Evolved massive stars in W33 and in GMC 23.3-0.3

NASA Astrophysics Data System (ADS)

Messineo, Maria; Clark, J. Simon; Figer, Donald F.; Menten, Karl M.; Kudritzki, Rolf-Peter; Najarro, Francisco; Rich, Michael; Ivanov, Valentin D.; Valenti, Elena; Trombley, Christine; Chen, Rosie; Davies, Ben; MacKenty, John W.

2015-08-01

We have conducted an infrared spectroscopic survey for massive evolved stars and/or clusters in the Galactic giant molecular clouds G23.3-0.3 and W33. A large number of extraordinary sub-clumps/clusters of massive stars were detected. The spatial and temporal distribution of these massive stars yields information on the star formation history of the clouds.In G23.3-0.3, we discovered a dozen massive O-type stars, one candidate luminous blue variable, and several red supergiants. The O-type stars have masses from 25 to 50 Msun and ages of 5-8 Myr, while the RSGs belong to a burst that occurred 20-30 Myr ago. Therefore, GMC G23.3-0.3 has had one of the longest known histories of star formation (20-30 Myr). GMC G23.3-0.3 is rich in HII regions and supernova remnants; we detected massive stars in the cores of SNR W41 and of SNR G22.7-0.2.In W33, we detected a few evolved O-type stars and one Wolf-Rayet star, but none of the late-type objects has the luminosity of a red supergiant. W33 is characterized by discrete sources and has had at least 3-5 Myr of star formation history, which is now propagating from west to east. While our detections of massive evolved stars in W33 are made on the west side of the cloud, several dense molecular cores that may harbor proto clusters have recently been detected on the east side of the cloud by Immer et al. (2014).Messineo, Maria; Menten, Karl M.; Figer, Donald F.; Davies, Ben; Clark, J. Simon; Ivanov, Valentin D.Kudritzki, Rolf-Peter; Rich, R. Michael; MacKenty, John W.; Trombley, Christine 2014A&A...569A..20MMessineo, Maria; Clark, J. Simon; Figer, Donald F.; Kudritzki, Rolf-Peter; Francisco, Najarro; Rich, R. Michael; Menten, Karl M.; Ivanov, Valentin D.; Valenti, Elena; Trombley, Christine; Chen, C.H. Rosie; Davies, Ben; submitted to ApJ.

Hydrodynamic models for novae with ejecta rich in oxygen, neon and magnesium

NASA Technical Reports Server (NTRS)

Starrfield, S.; Sparks, W. M.; Truran, J. W.

1985-01-01

The characteristics of a new class of novae are identified and explained. This class consists of those objects that have been observed to eject material rich in oxygen, neon, magnesium, and aluminum at high velocities. We propose that for this class of novae the outburst is occurring not on a carbon-oxygen white dwarf but on an oxygen-neon-magnesium white dwarf which has evolved from a star which had a main sequence mass of approx. 8 solar masses to approx. 12 solar masses. An outburst was simulated by evolving 1.25 solar mass white dwarfs accreting hydrogen rich material at various rates. The effective enrichment of the envelope by ONeMg material from the core is simulated by enhancing oxygen in the accreted layers. The resulting evolutionary sequences can eject the entire accreted envelope plus core material at high velocities. They can also become super-Eddington at maximum bolometric luminosity. The expected frequency of such events (approx. 1/4) is in good agreement with the observed numbers of these novae.

The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. VI. Luminosities and Mass-loss Rates on Population Scales

NASA Astrophysics Data System (ADS)

Riebel, D.; Srinivasan, S.; Sargent, B.; Meixner, M.

2012-07-01

We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to ~30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionary parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 × 10-5 M ⊙ yr-1, equivalent to a total mass injection rate (including the gas) into the ISM of ~6 × 10-3 M ⊙ yr-1. Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K s band as a function of J - K s color, BC_{K_{s}} = -0.40(J-K_{s})^2 + 1.83(J-K_{s}) + 1.29. We determine several IR color proxies for the dust mass-loss rate (\\dot{M}_{d}) from C-rich AGB stars, such as log \\dot{M_{d}} = ({-18.90}/({(K_{s}-[8.0])+3.37}))-5.93. We find that a larger fraction of AGB stars exhibiting the "long-secondary period" phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.

Widespread HCN maser emission in carbon-rich evolved stars

NASA Astrophysics Data System (ADS)

Menten, K. M.; Wyrowski, F.; Keller, D.; Kamiński, T.

2018-05-01

Context. HCN is a major constituent of the circumstellar envelopes of carbon-rich evolved stars, and rotational lines from within its vibrationally excited states probe parts of these regions closest to the stellar surface. A number of such lines are known to show maser action. Historically, in one of them, the 177 GHz J = 2 → 1 line in the l-doubled bending mode has been found to show relatively strong maser action, with results only published for a single object, the archetypical high-mass loss asymptotic giant branch (AGB) star IRC+10216. Aims: To examine how common 177 GHz HCN maser emission is, we conducted an exploratory survey for this line toward a select sample of carbon-rich asymptotic giant branch stars that are observable from the southern hemisphere. Methods: We used the Atacama Pathfinder Experiment 12 meter submillimeter Telescope (APEX) equipped with a new receiver to simultaneously observe three J = 2 → 1 HCN rotational transitions, the (0, 11c, 0) and (0, 11d, 0) l-doublet components, and the line from the (0,0,0) ground state. Results: The (0, 11c, 0) maser line is detected toward 11 of 13 observed sources, which all show emission in the (0,0,0) transition. In most of the sources, the peak intensity of the (0, 11c, 0) line rivals that of the (0,0,0) line; in two sources, it is even stronger. Except for the object with the highest mass-loss rate, IRC+10216, the (0, 11c, 0) line covers a smaller velocity range than the (0,0,0) line. The (0, 11d, 0) line, which is detected in four of the sources, is much weaker than the other two lines and covers a velocity range that is smaller yet, again except for IRC+10216. Compared to its first detection in 1989, the profile of the (0, 11c, 0) line observed toward IRC+10216 looks very different, and we also appear to see variability in the (0,0,0) line profile (at a much lower degree). Our limited information on temporal variabilitydisfavors a strong correlation of maser and stellar continuum flux. Conclusions: Maser emission in the 177 GHz J = 2 → 1 (0, 11c, 0) line of HCN appears to be common in carbon-rich AGB stars. Like for other vibrationally excited HCN lines, our observations indicate that the origin of these lines is in the acceleration zone of the stellar outflow in which dust is forming. For all the stars toward which we detect the maser line, the number of photons available at 7 and 14 μm, corresponding to transitions to vibrationally excited states possibly involved in its pumping, is found to be far greater than that of the maser photons, which makes radiative pumping feasible. Other findings point to a collisional pumping scheme, however. The reduced spectra (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/613/A49

Transcriptome comparisons shed light on the pre-condition and potential barrier for C4 photosynthesis evolution in eudicots.

PubMed

Tao, Yimin; Lyu, Ming-Ju Amy; Zhu, Xin-Guang

2016-05-01

C4 photosynthesis evolved independently from C3 photosynthesis in more than 60 lineages. Most of the C4 lineages are clustered together in the order Poales and the order Caryophyllales while many other angiosperm orders do not have C4 species, suggesting the existence of biological pre-conditions in the ancestral C3 species that facilitate the evolution of C4 photosynthesis in these lineages. To explore pre-adaptations for C4 photosynthesis evolution, we classified C4 lineages into the C4-poor and the C4-rich groups based on the percentage of C4 species in different genera and conducted a comprehensive comparison on the transcriptomic changes between the non-C4 species from the C4-poor and the C4-rich groups. Results show that species in the C4-rich group showed higher expression of genes related to oxidoreductase activity, light reaction components, terpene synthesis, secondary cell synthesis, C4 cycle related genes and genes related to nucleotide metabolism and senescence. In contrast, C4-poor group showed up-regulation of a PEP/Pi translocator, genes related to signaling pathway, stress response, defense response and plant hormone metabolism (ethylene and brassinosteroid). The implications of these transcriptomic differences between the C4-rich and C4-poor groups to C4 evolution are discussed.

Combustion of Organic Molecules by the Thermal Decomposition of Perchlorate Salts: Implications for Organics at the Mars Phoenix Scout Landing Site

NASA Technical Reports Server (NTRS)

Ming, D.W.; Morris, R.V.; Niles, B.; Lauer, H.V.; Archer, P.D.; Sutter, B.; Boynton, W.V.; Golden, D.C.

2009-01-01

The Mars 2007 Phoenix Scout Mission successfully landed on May 25, 2008 and operated on the northern plains of Mars for 150 sols. The primary mission objective was to study the history of water and evaluate the potential for past and present habitability in Martian arctic ice-rich soil [1]. Phoenix landed near 68 N latitude on polygonal terrain created by ice layers that are a few centimeters under loose soil materials. The Phoenix Mission is assessing the potential for habitability by searching for organic molecules in the ice or icy soils at the landing site. Organic molecules are necessary building blocks for life, although their presence in the ice or soil does not indicate life itself. Phoenix searched for organic molecules by heating soil/ice samples in the Thermal and Evolved-Gas Analyzer (TEGA, [2]). TEGA consists of 8 differential scanning calorimeter (DSC) ovens integrated with a magnetic-sector mass spectrometer with a mass range of 2-140 daltons [2]. Endothermic and exothermic reactions are recorded by the TEGA DSC as samples are heated from ambient to 1000 C. Evolved gases, including any organic molecules and their fragments, are simultaneously measured by the mass spectrometer during heating. Phoenix TEGA data are still under analysis; however, no organic fragments have been identified to date in the evolved gas analysis (EGA). The MECA Wet Chemistry Lab (WCL) discovered a perchlorate salt in the Phoenix soils and a mass 32 peak evolved between 325 and 625 C for one surface sample dubbed Baby Bear [3]. The mass 32 peak is attributed to evolved O2 generated during the thermal decomposition of the perchlorate salt. Perchlorates are very strong oxidizers when heated, so it is possible that organic fragments evolved in the temperature range of 300-600 C were combusted by the O2 released during the thermal decomposition of the perchlorate salt. The byproduct of the combustion of organic molecules is CO2. There is a prominent release of CO2 between 200-600 C for several of the Phoenix soils analyzed by TEGA. This low temperature release of CO2 might be any combination of 1) desorption of adsorbed CO2, 2) thermal decomposition of Fe- and Mg-carbonates, and 3) combustion of organic molecules [2].

New CO and HCN sources associated with IRAS carbon stars

NASA Technical Reports Server (NTRS)

NGUYEN-Q-RIEU; Epchtein, N.; TRUONG-BACH; Cohen, M.

1987-01-01

Emission of CO and HCN was detected in 22 out of a sample of 53 IRAS sources classified as unidentified carbon-rich objects. The sample was selected according to the presence of the silicon carbide feature as revealed by low-resolution spectra. The molecular line widths indicate that the CO and HCN emission arises from the circumstellar envelopes of very highly evolved stars undergoing mass loss. The visible stars tend to be deficient in CO as compared with unidentified sources. Most the detected CO and HCN IRAS stars are distinct and thick-shelled objects, but their infrared and CO luminosities are similar to those of IRC + 102156 AFGL and IRC-CO evolved stars. The 12 micron flux seems to be a good indicator of the distance, hence a guide for molecular searches.

THE MASS-LOSS RETURN FROM EVOLVED STARS TO THE LARGE MAGELLANIC CLOUD. VI. LUMINOSITIES AND MASS-LOSS RATES ON POPULATION SCALES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riebel, D.; Meixner, M.; Srinivasan, S.

We present results from the first application of the Grid of Red Supergiant and Asymptotic Giant Branch ModelS (GRAMS) model grid to the entire evolved stellar population of the Large Magellanic Cloud (LMC). GRAMS is a pre-computed grid of 80,843 radiative transfer models of evolved stars and circumstellar dust shells composed of either silicate or carbonaceous dust. We fit GRAMS models to {approx}30,000 asymptotic giant branch (AGB) and red supergiant (RSG) stars in the LMC, using 12 bands of photometry from the optical to the mid-infrared. Our published data set consists of thousands of evolved stars with individually determined evolutionarymore » parameters such as luminosity and mass-loss rate. The GRAMS grid has a greater than 80% accuracy rate discriminating between oxygen- and carbon-rich chemistry. The global dust injection rate to the interstellar medium (ISM) of the LMC from RSGs and AGB stars is on the order of 2.1 Multiplication-Sign 10{sup -5} M{sub Sun} yr{sup -1}, equivalent to a total mass injection rate (including the gas) into the ISM of {approx}6 Multiplication-Sign 10{sup -3} M{sub Sun} yr{sup -1}. Carbon stars inject two and a half times as much dust into the ISM as do O-rich AGB stars, but the same amount of mass. We determine a bolometric correction factor for C-rich AGB stars in the K{sub s} band as a function of J - K{sub s} color, BC{sub K{sub s}}= -0.40(J-K{sub s}){sup 2} + 1.83(J-K{sub s}) + 1.29. We determine several IR color proxies for the dust mass-loss rate (M-dot{sub d}) from C-rich AGB stars, such as log M-dot{sub d} = (-18.90/((K{sub s}-[8.0])+3.37) - 5.93. We find that a larger fraction of AGB stars exhibiting the 'long-secondary period' phenomenon are more O-rich than stars dominated by radial pulsations, and AGB stars without detectable mass loss do not appear on either the first-overtone or fundamental-mode pulsation sequences.« less

The VLTI/MIDI view on the inner mass loss of evolved stars from the Herschel MESS sample

NASA Astrophysics Data System (ADS)

Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; Wittkowski, M.; Richichi, A.; Hron, J.; Jorissen, A.; Groenewegen, M. A. T.; Kerschbaum, F.; Verhoelst, T.; Rau, G.; Olofsson, H.; Zhao-Geisler, R.; Matter, A.

2017-04-01

Context. The mass-loss process from evolved stars is a key ingredient for our understanding of many fields of astrophysics, including stellar evolution and the chemical enrichment of the interstellar medium (ISM) via stellar yields. Nevertheless, many questions are still unsolved, one of which is the geometry of the mass-loss process. Aims: Taking advantage of the results from the Herschel Mass loss of Evolved StarS (MESS) programme, we initiated a coordinated effort to characterise the geometry of mass loss from evolved red giants at various spatial scales. Methods: For this purpose we used the MID-infrared interferometric Instrument (MIDI) to resolve the inner envelope of 14 asymptotic giant branch stars (AGBs) in the MESS sample. In this contribution we present an overview of the interferometric data collected within the frame of our Large Programme, and we also add archive data for completeness. We studied the geometry of the inner atmosphere by comparing the observations with predictions from different geometric models. Results: Asymmetries are detected for the following five stars: R Leo, RT Vir, π1Gruis, omi Ori, and R Crt. All the objects are O-rich or S-type, suggesting that asymmetries in the N band are more common among stars with such chemistry. We speculate that this fact is related to the characteristics of the dust grains. Except for one star, no interferometric variability is detected, I.e. the changes in size of the shells of non-mira stars correspond to changes of the visibility of less than 10%. The observed spectral variability confirms previous findings from the literature. The detection of dust in our sample follows the location of the AGBs in the IRAS colour-colour diagram: more dust is detected around oxygen-rich stars in region II and in the carbon stars in region VII. The SiC dust feature does not appear in the visibility spectrum of the U Ant and S Sct, which are two carbon stars with detached shells. This finding has implications for the theory of SiC dust formation. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 073.D-0711, 076.D-0620, 077.D-0294, 078.D-0122, 080.D-0801, 081.D-0021, 083.D-0234, 086.D-0737, 086.D-899, 187.D-0924, 089.D-0562, 090.D-410, 091.C-0468, 091.D-0344.

Electrically Conducting, Ca-Rich Brines, Rather Than Water, Expected in the Martian Subsurface

NASA Technical Reports Server (NTRS)

Burt, D. M.; Knauth, L. P.

2003-01-01

If Mars ever possessed a salty liquid hydrosphere, which later partly evaporated and froze down, then any aqueous fluids left near the surface could have evolved to become dense eutectic brines. Eutectic brines, by definition, are the last to freeze and the first to melt. If CaC12-rich, such brines can remain liquid until temperatures below 220 K, close to the average surface temperature of Mars. In the Martian subsurface, in intimate contact with the Ca-rich basaltic regolith, NaC1-rich early brines should have reacted to become Ca-rich. Fractional crystallization (freezing) and partial melting would also drive brines toward CaC12-rich compositions. In other words, eutectic brine compositions could be present in the shallow subsurface of Mars, for the same reasons that eutectic magma compositions are common on Earth. Don Juan Pond, Antarctica, a CaC12-rich eutectic brine, provides a possible terrestrial analog, particularly because it is fed from a basaltic aquifer. Owing to their relative density and fluid nature, brines in the Martian regolith should eventually become sandwiched between ice above and salts beneath. A thawing brine sandwich provides one explanation (among many) for the young gullies recently attributed to seepage of liquid water on Mars. Whether or not brine seepage explains the gullies phenomenon, dense, CaC12-rich brines are to be expected in the deep subsurface of Mars, although they might be somewhat diluted (temperatures permitting) and of variable salt composition. In any case, they should be good conductors of electricity.

Following the Interstellar History of Carbon: From the Interiors of Stars to the Surfaces of Planets.

PubMed

Ziurys, L M; Halfen, D T; Geppert, W; Aikawa, Y

2016-12-01

The chemical history of carbon is traced from its origin in stellar nucleosynthesis to its delivery to planet surfaces. The molecular carriers of this element are examined at each stage in the cycling of interstellar organic material and their eventual incorporation into solar system bodies. The connection between the various interstellar carbon reservoirs is also examined. Carbon has two stellar sources: supernova explosions and mass loss from evolved stars. In the latter case, the carbon is dredged up from the interior and then ejected into a circumstellar envelope, where a rich and unusual C-based chemistry occurs. This molecular material is eventually released into the general interstellar medium through planetary nebulae. It is first incorporated into diffuse clouds, where carbon is found in polyatomic molecules such as H 2 CO, HCN, HNC, c-C 3 H 2 , and even C 60 + . These objects then collapse into dense clouds, the sites of star and planet formation. Such clouds foster an active organic chemistry, producing compounds with a wide range of functional groups with both gas-phase and surface mechanisms. As stars and planets form, the chemical composition is altered by increasing stellar radiation, as well as possibly by reactions in the presolar nebula. Some molecular, carbon-rich material remains pristine, however, encapsulated in comets, meteorites, and interplanetary dust particles, and is delivered to planet surfaces. Key Words: Carbon isotopes-Prebiotic evolution-Interstellar molecules-Comets-Meteorites. Astrobiology 16, 997-1012.

MSL SAM-Like Evolved Gas Analyses of Si-rich Amorphous Materials

NASA Technical Reports Server (NTRS)

McAdam, Amy; Knudson, Christine; Sutter, Brad; Andrejkovicova, Slavka; Archer, P. Douglas; Franz, Heather; Eigenbrode, Jennifer; Morris, Richard; Ming, Douglas; Sun, Vivian;

Petrogenesis of KREEP

NASA Technical Reports Server (NTRS)

Mckay, G. A.; Weill, D. F.

1975-01-01

Solid/liquid distribution coefficients (weight basis) were experimentally determined for a number of trace elements for olivine, orthopyroxene, plagioclase and ilmenite. Values of distribution coefficients were measured at 1200 C and a f sub O2 of 10 to the -13.0 power for liquids similar in composition to the olivine-opx-plagioclase peritectic in the pseudoternary system (Fe,Mg)2SiO4-CaAl2Si2O8-SiO2. Values were also measured at 1140 C and a f sub O2 of 10 to the -12.8 power for liquids similar in composition to high-Ti mare basalts. Major and trace element partitioning and relevant phase equilibria were used to investigate possible parent-daughter relationships between a number of highland samples and highly evolved KREEP-rich materials. Out of about 80 highlands samples tested, 33 were found to be possible parents to the KREEP-rich materials. The average composition of these samples is very similar to that of the Low-K Fra Mauro basalt (LKFM). A model is proposed to explain the production of LKFM-type material and more evolved members of the KREEP suite.

The Mass-loss Return from Evolved Stars to the Large Magellanic Cloud. IV. Construction and Validation of a Grid of Models for Oxygen-rich AGB Stars, Red Supergiants, and Extreme AGB Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, S.; Meixner, M.

2011-02-01

To measure the mass loss from dusty oxygen-rich (O-rich) evolved stars in the Large Magellanic Cloud (LMC), we have constructed a grid of models of spherically symmetric dust shells around stars with constant mass-loss rates using 2Dust. These models will constitute the O-rich model part of the "Grid of Red supergiant and Asymptotic giant branch star ModelS" (GRAMS). This model grid explores four parameters—stellar effective temperature from 2100 K to 4700 K luminosity from 103 to 106 L sun; dust shell inner radii of 3, 7, 11, and 15 R star; and 10.0 μm optical depth from 10-4 to 26. From an initial grid of ~1200 2Dust models, we create a larger grid of ~69,000 models by scaling to cover the luminosity range required by the data. These models are available online to the public. The matching in color-magnitude diagrams and color-color diagrams to observed O-rich asymptotic giant branch (AGB) and red supergiant (RSG) candidate stars from the SAGE and SAGE-Spec LMC samples and a small sample of OH/IR stars is generally very good. The extreme AGB star candidates from SAGE are more consistent with carbon-rich (C-rich) than O-rich dust composition. Our model grid suggests lower limits to the mid-infrared colors of the dustiest AGB stars for which the chemistry could be O-rich. Finally, the fitting of GRAMS models to spectral energy distributions of sources fit by other studies provides additional verification of our grid and anticipates future, more expansive efforts.

On the nature of hydrogen-rich superluminous supernovae

NASA Astrophysics Data System (ADS)

Inserra, C.; Smartt, S. J.; Gall, E. E. E.; Leloudas, G.; Chen, T.-W.; Schulze, S.; Jerkstrand, A.; Nicholl, M.; Anderson, J. P.; Arcavi, I.; Benetti, S.; Cartier, R. A.; Childress, M.; Della Valle, M.; Flewelling, H.; Fraser, M.; Gal-Yam, A.; Gutiérrez, C. P.; Hosseinzadeh, G.; Howell, D. A.; Huber, M.; Kankare, E.; Krühler, T.; Magnier, E. A.; Maguire, K.; McCully, C.; Prajs, S.; Primak, N.; Scalzo, R.; Schmidt, B. P.; Smith, M.; Smith, K. W.; Tucker, B. E.; Valenti, S.; Wilman, M.; Young, D. R.; Yuan, F.

2018-03-01

We present two hydrogen-rich superluminous supernovae (SLSNe): SN2103hx and PS15br. These objects, together with SN2008es, are the only SLSNe showing a distinct, broad H α feature during the photospheric phase; also, they show no sign of strong interaction between fast moving ejecta and circumstellar shells in their early spectra. Despite the fact that the peak luminosity of PS15br is fainter than that of the other two objects, the spectrophotometric evolution is similar to SN2103hx and different from any other supernova in a similar luminosity space. We group all of them as SLSNe II and hence they are distinct from the known class of SLSN IIn. Both transients show a strong, multicomponent H α emission after 200 d past maximum, which we interpret as an indication of the interaction of the ejecta with an asymmetric, clumpy circumstellar material. The spectra and photometric evolution of the two objects are similar to Type II supernovae, although they have much higher luminosity and evolve on slower time-scales. This is qualitatively similar to how SLSNe I compare with normal type Ic, in that the former are brighter and evolve more slowly. We apply a magnetar and an interaction semi-analytical code to fit the light curves of our two objects and SN2008es. The overall observational data set would tend to favour the magnetar, or central engine, model as the source of the peak luminosity, although the clear signature of late-time interaction indicates that interaction can play a role in the luminosity evolution of SLSNe II at some phases.

Production of C-14 and neutrons in red giants

NASA Technical Reports Server (NTRS)

Cowan, J. J.; Rose, W. K.

1977-01-01

We have examined the effects of mixing various amounts of hydrogen-rich material into the intershell convective region of red giants undergoing helium shell flashes. We find that significant amounts of C-14 can be produced via the N-14(n, p)C-14 reaction. If substantial portions of this intershell region are mixed out into the envelopes of red giants, then C-14 may be detectable in evolved stars. We find a neutron flux many orders of magnitude above the flux required for the classical s-process, and thus an intermediate neutron process (i-process) may operate in evolved red giants. In all cases studied we find substantial enhancements of O-17. These mixing models offer a plausible explanation of the observations of enhanced O-17 in the carbon star IRC 10216. For certain physical conditions we find significant enhancements of N-15 in the intershell region.

The Evolution of Carbon Stars

NASA Astrophysics Data System (ADS)

Chan, S. Josephine

1993-04-01

This dissertation is concerned with the nature of the carbon stars, unusual late-type stars in which the abundance of carbon in the photosphere is greater than that of oxygen. Data from the Infrared Astronomical Satellite (IRAS) survey has shown that carbon stars which were identified from optical surveys and those identified from the SiC dust features in their IRAS Low Resolution Spectrometer LRS spectra have different IRAS colours. The former (which will be referred to as visual carbon stars) are visually bright and have large excesses at 6 microns, while the latter group (which will be referred to as infrared carbon stars) have blackbody energy distributions. The origin of visual carbon stars has been discussed by Chan and Kwok (1988) based on the hypothesis of Willems and de Jong (1988). A complete sample of visual carbon stars detected by IRAS with 12 microns flux densities greater than 5 Jy was selected, and 207 LRS spectra were extracted for those sources without previous \\lrs data. Of these, 152 sources had new LRS spectra with reasonably good signal-to-noise ratio and 575 sources had previously released LRS spectra. All these spectra have been classified with the scheme of Volk and Cohen (1989). When the LRS spectra of these 727 IRAS CCGCS sources were examined, 15 were found to show the 9.7 microns silicate emission feature which is expected to occur only in an oxygen-rich circumstellar shell. Eight of these are reported for the first time in this dissertation. This group of visual carbon stars (hereafter called silicate carbon stars) may represent transition objects between oxygen-rich and carbon stars on the asymptotic giant branch (AGB) because the photosphere is carbon-rich while the circumstellar material resembles that from a typical M-type star. A radiative transfer dust shell model for these silicate carbon stars is presented. The model spectra produce excellent fits to the observed energy distributions of these silicate carbon stars. The J-type stars (^13C-rich carbon stars) have been suggested to be transition objects between M-type stars and C-type stars. An optical spectroscopic study of these silicate carbon stars was performed at the Dominion Astrophysical Observatory (DAO) in Victoria in 1991. CCGCS 1653, CCGCS 4222, CCGCS 4923 and CCGCS 5848 have been confirmed to be J stars. CCGCS 1158 and CCGCS 4729 are provisionally identified as J stars. A preliminary spectral analysis has also been carried out. Model calculations are presented on the evolution from the visual carbon stars to infrared carbon stars, and on the evolution of infrared carbon stars. A new empirical opacity function for the SiC grain is derived based on the LRS spectra of a selected sample of infrared carbon stars. A two-shell model has been developed with an oxygen-rich detached shell and a newly-forming SiC dust shell. The energy distributions of ~110 transition objects which are late-stage visual carbon stars or early-stage infrared carbon stars are fitted with this Interrupted Mass Loss Model. Furthermore, the model tracks successfully explain the "C" shaped distribution of the transition objects in the IRAS 12 microns/25 microns/60 microns colour-colour diagram. The energy distributions of ~150 infrared carbon stars are also matched with a radiative transfer dust shell model using only SiC dust. The colour evolution of infrared carbon stars can be explained with a continuous increase in mass loss rate on the AGB. An evolutionary scenario of AGB stars is suggested. There is a branching of M-type and C-type stars on the AGB with each branch evolving independently to the planetary nebula stage. The initial mass of the star in the main sequence may be the factor that determines which branch the star will follow. (SECTION: Dissertation Abstracts)

Clustering environments of BL Lac objects

NASA Technical Reports Server (NTRS)

Wurtz, Ronald; Ellingson, Erica; Stocke, John T.; Yee, H. K. C.

1993-01-01

We report measurements of the amplitude of the BL Lac galaxy spatial covariance function, B(gb), for the fields of five BL Lacertae objects. We present evidence for rich clusters around MS 1207+39 and MS 1407+59, and confirm high richness for the cluster containing H0414+009. We discuss the ease of 3C 66 A and find evidence for a poor cluster based on an uncertain redshift of z = 0.444. These data suggest that at least some BL Lac objects are consistent with being FR 1 radio galaxies in rich clusters.

Co-production of Nitrogen-15 and Oxygen-18 in Explosive Helium Burning and Implications for Supernova Graphite Grains

NASA Astrophysics Data System (ADS)

Bojazi, Michael

My Masters research involves simulations of a supernova whereby a shock wave of constant Mach number is sent through a 15-solar-mass star evolved to the point of core-collapse. The resulting nucleosynthesis is examined with the intent of explaining the overproduction, relative to solar values, of nitrogen-15 and oxygen-18 abundances in supernova presolar graphite grains, as experimentally determined by Groopman et al. via a NanoSIMS analysis. We find such overabundances to be present in the helium-rich zone. Oxygen-18 is leftover from presupernova helium burning while nitrogen-15 is produced by explosive helium burning. Interestingly, anomalous excesses in molybdenum-95 and molybdenum-97 abundances in SiC X grains, discovered by Pellin et al. using the CHARISMA instrument, probably arise from explosive helium burning as well. These results signal the importance of the helium-rich zone for supernova presolar grain growth. We suggest that matter deep from the supernova, which is rich in iron-peak elements, gets injected into the helium-rich zone. Small TiC grains form in this material. These subgrains then traverse the helium-rich zone and serve as seeds for the growth of the graphite or SiC X grains.

The 11 Micron Emissions of Carbon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature.

The 11 Micron Emissions of Cabon Stars

NASA Technical Reports Server (NTRS)

Goebel, J. H.; Cheeseman, P.; Gerbault, F.

1995-01-01

A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this 11.9 micron emission feature to the 11.3 micron feature.

CHARACTERIZING THE POPULATION OF BRIGHT INFRARED SOURCES IN THE SMALL MAGELLANIC CLOUD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kraemer, K. E.; Sloan, G. C.; Wood, P. R.

We have used the Infrared Spectrograph (IRS) on the Spitzer Space Telescope to observe stars in the Small Magellanic Cloud (SMC) selected from the Point Source Catalog of the Midcourse Space Experiment (MSX). We concentrate on the dust properties of the oxygen-rich evolved stars. The dust composition has smaller contributions from alumina compared to the Galaxy. This difference may arise from the lower metallicity in the SMC, but it could be a selection effect, as the SMC sample includes more stars that are brighter and thus more massive. The distribution of the SMC stars along the silicate sequence looks moremore » like the Galactic sample of red supergiants than asymptotic giant branch stars (AGBs). While many of the SMC stars are definitively on the AGB, several also show evidence of hot bottom burning. Three of the supergiants show PAH emission at 11.3 μ m. Two other sources show mixed chemistry, with both carbon-rich and oxygen-rich spectral features. One, MSX SMC 134, may be the first confirmed silicate/carbon star in the SMC. The other, MSX SMC 049, is a candidate post-AGB star. MSX SMC 145, previously considered a candidate OH/IR star, is actually an AGB star with a background galaxy at z  = 0.16 along the same line of sight. We consider the overall characteristics of all the MSX sources, the most infrared-bright objects in the SMC, in light of the higher sensitivity and resolution of Spitzer , and compare them with the object types expected from the original selection criteria. This population represents what will be seen in more distant galaxies by the upcoming James Webb Space Telescope ( JWST ). Color–color diagrams generated from the IRS spectra and the mid-infrared filters on JWST show how one can separate evolved stars from young stellar objects (YSOs) and distinguish among different classes of YSOs.« less

Characterizing the Population of Bright Infrared Sources in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Kraemer, K. E.; Sloan, G. C.; Wood, P. R.; Jones, O. C.; Egan, M. P.

2017-01-01

We have used the Infrared Spectrograph (IRS) on the Spitzer Space Telescope to observe stars in the Small Magellanic Cloud (SMC) selected from the Point Source Catalog of the Midcourse Space Experiment (MSX). We concentrate on the dust properties of the oxygen-rich evolved stars. The dust composition has smaller contributions from alumina compared to the Galaxy. This difference may arise from the lower metallicity in the SMC, but it could be a selection effect, as the SMC sample includes more stars that are brighter and thus more massive. The distribution of the SMC stars along the silicate sequence looks more like the Galactic sample of red supergiants than asymptotic giant branch stars (AGBs). While many of the SMC stars are definitively on the AGB, several also show evidence of hot bottom burning. Three of the supergiants show PAH emission at 11.3 μm. Two other sources show mixed chemistry, with both carbon-rich and oxygen-rich spectral features. One, MSX SMC 134, may be the first confirmed silicate/carbon star in the SMC. The other, MSX SMC 049, is a candidate post-AGB star. MSX SMC 145, previously considered a candidate OH/IR star, is actually an AGB star with a background galaxy at z = 0.16 along the same line of sight. We consider the overall characteristics of all the MSX sources, the most infrared-bright objects in the SMC, in light of the higher sensitivity and resolution of Spitzer, and compare them with the object types expected from the original selection criteria. This population represents what will be seen in more distant galaxies by the upcoming James Webb Space Telescope (JWST). Color-color diagrams generated from the IRS spectra and the mid-infrared filters on JWST show how one can separate evolved stars from young stellar objects (YSOs) and distinguish among different classes of YSOs.

Influence of Tool Rotational Speed and Post-Weld Heat Treatments on Friction Stir Welded Reduced Activation Ferritic-Martensitic Steel

NASA Astrophysics Data System (ADS)

Manugula, Vijaya L.; Rajulapati, Koteswararao V.; Reddy, G. Madhusudhan; Mythili, R.; Bhanu Sankara Rao, K.

2017-08-01

The effects of tool rotational speed (200 and 700 rpm) on evolving microstructure during friction stir welding (FSW) of a reduced activation ferritic-martensitic steel (RAFMS) in the stir zone (SZ), thermo-mechanically affected zone (TMAZ), and heat-affected zone (HAZ) have been explored in detail. The influence of post-weld direct tempering (PWDT: 1033 K (760 °C)/ 90 minutes + air cooling) and post-weld normalizing and tempering (PWNT: 1253 K (980 °C)/30 minutes + air cooling + tempering 1033 K (760 °C)/90 minutes + air cooling) treatments on microstructure and mechanical properties has also been assessed. The base metal (BM) microstructure was tempered martensite comprising Cr-rich M23C6 on prior austenite grain and lath boundaries with intra-lath precipitation of V- and Ta-rich MC precipitates. The tool rotational speed exerted profound influence on evolving microstructure in SZ, TMAZ, and HAZ in the as-welded and post-weld heat-treated states. Very high proportion of prior austenitic grains and martensite lath boundaries in SZ and TMAZ in the as-welded state showed lack of strengthening precipitates, though very high hardness was recorded in SZ irrespective of the tool speed. Very fine-needle-like Fe3C precipitates were found at both the rotational speeds in SZ. The Fe3C was dissolved and fresh precipitation of strengthening precipitates occurred on both prior austenite grain and sub-grain boundaries in SZ during PWNT and PWDT. The post-weld direct tempering caused coarsening and coalescence of strengthening precipitates, in both matrix and grain boundary regions of TMAZ and HAZ, which led to inhomogeneous distribution of hardness across the weld joint. The PWNT heat treatment has shown fresh precipitation of M23C6 on lath and grain boundaries and very fine V-rich MC precipitates in the intragranular regions, which is very much similar to that prevailed in BM prior to FSW. Both the PWDT and PWNT treatments caused considerable reduction in the hardness of SZ. In the as-welded state, the 200 rpm joints have shown room temperature impact toughness close to that of BM, whereas 700 rpm joints exhibited very poor impact toughness. The best combination of microstructure and mechanical properties could be obtained by employing low rotational speed of 200 rpm followed by PWNT cycle. The type and size of various precipitates, grain size, and evolving dislocation substructure have been presented and comprehensively discussed.

Mars 2007 Phoenix Scout Mission Organic Free Blank: Method to Distinguish Mars Organics from Terrestrial Organics

NASA Technical Reports Server (NTRS)

Ming, D. W.; Morris, R. V.; Woida, R.; Sutter, B.; Lauer, H. V.; Shinohara, C.; Golden, D. C.; Boynton, W. V.; Arvidson, R. E.; Stewart, R. L.;

Improved Thermal Stability of Lithium-Rich Layered Oxide by Fluorine Doping.

PubMed

Kapylou, Andrei; Song, Jay Hyok; Missiul, Aleksandr; Ham, Dong Jin; Kim, Dong Han; Moon, San; Park, Jin Hwan

2018-01-05

The thermal stability of lithium-rich layered oxide with the composition Li(Li 1/6 Ni 1/6 Co 1/6 Mn 1/2 )O 2-x F x (x=0.00 and 0.05) is evaluated for use as a cathode material in lithium-ion batteries. Thermogravimetric analysis, evolved gas analysis, and differential scanning calorimetry show that, upon fluorine doping, degradation of the lithium-rich layered oxides commences at higher temperatures and the exothermic reaction is suppressed. Hot box tests also reveal that the prismatic cell with the fluorine-doped powder does not explode, whereas that with the undoped one explodes at about 135 °C with a sudden temperature increase. XRD analysis indicates that fluorine doping imparts the lithium-rich layered oxide with better thermal stability by mitigating oxygen release at elevated temperatures that cause an exothermic reaction with the electrolyte. The origin of the reduced oxygen release from the fluorinated lithium-rich layered oxide is also discussed. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The environmental impacts on the star formation main sequence: An Hα study of the newly discovered rich cluster at z = 1.52

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koyama, Yusei; Kodama, Tadayuki; Tadaki, Ken-ichi

2014-07-01

We report the discovery of a strong over-density of galaxies in the field of a radio galaxy at z = 1.52 (4C 65.22) based on our broadband and narrow-band (Hα) photometry with the Subaru Telescope. We find that Hα emitters are located in the outskirts of the density peak (cluster core) dominated by passive red-sequence galaxies. This resembles the situation in lower-redshift clusters, suggesting that the newly discovered structure is a well-evolved rich galaxy cluster at z = 1.5. Our data suggest that the color-density and stellar mass-density relations are already in place at z ∼ 1.5, mostly driven bymore » the passive red massive galaxies residing within r{sub c} ≲ 200 kpc from the cluster core. These environmental trends almost disappear when we consider only star-forming (SF) galaxies. We do not find SFR-density or SSFR-density relations amongst SF galaxies, and the location of the SF main sequence does not significantly change with environment. Nevertheless, we find a tentative hint that star-bursting galaxies (up-scattered objects from the main sequence) are preferentially located in a small group at ∼1 Mpc away from the main body of the cluster. We also argue that the scatter of the SF main sequence could be dependent on the distance to the nearest neighboring galaxy.« less

Revisiting Robustness and Evolvability: Evolution in Weighted Genotype Spaces

PubMed Central

Partha, Raghavendran; Raman, Karthik

2014-01-01

Robustness and evolvability are highly intertwined properties of biological systems. The relationship between these properties determines how biological systems are able to withstand mutations and show variation in response to them. Computational studies have explored the relationship between these two properties using neutral networks of RNA sequences (genotype) and their secondary structures (phenotype) as a model system. However, these studies have assumed every mutation to a sequence to be equally likely; the differences in the likelihood of the occurrence of various mutations, and the consequence of probabilistic nature of the mutations in such a system have previously been ignored. Associating probabilities to mutations essentially results in the weighting of genotype space. We here perform a comparative analysis of weighted and unweighted neutral networks of RNA sequences, and subsequently explore the relationship between robustness and evolvability. We show that assuming an equal likelihood for all mutations (as in an unweighted network), underestimates robustness and overestimates evolvability of a system. In spite of discarding this assumption, we observe that a negative correlation between sequence (genotype) robustness and sequence evolvability persists, and also that structure (phenotype) robustness promotes structure evolvability, as observed in earlier studies using unweighted networks. We also study the effects of base composition bias on robustness and evolvability. Particularly, we explore the association between robustness and evolvability in a sequence space that is AU-rich – sequences with an AU content of 80% or higher, compared to a normal (unbiased) sequence space. We find that evolvability of both sequences and structures in an AU-rich space is lesser compared to the normal space, and robustness higher. We also observe that AU-rich populations evolving on neutral networks of phenotypes, can access less phenotypic variation compared to normal populations evolving on neutral networks. PMID:25390641

PyEvolve: a toolkit for statistical modelling of molecular evolution.

PubMed

Butterfield, Andrew; Vedagiri, Vivek; Lang, Edward; Lawrence, Cath; Wakefield, Matthew J; Isaev, Alexander; Huttley, Gavin A

2004-01-05

Examining the distribution of variation has proven an extremely profitable technique in the effort to identify sequences of biological significance. Most approaches in the field, however, evaluate only the conserved portions of sequences - ignoring the biological significance of sequence differences. A suite of sophisticated likelihood based statistical models from the field of molecular evolution provides the basis for extracting the information from the full distribution of sequence variation. The number of different problems to which phylogeny-based maximum likelihood calculations can be applied is extensive. Available software packages that can perform likelihood calculations suffer from a lack of flexibility and scalability, or employ error-prone approaches to model parameterisation. Here we describe the implementation of PyEvolve, a toolkit for the application of existing, and development of new, statistical methods for molecular evolution. We present the object architecture and design schema of PyEvolve, which includes an adaptable multi-level parallelisation schema. The approach for defining new methods is illustrated by implementing a novel dinucleotide model of substitution that includes a parameter for mutation of methylated CpG's, which required 8 lines of standard Python code to define. Benchmarking was performed using either a dinucleotide or codon substitution model applied to an alignment of BRCA1 sequences from 20 mammals, or a 10 species subset. Up to five-fold parallel performance gains over serial were recorded. Compared to leading alternative software, PyEvolve exhibited significantly better real world performance for parameter rich models with a large data set, reducing the time required for optimisation from approximately 10 days to approximately 6 hours. PyEvolve provides flexible functionality that can be used either for statistical modelling of molecular evolution, or the development of new methods in the field. The toolkit can be used interactively or by writing and executing scripts. The toolkit uses efficient processes for specifying the parameterisation of statistical models, and implements numerous optimisations that make highly parameter rich likelihood functions solvable within hours on multi-cpu hardware. PyEvolve can be readily adapted in response to changing computational demands and hardware configurations to maximise performance. PyEvolve is released under the GPL and can be downloaded from http://cbis.anu.edu.au/software.

Differential Evolution and Neofunctionalization of Snake Venom Metalloprotease Domains*

PubMed Central

Brust, Andreas; Sunagar, Kartik; Undheim, Eivind A.B.; Vetter, Irina; Yang, Daryl C.; Casewell, Nicholas R.; Jackson, Timothy N. W.; Koludarov, Ivan; Alewood, Paul F.; Hodgson, Wayne C.; Lewis, Richard J.; King, Glenn F.; Antunes, Agostinho; Hendrikx, Iwan; Fry, Bryan G.

2013-01-01

Snake venom metalloproteases (SVMP) are composed of five domains: signal peptide, propeptide, metalloprotease, disintegrin, and cysteine-rich. Secreted toxins are typically combinatorial variations of the latter three domains. The SVMP-encoding genes of Psammophis mossambicus venom are unique in containing only the signal and propeptide domains. We show that the Psammophis SVMP propeptide evolves rapidly and is subject to a high degree of positive selection. Unlike Psammophis, some species of Echis express both the typical multidomain and the unusual monodomain (propeptide only) SVMP, with the result that a lower level of variation is exerted upon the latter. We showed that most mutations in the multidomain Echis SVMP occurred in the protease domain responsible for proteolytic and hemorrhagic activities. The cysteine-rich and disintegrin-like domains, which are putatively responsible for making the P-III SVMPs more potent than the P-I and P-II forms, accumulate the remaining variation. Thus, the binding sites on the molecule's surface are evolving rapidly whereas the core remains relatively conserved. Bioassays conducted on two post-translationally cleaved novel proline-rich peptides from the P. mossambicus propeptide domain showed them to have been neofunctionalized for specific inhibition of mammalian a7 neuronal nicotinic acetylcholine receptors. We show that the proline rich postsynaptic specific neurotoxic peptides from Azemiops feae are the result of convergent evolution within the precursor region of the C-type natriuretic peptide instead of the SVMP. The results of this study reinforce the value of studying obscure venoms for biodiscovery of novel investigational ligands. PMID:23242553

Differential evolution and neofunctionalization of snake venom metalloprotease domains.

PubMed

Brust, Andreas; Sunagar, Kartik; Undheim, Eivind A B; Vetter, Irina; Yang, Daryl C; Yang, Dary C; Casewell, Nicholas R; Jackson, Timothy N W; Koludarov, Ivan; Alewood, Paul F; Hodgson, Wayne C; Lewis, Richard J; King, Glenn F; Antunes, Agostinho; Hendrikx, Iwan; Fry, Bryan G

2013-03-01

Snake venom metalloproteases (SVMP) are composed of five domains: signal peptide, propeptide, metalloprotease, disintegrin, and cysteine-rich. Secreted toxins are typically combinatorial variations of the latter three domains. The SVMP-encoding genes of Psammophis mossambicus venom are unique in containing only the signal and propeptide domains. We show that the Psammophis SVMP propeptide evolves rapidly and is subject to a high degree of positive selection. Unlike Psammophis, some species of Echis express both the typical multidomain and the unusual monodomain (propeptide only) SVMP, with the result that a lower level of variation is exerted upon the latter. We showed that most mutations in the multidomain Echis SVMP occurred in the protease domain responsible for proteolytic and hemorrhagic activities. The cysteine-rich and disintegrin-like domains, which are putatively responsible for making the P-III SVMPs more potent than the P-I and P-II forms, accumulate the remaining variation. Thus, the binding sites on the molecule's surface are evolving rapidly whereas the core remains relatively conserved. Bioassays conducted on two post-translationally cleaved novel proline-rich peptides from the P. mossambicus propeptide domain showed them to have been neofunctionalized for specific inhibition of mammalian a7 neuronal nicotinic acetylcholine receptors. We show that the proline rich postsynaptic specific neurotoxic peptides from Azemiops feae are the result of convergent evolution within the precursor region of the C-type natriuretic peptide instead of the SVMP. The results of this study reinforce the value of studying obscure venoms for biodiscovery of novel investigational ligands.

Structural polymorphism of a cytosine-rich DNA sequence forming i-motif structure: Exploring pH based biosensors.

PubMed

Ahmed, Saami; Kaushik, Mahima; Chaudhary, Swati; Kukreti, Shrikant

2018-05-01

Sequence recognition and conformational polymorphism enable DNA to emerge out as a substantial tool in fabricating the devices within nano-dimensions. These DNA associated nano devices work on the principle of conformational switches, which can be facilitated by many factors like sequence of DNA/RNA strand, change in pH or temperature, enzyme or ligand interactions etc. Thus, controlling these DNA conformational changes to acquire the desired function is significant for evolving DNA hybridization biosensor, used in genetic screening and molecular diagnosis. For exploring this conformational switching ability of cytosine-rich DNA oligonucleotides as a function of pH for their potential usage as biosensors, this study has been designed. A C-rich stretch of DNA sequence (5'-TCCCCCAATTAATTCCCCCA-3'; SG20c) has been investigated using UV-Thermal denaturation, poly-acrylamide gel electrophoresis and CD spectroscopy. The SG20c sequence is shown to adopt various topologies of i-motif structure at low pH. This pH dependent transition of SG20c from unstructured single strand to unimolecular and bimolecular i-motif structures can further be exploited for its utilization as switching on/off pH-based biosensors. Copyright © 2018. Published by Elsevier B.V.

Synthesis of C-rich dust in CO nova outbursts

NASA Astrophysics Data System (ADS)

José, Jordi; Halabi, Ghina M.; El Eid, Mounib F.

2016-09-01

Context. Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material transferred onto the white dwarf piles up under degenerate conditions, driving a thermonuclear runaway. In these outbursts, about 10-7-10-3 M⊙, enriched in CNO and sometimes other intermediate-mass elements (e.g., Ne, Na, Mg, or Al for ONe novae) are ejected into the interstellar medium. The large concentrations of metals spectroscopically inferred in the nova ejecta reveal that the solar-like material transferred from the secondary mixes with the outermost layers of the underlying white dwarf. Aims: Most theoretical models of nova outbursts reported to date yield, on average, outflows characterized by O > C, from which, in principle, only oxidized condensates (e.g., O-rich grains) would be expected. Methods: To specifically address whether CO novae can actually produce C-rich dust, six different hydrodynamic nova models have been evolved, from accretion to the expansion and ejection stages, with different choices for the composition of the substrate with which the solar-like accreted material mixes. Updated chemical profiles inside the H-exhausted core have been used, based on stellar evolution calculations for a progenitor of 8 M⊙ through H- and He-burning phases. Results: We show that these profiles lead to C-rich ejecta after the nova outburst. This extends the possible contribution of novae to the inventory of presolar grains identified in meteorites, particularly in a number of carbonaceous phases (I.e., nanodiamonds, silicon carbides, and graphites).

Discovery of carbon-rich Miras in the Galactic bulge

NASA Astrophysics Data System (ADS)

Matsunaga, Noriyuki; Menzies, John W.; Feast, Michael W.; Whitelock, Patricia A.; Onozato, Hiroki; Barway, Sudhanshu; Aydi, Elias

2017-08-01

Only one carbon-rich (C-rich, hereinafter) Mira variable has so far been suggested as a member of the Galactic bulge and this is in a symbiotic system. Here we describe a method for selecting C-rich candidates from an infrared colour-colour diagram, (J - Ks) versus ([9] - [18]). Follow-up low-resolution spectroscopy resulted in the detection of eight C-rich Mira variables from a sample of 36 candidates towards the Galactic bulge. Our near-infrared photometry indicates that two of these, including the known symbiotic, are closer than the main body of the bulge while a third is a known foreground object. Of the five bulge members, one shows He I and [O II] emission and is possibly another symbiotic star. Our method is useful for identifying rare C-rich stars in the Galactic bulge and elsewhere. The age of these C-rich stars and the evolutionary process which produced them remain uncertain. They could be old and the products of either binary mass transfer or mergers, I.e. the descendants of blue stragglers, but we cannot rule out the possibility that they belong to a small in situ population of metal-poor intermediate age (<5 Gyr) stars in the bulge or that they have been accreted from a dwarf galaxy.

Kassiopeia: a modern, extensible C++ particle tracking package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Furse, Daniel; Groh, Stefan; Trost, Nikolaus

The Kassiopeia particle tracking framework is an object-oriented software package using modern C++ techniques, written originally to meet the needs of the KATRIN collaboration. Kassiopeia features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease-of-use for novice programmers. To solve Kassiopeia's target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur inmore » flight such as bulk scattering and decay, and stochastic surface processes occurring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle's state evolves. Thanks to the very general approach taken by Kassiopeia it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopeia.« less

Kassiopeia: a modern, extensible C++ particle tracking package

DOE PAGES

Furse, Daniel; Groh, Stefan; Trost, Nikolaus; ...

2017-05-16

The Kassiopeia particle tracking framework is an object-oriented software package using modern C++ techniques, written originally to meet the needs of the KATRIN collaboration. Kassiopeia features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease-of-use for novice programmers. To solve Kassiopeia's target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur inmore » flight such as bulk scattering and decay, and stochastic surface processes occurring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle's state evolves. Thanks to the very general approach taken by Kassiopeia it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopeia.« less

Kassiopeia: a modern, extensible C++ particle tracking package

NASA Astrophysics Data System (ADS)

Furse, Daniel; Groh, Stefan; Trost, Nikolaus; Babutzka, Martin; Barrett, John P.; Behrens, Jan; Buzinsky, Nicholas; Corona, Thomas; Enomoto, Sanshiro; Erhard, Moritz; Formaggio, Joseph A.; Glück, Ferenc; Harms, Fabian; Heizmann, Florian; Hilk, Daniel; Käfer, Wolfgang; Kleesiek, Marco; Leiber, Benjamin; Mertens, Susanne; Oblath, Noah S.; Renschler, Pascal; Schwarz, Johannes; Slocum, Penny L.; Wandkowsky, Nancy; Wierman, Kevin; Zacher, Michael

2017-05-01

The Kassiopeia particle tracking framework is an object-oriented software package using modern C++ techniques, written originally to meet the needs of the KATRIN collaboration. Kassiopeia features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease-of-use for novice programmers. To solve Kassiopeia's target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur in flight such as bulk scattering and decay, and stochastic surface processes occurring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle’s state evolves. Thanks to the very general approach taken by Kassiopeia it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopeia.

Energy storage and fecundity explain deviations from ecological stoichiometry predictions under global warming and size-selective predation.

PubMed

Zhang, Chao; Jansen, Mieke; De Meester, Luc; Stoks, Robby

2016-11-01

A key challenge for ecologists is to predict how single and joint effects of global warming and predation risk translate from the individual level up to ecosystem functions. Recently, stoichiometric theory linked these levels through changes in body stoichiometry, predicting that both higher temperatures and predation risk induce shifts in energy storage (increases in C-rich carbohydrates and reductions in N-rich proteins) and body stoichiometry (increases in C : N and C : P). This promising theory, however, is rarely tested and assumes that prey will divert energy away from reproduction under predation risk, while under size-selective predation, prey instead increase fecundity. We exposed the water flea Daphnia magna to 4 °C warming and fish predation risk to test whether C-rich carbohydrates increase and N-rich proteins decrease, and as a result, C : N and C : P increase under warming and predation risk. Unexpectedly, warming decreased body C : N, which was driven by reductions in C-rich fat and sugar contents while the protein content did not change. This reflected a trade-off where the accelerated intrinsic growth rate under warming occurred at the cost of a reduced energy storage. Warming reduced C : N less and only increased C : P and N : P in the fish-period Daphnia. These evolved stoichiometric responses to warming were largely driven by stronger warming-induced reductions in P than in C and N and could be explained by the better ability to deal with warming in the fish-period Daphnia. In contrast to theory predictions, body C : N decreased under predation risk due to a strong increase in the N-rich protein content that offsets the increase in C-rich fat content. The higher investment in fecundity (more N-rich eggs) under predation risk contributed to this stronger increase in protein content. Similarly, the lower body C : N of pre-fish Daphnia also matched their higher fecundity. Warming and predation risk independently shaped body stoichiometry, largely by changing levels of energy storage molecules. Our results highlight that two widespread patterns, the trade-off between rapid development and energy storage and the increased investment in reproduction under size-selective predation, cause predictable deviations from current ecological stoichiometry theory. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Recurring Necrotic Enteritis Outbreaks in Commercial Broiler Chicken Flocks Strongly Influence Toxin Gene Carriage and Species Richness in the Resident Clostridium perfringens Population

PubMed Central

Gaucher, Marie-Lou; Perron, Gabriel G.; Arsenault, Julie; Letellier, Ann; Boulianne, Martine; Quessy, Sylvain

2017-01-01

Extensive use of antibiotic growth promoters (AGPs) in food animals has been questioned due to the globally increasing problem of antibiotic resistance. For the poultry industry, digestive health management following AGP withdrawal in Europe has been a challenge, especially the control of necrotic enteritis. Much research work has focused on gut health in commercial broiler chicken husbandry. Understanding the behavior of Clostridium perfringens in its ecological niche, the poultry barn, is key to a sustainable and cost-effective production in the absence of AGPs. Using polymerase chain reaction and pulsed-field gel electrophoresis, we evaluated how the C. perfringens population evolved in drug-free commercial broiler chicken farms, either healthy or affected with recurring clinical necrotic enteritis outbreaks, over a 14-month period. We show that a high genotypic richness was associated with an increased risk of clinical necrotic enteritis. Also, necrotic enteritis-affected farms had a significant reduction of C. perfringens genotypic richness over time, an increase in the proportion of C. perfringens strains harboring the cpb2 gene, the netB gene, or both. Thus, necrotic enteritis occurrence is correlated with the presence of an initial highly diverse C. perfringens population, increasing the opportunity for the selective sweep of particularly virulent genotypes. Disease outbreaks also appear to largely influence the evolution of this bacterial species in poultry farms over time. PMID:28567032

Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC 6720

PubMed Central

Cox, N. L. J.; Pilleri, P.; Berné, O.; Cernicharo, J.; Joblin, C.

2015-01-01

Evolved stars are primary sources for the formation of polycyclic aromatic hydrocarbons (PAHs) and dust grains. Their circumstellar chemistry is usually designated as either oxygen-rich or carbon-rich, although dual-dust chemistry objects, whose infrared spectra reveal both silicate- and carbon-dust features, are also known. The exact origin and nature of this dual-dust chemistry is not yet understood. Spitzer-IRS mid-infrared spectroscopic imaging of the nearby, oxygen-rich planetary nebula NGC 6720 reveals the presence of the 11.3 μm aromatic (PAH) emission band. It is attributed to emission from neutral PAHs, since no band is observed in the 7–8 μm range. The spatial distribution of PAHs is found to closely follow that of the warm clumpy molecular hydrogen emission. Emission from both neutral PAHs and warm H2 is likely to arise from photo-dissociation regions associated with dense knots that are located within the main ring. The presence of PAHs together with the previously derived high abundance of free carbon (relative to CO) suggest that the local conditions in an oxygen-rich environment can also become conducive to in-situ formation of large carbonaceous molecules, such as PAHs, via a bottom-up chemical pathway. In this scenario, the same stellar source can enrich the interstellar medium with both oxygen-rich dust and large carbonaceous molecules. PMID:26924856

Magmatic and hydrothermal R.E.E. fractionation in the Xihuashan granites (SE China)

NASA Astrophysics Data System (ADS)

Maruéjol, Patricia; Cuney, Michel; Turpin, Laurent

1990-11-01

The Xihuashan stock (South Jiangxi, China) is composed of cogenetic granitic units (granites Xe, γa, γc, γd and γb) and emplaced during the Yanshanian orogeny (153±0.2 Ma). They are two feldspars, Fe-rich biotite±garnet and slightly peraluminous granites. Primary accessory minerals are apatite 1, monazite, zircon, uranothorite±xenotime in granites Xe and γa, zircon, uranothorite, uraninite, betafite, xenotime 1; hydrothermal minerals are monazite altered into parisite and apatite 2, Y-rich parisite, yttroparisite, Y-rich fluorite and xenotime 2 in granites γc and γb. Petrographic observations, major element, REE, Y and Rb-Sr isotropic data point to a magmatic suite (granites Xe and γa → granites γc and γd → granite γb) distinct from hydrothermal Na-or K-alteration of γb. From granite Xe to granite γb, LREE, Eu, Th and Zr content are strongly depleted, while HREE, Y and U content increase. During K-alteration of γb, these variations are of minor importance. Major and accessory mineral evidences, geochemical and fluid inclusion results indicate two successive alteration fluids interacting with γb, (1) a late-magmatic F- and CO2-rich fluid and (2) a post-magmatic, aqueous and slightly saline fluid. The depletion of LREE and Th content and the increase in HREE, Y and U content correspond, in the magmatic suite to the early fractionation of monazite in the granites where there is no hydrothermal alteration (granites Xe and γe) and to the hydrothermal alteration of monazite into parisite and secondary apatite, intense new formation of yttroparisite, Y enrichment and U loss in the uranothorite and late crystallization of uraninite in the granites γc and γb. Moreover, simulated crystallization of monazite and temperature of monazite saturation show early fractionation of monazite from the magma in the less evolved granites (Xe and γe) and prevailing hydrothermal leaching of monazite in the most evolved granites (γc-γd and γb) related to a late-magmetic event. The slight variations of REE, Y, Th and U content in the K-altered granites compared to granite γb emphazes the distinct chemical nature of the successive hydrothermal fluids. Rb-Sr and Sm-Nd isotopic results point to a 30 Ma period of time between the late-magmatic and the post-magmatic fluid circulation.

