3,204 research outputs found
A Search For Solar Hadronic Axions Using Kr-83
We introduce a new experimental method for solar hadronic axions search. It
is suggested that these axions are created in the Sun during M1 transition
between the first thermally excited level at 9.4 keV and the ground state in
. Our method is based on axion detection via resonant absorption
process by the same nucleus in the laboratory. We use proportional gas counter
filled with krypton to detect signals for axions. With this setup, target and
detector are the same which increases the efficiency of the experiment. At
present, an upper limit on hadronic axion mass of 5.5 keV at the 95% confidence
level is obtained.Comment: 3 pages, contribution to ISRP9 Conference in Cape Town 2003. Version
accepted by Radiat. Phys. Che
Search for energetic cosmic axions utilizing terrestrial/celestial magnetic fields
Orbiting -detectors combined with the magnetic field of the Earth or
the Sun can work parasitically as cosmic axion telescopes. The relatively short
field lengths allow the axion-to-photon conversion to be coherent for
eV, if the axion kinetic energy is above
keV (Earth's field), or, MeV (Sun's field), allowing thus to search
for axions from annihilations, from supernova explosions, etc. With a
detector angular resolution of , a more efficient sky survey for
energetic cosmic axions passing {\it through the Sun} can be performed. Axions
or other axion-like particles might be created by the interaction of the cosmic
radiation with the Sun, similarly to the axion searches in accelerator beam
dump experiments; the enormous cosmic energy combined with the built-in
coherent Primakoff effect might provide a sensitive detection scheme, being out
of reach with accelerators. The axion signal will be an excess in -rays
coming either from a specific celestial place behind the Sun, e.g. the Galactic
Center, or, from any other direction in the sky being associated with a violent
astrophysical event, e.g. a supernova. Earth bound detectors are also of
potential interest. The axion scenario also applies to other stars or binary
systems in the Universe, in particular to those with superstrong magnetic
fields.Comment: 9 pages, LaTeX, small changes in text and bibliograph
Four-electron shell structures and an interacting two-electron system in carbon nanotube quantum dots
Low-temperature transport measurements have been carried out on single-wall
carbon nanotube quantum dots in a weakly coupled regime in magnetic fields up
to 8 Tesla. Four-electron shell filling was observed, and the magnetic field
evolution of each Coulomb peak was investigated, in which magnetic field
induced spin flip and resulting spin polarization were observed. Excitation
spectroscopy measurements have revealed Zeeman splitting of single particle
states for one electron in the shell, and demonstrated singlet and triplet
states with direct observation of the exchange splitting at zero-magnetic field
for two electrons in the shell, the simplest example of the Hund's rule. The
latter indicates the direct analogy to an artificial He atom.Comment: 4 pages, 3 figures, submitted to Physical Review Letter
Nonstructural Carbohydrate Reserves of Temperate Perennial Grasses in Autumn Early Growth
The objective of this study was to determine levels of nonstructural carbohydrate reserves of four temperate perennial grasses: Orchardgrass (Dactylis glomerata L.), Timothy (Phleum pratense L.), Perennial ryegrass (Lolium perenne L.), and Reed canarygrass (Phalaris arundinacea L.) in their early growth stages during the cool autumn temperatures in northern Japan. At the time of sampling, all grasses were in their vegetative stage, and Reed canarygrass was not forming rhizomes. Fructosan concentration in reed canarygrass roots (8.04%) was 22 times that of the leaf blade (0.36%) and twice that of the stem (3.40%); the concentration in reed canarygrass root was the highest of the four grasses. Timothy stored fructosan in the root at a significantly higher concentration (1.65%) than did the orchardgrass (0.58%) and perennial ryegrass (0.83%). The concentration of fructosan in the timothy was the highest in the stem, the lowest in the leaf blade and intermediate in the root. On the other hand, orchardgrass and perennial ryegrass stored the highest amount of fructosan in the stem, the lowest amount in the root, and an intermediate amount in the leaf blade. In addition, the root dry weight and the ratio of the root dry weight to the total dry weight were significantly higher in reed canarygrass than in the other three grasses. Timothy was in second place surpassing orchardgrass and perennial ryegrass. We considered that winter survival is the highest in reed canarygrass and second highest in timothy over orchard grass and perennial ryegrass
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