WorldWideScience

Sample records for extremely poor escapement

  1. Extreme hydrodynamic atmospheric loss near the critical thermal escape regime

    CERN Document Server

    Erkaev, N V; Odert, P; Kulikov, Yu N; Kislyakova, K G

    2015-01-01

    By considering martian-like planetary embryos inside the habitable zone of solar-like stars we study the behavior of the hydrodynamic atmospheric escape of hydrogen for small values of the Jeans escape parameter $\\beta < 3$, near the base of the thermosphere, that is defined as a ratio of the gravitational and thermal energy. Our study is based on a 1-D hydrodynamic upper atmosphere model that calculates the volume heating rate in a hydrogen dominated thermosphere due to the absorption of the stellar soft X-ray and extreme ultraviolet (XUV) flux. We find that when the $\\beta$ value near the mesopause/homopause level exceeds a critical value of $\\sim$2.5, there exists a steady hydrodynamic solution with a smooth transition from subsonic to supersonic flow. For a fixed XUV flux, the escape rate of the upper atmosphere is an increasing function of the temperature at the lower boundary. Our model results indicate a crucial enhancement of the atmospheric escape rate, when the Jeans escape parameter $\\beta$ decr...

  2. Review of One Illness Away: Why People Become Poor and How They Escape Poverty

    OpenAIRE

    Afia B. Yamoah

    2011-01-01

    Afia B. Yamoah reviews One Illness Away: Why People Become Poor and How They Escape Poverty, by Anirudh Krishna. Krishna argues that poverty policy needs to address reasons why people become poor and how they can escape poverty.

  3. EXTREMELY METAL-POOR GALAXIES: THE ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Filho, M. E. [Universidad de Las Palmas de Gran Canaria–Universidad de La Laguna, CIE Canarias: Tri-Continental Atlantic Campus, Canary Islands (Spain); Almeida, J. Sánchez; Muñoz-Tuñón, C. [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Nuza, S. E.; Kitaura, F.; Heß, S., E-mail: mfilho@astro.up.pt [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany)

    2015-04-01

    We have analyzed bibliographical observational data and theoretical predictions, in order to probe the environment in which extremely metal-poor dwarf galaxies (XMPs) reside. We have assessed the H i component and its relation to the optical galaxy, the cosmic web type (voids, sheets, filaments and knots), the overdensity parameter and analyzed the nearest galaxy neighbors. The aim is to understand the role of interactions and cosmological accretion flows in the XMP observational properties, particularly the triggering and feeding of the star formation. We find that XMPs behave similarly to Blue Compact Dwarfs; they preferably populate low-density environments in the local universe: ∼60% occupy underdense regions, and ∼75% reside in voids and sheets. This is more extreme than the distribution of irregular galaxies, and in contrast to those regions preferred by elliptical galaxies (knots and filaments). We further find results consistent with previous observations; while the environment does determine the fraction of a certain galaxy type, it does not determine the overall observational properties. With the exception of five documented cases (four sources with companions and one recent merger), XMPs do not generally show signatures of major mergers and interactions; we find only one XMP with a companion galaxy within a distance of 100 kpc, and the H i gas in XMPs is typically well-behaved, demonstrating asymmetries mostly in the outskirts. We conclude that metal-poor accretion flows may be driving the XMP evolution. Such cosmological accretion could explain all the major XMP observational properties: isolation, lack of interaction/merger signatures, asymmetric optical morphology, large amounts of unsettled, metal-poor H i gas, metallicity inhomogeneities, and large specific star formation.

  4. Toward ab initio extremely metal poor stars

    CERN Document Server

    Ritter, Jeremy S; Milosavljevic, Milos; Bromm, Volker

    2016-01-01

    Extremely metal poor stars have been the focus of much recent attention owing to the expectation that their chemical abundances can shed light on the metal and dust yields of the earliest supernovae. We present our most realistic simulation to date of the astrophysical pathway to the first metal enriched stars. We simulate the radiative and supernova hydrodynamic feedback of a 60 Msun Population III star starting from cosmological initial conditions realizing Gaussian density fluctuations. We follow the gravitational hydrodynamics of the supernova remnant at high spatial resolution through its freely-expanding, adiabatic, and radiative phases, until gas, now metal-enriched, has resumed runaway gravitational collapse. Our findings are surprising: while the Population III progenitor exploded with a low energy of 10^51 erg and injected an ample metal mass of 6 Msun, the first cloud to collapse after the supernova explosion is a dense surviving primordial cloud on which the supernova blastwave deposited metals on...

  5. A New Type of Extremely Metal Poor Star

    CERN Document Server

    Cohen, J G; Christlieb, N; Shectman, S; Thompson, I; Melendez, J; Reimers, L W D; Cohen, Judith G.; William, Andrew Mc; Christlieb, Norbert; Shectman, Stephen; Thompson, Ian; Melendez, Jorge; Reimers, Lutz Wisotzki & Dieter

    2007-01-01

    We present an abundance analysis for the extremely metal poor star HE1424-0241 based on high dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ~ -4.0 dex. Relative to Fe, HE1424-0241 has normal Mg, but it shows a very large deficiency of Si, with epsilon(Si)/epsilon(Fe) ~ 1/10 and epsilon(Si)/epsilon(Mg) ~ 1/25 that of all previously known extremely metal poor giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNII contributing to the chemical inventory of HE1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE1424-0241 shows a deficiency of the explosive alpha-burning elements Si, Ca and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic...

  6. Spatially resolved dust emission of extremely metal-poor galaxies

    OpenAIRE

    Zhou, Luwenjia; Shi, Yong; Diaz-Santos, Taino; Armus, Lee; Helou, George; Stierwalt, Sabrina; Li, Aigen

    2016-01-01

    We present infrared (IR) spectral energy distributions (SEDs) of individual star-forming regions in four extremely metal-poor (EMP) galaxies with metallicity Z ≲ Z_⊙/10 as observed by the Herschel Space Observatory. With the good wavelength coverage of the SED, it is found that these EMP star-forming regions show distinct SED shapes as compared to those of grand design Spirals and higher metallicity dwarfs: they have on average much higher f_(70μm)/f_(160 μm) ratios at a given f_(160 μm)/f_(2...

  7. Supernova Nucleosynthesis and Extremely Metal-Poor Stars

    CERN Document Server

    Tominaga, Nozomu; Maeda, Keiichi; Iwamoto, Nobuyuki; Nomoto, Ken'ichi

    2008-01-01

    We investigate hydrodynamical and nucleosynthetic properties of the jet-induced explosion of a population III $40M_\\odot$ star and compare the abundance patterns of the yields with those of the metal-poor stars. We conclude that (1) the ejection of Fe-peak products and the fallback of unprocessed materials can account for the abundance patterns of the extremely metal-poor (EMP) stars and that (2) the jet-induced explosion with different energy deposition rates can explain the diversity of the abundance patterns of the metal-poor stars. Furthermore, the abundance distribution after the explosion and the angular dependence of the yield are shown for the models with high and low energy deposition rates $\\dot{E}_{\\rm dep}=120\\times10^{51} {\\rm ergs s^{-1}}$ and $1.5\\times10^{51} {\\rm ergs s^{-1}}$. We also find that the peculiar abundance pattern of a Si-deficient metal-poor star HE 1424--0241 can be reproduced by the angle-delimited yield for $\\theta=30^\\circ-35^\\circ$ of the model with $\\dot{E}_{\\rm dep}=120\\ti...

  8. Extremely metal-poor stars in SDSS fields

    CERN Document Server

    Bonifacio, Piercarlo; François, Patrick; Sbordone, Luca; Ludwig, Hans-G; Spite, Monique; Molaro, Paolo; Spite, François; Cayrel, Roger; Hammer, François; Hill, Vanessa; Nonino, Mario; Randich, Sofia; Stelzer, Beate; Zaggia, Simone

    2011-01-01

    Some insight on the first generation of stars can be obtained from the chemical composition of their direct descendants, extremely metal-poor stars (EMP), with metallicity less than or equal to 1/1000 of the solar metalllicity. Such stars are exceedingly rare, the most successful surveys, for this purpose, have so far provided only about 100 stars with 1/1000 the solar metallicity and 4 stars with about 1/10000 of the solar metallicity. The Sloan Digital Sky Survey has the potential to provide a large number of candidates of extremely low metallicity. X-Shooter has the unique capability of performing the necessary follow-up spectroscopy providing accurate metallicities and abundance ratios for several elements (Mg, Al, Ca, Ti, Cr, Sr,...) for EMP candidates. We here report on the results for the first two stars observed in the course of our franco-italian X-Shooter GTO. The two stars were targeted to be of metallicity around -3.0, the analysis of the X-Shooter spectra showed them to be of metallicity around -...

  9. Chemical abundances of distant extremely metal-poor unevolved stars

    CERN Document Server

    Bonifacio, P; Caffau, E; Ludwig, H -G; Spite, M; Hernández, J I González; Behara, N T

    2012-01-01

    Aims: The purpose of our study is to determine the chemical composition of a sample of 16 candidate Extremely Metal-Poor (EMP) dwarf stars, extracted from the Sloan Digital Sky Survey (SDSS). There are two main purposes: in the first place to verify the reliability of the metallicity estimates derived from the SDSS spectra; in the second place to see if the abundance trends found for the brighter nearer stars studied previously also hold for this sample of fainter, more distant stars. Methods: We used the UVES at the VLT to obtain high-resolution spectra of the programme stars. The abundances were determined by an automatic analysis with the MyGIsFOS code, with the exception of lithium, for which the abundances were determined from the measured equivalent widths of the Li I resonance doublet. Results: All candidates are confirmed to be EMP stars, with [Fe/H]<= -3.0. The chemical composition of the sample of stars is similar to that of brighter and nearer samples. We measured the lithium abundance for 12 st...

  10. Spatially resolved dust emission of extremely metal poor galaxies

    CERN Document Server

    Zhou, Luwenjia; Diaz-Santos, Taino; Armus, Lee; Helou, George; Stierwalt, Sabrina; Li, Aigen

    2016-01-01

    We present infrared (IR) spectral energy distributions (SEDs) of individual star-forming regions in four extremely metal poor (EMP) galaxies with metallicity Z around Zsun/10 as observed by the Herschel Space Observatory. With the good wavelength coverage of the SED, it is found that these EMP star-forming regions show distinct SED shapes as compared to those of grand design Spirals and higher metallicity dwarfs: they have on average much higher f70um/f160um ratios at a given f160um/f250um ratio; single modified black-body (MBB) fittings to the SED at \\lambda >= 100 um still reveal higher dust temperatures and lower emissivity indices compared to that of Spirals, while two MBB fittings to the full SED with a fixed emissivity index (beta = 2) show that even at 100 um about half of the emission comes from warm (50 K) dust, in contrast to the cold (~20 K) dust component. Our spatially resolved images further reveal that the far-IR colors including f70um/f160um, f160um/f250um and f250um/f350um are all related to ...

  11. Inefficient star formation in extremely metal poor galaxies.

    Science.gov (United States)

    Shi, Yong; Armus, Lee; Helou, George; Stierwalt, Sabrina; Gao, Yu; Wang, Junzhi; Zhang, Zhi-Yu; Gu, Qiusheng

    2014-10-16

    The first galaxies contain stars born out of gas with few or no 'metals' (that is, elements heavier than helium). The lack of metals is expected to inhibit efficient gas cooling and star formation, but this effect has yet to be observed in galaxies with an oxygen abundance (relative to hydrogen) below a tenth of that of the Sun. Extremely metal poor nearby galaxies may be our best local laboratories for studying in detail the conditions that prevailed in low metallicity galaxies at early epochs. Carbon monoxide emission is unreliable as a tracer of gas at low metallicities, and while dust has been used to trace gas in low-metallicity galaxies, low spatial resolution in the far-infrared has typically led to large uncertainties. Here we report spatially resolved infrared observations of two galaxies with oxygen abundances below ten per cent of the solar value, and show that stars formed very inefficiently in seven star-forming clumps in these galaxies. The efficiencies are less than a tenth of those found in normal, metal rich galaxies today, suggesting that star formation may have been very inefficient in the early Universe.

  12. Spatially resolved dust emission of extremely metal-poor galaxies*

    Science.gov (United States)

    Zhou, Luwenjia; Shi, Yong; Diaz-Santos, Taino; Armus, Lee; Helou, George; Stierwalt, Sabrina; Li, Aigen

    2016-05-01

    We present infrared (IR) spectral energy distributions (SEDs) of individual star-forming regions in four extremely metal-poor (EMP) galaxies with metallicity Z ≲ Z⊙/10 as observed by the Herschel Space Observatory. With the good wavelength coverage of the SED, it is found that these EMP star-forming regions show distinct SED shapes as compared to those of grand design Spirals and higher metallicity dwarfs: they have on average much higher f70μm/f160 μm ratios at a given f160 μm/f250 μm ratio; single modified blackbody (MBB) fittings to the SED at λ ≥ 100 μm still reveal higher dust temperatures and lower emissivity indices compared to that of Spirals, while two MBB fittings to the full SED with a fixed emissivity index (β = 2) show that even at 100 μm, about half of the emission comes from warm (50 K) dust, in contrast to the cold (˜20 K) dust component. Our spatially resolved images furthermore reveal that the far-IR colours including f70 μm/f160 μm, f160 μm/f250 μm and f250 μm/f350 μm are all related to the surface densities of young stars as traced by far-UV, 24 μm and star formation rates (SFRs), but not to the stellar mass surface densities. This suggests that the dust emitting at wavelengths from 70 to 350 μm is primarily heated by radiation from young stars.

  13. Kinematics of Extremely Metal-poor Galaxies: Evidence for Stellar Feedback

    Science.gov (United States)

    Olmo-García, A.; Sánchez Almeida, J.; Muñoz-Tuñón, C.; Filho, M. E.; Elmegreen, B. G.; Elmegreen, D. M.; Pérez-Montero, E.; Méndez-Abreu, J.

    2017-01-01

    The extremely metal-poor (XMP) galaxies analyzed in a previous paper have large star-forming regions with a metallicity lower than the rest of the galaxy. Such a chemical inhomogeneity reveals the external origin of the metal-poor gas fueling star formation, possibly indicating accretion from the cosmic web. This paper studies the kinematic properties of the ionized gas in these galaxies. Most XMPs have a rotation velocity around a few tens of km s‑1. The star-forming regions appear to move coherently. The velocity is constant within each region, and the velocity dispersion sometimes increases within the star-forming clump toward the galaxy midpoint, suggesting inspiral motion toward the galaxy center. Other regions present a local maximum in velocity dispersion at their center, suggesting a moderate global expansion. The Hα line wings show a number of faint emission features with amplitudes around a few per cent of the main Hα component, and wavelength shifts between 100 and 400 km s‑1. The components are often paired, so that red and blue emission features with similar amplitudes and shifts appear simultaneously. Assuming the faint emission to be produced by expanding shell-like structures, the inferred mass loading factor (mass loss rate divided by star formation rate) exceeds 10. Since the expansion velocity far exceeds the rotational and turbulent velocities, the gas may eventually escape from the galaxy disk. The observed motions involve energies consistent with the kinetic energy released by individual core-collapse supernovae. Alternative explanations for the faint emission have been considered and discarded.

  14. Sputtering at Mars: MAVEN observations of precipitating and escaping oxygen during nominal and extreme conditions

    Science.gov (United States)

    Curry, Shannon; Luhmann, Janet; Dong, Chuanfei; Ma, Yingjuan; Leblanc, Francois; Modolo, Ronan; Brain, David; Gruesbeck, Jacob; Hara, Takuya; Halekas, Jasper; Dong, Yaxue; Williamson, Hayley N.; Johnson, Robert E.; McFadden, James; Espley, Jared R.; Mitchell, David; Connerney, Jack; Eparvier, Frank; Lillis, Robert J.; Jakosky, Bruce

    2016-10-01

    Sputtering is believed to be one of the dominant escape mechanisms during the early epochs of our solar system when the solar activity and EUV intensities were much higher than the present day. Mars lacks a global dynamo magnetic field, which creates a scenario where the solar wind directly interacts with the upper atmosphere and newly created ions can be picked up and swept away by the background convection electric field. These pick-up ions can directly escape or precipitate back into the atmosphere and induce atmospheric sputtering of neutrals.The MAVEN spacecraft has observed the Mars upper atmosphere, ionosphere, magnetic topology and interactions with the Sun and solar wind during numerous Interplanetary Coronal Mass Ejection (ICME) impacts spanning from March 2015 to June 2016. ICMEs are associated with enhanced solar wind velocities, densities and magnetic field strength, and often drive heavy ion precipitation at much higher rates than during nominal conditions. Thus, ICMEs provide a unique environment for observing sputtering. We will compare MAVEN observations of heavy ion precipitation during nominal conditions as well as during ICMEs. Additionally, we will present global MHD and test particle simulations of the ICMEs in order to calculate sputtering escape rates for oxygen. Finally, we will use the observed and modeled sputtering escape rates to provide an initial estimate of the total sputtered atmospheric escape from Mars over billions of years.

  15. Extremely metal-poor star candidates in the SDSS

    Institute of Scientific and Technical Information of China (English)

    Si-Yao Xu; Hua-Wei Zhang; Xiao-Wei Liu

    2013-01-01

    For a sample of metal-poor stars (-3.3 ≤ [Fe/H] ≤-2.2) that have highresolution spectroscopic abundance determinations,we have measured equivalent widths of the Ca Ⅱ K,Mg Ⅰ b and near-infrared Ca Ⅱ triplet lines using low-resolution spectra from the Sloan Digital Sky Survey (SDSS),calculated effective temperatures from (g-z)o color,deduced stellar surface gravities by fitting stellar isochrones,and determined metallicities based on the aforementioned quantities.Metallicities thus derived from the Ca Ⅱ K line are in much better agreement with the results determined from high-resolution spectra than the values given in the SDSS Data Release 7.The metallicities derived from the Mg Ⅰ b lines have a large dispersion owing to the large measurement errors,whereas those deduced from the Ca Ⅱ triplet lines are too high due to both non-local thermodynamical equilibrium (NLTE) effects and measurement errors.Abundances after correction for the NLTE effect for the Mg Ⅰ b lines and Ca Ⅱ triplet lines are also presented.Following this method,we have identified six candidates of ultra-metal-poor stars with [Fe/H] ~-4.0 from a sample of 166 metal-poor star candidates.One of them,SDSS J102915+172927,was recently confirmed to be an ultra-metal-poor ([Fe/H] <-4.0) star with the lowest metallicity ever measured.Follow-up high-resolution spectroscopy for the other five ultra-metal-poor stars in our sample will therefore be of great interest.

  16. Molecular bands in extremely metal-poor stars. Granulation effects

    CERN Document Server

    Bonifacio, Piercarlo; Ludwig, Hans-Günter; Spite, Monique; Plez, Bertrand; Steffen, Matthias; Spite, François

    2013-01-01

    The bands of diatomic molecules are important abundance indicators, especially in metal-poor stars, where they are still measurable in metallicity regimes where the atomic lines of their constituting metallic elements have become vanishingly small. In order to use them for abundance determinations it is imperative to understand the formation of these bands. In this contribution we report on our results obtained using CO5BOLD hydrodynamical simulations. Some effects that are qualitatively different from what found in 1D computations are highlighted. Due to the large number of lines that form the bands, their spectrum synthesis is computationally challenging. We discuss some of the computational strategies we employed to parallelise the computation and possible future developments.

  17. First stars VII. Lithium in extremely metal poor dwarfs

    CERN Document Server

    Bonifacio, P; Sivarani, T; Cayrel, R; Spite, M; Spite, F; Plez, B; Andersen, J; Barbuy, B; Beers, T C; Depagne, E; Hill, V; François, P; Nordström, B; Primas, F

    2006-01-01

    Aims. This study aims to determine the level and constancy of the Spite plateau as definitively as possible from homogeneous high-quality VLT-UVES spectra of 19 of the most metal-poor dwarf stars known. Methods. Our high-resolution (R ~ 43000), high S/N spectra are analysed with OSMARCS 1D LTE model atmospheres and turbospectrum synthetic spectra to determine effective temperatures, surface gravities, and metallicities as well as Li abundances for our stars. Results. Eliminating a cool subgiant and a spectroscopic binary, we find 8 stars to have -3.5 < [Fe/H] < -3.0 and 9 stars with -3.0 < [Fe/H] < -2.5. Our best value for the mean level of the plateau is A(Li) =2.10 +- 0.09. The scatter around the mean is entirely explained by our estimate of the observational error and does not allow for any intrinsic scatter in the Li abundances. In addition, we conclude that a systematic error of the order of 200 K in any of the current temperature scales remains possible. The iron excitation equilibria in our...

  18. Extremely Metal-Poor Star Candidates in the SDSS

    CERN Document Server

    Xu, Siyao; Liu, Xiaowei

    2012-01-01

    For a sample of metal-poor stars (-3.3< [Fe/H] <-2.2) that have high-resolution spectroscopic abundance determinations, we have measured equivalent widths (EW) of the Ca II K, Mg I b and near-infrared (NIR) Ca II triplet lines using low-resolution spectra of the Sloan Digital Sky Survey (SDSS), calculated effective temperatures from (g-z)0 color, deduced stellar surface gravities by fitting stellar isochrones, and determined metallicities based on the aforementioned quantities. Metallicities thus derived from the Ca II K line are in much better agreement with the results determined from high-resolution spectra than the values given in the SDSS Data Release 7 (DR7). The metallicities derived from the Mg I b lines have a large dispersion owing to the large measurement errors, whereas those deduced from the Ca II triplet lines are too high due to both non-local thermodynamical equilibrium (NLTE) effects and measurement errors. Abundances after corrected for the NLTE effect for the Mg I b lines and Ca II tr...

  19. Extremely metal-poor stars in classical dwarf spheroidal galaxies : Fornax, Sculptor, and Sextans

    NARCIS (Netherlands)

    Tafelmeyer, M.; Jablonka, P.; Hill, V.; Shetrone, M.; Tolstoy, E.; Irwin, M. J.; Battaglia, G.; Helmi, A.; Starkenburg, E.; Venn, K. A.; Abel, T.; Francois, P.; Kaufer, A.; North, P.; Primas, F.; Szeifert, T.

    2010-01-01

    We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor, and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to hav

  20. Extremely metal-poor stars in classical dwarf spheroidal galaxies : Fornax, Sculptor, and Sextans

    NARCIS (Netherlands)

    Tafelmeyer, M.; Jablonka, P.; Hill, V.; Shetrone, M.; Tolstoy, E.; Irwin, M. J.; Battaglia, G.; Helmi, A.; Starkenburg, E.; Venn, K. A.; Abel, T.; Francois, P.; Kaufer, A.; North, P.; Primas, F.; Szeifert, T.

    2010-01-01

    We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor, and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to hav

  1. Extremely metal-poor stars in classical dwarf spheroidal galaxies: Fornax, Sculptor and Sextans

    CERN Document Server

    Tafelmeyer, M; Hill, V; Shetrone, M; Tolstoy, E; Irwin, M J; Battaglia, G; Helmi, A; Starkenburg, E; Venn, K A; Abel, T; Francois, P; Kaufer, A; North, P; Primas, F; Szeifert, T

    2010-01-01

    We present the results of a dedicated search for extremely metal-poor stars in the Fornax, Sculptor and Sextans dSphs. Five stars were selected from two earlier VLT/Giraffe and HET/HRS surveys and subsequently followed up at high spectroscopic resolution with VLT/UVES. All of them turned out to have [Fe/H] <= -3 and three stars are below [Fe/H]~-3.5. This constitutes the first evidence that the classical dSphs Fornax and Sextans join Sculptor in containing extremely metal-poor stars and suggests that all of the classical dSphs contain extremely metal-poor stars. One giant in Sculptor at [Fe/H]=-3.96 +- 0.10 is the most metal-poor star ever observed in an external galaxy. We carried out a detailed analysis of the chemical abundances of the alpha, iron peak, and the heavy elements, and we performed a comparison with the Milky Way halo and the ultra faint dwarf stellar populations. Carbon, barium and strontium show distinct features characterized by the early stages of galaxy formation and can constrain the o...

  2. Rest-frame ultraviolet-to-optical spectral characteristics of extremely metal-poor and metal-free galaxies

    CERN Document Server

    Inoue, Akio K

    2011-01-01

    Finding the first generation of galaxies in the early Universe is the greatest step forward for understanding galaxy formation and evolution. For strategic survey of such galaxies and interpretation of the obtained data, this paper presents an ultraviolet-to-optical spectral model of galaxies with a great care of the nebular emission. In particular, we present a machine-readable table of intensities of 119 nebular emission lines from Ly$\\alpha$ to the rest-frame 1 $\\mu$m as a function of metallicity from zero to the Solar one. Based on the spectral model, we present criteria of broad-band colours and equivalent widths of Ly$\\alpha$, He {\\sc ii} $\\lambda1640$, H$\\alpha$, H$\\beta$, [O {\\sc iii}] $\\lambda5007$ to select extremely metal-poor and metal-free galaxies although these criteria have uncertainty caused by the Lyman continuum escape fraction and the star formation duration. The criteria of broad-band colours will be useful to select candidates for spectroscopic follow-up from drop-out galaxies. We propos...

  3. The Extreme Overabundance of Molybdenum in Two Metal-Poor Stars

    CERN Document Server

    Peterson, Ruth C

    2011-01-01

    We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000A. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the neighboring even-Z elements ruthenium and zirconium. Of the several nucleosynthesis scenarios envisioned for the production of nuclei in this mass range in the oldest stars, a high-entropy wind (HEW) acting in a core-collapse supernova seems uniquely capable of the twin aspects of a high molybdenum overproduction confined to a narrow mass range. Whatever the details of the nucleosynthesis mechanism, however, this unusual excess suggests that very few individual nucleosynthesis events were responsible for the synthesis of the light trans-Fe heavy elements in these cases, an unexpected result given that both are only moderately metal-poor.

  4. Rocky Worlds Limited to ˜1.8 Earth Radii by Atmospheric Escape during a Star’s Extreme UV Saturation

    Science.gov (United States)

    Lehmer, Owen R.; Catling, David C.

    2017-08-01

    Recent observations and analysis of low-mass (planets only have radii up to 1.5-2 R ⊕. Two general hypotheses exist for the cause of the dichotomy between rocky and gas-enveloped planets (or possible water worlds): either low-mass planets do not necessarily form thick atmospheres of a few wt.%, or the thick atmospheres on these planets easily escape, driven by X-ray and extreme ultraviolet (XUV) emissions from young parent stars. Here, we show that a cutoff between rocky and gas-enveloped planets due to hydrodynamic escape is most likely to occur at a mean radius of 1.76 ± 0.38 (2σ) R ⊕ around Sun-like stars. We examine the limit in rocky planet radii predicted by hydrodynamic escape across a wide range of possible model inputs, using 10,000 parameter combinations drawn randomly from plausible parameter ranges. We find a cutoff between rocky and gas-enveloped planets that agrees with the observed cutoff. The large cross-section available for XUV absorption in the extremely distended primitive atmospheres of low-mass planets results in complete loss of atmospheres during the ˜100 Myr phase of stellar XUV saturation. In contrast, more-massive planets have less-distended atmospheres and less escape, and so retain thick atmospheres through XUV saturation—and then indefinitely as the XUV and escape fluxes drop over time. The agreement between our model and exoplanet data leads us to conclude that hydrodynamic escape plausibly explains the observed upper limit on rocky planet size and few planets (a “valley”, or “radius gap”) in the 1.5-2 R ⊕ range.

  5. Poverty Reduction for Extremely Poor Households of Malang City by the Implementation of Program Keluarga Harapan

    Directory of Open Access Journals (Sweden)

    Wimmy Haliim

    2016-11-01

    Full Text Available This research is based on the low access of poor families to basic education and health care in Malang City that have an impact on social welfare and poverty problem. To overcome these problems, Ministry of Social Affairs of the Republic of Indonesia through Malang City Government and Social Department of Malang City implements Program Keluarga Harapan (PKH in the form of conditional cash transfers to the Extremely Poor Households (RTSM. The result showed that the implementation of PKH has been implemented properly and according to the procedure and the number of RTSM recipients of PKH from year to year has decreased. Nevertheless, this program implementation does not significantly impact the number of poor people in the city of Malang in general.

  6. Lithium abundances in extremely metal-poor turn-off stars

    CERN Document Server

    Sbordone, L; Caffau, E

    2012-01-01

    We discuss the current status of the sample of Lithium abundances in extremely metal poor (EMP) turn-off (TO) stars collected by our group, and compare it with the available literature results. In the last years, evidences have accumulated of a progressive disruption of the Spite plateau in stars of extremely low metallicity. What appears to be a flat, thin plateau above [Fe/H]\\sim-2.8 turns, at lower metallicities, into a broader distribution for which the plateau level constitutes the upper limit, but more and more stars show lower Li abundances. The sample we have collected currently counts abundances or upper limits for 44 EMP TO stars between [Fe/H]=-2.5 and -3.5, plus the ultra-metal poor star SDSS J102915+172927 at [Fe/H]=-4.9. The "meltdown" of the Spite plateau is quite evident and, at the current status of the sample, does not appear to be restricted to the cool end of the effective temperature distribution. SDSS J102915+172927 displays an extreme Li depletion that contrasts with its otherwise quite...

  7. S-process in low-mass extremely metal-poor stars

    CERN Document Server

    Cruz, Monique A; Weiss, Achim

    2013-01-01

    Extremely metal-poor low-mass stars experience an ingestion of protons into the helium-rich layer during the core He-flash, resulting in the production of neutrons through the reactions ^{12}C(p,\\gamma)^{13}N(\\beta)^{13}C(\\alpha,n)^{16}O. This is a potential site for the production of s-process elements in extremely metal-poor stars not occurring in more metal-rich counterparts. Observationally, the signatures of s-process elements in the two most iron deficient stars observed to date, HE1327-2326 & HE0107-5240, still await for an explanation. We investigate the possibility that low-mass EMP stars could be the source of s-process elements observed in extremely iron deficient stars, either as a result of self-enrichment or in a binary scenario as the consequence of a mass transfer episode. We present evolutionary and post-processing s-process calculations of a 1Msun stellar model with metallicities Z=0, 10^{-8} and 10^{-7}. We assess the sensitivity of nucleosynthesis results to uncertainties in the input ...

  8. Oxygen Overabundance in the Extremely Iron-Poor Star CS29498-043

    CERN Document Server

    Aoki, W; Ryan, S G; Beers, T C; Christlieb, N; Tsangarides, S A; Ando, H; Aoki, Wako; Norris, John E.; Ryan, Sean G.; Beers, Timothy C.; Christlieb, Norbert; Tsangarides, Stelios; Ando, Hiroyasu

    2004-01-01

    An abundance analysis for the carbon-enhanced, extremely iron-poor ([Fe/H] -3.5) star CS29498-043 has been obtained using new high-resolution, high signal-to-noise spectra from the Subaru Telescope. The [O I] forbidden line at 6300A and the O I triplet feature at 7771-7776A are both clearly detected. The overabundance of oxygen is significant ([O/Fe]>2). In addition, Na, Co, and Ni abundances have been newly measured. The abundance pattern from C to Ni of this object is quite similar to that of CS 22949--037, another extremely metal-poor star with large excesses of C, N, O, and the alpha-elements. The abundance patterns of these two stars suggest the existence of supernovae progenitors that ejected relatively little material fromtheir iron cores during the very early era of nucleosynthesis in the Galaxy. Themetallicity in these objects, when one includes the elements C, N, and O in the tally of total metals, is not as low as in the most metal-poor stars, suggesting the existence of quite different formation p...

  9. THE ORIGIN OF LOW [α/Fe] RATIOS IN EXTREMELY METAL-POOR STARS

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, Chiaki [School of Physics, Astronomy and Mathematics, Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Ishigaki, Miho N.; Tominaga, Nozomu; Nomoto, Ken' ichi, E-mail: c.kobayashi@herts.ac.uk [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan)

    2014-04-10

    We show that the low ratios of α elements (Mg, Si, and Ca) to Fe recently found for a small fraction of extremely metal-poor stars can be naturally explained with the nucleosynthesis yields of core-collapse supernovae, i.e., 13-25 M {sub ☉} supernovae, or hypernovae. For the case without carbon enhancement, the ejected iron mass is normal, consistent with observed light curves and spectra of nearby supernovae. On the other hand, the carbon enhancement requires much smaller iron production, and the low [α/Fe] of carbon-enhanced metal-poor stars can also be reproduced with 13-25 M {sub ☉} faint supernovae or faint hypernovae. Iron-peak element abundances, in particular Zn abundances, are important to put further constraints on the enrichment sources from galactic archaeology surveys.

  10. WHT follow-up observations of extremely metal-poor stars identified from SDSS and LAMOST

    Science.gov (United States)

    Aguado, D. S.; González Hernández, J. I.; Allende Prieto, C.; Rebolo, R.

    2017-09-01

    Aims: We have identified several tens of extremely metal-poor star candidates from SDSS and LAMOST, which we follow up with the 4.2 m William Herschel Telescope (WHT) telescope to confirm their metallicity. Methods: We followed a robust two-step methodology. We first analyzed the SDSS and LAMOST spectra. A first set of stellar parameters was derived from these spectra with the FERRE code, taking advantage of the continuum shape to determine the atmospheric parameters, in particular, the effective temperature. Second, we selected interesting targets for follow-up observations, some of them with very low-quality SDSS or LAMOST data. We then obtained and analyzed higher-quality medium-resolution spectra obtained with the Intermediate dispersion Spectrograph and Imaging System (ISIS) on the WHT to arrive at a second more reliable set of atmospheric parameters. This allowed us to derive the metallicity with accuracy, and we confirm the extremely metal-poor nature in most cases. In this second step we also employed FERRE, but we took a running mean to normalize both the observed and the synthetic spectra, and therefore the final parameters do not rely on having an accurate flux calibration or continuum placement. We have analyzed with the same tools and following the same procedure six well-known metal-poor stars, five of them at [Fe/H] http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/605/A40

  11. Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way

    CERN Document Server

    Howes, L M; Asplund, M; Keller, S C; Yong, D; Nataf, D M; Poleski, R; Lind, K; Kobayashi, C; Owen, C I; Ness, M; Bessell, M S; Da Costa, G S; Schmidt, B P; Tisserand, P; Udalski, A; Szymański, M K; Soszyński, I; Pietrzyński, G; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Skowron, J; Kozłowski, S; Mróz, P

    2015-01-01

    The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that the most metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through...

  12. Extremely metal-poor stars from the cosmic dawn in the bulge of the Milky Way.

    Science.gov (United States)

    Howes, L M; Casey, A R; Asplund, M; Keller, S C; Yong, D; Nataf, D M; Poleski, R; Lind, K; Kobayashi, C; Owen, C I; Ness, M; Bessell, M S; Da Costa, G S; Schmidt, B P; Tisserand, P; Udalski, A; Szymański, M K; Soszyński, I; Pietrzyński, G; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Skowron, J; Kozłowski, S; Mróz, P

    2015-11-26

    The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.

  13. The Kennicutt-Schmidt Relation in Extremely Metal-Poor Dwarf Galaxies

    CERN Document Server

    Filho, M E; Amorín, R; Muñoz-Tuñón, C; Elmegreen, B G; Elmegreen, D M

    2016-01-01

    The Kennicutt-Schmidt (KS) relation between the gas mass and star formation rate (SFR) describes the star formation regulation in disk galaxies. It is a function of gas metallicity, but the low metallicity regime of the KS diagram is poorly sampled. We have analyzed data for a representative set of extremely metal-poor galaxies (XMPs), as well as auxiliary data, and compared these to empirical and theoretical predictions. The majority of the XMPs possess high specific SFRs, similar to high redshift star-forming galaxies. On the KS plot, the XMP HI data occupy the same region as dwarfs, and extend the relation for low surface brightness galaxies. Considering the HI gas alone, a considerable fraction of the XMPs already fall off the KS law. Significant quantities of 'dark' H$_2$ mass (i.e., not traced by CO) would imply that XMPs possess low star formation efficiencies (SFE$_{\\rm gas}$). Low SFE$_{\\rm gas}$ in XMPs may be the result of the metal-poor nature of the HI gas. Alternatively, the HI reservoir may be ...

  14. Detailed abundances in extremely metal poor dwarf stars extracted from SDSS

    CERN Document Server

    Sbordone, Luca; Caffau, Elisabetta; Ludwig, Hans-Gunther

    2012-01-01

    We report on the result of an ongoing campaign to determine chemical abundances in extremely metal poor (EMP) turn-off (TO) stars selected from the Sloan Digital Sky Survey (SDSS) low resolution spectra. This contribution focuses principally on the largest part of the sample (18 stars out of 29), observed with UVES@VLT and analyzed by means of the automatic abundance analysis code MyGIsFOS to derive atmosphere parameters and detailed compositions. The most significant findings include i) the detection of a C-rich, strongly Mg-enhanced star ([Mg/Fe]=1.45); ii) a group of Mn-rich stars ([Mn/Fe]>-0.4); iii) a group of Ni-rich stars ([Ni/Fe]>0.2). Li is measured in twelve stars, while for three upper limits are derived.

  15. SBS 1150+599A an extremely oxygen-poor planetary nebula in the Galactic halo?

    CERN Document Server

    Tovmassian, G H; Chavushyan, V H; Zharikov, S V; Gutíerrez, C; Prada, F

    2001-01-01

    We report results of a spectrophotometric study of SBS 1150+599A and discuss the nature of this object based upon our data. Our study shows that SBS 1150+599A is most probably a planetary nebula located in the Galactic halo and not a cataclysmic variable as originally proposed by the authors of the Second Byurakan Survey from low resolution spectroscopy. We have further elaborated on the properties of SBS 1150+599A (now becoming PN G135.9+55.9) with tools used for planetary nebula analysis. Our photoionization models show that, in order to match the observational constraints, the oxygen abundance in the nebula is probably extremely low, around 1/500 solar, which is one order of magnitude lower than the most oxygen-poor planetary nebulae known so far. This finding has strong implications on our understanding of the formation of planetary nebulae and of the evolution of the Galactic halo.

  16. Early-Age Evolution of the Milky Way Related by Extremely Metal-Poor Stars

    CERN Document Server

    Komiya, Yutaka; Fujimoto, Masayuki Y

    2009-01-01

    We exploit the recent observations of extremely metal-poor (EMP) stars in the Galactic halo and investigate the constraints on the IMF of the stellar population that left these low-mass survivors of [Fe/H]<-2.5 and the chemical evolution that they took part in. A high-mass IMF with the typical mass~10Msun and the overwhelming contribution of low-mass members of binaries to the EMP survivors are derived from the statistics of carbon-enriched EMP stars with and without the enhancement of s-process elements (Komiya et al. 2007). We first examine the analysis to confirm their results for various assumptions on the mass-ratio distribution function. As compared with the uniform distribution, the increase or decrease function of the mass ratio gives a higher- or lower-mass IMF, and a lower-mass IMF results for the independent distribution with the both members in the same IMF, but the derived ranges of typical mass differ less than by a factor of two and overlap for the extreme cases. Furthermore, we prove that t...

  17. First stars XIII. Two extremely metal-poor RR Lyrae stars?

    CERN Document Server

    Hansen, C J; Bonifacio, P; Spite, M; Andersen, J; Beers, T C; Cayrel, R; Spite, F; Molaro, P; Barbuy, B; Depagne, E; Hill, P Francois V; Plez, B; Sivarani, T

    2011-01-01

    The chemical composition of extremely metal-poor stars (EMP stars; [Fe/H]<~ -3) is a unique tracer of early nucleosynthesis in the Galaxy. As such stars are rare, we wish to find classes of luminous stars which can be studied at high resolution. We aim to determine the detailed chemical composition of the two EMP stars CS30317-056 and CS22881-039, originally thought to be red horizontal-branch (RHB) stars, and compare it to earlier results for EMP stars as well as to nucleosynthesis yields from various supernova (SN) models. In the analysis, we discovered that our targets are in fact the two most metal-poor RR Lyrae stars known. Our detailed abundance analysis, taking into account the variability of the stars, is based on VLT/UVES spectra (R~ 43000) and 1D LTE OSMARCS model atmospheres and synthetic spectra. For comparison with SN models we also estimate NLTE corrections for a number of elements. We derive LTE abundances for the 16 elements O, Na, Mg, Al, Si, S, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Sr and Ba, i...

  18. Abundance Profiling of Extremely Metal-Poor Stars and Supernova Properties in the Early Universe

    CERN Document Server

    Tominaga, Nozomu; Nomoto, Ken'ichi

    2013-01-01

    The first metal enrichment in the universe was made by a supernova (SN) explosion of a population (Pop) III star and chemical evolution of the universe is recorded in abundance patterns of extremely metal-poor (EMP) stars. Increasing number of the EMP stars are now being discovered. This allows us to statistically constrain properties of SNe of Pop III stars (Pop III SNe). We investigate the properties of Pop III SNe by comparing their nucleosynthetic yields with the abundance patterns of the EMP stars. We focus on the most metal-poor stars with [Fe/H] $\\lsim-3.5$ and present Pop III SN models that reproduce well their individual abundance patterns. From these models we derive relations between abundance ratios and properties of Pop III SNe: [(C+N)/Fe] vs. an ejected Fe mass, and [(C+N)/Mg] vs. a remnant mass. Using fitting formulae, distribution of the abundance ratios of EMP stars is converted to those of the properties of Pop III SNe, which can be compared with SNe in the present day. Large samples of EMP ...

  19. Lithium Abundances of Extremely Metal-Poor Turn-off Stars

    CERN Document Server

    Aoki, Wako; Beers, Timothy C; Christlieb, Norbert; Inoue, Susumu; Perez, Ana E Garcia; Norris, John E; Carollo, Daniela

    2009-01-01

    We have determined Li abundances for eleven metal-poor turn-off stars, among which eight have [Fe/H]<-3, based on LTE analyses of high-resolution spectra obtained with the HDS on the Subaru telescope. The Li abundances for four of these eight stars are determined for the first time by this study. Effective temperatures are determined by a profile analysis of H-alpha and H-beta. While seven stars have Li abundances as high as the Spite Plateau value, the remaining four objects with [Fe/H] <-3 have A(Li)=log(Li/H)+12 ~< 2.0, confirming the existence of extremely metal-poor turn-off stars having low Li abundances, as reported by previous work. The average of the Li abundances for stars with [Fe/H]<-3 is lower by 0.2 dex than that of the stars with higher metallicity. No clear constraint on the metallicity dependence or scatter of the Li abundances is derived from our measurements for the stars with [Fe/H]<-3. Correlations of the Li abundance with effective temperatures, with abundances of Na, Mg a...

  20. Chemical Abundance Analysis of the Extremely Metal-Poor Star HE 1300+0157

    CERN Document Server

    Frebel, A; Aoki, W; Honda, S; Bessell, M S; Takada-Hidai, M; Beers, T C; Christlieb, N; Frebel, Anna; Norris, John E.; Aoki, Wako; Honda, Satoshi; Bessell, Michael S.; Takada-Hidai, Masahide; Beers, Timothy C.; Christlieb, Norbert

    2006-01-01

    We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with [Fe/H]=-3.9. From a high-resolution, high-S/N Subaru/HDS spectrum we find the star to be enriched in C ([C/Fe]_1D ~ +1.4) and O ([O/Fe]_1D ~ +1.8). With the exception of these species, HE 1300+0157 exhibits an elemental abundance pattern similar to that found in many other very and extremely metal-poor stars. The Li abundance is lower than the Spite-plateau value, in agreement with expectation for its evolutionary status. Of particular interest, no neutron-capture elements are detected in HE 1300+0157. This type of abundance pattern has been found by recent studies in several other metal-poor giants. We suggest that HE 1300+0157 is an unevolved example of this group of stars, which exhibit high C abundances together with low (or absent) abundances of neutron-capture elements. Several potential enrichment scenarios are presented. The low neutron-capture elements, including Sr, Ba, and Pb, suggests that the carbon excess observed...

  1. Kinematics of Extremely Metal-poor Galaxies: Evidence for Stellar Feedback

    CERN Document Server

    Olmo-Garcia, A; Munoz-Tunon, C; Filho, M E; Elmegreen, B G; Elmegreen, D M; Perez-Montero, E; Mendez-Abreu, J

    2016-01-01

    The extremely metal-poor (XMP) galaxies analyzed in a previous paper have large star-forming regions with a metallicity lower than the rest of the galaxy. Such a chemical inhomogeneity reveals the external origin of the metal-poor gas fueling star formation, possibly indicating accretion from the cosmic web. This paper studies the kinematic properties of the ionized gas in these galaxies. Most XMPs have rotation velocity around a few tens of km/s. The star-forming regions appear to move coherently. The velocity is constant within each region, and the velocity dispersion sometimes increases within the star-forming clump towards the galaxy midpoint, suggesting inspiral motion toward the galaxy center. Other regions present a local maximum in velocity dispersion at their center, suggesting a moderate global expansion. The Halpha line wings show a number of faint emission features with amplitudes around a few percent of the main Halpha component, and wavelength shifts between 100 and 400 km/s. The components are ...

  2. On the Dearth of Ultra-faint Extremely Metal-poor Galaxies

    Science.gov (United States)

    Sánchez Almeida, J.; Filho, M. E.; Dalla Vecchia, C.; Skillman, E. D.

    2017-02-01

    Local extremely metal-poor galaxies (XMPs) are of particular astrophysical interest since they allow us to look into physical processes characteristic of the early universe, from the assembly of galaxy disks to the formation of stars in conditions of low metallicity. Given the luminosity–metallicity relationship, all galaxies fainter than Mr ≃ ‑13 are expected to be XMPs. Therefore, XMPs should be common in galaxy surveys. However, they are not common, because several observational biases hamper their detection. This work compares the number of faint XMPs in the SDSS-DR7 spectroscopic survey with the expected number, given the known biases and the observed galaxy luminosity function (LF). The faint end of the LF is poorly constrained observationally, but it determines the expected number of XMPs. Surprisingly, the number of observed faint XMPs (∼10) is overpredicted by our calculation, unless the upturn in the faint end of the LF is not present in the model. The lack of an upturn can be naturally understood if most XMPs are central galaxies in their low-mass dark matter halos, which are highly depleted in baryons due to interaction with the cosmic ultraviolet background and to other physical processes. Our result also suggests that the upturn toward low luminosity of the observed galaxy LF is due to satellite galaxies.

  3. First Stars XIV. Sulphur abundances in extremely metal-poor (EMP) stars

    CERN Document Server

    Spite, Monique; Andrievsky, S M; Korotin, S A; Depagne, E; Spite, F; Bonifacio, P; Ludwig, H -G; Cayrel, R; Francois, P; Hill, V; Plez, B; Andersen, J; Barbuy, B; Beers, T C; Molaro, P; Nordstrom, B; Primas, F

    2010-01-01

    Sulphur is important: the site of its formation is uncertain, and at very low metallicity the trend of [S/Fe] against [Fe/H] is controversial. Below [Fe/H]=-2.0, [S/Fe] remains constant or it decreases with [Fe/H], depending on the author and the multiplet used in the analysis. Moreover, although sulphur is not significantly bound in dust grains in the ISM, it seems to behave differently in DLAs and in old metal-poor stars. We aim to determine precise S abundance in a sample of extremely metal-poor stars taking into account NLTE and 3D effects. NLTE profiles of the lines of the multiplet 1 of SI have been computed using a new model atom for S. We find sulphur in EMP stars to behave like the other alpha-elements, with [S/Fe] remaining approximately constant below [Fe/H]=-3. However, [S/Mg] seems to decrease slightly as a function of [Mg/H]. The overall abundance patterns of O, Na, Mg, Al, S, and K are best matched by the SN model yields by Heger & Woosley. The [S/Zn] ratio in EMP stars is solar, as found a...

  4. Follow-up observations of extremely metal-poor stars identified from SDSS

    CERN Document Server

    Aguado, D S; Hernández, J I González; Carrera, R; Rebolo, Rafael; Shetrone, M; Lambert, D L; Fernández-Alvar, E

    2016-01-01

    The most metal-poor stars in the Milky Way witnessed the early phases of formation of the Galaxy, and have chemical compositions that are close to the pristine mixture from Big Bang nucleosynthesis, polluted by one or few supernovae. Only two dozen stars with ([Fe/H]< -4) are known, and they show a wide range of abundance patterns. It is therefore important to enlarge this sample. We present the first results of an effort to identify new extremely metal-poor stars in the Milky Way halo. Our targets have been selected from low-resolution spectra obtained as part of the Sloan Digital Sky Survey, and followed-up with medium resolution spectroscopy on the 4.2 m William Herschel Telescope and, in a few cases, at high resolution on the the 9.2 m Hobby-Eberly Telescope. Stellar parameters and the abundances of magnesium, calcium, iron, and strontium have been inferred from the spectra using classical model atmospheres. We have also derived carbon abundances from the G band. We find consistency between the metalli...

  5. On the dearth of ultra-faint extremely metal poor galaxies

    CERN Document Server

    Almeida, J Sanchez; Vecchia, C Dalla; Skillman, E D

    2016-01-01

    Local extremely metal-poor (XMP) galaxies are of particular astrophysical interest since they allow us to look into physical processes characteristic of the early Universe, from the assembly of galaxy disks to the formation of stars in conditions of low metallicity. Given the luminosity-metallicity relationship, all galaxies fainter than Mr < -13 are expected to be XMPs. Therefore, XMPs should be common in galaxy surveys. However, they are not, because several observational biases hamper their detection. This work compares the number of faint XMPs in the SDSS-DR7 spectroscopic survey with the expected number, given the known biases and the observed galaxy luminosity function. The faint end of the luminosity function is poorly constrained observationally, but it determines the expected number of XMPs. Surprisingly, the number of observed faint XMPs (around 10) is over-predicted by our calculation, unless the upturn in the faint end of the luminosity function is not present in the model. The lack of an uptur...

  6. THE KENNICUTT–SCHMIDT RELATION IN EXTREMELY METAL-POOR DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Filho, M. E.; Almeida, J. Sánchez; Muñoz-Tuñón, C. [Instituto Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Amorín, R. [National Institute for Astrophysics, Astronomical Observatory of Rome, Via Frascati 33, I-00040 Monteporzio Catone (Rome) (Italy); Elmegreen, B. G. [IBM, T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, NY 10598 (United States); Elmegreen, D. M., E-mail: mfilho@astro.up.pt [Department of Physics and Astronomy, Vassar College, Poughkeepsie, NY 12604 (United States)

    2016-04-01

    The Kennicutt–Schmidt (KS) relation between the gas mass and star formation rate (SFR) describes the star formation regulation in disk galaxies. It is a function of gas metallicity, but the low-metallicity regime of the KS diagram is poorly sampled. We have analyzed data for a representative set of extremely metal-poor galaxies (XMPs), as well as auxiliary data, and compared these to empirical and theoretical predictions. The majority of the XMPs possess high specific SFRs, similar to high-redshift star-forming galaxies. On the KS plot, the XMP H i data occupy the same region as dwarfs and extend the relation for low surface brightness galaxies. Considering the H i gas alone, a considerable fraction of the XMPs already fall off the KS law. Significant quantities of “dark” H{sub 2} mass (i.e., not traced by CO) would imply that XMPs possess low star formation efficiencies (SFE{sub gas}). Low SFE{sub gas} in XMPs may be the result of the metal-poor nature of the H i gas. Alternatively, the H i reservoir may be largely inert, the star formation being dominated by cosmological accretion. Time lags between gas accretion and star formation may also reduce the apparent SFE{sub gas}, as may galaxy winds, which can expel most of the gas into the intergalactic medium. Hence, on global scales, XMPs could be H i-dominated, high-specific-SFR (≳10{sup −10} yr{sup −1}), low-SFE{sub gas} (≲10{sup −9} yr{sup −1}) systems, in which the total H i mass is likely not a good predictor of the total H{sub 2} mass, nor of the SFR.

  7. Discovery of a Gas-Rich Companion to the Extremely Metal-Poor Galaxy DDO 68

    CERN Document Server

    Cannon, John M; McQuinn, Kristen B W; Alfvin, Erik D; Bailin, Jeremy; Ford, H Alyson; Girardi, Léo; Hirschauer, Alec S; Janowiecki, Steven; Salzer, John J; Van Sistine, Angela; Dolphin, Andrew; Elson, E C; Koribalski, Baerbel; Marigo, Paola; Rosenberg, Jessica L; Rosenfield, Philip; Skillman, Evan D; Venkatesan, Aparna; Warren, Steven R

    2014-01-01

    We present HI spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only 3% Z$_{\\odot}$, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during a gravitational interaction. Using archival HI spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass (M$_{\\rm HI}$ $=$ 2.8$\\times$10$^{7}$ M$_{\\odot}$), recently star-forming (SFR$_{\\rm FUV}$ $=$ 1.4$\\times$10$^{-3}$ M$_{\\odot}$ yr$^{-1}$, SFR$_{\\rm H\\alpha}$ $<$ 7$\\times$10$^{-5}$ M$_{\\...

  8. The low Sr/Ba ratio on some extremely metal-poor stars

    CERN Document Server

    Spite, M; Bonifacio, P; Caffau, E; François, P; Sbordone, L

    2014-01-01

    It has been noted that, in classical extremely metal-poor (EMP) stars, the abundance ratio of Sr and Ba, is always higher than [Sr/Ba] = -0.5, the value of the solar r-only process; however, a handful of EMP stars have recently been found with a very low Sr/Ba ratio. We try to understand the origin of this anomaly by comparing the abundance pattern of the elements in these stars and in the classical EMP stars. Four stars with very low Sr/Ba ratios were observed and analyzed within LTE approximation through 1D (hydrostatic) model atmosphere, providing homogeneous abundances of nine neutron-capture elements. In CS 22950-173, the only turnoff star of the sample, the Sr/Ba ratio is, in fact, found to be higher than the r-only solar ratio, so the star is discarded. The remaining stars (CS 29493-090, CS 30322-023, HE 305-4520) are cool evolved giants. They do not present a clear carbon enrichment. The abundance patterns of the neutron-capture elements in the three stars are strikingly similar to a theoretical s-pro...

  9. Extremely Metal-Poor Stars and a Hierarchical Chemical Evolution Model

    CERN Document Server

    Komiya, Yutaka

    2011-01-01

    Early phases of the chemical evolution and formation history of extremely metal poor (EMP) stars are investigated using hierarchical galaxy formation models. We build a merger tree of the Galaxy according to the extended Press-Schechter theory. We follow the chemical evolution along the tree, and compare the model results to the metallicity distribution function (MDF) and abundance ratio distribution of the Milky Way halo. We adopt three different initial mass functions (IMFs). In a previous studies, we argue that typical mass of EMP stars should be high-mass(~10Msun) based on studies of binary origin carbon-rich EMP stars. In this study, we show that only the high-mass IMF can explain a observed small number of EMP stars. For relative element abundances, the high-mass IMF and the Salpeter IMF predict similar distributions. We also investigate dependence on nucleosynthetic yields of supernovae (SNe). The theoretical SN yields by Kobayashi et al.(2006) and Chieffi & Limonge (2004) show reasonable agreement...

  10. Leo P: A very low-mass, extremely metal-poor, star-forming galaxy

    Science.gov (United States)

    McQuinn, Kristen B.; Leo P Team

    2017-01-01

    Leo P is a low-luminosity dwarf galaxy just outside the Local Group with properties that make it an ideal probe of galaxy evolution at the faint-end of the luminosity function. Using combined data from 2 Hubble Space Telescope (HST) observing campaigns, the Very Large Array, the Spitzer Space telescope, as well as ground based data, we have constructed a robust evolutionary picture of Leo P. Leo P is one the most metal-poor, gas-rich galaxies ever discovered, has a stellar mass of a 5x105 Msun, comparable gas mass, and a single HII region. The star formation history reconstructed from the resolved stellar populations in Leo P shows it is unquenched, despite its very low mass. Based on the star formation history and metallicity measurements, the galaxy has lost 95% of its oxygen produced via nucleosynthesis, presumably to outflows. The neutral gas in the galaxy shows signs of rotation, although the velocity dispersion is comparable to the rotation velocity. Thus, Leo P bridges the gap between more massive dwarf irregular and less massive dwarf spheroidals on the baryonic Tully-Fisher relation. Furthermore, the galaxy hosts several, extremely dusty AGB candidates which will be probed with new HST and Spitzer observations. If confirmed as AGB stars, these may be our best local proxies for studying chemically unevolved star formation and subsequent dust production in metallicity environments comparable to the early universe.

  11. The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

    Science.gov (United States)

    Schulte-Ladbeck, Regina E.; Hopp, Ulrich; Drozdovsky, Igor O.; Greggio, Laura; Crone, Mary M.

    2002-08-01

    We present deep Hubble Space Telescope (HST) single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters that exhibit red horizontal branches and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but we lack the detection of main-sequence turnoffs that would provide unambiguous proof of ancient (>10 Gyr) stellar generations. Blue horizontal branch stars are above the detection limits but difficult to distinguish from young stars with similar colors and magnitudes. Synthetic color-magnitude diagrams show it is possible to populate the blue horizontal branch in the halo of Leo A. The models also suggest ~50% of the total astrated mass in our pointing to be attributed to an ancient (>10 Gyr) stellar population. We conclude that Leo A started to form stars at least about 9 Gyr ago. Leo A exhibits an extremely low oxygen abundance, only 3% of solar, in its ionized interstellar medium. The existence of old stars in this very oxygen-deficient galaxy illustrates that a low oxygen abundance does not preclude a history of early star formation. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  12. DISCOVERY OF A GAS-RICH COMPANION TO THE EXTREMELY METAL-POOR GALAXY DDO 68

    Energy Technology Data Exchange (ETDEWEB)

    Cannon, John M.; Alfvin, Erik D. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); Johnson, Megan; Koribalski, Baerbel [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, NSW 1710, Epping (Australia); McQuinn, Kristen B. W.; Skillman, Evan D. [Minnesota Institute for Astrophysics, University of Minnesota, Minneapolis, MN 55455 (United States); Bailin, Jeremy [Department of Physics and Astronomy, University of Alabama, P.O. Box 870324, Tuscaloosa, AL 35487-0324 (United States); Ford, H. Alyson [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Girardi, Léo [Osservatorio Astronomico di Padova—INAF, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Hirschauer, Alec S.; Janowiecki, Steven; Salzer, John J.; Van Sistine, Angela [Department of Astronomy, Indiana University, 727 East Third Street, Bloomington, IN 47405 (United States); Dolphin, Andrew [Raytheon Company, 1151 E. Hermans Road, Tucson, AZ 85756 (United States); Elson, E. C. [Astrophysics, Cosmology and Gravity Centre (ACGC), Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Marigo, Paola; Rosenfield, Philip [Dipartimento di Fisica e Astronomia Galileo Galilei, Universitá degli Studi di Padova, Vicolo dell' Osservatorio 3, I-35122 Padova (Italy); Rosenberg, Jessica L. [School of Physics, Astronomy, and Computational Science, George Mason University, Fairfax, VA 22030 (United States); Venkatesan, Aparna [Department of Physics and Astronomy, University of San Francisco, 2130 Fulton Street, San Francisco, CA 94117 (United States); Warren, Steven R., E-mail: jcannon@macalester.edu [Department of Astronomy, University of Maryland, CSS Bldg., Rm. 1024, Stadium Drive, College Park, MD 20742-2421 (United States)

    2014-05-20

    We present H I spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only ∼3% Z {sub ☉}, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during a gravitational interaction. Using archival H I spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass (M{sub H} {sub I} = 2.8 × 10{sup 7} M {sub ☉}), recently star-forming (SFR{sub FUV} = 1.4 × 10{sup –3} M {sub ☉} yr{sup –1}, SFR{sub Hα} < 7 × 10{sup –5} M {sub ☉} yr{sup –1}) companion has the same systemic velocity as DDO 68 (V {sub sys} = 506 km s{sup –1}; D = 12.74 ± 0.27 Mpc) and is located at a projected distance of ∼42 kpc. New H I maps obtained with the 100 m Robert C. Byrd Green Bank Telescope provide evidence that DDO 68 and this companion are gravitationally interacting at the present time. Low surface brightness H I gas forms a bridge between these objects.

  13. Escaping Poverty

    Institute of Scientific and Technical Information of China (English)

    LI LI

    2010-01-01

    @@ While the global economic crisis still threatens to trap tens of millions of people in extreme poverty, alleviation initiatives in China are gaining new momentum and increasing recognition from the international community. From lifting innumerable people out of poverty by satisfying basic needs of food, clothes and shelter during the past three decades, the Chinese Government's antipoverty drive is now to focus more on helping rural poor to start small businesses and guaranteeing access to public services and social welfare.

  14. The s-Process Nucleosynthesis in Extremely Metal-Poor Stars as the Generating Mechanism of Carbon Enhanced Metal-Poor Stars

    CERN Document Server

    Suda, Takuma; Fujimoto, Masayuki Y

    2016-01-01

    The origin of carbon-enhanced metal-poor (CEMP) stars plays a key role in characterising the formation and evolution of the first stars and the Galaxy since the extremely-poor (EMP) stars with [Fe/H] \\leq -2.5 share the common features of carbon enhancement in their surface chemical compositions. The origin of these stars is not yet established due to the controversy of the origin of CEMP stars without the enhancement of s-process element abundances, i.e., so called CEMP-no stars. In this paper, we elaborate the s-process nucleosynthesis in the EMP AGB stars and explore the origin of CEMP stars. We find that the efficiency of the s-process is controlled by O rather than Fe at [Fe/H] \\lesssim -2. We demonstrate that the relative abundances of Sr, Ba, Pb to C are explained in terms of the wind accretion from AGB stars in binary systems.

  15. Two spatial scales in a bleaching event: Corals from the mildest and the most extreme thermal environments escape mortality

    KAUST Repository

    Pineda, Jesús

    2013-07-28

    In summer 2010, a bleaching event decimated the abundant reef flat coral Stylophora pistillata in some areas of the central Red Sea, where a series of coral reefs 100–300 m wide by several kilometers long extends from the coastline to about 20 km offshore. Mortality of corals along the exposed and protected sides of inner (inshore) and mid and outer (offshore) reefs and in situ and satellite sea surface temperatures (SSTs) revealed that the variability in the mortality event corresponded to two spatial scales of temperature variability: 300 m across the reef flat and 20 km across a series of reefs. However, the relationship between coral mortality and habitat thermal severity was opposite at the two scales. SSTs in summer 2010 were similar or increased modestly (0.5°C) in the outer and mid reefs relative to 2009. In the inner reef, 2010 temperatures were 1.4°C above the 2009 seasonal maximum for several weeks. We detected little or no coral mortality in mid and outer reefs. In the inner reef, mortality depended on exposure. Within the inner reef, mortality was modest on the protected (shoreward) side, the most severe thermal environment, with highest overall mean and maximum temperatures. In contrast, acute mortality was observed in the exposed (seaward) side, where temperature fluctuations and upper water temperature values were relatively less extreme. Refuges to thermally induced coral bleaching may include sites where extreme, high-frequency thermal variability may select for coral holobionts preadapted to, and physiologically condition corals to withstand, regional increases in water temperature.

  16. Follow-up observations of extremely metal-poor stars identified from SDSS

    Science.gov (United States)

    Aguado, D. S.; Allende Prieto, C.; González Hernández, J. I.; Carrera, R.; Rebolo, R.; Shetrone, M.; Lambert, D. L.; Fernández-Alvar, E.

