WorldWideScience

Sample records for spheroidal stellar systems

  1. Spheroidal Populated Star Systems

    Science.gov (United States)

    Angeletti, Lucio; Giannone, Pietro

    2008-10-01

    Globular clusters and low-ellipticity early-type galaxies can be treated as systems populated by a large number of stars and whose structures can be schematized as spherically symmetric. Their studies profit from the synthesis of stellar populations. The computation of synthetic models makes use of various contributions from star evolution and stellar dynamics. In the first sections of the paper we present a short review of our results on the occurrence of galactic winds in star systems ranging from globular clusters to elliptical galaxies, and the dynamical evolution of a typical massive globular cluster. In the subsequent sections we describe our approach to the problem of the stellar populations in elliptical galaxies. The projected radial behaviours of spectro-photometric indices for a sample of eleven galaxies are compared with preliminary model results. The best agreement between observation and theory shows that our galaxies share a certain degree of heterogeneity. The gas energy dissipation varies from moderate to large, the metal yield ranges from solar to significantly oversolar, the dispersion of velocities is isotropic in most of the cases and anisotropic in the remaining instances.

  2. A new study of stellar substructures in the Fornax dwarf spheroidal galaxy

    NARCIS (Netherlands)

    de Boer, T. J. L.; Tolstoy, E.; Saha, A.; Olszewski, E. W.

    Using deep V, B - V wide-field photometry, we have conducted a new study of stellar over-densities in the Fornax dwarf spheroidal galaxy by determining detailed star formation histories from colour-magnitude diagram analysis. We have concentrated on the relatively young stellar component ( We have

  3. THE STELLAR STRUCTURE AND KINEMATICS OF DWARF SPHEROIDAL GALAXIES FORMED BY TIDAL STIRRING

    International Nuclear Information System (INIS)

    Lokas, Ewa L.; Klimentowski, Jaroslaw; Kazantzidis, Stelios; Mayer, Lucio; Callegari, Simone

    2010-01-01

    Using high-resolution N-body simulations, we study the stellar properties of dwarf spheroidal (dSph) galaxies resulting from the tidally induced morphological transformation of disky dwarfs on a cosmologically motivated eccentric orbit around the Milky Way. The dwarf galaxy models initially consist of an exponential stellar disk embedded in an extended spherical dark matter halo. Depending on the initial orientation of the disk with respect to the orbital plane, different final configurations are obtained. The least evolved dwarf is triaxial and retains a significant amount of rotation. The more evolved dwarfs are prolate spheroids with little rotation. We show that in this scenario the final density distribution of stars can be approximated by a simple modification of the Plummer law. The kinematics of the dwarfs is significantly different depending on the line of sight which has important implications for mapping the observed stellar velocity dispersions of dwarfs to subhalo circular velocities. When the dwarfs are observed along the long axis, the measured velocity dispersion is higher and decreases faster with radius. In the case where rotation is significant, when viewed perpendicular to the long axis, the effect of minor axis rotation is detected, as expected for triaxial systems. We model the velocity dispersion profiles and rotation curves of the dwarfs under the assumption of constant mass-to-light ratio by solving the Jeans equations for spherical and axisymmetric systems and adjusting different sets of free parameters, including the total mass. We find that the mass is typically overestimated when the dwarf is seen along the long axis and underestimated when the observation is along the short or intermediate axis. For the studied cases, the effect of non-sphericity cannot, however, bias the inferred mass by more than 60% in either direction, even for the most strongly stripped dwarf which is close to disruption.

  4. Can physical stellar collisions explain the blue stragglers in the dwarf spheroidal galaxies?

    International Nuclear Information System (INIS)

    Leonard, P.J.T.

    1993-01-01

    The hypothesis that the blue stragglers in the dwarf spheroidal galaxie have a collisional origin is considered. If all of the dark matter in these galaxies is in the form of low-mass stars and the binary frequency is ≅ 50%, then it is quite possible that ≅ 10% to 20% of their blue stragglers have been produced by physical stellar collisions

  5. THE STELLAR SPHEROID, THE DISK, AND THE DYNAMICS OF THE COSMIC WEB

    International Nuclear Information System (INIS)

    Domínguez-Tenreiro, R.; Obreja, A.; Brook, C. B.; Martínez-Serrano, F. J.; Serna, A.; Stinson, G.

    2015-01-01

    Models of the advanced stages of gravitational instability predict that baryons that form the stellar populations of current galaxies at z = 0 displayed a web-like structure at high z, as part of the cosmic web (CW). We explore details of these predictions using cosmological hydrodynamical simulations. When the stellar populations of the spheroid and disk components of simulated late-type galaxies are traced back separately to high zs we found CW-like structures where spheroid progenitors are more evolved than disk progenitors. The distinction between the corresponding stellar populations, as driven by their specific angular momentum content j, can be explained in terms of the CW evolution, extended to two processes occurring at lower z. First, the spheroid progenitors strongly lose j at collapse, which contrasts with the insignificant j loss of the disk progenitors. The second is related to the lack of alignment, at assembly, between the spheroid-to-be material and the already settled proto-disk, in contrast to the alignment of disk-to-be material, in some cases resulting from circumgalactic, disk-induced gravitational torques. The different final outcomes of these low-z processes have their origins in the different initial conditions driven by the CW dynamics

  6. Design of a Uranium Dioxide Spheroidization System

    Science.gov (United States)

    Cavender, Daniel P.; Mireles, Omar R.; Frendi, Abdelkader

    2013-01-01

    The plasma spheroidization system (PSS) is the first process in the development of tungsten-uranium dioxide (W-UO2) fuel cermets. The PSS process improves particle spherocity and surface morphology for coating by chemical vapor deposition (CVD) process. Angular fully dense particles melt in an argon-hydrogen plasma jet at between 32-36 kW, and become spherical due to surface tension. Surrogate CeO2 powder was used in place of UO2 for system and process parameter development. Particles range in size from 100 - 50 microns in diameter. Student s t-test and hypothesis testing of two proportions statistical methods were applied to characterize and compare the spherocity of pre and post process powders. Particle spherocity was determined by irregularity parameter. Processed powders show great than 800% increase in the number of spherical particles over the stock powder with the mean spherocity only mildly improved. It is recommended that powders be processed two-three times in order to reach the desired spherocity, and that process parameters be optimized for a more narrow particles size range. Keywords: spherocity, spheroidization, plasma, uranium-dioxide, cermet, nuclear, propulsion

  7. Evolution of stellar systems

    International Nuclear Information System (INIS)

    Vader, P.

    1981-01-01

    The stellar systems of which the evolution will be considered in this thesis, are either galaxies, which contain about 10 11 stars, or binary systems, which consist of only two stars. It is seen that binary systems can give us some insight into the relative age of the nucleus of M31. The positive correlation between the metal content of a galaxy and its mass, first noted for elliptical galaxies, seems to be a general property of galaxies of all types. The observed increase of metallicity with galaxy mass is too large to be accounted for by differences in the evolutionary stage of galaxies. To explain the observed correlation it is proposed that a relatively larger proportion of massive stars is formed in more massive galaxies. The physical basis is that the formation of massive stars seems to be tied to the enhanced gas-dynamical activity in more massive galaxies. A specific aspect of the production of heavy elements by massive stars is investigated in some detail. In 1979 a cluster of 18 point X-ray sources within 400 pc of the centre of M31 was detected with the Einstein satellite. This is a remarkable result since no equivalent of this cluster has been observed in the nucleus of our own Galaxy, which otherwise is very similar to that of M31. An explanation for this phenomenon is proposed, suggesting that X-ray binaries are the products of the long-term evolution of nova systems. (Auth.)

  8. A Kinematic Study of the Andromeda Dwarf Spheroidal System

    Science.gov (United States)

    Collins, Michelle L. M.; Chapman, Scott C.; Rich, R. Michael; Ibata, Rodrigo A.; Martin, Nicolas F.; Irwin, Michael J.; Bate, Nicholas F.; Lewis, Geraint F.; Peñarrubia, Jorge; Arimoto, Nobuo; Casey, Caitlin M.; Ferguson, Annette M. N.; Koch, Andreas; McConnachie, Alan W.; Tanvir, Nial

    2013-05-01

    We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g - i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii (gsim 700 pc) and low velocity dispersions (σ v ratio within its half-light radius of just [M/L]_half=10.3^{+7.0}_{-6.7}, making it consistent with a simple stellar system with no appreciable dark matter component within its 1σ uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.

  9. A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Collins, Michelle L. M.; Martin, Nicolas F. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Chapman, Scott C.; Irwin, Michael J. [Institute of Astronomy, Madingley Rise, Cambridge CB3 0HA (United Kingdom); Rich, R. Michael [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Ibata, Rodrigo A. [Observatoire astronomique de Strasbourg, Universite de Strasbourg, CNRS, UMR 7550, 11 rue de l' Universite, F-67000 Strasbourg (France); Bate, Nicholas F.; Lewis, Geraint F. [Sydney Institute for Astronomy, School of Physics, A28, University of Sydney, NSW 2006 (Australia); Penarrubia, Jorge [Instituto de Astrofisica de Andalucia-CSIC, Glorieta de la Astronomia s/n, E-18008 Granada (Spain); Arimoto, Nobuo [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Casey, Caitlin M. [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1839 (United States); Ferguson, Annette M. N. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Koch, Andreas [Zentrum fuer Astronomie der Universitaet Heidelberg, Landessternwarte, Koenigstuhl 12, D-69117 Heidelberg (Germany); McConnachie, Alan W. [NRC Herzberg Institute of Astrophysics, 5071 West Saanich Road, British Columbia, Victoria V9E 2E7 (Canada); Tanvir, Nial [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

    2013-05-10

    We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g - i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii ({approx}> 700 pc) and low velocity dispersions ({sigma}{sub v} < 5 km s{sup -1}). In addition, And XXV has a mass-to-light ratio within its half-light radius of just [M/L]{sub half}=10.3{sup +7.0}{sub -6.7}, making it consistent with a simple stellar system with no appreciable dark matter component within its 1{sigma} uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.

  10. A KINEMATIC STUDY OF THE ANDROMEDA DWARF SPHEROIDAL SYSTEM

    International Nuclear Information System (INIS)

    Collins, Michelle L. M.; Martin, Nicolas F.; Chapman, Scott C.; Irwin, Michael J.; Rich, R. Michael; Ibata, Rodrigo A.; Bate, Nicholas F.; Lewis, Geraint F.; Peñarrubia, Jorge; Arimoto, Nobuo; Casey, Caitlin M.; Ferguson, Annette M. N.; Koch, Andreas; McConnachie, Alan W.; Tanvir, Nial

    2013-01-01

    We present a homogeneous kinematic analysis of red giant branch stars within 18 of the 28 Andromeda dwarf spheroidal (dSph) galaxies, obtained using the Keck I/LRIS and Keck II/DEIMOS spectrographs. Based on their g – i colors (taken with the CFHT/MegaCam imager), physical positions on the sky, and radial velocities, we assign probabilities of dSph membership to each observed star. Using this information, the velocity dispersions, central masses, and central densities of the dark matter halos are calculated for these objects, and compared with the properties of the Milky Way dSph population. We also measure the average metallicity ([Fe/H]) from the co-added spectra of member stars for each M31 dSph and find that they are consistent with the trend of decreasing [Fe/H] with luminosity observed in the Milky Way population. We find that three of our studied M31 dSphs appear as significant outliers in terms of their central velocity dispersion, And XIX, XXI, and XXV, all of which have large half-light radii (∼> 700 pc) and low velocity dispersions (σ v –1 ). In addition, And XXV has a mass-to-light ratio within its half-light radius of just [M/L] half =10.3 +7.0 -6.7 , making it consistent with a simple stellar system with no appreciable dark matter component within its 1σ uncertainties. We suggest that the structure of the dark matter halos of these outliers have been significantly altered by tides.

  11. Dwarf spheroidal satellites of M31. I. Variable stars and stellar populations in Andromeda XIX

    Energy Technology Data Exchange (ETDEWEB)

    Cusano, Felice; Clementini, Gisella; Garofalo, Alessia; Federici, Luciana, E-mail: felice.cusano@oabo.inaf.it, E-mail: gisella.clementini@oabo.inaf.it, E-mail: luciana.federici@oabo.inaf.it, E-mail: alessia.garofalo@studio.unibo.it [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); and others

    2013-12-10

    We present B, V time-series photometry of Andromeda XIX (And XIX), the most extended (half-light radius of 6.'2) of Andromeda's dwarf spheroidal companions, which we observed with the Large Binocular Cameras at the Large Binocular Telescope. We surveyed a 23' × 23' area centered on And XIX and present the deepest color-magnitude diagram (CMD) ever obtained for this galaxy, reaching, at V ∼ 26.3 mag, about one magnitude below the horizontal branch (HB). The CMD shows a prominent and slightly widened red giant branch, along with a predominantly red HB, which extends to the blue to significantly populate the classical instability strip. We have identified 39 pulsating variable stars, of which 31 are of RR Lyrae type and 8 are Anomalous Cepheids (ACs). Twelve of the RR Lyrae variables and three of the ACs are located within And XIX's half light radius. The average period of the fundamental mode RR Lyrae stars ((P {sub ab}) = 0.62 days, σ = 0.03 days) and the period-amplitude diagram qualify And XIX as an Oosterhoff-Intermediate system. From the average luminosity of the RR Lyrae stars ((V(RR)) = 25.34 mag, σ = 0.10 mag), we determine a distance modulus of (m – M){sub 0} = 24.52 ± 0.23 mag in a scale where the distance to the Large Magellanic Cloud (LMC) is 18.5 ± 0.1 mag. The ACs follow a well-defined Period-Wesenheit (PW) relation that appears to be in very good agreement with the PW relationship defined by the ACs in the LMC.

  12. Planets, stars and stellar systems

    CERN Document Server

    Bond, Howard; McLean, Ian; Barstow, Martin; Gilmore, Gerard; Keel, William; French, Linda

    2013-01-01

    This is volume 3 of Planets, Stars and Stellar Systems, a six-volume compendium of modern astronomical research covering subjects of key interest to the main fields of contemporary astronomy. This volume on “Solar and Stellar Planetary Systems” edited by Linda French and Paul Kalas presents accessible review chapters From Disks to Planets, Dynamical Evolution of Planetary Systems, The Terrestrial Planets, Gas and Ice Giant Interiors, Atmospheres of Jovian Planets, Planetary Magnetospheres, Planetary Rings, An Overview of the Asteroids and Meteorites, Dusty Planetary Systems and Exoplanet Detection Methods. All chapters of the handbook were written by practicing professionals. They include sufficient background material and references to the current literature to allow readers to learn enough about a specialty within astronomy, astrophysics and cosmology to get started on their own practical research projects. In the spirit of the series Stars and Stellar Systems published by Chicago University Press in...

  13. Models of hot stellar systems

    International Nuclear Information System (INIS)

    Van Albada, T.S.

    1986-01-01

    Elliptical galaxies consist almost entirely of stars. Sites of recent star formation are rare, and most stars are believed to be several billion years old, perhaps as old as the Universe itself (--10/sup 10/ yrs). Stellar motions in ellipticals show a modest amount of circulation about the center of the system, but most support against the force of gravity is provided by random motions; for this reason ellipticals are called 'hot' stellar systems. Spiral galaxies usually also contain an appreciable amount of gas (--10%, mainly atomic hydrogen) and new stars are continually being formed out of this gas, especially in the spiral arms. In contrast to ellipticals, support against gravity in spiral galaxies comes almost entirely from rotation; random motions of the stars with respect to rotation are small. Consequently, spiral galaxies are called 'cold' stellar systems. Other than in hot systems, in cold systems the collective response of stars to variations in the force field is an essential part of the dynamics. The present overview is limited to mathematical models of hot systems. Computational methods are also discussed

  14. Neutron diffusion in spheroidal, bispherical, and toroidal systems

    International Nuclear Information System (INIS)

    Williams, M.M.R.

    1986-01-01

    The neutron flux has been studied around absorbing bodies of spheroidal, bispherical, and toroidal shapes in an infinite nonabsorbing medium. Exact solutions have been obtained by using effective boundary conditions at the surfaces of the absorbing bodies. The problems considered are as follows: 1. Neutron flux and current distributions around prolate and oblate spheroids. It is shown that an equivalent sphere approximation can lead to accurate values for the rate of absorption. 2. Neutron flux and current in a bispherical system of unequal spheres. Three separate situations arise here: (a) two absorbing spheres, (b) two spherical sources, and (c) one spherical source and one absorbing sphere. It is shown how the absorption rate in the two spheres depends on their separation. 3. Neutron flux and current in a toroidal system: (a) an absorbing toroid and (b) a toroidal source. The latter case simulates the flux distribution from a thermonuclear reactor vessel. Finally, a brief description of how these techniques can be extended to multiregion problems is given

  15. Black holes in binary stellar systems and galactic nuclei

    Science.gov (United States)

    Cherepashchuk, A. M.

    2014-04-01

    In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M_BH = (4{-}20) M_\\odot) in X-ray binary systems and of several hundred supermassive black holes (M_BH = (10^{6}{-}10^{10}) M_\\odot) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a_* have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a_* = 0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths \\lambda \\lesssim 1 mm (the international program, Event Horizon Telescope).

  16. Three-dimensional alginate spheroid culture system of murine osteosarcoma.

    Science.gov (United States)

    Akeda, Koji; Nishimura, Akinobu; Satonaka, Haruhiko; Shintani, Ken; Kusuzaki, Katsuyuki; Matsumine, Akihiko; Kasai, Yuichi; Masuda, Koichi; Uchida, Atsumasa

    2009-11-01

    Osteosarcoma (OS) is the most common primary malignant tumor of the bone and often forms pulmonary metastases, which are the most important prognostic factor. For further elucidation of the mechanism underlying the progression and metastasis of human OS, a culture system mimicking the microenvironment of the tumor in vivo is needed. We report a novel three-dimensional (3D) alginate spheroid culture system of murine osteosarcoma. Two different metastatic clones, the parental Dunn and its derivative line LM8, which has a higher metastatic potential to the lungs, were encapsulated in alginate beads to develop the 3D culture system. The beads containing murine OS cells were also transplanted into mice to determine their metastatic potential in vivo. In this culture system, murine OS cells encapsulated in alginate beads were able to grow in a 3D structure with cells detaching from the alginate environment. The number of detaching cells was higher in the LM8 cell line than the Dunn cell line. In the in vivo alginate bead transplantation model, the rate of pulmonary metastasis was higher with LM8 cells compared with that of Dunn cells. The cell characteristics and kinetics in this culture system closely reflect the original malignant potential of the cells in vivo.

  17. An injectable spheroid system with genetic modification for cell transplantation therapy.

    Science.gov (United States)

    Uchida, Satoshi; Itaka, Keiji; Nomoto, Takahiro; Endo, Taisuke; Matsumoto, Yu; Ishii, Takehiko; Kataoka, Kazunori

    2014-03-01

    The new methodology to increase a therapeutic potential of cell transplantation was developed here by the use of three-dimensional spheroids of transplanting cells subsequent to the genetic modification with non-viral DNA vectors, polyplex nanomicelles. Particularly, spheroids in regulated size of 100-μm of primary hepatocytes transfected with luciferase gene were formed on the micropatterned culture plates coated with thermosensitive polymer, and were recovered in the form of injectable liquid suspension simply by cooling the plates. After subcutaneously transplanting these hepatocyte spheroids, efficient transgene expression was observed in host tissue for more than a month, whereas transplantation of a single-cell suspension from a monolayer culture resulted in an only transient expression. The spheroid system contributed to the preservation of innate functions of transplanted hepatocytes in the host tissue, such as albumin expression, thereby possessing high potential for expressing transgene. Intravital observation of transplanted cells showed that those from spheroid cultures had a tendency to localize in the vicinity of blood vessels, making a favorable microenvironment for preserving cell functionality. Furthermore, spheroids transfected with erythropoietin-expressing DNA showed a significantly higher hematopoietic effect than that of cell suspensions from monolayer cultures, demonstrating high potential of this genetically-modified spheroid transplantation system for therapeutic applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Stellar Kinematics and Metallicities in the Draco and Ursa Minor Dwarf Spheroidal Galaxies from WHT/AF2-WYFFOS

    NARCIS (Netherlands)

    Jin, S.; Irwin, M.; Tolstoy, E.; Lewis, J.; Hartke, J.; Skillen, I.; Barcells, M.; Trager, S.

    2016-01-01

    We present preliminary results from our chemo-dynamical survey of two Milky Way dwarf spheroidal (dSph) galaxies, Draco and Ursa Minor. The two galaxies have similar radial velocities and reside in close proximity in the outskirts of the Milky Way halo, yet exhibit noteworthy differences in their

  19. Proteomic approach toward molecular backgrounds of drug resistance of osteosarcoma cells in spheroid culture system.

    Science.gov (United States)

    Arai, Kazuya; Sakamoto, Ruriko; Kubota, Daisuke; Kondo, Tadashi

    2013-08-01

    Chemoresistance is one of the most critical prognostic factors in osteosarcoma, and elucidation of the molecular backgrounds of chemoresistance may lead to better clinical outcomes. Spheroid cells resemble in vivo cells and are considered an in vitro model for the drug discovery. We found that spheroid cells displayed more chemoresistance than conventional monolayer cells across 11 osteosarcoma cell lines. To investigate the molecular mechanisms underlying the resistance to chemotherapy, we examined the proteomic differences between the monolayer and spheroid cells by 2D-DIGE. Of the 4762 protein species observed, we further investigated 435 species with annotated mass spectra in the public proteome database, Genome Medicine Database of Japan Proteomics. Among the 435 protein species, we found that 17 species exhibited expression level differences when the cells formed spheroids in more than five cell lines and four species out of these 17 were associated with spheroid-formation associated resistance to doxorubicin. We confirmed the upregulation of cathepsin D in spheroid cells by western blotting. Cathepsin D has been implicated in chemoresistance of various malignancies but has not previously been implemented in osteosarcoma. Our study suggested that the spheroid system may be a useful tool to reveal the molecular backgrounds of chemoresistance in osteosarcoma. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Coulomb energy of uniformly charged spheroidal shell systems.

    Science.gov (United States)

    Jadhao, Vikram; Yao, Zhenwei; Thomas, Creighton K; de la Cruz, Monica Olvera

    2015-03-01

    We provide exact expressions for the electrostatic energy of uniformly charged prolate and oblate spheroidal shells. We find that uniformly charged prolate spheroids of eccentricity greater than 0.9 have lower Coulomb energy than a sphere of the same area. For the volume-constrained case, we find that a sphere has the highest Coulomb energy among all spheroidal shells. Further, we derive the change in the Coulomb energy of a uniformly charged shell due to small, area-conserving perturbations on the spherical shape. Our perturbation calculations show that buckling-type deformations on a sphere can lower the Coulomb energy. Finally, we consider the possibility of counterion condensation on the spheroidal shell surface. We employ a Manning-Oosawa two-state model approximation to evaluate the renormalized charge and analyze the behavior of the equilibrium free energy as a function of the shell's aspect ratio for both area-constrained and volume-constrained cases. Counterion condensation is seen to favor the formation of spheroidal structures over a sphere of equal area for high values of shell volume fractions.

  1. Optimisation of stellarator systems: Possible ways

    International Nuclear Information System (INIS)

    Cooper, W.A.; Isaev, M.; Leneva, A.E.; Mikhailov, M.; Shafranov, V.D.; Subbotin, A.A.

    2001-01-01

    The results of our search for advanced helical (stellarator) systems with a small number of field periods over the last five years are presented. The comparison of stellarator systems with toroidal (helical or axial) and poloidal directions of the contours with B = constant on the magnetic surface as well as systems with Helias and Heliac-like orientation of the magnetic surfaces cross-sections with respect to the principal normal to the magnetic axis is undertaken. Particular attention is paid to some attractive features of the systems with constant B-lines in the poloidal direction. (author)

  2. Optimisation of stellarator systems: Possible ways

    International Nuclear Information System (INIS)

    Cooper, W.A.; Isaev, M.Yu.; Leneva, A.E.; Mikhailov, M.I.; Sharfranov, V.D.; Subbotin, A.A.

    1999-01-01

    The results of our search for advanced helical (stellarator) systems with a small number of field periods over the last five years are presented. The comparison of stellarator systems with toroidal (helical or axial) and poloidal directions of the contours with B = constant on the magnetic surface as well as systems with Helias and Heliac-like orientation of the magnetic surfaces cross-sections with respect to the principal normal to the magnetic axis is undertaken. Particular attention is paid to some attractive features of the systems with constant B-lines in the poloidal direction. (author)

  3. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    Science.gov (United States)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  4. On Utmost Multiplicity of Hierarchical Stellar Systems

    Directory of Open Access Journals (Sweden)

    Gebrehiwot Y. M.

    2016-12-01

    Full Text Available According to theoretical considerations, multiplicity of hierarchical stellar systems can reach, depending on masses and orbital parameters, several hundred, while observational data confirm the existence of at most septuple (seven-component systems. In this study, we cross-match the stellar systems of very high multiplicity (six and more components in modern catalogues of visual double and multiple stars to find among them the candidates to hierarchical systems. After cross-matching the catalogues of closer binaries (eclipsing, spectroscopic, etc., some of their components were found to be binary/multiple themselves, what increases the system's degree of multiplicity. Optical pairs, known from literature or filtered by the authors, were flagged and excluded from the statistics. We compiled a list of hierarchical systems with potentially very high multiplicity that contains ten objects. Their multiplicity does not exceed 12, and we discuss a number of ways to explain the lack of extremely high multiplicity systems.

  5. Black holes in binary stellar systems and galactic nuclei

    International Nuclear Information System (INIS)

    Cherepashchuk, A M

    2014-01-01

    In the last 40 years, following pioneering papers by Ya B Zeldovich and E E Salpeter, in which a powerful energy release from nonspherical accretion of matter onto a black hole (BH) was predicted, many observational studies of black holes in the Universe have been carried out. To date, the masses of several dozen stellar-mass black holes (M BH =(4−20)M ⊙ ) in X-ray binary systems and of several hundred supermassive black holes (M BH =(10 6 −10 10 )M ⊙ ) in galactic nuclei have been measured. The estimated radii of these massive and compact objects do not exceed several gravitational radii. For about ten stellar-mass black holes and several dozen supermassive black holes, the values of the dimensionless angular momentum a ∗ have been estimated, which, in agreement with theoretical predictions, do not exceed the limiting value a ∗ =0.998. A new field of astrophysics, so-called black hole demography, which studies the birth and growth of black holes and their evolutionary connection to other objects in the Universe, namely stars, galaxies, etc., is rapidly developing. In addition to supermassive black holes, massive stellar clusters are observed in galactic nuclei, and their evolution is distinct from that of supermassive black holes. The evolutionary relations between supermassive black holes in galactic centers and spheroidal stellar components (bulges) of galaxies, as well as dark-matter galactic haloes are brought out. The launch into Earth's orbit of the space radio interferometer RadioAstron opened up the real possibility of finally proving that numerous discovered massive and highly compact objects with properties very similar to those of black holes make up real black holes in the sense of Albert Einstein's General Relativity. Similar proofs of the existence of black holes in the Universe can be obtained by intercontinental radio interferometry at short wavelengths λ≲1 mm (the international program, Event Horizon Telescope). (100

  6. Stellar physics with the ALHAMBRA photometric system

    International Nuclear Information System (INIS)

    Villegas, T Aparicio; Alfaro, E J; Moles, M; Benítez, N; Perea, J; Olmo, A del; Cristóbal-Hornillos, D; Cervio, M; Delgado, R M González; Márquez, I; Masegosa, J; Prada, F; Cabrera-Caño, J; Fernández-Soto, A; Aguerri, J A L; Cepa, J; Broadhurst, T; Castander, F J; Infante, L; Martínez, V J

    2011-01-01

    The ALHAMBRA photometric system was specifically designed to perform a tomography of the Universe in some selected areas. Although mainly designed for extragalactic purposes, its 20 contiguous, equal-width, medium-band photometric system in the optical wavelength range, shows a great capacity for stellar classification. In this contribution we propose a methodology for stellar classification and physical parameter estimation (T eff , log g, [Fe/H], and color excess E(B – V)) based on 18 independent reddening-free Q-values from the ALHAMBRA photometry. Based on the theoretical Spectral library BaSeL 2.2, and applied to 288 stars from the Next Generation spectral Library (NGSL), we discuss the reliability of the method and its dependence on the extinction law used.

  7. Nonlocal and collective relaxation in stellar systems

    Science.gov (United States)

    Weinberg, Martin D.

    1993-01-01

    The modal response of stellar systems to fluctuations at large scales is presently investigated by means of analytic theory and n-body simulation; the stochastic excitation of these modes is shown to increase the relaxation rate even for a system which is moderately far from instability. The n-body simulations, when designed to suppress relaxation at small scales, clearly show the effects of large-scale fluctuations. It is predicted that large-scale fluctuations will be largest for such marginally bound systems as forming star clusters and associations.

  8. Design of a uranium-dioxide powder spheroidization system by plasma processing

    Science.gov (United States)

    Cavender, Daniel

    The plasma spheroidization system (PSS) is the first process in the development of a tungsten-uranium dioxide (W-UO2) ceramic-metallic (cermet) fuel for nuclear thermal rocket (NTR) propulsion. For the purposes of fissile fuel retention, UO2 spheroids ranging in size from 50 - 100 micrometers (μm) in diameter will be encapsulated in a tungsten shell. The PSS produces spherical particles by melting angular stock particles in an argon-hydrogen plasma jet where they become spherical due to surface tension. Surrogate CeO 2 powder was used in place of UO2 for system and process parameter development. Stock and spheroidized powders were micrographed using optical and scanning electron microscopy and evaluated by statistical methods to characterize and compare the spherocity of pre and post process powders. Particle spherocity was determined by irregularity parameter. Processed powders showed a statistically significant improvement in spherocity, with greater that 60% of the examined particles having an irregularity parameter of equal to or lower than 1.2, compared to stock powder.

  9. On the evolution of stellar systems with a massive center

    International Nuclear Information System (INIS)

    Gurzadyan, V.G.; Kocharyan, A.A.

    1986-01-01

    The evolution of stellar systems with the massive center is investigated within the framework of dynamic system theory. Open dissipative systems, for which the Liouville theorem of the phase volume preservation is not implemented, are considered. Equations determining variation, in time, of main physical system parameters have been derived and studied. Results of the investigation show a principal possibility for determining the evolution path of stellar systems with the massive centers depending on physical parameters

  10. Encapsulation by Janus spheroids

    OpenAIRE

    Li, Wei; Liu, Ya; Brett, Genevieve; Gunton, James D.

    2011-01-01

    The micro/nano encapsulation technology has acquired considerable attention in the fields of drug delivery, biomaterial engineering, and materials science. Based on recent advances in chemical particle synthesis, we propose a primitive model of an encapsulation system produced by the self-assembly of Janus oblate spheroids, particles with oblate spheroidal bodies and two hemi-surfaces coded with dissimilar chemical properties. Using Monte Carlo simulation, we investigate the encapsulation sys...

  11. The Effects of Stellar Dynamics on the Evolution of Young, Dense Stellar Systems

    Science.gov (United States)

    Belkus, H.; van Bever, J.; Vanbeveren, D.

    In this paper, we report on first results of a project in Brussels in which we study the effects of stellar dynamics on the evolution of young dense stellar systems using 3 decades of expertise in massive-star evolution and our population (number and spectral) synthesis code. We highlight an unconventionally formed object scenario (UFO-scenario) for Wolf Rayet binaries and study the effects of a luminous blue variable-type instability wind mass-loss formalism on the formation of intermediate-mass black holes.

  12. A novel hanging spherical drop system for the generation of cellular spheroids and high throughput combinatorial drug screening.

    Science.gov (United States)

    Neto, A I; Correia, C R; Oliveira, M B; Rial-Hermida, M I; Alvarez-Lorenzo, C; Reis, R L; Mano, J F

    2015-04-01

    We propose a novel hanging spherical drop system for anchoring arrays of droplets of cell suspension based on the use of biomimetic superhydrophobic flat substrates, with controlled positional adhesion and minimum contact with a solid substrate. By facing down the platform, it was possible to generate independent spheroid bodies in a high throughput manner, in order to mimic in vivo tumour models on the lab-on-chip scale. To validate this system for drug screening purposes, the toxicity of the anti-cancer drug doxorubicin in cell spheroids was tested and compared to cells in 2D culture. The advantages presented by this platform, such as feasibility of the system and the ability to control the size uniformity of the spheroid, emphasize its potential to be used as a new low cost toolbox for high-throughput drug screening and in cell or tissue engineering.

  13. On the universal stellar law

    Science.gov (United States)

    Krot, Alexander

    In this work, we consider a statistical theory of gravitating spheroidal bodies to derive and develop the universal stellar law for extrasolar systems. Previously, the statistical theory for a cosmogonic body forming (so-called spheroidal body)has been proposed [1-3]. This theory starts from the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula; it permits us to derive the form of distribution functions, mass density, gravitational potentials and strengths both for immovable and rotating spheroidal bodies as well as to find the distribution function of specific angular momentum[1-3]. If we start from the conception for forming a spheroidal body as a protostar (in particular, proto-Sun) inside a prestellar (presolar) nebula then the derived distribution functions of particle (as well as the mass density of an immovable spheroidal body) characterizes the first stage of evolution: from a prestellar molecular cloud (the presolar nebula) to the forming core of protostar (the proto-Sun) together with its shell as a stellar nebula (the solar nebula). This work derives the equation of state of an ideal stellar substance based on conception of gravitating spheroidal body. Using this equation, we obtain the universal stellar law (USL) for the planetary systems connecting temperature, size and mass of each of stars. This work also considers the Solar corona in the connection with USL. Then it is accounting under calculation of the ratio of temperature of the Solar corona to effective temperature of the Sun’ surfaceand modification of USL. To test justice of the modified USLfor different types of stars, the temperature of stellar corona is estimated. The prediction of parameters of stars is carrying out by means of the modified USL,as well as the Hertzsprung-Russell’s dependence [5-7]is derivedby means of USL directly. This paper also shows that knowledge of some characteristics for multi-planet extrasolar systems refines own parameters of

  14. On the dynamics of slowly rotating stellar systems

    International Nuclear Information System (INIS)

    Davoust, E.

    1989-01-01

    Kinematical observations are now available for stellar systems which might rotate slowly. The study of periodic orbits in model stellar systems shows that a mean motion in epicyclic or circular orbits contributes to balance the centrifugal force, in addition to the velocity dispersions. Two dynamical models, the generalized Toomre and Plummer models, are adapted to the case of slow rotation. They are applied to two globular clusters, M 3 and 47 Tucanae, and 12 clusters of galaxies. 47 Tucanae is found to rotate, but none of the clusters of galaxies has any significant mean motion, except SC 316-44. 34 refs., 1 fig., 3 tabs. (author)

  15. The Resilience of Kepler Systems to Stellar Obliquity

    Science.gov (United States)

    Spalding, Christopher; Marx, Noah W.; Batygin, Konstantin

    2018-04-01

    The Kepler mission and its successor K2 have brought forth a cascade of transiting planets. Many of these planetary systems exhibit multiple members, but a large fraction possess only a single transiting example. This overabundance of singles has led to the suggestion that up to half of Kepler systems might possess significant mutual inclinations between orbits, reducing the transiting number (the so-called “Kepler Dichotomy”). In a recent paper, Spalding & Batygin demonstrated that the quadrupole moment arising from a young, oblate star is capable of misaligning the constituent orbits of a close-in planetary system enough to reduce their transit number, provided that the stellar spin axis is sufficiently misaligned with respect to the planetary orbital plane. Moreover, tightly packed planetary systems were shown to be susceptible to becoming destabilized during this process. Here, we investigate the ubiquity of the stellar obliquity-driven instability within systems with a range of multiplicities. We find that most planetary systems analyzed, including those possessing only two planets, underwent instability for stellar spin periods below ∼3 days and stellar tilts of order 30°. Moreover, we are able to place upper limits on the stellar obliquity in systems such as K2-38 (obliquity ≲20°), where other methods of measuring the spin–orbit misalignment are not currently available. Given the known parameters of T-Tauri stars, we predict that up to one-half of super-Earth-mass systems may encounter the instability, in general agreement with the fraction typically proposed to explain the observed abundance of single-transiting systems.

  16. Direct Measurements of Oxygen Gradients in Spheroid Culture System Using Electron Parametric Resonance Oximetry.

    Directory of Open Access Journals (Sweden)

    Laura M Langan

    Full Text Available Advanced in vitro culture from tissues of different origin includes three-dimensional (3D organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells using Electron Paramagnetic Resonance (EPR oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid and absolute size (118±32 μm allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid cultures in biomedical and

  17. The CAD concept for stellarator-type magnetic systems

    International Nuclear Information System (INIS)

    Vorobyova, V.P.; Martynov, S.A.; Khazhmuradov, M.A.

    2002-01-01

    The paper describes the computer-aided design (CAD) concept for stellarator-type magnetic systems. Consideration is given to the main peculiarities, principles, and dialog organization and design stages of the CAD. The practical realization of the concept is illustrated by specific examples

  18. Control system for the Spanish Stellarator TJ-II

    International Nuclear Information System (INIS)

    Pacios, L.; Blaumoser, M.; Pena, A. de la; Carrasco, R.; Labrador, I.; Lapayese, F.; Diaz, J.C.; Laso, L.M.

    1995-01-01

    We describe the distributed control and monitoring system for the Spanish Stellarator TJ-II, which is under construction at CIEMAT in Madrid. It consists of one central UNIX workstation and several autonomous subsystems based on VME crates with embedded processors under OS-9 real-time operating system and PLCs. The system integrates the machine and discharge control. An operator can perform the control and plasma discharge by means of a user-friendly graphic interface. (orig.)

  19. The Resilience of Kepler Multi-systems to Stellar Obliquity

    Science.gov (United States)

    Spalding, Christopher; Marx, Noah W.; Batygin, Konstantin

    2018-04-01

    The Kepler mission and its successor K2 have brought forth a cascade of transiting planets. Many of these planetary systems exhibit multiple transiting members. However, a large fraction possesses only a single transiting planet. This high abundance of singles, dubbed the "Kepler Dichotomy," has been hypothesized to arise from significant mutual inclinations between orbits in multi-planet systems. Alternatively, the single-transiting population truly possesses no other planets in the system, but the true origin of the overabundance of single systems remains unresolved. In this work, we propose that planetary systems typically form with a coplanar, multiple-planetary architecture, but that quadrupolar gravitational perturbations from their rapidly-rotating host star subsequently disrupt this primordial coplanarity. We demonstrate that, given sufficient stellar obliquity, even systems beginning with 2 planetary constituents are susceptible to dynamical instability soon after planet formation, as a result of the stellar quadrupole moment. This mechanism stands as a widespread, yet poorly explored pathway toward planetary system instability. Moreover, by requiring that observed multi-systems remain coplanar on Gyr timescales, we are able to place upper limits on the stellar obliquity in systems such as K2-38 (obliquity < 20 degrees), where other methods of measuring spin-orbit misalignment are not currently available.

  20. Acoustic scattering on spheroidal shapes near boundaries

    Science.gov (United States)

    Miloh, Touvia

    2016-11-01

    A new expression for the Lamé product of prolate spheroidal wave functions is presented in terms of a distribution of multipoles along the axis of the spheroid between its foci (generalizing a corresponding theorem for spheroidal harmonics). Such an "ultimate" singularity system can be effectively used for solving various linear boundary-value problems governed by the Helmholtz equation involving prolate spheroidal bodies near planar or other boundaries. The general methodology is formally demonstrated for the axisymmetric acoustic scattering problem of a rigid (hard) spheroid placed near a hard/soft wall or inside a cylindrical duct under an axial incidence of a plane acoustic wave.

  1. Gravitational physics of stellar and galactic systems

    International Nuclear Information System (INIS)

    Saslaw, W.C.

    1985-01-01

    The book concerns the gravitational interactions and evolution of astronomical systems on all scales, and is aimed at the graduate student of physics and astronomy. The text is divided into four parts, and each describes areas of the subject in order of decreasing symmetry. The four parts include: idealized homogeneous systems-basic ideas and gentle relaxation; infinite inhomogeneous systems and galaxy clustering; finite spherical systems including clusters of galaxies; galactic nuclei and globular clusters; and finite flattened systems and galaxies. (U.K.)

  2. N-Body simulations of tidal encounters between stellar systems

    International Nuclear Information System (INIS)

    Rao, P.D.; Ramamani, N.; Alladin, S.M.

    1985-10-01

    N-Body simulations have been performed to study the tidal effects of a primary stellar system on a secondary stellar system of density close to the Roche density. Two hyperbolic, one parabolic and one elliptic encounters have been simulated. The changes in energy, angular momentum, mass distribution, and shape of the secondary system have been determined in each case. The inner region containing about 40% of the mass was found to be practically unchanged and the mass exterior to the tidal radius was found to escape. The intermediate region showed tidal distension. The thickness of this region decreased as we went from hyperbolic encounters to the elliptic encounter keeping the distance of closest approach constant. The numerical results for the fractional change in energy have been compared with the predictions of the available analytic formulae and the usefulness and limitations of the formulae have been discussed. (author)

  3. Theory and computation of spheroidal wavefunctions

    International Nuclear Information System (INIS)

    Falloon, P E; Abbott, P C; Wang, J B

    2003-01-01

    In this paper we report on a package, written in the Mathematica computer algebra system, which has been developed to compute the spheroidal wavefunctions of Meixner and Schaefke (1954 Mathieusche Funktionen und Sphaeroidfunktionen) and is available online (physics.uwa.edu.au/~falloon/spheroidal/spheroidal.html). This package represents a substantial contribution to the existing software, since it computes the spheroidal wavefunctions to arbitrary precision for general complex parameters μ, ν, γ and argument z; existing software can only handle integer μ, ν and does not give arbitrary precision. The package also incorporates various special cases and computes analytic power series and asymptotic expansions in the parameter γ. The spheroidal wavefunctions of Flammer (1957 Spheroidal Wave functions) are included as a special case of Meixner's more general functions. This paper presents a concise review of the general theory of spheroidal wavefunctions and a description of the formulae and algorithms used in their computation, and gives high precision numerical examples

  4. Improvement of In-Flight Alumina Spheroidization Process Using a Small Power Argon DC-RF Hybrid Plasma Flow System by Helium Mixture

    Science.gov (United States)

    Takana, Hidemasa; Jang, Juyong; Igawa, Junji; Nakajima, Tomoki; Solonenko, Oleg P.; Nishiyama, Hideya

    2011-03-01

    For the further improvement of in-flight alumina spheroidization process with a low-power direct-current radiofrequency (DC-RF) hybrid plasma flow system, the effect of a small amount of helium gas mixture in argon main gas and also the effect of increasing DC nozzle diameter on powder spheroidization ratio have been experimentally clarified with correlating helium gas mixture percentage, plasma enthalpy, powder in-flight velocity, and temperature. The alumina spheroidization ratio increases by helium gas mixture as a result of enhancement of plasma enthalpy. The highest spheroidization ratio is obtained by 4% mixture of helium in central gas with enlarging nozzle diameter from 3 to 4 mm, even under the constant low input electric power given to a DC-RF hybrid plasma flow system.

  5. MASSIVE BLACK HOLES IN STELLAR SYSTEMS: 'QUIESCENT' ACCRETION AND LUMINOSITY

    International Nuclear Information System (INIS)

    Volonteri, M.; Campbell, D.; Mateo, M.; Dotti, M.

    2011-01-01

    Only a small fraction of local galaxies harbor an accreting black hole, classified as an active galactic nucleus. However, many stellar systems are plausibly expected to host black holes, from globular clusters to nuclear star clusters, to massive galaxies. The mere presence of stars in the vicinity of a black hole provides a source of fuel via mass loss of evolved stars. In this paper, we assess the expected luminosities of black holes embedded in stellar systems of different sizes and properties, spanning a large range of masses. We model the distribution of stars and derive the amount of gas available to a central black hole through a geometrical model. We estimate the luminosity of the black holes under simple, but physically grounded, assumptions on the accretion flow. Finally, we discuss the detectability of 'quiescent' black holes in the local universe.

  6. On the dynamics of non-stationary binary stellar systems

    International Nuclear Information System (INIS)

    Bekov, A. A.; Bejsekov, A.N.; Aldibaeva, L.T.

    2005-01-01

    The motion of test body in the external gravitational field of the binary stellar system with slowly variable some physical parameters of radiating components is considered on the base of restricted non-stationary photo-gravitational three and two bodies problem. The family of polar and coplanar solutions are obtained. These solutions give the possibility of the dynamical and structure interpretation of the binary young evolving stars and galaxies. (author)

  7. Hypercompact Stellar Systems Around Recoiling Supermassive Black Holes

    Science.gov (United States)

    Merritt, David; Schnittman, Jeremy D.; Komossa, S.

    2009-07-01

    A supermassive black hole ejected from the center of a galaxy by gravitational-wave recoil carries a retinue of bound stars—a "hypercompact stellar system" (HCSS). The numbers and properties of HCSSs contain information about the merger histories of galaxies, the late evolution of binary black holes, and the distribution of gravitational-wave kicks. We relate the structural properties (size, mass, density profile) of HCSSs to the properties of their host galaxies and to the size of the kick in two regimes: collisional (M BH lsim 107 M sun), i.e., short nuclear relaxation times, and collisionless (M BH gsim 107 M sun), i.e., long nuclear relaxation times. HCSSs are expected to be similar in size and luminosity to globular clusters, but in extreme cases (large galaxies, kicks just above escape velocity) their stellar mass can approach that of ultracompact dwarf galaxies. However, they differ from all other classes of compact stellar system in having very high internal velocities. We show that the kick velocity is encoded in the velocity dispersion of the bound stars. Given a large enough sample of HCSSs, the distribution of gravitational-wave kicks can therefore be empirically determined. We combine a hierarchical merger algorithm with stellar population models to compute the rate of production of HCSSs over time and the probability of observing HCSSs in the local universe as a function of their apparent magnitude, color, size, and velocity dispersion, under two different assumptions about the star formation history prior to the kick. We predict that ~102 HCSSs should be detectable within 2 Mpc of the center of the Virgo cluster, and that many of these should be bright enough that their kick velocities (i.e., velocity dispersions) could be measured with reasonable exposure times. We discuss other strategies for detecting HCSSs and speculate on some exotic manifestations.

  8. Expanding CME-flare relations to other stellar systems

    Science.gov (United States)

    Moschou, Sofia P.; Drake, Jeremy J.; Cohen, Ofer

    2017-05-01

    Stellar activity is one of the main parameters in exoplanet habitability studies. While the effects of UV to X-ray emission from extreme flares on exoplanets are beginning to be investigated, the impact of coronal mass ejections is currently highly speculative because CMEs and their properties cannot yet be directly observed on other stars. An extreme superflare was observed in X-rays on the Algol binary system on August 30 1997, emitting a total of energy 1.4x 10^{37} erg and making it a great candidate for studying the upper energy limits of stellar superflares in solar-type (GK) stars. A simultaneous increase and subsequent decline in absorption during the flare was also observed and interpretted as being caused by a CME. Here we investigate the dynamic properties of a CME that could explain such time-dependent absorption and appeal to trends revealed from solar flare and CME statistics as a guide. Using the ice-cream cone model that is extensively used in solar physics to describe the three-dimensional CME structure, in combination with the temporal profile of the hydrogen column density evolution, we are able to characterize the CME and estimate its kinetic energy and mass. We examine the mass, kinetic and flare X-ray fluence in the context of solar relations to examine the extent to which such relations can be extrapolated to much more extreme stellar events.

  9. Investigation of nonplanar modular coil systems for stellarator fusion reactors

    International Nuclear Information System (INIS)

    Harmeyer, E.

    1988-12-01

    Steady-state stellarators constitute an important option for a future fusion reactor. The helical magnetic field required for plasma confinement can be produced by means of a set of modular nonplanar coils. In order to achieve optimum power density of the plasma, the magnetic flux density inside the torus is made as high as possible. State-of-the-art estimates allow values of the magnetic flux density on axis of B 0 = 4-7 T. The present report is concerned with investigations on modular nonplanar stellarator coil systems. Coil systems with poloidal periodicity l=2 and a coil system of the W VII-AS type with superposed l=0, 1, 2, 3 terms are treated. Furthermore, the parameters are simultaneously varied while keeping constant the ratios of certain magnitudes. In the parameter space of the geometric values and coil number the following quantities are evaluated: maximum magnetic flux density in the coil domain, stored magnetic energy of the coil system, magnetic force density distribution or magnetic forces, and mechanical stress distribution in the coils. Numerical methods are applied in the programme systems used for these calculations. The aim of the study is to determine an optimum regime for the above parameters. The numerical results are compared with those of analytical approximation solutions. (orig.)

  10. THE AGE OF THE YOUNG BULGE-LIKE POPULATION IN THE STELLAR SYSTEM TERZAN 5: LINKING THE GALACTIC BULGE TO THE HIGH- Z UNIVERSE

    Energy Technology Data Exchange (ETDEWEB)

    Ferraro, F. R.; Dalessandro, E.; Lanzoni, B.; Mucciarelli, A. [Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Viale Berti Pichat 6/2, I–40127 Bologna (Italy); Massari, D. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani, 1, I-40127 Bologna (Italy); Origlia, L. [Kapteyn Astronomical Institute, University of Gröningen, Kapteyn Astron Institute, NL-9747 AD Gröningen (Netherlands); Rich, R. M. [Department of Physics and Astronomy, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States)

    2016-09-10

    The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations with iron content varying by more than one order of magnitude (from 0.2 up to two times the solar value), with chemical abundance patterns strikingly similar to those observed in bulge field stars. Here we report on the detection of two distinct main-sequence turnoff points in Terzan 5, providing the age of the two main stellar populations: 12 Gyr for the (dominant) sub-solar component and 4.5 Gyr for the component at super-solar metallicity. This discovery classifies Terzan 5 as a site in the Galactic bulge where multiple bursts of star formation occurred, thus suggesting a quite massive progenitor possibly resembling the giant clumps observed in star-forming galaxies at high redshifts. This connection opens a new route of investigation into the formation process and evolution of spheroids and their stellar content.

  11. Parametric systems analysis of the Modular Stellarator Reactor (MSR)

    International Nuclear Information System (INIS)

    Miller, R.L.; Krakowski, R.A.; Bathke, C.G.

    1982-05-01

    The close coupling in the stellarator/torsatron/heliotron (S/T/H) between coil design (peak field, current density, forces), magnetics topology (transform, shear, well depth), and plasma performance (equilibrium, stability, transport, beta) complicates the reactor assessment more so than for most magnetic confinement systems. In order to provide an additional degree of resolution of this problem for the Modular Stellarator Reactor (MSR), a parametric systems model has been developed and applied. This model reduces key issues associted ith plasma performance, first-wall/blanket/shield (FW/B/S), and coil design to a simple relationship between beta, system geometry, and a number of indicators of overall plant performance. The results of this analysis can then be used to guide more detailed, multidimensional plasma, magnetics, and coil design efforts towards technically and economically viable operating regimes. In general, it is shown that beta values > 0.08 may be needed if the MSR approach is to be substantially competitive with other approaches to magnetic fusion in terms of system power density, mass utilization, and cost for total power output around 4.0 GWt; lower powers will require even higher betas

  12. Terrestrial aurora: astrophysical laboratory for anomalous abundances in stellar systems

    Directory of Open Access Journals (Sweden)

    I. Roth

    2014-02-01

    Full Text Available The unique magnetic structure of the terrestrial aurora as a conduit of information between the ionosphere and magnetosphere can be utilized as a laboratory for physical processes at similar magnetic configurations and applied to various evolutionary phases of the solar (stellar system. The most spectacular heliospheric abundance enhancement involves the 3He isotope and selective heavy elements in impulsive solar flares. In situ observations of electromagnetic waves on active aurora are extrapolated to flaring corona in an analysis of solar acceleration processes of 3He, the only element that may resonate strongly with the waves, as well as heavy ions with specific charge-to-mass ratios, which may resonate weaker via their higher gyroharmonics. These results are applied to two observed anomalous astrophysical abundances: (1 enhanced abundance of 3He and possibly 13C in the late stellar evolutionary stages of planetary nebulae; and (2 enhanced abundance of the observed fossil element 26Mg in meteorites as a decay product of radioactive 26Al isotope due to interaction with the flare-energized 3He in the early solar system.

  13. An Advanced N -body Model for Interacting Multiple Stellar Systems

    Energy Technology Data Exchange (ETDEWEB)

    Brož, Miroslav [Astronomical Institute of the Charles University, Faculty of Mathematics and Physics, V Holešovičkách 2, CZ-18000 Praha 8 (Czech Republic)

    2017-06-01

    We construct an advanced model for interacting multiple stellar systems in which we compute all trajectories with a numerical N -body integrator, namely the Bulirsch–Stoer from the SWIFT package. We can then derive various observables: astrometric positions, radial velocities, minima timings (TTVs), eclipse durations, interferometric visibilities, closure phases, synthetic spectra, spectral energy distribution, and even complete light curves. We use a modified version of the Wilson–Devinney code for the latter, in which the instantaneous true phase and inclination of the eclipsing binary are governed by the N -body integration. If all of these types of observations are at one’s disposal, a joint χ {sup 2} metric and an optimization algorithm (a simplex or simulated annealing) allow one to search for a global minimum and construct very robust models of stellar systems. At the same time, our N -body model is free from artifacts that may arise if mutual gravitational interactions among all components are not self-consistently accounted for. Finally, we present a number of examples showing dynamical effects that can be studied with our code and we discuss how systematic errors may affect the results (and how to prevent this from happening).

  14. The stellar content of the isolated transition dwarf galaxy DDO210

    NARCIS (Netherlands)

    McConnachie, Alan W.; Arimoto, Nobuo; Irwin, Mike; Tolstoy, Eline

    2006-01-01

    We use Subaru Suprime-Cam and VLT FORS1 photometry of the dwarf galaxy DDO210 to study the global stellar content and structural properties of a transition-type galaxy (with properties intermediate between dwarf irregular and dwarf spheroidal systems). This galaxy is sufficiently isolated that tidal

  15. EXPLOSIVE DISINTEGRATION OF A MASSIVE YOUNG STELLAR SYSTEM IN ORION

    International Nuclear Information System (INIS)

    Zapata, Luis A.; Schmid-Burgk, Johannes; Menten, Karl M.; Ho, Paul T. P.; Rodriguez, Luis F.

    2009-01-01

    Young massive stars in the center of crowded star clusters are expected to undergo close dynamical encounters that could lead to energetic, explosive events. However, there has so far never been clear observational evidence of such a remarkable phenomenon. We here report new interferometric observations that indicate the well-known enigmatic wide-angle outflow located in the Orion BN/KL star-forming region to have been produced by such a violent explosion during the disruption of a massive young stellar system, and that this was caused by a close dynamical interaction about 500 years ago. This outflow thus belongs to a totally different family of molecular flows that is not related to the classical bipolar flows that are generated by stars during their formation process. Our molecular data allow us to create a three-dimensional view of the debris flow and to link this directly to the well-known Orion H 2 'fingers' farther out.

  16. Explosive Disintegration of a Massive Young Stellar System in Orion

    Science.gov (United States)

    Zapata, Luis A.; Schmid-Burgk, Johannes; Ho, Paul T. P.; Rodríguez, Luis F.; Menten, Karl M.

    2009-10-01

    Young massive stars in the center of crowded star clusters are expected to undergo close dynamical encounters that could lead to energetic, explosive events. However, there has so far never been clear observational evidence of such a remarkable phenomenon. We here report new interferometric observations that indicate the well-known enigmatic wide-angle outflow located in the Orion BN/KL star-forming region to have been produced by such a violent explosion during the disruption of a massive young stellar system, and that this was caused by a close dynamical interaction about 500 years ago. This outflow thus belongs to a totally different family of molecular flows that is not related to the classical bipolar flows that are generated by stars during their formation process. Our molecular data allow us to create a three-dimensional view of the debris flow and to link this directly to the well-known Orion H2 "fingers" farther out.

  17. Hepatocyte spheroids as a competent in vitro system for drug biotransformation studies: nevirapine as a bioactivation case study.

    Science.gov (United States)

    Pinheiro, Pedro F; Pereira, Sofia A; Harjivan, Shrika G; Martins, Inês L; Marinho, Aline T; Cipriano, Madalena; Jacob, Cristina C; Oliveira, Nuno G; Castro, Matilde F; Marques, M Matilde; Antunes, Alexandra M M; Miranda, Joana P

    2017-03-01

    The development of metabolically competent in vitro models is of utmost importance for predicting adverse drug reactions, thereby preventing attrition-related economical and clinical burdens. Using the antiretroviral drug nevirapine (NVP) as a model, this work aimed to validate rat hepatocyte 3D spheroid cultures as competent in vitro systems to assess drug metabolism and bioactivation. Hepatocyte spheroids were cultured for 12 days in a stirred tank system (3D cultures) and exposed to equimolar dosages of NVP and its two major Phase I metabolites, 12-OH-NVP and 2-OH-NVP. Phase I NVP metabolites were detected in the 3D cultures during the whole culture time in the same relative proportions reported in in vivo studies. Moreover, the modulation of SULT1A1 activity by NVP and 2-OH-NVP was observed for the first time, pointing their synergistic effect as a key factor in the formation of the toxic metabolite (12-sulfoxy-NVP). Covalent adducts formed by reactive NVP metabolites with N-acetyl-L-cysteine and bovine serum albumin were also detected by high-resolution mass spectrometry, providing new evidence on the relative role of the reactive NVP metabolites, 12-sulfoxy-NVP, and NVP quinone methide, in toxicity versus excretion pathways. In conclusion, these results demonstrate the validity of the 3D culture system to evaluate drug bioactivation, enabling the identification of potential biomarkers of bioactivation/toxicity, and providing new evidence to the mechanisms underlying NVP-induced toxic events. This model, integrated with the analytical strategies described herein, is of anticipated usefulness to the pharmaceutical industry, as an upstream methodology for flagging drug safety alerts in early stages of drug development.

  18. Metal-rich, Metal-poor: Updated Stellar Population Models for Old Stellar Systems

    Science.gov (United States)

    Conroy, Charlie; Villaume, Alexa; van Dokkum, Pieter G.; Lind, Karin

    2018-02-01

    We present updated stellar population models appropriate for old ages (>1 Gyr) and covering a wide range in metallicities (‑1.5 ≲ [Fe/H] ≲ 0.3). These models predict the full spectral variation associated with individual element abundance variation as a function of metallicity and age. The models span the optical–NIR wavelength range (0.37–2.4 μm), include a range of initial mass functions, and contain the flexibility to vary 18 individual elements including C, N, O, Mg, Si, Ca, Ti, and Fe. To test the fidelity of the models, we fit them to integrated light optical spectra of 41 Galactic globular clusters (GCs). The value of testing models against GCs is that their ages, metallicities, and detailed abundance patterns have been derived from the Hertzsprung–Russell diagram in combination with high-resolution spectroscopy of individual stars. We determine stellar population parameters from fits to all wavelengths simultaneously (“full spectrum fitting”), and demonstrate explicitly with mock tests that this approach produces smaller uncertainties at fixed signal-to-noise ratio than fitting a standard set of 14 line indices. Comparison of our integrated-light results to literature values reveals good agreement in metallicity, [Fe/H]. When restricting to GCs without prominent blue horizontal branch populations, we also find good agreement with literature values for ages, [Mg/Fe], [Si/Fe], and [Ti/Fe].

  19. Development of a conception of the stellarator based on torsatron and modular systems

    International Nuclear Information System (INIS)

    Georgiyevskiy, A.V.; Rudakov, V.A.; Tolok, V.T.

    2003-01-01

    The paper presents the historical review of the stellarator conception development on the example of thermonuclear research at the Kharkov Institute of Physics and Technology. The given material covers a period from the time of the large-scale stellarator 'Ukraine' offered by I.V.Kurchatov up to the present. The main attention put to torsatron and modular systems

  20. Stellar winds in binary X-ray systems

    Science.gov (United States)

    Macgregor, K. B.; Vitello, P. A. J.

    1982-01-01

    It is thought that accretion from a strong stellar wind by a compact object may be responsible for the X-ray emission from binary systems containing a massive early-type primary. To investigate the effect of X-ray heating and ionization on the mass transfer process in systems of this type, an idealized model is constructed for the flow of a radiation-driven wind in the presence of an X-ray source of specified luminosity, L sub x. It is noted that for low values of L sub x, X-ray photoionization gives rise to additional ions having spectral lines with wavelengths situated near the peak of the primary continuum flux distribution. As a consequence, the radiation force acting on the gas increases in relation to its value in the absence of X-rays, and the wind is accelerated to higher velocities. As L sub x is increased, the degree of ionization of the wind increases, and the magnitude of the radiation force is diminished in comparison with the case in which L sub x = 0. This reduction leads at first to a decrease in the wind velocity and ultimately (for L sub x sufficiently large) to the termination of radiatively driven mass loss.

  1. Evolution of highly compact binary stellar systems in globular clusters

    International Nuclear Information System (INIS)

    Krolik, J.H.; Meiksin, A.; Joss, P.C.

    1984-01-01

    We have calculated the secular evolution of a highly compact binary stellar system, composed of a collapsed object and a low-mass secondary star, in the core of a globular cluster. The binary evolves under the combined influences of (i) gravitational radiation losses from the system, (ii) the evolution of the secondary star, (iii) the resultant gradual mass transfer, if any, from the secondary to the collapsed object, and (iv) occasional encounters with passing field stars. We calculate all these effects in detail, utilizing some simplifying approximations appropriate to low-mass secondaries. The times of encounters with field stars, and the initial parameter specifying those encounters, were chosen by use of a Monte Carlo technique; the subsequent gravitational interactions were calculated utilzing a three-body integrator, and the changes in the binary orbital parmeters were thereby determined. We carried out a total of 20 such evolutionary calculations for each of two cluster core densities (1 and 3 x 10 3 stars pc -3 ). Each calculation was continued until the binary was disrupted or until 2 x 10 10 yr had elapsed

  2. A millisecond pulsar in a stellar triple system.

    Science.gov (United States)

    Ransom, S M; Stairs, I H; Archibald, A M; Hessels, J W T; Kaplan, D L; van Kerkwijk, M H; Boyles, J; Deller, A T; Chatterjee, S; Schechtman-Rook, A; Berndsen, A; Lynch, R S; Lorimer, D R; Karako-Argaman, C; Kaspi, V M; Kondratiev, V I; McLaughlin, M A; van Leeuwen, J; Rosen, R; Roberts, M S E; Stovall, K

    2014-01-23

    Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar M[Symbol: see text](1.4378(13), where M[Symbol: see text]is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)M[Symbol: see text] and 0.4101(3))M[Symbol: see text], as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.

  3. Photometric analyses of abundances in dwarf spheroidal galaxies and globular clusters

    International Nuclear Information System (INIS)

    Light, R.M.

    1988-01-01

    This study investigated the abundance characteristics of several dwarf spheroidal galaxies. The chemical properties of stars in these galaxies are tracers of the origin and evolution of their stellar populations, and thus can provide constraints on the theories of their formation. To derive this abundance information, photometric observations of stars in a sample of globular clusters, covering a large range in metallicity, were analyzed. Parameters describing the position of the red giant branch were found to correlate very well with cluster metallicity over a large range in abundance. These measurements, made in the Thuan-Gunn photometry system, provide ranking schemes which are, with accurate photometry, more sensitive to changes in metallicity than similar broadband BV parameters. The relations were used to derive an improved estimate of the metallicity of cluster NGC 5053. These metallicity relations were used to analyze the Thuan-Gunn system photometry produced for the Sculptor, Ursa Minor, and Carina galaxies. The excellent agreement between their metallicities and those from other previous studies indicates that globular cluster red giant branch parameters are very useful in ranking dwarf spheroidal populations by metallicity. Together with other galaxian data, strong correlations can be seen between the mean metallicities and dispersions in metallicity and the luminosities of the dwarf spheroidal galaxies. These trends also seem to apply to members of the dwarf elliptical class of galaxies. The ramifications that these correlations and the existence of a metallicity gradient in Sculptor have on the formation of the dwarf spheroidals are discussed

  4. Dynamical effects of successive mergers on the evolution of spherical stellar systems

    International Nuclear Information System (INIS)

    Lee, H.M.

    1987-01-01

    Numerical investigations are carried out to study the dynamical effects of high-mass stars formed out of successive mergers among tidally captured binaries on the evolution of spherical stellar systems. It is assumed that all tidally captured systems become mergers in order to maximize these effects. Stellar systems with N greater than about 10 to the 7th are susceptible to merger instability which may lead to the formation of a central black hole. It is shown that globular clusters are likely to achieve postcollapse expansion due to three-body binary heating and stellar evolution, while galactic nuclei can easily be overcome by the merger instability in the core. 25 references

  5. Solution of diffusion equation in deformable spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Ayyoubzadeh, Seyed Mohsen [Department of Energy Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Safari, Mohammad Javad, E-mail: iFluka@gmail.com [Department of Energy Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Vosoughi, Naser [Department of Energy Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2011-05-15

    Research highlights: > Developing an explicit solution for the diffusion equation in spheroidal geometry. > Proving an orthogonality relation for spheroidal eigenfunctions. > Developing a relation for the extrapolation distance in spheroidal geometry. > Considering the sphere and slab as limiting cases for a spheroid. > Cross-validation of the analytical solution with Monte Carlo simulations. - Abstract: The time-dependent diffusion of neutrons in a spheroid as a function of the focal distance has been studied. The solution is based on an orthogonal basis and an extrapolation distanced related boundary condition for the spheroidal geometry. It has been shown that spheres and disks are two limiting cases for the spheroids, for which there is a smooth transition for the systems properties between these two limits. Furthermore, it is demonstrated that a slight deformation from a sphere does not affect the fundamental mode properties, to the first order. The calculations for both multiplying and non-multiplying media have been undertaken, showing good agreement with direct Monte Carlo simulations.

  6. Some kinematics and dynamics from a superposition of two axisymmetric stellar systems

    International Nuclear Information System (INIS)

    Cubarsi i Morera, R.

    1990-01-01

    Some kinematic and dynamic implications of a superposition of two stellar systems are studied. In the general case of a stellar system in nonsteady states, Chandrasekhar's axially symmetrical model has been adopted for each one of the subsystems. The solution obtained for the potential function provides some kinematical constraints between the subsystems. These relationships are derived using the partial centered moments of the velocity distribution and the subcentroid velocities in order to study the velocity distribution. These relationships are used to prove that, only in a stellar system where the potential function is assumed to be stationary, the relative movement of the local subcentroids (not only in rotation), the vertex deviation phenomenon, and the whole set of the second-order-centered moments may be explained. A qualitative verification with three stellar samples in the solar neighborhood is carried out. 41 refs

  7. Palomar 13: An Unusual Stellar System in the Galactic Halo

    Science.gov (United States)

    Côté, Patrick; Djorgovski, S. G.; Meylan, G.; Castro, Sandra; McCarthy, J. K.