Affect influences feature binding in memory: Trading between richness and strength of memory representations.

PubMed

Spachtholz, Philipp; Kuhbandner, Christof; Pekrun, Reinhard

2016-10-01

Research has shown that long-term memory representations of objects are formed as a natural product of perception even without any intentional memorization. It is not known, however, how rich these representations are in terms of the number of bound object features. In particular, because feature binding rests on resource-limited processes, there may be a context-dependent trade-off between the quantity of stored features and their memory strength. The authors examined whether affective state may bring about such a trade-off. Participants incidentally encoded pictures of real-world objects while experiencing positive or negative affect, and the authors later measured memory for 2 features. Results showed that participants traded between richness and strength of memory representations as a function of affect, with positive affect tuning memory formation toward richness and negative affect tuning memory formation toward strength. These findings demonstrate that memory binding is a flexible process that is modulated by affective state. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Observations and modeling of cool, evolved stars: from chromospheric to wind regions

NASA Astrophysics Data System (ADS)

Rau, Gioia; Carpenter, Ken G.; Nielsen, Krister E.; Kober, Gladys V.; Josef Hron, Bernard Aringer, Kjell Eriksson, Paola Marigo, Claudia Paladini

2018-01-01

Evolved stars are fundamental contributors to the enrichment of the interstellar medium, via their mass loss, with heavy elements produced in their interior, and with the dust formed in their envelope. We present the results of the first systematic comparison (Rau et al. 2017, 2015) of multi-technique observations of a sample of C-rich Mira, semi-regular and irregular stars with the predictions from dynamic model atmospheres (Mattsson et al. 2010) and simpler models based on hydrostatic atmospheres combined with dusty envelopes. The chromosphere, located in the outer atmosphere of these stars, plays a crucial role in driving the mass loss in evolved K-M giant stars (see e.g. Carpenter et al. 2014, 1988). Despite recent efforts, details of the mass-loss scenario remain mysterious, as well as a complete understanding of the dynamic line formation regions, profiles, and structures. To solve these riddles, we present observation of flow and turbulent velocities, together with preliminary derivation of thermodynamic constraints for theoretical models (Rau, Carpenter, et al., in prep).

Dusty Mass Loss from Galactic Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, Sundar; Meixner, Margaret; Kastner, Joel H.

2016-06-01

We are probing how mass loss from Asymptotic Giant Branch (AGB) stars depends upon their metallicity. Asymptotic giant branch (AGB) stars are evolved stars that eject large parts of their mass in outflows of dust and gas in the final stages of their lives. Our previous studies focused on mass loss from AGB stars in lower metallicity galaxies: the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). In our present study, we analyze AGB star mass loss in the Galaxy, with special attention to the Bulge, to investigate how mass loss differs in an overall higher metallicity environment. We construct radiative transfer models of the spectral energy distributions (SEDs) of stars in the Galaxy identified as AGB stars from infrared and optical surveys. Our Magellanic Cloud studies found that the AGB stars with the highest mass loss rates tended to have outflows with carbon-rich dust, and that overall more carbon-rich (C-rich) dust than oxygen-rich (O-rich) was produced by AGB stars in both LMC and SMC. Our radiative transfer models have enabled us to determine reliably the dust chemistry of the AGB star from the best-fit model. For our Galactic sample, we are investigating both the dust chemistries of the AGB stars and their mass-loss rates, to compare the balance of C-rich dust to O-rich dust between the Galactic bulge and the Magellanic Clouds. We are also constructing detailed dust opacity models of AGB stars in the Galaxy for which we have infrared spectra; e.g., from the Spitzer Space Telescope Infrared Spectrograph (IRS). This detailed dust modeling of spectra informs our choice of dust properties to use in radiative transfer modeling of SEDs of Galactic AGB stars. BAS acknowledges funding from NASA ADAP grant NNX15AF15G.

SALT Spectroscopy of Evolved Massive Stars

NASA Astrophysics Data System (ADS)

Kniazev, A. Y.; Gvaramadze, V. V.; Berdnikov, L. N.

2017-06-01

Long-slit spectroscopy with the Southern African Large Telescope (SALT) of central stars of mid-infrared nebulae detected with the Spitzer Space Telescope and Wide-Field Infrared Survey Explorer (WISE) led to the discovery of numerous candidate luminous blue variables (cLBVs) and other rare evolved massive stars. With the recent advent of the SALT fiber-fed high-resolution echelle spectrograph (HRS), a new perspective for the study of these interesting objects is appeared. Using the HRS we obtained spectra of a dozen newly identified massive stars. Some results on the recently identified cLBV Hen 3-729 are presented.

Predictions for the secondary CO, C and O gas content of debris discs from the destruction of volatile-rich planetesimals

NASA Astrophysics Data System (ADS)

Kral, Quentin; Matrà, Luca; Wyatt, Mark C.; Kennedy, Grant M.

2017-07-01

This paper uses observations of dusty debris discs, including a growing number of gas detections in these systems, to test our understanding of the origin and evolution of this gaseous component. It is assumed that all debris discs with icy planetesimals create second generation CO, C and O gas at some level, and the aim of this paper is to predict that level and assess its observability. We present a new semi-analytical equivalent of the numerical model of Kral et al. allowing application to large numbers of systems. That model assumes CO is produced from volatile-rich solid bodies at a rate that can be predicted from the debris discs fractional luminosity. CO photodissociates rapidly into C and O that then evolve by viscous spreading. This model provides a good qualitative explanation of all current observations, with a few exceptional systems that likely have primordial gas. The radial location of the debris and stellar luminosity explain some non-detections, e.g. close-in debris (like HD 172555) is too warm to retain CO, while high stellar luminosities (like η Tel) result in short CO lifetimes. We list the most promising targets for gas detections, predicting >15 CO detections and >30 C I detections with ALMA, and tens of C II and O I detections with future far-IR missions. We find that CO, C I, C II and O I gas should be modelled in non-LTE for most stars, and that CO, C I and O I lines will be optically thick for the most gas-rich systems. Finally, we find that radiation pressure, which can blow out C I around early-type stars, can be suppressed by self-shielding.

Saturating effects of species diversity on life-history evolution in bacteria.

PubMed

Fiegna, Francesca; Scheuerl, Thomas; Moreno-Letelier, Alejandra; Bell, Thomas; Barraclough, Timothy G

2015-09-22

Species interactions can play a major role in shaping evolution in new environments. In theory, species interactions can either stimulate evolution by promoting coevolution or inhibit evolution by constraining ecological opportunity. The relative strength of these effects should vary as species richness increases, and yet there has been little evidence for evolution of component species in communities. We evolved bacterial microcosms containing between 1 and 12 species in three different environments. Growth rates and yields of isolates that evolved in communities were lower than those that evolved in monocultures, consistent with recent theory that competition constrains species to specialize on narrower sets of resources. This effect saturated or reversed at higher levels of richness, consistent with theory that directional effects of species interactions should weaken in more diverse communities. Species varied considerably, however, in their responses to both environment and richness levels. Mechanistic models and experiments are now needed to understand and predict joint evolutionary dynamics of species in diverse communities. © 2015 The Authors.

To be or not to be Asymmetric? VLTI/MIDI and the Mass-loss Geometry of AGB Stars

NASA Astrophysics Data System (ADS)

Paladini, C.; Klotz, D.; Sacuto, S.; Lagadec, E.; Wittkowski, M.; Richichi, A.; Hron, J.; Jorissen, A.; Groenewegen, M. A. T.; Kerschbaum, F.; Verhoelst, T.; Rau, G.; Olofsson, H.; Zhao-Geisler, R.; Matter, A.

2017-06-01

The Mid-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) has been used to spatially resolve the dust-forming region of 14 asymptotic giant branch (AGB) stars with different chemistry (O-rich and C-rich) and variability types (Miras, semi-regular, and irregular variables). The main goal of the programme was to detect deviations from spherical symmetry in the dust-forming region of these stars. All the stars of the sample are well resolved with the VLTI, and five are asymmetric and O-rich. This finding contrasts with observations in the near-infrared, where the C-rich objects are found to be more asymmetric than the O-rich ones. The nature of the asymmetric structures so far detected (dusty discs versus blobs)remains uncertain and will require imaging on milli-arcsecond scales.

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

NASA Astrophysics Data System (ADS)

Jones, O. C.; Kemper, F.; Sargent, B. A.; McDonald, I.; Gielen, C.; Woods, Paul M.; Sloan, G. C.; Boyer, M. L.; Zijlstra, A. A.; Clayton, G. C.; Kraemer, K. E.; Srinivasan, S.; Ruffle, P. M. E.

2012-12-01

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer Infrared Spectrograph and Infrared Space Observatory Short Wavelength Spectrometer spectra of 217 oxygen-rich asymptotic giant branch and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds, and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 μm. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ˜10-9 M⊙ yr-1. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-μm feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-μm band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.

The Quality Control Circle: Is It for Education?

ERIC Educational Resources Information Center

Land, Arthur J.

From its start in Japan after World War II, the Quality Control Circle (Q.C.) approach to management and organizational operation evolved into what it is today: people doing similar work meeting regularly to identify, objectively analyze, and develop solutions to problems. The Q.C. approach meets Maslow's theory of motivation by inviting…

Sphene and zircon in the Highland Range volcanic sequence (Miocene, southern Nevada, USA): Elemental partitioning, phase relations, and influence on evolution of silicic magma

USGS Publications Warehouse

Colombini, L.L.; Miller, C.F.; Gualda, G.A.R.; Wooden, J.L.; Miller, J.S.

2011-01-01

Sphene is prominent in Miocene plutonic rocks ranging from diorite to granite in southern Nevada, USA, but it is restricted to rhyolites in coeval volcanic sequences. In the Highland Range volcanic sequence, sphene appears as a phenocryst only in the most evolved rocks (72-77 mass% SiO2; matrix glass 77-78 mass% SiO2). Zr-in-sphene temperatures of crystallization are mostly restricted to 715 and 755??C, in contrast to zircon (710-920??C, Ti-in-zircon thermometry). Sphene rim/glass Kds for rare earth elements are extremely high (La 120, Sm 1200, Gd 1300, Lu 240). Rare earth elements, especially the middle REE (MREE), decrease from centers to rims of sphene phenocrysts along with Zr, demonstrating the effect of progressive sphene fractionation. Whole rocks and glasses have MREE-depleted, U-shaped REE patterns as a consequence of sphene fractionation. Within the co-genetic, sphene-rich Searchlight pluton, only evolved leucogranites show comparable MREE depletion. These results indicate that sphene saturation in intruded and extruded magmas occurred only in highly evolved melts: abundant sphene in less silicic plutonic rocks represents a late-stage 'bloom' in fractionated interstitial melt. ?? 2011 Springer-Verlag.

Low-mass White Dwarfs with Hydrogen Envelopes as a Missing Link in the Tidal Disruption Menu

NASA Astrophysics Data System (ADS)

Law-Smith, Jamie; MacLeod, Morgan; Guillochon, James; Macias, Phillip; Ramirez-Ruiz, Enrico

2017-06-01

We construct a menu of objects that can give rise to bright flares when disrupted by massive black holes (BHs), ranging from planets to evolved stars. Through their tidal disruption, main sequence and evolved stars can effectively probe the existence of otherwise quiescent supermassive BHs, and white dwarfs can probe intermediate mass BHs. Many low-mass white dwarfs possess extended hydrogen envelopes, which allow for the production of prompt flares in disruptive encounters with moderately massive BHs of 105-{10}7 {M}⊙ —masses that may constitute the majority of massive BHs by number. These objects are a missing link in two ways: (1) for probing moderately massive BHs and (2) for understanding the hydrodynamics of the disruption of objects with tenuous envelopes. A flare arising from the tidal disruption of a 0.17 {M}⊙ white dwarf by a {10}5 {M}⊙ {BH} reaches a maximum between 0.6 and 11 days, with a peak fallback rate that is usually super-Eddington and results in a flare that is likely brighter than a typical tidal disruption event. Encounters stripping only the envelope can provide hydrogen-only fallback, while encounters disrupting the core evolve from H- to He-rich fallback. While most tidal disruption candidates observed thus far are consistent with the disruptions of main sequence stars, the rapid timescales of nuclear transients such as Dougie and PTF10iya are naturally explained by the disruption of low-mass white dwarfs. As the number of observed flares continues to increase, the menu presented here will be essential for characterizing nuclear BHs and their environments through tidal disruptions.

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

PubMed Central

Margutti, Raffaella; Kamble, A.; Milisavljevic, D.; Zapartas, E.; de Mink, S. E.; Drout, M.; Chornock, R.; Risaliti, G.; Zauderer, B. A.; Bietenholz, M.; Cantiello, M.; Chakraborti, S.; Chomiuk, L.; Fong, W.; Grefenstette, B.; Guidorzi, C.; Kirshner, R.; Parrent, J. T.; Patnaude, D.; Soderberg, A. M.; Gehrels, N. C.; Harrison, F.

2017-01-01

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ~40 keV. SN 2014C shows ordinary explosion parameters (Ek ~ 1.8 × 1051 erg and Mej ~ 1.7 M⊙). However, over an ~1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum, from radio to hard X-rays, and revealed the presence of a massive shell of ~1 M⊙of hydrogen-rich material at ~6 × 1016 cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ~10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 103–104 years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role. PMID:28684881

INFRARED TWO-COLOR DIAGRAMS FOR AGB STARS, POST-AGB STARS, AND PLANETARY NEBULAE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Suh, Kyung-Won, E-mail: kwsuh@chungbuk.ac.kr

2015-08-01

We present various infrared two-color diagrams (2CDs) for asymptotic giant branch (AGB) stars, post-AGB stars, and Planetary Nebulae (PNe) and investigate possible evolutionary tracks. We use catalogs from the available literature for the sample of 4903 AGB stars (3373 O-rich; 1168 C-rich; 362 S-type), 660 post-AGB stars (326 post-AGB; 334 pre-PN), and 1510 PNe in our Galaxy. For each object in the catalog, we cross-identify the IRAS, AKARI, Midcourse Space Experiment, and 2MASS counterparts. The IR 2CDs can provide useful information about the structure and evolution of the dust envelopes as well as the central stars. To find possible evolutionarymore » tracks from AGB stars to PNe on the 2CDs, we investigate spectral evolution of post-AGB stars by making simple but reasonable assumptions on the evolution of the central star and dust shell. We perform radiative transfer model calculations for the detached dust shells around evolving central stars in the post-AGB phase. We find that the theoretical dust shell model tracks using dust opacity functions of amorphous silicate and amorphous carbon roughly coincide with the densely populated observed points of AGB stars, post-AGB stars, and PNe on various IR 2CDs. Even though some discrepancies are inevitable, the end points of the theoretical post-AGB model tracks generally converge in the region of the observed points of PNe on most 2CDs.« less

An experimental approach to manufacturing technology of historical glass (XIII-XV centuries). Comparison with current glassmaking technology.

NASA Astrophysics Data System (ADS)

Tarrago, Mariona; Gimeno, Domingo; Bazzocchi, Flavia; Garcia-Valles, Maite; Martinez, Salvador

2015-04-01

One of the major and less explored issues in the characterization of historical glasses is the determination of their viscosity as a function of temperature in order to constrain technological aspects of glass production. Until now, assumptions on temperatures have been based on mathematical models based on chemical compositions. Hence, the topic of this work is to explore the technology of stained glass production related to the workability and melting process of the glass by experimental laboratory measurements. This work presents the analysis of viscosity of glasses from different historical sites and chemical compositions: four from Santes Creus (Tarragona, XIII century), two of classical medieval stained glass window from Santa Maria de Pedralbes (Barcelona, mid XIV century), and three of evolved late-medieval type from Santa Maria del Mar (Barcelona first half of XV century), and one sample of soda-lime industrial glass by means of Hot-Stage Microscopy and glass transformation temperature Tg by dilatometry. These data are then compared to the predictions on theoretical viscosity obtained from mathematical models based on chemical composition. These samples are classified according to their major modifier in: Na-rich (12-17% of Na2O, between 65-77% of SiO2 and less than 3 % of K2O); Ca-rich (29% of CaO, 54% of SiO2, 4% of K2O, and 4% of Na2O); K-Ca-rich (17 to 21% of K2O, more than 14% of CaO, 49-55% of SiO2and less than 2% of Na2O); Na-Ca-rich (12-14% of Na2O, 9-15% of CaO, 57-71% of SiO2 and < 6% of K2O). Glass transition temperature (Tg) is correlated to chemical composition: 464-492 °C for Na-rich, 645 °C for Ca-rich, 582-586 °C for K-Ca-rich and 497-542 °C for Na-Ca-rich glasses. Experimental viscosity-temperature curves are traced using Tg and fixed viscosity points measured by Hot-Stage microscopy (according to German standard 51730) in order to provide more accurate insight into the phases of glass production process (melting, working, conditioning and annealing ranges). These results are also compared to mathematical models of glass viscosity based on chemical composition. The annealing range (viscosity between 1013.5 and 1012 Pa-s) is reached at temperatures between 484-633°C (strain point) and 509-664°C (upper limit). The working point (viscosity of 103 Pa-s) has temperature values in the range between 958 and 1097°C.

Evolved α-factor prepro-leaders for directed laccase evolution in Saccharomyces cerevisiae.

PubMed

Mateljak, Ivan; Tron, Thierry; Alcalde, Miguel

2017-11-01

Although the functional expression of fungal laccases in Saccharomyces cerevisiae has proven to be complicated, the replacement of signal peptides appears to be a suitable approach to enhance secretion in directed evolution experiments. In this study, twelve constructs were prepared by fusing native and evolved α-factor prepro-leaders from S. cerevisiae to four different laccases with low-, medium- and high-redox potential (PM1L from basidiomycete PM1; PcL from Pycnoporus cinnabarinus; TspC30L from Trametes sp. strain C30; and MtL from Myceliophthora thermophila). Microcultures of the prepro-leader:laccase fusions were grown in selective expression medium that used galactose as both the sole carbon source and as the inducer of expression so that the secretion and activity were assessed with low- and high-redox potential mediators in a high-throughput screening context. With total activity improvements as high as sevenfold over those obtained with the native α-factor prepro-leader, the evolved prepro-leader from PcL (α PcL ) most strongly enhanced secretion of the high- and medium-redox potential laccases PcL, PM1L and TspC30L in the microtiter format with an expression pattern driven by prepro-leaders in the order α PcL  > α PM 1L  ~ α native . By contrast, the pattern of the low-redox potential MtL was α native  > α PcL  > α PM 1L . When produced in flask with rich medium, the evolved prepro-leaders outperformed the α native signal peptide irrespective of the laccase attached, enhancing secretion over 50-fold. Together, these results highlight the importance of using evolved α-factor prepro-leaders for functional expression of fungal laccases in directed evolution campaigns. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

From naughty goods to Nicole Miller: medicine and the marketing of American contraceptives.

PubMed

Tone, Andrea

2006-06-01

In the rich history of modern pharmaceutical advertising in the United States, few medical objects have been as controversial as contraceptives. Condemned in the 1870s as lascivious devices whose commercial visibility would tarnish female sexual purity, contraceptives have in the late twentieth century been repackaged by pharmaceutical companies as the smart, progressive, and fashion-conscious woman's ally. This article explores evolving perspectives on the place of birth control in public spaces from the mid-nineteenth century to the present. In so doing, it elucidates the changes and continuities in the long and contested history of marketing, medicine, sexuality, and reproductive control.

Theory of Metastable State Relaxation for Non-Critical Binary Systems with Non-Conserved Order Parameter

NASA Technical Reports Server (NTRS)

Izmailov, Alexander; Myerson, Allan S.

1993-01-01

A new mathematical ansatz for a solution of the time-dependent Ginzburg-Landau non-linear partial differential equation is developed for non-critical systems such as non-critical binary solutions (solute + solvent) described by the non-conserved scalar order parameter. It is demonstrated that in such systems metastability initiates heterogeneous solute redistribution which results in formation of the non-equilibrium singly-periodic spatial solute structure. It is found how the time-dependent period of this structure evolves in time. In addition, the critical radius r(sub c) for solute embryo of the new solute rich phase together with the metastable state lifetime t(sub c) are determined analytically and analyzed.

The Abundance of SiC2 in Carbon Star Envelopes⋆: Evidence that SiC2 is a gas-phase precursor of SiC dust

PubMed Central

Massalkhi, Sarah; Agúndez, M.; Cernicharo, J.; Velilla Prieto, L.; Goicoechea, J. R.; Quintana-Lacaci, G.; Fonfría, J. P.; Alcolea, J.; Bujarrabal, V.

2017-01-01

Context Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich AGB stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si–C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216. Aims We aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars. Methods We carried out sensitive observations with the IRAM 30m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes. Results We detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source, at the exception of IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked, the SiC radical probably being the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend in which the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as an evidence of efficient incorporation of SiC2 onto dust grains, a process which is favored at high densities owing to the higher rate at which collisions between particles take place. Conclusions The observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars. PMID:29628518

The Abundance of SiC2 in Carbon Star Envelopes: Evidence that SiC2 is a gas-phase precursor of SiC dust.

PubMed

Massalkhi, Sarah; Agúndez, M; Cernicharo, J; Velilla Prieto, L; Goicoechea, J R; Quintana-Lacaci, G; Fonfría, J P; Alcolea, J; Bujarrabal, V

2018-03-01

Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich AGB stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si-C bond detected in C-rich AGB stars are SiC 2 , SiC, and Si 2 C. To date, the ring molecule SiC 2 has been observed in a handful of evolved stars, while SiC and Si 2 C have only been detected in the C-star envelope IRC +10216. We aim to study how widespread and abundant SiC 2 , SiC, and Si 2 C are in envelopes around C-rich AGB stars and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars. We carried out sensitive observations with the IRAM 30m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC 2 , SiC, and Si 2 C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC 2 and to derive SiC 2 fractional abundances in the observed envelopes. We detect SiC 2 in most of the sources, SiC in about half of them, and do not detect Si 2 C in any source, at the exception of IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC 2 line emission, which suggests that both species are chemically linked, the SiC radical probably being the photodissociation product of SiC 2 in the external layer of the envelope. We find a clear trend in which the denser the envelope, the less abundant SiC 2 is. The observed trend is interpreted as an evidence of efficient incorporation of SiC 2 onto dust grains, a process which is favored at high densities owing to the higher rate at which collisions between particles take place. The observed behavior of a decline in the SiC 2 abundance with increasing density strongly suggests that SiC 2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars.

Abundance of SiC2 in carbon star envelopes

NASA Astrophysics Data System (ADS)

Massalkhi, S.; Agúndez, M.; Cernicharo, J.; Velilla Prieto, L.; Goicoechea, J. R.; Quintana-Lacaci, G.; Fonfría, J. P.; Alcolea, J.; Bujarrabal, V.

2018-03-01

Context. Silicon carbide dust is ubiquitous in circumstellar envelopes around C-rich asymptotic giant branch (AGB) stars. However, the main gas-phase precursors leading to the formation of SiC dust have not yet been identified. The most obvious candidates among the molecules containing an Si-C bond detected in C-rich AGB stars are SiC2, SiC, and Si2C. To date, the ring molecule SiC2 has been observed in a handful of evolved stars, while SiC and Si2C have only been detected in the C-star envelope IRC +10216. Aim. We aim to study how widespread and abundant SiC2, SiC, and Si2C are in envelopes around C-rich AGB stars, and whether or not these species play an active role as gas-phase precursors of silicon carbide dust in the ejecta of carbon stars. Methods: We carried out sensitive observations with the IRAM 30 m telescope of a sample of 25 C-rich AGB stars to search for emission lines of SiC2, SiC, and Si2C in the λ 2 mm band. We performed non-LTE excitation and radiative transfer calculations based on the LVG method to model the observed lines of SiC2 and to derive SiC2 fractional abundances in the observed envelopes. Results: We detect SiC2 in most of the sources, SiC in about half of them, and do not detect Si2C in any source except IRC +10216. Most of these detections are reported for the first time in this work. We find a positive correlation between the SiC and SiC2 line emission, which suggests that both species are chemically linked; the SiC radical is probably the photodissociation product of SiC2 in the external layer of the envelope. We find a clear trend where the denser the envelope, the less abundant SiC2 is. The observed trend is interpreted as evidence of efficient incorporation of SiC2 onto dust grains, a process that is favored at high densities owing to the higher rate at which collisions between particles take place. Conclusions: The observed behavior of a decline in the SiC2 abundance with increasing density strongly suggests that SiC2 is an important gas-phase precursor of SiC dust in envelopes around carbon stars. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).

Characterization of clay scales forming in Philippine geothermal wells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reyes, A.G.; Cardile, C.M.

1989-01-01

Smectite scales occur in 24 out of the 36 blocked wells located in Tongonan, Palinpinon and Bacon-Manito. These comprise 2-85% of the well scales and form at depths of 33-2620 m, where measured and fluid inclusion temperatures are 40-320{sup 0}C. Most, however, occur below the production casing show where temperatures are {ge}230{sup 0}C, often at depths coinciding with aquifers. The clay scales are compositionally and structurally different from the bentonite used in drilling, which is essentially sodium-rich montmorillonite. The clay deposits are expanding, generally disordered, and combine the characteristics of a montmorillonite, saponite and vermiculite in terms of reaction tomore » cationic exchange treatments, structure and composition. Six types of clay scales are identified, but the predominant one, comprising 60-100% of the clay deposits in a well, is Mg- and Fe-rich and referred to as a vermiculitic species. The crystallinity, degree of disorder, textures, optical characteristics, structure and relative amounts of structural Al, Mg and Fe vary with time, temperature and fluid composition, but not with depth and measured pressure. Despite its variance from bentonite characteristics, one of the dominant suggested mechanisms of clay scale formation uses the drilling mud in the well as a substrate, from which the Mg- and Fe-rich clay evolves.« less

Habitable zones around low mass stars and the search for extraterrestrial life.

PubMed

Kasting, J F

1997-06-01

Habitable planets are likely to exist around stars not too different from the Sun if current theories about terrestrial climate evolution are correct. Some of these planets may have evolved life, and some of the inhabited planets may have evolved O2-rich atmospheres. Such atmospheres could be detected spectroscopically on planets around nearby stars using a space-based interferometer to search for the 9.6 micron band of O3. Planets with O2-rich atmospheres that lie within the habitable zone around their parent star are, in all probability, inhabited.

Cosmic Collisions: Galaxy Mergers and Evolution

NASA Astrophysics Data System (ADS)

Trouille, Laura; Willett, Kyle; Masters, Karen; Lintott, Christopher; Whyte, Laura; Lynn, Stuart; Tremonti, Christina A.

2014-08-01

Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, spiral galaxies; starbursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, elliptical galaxies, as objects representing different phases of major galaxy mergers. The post-starburst phase is particularly interesting because nearly every galaxy that evolves from star-forming to quiescent must pass through it. In essence, this phase is a sort of galaxy evolution “bottleneck” that indicates that a galaxy is actively evolving through important physical transitions. In this talk I will present the results from the ‘Galaxy Zoo Quench’ project - using post-starburst galaxies to place observational constraints on the role of mergers and AGN activity in quenching star formation. `Quench’ is the first fully collaborative research project with Zooniverse citizen scientists online; engaging the public in all phases of research, from classification to data analysis and discussion to writing the article and submission to a refereed journal.

Engineering the object-relation database model in O-Raid

NASA Technical Reports Server (NTRS)

Dewan, Prasun; Vikram, Ashish; Bhargava, Bharat

1989-01-01

Raid is a distributed database system based on the relational model. O-raid is an extension of the Raid system and will support complex data objects. The design of O-Raid is evolutionary and retains all features of relational data base systems and those of a general purpose object-oriented programming language. O-Raid has several novel properties. Objects, classes, and inheritance are supported together with a predicate-base relational query language. O-Raid objects are compatible with C++ objects and may be read and manipulated by a C++ program without any 'impedance mismatch'. Relations and columns within relations may themselves be treated as objects with associated variables and methods. Relations may contain heterogeneous objects, that is, objects of more than one class in a certain column, which can individually evolve by being reclassified. Special facilities are provided to reduce the data search in a relation containing complex objects.

Oxo Crater on (1) Ceres: Geological History and the Role of Water-ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathues, A.; Platz, T.; Hoffmann, M.

Dwarf planet Ceres (∅ ∼ 940 km) is the largest object in the main asteroid belt. Investigations suggest that Ceres is a thermally evolved, volatile-rich body with potential geological activity, a body that was never completely molten, but one that possibly partially differentiated into a rocky core and an ice-rich mantle, and may contain remnant internal liquid water. Thermal alteration and the infall of exogenic material contribute to producing a (dark) carbonaceous chondritic-like surface containing ammoniated phyllosilicates. Here we report imaging and spectroscopic analyses of data on the bright Oxo crater derived from the Framing Camera and the Visible andmore » Infrared Spectrometer on board the Dawn spacecraft. We confirm that the transitional complex crater Oxo (∅ ∼ 9 km) exhibits exposed surface water-ice. We show that this water-ice-rich material is associated exclusively with two lobate deposits at pole-facing scarps, deposits that also contain carbonates and admixed phyllosilicates. Due to Oxo’s location at −4802 m below the cerean reference ellipsoid and its very young age of only 190 ka (1 σ : +100 ka, −70 ka), Oxo is predestined for ongoing water-ice sublimation.« less

Desert Varnish - Preservation of Biofabrics/Implcations for Mars

NASA Technical Reports Server (NTRS)

Probst, Luke W.; Allen, Carlton C.; Thomas-Keprta, Kathie L.; Clemett, Simon J.; Longazo, Teresa G.; Nelman-Gonzalez, Mayra A.; Sams, Clarence

2002-01-01

Desert varnish is the orange to dark brown rind that accumulates on exposed rock surfaces in many arid environments. Samples from the Sonoran Desert of Arizona are composed predominantly of clays (illite, smectite) and Mn- and Fe- oxides (birnessite, hematite). Features that appear to be single organisms are found within the varnish and at the rock-varnish interface. Many of these features are embedded in films that strongly resemble the water-rich extracellular polysaccharides produced by diverse microorganisms. Most common are rod-shaped celllike objects, 0.5-2 microns in the longest dimension, located within the varnish coatings. Some of these objects are shown to contain amines by fluorescence microscopy. The rod-shaped objects are observed in various states of degradation, as indicated by C and S abundances. Rods with higher C and S abundances appear less degraded than those with lower concentrations of these two elements. Regions rich in apparent microbes are present, while other regions display Mn- and Fe-rich mineral fabrics with microbe-sized voids and no obvious cells. These textures are interpreted as biofabrics, preserved by the precipitation of Mn and Fe minerals. We are researching the preservation of biofabrics by desert varnish in Earth's geological record. Rock coatings may similarly preserve evidence of microbial life on the hyper-arid surface of Mars.

A λ 3 mm and 1 mm line survey toward the yellow hypergiant IRC +10420⋆

PubMed Central

Quintana-Lacaci, G.; Agúndez, M.; Cernicharo, J.; Bujarrabal, V.; Sánchez Contreras, C.; Castro-Carrizo, A.; Alcolea, J.

2016-01-01

Aims Our knowledge of the chemical properties of the circumstellar ejecta of the most massive evolved stars is particularly poor. We aim to study the chemical characteristics of the prototypical yellow hypergiant star, IRC +10420. For this purpose, we obtained full line surveys at 1 and 3 mm atmospheric windows. Methods We have identified 106 molecular emission lines from 22 molecular species. Approximately half of the molecules detected are N-bearing species, in particular HCN, HNC, CN, NO, NS, PN, and N2H+. We used rotational diagrams to derive the density and rotational temperature of the different molecular species detected. We introduced an iterative method that allows us to take moderate line opacities into account. Results We have found that IRC +10420 presents high abundances of the N-bearing molecules compared with O-rich evolved stars. This result supports the presence of a N-rich chemistry, expected for massive stars. Our analysis also suggests a decrease of the 12C/13C ratio from ≳ 7 to ~ 3.7 in the last 3800 years, which can be directly related to the nitrogen enrichment observed. In addition, we found that SiO emission presents a significant intensity decrease for high-J lines when compared with older observations. Radiative transfer modeling shows that this variation can be explained by a decrease in the infrared (IR) flux of the dust. The origin of this decrease might be an expansion of the dust shell or a lower stellar temperature due to the pulsation of the star. PMID:27458319

Effect of the tocotrienol-rich fraction on the lifespan and oxidative biomarkers in Caenorhabditis elegans under oxidative stress

PubMed Central

Aan, Goon Jo; Zainudin, Mohd Shahril Aszrin; Karim, Noralisa Abdul; Ngah, Wan Zurinah Wan

2013-01-01

OBJECTIVE: This study was performed to determine the effect of the tocotrienol-rich fraction on the lifespan and oxidative status of C. elegans under oxidative stress. METHOD: Lifespan was determined by counting the number of surviving nematodes daily under a dissecting microscope after treatment with hydrogen peroxide and the tocotrienol-rich fraction. The evaluated oxidative markers included lipofuscin, which was measured using a fluorescent microscope, and protein carbonyl and 8-hydroxy-2′-deoxyguanosine, which were measured using commercially available kits. RESULTS: Hydrogen peroxide-induced oxidative stress significantly decreased the mean lifespan of C. elegans, which was restored to that of the control by the tocotrienol-rich fraction when administered before or both before and after the hydrogen peroxide. The accumulation of the age marker lipofuscin, which increased with hydrogen peroxide exposure, was decreased with upon treatment with the tocotrienol-rich fraction (p<0.05). The level of 8-hydroxy-2′-deoxyguanosine significantly increased in the hydrogen peroxide-induced group relative to the control. Treatment with the tocotrienol-rich fraction before or after hydrogen peroxide induction also increased the level of 8-hydroxy-2′-deoxyguanosine relative to the control. However, neither hydrogen peroxide nor the tocotrienol-rich fraction treatment affected the protein carbonyl content of the nematodes. CONCLUSION: The tocotrienol-rich fraction restored the lifespan of oxidative stress-induced C. elegans and reduced the accumulation of lipofuscin but did not affect protein damage. In addition, DNA oxidation was increased. PMID:23778402

Mass-loss From Evolved Stellar Populations In The Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Riebel, David

2012-01-01

I have conducted a study of a sample of 30,000 evolved stars in the Large Magellanic Cloud (LMC) and 6,000 in the Small Magellanic Cloud (SMC), covering their variability, mass-loss properties, and chemistry. The initial stages of of my thesis work focused on the infrared variability of Asymptotic Giant Branch (AGB) stars in the LMC. I determined the period-luminosity (P-L) relations for 6 separate sequences of 30,000 evolved star candidates at 8 wavelengths, as a function of photometrically assigned chemistry, and showed that the P-L relations are different for different chemical populations (O-rich or C-rich). I also present results from the Grid of Red supergiant and Asymptotic giant branch star ModelS (GRAMS) radiative transfer (RT) model grid applied to the evolved stellar population of the LMC. GRAMS is a pre-computed grid of RT models of RSG and AGB stars and surrounding circumstellar dust. Best-fit models are determined based on 12 bands of photometry from the optical to the mid-infrared. Using a pre-computed grid, I can present the first reasonably detailed radiative transfer modeling for tens of thousands of stars, allowing me to make statistically accurate estimations of the carbon-star luminosity function and the global dust mass return to the interstellar medium from AGB stars, both key parameters for stellar population synthesis models to reproduce. In the SAGE-Var program, I used the warm Spitzer mission to take 4 additional epochs of observations of 7500 AGB stars in the LMC and SMC. These epochs, combined with existing data, enable me to derive mean fluxes at 3.6 and 4.5 microns, that will be used for tighter constraints for GRAMS, which is currently limited by the variability induced error on the photometry. This work is support by NASA NAG5-12595 and Spitzer contract 1415784.

A network-based distributed, media-rich computing and information environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Phillips, R.L.

1995-12-31

Sunrise is a Los Alamos National Laboratory (LANL) project started in October 1993. It is intended to be a prototype National Information Infrastructure development project. A main focus of Sunrise is to tie together enabling technologies (networking, object-oriented distributed computing, graphical interfaces, security, multi-media technologies, and data-mining technologies) with several specific applications. A diverse set of application areas was chosen to ensure that the solutions developed in the project are as generic as possible. Some of the application areas are materials modeling, medical records and image analysis, transportation simulations, and K-12 education. This paper provides a description of Sunrise andmore » a view of the architecture and objectives of this evolving project. The primary objectives of Sunrise are three-fold: (1) To develop common information-enabling tools for advanced scientific research and its applications to industry; (2) To enhance the capabilities of important research programs at the Laboratory; (3) To define a new way of collaboration between computer science and industrially-relevant research.« less

Building Blocks of Dust and Large Organic Molecules: a Coordinated Laboratory and Astronomical Study of AGB Stars

NASA Astrophysics Data System (ADS)

McCarthy, Michael C.; Gottlieb, Carl A.; Cernicharo, Jose

2017-06-01

The increased sensitivity and angular resolution of high-altitude ground-based interferometers in the sub-millimeter band has enabled the physics and chemistry of carbon- and oxygen-rich evolved stars to be re-examined at an unprecedented level of detail. Observations of rotational lines in the inner envelope - the region within a few stellar radii of the central star where the molecular seeds of dust are formed - allows one to critically assess models of dust growth. Interferometric observations of the outer envelope provide stringent tests of neutral and ionized molecule formation. All of the astronomical studies are crucially dependent on precise laboratory measurements of the rotational spectra of new species and of vibrationally excited levels of known molecules and their rare isotopic species. By means of a closely coordinated laboratory and astronomical program, a number of exotic species including the disilicon carbide SiCSi, titanium oxides TiO and TiO_2, and carbon chain anions ranging from CN^- to C_8H^- have recently been observed in evolved stars. This talk will provide overview of these findings, and how they impact current models of the ``chemical laboratories'' of evolved stars. Ongoing laboratory studies of small silicon-bearing molecules such as H_2SiO_2 and vibrationally excited SiC_2 will be highlighted.

Hydrocarbons in the ISM: Their Evolution and the Grain-to-Molecule Transition

NASA Astrophysics Data System (ADS)

Jones, Anthony P.

The evolution of hydrocarbon grains in the ISM is determined, principally, by the effects of photo-processing (annealing) which lead to a progressive loss of hydrogen from the structure and an associated 'graphitisation' of the material. Eventually this 'graphitisation' results in a low-density, highly aromatic material that can disaggregate into its aromatic-rich molecular components. These changes are followed through the use of an extended random covalent network (RCN) model for the hydrocarbon structure. This type of 'top down' process could be a significant source of the large molecular infrared band carriers in photon dominated regions. On the basis of this simple model there should thus be a relationship between the small grain and large molecule infrared emission bands across, and within, astrophysical boundaries such as photo-dissociation regions. 1. Introduction Carbon is the most abundant dust-forming element in the ISM and a large fraction of this carbon is in the form of grains comprised, principally, of hydrocarbon materials, including those where the hydrogen content is minimal. Interstellar hydrocarbon grains include: graphite, hydrogenated amorphous aliphatic and/or aromatic hydrocarbons (a-C, a-C:H) and (nano)diamond. These hydrocarbon dusts play a pivotal role in determining, amongst other things, the interstellar extinction, the dust thermal emission and the photo-electric heating of the gas in the ISM. 2. Hydrocarbon grains in the ISM Hydrocarbon grains are formed in the circumstellar shells around C-rich evolved stars, in supernova ejecta and also in the ISM itself via accretion and solid-state chemistry. The physical and chemical properties of hydrocarbon grains are indeed complex and vary in response to the ambient conditions (density, temperature, radiation field, ...). For example they can undergo both chemical and physical processing (growth and changes in chemical composition through accretion and reaction, erosion via inertial or chemi-sputtering, photo-darkening or 'graphitisation', photo-disruption in intense radiation fields and fragmentation in interstellar shock waves). Recently, using laboratory simulations of carbon dust analogues, Dartois, Muñoz Caro, Deboffle, et al. (2004,2005) have shown that hydrogen-rich (> 50 atomic % H) hydrocarbon solids can explain the observed interstellar absorption bands at 3.4, 6.85 and 7.25 μm. They also show that the thermal annealing of this material is accompanied by an increase in the aromatic component, i.e., a 'graphitisation'. Such a transformation and evolution of interstellar hydrocarbons was proposed by Duley, Jones & Williams (1989) and Jones, Duley & Wiliams (1990). This photon-driven process, acting on the hydrogen-rich hydrocarbon grains in the ISM that originate predominantly from carbon-rich evolved stars, will lead to a progressive loss of hydrogen and an associated 'graphitisation' and 'openingup' of the structure. The end point of the 'graphitisation' process is then a low-density material that will disaggregate into its constituent aromatic molecular components and the necessarily-associated sp3 and sp2 carbon and hydrogen atom bridging structures, e.g., Duley (2000), Petrie, Stranger & Duley (2003). In this work we follow the 'graphitisation' process using a random covalent network (RCN) approach that extends the work of Jones (1990). To summarise, the RCN model characterises a series of hydrocarbons based upon the sp3/sp2 carbon atom ratio (R) and the atomic fraction of hydrogen (XH) within the material. This model allows an essentially one-parameter determination of the a-C:H structure and a prediction of the major infrared bands. We find that the large hydrocarbon grains, with temperatures in equilibrium with the local radiation field, will be rather hydrogen-rich and that the smaller grains, which undergo stochastic heating to high temperatures, will be converted into hydrogen-poorer and more graphitic materials. The photo-fragmentation of the smaller aromatic grains can be an important source of molecular aromatic species. The infrared spectrum of a given RCN hydrocarbon depends, principally, upon only its hydrogen content XH. The spectra predicted from this RCN model can then be compared with the interstellar absorption and emission bands in the 32 μm range. The compositional changes of a-C:H, and its constituent 'molecular' components, can then be mapped across a given region. 3. Conclusions The physics and chemistry of hydrocarbon grains is complex. Interstellar hydrocarbon grains will be a mixture of many different forms arising from many different sources and modified in many different regions of the ISM. Nevertheless, we can appreciate how this complex material evolves chemically, structurally and physically as a function of the ambient conditions through the use of a rather simple, and extended, RCN model. The transition/evolution of hydrocarbons in the ISM is, generally, from hydrogen-rich a-C:H, in the form of large grains formed around evolved stars, through to smaller, hydrogen-poor, low-density, aromatic a-C:H materials. The subsequent photo-fragmentation of the small aromatic grains could then be the origin of the aromatic emission band carriers within the ISM. We find that the spectral and physical properties of hydrocarbons in the ISM vary in a systematic way across, and also within, astrophysical environments. However, the history of the particles, prior to their incorporation into a given region, could also play a major role in determining their physical properties in that region. Thus, the evolution of hydrocarbon grains in the ISM will be size-, time- and history-dependent. It is therefore necessary that dust models take into account this complexity in predicting the properties of hydrocarbons in the ISM.

SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618

NASA Astrophysics Data System (ADS)

Patel, Nimesh A.; Gottlieb, Carl; Young, Ken; Kaminski, Tomasz Tomek; McCarthy, Michael; Menten, Karl; Primiani, Rurik; Lee, Chin-Fei; Gupta, Harshal

2018-01-01

Carbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. AGB stars remain in their evolutionary stage for 1 to 10 Myrs, during which they have very high mass loss rates that increase at the end. During the brief (~1000 yr) period in the evolution from the AGB to the Planetary Nebula (PN) stage there are dramatic changes in the morphology from nearly spherical symmetry, to bipolar, quadrupolar and more complex structures, with the development of both slow and fast (100 km/s) outflows. The molecular composition of these objects' cirumstellar envelopes also evolves from being similar to that of parent AGB star (mainly diatomic and small polyatomic species), to more complex molecules (including ions).We have started an observational study of a sample of Proto-Planetary nebulae (PPN) with the Submillimeter Array to carry out spectral-line surveys of ~60 GHz frequency coverage in the 345 GHz band (similar to our published IRC+10216 line survey of 2011). Here we present preliminary results from the line survey of the carbon-rich PPN CRL 618, covering a frequency range of 281.9 to 359.4 GHz. Observations were carried out in January 2016 and September 2017, with the SMA in compact (3" angular resolution) and very extended (0.5") configurations, respectively.More than 1100 lines were detected in CRL 618. The majority of them can be attributed to HC3N and c-C3H2, and their isotopologues. About 350 lines are as yet unassigned. The continuum emission is unresolved even at 0.5" resolution. Several hydrogen recombination lines are detected from the central HII region. Lines of CO, HCO+, CS show the fast outflow wings, while the majority of molecular emission arises from a compact region of about 1" diameter. We present LTEmodeling and rotation temperature diagram analysis of HC3N, c-C3H2, CH3CN, and their isotopologues. We plan to observe another PPN, CRL 2688 with the SMA in 2018. Together, these imaging line surveys will provide observational constraints on models of the chemical evolution from AGB stars to Planetary Nebulae.

Cosmological surveys with multi-object spectrographs

NASA Astrophysics Data System (ADS)

Colless, Matthew

2016-08-01

Multi-object spectroscopy has been a key technique contributing to the current era of `precision cosmology.' From the first exploratory surveys of the large-scale structure and evolution of the universe to the current generation of superbly detailed maps spanning a wide range of redshifts, multi-object spectroscopy has been a fundamentally important tool for mapping the rich structure of the cosmic web and extracting cosmological information of increasing variety and precision. This will continue to be true for the foreseeable future, as we seek to map the evolving geometry and structure of the universe over the full extent of cosmic history in order to obtain the most precise and comprehensive measurements of cosmological parameters. Here I briefly summarize the contributions that multi-object spectroscopy has made to cosmology so far, then review the major surveys and instruments currently in play and their prospects for pushing back the cosmological frontier. Finally, I examine some of the next generation of instruments and surveys to explore how the field will develop in coming years, with a particular focus on specialised multi-object spectrographs for cosmology and the capabilities of multi-object spectrographs on the new generation of extremely large telescopes.

Evolution of Occator Crater on (1) Ceres

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathues, A.; Platz, T.; Thangjam, G.

2017-03-01

The dwarf planet Ceres (diameter 939 km) is the largest object in the main asteroid belt. Recent investigations suggest that Ceres is a thermally evolved, volatile-rich body with potential geological activity, a body which was never completely molten but possibly differentiated into a rocky core, an ice-rich mantle, and which may contain remnant internal liquid water. Thermal alteration and exogenic material infall contribute to producing a (dark) carbonaceous chondritic-like surface containing ammoniated phyllosilicates. Here we report imaging and spectroscopic analyses of Occator crater derived from the Framing Camera and the Visible and Infrared Spectrometer onboard Dawn. We found that themore » central bright spot (Cerealia Facula) of Occator is ∼30 Myr younger than the crater itself. The central spot is located in a central pit which contains a dome that is spectrally homogenous, exhibiting absorption features that are consistent with carbonates. Multiple radial fractures across the dome indicate an extrusive formation process. Our results lead us to conclude that the floor region was subject to past endogenic activity. Dome and bright material in its vicinity formed likely due to a long-lasting, periodic, or episodic ascent of bright material from a subsurface reservoir rich in carbonates. Originally triggered by an impact event, gases, possibly dissolved from a subsurface water/brine layer, enabled material rich in carbonates to ascend through fractures and be deposited onto the surface.« less

Geology, geochemistry and geochronology of the Songwe Hill carbonatite, Malawi

NASA Astrophysics Data System (ADS)

Broom-Fendley, Sam; Brady, Aoife E.; Horstwood, Matthew S. A.; Woolley, Alan R.; Mtegha, James; Wall, Frances; Dawes, Will; Gunn, Gus

2017-10-01

Songwe Hill, Malawi, is one of the least studied carbonatites but has now become particularly important as it hosts a relatively large rare earth deposit. The results of new mapping, petrography, geochemistry and geochronology indicate that the 0.8 km diameter Songwe Hill is distinct from the other Chilwa Alkaline Province carbonatites in that it intruded the side of the much larger (4 × 6 km) and slightly older (134.6 ± 4.4 Ma) Mauze nepheline syenite and then evolved through three different carbonatite compositions (C1-C3). Early C1 carbonatite is scarce and is composed of medium-coarse-grained calcite carbonatite containing zircons with a U-Pb age of 132.9 ± 6.7 Ma. It is similar to magmatic carbonatite in other carbonatite complexes at Chilwa Island and Tundulu in the Chilwa Alkaline Province and others worldwide. The fine-grained calcite carbonatite (C2) is the most abundant stage at Songwe Hill, followed by a more REE- and Sr-rich ferroan calcite carbonatite (C3). Both stages C2 and C3 display evidence of extensive (carbo)-hydrothermal overprinting that has produced apatite enriched in HREE (<2000 ppm Y) and, in C3, synchysite-(Ce). The final stages comprise HREE-rich apatite fluorite veins and Mn-Fe-rich veins. Widespread brecciation and incorporation of fenite into carbonatite, brittle fracturing, rounded clasts and a fenite carapace at the top of the hill indicate a shallow level of emplacement into the crust. This shallow intrusion level acted as a reservoir for multiple stages of carbonatite-derived fluid and HREE-enriched apatite mineralisation as well as LREE-enriched synchysite-(Ce). The close proximity and similar age of the large Mauze nepheline syenite suggests it may have acted as a heat source driving a hydrothermal system that has differentiated Songwe Hill from other Chilwa carbonatites.

Two years' outcome of thread lifting with absorbable barbed PDO threads: Innovative score for objective and subjective assessment.

PubMed

Ali, Yasser Helmy

2018-02-01

Thread-lifting rejuvenation procedures have evolved again, with the development of absorbable threads. Although they have gained popularity among plastic surgeons and dermatologists, very few articles have been written in literature about absorbable threads. This study aims to evaluate two years' outcome of thread lifting using absorbable barbed threads for facial rejuvenation. Prospective comparative stud both objectively and subjectively and follow-up assessment for 24 months. Thread lifting for face rejuvenation has significant long-lasting effects that include skin lifting from 3-10 mm and high degree of patients' satisfaction with less incidence rate of complications, about 4.8%. Augmented results are obtained when thread lifting is combined with other lifting and rejuvenation modalities. Significant facial rejuvenation is achieved by thread lifting and highly augmented results are observed when they are combined with Botox, fillers, and/or platelet rich plasma (PRP) rejuvenations.

Magma storage and evolution of the most recent effusive and explosive eruptions from Yellowstone Caldera

NASA Astrophysics Data System (ADS)

Befus, Kenneth S.; Gardner, James E.

2016-04-01

Between 70 and 175 ka, over 350 km3 of high-silica rhyolite magma erupted both effusively and explosively from within the Yellowstone Caldera. Phenocrysts in all studied lavas and tuffs are remarkably homogenous at the crystal, eruption, and caldera-scale, and yield QUILF temperatures of 750 ± 25 °C. Phase equilibrium experiments replicate the observed phenocryst assemblage at those temperatures and suggest that the magmas were all stored in the upper crust. Quartz-hosted glass inclusions contain 1.0-2.5 % H2O and 50-600 ppm CO2, but some units are relatively rich in CO2 (300-600 ppm) and some are CO2-poor (50-200 ppm). The CO2-rich magmas were stored at 90-150 MPa and contained a fluid that was 60-75 mol% CO2. CO2-poor magmas were stored at 50-70 MPa, with a more H2O-rich fluid (X_{{{text{CO}}2 }} = 40-60 %). Storage pressures and volatiles do not correlate with eruption age, volume, or style. Trace-element contents in glass inclusions and host matrix glass preserve a systematic evolution produced by crystal fractionation, estimated to range from 36 ± 12 to 52 ± 12 wt%. Because the erupted products contain <10 wt% crystals, crystal-poor melts likely separated from evolving crystal-rich mushes prior to eruption. In the Tuffs of Bluff Point and Cold Mountain Creek, matrix glass is less evolved than most inclusions, which may indicate that more primitive rhyolite was injected into the reservoir just before those eruptions. The presence and dissolution of granophyre in one flow may record evidence for heating prior to eruption and also demonstrate that the Yellowstone magmatic system may undergo rapid changes. The variations in depth suggest the magmas were sourced from multiple chambers that follow similar evolutionary paths in the upper crust.

Spectra from the IRS of Bright Oxygen-Rich Evolved Stars in the SMC

NASA Astrophysics Data System (ADS)

Kraemer, Kathleen E.; Sloan, Greg; Wood, Peter

2016-06-01

We have used Spitzer's Infrared Spectrograph (IRS) to obtain spectra of stars in the Small Magellanic Cloud (SMC). The targets were chosen from the Point Source Catalog of the Mid-Course Space Experiment (MSX), which detected the 243 brightest infrared sources in the SMC. Our SMC sample of oxygen-rich evolved stars shows more dust than found in previous samples, and the dust tends to be dominated by silicates, with little contribution from alumina. Both results may arise from the selection bias in the MSX sample and our sample toward more massive stars. Additionally, several sources show peculiar spectral features such as PAHs, crystalline silicates, or both carbon-rich and silicate features. The spectrum of one source, MSX SMC 145, is a combination of an ordinary AGB star and a background galaxy at z~0.16, rather than an OH/IR star as previously suggested.

C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines

NASA Astrophysics Data System (ADS)

García-Rojas, J.; Delgado-Inglada, G.; García-Hernández, D. A.; Dell'Agli, F.; Lugaro, M.; Karakas, A. I.; Rodríguez, M.

2018-02-01

We present deep high-resolution (R ˜ 15 000) and high-quality UVES optical spectrophotometry of nine planetary nebulae with dual-dust chemistry. We compute physical conditions from several diagnostics. Ionic abundances for a large number of ions of N, O, Ne, S, Cl, Ar, K, Fe and Kr are derived from collisionally excited lines. Elemental abundances are computed using state-of-the-art ionization correction factors. We derive accurate C/O ratios from optical recombination lines. We have re-analysed additional high-quality spectra of 14 PNe from the literature following the same methodology. Comparison with asymptotic giant branch models reveals that about half of the total sample objects are consistent with being descendants of low-mass progenitor stars (M < 1.5 M⊙). Given the observed N/O, C/O and He/H ratios, we cannot discard that some of the objects come from more massive progenitor stars (M > 3-4 M⊙) that have suffered a mild hot bottom burning. None of the objects seem to be descendant of very massive progenitors. We propose that in most of the planetary nebulae studied here, the polycyclic aromatic hydrocarbons have been formed through the dissociation of the CO molecule. The hypothesis of a last thermal pulse that turns O-rich PNe into C-rich PNe is discarded, except in three objects, that show C/O > 1. We also discuss the possibility of an He pre-enrichment to explain the most He-enriched objects. We cannot discard another scenarios like extra mixing, stellar rotation or binary interactions to explain the chemical abundances behaviour observed in our sample.

Atmospheric, Magnetospheric and Plasmas in Space (AMPS) spacelab payload definition study - program analysis and planning for phase C/D document - Volume 7

NASA Technical Reports Server (NTRS)

Keeley, J. T.

1976-01-01

Typical missions identified for AMPS flights in the arly 1980's are described. Experiment objectives and typical scientific instruments selected to accomplish these objectives are discussed along with mission requirements and shuttle and Spacelab capabilities assessed to determine any AMPS unique requirements. Preliminary design concepts for the first two AMPS flights form the basis for the Phase C/D program plan. This plan implements flights 1 and 2 and indicates how both the scientific and flight support hardware can be systematically evolved for future AMPS flights.

Evolutionary bursts in Euphorbia (Euphorbiaceae) are linked with photosynthetic pathway.

PubMed

Horn, James W; Xi, Zhenxiang; Riina, Ricarda; Peirson, Jess A; Yang, Ya; Dorsey, Brian L; Berry, Paul E; Davis, Charles C; Wurdack, Kenneth J

2014-12-01

The mid-Cenozoic decline of atmospheric CO2 levels that promoted global climate change was critical to shaping contemporary arid ecosystems. Within angiosperms, two CO2 -concentrating mechanisms (CCMs)-crassulacean acid metabolism (CAM) and C4 -evolved from the C3 photosynthetic pathway, enabling more efficient whole-plant function in such environments. Many angiosperm clades with CCMs are thought to have diversified rapidly due to Miocene aridification, but links between this climate change, CCM evolution, and increased net diversification rates (r) remain to be further understood. Euphorbia (∼2000 species) includes a diversity of CAM-using stem succulents, plus a single species-rich C4 subclade. We used ancestral state reconstructions with a dated molecular phylogeny to reveal that CCMs independently evolved 17-22 times in Euphorbia, principally from the Miocene onwards. Analyses assessing among-lineage variation in r identified eight Euphorbia subclades with significantly increased r, six of which have a close temporal relationship with a lineage-corresponding CCM origin. Our trait-dependent diversification analysis indicated that r of Euphorbia CCM lineages is approximately threefold greater than C3 lineages. Overall, these results suggest that CCM evolution in Euphorbia was likely an adaptive strategy that enabled the occupation of increased arid niche space accompanying Miocene expansion of arid ecosystems. These opportunities evidently facilitated recent, replicated bursts of diversification in Euphorbia. © 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study

NASA Astrophysics Data System (ADS)

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

2002-09-01

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

The behaviour of boron in a peraluminous granite-pegmatite system and associated hydrothermal solutions: a melt and fluid-inclusion study

NASA Astrophysics Data System (ADS)

Thomas, Rainer; Förster, Hans-Jürgen; Heinrich, Wilhelm

Detailed analyses of melt and fluid inclusions combined with an electron-microprobe survey of boron-bearing minerals reveal the evolution of boron in a highly evolved peraluminous granite-pegmatite complex and the associated high- and medium-temperature ore-forming hydrothermal fluids (Ehrenfriedersdorf, Erzgebirge, Germany). Melt inclusions in granite represent embryonic pegmatite-forming melts containing about 10 wt% H2O and 1.8 wt% B2O3. These melts are also enriched in F, P, and other incompatible elements such as Be, Sn, Rb, and Cs. Ongoing differentiation and volatile enrichment drove the system into a solvus, where two pegmatite-forming melts coexisted. The critical point is at about 712 °C, 100 MPa, 20 wt% H2O and 4.1 wt% B2O3. Cooling and concomitant fractional crystallisation from 700 to 500 °C induced development of two conjugate melts, an H2O-poor (A-melt) and an H2O-rich melt (B-melt) along the opening solvus. Boron is a major element in both melts and is preferentially partitioned into the H2O-rich melt. Temperature-dependent distribution coefficients $ D{boron}{{B - melt/A - melt}} $ are 1.3 at 650 °C, 1.5 at 600 °C, and 1.8 at 500 °C. In both melts, boron concentrations decreased during cooling because of exsolution of a boron-rich hypersaline brine throughout the pegmatitic stage. Boromuscovite containing up to 8.5 wt% was another sink for boron at this stage. The end of the melt-dominated pegmatitic stage was attained at a solidus temperature of around 490 °C. Fluid inclusions of the hydrothermal stage reveal trapping temperatures of 480 to 370 °C, along with varying densities and highly variable B2O3 contents ranging from 0.20 to 2.94 wt%. A boiling system evolved, indicating a complex interplay between closed- and open-system behaviour. Pressure switched from lithostatic to hydrostatic and back, generating hydrothermal convection cells where meteoric waters were introduced and mixed with magmatic fluids. Boron-rich solutions originated from magmatic fluids, whereas boron-depleted fluids were mainly of meteoric origin. This highlights the potential of boron for discriminating fluids of different origin. Tin is continuously enriched during the evolution because tin and boron are cross-linked by formation of boron-, fluorine- and tin-fluorine-bearing complexes and is finally deposited within quartz-cassiterite veins during the transition from closed- to open-system behaviour. Boron does not only trace the complex evolution of the Ehrenfriedersdorf complex but exerts, together with H2O, F and P, an important control on the physical and chemical properties of pegmatite-forming melts, and particularly on the formation of a two-melt solvus at low pressure. We discuss this with respect to experimental results on H2O solubility and the critical behaviour of the haplogranite-water system which contained variable concentrations of volatiles.

