1,420 research outputs found
Improvement of solar cycle prediction: Plateau of solar axial dipole moment
Aims. We report the small temporal variation of the axial dipole moment near
the solar minimum and its application to the solar cycle prediction by the
surface flux transport (SFT) model. Methods. We measure the axial dipole moment
using the photospheric synoptic magnetogram observed by the Wilcox Solar
Observatory (WSO), the ESA/NASA Solar and Heliospheric Observatory Michelson
Doppler Imager (MDI), and the NASA Solar Dynamics Observatory Helioseismic and
Magnetic Imager (HMI). We also use the surface flux transport model for the
interpretation and prediction of the observed axial dipole moment. Results. We
find that the observed axial dipole moment becomes approximately constant
during the period of several years before each cycle minimum, which we call the
axial dipole moment plateau. The cross-equatorial magnetic flux transport is
found to be small during the period, although the significant number of
sunspots are still emerging. The results indicates that the newly emerged
magnetic flux does not contributes to the build up of the axial dipole moment
near the end of each cycle. This is confirmed by showing that the time
variation of the observed axial dipole moment agrees well with that predicted
by the SFT model without introducing new emergence of magnetic flux. These
results allows us to predict the axial dipole moment in Cycle 24/25 minimum
using the SFT model without introducing new flux emergence. The predicted axial
dipole moment of Cycle 24/25 minimum is 60--80 percent of Cycle 23/24 minimum,
which suggests the amplitude of Cycle 25 even weaker than the current Cycle 24.
Conclusions. The plateau of the solar axial dipole moment is an important
feature for the longer prediction of the solar cycle based on the SFT model.Comment: 5 pages, 3 figures, accepted for publication in A&A Lette
Mechanical properties of Pt monatomic chains
The mechanical properties of platinum monatomic chains were investigated by
simultaneous measurement of an effective stiffness and the conductance using
our newly developed mechanically controllable break junction (MCBJ) technique
with a tuning fork as a force sensor. When stretching a monatomic contact
(two-atom chain), the stiffness and conductance increases at the early stage of
stretching and then decreases just before breaking, which is attributed to a
transition of the chain configuration and bond weakening. A statistical
analysis was made to investigate the mechanical properties of monatomic chains.
The average stiffness shows minima at the peak positions of the
length-histogram. From this result we conclude that the peaks in the
length-histogram are a measure of the number of atoms in the chains, and that
the chains break from a strained state. Additionally, we find that the smaller
the initial stiffness of the chain is, the longer the chain becomes. This shows
that softer chains can be stretched longer.Comment: 6 pages, 5 figure
The effect of thermal annealing on the properties of Al-AlOx-Al single electron tunneling transistors
The effect of thermal annealing on the properties of Al-AlOx-Al single
electron tunneling transistors is reported. After treatment of the devices by
annealing processes in forming gas atmosphere at different temperatures and for
different times, distinct and reproducible changes of their resistance and
capacitance values were found. According to the temperature regime, we observed
different behaviors as regards the resistance changes, namely the tendency to
decrease the resistance by annealing at T = 200 degree C, but to increase the
resistance by annealing at T = 400 degree C. We attribute this behavior to
changes in the aluminum oxide barriers of the tunnel junctions. The good
reproducibility of these effects with respect to the changes observed allows
the proper annealing treatment to be used for post-process tuning of tunnel
junction parameters. Also, the influence of the annealing treatment on the
noise properties of the transistors at low frequency was investigated. In no
case did the noise figures in the 1/f-regime show significant changes.Comment: 6 pages, 7 eps-figure
Final Report for: "Bis-pi-allylpalladium Complexes in Catalysis of Multicomponent Reactions"
The research project involved the development of new and functionally improved Pd(II) catalyst for a three-component reaction of boronic acids, allenes and imines to afford homoallylic amines that are useful in synthesis of biologically active heterocycles. Furthermore, insights into the reaction mechanism and the structure and reactivity of the catalytically active intermediates involved in this process were sought. As a result of this work, a new type of Pd-catalysts possessing an auxiliary ligand attached to the Pd center via a C-Pd and N-Pd bonds were identified, and found to be more active than the traditional catalysts derived from Pd(OAc)2. The new catalysts provided an access to a broader range of homoallylic amine products. Although the final unequivocal evidence regarding the structure of the Pd(II) complex involved in the nucleophilic transfer of the allyl fragment from the palladium center to the imine could not be obtained, mechanistic insights into the events that are detrimental to the activity of the originally reported Pd(OAc)2-based catalytic systems were uncovered
Bispectral KP Solutions and Linearization of Calogero-Moser Particle Systems
A new construction using finite dimensional dual grassmannians is developed
to study rational and soliton solutions of the KP hierarchy. In the rational
case, properties of the tau function which are equivalent to bispectrality of
the associated wave function are identified. In particular, it is shown that
there exists a bound on the degree of all time variables in tau if and only if
the wave function is rank one and bispectral. The action of the bispectral
involution, beta, in the generic rational case is determined explicitly in
terms of dual grassmannian parameters. Using the correspondence between
rational solutions and particle systems, it is demonstrated that beta is a
linearizing map of the Calogero-Moser particle system and is essentially the
map sigma introduced by Airault, McKean and Moser in 1977.Comment: LaTeX, 24 page
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