1,471 research outputs found
Why are Prices Sticky? Evidence from Business Survey Data
This paper offers new insights on the price setting behaviour of German retail firms using a novel dataset that
consists of a large panel of monthly business surveys from 1991-2006. The firm-level data allows matching changes
in firms' prices to several other firm-characteristics. Moreover, information on price expectations allow analyzing
the determinants of price updating. Using univariate and bivariate ordered probit specifications, empirical menu
cost models are estimated relating the probability of price adjustment and price updating, respectively, to both
time- and state- dependent variables. First, results suggest an important role for state-dependence; changes in
the macroeconomic and institutional environment as well as firm-specific factors are significantly related to the
timing of price adjustment. These findings imply that price setting models should endogenize the timing of price
adjustment in order to generate realistic predictions concerning the transmission of monetary policy. Second, an
analysis of price expectations yields similar results providing evidence in favour of state-dependent sticky plan
models. Third, intermediate input cost changes are among the most important determinants of price adjustment
suggesting that pricing models should explicitly incorporate price setting at different production stages. However, the results show that adjustment to input cost changes takes time indicating "additional stickiness" at the last stage of processing
Breeding Small Grains as a Forage, Silage and Cover Crop for the Southern Coastal Plain (USA) in a Changing Climatic Environment
Forage breeding of small grains in the southern Coastal Plains region of the U.S. mimic many other countries experiencing climate changes and breeding strategies should be similar for improving small grains grown for forage, silage or as cover crops. Significant focus on improvements in stress-adaptation has encouraged members of the SunGrains cooperative to cross, evaluate and develop experimental lines with inherent adaptation to climatic conditions including heat stress, drought tolerance, short-day and long-day forage production periods, and flooded conditions for events with storm-related, short-term durations. Many new cultivars, grown throughout the southeastern U.S. have resulted from breeding selection under abiotic and biotic stresses, adapted to climate change and related concerns, such as disease and insect pests
Measurement of event-by-event transverse momentum and multiplicity fluctuations using strongly intensive measures and in nucleus-nucleus collisions at the CERN Super Proton Synchrotron
Results from the NA49 experiment at the CERN SPS are presented on
event-by-event transverse momentum and multiplicity fluctuations of charged
particles, produced at forward rapidities in central Pb+Pb interactions at beam
momenta 20, 30, 40, 80, and 158 GeV/c, as well as in systems of
different size (, C+C, Si+Si, and Pb+Pb) at 158 GeV/c. This publication
extends the previous NA49 measurements of the strongly intensive measure
by a study of the recently proposed strongly intensive measures of
fluctuations and . In the explored kinematic
region transverse momentum and multiplicity fluctuations show no significant
energy dependence in the SPS energy range. However, a remarkable system size
dependence is observed for both and , with the
largest values measured in peripheral Pb+Pb interactions. The results are
compared with NA61/SHINE measurements in collisions, as well as with
predictions of the UrQMD and EPOS models.Comment: 12 pages, 14 figures, to be submitted to PR
Combined Free-running 4D anatomical and flow MRI with native contrast using Synchronization of Neighboring Acquisitions by Physiological Signals (SyNAPS).
BACKGROUND
4D flow MRI often relies on the injection of gadolinium- or iron-oxide-based contrast agents to improve vessel delineation. In this work, a novel technique is developed to acquire and reconstruct 4D flow data with excellent dynamic visualization of blood vessels but without the need for contrast injection. Synchronization of Neighboring Acquisitions by Physiological Signals (SyNAPS) uses Pilot Tone (PT) navigation to retrospectively synchronize the reconstruction of two free-running 3D radial acquisitions, to create co-registered anatomy and flow images.