    2002-08-01

    process of dissolving into the Galactic halo or a faint, dark matter-dominated stellar system. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  8. Youngest Brown Dwarf Yet in a Multiple Stellar System

    Science.gov (United States)

    2000-07-01

    ... and the Sharpest Optical Image (0.18 arcsec) from the VLT so far...! Astronomers are eager to better understand the formation of stars and planets - with an eye on the complex processes that lead to the emergence of our own solar system some 4600 million years ago. Brown Dwarfs (BDs) play a special role in this context. Within the cosmic zoo, they represent a class of "intermediate" objects. While they are smaller than normal stars, they shine by their own energy for a limited time, in contrast to planets. Recent observations with the ESO Very Large Telescope (VLT) of a "young" Brown Dwarf in a multiple stellar system are taking on a particular importance in this connection. An evaluation of the new data by an international team of astronomers [1] shows that it is by far the youngest of only four such objects found in a stellar system so far. The results are now providing new insights into the stellar formation process. This small object is known as TWA-5 B and with a mass of only 15 - 40 times that of Jupiter, it is near the borderline between planets and Brown Dwarfs, cf. the explanatory Appendix to this Press Release. However, visible and infrared VLT spectra unambiguously classify it in the latter category. Accurate positional measurements with the Hubble Space Telescope (HST) and the VLT hint that it is orbiting the central, much heavier and brighter star in this system, TWA-5 A (itself a close double star of which each component presumably has a mass of 0.75 solar masses), with a period that may be as long as 900 years. And, by the way, an (I-band) image of the TWA-5 system is the sharpest delivered by the VLT so far, with an image size of only 0.18 arcsec [2]! Brown Dwarfs: a cool subject In current astronomical terminology, Brown Dwarfs (BDs) are objects whose masses are below those of normal stars - the borderline is believed to be about 8% of the mass of our Sun - but larger than those of planets, cf. [3]. Unlike normal stars, Brown Dwarfs are unable

  9. Sulphur, zinc and carbon in the Sculptor dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Skúladóttir, Ása

    2016-01-01

    The Sculptor dwarf spheroidal galaxy is a Milky Way satellite with predominantly old stellar population, and therefore the ideal target to study early chemical evolution. The chemical abundances of photospheres of stars reveal the composition of their birth environment; studying stars of different

  10. James Webb Space Telescope Observations of Stellar Occultations by Solar System Bodies and Rings

    Science.gov (United States)

    Santos-Sanz, P.; French, R. G.; Pinilla-Alonso, N.; Stansberry, J.; Lin, Z-Y.; Zhang, Z-W.; Vilenius, E.; Mueller, Th.; Ortiz, J. L.; Braga-Ribas, F.; hide

    2016-01-01

    In this paper, we investigate the opportunities provided by the James Webb Space Telescope (JWST) for significant scientific advances in the study of Solar System bodies and rings using stellar occultations. The strengths and weaknesses of the stellar occultation technique are evaluated in light of JWST's unique capabilities. We identify several possible JWST occultation events by minor bodies and rings and evaluate their potential scientific value. These predictions depend critically on accurate a priori knowledge of the orbit of JWST near the Sun–Earth Lagrange point 2 (L2). We also explore the possibility of serendipitous stellar occultations by very small minor bodies as a byproduct of other JWST observing programs. Finally, to optimize the potential scientific return of stellar occultation observations, we identify several characteristics of JWST's orbit and instrumentation that should be taken into account during JWST's development.

  11. Magnetically levitated mesenchymal stem cell spheroids cultured with a collagen gel maintain phenotype and quiescence

    Directory of Open Access Journals (Sweden)

    Natasha S Lewis

    2017-04-01

    Full Text Available Multicellular spheroids are an established system for three-dimensional cell culture. Spheroids are typically generated using hanging drop or non-adherent culture; however, an emerging technique is to use magnetic levitation. Herein, mesenchymal stem cell spheroids were generated using magnetic nanoparticles and subsequently cultured within a type I collagen gel, with a view towards developing a bone marrow niche environment. Cells were loaded with magnetic nanoparticles, and suspended beneath an external magnet, inducing self-assembly of multicellular spheroids. Cells in spheroids were viable and compared to corresponding monolayer controls, maintained stem cell phenotype and were quiescent. Interestingly, core spheroid necrosis was not observed, even with increasing spheroid size, in contrast to other commonly used spheroid systems. This mesenchymal stem cell spheroid culture presents a potential platform for modelling in vitro bone marrow stem cell niches, elucidating interactions between cells, as well as a useful model for drug delivery studies.

  12. Effects of luteinizing hormone and human chorionic gonadotropin on corpus luteum cells in a spheroid cell culture system.

    Science.gov (United States)

    Walz, A; Keck, C; Weber, H; Kissel, C; Pietrowski, D

    2005-09-01

    The human corpus luteum (CL) is a highly vascularized, temporarily active endocrine gland and consists mainly of granulosa cells (GCs), theca cells (TCs), and endothelial cells (ECs). Its cyclic growth and development takes place under the influence of gonadotropic hormones. If pregnancy does occur, human chorionic gonadotropin (hCG) takes over the function of luteinizing hormone (LH) and, in contrast to LH, extends the functional life span of the CL. In this study, we investigated the effects of hCG and LH in a spheroidal cell culture model of CL development. Our data indicate that GCs secrete factors under the control of hCG that increase sprout formation of EC-spheroids. We demonstrate that the most prominent of these factors is VEGF-A. Furthermore, we found that both LH and hCG decrease sprout formation of GC-spheroids. After forming EC-GC coculture spheroids and consequently bringing GCs and ECs in close contact, sprouting increased under the influence of hCG, however not under LH. These experiments provide evidence for an hCG dependent functional switch in the GCs after coming in contact with ECs. Moreover, it demonstrates the considerably different effects of hCG and LH on GCs although their signaling is transmitted via the same receptor.

  13. A tunable integrated system to simulate colder stellar radiation

    Science.gov (United States)

    Erculiani, Marco S.; Claudi, Riccardo; Barbisan, Diego; Giro, Enrico; Bonato, Matteo; Cocola, Lorenzo; Farisato, Giancarlo; Meneghini, Metteo; Poletto, Luca; Salasnich, Bernardo; Trivellin, Nicola

    2015-09-01

    In the last years, a lot of extrasolar planets have been discovered in any direction of the Galaxy. More interesting, some of them have been found in the habitable zone of their host stars. A large diversity of spectral type, from early types (A) to colder ones (M), is covered by the planetary system host stars. A lot of efforts are done in order to find habitable planets around M stars and indeed some habitable super earths were found. In this framework, "Atmosphere in a Test Tube", a project started at Astronomical observatory of Padua, simulates planetary environmental condition in order to understand how and how much the behavior of photosynthetic bacteria in different planetary/star scenarios can modify the planet atmosphere. The particular case of an habitable planet orbiting a M dwarf star is under study for the time being. The irradiation of an M star, due to its lower surface temperature is very different in quality and quantity by the irradiation of a star like our Sun. We would like to describe the study of feasibility of a new kind of tunable led stellarlight simulator capable to recreate the radiation spectrum of M type stars (but with the potential to be expanded even to F, G, K star spectra types) incident on the planet. The radiation source is a multiple LED matrix cooled by means of air fan technology. In order to endow it with modularity this device will be composed by a mosaic of circuit boards arranged in a pie-chart shape, on the surface of which will be welded the LEDs. This concept is a smart way in order to replace blown out pieces instead of changing the entire platform as well as implement the device with new modules suitable to reproduce other type of stars. The device can be driven by a PC to raise or lower the intensity of both each LED and the lamp, in order to simulate as close as possible a portion of the star spectrum. The wavelength intervals overlap the limits of photosynthetic pigment absorption range (280-850 nm), while the

  14. Morphological and Immunohistochemical Characterization of Canine Osteosarcoma Spheroid Cell Cultures.

    Science.gov (United States)

    Gebhard, C; Gabriel, C; Walter, I

    2016-06-01

    Spheroid cell culture emerges as powerful in vitro tool for experimental tumour research. In this study, we established a scaffold-free three-dimensional spheroid system built from canine osteosarcoma (OS) cells (D17). Spheroids (7, 14 and 19 days of cultivation) and monolayer cultures (2 and 7 days of cultivation) were evaluated and compared on light and electron microscopy. Monolayer and spheroid cultures were tested for vimentin, cytokeratin, alkaline phosphatase, osteocalcin and collagen I by means of immunohistochemistry. The spheroid cell culture exhibited a distinct network of collagen I in particular after 19-day cultivation, whereas in monolayer cultures, collagen I was arranged as a lamellar basal structure. Necrotic centres of large spheroids, as observed in 14- and 19-day cultures, were characterized by significant amounts of osteocalcin. Proliferative activity as determined by Ki-67 immunoreactivity showed an even distribution in two-dimensional cultures. In spheroids, proliferation was predominating in the peripheral areas. Metastasis-associated markers ezrin and S100A4 were shown to be continuously expressed in monolayer and spheroid cultures. We conclude that the scaffold-free spheroid system from canine OS cells has the ability to mimic the architecture of the in vivo tumour, in particular cell-cell and cell-matrix interactions. © 2015 The Authors. Anatomia, Histologia, Embryologia Published by Blackwell Verlag GmbH.

  15. Further evidence for the absence of a hypoxic fraction in the 9L rat tumour multicellular spheroid system

    International Nuclear Information System (INIS)

    Gutin, P.H.; Barcellos, M.H.; Shrieve, D.C.; Sano, Y.; Bernstein, M.; Deen, D.F.

    1982-01-01

    The 9L gliosarcoma is an N-methylnitrosourea-induced rat brain tumour that has served as a predictive model for the efficacy of various chemotherapeutic agents against human brain tumours. Because it is one of two known animal tumour models that has no hypoxic fraction, the 9L model is of questionable value for the study of the radiobiology of hypoxic cell sensitizers. Hypoxic 9L monolayer cells are sensitive to misonidazole, as shown by the abrupt decrease in survival after a 2-4 h radiation exposure. However, when 9L spheroids in the size ranges of 200-300, 300-400, 500-600 and 1027+-33μm were incubated in euoxic spinner culture for up to 96 h in 1.5 or 3.0 mM misonidazole, there was no effect on the survival of the dissociated cells over a dose range 0-20 Gy. It is concluded that, in view of the demonstrated sensitivity to misonidazole of hypoxic 9L cells in monolayer culture, this finding provides further evidence that there are no hypoxic cells even in large 9L spheroids with a histologically distinct zone of central necrosis. Moreover, 9L spheroids irradiated in the presence of 3.0 mM misonidazole showed no dose enhancement. (U.K.)

  16. EVOLUTION OF THE BINARY FRACTION IN DENSE STELLAR SYSTEMS

    International Nuclear Information System (INIS)

    Fregeau, John M.; Ivanova, Natalia; Rasio, Frederic A.

    2009-01-01

    Using our recently improved Monte Carlo evolution code, we study the evolution of the binary fraction in globular clusters. In agreement with previous N-body simulations, we find generally that the hard binary fraction in the core tends to increase with time over a range of initial cluster central densities for initial binary fractions ∼<90%. The dominant processes driving the evolution of the core binary fraction are mass segregation of binaries into the cluster core and preferential destruction of binaries there. On a global scale, these effects and the preferential tidal stripping of single stars tend to roughly balance, leading to overall cluster binary fractions that are roughly constant with time. Our findings suggest that the current hard binary fraction near the half-mass radius is a good indicator of the hard primordial binary fraction. However, the relationship between the true binary fraction and the fraction of main-sequence stars in binaries (which is typically what observers measure) is nonlinear and rather complicated. We also consider the importance of soft binaries, which not only modify the evolution of the binary fraction, but can also drastically change the evolution of the cluster as a whole. Finally, we briefly describe the recent addition of single and binary stellar evolution to our cluster evolution code.

  17. The Structure and Dark Halo Core Properties of Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Burkert, A.

    2015-08-01

    The structure and dark matter halo core properties of dwarf spheroidal galaxies (dSphs) are investigated. A double-isothermal (DIS) model of an isothermal, non-self-gravitating stellar system embedded in an isothermal dark halo core provides an excellent fit to the various observed stellar surface density distributions. The stellar core scale length a* is sensitive to the central dark matter density ρ0,d. The maximum stellar radius traces the dark halo core radius {r}c,d. The concentration c* of the stellar system, determined by a King profile fit, depends on the ratio of the stellar-to-dark-matter velocity dispersion {σ }*/{σ }d. Simple empirical relationships are derived that allow us to calculate the dark halo core parameters ρ0,d, {r}c,d, and σd given the observable stellar quantities σ*, a*, and c*. The DIS model is applied to the Milky Way’s dSphs. All dSphs closely follow the same universal dark halo scaling relations {ρ }0,d× {r}c,d={75}-45+85 M⊙ pc-2 that characterize the cores of more massive galaxies over a large range in masses. The dark halo core mass is a strong function of core radius, {M}c,d˜ {r}c,d2. Inside a fixed radius of ˜400 pc the total dark matter mass is, however, roughly constant with {M}d=2.6+/- 1.4× {10}7 M⊙, although outliers are expected. The dark halo core densities of the Galaxy’s dSphs are very high, with {ρ }0,d ≈ 0.2 M⊙ pc-3. dSphs should therefore be tidally undisturbed. Evidence for tidal effects might then provide a serious challenge for the CDM scenario.

  18. Exploring small bodies in the outer solar system with stellar occultations

    Science.gov (United States)

    Elliot, Jim L.; Dunham, Edward W.; Olkin, C. B.

    1995-01-01

    Stellar occultation observations probe the atmospheric structure and extinction of outer solar system bodies with a spatial resolution of a few kilometers, and an airborne platform allows the observation of occultations by small bodies that are not visible from fixed telescopes. Results from occultations by Triton, Pluto, and Chiron observed with KAO are discussed, and future directions for this program are presented.

  19. Repair during multifraction exposures: spheroids versus monolayers

    International Nuclear Information System (INIS)

    Durand, R.E.

    1984-01-01

    Many type of mammalian cells, when grown in culture as multicell spheroids, display an increased ability to accumulate and repair sublethal radiation damage which has been called the ''contact effect''. Since this effect has the potential to markedly modify the multifraction radiation response of cells in V79 spheroids relative to cells in monolayer cultures, an investigation was made of regimens ranging from 1 to 100 fractions. Effective dose rates were chosen near 1 Gy h -1 to inhibit cell progression and thus simplify analysis of the results. As expected, larger doses per fraction produced more net cell killing in both systems than lower doses per fraction. Additionally, less killing of spheroid cells was observed in all regimens, in accord with their greater potential for repair. However, when the data were expressed as isoeffect curves, the spheroid and monolayer curves converged as the number of fractions increased. Thus, quite similar inherent sensitivity and repair capabilities would be predicted for ultra-low doses per fraction. High precision techniques for defining survival after doses of radiation from 0.2 to 1 Gy were, however, still able to demonstrate a survival advantage for cells grown as spheroids. (author)

  20. Advancement of In-Flight Alumina Powder Spheroidization Process with Water Droplet Injection Using a Small Power DC-RF Hybrid Plasma Flow System

    Science.gov (United States)

    Jang, Juyong; Takana, Hidemasa; Park, Sangkyu; Nishiyama, Hideya

    2012-09-01

    The correlation between plasma thermofluid characteristics and alumina powder spheroidization processes with water droplet injection using a small power DC-RF hybrid plasma flow system was experimentally clarified. Micro-sized water droplets with a low water flow rate were injected into the tail of thermal plasma flow so as not to disturb the plasma flow directly. Injected water droplets were vaporized in the thermal plasma flow and were transported upstream in the plasma flow to the torch by the backflow. After dissociation of water, the production of hydrogen was detected by the optical emission spectroscopy in the downstream RF plasma flow. The emission area of the DC plasma jet expanded and elongated in the vicinity of the RF coils. Additionally, the emission area of RF plasma flow enlarged and was visible as red emission in the downstream RF plasma flow in the vicinity below the RF coils due to hydrogen production. Therefore, the plasma flow mixed with produced hydrogen increased the plasma enthalpy and the highest spheroidization rate of 97% was obtained at a water flow rate of 15 Sm l/min and an atomizing gas flow rate of 8 S l/min using a small power DC-RF hybrid plasma flow system.

  1. Distinct responses of human granulosa lutein cells after hCG or LH stimulation in a spheroidal cell culture system.

    Science.gov (United States)

    Becker, Julia; Walz, Andrea; Daube, Stefanie; Keck, Christoph; Pietrowski, Detlef

    2007-10-01

    The growth and development of the corpus luteum (CL) is regulated by gonadotropic hormones. It is formed by granulosa cells (GCs), theca cells, and endothelial cells, and is the primary source of circulating progesterone. During early pregnancy only human chorionic gonadotropin (hCG) but not luteinizing hormone (LH) extends the life span of the CL, although hCG and LH interact with the same receptor and have similar actions on the CL. In this study a recently by our group established spheroidal GC culture assay served as a model of CL development on which we compared the actions of the gonadotropic hormones LH and hCG. To find out which signal pathways take part in the hormonal regulation of GC we stimulated GC-spheroids with modulators of protein kinases A and C dependent signaling cascades and determined their impact on sprout forming activity in GC. Our results indicate that PKA-dependent signaling pathways play a major role in mediating the hormonal-induced signaling cascades leading to sprouting in GC. Furthermore, this study strongly indicates that the different effects of hCG and LH in the maintenance of the CL may be reasoned in different signal transduction pathways triggered by hCG or LH. (c) 2007 Wiley-Liss, Inc.

  2. Sulphur, zinc and carbon in the Sculptor dwarf spheroidal galaxy

    OpenAIRE

    Skúladóttir, Ása

    2016-01-01

    The Sculptor dwarf spheroidal galaxy is a Milky Way satellite with predominantly old stellar population, and therefore the ideal target to study early chemical evolution. The chemical abundances of photospheres of stars reveal the composition of their birth environment; studying stars of different ages, therefore, provides insight into the chemical enrichment history of the galaxy in which they dwell. High-resolution spectra of 100 stars were used to further explore the chemical enrichment hi...

  3. Chemical Enrichment of the Solar System by Stellar Ejecta

    Science.gov (United States)

    Kwok, Sun

    2015-03-01

    Spectroscopic observations of evolved stars have shown signatures of aromatic and aliphatic compounds. This suggests that complex organics with chemical structures similar to those of insoluble organic matter (IOM) found in carbonaceous meteorites are made in stars. This raises the possibility that in addition to known pre-solar grains such as silicon carbide, organic star dust may also have traveled across the Galaxy to the Solar System.

  4. On the dynamics of non-stationary binary stellar system with non-isotropic mass flow

    International Nuclear Information System (INIS)

    Bekov, A.A.; Bejsekov, A.N.; Aldibaeva, L.T.

    2006-01-01

    The motion of test body in the external gravitational field of the binary stellar systems with slowly variable some physical parameters of radiating components is considered on the base of restricted nonstationary photo-gravitational three and two bodies problem with non-isotropic mass flow. The family of polar and coplanar solutions are obtained. The solutions give the possibility of the dynamical and structure interpretation of binary young evolving stars and galaxies. (author)

  5. Stellar systems fed by outside stars: the evolution of model galactic nuclei

    International Nuclear Information System (INIS)

    Dokuchaev, V.I.; Ozernoi, L.M.

    1985-01-01

    Through relaxation mechanisms, a dense central core surrounded by an extended, rarefied stellar system in a nonisothermal galactic nuclear region can be kept supplied with energy and mass conveyed by incoming stars. These factors may significantly influence the secular evolution of the core, competing with the conventional star-evaporation process. Under certain circumstances the outside environment will in fact dominate the core evolution, causing not collapse but expansion

  6. Stellar chemical signatures and hierarchical galaxy formation

    NARCIS (Netherlands)

    Venn, KA; Irwin, M; Shetrone, MD; Tout, CA; Hill, [No Value; Tolstoy, E

    To compare the chemistries of stars in the Milky Way dwarf spheroidal (dSph) satellite galaxies with stars in the Galaxy, we have compiled a large sample of Galactic stellar abundances from the literature. When kinematic information is available, we have assigned the stars to standard Galactic

  7. Unique Stellar System Gives Einstein a Thumbs-Up

    Science.gov (United States)

    2008-07-01

    Taking advantage of a unique cosmic coincidence, astronomers have measured an effect predicted by Albert Einstein's theory of General Relativity in the extremely strong gravity of a pair of superdense neutron stars. The new data indicate that the famed physicist's 93-year-old theory has passed yet another test. Double Pulsar Graphic Artist's Conception of Double Pulsar System PSR J0737-3039A/B CREDIT: Daniel Cantin, DarwinDimensions, McGill University Click on image for more graphics. The scientists used the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to make a four-year study of a double-star system unlike any other known in the Universe. The system is a pair of neutron stars, both of which are seen as pulsars that emit lighthouse-like beams of radio waves. "Of about 1700 known pulsars, this is the only case where two pulsars are in orbit around each other," said Rene Breton, a graduate student at McGill University in Montreal, Canada. In addition, the stars' orbital plane is aligned nearly perfectly with their line of sight to the Earth, so that one passes behind a doughnut-shaped region of ionized gas surrounding the other, eclipsing the signal from the pulsar in back. "Those eclipses are the key to making a measurement that could never be done before," Breton said. Einstein's 1915 theory predicted that, in a close system of two very massive objects, such as neutron stars, one object's gravitational tug, along with an effect of its spinning around its axis, should cause the spin axis of the other to wobble, or precess. Studies of other pulsars in binary systems had indicated that such wobbling occurred, but could not produce precise measurements of the amount of wobbling. "Measuring the amount of wobbling is what tests the details of Einstein's theory and gives a benchmark that any alternative gravitational theories must meet," said Scott Ransom of the National Radio Astronomy Observatory. The eclipses allowed the astronomers to pin

  8. Planet-induced Stellar Pulsations in HAT-P-2's Eccentric System

    International Nuclear Information System (INIS)

    Wit, Julien de; Lewis, Nikole K.; Knutson, Heather A.; Batygin, Konstantin; Fuller, Jim; Antoci, Victoria; Fulton, Benjamin J.; Laughlin, Gregory; Deming, Drake; Shporer, Avi; Cowan, Nicolas B.; Agol, Eric; Burrows, Adam S.; Fortney, Jonathan J.; Langton, Jonathan; Showman, Adam P.

    2017-01-01

    Extrasolar planets on eccentric short-period orbits provide a laboratory in which to study radiative and tidal interactions between a planet and its host star under extreme forcing conditions. Studying such systems probes how the planet’s atmosphere redistributes the time-varying heat flux from its host and how the host star responds to transient tidal distortion. Here, we report the insights into the planet–star interactions in HAT-P-2's eccentric planetary system gained from the analysis of ∼350 hr of 4.5 μ m observations with the Spitzer Space Telescope . The observations show no sign of orbit-to-orbit variability nor of orbital evolution of the eccentric planetary companion, HAT-P-2 b. The extensive coverage allows us to better differentiate instrumental systematics from the transient heating of HAT-P-2 b’s 4.5 μ m photosphere and yields the detection of stellar pulsations with an amplitude of approximately 40 ppm. These pulsation modes correspond to exact harmonics of the planet’s orbital frequency, indicative of a tidal origin. Transient tidal effects can excite pulsation modes in the envelope of a star, but, to date, such pulsations had only been detected in highly eccentric stellar binaries. Current stellar models are unable to reproduce HAT-P-2's pulsations, suggesting that our understanding of the interactions at play in this system is incomplete.

  9. Planet-induced Stellar Pulsations in HAT-P-2's Eccentric System

    Energy Technology Data Exchange (ETDEWEB)

    Wit, Julien de [Department of Earth, Atmospheric and Planetary Sciences, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Lewis, Nikole K. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Knutson, Heather A.; Batygin, Konstantin [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Fuller, Jim [TAPIR, Walter Burke Institute for Theoretical Physics, Mailcode 350-17, California Institute of Technology, Pasadena, CA 91125 (United States); Antoci, Victoria [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Fulton, Benjamin J. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Laughlin, Gregory [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Deming, Drake [Department of Astronomy, University of Maryland at College Park, College Park, MD 20742 (United States); Shporer, Avi [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91009 (United States); Cowan, Nicolas B. [Department of Physics, Department of Earth and Planetary Sciences, McGill University, 3550 rue University, Montreal, QC H3A 2A7 (Canada); Agol, Eric [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Burrows, Adam S. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Langton, Jonathan [Department of Physics, Principia College, Elsah, IL 62028 (United States); Showman, Adam P. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2017-02-20

    Extrasolar planets on eccentric short-period orbits provide a laboratory in which to study radiative and tidal interactions between a planet and its host star under extreme forcing conditions. Studying such systems probes how the planet’s atmosphere redistributes the time-varying heat flux from its host and how the host star responds to transient tidal distortion. Here, we report the insights into the planet–star interactions in HAT-P-2's eccentric planetary system gained from the analysis of ∼350 hr of 4.5 μ m observations with the Spitzer Space Telescope . The observations show no sign of orbit-to-orbit variability nor of orbital evolution of the eccentric planetary companion, HAT-P-2 b. The extensive coverage allows us to better differentiate instrumental systematics from the transient heating of HAT-P-2 b’s 4.5 μ m photosphere and yields the detection of stellar pulsations with an amplitude of approximately 40 ppm. These pulsation modes correspond to exact harmonics of the planet’s orbital frequency, indicative of a tidal origin. Transient tidal effects can excite pulsation modes in the envelope of a star, but, to date, such pulsations had only been detected in highly eccentric stellar binaries. Current stellar models are unable to reproduce HAT-P-2's pulsations, suggesting that our understanding of the interactions at play in this system is incomplete.

  10. The MEDIDO Survey: Dark Matter in Low Dispersion Stellar Systems

    Science.gov (United States)

    Noyola, Eva; Bustamante, Maria Jose

    2017-06-01

    We will present preliminary results of the Medido Survey. The Survey focuses on dwarf galaxies of various types, as well as Milky Way globular clusters. We have been gathering data at the McDonald Observatory using the VIRUS-W spectrograph, which is capable of resolving velocity dispersions slightly above 10 km/s. For the galaxies, our focus is to improve kinematics in the central regions in order to tackle the cusp/core discrepancy between observations and models. In the case of the globular clusters, we map kinematics out to about 2 half-light radii with the goal of testing if any dark matter content can be detected or if dark matter can be confidently ruled out for these systems.

  11. Studies on a Stellarator reactor of the Helias type: The modular coil system

    International Nuclear Information System (INIS)

    Harmeyer, E.; Kisslinger, J.; Rau, F.; Wobig, H.

    1993-02-01

    Helias Stellarator Reactors (HSR) are considered, focussing on the superconducting modular coil system which generates the magnetic field, aiming to clarify critical issues of such systems. The development of the coil system is presented and the properties of the vacuum magnetic field are discussed. Electromagnetic forces and the resulting mechanical stresses and strains inside the coils and the surrounding structure are calculated. Parameter studies are made varying the major radius R 0 between 18 m and 24 m in order to investigate the engineering parameters for the superconducting coil system. The total mass and the fusion power output of HSR are compared with values evaluated for tokamak reactors. (orig.). 36 figs

  12. Differentiation of human mesenchymal stem cell spheroids under microgravity conditions

    Directory of Open Access Journals (Sweden)

    Wolfgang H Cerwinka

    2012-01-01

    Full Text Available To develop and characterize a novel cell culture method for the generation of undifferentiated and differentiated human mesenchymal stem cell 3D structures, we utilized the RWV system with a gelatin-based scaffold. 3 × 106 cells generated homogeneous spheroids and maximum spheroid loading was accomplished after 3 days of culture. Spheroids cultured in undifferentiated spheroids of 3 and 10 days retained expression of CD44, without expression of differentiation markers. Spheroids cultured in adipogenic and osteogenic differentiation media exhibited oil red O staining and von Kossa staining, respectively. Further characterization of osteogenic lineage, showed that 10 day spheroids exhibited stronger calcification than any other experimental group corresponding with significant expression of vitamin D receptor, alkaline phosphatase, and ERp60 . In conclusion this study describes a novel RWV culture method that allowed efficacious engineering of undifferentiated human mesenchymal stem cell spheroids and rapid osteogenic differentiation. The use of gelatin scaffolds holds promise to design implantable stem cell tissue of various sizes and shapes for future regenerative treatment.

  13. Information-measurement and control system of the five-channel stellar spectrophotometer

    International Nuclear Information System (INIS)

    Granitskij, L.V.; Bukach, A.B.; Kaplin, Yu.V.; Bondarenko, V.P.; Smirnov, A.I.

    1979-01-01

    The multichannel information-measurement control system of the five-channel stellar spectrophotometer working in photon counting regime is described. The detecting part is synthesized taking into account the principles of multifunctional use of elements of the system. In the part of the photometer scanning mechanism control a discrete drive with the step motor is used. The data are detected on the punched tape, which is convenient for putting them into computer, into a digit printing device with the decimal code or on a diagram tape of the automatic potentiometer

  14. The Two-Component Virial Theorem and the Physical Properties of Stellar Systems.

    Science.gov (United States)

    Dantas; Ribeiro; Capelato; de Carvalho RR

    2000-01-01

    Motivated by present indirect evidence that galaxies are surrounded by dark matter halos, we investigate whether their physical properties can be described by a formulation of the virial theorem that explicitly takes into account the gravitational potential term representing the interaction of the dark halo with the baryonic or luminous component. Our analysis shows that the application of such a "two-component virial theorem" not only accounts for the scaling relations displayed by, in particular, elliptical galaxies, but also for the observed properties of all virialized stellar systems, ranging from globular clusters to galaxy clusters.

  15. Transfer, imaging, and analysis plate for facile handling of 384 hanging drop 3D tissue spheroids.

    Science.gov (United States)

    Cavnar, Stephen P; Salomonsson, Emma; Luker, Kathryn E; Luker, Gary D; Takayama, Shuichi

    2014-04-01

    Three-dimensional culture systems bridge the experimental gap between in vivo and in vitro physiology. However, nonstandardized formation and limited downstream adaptability of 3D cultures have hindered mainstream adoption of these systems for biological applications, especially for low- and moderate-throughput assays commonly used in biomedical research. Here we build on our recent development of a 384-well hanging drop plate for spheroid culture to design a complementary spheroid transfer and imaging (TRIM) plate. The low-aspect ratio wells of the TRIM plate facilitated high-fidelity, user-independent, contact-based collection of hanging drop spheroids. Using the TRIM plate, we demonstrated several downstream analyses, including bulk tissue collection for flow cytometry, high-resolution low working-distance immersion imaging, and timely reagent delivery for enzymatic studies. Low working-distance multiphoton imaging revealed a cell type-dependent, macroscopic spheroid structure. Unlike ovarian cancer spheroids, which formed loose, disk-shaped spheroids, human mammary fibroblasts formed tight, spherical, and nutrient-limited spheroids. Beyond the applications we describe here, we expect the hanging drop spheroid plate and complementary TRIM plate to facilitate analyses of spheroids across the spectrum of throughput, particularly for bulk collection of spheroids and high-content imaging.

  16. ON THE r -PROCESS ENRICHMENT OF DWARF SPHEROIDAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Bramante, Joseph [Department of Physics, 225 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556 (United States); Linden, Tim [Center for Cosmology and AstroParticle Physics (CCAPP) and Department of Physics The Ohio State University, Columbus OH, 43210 (United States)

    2016-07-20

    Recent observations of Reticulum II have uncovered an overabundance of r -process elements compared to similar ultra-faint dwarf spheroidal galaxies (UFDs). Because the metallicity and star formation history of Reticulum II appear consistent with all known UFDs, the high r -process abundance of Reticulum II suggests enrichment through a single, rare event, such as a double neutron star (NS) merger. However, we note that this scenario is extremely unlikely, as binary stellar evolution models require significant supernova natal kicks to produce NS–NS or NS–black hole (BH) mergers, and these kicks would efficiently remove compact binary systems from the weak gravitational potentials of UFDs. We examine alternative mechanisms for the production of r -process elements in UFDs, including a novel mechanism wherein NSs in regions of high dark matter (DM) density implode after accumulating a BH-forming mass of DM. We find that r -process proto-material ejection by tidal forces, when a single NS implodes into a BH, can occur at a rate matching the r -process abundance of both Reticulum II and the Milky Way. Remarkably, DM models which collapse a single NS in observed UFDs also solve the missing pulsar problem in the Milky Way Galactic Center. We propose tests specific to DM r -process production which may uncover or rule out this model.

  17. Isotropic oscillator: spheroidal wave functions

    International Nuclear Information System (INIS)

    Mardoyan, L.G.; Pogosyan, G.S.; Ter-Antonyan, V.M.; Sisakyan, A.N.

    1985-01-01

    Solutions of the Schroedinger equation are found for an isotropic oscillator (10) in prolate and oblate spheroidal coordinates. It is shown that the obtained solutions turn into spherical and cylindrical bases of the isotropic oscillator at R→0 and R→ infinity (R is the dimensional parameter entering into the definition of prolate and oblate spheroidal coordinates). The explicit form is given for both prolate and oblate basis of the isotropic oscillator for the lowest quantum states

  18. The Andromeda Dwarf Spheroidal Galaxies

    OpenAIRE

    Armandroff, Taft E.; Da Costa, Gary S.

    1998-01-01

    Our current knowledge of M31's dwarf spheroidal companions is reviewed. Two topics of recent interest constitute the bulk of this review. First, color-magnitude diagrams reaching below the horizontal branch have been constructed for two M31 dwarf spheroidals based on images from HST/WFPC2. The horizontal branches are predominantly red in both galaxies, redder than expected for their metallicity based on Galactic globular clusters. Thus, the second parameter effect is seen in the M31 halo. Sec...

  19. Relations between pH, oxygen partial pressure and growth in cultured cell spheroids.

    Science.gov (United States)

    Carlsson, J; Acker, H

    1988-11-15

    The pH gradients, oxygen partial-pressure gradients and growth curves were measured for 7 different types of spheroids. Growth curves were measured in liquid overlay culture and thereafter the spheroids were attached to cover glasses and transferred to a chamber for micro-electrode measurements. The spheroids were randomly divided for pH or pO2 measurements which then were made under conditions as identical as possible. The decreases in pO2 and pH, delta pO2 and delta pH were calculated as the difference between the values in the culture medium and the values 200 micron inside the spheroids. Each type of spheroid had a certain relation between delta pO2 and delta pH. The human colon carcinoma HT29, the mouse mammary carcinoma EMT6 and the hamster lung V79-379A spheroids had high values of the quotient delta pO2/delta pH. The human thyroid carcinoma HTh7 spheroids and the 3 types of human glioma spheroids had lower quotients. There was a tendency for fast-growing spheroids to have high quotients. Two extreme types of spheroids, HT29 (high quotient) and U-118 MG (low quotient) were analyzed for lactate production and oxygen consumption. The U-118 MG spheroids produced about 3 times more lactate and consumed about 3 times less oxygen than the HT29 spheroids. The differences in lactate production could not be explained by differences in the pyruvate Km values of lactate dehydrogenase. The results indicate that there are significant metabolic differences between the spheroid systems studied.

  20. Implications of the dwarfs spheroidal galaxy mass-metallicity relation

    International Nuclear Information System (INIS)

    Smith, G.H.

    1985-01-01

    The properties of the mass-metallicity relation among dwarf spheroidal galaxies are discussed in terms of a model which assumes that the internal chemical evolution of the dwarf spheroidals was promoted by supernova activity. The model can be used to explain the observed dwarf spheroidal mass-metallicity relation assuming the present mass of these systems M sub s is proportional to their initial masses M as M sub s varies according to a power-law index of exp 7/4. It is inferred from the power-law dependence of M on the proto-cloud radius that the most massive dwarf spheroids were formed from the densest clouds. The observed slope of the mass-metallicity relation for dwarf spheroidal galaxies is found to be significantly different from theoretical estimates of this slope for elliptical galaxies. It is suggested that the difference may imply that spheroidal dwarfs and elliptical galaxies had different formation histories, confirming Kormendy's (1985) observations of differences in the brightness and luminosity trends. 54 references

  1. The Centaur Chariklo and its rings system from stellar occultations in 2017

    Science.gov (United States)

    Leiva, Rodrigo; Sicardy, Bruno; Camargo, Julio; Ortiz, Jose Luis; Berard, Diane; Desmars, Josselin; Chariklo Occultations Team; Rio Group; Lucky Star Occultation Team; Granada Occultation Team

    2017-10-01

    A stellar occultation in June 3, 2013 revealed the presence of a dense ring system around the Centaur object (10199) Chariklo (Braga-Ribas et al., Nature 2014). Subsequent analysis of occultation data and long-term photometric variations indicate that Chariklo's body is elongated (Leiva et al. 2017, submitted) and that the main ring exhibits significant longitudinal variations of the radial width (Bérard et al. 2017, in press). We report three multi-chord high-quality stellar occultation by Chariklo on April 9, 2017 and June 22, 2017 from Namibia, and July 23 2017 from South America. The analysis of this new data set is underway, but preliminary results are consistent with triaxial ellipsoidal models. From this analysis we will:-present refined models for the size and shape of Chariklo's main body andevaluate the heights and slopes of its topographic features.-give constraints on the longitudinal width variations of Chariklo's rings andexplore the possibility to obtain the rings apsidal precession rate.Chariklo's shape and topography have strong consequences on the dynamics of the rings through Lindblad-type resonances between mean motion of the ring particles and the spin of the main body, while the rings precession rate gives constraints on the dynamical oblateness of the main body.**Part of the research leading to these results has received funding from the European Research Council under the European Community’s H2020 (2014-2020/ ERC Grant Agreement n 669416 ”LUCKY STAR”).

  2. The stellar content of the isolated transition dwarf galaxy DDO210

    OpenAIRE

    McConnachie, Alan W.; Arimoto, Nobuo; Irwin, Mike; Tolstoy, Eline

    2006-01-01

    We use Subaru Suprime-Cam and VLT FORS1 photometry of the dwarf galaxy DDO210 to study the global stellar content and structural properties of a transition-type galaxy (with properties intermediate between dwarf irregular and dwarf spheroidal systems). This galaxy is sufficiently isolated that tidal interactions are not likely to have affected its evolution in any way. The colour-magnitude diagrams of DDO210 show a red giant branch (RGB) population (with an RGB bump), a bright asymptotic gian...

  3. A Catalog of Stellar Evolution Profiles and the Effects of Variable Composition on Habitable Systems

    OpenAIRE

    Truitt, Amanda; Young, Patrick A.; Spacek, Alexander; Probst, Luke; Dietrich, Jeremy

    2015-01-01

    We present stellar evolution models for 0.5 - 1.2 \\Msol at scaled metallicities of 0.1 - 1.5 Z\\sol and O/Fe values of 0.44 - 2.28 O/Fe\\sol. The time dependent evolution of habitable zone boundaries are calculated for each stellar evolution track based on stellar mass, effective temperature, and luminosity parameterizations. The rate of change of stellar surface quantities and the surrounding habitable zone position are strong functions of all three quantities explored. The range of orbits tha...

  4. STELLAR ACTIVITY AND EXCLUSION OF THE OUTER PLANET IN THE HD 99492 SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Kane, Stephen R.; Thirumalachari, Badrinath; Hinkel, Natalie R. [Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, CA 94132 (United States); Henry, Gregory W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box 9501, Nashville, TN 37209 (United States); Jensen, Eric L. N. [Dept of Physics and Astronomy, Swarthmore College, Swarthmore, PA 19081 (United States); Boyajian, Tabetha S.; Fischer, Debra A. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Howard, Andrew W. [Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 (United States); Isaacson, Howard T. [Astronomy Department, University of California, Berkeley, CA 94720 (United States); Wright, Jason T., E-mail: skane@sfsu.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)

    2016-03-20

    A historical problem for indirect exoplanet detection has been contending with the intrinsic variability of the host star. If the variability is periodic, it can easily mimic various exoplanet signatures, such as radial velocity (RV) variations that originate with the stellar surface rather than the presence of a planet. Here we present an update for the HD 99492 planetary system, using new RV and photometric measurements from the Transit Ephemeris Refinement and Monitoring Survey. Our extended time series and subsequent analyses of the Ca ii H and K emission lines show that the host star has an activity cycle of ∼13 years. The activity cycle correlates with the purported orbital period of the outer planet, the signature of which is thus likely due to the host star activity. We further include a revised Keplerian orbital solution for the remaining planet, along with a new transit ephemeris. Our transit-search observations were inconclusive.

  5. RF induction plasma spheroidization of tungsten powders

    International Nuclear Information System (INIS)

    Gu Zhogntao; Ye Gaoying; Liu Chuandong; Tong Honghui

    2009-01-01

    Irregularly-shaped tungsten powders (average granular sizes of 512 μm) have been spheroidized by radio frequency (RF)induction plasma. The effects of feed rate, mode of material dispersion, particle size on spheroidization efficiency are investigated. Experimental results show that the spheroidization efficiency decreases rapidly when the feed rate increases to more than 95 g/min. Only 30% spheroidization efficiency is gained at the feed rate of 135.75 g/min. The spheroidization efficiency is also affected by the flow rate of carrier gas. When the flow rate of carrier gas is 0.12 m 3 /h, the dispersion effect is the best, and the spheroidization efficiency is almost 100%. The apparent density of tungsten powders increases a bit with the increase of spheroidization efficiency. And the particle size uniformity of spheroidized tungsten powders is in accordance with that of original powders. (authors)

  6. Double-helix stellarator

    International Nuclear Information System (INIS)

    Moroz, P.E.

    1997-09-01

    A new stellarator configuration, the Double-Helix Stellarator (DHS), is introduced. This novel configuration features a double-helix center post as the only helical element of the stellarator coil system. The DHS configuration has many unique characteristics. One of them is the extreme low plasma aspect ratio, A ∼ 1--1.2. Other advantages include a high enclosed volume, appreciable rotational transform, and a possibility of extreme-high-β MHD equilibria. Moreover, the DHS features improved transport characteristics caused by the absence of the magnetic field ripple on the outboard of the torus. Compactness, simplicity and modularity of the coil system add to the DHS advantages for fusion applications

  7. Response of the MG-63 human osteosarcoma cell line grown as multicellular spheroids to neutron irradiation

    International Nuclear Information System (INIS)

    Kubota, Nobuo; Kakehi, Masae; Matsubara, Shou; Koike, Sachiko; Ando, Koichi.

    1993-01-01

    Multicellular tumor spheroids are composed of the mixed populations of cells with regard to cell proliferation, nutrition, oxygenation and radiosensitivity. Human osteogenic sarcoma is generally considered clinically radioresistant. However, the in vitro cell survival curves for human osteogenic sarcoma cell lines do not differ from those of other tumor cell lines. In this study, the responses of human osteogenic sarcoma cell line to gamma ray and neutrons were investigated by using spheroid system. The spheroids of the osteogenic sarcoma cell line are considered to be a good in vitro model of radioresistant tumors. The purpose of this study is to measure the response of the spheroids to fast neutron irradiation. MG-63 human osteogenic sarcoma cell line was used for this study. The cell line was cultured in alpha-MEM with supplement. Cell survival was estimated after the trypsinization of spheroids 24 hours after irradiation. The method of measuring spheroid cure is explained. The mean number of surviving cells per spheroid can be obtained from the mean clonogenic number and cell survival curve. The cell survival of MG-63 spheroids exposed to gamma ray and neutrons and the dose effect curves for spheroid cure after irradiation are shown. (K.I.)

  8. An analytic distribution function for a mass-less cored stellar system in a cuspy dark-matter halo

    NARCIS (Netherlands)

    Breddels, Maarten A.; Helmi, Amina

    2013-01-01

    We demonstrate the existence of a distribution function that can be used to represent spherical mass-less cored stellar systems having constant mildly tangential velocity anisotropy embedded in cuspy dark-matter halos. In particular, we derived analytically the functional form of the distribution

  9. SIZE AND SHAPE FACTOR EXTREMES OF SPHEROIDS

    Directory of Open Access Journals (Sweden)

    Daniel Hlubinka

    2011-05-01

    Full Text Available In the paper we consider random prolate (oblate spheroids and their random profiles. The limiting distribution of the extremal characteristics of the spheroids is related to the limiting distribution of the corresponding extremal characteristics of the profiles. The difference between the analysis of the prolate and oblate spheroids is discussed. We propose the possible application of the theoretical results.

  10. Development of a 3-D visible limiter imaging system for the HSX stellarator

    Science.gov (United States)

    Buelo, C.; Stephey, L.; Anderson, F. S. B.; Eisert, D.; Anderson, D. T.

    2017-12-01

    A visible camera diagnostic has been developed to study the Helically Symmetric eXperiment (HSX) limiter plasma interaction. A straight line view from the camera location to the limiter was not possible due to the complex 3D stellarator geometry of HSX, so it was necessary to insert a mirror/lens system into the plasma edge. A custom support structure for this optical system tailored to the HSX geometry was designed and installed. This system holds the optics tube assembly at the required angle for the desired view to both minimize system stress and facilitate robust and repeatable camera positioning. The camera system has been absolutely calibrated and using Hα and C-III filters can provide hydrogen and carbon photon fluxes, which through an S/XB coefficient can be converted into particle fluxes. The resulting measurements have been used to obtain the characteristic penetration length of hydrogen and C-III species. The hydrogen λiz value shows reasonable agreement with the value predicted by a 1D penetration length calculation.

  11. Metallicities for old stellar systems from Ca II triplet strengths in member giants

    International Nuclear Information System (INIS)

    Armandroff, T.E.; Da costa, G.S.

    1991-01-01

    The spectra of giants in six well-studied Galactic globulars spanning a wide range of abundance are used to investigate the utility of the Ca II triplet as an abundance indicator. The calibration resulting from these clusters is used to derive metal abundances from the spectra of giants in Eridanus, Pal 12, and the Carina dwarf spheroidal galaxy. The results obtained are compared with earlier determinations based on giant branch photometry. 37 refs

  12. Stellar Image Interpretation System using Artificial Neural Networks: Unipolar Function Case

    Directory of Open Access Journals (Sweden)

    F. I. Younis

    2001-01-01

    Full Text Available An artificial neural network based system for interpreting astronomical images has been developed. The system is based on feed-forward Artificial Neural Networks (ANNs with error back-propagation learning. Knowledge about images of stars, cosmic ray events and noise found in images is used to prepare two sets of input patterns to train and test our approach. The system has been developed and implemented to scan astronomical digital images in order to segregate stellar images from other entities. It has been coded in C language for users of personal computers. An astronomical image of a star cluster from other objects is undertaken as a test case. The obtained results are found to be in very good agreement with those derived from the DAOPHOTII package, which is widely used in the astronomical community. It is proved that our system is simpler, much faster and more reliable. Moreover, no prior knowledge, or initial data from the frame to be analysed is required.

  13. MODEL-INDEPENDENT STELLAR AND PLANETARY MASSES FROM MULTI-TRANSITING EXOPLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    Montet, Benjamin T.; Johnson, John Asher

    2013-01-01

    Precise exoplanet characterization requires precise classification of exoplanet host stars. The masses of host stars are commonly estimated by comparing their spectra to those predicted by stellar evolution models. However, spectroscopically determined properties are difficult to measure accurately for stars that are substantially different from the Sun, such as M-dwarfs and evolved stars. Here, we propose a new method to dynamically measure the masses of transiting planets near mean-motion resonances and their host stars by combining observations of transit timing variations with radial velocity (RV) measurements. We derive expressions to analytically determine the mass of each member of the system and demonstrate the technique on the Kepler-18 system. We compare these analytic results to numerical simulations and find that the two are consistent. We identify eight systems for which our technique could be applied if follow-up RV measurements are collected. We conclude that this analysis would be optimal for systems discovered by next-generation missions similar to TESS or PLATO, which will target bright stars that are amenable to efficient RV follow-up.

  14. A Dynamic Precision Evaluation Method for the Star Sensor in the Stellar-Inertial Navigation System.

    Science.gov (United States)

    Lu, Jiazhen; Lei, Chaohua; Yang, Yanqiang

    2017-06-28

    Integrating the advantages of INS (inertial navigation system) and the star sensor, the stellar-inertial navigation system has been used for a wide variety of applications. The star sensor is a high-precision attitude measurement instrument; therefore, determining how to validate its accuracy is critical in guaranteeing its practical precision. The dynamic precision evaluation of the star sensor is more difficult than a static precision evaluation because of dynamic reference values and other impacts. This paper proposes a dynamic precision verification method of star sensor with the aid of inertial navigation device to realize real-time attitude accuracy measurement. Based on the gold-standard reference generated by the star simulator, the altitude and azimuth angle errors of the star sensor are calculated for evaluation criteria. With the goal of diminishing the impacts of factors such as the sensors' drift and devices, the innovative aspect of this method is to employ static accuracy for comparison. If the dynamic results are as good as the static results, which have accuracy comparable to the single star sensor's precision, the practical precision of the star sensor is sufficiently high to meet the requirements of the system specification. The experiments demonstrate the feasibility and effectiveness of the proposed method.

  15. Supernova-driven outflows and chemical evolution of dwarf spheroidal galaxies.

    Science.gov (United States)

    Qian, Yong-Zhong; Wasserburg, G J

    2012-03-27

    We present a general phenomenological model for the metallicity distribution (MD) in terms of [Fe/H] for dwarf spheroidal galaxies (dSphs). These galaxies appear to have stopped accreting gas from the intergalactic medium and are fossilized systems with their stars undergoing slow internal evolution. For a wide variety of infall histories of unprocessed baryonic matter to feed star formation, most of the observed MDs can be well described by our model. The key requirement is that the fraction of the gas mass lost by supernova-driven outflows is close to unity. This model also predicts a relationship between the total stellar mass and the mean metallicity for dSphs in accord with properties of their dark matter halos. The model further predicts as a natural consequence that the abundance ratios [E/Fe] for elements such as O, Mg, and Si decrease for stellar populations at the higher end of the [Fe/H] range in a dSph. We show that, for infall rates far below the net rate of gas loss to star formation and outflows, the MD in our model is very sharply peaked at one [Fe/H] value, similar to what is observed in most globular clusters. This result suggests that globular clusters may be end members of the same family as dSphs.

  16. The Age of the Young Bulge-like Population in the Stellar System Terzan 5: Linking the Galactic Bulge to the High-z Universe

    NARCIS (Netherlands)

    Ferraro, F. R.; Massari, D.; Dalessandro, E.; Lanzoni, B.; Origlia, L.; Rich, R. M.; Mucciarelli, A.

    2016-01-01

    The Galactic bulge is dominated by an old, metal-rich stellar population. The possible presence and the amount of a young (a few gigayears old) minor component is one of the major issues debated in the literature. Recently, the bulge stellar system Terzan 5 was found to harbor three sub-populations

  17. Chitosan derived co-spheroids of neural stem cells and mesenchymal stem cells for neural regeneration.

    Science.gov (United States)

    Han, Hao-Wei; Hsu, Shan-Hui

    2017-10-01

    Chitosan has been considered as candidate biomaterials for neural applications. The effective treatment of neurodegeneration or injury to the central nervous system (CNS) is still in lack nowadays. Adult neural stem cells (NSCs) represents a promising cell source to treat the CNS diseases but they are limited in number. Here, we developed the core-shell spheroids of NSCs (shell) and mesenchymal stem cells (MSCs, core) by co-culturing cells on the chitosan surface. The NSCs in chitosan derived co-spheroids displayed a higher survival rate than those in NSC homo-spheroids. The direct interaction of NSCs with MSCs in the co-spheroids increased the Notch activity and differentiation tendency of NSCs. Meanwhile, the differentiation potential of MSCs in chitosan derived co-spheroids was significantly enhanced toward neural lineages. Furthermore, NSC homo-spheroids and NSC/MSC co-spheroids derived on chitosan were evaluated for their in vivo efficacy by the embryonic and adult zebrafish brain injury models. The locomotion activity of zebrafish receiving chitosan derived NSC homo-spheroids or NSC/MSC co-spheroids was partially rescued in both models. Meanwhile, the higher survival rate was observed in the group of adult zebrafish implanted with chitosan derived NSC/MSC co-spheroids as compared to NSC homo-spheroids. These evidences indicate that chitosan may provide an extracellular matrix-like environment to drive the interaction and the morphological assembly between NSCs and MSCs and promote their neural differentiation capacities, which can be used for neural regeneration. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Characterizing the X-ray & Stellar Wind Environment in the ~1 Gyr Late Heavy Bombardment System Eta Corvi

    Science.gov (United States)

    Lisse, Carey

    2012-09-01

    We propose a 40 ksec ACIS-S observation of the 1 Gyr old system Eta Corvi, the site of an on-going Late Heavy Bombardment (Lisse et al. 2012), in order to determine the spectrum of x-ray radiation in the burgeoning system, its origin in the stellar coronae and circumstellar debris belts, and its impact on the water and organics recently delivered to a rocky planet in the terrestrial habitability zone.

  19. Technology development of the soft X-ray tomography system in Wendelstein 7-X stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Schülke, M., E-mail: mathias.schuelke@ipp.mpg.de [Max Planck Institute for Plasma Physics, EURATOM Association, Wendelsteinstr. 1, 17491 Greifswald (Germany); Cardella, A.; Hathiramani, D.; Mettchen, S.; Thomsen, H.; Weißflog, S.; Zacharias, D. [Max Planck Institute for Plasma Physics, EURATOM Association, Wendelsteinstr. 1, 17491 Greifswald (Germany)

    2013-10-15

    Highlights: ► Engineering and design of soft X-ray Multi Camera Tomography System. ► Requirements of in-vessel diagnostics in Wendelstein 7-X. ► Development of internal cooling system including FEM-Analysis. ► Development of lateral shield system with testing for microwave stray radiation compatibility. ► Development of multipin feedthrough including welding qualification and leak tests. -- Abstract: The engineering and design of the soft X-ray Multi Camera Tomography System (XMCTS) in Wendelstein 7-X stellarator (W7-X) must fulfill several additional requirements compared to short pulse machines. The XMCTS has to withstand irradiation and electron cyclotron microwave loads in addition to being ultra high vacuum compatible, having low magnetic permeability and using low neutron activation materials (e.g. Co ≤ 2000 ppm). A further difficulty is the limited space inside the plasma vessel, which requires special engineering solutions. After detailed design development, supported by finite element analyses, prototypes have been manufactured and tested. At the end all test results have successfully proven that the components fulfill the requirements and that reliable and stable measurements will be possible with the XMCTS diagnostics during W7-X operation. The paper describes the design and the technological development, in particular on the electric multipin feedthrough (UHV barrier between in vessel detectors and the preamplifiers), the active cooling of the electronic components (reducing dark current/noise increase), the pneumatic shutter (protection of the detectors from sputtering and during baking) and the fiber optics illumination system (calibration of the detectors)

  20. CONCENTRIC MACLAURIN SPHEROID MODELS OF ROTATING LIQUID PLANETS

    International Nuclear Information System (INIS)

    Hubbard, W. B.

    2013-01-01

    I present exact expressions for the interior gravitational potential V of a system of N concentric constant-density (Maclaurin) spheroids. I demonstrate an iteration procedure to find a self-consistent solution for the shapes of the interfaces between spheroids, and for the interior gravitational potential. The external free-space potential, expressed as a multipole expansion, emerges as part of the self-consistent solution. The procedure is both simpler and more precise than perturbation methods. One can choose the distribution and mass densities of the concentric spheroids so as to reproduce a prescribed barotrope to a specified accuracy. I demonstrate the method's efficacy by comparing its results with several published test cases.

  1. Synthesis of Hα absorption in old stellar systems: formation of the cluster red sequence by `downsizing'

    Science.gov (United States)

    Smith, Russell J.

    2005-05-01

    We compute population synthesis models for the variation of Hα absorption indices (HαA and HαF), as a function of age and metallicity in old stellar systems. The models are based on the STELIB spectral library of Le Borgne et al., and defined at a resolution of 3Åfull width at half-maximum. Errors in the age and metallicity responses are derived by bootstrap resampling the input measurements on the stellar library. The indices are found to be highly sensitive to age variation, with only moderate response to metallicity. For galaxies uncontaminated by nebular emission, our HαA index is more powerful in breaking the age-metallicity degeneracy than Hβ or HγF. Using a sample of red cluster galaxies from Nelan et al., carefully selected to exclude objects with emission, we find a steep decline of HαA with velocity dispersion (slope -0.75 +/- 0.07Ådex-1). The slope can be translated to constraints on age and metallicity scaling relations, incorporating measurement errors and also the model errors determined from the bootstrap method. If the HαA-σ slope is due only to age, we obtain Age ~σ0.95+/-0.12. Because HαA depends quite weakly on [Fe/H], a metallicity interpretation would require Fe/H ~σ1.2 or steeper. The HαA-σ slope is consistent with the combined age and metallicity scaling relations reported by Nelan et al. from classical Lick indices. The relations obtained by Thomas et al. significantly underpredict the observed slope. The discrepancy could arise from differences in the sample selection. In particular, our sample probes a lower mass range, is not explicitly selected on morphological criteria, and excludes objects significantly bluer than the red sequence. We discuss in detail the impact of emission contamination on the results, and conclude that this effect is unlikely to yield the observed behaviour in the Hα-σ relations. Indeed, similar results are obtained using HαF, despite its different sensitivity to Hα and [NII] emission lines. The

  2. THE QUADRUPLE PRE-MAIN-SEQUENCE SYSTEM LkCa 3: IMPLICATIONS FOR STELLAR EVOLUTION MODELS

    International Nuclear Information System (INIS)

    Torres, Guillermo; Latham, David W.; Ruíz-Rodríguez, Dary; Prato, L.; Wasserman, Lawrence H.; Badenas, Mariona; Schaefer, G. H.; Mathieu, Robert D.

    2013-01-01

    We report the discovery that the pre-main-sequence (PMS) object LkCa 3 in the Taurus-Auriga star-forming region is a hierarchical quadruple system of M stars. It was previously known to be a close (∼0.''5) visual pair, with one component being a moderately eccentric 12.94 day single-lined spectroscopic binary. A re-analysis of archival optical spectra complemented by new near-infrared (NIR) spectroscopy shows both visual components to be double lined; the second one has a period of 4.06 days and a circular orbit. In addition to the orbital elements, we determine optical and NIR flux ratios, effective temperatures, and projected rotational velocities for all four stars. Using existing photometric monitoring observations of the system that had previously revealed the rotational period of the primary in the longer-period binary, we also detect the rotational signal of the primary in the 4.06 day binary, which is synchronized with the orbital motion. With only the assumption of coevality, a comparison of all of these constraints with current stellar evolution models from the Dartmouth series points to an age of 1.4 Myr and a distance of 133 pc, consistent with previous estimates for the region and suggesting that the system is on the near side of the Taurus complex. Similar comparisons of the properties of LkCa 3 and the well-known quadruple PMS system GG Tau with the widely used models from the Lyon series for a mixing length parameter of α ML = 1.0 strongly favor the Dartmouth models

  3. Two distinct ancient components in the Sculptor dwarf spheroidal galaxy : First results from the dwarf abundances and radial velocities team

    NARCIS (Netherlands)

    Tolstoy, E; Irwin, MJ; Helmi, A; Battaglia, G; Jablonka, P; Hill, [No Value; Venn, KA; Shetrone, MD; Letarte, B; Cole, AA; Primas, F; Francois, P; Arimoto, N; Sadakane, K; Kaufer, A; Szeifert, T; Abel, T

    2004-01-01

    We have found evidence for the presence of two distinct ancient stellar components (bothgreater than or equal to10 Gyr old) in the Sculptor dwarf spheroidal galaxy. We used the ESO Wide Field Imager in conjunction with the Very Large Telescope/FLAMES spectrograph to study the properties of the

  4. VLT/UVES spectroscopy of individual stars in three globular clusters in the Fornax dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Letarte, B; Hill, [No Value; Jablonka, P; Tolstoy, E; Francois, P; Meylan, G

    We present a high resolution ( R similar to 43 000) abundance analysis of a total of nine stars in three of the five globular clusters associated with the nearby Fornax dwarf spheroidal galaxy. These three clusters ( 1, 2 and 3) trace the oldest, most metal-poor stellar populations in Fornax. We

  5. An explanation of forms of planetary orbits and estimation of angular shift of the Mercury' perihelion using the statistical theory of gravitating spheroidal bodies

    Science.gov (United States)

    Krot, A. M.

    2013-09-01

    This work develops a statistical theory of gravitating spheroidal bodies to calculate the orbits of planets and explore forms of planetary orbits with regard to the Alfvén oscillating force [1] in the Solar system and other exoplanetary systems. The statistical theory of formation of gravitating spheroidal bodies has been proposed in [2]-[5]. Starting the conception for forming a spheroidal body inside a gas-dust protoplanetary nebula, this theory solves the problem of gravitational condensation of a gas-dust protoplanetary cloud with a view to planetary formation in its own gravitational field [3] as well as derives a new law of the Solar system planetary distances which generalizes the wellknown laws [2], [3]. This work also explains an origin of the Alfvén oscillating force modifying forms of planetary orbits within the framework of the statistical theory of gravitating spheroidal bodies [5]. Due to the Alfvén oscillating force moving solid bodies in a distant zone of a rotating spheroidal body have elliptic trajectories. It means that orbits for the enough remote planets from the Sun in Solar system are described by ellipses with focus in the origin of coordinates and with small eccentricities. The nearby planet to Sun named Mercury has more complex trajectory. Namely, in case of Mercury the angular displacement of a Newtonian ellipse is observed during its one rotation on an orbit, i.e. a regular (century) shift of the perihelion of Mercury' orbit occurs. According to the statistical theory of gravitating spheroidal bodies [2]-[5] under the usage of laws of celestial mechanics in conformity to cosmogonic bodies (especially, to stars) it is necessary to take into account an extended substance called a stellar corona. In this connection the stellar corona can be described by means of model of rotating and gravitating spheroidal body [5]. Moreover, the parameter of gravitational compression α of a spheroidal body (describing the Sun, in particular) has been

  6. Multiscale image analysis reveals structural heterogeneity of the cell microenvironment in homotypic spheroids.

    Science.gov (United States)

    Schmitz, Alexander; Fischer, Sabine C; Mattheyer, Christian; Pampaloni, Francesco; Stelzer, Ernst H K

    2017-03-03

    Three-dimensional multicellular aggregates such as spheroids provide reliable in vitro substitutes for tissues. Quantitative characterization of spheroids at the cellular level is fundamental. We present the first pipeline that provides three-dimensional, high-quality images of intact spheroids at cellular resolution and a comprehensive image analysis that completes traditional image segmentation by algorithms from other fields. The pipeline combines light sheet-based fluorescence microscopy of optically cleared spheroids with automated nuclei segmentation (F score: 0.88) and concepts from graph analysis and computational topology. Incorporating cell graphs and alpha shapes provided more than 30 features of individual nuclei, the cellular neighborhood and the spheroid morphology. The application of our pipeline to a set of breast carcinoma spheroids revealed two concentric layers of different cell density for more than 30,000 cells. The thickness of the outer cell layer depends on a spheroid's size and varies between 50% and 75% of its radius. In differently-sized spheroids, we detected patches of different cell densities ranging from 5 × 10 5 to 1 × 10 6  cells/mm 3 . Since cell density affects cell behavior in tissues, structural heterogeneities need to be incorporated into existing models. Our image analysis pipeline provides a multiscale approach to obtain the relevant data for a system-level understanding of tissue architecture.

  7. Chemical evolution of Local Group dwarf galaxies in a cosmological context - I. A new modelling approach and its application to the Sculptor dwarf spheroidal galaxy

    Science.gov (United States)

    Romano, Donatella; Starkenburg, Else

    2013-09-01

    We present a new approach for chemical evolution modelling, specifically designed to investigate the chemical properties of dwarf galaxies in a full cosmological framework. In particular, we focus on the Sculptor dwarf spheroidal galaxy, for which a wealth of observational data exists, as a test bed for our model. We select four candidate Sculptor-like galaxies from the satellite galaxy catalogue generated by implementation of a version of the Munich semi-analytic model for galaxy formation on the level 2 Aquarius dark matter simulations and use the mass assembly and star formation histories predicted for these four systems as an input for the chemical evolution code. We follow explicitly the evolution of several chemical elements, both in the cold gas out of which the stars form and in the hot medium residing in the halo. We take into account in detail the lifetimes of stars of different initial masses, the distribution of the delay times for Type Ia supernova explosions and the dependence of the stellar yields from the initial metallicity of the stars. We allow large fractions of metals to be deposited into the hot phase, either directly as stars die or through reheated gas flows powered by supernova explosions. We find that, in order to reproduce both the observed metallicity distribution function and the observed abundance ratios of long-lived stars of Sculptor, large fractions of the reheated metals must never re-enter regions of active star formation. With this prescription, all the four analogues to the Sculptor dwarf spheroidal galaxy extracted from the simulated satellites catalogue on the basis of luminosity and stellar population ages are found to reasonably match the detailed chemical properties of real Sculptor stars. However, all model galaxies do severely underestimate the fraction of very metal poor stars observed in Sculptor. Our analysis thus sets further constraints on the semi-analytical models and, at large, on possible metal enrichment

  8. Numerical simulations of the metallicity distribution in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Ripamonti, E.; Tolstoy, E.; Helmi, A.; Battaglia, G.; Abel, T.

    2006-01-01

    Abstract: Recent observations show that the number of stars with very low metallicities in the dwarf spheroidal satellites of the Milky Way is low, despite the low average metallicities of stars in these systems. We undertake numerical simulations of star formation and metal enrichment of dwarf

  9. Stellar formation

    CERN Document Server

    Reddish, V C

    1978-01-01

    Stellar Formation brings together knowledge about the formation of stars. In seeking to determine the conditions necessary for star formation, this book examines questions such as how, where, and why stars form, and at what rate and with what properties. This text also considers whether the formation of a star is an accident or an integral part of the physical properties of matter. This book consists of 13 chapters divided into two sections and begins with an overview of theories that explain star formation as well as the state of knowledge of star formation in comparison to stellar structure

  10. HIDING IN PLAIN SIGHT: RECORD-BREAKING COMPACT STELLAR SYSTEMS IN THE SLOAN DIGITAL SKY SURVEY

    International Nuclear Information System (INIS)

    Sandoval, Michael A.; Vo, Richard P.; Romanowsky, Aaron J.; Strader, Jay; Choi, Jieun; Conroy, Charlie; Jennings, Zachary G.; Villaume, Alexa; Brodie, Jean P.; Foster, Caroline; Norris, Mark A.; Janz, Joachim; Forbes, Duncan A.

