441 research outputs found
Search for particle-stable tetraneutrons in thermal fission of U
Background: The existence of a tetraneutron comprising four neutrons has long
been debated.
Purpose: Motivated by a recent observation of particle-stable tetraneutrons,
we investigated potential particle-stable tetraneutron emission in thermal
neutron-induced U fission using a nuclear research reactor.
Methods: We performed -ray spectroscopy for a SrCO sample
irradiated in a reactor core. Stable Sr was expected to produce
Sr by a tetraneutron-induced (,n) reaction; hence, observation of
-rays followed by decay of Sr would indicate
particle-stable tetraneutron emission.
Results: The -ray spectrum of an irradiated SrCO sample
did not show any photopeak for Sr.
Conclusion: The emission rate of particle-stable tetraneutrons, if they
exist, is estimated to be lower than per fission at the 95%
confidence level, assuming the cross-sections of reactions induced by
hypothetical particle-stable tetraneutrons.Comment: 6 pages, 2 figures, accepted for publication in Phys. Rev.
Search for Tetraneutron by Pion Double Charge Exchange Reaction at J-PARC
Tetraneutron () has come back in the limelight, because of recent
observation of a candidate resonant state at RIBF. We propose to investigate
the pion double charge exchange (DCX) reaction, i.e. , as an alternative way to populate tetraneutron. An intense
beam with the kinetic energy of ~850 MeV, much higher than that in past
experiments at LAMPF and TRIUMF, will open up a possibility to improve the
experimental sensitivity of the formation cross section, which will be much
smaller than hitherto known DCX cross sections such as .Comment: 4 pages, 1 figure; proceedings of the 14th International Conference
on Meson-Nucleon Physics and the Structure of the Nucleon (MENU2016), Kyoto,
Japan, 25-30 July 201
Further evaluation of empirical management procedures based on longline CPUE index and aerial survey index
Based on recommendations made during the third Operating Model and Management Procedure Technical Meeting (June 2010, Seattle), we have revised and evaluated “HK” Management Procedures (MPs) using empirical algorithms to determine TACs using information from the longline CPUE series and the aerial survey (AS) index. The exploration of HK variants showed that this MP can behave in a variety of ways as its control parameters and sub-algorithms are changed. As evident also from previous trials, MPs with larger TAC reduction in the early years, which might not be preferred from a socio-economic viewpoint, enable quicker stock rebuilding and greater TAC increases in later years, while still achieving the same long-term management target for spawning biomass recovery (though this comparison is complicated by transient effects)
Pressure-induced phase transition for single crystalline LaO0.5F0.5BiSe2
We have demonstrated a pressure-induced phase transition from a low-Tc phase
to a high-Tc phase in a single crystal of the superconductor LaO0.5F0.5BiSe2.
The high-Tc phase appears at 2.16 GPa and the maximum superconducting
transition temperature (Tc) is observed at 6.7 K under 2.44 GPa. Although the
anisotropy ({\gamma}) for the low-Tc phase is estimated to be 20, it is reduced
by around half (9.3) in the high-Tc phase. This tendency is the same for the
BiS2 system. The Tc of LaO0.5F0.5BiSe2 has continued to increase up to the
maximum pressure of this study (2.44 GPa). Therefore applied further pressure
has the potential to induce a much higher Tc in this system.Comment: 12 pages, 4 figure
Crystallization characteristics of amorphous trehalose dried from alcohol
Trehalose forms a glass that can be used to preserve labile substances under desiccation. The crystallization characteristics, namely crystallization temperature (Tcry) and isothermal crystallization behavior of amorphous trehalose, dried from alcohol (methanol, ethanol), was analyzed and the results were compared with those for the amorphous trehalose freeze-dried from water. The use of alcohol as a solvent lowered the Tcry from 184 ± 6 °C for the case of an aqueous solvent to 103 ± 5 °C/methanol and 120 ± 8 °C/ethanol. The formation of multiple forms of crystals and partial melting were suggested by the thermal analysis. Isothermal crystallization experiments showed that the alcohol-originated amorphous trehalose was eventually exclusively converted into β-form crystals. The induction period (tind) before the start of isothermal crystallization was markedly shortened when alcohol was used as the solvent compared to water. The tind values for various amorphous sugar samples including the alcohol-originated ones could be correlated with difference between Tcry and the sample temperature
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