    2016-08-01

    Context. The most metal-poor stars in the Milky Way witnessed the early phases of formation of the Galaxy, and have chemical compositions that are close to the pristine mixture from Big Bang nucleosynthesis, polluted by one or few supernovae. Aims: Only two dozen stars with ([Fe/H] cases, at high resolution on the 9.2 m Hobby-Eberly Telescope. Stellar parameters and the abundances of magnesium, calcium, iron, and strontium have been inferred from the spectra using classical model atmospheres. We have also derived carbon abundances from the G band. Results: We find consistency between the metallicities estimated from SDSS and those from new data at the level of 0.3 dex. The analysis of medium resolution data obtained with ISIS on the WHT allows us to refine the metallicities and in some cases measure other elemental abundances. Our sample contains 11 new metal-poor stars with [Fe/H] < -3.0, one of them with an estimated metallicity of [Fe/H] ~ -4.0. We also discuss metallicity discrepancies of some stars in common with previous works in the literature. Only one of these stars is found to be C-enhanced at about [C/Fe] ~ + 1, whereas the other metal-poor stars show C abundances at the level of [C/Fe] ~ + 0.45. Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.The reduced spectra as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/593/A10

  17. Hot, Massive Stars in the Extremely Metal-Poor Galaxy, I Zw 18

    Science.gov (United States)

    Heap, Sara R.; Malumuth, Eliot M.

    2010-01-01

    The carbon-enhanced metal-poor galaxy, I Zw 18, is the Rosetta Stone for understanding galaxies in the early universe by providing constraints on the IMF of massive stars, the role of galaxies in reionization of the universe, mixing of newly synthesized material in the ISM, and gamma-ray bursts at low metallicity, and on the earliest generations of stars producing the observed abundance pattern. We describe these constraints as derived from analyses of HST/COS spectra of I Zw 18 including stellar atmosphere analysis and photo-ionization modeling of both the emission and absorption spectra of the nebular material and interstellar medium.

  18. CARMA CO Observations of Three Extremely Metal-Poor, Star-Forming Galaxies

    CERN Document Server

    Warren, Steven R; Cannon, John M; Bolatto, Alberto D; Adams, Elizabeth A K; Bernstein-Cooper, Elijah Z; Giovanelli, Riccardo; Haynes, Martha P; Herrera-Camus, Rodrigo; Jameson, Katie; McQuinn, Kristen B W; Rhode, Katherine L; Salzer, John J; Skillman, Evan D

    2015-01-01

    We present sensitive CO (J = 1 - 0) emission line observations of three metal-poor dwarf irregular galaxies Leo P (Z ~ 3% Z_Solar), Sextans A (Z ~ 7.5% Z_Solar), and Sextans B (Z ~ 7.5% Z_Solar), all obtained with the Combined Array for Millimeter-wave Astronomy (CARMA) interferometer. While no CO emission was detected, the proximity of the three systems allows us to place very stringent (4 sigma) upper limits on the CO luminosity (L_CO) in these metal-poor galaxies. We find the CO luminosities to be L_CO < 2900 K km/s pc^2 for Leo P, L_CO < 12400 K km/s pc^2 for Sextans A, and L_CO < 9700 K km/s pc^2 for Sextans B. Comparison of our results with recent observational estimates of the factor for converting between L_CO and the mass of molecular hydrogen, as well as theoretical models, provides further evidence that either the CO-to-H_2 conversion factor increases sharply as metallicity decreases, or that stars are forming in these three galaxies very efficiently, requiring little molecular hydrogen.

  19. Spectroscopic Studies of Extremely Metal-Poor Stars with Subaru/HDS:I. Observational Data

    CERN Document Server

    Honda, S; Ando, H; Izumiura, H; Kajino, T; Kambe, E; Kawanomoto, S; Noguchi, K; Okita, K; Sadakane, K; Sato, B; Takada-Hidai, M; Takeda, Y; Watanabe, E; Beers, T C; Norris, J E; Ryan, S G

    2004-01-01

    We have obtained high-resolution (R $\\simeq$ 50,000 or 90,000), high-quality (S/N $\\ga$ 100) spectra of 22 very metal-poor stars ([Fe/H] $\\la$ -2.5) with the High Dispersion Spectrograph fabricated for the 8.2m Subaru Telescope. The spectra cover the wavelength range from 3500 to 5100 {\\AA}; equivalent widths are measured for isolated lines of numerous elemental species, including the $\\alpha$ elements, the iron-peak elements, and the light and heavy neutron-capture elements. Errors in the measurements and comparisons with previous studies are discussed. These data will be used to perform detailed abundance analyses in the following papers of this series. Radial velocities are also reported, and are compared with previous studies. At least one moderately r-process-enhanced metal-poor star, HD 186478, exhibits evidence of a small-amplitude radial velocity variation, confirming the binary status noted previously. During the course of this initial program, we have discovered a new moderately r-process-enhanced, ...

  20. The Oldest Stars of the Extremely Metal-Poor Local Group Dwarf Irregular Galaxy Leo A

    CERN Document Server

    Schulte-Ladbeck, R E; Drozdovsky, I O; Greggio, L; Crone, M M; Schulte-Ladbeck, Regina E.; Hopp, Ulrich; Drozdovsky, Igor O.; Greggio, Laura; Crone, Mary M.

    2002-01-01

    We present deep Hubble Space Telescope single-star photometry of Leo A in B, V, and I. Our new field of view is offset from the centrally located field observed by Tolstoy et al. (1998) in order to expose the halo population of this galaxy. We report the detection of metal-poor red horizontal branch stars, which demonstrate that Leo A is not a young galaxy. In fact, Leo A is as least as old as metal-poor Galactic Globular Clusters which exhibit red horizontal branches, and are considered to have a minimum age of about 9 Gyr. We discuss the distance to Leo A, and perform an extensive comparison of the data with stellar isochrones. For a distance modulus of 24.5, the data are better than 50% complete down to absolute magnitudes of 2 or more. We can easily identify stars with metallicities between 0.0001 and 0.0004, and ages between about 5 and 10 Gyr, in their post-main-sequence phases, but lack the detection of main-sequence turnoffs which would provide unambiguous proof of ancient (>10 Gyr) stellar generation...

  1. An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars

    CERN Document Server

    Hansen, T; Christlieb, N; Beers, T C; Yong, D; Bessell, M S; Frebel, A; Perez, A E Garcia; Placco, V M; Norris, J E; Asplund, M

    2015-01-01

    We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor (VMP; [Fe/H] 0. The stars with [C/N] < 0 suggest a larger degree of mixing; the few CEMP-no stars that exhibit this signature are only found at [Fe/H] < -3.4, a metallicity below which we also find the CEMP-no stars with large enhancements in Na, Mg, and Al. We confirm the existence of two plateaus in the absolute carbon abundances of CEMP stars, as suggested by Spite et al. We also present evidence for a "floor" in the absolute Ba abundances of CEMP-no stars at A(Ba)~ -2.0.

  2. Low-energy Population III supernovae and the origin of extremely metal-poor stars

    Science.gov (United States)

    Chen, Ke-Jung; Heger, Alexander; Whalen, Daniel J.; Moriya, Takashi J.; Bromm, Volker; Woosley, S. E.

    2017-06-01

    Some ancient, dim, metal-poor stars may have formed in the ashes of the first supernovae (SNe). If their chemical abundances can be reconciled with the elemental yields of specific Population III (Pop III) explosions, they could reveal the properties of primordial stars. But multidimensional simulations of such explosions are required to predict their yields because dynamical instabilities can dredge material up from deep in the ejecta that would otherwise be predicted to fall back on to the central remnant and be lost in one-dimensional (1D) models. We have performed two-dimensional (2D) numerical simulations of two low-energy Pop III SNe, a 12.4 M⊙ explosion and a 60 M⊙ explosion, and find that they produce elemental yields that are a good fit to those measured in the most iron-poor star discovered to date, SMSS J031300.36-670839.3 (J031300). Fallback on to the compact remnant in these weak explosions accounts for the lack of measurable iron in J031300 and its low iron-group abundances in general. Our 2D explosions produce higher abundances of heavy elements (atomic number Z > 20) than their 1D counterparts due to dredge-up by fluid instabilities. Since almost no 56Ni is ejected by these weak SNe, their low luminosities will prevent their detection in the near-infrared with the James Webb Space Telescope and future 30-m telescopes on the ground. The only evidence that they ever occurred will be in the fossil abundance record.

  3. High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE: II. Binary Fraction

    CERN Document Server

    Aoki, Wako; Beers, Timothy C; Honda, Satoshi

    2014-01-01

    The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor, Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] < -3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-mass stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey, and observed at high spectral resolution in a previous study by Aoki et al. That survey reported three double-lined spectroscopic...

  4. Giant Eruption of the Extremely Metal-Poor LBV in DDO 68

    Science.gov (United States)

    Perepelitsyna, Y. A.; Pustilnik, S. A.

    2017-06-01

    Understanding the evolution of massive stars with metallicities much lower than that of the Sun (e.g., Zresearch until extremely large telescopes (ELTs) are in operation. Meantime, selection of good targets for future ELT research becomes actual. Here we present one of such important targets. The unusual void galaxy DDO68 has several star-forming (SF) regions with the gas metallicity Z = Z⊙/35 [12+log(O/H)=7.14]. In 2008, we discovered a luminous blue variable (LBV) star in its HII-region Knot 3. We present the LBV's V-band lightcurve for the time range of 1988 to 2016 using both our new and published data for Knot 3 brightness as well as the archive data from eleven telescopes. The prerequisite is an accurate estimate of the ‘minimal' (non-variable) V-band light for the Knot 3 underlying HII region. Its subtraction from the variable light of Knot 3 allows us to determine the full amplitude of the LBV variability at the level of δV ≳4m. This implies that the LBV has experienced a very rare event of a giant eruption during the years 2008-2011.

  5. DUST-TO-GAS RATIO IN THE EXTREMELY METAL-POOR GALAXY I Zw 18

    Energy Technology Data Exchange (ETDEWEB)

    Herrera-Camus, Rodrigo; Fisher, David B.; Bolatto, Alberto D. [Department of Astronomy and Laboratory of Millimeter Astronomy, University of Maryland, College Park, MD 20742 (United States); Leroy, Adam K. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903-2475 (United States); Walter, Fabian [Max-Planck-Institut fuer Astronomie, Konigstuehl 17, D-69117 Heidelberg (Germany); Gordon, Karl D.; Roman-Duval, Julia [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Donaldson, Jessica; Melendez, Marcio [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Cannon, John M. [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States)

    2012-06-20

    The blue compact dwarf galaxy I Zw 18 is one of the most metal-poor systems known in the local universe (12+log(O/H) = 7.17). In this work we study I Zw 18 using data from Spitzer, Herschel Space Telescope, and IRAM Plateau de Bure Interferometer. Our data set includes the most sensitive maps of I Zw 18, to date, in both the far-infrared and the CO J = 1 {yields} 0 transition. We use dust emission models to derive a dust mass upper limit of only M{sub dust} {<=} 1.1 Multiplication-Sign 10{sup 4} M{sub Sun} (3{sigma} limit). This upper limit is driven by the non-detection at 160 {mu}m, and it is a factor of 4-10 times smaller than previous estimates (depending on the model used). We also estimate an upper limit to the total dust-to-gas mass ratio of M{sub Dust}/M{sub gas} {<=} 5.0 Multiplication-Sign 10{sup -5}. If a linear correlation between the dust-to-gas mass ratio and metallicity (measured as O/H) were to hold, we would expect a ratio of 3.9 Multiplication-Sign 10{sup -4}. We also show that the infrared spectral energy distribution is similar to that of starbursting systems.

  6. Dust-to-Gas Ratio in the Extremely Metal Poor Galaxy I ZW 18

    CERN Document Server

    Herrera-Camus, Rodrigo; Bolatto, Alberto D; Leroy, Adam K; Walter, Fabian; Gordon, Karl D; Roman-Duval, Julia; Donaldson, Jessica; Meléndez, Marcio; Cannon, John M

    2012-01-01

    The blue compact dwarf galaxy I Zw 18 is one of the most metal poor systems known in the local Universe (12 + log(O/H) $=$ 7.17). In this work we study I Zw 18 using data from {\\it Spitzer}, {\\it Herschel Space Telescope} and IRAM Plateau de Bure Interferometer. Our data set includes the most sensitive maps of I Zw 18, to date, in both, the far infrared and the CO $J=1\\rightarrow0$ transition. We use dust emission models to derive a dust mass upper limit of only M$_{dust}\\leq1.1\\times10^4$ M$_{\\odot}$ ($3\\sigma$ limit). This upper limit is driven by the non-detection at 160 $\\mu$m, and it is a factor of 4-10 times smaller than previous estimates (depending upon the model used). We also estimate an upper limit to the total dust-to-gas mass ratio of M$_{Dust}$/M$_{gas}\\leq5.0\\times10^{-5}$. If a linear correlation between the dust-to-gas mass ratio and metallicity (measure as O/H) were to hold, we would expect a ratio of 3.9$\\times10^{-4}$. We also show that the infrared SED is similar to that of starbursting s...

  7. Simulating extremely metal-poor gas and DLA metal content at redshift z=7

    CERN Document Server

    Maio, Umberto; Mueller, Volker

    2013-01-01

    We present the first theoretical study of metals in damped Ly-alpha (DLA) systems at redshift z=7. The features of cold, primordial gas are studied by means of N-body, hydro, chemistry simulations, including atomic and molecular non-equilibrium chemistry, cooling, star formation for population III and population II-I regimes, stellar evolution, cosmic metal spreading according to proper yields (for He, C, O, Si, Fe, Mg, S, etc.) and lifetimes, and feedback effects. Theoretical expectations are then compared to recently available constraints from DLA observations. We find that DLA galaxies at z=7 account for 10 per cent of the whole galaxy population and for most of the metal-poor galaxies at these epochs. About 7 per cent of these DLA galaxies contain purely pristine material and 34 per cent of them consist of very weakly polluted gas, being, therefore, suitable candidate s as population III sites. The remaining 59 per cent are enriched above ~10^{-4} Zsun. Additionally, DLA candidates appear to have: gas mas...

  8. Discovery of An Extremely Metal--Poor Galaxy Optical Spectroscopy of UGCA 292

    CERN Document Server

    Van Zee, L

    2000-01-01

    The results of optical spectroscopy of two HII regions in UGCA 292 (CVn I dwA) are presented. UGCA 292 is a nearby (D=3.1 Mpc) gas-rich dwarf irregular galaxy (M_H/L_B ~ 6.9) which was first discovered in a blind HI survey. The derived oxygen abundance is the third lowest of known star-forming galaxies [12 + log(O/H) = 7.30 +/- 0.05], making UGCA 292 one of the nearest metal-poor galaxies known. The derived N/O ratio is similar to that found in other low metallicity galaxies [log(N/O) = -1.47 +/- 0.10], and is indicative of a primary origin for nitrogen. The derived oxygen abundance is consistent with closed-box chemical evolution for this low mass galaxy. The observed blue colors, high gas mass fraction, and low metallicity suggest that UGCA 292 is relatively unevolved. The possibility that future blind HI surveys may yield similar low metallicity galaxies is discussed.

  9. Proximal location in extremity long bones is a poor prognostic factor for osteosarcoma: A retrospective cohort study of 153 patients.

    Science.gov (United States)

    Cates, Justin M M; Schoenecker, Jonathan G

    2016-08-01

    Osteosarcomas arising in the proximal femur, humerus, and tibia appear to have poorer outcomes than those arising in distal long bones. However, the strength of this association is uncertain, particularly in light of other prognostic factors. Therefore, this retrospective cohort study was performed to compare patient outcomes between proximal and distal tumor location within extremity long bones. A total of 153 patients with conventional high-grade osteosarcoma of the extremity long bones, pelvis, or axial skeleton who had undergone neoadjuvant chemotherapy and surgical resection between 1985 and 2010 were identified in the Surgical Pathology files at Vanderbilt Medical Center. Effect of anatomic location within a proximal long bone was assessed using multivariable Cox proportional hazard regression. Proximal tumor location was a strong predictor of poor prognosis in univariate survival analysis. Multivariate regression analysis showed that after controlling for American Joint Committee on Cancer (AJCC) stage, histologic response to chemotherapy, surgical resection margin status, and histologic type, location in the proximal femur, tibia, and humerus were independent risk factors for death due to osteosarcoma, but not event-free survival. Osteosarcomas of the proximal extremity long bones are associated with decreased disease-specific survival compared to tumors of the distal long bones, even after accounting for other key prognostic covariates.

  10. NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy

    CERN Document Server

    Andrievsky, S M; Korotin, S A; Francois, P; Spite, M; Bonifacio, P; Cayrel, R; Hill, V

    2011-01-01

    Heavy element abundances in extremely metal-poor stars provide strong constraints on the processes of forming these elements in the first stars. We attempt to determine precise abundances of strontium in a homogeneous sample of extremely metal-poor stars. The abundances of strontium in 54 very or extremely metal-poor stars, was redetermined by abandoning the local thermodynamic equilibrium (LTE) hypothesis, and fitting non-LTE (NLTE) profiles to the observed spectral lines. The corrected Sr abundances and previously obtained NLTE Ba abundances are compared to the predictions of several hypothetical formation processes for the lighter neutron-capture elements. Our NLTE abundances confirm the previously determined huge scatter of the strontium abundance in low metallicity stars. This scatter is also found (and is even larger) at very low metallicities (i. e. early in the chemical evolution). The Sr abundance in the extremely metal-poor (EMP) stars is compatible with the main r-process involved in other processe...

  11. High-resolution spectroscopy of extremely metal-poor stars from SDSS/Segue. II. Binary fraction

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Wako; Suda, Takuma [National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan); Beers, Timothy C. [Department of Physics and JINA Center for the Evolution of the Elements, University of Notre Dame,225 Nieuwland Science Hall, Notre Dame, IN 46656 (United States); Honda, Satoshi, E-mail: aoki.wako@nao.ac.jp, E-mail: takuma.suda@nao.ac.jp, E-mail: tbeers@nd.edu, E-mail: honda@nhao.jp [Center for Astronomy, University of Hyogo, 407-2, Nishigaichi, Sayo-cho, Sayo, Hyogo 679-5313 (Japan)

    2015-02-01

    The fraction of binary systems in various stellar populations of the Galaxy and the distribution of their orbital parameters are important but not well-determined factors in studies of star formation, stellar evolution, and Galactic chemical evolution. While observational studies have been carried out for a large sample of nearby stars, including some metal-poor Population II stars, almost no constraints on the binary nature for extremely metal-poor (EMP; [Fe/H] <−3.0) stars have yet been obtained. Here we investigate the fraction of double-lined spectroscopic binaries and carbon-enhanced metal-poor (CEMP) stars, many of which could have formed as pairs of low-mass and intermediate-mass stars, to estimate the lower limit of the fraction of binary systems having short periods. The estimate is based on a sample of very metal-poor stars selected from the Sloan Digital Sky Survey and observed at high spectral resolution in a previous study by Aoki et al. That survey reported 3 double-lined spectroscopic binaries and 11 CEMP stars, which we consider along with a sample of EMP stars from the literature compiled in the SAGA database. We have conducted measurements of the velocity components for stacked absorption features of different spectral lines for each double-lined spectroscopic binary. Our estimate indicates that the fraction of binary stars having orbital periods shorter than 1000 days is at least 10%, and possibly as high as 20% if the majority of CEMP stars are formed in such short-period binaries. This result suggests that the period distribution of EMP binary systems is biased toward short periods, unless the binary fraction of low-mass EMP stars is significantly higher than that of other nearby stars.

  12. Detection of low Eu abundances in extremely metal-poor stars and the origin of r-process elements

    CERN Document Server

    Ishimaru, Y; Aoki, W; Ryan, S G; Aoki, Wako; Ishimaru, Yuhri; Ryan, Sean G.; Wanajo, Shinya

    2003-01-01

    We report detailed abundance analyses for three extremely metal-poor stars with [Fe/H] lesssim -3 in the Galactic halo, using the Subaru High Dispersion Spectrograph (HDS). All these stars are found to have sub-solar relative abundances of [Eu/Fe], and exhibit the lowest [Eu/H] values at their metallicities. Comparison of these low Eu abundances with our chemical evolution model of the Galactic halo implies the dominant source of Eu to be the low-mass end of the Type II supernova mass range. This suggests that collapsing O-Ne-Mg cores resulting from 8-10 Msun stars are the major r-process site.

  13. The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars

    CERN Document Server

    Suda, Takuma; Yamada, Shimako; Suwa, Tamon; Ishizuka, Chikako; Komiya, Yutaka; Sorai, Kazuo; Aikawa, Masayuki; Fujimoto, Masayuki Y

    2008-01-01

    We describe the construction of a database of extremely metal-poor (EMP) stars in the Galactic halo whose elemental abundances have been determined. Our database contains detailed elemental abundances, reported equivalent widths, atmospheric parameters, photometry, and binarity status, compiled from papers in the recent literature that report studies of EMP halo stars with [Fe/H] < -2.5. The compilation procedures for this database have been designed to assemble the data effectively from electronic tables available from online journals. We have also developed a data retrieval system that enables data searches by various criteria, and permits the user to explore relationships between the stored variables graphically. Currently, our sample includes 1212 unique stars (many of which are studied by more than one group) with more than 15000 individual reported elemental abundances, covering all of the relevant papers published by December 2007. We discuss the global characteristics of the present database, as re...

  14. Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies

    CERN Document Server

    Leloudas, G; Kruehler, T; Gorosabel, J; Christensen, L; Mehner, A; Postigo, A de Ugarte; Amorin, R; Thoene, C C; Anderson, J P; Bauer, F E; Gallazzi, A; Helminiak, K G; Hjorth, J; Ibar, E; Malesani, D; Morell, N; Vinko, J; Wheeler, J C

    2014-01-01

    Superluminous supernovae (SLSNe) were only discovered recently due to their preference for occurring in faint dwarf galaxies. Understanding why stellar evolution yields different types of stellar explosions in these environments is fundamental in order to both uncover the elusive progenitors of SLSNe and to study star formation in dwarf galaxies. In this paper, we present the first results of our project to study SUperluminous Supernova Host galaxIES (SUSHIES), focusing on the sample for which we have obtained spectroscopy. We show that SLSNe-I and SLSNe-R (hydrogen-poor) often (~50% in our sample) occur in a class of galaxies that is known as Extreme Emission Line Galaxies (EELGs). The probability of this happening by chance is negligible and we therefore conclude that the extreme environmental conditions and the SLSN phenomenon are related. In contrast, SLSNe-II (hydrogen-rich) occur in more massive, more metal-rich galaxies with softer radiation fields. Therefore, if SLSNe-II constitute a uniform class, th...

  15. Metal-Poor Stars Observed with the Magellan Telescope. III. New Extremely and Ultra Metal-Poor Stars from SDSS/SEGUE and Insights on the Formation of Ultra Metal-Poor Stars

    CERN Document Server

    Placco, Vinicius M; Lee, Young Sun; Jacobson, Heather R; Beers, Timothy C; Pena, Jose M; Chan, Conrad; Heger, Alexander

    2015-01-01

    We report the discovery of one extremely metal-poor (EMP; [Fe/H]<-3) and one ultra metal-poor (UMP; [Fe/H]<-4) star selected from the SDSS/SEGUE survey. These stars were identified as EMP candidates based on their medium-resolution (R~2,000) spectra, and were followed-up with high-resolution (R~35,000) spectroscopy with the Magellan-Clay Telescope. Their derived chemical abundances exhibit good agreement with those of stars with similar metallicities. We also provide new insights on the formation of the UMP stars, based on comparison with a new set of theoretical models of supernovae nucleosynthesis. The models were matched with 20 UMP stars found in the literature, together with one of the program stars (SDSS J1204+1201), with [Fe/H]=-4.34. From fitting their abundances, we find that the supernovae progenitors, for stars where carbon and nitrogen are measured, had masses ranging from 20.5 M_sun to 28 M_sun and explosion energies from 0.3 to 0.9x10^51 erg. These results are highly sensitive to the carbo...

  16. Discovery of a strongly r-process enhanced extremely metal-poor star LAMOST J110901.22+075441.8

    CERN Document Server

    Li, Haining; Honda, Satoshi; Zhao, Gang; Christlieb, Norbert; Suda, Takuma

    2015-01-01

    We report the discovery of an extremely metal-poor (EMP) giant, LAMOST J110901.22+075441.8, which exhibits large excess of r-process elements with [Eu/Fe] ~ +1.16. The star is one of the newly discovered EMP stars identified from LAMOST low-resolution spectroscopic survey and the high-resolution follow-up observation with the Subaru Telescope. Stellar parameters and elemental abundances have been determined from the Subaru spectrum. Accurate abundances for a total of 23 elements including 11 neutron-capture elements from Sr through Dy have been derived for LAMOST J110901.22+075441.8. The abundance pattern of LAMOST J110901.22+075441.8 in the range of C through Zn is in line with the "normal" population of EMP halo stars, except that it shows a notable underabundance in carbon. The heavy element abundance pattern of LAMOST J110901.22+075441.8 is in agreement with other well studied cool r-II metal-poor giants such as CS 22892-052 and CS 31082-001. The abundances of elements in the range from Ba through Dy well...

  17. Search for Extremely Metal-poor Galaxies in the Sloan Digital Sky Survey (II): high electron temperature objects

    CERN Document Server

    Almeida, J Sanchez; Morales-Luis, A B; Munoz-Tunon, C; Garcia-Benito, R; Nuza, S E; Kitaura, F S

    2016-01-01

    Extremely metal-poor (XMP) galaxies are defined to have gas-phase metallicity smaller than a tenth of the solar value (12 + log[O/H] < 7.69). They are uncommon, chemically and possibly dynamically primitive, with physical conditions characteristic of earlier phases of the Universe. We search for new XMPs in the Sloan Digital Sky Survey (SDSS) in a work that complements Paper I. This time high electron temperature objects are selected; since metals are a main coolant of the gas, metal- poor objects contain high-temperature gas. Using the algorithm k-means, we classify 788677 spectra to select 1281 galaxies having particularly intense [OIII]4363 with respect to [OIII]5007, which is a proxy for high electron temperature. The metallicity of these candidates was computed using a hybrid technique consistent with the direct method, rendering 196 XMPs. A less restrictive noise constraint provides a larger set with 332 candidates. Both lists are provided in electronic format. The selected XMP sample have mean stell...

  18. Deep SDSS Optical Spectroscopy of Distant Halo Stars. III. Chemical analysis of extremely metal-poor stars

    CERN Document Server

    Fernandez-Alvar, E; Beers, T C; Lee, Y S; Masseron, T; Schneider, D P

    2016-01-01

    We present the results of an analysis for 107 extremely metal-poor (EMP) stars with metallicities less than [Fe/H] = -3.0, identified from medium-resolution spectra in SDSS. We follow a methodology based on comparisons of the observed spectra with synthetic spectra. The abundances of Fe, Ca, and Mg are determined by fitting spectral regions dominated by lines of each element. In addition, we present a technique to determine upper limits for elements whose features are not detected in a given spectrum. We also analyse our sample with the SEGUE Stellar Parameter Pipeline, in order to obtain additional determinations of the atmospheric parameters, iron and alpha-element abundances, to compare with ours, and to infer [C/Fe] ratios. We find that, in these moderate to low signal-to-noise and medium-resolution spectra in this metallicity regime, Ca is usually the only element that exhibits lines that are sufficiently strong to reliably measure its abundance. Fe and Mg exhibit weaker features that, in most cases, onl...

  19. First stars XII. Abundances in extremely metal-poor turnoff stars,and comparison with the giants

    CERN Document Server

    Bonifacio, P; Cayrel, R; Hill, V; Spite, F; François, P; Plez, B; Ludwig, H -G; Caffau, E; Molaro, P; Depagne, E; Andersen, J; Barbuy, B; Beers, T C; Nordström, B; Primas, F

    2009-01-01

    CONTEXT:The detailed chemical abundances of extremely metal-poor (EMP) stars are key guides to understanding the early chemical evolution of the Galaxy. Most existing data are, however, for giant stars which may have experienced internal mixing later. AIMS: We aim to compare the results for giants with new, accurate abundances for all observable elements in 18 EMP turnoff stars. METHODS:VLT/UVES spectra at R ~45,000 and S/N~ 130 per pixel (330-1000 nm) are analysed with OSMARCS model atmospheres and the TURBOSPECTRUM code to derive abundances for C, Mg, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Sr, and Ba. RESULTS: For Ca, Ni, Sr, and Ba, we find excellent consistency with our earlier sample of EMP giants, at all metallicities. However, our abundances of C, Sc, Ti, Cr, Mn and Co are ~0.2 dex larger than in giants of similar metallicity. Mg and Si abundances are ~0.2 dex lower (the giant [Mg/Fe] values are slightly revised), while Zn is again ~0.4 dex higher than in giants of similar [Fe/H] (6 stars only). CONCLUSIO...

  20. High-Resolution Spectroscopy of Extremely Metal-Poor Stars from SDSS/SEGUE: I. Atmospheric Parameters and Chemical Compositions

    CERN Document Server

    Aoki, Wako; Lee, Young Sun; Honda, Satoshi; Ito, Hiroko; Takada-Hidai, Masahide; Frebel, Anna; Suda, Takuma; Fujimoto, Masatuki Y; Carollo, Daniela; Sivarani, Thirupathi

    2012-01-01

    Chemical compositions are determined based on high-resolution spectroscopy for 137 candidate extremely metal-poor (EMP) stars selected from the Sloan Digital Sky Survey (SDSS) and its first stellar extension, the Sloan Extension for Galactic Understanding and Exploration (SEGUE). High-resolution spectra with moderate signal-to-noise (S/N) ratios were obtained with the High Dispersion Spectrograph of the Subaru Telescope. Most of the sample (approximately 80%) are main-sequence turn-off stars, including dwarfs and subgiants. Four cool main-sequence stars, the most metal-deficient such stars known, are included in the remaining sample. Good agreement is found between effective temperatures estimated by the SEGUE stellar parameter pipeline, based on the SDSS/SEGUE medium-resolution spectra, and those estimated from the broadband $(V-K)_0$ and $(g-r)_0$ colors. Our abundance measurements reveal that 70 stars in our sample have [Fe/H] $ +0.7$) among the 25 giants in our sample is as high as 36%, while only a lowe...

  1. Probing the Site for r-Process Nucleosyntheis with Abundances of Barium and Magnesium in Extremely Metal-Poor Stars

    CERN Document Server

    Tsujimoto, T; Yoshii, Y; Tsujimoto, Takuji; Shigeyama, Toshikazu; Yoshii, Yuzuru

    2000-01-01

    We suggest that if the astrophysical site for r-process nucleosynthesis in the early Galaxy is confined to a narrow mass range of Type II supernova (SN II) progenitors, with a lower mass limit of Mms = 20 Msun, a unique feature in the observed distribution of [Ba/Mg] vs.[Mg/H] for extremely metal-poor stars can be adequately reproduced. We associate this feature, a bifurcation of the observed elemental ratios into two branches in the Mg abundance interval -2.7 20 Msun. The second branch, which we call the ``i''-branch, is associated with the elemental abundance ratios of stars which were formed in the dense shells of the interstellar medium swept up by SNe II with Mms < 20 Msun that do not synthesize r-process elements, and applies to stars with observed Mg abundances in the range [Mg/H] < -2.7. The Ba abundances in these stars reflect those of the interstellar gas at the (later) time of their formation. The existence of a [Ba/Mg] i-branch strongly suggests that SNe II which are associated with stars o...

  2. A combination mode of climate variability responsible for extremely poor recruitment of the Japanese eel (Anguilla japonica)

    Science.gov (United States)

    Lin, Yong-Fu; Wu, Chau-Ron; Han, Yu-San

    2017-03-01

    Satellite data and assimilation products are used to investigate fluctuations in the catch of Japanese eel (Anguilla japonica) in eastern Asian countries. It has been reported that the salinity front has extended farther south, which has shifted the eel’s spawning grounds to a lower latitude, resulting in smaller eel catches in 1983, 1992, and 1998. This study demonstrates that interannual variability in the eel catch is strongly correlated with the combination mode (C-mode), but not with the El Niño–Southern Oscillation. These eels continue to spawn within the North Equatorial Current (NEC), but the salinity front shifts south during a canonical El Niño. On the other hand, the spawning grounds accompanied by the salinity front extend farther south during the C-mode of climate variability, and eel larvae fail to join the nursery in the NEC, resulting in extremely poor recruitment in East Asia. We propose an appropriate sea surface temperature index to project Japanese eel larval catch.

  3. A Lucky Escape

    Institute of Scientific and Technical Information of China (English)

    王道庚

    2009-01-01

    @@ This story concerns(有关)a spider(蜘蛛)and a certain general of ancient times who had lost a battle and,in the company of(在……陪同下)a faithful(忠诚的)servant,was trying to escape(逃脱)from the enemy.Both were extremely(极度,非常)tired,and both were hungry and thirsty,but they did not dare to go into any town for fear of (担心,害怕)being discovered and captured(捉)by the enemy.Toward evening they arrived at a mountain where there was a small cave.

  4. Deep SDSS optical spectroscopy of distant halo stars. III. Chemical analysis of extremely metal-poor stars

    Science.gov (United States)

    Fernández-Alvar, E.; Allende Prieto, C.; Beers, T. C.; Lee, Y. S.; Masseron, T.; Schneider, D. P.

    2016-09-01

    Aims: We present the results of an analysis of 107 extremely metal-poor (EMP) stars with metallicities lower than [Fe/H] =- 3.0, identified in medium-resolution spectra in the Sloan Digital Sky Survey (SDSS). Our analysis provides estimates of the stellar effective temperatures and surface gravities, as well as iron, calcium, and magnesium abundances. Methods: We followed the same method as in previous papers of this series. The method is based on comparisons of the observed spectra with synthetic spectra. The abundances of Fe, Ca, and Mg were determined by fitting spectral regions that are dominated by lines of each element. In addition, we present a technique to determine upper limits for elements whose features are not detected in a given spectrum. We also analyzed our sample with the SEGUE stellar parameter pipeline to obtain additional determinations of the atmospheric parameters and iron and alpha-element abundances, which we thend compare with ours. In addition, we used these parameters to infer [C/Fe] ratios. Results: Ca is typically the only element in these spectra with a moderate to low signal-to-noise ratio and medium resolution in this metallicity regime with lines that are sufficiently strong to reliably measure its abundance. Fe and Mg exhibit weaker features that in most cases only provide upper limits. We measured [Ca/Fe] and [Mg/Fe] for EMP stars in the SDSS spectra and conclude that most of the stars exhibit the typical enhancement level for α-elements, ~+0.4, although some stars for which only [Fe/H] upper limits could be estimated indicate higher [α/Fe] ratios. We also find that 26% of the stars in our sample can be classified as carbon-enhanced metal-poor (CEMP) stars and that the frequency of CEMP stars also increases with decreasing metallicity, as has been reported for previous samples. We identify a rare, bright (g = 11.90) EMP star, SDSS J134144.61+474128.6, with [Fe/H] =- 3.27, [C/Fe] = + 0.95, and elevated magnesium ([Mg/Fe] =+ 0

  5. The extremely metal-poor galaxy DDO 68: the luminous blue variable, Hα shells and the most luminous stars

    Science.gov (United States)

    Pustilnik, S. A.; Makarova, L. N.; Perepelitsyna, Y. A.; Moiseev, A. V.; Makarov, D. I.

    2017-03-01

    This paper presents new results from the ongoing study of the unusual Lynx-Cancer void galaxy DDO 68, which has star-forming regions of record low metallicity [12+log (O/H) ∼7.14]. The results include the following. (i) A new spectrum and photometry have been obtained with the 6-m SAO RAS telescope (BTA) for the luminous blue variable (LBV = DDO68-V1). Photometric data sets were complemented with others based on the Sloan Digital Sky Survey (SDSS) and the Hubble Space Telescope (HST) archive images. (ii) We performed an analysis of the DDO 68 supergiant shell (SGS) and the prominent smaller Hα arcs/shells visible in the HST image coupled with kinematic maps in Hα obtained with the Fabry-Perot interferometer (FPI) at the BTA. (iii) We compiled a list of about 50 of the most luminous stars (-9.1 mag science to be investigated with the next generation of giant telescopes. We have confirmed earlier hints of significant variation of the LBV optical light, deriving its amplitude as ΔV ≳ 3.7 mag for the first time. New data suggest that in 2008-2010 the LBV reached MV = -10.5 mag and probably underwent a giant eruption. We argue that the structure of star-forming complexes along the SGS ('Northern Ring') perimeter provides evidence for sequential induced star-formation episodes caused by the shell gas instabilities and gravitational collapse. The variability of some luminous extremely metal-poor stars in DDO 68 can currently be monitored with medium-size telescopes at sites with superb seeing.

  6. Spectroscopic Studies of Extremly Metal-Poor Stars with Subaru/HDS:II.The r-process Elements, Including Thorium

    CERN Document Server

    Honda, S; Kajino, T; Ando, H; Beers, T C; Izumiura, H; Sadakane, K; Takada-Hidai, M

    2004-01-01

    We present the abundance analyses for the neutron-capture elements, and discuss the observed abundance distributions in very metal-poor stars with excesses of r-process elements. As has been found by previous abundance studies, the star-to-star scatter in the abundances of neutron-capture elements are very large. The abundance patterns of the heavy neutron-capture elements (56 $\\leq$ Z $\\leq$ 70) in seven objects with moderate to large excesses of the neutron-capture elements are similar to that of the solar system r-process component. These results strongly suggest that the heavy neutron-capture elements in these objects are primarily synthesized by the r-process. On the other hand, the abundance ratios of the light neutron-capture elements (38 $\\leq$ Z $\\leq$ 46) exhibit a rather large dispersion. Our inspection of the correlation between Sr and Ba abundances in very metal-poor stars reveals that the dispersion of the Sr abundances clearly decreases with increasing Ba abundance. This results support previou...

  7. Small for gestational age and poor fluid intelligence in childhood predict externalizing behaviors among young adults born at extremely low birth weight.

    Science.gov (United States)

    Lahat, Ayelet; Van Lieshout, Ryan J; Saigal, Saroj; Boyle, Michael H; Schmidt, Louis A

    2015-02-01

    Although infants born at extremely low birth weight (ELBW; birth weight intelligence. As young adults, a subset of ELBW survivors free of major neurosensory impairments provided self-reports of personality characteristics related to psychopathology. Data from 66 participants indicated that, as predicted, the association between ELBW and externalizing behaviors was moderated by fluid intelligence. Specifically, ELBW individuals with poor fluid intelligence who were born small for gestational age (birth weight intelligence might be a cognitive mechanism contributing to the development of psychopathology among nonimpaired individuals who were born at ELBW and small for gestational age.

  8. First Stars XI. Chemical composition of the extremely metal-poor dwarfs in the binary CS 22876--032

    CERN Document Server

    Hernández, J I González; Ludwig, H -G; Caffau, E; Spite, M; Spite, F; Cayrel, R; Molaro, P; Hill, V; François, P; Plez, B; Beers, T C; Sivarani, T; Andersen, J; Barbuy, B; Depagne, E; Nordström, B; Primas, F

    2007-01-01

    We have used high-resolution, high-S/N ratio spectra from the UVES spectrograph at the ESO VLT telescope. Long-term radial-velocity measurements and broad-band photometry allow us to determine improved orbital elements and stellar parameters for both components. We use OSMARCS 1D models and the {{\\scshape turbospectrum}} spectral synthesis code to determine the abundances of Li, O, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Co and Ni. We also use the CO$^5$BOLD model atmosphere code to compute the 3D abundance corrections, especially for Li and O. We find a metallicity of [Fe/H]$\\sim -3.6$ for both stars, using 1D models with 3D corrections of $\\sim -0.1$ dex from averaged 3D models. We determine the oxygen abundance from the near-UV OH bands; the 3D corrections are large, -1 and -1.5 dex for the secondary and primary respectively, and yield [O/Fe] $\\sim 0.8$, close to the high-quality results obtained from the [OI] 630 nm line in metal-poor giants. Other [$\\alpha$/Fe] ratios are consistent with those measured i...

  9. HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Alexander P.; Frebel, Anna [Department of Physics and Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Simon, Joshua D. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Geha, Marla, E-mail: alexji@mit.edu [Astronomy Department, Yale University, New Haven, CT 06520 (United States)

    2016-01-20

    We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.

  10. Statin escape phenomenon: Fact or fiction?

    Science.gov (United States)

    Barkas, Fotios; Elisaf, Moses; Klouras, Eleftherios; Dimitriou, Theodora; Tentolouris, Nikolaos; Liberopoulos, Evangelos

    2017-01-01

    AIM To evaluate the presence of the so called “statin escape” phenomenon among hyperlipidemic subjects attending a lipid clinic. METHODS This was a retrospective analysis of 1240 hyperlipidemic individuals followed-up for ≥ 3 years. We excluded those individuals meeting one of the following criteria: Use of statin therapy at baseline visit, discontinuation of statin treatment at most recent visit, change in statin treatment during follow-up and poor compliance to treatment. Statin escape phenomenon was defined as an increase in low-density lipoprotein cholesterol (LDL-C) levels at the most recent visit by > 10% compared with the value at 6 mo following initiation of statin treatment. RESULTS Of 181 eligible subjects, 31% exhibited the statin escape phenomenon. No major differences regarding baseline characteristics were found between statin escapers and non-statin escapers. Both escapers and non-escapers had similar baseline LDL-C levels [174 (152-189) and 177 (152-205) mg/dL, respectively]. In comparison with non-escapers, statin escapers demonstrated lower LDL-C levels at 6 mo after treatment initiation [88 (78-97) mg/dL vs 109 (91-129) mg/dL, P statin-treated individuals. The clinical significance of this phenomenon remains uncertain.

  11. Abundance analysis of SDSS J134338.67+484426.6; an extremely metal-poor star from the MARVELS pre-survey

    Science.gov (United States)

    Susmitha Rani, A.; Sivarani, T.; Beers, T. C.; Fleming, S.; Mahadevan, S.; Ge, J.

    2016-05-01

    We present an elemental-abundance analysis of an extremely metal-poor (EMP; [Fe/H] EMP stars that are this bright or brighter. Our high-resolution spectroscopic analysis shows that this star is a subgiant with [Fe/H] = -3.42, having `normal' carbon and no enhancement of neutron-capture abundances. Strontium is underabundant, [Sr/Fe] = -0.47, but the derived lower limit on [Sr/Ba] indicates that Sr is likely enhanced relative to Ba. This star belongs to the sparsely populated class of α-poor EMP stars that exhibit low ratios of [Mg/Fe], [Si/Fe], and [Ca/Fe] compared to typical halo stars at similar metallicity. The observed variations in radial velocity from several epochs of (low- and high-resolution) spectroscopic follow-up indicate that SDSS J134338.67+484426.6 is a possible long-period binary. We also discuss the abundance trends in EMP stars for r-process elements, and compare with other magnesium-poor stars.

  12. Atmospheric escape, redox evolution, and planetary habitability

    Science.gov (United States)

    Catling, D. C.; Zahnle, K. J.

    2011-12-01

    net escape of hydrogen relative to heavier oxygen is the generally accepted explanation for the present oxidation state: Venus and Mars amongst the planets, and Ganymede, Europa, and Rhea amongst bodies with extremely tenuous atmospheres. We also argue that hydrogen escape was the key factor for oxidizing the Earth and facilitating the increase of photosynthetically-produced oxygen in the Proterozoic atmosphere. Our view about the primacy of hydrogen escape with regard to the Earth's atmospheric oxygenation is perhaps less widely accepted. However, it was inevitable that hydrogen escaped from Earth's early anoxic atmosphere at a significant rate. The result was a very big integrated oxidation consistent with what is observed in the Earth's crust in addition to some export to the mantle. In conclusion, a better understanding of atmospheric escape processes appears critical for understanding the suitability of planets for harboring life from simple to advanced forms.

  13. Dust escape from Io

    Science.gov (United States)

    Flandes, Alberto

    2004-08-01

    The Dust ballerina skirt is a set of well defined streams composed of nanometric sized dust particles that escape from the Jovian system and may be accelerated up to >=200 km/s. The source of this dust is Jupiter's moon Io, the most volcanically active body in the Solar system. The escape of dust grains from Jupiter requires first the escape of these grains from Io. This work is basically devoted to explain this escape given that the driving of dust particles to great heights and later injection into the ionosphere of Io may give the particles an equilibrium potential that allow the magnetic field to accelerate them away from Io. The grain sizes obtained through this study match very well to the values required for the particles to escape from the Jovian system.

  14. Abundance analysis of SDSS J134338.67+484426.6; an extremely metal-poor star from the MARVELS pre-survey

    CERN Document Server

    Rani, A Susmitha; Beers, T C; Fleming, S; Mahadevan, S; Ge, J

    2016-01-01

    We present an elemental-abundance analysis of an extremely metal-poor (EMP; [Fe/H] < -3.0) star, SDSS J134338.67+484426.6, identified during the course of the MARVELS spectroscopic pre-survey of some 20000 stars to identify suitable candidates for exoplanet searches. This star, with an apparent magnitude V = 12.14, is the lowest metallicity star found in the pre-survey, and is one of only ~20 known EMP stars that are this bright or brighter. Our high-resolution spectroscopic analysis shows that this star is a subgiant with [Fe/H] = -3.42, having "normal" carbon and no enhancement of neutron-capture abundances. Strontium is under-abundant, [Sr/Fe] =-0.47, but the derived lower limit on [Sr/Ba] indicates that Sr is likely enhanced relative to Ba. This star belongs to the sparsely populated class of alpha-poor EMP stars that exhibit low ratios of [Mg/Fe], [Si/Fe], and [Ca/Fe] compared to typical halo stars at similar metallicity. The observed variations in radial velocity from several epochs of (low- and high...

  15. A multiprofessional perspective on the principal barriers to universal health coverage and universal access to health in extremely poor territories: the contributions of nursing1

    Science.gov (United States)

    de França, Viviane Helena; Modena, Celina Maria; Confalonieri, Ulisses Eugenio Cavalcanti

    2016-01-01

    Objective: to investigate the knowledge of managers and health professionals, social workers and education professionals regarding the principal barriers to universal health coverage and universal access to health on the part of the extremely poor population; and to point to the contributions made by nursing for the promotion of this right. Method: a qualitative study whose reference was, for ensuring the right to health, the reorientation of the Brazilian Unified Health System (SUS) towards universal coverage and access in these territories. Interviews were held with 27 members of the multi-professional team of a municipality with high social vulnerability. The data were worked on using thematic content analysis. Results: the following were ascertained as the principal barriers to universal health coverage and access to health: failures in the expansion and strengthening of the services; absence of diagnosis of the priority demands; shortage of technology, equipment, and material and human resources; poor local infrastructure; and actions with low resolutive power and absence of interdepartmental policies. Within the multi-professional team, nursing acts in the SUS in unique health actions and social practices in these territories, presenting an in-depth perspective on this harsh reality, being able to contribute with indispensable support for confronting these disparities in universal health coverage and universal access to health. Conclusion: nursing's in-depth understanding regarding these barriers is essential for encouraging the processes reorienting the SUS, geared towards equality in the right to health. PMID:27143541

  16. First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements

    CERN Document Server

    Spite, M; Plez, B; Hill, V; Spite, F; Depagne, E; François, P; Bonifacio, P; Barbuy, B; Beers, T; Andersen, J; Molaro, P; Nordström, B; Primas, F

    2004-01-01

    We have investigated the poorly-understood origin of nitrogen in the early Galaxy by determining N abundances in 35 extremely metal-poor halo giants (22 stars have [Fe/H]<-3.0) using the C and O abundances determined in Paper V. Because any dredge-up of CNO processed material to the surface may complicate the interpretation of CNO abundances in giants, we have also measured the surface abundance of lithium. Our sample shows a clear dichotomy between two groups of stars. The first group shows evidence of C to N conversion through CN cycling and strong Li dilution, a signature of mixing. The second group shows no evidence for C to N conversion, and Li is only moderately diluted, and we conclude that their C and N abundances are very close to those of the gas from which they formed in the early Galaxy. These "unmixed" stars reflect the abundances in the early Galaxy: the [C/Fe] ratio is constant (about +0.2 dex) and the [C/Mg] ratio is close to solar at low metallicity, favouring a high C production by massiv...

  17. First stars IX -Mixing in extremely metal-poor giants. Variation of the 12C/13C, [Na/Mg] and [Al/Mg] ratios

    CERN Document Server

    Spite, M; Hill, V; Spite, F; François, P; Plez, B; Bonifacio, P; Molaro, P; Depagne, E; Andersen, J; Barbuy, B; Beers, T C; Nordström, B; Primas, F

    2006-01-01

    Extremely metal-poor (EMP) stars preserve a fossil record of the composition of the ISM when the Galaxy formed. It is crucial, however, to verify whether internal mixing has modified their surface. We aim to understand the CNO abundance variations found in some, but not all EMP field giants analysed earlier. Mixing beyond the first dredge-up of standard models is required, and its origin needs clarification.The 12C/13C ratio is the most robust diagnostic of deep mixing, because it is insensitive to the adopted stellar parameters and should be uniformly high in near-primordial gas. We have measured 12C and 13C abundances in 35 EMP giants from high-quality VLT/UVES spectra. Correlations with other abundance data are used to study the depth of mixing.The 12C/13C ratio is found to correlate with [C/Fe] (and Li/H), and clearly anti-correlate with [N/Fe]. Evidence for such deep mixing is observed in giants above log L/Lsolar = 2.6, brighter than in less metal-poor stars, but matching the bump in the luminosity func...

  18. Hydrodynamical Modeling of Hydrogen Escape from Rocky Planets

    Science.gov (United States)

    Barringer, Daniel; Zugger, M.; Kasting, J.

    2013-01-01

    Hydrogen escape affects both the composition of primitive atmospheres of terrestrial planets and the planet’s state of oxidation. On Mars, hydrogen escape played a critical role in how long the planet remained in a warm wet state amenable to life. For both solar and extrasolar planets, hydrogen-rich atmospheres are better candidates for originating life by way of Miller-Urey-type prebiotic synthesis. However, calculating the rate of atmospheric hydrogen escape is difficult, for a number of reasons. First, the escape can be controlled either by diffusion through the homopause or by conditions in the upper atmosphere, whichever is slower. Second, both thermal and non-thermal escape mechanisms are typically important. Third, thermal escape itself can be subdivided into Jeans escape (thin upper atmosphere), and hydrodynamic escape, and hydrodynamic escape can be further subdivided into transonic escape and slower subsonic escape, depending on whether the exobase occurs above or below the sonic point. Additionally, the rate of escape for real terrestrial planet atmospheres, which are not 100% hydrogen, depends upon the concentration of infrared coolants, and upon heating and photochemistry driven largely by extreme ultraviolet (EUV) radiation. We have modified an existing 1-D model of hydrodynamic escape (F. Tian et al., JGR, 2008) to work in the high- hydrogen regime. Calculations are underway to determine hydrogen escape rates as a function of atmospheric H2 mixing ratio and the solar EUV flux. We will compare these rates with the estimated upper limit on the escape rate based on diffusion. Initial results for early Earth and Mars will later be extended to rocky exoplanets.

  19. Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars. IV. Oxygen diagnostics in extremely metal-poor red giants with infrared OH lines

    CERN Document Server

    Dobrovolskas, V; Bonifacio, P; Caffau, E; Ludwig, H -G; Steffen, M; Spite, M

    2015-01-01

    Context. Although oxygen is an important tracer of Galactic chemical evolution, measurements of its abundance in the atmospheres of the oldest Galactic stars are still scarce and rather imprecise. At the lowest end of the metallicity scale, oxygen can only be measured in giant stars and in most of cases such measurements rely on a single forbidden [O I] 630 nm line that is very weak and frequently blended with telluric lines. Although molecular OH lines located in the ultraviolet and infrared could also be used for the diagnostics, oxygen abundances obtained from the OH lines and the [O I] 630 nm line are usually discrepant to a level of ~0.3-0.4 dex. Aims. We study the influence of convection on the formation of the infrared (IR) OH lines and the forbidden [O I] 630 nm line in the atmospheres of extremely metal-poor (EMP) red giant stars. Methods. We used high-resolution and high signal-to-noise ratio spectra of four EMP red giant stars obtained with the VLT CRIRES spectrograph. For each EMP star, 4-14 IR OH...

  20. The IMF of Extremely Metal-Poor Stars and the Probe into the Star-Formation Process of the Milky Way

    CERN Document Server

    Komiya, Yutaka; Habe, Asao; Fujimoto, Masayuki Y

    2007-01-01

    We discuss the star formation history of the Galaxy, based on the observations of extremely metal-poor stars (EMP) in the Galactic halo, to gain an insight into the evolution and structure formation in the early universe. The initialmass function (IMF) of EMP stars is derived from the observed fraction of carbon-enhanced EXP (CEMP) stars among the EMP survivors, which are thought to originate from the evolution in the close binary systems with mass transfer. Relying upon the theory of the evolution of EMP stars and of their binary evolution, we find that stars of metallicity [Fe/H]<-2.5 were formed at typical mass of ~10M_sun. The top heavy IMF thus obtained is applied to study the early chemical evolution of the Galaxy. We construct the merging history of our Galaxy semi-analytically and derive the metallicity distribution function (MDF) of low-mass EMP stars that survive to date with taking into account the contribution of binary systems. It is shown that the resultant MDF can well reproduce the observed...

  1. The Abundance Evolution of Oxygen, Sodium and Magnesium in Extremely Metal-Poor Intermediate Mass Stars: Implications for the Self-Polution Scenario in Globular Clusters

    CERN Document Server

    Denissenkov, P A

    2003-01-01

    We present full stellar evolution and parametric models of the surface abundance evolution of O16, Ne22, Na23 and the magnesium isotopes in an extremely metal-poor intermediate mass star M_ZAMS=5M_sun, Z=0.0001. O16 and Ne22 are injected into the envelope by the third dredge-up following thermal pulses on the asymptotic giant branch. These species and the initially present Mg24 are depleted by hot bottom burning (HBB) during the interpulse phase. As a result, Na23, Mg25 and Mg26 are enhanced. If the HBB temperatures are sufficiently high for this process to deplete oxygen efficiently, Na23 is first produced and then depleted during the interpulse phase. Although the simultaneous depletion of O16 and enhancement of Na23 is possible, the required fine tuning of the dredge-up and HBB casts some doubt on the robustness of this process as the origin of the O-Na anti-correlation observed in globular cluster stars. However, a very robust prediction of our models are low Mg24/Mg25 and Mg24/Mg26 ratios whenever signif...

  2. Oxygen and light element synthesis by neutron-capture reactions in metal-free and extremely metal-poor AGB stars

    CERN Document Server

    Nishimura, Takanori; Suda, Takuma; Fujimoto, Masayuki Y

    2009-01-01

    The metal-free (Pop. III) and extremely metal-poor (EMP) stars of low- and intermediate-masses experience mixing of hydrogen into the helium convection during the early TP-AGB phase, differently from the meal-rich stars. We study the nucleosynthesis in the helium convective zone with 13C formed from mixed protons as neutron source by using a nuclear network from H through S. In the absence or scarcity of the pristine metals, the neutron-recycling reactions, 12C(n,g)13C(a,n)16O and also 16O(n,g)17O(a,n)20Ne promote the synthesis of O and light elements, including their neutron-rich isotopes and the odd atomic number elements. Based on the results, we demonstrate that the peculiar abundance patterns of C through Al observed for the three most iron-deficient, carbon-rich stars can be reproduced in terms of the nucleosynthesis in Pop. III, AGB stars in the different mass range. We argue that these three stars were born as the low-mass members of Pop. III binaries and later subject to the surface pollution by the ...

  3. Escape in Hill's Problem

    CERN Document Server

    Heggie, D C

    2000-01-01

    This didactic paper is motivated by the problem of understanding how stars escape from globular star clusters. One formulation of this problem is known, in dynamical astronomy, as Hill's problem. Originally intended as a model for the motion of the moon around the earth with perturbations by the sun, with simple modifications it also serves as a model for the motion of a star in a star cluster with perturbations by the galaxy. The paper includes introductory sections on the derivation of the equations of motion of Hill's problem, their elementary properties, and extensions to deal with non-point masses and non-circular orbits. We then show how the rate of escape may be calculated numerically and estimated theoretically, and discuss how this simple picture is modified if the stars in a cluster are also undergoing two-body relaxation. Finally we introduce some established ideas for obtaining the distribution of escape times.

  4. Energy-limited escape revised

    CERN Document Server

    Salz, M; Czesla, S; Schmitt, J H M M

    2016-01-01

    Gas planets in close proximity to their host stars experience photoevaporative mass loss. The energy-limited escape concept is generally used to derive estimates for the planetary mass-loss rates. Our photoionization hydrodynamics simulations of the thermospheres of hot gas planets show that the energy-limited escape concept is valid only for planets with a gravitational potential lower than $\\log_\\mathrm{10}\\left( -\\Phi_{\\mathrm{G}}\\right) < 13.11~$erg$\\,$g$^{-1}$ because in these planets the radiative energy input is efficiently used to drive the planetary wind. Massive and compact planets with $\\log_\\mathrm{10}\\left( -\\Phi_{\\mathrm{G}}\\right) \\gtrsim 13.6~$erg$\\,$g$^{-1}$ exhibit more tightly bound atmospheres in which the complete radiative energy input is re-emitted through hydrogen Ly$\\alpha$ and free-free emission. These planets therefore host hydrodynamically stable thermospheres. Between these two extremes the strength of the planetary winds rapidly declines as a result of a decreasing heating eff...

  5. Escape from the Alternative

    Directory of Open Access Journals (Sweden)

    Marin Dinu

    2006-12-01

    Full Text Available This paper sets out to elaborate on Romania’s specific agenda regarding the approach to the integration process in the EU as a project of modernization. The focus is on the functional aspects, the type of strategic solutions destined to consolidate the specific transformations belonging to post-communist transition seen as an internal transition, on the one hand and on the other hand to push convergence as the essence of integration, marked by the vision of EU integration as a continuation of change, which is the stage of external transition. Identifying the prominent factors and the pragmatic priorities of the escape from the peripheries of development by engaging in evolution by way of the second modernization constitutes as well a target for analysis. One particularity of the method of analysis is the review if the value-set of the bobsled effect of path dependency – the path of the peripheries – as well as of the set of values of the escape from the peripheries.

  6. Mars - an escaping planet?

    CERN Document Server

    Dvorak, R

    2005-01-01

    The chaotic behaviour of the motion of the planets in our Solar System is well established. Numerical experiments with a modified Solar System consisting of a more massive Earth have shown, that for special values of an enlargement factor K around 5 the dynamical state of a truncated planetary system (excluding Mercury and the outer planets Uranus and Neptune) is highly chaotic. On the contrary for values of the mass of the Earth up to the mass of Saturn no irregular dynamical behaviour was observed. We extended our investigations to the complete planetary system and showed, that this chaotic window found before still exists. Tests in different 'Solar Systems' showed that only including Jupiter and Saturn with their actual masses together with a 'massive' Earth (between 4 and 6 times more massive) destabilize the orbit of Mars so that even escapes from the system are possible.

  7. The Explosive Yields Produced by the First Generation of Core Collapse Supernovae and the Chemical Composition of Extremely Metal Poor Stars

    CERN Document Server

    Chieffi, A; Chieffi, Alessandro; Limongi, Marco

    2002-01-01

    We present a detailed comparison between an extended set of elemental abundances observed in some of the most metal poor stars presently known and the ejecta produced by a generation of primordial core collapse supernovae. We used five stars which form our initial database and define a "template" ultra metal poor star which is then compared to the theoretical predictions. Our main findings are as follows: a) the fit to [Si/Mg] and [Ca/Mg] of these very metal poor stars seems to favor the presence of a rather large C abundance at the end of the central He burning; in a classical scenario in which the border of the convective core is strictly determined by the Schwarzschild criterion, such a large C abundance would imply a rather low C12(alpha,gamma)O16 reaction rate; b) a low C abundance left by the central He burning would imply a low [Al/Mg] (<-1.2 dex) independently on the initial mass of the exploding star while a rather large C abundance would produce such a low [Al/Mg] only for the most massive stella...

  8. Discovering extremely compact and metal-poor, star-forming dwarf galaxies out to z ~ 0.9 in the VIMOS Ultra-Deep Survey

    CERN Document Server

    Amorín, Ricardo; Castellano, M; Grazian, A; Tasca, L A M; Fontana, A; Pentericci, L; Cassata, P; Garilli, B; Brun, V Le; Fèvre, O Le; Maccagni, D; Thomas, R; Vanzella, E; Zamorani, G; Zucca, E; Bardelli, S; Capak, P; Cassará, L; Cimatti, A; Cuby, J G; Cucciati, O; de la Torre, S; Durkalec, A; Giavalisco, M; Hathi, N P; Ilbert, O; Lemaux, B C; Moreau, C; Paltani, S; Ribeiro, B; Salvato, M; Schaerer, D; Scodeggio, M; Talia, M; Taniguchi, Y; Tresse, L; Vergani, D; Wang, P W; Charlot, S; Contini, T; Fotopoulou, S; López-Sanjuan, C; Mellier, Y; Scoville, N

    2014-01-01

    We report the discovery of 31 low-luminosity (-14.5 < M_{AB}(B) < -18.8), extreme emission line galaxies (EELGs) at 0.3 < z < 0.9 identified by their unusually high rest-frame equivalent widths (100 < EW[OIII] < 1700 A) as part of the VIMOS Ultra Deep Survey (VUDS). VIMOS optical spectra of unprecedented sensitivity ($I_{AB}$ ~ 25 mag) along with multiwavelength photometry and HST imaging are used to investigate spectrophotometric properties of this unique sample and explore, for the first time, the very low stellar mass end (M* < 10^8 M$_{\\odot}$) of the luminosity-metallicity (LZR) and mass-metallicity (MZR) relations at z < 1. Characterized by their extreme compactness (R50 < 1 kpc), low stellar mass and enhanced specific star formation rates (SFR/M* ~ 10^{-9} - 10^{-7} yr^{-1}), the VUDS EELGs are blue dwarf galaxies likely experiencing the first stages of a vigorous galaxy-wide starburst. Using T_e-sensitive direct and strong-line methods, we find that VUDS EELGs are low-metall...

  9. Low Energy Population III Supernovae and the Origin of the Extremely Metal-Poor Star SMSS J031300.36-670839.3

    CERN Document Server

    Chen, Ke-Jung; Whalen, Daniel J; Moriya, Takashi J; Bromm, Volker; Woosley, Stan; Almgren, Ann

    2016-01-01

    Ancient, dim metal-poor stars may have formed in the ashes of the first supernovae. If their chemical abundances can be reconciled with the nucleosynthetic yields of specific Pop III explosions, they could reveal the properties of primordial stars. But simulations of such explosions must be multidimensional because dynamical instabilities can dredge material up from deep in the ejecta that would be predicted to fall back onto the compact remnant and be lost in one-dimensional models. We have performed two-dimensional numerical simulations of two low-energy Pop III supernovae, a 12.4 Msun explosion and a 60 Msun explosion, and find that they have elemental yields that are a good fit to those measured in the most iron-poor star discovered to date, SMSS J031300.36-670839.3 (J031300). Fallback onto the compact remnant in these weak explosions accounts for the lack of measurable iron in J031300 and its low iron-group abundances in general. The low energies of these dim events will prevent their detection in the ne...

