Search

Astrophysical reactions involving radioactive isotopes (RI) often play an important role in high-temperature stellar environments. The experimental studies on the reaction rates for those are still limited mainly due to the technical difficulties in producing high-quality RI beams. A direct measurement of those reactions would be still challenging in many cases, however, we can make a reliable evaluation of the reaction rates by an indirect method or by studying the resonance prorerties. Here we ntroduce recent examples of experimental studies on such RI-involving astrophysical reactions, performed at Center for Nuclear Study, the University of Tokyo, using the low-energy RI beam separator CRIB. One is for the neutron-induced destruction reactions of 7Be in the Big-Bang nucleosynthesis, and the other is the study on the 22Mg(α, p) reaction relevant in X-ray bursts, which was performed with the resonant scattering method from the inverse reaction channel.

The new isotope ^{39}Na, the most neutron-rich sodium nucleus observed so far, was discovered at the RIKEN Nishina Center Radioactive Isotope Beam Factory using the projectile fragmentation of an intense ^{48}Ca beam at 345 MeV/nucleon on a beryllium target. Projectile fragments were separated and identified in flight with the large-acceptance two-stage separator BigRIPS. Nine ^{39}Na events have been unambiguously observed in this work and clearly establish the particle stability of ^{39}Na. Furthermore, the lack of observation of ^{35,36}Ne isotopes in this experiment significantly improves the overall confidence that ^{34}Ne is the neutron dripline nucleus of neon. These results provide new key information to understand nuclear binding and nuclear structure under extremely neutron-rich conditions. The newly established stability of ^{39}Na has a significant impact on nuclear models and theories predicting the neutron dripline and also provides a key to understanding the nuclear shell property of ^{39}Na at the neutron number N=28, which is normally a magic number.

Experimental studies on astrophysical reactions involving radioactive isotopes (RI) often accompany technical challenges. Studies on such nuclear reactions have been conducted at the low-energy RI beam separator CRIB, operated by Center for Nuclear Study, the University of Tokyo. We discuss two cases of astrophysical reaction studies at CRIB; one is for the 7Be+n reactions which may affect the primordial 7Li abundance in the Big-Bang nucleosynthesis, and the other is for the 22Mg(α, p) reaction relevantin X-raybursts.

Background: Neural precursor cells (NPCs) hold great promise for neural repair. Endogenous NPCs, found in the subventricular zone of the adult brain, proliferate and migrate toward lesion sites; however, it is not sufficient for neural repair. NPCs are electrosensitive cells that undergo directed migration in an electric field (EF). Here, we examined the EF-induced migration of a clinically relevant human NPC population. Materials & Methods: We examined the effects of different substrates and microenvironments on human NPC galvanotaxis. Results: Human NPCs increased their migration speed in the presence of an EF, and the direction of migration (anodal vs. cathodal) varied between substrates. The secretome and extracellular pH were not significant factors in EF-induced migration; however, our results are consistent with substrate stiffness playing a role in the direction of cell migration. Conclusion: These findings provide insight into the importance of the microenvironment on modulating human NPC migration and highlight substrate-dependent considerations for neurorepair.

Resident brain neural precursor cells (NPCs) are electrosensitive cells that respond to electric field application by proliferating, differentiating, and undergoing rapid and directed cathodal migration. Harnessing NPC potential is a promising strategy to facilitate neural repair following injury or disease. The use of electric fields to activate NPCs is limited by current electrode designs which are typically made of conductive metals that are stiff and can lead to neuroinflammation following implantation, in part due to the mechanical mismatch between physiological conditions and material. Herein, the design of a novel, injectable biobased soft electrode with properties suitable for electrical stimulation in vivo is explored. The recent interest in using biologically derived polymers which are relatively abundant and afford economic feasibility have been built upon. Sodium alginate is utilized to form soft hydrogels, thereby addressing the issue of mechanical mismatch, and the conductive polymer, poly(3,4-ethylenedioxythiophene) (PEDOT), to generate an innovative new material. It is demonstrated that the optimized alginate PEDOT blend matches the modulus of the brain and is suitable for injection and is not cytotoxic to neural cells. Furthermore, in vivo studies demonstrate minimal activation of inflammatory cells upon implantation in the brain compared to classically used platinum-based electrodes.