Apollo 16 Evolved Lithology Sodic Ferrogabbro

NASA Technical Reports Server (NTRS)

Zeigler, Ryan; Jolliff, B. L.; Korotev, R. L.

2014-01-01

Evolved lunar igneous lithologies, often referred to as the alkali suite, are a minor but important component of the lunar crust. These evolved samples are incompatible-element rich samples, and are, not surprisingly, most common in the Apollo sites in (or near) the incompatible-element rich region of the Moon known as the Procellarum KREEP Terrane (PKT). The most commonly occurring lithologies are granites (A12, A14, A15, A17), monzogabbro (A14, A15), alkali anorthosites (A12, A14), and KREEP basalts (A15, A17). The Feldspathic Highlands Terrane is not entirely devoid of evolved lithologies, and rare clasts of alkali gabbronorite and sodic ferrogabbro (SFG) have been identified in Apollo 16 station 11 breccias 67915 and 67016. Curiously, nearly all pristine evolved lithologies have been found as small clasts or soil particles, exceptions being KREEP basalts 15382/6 and granitic sample 12013 (which is itself a breccia). Here we reexamine the petrography and geochemistry of two SFG-like particles found in a survey of Apollo 16 2-4 mm particles from the Cayley Plains 62283,7-15 and 62243,10-3 (hereafter 7-15 and 10-3 respectively). We will compare these to previously reported SFG samples, including recent analyses on the type specimen of SFG from lunar breccia 67915.

Above-ground carbon storage, downed wood, and understory plant species richness after thinning in western Oregon

Treesearch

Julia I. Burton; Adrian Ares; Sara E. Mulford; Deanna H. Olson; Klaus J. Puettmann

2013-01-01

Concerns about climate change have generated worldwide interest in managing forests for the uptake and storage of carbon (C). Simultaneously, preserving and enhancing structural, functional, and species diversity in forests remains an important objective. Therefore, understanding tradeoffs and synergies among C storage and sequestration and diversity in managed forests...

Feasibility of cuphea as a new oilseed crop to climate and soil environments

USDA-ARS?s Scientific Manuscript database

Cuphea, a new oilseed crop rich in medium-chain fatty acids (C8:0 to C14:0), may serve as a renewable, biodegradable source of oil for lubricants, motor oil, and aircraft fuel. Impacts of climate and soil environment on cuphea growth and development are not well understood. The objective of this stu...

Adaptability of cuphea, a new oilseed crop, to climate and soil environments

USDA-ARS?s Scientific Manuscript database

Cuphea, a new oilseed crop rich in medium-chain fatty acids (C8:0 to C14:0), may serve as a renewable, biodegradable source of oil for lubricants, motor oil, and aircraft fuel. Impacts of climate and soil environment on cuphea growth and development are not well understood. The objective of this stu...

Indicators of an "Immigrant Advantage" in the Writing of L3 French Learners

ERIC Educational Resources Information Center

Knouzi, Ibtissem; Mady, Callie

2017-01-01

Grounded in the cross-linguistic influence(s) (CLI) literature, this study used objective measures to compare the use of English, lexical richness and syntactic complexity, and grammatical accuracy and fluency in the texts of three groups of Grade 6 French immersion students: Canadian-born anglophones (C-A), Canadian-born multilinguals (C-M), and…

Ejection of the Massive Hydrogen-rich Envelope Timed with the Collapse of the Stripped SN 2014C

DOE Office of Scientific and Technical Information (OSTI.GOV)

Margutti, Raffaella; Kamble, A.; Milisavljevic, D.

2017-02-01

We present multi-wavelength observations of SN 2014C during the first 500 days. These observations represent the first solid detection of a young extragalactic stripped-envelope SN out to high-energy X-rays ∼40 keV. SN 2014C shows ordinary explosion parameters ( E {sub k} ∼ 1.8 × 10{sup 51} erg and M {sub ej} ∼ 1.7 M{sub ⊙}). However, over an ∼1 year timescale, SN 2014C evolved from an ordinary hydrogen-poor supernova into a strongly interacting, hydrogen-rich supernova, violating the traditional classification scheme of type-I versus type-II SNe. Signatures of the SN shock interaction with a dense medium are observed across the spectrum,more » from radio to hard X-rays, and revealed the presence of a massive shell of ∼1 M {sub ⊙} of hydrogen-rich material at ∼6 × 10{sup 16} cm. The shell was ejected by the progenitor star in the decades to centuries before collapse. This result challenges current theories of massive star evolution, as it requires a physical mechanism responsible for the ejection of the deepest hydrogen layer of H-poor SN progenitors synchronized with the onset of stellar collapse. Theoretical investigations point at binary interactions and/or instabilities during the last nuclear burning stages as potential triggers of the highly time-dependent mass loss. We constrain these scenarios utilizing the sample of 183 SNe Ib/c with public radio observations. Our analysis identifies SN 2014C-like signatures in ∼10% of SNe. This fraction is reasonably consistent with the expectation from the theory of recent envelope ejection due to binary evolution if the ejected material can survive in the close environment for 10{sup 3}–10{sup 4} years. Alternatively, nuclear burning instabilities extending to core C-burning might play a critical role.« less

Melting Processes at the Base of the Mantle Wedge: Melt Compositions and Melting Reactions for the First Melts of Vapor-Saturated Lherzolite

NASA Astrophysics Data System (ADS)

Grove, T. L.; Till, C. B.

2014-12-01

Vapor-saturated melting experiments have been performed at pressures near the base of the mantle wedge (3.2 GPa). The starting composition is a metasomatized lherzolite containing 3 wt. % H2O. Near-solidus melts and coexisting mineral phases have been characterized in experiments that span 925 to 1100 oC with melt % varying from 6 to 9 wt. %. Olivine, orthopyroxene, clinopyroxene and garnet coexist with melt over the entire interval and rutile is also present at < 1000 oC. Melt is andesitic in composition and varies from 60 wt. % SiO2 at 950 oC to 52 wt. % at 1075 oC. The Al2O3 contents of the melt are 13 to 14 wt. %, and CaO contents range from 1 and 4 wt. %. Melting is peritectic with orthopyroxene + liquid produced by melting of garnet + olivine + high-Ca pyroxene. In addition to quenched melt, we observe a quenched silicate component that is rhyolitic (>72 % SiO2) that we interpret as a precipitate from the coexisting supercritical H2O-rich vapor. Extrapolation of the measured compositional variation toward the solidus suggests that the first melt may be very SiO2 rich (i.e., granitic). We suggest that these granitic melts are the first melts of the mantle near the slab-wedge interface. As these SiO2-rich melts ascend into shallower, hotter overlying mantle, they continue to interact with the surrounding mantle and evolve in composition. These first melts may elucidate the geochemical and physical processes that accompany the beginnings of H2O flux melting.

Abundance patterns of evolved stars with Hipparcos parallaxes and ages based on the APOGEE data base

NASA Astrophysics Data System (ADS)

Jia, Y. P.; Chen, Y. Q.; Zhao, G.; Bari, M. A.; Zhao, J. K.; Tan, K. F.

2018-01-01

We investigate the abundance patterns for four groups of stars at evolutionary phases from sub-giant to red clump (RC) and trace the chemical evolution of the disc by taking 21 individual elemental abundances from APOGEE and ages from evolutionary models with the aid of Hipparcos distances. We find that the abundances of six elements (Si, S, K, Ca, Mn and Ni) are similar from the sub-giant phase to the RC phase. In particular, we find that a group of stars with low [C/N] ratios, mainly from the second sequence of RC stars, show that there is a difference in the transfer efficiency of the C-N-O cycle between the main and the secondary RC sequences. We also compare the abundance patterns of C-N, Mg-Al and Na-O with giant stars in globular clusters from APOGEE and find that field stars follow similar patterns as M107, a metal-rich globular cluster with [M/H] ∼- 1.0, which shows that the self-enrichment mechanism represented by strong C-N, Mg-Al and Na-O anti-correlations may not be important as the metallicity reaches [M/H] > -1.0 dex. Based on the abundances of above-mentioned six elements and [Fe/H], we investigate age versus abundance relations and find some old super-metal-rich stars in our sample. Their properties of old age and being rich in metal are evidence for stellar migration. The age versus metallicity relations in low-[α/M] bins show unexpectedly positive slopes. We propose that the fresh metal-poor gas infalling on to the Galactic disc may be the precursor for this unexpected finding.

Distribution and Evolution of Yersinia Leucine-Rich Repeat Proteins

PubMed Central

Hu, Yueming; Huang, He; Hui, Xinjie; Cheng, Xi; White, Aaron P.

2016-01-01

Leucine-rich repeat (LRR) proteins are widely distributed in bacteria, playing important roles in various protein-protein interaction processes. In Yersinia, the well-characterized type III secreted effector YopM also belongs to the LRR protein family and is encoded by virulence plasmids. However, little has been known about other LRR members encoded by Yersinia genomes or their evolution. In this study, the Yersinia LRR proteins were comprehensively screened, categorized, and compared. The LRR proteins encoded by chromosomes (LRR1 proteins) appeared to be more similar to each other and different from those encoded by plasmids (LRR2 proteins) with regard to repeat-unit length, amino acid composition profile, and gene expression regulation circuits. LRR1 proteins were also different from LRR2 proteins in that the LRR1 proteins contained an E3 ligase domain (NEL domain) in the C-terminal region or an NEL domain-encoding nucleotide relic in flanking genomic sequences. The LRR1 protein-encoding genes (LRR1 genes) varied dramatically and were categorized into 4 subgroups (a to d), with the LRR1a to -c genes evolving from the same ancestor and LRR1d genes evolving from another ancestor. The consensus and ancestor repeat-unit sequences were inferred for different LRR1 protein subgroups by use of a maximum parsimony modeling strategy. Structural modeling disclosed very similar repeat-unit structures between LRR1 and LRR2 proteins despite the different unit lengths and amino acid compositions. Structural constraints may serve as the driving force to explain the observed mutations in the LRR regions. This study suggests that there may be functional variation and lays the foundation for future experiments investigating the functions of the chromosomally encoded LRR proteins of Yersinia. PMID:27217422

Water and ice in asteroids: Connections between asteroid observations and the chondritic meteorite record

NASA Astrophysics Data System (ADS)

Schmidt, B.; Dyl, K.

2014-07-01

The mid-outer main belt is rich in possible parent bodies for the water-bearing carbonaceous chondrites, given their dark surfaces and frequent presence of hydrated minerals (e.g., Feierberg et al. 1985). Ceres (Thomas et al. 2005) and Pallas (Schmidt et al. 2009) possess shapes that indicate that these bodies have achieved hydrostatic equilibrium and may be differentiated (rock from ice). Dynamical calculations suggest asteroids formed rapidly to large sizes to produce the size frequency distribution within today's main belt (e.g., Morbidelli et al. 2009). Water-ice bound to organics has now been detected on the surface of Themis (Rivkin and Emery 2009, Campins et al. 2009), and indirect evidence for ice on many of the remaining family members, including main-belt comets (Hsieh & Jewitt 2006, Castillo-Rogez & Schmidt 2010), supports the theory that the ''C-class'' asteroids formed early and ice-rich. The carbonaceous chondrites represent a rich history of the thermal and aqueous evolution of early planetesimals (e.g., McSween 1979, Bunch and Chang, 1980, Zolensky and McSween 1988, Clayton 1993, Rowe et al., 1994). The composition of these meteorites reflects the timing and duration of water flow, as well as subsequent mineral alteration and isotopic evolution that can constrain temperature and water-rock ratios in which these systematics were set (e.g., Young et al. 1999, Dyl et al. 2012). Debate exists as to how the chemical and thermal consequences of fluid flow on carbonaceous chondrite parent bodies relate to parent-body characteristics: small, static water bodies (e.g., McSween 1979); small, convecting but homogeneous bodies (e.g., Young et al. 1999, 2003); or larger convecting bodies (e.g., Grimm and McSween 1989, Palguta et al. 2010). Heterogeneous thermal and aqueous evolution on larger asteroids that suggests more than one class of carbonaceous chondrite may be produced on the same body (e.g., Castillo-Rogez & Schmidt 2010, Elkins-Tanton et al. 2011, Schmidt & Castillo-Rogez 2012) if the chemical consequences can be reconciled (e.g., Young 2001, Young et al. 2003). Both models (Schmidt and Castillo-Rogez 2012) and experiments (e.g., Hiroi et al. 1996) suggest that water loss from asteroids is an important factor in interpreting the connections between the C-class asteroids and meteorites. The arrival of the Dawn spacecraft to Ceres will determine its much-debated internal structure and finally answer the following question: did large, icy planetesimals form and thermally evolve in the inner solar system? Even if Ceres is not icy, Dawn observations will shed light on its surface composition, and by extension on the surfaces of objects with similar surface properties. This presentation will focus on tying the observational evidence for water on evolving and contemporary asteroids with detailed studies of the carbonaceous chondrites in an effort to synthesize physical and chemical realities with the observational record, bridging the gap between the asteroid and meteorite communities.

Development of cataclastic foliation in deformation bands in feldspar-rich conglomerates of the Rio do Peixe Basin, NE Brazil

NASA Astrophysics Data System (ADS)

Nicchio, Matheus A.; Nogueira, Francisco C. C.; Balsamo, Fabrizio; Souza, Jorge A. B.; Carvalho, Bruno R. B. M.; Bezerra, Francisco H. R.

2018-02-01

In this work we describe the deformation mechanisms and processes that occurred during the evolution of cataclastic deformation bands developed in the feldspar-rich conglomerates of the Rio do Peixe Basin, NE Brazil. We studied bands with different deformation intensities, ranging from single cm-thick tabular bands to more evolved clustering zones. The chemical identification of cataclastic material within deformation bands was performed using compositional mapping in SEM images, EDX and XRD analyses. Deformation processes were identified by microstructural analysis and by the quantification of comminution intensity, performed using digital image processing. The deformation bands are internally non homogeneous and developed during five evolutionary stages: (1) moderate grain size reduction, grain rotation and grain border comminution; (2) intense grain size reduction with preferential feldspar fragmentation; (3) formation of subparallel C-type slip zones; (4) formation of S-type structures, generating S-C-like fabric; and (5) formation of C‧-type slip zones, generating well-developed foliation that resembles S-C-C‧-type structures in a ductile environment. Such deformation fabric is mostly imparted by the preferential alignment of intensely comminuted feldspar fragments along thin slip zones developed within deformation bands. These processes were purely mechanical (i.e., grain crushing and reorientation). No clays or fluids were involved in such processes.

Chemistry in the final stages of stellar evolution: Millimeter and submillimeter observations of supergiants and planetary nebulae

NASA Astrophysics Data System (ADS)

Edwards, Jessica Louise

High mass loss rates in evolved stars make them the major contributors to recycling processed material back into the interstellar medium. This mass loss creates large circumstellar shells, rich in molecular material. This dissertation presents millimeter and submillimeter studies of the end stages of low mass and high mass stars in order to probe their molecular content in more detail. In low mass stars, the molecular material is carried on into the planetary nebula (PN) stage. Observations of CS, HCO+, and CO in planetary nebulae (PNe) of various post-asymptotic giant branch ages have shown that molecular abundances in these objects do not significantly vary with age, as previously thought. More detailed observations of the slightly oxygen-rich PN NGC 6537 resulted in the detection of CN, HCN, HNC, CCH, CS, SO, H 2CO, HCO+ and N2H+, as well as numerous 13C isotopologues. Observations of the middle-aged PN M2-48 showed the presence of CN, HCN, HNC, CS, SO, SO2, SiO, HCO+, N2H+, and several 13C isotopologues. These observations represent the first detections of CS, SO, SO2, and SiO in any planetary nebula. The implications of these observations are discussed. A 1 mm spectral survey of the supergiant star NML Cygni has been carried out with the Arizona Radio Observatory Submillimeter Telescope resulting in the observation of 102 emission features arising from 17 different molecules and 4 unidentified features. The line profiles observed in this circumstellar shell are asymmetric and vary between different molecules, akin to what has been seen in another supergiant, VY Canis Majoris. The non-LTE radiative transfer code ESCAPADE has been used to model molecular abundances in the various asymmetric outflows of VY Canis Majoris, showing just how chemically and kinematically complex these supergiant circumstellar envelopes really are.

Cannibals in the thick disk: the young α-rich stars as evolved blue stragglers

NASA Astrophysics Data System (ADS)

Jofré, P.; Jorissen, A.; Van Eck, S.; Izzard, R. G.; Masseron, T.; Hawkins, K.; Gilmore, G.; Paladini, C.; Escorza, A.; Blanco-Cuaresma, S.; Manick, R.

2016-10-01

Spectro-seismic measurements of red giants enabled the recent discovery of stars in the thick disk that are more massive than 1.4 M⊙. While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 "young" stars and 13 "old" stars with similar stellar parameters but with masses below 1.2 M⊙ and found that more of the young starsappear to be in binary systems with respect to the old stars.Furthermore, we show that the young stars do not follow the expected trend of [C/H] ratios versus mass for individual stars. However, with a population synthesis of low-mass stars including binary evolution and mass transfer, we can reproduce the observed [C/N] ratios versus mass. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study the evolution of field blue stragglers after they have left the main-sequence.

Tracing the potential planet-forming regions around seven pre-main-sequence stars

NASA Astrophysics Data System (ADS)

Schegerer, A. A.; Wolf, S.; Hummel, C. A.; Quanz, S. P.; Richichi, A.

2009-07-01

Aims: We investigate the nature of the innermost regions with radii of several AUs of seven circumstellar disks around pre-main-sequence stars, T Tauri stars in particular. Our object sample contains disks apparently at various stages of their evolution. Both single stars and spatially resolved binaries are considered. In particular, we search for inner disk gaps as proposed for several young stellar objects (YSOs). When analyzing the underlying dust population in the atmosphere of circumstellar disks, the shape of the 10 μm feature should additionally be investigated. Methods: We performed interferometric observations in N band (8-13 μm) with the Mid-Infrared Interferometric Instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) using baseline lengths of between 54 m and 127 m. The data analysis is based on radiative-transfer simulations using the Monte Carlo code MC3D by modeling simultaneously the spectral energy distribution (SED), N band spectra, and interferometric visibilities. Correlated and uncorrelated N band spectra are compared to investigate the radial distribution of the dust composition of the disk atmosphere. Results: Spatially resolved mid-infrared (MIR) emission was detected in all objects. For four objects (DR Tau, RU Lup, S CrA N, and S CrA S), the observed N band visibilities and corresponding SEDs could be simultaneously simulated using a parameterized active disk-model. For the more evolved objects of our sample, HD 72106 and HBC 639, a purely passive disk-model provides the closest fit. The visibilities inferred for the source RU Lup allow the presence of an inner disk gap. For the YSO GW Ori, one of two visibility measurements could not be simulated by our modeling approach. All uncorrelated spectra reveal the 10 μm silicate emission feature. In contrast to this, some correlated spectra of the observations of the more evolved objects do not show this feature, indicating a lack of small silicates in the inner versus the outer regions of these disks. We conclude from this observational result that more evolved dust grains can be found in the more central disk regions. Based on observations made with Telescopes of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) at the Paranal Observatory, Chile, under the programs 074.C-0342(A), 075.C-0064(A,B), 075.C-0413(A,B), and 076.C-0356(A). Appendix A is only available in electronic form at http://www.aanda.org

Leveraging object-oriented development at Ames

NASA Technical Reports Server (NTRS)

Wenneson, Greg; Connell, John

1994-01-01

This paper presents lessons learned by the Software Engineering Process Group (SEPG) from results of supporting two projects at NASA Ames using an Object Oriented Rapid Prototyping (OORP) approach supported by a full featured visual development environment. Supplemental lessons learned from a large project in progress and a requirements definition are also incorporated. The paper demonstrates how productivity gains can be made by leveraging the developer with a rich development environment, correct and early requirements definition using rapid prototyping, and earlier and better effort estimation and software sizing through object-oriented methods and metrics. Although the individual elements of OO methods, RP approach and OO metrics had been used on other separate projects, the reported projects were the first integrated usage supported by a rich development environment. Overall the approach used was twice as productive (measured by hours per OO Unit) as a C++ development.

New and updated stellar parameters for 71 evolved planet hosts. On the metallicity-giant planet connection

NASA Astrophysics Data System (ADS)

Mortier, A.; Santos, N. C.; Sousa, S. G.; Adibekyan, V. Zh.; Delgado Mena, E.; Tsantaki, M.; Israelian, G.; Mayor, M.

2013-09-01

Context. It is still being debated whether the well-known metallicity-giant planet correlation for dwarf stars is also valid for giant stars. For this reason, having precise metallicities is very important. Precise stellar parameters are also crucial to planetary research for several other reasons. Different methods can provide different results that lead to discrepancies in the analysis of planet hosts. Aims: To study the impact of different analyses on the metallicity scale for evolved stars, we compare different iron line lists to use in the atmospheric parameter derivation of evolved stars. Therefore, we use a sample of 71 evolved stars with planets. With these new homogeneous parameters, we revisit the metallicity-giant planet connection for evolved stars. Methods: A spectroscopic analysis based on Kurucz models in local thermodynamic equilibrium (LTE) was performed through the MOOG code to derive the atmospheric parameters. Two different iron line list sets were used, one built for cool FGK stars in general, and the other for giant FGK stars. Masses were calculated through isochrone fitting, using the Padova models. Kolmogorov-Smirnov tests (K-S tests) were then performed on the metallicity distributions of various different samples of evolved stars and red giants. Results: All parameters compare well using a line list set, designed specifically for cool and solar-like stars to provide more accurate temperatures. All parameters derived with this line list set are preferred and are thus adopted for future analysis. We find that evolved planet hosts are more metal-poor than dwarf stars with giant planets. However, a bias in giant stellar samples that are searched for planets is present. Because of a colour cut-off, metal-rich low-gravity stars are left out of the samples, making it hard to compare dwarf stars with giant stars. Furthermore, no metallicity enhancement is found for red giants with planets (log g < 3.0 dex) with respect to red giants without planets. The data presented here are based on observations collected at the La Silla Paranal Observatory, ESO (Chile) with the FEROS spectrograph at the 2.2 m telescope (ESO runs ID 70.C-0084, 088.C-0892, 089.C-0444, and 090.C-0146) and the HARPS spectrograph at the 3.6 m telescope (ESO run ID 72.C-0488); at the Paranal Observatory, ESO (Chile) with the UVES spectrograph at the VLT Kueyen telescope (ESO runs ID 074.C-0134, 079.C-0131, 380.C-0083, and 083.C-0174); at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with the FIES spectrograph at the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden (program ID 44-210); and at the Observatoire de Haute-Provence (OHP, CNRS/OAMP), France with the SOPHIE spectrographs at the 1.93 m telescope (program ID 11B.DISC.SOUS).Tables 1, 5, 6 and Appendix A are available in electronic form at http://www.aanda.orgTables 5, 6, and A.1 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A70

The Role of Coherent Detection

NASA Technical Reports Server (NTRS)

Zmuidzinas, J.

2004-01-01

Many interesting astronomical objects, such as galaxies, molecular clouds, PDRs, star - forming regions, protostars, evolved stars, planets, and comets, have rich submillimeter spectra. In order to avoid line blending, and to be able to resolve the line shape, it is often necessary to measure these spectra at high resolution. This paper discusses the relative advantages and limitations of coherent and direct detection for high resolution spectroscopy in the submillimeter and far - infrared. In principle, direct detection has a fundamental sensitivity advantage. In practice, it is di.cult to realize this advantage given the sensitivities of existing detectors and reasonable constraints on the instrument volume. Thus, coherent detection can be expected to play an important role in submillimeter and far - infrared astrophysics well into the future.

CPD -20 1123 (Albus 1) Is a Bright He-B Subdwarf

NASA Astrophysics Data System (ADS)

Vennes, Stéphane; Kawka, Adéla; Smith, J. Allyn

2007-10-01

Based on photometric and astrometric data it has been proposed that Albus 1 (also known as CPD -20 1123) might be a hot white dwarf similar to G191-B2B or, alternatively, a hot subdwarf. We obtained a series of optical spectra showing that CPD -20 1123 is a bright He-B subdwarf. We analyzed the H I Balmer and He I line spectra and measured Teff = 19,800 +/- 400 K, logg=4.55+/-0.10, and logN(He)/N(H)=0.15+/-0.15. This peculiar object belongs to a family of evolved helium-rich stars that may be the products of double-degenerate mergers, or, alternatively, the products of post horizontal- or giant-branch evolution.

Hints of a rotating spiral structure in the innermost regions around IRC +10216

PubMed Central

Quintana-Lacaci, G.; Cernicharo, J.; Agúndez, M.; Prieto, L. Velilla; Castro-Carrizo, A.; Marcelino, N.; Cabezas, C.; Peña, I.; Alonso, J.L.; Zúñiga, J.; Requena, A.; Bastida, A.; Kalugina, Y.; Lique, F.; Guélin, M.

2016-01-01

The Atacama Large Millimeter/submillimeter Array (ALMA) is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with un-precedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions, with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08M☉. Alternatively, a torus of gas and dust would result in similar structures as those observed. From the torus scenario we derive a mass of ~ 1.1 × 10−4M☉. In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species. PMID:26997665

Hints of a rotating spiral structure in the innermost regions around IRC +10216.

PubMed

Quintana-Lacaci, G; Cernicharo, J; Agúndez, M; Prieto, L Velilla; Castro-Carrizo, A; Marcelino, N; Cabezas, C; Peña, I; Alonso, J L; Zúñiga, J; Requena, A; Bastida, A; Kalugina, Y; Lique, F; Guélin, M

2016-02-20

The Atacama Large Millimeter/submillimeter Array (ALMA) is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with un-precedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules towards the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions, with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08 M ☉ . Alternatively, a torus of gas and dust would result in similar structures as those observed. From the torus scenario we derive a mass of ~ 1.1 × 10 -4 M ☉ . In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species.

Hints of a Rotating Spiral Structure in the Innermost Regions around IRC+10216

NASA Astrophysics Data System (ADS)

Quintana-Lacaci, G.; Cernicharo, J.; Agúndez, M.; Velilla Prieto, L.; Castro-Carrizo, A.; Marcelino, N.; Cabezas, C.; Peña, I.; Alonso, J. L.; Zúñiga, J.; Requena, A.; Bastida, A.; Kalugina, Y.; Lique, F.; Guélin, M.

2016-02-01

The Atacama Large Millimeter/submillimeter Array is allowing us to study the innermost regions of the circumstellar envelopes of evolved stars with unprecedented precision and sensitivity. Key processes in the ejection of matter and dust from these objects occur in their inner zones. In this work, we present sub-arcsecond interferometric maps of transitions of metal-bearing molecules toward the prototypical C-rich evolved star IRC +10216. While Al-bearing molecules seem to be present as a roughly spherical shell, the molecular emission from the salts NaCl and KCl presents an elongation in the inner regions with a central minimum. In order to accurately analyze the emission from the NaCl rotational lines, we present new calculations of the collisional rates for this molecule based on new spectroscopic constants. The most plausible interpretation for the spatial distribution of the salts is a spiral with a NaCl mass of 0.08 {M}⊙ . Alternatively, a torus of gas and dust would result in structures similar to those observed. From the torus scenario we derive a mass of ˜1.1 × 10-4 {M}⊙ . In both cases, the spiral and the torus, the NaCl structure presents an inner minimum of 27 AU. In the case of the torus, the outer radius is 73 AU. The kinematics of both the spiral and the torus suggests that they are slowly expanding and rotating. Alternative explanations for the presence of the elongation are explored. The presence of these features only in KCl and NaCl might be a result of their comparatively high dipole moment with respect to the Al-bearing species.

Reliable samples of quasars and hot stars from a spectrophotometric survey of the U.S. catalogs

NASA Technical Reports Server (NTRS)

Mitchell, Kenneth J.

1987-01-01

The U.S. survey for blue- and ultraviolet-excess starlike objects is reviewed, focusing on the features which have contributed to its accuracy. The spectrophotometric survey is described in terms of the observational setup and procedures. It is suggested that the survey has produced reliably classified samples of quasars and hot evolved stars and that the procedures used in the study provide a means of deriving distance and luminosity information about these objects. Several cumulative number counts and spectra of a DA white dwarf and a quasar with prominent C IV and C III emission are given as examples.

X-ray Scaling Relations of Early Type Galaxies

NASA Astrophysics Data System (ADS)

Kim, Dong-Woo

2015-08-01

We will review recent results of the X-ray scaling relations of early type galaxies. With high quality Chandra X-ray data, the properties (Lx and T) of hot ISM are accurately measured from gas-poor to gas-rich galaxies. We found a strong correlation between Lx(gas) and M(total) among ETGs with independently measured M(total), indicating that the total mass is the primary factor in regulating the amount of hot gas. We found a tight correlation between Lx(gas) and T(gas) among normal (non-cD), genuine (passively evolving, sigma-supported) ellipticals. This relation holds in a large range of Lx (several 1038 - a few 1041 erg/s). While this relation can be understood among gas-rich galaxies (Lx > 1040 erg/s) as a consequence of virialized gaseous halos in the dark matter potentials, the same tight relation is unexpected among gas-poor galaxies where the hot gas is in a wind/outflow state. We also found an interesting difference between cDs and giant Es, the former having an order of magnitude higher Lx(gas) with a similar T(gas). We will discuss the implications of our results by comparing with other observations of galaxies/groups and recent simulations.

Volatile element chemistry of selected lunar, meteoritic, and terrestrial samples

NASA Technical Reports Server (NTRS)

Simoneit, B. R.; Christiansen, P. C.; Burlingame, A. L.

1973-01-01

Using vacuum pyrolysis and high resolution mass spectrometry, a study is made of the gas release patterns of representative lunar samples, meteorites, terrestrial samples, and synthetic samples doped with various sources of carbon and nitrogen. The pyrolytic gas evolution patterns were intercorrelated, allowing an assessment of the possible sources of the volatilizable material in the lunar samples to be made. Lightly surface adsorbed species and more strongly chemisorbed species are released from ambient to 300 C and from 300 to 500 C, respectively. The low-temperature volatiles (less than 500 C) derived from various chondrites correlate well with the gas evolution patterns of volatile-rich samples, as for example 74220 and 61221. Solar wind entrapped species and molecules derived from reactions probably in the grain surfaces are evolved from about 500 to 700 C, respectively. Solar wind implanted C, N, and S species are generated from 750 to 1150 C, probably by reaction with the mineral matrix during the annealing process. Possible indigenous and/or refractory carbide, nitride, and sulfide C, N, and S are released in the region from 1200 C to fusion.

Relation of Cholesterol and Lipoprotein Parameters with Carotid Artery Plaque Characteristics: the Atherosclerosis Risk in Communities (ARIC) Carotid MRI Study

PubMed Central

Virani, Salim S.; Catellier, Diane J.; Pompeii, Lisa A.; Nambi, Vijay; Hoogeveen, Ron C.; Wasserman, Bruce A.; Coresh, Josef; Mosley, Thomas H.; Otvos, James D.; Sharrett, A. Richey; Boerwinkle, Eric; Ballantyne, Christie M.

2011-01-01

Objective There is a paucity of data regarding relations of apolipoproteins (apolipoprotein B [ApoB] and apolipoprotein A-1 [Apo A-1]), lipoprotein particle measures (low-density lipoprotein particle concentration [LDLp] and high-density lipoprotein particle concentration [HDLp]), and lipoprotein cholesterol measures (low-density lipoprotein cholesterol [LDL-C], non–high-density lipoprotein cholesterol [non– HDL-C], and high-density lipoprotein cholesterol [HDL-C]) with atherosclerotic plaque burden, plaque eccentricity, and lipid-rich core presence as a marker of high-risk plaques. Methods Carotid artery magnetic resonance imaging was performed in 1,670 Atherosclerosis Risk in Communities study participants. Vessel wall and lipid cores were measured; normalized wall index (NWI), standard deviation (SD) of wall thickness (measure of plaque eccentricity) were calculated; and lipid cores were detected in vessels with ≥1.5 mm thickness. Fasting concentrations of cholesterol, ApoB and Apo A-1, and LDLp and HDLp were measured. Results Measures of plaque burden (carotid wall volume, wall thickness, and NWI) were positively associated with atherogenic cholesterol and lipoproteins (p<0.05 for total cholesterol, LDL-C, non–HDL-C, ApoB, and LDLp), but not with HDL-C, Apo A-1, or HDLp. SD of wall thickness was associated with total cholesterol (p 0.01) and non-HDL-C (p 0.02). Although measures of atherogenic or anti-atherogenic cholesterol or lipoprotein were not individually associated with detection of a lipid-rich core, their ratios (total cholesterol/HDL-C, non–HDL-C/ HDL-C, and LDLp/HDLp) were associated with lipid-rich core presence (p≤0.05). Conclusion Extent of carotid atherosclerosis is associated with atherogenic cholesterol and lipoproteins. Atherogenic/anti-atherogenic cholesterol or particle ratios were associated with presence of a detectable lipid-rich core. PMID:21868017

Complex Formation History of Highly Evolved Basaltic Shergottite, Zagami

NASA Technical Reports Server (NTRS)

Niihara, T.; Misawa, K.; Mikouchi, T.; Nyquist, L. E.; Park, J.; Hirata, D.

2012-01-01

Zagami, a basaltic shergottite, contains several kinds of lithologies such as Normal Zagami consisting of Fine-grained (FG) and Coarse-grained (CG), Dark Mottled lithology (DML), and Olivine-rich late-stage melt pocket (DN). Treiman and Sutton concluded that Zagami (Normal Zagami) is a fractional crystallization product from a single magma. It has been suggested that there were two igneous stages (deep magma chamber and shallow magma chamber or surface lava flow) on the basis of chemical zoning features of pyroxenes which have homogeneous Mg-rich cores and FeO, CaO zoning at the rims. Nyquist et al. reported that FG has a different initial Sr isotopic ratio than CG and DML, and suggested the possibility of magma mixing on Mars. Here we report new results of petrology and mineralogy for DML and the Olivine-rich lithology (we do not use DN here), the most evolved lithology in this rock, to understand the relationship among lithologies and reveal Zagami s formation history

Sample Handling and Instruments for the In-Situ Exploration of Ice-Rich Planets. Chapter 9

NASA Technical Reports Server (NTRS)

Castillo, Julie C.; Bar-Cohen, Yoseph; Vance, Steve; Choukroun, Mathieu; Lee, Hyeong Jae; Bao, Xiaoqi; Badescu, Mircea; Sherrit, Stewart; Trainer, Melissa G.; Getty, Stephanie A.

2016-01-01

NASA's key science goals for the exploration of the solar system seek a better understanding of the formation and evolutionary processes that have shaped planetary bodies and emphasize the search for habitable environments. Efforts are also made to detect and quantify resources that could be used for the support of human exploration. These themes call for chemistry and physical property observations that may be best approached by in situ measurements. NASA's planetary missions have progressively evolved from remote reconnaissance to in situ exploration with the ultimate goal to return samples. This chapter focuses on the techniques, available or in development, for advanced geophysical and chemical characterization of icy bodies, especially Mars polar areas, Enceladus, Titan, Europa, and Ceres. These astrobiological targets are the objects of recent or ongoing exploration whose findings are driving the formulation of new missions that involve in situ exploration. After reviewing the overall objectives of icy body exploration (Section 9.1) we describe key techniques used for addressing these objectives from surface platforms via geophysical observations (Section 9.2) and chemical measurements (Section 9.3).

Morphological Characterization Of Titania Slag Obtained From Red Sediment Placer Ilmenite Using Microwave Energy

NASA Astrophysics Data System (ADS)

Srikant, S. S.; Mukherjee, P. S.; Bhima Rao, R.

2015-04-01

This paper deals with the main objective to observe the effect of microwave heat treatment for the production of Titania rich slag and pig iron from placer ilmenite. The experiments carried out in the present investigation on the oxidized ilmenite sample for microwave heat treatment in microwave sintering furnace reveals that a product can be obtained containing Titania rich slag and metalized iron. The in-depth characterisation of these products using SEM-EDAX shows that around 75-85 % of titanium dioxide is formed in terms of titania rich slag by using microwave sintering furnace after reduction of oxidized ilmenite with proper stoichiometric graphitic carbon and silicon carbide (SiC) susceptor. The titania rich slag is considered to be better input material for production of pigment grade titanium dioxide. On the other hand, the pig iron obtained as by product from titania rich slag is also important for automobile and steel industries application.

Rich media streaming for just-in-time training of first responders

NASA Astrophysics Data System (ADS)

Bandera, Cesar; Marsico, Michael

2005-05-01

The diversity of first responders and of asymmetric threats precludes the effectiveness of any single training syllabus. Just-in-time training (JITT) addresses this variability, but requires training content to be quickly tailored to the subject (the threat), the learner (the responder), and the infrastructure (the C2 chain from DHS to the responder"s equipment). We present a distributed system for personalized just-in-time training of first responders. The authoring and delivery of interactive rich media and simulations, and the integration of JITT with C2 centers, are demonstrated. Live and archived video, imagery, 2-D and 3-D models, and simulations are autonomously (1) aggregated from object-oriented databases into SCORM-compliant objects, (2) tailored to the individual learner"s training history, preferences, connectivity and computing platform (from workstations to wireless PDAs), (3) conveyed as secure and reliable MPEG-4 compliant streams with data rights management, and (4) rendered as interactive high-definition rich media that promotes knowledge retention and the refinement of learner skills without the need of special hardware. We review the object-oriented implications of SCORM and the higher level profiles of the MPEG-4 standard, and show how JITT can be integrated into - and improve the ROI of - existing training infrastructures, including COTS content authoring tools, LMS/CMS, man-in-the-loop simulators, and legacy content. Lastly, we compare the audiovisual quality of different streaming platforms under varying connectivity conditions.

Studying Antarctic Ordinary Chondrite (OC) and Miller Range (MIL) Nakhlite Meteorites to Assess Carbonate Formation on Earth and Mars

NASA Astrophysics Data System (ADS)

Evans, Michael Ellis

Carbonates are found in meteorites collected from Antarctica. The stable isotope composition of these carbonates records their formation environment on either Earth or Mars. The first research objective of this dissertation is to characterize the delta18O and delta 13C values of terrestrial carbonates formed on Ordinary Chondrites (OCs) collected in regions near known martian meteorites. The second objective is to characterize the delta18O and delta13C values of martian carbonates from Nakhlites collected from the Miller Range (MIL). The third objective is to assess environmental changes on Mars since the Noachian period. The OCs selected had no pre-terrestrial carbonates so any carbonates detected are presumed terrestrial in origin. The study methodology is stepped extraction of CO2 created from phosphoric acid reaction with meteorite carbonate. Stable isotope results show that two distinct terrestrial carbonate species (Ca-rich and Fe/Mg-rich) formed in Antarctica on OCs from a thin-film of meltwater containing dissolved CO2. Carbon isotope data suggests the terrestrial carbonates formed in equilibrium with atmospheric CO2 delta 13C = -7.5‰ at >15°C. The wide variation in delta 18O suggests the carbonates did not form in equilibrium with meteoric water alone, but possibly formed from an exchange of oxygen isotopes in both water and dissolved CO2. Antarctica provides a model for carbonate formation in a low water/rock ratio, near 0°C environment like modern Mars. Nakhlite parent basalt formed on Mars 1.3 billion years ago and the meteorites were ejected by a single impact approximately 11 million years ago. They traveled thru space before eventually falling to the Earth surface 10,000-40,000 years ago. Nakhlite samples for this research were all collected from the Miller Range (MIL) in Antarctica. The Nakhlite stable isotope results show two carbonate species (Ca-rich and Fe/Mg-rich) with a range of delta18O values that are similar to the terrestrial OC carbonates. The Nakhlite carbonates have distinctly different, heavier delta13C values from a presumed martian carbon reservoir. These carbonates cannot form in equilibrium at 15°C with the modern Mars atmospheric CO2 (measured by the Curiosity rover) delta13C = 46‰, but may reflect kinetic carbonate formation from a high pH fluid. Alternatively, the Nakhlite carbonates may have formed with a lighter, early Amazonian atmosphere of delta 13C ≈ 30‰. Assuming the martian carbonates formed in a thin-film environment like the OC terrestrial carbonates, an oxygen mixing model predicts early Amazonian martian meteoric water delta18O = -30‰.

Carbon Characteristics and Biogeochemical Processes of Uranium Accumulating Organic Matter Rich Sediments in the Upper Colorado River Basin

NASA Astrophysics Data System (ADS)

Boye, K.; Noel, V.; Tfaily, M. M.; Dam, W. L.; Bargar, J.; Fendorf, S. E.

2015-12-01

Uranium plume persistence in groundwater aquifers is a problem on several former ore processing sites on floodplains in the upper Colorado River Basin. Earlier observations by our group and others at the Old Rifle Site, CO, have noted that U concentrations are highest in organic rich, fine-grained, and, therefore, diffusion limited sediment material. Due to the constantly evolving depositional environments of floodplains, surficial organic matter may become buried at various stages of decomposition, through sudden events such as overbank flooding and through the slower progression of river meandering. This creates a discontinuous subsurface distribution of organic-rich sediments, which are hotspots for microbial activity and thereby central to the subsurface cycling of contaminants (e.g. U) and biologically relevant elements (e.g. C, N, P, Fe). However, the organic matter itself is poorly characterized. Consequently, little is known about its relevance in driving biogeochemical processes that control U fate and transport in the subsurface. In an investigation of soil/sediment cores from five former uranium ore processing sites on floodplains distributed across the Upper Colorado River Basin we confirmed consistent co-enrichment of U with organic-rich layers in all profiles. However, using C K-edge X-ray Absorption Spectroscopy (XAS) coupled with Fourier-Transformed Ion-Cyclotron-Resonance Mass-Spectroscopy (FT-ICR-MS) on bulk sediments and density-separated organic matter fractions, we did not detect any chemical difference in the organic rich sediments compared to the surrounding coarser-grained aquifer material within the same profile, even though there were differences in organic matter composition between the 5 sites. This suggests that U retention and reduction to U(IV) is independent of C chemical composition on the bulk scale. Instead it appears to be the abundance of organic matter in combination with a limited O2 supply in the fine-grained material that stimulate anaerobic microbial processes responsible for U enrichment. Thus, the chemical composition of organic matter is subordinate to the physical environment and total organic matter content in controlling U reduction and retention processes.

The frequency and properties of young tidal dwarf galaxies in nearby gas-rich groups

NASA Astrophysics Data System (ADS)

Lee-Waddell, K.; Spekkens, K.; Chandra, P.; Patra, N.; Cuillandre, J.-C.; Wang, J.; Haynes, M. P.; Cannon, J.; Stierwalt, S.; Sick, J.; Giovanelli, R.

2016-08-01

We present high-resolution Giant Metrewave Radio Telescope (GMRT) H I observations and deep Canada-France-Hawaii Telescope (CFHT) optical imaging of two galaxy groups: NGC 4725/47 and NGC 3166/9. These data are part of a multi-wavelength unbiased survey of the gas-rich dwarf galaxy populations in three nearby interacting galaxy groups. The NGC 4725/47 group hosts two tidal knots and one dwarf irregular galaxy (dIrr). Both tidal knots are located within a prominent H I tidal tail, appear to have sufficient mass (Mgas ≈ 108 M⊙) to evolve into long-lived tidal dwarf galaxies (TDGs) and are fairly young in age. The NGC 3166/9 group contains a TDG candidate, AGC 208457, at least three dIrrs and four H I knots. Deep CFHT imaging confirms that the optical component of AGC 208457 is bluer - with a 0.28 mag g - r colour - and a few Gyr younger than its purported parent galaxies. Combining the results for these groups with those from the NGC 871/6/7 group reported earlier, we find that the H I properties, estimated stellar ages and baryonic content of the gas-rich dwarfs clearly distinguish tidal features from their classical counterparts. We optimistically identify four potentially long-lived tidal objects associated with three separate pairs of interacting galaxies, implying that TDGs are not readily produced during interaction events as suggested by some recent simulations. The tidal objects examined in this survey also appear to have a wider variety of properties than TDGs of similar mass formed in current simulations of interacting galaxies, which could be the result of pre- or post-formation environmental influences.

Spectral analysis of four surprisingly similar hot hydrogen-rich subdwarf O stars

NASA Astrophysics Data System (ADS)

Latour, M.; Chayer, P.; Green, E. M.; Irrgang, A.; Fontaine, G.

2018-01-01

Context. Post-extreme horizontal branch stars (post-EHB) are helium-shell burning objects evolving away from the EHB and contracting directly towards the white dwarf regime. While the stars forming the EHB have been extensively studied in the past, their hotter and more evolved progeny are not so well characterized. Aims: We perform a comprehensive spectroscopic analysis of four such bright sdO stars, namely Feige 34, Feige 67, AGK+81°266, and LS II+18°9, among which the first three are used as standard stars for flux calibration. Our goal is to determine their atmospheric parameters, chemical properties, and evolutionary status to better understand this class of stars that are en route to become white dwarfs. Methods: We used non-local thermodynamic equilibrium model atmospheres in combination with high quality optical and UV spectra. Photometric data were also used to compute the spectroscopic distances of our stars and to characterize the companion responsible for the infrared excess of Feige 34. Results: The four bright sdO stars have very similar atmospheric parameters with Teff between 60 000 and 63 000 K and log g (cm s-2) in the range 5.9 to 6.1. This places these objects right on the theoretical post-EHB evolutionary tracks. The UV spectra are dominated by strong iron and nickel lines and suggest abundances that are enriched with respect to those of the Sun by factors of 25 and 60. On the other hand, the lighter elements, C, N, O, Mg, Si, P, and S are depleted. The stars have very similar abundances, although AGK+81°266 shows differences in its light element abundances. For instance, the helium abundance of this object is 10 times lower than that observed in the other three stars. All our stars show UV spectral lines that require additional line broadening that is consistent with a rotational velocity of about 25 km s-1. The infrared excess of Feige 34 is well reproduced by a M0 main-sequence companion and the surface area ratio of the two stars suggests that the system is a physical binary. However, the lack of radial velocity variations points towards a low inclination and/or long orbital period. Spectroscopic and Hipparcos distances are in good agreement for our three brightest stars. Conclusions: We performed a spectroscopic analysis of four hot sdO stars that are very similar in terms of atmospheric parameters and chemical compositions. The rotation velocities of our stars are significantly higher than what is observed in their immediate progenitors on the EHB, suggesting that angular momentum may be conserved as the stars evolve away from the EHB.

Forms of Memory for Representation of Visual Objects

DTIC Science & Technology

1991-04-15

neuropsychological syndromes that involve disruption of perceptual representation systems should pay rich dividends for implicit memory research (Schacter et al...BLACKORDi. 1988b. Deficits in the implicit retention of new associations by alcoholic Korsakoff patients. Brain and Cognition 7: 145-156. COFER, C. C...MOREINES & N. BUTTERS. 1973. Retrieving information from Korsakoff patients: Effects of categorical cues and reference to the task. Cortex 9: 165

Modelling a set of C-rich AGB stars: the cases of RU Vir and R Lep

NASA Astrophysics Data System (ADS)

Rau, G.; Paladini, C.; Hron, J.; Aringer, B.; Groenewegen, M. A. T.; Nowotny, W.

We study the atmospheres of a set of carbon-rich asymptotic giant branch AGB stars to improve our understanding of the dynamic processes happening there. We compare in a systematic way spectrometric, photometric and mid-infrared (VLTI/MIDI) interferometric measurements with different types of model atmospheres: (1) hydrostatic models + MOD-dusty models added a posteriori; (2) self-consistent dynamic model atmospheres. These allow us to interpret in a coherent way the dynamic behavior of gas and dust. The results underline that the joint use of different kinds of observations, as photometry, spectroscopy and interferometry, is essential for understanding the atmospheres of pulsating C-rich AGB stars. For our first target, the carbon-rich Mira star RU Vir, the dynamic model atmospheres fit well the ISO/SWS spectrum in the wavelength range lambda = [2.9, 13.0] mu m. However, the object turned out to be somehow ''peculiar''. The other target we present is R Lep. Here the agreement between models and observations is much better although the MIDI data at 11.4 mu m cannot be properly modelled.

The effect of grain boundary misorientation on the intergranular M 23C 6 carbide precipitation in thermally treated Alloy 690

NASA Astrophysics Data System (ADS)

Lim, Yun Soo; Kim, Joung Soo; Kim, Hong Pyo; Cho, Hai Dong

2004-10-01

The precipitation characteristics of chromium carbides on various types of grain boundaries in Alloy 690 thermally treated at 720 °C for 10 h were studied through transmission electron microscopy. Precipitation of the intergranular chromium carbides, identified as Cr-rich M 23C 6, was retarded on the low angle grain boundaries, compared to that on the random high angle grain boundaries on which coarse and discrete ones were found. They were rarely found on the coherent twin boundaries, however, needle-like ones were evolved on the incoherent twin and twin related Σ9 boundaries. Precipitation of the chromium carbides was also suppressed on the nearly exact coincidence site lattice boundaries such as Σ11 and Σ15, for which the Brandon criterion was fulfilled. The results of the intergranular M 23C 6 carbide precipitation were explained in terms of the influence of the grain boundary energy.

The Physics and Chemistry of Oxygen-Rich Circumstellar Envelopes as Traced by Simple Molecules

NASA Astrophysics Data System (ADS)

Wong, Ka Tat

2018-04-01

The physics and chemistry of the circumstellar envelopes (CSEs) of evolved stars are not fully understood despite decades of research. This thesis addresses two issues in the study of the CSEs of oxygen-rich (O-rich) evolved stars. In the first project, the ammonia (NH3) chemistry of O-rich stars is investigated with multi-wavelength observations; in the second project, the extended atmosphere and inner wind of the archetypal asymptotic giant branch (AGB) star o Ceti (Mira) is studied with high-angular resolution observations. One of the long-standing mysteries in circumstellar chemistry is the perplexing overabundance of the NH3 molecule. NH3 in O-rich evolved stars has been found in much higher abundance, by several orders of magnitude, than that expected in equilibrium chemistry. Several mechanisms have been suggested in the literature to explain this high NH3 abundance, including shocks in the inner wind, photodissociation of nitrogen by interstellar ultraviolet radiation, and nitrogen enrichment in stellar nucleosynthesis; however, none of these suggestions can fully explain the abundances of NH3 and various other molecular species in the CSEs of O-rich stars. In order to investigate the distribution of NH3 in O-rich CSEs, observations of the spectral lines of NH3 from a diverse sample of evolved stars and in different wavelength regimes are necessary. In this thesis, the NH3 line emission and absorption from four O-rich stars are studied. These targets include the AGB star IK Tauri, the pre-planetary nebula OH 231.8+4.2, the red supergiant VY Canis Majoris, and the yellow hypergiant IRC +10420. The amount of NH3 observational data has increased drastically thanks to the recent advancement of instrumentation. Observations of NH3 rotational line emission at submillimetre/far-infrared wavelengths were possible with the Herschel Space Observatory (2009–2013). The new wideband correlator in the upgraded Karl G. Janksy Very Large Array (VLA) provided data of multiple radio inversion lines of NH3. Furthermore, mid-infrared absorption of NH3 has been observed by the NASA Infrared Telescope Facility (IRTF) for IK Tau and VY CMa. Full radiative transfer modelling including mid-infrared pumping to the first vibrationally excited state (v2=1) has been carried out to reproduce the observed emission and absorption spectra and to retrieve the NH3 abundances in the targets. It is found that the NH3 emission in the CSEs of the targets arises from localised spatial-kinematic structures in which the gas density may be higher than in the surrounding gas. Circumstellar shocks may contribute to, but cannot fully account for, the formation of the molecule. Besides circumstellar chemistry, our understanding of the dust formation and wind-driving mechanisms of oxygen-rich evolved stars is still incomplete. One of the obstacles in the past was the difficulty in imaging the dust condensation and wind acceleration zones due to the lack of high-angular resolution instruments. Thanks to the Atacama Large Millimeter/submillimeter Array (ALMA), which has the longest baseline of about 15 km, we are now able to produce high-fidelity images at unprecedented angular resolutions of tens of milliarcseconds (mas) in the (sub)millimetre regime. Such angular resolutions, which are comparable to the stellar radii of nearby objects, are necessary to understand the gas dynamics and chemical evolution in the pulsating atmosphere and dust formation zone of nearby AGB stars. The eponymous Mira-type long-period variable, o Cet, was observed as a Science Verification target during the first ALMA Long Baseline Campaign that took place in 2014. The observations produced images of the stellar radio photosphere and the molecular transitions of SiO and H2O at an angular resolution of about 30 mas near 220 GHz (1.3 mm). The millimetre stellar disc of o Cet was resolved and modelled. More importantly, this is the first time that molecular line absorption against the background stellar continuum has been clearly imaged in the (sub)millimetre wavelength regime. Through radiative transfer modelling of the SiO and H2O line absorption and emission, it is found that during the ALMA observations, the extended atmosphere of the star exhibited infall motions in general with a shock front of velocity

A Candidate Tidal Disruption Event in a Quasar at z = 2.359 from Abundance Ratio Variability

NASA Astrophysics Data System (ADS)

Liu, Xin; Dittmann, Alexander; Shen, Yue; Jiang, Linhua

2018-05-01

A small fraction of quasars show an unusually high nitrogen-to-carbon ratio (N/C) in their spectra. These “nitrogen-rich” (N-rich) quasars are a long-standing puzzle because their interstellar medium implies stellar populations with abnormally high metallicities. It has recently been proposed that N-rich quasars may result from tidal disruption events (TDEs) of stars by supermassive black holes. The rapid enhancement of nitrogen and the depletion of carbon due to the carbon–nitrogen–oxygen cycle in supersolar mass stars could naturally produce high N/C. However, the TDE hypothesis predicts that the N/C should change with time, which has never hitherto been observed. Here we report the discovery of the first N-rich quasar with rapid N/C variability that could be caused by a TDE. Two spectra separated by 1.7 years (rest-frame) show that the N III] λ1750/C III] λ1909 intensity ratio decayed by ∼86% ± 14% (1σ). Optical (rest-frame UV) light-curve and X-ray observations are qualitatively consistent with the TDE hypothesis; though, the time baseline falls short of a definitive proof. Putting the single-object discovery into context, statistical analyses of the ∼80 known N-rich quasars with high-quality archival spectra show evidence (at a 5σ significance level) of a decrease in N/C on timescales of >1 year (rest-frame) and a constant level of ionization (indicated by the C III] λ1909/C IV λ1549 intensity ratio). If confirmed, our results demonstrate the method of identifying TDE candidates in quasars via abundance ratio variability, opening a new window of TDE observations at high redshift (z > 2) with upcoming large-scale time-domain spectroscopic surveys.

Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST/MIRI

NASA Astrophysics Data System (ADS)

Jones, Olivia C.; Meixner, Margaret; Justtanont, Kay; Glasse, Alistair

2017-05-01

The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope (JWST) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer-IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)-Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the JWST/MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.

Evolution of the NASA/IPAC Extragalactic Database (NED) into a Data Mining Discovery Engine

NASA Astrophysics Data System (ADS)

Mazzarella, Joseph M.; NED Team

2017-06-01

We review recent advances and ongoing work in evolving the NASA/IPAC Extragalactic Database (NED) beyond an object reference database into a data mining discovery engine. Updates to the infrastructure and data integration techniques are enabling more than a 10-fold expansion; NED will soon contain over a billion objects with their fundamental attributes fused across the spectrum via cross-identifications among the largest sky surveys (e.g., GALEX, SDSS, 2MASS, AllWISE, EMU), and over 100,000 smaller but scientifically important catalogs and journal articles. The recent discovery of super-luminous spiral galaxies exemplifies the opportunities for data mining and science discovery directly from NED's rich data synthesis. Enhancements to the user interface, including new APIs, VO protocols, and queries involving derived physical quantities, are opening new pathways for panchromatic studies of large galaxy samples. Examples are shown of graphics characterizing the content of NED, as well as initial steps in exploring the database via interactive statistical visualizations.

The nature of dust around the post-asymptotic giant branch objects HD 161796 and HD 179821

NASA Technical Reports Server (NTRS)

Justtanont, K.; Barlow, M. J.; Skinner, C. J.; Tielens, A. G. G. M.

1992-01-01

Ground-based 7.4-24-micron spectra of two post-AGB objects, HD 161796 and HD 179821, are reported, and they are compared to those of other preplanetary nebulae. HD 161796 and HD 17982 show emission features at 10-12 microns and at 10 microns, and they exhibit a very rapid increase in flux between 13 and 15.5 microns. In view of the O-rich photosphere of HD 161796 and the presence of OH maser emission around all three objects, these features are ascribed to various oxides. The observed spectral features are quite different from the canonical silicate features observed in most O-rich giants. It is argued that HD 161796 and the bipolar nebulae Roberts 22 and NGC 6302 have all undergone the third dredge-up, with most of the dredged-up carbon having been converted to nitrogen by envelope-burning. It is concluded that carbon-rich grain material, produced during the interval between the end of the third dredge-up and the moment when envelope burning finally reduced the C/O ratio below unity again, could be responsible for the UIR bands now being excited in Roberts 22 and NGC 6302.

Experimental melting of phlogopite-bearing mantle at 1 GPa: Implications for potassic magmatism

NASA Astrophysics Data System (ADS)

Condamine, Pierre; Médard, Etienne

2014-07-01

We have experimentally investigated the fluid-absent melting of a phlogopite peridotite at 1.0 GPa (1000-1300 °C) to understand the source of K2O- and SiO2-rich magmas that occur in continental, post-collisional and island arc settings. Using a new extraction technique specially developed for hydrous conditions combined with iterative sandwich experiments, we have determined the composition of low- to high-degree melts (Φ=1.4 to 24.2 wt.%) of metasomatized lherzolite and harzburgite sources. Due to small amounts of adsorbed water in the starting material, amphibole crystallized at the lowest investigated temperatures. Amphibole breaks down at 1050-1075 °C, while phlogopite-breakdown occurs at 1150-1200 °C. This last temperature is higher than the previously determined in a mantle assemblage, due to the presence of stabilizing F and Ti. Phlogopite-lherzolite melts incongruently according to the continuous reaction: 0.49 phlogopite + 0.56 orthopyroxene + 0.47 clinopyroxene + 0.05 spinel = 0.58 olivine + 1.00 melt. In the phlogopite-harzburgite, the reaction is: 0.70 phlogopite + 1.24 orthopyroxene + 0.05 spinel = 0.99 olivine + 1.00 melt. The K2O content of water-undersaturated melts in equilibrium with residual phlogopite is buffered, depending on the source fertility: from ∼3.9 wt.% in lherzolite to ∼6.7 wt.% in harzburgite. Primary melts are silica-saturated and evolve from trachyte to basaltic andesite (63.5-52.1 wt.% SiO2) with increasing temperature. Calculations indicate that such silica-rich melts can readily be extracted from their mantle source, due to their low viscosity. Our results confirm that potassic, silica-rich magmas described worldwide in post-collisional settings are generated by melting of a metasomatized phlogopite-bearing mantle in the spinel stability field.

