94 β-Decay Half-Lives of Neutron-Rich _{55}Cs to _{67}Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation

The β-decay half-lives of 94 neutron-rich nuclei ^{144-151}Cs, ^{146-154}Ba, ^{148-156}La, ^{150-158}Ce, ^{153-160}Pr, ^{156-162}Nd, ^{159-163}Pm, ^{160-166}Sm, ^{161-168}Eu, ^{165-170}Gd, ^{166-172}Tb, ^{169-173}Dy, ^{172-175}Ho, and two isomeric states ^{174m}Er, ^{172m}Dy were measured at the Radioactive Isotope Beam Factory, providing a new experimental basis to test theoretical models. Strikingly large drops of β-decay half-lives are observed at neutron-number N=97 for _{58}Ce, _{59}Pr, _{60}Nd, and _{62}Sm, and N=105 for _{63}Eu, _{64}Gd, _{65}Tb, and _{66}Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

Time-Reversal Measurement of the p-Wave Cross Sections of the ^{7}Be(n,α)^{4}He Reaction for the Cosmological Li Problem

The cross sections of the ^{7}Be(n,α)^{4}He reaction for p-wave neutrons were experimentally determined at E_{c.m.}=0.20-0.81  MeV slightly above the big bang nucleosynthesis (BBN) energy window for the first time on the basis of the detailed balance principle by measuring the time-reverse reaction. The obtained cross sections are much larger than the cross sections for s-wave neutrons inferred from the recent measurement at the n_TOF facility in CERN, but significantly smaller than the theoretical estimation widely used in the BBN calculations. The present results suggest the ^{7}Be(n,α)^{4}He reaction rate is not large enough to solve the cosmological lithium problem, and this conclusion agrees with the recent result from the direct measurement of the s-wave cross sections using a low-energy neutron beam and the evaluated nuclear data library ENDF/B-VII.1.

Two-Proton Radioactivity of ^{67}Kr

In an experiment with the BigRIPS separator at the RIKEN Nishina Center, we observed two-proton (2p) emission from ^{67}Kr. At the same time, no evidence for 2p emission of ^{59}Ge and ^{63}Se, two other potential candidates for this exotic radioactivity, could be observed. This observation is in line with Q value predictions which pointed to ^{67}Kr as being the best new candidate among the three for two-proton radioactivity. ^{67}Kr is only the fourth 2p ground-state emitter to be observed with a half-life of the order of a few milliseconds. The decay energy was determined to be 1690(17) keV, the 2p emission branching ratio is 37(14)%, and the half-life of ^{67}Kr is 7.4(30) ms.

Mutations in transmembrane domain of c-erbB-2 gene in human malignant tumours of the central nervous system

Point mutations in the transmembrane domain of c-erbB-2 gene in human brain tumours were studied by DNA amplification with the polymerase chain reaction method. Amplified gene fragments in M13 phage vector were cloned, and subsequent nucleotide sequences were determined. Studied specimens were 10 human malignant and 3 human benign tumours of the central nervous system, and a normal human placenta. In malignant tissues, Val-to-Glu mutation that induces transforming activity of c-erbB-2 did not appear to codon 659 of c-erbB-2. In malignant tissues, many other types of mutations appeared in low frequency, either at codon 659 or other positions of the transmembrane domain of c-erbB-2. The ratio of mutated genes to normal genes was very low in all specimens of malignant tumours. The point mutations were not observed in benign brain tumour or normal human placental tissues. The transmembrane domain of c-erbB-2 may have several highly mutable hot spots, where brain tumour tissues show a predilection for point mutation.

Alterations in 18F-FDG accumulation into neck-related muscles after neck dissection for patients with oral cancers

BACKGROUND

18F-fluoro-2-deoxy-D-glucose (18F-FDG) accumulations are commonly seen in the neck-related muscles of the surgical and non-surgical sides after surgery with neck dissection (ND) for oral cancers, which leads to radiologists having difficulty in diagnosing the lesions. To examine the alterations in 18F-FDG accumulation in neck-related muscles of patients after ND for oral cancer.