    2015-01-01

    Motivated by the recent, serendipitous discovery of the densest known galaxy, M60-UCD1, we present two initial findings from a follow-up search, using the Sloan Digital Sky Survey, Subaru/Suprime-Cam, and Hubble Space Telescope imaging, and SOuthern Astrophysical Research (SOAR)/Goodman spectroscopy. The first object discovered, M59-UCD3, has a similar size to M60-UCD1 (half-light radius of r h ∼ 20 pc) but is 40% more luminous (M V ∼ −14.6), making it the new densest-known galaxy. The second, M85-HCC1, has a size like a typical globular cluster (GC; r h ∼ 1.8 pc) but is much more luminous (M V ∼ −12.5). This hypercompact cluster is by far the densest confirmed free-floating stellar system, and is equivalent to the densest known nuclear star clusters. From spectroscopy, we find that both objects are relatively young (∼9 and ∼3 Gyr, respectively), with metal-abundances that resemble those of galaxy centers. Their host galaxies show clear signs of large-scale disturbances, and we conclude that these dense objects are the remnant nuclei of recently accreted galaxies. M59-UCD3 is an ideal target for follow-up with high-resolution imaging and spectroscopy to search for an overweight central supermassive black hole as was discovered in M60-UCD1. These findings also emphasize the potential value of ultra-compact dwarfs and massive GCs as tracers of the assembly histories of galaxies

  11. HIDING IN PLAIN SIGHT: RECORD-BREAKING COMPACT STELLAR SYSTEMS IN THE SLOAN DIGITAL SKY SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval, Michael A.; Vo, Richard P.; Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, One Washington Square, San Jose, CA 95192 (United States); Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Choi, Jieun; Conroy, Charlie [Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Jennings, Zachary G.; Villaume, Alexa [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Brodie, Jean P. [University of California Observatories, 1156 High Street, Santa Cruz, CA 95064 (United States); Foster, Caroline [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); Norris, Mark A. [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Janz, Joachim; Forbes, Duncan A. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia)

    2015-07-20

    Motivated by the recent, serendipitous discovery of the densest known galaxy, M60-UCD1, we present two initial findings from a follow-up search, using the Sloan Digital Sky Survey, Subaru/Suprime-Cam, and Hubble Space Telescope imaging, and SOuthern Astrophysical Research (SOAR)/Goodman spectroscopy. The first object discovered, M59-UCD3, has a similar size to M60-UCD1 (half-light radius of r{sub h} ∼ 20 pc) but is 40% more luminous (M{sub V} ∼ −14.6), making it the new densest-known galaxy. The second, M85-HCC1, has a size like a typical globular cluster (GC; r{sub h} ∼ 1.8 pc) but is much more luminous (M{sub V} ∼ −12.5). This hypercompact cluster is by far the densest confirmed free-floating stellar system, and is equivalent to the densest known nuclear star clusters. From spectroscopy, we find that both objects are relatively young (∼9 and ∼3 Gyr, respectively), with metal-abundances that resemble those of galaxy centers. Their host galaxies show clear signs of large-scale disturbances, and we conclude that these dense objects are the remnant nuclei of recently accreted galaxies. M59-UCD3 is an ideal target for follow-up with high-resolution imaging and spectroscopy to search for an overweight central supermassive black hole as was discovered in M60-UCD1. These findings also emphasize the potential value of ultra-compact dwarfs and massive GCs as tracers of the assembly histories of galaxies.

  12. Laboratory studies of stagnating plasma flows with applications to inner solar system and stellar bow shocks

    Science.gov (United States)

    Weber, T. E.; Smith, R. J.; Hsu, S. C.

    2016-10-01

    Supercritical magnetized collisionless shocks are thought to play a dominant role in the overall partition of energy throughout the universe by converting flow kinetic energy to other forms such as thermal and supra-thermal populations, magnetic field enhancement, turbulence, and energetic particles. The Magnetized Shock Experiment (MSX) at LANL creates conditions similar to those of inner solar system and stellar bow shocks by accelerating hot (100s of eV during translation) dense (1022 - 1023 m-3) Field Reversed Configuration (FRC) plasmoids to 100s of km/s; resulting in β 1, collisionless plasma flows with Msonic and MAlfvén 10. The drifting FRC can be made to impinge upon a variety of static obstacles including: a strong mirror or cusp magnetic field (mimicking magnetically excited shocks such as the Earth's bow shock), plasma pileup from a solid obstacle (similar to the bow shocks of Mercury and the Moon), and a neural gas puff (bow shocks of Venus or the comets). Characteristic shock length and time scales that are both large enough to observe yet small enough to fit within the experiment, enabling study of the complex interplay of kinetic and fluid processes that mediate cosmic shocks and can generate non-thermal distributions, produce density and magnetic field enhancements much greater than predicted by fluid theory, and accelerate particles. An overview of the experimental program will be presented, including recent results. This work is supported by the U.S. DOE, Office of Science, Office of Fusion Energy Sciences under Contract No. DE-AC52-06NA25369.

  13. WFPC2 Observations of the URSA Minor Dwarf Spheroidal Galaxy

    Science.gov (United States)

    Mighell, Kenneth J.; Burke, Christopher J.

    1999-01-01

    We present our analysis of archival Hubble Space Telescope Wide Field Planetary Camera 2 (WFPC2) observations in F555W (approximately V) and F814W (approximately I) of the central region of the Ursa Minor dwarf spheroidal galaxy. The V versus V - I color-magnitude diagram features a sparsely populated blue horizontal branch, a steep thin red giant branch, and a narrow subgiant branch. The main sequence reaches approximately 2 magnitudes below the main-sequence turnoff (V(sup UMi, sub TO) approximately equals 23.27 +/- 0.11 mag) of the median stellar population. We compare the fiducial sequence of the Galactic globular cluster M92 (NGC 6341). The excellent match between Ursa Minor and M92 confirms that the median stellar population of the UMi dSph galaxy is metal poor ([Fe/H](sub UMi) approximately equals [Fe/H](sub M92) approximately equals -2.2 dex) and ancient (age(sub UMi)approximately equalsage(sub M92) approximately equals 14 Gyr). The B - V reddening and the absorption in V are estimated to be E(B - V) = 0.03 +/- 0.01 mag and A(sup UMi, sub V) = 0.09 +/- 0.03 mag. A new estimate of the distance modulus of Ursa Minor, (m - M)(sup UMi, sub 0) = 19.18 +/- 0.12 mag, has been derived based on fiducial-sequence fitting M92 [DELTA.V(sub UMi - M92) = 4.60 +/- 0.03 mag and DELTA(V - I)(sub UMi - M92) = 0.010 +/- 0.005 mag] and the adoption of the apparent V distance modulus for M92 of (m - M)(sup M92, sub V) = 14.67 +/- 0.08 mag (Pont et al. 1998, A&A, 329, 87). The Ursa Minor dwarf spheroidal galaxy is then at a distance of 69 +/- 4 kpc from the Sun. These HST observations indicate that Ursa Minor has had a very simple star formation history consisting mainly of a single major burst of star formation about 14 Gyr ago which lasted approximately stars in the central region Ursa Minor dwarf spheroidal galaxy are ancient. If the ancient Galactic globular clusters, like M92, formed concurrently with the early formation of the Milky Way galaxy itself, then the Ursa Minor

  14. Scalable robotic biofabrication of tissue spheroids

    International Nuclear Information System (INIS)

    Mehesz, A Nagy; Hajdu, Z; Visconti, R P; Markwald, R R; Mironov, V; Brown, J; Beaver, W; Da Silva, J V L

    2011-01-01

    Development of methods for scalable biofabrication of uniformly sized tissue spheroids is essential for tissue spheroid-based bioprinting of large size tissue and organ constructs. The most recent scalable technique for tissue spheroid fabrication employs a micromolded recessed template prepared in a non-adhesive hydrogel, wherein the cells loaded into the template self-assemble into tissue spheroids due to gravitational force. In this study, we present an improved version of this technique. A new mold was designed to enable generation of 61 microrecessions in each well of a 96-well plate. The microrecessions were seeded with cells using an EpMotion 5070 automated pipetting machine. After 48 h of incubation, tissue spheroids formed at the bottom of each microrecession. To assess the quality of constructs generated using this technology, 600 tissue spheroids made by this method were compared with 600 spheroids generated by the conventional hanging drop method. These analyses showed that tissue spheroids fabricated by the micromolded method are more uniform in diameter. Thus, use of micromolded recessions in a non-adhesive hydrogel, combined with automated cell seeding, is a reliable method for scalable robotic fabrication of uniform-sized tissue spheroids.

  15. Scalable robotic biofabrication of tissue spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Mehesz, A Nagy; Hajdu, Z; Visconti, R P; Markwald, R R; Mironov, V [Advanced Tissue Biofabrication Center, Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC (United States); Brown, J [Department of Mechanical Engineering, Clemson University, Clemson, SC (United States); Beaver, W [York Technical College, Rock Hill, SC (United States); Da Silva, J V L, E-mail: mironovv@musc.edu [Renato Archer Information Technology Center-CTI, Campinas (Brazil)

    2011-06-15

    Development of methods for scalable biofabrication of uniformly sized tissue spheroids is essential for tissue spheroid-based bioprinting of large size tissue and organ constructs. The most recent scalable technique for tissue spheroid fabrication employs a micromolded recessed template prepared in a non-adhesive hydrogel, wherein the cells loaded into the template self-assemble into tissue spheroids due to gravitational force. In this study, we present an improved version of this technique. A new mold was designed to enable generation of 61 microrecessions in each well of a 96-well plate. The microrecessions were seeded with cells using an EpMotion 5070 automated pipetting machine. After 48 h of incubation, tissue spheroids formed at the bottom of each microrecession. To assess the quality of constructs generated using this technology, 600 tissue spheroids made by this method were compared with 600 spheroids generated by the conventional hanging drop method. These analyses showed that tissue spheroids fabricated by the micromolded method are more uniform in diameter. Thus, use of micromolded recessions in a non-adhesive hydrogel, combined with automated cell seeding, is a reliable method for scalable robotic fabrication of uniform-sized tissue spheroids.

  16. Evolutionary stellar population synthesis with MILES : I. The base models and a new line index system

    NARCIS (Netherlands)

    Vazdekis, A.; Sanchez-Blazquez, P.; Falcon-Barroso, J.; Cenarro, A. J.; Beasley, M. A.; Cardiel, N.; Gorgas, J.; Peletier, R. F.

    2010-01-01

    We present synthetic spectral energy distributions (SEDs) for single-age, single-metallicity stellar populations (SSPs) covering the full optical spectral range at moderately high resolution [full width at half-maximum (FWHM) = 2.3Å]. These SEDs constitute our base models, as they combine

  17. The Dependence of Convective Core Overshooting on Stellar Mass: Additional Binary Systems and Improved Calibration

    Science.gov (United States)

    Claret, Antonio; Torres, Guillermo

    2018-06-01

    Many current stellar evolution models assume some dependence of the strength of convective core overshooting on mass for stars more massive than 1.1–1.2 M ⊙, but the adopted shapes for that relation have remained somewhat arbitrary for lack of strong observational constraints. In previous work, we compared stellar evolution models to well-measured eclipsing binaries to show that, when overshooting is implemented as a diffusive process, the fitted free parameter f ov rises sharply up to about 2 M ⊙, and remains largely constant thereafter. Here, we analyze a new sample of eight binaries selected to be in the critical mass range below 2 M ⊙ where f ov is changing the most, nearly doubling the number of individual stars in this regime. This interval is important because the precise way in which f ov changes determines the shape of isochrones in the turnoff region of ∼1–5 Gyr clusters, and can thus affect their inferred ages. It also has a significant influence on estimates of stellar properties for exoplanet hosts, on stellar population synthesis, and on the detailed modeling of interior stellar structures, including the calculation of oscillation frequencies that are observable with asteroseismic techniques. We find that the derived f ov values for our new sample are consistent with the trend defined by our earlier determinations, and strengthen the relation. This provides an opportunity for future series of models to test the new prescription, grounded on observations, against independent observations that may constrain overshooting in a different way.

  18. Stellar remnants

    CERN Document Server

    Kawaler, S D; Srinivasan, G

    1997-01-01

    This volume examines the internal structure, origin and evolution of white dwarfs, neutron stars and black holes, all objects at the final stage of stellar evolution. It covers topics such as: pulsation of white dwarfs; millisecond pulsars; and the dynamics around black holes.

  19. DWARFS GOBBLING DWARFS: A STELLAR TIDAL STREAM AROUND NGC 4449 AND HIERARCHICAL GALAXY FORMATION ON SMALL SCALES

    International Nuclear Information System (INIS)

    Martínez-Delgado, David; Rix, Hans-Walter; Macciò, Andrea V.; Romanowsky, Aaron J.; Arnold, Jacob A.; Brodie, Jean P.; Jay Gabany, R.; Annibali, Francesca; Fliri, Jürgen; Zibetti, Stefano; Van der Marel, Roeland P.; Aloisi, Alessandra; Chonis, Taylor S.; Carballo-Bello, Julio A.; Gallego-Laborda, J.; Merrifield, Michael R.

    2012-01-01

    A candidate diffuse stellar substructure was previously reported in the halo of the nearby dwarf starburst galaxy NGC 4449 by Karachentsev et al. We map and analyze this feature using a unique combination of deep integrated-light images from the BlackBird 0.5 m telescope, and high-resolution wide-field images from the 8 m Subaru Telescope, which resolve the nebulosity into a stream of red giant branch stars, and confirm its physical association with NGC 4449. The properties of the stream imply a massive dwarf spheroidal progenitor, which after complete disruption will deposit an amount of stellar mass that is comparable to the existing stellar halo of the main galaxy. The stellar mass ratio between the two galaxies is ∼1:50, while the indirectly measured dynamical mass ratio, when including dark matter, may be ∼1:10-1:5. This system may thus represent a 'stealth' merger, where an infalling satellite galaxy is nearly undetectable by conventional means, yet has a substantial dynamical influence on its host galaxy. This singular discovery also suggests that satellite accretion can play a significant role in building up the stellar halos of low-mass galaxies, and possibly in triggering their starbursts.

  20. Formation of stable small cell number three-dimensional ovarian cancer spheroids using hanging drop arrays for preclinical drug sensitivity assays.

    Science.gov (United States)

    Raghavan, Shreya; Ward, Maria R; Rowley, Katelyn R; Wold, Rachel M; Takayama, Shuichi; Buckanovich, Ronald J; Mehta, Geeta

    2015-07-01

    Ovarian cancer grows and metastasizes from multicellular spheroidal aggregates within the ascites fluid. Multicellular tumor spheroids are therefore physiologically significant 3D in vitro models for ovarian cancer research. Conventional hanging drop cultures require high starting cell numbers, and are tedious for long-term maintenance. In this study, we generate stable, uniform multicellular spheroids using very small number of ovarian cancer cells in a novel 384 well hanging drop array platform. We used novel tumor spheroid platform and two ovarian cancer cell lines (A2780 and OVCAR3) to demonstrate the stable incorporation of as few as 10 cells into a single spheroid. Spheroids had uniform geometry, with projected areas (42.60×10(3)μm-475.22×10(3)μm(2) for A2780 spheroids and 37.24×10(3)μm(2)-281.01×10(3)μm(2) for OVCAR3 spheroids) that varied as a function of the initial cell seeding density. Phalloidin and nuclear stains indicated cells formed tightly packed spheroids with demarcated boundaries and cell-cell interaction within spheroids. Cells within spheroids demonstrated over 85% viability. 3D tumor spheroids demonstrated greater resistance (70-80% viability) to cisplatin chemotherapy compared to 2D cultures (30-50% viability). Ovarian cancer spheroids can be generated from limited cell numbers in high throughput 384 well plates with high viability. Spheroids demonstrate therapeutic resistance relative to cells in traditional 2D culture. Stable incorporation of low cell numbers is advantageous when translating this research to rare patient-derived cells. This system can be used to understand ovarian cancer spheroid biology, as well as carry out preclinical drug sensitivity assays. Copyright © 2015 Elsevier Inc. All rights reserved.

  1. Stellar population synthesis

    International Nuclear Information System (INIS)

    Pickles, A.J.

    1989-01-01

    The techniques used to derive astrophysically useful information from observations of the integrated light of composite stellar systems are briefly reviewed. A synthesis technique, designed to separate and describe on a standard system the competing effects of age and metallicity variations is introduced, and illustrated by its application to the study of the history of star formation in bright elliptical galaxies in clusters. (author)

  2. K-KIDS: The Imaging Survey for Stellar Companions at Solar System Scales Around More than 1000 K Dwarfs

    Science.gov (United States)

    Nusdeo, Daniel A.

    2018-01-01

    An initial sample of 1048 K dwarfs, hereafter known as the “K-KIDS” targets, was built from the Hipparcos and 2MASS catalogs in order to construct a robust list for a multiplicity survey. There have been two recent comprehensive stellar multiplicity surveys of low mass stars: Raghavan et. al. (2010) searched 454 solar-type stars and found a stellar multiplicity rate of 50%, and Winters et. al. (2017) surveyed 1121 M dwarfs and found a rate of 27%. A gap still remains in our understanding of the multiplicity rate of K dwarfs.For observational purposes, K-KIDS is confined equatorally to -30 < DEC < +30 to ensure that all stars are observable from either hemisphere, thereby creating a legacy sample that can be investigated for decades for stellar, brown dwarf, and planetary companions of various types. The RECONS team is conducting four companion surveys of these 1048 stars, including imaging surveys at various separations --- large (10+ arcseconds), medium (2–10 arcseconds), and small (0.02–2 arcseconds) --- and a radial velocity survey for the closest companions. Here we report on the small separation survey that targets scales similar to our Solar System, 0.1-100 AU, carried out using the Differential Speckle Survey Instrument on the Gemini and WIYN telescopes. To date, we have observed 964 out of 1048 systems, already finding 135 companions. We present a sample of K dwarf double stars with separations less than 100 AU, of which the vast majority are new discoveries. Further progress on the medium and large separation regimes ensures that a statistically significant stellar multiplicity rate for K dwarfs will soon be in achieved, which can then be investigated for dependences on, for example, stellar age and metallicity.This effort has been supported by the NSF through grant AST-1517413 and via observations obtained at the Gemini Observatory (North and South telescopes), which is operated by AURA under a cooperative agreement with the NSF on behalf of the

  3. S-TYPE AND P-TYPE HABITABILITY IN STELLAR BINARY SYSTEMS: A COMPREHENSIVE APPROACH. II. ELLIPTICAL ORBITS

    Energy Technology Data Exchange (ETDEWEB)

    Cuntz, M., E-mail: cuntz@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019-0059 (United States)

    2015-01-10

    In the first paper of this series, a comprehensive approach has been provided for the study of S-type and P-type habitable regions in stellar binary systems, which was, however, restricted to circular orbits of the stellar components. Fortunately, a modest modification of the method also allows for the consideration of elliptical orbits, which of course entails a much broader range of applicability. This augmented method is presented here, and numerous applications are conveyed. In alignment with Paper I, the selected approach considers a variety of aspects, which comprise the consideration of a joint constraint including orbital stability and a habitable region for a possible system planet through the stellar radiative energy fluxes ({sup r}adiative habitable zone{sup ;} RHZ). The devised method is based on a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are deduced for which kinds of systems S-type and P-type habitable zones are realized. If the RHZs are truncated by the additional constraint of orbital stability, the notation of ST-type and PT-type habitability applies. In comparison to the circular case, it is found that in systems of higher eccentricity, the range of the RHZs is significantly reduced. Moreover, for a considerable number of models, the orbital stability constraint also reduces the range of S-type and P-type habitability. Nonetheless, S-, P-, ST-, and PT-type habitability is identified for a considerable set of system parameters. The method as presented is utilized for BinHab, an online code available at The University of Texas at Arlington.

  4. S-TYPE AND P-TYPE HABITABILITY IN STELLAR BINARY SYSTEMS: A COMPREHENSIVE APPROACH. II. ELLIPTICAL ORBITS

    International Nuclear Information System (INIS)

    Cuntz, M.

    2015-01-01

    In the first paper of this series, a comprehensive approach has been provided for the study of S-type and P-type habitable regions in stellar binary systems, which was, however, restricted to circular orbits of the stellar components. Fortunately, a modest modification of the method also allows for the consideration of elliptical orbits, which of course entails a much broader range of applicability. This augmented method is presented here, and numerous applications are conveyed. In alignment with Paper I, the selected approach considers a variety of aspects, which comprise the consideration of a joint constraint including orbital stability and a habitable region for a possible system planet through the stellar radiative energy fluxes ( r adiative habitable zone ; RHZ). The devised method is based on a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are deduced for which kinds of systems S-type and P-type habitable zones are realized. If the RHZs are truncated by the additional constraint of orbital stability, the notation of ST-type and PT-type habitability applies. In comparison to the circular case, it is found that in systems of higher eccentricity, the range of the RHZs is significantly reduced. Moreover, for a considerable number of models, the orbital stability constraint also reduces the range of S-type and P-type habitability. Nonetheless, S-, P-, ST-, and PT-type habitability is identified for a considerable set of system parameters. The method as presented is utilized for BinHab, an online code available at The University of Texas at Arlington

  5. Experimental evidence for several spheroid growth mechanisms in the liquid-phase sintered tungsten-base composites

    International Nuclear Information System (INIS)

    Zukas, E.G.; Rogers, P.S.Z.; Rogers, R.S.

    1976-01-01

    The generally accepted mechanism for spheroid growth during sintering of tungsten-base composites in the presence of a liquid phase is the dissolution of the small spheroids with simultaneous precipitation of tungsten from the molten matrix onto the larger spheroids, the process being driven by the difference in surface energy between the larger and smaller spheroids. From theoretical considerations, the slope of the straight line of log diameter versus log time should be 1 / 3 for this process. The experimental evidence for the dissolution and reprecipitation mechanism is meager, being based primarily on the spheroid growth rate during the latter stages of liquid-phase sintering. Experimental evidence is presented that shows spheroid growth taking place in systems where the tungsten and the matrix are mutually insoluble thereby making dissolution and reprecipitation impossible. Furthermore, the results from these studies and others using the usual matrix compositions indicate that spheroid growth takes place predominantly by the combination or coalescence of two or more spheroids. Deposition of tungsten from the molten matrix also occurs, although not necessarily on spheroid surfaces which have the lowest surface energy. Thus, many mechanisms, each depending on temperature and other variables, operate simultaneously. A satisfactory theoretical treatment must include them all

  6. Stellar winds

    International Nuclear Information System (INIS)

    Weymann, R.J.

    1978-01-01

    It is known that a steady outflow of material at comparable rates of mass loss but vastly different speeds is now known to be ubiquitous phenomenon among both the luminous hot stars and the luminous but cool red giants. The flows are probably massive enough in both cases to give rise to significant effects on stellar evolution and the mass balance between stars and the interstellar medium. The possible mechanisms for these phenomena as well as the methods of observation used are described. In particular, the mass-loss processes in stars other than the sun that also involve a steady flow of matter are considered. The evidence for their existence is described, and then the question of whether the process thought to produce the solar wind is also responsible for producing these stellar winds is explored

  7. Supermassive Black Holes and Their Host Spheroids. I. Disassembling Galaxies

    Science.gov (United States)

    Savorgnan, G. A. D.; Graham, A. W.

    2016-01-01

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids large-scale, intermediate-scale, and nuclear disks bars rings spiral arms halos extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

  8. SUPERMASSIVE BLACK HOLES AND THEIR HOST SPHEROIDS. I. DISASSEMBLING GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Savorgnan, G. A. D.; Graham, A. W., E-mail: gsavorgn@astro.swin.edu.au [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122 (Australia)

    2016-01-15

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors.

  9. SUPERMASSIVE BLACK HOLES AND THEIR HOST SPHEROIDS. I. DISASSEMBLING GALAXIES

    International Nuclear Information System (INIS)

    Savorgnan, G. A. D.; Graham, A. W.

    2016-01-01

    Several recent studies have performed galaxy decompositions to investigate correlations between the black hole mass and various properties of the host spheroid, but they have not converged on the same conclusions. This is because their models for the same galaxy were often significantly different and not consistent with each other in terms of fitted components. Using 3.6 μm Spitzer imagery, which is a superb tracer of the stellar mass (superior to the K band), we have performed state-of-the-art multicomponent decompositions for 66 galaxies with directly measured black hole masses. Our sample is the largest to date and, unlike previous studies, contains a large number (17) of spiral galaxies with low black hole masses. We paid careful attention to the image mosaicking, sky subtraction, and masking of contaminating sources. After a scrupulous inspection of the galaxy photometry (through isophotal analysis and unsharp masking) and—for the first time—2D kinematics, we were able to account for spheroids; large-scale, intermediate-scale, and nuclear disks; bars; rings; spiral arms; halos; extended or unresolved nuclear sources; and partially depleted cores. For each individual galaxy, we compared our best-fit model with previous studies, explained the discrepancies, and identified the optimal decomposition. Moreover, we have independently performed one-dimensional (1D) and two-dimensional (2D) decompositions and concluded that, at least when modeling large, nearby galaxies, 1D techniques have more advantages than 2D techniques. Finally, we developed a prescription to estimate the uncertainties on the 1D best-fit parameters for the 66 spheroids that takes into account systematic errors, unlike popular 2D codes that only consider statistical errors

  10. Stellarator physics

    International Nuclear Information System (INIS)

    1990-07-01

    This document consists of the proceedings of the Seventh International Workshop on Stellarators, held in Oak Ridge, Tennessee, USA, 10-14 April, 1989. The document consists of a summary of presentations, an overview of experimental results, and papers presented at the workshop on transport, impurities and divertors, diagnostics, ECH confinement experiments, equilibrium and stability studies, RF heating, confinement, magnetic configurations, and new experiments. Refs, figs and tabs

  11. Identification of Lgr5-Independent Spheroid-Generating Progenitors of the Mouse Fetal Intestinal Epithelium

    Directory of Open Access Journals (Sweden)

    Roxana C. Mustata

    2013-10-01

    Full Text Available Immortal spheroids were generated from fetal mouse intestine using the culture system initially developed to culture organoids from adult intestinal epithelium. Spheroid proportion progressively decreases from fetal to postnatal period, with a corresponding increase in production of organoids. Like organoids, spheroids show Wnt-dependent indefinite self-renewing properties but display a poorly differentiated phenotype reminiscent of incompletely caudalized progenitors. The spheroid transcriptome is strikingly different from that of adult intestinal stem cells, with minimal overlap of Wnt target gene expression. The receptor LGR4, but not LGR5, is essential for their growth. Trop2/Tacstd2 and Cnx43/Gja1, two markers highly enriched in spheroids, are expressed throughout the embryonic-day-14 intestinal epithelium. Comparison of in utero and neonatal lineage tracing using Cnx43-CreER and Lgr5-CreERT2 mice identified spheroid-generating cells as developmental progenitors involved in generation of the prenatal intestinal epithelium. Ex vivo, spheroid cells have the potential to differentiate into organoids, qualifying as a fetal type of intestinal stem cell.

  12. Electron, proton, neutron as spheroidical particles

    International Nuclear Information System (INIS)

    Bagge, E.R.

    1993-01-01

    It is shown that it is possible to describe the electron and the proton at rest within the framework of Dirac's relativistic theory of particles as electro-magnetic stable, spheroidal particles like balloons with very thin envelopes. Their properties, especially their spins and their magnetic momenta, are exactly those, which have been measured at first and later on derived by Dirac. In this picture the neutron plays the role of a system of two concentric and synchronically rotating balloons with a small distance between them at a positive energetic minimum of balance at 1.26 MeV. The magnetic moment of this particle has a negative sign and is of the correct size. (orig.)

  13. The SPT+Herschel+ALMA+Spitzer Legacy Survey: The stellar content of high redshift strongly lensed systems

    Science.gov (United States)

    Vieira, Joaquin; Ashby, Matt; Carlstrom, John; Chapman, Scott; DeBreuck, Carlos; Fassnacht, Chris; Gonzalez, Anthony; Phadke, Kedar; Marrone, Dan; Malkan, Matt; Reuter, Cassie; Rotermund, Kaja; Spilker, Justin; Weiss, Axel

    2018-05-01

    The South Pole Telescope (SPT) has systematically identified 90 high-redshift strongly gravitationally lensed submillimeter galaxies (SMGs) in a 2500 square-degree cosmological survey of the millimeter (mm) sky. These sources are selected by their extreme mm flux, which is largely independent of redshift and lensing configuration. We are undertaking a comprehensive and systematic followup campaign to use these "cosmic magnifying glasses" to study the infrared background in unprecedented detail, inform the condition of the interstellar medium in starburst galaxies at high redshift, and place limits on dark matter substructure. Here we ask for 115.4 hours of deep Spitzer/IRAC imaging to complete our survey of 90 systems to a uniform depth of 30min integrations at 3.6um and 60min at 4.5um. In our sample of 90 systems, 16 have already been fully observed, 30 have been partially observed, and 44 have not been observed at all. Our immediate goals are to: 1) constrain the specific star formation rates of the background high-redshift submillimeter galaxies by combining these Spitzer observations with our APEX, Herschel, and ALMA data, 2) robustly determine the stellar masses and mass-to-light ratios of all the foreground lensing galaxies in the sample by combining these observations with our VLT and Gemini data, the Dark Energy Survey, and ALMA; and 3) provide complete, deep, and uniform NIR coverage of our entire sample of lensed systems to characterize the environments of high redshift SMGs, maximize the discovery potential for additional spectacular and rare sources, and prepare for JWST. This program will provide the cornerstone data set for two PhD theses: Kedar Phadke at Illinois will lead the analysis of stellar masses for the background SMGs, and Kaja Rotermund at Dalhousie will lead the analysis of stellar masses for the foreground lenses.

  14. Spatio-temporal cell dynamics in tumour spheroid irradiation

    International Nuclear Information System (INIS)

    Kempf, H.; Bleicher, M.; Meyer-Hermann, M.; Kempf, H.; Bleicher, M.; Kempf, H.; Meyer-Hermann, M.

    2010-01-01

    Multicellular tumour spheroids are realistic in vitro systems in radiation research that integrate cell-cell interaction and cell cycle control by factors in the medium. The dynamic reaction inside a tumour spheroid triggered by radiation is not well understood. Of special interest is the amount of cell cycle synchronization which could be triggered by irradiation, since this would allow follow-up irradiations to exploit the increased sensitivity of certain cell cycle phases. In order to investigate these questions we need to support irradiation experiments with mathematical models. In this article a new model is introduced combining the dynamics of tumour growth and irradiation treatments. The tumour spheroid growth is modelled using an agent-based Delaunay/Voronoi hybrid model in which the cells are represented by weighted dynamic vertices. Cell properties like full cell cycle dynamics are included. In order to be able to distinguish between different cell reactions in response to irradiation quality we introduce a probabilistic model for damage dynamics. The overall cell survival from this model is in agreement with predictions from the linear-quadratic model. Our model can describe the growth of avascular tumour spheroids in agreement to experimental results. Using the probabilistic model for irradiation damage dynamics the classic 'four Rs' of radiotherapy can be studied in silico. We found a pronounced reactivation of the tumour spheroid in response to irradiation. A majority of the surviving cells is synchronized in their cell cycle progression after irradiation. The cell synchronization could be actively triggered and should be exploited in an advanced fractionation scheme. Thus it has been demonstrated that our model could be used to understand the dynamics of tumour growth after irradiation and to propose optimized fractionation schemes in cooperation with experimental investigations. (authors)

  15. Relativistic stellar dynamics

    International Nuclear Information System (INIS)

    Contopoulos, G.

    1983-01-01

    In this paper, three main areas of relativistic stellar dynamics are reviewed: (a) The dynamics of clusters, or nuclei of galaxies, of very high density; (b) The dynamics of systems containing a massive black hole; and (c) The dynamics of particles (and photons) in an expanding Universe. The emphasis is on the use of orbit perturbations. (Auth.)

  16. Supermassive Black Holes and their Host Spheroids III. The Mbh-nsph Correlation

    Science.gov (United States)

    Savorgnan, Giulia A. D.

    2016-04-01

    The Sérsic {R}1/n model is the best approximation known to date for describing the light distribution of stellar spheroidal and disk components, with the Sérsic index n providing a direct measure of the central radial concentration of stars. The Sérsic index of a galaxy’s spheroidal component, nsph, has been shown to tightly correlate with the mass of the central supermassive black hole, MBH. The {M}{BH}{--}{n}{sph} correlation is also expected from other two well known scaling relations involving the spheroid luminosity, Lsph: the {L}{sph}{--}{n}{sph} and the {M}{BH}{--}{L}{sph}. Obtaining an accurate estimate of the spheroid Sérsic index requires a careful modeling of a galaxy’s light distribution and some studies have failed to recover a statistically significant {M}{BH}{--}{n}{sph} correlation. With the aim of re-investigating the {M}{BH}{--}{n}{sph} and other black hole mass scaling relations, we performed a detailed (I.e., bulge, disks, bars, spiral arms, rings, halo, nucleus, etc.) decomposition of 66 galaxies, with directly measured black hole masses, that had been imaged at 3.6 μm with Spitzer. In this paper, the third of this series, we present an analysis of the {L}{sph}{--}{n}{sph} and {M}{BH}{--}{n}{sph} diagrams. While early-type (elliptical+lenticular) and late-type (spiral) galaxies split into two separate relations in the {L}{sph}{--}{n}{sph} and {M}{BH}{--}{L}{sph} diagrams, they reunite into a single {M}{BH}\\propto {n}{sph}3.39+/- 0.15 sequence with relatively small intrinsic scatter (ɛ ≃ 0.25 {dex}). The black hole mass appears to be closely related to the spheroid central concentration of stars, which mirrors the inner gradient of the spheroid gravitational potential.

  17. Results from the Splash Survey: Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo

    Science.gov (United States)

    Guhathakurta, Puragra; SPLASH Collaboration

    2009-01-01

    Detailed studies of nearby galaxies provide vital clues about their formation and evolutionary history. This "fossil record" approach is complementary to direct look-back studies of distant galaxies. Our Galaxy and the Andromeda spiral galaxy (M31) have long been cornerstones in the former category. M31 provides an external perspective on a large galaxy similar to our own and yet is close enough to allow detailed studies of individual stars. In my talk, I will present results from the SPLASH collaboration: Spectroscopic and Photometric Landscape of Andromeda's Stellar Halo. The collective data set from this large international team includes thousands of Keck/DEIMOS spectra of individual red giant branch stars, ground-based deep wide-field imaging and photometry with KPNO/Mosaic, CFHT/MegaCam, and Subaru/Suprime-Cam, and ultra-deep pencil-beam probes with HST/ACS imaging reaching below the main-sequence turnoff. Our recent discovery of an extended stellar halo in M31 (R > 150 kpc) shows that most previous studies of its spheroid have been sampling its inner bulge-like spheroidal component, not its halo. In my talk I will touch upon several related topics related to the general theme of hierarchical galaxy formation including: M31's global structure and subcomponents (halo, bulge/central bar, and disk), stellar dynamics, statistical properties of substructure, detailed chemical abundance measurements, detailed forensic reconstruction of recent collision events, dwarf satellites as tracers and building blocks of larger galaxies, and empirical constraints on the tangential motion of the M31 system. I will also discuss recent results on the chemical abundance of the lowest luminosity Galactic satellites (recently discovered by SDSS) and implications for the formation of the Milky Way halo. This research was supported by funds from the National Science Foundation, NASA, and the Institute for Geophysics and Planetary Physics.

  18. Translation and rotation of a porous spheroid in a spheroidal container

    International Nuclear Information System (INIS)

    Saad, E.I.

    2010-01-01

    The flow problem of an incompressible axisymmetrical quasisteady translation and steady rotation of a porous spheroid in a concentric spheroidal container are studied analytically. The same small departure from a sphere is considered for each spheroidal surface. In the limit of small Reynolds number, the Brinkman equation for the flow inside the porous region and the Stokes equation for the outside region in their stream functions formulations and velocity components, which are proportional to the translational and angular velocities, respectively, are used. Explicit expressions are obtained for both inside and outside flow fields to the first order in a small parameter characterizing the deformation of the spheroidal surface from the spherical shape. The hydrodynamic drag force and couple exerted on the porous spheroid are obtained for the special cases of prolate and oblate spheroids in closed forms. The dependence of the normalized wall-corrected translational and rotational mobilities on permeability for a porous spheroid in an unbounded medium and for a solid spheroid in a cell on the particle volume fraction is discussed numerically and graphically for various values of the deformation parameter. In the limiting cases, the analytical solutions describing the drag force and torque or mobilities for a porous spheroid in the spheroidal vessel reduce to those for a solid sphere and for a porous sphere in a spherical cell. (author)

  19. OGLE-ing the Magellanic system: stellar populations in the Magellanic Bridge

    International Nuclear Information System (INIS)

    Skowron, D. M.; Jacyszyn, A. M.; Udalski, A.; Szymański, M. K.; Skowron, J.; Poleski, R.; Kozłowski, S.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Mróz, P.; Pietrukowicz, P.; Ulaczyk, K.; Wyrzykowski, Ł.

    2014-01-01

    We report the discovery of a young stellar bridge that forms a continuous connection between the Magellanic Clouds. This finding is based on number density maps for stellar populations found in data gathered by OGLE-IV that fully cover over 270 deg 2 of the sky in the Magellanic Bridge area. This is the most extensive optical survey of this region to date. We find that the young population is present mainly in the western half of the MBR, which, together with the newly discovered young population in the eastern Bridge, form a continuous stream of stars connecting both galaxies along δ ∼ –73.5 deg. The young population distribution is clumped, with one of the major densities close to the SMC and the other fairly isolated and located approximately mid-way between the Clouds, which we call the OGLE island. These overdensities are well matched by H I surface density contours, although the newly found young population in the eastern Bridge is offset by ∼2 deg north from the highest H I density contour. We observe a continuity of red clump stars between the Magellanic Clouds which represent an intermediate-age population. Red clump stars are present mainly in the southern and central parts of the Magellanic Bridge, below its gaseous part, and their presence is reflected by a strong deviation from the radial density profiles of the two galaxies. This may indicate either a tidal stream of stars, or that the stellar halos of the two galaxies overlap. On the other hand, we do not observe such an overlap within an intermediate-age population represented by the top of the red giant branch and the asymptotic giant branch stars. We also see only minor mixing of the old populations of the Clouds in the southern part of the Bridge, represented by the lowest part of the red giant branch.

  20. OGLE-ing the Magellanic system: stellar populations in the Magellanic Bridge

    Energy Technology Data Exchange (ETDEWEB)

    Skowron, D. M.; Jacyszyn, A. M.; Udalski, A.; Szymański, M. K.; Skowron, J.; Poleski, R.; Kozłowski, S.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Mróz, P.; Pietrukowicz, P.; Ulaczyk, K.; Wyrzykowski, Ł., E-mail: dszczyg@astrouw.edu.pl [Warsaw University Astronomical Observatory, Aleje Ujazdowskie 4, 00-478 Warszawa (Poland)

    2014-11-10

    We report the discovery of a young stellar bridge that forms a continuous connection between the Magellanic Clouds. This finding is based on number density maps for stellar populations found in data gathered by OGLE-IV that fully cover over 270 deg{sup 2} of the sky in the Magellanic Bridge area. This is the most extensive optical survey of this region to date. We find that the young population is present mainly in the western half of the MBR, which, together with the newly discovered young population in the eastern Bridge, form a continuous stream of stars connecting both galaxies along δ ∼ –73.5 deg. The young population distribution is clumped, with one of the major densities close to the SMC and the other fairly isolated and located approximately mid-way between the Clouds, which we call the OGLE island. These overdensities are well matched by H I surface density contours, although the newly found young population in the eastern Bridge is offset by ∼2 deg north from the highest H I density contour. We observe a continuity of red clump stars between the Magellanic Clouds which represent an intermediate-age population. Red clump stars are present mainly in the southern and central parts of the Magellanic Bridge, below its gaseous part, and their presence is reflected by a strong deviation from the radial density profiles of the two galaxies. This may indicate either a tidal stream of stars, or that the stellar halos of the two galaxies overlap. On the other hand, we do not observe such an overlap within an intermediate-age population represented by the top of the red giant branch and the asymptotic giant branch stars. We also see only minor mixing of the old populations of the Clouds in the southern part of the Bridge, represented by the lowest part of the red giant branch.

  1. DISCOVERY OF MIRA VARIABLE STARS IN THE METAL-POOR SEXTANS DWARF SPHEROIDAL GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, Tsuyoshi [Japan Spaceguard Association, 1716-3 Ookura, Bisei, Ibara, Okayama 714-1411 (Japan); Matsunaga, Noriyuki; Nakada, Yoshikazu [Kiso Observatory, Institute of Astronomy, School of Science, University of Tokyo, 10762-30 Mitake, Kiso-machi, Kiso-gun, Nagano 397-0101 (Japan); Hasegawa, Takashi, E-mail: sakamoto@spaceguard.or.jp [Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma, Gunma 377-0702 (Japan)

    2012-12-10

    We report the discovery of two Mira variable stars (Miras) toward the Sextans dwarf spheroidal galaxy (dSph). We performed optical long-term monitoring observations for two red stars in the Sextans dSph. The light curves of both stars in the I{sub c} band show large-amplitude (3.7 and 0.9 mag) and long-period (326 {+-} 15 and 122 {+-} 5 days) variations, suggesting that they are Miras. We combine our own infrared data with previously published data to estimate the mean infrared magnitudes. The distances obtained from the period-luminosity relation of the Miras (75.3{sup +12.8}{sub -10.9} and 79.8{sup +11.5}{sub -9.9} kpc, respectively), together with the radial velocities available, support memberships of the Sextans dSph (90.0 {+-} 10.0 kpc). These are the first Miras found in a stellar system with a metallicity as low as [Fe/H] {approx} -1.9 than any other known system with Miras.

  2. The stellar and solar tracking system of the Geneva Observatory gondola

    Science.gov (United States)

    Huguenin, D.

    1974-01-01

    Sun and star trackers have been added to the latest version of the Geneva Observatory gondola. They perform an image motion compensation with an accuracy of plus or minus 1 minute of arc. The structure is held in the vertical position by gravity; the azimuth is controlled by a torque motor in the suspension bearing using solar or geomagnetic references. The image motion compensation is performed by a flat mirror, located in front of the telescope, controlled by pitch and yaw servo-loops. Offset pointing is possible within the solar disc and in a 3 degree by 3 degree stellar field. A T.V. camera facilitates the star identification and acquisition.

  3. Vacuum magnetic field and modular coil system of the advanced stellarator Wendelstein VII-AS

    International Nuclear Information System (INIS)

    Rau, F.; Kisslinger, J.; Wobig, H.

    1982-06-01

    The vacuum field and the modular coils of the advanced stellarator WENDELSTEIN VII-AS are described. Each of the five field periods contains 9 different twisted coils, one of them with increased dimensions and current in order to provide sufficient access. The standard vacuum field configuration (B=3 T, t=0.39, aspect ratio approx. equal to 10, low shear, and magnetic well) can be varied by toroidal and vertical fields, or by changing independently the current in the large special coils. From a study of magnetic field perturbations some estimates are derived for the admissible coil tolerances. (orig.)

  4. Charged fluid distribution in higher dimensional spheroidal space-time

    Indian Academy of Sciences (India)

    associated 3-spaces obtained as hypersurfaces t = constant, 3-spheroids, are suit- ... pressure. Considering the Vaidya–Tikekar [12] spheroidal geometry, ... a relativistic star in hydrostatic equilibrium having the spheroidal geometry of the .... K = 1, the spheroidal 3-space degenerates into a flat 3-space and when K = 0 it.

  5. Stellar evolution

    CERN Document Server

    Meadows, A J

    2013-01-01

    Stellar Evolution, Second Edition covers the significant advances in the understanding of birth, life, and death of stars.This book is divided into nine chapters and begins with a description of the characteristics of stars according to their brightness, distance, size, mass, age, and chemical composition. The next chapters deal with the families, structure, and birth of stars. These topics are followed by discussions of the chemical composition and the evolution of main-sequence stars. A chapter focuses on the unique features of the sun as a star, including its evolution, magnetic fields, act

  6. System for data acquisition and processing on the base of the minicomputers and CAMAC interfaces in the experiments on the L-2 stellarator

    International Nuclear Information System (INIS)

    Blokh, M.A.; Kamolova, T.I.; Kutsenko, A.V.; Kutsenko, V.A.; Nechaev, YU.I.; Fedyanin, O.I.; Shelobkov, V.I.

    1983-01-01

    The system for data acquisition and processing intended for automation of experiments on the L-2 stellarator is described. Hardware peculiarities and sofrware flowsheet are considered. The system is realized on the base of the TRAI minicomputer and CAMAC modules. The system provides data input from diagnostic sensors into the computer memory during the stellarator operational pulse and preliminary data processing in the interval between stellarator pulses, putout of the results a display device or a printer. For programming the Focal language is chosen. CAMAC module control and organization of the whole numbers massive for experimental data storage is realized by means of new functions written in Assembler. The system successfully operates since 1976. In 1978 the system is switched on through the CAMAC interfaces to the EC computer in order to provide the long-term information storage

  7. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid

    OpenAIRE

    Mitri, F. G.

    2015-01-01

    Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (\\theta = \\pi) in the near-field an...

  8. Theory of electrostatic fluid modes in a cold spheroidal non-neutral plasma

    International Nuclear Information System (INIS)

    Dubin, D.H.E.

    1991-01-01

    The normal modes of a magnetized spheroidally shaped pure ion plasma have recently been measured. Here the theory of these modes is presented. Although one might expect that a numerical solution is required (because the plasma dielectric is anisotropic and the plasma is inhomogeneous), the problem is actually separable in an unusual coordinate system. The result is a simple electrostatic fluid dispersion relation for modes in a cloud of any spheroidal shape

  9. Transmission lines and launching systems for ECRH on the garching stellarators W VIIa and W VII-AS

    International Nuclear Information System (INIS)

    Thumm, M.; Janzen, G.; Mueller, G.; Schueller, P.G.; Wilhelm, R.; Erckmann, V.

    1983-01-01

    The transmission lines and launching systems for non ohmic plasma production and heating by ECR-waves at 28 GHz (200 kW, 40 ms) and 70 GHz (200 kW, 100 ms) in the Garching Wendelstein Stellarator W VIIa and at 70 GHz (800 kW, cw) in the future Advanced Stellarator W VII-AS are described. The ECRH systems meet the requirements for neutral gas breakdown (R-wave), heating of a cold plasma (X-mode) and heating of a warm plasma (0-mode) in a combined way. Periodically modulated wall mode converters (sinusoidal m=0 radius modulation, a 0 =31.75 mm at 28 GHz, a 0 =13.9 mm at 70 GHz) convert the circular electric TE/sub on/ gyrotron output mode mixture (mainly TE 02 mode) into a pure TE 01 wave which is used for the long distance transmission in smooth overmoded waveguides (I.D. = 63.5 mm). At the converter inputs the phases between the TE/sub on/ modes are matched by phase shifters. The measured conversion efficiency for characteristic mode mixtures (TE 02 /TE 01 /TE 03 ) at 28 GHz is about 98 %. For the geometrical and electrical matching of different waveguide diameters waveguide tapers with approximate Tschebycheff mode-conversion responses are used

  10. S-type and P-type habitability in stellar binary systems: A comprehensive approach. I. Method and applications

    Energy Technology Data Exchange (ETDEWEB)

    Cuntz, M., E-mail: cuntz@uta.edu [Department of Physics, University of Texas at Arlington, Arlington, TX 76019-0059 (United States)

    2014-01-01

    A comprehensive approach is provided for the study of both S-type and P-type habitability in stellar binary systems, which in principle can also be expanded to systems of higher order. P-type orbits occur when the planet orbits both binary components, whereas in the case of S-type orbits, the planet orbits only one of the binary components with the second component considered a perturbator. The selected approach encapsulates a variety of different aspects, which include: (1) the consideration of a joint constraint, including orbital stability and a habitable region for a putative system planet through the stellar radiative energy fluxes ({sup r}adiative habitable zone{sup ;} RHZ), needs to be met; (2) the treatment of conservative, general, and extended zones of habitability for the various systems as defined for the solar system and beyond; (3) the provision of a combined formalism for the assessment of both S-type and P-type habitability; in particular, mathematical criteria are presented for the kind of system in which S-type and P-type habitability is realized; (4) applications of the attained theoretical approach to standard (theoretical) main-sequence stars. In principle, five different cases of habitability are identified, which are S-type and P-type habitability provided by the full extent of the RHZs; habitability, where the RHZs are truncated by the additional constraint of planetary orbital stability (referred to as ST- and PT-type, respectively); and cases of no habitability at all. Regarding the treatment of planetary orbital stability, we utilize the formulae of Holman and Wiegert as also used in previous studies. In this work, we focus on binary systems in circular orbits. Future applications will also consider binary systems in elliptical orbits and provide thorough comparisons to other methods and results given in the literature.

  11. MEASURING DARK MATTER PROFILES NON-PARAMETRICALLY IN DWARF SPHEROIDALS: AN APPLICATION TO DRACO

    International Nuclear Information System (INIS)

    Jardel, John R.; Gebhardt, Karl; Fabricius, Maximilian H.; Williams, Michael J.; Drory, Niv

    2013-01-01

    We introduce a novel implementation of orbit-based (or Schwarzschild) modeling that allows dark matter density profiles to be calculated non-parametrically in nearby galaxies. Our models require no assumptions to be made about velocity anisotropy or the dark matter profile. The technique can be applied to any dispersion-supported stellar system, and we demonstrate its use by studying the Local Group dwarf spheroidal galaxy (dSph) Draco. We use existing kinematic data at larger radii and also present 12 new radial velocities within the central 13 pc obtained with the VIRUS-W integral field spectrograph on the 2.7 m telescope at McDonald Observatory. Our non-parametric Schwarzschild models find strong evidence that the dark matter profile in Draco is cuspy for 20 ≤ r ≤ 700 pc. The profile for r ≥ 20 pc is well fit by a power law with slope α = –1.0 ± 0.2, consistent with predictions from cold dark matter simulations. Our models confirm that, despite its low baryon content relative to other dSphs, Draco lives in a massive halo.

  12. Bar-spheroid interaction in galaxies

    Science.gov (United States)

    Hernquist, Lars; Weinberg, Martin D.

    1992-01-01

    N-body simulation and linear analysis is employed to investigate the secular evolution of barred galaxies, with emphasis on the interaction between bars and spheroidal components of galaxies. This interaction is argued to drive secular transfer of angular momentum from bars to spheroids, primarily through resonant coupling. A moderately strong bar, having mass within corotation about 0.3 times the enclosed spheroid mass, is predicted to shed all its angular momentum typically in less than about 10 exp 9 yr. Even shorter depletion time scales are found for relatively more massive bars. It is suggested either that spheroids around barred galaxies are structured so as to inhibit strong coupling with bars, or that bars can form by unknown processes long after disks are established. The present models reinforce the notion that bars can drive secular evolution in galaxies.

  13. Plasma spheroidization and cladding of powders

    Energy Technology Data Exchange (ETDEWEB)

    Petrunichev, V.A.; Averin, V.V.; Sorokin, L.M.; Koroleva, E.B.

    1987-02-01

    With reference to experimental results for nickel and chromium alloys, it is shown that complex alloy powders can be spheroidized in plasma discharges using an argon plasma with hydrogen. The spheroidizing process is accompanied by the reduction of surface oxides, with uniform element distribution within the particles; the granulometric composition of the particles is preserved. It is also shown that plasma technology can be used for producing metal-clad oxide and carbide powders, which improve the performance of cermets and coatings.

  14. A possible formation scenario for dwarf spheroidal galaxies - III. Adding star formation histories to the fiducial model

    Science.gov (United States)

    Alarcón Jara, A. G.; Fellhauer, M.; Matus Carrillo, D. R.; Assmann, P.; Urrutia Zapata, F.; Hazeldine, J.; Aravena, C. A.

    2018-02-01

    Dwarf spheroidal galaxies are regarded as the basic building blocks in the formation of larger galaxies and are the most dark matter dominated systems in the Universe, known so far. There are several models that attempt to explain their formation and evolution, but they have problems modelling the formation of isolated dwarf spheroidal galaxies. Here, we will explain a possible formation scenario in which star clusters form inside the dark matter halo of a dwarf spheroidal galaxy. These star clusters suffer from low star formation efficiency and dissolve while orbiting inside the dark matter halo. Thereby, they build the faint luminous components that we observe in dwarf spheroidal galaxies. In this paper, we study this model by adding different star formation histories to the simulations and compare the results with our previous work and observational data to show that we can explain the formation of dwarf spheroidal galaxies.

  15. Unsuccessful mitosis in multicellular tumour spheroids.

    Science.gov (United States)

    Molla, Annie; Couvet, Morgane; Coll, Jean-Luc

    2017-04-25

    Multicellular spheroids are very attractive models in oncology because they mimic the 3D organization of the tumour cells with their microenvironment. We show here using 3 different cell types (mammary TSA/pc, embryonic kidney Hek293 and cervical cancer HeLa), that when the cells are growing as spheroids the frequency of binucleated cells is augmented as occurs in some human tumours.We therefore describe mitosis in multicellular spheroids by following mitotic markers and by time-lapse experiments. Chromosomes alignment appears to be correct on the metaphasic plate and the passenger complex is well localized on centromere. Moreover aurora kinases are fully active and histone H3 is phosphorylated on Ser 10. Consequently, the mitotic spindle checkpoint is satisfied and, anaphase proceeds as illustrated by the transfer of survivin on the spindle and by the segregation of the two lots of chromosomes. However, the segregation plane is not well defined and oscillations of the dividing cells are observed. Finally, cytokinesis fails and the absence of separation of the two daughter cells gives rise to binucleated cells.Division orientation is specified during interphase and persists throughout mitosis. Our data indicate that the cancer cells, in multicellular spheroids, lose their ability to regulate their orientation, a feature commonly encountered in tumours.Moreover, multicellular spheroid expansion is still sensitive to mitotic drugs as pactlitaxel and aurora kinase inhibitors. The spheroids thus represent a highly relevant model for studying drug efficiency in tumours.

  16. Mass transfer inside oblate spheroidal solids: modelling and simulation

    Directory of Open Access Journals (Sweden)

    J. E. F. Carmo

    2008-03-01

    Full Text Available A numerical solution of the unsteady diffusion equation describing mass transfer inside oblate spheroids, considering a constant diffusion coefficient and the convective boundary condition, is presented. The diffusion equation written in the oblate spheroidal coordinate system was used for a two-dimensional case. The finite-volume method was employed to discretize the basic equation. The linear equation set was solved iteratively using the Gauss-Seidel method. As applications, the effects of the Fourier number, the Biot number and the aspect ratio of the body on the drying rate and moisture content during the process are presented. To validate the methodology, results obtained in this work are compared with analytical results of the moisture content encountered in the literature and good agreement was obtained. The results show that the model is consistent and it may be used to solve cases such as those that include disks and spheres and/or those with variable properties with small modifications.

  17. CHEMODYNAMICS OF COMPACT STELLAR SYSTEMS IN NGC 5128: HOW SIMILAR ARE GLOBULAR CLUSTERS, ULTRA-COMPACT DWARFS, AND DWARF GALAXIES?

    International Nuclear Information System (INIS)

    Taylor, Matthew A.; Puzia, Thomas H.; Harris, Gretchen L.; Harris, William E.; Kissler-Patig, Markus; Hilker, Michael

    2010-01-01

    Velocity dispersion measurements are presented for several of the most luminous globular clusters (GCs) in NGC 5128 (Centaurus A) derived from high-resolution spectra obtained with the UVES echelle spectrograph on the 8.2 m ESO/Very Large Telescope. The measurements are made utilizing a penalized pixel-fitting method that parametrically recovers line-of-sight velocity dispersions. Combining the measured velocity dispersions with surface photometry and structural parameter data from the Hubble Space Telescope enables both dynamical masses and mass-to-light ratios to be derived. The properties of these massive stellar systems are similar to those of both massive GCs contained within the Local Group and nuclear star clusters and ultra-compact dwarf galaxies (UCDs). The fundamental plane relations of these clusters are investigated in order to fill the apparent gap between the relations of Local Group GCs and more massive early-type galaxies. It is found that the properties of these massive stellar systems match those of nuclear clusters in dwarf elliptical galaxies and UCDs better than those of Local Group GCs, and that all objects share similarly old (∼>8 Gyr) ages, suggesting a possible link between the formation and evolution of nuclear star clusters in dwarf elliptical galaxies (dE,Ns), UCDs, and massive GCs. We find a very steep correlation between dynamical mass-to-light ratio and dynamical mass of the form Υ V dyn ∝ M dyn 0.24±0.02 above M dyn ∼ 2x10 6 M sun . Formation scenarios are investigated with a chemical abundance analysis using absorption-line strengths calibrated to the Lick/IDS index system. The results lend support to two scenarios contained within a single general formation scheme. Old, massive, super-solar [α/Fe] systems are formed on short (∼ 13 -10 15 M sun potential wells of massive galaxies and galaxy clusters.

  18. Radioresistance of human glioma spheroids and expression of HSP70, p53 and EGFr

    International Nuclear Information System (INIS)

    Fedrigo, Carlos A; Rocha, Adriana B da; Grivicich, Ivana; Schunemann, Daniel P; Chemale, Ivan M; Santos, Daiane dos; Jacovas, Thais; Boschetti, Patryck S; Jotz, Geraldo P; Filho, Aroldo Braga

    2011-01-01

    Radiation therapy is routinely prescribed for high-grade malignant gliomas. However, the efficacy of this therapeutic modality is often limited by the occurrence of radioresistance, reflected as a diminished susceptibility of the irradiated cells to undergo cell death. Thus, cells have evolved an elegant system in response to ionizing radiation induced DNA damage, where p53, Hsp70 and/or EGFr may play an important role in the process. In the present study, we investigated whether the content of p53, Hsp70 and EGFr are associated to glioblastoma (GBM) cell radioresistance. Spheroids from U-87MG and MO59J cell lines as well as spheroids derived from primary culture of tumor tissue of one GBM patient (UGBM1) were irradiated (5, 10 and 20 Gy), their relative radioresistance were established and the p53, Hsp70 and EGFr contents were immunohistochemically determined. Moreover, we investigated whether EGFr-phospho-Akt and EGFr-MEK-ERK pathways can induce GBM radioresistance using inhibitors of activation of ERK (PD098059) and Akt (wortmannin). At 5 Gy irradiation UGBM1 and U-87MG spheroids showed growth inhibition whereas the MO59J spheroid was relatively radioresistant. Overall, no significant changes in p53 and Hsp70 expression were found following 5 Gy irradiation treatment in all spheroids studied. The only difference observed in Hsp70 content was the periphery distribution in MO59J spheroids. However, 5 Gy treatment induced a significant increase on the EGFr levels in MO59J spheroids. Furthermore, treatment with inhibitors of activation of ERK (PD098059) and Akt (wortmannin) leads to radiosensitization of MO59J spheroids. These results indicate that the PI3K-Akt and MEK-ERK pathways triggered by EGFr confer GBM radioresistance

  19. Imaging Herpes Simplex Virus Type 1 Amplicon Vector–Mediated Gene Expression in Human Glioma Spheroids

    Directory of Open Access Journals (Sweden)

    Christine Kaestle

    2011-05-01

    Full Text Available Vectors derived from herpes simplex virus type 1 (HSV-1 have great potential for transducing therapeutic genes into the central nervous system; however, inefficient distribution of vector particles in vivo may limit their therapeutic potential in patients with gliomas. This study was performed to investigate the extent of HSV-1 amplicon vector–mediated gene expression in a three-dimensional glioma model of multicellular spheroids by imaging highly infectious HSV-1 virions expressing green fluorescent protein (HSV-GFP. After infection or microscopy-guided vector injection of glioma spheroids at various spheroid sizes, injection pressures and injection times, the extent of HSV-1 vector–mediated gene expression was investigated via laser scanning microscopy. Infection of spheroids with HSV-GFP demonstrated a maximal depth of vector-mediated GFP expression at 70 to 80 μm. A > 80% transduction efficiency was reached only in small spheroids with a diameter of 90%. The results demonstrated that vector-mediated gene expression in glioma spheroids was strongly dependent on the mode of vector application—injection pressure and injection time being the most important parameters. The assessment of these vector application parameters in tissue models will contribute to the development of safe and efficient gene therapy protocols for clinical application.

  20. LUT REVEALS AN ALGOL-TYPE ECLIPSING BINARY WITH THREE ADDITIONAL STELLAR COMPANIONS IN A MULTIPLE SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, L.-Y.; Zhou, X.; Qian, S.-B.; Li, L.-J.; Liao, W.-P.; Tian, X.-M.; Wang, Z.-H. [Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China); Hu, J.-Y., E-mail: zhuly@ynao.ac.cn [National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing (China)

    2016-04-15

    A complete light curve of the neglected eclipsing binary Algol V548 Cygni in the UV band was obtained with the Lunar-based Ultraviolet Telescope in 2014 May. Photometric solutions are obtained using the Wilson–Devinney method. It is found that solutions with and without third light are quite different. The mass ratio without third light is determined to be q = 0.307, while that derived with third light is q = 0.606. It is shown that V548 Cygni is a semi-detached binary where the secondary component is filling the critical Roche lobe. An analysis of all available eclipse times suggests that there are three cyclic variations in the O–C diagram that are interpreted by the light travel-time effect via the presence of three additional stellar companions. This is in agreement with the presence of a large quantity of third light in the system. The masses of these companions are estimated as m sin i′ ∼ 1.09, 0.20, and 0.52 M{sub ⊙}. They are orbiting the central binary with orbital periods of about 5.5, 23.3, and 69.9 years, i.e., in 1:4:12 resonance orbit. Their orbital separations are about 4.5, 13.2, and 26.4 au, respectively. Our photometric solutions suggest that they contribute about 32.4% to the total light of the multiple system. No obvious long-term changes in the orbital period were found, indicating that the contributions of the mass transfer and the mass loss due to magnetic braking to the period variations are comparable. The detection of three possible additional stellar components orbiting a typical Algol in a multiple system make V548 Cygni a very interesting binary to study in the future.

  1. Towards a measurement of the half-life of {sup 60}Fe for stellar and early Solar System models

    Energy Technology Data Exchange (ETDEWEB)

    Ostdiek, K.; Anderson, T. [University of Notre Dame, Notre Dame, IN 46556 (United States); Bauder, W. [University of Notre Dame, Notre Dame, IN 46556 (United States); Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Bowers, M.; Collon, P. [University of Notre Dame, Notre Dame, IN 46556 (United States); Dressler, R. [Paul Scherrer Institute – Laboratory for Radiochemistry and Environmental Chemistry, 5232 Villigen (Switzerland); Greene, J. [Argonne National Laboratory, 9700 South Cass Avenue, Lemont, IL 60439 (United States); Kutschera, W. [Vienna Environmental Research Accelerator Laboratory, Waehringer Strasse 17, 1090 Vienna (Austria); Lu, W. [University of Notre Dame, Notre Dame, IN 46556 (United States); Paul, M. [Racah Institute of Physics, Hebrew University, Jerusalem 91904 (Israel); Robertson, D. [University of Notre Dame, Notre Dame, IN 46556 (United States); Schumann, D. [Paul Scherrer Institute – Laboratory for Radiochemistry and Environmental Chemistry, 5232 Villigen (Switzerland); Skulski, M. [University of Notre Dame, Notre Dame, IN 46556 (United States); Wallner, A. [The Australian National University, Canberra, ACT 0200 (Australia)

    2015-10-15

    Radioisotopes, produced in stars and ejected into the Interstellar Medium, are important for constraining stellar and early Solar System (ESS) models. In particular, the half-life of the radioisotope, {sup 60}Fe, can have an impact on calculations for the timing for ESS events, the distance to nearby Supernovae, and the brightness of individual, non-steady-state {sup 60}Fe gamma ray sources in the Galaxy. A half-life measurement has been undertaken at the University of Notre Dame and measurements of the {sup 60}Fe/{sup 56}Fe concentration of our samples using Accelerator Mass Spectrometry has begun. This result will be coupled with an activity measurement of the isomeric decay in {sup 60}Co, which is the decay product of {sup 60}Fe. Preliminary half-life estimates of (2.53 ± 0.24) × 10{sup 6} years seem to confirm the recent measurement by Rugel et al. (2009).

  2. The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies

    OpenAIRE

    Kirby, Evan N.; Cohen, Judith G.; Guhathakurta, Puragra; Cheng, Lucy; Bullock, James S.; Gallazzi, Anna

    2013-01-01

    We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same massmetallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z * σ M * 0.30±0. 02 . The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar massstellar metallicity relation for galaxies as massive asM*...

  3. On the swimming motion of spheroidal magnetotactic bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Cui Zhen; Kong Dali; Zhang Keke [Department of Mathematical Sciences, University of Exeter, Exeter EX4 4QF (United Kingdom); Pan Yongxin, E-mail: kzhang@ex.ac.uk [Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing (China)

    2012-10-15

    We investigate, via both theoretical and experimental methods, the swimming motion of magnetotactic bacteria having the shape of an elongated prolate spheroid in a viscous liquid under the influence of an imposed magnetic field. A fully three-dimensional Stokes flow, driven by the translation and rotation of a swimming bacterium, exerts a complicated viscous drag/torque on the motion of a non-spherical bacterium. By assuming that the body of the bacterium is non-deformable and that the interaction between different bacteria is weak and hence negligible, we have derived a system of 12 coupled nonlinear ordinary differential equations that govern both the motion and the orientation of a swimming spheroidal magnetotactic bacterium. The focus of the study is on how the shape of a non-spherical magnetotactic bacterium, marked by the size of its eccentricity, affects the pattern of its swimming motion. It is revealed that the pattern/speed of a swimming spheroidal magnetotactic bacterium is highly sensitive not only to the direction of its magnetic moment but also to its shape. We also compare the theoretical pattern obtained from the solutions of the 12 coupled differential equations with that observed in the laboratory experiments using the magnetotactic bacteria found in Lake Miyun near Beijing, China, showing that the observed pattern can be largely reproduced with an appropriate set of parameters in our theoretical model. (paper)

  4. On the swimming motion of spheroidal magnetotactic bacteria

    International Nuclear Information System (INIS)

    Cui Zhen; Kong Dali; Zhang Keke; Pan Yongxin

    2012-01-01

    We investigate, via both theoretical and experimental methods, the swimming motion of magnetotactic bacteria having the shape of an elongated prolate spheroid in a viscous liquid under the influence of an imposed magnetic field. A fully three-dimensional Stokes flow, driven by the translation and rotation of a swimming bacterium, exerts a complicated viscous drag/torque on the motion of a non-spherical bacterium. By assuming that the body of the bacterium is non-deformable and that the interaction between different bacteria is weak and hence negligible, we have derived a system of 12 coupled nonlinear ordinary differential equations that govern both the motion and the orientation of a swimming spheroidal magnetotactic bacterium. The focus of the study is on how the shape of a non-spherical magnetotactic bacterium, marked by the size of its eccentricity, affects the pattern of its swimming motion. It is revealed that the pattern/speed of a swimming spheroidal magnetotactic bacterium is highly sensitive not only to the direction of its magnetic moment but also to its shape. We also compare the theoretical pattern obtained from the solutions of the 12 coupled differential equations with that observed in the laboratory experiments using the magnetotactic bacteria found in Lake Miyun near Beijing, China, showing that the observed pattern can be largely reproduced with an appropriate set of parameters in our theoretical model. (paper)

  5. Stellar astrophysics

    International Nuclear Information System (INIS)

    1988-01-01

    Enhanced mass loss occurs at critical stages in the evolution of stars over a wide range of stellar mass. Observationally, these stages are difficult to identify because of their short duration and because the star is often obscured by dust which condenses in the ejecta. A study of a G-type star, of which only the outer envelope was directly visible, was undertaken by the South African Astronomical Observatory (SAAO). The star itself was obscured by dust clouds and its light was only feebly seen by reflection from some of these clouds. Other studies of the galaxy undertaken by the SAAO include observations of the following: the extreme carbon star IRAS 15194-5115; RV Tauri and T Tauri stars; pre-main sequence stars; the properties of circumstellar dust; rotational modulation and flares on RS CVn and BY Dra stars; heavy-element stars; hydrogen-deficient stars; the open cluster NGC6192; stars in Omega Centauri, and lunar occulations of stars. Simultaneous x-ray, radio and optical data of the flare star YZ CMi were also obtained. 1 fig

  6. Suppressed Far-UV Stellar Activity and Low Planetary Mass Loss in the WASP-18 System

    Science.gov (United States)

    Fossati, L.; Koskinen, T.; France, K.; Cubillos, P. E.; Haswell, C. A.; Lanza, A. F.; Pillitteri, I.