Hot subdwarfs formed from the merger of two He white dwarfs

NASA Astrophysics Data System (ADS)

Schwab, Josiah

2018-06-01

We perform stellar evolution calculations of the remnant of the merger of two He white dwarfs (WDs). Our initial conditions are taken from hydrodynamic simulations of double WD mergers and the viscous disc phase that follows. We evolve these objects from shortly after the merger into their core He-burning phase, when they appear as hot subdwarf stars. We use our models to quantify the amount of H that survives the merger, finding that it is difficult for ≳ 10^{-4} M_{⊙} of H to survive, with even less being concentrated in the surface layers of the object. We also study the rotational evolution of these merger remnants. We find that mass-loss over the {˜ } 10^4 yr following the merger can significantly reduce the angular momentum of these objects. As hot subdwarfs, our models have moderate surface rotation velocities of 30-100 km s-1. The properties of our models are not representative of many apparently isolated hot subdwarfs, suggesting that those objects may form via other channels or that our modelling is incomplete. However, a sub-population of hot subdwarfs are moderate-to-rapid rotators and/or have He-rich atmospheres. Our models help to connect the observed properties of these objects to their progenitor systems.

A model for protocellular coordination of nucleic acid and protein syntheses

NASA Technical Reports Server (NTRS)

Fox, S. W.

1981-01-01

The proteinoid model for the coordination of protein synthesis with nucleic acid coding within the evolving protocell is discussed. Evidence for the self-ordering of amino acid chains, which would enhance the catalytic activity of a lysine-rich proteinoid, is presented, along with that for the preferential formation of microparticles, particularly proteinoid microparticles, in various solutions. Demonstrations of the catalytic activity of lysine-rich proteinoids in the synthesis of peptide and internucleotide bonds are pointed out. The view of evolution as a two stage sequence in which the geological synthesis of peptides evolved to the protocellular synthesis of peptides and oligonucleotides is discussed, and contrasted with the alternative view, in accord with the central dogma, that nucleic acids arose first then governed the production of proteins and protocells.

An evolving trio of hybrid stars: C111

NASA Technical Reports Server (NTRS)

Sonneborn, George (Technical Monitor); Dupree, Andrea K.

2005-01-01

Hybrid stars are a class of cool, luminous single stars originally identified based on the appearance of their ultraviolet IUE spectra. C IV emission is present (signifying temperatures of at least lo5 K), and asymmetric emission cores of Mg I1 are found, accompanied by absorption features at low and high velocities, indicating a massive stellar wind and circumstellar material. Many members of this class have been identified and X-rays have been detected from most hybrids. They represent the critical evolutionary state between coronal-like objects and the Alpha Ori-like objects and assume a pivotal role in the definition of coronal evolution, atmospheric heating processes, and mechanisms to drive winds of cool stars.

The insignificant evolution of the richness-mass relation of galaxy clusters

NASA Astrophysics Data System (ADS)

Andreon, S.; Congdon, P.

2014-08-01

We analysed the richness-mass scaling of 23 very massive clusters at 0.15 < z < 0.55 with homogenously measured weak-lensing masses and richnesses within a fixed aperture of 0.5 Mpc radius. We found that the richness-mass scaling is very tight (the scatter is <0.09 dex with 90% probability) and independent of cluster evolutionary status and morphology. This implies a close association between infall and evolution of dark matter and galaxies in the central region of clusters. We also found that the evolution of the richness-mass intercept is minor at most, and, given the minor mass evolution across the studied redshift range, the richness evolution of individual massive clusters also turns out to be very small. Finally, it was paramount to account for the cluster mass function and the selection function. Ignoring them would lead to larger biases than the (otherwise quoted) errors. Our study benefits from: a) weak-lensing masses instead of proxy-based masses thereby removing the ambiguity between a real trend and one induced by an accounted evolution of the used mass proxy; b) the use of projected masses that simplify the statistical analysis thereby not requiring consideration of the unknown covariance induced by the cluster orientation/triaxiality; c) the use of aperture masses as they are free of the pseudo-evolution of mass definitions anchored to the evolving density of the Universe; d) a proper accounting of the sample selection function and of the Malmquist-like effect induced by the cluster mass function; e) cosmological simulations for the computation of the cluster mass function, its evolution, and the mass growth of each individual cluster.

Fundamentals of the Pedagogy of a Teaching Artist

ERIC Educational Resources Information Center

Campbell, Elena Stephenson

2017-01-01

This article examines the contemporary role of teaching artists, affirming the arts as methods of investigating complex academic/psychosocial material and engaging in rich cultural and ever evolving explorations.

Optical Spectrum of the Compact Planetary Nebula IC 5117

NASA Technical Reports Server (NTRS)

Hyung, Siek; Aller, Lawrence H.; Feibelman, Walter A.; Lee, Seong-Jae; Fisher, Richard R. (Technical Monitor)

2001-01-01

High resolution spectroscopic data of the very compact planetary nebula IC 5117 are obtained in the optical wavelengths, 3700A - 10050A, with the Hamilton Echelle Spectrograph at Lick Observatory, and which have been analyzed along with the International Ultraviolet Explorer (IUE) UV archive data. Although a diagnostic diagram shows significant density and temperature fluctuations, our analysis indicates that the nebular gas may be represented by a homogeneous shell of extremely high density gas, N(sub epsilon) approx. 90 000 /cu cm. The average electron temperatures, e.g. indicated by the [OIII] diagnostics, are around 12 000 K. We construct a photoionization model to represent most of the observed line intensities, and the physical condition of this compact nebulosity. Based on the semi-empirical ionization correction approach, and model indications, we derived the elemental abundances: He, C, N, O, Ne, and Ar appear to be normal or marginally depleted compared to the average planetary nebula, while the remaining elements, S, Cl, and K appear to be enhanced. IC 5117 is perhaps a very young compact planetary nebula, slightly more evolved than the other well-known compact planetary nebula IC 4997. The central stellar temperature is likely to be around 120 000 K, evolved from a C-rich AGB progenitor.

Evolving science of marine reserves: New developments and emerging research frontiers

PubMed Central

Gaines, Steven D.; Lester, Sarah E.; Grorud-Colvert, Kirsten; Costello, Christopher; Pollnac, Richard

2010-01-01

The field of marine reserve science has matured greatly over the last decade, moving beyond studies of single reserves and beyond perspectives from single disciplines. This Special Feature exemplifies recent advances in marine reserve research, showing insights gained from synthetic studies of reserve networks, long-term changes within reserves, integration of social and ecological science research, and balance between reserve design for conservation as well as fishery and other commercial objectives. This rich body of research helps to inform conservation planning for marine ecosystems but also poses new challenges for further study, including how to best design integrated fisheries management and conservation systems, how to effectively evaluate the performance of entire reserve networks, and how to examine the complex coupling between ecological and socioeconomic responses to reserve networks. PMID:20978212

Evolution of an arsenal: structural and functional diversification of the venom system in the advanced snakes (Caenophidia).

PubMed

Fry, Bryan G; Scheib, Holger; van der Weerd, Louise; Young, Bruce; McNaughtan, Judith; Ramjan, S F Ryan; Vidal, Nicolas; Poelmann, Robert E; Norman, Janette A

2008-02-01

Venom is a key innovation underlying the evolution of advanced snakes (Caenophidia). Despite this, very little is known about venom system structural diversification, toxin recruitment event timings, or toxin molecular evolution. A multidisciplinary approach was used to examine the diversification of the venom system and associated toxins across the full range of the approximately 100 million-year-old advanced snake clade with a particular emphasis upon families that have not secondarily evolved a front-fanged venom system ( approximately 80% of the 2500 species). Analysis of cDNA libraries revealed complex venom transcriptomes containing multiple toxin types including three finger toxins, cobra venom factor, cysteine-rich secretory protein, hyaluronidase, kallikrein, kunitz, lectin, matrix metalloprotease, phospholipase A(2), snake venom metalloprotease/a disintegrin and metalloprotease, and waprin. High levels of sequence diversity were observed, including mutations in structural and functional residues, changes in cysteine spacing, and major deletions/truncations. Morphological analysis comprising gross dissection, histology, and magnetic resonance imaging also demonstrated extensive modification of the venom system architecture in non-front-fanged snakes in contrast to the conserved structure of the venom system within the independently evolved front-fanged elapid or viperid snakes. Further, a reduction in the size and complexity of the venom system was observed in species in which constriction has been secondarily evolved as the preferred method of prey capture or dietary preference has switched from live prey to eggs or to slugs/snails. Investigation of the timing of toxin recruitment events across the entire advanced snake radiation indicates that the evolution of advanced venom systems in three front-fanged lineages is associated with recruitment of new toxin types or explosive diversification of existing toxin types. These results support the role of venom as a key evolutionary innovation in the diversification of advanced snakes and identify a potential role for non-front-fanged venom toxins as a rich source for lead compounds for drug design and development.

The cD galaxy in Abell cluster 1775

NASA Technical Reports Server (NTRS)

Hayes, J. J. E.; Bhattacharya, B.

1990-01-01

Over the last 20 years, a number of workers have studied the multiple nuclei cD galaxy in the rich Abell cluster 1775, trying to discover its nature. In all the cases though, very little has been published concerning its morphology. The majority of arguments about the nature of this object have been based on the relative radial velocities of the 2 components with each other and with the other galaxies in the cluster, or its radio morphology. Very little work has been done on the optical morphology. To rectify that lack of data, the authors have obtained charge coupled device (CCD) images of the cD. The authors find from the CCD data that the cD is unlikely to be a bound object and that there is strong evidence for a collision.

Petrologic evolution of the Caetano magmatic system: What can we learn from a dissected, 34 Ma caldera in the northern Great Basin, western U.S.A.?

NASA Astrophysics Data System (ADS)

Watts, K. E.; Colgan, J. P.; John, D. A.; Henry, C. D.

2012-12-01

Eruption of the >1,100 km3 Caetano Tuff and formation of the Caetano caldera occurred during the mid-Tertiary ignimbrite flare-up in the Great Basin. Post-collapse extension and faulting created a series of tilted fault blocks that expose >4 km thick intracaldera tuff, two generations of resurgent granitic plutons, silicic ring-fracture intrusions, a tuff dike that fed the early eruption, and pre- and post-caldera andesites. We integrate new petrologic data for extrusive and intrusive Caetano units with geologic mapping and geochronology to provide an exceptional view into the inner workings of a large caldera center. The Caetano Tuff is a phenocryst-rich (~30-50%) ignimbrite with a mineralogy of plagioclase + sanidine + quartz + biotite + orthopyroxene + Fe-Ti oxides ± hornblende + accessory zircon and allanite. Plagioclase crystals in the Caetano Tuff and cogenetic intrusive units span a wide compositional range (>30 mol% An) and have diverse petrographic textures ranging from euhedral phenocrysts to anhedral, sieved crystals with melt-rich cores. Plagioclase compositions measured by electron microprobe for whole rock thin sections are consistent with compositional zoning of the intracaldera tuff shown by XRF whole rock analyses, oligoclase (~10-30 mol% An) and andesine (~30-50 mol% An) in the most evolved (75-77% SiO2) and least evolved (72-74% SiO2) tuff units, respectively. However, orthopyroxene compositions are apparently decoupled from the host tuff composition, with the highest Mg#s (~60-70%) occurring in the most evolved tuff samples. In the Caetano Tuff, equilibrium pairs of Fe-Ti oxides yield an average eruption temperature of 745°C, which is consistent with the average Ti-in-zircon temperature of 750±70°C (1 stdev, n=90 spots) obtained from Ti concentrations measured by SHRIMP for single zircons. Application of Al-in-hornblende geobarometry indicates an average equilibration pressure of 4.5±0.1 kbar, corresponding to mid-crustal magma storage depths of ~14-15 km. In light of our new petrologic data, we highlight the following key points: (1) Diverse crystal cargoes, disequilibrium textures, and wide compositional oscillations in single phenocrysts and among discrete mineral populations indicate prolonged and complex episodes of magma assembly and growth. Based on zircon U-Pb SHRIMP ages that range from ~34-37 Ma, assembly and growth may have spanned ~2-3 Ma, or a 34 Ma Caetano magma chamber may have assimilated older igneous rocks in and around the caldera. (2) Mineral chemistry, U-Pb and Ar-Ar geochronology, O isotope geochemistry, and whole rock major and trace element geochemistry indicate a genetic connection between the Caetano Tuff and resurgent granitic plutons, supporting the role of linked volcanic-plutonic components in caldera settings. (3) Generation and eruption of crystal-rich "monotonous" rhyolite calls into question the prevailing paradigms of crystal-poor rhyolites derived from crystal mushes, or crystal-rich "monotonous intermediates" derived from homogeneous dacitic magma reservoirs. The Caetano Tuff may be a representative end member of caldera-forming eruptions that is important for understanding large-volume rhyolite genesis in the shallow-middle crust.

THE EXTREMELY RED HOST GALAXY OF GRB 080207

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hunt, Leslie; Cresci, Giovanni; Palazzi, Eliana

2011-08-01

We present optical, near-infrared, and Spitzer IRAC and MIPS observations of the host galaxy of the dark Swift gamma-ray burst GRB 080207. The host is faint, with extremely red optical-infrared colors (R - K = 6.3, 24 {mu}m/R-band flux {approx}1000) making it an extremely red object (ERO) and a dust-obscured galaxy (DOG). The spectral energy distribution (SED) shows the clear signature of the 1.6 {mu}m photometric 'bump', typical of evolved stellar populations. We use this bump to establish the photometric redshift z{sub phot} as 2.2{sup +0.2}{sub -0.3}, using a vast library of SED templates, including M 82. The star formationmore » rate (SFR) inferred from the SED fitting is {approx}119 M{sub sun} yr{sup -1}, the stellar mass 3 x 10{sup 11} M{sub sun}, and A{sub V} extinction from 1 to 2 mag. The ERO and DOG nature of the host galaxy of the dark GRB 080207 may be emblematic of a distinct class of dark GRB hosts, with high SFRs, evolved and metal-rich stellar populations, and significant dust extinction within the host galaxy.« less

Mars Phoenix Scout Thermal Evolved Gas Analyzer (TEGA) Database: Thermal Database Development and Analysis

NASA Technical Reports Server (NTRS)

Sutter, B.; Archer, D.; Niles, P. B.; Stein, T. C.; Hamara, D.; Boynton, W. V.; Ming, D. W.

2017-01-01

The Mars Phoenix Scout Lander mission in 2008 examined the history of water, searched for organics, and evaluated the potential for past/present microbial habitability in a martian arctic ice-rich soil [1]. The Thermal Evolved Gas Analyzer (TEGA) instrument measured the isotopic composition of atmospheric CO2 and detected volatile bearing mineralogy (perchlorate, carbonate, hydrated mineral phases) in the martian soil [2-7]. The TEGA data are archived at the Planetary Data System (PDS) Geosciences Node but are reported in forms that require further processing to be of use to the non-TEGA expert. The soil and blank TEGA thermal data are reported as duty cycle and must be converted to differential power (mW) to allow for enthalpy calculations of exothermic/endothermic transitions. The exothermic/endothermic temperatures are also used to determine what phases (inorganic/organic) are present in the sample. The objectives of this work are to: 1) Describe how interpretable thermal data can be created from TEGA data sets on the PDS and 2) Provide additional thermal data interpretation of two Phoenix soils (Baby Bear, Wicked Witch) and include interpretations from three unreported soils (Rosy Red 1, 2, and Burning Coals).

Páramo is the world's fastest evolving and coolest biodiversity hotspot

PubMed Central

Madriñán, Santiago; Cortés, Andrés J.; Richardson, James E.

2013-01-01

Understanding the processes that cause speciation is a key aim of evolutionary biology. Lineages or biomes that exhibit recent and rapid diversification are ideal model systems for determining these processes. Species rich biomes reported to be of relatively recent origin, i.e., since the beginning of the Miocene, include Mediterranean ecosystems such as the California Floristic Province, oceanic islands such as the Hawaiian archipelago and the Neotropical high elevation ecosystem of the Páramos. Páramos constitute grasslands above the forest tree-line (at elevations of c. 2800–4700 m) with high species endemism. Organisms that occupy this ecosystem are a likely product of unique adaptations to an extreme environment that evolved during the last three to five million years when the Andes reached an altitude that was capable of sustaining this type of vegetation. We compared net diversification rates of lineages in fast evolving biomes using 73 dated molecular phylogenies. Based on our sample, we demonstrate that average net diversification rates of Páramo plant lineages are faster than those of other reportedly fast evolving hotspots and that the faster evolving lineages are more likely to be found in Páramos than the other hotspots. Páramos therefore represent the ideal model system for studying diversification processes. Most of the speciation events that we observed in the Páramos (144 out of 177) occurred during the Pleistocene possibly due to the effects of species range contraction and expansion that may have resulted from the well-documented climatic changes during that period. Understanding these effects will assist with efforts to determine how future climatic changes will impact plant populations. PMID:24130570

Páramo is the world's fastest evolving and coolest biodiversity hotspot.

PubMed

Madriñán, Santiago; Cortés, Andrés J; Richardson, James E

2013-10-09

Understanding the processes that cause speciation is a key aim of evolutionary biology. Lineages or biomes that exhibit recent and rapid diversification are ideal model systems for determining these processes. Species rich biomes reported to be of relatively recent origin, i.e., since the beginning of the Miocene, include Mediterranean ecosystems such as the California Floristic Province, oceanic islands such as the Hawaiian archipelago and the Neotropical high elevation ecosystem of the Páramos. Páramos constitute grasslands above the forest tree-line (at elevations of c. 2800-4700 m) with high species endemism. Organisms that occupy this ecosystem are a likely product of unique adaptations to an extreme environment that evolved during the last three to five million years when the Andes reached an altitude that was capable of sustaining this type of vegetation. We compared net diversification rates of lineages in fast evolving biomes using 73 dated molecular phylogenies. Based on our sample, we demonstrate that average net diversification rates of Páramo plant lineages are faster than those of other reportedly fast evolving hotspots and that the faster evolving lineages are more likely to be found in Páramos than the other hotspots. Páramos therefore represent the ideal model system for studying diversification processes. Most of the speciation events that we observed in the Páramos (144 out of 177) occurred during the Pleistocene possibly due to the effects of species range contraction and expansion that may have resulted from the well-documented climatic changes during that period. Understanding these effects will assist with efforts to determine how future climatic changes will impact plant populations.

Antioxidants in vegan diet and rheumatic disorders.

PubMed

Hänninen; Kaartinen, K; Rauma, A L; Nenonen, M; Törrönen, R; Häkkinen, A S; Adlercreutz, H; Laakso, J

2000-11-30

Plants are rich natural sources of antioxidants in addition to other nutrients. Interventions and cross sectional studies on subjects consuming uncooked vegan diet called living food (LF) have been carried out. We have clarified the efficacy of LF in rheumatoid diseases as an example of a health problem where inflammation is one of the main concerns. LF is an uncooked vegan diet and consists of berries, fruits, vegetables and roots, nuts, germinated seeds and sprouts, i.e. rich sources of carotenoids, vitamins C and E. The subjects eating LF showed highly increased levels of beta and alfa carotenes, lycopen and lutein in their sera. Also the increases of vitamin C and vitamin E (adjusted to cholesterol) were statistically significant. As the berry intake was 3-fold compared to controls the intake of polyphenolic compounds like quercetin, myricetin and kaempherol was much higher than in the omnivorous controls. The LF diet is rich in fibre, substrate of lignan production, and the urinary excretion of polyphenols like enterodiol and enterolactone as well as secoisolaricirecinol were much increased in subjects eating LF. The shift of fibromyalgic subjects to LF resulted in a decrease of their joint stiffness and pain as well as an improvement of their self-experienced health. The rheumatoid arthritis patients eating the LF diet also reported similar positive responses and the objective measures supported this finding. The improvement of rheumatoid arthritis was significantly correlated with the day-to-day fluctuation of subjective symptoms. In conclusion the rheumatoid patients subjectively benefited from the vegan diet rich in antioxidants, lactobacilli and fibre, and this was also seen in objective measures.

Space qualification of silicon carbide for mirror applications: progress and future objectives

NASA Astrophysics Data System (ADS)

Palusinski, Iwona A.; Ghozeil, Isaac

2006-09-01

Production of optical silicon carbide (SiC) for mirror applications continues to evolve and there are renewed plans to use this material in future space-based systems. While SiC has the potential for rapid and cost-effective manufacturing of large, lightweight, athermal optical systems, this material's use in mirror applications is relatively new and has limited flight heritage. This combination of drivers stresses the necessity for a space qualification program for this material. Successful space qualification will require independent collaboration to absorb the high cost of executing this program while taking advantage of each contributing group's laboratory expertise to develop a comprehensive SiC database. This paper provides an overview of the trends and progress in the production of SiC, and identifies future objectives such as non-destructive evaluation and space-effects modeling to ensure proper implementation of this material into future space-based systems.

The evolved central star of the planetary nebula ESO 166-PN 21.

NASA Astrophysics Data System (ADS)

Pena, M.; Ruiz, M. T.; Bergeron, P.; Torres-Peimbert, S.; Heathcote, S.

1997-02-01

Optical and UV spectrophotometric data of the nebula and the central star of the planetary nebula ESO 166-PN 21 are presented. The analysis of the nebular lines confirms that it is a He- and N-rich PN, with He/H=0.138+/-0.005 and N/O=0.58+/-0.08. The oxygen abundance is 12+logO/H=8.60+/-0.10. A distance of 1.2+/-0.2 kpc is derived for the nebula. The central star is very faint and blue, with an apparent magnitude V=17.94+/-0.03mag and a dereddened color index (B-V)_0_=-0.38mag. It shows faint wide H and He absorption lines typical of a DAO star. By modeling the line profiles we derived T_eff_=69200+/-8700K, logg=7.14+/-0.39 and logHe/H=-1.50+/-0.49 for the star. The position of the star in a HR diagram compared with evolutionary tracks indicates a stellar mass of ~0.55Msun_. The bolometric correction derived from the model atmosphere is -5.6mag which, combined with the mass, yields an absolute visual magnitude M_V_=6.95, a luminosity of 22Lsun_ and a distance of 1185+/-700pc, in good agreement with the nebular distance. Therefore, ESO 166-PN 21 central star is among the hottest and most helium-rich DAO stars and it is one of the most evolved PN nuclei known, similar to the central stars of S216 and NGC7293. A kinematical age of 16100yr is deduced for the nebula which is lower by about two orders of magnitude than the age of the central star. The possibility that this object is a member of a close binary system is suggested.

Inulin supplementation reduces the negative effect of a high-fat diet rich in SFA on bone health of growing pigs.

PubMed

Sobol, Monika; Raj, Stanisława; Skiba, Grzegorz

2018-05-01

Consumption of a high-fat diet, rich in SFA, causes deterioration of bone properties. Some studies suggest that feeding inulin to animals may increase mineral absorption and positively affect bone quality; however, these studies have been carried out only on rodents fed a standard diet. The primary objective of this study was to determine the effect of inulin on bone health of pigs (using it as an animal model for humans) fed a high-fat diet rich in SFA, having an unbalanced ratio of lysine:metabolisable energy. It was hypothesised that inulin reduces the negative effects of such a diet on bone health. At 50 d of age, twenty-one pigs were randomly allotted to three groups: the control (C) group fed a standard diet, and two experimental (T and TI) groups fed a high-fat diet rich in SFA. Moreover, TI pigs consumed an extra inulin supply (7 % of daily feed intake). After 10 weeks, whole-body bone mineral content (P=0·0054) and bone mineral density (P=0·0322) were higher in pigs of groups TI and C compared with those of group T. Femur bone mineral density was highest in pigs in group C, lower in group TI and lowest in group T (P=0·001). Femurs of pigs in groups TI and C had similar, but higher, maximum strength compared with femurs of pigs in group T (P=0·0082). In conclusion, consumption of a high-fat diet rich in SFA adversely affected bone health, but inulin supplementation in such a diet diminishes this negative effect.

The occurrence of fluor-wagnerite in UHT granulites and its implications towards understanding fluid regimes in the evolution of deep crust: a case study from the Eastern Ghats Belt, India

NASA Astrophysics Data System (ADS)

Das, Kaushik; Tomioka, Naotaka; Bose, Sankar; Ando, Jun-ichi; Ohnishi, Ichiro

2017-06-01

We report the occurrence of a rare phosphate mineral, fluor-wagnerite (Mg1.91-1.94Fe0.06-0.07Ca<0.01) (P0.99-1.00O4)(OH0.02-0.17F0.98-0.83) from the Eastern Ghats Belt of India, an orogenic belt evolved during Meso- to Neoproterozoic time. The host rock, i.e. high- to ultrahigh temperature (UHT) granulites ( 1000 °C, 8-9 kbar) of the studied area was retrogressed after emplacement to mid-crustal level (800-850 °C, 6-6.5 kbar) as deduced from their pressure -temperature histories. Based on mineral chemical data and micro-Raman analyses, we document an unusual high Mg-F-rich chemistry of the F-wagnerite, which occur both in peak metamorphic porphyroblastic assemblages as well as in the retrograde matrix assemblage. Therefore, in absence of other common phosphates like apatite, fluor-wagnerite can act as an indicator for the presence of F-bearing fluids for rocks with high X Mg and/or fO2. The occurrence of F-rich minerals as monitors for fluid compositions has important implications for the onset of biotite dehydration melting and hence melt production in the deep crust. We propose that fluor-wagnerite can occur as an accessory mineral associated with F-rich fluids in lower-mid crustal rocks, and F in coexisting minerals should be taken into consideration when reconciling the petrogenetic grid of biotite-dehydration melting.

Spiny plants, mammal browsers, and the origin of African savannas.

PubMed

Charles-Dominique, Tristan; Davies, T Jonathan; Hempson, Gareth P; Bezeng, Bezeng S; Daru, Barnabas H; Kabongo, Ronny M; Maurin, Olivier; Muasya, A Muthama; van der Bank, Michelle; Bond, William J

2016-09-20

Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils.

Spiny plants, mammal browsers, and the origin of African savannas

PubMed Central

Charles-Dominique, Tristan; Davies, T. Jonathan; Hempson, Gareth P.; Bezeng, Bezeng S.; Kabongo, Ronny M.; Maurin, Olivier; Muasya, A. Muthama; van der Bank, Michelle; Bond, William J.

2016-01-01

Savannas first began to spread across Africa during the Miocene. A major hypothesis for explaining this vegetation change is the increase in C4 grasses, promoting fire. We investigated whether mammals could also have contributed to savanna expansion by using spinescence as a marker of mammal herbivory. Looking at the present distribution of 1,852 tree species, we established that spinescence is mainly associated with two functional types of mammals: large browsers and medium-sized mixed feeders. Using a dated phylogeny for the same tree species, we found that spinescence evolved at least 55 times. The diversification of spiny plants occurred long after the evolution of Afrotherian proboscideans and hyracoids. However, it is remarkably congruent with diversification of bovids, the lineage including the antelope that predominantly browse these plants today. Our findings suggest that herbivore-adapted savannas evolved several million years before fire-maintained savannas and probably, in different environmental conditions. Spiny savannas with abundant mammal herbivores occur in drier climates and on nutrient-rich soils, whereas fire-maintained savannas occur in wetter climates on nutrient-poor soils. PMID:27601649

Al-rich objects in ordinary chondrites - Related origin of carbonaceous and ordinary chondrites and their constituents

NASA Technical Reports Server (NTRS)

Bischoff, A.; Keil, K.

1984-01-01

A description is given of 169 Al-rich objects (arbitrarily defined as having 10 wt pct or more of Al2O3) from 24 ordinary chondrites of types 3 and 4, five regolith breccias containing unequilibrated material, the unique meteorite Kakangari, and a few ordinary chondrites of types 5 and 6. On the basis of shape and texture, the Al-rich objects are divided into chondrules (round, with igneous textures), irregularly shaped inclusions (similar to type F and spinel-rich complex Ca-Al-rich inclusions), and fragments (probably fragments of Al-rich chondrules and inclusions). For descriptive purposes, the Al-rich chondrules are further subdivided into compositional subgroups, although they are entirely transitional.

Evolved Gas Measurements Planned for the Lower Layers of the Gale Crater Mound with the Sample Analysis at Mars Instrument Suite

NASA Technical Reports Server (NTRS)

Mahaffy, Paul; Brunner, Anna; McAdam, Amy; Franz, Heather; Conrad, Pamela; Webster, Chris; Cabane, Michel

2009-01-01

The lower mound strata of Gale Crater provide a diverse set of chemical environments for exploration by the varied tools of the Curiosity Rover of the Mars Science Laboratory (MSL) Mission. Orbital imaging and spectroscopy clearly reveal distinct layers of hydrated minerals, sulfates, and clays with abundant evidence of a variety of fluvial processes. The three instruments of the MSL Sample Analysis at aMars (SAM) investigation, the Quadrupole Mass Spectrometer (QMS), the Tunable Laser Spectrometer (TLS), and the Gas Chromatograph (GC) are designed to analyze either atmospheric gases or volatiles thermally evolved or chemically extracted from powdered rock or soil. The presence or absence of organic compounds in these layers is of great interest since such an in situ search for this type of record has not been successfully implemented since the mid-60s Viking GCMS experiments. However, regardless of the outcome of the analysis for organics, the abundance and isotopic composition of thermally evolved inorganic compounds should also provide a rich data set to complement the mineralogical and elemental information provided by other MSL instruments. In addition, these evolved gas analysis (EGA) experiments will help test sedimentary models proposed by Malin and Edgett (2000) and then further developed by Milliken et al (2010) for Gale Crater. In the SAM EGA experiments the evolution temperatures of H2O, CO2, SO2, O2, or other simple compounds as the samples are heated in a helium stream to 1000 C provides information on mineral types and their associations. The isotopic composition of O, H, C, and S can be precisely determined in several evolved compounds and compared with the present day atmosphere. Such SAM results might be able to test mineralogical evidence of changing sedimentary and alteration processes over an extended period of time. For example, Bibring et al (2006) have suggested such a major shift from early nonacidic to later acidic alteration. We will illustrate through a variety of evolved gas experiments implemented under SAM-like gas flow and temperature ramp conditions on terrestrial analog minerals on high fidelity Sam breadboards the type of chemical information we expect SAM to provide.

Chaotic Dynamics of Trans-Neptunian Objects Perturbed by Planet Nine

NASA Astrophysics Data System (ADS)

Hadden, Sam; Li, Gongjie; Payne, Matthew J.; Holman, Matthew J.

2018-06-01

Observations of clustering among the orbits of the most distant trans-Neptunian objects (TNOs) has inspired interest in the possibility of an undiscovered ninth planet lurking in the outskirts of the solar system. Numerical simulations by a number of authors have demonstrated that, with appropriate choices of planet mass and orbit, such a planet can maintain clustering in the orbital elements of the population of distant TNOs, similar to the observed sample. However, many aspects of the rich underlying dynamical processes induced by such a distant eccentric perturber have not been fully explored. We report the results of our investigation of the dynamics of coplanar test-particles that interact with a massive body on an circular orbit (Neptune) and a massive body on a more distant, highly eccentric orbit (the putative Planet Nine). We find that a detailed examination of our idealized simulations affords tremendous insight into the rich test-particle dynamics that are possible. In particular, we find that chaos and resonance overlap plays an important role in particles’ dynamical evolution. We develop a simple mapping model that allows us to understand, in detail, the web of overlapped mean-motion resonances explored by chaotically evolving particles. We also demonstrate that gravitational interactions with Neptune can have profound effects on the orbital evolution of particles. Our results serve as a starting point for a better understanding of the dynamical behavior observed in more complicated simulations that can be used to constrain the mass and orbit of Planet Nine.

Final Report

NASA Technical Reports Server (NTRS)

1995-01-01

This cooperative agreement explored the novel polymerization of vinylsilane, alone and in combination with other alkenylsilanes, alkylsilanes, and/or crosslinking agents, using dimethyltitanocene as homogeneous catalyst. The reactions were found to be initiated photochemically under mild conditions, and no hydrogen gas was evolved when alkenylsilanes were polymerized. The polymers were found to have predominately a carbosilane-type backbone containing -SiH2-CH2-CH2-Si and -SiH2-CH(CH3)-Si type linkages. The mechanism of polymerization was found to be step-growth. Despite the relatively low molecular weight of the polymer (M(sub n) - 500 and M(sub W) - 1500), pyrolysis resulted in conversion to C-rich SiC ceramic in high char yields (-60%). Copolymerization with methylsilane resulted in higher chars and more crystalline polymer. Addition of crosslinking agents such as polybutadiene or methyltrivinylsilane increased the viscosity of the polymer produced and enabled application as coatings to fiber toes.

Two forsterite-bearing FUN inclusions in the Allende meteorite. [Fractionation and Unknown Nuclear effects

NASA Technical Reports Server (NTRS)

Clayton, R. N.; Macpherson, G. J.; Hutcheon, I. D.; Davis, A. M.; Grossman, L.; Mayeda, T. K.; Molini-Velsko, C.; Allen, J. M.; El Goresy, A.

1984-01-01

Two forsterite-, fassaite-, spinel-rich inclusions in Allende which share common mineralogy and texture with three previously described inclusions are described. These inclusions were at least partially molten at temperatures over 1400 C, and their crystallization sequence was spinel, olivine, fassaite, and Mg-rich melilite. At least some of them experienced partial volatilization of MgO and SiO2 from their outer margins. At least one of the inclusions is highly enriched in MgO relative to CaO and Al2O3 compared to Allende coarse-grained inclusions, although it is just as strongly enriched in refractory trace elements as the latter, relative to C1 chondrites. Two of the objects are FUN inclusions on the basis of their oxygen, magnesium, and silicon isotopic compositions.

Addressing Environmental Justice in EPA Brownfields Communities

EPA Pesticide Factsheets

The EPA Brownfields Program has a rich history rooted in environmental justice. The Brownfields Program and the environmental justice movement have evolved over a similar timeline, fueling one another and helping to build strong communities.

Grassland invader responses to realistic changes in native species richness.

PubMed

Rinella, Matthew J; Pokorny, Monica L; Rekaya, Romdhane

2007-09-01

The importance of species richness for repelling exotic plant invasions varies from ecosystem to ecosystem. Thus, in order to prioritize conservation objectives, it is critical to identify those ecosystems where decreasing richness will most greatly magnify invasion risks. Our goal was to determine if invasion risks greatly increase in response to common reductions in grassland species richness. We imposed treatments that mimic management-induced reductions in grassland species richness (i.e., removal of shallow- and/or deep-rooted forbs and/or grasses and/or cryptogam layers). Then we introduced and monitored the performance of a notorious invasive species (i.e., Centaurea maculosa). We found that, on a per-gram-of-biomass basis, each resident plant group similarly suppressed invader growth. Hence, with respect to preventing C. maculosa invasions, maintaining overall productivity is probably more important than maintaining the productivity of particular plant groups or species. But at the sites we studied, all plant groups may be needed to maintain overall productivity because removing forbs decreased overall productivity in two of three years. Alternatively, removing forbs increased productivity in another year, and this led us to posit that removing forbs may inflate the temporal productivity variance as opposed to greatly affecting time-averaged productivity. In either case, overall productivity responses to single plant group removals were inconsistent and fairly modest, and only when all plant groups were removed did C. maculosa growth increase substantially over a no-removal treatment. As such, it seems that intense disturbances (e.g., prolonged drought, overgrazing) that deplete multiple plant groups may often be a prerequisite for C. maculosa invasion.

An experimental study of chondrule formation from chondritic precursors via evaporation and condensation in Knudsen cell: Shock heating model of dust aggregates

NASA Astrophysics Data System (ADS)

Imae, Naoya; Isobe, Hiroshi

2017-09-01

Chondrules, igneous objects of ∼1 mm in diameter, formed in the earliest solar system via a transient heating event, are divided into two types: main (type I, FeO-poor) and minor (type II, FeO-rich). Using various chondritic materials for different redox conditions and grain sizes, chondrule reproduction experiments were carried out at IW-2 to IW-3.8, with cooling rates mainly ∼100°C/h, with peak temperatures mainly at 1450 °C, and mainly at 100 Pa in a Knudsen cell providing near chemical equilibrium between the charge and the surrounding gas at the peak temperatures. Vapor pressures in the capsule were controlled using solid buffers. After and during the significant evaporation of the iron component from the metallic iron-poor starting materials in near equilibrium, crystallization occurred. This resulted in the formation of a product similar to the type I chondrules. Dusty olivine grains occurred in charges that had precursor type II chondrules containing coarse ferroan olivine, but such grains are not common in type I chondrules. Therefore fine-grained ferroan matrices rather than type II chondrules are main precursor for type I chondrules. The type I chondrules would have evolved via evaporation and condensation in the similar conditions to the present experimental system. Residual gas, which escaped in experiments, could have condensed to form matrices, leading to complementary compositions. Clusters of matrices and primordial chondrules could have been recycled to form main-generation chondrules originated from the shock heating.

Onboard Image Registration from Invariant Features

NASA Technical Reports Server (NTRS)

Wang, Yi; Ng, Justin; Garay, Michael J.; Burl, Michael C

2008-01-01

This paper describes a feature-based image registration technique that is potentially well-suited for onboard deployment. The overall goal is to provide a fast, robust method for dynamically combining observations from multiple platforms into sensors webs that respond quickly to short-lived events and provide rich observations of objects that evolve in space and time. The approach, which has enjoyed considerable success in mainstream computer vision applications, uses invariant SIFT descriptors extracted at image interest points together with the RANSAC algorithm to robustly estimate transformation parameters that relate one image to another. Experimental results for two satellite image registration tasks are presented: (1) automatic registration of images from the MODIS instrument on Terra to the MODIS instrument on Aqua and (2) automatic stabilization of a multi-day sequence of GOES-West images collected during the October 2007 Southern California wildfires.

Valorisation of mixed bakery waste in non-sterilized fermentation for L-lactic acid production by an evolved Thermoanaerobacterium sp. strain.

PubMed

Yang, Xiaofeng; Zhu, Muzi; Huang, Xiongliang; Lin, Carol Sze Ki; Wang, Jufang; Li, Shuang

2015-12-01

In this study, an advanced biorefinery technology that uses mixed bakery waste has been developed to produce l-lactic acid using an adaptively evolved Thermoanaerobacterium aotearoense LA1002-G40 in a non-sterilized system. Under these conditions, mixed bakery waste was directly hydrolysed by Aspergillus awamori and Aspergillus oryzae, resulting in a nutrient-rich hydrolysate containing 83.6g/L glucose, 9.5 g/L fructose and 612 mg/L free amino nitrogen. T. aotearoense LA1002-G40 was evaluated and then adaptively evolved to grow in this nutrient-rich hydrolysate. Using a 5-L fermenter, the overall lactic acid production from mixed bakery waste was 0.18 g/g with a titer, productivity and yield of 78.5 g/L, 1.63 g/L/h and 0.85 g/g, respectively. This is an innovative procedure involving a complete bioconversion process for l-lactic acid produced from mixed bakery waste under non-sterilized conditions. The proposed process could be potentially applied to turn food waste into l-lactic acid in an economically feasible way. Copyright © 2015 Elsevier Ltd. All rights reserved.

Genomic basis for natural product biosynthetic diversity in the actinomycetes†

PubMed Central

Nett, Markus; Ikeda, Haruo; Moore, Bradley S.

2010-01-01

The phylum Actinobacteria hosts diverse high G + C, Gram-positive bacteria that have evolved a complex chemical language of natural product chemistry to help navigate their fascinatingly varied lifestyles. To date, 71 Actinobacteria genomes have been completed and annotated, with the vast majority representing the Actinomycetales, which are the source of numerous antibiotics and other drugs from genera such as Streptomyces, Saccharopolyspora and Salinispora. These genomic analyses have illuminated the secondary metabolic proficiency of these microbes – underappreciated for years based on conventional isolation programs – and have helped set the foundation for a new natural product discovery paradigm based on genome mining. Trends in the secondary metabolomes of natural product-rich actinomycetes are highlighted in this review article, which contains 199 references. PMID:19844637

Molecular and bioinformatical characterization of a novel superfamily of cysteine-rich peptides from arthropods.

PubMed

Zeng, Xian-Chun; Nie, Yao; Luo, Xuesong; Wu, Shifen; Shi, Wanxia; Zhang, Lei; Liu, Yichen; Cao, Hanjun; Yang, Ye; Zhou, Jianping

2013-03-01

The full-length cDNA sequences of two novel cysteine-rich peptides (referred to as HsVx1 and MmKTx1) were obtained from scorpions. The two peptides represent a novel class of cysteine-rich peptides with a unique cysteine pattern. The genomic sequence of HsVx1 is composed of three exons interrupted by two introns that are localized in the mature peptide encoding region and inserted in phase 1 and phase 2, respectively. Such a genomic organization markedly differs from those of other peptides from scorpions described previously. Genome-wide search for the orthologs of HsVx1 identified 59 novel cysteine-rich peptides from arthropods. These peptides share a consistent cysteine pattern with HsVx1. Genomic comparison revealed extensive intron length differences and intronic number and position polymorphisms among the genes of these peptides. Further analysis identified 30 cases of intron sliding, 1 case of intron gain and 22 cases of intron loss occurred with the genes of the HsVx1 and HsVx1-like peptides. It is interesting to see that three HsVx1-like peptides XP_001658928, XP_001658929 and XP_001658930 were derived from a single gene (XP gene): the former two were generated from alternative splicing; the third one was encoded by a DNA region in the reverse complementary strand of the third intron of the XP gene. These findings strongly suggest that the genes of these cysteine-rich peptides were evolved by intron sliding, intron gain/loss, gene recombination and alternative splicing events in response to selective forces without changing their cysteine pattern. The evolution of these genes is dominated by intron sliding and intron loss. Copyright © 2012 Elsevier Inc. All rights reserved.

Non-Equilibrium Chemistry of O-Rich AGB Stars as Revealed by ALMA

NASA Astrophysics Data System (ADS)

Wong, Ka Tat

2018-04-01

Chemical models suggest that pulsation driven shocks propagating from the stellar surfaces of oxygen-rich evolved stars to the dust formation zone trigger non-equilibrium chemistry in the shocked gas near the star, including the formation of carbon-bearing molecules in the stellar winds dominated by oxygen-rich chemistry. Recent long-baseline ALMA observations are able to give us a detailed view of the molecular line emission and absorption at an angular resolution of a few stellar radii. I am going to present the latest results from the ALMA observations of IK Tau and o Cet in late 2017, with a particular focus on HCN.

Probing the Dusty Stellar Populations of the Local Volume Galaxies with JWST /MIRI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jones, Olivia C.; Meixner, Margaret; Justtanont, Kay

The Mid-Infrared Instrument (MIRI) for the James Webb Space Telescope ( JWST ) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich Spitzer -IRS spectroscopic data set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)–Spectroscopic survey of more than 1000 objects in the Magellanic Clouds, the Grid of Red Supergiant and Asymptotic Giant Branch Star Model (grams), and the grid of YSO models by Robitaille et al., we calculate the expected flux densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes tomore » explore the JWST /MIRI colors and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI color classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars, and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colors.« less

Pathways to Earth-like atmospheres. Extreme ultraviolet (EUV)-powered escape of hydrogen-rich protoatmospheres.

PubMed

Lammer, Helmut; Kislyakova, K G; Odert, P; Leitzinger, M; Schwarz, R; Pilat-Lohinger, E; Kulikov, Yu N; Khodachenko, M L; Güdel, M; Hanslmeier, M

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.

Infrared Spectroscopic Studies of the Properties of Dust in the Ejecta of Galactic Oxygen-Rich Asymptotic Giant Branch Stars

NASA Astrophysics Data System (ADS)

Sargent, Benjamin A.; Srinivasan, Sundar; Kastner, Joel; Meixner, Margaret; Riley, Allyssa

2018-06-01

We are conducting a series of infrared studies of large samples of mass-losing asymptotic giant branch (AGB) stars to explore the relationship between the composition of evolved star ejecta and host galaxy metallicity. Our previous studies focused on mass loss from evolved stars in the relatively low-metallicity Large and Small Magellanic Clouds. In our present study, we analyze dust in the mass-losing envelopes of AGB stars in the Galaxy, with special focus on the ejecta of oxygen-rich (O-rich) AGB stars. We have constructed detailed dust opacity models of AGB stars in the Galaxy for which we have infrared spectra from, e.g., the Spitzer Space Telescope Infrared Spectrograph (IRS). This detailed modeling of dust features in IRS spectra informs our choice of dust properties to use in radiative transfer modeling of the broadband SEDs of Bulge AGB stars. We investigate the effects of dust grain composition, size, shape, etc. on the AGB stars' infrared spectra, studying both the silicate dust and the opacity source(s) commonly attributed to alumina (Al2O3). BAS acknowledges funding from NASA ADAP grant 80NSSC17K0057.

Aluminum Rich Epoxy Primer for Ground and Air Vehicles

DTIC Science & Technology

2017-03-01

UNCLASSIFIED DOCUMENT Aluminum Rich Epoxy Primer for Ground and Air Vehicles Monthly Technical Report for the Period: January 20, 2017...Objective: To further develop the Aluminum Rich Epoxy Primer systems for Air and Ground Vehicles while addressing the objective requirements

Evolving virtual creatures and catapults.

PubMed

Chaumont, Nicolas; Egli, Richard; Adami, Christoph

2007-01-01

We present a system that can evolve the morphology and the controller of virtual walking and block-throwing creatures (catapults) using a genetic algorithm. The system is based on Sims' work, implemented as a flexible platform with an off-the-shelf dynamics engine. Experiments aimed at evolving Sims-type walkers resulted in the emergence of various realistic gaits while using fairly simple objective functions. Due to the flexibility of the system, drastically different morphologies and functions evolved with only minor modifications to the system and objective function. For example, various throwing techniques evolved when selecting for catapults that propel a block as far as possible. Among the strategies and morphologies evolved, we find the drop-kick strategy, as well as the systematic invention of the principle behind the wheel, when allowing mutations to the projectile.

Evolved Gas Measurements Planned for the Lower Layers of the Gale Crater Mound with the Sample Analysis at Mars Instrument Suite

NASA Astrophysics Data System (ADS)

Mahaffy, P. R.; Franz, H.; McAdam, A.; Conrad, P. G.; Brunner, A.; Cabane, M.; Webster, C. R.

2011-12-01

The lower mound strata of Gale Crater provide a diverse set of chemical environments for exploration by the varied tools of the Curiosity Rover of the Mars Science Laboratory (MSL) Mission. Orbital imaging and spectroscopy clearly reveal distinct layers of hydrated minerals, sulfates, and clays with abundant evidence of a variety of fluvial processes. The three instruments of the MSL Sample Analysis at Mars (SAM) investigation, the Quadrupole Mass Spectrometer (QMS), the Tunable Laser Spectrometer (TLS), and the Gas Chromatograph (GC) are designed to analyze either atmospheric gases or volatiles thermally evolved or chemically extracted from powdered rock or soil. The presence or absence of organic compounds in these layers is of great interest since such an in situ search for this type of record has not been successfully implemented since the mid-70s Viking GCMS experiments. However, regardless of the outcome of the analysis for organics, the abundance and isotopic composition of thermally evolved inorganic compounds should also provide a rich data set to complement the mineralogical and elemental information provided by other MSL instruments. In addition, these evolved gas analysis (EGA) experiments will help test sedimentary models proposed by Malin and Edgett (2000) and then further developed by Milliken et al (2010) for Gale Crater. In the SAM EGA experiments the evolution temperatures of H2O, CO2, SO2, O2, or other simple compounds as the samples are heated in a helium stream to 1000C provides information on mineral types and their associations. The isotopic composition of O, H, C, and S can be precisely determined in several evolved compounds and compared with the present day atmosphere. Such SAM results might be able to test mineralogical evidence of changing sedimentary and alteration processes over an extended period of time. For example, Bibring et al (2006) have suggested such a major shift from early nonacidic to later acidic alteration. We will illustrate through a variety of evolved gas experiments implemented under SAM-like gas flow and temperature ramp conditions on terrestrial analog minerals on high fidelity SAM breadboards the type of chemical information we expect SAM to provide. Bibring, J.-P., et al. (2006), Global mineralogical and aqueous Mars history derived from OMEGA/Mars Express data, Science, 312, 400-404, doi:10.1126/science.1122659. Malin, M. C., and K. S. Edgett (2000), Sedimentary rocks of early Mars, Science, 290, 1927-1937, doi:10.1126/science.290.5498.1927. Milliken, R. E., J. P. Grotzinger, and B. J. Thomson (2010), Paleoclimate of Mars as captured by the strati- graphic record in Gale Crater, Geophys. Res. Lett., 37, L04201, doi:10.1029/2009GL041870.

Carbon chemistry in dense molecular clouds: Theory and observational constraints

NASA Technical Reports Server (NTRS)

Blake, Geoffrey A.

1990-01-01

For the most part, gas phase models of the chemistry of dense molecular clouds predict the abundances of simple species rather well. However, for larger molecules and even for small systems rich in carbon these models often fail spectacularly. Researchers present a brief review of the basic assumptions and results of large scale modeling of the carbon chemistry in dense molecular clouds. Particular attention is to the influence of the gas phase C/O ratio in molecular clouds, and the likely role grains play in maintaining this ratio as clouds evolve from initially diffuse objects to denser cores with associated stellar and planetary formation. Recent spectral line surveys at centimeter and millimeter wavelengths along with selected observations in the submillimeter have now produced an accurate inventory of the gas phase carbon budget in several different types of molecular clouds, though gaps in our knowledge clearly remain. The constraints these observations place on theoretical models of interstellar chemistry can be used to gain insights into why the models fail, and show also which neglected processes must be included in more complete analyses. Looking toward the future, larger molecules are especially difficult to study both experimentally and theoretically in such dense, cold regions, and some new methods are therefore outlined which may ultimately push the detectability of small carbon chains and rings to much heavier species.

A refractory inclusion in the Kaba CV3 chondrite - Some implications for the origin of spinel-rich objects in chondrites

NASA Technical Reports Server (NTRS)

Fegley, B., Jr.; Post, J. E.

1985-01-01

The first detailed petrographic and mineralogical study of a Ca, Al-rich inclusion (CAI) from the Kaba CV3 chondrite is reported. This 'fine-grained' CAI contains abundant small, rounded, rimmed, spinel-rich objects which have important features in common with the spinel-rich objects in other carbonaceous and ordinary chondrites. These nodules are interpreted as fractionated distillation residues of primitive dust. However, the available data do not unambiguously rule out a condensation origin for at least some of these objects. Finally, the preservation of distinct diopside-hedenbergite rims on the spinel-rich bodies and the small grain size of many minerals in the CAI matrix material both suggest that the CAI accreted cool and had a relatively cool thermal history in the Kaba parent body.

Related Progenitor Models for Long-duration Gamma-Ray Bursts and Type Ic Superluminous Supernovae

NASA Astrophysics Data System (ADS)

Aguilera-Dena, David R.; Langer, Norbert; Moriya, Takashi J.; Schootemeijer, Abel

2018-05-01

We model the late evolution and mass loss history of rapidly rotating Wolf–Rayet stars in the mass range 5 M ⊙…100 M ⊙). We find that quasi-chemically homogeneously evolving single stars computed with enhanced mixing retain very little or no helium and are compatible with Type Ic supernovae. The more efficient removal of core angular momentum and the expected smaller compact object mass in our lower-mass models lead to core spins in the range suggested for magnetar-driven superluminous supernovae. Our higher-mass models retain larger specific core angular momenta, expected for long-duration gamma-ray bursts in the collapsar scenario. Due to the absence of a significant He envelope, the rapidly increasing neutrino emission after core helium exhaustion leads to an accelerated contraction of the whole star, inducing a strong spin-up and centrifugally driven mass loss at rates of up to {10}-2 {M}ȯ {yr}}-1 in the last years to decades before core collapse. Because the angular momentum transport in our lower-mass models enhances the envelope spin-up, they show the largest relative amounts of centrifugally enforced mass loss, i.e., up to 25% of the expected ejecta mass. Our most massive models evolve into the pulsational pair-instability regime. We would thus expect signatures of interaction with a C/O-rich circumstellar medium for Type Ic superluminous supernovae with ejecta masses below ∼10 M ⊙ as well as for the most massive engine-driven explosions with ejecta masses above ∼30 M ⊙. Signs of such interaction should be observable at early epochs of the supernova explosion; they may be related to bumps observed in the light curves of superluminous supernovae, or to the massive circumstellar CO-shell proposed for Type Ic superluminous supernova Gaia16apd.

The solid fat content of stearic acid-rich fats determines their postprandial effects.

PubMed

Berry, Sarah E E; Miller, George J; Sanders, Thomas A B

2007-06-01

The process of randomization is used commercially to harden fats as an alternative to partial hydrogenation, but its effects on cardiovascular disease risk factors are uncertain. The objective was to compare the chronic and acute effects of randomization of a fat rich in 1,3-distearyl, 2-oleyl glycerol on fasting and postprandial lipids, glucose, insulin, and activated clotting factor VII (FVIIa) concentrations. A crossover design study in 16 men compared fasting and postprandial lipid, glucose, insulin, and FVIIa concentrations at baseline and after a 3-wk diet providing 30 g unrandomized or randomized shea butter and sunflower oil blends (SSOBs), both of which contained approximately 50% stearic acid. Fecal fat excretion was measured during each dietary period. Postprandial changes were assessed after the consumption of meals providing 50 g test fat. A subsequent study compared postprandial changes after the consumption of an oleic acid-rich sunflower oil meal and an unrandomized SSOB meal. Both SSOBs were well digested and absorbed. Randomization did not affect fasting or postprandial lipid, glucose, insulin, or FVIIa concentrations. Compared with the oleic acid-rich meal, the unrandomized SSOB resulted in 53% lower postprandial lipemia, 23% higher hepatic lipase activity, and a 25% lower postprandial increase in FVIIa concentration. The solid fat contents at 37 degrees C were 22%, 41%, and 0% with the unrandomized SSOB, randomized SSOB, and oleic acid-rich meals, respectively. Stearic acid-rich triacylglycerol in both unrandomized and randomized forms does not adversely affect lipid risk factors for cardiovascular disease. The high proportion of solid fat at 37 degrees C may explain the decreased postprandial lipemic response.

Synaptic Plasticity and Spike Synchronisation in Neuronal Networks

NASA Astrophysics Data System (ADS)

Borges, Rafael R.; Borges, Fernando S.; Lameu, Ewandson L.; Protachevicz, Paulo R.; Iarosz, Kelly C.; Caldas, Iberê L.; Viana, Ricardo L.; Macau, Elbert E. N.; Baptista, Murilo S.; Grebogi, Celso; Batista, Antonio M.

2017-12-01

Brain plasticity, also known as neuroplasticity, is a fundamental mechanism of neuronal adaptation in response to changes in the environment or due to brain injury. In this review, we show our results about the effects of synaptic plasticity on neuronal networks composed by Hodgkin-Huxley neurons. We show that the final topology of the evolved network depends crucially on the ratio between the strengths of the inhibitory and excitatory synapses. Excitation of the same order of inhibition revels an evolved network that presents the rich-club phenomenon, well known to exist in the brain. For initial networks with considerably larger inhibitory strengths, we observe the emergence of a complex evolved topology, where neurons sparsely connected to other neurons, also a typical topology of the brain. The presence of noise enhances the strength of both types of synapses, but if the initial network has synapses of both natures with similar strengths. Finally, we show how the synchronous behaviour of the evolved network will reflect its evolved topology.

40 CFR 721.10024 - 10H-Phenothiazine, ar-(C9-rich C8-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 10H-Phenothiazine, ar-(C9-rich C8-10... New Uses for Specific Chemical Substances § 721.10024 10H-Phenothiazine, ar-(C9-rich C8-10-branched... substance identified as 10H-phenothiazine, ar-(C9-rich C8-10-branched alkyl) derivs (PMN P-01-771; CAS No...

Renewable chemical feedstocks from integrated liquefaction processing of lingocellulosic materials using microwave energy

Treesearch

Junming Xu; Jianchun Jiang; Chung-Yun Hse; Todd F. Shupe

2012-01-01

The objective of this investigation was to find a simple method for the production of phenolic rich products and sugar derivatives (biopolyols) via separation of liquefied lingocellulosic materials. Liquefaction of lignocellulosic materials was conducted in methanol at 180 °C for 15 min with the conversion of raw materials at about 75%. After liquefaction, the...

40 CFR 721.10025 - 10H-Phenothiazine, ar, ar′-(C9-rich C8-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 10H-Phenothiazine, ar, arâ²-(C9-rich... Significant New Uses for Specific Chemical Substances § 721.10025 10H-Phenothiazine, ar, ar′-(C9-rich C8-10... chemical substances identified as 10H-phenothiazine, ar, ar′-(C9-rich C8-10-branched alkyl) derivs (PMN P...

New Galactic Candidate Luminous Blue Variables and Wolf-Rayet Stars

NASA Astrophysics Data System (ADS)

Stringfellow, Guy S.; Gvaramadze, Vasilii V.; Beletsky, Yuri; Kniazev, Alexei Y.

2012-04-01

We have undertaken a near-infrared spectral survey of stars associated with compact mid-IR shells recently revealed by the MIPSGAL (24 μm) and GLIMPSE (8 μm) Spitzer surveys, whose morphologies are typical of circumstellar shells produced by massive evolved stars. Through spectral similarity with known Luminous Blue Variable (LBV) and Wolf-Rayet (WR) stars, a large population of candidate LBVs (cLBVs) and a smaller number of new WR stars are being discovered. This significantly increases the Galactic cLBV population and confirms that nebulae are inherent to most (if not all) objects of this class.

Crypto-magma chambers beneath Mt. Fuji

NASA Astrophysics Data System (ADS)

Kaneko, Takayuki; Yasuda, Atsushi; Fujii, Toshitsugu; Yoshimoto, Mitsuhiro

2010-06-01

Mt. Fuji consists dominantly of basalt. A study of olivine-hosted melt-inclusions from layers of air-fall scoria, however, shows clear evidence of andesitic liquids. Whole rock compositions show a narrow range of SiO 2, but a wide range of FeO*/MgO and incompatible elements. Phenocrystic plagioclase generally shows bi-modal distributions in compositional frequency, while most olivine phenocrysts show uni-modal distribution with reverse zoning and often contain andesitic melt-inclusions. These suggest that magmas erupted from Fuji are generated through mixing between basaltic and more SiO 2-rich (often andesitic) end-members. We propose that Fuji's magmatic plumbing system consists of at least two magma chambers: a relatively deep (˜20 km) basaltic one and a relatively shallow (˜ 8-9 km) and more SiO 2-rich one. Evolved basalts with wide compositional ranges of incompatible elements are generated in the deep basaltic magma chamber by prevalent fractional crystallization of pyroxenes with olivine and calcic plagioclase at high pressure. Meanwhile basaltic magma left behind by the previous eruption in the conduit accumulates in a shallow magma chamber, and is differentiated to more SiO 2-rich composition by fractional crystallization of olivine, less-calcic plagioclase, and clinopyroxene. Shortly before a new eruption, a large amount of evolved basaltic magma containing calcic plagioclase rises from the deeper magma chamber and is mixed with the more SiO 2-rich magma in the shallow chamber, to generate the hybrid basaltic magma.

