Stochastic Estimation of Nuclear Level Density in the Nuclear Shell Model: An Application to Parity-Dependent Level Density in 58^{58}Ni

We introduce a novel method to obtain level densities in large-scale shell-model calculations. Our method is a stochastic estimation of eigenvalue count based on a shifted Krylov-subspace method, which enables us to obtain level densities of huge Hamiltonian matrices. This framework leads to a successful description of both low-lying spectroscopy and the experimentally observed equilibration of $J^\pi=2^+$ and $2^-$ states in $^{58}$Ni in a unified manner.Comment: 13 pages, 4 figure

Triethylamine Enables Catalytic Generation of Oxidopyrylium Ylides for [5+2] Cycloadditions with Alkenes: An Efficient Entry to 8-Oxabicyclo[3.2.1]octane Frameworks

An efficient method for the preparation of a range of 8-oxabicyclo[3.2.1]octane derivatives including synthetic intermediates of natural products is described, in which triethylamine effectively catalyzes [5+2] cycloaddition reactions between oxidopyrylium ylides and alkenes. This method can be applied not only to intermolecular cycloadditions with various alkenes but also to intramolecular cycloadditions. The key finding is that the combined use of organic bases having appropriate basicity and oxidopyrylium ylide precursors bearing a suitable leaving group facilitates the base-assisted generation of oxidopyrylium ylides in a catalytic manner.ArticleADVANCED SYNTHESIS & CATALYSIS.360(12):2377-2381(2018)journal articl

High-contrast Imaging around a 2 Myr-old CI Tau with a Close-in Gas Giant

Giant planets around young stars serve as a clue to unveiling their formation history and orbital evolution. CI Tau is a 2\,Myr-old classical T-Tauri star hosting an eccentric hot Jupiter, CI Tau\,b. The standard formation scenario of a hot Jupiter predicts that planets formed further out and migrated inward. A high eccentricity of CI Tau b may be suggestive of high-$e$ migration due to secular gravitational perturbations by an outer companion. Also, ALMA 1.3\,mm-continuum observations show that CI Tau has at least three annular gaps in which unseen planets may exist. We present high-contrast imaging around CI Tau taken from Keck/NIRC2 $L^{\prime}$-band filter and vortex coronagraph that allows us to search for an outer companion. We did not detect any outer companion around CI Tau from angular differential imaging (ADI) using two deep imaging data sets. The detection limits from ADI-reduced images rule out the existence of an outer companion beyond $\sim30$\,au that can cause the Kozai-Lidov migration of CI Tau\,b. Our results suggest that CI Tau\,b may have experienced Type II migration from $\lesssim 2$\,au in Myrs. We also confirm that no planets with $\geq 2-4\,M_\mathrm{Jup}$ are hidden in two outer gaps.Comment: 7 pages, 6 figures, accepted in A

Efficient generation of an oxidopyrylium ylide using a Pd catalyst and its [5+2] cycloadditions with several dipolarophiles

An efficient method for the generation of an oxidopyrylium ylide from 6-acetoxy-6-acetoxymethyl-2H-pyran-3(6H)-one using a Pd catalyst and [5+2] cycloadditions of the resulting ylide are described. Among substituted styrene derivatives as dipolarophiles, electron-rich styrenes showed higher yield (up to 80%). The [5+2] cycloaddition reactions can also be applied to exo-methylene cyclic compounds, and an improved method for the synthesis of polygalolide intermediate has been demonstrated.ArticleCHEMICAL COMMUNICATIONS.54(9):1109-1112(2018)journal articl

Distribution of Mast Cells in Mediastinal Lymph Nodes from Lung Cancer Patients

BACKGROUND: Mast cells have been documented to have several key functions with regards to malignant neoplasms. However, the functional significance of their accumulation is largely unknown. An analysis of the mast cell profile in mediastinal lymph nodes from lung cancer patients is reported here. METHODS: One hundred thirty-four, randomly selected lymph nodes (63 with positive pathological lymph node status) from 39 surgically treated lung cancer patients were examined. All cancer negative nodes were obtained from stage I patients. Mast cells were stained with Alcian blue and safranin O. Metastatic cancer cells were stained using anti-cytokeratin antibody. RESULTS: Immunohistochemical studies with cytokeratin revealed micro metastasis in 9/71 (12.68%) nodes previously diagnosed as histological negative. In tumor-free mediastinal lymph nodes, the mast cell count was significantly higher than in metastatic nodes. In all cases, mast cells were observed primarily in the T-cell area. CONCLUSIONS: An inverse relationship was observed between the number of mast cells and the amount of tumor tissue. The presence of mast cells primarily in the T-cell area implies a relationship between mast cells and the T-cell system. From the present study it is not possible to conclude whether mast cells in lymph nodes are for or against tumor spread