    2018-03-01

    WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (extinction (E(B-V) ≈ 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C II, C III, C IV, Si IV). Comparing the C II/C IV flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star–planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si IV line, yields an XUV integrated flux at the planet orbit of 10.2 erg s‑1 cm‑2. We employ the rescaled XUV solar fluxes to models of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10‑20 M J Gyr‑1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #13859. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 092.D-0587.

  7. Bistable flows in precessing spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Cébron, D, E-mail: david.cebron@ujf-grenoble.fr [Université Grenoble Alpes, CNRS, ISTerre, Grenoble (France)

    2015-04-15

    Precession driven flows are found in any rotating container filled with liquid, when the rotation axis itself rotates about a secondary axis that is fixed in an inertial frame of reference. Because of its relevance for planetary fluid layers, many works consider spheroidal containers, where the uniform vorticity component of the bulk flow is reliably given by the well-known equations obtained by Busse (1968 J. Fluid Mech. 33 739–51). So far however, no analytical result for the solutions is available. Moreover, the cases where multiple flows can coexist have not been investigated in detail since their discovery by Noir et al (2003 Geophys. J. Int. 154 407–16). In this work we aim at deriving analytical results for the solutions, aiming in particular at first estimating the ranges of parameters where multiple solutions exist, and second studying quantitatively their stability. Using the models recently proposed by Noir and Cébron (2013 J. Fluid Mech. 737 412–39), which are more generic in the inviscid limit than the equations of Busse, we analytically describe these solutions, their conditions of existence, and their stability in a systematic manner. We then successfully compare these analytical results with the theory of Busse (1968). Dynamical model equations are finally proposed to investigate the stability of the solutions, which describe the bifurcation of the unstable flow solution. We also report for the first time the possibility that time-dependent multiple flows can coexist in precessing triaxial ellipsoids. Numerical integrations of the algebraic and differential equations have been efficiently performed with the dedicated script FLIPPER (supplementary material). (paper)

  8. UVES Abundances of Stars in Nearby Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Tolstoy, Eline; Venn, Kim; Shetrone, Matt; Primas, Francesca; Hill, Vanessa; Kaufer, Andreas; Szeifert, Thomas

    2002-07-01

    It is a truth universally acknowledged, that a galaxy in possession of a good quantity of gas must want to form stars. It is the details of how and why that baffle us all. The simplest theories either would have this process a carefully self-regulated affair, or one that goes completely out of control and is capable of wrecking the galaxy which hosts it. Of course the majority of galaxies seem to amble along somewhere between these two extremes, and the mean properties tend to favour a quiescent self-regulated evolutionary scenario. But there area variety of observations which require us to invoke transitory ‘bursts’ of star-formation at one time or another in most galaxy types. Several nearby dwarf spheroidal galaxies have clearly determined star-formation histories with apparent periods of zero star formation followed by periods of fairly active star formation. If we are able to understand what separated these bursts we would understand several important phenomena in galaxy evolution. Were these galaxies able to clear out their gas reservoir in a burst of star formation? How did this gas return? or did it? Have these galaxies receieved gas from the IGM instead? Could stars from these types of galaxy contribute significantly to the halo population in our Galaxy? To answer these questions we need to combine accurate stellar photometry and Colour-Magnitude Diagram interpretation with detailed metal abundances to combine a star-formation rate versus time with a range of element abundances with time. Different elements trace different evolutionary process (e.g., relative contributions of type I and II supernovae). We often aren't even sure of the abundance spread in these galaxies. We have collected detailed high resolution UVES spectra of four nearby dwarf spheroidal galaxies (Sculptor, Fornax, Leo I & Carina) to begin to answer these questions. This is a precursor study to a more complete study with FLAMES. We presented at this meeting the initial results for

  9. Baking of the vacuum vessel prototype of the Spanish stellarator with a control system based on neural network

    International Nuclear Information System (INIS)

    Botija, J.; Alonso, J.; Blaumoser, M.

    1995-01-01

    To bake uniformly, up to 150 C, the vacuum vessel of the Spanish Stellarator TJ-II represents a difficult task to be demonstrated. In order to study the temperature distribution in the vessel, a prototype of this vacuum vessel, mounted in a stainless steel structure, has been heated by means of electrical panels and eddy currents. The induction heating system is provided applying 498 A/11.7 V at 50 Hz to the toroidal field coil located in the middle of the vessel prototype. Practically, this system only heats adequately the rings and poorly the so called groove of the vacuum vessel. On the contrary, the electrical heaters, with a power density of 0.5 W/cm 2 , heat the external part of the sectors and ports. The high density of temperature sensors ensures the uniformity of the heating process during the long heating cycles, making advisable a fault-tolerant control system based on Artificial Neural Networks (ANNs) that implements the control loop to regulate and protect both heating systems. This paper deals with the results of this experiment

  10. Misorientations in spheroidal graphite: some new insights about spheroidal graphite growth in cast irons

    International Nuclear Information System (INIS)

    Lacaze, J; Theuwissen, K; Laffont, L; Véron, M

    2016-01-01

    Local diffraction patterning, orientation mapping and high resolution transmission electron microscopy imaging have been used to characterize misorientations in graphite spheroids of cast irons. Emphasis is put here on bulk graphite, away from the nucleus as well as from the outer surface of the spheroids in order to get information on their growth during solidification. The results show that spheroidal graphite consists in conical sectors made of elementary blocks piled up on each other. These blocks are elongated along the prismatic a direction of graphite with the c axes roughly parallel to the radius of the spheroids. This implies that the orientation of the blocks rotates around the spheroid centre giving low angle tilting misorientations along tangential direction within each sector. Misorientations between neighbouring sectors are of higher values and their interfaces show rippled layers which are characteristic of defects in graphene. Along a radius of the spheroid, clockwise and anticlockwise twisting between blocks is observed. These observations help challenging some of the models proposed to explain spheroidal growth in cast ions. (paper)

  11. Charged fluid distribution in higher dimensional spheroidal space-time

    Indian Academy of Sciences (India)

    A general solution of Einstein field equations corresponding to a charged fluid distribution on the background of higher dimensional spheroidal space-time is obtained. The solution generates several known solutions for superdense star having spheroidal space-time geometry.

  12. Status of stellarator research

    International Nuclear Information System (INIS)

    Wobig, H.

    1985-01-01

    In recent years main activities in stellarator research were focussed on production and investigation of currentless plasmas. Several heating methods have been applied: electron cyclotron heating, ion cyclotron heating and neutral beam injection. The parameters achieved in HELIOTRON E and W VII-A are: antin 20 m 3 , Tsub(i) <= 1 keV. The confinement is improved as compared with ohmically heated discharges. By ECRH (P = 200 kW) it is possible to heat electrons up to 1.4 keV, confinement in this regime is dominated already by trapped particle effects. Toroidal currents up to 2 kA - either bootstrap currents or externally driven currents - were observed. High β-values (antiβ = 2%) have been obtained in HELIOTRON E, in this regime already pressure driven MHD-modes were observed. Future experiments (ATF-1 and W VII-AS) will extend the parameter regime to temperatures of several keV. These experiments will give important information about critical problems of the stellarator line (β-limit, neoclassical confinement impurity transport). A few reactor studies of stellarators exist, attention is mainly concentrated on technical problems of the modular coil system

  13. Analytical study of spheroidal dust grains in plasma

    International Nuclear Information System (INIS)

    Zahed, H.; Mahmoodi, J.; Sobhanian, S.

    2006-01-01

    Using the modified spheroidal equations, the potential of a spheroidal conducting grain, floated in a plasma, is calculated. The electric field and capacitance for both prolate and oblate spheroidal grains are investigated. The solutions, obtained up to the second-order approximation, show that the plasma screening causes the equipotential surfaces around the grain to be more elongated or flattened than the potential spheroids of the Laplace equation. This leads to the variation of the plasma concentration around the grain

  14. Stellar Metamorphosis:

    Science.gov (United States)

    2002-01-01

    [TOP LEFT AND RIGHT] The Hubble Space Telescope's Wide Field and Planetary Camera 2 has captured images of the birth of two planetary nebulae as they emerge from wrappings of gas and dust, like butterflies breaking out of their cocoons. These images highlight a fleeting phase in the stellar burnout process, occurring just before dying stars are transformed into planetary nebulae. The left-hand image is the Cotton Candy nebula, IRAS 17150-3224; the right-hand image, the Silkworm nebula, IRAS 17441-2411. Called proto-planetary nebulae, these dying stars have been caught in a transition phase between a red giant and a planetary nebula. This phase is only about 1,000 years long, very short in comparison to the 1 billion-year lifetime of a star. These images provide the earliest snapshots of the transition process. Studying images of proto-planetary nebulae is important to understanding the process of star death. A star begins to die when it has exhausted its thermonuclear fuel - hydrogen and helium. The star then becomes bright and cool (red giant phase) and swells to several tens of times its normal size. It begins puffing thin shells of gas off into space. These shells become the star's cocoon. In the Hubble images, the shells are the concentric rings seen around each nebula. But the images also reveal the nebulae breaking out from those shells. The butterfly-like wings of gas and dust are a common shape of planetary nebulae. Such butterfly shapes are created by the 'interacting winds' process, in which a more recent 'fast wind' - material propelled by radiation from the hot central star - punches a hole in the cocoon, allowing the nebula to emerge. (This 'interacting wind' theory was first proposed by Dr. Sun Kwok to explain the origin of planetary nebulae, and has been subsequently proven successful in explaining their shapes.) The nebulae are being illuminated by light from the invisible central star, which is then reflected toward us. We are viewing the nebulae

  15. Differential thermo-resistance of multicellular tumor spheroids

    International Nuclear Information System (INIS)

    Khoei, S.; Goliaei, B.; Neshasteh-Rize, A.

    2004-01-01

    Many cell lines, when cultured under proper conditions, can form three dimensional structures called multicellular spheroids. These spheroids resemble in vivo tumor models in several aspects. Therefore, studying growth characteristics and behavior of spheroids is beneficial in understanding the behavior of tumors under various experimental conditions. In this work, we have studied the growth properties, along with the thermal characteristics of spheroids of Du 145 human prostate carcinoma cell lines and compared the results to monolayer cultures of these cells. For this purpose, The Du 145 cells were cultured either as monolayer or spheroids. At various times after initiation of cultures, the growth properties of spheroids as a function of seeding cell number was determined. To evaluate the thermal characteristics of spheroids, they were heated at various stages of growth at 43 d ig c for various periods. The thermal response was judged by the survival fraction of colony forming cells in spheroids or monolayer culture following heat treatment. The results showed spheroids were more resistant to heat than monolayer cultures at all stages of development. However, the extent of this thermal resistant was dependent on the age, and consequently, the size of the spheroid. The result suggests that the differential thermal resistance of the spheroid cultures develop gradually during the growth of spheroid cultures of Du 145 cell line

  16. Acoustic scattering of a Bessel vortex beam by a rigid fixed spheroid

    Science.gov (United States)

    Mitri, F. G.

    2015-12-01

    Partial-wave series representation of the acoustic scattering field of high-order Bessel vortex beams by rigid oblate and prolate spheroids using the modal matching method is developed. The method, which is applicable to slightly elongated objects at low-to-moderate frequencies, requires solving a system of linear equations which depends on the partial-wave index n and the order of the Bessel vortex beam m using truncated partial-wave series expansions (PWSEs), and satisfying the Neumann boundary condition for a rigid immovable surface in the least-squares sense. This original semi-analytical approach developed for Bessel vortex beams is demonstrated for finite oblate and prolate spheroids, where the mathematical functions describing the spheroidal geometry are written in a form involving single angular (polar) integrals that are numerically computed. The transverse (θ = π / 2) and 3D scattering directivity patterns are evaluated in the far-field for both prolate and oblate spheroids, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid) not exceeding 3:1, the half-cone angle β and order m of the Bessel vortex beam, as well as the dimensionless size parameter kr0. Periodic oscillations in the magnitude plots of the far-field scattering form function are observed, which result from the interference of the reflected waves with the circumferential (Franz') waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3D directivity patterns illustrate the far-field scattering from the spheroid, that vanishes in the forward (θ = 0) and backward (θ = π) directions. Particular applications in underwater acoustics and scattering, acoustic levitation and the detection of submerged elongated objects using Bessel vortex waves to name a few, would benefit from the results of the present investigation.

  17. Partial discharges in spheroidal voids: Void orientation

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1997-01-01

    Partial discharge transients can be described in terms of the charge induced on the detecting electrode. The influence of the void parameters upon the induced charge is examined and discussed for spheroidal voids. It is shown that a quantitative interpretation of the induced charge requires...

  18. Zero-point energy in spheroidal geometries

    OpenAIRE

    Kitson, A. R.; Signal, A. I.

    2005-01-01

    We study the zero-point energy of a massless scalar field subject to spheroidal boundary conditions. Using the zeta-function method, the zero-point energy is evaluated for small ellipticity. Axially symmetric vector fields are also considered. The results are interpreted within the context of QCD flux tubes and the MIT bag model.

  19. Convection in Slab and Spheroidal Geometries

    Science.gov (United States)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  20. The ISLAnds Project. III. Variable Stars in Six Andromeda Dwarf Spheroidal Galaxies

    Science.gov (United States)

    Martínez-Vázquez, Clara E.; Monelli, Matteo; Bernard, Edouard J.; Gallart, Carme; Stetson, Peter B.; Skillman, Evan D.; Bono, Giuseppe; Cassisi, Santi; Fiorentino, Giuliana; McQuinn, Kristen B. W.; Cole, Andrew A.; McConnachie, Alan W.; Martin, Nicolas F.; Dolphin, Andrew E.; Boylan-Kolchin, Michael; Aparicio, Antonio; Hidalgo, Sebastian L.; Weisz, Daniel R.

    2017-12-01

    We present a census of variable stars in six M31 dwarf spheroidal satellites observed with the Hubble Space Telescope. We detect 870 RR Lyrae (RRL) stars in the fields of And I (296), II (251), III (111), XV (117), XVI (8), and XXVIII (87). We also detect a total of 15 Anomalous Cepheids, three eclipsing binaries, and seven field RRL stars compatible with being members of the M31 halo or the Giant Stellar Stream. We derive robust and homogeneous distances to the six galaxies using different methods based on the properties of the RRL stars. Working with the up-to-date set of Period-Wesenheit (I, B-I) relations published by Marconi et al., we obtain distance moduli of μ 0 = [24.49, 24.16, 24.36, 24.42, 23.70, 24.43] mag (respectively), with systematic uncertainties of 0.08 mag and statistical uncertainties <0.11 mag. We have considered an enlarged sample of 16 M31 satellites with published variability studies, and compared their pulsational observables (e.g., periods and amplitudes) with those of 15 Milky Way satellites for which similar data are available. The properties of the (strictly old) RRL in both satellite systems do not show any significant difference. In particular, we found a strikingly similar correlation between the mean period distribution of the fundamental RRL pulsators (RRab) and the mean metallicities of the galaxies. This indicates that the old RRL progenitors were similar at the early stage in the two environments, suggesting very similar characteristics for the earliest stages of evolution of both satellite systems. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programs 13028 and 13739.

  1. Advanced stellarator power plants

    International Nuclear Information System (INIS)

    Miller, R.L.

    1994-01-01

    The stellarator is a class of helical/toroidal magnetic fusion devices. Recent international progress in stellarator power plant conceptual design is reviewed and comparisons in the areas of physics, engineering, and economics are made with recent tokamak design studies

  2. ON THE EFFICIENCY OF THE TIDAL STIRRING MECHANISM FOR THE ORIGIN OF DWARF SPHEROIDALS: DEPENDENCE ON THE ORBITAL AND STRUCTURAL PARAMETERS OF THE PROGENITOR DISKY DWARFS

    International Nuclear Information System (INIS)

    Kazantzidis, Stelios; Lokas, Ewa L.; Callegari, Simone; Mayer, Lucio; Moustakas, Leonidas A.

    2011-01-01

    The tidal stirring model posits the formation of dwarf spheroidal galaxies (dSphs) via the tidal interactions between late-type, rotationally supported dwarfs and Milky-Way-sized host galaxies. Using a comprehensive set of collisionless N-body simulations, we investigate the efficiency of the tidal stirring mechanism for the origin of dSphs. In particular, we examine the degree to which the tidal field of the primary galaxy affects the sizes, masses, shapes, and kinematics of the disky dwarfs for a range of dwarf orbital and structural parameters. Our study is the first to employ self-consistent, equilibrium models for the progenitor dwarf galaxies constructed from a composite distribution function and consisting of exponential stellar disks embedded in massive, cosmologically motivated dark matter halos. Exploring a wide variety of dwarf orbital configurations and initial structures, we demonstrate that in the majority of cases the disky dwarfs experience significant mass loss and their stellar distributions undergo a dramatic morphological, as well as dynamical, transformation. Specifically, the stellar components evolve from disks to bars and finally to pressure-supported, spheroidal systems with kinematic and structural properties akin to those of the classic dSphs in the Local Group (LG) and similar environments. The self-consistency of the adopted dwarf models is crucial for confirming this complex transformation process via tidally induced dynamical instabilities and impulsive tidal heating of the stellar distribution. Our results suggest that such tidal transformations should be common occurrences within the currently favored cosmological paradigm and highlight the key factor responsible for an effective metamorphosis to be the strength of the tidal shocks at the pericenters of the orbit. We also demonstrate that the combination of short orbital times and small pericentric distances, characteristic of dwarfs being accreted by their hosts at high redshift

  3. Axisymmetric scattering of an acoustical Bessel beam by a rigid fixed spheroid.

    Science.gov (United States)

    Mitri, Farid G

    2015-10-01

    Based on the partial-wave series expansion (PWSE) method in spherical coordinates, a formal analytical solution for the acoustic scattering of a zeroth-order Bessel acoustic beam centered on a rigid fixed (oblate or prolate) spheroid is provided. The unknown scattering coefficients of the spheroid are determined by solving a system of linear equations derived for the Neumann boundary condition. Numerical results for the modulus of the backscattered pressure (θ = π) in the near field and the backscattering form function in the far field for both prolate and oblate spheroids are presented and discussed, with particular emphasis on the aspect ratio (i.e., the ratio of the major axis over the minor axis of the spheroid), the half-cone angle of the Bessel beam, and the dimensionless frequency. The plots display periodic oscillations (versus the dimensionless frequency) because of the interference of specularly reflected waves in the backscattering direction with circumferential Franz' waves circumnavigating the surface of the spheroid in the surrounding fluid. Moreover, the 3-D directivity patterns illustrate the near- and far-field axisymmetric scattering. Investigations in underwater acoustics, particle levitation, scattering, and the detection of submerged elongated objects and other related applications utilizing Bessel waves would benefit from the results of the present study.

  4. Engineered Breast Cancer Cell Spheroids Reproduce Biologic Properties of Solid Tumors.

    Science.gov (United States)

    Ham, Stephanie L; Joshi, Ramila; Luker, Gary D; Tavana, Hossein

    2016-11-01

    Solid tumors develop as 3D tissue constructs. As tumors grow larger, spatial gradients of nutrients and oxygen and inadequate diffusive supply to cells distant from vasculature develops. Hypoxia initiates signaling and transcriptional alterations to promote survival of cancer cells and generation of cancer stem cells (CSCs) that have self-renewal and tumor-initiation capabilities. Both hypoxia and CSCs are associated with resistance to therapies and tumor relapse. This study demonstrates that 3D cancer cell models, known as tumor spheroids, generated with a polymeric aqueous two-phase system (ATPS) technology capture these important biological processes. Similar to solid tumors, spheroids of triple negative breast cancer cells deposit major extracellular matrix proteins. The molecular analysis establishes presence of hypoxic cells in the core region and expression of CSC gene and protein markers including CD24, CD133, and Nanog. Importantly, these spheroids resist treatment with chemotherapy drugs. A combination treatment approach using a hypoxia-activated prodrug, TH-302, and a chemotherapy drug, doxorubicin, successfully targets drug resistant spheroids. This study demonstrates that ATPS spheroids recapitulate important biological and functional properties of solid tumors and provide a unique model for studies in cancer research. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Web-based ground loop supervision system for the TJ-II Stellarator

    International Nuclear Information System (INIS)

    Pena, A. de la; Lapayese, F.; Pacios, L.; Carrasco, R.

    2005-01-01

    To minimize electromagnetic interferences in diagnostic and control signals, and to guarantee safe operation of TJ-II, ground loops must be avoided. In order to meet this goal, the whole grounding system of the TJ-II was split into multiple single branches that are connected at a single earth point located near the TJ-II structure in the torus hall. A real-time ground loop supervision system (GLSS) has been designed, manufactured and tested by the TJ-II control group for detecting unintentional short circuits between isolated grounded parts. A web server running on the real-time operating system OS-9 provides remote access to the real-time ground loops measurement. Ground loops monitoring and different operation modes can be configured via any web browser. This paper gives the detailed design of the whole TJ-II ground loop supervision system and its results during its operation

  6. Web-based ground loop supervision system for the TJ-II Stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Pena, A. de la [Asociacion EURATOM-CIEMAT Para Fusion, Avd. Complutense 22, 28040 Madrid (Spain)]. E-mail: a.delapena@ciemat.es; Lapayese, F. [Asociacion EURATOM-CIEMAT Para Fusion, Avd. Complutense 22, 28040 Madrid (Spain); Pacios, L. [Asociacion EURATOM-CIEMAT Para Fusion, Avd. Complutense 22, 28040 Madrid (Spain); Carrasco, R. [Asociacion EURATOM-CIEMAT Para Fusion, Avd. Complutense 22, 28040 Madrid (Spain)

    2005-11-15

    To minimize electromagnetic interferences in diagnostic and control signals, and to guarantee safe operation of TJ-II, ground loops must be avoided. In order to meet this goal, the whole grounding system of the TJ-II was split into multiple single branches that are connected at a single earth point located near the TJ-II structure in the torus hall. A real-time ground loop supervision system (GLSS) has been designed, manufactured and tested by the TJ-II control group for detecting unintentional short circuits between isolated grounded parts. A web server running on the real-time operating system OS-9 provides remote access to the real-time ground loops measurement. Ground loops monitoring and different operation modes can be configured via any web browser. This paper gives the detailed design of the whole TJ-II ground loop supervision system and its results during its operation.

  7. Pulsars in binary systems: probing binary stellar evolution and general relativity.

    Science.gov (United States)

    Stairs, Ingrid H

    2004-04-23

    Radio pulsars in binary orbits often have short millisecond spin periods as a result of mass transfer from their companion stars. They therefore act as very precise, stable, moving clocks that allow us to investigate a large set of otherwise inaccessible astrophysical problems. The orbital parameters derived from high-precision binary pulsar timing provide constraints on binary evolution, characteristics of the binary pulsar population, and the masses of neutron stars with different mass-transfer histories. These binary systems also test gravitational theories, setting strong limits on deviations from general relativity. Surveys for new pulsars yield new binary systems that increase our understanding of all these fields and may open up whole new areas of physics, as most spectacularly evidenced by the recent discovery of an extremely relativistic double-pulsar system.

  8. Modeling mechanical inhomogeneities in small populations of proliferating monolayers and spheroids.

    Science.gov (United States)

    Lejeune, Emma; Linder, Christian

    2018-06-01

    Understanding the mechanical behavior of multicellular monolayers and spheroids is fundamental to tissue culture, organism development, and the early stages of tumor growth. Proliferating cells in monolayers and spheroids experience mechanical forces as they grow and divide and local inhomogeneities in the mechanical microenvironment can cause individual cells within the multicellular system to grow and divide at different rates. This differential growth, combined with cell division and reorganization, leads to residual stress. Multiple different modeling approaches have been taken to understand and predict the residual stresses that arise in growing multicellular systems, particularly tumor spheroids. Here, we show that by using a mechanically robust agent-based model constructed with the peridynamic framework, we gain a better understanding of residual stresses in multicellular systems as they grow from a single cell. In particular, we focus on small populations of cells (1-100 s) where population behavior is highly stochastic and prior investigation has been limited. We compare the average strain energy density of cells in monolayers and spheroids using different growth and division rules and find that, on average, cells in spheroids have a higher strain energy density than cells in monolayers. We also find that cells in the interior of a growing spheroid are, on average, in compression. Finally, we demonstrate the importance of accounting for stochastic fluctuations in the mechanical environment, particularly when the cellular response to mechanical cues is nonlinear. The results presented here serve as a starting point for both further investigation with agent-based models, and for the incorporation of major findings from agent-based models into continuum scale models when explicit representation of individual cells is not computationally feasible.

  9. Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. IV. Measurement for Sculptor

    Science.gov (United States)

    Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

    2006-03-01

    This article presents a measurement of the proper motion of the Sculptor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope using the Space Telescope Imaging Spectrograph in the imaging mode. Each of two distinct fields contains a quasi-stellar object that serves as the ``reference point.'' The measured proper motion of Sculptor, expressed in the equatorial coordinate system, is (μα, μδ)=(9+/-13, 2+/-13) mas century-1. Removing the contributions from the motion of the Sun and the motion of the local standard of rest produces the proper motion in the Galactic rest frame: (μGrfα, μGrfδ)=(-23+/-13, 45+/-13) mas century-1. The implied space velocity with respect to the Galactic center has a radial component of Vr=79+/-6 km s-1 and a tangential component of Vt=198+/-50 km s-1. Integrating the motion of Sculptor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 68 (31, 83) and 122 (97, 313) kpc, respectively, where the values in the parentheses represent the 95% confidence interval derived from Monte Carlo experiments. The eccentricity of the orbit is 0.29 (0.26, 0.60), and the orbital period is 2.2 (1.5, 4.9) Gyr. Sculptor is on a polar orbit around the Milky Way: the angle of inclination is 86° (83°, 90°). Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  10. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    Craig, Jonathan; Krumholz, Mark R.

    2013-01-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  11. Exploring the Dynamics of Exoplanetary Systems in a Young Stellar Cluster

    Science.gov (United States)

    Thornton, Jonathan Daniel; Glaser, Joseph Paul; Wall, Joshua Edward

    2018-01-01

    I describe a dynamical simulation of planetary systems in a young star cluster. One rather arbitrary aspect of cluster simulations is the choice of initial conditions. These are typically chosen from some standard model, such as Plummer or King, or from a “fractal” distribution to try to model young clumpy systems. Here I adopt the approach of realizing an initial cluster model directly from a detailed magnetohydrodynamical model of cluster formation from a 1000-solar-mass interstellar gas cloud, with magnetic fields and radiative and wind feedback from massive stars included self-consistently. The N-body simulation of the stars and planets starts once star formation is largely over and feedback has cleared much of the gas from the region where the newborn stars reside. It continues until the cluster dissolves in the galactic field. Of particular interest is what would happen to the free-floating planets created in the gas cloud simulation. Are they captured by a star or are they ejected from the cluster? This method of building a dynamical cluster simulation directly from the results of a cluster formation model allows us to better understand the evolution of young star clusters and enriches our understanding of extrasolar planet development in them. These simulations were performed within the AMUSE simulation framework, and combine N-body, multiples and background potential code.

  12. CLOSE STELLAR ENCOUNTERS IN YOUNG, SUBSTRUCTURED, DISSOLVING STAR CLUSTERS: STATISTICS AND EFFECTS ON PLANETARY SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Craig, Jonathan; Krumholz, Mark R., E-mail: krumholz@ucolick.org [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  13. Close Stellar Encounters in Young, Substructured, Dissolving Star Clusters: Statistics and Effects on Planetary Systems

    Science.gov (United States)

    Craig, Jonathan; Krumholz, Mark R.

    2013-06-01

    Both simulations and observations indicate that stars form in filamentary, hierarchically clustered associations, most of which disperse into their galactic field once feedback destroys their parent clouds. However, during their early evolution in these substructured environments, stars can undergo close encounters with one another that might have significant impacts on their protoplanetary disks or young planetary systems. We perform N-body simulations of the early evolution of dissolving, substructured clusters with a wide range of properties, with the aim of quantifying the expected number and orbital element distributions of encounters as a function of cluster properties. We show that the presence of substructure both boosts the encounter rate and modifies the distribution of encounter velocities compared to what would be expected for a dynamically relaxed cluster. However, the boost only lasts for a dynamical time, and as a result the overall number of encounters expected remains low enough that gravitational stripping is unlikely to be a significant effect for the vast majority of star-forming environments in the Galaxy. We briefly discuss the implications of this result for models of the origin of the solar system, and of free-floating planets. We also provide tabulated encounter rates and orbital element distributions suitable for inclusion in population synthesis models of planet formation in a clustered environment.

  14. Manufacturing of a high precision coil system for the Spanish Stellarator TJ-II

    International Nuclear Information System (INIS)

    Alonso, J.; Blaumoser, M.; Bieder, H.E.; Theisen, E.; Jeckle, A.; Brandl, M.; Mione, M.

    1995-01-01

    The flexible Heliac TJ-II is under construction at Ciemat in Madrid, Spain. This experimental device allows the investigation of plasmas in a wide range of magnetic field configurations. The rotational transform can be varied between 0.9 and 2.5. Shear variation is possible from -1% to 10%. The magnetic well ranges from 0 to 6%. The average major plasma radius is 1.5 m and the minor plasma dimensions are 0.4 m by 0.2 m. The average toroidal magnetic field is 1 T. The central part of TJ-II is a coil system called Hard Core. The manufacturing aspects of this component are described hereafter. The narrow range of tolerances of the different elements is consequence of the necessary precision of the coils that are located very close to the plasma. (orig.)

  15. THE 2008 OUTBURST IN THE YOUNG STELLAR SYSTEM Z CMa: THE FIRST DETECTION OF TWIN JETS

    International Nuclear Information System (INIS)

    Whelan, E. T.; Dougados, C.; Bonnefoy, M.; Bouvier, J.; Chauvin, G.; Garcia, P. J. V.; Malbet, F.; Perrin, M. D.; Bains, I.; Redman, M. P.; Ray, T. P.; Bouy, H.; Benisty, M.; Grankvin, K.

    2010-01-01

    The Z CMa binary is understood to undergo both FU Orionis (FUOR) and EX Orionis (EXOR) type outbursts. While the SE component has been spectroscopically classified as an FUOR, the NW component, a Herbig Be star, is the source of the EXOR outbursts. The system has been identified as the source of a large outflow; however, previous studies have failed to identify the driver. Here, we present adaptive optics assisted [Fe II] spectro-images which reveal for the first time the presence of two small-scale jets. Observations made using OSIRIS at the Keck Observatory show the Herbig Be star to be the source of the parsec-scale outflow, which within 2'' of the source shows signs of wiggling and the FUOR to be driving a ∼0.''4 jet. The wiggling of the Herbig Be star's jet is evidence for an additional companion which could in fact be generating the EXOR outbursts, the last of which began in 2008. Indeed, the dynamical scale of the wiggling corresponds to a timescale of 4-8 years which is in agreement with the timescale of these outbursts. The spectro-images also show a bow-shock-shaped feature and possible associated knots. The origin of this structure is as of yet unclear. Finally, interesting low velocity structure is also observed. One possibility is that it originates in a wide-angle outflow launched from a circumbinary disk.

  16. Structure and Formation of Elliptical and Spheroidal Galaxies

    Science.gov (United States)

    Kormendy, John; Fisher, David B.; Cornell, Mark E.; Bender, Ralf

    2009-05-01

    New surface photometry of all known elliptical galaxies in the Virgo cluster is combined with published data to derive composite profiles of brightness, ellipticity, position angle, isophote shape, and color over large radius ranges. These provide enough leverage to show that Sérsic log I vprop r 1/n functions fit the brightness profiles I(r) of nearly all ellipticals remarkably well over large dynamic ranges. Therefore, we can confidently identify departures from these profiles that are diagnostic of galaxy formation. Two kinds of departures are seen at small radii. All 10 of our ellipticals with total absolute magnitudes MVT 4 uncorrelated with MVT . They also are α-element enhanced, implying short star-formation timescales. And their stellar populations have a variety of ages but mostly are very old. Extra light ellipticals generally rotate rapidly, are more isotropic than core Es, and have disky isophotes. We show that they have n sime 3 ± 1 almost uncorrelated with MVT and younger and less α-enhanced stellar populations. These are new clues to galaxy formation. We suggest that extra light ellipticals got their low Sérsic indices by forming in relatively few binary mergers, whereas giant ellipticals have n > 4 because they formed in larger numbers of mergers of more galaxies at once plus later heating during hierarchical clustering. We confirm that core Es contain X-ray-emitting gas whereas extra light Es generally do not. This leads us to suggest why the E-E dichotomy arose. If energy feedback from active galactic nuclei (AGNs) requires a "working surface" of hot gas, then this is present in core galaxies but absent in extra light galaxies. We suggest that AGN energy feedback is a strong function of galaxy mass: it is weak enough in small Es not to prevent merger starbursts but strong enough in giant Es and their progenitors to make dry mergers dry and to protect old stellar populations from late star formation. Finally, we verify that there is a strong

  17. A POSSIBLE BINARY SYSTEM OF A STELLAR REMNANT IN THE HIGH-MAGNIFICATION GRAVITATIONAL MICROLENSING EVENT OGLE-2007-BLG-514

    International Nuclear Information System (INIS)

    Miyake, N.; Abe, F.; Furusawa, K.; Itow, Y.; Udalski, A.; Kubiak, M.; Szymański, M. K.; Pietrzyński, G.; Soszyński, I.; Ulaczyk, K.; Wyrzykowski, L.; Sumi, T.; Bennett, D. P.; Dong, S.; Gould, A.; Street, R. A.; Greenhill, J.; Bond, I. A.; Fukui, A.; Holderness, S.

    2012-01-01

    We report the extremely high-magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 ± 0.007 and a projected separation of s = 0.072 ± 0.001 in units of the Einstein radius. The parallax parameters allow us to determine the lens distance D L = 3.11 ± 0.39 kpc and total mass M L = 1.40 ± 0.18 M ☉ ; this leads to the primary and secondary components having masses of M 1 = 1.06 ± 0.13 M ☉ and M 2 = 0.34 ± 0.04 M ☉ , respectively. The parallax model indicates that the binary lens system is likely constructed by the main-sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 ± 0.005, s = 0.083 ± 0.001). The primary component of the binary lens is relatively massive, with M 1 = 0.9 +4.6 –0.3 M ☉ and it is at a distance of D L = 2.6 +3.8 –0.9 kpc. Given the secure mass ratio measurement, the companion mass is therefore M 2 = 0.2 +1.2 –0.1 M ☉ . The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star, or a black hole.

  18. First results of the multi-purpose real-time processing video camera system on the Wendelstein 7-X stellarator and implications for future devices

    Science.gov (United States)

    Zoletnik, S.; Biedermann, C.; Cseh, G.; Kocsis, G.; König, R.; Szabolics, T.; Szepesi, T.; Wendelstein 7-X Team

    2018-01-01

    A special video camera has been developed for the 10-camera overview video system of the Wendelstein 7-X (W7-X) stellarator considering multiple application needs and limitations resulting from this complex long-pulse superconducting stellarator experiment. The event detection intelligent camera (EDICAM) uses a special 1.3 Mpixel CMOS sensor with non-destructive read capability which enables fast monitoring of smaller Regions of Interest (ROIs) even during long exposures. The camera can perform simple data evaluation algorithms (minimum/maximum, mean comparison to levels) on the ROI data which can dynamically change the readout process and generate output signals. Multiple EDICAM cameras were operated in the first campaign of W7-X and capabilities were explored in the real environment. Data prove that the camera can be used for taking long exposure (10-100 ms) overview images of the plasma while sub-ms monitoring and even multi-camera correlated edge plasma turbulence measurements of smaller areas can be done in parallel. These latter revealed that filamentary turbulence structures extend between neighboring modules of the stellarator. Considerations emerging for future upgrades of this system and similar setups on future long-pulse fusion experiments such as ITER are discussed.

  19. Mass Spectrometry Analyses of Multicellular Tumor Spheroids.

    Science.gov (United States)

    Acland, Mitchell; Mittal, Parul; Lokman, Noor A; Klingler-Hoffmann, Manuela; Oehler, Martin K; Hoffmann, Peter

    2018-05-01

    Multicellular tumor spheroids (MCTS) are a powerful biological in vitro model, which closely mimics the 3D structure of primary avascularized tumors. Mass spectrometry (MS) has established itself as a powerful analytical tool, not only to better understand and describe the complex structure of MCTS, but also to monitor their response to cancer therapeutics. The first part of this review focuses on traditional mass spectrometry approaches with an emphasis on elucidating the molecular characteristics of these structures. Then the mass spectrometry imaging (MSI) approaches used to obtain spatially defined information from MCTS is described. Finally the analysis of primary spheroids, such as those present in ovarian cancer, and the great potential that mass spectrometry analysis of these structures has for improved understanding of cancer progression and for personalized in vitro therapeutic testing is discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Axisymmetric Eigenmodes of Spheroidal Pure Electron Plasmas

    Science.gov (United States)

    Kawai, Yosuke; Saitoh, Haruhiko; Yoshida, Zensho; Kiwamoto, Yasuhito

    2010-11-01

    The axisymmetric electrostatic eigenmodes of spheroidal pure electron plasmas have been studied experimentally. It is confirmed that the observed spheroidal plasma attains a theoretically expected equilibrium density distribution, with the exception of a low-density halo distribution surrounding the plasma. When the eigenmode frequency observed for the plasma is compared with the frequency predicted by the dispersion relation derived under ideal conditions wherein the temperature is zero and the boundary is located at an infinite distance from the plasma, it is observed that the absolute value of the observed frequency is systematically higher than the theoretical prediction. Experimental examinations and numerical calculations indicate that the upward shift of the eigenmode frequency cannot be accounted for solely by the finite temperature effect, but is significantly affected by image charges induced on the conducting boundary and the resulting distortion of the density profile from the theoretical expectation.

  1. The Intermediate-mass Young Stellar Object 08576nr292: Discovery of A Disk-Jet System

    NARCIS (Netherlands)

    Ellerbroek, L.E.; Kaper, L.; Bik, A.; de Koter, A.; Horrobin, M.; Puga, E.; Sana, H.; Waters, L.B.F.M.

    2011-01-01

    We present observations of the embedded massive young stellar object (YSO) candidate 08576nr292, obtained with X-shooter and SINFONI on the ESO Very Large Telescope (VLT). The flux-calibrated, medium-resolution X-shooter spectrum (300–2500 nm) includes over 300 emission lines, but no (photospheric)

  2. Non-existence of separable spheroidal beams

    International Nuclear Information System (INIS)

    Boyack, Rufus; Lekner, John

    2011-01-01

    We show that ψ = R(ξ)S(η) e imφ , a product of radial and angular oblate spheroidal functions and an azimuthal factor, cannot represent physical free-space scalar beams. The reason lies in the discontinuity in the longitudinal derivative of ψ in the focal plane, where ψ is not a solution of the Helmholtz equation on the disc ξ = 0

  3. Stellar CME candidates: towards a stellar CME-flare relation

    Science.gov (United States)

    Paraskevi Moschou, Sofia; Drake, Jeremy J.; Cohen, Ofer; Alvarado-Gomez, Julian D.; Garraffo, Cecilia

    2018-06-01

    For decades the Sun has been the only star that allowed for direct CME observations. Recently, with the discovery of multiple extrasolar systems, it has become imperative that the role of stellar CMEs be assessed in the context of exoplanetary habitability. Solar CMEs and flares show a higher association with increasing flaring energy, with strong flares corresponding to large and fast CMEs. As argued in earlier studies, extrasolar environments around active stars are potentially dominated by CMEs, as a result of their extreme flaring activity. This has strong implications for the energy budget of the system and the atmospheric erosion of orbiting planets.Nevertheless, with current instrumentation we are unable to directly observe CMEs in even the closest stars, and thus we have to look for indirect techniques and observational evidence and signatures for the eruption of stellar CMEs. There are three major observational techniques for tracing CME signatures in other stellar systems, namely measuring Type II radio bursts, Doppler shifts in UV/optical lines or transient absorption in the X-ray spectrum. We present observations of the most probable stellar CME candidates captured so far and examine the different observational techniques used together with their levels of uncertainty. Assuming that they were CMEs, we try to asses their kinematic and energetic characteristics and place them in an extension of the well-established solar CME-flare energy scaling law. We finish by discussing future observations for direct measurements.

  4. Cannibalization and rebirth in the NGC 5387 system. I. The stellar stream and star-forming region

    Energy Technology Data Exchange (ETDEWEB)

    Beaton, Rachael L.; Majewski, Steven R.; Johnson, Kelsey E.; Verbiscer, Anne [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Martínez-Delgado, David [Max Planck Institut fur Astronomie, D-69117 Heidelberg (Germany); D' Onghia, Elena [Department of Astronomy, University of Wisconsin-Madison, Madison, WI 53706 (United States); Zibetti, Stefano [INAF-Osservatorio Astrofisico di Arcetri, I-50125 Firenze (Italy); Gabany, R. Jay [Black Bird II Observatory, Alder Springs, CA 93602 (United States); Blanton, Michael, E-mail: rbeaton@virginia.edu [Department of Physics, New York University, New York, NY 10003 (United States)

    2014-08-01

    We have identified a low surface brightness stellar stream from visual inspection of Sloan Digital Sky Survey (SDSS) imaging for the edge-on, spiral galaxy NGC 5387. An optically blue overdensity coincident with the stream intersection with the NGC 5387 disk was also identified in SDSS and in the Galaxy Evolution Explorer Deep Imaging Survey contributing 38% of the total far-UV integrated flux from NGC 5387. Deeper optical imaging was acquired with the Vatican Advanced Technology Telescope that confirmed the presence of both features. The stellar stream is red in color, (B – V) = 0.7, has a stellar mass of 6 × 10{sup 8} M{sub ☉}, which implies a 1:50 merger ratio, has a circular radius, R{sub circ} ∼ 11.7 kpc, formed in ∼240 Myr, and the progenitor had a total mass of ∼4 × 10{sup 10} M{sub ☉}. Spectroscopy from LBT+MODS1 was used to determine that the blue overdensity is at the same redshift as NGC 5387, consists of young stellar populations (∼10 Myr), is metal-poor (12 + log (O/H) = 8.03), and is forming stars at an enhanced rate (∼1-3 M{sub ☉} yr{sup –1}). The most likely interpretations are that the blue overdensity is (1) a region of enhanced star formation in the outer disk of NGC 5387 induced by the minor accretion event or (2) the progenitor of the stellar stream experiencing enhanced star formation. Additional exploration of these scenarios is presented in a companion paper.

  5. Cannibalization and rebirth in the NGC 5387 system. I. The stellar stream and star-forming region

    International Nuclear Information System (INIS)

    Beaton, Rachael L.; Majewski, Steven R.; Johnson, Kelsey E.; Verbiscer, Anne; Martínez-Delgado, David; D'Onghia, Elena; Zibetti, Stefano; Gabany, R. Jay; Blanton, Michael

    2014-01-01

    We have identified a low surface brightness stellar stream from visual inspection of Sloan Digital Sky Survey (SDSS) imaging for the edge-on, spiral galaxy NGC 5387. An optically blue overdensity coincident with the stream intersection with the NGC 5387 disk was also identified in SDSS and in the Galaxy Evolution Explorer Deep Imaging Survey contributing 38% of the total far-UV integrated flux from NGC 5387. Deeper optical imaging was acquired with the Vatican Advanced Technology Telescope that confirmed the presence of both features. The stellar stream is red in color, (B – V) = 0.7, has a stellar mass of 6 × 10 8 M ☉ , which implies a 1:50 merger ratio, has a circular radius, R circ ∼ 11.7 kpc, formed in ∼240 Myr, and the progenitor had a total mass of ∼4 × 10 10 M ☉ . Spectroscopy from LBT+MODS1 was used to determine that the blue overdensity is at the same redshift as NGC 5387, consists of young stellar populations (∼10 Myr), is metal-poor (12 + log (O/H) = 8.03), and is forming stars at an enhanced rate (∼1-3 M ☉ yr –1 ). The most likely interpretations are that the blue overdensity is (1) a region of enhanced star formation in the outer disk of NGC 5387 induced by the minor accretion event or (2) the progenitor of the stellar stream experiencing enhanced star formation. Additional exploration of these scenarios is presented in a companion paper.

  6. Monitoring the effects of doxorubicin on 3D-spheroid tumor cells in real-time

    Directory of Open Access Journals (Sweden)

    Baek N

    2016-11-01

    Full Text Available NamHuk Baek,1,* Ok Won Seo,1,* MinSung Kim,1 John Hulme,2 Seong Soo A An2 1Department of R & D, NanoEntek Inc., Seoul, Republic of Korea; 2Department of BioNano Technology Gachon University, Gyeonggi-do, Republic of Korea *These authors contributed equally to this work Abstract: Recently, increasing numbers of cell culture experiments with 3D spheroids presented better correlating results in vivo than traditional 2D cell culture systems. 3D spheroids could offer a simple and highly reproducible model that would exhibit many characteristics of natural tissue, such as the production of extracellular matrix. In this paper numerous cell lines were screened and selected depending on their ability to form and maintain a spherical shape. The effects of increasing concentrations of doxorubicin (DXR on the integrity and viability of the selected spheroids were then measured at regular intervals and in real-time. In total 12 cell lines, adenocarcinomic alveolar basal epithelial (A549, muscle (C2C12, prostate (DU145, testis (F9, pituitary epithelial-like (GH3, cervical cancer (HeLa, HeLa contaminant (HEp2, embryo (NIH3T3, embryo (PA317, neuroblastoma (SH-SY5Y, osteosarcoma U2OS, and embryonic kidney cells (293T, were screened. Out of the 12, 8 cell lines, NIH3T3, C2C12, 293T, SH-SY5Y, A549, HeLa, PA317, and U2OS formed regular spheroids and the effects of DXR on these structures were measured at regular intervals. Finally, 5 cell lines, A549, HeLa, SH-SY5Y, U2OS, and 293T, were selected for real-time monitoring and the effects of DXR treatment on their behavior were continuously recorded for 5 days. A potential correlation regarding the effects of DXR on spheroid viability and ATP production was measured on days 1, 3, and 5. Cytotoxicity of DXR seemed to occur after endocytosis, since the cellular activities and ATP productions were still viable after 1 day of the treatment in all spheroids, except SH-SY5Y. Both cellular activity and ATP production were

  7. Imaging- and Flow Cytometry-based Analysis of Cell Position and the Cell Cycle in 3D Melanoma Spheroids

    Science.gov (United States)

    Beaumont, Kimberley A.; Anfosso, Andrea; Ahmed, Farzana

    2015-01-01

    Three-dimensional (3D) tumor spheroids are utilized in cancer research as a more accurate model of the in vivo tumor microenvironment, compared to traditional two-dimensional (2D) cell culture. The spheroid model is able to mimic the effects of cell-cell interaction, hypoxia and nutrient deprivation, and drug penetration. One characteristic of this model is the development of a necrotic core, surrounded by a ring of G1 arrested cells, with proliferating cells on the outer layers of the spheroid. Of interest in the cancer field is how different regions of the spheroid respond to drug therapies as well as genetic or environmental manipulation. We describe here the use of the fluorescence ubiquitination cell cycle indicator (FUCCI) system along with cytometry and image analysis using commercial software to characterize the cell cycle status of cells with respect to their position inside melanoma spheroids. These methods may be used to track changes in cell cycle status, gene/protein expression or cell viability in different sub-regions of tumor spheroids over time and under different conditions. PMID:26779761

  8. Cardiac spheroids as promising in vitro models to study the human heart microenvironment

    DEFF Research Database (Denmark)

    Polonchuk, Liudmila; Chabria, Mamta; Badi, Laura

    2017-01-01

    Three-dimensional in vitro cell systems are a promising alternative to animals to study cardiac biology and disease. We have generated three-dimensional in vitro models of the human heart ("cardiac spheroids", CSs) by co-culturing human primary or iPSC-derived cardiomyocytes, endothelial cells an...

  9. Detailed Studies of the Sculptor Dwarf Spheroidal Galaxy in the Milky Way halo

    NARCIS (Netherlands)

    Tolstoy, Eline

    In and around the Milky Way halo there are a number of low mass low luminosity dwarf galaxies. Several of these systems have been studied in great detail. I describe recent photometric and spectroscopic studies of the Sculptor dwarf spheroidal galaxy made as part of the DART survey of nearby dwarf

  10. Universal timescales in the rheology of spheroid cell aggregates

    Science.gov (United States)

    Yu, Miao; Mahtabfar, Aria; Beleen, Paul; Foty, Ramsey; Zahn, Jeffrey; Shreiber, David; Liu, Liping; Lin, Hao

    2017-11-01

    The rheological properties of tissue play important roles in key biological processes including embryogenesis, cancer metastasis, and wound healing. Spheroid cell aggregate is a particularly interesting model system for the study of these phenomena. In the long time, they behave like drops with a surface tension. In the short, viscoelasticity also needs to be considered. In this work, we discover two coupled and universal timescales for spheroid aggregates. A total of 12 aggregate types (total aggregate number n =290) derived from L and GBM (glioblastoma multiforme) cells are studied with microtensiometer to obtain their surface tension. They are also allowed to relax upon release of the compression forces. The two timescales are observed during the relaxation process; their values do not depend on compression time nor the degree of deformation, and are consistent among all 12 types. Following prior work (Yu et al., Phys. Rev. Lett., 115:128303; Liu et al., J. Mech. Phys. Solids, 98:309-329) we use a rigorous mathematical theory to interpret the results, which reveals intriguing properties of the aggregates on both tissue and cellular levels. The mechanics of multicellular organization reflects both complexity and regularity due to strong active regulation.

  11. Cell survival in spheroids irradiated with heavy-ion beams

    International Nuclear Information System (INIS)

    Rodriguez, A.; Alpen, E.L.

    1981-01-01

    Biological investigations with accelerated heavy ions have been carried out regularly at the Lawrence Berkeley Laboratory Bevalac for the past four years. Most of the cellular investigations have been conducted on cell monolayer and suspension culture systems. The studies to date suggest that heavy charged particle beams may offer some radiotherapeutic advantages over conventional radiotherapy sources. The advantages are thought to lie primarily in an increased relative biological effectiveness (RBE), a decrease in the oxygen enhancement ratio (OER), and better tissue distribution dose. Experiments reported here were conducted with 400 MeV/amu carbon ions and 425 MeV/amu neon ions, using a rat brain gliosarcoma cell line grown as multicellular spheroids. Studies have been carried out with x-rays and high-energy carbon and neon ion beams. These studies evaluate high-LET (linear energy transfer) cell survival in terms of RBE and the possible contributions of intercellular communication. Comparisons were made of the post-irradiation survival characteristics for cells irradiated as multicellular spheroids (approximately 100 μm and 300 μm diameters) and for cells irradiated in suspension. These comparisons were made between 225-kVp x-rays, 400 MeV/amu carbon ions, and 425 MeV/amu neon ions

  12. Stellar structure and evolution

    International Nuclear Information System (INIS)

    Kippernhahn, R.; Weigert, A.

    1990-01-01

    This book introduces the theory of the internal structure of stars and their evolution in time. It presents the basic physics of stellar interiors, methods for solving the underlying equations, and the most important results necessary for understanding the wide variety of stellar types and phenomena. The evolution of stars is discussed from their birth through normal evolution to possibly spectacular final stages. Chapters on stellar oscillations and rotation are included

  13. A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

    Science.gov (United States)

    van de Sande, Jesse; Scott, Nicholas; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Cortese, Luca; Croom, Scott M.; d'Eugenio, Francesco; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; McDermid, Richard M.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.; Sharp, Rob

    2018-04-01

    Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1-3. A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions5. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI6 and MaNGA7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8), CALIFA9, MASSIVE10), it is now feasible to connect a galaxy's star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, ɛe) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.

  14. A relation between the characteristic stellar ages of galaxies and their intrinsic shapes

    Science.gov (United States)

    van de Sande, Jesse; Scott, Nicholas; Bland-Hawthorn, Joss; Brough, Sarah; Bryant, Julia J.; Colless, Matthew; Cortese, Luca; Croom, Scott M.; d'Eugenio, Francesco; Foster, Caroline; Goodwin, Michael; Konstantopoulos, Iraklis S.; Lawrence, Jon S.; McDermid, Richard M.; Medling, Anne M.; Owers, Matt S.; Richards, Samuel N.; Sharp, Rob

    2018-06-01

    Stellar population and stellar kinematic studies provide unique but complementary insights into how galaxies build-up their stellar mass and angular momentum1-3. A galaxy's mean stellar age reveals when stars were formed, but provides little constraint on how the galaxy's mass was assembled. Resolved stellar dynamics4 trace the change in angular momentum due to mergers, but major mergers tend to obscure the effect of earlier interactions5. With the rise of large multi-object integral field spectroscopic surveys, such as SAMI6 and MaNGA7, and single-object integral field spectroscopic surveys (for example, ATLAS3D (ref. 8), CALIFA9, MASSIVE10), it is now feasible to connect a galaxy's star formation and merger history on the same resolved physical scales, over a large range in galaxy mass, morphology and environment4,11,12. Using the SAMI Galaxy Survey, here we present a combined study of spatially resolved stellar kinematics and global stellar populations. We find a strong correlation of stellar population age with location in the (V/σ, ɛe) diagram that links the ratio of ordered rotation to random motions in a galaxy to its observed ellipticity. For the large majority of galaxies that are oblate rotating spheroids, we find that characteristic stellar age follows the intrinsic ellipticity of galaxies remarkably well.

  15. Models for stellar flares

    International Nuclear Information System (INIS)

    Cram, L.E.; Woods, D.T.

    1982-01-01

    We study the response of certain spectral signatures of stellar flares (such as Balmer line profiles and the broad-band continuum) to changes in atmospheric structure which might result from physical processes akin to those thought to occur in solar flares. While each physical process does not have a unique signature, we can show that some of the observed properties of stellar flares can be explained by a model which involves increased pressures and temperatures in the flaring stellar chromosphere. We suggest that changes in stellar flare area, both with time and with depth in the atmosphere, may play an important role in producing the observed flare spectrum

  16. CHEMICAL ENRICHMENT IN THE FAINTEST GALAXIES: THE CARBON AND IRON ABUNDANCE SPREADS IN THE BOOeTES I DWARF SPHEROIDAL GALAXY AND THE SEGUE 1 SYSTEM

    International Nuclear Information System (INIS)

    Norris, John E.; Yong, David; Wyse, Rosemary F. G.; Gilmore, Gerard; Belokurov, V.; Zucker, Daniel B.; Frebel, Anna; Wilkinson, Mark I.

    2010-01-01

    We present an AAOmega spectroscopic study of red giants in the ultra-faint dwarf galaxy Booetes I (M V ∼ -6) and the Segue 1 system (M V ∼ -1.5), either an extremely low luminosity dwarf galaxy or an unusually extended globular cluster. Both Booetes I and Segue 1 have significant abundance dispersions in iron and carbon. Booetes I has a mean abundance of [Fe/H] = -2.55 ± 0.11 with an [Fe/H] dispersion of σ = 0.37 ± 0.08, and abundance spreads of Δ[Fe/H] = 1.7 and Δ[C/H] = 1.5. Segue 1 has a mean of [Fe/H] = -2.7 ± 0.4 with [Fe/H] dispersion of σ = 0.7 ± 0.3, and abundances spreads of Δ[Fe/H] = 1.6 and Δ[C/H] = 1.2. Moreover, Segue 1 has a radial-velocity member at four half-light radii that is extremely metal-poor and carbon-rich, with [Fe/H] = -3.5, and [C/Fe] = +2.3. Modulo an unlikely non-member contamination, the [Fe/H] abundance dispersion confirms Segue 1 as the least-luminous ultra-faint dwarf galaxy known. For [Fe/H] V = -5. The very low mean iron abundances and the high carbon and iron abundance dispersions in Segue 1 and Booetes I are consistent with highly inhomogeneous chemical evolution starting in near zero-abundance gas. These ultra-faint dwarf galaxies are apparently surviving examples of the very first bound systems.

  17. A LOW STELLAR OBLIQUITY FOR WASP-47, A COMPACT MULTIPLANET SYSTEM WITH A HOT JUPITER AND AN ULTRA-SHORT PERIOD PLANET

    Energy Technology Data Exchange (ETDEWEB)

    Sanchis-Ojeda, Roberto; Isaacson, Howard; Marcy, Geoffrey W.; Weiss, Lauren [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Winn, Joshua N.; Dai, Fei [Department of Physics, and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Howard, Andrew W.; Sinukoff, Evan [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Petigura, Erik; Rogers, Leslie [Department of Astronomy and Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Albrecht, Simon [Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Hirano, Teruyuki, E-mail: sanchisojeda@berkeley.edu [Department of Earth and Planetary Sciences, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2015-10-10

    We have detected the Rossiter–Mclaughlin effect during a transit of WASP-47b, the only known hot Jupiter with close planetary companions. By combining our spectroscopic observations with Kepler photometry, we show that the projected stellar obliquity is λ = 0° ± 24°. We can firmly exclude a retrograde orbit for WASP-47b, and rule out strongly misaligned prograde orbits. Low obliquities have also been found for most of the other compact multiplanet systems that have been investigated. The Kepler-56 system, with two close-in gas giants transiting their subgiant host star with an obliquity of at least 45{sup ◦}, remains the only clear counterexample.

  18. Stellar Physics 2: Stellar Evolution and Stability

    CERN Document Server

    Bisnovatyi-Kogan, Gennady S

    2011-01-01

    "Stellar Physics" is a an outstanding book in the growing body of literature on star formation and evolution. Not only does the author, a leading expert in the field, very thoroughly present the current state of knowledge on stellar physics, but he handles with equal care the many problems that this field of research still faces. A bibliography with well over 1000 entries makes this book an unparalleled reference source. "Stellar Evolution and Stability" is the second of two volumes and can be read, as can the first volume "Fundamental Concepts and Stellar Equilibrium," as a largely independent work. It traces in great detail the evolution of protostars towards the main sequence and beyond this to the last stage of stellar evolution, with the corresponding vast range from white dwarfs to supernovae explosions, gamma-ray bursts and black hole formation. The book concludes with special chapters on the dynamical, thermal and pulsing stability of stars. This second edition is carefully updated in the areas of pre...

  19. McDonald Observatory Planetary Search - A high precision stellar radial velocity survey for other planetary systems

    Science.gov (United States)

    Cochran, William D.; Hatzes, Artie P.

    1993-01-01

    The McDonald Observatory Planetary Search program surveyed a sample of 33 nearby F, G, and K stars since September 1987 to search for substellar companion objects. Measurements of stellar radial velocity variations to a precision of better than 10 m/s were performed as routine observations to detect Jovian planets in orbit around solar type stars. Results confirm the detection of a companion object to HD114762.

  20. A POSSIBLE BINARY SYSTEM OF A STELLAR REMNANT IN THE HIGH-MAGNIFICATION GRAVITATIONAL MICROLENSING EVENT OGLE-2007-BLG-514

    Energy Technology Data Exchange (ETDEWEB)

    Miyake, N.; Abe, F.; Furusawa, K.; Itow, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Udalski, A.; Kubiak, M.; Szymanski, M. K.; Pietrzynski, G.; Soszynski, I.; Ulaczyk, K.; Wyrzykowski, L. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Dong, S.; Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Street, R. A. [Las Cumbres Observatory, 6740B Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Greenhill, J. [School of Maths and Physics, University of Tasmania, Private bag 37, GPO Hobart, Tasmania 7001 (Australia); Bond, I. A. [Institute for Information and Mathematical Sciences, Massey University, Private Bag 102-904, Auckland 1330 (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Okayama 719-0232 (Japan); Holderness, S., E-mail: nmiyake@stelab.nagoya-u.ac.jp [Computer Science Department, University of Auckland, Auckland (New Zealand); Collaboration: OGLE Collaboration; MOA Collaboration; muFUN Collaboration; RoboNet Collaboration; PLANET Collaboration; and others

    2012-06-20

    We report the extremely high-magnification (A > 1000) binary microlensing event OGLE-2007-BLG-514. We obtained good coverage around the double peak structure in the light curve via follow-up observations from different observatories. The binary lens model that includes the effects of parallax (known orbital motion of the Earth) and orbital motion of the lens yields a binary lens mass ratio of q = 0.321 {+-} 0.007 and a projected separation of s = 0.072 {+-} 0.001 in units of the Einstein radius. The parallax parameters allow us to determine the lens distance D{sub L} = 3.11 {+-} 0.39 kpc and total mass M{sub L} = 1.40 {+-} 0.18 M{sub Sun }; this leads to the primary and secondary components having masses of M{sub 1} = 1.06 {+-} 0.13 M{sub Sun} and M{sub 2} = 0.34 {+-} 0.04 M{sub Sun }, respectively. The parallax model indicates that the binary lens system is likely constructed by the main-sequence stars. On the other hand, we used a Bayesian analysis to estimate probability distributions by the model that includes the effects of xallarap (possible orbital motion of the source around a companion) and parallax (q = 0.270 {+-} 0.005, s = 0.083 {+-} 0.001). The primary component of the binary lens is relatively massive, with M{sub 1} = 0.9{sup +4.6}{sub -0.3} M{sub Sun} and it is at a distance of D{sub L} = 2.6{sup +3.8}{sub -0.9} kpc. Given the secure mass ratio measurement, the companion mass is therefore M{sub 2} = 0.2{sup +1.2}{sub -0.1} M{sub Sun }. The xallarap model implies that the primary lens is likely a stellar remnant, such as a white dwarf, a neutron star, or a black hole.

  1. Does the stellar distribution flare? A comparison of stellar scale heights with LAB H I data

    Energy Technology Data Exchange (ETDEWEB)

    Kalberla, P. M. W.; Kerp, J.; Dedes, L. [Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn (Germany); Haud, U., E-mail: pkalberla@astro.uni-bonn.de [Tartu Observatory, 61602 Tõravere (Estonia)

    2014-10-10

    The question of whether the stellar populations in the Milky Way take part in the flaring of scale heights as observed for the H I gas is a matter of debate. Standard mass models for the Milky Way assume a constant scale height for each of the different stellar distributions. However, there is mounting evidence that at least some of the stellar distributions reach, at large galactocentric distances, high altitudes, which are incompatible with a constant scale height. We discuss recent observational evidence for stellar flaring and compare it with H I data from the Leiden/Argentine/Bonn survey. Within the systemic and statistical uncertainties we find a good agreement between both.

  2. Three-dimensional in vitro cancer spheroid models for Photodynamic Therapy: Strengths and Opportunities

    Science.gov (United States)

    Evans, Conor

    2015-03-01

    Three dimensional, in vitro spheroid cultures offer considerable utility for the development and testing of anticancer photodynamic therapy regimens. More complex than monolayer cultures, three-dimensional spheroid systems replicate many of the important cell-cell and cell-matrix interactions that modulate treatment response in vivo. Simple enough to be grown by the thousands and small enough to be optically interrogated, spheroid cultures lend themselves to high-content and high-throughput imaging approaches. These advantages have enabled studies investigating photosensitizer uptake, spatiotemporal patterns of therapeutic response, alterations in oxygen diffusion and consumption during therapy, and the exploration of mechanisms that underlie therapeutic synergy. The use of quantitative imaging methods, in particular, has accelerated the pace of three-dimensional in vitro photodynamic therapy studies, enabling the rapid compilation of multiple treatment response parameters in a single experiment. Improvements in model cultures, the creation of new molecular probes of cell state and function, and innovations in imaging toolkits will be important for the advancement of spheroid culture systems for future photodynamic therapy studies.

  3. INSIGHTS ON THE STELLAR MASS-METALLICITY RELATION FROM THE CALIFA SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    González Delgado, R. M.; García-Benito, R.; Pérez, E.; Cortijo-Ferrero, C.; López Fernández, R.; Sánchez, S. F. [Instituto de Astrofísica de Andalucía (CSIC), Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Cid Fernandes, R.; De Amorim, A. L.; Lacerda, E. A. D.; Vale Asari, N. [Departamento de Física, Universidade Federal de Santa Catarina, P.O. Box 476, 88040-900 Florianópolis, SC (Brazil); Alves, J. [University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna (Austria); Bland-Hawthorn, J. [Sydney Institute for Astronomy, The University of Sydney, NSW 2006 (Australia); Galbany, L. [Millennium Institute of Astrophysics and Departamento de Astronomía, Universidad de Chile, Casilla 36-D, Santiago (Chile); Gallazzi, A. [INAF—Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Husemann, B. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching b. München (Germany); Bekeraite, S. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Jungwiert, B. [Astronomical Institute of the Academy of Sciences of the Czech Republic, v.v.i., Bocni II 1401, 14131 Prague (Czech Republic); López-Sánchez, A. R. [Australian Astronomical Observatory, P.O. Box 915, North Ryde, NSW 1670 (Australia); De Lorenzo-Cáceres, A. [School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Marino, R. A. [CEI Campus Moncloa, UCM-UPM, Departamento de Astrofísica y CC. de la Atmósfera, Facultad de CC. Físicas, Universidad Complutense de Madrid, Avda. Complutense s/n, E-28040 Madrid (Spain); Collaboration: CALIFA collaboration920; and others

    2014-08-10

    We use spatially and temporally resolved maps of stellar population properties of 300 galaxies from the CALIFA integral field survey to investigate how the stellar metallicity (Z {sub *}) relates to the total stellar mass (M {sub *}) and the local mass surface density (μ{sub *}) in both spheroidal- and disk-dominated galaxies. The galaxies are shown to follow a clear stellar mass-metallicity relation (MZR) over the whole 10{sup 9}-10{sup 12} M {sub ☉} range. This relation is steeper than the one derived from nebular abundances, which is similar to the flatter stellar MZR derived when we consider only young stars. We also find a strong relation between the local values of μ{sub *} and Z {sub *} (the μZR), betraying the influence of local factors in determining Z {sub *}. This shows that both local (μ{sub *}-driven) and global (M {sub *}-driven) processes are important in determining metallicity in galaxies. We find that the overall balance between local and global effects varies with the location within a galaxy. In disks, μ{sub *} regulates Z {sub *}, producing a strong μZR whose amplitude is modulated by M {sub *}. In spheroids it is M {sub *} that dominates the physics of star formation and chemical enrichment, with μ{sub *} playing a minor, secondary role. These findings agree with our previous analysis of the star formation histories of CALIFA galaxies, which showed that mean stellar ages are mainly governed by surface density in galaxy disks and by total mass in spheroids.

  4. Kinematics and stellar populations of 17 dwarf early-type galaxies

    OpenAIRE

    Thomas, D.; Bender, R.; Hopp, U.; Maraston, C.; Greggio, L.

    2002-01-01

    We present kinematics and stellar population properties of 17 dwarf early-type galaxies in the luminosity range -14> M_B> -19. Our sample fills the gap between the intensively studied giant elliptical and Local Group dwarf spheroidal galaxies. The dwarf ellipticals of the present sample have constant velocity dispersion profiles within their effective radii and do not show significant rotation, hence are clearly anisotropic. The dwarf lenticulars, instead, rotate faster and are, at least part...

  5. Stellar photometry and polarimetry

    International Nuclear Information System (INIS)

    Golay, M.; Serkowski, K.

    1976-01-01

    A critical review of progress made in stellar photometry and polarimetry over the period 1973-1975 is presented. Reports of photometric measurements from various observatories throughout the world are summarized. The summary of work on stellar polarimetry lists the review papers, the catalogues and lists of standard stars, and descriptions of new observing techniques. (B.R.H.)

  6. Global Landslides on Rapidly Spinning Spheroids

    Science.gov (United States)

    Scheeres, Daniel J.; Sanchez, P.