Luminosities and mass-loss rates of Local Group AGB stars and red supergiants

NASA Astrophysics Data System (ADS)

Groenewegen, M. A. T.; Sloan, G. C.

2018-01-01

Context. Mass loss is one of the fundamental properties of asymptotic giant branch (AGB) stars, and through the enrichment of the interstellar medium, AGB stars are key players in the life cycle of dust and gas in the universe. However, a quantitative understanding of the mass-loss process is still largely lacking. Aims: We aim to investigate mass loss and luminosity in a large sample of evolved stars in several Local Group galaxies with a variety of metalliticies and star-formation histories: the Small and Large Magellanic Cloud, and the Fornax, Carina, and Sculptor dwarf spheroidal galaxies (dSphs). Methods: Dust radiative transfer models are presented for 225 carbon stars and 171 oxygen-rich evolved stars in several Local Group galaxies for which spectra from the Infrared Spectrograph on Spitzer are available. The spectra are complemented with available optical and infrared photometry to construct spectral energy distributions. A minimization procedure was used to determine luminosity and mass-loss rate (MLR). Pulsation periods were derived for a large fraction of the sample based on a re-analysis of existing data. Results: New deep K-band photometry from the VMC survey and multi-epoch data from IRAC (at 4.5 μm) and AllWISE and NEOWISE have allowed us to derive pulsation periods longer than 1000 days for some of the most heavily obscured and reddened objects. We derive (dust) MLRs and luminosities for the entire sample. The estimated MLRs can differ significantly from estimates for the same objects in the literature due to differences in adopted optical constants (up to factors of several) and details in the radiative transfer modelling. Updated parameters for the super-AGB candidate MSX SMC 055 (IRAS 00483-7347) are presented. Its current mass is estimated to be 8.5 ± 1.6 M⊙, suggesting an initial mass well above 8 M⊙ in agreement with estimates based on its large Rubidium abundance. Using synthetic photometry, we present and discuss colour-colour and colour-magnitude diagrams which can be expected from the James Webb Space Telescope. Tables A.1, A.2, B.1, B.2, and C.1 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/609/A114

Genomes Behave as Social Entities: Alien Chromatin Minorities Evolve Through Specificities Reduction

USDA-ARS?s Scientific Manuscript database

Hybridization and chromosome doubling entailed by allopolyploidization requires genetic and epigenetic modifications, resulting in the adjustment of different genomes to the same nuclear environment. Recently, the main role of retrotransposon/microsatellite-rich regions of the genome in DNA sequenc...

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

Simultaneous iron and nickel isotopic analyses of presolar silicon carbide grains

DOE PAGES

Trappitsch, Reto; Stephan, Thomas; Savina, Michael R.; ...

2018-01-01

Aside from recording stellar nucleosynthesis, a few elements in presolar grains can also provide insights into the galactic chemical evolution (GCE) of nuclides. We have studied the carbon, silicon, iron, and nickel isotopic compositions of presolar silicon carbide (SiC) grains from asymptotic giant branch (AGB) stars to better understand GCE. Since only the neutron-rich nuclides in these grains have been heavily in uenced by the parent star, the neutron-poor nuclides serve as GCE proxies. Using CHILI, a new resonance ionization mass spectrometry (RIMS) instrument, we measured 74 presolar SiC grains for all iron and nickel isotopes. With the CHARISMA instrument,more » 13 presolar SiC grains were analyzed for iron isotopes. All grains were also measured by NanoSIMS for their carbon and silicon isotopic compositions. A comparison of the measured neutron-rich isotopes with models for AGB star nucleosynthesis shows that our measurements are consistent with AGB star predictions for low-mass stars between half-solar and solar metallicity. Furthermore, our measurements give an indication on the 22Ne( ,n) 25Mg reaction rate. In terms of GCE, we nd that the GCE-dominated iron and nickel isotope ratios, 54Fe/56Fe and 60Ni/ 58Ni, correlate with their GCE-dominated counterpart in silicon, 29Si/ 28Si. The measured GCE trends include the Solar System composition, showing that the Solar System is not a special case. However, as seen in silicon and titanium, many presolar SiC grains are more evolved for iron and nickel than the Solar System. This con rms prior ndings and agrees with observations of large stellar samples that a simple age-metallicity relationship for GCE cannot explain the composition of the solar neighborhood.« less

Women's fertility across the cycle increases the short-term attractiveness of creative intelligence.

PubMed

Haselton, Martie G; Miller, Geoffrey F

2006-03-01

Male provisioning ability may have evolved as a "good dad" indicator through sexual selection, whereas male creativity may have evolved partly as a "good genes" indicator. If so, women near peak fertility (midcycle) should prefer creativity over wealth, especially in short-term mating. Forty-one normally cycling women read vignettes describing creative but poor men vs. uncreative but rich men. Women's estimated fertility predicted their short-term (but not long-term) preference for creativity over wealth, in both their desirability ratings of individual men (r=.40, p<.01) and their forced-choice decisions between men (r=.46, p<.01). These preliminary results are consistent with the view that creativity evolved at least partly as a good genes indicator through mate choice.

Evolving approaches to the ethical management of genomic data.

PubMed

McEwen, Jean E; Boyer, Joy T; Sun, Kathie Y

2013-06-01

The ethical landscape in the field of genomics is rapidly shifting. Plummeting sequencing costs, along with ongoing advances in bioinformatics, now make it possible to generate an enormous volume of genomic data about vast numbers of people. The informational richness, complexity, and frequently uncertain meaning of these data, coupled with evolving norms surrounding the sharing of data and samples and persistent privacy concerns, have generated a range of approaches to the ethical management of genomic information. As calls increase for the expanded use of broad or even open consent, and as controversy grows about how best to handle incidental genomic findings, these approaches, informed by normative analysis and empirical data, will continue to evolve alongside the science. Published by Elsevier Ltd.

Evolving Approaches to the Ethical Management of Genomic Data

PubMed Central

Boyer, Joy T.; Sun, Kathie Y.

2013-01-01

The ethical landscape in the field of genomics is rapidly shifting. Plummeting sequencing costs, along with ongoing advances in bioinformatics, now make it possible to generate an enormous volume of genomic data about vast numbers of people. The informational richness, complexity, and frequently uncertain meaning of these data, coupled with evolving norms surrounding the sharing of data and samples and persistent privacy concerns, have generated a range of approaches to the ethical management of genomic information. As calls increase for the expanded use of broad or even open consent, and as controversy grows about how best to handle incidental genomic findings, these approaches, informed by normative analysis and empirical data, will continue to evolve alongside the science. PMID:23453621

A manganese-rich environment supports superoxide dismutase activity in a Lyme disease pathogen, Borrelia burgdorferi.

PubMed

Aguirre, J Dafhne; Clark, Hillary M; McIlvin, Matthew; Vazquez, Christine; Palmere, Shaina L; Grab, Dennis J; Seshu, J; Hart, P John; Saito, Mak; Culotta, Valeria C

2013-03-22

The Lyme disease pathogen Borrelia burgdorferi represents a novel organism in which to study metalloprotein biology in that this spirochete has uniquely evolved with no requirement for iron. Not only is iron low, but we show here that B. burgdorferi has the capacity to accumulate remarkably high levels of manganese. This high manganese is necessary to activate the SodA superoxide dismutase (SOD) essential for virulence. Using a metalloproteomic approach, we demonstrate that a bulk of B. burgdorferi SodA directly associates with manganese, and a smaller pool of inactive enzyme accumulates as apoprotein. Other metalloproteins may have similarly adapted to using manganese as co-factor, including the BB0366 aminopeptidase. Whereas B. burgdorferi SodA has evolved in a manganese-rich, iron-poor environment, the opposite is true for Mn-SODs of organisms such as Escherichia coli and bakers' yeast. These Mn-SODs still capture manganese in an iron-rich cell, and we tested whether the same is true for Borrelia SodA. When expressed in the iron-rich mitochondria of Saccharomyces cerevisiae, B. burgdorferi SodA was inactive. Activity was only possible when cells accumulated extremely high levels of manganese that exceeded cellular iron. Moreover, there was no evidence for iron inactivation of the SOD. B. burgdorferi SodA shows strong overall homology with other members of the Mn-SOD family, but computer-assisted modeling revealed some unusual features of the hydrogen bonding network near the enzyme's active site. The unique properties of B. burgdorferi SodA may represent adaptation to expression in the manganese-rich and iron-poor environment of the spirochete.

ALMA Detections of CO Emission in the Most Luminous, Heavily Dust-obscured Quasars at z > 3

NASA Astrophysics Data System (ADS)

Fan, Lulu; Knudsen, Kirsten K.; Fogasy, Judit; Drouart, Guillaume

2018-03-01

We report the results of a pilot study of CO(4 ‑ 3) emission line of three Wide-field Infrared Survey Explorer (WISE)-selected hyper-luminous, dust-obscured quasars (QSOs) with sensitive ALMA Band 3 observations. These obscured QSOs with L bol > 1014 L ⊙ are among the most luminous objects in the universe. All three QSO hosts are clearly detected both in continuum and in CO(4 ‑ 3) emission line. Based on CO(4 ‑ 3) emission line detection, we derive the molecular gas masses (∼1010‑11 M ⊙), suggesting that these QSOs are gas-rich systems. We find that the obscured QSOs in our sample follow the similar {L}CO}{\\prime }{--}{L}FIR} relation as unobscured QSOs at high redshifts. We also find the complex velocity structures of CO(4 ‑ 3) emission line, which provide the possible evidence for a gas-rich merger in W0149+2350 and possible molecular outflow in W0220+0137 and W0410‑0913. Massive molecular outflow can blow away the obscured interstellar medium and make obscured QSOs evolve toward the UV/optical bright, unobscured phase. Our result is consistent with the popular active galactic nucleus (AGN) feedback scenario involving the co-evolution between the supermassive black holes and host galaxy.

Evolutionary Consequence of a Trade-Off between Growth and Maintenance along with Ribosomal Damages.

PubMed

Ying, Bei-Wen; Honda, Tomoya; Tsuru, Saburo; Seno, Shigeto; Matsuda, Hideo; Kazuta, Yasuaki; Yomo, Tetsuya

2015-01-01

Microorganisms in nature are constantly subjected to a limited availability of resources and experience repeated starvation and nutrition. Therefore, microbial life may evolve for both growth fitness and sustainability. By contrast, experimental evolution, as a powerful approach to investigate microbial evolutionary strategies, often targets the increased growth fitness in controlled, steady-state conditions. Here, we address evolutionary changes balanced between growth and maintenance while taking nutritional fluctuations into account. We performed a 290-day-long evolution experiment with a histidine-requiring Escherichia coli strain that encountered repeated histidine-rich and histidine-starved conditions. The cells that experienced seven rounds of starvation and re-feed grew more sustainably under prolonged starvation but dramatically lost growth fitness under rich conditions. The improved sustainability arose from the evolved capability to use a trace amount of histidine for cell propagation. The reduced growth rate was attributed to mutations genetically disturbing the translation machinery, that is, the ribosome, ultimately slowing protein translation. This study provides the experimental demonstration of slow growth accompanied by an enhanced affinity to resources as an evolutionary adaptation to oscillated environments and verifies that it is possible to evolve for reduced growth fitness. Growth economics favored for population increase under extreme resource limitations is most likely a common survival strategy adopted by natural microbes.

The Glass Bead Game: experimental sintering of rhyolitic ash reveals complex behaviour of irregular multiphase particles

NASA Astrophysics Data System (ADS)

Pope, Robyn; Tuffen, Hugh; Owen, Jacqueline; James, Mike; Wadsworth, Fabian

2016-04-01

Sintering of magmatic particles profoundly influences the permeability, strength and compaction of fragmented magma in conduits and pyroclastic deposits. It involves initial rounding and agglutination of particles, with formation of inter-particle necks, followed by progressive viscous collapse of pores. The sintering behaviour of ash particles within tuffisite veins, which may mediate shallow outgassing in silicic eruptions, is of particular interest. Experimental studies on homogeneous synthetic glasses[1] have shown sintering rates to be time, temperature and grainsize-dependent, reflecting the influence of melt viscosity and pore-melt interfacial tension. A key objective is to reconstruct the temperature-time path of naturally sintered samples, so here we investigate the sintering of natural, angular ash fragments, to explore whether similar simple relationships emerge for more complex particle morphologies and internal textures. A glass-rich ballistic rhyolite bomb from the Cordón Caulle 2011-2012 eruption was ground and sieved to create various grainsizes of angular ash particles. The bomb contains 70 wt.% SiO2, 0.25 wt.% H2O, and ~30 vol.% crystal phases, as phenocrysts and microlites of plagioclase and pyroxenes. Particles were spread thinly over a sapphire surface in an N2-purged heated stage, and heated to 900, 1000 and 1100 °C, corresponding to melt viscosities of 105.4-107.7 Pa.s. Images were collected every 10-600 s during isothermal sintering over tens of minutes to hours. Quantitative image analysis using ImageJ allowed quantification of evolving particle size and shape (diameter and roundness) and inter-particle neck width. The rate of particle rounding was expected to be highest for smallest particles, and to decrease through time, but unlike synthetic glass bead experiments, no simple trends emerged. When the temporal evolution of particle roundness was tracked, some particles showed an unexpected, systematic increase in rounding rate with time (type A), whereas others showed the expected decrease (type B), or an increase followed by a decrease (type C). The relationship between evolving particle roundness and diameter showed similarly diverse trends, and no distinction could be made between type A, B and C based on initial roundness, size or other characteristic. The development of inter-particle necks was quantified via measurements of the rate of neck width evolution. These rates proved broadly similar for different grain sizes at a given temperature, suggesting that the initial grain size was not the primary controlling factor on neck width growth. Our results highlight both the complexity of sintering in multiphase magmas with irregular particle shapes, and the difficulty of adequately using two-dimensional imagery to characterise evolving three-dimensional morphologies. Future work should employ tomographic techniques to characterise four-dimensional sintering, and analyse large particle populations to overcome the stochastic effects of variable particle texture and morphology. [1] Vasseur J et al. 2013, GRL 40, 5658-5664.

Global grass (Poaceae) success underpinned by traits facilitating colonization, persistence and habitat transformation.

PubMed

Linder, H P; Lehmann, Caroline E R; Archibald, Sally; Osborne, Colin P; Richardson, David M

2018-05-01

Poaceae (the grasses) is arguably the most successful plant family, in terms of its global occurrence in (almost) all ecosystems with angiosperms, its ecological dominance in many ecosystems, and high species richness. We suggest that the success of grasses is best understood in context of their capacity to colonize, persist, and transform environments (the "Viking syndrome"). This results from combining effective long-distance dispersal, efficacious establishment biology, ecological flexibility, resilience to disturbance and the capacity to modify environments by changing the nature of fire and mammalian herbivory. We identify a diverse set of functional traits linked to dispersal, establishment and competitive abilities. Enhanced long-distance dispersal is determined by anemochory, epizoochory and endozoochory and is facilitated via the spikelet (and especially the awned lemma) which functions as the dispersal unit. Establishment success could be a consequence of the precocious embryo and large starch reserves, which may underpin the extremely short generation times in grasses. Post-establishment genetic bottlenecks may be mitigated by wind pollination and the widespread occurrence of polyploidy, in combination with gametic self-incompatibility. The ecological competitiveness of grasses is corroborated by their dominance across the range of environmental extremes tolerated by angiosperms, facilitated by both C 3 and C 4 photosynthesis, well-developed frost tolerance in several clades, and a sympodial growth form that enabled the evolution of both annual and long-lived life forms. Finally, absence of investment in wood (except in bamboos), and the presence of persistent buds at or below ground level, provides tolerance of repeated defoliation (whether by fire, frost, drought or herbivores). Biotic modification of environments via feedbacks with herbivory or fire reinforce grass dominance leading to open ecosystems. Grasses can be both palatable and productive, fostering high biomass and diversity of mammalian herbivores. Many grasses have a suite of architectural and functional traits that facilitate frequent fire, including a tufted growth form, and tannin-like substances in leaves which slow decomposition. We mapped these traits over the phylogeny of the Poales, spanning the grasses and their relatives, and demonstrated the accumulation of traits since monocots originated in the mid-Cretaceous. Although the sympodial growth form is a monocot trait, tillering resulting in the tufted growth form most likely evolved within the grasses. Similarly, although an ovary apparently constructed of a single carpel evolved in the most recent grass ancestor, spikelets and the awned lemma dispersal units evolved within the grasses. Frost tolerance and C 4 photosynthesis evolved relatively late (late Palaeogene), and the last significant trait to evolve was probably the production of tannins, associated with pyrophytic savannas. This fits palaeobotanical data, suggesting several phases in the grass success story: from a late Cretaceous origin, to occasional tropical grassland patches in the later Palaeogene, to extensive C 3 grassy woodlands in the early-middle Miocene, to the dramatic expansion of the tropical C 4 grass savannas and grasslands in the Pliocene, and the C 3 steppe grasslands during the Pleistocene glacial periods. Modern grasslands depend heavily on strongly seasonal climates, making them sensitive to climate change. © 2017 Cambridge Philosophical Society.

The Natural Biotic Environment of Caenorhabditis elegans.

PubMed

Schulenburg, Hinrich; Félix, Marie-Anne

2017-05-01

Organisms evolve in response to their natural environment. Consideration of natural ecological parameters are thus of key importance for our understanding of an organism's biology. Curiously, the natural ecology of the model species Caenorhabditis elegans has long been neglected, even though this nematode has become one of the most intensively studied models in biological research. This lack of interest changed ∼10 yr ago. Since then, an increasing number of studies have focused on the nematode's natural ecology. Yet many unknowns still remain. Here, we provide an overview of the currently available information on the natural environment of C. elegans We focus on the biotic environment, which is usually less predictable and thus can create high selective constraints that are likely to have had a strong impact on C. elegans evolution. This nematode is particularly abundant in microbe-rich environments, especially rotting plant matter such as decomposing fruits and stems. In this environment, it is part of a complex interaction network, which is particularly shaped by a species-rich microbial community. These microbes can be food, part of a beneficial gut microbiome, parasites and pathogens, and possibly competitors. C. elegans is additionally confronted with predators; it interacts with vector organisms that facilitate dispersal to new habitats, and also with competitors for similar food environments, including competitors from congeneric and also the same species. Full appreciation of this nematode's biology warrants further exploration of its natural environment and subsequent integration of this information into the well-established laboratory-based research approaches. Copyright © 2017 by the Genetics Society of America.

Oxygen isotopic composition of chondritic interplanetary dust particles: A genetic link between carbonaceous chondrites and comets

NASA Astrophysics Data System (ADS)

Aléon, J.; Engrand, C.; Leshin, L. A.; McKeegan, K. D.

2009-08-01

Oxygen isotopes were measured in four chondritic hydrated interplanetary dust particles (IDPs) and five chondritic anhydrous IDPs including two GEMS-rich particles (Glass embedded with metal and sulfides) by a combination of high precision and high lateral resolution ion microprobe techniques. All IDPs have isotopic compositions tightly clustered around that of solar system planetary materials. Hydrated IDPs have mass-fractionated oxygen isotopic compositions similar to those of CI and CM carbonaceous chondrites, consistent with hydration of initially anhydrous protosolar dust. Anhydrous IDPs have small 16O excesses and depletions similar to those of carbonaceous chondrites, the largest 16O variations being hosted by the two GEMS-rich IDPs. Coarse-grained forsteritic olivine and enstatite in anhydrous IDPs are isotopically similar to their counterparts in comet Wild 2 and in chondrules suggesting a high temperature inner solar system origin. The small variations in the 16O content of GEMS-rich IDPs suggest that most GEMS either do not preserve a record of interstellar processes or the initial interstellar dust is not 16O-rich as expected by self-shielding models, although a larger dataset is required to verify these conclusions. Together with other chemical and mineralogical indicators, O isotopes show that the parent-bodies of carbonaceous chondrites, of chondritic IDPs, of most Antarctic micrometeorites, and comet Wild 2 belong to a single family of objects of carbonaceous chondrite chemical affinity as distinct from ordinary, enstatite, K- and R-chondrites. Comparison with astronomical observations thus suggests a chemical continuum of objects including main belt and outer solar system asteroids such as C-type, P-type and D-type asteroids, Trojans and Centaurs as well as short-period comets and other Kuiper Belt Objects.

K2 & Solar System Science

NASA Technical Reports Server (NTRS)

Lissauer, Jack

2015-01-01

All of the fields that K2 observes are near the ecliptic plane in order to minimize the spin-up of the spacecraft in response to the effects of solar irradiation. The fields observed by K2 are thus rich in Solar System objects including planets, asteroids and trans-Neptunian objects (TNOs). K2 has already performed observations of Neptune and its large moon Triton, 68 Trojan and Hilda asteroids, 5 TNOs (including Pluto) and Comet C/2013 A1 (Siding Springs). About 10,000 main-belt asteroids that fell into the pixel masks of stars have been serendipitously observed. Observations of small bodies are especially useful for determining rotation periods. Uranus will be observed in a future campaign (C8), as will many more small Solar System bodies. The status of various K2 Solar System studies will be reviewed and placed within the context of our current knowledge of the objects being observed.

Time-dependent inhibition by glyceryl trinitrate of platelet aggregation caused by U46619 (a thromboxane/endoperoxide receptor agonist).

PubMed Central

Kampf, G; Ritter, J M

1994-01-01

Glyceryl trinitrate is a weak inhibitor of platelet aggregation in vitro. Its effect on platelet aggregation in response to U46619 (a thromboxane/endoperoxide receptor agonist) was studied turbidometrically in platelet-rich plasma from healthy volunteers. The object was to determine whether inhibition was influenced by a period of preincubation between preparation of platelet-rich plasma and addition of glyceryl trinitrate. Incubation was performed at 37 degrees C and 22 degrees C. Samples were removed at intervals and transferred to an aggregometer cuvette at 37 degrees C. Glyceryl trinitrate (100 microM) or an equal volume of distilled water was added 5 min before U46619 (2 microM), and aggregation recorded as change in light transmission. Inhibition by glyceryl trinitrate was markedly time and temperature dependent, with a progressive increase in inhibitory potency between 120 and 300 min preincubation at 37 degrees C but not at 22 degrees C. The explanation of this is unknown but the effect was not influenced by lipopolysaccharide or by cycloheximide, so it does not appear to be due to exposure to endotoxin or to enzyme induction in vitro. PMID:7946941

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaluarachchi, Udhara S.; Taufour, Valentin; Bud'ko, Sergey L.

We report the temperature-pressure-magnetic eld phase diagram of the ferromagnetic Kondolattice CeTiGe 3 determined by means of electrical resistivity measurements. Measurements up to ~5.8GPa reveal a rich phase diagram with multiple phase transitions. At ambient pressure, CeTiGe 3 orders ferromagnetically at T C =14 K. Application of pressure suppresses T C, but a pressure induced ferromagnetic quantum criticality is avoided by the appearance of two new successive transitions for p>4.1GPa that are probably antiferromagnetic in nature. These two transitions are suppressed under pressure, with the lower temperature phase being fully suppressed above 5.3GPa. The critical pressures for the presumed quantummore » phase transitions are p1≅4.1GPa and p2≅5.3GPa. Above 4.1GPa, application of magnetic eld shows a tricritical point evolving into a wing structure phase with a quantum tricritical point at 2.8T at 5.4GPa, where the rst order antiferromagneticferromagnetic transition changes into the second order antiferromagnetic-ferromagnetic transition.« less

Oxygen buffering of Kilauea volcanic gases and the oxygen fugacity of Kilauea basalt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerlach, T.M.

1993-02-01

Volcanic gases collected during episode 1 of the Puu Oo eruption along the east rift zone of Kilauea Volcano, Hawaii, have uniform C-O-H-S-Cl-F compositions that are sharply depleted in CO[sub 2]. The CO[sub 2]-poor gases are typical of Type II volcanic gases (GERLACH and GRAEBER, 1985) and were emitted from evolved magma stored for a prolonged period of time in the east rift zone after releasing CO[sub 2]-rich gases during an earlier period of temporary residence in the summit magma chamber. The samples are remarkably free of contamination by atmospheric gases and meteoric water. Thermodynamic evaluation of the analytical datamore » shows that the episode 1 gases have equilibrium compositions appropriate for temperatures between 935 and 1032[degrees]C. Open- and closed-system equilibrium models of species distributions for the episode 1 gases show unequivocally that coexisting lavas buffered the gas oxygen fugacities during cooling. These models indicate that the F[sub o[sub 2

Modeling the suppression of boron transient enhanced diffusion in silicon by substitutional carbon incorporation

NASA Astrophysics Data System (ADS)

Ngau, Julie L.; Griffin, Peter B.; Plummer, James D.

2001-08-01

Recent work has indicated that the suppression of boron transient enhanced diffusion (TED) in carbon-rich Si is caused by nonequilibrium Si point defect concentrations, specifically the undersaturation of Si self-interstitials, that result from the coupled out-diffusion of carbon interstitials via the kick-out and Frank-Turnbull reactions. This study of boron TED reduction in Si1-x-yGexCy during 750 °C inert anneals has revealed that the use of an additional reaction that further reduces the Si self-interstitial concentration is necessary to describe accurately the time evolved diffusion behavior of boron. In this article, we present a comprehensive model which includes {311} defects, boron-interstitial clusters, a carbon kick-out reaction, a carbon Frank-Turnbull reaction, and a carbon interstitial-carbon substitutional (CiCs) pairing reaction that successfully simulates carbon suppression of boron TED at 750 °C for anneal times ranging from 10 s to 60 min.

The Basics of Blended Instruction

ERIC Educational Resources Information Center

Tucker, Catlin R.

2013-01-01

Even though many of teachers do not have technology-rich classrooms, the rapidly evolving education landscape increasingly requires them to incorporate technology to customize student learning. Blended learning, with its mix of technology and traditional face-to-face instruction, is a great approach. Blended learning combines classroom learning…

On the nature of upsilon Sagittarii

NASA Technical Reports Server (NTRS)

Schoenberner, D.; Drilling, J. S.

1982-01-01

An explanation for the nature and evolution of the extremely hydrogen deficient binary Upsilon Sagittarii which is consistent with all observational and theoretical facts. First, the system goes through a Case B mass exchange in which most of the hydrogen rich envelope of a massive primary (5 to 14 solar masses) is lost. The remaining envelope still contains about 50% hydrogen (by number), but is now of negligible mass, so that the star evolves like a pure helium star. If its mass is between 1 and 2 solar masses the star reaches low surface temperatures and becomes a supergiant before the onset of carbon burning. This star (the original primary) then fills its Roche lobe a second time, spilling its now helium rich envelope over onto the secondary (Case BB mass exchange). It is argued that Upsilon Sagrittarii is in this state at the present time, and that the visible star is an evolved helium star of about 1 solar mass with a degenerate carbon-oxygen core and a helium burning shell which provides the high luminosity.

Good Samaritans in Networks: An Experiment on How Networks Influence Egalitarian Sharing and the Evolution of Inequality

PubMed Central

Chiang, Yen-Sheng

2015-01-01

The fact that the more resourceful people are sharing with the poor to mitigate inequality—egalitarian sharing—is well documented in the behavioral science research. How inequality evolves as a result of egalitarian sharing is determined by the structure of “who gives whom”. While most prior experimental research investigates allocation of resources in dyads and groups, the paper extends the research of egalitarian sharing to networks for a more generalized structure of social interaction. An agent-based model is proposed to predict how actors, linked in networks, share their incomes with neighbors. A laboratory experiment with human subjects further shows that income distributions evolve to different states in different network topologies. Inequality is significantly reduced in networks where the very rich and the very poor are connected so that income discrepancy is salient enough to motivate the rich to share their incomes with the poor. The study suggests that social networks make a difference in how egalitarian sharing influences the evolution of inequality. PMID:26061642

40 CFR 721.10022 - Benzenamine, N-phenyl-, ar′-(C9-rich C8-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Significant New Uses for Specific Chemical Substances § 721.10022 Benzenamine, N-phenyl-, ar′-(C9-rich C8-10... chemical substance identified as benzenamine, N-phenyl-, ar′-(C9-rich C8-10-branched alkyl) derivs (PMN P...

The right half of the Escherichia coli replication origin is not essential for viability, but facilitates multi-forked replication

PubMed Central

Stepankiw, Nicholas; Kaidow, Akihiro; Boye, Erik; Bates, David

2010-01-01

Summary Replication initiation is a key event in the cell cycle of all organisms and oriC, the replication origin in Escherichia coli, serves as the prototypical model for this process. The minimal sequence required for oriC function was originally determined entirely from plasmid studies using cloned origin fragments, which have previously been shown to differ dramatically in sequence requirement from the chromosome. Using an in vivo recombineering strategy to exchange wt oriCs for mutated ones regardless of whether they are functional origins or not, we have determined the minimal origin sequence that will support chromosome replication. Nearly the entire right half of oriC could be deleted without loss of origin function, demanding a reassessment of existing models for initiation. Cells carrying the new DnaA box-depleted 163 bp minimal oriC exhibited little or no loss of fitness under slow-growth conditions, but were sensitive to rich medium, suggesting that the dense packing of initiator binding sites that is a hallmark of prokaryotic origins, has likely evolved to support the increased demands of multi-forked replication. PMID:19737351

φ-evo: A program to evolve phenotypic models of biological networks.

PubMed

Henry, Adrien; Hemery, Mathieu; François, Paul

2018-06-01

Molecular networks are at the core of most cellular decisions, but are often difficult to comprehend. Reverse engineering of network architecture from their functions has proved fruitful to classify and predict the structure and function of molecular networks, suggesting new experimental tests and biological predictions. We present φ-evo, an open-source program to evolve in silico phenotypic networks performing a given biological function. We include implementations for evolution of biochemical adaptation, adaptive sorting for immune recognition, metazoan development (somitogenesis, hox patterning), as well as Pareto evolution. We detail the program architecture based on C, Python 3, and a Jupyter interface for project configuration and network analysis. We illustrate the predictive power of φ-evo by first recovering the asymmetrical structure of the lac operon regulation from an objective function with symmetrical constraints. Second, we use the problem of hox-like embryonic patterning to show how a single effective fitness can emerge from multi-objective (Pareto) evolution. φ-evo provides an efficient approach and user-friendly interface for the phenotypic prediction of networks and the numerical study of evolution itself.

Defining the Brittle Failure Envelopes of Individual Reaction Zones Observed in CO2-Exposed Wellbore Cement.

PubMed

Hangx, Suzanne J T; van der Linden, Arjan; Marcelis, Fons; Liteanu, Emilia

2016-01-19

To predict the behavior of the cement sheath after CO2 injection and the potential for leakage pathways, it is key to understand how the mechanical properties of the cement evolves with CO2 exposure time. We performed scratch-hardness tests on hardened samples of class G cement before and after CO2 exposure. The cement was exposed to CO2-rich fluid for one to six months at 65 °C and 8 MPa Ptotal. Detailed SEM-EDX analyses showed reaction zones similar to those previously reported in the literature: (1) an outer-reacted, porous silica-rich zone; (2) a dense, carbonated zone; and (3) a more porous, Ca-depleted inner zone. The quantitative mechanical data (brittle compressive strength and friction coefficient) obtained for each of the zones suggest that the heterogeneity of reacted cement leads to a wide range of brittle strength values in any of the reaction zones, with only a rough dependence on exposure time. However, the data can be used to guide numerical modeling efforts needed to assess the impact of reaction-induced mechanical failure of wellbore cement by coupling sensitivity analysis and mechanical predictions.

Nano-engineered intrapores in nanoparticles of PtNi networks for increased oxygen reduction reaction activity

NASA Astrophysics Data System (ADS)

Ding, Jieting; Ji, Shan; Wang, Hui; Key, Julian; Brett, Dan J. L.; Wang, Rongfang

2018-01-01

Network-like metallic alloys of solid nanoparticles have been frequently reported as promising electrocatalysts for fuel cells. The three-dimensional structure of such networks is rich in pores in the form of voids between nanoparticles, which collectively expose a large surface area for catalytic activity. Herein, we present a novel solution to this problem using a precursor comprising a flocculent core-shell PtNi@Ni to produce PtNi network catalysts with nanoparticle intraporosity after carefully controlled electrochemical dealloying. Physical characterization shows a hierarchical level of nanoporosity (intrapores within nanoparticles and pores between them) evolves during the controlled electrochemical dealloying, and that a Pt-rich surface also forms after 22 cycles of Ni leaching. In ORR cycling, the PtNi networks gain 4-fold activity in both jECSA and jmass over a state of the art Pt/C electrocatalyst, and also significantly exceed previously reported PtNi networks. In ORR degradation tests, the PtNi networks also proved stable, dropping by 30.4% and 62.6% in jECSA and jmass respectively. The enhanced performance of the catalyst is evident, and we also propose that the presented synthesis procedure can be generally applied to developing other metallic networks.

Spherulitic Growth of Hematite Under Hydrothermal Conditions: Insights into the Growth Mechanism of Hematite Spherules at Meridiani Planum Mars.

NASA Technical Reports Server (NTRS)

Ming, Douglas W.; Golden, D. C.; Morris, R. V.

2010-01-01

Hematite-rich spherules were discovered embedded in sulfate-rich outcrop rock and as lag deposits of whole and broken spherules by the Opportunity rover at Meridiani Planem [1-6]. The Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES), which has a wider spectral range compared to the Mars Exploration Rover Mini-TES, provided an important constraint that hematite-rich spherules are dominated by emission along the crystallographic c-axis [7-10]. We have previously synthesized hematite spherules whose mineralogic, chemical, and crystallographic properties are strikingly similar to those for the hematite-rich spherules at Meridiani Planum [11]. The spherules were synthesized in the laboratory along with hydronium jarosite and minor hydronium alunite from Fe-Al-Mg-S-Cl acid sulfate solutions under hydrothermal conditions. The reaction sequence was (1) precipitation of hydronium jarosite, (2) jarosite dissolution and precipitation of hematite spherules, and (3) precipitation of hydronium alunite upon depletion of hydronium jarosite. The spherules exhibit a radial growth texture with the crystallographic c-axis aligned along the radial direction, so that thermal emission spectra have no hematite emissivity minimum at approx.390/cm similar to the emission spectra returned by MGS TES. The objective of this paper is to expand on our initial studies [11] to examine the morphological evolution during growth of spherules starting from sub-micrometer crystals to spherules many orders of magnitude in size.

Grosnaja ABCs: Magnesium isotope compositions

NASA Technical Reports Server (NTRS)

Goswami, J. N.; Srinivasan, G.; Ulyanov, A. A.

1993-01-01

Three CAI's from the Grosnaja CV3 chondrite were analyzed for their magnesium isotopic compositions by the ion microprobe. The selected CAI's represent three distinct types: GR4(compact Type A), GR7(Type B) and GR2(Type C). Petrographic studies indicate that all three Grosnaja inclusions were subjected to secondary alterations. The Type A CAI GR4 is primarily composed of melilite with spinel and pyroxene occurring as minor phases. The rim of the inclusion does not exhibit distinct layered structure and secondary alteration products (garnet, Fe-rich olivine and Na-rich plagioclase) are present in some localized areas near the rim region. The average major element compositions of different mineral phases in GR4 are given. Preliminary REE data suggest a depletion of HREE relative to LREE by about a factor of 3 without any clear indication of interelement fractionation. The CAI GR7 has textural and minerological characteristics similar to Type B inclusions. The REE data show a pattern that is similar to Group 6 with enrichment in Eu and Yb. In addition, a depletion of HREE compared to LREE is also evident in this object. Melilite composition shows a broad range of akermanite content (Ak(sub 15-55)). Detailed petrographic study is in progress. GR2 is a anorthite-rich Type C inclusion with large plagioclase laths intergrown with Ti-rich pyroxene. The average plagioclase composition is close to pure anorthite (An99).

Looking for a Source of Water in Martian Basltic Breccia NWA 7034

NASA Technical Reports Server (NTRS)

Muttik, N.; Agee, C. B.; McCubbin, F. M.; McCuttcheon, W. A.; Provencio, P. P.; Keller, L. P.; Santos, A. R..; Shearer, C. K.

2014-01-01

The recently described martian meteorite NWA 7034 has high water content compared to other SNC meteorites. Deuterium to hydrogen isotope ratio measurements indicates that there are two distinct delta-D components in NWA 7034, a low temperature (150-500degC) light component around -100per mille and a high temperature (300-1000degC) heavy component around +300per mille. NWA 7034 contains iron-rich phases that are likely secondary aqueous alteration products. They are commonly found as spheroidal objects of various sizes that are often rich in Fe-Ti oxides and possibly iron hydroxides. Iron oxides and oxyhydroxides are very common in weathered rocks and soils on Earth and Mars and they are important components of terrestrial and Martian dust. In NWA 7034 iron-rich phases are found throughout the fine-grained basaltic groundmass of the meteorite. The total amount of martian H2O in NWA 7034 is reported to be 6000 ppm, and in this study we attempt to determine the phase distribution of this H2O by texturally describing and characterizing hydrous phases in NWA 7034, using Fourier transform infrared spectrometry (FTIR) and transmission electron microscopy (TEM).

Social influence on selection behaviour: Distinguishing local- and global-driven preferential attachment

PubMed Central

Pan, Xue; Liu, Kecheng

2017-01-01

Social influence drives human selection behaviours when numerous objects competing for limited attentions, which leads to the ‘rich get richer’ dynamics where popular objects tend to get more attentions. However, evidences have been found that, both the global information of the whole system and the local information among one’s friends have significant influence over the one’s selection. Consequently, a key question raises that, it is the local information or the global information more determinative for one’s selection? Here we compare the local-based influence and global-based influence. We show that, the selection behaviour is mainly driven by the local popularity of the objects while the global popularity plays a supplementary role driving the behaviour only when there is little local information for the user to refer to. Thereby, we propose a network model to describe the mechanism of user-object interaction evolution with social influence, where the users perform either local-driven or global-driven preferential attachments to the objects, i.e., the probability of an objects to be selected by a target user is proportional to either its local popularity or global popularity. The simulation suggests that, about 75% of the attachments should be driven by the local popularity to reproduce the empirical observations. It means that, at least in the studied context where users chose businesses on Yelp, there is a probability of 75% for a user to make a selection according to the local popularity. The proposed model and the numerical findings may shed some light on the study of social influence and evolving social systems. PMID:28406984

Structured Course Objects in a Digital Library

NASA Technical Reports Server (NTRS)

Maly, K.; Zubair, M.; Liu, X.; Nelson, M.; Zeil, S.

1999-01-01

We are developing an Undergraduate Digital Library Framework (UDLF) that will support creation/archiving of courses and reuse of existing course material to evolve courses. UDLF supports the publication of course materials for later instantiation for a specific offering and allows the addition of time-dependent and student-specific information and structures. Instructors and, depending on permissions, students can access the general course materials or the materials for a specific offering. We are building a reference implementation based on NCSTRL+, a digital library derived from NCSTRL. Digital objects in NCSTRL+ are called buckets, self-contained entities that carry their own methods for access and display. Current bucket implementations have a two level structure of packages and elements. This is not a rich enough structure for course objects in UDLF. Typically, courses can only be modeled as a multilevel hierarchy and among different courses, both the syntax and semantics of terms may vary. Therefore, we need a mechanism to define, within a particular library, course models, their constituent objects, and the associated semantics in a flexible, extensible way. In this paper, we describe our approach to define and implement these multilayered course objects. We use XML technology to emulate complex data structures within the NCSTRL+ buckets. We have developed authoring and browsing tools to manipulate these course objects. In our current implementation a user downloading an XML based course bucket also downloads the XML-aware tools: an applet that enables the user to edit or browse the bucket. We claim that XML provides an effective means to represent multi-level structure of a course bucket.

Social influence on selection behaviour: Distinguishing local- and global-driven preferential attachment.

PubMed

Pan, Xue; Hou, Lei; Liu, Kecheng

2017-01-01

Social influence drives human selection behaviours when numerous objects competing for limited attentions, which leads to the 'rich get richer' dynamics where popular objects tend to get more attentions. However, evidences have been found that, both the global information of the whole system and the local information among one's friends have significant influence over the one's selection. Consequently, a key question raises that, it is the local information or the global information more determinative for one's selection? Here we compare the local-based influence and global-based influence. We show that, the selection behaviour is mainly driven by the local popularity of the objects while the global popularity plays a supplementary role driving the behaviour only when there is little local information for the user to refer to. Thereby, we propose a network model to describe the mechanism of user-object interaction evolution with social influence, where the users perform either local-driven or global-driven preferential attachments to the objects, i.e., the probability of an objects to be selected by a target user is proportional to either its local popularity or global popularity. The simulation suggests that, about 75% of the attachments should be driven by the local popularity to reproduce the empirical observations. It means that, at least in the studied context where users chose businesses on Yelp, there is a probability of 75% for a user to make a selection according to the local popularity. The proposed model and the numerical findings may shed some light on the study of social influence and evolving social systems.

Adaptation to fluctuations in temperature by nine species of bacteria.

PubMed

Saarinen, Kati; Laakso, Jouni; Lindström, Leena; Ketola, Tarmo

2018-03-01

Rapid environmental fluctuations are ubiquitous in the wild, yet majority of experimental studies mostly consider effects of slow fluctuations on organism. To test the evolutionary consequences of fast fluctuations, we conducted nine independent experimental evolution experiments with bacteria. Experimental conditions were same for all species, and we allowed them to evolve either in fluctuating temperature alternating rapidly between 20°C and 40°C or at constant 30°C temperature. After experimental evolution, we tested the performance of the clones in both rapid fluctuation and in constant environments (20°C, 30°C and 40°C). Results from experiments on these nine species were combined meta-analytically. We found that overall the clones evolved in the fluctuating environment had evolved better efficiency in tolerating fluctuations (i.e., they had higher yield in fluctuating conditions) than the clones evolved in the constant environment. However, we did not find any evidence that fluctuation-adapted clones would have evolved better tolerance to any measured constant environments (20°C, 30°C, and 40°C). Our results back up recent empirical findings reporting that it is hard to predict adaptations to fast fluctuations using tolerance curves.

Origin of spinel-rich chondrules and inclusions in carbonaceous and ordinary chondrites

NASA Technical Reports Server (NTRS)

Kornacki, A. S.; Fegley, B., Jr.

1984-01-01

The evaluation of three models of the origin of spinel-rich chondrules and inclusions presented here includes new calculations of the major-element refractory mineral condensation sequence from a gas of solar composition over a wide pressure interval. Condensation calculations show that spinel-rich chondrules did not crystallize from metastable liquid condensates, and that spinel-rich inclusions are not aggregates of refractory nebular condensates. It is proposed that spinel-rich objects are fractionated distillation residues of small aggregates of primitive dust that lost Ca, Si-rich partial melts by evaporation, ablation, or splashing during collisions. This model also explains why spinel-rich chondrules and inclusions (1) are usually smaller than melilite-rich chondrules and inclusions; (2) often have highly fractionated trace-element compositions; and (3) usually do not contain Pt-metal nuggets even when they are more enriched in the Pt-group metals than nugget-bearing melilite-rich objects.

Constructing Virtual Worlds: Tracing the Historical Development of Learner Practices.

ERIC Educational Resources Information Center

Barab, Sasha A.; Hay, Kenneth E.; Barnett, Michael; Squire, Kurt

2001-01-01

Explored learning and instruction within a technology-rich, collaborative, participatory learning environment by tracking the emergence of shared understanding and products through student and teacher practices. Found that becoming knowledgeably skillful with respect to a particular practice or concept is a multigenerational process, evolving in…

The Manu-Facturing of a Language.

ERIC Educational Resources Information Center

Washabaugh, William

1980-01-01

Discusses Providence Island Sign Language (PSL), an autochthonous and relatively immature language of about 20 speakers. It is a nascent and evolving language whose description can produce rich results for linguistic theory. Such a description will also be an explanation of the phylogeny of a linguistic system. (Author/PJM)

Three-Body Forces and the Limit of Oxygen Isotopes

NASA Astrophysics Data System (ADS)

Otsuka, Takaharu; Suzuki, Toshio; Holt, Jason D.; Schwenk, Achim; Akaishi, Yoshinori

2010-07-01

The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from O28 to the experimentally observed O24. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments.

The use of kerogen data in understanding the properties and evolution of interstellar carbonaceous dust

NASA Astrophysics Data System (ADS)

Papoular, R.

2001-11-01

A number of authors have, in the past decade, pointed to the similarity of the 3.4-mu m band of kerogen with that of the Galactic Centre (GC). Kerogen is a family of solid terrestrial sedimentary materials essentially made of C, H and O interlocked in a disordered, more or less aliphatic, structure. Here, the most recent results of the astronomical literature and the rich quantitative geochemical literature are tapped with two purposes in mind: extend the analogy to the mid-IR bands and, based on these new constraints, quantitatively assess the properties of the carrier dust. It is shown that the great diversity of IR astronomical IS (interstellar) dust is paralleled by the changes in kerogen spectra as the material spontaneously and continuously evolves (aromatizes) in the earth. Since the composition and structure of kerogen are known all along its evolution, it is possible, by spectral analogy, to estimate these properties for the corresponding astronomical carriers. The Galactic Centre 3.4 mu m feature is thus found to correspond to an early stage of evolution, for which the composition in C, H and O and the structure of the corresponding kerogen are known and reported here. The role of oxygen in the subsequent evolution and its contribution to different bands are stressed. The above provides new arguments in favour of the 3.4-mu m band, as well as the observed accompanying mid-IR bands, being carried by kerogen-like dust born in CS (circumstellar) envelopes, mostly of AGB (asymptotic giant branch) objects. Subsequent dust evolution in composition and structure (aromatization) is fast enough that the unidentified infrared bands can already show up in well-developed planetary nebulae (PNe), as observed. A fraction of incompletely evolved dust can escape into the diffuse IS medium and molecular clouds. As a consequence, aliphatic and aromatic features can both be detected in the sky, in emission (Proto-PNe, PNe and PDRs (photo-dissociation regions)) as well as in absorption (dense molecular clouds and diffuse ISM). Changes in wavelength and band width with line of sight are explained by changes in the nature and number of chemical functional groups composing the carrier material. Predictions of the kerogen model in the UV and far IR are proposed for testing.

Young stellar population and ongoing star formation in the H II complex Sh2-252

NASA Astrophysics Data System (ADS)

Jose, Jessy; Pandey, A. K.; Samal, M. R.; Ojha, D. K.; Ogura, K.; Kim, J. S.; Kobayashi, N.; Goyal, A.; Chauhan, N.; Eswaraiah, C.

2013-07-01

In this paper, an extensive survey of the star-forming complex Sh2-252 has been undertaken with an aim to explore its hidden young stellar population as well as to understand the structure and star formation history for the first time. This complex is composed of five prominent embedded clusters associated with the subregions A, C, E, NGC 2175s and Teu 136. We used Two Micron All Sky Survey-near-infrared and Spitzer-Infrared Array Camera, Multiband Imaging Photometer for Spitzer photometry to identify and classify the young stellar objects (YSOs) by their infrared (IR) excess emission. Using the IR colour-colour criteria, we identified 577 YSOs, of which, 163 are Class I, 400 are Class II and 14 are transition disc YSOs, suggesting a moderately rich number of YSOs in this complex. Spatial distribution of the candidate YSOs shows that they are mostly clustered around the subregions in the western half of the complex, suggesting enhanced star formation activity towards its west. Using the spectral energy distribution and optical colour-magnitude diagram-based age analyses, we derived probable evolutionary status of the subregions of Sh2-252. Our analysis shows that the region A is the youngest (˜0.5 Myr), the regions B, C and E are of similar evolutionary stage (˜1-2 Myr) and the clusters NGC 2175s and Teu 136 are slightly evolved (˜2-3 Myr). Morphology of the region in the 1.1 mm map shows a semicircular shaped molecular shell composed of several clumps and YSOs bordering the western ionization front of Sh2-252. Our analyses suggest that next generation star formation is currently under way along this border and that possibly fragmentation of the matter collected during the expansion of the H II region as one of the major processes is responsible for such stars. We observed the densest concentration of YSOs (mostly Class I, ˜0.5 Myr) at the western outskirts of the complex, within a molecular clump associated with water and methanol masers and we suggest that it is indeed a site of cluster formation at a very early evolutionary stage, sandwiched between the two relatively evolved CH II regions A and B.

Dust in brown dwarfs and extrasolar planets. V. Cloud formation in carbon- and oxygen-rich environments

NASA Astrophysics Data System (ADS)

Helling, Ch.; Tootill, D.; Woitke, P.; Lee, G.

2017-07-01

Context. Recent observations indicate potentially carbon-rich (C/O > 1) exoplanet atmospheres. Spectral fitting methods for brown dwarfs and exoplanets have invoked the C/O ratio as additional parameter but carbon-rich cloud formation modeling is a challenge for the models applied. The determination of the habitable zone for exoplanets requires the treatment of cloud formation in chemically different regimes. Aims: We aim to model cloud formation processes for carbon-rich exoplanetary atmospheres. Disk models show that carbon-rich or near-carbon-rich niches may emerge and cool carbon planets may trace these particular stages of planetary evolution. Methods: We extended our kinetic cloud formation model by including carbon seed formation and the formation of C[s], TiC[s], SiC[s], KCl[s], and MgS[s] by gas-surface reactions. We solved a system of dust moment equations and element conservation for a prescribed Drift-Phoenixatmosphere structure to study how a cloud structure would change with changing initial C/O0 = 0.43...10.0. Results: The seed formation efficiency is lower in carbon-rich atmospheres than in oxygen-rich gases because carbon is a very effective growth species. The consequence is that fewer particles make up a cloud if C/O0 > 1. The cloud particles are smaller in size than in an oxygen-rich atmosphere. An increasing initial C/O ratio does not revert this trend because a much greater abundance of condensible gas species exists in a carbon-rich environment. Cloud particles are generally made of a mix of materials: carbon dominates if C/O0 > 1 and silicates dominate if C/O0 < 1. A carbon content of 80-90% carbon is reached only in extreme cases where C/O0 = 3.0 or 10.0. Conclusions: Carbon-rich atmospheres form clouds that are made of particles of height-dependent mixed compositions, sizes and numbers. The remaining gas phase is far less depleted than in an oxygen-rich atmosphere. Typical tracer molecules are HCN and C2H2 in combination with a featureless, smooth continuum due to a carbonaceous cloud cover, unless the cloud particles become crystalline.

Effects of Perceptually Rich Manipulatives on Preschoolers' Counting Performance: Established Knowledge Counts

ERIC Educational Resources Information Center

Petersen, Lori A.; McNeil, Nicole M.

2013-01-01

Educators often use concrete objects to help children understand mathematics concepts. However, findings on the effectiveness of concrete objects are mixed. The present study examined how two factors--perceptual richness and established knowledge of the objects--combine to influence children's counting performance. In two experiments, preschoolers…

Processing of presolar grains around post-AGB stars: SiC as the carrier of the ``21''μ m feature

NASA Astrophysics Data System (ADS)

Hofmeister, A. M.; Speck, A. K.

2003-12-01

Intermediate mass stars (0.8-8.0 Msolar) eventually evolve on the H-R diagram, up the asymptotic giant branch (AGB). The intensive mass loss which characterizes the AGB produces a circumstellar shell of dust and neutral gas. At the end of the AGB, mass loss virtually stops and the circumstellar shell begins to drift away from the star. At the same time the central star begins to shrink and heat up. This is the proto-planetary nebula (PPN) phase. Some PPNe exhibit an enigmatic feature in their infrared (IR) spectra at ˜21μ m. This feature is not seen in the spectra of either the precursors to PPNe, the AGB stars, or the successors of PPNe, ``normal'' planetary nebulae (PNe). However the ``21''μ m feature has been seen in the spectra of PNe with Wolf-Rayet central stars. Therefore the carrier of this feature is unlikely to be a transient species that only exists in the PPNe phase. This feature has been attributed to various molecular and solid state species, none of which satisfy all constraints, although titanium carbide (TiC) and polycyclic aromatic hydrocarbons (PAHs) have seemed the most viable. We present new laboratory data for silicon carbide (SiC) and show that it has a spectral feature which is a good candidate for the carrier of the 21μ m feature. The SiC spectral feature appears at approximately the same wavelength (depending on polytype/grain size) and has the same asymmetric profile as the observed astronomical feature. We suggest that processing and cooling of the SiC grains known to exist around carbon-rich AGB stars are responsible for the emergence of the enigmatic 21μ m feature. The emergence of this feature in the spectra of post-AGB stars demonstrates the processing of dust due to the changing physical environments around evolving stars.

A Search for Phosphine in Circumstellar Envelopes: PH3 in IRC +10216 and CRL 2688?

NASA Astrophysics Data System (ADS)

Tenenbaum, E. D.; Ziurys, L. M.

2008-06-01

We present the results of a search for the JK = 10→ 00 transition of PH3 (phosphine) at 267 GHz toward several circumstellar envelopes using the Arizona Radio Observatory 10 m Submillimeter Telescope (SMT). In the carbon-rich shells of IRC +10216 and CRL 2688, we have detected emission lines exactly at the PH3 frequency. Toward the oxygen-rich supergiant VY Canis Majoris, only an upper limit was obtained, while in the evolved carbon-rich proto-planetary nebula CRL 618, the transition is contaminated by vibrationally excited HC3N (ν7 = 4). The line shape in IRC +10216 appears to consist of two distinct components: a flat-topped profile with a width of ~28 km s-1, as is typical for this source, and a narrower feature approximately 4 km s-1 wide. The narrow component likely arises from the inner envelope (r < 8R*) where the gas has not reached the terminal expansion velocity, or it is nonthermal emission. Based on the broader component, the abundance of PH3 with respect to H2 is estimated to be 5 × 10-8 in a region with a radius of r < 150R*. If the narrower component is thermal, it implies a phosphine abundance of ~5 × 10-7 close to the stellar photosphere (r < 8R*). In CRL 2688, the PH3 abundance is less constrained, with plausible values ranging from 3 × 10-8 to 4 × 10-7, assuming a spherical distribution. Phosphine appears to be present in large concentrations in the inner envelope of C-rich AGB stars, and thus may function as a parent molecule for other phosphorus species.

The Characteristics and Generating Mechanism of Large Precipitates in Ti-Containing H13 Tool Steel

NASA Astrophysics Data System (ADS)

Xie, You; Cheng, Guoguang; Chen, Lie; Zhang, Yandong; Yan, Qingzhong

2017-02-01

The characteristics of large precipitates in H13 tool steel with 0.015wt% Ti were studied. The result shows that three types of phases larger than 1 μm exist in the as-cast ingot, that is, (Ti, V) (C, N) type phase, (V, Mo, Cr)C type phase and sulfide. (Ti, V) (C, N) type phase could be further classified as the homogeneous Ti-rich one and the Ti-V-rich one in which Ti/V ratio gradually changes. (V, Mo, Cr)C type phase contains the V-rich one and the Mo-Cr-rich one. The compositional characteristics in all of them have little relation with the cutting position or cooling rate. The precipitating process could be well described through calculation by Thermo-Calc software. During solidification, the primary phase (Ti, V)(C, N) first starts to precipitate in the form of Ti-rich carbonitride. With the development of solidification, the ratio of Ti decreases and that of V increases. Then the primary phase Ti-V-rich (Ti, V)(C, N) and V-rich (V, Mo, Cr)C appears successively. Mo-Cr-rich (V, Mo, Cr)C phase does not precipitate until the solidification process reaches to the end. Sulfide precipitates before (V, Mo, Cr)C type phase and it could act as the nucleus of (V, Mo, Cr)C.

A Spectroscopic Study of the Rich Supernova Remnant Population in M83

NASA Astrophysics Data System (ADS)

Winkler, P. Frank; Blair, William P.; Long, Knox S.

2017-04-01

We report the results from a spectrophotometric study sampling the ≳ 300 candidate supernova remnants (SNRs) in M83 identified through optical imaging with Magellan/IMACS and Hubble Space Telescope/WFC3. Of the 118 candidates identified based on a high [S II] λλ 6716, 6731 to Hα emission ratio, 117 show spectroscopic signatures of shock-heated gas, confirming them as SNRs—the largest uniform set of SNR spectra for any galaxy. Spectra of 22 objects with a high [O III] λ5007 to Hα emission ratio, selected in an attempt to identify young ejecta-dominated SNRs like Cas A, reveal only one (previously reported) object with the broad (≳ 1000 {km} {{{s}}}-1) emission lines characteristic of ejecta-dominated SNRs, beyond the known SN1957D remnant. The other 20 [O III]-selected candidates include planetary nebulae, compact H II regions, and one background QSO. Although our spectroscopic sample includes 22 SNRs smaller than 11 pc, none of the other objects show broad emission lines; instead their spectra stem from relatively slow (˜ 200 {km} {{{s}}}-1) radiative shocks propagating into the metal-rich interstellar medium of M83. With six SNe in the past century, one might expect more of M83's small-diameter SNRs to show evidence of ejecta; this appears not to be the case. We attribute their absence to several factors, including that SNRs expanding into a dense medium evolve quickly to the ISM-dominated phase, and that SNRs expanding into regions already evacuated by earlier SNe are probably very faint. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

Raman microscopy of lithium-manganese-rich transition metal oxide cathodes

DOE PAGES

Ruther, Rose E.; Callender, Andrew F.; Zhou, Hui; ...

2014-11-15

Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi 2MnO 3·(1-x)LiMO 2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this paper, Raman microscopymore » is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. Finally, the results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets.« less

Melting phase relation of nominally anhydrous, carbonated pelitic-eclogite at 2.5-3.0 GPa and deep cycling of sedimentary carbon

NASA Astrophysics Data System (ADS)

Tsuno, Kyusei; Dasgupta, Rajdeep

2011-05-01

We have experimentally investigated melting phase relation of a nominally anhydrous, carbonated pelitic eclogite (HPLC1) at 2.5 and 3.0 GPa at 900-1,350°C in order to constrain the cycling of sedimentary carbon in subduction zones. The starting composition HPLC1 (with 5 wt% bulk CO2) is a model composition, on a water-free basis, and is aimed to represent a mixture of 10 wt% pelagic carbonate unit and 90 wt% hemipelagic mud unit that enter the Central American trench. Sub-solidus assemblage comprises clinopyroxene + garnet + K-feldspar + quartz/coesite + rutile + calcio-ankerite/ankeritess. Solidus temperature is at 900-950°C at 2.5 GPa and at 900-1,000°C at 3.0 GPa, and the near-solidus melt is K-rich granitic. Crystalline carbonates persist only 50-100°C above the solidus and at temperatures above carbonate breakdown, carbon exists in the form of dissolved CO2 in silica-rich melts and as a vapor phase. The rhyodacitic to dacitic partial melt evolves from a K-rich composition at near-solidus condition to K-poor, and Na- and Ca-rich composition with increasing temperature. The low breakdown temperatures of crystalline carbonate in our study compared to those of recent studies on carbonated basaltic eclogite and peridotite owes to Fe-enrichment of carbonates in pelitic lithologies. However, the conditions of carbonate release in our study still remain higher than the modern depth-temperature trajectories of slab-mantle interface at sub-arc depths, suggesting that the release of sedimentary carbonates is unlikely in modern subduction zones. One possible scenario of carbonate release in modern subduction zones is the detachment and advection of sedimentary piles to hotter mantle wedge and consequent dissolution of carbonate in rhyodacitic partial melt. In the Paleo-NeoProterozoic Earth, on the other hand, the hotter slab-surface temperatures at subduction zones likely caused efficient liberation of carbon from subducting sedimentary carbonates. Deeply subducted carbonated sediments, similar to HPLC1, upon encountering a hotter mantle geotherm in the oceanic province can release carbon-bearing melts with high K2O, K2O/TiO2, and high silica, and can contribute to EM2-type ocean island basalts. Generation of EM2-type mantle end-member may also occur through metasomatism of mantle wedge by carbonated metapelite plume-derived partial melts.

