438 research outputs found

    A Case of 48, XYY, +21

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    A 3 month-old boy with a karyotype of 48, XYY, + 21 is reported. The patient had the typical features of Down syndrome and normal male genitalia. Analysis of Q- and R-banded chromosome heteromorphisms of the patient and the parents showed that two of the three chromosomes 21 in the patient originated as a result of failure of the paternal second meiotic division. Therefore both additional chromosomes in the patient resulted from nondisjunction at paternal meiosis II

    Effective nonlocal kernels on Reaction-diffusion networks

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    A new method to derive an essential integral kernel from any given reaction-diffusion network is proposed. Any network describing metabolites or signals with arbitrary many factors can be reduced to a single or a simpler system of integro-differential equations called "effective equation" including the reduced integral kernel (called "effective kernel" ) in the convolution type. As one typical example, the Mexican hat shaped kernel is theoretically derived from two component activator-inhibitor systems. It is also shown that a three component system with quite different appearance from activator-inhibitor systems is reduced to an effective equation with the Mexican hat shaped kernel. It means that the two different systems have essentially the same effective equations and that they exhibit essentially the same spatial and temporal patterns. Thus, we can identify two different systems with the understanding in unified concept through the reduced effective kernels. Other two applications of this method are also given: Applications to pigment patterns on skins (two factors network with long range interaction) and waves of differentiation (called proneural waves) in visual systems on brains (four factors network with long range interaction). In the applications, we observe the reproduction of the same spatial and temporal patterns as those appearing in pre-existing models through the numerical simulations of the effective equations

    Momentum-resolved resonant photoelectron spectroscopic study for 1T-TiSe2_2: Observation of negative q in the Fano resonance due to inter-atomic interaction in the valence band

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    The remarkable properties of (1T-)TiSe2_2 among the transition metal dichalcogenides have attracted the attention of many researchers due to its peculiar behavior during the charge density wave (CDW) transition. Therefore, it is highly desirable to study its electronic structure down to the atomic orbitals. In the present research, we applied momentum-resolved resonant photoelectron spectroscopy to study TiSe2_2 at the Ti2p-Ti3d absorption edge by using a momentum microscope, which can simultaneously detect the electronic states in a wide (kx,ky)(k_x,k_y) range. We have also used constant initial state (CIS) spectroscopy and density functional theory (DFT) calculations to reveal the hybridization between the Ti3d and Se4p orbitals within the valence band at the Gamma point at room temperature. In addition, an interesting result comes from our analysis of the CIS spectrum for the energy band located at a binding energy of 2 eV at the M-point. This band, mainly composed of the Se4p orbital, exhibited a Fano line profile at the Ti2p edge, with a negative value of the parameter "qq". This is the first clear evidence of the inter-atomic interaction during the valence band photoelectron emission process. This behavior differs significantly from the standard resonant photoelectron emission, which usually involves intra-atomic interactions. It also differs from the multi-atom resonant photoelectron emission (MARPE) observed in the core-level photoelectron emission, as we focus on the photoelectron emission from the valence band in this research

    Phonon-assisted indirect transitions in angle-resolved photoemission spectra of graphite and graphene

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    Indirect transitions of electrons in graphene and graphite are investigated by means of angle-resolved photoemission spectroscopy (ARPES) with several different incident photon energies and light polarizations. The theoretical calculations of the indirect transition for graphene and for a single crystal of graphite are compared with the experimental measurements for highly-oriented pyrolytic graphite and a single crystal of graphite. The dispersion relations for the transverse optical (TO) and the out-of-plane longitudinal acoustic (ZA) phonon modes of graphite and the TO phonon mode of graphene can be extracted from the inelastic ARPES intensity. We find that the TO phonon mode for k points along the Γ-K and K-M-K′ directions in the Brillouin zone can be observed in the ARPES spectra of graphite and graphene by using a photon energy ≈11.1 eV. The relevant mechanism in the ARPES process for this case is the resonant indirect transition. On the other hand, the ZA phonon mode of graphite can be observed by using a photon energy ≈6.3 eV through a nonresonant indirect transition, while the ZA phonon mode of graphene within the same mechanism should not be observed.National Science Foundation (U.S.) (Grant No. DMR- 1507806

    Lithium production on a low-mass secondary in a black hole soft X-ray transient

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    We examine production of Li on the surface of a low-mass secondary in a black hole soft X-ray transient (BHSXT) through the spallation of CNO nuclei by neutrons which are ejected from a hot (> 10 MeV) advection-dominated accretion flow (ADAF) around the black hole. Using updated binary parameters, cross sections of neutron-induced spallation reactions, and mass accretion rates in ADAF derived from the spectrum fitting of multi-wavelength observations of quiescent BHSXTs, we obtain the equilibrium abundances of Li by equating the production rate of Li and the mass transfer rate through accretion to the black hole. The resulting abundances are found to be in good agreement with the observed values in seven BHSXTs. We note that the abundances vary in a timescale longer than a few months in our model. Moreover, the isotopic ratio Li6/Li7 is calculated to be about 0.7--0.8 on the secondaries, which is much higher than the ratio measured in meteorites. Detection of such a high value is favorable to the production of Li via spallation and the existence of a hot accretion flow, rather than an accretion disk corona system in quiescent BHSXT.Comment: 4 pages, 3 figures, and 2 tables, submitted to Astrophyscal Jounal Letter
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