MATERIAL AND METHODS

18F-FDG accumulations on positron emission tomography (PET)-computed tomography (CT) in neck-related muscles were retrospectively analyzed after surgical dissection of cervical lymph nodes in oral cancers.

RESULTS

According to the extent of ND of cervical lymph nodes, the rate of patients with 18F-FDG-PET-positive areas increased in the trapezius, sternocleidomastoid, and posterior neck muscles of the surgical and/or non-surgical sides. In addition, SUVmax of 18F-FDG-PET-positive areas in the trapezius and sternocleidomastoid muscles were increased according to the extent of the ND.

CONCLUSIONS

In evaluating 18F-FDG accumulations after ND for oral cancers, we should pay attention to the 18F-FDG distributions in neck-related muscles including the non-surgical side as false-positive findings.

New Isotopes and Proton Emitters-Crossing the Drip Line in the Vicinity of ^{100}Sn

Several new isotopes, ^{96}In, ^{94}Cd, ^{92}Ag, and ^{90}Pd, have been identified at the RIKEN Nishina Center. The study of proton drip-line nuclei in the vicinity of ^{100}Sn led to the discovery of new proton emitters ^{93}Ag and ^{89}Rh with half-lives in the submicrosecond range. The systematics of the half-lives of odd-Z nuclei with T_{z}=-1/2 toward ^{99}Sn shows a stabilizing effect of the Z=50 shell closure. Production cross sections for nuclei in the vicinity of ^{100}Sn measured at different energies and target thicknesses were compared to the cross sections calculated by epax taking into account contributions of secondary reactions in the primary target.

Centrality-Dependent Modification of Jet-Production Rates in Deuteron-Gold Collisions at √[s(NN)]=200 GeV

Jet production rates are measured in p+p and d+Au collisions at sqrt[s_{NN}]=200  GeV recorded in 2008 with the PHENIX detector at the Relativistic Heavy Ion Collider. Jets are reconstructed using the R=0.3 anti-k_{t} algorithm from energy deposits in the electromagnetic calorimeter and charged tracks in multiwire proportional chambers, and the jet transverse momentum (p_{T}) spectra are corrected for the detector response. Spectra are reported for jets with 12<p_{T}<50  GeV/c, within a pseudorapidity acceptance of |η|<0.3. The nuclear-modification factor (R_{dAu}) values for 0%-100% d+Au events are found to be consistent with unity, constraining the role of initial state effects on jet production. However, the centrality-selected R_{dAu} values and central-to-peripheral ratios (R_{CP}) show large, p_{T}-dependent deviations from unity, challenging the conventional models that relate hard-process rates and soft-particle production in collisions involving nuclei.

Abstract P6-07-10: Cytogenetic analysis of squamous cell carcinoma of the breast reveals inter- and intra-tumoral heterogeneity

Background: Squamous cell carcinoma (SCC) of the breast is a rare and generally aggressive disease constituting less than 0.1 % of all breast carcinomas. Although they have distinct morphological features, the origin and cytogenetic profiles of SCCs are still not well understood. In this study, five cases of SCC of the breast, three of which had an SCC component and an invasive or noninvasive ductal carcinoma of no special type (NST) component, were analyzed to evaluate their cytogenetic inter- and intra-tumoral heterogeneity.

Methods: Using a pathological database of approximately 3,000 patients with breast cancer, five patients with SCC were identified. Their medical records were retrospectively reviewed to obtain clinicopathological, radiological, therapeutic and prognostic information. The area largely consisting of the SCC component was macro-dissected from five 10 μm-thick sections and tumor DNA was extracted using the QIAmp DNA Mini Kit (Qiagen). Three cases contained a component of invasive or noninvasive ductal carcinoma of NST as well as an SCC component, and tumor DNA from NST components were also extracted as described above. Tumor DNA from each case were used for array comparative genomic hybridization (aCGH) analysis using a high-density oligonucleotide microarray (Agilent® SurePrint G3 8x60k microarray) and the cytogenetic profiles of SCC components were compared with each other and in three of the five cases with their paired NST components.