The Richness Dependence of Galaxy Cluster Correlations: Results From A Redshift Survey Of Rich APM Clusters

NASA Technical Reports Server (NTRS)

Croft, R. A. C.; Dalton, G. B.; Efstathiou, G.; Sutherland, W. J.; Maddox, S. J.

1997-01-01

We analyze the spatial clustering properties of a new catalog of very rich galaxy clusters selected from the APM Galaxy Survey. These clusters are of comparable richness and space density to Abell Richness Class greater than or equal to 1 clusters, but selected using an objective algorithm from a catalog demonstrably free of artificial inhomogeneities. Evaluation of the two-point correlation function xi(sub cc)(r) for the full sample and for richer subsamples reveals that the correlation amplitude is consistent with that measured for lower richness APM clusters and X-ray selected clusters. We apply a maximum likelihood estimator to find the best fitting slope and amplitude of a power law fit to x(sub cc)(r), and to estimate the correlation length r(sub 0) (the value of r at which xi(sub cc)(r) is equal to unity). For clusters with a mean space density of 1.6 x 10(exp -6) h(exp 3) MpC(exp -3) (equivalent to the space density of Abell Richness greater than or equal to 2 clusters), we find r(sub 0) = 21.3(+11.1/-9.3) h(exp -1) Mpc (95% confidence limits). This is consistent with the weak richness dependence of xi(sub cc)(r) expected in Gaussian models of structure formation. In particular, the amplitude of xi(sub cc)(r) at all richnesses matches that of xi(sub cc)(r) for clusters selected in N-Body simulations of a low density Cold Dark Matter model.

Visualising the Future: Surfacing Student Perspectives on Post-Graduation Prospects Using Rich Pictures

ERIC Educational Resources Information Center

Berg, Tessa; Bowen, Tracey; Smith, Colin; Smith, Sally

2017-01-01

The gradual commodification of higher education in the context of an increased focus on graduate employability attributes together with evolving labour markets is creating challenges for universities and students alike. For universities, there has been significant investment in careers services and, through institution-wide initiatives,…

E-Texts, Mobile Browsing, and Rich Internet Applications

ERIC Educational Resources Information Center

Godwin-Jones, Robert

2007-01-01

Online reading is evolving beyond the perusal of static documents with Web pages inviting readers to become commentators, collaborators, and critics. The much-ballyhooed Web 2.0 is essentially a transition from online consumer to consumer/producer/participant. An online document may well include embedded multimedia or contain other forms of…

Art off the Beaten Track

ERIC Educational Resources Information Center

Fogg, Piper

2007-01-01

When the nearest metropolis is hundreds of miles away, cultural enrichment is not always easy to come by. Arts programs have evolved to reflect the needs of such regions, providing a rich diet for culture-starved residents. Some colleges have created choirs or theater groups that welcome local participation, while others have developed elaborate…

Allelic barley MLA immune receptors recognize sequence-unrelated avirulence effectors of the powdery mildew pathogen

USDA-ARS?s Scientific Manuscript database

Disease resistance (R) genes encoding intracellular nucleotide-binding domain and leucine-rich repeat proteins (NLRs) are key components of the plant innate immune system and typically detect the presence of isolate-specific avirulence (AVR) effectors from pathogens. NLRs define the fastest evolving...

Australia’s food system is highly dependent on foreign crop diversity

USDA-ARS?s Scientific Manuscript database

The food crops that are now produced or consumed in Australia were initially domesticated and evolved over time in specific geographic regions across the planet. Genetic diversity within these crops and their wild relatives is considered to be historically particularly rich within these regions. Los...

Content Management for a Content-Rich Website.

ERIC Educational Resources Information Center

Honeysett, Nik

Over the last year the J. Paul Getty Trust's Web presence has evolved from a group of disparate, independently maintained Web sites into a homogeneous consistently branded one. This transformation recently culminated with the implementation of a leading Content Management System (CMS). There were and are many process-changes and challenges in…

Brine/Rock Interaction in Deep Oceanic Layered Gabbros: Petrological Evidence from Cl-Rich Amphibole, High-Temperature Hydrothermal Veins, and Experiments

NASA Astrophysics Data System (ADS)

Currin Sala, A. M.; Koepke, J.; Almeev, R. R.; Teagle, D. A. H.; Zihlmann, B.; Wolff, P. E.

2017-12-01

Evidence of high temperature brine/rock interaction is found in hydrothermal veins and dykelets that cross-cut layered olivine gabbros in the deep palaeocrust of the Sumail Ophiolite, Sultanate of Oman. Here we present petrological and geochemical data from these samples, and an experimental attempt to simulate brine/gabbro interaction using externally heated cold seal pressure vessels. The studied natural veins and dykelets contain pargasite, hornblende, actinolite, and Cl-rich pargasite with up to 5 wt% Cl, showing a range of formation conditions from magmatic to metamorphic (hydrothermal) and thus a complex history of brine/rock interaction. In addition, the isotopic study of the radiogenic 87/86Sr and stable 18O in different amphibole types provide an estimate for the extent of seawater influence as alteration agent in the veins of the studied samples. Experiments performed at 750 °C and 200 MPa with different starting materials (chlorine-free amphibole, olivine gabbro powder) and 20 wt% NaCl aqueous brine, illustrate the process by which gabbro-hosted amphibole-rich veins evolve at subsolidus temperatures in the presence of a seawater-derived fluid. Our results demonstrate a decrease in olivine, plagioclase and magnetite content in favour of hastingsite, pargasite and magnesiohornblende, a decrease of IVAl and Ti in the starting amphibole, and an increase in Cl in amphibole, up to 0.2 Cl wt%. Our experiments show the change of magmatic pargasite towards more magnesium and silica-rich end members with results comparable to mildly chlorine-rich pargasites and hornblendes found in the natural samples studied. However, the experimental setup also presents limitations in the attainment of very high-chlorine amphibole (up to 5 wt%). Our analytical and experimental results provide further evidence for the existence of a hydrothermal cooling system in the deep oceanic crust.

Why are there apes? Evidence for the co-evolution of ape and monkey ecomorphology.

PubMed

Hunt, Kevin D

2016-04-01

Apes, members of the superfamily Hominoidea, possess a distinctive suite of anatomical and behavioral characters which appear to have evolved relatively late and relatively independently. The timing of paleontological events, extant cercopithecine and hominoid ecomorphology and other evidence suggests that many distinctive ape features evolved to facilitate harvesting ripe fruits among compliant terminal branches in tree edges. Precarious, unpredictably oriented, compliant supports in the canopy periphery require apes to maneuver using suspensory and non-sterotypical postures (i.e. postures with eccentric limb orientations or extreme joint excursions). Diet differences among extant species, extant species numbers and evidence of cercopithecoid diversification and expansion, in concert with a reciprocal decrease in hominoid species, suggest intense competition between monkeys and apes over the last 20 Ma. It may be that larger body masses allow great apes to succeed in contest competitions for highly desired food items, while the ability of monkeys to digest antifeedant-rich unripe fruits allows them to win scramble competitions. Evolutionary trends in morphology and inferred ecology suggest that as monkeys evolved to harvest fruit ever earlier in the fruiting cycle they broadened their niche to encompass first more fibrous, tannin- and toxin-rich unripe fruits and later, for some lineages, mature leaves. Early depletion of unripe fruit in the central core of the tree canopy by monkeys leaves a hollow sphere of ripening fruits, displacing antifeedant-intolerant, later-arriving apes to small-diameter, compliant terminal branches. Hylobatids, orangutans, Pan species, gorillas and the New World atelines may have each evolved suspensory behavior independently in response to local competition from an expanding population of monkeys. Genetic evidence of rapid evolution among chimpanzees suggests that adaptations to suspensory behavior, vertical climbing, knuckle-walking, consumption of terrestrial piths and intercommunity violence had not yet evolved or were still being refined when panins (chimpanzees and bonobos) and hominins diverged. © 2016 Anatomical Society.

[Star fruit as a cause of acute kidney injury].

PubMed

Scaranello, Karilla Lany; Alvares, Valeria Regina de Cristo; Carneiro, Daniely Maria Queiroz; Barros, Flávio Henrique Soares; Gentil, Thais Marques Sanches; Thomaz, Myriam José; Pereira, Benedito Jorge; Pereira, Mariana Batista; Leme, Graziella Malzoni; Diz, Mary Carla Esteves; Laranja, Sandra Maria Rodrigues

2014-01-01

The star fruit belongs to the family Oxalidacea, species Averrhoa carambola. It is rich in minerals, vitamin A, C, B complex vitamins and oxalic acid. Recent studies show that the toxicity of the fruit differs between the patients and may be explained by single biological responses, age, and the intake quantity of the neurotoxin in each fruit in addition to glomerular filtration rate given by each patient. Additionally, the nephrotoxicity caused by the fruit is dose-dependent and may lead to the deposition of crystals of calcium oxalate intratubular, as well as by direct injury to the renal tubular epithelium, leading to apoptosis of the same. We report the case of a patient who after ingestion of the juice and fresh fruit, developed acute renal failure requiring dialysis, evolving with favourable outcome and recovery of renal function.

Evolving prosocial and sustainable neighborhoods and communities.

PubMed

Biglan, Anthony; Hinds, Erika

2009-01-01

In this review, we examine randomized controlled trials of community interventions to affect health. The evidence supports the efficacy of community interventions for preventing tobacco, alcohol, and other drug use; several recent trials have shown the benefits of community interventions for preventing multiple problems of young people, including antisocial behavior. However, the next generation of community intervention research needs to reflect more fully the fact that most psychological and behavioral problems of humans are interrelated and result from the same environmental conditions. The evidence supports testing new comprehensive community interventions that focus on increasing nurturance in communities. Nurturing communities will be ones in which families, schools, neighborhoods, and workplaces (a) minimize biologically and socially toxic events, (b) richly reinforce prosocial behavior, and (c) foster psychological acceptance. Such interventions also have the potential to make neighborhoods more sustainable.

Evolving Prosocial and Sustainable Neighborhoods and Communities

PubMed Central

Biglan, Anthony; Hinds, Erika

2008-01-01

In this chapter, we review randomized controlled trials of community interventions to affect health. The evidence supports the efficacy of community interventions for preventing tobacco, alcohol, and other drug use; several recent trials have shown the benefits of community interventions for preventing multiple problems of young people, including antisocial behavior. However, the next generation of community intervention research needs to reflect more fully the fact that most psychological and behavioral problems of humans are inter-related and result from the same environmental conditions. The evidence supports testing a new set of comprehensive community interventions that focus on increasing nurturance in communities. Nurturing communities will be ones in which families, schools, neighborhoods, and workplaces (a) minimize biologically and socially toxic events, (b) richly reinforce prosocial behavior, and (c) foster psychological acceptance. Such interventions also have the potential to make neighborhoods more sustainable. PMID:19327029

Mechanism of generation of large (Ti,Nb,V)(C,N)-type precipitates in H13 + Nb tool steel

NASA Astrophysics Data System (ADS)

Xie, You; Cheng, Guo-guang; Chen, Lie; Zhang, Yan-dong; Yan, Qing-zhong

2016-11-01

The characteristics and generation mechanism of (Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of (Ti,Nb,V)(C,N) phases exist—a Ti-V-rich one and an Nb-rich one—in the form of single or complex precipitates. The sizes of the single Ti-V-rich (Ti,Nb,V)(C,N) precipitates are mostly within 5 to 10 μm, whereas the sizes of the single Nb-rich precipitates are mostly 2-5 μm. The complex precipitates are larger and contain an inner Ti-V-rich layer and an outer Nb-rich layer. The compositional distribution of (Ti,Nb,V)(C,N) is concentrated. The average composition of the single Ti-V-rich phase is (Ti0.511V0.356Nb0.133)(C x N y ), whereas that for the single Nb-rich phase is (Ti0.061V0.263Nb0.676)(C x N y ). The calculation results based on the Scheil-Gulliver model in the Thermo-Calc software combining with the thermal stability experiments show that the large phases precipitate during the solidification process. With the development of solidification, the Ti-V-rich phase precipitates first and becomes homogeneous during the subsequent temperature reduction and heat treatment processes. The Nb-rich phase appears later.

Zelda and company - Petrogenesis of sulfide-rich Fremdlinge and constraints on solar nebula processes

NASA Technical Reports Server (NTRS)

Armstrong, John T.; Hutcheon, Ian D.; Wasserburg, G. J.

1987-01-01

A detailed petrographic and chemical study of Zelda (a gigantic sulfide-rich Fremdling from the Allende Ca-rich inclusion, CAI, Egg 6) and its contact with the host was conducted using analytical SEM and electron-microprobe techniques, and the results were compared with those obtained on other sulfide-rich and oxide-rich Fremdlinge. Strong evidence is presented that Zelda, a type-example of sulfide-rich Fremdlinge, has been formed from a preexisting Ur-Fremdling, similar by composition to Willy, by closed-system sulfidization of magnetite and metal. At least two different sulfidization mechanisms appear to have occurred in altering Fremdlinge: one producing compositionally homogeneous equigranular objects such as Zelda, the other producing compositionally and texturally heterogeneous objects.

Molecular equilibria and condensation sequences in carbon rich gases

NASA Technical Reports Server (NTRS)

Sharp, C. M.; Wasserburg, G. J.

1993-01-01

Chemical equilibria in stellar atmospheres have been investigated by many authors. Lattimer, Schramm, and Grossman presented calculations in both O rich and C rich environments and predicted possible presolar condensates. A recent paper by Cherchneff and Barker considered a C rich composition with PAH's included in the calculations. However, the condensation sequences of C bearing species have not been investigated in detail. In a carbon rich gas surrounding an AGB star, it is often assumed that graphite (or diamond) condenses out before TiC and SiC. However, Lattimer et al. found some conditions under which TiC condenses before graphite. We have performed molecular equilibrium calculations to establish the stability fields of C(s), TiC(s), and SiC(s) and other high temperature phases under conditions of different pressures and C/O. The preserved presolar interstellar dust grains so far discovered in meteorites are graphite, diamond, SiC, TiC, and possibly Al2O3.

The structural role of high molecular weight tropomyosins in dipteran indirect flight muscle and the effect of phosphorylation.

PubMed

Mateos, Jesús; Herranz, Raúl; Domingo, Alberto; Sparrow, John; Marco, Roberto

2006-01-01

In Drosophila melanogaster two high molecular weight tropomyosin isoforms, historically named heavy troponins (TnH-33 and TnH-34), are encoded by the Tm1 tropomyosin gene. They are specifically expressed in the indirect flight muscles (IFM). Their N-termini are conventional and complete tropomyosin sequences, but their C-termini consist of different IFM-specific domains that are rich in proline, alanine, glycine and glutamate. The evidence indicates that in Diptera these IFM-specific isoforms are conserved and are not troponins, but heavy tropomyosins (TmH). We report here that they are post-translationally modified by several phosphorylations in their C-termini in mature flies, but not in recently emerged flies that are incapable of flight. From stoichiometric measurements of thin filament proteins and interactions of the TmH isoforms with the standard Drosophila IFM tropomyosin isoform (protein 129), we propose that the TmH N-termini are integrated into the thin filament structural unit as tropomyosin dimers. The phosphorylated C-termini remain unlocated and may be important in IFM stretch-activation. Comparison of the Tm1 and Tm2 gene sequences shows a complete conservation of gene organisation in other Drosophilidae, such as Drosophila pseudoobscura, while in Anopheles gambiae only one exon encodes a single C-terminal domain, though overall gene organization is maintained. Interestingly, in Apis mellifera (hymenopteran), while most of the Tm1 and Tm2 gene features are conserved, the gene lacks any C-terminal exons. Instead these sequences are found at the 3' end of the troponin I gene. In this insect order, as in Lethocerus (hemipteran), the original designation of troponin H (TnH) should be retained. We discuss whether the insertion of the IFM-specific pro-ala-gly-glu-rich domain into the tropomyosin or troponin I genes in different insect orders may be related to proposals that the IFM stretch activation mechanism has evolved independently several times in higher insects.

Proteome Analysis of Cytoplasmatic and Plastidic β-Carotene Lipid Droplets in Dunaliella bardawil1[OPEN

PubMed Central

Davidi, Lital; Levin, Yishai; Ben-Dor, Shifra; Pick, Uri

2015-01-01

The halotolerant green alga Dunaliella bardawil is unique in that it accumulates under stress two types of lipid droplets: cytoplasmatic lipid droplets (CLD) and β-carotene-rich (βC) plastoglobuli. Recently, we isolated and analyzed the lipid and pigment compositions of these lipid droplets. Here, we describe their proteome analysis. A contamination filter and an enrichment filter were utilized to define core proteins. A proteome database of Dunaliella salina/D. bardawil was constructed to aid the identification of lipid droplet proteins. A total of 124 and 42 core proteins were identified in βC-plastoglobuli and CLD, respectively, with only eight common proteins. Dunaliella spp. CLD resemble cytoplasmic droplets from Chlamydomonas reinhardtii and contain major lipid droplet-associated protein and enzymes involved in lipid and sterol metabolism. The βC-plastoglobuli proteome resembles the C. reinhardtii eyespot and Arabidopsis (Arabidopsis thaliana) plastoglobule proteomes and contains carotene-globule-associated protein, plastid-lipid-associated protein-fibrillins, SOUL heme-binding proteins, phytyl ester synthases, β-carotene biosynthesis enzymes, and proteins involved in membrane remodeling/lipid droplet biogenesis: VESICLE-INDUCING PLASTID PROTEIN1, synaptotagmin, and the eyespot assembly proteins EYE3 and SOUL3. Based on these and previous results, we propose models for the biogenesis of βC-plastoglobuli and the biosynthesis of β-carotene within βC-plastoglobuli and hypothesize that βC-plastoglobuli evolved from eyespot lipid droplets. PMID:25404729

Revealing evolved massive stars with Spitzer

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.; Kniazev, A. Y.; Fabrika, S.

2010-06-01

Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24-μm data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf-Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). We interpret this similarity as an indication that the central stars of detected nebulae are either LBVs or related evolved massive stars. Our interpretation is supported by follow-up spectroscopy of two dozen of these central stars, most of which turn out to be either candidate LBVs (cLBVs), blue supergiants or WNL stars. We expect that the forthcoming spectroscopy of the remaining objects from our list, accompanied by the spectrophotometric monitoring of the already discovered cLBVs, will further increase the known population of Galactic LBVs. This, in turn, will have profound consequences for better understanding the LBV phenomenon and its role in the transition between hydrogen-burning O stars and helium-burning WR stars. We also report on the detection of an arc-like structure attached to the cLBV HD 326823 and an arc associated with the LBV R99 (HD 269445) in the LMC. Partially based on observations collected at the German-Spanish Astronomical Centre, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC). E-mail: vgvaram@mx.iki.rssi.ru (VVG); akniazev@saao.ac.za (AYK); fabrika@sao.ru (SF)

Investigating the Near-Infrared Properties of Planetary Nebulae II. Medium Resolution Spectra. 2; Medium Resolution Spectra

NASA Technical Reports Server (NTRS)

Hora, Joseph L.; Latter, William B.; Deutsch, Lynne K.

1998-01-01

We present medium-resolution (R approximately 700) near-infrared (lambda = 1 - 2.5 micrometers) spectra of a sample of planetary nebulae (PNe). A narrow slit was used which sampled discrete locations within the nebulae; observations were obtained at one or more positions in the 41 objects included in the survey. The PN spectra fall into one of four general categories: H1 emission line-dominated PNe, H1 and H2 emission line PNe, H2 emission line-dominated PNe, and continuum-dominated PNe. These categories correlate with morphological type, with the elliptical PNe falling into the first group, and the bipolar PNe primarily in the H2 and continuum emission groups. The categories also correlate with C/O ratio, with the O-rich objects falling into the first group and the C-rich objects in the groups. Other spectral features were observed in all catagories, such as continuum emission from the central star, and warm dust continuum emission towards the long wavelength end of the spectra. H2 was detected in four PNe in this survey for the first time. An analysis was performed using the H2 line ratios in all of the PN spectra in the survey where a sufficient number of lines were observed to determine the ortho-to-para ratio and the rotational and vibrational excitation temperatures of the H-2 in those objects. One unexpected result from this analysis is that the H-2 is excited by absorption of ultraviolet photons in most of the PNe, although there are several PNe in which collisional excitation plays an important role. The correlation between bipolar morphology and H2 emission has been strengthened with the new detections of H2 in this survey.

The Paradox of the Axial Melt Lens: Petrology and Geochemistry of the Upper Plutonics at Hess Deep

NASA Astrophysics Data System (ADS)

Lissenberg, C. J.; Loocke, M. P.; MacLeod, C. J.

2014-12-01

The axial melt lens (AML) is a steady-state magma-rich body located at the dyke-gabbro transition at intermediate- and fast-spreading ridges. It is widely believed to be the reservoir from which mid-ocean ridge basalt (MORB) is erupted. The paradox of the axial melt lens is that the plutonic rocks that occur at this level are far too evolved to be in equilibrium with MORB, which is basaltic by definition; hence, the plutonic and volcanic records do not match. We explore this paradox by study of the first comprehensive sample suite of the uppermost plutonics of a fast-spreading ridge, taken by remotely-operated vehicle from the Hess Deep rift during cruise JC21. 23 samples (8 dolerites, 14 gabbronorites, and 1 gabbro) were collected from a section containing the transition from the uppermost gabbroic section into sheeted dykes. We present the results of a detailed petrographic and microanalytical investigation of these samples. They are dominated by evolved, varitextured (both in hand sample and thin section) oxide gabbronorites; olivine occurs in only one sample. A preponderance of the samples have positive Eu/Eu* and Sr/Sr*, indicating a cumulate origin. However, the minerals have evolved compositions, and are in equilibrium with melts significantly more evolved than East Pacific Rise MORB. Furthermore, the trace element contents of clinopyroxene differ significantly from clinopyroxene in equilibrium with MORB, being more enriched in incompatible elements. To account for both the evidence of derivation of MORB from the AML and the evolved nature of its rock record, we posit that the AML must be fed by melts on two different timescales: continual low-volume feeding by evolved interstitial melt from the cumulus pile below is augmented episodically by delivery of high volumes of more primitive melt. The latter episodes may trigger eruptions; hence the primitive melts are held in the magma chamber for only short periods, and erupt on the seafloor before significant crystallisation in the AML has taken place. This model for the feeding of the AML provides ample opportunity for mixing between the relatively primitive melts and the evolved, trace-element-rich melt, and accounts for the observed over-enrichment in incompatible elements of MORB.

40 CFR 721.10023 - Benzenamine, N-phenyl-, ar ar′-(C9-rich C88-10-branched alkyl) derivs.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Benzenamine, N-phenyl-, ar arâ²-(C9... Significant New Uses for Specific Chemical Substances § 721.10023 Benzenamine, N-phenyl-, ar ar′-(C9-rich C88...) The chemical substance identified as benzenamine, N-phenyl-, ar,ar′-(C9-rich C8-10-branched alkyl...

Thermonuclear runaways in thick hydrogen rich envelopes of neutron stars

NASA Technical Reports Server (NTRS)

Starrfield, S. G.; Kenyon, S.; Truran, J. W.; Sparks, W. M.

1981-01-01

A Lagrangian, fully implicit, one dimensional hydrodynamic computer code was used to evolve thermonuclear runaways in the accreted hydrogen rich envelopes of 1.0 Msub solar neutron stars with radii of 10 km and 20 km. Simulations produce outbursts which last from about 750 seconds to about one week. Peak effective temeratures and luninosities were 26 million K and 80 thousand Lsub solar for the 10 km study and 5.3 millison and 600 Lsub solar for the 20 km study. Hydrodynamic expansion on the 10 km neutron star produced a precursor lasting about one ten thousandth seconds.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Kuo-Chuan; Ricker, Paul M.; Taam, Ronald E., E-mail: kpan2@illinois.edu, E-mail: pmricker@illinois.edu, E-mail: r-taam@northwestern.edu

The progenitor systems of Type Ia supernovae (SNe Ia) are still under debate. Based on recent hydrodynamics simulations, non-degenerate companions in the single-degenerate scenario (SDS) should survive the supernova (SN) impact. One way to distinguish between the SDS and the double-degenerate scenario is to search for the post-impact remnant stars (PIRSs) in SN Ia remnants. Using a technique that combines multi-dimensional hydrodynamics simulations with one-dimensional stellar evolution simulations, we have examined the post-impact evolution of helium-rich binary companions in the SDS. It is found that these helium-rich PIRSs (He PIRSs) dramatically expand and evolve to a luminous phase (L {approx}more » 10{sup 4} L{sub Sun }) about 10 yr after an SN explosion. Subsequently, they contract and evolve to become hot blue-subdwarf-like (sdO-like) stars by releasing gravitational energy, persisting as sdO-like stars for several million years before evolving to the helium red-giant phase. We therefore predict that a luminous OB-like star should be detectable within {approx}30 yr after the SN explosion. Thereafter, it will shrink and become an sdO-like star in the central regions of SN Ia remnants within star-forming regions for SN Ia progenitors evolved via the helium-star channel in the SDS. These He PIRSs are predicted to be rapidly rotating (v{sub rot} {approx}> 50 km s{sup -1}) and to have high spatial velocities (v{sub linear} {approx}> 500 km s{sup -1}). Furthermore, if SN remnants have diffused away and are not recognizable at a later stage, He PIRSs could be an additional source of single sdO stars and/or hypervelocity stars.« less

2060 Chiron - Colorimetry and cometary behavior

NASA Technical Reports Server (NTRS)

Hartmann, William K.; Tholen, David J.; Meech, Karen J.; Cruikshank, Dale P.

1990-01-01

Ambiguities concerning the fit of the 2060 Chiron's visible spectrum to its IR spectrum have been resolved by resort to VRIJHK colorimetry obtained in 1988, which also confirms the neutrality of Chiron's taxonomic class C spectrum and indicates that Chiron has anomalously brightened since 1980-1983. This brightening, and one reported in 1978, are consistent with the hypothesis that Chiron sporadically undergoes weak cometary outbursts similar to those of comet P/Schwassmann-Wachmann 1; Chiron is further speculated to be an ice-rich object darkened by C-class carbonaceous soil, and may have been scattered from the Oort cloud in recent solar system history.

K-Ca and Rb-Sr Dating of Lunar Granite 14321 Revisited

NASA Technical Reports Server (NTRS)

Simon, Justin I.; Shih, C.-Y.; Nyquist, L. E.

2011-01-01

K-Ca and Rb-Sr age determinations were made for a bulk feldspar-rich portion of an Apollo rock fragment of the pristine lunar granite clast (14321,1062), an acid-leached split of the sample, and the leachate. K-Ca and Rb-Sr data were also obtained for a whole rock sample of Apollo ferroan anorthosite (FAN, 15415). The recent detection [1] of widespread intermediate composition plagioclase indicates that the generation of a diversity of evolved lunar magmas maybe more common and therefore more important to our understanding of crust formation than previously believed. Our new data strengthen the K-Ca and Rb-Sr internal isochrons of the well-studied Apollo sample 14321 [2], which along with a renewed effort to study evolved lunar magmas will provide an improved understanding of the petrogenetic history of evolved rocks on the Moon.

Vision for perception and vision for action in the primate brain.

PubMed

Goodale, M A

1998-01-01

Visual systems first evolved not to enable animals to see, but to provide distal sensory control of their movements. Vision as 'sight' is a relative newcomer to the evolutionary landscape, but its emergence has enabled animals to carry out complex cognitive operations on perceptual representations of the world. The two streams of visual processing that have been identified in the primate cerebral cortex are a reflection of these two functions of vision. The dorsal 'action' stream projecting from primary visual cortex to the posterior parietal cortex provides flexible control of more ancient subcortical visuomotor modules for the production of motor acts. The ventral 'perceptual' stream projecting from the primary visual cortex to the temporal lobe provides the rich and detailed representation of the world required for cognitive operations. Both streams process information about the structure of objects and about their spatial locations--and both are subject to the modulatory influences of attention. Each stream, however, uses visual information in different ways. Transformations carried out in the ventral stream permit the formation of perceptual representations that embody the enduring characteristics of objects and their relations; those carried out in the dorsal stream which utilize moment-to-moment information about objects within egocentric frames of reference, mediate the control of skilled actions. Both streams work together in the production of goal-directed behaviour.

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

NASA Astrophysics Data System (ADS)

De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.; Kilcoyne, A. L. David

2017-10-01

Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ˜20 μm particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorly graphitized carbon (PGC). The PGC forms conformal shells around tiny 5-15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core-shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.

FC colour images of dwarf planet Ceres reveal a complicated geological history

NASA Astrophysics Data System (ADS)

Nathues, A.; Hoffmann, M.; Platz, T.; Thangjam, G. S.; Cloutis, E. A.; Reddy, V.; Le Corre, L.; Li, J.-Y.; Mengel, K.; Rivkin, A.; Applin, D. M.; Schaefer, M.; Christensen, U.; Sierks, H.; Ripken, J.; Schmidt, B. E.; Hiesinger, H.; Sykes, M. V.; Sizemore, H. G.; Preusker, F.; Russell, C. T.

2016-12-01

The dwarf planet Ceres (equatorial diameter 963km) is the largest object that has remained in the main asteroid belt (Russell and Raymond, 2012), while most large bodies have been destroyed or removed by dynamical processes (Petit et al. 2001; Minton and Malhotra, 2009). Pre-Dawn investigations (McCord and Sotin, 2005; Castillo-Rogez and McCord, 2010; Castillo-Rogez et al., 2011) suggest that Ceres is a thermally evolved, but still volatile-rich body with potential geological activity, that was never completely molten, but possibly differentiated into a rocky core, an ice-rich mantle, and may contain remnant internal liquid water. Thermal alteration should contribute to producing a (dark) carbonaceous chondritic-like surface (McCord and Sotin, 2005; Castillo-Rogez and McCord, 2010; Castillo-Rogez et al., 2011; Nathues et al., 2015) containing ammoniated phyllosilicates (King et al., 1992; De Sanctis et al., 2015 and 2016). Here we show and analyse global contrast-rich colour mosaics, derived from a camera on-board Dawn at Ceres (Russell et al., 2016). Colours are unexpectedly more diverse on global scale than anticipated by Hubble Space Telescope (Li et al., 2006) and ground-based observations (Reddy et al. 2015). Dawn data led to the identification of five major colour units. The youngest units identified by crater counting, termed bright and bluish units, are exclusively found at equatorial and intermediate latitudes. We identified correlations between the distribution of the colour units, crater size, and formation age, inferring a crustal stratigraphy. Surface brightness and spectral properties are not correlated. The youngest surface features are the bright spots at crater Occator ( Ø 92km). Their colour spectra are highly consistent with the presence of carbonates while most of the remaining surface resembles modifications of various types of ordinary carbonaceous chondrites.

Designing a Marketing Analytics Course for the Digital Age

ERIC Educational Resources Information Center

Liu, Xia; Burns, Alvin C.

2018-01-01

Marketing analytics is receiving great attention because of evolving technology and the radical changes in the marketing environment. This study aims to assist the design and implementation of a marketing analytics course. We assembled a rich data set from four sources: business executives, 400 employers' job postings, one million tweets about…

The Changing Nature of Parent-Teacher Communication: Mode Selection in the Smartphone Era

ERIC Educational Resources Information Center

Thompson, Blair Christopher; Mazer, Joseph P.; Flood Grady, Elizabeth

2015-01-01

Parent-teacher communication continues to evolve due to smartphones and other new communication technologies. In all, 1,349 parents completed the Parental Academic Support Scale to assess the frequency and importance of communication across modes. Confirmatory analysis revealed a good model fit. Media richness theory was applied to parents'…

Darwin and Emotion Expression

ERIC Educational Resources Information Center

Hess, Ursula; Thibault, Pascal

2009-01-01

In his book "The Expression of the Emotions in Man and Animals," Charles Darwin (1872/1965) defended the argument that emotion expressions are evolved and adaptive (at least at some point in the past) and serve an important communicative function. The ideas he developed in his book had an important impact on the field and spawned rich domains of…

Developing the next generation of forest ecosystem models

Treesearch

Christopher R. Schwalm; Alan R. Ek

2002-01-01

Forest ecology and management are model-rich areas for research. Models are often cast as either empirical or mechanistic. With evolving climate change, hybrid models gain new relevance because of their ability to integrate existing mechanistic knowledge with empiricism based on causal thinking. The utility of hybrid platforms results in the combination of...

Agility in Business School Education through Richness and Reach: A Conceptual Model

ERIC Educational Resources Information Center

Gupta, Nakul; Bharadwaj, Sangeeta Shah

2013-01-01

Purpose: Pedagogy today has become a function of technology and this relationship becomes all the more promising when used to address the educational needs of the constantly changing and fast evolving business school education. Business schools today are responsible for empowering future managers and leaders with not only the knowledge and…

On the nature of Upsilon Sagittarii

NASA Technical Reports Server (NTRS)

Schoenberner, D.; Drilling, J. S.

1983-01-01

An explanation for the nature and evolution of the extremely hydrogen deficient binary Upsilon Sagittarii which is consistent with all observational and theoretical facts. First, the system goes through a Case B mass exchange in which most of the hydrogen rich envelope of a massive primary (5 to 14 solar masses) is lost. The remaining envelope still contains about 50 percent hydrogen (by number), but is now of negligible mass, so that the star evolves like a pure helium star. If its mass is between 1 and 2 solar masses the star reaches low surface temperatures and becomes a supergiant before the onset of carbon burning. This star (the original primary) then fills its Roche lobe a second time,spilling its now helium rich envelope over onto the secondary (Case BB mass exchange). It is argued that Upsilon Sagittarii is in this state at the present time, and that the visible star is an evolved helium star of about 1 solar mass with a degenerate carbon-oxygen core and a helium burning shell which provides the high luminosity. Previously announced in Star as N26117

Hydrothermal fluoride and chloride complexation of indium: an EXAFS study

NASA Astrophysics Data System (ADS)

Loges, Anselm; Testemale, Denis; Huotari, Simo; Honkanen, Ari-Pekka; Potapkin, Vasily; Wagner, Thomas

2017-04-01

Indium (In) is one of the geochemically lesser studied ore metals, and the factors that control the hydrothermal transport and deposition are largely unknown. It has no ore deposits of its own and is commonly mined as a by-product of Zn ores, and there are very few minerals that contain In as an essential structural component. Recently, industrial application of In in touch screen devices has drastically increased demand, which is projected to exceed supply from the current sources in the near future. Since the most relevant In sources are hydrothermal sphalerite ores and to a lesser extent hydrothermal greisen-type deposits in evolved granitic plutons, the aqueous geochemistry of In is of particular interest for understanding its ore forming processes. As a first step towards a comprehensive model for hydrothermal In solubility and speciation, we have studied In speciation in fluoride and chloride bearing solutions at 30-400˚ C and 500 bar using X-Ray Absorption Spectroscopy (XAS) measurements. The experiments were conducted in a unique hydrothermal autoclave setup at beamline BM30B-FAME at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Our results show that the complexation of In changes dramatically between 30 and 400˚ C. Below ca. 200˚ C, fluoride complexes are the most stable ones, but they break down at higher temperatures. Chloride complexes on the other hand become increasingly stable with increasing temperature. This behavior has interesting consequences for natural ore forming systems. In Cl-rich systems (e.g. massive sulfide ores formed in sea floor environments), cooling can be an effective precipitating mechanism. In F-rich systems, fluoride complexation can extend In mobility to low temperatures and In will only precipitate when F is effectively removed from the fluid, e.g. by mixing with a Ca-rich fluid and precipitation of fluorite (CaF2) as is commonly observed in skarn or greisen-type deposits. Due to In complexing with both F and Cl, depending on temperature, In distribution also has great potential as a fluid chemistry/temperature indicator in a wide range of different hydrothermal ore-forming systems.

Period doubling in period-one steady states

NASA Astrophysics Data System (ADS)

Wang, Reuben R. W.; Xing, Bo; Carlo, Gabriel G.; Poletti, Dario

2018-02-01

Nonlinear classical dissipative systems present a rich phenomenology in their "route to chaos," including period doubling, i.e., the system evolves with a period which is twice that of the driving. However, typically the attractor of a periodically driven quantum open system evolves with a period which exactly matches that of the driving. Here, we analyze a periodically driven many-body open quantum system whose classical correspondent presents period doubling. We show that by studying the dynamical correlations, it is possible to show the occurrence of period doubling in the quantum (period-one) steady state. We also discuss that such systems are natural candidates for clean and intrinsically robust Floquet time crystals.

Origin of high-grade gold ore, source of ore fluid components, and genesis of the Meikle and neighboring Carlin-type deposits, Northern Carlin Trend, Nevada

USGS Publications Warehouse

Emsbo, P.; Hofstra, A.H.; Lauha, E.A.; Griffin, G.L.; Hutchinson, R.W.

2003-01-01

The Meikle mine exploits one of the world's highest grade Carlin-type gold deposits with reserves of ca. 220 t gold at an average grade of 24.7 g/t. Locally, gold grades exceed 400 g/t. Several geologic events converged at Meikle to create these spectacular gold grades. Prior to mineralization, a Devonian hydrothermal system altered the Bootstrap limestone to Fe-rich dolomite. Subsequently the rocks were brecciated by faulting and Late Jurassic intrusive activity. The resulting permeability focused flow of late Eocene Carlin-type ore fluids and allowed them to react with the Fe-rich dolomite. Fluid inclusion data and mineral assemblages indicate that these fluids were hot (ca. 220??C),of moderate salinity (400 g/t. Petrographic observations, geochemical data, and stable isotope results from the Meikle mine and other deposits at the Goldstrike mine place important constraints on genetic models for Meikle and other Carlin-type gold deposits on the northern Carlin trend. The ore fluids were meteoric water (??D = -135???, ??18O = -5???) that interacted with sedimentary rocks at a water/rock ratio of ca. 1 and temperatures of ca. 220??C. The absence of significant silicification suggests that there was little cooling of the ore fluids during mineralization. These two observations strongly suggest that ore fluids were not derived from deep sources but instead flowed parallel to isotherms. The gold was transported by H2S (??34S = 9???), which was derived from Paleozoic sedimentary rocks. The presence of auriferous sedimentary exhalative mineralization in the local stratigraphic sequence raises the possibility that preexisting concentrations of gold contributed to the Carlin-type deposits. Taken together our observations suggest that meteoric water evolved to become an ore fluid by shallow circulation through previously gold- and sulfur-enriched rocks. Carlin-type gold deposits formed where these fluids encountered permeable, reactive Fe-rich rocks.

Constraining Phosphorus Chemistry in Carbon- and Oxygen-Rich Circumstellar Envelopes: Observations of PN, HCP, and CP

NASA Astrophysics Data System (ADS)

Milam, S. N.; Halfen, D. T.; Tenenbaum, E. D.; Apponi, A. J.; Woolf, N. J.; Ziurys, L. M.

2008-09-01

Millimeter-wave observations of PN, CP, and HCP have been carried out toward circumstellar envelopes of evolved stars using the Arizona Radio Observatory (ARO). HCP and PN have been identified in the carbon-rich source CRL 2688 via observations at 1 mm using the Submillimeter Telescope (SMT) and 2-3 mm with the Kitt Peak 12 m. An identical set of measurements were carried out toward IRC +10216, as well as observations of CP at 1 mm. PN was also observed toward VY Canis Majoris (VY CMa), an oxygen-rich supergiant star. The PN and HCP line profiles in CRL 2688 and IRC +10216 are roughly flat topped, indicating unresolved, optically thin emission; CP, in contrast, has a distinct "U" shape in IRC +10216. Modeling of the line profiles suggests abundances, relative to H2, of f(PN) ~ (3-5) × 10-9 and f(HCP) ~ 2 × 10-7 in CRL 2688, about an order of magnitude higher than in IRC +10216. In VY CMa, f(PN) is ~4 × 10-8. The data in CRL 2688 and IRC +10216 are consistent with LTE formation of HCP and PN in the inner envelope, as predicted by theoretical calculations, with CP a photodissociation product at larger radii. The observed abundance of PN in VY CMa is a factor of 100 higher than LTE predictions. In IRC +10216, the chemistry of HCP/CP mimics that of HCN/CN and suggests an N2 abundance of f ~ 1 × 10-7. The chemistry of phosphorus appears active in both carbon- and oxygen-rich envelopes of evolved stars.

Rich burn combustor technology at Pratt and Whitney

NASA Technical Reports Server (NTRS)

Lohmann, Robert P.; Rosfjord, T. J.

1992-01-01

The topics covered include the following: near term objectives; rich burn quick quench combustor (RBQC); RBQC critical technology areas; cylindrical RBQQ combustor rig; modular RBQQ combustor; cylindrical rig objectives; quench zone mixing; noneffusive cooled liner; variable geometry requirements; and sector combustor rig.

Geochemistry and thermodynamics of an earthquake: A case study of pseudotachylites within mylonitic granitoid

NASA Astrophysics Data System (ADS)

Jiang, Hehe; Lee, Cin-Ty A.; Morgan, Julia K.; Ross, Catherine H.

2015-11-01

Pseudotachylites are melts produced by frictional heating during seismic slip. Understanding their origin and their influence on slip behavior is critical to understanding the physics of earthquakes. To provide insight into this topic, we conducted a case study in the proto-mylonitic to mylonitic Asbestos Mountain granitoid in the eastern Peninsular Ranges batholith (California), which records both ductile (mylonites) and brittle deformation features (pseudotachylites and ultracataclasites). U-Pb chronology and Zr thermometry of titanite porphyroblasts in the mylonites indicate that mylonitization of the plutons occurred at near solidus conditions (∼ 750 °C) over a 10 Ma interval from 89 to 78 Ma. Mylonitization resulted in recrystallization of quartz, plagioclase and biotite, with the biotite concentrated into biotite-rich foliation planes. Subsequent brittle deformation is superimposed on the ductile fabrics. Micro-XRF elemental mapping and in situ LA-ICP-MS analyses on these brittle deformation products show that the pseudotachylites are more mafic (lower Si, but higher Fe) and K-rich than the host mylonite, while the ultracataclasites are intermediate between the host and the pseudotachylites. Inverse mass balance calculations show that both brittle deformation products are depleted in quartz but enriched in biotite, with the pseudotachylites showing the most significant enrichment in biotite, indicating preferential involvement of biotite during brittle deformation. We suggest that biotite-rich layers generated during ductile deformation may have been the preferred locus of subsequent brittle deformation, presumably because such layers represent zones of weakness. Frictional heating associated with slip along such planes results in melting, which causes a decrease in viscosity, in turn leading to further strain localization. During the short time span of an earthquake, frictional melting appears to be a disequilibrium process, in which the minerals are melted in order of their melting points, from biotite (∼ 800 °C) to plagioclase (∼ 1400 °C) and finally to quartz (∼ 1700 °C), rather than by equilibrium melting, which results in silicic eutectoid melts at lower temperatures (∼ 650 °C). Thus, with progressive slip, melt composition should evolve from mafic to felsic, eventually approaching the bulk composition of the host rock. The mafic composition of the pseudotachylites thus indicates that they formed between the melting point of biotite and plagioclase (800- 1400 °C). Our chemical and modeling analyses on the pseudotachylites suggest that the chemical composition of pseudotachylites can potentially be used to constrain the thermodynamic conditions in the shear zone as well as earthquake source mechanics.

Complex network view of evolving manifolds

NASA Astrophysics Data System (ADS)

da Silva, Diamantino C.; Bianconi, Ginestra; da Costa, Rui A.; Dorogovtsev, Sergey N.; Mendes, José F. F.

2018-03-01

We study complex networks formed by triangulations and higher-dimensional simplicial complexes representing closed evolving manifolds. In particular, for triangulations, the set of possible transformations of these networks is restricted by the condition that at each step, all the faces must be triangles. Stochastic application of these operations leads to random networks with different architectures. We perform extensive numerical simulations and explore the geometries of growing and equilibrium complex networks generated by these transformations and their local structural properties. This characterization includes the Hausdorff and spectral dimensions of the resulting networks, their degree distributions, and various structural correlations. Our results reveal a rich zoo of architectures and geometries of these networks, some of which appear to be small worlds while others are finite dimensional with Hausdorff dimension equal or higher than the original dimensionality of their simplices. The range of spectral dimensions of the evolving triangulations turns out to be from about 1.4 to infinity. Our models include simplicial complexes representing manifolds with evolving topologies, for example, an h -holed torus with a progressively growing number of holes. This evolving graph demonstrates features of a small-world network and has a particularly heavy-tailed degree distribution.

A VLT/FORS2 spectroscopic survey of individual stars in a transforming dwarf galaxy

NASA Astrophysics Data System (ADS)

Battaglia, G.; Kacharov, N.; Rejkuba, M.

2017-03-01

Understanding the properties of dwarf galaxies is important not only to put them in their proper cosmological context, but also to understand the formation and evolution of the most common type of galaxies. Dwarf galaxies are divided into two main classes, dwarf irregulars (dIrrs) and dwarf spheroidals (dSphs), which differ from each other mainly because the former are gas-rich objects currently forming stars, while the latter are gas-deficient with no on-going star formation. Transition types (dT) are thought to represent dIs in the process of losing their gas, and can therefore shed light into the possible process of dwarf irregulars (dIrrs) becoming gas-deficient, passively evolving galaxies. Here we present preliminary results from our wide-area VLT/FORS2 MXU spectroscopic survey of the Phoenix dT, from which we obtained line-of-sight velocities and metallicities from the nIR Ca II triplet lines for a large sample of individual Red Giant Branch stars.

Antihyperlipidemic effects of Citrus sinensis, Citrus paradisi, and their combinations

PubMed Central

Mallick, Neelam; Khan, Rafeeq Alam

2016-01-01

Objective: Hyperlipidemia, extensively contributes in the progression of coronary heart diseases and atherosclerosis, but may be managed through alterations in the nutritional pattern. Several studies show that diet rich in polyphenols and antioxidants have antiatherogenic effects. Citrus sinensis and Citrus paradisi are widely known for health benefits and have found to produce antioxidant, anti-inflammatory, and hypolipidemic effects, hence current research was planned to determine the hypolipidemic effects of C. sinensis and C. paradisi in rats receiving diet rich in cholesterol. Materials and Methods: All rats were divided into 11 groups each comprising 10 animals: Normal control group and hyperlipidemic control. C. sinensis treated three groups, C. paradisi treated three groups, C. sinensis and C. paradisi combination treated two groups, and group treated atorvastatin. All rats in the respective groups were treated orally with sterile water, juices, and standard drug for 8 weeks and lipid profile was estimated at the end of dosing. Results: Cholesterol, triglycerides (TGs), and low-density lipoprotein (LDL) were decreased at all the three doses of C. sinensis and C. paradisi but rise in high-density lipoprotein (HDL) was only significant at 8 ml/kg, and 0.3 ml/kg, respectively. Animals received the combination doses of C. sinensis and C. paradisi also showed a highly significant fall in cholesterol, LDL, and TGs, however HDL level was significantly elevated by SPJ-2 combination. Conclusion: Results suggest that C. sinensis and C. paradisi possess antihyperlipidemic activity due to phytochemicals and other essential nutrients, hence may serve as cardioprotective by preventing thrombosis. PMID:27134462

Variation and Evolution in the Glutamine-Rich Repeat Region of Drosophila Argonaute-2

PubMed Central

Palmer, William H.; Obbard, Darren J.

2016-01-01

RNA interference pathways mediate biological processes through Argonaute-family proteins, which bind small RNAs as guides to silence complementary target nucleic acids . In insects and crustaceans Argonaute-2 silences viral nucleic acids, and therefore acts as a primary effector of innate antiviral immunity. Although the function of the major Argonaute-2 domains, which are conserved across most Argonaute-family proteins, are known, many invertebrate Argonaute-2 homologs contain a glutamine-rich repeat (GRR) region of unknown function at the N-terminus . Here we combine long-read amplicon sequencing of Drosophila Genetic Reference Panel (DGRP) lines with publicly available sequence data from many insect species to show that this region evolves extremely rapidly and is hyper-variable within species. We identify distinct GRR haplotype groups in Drosophila melanogaster, and suggest that one of these haplotype groups has recently risen to high frequency in a North American population. Finally, we use published data from genome-wide association studies of viral resistance in D. melanogaster to test whether GRR haplotypes are associated with survival after virus challenge. We find a marginally significant association with survival after challenge with Drosophila C Virus in the DGRP, but we were unable to replicate this finding using lines from the Drosophila Synthetic Population Resource panel. PMID:27317784

Effects of plant species richness on 13C assimilate partitioning in artificial grasslands of different established ages

PubMed Central

Xu, Longhua; Yao, Buqing; Wang, Wenying; Wang, Fangping; Zhou, Huakun; Shi, Jianjun; Zhao, Xinquan

2017-01-01

Artificial grasslands play a role in carbon storage on the Qinghai–Tibetan Plateau. The artificial grasslands exhibit decreased proportions of graminate and increased species richness with age. However, the effect of the graminate proportions and species richness on ecosystem C stocks in artificial grasslands have not been elucidated. We conducted an in situ13C pulse-labeling experiment in August 2012 using artificial grasslands that had been established for two years (2Y), five years (5Y), and twelve years (12Y). Each region was plowed fallow from severely degraded alpine meadow in the Qinghai-Tibetan Plateau. The 12Y grassland had moderate proportions of graminate and the highest species richness. This region showed more recovered 13C in soil and a longer mean residence time, which suggests species richness controls the ecosystem C stock. The loss rate of leaf-assimilated C of the graminate-dominant plant species Elymus nutans in artificial grasslands of different ages was lowest in the 12Y grassland, which also had the highest species richness. Thus the lower loss rate of leaf-assimilated C can be partially responsible for the larger ecosystem carbon stocks in the 12Y grassland. This finding is a novel mechanism for the effects of species richness on the increase in ecosystem functioning. PMID:28067300

Quantum tricritical point in the temperature-pressure-magnetic field phase diagram of CeTiGe 3

DOE PAGES

Kaluarachchi, Udhara S.; Taufour, Valentin; Bud'ko, Sergey L.; ...

2018-01-22

We report the temperature-pressure-magnetic eld phase diagram of the ferromagnetic Kondolattice CeTiGe 3 determined by means of electrical resistivity measurements. Measurements up to ~5.8GPa reveal a rich phase diagram with multiple phase transitions. At ambient pressure, CeTiGe 3 orders ferromagnetically at T C =14 K. Application of pressure suppresses T C, but a pressure induced ferromagnetic quantum criticality is avoided by the appearance of two new successive transitions for p>4.1GPa that are probably antiferromagnetic in nature. These two transitions are suppressed under pressure, with the lower temperature phase being fully suppressed above 5.3GPa. The critical pressures for the presumed quantummore » phase transitions are p1≅4.1GPa and p2≅5.3GPa. Above 4.1GPa, application of magnetic eld shows a tricritical point evolving into a wing structure phase with a quantum tricritical point at 2.8T at 5.4GPa, where the rst order antiferromagneticferromagnetic transition changes into the second order antiferromagnetic-ferromagnetic transition.« less

THE SPECTRAL EVOLUTION OF CONVECTIVE MIXING WHITE DWARFS, THE NON-DA GAP, AND WHITE DWARF COSMOCHRONOLOGY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Eugene Y.; Hansen, Brad M. S., E-mail: eyc@mail.utexas.edu, E-mail: hansen@astro.ucla.edu

The spectral distribution of field white dwarfs shows a feature called the 'non-DA gap'. As defined by Bergeron et al., this is a temperature range (5100-6100 K) where relatively few non-DA stars are found, even though such stars are abundant on either side of the gap. It is usually viewed as an indication that a significant fraction of white dwarfs switch their atmospheric compositions back and forth between hydrogen-rich and helium-rich as they cool. In this Letter, we present a Monte Carlo model of the Galactic disk white dwarf population, based on the spectral evolution model of Chen and Hansen.more » We find that the non-DA gap emerges naturally, even though our model only allows white dwarf atmospheres to evolve monotonically from hydrogen-rich to helium-rich through convective mixing. We conclude by discussing the effects of convective mixing on the white dwarf luminosity function and the use thereof for Cosmochronology.« less

Nitriding kinetics of Si-SiC powder mixtures as simulations of reaction bonded Si3N4-SiC composites

NASA Technical Reports Server (NTRS)

Lightfoot, A.; Sheldon, B. W.; Flint, J. H.; Haggerty, J. S.

1989-01-01

The nitriding kinetics of Si and Si plus SiC powder mixtures were studied to simulate the fabrication of RBSN-SiC ceramic matrix composites. Very clean, assynthesized, and solvent-exposed powders were studied; C-rich and Si-rich SiC 0.04-0.05 micron diameter powders were mixed in varying concentrations with SiH4-derived 0.2-0.3 micron diameter Si powder. Complete nitridation is achieved with C-rich SiC powders in 140 min at 1250 C, and in the centers of Si-rich SiC powders in 15 min. The effects on the incubation periods, fast reaction periods, and slow reaction periods that characterize these nitriding processes were studied to explain unusual reverse reaction gradients and other effects of contamination.

Seeing the tipping point: Balance perception and visual shape.

PubMed

Firestone, Chaz; Keil, Frank C

2016-07-01

In a brief glance at an object or shape, we can appreciate a rich suite of its functional properties, including the organization of the object's parts, its optimal contact points for grasping, and its center of mass, or balancing point. However, in the real world and the laboratory, balance perception shows systematic biases whereby observers may misjudge a shape's center of mass by a severe margin. Are such biases simply quirks of physical reasoning? Or might they instead reflect more fundamental principles of object representation? Here we demonstrate systematically biased center-of-mass estimation for two-dimensional (2D) shapes (Study 1) and advance a surprising explanation of such biases. We suggest that the mind implicitly represents ordinary 2D shapes as rich, volumetric, three-dimensional (3D) objects, and that these "inflated" shape representations intrude on and bias perception of the 2D shape's geometric properties. Such "inflation" is a computer-graphics technique for segmenting shapes into parts, and we show that a model derived from this technique best accounts for the biases in center-of-mass estimation in Study 1. Further supporting this account, we show that reducing the need for inflated shape representations diminishes such biases: Center-of-mass estimation improved when cues to shapehood were attenuated (Study 2) and when shapes' depths were explicitly depicted using real-life objects laser-cut from wood (Study 3). We suggest that the technique of shape inflation is actually implemented in the mind; thus, biases in our impressions of balance reflect a more general functional characteristic of object perception. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Antioxidant enzyme activity and malondialdehyde levels can be modulated by Piper betle, tocotrienol rich fraction and Chlorella vulgaris in aging C57BL/6 mice

PubMed Central

Aliahmat, Nor Syahida; Noor, Mohd Razman Mohd; Yusof, Wan Junizam Wan; Makpol, Suzana; Ngah, Wan Zurinah Wan; Yusof, Yasmin Anum Mohd

2012-01-01

OBJECTIVE: The aim of this study was to determine the erythrocyte antioxidant enzyme activity and the superoxide dismutase, catalase, glutathione peroxidase, and plasma malondialdehyde levels in aging mice and to evaluate how these measures are modulated by potential antioxidants, including the tocotrienol-rich fraction, Piper betle, and Chlorella vulgaris. METHOD: One hundred and twenty male C57BL/6 inbred mice were divided into three age groups: young (6 months old), middle-aged (12 months old), and old (18 months old). Each age group consisted of two control groups (distilled water and olive oil) and three treatment groups: Piper betle (50 mg/kg body weight), tocotrienol-rich fraction (30 mg/kg), and Chlorella vulgaris (50 mg/kg). The duration of treatment for all three age groups was two months. Blood was withdrawn from the orbital sinus to determine the antioxidant enzyme activity and the malondialdehyde level. RESULTS: Piper betle increased the activities of catalase, glutathione peroxidase, and superoxide dismutase in the young, middle, and old age groups, respectively, when compared to control. The tocotrienol-rich fraction decreased the superoxide dismutase activity in the middle and the old age groups but had no effect on catalase or glutathione peroxidase activity for all age groups. Chlorella vulgaris had no effect on superoxide dismutase activity for all age groups but increased glutathione peroxidase and decreased catalase activity in the middle and the young age groups, respectively. Chlorella vulgaris reduced lipid peroxidation (malondialdehyde levels) in all age groups, but no significant changes were observed with the tocotrienol-rich fraction and the Piper betle treatments. CONCLUSION: We found equivocal age-related changes in erythrocyte antioxidant enzyme activity when mice were treated with Piper betle, the tocotrienol-rich fraction, and Chlorella vulgaris. However, Piper betle treatment showed increased antioxidant enzymes activity during aging. PMID:23295600

Upside-down: Perceived space affects object-based attention.

PubMed

Papenmeier, Frank; Meyerhoff, Hauke S; Brockhoff, Alisa; Jahn, Georg; Huff, Markus

2017-07-01

Object-based attention influences the subjective metrics of surrounding space. However, does perceived space influence object-based attention, as well? We used an attentive tracking task that required sustained object-based attention while objects moved within a tracking space. We manipulated perceived space through the availability of depth cues and varied the orientation of the tracking space. When rich depth cues were available (appearance of a voluminous tracking space), the upside-down orientation of the tracking space (objects appeared to move high on a ceiling) caused a pronounced impairment of tracking performance compared with an upright orientation of the tracking space (objects appeared to move on a floor plane). In contrast, this was not the case when reduced depth cues were available (appearance of a flat tracking space). With a preregistered second experiment, we showed that those effects were driven by scene-based depth cues and not object-based depth cues. We conclude that perceived space affects object-based attention and that object-based attention and perceived space are closely interlinked. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Occurrence of fluororichterite and fluorian biotite in the In Tifar trachyte neck (Tazrouk district, Hoggar volcanic province, Sahara, Algeria)

NASA Astrophysics Data System (ADS)

Azzouni-Sekkal, Abla; Bonin, Bernard; Ben El Khaznadji, Riad

2013-09-01

The unusual occurrence in the In Tifar trachyte neck (Tazrouk district, Hoggar volcanic province, Sahara, Algeria) of the fluorian biotite-fluororichterite association is presented. The two mineral species were previously unknown in the Hoggar and their association is uncommon worldwide. Ti-rich biotite has 28-40% OH sites occupied by fluorine, hence the use of the modifier "fluorian". Sodic-calcic fluororichterite has more than 55% OH sites filled by fluorine, hence the use of the prefix "fluoro". Well-defined F-Mg affinities are documented in both cases, while Cl remains very low. Temperatures are estimated roughly at 775-700 °C at low pressures. The fluorian biotite → fluororichterite sequence of crystallisation implies increasingly high fH2F2/fH2O ratios in metaluminous H2O-dominated evolving to peralkaline F-enriched fluids.