Objectives This study aimed to investigate the clinical benefit of dose-dense paclitaxel plus carboplatin (ddTC) with bevacizumab (Bev) therapy in neoadjuvant setting for advanced ovarian, fallopian tube and primary peritoneal cancer patients (UMIN-CTR: 000016176). Methods Ovarian, fallopian tube or primary peritoneal cancer patients with estimated stage III-IV were included. They received paclitaxel (80 mg/m2) on day1, 8, 15, carboplatin (AUC 6.0 mg/mL x minute) on day 1, and Bev (15 mg/kg) on day 1 every 3 weeks as neoadjuvant chemotherapy. Interval debulking surgery (IDS) was performed after 3 cycles of ddTC+Bev therapy. The primary endpoint was rate of complete surgery. Secondary endpoints were response rate and adverse events. Results Twenty-four patients were included in this study. The median age was 55.5 years (37–80 years), and high-grade serous carcinoma accounted for 18 patients. IDS was performed in all patients and the rate of complete surgery was 75%. The response rate in NAC was 79%, and CA125 declined below the cut-off in 58% of patients. Grade 4 hematological toxicities and grade 3/4 non-hematological toxicities were observed in 29% and 17% of patients during NAC respectively. Grade 3/4 perioperative complications were found in 29% of patients, but there was no gastrointestinal perforation or treatment-related death. Conclusions Neoadjuvant ddTC+Bev therapy was well tolerated, and the sufficient rate of complete surgery in IDS was obtained.

Many cell types respond to electric fields (EFs) through cell migration, a process termed galvanotaxis. The galvanotactic response is critical for development and wound healing. Here we investigate whether skin-derived precursor cells (SKPs), which have the potential to differentiate into mesodermal and peripheral neural cell types, undergo directed migration in the presence of an EF. We found that EF application promotes SKP migration towards the anode. The migratory response is substrate-dependent as SKPs undergo directed migration on laminin and Matrigel, but not collagen. The majority of SKPs express the undifferentiated cell markers nestin, fibronectin and Sox2, after both EF application and in sister cultures with no EF application, suggesting that EFs do not promote cell differentiation. Co-cultures of SKPs and brain-derived neural precursor cells (NPCs), a population of cells that undergo rapid, cathode-directed migration, reveal that in the presence of NPCs an increased percentage of SKPs undergo galvanotaxis, providing evidence that cells can provide cues to modify the galvanotactic response. We propose that a better understanding of SKP migration in the presence of EFs may provide insight into improved strategies for wound repair. Keywords: Skin-derived precursors, Electric field, Cell migration, Galvanotaxis, Substrates, Co-cultures

First Place Award Submission - CA147Category: Clinical ApplicationManagement of obesity after spinal cord injury: a systematic reviewMir Hatef Shojaei1, Mohammad Alavinia1, B. Catharine Craven1,21N...

A rock bolt with a facing plate is one of the soil nailing methods against relatively shallow sliding failure, which can be applied to natural slopes without cutting trees. In this research, dynamic centrifuge model tests were conducted to study the reinforcement mechanism of the nailing with individual facing plates and the effects of facing plate width, bolt spacing and bolt inclination angle on the seismic stability of reinforced slope. From the test results, it was confirmed that the facing plate resistance works well against the seismic load, which suppresses the slope deformation during shaking, and the mobilised resistance increases with increasing plate size. Plate bearing failure and local surface failure are critical failure mechanisms. The bearing failure could occur for small plates, while for relatively large plates, the local failure causes reduction of plate resistance and triggers large deformation and slip failure of the slope. These failures could be controlled by slope acceleration and uncovered width. Downward inclined installation of the nailing from the normal to the slope surface can effectively prevent the movement and secure the slope stability with less mobilised resistance.

Electric fields (EFs) can direct cell migration and are crucial during development and tissue repair. We previously reported neural precursor cells (NPCs) are electrosensitive cells that can undergo rapid and directed migration towards the cathode using charge-balanced electrical stimulationin vitro. Here, we investigate the ability of electrical stimulation to direct neural precursor migration in mouse brainsin vivo. To visualize migration, fluorescent adult murine neural precursors were transplanted onto the corpus callosum of adult male mice and intracortical platinum wire electrodes were implanted medial (cathode) and lateral (anode) to the injection site. We applied a charge-balanced biphasic monopolar stimulation waveform for three sessions per day, for 3 or 6 d. Irrespective of stimulation, the transplanted neural precursors had a propensity to migrate laterally along the corpus callosum, and applied stimulation affected that migration. Further investigation revealed an endogenous EF along the corpus callosum that correlated with the lateral migration, suggesting that the applied EF would need to overcome endogenous cues. There was no difference in transplanted cell differentiation and proliferation, or inflammatory cell numbers near the electrode leads and injection site comparing stimulated and implanted non-stimulated brains. Our results support that endogenous and applied EFs are important considerations for designing cell therapies for tissue repairin vivo.

