Spectrum of heavy baryons in the quark model Yoshida, T.; Hiyama, E.; Hosaka, A. ...
Physical review. D, Particles, fields, gravitation, and cosmology,
12/2015, Letnik:
92, Številka:
11
Journal Article
Recenzirano
Odprti dostop
Single- and double-heavy baryons are studied in the constituent quark model. The model Hamiltonian is chosen as a standard one with two exceptions: (1) the color-Coulomb term depends on quark masses ...and (2) an antisymmetric LS (spin-orbit) force is introduced. Model parameters are fixed by the strange baryon spectra, A and Sigma baryons. The masses of the observed charmed and bottomed baryons are, then, fairly well reproduced. Our focus is on the low-lying negative-parity states, in which the heavy baryons show specific excitation modes reflecting the mass differences of heavy and light quarks. By changing quark masses from the SU(3) limit to the strange quark mass, and, further, to the charm and bottom quark masses, we demonstrate that the spectra change from the SU(3) symmetry patterns to the heavy-quark-symmetry ones.
Context.
Massive stars end their lives in catastrophic supernova (SN) explosions. Key information on the explosion processes and on the progenitor stars can be extracted from observations of ...supernova remnants (SNRs), which are the outcome of SNe. Deciphering these observations, however, is challenging because of the complex morphology of SNRs.
Aims.
We aim to link the dynamical and radiative properties of the remnant of SN 1987A to the geometrical and physical characteristics of the parent aspherical SN explosion and to the internal structure of its progenitor star.
Methods.
We performed comprehensive three-dimensional hydrodynamic simulations which describe the long-term evolution of SN 1987A from the onset of the SN to the full-fledged remnant at the age of 50 years, accounting for the pre-SN structure of the progenitor star. The simulations include all physical processes relevant for the complex phases of SN evolution and for the interaction of the SNR with the highly inhomogeneous ambient environment around SN 1987A. Furthermore, the simulations follow the life cycle of elements from the synthesis in the progenitor star through the nuclear reaction network of the SN to the enrichment of the circumstellar medium as a result of the mixing of chemically homogeneous layers of ejecta. From the simulations, we synthesize observables that are to be compared with observations.
Results.
By comparing the model results with observations, we constrained the initial SN anisotropy causing Doppler shifts, observed in the emission lines of heavy elements from ejecta, and leading to the remnant evolution observed in the X-ray band in the last thirty years. In particular, we found that the high mixing of ejecta unveiled by high redshifts and broadenings of Fe II and
44
Ti lines require a highly asymmetric SN explosion channeling a significant fraction of energy along an axis that is almost lying in the plane of the central equatorial ring around SN 1987A, roughly along the line-of-sight, but with an offset of 40°, with the lobe propagating away from the observer slightly more energetic than the other. Furthermore, we found unambiguously that the observed distribution of ejecta and the dynamical and radiative properties of the SNR can be best reproduced if the structure of the progenitor star was that of a blue supergiant which had resulted from the merging of two massive stars.
A long-standing crucial question with atomic nuclei is whether or not α clustering occurs there. An α particle (helium-4 nucleus) comprises two protons and two neutrons, and may be the building block ...of some nuclei. This is a very beautiful and fascinating idea, and is indeed plausible because the α particle is particularly stable with a large binding energy. However, direct experimental evidence has never been provided. Here, we show whether and how α(-like) objects emerge in atomic nuclei, by means of state-of-the-art quantum many-body simulations formulated from first principles, utilizing supercomputers including K/Fugaku. The obtained physical quantities exhibit agreement with experimental data. The appearance and variation of the α clustering are shown by utilizing density profiles for the nuclei beryllium-8, -10 and carbon-12. With additional insight by statistical learning, an unexpected crossover picture is presented for the Hoyle state, a critical gateway to the birth of life.
The efficacy of programmed death-1 blockade in epidermal growth factor receptor gene (EGFR) mutation-positive non-small-cell lung cancer (NSCLC) patients with different mechanisms of acquired ...resistance to EGFR tyrosine kinase inhibitors (TKIs) is unknown. We retrospectively evaluated nivolumab efficacy and immune-related factors in such patients according to their status for the T790M resistance mutation of EGFR.