  10. Efficiently estimating salmon escapement uncertainty using systematically sampled data

    Science.gov (United States)

    Reynolds, Joel H.; Woody, Carol Ann; Gove, Nancy E.; Fair, Lowell F.

    2007-01-01

    Fish escapement is generally monitored using nonreplicated systematic sampling designs (e.g., via visual counts from towers or hydroacoustic counts). These sampling designs support a variety of methods for estimating the variance of the total escapement. Unfortunately, all the methods give biased results, with the magnitude of the bias being determined by the underlying process patterns. Fish escapement commonly exhibits positive autocorrelation and nonlinear patterns, such as diurnal and seasonal patterns. For these patterns, poor choice of variance estimator can needlessly increase the uncertainty managers have to deal with in sustaining fish populations. We illustrate the effect of sampling design and variance estimator choice on variance estimates of total escapement for anadromous salmonids from systematic samples of fish passage. Using simulated tower counts of sockeye salmon Oncorhynchus nerka escapement on the Kvichak River, Alaska, five variance estimators for nonreplicated systematic samples were compared to determine the least biased. Using the least biased variance estimator, four confidence interval estimators were compared for expected coverage and mean interval width. Finally, five systematic sampling designs were compared to determine the design giving the smallest average variance estimate for total annual escapement. For nonreplicated systematic samples of fish escapement, all variance estimators were positively biased. Compared to the other estimators, the least biased estimator reduced bias by, on average, from 12% to 98%. All confidence intervals gave effectively identical results. Replicated systematic sampling designs consistently provided the smallest average estimated variance among those compared.

  11. 极贫金属环境下超新星爆发的中子俘获元素核合成产量%Nucleosynthetic yield of neutron-capture elements from extremely metal-poor stars

    Institute of Scientific and Technical Information of China (English)

    马文娟; 单勇; 张波

    2011-01-01

    The extremely metal-poor stars ([Fe/H]< -2. 5)was formed in the early universe. Studies on the nucleosynthesis yield of the extremely metal-poor stars play a key role in the exploration of the formation of the solar system, the chemical evolution of galaxies and the fundamental issues in the nuclear astrophysics. In this paper, the neutron-capture element's nucleosynthesis yields of the extremely metal-poor stars are calculated on the basis of the observed correlations between the neutron-capture process elements Sr, Y, Ba and Si elements and the theoretical yields of Si.%极贫金属环境下超新星爆发([Fe/H]<-2.5)形成于星系演化的早期,研究极贫金属环境下超新星爆发的重元素丰度分布及核合成,对于探索星系形成及化学演化和核天体物理学中的基本问题都起着关键作用.分析了大量极贫金属环境下超新星爆发的元素丰度的观测数据,得出中子俘获元素Sr,Y和Ba与元素Si的相关性规律,计算了极贫金属环境下超新星爆发的元素Sr,Y和Ba的核合成产量.

  12. Effects of being uninsured or underinsured and living in extremely poor neighborhoods on colon cancer care and survival in California: historical cohort analysis, 1996—2011

    Directory of Open Access Journals (Sweden)

    Gorey Kevin M

    2012-10-01

    Full Text Available Abstract Background We examined the mediating effects of health insurance on poverty-colon cancer care and survival relationships and the moderating effects of poverty on health insurance-colon cancer care and survival relationships among women and men in California. Methods We analyzed registry data for 3,291 women and 3,009 men diagnosed with colon cancer between 1996 and 2000 and followed until 2011 on lymph node investigation, stage at diagnosis, surgery, chemotherapy, wait times and survival. We obtained socioeconomic data for individual residences from the 2000 census to categorize the following neighborhoods: high poverty (30% or more poor, middle poverty (5-29% poor and low poverty (less than 5% poor. Primary health insurers were Medicaid, Medicare, private or none. Results Evidence of mediation was observed for women, but not for men. For women, the apparent effect of poverty disappeared in the presence of payer, and the effects of all forms of health insurance seemed strengthened. All were advantaged on 6-year survival compared to the uninsured: Medicaid (RR = 1.83, Medicare (RR = 1.92 and private (RR = 1.83. Evidence of moderation was also only observed for women. The effects of all forms of health insurance were stronger for women in low poverty neighborhoods: Medicaid (RR = 2.90, Medicare (RR = 2.91 and private (RR = 2.60. For men, only main effects of poverty and payers were observed, the advantaging effect of private insurance being largest. Across colon cancer care processes, Medicare seemed most instrumental for women, private payers for men. Conclusions Health insurance substantially mediates the quality of colon cancer care and poverty seems to make the effects of being uninsured or underinsured even worse, especially among women in the United States. These findings are consistent with the theory that more facilitative social and economic capital is available in more affluent neighborhoods, where women

  13. Hunger, escaping excess.

    Science.gov (United States)

    Gardner, G; Halweil, B

    2000-01-01

    According to the WHO, in spite of decades of global food surpluses, half of humanity, in both rich and poor nations, is still malnourished. Malnutrition has become a significant impediment to development in rich and poor countries, alike. At the individual level, both hunger and poor eating habits reduce a person's physical fitness, increase susceptibility to illness, and shorten lifespan. In addition, children deprived of adequate nutrients during development can suffer from permanently reduced mental capacity. At the national level, poor eating hampers educational performance, curtails economic productivity, increases the burden on health care, and reduces well-being. Confronting this epidemic of poor eating will have widespread benefits, but the myths and misconceptions permeating humanity¿s understanding of malnutrition should be addressed first. It is noted that the major cause of hunger is poverty, not scarcity of food; it is the lack of access to the goods and services essential for a healthy life. On the other hand, for those who have access to plenty of food, dietary intake includes meat, dairy products, and highly processed items loaded with fat and sugar. This leads to the problem of obesity, a condition that increases susceptibility to disease and disability, reduces worker productivity, and shortens lifespan. In view of this, efforts to improve nutrition should focus on poverty eradication, health education, agricultural change, and policy change towards promotion of good nutrition.

  14. Hunting for extremely metal-poor emission-line galaxies in the Sloan Digital Sky Survey: MMT and 3.5m APO observations

    CERN Document Server

    Izotov, Y I; Guseva, N G

    2012-01-01

    We present 6.5-meter MMT and 3.5m APO spectrophotometry of 69 H II regions in 42 low-metallicity emission-line galaxies, selected from the Data Release 7 of the Sloan Digital Sky Survey to have mostly [O III]4959/Hbeta < 1 and [N II]6583/Hbeta < 0.1. The electron temperature-sensitive emission line [O III] 4363 is detected in 53 H II regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 H II regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12 + log O/H ~ 7.1 to ~ 7.9, with 14 H II regions in 7 galaxies with 12 +log O/H < 7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12 +log O/H < 7.35) emission-line galaxies known in the local universe. There appears to ...

  15. Extremely Metal-Poor Stars. VIII. High-Resolution, High-Signal-To-Noise Analysis of Five Stars with [Fe/H] < -3.5

    CERN Document Server

    Norris, J E; Beers, T C; Norris, John E.; Ryan, Sean G.; Beers, Timothy C.

    2001-01-01

    High-resolution, high-signal-to-noise ( = 85) spectra have been obtained for five stars -- CD-24:17504, CD-38:245, CS 22172-002, CS 22885-096, and CS 22949-037 -- having [Fe/H] < -3.5 according to previous lower S/N material. LTE model-atmosphere techniques are used to determine [Fe/H] and relative abundances, or their limits, for some 18 elements, and to constrain more tightly the early enrichment history of the Galaxy than is possible based on previous analyses. We compare our results with high-quality higher-abundance literature data for other metal-poor stars and with the canonical Galactic chemical enrichment results of Timmes et al. (1995) and obtain the following basic results: (1) Large supersolar values of [C/Fe] and [N/Fe], not predicted by the canonical models, exist at lowest abundance. For C at least, the result is difficult to attribute to internal mixing effects; (2) We confirm that there is {\\it no upward trend} in [$\\alpha$/Fe] as a function of [Fe/H], in contradistinction to some reports ...

  16. Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars II. s-process nucleosynthesis during the core He flash

    CERN Document Server

    Campbell, Simon W; Karakas, Amanda I

    2010-01-01

    Models of primordial and hyper-metal-poor stars with masses similar to the Sun experience an ingestion of protons into the hot core during the core helium flash phase at the end of their red giant branch evolution. This produces a concurrent secondary flash powered by hydrogen burning that gives rise to further nucleosynthesis in the core. We perform post-process nucleosynthesis calculations on a one-dimensional stellar evolution calculation of a star of 1 solar mass and metallicity [Fe/H] = -6.5 that suffers a proton ingestion episode. Our network includes 320 nuclear species and 2,366 reactions and treats mixing and burning simultaneously. The mixing and burning of protons into the hot convective core leads to the production of 13C, which then burns via the 13C(alpha,n)16O reaction releasing a large number of free neutrons. During the first two years of neutron production the neutron poison 14N abundance is low, allowing the prodigious production of heavy elements such as strontium, barium, and lead via slo...

  17. An escape from crowding.

    Science.gov (United States)

    Freeman, Jeremy; Pelli, Denis G

    2007-10-26

    Crowding occurs when nearby flankers jumble the appearance of a target object, making it hard to identify. Crowding is feature integration over an inappropriately large region. What determines the size of that region? According to bottom-up proposals, the size is that of an anatomically determined isolation field. According to top-down proposals, the size is that of the spotlight of attention. Intriligator and Cavanagh (2001) proposed the latter, but we show that their conclusion rests on an implausible assumption. Here we investigate the role of attention in crowding using the change blindness paradigm. We measure capacity for widely and narrowly spaced letters during a change detection task, both with and without an interstimulus cue. We find that standard crowding manipulations-reducing spacing and adding flankers-severely impair uncued change detection but have no effect on cued change detection. Because crowded letters look less familiar, we must use longer internal descriptions (less compact representations) to remember them. Thus, fewer fit into working memory. The memory limit does not apply to the cued condition because the observer need remember only the cued letter. Cued performance escapes the effects of crowding, as predicted by a top-down account. However, our most parsimonious account of the results is bottom-up: Cued change detection is so easy that the observer can tolerate feature degradation and letter distortion, making the observer immune to crowding. The change detection task enhances the classic partial report paradigm by making the test easier (same/different instead of identifying one of many possible targets), which increases its sensitivity, so it can reveal degraded memory traces.

  18. Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg] and [K/Mg] in the Milky Way

    CERN Document Server

    Andrievsky, S M; Korotin, S A; Spite, F; Bonifacio, P; Cayrel, R; François, P; Hill, V

    2010-01-01

    LTE abundances of light elements in extremely metal-poor (EMP) stars have been previously derived from high quality spectra. New derivations, free from the NLTE effects, will better constrain the models of the Galactic chemical evolution and the yields of the very first supernovae. The NLTE profiles of the magnesium and potassium lines have been computed in a sample of 53 extremely metal-poor stars with a modified version of the program MULTI and adjusted to the observed lines in order to derive the abundances of these elements. The NLTE corrections for magnesium and potassium are in good agreement with the works found in the literature. The abundances are slightly changed, reaching a better precision: the scatter around the mean of the abundance ratios has decreased. Magnesium may be used with confidence as reference element. Together with previously determined NLTE abundances of sodium and aluminum, the new ratios are displayed, for comparison, along the theoretical trends proposed by some models of the che...

  19. MAVEN in situ measurements of photochemical escape of oxygen from Mars

    Science.gov (United States)

    Lillis, Robert; Deighan, Justin; Fox, Jane; Bougher, Stephen; Lee, Yuni; Cravens, Thomas; Rahmati, Ali; Mahaffy, Paul; Benna, Mehdi; Groller, Hannes; Jakosky, Bruce

    2016-04-01

    One of the primary goals of the MAVEN mission is to characterize rates of atmospheric escape from Mars at the present epoch and relate those escape rates to solar drivers. One of the known escape processes is photochemical escape, where a) an exothermic chemical reaction in the atmosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through subsequent collisions. At Mars, photochemical escape of oxygen is expected to be a significant channel for atmospheric escape, particularly in the early solar system when extreme ultraviolet (EUV) fluxes were much higher. Thus characterizing this escape process and its variability with solar drivers is central to understanding the role escape to space has played in Mars' climate evolution. We use near-periapsis (atoms. The second is a Monte Carlo hot atom transport model that takes that distribution of initial O energies and the measured neutral density profiles and calculates the probability that a hot atom born at that altitude will escape. The third takes the measured electron and ion densities and electron temperatures and calculates the production rate of hot O atoms. We then multiply together the profiles of hot atom production and escape probability to get profiles of the production rate of escaping atoms. We integrate with respect to altitude to give us the escape flux of hot oxygen atoms for that periapsis pass. We have sufficient coverage in solar zenith angle (SZA) to estimate total escape rates for two intervals with the obvious assumption that escape rates are the same at all points with the same SZA. We estimate total escape rates of 3.5-5.8 x 1025 s-1 for Ls = 289° to 319° and 1.6-2.6 x 1025 s-1 for Ls = 326° to 348°. The latter is the most directly comparable to previous model-based estimates and is roughly in line with several of them. Total photochemical loss over Mars history is not very useful to

  20. Escape rates for Gibbs measures

    CERN Document Server

    Ferguson, Andrew

    2010-01-01

    We study the asymptotic behaviour of the escape rate of a Gibbs measure supported on a conformal repeller through a small hole. There are additional applications to the convergence of Hausdorff dimension of the survivor set.

  1. Direction of escape in reindeer

    OpenAIRE

    Baskin, Leonid M.; Terje Skogland

    1997-01-01

    We tested the hypothesis that reindeer prefer to run uphill and upwind when escaping from man. Groups of wild and feral reindeer in Norway, Svalbard and on Wrangel Island were approached and their behaviour and direction of escape were recorded. Two stages of interaction with man were studied: first flight and final withdrawal. First flights proved to be away from man, upwind and uphill. Most final withdrawals were in the direction reindeer were moving when first observed.

  2. Direction of escape in reindeer

    Directory of Open Access Journals (Sweden)

    Leonid M. Baskin

    1997-04-01

    Full Text Available We tested the hypothesis that reindeer prefer to run uphill and upwind when escaping from man. Groups of wild and feral reindeer in Norway, Svalbard and on Wrangel Island were approached and their behaviour and direction of escape were recorded. Two stages of interaction with man were studied: first flight and final withdrawal. First flights proved to be away from man, upwind and uphill. Most final withdrawals were in the direction reindeer were moving when first observed.

  3. Broad CTL Response in Early HIV Infection Drives Multiple Concurrent CTL Escapes.

    Science.gov (United States)

    Leviyang, Sivan; Ganusov, Vitaly V

    2015-10-01

    Recent studies have highlighted the ability of HIV to escape from cytotoxic T lymphocyte (CTL) responses that concurrently target multiple viral epitopes. Yet, the viral dynamics involved in such escape are incompletely understood. Previous analyses have made several strong assumptions regarding HIV escape from CTL responses such as independent or non-concurrent escape from individual CTL responses. Using experimental data from evolution of HIV half genomes in four patients we observe concurrent viral escape from multiple CTL responses during early infection (first 100 days of infection), providing confirmation of a recent result found in a study of one HIV-infected patient. We show that current methods of estimating CTL escape rates, based on the assumption of independent escapes, are biased and perform poorly when CTL escape proceeds concurrently at multiple epitopes. We propose a new method for analyzing longitudinal sequence data to estimate the rate of CTL escape across multiple epitopes; this method involves few parameters and performs well in simulation studies. By applying our novel method to experimental data, we find that concurrent multiple escapes occur at rates between 0.03 and 0.4 day(-1), a relatively broad range that reflects uncertainty due to sparse sampling and wide ranges of parameter values. However, we show that concurrent escape at rates 0.1-0.2 day(-1) across multiple epitopes is consistent with our patient datasets.

  4. Pioneer Venus Orbiter (PVO) Ionosphere Evidence for Atmospheric Escape

    Science.gov (United States)

    Grebowsky, J. M.; Hoegy, W. R.

    2009-12-01

    An early estimate of escape of H2O from Venus [McElroy et al., 1982] using observed hot oxygen densities inferred by Nagy et al. [1981] from PVO OUVS 1304 Å dayglow and using ionization rates from photoionization and electron impact. This resulted in an estimated oxygen ionization rate planet-wide above the plasmapause of 3x1025 atoms/s. Based on the energetic O+ being swept up and removed by solar wind, McElroy et al. [1982] gave an estimate of a loss rate for O of 6x106 atoms/cm2/s. Using a different method of estimating escape based data in the ionotail of Venus, Brace et al. [1987] estimated a total planetary O+ escape rate of 5x1025 ions/s. Their estimate was based on PVO measurements of superthermal O+ (energy range 9-16 eV) in the tail ray plasma between 2000 and 3000 km. Their estimated global mean flux was 107 atoms/cm2/s. The two escape rates are remarkably close considering all the errors involved in such estimates of escape. A study of escape by Luhmann et al. [2008] using VEX observations at low solar activity finds modest escape rates, prompting the authors to reconsider the evidence from both PVO and VEX of the possibility of enhanced escape during extreme interplanetary conditions. We reexamine the variation of escape under different solar wind conditions using ion densities and plasma content in the dayside and nightside of Venus using PVO ionosphere density during times of high solar activity. Citations: Brace, L.H., W. T. Kasprzak, H.A. Taylor, R. F. Theis, C. T. Russess, A. Barnes, J. D. Mihalov, and D. M. Hunten, "The Ionotail of Venus: Its Configuration and Evidence for Ion Escape", J. Geophys. Res. 92, 15-26, 1987. Luhmann, J.G., A. Fedorov, S. Barabash, E. Carlsson, Y. Futaana, T.L. Zhang, C.T. Russell, J.G. Lyon, S.A. Ledvina, and D.A. Brain, “Venus Express observations of atmospheric oxygen escape during the passage of several coronal mass ejections”, J. Geophys. Res., 113, 2008. McElroy, M. B., M. J. Prather, J. M. Rodiquez, " Loss

  5. Analysis of Extreme Aesthetical Standpoint in Works About Poor People in New Century%新世纪小说底层写作中的单极化审美取向透析

    Institute of Scientific and Technical Information of China (English)

    祝嘉琳

    2011-01-01

    新世纪小说底层写作中存在着单极化审美取向:重物质、崇苦难、崇恶。这无法达到产生一种震撼人心的悲剧力量的审美目标;不符合现实主义美学思想;从文学的本质和价值来看,这样的写作无法产生一种超越的力量。%These works which write the lives of poor people always have extreme aesthetic standpoint.They always emphasize about materials,tragedy,evils,which can not obtain the powerful strength of tragedy,and are not in compliance with aesthetic view of realism,at the same time,from the view of literature essence,can not surpass our lives.

  6. Escape probability of the super-Penrose process

    CERN Document Server

    Ogasawara, Kota; Miyamoto, Umpei; Igata, Takahisa; Patil, Mandar

    2016-01-01

    We consider a head-on collision of two massive particles that move in the equatorial plane of an extremal Kerr black hole, which results in the production of two massless particles. Focusing a typical case, where both of the colliding particles have zero angular momenta, we show that a massless particle produced in such a collision can escape to infinity with arbitrarily large energy in the near-horizon limit of the collision point. Furthermore, if we assume that the emission of the produced massless particles is isotropic in the center-of-mass frame but confined to the equatorial plane, the escape probability of the produced massless particle approaches $5/12$ and almost all escaping massless particles have arbitrarily large energy at infinity and an impact parameter approaching $2M$.

  7. Submarine Escape Set Test Facilities

    Directory of Open Access Journals (Sweden)

    G.S.N. Murthy

    2009-07-01

    Full Text Available Submarine Escape Set (SES is used by submariners to escape from a sunken submarine. This set caters for breathing needs of the submariner under water, until he reaches the surface. Evaluation of such life-saving equipment is of paramount importance. This paper describes the submarine escape set and various constructional features and schedules of operation of test facilities designed indegenously and which can evaluate the SES. The test facility is divided into two parts: the reducer test facility, and the breathing bag test facility. The equipment has been rigorously tested and accepted by Indian Navy. Two such test facilities have been developed, one of which is installed at INS Satavahana, Visakhapatnam, and are working satisfactorily.

  8. DYNAMICS OF THE ESCAPE RESPONSE.

    Science.gov (United States)

    requirements. It has been shown that force is a lawful response measure under positive reinforcement (Notterman and Mintz, 1965). Subjects will adjust...concluded that response force in an escape situation is a lawful response measure, and that it operates in a manner similar to force under positive reinforcement .

  9. Structural controls on fluid escape from the subduction interface

    Science.gov (United States)

    Reynard, Bruno; Tauzin, Benoit; Bodin, Thomas; Perrillat, Jean-Philippe; Debayle, Eric

    2017-04-01

    Seismic activity and non-volcanic tremors are often associated with fluid circulation resulting from the dehydration of subducting plates. Tremors in the overriding continental crust of several subduction zones suggest fluid circulation at shallower depths, but potential fluid pathways are still poorly documented. Fluids are also released at different depths in hot and cold subduction zones, which may result in different schemes of fluid escape. We document potential fluid pathways in Cascadia, one of the hottest subduction zone, using receiver function analysis. We provide evidence for a seismic discontinuity near 15 km depth in the crust of the overriding North American plate. This interface is segmented, and its interruptions are spatially correlated with conductive regions of the forearc and shallow swarms of seismicity and non-volcanic tremors. The comparison of seismological and electrical conductivity profiles suggests that fluid escape is controlled by fault zones between blocks of accreted terranes in the overriding plate. These zones constitute fluid escape routes that may influence the seismic cycle by releasing fluid pressure from the megathrust. Results on Cascadia are compared to fluid escape routes suggested by former geophysical observations in NE Japan, one of the coldest subduction zones. Links between fluid escape, permeability and fluid-rock reactions at or above the plate interface are discussed.

  10. On the properties of the interstellar medium in extremely metal-poor blue compact dwarf galaxies: GMOS-IFU spectroscopy and SDSS photometry of the double-knot galaxy HS 2236+1344

    CERN Document Server

    Lagos, P; Gomes, J M; Castelli, A V Smith; Vega, L R; .,

    2014-01-01

    The main goal of this study is to carry out a spatially resolved investigation of the warm interstellar medium (ISM) in the extremely metal-poor Blue Compact Dwarf (BCD) galaxy HS 2236+1344. Special emphasis is laid on the analysis of the spatial distribution of chemical abundances, emission-line ratios and kinematics of the ISM, and to the recent star-forming activity in this galaxy. This study is based on optical integral field unit spectroscopy data from Gemini Multi-Object Spectrograph at the Gemini North telescope and archival Sloan Digital Sky Survey images. The data were obtained in two different positions across the galaxy, obtaining a total 4 arcsec X 8 arcsec field which encompasses most of its ISM. Emission-line maps and broad-band images obtained in this study indicate that HS 2236+1344 hosts three Giant HII regions. Our data also reveal some faint curved features in the BCD periphery that might be due to tidal perturbations or expanding ionized-gas shells. The ISM velocity field shows systematic ...

  11. Cold Ion Escape from Mars

    Science.gov (United States)

    Fränz, M.; Dubinin, E.; Wei, Y.; Morgan, D.; Andrews, D.; Barabash, S.; Lundin, R.; Fedorov, A.

    2013-09-01

    It has always been challenging to observe the flux of ions with energies of less than 10eV escaping from the planetary ionospheres. We here report on new measurements of the ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express in combination with the MARSIS radar experiment. We first compare calculations of the mean ion flux observed by ASPERA-3 alone with previously published results. We then combine observations of the cold ion velocity by ASPERA-3 with observations of the cold plasma density by MARSIS since ASPERA-3 misses the cold core of the ion distribution. We show that the mean density of the nightside plasma observed by MARSIS is about two orders higher than observed by ASPERA-3 (Fig.1). Combining both datasets we show that the main escape channel is along the shadow boundary on the tailside of Mars (Fig. 2). At a distance of about 0.5 R_M the flux settles at a constant value (Fig. 3) which indicates that about half of the transterminator ionospheric flow escapes from the planet. Possible mechanism to generate this flux can be the ionospheric pressure gradient between dayside and nightside or momentum transfer from the solar wind via the induced magnetic field since the flow velocity is in the Alfvénic regime.

  12. EscapED: A Framework for Creating Educational Escape Rooms and Interactive Games to For Higher/Further Education.

    Directory of Open Access Journals (Sweden)

    Samantha Jane Clarke

    2017-09-01

    Full Text Available Game-based learning (GBL is often found to be technologically driven and more often than not, serious games for instance, are conceptualised and designed solely for digital platforms and state of the art technologies. To encourage a greater discussion on the potential benefits and challenges of a more holistic approach to developing GBL that promote human centered interactions and play for learning, the authors present the escapED programme. The escapED programme was conceived following the recent entertainment trend of escape rooms and is used for developing non-digital GBL approaches within education. escapED aids the design and creation of educational Escape Rooms and Interactive Gaming Experiences for staff and students in further/higher education settings. The paper first presents a pilot study that was used to assess the feasibility and acceptance of University teaching staff of embedding interactive GBL into a higher education environment. The authors then present the escapED theoretical framework that was used to create the prototype game for the pilot study as a tool to aid future design and development of on-site interactive experiences. The paper also presents an external developer report of using the escapED framework to develop a prototype game for teaching research methods to Southampton University students. Finally, the authors present a discussion on the use of the escapED framework so far and plans for future work and evaluation in order to provide engaging alternatives for learning and soft skills development amongst higher education staff andstudents.

  13. ESCAPE AS REINFORCEMENT AND ESCAPE EXTINCTION IN THE TREATMENT OF FEEDING PROBLEMS

    OpenAIRE

    LaRue, Robert H; Stewart, Victoria; Piazza, Cathleen C; Volkert, Valerie M.; Patel, Meeta R; Zeleny, Jason

    2011-01-01

    Given the effectiveness of putative escape extinction as treatment for feeding problems, it is surprising that little is known about the effects of escape as reinforcement for appropriate eating during treatment. In the current investigation, we examined the effectiveness of escape as reinforcement for mouth clean (a product measure of swallowing), escape as reinforcement for mouth clean plus escape extinction (EE), and EE alone as treatment for the food refusal of 5 children. Results were si...

  14. Photochemical Escape of Oxygen from Early Mars

    CERN Document Server

    Zhao, Jinjin

    2015-01-01

    Photochemical escape is an important process for oxygen escape from present Mars. In this work, a 1-D Monte-Carlo Model is developed to calculate escape rates of energetic oxygen atoms produced from O2+ dissociative recombination reactions (DR) under 1, 3, 10, and 20 times present solar XUV fluxes. We found that although the overall DR rates increase with solar XUV flux almost linearly, oxygen escape rate increases from 1 to 10 times present solar XUV conditions but decreases when increasing solar XUV flux further. Analysis shows that atomic species in the upper thermosphere of early Mars increases more rapidly than O2+ when increasing XUV fluxes. While the latter is the source of energetic O atoms, the former increases the collision probability and thus decreases the escape probability of energetic O. Our results suggest that photochemical escape be a less important escape mechanism than previously thought for the loss of water and/or CO2 from early Mars.

  15. Brain size as a driver of avian escape strategy.

    Science.gov (United States)

    Samia, Diogo S M; Pape Møller, Anders; Blumstein, Daniel T

    2015-07-03

    After detecting an approaching predator, animals make a decision when to flee. Prey will initiate flight soon after detecting a predator so as to minimize attentional costs related to on-going monitoring of the whereabouts of the predator. Such costs may compete with foraging and other maintenance activities and hence be larger than the costs of immediate flight. The drivers of interspecific variation in escape strategy are poorly known. Here we investigated the morphological, life history and natural history traits that correlate with variation in avian escape strategy across a sample of 96 species of birds. Brain mass, body size, habitat structure and group size were the main predictors of escape strategy. The direction of the effect of these traits was consistent with selection for a reduction of monitoring costs. Therefore, attentional costs depend on relative brain size, which determines the ability to monitor the whereabouts of potential predators and the difficulty of this task as reflected by habitat and social complexity. Thus brain size, and the cognitive functions associated with it, constitute a general framework for explaining the effects of body size, habitat structure and sociality identified as determinants of avian escape strategy.

  16. Escaping the poverty trap: modeling the interplay between economic growth and the ecology of infectious disease

    CERN Document Server

    Goerg, Georg M; Hébert-Dufresne, Laurent; Althouse, Benjamin M

    2013-01-01

    The dynamics of economies and infectious disease are inexorably linked: economic well-being influences health (sanitation, nutrition, treatment capacity, etc.) and health influences economic well-being (labor productivity lost to sickness and disease). Often societies are locked into ``poverty traps'' of poor health and poor economy. Here, using a simplified coupled disease-economic model with endogenous capital growth we demonstrate the formation of poverty traps, as well as ways to escape them. We suggest two possible mechanisms of escape both motivated by empirical data: one, through an influx of capital (development aid), and another through changing the percentage of GDP spent on healthcare. We find that a large influx of capital is successful in escaping the poverty trap, but increasing health spending alone is not. Our results demonstrate that escape from a poverty trap may be possible, and carry important policy implications in the world-wide distribution of aid and within-country healthcare spending.

  17. How extreme are extremes?

    Science.gov (United States)

    Cucchi, Marco; Petitta, Marcello; Calmanti, Sandro

    2016-04-01

    High temperatures have an impact on the energy balance of any living organism and on the operational capabilities of critical infrastructures. Heat-wave indicators have been mainly developed with the aim of capturing the potential impacts on specific sectors (agriculture, health, wildfires, transport, power generation and distribution). However, the ability to capture the occurrence of extreme temperature events is an essential property of a multi-hazard extreme climate indicator. Aim of this study is to develop a standardized heat-wave indicator, that can be combined with other indices in order to describe multiple hazards in a single indicator. The proposed approach can be used in order to have a quantified indicator of the strenght of a certain extreme. As a matter of fact, extremes are usually distributed in exponential or exponential-exponential functions and it is difficult to quickly asses how strong was an extreme events considering only its magnitude. The proposed approach simplify the quantitative and qualitative communication of extreme magnitude

  18. Wind-Induced Atmospheric Escape: Titan

    Science.gov (United States)

    Hartle, Richard; Johnson, Robert; Sittler, Edward, Jr.; Sarantos, Menelaos; Simpson, David

    2012-01-01

    Rapid thermospheric flows can significantly enhance the estimates of the atmospheric loss rate and the structure of the atmospheric corona of a planetary body. In particular, rapid horizontal flow at the exobase can increase the corresponding constituent escape rate. Here we show that such corrections, for both thermal and non-thermal escape, cannot be ignored when calculating the escape of methane from Titan, for which drastically different rates have been proposed. Such enhancements are also relevant to Pluto and exoplanets.

  19. DR-induced escape of O and C from early Mars

    Science.gov (United States)

    Zhao, Jinjin; Tian, Feng; Ni, Yufang; Huang, Xiaomeng

    2017-03-01

    Energetic particles produced in Dissociative recombination (DR) reactions could escape planets with low gravity, such as Mars, if they could overcome collisions with the surrounding background gases. In this work, a 3-D Monte Carlo model is developed to study these photochemical escape processes on early Mars. Although the DR reaction rates of O2+, CO2+, and CO+ increase monotonically with solar soft X-ray and extreme ultraviolet (XUV) flux, the peak of the calculated DR-induced escape rates of O is near 3 × XUV, and the DR-induced escape rates of C increase with XUV until 10 × XUV. The non-monotonic behavior can be explained by the increased column densities of background species in high XUV conditions, which can deflect energetic particles through collisions more efficiently. At 20 × XUV, CO+ DR is the main source of escaping O and C, and the escape of secondary particles could contribute to 30∼40% and 10% of the total escape of O and C respectively. The time-integrated DR-induced escape of O and C is equivalent to 1 m of H2O and 20 mbar of CO2 escaping early Mars since 4.5 billion years ago. The accumulated CO2 loss is much lower than what's needed to explain the carbon isotopic ratios on Mars and much lower than the total CO2 needed to warm up early Mars. If more vigorous escape mechanisms were absent on early Mars, substantial inventories of volatiles have not been detected yet.

  20. Escaping the resource curse in China.

    Science.gov (United States)

    Cao, Shixiong; Li, Shurong; Ma, Hua; Sun, Yutong

    2015-02-01

    Many societies face an income gap between rich regions with access to advanced technology and regions that are rich in natural resources but poorer in technology. This "resource curse" can lead to a Kuznets trap, in which economic inequalities between the rich and the poor increase during the process of socioeconomic development. This can also lead to depletion of natural resources, environmental degradation, social instability, and declining socioeconomic development. These problems will jeopardize China's achievements if the current path continues to be pursued without intervention by the government to solve the problems. To mitigate the socioeconomic development gap between western and eastern China, the government implemented its Western Development Program in 2000. However, recent data suggest that this program has instead worsened the resource curse. Because each region has its own unique strengths and weaknesses, China must escape the resource curse by accounting for this difference; in western China, this can be done by improving education, promoting high-tech industry, adjusting its economic strategy to balance regional development, and seeking more sustainable approaches to socioeconomic development.

  1. Escape as Reinforcement and Escape Extinction in the Treatment of Feeding Problems

    Science.gov (United States)

    LaRue, Robert H.; Stewart, Victoria; Piazza, Cathleen C.; Volkert, Valerie M.; Patel, Meeta R.; Zeleny, Jason

    2011-01-01

    Given the effectiveness of putative escape extinction as treatment for feeding problems, it is surprising that little is known about the effects of escape as reinforcement for appropriate eating during treatment. In the current investigation, we examined the effectiveness of escape as reinforcement for mouth clean (a product measure of…

  2. Learning from escaped prescribed fire reviews [Abstract

    Science.gov (United States)

    Anne Black; Dave Thomas; James Saveland

    2011-01-01

    Over the past decade, the wildland fire community has developed a number of innovative methods for conducting a review following escape of a prescribed fire. The stated purpose been to identify methods that not only meet policy requirements, but to reduce future escapes. Implicit is the assumption that a review leads to learning. Yet, as organizational learning expert...

  3. Escape of atmospheric gases from the Moon

    Indian Academy of Sciences (India)

    Da Dao-an; Yang Ya-tian

    2005-12-01

    The escape rate of atmospheric molecules on the Moon is calculated.Based on the assumption that the rates of emission and escape of gases attain equilibrium, the ratio of molecular number densities during day and night, 0/0, can be explained. The plausible emission rate of helium and radioactive elements present in the Moon has also been calculated.

  4. Escaping in Literature. Teaching in the Library.

    Science.gov (United States)

    Hurst, Carol Otis

    1993-01-01

    Explores the "escape" genre of children's literature, and recommends and describes several books that deal with such topics as escape from prison camps, from slavery, from the Holocaust, from war, and from Utopian societies. These books should provoke meaningful classroom discussions and allow children to view their own world from different…

  5. Poor People's Income to Be Increased

    Institute of Scientific and Technical Information of China (English)

    Wen Duoduo

    2005-01-01

    @@ During the period of the 11 th FiveYear Program, Chinese govern ment will be inclined to take policies to realize a balanced economic growth, equalized opportunities and social justice so as to avoid that the poor people become extremely poor and the gap between poor and wealthy become larger, according to the analysts.

  6. Poor People's Income to Be Increased

    Institute of Scientific and Technical Information of China (English)

    Wen; Duoduo

    2005-01-01

      During the period of the 11 th FiveYear Program, Chinese govern ment will be inclined to take policies to realize a balanced economic growth, equalized opportunities and social justice so as to avoid that the poor people become extremely poor and the gap between poor and wealthy become larger, according to the analysts.……

  7. Optimal escape theory predicts escape behaviors beyond flight initiation distance: risk assessment and escape by striped plateau lizards Sceloporus virgatus

    Institute of Scientific and Technical Information of China (English)

    William E.COOPER Jr

    2009-01-01

    Escape theory predicts that flight initiation distance (FID=distance between predator and prey when escape begins) is longer when risk is greater and shorter when escape is more costly. A few tests suggest that escape theory applies to distance fled. Escape models have not addressed stochastic variables, such as probability of fleeing and of entering refuge, but their economic logic might be applicable. Experiments on several risk factors in the lizard Sceloporus virgatus confirmed all predictions for the above escape variables. FID was greater when approach was faster and more direct, for lizards on ground than on trees, for lizards rarely exposed to humans, for the second of two approaches, and when the predator turned toward lizards rather than away. Lizards fled further during rapid and second consecutive approaches. They were more likely to flee when approached directly, when a predator turned toward them, and during second approaches. They were more likely to enter refuge when approached rapidly. A novel finding is that perch height in trees was unrelated to FID because lizards escaped by moving out of sight, then moving up or down unpredictably. These findings add to a growing body of evidence supporting predictions of escape theory for FID and distance fled. They show that two probabilistic aspects of escape are predictable based on relative predation risk levels. Because individuals differ in boldness, the assessed optimal FID and threshold risks for fleeing and entering refuge are exceeded for an increasing proportion of individuals as risk increases[Current Zoology 55(2):123-131,2009].

  8. Atmospheric Escape from Hot Jupiters

    CERN Document Server

    Murray-Clay, Ruth; Murray, Norman

    2008-01-01

    Photoionization heating from UV radiation incident on the atmospheres of hot Jupiters may drive planetary mass loss. We construct a model of escape that includes realistic heating and cooling, ionization balance, tidal gravity, and pressure confinement by the host star wind. We show that mass loss takes the form of a hydrodynamic ("Parker") wind, emitted from the planet's dayside during lulls in the stellar wind. When dayside winds are suppressed by the confining action of the stellar wind, nightside winds might pick up if there is sufficient horizontal transport of heat. A hot Jupiter loses mass at maximum rates of ~2 x 10^12 g/s during its host star's pre-main-sequence phase and ~2 x10^10 g/s during the star's main sequence lifetime, for total maximum losses of ~0.06% and ~0.6% of the planet's mass, respectively. For UV fluxes F_UV < 10^4 erg/cm^2/s, the mass loss rate is approximately energy-limited and is proportional to F_UV^0.9. For larger UV fluxes, such as those typical of T Tauri stars, radiative ...

  9. Quantifying factors determining the rate of CTL escape and reversion during acute and chronic phases of HIV infection

    Energy Technology Data Exchange (ETDEWEB)

    Ganusov, Vitaly V [Los Alamos National Laboratory; Korber, Bette M [Los Alamos National Laboratory; Perelson, Alan S [Los Alamos National Laboratory

    2009-01-01

    Human immunodeficiency virus (HIV) often evades cytotoxic T cell (CTL) responses by generating variants that are not recognized by CTLs. However, the importance and quantitative details of CTL escape in humans are poorly understood. In part, this is because most studies looking at escape of HIV from CTL responses are cross-sectional and are limited to early or chronic phases of the infection. We use a novel technique of single genome amplification (SGA) to identify longitudinal changes in the transmitted/founder virus from the establishment of infection to the viral set point at 1 year after the infection. We find that HIV escapes from virus-specific CTL responses as early as 30-50 days since the infection, and the rates of viral escapes during acute phase of the infection are much higher than was estimated in previous studies. However, even though with time virus acquires additional escape mutations, these late mutations accumulate at a slower rate. A poor correlation between the rate of CTL escape in a particular epitope and the magnitude of the epitope-specific CTL response suggests that the lower rate of late escapes is unlikely due to a low efficacy of the HIV-specific CTL responses in the chronic phase of the infection. Instead, our results suggest that late and slow escapes are likely to arise because of high fitness cost to the viral replication associated with such CTL escapes. Targeting epitopes in which virus escapes slowly or does not escape at all by CTL responses may, therefore, be a promising direction for the development of T cell based HIV vaccines.

  10. Quantifying Distributions of Lyman Continuum Escape Fraction

    CERN Document Server

    Cen, Renyue

    2015-01-01

    Simulations have indicated that most of the escaped Lyman continuum photons escape through a minority of solid angles with near complete transparency, with the remaining majority of the solid angles largely opaque, resulting in a very broad and skewed probability distribution function (PDF) of the escape fraction when viewed at different angles. Thus, the escape fraction of Lyman continuum photons of a galaxy observed along a line of sight merely represents the properties of the interstellar medium along that line of sight, which may be an ill-representation of true escape fraction of the galaxy averaged over its full sky. Here we study how Lyman continuum photons escape from galaxies at $z=4-6$, utilizing high-resolution large-scale cosmological radiation-hydrodynamic simulations. We compute the PDF of the mean escape fraction ($\\left$) averaged over mock observational samples, as a function of the sample size, compared to the true mean (had you an infinite sample size). We find that, when the sample size is...

  11. Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

    Science.gov (United States)

    Cravens, T. E.; Rahmati, A.; Fox, Jane L.; Lillis, R.; Bougher, S.; Luhmann, J.; Sakai, S.; Deighan, J.; Lee, Yuni; Combi, M.; Jakosky, B.

    2017-01-01

    The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system is a key topic in planetary science. An important loss process for atomic species, such as oxygen, is ionospheric photochemical escape. Dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Many theoretical hot O models have been constructed over the years, although a number of uncertainties are present in these models, particularly concerning the elastic cross sections of O atoms with CO2. Recently, the Mars Atmosphere and Volatile Evolution mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., solar wind), allowing a new assessment of this important loss process. The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to (1) study the role that variations in solar radiation or solar wind fluxes could have on escape in a transparent fashion and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. In agreement with several more elaborate numerical models, we find that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The amount of O lost due to ion transport in the topside ionosphere is found to be about 5-10% of the total.

  12. The escape velocity and Schwarzschild metric

    CERN Document Server

    Murzagalieva, A G; Murzagaliev, G Z

    2002-01-01

    The escape velocity value in the terms of general relativity by means Schwarzschild metric is provided to make of the motion equation with Friedman cosmological model behavior build in the terms of Robertson-Worker metric. (author)

  13. St.Petersburg Escape Experience Tour

    OpenAIRE

    Palagina, Mariia; Zhak, Svetlana

    2017-01-01

    The growing popularity of Russia as a tourist destination and the high interest towards escape rooms and quests opens new business opportunities and market niches. The aim of this thesis is to develop a tourist product based on the new escape room tourism concept combining the historical, cultural and game experiences. The choice of the theme and destination was determined by the authors’ personal backgrounds and the destination proximity to Finland. The theoretical research was implement...

  14. Polymer escape from a confining potential

    Energy Technology Data Exchange (ETDEWEB)

    Mökkönen, Harri, E-mail: harri.mokkonen@aalto.fi [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Ikonen, Timo [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Jónsson, Hannes [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Faculty of Physical Sciences, University of Iceland, Reykjavík (Iceland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States); Ala-Nissila, Tapio [Department of Applied Physics and COMP CoE, Aalto University School of Science, P.O. Box 11100, FIN-00076 Aalto, Espoo (Finland); Department of Physics, Brown University, Providence, Rhode Island 02912-1843 (United States)

    2014-02-07

    The rate of escape of polymers from a two-dimensionally confining potential well has been evaluated using self-avoiding as well as ideal chain representations of varying length, up to 80 beads. Long timescale Langevin trajectories were calculated using the path integral hyperdynamics method to evaluate the escape rate. A minimum is found in the rate for self-avoiding polymers of intermediate length while the escape rate decreases monotonically with polymer length for ideal polymers. The increase in the rate for long, self-avoiding polymers is ascribed to crowding in the potential well which reduces the free energy escape barrier. An effective potential curve obtained using the centroid as an independent variable was evaluated by thermodynamic averaging and Kramers rate theory then applied to estimate the escape rate. While the qualitative features are well reproduced by this approach, it significantly overestimates the rate, especially for the longer polymers. The reason for this is illustrated by constructing a two-dimensional effective energy surface using the radius of gyration as well as the centroid as controlled variables. This shows that the description of a transition state dividing surface using only the centroid fails to confine the system to the region corresponding to the free energy barrier and this problem becomes more pronounced the longer the polymer is. A proper definition of a transition state for polymer escape needs to take into account the shape as well as the location of the polymer.

  15. Quantifying the Escape Mortality of Trawl Caught Antarctic Krill (Euphausia superba)

    Science.gov (United States)

    Krafft, Bjørn A.; Krag, Ludvig A.; Engås, Arill; Nordrum, Sigve; Bruheim, Inge; Herrmann, Bent

    2016-01-01

    Antarctic krill (Euphausia superba) is an abundant fishery resource, the harvest levels of which are expected to increase. However, many of the length classes of krill can escape through commonly used commercial trawl mesh sizes. A vital component of the overall management of a fishery is to estimate the total fishing mortality and quantify the mortality rate of individuals that escape from fishing gear. The methods for determining fishing mortality in krill are still poorly developed. We used a covered codend sampling technique followed by onboard observations made in holding tanks to monitor mortality rates of escaped krill. Haul duration, hydrological conditions, maximum fishing depth and catch composition all had no significant effect on mortality of krill escaping 16 mm mesh size nets, nor was any further mortality associated with the holding tank conditions. A non- parametric Kaplan-Meier analysis was used to model the relationship between mortality rates of escapees and time. There was a weak tendency, though not significant, for smaller individuals to suffer higher mortality than larger individuals. The mortality of krill escaping the trawl nets in our study was 4.4 ± 4.4%, suggesting that krill are fairly tolerant of the capture-and-escape process in trawls. PMID:27622510

  16. Genes that escape from X inactivation.

    Science.gov (United States)

    Berletch, Joel B; Yang, Fan; Xu, Jun; Carrel, Laura; Disteche, Christine M

    2011-08-01

    To achieve a balanced gene expression dosage between males (XY) and females (XX), mammals have evolved a compensatory mechanism to randomly inactivate one of the female X chromosomes. Despite this chromosome-wide silencing, a number of genes escape X inactivation: in women about 15% of X-linked genes are bi-allelically expressed and in mice, about 3%. Expression from the inactive X allele varies from a few percent of that from the active allele to near equal expression. While most genes have a stable inactivation pattern, a subset of genes exhibit tissue-specific differences in escape from X inactivation. Escape genes appear to be protected from the repressive chromatin modifications associated with X inactivation. Differences in the identity and distribution of escape genes between species and tissues suggest a role for these genes in the evolution of sex differences in specific phenotypes. The higher expression of escape genes in females than in males implies that they may have female-specific roles and may be responsible for some of the phenotypes observed in X aneuploidy.

  17. Extreme Heat

    Science.gov (United States)

    ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ...

  18. Studying Lyman-alpha escape and reionization in Green Pea galaxies

    Science.gov (United States)

    Yang, Huan; Malhotra, Sangeeta; Rhoads, James E.; Gronke, Max; Leitherer, Claus; Wofford, Aida; Dijkstra, Mark

    2017-01-01

    Green Pea galaxies are low-redshift galaxies with extreme [OIII]5007 emission line. We built the first statistical sample of Green Peas observed by HST/COS and used them as analogs of high-z Lyman-alpha emitters to study Ly-alpha escape and Ly-alpha sizes. Using the HST/COS 2D spectra, we found that Ly-alpha sizes of Green Peas are larger than the UV continuum sizes. We found many correlations between Ly-alpha escape fraction and galactic properties -- dust extinction, Ly-alpha kinematic features, [OIII]/[OII] ratio, and gas outflow velocities. We fit an empirical relation to predict Ly-alpha escape fraction from dust extinction and Ly-alpha red-peak velocity. In the JWST era, we can use this relation to derive the IGM HI column density along the line of sight of each high-z Ly-alpha emitter and probe the reionization process.

  19. Mandelbrot's Extremism

    NARCIS (Netherlands)

    Beirlant, J.; Schoutens, W.; Segers, J.J.J.

    2004-01-01

    In the sixties Mandelbrot already showed that extreme price swings are more likely than some of us think or incorporate in our models.A modern toolbox for analyzing such rare events can be found in the field of extreme value theory.At the core of extreme value theory lies the modelling of maxima

  20. Escape statistics for parameter sweeps through bifurcations.

    Science.gov (United States)

    Miller, Nicholas J; Shaw, Steven W

    2012-04-01

    We consider the dynamics of systems undergoing parameter sweeps through bifurcation points in the presence of noise. Of interest here are local codimension-one bifurcations that result in large excursions away from an operating point that is transitioning from stable to unstable during the sweep, since information about these "escape events" can be used for system identification, sensing, and other applications. The analysis is based on stochastic normal forms for the dynamic saddle-node and subcritical pitchfork bifurcations with a time-varying bifurcation parameter and additive noise. The results include formulation and numerical solution for the distribution of escape events in the general case and analytical approximations for delayed bifurcations for which escape occurs well beyond the corresponding quasistatic bifurcation points. These bifurcations result in amplitude jumps encountered during parameter sweeps and are particularly relevant to nano- and microelectromechanical systems, for which noise can play a significant role.

  1. Cosmic ray escape from supernova remnants

    CERN Document Server

    Gabici, Stefano

    2011-01-01

    Galactic cosmic rays are believed to be accelerated at supernova remnants via diffusive shock acceleration. Though this mechanism gives fairly robust predictions for the spectrum of particles accelerated at the shock, the spectrum of the cosmic rays which are eventually injected in the interstellar medium is more uncertain and depends on the details of the process of particle escape from the shock. Knowing the spectral shape of these escaping particles is of crucial importance in order to assess the validity of the supernova remnant paradigm for cosmic ray origin. Moreover, after escaping from a supernova remnant, cosmic rays interact with the surrounding ambient gas and produce gamma rays in the vicinity of the remnant itself. The detection of this radiation can be used as an indirect proof of the fact that the supernova remnant was indeed accelerating cosmic rays in the past.

  2. Thermal escape from extrasolar giant planets.

    Science.gov (United States)

    Koskinen, Tommi T; Lavvas, Panayotis; Harris, Matthew J; Yelle, Roger V

    2014-04-28

    The detection of hot atomic hydrogen and heavy atoms and ions at high altitudes around close-in extrasolar giant planets (EGPs) such as HD209458b implies that these planets have hot and rapidly escaping atmospheres that extend to several planetary radii. These characteristics, however, cannot be generalized to all close-in EGPs. The thermal escape mechanism and mass loss rate from EGPs depend on a complex interplay between photochemistry and radiative transfer driven by the stellar UV radiation. In this study, we explore how these processes change under different levels of irradiation on giant planets with different characteristics. We confirm that there are two distinct regimes of thermal escape from EGPs, and that the transition between these regimes is relatively sharp. Our results have implications for thermal mass loss rates from different EGPs that we discuss in the context of currently known planets and the detectability of their upper atmospheres.

  3. Bacillus anthracis factors for phagosomal escape.

    Science.gov (United States)

    Tonello, Fiorella; Zornetta, Irene

    2012-07-01

    The mechanism of phagosome escape by intracellular pathogens is an important step in the infectious cycle. During the establishment of anthrax, Bacillus anthracis undergoes a transient intracellular phase in which spores are engulfed by local phagocytes. Spores germinate inside phagosomes and grow to vegetative bacilli, which emerge from their resident intracellular compartments, replicate and eventually exit from the plasma membrane. During germination, B. anthracis secretes multiple factors that can help its resistance to the phagocytes. Here the possible role of B. anthracis toxins, phospholipases, antioxidant enzymes and capsules in the phagosomal escape and survival, is analyzed and compared with that of factors of other microbial pathogens involved in the same type of process.

  4. How Hospitable Are Space Weather Affected Habitable Zones? The Role of Ion Escape

    Science.gov (United States)

    Airapetian, Vladimir S.; Glocer, Alex; Khazanov, George V.; Loyd, R. O. P.; France, Kevin; Sojka, Jan; Danchi, William C.; Liemohn, Michael W.

    2017-02-01

    Atmospheres of exoplanets in the habitable zones around active young G-K-M stars are subject to extreme X-ray and EUV (XUV) fluxes from their host stars that can initiate atmospheric erosion. Atmospheric loss affects exoplanetary habitability in terms of surface water inventory, atmospheric pressure, the efficiency of greenhouse warming, and the dosage of the UV surface irradiation. Thermal escape models suggest that exoplanetary atmospheres around active K-M stars should undergo massive hydrogen escape, while heavier species including oxygen will accumulate forming an oxidizing atmosphere. Here, we show that non-thermal oxygen ion escape could be as important as thermal, hydrodynamic H escape in removing the constituents of water from exoplanetary atmospheres under supersolar XUV irradiation. Our models suggest that the atmospheres of a significant fraction of Earth-like exoplanets around M dwarfs and active K stars exposed to high XUV fluxes will incur a significant atmospheric loss rate of oxygen and nitrogen, which will make them uninhabitable within a few tens to hundreds of Myr, given a low replenishment rate from volcanism or cometary bombardment. Our non-thermal escape models have important implications for the habitability of the Proxima Centauri’s terrestrial planet.

  5. Martian Atmospheric and Ionospheric plasma Escape

    Science.gov (United States)

    Lundin, Rickard

    2016-04-01

    Solar forcing is responsible for the heating, ionization, photochemistry, and erosion processes in the upper atmosphere throughout the lifetime of the terrestrial planets. Of the four terrestrial planets, the Earth is the only one with a fully developed biosphere, while our kin Venus and Mars have evolved into arid inhabitable planets. As for Mars, there are ample evidences for an early Noachian, water rich period on Mars. The question is, what made Mars evolve so differently compared to the Earth? Various hydrosphere and atmospheric evolution scenarios for Mars have been forwarded based on surface morphology, chemical composition, simulations, semi-empiric (in-situ data) models, and the long-term evolution of the Sun. Progress has been made, but the case is still open regarding the changes that led to the present arid surface and tenuous atmosphere at Mars. This presentation addresses the long-term variability of the Sun, the solar forcing impact on the Martian atmosphere, and its interaction with the space environment - an electromagnetic wave and particle interaction with the upper atmosphere that has implications for its photochemistry, composition, and energization that governs thermal and non-thermal escape. Non-thermal escape implies an electromagnetic upward energization of planetary ions and molecules to velocities above escape velocity, a process governed by a combination of solar EUV radiation (ionization), and energy and momentum transfer by the solar wind. The ion escape issue dates back to the early Soviet and US-missions to Mars, but the first more accurate estimates of escape rates came with the Phobos-2 mission in 1989. Better-quality ion composition measurement results of atmospheric/ionospheric ion escape from Mars, obtained from ESA Mars Express (MEX) instruments, have improved our understanding of the ion escape mechanism. With the NASA MAVEN spacecraft orbiting Mars since Sept. 2014, dual in-situ measurement with plasma instruments are now

  6. Do the visual conditions at the point of escape affect European sea bass escape behavior?

    Directory of Open Access Journals (Sweden)

    I.E. PAPADAKIS

    2013-04-01

    Full Text Available European sea bass (Dicentrarchus labrax, an important species for the Mediterranean aquaculture industry, has been reported to escape from sea cage installations. Fish escapes are caused mainly by operational and technical failures that eventually result into a creation of a tear. Escapees may interact with wild stocks through interbreeding, transfer of pathogens and competition for food. The aim of this study was to examine at which extent the presence of a visible obstacle close to a tear on the net have an influence on sea bass propensity to escape. Fish were initially confined into small sea cages, with a tear at one side. The escape behavior was tested under experimental conditions. It is clearly demonstrated that sea bass was able to locate a tear on the net pen, immediately after its appearance. Crossings occurred in all cages, in singles or in a series of up to seven individuals. The presence of an obstacle close to the net tear altered the escape behavior of D. labrax resulting in a delay that eventually reduced the escape rate. Concluding, it is highly recommended that sea bass cages should be kept internally the culture array. Furthermore, the placement of artificial obstacles close to the sea cages could be an efficient practice that mitigates the escape risk after severe environmental conditions.

  7. Do the visual conditions at the point of escape affect European sea bass escape behavior?

    Directory of Open Access Journals (Sweden)

    I.E. PAPADAKIS

    2013-03-01

    Full Text Available European sea bass (Dicentrarchus labrax, an important species for the Mediterranean aquaculture industry, has been reported to escape from sea cage installations. Fish escapes are caused mainly by operational and technical failures that eventually result into a creation of a tear. Escapees may interact with wild stocks through interbreeding, transfer of pathogens and competition for food. The aim of this study was to examine at which extent the presence of a visible obstacle close to a tear on the net have an influence on sea bass propensity to escape. Fish were initially confined into small sea cages, with a tear at one side. The escape behavior was tested under experimental conditions. It is clearly demonstrated that sea bass was able to locate a tear on the net pen, immediately after its appearance. Crossings occurred in all cages, in singles or in a series of up to seven individuals. The presence of an obstacle close to the net tear altered the escape behavior of D. labrax resulting in a delay that eventually reduced the escape rate. Concluding, it is highly recommended that sea bass cages should be kept internally the culture array. Furthermore, the placement of artificial obstacles close to the sea cages could be an efficient practice that mitigates the escape risk after severe environmental conditions.

  8. Learning from escaped prescribed fire reviews

    Science.gov (United States)

    Anne E. Black; Dave Thomas; James Saveland; Jennifer D. Ziegler

    2011-01-01

    The U.S. wildland fire community has developed a number of innovative methods for conducting a review following escape of a prescribed fire (expanding on the typical regional or local reviews, to include more of a learning focus - expanded After Action Reviews, reviews that incorporate High Reliability Organizing, Facilitated Learning Analyses, etc). The stated purpose...

  9. Centrifugally Stimulated Exospheric Ion Escape at Mercury

    Science.gov (United States)

    Delcourt, Dominique; Seki, K.; Terada, N.; Moore, Thomas E.

    2012-01-01

    We investigate the transport of ions in the low-altitude magnetosphere magnetosphere of Mercury. We show that, because of small spatial scales, the centrifugal effect due to curvature of the E B drift paths can lead to significant particle energization in the parallel direction. We demonstrate that because of this effect, ions with initial speed smaller than the escape speed such as those produced via thermal desorption can overcome gravity and escape into the magnetosphere. The escape route of this low-energy exosphere originating material is largely controlled by the magnetospheric convection rate. This escape route spreads over a narrower range of altitudes when the convection rate increases. Bulk transport of low-energy planetary material thus occurs within a limited region of space once moderate magnetospheric convection is established. These results suggest that, via release of material otherwise gravitationally trapped, the E B related centrifugal acceleration is an important mechanism for the net supply of plasma to the magnetosphere of Mercury.

  10. Net escapement of Antartic krill in trawls

    DEFF Research Database (Denmark)

    Krafft, B.A.; Krag, Ludvig Ahm; Herrmann, Bent;

    This document describes the aims and methodology of a three year project (commenced in 2012) entitled Net Escapement of Antarctic krill in Trawls (NEAT). The study will include a morphology based mathematical modeling (FISHSELECT) of different sex and maturity groups of Antarctic krill (Euphausia...

  11. Nociception and escape behavior in planarians

    Science.gov (United States)

    Schoetz Collins, Eva-Maria

    2015-03-01

    Planarians are famous and widely studied for their regenerative capabilities. When a moving planarian is cut through the middle, the resulting head and tail pieces instantaneously retract and exhibit a characteristic escape response that differs from normal locomotion. In asexual animals, a similar reaction is observed when the planarian undergoes fission, suggesting that reproduction through self-tearing is a rather traumatic event for the animal. Using a multiscale approach, we unravel the dynamics, mechanics, and functional aspects of the planarian escape response. This musculature-driven gait was found to be a dominating response that supersedes the urge to feed or reproduce and quantitatively differs from other modes of planarian locomotion (gliding, peristalsis). We show that this escape gait constitutes the animal's pain response mediated by TRP like receptors and the neurotransmitter histamine, and that it can be induced through adverse thermal, mechanical, electrical or chemical stimuli. Ultimately, we will examine the neuronal subpopulations involved in mediating escape reflexes in planarians and how they are functionally restored during regeneration, thereby gaining mechanistic insight into the neuronal circuits required for specific behaviors. Supported by BWF CASI and Sloan Foundation.

  12. Life events and escape in conversion disorder.

    Science.gov (United States)

    Nicholson, T R; Aybek, S; Craig, T; Harris, T; Wojcik, W; David, A S; Kanaan, R A

    2016-09-01

    Psychological models of conversion disorder (CD) traditionally assume that psychosocial stressors are identifiable around symptom onset. In the face of limited supportive evidence such models are being challenged. Forty-three motor CD patients, 28 depression patients and 28 healthy controls were assessed using the Life Events and Difficulties Schedule in the year before symptom onset. A novel 'escape' rating for events was developed to test the Freudian theory that physical symptoms of CD could provide escape from stressors, a form of 'secondary gain'. CD patients had significantly more severe life events and 'escape' events than controls. In the month before symptom onset at least one severe event was identified in 56% of CD patients - significantly more than 21% of depression patients [odds ratio (OR) 4.63, 95% confidence interval (CI) 1.56-13.70] and healthy controls (OR 5.81, 95% CI 1.86-18.2). In the same time period 53% of CD patients had at least one 'high escape' event - again significantly higher than 14% in depression patients (OR 6.90, 95% CI 2.05-23.6) and 0% in healthy controls. Previous sexual abuse was more commonly reported in CD than controls, and in one third of female patients was contextually relevant to life events at symptom onset. The majority (88%) of life events of potential aetiological relevance were not identified by routine clinical assessments. Nine per cent of CD patients had no identifiable severe life events. Evidence was found supporting the psychological model of CD, the Freudian notion of escape and the potential aetiological relevance of childhood traumas in some patients. Uncovering stressors of potential aetiological relevance requires thorough psychosocial evaluation.

  13. Novel Anti-Melanoma Immunotherapies: Disarming Tumor Escape Mechanisms

    Directory of Open Access Journals (Sweden)

    Sivan Sapoznik

    2012-01-01

    Full Text Available The immune system fights cancer and sometimes temporarily eliminates it or reaches an equilibrium stage of tumor growth. However, continuous immunological pressure also selects poorly immunogenic tumor variants that eventually escape the immune control system. Here, we focus on metastatic melanoma, a highly immunogenic tumor, and on anti-melanoma immunotherapies, which recently, especially following the FDA approval of Ipilimumab, gained interest from drug development companies. We describe new immunomodulatory approaches currently in the development pipeline, focus on the novel CEACAM1 immune checkpoint, and compare its potential to the extensively described targets, CTLA4 and PD1. This paper combines multi-disciplinary approaches and describes anti-melanoma immunotherapies from molecular, medical, and business angles.

  14. Launch Pad Escape System Design (Human Spaceflight)

    Science.gov (United States)

    Maloney, Kelli

    2011-01-01

    A launch pad escape system for human spaceflight is one of those things that everyone hopes they will never need but is critical for every manned space program. Since men were first put into space in the early 1960s, the need for such an Emergency Escape System (EES) has become apparent. The National Aeronautics and Space Administration (NASA) has made use of various types of these EESs over the past 50 years. Early programs, like Mercury and Gemini, did not have an official launch pad escape system. Rather, they relied on a Launch Escape System (LES) of a separate solid rocket motor attached to the manned capsule that could pull the astronauts to safety in the event of an emergency. This could only occur after hatch closure at the launch pad or during the first stage of flight. A version of a LES, now called a Launch Abort System (LAS) is still used today for all manned capsule type launch vehicles. However, this system is very limited in that it can only be used after hatch closure and it is for flight crew only. In addition, the forces necessary for the LES/LAS to get the capsule away from a rocket during the first stage of flight are quite high and can cause injury to the crew. These shortcomings led to the development of a ground based EES for the flight crew and ground support personnel as well. This way, a much less dangerous mode of egress is available for any flight or ground personnel up to a few seconds before launch. The early EESs were fairly simple, gravity-powered systems to use when thing's go bad. And things can go bad very quickly and catastrophically when dealing with a flight vehicle fueled with millions of pounds of hazardous propellant. With this in mind, early EES designers saw such a passive/unpowered system as a must for last minute escapes. This and other design requirements had to be derived for an EES, and this section will take a look at the safety design requirements had to be derived for an EES, and this section will take a look at

  15. The Lyman Continuum Escape Fraction of the Cosmic Horseshoe: A Test of Indirect Estimates

    Science.gov (United States)

    Vasei, Kaveh; Siana, Brian; Shapley, Alice E.; Quider, Anna M.; Alavi, Anahita; Rafelski, Marc; Steidel, Charles C.; Pettini, Max; Lewis, Geraint F.

