45 research outputs found
Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators
A magnetoresistance effect induced by the Rashba spin-orbit interaction was
predicted, but not yet observed, in bilayers consisting of normal metal and
ferromagnetic insulator. Here, we present an experimental observation of this
new type of spin-orbit magnetoresistance (SOMR) effect in a bilayer structure
Cu[Pt]/Y3Fe5O12 (YIG), where the Cu/YIG interface is decorated with nanosize Pt
islands. This new MR is apparently not caused by the bulk spin-orbit
interaction because of the negligible spin-orbit interaction in Cu and the
discontinuity of the Pt islands. This SOMR disappears when the Pt islands are
absent or located away from the Cu/YIG interface, therefore we can
unambiguously ascribe it to the Rashba spin-orbit interaction at the interface
enhanced by the Pt decoration. The numerical Boltzmann simulations are
consistent with the experimental SOMR results in the angular dependence of
magnetic field and the Cu thickness dependence. Our finding demonstrates the
realization of the spin manipulation by interface engineering.Comment: 12 pages, 4 figures, 14 pages in supplementary. To appear on Science
Advance
Problems of QCD factorization in exclusive decays of B meson to charmonium
We study the exclusive decays of meson into P-wave charmonium states
in the QCD factorization approach with light-cone
distribution functions describing the mesons in the processes. For decay, we find that there are logarithmic divergences arising from
nonfactorizable spectator interactions even at twist-2 order and the decay rate
is too small to accommodate the experimental data. For
decay, we find that aside from the logarithmic divergences arising from
spectator interactions at leading-twist order, more importantly, the
factorization will break down due to the infrared divergence arising from
nonfactorizable vertex corrections, which is independent of the specific form
of the light-cone distribution functions. Our results may indicate that QCD
factorization in the present form may not be safely applied to -meson
exclusive decays to charmonium states.Comment: Latex, 7 pages, 1 eps figure, final version to appear in Phys.Lett.B;
a few references are added, the expression of chi_c1 decay constant is give
Anomalous behavior of trapping on a fractal scale-free network
It is known that the heterogeneity of scale-free networks helps enhancing the
efficiency of trapping processes performed on them. In this paper, we show that
transport efficiency is much lower in a fractal scale-free network than in
non-fractal networks. To this end, we examine a simple random walk with a fixed
trap at a given position on a fractal scale-free network. We calculate
analytically the mean first-passage time (MFPT) as a measure of the efficiency
for the trapping process, and obtain a closed-form expression for MFPT, which
agrees with direct numerical calculations. We find that, in the limit of a
large network order , the MFPT behaves superlinearly as with an exponent 3/2 much larger than 1, which is in sharp contrast
to the scaling with , previously obtained
for non-fractal scale-free networks. Our results indicate that the degree
distribution of scale-free networks is not sufficient to characterize trapping
processes taking place on them. Since various real-world networks are
simultaneously scale-free and fractal, our results may shed light on the
understanding of trapping processes running on real-life systems.Comment: 6 pages, 5 figures; Definitive version accepted for publication in
EPL (Europhysics Letters
Diffractive D_s production in charged current DIS
We present a perturbative QCD calculation of diffractive production in
charged current deep inelastic scattering. In the two-gluon exchange model, we
analyze the diffractive process \nu N \to \mu^- N \Ds, which may provide
useful information for the gluon structure of nucleons and the diffraction
mechanism in QCD. The cross section of diffractive production with
\xBj=0.005-0.05 and Gev is found to be pb. In
spite of this small cross section, the high luminosity available at the
-Factory in the future would lead to a sizable number of diffraction
events.Comment: 6 pages, 5 eps figures, final version to appear in PL
Transition from fractal to non-fractal scalings in growing scale-free networks
Real networks can be classified into two categories: fractal networks and
non-fractal networks. Here we introduce a unifying model for the two types of
networks. Our model network is governed by a parameter . We obtain the
topological properties of the network including the degree distribution,
average path length, diameter, fractal dimensions, and betweenness centrality
distribution, which are controlled by parameter . Interestingly, we show
that by adjusting , the networks undergo a transition from fractal to
non-fractal scalings, and exhibit a crossover from `large' to small worlds at
the same time. Our research may shed some light on understanding the evolution
and relationships of fractal and non-fractal networks.Comment: 7 pages, 3 figures, definitive version accepted for publication in
EPJ
Deterministic weighted scale-free small-world networks
We propose a deterministic weighted scale-free small-world model for
considering pseudofractal web with the coevolution of topology and weight. In
the model, we have the degree distribution exponent restricted to a
range between 2 and 3, simultaneously tunable with two parameters. At the same
time, we provide a relatively complete view of topological structure and weight