We identified 25 patients with EGFR mutation-positive NSCLC who were treated with nivolumab after disease progression during EGFR-TKI treatment (cohort A). Programmed death-ligand 1 (PD-L1) expression and tumor-infiltrating lymphocyte (TIL) density in tumor specimens obtained after acquisition of EGFR-TKI resistance were determined by immunohistochemistry. Whole-exome sequencing of tumor DNA was carried out to identify gene alterations. The relation of T790M status to PD-L1 expression or TIL density was also examined in an independent cohort of 60 patients (cohort B).
In cohort A, median progression-free survival (PFS) was 2.1 and 1.3months for T790M-negative and T790M-positive patients, respectively (P=0.099; hazard ratio of 0.48 with a 95% confidence interval of 0.20–1.24). Median PFS was 2.1 and 1.3months for patients with a PD-L1 expression level of≥1% or<1%, respectively (P=0.084; hazard ratio of 0.37, 95% confidence interval of 0.10–1.21). PFS tended to increase as the PD-L1 expression level increased with cutoff values of≥10% and≥50%. The proportion of tumors with a PD-L1 level of≥10% or≥50% was higher among T790M-negative patients than among T790M-positive patients of both cohorts A and B. Nivolumab responders had a significantly higher CD8+ TIL density and nonsynonymous mutation burden.
T790M-negative patients with EGFR mutation-positive NSCLC are more likely to benefit from nivolumab after EGFR-TKI treatment, possibly as a result of a higher PD-L1 expression level, than are T790M-positive patients.
Eribulin mesilate (eribulin), a non-taxane microtubule dynamics inhibitor, has shown trends towards greater overall survival (OS) compared with progression-free survival in late-stage metastatic ...breast cancer patients in the clinic. This finding suggests that eribulin may have additional, previously unrecognised antitumour mechanisms beyond its established antimitotic activity. To investigate this possibility, eribulin's effects on the balance between epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) in human breast cancer cells were investigated.
Triple negative breast cancer (TNBC) cells, which are oestrogen receptor (ER-)/progesterone receptor (PR-)/human epithelial growth receptor 2 (HER2-) and have a mesenchymal phenotype, were treated with eribulin for 7 days, followed by measurement of EMT-related gene and protein expression changes in the surviving cells by quantitative real-time PCR (qPCR) and immunoblot, respectively. In addition, proliferation, migration, and invasion assays were also conducted in eribulin-treated cells. To investigate the effects of eribulin on TGF-β/Smad signalling, the phosphorylation status of Smad proteins was analysed. In vivo, the EMT/MET status of TNBC xenografts in mice treated with eribulin was examined by qPCR, immunoblot, and immunohistochemical analysis. Finally, an experimental lung metastasis model was utilised to gauge the metastatic activity of eribulin-treated TNBC in the in vivo setting.
Treatment of TNBC cells with eribulin in vitro led to morphological changes consistent with transition from a mesenchymal to an epithelial phenotype. Expression analyses of EMT markers showed that eribulin treatment led to decreased expression of several mesenchymal marker genes, together with increased expression of several epithelial markers. In the TGF-β induced EMT model, eribulin treatment reversed EMT, coincident with inhibition of Smad2 and Smad3 phosphorylation. Consistent with these changes, TNBC cells treated with eribulin for 7 days showed decreased capacity for in vitro migration and invasiveness. In in vivo xenograft models, eribulin treatment reversed EMT and induced MET as assessed by qPCR, immunoblot, and immunohistochemical analyses of epithelial and mesenchymal marker proteins. Finally, surviving TNBC cells pretreated in vitro with eribulin for 7 days led to decreased numbers of lung metastasis when assessed in an in vivo experimental metastasis model.
Eribulin exerted significant effects on EMT/MET-related pathway components in human breast cancer cells in vitro and in vivo, consistent with a phenotypic switch from mesenchymal to epithelial states, and corresponding to observed decreases in migration and invasiveness in vitro as well as experimental metastasis in vivo. These preclinical findings may provide a plausible scientific basis for clinical observations of prolonged OS by suppression of further spread of metastasis in breast cancer patients treated with eribulin.
In water splitting by using heterogeneous photocatalysts, the use of a suitable cocatalyst has been recognized as one of the key factors in enhancing the photocatalytic activity. Although platinum is ...a representative cocatalyst for many heterogeneous photocatalytic reactions, it has not been used for photocatalytic water splitting, owing to its high catalytic activity for the reverse reaction of water splitting. In the present study, platinum nanoparticles were loaded as a cocatalyst on a calcium titanate photocatalyst by a conventional impregnation method and a photodeposition method and examined for photocatalytic water splitting in a flow of water vapor. Platinum nanoparticles loaded by the impregnation method were found to retain the oxidized form on the calcium titanate photocatalyst, even under photoirradiation, and promoted hydrogen and oxygen production by photocatalytic water vapor splitting without promoting the reverse reaction.