    2016-11-01

    High-redshift star-forming galaxies are likely responsible for the reionization of the universe, yet direct detection of their escaping ionizing (Lyman continuum [LyC]) photons has proven to be extremely challenging. In this study, we search for escaping LyC of the Cosmic Horseshoe, a gravitationally lensed, star-forming galaxy at z = 2.38 with a large magnification of ∼24. Transmission at wavelengths of low-ionization interstellar absorption lines in the rest-frame ultraviolet suggests a patchy, partially transparent interstellar medium. This makes it an ideal candidate for direct detection of the LyC. We obtained a 10-orbit Hubble near-UV image using the Wide Field Camera 3 (WFC3)/UVIS F275W filter that probes wavelengths just below the Lyman limit at the redshift of the Horseshoe in an attempt to detect escaping LyC radiation. After fully accounting for the uncertainties in the opacity of the intergalactic medium (IGM) and accounting for the charge transfer inefficiency in the WFC3 CCDs, we find a 3σ upper limit for the relative escape fraction of {f}{esc,{rel}}\\lt 0.08. This value is a factor of five lower than the value (0.4) predicted by the 40% transmission in the low-ion absorption lines. Though possible, it is unlikely that the nondetection is due to a high-opacity line of sight through the IGM (\\lt 20% chance). We discuss several possible causes for the discrepancy between the escape fraction and the covering fraction and consider the implications for future attempts at both direct LyC detection and indirect estimates of the escape fraction.

  16. The escape problem for mortal walkers

    CERN Document Server

    Grebenkov, D S

    2016-01-01

    We introduce and investigate the escape problem for random walkers that may eventually die, decay, bleach, or lose activity during their diffusion towards an escape or reactive region on the boundary of a confining domain. In the case of a first-order kinetics (i.e., exponentially distributed lifetimes), we study the effect of the associated death rate onto the survival probability, the exit probability, and the mean first passage time. We derive the upper and lower bounds and some approximations for these quantities. We reveal three asymptotic regimes of small, intermediate and large death rates. General estimates and asymptotics are compared to several explicit solutions for simple domains, and to numerical simulations. These results allow one to account for stochastic photobleaching of fluorescent tracers in bio-imaging, degradation of mRNA molecules in genetic translation mechanisms, or high mortality rates of spermatozoa in the fertilization process. This is also a mathematical ground for optimizing stor...

  17. The Escaping Upper Atmospheres of Hot Jupiters

    Science.gov (United States)

    Davidson, Eric; Jones, Gabrielle; Uribe, Ana; Carson, Joseph

    2017-01-01

    Hot Jupiters are massive gaseous planets which orbit closely to their parent star. The strong stellar irradiation at these small orbital separations causes the temperature of the upper atmosphere of the planet to rise. This can cause the planet's atmosphere to escape into space, creating an exoplanet outflow. We ascertained which factors determine the presence and structure of these outflows by creating one dimensional simulations of the density, pressure, velocity, optical depth, and neutral fraction of hot Jupiter atmospheres. This was done for planets of masses and radii ranging from 0.5-1.5 Mj and 0.5-1.5 Rj. We found the outflow rate to be highest for a planet of 0.5 Mj and 1.5 Rj at 5.3×10-14 Mj/Yr. We also found that the higher the escape velocity, the lower the chance of the planet having an outflow.

  18. Escape and Stand of the Pluto Atmosphere

    Institute of Scientific and Technical Information of China (English)

    GAO Chong-Yi

    2002-01-01

    Molar mass μmin of the lightest gas, which will exist "forever" in the atmosphere at the planet surface,can be evaluated by Jeans rule. The μmin of Pluto is 17.3 g@ mol-1. It is evident that both N2 and CO can be major atmospheric composition at the Pluto surface, and will exist "forever". CH4 can only be escaping slowly from Pluto atmosphere, and still holds quite a proportion in current Pluto atmosphere. However, it will not escape from Titan (or Jupiter, Saturn) atmosphere largely, and will exist "forever". Given the quantitylevelof partial pressure of CH4 in Pluto and Titan (or Jupiter, Saturn) original atmosphere is the same, it will be clear that the current partial pressure of CH4 in Pluto surface atmosphere is 10-3 Pa.

  19. Effects of submarine escape training on the pulmonary function and carbon dioxide retention in the escape

    Institute of Scientific and Technical Information of China (English)

    CHEN Rui-yong; WANG Wen-bo; FANG Yi-qun; XU Ji; XU Lin-jun

    2011-01-01

    Objective Fast buoyancy ascent escape used in submarine escape is the most probable choice of survival in case of a submarine accident.Rate of success for escape depends very much on the extent of training,in spite of the fact that rapid compression and decompression pose great challenges to the human body in terms of enormous stresses.To minimize stresses experienced during sub escape training has always been a research subject for us.Lungs are susceptible to rapid change in pressure during escape.Dynamic pulmonary function and the end-tidal PCO2 ( PETCO2 ) might be the best indicator for its effect on the pulmonary function of the submarine escapee.Methods Five male navy divers received submarine escape trainings,at different depths from 3-60 m.They were compressed at different rates (with pressure doubled every 20 s or 30 s),in the simulated submarine escape tower located in the Naval Medical Research Institute.The gas of end-expiration was collected immediately after escape,respiratory rate (RR) and dynamic pulmonary function were closely monitored,and PETCO2 was determined with the mass spectrometer.Results Experimental results showed that forced expiratory volume in 1 second (FEV1.0) tended to increase with increasing depth,and that it increased significantly at 50 m and 60 m,when compared with the basic data (P < 0.05 ),and it was coupled with a decrease in forced expiratory flow at 25 % ( FEF25% ),indicating that it had certain effect on the function of small airways.PETCO2 and RR all elevated markedly following escapes.No significant differences could be seen in RR following escapes at various depths.PETCO2 and depth ( r =0.387,P < 0.01 ) were positively correlated with compression rate ( r =0.459,P < 0.01 ) and RR ( r =0.467,P < 0.01 ).CO2 retention might be attributed to pulmonary ventilation disorder induced by rapid changes in pressure.PETCO2 was within normal range,following escapes at various depths,suggesting that increased RR might be

  20. Communication path for extreme environments

    Science.gov (United States)

    Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)

    2010-01-01

    Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

  1. Extreme cosmos

    CERN Document Server

    Gaensler, Bryan

    2011-01-01

    The universe is all about extremes. Space has a temperature 270°C below freezing. Stars die in catastrophic supernova explosions a billion times brighter than the Sun. A black hole can generate 10 million trillion volts of electricity. And hypergiants are stars 2 billion kilometres across, larger than the orbit of Jupiter. Extreme Cosmos provides a stunning new view of the way the Universe works, seen through the lens of extremes: the fastest, hottest, heaviest, brightest, oldest, densest and even the loudest. This is an astronomy book that not only offers amazing facts and figures but also re

  2. Chaotic behavior in an algorithm to escape from poor local minima in lens design

    NARCIS (Netherlands)

    Van Turnhout, M.; Bociort, F.

    2009-01-01

    In lens design, damped least-squares methods are typically used to find the nearest local minimum to a starting configuration in the merit function landscape. In this paper, we explore the use of such a method for a purpose that goes beyond local optimization. The merit function barrier, which

  3. Scrunching: a novel escape gait in planarians

    Science.gov (United States)

    Cochet-Escartin, Olivier; Mickolajczyk, Keith J.; Collins, Eva-Maria S.

    2015-10-01

    The ability to escape a predator or other life-threatening situations is central to animal survival. Different species have evolved unique strategies under anatomical and environmental constraints. In this study, we describe a novel musculature-driven escape gait in planarians, ‘scrunching’, which is quantitatively different from other planarian gaits, such as gliding and peristalsis. We show that scrunching is a conserved gait among different flatworm species, underlying its importance as an escape mechanism. We further demonstrate that it can be induced by a variety of physical stimuli, including amputation, high temperature, electric shock and low pH. We discuss the functional basis for scrunching as the preferential gait when gliding is impaired due to a disruption of mucus production. Finally, we show that the key mechanical features of scrunching are adequately captured by a simple biomechanical model that is solely based on experimental data from traction force microscopy and tissue rheology without fit parameters. Together, our results form a complete description of this novel form of planarian locomotion. Because scrunching has distinct dynamics, this gait can serve as a robust behavioral readout for studies of motor neuron and muscular functions in planarians and in particular the restoration of these functions during regeneration.

  4. Xenon Fractionation and Archean Hydrogen Escape

    Science.gov (United States)

    Zahnle, K. J.

    2015-01-01

    Xenon is the heaviest gas found in significant quantities in natural planetary atmospheres. It would seem the least likely to escape. Yet there is more evidence for xenon escape from Earth than for any element other than helium and perhaps neon. The most straightforward evidence is that most of the radiogenic Xe from the decay of (129)I (half-life 15.7 Myr) and (244)Pu (half-life 81 Myr) that is Earth's birthright is missing. The missing xenon is often attributed to the impact erosion of early atmospheres of Earth and its ancestors. It is obvious that if most of the radiogenic xenon were driven off by impacts, most of the rest of the atmophiles fared the same fate. The other line of evidence is in the nonradiogenic isotopes of xenon and its silent partner, krypton. Atmospheric xenon is strongly mass fractionated (at about 4% per amu) compared to any known solar system source (Figure 1). This is in stark contrast to krypton, which may not be fractionated at all: atmospheric Kr is slightly heavier than solar Kr (at about 0.5% per amu), but it is the same as in carbonaceous chondrites. Nonradiogenic xenon is also under abundant relative to krypton (the so-called "missing xenon" problem). Together these observations imply that xenon has been subject to fractionating escape and krypton not.

  5. Phenotypic mismatches reveal escape from arms-race coevolution.

    Science.gov (United States)

    Hanifin, Charles T; Brodie, Edmund D; Brodie, Edmund D

    2008-03-11

    Because coevolution takes place across a broad scale of time and space, it is virtually impossible to understand its dynamics and trajectories by studying a single pair of interacting populations at one time. Comparing populations across a range of an interaction, especially for long-lived species, can provide insight into these features of coevolution by sampling across a diverse set of conditions and histories. We used measures of prey traits (tetrodotoxin toxicity in newts) and predator traits (tetrodotoxin resistance of snakes) to assess the degree of phenotypic mismatch across the range of their coevolutionary interaction. Geographic patterns of phenotypic exaggeration were similar in prey and predators, with most phenotypically elevated localities occurring along the central Oregon coast and central California. Contrary to expectations, however, these areas of elevated traits did not coincide with the most intense coevolutionary selection. Measures of functional trait mismatch revealed that over one-third of sampled localities were so mismatched that reciprocal selection could not occur given current trait distributions. Estimates of current locality-specific interaction selection gradients confirmed this interpretation. In every case of mismatch, predators were "ahead" of prey in the arms race; the converse escape of prey was never observed. The emergent pattern suggests a dynamic in which interacting species experience reciprocal selection that drives arms-race escalation of both prey and predator phenotypes at a subset of localities across the interaction. This coadaptation proceeds until the evolution of extreme phenotypes by predators, through genes of large effect, allows snakes to, at least temporarily, escape the arms race.

  6. Phenotypic mismatches reveal escape from arms-race coevolution.

    Directory of Open Access Journals (Sweden)

    Charles T Hanifin

    2008-03-01

    Full Text Available Because coevolution takes place across a broad scale of time and space, it is virtually impossible to understand its dynamics and trajectories by studying a single pair of interacting populations at one time. Comparing populations across a range of an interaction, especially for long-lived species, can provide insight into these features of coevolution by sampling across a diverse set of conditions and histories. We used measures of prey traits (tetrodotoxin toxicity in newts and predator traits (tetrodotoxin resistance of snakes to assess the degree of phenotypic mismatch across the range of their coevolutionary interaction. Geographic patterns of phenotypic exaggeration were similar in prey and predators, with most phenotypically elevated localities occurring along the central Oregon coast and central California. Contrary to expectations, however, these areas of elevated traits did not coincide with the most intense coevolutionary selection. Measures of functional trait mismatch revealed that over one-third of sampled localities were so mismatched that reciprocal selection could not occur given current trait distributions. Estimates of current locality-specific interaction selection gradients confirmed this interpretation. In every case of mismatch, predators were "ahead" of prey in the arms race; the converse escape of prey was never observed. The emergent pattern suggests a dynamic in which interacting species experience reciprocal selection that drives arms-race escalation of both prey and predator phenotypes at a subset of localities across the interaction. This coadaptation proceeds until the evolution of extreme phenotypes by predators, through genes of large effect, allows snakes to, at least temporarily, escape the arms race.

  7. Characterization of escape times of Josephson junctions for signal detection.

    Science.gov (United States)

    Addesso, Paolo; Filatrella, Giovanni; Pierro, Vincenzo

    2012-01-01

    The measurement of the escape time of a Josephson junction might be used to detect the presence of a sinusoidal signal embedded in noise when use of standard signal processing tools can be prohibitive due to the extreme weakness of the source or to the huge amount of data. In this paper we show that the prescriptions for the experimental setup and some physical behaviors depend on the detection strategy. More specifically, by exploitation of the sample mean of escape times to perform detection, two resonant regions are identified. At low frequencies there is a stochastic resonance or activation phenomenon, while near the plasma frequency a geometric resonance appears. Furthermore, detection performance in the geometric resonance region is maximized at the prescribed value of the bias current. The naive sample mean detector is outperformed, in terms of error probability, by the optimal likelihood ratio test. The latter exhibits only geometric resonance, showing monotonically increasing performance as the bias current approaches the junction critical current. In this regime the escape times are vanishingly small and therefore performance is essentially limited by measurement electronics. The behavior of the likelihood ratio and sample mean detector for different values of incoming signal to noise ratio is discussed, and a relationship with the error probability is found. Detectors based on the likelihood ratio test could be employed also to estimate unknown parameters in the applied input signal. As a prototypical example we study the phase estimation problem of a sinusoidal current, which is accomplished by using the filter bank approach. Finally we show that for a physically feasible detector the performances are found to be very close to the Cramer-Rao theoretical bound. Applications might be found, for example, in some astronomical detection problems (where the all-sky gravitational and/or radio wave search for pulsars requires the analysis of nearly sinusoidal

  8. Risks incurred by hydrogen escaping from containers and conduits

    Energy Technology Data Exchange (ETDEWEB)

    Swain, M.R.; Grilliot, E.S. [Univ. of Miami, Coral Gables, FL (United States); Swain, M.N. [Analytical Technologies, Inc., Miami, FL (United States)

    1998-08-01

    This paper is a discussion of a method for hydrogen leak classification. Leaks are classified as; gas escapes into enclosed spaces, gas escapes into partially enclosed spaces (vented), and gas escapes into unenclosed spaces. Each of the three enclosure classifications is further divided into two subclasses; total volume of hydrogen escaped and flow rate of escaping hydrogen. A method to aid in risk assessment determination in partially enclosed spaces is proposed and verified for several enclosure geometries. Examples are discussed for additional enclosure geometries.

  9. The cost of the sword: escape performance in male swordtails.

    Directory of Open Access Journals (Sweden)

    Alex Baumgartner

    Full Text Available The handicap theory of sexual selection posits that male display traits that are favored in mate choice come at a significant cost to performance. We tested one facet of this hypothesis in the green swordtail (Xiphophorus helleri. In this species, the lower ray of male caudal fin is extended into a 'sword', which serves to attract potential mates. However, bearing a long sword may increase drag and thus compromise a male's ability to swim effectively. We tested escape performance in this species by eliciting C-start escape responses, an instinctive escape behavior, in males with various sword lengths. We then removed males' swords and retested escape performance. We found no relationship between escape performance and sword length and no effect of sword removal on escape performance. While having a large sword may attract a predator's attention, our results suggest that sword size does not compromise a male's escape performance.

  10. Escape from attracting sets in randomly perturbed systems.

    Science.gov (United States)

    Rodrigues, Christian S; Grebogi, Celso; de Moura, Alessandro P S

    2010-10-01

    The dynamics of escape from an attractive state due to random perturbations is of central interest to many areas in science. Previous studies of escape in chaotic systems have rather focused on the case of unbounded noise, usually assumed to have Gaussian distribution. In this paper, we address the problem of escape induced by bounded noise. We show that the dynamics of escape from an attractor's basin is equivalent to that of a closed system with an appropriately chosen "hole." Using this equivalence, we show that there is a minimum noise amplitude above which escape takes place, and we derive analytical expressions for the scaling of the escape rate with noise amplitude near the escape transition. We verify our analytical predictions through numerical simulations of two well-known two-dimensional maps with noise.

  11. Room escape at class: Escape games activities to facilitate the motivation and learning in computer science

    Directory of Open Access Journals (Sweden)

    Carlos Borrego

    2017-06-01

    Full Text Available Real-life room-escape games are ludic activities in which participants enter a room in order to get out of it only after solving some riddles. In this paper, we explain a Room Escape teaching experience developed in the Engineering School at Universitat Autònoma de Barcelona. The goal of this activity is to increase student’s motivation and to improve their learning on two courses of the second year in the Computer Engineering degree: Computer Networksand Information and Security.

  12. [Crossing borders. The motivation of extreme sportsmen].

    Science.gov (United States)

    Opaschowski, H W

    2005-08-01

    In his article "Crossing borders -- the motivation of extreme sportsmen" the author gets systematically to the bottom of the question of why extreme sportsmen voluntarily take risks and endanger themselves. Within the scope of a representative sampling 217 extreme sportsmen -- from the fields of mountain biking, trekking and free climbing, canoyning, river rafting and deep sea diving, paragliding, parachuting, bungee jumping and survival training -- give information about their personal motives. What fascinates them? The attraction of risk? The search for sensation? Or the drop out of everyday life? And what comes afterwards? Does in the end the whole life become an extreme sport? Fact is: they live extremely, because they want to move beyond well-trodden paths. To escape the boredom of everyday life they are searching for the kick, the thrill, the no-limit experience. It's about calculated risk between altitude flight and deep sea adventure.

  13. Evolution and Yields of Extremely Metal Poor Intermediate Mass Stars

    CERN Document Server

    Herwig, Falk

    2004-01-01

    Intermediate mass stellar evolution tracks from the main sequence to the tip of the AGB for five initial masses (2 to 6Msun) and metallicity Z=0.0001 have been computed. The detailed 1D structure and evolution models include exponential overshooting, mass loss and a detailed nucleosynthesis network with updated nuclear reaction rates. The network includes a two-particle heavy neutron sink for approximating neutron density in the He-shell flash. It is shown how the neutron-capture nucleosynthesis is important in models of very low metallicity for the formation of light neutron-heavy species, like sodium or the heavy neon and magnesium isotopes. The models have high resolution, as required for modeling the third dredge-up. All sequences have been followed from the pre-main sequence to the end of the AGB when all envelope mass is lost. Detailed structural and chemical model properties as well as yields are presented. This set of stellar models is based on standard assumptions and updated input physics. It can be...

  14. Evolutionary escape from the prisoner's dilemma.

    Science.gov (United States)

    Worden, Lee; Levin, Simon A

    2007-04-07

    The classic prisoner's dilemma model of game theory is modified by introducing occasional variations on the options available to players. Mutation and selection of game options reliably change the game matrix, gradually, from a prisoner's dilemma game into a byproduct mutualism one, in which cooperation is stable, and "temptation to defect" is replaced by temptation to cooperate. This result suggests that when there are many different potential ways of interacting, exploring those possibilities may make escape from prisoner's dilemmas a common outcome in the world. A consequence is that persistent prisoner's dilemma structures may be less common than one might otherwise expect.

  15. Arduino adventures escape from Gemini station

    CERN Document Server

    Kelly, James Floyd

    2013-01-01

    Arduino Adventures: Escape from Gemini Station provides a fun introduction to the Arduino microcontroller by putting you (the reader) into the action of a science fiction adventure story.  You'll find yourself following along as Cade and Elle explore Gemini Station-an orbiting museum dedicated to preserving and sharing technology throughout the centuries. Trouble ensues. The station is evacuated, including Cade and Elle's class that was visiting the station on a field trip. Cade and Elle don't make it aboard their shuttle and are trapped on the station along with a friendly artificial intellig

  16. Immune escape mechanisms in acute myeloid leukemia

    OpenAIRE

    Kolbeck, Alexandra

    2012-01-01

    Obwohl in den letzten Jahren in der Therapie der AML große Fortschritte erzielt wurden, sind die Ursachen für die hohen Rezidivraten nach allogener SZT weiterhin nicht vollständig geklärt. Als Ursache werden Immune Escape Mechanismen diskutiert, mit deren Hilfe sich Tumorzellen vor der Elimination durch das Immunsystem schützen. Nach einer allogenen Stammzelltransplantation spielen Zytokine bei der Entwicklung einer GvHD, bzw. des GvL-Effektes eine zentrale Rolle. Besonders IFNγ ist ein Schlü...

  17. Serial Escape System For Aircraft Crews

    Science.gov (United States)

    Wood, Kenneth E.

    1990-01-01

    Emergency escape system for aircraft and aerospace vehicles ejects up to seven crewmembers, one by one, within 120 s. Intended for emergencies in which disabled craft still in stable flight at no more than 220 kn (113 m/s) equivalent airspeed and sinking no faster than 110 ft/s (33.5 m/s) at altitudes up to 50,000 ft (15.2 km). Ejection rockets load themselves from magazine after each crewmember ejected. Jumpmaster queues other crewmembers and helps them position themselves on egress ramp. Rockets pull crewmembers clear of aircraft structure. Provides orderly, controlled exit and avoids ditching at sea or landing in rough terrain.

  18. Belt fires and mine escape problems

    Energy Technology Data Exchange (ETDEWEB)

    Kovac, J.G.; Lazzara, C.P. [Bureau of Mines, Pittsburgh, PA (United States); Kravitz, J.H.

    1996-12-31

    A conveyor belt fire in an underground coal mine is a serious threat to life and property. About 30% of the reportable underground coal mine fires from 1988 through 1992 occurred in belt entries. In one instance, a fire started in the drive area of a belt line, spread rapidly, and resulted in seating of the entire mine. Large-scale studies conducted by the U.S. Bureau of Mines in an aboveground fire gallery at Lake Lynn Laboratory clearly show the hazards of conveyor belt fires. Mine conveyor belt formulations which passed the current Federal acceptance test for fire-resistant betting were completely consumed by propagating fires or propagated flame, with flame spread rates ranging from 0.3 to 9 m/min. High downstream temperatures and large quantities of smoke and toxic gases, such as carbon monoxide, were generated as the belting burned. The smoke and gases can be spread by the mine`s ventilation system and can create significant problems for miners in the process of evacuation, such as reduction in visibility and incapacitation. In the aftermath of a belt fire, the atmosphere inside of the mine can become smoke filled or unbreathable, forcing miners to evacuate while wearing Self-Contained Self-Rescuers (SCSR`s), Sometimes there is confusion about how to regard the rated duration of an MSHA/NIOSH-approved 60-min. SCSR, especially when an SCSR is used in a way which takes it outside of the test conditions under which it was approved. As examples, for a mine escape that takes a miner from the deepest point of penetration in the mine to the surface: How long will a 60-min. SCSR actually last? and How many SCSR`s will a miner need? To answer these kinds of questions, in-mine data being gathered on escape times, distance and heart rates using miners escaping on foot and under oxygen. A model will be developed and validated which predicts how much oxygen is actually needed for a mine escape, and compares oxygen consumption bare faced versus wearing an SCSR.

  19. X-chromosome inactivation and escape

    Indian Academy of Sciences (India)

    Christine M. Disteche; Joel B. Berletch

    2015-12-01

    X-chromosome inactivation, which was discovered by Mary Lyon in 1961 results in random silencing of one X chromosome in female mammals. This review is dedicated to Mary Lyon, who passed away last year. She predicted many of the features of X inactivation, for e.g., the existence of an X inactivation center, the role of L1 elements in spreading of silencing and the existence of genes that escape X inactivation. Starting from her published work here we summarize advances in the field.

  20. Molecular Dications in Planetary Atmospheric Escape

    Directory of Open Access Journals (Sweden)

    Stefano Falcinelli

    2016-08-01

    Full Text Available Fundamental properties of multiply charged molecular ions, such as energetics, structure, stability, lifetime and fragmentation dynamics, are relevant to understand and model the behavior of gaseous plasmas as well as ionosphere and astrophysical environments. Experimental determinations of the Kinetic Energy Released (KER for ions originating from dissociations reactions, induced by Coulomb explosion of doubly charged molecular ions (molecular dications produced by double photoionization of CO2, N2O and C2H2 molecules of interest in planetary atmospheres, are reported. The KER measurement as a function of the ultraviolet (UV photon energy in the range of 28–65 eV was extracted from the electron-ion-ion coincidence spectra obtained by using tunable synchrotron radiation coupled with ion imaging techniques at the ELETTRA Synchrotron Light Laboratory Trieste, Italy. These experiments, coupled with a computational analysis based on a Monte Carlo trajectory simulation, allow assessing the probability of escape for simple ionic species in the upper atmosphere of Mars, Venus and Titan. The measured KER in the case of H+, C+, CH+, CH2+, N+, O+, CO+, N2+ and NO+ fragment ions range between 1.0 and 5.5 eV, being large enough to allow these ionic species to participate in the atmospheric escape from such planets into space. In the case of Mars, we suggest a possible explanation for the observed behavior of the O+ and CO22+ ion density profiles.

  1. Escape mechanisms of dust in Io

    Science.gov (United States)

    Flandes, A.

    The injection of material into the jovian magnetosphere through Io's volcanic activity makes possible the formation of structures such as the plasma torus and the dust ballerina skirt. Io's high temperature volcanism produces spectacular plumes, but even the tallest plumes, as those of Pelen Patera, will not produce enough energy to defeat the gravitational attraction of Io. The fact is that dust escapes from Io, which implies that a second mechanism is acting on the grains. Grains brought to the top of the highest plumes by the volcanic forces are still under Io's gravitational pull, but need only a minimum charge (~10-1 4 C) so that the Lorentz force due to the Jovian magnetic field equilibrates this attraction. In the volcanic vents, the escape velocity of the ejected material and its own density produces enough collisions to create charges. On top of the highest plumes (~500km) charged grains are exposed to the plasma torus that co-rotates rigidly with Jupiter and, due to the relative velocity among Io and the torus, the grains will be dragged away from Io. As it is well known, these dust grains will also be dragged away from Jupiter.

  2. Escape of water molecular from Carbon Nanotubes

    Science.gov (United States)

    Li, Jiaxi; Li, Wenfeng; Zhang, Jianwei

    2014-03-01

    Understanding and controlling the transport of water molecules through nanopores have attracted great interest due to potential applications for designing novel nanofluidic devices, machines and sensors. In this work, we theoretically investigate the effects of an external nonuniform electric field on the escape of water molecules through single-walled carbon nanotubes (SWNTs) by using of molecular dynamics (MD) simulations. When polar water molecules are placed in the gradient electric field, the electric force is experienced that can drive the water molecules. Molecular dynamics simulations show that the escape probability of water obeys the Boltzmann distribution. Our results show that energy barrier delta E is independent of temperature which indicates that it is a single-barrier system. From the MD results statistics, the key parameters could be determined such that the relationship between energy barrier delta E and diameter of SWNTs and nozzle distance of the charge r would be revealed that could deepen our current theoretical understanding on transport of water molecular inside SWNTs with the nonuniform electric field.

  3. Fast escaping points of entire functions

    CERN Document Server

    Rippon, P J

    2010-01-01

    Let $f$ be a transcendental entire function and let $A(f)$ denote the set of points that escape to infinity `as fast as possible' under iteration. By writing $A(f)$ as a countable union of closed sets, called `levels' of $A(f)$, we obtain a new understanding of the structure of this set. For example, we show that if $U$ is a Fatou component in $A(f)$, then $\\partial U\\subset A(f)$ and this leads to significant new results and considerable improvements to existing results about $A(f)$. In particular, we study functions for which $A(f)$, and each of its levels, has the structure of an `infinite spider's web'. We show that there are many such functions and that they have a number of strong dynamical properties. This new structure provides an unexpected connection between a conjecture of Baker concerning the components of the Fatou set and a conjecture of Eremenko concerning the components of the escaping set.

  4. Uremic escape of renal allograft rejection

    Energy Technology Data Exchange (ETDEWEB)

    van Schilfgaarde, R. (Rijksuniversiteit Leiden (Netherlands). Academisch Ziekenhuis); van Breda Vriesman, P.J.C. (Rijksuniversiteit Limburg Maastricht (Netherlands). Dept. of Immunopathology)

    1981-10-01

    It is demonstrated in rats that, in the presence of early postoperative severe but transient uremia, the survival of first set Brown-Norway (BN) renal allografts in Lewis (LEW) recipients is at least three times prolonged when compared to non-uremic controls. This phenomenon is called 'uremic escape of renal allograft rejection'. By means of lethal X-irradiation of donors of BN kidneys transplanted into transiently uremic and non-uremic LEW recipients, the presence of passenger lymphocyte immunocompetence is demonstrated to be obilgatory for this phenomenon to occur. As a result of mobile passenger lymphocyte immunocompetence, a graft-versus-host (GVH) reaction is elicited in the spleens of LEW recipients of BN kidneys which amplifies the host response. The splenomegaly observed in LEW recipients of BN kidneys is caused not only by this GVH reaction, which is shown to be exquisitely sensitive to even mild uremia. It is also contributed to by a proliferative response of the host against the graft (which latter response is equated with an in vivo equivalent of a unilateral mixed lymphocyte reaction (MLR)), since the reduction in spleen weights caused by abrogation of mobile passenger lymphocyte immunocompetence brought about by lethal donor X-irradiation is increased significantly by early postoperative severe but transient uremia. It is concluded that in uremic escape of renal allograft rejection both reactions are suppressed by uremia during the early post-operative period.

  5. Escape from viscosity : the kinematics and hydrodynamics of copepod foraging and escape swimming

    NARCIS (Netherlands)

    van Duren, LA; Videler, JJ

    2003-01-01

    Feeding and escape swimming in adult females of the calanoid copepod. Temora lopgicornis Muller were investigated and compared. Swimming velocities were calculated using a 3-D filming setup., Foraging velocities ranged between 2 and 6 min s(-1), while maximum velocities of up to 80 mm s(-1) were rea

  6. Oxygen escape from the Earth during geomagnetic reversals: Implications to mass extinction

    Science.gov (United States)

    Wei, Yong; Pu, Zuyin; Zong, Qiugang; Wan, Weixing; Ren, Zhipeng; Fraenz, Markus; Dubinin, Eduard; Tian, Feng; Shi, Quanqi; Fu, Suiyan; Hong, Minghua

    2014-05-01

    The evolution of life is affected by variations of atmospheric oxygen level and geomagnetic field intensity. Oxygen can escape into interplanetary space as ions after gaining momentum from solar wind, but Earth's strong dipole field reduces the momentum transfer efficiency and the ion outflow rate, except for the time of geomagnetic polarity reversals when the field is significantly weakened in strength and becomes Mars-like in morphology. The newest databases available for the Phanerozoic era illustrate that the reversal rate increased and the atmospheric oxygen level decreased when the marine diversity showed a gradual pattern of mass extinctions lasting millions of years. We propose that accumulated oxygen escape during an interval of increased reversal rate could have led to the catastrophic drop of oxygen level, which is known to be a cause of mass extinction. We simulated the oxygen ion escape rate for the Triassic-Jurassic event, using a modified Martian ion escape model with an input of quiet solar wind inferred from Sun-like stars. The results show that geomagnetic reversal could enhance the oxygen escape rate by 3-4 orders only if the magnetic field was extremely weak, even without consideration of space weather effects. This suggests that our hypothesis could be a possible explanation of a correlation between geomagnetic reversals and mass extinction. Therefore, if this causal relation indeed exists, it should be a "many-to-one" scenario rather the previously considered "one-to-one", and planetary magnetic field should be much more important than previously thought for planetary habitability.

  7. Exploiting the Poor

    DEFF Research Database (Denmark)

    Kamp Justesen, Mogens; Bjørnskov, Christian

    2014-01-01

    While extant research has focused on the causes and consequences of corruption at the macro-level, less effort has been devoted to understanding the micro-foundation of corruption. We argue that poor people are more likely to be victims of corrupt behavior by street-level bureaucrats as the poor ...

  8. Inference in `poor` languages

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, S.

    1996-10-01

    Languages with a solvable implication problem but without complete and consistent systems of inference rules (`poor` languages) are considered. The problem of existence of finite complete and consistent inference rule system for a ``poor`` language is stated independently of the language or rules syntax. Several properties of the problem arc proved. An application of results to the language of join dependencies is given.

  9. Strong purifying selection at genes escaping X chromosome inactivation.

    Science.gov (United States)

    Park, Chungoo; Carrel, Laura; Makova, Kateryna D

    2010-11-01

    To achieve dosage balance of X-linked genes between mammalian males and females, one female X chromosome becomes inactivated. However, approximately 15% of genes on this inactivated chromosome escape X chromosome inactivation (XCI). Here, using a chromosome-wide analysis of primate X-linked orthologs, we test a hypothesis that such genes evolve under a unique selective pressure. We find that escape genes are subject to stronger purifying selection than inactivated genes and that positive selection does not significantly affect the evolution of these genes. The strength of selection does not differ between escape genes with similar versus different expression levels in males versus females. Intriguingly, escape genes possessing Y homologs evolve under the strongest purifying selection. We also found evidence of stronger conservation in gene expression levels in escape than inactivated genes. We hypothesize that divergence in function and expression between X and Y gametologs is driving such strong purifying selection for escape genes.

  10. Dynamical correlations in the escape strategy of Influenza A virus

    Science.gov (United States)

    Taggi, L.; Colaiori, F.; Loreto, V.; Tria, F.

    2013-03-01

    The evolutionary dynamics of human Influenza A virus presents a challenging theoretical problem. An extremely high mutation rate allows the virus to escape, at each epidemic season, the host immune protection elicited by previous infections. At the same time, at each given epidemic season a single quasi-species, that is a set of closely related strains, is observed. A non-trivial relation between the genetic (i.e., at the sequence level) and the antigenic (i.e., related to the host immune response) distances can shed light into this puzzle. In this paper we introduce a model in which, in accordance with experimental observations, a simple interaction rule based on spatial correlations among point mutations dynamically defines an immunity space in the space of sequences. We investigate the static and dynamic structure of this space and we discuss how it affects the dynamics of the virus-host interaction. Interestingly we observe a staggered time structure in the virus evolution as in the real Influenza evolutionary dynamics.

  11. Escape of the martian protoatmosphere and initial water inventory

    CERN Document Server

    Erkaev, N V; Elkins-Tanton, L; Stökl, A; Odert, P; Marcq, E; Dorfi, E A; Kislyakova, K G; Kulikov, Yu N; Leitzinger, M; Güdel, M

    2013-01-01

    Latest research in planet formation indicate that Mars formed within a few million years (Myr) and remained a planetary embryo that never grew to a more massive planet. It can also be expected from dynamical models, that most of Mars' building blocks consisted of material that formed in orbital locations just beyond the ice line which could have contained ~0.1-0.2 wt. % of H2O. By using these constraints, we estimate the nebula-captured and catastrophically outgassed volatile contents during the solidification of Mars' magma ocean and apply a hydrodynamic upper atmosphere model for the study of the soft X-ray and extreme ultraviolet (XUV) driven thermal escape of the martian protoatmosphere during the early active epoch of the young Sun. The amount of gas that has been captured from the protoplanetary disk into the planetary atmosphere is calculated by solving the hydrostatic structure equations in the protoplanetary nebula. Depending on nebular properties such as the dust grain depletion factor, planetesimal...

  12. Interplay and escape in three-body scattering.

    Science.gov (United States)

    Shebalin, J. V.; Tippens, A. L.

    1996-05-01

    The problem of three gravitationally interacting bodies, with total energy less than zero, is investigated numerically. After introducing the concepts of `periastron graphs' and `composite binaries', time-of-escape and interplay are precisely defined. These definitions are useful in characterizing the complete scattering process: escape to t=-{infinity}, interplay, and escape to t=+{infinity}. These definitions are also useful for the efficient and automatic termination of a numerical simulation of interplay.

  13. Experimental self-punishment and superstitious escape behavior.

    Science.gov (United States)

    MIGLER, B

    1963-07-01

    Rats were trained to escape from shock by pressing a bar. Bar holding was subsequently punished with very brief shocks. This treatment failed to depress bar-holding behavior. In some cases, although the escape shocks were delivered very infrequently, bar holding was maintained and resulted in the delivery of several thousand punishments per session. These and other effects of the punishment treatment were investigated. Finally, some of the possibilities of superstitious escape responding were explored by presenting inescapable shocks to rats that had been trained to escape shock by lever pressing. Although responding during these shocks had no programmed consequences, responding was sustained.

  14. Cockroaches keep predators guessing by using preferred escape trajectories

    Science.gov (United States)

    Domenici, P.; Booth, D.; Blagburn, J.M.; Bacon, J. P.

    2009-01-01

    Summary Anti-predator behaviour is vital for most animals, and calls for accurate timing and swift motion. While fast reaction times [1] and predictable, context-dependent, escape initiation distances [2] are common features of most escape systems, previous work has highlighted the need for unpredictability in escape directions, in order to prevent predators from learning a repeated, fixed pattern [3–5]. Ultimate unpredictability would result from random escape trajectories. Although this strategy would deny any predictive power to the predator, it would also result in some escape trajectories towards the threat. Previous work has shown that escape trajectories are in fact generally directed away from the threat, although with a high variability [5–8]. However, the rules governing this variability are largely unknown. Here, we demonstrate tha t individual cockroaches (Periplaneta americana, a much studied model prey species [9–14]) keep each escape unpredictable by running along one of a set of preferred trajectories at fixed angles from the direction of the threatening stimulus. These results provide a new paradigm for understanding the behavio ural strategies for escape responses, underscoring the need to revisit the neural mechanisms controlling escape directions in the cockroach and similar animal models, and the evolutionary forces driving unpredictable, or “protean” [3], anti-predator behaviour. PMID:19013065

  15. The Fastest Saccadic Responses Escape Visual Masking

    DEFF Research Database (Denmark)

    M. Crouzet, Sébastien; Overgaard, Morten; Busch, Niko A.

    2014-01-01

    , which gives access to very early stages of visual processing, target visibility was reduced either by OSM, conventional backward masking, or low stimulus contrast. A general reduction of performance was observed in all three conditions. However, the fastest saccades did not show any sign of interference......Object-substitution masking (OSM) occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears. The reduction of target visibility occurring after OSM has been suggested to result from a specific interference with reentrant...... visual processing while the initial feedforward processing is thought to be left intact. We tested a prediction derived from this hypothesis: the fastest responses, being triggered before the beginning of reentrant processing, should escape the OSM interference. In a saccadic choice reaction time task...

  16. Escape dynamics through a continuously growing leak

    Science.gov (United States)

    Kovács, Tamás; Vanyó, József

    2017-06-01

    We formulate a model that describes the escape dynamics in a leaky chaotic system in which the size of the leak depends on the number of the in-falling particles. The basic motivation of this work is the astrophysical process, which describes the planetary accretion. In order to study the dynamics generally, the standard map is investigated in two cases when the dynamics is fully hyperbolic and in the presence of Kolmogorov-Arnold-Moser islands. In addition to the numerical calculations, an analytic solution to the temporal behavior of the model is also derived. We show that in the early phase of the leak expansion, as long as there are enough particles in the system, the number of survivors deviates from the well-known exponential decay. Furthermore, the analytic solution returns the classical result in the limiting case when the number of particles does not affect the leak size.

  17. Modeling extreme risks in ecology.

    Science.gov (United States)

    Burgman, Mark; Franklin, James; Hayes, Keith R; Hosack, Geoffrey R; Peters, Gareth W; Sisson, Scott A

    2012-11-01

    Extreme risks in ecology are typified by circumstances in which data are sporadic or unavailable, understanding is poor, and decisions are urgently needed. Expert judgments are pervasive and disagreements among experts are commonplace. We outline approaches to evaluating extreme risks in ecology that rely on stochastic simulation, with a particular focus on methods to evaluate the likelihood of extinction and quasi-extinction of threatened species, and the likelihood of establishment and spread of invasive pests. We evaluate the importance of assumptions in these assessments and the potential of some new approaches to account for these uncertainties, including hierarchical estimation procedures and generalized extreme value distributions. We conclude by examining the treatment of consequences in extreme risk analysis in ecology and how expert judgment may better be harnessed to evaluate extreme risks.

  18. Testosterone for Poor Ovarian Responders

    DEFF Research Database (Denmark)

    Polyzos, Nikolaos P; Davis, Susan R; Drakopoulos, Panagiotis

    2016-01-01

    ovarian stimulation with a duration varying from 5 to 21 days. Nevertheless, the key question to be asked is whether, based on ovarian physiology and testosterone pharmacokinetics, a short course of testosterone administration of more than 10 mg could be expected to have any beneficial effect...... on reproductive outcome. The rationale for asking this question lies in the existing scientific evidence derived from basic research and animal studies regarding the action of androgens during folliculogenesis, showing that their main effect in follicular development is defined during the earlier developmental...... stages. In addition, extreme testosterone excess is not only likely to induce adverse events but has also the potential to be ineffective and even detrimental. Thus, evidence from clinical studies is not enough to either "reopen" or "close" the "androgen chapter" in poor responders, mainly because...

  19. Escape behaviour in the stomatopod crustacean Squilla mantis, and the evolution of the caridoid escape reaction.

    Science.gov (United States)

    Heitler, W J; Fraser, K; Ferrero, E A

    2000-01-01

    The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards 'lurch' or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll. A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably. The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.

  20. The Origins and Underpinning Principles of E-Scape

    Science.gov (United States)

    Kimbell, Richard

    2012-01-01

    In this article I describe the context within which we developed project e-scape and the early work that laid the foundations of the project. E-scape (e-solutions for creative assessment in portfolio environments) is centred on two innovations. The first concerns a web-based approach to portfolio building; allowing learners to build their…

  1. How many ions have escaped the Martian atmosphere?

    Science.gov (United States)

    Brain, David; McFadden, James; Halekas, Jasper; Connerney, J. E. P.; Eparvier, Frank; Mitchell, David; Bougher, Stephen W.; Bowers, Charlie; Curry, Shannon; Dong, Chuanfei; Dong, Yaxue; Egan, Hilary; Fang, Xiaohua; Harada, Yuki; Jakosky, Bruce; Lillis, Robert; Luhmann, Janet; Ma, Yingjuan; Modolo, Ronan; Weber, Tristan

    2016-10-01

    The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission has been making science measurements of the Martian upper atmosphere and its escape to space since November 2014. A key part of this effort is the measurement of the escape rates of charged particles (ions) at present and over solar system history. The lack of a global dynamo magnetic field at Mars leaves its upper atmosphere more directly exposed to the impinging solar wind than magnetized planets such as Earth. For this reason it is thought that ion escape at Mars may have played a significant role in long term climate change. MAVEN measures escaping planetary ions directly, with high energy, mass, and time resolution.With nearly two years of observations in hand, we will report the average ion escape rate and the spatial distribution of escaping ions as measured by MAVEN and place them in context with previous measurements of ion loss by other spacecraft (e.g. Phobos 2 and Mars Express). We will then report on the measured variability in ion escape rates with different drivers (e.g. solar EUV, solar wind pressure, etc.). Finally, we will use these results to provide an initial estimate of the total ion escape from Mars over billions of years.

  2. Entrapment and escape of liquid lubricant in metal forming

    DEFF Research Database (Denmark)

    Bech, Jakob Ilsted; Bay, Niels; Eriksen, Morten

    1999-01-01

    Using a transparent tool entrapment, compression and eventual escape of liquid lubricant in surface pockets is observed in plane strip drawing. The two mechanisms of lubricant escape. Micro Plasto HydroDynamic and Hydrostatic Lubrication (MPHDL and MPHSL), are observed and quantified experimentally...

  3. 46 CFR 169.313 - Means of escape.

    Science.gov (United States)

    2010-10-01

    ... a hold-back to hold the scuttle in an open position. (e) The required means of escape must not have... escape is acceptable provided that— (1) There is no source of fire in the space, such as a galley stove... back of the ladder; and (4) Except when unavoidable obstructions are encountered, there must be...

  4. 46 CFR 177.500 - Means of escape.

    Science.gov (United States)

    2010-10-01

    ...) There is no stove, heater, or other source of fire in the space; (3) The means of escape is located as... this section, each space accessible to passengers or used by the crew on a regular basis, must have at... escape must be widely separated and, if possible, at opposite ends or sides of the space to minimize the...

  5. Behavioural asymmetry affects escape performance in a teleost fish

    NARCIS (Netherlands)

    Dadda, Marco; Koolhaas, Wouter H.; Domenici, Paolo

    2010-01-01

    Escape performance is fundamental for survival in fish and most other animals. While previous work has shown that both intrinsic (e.g. size, shape) and extrinsic (e.g. temperature, hypoxia) factors can affect escape performance, the possibility that behavioural asymmetry may affect timing and locomo

  6. Green Pea Galaxies Reveal Secrets of Lyα Escape

    Science.gov (United States)

    Yang, Huan; Malhotra, Sangeeta; Gronke, Max; Rhoads, James E.; Dijkstra, Mark; Jaskot, Anne; Zheng, Zhenya; Wang, Junxian

    2016-04-01

    We analyze archival Lyα spectra of 12 “Green Pea” galaxies observed with the Hubble Space Telescope, model their Lyα profiles with radiative transfer models, and explore the dependence of the Lyα escape fraction on various properties. Green Pea galaxies are nearby compact starburst galaxies with [O iii] λ5007 equivalent widths (EWs) of hundreds of Å. All 12 Green Pea galaxies in our sample show Lyα lines in emission, with an Lyα EW distribution similar to high-redshift Lyα emitters. Combining the optical and UV spectra of Green Pea galaxies, we estimate their Lyα escape fractions and find correlations between Lyα escape fraction and kinematic features of Lyα profiles. The escape fraction of Lyα in these galaxies ranges from 1.4% to 67%. We also find that the Lyα escape fraction depends strongly on metallicity and moderately on dust extinction. We compare their high-quality Lyα profiles with single H i shell radiative transfer models and find that the Lyα escape fraction anticorrelates with the derived H i column densities. Single-shell models fit most Lyα profiles well, but not the ones with the highest escape fractions of Lyα. Our results suggest that low H i column density and low metallicity are essential for Lyα escape and make a galaxy an Lyα emitter.

  7. Escape response of planktonic protists to fluid mechanical signals

    DEFF Research Database (Denmark)

    Jakobsen, Hans Henrik

    2001-01-01

    The escape response to fluid mechanical signals was examined in 6 protists, 4 ciliates and 2 dinoflagellates. When exposed to a siphon flow. 3 species of ciliates, Balanion comatum, Strobilidium sp., and Mesodinium pulex, responded with escape jumps. The threshold deformation rates required...

  8. Escape for the Slow Solar Wind

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    Plasma from the Sun known as the slow solar wind has been observed far away from where scientists thought it was produced. Now new simulations may have resolved the puzzle of where the slow solar wind comes from and how it escapes the Sun to travel through our solar system.An Origin PuzzleA full view of a coronal hole (dark portion) from SDO. The edges of the coronal hole mark the boundary between open and closed magnetic field lines. [SDO; adapted from Higginson et al. 2017]The Suns atmosphere, known as the corona, is divided into two types of regions based on the behavior of magnetic field lines. In closed-field regions, the magnetic field is firmly anchored in the photosphere at both ends of field lines, so traveling plasma is confined to coronal loops and must return to the Suns surface. In open-field regions, only one end of each magnetic field line is anchored in the photosphere, so plasma is able to stream from the Suns surface out into the solar system.This second type of region known as a coronal hole is thought to be the origin of fast-moving plasma measured in our solar system and known as the fast solar wind. But we also observe a slow solar wind: plasma that moves at speeds of less than 500 km/s.The slow solar wind presents a conundrum. Its observational properties strongly suggest it originates in the hot, closed corona rather than the cooler, open regions. But if the slow solar wind plasma originates in closed-field regions of the Suns atmosphere, then how does it escape from the Sun?Slow Wind from Closed FieldsA team of scientists led by Aleida Higginson (University of Michigan) has now used high-resolution, three-dimensional magnetohydrodynamic simulations to show how the slow solar wind can be generated from plasma that starts outin closed-field parts of the Sun.A simulated heliospheric arc, composed of open magnetic field lines. [Higginson et al. 2017]Motions on the Suns surface near the boundary between open and closed-field regions the boundary

  9. Escaping in couples facilitates evacuation: Experimental study and modeling

    CERN Document Server

    Guo, Ning; Hu, Mao-Bin; Ding, Jian-Xun; Ding, Zhong-Jun

    2015-01-01

    In this paper, the impact of escaping in couples on the evacuation dynamics has been investigated via experiments and modeling. Two sets of experiments have been implemented, in which pedestrians are asked to escape either in individual or in couples. The experiments show that escaping in couples can decrease the average evacuation time. Moreover, it is found that the average evacuation time gap is essentially constant, which means that the evacuation speed essentially does not depend on the number of pedestrians that have not yet escaped. To model the evacuation dynamics, an improved social force model has been proposed, in which it is assumed that the driving force of a pedestrian cannot be fulfilled when the composition of physical forces exceeds a threshold because the pedestrian cannot keep his/her body balance under this circumstance. To model the effect of escaping in couples, attraction force has been introduced between the partners. Simulation results are in good agreement with the experimental ones.

  10. Split-second escape decisions in blue tits (Parus caeruleus)

    Science.gov (United States)

    Lind, Johan; Kaby, Ulrika; Jakobsson, Sven

    2002-07-01

    Bird mortality is heavily affected by birds of prey. Under attack, take-off is crucial for survival and even minor mistakes in initial escape response can have devastating consequences. Birds may respond differently depending on the character of the predator's attack and these split-second decisions were studied using a model merlin (Falco columbarius) that attacked feeding blue tits (Parus caeruleus) from two different attack angles in two different speeds. When attacked from a low attack angle they took off more steeply than when attacked from a high angle. This is the first study to show that escape behaviour also depends on predator attack speed. The blue tits responded to a high-speed attack by dodging sideways more often than when attacked at a low speed. Escape speed was not significantly affected by the different treatments. Although they have only a split-second before escaping an attack, blue tits do adjust their escape strategy to the prevailing attack conditions.

  11. Finite escape fraction for ultrahigh energy collisions around Kerr naked singularity

    Indian Academy of Sciences (India)

    Mandar Patil; Pankaj S Joshi

    2015-04-01

    We investigate the issue of observability of high-energy collisions around Kerr naked singularity and show that results are in contrast with the Kerr black hole case. We had shown that it would be possible to have ultrahigh energy collisions between the particles close to the location = M around the Kerr naked singularity if the Kerr spin parameter transcends unity by an infinitesimally small amount → 1+. The collision is between initially ingoing particle that turns back as an outgoing particle due to angular momentum barrier, with another ingoing particle. We assume that two massless particles are produced in such a collision and their angular distribution is isotropic in the centre-of-mass frame. We calculated the escape fraction for the massless particles to reach infinity. We showed that the escape fraction is finite and approximately equal to half for the ultrahigh energy collisions. Therefore, the particles produced in high-energy collisions would escape to infinity providing the signature of the nature of basic interactions at those energies. This result is in contrast with the case of extremal Kerr black hole where almost all particles produced in high-energy collisions are absorbed by the black hole rendering collisions unobservable.

  12. Direct activation of the Mauthner cell by electric field pulses drives ultrarapid escape responses

    Science.gov (United States)

    Tabor, Kathryn M.; Bergeron, Sadie A.; Horstick, Eric J.; Jordan, Diana C.; Aho, Vilma; Porkka-Heiskanen, Tarja; Haspel, Gal

    2014-01-01

    Rapid escape swims in fish are initiated by the Mauthner cells, giant reticulospinal neurons with unique specializations for swift responses. The Mauthner cells directly activate motoneurons and facilitate predator detection by integrating acoustic, mechanosensory, and visual stimuli. In addition, larval fish show well-coordinated escape responses when exposed to electric field pulses (EFPs). Sensitization of the Mauthner cell by genetic overexpression of the voltage-gated sodium channel SCN5 increased EFP responsiveness, whereas Mauthner ablation with an engineered variant of nitroreductase with increased activity (epNTR) eliminated the response. The reaction time to EFPs is extremely short, with many responses initiated within 2 ms of the EFP. Large neurons, such as Mauthner cells, show heightened sensitivity to extracellular voltage gradients. We therefore tested whether the rapid response to EFPs was due to direct activation of the Mauthner cells, bypassing delays imposed by stimulus detection and transmission by sensory cells. Consistent with this, calcium imaging indicated that EFPs robustly activated the Mauthner cell but only rarely fired other reticulospinal neurons. Further supporting this idea, pharmacological blockade of synaptic transmission in zebrafish did not affect Mauthner cell activity in response to EFPs. Moreover, Mauthner cells transgenically expressing a tetrodotoxin (TTX)-resistant voltage-gated sodium channel retained responses to EFPs despite TTX suppression of action potentials in the rest of the brain. We propose that EFPs directly activate Mauthner cells because of their large size, thereby driving ultrarapid escape responses in fish. PMID:24848468

  13. Poor school performance.

    Science.gov (United States)

    Karande, Sunil; Kulkarni, Madhuri

    2005-11-01

    Education is one of the most important aspects of human resource development. Poor school performance not only results in the child having a low self-esteem, but also causes significant stress to the parents. There are many reasons for children to under perform at school, such as, medical problems, below average intelligence, specific learning disability, attention deficit hyperactivity disorder, emotional problems, poor socio-cultural home environment, psychiatric disorders and even environmental causes. The information provided by the parents, classroom teacher and school counselor about the child's academic difficulties guides the pediatrician to form an initial diagnosis. However, a multidisciplinary evaluation by an ophthalmologist, otolaryngologist, counselor, clinical psychologist, special educator, and child psychiatrist is usually necessary before making the final diagnosis. It is important to find the reason(s) for a child's poor school performance and come up with a treatment plan early so that the child can perform up to full potential.

  14. The fastest saccadic responses escape visual masking.

    Directory of Open Access Journals (Sweden)

    Sébastien M Crouzet

    Full Text Available Object-substitution masking (OSM occurs when a briefly presented target in a search array is surrounded by small dots that remain visible after the target disappears. The reduction of target visibility occurring after OSM has been suggested to result from a specific interference with reentrant visual processing while the initial feedforward processing is thought to be left intact. We tested a prediction derived from this hypothesis: the fastest responses, being triggered before the beginning of reentrant processing, should escape the OSM interference. In a saccadic choice reaction time task, which gives access to very early stages of visual processing, target visibility was reduced either by OSM, conventional backward masking, or low stimulus contrast. A general reduction of performance was observed in all three conditions. However, the fastest saccades did not show any sign of interference under either OSM or backward masking, as they did under the low-contrast condition. This finding supports the hypothesis that masking interferes mostly with reentrant processing at later stages, while leaving early feedforward processing largely intact.

  15. Immune Escape Strategies of Malaria Parasites

    Science.gov (United States)

    Gomes, Pollyanna S.; Bhardwaj, Jyoti; Rivera-Correa, Juan; Freire-De-Lima, Celio G.; Morrot, Alexandre

    2016-01-01

    Malaria is one of the most life-threatening infectious diseases worldwide. Immunity to malaria is slow and short-lived despite the repeated parasite exposure in endemic areas. Malaria parasites have evolved refined machinery to evade the immune system based on a range of genetic changes that include allelic variation, biomolecular exposure of proteins, and intracellular replication. All of these features increase the probability of survival in both mosquitoes and the vertebrate host. Plasmodium species escape from the first immunological trap in its invertebrate vector host, the Anopheles mosquitoes. The parasites have to pass through various immunological barriers within the mosquito such as anti-microbial molecules and the mosquito microbiota in order to achieve successful transmission to the vertebrate host. Within these hosts, Plasmodium species employ various immune evasion strategies during different life cycle stages. Parasite persistence against the vertebrate immune response depends on the balance among virulence factors, pathology, metabolic cost of the host immune response, and the parasites ability to evade the immune response. In this review we discuss the strategies that Plasmodium parasites use to avoid the vertebrate host immune system and how they promote successful infection and transmission. PMID:27799922

  16. Candida albicans escapes from mouse neutrophils.

    Science.gov (United States)

    Ermert, David; Niemiec, Maria J; Röhm, Marc; Glenthøj, Andreas; Borregaard, Niels; Urban, Constantin F

    2013-08-01

    Candida albicans, the most commonly isolated human fungal pathogen, is able to grow as budding yeasts or filamentous forms, such as hyphae. The ability to switch morphology has been attributed a crucial role for the pathogenesis of C. albicans. To mimic disseminated candidiasis in humans, the mouse is the most widely used model organism. Neutrophils are essential immune cells to prevent opportunistic mycoses. To explore potential differences between the rodent infection model and the human host, we compared the interactions of C. albicans with neutrophil granulocytes from mice and humans. We revealed that murine neutrophils exhibited a significantly lower ability to kill C. albicans than their human counterparts. Strikingly, C. albicans yeast cells formed germ tubes upon internalization by murine neutrophils, eventually rupturing the neutrophil membrane and thereby, killing the phagocyte. On the contrary, growth and subsequent escape of C. albicans are blocked inside human neutrophils. According to our findings, this blockage in human neutrophils might be a result of higher levels of MPO activity and the presence of α-defensins. We therefore outline differences in antifungal immune defense between humans and mouse strains, which facilitates a more accurate interpretation of in vivo results.

  17. The Poor Pay More.

    Science.gov (United States)

    Folse, Kimberly A.

    2002-01-01

    Describes a sociology experiential learning assignment where students learned why people living in poverty can sometimes pay more for products than people with better incomes. Focuses specifically on the rent to own concept. States students achieved the goal of learning how life constraints of poverty can hinder the poor from overcoming their…

  18. Becoming poor in Ghana

    African Journals Online (AJOL)

    ing to poverty, counteract risk-averse economic behaviour and serve as a substitute for the ... so focus their attention on the vulnerable non-poor (World Bank 2009, Hanlon et al. 2010,. Adato and .... The influx of low cost foreign clothing ... other loans they lost the business as well as the car and valuable household items.

  19. Alternative strategies of seed predator escape by early-germinating oaks in Asia and North America.

    Science.gov (United States)

    Yi, Xianfeng; Yang, Yueqin; Curtis, Rachel; Bartlow, Andrew W; Agosta, Salvatore J; Steele, Michael A

    2012-03-01

    Early germination of white oaks is widely viewed as an evolutionary strategy to escape rodent predation; yet, the mechanism by which this is accomplished is poorly understood. We report that chestnut oak Quercus montana (CO) and white oak Q. alba (WO) (from North America), and oriental cork oak Q. variabilis (OO) and Mongolian oak Q. mongolica (MO) (from Asia) can escape predation and successfully establish from only taproots. During germination in autumn, cotyledonary petioles of acorns of CO and WO elongate and push the plumule out of the cotyledons, whereas OO and MO extend only the hypocotyls and retain the plumule within the cotyledons. Experiments showed that the pruned taproots (>6 cm) of CO and WO acorns containing the plumule successfully germinated and survived, and the pruned taproots (≥12 cm) of OO and MO acorns without the plumule successfully regenerated along with the detached acorns, thus producing two seedlings. We argue that these two distinct regeneration morphologies reflect alternative strategies for escaping seed predation.

  20. Lyman-Werner UV escape fractions from primordial haloes

    Science.gov (United States)

    Schauer, Anna T. P.; Whalen, Daniel J.; Glover, Simon C. O.; Klessen, Ralf S.

    2015-12-01

    Population III (Pop III) stars can regulate star formation in the primordial Universe in several ways. They can ionize nearby haloes, and even if their ionizing photons are trapped by their own haloes, their Lyman-Werner (LW) photons can still escape and destroy H2 in other haloes, preventing them from cooling and forming stars. LW escape fractions are thus a key parameter in cosmological simulations of early reionization and star formation but have not yet been parametrized for realistic haloes by halo or stellar mass. To do so, we perform radiation hydrodynamical simulations of LW UV escape from 9-120 M⊙ Pop III stars in 105-107 M⊙ haloes with ZEUS-MP. We find that photons in the LW lines (i.e. those responsible for destroying H2 in nearby systems) have escape fractions ranging from 0 to 85 per cent. No LW photons escape the most massive halo in our sample, even from the most massive star. Escape fractions for photons elsewhere in the 11.18-13.6 eV energy range, which can be redshifted into the LW lines at cosmological distances, are generally much higher, being above 60 per cent for all but the least massive stars in the most massive haloes. We find that shielding of H2 by neutral hydrogen, which has been neglected in most studies to date, produces escape fractions that are up to a factor of 3 smaller than those predicted by H2 self-shielding alone.

  1. A new paradigm for evaluating avoidance/escape motivation.

    Science.gov (United States)

    Tsutsui-Kimura, Iku; Bouchekioua, Youcef; Mimura, Masaru; Tanaka, Kenji F

    2017-05-06

    Organisms have evolved to approach pleasurable opportunities and to avoid or escape from aversive experiences. These two distinct motivations are referred to as approach and avoidance/escape motivations and are both considered vital for survival. Despite several recent advances in understanding the neurobiology of motivation, most studies addressed approach but not avoidance/escape motivation. Here we develop a new experimental paradigm to quantify avoidance/escape motivation and examine the pharmacological validity. We set up an avoidance variable ratio 5 (VR-5) task in which mice were required to press a lever for variable times to avoid an upcoming aversive stimulus (foot shock) or to escape the ongoing aversive event if mice failed to avoid it. We intraperitoneally injected ketamine (0, 1, or 5 mg/kg) or buspirone (0, 5, or 10 mg/kg) 20 or 30 minutes before the behavioral task in order to see if ketamine enhanced avoidance/escape behavior and buspirone diminished it as previously reported. We found that the performance on the avoidance VR-5 task was sensitive to the intensity of the aversive stimulus. Treatment with ketamine increased, while that with buspirone decreased, the probability of avoidance from an aversive stimulus in the VR-5 task, being consistent with previous reports. Our new paradigm will prove usefulness for quantifying avoidance/escape motivation and will contribute to a more comprehensive understanding of motivation.

  2. Xenon Fractionation, Hydrogen Escape, and the Oxidation of the Earth

    Science.gov (United States)

    Zahnle, K. J.; Catling, D. C.