Deep brain stimulation (DBS), which uses electrical stimulation, is a well-established neurosurgical technique used to treat neurological disorders. Despite its broad therapeutic use, the effects of electrical stimulation on brain cells is not fully understood. Here, we examine the effects of electrical stimulation on neural stem and progenitor cells (collectively neural precursor cells; NPCs) C57BLJ/6 mice found in the subventricular zone (SVZ) of the adult forebrain. Previous work has demonstrated that adult-derived NPCs are electro-sensitive and undergo rapid and directed migration in response to application of clinically relevant electric fields. We examine NPC proliferation kinetics and their differentiation profile following electric field application using in vitro and in vivo assays. In vitro direct current electrical stimulation of 250 mV/mm is sufficient to elicit a 2-fold increase in the neural stem cell pool and increases neurogenesis and oligogenesis. In vivo, asymmetric biphasic electrical stimulation similarly increases the size of the NPC pool and alters neurogenesis. These findings provide insight into the effects of electrical stimulation on NPCs and suggest its potential use as a regenerative approach to neural repair. Significance Statement Electrical stimulation promotes neural precursor cell migration. In this study we demonstrate that electrical stimulation in addition to cell migration can also expand the size of the NPC pool and enhance neurogenesis, both in vitro and in vivo. Using electrical stimulation to activate neural stem cells could be a powerful tool to promote tissue repair.

The discovery of the important neutron-rich nucleus _{20}^{60}Ca_{40} and seven others near the limits of nuclear stability is reported from the fragmentation of a 345 MeV/u ^{70}Zn projectile beam on ^{9}Be targets at the radioactive ion-beam factory of the RIKEN Nishina Center. The produced fragments were analyzed and unambiguously identified using the BigRIPS two-stage in-flight separator. The eight new neutron-rich nuclei discovered, ^{47}P, ^{49}S, ^{52}Cl, ^{54}Ar, ^{57}K, ^{59,60}Ca, and ^{62}Sc, are the most neutron-rich isotopes of the respective elements. In addition, one event consistent with ^{59}K was registered. The results are compared with the drip lines predicted by a variety of mass models and it is found that the models in best agreement with the observed limits of existence in the explored region tend to predict the even-mass Ca isotopes to be bound out to at least ^{70}Ca.

R. Reifarth et al: ; 12 págs.; 9 figs.; Open Access funded by Creative Commons Atribution Licence 3.0 ; Nuclear Physics in Astrophysics VI (NPA6), The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process ow and r-process -decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will oer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes., This project was supported by the HGF Young Investigators Project VH-NG-327, EMMI, H4F, HGS-HIRe, JINA, NAVI, DFG and ATHENA.

The 22Mg nucleus plays an important role in nuclear astrophysics, specially in the 22Mg(α,p)25Al and proton capture 22Mg(p,γ)23Al reactions. It is believed that 22Mg is a waiting point in the αp-process of nucleosynthesis in novae. We proposed a direct measurement of the 22Mg+α resonance reaction in inverse kinematics using a radioactive ion (RI) beam. A 22Mg beam of 3.73 MeV/u was produced at CRIB (Center for Nuclear Study (CNS) low-energy RI Beam) facility of the University of Tokyo located at RIKEN (Japan) in 2011. In this paper we present the results about the production of the 22Mg beam used for the direct measurement of the scattering reaction 22Mg(α,α)22Mg, and the stellar reaction 22Mg(α,p)25Al in the energy region concerning an astrophysical temperature of T9=1–3 GK.

We review the progress in the field of InGaN-based light-emitting diodes (LEDs) and discuss the issue of threading dislocations and the luminous efficiency. The first candela-class blue LEDs have been developed. An InGaN layer was used to produce these LEDs instead of a GaN active layer. The quantum-well structure InGaN active layer dramatically improved the external quantum efficiency. There are a number of threading dislocations in nitride-based LEDs. InGaN LEDs, however, have quite high external quantum efficiency. With regard to this, it is thought that the fluctuation of the indium mole fraction is strongly related to the high external quantum efficiency. Considering the density of threading dislocations in the nitride-based LEDs, we discuss what can improve the external quantum efficiency of nitride-based LEDs.

