Magnetized Accretion Inside the Marginally Stable Orbit around a Black Hole

Qualitative arguments are presented to demonstrate that the energy density of magnetic fields in matter accreting onto a black hole inside the marginally stable orbit is automatically comparable to the rest-mass energy density of the accretion flow. Several consequences follow: magnetic effects must be dynamically significant, but cannot be so strong as to dominate; outward energy transport in Alfven waves may alter the effective efficiency of energy liberation; and vertical magnetic stresses in this region may contribute to "coronal" activity.Comment: to appear in Ap. J. Letter

U redox state and speciation of U in contact with magnetite nanoparticles : High resolution XANES, EXAFS, XPS and TEM study

Long-term storage of high-level radioactive waste is associated with potential radioecological hazards. One chemical element of high interest is uranium (U), which can mainly exists as a mobile U(VI) (oxidizing conditions) and sparingly soluble U(IV) (reducing conditions) species. It is expected that the main inorganic reducing agent for U(VI) in the environment are ferrous species in magnetite, formed on the steel canisters surface as an intermediate iron (Fe) corrosion product [1]. Results obtained from laboratory experiments for the interaction of U(VI) with magnetite nanoparticles point to partial reduction of U(VI) [2] or the formation of ~3 nm uranium dioxide (UO₂) particles on the surface layer [3]. The evidence for U(VI) reduction to intermediate U(V) state was found with no direct evidence of U(IV), which is in contradiction with thermodynamic calculations [4]. Continuous interaction and related phase dissolution/recrystallization processes can also lead to U redox changes and structural U incorporation into Fe oxides, resulting in U immobilization [5]. U redox state and speciation analyses are still very challenging due to simultaneous formation of several different species in such mineral systems. New advanced spectroscopic methods for characterization of such systems will provide more precise results from speciation studies. The main goal of our investigation is to assess the U M4 edge high energy resolution X-ray absorption near edge structure (HR-XANES) spectroscopy technique for detection of U(V) possibly co-existing with U(IV) and U(VI) under reducing conditions on/in Fe containing minerals. The U M4 edge HR-XANES has an advantage compared to the conventional U L3 edge XANES, as the measured spectra are less dominated by corehole lifetime broadening effects and therefore have narrower spectral features [6-8]. This technique facilitates the detection of minor contribution of one oxidation state in mixtures. We have investigated the U redox states and speciation in a set of samples where U coprecipitated with magnetite nanoparticles (~ 20 nm) with U concentrations varying in the 1000-10000 ppm range (1000, 3000, 6000 and 10000 ppm). In addition to U M4 edge HR-XANES, U L3 edge extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques have been applied. The studied system models the interaction of U(VI) with magnetite in aqueous solution, important for the understanding of the retarding effect of Fe corrosion products on U in the context of deep geological spent nuclear fuel disposal. These spectroscopic results can be compared with thermodynamic calculations and geochemical models describing this interaction. After 10 days U interaction with magnetite U M4 edge HR-XANES results indicate the formation of U(IV), U(V) and U(VI) mixtures in varying ratios, depending on the initial U loading. Going from 10000 to 3000 ppm, the U(VI) content decreases continuously and is no longer found in the 1000 ppm sample. At the same time the U(IV) and U(V) fractions increase. U(V) is stabilized as the main U redox state in the 1000 ppm sample along with a smaller U(IV) contribution. After 20 days of contact time XPS data show the predominance of U(IV) and U(V) species in the 6000 ppm sample. However, mostly U(V) and some U(IV) is found for the 1000 ppm sample. For all samples aged for 240 days U L3 XANES and EXAFS strongly suggest the formation of a UO₂ phase, UO₂ is the dominating species in the 10000 ppm sample with U-O bond distance 2.33. Å as determined by EXAFS. UO₂ crystalline clusters with about 5 nm size formed on the surface of the magnetite nanoparticles are also found by TEM in the 10000 and 3000 ppm samples. The major and minor contributions of U(V) and U(IV), respectively, for the 1000 ppm sample after 240 days confirm the assumption that the U redox kinetics has completed within less than 10 days at this U concentration. EXAFS analyses reveal U(V)-Fe interaction in the second U coordination sphere, which substantially increases from the 10000 to 1000 ppm sample and is the dominating species in the 1000 ppm sample

Magnetohydrodynamics in full general relativity: Formulation and tests

A new implementation for magnetohydrodynamics (MHD) simulations in full general relativity (involving dynamical spacetimes) is presented. In our implementation, Einstein's evolution equations are evolved by a BSSN formalism, MHD equations by a high-resolution central scheme, and induction equation by a constraint transport method. We perform numerical simulations for standard test problems in relativistic MHD, including special relativistic magnetized shocks, general relativistic magnetized Bondi flow in stationary spacetime, and a longterm evolution for self-gravitating system composed of a neutron star and a magnetized disk in full general relativity. In the final test, we illustrate that our implementation can follow winding-up of the magnetic field lines of magnetized and differentially rotating accretion disks around a compact object until saturation, after which magnetically driven wind and angular momentum transport inside the disk turn on.Comment: 28 pages, to be published in Phys. Rev.