    2014-12-01

    Xenon in Earth's atmosphere is severely mass fractionated and depleted compared to any plausible solar system source material, yet Kr is unfractionated. These observations seem to imply that Xe has escaped from Earth. Vigorous hydrodynamic hydrogen escape can produce mass fractionation in heavy gases. The required hydrogen flux is very high but within the range permitted by solar EUV heating when Earth was 100 Myrs old or younger. However this model cannot explain why Xe escapes but Kr does not. Recently, what appears to be ancient atmospheric xenon has been recovered from several very ancient (3-3.5 Ga) terrestrial hydrothermal barites and cherts (Pujol 2011, 2013). What is eye-catching about this ancient Xe is that it is less fractionated that Xe in modern air. In other words, it appears that a process was active on Earth some 3 to 3.5 billion years ago that caused xenon to fractionate. By this time the Sun was no longer the EUV source that it used to be. If xenon was being fractionated by escape — currently the only viable hypothesis — it had to be in Earth's Archean atmosphere and under rather modest levels of EUV forcing. It should be possible for Xe, but not Kr, to escape from Earth as an ion. In a hydrodynamically escaping hydrogen wind the hydrogen is partially ionized. The key concepts are that ions are much more strongly coupled to the escaping flow than are neutrals (so that a relatively modest flow of H and H+ to space could carry Xe+ along with it, the flux can be small enough to be consistent with diffusion-limited flux), and that Xe alone among the noble gases is more easily ionized than hydrogen. This sort of escape is possible along the polar field lines, although a weak or absent magnetic field would likely work as well. The extended history of hydrogen escape implicit in Xe escape in the Archean is consistent with other suggestions that hydrogen escape in the Archean was considerable. Hydrogen escape plausibly played the key role in creating

  3. Escape of Hydrogen from HD209458b

    Science.gov (United States)

    Erwin, Justin; Yelle, Roger; Koskinen, Tommi

    2017-04-01

    Recent modeling of the atmosphere of HD209458b has been used to interpret the Lyman-α line and other observations during transits. Koskinen et al. (2010) used a hydrostatic density profile in the thermosphere combined with the Voigt profile to estimate the Lyman-alpha transit depths for an array of model parameters. A detailed photochemical-dynamical model of the thermosphere was developed by Koskinen et al. (2013a) and used to again estimate model parameters to fit not only the Lyman-alpha transits, but also the transits in the O I, C II and Si III lines (Koskinen et al., 2013b). Recently, Bourrier and Lecavelier (2013) modeled the escape of hydrogen from the extended atmospheres of HD209458b and HD189733b and used the results to interpret Lyman-alpha observations. They included acceleration of hydrogen by radiation pressure and stellar wind protons to simulate the high velocity tails of the velocity distribution, arguing that the observations are explained by high velocity gas in the system while Voigt broadening is negligible. In this work we connect a free molecular flow (FMF) model similar to Bourrier and Lecavelier (2013) to the results of Koskinen et al. (2013b) and properly include absorption by the extended thermosphere in the transit model. In this manner, we can interpret the necessity of the various physical processes in matching the observed line profiles. Furthermore, the transit depths of this model can be used to re-evaluate the atmospheric model parameters to determine if they need to be adjusted due

  4. Banker to the Poor

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Bangladeshi economist Muhammad Yunus has been awarded this year's Nobel Peace Prize for making small loans to the poorest of the poor through his Grameen Bank. Grameen, meaning "rural" or "village" in Bangla language, is the world's first microcreditor on this scale. By offering microcredit to the impoverished, Yunus helps those desperately struggling in poverty be more accessible to small business startup. The 66-year-old banker allows those who borrow to change their lives through self-employment, by u...

  5. Serving the world's poor, profitably.

    Science.gov (United States)

    Prahalad, C K; Hammond, Allen

    2002-09-01

    By stimulating commerce and development at the bottom of the economic pyramid, multi-nationals could radically improve the lives of billions of people and help create a more stable, less dangerous world. Achieving this goal does not require MNCs to spearhead global social-development initiatives for charitable purposes. They need only act in their own self-interest. How? The authors lay out the business case for entering the world's poorest markets. Fully 65% of the world's population earns less than $2,000 per year--that's 4 billion people. But despite the vastness of this market, it remains largely untapped. The reluctance to invest is easy to understand, but it is, by and large, based on outdated assumptions of the developing world. While individual incomes may be low, the aggregate buying power of poor communities is actually quite large, representing a substantial market in many countries for what some might consider luxury goods like satellite television and phone services. Prices, and margins, are often much higher in poor neighborhoods than in their middle-class counterparts. And new technologies are already steadily reducing the effects of corruption, illiteracy, inadequate infrastructure, and other such barriers. Because these markets are in the earliest stages of economic development, revenue growth for multi-nationals entering them can be extremely rapid. MNCs can also lower costs, not only through low-cost labor but by transferring operating efficiencies and innovations developed to serve their existing operations. Certainly, succeeding in such markets requires MNCs to think creatively. The biggest change, though, has to come from executives: Unless business leaders confront their own preconceptions--particularly about the value of high-volume, low-margin businesses--companies are unlikely to master the challenges or reap the rewards of these developing markets.

  6. Behavior of the Escape Rate Function in Hyperbolic Dynamical Systems

    CERN Document Server

    Demers, Mark

    2011-01-01

    For a fixed initial reference measure, we study the dependence of the escape rate on the hole for a smooth or piecewise smooth hyperbolic map. First, we prove the existence and Holder continuity of the escape rate for systems with small holes admitting Young towers. Then we consider general holes for Anosov diffeomorphisms, without size or Markovian restrictions. We prove bounds on the upper and lower escape rates using the notion of pressure on the survivor set and show that a variational principle holds under generic conditions. However, we also show that the escape rate function forms a devil's staircase with jumps along sequences of regular holes and present examples to elucidate some of the difficulties involved in formulating a general theory.

  7. On the large escape of ionizing radiation from GEHRs

    CERN Document Server

    Castellanos, M; Tenorio-Tagle, G

    2001-01-01

    A thorough analysis of well studied giant HII regions on galactic discs for which we know the ionizing stellar population, the gas metallicity and the Wolf-Rayet population, leads to photoionization models which can only match all observed line intensity ratios ([OIII], [OII], [NII], [SII] and [SIII] with respect to the intensity of H$\\beta$), as well as the H$\\beta$ luminosity and equivalent width if one allows for an important escape of energetic ionizing radiation. For the three regions presented here, the fractions of escaping Lyman continuum photons amount to 10 to 73 % and, in all cases, the larger fraction of escaping photons has energies between 13.6 and 24.4 eV. These escaping photons clearly must have an important impact as a source of ionization of the diffuse ionized gas (DIG) found surrounding many galaxies, as well as of the intergalactic medium (IGM).

  8. Theoretical Study on Ion Escape in Martian Atmosphere

    Institute of Scientific and Technical Information of China (English)

    SHI Jian-Kui; LIU Zhen-Xing; Klaus TORKAR; Tielong ZHANG

    2007-01-01

    @@ Based on the observation that Martian magnetic moment is gradually reducing from the ancient to the present,we investigate the O+ ion flux distribution along magnetic field lines and the ion escaping flux in Martian tail with different assumed Martian magnetic moments. The results show that the O+ ion flux along magnetic field lines decreases with distance from Mars; the ion flux along the field line decreases more quickly if the magnetic moment is larger; the larger the magnetic moment, the smaller the ion escaping flux in the Martian tail. The ion escaping flux depends on Z-coordinate in the Martian tail. With decrease of the magnetic moment, the ion escaping flux in the Martian tail increases. The results are significant for studying the water loss from Mars surface.

  9. Experimental Analysis and Extinction of Self-Injurious Escape Behavior.

    Science.gov (United States)

    Iwata, Brian A.; And Others

    1990-01-01

    Three studies investigated environmental correlates of self-injurious behavior in seven developmentally disabled children and adolescents which were then later used for treatment. Correlates investigated included positive reinforcement, negative reinforcement, automatic reinforcement, and control. "Escape extinction" was successfully…

  10. Amplitude modulation control of escape from a potential well

    Energy Technology Data Exchange (ETDEWEB)

    Chacón, R. [Departamento de Física Aplicada, Escuela de Ingenierías Industriales, Universidad de Extremadura, Apartado Postal 382, E-06006 Badajoz (Spain); Martínez García-Hoz, A. [Departamento de Física Aplicada, Escuela Universitaria Politécnica, Universidad de Castilla-La Mancha, E-13400 Almadén (Ciudad Real) (Spain); Miralles, J.J. [Departamento de Física Aplicada, Escuela de Ingenieros Industriales, Universidad de Castilla-La Mancha, E-02071 Albacete (Spain); Martínez, P.J. [Departamento de Física Aplicada, E.I.N.A., Universidad de Zaragoza, E-50018 Zaragoza (Spain); Instituto de Ciencia de Materiales de Aragón, CSIC – Universidad de Zaragoza, E-50009 Zaragoza (Spain)

    2014-03-01

    We demonstrate the effectiveness of periodic amplitude modulations in controlling (suppressing and enhancing) escape from a potential well through the universal model of a damped Helmholtz oscillator subjected to an external periodic excitation (the escape-inducing excitation) whose amplitude is periodically modulated (the escape-controlling excitation). Analytical and numerical results show that this multiplicative control works reliably for different subharmonic resonances between the two periodic excitations involved, and that its effectiveness is comparable to those of different methods of additive control. Additionally, we demonstrate the robustness of the multiplicative control against the presence of low-intensity Gaussian noise. -- Highlights: •Multiplicative control of escape from a potential well has been demonstrated. •Theoretical predictions are obtained from a Melnikov analysis. •It has been shown the robustness of the multiplicative control against noise.

  11. Oxygen Escape from Venus During High Dynamic Pressure ICMEs

    Science.gov (United States)

    McEnulty, Tess; Luhmann, J. G.; Brain, D. A.; Fedorov, A.; Jian, L. K.; Russell, C. T.; Zhang, T.; Möstl, C.; Futaana, Y.; de Pater, I.

    2013-10-01

    Previous studies using data from Pioneer Venus suggested that oxygen ion escape flux may be enhanced by orders of magnitude during Interplanetary Coronal Mass Ejections. However, this large enhancement has been ambiguous in Venus Express ion data - with some analyses showing no flux enhancement or a small enhancement (within 2 times undisturbed cases). One possible explanation is that high escape flux may be due to high dynamic pressure in the solar wind, and the dynamic pressure has been lower during the VEX time period. So, we focus on ICMEs with the largest dynamic pressure and with VEX sampling of the escaping ions during the sheath of the ICMEs (during which the highest dynamic pressures in the solar wind occur). We will show the characteristics of these large events measured by VEX, and compare them to the largest ICMEs measured by PVO. We will then discuss estimates of the oxygen ion escape flux during these events.

  12. Estimation of coho salmon escapement in the Ugashik lakes

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — From 26 July to 24 September 2002, hourly counts were conducted from counting towers to estimate the escapement of coho salmon Oncorhynchus kisutch into the Ugashik...

  13. GREEN PEA GALAXIES REVEAL SECRETS OF Lyα ESCAPE

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Huan; Wang, Junxian [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China (China); Malhotra, Sangeeta; Rhoads, James E. [Arizona State University, School of Earth and Space Exploration (United States); Gronke, Max; Dijkstra, Mark [Institute of Theoretical Astrophysics, University of Oslo (Norway); Jaskot, Anne [Smith College, Northampton, MA (United States); Zheng, Zhenya, E-mail: yanghuan@mail.ustc.edu.cn, E-mail: huan.y@asu.edu, E-mail: Sangeeta.Malhotra@asu.edu, E-mail: James.Rhoads@asu.edu [Pontificia Universidad Católica de Chile, Santiago (Chile)

    2016-04-01

    We analyze archival Lyα spectra of 12 “Green Pea” galaxies observed with the Hubble Space Telescope, model their Lyα profiles with radiative transfer models, and explore the dependence of the Lyα escape fraction on various properties. Green Pea galaxies are nearby compact starburst galaxies with [O iii] λ5007 equivalent widths (EWs) of hundreds of Å. All 12 Green Pea galaxies in our sample show Lyα lines in emission, with an Lyα EW distribution similar to high-redshift Lyα emitters. Combining the optical and UV spectra of Green Pea galaxies, we estimate their Lyα escape fractions and find correlations between Lyα escape fraction and kinematic features of Lyα profiles. The escape fraction of Lyα in these galaxies ranges from 1.4% to 67%. We also find that the Lyα escape fraction depends strongly on metallicity and moderately on dust extinction. We compare their high-quality Lyα profiles with single H i shell radiative transfer models and find that the Lyα escape fraction anticorrelates with the derived H i column densities. Single-shell models fit most Lyα profiles well, but not the ones with the highest escape fractions of Lyα. Our results suggest that low H i column density and low metallicity are essential for Lyα escape and make a galaxy an Lyα emitter.

  14. Purinergic Inhibition of ENaC Produces Aldosterone Escape

    OpenAIRE

    Stockand, James D.; Mironova, Elena; Bugaj, Vladislav; Rieg, Timo; Insel, Paul A.; Vallon, Volker; Peti-Peterdi, Janos; Pochynyuk, Oleh

    2010-01-01

    The mechanisms underlying “aldosterone escape,” which refers to the excretion of sodium (Na+) during high Na+ intake despite inappropriately increased levels of mineralocorticoids, are incompletely understood. Because local purinergic tone in the aldosterone-sensitive distal nephron downregulates epithelial Na+ channel (ENaC) activity, we tested whether this mechanism mediates aldosterone escape. Here, urinary ATP concentration increased with dietary Na+ intake in mice. Physiologic concentrat...

  15. Group chase and escape with sight-limited chasers

    Science.gov (United States)

    Wang, Huodong; Han, Wenchen; Yang, Junzhong

    2017-01-01

    We study group chase and escape with sight-limited chasers. Two search strategies, random-walk-strategy and relocation-strategy, are introduced for chasers when escapers are out of their fields of vision. There exist two regimes for the group lifetime of escapers. In the narrow sight regime, the group lifetime is a decreasing function of chasers' sight range. In the wide sight regime, the group lifetime stays at a constant when chasers adopting random-walk-strategy while increases with the sight range when chasers adopting relocation-strategy. The impacts of the two search strategies on group chase and escape are studied by investigating the lifetime distribution of all escapers and the dependence of the minimum lifetime on the number of chasers. We also find that, to reach the most efficient and the lowest energy cost chase for chasers, the ratio between the number of chasers and escapers stays at around 6 under random-walk-strategy. However, the optimal number of chasers vanishes and the energy cost monotonically increases with increasing the number of chasers under relocation-strategy.

  16. Green Pea Galaxies Reveal Secrets of Ly$\\alpha$ Escape

    CERN Document Server

    Yang, Huan; Gronke, Max; Rhoads, James E; Jaskot, Anne; Zheng, Zhenya; Dijkstra, Mark

    2015-01-01

    Star-formation in galaxies generates a lot of Ly$\\alpha$ photons. Understanding the escape of Ly$\\alpha$ photons from galaxies is a key issue in studying high redshift galaxies and probing cosmic reionization with Ly$\\alpha$. To understand Ly$\\alpha$ escape, it is valuable to study analogs of high redshift Ly$\\alpha$ emitters in nearby universe. However, most nearby analogs have too small a Ly$\\alpha$ equivalent width and escape fraction compared to high redshift Ly$\\alpha$ emitters. One different group of nearby analogs are "Green Pea" galaxies, selected by their high equivalent width optical emission lines. Here we show that Green Pea galaxies have strong Ly$\\alpha$ emission lines and high Ly$\\alpha$ escape fraction (see also Henry et al. 2015), providing an opportunity to solve Ly$\\alpha$ escape problem. Green Peas have a Ly$\\alpha$ equivalent width distribution similar to high redshift Ly$\\alpha$ emitters. The Ly$\\alpha$ escape fraction correlates with many quantities of Ly$\\alpha$ profile, especially the...

  17. Lyman-Werner UV Escape Fractions from Primordial Halos

    CERN Document Server

    Schauer, Anna T P; Glover, Simon C O; Klessen, Ralf S

    2015-01-01

    Population III stars can regulate star formation in the primordial Universe in several ways. They can ionize nearby halos, and even if their ionizing photons are trapped by their own halos, their Lyman-Werner (LW) photons can still escape and destroy H$_2$ in other halos, preventing them from cooling and forming stars. LW escape fractions are thus a key parameter in cosmological simulations of early reionization and star formation but have not yet been parametrized for realistic halos by halo or stellar mass. To do so, we perform radiation hydrodynamical simulations of LW UV escape from 9--120 M$_{\\odot}$ Pop III stars in $10^5$ to $10^7$ M$_{\\odot}$ halos with ZEUS-MP. We find that photons in the LW lines (i.e. those responsible for destroying H$_{2}$ in nearby systems) have escape fractions ranging from 0% to 85%. No LW photons escape the most massive halo in our sample, even from the most massive star. Escape fractions for photons elsewhere in the 11.18--13.6~eV energy range, which can be redshifted into t...

  18. Dynamics of immune escape during HIV/SIV infection.

    Directory of Open Access Journals (Sweden)

    Christian L Althaus

    Full Text Available Several studies have shown that cytotoxic T lymphocytes (CTLs play an important role in controlling HIV/SIV infection. Notably, the observation of escape mutants suggests a selective pressure induced by the CTL response. However, it remains difficult to assess the definite role of the cellular immune response. We devise a computational model of HIV/SIV infection having a broad cellular immune response targeting different viral epitopes. The CTL clones are stimulated by viral antigen and interact with the virus population through cytotoxic killing of infected cells. Consequently, the virus population reacts through the acquisition of CTL escape mutations. Our model provides realistic virus dynamics and describes several experimental observations. We postulate that inter-clonal competition and immunodominance may be critical factors determining the sequential emergence of escapes. We show that even though the total killing induced by the CTL response can be high, escape rates against a single CTL clone are often slow and difficult to estimate from infrequent sequence measurements. Finally, our simulations show that a higher degree of immunodominance leads to more frequent escape with a reduced control of viral replication but a substantially impaired replicative capacity of the virus. This result suggests two strategies for vaccine design: Vaccines inducing a broad CTL response should decrease the viral load, whereas vaccines stimulating a narrow but dominant CTL response are likely to induce escape but may dramatically reduce the replicative capacity of the virus.

  19. Escape dynamics and fractal basin boundaries in Seyfert galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2015-01-01

    The escape dynamics in a simple analytical gravitational model which describes the motion of stars in a Seyfert galaxy is investigated in detail. We conduct a thorough numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion, we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $L_1$ and $L_2$ and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the physical $(x,y)$ and in the phase $(x,\\dot{x})$ space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the considered escape basins with the...

  20. Indirect Evidence for Escaping Lyman Continuum Photons in Local Lyman Break Galaxy Analogs

    Science.gov (United States)

    Alexandroff, Rachael; Heckman, Timothy M.; Borthakur, Sanchayeeta; Overzier, Roderik

    2015-01-01

    A population of early star-forming galaxies is the leading candidate for the re-ionization of the universe. It is still unclear, however, what conditions and physical processes would enable a significant fraction of the ionizing photons to escape from these gas-rich galaxies. In addition, studies of high redshift galaxies have yet to uncover a large sample of galaxies with the required high escape fraction of ionizing photons.We have uncovered a sample of local analogs to high-redshift, star-forming Lyman Break Galaxies (LBGs) called Lyman Break Analogs (LBAs) by matching the Sloan Digital Sky Survey (SDSS) and Galaxy Evolution Explorer (GALEX) catalogs. These galaxies are remarkably similar to LBGs in their properties-- morphology, size, UV luminosity, SFR, mass, velocity dispersion, metallicity and dust content. We obtained HST COS far-UV spectroscopy plus ancillary multi-waveband data of a sample of 22 LBAs to look for indirect evidence of escaping ionizing radiation (leakiness).We measure three parameters: (1) the residual intensity in the cores of saturated interstellar low-ionization absorption-lines, which indicates incomplete covering by that gas in the galaxy. (2) The relative amount of blue-shifted Lyman alpha line emission, which can indicate the existence of holes in the neutral hydrogen on the front-side of the galaxy outflow, and (3) the relative weakness of the [SII] optical emission lines that trace matter-bounded HII regions. We find all three diagnostics agree well with one another. Finally, we find the strongest correlation between these leakiness indicators and both the compactness of the galactic star-forming region (size and star formation rate/area) and the speed of the galactic outflow. This suggests that extreme feedback- a high intensity of ionizing radiation and strong pressure from both radiation and a hot galactic wind- combines to create significant holes in the neutral gas. These results not only shed new light on the physical

  1. Escape of the martian protoatmosphere and initial water inventory.

    Science.gov (United States)

    Erkaev, N V; Lammer, H; Elkins-Tanton, L T; Stökl, A; Odert, P; Marcq, E; Dorfi, E A; Kislyakova, K G; Kulikov, Yu N; Leitzinger, M; Güdel, M

    2014-08-01

    Latest research in planet formation indicates that Mars formed within a few million years (Myr) and remained as a planetary embryo that never grew to a more massive planet. It can also be expected from dynamical models that most of Mars' building blocks consisted of material that formed in orbital locations just beyond the ice line which could have contained [Formula: see text] of H2O. By using these constraints, we estimate the nebula-captured and catastrophically outgassed volatile contents during the solidification of Mars' magma ocean and apply a hydrodynamic upper atmosphere model for the study of the soft X-ray and extreme ultraviolet (XUV) driven thermal escape of the martian protoatmosphere during the early active epoch of the young Sun. The amount of gas that has been captured from the protoplanetary disk into the planetary atmosphere is calculated by solving the hydrostatic structure equations in the protoplanetary nebula. Depending on nebular properties such as the dust grain depletion factor, planetesimal accretion rates and luminosities, hydrogen envelopes with masses [Formula: see text] to [Formula: see text] could have been captured from the nebula around early Mars. Depending on the before mentioned parameters, due to the planets low gravity and a solar XUV flux that was [Formula: see text] times stronger compared to the present value, our results indicate that early Mars would have lost its nebular captured hydrogen envelope after the nebula gas evaporated, during a fast period of [Formula: see text]. After the solidification of early Mars' magma ocean, catastrophically outgassed volatiles with the amount of [Formula: see text] H2O and [Formula: see text] CO2 could have been lost during [Formula: see text], if the impact related energy flux of large planetesimals and small embryos to the planet's surface lasted long enough, that the steam atmosphere could have been prevented from condensing. If this was not the case, then our results suggest that

  2. Fluctuating feedback-regulated escape fraction of ionizing radiation in low-mass, high-redshift galaxies

    Science.gov (United States)

    Trebitsch, Maxime; Blaizot, Jérémy; Rosdahl, Joakim; Devriendt, Julien; Slyz, Adrianne

    2017-09-01

    Low-mass galaxies are thought to provide the bulk of the ionizing radiation necessary to reionize the Universe. The amount of photons escaping the galaxies is poorly constrained theoretically, and difficult to measure observationally. Yet it is an essential parameter of reionization models. We study in detail how ionizing radiation can leak from high-redshift galaxies. For this purpose, we use a series of high-resolution radiation hydrodynamics simulations, zooming on three dwarf galaxies in a cosmological context. We find that the energy and momentum input from the supernova explosions has a pivotal role in regulating the escape fraction by disrupting dense star-forming clumps, and clearing sightlines in the halo. In the absence of supernovae, photons are absorbed very locally, within the birth clouds of massive stars. We follow the time evolution of the escape fraction and find that it can vary by more than six orders of magnitude. This explains the large scatter in the value of the escape fraction found by previous studies. This fast variability also impacts the observability of the sources of reionization: a survey even as deep as M1500 = -14 would miss about half of the underlying population of Lyman-continuum emitters.

  3. Poor ovarian reserve

    Directory of Open Access Journals (Sweden)

    Padma Rekha Jirge

    2016-01-01

    Full Text Available Poor ovarian reserve (POR is an important limiting factor for the success of any treatment modality for infertility. It indicates a reduction in quantity and quality of oocytes in women of reproductive age group. It may be age related as seen in advanced years of reproductive life or may occur in young women due to diverse etiological factors. Evaluating ovarian reserve and individualizing the therapeutic strategies are very important for optimizing the success rate. Majority or women with POR need to undergo in vitro fertilization to achieve pregnancy. However, pregnancy rate remains low despite a plethora of interventions and is associated with high pregnancy loss. Early detection and active management are essential to minimize the need for egg donation in these women.

  4. 78 FR 54585 - Safety Zone; Escape to Miami Triathlon, Biscayne Bay, Miami, FL

    Science.gov (United States)

    2013-09-05

    ... SECURITY Coast Guard 33 CFR Part 165 RIN 1625-AA00 Safety Zone; Escape to Miami Triathlon, Biscayne Bay... during the Publix Escape to Miami Triathlon. The Publix Escape to Miami Triathlon is scheduled to take... of life on navigable waters of the United States during the Publix Escape to Miami Triathlon....

  5. Women in extreme poverty.

    Science.gov (United States)

    1994-01-01

    Population is estimated to increase from 5.5 billion in 1990 to 10 billion by 2050; the poverty level is expected to increase from 1 billion to 2-3 billion people. Women in development has been promoted throughout the UN and development system, but women in poverty who perform work in the informal sector are still uncounted, and solutions are elusive. The issue of extreme poverty can not be approached as just another natural disaster with immediate emergency relief. Many people live in precarious economic circumstances throughout their lives. Recent research reveals a greater understanding of the underlying causes and the need for inclusion of poor women in sustainable development. Sanitation, water, housing, health facilities need to be improved. Women must have access to education, opportunities for trading, and loans on reasonable terms. UNESCO makes available a book on survival strategies for poor women in the informal sector. The profile shows common problems of illiteracy, broken marriages, and full time involvement in provision of subsistence level existence. Existence is a fragile balance. Jeanne Vickers' "Women and the World" offers simple, low cost interventions for aiding extremely poor women. The 1992 Commission on the Status of Women was held in Vienna. Excerpts from several speeches are provided. The emphasis is on some global responses and an analysis of solutions. The recommendation is for attention to the gender dimension of poverty. Women's dual role contributes to greater disadvantages. Women are affected differently by macroeconomic factors, and that there is intergenerational transfer of poverty. Social services should be viewed as investments and directed to easing the burdens on time and energy. Public programs must be equipped to deal with poverty and to bring about social and economic change. Programs must be aware of the different distribution of resources within households. Women must be recognized as principal economic providers within

  6. Mechanical properties of the cuticles of three cockroach species that differ in their wind-evoked escape behavior

    Directory of Open Access Journals (Sweden)

    Andrew J. Clark

    2014-07-01

    Full Text Available The structural and material properties of insect cuticle remain largely unexplored, even though they comprise the majority (approximately 80% of animals. Insect cuticle serves many functions, including protection against predatory attacks, which is especially beneficial to species failing to employ effective running escape responses. Despite recent advances in our understanding of insect escape behaviors and the biomechanics of insect cuticle, there are limited studies on the protective qualities of cuticle to extreme mechanical stresses and strains imposed by predatory attacks, and how these qualities vary between species employing different escape responses. Blattarians (cockroaches provide an appropriate model system for such studies. Wind-evoked running escape responses are strong in Periplaneta americana, weak in Blaberus craniifer and absent in Gromphodorhina portentosa, putting the latter two species at greater risk of being struck by a predator. We hypothesized that the exoskeletons in these two larger species could provide more protection from predatory strikes relative to the exoskeleton of P. americana. We quantified the protective qualities of the exoskeletons by measuring the puncture resistance, tensile strength, strain energy storage, and peak strain in fresh samples of thoracic and abdominal cuticles from these three species. We found a continuum in puncture resistance, tensile strength, and strain energy storage between the three species, which were greatest in G. portentosa, moderate in B. craniifer, and smallest in P. americana. Histological measurements of total cuticle thickness followed this same pattern. However, peak strain followed a different trend between species. The comparisons in the material properties drawn between the cuticles of G. portentosa, B. craniifer, and P. americana demonstrate parallels between cuticular biomechanics and predator running escape responses.

  7. Inferring HIV escape rates from multi-locus genotype data

    Directory of Open Access Journals (Sweden)

    Taylor A Kessinger

    2013-09-01

    Full Text Available Cytotoxic T-lymphocytes (CTLs recognize viral protein fragments displayed by major histocompatibility complex (MHC molecules on the surface of virally infected cells and generate an anti-viral response that can kill the infected cells. Virus variants whose protein fragments are not efficiently presented on infected cells or whose fragments are presented but not recognized by CTLs therefore have a competitive advantage and spread rapidly through the population. We present a method that allows a more robust estimation of these escape rates from serially sampled sequence data. The proposed method accounts for competition between multiple escapes by explicitly modeling the accumulation of escape mutations and the stochastic effects of rare multiple mutants. Applying our method to serially sampled HIV sequence data, we estimate rates of HIV escape that are substantially larger than those previously reported. The method can be extended to complex escapes that require compensatory mutations. We expect our method to be applicable in other contexts such as cancer evolution where time series data is also available.

  8. Comparison of spacecraft crew escape systems through dynamic optimization

    Science.gov (United States)

    Hart, William G., III

    Crew escape systems have been a vital component of ensuring safety onboard manned spacecraft. Although there have been only a few aborts involving their use, their operation helps decrease risk in what is known to be a hazardous field. But despite their high reliability, crew escape systems typically suffer from heavy weight, lack of control and hazardous chemical propellants. Hybrid propulsion systems could be a viable solution to all of these problems. With their inert components, ability to throttle and higher specific impulse than solids, hybrids have obtained interest in recent years. This dissertation presents a method that can be used to compare solid and hybrid propulsion systems for the crew escape systems of spacecraft. The concepts of dynamic optimization, Monte Carlo simulation and propulsion system design are combined to produce a tool which can predict the probability of survival for a given abort scenario. The method can also determine the effect of uncertain variables, such as reaction time or the payload of the vehicle, in the safety of the crew. The method is then used to compare crew escape systems for two separate vehicles: a separable crew cabin proposed for the Space Shuttle Launch Vehicle and the Launch Escape System for the Crew Exploration Vehicle scheduled to begin operation in 2012. The effects of uncertain parameters are also studied. The results show the utility of this method and the objective function, and how it could be used in the design process for future space vehicles.

  9. Single-File Escape of Colloidal Particles from Microfluidic Channels

    Science.gov (United States)

    Locatelli, Emanuele; Pierno, Matteo; Baldovin, Fulvio; Orlandini, Enzo; Tan, Yizhou; Pagliara, Stefano

    2016-07-01

    Single-file diffusion is a ubiquitous physical process exploited by living and synthetic systems to exchange molecules with their environment. It is paramount to quantify the escape time needed for single files of particles to exit from constraining synthetic channels and biological pores. This quantity depends on complex cooperative effects, whose predominance can only be established through a strict comparison between theory and experiments. By using colloidal particles, optical manipulation, microfluidics, digital microscopy, and theoretical analysis we uncover the self-similar character of the escape process and provide closed-formula evaluations of the escape time. We find that the escape time scales inversely with the diffusion coefficient of the last particle to leave the channel. Importantly, we find that at the investigated microscale, bias forces as tiny as 10-15 N determine the magnitude of the escape time by drastically reducing interparticle collisions. Our findings provide crucial guidelines to optimize the design of micro- and nanodevices for a variety of applications including drug delivery, particle filtering, and transport in geometrical constrictions.

  10. Immunosuppressive cells in tumor immune escape and metastasis.

    Science.gov (United States)

    Liu, Yang; Cao, Xuetao

    2016-05-01

    Tumor immune escape and the initiation of metastasis are critical steps in malignant progression of tumors and have been implicated in the failure of some clinical cancer immunotherapy. Tumors develop numerous strategies to escape immune surveillance or metastasize: Tumors not only modulate the recruitment and expansion of immunosuppressive cell populations to develop the tumor microenvironment or pre-metastatic niche but also switch the phenotype and function of normal immune cells from a potentially tumor-reactive state to a tumor-promoting state. Immunosuppressive cells facilitate tumor immune escape by inhibiting antitumor immune responses and furthermore promote tumor metastasis by inducing immunosuppression, promoting tumor cell invasion and intravasation, establishing a pre-metastatic niche, facilitating epithelial-mesenchymal transition, and inducing angiogenesis at primary tumor or metastatic sites. Numerous translational studies indicate that it is possible to inhibit tumor immune escape and prevent tumor metastasis by blocking immunosuppressive cells and eliminating immunosuppressive mechanisms that are induced by either immunosuppressive cells or tumor cells. Furthermore, many clinical trials targeting immunosuppressive cells have also achieved good outcome. In this review, we focus on the underlying mechanisms of immunosuppressive cells in promoting tumor immune escape and metastasis, discuss our current understanding of the interactions between immunosuppressive cells and tumor cells in the tumor microenvironment, and suggest future research directions as well as potential clinical strategies in cancer immunotherapy.

  11. Escape dynamics in a binary system of interacting galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2016-01-01

    The escape dynamics in an analytical gravitational model which describes the motion of stars in a binary system of interacting dwarf spheroidal galaxies is investigated in detail. We conduct a numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion, we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $L_1$ and $L_2$ and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the configuration $(x,y)$ and in the phase $(x,\\dot{x})$ space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the con...

  12. Enhancing endosomal escape for nanoparticle mediated siRNA delivery

    Science.gov (United States)

    Ma, Da

    2014-05-01

    Gene therapy with siRNA is a promising biotechnology to treat cancer and other diseases. To realize siRNA-based gene therapy, a safe and efficient delivery method is essential. Nanoparticle mediated siRNA delivery is of great importance to overcome biological barriers for systemic delivery in vivo. Based on recent discoveries, endosomal escape is a critical biological barrier to be overcome for siRNA delivery. This feature article focuses on endosomal escape strategies used for nanoparticle mediated siRNA delivery, including cationic polymers, pH sensitive polymers, calcium phosphate, and cell penetrating peptides. Work has been done to develop different endosomal escape strategies based on nanoparticle types, administration routes, and target organ/cell types. Also, enhancement of endosomal escape has been considered along with other aspects of siRNA delivery to ensure target specific accumulation, high cell uptake, and low toxicity. By enhancing endosomal escape and overcoming other biological barriers, great progress has been achieved in nanoparticle mediated siRNA delivery.

  13. Enhancing Endosomal Escape for Intracellular Delivery of Macromolecular Biologic Therapeutics.

    Science.gov (United States)

    Lönn, Peter; Kacsinta, Apollo D; Cui, Xian-Shu; Hamil, Alexander S; Kaulich, Manuel; Gogoi, Khirud; Dowdy, Steven F

    2016-09-08

    Bioactive macromolecular peptides and oligonucleotides have significant therapeutic potential. However, due to their size, they have no ability to enter the cytoplasm of cells. Peptide/Protein transduction domains (PTDs), also called cell-penetrating peptides (CPPs), can promote uptake of macromolecules via endocytosis. However, overcoming the rate-limiting step of endosomal escape into the cytoplasm remains a major challenge. Hydrophobic amino acid R groups are known to play a vital role in viral escape from endosomes. Here we utilize a real-time, quantitative live cell split-GFP fluorescence complementation phenotypic assay to systematically analyze and optimize a series of synthetic endosomal escape domains (EEDs). By conjugating EEDs to a TAT-PTD/CPP spilt-GFP peptide complementation assay, we were able to quantitatively measure endosomal escape into the cytoplasm of live cells via restoration of GFP fluorescence by intracellular molecular complementation. We found that EEDs containing two aromatic indole rings or one indole ring and two aromatic phenyl groups at a fixed distance of six polyethylene glycol (PEG) units from the TAT-PTD-cargo significantly enhanced cytoplasmic delivery in the absence of cytotoxicity. EEDs address the critical rate-limiting step of endosomal escape in delivery of macromolecular biologic peptide, protein and siRNA therapeutics into cells.

  14. Urban poor program launched.

    Science.gov (United States)

    1991-01-01

    The government of the Philippines has launched a program to deal with the rapidly growing urban poor population. 60 cities (including Metro Manila) are expected to increase their bloated population by 3.8% over 1990 which would be 27.7 million for 1991. Currently there is an exodus of people from the rural areas and by 2000 half the urban population will be squatters and slum dwellers. Basic services like health and nutrition are not expected to be able to handle this type of volume without a loss in the quality of service. The basic strategy of the new program is to recruit private medical practitioners to fortify the health care delivery and nutrition services. Currently the doctor/urban dweller ration is 1:9000. The program will develop a system to pool the efforts of government and private physicians in servicing the target population. Barangay Escopa has been chosen as the pilot city because it typifies the conditions of a highly populated urban area. The projects has 2 objectives: 1) demonstrate the systematic delivery of health and nutrition services by the private sector through the coordination of the government, 2) reduce mortality and morbidity in the community, especially in the 0-6 age group as well as pregnant women and lactating mothers.

  15. Characterizing Extreme Ionospheric Storms

    Science.gov (United States)

    Sparks, L.; Komjathy, A.; Altshuler, E.

    2011-12-01

    Ionospheric storms consist of disturbances of the upper atmosphere that generate regions of enhanced electron density typically lasting several hours. Depending upon the storm magnitude, gradients in electron density can sometimes become large and highly localized. The existence of such localized, dense irregularities is a major source of positioning error for users of the Global Positioning System (GPS). Consequently, satellite-based augmentation systems have been implemented to improve the accuracy and to ensure the integrity of user position estimates derived from GPS measurements. Large-scale irregularities generally do not pose a serious threat to estimate integrity as they can be readily detected by such systems. Of greater concern, however, are highly localized irregularities that interfere with the propagation of a signal detected by a user measurement but are poorly sampled by the receivers in the system network. The most challenging conditions have been found to arise following disturbances of large magnitude that occur only rarely over the course of a solar cycle. These extremely disturbed conditions exhibit behavior distinct from moderately disturbed conditions and, hence, have been designated "extreme storms". In this paper we examine and compare the behavior of the extreme ionospheric storms of solar cycle 23 (or, more precisely, extreme storms occurring between January 1, 2000, and December 31, 2008), as represented in maps of vertical total electron content. To identify these storms, we present a robust means of quantifying the regional magnitude of an ionospheric storm. Ionospheric storms are observed frequently to occur in conjunction with magnetic storms, i.e., periods of geophysical activity as measured by magnetometers. While various geomagnetic indices, such as the disturbance storm time (Dst) and the planetary Kp index, have long been used to rank the magnitudes of distinct magnetic storms, no comparable, generally recognized index exists for

  16. Extremely Preterm Birth

    Science.gov (United States)

    ... Events Advocacy For Patients About ACOG Extremely Preterm Birth Home For Patients Search FAQs Extremely Preterm Birth ... Spanish FAQ173, June 2016 PDF Format Extremely Preterm Birth Pregnancy When is a baby considered “preterm” or “ ...

  17. Behavior of Ants Escaping from a Single-Exit Room

    Science.gov (United States)

    Wang, Shujie; Lv, Wei; Song, Weiguo

    2015-01-01

    To study the rules of ant behavior and group-formation phenomena, we examined the behaviors of Camponotus japonicus, a species of large ant, in a range of situations. For these experiments, ants were placed inside a rectangular chamber with a single exit that also contained a filter paper soaked in citronella oil, a powerful repellent. The ants formed several groups as they moved toward the exit to escape. We measured the time intervals between individual escapes in six versions of the experiment, each containing an exit of a different width, to quantify the movement of the groups. As the ants exited the chamber, the time intervals between individual escapes changed and the frequency distribution of the time intervals exhibited exponential decay. We also investigated the relationship between the number of ants in a group and the group flow rate. PMID:26125191

  18. Escape rate and diffusion of a Stochastically Driven particle

    Science.gov (United States)

    Piscitelli, Antonio; Pica Ciamarra, Massimo

    2017-01-01

    The dynamical properties of a tracer repeatedly colliding with heat bath particles can be described within a Langevin framework provided that the tracer is more massive than the bath particles, and that the collisions are frequent. Here we consider the escape of a particle from a potential well, and the diffusion coefficient in a periodic potential, without making these assumptions. We have thus investigated the dynamical properties of a Stochastically Driven particle that moves under the influence of the confining potential in between successive collisions with the heat bath. In the overdamped limit, both the escape rate and the diffusion coefficient coincide with those of a Langevin particle. Conversely, in the underdamped limit the two dynamics have a different temperature dependence. In particular, at low temperature the Stochastically Driven particle has a smaller escape rate, but a larger diffusion coefficient. PMID:28120904

  19. Mutator suppression and escape from replication error-induced extinction in yeast.

    Directory of Open Access Journals (Sweden)

    Alan J Herr

    2011-10-01

    Full Text Available Cells rely on a network of conserved pathways to govern DNA replication fidelity. Loss of polymerase proofreading or mismatch repair elevates spontaneous mutation and facilitates cellular adaptation. However, double mutants are inviable, suggesting that extreme mutation rates exceed an error threshold. Here we combine alleles that affect DNA polymerase δ (Pol δ proofreading and mismatch repair to define the maximal error rate in haploid yeast and to characterize genetic suppressors of mutator phenotypes. We show that populations tolerate mutation rates 1,000-fold above wild-type levels but collapse when the rate exceeds 10⁻³ inactivating mutations per gene per cell division. Variants that escape this error-induced extinction (eex rapidly emerge from mutator clones. One-third of the escape mutants result from second-site changes in Pol δ that suppress the proofreading-deficient phenotype, while two-thirds are extragenic. The structural locations of the Pol δ changes suggest multiple antimutator mechanisms. Our studies reveal the transient nature of eukaryotic mutators and show that mutator phenotypes are readily suppressed by genetic adaptation. This has implications for the role of mutator phenotypes in cancer.

  20. [Selection of digital filtering in the escaping ammonia monitoring with TDLAS].

    Science.gov (United States)

    Zou, De-Bao; Chen, Wen-Liang; Du, Zhen-Hui; Jia, Hao; Qi, Ru-Bin; Li, Hong-Lian; Zhen, Yang; Hou, Yan-Xia; Xu, Ke-Xin

    2012-09-01

    Tunable diode laser absorption spectroscopy technology (TDLAS), with its advantages of high selectivity and accuracy, provides a reliable approach to the on-line detection of escaping ammonia. Firstly, the present paper introduces the TDLAS principle, experimental system and the analyses of system noise. Then with the concentration of 90 x 10(-6) and 30 x 10(-6) NH3 for example, we used TDLAS system to collect their second harmonic original spectrum with all kinds of noise interference. To improve the signal spectrum, five types of digital filtering methods were respectively used to filter the original spectrum. Finally we did the NH3 experiments of concentration gradient and the long time monitoring: NH3 experiment of 20 x 10(-6). The analysis indicated that the averaging-wavelet filtering is validated to be more accurate than the other filtering methods in the noise reduction, which can improve the precision of the monitoring system from 10 x 10(-6) to 1.25 x 10(-6) and the SNR also increases by 14 times. It provides an effective pretreatment during the monitoring of escaping ammonia of extremely low concentration.

  1. Mutations That Alter Use of Hepatitis C Virus Cell Entry Factors Mediate Escape From Neutralizing Antibodies

    Science.gov (United States)

    FAUVELLE, CATHERINE; ZAHID, MUHAMMAD NAUMAN; TUREK, MARINE; HEYDMANN, LAURA; CURY, KARINE; HAYER, JULIETTE; COMBET, CHRISTOPHE; COSSET, FRANÇOIS–LOÏC; PIETSCHMANN, THOMAS; HIET, MARIE–SOPHIE; BARTENSCHLAGER, RALF; HABERSETZER, FRANÇOIS; DOFFOËL, MICHEL; KECK, ZHEN–YONG; FOUNG, STEVEN K. H.; ZEISEL, MIRJAM B.; STOLL–KELLER, FRANÇOISE; BAUMERT, THOMAS F.

    2017-01-01

    BACKGROUND & AIMS The development of vaccines and other strategies to prevent hepatitis C virus (HCV) infection is limited by rapid viral evasion. HCV entry is the first step of infection; this process involves several viral and host factors and is targeted by host-neutralizing responses. Although the roles of host factors in HCV entry have been well characterized, their involvement in evasion of immune responses is poorly understood. We used acute infection of liver graft as a model to investigate the molecular mechanisms of viral evasion. METHODS We studied factors that contribute to evasion of host immune responses using patient-derived antibodies, HCV pseudoparticles, and cell culture–derived HCV that express viral envelopes from patients who have undergone liver transplantation. These viruses were used to infect hepatoma cell lines that express different levels of HCV entry factors. RESULTS By using reverse genetic analyses, we identified altered use of host-cell entry factors as a mechanism by which HCV evades host immune responses. Mutations that alter use of the CD81 receptor also allowed the virus to escape neutralizing antibodies. Kinetic studies showed that these mutations affect virus–antibody interactions during postbinding steps of the HCV entry process. Functional studies with a large panel of patient-derived antibodies showed that this mechanism mediates viral escape, leading to persistent infection in general. CONCLUSIONS We identified a mechanism by which HCV evades host immune responses, in which use of cell entry factors evolves with escape from neutralizing antibodies. These findings advance our understanding of the pathogenesis of HCV infection and might be used to develop antiviral strategies and vaccines. PMID:22503792

  2. Rapid endosomal escape of prickly nanodiamonds: implications for gene delivery

    Science.gov (United States)

    Chu, Zhiqin; Miu, Kaikei; Lung, Pingsai; Zhang, Silu; Zhao, Saisai; Chang, Huan-Cheng; Lin, Ge; Li, Quan

    2015-06-01

    The prickly nanodiamonds easily entered cells via endocytosis followed by unique intracellular translocation characteristics—quick endosomal escape followed by stable residence in cytoplasm. Endosomal membrane rupturing is identified as the major route of nanodiamonds’ escaping the vesicle confinement and to the cytoplasm. Little cytotoxicity is observed to associate with the nanodiamonds’ cytosolic release. Such features enable its application for gene delivery, which requires both effective cellular uptake and cytosolic release of the gene. Taking green fluorescent protein gene as an example, we demonstrate the successful cytosolic delivery and expression of such a gene using the prickly nanodiamonds as carrier.

  3. Escape probability based routing for ad hoc networks

    Institute of Scientific and Technical Information of China (English)

    Zhang Xuanping; Qin Zheng; Li Xin

    2006-01-01

    Routes in an ad hoc network may fail frequently because of node mobility. Stability therefore can be an important element in the design of routing protocols. The node escape probability is introduced to estimate the lifetime and stability of link between neighboring nodes and the escape probability based routing (EPBR) scheme to discover stable routes is proposed. Simulation results show that the EPBR can discover stable routes to reduce the number of route rediscovery, and is applicable for the situation that has highly dynamic network topology with broad area of communication.

  4. Escape of protists in predator-generated feeding currents

    DEFF Research Database (Denmark)

    Jakobsen, Hans Henrik

    2002-01-01

    The ciliate Strobilidium sp. and 2 flagellates, Chrysochromulina simplex and Gymnodinium sp., were exposed to predator-generated feeding currents, and their escape responses were quantified using 2- and 3-dimensional video techniques. All 3 studied organisms responded by escaping at a defined...... of Strobilidium sp. to the copepod Temora longicornis. The predicted reaction distance fit closely that measured, When the flagellates were exposed to the flow field of the ciliate Uronema filificum, they both responded up-stream to the feeding current. From the distance at which the flagellates responded...

  5. Anti-Tumor Immunity in Head and Neck Cancer: Understanding the Evidence, How Tumors Escape and Immunotherapeutic Approaches

    Directory of Open Access Journals (Sweden)

    Clint T. Allen

    2015-12-01

    Full Text Available Many carcinogen- and human papilloma virus (HPV-associated head and neck cancers (HNSCC display a hematopoietic cell infiltrate indicative of a T-cell inflamed phenotype and an underlying anti-tumor immune response. However, by definition, these tumors have escaped immune elimination and formed a clinically significant malignancy. A number of both genetic and environmental mechanisms may allow such immune escape, including selection of poorly antigenic cancer cell subsets, tumor produced proinflammatory and immunosuppressive cytokines, recruitment of immunosuppressive immune cell subsets into the tumor and expression of checkpoint pathway components that limit T-cell responses. Here, we explore concepts of antigenicity and immunogenicity in solid tumors, summarize the scientific and clinical data that supports the use of immunotherapeutic approaches in patients with head and neck cancer, and discuss immune-based treatment approaches currently in clinical trials.

  6. DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

    DEFF Research Database (Denmark)

    Chassefiere, E.; Nagy, A.; Mandea, M.

    2004-01-01

    DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure...... and evolution of Mars is thought to have influenced climate evolution. The collapse of the primitive magnetosphere early in Mars history could have enhanced atmospheric escape and favored transition to the present and climate. These objectives are achieved by using a low periapsis orbit. DYNAMO has been...... proposed in response to the AO released in February 2002 for instruments to be flown as a complementary payload onboard the CNES Orbiter to Mars (MO-07), foreseen to be launched in 2007 in the framework of the French PREMIER Mars exploration program. MO-07 orbital phase 2b (with an elliptical orbit...

  7. Autologous HIV-1 neutralizing antibodies: emergence of neutralization-resistant escape virus and subsequent development of escape virus neutralizing antibodies

    DEFF Research Database (Denmark)

    Arendrup, M; Nielsen, C; Hansen, J E;

    1992-01-01

    The capacity of consecutive human sera to neutralize sequentially obtained autologous virus isolates was studied. HIV-1 was isolated three times over a 48-164-week period from three individuals immediately after seroconversion and from two individuals in later stages of infection. Development of ...... escape virus may be part of the explanation of the apparent failure of the immune system to control HIV infection.......The capacity of consecutive human sera to neutralize sequentially obtained autologous virus isolates was studied. HIV-1 was isolated three times over a 48-164-week period from three individuals immediately after seroconversion and from two individuals in later stages of infection. Development...... of neutralizing antibodies to the primary virus isolates was detected 13-45 weeks after seroconversion. Emergence of escape virus with reduced sensitivity to neutralization by autologous sera was demonstrated. The patients subsequently developed neutralizing antibodies against the escape virus but after a delay...

  8. A giant cloud of hydrogen escaping the warm Neptune-mass planet GJ 436b

    Science.gov (United States)

    Ehrenreich, David

    2015-12-01

    Exoplanets in extreme irradiation environments, close to their parent stars, could lose some fraction of their atmospheres because of the extreme irradiation. Atmospheric mass loss has been observed during the past 12 years for hot gas giants, as large (~10%) ultraviolet absorption signals during transits. Meanwhile, no confident detection have been obtained for lower-mass planets, which are most likely to be significantly affected by atmospheric escape. In fact, hot rocky planets observed by Corot and Kepler might have lost all of their atmosphere, having begun as Neptune-like. The signature of this loss could be observed in the ultraviolet, when the planet and its escaping atmosphere transit the star, giving rise to deeper and longer transit signatures than in the optical. I will report on new Hubble observations of the Neptune-mass exoplanet GJ 436b, around which an extended atmosphere has been tentatively detected in 2014. The new data reveal that GJ 436b has huge transit depths of 56.3±3.5% in the hydrogen Lyman-alpha line, far beyond the 0.69% optical transit depth, and even far beyond mass loss signatures observed at the same wavelength from more irradiated gas giants. We infer from this repeated observations that the planet is surrounded and trailed by a large exospheric cloud of hydrogen, shaped as a giant comet, much bigger than the star. We estimate a mass-loss rate, which today is far too small to deplete the atmosphere of a Neptune-like planet in the lifetime of the parent star, but would have been much greater in the past. This 16-sigma detection opens exciting perspectives for the atmospheric characterization of low-mass and moderately-irradiated exoplanets, a large number of which will be detected by forthcoming transit surveys.

  9. Multidimensional extremal dependence coefficients

    OpenAIRE

    2017-01-01

    Extreme values modeling has attracting the attention of researchers in diverse areas such as the environment, engineering, or finance. Multivariate extreme value distributions are particularly suitable to model the tails of multidimensional phenomena. The analysis of the dependence among multivariate maxima is useful to evaluate risk. Here we present new multivariate extreme value models, as well as, coefficients to assess multivariate extremal dependence.

  10. The European Extreme Right and Religious Extremism

    Directory of Open Access Journals (Sweden)

    Jean-Yves Camus

    2007-12-01

    Full Text Available The ideology of the Extreme Right in Western Europe is rooted in Catholic fundamentalism and Counter-Revolutionary ideas. However, the Extreme Right, like all other political families, has had to adjust to an increasingly secular society. The old link between religion and the Extreme Right has thus been broken and in fact already was when Fascism overtook Europe: Fascism was secular, sometimes even anti-religious, in its essence. Although Catholic fundamentalists still retain strong positions within the apparatus of several Extreme Right parties (Front National, the vote for the Extreme Right is generally weak among regular churchgoers and strong among non-believers. In several countries, the vote for the Extreme Right is stronger among Protestant voters than among Catholics, since while Catholics may support Christian-Democratic parties, there are very few political parties linked to Protestant churches. Presently, it also seems that Paganism is becoming the dominant religious creed within the Extreme Right. In a multicultural Europe, non-Christian forms of religious fundamentalism such as Islamism also exist with ideological similarities to the Extreme Right, but this is not sufficient to categorize Islamism as a form of Fascism. Some Islamist groups seek alliances with the Extreme Right on the basis of their common dislike for Israel and the West, globalization and individual freedom of thought.

  11. Purinergic inhibition of ENaC produces aldosterone escape.

    Science.gov (United States)

    Stockand, James D; Mironova, Elena; Bugaj, Vladislav; Rieg, Timo; Insel, Paul A; Vallon, Volker; Peti-Peterdi, Janos; Pochynyuk, Oleh

    2010-11-01

    The mechanisms underlying "aldosterone escape," which refers to the excretion of sodium (Na(+)) during high Na(+) intake despite inappropriately increased levels of mineralocorticoids, are incompletely understood. Because local purinergic tone in the aldosterone-sensitive distal nephron downregulates epithelial Na(+) channel (ENaC) activity, we tested whether this mechanism mediates aldosterone escape. Here, urinary ATP concentration increased with dietary Na(+) intake in mice. Physiologic concentrations of ATP decreased ENaC activity in a dosage-dependent manner. P2Y(2)(-/-) mice, which lack the purinergic receptor, had significantly less increased Na(+) excretion than wild-type mice in response to high-Na(+) intake. Exogenous deoxycorticosterone acetate and deletion of the P2Y(2) receptor each modestly increased the resistance of ENaC to changes in Na(+) intake; together, they markedly increased resistance. Under the latter condition, ENaC could not respond to changes in Na(+) intake. In contrast, as a result of aldosterone escape, wild-type mice had increased Na(+) excretion in response to high-Na(+) intake regardless of the presence of high deoxycorticosterone acetate. These data suggest that control of ENaC by purinergic signaling is necessary for aldosterone escape.

  12. The Dutch approach to the escape from large compartments

    NARCIS (Netherlands)

    Janse, E.W.; Leur, P.H.E. van de

    1999-01-01

    In the Netherlands, the building regulations have no design mies for large fire compartments (over 1000 m2). With respect to the ability of people to escape from a fire in such large spaces, the Centre for Fire Research of TNO Building and Construction Research has developed a guideline that integra

  13. Entropy, Lyapunov Exponents and Escape Rates in Open Systems

    CERN Document Server

    Demers, Mark; Young, Lai-Sang

    2011-01-01

    We study the relation between escape rates and pressure in general dynamical systems with holes, where pressure is defined to be the difference between entropy and the sum of positive Lyapunov exponents. Central to the discussion is the formulation of a class of invariant measures supported on the survivor set over which we take the supremum to measure the pressure. Upper bounds for escape rates are proved for general diffeomorphisms of manifolds, possibly with singularities, for arbitrary holes and natural initial distributions including Lebesgue and SRB measures. Lower bounds do not hold in such generality, but for systems admitting Markov tower extensions with spectral gaps, we prove the equality of the escape rate with the absolute value of the pressure and the existence of an invariant measure realizing the escape rate, i.e. we prove a full variational principle. As an application of our results, we prove a variational principle for the billiard map associated with a planar Lorentz gas of finite horizon ...

  14. Escaping Embarrassment: Face-Work in the Rap Cipher

    Science.gov (United States)

    Lee, Jooyoung

    2009-01-01

    How do individuals escape embarrassing moments in interaction? Drawing from ethnographic fieldwork, in-depth interviews, and video recordings of weekly street corner ciphers (impromptu rap sessions), this paper expands Goffman's theory of defensive and protective face-work. The findings reveal formulaic and indirect dimensions of face-work. First,…

  15. A Slam Simulation Base Escape Model Using Response Surface Methodology.

    Science.gov (United States)

    1986-03-01

    OS/84D-8. School of Engineering, Air Force Institute of Technology (AU), Wright-Patterson AFB, OH December 1984. 19. Modianos , Doan T. and others...Pritsker & Associates, Inc, West Lafayette, In--ana, 1984. 21. Patrick , Rayford P. Nuclear Hardness and Base Escape, Engineering Report No. S-112. Omaha

  16. Hepatitis B escape mutants in Scottish blood donors.

    Science.gov (United States)

    Larralde, Osmany; Dow, Brian; Jarvis, Lisa; Davidson, Fiona; Petrik, Juraj

    2013-06-01

    Hepatitis B virus (HBV) remains as the viral infection with the highest risk of transmission by transfusion. This risk is associated with window period donations, occult HBV infection (OBI) and the emergence of escape mutants, which render blood donations false negative for hepatitis B surface antigen (HBsAg) serological testing. A retrospective study was conducted to gain insights into the molecular epidemiology of HBV escape mutants in Scottish blood donors. The criterion for selection was HBV positivity either by serology or nucleic acid testing (NAT). HBsAg detection was compared across several commercial immunoassays. The full length S gene from plasma samples was PCR amplified, cloned and expressed in HepG2 cells. Eight samples showed HBsAg discordant results, while 5 OBI samples were found. Four escape mutants, containing missense mutations in the S gene, are described here. These mutations impaired HBsAg detection both from HBV infected plasma samples and from recombinant proteins derived from its infected donors. Phylogenetic analysis showed that most of the mutants were clustered in the genotype D and were closely related to strains from Asia and the Middle East. We report here a proline substitution, outside the major hydrophilic region, that impaired HBsAg detection in vivo and in vitro, warning about the risk for the emergence of vaccine escape mutants with mutations outside the major neutralisation site.

  17. Enuresis Control through Fading, Escape, and Avoidance Training.

    Science.gov (United States)

    Hansen, Gordon D.

    1979-01-01

    A twin signal device that provides both escape and avoidance conditioning in enuresis control was documented with case studies of two enuretic children (eight and nine years old). In addition, a technique of fading as an adjunct to the process was utilized with one subject. (Author/SBH)

  18. The spectrum of Cosmic Rays escaping from relativistic shocks

    CERN Document Server

    Katz, Boaz; Waxman, Eli

    2010-01-01

    We derive expressions for the time integrated spectrum of Cosmic Rays (CRs) that are accelerated in a decelerating relativistic shock wave and escape ahead of the shock. It is assumed that at any given time the CRs have a power law form, carry a constant fraction of the energy E_tot of the shocked plasma, and escape continuously at the maximal energy attainable. The spectrum of escaping particles is highly sensitive to the instantaneous spectral index due to the fact that the minimal energy, E_min ~ \\Gamma^2 m_pc^2 where \\Gamma is the shock Lorentz factor, changes with time. In particular, the escaping spectrum may be considerably harder than the canonical N(E)\\propto E^-2 spectrum. For a shock expanding into a plasma of density n, a spectral break is expected at the maximal energy attainable at the transition to non relativistic velocities, E ~ 10^19 (\\epsilon_B/0.1)(n/1 cm^-3)^(1/6)(E_tot/10^51 erg)^(1/3) eV where \\epsilon_B is the fraction of the energy flux carried by the magnetic field. If ultra-high ene...

  19. Spatial and Nonspatial Escape Strategies in the Barnes Maze

    Science.gov (United States)

    Harrison, Fiona E.; Reiserer, Randall S.; Tomarken, Andrew J.; McDonald, Michael P.

    2006-01-01

    The Barnes maze is a spatial memory task that requires subjects to learn the position of a hole that can be used to escape the brightly lit, open surface of the maze. Two experiments assessed the relative importance of spatial (extra-maze) versus proximal visible cues in solving the maze. In Experiment 1, four groups of mice were trained either…

  20. Escaping Embarrassment: Face-Work in the Rap Cipher

    Science.gov (United States)

    Lee, Jooyoung

    2009-01-01

    How do individuals escape embarrassing moments in interaction? Drawing from ethnographic fieldwork, in-depth interviews, and video recordings of weekly street corner ciphers (impromptu rap sessions), this paper expands Goffman's theory of defensive and protective face-work. The findings reveal formulaic and indirect dimensions of face-work. First,…

  1. Plasma-induced Escape and Alterations of Planetary Atmospheres

    Science.gov (United States)

    Johnson, R. E.; Tucker, O. J.; Ewrin, J.; Cassidy, T. A.; Leblanc, F.

    2009-12-01

    The atmospheres of planets and planetary satellites are typically imbedded in space plasmas. Depending on the interaction with the induced or intrinsic fields energetic ions can have access to the thermosphere and the corona affecting their composition and thermal structure and causing loss to space. These processes are often lumped together as ‘atmospheric sputtering’ (Johnson 1994). In this talk I will review the results of simulations of the plasma bombardment at a number of solar system bodies and use those data to describe the effect on the upper atmosphere and on escape. Of considerable recent interest is the modeling of escape from Titan. Prior to Cassini’s tour of the Saturnian system, plasma-induced escape was suggested to be the dominant loss process, but recent models of enhanced thermal escape, often referred to as ‘slow hydrodynamic’ escape, have been suggested to lead to much larger Titan atmospheric loss rates (Strobel 2008; Cui et al. 2008). Such a process has been suggested to be active at some point in time on a number of solar system bodies. I will present hybrid fluid/ kinetic models of the upper atmosphere of certain bodies in order to test both the plasma-induced and thermal escape processes. Preliminary results suggest that the loss rates estimated using the ‘slow hydrodynamic’ escape process can be orders of magnitude too large. The implications for Mars, Titan and Pluto will be discussed. Background for this talk is contained in the following papers (Johnson 2004; 2009; Chaufray et al. 2007; Johnson et al. 2008; 2009; Tucker and Johnson 2009). References: Chaufray, J.Y., R. Modolo, F. Leblanc, G. Chanteur, R.E. Johnson, and J.G. Luhmann, Mars Solar Wind interaction: formation of the Martian corona and atmosphric loss to space, JGR 112, E09009, doi:10.1029/2007JE002915 (2007) Cui, J., Yelle, R. V., Volk, K. Distribution and escape of molecular hydrogen in Titan's thermosphere and exosphere. J. Geophys. Res. 113, doi:10

  2. Escape chambers in the German coal mining industry. Fluchtkammern im deutschen Steinkohlenbergbau

    Energy Technology Data Exchange (ETDEWEB)

    Kock, F.J.; Langer, G. (Bergbau-Forschung G.m.b.H. - Forschungsinstitut des Steinkohlenbergbauvereins, Essen (Germany, F.R.). Hauptstelle fuer das Grubenrettungswesen); Velsen-Zerweck, R. von; Boettcher, K. (Bergbau AG Westfalen, Dortmund (Germany, F.R.). Hauptabteilung Sicherheitswesen)

    1989-08-17

    Escape chambers are used in special cases in German mines for self-rescue of the work force. On the basis of the newly laid down requirements concerning escape chambers a specification for mobile escape chambers was drawn up. The Safety Department of Bergbau AG Westfalen purchased two escape chambers of different manufacturers for 10 persons in each case, which are curently being tested at collieries of Bergbau AG Westfalen. The German coal mining industry thus has escape chambers at its disposal to make self-rescue of the work force even safer in the event of difficult and long escape routes. (orig.).

