11,301 research outputs found
Detection of flux emergence, splitting, merging, and cancellation of network field. I Splitting and Merging
Frequencies of magnetic patch processes on supergranule boundary, namely flux
emergence, splitting, merging, and cancellation, are investigated through an
automatic detection. We use a set of line of sight magnetograms taken by the
Solar Optical Telescope (SOT) on board Hinode satellite. We found 1636 positive
patches and 1637 negative patches in the data set, whose time duration is 3.5
hours and field of view is 112" \times 112". Total numbers of magnetic
processes are followed: 493 positive and 482 negative splittings, 536 positive
and 535 negative mergings, 86 cancellations, and 3 emergences. Total numbers of
emergence and cancellation are significantly smaller than those of splitting
and merging. Further, frequency dependences of merging and splitting processes
on flux content are investigated. Merging has a weak dependence on flux content
only with a power- law index of 0.28. Timescale for splitting is found to be
independent of parent flux content before splitting, which corresponds to \sim
33 minutes. It is also found that patches split into any flux contents with a
same probability. This splitting has a power-law distribution of flux content
with an index of -2 as a time independent solution. These results support that
the frequency distribution of flux content in the analyzed flux range is
rapidly maintained by merging and splitting, namely surface processes. We
suggest a model for frequency distributions of cancellation and emergence based
on this idea.Comment: 32 pages, 10 figures, 1 table, accepted to Ap
Recommended from our members
Differences in virus receptor for type I and type II feline infectious peritonitis virus.
Feline infectious peritonitis viruses (FIPVs) are classified into type I and type II serogroups. Here, we report that feline aminopeptidase N (APN), a cell-surface metalloprotease on the intestinal, lung and kidney epithelial cells, is a receptor for type II FIPV but not for type I FIPV. A monoclonal antibody (MAb) R-G-4, which blocks infection of Felis catus whole fetus (fcwf-4) cells by type II FIPV, was obtained by immunizing mice with fcwf-4 cells which are highly susceptible to FIPV. This MAb also blocked infection of fcwf-4 cells by type II feline enteric coronavirus (FECV), canine coronavirus (CCV), and transmissible gastroenteritis virus (TGEV). On the other hand, it did not block infection by type I FIPVs. MAb R-G-4 recognized a polypeptide of relative molecular mass 120-130 kDa in feline intestinal brush-border membrane (BBM) proteins. The polypeptide possessed aminopeptidase activity, and the first 15 N-terminal amino acid sequence was identical to that of the feline APN. Feline intestinal BBM proteins and the polypeptide reacted with MAb R-G-4 (feline APN) inhibited the infectivity of type II FIPV, type II FECV, CCV and TGEV to fcwf-4 cells, but did not inhibit the infectivity of type I FIPVs
Influence of magnetic impurities on charge transport in diffusive-normal-metal / superconductor junctions
Charge transport in the diffusive normal metal (DN) / insulator / - and -wave superconductor junctions is studied in the presence of magnetic
impurities in DN in the framework of the quasiclassical Usadel equations with
the generalized boundary conditions. The cases of - and d-wave
superconducting electrodes are considered. The junction conductance is
calculated as a function of a bias voltage for various parameters of the DN
metal: resistivity, Thouless energy, the magnetic impurity scattering rate and
the transparency of the insulating barrier between DN and a superconductor. It
is shown that the proximity effect is suppressed by magnetic impurity
scattering in DN for any value of the barrier transparency. In low-transparent
s-wave junctions this leads to the suppression of the normalized zero-bias
conductance. In contrast to that, in high transparent junctions zero-bias
conductance is enhanced by magnetic impurity scattering. The physical origin of
this effect is discussed. For the d-wave junctions, the dependence on the
misorientation angle between the interface normal and the crystal axis
of a superconductor is studied. The zero-bias conductance peak is suppressed by
the magnetic impurity scattering only for low transparent junctions with
. In other cases the conductance of the d-wave junctions does
not depend on the magnetic impurity scattering due to strong suppression of the
proximity effect by the midgap Andreev resonant states.Comment: 11 pages, 13 figures;d-wave case adde
Stark effect of excitons in individual air-suspended carbon nanotubes
We investigate electric-field induced redshifts of photoluminescence from
individual single-walled carbon nanotubes. The shifts scale quadratically with
field, while measurements with different excitation powers and energies show
that effects from heating and relaxation pathways are small. We attribute the
shifts to the Stark effect, and characterize nanotubes with different
chiralities. By taking into account exciton binding energies for air-suspended
tubes, we find that theoretical predictions are in quantitative agreement.Comment: 4 pages, 3 figure
Specific-heat study for ferromagnetic and antiferromagnetic phases in SrRu_{1-x}Mn_xO3
Low-temperature electronic states in SrRu_{1-x}Mn_xO_3 for x <= 0.6 have been
investigated by means of specific-heat C_p measurements. We have found that a
jump anomaly observed in C_p at the ferromagnetic (FM) transition temperature
for SrRuO_3 changes into a broad peak by only 5% substitution of Mn for Ru.
With further doping Mn, the low-temperature electronic specific-heat
coefficient gamma is markedly reduced from the value at x=0 (33 mJ/K^2 mol), in
connection with the suppression of the FM phase as well as the enhancement of
the resistivity. For x >= 0.4, gamma approaches to ~ 5 mJ/K^2 mol or less,
where the antiferromagnetic order with an insulating feature in resistivity is
generated. We suggest from these results that both disorder and reconstruction
of the electronic states induced by doping Mn are coupled with the magnetic
ground states and transport properties.Comment: 4 pages, 2 figures, submitted to the proceedings of ICM2009
(Karlsruhe
Spontaneous exciton dissociation in carbon nanotubes
Simultaneous photoluminescence and photocurrent measurements on individual
single-walled carbon nanotubes reveal spontaneous dissociation of excitons into
free electron-hole pairs. Correlation of luminescence intensity and
photocurrent shows that a significant fraction of excitons are dissociating
during their relaxation into the lowest exciton state. Furthermore, the
combination of optical and electrical signals also allows for extraction of the
absorption cross section and the oscillator strength. Our observations explain
the reasons for photoconductivity measurements in single-walled carbon
nanotubes being straightforward despite the large exciton binding energies.Comment: 4 pages, 3 figure
- …