1,575 research outputs found
Can surface flux transport account for the weak polar field in cycle 23?
To reproduce the weak magnetic field on the polar caps of the Sun observed
during the declining phase of cycle 23 poses a challenge to surface flux
transport models since this cycle has not been particularly weak. We use a
well-calibrated model to evaluate the parameter changes required to obtain
simulated polar fields and open flux that are consistent with the observations.
We find that the low polar field of cycle 23 could be reproduced by an increase
of the meridional flow by 55% in the last cycle. Alternatively, a decrease of
the mean tilt angle of sunspot groups by 28% would also lead to a similarly low
polar field, but cause a delay of the polar field reversals by 1.5 years in
comparison to the observations.Comment: 9 pages, 8 figures, Space Science Reviews, accepte
Global Incidence and mortality of oesophageal cancer and their correlation with socioeconomic indicators temporal patterns and trends in 41 countries
Oesophageal cancers (adenocarcinomas [AC] and squamous cell carcinomas [SCC]) are characterized by high incidence/mortality in many countries. We aimed to delineate its global incidence and mortality, and studied whether socioeconomic development and its incidence rate were correlated. The age-standardized rates (ASRs) of incidence and mortality of this medical condition in 2012 for 184 nations from the GLOBOCAN database; national databases capturing incidence rates, and the WHO mortality database were examined. Their correlations with two indicators of socioeconomic development were evaluated. Joinpoint regression analysis was used to generate trends. The ratio between the ASR of AC and SCC was strongly correlated with HDI (r = 0.535 [men]; r = 0.661 [women]) and GDP (r = 0.594 [men]; r = 0.550 [women], both p < 0.001). Countries that reported the largest reduction in incidence in male included Poland (Average Annual Percent Change [AAPC] = −7.1, 95%C.I. = −12,−1.9) and Singapore (AAPC = −5.8, 95%C.I. = −9.5,−1.9), whereas for women the greatest decline was seen in Singapore (AAPC = −12.3, 95%C.I. = −17.3,−6.9) and China (AAPC = −5.6, 95%C.I. = −7.6,−3.4). The Philippines (AAPC = 4.3, 95%C.I. = 2,6.6) and Bulgaria (AAPC = 2.8, 95%C.I. = 0.5,5.1) had a significant mortality increase in men; whilst Columbia (AAPC = −6.1, 95%C.I. = −7.5,−4.6) and Slovenia (AAPC = −4.6, 95%C.I. = −7.9,−1.3) reported mortality decline in women. These findings inform individuals at increased risk for primary prevention
Delay-induced Synchronization Phenomena in an Array of Globally Coupled Logistic Maps
We study the synchronization of a linear array of globally coupled identical
logistic maps. We consider a time-delayed coupling that takes into account the
finite velocity of propagation of the interactions. We find globally
synchronized states in which the elements of the array evolve along a periodic
orbit of the uncoupled map, while the spatial correlation along the array is
such that an individual map sees all other maps in his present, current, state.
For values of the nonlinear parameter such that the uncoupled maps are chaotic,
time-delayed mutual coupling suppress the chaotic behavior by stabilizing a
periodic orbit which is unstable for the uncoupled maps. The stability analysis
of the synchronized state allows us to calculate the range of the coupling
strength in which global synchronization can be obtained.Comment: 8 pages, 7 figures, changed content, added reference
Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24
Recently, using Greenwich and Solar Optical Observing Network sunspot group
data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I),
has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg
latitude interval of the Sun's northern hemisphere and in the time-interval of
-1.35 year to +2.15 year from the time of the preceding minimum of a solar
cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of
the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the
areas of the spot groups in 0-10 deg latitude interval of the southern
hemisphere and in the time-interval of 1.0 year to 1.75 year just after the
time of the maximum of the cycle n correlates very well (r=0.966) with the
amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or
- 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude
of the upcoming cycle 24. Here we found that in case of (1), the north-south
asymmetry in the area sum of a cycle n also has a relationship, say (3), with
the amplitude of cycle n+1, which is similar to (1) but more statistically
significant (r=0.968) like (2). By using (3) it is possible to predict the
amplitude of a cycle with a better accuracy by about 13 years in advance, and
we get 103 + or -10 for the amplitude of the upcoming cycle 24. However, we
found a similar but a more statistically significant (r=0.983) relationship,
say (4), by using the sum of the area sum used in (2) and the north-south
difference used in (3). By using (4) it is possible to predict the amplitude of
a cycle by about 9 years in advance with a high accuracy and we get 87 + or - 7