  3. Who became Poor, Who Escaped Poverty, and Why? Developing and Using a Retrospective Methodology in Live Countries

    Science.gov (United States)

    Krishna, Anirudh

    2010-01-01

    The Stages-of-Progress methodology helps identify context-specific reasons associated with households' movements into or out of poverty. Developed in 2002, it was used over the next seven years for examining the experiences of 35,567 households in 398 diverse communities of India, Kenya, Uganda, Peru, and North Carolina. This essay looks at the…

  4. Information escaping the correlation hierarchy of the convergence field in the study of cosmological parameters.

    Science.gov (United States)

    Carron, Julien

    2012-02-17

    Using fits to numerical simulations, we show that the entire hierarchy of moments quickly ceases to provide a complete description of the convergence one-point probability density function leaving the linear regime. This suggests that the full N-point correlation function hierarchy of the convergence field becomes quickly generically incomplete and a very poor cosmological probe on nonlinear scales. At the scale of unit variance, only 5% of the Fisher information content of the one-point probability density function is still contained in its hierarchy of moments, making clear that information escaping the hierarchy is a far stronger effect than information propagating to higher order moments. It follows that the constraints on cosmological parameters achievable through extraction of the entire hierarchy become suboptimal by large amounts. A simple logarithmic mapping makes the moment hierarchy well suited again for parameter extraction.

  5. Formulation of a Cooperative-Confinement-Escape problem of multiple cooperative defenders against an evader escaping from a circular region

    Science.gov (United States)

    Li, Wei

    2016-10-01

    In this paper, we propose and formulate the Cooperative-Confinement-Escape (CCE) problem of multiple cooperative defenders against an evader escaping from a circular region, in which the defenders are moving on the circle with attempt to prevent possible escape of a single evader who is initially located inside the circle. The main contributions are summarized as follows: (1) we first provide an effective formulation of the CCE problem, which is an emphasis of this paper, with design of two nonlinear control strategies for the cooperative defenders and the adversarial evader, respectively. Particularly, we consider to include a proper interaction between each pair of the nearest-neighbor defenders, and an adaptive trajectory prediction mechanism in the strategies of the defenders to increase the chance of successful confinement. (2) For the first attempt on analyzing the CCE dynamics which is unavoidably strongly nonlinear, we analyze the minimum energy of the evader for possible escape. (3) For understanding of the behaviors of the system under different parameters, (i) we illustrate the effectiveness of the confinement strategy using the adaptive trajectory prediction mechanism, and (ii) the physical roles of the system parameters with respect to the system dynamics, some of which may be unexpected or not straightforward. A separate paper will be presented for systematic analysis of the agents' behaviors with respect to the large intervals of the parameter settings.

  6. An Empirical Investigation of Time-Out with and without Escape Extinction to Treat Escape-Maintained Noncompliance

    Science.gov (United States)

    Everett, Gregory E.; Olmi, D. Joe; Edwards, Ron P.; Tingstrom, Daniel H.; Sterling-Turner, Heather E.; Christ, Theodore J.

    2007-01-01

    The present study evaluates the effectiveness of two time-out (TO) procedures in reducing escape-maintained noncompliance of 4 children. Noncompliant behavioral function was established via a functional assessment (FA), including indirect and direct descriptive procedures and brief confirmatory experimental analyses. Following FA, parents were…

  7. Stream life of spawning pink salmon and the method of escapement enumeration by aerial survey: Draft

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Aerial surveys are currently used as the method tor escapement enumeration of pink salmon throughout Alaska. Other escapement enumeration methods cannot be...

  8. Parameter Optimization on Experimental Study to Reduce Ammonia Escape in CO2 Absorption by Ammonia Scrubbing

    Institute of Scientific and Technical Information of China (English)

    Hao Leng; Jianmin Gao; Mingyue He; Min Xie; Qian Du; Rui Sun; Shaohua Wu

    2016-01-01

    In order to research ammonia escape in CO2 absorption by ammonia scrubbing, ammonia escape was studied in CO2 absorption process using the bubbling reactor in different conditions as gas flow rate, CO2 ratio, absorbent temperature and ammonia concentration and quantity of escaped ammonia was measured by chemical titration. The results indicated that, the amount of ammonia escape can be around 20% of original amount in 90 min and the escaped amount will increase with the rise of gas flow rate, absorbent temperature, concentration of ammonia while decrease as CO2 ratio goes up. Through the analysis of the law of ammonia escape, at the same time, combined with ammonia escape and the influence of the relationship between the CO2 absorption efficiency, reducing ammonia escape working condition parameter optimization is given.

  9. Origins of carbon enhanced metal poor stars

    CERN Document Server

    Sharma, Mahavir; Frenk, Carlos; Cooke, Ryan

    2016-01-01

    We investigate the nature of carbon-enhanced metal poor (CEMP) stars in Milky Way (MW) analogues selected from the EAGLE cosmological hydrodynamical simulation. The stellar evolution model in EAGLE includes the physics of enrichment by asymptotic giant branch (AGB) stars, winds from massive stars, and type I and type II supernovae (SNe). In the simulation, star formation in young MW progenitors is bursty due to efficient stellar feedback, which causes poor metal mixing leading to the formation of CEMP stars with extreme abundance patterns. In this scenario, two classes of CEMP stars emerge: those mostly enriched by low-metallicity type II SNe with low Fe yields that drive galactic outflows, and those mostly enriched by AGB stars when a gas-poor progenitor accretes pristine gas. The first class resembles CEMP-no stars with high [C/Fe] and low [C/O], the second class resembles CEMP-s stars overabundant in s-process elements and high values of [C/O]. This scenario explains several trends seen in data: (i) the in...

  10. Interplanetary shocks and solar wind extremes

    Science.gov (United States)

    Vats, Hari

    The interplanetary shocks have a very high correlation with the annual sunspot numbers during the solar cycle; however the correlation falls very low on shorter time scale. Thus poses questions and difficulty in the predictability. Space weather is largely controlled by these interplanetary shocks, solar energetic events and the extremes of solar wind. In fact most of the solar wind extremes are related to the solar energetic phenomena. It is quite well understood that the energetic events like flares, filament eruptions etc. occurring on the Sun produce high speed extremes both in terms of density and speed. There is also high speed solar wind steams associated with the coronal holes mainly because the magnetic field lines are open there and the solar plasma finds it easy to escape from there. These are relatively tenuous high speed streams and hence create low intensity geomagnetic storms of higher duration. The solar flares and/or filament eruptions usually release excess coronal mass into the interplanetary medium and thus these energetic events send out high density and high speed solar wind which statistically found to produce more intense storms. The other extremes of solar wind are those in which density and speed are much lower than the normal values. Several such events have been observed and are found to produce space weather consequences of different kind. It is found that such extremes are more common around the maximum of solar cycle 20 and 23. Most of these have significantly low Alfven Mach number. This article is intended to outline the interplanetary and geomagnetic consequences of observed by ground based and satellite systems for the solar wind extremes.

  11. Legacy to the extreme

    NARCIS (Netherlands)

    A. van Deursen (Arie); T. Kuipers (Tobias); L.M.F. Moonen (Leon)

    2000-01-01

    textabstractWe explore the differences between developing a system using extreme programming techniques, and maintaining a legacy system. We investigate whether applying extreme programming techniques to legacy maintenance is useful and feasible.

  12. Legacy to the extreme

    NARCIS (Netherlands)

    Deursen, A. van; Kuipers, T.; Moonen, L.M.F.

    2000-01-01

    We explore the differences between developing a system using extreme programming techniques, and maintaining a legacy system. We investigate whether applying extreme programming techniques to legacy maintenance is useful and feasible.

  13. The DYNAMO Orbiter Project: High Resolution Mapping of Gravity/Magnetic Fields and In Situ Investigation of Mars Atmospheric Escape

    Science.gov (United States)

    Smrekar, S.; Chassefiere, E.; Forget, F.; Reme, H.; Mazelle, C.; Blelly, P. -L.; Acuna, M.; Connerney, J.; Purucker, M.; Lin, R.

    2000-01-01

    Dynamo is a small Mars orbiter planned to be launched in 2005 or 2007, in the frame of the NASA/CNES Mars exploration program. It is aimed at improving gravity and magnetic field resolution, in order to better understand the magnetic, geologic and thermal history of Mars, and at characterizing current atmospheric escape, which is still poorly constrained. These objectives are achieved by using a low periapsis orbit, similar to the one used by the Mars Global Surveyor spacecraft during its aerobraking phases. The proposed periapsis altitude for Dynamo of 120-130 km, coupled with the global distribution of periapses to be obtained during one Martian year of operation, through about 5000 low passes, will produce a magnetic/gravity field data set with approximately five times the spatial resolution of MGS. Low periapsis provides a unique opportunity to investigate the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, therefore atmospheric escape, which may have played a crucial role in removing atmosphere, and water, from the planet. There is much room for debate on the importance of current atmosphere escape processes in the evolution of the Martian atmosphere, as early "exotic" processes including hydrodynamic escape and impact erosion are traditionally invoked to explain the apparent sparse inventory of present-day volatiles. Yet, the combination of low surface gravity and the absence of a substantial internally generated magnetic field have undeniable effects on what we observe today. In addition to the current losses in the forms of Jeans and photochemical escape of neutrals, there are solar wind interaction-related erosion mechanisms because the upper atmosphere is directly exposed to the solar wind. The solar wind related loss rates, while now comparable to those of a modest comet, nonetheless occur continuously, with the intriguing possibility of important cumulative and

  14. Extreme environment electronics

    CERN Document Server

    Cressler, John D

    2012-01-01

    Unfriendly to conventional electronic devices, circuits, and systems, extreme environments represent a serious challenge to designers and mission architects. The first truly comprehensive guide to this specialized field, Extreme Environment Electronics explains the essential aspects of designing and using devices, circuits, and electronic systems intended to operate in extreme environments, including across wide temperature ranges and in radiation-intense scenarios such as space. The Definitive Guide to Extreme Environment Electronics Featuring contributions by some of the world's foremost exp

  15. Extreme values and the level-crossing problem: an application to the Feller process.

    Science.gov (United States)

    Masoliver, Jaume

    2014-04-01

    We review the question of the extreme values attained by a random process. We relate it to level crossings to one boundary (first-passage problems) as well as to two boundaries (escape problems). The extremes studied are the maximum, the minimum, the maximum absolute value, and the range or span. We specialize in diffusion processes and present detailed results for the Wiener and Feller processes.

  16. Extreme values and the level-crossing problem: An application to the Feller process

    Science.gov (United States)

    Masoliver, Jaume

    2014-04-01

    We review the question of the extreme values attained by a random process. We relate it to level crossings to one boundary (first-passage problems) as well as to two boundaries (escape problems). The extremes studied are the maximum, the minimum, the maximum absolute value, and the range or span. We specialize in diffusion processes and present detailed results for the Wiener and Feller processes.

  17. Deficiently Extremal Gorenstein Algebras

    Indian Academy of Sciences (India)

    Pavinder Singh

    2011-08-01

    The aim of this article is to study the homological properties of deficiently extremal Gorenstein algebras. We prove that if / is an odd deficiently extremal Gorenstein algebra with pure minimal free resolution, then the codimension of / must be odd. As an application, the structure of pure minimal free resolution of a nearly extremal Gorenstein algebra is obtained.

  18. Bacillus anthracis Factors for Phagosomal Escape

    Directory of Open Access Journals (Sweden)

    Irene Zornetta

    2012-07-01

    Full Text Available The mechanism of phagosome escape by intracellular pathogens is an important step in the infectious cycle. During the establishment of anthrax, Bacillus anthracis undergoes a transient intracellular phase in which spores are engulfed by local phagocytes. Spores germinate inside phagosomes and grow to vegetative bacilli, which emerge from their resident intracellular compartments, replicate and eventually exit from the plasma membrane. During germination, B. anthracis secretes multiple factors that can help its resistance to the phagocytes. Here the possible role of B. anthracis toxins, phospholipases, antioxidant enzymes and capsules in the phagosomal escape and survival, is analyzed and compared with that of factors of other microbial pathogens involved in the same type of process.

  19. Dynamics of the verge and foliot clock escapement

    CERN Document Server

    Hoyng, P

    2016-01-01

    The verge and foliot escapement has received relatively little attention in horology, despite the fact that it has been used in clocks for ages. We analyse the operation of a verge and foliot escapement in stationary swing. It is driven by a torque $m=\\pm\\mu$, switching sign at fixed swing angles $\\pm\\phi_0$, and $\\mu$ is taken to be constant. Friction is assumed to exert a torque proportional to the angular speed. We determine the shape of the swing angle $\\varphi(t)$, and compute the period and the swing amplitude of the foliot as a function of the model parameters. We find that the period of the foliot scales as $P\\propto\\mu^{-1}$ for weak driving, gradually changing into $P\\propto\\mu^{-1/3}$ for strong driving (large $\\mu$), which underlines that the motion of the foliot is not isochonous.

  20. Quantum and thermal phase escape in extended Josephson systems

    Energy Technology Data Exchange (ETDEWEB)

    Kemp, A.

    2006-07-12

    In this work I examine phase escape in long annular Josephson tunnel junctions. The sine-Gordon equation governs the dynamics of the phase variable along the junction. This equation supports topological soliton solutions, which correspond to quanta of magnetic flux trapped in the junction barrier. For such Josephson vortices an effective potential is formed by an external magnetic field, while a bias current acts as a driving force. Both together form a metastable potential well, which the vortex is trapped in. When the driving force exceeds the pinning force of the potential, the vortex escapes and the junction switches to the voltage state. At a finite temperature the driving force fluctuates. If the junction's energy scale is small, the phase variable can undergo a macroscopic quantum tunneling (MQT) process at temperatures below the crossover temperature. Without a vortex trapped, the metastable state is not a potential minimum in space, but a potential minimum at zero phase difference. (orig.)

  1. Escape Time of Josephson Junctions for Signal Detection

    CERN Document Server

    Addesso, P; Pierro, V

    2014-01-01

    In this Chapter we investigate with the methods of signal detection the response of a Josephson junction to a perturbation to decide if the perturbation contains a coherent oscillation embedded in the background noise. When a Josephson Junction is irradiated by an external noisy source, it eventually leaves the static state and reaches a steady voltage state. The appearance of a voltage step allows to measure the time spent in the metastable state before the transition to the running state, thus defining an escape time. The distribution of the escape times depends upon the characteristics of the noise and the Josephson junction. Moreover, the properties of the distribution depends on the features of the signal (amplitude, frequency and phase), which can be therefore inferred through the appropriate signal processing methods. Signal detection with JJ is interesting for practical purposes, inasmuch as the superconductive elements can be (in principle) cooled to the absolute zero and therefore can add (in practi...

  2. Behavioral analysis of the escape response in larval zebrafish

    Science.gov (United States)

    Feng, Ruopei; Girdhar, Kiran; Chemla, Yann; Gruebele, Martin

    The behavior of larval zebrafish is of great interest because the limited number of locomotor neurons in larval zebrafish couples with its rich repertoire of movements as a vertebrate animal. Current research uses a priori-selected parameters to describe their swimming behavior while our lab has built a parameter-free model based on singular value decomposition analysis to characterize it. Our previous work has analyzed the free swimming of larval zebrafish and presented a different picture from the current classification of larval zebrafish locomotion. Now we are extending this work to the studies of their escape response to acoustic stimulus. Analysis has shown intrinsic difference in the locomotion between escape response and free swimming.

  3. Escape rate of active particles in the effective equilibrium approach

    Science.gov (United States)

    Sharma, A.; Wittmann, R.; Brader, J. M.

    2017-01-01

    The escape rate of a Brownian particle over a potential barrier is accurately described by the Kramers theory. A quantitative theory explicitly taking the activity of Brownian particles into account has been lacking due to the inherently out-of-equilibrium nature of these particles. Using an effective equilibrium approach [Farage et al., Phys. Rev. E 91, 042310 (2015), 10.1103/PhysRevE.91.042310] we study the escape rate of active particles over a potential barrier and compare our analytical results with data from direct numerical simulation of the colored noise Langevin equation. The effective equilibrium approach generates an effective potential that, when used as input to Kramers rate theory, provides results in excellent agreement with the simulation data.

  4. Partial control of chaotic transients using escape times

    Energy Technology Data Exchange (ETDEWEB)

    Sabuco, Juan; Zambrano, Samuel; Sanjuan, Miguel A F, E-mail: juan.sabuco@urjc.e [Departamento de Fisica, Universidad Rey Juan Carlos, Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2010-11-15

    The partial control technique allows one to keep the trajectories of a dynamical system inside a region where there is a chaotic saddle and from which nearly all the trajectories diverge. Its main advantage is that this goal is achieved even if the corrections applied to the trajectories are smaller than the action of environmental noise on the dynamics, a counterintuitive result that is obtained by using certain safe sets. Using the Henon map as a paradigm, we show here the deep relationship between the safe sets and the sets of points with different escape times, the escape time sets. Furthermore, we show that it is possible to find certain extended safe sets that can be used instead of the safe sets in the partial control technique. Numerical simulations confirm our findings and show that in some situations, the use of extended safe sets can be more advantageous.

  5. Failed Escape: Solid Surfaces Prevent Tumbling of Escherichia coli

    Science.gov (United States)

    Molaei, Mehdi; Barry, Michael; Stocker, Roman; Sheng, Jian

    2014-08-01

    Understanding how bacteria move close to surfaces is crucial for a broad range of microbial processes including biofilm formation, bacterial dispersion, and pathogenic infections. We used digital holographic microscopy to capture a large number (>103) of three-dimensional Escherichia coli trajectories near and far from a surface. We found that within 20 μm from a surface tumbles are suppressed by 50% and reorientations are largely confined to surface-parallel directions, preventing escape of bacteria from the near-surface region. A hydrodynamic model indicates that the tumble suppression is likely due to a surface-induced reduction in the hydrodynamic force responsible for the flagellar unbundling that causes tumbling. These findings imply that tumbling does not provide an effective means to escape trapping near surfaces.

  6. Escape of Mars atmospheric carbon through time by photochemical means

    Science.gov (United States)

    Luhmann, J. G.; Kim, J.; Nagy, A. F.

    Luhmann et al. recently suggested that sputtering of the Martian atmosphere by re-entering O(+) pickup ions could have provided a significant route of escape for CO2 and its products throughout Mars' history. They estimated that the equivalent of C in an approximately 140-mbar CO2 atmosphere should have been lost this way if the Sun and solar wind evolved according to available models. Another source of escaping C (and O) that is potentially important is the dissociative recombination of ionospheric CO(+) near the exobase. We have evaluated the loss rates due to this process for 'ancient' solar EUV radiation fluxes of 1, 3, and 6 times the present flux in order to calculate the possible cumulative loss over the last 3.5 Gyr.

  7. Investigating Extreme Lifestyles through Mangrove Transcriptomics

    Science.gov (United States)

    Dassanayake, Maheshi

    2009-01-01

    Mangroves represent phylogenetically diverse taxa in tropical coastal terrestrial habitats. They are extremophiles, evolutionarily adapted to tolerate flooding, anoxia, high temperatures, wind, and high and extremely variable salt conditions in typically resource-poor environments. The genetic basis for these adaptations is, however, virtually…

  8. The C. elegans touch response facilitates escape from predacious fungi

    OpenAIRE

    Maguire, Sean M.; Clark, Christopher M.; Nunnari, John; Pirri, Jennifer K.; Alkema, Mark J.

    2011-01-01

    Predator-prey interactions are vital determinants in the natural selection of behavioral traits. However, we have few insights into both the neural mechanisms and the selective advantage of specific behavioral traits. Gentle touch to the anterior half of the body of Caenorhabditis elegans elicits an escape response in which the animal quickly reverses and suppresses exploratory head movements [1]. Even though the C. elegans touch response has provided one of the rare examples of how neural ne...

  9. On the Relative Contributions of Noncontingent Reinforcement and Escape Extinction in the Treatment of Food Refusal

    Science.gov (United States)

    Reed, Gregory K.; Piazza, Cathleen C.; Patel, Meeta R.; Layer, Stacy A.; Bachmeyer, Melanie H.; Bethke, Stephanie D.; Gutshall, Katharine A.

    2004-01-01

    In the current investigation, we evaluated the relative effects of noncontingent reinforcement (NCR), escape extinction, and a combination of NCR and escape extinction as treatment for the feeding problems exhibited by 4 children. For each participant, consumption increased only when escape extinction was implemented, independent of whether NCR…

  10. 46 CFR 56.50-25 - Safety and relief valve escape piping.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Safety and relief valve escape piping. 56.50-25 Section 56.50-25 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PIPING SYSTEMS AND APPURTENANCES Design Requirements Pertaining to Specific Systems § 56.50-25 Safety and relief valve escape piping. (a) Escape piping...

  11. Escape Geography--Developing Middle-School Students' Sense of Place.

    Science.gov (United States)

    Allen, Rodney F.; Molina, Laurie E. S.

    1992-01-01

    Suggests a social studies unit on escaping geography. Examines escape from dangerous places including an airliner, hotel fire, or war zone or from a social situation such as a boring speech or party. Describes historic escapes such as the Underground Railroad and the Berlin Wall. Lists learning strategies such as awareness of space and cognitive…

  12. Extreme value distributions

    CERN Document Server

    Ahsanullah, Mohammad

    2016-01-01

    The aim of the book is to give a through account of the basic theory of extreme value distributions. The book cover a wide range of materials available to date. The central ideas and results of extreme value distributions are presented. The book rwill be useful o applied statisticians as well statisticians interrested to work in the area of extreme value distributions.vmonograph presents the central ideas and results of extreme value distributions.The monograph gives self-contained of theory and applications of extreme value distributions.

  13. Poor-data and data-poor species stock assessment using a Bayesian hierarchical approach.

    Science.gov (United States)

    Jiao, Yan; Cortés, Enric; Andrews, Kate; Guo, Feng

    2011-10-01

    Appropriate inference for stocks or species with low-quality data (poor data) or limited data (data poor) is extremely important. Hierarchical Bayesian methods are especially applicable to small-area, small-sample-size estimation problems because they allow poor-data species to borrow strength from species with good-quality data. We used a hammerhead shark complex as an example to investigate the advantages of using hierarchical Bayesian models in assessing the status of poor-data and data-poor exploited species. The hammerhead shark complex (Sphyrna spp.) along the Atlantic and Gulf of Mexico coasts of the United States is composed of three species: the scalloped hammerhead (S. lewini), the great hammerhead (S. mokarran), and the smooth hammerhead (S. zygaena) sharks. The scalloped hammerhead comprises 70-80% of the catch and has catch and relative abundance data of good quality, whereas great and smooth hammerheads have relative abundance indices that are both limited and of low quality presumably because of low stock density and limited sampling. Four hierarchical Bayesian state-space surplus production models were developed to simulate variability in population growth rates, carrying capacity, and catchability of the species. The results from the hierarchical Bayesian models were considerably more robust than those of the nonhierarchical models. The hierarchical Bayesian approach represents an intermediate strategy between traditional models that assume different population parameters for each species and those that assume all species share identical parameters. Use of the hierarchical Bayesian approach is suggested for future hammerhead shark stock assessments and for modeling fish complexes with species-specific data, because the poor-data species can borrow strength from the species with good data, making the estimation more stable and robust.

  14. Safety Umbrella for Rural Poor

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    For lower-income farmers in China,from those living in the generally well-off coastal regions in the east,to those in the relatively poor landlocked interior in the west,the recent news from Beijing no doubt brought smiles to tired and worried faces:the Central Government has decided to extend the safety net,literally dubbed the basic living guarantee system,to all the rural poor from this year.

  15. Action and mechanism of Fas and Fas ligand in immune escape of gallbladder carcinoma

    Institute of Scientific and Technical Information of China (English)

    Li-Ning Xu; Sheng-Quan Zou; Jian-Ming Wang

    2005-01-01

    AIM: To study the role of Fas and Fas ligand (FasL) in biological behaviors of gallbladder carcinoma, and their correlated action and mechanism in tumor escape.METHODS: Streptavidin-biotin-peroxidase immunohistochemistry technique was used to study the expression of Fas and FasL protein in 26 gallbladder carcinoma tissues,18 gallbladder adenoma tissues, 3 gallbladder dysplasia tissues and 20 chronic cholecystitis tissues. Apoptosis of the infiltrating lymphocytes in these tissues was studied by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) method. Expression of both proteins and apoptosis of the tumor infiltrating lymphocytes in cancer tissues of primary foci was compared with clinicopathological features of gallbladder carcinoma.RESULTS: The positive rates of Fas were not significantly different among carcinoma, adenoma, dysplasia and chronic cholecystitis. The positive rate of FasL in carcinoma was significantly higher than that in chronic cholecystitis (x2 = 4.89, P<0.05). The apoptotic index (AI) in carcinoma was significantly higher than that in adenoma (t'= 4.19, P<0.01) and chronic cholecystitis (t'= 8.06, P<0.01). The AI was significantly lower in well-differentiated carcinoma and Nevin Ⅰ-Ⅲ carcinoma than that in poorly-differentiated carcinoma (t'= 2.63, P<0.05) and Nevin Ⅳ-Ⅴ carcinoma(t'= 3.33, P<0.01). The confidence interval (CI) ofinfiltrating lymphocytes in adenoma, chronic cholecystitis, well-differentiated carcinoma and Nevin Ⅰ-Ⅲ carcinoma wasvery significantly lower than that in carcinoma (t' = 6.99,P<0.01), adenoma (t' = 3.66, P<0.01), poorly-differentiated carcinoma (t' = 5.31, P<0.01) and Nevin Ⅳ-Ⅴ carcinoma(t' = 3.76, P<0.01), respectively. The CI of apoptosis of infiltrating lymphocytes in well-differentiated carcinoma was significantly lower than that in poorly-differentiated carcinoma (t = 2.52, P<0.05), and was not significantly lower in Nevin Ⅰ-Ⅲ carcinoma than

  16. A comparison of positive and negative reinforcement for compliance to treat problem behavior maintained by escape.

    Science.gov (United States)

    Slocum, Sarah K; Vollmer, Timothy R

    2015-09-01

    Previous research has shown that problem behavior maintained by escape can be treated using positive reinforcement. In the current study, we directly compared functional (escape) and nonfunctional (edible) reinforcers in the treatment of escape-maintained problem behavior for 5 subjects. In the first treatment, compliance produced a break from instructions. In the second treatment, compliance produced a small edible item. Neither treatment included escape extinction. Results suggested that the delivery of a positive reinforcer for compliance was effective for treating escape-maintained problem behavior for all 5 subjects, and the delivery of escape for compliance was ineffective for 3 of the 5 subjects. Implications and future directions related to the use of positive reinforcers in the treatment of escape behavior are discussed.

  17. Extreme Velocity Wind Sensor

    Science.gov (United States)

    Perotti, Jose; Voska, Ned (Technical Monitor)

    2002-01-01

    This presentation provides an overview of the development of new hurricane wind sensor (Extreme Velocity Wind Sensor) for the Kennedy Space Center (KSC) which is designed to withstand winds of up to three hundred miles an hour. The proposed Extreme Velocity Wind Sensor contains no moveable components that would be exposed to extreme wind conditions. Topics covered include: need for new hurricane wind sensor, conceptual design, software applications, computational fluid dynamic simulations of design concept, preliminary performance tests, and project status.

  18. Do galaxies that leak ionizing photons have extreme outflows?

    Science.gov (United States)

    Chisholm, J.; Orlitová, I.; Schaerer, D.; Verhamme, A.; Worseck, G.; Izotov, Y. I.; Thuan, T. X.; Guseva, N. G.

    2017-09-01

    Context. To reionize the early universe, high-energy photons must escape the galaxies that produce them. How these photons escape is debated because too many ionizing photons are absorbed even at small H i column densities. It has been suggested that stellar feedback drives galactic outflows out of star-forming regions, creating low density channels through which ionizing photons escape into the inter-galactic medium. Aims: We compare the galactic outflow properties of confirmed Lyman continuum (LyC) leaking galaxies to a control sample of nearby star-forming galaxies to explore whether the outflows from leakers are extreme as compared to the control sample. Methods: We use data from the Cosmic Origins Spectrograph on the Hubble Space Telescope to measure the equivalent widths and velocities of Si ii and Si iii absorption lines, tracing neutral and ionized galactic outflows. We explore whether the leakers have similar outflow properties to the control sample, and whether the outflows from the leakers follow similar scaling relations with host galaxy properties as the control sample. We rederive the escape fraction of ionizing photons for each leaker, and study whether the outflow properties influence the LyC escape fractions. Results: We find that the Si ii and Si iii equivalent widths of the LyC leakers reside on the low-end of the trend established by the control sample. The leakers' velocities are not statistically different than the control sample, but their absorption line profiles have a different asymmetry: their central velocities are closer to their maximum velocities. This possibly indicates a more rapidly accelerated outflow due to the compact size of the leakers. The outflow kinematics and equivalent widths are consistent with the scaling relations between outflow properties and host galaxy properties - most notably metallicity - defined by the control sample. Additionally, we use the Lyα profiles to show that the Si ii equivalent width scales with the

  19. Poor smokers, poor quitters, and cigarette tax regressivity.

    Science.gov (United States)

    Remler, Dahlia K

    2004-02-01

    The traditional view that excise taxes are regressive has been challenged. I document the history of the term regressive tax, show that traditional definitions have always found cigarette taxes to be regressive, and illustrate the implications of the greater price responsiveness observed among the poor. I explain the different definitions of tax burden: accounting, welfare-based willingness to pay, and welfare-based time inconsistent. Progressivity (equity across income groups) is sensitive to the way in which tax burden is assessed. Analysis of horizontal equity (fairness within a given income group) shows that cigarette taxes heavily burden poor smokers who do not quit, no matter how tax burden is assessed.

  20. How extreme is extreme hourly precipitation?

    Science.gov (United States)

    Papalexiou, Simon Michael; Dialynas, Yannis G.; Pappas, Christoforos

    2016-04-01

    The importance of accurate representation of precipitation at fine time scales (e.g., hourly), directly associated with flash flood events, is crucial in hydrological design and prediction. The upper part of a probability distribution, known as the distribution tail, determines the behavior of extreme events. In general, and loosely speaking, tails can be categorized in two families: the subexponential and the hyperexponential family, with the first generating more intense and more frequent extremes compared to the latter. In past studies, the focus has been mainly on daily precipitation, with the Gamma distribution being the most popular model. Here, we investigate the behaviour of tails of hourly precipitation by comparing the upper part of empirical distributions of thousands of records with three general types of tails corresponding to the Pareto, Lognormal, and Weibull distributions. Specifically, we use thousands of hourly rainfall records from all over the USA. The analysis indicates that heavier-tailed distributions describe better the observed hourly rainfall extremes in comparison to lighter tails. Traditional representations of the marginal distribution of hourly rainfall may significantly deviate from observed behaviours of extremes, with direct implications on hydroclimatic variables modelling and engineering design.

  1. Abundances In Very Metal Poor Dwarf Stars

    CERN Document Server

    Cohen, J G; McWilliam, A; Shectman, S; Thompson, I; Wasserburg, G J; Ivans, I I; Dehn, M; Karlsson, T; Melendez, J; Cohen, Judith G.; Christlieb, Norbert; William, Andrew Mc; Shectman, Steve; Thompson, Ian; Ivans, Inese; Dehn, Matthias; Karlsson, Torgny

    2004-01-01

    We discuss the detailed composition of 28 extremely metal-poor dwarfs, 22 of which are from the Hamburg/ESO Survey, based on Keck Echelle spectra. Our sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK,HES) determined from low resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below [Fe/H] = -3.0 dex. So far no additional turnoff stars with [Fe/H]}<-3.5 have been identified in our follow up efforts. For the best observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e. [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II SN with a narrow range in mass and explosion parameters; high mass Type II SN progenitors are requir...

  2. Escaping the Self: Identity, Group Identification and Violence

    Directory of Open Access Journals (Sweden)

    James Hardie-Bick

    2016-12-01

    Full Text Available This article draws on the early work of Erich Fromm. In Escape from Freedom Fromm (1969 [1941] directly addressed the psychological mechanisms of escape modern individuals employ to protect themselves from feelings of ontological insecurity and existential estrangement. The article builds on Fromm’s analysis by discussing the significance of his escape mechanisms for understanding the dynamic psychological attractions of identifying with entitative groups. Fromm’s work will be discussed in relation to Hogg’s recent work on uncertainty-identity theory. The aim of the article is to examine the advantages of combining Fromm’s psychoanalytic analysis with Hogg’s uncertainty-identity theory and to highlight the potential this approach has for understanding why groups engage in violent and destructive behaviour. Este artículo se inspira en las primeras obras de Erich Fromm. En El miedo a la libertad, Fromm (1969 [1941] abordó directamente los mecanismos psicológicos de evasión que los individuos modernos emplean para protegerse de los sentimientos de inseguridad ontológica y distanciamiento existencial. Este artículo se basa en el análisis de Fromm exponiendo el significado de sus mecanismos de evasión para entender las atracciones psicológicas dinámicas de identificación con grupos entitativos. Se analizará la obra de Fromm en relación con la obra reciente de Hogg sobre la teoría de incertidumbre identitaria. El objetivo del artículo es examinar las ventajas de combinar el análisis psicoanalítico de Fromm con la teoría de incertidumbre identitaria de Hogg, y destacar el potencial que tiene esta aproximación para comprender por qué los grupos adoptan un comportamiento violento y destructivo. DOWNLOAD THIS PAPER FROM SSRN: https://ssrn.com/abstract=2875737

  3. Experimental analysis and extinction of self-injurious escape behavior.

    Science.gov (United States)

    Iwata, B A; Pace, G M; Kalsher, M J; Cowdery, G E; Cataldo, M F

    1990-01-01

    Three studies are presented in which environmental correlates of self-injurious behavior were systematically examined and later used as the basis for treatment. In Study 1, 7 developmentally disabled subjects were exposed to a series of conditions designed to identify factors that maintain self-injurious behavior: attention contingent on self-injurious behavior (positive reinforcement), escape from or avoidance of demands contingent on self-injurious behaviour (negative reinforcement), alone (automatic reinforcement), and play (control). Results of a multielement design showed that each subject's self-injurious behavior occurred more frequently in the demand condition, suggesting that the behavior served an avoidance or escape function. Six of the 7 subjects participated in Study 2. During educational sessions, "escape extinction" was applied as treatment for their self-injurious behavior in a multiple baseline across subjects design. Results showed noticeable reduction or elimination of self-injurious behavior for each subject and an increase in compliance with instructions in all subjects for whom compliance data were taken. The 7th subject, whose self-injurious behavior during Study 1 occurred in response to medical demands (i.e., physical examinations), participated in Study 3. Treatment was comprised of extinction, as in Study 2, plus reinforcement for tolerance of the examination procedure, and was evaluated in a multiple baseline across settings design. Results showed that the treatment was successful in eliminating self-injurious behavior and that its effects transferred across eight new therapists and three physicians. General implications for the design, interpretation, and uses of assessment studies are discussed.

  4. Experimental study of subsonic microjet escaping from a rectangular nozzle

    Science.gov (United States)

    Aniskin, V. M.; Maslov, A. A.; Mukhin, K. A.

    2016-10-01

    The first experiments on the subsonic laminar microjets escaping from the nozzles of rectangular shape are carried out. The nozzle size is 83.3x3823 microns. Reynolds number calculated by the nozzle height and the average flow velocity at the nozzle exit ranged from 58 to 154. The working gas was air at room temperature. The velocity decay and velocity fluctuations along the center line of the jet are determined. The fundamental difference between the laminar microjets characteristics and subsonic turbulent jets of macro size is shown. Based on measurements of velocity fluctuations it is shown the presence of laminar-turbulent transition in microjets and its location is determined.

  5. The mirror of the escaped God – Alejandra Pizarnik

    Directory of Open Access Journals (Sweden)

    Mariano Carou

    2015-04-01

    Full Text Available Alejandra Pizarnik (1936-1972 shows many different stands regarding to “God’s escape” in her poetry and his diaries: from the psalmist’s request to the more combative atheism. There is, however, a constant development of a symbolic constellation to speak about God’s mistery, and the certitude –inherited from German romanticism– that the poet has always something to say about God’s escape, searching for a new hope in which is maybe a new form of mysticism.

  6. First-passage and escape problems in the Feller process

    CERN Document Server

    Masoliver, Jaume

    2012-01-01

    The Feller process is an one-dimensional diffusion process with linear drift and state-dependent diffusion coefficient vanishing at the origin. The process is positive definite and it is this property along with its linear character that have made Feller process a convenient candidate for the modeling of a number of phenomena ranging from single neuron firing to volatility of financial assets. While general properties of the process are well known since long, less known are properties related to level crossing such as the first-passage and the escape problems. In this work we thoroughly address these questions.

  7. First-passage and escape problems in the Feller process

    Science.gov (United States)

    Masoliver, Jaume; Perelló, Josep

    2012-10-01

    The Feller process is an one-dimensional diffusion process with linear drift and state-dependent diffusion coefficient vanishing at the origin. The process is positive definite and it is this property along with its linear character that have made Feller process a convenient candidate for the modeling of a number of phenomena ranging from single-neuron firing to volatility of financial assets. While general properties of the process have long been well known, less known are properties related to level crossing such as the first-passage and the escape problems. In this work we thoroughly address these questions.

  8. Chases and escapes the mathematics of pursuit and evasion

    CERN Document Server

    Nahin, Paul J

    2012-01-01

    We all played tag when we were kids. What most of us don't realize is that this simple chase game is in fact an application of pursuit theory, and that the same principles of games like tag, dodgeball, and hide-and-seek are also at play in military strategy, high-seas chases by the Coast Guard, and even romantic pursuits. In Chases and Escapes, Paul Nahin gives us the first complete history of this fascinating area of mathematics, from its classical analytical beginnings to the present day. Drawing on game theory, geometry, linear algebra, target-tracking algorithms, and much

  9. Test of time: what if little Albert had escaped?

    Science.gov (United States)

    Field, Andy P; Nightingale, Zoë C

    2009-04-01

    Watson and Rayner's (1920) ;Little Albert' experiment has become one of the most famous studies in psychology. It is a staple of many general psychology textbooks and is part of the very fabric of the discipline's folklore. Despite this fame, the study has been widely criticized in the nearly 90 years since it was published for its lack of methodological rigour. This article attempts to evaluate the contribution of the ;little Albert' study to modern clinical psychology by speculating on what theories and treatments of child anxiety would look like in a parallel universe in which the study never took place because ;little Albert' escaped from the hospital in which Watson tested him.

  10. The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

    Directory of Open Access Journals (Sweden)

    Rebecca Batorsky

    2014-10-01

    Full Text Available Cytotoxic T lymphocytes (CTL are a major factor in the control of HIV replication. CTL arise in acute infection, causing escape mutations to spread rapidly through the population of infected cells. As a result, the virus develops partial resistance to the immune response. The factors controlling the order of mutating epitope sites are currently unknown and would provide a valuable tool for predicting conserved epitopes. In this work, we adapt a well-established mathematical model of HIV evolution under dynamical selection pressure from multiple CTL clones to include partial impairment of CTL recognition, [Formula: see text], as well as cost to viral replication, [Formula: see text]. The process of escape is described in terms of the cost-benefit tradeoff of escape mutations and predicts a trajectory in the cost-benefit plane connecting sequentially escaped sites, which moves from high recognition loss/low fitness cost to low recognition loss/high fitness cost and has a larger slope for early escapes than for late escapes. The slope of the trajectory offers an interpretation of positive correlation between fitness costs and HLA binding impairment to HLA-A molecules and a protective subset of HLA-B molecules that was observed for clinically relevant escape mutations in the Pol gene. We estimate the value of [Formula: see text] from published experimental studies to be in the range (0.01-0.86 and show that the assumption of complete recognition loss ([Formula: see text] leads to an overestimate of mutation cost. Our analysis offers a consistent interpretation of the commonly observed pattern of escape, in which several escape mutations are observed transiently in an epitope. This non-nested pattern is a combined effect of temporal changes in selection pressure and partial recognition loss. We conclude that partial recognition loss is as important as fitness loss for predicting the order of escapes and, ultimately, for predicting conserved epitopes

  11. The route of HIV escape from immune response targeting multiple sites is determined by the cost-benefit tradeoff of escape mutations.

    Science.gov (United States)

    Batorsky, Rebecca; Sergeev, Rinat A; Rouzine, Igor M

    2014-10-01

    Cytotoxic T lymphocytes (CTL) are a major factor in the control of HIV replication. CTL arise in acute infection, causing escape mutations to spread rapidly through the population of infected cells. As a result, the virus develops partial resistance to the immune response. The factors controlling the order of mutating epitope sites are currently unknown and would provide a valuable tool for predicting conserved epitopes. In this work, we adapt a well-established mathematical model of HIV evolution under dynamical selection pressure from multiple CTL clones to include partial impairment of CTL recognition, [Formula: see text], as well as cost to viral replication, [Formula: see text]. The process of escape is described in terms of the cost-benefit tradeoff of escape mutations and predicts a trajectory in the cost-benefit plane connecting sequentially escaped sites, which moves from high recognition loss/low fitness cost to low recognition loss/high fitness cost and has a larger slope for early escapes than for late escapes. The slope of the trajectory offers an interpretation of positive correlation between fitness costs and HLA binding impairment to HLA-A molecules and a protective subset of HLA-B molecules that was observed for clinically relevant escape mutations in the Pol gene. We estimate the value of [Formula: see text] from published experimental studies to be in the range (0.01-0.86) and show that the assumption of complete recognition loss ([Formula: see text]) leads to an overestimate of mutation cost. Our analysis offers a consistent interpretation of the commonly observed pattern of escape, in which several escape mutations are observed transiently in an epitope. This non-nested pattern is a combined effect of temporal changes in selection pressure and partial recognition loss. We conclude that partial recognition loss is as important as fitness loss for predicting the order of escapes and, ultimately, for predicting conserved epitopes that can be

  12. 中国贫富悬殊的成因与对策:制度层面的考察%The Causes and Countermeasures of Extreme Disparity between the Rich and the Poor in Current China: From the Perspective of Institution

    Institute of Scientific and Technical Information of China (English)

    熊光清

    2012-01-01

    The institution is the sum of norms duct, which prescribes and shapes the behavior of stitution can exacerbate the disparity between the 'fi even narrow the disparity between the rich and the rent China, and a number of studies show that the of individuals or organizations con- ons. It seems that unreasonable in- reasonable institution can Control or poor. Disparity has become disparity tends to continue. a very serious problem in cur- In the process of institutional transformation, the institution exists imperfect and unreasonable elements which lead to the disparity between the rich and .the poor in China. Therefore, from the perspective of institution, it is crucial to make practical policy and take effective measures to control further weidenin's the disparity between the rich and the poor in China. Presently, the income distribution system should be reformed by means of tax leverage to regulate ex- cessive high incomes in order to narrow the income gap between the rich and the poor; the coordinated devel- opment should be promoted between urban -rural and among regional ecotiomy for the sake of narrowing the gap between urban - rural and among regional disparities ; the social security system should be established and perfected in the interests of promoting the harmonious development of society.%制度是关于人或组织的行为规范、规则和惯例的总和,它规定并塑造着个人或组织的行为。不合理的制度能够加剧贫富悬殊,而合理的制度则可以控制并缩小贫富悬殊。当前中国贫富悬殊现象已经到了非常严重的地步,并且多项研究表明中国的贫富差距存在继续扩大的趋势。在制度转型的过程中,制度的不完善和不合理是造成贫富悬殊的重要原因,因此从制度层面采取切实可行的政策措施来遏制贫富悬殊的进一步扩大至关重要。当前,应理顺收入分配体制,利用税收杠杆调节过高收入,缩小居民个人收入差

  13. Classifying Returns as Extreme

    DEFF Research Database (Denmark)

    Christiansen, Charlotte

    2014-01-01

    I consider extreme returns for the stock and bond markets of 14 EU countries using two classification schemes: One, the univariate classification scheme from the previous literature that classifies extreme returns for each market separately, and two, a novel multivariate classification scheme tha...

  14. Slow and Fast Escape for Open Intermittent Maps

    Science.gov (United States)

    Demers, Mark F.; Todd, Mike

    2017-04-01

    If a system mixes too slowly, putting a hole in it can completely destroy the richness of the dynamics. Here we study this instability for a class of intermittent maps with a family of slowly mixing measures. We show that there are three regimes: (1) standard hyperbolic-like behavior where the rate of mixing is faster than the rate of escape through the hole, there is a unique limiting absolutely continuous conditionally invariant measure (accim) and there is a complete thermodynamic description of the dynamics on the survivor set; (2) an intermediate regime, where the rate of mixing and escape through the hole coincide, limiting accims exist, but much of the thermodynamic picture breaks down; (3) a subexponentially mixing regime where the slow mixing means that mass simply accumulates on the parabolic fixed point. We give a complete picture of the transitions and stability properties (in the size of the hole and as we move through the family) in this class of open systems. In particular, we are able to recover a form of stability in the third regime above via the dynamics on the survivor set, even when no limiting accim exists.

  15. Ultra-fast Escape of a Octopus-inspired Rocket

    Science.gov (United States)

    Weymouth, Gabriel; Triantafyllou, Michael

    2013-11-01

    The octopus, squid, and other cephalopods inflate with water and then release a jet to accelerate in the opposite direction. This escape mechanism is particularly interesting in the octopus because they become initially quite bluff, yet this does not hinder them in achieving impressive bursts of speed. We examine this somewhat paradoxical maneuver using a simple deflating spheroid model in both potential and viscous flow. We demonstrate that the dynamic reduction of the width of the body completely changes the flow and forces acting on the escaping rocket in three ways. First, a body which reduces in size can generate an added mass thrust which counteracts the added mass inertia. Second, the motion of the shrinking wall acts similar to suction on a static wall, reducing separation and drag forces in a viscous fluid, but that this effects depends on the rate of size change. Third, using a combination of these two features it is possible to initially load the fluid with kinetic energy when heavy and bluff and then recover that energy when streamlined and light, enabling ultra-fast accelerations. As a notable example, these mechanisms allow a shrinking spheroid rocket in a heavy inviscid fluid to achieve speeds greater than an identical rocket in the vacuum of space. Southampton Marine and Maritime Institute.

  16. Escape of Hydrogen from the Exosphere of Mars

    Science.gov (United States)

    Bhattacharyya, Dolon; Clarke, John T.; Bertaux, Jean-Loup; Chaufray, Jean-Yves; Mayyasi-Matta, Majd A.

    2016-10-01

    After decades of exploration, the martian neutral hydrogen exosphere has remained largely uncharacterized even today. In my dissertation I have attempted to constrain the characteristics of the martian hydrogen exosphere using Hubble Space Telescope observations obtained during October-November 2007 and 2014. These observations reveal short-term seasonal changes exhibited by the martian hydrogen exosphere that are inconsistent with the diffusion-limited escape scenario. This seasonal behavior adds a new element towards backtracking the history of water loss from Mars. Modeling of the data also indicates the likely presence of a superthermal population of hydrogen created by non-thermal processes at Mars, another key element to understand the present-day escape. Exploration of the latitudinal symmetry of the martian exosphere indicates that it is symmetric above 2.5 martian radii and asymmetric below this altitude, which could be due to temperature differences between the day and night sides. Finally, the large uncertainties in determining the characteristics of the martian exosphere after decades of exploration is due to various assumptions about the intrinsic characteristics of the martian exosphere in the modeling process, degeneracy in the two modeling parameters temperature and density of the hydrogen atoms, unaccounted seasonal effects, and uncertainties introduced from spacecraft instrumentation as well as their viewing geometry.

  17. Random fluctuation leads to forbidden escape of particles.

    Science.gov (United States)

    Rodrigues, Christian S; de Moura, Alessandro P S; Grebogi, Celso

    2010-08-01

    A great number of physical processes are described within the context of Hamiltonian scattering. Previous studies have rather been focused on trajectories starting outside invariant structures, since the ones starting inside are expected to stay trapped there forever. This is true though only for the deterministic case. We show however that, under finitely small random fluctuations of the field, trajectories starting inside Kolmogorov-Arnold-Moser (KAM) islands escape within finite time. The nonhyperbolic dynamics gains then hyperbolic characteristics due to the effect of the random perturbed field. As a consequence, trajectories which are started inside KAM curves escape with hyperboliclike time decay distribution, and the fractal dimension of a set of particles that remain in the scattering region approaches that for hyperbolic systems. We show a universal quadratic power law relating the exponential decay to the amplitude of noise. We present a random walk model to relate this distribution to the amplitude of noise, and investigate these phenomena with a numerical study applying random maps.

  18. Numerical simulation of a self-propelled copepod during escape

    Science.gov (United States)

    Sotiropoulos, Fotis; Borazjani, Iman; Malkiel, Edwin; Katz, Josef

    2008-11-01

    Obtaining the 3D flow field, forces, and power is essential for understanding the high accelerations of a copepod during the escap. We carry out numerical simulations to study a free swimming copepod using the sharp-interface immersed boundary, fluid-structure interaction (FSI) approach of Borazjani et al. (J Compu Phys, 2008, 227, p 7587-7620). We use our previous tethered copepod model with a realistic copepod-like body, including all the appendages with the appendages motion prescribed from high-resolution, cinematic dual digital holography. The simulations are performed in a frame of reference attached to the copepod whose velocity is calculated by considering the forces acting on the copepod. The self-propelled simulations are challenging due to the destabilizing effects of the large added mass resulting from the low copepod mass and fast acceleration during the escape. Strongly-coupled FSI with under-relaxation and the Aitken acceleration technique is used to obtain stable and robust FSI iterations. The computed results for the self-propelled model are analyzed and compared with our earlier results for the tethered model.

  19. Metastatic Tumor Dormancy in Cutaneous Melanoma: Does Surgery Induce Escape?

    Energy Technology Data Exchange (ETDEWEB)

    Tseng, William W. [Department of Surgery, University of California at San Francisco, 513 Parnassus Avenue, Room S-321, San Francisco, CA 94143 (United States); Fadaki, Niloofar; Leong, Stanley P., E-mail: leongsx@cpmcri.org [Department of Surgery and Center for Melanoma Research and Treatment, California Pacific Medical Center and Research Institute, 2340 Clay Street, 2nd floor, San Francisco, CA 94115 (United States)

    2011-02-21

    According to the concept of tumor dormancy, tumor cells may exist as single cells or microscopic clusters of cells that are clinically undetectable, but remain viable and have the potential for malignant outgrowth. At metastatic sites, escape from tumor dormancy under more favorable local microenvironmental conditions or through other, yet undefined stimuli, may account for distant recurrence after supposed “cure” following surgical treatment of the primary tumor. The vast majority of evidence to date in support of the concept of tumor dormancy originates from animal studies; however, extensive epidemiologic data from breast cancer strongly suggests that this process does occur in human disease. In this review, we aim to demonstrate that metastatic tumor dormancy does exist in cutaneous melanoma based on evidence from mouse models and clinical observations of late recurrence and occult transmission by organ transplantation. Experimental data underscores the critical role of impaired angiogenesis and immune regulation as major mechanisms for maintenance of tumor dormancy. Finally, we examine evidence for the role of surgery in promoting escape from tumor dormancy at metastatic sites in cutaneous melanoma.

  20. Metastatic Tumor Dormancy in Cutaneous Melanoma: Does Surgery Induce Escape?

    Directory of Open Access Journals (Sweden)

    William W. Tseng

    2011-02-01

    Full Text Available According to the concept of tumor dormancy, tumor cells may exist as single cells or microscopic clusters of cells that are clinically undetectable, but remain viable and have the potential for malignant outgrowth. At metastatic sites, escape from tumor dormancy under more favorable local microenvironmental conditions or through other, yet undefined stimuli, may account for distant recurrence after supposed “cure” following surgical treatment of the primary tumor. The vast majority of evidence to date in support of the concept of tumor dormancy originates from animal studies; however, extensive epidemiologic data from breast cancer strongly suggests that this process does occur in human disease. In this review, we aim to demonstrate that metastatic tumor dormancy does exist in cutaneous melanoma based on evidence from mouse models and clinical observations of late recurrence and occult transmission by organ transplantation. Experimental data underscores the critical role of impaired angiogenesis and immune regulation as major mechanisms for maintenance of tumor dormancy. Finally, we examine evidence for the role of surgery in promoting escape from tumor dormancy at metastatic sites in cutaneous melanoma.

  1. The C. elegans touch response facilitates escape from predacious fungi.

    Science.gov (United States)

    Maguire, Sean M; Clark, Christopher M; Nunnari, John; Pirri, Jennifer K; Alkema, Mark J

    2011-08-09

    Predator-prey interactions are vital determinants in the natural selection of behavioral traits. Gentle touch to the anterior half of the body of Caenorhabditis elegans elicits an escape response in which the animal quickly reverses and suppresses exploratory head movements [1, 2]. Here, we investigate the ecological significance of the touch response in predator-prey interactions between C. elegans and predacious fungi that catch nematodes using constricting hyphal rings. We show that the constricting rings of Drechslerella doedycoides catch early larval stages with a diameter similar to the trap opening. There is a delay between the ring entry and ring closure, which allows the animal to withdraw from the trap before being caught. Mutants that fail to suppress head movements in response to touch are caught more efficiently than the wild-type. This demonstrates that the coordination of motor programs allows C. elegans to smoothly retract from a fungal noose and evade capture. Our results suggest that selective pressures imposed by predacious fungi have shaped the evolution of C. elegans escape behavior.

  2. Tectonic escape in the evolution of the continental crust

    Science.gov (United States)

    Burke, K.; Sengor, C.

    1986-01-01

    The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

  3. Autologous HIV-1 neutralizing antibodies: emergence of neutralization-resistant escape virus and subsequent development of escape virus neutralizing antibodies

    DEFF Research Database (Denmark)

    Arendrup, M; Nielsen, C; Hansen, J E

    1992-01-01

    The capacity of consecutive human sera to neutralize sequentially obtained autologous virus isolates was studied. HIV-1 was isolated three times over a 48-164-week period from three individuals immediately after seroconversion and from two individuals in later stages of infection. Development of ...... escape virus may be part of the explanation of the apparent failure of the immune system to control HIV infection.......The capacity of consecutive human sera to neutralize sequentially obtained autologous virus isolates was studied. HIV-1 was isolated three times over a 48-164-week period from three individuals immediately after seroconversion and from two individuals in later stages of infection. Development...

  4. Replicative Homeostasis: A fundamental mechanism mediating selective viral replication and escape mutation

    Directory of Open Access Journals (Sweden)

    Sallie Richard

    2005-02-01

    Full Text Available Abstract Hepatitis C (HCV, hepatitis B (HBV, the human immunodeficiency viruses (HIV, and other viruses that replicate via RNA intermediaries, cause an enormous burden of disease and premature death worldwide. These viruses circulate within infected hosts as vast populations of closely related, but genetically diverse, molecules known as "quasispecies". The mechanism(s by which this extreme genetic and antigenic diversity is stably maintained are unclear, but are fundamental to understanding viral persistence and pathobiology. The persistence of HCV, an RNA virus, is especially problematic and HCV stability, maintained despite rapid genomic mutation, is highly paradoxical. This paper presents the hypothesis, and evidence, that viruses capable of persistent infection autoregulate replication and the likely mechanism mediating autoregulation – Replicative Homeostasis – is described. Replicative homeostasis causes formation of stable, but highly reactive, equilibria that drive quasispecies expansion and generates escape mutation. Replicative homeostasis explains both viral kinetics and the enigma of RNA quasispecies stability and provides a rational, mechanistic basis for all observed viral behaviours and host responses. More importantly, this paradigm has specific therapeutic implication and defines, precisely, new approaches to antiviral therapy. Replicative homeostasis may also modulate cellular gene expression.

  5. Moving in extreme environments

    DEFF Research Database (Denmark)

    Lucas, Samuel J E; Helge, Jørn W; Schütz, Uwe H W;

    2016-01-01

    This review addresses human capacity for movement in the context of extreme loading and with it the combined effects of metabolic, biomechanical and gravitational stress on the human body. This topic encompasses extreme duration, as occurs in ultra-endurance competitions (e.g. adventure racing...... and transcontinental races) and expeditions (e.g. polar crossings), to the more gravitationally limited load carriage (e.g. in the military context). Juxtaposed to these circumstances is the extreme metabolic and mechanical unloading associated with space travel, prolonged bedrest and sedentary lifestyle, which may...

  6. Extremal surface barriers

    Energy Technology Data Exchange (ETDEWEB)

    Engelhardt, Netta; Wall, Aron C. [Department of Physics, University of California,Santa Barbara, CA 93106 (United States)

    2014-03-13

    We present a generic condition for Lorentzian manifolds to have a barrier that limits the reach of boundary-anchored extremal surfaces of arbitrary dimension. We show that any surface with nonpositive extrinsic curvature is a barrier, in the sense that extremal surfaces cannot be continuously deformed past it. Furthermore, the outermost barrier surface has nonnegative extrinsic curvature. Under certain conditions, we show that the existence of trapped surfaces implies a barrier, and conversely. In the context of AdS/CFT, these barriers imply that it is impossible to reconstruct the entire bulk using extremal surfaces. We comment on the implications for the firewall controversy.

  7. Momentum versus extinction effects in the treatment of self-injurious escape behavior.

    OpenAIRE

    Zarcone, J R; Iwata, B A; Hughes, C.E; Vollmer, T R

    1993-01-01

    An individual's self-injurious escape behavior was treated using a high-probability instructional sequence with and without extinction. When presented alone, the high-probability sequence did not reduce self-injurious behavior. When escape extinction was implemented either alone or in combination with the high-probability sequence, self-injury decreased and compliance increased, suggesting that extinction may be a necessary component of the treatment for behavior problems maintained by escape.

  8. On the relative contributions of positive reinforcement and escape extinction in the treatment of food refusal.

    OpenAIRE

    Piazza, Cathleen C; Patel, Meeta R; Gulotta, Charles S; Sevin, Bari M; Layer, Stacy A

    2003-01-01

    We compared the effects of positive reinforcement alone, escape extinction alone, and positive reinforcement with escape extinction in the treatment of the food and fluid refusal of 4 children who had been diagnosed with a pediatric feeding disorder. Consumption did not increase when positive reinforcement was implemented alone. By contrast, consumption increased for all participants when escape extinction was implemented, independent of the presence or absence of positive reinforcement. Howe...

  9. Vaccination and timing influence SIV immune escape viral dynamics in vivo.

    Directory of Open Access Journals (Sweden)

    Liyen Loh

    2008-01-01

    Full Text Available CD8+ cytotoxic T lymphocytes (CTL can be effective at controlling HIV-1 in humans and SIV in macaques, but their utility is partly offset by mutational escape. The kinetics of CTL escape and reversion of escape mutant viruses upon transmission to MHC-mismatched hosts can help us understand CTL-mediated viral control and the fitness cost extracted by immune escape mutation. Traditional methods for following CTL escape and reversion are, however, insensitive to minor viral quasispecies. We developed sensitive quantitative real-time PCR assays to track the viral load of SIV Gag164-172 KP9 wild-type (WT and escape mutant (EM variants in pigtail macaques. Rapid outgrowth of EM virus occurs during the first few weeks of infection. However, the rate of escape plateaued soon after, revealing a prolonged persistence of WT viremia not detectable by standard cloning and sequencing methods. The rate of escape of KP9 correlated with levels of vaccine-primed KP9-specific CD8+ T cells present at that time. Similarly, when non-KP9 responder (lacking the restricting Mane-A*10 allele macaques were infected with SHIVmn229 stock containing a mixture of EM and WT virus, rapid reversion to WT was observed over the first 2 weeks following infection. However, the rate of reversion to WT slowed dramatically over the first month of infection. The serial quantitation of escape mutant viruses evolving during SIV infection shows that rapid dynamics of immune escape and reversion can be observed in early infection, particularly when CD8 T cells are primed by vaccination. However, these early rapid rates of escape and reversion are transient and followed by a significant slowing in these rates later during infection, highlighting that the rate of escape is significantly influenced by the timing of its occurrence.

  10. Multiscale Micro-Nano Nested Structures: Engineered Surface Morphology for Efficient Light Escaping in Organic Light-Emitting Diodes.

    Science.gov (United States)

    Zhou, Lei; Dong, Xiaoxuan; Zhou, Yun; Su, Wenming; Chen, Xiaolian; Zhu, Yufu; Shen, Su

    2015-12-01

    Various micro-to-nanometer scale structures are extremely attractive for light escaping in organic light-emitting diodes. To develop and optimize such structures, an innovative approach was demonstrated for the first time to fabricate multiscale micro-nano nested structures by photolithography with a well-designed mask pattern followed by a controllable thermal reflow process. The experimental and theoretical characterizations verify that these unique nested structures hold the capability of light concentration, noticeable low haze, and efficient antireflection. As a proof-of-concept, the incorporation of this pattern onto the glass substrate efficiently facilitates light escaping from the device, resulting in current efficiency 1.60 times and external quantum efficiency 1.63 times that of a control flat device, respectively. Moreover, compared to a hexagonally arranged microlens array and quasi-random biomimetic moth eye nanostructures, the nested structures proposed here can magically tune the spatial emission profile to comply with the Lambertian radiation pattern. Hence, this novel structure is expected to be of great potential in related ubiquitous optoelectronic applications and provide scientific inspiration to other novel multiscale micro-nanostructure research.

  11. Experiment for Development of Simple Escape Countermeasures for Frogs Falling into Concrete Canals

    Science.gov (United States)

    Watabe, Keiji; Mori, Atsushi; Koizumi, Noriyuki; Takemura, Takeshi; Park, Myeong Soo

    Three prototype escape countermeasures for frogs that can be easily installed in U-shaped canals with widths of 30-50 cm and depths of 30-50 cm were experimentally produced because frogs cannot escape from agricultural canals with deep concrete walls after falling into the canal. The differences of effectiveness of the 3 prototypes in places for the countermeasures (1 and 2) and flow conditions (dry and water running) were investigated for 2 frog species (Tokyo Daruma Pond Frog and Japanese Brown Frog). The brown frogs escaped from the canals more easily than the pond frogs. The brown frogs escaped regardless of their body size, but the small pond frogs escaped more easily than the large pond frogs. The prototype with slopes beside both canal walls and a net spread across the center line of the canal enabled frogs to escape from the canal more easily than the prototypes with only slopes or nets beside both canal walls. Increasing the number of places for the countermeasures enhanced frog escape. The differences in frog escape between dry canals and canals with water running were not significant. Therefore, the prototypes were confirmed sufficient as escape countermeasures that is inexpensive and can be easily placed in and removed from agricultural canals.

  12. Sharks modulate their escape behavior in response to predator size, speed and approach orientation.

    Science.gov (United States)

    Seamone, Scott; Blaine, Tristan; Higham, Timothy E

    2014-12-01

    Escape responses are often critical for surviving predator-prey interactions. Nevertheless, little is known about how predator size, speed and approach orientation impact escape performance, especially in larger prey that are primarily viewed as predators. We used realistic shark models to examine how altering predatory behavior and morphology (size, speed and approach orientation) influences escape behavior and performance in Squalus acanthias, a shark that is preyed upon by apex marine predators. Predator models induced C-start escape responses, and increasing the size and speed of the models triggered a more intense response (increased escape turning rate and acceleration). In addition, increased predator size resulted in greater responsiveness from the sharks. Among the responses, predator approach orientation had the most significant impact on escapes, such that the head-on approach, as compared to the tail-on approach, induced greater reaction distances and increased escape turning rate, speed and acceleration. Thus, the anterior binocular vision in sharks renders them less effective at detecting predators approaching from behind. However, it appears that sharks compensate by performing high-intensity escapes, likely induced by the lateral line system, or by a sudden visual flash of the predator entering their field of view. Our study reveals key aspects of escape behavior in sharks, highlighting the modulation of performance in response to predator approach.