This work demonstrates the feasibility of in-beam γ-spectroscopy employing radioactive ion beam species at relativistic energies of E = 210 ∼ 280 A· MeV. Neutron-rich nuclei below 48Ca with neutron number between the two magic numbers 20 and 28 have been investigated. Using a Pb target, single step inelastic excitation originating mainly from Coulomb interaction takes place populating preferentially low-lying low-spin states and enabling the extraction of B(E2) values. On a C target, nucleon removal reactions are dominating and medium-spin states are populated thus offering spectroscopic information in neighboring nuclei. Cross sections of inelastic excitation are determined and compared to coupled-channels calculations. Two new states of the very neutron-rich nucleus 44Ar at 1.78(8) MeV and 2.61(16) MeV are deduced from γ-transitions.

The evolution of massive stars with very low-metallicities depends critically on the amount of CNO nuclides which they produce. The ${}^{12}$N($p,\ensuremath{\gamma}$)${}^{13}$O reaction is an important branching point in the rap processes, which are believed to be alternative paths to the slow $3\ensuremath{\alpha}$ process for producing CNO seed nuclei and thus could change the fate of massive stars. In the present work, the angular distribution of the ${}^{2}$H(${}^{12}$N, ${}^{13}$O)$n$ proton transfer reaction at ${E}_{\mathrm{c}.\mathrm{m}.}=8.4$ MeV has been measured for the first time. Based on the Johnson-Soper approach, the square of the asymptotic normalization coefficient (ANC) for the virtual decay of ${}^{13}$O${}_{\mathrm{g}}.\mathrm{s}.$ $\ensuremath{\rightarrow}$ ${}^{12}$N+$p$ was extracted to be $3.92\ifmmode\pm\else\textpm\fi{}1.47$ fm${}^{\ensuremath{-}1}$ from the measured angular distribution and utilized to compute the direct component in the ${}^{12}$N($p,\ensuremath{\gamma}$)${}^{13}$O reaction. The direct astrophysical $S$ factor at zero energy was then found to be $0.39\ifmmode\pm\else\textpm\fi{}0.15$ keV b. By considering the direct capture into the ground state of ${}^{13}$O, the resonant capture via the first excited state of ${}^{13}$O and their interference, we determined the total astrophysical $S$ factors and rates of the ${}^{12}$N($p,\ensuremath{\gamma}$)${}^{13}$O reaction. The new rate is two orders of magnitude slower than that from the REACLIB compilation. Our reaction network calculations with the present rate imply that ${}^{12}$N($p,\ensuremath{\gamma}$)${}^{13}$O will only compete successfully with the ${\ensuremath{\beta}}^{+}$ decay of ${}^{12}$N at higher ($\ensuremath{\sim}2$ orders of magnitude) densities than initially predicted.

The reduced transition probability B(E2;0(gs)(+)→2(1)(+)) for (28)S was obtained experimentally using Coulomb excitation at 53 MeV/nucleon. The resultant B(E2) value 181(31) e(2)fm(4) is smaller than the expectation based on empirical B(E2) systematics. The double ratio |M(n)/M(p)|/(N/Z) of the 0(gs)(+)→2(1)(+) transition in (28)S was determined to be 1.9(2) by evaluating the M(n) value from the known B(E2) value of the mirror nucleus (28)Mg, showing the hindrance of proton collectivity relative to that of neutrons. These results indicate the emergence of the magic number Z=16 in the |T(z)|=2 nucleus (28)S.

Astrophysical 18Ne(α,p)21Na reaction is one of the most probable breakout routes, which lead to the rp-process from the hot-CNO cycle, converting the initial CNO elements into heavier elements in Type I x-ray bursters. Presently, there is no much experimental cross-section data reported at the energy of astrophysical interest, and resonant spectroscopic information in compound 22Mg is scarce as well. The experiment has been carried out by using the CNS radioactive ion beam separator (CRIB). Resonant properties in 22Mg have been studied via the resonant elastic scattering of 21Na+p, and cross section of the time-reversal reaction of 21Na(p,α)18Ne been measured simultaneously. A wide excitation energy region up to Ex ∼ 9.5 MeV in 22Mg has been scanned with a thick-target method. Some preliminary results will be reported.