for the amplitude of cycle 24.Comment: 21 pages, 7 figures, Published in Solar Physics 252, 419-439 (2008
Search for exotic baryons in double radiative capture on pionic hydrogen
We report a search for low-lying exotic baryons via double radiative capture
on pionic hydrogen. The data were collected at the TRIUMF cyclotron using the
RMC spectrometer by detecting gamma-ray pairs from pion stops in liquid
hydrogen. No evidence was found to support an earlier claim for exotic baryons
of masses 1004 and 1044 MeV/. We obtain upper limits on the branching
ratios for double radiative capture via these exotic states of and respectively.Comment: 13 pages, 4 figure
Photosynthetic characteristics of summer maize under different planting patterns and the responses to nitrogen application of previous crop
Maize (Zea mays L.) is one of the most important grain crops in the North China Plain. Management practices affect the photosynthetic characteristics and the production of summer maize. This two-year (2014-2015) study examined the effects of different planting patterns and the application of nitrogen to previous winter wheat (Triticum aestivum L.) on the photosynthetic characteristics, yield and radiation use efficiency (RUE) of summer maize. Field experiments used a two-factor split-plot design with three replicates at Taian, Shandong Province, China (36°09′ N, 117°09′ E). The experiments involved two planting patterns (ridge planting, RP; and uniform row planting, UR) and two nitrogen application levels of previous winter wheat (N1, 112.50 kg ha-1; N2, 225.00 kg ha-1). The results indicated that the application of nitrogen on previous crop and ridge planting of the following crop had significant effects on the photosynthetic characteristics and yields of summer maize. Compared with UR, this study found that RP increased the chlorophyll content index (CCI), leaf area index (LAI), net photosynthetic rate (Pn), dry matter (DM), yield and grain RUE by 4.1%, 6.3%, 5.2%, 6.4%, 8.9% and 9.4%, respectively. The CCI, LAI, Pn, yield, and grain RUE of N2 were 9.7%, 3.3%, 3.7%, 10.0% and 10.1% higher than those of N1, respectively. RP combined with the application of nitrogen on previous crop of winter wheat could increase the CCI, LAI, Pn, DM, ultimately increasing the grain yield and RUE of the following summer’s maize. It was concluded that previous crop nitrogen application and RP pattern treatment resulted in optimal cropping conditions for the North China plain
Long range forces and limits on unparticle interactions
Couplings between standard model particles and unparticles from a nontrivial
scale invariant sector can lead to long range forces. If the forces couple to
quantities such as baryon or lepton (electron) number, stringent limits result
from tests of the gravitational inverse square law. These limits are much
stronger than from collider phenomenology and astrophysics.Comment: 7 pages, revtex; v2 minor changes and added reference
Hamiltonian Theory of the Composite Fermion Wigner Crystal
Experimental results indicating the existence of the high magnetic field
Wigner Crystal have been available for a number of years. While variational
wavefunctions have demonstrated the instability of the Laughlin liquid to a
Wigner Crystal at sufficiently small filling, calculations of the excitation
gaps have been hampered by the strong correlations. Recently a new Hamiltonian
formulation of the fractional quantum Hall problem has been developed. In this
work we extend the Hamiltonian approach to include states of nonuniform
density, and use it to compute the excitation gaps of the Wigner Crystal
states. We find that the Wigner Crystal states near are
quantitatively well described as crystals of Composite Fermions with four
vortices attached. Predictions for gaps and the shear modulus of the crystal
are presented, and found to be in reasonable agreement with experiments.Comment: 41 page, 6 figures, 3 table
Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-potential Simulations
Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic-field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models cannot. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux-transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux-transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude–time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed
Muon-spin rotation and magnetization studies of chemical and hydrostatic pressure effects in EuFe_{2}(As_{1-x}P_{x})_{2}
The magnetic phase diagram of EuFe(AsP) was
investigated by means of magnetization and muon-spin rotation studies as a
function of chemical (isovalent substitution of As by P) and hydrostatic
pressure. The magnetic phase diagrams of the magnetic ordering of the Eu and Fe
spins with respect to P content and hydrostatic pressure are determined and
discussed. The present investigations reveal that the magnetic coupling between
the Eu and the Fe sublattices strongly depends on chemical and hydrostatic
pressure. It is found that chemical and hydrostatic pressure have a similar
effect on the Eu and Fe magnetic order.Comment: 11 pages, 10 figure
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