METHODS
Thirteen volunteers and two Marfan Syndrome patients were scanned without contrast agent using one free-running fast interrupted steady-state (FISS) sequence and one free-running phase-contrast MRI (PC-MRI) sequence. PT signals spanning the two sequences were recorded for retrospective respiratory motion correction and cardiac binning. The magnitude and phase images reconstructed, respectively, from FISS and PC-MRI, were synchronized to create SyNAPS 4D flow datasets. Conventional 2D flow data were acquired for reference in ascending (AAo) and descending aorta (DAo). The blood-to-myocardium contrast ratio, dynamic vessel area, net volume, and peak flow were used to compare SyNAPS 4D flow with Native 4D flow (without FISS information) and 2D flow. A score of 0-4 was given to each dataset by two blinded experts regarding the feasibility of performing vessel delineation.
RESULTS
Blood-to-myocardium contrast ratio for SyNAPS 4D flow magnitude images (1.5±0.3) was significantly higher than for Native 4D flow (0.7±0.1, p<0.01), and was comparable to 2D flow (2.3±0.9, p=0.02). Image quality scores of SyNAPS 4D flow from the experts (MP: 1.9±0.3, ET: 2.5±0.5) were overall significantly higher than the scores from Native 4D flow (MP: 1.6±0.6, p=0.03, ET: 0.8±0.4, p<0.01) but still significantly lower than the scores from the reference 2D flow datasets (MP: 2.8±0.4, p<0.01, ET: 3.5±0.7, p<0.01). The Pearson correlation coefficient between the dynamic vessel area measured on SyNAPS 4D flow and that from 2D flow was 0.69±0.24 for the AAo and 0.83±0.10 for the DAo, whereas the Pearson correlation between Native 4D flow and 2D flow measurements was 0.12±0.48 for the AAo and 0.08±0.39 for the DAo. Linear correlations between SyNAPS 4D flow and 2D flow measurements of net volume (r2=0.83) and peak flow (r2=0.87) were larger than the correlations between Native 4D flow and 2D flow measurements of net volume (r2=0.79) and peak flow (r2=0.76).
DISCUSSION AND CONCLUSION
The feasibility and utility of SyNAPS was demonstrated for joint whole-heart anatomical and flow MRI without requiring ECG gating, respiratory navigators, or contrast agents. Using SyNAPS a high-contrast anatomical imaging sequence can be used to improve 4D flow measurements that often suffer from poor delineation of vessel boundaries in the absence of contrast agents
System-size and centrality dependence of charged kaon and pion production in nucleus-nucleus collisions at 40A GeV and158A GeV beam energy
Measurements of charged pion and kaon production are presented in centrality
selected Pb+Pb collisions at 40A GeV and 158A GeV beam energy as well as in
semi-central C+C and Si+Si interactions at 40A GeV. Transverse mass spectra,
rapidity spectra and total yields are determined as a function of centrality.
The system-size and centrality dependence of relative strangeness production in
nucleus-nucleus collisions at 40A GeV and 158A GeV beam energy are derived from
the data presented here and published data for C+C and Si+Si collisions at 158A
GeV beam energy. At both energies a steep increase with centrality is observed
for small systems followed by a weak rise or even saturation for higher
centralities. This behavior is compared to calculations using transport models
(UrQMD and HSD), a percolation model and the core-corona approach.Comment: 32 pages, 14 figures, 4 tables, typo table II correcte
Energy dependence of kaon-to-proton ratio fluctuations in central Pb+Pb collisions from = 6.3 to 17.3 GeV
Kaons and protons carry large parts of two conserved quantities, strangeness
and baryon number. It is argued that their correlation and thus also
fluctuations are sensitive to conditions prevailing at the anticipated
parton-hadron phase boundary. Fluctuations of the and
ratios have been measured for the first time by NA49 in central Pb+Pb
collisions at 5 SPS energies between = 6.3 GeV and 17.3 GeV.