Orthobiologics and platelet rich plasma

PubMed Central

Dhillon, Mandeep S; Behera, Prateek; Patel, Sandeep; Shetty, Vijay

2014-01-01

Orthobiologics have evolved to the extent that they significantly influence modern orthopedic surgical practice. A better understanding of the role of various growth factors and cells in the process of tendon healing, ligament repair, cartilage regeneration and bone formation has stimulated focused research in many chronic musculoskeletal ailments. Investigators have published results of laboratory as well as clinical studies, using orthobiologics like platelet rich plasma, stem cells, autologous conditioned serum etc., with variable results. However, a clear consensus over the best orthobiologic substance and the method of preparation and usage of these substances is lacking. Much of the confusion is due to the fact that studies ranging from RCTs to case reports present variable results, and the interpretations are wide-ranging. We have reviewed the available orthobiologics related data with a focus on platelet rich plasma in orthopedic conditions. PMID:24600055

A Comparative Analysis of Financial Reporting Models for Private and Public Sector Organizations.

DTIC Science & Technology

1995-12-01

The objective of this thesis was to describe and compare different existing and evolving financial reporting models used in both the public and...private sector. To accomplish the objective, this thesis identified the existing financial reporting models for private sector business organizations...private sector nonprofit organizations, and state and local governments, as well as the evolving financial reporting model for the federal government

Emergence of CD134 cysteine-rich domain 2 (CRD2)-independent strains of feline immunodeficiency virus (FIV) is associated with disease progression in naturally infected cats.

PubMed

Bęczkowski, Paweł M; Techakriengkrai, Navapon; Logan, Nicola; McMonagle, Elizabeth; Litster, Annette; Willett, Brian J; Hosie, Margaret J

2014-11-28

Feline immunodeficiency virus (FIV) infection is mediated by sequential interactions with CD134 and CXCR4. Field strains of virus vary in their dependence on cysteine-rich domain 2 (CRD2) of CD134 for infection. Here, we analyse the receptor usage of viral variants in the blood of 39 naturally infected cats, revealing that CRD2-dependent viral variants dominate in early infection, evolving towards CRD2-independence with disease progression. These findings are consistent with a shift in CRD2 of CD134 usage with disease progression.

Enhancement of the repair of dog alveolar cleft by an autologous iliac bone, bone marrow-derived mesenchymal stem cell, and platelet-rich fibrin mixture.

PubMed

Yuanzheng, Chen; Yan, Gao; Ting, Li; Yanjie, Fu; Peng, Wu; Nan, Bai

2015-05-01

Autologous bone graft has been regarded as the criterion standard for the repair of alveolar cleft. However, the most prominent issue in alveolar cleft treatment is the high absorption rate of the bone graft. The authors' objective was to investigate the effects of an autologous iliac bone, bone marrow-derived mesenchymal stem cell, and platelet-rich fibrin mixture on the repair of dog alveolar cleft. Twenty beagle dogs with unilateral alveolar clefts created by surgery were divided randomly into four groups: group A underwent repair with an autologous iliac bone, bone marrow-derived mesenchymal stem cell, and platelet-rich fibrin mixture; group B underwent repair with autologous iliac bone and bone marrow-derived mesenchymal stem cells; group C underwent repair with autologous iliac bone and platelet-rich fibrin; and group D underwent repair with autologous iliac bone as the control. One day and 6 months after transplantation, the transplant volumes and bone mineral density were assessed by quantitative computed tomography. All of the transplants were harvested for hematoxylin and eosin staining 6 months later. Bone marrow-derived mesenchymal stem cells and platelet-rich fibrin transplants formed the greatest amounts of new bone among the four groups. The new bone formed an extensive union with the underlying maxilla in groups A, B, and C. Transplants with the bone marrow-derived mesenchymal stem cells, platelet-rich fibrin, and their mixture retained the majority of their initial volume, whereas the transplants in the control group showed the highest absorption rate. Bone mineral density of transplants with the bone marrow-derived mesenchymal stem cells, platelet-rich fibrin, and their mixture 6 months later was significantly higher than in the control group (p < 0.05), and was the highest in bone marrow-derived mesenchymal stem cells and platelet-rich fibrin mixed transplants. Hematoxylin and eosin staining showed that the structure of new bones formed the best in group A. Both bone marrow-derived mesenchymal stem cells and platelet-rich fibrin are capable of improving the repair of dog alveolar cleft, and the mixture of them is more potent than each one of them used singly for enhancing new bone regeneration.

Blog Attack: New Teaching Strategies to Engage Today's College Students

ERIC Educational Resources Information Center

Castro, Denise

2012-01-01

The growing need to match pedagogy with the evolving needs of a new generation of learners has stirred and interest in Web 2.0 Blogging can bring a surprisingly rich experience to class projects by increasing collaboration between students and teacher. As a teaching tool, blogging can bring greater complexity to learning that would have otherwise…

Currents in Environmental Education: Mapping a Complex and Evolving Pedagogical Field

ERIC Educational Resources Information Center

Sauve, Lucie

2005-01-01

The purpose of this article is to bring to light and celebrate the richness of the environmental education field, thereby paying homage to the pedagogical creativity of its architects over the course of the last thirty years, as well as to their contribution in reflecting on the meaning, problems and possibilities of our relationship to the…

Evolving targets for lipid-modifying therapy

PubMed Central

Do, Rose Q; Nicholls, Stephen J; Schwartz, Gregory G

2014-01-01

The pathogenesis and progression of atherosclerosis are integrally connected to the concentration and function of lipoproteins in various classes. This review examines existing and emerging approaches to modify low-density lipoprotein and lipoprotein (a), triglyceride-rich lipoproteins, and high-density lipoproteins, emphasizing approaches that have progressed to clinical evaluation. Targeting of nuclear receptors and phospholipases is also discussed. PMID:25172365

The Mairan domes: silicic volcanic constructs on the Moon

USGS Publications Warehouse

Glotch, Timothy D.; Hagerty, Justin J.; Lucey, Paul G.; Hawke, B. Ray; Giguere, Thomas A.; Arnold, Jessica A.; Williams, Jean-Pierre; Jolliff, Bradley L.; Paige, David A.

2011-01-01

The Mairan domes are four features located in northern Oceanus Procellarum at ∼312.3E, 41.4N on the Moon. High resolution visible imagery, visible-to-mid-IR spectra, and Lunar Prospector Th abundance data all indicate that these four domes have a composition that is consistent with derivation from a Si-rich, highly evolved magma.

Design Interactive: A Nonlinear, Multimedia Approach to Teaching Introduction to Visual Communication and Principles of Design

ERIC Educational Resources Information Center

Palilonis, Jennifer; Butler, Darrell; Leidig-Farmen, Pamela

2013-01-01

As online teaching techniques continue to evolve, new opportunities surface for research and insight regarding best practices for the development and implementation of interactive, multimedia teaching and learning tools. These tools are particularly attractive for courses that lend themselves to a rich media approach. Such is the case for visual…

Unlocking Learning Using Tony Ryan's "Thinker's Keys"

ERIC Educational Resources Information Center

Robinson, Linda

2017-01-01

The learning of science keeps evolving, just like the subject of science itself. With this in mind, teachers know the importance of keeping up to date and researching different ways of providing a rich learning experience for children. Teachers are developing not only children's learning, but how they progress as learners. This is where Tony…

Two evolved supernova remnants with newly identified Fe-rich cores in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Kavanagh, P. J.; Sasaki, M.; Bozzetto, L. M.; Points, S. D.; Crawford, E. J.; Dickel, J.; Filipović, M. D.; Haberl, F.; Maggi, P.; Whelan, E. T.

2016-02-01

Aims: We present a multi-wavelength analysis of the evolved supernova remnants MCSNR J0506-7025 and MCSNR J0527-7104 in the Large Magellanic Cloud. Methods: We used observational data from XMM-Newton, the Australian Telescope Compact Array, and the Magellanic Cloud Emission Line Survey to study their broad-band emission and used Spitzer and H I data to gain a picture of the environment into which the remnants are expanding. We performed a multi-wavelength morphological study and detailed radio and X-ray spectral analyses to determine their physical characteristics. Results: Both remnants were found to have bright X-ray cores, dominated by Fe L-shell emission, which is consistent with reverse shock-heated ejecta with determined Fe masses in agreement with Type Ia explosion yields. A soft X-ray shell, which is consistent with swept-up interstellar medium, was observed in MCSNR J0506-7025, suggestive of a remnant in the Sedov phase. Using the spectral fit results and the Sedov self-similar solution, we estimated the age of MCSNR J0506-7025 to be ~16-28 kyr, with an initial explosion energy of (0.07-0.84) × 1051 erg. A soft shell was absent in MCSNR J0527-7104, with only ejecta emission visible in an extremely elongated morphology that extends beyond the optical shell. We suggest that the blast wave has broken out into a low density cavity, allowing the shock heated ejecta to escape. We find that the radio spectral index of MCSNR J0506-7025 is consistent with the standard -0.5 for supernova remnants. Radio polarisation at 6 cm indicates a higher degree of polarisation along the western front and at the eastern knot with a mean fractional polarisation across the remnant of P ≅ (20 ± 6)%. Conclusions: The detection of Fe-rich ejecta in the remnants suggests that both resulted from Type Ia explosions. The newly identified Fe-rich cores in MCSNR J0506-7025 and MCSNR J0527-7104 make them members of the expanding class of evolved Fe-rich remnants in the Magellanic Clouds. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA.

Bioactive compounds in pindo palm (Butia capitata) juice and in pomace resulting of the extraction process.

PubMed

Jachna, Tiphaine J; Hermes, Vanessa S; Flôres, Simone H; Rios, Alessandro O

2016-03-15

Pindo palm (Butia capitata, Becc. 1916) is a tropical fruit native to South America and is relatively rich in bioactive compounds. It is often consumed as juice. The aim of this study was, first, to identify the degradation of these compounds by pasteurization and by cold storage (4 °C) of pindo palm juice. Physicochemical properties and concentrations of phenolic compounds, carotenoids and vitamin C have been evaluated on fresh and pasteurized juices. Moreover, another objective was to characterize the nutritional composition and the bioactive compounds of pindo palm pomace, the by-product of juice processing. The results demonstrated a degradation of carotenoids with pasteurization and a degradation of vitamin C with both pasteurization and cold storage of juices. Furthermore, the evaluation of pindo palm pomace showed that it is relatively rich in total phenols (20.06 g gallic acid equivalents kg(-1) dry matter) and in β-carotene (0.22 g kg(-1) dry matter). Thus, from the nutrition viewpoint, it does not seem interesting to pasteurize juice. On the other hand, extraction of carotenoids and phenolic compounds from the pomace appears to be a relevant process. © 2015 Society of Chemical Industry.

Virtual Genomes in Flux: An Interplay of Neutrality and Adaptability Explains Genome Expansion and Streamlining

PubMed Central

Cuypers, Thomas D.; Hogeweg, Paulien

2012-01-01

The picture that emerges from phylogenetic gene content reconstructions is that genomes evolve in a dynamic pattern of rapid expansion and gradual streamlining. Ancestral organisms have been estimated to possess remarkably rich gene complements, although gene loss is a driving force in subsequent lineage adaptation and diversification. Here, we study genome dynamics in a model of virtual cells evolving to maintain homeostasis. We observe a pattern of an initial rapid expansion of the genome and a prolonged phase of mutational load reduction. Generally, load reduction is achieved by the deletion of redundant genes, generating a streamlining pattern. Load reduction can also occur as a result of the generation of highly neutral genomic regions. These regions can expand and contract in a neutral fashion. Our study suggests that genome expansion and streamlining are generic patterns of evolving systems. We propose that the complex genotype to phenotype mapping in virtual cells as well as in their biological counterparts drives genome size dynamics, due to an emerging interplay between adaptation, neutrality, and evolvability. PMID:22234601

Combinatorial stresses kill pathogenic Candida species

PubMed Central

Kaloriti, Despoina; Tillmann, Anna; Cook, Emily; Jacobsen, Mette; You, Tao; Lenardon, Megan; Ames, Lauren; Barahona, Mauricio; Chandrasekaran, Komelapriya; Coghill, George; Goodman, Daniel; Gow, Neil A. R.; Grebogi, Celso; Ho, Hsueh-Lui; Ingram, Piers; McDonagh, Andrew; De Moura, Alessandro P. S.; Pang, Wei; Puttnam, Melanie; Radmaneshfar, Elahe; Romano, Maria Carmen; Silk, Daniel; Stark, Jaroslav; Stumpf, Michael; Thiel, Marco; Thorne, Thomas; Usher, Jane; Yin, Zhikang; Haynes, Ken; Brown, Alistair J. P.

2012-01-01

Pathogenic microbes exist in dynamic niches and have evolved robust adaptive responses to promote survival in their hosts. The major fungal pathogens of humans, Candida albicans and Candida glabrata, are exposed to a range of environmental stresses in their hosts including osmotic, oxidative and nitrosative stresses. Significant efforts have been devoted to the characterization of the adaptive responses to each of these stresses. In the wild, cells are frequently exposed simultaneously to combinations of these stresses and yet the effects of such combinatorial stresses have not been explored. We have developed a common experimental platform to facilitate the comparison of combinatorial stress responses in C. glabrata and C. albicans. This platform is based on the growth of cells in buffered rich medium at 30°C, and was used to define relatively low, medium and high doses of osmotic (NaCl), oxidative (H 2O2) and nitrosative stresses (e.g., dipropylenetriamine (DPTA)-NONOate). The effects of combinatorial stresses were compared with the corresponding individual stresses under these growth conditions. We show for the first time that certain combinations of combinatorial stress are especially potent in terms of their ability to kill C. albicans and C. glabrata and/or inhibit their growth. This was the case for combinations of osmotic plus oxidative stress and for oxidative plus nitrosative stress. We predict that combinatorial stresses may be highly signif cant in host defences against these pathogenic yeasts. PMID:22463109

Variations on a theme - the evolution of hydrocarbon solids. I. Compositional and spectral modelling - the eRCN and DG models

NASA Astrophysics Data System (ADS)

Jones, A. P.

2012-04-01

Context. The compositional properties of hydrogenated amorphous carbons are known to evolve in response to the local conditions. Aims: We present a model for low-temperature, amorphous hydrocarbon solids, based on the microphysical properties of random and defected networks of carbon and hydrogen atoms, that can be used to study and predict the evolution of their properties in the interstellar medium. Methods: We adopt an adaptable and prescriptive approach to model these materials, which is based on a random covalent network (RCN) model, extended here to a full compositional derivation (the eRCN model), and a defective graphite (DG) model for the hydrogen poorer materials where the eRCN model is no longer valid. Results: We provide simple expressions that enable the determination of the structural, infrared and spectral properties of amorphous hydrocarbon grains as a function of the hydrogen atomic fraction, XH. Structural annealing, resulting from hydrogen atom loss, results in a transition from H-rich, aliphatic-rich to H-poor, aromatic-rich materials. Conclusions: The model predicts changes in the optical properties of hydrogenated amorphous carbon dust in response to the likely UV photon-driven and/or thermal annealing processes resulting, principally, from the radiation field in the environment. We show how this dust component will evolve, compositionally and structurally in the interstellar medium in response to the local conditions. Appendices A and B are available in electronic form at http://www.aanda.org

The attribution of navigational- and goal-directed agency in dogs (Canis familiaris) and human toddlers (Homo sapiens).

PubMed

Tauzin, Tibor; Csík, Andor; Lovas, Kata; Gergely, György; Topál, József

2017-02-01

Both human infants and nonhuman primates can recognize unfamiliar entities as instrumental agents ascribing to them goals and efficiency of goal-pursuit. This competence relies on movement cues indicating distal sensitivity to the environment and choice of efficient goal-approach. Although dogs' evolved sensitivity to social cues allow them to recognize humans as communicative agents, it remains unclear whether they have also evolved a basic concept of instrumental agency. We used a preferential object-choice procedure to test whether adult pet dogs and human toddlers can identify unfamiliar entities as agents based on different types of movement cues that specify different levels of agency. In the navigational agency condition, dogs preferentially chose an object that modified its pathway to avoid collision with obstacles over another object showing no evidence of distal sensitivity (regularly bumping into obstacles). However, in the goal-efficiency condition where neither object collided with obstacles as it navigated toward a distal target, but only 1 of them exhibited efficient goal-approach as well, toddlers, but not dogs, showed a preference toward the efficient goal-directed agent. These findings indicate that dogs possess a limited concept of environmentally sensitive navigational agency that they attribute to self-propelled entities capable of modifying their movement to avoid colliding with obstacles. Toddlers, in contrast, demonstrated clear sensitivity to cues of efficient variability of goal-approach as the basis for differentiating, attributing, and showing preference for goal-directed instrumental agency. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The Main-belt Asteroid and NEO Tour with Imaging and Spectroscopy (MANTIS)

NASA Astrophysics Data System (ADS)

Rivkin, A.; Cohen, B. A.; Barnouin, O. S.; Chabot, N. L.; Ernst, C. M.; Klima, R. L.; Helbert, J.; Sternovsky, Z.

2015-12-01

The asteroids preserve information from the earliest times in solar system history, with compositions in the population reflecting the material in the solar nebula and experiencing a wide range of temperatures. Today they experience ongoing processes, some of which are shared with larger bodies but some of which are unique to their size regime. They are critical to humanity's future as potential threats, resource sites, and targets for human visitation. However, over twenty years since the first spacecraft encounters with asteroids, they remain poorly understood. The mission we propose here, the Main-belt Asteroid and NEO Tour with Imaging and Spectroscopy (MANTIS), explores the diversity of asteroids to understand our solar system's past history, its present processes, and future opportunities and hazards. MANTIS addresses many of NASA's highest priorities as laid out in its 2014 Science Plan and provides additional benefit to the Planetary Defense and Human Exploration communities via a low-risk, cost-effective tour of the near-Earth and inner asteroid belt. MANTIS visits the materials that witnessed solar system formation and its earliest history, addressing the NASA goal of exploring and observing the objects in the solar system to understand how they formed and evolve. MANTIS measures OH, water, and organic materials via several complementary techniques, visiting and sampling objects known to have hydrated minerals and addressing the NASA goal of improving our understanding of the origin and evolution of life on Earth. MANTIS studies the geology and geophysics of nine diverse asteroids, with compositions ranging from water-rich to metallic, representatives of both binary and non-binary asteroids, and sizes covering over two orders of magnitude, providing unique information about the chemical and physical processes shaping the asteroids, addressing the NASA goal of advancing the understanding of how the chemical and physical processes in our solar system operate, interact, and evolve. Finally, the set of measurements carried out by MANTIS at near-Earth and main-belt asteroids will by definition characterize objects in the solar system that pose threats to Earth or offer resources for human exploration, a final goal in the NASA Science Plan.

Infrared spectroscopy of organics of planetological interest at low temperatures

NASA Technical Reports Server (NTRS)

Khanna, R. K.

1994-01-01

In the context of prebiotic chemistry in space, some of the outer planetary objects display H, C, N and O rich chemistry similar to the one in the biosphere of Earth. Of particular interest are Saturn's moon, Titan; Neptune's moon, Triton; and Pluto where extreme cold conditions prevail. Identifications of chemical species on these objects (surfaces and atmospheres) is essential to a better understanding of the radiation induced chemical reactions occuring thereon. There have been several ground based observations of these planetary objects in the infrared windows from 1 to 2.5 micrometers. Voyager also provided spectra in the thermal infrared (6 to 50 micrometers) region. Interpretation of these data require laboratory infrared spectra of relevant species under the temperature conditions appropriate to these objects. The results of some of these studies carried out in our laboratory and elsewhere and their impact on the analyses of the observed data will be summarized.

Mars Surface Habitability Options

NASA Technical Reports Server (NTRS)

Howe, A. Scott; Simon, Matthew; Smitherman, David; Howard, Robert; Toups, Larry; Hoffman, Stephen J.

2015-01-01

This paper reports on current habitability concepts for an Evolvable Mars Campaign (EMC) prepared by the NASA Human Spaceflight Architecture Team (HAT). For many years NASA has investigated alternative human Mars missions, examining different mission objectives, trajectories, vehicles, and technologies; the combinations of which have been referred to as reference missions or architectures. At the highest levels, decisions regarding the timing and objectives for a human mission to Mars continue to evolve while at the lowest levels, applicable technologies continue to advance. This results in an on-going need for assessments of alternative system designs such as the habitat, a significant element in any human Mars mission scenario, to provide meaningful design sensitivity characterizations to assist decision-makers regarding timing, objectives, and technologies. As a subset of the Evolvable Mars Campaign activities, the habitability team builds upon results from past studies and recommends options for Mars surface habitability compatible with updated technologies.

The MACHO Project Sample of Galactic Bulge High-Amplitude δ Scuti Stars: Pulsation Behavior and Stellar Properties

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D. R.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Freeman, K. C.; Geha, M.; Griest, K.; Lehner, M. J.; Marshall, S. L.; McNamara, B. J.; Minniti, D.; Nelson, C.; Peterson, B. A.; Popowski, P.; Pratt, M. R.; Quinn, P. J.; Rodgers, A. W.; Sutherland, W.; Templeton, M. R.; Vandehei, T.; Welch, D. L.

2000-06-01

We have detected 90 objects with periods and light-curve structures similar to those of field δ Scuti stars using the Massive Compact Halo Object (MACHO) Project database of Galactic bulge photometry. If we assume similar extinction values for all candidates and absolute magnitudes similar to those of other field high-amplitude δ Scuti stars (HADS), the majority of these objects lie in or near the Galactic bulge. At least two of these objects are likely foreground δ Scuti stars, one of which may be an evolved nonradial pulsator, similar to other evolved, disk-population δ Scuti stars. We have analyzed the light curves of these objects and find that they are similar to the light curves of field δ Scuti stars and the δ Scuti stars found by the Optical Gravitational Lens Experiment (OGLE). However, the amplitude distribution of these sources lies between those of low- and high-amplitude δ Scuti stars, which suggests that they may be an intermediate population. We have found nine double-mode HADS with frequency ratios ranging from 0.75 to 0.79, four probable double- and multiple-mode objects, and another four objects with marginal detections of secondary modes. The low frequencies (5-14 cycles day-1) and the observed period ratios of ~0.77 suggest that the majority of these objects are evolved stars pulsating in fundamental or first overtone radial modes.

Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

DOE Office of Scientific and Technical Information (OSTI.GOV)

De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.

Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ∼20 μ m particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorlymore » graphitized carbon (PGC). The PGC forms conformal shells around tiny 5–15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core–shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.« less

Antimicrobial Peptides from Plants

PubMed Central

Tam, James P.; Wang, Shujing; Wong, Ka H.; Tan, Wei Liang

2015-01-01

Plant antimicrobial peptides (AMPs) have evolved differently from AMPs from other life forms. They are generally rich in cysteine residues which form multiple disulfides. In turn, the disulfides cross-braced plant AMPs as cystine-rich peptides to confer them with extraordinary high chemical, thermal and proteolytic stability. The cystine-rich or commonly known as cysteine-rich peptides (CRPs) of plant AMPs are classified into families based on their sequence similarity, cysteine motifs that determine their distinctive disulfide bond patterns and tertiary structure fold. Cystine-rich plant AMP families include thionins, defensins, hevein-like peptides, knottin-type peptides (linear and cyclic), lipid transfer proteins, α-hairpinin and snakins family. In addition, there are AMPs which are rich in other amino acids. The ability of plant AMPs to organize into specific families with conserved structural folds that enable sequence variation of non-Cys residues encased in the same scaffold within a particular family to play multiple functions. Furthermore, the ability of plant AMPs to tolerate hypervariable sequences using a conserved scaffold provides diversity to recognize different targets by varying the sequence of the non-cysteine residues. These properties bode well for developing plant AMPs as potential therapeutics and for protection of crops through transgenic methods. This review provides an overview of the major families of plant AMPs, including their structures, functions, and putative mechanisms. PMID:26580629

What Explains Patterns of Diversification and Richness among Animal Phyla?

PubMed Central

Jezkova, Tereza; Wiens, John J.

2016-01-01

Animal phyla vary dramatically in species richness (from 1 species to >1.2 million), but the causes of this variation remain largely unknown. Animals have also evolved striking variation in morphology and ecology, including sessile marine taxa lacking heads, eyes, limbs, and complex organs (e.g. sponges), parasitic worms (e.g. nematodes, platyhelminths), and taxa with eyes, skeletons, limbs, and complex organs that dominate terrestrial ecosystems (arthropods, chordates). Relating this remarkable variation in traits to the diversification and richness of animal phyla is a fundamental yet unresolved problem in biology. Here, we test the impacts of 18 traits (including morphology, ecology, reproduction, and development) on diversification and richness of extant animal phyla. Using phylogenetic multiple regression, the best-fitting model includes five traits that explain ~74% of the variation in diversification rates (dioecy, parasitism, eyes/photoreceptors, a skeleton, non-marine habitat). However, a model including just three (skeleton, parasitism, habitat) explains nearly as much variation (~67%). Diversification rates then largely explain richness patterns. Our results also identify many striking traits that have surprisingly little impact on diversification (e.g. head, limbs, and complex circulatory and digestive systems). Overall, our results reveal the key factors that shape large-scale patterns of diversification and richness across >80% of all extant, described species. PMID:28221832

What Explains Patterns of Diversification and Richness among Animal Phyla?

PubMed

Jezkova, Tereza; Wiens, John J

2017-03-01

Animal phyla vary dramatically in species richness (from one species to >1.2 million), but the causes of this variation remain largely unknown. Animals have also evolved striking variation in morphology and ecology, including sessile marine taxa lacking heads, eyes, limbs, and complex organs (e.g., sponges), parasitic worms (e.g., nematodes, platyhelminths), and taxa with eyes, skeletons, limbs, and complex organs that dominate terrestrial ecosystems (arthropods, chordates). Relating this remarkable variation in traits to the diversification and richness of animal phyla is a fundamental yet unresolved problem in biology. Here, we test the impacts of 18 traits (including morphology, ecology, reproduction, and development) on diversification and richness of extant animal phyla. Using phylogenetic multiple regression, the best-fitting model includes five traits that explain ∼74% of the variation in diversification rates (dioecy, parasitism, eyes/photoreceptors, a skeleton, nonmarine habitat). However, a model including just three (skeleton, parasitism, habitat) explains nearly as much variation (∼67%). Diversification rates then largely explain richness patterns. Our results also identify many striking traits that have surprisingly little impact on diversification (e.g., head, limbs, and complex circulatory and digestive systems). Overall, our results reveal the key factors that shape large-scale patterns of diversification and richness across >80% of all extant, described species.

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation.

PubMed

Levy, Amalie T; Lee, Kelvin H; Hanson, Thomas E

2016-11-01

Microbial sulfur metabolism, particularly the formation and consumption of insoluble elemental sulfur (S 0 ), is an important biogeochemical engine that has been harnessed for applications ranging from bioleaching and biomining to remediation of waste streams. Chlorobaculum tepidum, a low-light-adapted photoautolithotrophic sulfur-oxidizing bacterium, oxidizes multiple sulfur species and displays a preference for more reduced electron donors: sulfide > S 0 > thiosulfate. To understand this preference in the context of light energy availability, an "energy landscape" of phototrophic sulfur oxidation was constructed by varying electron donor identity, light flux, and culture duration. Biomass and cellular parameters of C. tepidum cultures grown across this landscape were analyzed. From these data, a correction factor for colorimetric protein assays was developed, enabling more accurate biomass measurements for C. tepidum, as well as other organisms. C. tepidum's bulk amino acid composition correlated with energy landscape parameters, including a tendency toward less energetically expensive amino acids under reduced light flux. This correlation, paired with an observation of increased cell size and storage carbon production under electron-rich growth conditions, suggests that C. tepidum has evolved to cope with changing energy availability by tuning its proteome for energetic efficiency and storing compounds for leaner times. How microbes cope with and adapt to varying energy availability is an important factor in understanding microbial ecology and in designing efficient biotechnological processes. We explored the response of a model phototrophic organism, Chlorobaculum tepidum, across a factorial experimental design that enabled simultaneous variation and analysis of multiple growth conditions, what we term the "energy landscape." C. tepidum biomass composition shifted toward less energetically expensive amino acids at low light levels. This observation provides experimental evidence for evolved efficiencies in microbial proteomes and emphasizes the role that energy flux may play in the adaptive responses of organisms. From a practical standpoint, our data suggest that bulk biomass amino acid composition could provide a simple proxy to monitor and identify energy stress in microbial systems. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation

PubMed Central

2016-01-01

ABSTRACT Microbial sulfur metabolism, particularly the formation and consumption of insoluble elemental sulfur (S0), is an important biogeochemical engine that has been harnessed for applications ranging from bioleaching and biomining to remediation of waste streams. Chlorobaculum tepidum, a low-light-adapted photoautolithotrophic sulfur-oxidizing bacterium, oxidizes multiple sulfur species and displays a preference for more reduced electron donors: sulfide > S0 > thiosulfate. To understand this preference in the context of light energy availability, an “energy landscape” of phototrophic sulfur oxidation was constructed by varying electron donor identity, light flux, and culture duration. Biomass and cellular parameters of C. tepidum cultures grown across this landscape were analyzed. From these data, a correction factor for colorimetric protein assays was developed, enabling more accurate biomass measurements for C. tepidum, as well as other organisms. C. tepidum's bulk amino acid composition correlated with energy landscape parameters, including a tendency toward less energetically expensive amino acids under reduced light flux. This correlation, paired with an observation of increased cell size and storage carbon production under electron-rich growth conditions, suggests that C. tepidum has evolved to cope with changing energy availability by tuning its proteome for energetic efficiency and storing compounds for leaner times. IMPORTANCE How microbes cope with and adapt to varying energy availability is an important factor in understanding microbial ecology and in designing efficient biotechnological processes. We explored the response of a model phototrophic organism, Chlorobaculum tepidum, across a factorial experimental design that enabled simultaneous variation and analysis of multiple growth conditions, what we term the “energy landscape.” C. tepidum biomass composition shifted toward less energetically expensive amino acids at low light levels. This observation provides experimental evidence for evolved efficiencies in microbial proteomes and emphasizes the role that energy flux may play in the adaptive responses of organisms. From a practical standpoint, our data suggest that bulk biomass amino acid composition could provide a simple proxy to monitor and identify energy stress in microbial systems. PMID:27565613

Common-envelope ejection in massive binary stars. Implications for the progenitors of GW150914 and GW151226

NASA Astrophysics Data System (ADS)

Kruckow, M. U.; Tauris, T. M.; Langer, N.; Szécsi, D.; Marchant, P.; Podsiadlowski, Ph.

2016-11-01

Context. The recently detected gravitational wave signals (GW150914 and GW151226) of the merger event of a pair of relatively massive stellar-mass black holes (BHs) calls for an investigation of the formation of such progenitor systems in general. Aims: We analyse the common-envelope (CE) stage of the traditional formation channel in binaries where the first-formed compact object undergoes an in-spiral inside the envelope of its evolved companion star and ejects the envelope in this process. Methods: We calculated envelope binding energies of donor stars with initial masses between 4 and 115M⊙ for metallicities of Z = ZMilky Way ≃ Z⊙/ 2 and Z = Z⊙/ 50, and derived minimum masses of in-spiralling objects needed to eject these envelopes. Results: In addition to producing double white dwarf and double neutron star binaries, CE evolution may also produce massive BH-BH systems with individual BH component masses of up to 50 - 60M⊙, in particular for donor stars evolved to giants beyond the Hertzsprung gap. However, the physics of envelope ejection of massive stars remains uncertain. We discuss the applicability of the energy-budget formalism, the location of the bifurcation point, the recombination energy, and the accretion energy during in-spiral as possible energy sources, and also comment on the effect of inflated helium cores. Conclusions: Massive stars in a wide range of metallicities and with initial masses of up to at least 115M⊙ may shed their envelopes and survive CE evolution, depending on their initial orbital parameters, similarly to the situation for intermediate- and low-mass stars with degenerate cores. In addition to being dependent on stellar radius, the envelope binding energies and λ-values also depend on the applied convective core-overshooting parameter, whereas these structure parameters are basically independent of metallicity for stars with initial masses below 60M⊙. Metal-rich stars ≳60M⊙ become luminous blue variables and do not evolve to reach the red giant stage. We conclude that based on stellar structure calculations, and in the view of the usual simple energy budget analysis, events like GW150914 and GW151226 might be produced by the CE channel. Calculations of post-CE orbital separations, however, and thus the estimated LIGO detection rates, remain highly uncertain.

Large-scale distribution patterns of mangrove nematodes: A global meta-analysis.

PubMed

Brustolin, Marco C; Nagelkerken, Ivan; Fonseca, Gustavo

2018-05-01

Mangroves harbor diverse invertebrate communities, suggesting that macroecological distribution patterns of habitat-forming foundation species drive the associated faunal distribution. Whether these are driven by mangrove biogeography is still ambiguous. For small-bodied taxa, local factors and landscape metrics might be as important as macroecology. We performed a meta-analysis to address the following questions: (1) can richness of mangrove trees explain macroecological patterns of nematode richness? and (2) do local landscape attributes have equal or higher importance than biogeography in structuring nematode richness? Mangrove areas of Caribbean-Southwest Atlantic, Western Indian, Central Indo-Pacific, and Southwest Pacific biogeographic regions. We used random-effects meta-analyses based on natural logarithm of the response ratio (lnRR) to assess the importance of macroecology (i.e., biogeographic regions, latitude, longitude), local factors (i.e., aboveground mangrove biomass and tree richness), and landscape metrics (forest area and shape) in structuring nematode richness from 34 mangroves sites around the world. Latitude, mangrove forest area, and forest shape index explained 19% of the heterogeneity across studies. Richness was higher at low latitudes, closer to the equator. At local scales, richness increased slightly with landscape complexity and decreased with forest shape index. Our results contrast with biogeographic diversity patterns of mangrove-associated taxa. Global-scale nematode diversity may have evolved independently of mangrove tree richness, and diversity of small-bodied metazoans is probably more closely driven by latitude and associated climates, rather than local, landscape, or global biogeographic patterns.

Studies of hydrodynamic events in stellar evolution. 3: Ejection of planetary nebulae

NASA Technical Reports Server (NTRS)

Sparks, W. M.; Kutter, G. S.

1973-01-01

The dynamic behavior of the H-rich envelope (0.101 solar mass) of an evolved star (1.1 solar mass) as the luminosity rises to 19000 solar luminosity during the second ascent of the red giant branch. For luminosities in the range 3100 L 19000 solar luminosity the H-rich envelope pulsates like a long-period variable (LPV) with periods of the order of a year. As L reaches 19000 solar luminosity, the entire H-rich envelope is ejected as a shell with speeds of a few 10 km/s. The ejection occurs on a timescale of a few LPV pulsation periods. This ejection is associated with the formation of a planetary nebula. The computations are based on an implicit hydrodynamic computer code. T- and RHO-dependent opacities and excitation and ionization energies are included. As the H-rich envelope is accelerated off the stellar core, the gap between envelope and core is approximated by a vacuum, filled with radiation. Across the vacuum, the luminosity is conserved and the anisotropy of the radiation is considered as well as the solid angle subtended by the remnant star at the inner surface of the H-rich envelope. Spherical symmetry and the diffusion approximation are assumed.

Microstructural constraints on complex thermal histories of refractory CAI-like objects in an amoeboid olivine aggregate from the ALHA77307 CO3.0 chondrite

NASA Astrophysics Data System (ADS)

Han, Jangmi; Brearley, Adrian J.

2016-06-01

We have carried out a FIB/TEM study of refractory CAI-like objects in one AOA from the ALHA77307 CO3.0 chondrite. The CAI-like objects in the AOA consist of a zoned sequence with a spinel-rich core through an intergrowth layer of spinel and Al-Ti-rich diopside to a diopside rim. The spinel-rich core consists of polycrystalline aggregates of spinel and ±minor melilite showing equilibrated grain boundary textures. The intergrowth layer contains fine-grained diopside and spinel with minor anorthite with highly curved and embayed grain boundaries. The diopside rim consists of polycrystalline aggregates of diopside. The compositions of pyroxene change significantly outward from Al-Ti-rich diopside in contact with the spinel-rich core to Al-Ti-poor diopside next to the surrounding olivine of the AOA. Overall microstructural and chemical characteristics suggest that the spinel-rich core formed under equilibrium conditions whereas the intergrowth layer is the result of reactions that occurred under conditions that departed significantly from equilibrium. The remarkable changes in formation conditions of the CAI-like objects may have been achieved by transport and injection of refractory objects into a region of a partially-condensed, Ca,Ti-saturated gas which reacted with spinel and melilite to form Al-Ti-rich diopside. Crystallographically-oriented TiO2 nanoparticles decorate the grain boundaries between spinel grains and between spinel and Al-Ti-rich diopside grains. During the disequilibrium back-reaction of spinel with a partially-condensed, Ca,Ti-saturated gas, metastable TiO2 nanoparticles may have condensed by an epitaxial nucleation mechanism and grown on the surface of spinel. These TiO2 nanoparticles are disordered intergrowths of the two TiO2 polymorphs, anatase and rutile. These nanoparticles are inferred to have nucleated as anatase that underwent partial transformation into rutile. The local presence of the TiO2 nanoparticles and intergrowth of anatase and rutile imply that the disequilibrium back-reaction of spinel with the gas occurred on a short timescale, i.e., minutes to hours at maximum.

Platelet-rich plasma: a biomimetic approach to enhancement of surgical wound healing.

PubMed

Fernandez-Moure, Joseph S; Van Eps, Jeffrey L; Cabrera, Fernando J; Barbosa, Zonia; Medrano Del Rosal, Guillermo; Weiner, Bradley K; Ellsworth, Warren A; Tasciotti, Ennio

2017-01-01

Platelets are small anucleate cytoplasmic cell bodies released by megakaryocytes in response to various physiologic triggers. Traditionally thought to be solely involved in the mechanisms of hemostasis, platelets have gained much attention due to their involvement wound healing, immunomodulation, and antiseptic properties. As the field of surgery continues to evolve so does the need for therapies to aid in treating the increasingly complex patients seen. With over 14 million obstetric, musculoskeletal, and urological and gastrointestinal surgeries performed annually, the healing of surgical wounds continues to be of upmost importance to the surgeon and patient. Platelet-rich plasma, or platelet concentrate, has emerged as a possible adjuvant therapy to aid in the healing of surgical wounds and injuries. In this review, we will discuss the wound healing properties of platelet-rich plasma and various surgical applications. Copyright © 2016 Elsevier Inc. All rights reserved.

Mineralogical Characterization of Fe-Bearing AGB and Supernova Silicate Grains From the Queen Alexandra Range 99177 Meteorite

NASA Technical Reports Server (NTRS)

Nguyen, A. N.; Keller, L. P.; Messenger, S.; Rahman, Z.

2017-01-01

Spectroscopic observations of the circumstellar envelopes of evolved O-rich stars indicate the dust is mostly amorphous silicate with olivine-like compositions. Spectral modeling suggests these grains are Fe-rich [Mg/(Mg+Fe) 0.5], but it is not known whether the Fe is distributed within the silicate matrix or exists as metal inclusions. In contrast, the crystalline silicates are inferred to be extremely Mg-rich [Mg/(Mg+Fe) > 0.95]. The mineralogies and chemical compositions of dust in supernova (SN) remnants are not as well constrained, but abundant silicates of olivine-like and enstatite-like compositions have been fit to the infrared emission features. Silicates in the interstellar medium (ISM) are >99% amor-phous and Fe-bearing. The dearth of crystalline silicates in the ISM requires that some amorphization or destruction mechanisms process these grains.

The Future of Child Development Lab Schools: Applied Developmental Science in Action

ERIC Educational Resources Information Center

Barbour, Nancy, Ed.; McBride, Brent A., Ed.

2017-01-01

Child development laboratory schools are found on college and university campuses throughout the U.S. Over the last century, they have acquired a long, rich history. Originally seen as settings for the new field of child study in the early 1900s, their functions have evolved over time. These programs often play a central role in supporting…

A Case Analysis of Business English Teacher Development in China with GDUFS as an Example

ERIC Educational Resources Information Center

Wenzhong, Zhu; Jingzi, Deng

2015-01-01

Business English education has evolved into a cross-disciplinary programme in China as one of the hottest majors pursued by students and professionals. As Business English teaching develops in terms of diversity, richness, and depth, the demands placed on the teacher are also increasing. The paper assumes that the kind of teachers with…

The effect of heating on mineral composition and grain size distribution of flux calcined porcelanites from the Gafsa-Metlaoui basin, southwestern Tunisia

NASA Astrophysics Data System (ADS)

Saidi, Raja; Tlili, Ali; Jamoussi, Fakher

2016-12-01

The porcelanite rock of Ypresian phosphatic series of the Gafsa-Metlaoui basin (south-western Tunisia), is composed mainly of opal CT, and presents a variable percentage of carbonates and fibrous clays. This rock is treated with flux calcination at different temperatures in order to prepare a specific filter aid for cleaning melting sulfur which can be used for the production of sulfuric acid. This work presents the effect of heating on the mineralogy and grain size distribution of carbonate-rich porcelanite (Tm1) and clay-rich porcelanite (Gh) compared to flux calcined silica-rich porcelanite (CHM3) and diatomaceous filtration aids. The porcelanite samples used in this work come from three localities of the Gafsa-Metlaoui basin: Kef El Ghis (Gh), Tamarza (Tm1) and Mides (CHM3). Flux calcination at 1000 °C provokes a mineralogical transformation on carbonate-rich porcelanite samples. The opal CT transforms to opal C and becomes neater and more stable. The Thermal treatment of porcelanite (Tm1) incites also the apparition of new peaks of wollastonite. However, the structural change of opal CT to opal C by heat treatment is blocked for flux calcination of clay-rich porcelanite. The opal CT of fluxing clay-rich porcelanite becomes more ordered without significant change to opal C. The difference between fluxing carbonate-rich porcelanite (Tm1) and fluxing clay-rich porcelanite (Gh) appears also with granulometric distribution histogram of the tow heated samples. All raw samples have unimodal granulometric distribution (1-100 μm). After calcination with alkaline flux at 1000 °C fluxing carbonate-rich porcelanite displays bimodal granulometric distribution and a new mode appears systematically, between 0.1 μm and 1 μm. This occurs for fluxing silica-riche porcelanite and diatomaceous filtration aids as well and corresponds to the opal C formed after heat treatment. Whereas fluxing clay-rich porcelanite present trimodal granulometric distribution and a third mode appears (100-300 μm), which due to silica glass phase. Since, the granulometric rearrangement of porcelanite during thermal treatment may due to mineralogical transformation of opal CT to opal C and crystal grow.

Phase Transformation and Aging Behavior of Al0.5CoCrFeNiSi0.2 High-Entropy Alloy

NASA Astrophysics Data System (ADS)

Zhang, C.; Wu, G. F.; Dai, P. Q.

2015-05-01

An Al0.5CoCrFeNiSi0.2 high-entropy alloy was prepared by vacuum arc melting. The alloy was aged from 700 to 1100 °C. The effects of aging on the phase transformation and mechanical performances were explored. The as-cast alloy showed a dendritic (DR) microstructure. The DR region was an Fe,Cr-rich FCC phase, while the interdendritic (ID) region was a spinodal structure composed of Fe,Cr-rich BCC (A2) and Ni,Al-rich BCC (B2) phases. At aging temperatures between 700 and 900 °C, the Fe,Cr-rich BCC (A2) phase in the ID region transformed into σ and Fe,Cr-rich FCC phases. Meanwhile, some Ni,Al-rich FCC phase particles precipitated from the DR region. During aging at 1100 °C, the DR microstructure disappeared, and a microstructure composed of Fe,Cr-rich FCC and Ni,Al-rich BCC (B2) phases both possessing a lamellar shape was developed. The alloy exhibited evident hardening and lower tensile strain when the aging temperature was lower than 1000 °C, which was mainly attributed to the generation of the σ phase in the ID region. However, a contrasting behavior was observed when the aging temperature was higher than 1000 °C, which was attributed to the redissolution of the σ phase and the microstructure coarsening.

Structure and Bonding of Carbon in Clays from CI Carbonaceous Chondrites

NASA Technical Reports Server (NTRS)

Garview, Laurence a. J.; Buseck, Peter R.

2005-01-01

Carbonaceous chondrites (CC) contain a diverse suite of C-rich materials. Acid dissolution of these meteorites leaves a C-rich residue with chemical and structural affinities to kerogen. This material has primarily been analyzed in bulk, and much information has been provided regarding functional groups and elemental and isotopic compositions. However, comparatively little work has been done on C in unprocessed meteorites. Studies of CCs suggest a spatial relationship of some C-rich materials with products of aqueous alteration. Recent studies revealed discrete submicronsized, C-rich particles in Tagish Lake and a range of CM2 meteorites. A challenge is to correlate the findings from the bulk acid-residue studies with those of high-spatial resolution-mineralogical and spectroscopic observations of unprocessed meteorites. Hence, the relationship between the C-rich materials in the acid residues and its form and locations in the unprocessed meteorite remains unclear. Here we provide information on the structure and bonding of C associated with clays in CI carbonaceous chondrites. Additional information is included in the original extended abstract.

Ca-Al-rich chondrules and inclusions in ordinary chondrites

NASA Technical Reports Server (NTRS)

Bischoff, A.; Keil, K.

1983-01-01

Ca-Al-rich objects, hitherto mostly found in carbonaceous chondrites, are shown to be widespread, albeit rare, constituents of type 3 ordinary chondrites. Widespread occurrence and textural similarities of Ca-Al-rich chondrules to common, Mg-Fe-rich chondrules suggest that they formed by related processes. It is suggested in this article that Ca-Al-rich chondrules were formed by total melting and crystallization of heterogeneous, submillimeter- to submillimeter-sized dustballs made up of mixtures of high-temperature, Ca-Al-rich and lower-temperature, Na-K-rich components.

PLATELET-RICH PLASMA IN ARTHROSCOPIC REPAIRS OF COMPLETE TEARS OF THE ROTATOR CUFF

PubMed Central

Malavolta, Eduardo Angeli; Gracitelli, Mauro Emilio Conforto; Sunada, Edwin Eiji; Benegas, Eduardo; de Santis Prada, Flavia; Neto, Raul Bolliger; Rodrigues, Marcelo Bordalo; Neto, Arnaldo Amado Ferreira; de Camargo, Olavo Pires

2015-01-01

Objective: To evaluate shoulder functional results and the retear rate of arthroscopic repair of the rotator cuff augmented with platelet-rich plasma (PRP).Methods: Prospective case series with single-row arthroscopic repair of the rotator cuff augmented with PRP. Only cases of isolated supraspinatus tears with retraction of less than 3 cm were included in this series. The PRP used was obtained by apheresis. It was applied on liquid consistency in its activated form, with the addition of autologous thrombin. Patients were evaluated after 12 months of the surgical procedure. The Constant-Murley, UCLA and VAS scales were used, and the retear rate was assessed using magnetic resonance imaging (MRI). Results: Fourteen patients were evaluated (14 shoulders). The mean Constant-Murley score was 45.64 ± 12.29 before the operation and evolved to 80.78 ± 13.22 after the operation (p < 0.001). The UCLA score increased from 13.78 ± 5.66 to 31.43 ± 3.9 (p < 0.001). The patients’ pain level decreased from a median of 7.5 (p25% = 6, p75% = 8) to 0.5 (p25% = 0, p75% = 3) (p = 0.0013) according to the VAS score. None of the patients presented complete retear. Three patients (21.4%) showed partial retear, without transfixation. Only one patient developed complications (adhesive capsulitis). Conclusion: Patients submitted to arthroscopic rotator cuff repair augmented with PRP showed significant functional improvement and none of them had complete retearing. PMID:27047894

The Two Components of the Evolved Massive Binary LZ Cephei: Testing the Effects of Binarity on Stellar Evolution

NASA Technical Reports Server (NTRS)

Mahy, L.; Martins, F.; Donati, J.-F.; Bouret, J.-C.

2011-01-01

We present an in-dep(h study of the two components of the binary system LZ Cep to constrain the effects of binarity on the evolution of massive stars. Methods. We analyzed a set of high-resolution, high signal-to-noise ratio optical spectra obtained over the orbital period of the system to perform a spectroscopic disentangling and derive an orbital solution. We subsequently determine the stellar properties of each component by means of an analysis with the CMFGEN atmosphere code. Finally, with the derived stellar parameters, we model the Hipparcos photometric light curve using the program NIGHTFALL to obtain the orbit inclination and the stellar masses. Results.LZ Cep is a O9III+ON9.7V binary. It is as a semi-detailed system in which either the primary or the secondary star almost fills up its Roche lobe. The dynamical masses are about 16.0 Stellar Mass (primary) and 6.5 Stellar Mass (secondary). The latter is lower than the typical mass of late-type O stars. The secondary component is chemically more evolved than the primary (which barely shows any sign of CNO processing), with strong helium and nitrogen enhancements as well as carbon and oxygen depletions. These properties (surface abundances and mass) are typical of Wolf-Rayet stars, although the spectral type is ON9.7V. The luminosity of the secondary is consistent with that of core He-burning objects. The preferred, tentative evolutionary scenario to explain abe observed properties involves mass transfer from the secondary - which was initially more massive- towards the primary. The secondary is now almost a core He-burning object, probably with only a thin envelope of H-rich and CNO processed material. A very inefficient mass transfer is necessary to explain the chemical appearance of the primary. Alternative scenarios are discussed but they are affected by greater uncertainties.

The two components of the evolved massive binary LZ Cephei. Testing the effects of binarity on stellar evolution

NASA Astrophysics Data System (ADS)

Mahy, L.; Martins, F.; Machado, C.; Donati, J.-F.; Bouret, J.-C.

2011-09-01

Aims: We present an in-depth study of the two components of the binary system LZ Cep to constrain the effects of binarity on the evolution of massive stars. Methods: We analyzed a set of high-resolution, high signal-to-noise ratio optical spectra obtained over the orbital period of the system to perform a spectroscopic disentangling and derive an orbital solution. We subsequently determine the stellar properties of each component by means of an analysis with the CMFGEN atmosphere code. Finally, with the derived stellar parameters, we model the Hipparcos photometric light curve using the program NIGHTFALL to obtain the orbit inclination and the stellar masses. Results: LZ Cep is a O 9III+ON 9.7V binary. It is as a semi-detached system in which either the primary or the secondary star almost fills up its Roche lobe. The dynamical masses are about 16.0 M⊙ (primary) and 6.5 M⊙ (secondary). The latter is lower than the typical mass of late-type O stars. The secondary component is chemically more evolved than the primary (which barely shows any sign of CNO processing), with strong helium and nitrogen enhancements as well as carbon and oxygen depletions. These properties (surface abundances and mass) are typical of Wolf-Rayet stars, although the spectral type is ON 9.7V. The luminosity of the secondary is consistent with that of core He-burning objects. The preferred, tentative evolutionary scenario to explain the observed properties involves mass transfer from the secondary - which was initially more massive- towards the primary. The secondary is now almost a core He-burning object, probably with only a thin envelope of H-rich and CNO processed material. A very inefficient mass transfer is necessary to explain the chemical appearance of the primary. Alternative scenarios are discussed but they are affected by greater uncertainties.

Probing the nature of cataclysmic variables via photometric studies on multiple timescales

NASA Astrophysics Data System (ADS)

Armstrong, Eve

I examine the structure and evolution of hydrogen- and helium-rich cataclysmic variables (CVs), via their periodic variability captured by long-term time series photometry. Studies to be discussed address one of two sets of question. One set pertains to helium CVs, which are poorly understood relative to their hydrogen-rich counterparts: What is the long-term evolution - in terms of orbital period (Porb) - of He CVs, and what does this imply about the nature of their secondaries? Two methods of investigation are employed: i) using systems with positive superhump and orbital period detections (Chapter 3) in order to chart the distribution of Porb versus time for He CVs (Chapter 4); ii) direct pulse timing of Porb in one system, via an 18-year baseline of photometry (Chapter 5). Results of the first study indicate that helium CVs are evolving toward longer Porb and have secondaries that are well described as degenerate objects. The pulse timing of one object (and the same measurement in two other He CVs) shows no evidence for Porb lengthening, and is consistent with Porb shortening driven by angular momentum loss via gravitational wave radiation. Technically, the two results are not inconsistent, as AM CVn is the only point on the distribution with a Porb timing. The apparent contradiction, however, illuminates our poor understanding of this class of CV: their routes to birth and the range of paths that a star can take following core hydrogen burning. The second set of studies pertains to signals associated with the accretion disc: Can a CV's accretion disc tilt with respect to the orbital plane? And what is the geometry and behavior of matter at various annuli in a tilted disc? To this end, I examine orbital sideband signals in AM CVn (Chapter 6) and simultaneous orbital sidebands and superorbital signals in two hydrogen CVs (Chapter 7). I also tabulate, from the literature, ten additional CVs with reliable detections of these signals (Chapter 7). All results indicate that the mechanism of tilt is at work in these objects.

Formation and Cross-Cumulus Migration of Silica-Rich Liquids in the Skaergaard Intrusion, East Greenland

NASA Astrophysics Data System (ADS)

Larsen, R. B.; Sorensen, B. E.; Muller, A.

2008-12-01

In a recent publication on the Skaergaard intrusion evidence for the formation of silica-rich melts by silicate- silicate liquid immiscibility was proposed (Jakobsen et al., Geology 33, 2005). Coexisting iron-rich and silica- rich microscopic melt inclusions were trapped in apatite during crystallisation of the Skaergaard melts. Given this evidence for liquid immiscibility it is possible to explain the formation of macroscopic accumulations of silica rich entities throughout the magmatic stratigraphy. Previously, the formation and emplacement of these granophyric entities were challenging to explain. Examples include decimetre to metre size granophyric /melano-granophyric aggregates in either gabbroic pegmatite, in chimney shaped columns intersecting the layering or in isolated pods. Particularly, the presence of numerous granophyric pods a few metres above large gabbroic pegmatite were enigmatic. Moving the granophyric melts from the pegmatite where they formed (Larsen and Brooks, Journal of Petrology 35, 1994) and several metres across the magmatic stratigraphy would require unconsolidated cumulates i.e. a crystal mush. Geothermobarometric estimates from fluid inclusions, amphibole and feldspars show that the silica-rich aggregations solidified between 900 and 660 C at P from 1.8 to 2.9 kb. However, to be true products of liquid immiscibility they should form at T > 1050 C. With an average of 960 ppm Zr, the silica-rich aggregates are extremely Zr rich. Zr saturation thermometry imply minimum T's of 1070 (c. 2000 ppm Zr) to 900 C (c. 700 ppm Zr). Ti in Zr thermometry is progressing and may further constrain the T of formation. Although large uncertainties apply, a T of 1070 C or higher, would agree with a formation by liquid immiscibility. Assuming T > 1070 C the cumulus stratigraphy was unconsolidated with > 30 vol% intercumulus melts in the lower part of the magmachamber. With a density of 2.4-2.6 g/cm3, the silica-rich melts were much lighter than the ambient mush (c. 3.2 g/cm3) and may have migrated diapirically and/or along syn-magmatic semi-ductile fault systems (as observed in Lower Zone c and the Middle Zone). With an onset of silica-rich melt migration at T > 1070 C in the Lower Zone, large proportions of the magma chamber was molten and, at least theoretically, it was possible to reintroduce the silica-rich melts in the convecting magma. 19 chimney shaped structures of granophyric and melano-granophyric rocks in MZ with diameters of 2-5 metres, imply that the transfer of silica-rich melts was not only a trivial matter but substantially may have interacted with the cumulates they transgressed or the ambient convecting melt if they migrated this far.

Phoenix Lander's Thermal Evolved Gas Analyzer: Differential Scanning Calorimeter and Mass Spectrometer Database Development

NASA Technical Reports Server (NTRS)

Sutter, B.; Lauer, H. V.; Golden, D. C.; Ming, D. W.; Boynton, W. V.

2008-01-01

The Mars Scout Phoenix lander will land in the north polar region of Mars in May, 2008. One objective of the Phoenix lander is to search for evidence of past life in the form of molecular organics that may be preserved in the subsurface soil. The Thermal Evolved Gas Analyzer (TEGA) was developed to detect these organics by coupling a simultaneous differential thermal analyzer (SDTA) with a mass spectrometer. Martian soil will be heated to approx.1000 C and potential organic decomposition products such as CO2, CH4 etc. will be examined for with the MS. TEGA s SDTA will also assess the presence of endothermic and exothermic reactions that are characteristic of soil organics and minerals as the soil is heated. The MS in addition to detecting organic decompositon products, will also assess the levels of soil inorganic volatiles such as H2O, SO2, and CO2. Organic detection has a high priority for this mission; however, TEGA has the ability to provide valuable insight into the mineralogical composition of the soil. The overall goal of this work is to develop a TEGA database of minerals that will serve as a reference for the interpretation of Phoenix-TEGA. Previous databases for the ill-fated Mars Polar Lander (MPL)-TEGA instrument only went to 725 C. Furthermore, the MPL-TEGA could only detect CO2 and H2O while the Phoenix-TEGA MS can examine up to 144 atomic mass units. The higher temperature Phoenix-TEGA SDTA coupled with the more capable MS indicates that a higher temperature database is required for TEGA interpretation. The overall goal of this work is to develop a differential scanning calorimeter (DSC) database of minerals along with corresponding MS data of evolved gases that can used to interpret TEGA data during and after mission operations. While SDTA and DSC measurement techniques are slightly different (SDTA does not use a reference pan), the results are fundamentally similar and thus DSC is a useful technique in providing comparative data for the TEGA database. The objectives of this work is to conduct DSC and MS analysis up to 1000 C of select minerals that may be found in the martian soil.

Functional C-TERMINALLY ENCODED PEPTIDE (CEP) plant hormone domains evolved de novo in the plant parasite Rotylenchulus reniformis.

PubMed

Eves-Van Den Akker, Sebastian; Lilley, Catherine J; Yusup, Hazijah B; Jones, John T; Urwin, Peter E

2016-10-01

Sedentary plant-parasitic nematodes (PPNs) induce and maintain an intimate relationship with their host, stimulating cells adjacent to root vascular tissue to re-differentiate into unique and metabolically active 'feeding sites'. The interaction between PPNs and their host is mediated by nematode effectors. We describe the discovery of a large and diverse family of effector genes, encoding C-TERMINALLY ENCODED PEPTIDE (CEP) plant hormone mimics (RrCEPs), in the syncytia-forming plant parasite Rotylenchulus reniformis. The particular attributes of RrCEPs distinguish them from all other CEPs, regardless of origin. Together with the distant phylogenetic relationship of R. reniformis to the only other CEP-encoding nematode genus identified to date (Meloidogyne), this suggests that CEPs probably evolved de novo in R. reniformis. We have characterized the first member of this large gene family (RrCEP1), demonstrating its significant up-regulation during the plant-nematode interaction and expression in the effector-producing pharyngeal gland cell. All internal CEP domains of multi-domain RrCEPs are followed by di-basic residues, suggesting a mechanism for cleavage. A synthetic peptide corresponding to RrCEP1 domain 1 is biologically active and capable of up-regulating plant nitrate transporter (AtNRT2.1) expression, whilst simultaneously reducing primary root elongation. When a non-CEP-containing, syncytia-forming PPN species (Heterodera schachtii) infects Arabidopsis in a CEP-rich environment, a smaller feeding site is produced. We hypothesize that CEPs of R. reniformis represent a two-fold adaptation to sustained biotrophy in this species: (i) increasing host nitrate uptake, whilst (ii) limiting the size of the syncytial feeding site produced. © 2016 The Authors. Molecular Plant Pathology Published by British Society for Plant Pathology and John Wiley & Sons Ltd.