Aplicação da biônica no desenvolvimento de produtos: uma sinergia entre o design de calçados e os novos materiais

Este trabalho tem como objetivo verificar a potencialidade das resinas poliuretanas (PU) com a adição de cargas de celulolignina a 10, 20, 30, 40 e 50% na aplicação em solados de calçados e averiguar sua capacidade de moldagem da forma, geometrias e texturas com o uso das ferramentas da Biônica. O PU é utilizado na área calçadista devido à alta resistência a abrasão, flexão e rasgo, flexibilidade, elasticidade, conforto, fácil moldagem de formas e baixa densidade. Os compósitos com uso de fibra natural tem sido um atrativo pela redução do custo do produto, conceito de sustentabilidade e passíveis de reciclabilidade, alta resistência e propriedades específicas superiores aos componentes isolados. Por meio da Biônica realizam-se analogias que relacionam formas, funções e comportamentos dos meios naturais, solucionando problemas existentes ou geram-se possibilidades inovadoras no produto. Na metodologia foi realizado um estudo exploratório de planejamento das misturas da resina PU com variações de celulose e lignina em 10, 20, 30, 40, 50% de carga. Foi feita a Microscopia Eletrônica de Varredura (MEV) utilizando um aparelho tipo VP 1450 LMEDEMAR- EEL-USP. Utilizou-se como ferramenta de desenvolvimento de texturas a Biônica no Laboratório de Texturas, Materiais e Modelagem - FATEA. Os resultados preliminares obtidos pelo MEV foram: a partir de 30% lignina apresenta mudanças na morfologia, que contribui na fragilização estrutural, já mistura com a celulose a partir de 40% em sua composição proporciona alterações significativas em sua forma estrutural (morfologia da partícula) rompendo, ocasionando o aumento da dureza e a perda a maleabilidade e ductilidade. A reprodução da forma desenvolvida por meio da Biônica é plenamente reproduzível ao material

Nonlocal calculation for nonstrange dibaryons and tribaryons

We study the possible existence of nonstrange dibaryons and tribaryons by solving the bound-state problem of the two- and three-body systems composed of nucleons and deltas. The two-body systems are $NN$, $N\Delta$, and $\Delta\Delta$, while the three-body systems are $NNN$, $NN\Delta$, $N\Delta\Delta$, and $\Delta\Delta\Delta$. We use as input the nonlocal $NN$, $N\Delta$, and $\Delta\Delta$ potentials derived from the chiral quark cluster model by means of the resonating group method. We compare with previous results obtained from the local version based on the Born-Oppenheimer approximation.Comment: 19 pages. To be published in Physical Review

Essential role of gastric gland mucin in preventing gastric cancer in mice

信州大学博士（医学）・学位論文・平成24年3月31日授与（甲第916号）・唐澤文寿Gastric gland mucin secreted from the lower portion of the gastric mucosa contains unique O-linked oligosaccharides (O-glycans) having terminal alpha 1,4-linked N-acetylglucosamine residues (alpha GlcNAc). Previously, we identified human alpha 1,4-N-acetylglucosaminyltransferase (alpha 4GnT), which is responsible for the O-glycan biosynthesis and characterized alpha GlcNAc function in suppressing Helicobacter pylori in vitro. In the present study, we engineered A4gnt(-/-) mice to better understand its role in vivo. A4gnt(-/-) mice showed complete lack of alpha GlcNAc expression in gastric gland mucin. Surprisingly, all the mutant mice developed gastric adenocarcinoma through a hyperplasia-dysplasia-carcinoma sequence in the absence of H. pylori infection. Microarray and quantitative RT-PCR analysis revealed upregulation of genes encoding inflammatory chemokine ligands, proinflammatory cytokines, and growth factors, such as Ccl2, Il-11, and Hgf in the gastric mucosa of A4gnt(-/-) mice. Further supporting an important role for this O-glycan in cancer progression, we also observed significantly reduced alpha GlcNAc in human gastric adenocarcinoma and adenoma. Our results demonstrate that the absence of alpha GlcNAc triggers gastric tumorigenesis through inflammation-associated pathways in vivo. Thus, alpha GlcNAc-terminated gastric mucin plays dual roles in preventing gastric cancer by inhibiting H. pylori infection and also suppressing tumor-promoting inflammation.ArticleJOURNAL OF CLINICAL INVESTIGATION. 122(3):923-934 (2012)journal articl

The kinematics in the pc-scale jets of AGN The case of S5 1803+784

We present a kinematic analysis of jet component motion in the VLBI jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Understanding the complex kinematic phenomena can possibly provide insights into the differences between quasars and BL Lac objects. The blazar S5 1803+784 has been studied with VLBI at $\nu$ =1.6, 2.3, 5, 8.4, and 15 GHz between 1993.88 and 2005.68 in 26 observing runs. We (re)analyzed the data and present Gaussian model-fits. We collected the already published kinematic information for this source from the literature and re-identified the components according to the new scenario presented in this paper. Altogether, 94 epochs of observations have been investigated. A careful study of the long-term kinematics reveals a new picture for component motion in S5 1803+784. In contrast to previously discussed motion scenarios, we find that the jet structure within 12 mas of the core can most easily be described by the coexistence of several bright jet features that remain on the long-term at roughly constant core separations (in addition to the already known {\it stationary} jet component $\sim$ 1.4 mas) and one faint component moving with an apparent superluminal speed ($\sim$ 19c, based on 3 epochs). While most of the components maintain long-term roughly constant distances from the core, we observe significant, smooth changes in their position angles. We report on an evolution of the whole jet ridge line with time over the almost 12 years of observations. The width of the jet changes periodically with a period of $\sim$ 8 to 9 years. We find a correlation between changes in the position angle and maxima in the total flux-density. We present evidence for a geometric origin of the phenomena and discuss possible models.Comment: The manuscript will be published by A&