    2013-10-01

    The angle of repose and conditions for global landslides on the surfaces of small, rapidly spinning, spheroidal asteroids are studied. Applying techniques of soil mechanics, we develop a theory for, and examples of, how regolith will fail and flow in this microgravity environment. Our motivation is to develop an understanding of the "top-shaped" class of asteroids based on analytical soil mechanics. Our analysis transforms the entire asteroid surface into a local frame where we can model it as a conventional granular pile with a surface slope, acceleration and height variations as a function of the body's spin rate, shape and density. A general finding is that the lowest point on a rapidly spinning spheroid is at the equator with the effective height of surface material monotonically increasing towards the polar regions, where the height can be larger than the physical radius of the body. We study the failure conditions of both cohesionless and cohesive regolith, and develop specific predictions of the surface profile as a function of the regolith angle of friction and the maximum spin rate experienced by the body. The theory also provides simple guidelines on what the shape may look like, although we do not analyze gravitationally self-consistent evolution of the body shape. The theory is tested with soft-sphere discrete element method granular mechanics simulations to better understand the dynamical aspects of global asteroid landslides. We find significant differences between failure conditions for cohesive and cohesionless regolith. In the case of cohesive regolith, we show that extremely small values of strength (much less than that found in lunar regolith) can stabilize a surface even at very rapid spin rates. Cohesionless surfaces, as expected, fail whenever their surface slopes exceed the angle of friction. Based on our analysis we propose that global landslides and the flow of material towards the equator on spheroidal bodies are precipitated by exogenous

  7. Compact stellarators as reactors

    International Nuclear Information System (INIS)

    Lyon, J.F.; Valanju, P.; Zarnstorff, M.C.; Hirshman, S.; Spong, D.A.; Strickler, D.; Williamson, D.E.; Ware, A.

    2001-01-01

    Two types of compact stellarators are examined as reactors: two- and three-field-period (M=2 and 3) quasi-axisymmetric devices with volume-average =4-5% and M=2 and 3 quasi-poloidal devices with =10-15%. These low-aspect-ratio stellarator-tokamak hybrids differ from conventional stellarators in their use of the plasma-generated bootstrap current to supplement the poloidal field from external coils. Using the ARIES-AT model with B max =12T on the coils gives Compact Stellarator reactors with R=7.3-8.2m, a factor of 2-3 smaller R than other stellarator reactors for the same assumptions, and neutron wall loadings up to 3.7MWm -2 . (author)

  8. Structure of the Draco Dwarf Spheroidal Galaxy

    OpenAIRE

    Piatek, Slawomir; Pryor, Carlton; Armandroff, Taft E.; Olszewski, Edward W.

    2002-01-01

    This article studies the structure of the Draco dwarf spheroidal galaxy with an emphasis on the question of whether the spatial distribution of its stars has been affected by the tidal interaction with the Milky Way, using R- and V-band CCD photometry for eleven fields. The article reports coordinates for the center, a position angle of the major axis, and the ellipticity. It also reports the results of searches for asymmetries in the structure of Draco. These results, and searches for a ``br...

  9. Process for producing uranium carbide spheroids

    International Nuclear Information System (INIS)

    Shennan, J.V.; Ford, L.H.

    1977-01-01

    The invention deals with a method to fabricate UC spheroids which are filled into moulds made of refractory material for fuel elements. The UC fuel particles are double-coated: a first thin layer of pyrolytic carbon is coated at low temperature 1200-1400 0 C, a record layer of pyrolytic material (e.g. Si c) is coated at a higher temperature (above 1500 0 C) which holds back the fission products. The method is described more closely by means of an example. (GSC) [de

  10. Process for producing uranium carbide spheroids

    International Nuclear Information System (INIS)

    Shennan, J.V.; Ford, L.H.

    1976-01-01

    The invention deals with a method to produce UC spheroids which are filled into molded bodies of fire-proof material for fuel elements. The UC fuel particles are doubly coated: a first thin layer of pyrolytic carbon is coated at low temperature (1,200-1,400 0 C), a second layer of fire-proof material (e.g. SiC) is coated at a higher temperature (above 1,500 0 C) which holds back the fission products. The process is explained in more detail using an example. (GSCH) [de

  11. Numerical Simulation of Spheroidization Process of TiAl Alloy Powders in Radio Frequency Plasma

    Directory of Open Access Journals (Sweden)

    ZHU Langping

    2017-06-01

    Full Text Available A numerical simulation method was used to study the radio frequency plasma spheroidization process of TiAl alloy powder. The effects of velocity field and temperature field on the motion trajectory and mass change of TiAl alloy powder with different particle size were analyzed.The results show that the temperature of powder particles increases rapidly under high temperature plasma, surface evaporation cause the reduction of particle size, and particles with small size tend to evaporate quickly. The motion trajectory of particles with different sizes in the lower end of the cooling tube is different obviously, small particles tend to enter the air outlet,while the larger particles are easy to fall down to the bottom of the cooling tube to be collected. Increasing air flow rate can improve the velocity of air flow in the spheroidizing system, causing larger particles to be taken away by the air, resulting in yield reduction. The simulation results of TiAl alloy powder spheroidization are close to the experimental results refer to parameters such as powder size distribution, average particle size and powder yield, and the model is in good accordance with the actual process of the spheroidization.

  12. Development of the stellarator/heliotron research

    International Nuclear Information System (INIS)

    Iiyoshi, A.

    1991-05-01

    The author reviewed the history of the development of the stellarator/heliotron system, and pointed out the important role of the radial electric field in plasma transport in helical devices. (J.P.N.)

  13. Multiple stellar populations of globular clusters from homogeneous Ca-Cn photometry. II. M5 (NGC 5904) and a new filter system

    OpenAIRE

    Lee, Jae-Woo

    2017-01-01

    Using our ingeniously designed new filter systems, we investigate the multiple stellar populations of the RGB and AGB in the GC M5. Our results are the following. (1) Our cn_jwl index accurately traces the nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions both in the RGB and the AGB sequences, with the number ratios between the CN-weak (CN-w) and the CN-strong (CN-s) of n(CN-w):n(CN-s) = 29:71(+/- 2) and 21:79(+/- 7), respectively. (3) We...

  14. The BANANA Project. IV. Two Aligned Stellar Rotation Axes in the Young Eccentric Binary System EP Crucis: Primordial Orientation and Tidal Alignment

    Science.gov (United States)

    Albrecht, Simon; Setiawan, Johny; Torres, Guillermo; Fabrycky, Daniel C.; Winn, Joshua N.

    2013-04-01

    With observations of the EP Cru system, we continue our series of measurements of spin-orbit angles in eclipsing binary star systems, the BANANA project (Binaries Are Not Always Neatly Aligned). We find a close alignment between the sky projections of the rotational and orbital angular momentum vectors for both stars (βp = -1.°8 ± 1.°6 and |βs| < 17°). We also derive precise absolute dimensions and stellar ages for this system. The EP Cru and DI Her systems provide an interesting comparison: they have similar stellar types and orbital properties, but DI Her is younger and has major spin-orbit misalignments, raising the question of whether EP Cru also had a large misalignment at an earlier phase of evolution. We show that tidal dissipation is an unlikely explanation for the good alignment observed today, because realignment happens on the same timescale as spin-orbit synchronization, and the stars in EP Cru are far from synchronization (they are spinning nine times too quickly). Therefore it seems that some binaries form with aligned axes, while other superficially similar binaries are formed with misaligned axes. Based on observations made with ESOs 2.2 m Telescopes at the La Silla Paranal Observatory under program ID 084.C-1008 (12.5%) and under MPIA guaranteed time (87.5%).

  15. Digital microfluidics for automated hanging drop cell spheroid culture.

    Science.gov (United States)

    Aijian, Andrew P; Garrell, Robin L

    2015-06-01

    Cell spheroids are multicellular aggregates, grown in vitro, that mimic the three-dimensional morphology of physiological tissues. Although there are numerous benefits to using spheroids in cell-based assays, the adoption of spheroids in routine biomedical research has been limited, in part, by the tedious workflow associated with spheroid formation and analysis. Here we describe a digital microfluidic platform that has been developed to automate liquid-handling protocols for the formation, maintenance, and analysis of multicellular spheroids in hanging drop culture. We show that droplets of liquid can be added to and extracted from through-holes, or "wells," and fabricated in the bottom plate of a digital microfluidic device, enabling the formation and assaying of hanging drops. Using this digital microfluidic platform, spheroids of mouse mesenchymal stem cells were formed and maintained in situ for 72 h, exhibiting good viability (>90%) and size uniformity (% coefficient of variation <10% intraexperiment, <20% interexperiment). A proof-of-principle drug screen was performed on human colorectal adenocarcinoma spheroids to demonstrate the ability to recapitulate physiologically relevant phenomena such as insulin-induced drug resistance. With automatable and flexible liquid handling, and a wide range of in situ sample preparation and analysis capabilities, the digital microfluidic platform provides a viable tool for automating cell spheroid culture and analysis. © 2014 Society for Laboratory Automation and Screening.

  16. Multicellular spheroids as an in vitro tumor model

    International Nuclear Information System (INIS)

    Kozubek, S.; Erzgraber, G.

    1982-01-01

    Experiments with fractionated irradiation of multicellular spheroids were performed. Our data as well as the data of other works have been evaluated by means of simple mathematical formulae on the basis of several hypothesis. The spheroids are shown to exhibit similar behaviour as in vivo carcinomas. They offer the possibility of investigation of quantitative correlations for practical purposes

  17. Short-term effects of radiation in gliolalstoma spheroids

    DEFF Research Database (Denmark)

    Petterson, Stine Asferg; Jakobsen, Ida Pind; Jensen, Stine Skov

    2016-01-01

    was to investigate the short-term effects of radiation of spheroids containing tumor-initiating stem-like cells. We used a patient-derived glioblastoma stem cell enriched culture (T76) and the standard glioblastoma cell line U87. Primary spheroids were irradiated with doses between 2 and 50 Gy and assessed after two...

  18. Stellar and Planetary Parameters for K2 's Late-type Dwarf Systems from C1 to C5

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, Arturo O. [Department of Astronomy, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182 (United States); Crossfield, Ian J. M.; Peacock, Sarah [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721 (United States); Schlieder, Joshua E. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Dressing, Courtney D. [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Obermeier, Christian [Max Planck Institut für Astronomie, Heidelberg (Germany); Livingston, John; Petigura, Erik A. [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Bunkyo-ku, Tokyo 113-0033 (Japan); Ciceri, Simona [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Beichman, Charles A. [NASA Exoplanet Science Institute, California Institute of Technology, Pasadena, CA 91125 (United States); Lépine, Sébastien [Department of Physics and Astronomy, Georgia State University, 25 Park Pl NE #605, Atlanta, GA 30303 (United States); Aller, Kimberly M. [Institute for Astronomy, University of Hawai’i at Mānoa, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States); Chance, Quadry A. [Steward Observatory, University of Arizona, 933 N. Cherry Ave, Tucson, AZ 85719 (United States); Howard, Andrew W. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Werner, Michael W. [Jet Propulsion Laboratory, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States)

    2017-03-01

    The NASA K2 mission uses photometry to find planets transiting stars of various types. M dwarfs are of high interest since they host more short-period planets than any other type of main-sequence star and transiting planets around M dwarfs have deeper transits compared to other main-sequence stars. In this paper, we present stellar parameters from K and M dwarfs hosting transiting planet candidates discovered by our team. Using the SOFI spectrograph on the European Southern Observatory’s New Technology Telescope, we obtained R ≈ 1000 J -, H -, and K -band (0.95–2.52 μ m) spectra of 34 late-type K2 planet and candidate planet host systems and 12 bright K4–M5 dwarfs with interferometrically measured radii and effective temperatures. Out of our 34 late-type K2 targets, we identify 27 of these stars as M dwarfs. We measure equivalent widths of spectral features, derive calibration relations using stars with interferometric measurements, and estimate stellar radii, effective temperatures, masses, and luminosities for the K2 planet hosts. Our calibrations provide radii and temperatures with median uncertainties of 0.059 R {sub ⊙} (16.09%) and 160 K (4.33%), respectively. We then reassess the radii and equilibrium temperatures of known and candidate planets based on our spectroscopically derived stellar parameters. Since a planet’s radius and equilibrium temperature depend on the parameters of its host star, our study provides more precise planetary parameters for planets and candidates orbiting late-type stars observed with K2 . We find a median planet radius and an equilibrium temperature of approximately 3 R {sub ⊕} and 500 K, respectively, with several systems (K2-18b and K2-72e) receiving near-Earth-like levels of incident irradiation.

  19. Variable Stars in the M31 Dwarf Spheroidal Companion Cassiopeia

    Science.gov (United States)

    Pritzl, Barton J.; Armandroff, T. E.; Jacoby, G. H.; Da Costa, G. S.

    2007-12-01

    Dwarf spheroidal galaxies show very diverse star formation histories. For the Galactic dwarf spheroidal galaxies, a correlation exists between Galactocentric distance and the prominence of intermediate-age ( 2 - 10 Gyr) populations. To test whether this correlation exists for the M31 dwarf spheroidal galaxies, we observed the Cassiopeia (And VII) dwarf galaxy, which is one of the most distant M31 dwarf spheroidal galaxies. We will present the results of a variable star search using HST/ACS data, along with a preliminary color-magnitude diagram. From the RR Lyrae stars we can obtain an independent distance and metallicity estimate for the dwarf galaxy. These results will be compared to those found for the other M31 dwarf spheroidal galaxies.This research is supported in part by NASA through grant number GO-11081.11 from the Space Telescope Science Institute.

  20. Development of controlled release spheroids using Buchananiacochinchinesis gum

    Directory of Open Access Journals (Sweden)

    Narayan Babulal Gaikwad

    2013-03-01

    Full Text Available Chirauli nut gum was isolated from the bark of Buchanania cochinchinesis (fam. Anacadiacea and was used as a release modifier for the preparation of Diclofenac sodium spheroids using the extrusion spheronization technique. The process was studied for the effects on variables when making spheroids with satisfactory particle shape, size and size distribution. The prepared spheroids were characterized for surface morphology, qualitative surface porosity, friability, bulk density and flow properties. In vitro studies demonstrated that the release exhibited Fickian diffusion kinetics which was confirmed by the Higuchi and the Korsmeyer-Peppas models. The physico-chemical parameters of the gum could be correlated to the in vitro dissolution profile of the spheroids. The spheroids were not able to sustain the drug releases over 12 hours. A greater concentration of Chirauli nut gum and a process that can accommodate such greater concentrations may produce a formulation capable of significant sustained release.

  1. Studying stellar binary systems with the Laser Interferometer Space Antenna using delayed rejection Markov chain Monte Carlo methods

    International Nuclear Information System (INIS)

    Trias, Miquel; Vecchio, Alberto; Veitch, John

    2009-01-01

    Bayesian analysis of Laser Interferometer Space Antenna (LISA) data sets based on Markov chain Monte Carlo methods has been shown to be a challenging problem, in part due to the complicated structure of the likelihood function consisting of several isolated local maxima that dramatically reduces the efficiency of the sampling techniques. Here we introduce a new fully Markovian algorithm, a delayed rejection Metropolis-Hastings Markov chain Monte Carlo method, to efficiently explore these kind of structures and we demonstrate its performance on selected LISA data sets containing a known number of stellar-mass binary signals embedded in Gaussian stationary noise.

  2. Stellar Parameters for Trappist-1

    Science.gov (United States)

    Van Grootel, Valérie; Fernandes, Catarina S.; Gillon, Michael; Jehin, Emmanuel; Manfroid, Jean; Scuflaire, Richard; Burgasser, Adam J.; Barkaoui, Khalid; Benkhaldoun, Zouhair; Burdanov, Artem; Delrez, Laetitia; Demory, Brice-Olivier; de Wit, Julien; Queloz, Didier; Triaud, Amaury H. M. J.

    2018-01-01

    TRAPPIST-1 is an ultracool dwarf star transited by seven Earth-sized planets, for which thorough characterization of atmospheric properties, surface conditions encompassing habitability, and internal compositions is possible with current and next-generation telescopes. Accurate modeling of the star is essential to achieve this goal. We aim to obtain updated stellar parameters for TRAPPIST-1 based on new measurements and evolutionary models, compared to those used in discovery studies. We present a new measurement for the parallax of TRAPPIST-1, 82.4 ± 0.8 mas, based on 188 epochs of observations with the TRAPPIST and Liverpool Telescopes from 2013 to 2016. This revised parallax yields an updated luminosity of {L}* =(5.22+/- 0.19)× {10}-4 {L}ȯ , which is very close to the previous estimate but almost two times more precise. We next present an updated estimate for TRAPPIST-1 stellar mass, based on two approaches: mass from stellar evolution modeling, and empirical mass derived from dynamical masses of equivalently classified ultracool dwarfs in astrometric binaries. We combine them using a Monte-Carlo approach to derive a semi-empirical estimate for the mass of TRAPPIST-1. We also derive estimate for the radius by combining this mass with stellar density inferred from transits, as well as an estimate for the effective temperature from our revised luminosity and radius. Our final results are {M}* =0.089+/- 0.006 {M}ȯ , {R}* =0.121+/- 0.003 {R}ȯ , and {T}{eff} = 2516 ± 41 K. Considering the degree to which the TRAPPIST-1 system will be scrutinized in coming years, these revised and more precise stellar parameters should be considered when assessing the properties of TRAPPIST-1 planets.

  3. FORMATION OF MASSIVE GALAXIES AT HIGH REDSHIFT: COLD STREAMS, CLUMPY DISKS, AND COMPACT SPHEROIDS

    International Nuclear Information System (INIS)

    Dekel, Avishai; Sari, Re'em; Ceverino, Daniel

    2009-01-01

    We present a simple theoretical framework for massive galaxies at high redshift, where the main assembly and star formation occurred, and report on the first cosmological simulations that reveal clumpy disks consistent with our analysis. The evolution is governed by the interplay between smooth and clumpy cold streams, disk instability, and bulge formation. Intense, relatively smooth streams maintain an unstable dense gas-rich disk. Instability with high turbulence and giant clumps, each a few percent of the disk mass, is self-regulated by gravitational interactions within the disk. The clumps migrate into a bulge in ∼ sun yr -1 , and each clump converts into stars in ∼0.5 Gyr. While the clumps coalesce dissipatively to a compact bulge, the star-forming disk is extended because the incoming streams keep the outer disk dense and susceptible to instability and because of angular momentum transport. Passive spheroid-dominated galaxies form when the streams are more clumpy: the external clumps merge into a massive bulge and stir up disk turbulence that stabilize the disk and suppress in situ clump and star formation. We predict a bimodality in galaxy type by z ∼ 3, involving giant-clump star-forming disks and spheroid-dominated galaxies of suppressed star formation. After z ∼ 1, the disks tend to be stabilized by the dominant stellar disks and bulges. Most of the high-z massive disks are likely to end up as today's early-type galaxies.

  4. The puzzling assembly of the Milky Way halo – contributions from dwarf Spheroidals and globular clusters

    Directory of Open Access Journals (Sweden)

    Lépine S.

    2012-02-01

    Full Text Available While recent sky surveys have uncovered large numbers of ever fainter Milky Way satellites, their classification as star clusters, low-luminosity galaxies, or tidal overdensities remains often unclear. Likewise, their contributions to the build-up of the halo is yet debated. In this contribution we will discuss the current knowledge of the stellar populations and chemo-dynamics in these puzzling satellites, with a particular focus on dwarf spheroidal galaxies and the globular clusters in the outer Galactic halo. Also the question of whether some of the outermost halo objects are dynamically associated with the (Milky Way halo at all is addressed in terms of proper measurements in the remote Leo I and II dwarf galaxies.

  5. Stellarator-Spheromak

    International Nuclear Information System (INIS)

    Moroz, P.E.

    1997-03-01

    A novel concept for magnetic plasma confinement, Stellarator-Spheromak (SSP), is proposed. Numerical analysis with the classical-stellarator-type outboard stellarator windings demonstrates a number of potential advantages of SSP for controlled nuclear fusion. Among the main ones are: simple and compact magnet coil configuration, absence of material structures (e.g. magnet coils or conducting walls) in the center of the torus, high rotational transform, and a possibility of MHD equilibria with very high β (pressure/magnetic pressure) of the confined plasma

  6. A comparison of the reduced and approximate systems for the time dependent computation of the polar wind and multiconstituent stellar winds

    International Nuclear Information System (INIS)

    Browning, G.L.; Holzer, T.E.

    1992-01-01

    The reduced system of equations commonly used to describe the time evolution of the polar wind and multiconstituent stellar winds is derived from the equations for a multispecies plasma with known temperature profiles by assuming that the electron thermal speed approaches infinity. The reduced system is proved to have unbounded growth near the sonic point of the protons for many of the standard parameter cases. For the same parameter cases, however, the unmodified system (from which the reduced system is derived) exhibits growth in some of the Fourier modes, but this growth is bounded. An alternate system (the approximate system) in which the electron thermal speed is slowed down is introduced. The approximate system retains the mathematical behavior of the unmodified system and can be shown to accurately describe the smooth solutions of the unmodified system. The approximate system has a number of other advantages over the reduced system becomes inaccurate. Also, for three-dimensional flows the correct reduced system requires the solution of an elliptic equation, while the approximate system is hyperbolic and only requires a time step approximately 1 order of magnitude less than the reduced system. Numerical solutions from models based on the two systems are compared with each other to illustrate these points

  7. Morphological and Functional Analysis of Hepatocyte Spheroids Generated on Poly-HEMA-Treated Surfaces under the Influence of Fetal Calf Serum and Nonparenchymal Cells

    Directory of Open Access Journals (Sweden)

    Augustinus Bader

    2013-03-01

    Full Text Available Poly (2-hydroxyethyl methacrylate (HEMA has been used as a clinical material, in the form of a soft hydrogel, for various surgical procedures, including endovascular surgery of liver. It is a clear liquid compound and, as a soft, flexible, water-absorbing material, has been used to make soft contact lenses from small, concave, spinning molds. Primary rat hepatocyte spheroids were created on a poly-HEMA-coated surface with the intention of inducing hepatic tissue formation and improving liver functions. We investigated spheroid formation of primary adult rat hepatocyte cells and characterized hepatic-specific functions under the special influence of fetal calf serum (FCS and nonparencymal cells (NPC up to six days in different culture systems (e.g., hepatocytes + FCS, hepatocytes – FCS, NPC + FCS, NPC – FCS, co-culture + FCS, co-culture – FCS in both the spheroid model and sandwich model. Immunohistologically, we detected gap junctions, Ito cell/Kupffer cells, sinusoidal endothelial cells and an extracellular matrix in the spheroid model. FCS has no positive effect in the sandwich model, but has a negative effect in the spheroid model on albumin production, and no influence in urea production in either model. We found more cell viability in smaller diameter spheroids than larger ones by using the apoptosis test. Furthermore, there is no positive influence of the serum or NPC on spheroid formation, suggesting that it may only depend on the physical condition of the culture system. Since the sandwich culture has been considered a “gold standard” in vitro culture model, the hepatocyte spheroids generated on the poly-HEMA-coated surface were compared with those in the sandwich model. Major liver-specific functions, such as albumin secretion and urea synthesis, were evaluated in both the spheroid and sandwich model. The synthesis performance in the spheroid compared to the sandwich culture increases approximately by a factor of 1

  8. Grigori Kuzmin and Stellar Dynamics

    Directory of Open Access Journals (Sweden)

    Zeeuw P. Tim de

    2011-06-01

    Full Text Available Grigori Kuzmin was a very gifted dynamicist and one of the towering figures in the distinguished history of the Tartu Observatory. He obtained a number of important results in relative isolation which were later rediscovered in the West. This work laid the foundation for further advances in the theory of stellar systems in dynamical equilibrium, thereby substantially increasing our understanding of galaxy dynamics.

  9. Determination of acute lethal and chronic lethal dose thresholds of valproic acid using 3D spheroids constructed from the immortal human hepatocyte cell line HepG2/C3A

    DEFF Research Database (Denmark)

    Fey, S. J.; Wrzesinski, K.

    2013-01-01

    describe here a culture system based on 3D spheroid culture of immortal hepatocytes which can determine the toxicity of valproic acid (or structurally or functionally related molecules) in vitro. The spheroids were used to follow changes in ATP production, glucose uptake and adenylate kinase following...

  10. Wimps and stellar structure

    International Nuclear Information System (INIS)

    Bouquet, A.; Salati, P.

    1988-01-01

    We present the results of an analytic approximation to compute the effects of WIMPs on stellar structures in a self-consistent way. We examine in particular the case of the Sun and of horizontal branch stars

  11. Principles of Stellar Interferometry

    CERN Document Server

    Glindemann, Andreas

    2011-01-01

    Over the last decade, stellar interferometry has developed from a specialist tool to a mainstream observing technique, attracting scientists whose research benefits from milliarcsecond angular resolution. Stellar interferometry has become part of the astronomer’s toolbox, complementing single-telescope observations by providing unique capabilities that will advance astronomical research. This carefully written book is intended to provide a solid understanding of the principles of stellar interferometry to students starting an astronomical research project in this field or to develop instruments and to astronomers using interferometry but who are not interferometrists per se. Illustrated by excellent drawings and calculated graphs the imaging process in stellar interferometers is explained starting from first principles on light propagation and diffraction wave propagation through turbulence is described in detail using Kolmogorov statistics the impact of turbulence on the imaging process is discussed both f...

  12. Convection and stellar oscillations

    DEFF Research Database (Denmark)

    Aarslev, Magnus Johan

    2017-01-01

    for asteroseismology, because of the challenges inherent in modelling turbulent convection in 1D stellar models. As a result of oversimplifying the physics near the surface, theoretical calculations systematically overestimate the oscillation frequencies. This has become known as the asteroseismic surface effect. Due...... to lacking better options, this frequency difference is typically corrected for with ad-hoc formulae. The topic of this thesis is the improvement of 1D stellar convection models and the effects this has on asteroseismic properties. The source of improvements is 3D simulations of radiation...... atmospheres to replace the outer layers of stellar models. The additional turbulent pressure and asymmetrical opacity effects in the atmosphere model, compared to convection in stellar evolution models, serve to expand the atmosphere. The enlarged acoustic cavity lowers the pulsation frequencies bringing them...

  13. A New View of the Dwarf Spheroidal Satellites of the Milky Way From VLT/FLAMES: Where are the Very Metal Poor Stars?

    Energy Technology Data Exchange (ETDEWEB)

    Helmi, Amina; Irwin, M.J.; Tolstoy, E.; Battaglia, G.; Hill, V.; Jablonka, P.; Venn, K.; Shetrone, M.; Letarte, B.; Arimoto, N.; Abel, T.; Francois, P.; Kaufer, A.; Primas, F.; Sadakane, K.; Szeifert, T.; /Kapteyn Astron. Inst., Groningen /Cambridge U., Inst. of Astron. /Meudon Observ. /LASTRO Observ. /Victoria U. /Texas U., McDonald Observ.

    2006-11-20

    As part of the Dwarf galaxies Abundances and Radial-velocities Team (DART) Programme, we have measured the metallicities of a large sample of stars in four nearby dwarf spheroidal galaxies (dSph): Sculptor, Sextans, Fornax and Carina. The low mean metal abundances and the presence of very old stellar populations in these galaxies have supported the view that they are fossils from the early Universe. However, contrary to naive expectations, we find a significant lack of stars with metallicities below [Fe/H] {approx} -3 dex in all four systems. This suggests that the gas that made up the stars in these systems had been uniformly enriched prior to their formation. Furthermore, the metal-poor tail of the dSph metallicity distribution is significantly different from that of the Galactic halo. These findings show that the progenitors of nearby dSph appear to have been fundamentally different from the building blocks of the Milky Way, even at the earliest epochs.

  14. Tensile Forces Originating from Cancer Spheroids Facilitate Tumor Invasion.

    Directory of Open Access Journals (Sweden)

    Katarzyna S Kopanska

    Full Text Available The mechanical properties of tumors and the tumor environment provide important information for the progression and characterization of cancer. Tumors are surrounded by an extracellular matrix (ECM dominated by collagen I. The geometrical and mechanical properties of the ECM play an important role for the initial step in the formation of metastasis, presented by the migration of malignant cells towards new settlements as well as the vascular and lymphatic system. The extent of this cell invasion into the ECM is a key medical marker for cancer prognosis. In vivo studies reveal an increased stiffness and different architecture of tumor tissue when compared to its healthy counterparts. The observed parallel collagen organization on the tumor border and radial arrangement at the invasion zone has raised the question about the mechanisms organizing these structures. Here we study the effect of contractile forces originated from model tumor spheroids embedded in a biomimetic collagen I matrix. We show that contractile forces act immediately after seeding and deform the ECM, thus leading to tensile radial forces within the matrix. Relaxation of this tension via cutting the collagen does reduce invasion, showing a mechanical relation between the tensile state of the ECM and invasion. In turn, these results suggest that tensile forces in the ECM facilitate invasion. Furthermore, simultaneous contraction of the ECM and tumor growth leads to the condensation and reorientation of the collagen at the spheroid's surface. We propose a tension-based model to explain the collagen organization and the onset of invasion by forces originating from the tumor.

  15. The WEGA Stellarator: Results and Prospects

    International Nuclear Information System (INIS)

    Otte, M.; Andruczyk, D.; Koenig, R.; Laqua, H. P.; Lischtschenko, O.; Marsen, S.; Schacht, J.; Podoba, Y. Y.; Wagner, F.; Warr, G. B.; Holzhauer, E.; Howard, J.; Krupnik, L.; Zhezhera, A.; Urban, J.; Preinhalter, J.

    2008-01-01

    In this article an overview is given on results from magnetic flux surface measurements, applied ECR heating scenarios for 2.45 GHz and 28 GHz, fluctuation and transport studies and plasma edge biasing experiments performed in the WEGA stellarator. Examples for the development of new diagnostics and the machine control system are given that will be used at Wendelstein 7-X stellarator, which is currently under construction in Greifswald

  16. The Stellar-Dynamical Oeuvre James Binney

    Indian Academy of Sciences (India)

    tribpo

    of the eigenvalues of M. The variation of the stellar density from point to point .... of Σ,(ΔΕ)2 , where ∆ Ε is the change in energy that a star suffers during a binary ... could use these results to calculate the relaxation time in a stellar system if he .... the region of enhanced density that tails behind it like a wake behind a ship. By.

  17. Oscillations in stellar atmospheres

    International Nuclear Information System (INIS)

    Costa, A.; Ringuelet, A.E.; Fontenla, J.M.

    1989-01-01

    Atmospheric excitation and propagation of oscillations are analyzed for typical pulsating stars. The linear, plane-parallel approach for the pulsating atmosphere gives a local description of the phenomenon. From the local analysis of oscillations, the minimum frequencies are obtained for radially propagating waves. The comparison of the minimum frequencies obtained for a variety of stellar types is in good agreement with the observed periods of the oscillations. The role of the atmosphere in the globar stellar pulsations is thus emphasized. 7 refs

  18. A spectroscopic search for colliding stellar winds in O-type close binary systems. IV - Iota Orionis

    Science.gov (United States)

    Gies, Douglas R.; Wiggs, Michael S.; Bagnuolo, William G., Jr.

    1993-01-01

    We present H-alpha and He I 6678 A line profiles for the eccentric orbit binary Iota Ori. We have applied a tomography algorithm which uses the established orbital velocity curves and intensity ratio to reconstruct the spectral line profiles for each star. The He I profiles appear as pure photospheric lines, and H-alpha shows variable emission in the line core throughout the orbit (which is typical of O giants) and in the blue wing near periastron passage. We show that the blue wing emission is consistent with an origin between the stars which probably results from a dramatic focusing of the primary's stellar wind at periastron. We also present IUE archival spectra of the UV wind lines N V 1240 A and C IV 1550 A.

  19. Triple Microlens OGLE-2008-BLG-092L: Binary Stellar System with a Circumprimary Uranus-type Planet

    Science.gov (United States)

    Poleski, Radosław; Skowron, Jan; Udalski, Andrzej; Han, Cheongho; Kozłowski, Szymon; Wyrzykowski, Łukasz; Dong, Subo; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł; Gould, Andrew

    2014-11-01

    We present the gravitational microlensing discovery of a 4 M Uranus planet that orbits a 0.7 M ⊙ star at ≈18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main-sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only about three times smaller than that of the companion star, suggesting significant dynamical interactions.

  20. Triple microlens OGLE-2008-BLG-092L: binary stellar system with a circumprimary uranus-type planet

    Energy Technology Data Exchange (ETDEWEB)

    Poleski, Radosław; Gould, Andrew [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Skowron, Jan; Udalski, Andrzej; Kozłowski, Szymon; Wyrzykowski, Łukasz; Szymański, Michał K.; Kubiak, Marcin; Pietrzyński, Grzegorz; Soszyński, Igor; Ulaczyk, Krzysztof; Pietrukowicz, Paweł [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Han, Cheongho [Department of Physics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Dong, Subo, E-mail: poleski@astronomy.ohio-state.edu [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871 (China)

    2014-11-01

    We present the gravitational microlensing discovery of a 4 M {sub Uranus} planet that orbits a 0.7 M {sub ☉} star at ≈18 AU. This is the first known analog of Uranus. Similar planets, i.e., cold ice giants, are inaccessible to either radial velocity or transit methods because of the long orbital periods, while low reflected light prevents direct imaging. We discuss how similar planets may contaminate the sample of the very short microlensing events that are interpreted as free-floating planets with an estimated rate of 1.8 per main-sequence star. Moreover, the host star has a nearby stellar (or brown dwarf) companion. The projected separation of the planet is only about three times smaller than that of the companion star, suggesting significant dynamical interactions.

  1. Modular Stellarator Fusion Reactor concept

    International Nuclear Information System (INIS)

    Miller, R.L.; Krakowski, R.A.

    1981-08-01

    A preliminary conceptual study is made of the Modular Stellarator Reactor (MSR). A steady-state ignited, DT-fueled, magnetic fusion reactor is proposed for use as a central electric-power station. The MSR concept combines the physics of the classic stellarator confinement topology with an innovative, modular-coil design. Parametric tradeoff calculations are described, leading to the selection of an interim design point for a 4-GWt plant based on Alcator transport scaling and an average beta value of 0.04 in an l = 2 system with a plasma aspect ratio of 11. The physics basis of the design point is described together with supporting magnetics, coil-force, and stress computations. The approach and results presented herein will be modified in the course of ongoing work to form a firmer basis for a detailed conceptual design of the MSR

  2. Ellipticity behaviour of relativistic Maclaurin spheroids

    International Nuclear Information System (INIS)

    Abramowicz, M.A.; Miller, J.C.; International School of Advanced Studies, Trieste; Oxford Univ.

    1990-01-01

    Chandrasekhar and Miller (1974 Mon. Not. R. Astr. Soc., 167, 63) found that, according to the general theory of relativity, when slowly rotating spheroids contract, conserving angular momentum, their eccentricity does not increase monotonically, as is the case for Newtonian gravity, but instead reaches a maximum (when the mean radius is a few times the Schwarzschild radius) and then decreases again. We show here that this can be explained within the framework of the recent discussion of rotational effects in a strong gravitational field. We suggest that it can be convenient to introduce a 'corrected' Newtonian theory, incorporating terms to approximate strong field effects, and that such a corrected theory could be useful for numerical studies. (author)

  3. Plasma spheroidizing and cladding of powders

    International Nuclear Information System (INIS)

    Petrunichev, V.A.; Averin, V.V.; Sorokin, L.M.; Koroleva, E.B.

    1987-01-01

    Arc and high-frequency plasmatrons are used for spheroidizing nickel and chromium-base alloy particles. Different plasma-forming medium compositions are used in the arc variant and the effect of these media on the plasma treatment product is demonstrated. For a high-frequency plasmatron, a long time of plasma contact with the powder leads to the transfer of the part of the material from the treated particles into vaporous state with subsequent condensation at the outlet from the discharge zone. Results of investigations into the formation of metal coatings on oxide and carbide particles during plasma-arc action are also presented. Representative data on the output of particles with coating are obtained and factors, providing for the optimal particle cladding conditions, are indicated

  4. Magnetohydrodynamic equilibrium with spheroidal plasma-vacuum interface

    International Nuclear Information System (INIS)

    Kaneko, Shobu; Chiyoda, Katsuji; Hirota, Isao.

    1983-01-01

    The Grad-Shafranov equations for an oblate and a prolate spheroidal plasmas are solved analytically under the assumptions, Bsub(phi) = 0 and dp/dpsi = constant. Here Bsub(phi) is the toroidal magnetic field, p is the kinetic pressure, and psi is the magnetic flux function. The plasmas in magnetohydrodynamic equilibrium are shown to be toroidal. The equilibrium magnetic-field configurations outside the spheroidal plasmas are considerably different from that of a spherical plasma. A line cusp or two point cusps appear outside the oblate or the prolate spheroidal plasma, respectively. (author)

  5. [Reparative and neoplastic spheroid cellular structures and their mathematical model].

    Science.gov (United States)

    Kogan, E A; Namiot, V A; Demura, T A; Faĭzullina, N M; Sukhikh, G T

    2014-01-01

    Spheroid cell structures in the cell cultures have been described and are used for studying cell-cell and cell- matrix interactions. At the same time, spheroid cell structure participation in the repair and development of cancer in vivo remains unexplored. The aim of this study was to investigate the cellular composition of spherical structures and their functional significance in the repair of squamous epithelium in human papilloma virus-associated cervical pathology--chronic cervicitis and cervical intraepithelial neoplasia 1-3 degree, and also construct a mathematical model to explain the development and behavior of such spheroid cell structure.

  6. The metal-poor knee in the Fornax dwarf spheroidal galaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hendricks, Benjamin; Koch, Andreas [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117, Heidelberg (Germany); Lanfranchi, Gustavo A. [Núcleo de Astrofísica Teórica, Universidade Cruzeiro do Sul, R. Galvão Bueno 868, Liberdade, 01506-000, São Paulo, SP (Brazil); Boeche, Corrado [Zentrum für Astronomie der Universität Heidelberg, Astronomisches Rechen-Institut, Mönchhofstr. 12-14, D-69120, Heidelberg (Germany); Walker, Matthew [McWilliams Center for Cosmology, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Johnson, Christian I. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-15, Cambridge, MA 02138 (United States); Peñarrubia, Jorge [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Gilmore, Gerard, E-mail: ben.hendricks@lsw.uni-heidelberg.de [Institute of Astronomy, Cambridge University, Madingley Rd, Cambridge CB3 OHA (United Kingdom)

    2014-04-20

    We present α-element abundances of Mg, Si, and Ti for a large sample of field stars in two outer fields of the Fornax dwarf spheroidal (dSph) galaxy, obtained with Very Large Telescope/GIRAFFE (R ∼ 16, 000). Due to the large fraction of metal-poor (MP) stars in our sample, we are able to follow the α-element evolution from [Fe/H] ≈ –2.5 continuously to [Fe/H] ≈ –0.7. For the first time we are able to resolve the turnover from the Type II supernovae (SNe) dominated, α-enhanced plateau down to subsolar [α/Fe] values, due to the onset of SNe Ia, and thus to trace the chemical enrichment efficiency of the galaxy. Our data support the general concept of an α-enhanced plateau at early epochs, followed by a well-defined 'knee' caused by the onset of SNe Ia, and finally a second plateau with sub-solar [α/Fe] values. We find the position of this knee to be at [Fe/H] ≈ –1.9 and therefore significantly more MP than expected from comparison with other dSphs and standard evolutionary models. Surprisingly, this value is rather comparable to the knee in Sculptor, a dSph ∼10 times less luminous than Fornax. Using chemical evolution models, we find that the position of the knee and the subsequent plateau at the sub-solar level can hardly be explained unless the galaxy experienced several discrete star formation (SF) events with a drastic variation in SF efficiency, while a uniform SF can be ruled out. One possible evolutionary scenario is that Fornax experienced one or several major accretion events from gas-rich systems in the past, so that its current stellar mass is not indicative of the chemical evolution environment at ancient times. If Fornax is the product of several smaller buildings blocks, this may also have implications for the understanding of the formation process of dSphs in general.

  7. Proper Motions of Dwarf Spheroidal Galaxies from Hubble Space Telescope Imaging. III. Measurement for Ursa Minor

    Science.gov (United States)

    Piatek, Slawomir; Pryor, Carlton; Bristow, Paul; Olszewski, Edward W.; Harris, Hugh C.; Mateo, Mario; Minniti, Dante; Tinney, Christopher G.

    2005-07-01

    This article presents a measurement of the proper motion of the Ursa Minor dwarf spheroidal galaxy determined from images taken with the Hubble Space Telescope in two distinct fields. Each field contains a quasi-stellar object that serves as the ``reference point.'' The measured proper motion for Ursa Minor, expressed in the equatorial coordinate system, is (μα,μδ)=(-50+/-17,22+/-16) mas century-1. Removing the contributions of the solar motion and the motion of the local standard of rest yields the proper motion in the Galactic rest frame: (μGrfα,μGrfδ)=(-8+/-17,38+/-16) mas century-1. The implied space velocity with respect to the Galactic center has a radial component of Vr=-75+/-44 km s-1 and a tangential component of Vt=144+/-50 km s-1. Integrating the motion of Ursa Minor in a realistic potential for the Milky Way produces orbital elements. The perigalacticon and apogalacticon are 40 (10, 76) and 89 (78, 160) kpc, respectively, where the values in the parentheses represent the 95% confidence intervals derived from Monte Carlo experiments. The eccentricity of the orbit is 0.39 (0.09, 0.79), and the orbital period is 1.5 (1.1, 2.7) Gyr. The orbit is retrograde and inclined by 124° (94°, 136°) to the Galactic plane. Ursa Minor is not a likely member of a proposed stream of galaxies on similar orbits around the Milky Way, nor is the plane of its orbit coincident with a recently proposed planar alignment of galaxies around the Milky Way. Comparing the orbits of Ursa Minor and Carina shows no reason for the different star formation histories of these two galaxies. Ursa Minor must contain dark matter to have a high probability of having survived disruption by the Galactic tidal force until the present. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

  8. The episodic star formation history of the Carina dwarf spheroidal galaxy

    Science.gov (United States)

    de Boer, T. J. L.; Tolstoy, E.; Lemasle, B.; Saha, A.; Olszewski, E. W.; Mateo, M.; Irwin, M. J.; Battaglia, G.

    2014-12-01

    We present deep photometry of the Carina dwarf spheroidal galaxy in the B and V filters from CTIO/MOSAIC out to and beyond the tidal radius of rell ≈ 0.48 degrees. The accurately calibrated photometry is combined with spectroscopic metallicity distributions of red giant branch (RGB) stars to determine the detailed star formation and chemical evolution history of Carina. The star formation history (SFH) confirms the episodic formation history of Carina and quantifies the duration and strength of each episode in great detail as a function of radius from the centre. Two main episodes of star formation occurred at old (>8 Gyr) and intermediate (2-8 Gyr) ages, both enriching stars starting from low metallicities ([Fe/H] < - 2 dex). By dividing the SFH into two components, we determine that 60 ± 9 percent of the total number of stars formed within the intermediate-age episode. Furthermore, within the tidal radius (0.48 degrees or 888 pc) a total mass in stars of 1.07 ± 0.08 × 106 M⊙ was formed, giving Carina a stellar mass-to-light ratio of 1.8 ± 0.8. By combining the detailed SFH with spectroscopic observations of RGB stars, we determined the detailed age-metallicity relation of each episode and the timescale of α-element evolution of Carina from individual stars. The oldest episode displays a tight age-metallicity relation during ≈6 Gyr with steadily declining α-element abundances and a possible α-element "knee" visible at [Fe/H] ≈ - 2.5 dex. The intermediate-age sequence displays a more complex age-metallicity relation starting from low metallicity and a sequence in α-element abundances with a slope much steeper than observed in the old episode, starting from [Fe/H] = -1.8 dex and [Mg/Fe] ≈ 0.4 dex and declining to Mg-poor values ([Mg/Fe] ≤ - 0.5 dex). This clearly indicates that the two episodes of star formation formed from gas with different abundance patterns, which is inconsistent with simple evolution in an isolated system. Tables 1-3 are

  9. SI: The Stellar Imager

    Science.gov (United States)

    Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2006-01-01

    The ultra-sharp images of the Stellar Imager (SI) will revolutionize our view of many dynamic astrophysical processes: The 0.1 milliarcsec resolution of this deep-space telescope will transform point sources into extended sources, and simple snapshots into spellbinding evolving views. SI s science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI s prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era by imaging a sample of magnetically active stars with enough resolution to map their evolving dynamo patterns and their internal flows. By exploring the Universe at ultra-high resolution, SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled structures and processes in the Universe.

  10. Generalized prolate spheroidal wave functions for optical finite fractional Fourier and linear canonical transforms.

    Science.gov (United States)

    Pei, Soo-Chang; Ding, Jian-Jiun

    2005-03-01

    Prolate spheroidal wave functions (PSWFs) are known to be useful for analyzing the properties of the finite-extension Fourier transform (fi-FT). We extend the theory of PSWFs for the finite-extension fractional Fourier transform, the finite-extension linear canonical transform, and the finite-extension offset linear canonical transform. These finite transforms are more flexible than the fi-FT and can model much more generalized optical systems. We also illustrate how to use the generalized prolate spheroidal functions we derive to analyze the energy-preservation ratio, the self-imaging phenomenon, and the resonance phenomenon of the finite-sized one-stage or multiple-stage optical systems.

  11. Confinement of nonneutral spheroidal plasmas in multi-ring electrode traps

    International Nuclear Information System (INIS)

    Mohri, Akihiro; Yuyama, Tetsumori; Michishita, Toshinori; Higaki, Hiroyuki; Tanaka, Hitoshi; Yamazawa, Yohei; Aoyagi, Masayuki

    1998-01-01

    A nonneutral spheroidal plasma can be settled in a rigid rotor equilibrium inside a closed conducting cell independently of induced image charges on the cell wall if the electrostatic potential distribution on the wall surface is set equal to the sum of the external hyperbolic potential (r 2 -2z 2 ) and the self-potential produced by the plasma. A confinement system equipped with a train of properly biased ring electrodes can approximately generate any axisymmetric potential, including the above field. Experiments on confinement of electron spheroids in such a system showed that the confinement time became the longest when the condition to diminish the image charge effects was satisfied. The observed frequency of the centre-of-mass harmonic oscillation of the plasma in this configuration was in good agreement with the estimated one. (author)

  12. Hydrogen atom and the H+2 and HeH++ molecular ions inside prolate spheroidal boxes

    International Nuclear Information System (INIS)

    Ley-Koo, E.; Cruz, S.A.

    1981-01-01

    We formulate the exact solution of the Schroedinger equation for systems of one electron in the Coulomb field of one or two fixed nuclei at the foci inside prolate spheroidal boxes. Numerical results are obtained for the energy eigenvalues and eigenfunctions of the lowest states of the hydrogen atom and the H + 2 and HeH ++ molecular ions for boxes of different sizes and eccentricities. We also evaluate the hyperfine splitting of atomic hydrogen and of H + 2

  13. Imaging Herpes Simplex Virus Type 1 Amplicon Vector–Mediated Gene Expression in Human Glioma Spheroids

    OpenAIRE

    Christine Kaestle; Alexandra Winkeler; Raphaela Richter; Heinrich Sauer; Jürgen Hescheler; Cornel Fraefel; Maria Wartenberg; Andreas H. Jacobs

    2011-01-01

    Vectors derived from herpes simplex virus type 1 (HSV-1) have great potential for transducing therapeutic genes into the central nervous system; however, inefficient distribution of vector particles in vivo may limit their therapeutic potential in patients with gliomas. This study was performed to investigate the extent of HSV-1 amplicon vector–mediated gene expression in a three-dimensional glioma model of multicellular spheroids by imaging highly infectious HSV-1 virions expressing green fl...

  14. PREFACE: A Stellar Journey A Stellar Journey

    Science.gov (United States)

    Asplund, M.

    2008-10-01

    The conference A Stellar Journey was held in Uppsala, Sweden, 23 27June 2008, in honour of Professor Bengt Gustafsson's 65th birthday. The choice of Uppsala as the location for this event was obvious given Bengt's long-standing association with the city stemming back to his school days. With the exception of a two-year postdoc stint in Copenhagen, five years as professor at Stockholm University and two years as director of the Sigtuna foundation, Bengt has forged his illustrious professional career at Uppsala University. The symposium venue was Museum Gustavianum, once the main building of the oldest university in Scandinavia. The title of the symposium is a paraphrasing of Bengt's popular astronomy book Kosmisk Resa (in English: Cosmic Journey) written in the early eighties. I think this aptly symbolizes his career that has been an astronomical voyage from near to far, from the distant past to the present. The original book title was modified slightly to reflect that most of his work to date has dealt with stars in one way or another. In addition it also gives credit to Bengt's important role as a guiding light for a very large number of students, colleagues and collaborators, indeed for several generations of astronomers. For me personally, the book Kosmisk Resa bears particular significance as it has shaped my life rather profoundly. Although I had already decided to become an astronomer, when I first read the book as a 14-year-old I made up my mind then and there that I would study under Bengt Gustafsson and work on stars. Indeed I have remained true to this somewhat audacious resolution. I suspect that a great number of us have similar stories how Bengt has had a major influence on our lives, whether on the professional or personal level. Perhaps Bengt's most outstanding characteristic is his enthralling enthusiasm. This is equally true whether he is pondering some scientific conundrum, supervising students or performing in front of an audience, be it an

  15. Stellar magnetic activity

    International Nuclear Information System (INIS)

    Schrijver, C.J.

    1986-01-01

    The stellar emission in the chromospheric Ca II H+K lines is compared with the coronal soft X-ray emission, measuring the effects of non-radiative heating in the outer atmosphere at temperatures differing two orders of magnitude. The comparison of stellar flux densities in Ca II H+K and X-rays is extended to fluxes from the transition-region and the high-temperature chromosphere. The stellar magnetic field is probably generated in the differentially rotating convective envelope. The relation between rotation rate and the stellar level of activity measured in chromospheric, transition-region, and coronal radiative diagnostics is discovered. X-ray observations of the binary λ Andromedae are discussed. The departure of M-type dwarfs from the main relations, and the implications for the structure of the chromospheres of these stars are discussed. Variations of the average surface flux densities of the Sun during the 11-year activity cycle agree with flux-flux relations derived for other cool stars, suggesting that the interpretation of the stellar relations may be furthered by studying the solar analogue in more detail. (Auth.)

  16. Powder processing and spheroidizing with thermal inductively coupled plasma

    International Nuclear Information System (INIS)

    Nutsch, G.; Linke, P.; Zakharian, S.; Dzur, B.; Weiss, K.-H.

    2001-01-01

    Processing of advanced powder materials for the spraying industry is one of the most promising applications of the thermal RF inductively coupled plasma. By selecting the feedstock carefully and adjusting the RF plasma parameters, unique materials with high quality can be achieved. Powders injected in the hot plasma core emerge with modified shapes, morphology, crystal structure and chemical composition. Ceramic oxide powders such as Al 2 O 3 , ZrO 2 , SiO 2 are spheroidized with a high spheroidization rate. By using the RF induction plasma spheroidizing process tungsten melt carbide powders are obtained with a high spheroidization rate at high feeding rates by densification of agglomerated powders consisting of di-tungsten carbide and monocarbide with a definite composition. This kind of ball-like powders is particularly suited for wear resistant applications. (author)

  17. Spheroidization of transition metal carbides in low temperature plasma

    International Nuclear Information System (INIS)

    Klinskaya, N.A.; Koroleva, E.B.; Petrunichev, V.A.; Rybalko, O.F.; Solov'ev, P.V.; Ugol'nikova, T.A.

    1986-01-01

    Plasma process of preparation of titanium, tungsten and chromium carbide spherical powders with the main particle size 40-80 μm is considered. Spheroidization degree, granulometric and phase composition of the product are investigated

  18. Oxygen Partial Pressure Is a Rate-Limiting Parameter for Cell Proliferation in 3D Spheroids Grown in Physioxic Culture Condition.

    Science.gov (United States)

    Gomes, Aurélie; Guillaume, Ludivine; Grimes, David Robert; Fehrenbach, Jérôme; Lobjois, Valérie; Ducommun, Bernard

    2016-01-01

    The in situ oxygen partial pressure in normal and tumor tissues is in the range of a few percent. Therefore, when studying cell growth in 3D culture systems, it is essential to consider how the physiological oxygen concentration, rather than the one in the ambient air, influences the proliferation parameters. Here, we investigated the effect of reducing oxygen partial pressure from 21% to 5% on cell proliferation rate and regionalization in a 3D tumor spheroid model. We found that 5% oxygen concentration strongly inhibited spheroid growth, changed the proliferation gradient and reduced the 50% In Depth Proliferation index (IDP50), compared with culture at 21% oxygen. We then modeled the oxygen partial pressure profiles using the experimental data generated by culturing spheroids in physioxic and normoxic conditions. Although hypoxia occurred at similar depth in spheroids grown in the two conditions, oxygen partial pressure was a major rate-limiting factor with a critical effect on cell proliferation rate and regionalization only in spheroids grown in physioxic condition and not in spheroids grown at atmospheric normoxia. Our findings strengthen the need to consider conducting experiment in physioxic conditions (i.e., tissue normoxia) for proper understanding of cancer cell biology and the evaluation of anticancer drugs in 3D culture systems.

  19. Dwarf Spheroidal Satellite Formation in a Reionized Local Group

    OpenAIRE

    Milosavljevic, Milos; Bromm, Volker

    2013-01-01

    Dwarf spheroidal satellite galaxies have emerged a powerful probe of small-scale dark matter clustering and of cosmic reionization. They exhibit structural and chemical continuity with dwarf irregular galaxies in the field and with spheroidal galaxies in high-density environments. By combining empirical constraints derived for star formation at low gas column densities and metallicities in the local universe with a model for dark matter and baryonic mass assembly, we provide an analytical des...

  20. Helical axis stellarator equilibrium model

    International Nuclear Information System (INIS)

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift

  1. On modular stellarator reactor coils

    International Nuclear Information System (INIS)

    Rau, F.; Harmeyer, E.; Kisslinger, J.; Wobig, H.

    1985-01-01

    Modular twisted coils are discussed which produce magnetic fields of the Advanced Stellarator WENDELSTEIN VII-AS type. Reducing the number coils/FP offers advantage for maintenance of coils, but increases the magnetic ripple and B m /B o . Computation of force densities within the coils of ASR and ASB yield local maximum values of about 80 and 180 MN/m 3 , respectively. A system of mutual coil support is being developed. Twisted coils in helical arrangement provide a reactor-sized HELIAC system. In order to reduce the magnetic ripple, a large number of 14 coils/FP in special arrangement is used

  2. Introduction to stellar structure

    CERN Document Server

    Maciel, Walter J

    2016-01-01

    In the first part of this book, the author presents the basic properties of the stellar interior and describes them thoroughly, along with deriving the main stellar structure equations of temperature, density, pressure and luminosity, among others. The process and application of solving these equations is explained, as well as linking these results with actual observations.  The second part of the text describes what happens to a star over time, and how to determine this by solving the same equations at different points during a star’s lifetime. The fate of various stars is quite different depending on their masses, and this is described in the final parts of the book. This text can be used for an upper level undergraduate course or an introductory graduate course on stellar physics.

  3. Self-assembly of tissue spheroids on polymeric membranes.

    Science.gov (United States)

    Messina, Antonietta; Morelli, Sabrina; Forgacs, Gabor; Barbieri, Giuseppe; Drioli, Enrico; De Bartolo, Loredana

    2017-07-01

    In this study, multicellular tissue spheroids were fabricated on polymeric membranes in order to accelerate the fusion process and tissue formation. To this purpose, tissue spheroids composed of three different cell types, myoblasts, fibroblasts and neural cells, were formed and cultured on agarose and membranes of polycaprolactone (PCL) and chitosan (CHT). Membranes prepared by a phase-inversion technique display different physicochemical, mechanical and transport properties, which can affect the fusion process. The membranes accelerated the fusion process of a pair of spheroids with respect to the inert substrate. In this process, a critical role is played by the membrane properties, especially by their mechanical characteristics and oxygen and carbon dioxide mass transfer. The rate of fusion was quantified and found to be similar for fibroblast, myoblast and neural tissue spheroids on membranes, which completed the fusion within 3 days. These spheroids underwent faster fusion and maturation on PCL membrane than on agarose, the rate of fusion being proportional to the value of oxygen and carbon dioxide permeances and elastic characteristics. Consequently, tissue spheroids on the membranes expressed high biological activity in terms of oxygen uptake, making them more suitable as building blocks in the fabrication of tissues and organs. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  4. Correlation between grade of pearlite spheroidization and laser induced spectra

    Science.gov (United States)

    Yao, Shunchun; Dong, Meirong; Lu, Jidong; Li, Jun; Dong, Xuan

    2013-12-01

    Laser induced breakdown spectroscopy (LIBS) which is used traditionally as a spectrochemical analytical technique was employed to analyze the grade of pearlite spheroidization. Three 12Cr1MoV steel specimens with different grades of pearlite spheroidization were ablated to produce plasma by pulse laser at 266 nm. In order to determine the optimal temporal condition and plasma parameters for correlating the grade of pearlite spheroidization and laser induced spectra, a set of spectra at different delays were analyzed by the principal component analysis method. Then, the relationship between plasma temperature, intensity ratios of ionic to atomic lines and grade of pearlite spheroidization was studied. The analysis results show that the laser induced spectra of different grades of pearlite spheroidization can be readily identifiable by principal component analysis in the range of 271.941-289.672 nm with 1000 ns delay time. It is also found that a good agreement exists between the Fe ionic to atomic line ratios and the tensile strength, whereas there is no obvious difference in the plasma temperature. Therefore, LIBS may be applied not only as a spectrochemical analytical technique but also as a new way to estimate the grade of pearlite spheroidization.

  5. Correlation between grade of pearlite spheroidization and laser induced spectra

    International Nuclear Information System (INIS)

    Yao, Shunchun; Dong, Meirong; Lu, Jidong; Li, Jun; Dong, Xuan

    2013-01-01

    Laser induced breakdown spectroscopy (LIBS) which is used traditionally as a spectrochemical analytical technique was employed to analyze the grade of pearlite spheroidization. Three 12Cr1MoV steel specimens with different grades of pearlite spheroidization were ablated to produce plasma by pulse laser at 266 nm. In order to determine the optimal temporal condition and plasma parameters for correlating the grade of pearlite spheroidization and laser induced spectra, a set of spectra at different delays were analyzed by the principal component analysis method. Then, the relationship between plasma temperature, intensity ratios of ionic to atomic lines and grade of pearlite spheroidization was studied. The analysis results show that the laser induced spectra of different grades of pearlite spheroidization can be readily identifiable by principal component analysis in the range of 271.941–289.672 nm with 1000 ns delay time. It is also found that a good agreement exists between the Fe ionic to atomic line ratios and the tensile strength, whereas there is no obvious difference in the plasma temperature. Therefore, LIBS may be applied not only as a spectrochemical analytical technique but also as a new way to estimate the grade of pearlite spheroidization. (paper)

  6. On the role of the transformation eigenstrain in the growth or shrinkage of spheroidal isotropic precipitations

    International Nuclear Information System (INIS)

    Fischer, F.D.; Boehm, H.J.

    2005-01-01

    The jumps of the strain and stress tensors on the surface of elastic homogeneous or inhomogeneous ellipsoidal inclusions embedded in an elastic matrix are obtained from results reported in the literature. They are used to derive closed-form expressions for the thermodynamic force in such matrix-inclusion systems that are subjected to a generally defined homogeneous transformation eigenstrain. A detailed study is presented for an isotropic spheroidal inclusion in an isotropic matrix in which the most important parameters are the inclusion's aspect ratio α and an eigenstrain triaxiality parameter d-bar. The fluctuations of the thermodynamic force are investigated for a set of specific transformation eigenstrain tensors and are presented for inclusion shapes ranging from disk-like to fiber-like spheroids

  7. The Galactic stellar disc

    International Nuclear Information System (INIS)

    Feltzing, S; Bensby, T

    2008-01-01

    The study of the Milky Way stellar discs in the context of galaxy formation is discussed. In particular, we explore the properties of the Milky Way disc using a new sample of about 550 dwarf stars for which we have recently obtained elemental abundances and ages based on high-resolution spectroscopy. For all the stars we also have full kinematic information as well as information about their stellar orbits. We confirm results from previous studies that the thin and the thick discs have distinct abundance patterns. But we also explore a larger range of orbital parameters than what has been possible in our previous studies. Several new results are presented. We find that stars that reach high above the Galactic plane and have eccentric orbits show remarkably tight abundance trends. This implies that these stars formed out of well-mixed gas that had been homogenized over large volumes. We find some evidence that suggest that the event that most likely caused the heating of this stellar population happened a few billion years ago. Through a simple, kinematic exploration of stars with super-solar [Fe/H], we show that the solar neighbourhood contains metal-rich, high velocity stars that are very likely associated with the thick disc. Additionally, the HR1614 moving group and the Hercules and Arcturus stellar streams are discussed and it is concluded that, probably, a large fraction of the groups and streams so far identified in the disc are the result of evolution and interactions within the stellar disc rather than being dissolved stellar clusters or engulfed dwarf galaxies.

  8. A three-dimensional in vitro HepG2 cells liver spheroid model for genotoxicity studies.

    Science.gov (United States)

    Shah, Ume-Kulsoom; Mallia, Jefferson de Oliveira; Singh, Neenu; Chapman, Katherine E; Doak, Shareen H; Jenkins, Gareth J S

    2018-01-01

    The liver's role in metabolism of chemicals makes it an appropriate tissue for toxicity testing. Current testing protocols, such as animal testing and two-dimensional liver cell systems, offer limited resemblance to in vivo liver cell behaviour, in terms of gene expression profiles and metabolic competence; thus, they do not always accurately predict human toxicology. In vitro three-dimensional liver cell models offer an attractive alternative. This study reports on the development of a 3D liver model, using HepG2 cells, by a hanging-drop technique, with a focus on evaluating spheroid growth characteristics and suitability for genotoxicity testing. The cytokinesis-blocked micronucleus assay protocol was adapted to enable micronucleus (MN) detection in the 3D spheroid models. This involved evaluating the difference between hanging vs non-hanging drop positions for dosing of the test agents and comparison of automated Metafer scoring with manual scoring for MN detection in HepG2 spheroids. The initial seeding density, used for all experiments, was 5000 cells/20 μl drop hanging spheroids, harvested on day 4, with >75% cell viability. Albumin secretion (7.8 g/l) and both CYP1A1 and CYP1A2 gene expression were highest in the 3D environment at day 4. Exposure to metabolically activated genotoxicants for 24 h resulted in a 6-fold increase in CYP1A1 enzyme activity (3 μM B[a]P) and a 30-fold increase in CYP1A2 enzyme activity (5 μM PhIP) in 3D hanging spheroids. MN inductions in response to B[a]P or PhIP were 2-fold and 3-fold, respectively, and were greater in 3D hanging spheroids than in 2D format, showing that hanging spheroids are more sensitive to genotoxic agents. HepG2 hanging-drop spheroids are an exciting new alternative system for genotoxicity studies, due to their improved structural and physiological properties, relative to 2D cultures. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Transport in stellarators

    International Nuclear Information System (INIS)

    Maassberg, H.; Brakel, R.; Burhenn, R.; Gasparino, U.; Grigull, P.; Kick, M.; Kuehner, G.; Ringler, H.; Sardei, F.; Stroth, U.; Weller, A.

    1993-01-01

    The local electron and ion heat transport as well as the particle and impurity transport properties in stellarators are reviewed. In this context, neoclassical theory is used as a guideline for the comparison of the experimental results of the quite different confinement concepts. At sufficiently high temperatures depending on the specific magnetic configuration, neoclassical predictions are confirmed by experimental findings. The confinement properties in the LMFP collisionality regime are discussed with respect to the next stellarator generation, for which at higher temperatures the neoclassical transport is expected to become more important. (orig.)

  10. Solar and stellar oscillations

    International Nuclear Information System (INIS)

    Fossat, E.

    1981-01-01

    We try to explain in simple words what a stellar oscillation is, what kind of restoring forces and excitation mechanisms can be responsible for its occurence, what kind of questions the theoretician asks to the observer and what kind of tools the latter is using to look for the answers. A selected review of the most striking results obtained in the last few years in solar seismology and the present status of their consequences on solar models is presented. A brief discussion on the expected extension towards stellar seismology will end the paper. A selected bibliography on theory as well as observations and recent papers is also included. (orig.)

  11. Miniaturized microscope for high throughput screening of tumor spheroids in microfluidic devices

    Science.gov (United States)

    Uranga, Javier; Rodríguez-Pena, Alejandro; Gahigiro, Desiré; Ortiz-de-Solorzano, Carlos

    2018-02-01

    High-throughput in vitro screening of highly physiological three-dimensional cell cultures (3D-HTS) is rapidly gaining importance in preclinical studies, to study the effect of the microenvironment in tumor development, and to evaluate the efficacy of new anticancer drugs. Furthermore, it could also be envisioned the use of 3D-HTS systems in personalized anti-cancer treatment planning, based on tumor organoids or spheroids grown from tumor biopsies or isolated tumor circulating cells. Most commercial, multi-well plate based 3D-HTS systems are large, expensive, and are based on the use of multi-well plates that hardly provide a physiological environment and require the use of large amounts of biological material and reagents. In this paper we present a novel, miniaturized inverted microscope (hereinafter miniscospe), made up of low-cost, mass producible parts, that can be used to monitor the growth of living tumor cell spheroids within customized three-dimensional microfluidic platforms. Our 3D-HTS miniscope combines phase contrast imaging based on oblique back illumination technique with traditional widefield epi-fluorescence imaging, implemented using miniaturized electro-optical parts and gradient-index refraction lenses. This small (3x6x2cm), lightweight device can effectively image overtime the growth of (>200) tumor spheroids in a controlled and reproducible environment. Our miniscope can be used to acquire time-lapse images of cellular living spheroids over the course of several hours and captures their growth before and after drug treatment, to evaluate the effectiveness of the drug.

  12. Multiplicity in Early Stellar Evolution

    Science.gov (United States)

    Reipurth, B.; Clarke, C. J.; Boss, A. P.; Goodwin, S. P.; Rodríguez, L. F.; Stassun, K. G.; Tokovinin, A.; Zinnecker, H.

    Observations from optical to centimeter wavelengths have demonstrated that multiple systems of two or more bodies is the norm at all stellar evolutionary stages. Multiple systems are widely agreed to result from the collapse and fragmentation of cloud cores, despite the inhibiting influence of magnetic fields. Surveys of class 0 protostars with millimeter interferometers have revealed a very high multiplicity frequency of about 2/3, even though there are observational difficulties in resolving close protobinaries, thus supporting the possibility that all stars could be born in multiple systems. Near-infrared adaptive optics observations of class I protostars show a lower binary frequency relative to the class 0 phase, a declining trend that continues through the class II/III stages to the field population. This loss of companions is a natural consequence of dynamical interplay in small multiple systems, leading to ejection of members. We discuss observational consequences of this dynamical evolution, and its influence on circumstellar disks, and we review the evolution of circumbinary disks and their role in defining binary mass ratios. Special attention is paid to eclipsing PMS binaries, which allow for observational tests of evolutionary models of early stellar evolution. Many stars are born in clusters and small groups, and we discuss how interactions in dense stellar environments can significantly alter the distribution of binary separations through dissolution of wider binaries. The binaries and multiples we find in the field are the survivors of these internal and external destructive processes, and we provide a detailed overview of the multiplicity statistics of the field, which form a boundary condition for all models of binary evolution. Finally, we discuss various formation mechanisms for massive binaries, and the properties of massive trapezia.

