The local compression technique is used to achieve a straight crack front in weld specimens. However, some interested parties have reported that it decreases the fracture toughness value. The authors ...investigated the better local compression condition for securing a straight crack front while maintaining the fracture toughness value by a numerical analysis, and as a result, some local compression conditions, which do not involve compression of the crack tip, identified as promising. Fracture toughness tests were also conducted with these local compressions, and the test results showed that the fatigue precrack shape and fracture toughness value follows those estimated tendency by the numerical analysis. Two local compression conditions, which compress at the future notch side and ligament side by a square jig and at the ligament side by a circle jig, achieved a straight crack front while maintaining the fracture toughness value. The authors concluded that these new techniques are superior to that recommended in ISO 15,653.
Various isotopes of Ac, Ra, Fr, and Rn were produced by fusion-evaporation reactions using a 48Ca beam. The energetic ions were stopped in and extracted from a helium gas cell. The extracted ions ...were identified using a multi-reflection time-of-fight mass spectrograph. In all cases, it was observed that the predominant charge state for the extracted ions, including the alkali Fr, was 2+.
We have surveyed the neutron separation energies (S(n)) and the interaction cross sections (sigma(I)) for the neutron-rich p-sd and the sd shell region. Very recently, both measurements reached up to ...the neutron drip line, or close to the drip line, for nuclei of Z</=8. A neutron-number dependence of S(n) shows clear breaks at N = 16 near the neutron drip line (T(Z)>/=3), which shows the creation of a new magic number. A neutron-number dependence of sigma(I) shows a large increase of sigma(I) for N = 15, which supports the new magic number. The origin of the new magic number is also discussed.
•Fast cooling time: 2ms.•High efficiency: ≈27% for 23Na+ and ≈5.1% for 7Li+.•100% Duty cycle with double trap system.
A radiofrequency quadrupole ion trap system for use with a multi-reflection ...time-of-flight mass spectrograph (MRTOF) for short-lived nuclei has been developed. The trap system consists of two different parts, an asymmetric taper trap and a flat trap. The ions are cooled to a sufficient small bunch for precise mass measurement with MRTOF in only 2ms cooling time in the flat trap, then orthogonally ejected to the MRTOF for mass analysis. A trapping efficiency of ≈27% for 23Na+ and ≈5.1% for 7Li+ has been achieved.
We measured the energy dependence of the total reaction cross sections (σR) for the proton-drip-line nucleus,17Ne, using a solid hydrogen target. We compared the experimental data with theoretical ...calculations using the Glauber model. We found that the theoretical cross sections overestimate the experimental ones in the low-energy region (∼100A MeV), whereas they significantly underestimate the experimental data in the intermediate-energy region (∼300-500A MeV). These trends are the same as those for σR for carbon-proton collisions, which were measured previously. We discuss several possibilities for resolving this discrepancy. This work demonstrates the necessity of additional careful investigations of the energy dependence of σR for various nuclei on proton targets in order to determine nuclear size properties precisely.
•Demonstrated very fast mass measurements with a multi-reflection time of flight mass spectrograph.•Mass resolving power of Rm≈150,000 was achieved in 1.2-ms for A/q=39 ions.•Mass precision of ...δmm=7.7×108 was demonstrated for 40Ca+.•Effects of thermal and voltage instabilities are described.•Effects of thermal and voltage instabilities are described.
A multi-reflection time-of-flight (MRTOF) mass spectrograph has been implemented at RIKEN to provide high-precision mass measurements of very short-lived nuclei. Of particular interest are mass measurements of r-process nuclei and trans-uranium nuclei. In such nuclei, the MRTOF can perform on par with or better than traditional Penning trap systems. We demonstrate that the MRTOF-MS is capable of accurately attaining relative mass precision of δm/m<10-7 and describe it’s utility with heavy, short-lived nuclei.
In order to investigate nuclei produced via fusion–evaporation reactions, especially super-heavy elements (SHE), we have begun construction of a facility for conversion of fusion–evaporation residues ...(EVR) to low-energy beams. At the base of this facility is a small cryogenic gas cell utilizing a traveling wave RF-carpet, located directly following the gas-filled recoil ion separator GARIS-II, which will thermalize EVRs to convert them into ion beams amenable to ion trapping. We present here the results of initial studies of this small gas cell.
The molecular mechanisms that regulate the proliferation and differentiation of induced pluripotent stem (iPS) cells are of great interest. However, whether stimulation with nicotine enhances the ...proliferation and differentiation of iPS cells has not been investigated. In the present study, western blot analysis revealed that the α4-nAchR and α7-nAchR are expressed in mouse iPS cells. Mouse iPS cells were treated with nicotine for 24 h under feeder-free conditions. Mouse iPS cells were guided to differentiate into mesodermal progenitor cells on type IV collagen (Col IV)-coated dishes in differentiation medium. Mouse iPS cells were guided to differentiate into neural progenitor cells by embryoid body (EB) formation on ultra-low-attachment dishes. After 4 days of growth, all-trans retinoic acid (ATRA; 1 μM) or nicotine (300 nM) was added to the EB cultures and maintained for additional 4 days and plated onto fibronectincoated plates. A BrdU incorporation assay showed that treatment with 300 nM nicotine significantly increased the DNA synthesis of mouse iPS cells or mouse iPS cell-derived mesodermal progenitor cells. This effect was significantly inhibited by pretreatment with an α4-nAchR antagonist, an α7-nAchR antagonist, or a CaMKII inhibitor. The differentiation potential of mouse iPS cells into mesodermal progenitor cells or neural progenitor cells was not affected by the nicotine treatment. The present study indicates that stimulation of the α4-nAchR and α7-nAchR may lead to a significant increase in the proliferation of mouse iPS cells or mouse iPS cell-derived mesodermal progenitor cells through the CaMKII signaling pathway.
The spin-lattice relaxation times
T
1
of an unstable nucleus
19
O (
T
1/2
= 26.9 s,
I
= 5/2) implanted into Y
2
O
3
stabilized ZrO
2
(YSZ), which is a solid oxide fuel cell material, were measured at
...T
= 278 − 333 K by means of the
β
-NMR technique, using a highly spin polarized
19
O beam produced via the heavy ion reaction. The motional correlation times
τ
c
for oxygen motion derived from the
T
1
data are on the same straight line on the Arrhenius plot as those derived from the previous
17
O-NMR data at above the room temperature. This indicates that
19
O ions implanted into YSZ from outside seem to exhibit the same behavior as oxygen ions in the host YSZ material.
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