1,198 research outputs found
Neutron capture cross section measurements of 120
Preliminary neutron capture cross section of 120Sn, 122Sn and 124Sn were obtained in the energy range from 20 meV to 4 keV with the array of germanium detectors in ANNRI at MLF,J-PARC. The results of 120Sn, 122Sn and 124Sn were obtained by normalizing the relative cross sections to the data in JENDL-4.0 at the largest 426.7-, 107.0- and 62.05-eV resonances, respectively. The 67.32- and 150-eV resonances for 120Sn and the 579- and 950-eV resonances for 124Sn which are listed in JENDL-4.0 and/or ENDF/B VII.1 were not observed
Research and development for accuracy improvement of neutron nuclear data on minor actinides
To improve accuracy of neutron nuclear data on minor actinides, a Japanese nuclear data project entitled “Research and development for Accuracy Improvement of neutron nuclear data on Minor ACtinides (AIMAC)” has been implemented. Several independent measurement techniques were developed for improving measurement precision at J-PARC/MLF/ANNRI and KURRI/LINAC facilities. Effectiveness of combining the independent techniques has been demonstrated for identifying bias effects and improving accuracy, especially in characterization of samples used for nuclear data measurements. Capture cross sections and/or total cross sections have been measured for Am-241, Am-243, Np-237, Tc-99, Gd-155, and Gd-157. Systematic nuclear data evaluation has also been performed by taking into account the identified bias effect. Highlights of the AIMAC project are outlined
High precision analysis of isotopic composition for samples used for nuclear cross-section measurements
Technical developments for accurate determination of amount of samples used for TOF measurements
Mott Transition and Spin Structures of Spin-1 Bosons in Two-Dimensional Optical Lattice at Unit Filling
We study the ground state properties of spin-1 bosons in a two-dimensional
optical lattice, by applying a variational Monte Carlo method to the S=1
Bose-Hubbard model on a square lattice at unit filling. A doublon-holon binding
factor introduced in the trial state provides a noticeable improvement in the
variational energy over the conventional Gutzwiller wave function and allows us
to deal effectively with the inter-site correlations of particle densities and
spins. We systematically show how spin-dependent interactions modify the
superfluid-Mott insulator transitions in the S=1 Bose-Hubbard model due to the
interplay between the density and spin fluctuations of bosons. Furthermore,
regarding the magnetic phases in the Mott region, the calculated spin structure
factor elucidates the emergence of nematic and ferromagnetic spin orders for
antiferromagnetic () and ferromagnetic () couplings,
respectively.Comment: 5 pages, 5 figures, to appear in Journal of the Physical Society of
Japa
Superdeformation in Asymmetric NZ Nucleus Ar
A rotational band with five -ray transitions ranging from 2 to
12 states was identified in Ar. This band is linked through
transitions from the excited 2, 4 and 6 levels to
the low-lying states; this determines the excitation energy and the spin-parity
of the band. The deduced transition quadrupole moment of 1.45 indicates that the band has a superdeformed shape. The nature of the band
is revealed by cranked Hartree--Fock--Bogoliubov calculations and a
multiparticle--multihole configuration is assigned to the band
Metastatic skull tumors: MRI features and a new conventional classification
Skull metastases are malignant bone tumors which are increasing in incidence. The objectives of this study were to characterize the MR imaging features, locations, and extent of metastatic skull tumors to determine the frequency of the symptomatic disease, and to assess patient outcomes. Between September 2002 and March 2008, 175 patients undergoing routine head MR imaging were found to have metastatic skull tumors. Contrast-enhanced study with fat suppression was used in some cases when required. Classification of metastases was simplified to three yes/no questions: first, with regard to location (either in the calvarium or in the cranial base); second, with regard to distribution within the plane of the cranial bone (either “circumscribed” meaning clearly demarcated and confined to one bone, or “diffuse” and likely to spread across a suture to another bone); and third, with regard to invasion (“intraosseous” in cranial bones only, or “invasive” spreading from the skull, either out into the scalp or inward to the dura and perhaps further in). Primary sites were breast cancer (55%), lung cancer (14%), prostate cancer (6%), malignant lymphoma (5%), and others (20%). The mean time from primary diagnosis to skull metastasis diagnosis was 71 months for cases of breast cancer, 26 months for prostate cancer, 9 months for lung cancer, and 4 months for malignant lymphoma. Calvarial circumscribed intraosseous metastases were found most frequently (27%). The patients were mainly asymptomatic. However, some patients suffered from local pain or cranial nerve palsies that harmed their quality of life. Treatment, mainly for symptomatic cases, was by local or whole-skull irradiation. Metastatic skull tumors are not rare, and most are calvarial circumscribed intraosseous tumors. MR images contribute to understanding their type, location, and multiplicity, and their relationship to the brain, cranial nerves, and dural sinuses. Radiation therapy improved the QOL of patients with neurological symptoms
Monte Carlo study of the superfluid weight in doped antiferromagnets
The phase fluctuations of the condensate in doped antiferromagnets, described
by a t-t'-J model and a suitable 1/N expansion, provide a mechanism for a
Kosterlitz-Thouless (KT) type of transition to a superconducting state below
T_{c}. In this paper, we present a Monte Carlo study of the corresponding
superfluid weight D_{s}(T) in the classical (large-N) limit, as a function of
temperature and doping. Consistent with generic experimental trends, D_{s}(T)
exhibits a T-linear decrease at low temperatures, with the magnitude of the
slope D_{s}'(0) increasing upon doping. Finite-size scaling in the underdoped
regime predicts values for the dimensionless ratio A=k_{B}T_{c}/D_{s}(0) of
order unity, with A=0.4435(5) in the half-filled-band limit, thus confirming
D_{s}(0) as the fundamental energy scale determining T_{c}. Our Monte Carlo
results for D_{s}(T)/D_{s}(0) vs k_{B}T/D_{s}(0), at 10% hole doping, are found
to be in reasonable agreement with recent measurements on
La_{2-x}Sr_{x}CuO_{4}, with x=0.10, throughout the temperature range below the
theoretical KT transition temperature T_{c}.Comment: 9 pages, REVTEX file (4 Postscript figures). To appear in Phys. Rev.
Cancer cells that survive radiation therapy acquire HIF-1 activity and translocate towards tumour blood vessels
Tumour recurrence frequently occurs after radiotherapy, but the characteristics, intratumoural localization and post-irradiation behaviour of radioresistant cancer cells remain largely unknown. Here we develop a sophisticated strategy to track the post-irradiation fate of the cells, which exist in perinecrotic regions at the time of radiation. Although the perinecrotic tumour cells are originally hypoxia-inducible factor 1 (HIF-1)-negative, they acquire HIF-1 activity after surviving radiation, which triggers their translocation towards tumour blood vessels. HIF-1 inhibitors suppress the translocation and decrease the incidence of post-irradiation tumour recurrence. For the first time, our data unveil the HIF-1-dependent cellular dynamics during post-irradiation tumour recurrence and provide a rational basis for targeting HIF-1 after radiation therapy
Measurement of 73 Ge(n,γ) cross sections and implications for stellar nucleosynthesis
© 2019 The Author(s). Published by Elsevier B.V.73 Ge(n,γ) cross sections were measured at the neutron time-of-flight facility n_TOF at CERN up to neutron energies of 300 keV, providing for the first time experimental data above 8 keV. Results indicate that the stellar cross section at kT=30 keV is 1.5 to 1.7 times higher than most theoretical predictions. The new cross sections result in a substantial decrease of 73 Ge produced in stars, which would explain the low isotopic abundance of 73 Ge in the solar system.Peer reviewe
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