  13. Improving escape panel selectivity in Nephrops directed fisheries by actively stimulating fish behaviour

    DEFF Research Database (Denmark)

    Krag, Ludvig Ahm; Herrmann, Bent; Feekings, Jordan P.

    2016-01-01

    with it. To increase the efficiency of such panels, the contact probability needs to be improved. In this study, we investigate to what extent the efficiency of escape panels can be improved by actively stimulating the escape behaviour of fish. The performance of two identical panel sections was compared...... in a twin-trawl system, one with and one without a stimulation device. A new coupled analysis method was used to explicitly quantify the improvements in contact probability and release efficiency for the escape panel. The results demonstrate that by actively stimulating escape behaviour, the contact...

  14. Ancient village fire escape path planning based on improved ant colony algorithm

    Science.gov (United States)

    Xia, Wei; Cao, Kang; Hu, QianChuan

    2017-06-01

    The roadways are narrow and perplexing in ancient villages, it brings challenges and difficulties for people to choose route to escape when a fire occurs. In this paper, a fire escape path planning method based on ant colony algorithm is presented according to the problem. The factors in the fire environment which influence the escape speed is introduced to improve the heuristic function of the algorithm, optimal transfer strategy, and adjustment pheromone volatile factor to improve pheromone update strategy adaptively, improve its dynamic search ability and search speed. Through simulation, the dynamic adjustment of the optimal escape path is obtained, and the method is proved to be feasible.

  15. Antibody escape kinetics of equine infectious anemia virus infection of horses.

    Science.gov (United States)

    Schwartz, Elissa J; Nanda, Seema; Mealey, Robert H

    2015-07-01

    Lentivirus escape from neutralizing antibodies (NAbs) is not well understood. In this work, we quantified antibody escape of a lentivirus, using antibody escape data from horses infected with equine infectious anemia virus. We calculated antibody blocking rates of wild-type virus, fitness costs of mutant virus, and growth rates of both viruses. These quantitative kinetic estimates of antibody escape are important for understanding lentiviral control by antibody neutralization and in developing NAb-eliciting vaccine strategies. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  16. On the relative contributions of positive reinforcement and escape extinction in the treatment of food refusal.

    Science.gov (United States)

    Piazza, Cathleen C; Patel, Meeta R; Gulotta, Charles S; Sevin, Bari M; Layer, Stacy A

    2003-01-01

    We compared the effects of positive reinforcement alone, escape extinction alone, and positive reinforcement with escape extinction in the treatment of the food and fluid refusal of 4 children who had been diagnosed with a pediatric feeding disorder. Consumption did not increase when positive reinforcement was implemented alone. By contrast, consumption increased for all participants when escape extinction was implemented, independent of the presence or absence of positive reinforcement. However, the addition of positive reinforcement to escape extinction was associated with beneficial effects (e.g., greater decreases in negative vocalizations and inappropriate behavior) for some participants.

  17. Analysis of extreme events

    CSIR Research Space (South Africa)

    Khuluse, S

    2009-04-01

    Full Text Available ) determination of the distribution of the damage and (iii) preparation of products that enable prediction of future risk events. The methodology provided by extreme value theory can also be a powerful tool in risk analysis...

  18. Extreme environments and exobiology.

    Science.gov (United States)

    Friedmann, E I

    1993-01-01

    Ecological research on extreme environments can be applied to exobiological problems such as the question of life on Mars. If life forms (fossil or extant) are found on Mars, their study will help to solve fundamental questions about the nature of life on Earth. Extreme environments that are beyond the range of adaptability of their inhabitants are defined as "absolute extreme". Such environments can serve as terrestrial models for the last stages of life in the history of Mars, when the surface cooled down and atmosphere and water disappeared. The cryptoendolithic microbial community in porous rocks of the Ross Desert in Antarctica and the microbial mats at the bottom of frozen Antarctic lakes are such examples. The microbial communities of Siberian permafrost show that, in frozen but stable communities, long-term survival is possible. In the context of terraforming Mars, selected microorganisms isolated from absolute extreme environments are considered for use in creation of a biological carbon cycle.

  19. Venous Ultrasound (Extremities)

    Science.gov (United States)

    ... News Physician Resources Professions Site Index A-Z Ultrasound - Venous (Extremities) Venous ultrasound uses sound waves to ... limitations of Venous Ultrasound Imaging? What is Venous Ultrasound Imaging? Ultrasound is safe and painless, and produces ...

  20. Statistics of extremes

    CERN Document Server

    Gumbel, E J

    2012-01-01

    This classic text covers order statistics and their exceedances; exact distribution of extremes; the 1st asymptotic distribution; uses of the 1st, 2nd, and 3rd asymptotes; more. 1958 edition. Includes 44 tables and 97 graphs.

  1. Escape and avoidance learning in the earthworm Eisenia hortensis

    Directory of Open Access Journals (Sweden)

    W. Jeffrey Wilson

    2014-01-01

    Full Text Available Interest in instrumental learning in earthworms dates back to 1912 when Yerkes concluded that they can learn a spatial discrimination in a T-maze. Rosenkoetter and Boice determined in the 1970s that the “learning” that Yerkes observed was probably chemotaxis and not learning at all. We examined a different form of instrumental learning: the ability to learn both to escape and to avoid an aversive stimulus. Freely moving “master” worms could turn off an aversive white light by increasing their movement; the behavior of yoked controls had no effect on the light. We demonstrate that in as few as 12 trials the behavior of the master worms comes under the control of this contingency.

  2. Will 3552 Don Quixote escape from the Solar System?

    Directory of Open Access Journals (Sweden)

    Suryadi Siregar

    2011-05-01

    Full Text Available Asteroid 1983 SA, well known as 3552 Don Quixote, is one of Near Earth Asteroids (NEAs which is the most probable candidate for the cometary origin, or otherwise as Jupiter-Family-Comets (JFCs. The aim of this study is to investigate the possibility of 3552 Don Quixote to be ejected from the Solar System. This paper presents an orbital evolution of 100 hypothetical asteroids generated by cloning 3552 Don Quixote. Investigation of its orbital evolution is conducted by using the SWIFT subroutine package, where the gravitational perturbations of eight major planets in the Solar System are considered. Over very short time scales (220 kyr relative to the Solar System life time (10 Gyr, the asteroid 3552 Don Quixote gave an example of chaotic motion that can cause asteroid to move outward and may be followed by escaping from the Solar System. Probability of ejection within the 220 kyr time scale is 50%.

  3. Escape of Mycobacterium tuberculosis from oxidative killing by neutrophils.

    Science.gov (United States)

    Corleis, Björn; Korbel, Daniel; Wilson, Robert; Bylund, Johan; Chee, Ronnie; Schaible, Ulrich E

    2012-07-01

    Neutrophils enter sites of infection, where they can eliminate pathogenic bacteria in an oxidative manner. Despite their predominance in active tuberculosis lesions, the function of neutrophils in this important human infection is still highly controversial. We observed that virulent Mycobacterium tuberculosis survived inside human neutrophils despite prompt activation of these defence cells' microbicidal effectors. Survival of M. tuberculosis was accompanied by necrotic cell death of infected neutrophils. Necrotic cell death entirely depended on radical oxygen species production since chronic granulomatous disease neutrophils were protected from M. tuberculosis-triggered necrosis. More, importantly, the M. tuberculosis ΔRD1 mutant failed to induce neutrophil necrosis rendering this strain susceptible to radical oxygen species-mediated killing. We conclude that this virulence function is instrumental for M. tuberculosis to escape killing by neutrophils and contributes to pathogenesis in tuberculosis.

  4. Escaping Antiangiogenic Therapy: Strategies Employed by Cancer Cells

    Directory of Open Access Journals (Sweden)

    Mauricio P. Pinto

    2016-09-01

    Full Text Available Tumor angiogenesis is widely recognized as one of the “hallmarks of cancer”. Consequently, during the last decades the development and testing of commercial angiogenic inhibitors has been a central focus for both basic and clinical cancer research. While antiangiogenic drugs are now incorporated into standard clinical practice, as with all cancer therapies, tumors can eventually become resistant by employing a variety of strategies to receive nutrients and oxygen in the event of therapeutic assault. Herein, we concentrate and review in detail three of the principal mechanisms of antiangiogenic therapy escape: (1 upregulation of compensatory/alternative pathways for angiogenesis; (2 vasculogenic mimicry; and (3 vessel co-option. We suggest that an understanding of how a cancer cell adapts to antiangiogenic therapy may also parallel the mechanisms employed in the bourgeoning tumor and isolated metastatic cells delivering responsible for residual disease. Finally, we speculate on strategies to adapt antiangiogenic therapy for future clinical uses.

  5. The structure of spider's web fast escaping sets

    CERN Document Server

    Osborne, J W

    2010-01-01

    Building on recent work by Rippon and Stallard, we explore the intricate structure of the spider's web fast escaping sets associated with certain transcendental entire functions. Our results are expressed in terms of the components of the complement of the set (the 'holes' in the web). We describe the topology of such components and give a characterisation of their possible orbits under iteration. We show that there are uncountably many components having each of a number of orbit types, and we prove that components with bounded orbits are quasiconformally homeomorphic to components of the filled Julia set of a polynomial. We also show that there are singleton periodic components and that these are dense in the Julia set.

  6. Bacillus cereus immune escape: a journey within macrophages.

    Science.gov (United States)

    Tran, Seav-Ly; Ramarao, Nalini

    2013-10-01

    During bacterial infection, professional phagocytes are attracted to the site of infection, where they constitute a first line of host cell defense. Their function is to engulf and destroy the pathogens. Thus, bacteria must withstand the bactericidal activity of professional phagocytes, including macrophages to counteract the host immune system. Bacillus cereus infections are characterized by bacteremia despite the accumulation of inflammatory cells at the site of infection. This implies that the bacteria have developed means of resisting the host immune system. Bacillus cereus spores survive, germinate, and multiply in contact with macrophages, eventually producing toxins that kill these cells. However, the exact mechanism by which B. cereus evades immune attack remains unclear. This review addresses the interaction between B. cereus and macrophages, highlighting, in particular, the ways in which the bacteria escape the microbicidal activities of professional phagocytes.

  7. An Introduction to Survival, Evasion, Resistance, and Escape (SERE) Medicine.

    Science.gov (United States)

    Smith, Michael B

    2013-01-01

    When an individual finds himself/herself in a survival, evasion, resistance, or escape (SERE) scenario, the ability to treat injuries/illnesses can be the difference between life and death. SERE schools are responsible for preparing military members for these situations, but the concept of SERE medicine is not particularly well defined. To provide a comprehensive working description of SERE medicine, operational and training components were examined. Evidence suggests that SERE medicine is diverse, injury/illness patterns are situationally dependent, and treatment options often differ from conventional clinical medicine. Ideally, medical lessons taught in SERE training are based on actual documented events. Unfortunately, the existing body of literature is dated and does not appear to be expanding. In this article, four distinct facets of SERE medicine are presented to establish a basis for future discussion and research. Recommendations to improve SERE medical curricula and data-gathering processes are also provided.

  8. On Escaping a Galaxy Cluster in an Accelerating Universe

    CERN Document Server

    Stark, Alejo; Gifford, Daniel

    2016-01-01

    We derive the escape velocity profile for an Einasto density field in an accelerating universe and demonstrate its physical viability by comparing theoretical expectations to both light-cone data generated from N-body simulations and archival data on 20 galaxy clusters. We demonstrate that the projection function ($g(\\beta )$) is deemed physically viable only for the theoretical expectation that includes a cosmology-dependent term. Using simulations, we show that the inferred velocity anisotropy is more than 6{\\sigma} away from the expected value for the theoretical profile that ignores the acceleration of the universe. In the archival data, we constrain the average velocity anisotropy parameter of a sample of 20 clusters to be $\\beta ={0.248}_{-0.360}^{+0.164}$ at the 68% confidence level. Lastly, we briefly discuss how our analytic model may be used as a novel cosmological probe based on galaxy clusters.

  9. Fast Escape from Quantum Mazes in Integrated Photonics

    CERN Document Server

    Caruso, Filippo; Ciriolo, Anna Gabriella; Sciarrino, Fabio; Osellame, Roberto

    2015-01-01

    Escaping from a complex maze, by exploring different paths with several decision-making branches in order to reach the exit, has always been a very challenging and fascinating task. Wave field and quantum objects may explore a complex structure in parallel by interference effects, but without necessarily leading to more efficient transport. Here, inspired by recent observations in biological energy transport phenomena, we demonstrate how a quantum walker can efficiently reach the output of a maze by partially suppressing the presence of interference. In particular, we show theoretically an unprecedented improvement in transport efficiency for increasing maze size with respect to purely quantum and classical approaches. In addition, we investigate experimentally these hybrid transport phenomena, by mapping the maze problem in an integrated waveguide array, probed by coherent light, hence successfully testing our theoretical results. These achievements may lead towards future bio-inspired photonics technologies...

  10. An extremely primitive halo star

    CERN Document Server

    Caffau, E; François, P; Sbordone, L; Monaco, L; Spite, M; Spite, F; Ludwig, H -G; Cayrel, R; Zaggia, S; Hammer, F; Randich, S; Molaro, P; Hill, V; 10.1038/nature10377

    2012-01-01

    The early Universe had a chemical composition consisting of hydrogen, helium and traces of lithium1, almost all other elements were created in stars and supernovae. The mass fraction, Z, of elements more massive than helium, is called "metallicity". A number of very metal poor stars have been found some of which, while having a low iron abundance, are rich in carbon, nitrogen and oxygen. For theoretical reasons and because of an observed absence of stars with metallicities lower than Z=1.5E-5, it has been suggested that low mass stars (M<0.8M\\odot, the ones that survive to the present day) cannot form until the interstellar medium has been enriched above a critical value, estimated to lie in the range 1.5E-8\\leqZ\\leq1.5E-6, although competing theories claiming the contrary do exist. Here we report the chemical composition of a star with a very low Z\\leq6.9E-7 (4.5E-5 of that of the Sun) and a chemical pattern typical of classical extremely metal poor stars, meaning without the enrichment of carbon, nitroge...

  11. Initiating a watch list for Ebola virus antibody escape mutations

    Directory of Open Access Journals (Sweden)

    Craig R. Miller

    2016-02-01

    Full Text Available The 2014 Ebola virus (EBOV outbreak in West Africa is the largest in recorded history and resulted in over 11,000 deaths. It is essential that strategies for treatment and containment be developed to avoid future epidemics of this magnitude. With the development of vaccines and antibody-based therapies using the envelope glycoprotein (GP of the 1976 Mayinga strain, one important strategy is to anticipate how the evolution of EBOV might compromise these efforts. In this study we have initiated a watch list of potential antibody escape mutations of EBOV by modeling interactions between GP and the antibody KZ52. The watch list was generated using molecular modeling to estimate stability changes due to mutation. Every possible mutation of GP was considered and the list was generated from those that are predicted to disrupt GP-KZ52 binding but not to disrupt the ability of GP to fold and to form trimers. The resulting watch list contains 34 mutations (one of which has already been seen in humans at six sites in the GP2 subunit. Should mutations from the watch list appear and spread during an epidemic, it warrants attention as these mutations may reflect an evolutionary response from the virus that could reduce the effectiveness of interventions such as vaccination. However, this watch list is incomplete and emphasizes the need for more experimental structures of EBOV interacting with antibodies in order to expand the watch list to other epitopes. We hope that this work provokes experimental research on evolutionary escape in both Ebola and other viral pathogens.

  12. RpoS controls the Vibrio cholerae mucosal escape response.

    Directory of Open Access Journals (Sweden)

    Alex Toftgaard Nielsen

    2006-10-01

    Full Text Available Vibrio cholerae causes a severe diarrhoeal disease by secreting a toxin during colonization of the epithelium in the small intestine. Whereas the initial steps of the infectious process have been intensively studied, the last phases have received little attention. Confocal microscopy of V. cholerae O1-infected rabbit ileal loops captured a distinctive stage in the infectious process: 12 h post-inoculation, bacteria detach from the epithelial surface and move into the fluid-filled lumen. Designated the "mucosal escape response," this phenomenon requires RpoS, the stationary phase alternative sigma factor. Quantitative in vivo localization assays corroborated the rpoS phenotype and showed that it also requires HapR. Expression profiling of bacteria isolated from ileal loop fluid and mucus demonstrated a significant RpoS-dependent upregulation of many chemotaxis and motility genes coincident with the emigration of bacteria from the epithelial surface. In stationary phase cultures, RpoS was also required for upregulation of chemotaxis and motility genes, for production of flagella, and for movement of bacteria across low nutrient swarm plates. The hapR mutant produced near-normal numbers of flagellated cells, but was significantly less motile than the wild-type parent. During in vitro growth under virulence-inducing conditions, the rpoS mutant produced 10- to 100-fold more cholera toxin than the wild-type parent. Although the rpoS mutant caused only a small over-expression of the genes encoding cholera toxin in the ileal loop, it resulted in a 30% increase in fluid accumulation compared to the wild-type. Together, these results show that the mucosal escape response is orchestrated by an RpoS-dependent genetic program that activates chemotaxis and motility functions. This may furthermore coincide with reduced virulence gene expression, thus preparing the organism for the next stage in its life cycle.

  13. Whole-body volume regulation and escape from antidiuresis.

    Science.gov (United States)

    Verbalis, Joseph G

    2006-07-01

    Both individual cells and organs regulate their volume in response to sustained hypo-osmolality via solute and water losses. Similar processes occur in the whole body to regulate the volumes of extracellular fluid (ECF) and intravascular spaces toward normal levels. Body water losses occur via the phenomena "escape from antidiuresis"; solute losses occur through the secondary natriuresis induced by water retention. As a result of resistance to arginine vasopressin (AVP) signaling, escape from antidiuresis is caused by downregulation of kidney aquaporin-2 expression despite high AVP plasma levels. Recent data have implicated downregulation of vasopressin V2R as a potential mechanism of resistance, and suggest that this may be a result of decreased intrarenal angiotensin II signaling in combination with increased intrarenal nitric oxide and prostaglandin E2 signaling. The natriuresis that results in volume regulation of the ECF and vascular spaces is the result of intrarenal hemodynamic changes produced by volume expansion, but the degree to which these effects are modulated by aldosterone secretion and the activity of distal sodium cotransporters and channels remains to be elucidated. The clinical implication of these volume-regulatory processes is that the chronic hyponatremic state is one of water retention and solute losses from intracellular fluid and ECF compartments. The degree to which solute losses versus water retention contribute to hyponatremia will vary in association with many factors, including the etiology of the hyponatremia, the rapidity of development of the hyponatremia, the chronicity of the hyponatremia, the volume of daily water loading, and individual variability. Understanding these volume-regulatory processes allows a better understanding of many aspects of the conundrum of patients with "clinical euvolemia" and dilutional hyponatremia from AVP-induced water retention.

  14. RpoS controls the Vibrio cholerae mucosal escape response.

    Directory of Open Access Journals (Sweden)

    Alex Toftgaard Nielsen

    2006-10-01

    Full Text Available Vibrio cholerae causes a severe diarrhoeal disease by secreting a toxin during colonization of the epithelium in the small intestine. Whereas the initial steps of the infectious process have been intensively studied, the last phases have received little attention. Confocal microscopy of V. cholerae O1-infected rabbit ileal loops captured a distinctive stage in the infectious process: 12 h post-inoculation, bacteria detach from the epithelial surface and move into the fluid-filled lumen. Designated the "mucosal escape response," this phenomenon requires RpoS, the stationary phase alternative sigma factor. Quantitative in vivo localization assays corroborated the rpoS phenotype and showed that it also requires HapR. Expression profiling of bacteria isolated from ileal loop fluid and mucus demonstrated a significant RpoS-dependent upregulation of many chemotaxis and motility genes coincident with the emigration of bacteria from the epithelial surface. In stationary phase cultures, RpoS was also required for upregulation of chemotaxis and motility genes, for production of flagella, and for movement of bacteria across low nutrient swarm plates. The hapR mutant produced near-normal numbers of flagellated cells, but was significantly less motile than the wild-type parent. During in vitro growth under virulence-inducing conditions, the rpoS mutant produced 10- to 100-fold more cholera toxin than the wild-type parent. Although the rpoS mutant caused only a small over-expression of the genes encoding cholera toxin in the ileal loop, it resulted in a 30% increase in fluid accumulation compared to the wild-type. Together, these results show that the mucosal escape response is orchestrated by an RpoS-dependent genetic program that activates chemotaxis and motility functions. This may furthermore coincide with reduced virulence gene expression, thus preparing the organism for the next stage in its life cycle.

  15. Convergent evolution of escape from hepaciviral antagonism in primates.

    Science.gov (United States)

    Patel, Maulik R; Loo, Yueh-Ming; Horner, Stacy M; Gale, Michael; Malik, Harmit S

    2012-01-01

    The ability to mount an interferon response on sensing viral infection is a critical component of mammalian innate immunity. Several viruses directly antagonize viral sensing pathways to block activation of the host immune response. Here, we show that recurrent viral antagonism has shaped the evolution of the host protein MAVS--a crucial component of the viral-sensing pathway in primates. From sequencing and phylogenetic analyses of MAVS from 21 simian primates, we found that MAVS has evolved under strong positive selection. We focused on how this positive selection has shaped MAVS' susceptibility to Hepatitis C virus (HCV). We functionally tested MAVS proteins from diverse primate species for their ability to resist antagonism by HCV, which uses its protease NS3/4A to cleave human MAVS. We found that MAVS from multiple primates are resistant to inhibition by the HCV protease. This resistance maps to single changes within the protease cleavage site in MAVS, which protect MAVS from getting cleaved by the HCV protease. Remarkably, most of these changes have been independently acquired at a single residue 506 that evolved under positive selection. We show that "escape" mutations lower affinity of the NS3 protease for MAVS and allow it to better restrict HCV replication. We further show that NS3 proteases from all other primate hepaciviruses, including the highly divergent GBV-A and GBV-C viruses, are functionally similar to HCV. We conclude that convergent evolution at residue 506 in multiple primates has resulted in escape from antagonism by hepaciviruses. Our study provides a model whereby insights into the ancient history of viral infections in primates can be gained using extant host and virus genes. Our analyses also provide a means by which primates might clear infections by extant hepaciviruses like HCV.

  16. Escaped and Trapped Emission of Organic Light-Emitting Diodes

    Institute of Scientific and Technical Information of China (English)

    LIANG Shi-Xiong; WU Zhao-Xin; ZHAO Xuan-Ke; HOU Xun

    2012-01-01

    By locating the emitters around the first and second antinode of the metal electrode, the escaped and trapped emission of small molecule based bottom emission organic light-emitting diodes is investigated by using an integrating sphere, a fiber spectrometer and a glass hemisphere. It is found that the external coupling ratio by locating the emitters at the second antinode (at a distance of 220 nm from the cathode) is 70%, which is higher than that of an emitter at the first antinode (60 nm from the cathode) in theory and experiment. Extending the "half-space" dipole model by taking the dipole radiation pattern into account, we also calculate the optical coupling efficiency for the emitter at both the first and second antinode. Our experimental and theoretical results will benefit the optimization of device structures for the higher out-coupling efficiency.%By locating the emitters around the first and second antinode of the metal electrode,the escaped and trapped emission of small molecule based bottom emission organic light-emitting diodes is investigated by using an integrating sphere,a fiber spectrometer and a glass hemisphere.It is found that the external coupling ratio by locating the emitters at the second antinode (at a distance of 220 nm from the cathode) is 70%,which is higher than that of an emitter at the first antinode (60nm from the cathode) in theory and experiment.Extending the "half-space" dipole model by taking the dipole radiation pattern into account,we also calculate the optical coupling efficiency for the emitter at both the first and second antinode.Our experimental and theoretical results will benefit the optimization of device structures for the higher out-coupling efficiency.

  17. ESCAP holds expert group meeting on population issues facing adolescents.

    Science.gov (United States)

    1997-01-01

    This article summarizes the activities at the ESCAP Population Division Expert Group Meeting on Adolescents that was held during September-October 1997 in Bangkok, Thailand. The meeting was a follow-up to the 1994 International Conference on Population and Development (ICPD). The meeting considered 1) the ICPD recommendations; 2) the recommendations contained in the Jakarta Plan of Action on Human Resource Development; and 3) the Proposals for Action on Human Resources Development for Youth in Asia and the Pacific. Participants included about 25 people from Australia, Bangladesh, China, India, Indonesia, Philippines, Sri Lanka, and Thailand. The conference relied on 8 invited experts, two resource persons, advisors from the UNFPA Country Support Team for East and Southeast Asia, and representatives of UNFPA, the Population Council, and the East-West Center. A concern was the declining age of menarche of girls in the ESCAP region and the increasing age of marriage. During the time of menarche and marriage, girls are migrating and moving away from their family and community in rural areas. Family structure and relationships are changing. Increases are observed in adolescent premarital sexual activity, the incidence of sexually transmitted diseases, substance abuse, teenage pregnancy, and abortion. The mass media and information technologies have both a positive and a negative influence on adolescents. Parent-child communication exchanges and teacher-student exchanges are "less than ideal." Old traditions and practices change slower than people change. Boys and girls are affected differently by the sociocultural and economic environment. The societal norms set expectations for behavior that may conflict with individual beliefs and practices. Changes brought by globalization and rapid economic growth provide greater opportunity for young girls and women to obtain employment and autonomy.

  18. The escape from poverty among rural and urban elders.

    Science.gov (United States)

    Jensen, L; McLaughlin, D K

    1997-08-01

    Do poor elders really leave poverty? We explore the prevalence and nature of exits from poverty among poor elders, with special attention to rural-urban differences in this regard. Analyzing twenty years of data from the Panel Study of Income Dynamics, we find that 40% of poor elders leave poverty after one year. However, descriptive data suggest many of these exits resulted from small increases in income that merely nudged elders over the poverty line. Nonmetropolitan elders are less likely to exit poverty than their metropolitan counterparts, and this disadvantage widened when statistical controls were applied in multivariate models.

  19. The poor in the Psalms: A variety of views

    Directory of Open Access Journals (Sweden)

    Eben H. Scheffler

    2015-03-01

    Full Text Available Since the psalms are religious, poetic, existential expressions of life, entailing both extreme joy and intense suffering, it stands to reason that poverty (in its literal sense and otherwise would receive considerable attention. Focussing on material poverty and challenging the idea of a homogeneous view on poverty (e.g. Armenfr�mmigkeit in the psalms, the diversity of views on poverty in the psalms is explored. Attention is paid to YHWH or God caring for the poor, the (Israelite king as champion for the poor, the gods (heavenly assembly (noncaring for the poor, caring for the poor in Zion theology, God as crusher of the poor and mutual human charity. The article concludes with some remarks regarding the possible present-day appropriation of the views in the psalms.Intradisciplinary and/or interdisciplinary implications: The article challenges the traditional notion on Armenfr�mmigkeit in the psalms. This is important for contexts where identifying with the poor are fed by selfish interest and actually feeds exploitation. It also propounds that various views on poverty exist, demanding creative and contextual applicable measures to combat poverty in the present-day world.

  20. Near-Field Cosmology with Metal-Poor Stars

    CERN Document Server

    Frebel, Anna

    2015-01-01

    The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the Universe. We review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal-poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal enrichment events. We extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies and how metal-poor stars can be used to constrain these processes. Complementary abundance measurements in high-redshift gas clouds further help to establish the early chemical evolution of the Universe. The data appear consistent with the existence of two distinct channels of star formation at the earliest times.

  1. Listeriolysin O Membrane Damaging Activity Involves Arc Formation and Lineaction -- Implication for Listeria monocytogenes Escape from Phagocytic Vacuole.

    Directory of Open Access Journals (Sweden)

    Yi Ruan

    2016-04-01

    Full Text Available Listeriolysin-O (LLO plays a crucial role during infection by Listeria monocytogenes. It enables escape of bacteria from phagocytic vacuole, which is the basis for its spread to other cells and tissues. It is not clear how LLO acts at phagosomal membranes to allow bacterial escape. The mechanism of action of LLO remains poorly understood, probably due to unavailability of suitable experimental tools that could monitor LLO membrane disruptive activity in real time. Here, we used high-speed atomic force microscopy (HS-AFM featuring high spatio-temporal resolution on model membranes and optical microscopy on giant unilamellar vesicles (GUVs to investigate LLO activity. We analyze the assembly kinetics of toxin oligomers, the prepore-to-pore transition dynamics and the membrane disruption in real time. We reveal that LLO toxin efficiency and mode of action as a membrane-disrupting agent varies strongly depending on the membrane cholesterol concentration and the environmental pH. We discovered that LLO is able to form arc pores as well as damage lipid membranes as a lineactant, and this leads to large-scale membrane defects. These results altogether provide a mechanistic basis of how large-scale membrane disruption leads to release of Listeria from the phagocytic vacuole in the cellular context.

  2. Extreme Programming: Maestro Style

    Science.gov (United States)

    Norris, Jeffrey; Fox, Jason; Rabe, Kenneth; Shu, I-Hsiang; Powell, Mark

    2009-01-01

    "Extreme Programming: Maestro Style" is the name of a computer programming methodology that has evolved as a custom version of a methodology, called extreme programming that has been practiced in the software industry since the late 1990s. The name of this version reflects its origin in the work of the Maestro team at NASA's Jet Propulsion Laboratory that develops software for Mars exploration missions. Extreme programming is oriented toward agile development of software resting on values of simplicity, communication, testing, and aggressiveness. Extreme programming involves use of methods of rapidly building and disseminating institutional knowledge among members of a computer-programming team to give all the members a shared view that matches the view of the customers for whom the software system is to be developed. Extreme programming includes frequent planning by programmers in collaboration with customers, continually examining and rewriting code in striving for the simplest workable software designs, a system metaphor (basically, an abstraction of the system that provides easy-to-remember software-naming conventions and insight into the architecture of the system), programmers working in pairs, adherence to a set of coding standards, collaboration of customers and programmers, frequent verbal communication, frequent releases of software in small increments of development, repeated testing of the developmental software by both programmers and customers, and continuous interaction between the team and the customers. The environment in which the Maestro team works requires the team to quickly adapt to changing needs of its customers. In addition, the team cannot afford to accept unnecessary development risk. Extreme programming enables the Maestro team to remain agile and provide high-quality software and service to its customers. However, several factors in the Maestro environment have made it necessary to modify some of the conventional extreme

  3. Pathways to Earth-Like Atmospheres. Extreme Ultraviolet (EUV)-Powered Escape of Hydrogen-Rich Protoatmospheres

    Science.gov (United States)

    Lammer, Helmut; Kislyakova, K. G.; Odert, P.; Leitzinger, M.; Schwarz, R.; Pilat-Lohinger, E.; Kulikov, Yu. N.; Khodachenko, M. L.; Güdel, M.; Hanslmeier, A.

    2011-12-01

    We discuss the evolution of the atmosphere of early Earth and of terrestrial exoplanets which may be capable of sustaining liquid water oceans and continents where life may originate. The formation age of a terrestrial planet, its mass and size, as well as the lifetime in the EUV-saturated early phase of its host star play a significant role in its atmosphere evolution. We show that planets even in orbits within the habitable zone of their host stars might not lose nebular- or catastrophically outgassed initial protoatmospheres completely and could end up as water worlds with CO2 and hydrogen- or oxygen-rich upper atmospheres. If an atmosphere of a terrestrial planet evolves to an N2-rich atmosphere too early in its lifetime, the atmosphere may be lost. We show that the initial conditions set up by the formation of a terrestrial planet and by the evolution of the host star's EUV and plasma environment are very important factors owing to which a planet may evolve to a habitable world. Finally we present a method for studying the discussed atmosphere evolution hypotheses by future UV transit observations of terrestrial exoplanets.

  4. The Lack of Credit Services for Poverty Alleviation and the Innovation of Financing Guarantee Regime---based on an empirical analysis of leagues of extremely poor areas in Shaoyang Wuling mountain%扶贫开发信贷服务缺失与融资保障机制的创新完善--基于武陵山片区邵阳市特困区的实证分析

    Institute of Scientific and Technical Information of China (English)

    罗宏

    2015-01-01

    本文以武陵山片区邵阳市特困区为例,概述了当前扶贫开发金融服务中的信贷弱化现象,并运用典型调查验证不同信贷需求群体面临不同程度的信贷服务缺失问题。在此基础上分析了导致当前扶贫开发信贷服务存在问题的深层次原因。文章认为,银行业在当前和今后一段时间要提高扶贫开发信贷服务水平,需从信贷经济支撑、金融管理行为、信贷风险控制、信贷服务机制和信用体系等方面对信贷融资保障进行创新和完善。%Based on the example of leagues of extremely poor areas in Shaoyang Wuling mountain, the paper summarizes the cur-rent phenomenon that the financial services for rural poverty alleviation and development are being weakened from the angle of credit. By using typical investigations and evidence, it proved that groups of different demands for credit are faced with different levels of lack of credit services, so the financial industry will have a long way that implement the policies of strengthening financial services for poverty alleviation and development. On the basis of it , the paper analyses the deep reasons that causes the current problems of credit services for poverty alleviation and development. According to the article, how to improve the level of credit services for poverty alle-viation and development at present as well as in the future, and to ensure the policies for poverty alleviation and development, is that it needs some financial supports from credit behavior、 financial management、credit risk control、credit service mechanism and credit system to innovate and improve the financing guarantee regime.

  5. Lower extremities and iliopsoas pyomyositis with concurrent septic arthritis and spinal epidural abscess in a diabetic patient.

    Science.gov (United States)

    Vallianou, N; Gounari, P; Skourtis, A; Kougias, M; Sioula, E

    2013-10-01

    Pyomyositis is a rarely encountered infection among diabetics, which usually affects lower extremities. Herein, we present a case of lower extremities and iliopsoas pyomyositis with concurrent septic arthritis and spinal epidural abscess in a patient with poorly controlled diabetes mellitus.

  6. Hepatitis A Virus Vaccine Escape Variants and Potential New Serotype Emergence

    Science.gov (United States)

    Pérez-Sautu, Unai; Costafreda, M. Isabel; Caylà, Joan; Tortajada, Cecilia; Lite, Josep; Bosch, Albert

    2011-01-01

    Six hepatitis A virus antigenic variants that likely escaped the protective effect of available vaccines were isolated, mostly from men who have sex with men. The need to complete the proper vaccination schedules is critical, particularly in the immunocompromised population, to prevent the emergence of vaccine-escaping variants. PMID:21470474

  7. Hepatitis A Virus Vaccine Escape Variants and Potential New Serotype Emergence

    OpenAIRE

    Pérez-Sautu, Unai; Costafreda, M. Isabel; Caylà, Joan; Tortajada, Cecilia; Lite, Josep; Bosch, Albert; Rosa M Pintó

    2011-01-01

    Six hepatitis A virus antigenic variants that likely escaped the protective effect of available vaccines were isolated, mostly from men who have sex with men. The need to complete the proper vaccination schedules is critical, particularly in the immunocompromised population, to prevent the emergence of vaccine-escaping variants.

  8. Computer Self-Efficacy, Competitive Anxiety and Flow State: Escaping from Firing Online Game

    Science.gov (United States)

    Hong, Jon-Chao; Pei-Yu, Chiu; Shih, Hsiao-Feng; Lin, Pei-Shin; Hong, Jon-Chao

    2012-01-01

    Flow state in game playing affected by computer self-efficacy and game competitive anxiety was studied. In order to examine the effect of those constructs with high competition, this study select "Escaping from firing online game" which require college students to escape from fire and rescue people and eliminate the fire damage along the way of…

  9. Hepatitis A Virus Vaccine Escape Variants and Potential New Serotype Emergence

    OpenAIRE

    Pérez-Sautu, Unai; Costafreda, M. Isabel; Caylà, Joan; Tortajada, Cecilia; Lite, Josep; Bosch, Albert; Pintó, Rosa M.

    2011-01-01

    Six hepatitis A virus antigenic variants that likely escaped the protective effect of available vaccines were isolated, mostly from men who have sex with men. The need to complete the proper vaccination schedules is critical, particularly in the immunocompromised population, to prevent the emergence of vaccine-escaping variants.

  10. The Effects of Fixed-Time Escape on Inappropriate and Appropriate Classroom Behavior

    Science.gov (United States)

    Waller, Rachael D.; Higbee, Thomas S.

    2010-01-01

    Few studies have explored the effects of fixed-time (FT) reinforcement on escape-maintained behavior of students in a classroom setting. We measured the effects of an FT schedule on the disruptive and appropriate academic behaviors of 2 junior high students in a public school setting. Results demonstrated that FT escape from tasks resulted in a…

  11. Competing Contingencies for Escape Behavior: Effects of Negative Reinforcement Magnitude and Quality

    Science.gov (United States)

    Hammond, Jennifer L.

    2009-01-01

    Previous research has shown that problem behavior maintained by social-negative reinforcement can be treated without escape extinction by enhancing the quality of positive reinforcement for an appropriate alternative response such as compliance. By contrast, negative reinforcement (escape) for compliance generally has been ineffective in the…

  12. Spoon Distance Fading with and without Escape Extinction as Treatment for Food Refusal

    Science.gov (United States)

    Rivas, Kristi D.; Piazza, Cathleen C.; Patel, Meeta R.; Bachmeyer, Melanie H.

    2010-01-01

    Little is known about the characteristics of meals that serve as motivating operations (MOs) for escape behavior. In the current investigation, we showed that the distance at which a therapist held a spoon from a child's lips served as an MO for escape behavior. Based on these results, we implemented spoon distance fading, compared fading with and…

  13. HIV-1 Viral Escape in Cerebrospinal Fluid of Subjects on Suppressive Antiretroviral Treatment

    OpenAIRE

    Edén, Arvid; Fuchs, Dietmar; Hagberg, Lars; Nilsson, Staffan; Spudich, Serena; SVENNERHOLM, BO; Price, Richard W.; Gisslén, Magnus

    2010-01-01

    Background. Occasional cases of viral escape in cerebrospinal fluid (CSF) despite suppression of plasma human immunodeficiency virus type 1 (HIV-1) RNA have been reported. We investigated CSF viral escape in subjects treated with commonly used antiretroviral therapy regimens in relation to intrathecal immune activation and central nervous system penetration effectiveness (CPE) rank.

  14. Treatment of Escape-Maintained Behavior with Positive Reinforcement: The Role of Reinforcement Contingency and Density

    Science.gov (United States)

    Ingvarsson, Einar T.; Hanley, Gregory P.; Welter, Katherine M.

    2009-01-01

    Functional analyses suggested that the disruptive behavior of three preschool children was maintained by escape from demands. While keeping the escape contingency intact, we conducted (a) a density analysis in which the children earned preferred items for task completion according to two schedules that varied in reinforcement density, and (b) a…

  15. Identification of genes escaping X inactivation by allelic expression analysis in a novel hybrid mouse model.

    Science.gov (United States)

    Berletch, Joel B; Ma, Wenxiu; Yang, Fan; Shendure, Jay; Noble, William S; Disteche, Christine M; Deng, Xinxian

    2015-12-01

    X chromosome inactivation (XCI) is a female-specific mechanism that serves to balance gene dosage between the sexes whereby one X chromosome in females is inactivated during early development. Despite this silencing, a small portion of genes escape inactivation and remain expressed from the inactive X (Xi). Little is known about the distribution of escape from XCI in different tissues in vivo and about the mechanisms that control tissue-specific differences. Using a new binomial model in conjunction with a mouse model with identifiable alleles and skewed X inactivation we are able to survey genes that escape XCI in vivo. We show that escape from X inactivation can be a common feature of some genes, whereas others escape in a tissue specific manner. Furthermore, we characterize the chromatin environment of escape genes and show that expression from the Xi correlates with factors associated with open chromatin and that CTCF co-localizes with escape genes. Here, we provide a detailed description of the experimental design and data analysis pipeline we used to assay allele-specific expression and epigenetic characteristics of genes escaping X inactivation. The data is publicly available through the GEO database under ascension numbers GSM1014171, GSE44255, and GSE59779. Interpretation and discussion of these data are included in a previously published study (Berletch et al., 2015) [1].

  16. Statistics of Extremes

    KAUST Repository

    Davison, Anthony C.

    2015-04-10

    Statistics of extremes concerns inference for rare events. Often the events have never yet been observed, and their probabilities must therefore be estimated by extrapolation of tail models fitted to available data. Because data concerning the event of interest may be very limited, efficient methods of inference play an important role. This article reviews this domain, emphasizing current research topics. We first sketch the classical theory of extremes for maxima and threshold exceedances of stationary series. We then review multivariate theory, distinguishing asymptotic independence and dependence models, followed by a description of models for spatial and spatiotemporal extreme events. Finally, we discuss inference and describe two applications. Animations illustrate some of the main ideas. © 2015 by Annual Reviews. All rights reserved.

  17. Extremely deformable structures

    CERN Document Server

    2015-01-01

    Recently, a new research stimulus has derived from the observation that soft structures, such as biological systems, but also rubber and gel, may work in a post critical regime, where elastic elements are subject to extreme deformations, though still exhibiting excellent mechanical performances. This is the realm of ‘extreme mechanics’, to which this book is addressed. The possibility of exploiting highly deformable structures opens new and unexpected technological possibilities. In particular, the challenge is the design of deformable and bi-stable mechanisms which can reach superior mechanical performances and can have a strong impact on several high-tech applications, including stretchable electronics, nanotube serpentines, deployable structures for aerospace engineering, cable deployment in the ocean, but also sensors and flexible actuators and vibration absorbers. Readers are introduced to a variety of interrelated topics involving the mechanics of extremely deformable structures, with emphasis on ...

  18. Precursors of extreme increments

    CERN Document Server

    Hallerberg, S; Holstein, D; Kantz, H; Hallerberg, Sarah; Altmann, Eduardo G.; Holstein, Detlef; Kantz, Holger

    2006-01-01

    We investigate precursors and predictability of extreme events in time series, which consist in large increments within successive time steps. In order to understand the predictability of this class of extreme events, we study analytically the prediction of extreme increments in AR(1)-processes. The resulting strategies are then applied to predict sudden increases in wind speed recordings. In both cases we evaluate the success of predictions via creating receiver operator characteristics (ROC-plots). Surprisingly, we obtain better ROC-plots for completely uncorrelated Gaussian random numbers than for AR(1)-correlated data. Furthermore, we observe an increase of predictability with increasing event size. Both effects can be understood by using the likelihood ratio as a summary index for smooth ROC-curves.

  19. Relation Between Dose of Loop Diuretics and Outcomes in a Heart Failure Population: Results of the ESCAPE Trial

    Science.gov (United States)

    Hasselblad, Vic; Stough, Wendy Gattis; Shah, Monica R.; Lokhnygina, Yuliya; O’Connor, Christopher M.; Califf, Robert M.; Adams, Kirkwood F.

    2007-01-01

    Background We examined the relation of maximal in-hospital diuretic dose to weight loss, changes in renal function, and mortality in hospitalised heart failure (HF) patients. Methods In ESCAPE, 395 patients received diuretics in-hospital. Weight was measured at baseline, discharge, and every other day before discharge. Weight loss was defined as the difference between baseline and last in-hospital weight. Mortality was assessed using a log-logistic model with non-zero background. Results Median weight loss: 2.8 kg (0.7, 6.1); mean: 3.7 kg (22% of values 300 mg/day. Dose remained a significant predictor of mortality after adjusting for baseline variables that significantly predicted mortality. Correlation between maximal dose and creatinine level change was not significant (r = 0.043; p = 0.412) Conclusions High diuretic doses during HF hospitalisation are associated with increased mortality and poor 6-month outcome. PMID:17719273

  20. DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

    DEFF Research Database (Denmark)

    Chassefiere, E.; Nagy, A.; Mandea, M.

    2004-01-01

    DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure....... Ultraviolet remote sensing is an essential complement to characterize high, tenuous, layers of the atmosphere. One Martian year of operation, with about 5,000 low passes, should allow DYNAMO to map in great detail the residual magnetic field, together with the gravity field. Additional data on the internal...... structure will be obtained by mapping the electric conductivity, sinergistically with the NETLANDER magnetic data. Three options have been recommended by the International Science and Technical Review Board (ISTRB), who met on July 1st and 2nd, 2002. One of them is centered on DYNAMO. The final choice...

  1. Farming-up coastal fish assemblages through a massive aquaculture escape event.

    Science.gov (United States)

    Toledo-Guedes, Kilian; Sanchez-Jerez, Pablo; Benjumea, María E; Brito, Alberto

    2014-07-01

    We investigated the changes on the mean trophic level of fish assemblages across different spatiotemporal scales, before and after a massive escape event occurred off La Palma (Canary Islands), which resulted in the release of 1.5 million fish (mostly Dicentrarchus labrax) into the wild. The presence of escaped fish altered significantly the mean trophic level of fish assemblages in shallow coastal waters. This alteration was exacerbated by the massive escape. A nearby marine protected area buffered the changes in mean trophic level but exhibited the same temporal patterns as highly fished areas. Moreover, escaped fish exploited natural resources according to their total length and possibly, time since escapement. New concerns arise as a "farming up" process is detected in shallow coastal fish assemblages where marine aquaculture is established.

  2. Weather and Climate Extremes.

    Science.gov (United States)

    1997-09-01

    Antarctica’s highest (New Zealand Antarctic Society, 1974). This extreme exceeded the record of 58°F (14.4°C) that occurred on 20 October 1956 at Esperanza ... Esperanza (also known as Bahia Esperanza , Hope Bay) was in operation from 1945 through the early 1960s. Meteorological/Climatological Factors: This extreme...cm) Location: Grand Ilet, La R’eunion Island [21°00’S, 55°30’E] Date: 26 January 1980 WORLD’S GREATEST 24-HOUR RAINFALL 72 in (182.5 cm

  3. Adventure and Extreme Sports.

    Science.gov (United States)

    Gomez, Andrew Thomas; Rao, Ashwin

    2016-03-01

    Adventure and extreme sports often involve unpredictable and inhospitable environments, high velocities, and stunts. These activities vary widely and include sports like BASE jumping, snowboarding, kayaking, and surfing. Increasing interest and participation in adventure and extreme sports warrants understanding by clinicians to facilitate prevention, identification, and treatment of injuries unique to each sport. This article covers alpine skiing and snowboarding, skateboarding, surfing, bungee jumping, BASE jumping, and whitewater sports with emphasis on epidemiology, demographics, general injury mechanisms, specific injuries, chronic injuries, fatality data, and prevention. Overall, most injuries are related to overuse, trauma, and environmental or microbial exposure.

  4. Extremal graph theory

    CERN Document Server

    Bollobas, Bela

    2004-01-01

    The ever-expanding field of extremal graph theory encompasses a diverse array of problem-solving methods, including applications to economics, computer science, and optimization theory. This volume, based on a series of lectures delivered to graduate students at the University of Cambridge, presents a concise yet comprehensive treatment of extremal graph theory.Unlike most graph theory treatises, this text features complete proofs for almost all of its results. Further insights into theory are provided by the numerous exercises of varying degrees of difficulty that accompany each chapter. A

  5. Photochemical escape of oxygen from the Martian atmosphere: new insights from MAVEN

    Science.gov (United States)

    Lillis, R. J.; Deighan, J.; Bougher, S. W.; Cravens, T.; Fox, J. L.; Lee, Y.; Rahmati, A.; McFadden, J. P.; Benna, M.; Mahaffy, P. R.; Elrod, M. K.; Andersson, L.; Fowler, C. M.; Curry, S.; Gröller, H.; Jakosky, B. M.

    2015-12-01

    One of the primary goals of the MAVEN mission is to characterize rates of atmospheric escape from Mars at the present epoch and relate those escape rates to solar drivers. One of the known escape processes is photochemical escape, where a) an exothermic chemical reaction in the atmosphere results in an upward-traveling neutral particle whose velocity exceeds planetary escape velocity and b) the particle is not prevented from escaping through any subsequent collisions. Because escaping hot atoms are not directly measured, models of production and transport (through the atmosphere) of such atoms must be used to constrain photochemical escape rates. These models require altitude profiles of neutral densities and electron and ion densities and temperatures, as well as compositional information, all of which are measured by MAVEN instruments at the relevant altitudes (150-300 km). For every altitude profile: Profiles of O2+ dissociative recombination (DR) rates will be calculated from electron temperature, electron density and O2+ density. Profiles of energy distributions of hot O atoms will be calculated from profiles of electron and ion temperatures. Profiles of all neutral densities will be input into models of hot O transport in order to calculate photochemical escape fluxes from DR of O2+. We will present photochemical escape fluxes as a function of several factors, in particular solar zenith angle and EUV flux. This, combined with further simulations with progressively higher EUV fluxes, will eventually enable a total integrated loss estimate over the course of Martian history and hence a determination of the impact of this loss process on the evolution of the Martian climate.

  6. Extremity perfusion for sarcoma

    NARCIS (Netherlands)

    Hoekstra, Harald Joan

    2008-01-01

    For more than 50 years, the technique of extremity perfusion has been explored in the limb salvage treatment of local, recurrent, and multifocal sarcomas. The "discovery" of tumor necrosis factor-or. in combination with melphalan was a real breakthrough in the treatment of primarily irresectable ext

  7. Hydrological extremes and security

    Science.gov (United States)

    Kundzewicz, Z. W.; Matczak, P.

    2015-04-01

    Economic losses caused by hydrological extremes - floods and droughts - have been on the rise. Hydrological extremes jeopardize human security and impact on societal livelihood and welfare. Security can be generally understood as freedom from threat and the ability of societies to maintain their independent identity and their functional integrity against forces of change. Several dimensions of security are reviewed in the context of hydrological extremes. The traditional interpretation of security, focused on the state military capabilities, has been replaced by a wider understanding, including economic, societal and environmental aspects that get increasing attention. Floods and droughts pose a burden and serious challenges to the state that is responsible for sustaining economic development, and societal and environmental security. The latter can be regarded as the maintenance of ecosystem services, on which a society depends. An important part of it is water security, which can be defined as the availability of an adequate quantity and quality of water for health, livelihoods, ecosystems and production, coupled with an acceptable level of water-related risks to people, environments and economies. Security concerns arise because, over large areas, hydrological extremes - floods and droughts - are becoming more frequent and more severe. In terms of dealing with water-related risks, climate change can increase uncertainties, which makes the state's task to deliver security more difficult and more expensive. However, changes in population size and development, and level of protection, drive exposure to hydrological hazards.

  8. Acute lower extremity ischaemia

    African Journals Online (AJOL)

    tend to impact at arterial bifurcations, the commonest site being the ... Other ominous signs of advanced ischaemia include bluish ... Recommended standards for lower extremity ischaemia*. Doppler signals ... of the embolectomy procedure. An ... in a cath-lab or angio-suite under local ... We serially measure the aPTT and.

  9. Extremity perfusion for sarcoma

    NARCIS (Netherlands)

    Hoekstra, Harald Joan

    2008-01-01

    For more than 50 years, the technique of extremity perfusion has been explored in the limb salvage treatment of local, recurrent, and multifocal sarcomas. The "discovery" of tumor necrosis factor-or. in combination with melphalan was a real breakthrough in the treatment of primarily irresectable

  10. Statistics of Local Extremes

    DEFF Research Database (Denmark)

    Larsen, Gunner Chr.; Bierbooms, W.; Hansen, Kurt Schaldemose

    2003-01-01

    . A theoretical expression for the probability density function associated with local extremes of a stochasticprocess is presented. The expression is basically based on the lower four statistical moments and a bandwidth parameter. The theoretical expression is subsequently verified by comparison with simulated...

  11. de Sitter Extremal Surfaces

    CERN Document Server

    Narayan, K

    2015-01-01

    We study extremal surfaces in de Sitter space in the Poincare slicing in the upper patch, anchored on spatial subregions at the future boundary ${\\cal I}^+$, restricted to constant boundary Euclidean time slices (focussing on strip subregions). We find real extremal surfaces of minimal area as the boundaries of past lightcone wedges of the subregions in question: these are null surfaces with vanishing area. We find also complex extremal surfaces as complex extrema of the area functional, and the area is not always real-valued. In $dS_4$ the area is real and has some structural resemblance with entanglement entropy in a dual $CFT_3$. There are parallels with analytic continuation from the Ryu-Takayanagi expressions for holographic entanglement entropy in $AdS$. We also discuss extremal surfaces in the $dS$ black brane and the de Sitter "bluewall" studied previously. The $dS_4$ black brane complex surfaces exhibit a real finite cutoff-independent extensive piece. In the bluewall geometry, there are real surface...

  12. Moving in extreme environments

    DEFF Research Database (Denmark)

    Lucas, Samuel J E; Helge, Jørn W; Schütz, Uwe H W

    2016-01-01

    and transcontinental races) and expeditions (e.g. polar crossings), to the more gravitationally limited load carriage (e.g. in the military context). Juxtaposed to these circumstances is the extreme metabolic and mechanical unloading associated with space travel, prolonged bedrest and sedentary lifestyle, which may...

  13. Complex Economies Have a Lateral Escape from the Poverty Trap

    Science.gov (United States)

    Pugliese, Emanuele; Chiarotti, Guido L.; Zaccaria, Andrea; Pietronero, Luciano

    2017-01-01

    We analyze the decisive role played by the complexity of economic systems at the onset of the industrialization process of countries over the past 50 years. Our analysis of the input growth dynamics, considering a further dimension through a recently introduced measure of economic complexity, reveals that more differentiated and more complex economies face a lower barrier (in terms of GDP per capita) when starting the transition towards industrialization. As a consequence, we can extend the classical concept of a one-dimensional poverty trap, by introducing a two-dimensional poverty trap: a country will start the industrialization process if it is rich enough (as in neo-classical economic theories), complex enough (using this new dimension and laterally escaping from the poverty trap), or a linear combination of the two. This naturally leads to the proposal of a Complex Index of Relative Development (CIRD) which shows, when analyzed as a function of the growth due to input, a shape of an upside down parabola similar to that expected from the standard economic theories when considering only the GDP per capita dimension. PMID:28072867

  14. Nosema Tolerant Honeybees (Apis mellifera) Escape Parasitic Manipulation of Apoptosis

    Science.gov (United States)

    Kurze, Christoph; Le Conte, Yves; Dussaubat, Claudia; Erler, Silvio; Kryger, Per; Lewkowski, Oleg; Müller, Thomas; Widder, Miriam; Moritz, Robin F. A.

    2015-01-01

    Apoptosis is not only pivotal for development, but also for pathogen defence in multicellular organisms. Although numerous intracellular pathogens are known to interfere with the host’s apoptotic machinery to overcome this defence, its importance for host-parasite coevolution has been neglected. We conducted three inoculation experiments to investigate in the apoptotic respond during infection with the intracellular gut pathogen Nosema ceranae, which is considered as potential global threat to the honeybee (Apis mellifera) and other bee pollinators, in sensitive and tolerant honeybees. To explore apoptotic processes in the gut epithelium, we visualised apoptotic cells using TUNEL assays and measured the relative expression levels of subset of candidate genes involved in the apoptotic machinery using qPCR. Our results suggest that N. ceranae reduces apoptosis in sensitive honeybees by enhancing inhibitor of apoptosis protein-(iap)-2 gene transcription. Interestingly, this seems not be the case in Nosema tolerant honeybees. We propose that these tolerant honeybees are able to escape the manipulation of apoptosis by N. ceranae, which may have evolved a mechanism to regulate an anti-apoptotic gene as key adaptation for improved host invasion. PMID:26445372

  15. Nosema Tolerant Honeybees (Apis mellifera Escape Parasitic Manipulation of Apoptosis.

    Directory of Open Access Journals (Sweden)

    Christoph Kurze

    Full Text Available Apoptosis is not only pivotal for development, but also for pathogen defence in multicellular organisms. Although numerous intracellular pathogens are known to interfere with the host's apoptotic machinery to overcome this defence, its importance for host-parasite coevolution has been neglected. We conducted three inoculation experiments to investigate in the apoptotic respond during infection with the intracellular gut pathogen Nosema ceranae, which is considered as potential global threat to the honeybee (Apis mellifera and other bee pollinators, in sensitive and tolerant honeybees. To explore apoptotic processes in the gut epithelium, we visualised apoptotic cells using TUNEL assays and measured the relative expression levels of subset of candidate genes involved in the apoptotic machinery using qPCR. Our results suggest that N. ceranae reduces apoptosis in sensitive honeybees by enhancing inhibitor of apoptosis protein-(iap-2 gene transcription. Interestingly, this seems not be the case in Nosema tolerant honeybees. We propose that these tolerant honeybees are able to escape the manipulation of apoptosis by N. ceranae, which may have evolved a mechanism to regulate an anti-apoptotic gene as key adaptation for improved host invasion.

  16. Complex Economies Have a Lateral Escape from the Poverty Trap.

    Science.gov (United States)

    Pugliese, Emanuele; Chiarotti, Guido L; Zaccaria, Andrea; Pietronero, Luciano

    2017-01-01

    We analyze the decisive role played by the complexity of economic systems at the onset of the industrialization process of countries over the past 50 years. Our analysis of the input growth dynamics, considering a further dimension through a recently introduced measure of economic complexity, reveals that more differentiated and more complex economies face a lower barrier (in terms of GDP per capita) when starting the transition towards industrialization. As a consequence, we can extend the classical concept of a one-dimensional poverty trap, by introducing a two-dimensional poverty trap: a country will start the industrialization process if it is rich enough (as in neo-classical economic theories), complex enough (using this new dimension and laterally escaping from the poverty trap), or a linear combination of the two. This naturally leads to the proposal of a Complex Index of Relative Development (CIRD) which shows, when analyzed as a function of the growth due to input, a shape of an upside down parabola similar to that expected from the standard economic theories when considering only the GDP per capita dimension.

  17. Epoxyeicosanoids stimulate multiorgan metastasis and tumor dormancy escape in mice

    Science.gov (United States)

    Panigrahy, Dipak; Edin, Matthew L.; Lee, Craig R.; Huang, Sui; Bielenberg, Diane R.; Butterfield, Catherine E.; Barnés, Carmen M.; Mammoto, Akiko; Mammoto, Tadanori; Luria, Ayala; Benny, Ofra; Chaponis, Deviney M.; Dudley, Andrew C.; Greene, Emily R.; Vergilio, Jo-Anne; Pietramaggiori, Giorgio; Scherer-Pietramaggiori, Sandra S.; Short, Sarah M.; Seth, Meetu; Lih, Fred B.; Tomer, Kenneth B.; Yang, Jun; Schwendener, Reto A.; Hammock, Bruce D.; Falck, John R.; Manthati, Vijaya L.; Ingber, Donald E.; Kaipainen, Arja; D’Amore, Patricia A.; Kieran, Mark W.; Zeldin, Darryl C.

    2011-01-01

    Epoxyeicosatrienoic acids (EETs) are small molecules produced by cytochrome P450 epoxygenases. They are lipid mediators that act as autocrine or paracrine factors to regulate inflammation and vascular tone. As a result, drugs that raise EET levels are in clinical trials for the treatment of hypertension and many other diseases. However, despite their pleiotropic effects on cells, little is known about the role of these epoxyeicosanoids in cancer. Here, using genetic and pharmacological manipulation of endogenous EET levels, we demonstrate that EETs are critical for primary tumor growth and metastasis in a variety of mouse models of cancer. Remarkably, we found that EETs stimulated extensive multiorgan metastasis and escape from tumor dormancy in several tumor models. This systemic metastasis was not caused by excessive primary tumor growth but depended on endothelium-derived EETs at the site of metastasis. Administration of synthetic EETs recapitulated these results, while EET antagonists suppressed tumor growth and metastasis, demonstrating in vivo that pharmacological modulation of EETs can affect cancer growth. Furthermore, inhibitors of soluble epoxide hydrolase (sEH), the enzyme that metabolizes EETs, elevated endogenous EET levels and promoted primary tumor growth and metastasis. Thus, our data indicate a central role for EETs in tumorigenesis, offering a mechanistic link between lipid signaling and cancer and emphasizing the critical importance of considering possible effects of EET-modulating drugs on cancer. PMID:22182838

  18. Intertextuality in Novel: An Escape from Patriarchal Soliloquy

    Directory of Open Access Journals (Sweden)

    Nargess Bagheri

    2015-12-01

    Full Text Available Hypertextuality is one of the intertextual relationships introduced by Gerard Genette. According to him, hypertextuality includes all the relationships which the hypertext has with the previous text, i.e. the hypotext. However, he does not consider the relationship between these two texts to be in such a way that the hypertext is the interpretation of the hypotext. On the other hand, other theorizers including Bakhtin, regard the conversation between texts a way to escape a one-voiced and dominant discourse. From this viewpoint, the intertextual relationships of Sadegh Hedayat’s The Blind Owl, with Shahrnoush Parsipour’s The Blue Mind and Abbas Maroufi’s The Body of Farhad are in such a way that The Blind Owl can be regarded as a hypotext for the other 2 novels but these two novels interpret the text differently. The present study aims to examine the intertextual relationships between these 3 novels and explore how a multiple-voiced conversation is formed between them.

  19. Modified guidance laws to escape microbursts with turbulence

    Directory of Open Access Journals (Sweden)

    Atilla Dogan

    2002-01-01

    Full Text Available This paper introduces Modified Altitude- and Dive-Guidance laws for escaping a microburst with turbulence. The goal is to develop a procedure to estimate the highest altitude at which an aircraft can fly through a microburst without running into stall. First, a new metric is constructed that quantifies the aircraft upward force capability in a microburst encounter. In the absence of turbulence, the metric is shown to be a decreasing function of altitude. This suggests that descending to a low altitude may improve safety in the sense that the aircraft will have more upward force capability to maintain its altitude. In the presence of stochastic turbulence, the metric is treated as a random variable and its probability distribution function is analytically approximated as a function of altitude. This approximation allows us to determine the highest safe altitude at which the aircraft may descend, hence avoiding to descend too low. This highest safe altitude is used as the commanded altitude in Modified Altitude- and Dive-Guidance. Monte Carlo simulations show that these Modified Altitude- and Dive-Guidance strategies can decrease the probability of minimum altitude being lower than a given value without significantly increasing the probability of crash.

  20. Breakdown of the escape dynamics in Josephson junctions

    Science.gov (United States)

    Massarotti, D.; Stornaiuolo, D.; Lucignano, P.; Galletti, L.; Born, D.; Rotoli, G.; Lombardi, F.; Longobardi, L.; Tagliacozzo, A.; Tafuri, F.

    2015-08-01

    We have identified anomalous behavior of the escape rate out of the zero-voltage state in Josephson junctions with a high critical current density Jc. For this study we have employed YBa2Cu3O7 -x grain boundary junctions, which span a wide range of Jc and have appropriate electrodynamical parameters. Such high Jc junctions, when hysteretic, do not switch from the superconducting to the normal state following the expected stochastic Josephson distribution, despite having standard Josephson properties such as a Fraunhofer magnetic field pattern. The switching current distributions (SCDs) are consistent with nonequilibrium dynamics taking place on a local rather than a global scale. This means that macroscopic quantum phenomena seem to be practically unattainable for high Jc junctions. We argue that SCDs are an accurate means to measure nonequilibrium effects. This transition from global to local dynamics is of relevance for all kinds of weak links, including the emergent family of nanohybrid Josephson junctions. Therefore caution should be applied in the use of such junctions in, for instance, the search for Majorana fermions.