No turning back: A Pt cocatalyst on a CaTiO3 photocatalyst, prepared by a conventional impregnation method, works to produce hydrogen and oxygen from water vapor. The Pt species are in the oxidized state on the CaTiO3 surface and catalytically inactive for the reverse reaction, which allows the production of hydrogen and oxygen by photocatalytic water splitting.
More than 30 years have passed since the successful detection of supernova (SN) neutrinos from SN 1987A. In the last few decades, remarkable progress has been made in neutrino detection techniques, ...through which it may be possible to detect neutrinos from a new source, presupernova (pre-SN) neutrinos. They are emitted from a massive star prior to core bounce. Because neutrinos escape from the core freely, they carry information about the stellar physics directly. Pre-SN neutrinos may play an important role in verifying our understanding of stellar evolution for massive stars. Observation of pre-SN neutrinos, moreover, may serve as an alarm regarding an SN explosion a few days in advance if the progenitor is located in our vicinity, enabling us to observe the next galactic SN. In this review, we summarize the current status of pre-SN neutrino studies from both the theoretical and observational points of view.
Calibration of global hydrological models (GHMs) has been attempted for over two decades; however, an effective and generic calibration method has not been explored. We present a novel framework for ...calibrating GHMs assuming that parameters can be regionalized by climate similarities. We calibrated four sensitive parameters of the H08 global hydrological model by aggregating the results of 5,000 simulations with randomly generated parameters into 11 Köppen climate classes and using an objective function Nash–Sutcliffe Efficiency (NSE) with random sampling from the proposed parameter distribution. From a 100‐fold split‐sampling test, we found that both the representativeness and robustness of the transferred parameter sets were guaranteed when the upper 5% of the samples were accepted and assign the median of each accepted parameter distribution for the climate class. The simulation with the climate‐based parameters yielded satisfactory (NSE > 0.0) and good (NSE > 0.5) performances at 480 and 234 stations (61.7% and 30.1% of 777 stations), respectively. The storage capacity (SD) and the conductive coefficient (CD) were sensitive to the climate classes and exhibited well‐constrained distributions of the accepted samples, whereas the recession parameters for the subsurface storage (γ and τ) showed little or no explanatory power to climate. The identified parameters for climate classes exhibited consistency with the physical interpretation of soil formation and efficiencies in vapor transfer. The consistency of the identified parameter values with physical underpinnings indicates that the appropriate parameters were determined, which ensured the robustness of parameters, especially when they are transferred to ungauged watersheds.
Key Points
We tested the hypothesis that the climate properties exert a dominant influence on parameter similarities at the global scale
The simulation with the climate‐based parameters yielded improvement from default parameters
Appropriate parameter values were determined, and results demonstrate their robustness, especially when applied to ungauged watersheds
Phytic acid (inositol hexakisphosphate InsP₆) is the storage compound of phosphorus in seeds. As phytic acid binds strongly to metallic cations, it also acts as a storage compound of metals. To ...understand the mechanisms underlying metal accumulation and localization in relation to phytic acid storage, we applied synchrotron-based x-ray microfluorescence imaging analysis to characterize the simultaneous subcellular distribution of some mineral elements (phosphorus, calcium, potassium, iron, zinc, and copper) in immature and mature rice (Oryza sativa) seeds. This fine-imaging method can reveal whether these elements colocalize. We also determined their accumulation patterns and the changes in phosphate and InsP₆ contents during seed development. While the InsP₆ content in the outer parts of seeds rapidly increased during seed development, the phosphate contents of both the outer and inner parts of seeds remained low. Phosphorus, calcium, potassium, and iron were most abundant in the aleurone layer, and they colocalized throughout seed development. Zinc was broadly distributed from the aleurone layer to the inner endosperm. Copper localized outside the aleurone layer and did not colocalize with phosphorus. From these results, we suggest that phosphorus translocated from source organs was immediately converted to InsP₆ and accumulated in aleurone layer cells and that calcium, potassium, and iron accumulated as phytic acid salt (phytate) in the aleurone layer, whereas zinc bound loosely to InsP₆ and accumulated not only in phytate but also in another storage form. Copper accumulated in the endosperm and may exhibit a storage form other than phytate.
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