  13. Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Forbes, Duncan; Hargis, Jonathan R.; Peter, Annika; Pucha, Ragadeepika; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay

    2018-06-01

    We discuss our ongoing observational program to comprehensively map the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. Our results will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. This program has already yielded the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB, and at least two additional candidate satellites. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.

  14. A galactic disk as a two-fluid system: Consequences for the critical stellar velocity dispersion and the formation of condensations in the gas

    International Nuclear Information System (INIS)

    Jog, C.J.; Solomon, P.M.

    1984-01-01

    We examine the consequences of treating a galactic disk as a two-fluid system for the stability of the entire disk and for the stability and form of the gas in the disk. We find that the existence of even a small fraction of the total disk surface density in a cold fluid (that is, the gas) makes it much harder to stabilize the entire two-fluid disk. (C/sub s/,min)/sub 2-f/, the critical stellar velocity dispersion for a two-fluid disk in an increasing function of μ/sub g//μ/sub s/, the gas fraction, and μ/sub t//kappa, where μ/sub g/, μ/sub s/, and μ/sub t/ are the gaseous, stellar, and total disk surface densities and kappa is the epicyclic frequency. In the Galaxy, we find that (C/sub s/,min)/sub 2-f/ as a function of R peaks when μ/sub t//kappa peaks-at galactocentric radii of Rapprox.5-7 kpc; two-fluid instabilities are most likely to occur in this region. This region is coincident with the peak in the molecular cloud distribution in the Galaxy. At the higher effective gas density resulting from the growth of a two-fluid instability, the gas may become unstble, even when originally the gas by itself is stable. The wavelength of a typical (induced) gas instability in the inner galaxy is approx.400 pc, and it contains approx.10 7 M/sub sun/ of interstellar matter; these instabilities may be identified with clusters of giant molecular clouds. We suggest that many of the spiral features seen in gas-rich spiral galaxies may be material arms or arm segments resulting from sheared two-fluid gravitational instabilities. The analysis presented here is applicable to any general disk galaxy consisting of stars and gas

  15. A near infra-red video system as a protective diagnostic for electron cyclotron resonance heating operation in the Wendelstein 7-X stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Preynas, M.; Laqua, H. P.; Marsen, S.; Reintrog, A. [Max-Planck-Institut für Plasmaphysik (IPP), D-17491 Greifswald (Germany); Corre, Y.; Moncada, V.; Travere, J.-M. [IRFM, CEA-Cadarache, 13108 Saint Paul lez Durance Cedex (France)

    2015-11-15

    The Wendelstein 7-X stellarator is a large nuclear fusion device based at Max-Planck-Institut für Plasmaphysik in Greifswald in Germany. The main plasma heating system for steady state operation in W7-X is electron cyclotron resonance heating (ECRH). During operation, part of plama facing components will be directly heated by the non-absorbed power of 1 MW rf beams of ECRH. In order to avoid damages of such components made of graphite tiles during the first operational phase, a near infra-red video system has been developed as a protective diagnostic for safe and secure ECRH operation. Both the mechanical design housing the camera and the optical system are very flexible and respect the requirements of steady state operation. The full system including data acquisition and control system has been successfully tested in the vacuum vessel, including on-line visualization and data storage of the four cameras equipping the ECRH equatorial launchers of W7-X.

  16. The fundamentals of stellar astrophysics

    International Nuclear Information System (INIS)

    Collins, G.W. II.

    1989-01-01

    A broad overview of theoretical stellar astrophysics is presented in a textbook intended for graduate students. Chapters are devoted to fundamental principles, assumptions, theorems, and polytropes; energy sources and sinks; the flow of energy through the star and the construction of stellar models; the theory of stellar evolution; relativistic stellar structure; the structure of distorted stars; stellar pulsation and oscillation. Also discussed are the flow of radiation through the stellar atmosphere, the solution of the radiative-transfer equation, the environment of the radiation field, the construction of a stellar model atmosphere, the formation and shape of spectral lines, LTE breakdown, illuminated and extended stellar atmospheres, and the transfer of polarized radiation. Diagrams, graphs, and sample problems are provided. 164 refs

  17. Progress Toward Attractive Stellarators

    International Nuclear Information System (INIS)

    Neilson, G.H.; Bromberg, L.; Brown, T.G.; Gates, D.A.; Ku, L.P.; Zarnstorff, M.C.; Boozer, A.H.; Harris, J.H.; Meneghini, O.; Mynick, H.E.; Pomphrey, N.; Reiman, A.H.; Xanthopoulos, P.

    2011-01-01

    The quasi-axisymmetric stellarator (QAS) concept offers a promising path to a more compact stellarator reactor, closer in linear dimensions to tokamak reactors than previous stellarator designs. Concept improvements are needed, however, to make it more maintainable and more compatible with high plant availability. Using the ARIES-CS design as a starting point, compact stellarator designs with improved maintenance characteristics have been developed. While the ARIES-CS features a through-the-port maintenance scheme, we have investigated configuration changes to enable a sector-maintenance approach, as envisioned for example in ARIES AT. Three approaches are reported. The first is to make tradeoffs within the QAS design space, giving greater emphasis to maintainability criteria. The second approach is to improve the optimization tools to more accurately and efficiently target the physics properties of importance. The third is to employ a hybrid coil topology, so that the plasma shaping functions of the main coils are shared more optimally, either with passive conductors made of high-temperature superconductor or with local compensation coils, allowing the main coils to become simpler. Optimization tools are being improved to test these approaches.

  18. Compact stellarator coils

    International Nuclear Information System (INIS)

    Pomphrey, N.; Berry, L.A.; Boozer, A.H.

    2001-01-01

    Experimental devices to study the physics of high-beta (β>∼4%), low aspect ratio (A<∼4.5) stellarator plasmas require coils that will produce plasmas satisfying a set of physics goals, provide experimental flexibility, and be practical to construct. In the course of designing a flexible coil set for the National Compact Stellarator Experiment, we have made several innovations that may be useful in future stellarator design efforts. These include: the use of Singular Value Decomposition methods for obtaining families of smooth current potentials on distant coil winding surfaces from which low current density solutions may be identified; the use of a Control Matrix Method for identifying which few of the many detailed elements of the stellarator boundary must be targeted if a coil set is to provide fields to control the essential physics of the plasma; the use of Genetic Algorithms for choosing an optimal set of discrete coils from a continuum of potential contours; the evaluation of alternate coil topologies for balancing the tradeoff between physics objective and engineering constraints; the development of a new coil optimization code for designing modular coils, and the identification of a 'natural' basis for describing current sheet distributions. (author)

  19. Stellar Structure and Evolution

    CERN Document Server

    Kippenhahn, Rudolf; Weiss, Achim

    2013-01-01

    This long-awaited second edition of the classical textbook on Stellar Structure and Evolution by Kippenhahn and Weigert is a thoroughly revised version of the original text. Taking into account modern observational constraints as well as additional physical effects such as mass loss and diffusion, Achim Weiss and Rudolf Kippenhahn have succeeded in bringing the book up to the state-of-the-art with respect to both the presentation of stellar physics and the presentation and interpretation of current sophisticated stellar models. The well-received and proven pedagogical approach of the first edition has been retained. The book provides a comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The models developed to explain the stability, dynamics and evolution of the stars are presented and great care is taken to detail the various stages in a star’s life. Just as the first edition, which remained a standard work for more than 20 years after its...

  20. 8. stellarator workshop

    International Nuclear Information System (INIS)

    1991-07-01

    The technical reports in this collection of papers were presented at the 8th International Workshop on Stellarators, and International Atomic Energy Agency Technical Committee Meeting. They include presentations on transport, magnetic configurations, fluctuations, equilibrium, stability, edge plasma and wall aspects, heating, diagnostics, new concepts and reactor studies. Refs, figs and tabs

  1. A 3D printed microfluidic perfusion device for multicellular spheroid cultures.

    Science.gov (United States)

    Ong, Louis Jun Ye; Islam, Anik; DasGupta, Ramanuj; Iyer, Narayanan Gopalakkrishna; Leo, Hwa Liang; Toh, Yi-Chin

    2017-09-11

    The advent of 3D printing technologies promises to make microfluidic organ-on-chip technologies more accessible for the biological research community. To date, hydrogel-encapsulated cells have been successfully incorporated into 3D printed microfluidic devices. However, there is currently no 3D printed microfluidic device that can support multicellular spheroid culture, which facilitates extensive cell-cell contacts important for recapitulating many multicellular functional biological structures. Here, we report a first instance of fabricating a 3D printed microfluidic cell culture device capable of directly immobilizing and maintaining the viability and functionality of 3D multicellular spheroids. We evaluated the feasibility of two common 3D printing technologies i.e. stereolithography (SLA) and PolyJet printing, and found that SLA could prototype a device comprising of cell immobilizing micro-structures that were housed within a microfluidic network with higher fidelity. We have also implemented a pump-free perfusion system, relying on gravity-driven flow to perform medium perfusion in order to reduce the complexity and footprint of the device setup, thereby improving its adaptability into a standard biological laboratory. Finally, we demonstrated the biological performance of the 3D printed device by performing pump-free perfusion cultures of patient-derived parental and metastatic oral squamous cell carcinoma tumor and liver cell (HepG2) spheroids with good cell viability and functionality. This paper presents a proof-of-concept in simplifying and integrating the prototyping and operation of a microfluidic spheroid culture device, which will facilitate its applications in various drug efficacy, metabolism and toxicity studies.

  2. Stellar wind theory

    International Nuclear Information System (INIS)

    Summers, D.

    1980-01-01

    The theory of stellar winds as given by the equations of classical fluid dynamics is considered. The equations of momentum and energy describing a steady, spherically symmetric, heat-conducting, viscous stellar wind are cast in a dimensionless form which involves a thermal conduction parameter E and a viscosity parameter γ. An asymptotic analysis is carried out, for fixed γ, in the cases E→O and E→infinity (corresponding to small and large thermal conductivity, respectively), and it is found that it is possible to construct critical solutions for the wind velocity and temperature over the entire flow. The E→O solution represents a wind which emanates from the star at low, subsonic speeds, accelerates through a sonic point, and then approaches a constant asymptotic speed, with its temperature varying as r/sup -4/3/ at large distances r from the star; the E→infinity solution represents a wind which, after reaching an approximately constant speed, with temperature varying as r/sup -2/7/, decelerates through a diffuse shock and approaches a finite pressure at infinity. A categorization is made of all critical stellar wind solutions for given values of γ and E, and actual numerical examples are given. Numerical solutions are obtained by integrating upstream 'from infinity' from initial values of the flow parameters given by appropriate asymptotic expansions. The role of viscosity in stellar wind theory is discussed, viscous and inviscid stellar wind solutions are compared, and it is suggested that with certain limitations, the theory presented may be useful in analyzing winds from solar-type stars

  3. Thermal Plasma Spheroidization of High-Nitrogen Stainless Steel Powder Alloys Synthesized by Mechanical Alloying

    Science.gov (United States)

    Razumov, Nikolay G.; Popovich, Anatoly A.; Wang, QingSheng

    2018-03-01

    This paper presents the results of experimental studies on the treatment of Fe-23Cr-11Mn-1N high-nitrogen stainless steel powder alloys, synthesized by the mechanical alloying (MA) of elemental powders in the flow of a thermal plasma. Fe-23Cr-11Mn-1N high-nitrogen stainless steel powder alloys were prepared by MA in the attritor under an argon atmosphere. For spheroidization of Fe-23Cr-11Mn-1N high-nitrogen stainless steel powder alloys, the TekSphero 15 plant manufactured by Tekna Plasma Systems Inc was used. The studies have shown the possibility of obtaining Fe-23Cr-11Mn-1N high-nitrogen spherical powders steel alloys from the powder obtained by MA. According to the results of a series of experiments, it was found that the results of plasma spheroidization of powders essentially depend on the size of the fraction due to some difference in the particle shape and flowability, and on the gas regime of the plasma torch. It is established that during the plasma spheroidization process, some of the nitrogen leaves the alloy. The loss rate of nitrogen depends on the size of the initial particles.

  4. Development of lacrimal gland spheroids for lacrimal gland tissue regeneration.

    Science.gov (United States)

    Massie, Isobel; Spaniol, Kristina; Barbian, Andreas; Geerling, Gerd; Metzger, Marco; Schrader, Stefan

    2018-04-01

    Severe dry eye syndrome resulting from lacrimal gland (LG) dysfunction can cause blindness, yet treatments remain palliative. In vitro reconstruction of LG tissue could provide a curative treatment. We aimed to combine epithelial cells with endothelial cells and mesenchymal stem cells (MSCs) to form a 3D functional unit. Epithelial cells and MSCs were isolated from porcine LG; endothelial cells were isolated from human foreskin. MSCs were characterised (flow cytometry and differentiation potential assays). All 3 cell types were combined on Matrigel and spheroid formation observed. Spheroids were characterised [immunohistochemistry (IHC) and transmission electron microscopy] and function assessed (β-hexosaminidase assay). Spheroids were transferred to decellularised jejunum (SIS-Muc) in dynamic cultures for 1 week before further characterisation. MSCs did not express CD31 but expressed CD44 and CD105 and differentiated towards osteogenic and adipogenic lineages. Spheroids formed on Matrigel within 18 hr, contracting to ~10% of the well area (p function was increased in spheroids cf. monolayer controls (p function (p < .05), viability (p < .05), and proliferation decreased, whilst apoptosis increased. On SIS-Muc under dynamic culture, however, spheroids continued to proliferate to repopulate SIS-Muc. IHC revealed LG epithelial cells coexpressing pan-cytokeratin and lysozyme, as well as endothelial cells and MSCs and cells remained capable of responding to carbachol (p < .05). These spheroids could form the basis of a regenerative medicine treatment approach for dry eye syndrome. In vivo studies are required to evaluate this further. Copyright © 2017 John Wiley & Sons, Ltd.

  5. Human Cardiac Progenitor Spheroids Exhibit Enhanced Engraftment Potential.

    Directory of Open Access Journals (Sweden)

    Francesca Oltolina

    Full Text Available A major obstacle to an effective myocardium stem cell therapy has always been the delivery and survival of implanted stem cells in the heart. Better engraftment can be achieved if cells are administered as cell aggregates, which maintain their extra-cellular matrix (ECM. We have generated spheroid aggregates in less than 24 h by seeding human cardiac progenitor cells (hCPCs onto methylcellulose hydrogel-coated microwells. Cells within spheroids maintained the expression of stemness/mesenchymal and ECM markers, growth factors and their cognate receptors, cardiac commitment factors, and metalloproteases, as detected by immunofluorescence, q-RT-PCR and immunoarray, and expressed a higher, but regulated, telomerase activity. Compared to cells in monolayers, 3D spheroids secreted also bFGF and showed MMP2 activity. When spheroids were seeded on culture plates, the cells quickly migrated, displaying an increased wound healing ability with or without pharmacological modulation, and reached confluence at a higher rate than cells from conventional monolayers. When spheroids were injected in the heart wall of healthy mice, some cells migrated from the spheroids, engrafted, and remained detectable for at least 1 week after transplantation, while, when the same amount of cells was injected as suspension, no cells were detectable three days after injection. Cells from spheroids displayed the same engraftment capability when they were injected in cardiotoxin-injured myocardium. Our study shows that spherical in vivo ready-to-implant scaffold-less aggregates of hCPCs able to engraft also in the hostile environment of an injured myocardium can be produced with an economic, easy and fast protocol.

  6. Radiobiological investigations of multicellular spheroids as an in vitro tumor model. 4

    International Nuclear Information System (INIS)

    Kopp, J.

    1978-01-01

    Multicellular spheroids of various size were irradiated with a single dose of X-rays or fast neutrons, incubated after irradiation in roller tubes for long time, and observed light-microscopically. The observed effects were found independent of the radiation used and dependent on dose (considering the RBE) and size of spheroids. After irradiation the spheroid surface showed a loosening phenomenon and the spheroid structure changed depending on dose in three various types. Up to the 10% survival fraction the spheroids recovered within some days to the structure of non-irradiated spheroids by the growth of the surviving cells. After higher doses single surviving cells inside the dead spheroid material seemed to migrate from the inner hypoxic into the rim zone. They can start proliferation many days after irradiation leading to repopulation of irradiated spheroids. The volume changes of irradiated spheroids were also dose-dependent, but the measurement of spheroid volume seems to be of limited value for predicting the effectiveness of irradiation because the spheroid volume of irradiated spheroids is not proportional to the number of cells per spheroid. (author)

  7. Verlinde's emergent gravity versus MOND and the case of dwarf spheroidals

    Science.gov (United States)

    Diez-Tejedor, Alberto; Gonzalez-Morales, Alma X.; Niz, Gustavo

    2018-06-01

    In a recent paper, Erik Verlinde has developed the interesting possibility that space-time and gravity may emerge from the entangled structure of an underlying microscopic theory. In this picture, dark matter arises as a response to the standard model of particle physics from the delocalized degrees of freedom that build up the dark energy component of the Universe. Dark matter physics is then regulated by a characteristic acceleration scale a0, identified with the radius of the (quasi)-de Sitter universe we inhabit. For a point particle matter source, or outside an extended spherically symmetric object, MOND's empirical fitting formula is recovered. However, Verlinde's theory critically departs from MOND when considering the inner structure of galaxies, differing by a factor of 2 at the centre of a regular massive body. For illustration, we use the eight classical dwarf spheroidal satellites of the Milky Way. These objects are perfect testbeds for the model given their approximate spherical symmetry, measured kinematics, and identified missing mass. We show that, without the assumption of a maximal deformation, Verlinde's theory can fit the velocity dispersion profile in dwarf spheroidals with no further need of an extra dark particle component. If a maximal deformation is considered, the theory leads to mass-to-light ratios that are marginally larger than expected from stellar population and formation history studies. We also compare our results with the recent phenomenological interpolating MOND function of McGaugh et al., and find a departure that, for these galaxies, is consistent with the scatter in current observations.

  8. Disk and dwarf spheroidal galaxies kinematics from general relativity with infrared renormalization group effects

    International Nuclear Information System (INIS)

    Rodrigues, Davi C.; Oliveira, Paulo L.C. de; Fabris, Julio C.; Shapiro, Ilya L.

    2011-01-01

    Full text: The running of coupling constants is a well known phenomenon within Quantum Field Theory. It is also known that the renormalization group method can be extended to quantum field theory on curved space time. Nonetheless, although we know that the beta function of QED go to zero in the infrared limit fast enough to lead to constant charge at the classical level (in conformity with both the Appelquist-Carazzone theorem and experimental data), no analogous proof exists for General Relativity. Some authors have proposed that the infrared beta function of General Relativity is not trivial, and as such certain small running of the gravitational coupling might take place at astrophysical scales, leading in particular to changes on the role of dark matter in galaxies. We review and extend our contribution to infrared Renormalization Group (RG) effects to General Relativity in the context of galaxies, an approach we call RGGR. We extend our previous results by analyzing a larger sample of galaxies, now also including elliptical and dwarf spheroidal galaxies, besides disk galaxies (both LSB and HSB). We compare our RGGR results to both standard dark matter profiles (NFW, Isothermal, Burkert) and alternative models of gravity (MOND, MSTG), showing that the RGGR results are similar in quality to the best dark matter profiles (the cored ones, e.g., Isothermal and Burkert), while displaying a better fitting to the data than NFW, MOND or MSTG. To the latter, we evaluated both the shape of the rotation curve and the expected stellar mass-to-light ratios. Dwarf spheroidal (dSph) galaxies are small galaxies believed to be dominated by dark matter, with the highest fraction do dark matter per baryonic matter. These galaxies provide a strong test to any theory that mimics either all or part of the dark matter behavior. In particular, this is the only type of galaxy that MOND seems incapable of fitting the data. (author)

  9. Robust Modeling of Stellar Triples in PHOEBE

    Science.gov (United States)

    Conroy, Kyle E.; Prsa, Andrej; Horvat, Martin; Stassun, Keivan G.

    2017-01-01

    The number of known mutually-eclipsing stellar triple and multiple systems has increased greatly during the Kepler era. These systems provide significant opportunities to both determine fundamental stellar parameters of benchmark systems to unprecedented precision as well as to study the dynamical interaction and formation mechanisms of stellar and planetary systems. Modeling these systems to their full potential, however, has not been feasible until recently. Most existing available codes are restricted to the two-body binary case and those that do provide N-body support for more components make sacrifices in precision by assuming no stellar surface distortion. We have completely redesigned and rewritten the PHOEBE binary modeling code to incorporate support for triple and higher-order systems while also robustly modeling data with Kepler precision. Here we present our approach, demonstrate several test cases based on real data, and discuss the current status of PHOEBE's support for modeling these types of systems. PHOEBE is funded in part by NSF grant #1517474.

  10. THE M BH-L SPHEROID RELATION AT HIGH AND LOW MASSES, THE QUADRATIC GROWTH OF BLACK HOLES, AND INTERMEDIATE-MASS BLACK HOLE CANDIDATES

    International Nuclear Information System (INIS)

    Graham, Alister W.; Scott, Nicholas

    2013-01-01

    From a sample of 72 galaxies with reliable supermassive black hole masses M bh , we derive the M bh -(host spheroid luminosity, L) relation for (1) the subsample of 24 core-Sérsic galaxies with partially depleted cores, and (2) the remaining subsample of 48 Sérsic galaxies. Using K s -band Two Micron All Sky Survey data, we find the near-linear relation M bh ∝L 1.10±0.20 K s for the core-Sérsic spheroids thought to be built in additive dry merger events, while we find the relation M bh ∝L 2.73±0.55 K s for the Sérsic spheroids built from gas-rich processes. After converting literature B-band disk galaxy magnitudes into inclination- and dust-corrected bulge magnitudes, via a useful new equation presented herein, we obtain a similar result. Unlike with the M bh -(velocity dispersion) diagram, which is also updated here using the same galaxy sample, it remains unknown whether barred and non-barred Sérsic galaxies are offset from each other in the M bh -L diagram. While black hole feedback has typically been invoked to explain what was previously thought to be a nearly constant M bh /M Spheroid mass ratio of ∼0.2%, we advocate that the near-linear M bh -L and M bh -M Spheroid relations observed at high masses may have instead arisen largely from the additive dry merging of galaxies. We argue that feedback results in a dramatically different scaling relation, such that black hole mass scales roughly quadratically with the spheroid mass in Sérsic galaxies. We therefore introduce a revised cold-gas 'quasar' mode feeding equation for semi-analytical models to reflect what we dub the quadratic growth of black holes in Sérsic galaxies built amidst gas-rich processes. Finally, we use our new Sérsic M bh -L equations to predict the masses of candidate intermediate mass black holes in almost 50 low-luminosity spheroids containing active galactic nuclei, finding many masses between that of stellar mass black holes and supermassive black holes.

  11. Ion transport in stellarators

    International Nuclear Information System (INIS)

    Ho, D.D.M.; Kulsrud, R.M.

    1985-09-01

    Stellarator ion transport in the low-collisionality regime with a radial electric field is calculated by a systematic expansion of the drift-Boltzmann equation. The shape of the helical well is taken into account in this calculation. It is found that the barely trapped ions with three to four times the thermal energy give the dominant contribution to the diffusion. Expressions for the ion particle and energy fluxes are derived

  12. First results from stellar occultations in the "GAIA era"

    Science.gov (United States)

    Benedetti-Rossi, G.; Vieira-Martins, R.; Sicardy, B.

    2017-09-01

    Stellar occultation is a powerful technique to study distant solar system bodies. It allows high angular resolution of the occulting body from the analysis of a light curve acquired with high temporal resolution with uncertainties comparable as probes. In the "GAIA era", stellar occultations is now able to obtain even more impressive results such as the presence of atmosphere, rings and topographic features.

  13. Operations of a non-stellar object tracker in space

    DEFF Research Database (Denmark)

    Riis, Troels; Jørgensen, John Leif; Betto, Maurizio

    1999-01-01

    The ability to detect and track non-stellar objects by utilizing a star tracker may seem rather straight forward, as any bright object, not recognized as a star by the system is a non stellar object. However, several pitfalls and errors exist, if a reliable and robust detection is required. To te...

  14. Cell proliferation kinetics and radiation response in 9L tumor spheroids

    Energy Technology Data Exchange (ETDEWEB)

    Sweigert, S.E.

    1984-05-01

    Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 ..mu..m to over 900 ..mu..m in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables.

  15. Cell shedding from X-irradiated multicellular spheroids of human lung carcinomas

    International Nuclear Information System (INIS)

    Sakata, K.; Okada, S.; Suzuki, N.; Majima, H.

    1991-01-01

    We studied the effect of radiation on cell shedding from the surface of multicellular spheroids. Spheroids were produced from two human lung cell lines, one adenocarcinoma (LCT1) and the other small cell carcinoma (LCT2), by using a liquid overlay culture technique. The number of cells shed from both kinds of spheroids did not change significantly when they were irradiated. The number of clonogenic cells shed from both kinds of irradiated spheroids decreased sharply as the dose of irradiation increases. There were no significant differences in clonogenic cell shedding per spheroid between LCT1 and LCT2 spheroids. 400 μm spheroids were more radioresistant to inhibition of clonogenic cell shedding than 250 μm spheroids. Shed cells were more radiosensitive than speroid cells. In these experiments, we did not obtain any results indicating that radiation enchances metastasis. (orig.) [de

  16. Cell proliferation kinetics and radiation response in 9L tumor spheroids

    International Nuclear Information System (INIS)

    Sweigert, S.E.

    1984-05-01

    Cell kinetic parameters, including population doubling-time, cell cycle time, and growth fraction, were measured in 9L gliosarcoma spheroids. These parameters were studied as the spheroids grew from 50 μm to over 900 μm in diameter. Experiments relating the cell kinetic parameters to the radiation response of 9L spheroids were also carried out. The major findings were that the average cell cycle time (T/sub c/), is considerably longer in large spheroids than in exponentially-growing monolayers, the radiosensitivity of noncycling (but still viable) cells in spheroids is not significantly different from that of cycling spheroid cells, and the radiation-induced division delay is approximately twice as long in spheroid cells as in monolayer cells given equal radiation doses. The cell loss factor for spheroids of various sizes was calculated, by using the measured kinetic parameters in the basic equations for growth of a cell population. 157 references, 6 figures, 3 tables

  17. Bioprinting-Based High-Throughput Fabrication of Three-Dimensional MCF-7 Human Breast Cancer Cellular Spheroids

    Directory of Open Access Journals (Sweden)

    Kai Ling

    2015-06-01

    Full Text Available Cellular spheroids serving as three-dimensional (3D in vitro tissue models have attracted increasing interest for pathological study and drug-screening applications. Various methods, including microwells in particular, have been developed for engineering cellular spheroids. However, these methods usually suffer from either destructive molding operations or cell loss and non-uniform cell distribution among the wells due to two-step molding and cell seeding. We have developed a facile method that utilizes cell-embedded hydrogel arrays as templates for concave well fabrication and in situ MCF-7 cellular spheroid formation on a chip. A custom-built bioprinting system was applied for the fabrication of sacrificial gelatin arrays and sequentially concave wells in a high-throughput, flexible, and controlled manner. The ability to achieve in situ cell seeding for cellular spheroid construction was demonstrated with the advantage of uniform cell seeding and the potential for programmed fabrication of tissue models on chips. The developed method holds great potential for applications in tissue engineering, regenerative medicine, and drug screening.

  18. Process for titanium powders spheroidization by RF induction plasma

    International Nuclear Information System (INIS)

    Gu Zhongtao; Ye Gaoying; Liu Chuandong; Tong Honghui

    2010-01-01

    Spherical titanium (Ti) particles were obtained by the process of heating irregularly shaped Ti powders under the radio frequency induction plasma (RF induction plasma) condition. The effect of feed rate, various dispersion methods and Ti particle size on the spheroidization efficiency was studied. The efficiency of the spheroidization is evaluated through the measurements of the percentage of powder spheroidized based on the electron microscopic observations and the tap density measurement of the processed powder. During the short flight of the particles in the plasma flow, of the order of a few milliseconds, the individual titanium particles of the powder are heated and melt, forming a spherical liquid droplet which upon freezing gives rise to the formation of a perfectly dense spherical solid particle. So RF induction plasma is a promising method for the preparation of spherical titanium powders with high flow ability. (authors)

  19. Spheroidization of glass powders for glass ionomer cements.

    Science.gov (United States)

    Gu, Y W; Yap, A U J; Cheang, P; Kumar, R

    2004-08-01

    Commercial angular glass powders were spheroidized using both the flame spraying and inductively coupled radio frequency plasma spraying techniques. Spherical powders with different particle size distributions were obtained after spheroidization. The effects of spherical glass powders on the mechanical properties of glass ionomer cements (GICs) were investigated. Results showed that the particle size distribution of the glass powders had a significant influence on the mechanical properties of GICs. Powders with a bimodal particle size distribution ensured a high packing density of glass ionomer cements, giving relatively high mechanical properties of GICs. GICs prepared by flame-spheroidized powders showed low strength values due to the loss of fine particles during flame spraying, leading to a low packing density and few metal ions reacting with polyacrylic acid to form cross-linking. GICs prepared by the nano-sized powders showed low strength because of the low bulk density of the nano-sized powders and hence low powder/liquid ratio of GICs.

  20. Monoenergetic electron parameters in a spheroid bubble model

    Science.gov (United States)

    Sattarian, H.; Sh., Rahmatallahpur; Tohidi, T.

    2013-02-01

    A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model. The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons ΔE/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions. As a result, the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model.

  1. Merging and Splitting of Plasma Spheroids in a Dusty Plasma

    Science.gov (United States)

    Mikikian, Maxime; Tawidian, Hagop; Lecas, Thomas

    2012-12-01

    Dust particle growth in a plasma is a strongly disturbing phenomenon for the plasma equilibrium. It can induce many different types of low-frequency instabilities that can be experimentally observed, especially using high-speed imaging. A spectacular case has been observed in a krypton plasma where a huge density of dust particles is grown by material sputtering. The instability consists of well-defined regions of enhanced optical emission that emerge from the electrode vicinity and propagate towards the discharge center. These plasma spheroids have complex motions resulting from their mutual interaction that can also lead to the merging of two plasma spheroids into a single one. The reverse situation is also observed with the splitting of a plasma spheroid into two parts. These results are presented for the first time and reveal new behaviors in dusty plasmas.

  2. Monoenergetic electron parameters in a spheroid bubble model

    International Nuclear Information System (INIS)

    Sattarian, H.; Rahmatallahpur, Sh.; Tohidi, T.

    2013-01-01

    A reliable analytical expression for the potential of plasma waves with phase velocities near the speed of light is derived. The presented spheroid cavity model is more consistent than the previous spherical and ellipsoidal models and it explains the mono-energetic electron trajectory more accurately, especially at the relativistic region. The maximum energy of electrons is calculated and it is shown that the maximum energy of the spheroid model is less than that of the spherical model. The electron energy spectrum is also calculated and it is found that the energy distribution ratio of electrons ΔE/E for the spheroid model under the conditions reported here is half that of the spherical model and it is in good agreement with the experimental value in the same conditions. As a result, the quasi-mono-energetic electron output beam interacting with the laser plasma can be more appropriately described with this model. (physics of gases, plasmas, and electric discharges)

  3. Off-center point explosion in a spheroid

    International Nuclear Information System (INIS)

    Morita, Kazuhiko; Sakashita, Shiro

    1978-01-01

    An off-center point explosion in a spheroid with exponential or Gaussian density distribution is investigated by applying the generalized Laumbach and Probstein method. For a typical example, we calculate the explosion in a spheroid with the eccentricity e = 0.7. If the separation distance between the center of the spheroid and the explosion point is larger than three times of the density scale height, the shock wave may almost propagate toward the direction of the minor axis of symmetry, within the polar angle of 30 0 . The shock envelope elongates toward the same direction and may form a polar jet and/or a tilted jet. But, in the case of an explosion in the equatorial plane (perpendicular to the minor axis of symmetry), two plasmas with the same form may be ejected into two different directions with the angle smaller than 180 0 . Explosion models of double radio sources and related objects are suggested. (author)

  4. Method for the determination of oxygen consumption rates and diffusion coefficients in multicellular spheroids

    OpenAIRE

    Mueller-Klieser, W.

    1984-01-01

    A method has been developed for the quantitative evaluation of oxygen tension (PO2) distributions in multicellular spheroids measured with O2-sensitive microelectrodes. The experimental data showed that multicellular tumor spheroids in stirred growth media were characterized by a diffusion-depleted zone surrounding the spheroids. This zone was elicited by an unstirred layer of medium next to the spheroid leading to a continuous decrease in the PO2 values from the bulk medium towards the spher...

  5. Halo carbon stars associated with dwarf spheroidal galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Van Den Bergh, S.; Lafontaine, A.

    1984-11-01

    Star counts have been performed for rings centered on the carbon star at 1 69 degrees, b + 55 degrees at a distance of 60 kpc. The counts were performed in order to determine whether halo carbon stars might be situated in dwarf spheroidal galaxies which are too star-poor to have been recognized as galaxies. The counts were made on a IIIa-J plate baked in forming gas that was exposed for 40 minutes through a 2C filter with the Palomar 1.2-m Schmidt telescope. It is shown that the carbon star is not situated in a dwarf spheroidal galaxy brighter than M(V) 5.7.

  6. Heavy-ion radiobiology of multicellular tumor spheroids

    International Nuclear Information System (INIS)

    Rodriguez, A.; Alpen, E.L.

    1980-01-01

    Experiments reported here were conducted with carbon ions, neon ions, and argon ions using rat brain gliosarcoma (9L) and Chinese hamster lung V79 cells grown as multicellular spheroids. Our studies were designed to evaluate high-LET radiation survival characteristics of cells grown in this relatively organized tissue-like environment. Our primary objectives were to determine the RBE values in plateau and spread Bragg peak regions of the carbon, neon, and argon beams, and evaluate with high and low LET radiation, the role of spheroid architecture in postirradiation survival of cells grown in this format

  7. Stellar Oxygen Abundances

    Science.gov (United States)

    King, Jeremy

    1994-04-01

    suggested, and supported with observational evidence, that this may be due to incomplete stellar models and the possibility that a significant fraction of O in gaseous nebulae is locked up in dust grains. Examining our results in a broader sense, we suggest that: a) the formation of the Galactic halo was a slow process but b) did not involve the merger of independent "fragments" c) Type Ia supernovae are dominated by CO-He white dwarf systems having Fe production timescales of a few Gyr d) The hiatus between the end of halo formation and the beginning of star formation in the disk, possibly required if CO-He white dwarfs are the dominant source of Type Ia supernovae, may be confirmed as the observed gap in the [O/H] distribution e) The long timescale (10^9 - 10^10 yr) of Fe production by CO-He white dwarf systems is also seen to be consistent with the lack of any correlation between age and [Fe/H] in our open cluster sample and the large scatter present in the [Fe/H] vs. age relations for field stars. (SECTION: Dissertation Summaries)

  8. THE TIDAL ORIGIN OF THE MAGELLANIC STREAM AND THE POSSIBILITY OF A STELLAR COUNTERPART

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Jonathan D.; Bekki, Kenji, E-mail: jdiaz@ast.cam.ac.uk [ICRAR, M468, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia, 6009 (Australia)

    2012-05-01

    We present an N-body model that reproduces the morphology and kinematics of the Magellanic Stream (MS), a vast neutral hydrogen (H I) structure that trails behind the Large and Small Magellanic Clouds (LMC and SMC, respectively) in their orbit about the Milky Way (MW). After investigating 8 Multiplication-Sign 10{sup 6} possible orbits consistent with the latest proper motions, we adopt an orbital history in which the LMC and SMC have only recently become a strongly interacting binary pair. We find that their first close encounter {approx}2 Gyr ago provides the necessary tidal forces to disrupt the disk of the SMC and thereby create the MS. The model also reproduces the on-sky bifurcation of the two filaments of the MS, and we suggest that a bound association with the MW is required to reproduce the bifurcation. Additional H I structures are created during the tidal evolution of the SMC disk, including the Magellanic Bridge, the 'Counter-Bridge', and two branches of leading material. Insights into the chemical evolution of the LMC are also provided, as a substantial fraction of the material stripped away from the SMC is engulfed by the LMC. Lastly, we compare three different N-body realizations of the stellar component of the SMC, which we model as a pressure-supported spheroid motivated by recent kinematical observations. We find that an extended spheroid is better able to explain the stellar periphery of the SMC, and the tidal evolution of the spheroid may imply the existence of a stellar stream akin to the gaseous MS.

  9. Effects of irradiation and cisplatin on human glioma spheroids: inhibition of cell proliferation and cell migration

    NARCIS (Netherlands)

    Fehlauer, Fabian; Muench, Martina; Rades, Dirk; Stalpers, Lukas J. A.; Leenstra, Sieger; van der Valk, Paul; Slotman, Ben; Smid, Ernst J.; Sminia, Peter

    2005-01-01

    Investigation of cell migration and proliferation of human glioma cell line spheroids (CLS) and evaluation of morphology, apoptosis, and immunohistochemical expression of MIB-1, p53, and p21 of organotypic muticellular spheroids (OMS) following cisplatin (CDDP) and irradiation (RT). Spheroids of the

  10. Biomaterial Substrate-Mediated Multicellular Spheroid Formation and Their Applications in Tissue Engineering.

    Science.gov (United States)

    Tseng, Ting-Chen; Wong, Chui-Wei; Hsieh, Fu-Yu; Hsu, Shan-Hui

    2017-12-01

    Three-dimentional (3D) multicellular aggregates (spheroids), compared to the traditional 2D monolayer cultured cells, are physiologically more similar to the cells in vivo. So far there are various techniques to generate 3D spheroids. Spheroids obtained from different methods have already been applied to regenerative medicine or cancer research. Among the cell spheroids created by different methods, the substrate-derived spheroids and their forming mechanism are unique. This review focuses on the formation of biomaterial substrate-mediated multicellular spheroids and their applications in tissue engineering and tumor models. First, the authors will describe the special chitosan substrate-derived mesenchymal stem cell (MSC) spheroids and their greater regenerative capacities in various tissues. Second, the authors will describe tumor spheroids derived on chitosan and hyaluronan substrates, which serve as a simple in vitro platform to study 3D tumor models or to perform cancer drug screening. Finally, the authors will mention the self-assembly process for substrate-derived multiple cell spheroids (co-spheroids), which may recapitulate the heterotypic cell-cell interaction for co-cultured cells or crosstalk between different types of cells. These unique multicellular mono-spheroids or co-spheroids represent a category of 3D cell culture with advantages of biomimetic cell-cell interaction, better functionalities, and imaging possibilities. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Modular Stellarator Reactor conceptual design study

    International Nuclear Information System (INIS)

    Miller, R.L.; Bathke, C.G.

    1983-01-01

    A conceptual design study of the Modular Stellarator Reactor is summarized. The physics basis of the approach is elucidated with emphasis on magnetics performance optimization. Key engineering features of the fusion power core are described. Comparisons with an analogous continuous-helical-coil (torsatron) system are made as the basis of a technical and economic assessment

  12. Survey of the MAgellanic Stellar History -- SMASH

    NARCIS (Netherlands)

    Nidever, David; Olsen, Knut; Besla, Gurtina; Gruendl, Robert; Saha, Abhijit; Gallart, Carme; Olszewski, Edward W.; Munoz, Ricardo; Monelli, Matteo; Kunder, Andrea; Kaleida, Catherine; Walker, Alistair; Stringfellow, Guy; Zaritsky, Dennis; van der Marel, Roeland; Blum, Robert; Vivas, Kathy; Chu, You-Hua; Martin, Nicolas; Conn, Blair; Noel, Noelia; Majewski, Steven; Jin, Shoko; Kim, Hwihyun; Cioni, Maria-Rosa; Bell, Eric; Monachesi, Antonela; de Boer, Thomas

    Over the last several years, various discoveries have drastically altered our view of the iconic Magellanic Clouds (MCs), the nearest interacting galaxy system. The best evidence is now that they are on first infall into the Milky Way, that their stellar populations extend much further than

  13. Modular stellarator reactor conceptual design study

    International Nuclear Information System (INIS)

    Miller, R.L.; Krakowski, R.A.; Bathke, C.G.

    1983-01-01

    A conceptual design study of the Modular Stellarator Reactor is summarized. The physics basis of the approach is elucidated with emphasis on magnetics performance optimization. Key engineering features of the fusion power core are described. Comparisons with an analogous continuous-helical-coil (torsatron) system are made as the basis of a technical and economic assessment

  14. THE ADVANCED STELLAR COMPASS

    DEFF Research Database (Denmark)

    Jørgensen, John Leif; Liebe, Carl Christian

    1997-01-01

    The science objective of the Danish Geomagnetic Research Satellite "Ørsted" is to map the magnetic field of the Earth, with a vector precision of a fraction of a nanotesla. This necessitates an attitude reference instrument with a precision of a few arcseconds onboard the satellite. To meet...... this demand the Advanced Stellar Compass (ASC), a fully autonomous miniature star tracker, was developed. This ASC is capable of both solving the "lost in space" problem and determine the attitude with arcseconds precision. The development, principles of operation and instrument autonomy of the ASC...

  15. Physics of Stellar Convection

    Science.gov (United States)

    Arnett, W. David

    2009-05-01

    We review recent progress using numerical simulations as a testbed for development of a theory of stellar convection, much as envisaged by John von Newmann. Necessary features of the theory, non-locality and fluctuations, are illustrated by computer movies. It is found that the common approximation of convection as a diffusive process presents the wrong physical picture, and improvements are suggested. New observational results discussed at the conference are gratifying in their validation of some of our theoretical ideas, especially the idea that SNIb and SNIc events are related to the explosion of massive star cores which have been stripped by mass loss and binary interactions [1

  16. The early days of the Sculptor dwarf spheroidal galaxy

    NARCIS (Netherlands)

    Jablonka, P.; North, P.; Mashonkina, L.; Hill, V.; Revaz, Y.; Shetrone, M.; Starkenburg, E.; Irwin, M.; Tolstoy, E.; Battaglia, G.; Venn, K.; Helmi, A.; Primas, F.; François, P.

    2015-01-01

    We present the high-resolution spectroscopic study of five -3.9 ≤ [Fe/H] ≤ -2.5 stars in the Local Group dwarf spheroidal, Sculptor, thereby doubling the number of stars with comparable observations in this metallicity range. We carry out a detailed analysis of the chemical abundances of α, iron

  17. Spheroidal Integral Equations for Geodetic Inversion of Geopotential Gradients

    Science.gov (United States)

    Novák, Pavel; Šprlák, Michal

    2018-03-01

    The static Earth's gravitational field has traditionally been described in geodesy and geophysics by the gravitational potential (geopotential for short), a scalar function of 3-D position. Although not directly observable, geopotential functionals such as its first- and second-order gradients are routinely measured by ground, airborne and/or satellite sensors. In geodesy, these observables are often used for recovery of the static geopotential at some simple reference surface approximating the actual Earth's surface. A generalized mathematical model is represented by a surface integral equation which originates in solving Dirichlet's boundary-value problem of the potential theory defined for the harmonic geopotential, spheroidal boundary and globally distributed gradient data. The mathematical model can be used for combining various geopotential gradients without necessity of their re-sampling or prior continuation in space. The model extends the apparatus of integral equations which results from solving boundary-value problems of the potential theory to all geopotential gradients observed by current ground, airborne and satellite sensors. Differences between spherical and spheroidal formulations of integral kernel functions of Green's kind are investigated. Estimated differences reach relative values at the level of 3% which demonstrates the significance of spheroidal approximation for flattened bodies such as the Earth. The observation model can be used for combined inversion of currently available geopotential gradients while exploring their spectral and stochastic characteristics. The model would be even more relevant to gravitational field modelling of other bodies in space with more pronounced spheroidal geometry than that of the Earth.

  18. The dwarf spheroidal galaxies around the milky way

    NARCIS (Netherlands)

    Tolstoy, E.; Battaglia, G.; Helmi, A.; Irwin, M. J.; Hill, V.; Vallenari, A; Tantalo, R; Portinari, L; Moretti, A

    2007-01-01

    We review the progress of ESO/WFI Imaging and VLT/FLAMES spectroscopy of large numbers of individual stars in nearby dwarf spheroidal galaxies by the Dwarf Abundances and Radial-velocities Team (DART). These observations have allowed us to show that neither the kinematics nor the abundance nor the

  19. Optical properties of spherical and oblate spheroidal gold shell colloids

    NARCIS (Netherlands)

    Penninkhof, J.J.; Moroz, A.; van Blaaderen, A.; Polman, A.

    2008-01-01

    The surface plasmon modes of spherical and oblate spheroidal core−shell colloids composed of a 312 nm diameter silica core and a 20 nm thick Au shell are investigated. Large arrays of uniaxially aligned core−shell colloids with size aspect ratios ranging from 1.0 to 1.7 are fabricated using a novel

  20. The dynamical and chemical evolution of dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Revaz, Y.; Jablonka, P.; Sawala, T.; Hill, V.; Letarte, B.; Irwin, M.; Battaglia, G.; Helmi, A.; Shetrone, M. D.; Tolstoy, E.; Venn, K. A.

    We present a large sample of fully self-consistent hydrodynamical Nbody/Tree-SPH simulations of isolated dwarf spheroidal galaxies (dSphs). It has enabled us to identify the key physical parameters and mechanisms at the origin of the observed variety in the Local Group dSph properties. The initial

  1. Estimation of scattering from a moist rough surface with spheroidal ...

    Indian Academy of Sciences (India)

    Administrator

    less than 5⋅5% of the magnetic wavelength. We empha- size that the surface deviation is responsible for scattering at a given electromagnetic wavelength. 2. Theoretical consideration (basic theory). We consider a horizontally rough surface with slight per- centage of moisture (2–4⋅5%) with spheroidal dust parti- cles.

  2. Cryopreservation of organotypic multicellular spheroids from human gliomas

    NARCIS (Netherlands)

    Kaaijk, P.; van den Berg, F.; van Amstel, P.; Troost, D.

    1996-01-01

    Fresh human glioma tissue can be cultured on agarose to form organotypic multicellular spheroids (OMS). The major advantage of OMS is the preservation of the cellular heterogeneity and the tumour architecture, which is lost in conventional monolayer cultures. The present study was undertaken to

  3. Void nucleation in spheroidized steels during tensile deformation

    International Nuclear Information System (INIS)

    Fisher, J.R. Jr.

    1980-04-01

    An investigation was conducted to determine the effects of various mechanical and material parameters on void formation at cementite particles in axisymmetric tensile specimens of spheroidized plain carbon steels. Desired microstructures for each of three steel types were obtained. Observations of void morphology with respect to various microstructural features were made using optical and scanning electron microscopy

  4. Stellar axion models

    Energy Technology Data Exchange (ETDEWEB)

    Nowakowski, Daniel; Kuster, Markus; Meister, Claudia V.; Fuelbert, Florian; Hoffmann, Dieter H.H. [TU Darmstadt (Germany). Institut fuer Kernphysik; Weiss, Achim [Max-Planck-Institut fuer Astrophysik, Garching (Germany)

    2010-07-01

    An axion helioscope is typically operated to observe the sun as an axion source. Additional pointings at celestial sources, e.g. stars in other galaxies, result in possible detections of axions from distant galactic objects. For the observation of supplementary axion sources we therefore calculate the thereotical axion flux from distant stars by extending axionic flux models for the axion Primakoff effect in the sun to other main sequence stars. The main sequence star models used for our calculations are based on full stellar structure calculations. To deduce the effective axion flux of stellar objects incident on the Earth the All-Sky catalogue was used to obtain the spectral class and distance of the stars treated. Our calculations of the axion flux in the galactic plane show that for a zero age main sequence star an maximum axion flux of {phi}{sub a}=303.43 cm{sup -2}s{sup -1} could be expected. Furthermore we present estimates of axion fluxes from time-evolved stars.

  5. The DEMO Quasisymmetric Stellarator

    Directory of Open Access Journals (Sweden)

    Geoffrey B. McFadden

    2010-02-01

    Full Text Available The NSTAB nonlinear stability code solves differential equations in conservation form, and the TRAN Monte Carlo test particle code tracks guiding center orbits in a fixed background, to provide simulations of equilibrium, stability, and transport in tokamaks and stellarators. These codes are well correlated with experimental observations and have been validated by convergence studies. Bifurcated 3D solutions of the 2D tokamak problem have been calculated that model persistent disruptions, neoclassical tearing modes (NTMs and edge localized modes (ELMs occurring in the International Thermonuclear Experimental Reactor (ITER, which does not pass the NSTAB simulation test for nonlinear stability. So we have designed a quasiaxially symmetric (QAS stellarator with similar proportions as a candidate for the demonstration (DEMO fusion reactor that does pass the test [1]. The configuration has two field periods and an exceptionally accurate 2D symmetry that furnishes excellent thermal confinement and good control of the prompt loss of alpha particles. Robust coils are found from a filtered form of the Biot-Savart law based on a distribution of current over a control surface for the coils and the current in the plasma defined by the equilibrium calculation. Computational science has addressed the issues of equilibrium, stability, and transport, so it remains to develop an effective plan to construct the coils and build a diverter.

  6. High-purity tungsten powder: spheroidizing, properties and use in electronics

    International Nuclear Information System (INIS)

    Kapustin, V.I.; Burov, I.V.

    1999-01-01

    A study was made on the method of spheroidizing of tungsten powder in plasma of super high-frequency (SHF) discharge for formation of matrices, cathodes with regular porous structure. Kinetics of interphase interaction in the basic W-Y 2 O 3 cathode system was investigated. Possibility of using small additions of Re 2 Yintermetallic compound as an activator of emission-active component of cathodes was analyzed, High efficiency of plasma SHF-treatment with the use of laminar plasma flow is shown [ru

  7. Analyzing the mechanisms of cell killing by ionizing radiation in monolayer, spheroids and xenografted tumours

    International Nuclear Information System (INIS)

    Horas, J.A.; Olguín, O.R.; Rizzotto, M.G.

    2017-01-01

    A relationship between oxygen enhancement ratio (OER) and parameters of Linear Quadratic (LQ) model in hypoxic and aerobic conditions in several cell lines grown as monolayer, spheroids and transplanted tumors (xenograft) is tested. By considering this relationship, the two mechanisms of cell death by radiation appear. Surviving Fraction (SF) fits are compared in both oxygenation conditions by using the LQ. The data are obtained from literature. The existence of such mechanisms and their implications in the different systems studied is shown. The validity of one or other mechanism in each case is determined and the OER dependence with dose. (authors) [es

  8. Comparative analysis of tumor spheroid generation techniques for differential in vitro drug toxicity

    Science.gov (United States)

    Raghavan, Shreya; Rowley, Katelyn R.; Mehta, Geeta

    2016-01-01

    Multicellular tumor spheroids are powerful in vitro models to perform preclinical chemosensitivity assays. We compare different methodologies to generate tumor spheroids in terms of resultant spheroid morphology, cellular arrangement and chemosensitivity. We used two cancer cell lines (MCF7 and OVCAR8) to generate spheroids using i) hanging drop array plates; ii) liquid overlay on ultra-low attachment plates; iii) liquid overlay on ultra-low attachment plates with rotating mixing (nutator plates). Analysis of spheroid morphometry indicated that cellular compaction was increased in spheroids generated on nutator and hanging drop array plates. Collagen staining also indicated higher compaction and remodeling in tumor spheroids on nutator and hanging drop arrays compared to conventional liquid overlay. Consequently, spheroids generated on nutator or hanging drop plates had increased chemoresistance to cisplatin treatment (20-60% viability) compared to spheroids on ultra low attachment plates (10-20% viability). Lastly, we used a mathematical model to demonstrate minimal changes in oxygen and cisplatin diffusion within experimentally generated spheroids. Our results demonstrate that in vitro methods of tumor spheroid generation result in varied cellular arrangement and chemosensitivity. PMID:26918944

  9. Media additives to promote spheroid circularity and compactness in hanging drop platform.

    Science.gov (United States)

    Leung, Brendan M; Lesher-Perez, Sasha Cai; Matsuoka, Toshiki; Moraes, Christopher; Takayama, Shuichi

    2015-02-01

    Three-dimensional spheroid cultures have become increasingly popular as drug screening platforms, especially with the advent of different high throughput spheroid forming technologies. However, comparing drug efficacy across different cell types in spheroid culture can be difficult due to variations in spheroid morphologies and transport characteristics. Improving the reproducibility of compact, circular spheroids contributes to standardizing and increasing the fidelity of the desired gradient profiles in these drug screening three-dimensional tissue cultures. In this study we discuss the role that circularity and compaction has on spheroids, and demonstrate the impact methylcellulose (MethoCel) and collagen additives in the culture media can contribute to more compact and circular spheroid morphology. We demonstrate that improved spheroid formation is not a simple function of increased viscosity of the different macromolecule additives, suggesting that other macromolecular characteristics contribute to improved spheroid formation. Of the various macromolecular additives tested for hanging drop culture, MethoCel provided the most desirable spheroid formation. Additionally, the higher viscosity of MethoCel-containing media improved the ease of imaging of cellular spheroids within hanging drop cultures by reducing motion-induced image blur.

  10. NEMO: A Stellar Dynamics Toolbox

    Science.gov (United States)

    Barnes, Joshua; Hut, Piet; Teuben, Peter

    2010-10-01

    NEMO is an extendible Stellar Dynamics Toolbox, following an Open-Source Software model. It has various programs to create, integrate, analyze and visualize N-body and SPH like systems, following the pipe and filter architecture. In addition there are various tools to operate on images, tables and orbits, including FITS files to export/import to/from other astronomical data reduction packages. A large growing fraction of NEMO has been contributed by a growing list of authors. The source code consist of a little over 4000 files and a little under 1,000,000 lines of code and documentation, mostly C, and some C++ and Fortran. NEMO development started in 1986 in Princeton (USA) by Barnes, Hut and Teuben. See also ZENO (ascl:1102.027) for the version that Barnes maintains.

  11. Fluid absorption related to ion transport in human airway epithelial spheroids

    DEFF Research Database (Denmark)

    Pedersen, P S; Holstein-Rathlou, N H; Larsen, P L

    1999-01-01

    , and amiloride inhibited both values. Fluid transport rates were calculated from repeated measurements of spheroid diameters. The results showed that 1) non-CF and CF spheroids absorbed fluid at identical rates (4.4 microl x cm(-2) x h(-1)), 2) amiloride inhibited fluid absorption to a lower residual level...... in non-CF than in CF spheroids, 3) Cl(-)-channel inhibitors increased fluid absorption in amiloride-treated non-CF spheroids to a level equal to that of amiloride-treated CF spheroids, 4) hydrochlorothiazide reduced the amiloride-insensitive fluid absorption in both non-CF and CF spheroids, and 5......) osmotic water permeabilities were equal in non-CF and CF spheroids ( approximately 27 x 10(-7) cm x s(-1) x atm(-1))....

  12. Plasma spheroidization of iron powders in a non-transferred DC thermal plasma jet

    International Nuclear Information System (INIS)

    Kumar, S.; Selvarajan, V.

    2008-01-01

    In this paper, the results of plasma spheroidization of iron powders using a DC non-transferred plasma spray torch are presented. The morphology of the processed powders was characterized through scanning electron microscopy (SEM) and optical microscopy (OM). The percentages of spheroidized powders were calculated by the shape factors such as the Irregularity Parameter (IP) and Roundness (RN). A maximum of 83% of spheroidization can be achieved. The spheroidization results are compared with the theoretical estimation and they are found to be in good agreement. The phase composition of the spheroidized powder was analyzed by XRD. The effect of plasma jet temperature and plasma gas flow rate on spheroidization is discussed. At low plasma gas flow rates and at high plasma jet temperatures, the percentage of spheroidization is high

  13. The LAMOST stellar spectroscopic survey and the Galactic halo

    International Nuclear Information System (INIS)

    Liu Chao; Deng Licai

    2015-01-01

    The formation and evolution of galaxies is an extremely important and fundamental question in modern astrophysics. Among the galaxies, the Milky Way is a very special sample not only because we live in it, but also because it is the only one in which we can carefully and individually observe its member stars. It has been confirmed that the Galactic halo, including both the stellar spheroid and the dark matter halo, contains fairly complicated structures, from which the overall shape, formation, and evolutionary history of our Galaxy can be unveiled. Moreover, some very rare and special stars in the Milky Way can be used as tracers to indirectly detect the core region of the Galaxy around the central super-massive black hole, which is also a hot topic of astrophysics. The LAMOST survey of the Milky Way will collect millions of stellar spectra at low wavelength resolution, making it the largest of such projects throughout the world. Its data base is very suitable for the study of the structure and evolution of the Milky Way. In this article, we report our on-going studies on the Galactic halo with LAMOST data, and present some early scientific results. (authors)

  14. Archaeology of the Sagittarius galaxy by means of its stellar clusters

    Science.gov (United States)

    Moni Bidin, C.

    2017-07-01

    The Sagittarius dwarf spheroidal (Sgr dSph) galaxy is a Milky Way satellite currently merging with the parent system. This small galaxy is undergoing disruption due to tidal forces, while stars and clusters lost along the orbit progressively mix with the general Galactic population. The Sgr system is also one of the very few local dSph's known to host stellar clusters, but the census of its cluster population is far from complete. This is very bad, both because the total amount of clusters can help estimating the mass of the original system, and because the age-metallicity relations of the so-far confirmed six members shows an age gap at intermediate ages similar to the well-known gap of the Large Magellanic Cloud. Still, this feature could be due only to the small number of confirmed members. Here we show the status of our project aimed at testing the membership to the Sgr galaxy of a series of candidates proposed in the literature. Our recent spectroscopic studies could exclude the Sgr membership of three candidates, namely Ruprecht 106, NGC 4147, and E 3, although a follow-up study of the latter is ongoing to confirm the previous results. On the other hand, our chemical analysis concluded that NGC 5634 is very likely a member of the Sgr cluster family, and NGC 5053 also could be. Finally, we present our preliminary results of our spectroscopic analysis for the last object, namely AM 4. This candidate is particularly important, because previous estimates of age and metallicity indicate that it closely follow the relation traced by confirmed clusters, but its intermediate age makes it fall exactly at the middle of the supposed age gap.

  15. The Magellanic Analog Dwarf Companions and Stellar Halos (MADCASH) Survey: Near-Field Cosmology with Resolved Stellar Populations Around Local Volume LMC Stellar-Mass Galaxies

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Willman, Beth; Brodie, Jean P.; Crnojevic, Denija; Peter, Annika; Price, Paul A.; Romanowsky, Aaron J.; Spekkens, Kristine; Strader, Jay

    2017-01-01

    We discuss the first results of our observational program to comprehensively map nearly the entire virial volumes of roughly LMC stellar mass galaxies at distances of ~2-4 Mpc. The MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey will deliver the first census of the dwarf satellite populations and stellar halo properties within LMC-like environments in the Local Volume. These will inform our understanding of the recent DES discoveries of dwarf satellites tentatively affiliated with the LMC/SMC system. We will detail our discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep Subaru+HyperSuprimeCam imaging reaching ~2 magnitudes below its TRGB. We will summarize the survey results and status to date, highlighting some challenges encountered and lessons learned as we process the data for this program through a prototype LSST pipeline. Our program will examine whether LMC stellar mass dwarfs have extended stellar halos, allowing us to assess the relative contributions of in-situ stars vs. merger debris to their stellar populations and halo density profiles. We outline the constraints on galaxy formation models that will be provided by our observations of low-mass galaxy halos and their satellites.

  16. CHEMICAL SIGNATURES OF THE FIRST SUPERNOVAE IN THE SCULPTOR DWARF SPHEROIDAL GALAXY

    International Nuclear Information System (INIS)

    Simon, Joshua D.; Thompson, Ian B.; Shectman, Stephen A.; Jacobson, Heather R.; Frebel, Anna; Adams, Joshua J.

    2015-01-01

    We present a homogeneous chemical abundance analysis of five of the most metal-poor stars in the Sculptor dwarf spheroidal galaxy. We analyze new and archival high resolution spectroscopy from Magellan/MIKE and VLT/UVES and determine stellar parameters and abundances in a consistent way for each star. Two of the stars in our sample, at [Fe/H] = −3.5 and [Fe/H] = −3.8, are new discoveries from our Ca K survey of Sculptor, while the other three were known in the literature. We confirm that Scl 07-50 is the lowest metallicity star identified in an external galaxy, at [Fe/H] = −4.1. The two most metal-poor stars both have very unusual abundance patterns, with striking deficiencies of the α elements, while the other three stars resemble typical extremely metal-poor Milky Way halo stars. We show that the star-to-star scatter for several elements in Sculptor is larger than that for halo stars in the same metallicity range. This scatter and the uncommon abundance patterns of the lowest metallicity stars indicate that the oldest surviving Sculptor stars were enriched by a small number of earlier supernovae, perhaps weighted toward high-mass progenitors from the first generation of stars the galaxy formed

  17. Multiple Stellar Populations of Globular Clusters from Homogeneous Ca-CN Photometry. II. M5 (NGC 5904) and a New Filter System

    Science.gov (United States)

    Lee, Jae-Woo

    2017-07-01

    Using our ingeniously designed new filter systems, we investigate multiple stellar populations of the red giant branch (RGB) and the asymptotic giant branch (AGB) in the globular cluster (GC) M5. Our results are the following. (1) Our {{cn}}{JWL} index accurately traces nitrogen abundances in M5, while other color indices fail to do so. (2) We find bimodal CN distributions in both RGB and AGB sequences, with number ratios between CN-weak (CN-w) and CN-strong (CN-s) of n(CN-w):n(CN-s) = 29:71 (±2) and 21:79 (±7), respectively. (3) We also find a bimodal photometric [N/Fe] distribution for M5 RGB stars. (4) Our {{cn}}{JWL}-[O/Fe] and {{cn}}{JWL}-[Na/Fe] relations show clear discontinuities between the two RGB populations. (5) Although small, the RGB bump of CN-s is slightly brighter, {{Δ }}{V}{bump} = 0.07 ± 0.04 mag. If real, the difference in the helium abundance becomes {{Δ }}Y = 0.028 ± 0.016, in the sense that CN-s is more helium enhanced. (6) Very similar radial but different spatial distributions with comparable center positions are found for the two RGB populations. The CN-s RGB and AGB stars are more elongated along the NW-SE direction. (7) The CN-s population shows a substantial net projected rotation, while that of the CN-w population is nil. (8) Our results confirm the deficiency of CN-w AGB stars previously noted by others. We show that it is most likely due to stochastic truncation in the outer part of the cluster. Finally, we discuss the formation scenario of M5. Based on observations made with the Cerro Tololo Inter-American Observatory (CTIO) 1 m telescope, which is operated by the SMARTS consortium.

  18. A catalog of stellar spectrophotometry

    Science.gov (United States)

    Adelman, S. J.; Pyper, D. M.; Shore, S. N.; White, R. E.; Warren, W. H., Jr.

    1989-01-01

    A machine-readable catalog of stellar spectrophotometric measurements made with rotating grating scanner is introduced. Consideration is given to the processes by which the stellar data were collected and calibrated with the fluxes of Vega (Hayes and Latham, 1975). A sample page from the spectrophotometric catalog is presented.

  19. Quasisymmetry equations for conventional stellarators

    International Nuclear Information System (INIS)

    Pustovitov, V.D.

    1994-11-01

    General quasisymmetry condition, which demands the independence of B 2 on one of the angular Boozer coordinates, is reduced to two equations containing only geometrical characteristics and helical field of a stellarator. The analysis is performed for conventional stellarators with a planar circular axis using standard stellarator expansion. As a basis, the invariant quasisymmetry condition is used. The quasisymmetry equations for stellarators are obtained from this condition also in an invariant form. Simplified analogs of these equations are given for the case when averaged magnetic surfaces are circular shifted torii. It is shown that quasisymmetry condition can be satisfied, in principle, in a conventional stellarator by a proper choice of two satellite harmonics of the helical field in addition to the main harmonic. Besides, there appears a restriction on the shift of magnetic surfaces. Thus, in general, the problem is closely related with that of self-consistent description of a configuration. (author)

  20. Detection of stellar oscillations in HWVir

    Directory of Open Access Journals (Sweden)

    Baran Andrzej S.

    2016-08-01

    Full Text Available We present our analysis of K2 observations of the binary system, HWVir. We processed the raw Kepler data and used Fourier analysis to search for periodic signals that could be associated with pulsations. We detect the binary frequency and its harmonic and discovered tens of peaks at both low and high frequencies. We interpreted those to be caused by stellar pulsations. Our discovery means we can apply the tools of asteroseismology to the HWVir system.

  1. n-capture elements in the Sculptor dwarf spheroidal galaxy

    Science.gov (United States)

    Skúladóttir, Ása

    2018-06-01

    Sculptor is a well studied dwarf galaxy in the Local Group, which is dominated by an old stellar population (>10 Gyr) and is therefore an ideal system to study early chemical evolution. With high-resolution VLT/FLAMES spectra, R~20,000, we are able to get accurate abundances of several n-capture elements in ~100 stars, from both the lighter n-capture elements (Y) as well as the heavier ones, both tracers of the s-process (e.g. Ba) and the r-process (e.g. Eu). I will discuss the similarities and differences in the n-capture elements in Sculptor and the Milky Way, as well as other dwarf galaxies.

  2. Estimate of stellar masses from their QPO frequencies

    Indian Academy of Sciences (India)

    For such a system, the stellar radius is very close to the marginally stable orbit ... The phenomenon of quasiperiodic oscillations was discovered in 1985 by ... QPOs are revealed in a power–density spectrum as a broad peak covering many.

  3. Nucleosynthesis in stellar explosions

    Energy Technology Data Exchange (ETDEWEB)

    Woosley, S.E.; Axelrod, T.S.; Weaver, T.A.

    1983-01-01

    The final evolution and explosion of stars from 10 M/sub solar/ to 10/sup 6/ M/sub solar/ are reviewed with emphasis on factors affecting the expected nucleosynthesis. We order our paper in a sequence of decreasing mass. If, as many suspect, the stellar birth function was peaked towards larger masses at earlier times (see e.g., Silk 1977; but also see Palla, Salpeter, and Stahler 1983), this sequence of masses might also be regarded as a temporal sequence. At each stage of Galactic chemical evolution stars form from the ashes of preceding generations which typically had greater mass. A wide variety of Type I supernova models, most based upon accreting white dwarf stars, are also explored using the expected light curves, spectra, and nucleosynthesis as diagnostics. No clearly favored Type I model emerges that is capable of simultaneously satisfying all three constraints.

  4. Nucleosynthesis in stellar explosions

    International Nuclear Information System (INIS)

    Woosley, S.E.; Axelrod, T.S.; Weaver, T.A.

    1983-01-01

    The final evolution and explosion of stars from 10 M/sub solar/ to 10 6 M/sub solar/ are reviewed with emphasis on factors affecting the expected nucleosynthesis. We order our paper in a sequence of decreasing mass. If, as many suspect, the stellar birth function was peaked towards larger masses at earlier times (see e.g., Silk 1977; but also see Palla, Salpeter, and Stahler 1983), this sequence of masses might also be regarded as a temporal sequence. At each stage of Galactic chemical evolution stars form from the ashes of preceding generations which typically had greater mass. A wide variety of Type I supernova models, most based upon accreting white dwarf stars, are also explored using the expected light curves, spectra, and nucleosynthesis as diagnostics. No clearly favored Type I model emerges that is capable of simultaneously satisfying all three constraints

  5. Remarks on stellar clusters

    International Nuclear Information System (INIS)

    Teller, E.