  1. XUV-exposed, non-hydrostatic hydrogen-rich upper atmospheres of terrestrial planets. Part I: atmospheric expansion and thermal escape.

    Science.gov (United States)

    Erkaev, Nikolai V; Lammer, Helmut; Odert, Petra; Kulikov, Yuri N; Kislyakova, Kristina G; Khodachenko, Maxim L; Güdel, Manuel; Hanslmeier, Arnold; Biernat, Helfried

    2013-11-01

    The recently discovered low-density "super-Earths" Kepler-11b, Kepler-11f, Kepler-11d, Kepler-11e, and planets such as GJ 1214b represent the most likely known planets that are surrounded by dense H/He envelopes or contain deep H₂O oceans also surrounded by dense hydrogen envelopes. Although these super-Earths are orbiting relatively close to their host stars, they have not lost their captured nebula-based hydrogen-rich or degassed volatile-rich steam protoatmospheres. Thus, it is interesting to estimate the maximum possible amount of atmospheric hydrogen loss from a terrestrial planet orbiting within the habitable zone of late main sequence host stars. For studying the thermosphere structure and escape, we apply a 1-D hydrodynamic upper atmosphere model that solves the equations of mass, momentum, and energy conservation for a planet with the mass and size of Earth and for a super-Earth with a size of 2 R(Earth) and a mass of 10 M(Earth). We calculate volume heating rates by the stellar soft X-ray and extreme ultraviolet radiation (XUV) and expansion of the upper atmosphere, its temperature, density, and velocity structure and related thermal escape rates during the planet's lifetime. Moreover, we investigate under which conditions both planets enter the blow-off escape regime and may therefore experience loss rates that are close to the energy-limited escape. Finally, we discuss the results in the context of atmospheric evolution and implications for habitability of terrestrial planets in general.

  2. Escape from neutralization by the respiratory syncytial virus-specific neutralizing monoclonal antibody palivizumab is driven by changes in on-rate of binding to the fusion protein

    Energy Technology Data Exchange (ETDEWEB)

    Bates, John T. [The Vanderbilt Vaccine Center, Departments of Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN (United States); Keefer, Christopher J. [The Vanderbilt Vaccine Center, Departments of Pediatrics, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN (United States); Slaughter, James C. [The Vanderbilt Vaccine Center, Departments of Biostatistics and Pathology, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN (United States); Kulp, Daniel W. [IAVI Neutralizing Antibody Center and Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA (United States); Schief, William R. [IAVI Neutralizing Antibody Center and Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA (United States); Center for HIV/AIDS Vaccine Immunology and Immunogen Discovery, The Scripps Research Institute, La Jolla, CA (United States); Crowe, James E., E-mail: james.crowe@vanderbilt.edu [The Vanderbilt Vaccine Center, Departments of Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN (United States); The Vanderbilt Vaccine Center, Departments of Pediatrics, Microbiology, and Immunology, Vanderbilt University Medical Center, Nashville, TN (United States)

    2014-04-15

    The role of binding kinetics in determining neutralizing potency for antiviral antibodies is poorly understood. While it is believed that increased steady-state affinity correlates positively with increased virus-neutralizing activity, the relationship between association or dissociation rate and neutralization potency is unclear. We investigated the effect of naturally-occurring antibody resistance mutations in the RSV F protein on the kinetics of binding to palivizumab. Escape from palivizumab-mediated neutralization of RSV occurred with reduced association rate (K{sub on}) for binding to RSV F protein, while alteration of dissociation rate (K{sub off}) did not significantly affect neutralizing activity. Interestingly, linkage of reduced K{sub on} with reduced potency mirrored the effect of increased K{sub on} found in a high-affinity enhanced potency palivizumab variant (motavizumab). These data suggest that association rate is the dominant factor driving neutralization potency for antibodies to RSV F protein antigenic site A and determines the potency of antibody somatic variants or efficiency of escape of viral glycoprotein variants. - Highlights: • The relationship of affinity to neutralization for virus antibodies is uncertain. • Palivizumab binds to RSV escape mutant fusion proteins, but with reduced affinity. • Association rate (K{sub on}) correlated well with the potency of neutralization.

  3. Reporter Assay for Endo/Lysosomal Escape of Toxin-Based Therapeutics

    Directory of Open Access Journals (Sweden)

    Roger Gilabert-Oriol

    2014-05-01

    Full Text Available Protein-based therapeutics with cytosolic targets are capable of exhibiting their therapeutic effect once they have escaped from the endosomes or lysosomes. In this study, the reporters—horseradish peroxidase (HRP, Alexa Fluor 488 (Alexa and ricin A-chain (RTA—were investigated for their capacity to monitor the endo/lysosomal escape of the ribosome-inactivating protein, saporin. The conjugates—saporin-HRP, Alexasaporin and saporin-KQ-RTA—were constructed, and the endo/lysosomal escape of these conjugates alone (lack of endo/lysosomal release or in combination with certain structurally-specific triterpenoidal saponins (efficient endo/lysosomal escape was characterized. HRP failed in reporting the endo/lysosomal escape of saporin. Contrastingly, Alexa Fluor 488 successfully allowed the report of the process at a toxin concentration of 1000 nM. In addition, single endo/lysosome analysis facilitated the determination of the amount of Alexasaporin released from each vesicle. RTA was also successful in reporting the endo/lysosomal escape of the enzymatically inactive mutant, saporin-KQ, but in this case, the sensitivity of the method reached a toxin concentration of 10 nM. In conclusion, the simultaneous usage of Alexa Fluor 488 and RTA as reporters may provide the possibility of monitoring the endo/lysosomal escape of protein-based therapeutics in the concentration range of 10–1000 nM.

  4. Heterochrony and the development of the escape response: prehatching movements in the rainbow trout Oncorhynchus mykiss.

    Science.gov (United States)

    Gibb, Alice C; Liu, Corina; Swanson, Brook O

    2007-10-01

    Teleost fishes produce coordinated escape responses (C-starts) at hatching. This implies that essential swimming morphologies and motor behaviors develop during the incubation interval while the embryo is in the chorion. We examined prehatching motor behaviors in rainbow trout Oncorhycus mykiss (considered morphologically mature at hatching) and compared this species with zebrafish Danio rerio (considered morphologically immature) and assessed two hypotheses concerning the development of escape behavior. (1) Escape behavior is associated with the formation of key elements of the musculoskeletal and nervous systems; thus, the escape response appears early in ontogeny, when these elements form. (2) Escape behavior is not directly associated with the formation of underlying morphological elements; instead, it appears at hatching (i.e. when needed). We find that rainbow trout, like zebrafish, respond to touch early in the incubation interval, but do not demonstrate a complete C-start (including the second, propulsive stage) until shortly before hatching. At hatching, rainbow trout and zebrafish are similar in the degree of development of the chondocranium, paired fins and visceral arches (which comprise the larval jaw and gill support); however, rainbow trout have incipient rays in their unpaired fins (dorsal, anal and caudal), whereas zebrafish retain the embryonic fin fold. Although rainbow trout are more mature in axial swimming morphology at hatching, the essential neural and musculoskeletal systems that produce a coordinated escape response are functional at hatching in both species. This finding supports the evolutionary hypothesis that an effective escape response is critical for the survival of newly hatched teleost fishes.

  5. Failure of rats to escape from a potentially lethal microwave field

    Energy Technology Data Exchange (ETDEWEB)

    Carroll, D.R.; Levinson, D.M.; Justesen, D.R.; Clarke, R.L.

    1980-01-01

    Ocularly pigmented rats, all mature females of the Long-Evans strain, were repeatedly presented an opportunity to escape from an intense 918-MHz field (whole-body dose rate . 60 mW/g) to a field of lower intensity (40, 30, 20, or 2 mW/g) by performing a simple locomotor response. Other rats could escape 800-microamperemeter faradic shock to the feet and tail by performing the same response in the same milieu, a multimode cavity. None of 20 irradiated rats learned to associate entry into a visually well-demarcated area of the cavity with immediate reduction of dose rate, in spite of field-induced elevations of body temperature to levels that exceeded 41 degrees C and would have been lethal but for a limit on durations of irradiation. In contrast, all of ten rats motivated by faradic shock rapidly learned to escape. The failure of escape learning by irradiated animals probably arose from deficiencies of motivation and, especially, sensory feedback. Whole-body hyperthermia induced by a multipath field may lack the painful or directional sensory properties that optimally promote the motive to escape. Moreover, a decline of body temperature after an escape-response-contingent reduction of field strength will be relatively slow because of the large thermal time constants of mammalian tissues. Without timely sensory feedback, which is an essential element of negative reinforcement, stimulus-response associability would be imparied, which could retard or preclude learning of an escape response.

  6. Reporter assay for endo/lysosomal escape of toxin-based therapeutics.

    Science.gov (United States)

    Gilabert-Oriol, Roger; Thakur, Mayank; von Mallinckrodt, Benedicta; Bhargava, Cheenu; Wiesner, Burkhard; Eichhorst, Jenny; Melzig, Matthias F; Fuchs, Hendrik; Weng, Alexander

    2014-05-22

    Protein-based therapeutics with cytosolic targets are capable of exhibiting their therapeutic effect once they have escaped from the endosomes or lysosomes. In this study, the reporters-horseradish peroxidase (HRP), Alexa Fluor 488 (Alexa) and ricin A-chain (RTA)-were investigated for their capacity to monitor the endo/lysosomal escape of the ribosome-inactivating protein, saporin. The conjugates-saporin-HRP, (Alexa)saporin and saporin-KQ-RTA-were constructed, and the endo/lysosomal escape of these conjugates alone (lack of endo/lysosomal release) or in combination with certain structurally-specific triterpenoidal saponins (efficient endo/lysosomal escape) was characterized. HRP failed in reporting the endo/lysosomal escape of saporin. Contrastingly, Alexa Fluor 488 successfully allowed the report of the process at a toxin concentration of 1000 nM. In addition, single endo/lysosome analysis facilitated the determination of the amount of (Alexa)saporin released from each vesicle. RTA was also successful in reporting the endo/lysosomal escape of the enzymatically inactive mutant, saporin-KQ, but in this case, the sensitivity of the method reached a toxin concentration of 10 nM. In conclusion, the simultaneous usage of Alexa Fluor 488 and RTA as reporters may provide the possibility of monitoring the endo/lysosomal escape of protein-based therapeutics in the concentration range of 10-1000 nM.

  7. H Escape Rates Inferred from MAVEN/IUVS Observations of the Mars Hydrogen Corona

    Science.gov (United States)

    Chaffin, Michael S.; Chaufray, Jean-Yves; Deighan, Justin; Schneider, Nicholas M.; McClintock, William; Stewart, A. Ian F.; Thiemann, E. M.; Clarke, John T.; Holsclaw, Gregory; Jain, Sonal Kumar; Crismani, Matteo; Stiepen, Arnaud; Montmessin, Franck; Eparvier, Francis; Jakosky, Bruce

    2016-10-01

    H escape oxidizes and dessicates the Mars atmosphere and surface, providing a key control on the present-day chemistry and long-term evolution of the planet. Recently, large variations in the escape rate of H as a function of season have been reported by several studies, making continued observation of the variation a high priority. We present escape rates derived from Mars Atmosphere and Volatile EvolutioN (MAVEN) mission Imaging UltraViolet Spectrograph (IUVS) observations of the extended atmosphere of Mars at H Lyman alpha (121.6 nm), which must be interpreted with a coupled density/radiative transfer model owing to the optically thick nature of the emission and the small fraction of H present in the corona on escaping trajectories. We recover densities, temperatures, and escape rates under the assumption of spherical symmetry for multiple periods across MAVEN's mission so far, beginning in December 2014 (escape rates ~4e8/cm2/s). We describe the observed variation and compare it with previously observed seasonal variation in retrieved H escape rates, providing a necessary input for future photochemical modeling studies and estimates of water loss from Mars over its history.

  8. Do malaria parasites manipulate the escape behaviour of their avian hosts? An experimental study.

    Science.gov (United States)

    Garcia-Longoria, Luz; Møller, Anders P; Balbontín, Javier; de Lope, Florentino; Marzal, Alfonso

    2015-12-01

    Escape behaviour is the behaviour that birds and other animals display when already caught by a predator. An individual exhibiting higher intensity of such anti-predator behaviour could have greater probabilities of escape from predators. Parasites are known to affect different aspects of host behaviour to increase their own fitness. Vector-transmitted parasites such as malaria parasites should gain by manipulating their hosts to enhance the probability of transmission. Several studies have shown that malaria parasites can manipulate their vectors leading to increased transmission success. However, little is known about whether malaria parasites can manipulate escape behaviour of their avian hosts thereby increasing the spread of the parasite. Here we used an experimental approach to explore if Plasmodium relictum can manipulate the escape behaviour of one of its most common avian hosts, the house sparrow Passer domesticus. We experimentally tested whether malaria parasites manipulate the escape behaviour of their avian host. We showed a decrease in the intensity of biting and tonic immobility after removal of infection with anti-malaria medication compared to pre-experimental behaviour. These outcomes suggest that infected sparrows performed more intense escape behaviour, which would increase the likelihood of individuals escaping from predators, but also benefit the parasite by increasing its transmission opportunities.

  9. Arctic sea ice, Eurasia snow, and extreme winter haze in China

    Science.gov (United States)

    Zou, Yufei; Wang, Yuhang; Zhang, Yuzhong; Koo, Ja-Ho

    2017-01-01

    The East China Plains (ECP) region experienced the worst haze pollution on record for January in 2013. We show that the unprecedented haze event is due to the extremely poor ventilation conditions, which had not been seen in the preceding three decades. Statistical analysis suggests that the extremely poor ventilation conditions are linked to Arctic sea ice loss in the preceding autumn and extensive boreal snowfall in the earlier winter. We identify the regional circulation mode that leads to extremely poor ventilation over the ECP region. Climate model simulations indicate that boreal cryospheric forcing enhances the regional circulation mode of poor ventilation in the ECP region and provides conducive conditions for extreme haze such as that of 2013. Consequently, extreme haze events in winter will likely occur at a higher frequency in China as a result of the changing boreal cryosphere, posing difficult challenges for winter haze mitigation but providing a strong incentive for greenhouse gas emission reduction. PMID:28345056

  10. Arctic sea ice, Eurasia snow, and extreme winter haze in China.

    Science.gov (United States)

    Zou, Yufei; Wang, Yuhang; Zhang, Yuzhong; Koo, Ja-Ho

    2017-03-01

    The East China Plains (ECP) region experienced the worst haze pollution on record for January in 2013. We show that the unprecedented haze event is due to the extremely poor ventilation conditions, which had not been seen in the preceding three decades. Statistical analysis suggests that the extremely poor ventilation conditions are linked to Arctic sea ice loss in the preceding autumn and extensive boreal snowfall in the earlier winter. We identify the regional circulation mode that leads to extremely poor ventilation over the ECP region. Climate model simulations indicate that boreal cryospheric forcing enhances the regional circulation mode of poor ventilation in the ECP region and provides conducive conditions for extreme haze such as that of 2013. Consequently, extreme haze events in winter will likely occur at a higher frequency in China as a result of the changing boreal cryosphere, posing difficult challenges for winter haze mitigation but providing a strong incentive for greenhouse gas emission reduction.

  11. The impact of escaped farmed Atlantic salmon (Salmo salar L. on catch statistics in Scotland.

    Directory of Open Access Journals (Sweden)

    Darren M Green

    Full Text Available In Scotland and elsewhere, there are concerns that escaped farmed Atlantic salmon (Salmo salar L. may impact on wild salmon stocks. Potential detrimental effects could arise through disease spread, competition, or inter-breeding. We investigated whether there is evidence of a direct effect of recorded salmon escape events on wild stocks in Scotland using anglers' counts of caught salmon (classified as wild or farmed and sea trout (Salmo trutta L.. This tests specifically whether documented escape events can be associated with reduced or elevated escapes detected in the catch over a five-year time window, after accounting for overall variation between areas and years. Alternate model frameworks were somewhat inconsistent, however no robust association was found between documented escape events and higher proportion of farm-origin salmon in anglers' catch, nor with overall catch size. A weak positive correlation was found between local escapes and subsequent sea trout catch. This is in the opposite direction to what would be expected if salmon escapes negatively affected wild fish numbers. Our approach specifically investigated documented escape events, contrasting with earlier studies examining potentially wider effects of salmon farming on wild catch size. This approach is more conservative, but alleviates some potential sources of confounding, which are always of concern in observational studies. Successful analysis of anglers' reports of escaped farmed salmon requires high data quality, particularly since reports of farmed salmon are a relatively rare event in the Scottish data. Therefore, as part of our analysis, we reviewed studies of potential sensitivity and specificity of determination of farmed origin. Specificity estimates are generally high in the literature, making an analysis of the form we have performed feasible.

  12. Quantifying the impact of human immunodeficiency virus-1 escape from cytotoxic T-lymphocytes.

    Directory of Open Access Journals (Sweden)

    Ulrich D Kadolsky

    Full Text Available HIV-1 escape from the cytotoxic T-lymphocyte (CTL response leads to a weakening of viral control and is likely to be detrimental to the patient. To date, the impact of escape on viral load and CD4(+ T cell count has not been quantified, primarily because of sparse longitudinal data and the difficulty of separating cause and effect in cross-sectional studies. We use two independent methods to quantify the impact of HIV-1 escape from CTLs in chronic infection: mathematical modelling of escape and statistical analysis of a cross-sectional cohort. Mathematical modelling revealed a modest increase in log viral load of 0.051 copies ml(-1 per escape event. Analysis of the cross-sectional cohort revealed a significant positive association between viral load and the number of "escape events", after correcting for length of infection and rate of replication. We estimate that a single CTL escape event leads to a viral load increase of 0.11 log copies ml(-1 (95% confidence interval: 0.040-0.18, consistent with the predictions from the mathematical modelling. Overall, the number of escape events could only account for approximately 6% of the viral load variation in the cohort. Our findings indicate that although the loss of the CTL response for a single epitope results in a highly statistically significant increase in viral load, the biological impact is modest. We suggest that this small increase in viral load is explained by the small growth advantage of the variant relative to the wildtype virus. Escape from CTLs had a measurable, but unexpectedly low, impact on viral load in chronic infection.

  13. Escape forces and trajectories in optical tweezers and their effect on calibration.

    Science.gov (United States)

    Bui, Ann A M; Stilgoe, Alexander B; Khatibzadeh, Nima; Nieminen, Timo A; Berns, Michael W; Rubinsztein-Dunlop, Halina

    2015-09-21

    Whether or not an external force can make a trapped particle escape from optical tweezers can be used to measure optical forces. Combined with the linear dependence of optical forces on trapping power, a quantitative measurement of the force can be obtained. For this measurement, the particle is at the edge of the trap, away from the region near the equilbrium position where the trap can be described as a linear spring. This method provides the ability to measure higher forces for the same beam power, compared with using the linear region of the trap, with lower risk of optical damage to trapped specimens. Calibration is typically performed by using an increasing fluid flow to exert an increasing force on a trapped particle until it escapes. In this calibration technique, the particle is usually assumed to escape along a straight line in the direction of fluid-flow. Here, we show that the particle instead follows a curved trajectory, which depends on the rate of application of the force (i.e., the acceleration of the fluid flow). In the limit of very low acceleration, the particle follows the surface of zero axial optical force during the escape. The force required to produce escape depends on the trajectory, and hence the acceleration. This can result in variations in the escape force of a factor of two. This can have a major impact on calibration to determine the escape force efficiency. Even when calibration measurements are all performed in the low acceleration regime, variations in the escape force efficiency of 20% or more can still occur. We present computational simulations using generalized Lorenz-Mie theory and experimental measurements to show how the escape force efficiency depends on rate of increase of force and trapping power, and discuss the impact on calibration.

  14. Turning pain into cues for goal-directed behavior : Implementation intentions reduce escape-avoidance behavior on a painful task

    NARCIS (Netherlands)

    Karsdorp, P.A.; Geenen, R.; Kroese, F.M.; Vlaeyen, J.W.S.

    2016-01-01

    Pain automatically elicits escape-avoidance behavior to avert bodily harm. In patients with chronic pain, long-term escape-avoidance behavior may increase the risk of chronic disability. The aim of the presents study was to examine whether implementation intentions reduce escape-avoidance behavior d

  15. Non-extremal branes

    Directory of Open Access Journals (Sweden)

    Pablo Bueno

    2015-04-01

    Full Text Available We prove that for arbitrary black brane solutions of generic Supergravities there is an adapted system of variables in which the equations of motion are exactly invariant under electric–magnetic duality, i.e. the interchange of a given extended object by its electromagnetic dual. We obtain thus a procedure to automatically construct the electromagnetic dual of a given brane without needing to solve any further equation. We apply this procedure to construct the non-extremal (p,q-string of Type-IIB String Theory (new in the literature, explicitly showing how the dual (p,q-five-brane automatically arises in this construction. In addition, we prove that the system of variables used is suitable for a generic characterization of every double-extremal Supergravity brane solution, which we perform in full generality.

  16. Tibetans at extreme altitude.

    Science.gov (United States)

    Wu, Tianyi; Li, Shupin; Ward, Michal P

    2005-01-01

    Between 1960 and 2003, 13 Chinese expeditions successfully reached the summit of Chomolungma (Mt Everest or Sagarmatha). Forty-five of the 80 summiteers were Tibetan highlanders. During these and other high-altitude expeditions in Tibet, a series of medical and physiological investigations were carried out on the Tibetan mountaineers. The results suggest that these individuals are better adapted to high altitude and that, at altitude, they have a greater physical capacity than Han (ethnic Chinese) lowland newcomers. They have higher maximal oxygen uptake, greater ventilation, more brisk hypoxic ventilatory responses, larger lung volumes, greater diffusing capacities, and a better quality of sleep. Tibetans also have a lower incidence of acute mountain sickness and less body weight loss. These differences appear to represent genetic adaptations and are obviously significant for humans at extreme altitude. This paper reviews what is known about the physiologic responses of Tibetans at extreme altitudes.

  17. Extremal periodic wave profiles

    Directory of Open Access Journals (Sweden)

    E. van Groesen

    2007-01-01

    Full Text Available As a contribution to deterministic investigations into extreme fluid surface waves, in this paper wave profiles of prescribed period that have maximal crest height will be investigated. As constraints the values of the momentum and energy integrals are used in a simplified description with the KdV model. The result is that at the boundary of the feasible region in the momentum-energy plane, the only possible profiles are the well known cnoidal wave profiles. Inside the feasible region the extremal profiles of maximal crest height are "cornered" cnoidal profiles: cnoidal profiles of larger period, cut-off and periodically continued with the prescribed period so that at the maximal crest height a corner results.

  18. Extreme Photonics & Applications

    CERN Document Server

    Hall, Trevor J; Paredes, Sofia A

    2010-01-01

    "Extreme Photonics & Applications" arises from the 2008 NATO Advanced Study Institute in Laser Control & Monitoring in New Materials, Biomedicine, Environment, Security and Defense. Leading experts in the manipulation of light offered by recent advances in laser physics and nanoscience were invited to give lectures in their fields of expertise and participate in discussions on current research, applications and new directions. The sum of their contributions to this book is a primer for the state of scientific knowledge and the issues within the subject of photonics taken to the extreme frontiers: molding light at the ultra-finest scales, which represents the beginning of the end to limitations in optical science for the benefit of 21st Century technological societies. Laser light is an exquisite tool for physical and chemical research. Physicists have recently developed pulsed lasers with such short durations that one laser shot takes the time of one molecular vibration or one electron rotation in an ...

  19. Extremal Hairy Black Holes

    CERN Document Server

    Gonzalez, P A; Saavedra, Joel; Vasquez, Yerko

    2014-01-01

    We consider a gravitating system consisting of a scalar field minimally coupled to gravity with a self-interacting potential and an U(1) electromagnetic field. Solving the coupled Einstein-Maxwell-scalar system we find exact hairy charged black hole solutions with the scalar field regular everywhere. We go to the zero temperature limit and we study the effect of the scalar field on the near horizon geometry of an extremal black hole. We find that except a critical value of the charge of the black hole there is also a critical value of the charge of the scalar field beyond of which the extremal black hole is destabilized. We study the thermodynamics of these solutions and we find that if the space is flat then at low temperature the Reissner-Nordstr\\"om black hole is thermodynamically preferred, while if the space is AdS the hairy charged black hole is thermodynamically preferred at low temperature.

  20. Optimal search and ambush for a hider who can escape the search region

    OpenAIRE

    Alpern, Steve; Fokkink, Robbert; Simanjuntak, Martin

    2016-01-01

    Search games for a mobile or immobile hider traditionally have the hider permanently confined to a compact ‘search region’ making eventual capture inevitable. Hence the payoff can be taken as time until capture. However in many real life search problems it is possible for the hider to escape an area in which he was known to be located (e.g. Bin Laden from Tora Bora) or for a prey animal to escape a predator’s hunting territory. We model and solve such continuous time problems with escape wher...

  1. Mean Exit Time and Escape Probability for a Tumor Growth System under Non-Gaussian Noise

    CERN Document Server

    Ren, Jian; Gao, Ting; Kan, Xingye; Duan, Jinqiao

    2011-01-01

    Effects of non-Gaussian $\\alpha-$stable L\\'evy noise on the Gompertz tumor growth model are quantified by considering the mean exit time and escape probability of the cancer cell density from inside a safe or benign domain. The mean exit time and escape probability problems are formulated in a differential-integral equation with a fractional Laplacian operator. Numerical simulations are conducted to evaluate how the mean exit time and escape probability vary or bifurcates when $\\alpha$ changes. Some bifurcation phenomena are observed and their impacts are discussed.

  2. Religious Extremism in Pakistan

    Science.gov (United States)

    2014-12-01

    Face (July 2008): 32. 21 Ahmed Rashid , Pakistan on the Brink: The Future of America, Pakistan, and Afghanistan (New York: Viking, 2012). 22 Brian J...promoting extremism. Commentators such as Jessica Stern, Alan Richards, Hussain Haqqani, Ahmed Rashid , and Ali Riaz are a few of the scholars who...www.jstor.org/stable/3183558; See also Ahmed Rashid , Descent Into Chaos: The United States and the Failure of Nation Building in Pakistan, Afghanistan, and

  3. USACE Extreme Sea levels

    Science.gov (United States)

    2014-03-14

    report summarising the results of the research, together with a set of recommendations arising from the research. This report describes progress to...Southampton University at HR Wallingford and subsequent teleconference with Heidi Moritz and Kate White. The notes summarising the findings of the...suggestion was made that we may want to begin talking about extreme water levels separate from storms. Ivan mentioned an analysis of storminess which

  4. Extreme geomagnetically induced currents

    Science.gov (United States)

    Kataoka, Ryuho; Ngwira, Chigomezyo

    2016-12-01

    We propose an emergency alert framework for geomagnetically induced currents (GICs), based on the empirically extreme values and theoretical upper limits of the solar wind parameters and of d B/d t, the time derivative of magnetic field variations at ground. We expect this framework to be useful for preparing against extreme events. Our analysis is based on a review of various papers, including those presented during Extreme Space Weather Workshops held in Japan in 2011, 2012, 2013, and 2014. Large-amplitude d B/d t values are the major cause of hazards associated with three different types of GICs: (1) slow d B/d t with ring current evolution (RC-type), (2) fast d B/d t associated with auroral electrojet activity (AE-type), and (3) transient d B/d t of sudden commencements (SC-type). We set "caution," "warning," and "emergency" alert levels during the main phase of superstorms with the peak Dst index of less than -300 nT (once per 10 years), -600 nT (once per 60 years), or -900 nT (once per 100 years), respectively. The extreme d B/d t values of the AE-type GICs are 2000, 4000, and 6000 nT/min at caution, warning, and emergency levels, respectively. For the SC-type GICs, a "transient alert" is also proposed for d B/d t values of 40 nT/s at low latitudes and 110 nT/s at high latitudes, especially when the solar energetic particle flux is unusually high.

  5. Extremes in nature

    CERN Document Server

    Salvadori, Gianfausto; Kottegoda, Nathabandu T

    2007-01-01

    This book is about the theoretical and practical aspects of the statistics of Extreme Events in Nature. Most importantly, this is the first text in which Copulas are introduced and used in Geophysics. Several topics are fully original, and show how standard models and calculations can be improved by exploiting the opportunities offered by Copulas. In addition, new quantities useful for design and risk assessment are introduced.

  6. Extreme Gravitational Lensing near Rotating Black Holes

    CERN Document Server

    Beckwith, K; Beckwith, Kris; Done, Chris

    2004-01-01

    We describe a new approach to calculating photon trajectories and gravitational lensing effects in the strong gravitational field of the Kerr black hole. These techniques are applied to explore both the imaging and spectral properties of photons that perform multiple orbits of the central mass before escaping to infinity. Viewed at large inclinations, these higher order photons contribute $\\sim 20 %$ of the total luminosity of the system for a Schwarzschild hole, whilst for an extreme Kerr black hole this fraction rises to $\\sim 60 %$. In more realistic models these photons will be re-absorbed by the disc at large distances from the hole, but this returning radiation could provide a physical mechanism to resolve the discrepancy between the predicted and observed optical/UV colours in AGN. Conversely, at low inclinations, higher order images re-intercept the disc plane close to the black hole, so need not be absorbed by the disc if this is within the plunging region. These photons form a bright ring carrying a...

  7. Biological Extreme Events - Past, Present, and Future

    Science.gov (United States)

    Gutschick, V. P.

    2010-12-01

    Biological extreme events span wide ranges temporally and spatially and in type - population dieoffs, extinctions, ecological reorganizations, changes in biogeochemical fluxes, and more. Driving variables consist in meteorology, tectonics, orbital changes, anthropogenic changes (land-use change, species introductions, reactive N injection into the biosphere), and evolution (esp. of diseases). However, the mapping of extremes in the drivers onto biological extremes as organismal responses is complex, as laid out originally in the theoretical framework of Gutschick and BassiriRad (New Phytologist [2003] 100:21-42). Responses are nonlinear and dependent on (mostly unknown and) complex temporal sequences - often of multiple environmental variables. The responses are species- and genotype specific. I review extreme events over from past to present over wide temporal scales, while noting that they are not wholly informative of responses to the current and near-future drivers for at least two reasons: 1) the current combination of numerous environmental extremes - changes in CO2, temperature, precipitation, reactive N, land fragmentation, O3, etc. -is unprecedented in scope, and 2) adaptive genetic variation for organismal responses is constrained by poorly-characterized genetic structures (in organisms and populations) and by loss of genetic variation by genetic drift over long periods. We may expect radical reorganizations of ecosystem and biogeochemical functions. These changes include many ecosystem services in flood control, crop pollination and insect/disease control, C-water-mineral cycling, and more, as well as direct effects on human health. Predictions of such changes will necessarily be very weak in the critical next few decades, given the great deal of observation, experimentation, and theory construction that will be necessary, on both organisms and drivers. To make the research efforts most effective will require extensive, insightful planning, beginning

  8. Living with the extreme demand

    Directory of Open Access Journals (Sweden)

    Teppo Eskelinen

    2013-05-01

    Full Text Available Most of the ethical literature on extreme poverty suggests, that some, if not most, of the incomes of the residents of rich countries ought to be donated to the global poor. Yet complying with this ethical demand becomes increasingly more difficult as the changes in lifestyle in the (postindustrial north demand ever more consumption in order to obtain the necessities for survival in such societies. In this article, I will discuss Peter Singer's famous arguments for the ethical duty to donate one's possessions, and elaborate the conception of needs prevalent in both Singer's theory and the theories of many of his critics. My argument is that we have to recognise a category of needs called 'social necessities' that are neither luxuries nor basic needs. This leads to two main conclusions: first, the space for ethical deliberation on whether to donate to life-saving purposes is socially conditioned; and second, ethical strategies of redistribution ought to be accompanied with institutional changes, which also concern the conditions in wealthy countries.http://dx.doi.org/10.5324/eip.v7i1.1791

  9. Evaluation of a program of systematic instructional procedures for extremely poor retarded children.

    Science.gov (United States)

    Haring, N G; Krug, D A

    1975-05-01

    A demonstration program was conducted in which 54 innercity children classified as educable mentally retarded were selected on the basis of age, IQ, family income, race, and achievement scores. They were then placed into self-contained classrooms with two classes being taught by precision-teaching procedures and two classes being taught by the methods particular to their teachers. Tesults showed that a high percentage (60 percent) of the children taught by precision-teaching procedured were capable of acquiring the basic skills necessary for regular-class placement.

  10. Mitochondrial DNA that escapes from autophagy causes inflammation and heart failure.

    Science.gov (United States)

    Oka, Takafumi; Hikoso, Shungo; Yamaguchi, Osamu; Taneike, Manabu; Takeda, Toshihiro; Tamai, Takahito; Oyabu, Jota; Murakawa, Tomokazu; Nakayama, Hiroyuki; Nishida, Kazuhiko; Akira, Shizuo; Yamamoto, Akitsugu; Komuro, Issei; Otsu, Kinya

    2012-05-10

    Heart failure is a leading cause of morbidity and mortality in industrialized countries. Although infection with microorganisms is not involved in the development of heart failure in most cases, inflammation has been implicated in the pathogenesis of heart failure. However, the mechanisms responsible for initiating and integrating inflammatory responses within the heart remain poorly defined. Mitochondria are evolutionary endosymbionts derived from bacteria and contain DNA similar to bacterial DNA. Mitochondria damaged by external haemodynamic stress are degraded by the autophagy/lysosome system in cardiomyocytes. Here we show that mitochondrial DNA that escapes from autophagy cell-autonomously leads to Toll-like receptor (TLR) 9-mediated inflammatory responses in cardiomyocytes and is capable of inducing myocarditis and dilated cardiomyopathy. Cardiac-specific deletion of lysosomal deoxyribonuclease (DNase) II showed no cardiac phenotypes under baseline conditions, but increased mortality and caused severe myocarditis and dilated cardiomyopathy 10 days after treatment with pressure overload. Early in the pathogenesis, DNase II-deficient hearts showed infiltration of inflammatory cells and increased messenger RNA expression of inflammatory cytokines, with accumulation of mitochondrial DNA deposits in autolysosomes in the myocardium. Administration of inhibitory oligodeoxynucleotides against TLR9, which is known to be activated by bacterial DNA, or ablation of Tlr9 attenuated the development of cardiomyopathy in DNase II-deficient mice. Furthermore, Tlr9 ablation improved pressure overload-induced cardiac dysfunction and inflammation even in mice with wild-type Dnase2a alleles. These data provide new perspectives on the mechanism of genesis of chronic inflammation in failing hearts.

  11. Born in an alien nest: how do social parasite male offspring escape from host aggression?

    Directory of Open Access Journals (Sweden)

    Patrick Lhomme

    Full Text Available Social parasites exploit the colony resources of social insects. Some of them exploit the host colony as a food resource or as a shelter whereas other species also exploit the brood care behavior of their social host. Some of these species have even lost the worker caste and rely completely on the host's worker force to rear their offspring. To avoid host defenses and bypass their recognition code, these social parasites have developed several sophisticated chemical infiltration strategies. These infiltration strategies have been highly studied in several hymenopterans. Once a social parasite has successfully entered a host nest and integrated its social system, its emerging offspring still face the same challenge of avoiding host recognition. However, the strategy used by the offspring to survive within the host nest without being killed is still poorly documented. In cuckoo bumblebees, the parasite males completely lack the morphological and chemical adaptations to social parasitism that the females possess. Moreover, young parasite males exhibit an early production of species-specific cephalic secretions, used as sexual pheromones. Host workers might thus be able to recognize them. Here we used a bumblebee host-social parasite system to test the hypothesis that social parasite male offspring exhibit a chemical defense strategy to escape from host aggression during their intranidal life. Using behavioral assays, we showed that extracts from the heads of young cuckoo bumblebee males contain a repellent odor that prevents parasite males from being attacked by host workers. We also show that social parasitism reduces host worker aggressiveness and helps parasite offspring acceptance.

  12. Standard and Poor's%穷与富

    Institute of Scientific and Technical Information of China (English)

    Mario Ritter

    2006-01-01

    @@ Recently,a listener from China asked why the financial company Standard and "Poor's"has a name that includes the word poor. In Chinese culture,businesses have names that suggest success and wealth.

  13. Public policies to promote productive occupation and increase formality among the moderately poor: the Mexican agenda

    OpenAIRE

    Sojo, Eduardo; Villarreal, Roberto

    2005-01-01

    Public policy aimed at building capacity among the extremely poor (support for food and nutrition; health; education and, more recently, financial services), combined with a stable macroeconomic environment, has proved to be successful for poverty alleviation in Mexico. Even though overall poverty is still very pronounced, about four million people originally in extreme or intermediate poverty registered real income gains during 2000-02 and entered moderate poverty, concentrated mostly in urb...

  14. Unsteady motion: escape jumps in planktonic copepods, their kinematics and energetics

    DEFF Research Database (Denmark)

    Kiørboe, Thomas; Andersen, Anders Peter; Langlois, Vincent J.;

    2010-01-01

    estimate the force and power output needed to accelerate and overcome drag. Both are very high compared with those of other organisms, as are the escape velocities in comparison to startle velocities of other aquatic animals. Thus, the maximum weight-specific force, which for muscle motors of other animals...... has been found to be near constant at 57 N (kg muscle)−1, is more than an order of magnitude higher for the escaping copepods. We argue that this is feasible because most copepods have different systems for steady propulsion (feeding appendages) and intensive escapes (swimming legs), with the muscular...... arrangement of the latter probably adapted for high force production during short-lasting bursts. The resulting escape velocities scale with body length to power 0.65, different from the size-scaling of both similar sized and larger animals moving at constant velocity, but similar to that found for startle...

  15. Escape dynamics in collinear atomic-like three mass point systems

    CERN Document Server

    Pasca, Daniel; Stoica, Cristina

    2009-01-01

    The present paper studies the escape mechanism in collinear three point mass systems with small-range-repulsive/large-range-attractive pairwise-interaction. Specifically, we focus on systems with non-negative total energy. We show that on the zero energy level set, most of the orbits lead to binary escape configurations and the set of initial conditions leading to escape configurations where all three separations infinitely increase as $t \\to \\infty 1$ has zero Lebesgue measure. We also give numerical evidence of the existence of a periodic orbit for the case when the two outer masses are equal. For positive energies, we prove that the set of initial conditions leading to escape configurations where all three separations infinitely increase as $t \\to \\infty$ has positive Lebesgue measure. Keywords: linear three point

  16. Escape of an inertial Lévy flight particle from a truncated quartic potential well

    Science.gov (United States)

    Bai, Zhan-Wu; Hu, Meng

    2017-08-01

    Motivated by that the quartic potential can confined Lévy flights, we investigate the escape rate of an inertial Lévy particle from a truncated quartic potential well via Langevin simulation. The escape rate still depends on the noise intensity in a power-law form in low noise intensity, but the exponent and the inverse coefficient vary significantly for different Lévy indexes compared with previous works. Trimodal structure of the probability density function was found in simulations. The probability density function in a quasi-stable state exhibits transition among unimodal, bimodal, and trimodal structures. A metastable state by stable state approach is developed to calculate the escape rate analytically, which may be applied to extensive escape problems. The theoretical approach is confirmed by Langevin simulation for the Cauchy case of Lévy flight in the applied potential.

  17. Effect Of Feedback On The Escape Of Ionizing Radiation From High-Z Galaxies

    Science.gov (United States)

    Trebitsch, Maxime; Blaizot, Jérémy; Rosdahl, Joakim; Devriendt, Julien; Slyz, Adrianne

    2017-06-01

    Quantifying how much of the ionizing radiation produced in high-redshift galaxies escapes in the IGM is one of the main challenges in understanding the sources of reionization. We investigate the radiative properties of simulated low mass galaxies (halos of a few 109 Msun at z=6), where radiation is modelled on-the-fly, and different sources of feedback (from stars and AGN) are included. Using radiation-hydrodynamic simulations performed with Ramses-RT we study how the energy and momentum input from supernovae and black hole activity modulates the properties of the interstellar medium and therefore how, and how many, photons can escape from the galaxy. I will present simulations showing (Trebitsch et al. 2017, https://arxiv.org/abs/1705.00941) that stellar feedback has a pivotal role in regulating the escape fraction in dwarf galaxies. Supernovae carve holes in the gas distribution, through which ionizing photons can escape.

  18. Pizza or Pancake? Formation Models of Gas Escape Biosignatures in Terrestrial and Martian Sediments

    Science.gov (United States)

    Bonaccorsi, R.; Fairen, A. G.; Baker, L.; McKay, C. P.; Willson, D.

    2016-05-01

    Fine-grained sedimentary hollowed structures were imaged in Gale Crater, but no biomarkers identified to support biology. Our observation-based (gas escape) terrestrial model could inform on possible martian paleoenvironments at time of formation.

  19. Elucidating poor decision-making in a rat gambling task.

    Directory of Open Access Journals (Sweden)

    Marion Rivalan

    Full Text Available Although poor decision-making is a hallmark of psychiatric conditions such as attention deficit/hyperactivity disorder, pathological gambling or substance abuse, a fraction of healthy individuals exhibit similar poor decision-making performances in everyday life and specific laboratory tasks such as the Iowa Gambling Task. These particular individuals may provide information on risk factors or common endophenotypes of these mental disorders. In a rodent version of the Iowa gambling task--the Rat Gambling Task (RGT, we identified a population of poor decision makers, and assessed how these rats scored for several behavioral traits relevant to executive disorders: risk taking, reward seeking, behavioral inflexibility, and several aspects of impulsivity. First, we found that poor decision-making could not be well predicted by single behavioral and cognitive characteristics when considered separately. By contrast, a combination of independent traits in the same individual, namely risk taking, reward seeking, behavioral inflexibility, as well as motor impulsivity, was highly predictive of poor decision-making. Second, using a reinforcement-learning model of the RGT, we confirmed that only the combination of extreme scores on these traits could induce maladaptive decision-making. Third, the model suggested that a combination of these behavioral traits results in an inaccurate representation of rewards and penalties and inefficient learning of the environment. Poor decision-making appears as a consequence of the over-valuation of high-reward-high-risk options in the task. Such a specific psychological profile could greatly impair clinically healthy individuals in decision-making tasks and may predispose to mental disorders with similar symptoms.

  20. Choices between positive and negative reinforcement during treatment for escape-maintained behavior.

    OpenAIRE

    DeLeon, I G; Neidert, P L; Anders, B M; Rodriguez-Catter, V

    2001-01-01

    Positive reinforcement was more effective than negative reinforcement in promoting compliance and reducing escape-maintained problem behavior for a child with autism. Escape extinction was then added while the child was given a choice between positive or negative reinforcement for compliance and the reinforcement schedule was thinned. When the reinforcement requirement reached 10 consecutive tasks, the treatment effects became inconsistent and reinforcer selection shifted from a strong prefer...

  1. Influence of throat configuration and fish density on escapement of channel catfish from hoop nets

    Science.gov (United States)

    Porath, Mark T.; Pape, Larry D.; Richters, Lindsey K.

    2011-01-01

    In recent years, several state agencies have adopted the use of baited, tandemset hoop nets to assess lentic channel catfish Ictalurus punctatus populations. Some level of escapement from the net is expected because an opening exists in each throat of the net, although factors influencing rates of escapement from hoop nets have not been quantified. We conducted experiments to quantify rates of escapement and to determine the influence of throat configuration and fish density within the net on escapement rates. An initial experiment to determine the rate of escapement from each net compartment utilized individually tagged channel catfish placed within the entrance (between the two throats) and cod (within the second throat) compartments of a single hoop net for overnight sets. From this experiment, the mean rate (±SE) of channel catfish escaping was 4.2% (±1.5) from the cod (cod throat was additionally restricted from the traditionally manufactured product), and 74% (±4.2) from the entrance compartments. In a subsequent experiment, channel catfish were placed only in the cod compartment with different throat configurations (restricted or unrestricted) and at two densities (low [6 fish per net] and high [60 fish per net]) for overnight sets to determine the influence of fish density and throat configuration on escapement rates. Escapement rates between throat configurations were doubled at low fish density (13.3 ± 5.4% restricted versus 26.7 ± 5.6% unrestricted) and tripled at high fish density (14.3 ± 4.9% restricted versus 51.9 ± 5.0% unrestricted). These results suggest that retention efficiency is high from cod compartments with restricted throat entrances. However, managers and researchers need to be aware that modification to the cod throats (restrictions) is needed for hoop nets ordered from manufacturers. Managers need to be consistent in their use and reporting of cod end throat configurations when using this gear.

  2. THE EFFECTS OF FIXED-TIME ESCAPE ON INAPPROPRIATE AND APPROPRIATE CLASSROOM BEHAVIOR

    OpenAIRE

    Waller, Rachael D; Higbee, Thomas S.

    2010-01-01

    Few studies have explored the effects of fixed-time (FT) reinforcement on escape-maintained behavior of students in a classroom setting. We measured the effects of an FT schedule on the disruptive and appropriate academic behaviors of 2 junior high students in a public school setting. Results demonstrated that FT escape from tasks resulted in a substantial decrease in disruptive behavior and an increase in time engaged in tasks for both participants.

  3. Choices between positive and negative reinforcement during treatment for escape-maintained behavior.

    Science.gov (United States)

    DeLeon, I G; Neidert, P L; Anders, B M; Rodriguez-Catter, V

    2001-01-01

    Positive reinforcement was more effective than negative reinforcement in promoting compliance and reducing escape-maintained problem behavior for a child with autism. Escape extinction was then added while the child was given a choice between positive or negative reinforcement for compliance and the reinforcement schedule was thinned. When the reinforcement requirement reached 10 consecutive tasks, the treatment effects became inconsistent and reinforcer selection shifted from a strong preference for positive reinforcement to an unstable selection pattern.

  4. Solution of the boundary value problem for optimal escape in continuous stochastic systems and maps.

    OpenAIRE

    S; Beri; Mannella, R.; Luchinsky, Dmitry G.; Silchenko, A. N.; McClintock, Peter V. E.

    2005-01-01

    Topologies of invariant manifolds and optimal trajectories are investigated in stochastic continuous systems and maps. A topological method is introduced that simplifies the solution of boundary value problems: The activation energy is calculated as a function of a set of parameters characterizing the initial conditions of the escape path. The method is applied explicitly to compute the optimal escape path and the activation energy for a variety of dynamical systems and maps.

  5. The relationship between migration and development in the ESCAP region.

    Science.gov (United States)

    Skeldon, R

    1991-01-01

    The relationship between migration and development in the ESCAP region including southeast and south Asian countries and the Pacific island of Fiji, Papua New Guinea, Vanuatu, Kiribati, Samoa, and the Solomon Islands is discussed in terms of mobility transition and origin and destination factors. The changing patterns of mobility in Asia are further delineated in the discussion of internal movements and international movement. Emigration in the smaller countries of the Pacific are treated separately. Future predictions are that the Asia Pacific region will experience continued fertility decline and stabilization of low rates over the next 20 years. The declines will result in slow labor force growth, and increased demand for labor in traditional core and neocore countries as defined and presented in table form by Friedman will be heightened. International movements are likely to increase in large urban areas within destination countries. Tokyo and Singapore are the principal cities in Asia. Tokyo by restrictive government policy has limited immigration, but future labor shortages of unskilled labor from southeast Asia and China are expected. Singapore is already dependent on foreign labor by 10%. Current labor shortages have led to the creation of a growth triangle between Singapore, Indonesia, and Malaysia. Other cities expected to emerge as primary cities in international regional complexes with spillover into the hinterlands include the Hong Kong, Guangzhou, and Macau triangle in the Pearl River delta, Taipei and Seoul, and possibly Kuala Lumpur. Internal migration is expected to increase in the capital cities of Bangkok, Manila,j and centers such as Shanghai, Beijing, and other large cities of southeast Asia. These cities will be linked through the flows of skilled international migrants, which began in the 1960s and is expected to become a future major flow. Recreational and resource niches will be left in much of the Pacific, the Himalayan Kingdoms, and

  6. Extreme Programming Pocket Guide

    CERN Document Server

    Chromatic

    2003-01-01

    Extreme Programming (XP) is a radical new approach to software development that has been accepted quickly because its core practices--the need for constant testing, programming in pairs, inviting customer input, and the communal ownership of code--resonate with developers everywhere. Although many developers feel that XP is rooted in commonsense, its vastly different approach can bring challenges, frustrations, and constant demands on your patience. Unless you've got unlimited time (and who does these days?), you can't always stop to thumb through hundreds of pages to find the piece of info

  7. Mycetoma of lower extremity

    Directory of Open Access Journals (Sweden)

    Sahariah S

    1978-01-01

    Full Text Available Ten cases of mycetoma of the lower extremity were seen and treated at the Postgraduate Institute of Medical Education & Research, Chandigarh, India, during the years 1973 to 1975. Six were treated by conservative method e.g. antibiotics, sulfonamides and immobilization of the part while remaining four were submitted t o surgery. Four out o f six from the first group had recurrence and has been put on second line of therapy. Recurrence occurred in only one case from the second group and he required an above knee amputation while the remaining three are free of disease and are well rehabilitated.

  8. Metagenomics of extreme environments.

    Science.gov (United States)

    Cowan, D A; Ramond, J-B; Makhalanyane, T P; De Maayer, P

    2015-06-01

    Whether they are exposed to extremes of heat or cold, or buried deep beneath the Earth's surface, microorganisms have an uncanny ability to survive under these conditions. This ability to survive has fascinated scientists for nearly a century, but the recent development of metagenomics and 'omics' tools has allowed us to make huge leaps in understanding the remarkable complexity and versatility of extremophile communities. Here, in the context of the recently developed metagenomic tools, we discuss recent research on the community composition, adaptive strategies and biological functions of extremophiles.

  9. Mapping onto Eq-5 D for patients in poor health

    Directory of Open Access Journals (Sweden)

    Brazier John E

    2010-11-01

    Full Text Available Abstract Background An increasing amount of studies report mapping algorithms which predict EQ-5 D utility values using disease specific non-preference-based measures. Yet many mapping algorithms have been found to systematically overpredict EQ-5 D utility values for patients in poor health. Currently there are no guidelines on how to deal with this problem. This paper is concerned with the question of why overestimation of EQ-5 D utility values occurs for patients in poor health, and explores possible solutions. Method Three existing datasets are used to estimate mapping algorithms and assess existing mapping algorithms from the literature mapping the cancer-specific EORTC-QLQ C-30 and the arthritis-specific Health Assessment Questionnaire (HAQ onto the EQ-5 D. Separate mapping algorithms are estimated for poor health states. Poor health states are defined using a cut-off point for QLQ-C30 and HAQ, which is determined using association with EQ-5 D values. Results All mapping algorithms suffer from overprediction of utility values for patients in poor health. The large decrement of reporting 'extreme problems' in the EQ-5 D tariff, few observations with the most severe level in any EQ-5 D dimension and many observations at the least severe level in any EQ-5 D dimension led to a bimodal distribution of EQ-5 D index values, which is related to the overprediction of utility values for patients in poor health. Separate algorithms are here proposed to predict utility values for patients in poor health, where these are selected using cut-off points for HAQ-DI (> 2.0 and QLQ C-30 ( Conclusion Mapping algorithms overpredict utility values for patients in poor health but are used in cost-effectiveness analyses nonetheless. Guidelines can be developed on when the use of a mapping algorithms is inappropriate, for instance through the identification of cut-off points. Cut-off points on a disease specific questionnaire can be identified through association

  10. Winter Storms and Extreme Cold

    Science.gov (United States)

    ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ... Landslides & Debris Flow Nuclear Blast Nuclear Power Plants Power Outages Pandemic Radiological Dispersion Device Severe Weather Snowstorms & Extreme ...

  11. Escape-Route Planning of Underground Coal Mine Based on Improved Ant Algorithm

    Directory of Open Access Journals (Sweden)

    Guangwei Yan

    2013-01-01

    Full Text Available When a mine disaster occurs, to lessen disaster losses and improve survival chances of the trapped miners, good escape routes need to be found and used. Based on the improved ant algorithm, we proposed a new escape-route planning method of underground mines. At first, six factors which influence escape difficulty are evaluated and a weight calculation model is built to form a weighted graph of the underground tunnels. Then an improved ant algorithm is designed and used to find good escape routes. We proposed a tunnel network zoning method to improve the searching efficiency of the ant algorithm. We use max-min ant system method to optimize the meeting strategy of ants and improve the performance of the ant algorithm. In addition, when a small part of the mine tunnel network changes, the system may fix the optimal routes and avoid starting a new processing procedure. Experiments show that the proposed method can find good escape routes efficiently and can be used in the escape-route planning of large and medium underground coal mines.

  12. Fundamental Experiment to Determine Escape Countermeasures for Frogs Falling into Agricultural Canals

    Science.gov (United States)

    Watabe, Keiji; Mori, Atsushi; Koizumi, Noriyuki; Takemura, Takeshi

    Frogs often drown in agricultural canals with deep concrete walls, which are installed commonly in paddy fields after land improvement projects in Japan, because they cannot escape after falling into the canal. Therefore, countermeasures that enable frogs to escape from canals are required in some rural areas. An experimental canal with partially sloped walls was used as an escape countermeasure to investigate the preferable angle of slope for the walls, water depth and flow velocity that enables Tokyo Daruma Pond Frogs (Rana porosa porosa), which have no adhesive discs, to easily escape. Walls with slopes of 30-45 degrees allowed 50-60% of frogs to escape from the experimental canals, frogs especially easily climbed the 30 degree sloped walls. When the water depth was 5 cm or flow velocity was greater than 20 cm/s, approximately 80% of the frogs moved downstream and reached the sloped walls because the frogs' toes did not reach the bottom of the canal. However, if the depth was 2 cm and the flow velocity was 5 cm/s, only 4% of the frogs climbed the sloped walls because they could move freely. The frogs appeared to not be good at long-distance swimming and could not remain a long-time under running water. Therefore, walls sloped less than 30 degrees and control of both water depth and flow velocity appears important for enabling frogs to easily escape from canals.

  13. CD4 binding site broadly neutralizing antibody selection of HIV-1 escape mutants.

    Science.gov (United States)

    Dreja, Hanna; Pade, Corinna; Chen, Lei; McKnight, Áine

    2015-07-01

    All human immunodeficiency virus type-1 (HIV-1) viruses use CD4 to enter cells. Consequently, the viral envelope CD4-binding site (CD4bs) is relatively conserved, making it a logical neutralizing antibody target. It is important to understand how CD4-binding site variation allows for escape from neutralizing antibodies. Alanine scanning mutagenesis identifies residues in antigenic sites, whereas escape mutant selection identifies viable mutants. We selected HIV-1 to escape CD4bs neutralizing mAbs b12, A12 and HJ16. Viruses that escape from A12 and b12 remained susceptible to HJ16, VRC01 and J3, whilst six different viruses that escape HJ16 remained sensitive to A12, b12 and J3. In contrast, their sensitivity to VRC01 was variable. Triple HJ16/A12/b12-resistant virus proved that HIV-1 could escape multiple broadly neutralizing monoclonal antibodies, but still retain sensitivity to VRC01 and the llama-derived J3 nanobody. This antigenic variability may reflect that occurring in circulating viruses, so studies like this can predict immunologically relevant antigenic forms of the CD4bs for inclusion in HIV-1 vaccines.

  14. Effects of Serotonergic and Opioidergic Drugs on Escape Behaviors and Social Status of Male Crickets

    Science.gov (United States)

    Dyakonova, V. E.; Schürmann, F.-W.; Sakharov, D. A.

    We examined the effects of selective serotonin depletion and opioid ligands on social rank and related escape behavior of the cricket Gryllus bimaculatus. Establishment of social rank in a pair of males affected their escape reactions. Losers showed a lower and dominants a higher percentage of jumps in response to tactile cercal stimulation than before a fight. The serotonin-depleting drug α-methyltryptophan (AMTP) caused an activation of the escape reactivity in socially naive crickets. AMTP-treated animals also showed a lower ability to become dominants. With an initial 51.6+/-3.6% of wins in the AMTP group, the percentage decreased to 26+/-1.6% on day 5 after injection. The opiate receptor antagonist naloxone affected fight and escape similarly as AMTP. In contrast to naloxone, the opioid agonist [d-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin decreased escape responsiveness to cercal stimulation in naive and subordinate crickets. We suggest that serotonergic and opioid systems are involved in the dominance induced depression of escape behavior.

  15. Heat-induced symmetry breaking in ant (Hymenoptera: Formicidae) escape behavior.

    Science.gov (United States)

    Chung, Yuan-Kai; Lin, Chung-Chi

    2017-01-01

    The collective egress of social insects is important in dangerous situations such as natural disasters or enemy attacks. Some studies have described the phenomenon of symmetry breaking in ants, with two exits induced by a repellent. However, whether symmetry breaking occurs under high temperature conditions, which are a common abiotic stress, remains unknown. In our study, we deposited a group of Polyrhachis dives ants on a heated platform and counted the number of escaping ants with two identical exits. We discovered that ants asymmetrically escaped through two exits when the temperature of the heated platform was >32.75°C. The degree of asymmetry increased linearly with the temperature of the platform. Furthermore, the higher the temperature of heated platform was, the more ants escaped from the heated platform. However, the number of escaping ants decreased for 3 min when the temperature was higher than the critical thermal limit (39.46°C), which is the threshold for ants to endure high temperature without a loss of performance. Moreover, the ants tended to form small groups to escape from the thermal stress. A preparatory formation of ant grouping was observed before they reached the exit, indicating that the ants actively clustered rather than accidentally gathered at the exits to escape. We suggest that a combination of individual and grouping ants may help to optimize the likelihood of survival during evacuation.

  16. Escape of Mars' CO2 atmosphere by suprathermal atoms during the past 4 Gyrs

    Science.gov (United States)

    Amerstorfer, Ute; Gröller, Hannes; Lichtenegger, Herbert; Lammer, Helmut; Tian, Feng

    2016-04-01

    The escape of atmospheric particles plays a crucial role in the evolution of the atmosphere of Mars. Especially, the escape of oxygen and carbon is thought to have influenced its amount of CO2. With a Monte-Carlo model we investigate the escape of hot oxygen and carbon from the martian atmosphere for three points in time in its history corresponding to 3, 10, and 20 times the present EUV level. We study and discuss different possible sources of hot oxygen and carbon atoms in the thermosphere and their changing importance with the EUV flux. We find that the escape due to photodissociation increases with increasing EUV level, as is a commonly assumed opinion. However, for the escape via other reactions, e.g. dissociative recombination, this is only true until the EUV level reaches 10 times the present EUV flux, but then the rates start to decrease. Our results thus suggest that some escape mechanisms related to the loss of CO2 are less important than previously thought for atmospheres exposed to higher EUV radiation. This work receives funding from the Austrian Science Fund (FWF): P 24247-N16.

  17. Orbital and escape dynamics in barred galaxies - I. The 2D system

    CERN Document Server

    Jung, Christof

    2016-01-01

    In this paper we use the two-dimensional (2D) version of a new analytical gravitational model in order to explore the orbital as well as the escape dynamics of the stars in a barred galaxy composed of a spherically symmetric central nucleus, a bar, a flat disk and a dark matter halo component. A thorough numerical investigation is conducted for distinguishing between bounded and escaping motion. Furthermore bounded orbits are further classified into non-escaping regular and trapped chaotic using the Smaller ALingment Index (SALI) method. Our aim is to determine the basins of escape through the two symmetrical escape channels around the Lagrange points $L_2$ and $L_3$ and also to relate them with the corresponding distribution of the escape rates of the orbits. We integrate initial conditions of orbits in several types of planes so as to obtain a more complete view of the overall orbital properties of the dynamical system. We also present evidence that the unstable manifolds which guide the orbits in and out t...

  18. Lobelia siphilitica plants that escape herbivory in time also have reduced latex production.

    Directory of Open Access Journals (Sweden)

    Amy L Parachnowitsch

    Full Text Available Flowering phenology is an important determinant of a plant's reproductive success. Both assortative mating and niche construction can result in the evolution of correlations between phenology and other reproductive, functional, and life history traits. Correlations between phenology and herbivore defence traits are particularly likely because the timing of flowering can allow a plant to escape herbivory. To test whether herbivore escape and defence are correlated, we estimated phenotypic and genetic correlations between flowering phenology and latex production in greenhouse-grown Lobelia siphilitica L. (Lobeliaceae. Lobelia siphilitica plants that flower later escape herbivory by a specialist pre-dispersal seed predator, and thus should invest fewer resources in defence. Consistent with this prediction, we found that later flowering was phenotypically and genetically correlated with reduced latex production. To test whether herbivore escape and latex production were costly, we also measured four fitness correlates. Flowering phenology was negatively genetically correlated with three out of four fitness estimates, suggesting that herbivore escape can be costly. In contrast, we did not find evidence for costs of latex production. Generally, our results suggest that herbivore escape and defence traits will not evolve independently in L. siphilitica.

  19. Lévy noise-induced escape in an excitable system

    Science.gov (United States)

    Cai, Rui; Chen, Xiaoli; Duan, Jinqiao; Kurths, Jürgen; Li, Xiaofan

    2017-06-01

    This paper considers the dynamics of escape in the stochastic FitzHugh-Nagumo (FHN) neuronal model driven by symmetric α-stable Lévy noise. External or internal stimulation may make the excitable system produce a pulse or not, which can be interpreted as an escape problem. A new method to analyse the state transition from the rest state to the excitatory state is presented. This approach consists of two deterministic indices: the first escape probability (FEP) and the mean first exit time (MFET). We find that higher FEP in the rest state (equilibrium) promotes such a transition and MFET reflects the stability of the rest state directly with the selected escape region. The developed two dimensional numerical simulation method to calculate FEP and MFET can not only avoid a dimension reduction, but is also applicable for the cases with large noise. In addition, FEP provides us with a new perspective to understand the seperatrix of the stochastic FHN model. It can be seen that smaller jumps of the Lévy motion and relatively small noise intensity are conducive to the production of spikes. In order to characterize the effect of noise on the selected escape region in which the equilibrium lies, the area of higher FEP and MFET in the escape region are calculated. Meanwhile, Brownian motion as a special case is also taken into account for comparison. This work was partly supported by the NSF grant 1620449, and NSFC grants 11531006, 11371367 and 11271290.

  20. Chaotic escape from an open vase-shaped cavity. I. Numerical and experimental results

    Science.gov (United States)

    Novick, Jaison; Keeler, Matthew L.; Giefer, Joshua; Delos, John B.

    2012-01-01

    We present part I in a two-part study of an open chaotic cavity shaped as a vase. The vase possesses an unstable periodic orbit in its neck. Trajectories passing through this orbit escape without return. For our analysis, we consider a family of trajectories launched from a point on the vase boundary. We imagine a vertical array of detectors past the unstable periodic orbit and, for each escaping trajectory, record the propagation time and the vertical detector position. We find that the escape time exhibits a complicated recursive structure. This recursive structure is explored in part I of our study. We present an approximation to the Helmholtz equation for waves escaping the vase. By choosing a set of detector points, we interpolate trajectories connecting the source to the different detector points. We use these interpolated classical trajectories to construct the solution to the wave equation at a detector point. Finally, we construct a plot of the detector position versus the escape time and compare this graph to the results of an experiment using classical ultrasound waves. We find that generally the classical trajectories organize the escaping ultrasound waves.