The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction. Their interaction, however, leads to other important ...effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray. This 'internal conversion' has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons. In the inverse process-nuclear excitation by electron capture (NEEC)-a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states. NEEC was predicted in 1976 and has not hitherto been observed. Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario. Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude. The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states. Such excitations may reduce the abundance of the isotope after its production. This is an example of 'isomer depletion', which has been investigated previously through other reactions, but is used here to obtain evidence for NEEC.
Reactions induced by photons may be used as a probe for bonds and correlations of nucleons inside a heavy target nucleus. In contrast to strongly interacting particles, electromagnetic radiation ...perturbs nucleons only slightly. The yield of (
γ
,
α
) reactions could be used to test theoretical models that assume complete alpha-particle clustering or the presence of multiquark objects in heavy nuclei. The relative yields of (
γ
,
n
), (
γ
,
p
), and (
γ
,
α
) reactions were measured at the bremsstrahlung endpoint energy of 23 MeV for several targets. A much lower probability of (
γ
,
α
) in relation to (
γ
,
p
) reactions was proved despite very close threshold and spin factors for the two reaction types being considered. Therefore, alpha-particle clustering in heavy targets was not confirmed. The mechanism of particle release in nuclear reactions is discussed, and some details are clarified.
Relative yields of photon-induced reactions are systematized in a function of the threshold parameter for moderately heavy targets at the bremsstrahlung end-point energy lower than 30 MeV. Regular ...dependence is established for the group of (
γ, n
), (
γ, p
), and (
γ, d
) reactions, while the yields of (
γ
, 2
n
) and (
γ,α
) reactions deviate from the regularity. Physical conclusions are discussed and possible application of this systematic for data processing is proposed. In particular, the constituent threshold and spin factors in the isomer-to-ground-state ratio could be isolated separately. For spin dependence of the yields, a new regularization parameter is introduced and previously hidden peculiarities are concluded.
Endometriosis is characterized by the presence of functional endometrial tissue in other pelvic organs. This gynecologic problem occurs in 35–50% of women with pain and infertility. Endometriotic ...cells share some characteristics such as proliferation, migration, and invasion with tumor cells. Pyrvinium pamoate, an anthelmintic drug approved by the Food and Drug Administration, could inhibit the Wnt/β-catenin signaling pathway and its anticancer effects were examined by several researchers. In this study, 12 ectopic and eutopic endometrial biopsies from females with ovarian endometrioma and 12 endometrial biopsies from nonendometriotic females were obtained. Ectopic (EESCs), eutopic (EuESCs), and control (CESCs) endometrial stromal cells were isolated. Then, the effect of pyrvinium pamoate on the proliferation and invasiveness of in vitro cultured cells was evaluated. The proliferation of CESCs, EuESCs, and EESCs was significantly decreased after treatment with pyrvinium pamoate. In addition, treatment with pyrvinium pamoate significantly inhibited the invasiveness of CESCs, EuESCs, and EESCs compared to nontreated groups. The results of the present research showed that pyrvinium pamoate inhibits the proliferation and invasion of human endometriotic stromal cells in vitro, further investigations on the therapeutic potential of this compound in endometriosis are required.
Rate of fission for highly-excited nuclei is affected by the viscose character of the systemmotion in deformation coordinates as was reported for very heavy nuclei with
Z
C
> 90. The long time-scale ...of fission can be described in a model of “fission by diffusion” that includes an assumption of the overdamped diabatic motion. The fission-to-spallation ratio at intermediate proton energy could be influenced by the viscosity, as well. Within a novel approach of the present work, the cross examination of the fission probability, time-scales, and pre-fission neutron multiplicities is resulted in the consistent interpretation of a whole set of the observables. Earlier, different aspects could be reproduced in partial simulations without careful coordination.
There are much data on neutron cross sections over the chart of nuclides for stable isotopes and not as much for the radioactive ones. Double neutron capture experiments could be fruitful to provide ...more data. Time-integrated mean flux of slow neutrons reaches the value of 2.3-1012 n cm2 s at the irradiation port near the active zone of the IBR-2 pulsed reactor of JINR. This is enough to detect the double neutron capture products by the activation method. A high capture cross section is obtained in the present experiment for intermediate radioactive 182Ta and 194Ir target nuclides. Together with the known data for 198Au, these values may prove an essential role of double neutron capture process for nucleosynthesis of 183W, 195Pt and 199Hg isotopes at stellar conditions.
In the present work, quantitative calculations were carried out for production and depletion of the sup.93mMo isomer in a relatively simple experiment using sup.91Zr beam ions. Such studies could be ...arranged at existing and operating accelerator facilities, e.g. at GSI or in JINR. The sup.93mMo nuclei produced in a He gas target due to the sup.4He(sup.91Zr, 2n) reaction will recoil into a gas stopper with a high velocity, being then depleted due to NEEC in highly-ionized species.
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