    1985-01-01

    In the following, a few simple remarks on the evolution and properties of stellar clusters will be collected. In particular, globular clusters will be considered. Though details of such clusters are often not known, a few questions can be clarified with the help of primitive arguments. These are:- why are spherical clusters spherical, why do they have high densities, why do they consist of approximately a million stars, how may a black hole of great mass form within them, may they be the origin of gamma-ray bursts, may their invisible remnants account for the missing mass of our galaxy. The available data do not warrant a detailed evaluation. However, it is remarkable that exceedingly simple models can shed some light on the questions enumerated above. (author)

  6. L = ± 1 stellarator

    International Nuclear Information System (INIS)

    Kikuchi, T.; Shiina, S.; Saito, K.; Gesso, H.; Aizawa, M.; Kawakami, I.

    1985-01-01

    We report the magnetic field configuration of helical magnetic axis stellarator. The magnetic field configuration is composed of large l=1 field and small l=-1 and l=0(bumpy) fields. The large l=1 field (combined with the small l=-1 field) is used to form helical magnetic axis with the helical curvature much larger than the toroidal curvature, which provides the high limiting values of β. The small l=-1 field, furthermore, as well as the large l=1 field reduces the Pfirsch-Schlueter currents by combining with l=0 field. Therefore, the large l=1 field and the combination of three field components may be favourable for the increase of limiting β value

  7. 3D high-content screening for the identification of compounds that target cells in dormant tumor spheroid regions

    International Nuclear Information System (INIS)

    Wenzel, Carsten; Riefke, Björn; Gründemann, Stephan; Krebs, Alice; Christian, Sven; Prinz, Florian; Osterland, Marc; Golfier, Sven; Räse, Sebastian; Ansari, Nariman; Esner, Milan; Bickle, Marc; Pampaloni, Francesco; Mattheyer, Christian; Stelzer, Ernst H.; Parczyk, Karsten; Prechtl, Stefan; Steigemann, Patrick

    2014-01-01

    Cancer cells in poorly vascularized tumor regions need to adapt to an unfavorable metabolic microenvironment. As distance from supplying blood vessels increases, oxygen and nutrient concentrations decrease and cancer cells react by stopping cell cycle progression and becoming dormant. As cytostatic drugs mainly target proliferating cells, cancer cell dormancy is considered as a major resistance mechanism to this class of anti-cancer drugs. Therefore, substances that target cancer cells in poorly vascularized tumor regions have the potential to enhance cytostatic-based chemotherapy of solid tumors. With three-dimensional growth conditions, multicellular tumor spheroids (MCTS) reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients as well as the development of dormant tumor regions. We here report the setup of a 3D cell culture compatible high-content screening system and the identification of nine substances from two commercially available drug libraries that specifically target cells in inner MCTS core regions, while cells in outer MCTS regions or in 2D cell culture remain unaffected. We elucidated the mode of action of the identified compounds as inhibitors of the respiratory chain and show that induction of cell death in inner MCTS core regions critically depends on extracellular glucose concentrations. Finally, combinational treatment with cytostatics showed increased induction of cell death in MCTS. The data presented here shows for the first time a high-content based screening setup on 3D tumor spheroids for the identification of substances that specifically induce cell death in inner tumor spheroid core regions. This validates the approach to use 3D cell culture screening systems to identify substances that would not be detectable by 2D based screening in otherwise similar culture conditions. - Highlights: • Establishment of a novel method for 3D cell culture based high-content screening. • First reported high

  8. 3D high-content screening for the identification of compounds that target cells in dormant tumor spheroid regions

    Energy Technology Data Exchange (ETDEWEB)

    Wenzel, Carsten; Riefke, Björn; Gründemann, Stephan; Krebs, Alice; Christian, Sven; Prinz, Florian; Osterland, Marc; Golfier, Sven; Räse, Sebastian [Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin (Germany); Ansari, Nariman [Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt (Germany); Esner, Milan; Bickle, Marc [Max Planck Institute of Molecular Cell Biology and Genetics, High-Throughput Technology Development Studio (TDS), Dresden (Germany); Pampaloni, Francesco; Mattheyer, Christian; Stelzer, Ernst H. [Physical Biology Group, Buchmann Institute for Molecular Life Sciences (BMLS), Goethe University Frankfurt (Germany); Parczyk, Karsten; Prechtl, Stefan [Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin (Germany); Steigemann, Patrick, E-mail: Patrick.Steigemann@bayer.com [Bayer Pharma AG, Global Drug Discovery, Muellerstrasse 178, 13353 Berlin (Germany)

    2014-04-15

    Cancer cells in poorly vascularized tumor regions need to adapt to an unfavorable metabolic microenvironment. As distance from supplying blood vessels increases, oxygen and nutrient concentrations decrease and cancer cells react by stopping cell cycle progression and becoming dormant. As cytostatic drugs mainly target proliferating cells, cancer cell dormancy is considered as a major resistance mechanism to this class of anti-cancer drugs. Therefore, substances that target cancer cells in poorly vascularized tumor regions have the potential to enhance cytostatic-based chemotherapy of solid tumors. With three-dimensional growth conditions, multicellular tumor spheroids (MCTS) reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients as well as the development of dormant tumor regions. We here report the setup of a 3D cell culture compatible high-content screening system and the identification of nine substances from two commercially available drug libraries that specifically target cells in inner MCTS core regions, while cells in outer MCTS regions or in 2D cell culture remain unaffected. We elucidated the mode of action of the identified compounds as inhibitors of the respiratory chain and show that induction of cell death in inner MCTS core regions critically depends on extracellular glucose concentrations. Finally, combinational treatment with cytostatics showed increased induction of cell death in MCTS. The data presented here shows for the first time a high-content based screening setup on 3D tumor spheroids for the identification of substances that specifically induce cell death in inner tumor spheroid core regions. This validates the approach to use 3D cell culture screening systems to identify substances that would not be detectable by 2D based screening in otherwise similar culture conditions. - Highlights: • Establishment of a novel method for 3D cell culture based high-content screening. • First reported high

  9. The Stellar Imager (SI) Project: Resolving Stellar Surfaces, Interiors, and Magnetic Activity

    Science.gov (United States)

    Carpenter, Kenneth G.; Schrijver, K.; Karovska, M.

    2007-01-01

    The Stellar Imager (SI) is a UV/Optical. Space-Based Interferometer designed to enable 0.1 milli-arcsec (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. The ultra-sharp images of SI will revolutionize our view of many dynamic astrophysical processes by transforming point sources into extended sources, and snapshots into evolving views. The science of SI focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. Its prime goal is to enable long-term forecasting of solar activity and the space weather that it drives. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. In this paper we discuss the science goals, technology needs, and baseline design of the SI mission.

  10. The Dark Energy Survey: Prospects for resolved stellar populations

    Energy Technology Data Exchange (ETDEWEB)

    Rossetto, Bruno M. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Santiago, Basílio X. [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Instituto de Fisica, Porto Alegre (Brazil); Girardi, Léo [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Osservatorio Astronomica di Padova-INAF, Padova (Italy); Camargo, Julio I. B. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Balbinot, Eduardo [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Instituto de Fisica, Porto Alegre (Brazil); da Costa, Luiz N. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Yanny, Brian [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Maia, Marcio A. G. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Makler, Martin [Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro (Brazil); Ogando, Ricardo L. C. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Pellegrini, Paulo S. [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Ramos, Beatriz [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); de Simoni, Fernando [Observatorio Nacional, Rio de Janeiro (Brazil); Lab. Interinstitucional de e-Astronomia-LIneA, Rio de Janeiro (Brazil); Armstrong, R. [Univ. of Illinois, Urbana, IL (United States); Bertin, E. [Univ. Pierre et Marie Curie, Paris (France); Desai, S. [Univ. of Illinois, Urbana, IL (United States); Kuropatkin, N. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lin, H. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Mohr, J. J. [Max-Planck-Institut fur extraterrestrische Physik, Garching (Germany); Tucker, D. L. [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2011-05-06

    Wide angle and deep surveys, regardless of their primary purpose, always sample a large number of stars in the Galaxy and in its satellite system. We here make a forecast of the expected stellar sample resulting from the Dark Energy Survey and the perspectives that it will open for studies of Galactic structure and resolved stellar populations in general. An estimated 1.2 x 108 stars will be sampled in DES grizY filters in the southern equatorial hemisphere. This roughly corresponds to 20% of all DES sources. Most of these stars belong to the stellar thick disk and halo of the Galaxy.

  11. The fluctuation theory of the stellar mass loss

    International Nuclear Information System (INIS)

    Andriesse, C.D.

    1981-01-01

    The idea that fluctuations in the mass flow are as significant as the very existence of the flow has led to the development of a fluctuation theory of the stellar mass loss. A general theory for fluctuations in non-equilibrium systems - and such are stellar atmospheres - was developed long ago. In developing the general theory to a specific stellar theory, however, the arguments have not come up in their logical order. The present sketch of this theory improves on that order and is offered as a framework for further study. (Auth.)

  12. Automated imaging of cellular spheroids with selective plane illumination microscopy on a chip (Conference Presentation)

    Science.gov (United States)

    Paiè, Petra; Bassi, Andrea; Bragheri, Francesca; Osellame, Roberto

    2017-02-01

    Selective plane illumination microscopy (SPIM) is an optical sectioning technique that allows imaging of biological samples at high spatio-temporal resolution. Standard SPIM devices require dedicated set-ups, complex sample preparation and accurate system alignment, thus limiting the automation of the technique, its accessibility and throughput. We present a millimeter-scaled optofluidic device that incorporates selective plane illumination and fully automatic sample delivery and scanning. To this end an integrated cylindrical lens and a three-dimensional fluidic network were fabricated by femtosecond laser micromachining into a single glass chip. This device can upgrade any standard fluorescence microscope to a SPIM system. We used SPIM on a CHIP to automatically scan biological samples under a conventional microscope, without the need of any motorized stage: tissue spheroids expressing fluorescent proteins were flowed in the microchannel at constant speed and their sections were acquired while passing through the light sheet. We demonstrate high-throughput imaging of the entire sample volume (with a rate of 30 samples/min), segmentation and quantification in thick (100-300 μm diameter) cellular spheroids. This optofluidic device gives access to SPIM analyses to non-expert end-users, opening the way to automatic and fast screening of a high number of samples at subcellular resolution.

  13. Enlarging the nosological spectrum of hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS).

    Science.gov (United States)

    Hoffmann, Sarah; Murrell, Jill; Harms, Lutz; Miller, Kelly; Meisel, Andreas; Brosch, Thomas; Scheel, Michael; Ghetti, Bernardino; Goebel, Hans-Hilmar; Stenzel, Werner

    2014-09-01

    Hereditary diffuse leukoencephalopathy with axonal spheroids (HDLS) is an autosomal dominant disease clinically characterized by cognitive decline, personality changes, motor impairment, parkinsonism and seizures. Recently, mutations in the colony-stimulating factor-1 receptor (CSF1R) gene have been shown to be associated with HDLS. We report clinical, neuropathological and molecular genetic findings of patients from a new family with a mutation in the CSF1R gene. Disease onset was earlier and disease progression was more rapid compared with previously reported patients. Psychiatric symptoms including personality changes, alcohol abuse and severe depression were the first symptoms in male patients. In the index, female patient, the initial symptom was cognitive decline. Magnetic resonance imaging (MRI) showed bilateral, confluent white matter lesions in the cerebrum. Stereotactic biopsy revealed loss of myelin and microglial activation as well as macrophage infiltration of the parenchyma. Numerous axonal swellings and spheroids were present. Ultrastructural analysis revealed pigment-containing macrophages. Axonal swellings were detected by electron microscopy not only in the central nervous system (CNS) but also in skin nerves. We identified a heterozygous mutation (c.2330G>A, p.R777Q) in the CSF1R gene. Through this report, we aim to enlarge the nosological spectrum of HDLS, providing new clinical descriptions as well as novel neuropathological findings from the peripheral nervous system. © 2014 International Society of Neuropathology.

  14. Dark matter annihilations search in dwarf spheroidal galaxies with fermi

    International Nuclear Information System (INIS)

    Farnier, C.; Nuss, E.; Cohen-Tanugi, J.

    2011-01-01

    Launched in June 2008, the Fermi Gamma-ray Telescope includes a pair conversion detector designed for the 20 MeV to ∼300GeV gamma-ray sky study, the Large Area Telescope (LAT). Operating in all-sky survey mode, its excellent sensitivity and angular resolution will allow either to discover or constrain a signal coming through the annihilation of dark matter particles. Predicted by cold dark matter scenarios as the largest clumps, dwarf spheroidal galaxies are amongst the most attractive targets for indirect search of dark matter by gamma-ray experiments. We present here an overview of the Fermi LAT Dark Matter and New Physics Working Group efforts in the searches of gamma-ray fluxes coming from WIMP pair annihilations in dwarf spheroidal galaxies.

  15. Magnetohydrodynamic stability of spheromak plasma in spheroidal flux conserver

    International Nuclear Information System (INIS)

    Kaneko, Shobu; Kamitani, Atsushi.

    1985-11-01

    The MHD equilibrium configurations of spheromak plasmas in a spheroidal flux conserver are determined by use of a pressure distribution whose derivative dp/dψ vanishes on the magnetic axis, and by use of an optimized distribution. Here p is the pressure and ψ is the flux function. These equilibria are shown to be stable for symmetric modes. The stability for localized modes is investigated by the Mercier criterion. The values of the maximum beta ratio β max are evaluated for both pressure distributions and are shown to become about two times larger by optimization. If the condition, q axis max are found to be less than 30 %. The oblate spheroidal flux conserver is shown to be better than the toroidal conserver with a rectangular cross section from the standpoint of stability. (author)

  16. A 2-D nucleation-growth model of spheroidal graphite

    International Nuclear Information System (INIS)

    Lacaze, Jacques; Bourdie, Jacques; Castro-Román, Manuel Jesus

    2017-01-01

    Analysis of recent experimental investigations, in particular by transmission electron microscopy, suggests spheroidal graphite grows by 2-D nucleation of new graphite layers at the outer surface of the nodules. These layers spread over the surface along the prismatic direction of graphite which is the energetically preferred growth direction of graphite when the apparent growth direction of the nodules is along the basal direction of graphite. 2-D nucleation-growth models first developed for precipitation of pure substances are then adapted to graphite growth from the liquid in spheroidal graphite cast irons. Lateral extension of the new graphite layers is controlled by carbon diffusion in the liquid. This allows describing quantitatively previous experimental results giving strong support to this approach.

  17. Shift of microRNA profile upon glioma cell migration using patient-derived spheroids and serum-free conditions

    DEFF Research Database (Denmark)

    Munthe, Sune; Halle, Bo; Boldt, Henning B

    2017-01-01

    Glioblastoma multiforme (GBM) is the most frequent malignant primary brain tumor. A major reason for the overall median survival being only 14.6 months is migrating tumor cells left behind after surgery. Another major reason is tumor cells having a so-called cancer stem cell phenotype being...... therefore resistant towards traditional chemo- and radiotherapy. A group of novel molecular targets are microRNAs (miRNAs). MiRNAs are small non-coding RNAs exerting post-transcriptional regulation of gene expression. The aim of this study was to identify differentially expressed miRNAs in migrating GBM...... cells using serum-free stem cell conditions. We used patient-derived GBM spheroid cultures for a novel serum-free migration assay. MiRNA expression of migrating tumor cells isolated at maximum migration speed was compared with corresponding spheroids using an OpenArray Real-Time PCR System. The mi...

  18. Astrophysically Satisfactory Solutions to Einstein's R-33 Gravitational Field Equations Exterior/Interior to Static Homogeneous Oblate Spheroidal Masses

    Directory of Open Access Journals (Sweden)

    Chifu E. N.

    2009-10-01

    Full Text Available In this article, we formulate solutions to Einstein's geometrical field equations derived using our new approach. Our field equations exterior and interior to the mass distribution have only one unknown function determined by the mass or pressure distribution. Our obtained solutions yield the unknown function as generalizations of Newton's gravitational scalar potential. Thus, our solution puts Einstein's geometrical theory of gravity on same footing with Newton's dynamical theory; with the dependence of the field on one and only one unknown function comparable to Newton's gravitational scalar potential. Our results in this article are of much significance as the Sun and planets in the solar system are known to be more precisely oblate spheroidal in geometry. The oblate spheroidal geometries of these bodies have effects on their gravitational fields and the motions of test particles and photons in these fields.

  19. Spheroidization of inorganic compounds by the LPPS method

    Czech Academy of Sciences Publication Activity Database

    Mastný, L.; Brožek, Vlastimil; Medřický, Jan; Marek, I.

    2017-01-01

    Roč. 13, č. 1 (2017), s. 162 ISSN 1336-7242. [Zjazd chemikov /69./. 11.09.2017-15.09.2017, Vysoké Tatry, Starý Smokovec] R&D Projects: GA ČR GA15-12145S Institutional support: RVO:61389021 Keywords : Water stabilized plasma * Liquid precursor plasma spraying * nanoparticles * spheroidization Subject RIV: BL - Plasma and Gas Discharge Physics OBOR OECD: Fluids and plasma physics (including surface physics)

  20. Method for Processing Liver Spheroids Using an Automatic Tissue Processor

    Science.gov (United States)

    2016-05-01

    alcohol dehydration and hot liquid wax infiltration. After the water in the tissue is replaced with wax and cooled, it then becomes possible to cut...effective for processing and preparing microscopy slides of liver spheroids. The general process involved formalin fixation, dehydration in a...DPBS);  formalin (37% neutral buffer formaldehyde);  series of alcohol solutions: 70, 80, 95, and 100% ethanol in water; 2  xylene

  1. A study on the spheroidization by palsma spraying

    International Nuclear Information System (INIS)

    Jung, In Ha; Ji, C. G.; Bae, S. O.; Yoon, J. H.; Kwon, H. I.

    2001-01-01

    Spheroidization of a powder in thermal plasma is a plausible method for powder morphology treatment. In this experiment, the spheroidization fraction was decreased with increasing the particle size. The higher fraction of H2 gas and higher probe position resulted in a higher spheroidization fraction. From this study, it follows that the good result could be attained from smaller size particle with higher hydrogen gas fraction and higher probe position. Through the statistical assessment, the results concluded that the effect of hydrogen gas content has more influence than particle size, and the probe position affects lower than the others. The interaction between the probe position and hydrogen gas fraction affects more than the other interactions. This alluded that the result largely depended on the particle size and hydrogen gas fraction, and there was an interaction between probe position and hydrogen gas fraction. Therefore, when altering the H2 gas fraction is considered, altering the probe position should also be considered. The fractions of each effect were roughly 25% by particle size, 9% by probe position and 35% by H2 gas fraction. At the results of X-ray diffraction patterns of the spheroidized particles, the large particle exhibited higher content of tetragonal phase, while smaller particle showed nearly cubic phase. This seemed to be the quenching rate; larger particle might have more time to phase separation upon cooling that smaller one. X-ray analysis results confirmed a relation between the particle size and tetragonal phase content, when the particles were sprayed at the same conditions. When particles were the same size but sprayed at different conditions, different content of tetragonal phase exhibited according to the experienced temperatures of particles. A particle wasting longer time for cooling to room temperature showed much tetragonal content which phase is stable at low temperatures

  2. A study on the spheroidization by palsma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Jung, In Ha; Ji, C. G.; Bae, S. O.; Yoon, J. H.; Kwon, H. I

    2001-01-01

    Spheroidization of a powder in thermal plasma is a plausible method for powder morphology treatment. In this experiment, the spheroidization fraction was decreased with increasing the particle size. The higher fraction of H2 gas and higher probe position resulted in a higher spheroidization fraction. From this study, it follows that the good result could be attained from smaller size particle with higher hydrogen gas fraction and higher probe position. Through the statistical assessment, the results concluded that the effect of hydrogen gas content has more influence than particle size, and the probe position affects lower than the others. The interaction between the probe position and hydrogen gas fraction affects more than the other interactions. This alluded that the result largely depended on the particle size and hydrogen gas fraction, and there was an interaction between probe position and hydrogen gas fraction. Therefore, when altering the H2 gas fraction is considered, altering the probe position should also be considered. The fractions of each effect were roughly 25% by particle size, 9% by probe position and 35% by H2 gas fraction. At the results of X-ray diffraction patterns of the spheroidized particles, the large particle exhibited higher content of tetragonal phase, while smaller particle showed nearly cubic phase. This seemed to be the quenching rate; larger particle might have more time to phase separation upon cooling that smaller one. X-ray analysis results confirmed a relation between the particle size and tetragonal phase content, when the particles were sprayed at the same conditions. When particles were the same size but sprayed at different conditions, different content of tetragonal phase exhibited according to the experienced temperatures of particles. A particle wasting longer time for cooling to room temperature showed much tetragonal content which phase is stable at low temperatures.

  3. Scaffold-free Prevascularized Microtissue Spheroids for Pulp Regeneration.

    Science.gov (United States)

    Dissanayaka, W L; Zhu, L; Hargreaves, K M; Jin, L; Zhang, C

    2014-12-01

    Creating an optimal microenvironment that mimics the extracellular matrix (ECM) of natural pulp and securing an adequate blood supply for the survival of cell transplants are major hurdles that need to be overcome in dental pulp regeneration. However, many currently available scaffolds fail to mimic essential functions of natural ECM. The present study investigated a novel approach involving the use of scaffold-free microtissue spheroids of dental pulp stem cells (DPSCs) prevascularized by human umbilical vein endothelial cells (HUVECs) in pulp regeneration. In vitro-fabricated microtissue spheroids were inserted into the canal space of tooth-root slices and were implanted subcutaneously into immunodeficient mice. Histological examination revealed that, after four-week implantation, tooth-root slices containing microtissue spheroids resulted in well-vascularized and cellular pulp-like tissues, compared with empty tooth-root slices, which were filled with only subcutaneous fat tissue. Immunohistochemical staining indicated that the tissue found in the tooth-root slices was of human origin, as characterized by the expression of human mitochondria, and contained odontoblast-like cells organized along the dentin, as assessed by immunostaining for nestin and dentin sialoprotein (DSP). Vascular structures formed by HUVECs in vitro were successfully anastomosed with the host vasculature upon transplantation in vivo, as shown by immunostaining for human CD31. Collectively, these findings demonstrate that prevascularized, scaffold-free, microtissue spheroids can successfully regenerate vascular dental pulp-like tissue and also highlight the significance of the microtissue microenvironment as an optimal environment for successful pulp-regeneration strategies. © International & American Associations for Dental Research.

  4. Inferring probabilistic stellar rotation periods using Gaussian processes

    Science.gov (United States)

    Angus, Ruth; Morton, Timothy; Aigrain, Suzanne; Foreman-Mackey, Daniel; Rajpaul, Vinesh

    2018-02-01

    Variability in the light curves of spotted, rotating stars is often non-sinusoidal and quasi-periodic - spots move on the stellar surface and have finite lifetimes, causing stellar flux variations to slowly shift in phase. A strictly periodic sinusoid therefore cannot accurately model a rotationally modulated stellar light curve. Physical models of stellar surfaces have many drawbacks preventing effective inference, such as highly degenerate or high-dimensional parameter spaces. In this work, we test an appropriate effective model: a Gaussian Process with a quasi-periodic covariance kernel function. This highly flexible model allows sampling of the posterior probability density function of the periodic parameter, marginalizing over the other kernel hyperparameters using a Markov Chain Monte Carlo approach. To test the effectiveness of this method, we infer rotation periods from 333 simulated stellar light curves, demonstrating that the Gaussian process method produces periods that are more accurate than both a sine-fitting periodogram and an autocorrelation function method. We also demonstrate that it works well on real data, by inferring rotation periods for 275 Kepler stars with previously measured periods. We provide a table of rotation periods for these and many more, altogether 1102 Kepler objects of interest, and their posterior probability density function samples. Because this method delivers posterior probability density functions, it will enable hierarchical studies involving stellar rotation, particularly those involving population modelling, such as inferring stellar ages, obliquities in exoplanet systems, or characterizing star-planet interactions. The code used to implement this method is available online.

  5. Reparative Spheroids in HPV-Associated Chronic Cervicitis

    Directory of Open Access Journals (Sweden)

    Gennadiy T. Sukhikh

    2013-09-01

    Full Text Available Background: Spheroid cell structures (SCS described in cell culture are used to study cell-cell and cell-matrix interactions. However, the role of the SCS in the repair process in vivo remains unexplored. The aim of the study was to examine the cellular composition of the spherical structures and their functional significance in the repair of the squamous epithelium in human papilloma virus-associated chronic cervicitis (HPV-CC. Methods and Results: The cytology and biopsy materials from 223 patients with HPV-CC were subjected to molecular testing for HPV DNA by Real-Time Polymerase Chain Reaction (Real-Time PCR with genotyping and chromogenic in situ hybridization (CISH, as well as immunocytological and immunohistochemical analyses of p16INK4A, Ki67, SMA, Vimentin, CD34, E-cadherin, Oct4, CD44, CKW markers. In the stem cell niche zone, these spheroid structures were discovered having proliferative activity and showing signs of producing stem cells involved in the repair of the cervical mucosa in HPV-CC. Conclusion: The persistence of the HPV in the stem cell niche zone cells in the cervix determines the chronization of inflammation in this area, with the ability to perform pathological repair. The immunophenotype of the spheroid cell structures in the HPV-CC includes cells with signs of stem cells (‘stemness’ and the mesenchymal-epithelial transition.

  6. Dipolar Excitation of a Perfectly Electrically Conducting Spheroid in a Lossless Medium at the Low-Frequency Regime

    Directory of Open Access Journals (Sweden)

    Panayiotis Vafeas

    2018-01-01

    Full Text Available The electromagnetic vector fields, which are scattered off a highly conductive spheroid that is embedded within an otherwise lossless medium, are investigated in this contribution. A time-harmonic magnetic dipolar source, located nearby and operating at low frequencies, serves as the excitation primary field, being arbitrarily orientated in the three-dimensional space. The main idea is to obtain an analytical solution of this scattering problem, using the appropriate system of spheroidal coordinates, such that a possibly fast numerical estimation of the scattered fields could be useful for real data inversion. To this end, incident and scattered as well as total fields are written in a rigorous low-frequency manner in terms of positive integral powers of the real-valued wave number of the exterior environment. Then, the Maxwell-type problem is converted to interconnected Laplace’s or Poisson’s equations, complemented by the perfectly conducting boundary conditions on the spheroidal object and the necessary radiation behavior at infinity. The static approximation and the three first dynamic contributors are sufficient for the present study, while terms of higher orders are neglected at the low-frequency regime. Henceforth, the 3D scattering boundary value problems are solved incrementally, whereas the determination of the unknown constant coefficients leads either to concrete expressions or to infinite linear algebraic systems, which can be readily solved by implementing standard cut-off techniques. The nonaxisymmetric scattered magnetic and electric fields follow and they are obtained in an analytical compact fashion via infinite series expansions in spheroidal eigenfunctions. In order to demonstrate the efficiency of our analytical approach, the results are degenerated so as to recover the spherical case, which validates this approach.

  7. Stellarator approach to toroidal plasma confinement

    International Nuclear Information System (INIS)

    Johnson, J.L.

    1981-12-01

    An overview is presented of the development and current status of the stellarator approach to controlled thermonuclear confinement. Recent experimental, theoretical, and systems developments have made this concept a viable option for the evolution of the toroidal confinement program. Some experimental study of specific problems associated with departure from two-dimensional symmetry must be undertaken before the full advantages and opportunities of steady-state, net-current-free operation can be realized

  8. AN EXAMINATION OF RECENT TRANSFORMATIONS TO THE BV(RI)C PHOTOMETRIC SYSTEM FROM THE PERSPECTIVE OF STELLAR MODELS FOR OLD STARS

    International Nuclear Information System (INIS)

    VandenBerg, Don A.; Casagrande, L.; Stetson, Peter B.

    2010-01-01

    Isochrones for ages ∼>4 Gyr and metallicities in the range -2.5∼ C photometric system for several open and globular star clusters. The adopted color-T eff relations include those which we have derived from the latest MARCS model atmospheres and the empirical transformations for dwarf and subgiant stars given by Casagrande et al. (CRMBA). Those reported by VandenBerg and Clem have also been considered, mainly to resolve some outstanding questions concerning them. Indeed, for the latter, V - I C colors should be corrected by ∼-0.02 mag, for all metal abundances, in order to obtain consistent interpretations of the observed (B - V, V), (V - R C , V), and (V - I C , V) diagrams for M 67 and the Hyades as well as for local subdwarfs. Remarkably, when the subdwarfs in the CRMBA data set that have σ π /π ≤ 0.15 are superimposed on a set of 12 Gyr isochrones spanning a wide range in [Fe/H], the inferred metallicities and effective temperatures agree, in the mean, with those given by CRMBA to within ±0.05 dex and ±10 K, respectively. Thus, the hot T eff scale derived by CRMBA is nearly identical with that predicted by stellar models; and consequently, there is excellent consistency between theory and observations on the Hertzsprung-Russell diagram and the different color-magnitude diagrams considered in this investigation. To obtain similar consistency, the colors obtained from the MARCS and VandenBerg and Clem (B - V)-T eff relations for metal-poor dwarf stars should be adjusted to the red by 0.02-0.03 mag. In general, isochrones that employ the CRMBA transformations provide reasonably consistent fits to our BV(RI) C photometry for main-sequence stars in the globular clusters 47 Tuc, M 3, M 5, M 92, and NGC 1851-but not the cluster giants (when adopting the synthetic MARCS colors). We speculate that differences between the actual heavy-element mixtures and those assumed in the theoretical models may be the primary cause of this difficulty.

  9. Stellar reaction rate for 22Mg+p→23Al from the asymptotic normalization coefficient in the mirror nuclear system 22Ne+n→23Ne

    International Nuclear Information System (INIS)

    Al-Abdullah, T.; Carstoiu, F.; Chen, X.; Clark, H. L.; Fu, C.; Gagliardi, C. A.; Lui, Y.-W.; Mukhamedzhanov, A.; Tabacaru, G.; Tokimoto, Y.; Trache, L.; Tribble, R. E.

    2010-01-01

    The production of 22 Na in ONe novae can be influenced by the 22 Mg(p,γ) 23 Al reaction. To investigate this reaction rate at stellar energies, we have determined the asymptotic normalization coefficient (ANC) for 22 Mg+p→ 23 Al through measurements of the ANCs in the mirror nuclear system 22 Ne+n→ 23 Ne. The peripheral neutron-transfer reactions 13 C( 12 C, 13 C) 12 C and 13 C( 22 Ne, 23 Ne) 12 C were studied. The identical entrance and exit channels of the first reaction make it possible to extract independently the ground-state ANC in 13 C. Our experiment gives C p 1/2 2 ( 13 C)=2.24±0.11 fm -1 , which agrees with the value obtained from several previous measurements. The weighted average for all the obtained C p 1/2 2 is 2.31±0.08 fm -1 . This value is adopted to be used in obtaining the ANCs in 23 Ne. The differential cross sections for the reaction 13 C( 22 Ne, 23 Ne) 12 C leading to the J π =5/2 + and 1/2 + states in 23 Ne have been measured at 12 MeV/u. Optical model parameters for use in the DWBA calculations were obtained from measurements of the elastic scatterings 22 Ne+ 13 C and 22 Ne+ 12 C. The extracted ANC for the ground state in 23 Ne, C d 5/2 2 =0.86±0.08±0.12 fm -1 , is converted to its corresponding value in 23 Al using mirror symmetry to give C d 5/2 2 ( 23 Al)=(4.63±0.77)x10 3 fm -1 . The astrophysical S factor S(0) for the 22 Mg(p,γ) reaction was determined to be 0.96±0.11 keV b. The consequences for nuclear astrophysics are discussed.

  10. Tumor penetration with intact MAb and fragments demonstrated in vitro on tumor spheroids and in vivo in the nude mouse model

    International Nuclear Information System (INIS)

    Buchegger, F.; Halpern, S.E.; Sutherland, R.M.; Schreyer, M.; Mach, J.P.

    1986-01-01

    Tumor spheroids grown in culture represent a good in vitro model for the study of tumor penetration phenomena of potential radiotherapeutics. Using this system, it was found that Fab-fragments penetrate tumors more quickly and deeply than complete antibodies. These results were confirmed in tumor bearing nephrectomized nude mice

  11. Formation mechanism of spheroidal carbide in ultra-low carbon ductile cast iron

    Directory of Open Access Journals (Sweden)

    Bin-guo Fu

    2016-09-01

    Full Text Available The formation mechanism of the spheroidal carbide in the ultra-low carbon ductile cast iron fabricated by the metal mold casting technique was systematically investigated. The results demonstrated that the spheroidal carbide belonged to eutectic carbide and crystallized in the isolated eutectic liquid phase area. The formation process of the spheroidal carbide was related to the contact and the intersection between the primary dendrite and the secondary dendrite of austenite. The oxides of magnesium, rare earths and other elements can act as heterogeneous nucleation sites for the spheroidal carbide. It was also found that the amount of the spheroidal carbide would increase with an increase in carbon content. The cooling rate has an important influence on the spheroidal carbide under the same chemical composition condition.

  12. Stellar extreme ultraviolet astronomy

    International Nuclear Information System (INIS)

    Cash, W.C. Jr.

    1978-01-01

    The design, calibration, and launch of a rocket-borne imaging telescope for extreme ultraviolet astronomy are described. The telescope, which employed diamond-turned grazing incidence optics and a ranicon detector, was launched November 19, 1976, from the White Sands Missile Range. The telescope performed well and returned data on several potential stellar sources of extreme ultraviolet radiation. Upper limits ten to twenty times more sensitive than previously available were obtained for the extreme ultraviolet flux from the white dwarf Sirius B. These limits fall a factor of seven below the flux predicted for the star and demonstrate that the temperature of Sirius B is not 32,000 K as previously measured, but is below 30,000 K. The new upper limits also rule out the photosphere of the white dwarf as the source of the recently reported soft x-rays from Sirius. Two other white dwarf stars, Feige 24 and G191-B2B, were observed. Upper limits on the flux at 300 A were interpreted as lower limits on the interstellar hydrogen column densities to these stars. The lower limits indicate interstellar hydrogen densitites of greater than .02 cm -3 . Four nearby stars (Sirius, Procyon, Capella, and Mirzam) were observed in a search for intense low temperature coronae or extended chromospheres. No extreme ultraviolet radiation from these stars was detected, and upper limits to their coronal emisson measures are derived

  13. Mapping stellar surface features

    International Nuclear Information System (INIS)

    Noah, P.V.

    1987-01-01

    New photometric and spectroscopic observations of the RS Canum Venaticorum binaries Sigma Geminorum and UX Arietis are reported along with details of the Doppler-imaging program SPOTPROF. The observations suggest that the starspot activity on Sigma Gem has decreased to 0.05 magnitude in two years. A photometric spot model for September 1984 to January 1985 found that a single spot covering 2% of the surface and 1000 K cooler than the surrounding photosphere could model the light variations. Equivalent-width observations contemporaneous with the photometric observations did not show any significant variations. Line-profile models from SPOTPROF predict that the variation of the equivalent width of the 6393 A Fe I line should be ∼ 1mA. Photometric observations of UX Ari from January 1984 to March 1985 show an 0.3 magnitude variation indicating a large spot group must cover the surface. Contemporaneous spectroscopic observations show asymmetric line profiles. The Doppler imaging and the photometric light-curve models were used in an iterative method to describe the stellar surface-spot distribution and successfully model both the photometric and the spectroscopic variations

  14. Stellar Presentations (Abstract)

    Science.gov (United States)

    Young, D.

    2015-12-01

    (Abstract only) The AAVSO is in the process of expanding its education, outreach and speakers bureau program. powerpoint presentations prepared for specific target audiences such as AAVSO members, educators, students, the general public, and Science Olympiad teams, coaches, event supervisors, and state directors will be available online for members to use. The presentations range from specific and general content relating to stellar evolution and variable stars to specific activities for a workshop environment. A presentation—even with a general topic—that works for high school students will not work for educators, Science Olympiad teams, or the general public. Each audience is unique and requires a different approach. The current environment necessitates presentations that are captivating for a younger generation that is embedded in a highly visual and sound-bite world of social media, twitter and U-Tube, and mobile devices. For educators, presentations and workshops for themselves and their students must support the Next Generation Science Standards (NGSS), the Common Core Content Standards, and the Science Technology, Engineering and Mathematics (STEM) initiative. Current best practices for developing relevant and engaging powerpoint presentations to deliver information to a variety of targeted audiences will be presented along with several examples.

  15. Turbulence optimisation in stellarator experiments

    Energy Technology Data Exchange (ETDEWEB)

    Proll, Josefine H.E. [Max-Planck/Princeton Center for Plasma Physics (Germany); Max-Planck-Institut fuer Plasmaphysik, Wendelsteinstr. 1, 17491 Greifswald (Germany); Faber, Benjamin J. [HSX Plasma Laboratory, University of Wisconsin-Madison, Madison, WI 53706 (United States); Helander, Per; Xanthopoulos, Pavlos [Max-Planck/Princeton Center for Plasma Physics (Germany); Lazerson, Samuel A.; Mynick, Harry E. [Plasma Physics Laboratory, Princeton University, P.O. Box 451 Princeton, New Jersey 08543-0451 (United States)

    2015-05-01

    Stellarators, the twisted siblings of the axisymmetric fusion experiments called tokamaks, have historically suffered from confining the heat of the plasma insufficiently compared with tokamaks and were therefore considered to be less promising candidates for a fusion reactor. This has changed, however, with the advent of stellarators in which the laminar transport is reduced to levels below that of tokamaks by shaping the magnetic field accordingly. As in tokamaks, the turbulent transport remains as the now dominant transport channel. Recent analytical theory suggests that the large configuration space of stellarators allows for an additional optimisation of the magnetic field to also reduce the turbulent transport. In this talk, the idea behind the turbulence optimisation is explained. We also present how an optimised equilibrium is obtained and how it might differ from the equilibrium field of an already existing device, and we compare experimental turbulence measurements in different configurations of the HSX stellarator in order to test the optimisation procedure.

  16. Optimizing Stellarators for Turbulent Transport

    International Nuclear Information System (INIS)

    Mynick, H.E.; Pomphrey, N.; Xanthopoulos, P.

    2010-01-01

    Up to now, the term 'transport-optimized' stellarators has meant optimized to minimize neoclassical transport, while the task of also mitigating turbulent transport, usually the dominant transport channel in such designs, has not been addressed, due to the complexity of plasma turbulence in stellarators. Here, we demonstrate that stellarators can also be designed to mitigate their turbulent transport, by making use of two powerful numerical tools not available until recently, namely gyrokinetic codes valid for 3D nonlinear simulations, and stellarator optimization codes. A first proof-of-principle configuration is obtained, reducing the level of ion temperature gradient turbulent transport from the NCSX baseline design by a factor of about 2.5.

  17. Stellar magnetic activity and exoplanets

    Directory of Open Access Journals (Sweden)

    Vidotto A.A.

    2017-01-01

    Full Text Available It has been proposed that magnetic activity could be enhanced due to interactions between close-in massive planets and their host stars. In this article, I present a brief overview of the connection between stellar magnetic activity and exoplanets. Stellar activity can be probed in chromospheric lines, coronal emission, surface spot coverage, etc. Since these are manifestations of stellar magnetism, these measurements are often used as proxies for the magnetic field of stars. Here, instead of focusing on the magnetic proxies, I overview some recent results of magnetic field measurements using spectropolarimetric observations. Firstly, I discuss the general trends found between large-scale magnetism, stellar rotation, and coronal emission and show that magnetism seems to be correlated to the internal structure of the star. Secondly, I overview some works that show evidence that exoplanets could (or not act as to enhance the activity of their host stars.

  18. Theory of a spheroidal probe in low-density continuum plasmas

    International Nuclear Information System (INIS)

    Kamitsuma, M.; Teii, S.

    1982-01-01

    A spheroidal probe theory for a low-density continuum plasma, i.e., one where the electron density is N/sub e/ 8 cm -3 and the gas pressure is P> or approx. =1 Torr has been developed using a spheroidal coordinate system in order to properly take into account the effect of the finite length of the probe. The numerical results of both the electron- and the ion-current characteristics are obtained for various values of R/sub p//lambda/sub D/ ranging from 0 to 1, epsilon = T/sub i//T/sub e/ from 0.1 to 1, and C/sub p/ = L/sub p//2R/sub p/ from 1 to 100, where lambda/sub D/ is the Debye length, R/sub p/ and L/sub p/ are the probe radius and the probe length, T/sub i/ and T/sub e/ are the ion and the electron temperature, respectively. Using these results, new methods to determine the electron temperature and the plasma space potential (consequently, the electron density) by practical measurements are also proposed and discussed

  19. Final phases of stellar evolution and the supernova phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Gallino, R [Torino, Universita, Turin, Italy; Masani, A [CNR, Laboratorio di Cosmo-geofisica, Turin, Italy

    1977-12-01

    Various theoretical aspects of the final stages of stellar evolution are reviewed in the framework of gravitational collapse and thermonuclear reactions (C-12 and O-16) in degenerate electron conditions. Attention is given to the evolution of supermassive stars, massive stars, and low-mass stars and to such topics as neutrino emission in intermediate-mass stars, white-dwarf supernovae, rotational instability, and stellar collisions and eclipsing binary systems.

  20. Superbanana orbits in stellarator geometries

    International Nuclear Information System (INIS)

    Derr, J.A.; Shohet, J.L.

    1979-04-01

    The presence of superbanana orbit types localized to either the interior or the exterior of stellarators and torsatrons is numerically investigated for 3.5 MeV alpha particles. The absence of the interior superbanana in both geometries is found to be due to non-conservation of the action. Exterior superbananas are found in the stellarator only, as a consequence of the existence of closed helical magnetic wells. No superbananas of either type are found in the torsatron

  1. On origin of stellar clusters

    International Nuclear Information System (INIS)

    Tovmasyan, G.M.

    1977-01-01

    The ratios of the gas component of the mass of young stellar clusters to their stellar mass are considered. They change by more than four orders from one cluster to another. The results are in direct contradiction with the hypothesis of formation of cluster stars from a preliminarily existing gas cloud by its condensation, and they favour the Ambartsumian hypothesis of the joint origin of stars and gas clouds from superdense protostellar matter

  2. Porous Nb-Ti based alloy produced from plasma spheroidized powder

    OpenAIRE

    Li, Qijun; Zhang, Lin; Wei, Dongbin; Ren, Shubin; Qu, Xuanhui

    2017-01-01

    Spherical Nb-Ti based alloy powder was prepared by the combination of plasma spheroidization and mechanical alloying. Phase constituents, microstructure and surface state of the powder, and pore characteristics of the resulting porous alloy were investigated. The results show that the undissolved W and V in the mechanically alloyed powder is fully alloyed after spheroidization, and single β phase is achieved. Particle size of the spheroidized powder is in the range of 20–110 μm. With the decr...

  3. Cell Spheroids with Enhanced Aggressiveness to Mimic Human Liver Cancer In Vitro and In Vivo.

    Science.gov (United States)

    Jung, Hong-Ryul; Kang, Hyun Mi; Ryu, Jea-Woon; Kim, Dae-Soo; Noh, Kyung Hee; Kim, Eun-Su; Lee, Ho-Joon; Chung, Kyung-Sook; Cho, Hyun-Soo; Kim, Nam-Soon; Im, Dong-Soo; Lim, Jung Hwa; Jung, Cho-Rok

    2017-09-05

    We fabricated a spheroid-forming unit (SFU) for efficient and economic production of cell spheroids. We optimized the protocol for generating large and homogenous liver cancer cell spheroids using Huh7 hepatocellular carcinoma (HCC) cells. The large Huh7 spheroids showed apoptotic and proliferative signals in the centre and at the surface, respectively. In particular, hypoxia-induced factor-1 alpha (HIF-1α) and ERK signal activation were detected in the cell spheroids. To diminish core necrosis and increase the oncogenic character, we co-cultured spheroids with 2% human umbilical vein endothelial cells (HUVECs). HUVECs promoted proliferation and gene expression of HCC-related genes and cancer stem cell markers in the Huh7 spheroidsby activating cytokine signalling, mimicking gene expression in liver cancer. HUVECs induced angiogenesis and vessel maturation in Huh7 spheroids in vivo by activating epithelial-mesenchymal transition and angiogenic pathways. The large Huh7 cell spheroids containing HUVECs survived at higher concentrations of anti-cancer drugs (doxorubicin and sorafenib) than did monolayer cells. Our large cell spheroid provides a useful in vitro HCC model to enable intuitive observation for anti-cancer drug testing.

  4. Measuring the light scattering and orientation of a spheroidal particle using in-line holography.

    Science.gov (United States)

    Seo, Kyung Won; Byeon, Hyeok Jun; Lee, Sang Joon

    2014-07-01

    The light scattering properties of a horizontally and vertically oriented spheroidal particle under laser illumination are experimentally investigated using digital in-line holography. The reconstructed wave field shows the bright singular points as a result of the condensed beam formed by a transparent spheroidal particle acting as a lens. The in-plane (θ) and out-of-plane (ϕ) rotating angles of an arbitrarily oriented spheroidal particle are measured by using these scattering properties. As a feasibility test, the 3D orientation of a transparent spheroidal particle suspended in a microscale pipe flow is successfully reconstructed by adapting the proposed method.

  5. Modular Stellarator Fusion Reactor (MSR) concept

    International Nuclear Information System (INIS)

    Miller, R.L.; Krakowski, R.A.

    1981-01-01

    A preliminary conceptual study has been made of the Modulator Stellarator Reactor (MSR) as a stedy-state, ignited, DT-fueled, magnetic fusion reactor. The MSR concept combines the physics of classic stellarator confinement with an innovative, modular-coil design. Parametric tradeoff calculations are described, leading to the selection of an interim design point for a 4.8-GWt plant based on Alcator transport scaling and an average beta value of 0.04 in an l = 2 system with a plasma aspect ratio of 11. Neither an economic analysis nor a detailed conceptual engineering design is presented here, as the primary intent of this scoping study is the elucidation of key physics tradeoffs, constraints, and uncertainties for the ultimate power-reactor embodiment

  6. STELLTRANS: A Transport Analysis Suite for Stellarators

    Science.gov (United States)

    Mittelstaedt, Joseph; Lazerson, Samuel; Pablant, Novimir; Weir, Gavin; W7-X Team

    2016-10-01

    The stellarator transport code STELLTRANS allows us to better analyze the power balance in W7-X. Although profiles of temperature and density are measured experimentally, geometrical factors are needed in conjunction with these measurements to properly analyze heat flux densities in stellarators. The STELLTRANS code interfaces with VMEC to find an equilibrium flux surface configuration and with TRAVIS to determine the RF heating and current drive in the plasma. Stationary transport equations are then considered which are solved using a boundary value differential equation solver. The equations and quantities considered are averaged over flux surfaces to reduce the system to an essentially one dimensional problem. We have applied this code to data from W-7X and were able to calculate the heat flux coefficients. We will also present extensions of the code to a predictive capacity which would utilize DKES to find neoclassical transport coefficients to update the temperature and density profiles.

  7. Energetic Particle Estimates for Stellar Flares

    Science.gov (United States)

    Youngblood, Allison; Chamberlin, Phil; Woods, Tom

    2018-01-01

    In the heliosphere, energetic particles are accelerated away from the Sun during solar flares and/or coronal mass ejections where they frequently impact the Earth and other solar system bodies. Solar (or stellar) energetic particles (SEPs) not only affect technological assets, but also influence mass loss and chemistry in planetary atmospheres (e.g., depletion of ozone). SEPs are increasingly recognized as an important factor in assessing exoplanet habitability, but we do not yet have constraints on SEP emission from any stars other than the Sun. Until indirect measurements are available, we must assume solar-like particle production and apply correlations between solar flares and SEPs detected near Earth to stellar flares. We present improved scaling relations between solar far-UV flare flux and >10 MeV proton flux near Earth. We apply these solar scaling relations to far-UV flares from exoplanet host stars and discuss the implications for modeling chemistry and mass loss in exoplanet atmospheres.

  8. Biomimicry 3D gastrointestinal spheroid platform for the assessment of toxicity and inflammatory effects of zinc oxide nanoparticles.

    Science.gov (United States)

    Chia, Sing Ling; Tay, Chor Yong; Setyawati, Magdiel I; Leong, David T

    2015-02-11

    Our current mechanistic understanding on the effects of engineered nanoparticles (NPs) on cellular physiology is derived mainly from 2D cell culture studies. However, conventional monolayer cell culture may not accurately model the mass transfer gradient that is expected in 3D tissue physiology and thus may lead to artifactual experimental conclusions. Herein, using a micropatterned agarose hydrogel platform, the effects of ZnO NPs (25 nm) on 3D colon cell spheroids of well-defined sizes are examined. The findings show that cell dimensionality plays a critical role in governing the spatiotemporal cellular outcomes like inflammatory response and cytotoxicity in response to ZnO NPs treatment. More importantly, ZnO NPs can induce different modes of cell death in 2D and 3D cell culture systems. Interestingly, the outer few layers of cells in 3D model could only protect the inner core of cells for a limited time and periodically slough off from the spheroids surface. These findings suggest that toxicological conclusions made from 2D cell models might overestimate the toxicity of ZnO NPs. This 3D cell spheroid model can serve as a reproducible platform to better reflect the actual cell response to NPs and to study a more realistic mechanism of nanoparticle-induced toxicity. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Evaluation of combination effects of 2-methoxyoestradiol and methoxyamine on IUdR-induced radiosensitization in glioma spheroids

    International Nuclear Information System (INIS)

    Neshasteh-Riz, A.; Babaloui, S.; Khoei, S.

    2010-01-01

    Glioblastoma is the most common and most malignant cancer of central nervous system. Targeted radiotherapy is an effective method toward its treatment. Iododeoxyuridine (IUdR) is a halogenated thymidine analogue known to be effective as a radiosensitizer in human cancer therapy. In this study we have evaluated the combination effects of 2-Methoxyoestradiol, an inhibitor of hypoxia inducible factor 1α (HIF-1α) and Methoxyamine, an inhibitor of base excision repair pathway on radiosensitization of Iododeoxyuridine in glioblastoma spheroid culture. Materials and Methods: The cytotoxic damages of DNA in U87MG cell line were compared using colony formation assay. Experiments were performed in large spheroids with a diameter of approximately 350μm. Results: Evaluation of the effects of Iododeoxyuridine with 2ME2 and MX pretreatment on spheroid cultured cell followed by ionizing irradiation showed more enhancemented (p≤0.001) Iododeoxyuridine induced-radiosensitization. These results introduced a key role for 2ME2 in Iododeoxyuridine related studies. Conclusion: Pretreatment of tumor cells with Iododeoxyuridine, MX and 2ME2 before Irradiation enhances tumor radiosensitization and may improve therapeutic index for Iododeoxyuridine and 2ME2.

  10. Direct Imaging of Stellar Surfaces: Results from the Stellar Imager (SI) Vision Mission Study

    Science.gov (United States)

    Carpenter, Kenneth; Schrijver, Carolus; Karovska, Margarita

    2006-01-01

    The Stellar Imager (SI) is a UV-Optical, Space-Based Interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and stellar interiors (via asteroseismology) and of the Universe in general. SI is identified as a "Flagship and Landmark Discovery Mission'' in the 2005 Sun Solar System Connection (SSSC) Roadmap and as a candidate for a "Pathways to Life Observatory'' in the Exploration of the Universe Division (EUD) Roadmap (May, 2005). The ultra-sharp images of the Stellar Imager will revolutionize our view of many dynamic astrophysical processes: The 0.1 mas resolution of this deep-space telescope will transform point sources into extended sources, and snapshots into evolving views. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives in support of the Living With a Star program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. In this paper we will discuss the results of the SI Vision Mission Study, elaborating on the science goals of the SI Mission and a mission architecture that could meet those goals.

  11. Plasma equilibrium and stability in stellarators

    International Nuclear Information System (INIS)

    Pustovitov, V.D.; Shafranov, V.D.

    1987-01-01

    A review of theoretical methods of investigating plasma equilibrium and stability in stellarators is given. Principles forming the basis of toroidal plasma equilibrium and its stabilization, and the main results of analytical theory and numerical calculations are presented. Configurations with spiral symmetry and usual stellarators with plane axis and spiral fields are considered in detail. Derivation of scalar two-dimensional equations, describing equilibrium in these systems is given. These equations were used to obtain one-dimensional equations for displacement and ellipticity of magnetic surfaces. The model of weak-elliptic displaced surfaces was used to consider the evolution of plasma equilibrium in stellarators after elevation of its pressure: change of profile of rotational transformation after change of plasma pressure, current generation during its fast heating and its successive damping due to finite plasma conductivity were described. The derivation of equations of small oscillations in the form, suitable for local disturbance investigation is presented. These equations were used to obtain Mercier criteria and ballon model equations. General sufficient conditions of plasma stability in systems with magnetic confinement were derived

  12. Space Weather: Linking Stellar Explosions to the Human Endeavor

    Science.gov (United States)

    Knipp, Delores

    2017-06-01

    Arguably humans have flourished as a result of stellar explosions; we are, after all, stardust. Nonetheless, rapid technology advances of the last 200 years sometimes put society and individuals on a collision course with the natural variability of stellar and solar atmospheres. Human space exploration, routine satellite navigation system applications, aviation safety, and electric power grids are examples of such vulnerable endeavors. In this presentation I will outline how global society relies on ‘normal’ solar and stellar emissions, yet becomes susceptible to extremes of these emissions. The imprints of these astronomical-terrestrial interactions abound. In particular, I will highlight ways in which stellar/solar bursts link with our space-atmosphere-interaction region, producing multi-year patterns in cosmic ray detection, gorgeous aurora, and deep concern for good order and function of global community.

  13. Constraining stellar physics from red-giant stars in binaries – stellar rotation, mixing processes and stellar activity

    Directory of Open Access Journals (Sweden)

    Beck P. G.

    2017-01-01

    Full Text Available The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to an improved understanding of stellar structure and evolution - in particular for solar-like oscillators in this context. Binary stars are fascinating objects. Because they were formed together, binary systems provide a set of two stars with very well constrained parameters. Those can be used to study properties and physical processes, such as the stellar rotation, dynamics and rotational mixing of elements and allows us to learn from the differences we find between the two components. In this work, we discussed a detailed study of the binary system KIC 9163796, discovered through Kepler photometry. The ground-based follow-up spectroscopy showed that this system is a double-lined spectroscopic binary, with a mass ratio close to unity. However, the fundamental parameters of the components of this system as well as their lithium abundances differ substantially. Kepler photometry of this system allows to perform a detailed seismic analysis as well as to derive the orbital period and the surface rotation rate of the primary component of the system. Indications of the seismic signature of the secondary are found. The differing parameters are best explained with both components located in the early and the late phase of the first dredge up at the bottom of the red-giant branch. Observed lithium abundances in both components are in good agreement with prediction of stellar models including rotational mixing. By combining observations and theory, a comprehensive picture of the system can be drawn.

  14. Partial discharges in ellipsoidal and spheroidal voids

    DEFF Research Database (Denmark)

    Crichton, George C; Karlsson, P. W.; Pedersen, Aage

    1989-01-01

    Transients associated with partial discharges in voids can be described in terms of the charges induced on the terminal electrodes of the system. The relationship between the induced charge and the properties which are usually measured is discussed. The method is illustrated by applying it to a s......Transients associated with partial discharges in voids can be described in terms of the charges induced on the terminal electrodes of the system. The relationship between the induced charge and the properties which are usually measured is discussed. The method is illustrated by applying...

  15. Stellar X-Ray Polarimetry

    Science.gov (United States)

    Swank, J.

    2011-01-01

    Most of the stellar end-state black holes, pulsars, and white dwarfs that are X-ray sources should have polarized X-ray fluxes. The degree will depend on the relative contributions of the unresolved structures. Fluxes from accretion disks and accretion disk corona may be polarized by scattering. Beams and jets may have contributions of polarized emission in strong magnetic fields. The Gravity and Extreme Magnetism Small Explorer (GEMS) will study the effects on polarization of strong gravity of black holes and strong magnetism of neutron stars. Some part of the flux from compact stars accreting from companion stars has been reflected from the companion, its wind, or accretion streams. Polarization of this component is a potential tool for studying the structure of the gas in these binary systems. Polarization due to scattering can also be present in X-ray emission from white dwarf binaries and binary normal stars such as RS CVn stars and colliding wind sources like Eta Car. Normal late type stars may have polarized flux from coronal flares. But X-ray polarization sensitivity is not at the level needed for single early type stars.

  16. Old stellar populations how to study the fossil record of galaxy formation

    CERN Document Server

    Cassisi, Santi

    2013-01-01

    The book discusses the theoretical path to decoding the information gathered from observations of old stellar systems. It focuses on old stellar systems because these are the fossil record of galaxy formation and provide invaluable information ont he evolution of cosmic structures and the universe as a whole. The aim is to present results obtained in the past few years for theoretical developments in low mass star research and in advances in our knowledge of the evolution of old stellar systems. A particularly representative case is the recent discovery of multiple stellar populations in galac

  17. The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity

    International Nuclear Information System (INIS)

    Christensen-Dalsgaard, Joergen; Carpenter, Kenneth G; Schrijver, Carolus J; Karovska, Margarita

    2011-01-01

    The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. SI is a 'Landmark/Discovery Mission' in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ('NASA Space Science Vision Missions' (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.

  18. The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity

    Energy Technology Data Exchange (ETDEWEB)

    Christensen-Dalsgaard, Joergen [Department of Physics and Astronomy, Aarhus University (Denmark); Carpenter, Kenneth G [Code 667 NASA-GSFC, Greenbelt, MD 20771 (United States); Schrijver, Carolus J [LMATC 3251 Hanover St., Bldg. 252, Palo Alto, CA 94304 (United States); Karovska, Margarita, E-mail: jcd@phys.au.d, E-mail: Kenneth.G.Carpenter@nasa.gov, E-mail: schryver@lmsal.com, E-mail: karovska@head.cfa.harvard.edu [60 Garden St., Cambridge, MA 02138 (United States)

    2011-01-01

    The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. SI is a 'Landmark/Discovery Mission' in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ('NASA Space Science Vision Missions' (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.

  19. The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity

    Science.gov (United States)

    Christensen-Dalsgaard, Jørgen; Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita; Si Team

    2011-01-01

    The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in the Universe. SI is a "Landmark/Discovery Mission" in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ("NASA Space Science Vision Missions" (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.

  20. The Stellar Imager (SI) - A Mission to Resolve Stellar Surfaces, Interiors, and Magnetic Activity

    Science.gov (United States)

    Christensen-Dalsgaard, Jorgen; Carpenter, Kenneth G.; Schrijver, Carolus J.; Karovska, Margarita

    2012-01-01

    The Stellar Imager (SI) is a space-based, UV/Optical Interferometer (UVOI) designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and of the Universe in general. It will also probe via asteroseismology flows and structures in stellar interiors. SI will enable the development and testing of a predictive dynamo model for the Sun, by observing patterns of surface activity and imaging of the structure and differential rotation of stellar interiors in a population study of Sun-like stars to determine the dependence of dynamo action on mass, internal structure and flows, and time. SI's science focuses on the role of magnetism in the Universe and will revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magnetohydrodynamically controlled processes in the Universe. SI is a "LandmarklDiscovery Mission" in the 2005 Heliophysics Roadmap, an implementation of the UVOI in the 2006 Astrophysics Strategic Plan, and a NASA Vision Mission ("NASA Space Science Vision Missions" (2008), ed. M. Allen). We present here the science goals of the SI Mission, a mission architecture that could meet those goals, and the technology development needed to enable this mission

  1. IN VITRO INVESTIGATION OF THE TRANSPLANTATION PROSPECTS OF MULTICELLULAR SPHEROID MICROAGGREGATES OF DONOR RETINAL PIGMENT EPITHELIUM

    Directory of Open Access Journals (Sweden)

    S. A. Borzenok

    2015-01-01

    Full Text Available Aim. To study in experiment the criteria for transplantability of multicellular spheroid microaggregates of retinal pigment epithelium (RPE, prepared by the method of 3D cell culture. Materials and Methods. 11 donor eyes (6 of adrenaline index «A», 5 of index «B» were used as a source of RPE cell cultures (group «A» – 6 cultures, group «B» – 5 cultures, of which over 2000 RPE spheroids were obtained by the method of three-dimensional cell culture. 1760 spheroids of them were selected for transplantability investigation (960 – group «A», 800 – group «B». Among the selected spheroids were equal numbers of spheroids of different morphology («smooth» and «rough» and of the initial cell seeding number (500, 1000, 5000, 25 000, 125 000 cells per hanging drop. We were taking out 12 spheroids of group «A» and 10 spheroids of group «B» of the 3D culture in terms of 7, 14, 21, 28 days of 3D culture to assess their viability. We were transferring the same number of spheroids in the same terms from 3D to 2D culture conditions to assess their adhesive properties. Viability of cells within spheroids was determined using the Trypan blue exclusion. The presence or absence of adhesion was determined by microscopic observation.Results. «Smooth» spheroids of 7 and 14 days of pretransplantation cultivation and derived from hanging drops containing 500 and 1000 cells showed the highest transplantability (cell viability varied from 0.83 ± 0.38 to 0.94 ± 0.24, a 100% adhesion. «Rough» spheroids were untransplantable in all variants, despite their partial preservation of viability (in comparison to “smooth” ones p < 0.05. 21 and 28 days of pretransplantation culturing and high cell seeding numbers signifi cantly lowered transplantability of obtained spheroids (p > 0.05 for low cell numbers, p < 0.05 for the high ones. Differences in adrenaline indexes A and B of donor eyes which were the primary sources of cellular

  2. Optimal formation of genetically modified and functional pancreatic islet spheroids by using hanging-drop strategy.

    Science.gov (United States)

    Kim, H J; Alam, Z; Hwang, J W; Hwang, Y H; Kim, M J; Yoon, S; Byun, Y; Lee, D Y

    2013-03-01

    Rejection and hypoxia are important factors causing islet loss at an early stage after pancreatic islet transplantation. Recently, islets have been dissociated into single cells for reaggregation into so-called islet spheroids. Herein, we used a hanging-drop strategy to form islet spheroids to achieve functional equivalence to intact islets. To obtain single islet cells, we dissociated islets with trypsin-EDTA digestion for 10 minutes. To obtain spheroids, we dropped various numbers of single cells (125, 250, or 500 cells/30 μL drop) onto a Petri dish, that was inverted for incubation in humidified air containing 5% CO(2) at 37 °C for 7 days. The aggregated spheroids in the droplets were harvested for further culture. The size of the aggregated islet spheroids depended on the number of single cells (125-500 cells/30 μL droplet). Their morphology was similar to that of intact islets without any cellular damage. When treated with various concentrations of glucose to evaluate responsiveness, their glucose-mediated stimulation index value was similar to that of intact islets, an observation that was attributed to strong cell-to-cell interactions in islet spheroids. However, islet spheroids aggregated in general culture dishes showed abnormal glucose responsiveness owing to weak cell-to-cell interactions. Cell-to-cell interactions in islet spheroids were confirmed with an anti-connexin-36 monoclonal antibody. Finally, nonviral poly(ethylene imine)-mediated interleukin-10 cytokine gene delivered beforehand into dissociated single cells before formation of islet spheroids increased the gene transfection efficacy and interleukin-10 secretion from islet spheroids >4-fold compared with intact islets. These results demonstrated the potential application of genetically modified, functional islet spheroids with of controlled size and morphology using an hanging-drop technique. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. In vitro characterization of self-assembled anterior cruciate ligament cell spheroids for ligament tissue engineering.

    Science.gov (United States)

    Hoyer, M; Meier, C; Breier, A; Hahner, J; Heinrich, G; Drechsel, N; Meyer, M; Rentsch, C; Garbe, L-A; Ertel, W; Lohan, A; Schulze-Tanzil, G

    2015-03-01

    Tissue engineering of an anterior cruciate ligament (ACL) implant with functional enthesis requires site-directed seeding of different cell types on the same scaffold. Therefore, we studied the suitability of self-assembled three-dimensional spheroids generated by lapine ACL ligament fibroblasts for directed scaffold colonization. The spheroids were characterized in vitro during 14 days in static and 7 days in dynamic culture. Size maintenance of self-assembled spheroids, the vitality, the morphology and the expression pattern of the cells were monitored. Additionally, we analyzed the total sulfated glycosaminoglycan, collagen contents and the expression of the ligament components type I collagen, decorin and tenascin C on protein and for COL1A1, DCN and TNMD on gene level in the spheroids. Subsequently, the cell colonization of polylactide-co-caprolactone [P(LA-CL)] and polydioxanone (PDS) polymer scaffolds was assessed in response to a directed, spheroid-based seeding technique. ACL cells were able to self-assemble spheroids and survive over 14 days. The spheroids decreased in size but not in cellularity depending on the culture time and maintained or even increased their differentiation state. The area of P[LA-CL] scaffolds, colonized after 14 days by the cells of one spheroid, was in average 4.57 ± 2.3 mm(2). Scaffolds consisting of the polymer P[LA-CL] were more suitable for colonization by spheroids than PDS embroideries. We conclude that ACL cell spheroids are suitable as site-directed seeding strategy for scaffolds in ACL tissue engineering approaches and recommend the use of freshly assembled spheroids for scaffold colonization, due to their balanced proliferation and differentiation.

  4. Generating Chondromimetic Mesenchymal Stem Cell Spheroids by Regulating Media Composition and Surface Coating.

    Science.gov (United States)

    Sridharan, BanuPriya; Laflin, Amy D; Detamore, Michael S

    2018-04-01

    Spheroids of mesenchymal stem cells (MSCs) in cartilage tissue engineering have been shown to enhance regenerative potential owing to their 3D structure. In this study, we explored the possibility of priming spheroids under different media to replace the use of inductive surface coatings for chondrogenic differentiation. Rat bone marrow-derived MSCs were organized into cell spheroids by the hanging drop technique and subsequently cultured on hyaluronic acid (HA) coated or non-coated well plates under different cell media conditions. Endpoint analysis included cell viability, DNA and Glycosaminoglycan (GAG) and collagen content, gene expression and immunohistochemistry. For chondrogenic applications, MSC spheroids derived on non-coated surfaces outperformed the spheroids derived from HA-coated surfaces in matrix synthesis and collagen II gene expression. Spheroids on non-coated surfaces gave rise to the highest collagen and GAG when primed with medium containing insulin-like growth factor (IGF) for 1 week during spheroid formation. Spheroids that were grown in chondroinductive raw material-inclusive media such as aggrecan or chondroitin sulfate exhibited the highest Collagen II gene expression in the non-coated surface at 1 week. Media priming by growth factors and raw materials might be a more predictive influencer of chondrogenesis compared to inductive-surfaces. Such tailored bioactivity of the stem cell spheroids in the stage of the spheroid formation may give rise to a platform technology that may eventually produce spheroids capable of chondrogenesis achieved by mere media manipulation, skipping the need for additional culture on a modified surface, that paves the way for cost-effective technologies.