Results: Sufficient amounts of DNA were obtained for aCGH analysis with an average of 0.78 μg (0.39–1.35 μg). The quality of the aCGH was acceptable, as judged by the mean derivative log ratio spread (DLRSpread) of 0.45 (0.20–0.55), which estimates the log ratio noise by calculating the spread of log ratio differences between consecutive probes along all chromosomes. The cytogenetic profiles of SCC components showed large inter-tumoral heterogeneity with between 2 and 160 copy number alterations per case and no common copy number alterations were found among cases. Meanwhile, cytogenetic profiles were almost identical between paired SCC and NST components,. However, in one case, a large number of copy number aberrant (CNA) regions were detected in the SCC component compared with the NST component and all aberrations in the NST component were also present in the SCC component, which implies that the SCC component originated from the NST component. There were no common SCC-component-specific aberrations in the three cases with NST components.

Conclusion: These results demonstrate the degree of cytogenetic inter- and intra-tumoral heterogeneity in SCC of the breast. The comparison of cytogenetic profiles in one case indicated that the SCC component originated from the NST component.

Citation Format: Oikawa M, Igawa A, Ishida M, Nakamura Y, Nishimura S, Koga C, Akiyoshi S, Koi Y, Taguchi K, Ohno S, Tokunaga E. Cytogenetic analysis of squamous cell carcinoma of the breast reveals inter- and intra-tumoral heterogeneity. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-07-10.

Extension of the N=40 Island of Inversion towards N=50: Spectroscopy of (66)Cr, (70,72)Fe

We report on the measurement of the first 2(+) and 4(+) states of (66)Cr and (70,72)Fe via in-beam γ-ray spectroscopy. The nuclei of interest were produced by (p,2p) reactions at incident energies of 260  MeV/nucleon. The experiment was performed at the Radioactive Isotope Beam Factory, RIKEN, using the DALI 2γ-ray detector array and the novel MINOS device, a thick liquid hydrogen target combined with a vertex tracker. A low-energy plateau of 2(1)(+) and 4(1)(+) energies as a function of the neutron number was observed for N≥38 and N≥40 for even-even Cr and Fe isotopes, respectively. State-of-the-art shell model calculations with a modified Lenzi-Nowacki-Poves-Sieja (LNPS) interaction in the pfg(9/2)d(5/2) valence space reproduce the observations. Interpretation within the shell model shows an extension of the island of inversion at N=40 for more neutron-rich isotopes towards N=50.

Accumulation of accident-derived radiocesium in lake and coastal sediments at 300-700 km distance from Fukushima area

The accumulation of accident-derived radiocesium was investigated in nine water bodies located 300-700 km from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP). (134)Cs from the accident was detected in surface sediment of five water bodies. The (134)Cs concentration, corrected to the time of the accident in 2011, was generally lower than that of (137)Cs, and its spatial pattern does not fully correspond to that of (137)Cs. These results suggest that radiocesium derived from both FDNPP and past global fallout can be separately observed and that the contributions of both sources are non-uniform within these sites. The (134)Cs inventory in surface sediments is smaller than its deposition, suggesting that almost all deposited (134)Cs remains within the catchment and/or a part has been discharged from the saline and brackish water bodies.

Measurements of Elliptic and Triangular Flow in High-Multiplicity 3He+Au Collisions at √(s(NN))=200 GeV

We present the first measurement of elliptic (v(2)) and triangular (v(3)) flow in high-multiplicity (3)He+Au collisions at √(s(NN))=200  GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in (3)He+Au and in p+p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the (3)He+Au system. The collective behavior is quantified in terms of elliptic v(2) and triangular v(3) anisotropy coefficients measured with respect to their corresponding event planes. The v(2) values are comparable to those previously measured in d+Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three (3)He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.