Both ratios exhibit a change of sign in , a measure of
non-statistical fluctuations, around = 8 GeV. Below this
energy, is positive, indicating higher fluctuation
compared to a mixed event background sample, while for higher energies,
is negative, indicating correlated emission of kaons
and protons. The results are compared to UrQMD calculations which which give a
good description at the higher SPS energies, but fail to reproduce the
transition to positive values.Comment: 5 pages, 4 figure
Multiplicity and transverse momentum fluctuations in inelastic proton-proton interactions at the CERN Super Proton Synchrotron
Measurements of multiplicity and transverse momentum fluctuations of charged
particles were performed in inelastic p+p interactions at 20, 31, 40, 80 and
158 GeV/c beam momentum. Results for the scaled variance of the multiplicity
distribution and for three strongly intensive measures of multiplicity and
transverse momentum fluctuations \$\Delta[P_{T},N]\$, \$\Sigma[P_{T},N]\$ and
\$\Phi_{p_T}\$ are presented. For the first time the results on fluctuations
are fully corrected for experimental biases. The results on multiplicity and
transverse momentum fluctuations significantly deviate from expectations for
the independent particle production. They also depend on charges of selected
hadrons. The string-resonance Monte Carlo models EPOS and UrQMD do not describe
the data. The scaled variance of multiplicity fluctuations is significantly
higher in inelastic p+p interactions than in central Pb+Pb collisions measured
by NA49 at the same energy per nucleon. This is in qualitative disagreement
with the predictions of the Wounded Nucleon Model. Within the statistical
framework the enhanced multiplicity fluctuations in inelastic p+p interactions
can be interpreted as due to event-by-event fluctuations of the fireball energy
and/or volume.Comment: 18 pages, 12 figure
Centrality dependence of proton and antiproton spectra in Pb+Pb collisions at 40A GeV and 158A GeV measured at the CERN SPS
The yields of (anti-)protons were measured by the NA49 Collaboration in
centrality selected Pb+Pb collisions at 40A GeV and 158A GeV. Particle
identification was obtained in the laboratory momentum range from 5 to 63 GeV/c
by the measurement of the energy loss dE/dx in the TPC detector gas. The
corresponding rapidity coverage extends 1.6 units from mid-rapidity into the
forward hemisphere. Transverse mass spectra, the rapidity dependences of the
average transverse mass, and rapidity density distributions were studied as a
function of collision centrality. The values of the average transverse mass as
well as the midrapidity yields of protons when normalized to the number of
wounded nucleons show only modest centrality dependences. In contrast, the
shape of the rapidity distribution changes significantly with collision
centrality, especially at 40A GeV. The experimental results are compared to
calculations of the HSD and UrQMD transport models.Comment: 25 pages, 12 figures, submitted to PR
Measurement of Production Properties of Positively Charged Kaons in Proton-Carbon Interactions at 31 GeV/c
Spectra of positively charged kaons in p+C interactions at 31 GeV/c were
measured with the NA61/SHINE spectrometer at the CERN SPS. The analysis is
based on the full set of data collected in 2007 with a graphite target with a
thickness of 4% of a nuclear interaction length. Interaction cross sections and
charged pion spectra were already measured using the same set of data. These
new measurements in combination with the published ones are required to improve
predictions of the neutrino flux for the T2K long baseline neutrino oscillation
experiment in Japan. In particular, the knowledge of kaon production is crucial
for precisely predicting the intrinsic electron neutrino component and the high
energy tail of the T2K beam. The results are presented as a function of
laboratory momentum in 2 intervals of the laboratory polar angle covering the
range from 20 up to 240 mrad. The kaon spectra are compared with predictions of
several hadron production models. Using the published pion results and the new
kaon data, the K+/\pi+ ratios are computed.Comment: 10 pages, 11 figure
Antideuteron and deuteron production in mid-central Pb+Pb collisions at 158 GeV
Production of deuterons and antideuterons was studied by the NA49 experiment
in the 23.5% most central Pb+Pb collisions at the top SPS energy of
=17.3 GeV. Invariant yields for and were measured
as a function of centrality in the center-of-mass rapidity range .
Results for together with previously published
measurements are discussed in the context of the coalescence model. The
coalescence parameters were deduced as a function of transverse momentum
and collision centrality.Comment: 9 figure
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