with SDSS photometry and spectroscopy, GALEX imaging and high-quality Arecibo
HI data, we investigate the partition of condensed baryons between stars,
atomic gas and molecular gas in 0.1-10L* galaxies. In this paper, we present CO
luminosities and molecular hydrogen masses for the first 222 galaxies. The
overall CO detection rate is 54%, but our survey also uncovers the existence of
sharp thresholds in galaxy structural parameters such as stellar mass surface
density and concentration index, below which all galaxies have a measurable
cold gas component but above which the detection rate of the CO line drops
suddenly. The mean molecular gas fraction MH2/M* of the CO detections is
0.066+/-0.039, and this fraction does not depend on stellar mass, but is a
strong function of NUV-r colour. Through stacking, we set a firm upper limit of
MH2/M*=0.0016+/-0.0005 for red galaxies with NUV-r>5.0. The average
molecular-to-atomic hydrogen ratio in present-day galaxies is 0.3, with
significant scatter from one galaxy to the next. The existence of strong
detection thresholds in both the HI and CO lines suggests that "quenching"
processes have occurred in these systems. Intriguingly, atomic gas strongly
dominates in the minority of galaxies with significant cold gas that lie above
these thresholds. This suggests that some re-accretion of gas may still be
possible following the quenching event.Comment: Accepted for publications in MNRAS. 32 pages, 25 figure
COLD GASS, an IRAM Legacy Survey of Molecular Gas in Massive Galaxies: II. The non-universality of the Molecular Gas Depletion Timescale
We study the relation between molecular gas and star formation in a
volume-limited sample of 222 galaxies from the COLD GASS survey, with
measurements of the CO(1-0) line from the IRAM 30m telescope. The galaxies are
at redshifts 0.025<z<0.05 and have stellar masses in the range
10.0<log(M*/Msun)<11.5. The IRAM measurements are complemented by deep Arecibo
HI observations and homogeneous SDSS and GALEX photometry. A reference sample
that includes both UV and far-IR data is used to calibrate our estimates of
star formation rates from the seven optical/UV bands. The mean molecular gas
depletion timescale, tdep(H2), for all the galaxies in our sample is 1 Gyr,
however tdep(H2) increases by a factor of 6 from a value of ~0.5 Gyr for
galaxies with stellar masses of 10^10 Msun to ~3 Gyr for galaxies with masses
of a few times 10^11 Msun. In contrast, the atomic gas depletion timescale
remains contant at a value of around 3 Gyr. This implies that in high mass
galaxies, molecular and atomic gas depletion timescales are comparable, but in
low mass galaxies, molecular gas is being consumed much more quickly than
atomic gas. The strongest dependences of tdep(H2) are on the stellar mass of
the galaxy (parameterized as log tdep(H2)= (0.36+/-0.07)(log M* -
10.70)+(9.03+/-0.99)), and on the specific star formation rate. A single
tdep(H2) versus sSFR relation is able to fit both "normal" star-forming
galaxies in our COLD GASS sample, as well as more extreme starburst galaxies
(LIRGs and ULIRGs), which have tdep(H2) < 10^8 yr. Normal galaxies at z=1-2 are
displaced with respect to the local galaxy population in the tdep(H2) versus
sSFR plane and have molecular gas depletion times that are a factor of 3-5
times longer at a given value of sSFR due to their significantly larger gas
fractions.Comment: Accepted for publication in MNRAS. 19 pages, 11 figure
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
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Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Biofuels: Current Technology and New Developments
2010 program of the “Open Forum on Energy and the Environment”, presented on October 7, 2010, from 4:00 PM-5:00 PM in room L1255, Ford Environmental Science & Technology Building (ES&T) on the Georgia Tech campus.Runtime: 50:41 minutesThe development of production routes for fuels and chemicals from alternative resources (e.g. coal, gas, biomass) is one of the great
scientific challenges of the 21st century. Biomass is a particularly interesting resource because it is CO2 neutral and the only renewable
source of organic carbon. Different types of biomass and processes for their conversion will be introduced. Biodiesel and bioethanol will
be discussed as case studies for processes that are currently operated on a commercial scale. Promising alternatives based on hydrolysis
and fermentation, pyrolysis as well as gasification will be presented
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