664 research outputs found
Cyclic and Long-term Variation of Sunspot Magnetic Fields
Measurements from the Mount Wilson Observatory (MWO) are used to study the
long-term variations of sunspot field strengths from 1920 to 1958. Following a
modified approach similar to that in Pevtsov et al. (2011), for each observing
week we select a single sunspot with the strongest field strength measured that
week and then compute monthly averages of these weekly maximum field strengths.
The data show the solar cycle variation of the peak field strengths with an
amplitude of about 500-700 gauss (G), but no statistically significant
long-term trends. Next, we use the sunspot observations from the Royal
Greenwich Observatory (RGO) to establish a relationship between the sunspot
areas and the sunspot field strengths for Cycles 15-19. This relationship is
then used to create a proxy of peak magnetic field strength based on sunspot
areas from the RGO and the USAF/NOAA network for the period from 1874 to early
2012. Over this interval, the magnetic field proxy shows a clear solar cycle
variation with an amplitude of 500-700 G and a weaker long-term trend. From
1874 to around 1920, the mean value of magnetic field proxy increases by about
300-350 G, and, following a broad maximum in 1920-1960, it decreases by about
300 G. Using the proxy for the magnetic field strength as the reference, we
scale the MWO field measurements to the measurements of the magnetic fields in
Pevtsov et al. (2011) to construct a combined data set of maximum sunspot field
strengths extending from 1920 to early 2012. This combined data set shows
strong solar cycle variations and no significant long-term trend (linear fit to
the data yields a slope of 0.8 G year). On the other hand, the
peak sunspot field strengths observed at the minimum of the solar cycle show a
gradual decline over the last three minima (corresponding to cycles 21-23) with
a mean downward trend of 15 G year
Surface state engineering of molecule-molecule interactions
Engineering the electronic structure of organics through interface
manipulation, particularly the interface dipole and the barriers to charge
carrier injection, is of essential importance to improved organic devices. This
requires the meticulous fabrication of desired organic structures by precisely
controlling the interactions between molecules. The well-known principles of
organic coordination chemistry cannot be applied without proper consideration
of extra molecular hybridization, charge transer and dipole formation at the
interfaces. Here we identify the interplay between energy level alignment,
charge transfer, surface dipole and charge pillow effect and show how these
effects collectively determine the net force between adsorbed porphyrin 2H-TPP
on Cu(111). We show that the forces between supported porphyrins can be altered
by controlling the amount of charge transferred across the interface accurately
through the relative alignment of molecular electronic levels with respect to
the Shockley surface state of the metal substrate, and hence govern the
self-assembly of the molecules
Chiral dynamics of p-wave in K^- p and coupled states
We perform an evaluation of the p-wave amplitudes of meson-baryon scattering
in the strangeness S=-1 sector starting from the lowest order chiral
Lagrangians and introducing explicitly the Sigma^* field with couplings to the
meson-baryon states obtained using SU(6) symmetry. The N/D method of
unitarization is used, equivalent, in practice, to the use of the
Bethe-Salpeter equation with a cut-off. The procedure leaves no freedom for the
p-waves once the s-waves are fixed and thus one obtains genuine predictions for
the p-wave scattering amplitudes, which are in good agreement with experimental
results for differential cross sections, as well as for the width and partial
decay widths of the Sigma^*(1385).Comment: LaTeX, 18 pages, 6 figure
Serum outperforms plasma in small extracellular vesicle microRNA biomarker studies of adenocarcinoma of the esophagus
Background: To compare computed tomography coronary angiography (CTCA) with intravascular ultrasound (IVUS) in quantitative and qualitative plaque assessment. Methods: Patients who underwent IVUS and CTCA within 3 months for suspected coronary artery disease were retrospectively studied. Plaque volumes on CTCA were quantified manually and with automated-software and were compared to IVUS. High-risk plaque features were compared between CTCA and IVUS. Results: There were 769 slices in 32 vessels (27 patients). Manual plaque quantification on CTCA was comparable to IVUS per slice (mean difference of 0.06 ± 0.07, p = 0.44; Bland-Altman 95% limits of agreement -2.19–2.08 mm3, bias of -0.06 mm3) and per vessel (3.1 mm3 ± -2.85 mm3, p = 0.92). In contrast, there was significant difference between automated-software and IVUS per slice (2.3 ± 0.09mm3, p < 0.001; 95% LoA -6.78 to 2.25 mm3, bias of -2.2 mm3) and per vessel (33.04 ± 10.3 mm3, p < 0.01). The sensitivity, specificity, positive and negative predictive value of CTCA to detect plaques that had features of echo-attenuation on IVUS was 93.3%, 99.6%, 93.3% and 99.6% respectively. The association of ≥2 high-risk plaque features on CTCA with echo attenuation (EA) plaque features on IVUS was excellent (86.7%, 99.6%, 92.9% and 99.2%). In comparison, the association of high-risk plaque features on CTCA and plaques with echo-lucency on IVUS was only modest. Conclusion: Plaque volume quantification by manual CTCA method is accurate when compared to IVUS. The presence of at least two high-risk plaque features on CTCA is associated with plaque features of echo attenuation on IVUS.Ravi Kiran Munnur, Jordan Andrews ... Dorothy Keefe ... Lorelle Smith ... Joanne Bowen ... Sarah Thompson ... et al
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV
We present the first measurement of directed flow () at RHIC. is
found to be consistent with zero at pseudorapidities from -1.2 to 1.2,
then rises to the level of a couple of percent over the range . The latter observation is similar to data from NA49 if the SPS rapidities
are shifted by the difference in beam rapidity between RHIC and SPS.
Back-to-back jets emitted out-of-plane are found to be suppressed more if
compared to those emitted in-plane, which is consistent with {\it jet
quenching}. Using the scalar product method, we systematically compared
azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow
from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure
Azimuthal anisotropy: the higher harmonics
We report the first observations of the fourth harmonic (v_4) in the
azimuthal distribution of particles at RHIC. The measurement was done taking
advantage of the large elliptic flow generated at RHIC. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding
Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV
Mid-rapidity transverse mass spectra and multiplicity densities of charged
and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC.
The spectra are exponential in transverse mass, with an inverse slope of about
280 MeV in central collisions. The multiplicity densities for these particles
scale with the negative hadron pseudo-rapidity density. The charged kaon to
pion ratios are and
for the most central collisions. The ratio is lower than the same
ratio observed at the SPS while the is higher than the SPS result.
Both ratios are enhanced by about 50% relative to p+p and +p
collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
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