  5. WEAK GALACTIC HALO-DWARF SPHEROIDAL CONNECTION FROM RR LYRAE STARS

    Energy Technology Data Exchange (ETDEWEB)

    Fiorentino, Giuliana [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bono, Giuseppe [Dipartimento di Fisica, Universitá di Roma Tor Vergata, Via della Ricerca Scientifica 1, I-00133 Roma (Italy); Monelli, Matteo; Gallart, Carme; Martínez-Vásquez, Clara E. [Instituto de Astrofísica de Canarias, Calle Via Lactea s/n, E-38205 La Laguna, Tenerife (Spain); Stetson, Peter B. [National Research Council, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Tolstoy, Eline [Kapteyn Astronomical Institute, University of Groningen, Postbus 800, 9700 AV Groningen (Netherlands); Salaris, Maurizio [Astrophysics Research Institute, Liverpool John Moores University IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L35RF (United Kingdom); Bernard, Edouard J., E-mail: giuliana.fiorentino@oabo.inaf.it [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom)

    2015-01-01

    We discuss the role that dwarf galaxies may have played in the formation of the Galactic halo (Halo) using RR Lyrae stars (RRL) as tracers of their ancient stellar component. The comparison is performed using two observables (periods, luminosity amplitudes) that are reddening and distance independent. Fundamental mode RRL in 6 dwarf spheroidals (dSphs) and 11 ultra faint dwarf galaxies (∼1300) show a Gaussian period distribution well peaked around a mean period of (Pab) = 0.610 ± 0.001 days (σ = 0.03). The Halo RRL (∼15,000) are characterized by a broader period distribution. The fundamental mode RRL in all the dSphs apart from Sagittarius are completely lacking in High Amplitude Short Period (HASP) variables, defined as those having P ≲ 0.48 days and A{sub V} ≥ 0.75 mag. Such variables are not uncommon in the Halo and among the globular clusters and massive dwarf irregulars. To further interpret this evidence, we considered 18 globulars covering a broad range in metallicity (–2.3 ≲ [Fe/H] ≲ –1.1) and hosting more than 35 RRL each. The metallicity turns out to be the main parameter, since only globulars more metal-rich than [Fe/H] ∼ –1.5 host RRL in the HASP region. This finding suggests that dSphs similar to the surviving ones do not appear to be the major building-blocks of the Halo. Leading physical arguments suggest an extreme upper limit of ∼50% to their contribution. On the other hand, massive dwarfs hosting an old population with a broad metallicity distribution (Large Magellanic Cloud, Sagittarius) may have played a primary role in the formation of the Halo.

  6. Foreground effect on the J-factor estimation of ultra-faint dwarf spheroidal galaxies

    Science.gov (United States)

    Ichikawa, Koji; Horigome, Shun-ichi; Ishigaki, Miho N.; Matsumoto, Shigeki; Ibe, Masahiro; Sugai, Hajime; Hayashi, Kohei

    2018-05-01

    Dwarf spheroidal galaxies (dSphs) are promising targets for the gamma-ray dark matter (DM) search. In particular, DM annihilation signal is expected to be strong in some of the recently discovered nearby ultra-faint dSphs, which potentially give stringent constraints on the O(1) TeV WIMP DM. However, various non-negligible systematic uncertainties complicate the estimation of the astrophysical factors relevant for the DM search in these objects. Among them, the effects of foreground stars particularly attract attention because the contamination is unavoidable even for the future kinematical survey. In this article, we assess the effects of the foreground contamination on the astrophysical J-factor estimation by generating mock samples of stars in the four ultra-faint dSphs and using a model of future spectrographs. We investigate various data cuts to optimize the quality of the data and apply a likelihood analysis which takes member and foreground stellar distributions into account. We show that the foreground star contaminations in the signal region (the region of interest) and their statistical uncertainty can be estimated by interpolating the foreground star distribution in the control region where the foreground stars dominate the member stars. Such regions can be secured at future spectroscopic observations utilizing a multiple object spectrograph with a large field of view; e.g. the Prime Focus Spectrograph mounted on Subaru Telescope. The above estimation has several advantages: The data-driven estimation of the contamination makes the analysis of the astrophysical factor stable against the complicated foreground distribution. Besides, foreground contamination effect is considered in the likelihood analysis.

  7. Engineering aspects of compact stellarators

    International Nuclear Information System (INIS)

    Nelson, B.E.; Benson, R.D.; Brooks, A.

    2003-01-01

    Compact stellarators could combine the good confinement and high beta of a tokamak with the inherently steady state, disruption-free characteristics of a stellarator. Two U.S. compact stellarator facilities are now in the conceptual design phase: the National Compact Stellarator Experiment (NCSX) and the Quasi- Poloidal Stellarator (QPS). NCSX has a major radius of 1.4 m and a toroidal field up to 2 T. The primary feature of both NCSX and QPS is the set of modular coils that provide the basic magnetic configuration. These coils represent a major engineering challenge due to the complex shape, precise geometric accuracy, and high current density of the windings. The winding geometry is too complex for conventional hollow copper conductor construction. Instead, the modular coils will be wound with flexible, multi strand cable conductor that has been compacted to a 75% copper packing fraction. Inside the NCSX coil set and surrounding the plasma is a highly contoured vacuum vessel. The vessel consists of three identical, 120 deg. segments that are bolted together at double sealed joints. The QPS device has a major radius of 0.9 m, a toroidal field of 1 T, and an aspect ratio of only 2.7. Instead of an internal vacuum vessel, the QPS modular coils will operate in an external vacuum tank. (author)

  8. Formation and field-driven dynamics of nematic spheroids.

    Science.gov (United States)

    Fu, Fred; Abukhdeir, Nasser Mohieddin

    2017-07-19

    Unlike the canonical application of liquid crystals (LCs), LC displays, emerging technologies based on LC materials are increasingly leveraging the presence of nanoscale defects. The inherent nanoscale characteristics of LC defects present both significant opportunities as well as barriers for the application of this fascinating class of materials. Simulation-based approaches to the study of the effects of confinement and interface anchoring conditions on LC domains has resulted in significant progress over the past decade, where simulations are now able to access experimentally-relevant length scales while simultaneously capturing nanoscale defect structures. In this work, continuum simulations were performed in order to study the dynamics of micron-scale nematic LC spheroids of varying shape. Nematic spheroids are one of the simplest inherently defect-containing LC structures and are relevant to polymer-dispersed LC-based "smart" window technology. Simulation results include nematic phase formation and external field-switching dynamics of nematic spheroids ranging in shape from oblate to prolate. Results include both qualitative and quantitative insight into the complex coupling of nanoscale defect dynamics and structure transitions to micron-scale reorientation. Dynamic mechanisms are presented and related to structural transitions in LC defects present in the nematic domain. Domain-averaged metrics including order parameters and response times are determined for a range of experimentally-accessible electric field strengths. These results have both fundamental and technological relevance, in that increased understanding of LC dynamics in the presence of defects is a key barrier to continued advancement in the field.

  9. PREDICTION OF THE EXTREMAL SHAPE FACTOR OF SPHEROIDAL PARTICLES

    Directory of Open Access Journals (Sweden)

    Daniel Hlubinka

    2011-05-01

    Full Text Available In the stereological unfolding problem for spheroidal particles the extremal shape factor is predicted. The theory of extreme values has been used to show that extremes of the planar shape factor of particle sections tend to the same limit distribution as extremes of the original shape factor for both the conditional and marginal distribution. Attention is then paid to the extreme shape factor conditioned by the particle size. Normalizing constants are evaluated for a parametric model and the numerical procedure is tested on real data from metallography.

  10. Modes of spheroidal ion plasmas at the Brillouin limit

    International Nuclear Information System (INIS)

    Tinkle, M. D.; Greaves, R. G.; Surko, C. M.

    1995-01-01

    Brillouin-density pure ion plasmas have been generated in a quadrupole Penning tray by electron-beam ionization of a low-pressure gas. Large, spheroidal, steady-state plasmas are produced that extend to one of the trap electrodes. With the density fixed at the Brillouin limit by the high ion production rate, the electrode potentials determine the plasma shape. The frequencies of azimuthally propagating cyclotron and diocotron modes are found to vary significantly with the plasma aspect ratio. For oblate plasmas, we are able to test theoretical predictions of a simple fluid model, and the frequencies are in good agreement

  11. Seamless Combination of Fluorescence-Activated Cell Sorting and Hanging-Drop Networks for Individual Handling and Culturing of Stem Cells and Microtissue Spheroids.

    Science.gov (United States)

    Birchler, Axel; Berger, Mischa; Jäggin, Verena; Lopes, Telma; Etzrodt, Martin; Misun, Patrick Mark; Pena-Francesch, Maria; Schroeder, Timm; Hierlemann, Andreas; Frey, Olivier

    2016-01-19

    Open microfluidic cell culturing devices offer new possibilities to simplify loading, culturing, and harvesting of individual cells or microtissues due to the fact that liquids and cells/microtissues are directly accessible. We present a complete workflow for microfluidic handling and culturing of individual cells and microtissue spheroids, which is based on the hanging-drop network concept: The open microfluidic devices are seamlessly combined with fluorescence-activated cell sorting (FACS), so that individual cells, including stem cells, can be directly sorted into specified culturing compartments in a fully automated way and at high accuracy. Moreover, already assembled microtissue spheroids can be loaded into the microfluidic structures by using a conventional pipet. Cell and microtissue culturing is then performed in hanging drops under controlled perfusion. On-chip drop size control measures were applied to stabilize the system. Cells and microtissue spheroids can be retrieved from the chip by using a parallelized transfer method. The presented methodology holds great promise for combinatorial screening of stem-cell and multicellular-spheroid cultures.

  12. Preliminary characterisation of an in vitro paradigm for the study of the delayed effects of organophosphorus compounds: hen embryo brain spheroids

    International Nuclear Information System (INIS)

    Sales, K.M.; Kingston, S.T.; Doyle, K.M.; Purcell, W.M.

    2004-01-01

    Organophosphate induced delayed neuropathy (OPIDN) has been studied extensively but the mechanisms of toxicity remain unclear. It is generally accepted that the inhibition and ageing (dealkylation) of the B-esterase neuropathy target esterase (NTE) is integral to axonal loss. At present, the only way of detecting compounds that induce OPIDN is the hen test, an animal model. In this study, we preliminary validated hen embryo brain spheroids (HEBS) for the study of organophosphate (OP) toxicity. Hen brain spheroids have been characterised previously, although they have never been fully optimised for OP testing. We optimised the levels of acetylcholine esterase (AChE) and neuropathy target esterase by adapting the culture technique and using chemically defined media. Spheroid cultures were maintained for 35 days and viability and enzyme levels were monitored over this time. Levels of AChE and NTE in this system remained stable over the 35 day period. Using transmission electron microscopy, we have shown synaptogenisis within HEBS earlier than previously suggested in spheroid culture. These studies indicate that HEBS may be useful for the study of OP-induced toxicity and that the long-term stability of the cultures makes it an ideal candidate for studying OPIDN

  13. Effects of combinations of chemotherapy and radiation on the emergence of drug resistant cells in 9L rat brain tumor spheroids

    International Nuclear Information System (INIS)

    Tofilon, P.J.; Arundel, C.; Vines, C.M.

    1987-01-01

    Repeated administration of antineoplastic chemotherapeutic agents is generally considered to induce and/or select for drug resistant cells. The authors recently begun to investigate whether chemotherapy interdigitated with radiation can minimize or eliminate the emergence of drug resiistent cells in 9L rat brain tumor spheroids grown from defined mixtures of cells sensitive (9L) and resistant (R/sub 3/) to BCNU. In this experimental system, the sister chromatid exchange (SCE) assay is used to quantitate the proportions of sensitive and resistant cells within the spheroids. While 9L and R/sub 3/ cell have different sensitivities to BCNU, they are equally sensitive to radiation. Mixed-cell spheroids consisting of 1% R/sub 3/ cells were treated with three doses of BCNU (10 μM) every 72 hr resulting in a shift in the 9L to R/sub 3/ ratio to greater than 50% R/sub 3/ cells. The combined protocols to be investigated will involve γ rays administered either 36 hr before or after each BCNU treatment. By initiating these combined protocols on spheroids of different sizes, the effectiveness of each protocol is evaluated with respect to the number of resistant cells present

  14. Design, construction and validation of the UST-1 modular stellarator

    Energy Technology Data Exchange (ETDEWEB)

    Queral, V., E-mail: vicentemanuel.queral@ciemat.es

    2016-11-15

    Highlights: • A small and simple low cost two period modular stellarator is reviewed. • It is defined as a monolithic circular surface torus with carved grooves. • The grooves are accurately mechanised by a new toroidal milling machine. • A very simple e-beam field mapping system has been built and utilized. - Abstract: Stellarator advancement is hindered, among others, by the requirement of geometric complexity at high accuracy and the still scarce universities and research centres following the stellarator line. In this framework, the objectives of the small UST-1 stellarator development were to: (i) explore and test the performance of one possible accurate construction method for stellarators (ii) encourage universities and small fusion research centres to build simple and economical stellarators (iii) educative purpose. Therefore, UST-1 was properly designed to be easily built by a milling machine working on toroidal coordinates, being the winding surface circular poloidally and toroidally. The coil frame is a sole monolithic toroidal thick surface equipped with grooves mechanised by the toroidal milling machine. Only one double pancake is wound in each groove so as to compress the conductor on the laterals of the groove in order to speed up and simplify the winding process. The physics design, the conceptual engineering design and the construction process of UST-1 is presented. The toroidal milling machine is described. The e-beam field line mapping experiments carried out to validate the resulting magnetic configuration are reported. The developed construction method has been proved for the small UST-1 stellarator. Small stellarators are valuable for quick tests of diagnostics, educative purposes, assessment of new confinement concepts, turbulence studies and other applications.

  15. Design, construction and validation of the UST-1 modular stellarator

    International Nuclear Information System (INIS)

    Queral, V.

    2016-01-01

    Highlights: • A small and simple low cost two period modular stellarator is reviewed. • It is defined as a monolithic circular surface torus with carved grooves. • The grooves are accurately mechanised by a new toroidal milling machine. • A very simple e-beam field mapping system has been built and utilized. - Abstract: Stellarator advancement is hindered, among others, by the requirement of geometric complexity at high accuracy and the still scarce universities and research centres following the stellarator line. In this framework, the objectives of the small UST-1 stellarator development were to: (i) explore and test the performance of one possible accurate construction method for stellarators (ii) encourage universities and small fusion research centres to build simple and economical stellarators (iii) educative purpose. Therefore, UST-1 was properly designed to be easily built by a milling machine working on toroidal coordinates, being the winding surface circular poloidally and toroidally. The coil frame is a sole monolithic toroidal thick surface equipped with grooves mechanised by the toroidal milling machine. Only one double pancake is wound in each groove so as to compress the conductor on the laterals of the groove in order to speed up and simplify the winding process. The physics design, the conceptual engineering design and the construction process of UST-1 is presented. The toroidal milling machine is described. The e-beam field line mapping experiments carried out to validate the resulting magnetic configuration are reported. The developed construction method has been proved for the small UST-1 stellarator. Small stellarators are valuable for quick tests of diagnostics, educative purposes, assessment of new confinement concepts, turbulence studies and other applications.

  16. The Prospect for Detecting Stellar Coronal Mass Ejections

    Science.gov (United States)

    Osten, Rachel A.; Crosley, Michael Kevin

    2018-06-01

    The astrophysical study of mass loss, both steady-state and transient, on the cool half of the HR diagram has implications bothfor the star itself and the conditions created around the star that can be hospitable or inimical to supporting life. Recent results from exoplanet studies show that planets around M dwarfs are exceedingly common, which together with the commonality of M dwarfs in our galaxy make this the dominant mode of star and planet configurations. The closeness of the exoplanets to the parent M star motivate a comprehensive understanding of habitability for these systems. Radio observations provide the most clear signature of accelerated particles and shocks in stars arising as the result of MHD processes in the stellar outer atmosphere. Stellar coronal mass ejections have not been conclusively detected, despite the ubiquity with which their radiative counterparts in an eruptive event (stellar flares) have. I will review some of the different observational methods which have been used and possibly could be used in the future in the stellar case, emphasizing some of the difficulties inherent in such attempts. I will provide a framework for interpreting potential transient stellar mass loss in light of the properties of flares known to occur on magnetically active stars. This uses a physically motivated way to connect the properties of flares and coronal mass ejections and provides a testable hypothesis for observing or constraining transient stellar mass loss. I will describe recent results using radio observations to detect stellar coronal mass ejections, and what those results imply about transient stellar mass loss. I will provide some motivation for what could be learned in this topic from space-based low frequency radio experiments.

  17. Stellar CCD Photometry: New Approach, Principles and Application

    Science.gov (United States)

    El-Bassuny Alawy, A.

    A new approach is proposed and developed to handle pre-processed CCD frames in order to identify stellar images and derive their relevant parameters. It relies on: 1) Identifying stellar images and assigning approximate positions of their centres using an artificial intelligence technique, (Knowledge Based System), 2) Accurate determination of the centre co-ordinates applying an elementary statistical concept and 3) Estimating the image peak intensity as a stellar magnitude measure employing simple numerical analysis approach. The method has been coded for personal computer users. A CCD frame of the star cluster M67 was adopted as a test case. The results obtained are discussed in comparison with the DAOPHOTII ones and the corresponding published data. Exact coincidence has been found between both results except in very few cases. These exceptions have been discussed in the light of the basis of both methods and the cluster plates. It has been realised that the method suggested represents a very simple, extremely fast, high precision method of stellar CCD photometry. Moreover, it is more capable than DAOPHOTII of handling blended and distorted stellar images. These characteristics show the usefulness of the present method in some astronomical applications, such as auto-focusing and auto-guiding, beside the main purpose, viz. stellar photometry.

  18. Advanced Stellar Compass - ROCSAT 2 - Proposal

    DEFF Research Database (Denmark)

    Riis, Troels; Betto, Maurizio; Jørgensen, John Leif

    1998-01-01

    System Integration is supposed to take place at NSPO facilities.The ASC is a highly advanced and autonomous Stellar Reference Unit designed, developed and produced by the Space Instrumentation Group of the Department of Automation of the Technical University of Denmark.The document is structured...... and in section 7 the mechanical and electrical interfaces are given. In section 8 and 9 we address issues like manufacturing, transportation and storage and to conclude in section 10 the requirements imposed by the ASC on the system are given....

  19. Equilibrium calculations for helical axis stellarators

    International Nuclear Information System (INIS)

    Hender, T.C.; Carreras, B.A.

    1984-04-01

    An average method based on a vacuum flux coordinate system is presented. This average method permits the study of helical axis stellarators with toroidally dominated shifts. An ordering is introduced, and to lowest order the toroidally averaged equilibrium equations are reduced to a Grad-Shafranov equation. Also, to lowest order, a Poisson-type equation is obtained for the toroidally varying corrections to the equilibium. By including these corrections, systems that are toroidally dominated, but with significant helical distortion to the equilibrium, may be studied. Numerical solutions of the average method equations are shown to agree well with three-dimensional calculations

  20. Scattering of Gaussian beam by a spherical particle with a spheroidal inclusion

    International Nuclear Information System (INIS)

    Zhang Huayong; Liao Tongqing

    2011-01-01

    A generalized Lorenz-Mie theory framework (GLMT) is applied to the study of Gaussian beam scattering by a spherical particle with an embedded spheroid at the center. By virtue of a transformation between the spherical and spheroidal vector wave functions, a theoretical procedure is developed to deal with the boundary conditions. Numerical results of the normalized differential scattering cross section are presented.

  1. Spheroidal corrections to the spherical and parabolic bases of the hydrogen atom

    International Nuclear Information System (INIS)

    Mardyan, L.G.; Pogosyan, G.S.; Sisakyan, A.N.

    1986-01-01

    This paper introduces the bases of the hydrogen atom and obtains recursion relations that determine the expansion of the spheroidal basis with respect to its parabolic basis. The leading spheroidal corrections to the spherical and parabolic bases are calculated by perturbation theory

  2. Stability of self-gravitating homogeneous spheroid with azimuthal magnetic field. I

    International Nuclear Information System (INIS)

    Antonov, V.A.; Zheleznyak, O.A.

    1988-01-01

    The influence of a frozen magnetic field on the stability of a self-gravitating homogeneous spheroid with respect to a deformation that transforms it into a triaxial ellipsoid is investigated. It is shown that an azimuthal magnetic field is a stabilizing factor, allowing the spheroid to be stable at e > e/sub cr/ = 0.95285

  3. Oxygenation and response to irradiation of organotypic multicellular spheroids of human glioma.

    Science.gov (United States)

    Sminia, Peter; Acker, Helmut; Eikesdal, Hans Petter; Kaaijk, Patricia; Enger, Per øvind; Slotman, Ben; Bjerkvig, Rolf

    2003-01-01

    Investigation of the oxygenation status of organotypic multicellular spheroids (OMS) and their response to irradiation. Tumour specimens of glioblastoma multiforme patients (n = 16) were initiated as OMS. Following 20 Gy gamma-irradiation, the cell migratory capacity was evaluated. Spheroid oxygenation was determined by micro-electrode pO2 measurements and pimonidazole immunostaining. Spheroids prepared from established human glioma cell lines were used as a reference. Irradiation inhibited spheroid outgrowth by 12 to 88% relative to the non-irradiated controls. A large interpatient variation was noticed. Oxygen measurements revealed a gradual decrease in pO2 level from the periphery to the core of the spheroids, but the pO2 values remained within an oxygenated range. However, in the cell line spheroids an intermediate layer of hypoxia surrounding the central core was observed. Cell line spheroids with a hypoxic cell fraction and well-oxygenated OMS both show high resistance to irradiation, indicating that hypoxia may not be the biological factor determining the radioresistance of glioma spheroids in vitro.

  4. Synergistic interaction between cisplatin and gemcitabine in neuroblastoma cell lines and multicellular tumor spheroids

    NARCIS (Netherlands)

    Besançon, Odette G.; Tytgat, Godelieve A. M.; Meinsma, Rutger; Leen, René; Hoebink, Jerry; Kalayda, Ganna V.; Jaehde, Ulrich; Caron, Huib N.; van Kuilenburg, André B. P.

    2012-01-01

    The efficacy and mechanism of action of cisplatin and gemcitabine were investigated in a panel of neuroblastoma cell lines and multicellular tumor spheroids. In neuroblastoma spheroids, the combination of cisplatin and gemcitabine induced a complete cytostasis at clinical relevant concentrations. A

  5. Solid freeform-fabricated scaffolds designed to carry multicellular mesenchymal stem cell spheroids for cartilage regeneration

    Directory of Open Access Journals (Sweden)

    G-S Huang

    2013-10-01

    Full Text Available Three-dimensional (3D cellular spheroids have recently emerged as a new trend to replace suspended single cells in modern cell-based therapies because of their greater regeneration capacities in vitro. They may lose the 3D structure during a change of microenvironment, which poses challenges to their translation in vivo. Besides, the conventional microporous scaffolds may have difficulty in accommodating these relatively large spheroids. Here we revealed a novel design of microenvironment for delivering and sustaining the 3D spheroids. Biodegradable scaffolds with macroporosity to accommodate mesenchymal stem cell (MSC spheroids were made by solid freeform fabrication (SFF from the solution of poly(D,L-lactide-co-glycolide. Their internal surface was modified with chitosan following air plasma treatment in order to preserve the morphology of the spheroids. It was demonstrated that human MSC spheroids loaded in SFF scaffolds produced a significantly larger amount of cartilage-associated extracellular matrix in vitro and in NOD/SCID mice compared to single cells in the same scaffolds. Implantation of MSC spheroid-loaded scaffolds into the chondral defects of rabbit knees showed superior cartilage regeneration. This study establishes new perspectives in designing the spheroid-sustaining microenvironment within a tissue engineering scaffold for in vivo applications.

  6. Comparative proteome analysis of monolayer and spheroid culture of canine osteosarcoma cells.

    Science.gov (United States)

    Gebhard, Christiane; Miller, Ingrid; Hummel, Karin; Neschi Née Ondrovics, Martina; Schlosser, Sarah; Walter, Ingrid

    2018-04-15

    Osteosarcoma is an aggressive bone tumor with high metastasis rate in the lungs and affects both humans and dogs in a similar way. Three-dimensional tumor cell cultures mimic the in vivo situation of micro-tumors and metastases and are therefore better experimental in vitro models than the often applied two-dimensional monolayer cultures. The aim of the present study was to perform comparative proteomics of standard monolayer cultures of canine osteosarcoma cells (D17) and three-dimensional spheroid cultures, to better characterize the 3D model before starting with experiments like migration assays. Using DIGE in combination with MALDI-TOF/TOF we found 27 unique canine proteins differently represented between these two culture systems, most of them being part of a functional network including mainly chaperones, structural proteins, stress-related proteins, proteins of the glycolysis/gluconeogenesis pathway and oxidoreductases. In monolayer cells, a noticeable shift to more acidic pI values was noticed for several proteins of medium to high abundance; two proteins (protein disulfide isomerase A3, stress-induced-phosphoprotein 1) showed an increase of phosphorylated protein species. Protein distribution within the cells, as detected by immunohistochemistry, displayed a switch of stress-induced-phosphoprotein 1 from the cytoplasm (in monolayer cultures) to the nucleus (in spheroid cultures). Additionally, Western blot testing revealed upregulated concentrations of metastasin (S100A4), triosephosphate isomerase 1 and septin 2 in spheroid cultures, in contrast to decreased concentrations of CCT2, a subunit of the T-complex. Results indicate regulation of stress proteins in the process of three-dimensional organization characterized by a hypoxic and nutrient-deficient environment comparable to tumor micro-metastases. Osteosarcoma is an aggressive bone tumor that early spreads to the lungs. Three-dimensional tumor cell cultures represent the avascular stage of micro

  7. Mass Modelling of Dwarf Spheroidal Galaxies: the Effect of Unbound Stars From Tidal Tails And the Milky Way

    Energy Technology Data Exchange (ETDEWEB)

    Klimentowski, Jaroslaw; Lokas, Ewa L.; /Warsaw, Copernicus Astron. Ctr.; Kazantzidis, Stelios; /KIPAC, Menlo Park; Prada, Francisco; /IAA, Granada; Mayer, Lucio; /Zurich,; Mamon, Gary A.; /Paris, Inst. Astrophys. /Meudon Observ.

    2006-11-14

    We study the origin and properties of the population of unbound stars in the kinematic samples of dwarf spheroidal galaxies. For this purpose we have run a high resolution N- body simulation of a two-component dwarf galaxy orbiting in a Milky Way potential. In agreement with the tidal stirring scenario of Mayer et al., the dwarf is placed on a highly eccentric orbit, its initial stellar component is in the form of an exponential disk and it has a NFW-like dark matter halo. After 10 Gyrs of evolution the dwarf produces a spheroidal stellar component and is strongly tidally stripped so that mass follows light and the stars are on almost isotropic orbits. From this final state, we create mock kinematic data sets for 200 stars by observing the dwarf in different directions.We find that when the dwarf is observed along the tidal tails the kinematic samples are strongly contaminated by unbound stars from the tails.We also study another source of possible contamination by adding stars from the Milky Way. We demonstrate that most of the unbound stars can be removed by the method of interloper rejection proposed by den Hartog & Katgert and recently tested on simulated dark matter haloes. We model the cleaned up kinematic samples using solutions of the Jeans equation with constant mass-to-light ratio and velocity anisotropy parameter. We show that even for such strongly stripped dwarf the Jeans analysis, when applied to cleaned samples, allows us to reproduce the mass and mass-to-light ratio of the dwarf with accuracy typically better than 25 percent and almost exactly in the case when the line of sight is perpendicular to the tidal tails. The analysis was applied to the new data for the Fornax dSph galaxy for which we find a mass-to-light ratio of 11 solar units and isotropic orbits. We demonstrate that most of the contamination in the kinematic sample of Fornax probably originates from the Milky Way.

  8. An mDia2/ROCK signaling axis regulates invasive egress from epithelial ovarian cancer spheroids.

    Science.gov (United States)

    Pettee, Krista M; Dvorak, Kaitlyn M; Nestor-Kalinoski, Andrea L; Eisenmann, Kathryn M

    2014-01-01

    Multi-cellular spheroids are enriched in ascites of epithelial ovarian cancer (OvCa) patients. They represent an invasive and chemoresistant cellular population fundamental to metastatic dissemination. The molecular mechanisms triggering single cell invasive egress from spheroids remain enigmatic. mDia formins are Rho GTPase effectors that are key regulators of F-actin cytoskeletal dynamics. We hypothesized that mDia2-driven F-actin dynamics promote single cell invasive transitions in clinically relevant three-dimensional (3D) OvCa spheroids. The current study is a dissection of the contribution of the F-actin assembly factor mDia2 formin in invasive transitions and using a clinically relevant ovarian cancer spheroid model. We show that RhoA-directed mDia2 activity is required for tight spheroid organization, and enrichment of mDia2 in the invasive cellular protrusions of collagen-embedded OVCA429 spheroids. Depleting mDia2 in ES-2 spheroids enhanced invasive dissemination of single amoeboid-shaped cells. This contrasts with spheroids treated with control siRNA, where a mesenchymal invasion program predominated. Inhibition of another RhoA effector, ROCK, had no impact on ES-2 spheroid formation but dramatically inhibited spheroid invasion through induction of a highly elongated morphology. Concurrent inhibition of ROCK and mDia2 blocked single cell invasion from ES-2 spheroids more effectively than inhibition of either protein alone, indicating that invasive egress of amoeboid cells from mDia2-depleted spheroids is ROCK-dependent. Our findings indicate that multiple GTPase effectors must be suppressed in order to fully block invasive egress from ovarian cancer spheroids. Furthermore, tightly regulated interplay between ROCK and mDia2 signaling pathways dictates the invasive capacities and the type of invasion program utilized by motile spheroid-derived ovarian cancer cells. As loss of the gene encoding mDia2, DRF3, has been linked to cancer progression and

  9. An mDia2/ROCK signaling axis regulates invasive egress from epithelial ovarian cancer spheroids.

    Directory of Open Access Journals (Sweden)

    Krista M Pettee

    Full Text Available Multi-cellular spheroids are enriched in ascites of epithelial ovarian cancer (OvCa patients. They represent an invasive and chemoresistant cellular population fundamental to metastatic dissemination. The molecular mechanisms triggering single cell invasive egress from spheroids remain enigmatic. mDia formins are Rho GTPase effectors that are key regulators of F-actin cytoskeletal dynamics. We hypothesized that mDia2-driven F-actin dynamics promote single cell invasive transitions in clinically relevant three-dimensional (3D OvCa spheroids. The current study is a dissection of the contribution of the F-actin assembly factor mDia2 formin in invasive transitions and using a clinically relevant ovarian cancer spheroid model. We show that RhoA-directed mDia2 activity is required for tight spheroid organization, and enrichment of mDia2 in the invasive cellular protrusions of collagen-embedded OVCA429 spheroids. Depleting mDia2 in ES-2 spheroids enhanced invasive dissemination of single amoeboid-shaped cells. This contrasts with spheroids treated with control siRNA, where a mesenchymal invasion program predominated. Inhibition of another RhoA effector, ROCK, had no impact on ES-2 spheroid formation but dramatically inhibited spheroid invasion through induction of a highly elongated morphology. Concurrent inhibition of ROCK and mDia2 blocked single cell invasion from ES-2 spheroids more effectively than inhibition of either protein alone, indicating that invasive egress of amoeboid cells from mDia2-depleted spheroids is ROCK-dependent. Our findings indicate that multiple GTPase effectors must be suppressed in order to fully block invasive egress from ovarian cancer spheroids. Furthermore, tightly regulated interplay between ROCK and mDia2 signaling pathways dictates the invasive capacities and the type of invasion program utilized by motile spheroid-derived ovarian cancer cells. As loss of the gene encoding mDia2, DRF3, has been linked to cancer

  10. Multiplexing spheroid volume, resazurin and acid phosphatase viability assays for high-throughput screening of tumour spheroids and stem cell neurospheres.

    Directory of Open Access Journals (Sweden)

    Delyan P Ivanov

    Full Text Available Three-dimensional cell culture has many advantages over monolayer cultures, and spheroids have been hailed as the best current representation of small avascular tumours in vitro. However their adoption in regular screening programs has been hindered by uneven culture growth, poor reproducibility and lack of high-throughput analysis methods for 3D. The objective of this study was to develop a method for a quick and reliable anticancer drug screen in 3D for tumour and human foetal brain tissue in order to investigate drug effectiveness and selective cytotoxic effects. Commercially available ultra-low attachment 96-well round-bottom plates were employed to culture spheroids in a rapid, reproducible manner amenable to automation. A set of three mechanistically different methods for spheroid health assessment (Spheroid volume, metabolic activity and acid phosphatase enzyme activity were validated against cell numbers in healthy and drug-treated spheroids. An automated open-source ImageJ macro was developed to enable high-throughput volume measurements. Although spheroid volume determination was superior to the other assays, multiplexing it with resazurin reduction and phosphatase activity produced a richer picture of spheroid condition. The ability to distinguish between effects on malignant and the proliferating component of normal brain was tested using etoposide on UW228-3 medulloblastoma cell line and human neural stem cells. At levels below 10 µM etoposide exhibited higher toxicity towards proliferating stem cells, whereas at concentrations above 10 µM the tumour spheroids were affected to a greater extent. The high-throughput assay procedures use ready-made plates, open-source software and are compatible with standard plate readers, therefore offering high predictive power with substantial savings in time and money.

  11. A theoretical study of the spheroidal droplet evaporation in forced convection

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jie, E-mail: leejay1986@163.com; Zhang, Jian

    2014-11-07

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time. - Highlights: • Fully algebraic solutions for the spheroidal droplet evaporation rate is obtained. • We examine the effect of aspect ratio on the droplet evaporation. • We propose a calculation method of Nusselt number for spheroidal droplet.

  12. Creation of Cardiac Tissue Exhibiting Mechanical Integration of Spheroids Using 3D Bioprinting.

    Science.gov (United States)

    Ong, Chin Siang; Fukunishi, Takuma; Nashed, Andrew; Blazeski, Adriana; Zhang, Huaitao; Hardy, Samantha; DiSilvestre, Deborah; Vricella, Luca; Conte, John; Tung, Leslie; Tomaselli, Gordon; Hibino, Narutoshi

    2017-07-02

    This protocol describes 3D bioprinting of cardiac tissue without the use of biomaterials, using only cells. Cardiomyocytes, endothelial cells and fibroblasts are first isolated, counted and mixed at desired cell ratios. They are co-cultured in individual wells in ultra-low attachment 96-well plates. Within 3 days, beating spheroids form. These spheroids are then picked up by a nozzle using vacuum suction and assembled on a needle array using a 3D bioprinter. The spheroids are then allowed to fuse on the needle array. Three days after 3D bioprinting, the spheroids are removed as an intact patch, which is already spontaneously beating. 3D bioprinted cardiac patches exhibit mechanical integration of component spheroids and are highly promising in cardiac tissue regeneration and as 3D models of heart disease.

  13. A theoretical study of the spheroidal droplet evaporation in forced convection

    International Nuclear Information System (INIS)

    Li, Jie; Zhang, Jian

    2014-01-01

    In many applications, the shape of a droplet may be assumed to be an oblate spheroid. A theoretical study is conducted on the evaporation of an oblate spheroidal droplet under forced convection conditions. Closed-form analytical expressions of the mass evaporation rate for an oblate spheroid are derived, in the regime of controlled mass-transfer and heat-transfer, respectively. The variation of droplet size during the evaporation process is presented in the regime of shrinking dynamic model. Comparing with the droplets having the same surface area, an increase in the aspect ratio enhances the mass evaporation rate and prolongs the burnout time. - Highlights: • Fully algebraic solutions for the spheroidal droplet evaporation rate is obtained. • We examine the effect of aspect ratio on the droplet evaporation. • We propose a calculation method of Nusselt number for spheroidal droplet

  14. Two step continuous method to synthesize colloidal spheroid gold nanorods.

    Science.gov (United States)

    Chandra, S; Doran, J; McCormack, S J

    2015-12-01

    This research investigated a two-step continuous process to synthesize colloidal suspension of spheroid gold nanorods. In the first step; gold precursor was reduced to seed-like particles in the presence of polyvinylpyrrolidone and ascorbic acid. In continuous second step; silver nitrate and alkaline sodium hydroxide produced various shape and size Au nanoparticles. The shape was manipulated through weight ratio of ascorbic acid to silver nitrate by varying silver nitrate concentration. The specific weight ratio of 1.35-1.75 grew spheroid gold nanorods of aspect ratio ∼1.85 to ∼2.2. Lower weight ratio of 0.5-1.1 formed spherical nanoparticle. The alkaline medium increased the yield of gold nanorods and reduced reaction time at room temperature. The synthesized gold nanorods retained their shape and size in ethanol. The surface plasmon resonance was red shifted by ∼5 nm due to higher refractive index of ethanol than water. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. BOOK REVIEW: Stellarator and Heliotron Devices

    Science.gov (United States)

    Johnson, John L.

    1999-02-01

    Stellarators and tokamaks are the most advanced devices that have been developed for magnetic fusion applications. The two approaches have much in common; tokamaks have received the most attention because their axisymmetry justifies the use of simpler models and provides a more forgiving geometry. However, recent advances in treating more complicated three dimensional systems have made it possible to design stellarators that are not susceptible to disruptions and do not need plasma current control. This has excited interest recently. The two largest new magnetic experiments in the world are the LHD device, which commenced operation in Toki, Japan, in 1998 and W7-X, which should become operational in Greifswald, Germany, in 2004. Other recently commissioned stellarators, including H-1 in Canberra, Australia, TJ-II in Madrid, Spain, and IMS in Madison, Wisconsin, have joined these in rejuvenating the stellarator programme. Thus, it is most appropriate that the author has made the lecture material that he presents to his students in the Graduate School of Energy Science at Kyoto University available to everyone. Stellarator and Heliotron Devices provides an excellent treatment of stellarator theory. It is aimed at graduate students who have a good understanding of classical mechanics and mathematical techniques. It contains good descriptions and derivations of essentially every aspect of fusion theory. The author provides an excellent qualitative introduction to each subject, pointing out the strengths and weaknesses of the models that are being used and describing our present understanding. He judiciously uses simple models which illustrate the similarities and differences between stellarators and tokamaks. To some extent the treatment is uneven, rigorous derivations starting with basic principles being given in some cases and relations and equations taken from the original papers being used as a starting point in others. This technique provides an excellent training

  16. Oxygen consumption rate and mitochondrial density in human melanoma monolayer cultures and multicellular spheroids.

    Science.gov (United States)

    Hystad, M E; Rofstad, E K

    1994-05-15

    Rate of oxygen consumption per cell has been shown in previous studies to decrease with increasing depth in the viable rim of multicellular spheroids initiated from rodent cells, human colon-carcinoma cells, and human glioma cells, due to progressive accumulation of quiescent cells during spheroid growth. The purpose of our work was to determine oxygen-consumption profiles in human melanoma spheroids. Monolayer cultures of 4 lines (BEX-c, COX-c, SAX-c, and WIX-c) and spheroid cultures of 2 lines (BEX-c and WIX-c) were subjected to investigation. Spheroids were initiated from monolayer cell cultures and grown in spinner flasks. Rate of oxygen consumption was measured with a Clarke-type electrode. Mitochondrial density was determined by stereological analysis of transmission electron micrographs. Thickness of viable rim and cell packing density were assessed by light microscopy of central spheroid sections. Cell-cycle distribution was determined by analysis of DNA histograms measured by flow cytometry. Cell volume was measured by an electronic particle counter. Rate of oxygen consumption per cell differed by a factor of approximately 1.8 between the 4 cell lines and was positively correlated to total volume of mitochondria per cell. Rate of oxygen consumption per cell and total volume of mitochondria per cell were equal for monolayer cell cultures, 600-microns spheroids and 1,200-microns spheroids of the same line. Mitochondrial density and location in the cell did not differ between cells at the spheroid surface, in the middle of the viable rim and adjacent to the central necrosis. Cell-cycle distribution, cell volume, and cell-packing density in the outer and inner halves of the viable rim were not significantly different. Consequently, the rate of oxygen consumption per cell in inner regions of the viable rim was probably equal to that at the spheroid surface, suggesting that oxygen diffusion distances may be shorter in some melanomas than in many other tumor

  17. The formation of Dwarf Spheroidal galaxies by the dissolving star cluster model.

    Science.gov (United States)

    Alarcon, Alex; Theory and Star Formation Group

    2018-01-01

    Dwarf spheroidal (dSph) galaxies are regarded as key object in the formation of larger galaxies and are believed to be the most dark matter dominated systems known. There are several model that attempt to explain their formation, but they have problems to model the formation of isolated dSph. Here we will explain a possible formation scenario in which star clusters form in the dark matter halo of a dSph. these cluster suffer from low star formation efficiency and dissolve while orbiting inside the halo. Thereby they build the faint luminous components that we observe in dSph galaxies. Here we will show the main results of this simulations and how they would be corroborated using observational data.

  18. THE METALLICITIES OF LOW STELLAR MASS GALAXIES AND THE SCATTER IN THE MASS-METALLICITY RELATION

    International Nuclear Information System (INIS)

    Zahid, H. J.; Bresolin, F.; Kewley, L. J.; Coil, A. L.; Davé, R.

    2012-01-01

    In this investigation, we quantify the metallicities of low-mass galaxies by constructing the most comprehensive census to date. We use galaxies from the Sloan Digital Sky Survey (SDSS) and DEEP2 survey and estimate metallicities from their optical emission lines. We also use two smaller samples from the literature that have metallicities determined by the direct method using the temperature sensitive [O III]λ4363 line. We examine the scatter in the local mass-metallicity (MZ) relation determined from ∼20,000 star-forming galaxies in the SDSS and show that it is larger at lower stellar masses, consistent with the theoretical scatter in the MZ relation determined from hydrodynamical simulations. We determine a lower limit for the scatter in metallicities of galaxies down to stellar masses of ∼10 7 M ☉ which is only slightly smaller than the expected scatter inferred from the SDSS MZ relation and significantly larger than what has been previously established in the literature. The average metallicity of star-forming galaxies increases with stellar mass. By examining the scatter in the SDSS MZ relation, we show that this is mostly due to the lowest metallicity galaxies. The population of low-mass, metal-rich galaxies have properties that are consistent with previously identified galaxies that may be transitional objects between gas-rich dwarf irregulars and gas-poor dwarf spheroidals and ellipticals.

  19. Science with Synthetic Stellar Surveys

    Science.gov (United States)

    Sanderson, Robyn Ellyn

    2018-04-01

    A new generation of observational projects is poised to revolutionize our understanding of the resolved stellar populations of Milky-Way-like galaxies at an unprecedented level of detail, ushering in an era of precision studies of galaxy formation. In the Milky Way itself, astrometric, spectroscopic and photometric surveys will measure three-dimensional positions and velocities and numerous chemical abundances for stars from the disk to the halo, as well as for many satellite dwarf galaxies. In the Local Group and beyond, HST, JWST and eventually WFIRST will deliver pristine views of resolved stars. The groundbreaking scale and dimensionality of this new view of resolved stellar populations in galaxies challenge us to develop new theoretical tools to robustly compare these surveys to simulated galaxies, in order to take full advantage of our new ability to make detailed predictions for stellar populations within a cosmological context. I will describe a framework for generating realistic synthetic star catalogs and mock surveys from state-of-the-art cosmological-hydrodynamical simulations, and present several early scientific results from, and predictions for, resolved stellar surveys of our Galaxy and its neighbors.

  20. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is significantly ...

  1. Maximum stellar iron core mass

    Indian Academy of Sciences (India)

    60, No. 3. — journal of. March 2003 physics pp. 415–422. Maximum stellar iron core mass. F W GIACOBBE. Chicago Research Center/American Air Liquide ... iron core compression due to the weight of non-ferrous matter overlying the iron cores within large .... thermal equilibrium velocities will tend to be non-relativistic.

  2. Integrated Circuit Stellar Magnitude Simulator

    Science.gov (United States)

    Blackburn, James A.

    1978-01-01

    Describes an electronic circuit which can be used to demonstrate the stellar magnitude scale. Six rectangular light-emitting diodes with independently adjustable duty cycles represent stars of magnitudes 1 through 6. Experimentally verifies the logarithmic response of the eye. (Author/GA)

  3. Stellar dynamics and black holes

    Indian Academy of Sciences (India)

    Chandrasekhar's most important contribution to stellar dynamics was the concept of dynamical friction. I briefly review that work, then discuss some implications of Chandrasekhar's theory of gravitational encounters for motion in galactic nuclei. Author Affiliations. David Merritt1. Department of Physics, Rochester Institute ...

  4. TEM turbulence optimisation in stellarators

    Science.gov (United States)

    Proll, J. H. E.; Mynick, H. E.; Xanthopoulos, P.; Lazerson, S. A.; Faber, B. J.

    2016-01-01

    With the advent of neoclassically optimised stellarators, optimising stellarators for turbulent transport is an important next step. The reduction of ion-temperature-gradient-driven turbulence has been achieved via shaping of the magnetic field, and the reduction of trapped-electron mode (TEM) turbulence is addressed in the present paper. Recent analytical and numerical findings suggest TEMs are stabilised when a large fraction of trapped particles experiences favourable bounce-averaged curvature. This is the case for example in Wendelstein 7-X (Beidler et al 1990 Fusion Technol. 17 148) and other Helias-type stellarators. Using this knowledge, a proxy function was designed to estimate the TEM dynamics, allowing optimal configurations for TEM stability to be determined with the STELLOPT (Spong et al 2001 Nucl. Fusion 41 711) code without extensive turbulence simulations. A first proof-of-principle optimised equilibrium stemming from the TEM-dominated stellarator experiment HSX (Anderson et al 1995 Fusion Technol. 27 273) is presented for which a reduction of the linear growth rates is achieved over a broad range of the operational parameter space. As an important consequence of this property, the turbulent heat flux levels are reduced compared with the initial configuration.

  5. Targeted Optimization of Quasi-Symmetric Stellarators

    International Nuclear Information System (INIS)

    Hegna, Chris C.; Talmadge, J. N.

    2016-01-01

    The proposed research focuses on targeted areas of plasma physics dedicated to improving the stellarator concept. Research was pursued in the technical areas of edge/divertor physics in 3D configurations, magnetic island physics in stellarators, the role of 3D shaping on microinstabilities and turbulent transport and energetic ion confinement in stellarators.

  6. Targeted Optimization of Quasi-Symmetric Stellarators

    Energy Technology Data Exchange (ETDEWEB)

    Hegna, Chris C. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Engineering Physics; Anderson, D. T. [Univ. of Wisconsin, Madison, WI (United States); Talmadge, J. N. [Univ. of Wisconsin, Madison, WI (United States)

    2016-10-06

    The proposed research focuses on targeted areas of plasma physics dedicated to improving the stellarator concept. Research was pursued in the technical areas of edge/divertor physics in 3D configurations, magnetic island physics in stellarators, the role of 3D shaping on microinstabilities and turbulent transport and energetic ion confinement in stellarators.

  7. Development of complex-shaped liver multicellular spheroids as a human-based model for nanoparticle toxicity assessment in vitro

    International Nuclear Information System (INIS)

    Dubiak-Szepietowska, Monika; Karczmarczyk, Aleksandra; Jönsson-Niedziółka, Martin; Winckler, Thomas; Feller, Karl-Heinz

    2016-01-01

    The emergence of human-based models is incontestably required for the study of complex physiological pathways and validation of reliable in vitro methods as alternative for in vivo studies in experimental animals for toxicity assessment. With this objective, we have developed and tested three dimensional environments for cells using different types of hydrogels including transglutaminase-cross-linked gelatin, collagen type I, and growth-factor depleted Matrigel. Cells grown in Matrigel exhibited the greatest cell proliferation and spheroid diameter. Moreover, analysis of urea and albumin biosynthesis revealed that the created system allowed the immortalized liver cell line HepG2 to re-establish normal hepatocyte-like properties which were not observed under the conditions of conventional cell cultures. This study presents a scalable technology for production of complex-shaped liver multicellular spheroids as a system which improves the predictive value of cell-based assays for safety and risk assessment. The time- and dose-dependent toxicity of nanoparticles demonstrates a higher cytotoxic effect when HepG2 cells grown as monolayer than embedded in hydrogels. The experimental setup provided evidence that the cell environment has significant influence on cell sensitivity and that liver spheroid is a useful and novel tool to examine nanoparticle dosing effect even at the level of in vitro studies. Therefore, this system can be applied to a wide variety of potentially hostile compounds in basic screening to provide initial warning of adverse effects and trigger subsequent analysis and remedial actions. - Highlights: • Comparison of HepG2 cells growth in Matrigel, Collagen I gel and gelatin gel. • Examination of nanoparticles (NP) dosing effect at the level of in vitro studies. • Influence of the cell culture media composition on the cytotoxic effect of NP.

  8. Development of complex-shaped liver multicellular spheroids as a human-based model for nanoparticle toxicity assessment in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Dubiak-Szepietowska, Monika, E-mail: Monika.Dubiak-Szepietowska@fh-jena.de [Department of Medical Engineering and Biotechnology, Ernst-Abbe-University of Applied Sciences Jena, Carl-Zeiss Promenade 2, 07745 Jena (Germany); Karczmarczyk, Aleksandra [Department of Medical Engineering and Biotechnology, Ernst-Abbe-University of Applied Sciences Jena, Carl-Zeiss Promenade 2, 07745 Jena (Germany); Jönsson-Niedziółka, Martin [Institute of Physical Chemistry, Polish Academy of Sciences, ul. Kasprzaka 44/52, 01-224 Warszawa (Poland); Winckler, Thomas [Institute of Pharmacy, Friedrich Schiller University Jena, Semmelweissstraße 10, 07743 Jena (Germany); Feller, Karl-Heinz [Department of Medical Engineering and Biotechnology, Ernst-Abbe-University of Applied Sciences Jena, Carl-Zeiss Promenade 2, 07745 Jena (Germany)

    2016-03-01

    The emergence of human-based models is incontestably required for the study of complex physiological pathways and validation of reliable in vitro methods as alternative for in vivo studies in experimental animals for toxicity assessment. With this objective, we have developed and tested three dimensional environments for cells using different types of hydrogels including transglutaminase-cross-linked gelatin, collagen type I, and growth-factor depleted Matrigel. Cells grown in Matrigel exhibited the greatest cell proliferation and spheroid diameter. Moreover, analysis of urea and albumin biosynthesis revealed that the created system allowed the immortalized liver cell line HepG2 to re-establish normal hepatocyte-like properties which were not observed under the conditions of conventional cell cultures. This study presents a scalable technology for production of complex-shaped liver multicellular spheroids as a system which improves the predictive value of cell-based assays for safety and risk assessment. The time- and dose-dependent toxicity of nanoparticles demonstrates a higher cytotoxic effect when HepG2 cells grown as monolayer than embedded in hydrogels. The experimental setup provided evidence that the cell environment has significant influence on cell sensitivity and that liver spheroid is a useful and novel tool to examine nanoparticle dosing effect even at the level of in vitro studies. Therefore, this system can be applied to a wide variety of potentially hostile compounds in basic screening to provide initial warning of adverse effects and trigger subsequent analysis and remedial actions. - Highlights: • Comparison of HepG2 cells growth in Matrigel, Collagen I gel and gelatin gel. • Examination of nanoparticles (NP) dosing effect at the level of in vitro studies. • Influence of the cell culture media composition on the cytotoxic effect of NP.

  9. Sarcoma Spheroids and Organoids—Promising Tools in the Era of Personalized Medicine

    Directory of Open Access Journals (Sweden)

    Gianluca Colella

    2018-02-01

    Full Text Available Cancer treatment is rapidly evolving toward personalized medicine, which takes into account the individual molecular and genetic variability of tumors. Sophisticated new in vitro disease models, such as three-dimensional cell cultures, may provide a tool for genetic, epigenetic, biomedical, and pharmacological research, and help determine the most promising individual treatment. Sarcomas, malignant neoplasms originating from mesenchymal cells, may have a multitude of genomic aberrations that give rise to more than 70 different histopathological subtypes. Their low incidence and high level of histopathological heterogeneity have greatly limited progress in their treatment, and trials of clinical sarcoma are less frequent than trials of other carcinomas. The main advantage of 3D cultures from tumor cells or biopsy is that they provide patient-specific models of solid tumors, and they overcome some limitations of traditional 2D monolayer cultures by reflecting cell heterogeneity, native histologic architectures, and cell–extracellular matrix interactions. Recent advances promise that these models can help bridge the gap between preclinical and clinical research by providing a relevant in vitro model of human cancer useful for drug testing and studying metastatic and dormancy mechanisms. However, additional improvements of 3D models are expected in the future, specifically the inclusion of tumor vasculature and the immune system, to enhance their full ability to capture the biological features of native tumors in high-throughput screening. Here, we summarize recent advances and future perspectives of spheroid and organoid in vitro models of rare sarcomas that can be used to investigate individual molecular biology and predict clinical responses. We also highlight how spheroid and organoid culture models could facilitate the personalization of sarcoma treatment, provide specific clinical scenarios, and discuss the relative strengths and limitations

  10. Direct UV/Optical Imaging of Stellar Surfaces: The Stellar Imager (SI) Vision Mission

    Science.gov (United States)

    Carpenter, Kenneth G.; Lyon, Richard G.; Schrijver, Carolus; Karovska, Margarita; Mozurkewich, David

    2007-01-01

    The Stellar Imager (SI) is a UV/optical, space-based interferometer designed to enable 0.1 milli-arcsecond (mas) spectral imaging of stellar surfaces and, via asteroseismology, stellar interiors and of the Universe in general. SI's science focuses on the role of magnetism in the Universe, particularly on magnetic activity on the surfaces of stars like the Sun. SI's prime goal is to enable long-term forecasting of solar activity and the space weather that it drives, in support of the Living with a Star program in the Exploration Era. SI will also revolutionize our understanding of the formation of planetary systems, of the habitability and climatology of distant planets, and of many magneto-hydrodynamically controlled processes in thc Universe. SI is a "Flagship and Landmark Discovery Mission" in the 2005 Sun Solar System Connection (SSSC) Roadmap and a candidate for a "Pathways to Life Observatory" in the Exploration of the Universe Division (EUD) Roadmap. We discuss herein the science goals of the SI Mission, a mission architecture that could meet those goals, and the technologies needed to enable this mission. Additional information on SI can be found at: http://hires.gsfc.nasa.gov/si/.

  11. Detachably assembled microfluidic device for perfusion culture and post-culture analysis of a spheroid array.

    Science.gov (United States)

    Sakai, Yusuke; Hattori, Koji; Yanagawa, Fumiki; Sugiura, Shinji; Kanamori, Toshiyuki; Nakazawa, Kohji

    2014-07-01

    Microfluidic devices permit perfusion culture of three-dimensional (3D) tissue, mimicking the flow of blood in vascularized 3D tissue in our body. Here, we report a microfluidic device composed of a two-part microfluidic chamber chip and multi-microwell array chip able to be disassembled at the culture endpoint. Within the microfluidic chamber, an array of 3D tissue aggregates (spheroids) can be formed and cultured under perfusion. Subsequently, detailed post-culture analysis of the spheroids collected from the disassembled device can be performed. This device facilitates uniform spheroid formation, growth analysis in a high-throughput format, controlled proliferation via perfusion flow rate, and post-culture analysis of spheroids. We used the device to culture spheroids of human hepatocellular carcinoma (HepG2) cells under two controlled perfusion flow rates. HepG2 spheroids exhibited greater cell growth at higher perfusion flow rates than at lower perfusion flow rates, and exhibited different metabolic activity and mRNA and protein expression under the different flow rate conditions. These results show the potential of perfusion culture to precisely control the culture environment in microfluidic devices. The construction of spheroid array chambers allows multiple culture conditions to be tested simultaneously, with potential applications in toxicity and drug screening. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Radiobiological studies of cells in multicellular spheroids using a sequential trypsinization technique

    International Nuclear Information System (INIS)

    Giesbrecht, J.L.; Wilson, W.R.; Hill, R.P.

    1981-01-01

    The radiation response of V79 Chinese hamster cells grown as multicellular spheroids has been investigated by determining survival curves for treatment under a variety of different oxygen concentrations. Spheroids were irradiated under fully oxygenated conditions in air-equilibrated medium at 37 0 C, in medium exposed to lower oxygen tension (5% O 2 ) for times varying from 1 hr to 3 days, or under anoxic conditions. For comparison with the spheroids, using identical treatment conditions, V79 cells were grown in suspension as a subconfluent monolayer attached to Sephadex (microcarrier) beads and irradiated under fully oxygenated or anoxic conditions. The radiation response of cells at different depths within the spheroid was investigated by using a sequential trypsinization technique developed to remove eight or nine shells of cells successively from the spheroid surface. When irradiation was given under fully oxygenated conditions the outer few cell layers were more sensitive than the inner cells, a finding which is not understood. As expected the inner cells in spheroids irradiated in air (at 37 0 C) or in 5% O 2 are more resistant than the outer cells. For an acute exposure to 5% O 2 (1 hr) in the inner cells displayed full radiobiological hypoxia; however, for chronic exposures to low oxygen this was not the case. These results with the sequential trypsinization procedure suggest that the radiation response of cells in spheroids is more complex than anticipted

  13. Promotion of malignant phenotype after disruption of the three-dimensional structure of cultured spheroids from colorectal cancer.

    Science.gov (United States)

    Piulats, Jose M; Kondo, Jumpei; Endo, Hiroko; Ono, Hiromasa; Hagihara, Takeshi; Okuyama, Hiroaki; Nishizawa, Yasuko; Tomita, Yasuhiko; Ohue, Masayuki; Okita, Kouki; Oyama, Hidejiro; Bono, Hidemasa; Masuko, Takashi; Inoue, Masahiro

    2018-03-23

    Individual and small clusters of cancer cells may detach from the edges of a main tumor and invade vessels, which can act as the origin of metastasis; however, the mechanism for this phenomenon is not well understood. Using cancer tissue-originated spheroids, we studied whether disturbing the 3D architecture of cancer spheroids can provoke the reformation process and progression of malignancy. We developed a mechanical disruption method to achieve homogenous disruption of the spheroids while maintaining cell-cell contact. After the disruption, 9 spheroid lines from 9 patient samples reformed within a few hours, and 3 of the 9 lines exhibited accelerated spheroid growth. Marker expression, spheroid forming capacity, and tumorigenesis indicated that stemness increased after spheroid disruption. In addition, the spheroid forming capacity increased in 6 of 11 spheroid lines. The disruption signature determined by gene expression profiling supported the incidence of remodeling and predicted the prognosis of patients with colorectal cancer. Furthermore, WNT and HER3 signaling were increased in the reformed spheroids, and suppression of these signaling pathways attenuated the increased proliferation and stemness after the disruption. Overall, the disruption and subsequent reformation of cancer spheroids promoted malignancy-related phenotypes through the activation of the WNT and ERBB pathways.

  14. Down-regulation of DNA mismatch repair enhances initiation and growth of neuroblastoma and brain tumour multicellular spheroids.

    Directory of Open Access Journals (Sweden)

    Samuel L Collins

    Full Text Available Multicellular tumour spheroid (MCTS cultures are excellent model systems for simulating the development and microenvironmental conditions of in vivo tumour growth. Many documented cell lines can generate differentiated MCTS when cultured in suspension or in a non-adhesive environment. While physiological and biochemical properties of MCTS have been extensively characterized, insight into the events and conditions responsible for initiation of these structures is lacking. MCTS are formed by only a small subpopulation of cells during surface-associated growth but the processes responsible for this differentiation are poorly understood and have not been previously studied experimentally. Analysis of gene expression within spheroids has provided clues but to date it is not known if the observed differences are a cause or consequence of MCTS growth. One mechanism linked to tumourigenesis in a number of cancers is genetic instability arising from impaired DNA mismatch repair (MMR. This study aimed to determine the role of MMR in MCTS initiation and development. Using surface-associated N2a and CHLA-02-ATRT culture systems we have investigated the impact of impaired MMR on MCTS growth. Analysis of the DNA MMR genes MLH1 and PMS2 revealed both to be significantly down-regulated at the mRNA level compared with non-spheroid-forming cells. By using small interfering RNA (siRNA against these genes we show that silencing of MLH1 and PMS2 enhances both MCTS initiation and subsequent expansion. This effect was prolonged over several passages following siRNA transfection. Down-regulation of DNA MMR can contribute to tumour initiation and progression in N2a and CHLA-02-ATRT MCTS models. Studies of surface-associated MCTS differentiation may have broader applications in studying events in the initiation of cancer foci.

  15. Nuclei of dwarf spheroidal galaxies KKs 3 and ESO 269-66 and their counterparts in our Galaxy

    Science.gov (United States)

    Sharina, M. E.; Shimansky, V. V.; Kniazev, A. Y.

    2017-10-01

    We present the analysis of medium-resolution spectra obtained at the Southern African Large Telescope for nuclear globular clusters (GCs) in two dwarf spheroidal galaxies (dSphs). The galaxies have similar star formation histories, but they are situated in completely different environments. ESO 269-66 is a close neighbour of the giant S0 NGC 5128. KKs 3 is one of the few truly isolated dSphs within 10 Mpc. We estimate the helium abundance Y = 0.3, age = 12.6 ± 1 Gyr, [Fe/H] = -1.5, -1.55 ± 0.2 dex, and abundances of C, N, Mg, Ca, Ti, and Cr for the nuclei of ESO 269-66 and KKs 3. Our surface photometry results using Hubble Space Telescope images yield the half-light radius of the cluster in KKs 3, rh = 4.8 ± 0.2 pc. We demonstrate the similarities of medium-resolution spectra, ages, chemical compositions, and structure for GCs in ESO 269-66 and KKs 3 and for several massive Galactic GCs with [Fe/H] ∼ -1.6 dex. All Galactic GCs posses Extended Blue Horizontal Branches and multiple stellar populations. Five of the selected Galactic objects are iron-complex GCs. Our results indicate that the sample GCs observed now in different environments had similar conditions of their formation ∼1 Gyr after the Big Bang.

  16. Pervasive plastisphere: First record of plastics in egagropiles (Posidonia spheroids).

    Science.gov (United States)

    Pietrelli, Loris; Di Gennaro, Alessia; Menegoni, Patrizia; Lecce, Francesca; Poeta, Gianluca; Acosta, Alicia T R; Battisti, Corrado; Iannilli, Valentina

    2017-10-01

    The ability of Posidonia oceanica spheroids (egagropiles, EG) to incorporate plastics was investigated along the central Italy coast. Plastics were found in the 52.84% of the egagropiles collected (n = 685). The more represented size of plastics has range within 1-1.5 cm, comparable to the size of natural fibres. Comparing plastics occurring both in EG and in surrounding sand, Polyethylene, Polyester and Nylon were the most abundant polymers in EG, while PSE, PE, PP and PET were the most represented in sand. In particular PE and PP were significantly more represented in sand, while PE, Nylon, Polyester and microfibers (as pills) were more represented in EG. Within plastics found in EG, 26.9% were microfibers as small pills (PET mixing. These microfibers might be produced by discharges from washing machines and currently represents an emerging pollutant with widespread distribution in marine and freshwater ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Modes of spheroidal ion plasmas at the Brillouin limit

    International Nuclear Information System (INIS)

    Tinkle, M.D.; Greaves, R.G.; Surko, C.M.

    1996-01-01

    The confinement properties and collective modes of single-component plasmas are investigated in a quadrupole Penning trap. Brillouin-density pure ion plasmas are generated by electron-beam ionization of a low-pressure gas. Large, spheroidal, steady-state plasmas are produced, extending out to contact one or more of the trap electrodes. With the density fixed at the Brillouin limit by the high ion production rate, the electrode potentials determine the plasma shape. The frequencies of azimuthally propagating cyclotron and diocotron modes are found to vary significantly with the plasma aspect ratio. For oblate plasmas, the frequencies are in good agreement with a simple fluid model. copyright 1996 American Institute of Physics

  18. Numerical simulations of bistable flows in precessing spheroidal shells

    Science.gov (United States)

    Vormann, J.; Hansen, U.

    2018-05-01

    Precession of the rotation axis is an often neglected mechanical driving mechanism for flows in planetary interiors, through viscous coupling at the boundaries and topographic forcing in non-spherical geometries. We investigate precession-driven flows in spheroidal shells over a wide range of parameters and test the results against theoretical predictions. For Ekman numbers down to 8.0 × 10-7, we see a good accordance with the work of Busse, who assumed the precession-driven flow to be dominated by a rigid rotation component that is tilted to the main rotation axis. The velocity fields show localized small-scale structures for lower Ekman numbers and clear signals of inertial waves for some parameters. For the case of moderate viscosity and strong deformation, we report the realization of multiple solutions at the same parameter combination, depending on the initial condition.

  19. The slow ionized wind and rotating disklike system that are associated with the high-mass young stellar object G345.4938+01.4677

    Energy Technology Data Exchange (ETDEWEB)

    Guzmán, Andrés E.; Garay, Guido; Bronfman, Leonardo; Mardones, Diego [Departamento de Astronomía, Universidad de Chile, Camino el Observatorio 1515, Las Condes, Santiago (Chile); Rodríguez, Luis F. [Centro de Radioastronomía y Astrofísica (UNAM), Morelia 58089 (Mexico); Moran, James [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA (United States); Brooks, Kate J. [CSIRO Astronomy and Space Science, P.O. Box 76, Epping, 1710 NSW (Australia); Nyman, Lars-Åke [Joint ALMA Observatory (JAO), Alonso de Córdova 3107, Vitacura, Santiago (Chile); Sanhueza, Patricio [Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States)

    2014-12-01

    We report the detection, made using ALMA, of the 92 GHz continuum and hydrogen recombination lines (HRLs) H40α, H42α, and H50β emission toward the ionized wind associated with the high-mass young stellar object G345.4938+01.4677. This is the luminous central dominating source located in the massive and dense molecular clump associated with IRAS 16562–3959. The HRLs exhibit Voigt profiles, which is a strong signature of Stark broadening. We successfully reproduce the observed continuum and HRLs simultaneously using a simple model of a slow ionized wind in local thermodynamic equilibrium, with no need for a high-velocity component. The Lorentzian line wings imply electron densities of 5 × 10{sup 7} cm{sup –3} on average. In addition, we detect SO and SO{sub 2} emission arising from a compact (∼3000 AU) molecular core associated with the central young star. The molecular core exhibits a velocity gradient that is perpendicular to the jet-axis, which we interpret as evidence of rotation. The set of observations toward G345.4938+01.4677 are consistent with it being a young high-mass star associated with a slow photo-ionized wind.

  20. Patient-specific three-dimensional explant spheroids derived from human nasal airway epithelium

    DEFF Research Database (Denmark)

    Marthin, June Kehlet; Stevens, Elizabeth Munkebjerg; Larsen, Lars Allan

    2017-01-01

    BACKGROUND: Three-dimensional explant spheroid formation is an ex vivo technique previously used in studies of airway epithelial ion and water transport. Explanted cells and sheets of nasal epithelium form fully differentiated spheroids enclosing a partly fluid-filled lumen with the ciliated apical...... surface facing the outside and accessible for analysis of ciliary function. METHODS: We performed a two-group comparison study of ciliary beat pattern and ciliary beat frequency in spheroids derived from nasal airway epithelium in patients with primary ciliary dyskinesia (PCD) and in healthy controls...... in the investigation of pathophysiological aspects and drug effects in human nasal airway epithelium....