Gamow-Teller (GT) transitions in atomic nuclei are sensitive to both nuclear shell structure and effective residual interactions. The nuclear GT excitations were studied for the mass number A = 42, ...46, 50, and 54 "f-shell" nuclei in ((3)He, t) charge-exchange reactions. In the (42)Ca → (42)Sc reaction, most of the GT strength is concentrated in the lowest excited state at 0.6 MeV, suggesting the existence of a low-energy GT phonon excitation. As A increases, a high-energy GT phonon excitation develops in the 6-11 MeV region. In the (54)Fe → (54)Co reaction, the high-energy GT phonon excitation mainly carries the GT strength. The existence of these two GT phonon excitations are attributed to the 2 fermionic degrees of freedom in nuclei.
Pancreatic cancer remains as one of the most deadly cancers with few treatment options at late stages and little information about how it develops through earlier stages. Activating mutation of the ...Kras gene has been implicated in, but is not sufficient for, tumorigenesis. In mouse models of pancreatic cancer, loss of tumor suppressor genes in conjunction with Kras mutation leads to gradual stochastic acquisition of neoplastic precursors and carcinomas, whereas many cells remain phenotypically unaltered in younger mice. Here, we demonstrate that two oncogenic events, mutation of Kras and production of the growth factor heparin-binding epidermal growth factor-like growth factor (HB-EGF), are sufficient for rapid and complete neoplastic transformation of the exocrine pancreas. We found that macrophages are the major source of HB-EGF production in pancreatic cancer tissue samples, and that macrophages are present in high density and in close association with human pancreatic cancer lesions. In a mouse model, high macrophage density was observed at the earliest stages of neoplastic transformation. The consequence of elevated HB-EGF signaling was investigated without the confounding effects of other macrophage-produced factors via transgenic overexpression of the active form of HB-EGF. In this model, HB-EGF was sufficient to promote Kras-initiated tumorigenesis, inducing rapid and complete neoplastic transformation of the entire exocrine pancreas shortly after birth. HB-EGF overexpression and Kras(G12D) together, but neither alone, increased proliferation with increased cyclinD1 and decreased Cdkn2a/2d (p16/p19(Ink4A/Arf)). These findings establish the importance of oncogenic synergy in cancer initiation and promotion, and establish a molecular link between inflammation and the earliest stages of tumor induction.
Optimizing Cs2LiYCl6 for fast neutron spectroscopy D'Olympia, N.; Chowdhury, P.; Guess, C.J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2012, Letnik:
694
Journal Article
Recenzirano
Cs2LiYCl6 (CLYC) has generated recent interest as a thermal neutron detector due to its excellent n/γ-ray pulse-shape discrimination and energy resolution. Here, the capabilities of CLYC as a fast ...neutron detector and spectrometer are reported. A 1in.×1in. CLYC detector was used to measure the response of mono-energetic neutrons over a range of 0.8–2.0MeV produced via the 7Li(p,n) reaction at the University of Massachusetts Lowell 5.5MV Van de Graaff accelerator. A broad continuum from the 6Li(n, α) reaction was observed, as well as additional peaks below the thermal capture peak. Based on possible reactions in CLYC, the additional peaks are determined to be due to the 35Cl(n,p)35S reaction, with a Q-value of +615keV, and corroborated in simulations using MCNPX. The average resolution of 9% for these peaks makes CLYC a promising candidate for a fast neutron spectrometer.
Nonyrast, excited states in neutron-rich 186W were populated via inelastic-scattering reactions using beams of 136Xe nuclei accelerated to 725 and 800 MeV. Levels populated in the reactions were ...investigated via particle-γ coincidence techniques using the Gammasphere array of high-purity germanium detectors and the compact heavy-ion counter, CHICO2. The Kπ = 2+ (γ ), Kπ = 0+ and Kπ = 2– (octupole) rotational side bands were extended to spins 14h¯, 12h¯, and 13h¯, respectively. A staggering pattern observed in the energies of levels in the Kπ = 2+ band was found to be consistent with a potential that gets softer to vibration in the γ degree of freedom with increasing spin. Furthermore, the odd-even staggering of states in the Kπ = 2– band was found to exhibit a phase opposite to that seen in the γ band; an effect most probably associated with Coriolis coupling to other, unobserved octupole vibrational bands in 186W.
24Mg is a strongly deformed nucleus in the ground state. Deformation effects can be observed in the structure of the isoscalar giant monopole and quadrupole resonances. 24Mg is also a nucleus that is ...well known to present different types of cluster-oscillation modes. Both giant resonances and cluster states are strongly populated by isoscalar transitions. To extract the E0, E1, and E2 transition strengths via 6Li scattering. The 6Li probe is a powerful tool for investigating the isoscalar nuclear response with a very favorable ratio of resonance-to-continuum background. Double-differential cross sections of 6Li inelastic scattering, at the beam energy of 100 MeV/u, were measured in the excitation-energy range 10 – 40 MeV and scattering angles 0 - 3°. A multipole-decomposition analysis was performed for extracting the isoscalar E0 , E1, and E2 strength distributions. Results: The extracted multipole strengths were compared with predictions from consistent quasiparticle random phase approximation calculations. The theoretical predictions are in fair agreement with the experimental data. The E0 strength was also compared with results from antisymmetrized molecular dynamics calculations found in the literature. A few peaks in the experimental data might be associated with clustering in 24Mg. Ground-state deformation effects were observed in the isoscalar giant monopole resonance (ISGMR) and isoscalar giant quadrupole resonance (ISGQR) distributions. The ISGMR strength is split in two peaks around 19 and 28 MeV. The ISGQR exhibits a pronounced peak at 20 MeV with a broadening at the low-energy region, similar to predictions from microscopic calculations. Signatures of excitation of cluster states were observed in the E0 response. Further studies including particle-decay measurements will be required to confirm the nature of the observed peaks.
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