dynamics characteristics of the networks: weight and strength distribution;
degree correlations; average clustering coefficient and degree-cluster
correlations; as well as the diameter. We show that our model is particularly
effective at mimicing weighted scale-free small-world networks with a high and
relatively stable clustering coefficient, which rapidly decline with the
network size in most previous models.Comment: a paper with 15 pages and 5 figure
Role of fractal dimension in random walks on scale-free networks
Fractal dimension is central to understanding dynamical processes occurring
on networks; however, the relation between fractal dimension and random walks
on fractal scale-free networks has been rarely addressed, despite the fact that
such networks are ubiquitous in real-life world. In this paper, we study the
trapping problem on two families of networks. The first is deterministic, often
called -flowers; the other is random, which is a combination of
-flower and -flower and thus called hybrid networks. The two
network families display rich behavior as observed in various real systems, as
well as some unique topological properties not shared by other networks. We
derive analytically the average trapping time for random walks on both the
-flowers and the hybrid networks with an immobile trap positioned at an
initial node, i.e., a hub node with the highest degree in the networks. Based
on these analytical formulae, we show how the average trapping time scales with
the network size. Comparing the obtained results, we further uncover that
fractal dimension plays a decisive role in the behavior of average trapping
time on fractal scale-free networks, i.e., the average trapping time decreases
with an increasing fractal dimension.Comment: Definitive version published in European Physical Journal
Mean first-passage time for random walks on undirected networks
In this paper, by using two different techniques we derive an explicit
formula for the mean first-passage time (MFPT) between any pair of nodes on a
general undirected network, which is expressed in terms of eigenvalues and
eigenvectors of an associated matrix similar to the transition matrix. We then
apply the formula to derive a lower bound for the MFPT to arrive at a given
node with the starting point chosen from the stationary distribution over the
set of nodes. We show that for a correlated scale-free network of size with
a degree distribution , the scaling of the lower bound is
. Also, we provide a simple derivation for an eigentime
identity. Our work leads to a comprehensive understanding of recent results
about random walks on complex networks, especially on scale-free networks.Comment: 7 pages, no figures; definitive version published in European
Physical Journal
Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial
Background: Previous cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.
Methods: We conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.
Results: Forty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference − 0.40 [95% CI − 0.71 to − 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference − 1.6% [95% CI − 4.3% to 1.2%]; P = 0.42) between groups.
Conclusions: In this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness. Trial registration: ISRCTN, ISRCTN12233792. Registered November 20th, 2017
Actively implementing an evidence-based feeding guideline for critically ill patients (NEED): a multicenter, cluster-randomized, controlled trial (vol 26, 46, 2022)
BackgroundPrevious cluster-randomized controlled trials evaluating the impact of implementing evidence-based guidelines for nutrition therapy in critical illness do not consistently demonstrate patient benefits. A large-scale, sufficiently powered study is therefore warranted to ascertain the effects of guideline implementation on patient-centered outcomes.MethodsWe conducted a multicenter, cluster-randomized, parallel-controlled trial in intensive care units (ICUs) across China. We developed an evidence-based feeding guideline. ICUs randomly allocated to the guideline group formed a local "intervention team", which actively implemented the guideline using standardized educational materials, a graphical feeding protocol, and live online education outreach meetings conducted by members of the study management committee. ICUs assigned to the control group remained unaware of the guideline content. All ICUs enrolled patients who were expected to stay in the ICU longer than seven days. The primary outcome was all-cause mortality within 28 days of enrollment.ResultsForty-eight ICUs were randomized to the guideline group and 49 to the control group. From March 2018 to July 2019, the guideline ICUs enrolled 1399 patients, and the control ICUs enrolled 1373 patients. Implementation of the guideline resulted in significantly earlier EN initiation (1.20 vs. 1.55 mean days to initiation of EN; difference - 0.40 [95% CI - 0.71 to - 0.09]; P = 0.01) and delayed PN initiation (1.29 vs. 0.80 mean days to start of PN; difference 1.06 [95% CI 0.44 to 1.67]; P = 0.001). There was no significant difference in 28-day mortality (14.2% vs. 15.2%; difference - 1.6% [95% CI - 4.3% to 1.2%]; P = 0.42) between groups.ConclusionsIn this large-scale, multicenter trial, active implementation of an evidence-based feeding guideline reduced the time to commencement of EN and overall PN use but did not translate to a reduction in mortality from critical illness.Trial registrationISRCTN, ISRCTN12233792 . Registered November 20th, 2017