The first direct measurement of the 11C(α, p)14N reaction cross section of astrophysical interest has been performed for the center‐of‐mass energies from 1 to 4.5 MeV with the CRIB (Center for Nuclear Study Radioactive Ion Beam separator). We successfully distinguished the transition to the ground state of 14N and that to the second excited state with a comparable yield. The resonant shapes in the preliminary excitation function for the ground state transition have been confirmed to be consistent with the ones from the time‐reversal reaction data of previous experiments.

International audience; The use of quasi-free reactions in studying nuclear reactions between charged particles of astrophysical interest has received much attention over the last two decades. The Trojan Horse Method is based on this approach and it has been used to study a number of reactions relevant for Nuclear Astrophysics. Recently we applied this method to the study of nuclear reactions that involve radioactive species, namely to the study of the 18F+p-->15O+α process at temperatures corresponding to the energies available in the classical novae scenario. Quasi-free reactions can also be exploited to study processes induced by neutrons. This technique is particularly interesting when applied to reaction induced by neutrons on unstable short-lived nuclei. Such processes are very important in the nucleosynthesis of elements in the sand r-processes scenarios and this technique can give hints for solving key questions in nuclear astrophysics where direct measurements are practically impossible.

We have measured two‐proton momentum and angular correlations for the 23Al excited states from the 23Al radioactive beam on a 12C target at an energy of 60∼70 A MeV at the projectile fragment separator beamline (RIPS) in the RIKEN Ring Cyclotron Facility. The decay products, namely 21Na+p+p from 23Al are clean identified. The relative momentum and opening angle between two protons in the rest frame of three body decay channels demonstrate that there are some diproton emission components from 2He cluster for the excited 23Al.

The measurement of the resonant alpha scattering and the 21Na(α, p) reaction were performed for the first time in inverse kinematics with the thick target method using a 21Na radioisotope (RI) beam. This paper reports the current result of alpha scattering measurement and its astrophysics implication.

Nuclear astrophysics activities with CNS RI beam separator (CRIB) are reported together with the present status of the CRIB facility which is supported by the AVF upgrade project for the total development of the low‐energy RIB facility. The activities include direct and indirect measurements of stellar reactions especially relevant to explosive burning processes such as nova and supernovae. Some recent results are discussed together with a scope of the facility.

CRIB (CNS Radioactive Ion Beam separator) is a low‐energy RI beam separator at the Center for Nuclear Study (CNS) of the University of Tokyo, used for various studies covering nuclear‐astrophysical topics. An application of the RI beam at CRIB for the astrophysical studies is a new measurement of the proton resonance scattering on 7Be. The measurement was performed up to the excitation energy of 6.8 MeV, ans the excitation function above 3.5 MeV was successfully measured for the first time, providing important information about the reaction rate of 7Be(p,γ)8B, which is the key reaction in the solar 8B neutrino production. A preliminary result of the 7Be+p experiment is presented.

The cluster structure of 7Li and 7Be has been investigated by the elastic‐transfer 4He(7Li,4He)7Li and 3He(7Be,3He)7Be reactions, respectively. Angular distribution for the elastic‐transfer of 7Li+4He has been measured in Sao Paulo at ECM = 9.67 MeV. Together with available elastic‐transfer angular distributions measured at other energies ranging from ECM = 2.29 to 32.13 MeV, a global optical model analysis has been performed. The measurement of the elastic‐transfer angular distribution at ELAB = 48.2 MeV for the 7Be+3He system is also described.

International audience; The abundance of 18F in Nova explosionsis an important issue in understanding this astrophysical phenomenon. For this reason it is necessary to study processes that produce or destroy this isotope in novae. Among these latter processes, the 18F(p,α)15O stands as one of the main 18F destruction channels. We report here on the status of a new experiment recently performed using the CRIB apparatus of the Center for Nuclear Study of the Tokyo University based at the RIKEN Wako branch.

Two techniques, one for estimating fatigue life of aluminum bonding wires and one for estimating fatigue life of solders under repeated thermal load, were developed. In one method, fracture mechanics with strain intensity factor (DeltaK epsiv) is used to estimate the fatigue life of aluminum bonding wires. In the other method, "electrical-thermal-structural coupled analysis" is used to estimate fatigue life of solders. The simulated crack propagation in aluminum bonding wires agrees well with the experimentally measured propagation. Moreover, the simulations show that fatigue life of aluminum bonding wires has a lower fatigue limit at a temperature-cycling range of 30degC.