Multiple photosynthetic transitions, polyploidy, and lateral gene transfer in the grass subtribe Neurachninae

PubMed Central

Ludwig, Martha

2012-01-01

The Neurachninae is the only grass lineage known to contain C3, C4, and C3–C4 intermediate species, and as such has been suggested as a model system for studies of photosynthetic pathway evolution in the Poaceae; however, a lack of a robust phylogenetic framework has hindered this possibility. In this study, plastid and nuclear markers were used to reconstruct evolutionary relationships among Neurachninae species. In addition, photosynthetic types were determined with carbon isotope ratios, and genome sizes with flow cytometry. A high frequency of autopolyploidy was found in the Neurachninae, including in Neurachne munroi F.Muell. and Paraneurachne muelleri S.T.Blake, which independently evolved C4 photosynthesis. Phylogenetic analyses also showed that following their separate C4 origins, these two taxa exchanged a gene encoding the C4 form of phosphoenolpyruvate carboxylase. The C3–C4 intermediate Neurachne minor S.T.Blake is phylogenetically distinct from the two C4 lineages, indicating that intermediacy in this species evolved separately from transitional stages preceding C4 origins. The Neurachninae shows a substantial capacity to evolve new photosynthetic pathways repeatedly. Enablers of these transitions might include anatomical pre-conditions in the C3 ancestor, and frequent autopolyploidization. Transfer of key C4 genetic elements between independently evolved C4 taxa may have also facilitated a rapid adaptation of photosynthesis in these grasses that had to survive in the harsh climate appearing during the late Pliocene in Australia. PMID:23077201

Multiple photosynthetic transitions, polyploidy, and lateral gene transfer in the grass subtribe Neurachninae.

PubMed

Christin, Pascal-Antoine; Wallace, Mark J; Clayton, Harmony; Edwards, Erika J; Furbank, Robert T; Hattersley, Paul W; Sage, Rowan F; Macfarlane, Terry D; Ludwig, Martha

2012-10-01

The Neurachninae is the only grass lineage known to contain C(3), C(4), and C(3)-C(4) intermediate species, and as such has been suggested as a model system for studies of photosynthetic pathway evolution in the Poaceae; however, a lack of a robust phylogenetic framework has hindered this possibility. In this study, plastid and nuclear markers were used to reconstruct evolutionary relationships among Neurachninae species. In addition, photosynthetic types were determined with carbon isotope ratios, and genome sizes with flow cytometry. A high frequency of autopolyploidy was found in the Neurachninae, including in Neurachne munroi F.Muell. and Paraneurachne muelleri S.T.Blake, which independently evolved C(4) photosynthesis. Phylogenetic analyses also showed that following their separate C(4) origins, these two taxa exchanged a gene encoding the C(4) form of phosphoenolpyruvate carboxylase. The C(3)-C(4) intermediate Neurachne minor S.T.Blake is phylogenetically distinct from the two C(4) lineages, indicating that intermediacy in this species evolved separately from transitional stages preceding C(4) origins. The Neurachninae shows a substantial capacity to evolve new photosynthetic pathways repeatedly. Enablers of these transitions might include anatomical pre-conditions in the C(3) ancestor, and frequent autopolyploidization. Transfer of key C(4) genetic elements between independently evolved C(4) taxa may have also facilitated a rapid adaptation of photosynthesis in these grasses that had to survive in the harsh climate appearing during the late Pliocene in Australia.

Transmission spectroscopy of the hot Jupiter WASP-12b from 0.7 to 5 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stevenson, Kevin B.; Bean, Jacob L.; Seifahrt, Andreas

2014-06-01

Since the first report of a potentially non-solar carbon-to-oxygen ratio (C/O) in its dayside atmosphere, the highly irradiated exoplanet WASP-12b has been under intense scrutiny and the subject of many follow-up observations. Additionally, the recent discovery of stellar binary companions ∼1'' from WASP-12 has obfuscated interpretation of the observational data. Here we present new ground-based multi-object transmission-spectroscopy observations of WASP-12b that we acquired over two consecutive nights in the red optical with Gemini-N/GMOS. After correcting for the influence of WASP-12's stellar companions, we find that these data rule out a cloud-free H{sub 2} atmosphere with no additional opacity sources. Wemore » detect features in the transmission spectrum that may be attributed to metal oxides (such as TiO and VO) for an O-rich atmosphere or to metal hydrides (such as TiH) for a C-rich atmosphere. We also reanalyzed NIR transit-spectroscopy observations of WASP-12b from HST/WFC3 and broadband transit photometry from Warm Spitzer. We attribute the broad spectral features in the WFC3 data to either H{sub 2}O or CH{sub 4} and HCN for an O-rich or C-rich atmosphere, respectively. The Spitzer data suggest shallower transit depths than the models predict at infrared wavelengths, albeit at low statistical significance. A multi-instrument, broad-wavelength analysis of WASP-12b suggests that the transmission spectrum is well approximated by a simple Rayleigh scattering model with a planet terminator temperature of 1870 ± 130 K. We conclude that additional high-precision data and isolated spectroscopic measurements of the companion stars are required to place definitive constraints on the composition of WASP-12b's atmosphere.« less

Genetic analysis of 430 Chinese Cynodon dactylon accessions using sequence-related amplified polymorphism markers.

PubMed

Huang, Chunqiong; Liu, Guodao; Bai, Changjun; Wang, Wenqiang

2014-10-21

Although Cynodon dactylon (C. dactylon) is widely distributed in China, information on its genetic diversity within the germplasm pool is limited. The objective of this study was to reveal the genetic variation and relationships of 430 C. dactylon accessions collected from 22 Chinese provinces using sequence-related amplified polymorphism (SRAP) markers. Fifteen primer pairs were used to amplify specific C. dactylon genomic sequences. A total of 481 SRAP fragments were generated, with fragment sizes ranging from 260-1800 base pairs (bp). Genetic similarity coefficients (GSC) among the 430 accessions averaged 0.72 and ranged from 0.53-0.96. Cluster analysis conducted by two methods, namely the unweighted pair-group method with arithmetic averages (UPGMA) and principle coordinate analysis (PCoA), separated the accessions into eight distinct groups. Our findings verify that Chinese C. dactylon germplasms have rich genetic diversity, which is an excellent basis for C. dactylon breeding for new cultivars.

The early development and evolution of the human brain.

PubMed

Crawford, M A

1990-01-01

THE CHEMISTRY OF THE BRAIN: The brain and nervous system is characterised by a heavy investment in lipid chemistry which accounts for up to 60% of its structural material. In the different mammalian species so far studied, only the 20 and 22 carbon chain length polyenoic fatty acids were present and the balance of the n-3 to n-6 fatty acids was consistently 1:1. The difference observed between species, was not in the chemistry but in the extent to which the brain is developed. This paper discusses the possibility that essential fatty acids may have played a part in it evolution. THE ORIGIN OF AIR BREATHING ANIMALS: The first phase of the planet's existence indulged in high temperature reactions in which oxygen combined with everything feasible: from silicon to make rocks to hydrogen to make water. Once the planet's temperature dropped to a point at which water could condense on the surface allowing chemical reactions to take place in it. The atmosphere was at that time devoid of oxygen so life evolved in a reducing atmosphere. Oxygen was liberated by photolysis of water and as a by-product of the blue-green algae through photosynthesis. When the point was reached at which oxidative metabolism became thermodynamically possible, animal life evolved with all the principle phyla establishing themselves within a relatively short space of geological time. (Bernal 1973). DHA and nerve cell membranes DHA AND NERVE CELL MEMBRANES: From the chemistry of contemporary algae it is likely that animal life evolved in an n-3 rich environment although not exclusively so as smaller amounts of n-6 fatty acids would have been present. A key feature of the first animals was the evolution of the photoreceptor: in examples of marine, amphibian and modern mammalian species, it has been found to use docosahexaenoic acid (DHA) as the principle membrane fatty acid in the phosphoglycerides. It is likely that the first animals did so as well. Coincidentally, the synaptic membranes involved in signal transduction also use high proportions of n-3 fatty acids. However, the n-6 fatty acids also find a place, in the inositol phosphoglyceride (IPG) which appears to be involved with calcium ion transport and hence signal activation and reception. Even in the photoreceptor, the IPG is an arachidonic acid rich phosphoglyceride. THE EVOLUTION OF MAMMALS AND THE LARGE BRAIN: The dominance of n-3 fatty acids in the food chain, persisted until the end of the Cretaceous period when the flowering plants followed on the disappearance of the giant cycads and ferns. A new set of species, the mammals, then evolved with a requirement for n-6 fatty acids for reproduction. This dependance was coincident with the flowering plants which for the first time produced protected seeds: these introduced a rich source of n-6 fatty acids. The brain size of the mammals tended to be relatively larger (that is in relation to body size) by comparison with the previous reptilian or egg laying systems. This process led to the large human brain. A crucial difference between man and other animals, is undoubtedly the extent to which the brain and its peripheral attributes have been developed. This paper will address the possibility that the potential for the evolution of the large human brain may have been released by the evolving human primate occupying an ecological niche which offered a rich source of those nutrients specifically required for the brain. That niche is at the land/water interface.

"A Richness Study of 14 Distant X-Ray Clusters from the 160 Square Degree Survey"

NASA Technical Reports Server (NTRS)

Jones, Christine; West, Donald (Technical Monitor)

2001-01-01

We have measured the surface density of galaxies toward 14 X-ray-selected cluster candidates at redshifts z(sub i) 0.46, and we show that they are associated with rich galaxy concentrations. These clusters, having X-ray luminosities of Lx(0.5-2 keV) approx. (0.5 - 2.6) x 10(exp 44) ergs/ sec are among the most distant and luminous in our 160 deg(exp 2) ROSAT Position Sensitive Proportional Counter cluster survey. We find that the clusters range between Abell richness classes 0 and 2 and have a most probable richness class of 1. We compare the richness distribution of our distant clusters to those for three samples of nearby clusters with similar X-ray luminosities. We find that the nearby and distant samples have similar richness distributions, which shows that clusters have apparently not evolved substantially in richness since redshift z=0.5. There is, however, a marginal tendency for the distant clusters to be slightly poorer than nearby clusters, although deeper multicolor data for a large sample would be required to confirm this trend. We compare the distribution of distant X-ray clusters in the L(sub X)-richness plane to the distribution of optically selected clusters from the Palomar Distant Cluster Survey. The optically selected clusters appear overly rich for their X-ray luminosities, when compared to X-ray-selected clusters. Apparently, X-ray and optical surveys do not necessarily sample identical mass concentrations at large redshifts. This may indicate the existence of a population of optically rich clusters with anomalously low X-ray emission, More likely, however, it reflects the tendency for optical surveys to select unvirialized mass concentrations, as might be expected when peering along large-scale filaments.

The El Teniente porphyry Cu-Mo deposit from a hydrothermal rutile perspective

NASA Astrophysics Data System (ADS)

Rabbia, Osvaldo M.; Hernández, Laura B.; French, David H.; King, Robert W.; Ayers, John C.

2009-11-01

Mineralogical, textural, and chemical analyses (EPMA and PIXE) of hydrothermal rutile in the El Teniente porphyry Cu-Mo deposit help to better constrain ore formation processes. Rutile formed from igneous Ti-rich phases (sphene, biotite, Ti-magnetite, and ilmenite) by re-equilibration and/or breakdown under hydrothermal conditions at temperatures ranging between 400°C and 700°C. Most rutile nucleate and grow at the original textural position of its Ti-rich igneous parent mineral phase. The distribution of Mo content in rutile indicates that low-temperature (˜400-550°C), Mo-poor rutile (5.4 ± 1.1 ppm) is dominantly in the Mo-rich mafic wallrocks (high-grade ore), while high-temperature (˜550-700°C), Mo-rich rutile (186 ± 20 ppm) is found in the Mo-poor felsic porphyries (low-grade ore). Rutile from late dacite ring dikes is a notable exception to this distribution pattern. The Sb content in rutile from the high-temperature potassic core of the deposit to its low-temperature propylitic fringe remains relatively constant (35 ± 3 ppm). Temperature and Mo content of the hydrothermal fluids in addition to Mo/Ti ratio, modal abundance and stability of Ti-rich parental phases are key factors constraining Mo content and provenance in high-temperature (≥550°C) rutile. The initial Mo content of parent mineral phases is controlled by melt composition and oxygen fugacity as well as timing and efficiency of fluid-melt separation. Enhanced reduction of SO2-rich fluids and sulfide deposition in the Fe-rich mafic wallrocks influences the low-temperature (≤550°C) rutile chemistry. The data are consistent with a model of fluid circulation of hot (>550°C), oxidized (ƒO2 ≥ NNO + 1.3), SO2-rich and Mo-bearing fluids, likely exsolved from deeper crystallizing parts of the porphyry system and fluxed through the upper dacite porphyries and related structures, with metal deposition dominantly in the Fe-rich mafic wallrocks.

Cl-rich hydrous mafic mineral assemblages in the Highiș massif, Apuseni Mountains, Romania

NASA Astrophysics Data System (ADS)

Bonin, Bernard; Tatu, Mihai

2016-08-01

The Guadalupian (Mid-Permian) Highiș massif (Apuseni Mountains, Romania) displays a bimodal igneous suite of mafic (gabbro, diorite) and A-type felsic (alkali feldspar granite, albite granite, and hybrid granodiorite) rocks. Amphibole is widespread throughout the suite, and yields markedly high chlorine contents. Three groups are identified: Cl-rich potassic hastingsite (2.60-3.40 wt% Cl) within A-type felsic rocks and diorite, mildly Cl-rich pargasite to hornblende (0.80-1.90 wt% Cl) within gabbro, and low F-Cl hornblende within gabbro and hybrid granodiorite. Coexisting biotite is either Cl-rich within diorite, or F-Cl-poor to F-rich within A-type felsic rocks. Chlorine and fluorine are distributed in both mafic phases, according to the F-Fe and Cl-Mg avoidance rules. The low-Ti contents suggest subsolidus compositions. Cl-rich amphibole within diorite and A-type felsic rocks yields a restricted temperature range - from 575 °C down to 400 °C, whereas mildly Cl-rich amphibole within gabbro displays the highest range - from 675 to 360 °C. Temperatures recorded by Cl-rich biotite within diorite range from 590 to 410 °C. Biotite within A-type felsic rocks yields higher temperatures than amphibole: the highest values- from 640 to 540 °C - are recorded in low-F-Cl varieties, whereas the lowest values- from 535 to 500 °C - are displayed by F-rich varieties. All data point to halogen-rich hydrothermal fluids at upper greenschist facies conditions percolating through fractures and shear zones and pervasively permeating the whole Highiș massif, with F precipitating as interstitial fluorite and Cl incorporating into amphibole, during one, or possibly several, hydrothermal episodes that would have occurred during a ~ 150 My-long period of time extending from the Guadalupian (Mid-Permian) to the Albian (Mid-Cretaceous).

Greater enrichment of triacylglycerol-rich lipoproteins with apolipoproteins E and C-III after meals rich in saturated fatty acids than after meals rich in unsaturated fatty acids.

PubMed

Jackson, Kim G; Wolstencroft, Emma J; Bateman, Paul A; Yaqoob, Parveen; Williams, Christine M

2005-01-01

Although there is considerable interest in the postprandial events involved in the absorption of dietary fats and the subsequent metabolism of diet-derived triacylglycerol-rich lipoproteins, little is known about the effects of meal fatty acids on the composition of these particles. We examined the effect of meal fatty acids on the lipid and apolipoprotein contents of triacylglycerol-rich lipoproteins. Ten normolipidemic men received in random order a mixed meal containing 50 g of a mixture of palm oil and cocoa butter [rich in saturated fatty acids (SFAs)], safflower oil [n-6 polyunsaturated fatty acids (PUFAs)], or olive oil [monounsaturated fatty acids (MUFAs)] on 3 occasions. Fasting and postprandial apolipoproteins B-48, B-100, E, C-II, and C-III and lipids (triacylglycerol and cholesterol) were measured in plasma fractions with Svedberg flotation rates (S(f)) >400, S(f) 60-400, and S(f) 20-60. Calculation of the composition of the triacylglycerol-rich lipoproteins (expressed per mole of apolipoprotein B) showed notable differences in the lipid and apolipoprotein contents of the SFA-enriched particles in the S(f) > 400 and S(f) 60-400 fractions. After the SFA meal, triacylglycerol-rich lipoproteins in these fractions showed significantly greater amounts of triacylglycerol and of apolipoproteins C-II (S(f) 60-400 fraction only), C-III, and E than were found after the MUFA meal (P < 0.02) and more cholesterol, apolipoprotein C-III (S(f) > 400 fraction only), and apolipoprotein E than after the PUFA meal (P < 0.02). Differences in the composition of S(f) > 400 and S(f) 60-400 triacylglycerol-rich lipoproteins formed after saturated compared with unsaturated fatty acid-rich meals may explain differences in the metabolic handling of dietary fats.

The acquisition of socio-motor improvisation in the mirror game.

PubMed

Gueugnon, Mathieu; Salesse, Robin N; Coste, Alexandre; Zhao, Zhong; Bardy, Benoît G; Marin, Ludovic

2016-04-01

Socio-motor improvisation is defined as the creative action of two or more people without a script or anticipated preparation. It is evaluated through two main parameters: movement synchronization and movement richness. Experts in art (e.g., dance, theater or music) are known to exhibit higher synchronization and to perform richer movements during interpersonal improvisation, but how these competences evolve over time is largely unknown. In the present study, we investigated whether performing more synchronized and richer movements over time can promote the acquisition of improvisation. Pairs of novice participants were instructed to play an improvisation mirror game in three different sessions. Between sessions, they performed an unintended interpersonal coordination task in which synchronization and richness were manipulated, resulting in four different groups of dyads. Our results demonstrate that synchronization during improvisation improved for all groups whereas movement richness only enhanced for dyads that performed synchronized movements during unintended coordination tasks. Our findings suggest that movement synchrony contributes more than movement richness to the acquisition of socio-motor improvisation in the mirror game. Copyright © 2015 Elsevier B.V. All rights reserved.

Fragments of quartz monzodiorite and felsite in Apollo 14 soil particles

NASA Technical Reports Server (NTRS)

Jolliff, B. L.

1991-01-01

Samples of 'evolved' lithologies, felsite, quartz monzodiorite (QMD), and whitlockite-rich quartz monzodiorite, were identified compositionally and petrographically among 2-4-mm soil particles from Apollo 14. Fragments of QMD were found to be extremely rare in the Apollo 14 samples. Felsite is similar to previously reported samples. QMD 14161,7069 is similar to 15405 QMD and has ITE concentrations in KREEP-like concentration ratios of about twice the ITE concentrations of average high-K KREEP. QMD cumulate has the highest measured REE concentrations of any lunar sample to date with the exception of individual whitlockite grains. Felsite and whitlockite-rich lithologies appear to be petrogenetically related and have complementary compositions representing separated fractions of the QMD or KREEP-like parental melt. Felsite is a silica-rich fraction of the residual liquid or it is a derivative of the silica-rich fraction. Felsite or lunar granite of this type results from residual liquid separation following crystal-liquid separation of a QMD-like parent melt with concentration ratios of ITEs similar to those of KREEP.

Adiponectin Gene Variants Are Associated with Insulin Sensitivity in Response to Dietary Fat Consumption in Caucasian Men2

PubMed Central

Pérez-Martínez, Pablo; López-Miranda, José; Cruz-Teno, Cristina; Delgado-Lista, Javier; Jiménez-Gómez, Yolanda; Fernández, Juan Marcelo; Gómez, Maria José; Marín, Carmen; Pérez-Jiménez, Francisco; Ordovás, José María

2008-01-01

Adiponectin (adipoQ) gene variants have been associated with type 2 diabetes mellitus and insulin resistance. Our aim was to examine whether the presence of several polymorphisms at the adipoQ gene locus (-11391 G > A, 11377 C > G, 45 T > G, and 276 G > T) influences the insulin sensitivity to dietary fat. Healthy volunteers (30 men and 29 women) consumed 3 diets for 4 wk each: an initial period during which all subjects consumed a SFA-rich diet (38% total fat, 20% SFA), followed by a carbohydrate-rich diet (CHO) (30% total fat, 55% carbohydrate) or a monounsaturated fatty acid (MUFA)-rich diet (38% total fat, 22% MUFA) following a randomized, crossover design. After participants consumed each diet, we tested peripheral insulin sensitivity with the insulin suppression test and measured plasma adiponectin concentrations. C/C homozygous men for the -11377 C > G single nucleotide polymorphism (SNP) had a significantly greater decrease in the steady-state plasma glucose concentrations when changing from the SFA-rich (8.95 ± 0.6 mmol/L) to the MUFA-rich (6.04 ± 0.31 mmol/L) and CHO-rich (6.35 ± 0.38 mmol/L) diets than did those carrying the minor G allele (SFA, 6.65 ± 0.4 mmol/L; MUFA, 6.45 ± 0.4 mmol/L; CHO, 5.83 ± 0.3 mmol/L) (P sex × gene × diet interaction = 0.016). These differences did not occur in female participants. Furthermore, C/C men had lower plasma adiponectin concentrations than did C/C women (P sex × gene interaction = 0.015), independently of the dietary fat consumed. None of the variables examined were significantly associated with -11426 A > G, 45T > G, or 276 G > T SNP. In conclusion, C/C homozygous men for the -11377 C > G SNP at adipoQ gene were significantly less insulin resistant after consumption of the MUFA- and CHO-rich diets compared with the SFA-rich diet. This information should help in the identification of vulnerable populations or persons who will benefit from more personalized and mechanism-based dietary recommendations. PMID:18716158

Secretome weaponries of Cochliobolus lunatus interacting with potato leaf at different temperature regimes reveal a CL[xxxx]LHM - motif

PubMed Central

2014-01-01

Background Plant and animal pathogenic fungus Cochliobolus lunatus cause great economic damages worldwide every year. C. lunatus displays an increased temperature dependent-virulence to a wide range of hosts. Nonetheless, this phenomenon is poorly understood due to lack of insights on the coordinated secretome weaponries produced by C. lunatus under heat-stress conditions on putative hosts. To understand the mechanism better, we dissected the secretome of C. lunatus interacting with potato (Solanum tuberosum L.) leaf at different temperature regimes. Results C. lunatus produced melanized colonizing hyphae in and on potato leaf, finely modulated the ambient pH as a function of temperature and secreted diverse set of proteins. Using two dimensional gel electrophoresis (2-D) and mass spectrometry (MS) technology, we observed discrete secretomes at 20°C, 28°C and 38°C. A total of 21 differentially expressed peptide spots and 10 unique peptide spots (that did not align on the gels) matched with 28 unique protein models predicted from C. lunatus m118 v.2 genome peptides. Furthermore, C. lunatus secreted peptides via classical and non-classical pathways related to virulence, proteolysis, nucleic acid metabolism, carbohydrate metabolism, heat stress, signal trafficking and some with unidentified catalytic domains. Conclusions We have identified a set of 5 soluble candidate effectors of unknown function from C. lunatus secretome weaponries against potato crop at different temperature regimes. Our findings demonstrate that C. lunatus has a repertoire of signature secretome which mediates thermo-pathogenicity and share a leucine rich “CL[xxxx]LHM”-motif. Considering the rapidly evolving temperature dependent-virulence and host diversity of C. lunatus, this data will be useful for designing new protection strategies. PMID:24650331

Secretome weaponries of Cochliobolus lunatus interacting with potato leaf at different temperature regimes reveal a CL[xxxx]LHM - motif.

PubMed

Louis, Bengyella; Waikhom, Sayanika Devi; Roy, Pranab; Bhardwaj, Pardeep Kumar; Singh, Mohendro Wakambam; Goyari, Sailendra; Sharma, Chandradev K; Talukdar, Narayan Chandra

2014-03-20

Plant and animal pathogenic fungus Cochliobolus lunatus cause great economic damages worldwide every year. C. lunatus displays an increased temperature dependent-virulence to a wide range of hosts. Nonetheless, this phenomenon is poorly understood due to lack of insights on the coordinated secretome weaponries produced by C. lunatus under heat-stress conditions on putative hosts. To understand the mechanism better, we dissected the secretome of C. lunatus interacting with potato (Solanum tuberosum L.) leaf at different temperature regimes. C. lunatus produced melanized colonizing hyphae in and on potato leaf, finely modulated the ambient pH as a function of temperature and secreted diverse set of proteins. Using two dimensional gel electrophoresis (2-D) and mass spectrometry (MS) technology, we observed discrete secretomes at 20°C, 28°C and 38°C. A total of 21 differentially expressed peptide spots and 10 unique peptide spots (that did not align on the gels) matched with 28 unique protein models predicted from C. lunatus m118 v.2 genome peptides. Furthermore, C. lunatus secreted peptides via classical and non-classical pathways related to virulence, proteolysis, nucleic acid metabolism, carbohydrate metabolism, heat stress, signal trafficking and some with unidentified catalytic domains. We have identified a set of 5 soluble candidate effectors of unknown function from C. lunatus secretome weaponries against potato crop at different temperature regimes. Our findings demonstrate that C. lunatus has a repertoire of signature secretome which mediates thermo-pathogenicity and share a leucine rich "CL[xxxx]LHM"-motif. Considering the rapidly evolving temperature dependent-virulence and host diversity of C. lunatus, this data will be useful for designing new protection strategies.

Mitochondrial complex I bridges a connection between regulation of carbon flexibility and gastrointestinal commensalism in the human fungal pathogen Candida albicans

PubMed Central

Yu, Xiaoyu; Li, Shanshan; Gao, Ning; Niu, Lida; Wang, Yuanyuan; Wu, Xianwei; Wu, Wenjuan; Wu, Jianhua; Zhou, Dongsheng; Zhan, Xiangjiang

2017-01-01

Efficient assimilation of alternative carbon sources in glucose-limited host niches is critical for colonization of Candida albicans, a commensal yeast that frequently causes opportunistic infection in human. C. albicans evolved mechanistically to regulate alternative carbon assimilation for the promotion of fungal growth and commensalism in mammalian hosts. However, this highly adaptive mechanism that C. albicans employs to cope with alternative carbon assimilation has yet to be clearly understood. Here we identified a novel role of C. albicans mitochondrial complex I (CI) in regulating assimilation of alternative carbon sources such as mannitol. Our data demonstrate that CI dysfunction by deleting the subunit Nuo2 decreases the level of NAD+, downregulates the NAD+-dependent mannitol dehydrogenase activity, and consequently inhibits hyphal growth and biofilm formation in conditions when the carbon source is mannitol, but not fermentative sugars like glucose. Mannitol-dependent morphogenesis is controlled by a ROS-induced signaling pathway involving Hog1 activation and Brg1 repression. In vivo studies show that nuo2Δ/Δ mutant cells are severely compromised in gastrointestinal colonization and the defect can be rescued by a glucose-rich diet. Thus, our findings unravel a mechanism by which C. albicans regulates carbon flexibility and commensalism. Alternative carbon assimilation might represent a fitness advantage for commensal fungi in successful colonization of host niches. PMID:28570675

Growing GaN LEDs on amorphous SiC buffer with variable C/Si compositions

PubMed Central

Cheng, Chih-Hsien; Tzou, An-Jye; Chang, Jung-Hung; Chi, Yu-Chieh; Lin, Yung-Hsiang; Shih, Min-Hsiung; Lee, Chao-Kuei; Wu, Chih-I; Kuo, Hao-Chung; Chang, Chun-Yen; Lin, Gong-Ru

2016-01-01

The epitaxy of high-power gallium nitride (GaN) light-emitting diode (LED) on amorphous silicon carbide (a-SixC1−x) buffer is demonstrated. The a-SixC1−x buffers with different nonstoichiometric C/Si composition ratios are synthesized on SiO2/Si substrate by using a low-temperature plasma enhanced chemical vapor deposition. The GaN LEDs on different SixC1−x buffers exhibit different EL and C-V characteristics because of the extended strain induced interfacial defects. The EL power decays when increasing the Si content of SixC1−x buffer. The C-rich SixC1−x favors the GaN epitaxy and enables the strain relaxation to suppress the probability of Auger recombination. When the SixC1−x buffer changes from Si-rich to C-rich condition, the EL peak wavelengh shifts from 446 nm to 450 nm. Moreover, the uniform distribution contour of EL intensity spreads between the anode and the cathode because the traping density of the interfacial defect gradually reduces. In comparison with the GaN LED grown on Si-rich SixC1−x buffer, the device deposited on C-rich SixC1−x buffer shows a lower turn-on voltage, a higher output power, an external quantum efficiency, and an efficiency droop of 2.48 V, 106 mW, 42.3%, and 7%, respectively. PMID:26794268

SiO maser polarization in evolved stars: magnetic field

NASA Astrophysics Data System (ADS)

Herpin, F.; Baudry, A.; Thum, C.; Morris, D.; Wiesemeyer, H.

The maser theory still needs to be improved, in particular in terms of polarization. The study of the maser geometry inside the circumstellar envelopes can also be achieved through polarization studies (e.g., VLBI observations). But the most exciting point is the determination of the magnetic field that can be made from polarization measurements: this is definitively a new field of investigation for these evolved objects. The magnetic field probably plays an important role in the AGB star's life and can be a major factor (magnetic rotator theory) on the origin of the high mass loss rates observed in evolved objects. Measurement of the magnetic field is thus essential to study the mass loss mechanisms and also the Alfven waves. During its transition most quasi spherical AGB stars (i.e. envelopes) become complicated aspherical objects. This shaping is well explained by the Interacting Stellar Winds theory (Kwok works), but the ISW model fails to reproduce very complicated structures with jets and ansae. A new model (Magnetized Wind Blown Bubble theory) was thus developed by Blackman et al. (2001) and A. Franck: a weak toroidal magnetic field, embedded in the stellar wind, acts as a collimating agent (cf. Garcia-Segura 1997) and can produce such structures. Three molecules can show polarized maser emission in the circumstellar envelopes: - OH traces the envelope far from the central star (1000-10000 AU) - H2O at intermediate distances (a few 100 AU) - SiO in the inner circumstellar layers (5-10 AU) Measurement of the polarization rate of the maser radiation emitted by these molecules can give us the averaged value B// of the magnetic field along the line of sight (for a single dish observation). We present here the first complete study of the SiO maser polarization in a large sample of evolved stars (more than 100). The 4 Stokes parameters I, U, Q, V were simultaneously measured with the polarimeter on the IRAM-30m telescope. From the Stokes parameters values we derive the linear (pL) and circular (pC) polarization rates and polarization angle. The circular polarization rate gives us directly the magnetic field B//: B// varies from 1 to 32 Gauss depending on the source, with an average value of 9 Gauss.

Implication of the monomineral eclogite thermobarometry for the reconstruction of the PT conditions and origin of mantle eclogites in the structure of Siberian and other cratons.

NASA Astrophysics Data System (ADS)

Ashchepkov, Igor; Logvinova, Alla; Spetsius, Zdislav; Ntaflos, Theodoros; Ravi, Subramanaian; Vladykin, Nikolai; Stegnitsky, Yuri; Babushkina, Svetlana; Ovchinnikov, Yuri

2016-04-01

Enhanced monomineral thermobarometry for clinopyroxenes and garnet (Ashchepkov et al., 2015) allow reconstruction of thermal conditions for the mantle eclogitic xenoliths and xenocrysts of omphacites and pyrope almandine garnets of eclogitic and megacrystic types. Three common groups according to Dawson,(1977) A. Mg - eclogites; B. common subduction-related basaltic eclogites and C. Na-Fe- rich eclogites. In addition group D compile Ca-Al rich varieties (Spetsius et al., 2008; Viljoen et al., 2010). We subdivided these groups and their positions in mantle lithosphere sections beneath the most studied pipes in Yakutia and most interesting localities Worldwide. Group A including Al-rich and low groups are restites or cumulates from the ancient komatiitic basalts or boninites. The Fe# for olivine in equilibrium is 0.05 -0.11 using melt -solid partition coefficient ~0.33 for Fe (Albarede, 1992). For the group B Fe# of the omphacites are ~ 0.11- 0.23 and they could be only cumulates from melted subducted MORB basalts or reactional products. The higher values of Fe -Na-Al rich group C (Fe# ~0.25-0.4) could relate to the subducted basalts or Al - rich sediments (Spetsius et al., 2008) or Mg-rich crustal rocks which were subducted without much melting. Group D Ca-rich eclogites are commonly low Fe but subduction related varieties (Dongre et al., 2015) could be higher in Fe and Na. Partition coefficients of the trace elements between Gar and Cpx for most mantle eclogites relate to equilibration with the melts and REE patterns show different inclinations, while crustal eclogites which re-equilibrated in the solid state often show the same inclinations. Groups A1: a Cr-bearing group formed after crystallization of partial melts produced by volatile fluxes generated by ancient subduction (Heaman et al., 2006; Smart et al., 2009); A2 - low - Al cumulates and restites from komatiitic melts (Aulbach et al., 2011); A3 - low-Cr group which could be restites (Wyman and Kerrich, 2009) or deep cumulates from tonalite- trondhjemite or Mg-rich boninitic arc magmas (Horodytskyi et al., 2007; Barth et al., 2002); A4 a group derived by crystallization of differentiated protokimberlite melts (Haggerty et al., 1979; Kamenetsky et al., 2009). The largest group B with Fe# (~ 0.15-0.25, moderate in Al and Na values, commonly reveal Eu anomalies. The GrB1 interpreted as subducted metagrabbro close to MORB (Jagoutz et al., 1974; Beard et al., 1996; Pearson, 1995; Snyder et al., 1997) reacted with oceanic water (Neal et al., 1990). Enriched Group B2 eclogites are thought to be products of fluid melting of ancient oceanic crust and interaction with peridotites during subduction (Aulbach et al., 2007). Group B3 eclogites (>3 GPa) may be basaltic cumulates derived from plume or ancient arc magmas in cratonic margins (Wyman and Kerrich, 2009); those near Moho may be eclogitized lower crustal cumulates (Shu et al., 2014). Group B4 eclogites are results of hybridization of subducted basalts with protokimberlite and other plume melts (Shatsky et al., 2008 -2015). High-Fe -Na Group C1 eclogites (Fe# > 0.27) may be subducted Fe- basalts; Ca-enriched varieties may be meta-tonalites or trondhjemites (Group C2) (Barth et al., 2002) and those which are very rich in Al could be metasediments (Group C3) (Mazzone and Haggerty, 1989). High -Ca- Al GrD1 are rare high-Ca and low-Fe varieties, commonly Al-rich and kyanite-bearing (sometimes with coesite) (grosspydites) which may be originally carbonate metasomatites (Smyth, 1977) or metapelites (Liou et al., 2014); Group GrD3 eclogites are high-Ca and moderate-Fe and may be ancient Mg-granites (Barth et al., 2002; Jacob et al., 2003) . According to the thermobarometry GrA eclogites are distributed mostly in the lower (L) and- middle parts of SCLM and correspond to low - temperature thermal gradients. GrB2 eclogites form trends of increasing Fe# for garnets and omphacites with decreasing pressure. This could be due to the progressive melting of subducted basalts (Rosenthal et al., 2014) or an opposite due to crystallization of evolving partial melts from primary eclogites. In USCLM the GrB3 omphacites show reactional trends with decreasing Fe# upward or an opposite progressive rise due to magmatic differentiation. GrC dominate the middle part of the SCLM (3-4 GPa) and mostly correspond to the layer originated in the Early Archean time at 3.5-4.0 GPa possibly due to subduction of the tonalitic crust and related metasediments. CrD1 -rich grosspyditic varieties from India, Siberia and South Africa are relatively low-Fe and Al-rich and possibly are metasomatites or products of interaction of sediments and peridotites. The other Ca- rich varieties most likely are subducted anorthosites or rare granites. Supported by the RFBR grants: 05-05-64718, 03-05-64146, 11 -05-00060, 11-05-91060-PICS, 16-05-00841, 16-05-00860 and projects 77-2, 65-03, 02-05 UIGGM SB RAS and ALROSA Stock Company

Carbon Chemistry in the Envelope of VY Canis Majoris: Implications for Oxygen-Rich Evolved Stars

NASA Astrophysics Data System (ADS)

Ziurys, L. M.; Tenenbaum, E. D.; Pulliam, R. L.; Woolf, N. J.; Milam, S. N.

2009-04-01

Observations of the carbon-bearing molecules CO, HCN, CS, HNC, CN, and HCO+ have been conducted toward the circumstellar envelope of the oxygen-rich red supergiant star, VY Canis Majoris (VY CMa), using the Arizona Radio Observatory (ARO). CO and HCN were also observed toward the O-rich shells of NML Cyg, TX Cam, IK Tau, and W Hya. Rotational transitions of these species at 1 mm, 0.8 mm, and 0.4 mm were measured with the ARO Submillimeter Telescope, including the J = 6 → 5 line of CO at 691 GHz toward TX Cam and W Hya. The ARO 12 m was used for 2 mm and 3 mm observations. Four transitions were observed for HCO+ in VY CMa, the first definitive identification of this ion in a circumstellar envelope. Molecular line profiles from VY CMa are complex, indicating three separate outflows: a roughly spherical flow and separate red- and blueshifted winds, as suggested by earlier observations. Spectra from the other sources appear to trace a single outflow component. The line data were modeled with a radiative transfer code to establish molecular abundances relative to H2 and source distributions. Abundances for CO derived for these objects vary over an order of magnitude, f ~ 0.4-5 × 10-4, with the lower values corresponding to the supergiants. For HCN, a similar range in abundance is found (f ~ 0.9-9 × 10-6), with no obvious dependence on the mass-loss rate. In VY CMa, HCO+ is present in all three outflows with f ~ 0.4-1.6 × 10-8 and a spatial extent similar to that of CO. HNC is found only in the red- and blueshifted components with [HCN]/[HNC] ~ 150-190, while [CN]/[HCN] ~ 0.01 in the spherical flow. All three velocity components are traced in CS, which has a confined spatial distribution and f ~ 2-6 × 10-7. These observations suggest that carbon-bearing molecules in O-rich shells are produced by a combination of photospheric shocks and photochemistry. Shocks may play a more prominent role in the supergiants because of their macroturbulent velocities.

Phase-dependent Photometric and Spectroscopic Characterization of the MASTER-Net Optical Transient J212444.87+321738.3: An Oxygen-rich Mira

NASA Astrophysics Data System (ADS)

Ghosh, Supriyo; Mondal, Soumen; Das, Ramkrishna; Banerjee, D. P. K.; Ashok, N. M.; Hambsch, Franz-Josef; Dutta, Somnath

2018-05-01

We describe the time-dependent properties of a new spectroscopically confirmed Mira variable, which was discovered in 2013 as MASTER-Net Optical Transient J212444.87+321738.3 toward the Cygnus constellation. We have performed long-term optical/near-infrared (NIR) photometric and spectroscopic observations to characterize the object. From the optical/NIR light curves, we estimate a variability period of 465 ± 30 days. The wavelength-dependent amplitudes of the observed light curves range from ΔI ∼ 4 mag to ΔK ∼ 1.5 mag. The (J ‑ K) color index varies from 1.78 to 2.62 mag over phases. Interestingly, a phase lag of ∼60 days between optical and NIR light curves is also seen, as in other Miras. Our optical/NIR spectra show molecular features of TiO, VO, CO, and strong water bands that are a typical signature of oxygen-rich Mira. We rule out S- or C-type as ZrO bands at 1.03 and 1.06 μm and C2 band at 1.77 μm are absent. We estimate the effective temperature of the object from the Spectral Energy Distribution, and distance and luminosity from standard Period–Luminosity relations. The optical/NIR spectra display time-dependent atomic and molecular features (e.g., TiO, Na I, Ca I, H2O, CO), as commonly observed in Miras. Such spectroscopic observations are useful for studying pulsation variability in Miras.

Inner solar system material discovered in the Oort cloud

PubMed Central

Meech, Karen J.; Yang, Bin; Kleyna, Jan; Hainaut, Olivier R.; Berdyugina, Svetlana; Keane, Jacqueline V.; Micheli, Marco; Morbidelli, Alessandro; Wainscoat, Richard J.

2016-01-01

We have observed C/2014 S3 (PANSTARRS), a recently discovered object on a cometary orbit coming from the Oort cloud that is physically similar to an inner main belt rocky S-type asteroid. Recent dynamical models successfully reproduce the key characteristics of our current solar system; some of these models require significant migration of the giant planets, whereas others do not. These models provide different predictions on the presence of rocky material expelled from the inner solar system in the Oort cloud. C/2014 S3 could be the key to verifying these predictions of the migration-based dynamical models. Furthermore, this object displays a very faint, weak level of comet-like activity, five to six orders of magnitude less than that of typical ice-rich comets on similar Orbits coming from the Oort cloud. For the nearly tailless appearance, we are calling C/2014 S3 a Manx object. Various arguments convince us that this activity is produced by sublimation of volatile ice, that is, normal cometary activity. The activity implies that C/2014 S3 has retained a tiny fraction of the water that is expected to be present at its formation distance in the inner solar system. We may be looking at fresh inner solar system Earth-forming material that was ejected from the inner solar system and preserved for billions of years in the Oort cloud. PMID:27386512

Inner solar system material discovered in the Oort cloud.

PubMed

Meech, Karen J; Yang, Bin; Kleyna, Jan; Hainaut, Olivier R; Berdyugina, Svetlana; Keane, Jacqueline V; Micheli, Marco; Morbidelli, Alessandro; Wainscoat, Richard J

2016-04-01

We have observed C/2014 S3 (PANSTARRS), a recently discovered object on a cometary orbit coming from the Oort cloud that is physically similar to an inner main belt rocky S-type asteroid. Recent dynamical models successfully reproduce the key characteristics of our current solar system; some of these models require significant migration of the giant planets, whereas others do not. These models provide different predictions on the presence of rocky material expelled from the inner solar system in the Oort cloud. C/2014 S3 could be the key to verifying these predictions of the migration-based dynamical models. Furthermore, this object displays a very faint, weak level of comet-like activity, five to six orders of magnitude less than that of typical ice-rich comets on similar Orbits coming from the Oort cloud. For the nearly tailless appearance, we are calling C/2014 S3 a Manx object. Various arguments convince us that this activity is produced by sublimation of volatile ice, that is, normal cometary activity. The activity implies that C/2014 S3 has retained a tiny fraction of the water that is expected to be present at its formation distance in the inner solar system. We may be looking at fresh inner solar system Earth-forming material that was ejected from the inner solar system and preserved for billions of years in the Oort cloud.

c9t11-Conjugated linoleic acid-rich oil fails to attenuate wasting in colon-26 tumor-induced late-stage cancer cachexia in male CD2F1 mice.

PubMed

Tian, Min; Kliewer, Kara L; Asp, Michelle L; Stout, Michael B; Belury, Martha A

2011-02-01

Cancer cachexia is characterized by muscle and adipose tissue wasting caused partly by chronic, systemic inflammation. Conjugated linoleic acids (CLAs) are a group of fatty acids with various properties including anti-inflammatory cis9, trans11 (c9t11)-CLA and lipid-mobilizing trans10, cis12 (t10c12)-CLA. The purpose of this study was to test whether dietary supplementation of a c9t11-CLA-rich oil (6:1 c9t11:t10c12) could attenuate wasting of muscle and adipose tissue in colon-26 adenocarcinoma-induced cachexia in mice. Loss of body weight, muscle and adipose tissue mass caused by tumors were not rescued by supplementation with the c9t11-CLA-rich oil. In quadriceps muscle, c9t11-CLA-rich oil exacerbated tumor-induced gene expression of inflammatory markers tumor necrosis factor-α, IL-6 receptor and the E3 ligase MuRF-1 involved in muscle proteolysis. In epididymal adipose tissue, tumor-driven delipidation and atrophy was aggravated by the c9,t11-CLA-rich oil, demonstrated by further reduced adipocyte size and lower adiponectin expression. However, expression of inflammatory cytokines and macrophage markers were not altered by tumors, or CLA supplementation. These data suggest that addition of c9t11-CLA-rich oil (0.6% c9t11, 0.1% t10c12) in diet did not ameliorate wasting in mice with cancer cachexia. Instead, it increased expression of inflammatory markers in the muscle and increased adipose delipidation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Density functional study of carbon vacancies in titanium carbide

NASA Astrophysics Data System (ADS)

Råsander, Mikael; Hugosson, Håkan W.; Delin, Anna

2018-01-01

It is well established that TiC contains carbon vacancies not only in carbon-deficient environments but also in carbon-rich environments. We have performed density functional calculations of the vacancy formation energy in TiC for C- as well as Ti-rich conditions using several different approximations to the exchange-correlation functional, and also carefully considering the nature and thermodynamics of the carbon reference state, as well as the effect of varying growth conditions. We find that the formation of carbon vacancies is clearly favorable under Ti-rich conditions, whereas it is slightly energetically unfavorable under C-rich conditions. Furthermore, we find that the relaxations of the atoms close to the vacancy site are rather long-ranged, and that these relaxations contribute significantly to the stabilization of the vacancy. Since carbon vacancies in TiC are also experimentally observed in carbon-rich environments, we conclude that kinetics may play an important role. This conclusion is consistent with the experimentally observed high activation energies and sluggish diffusion of vacancies in TiC, effectively causing a freezing in of the vacancies.

Numerical Analysis of Extremely-rich CH4/O2/H2O Premixed Flames at High Pressure and High Temperature Considering Production of Higher Hydrocarbons

NASA Astrophysics Data System (ADS)

Kumagami, Manabu; Ogami, Yasuhiro; Tamaki, Yuichi; Kobayashi, Hideaki

Numerical analysis of CH4/O2/H2O laminar premixed flame under various conditions of pressure, equivalence ratio and steam concentration was performed using GRI-Mech 3.0 and the mechanism proposed by Davis and Law, which consists of C1 to C6 hydrocarbons in addition to GRI-Mech 3.0. The pressure dependence of laminar burning velocity and flame structure under fuel-rich conditions was focused on. Effects of the formation of higher hydrocarbons under fuel-rich conditions were also clarified using the mechanism proposed by Davis and Law. Results showed that for extremely fuel-rich conditions, laminar burning velocity increases as pressure increases for both mechanisms. The increase of laminar burning velocity is caused by the shift of the oxidation pathway of CH3 radical from the C2 Route to the C1 Route. The formation of C3-C6 hydrocarbons has only a small effect on laminar burning velocity. Under fuel-rich conditions, super-adiabatic flame temperature (SAFT) occurs and its pressure dependency was clarified.

The Physcomitrella patens chromosome-scale assembly reveals moss genome structure and evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lang, Daniel; Ullrich, Kristian K.; Murat, Florent

Here, the draft genome of the moss model, Physcomitrella patens, comprised approximately 2000 unordered scaffolds. In order to enable analyses of genome structure and evolution we generated a chromosome–scale genome assembly using genetic linkage as well as (end) sequencing of long DNA fragments. We find that 57% of the genome comprises transposable elements (TEs), some of which may be actively transposing during the life cycle. Unlike in flowering plant genomes, gene– and TE–rich regions show an overall even distribution along the chromosomes. However, the chromosomes are mono–centric with peaks of a class of Copia elements potentially coinciding with centromeres. Genemore » body methylation is evident in 5.7% of the protein–coding genes, typically coinciding with low GC and low expression. Some giant virus insertions are transcriptionally active and might protect gametes from viral infection via siRNA mediated silencing. Structure–based detection methods show that the genome evolved via two rounds of whole genome duplications (WGDs), apparently common in mosses but not in liverworts and hornworts. Several hundred genes are present in colinear regions conserved since the last common ancestor of plants. These syntenic regions are enriched for functions related to plant–specific cell growth and tissue organization. The P. patens genome lacks the TE–rich pericentromeric and gene–rich distal regions typical for most flowering plant genomes. More non–seed plant genomes are needed to unravel how plant genomes evolve, and to understand whether the P. patens genome structure is typical for mosses or bryophytes.« less

The Physcomitrella patens chromosome-scale assembly reveals moss genome structure and evolution

DOE PAGES

Lang, Daniel; Ullrich, Kristian K.; Murat, Florent; ...

2017-12-13

Here, the draft genome of the moss model, Physcomitrella patens, comprised approximately 2000 unordered scaffolds. In order to enable analyses of genome structure and evolution we generated a chromosome–scale genome assembly using genetic linkage as well as (end) sequencing of long DNA fragments. We find that 57% of the genome comprises transposable elements (TEs), some of which may be actively transposing during the life cycle. Unlike in flowering plant genomes, gene– and TE–rich regions show an overall even distribution along the chromosomes. However, the chromosomes are mono–centric with peaks of a class of Copia elements potentially coinciding with centromeres. Genemore » body methylation is evident in 5.7% of the protein–coding genes, typically coinciding with low GC and low expression. Some giant virus insertions are transcriptionally active and might protect gametes from viral infection via siRNA mediated silencing. Structure–based detection methods show that the genome evolved via two rounds of whole genome duplications (WGDs), apparently common in mosses but not in liverworts and hornworts. Several hundred genes are present in colinear regions conserved since the last common ancestor of plants. These syntenic regions are enriched for functions related to plant–specific cell growth and tissue organization. The P. patens genome lacks the TE–rich pericentromeric and gene–rich distal regions typical for most flowering plant genomes. More non–seed plant genomes are needed to unravel how plant genomes evolve, and to understand whether the P. patens genome structure is typical for mosses or bryophytes.« less

Shadowfax: Moving mesh hydrodynamical integration code

NASA Astrophysics Data System (ADS)

Vandenbroucke, Bert

2016-05-01

Shadowfax simulates galaxy evolution. Written in object-oriented modular C++, it evolves a mixture of gas, subject to the laws of hydrodynamics and gravity, and any collisionless fluid only subject to gravity, such as cold dark matter or stars. For the hydrodynamical integration, it makes use of a (co-) moving Lagrangian mesh. The code has a 2D and 3D version, contains utility programs to generate initial conditions and visualize simulation snapshots, and its input/output is compatible with a number of other simulation codes, e.g. Gadget2 (ascl:0003.001) and GIZMO (ascl:1410.003).

KSC-2009-3662

NASA Image and Video Library

2009-05-01

CAPE CANAVERAL, Fla. – At NASA Kennedy Space Center's Shuttle Landing Facility, the shipping container with the STSS Demonstrator SV-2spacecraft moves out of the U.S. Air Force C-17 aircraft. The spacecraft will be transferred to the Astrotech payload processing facility in Titusville, Fla. The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Jack Pfaller (Approved for Public Release 09-MDA-4616 [27 May 09])

KSC-2009-3658

NASA Image and Video Library

2009-05-01

CAPE CANAVERAL, Fla. – The U.S. Air Force C-17 aircraft arrives at NASA Kennedy Space Center's Shuttle Landing Facility with its cargo of the STSS Demonstrator SV-2 spacecraft. The spacecraft will be transferred to the Astrotech payload processing facility in Titusville, Fla. The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Jack Pfaller (Approved for Public Release 09-MDA-4616 [27 May 09])

KSC-2009-4611

NASA Image and Video Library

2009-06-25

CAPE CANAVERAL, Fla. – The U.S. Air Force C-17 aircraft arrives at NASA Kennedy Space Center's Shuttle Landing Facility with its SV-1 cargo of the STSS Demonstrator spacecraft. The cargo will be transferred to the Astrotech payload processing facility in Titusville, Fla. The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Kim Shiflett (Approved for Public Release 09-MDA-4804 [4 Aug 09] )

KSC-2009-4612

NASA Image and Video Library

2009-06-25

CAPE CANAVERAL, Fla. – At NASA Kennedy Space Center's Shuttle Landing Facility, the SV-1 cargo of the STSS Demonstrator spacecraft moves out of the U.S. Air Force C-17. The cargo will be transferred to the Astrotech payload processing facility in Titusville, Fla. The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Kim Shiflett (Approved for Public Release 09-MDA-4804 [4 Aug 09] )

KSC-2009-3660

NASA Image and Video Library

2009-05-01

CAPE CANAVERAL, Fla. – At NASA Kennedy Space Center's Shuttle Landing Facility, more equipment for the STSS Demonstrator SV-2 spacecraft is offloaded from the U.S. Air Force C-17 aircraft. The spacecraft will be transferred to the Astrotech payload processing facility in Titusville, Fla.The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Jack Pfaller (Approved for Public Release 09-MDA-4616 [27 May 09])

KSC-2009-4613

NASA Image and Video Library

2009-06-25

CAPE CANAVERAL, Fla. – At NASA Kennedy Space Center's Shuttle Landing Facility, the SV-1 cargo of the STSS Demonstrator spacecraft moves out of the U.S. Air Force C-17. The cargo will be transferred to the Astrotech payload processing facility in Titusville, Fla. The spacecraft is a midcourse tracking technology demonstrator, part of an evolving ballistic missile defense system. STSS is capable of tracking objects after boost phase and provides trajectory information to other sensors. It will be launched by NASA for the Missile Defense Agency in late summer. Photo credit: NASA/Kim Shiflett (Approved for Public Release 09-MDA-4804 [4 Aug 09] )

Lithium Inventory of 2 Solar Mass Red Clump Stars in Open Clusters: A Test of the Helium Flash Mechanism

NASA Technical Reports Server (NTRS)

Carlberg, Joleen K.; Cunha, Katia; Smith, Verne V.

2016-01-01

The temperature distribution of field Li-rich red giants suggests the presence of a population of Li-rich red clump (RC) stars. One proposed explanation for this population is that all stars with masses near 2 solar mass experience a shortlived phase of Li-richness at the onset of core He-burning. Many of these stars have low C-12/C-13, a signature of deep mixing that is presumably associated with the Li regeneration. To test this purported mechanism of Li enrichment, we measured abundances in 38 RC stars and 6 red giant branch (RGB) stars in four open clusters selected to have RC masses near 2 solar mass. We find six Li-rich stars (A(Li) greater than or equal to 1.50 dex) of which only two may be RC stars. None of the RC stars have Li exceeding the levels observed in the RGB stars, but given the brevity of the suggested Li-rich phase and the modest sample size, it is probable that stars with larger Li-enrichments were missed simply by chance. However, we find very few stars in our sample with low C-12/C-13. Such low C-12/C-13, seen in many field Li-rich stars, should persist even after lithium has returned to normal low levels. Thus, if Li synthesis during the He flash occurs, it is a rare, but potentially long-lived occurrence rather than a short-lived phase for all stars. We estimate a conservative upper limit of the fraction of stars going through a Li-rich phase to be less than 47%, based on stars that have low C-12/C-13 for their observed A(Li).

Three-strategy N-person snowdrift game incorporating loners

NASA Astrophysics Data System (ADS)

Xu, Meng; Zheng, Da-Fang; Xu, C.; Hui, P. M.

2017-02-01

The N-person snowdrift game is generalized to incorporate a third strategy. In addition to the cooperative C and non-cooperative D strategies, a strategy L representing a loner behavior is introduced. Agents taking on the L strategy (L-agents) do not contribute to the game as the C-agents do but they do not take advantage of the C-agents. Instead, they would rather settle with a fixed payoff L. Dynamical equations governing the time evolution of the frequencies of the strategies in a well-mixed population are derived. The dynamics and the frequencies of the steady state reveal the rich behavior resulting from the interplay between the payoff r, which promotes the non-cooperative behavior, and L. Detailed studies on how a system evolves indicated that the steady state could be an AllL, AllC, or C+D state, depending on the parameters r, L, and group size N. In contrast, only a C+D state results for r > 0 and an AllC state is possible only at r = 0 without the strategy L. With the strategy L, the AllC phase occupies a finite, though tiny, region of the r- L parameter space. The L-agents play an important role in the dynamics leading to the AllC phase. They help eliminate the D strategy in the transient and later only to be replaced by the C strategy. Phase diagrams in the r- L space are presented for different values of N. The strategy L plays two roles. It leads to an AllL phase and helps give an AllC phase. An algorithm for simulating the model numerically is described and validated. The algorithm will be useful in studying our model in various structured populations.

Changing Personas and Evolving Identities: The Contestation and Renegotiation of Researcher Roles in Fieldwork

ERIC Educational Resources Information Center

Purdy, Laura; Jones, Robyn

2013-01-01

The aim of this paper is to discuss the development and evolution of particular personas adopted by researchers in the quest for rich exchanges within the social field. It analyses my role (the principal author) as a female ethnographer (and the sole female) in the world of elite male rowing. Data are drawn from personal notes, reflections and…

Intrinsic evolution of controllable oscillators in FPTA-2

NASA Technical Reports Server (NTRS)

Sekanina, Lukas; Zebulum, Ricardo S.

2005-01-01

Simple one- and two-bit controllable oscillators were intrinsically evolved using only four cells of Field Programmable Transistor Array (FPTA-2). These oscillators can produce different oscillations for different setting of control signals. Therefore, they could be used, in principle, to compose complex networks of oscillators that could exhibit rich dynamical behavior in order to perform a computation or to model a desired system.

Evolution in thermodynamics

NASA Astrophysics Data System (ADS)

Bejan, Adrian

2017-03-01

This review covers two aspects of "evolution" in thermodynamics. First, with the constructal law, thermodynamics is becoming the domain of physics that accounts for the phenomenon of evolution in nature, in general. Second, thermodynamics (and science generally) is the evolving add-on that empowers humans to predict the future and move more easily on earth, farther and longer in time. The part of nature that thermodynamics represents is this: nothing moves by itself unless it is driven by power, which is then destroyed (dissipated) during movement. Nothing evolves unless it flows and has the freedom to change its architecture such that it provides greater and easier access to the available space. Thermodynamics is the modern science of heat and work and their usefulness, which comes from converting the work (power) into movement (life) in flow architectures that evolve over time to facilitate movement. I also review the rich history of the science, and I clarify misconceptions regarding the second law, entropy, disorder, and the arrow of time, and the supposed analogy between heat and work.

Holocentric chromosomes of psocids (Insecta, Psocoptera) analysed by C-banding, silver impregnation and sequence specific fluorochromes CMA3 and DAPI.

PubMed

Golub, Natalia V; Nokkala, Seppo; Kuznetsova, Valentina G

2004-01-01

The pattern of nucleolus attachment and C-heterochromatin distribution and molecular composition in the karyotypes of psocid species Psococerastis gibbosa (2n = 16+X), Blaste conspurcata (2n = 16+X) and Amphipsocus japonicus (2n = 14+neo-XY) were studied by C-banding, silver impregnation and sequence specific fluorochromes CMA3 and DAPI. Every species was found to have a single nucleolus in male meiosis. In P. gibbosa the nucleolus is attached to an autosomal bivalent; in B. conspurcata to the X-chromosome; in A. japonicus to the neo-XY bivalent. The species show a rather small amount of constitutive heterochromatin, C-blocks demonstrating telomeric localization with rare exceptions. P. gibbosa is characterized by a polymorphism for C-blocks occurrence and distribution. In the autosomes of this species, C-heterochromatin consists of AT-rich DNA except for the nucleolus organizing region, which is also GC-rich; the X-chromosome shows both AT- and GC-rich clusters. In A. japonicus and B. conspurcata, C-heterochromatin of the autosomes and sex chromosomes consists of both GC-rich and AT-rich DNA clusters, which are largely co-localized.

Organic Chemistry of Low-Mass Star-Forming Cores. I. 7 mm Spectroscopy of Chamaeleon MMSl

NASA Technical Reports Server (NTRS)

Cordiner, Martn A.; Charnley, Steven B.; Wirtstroem, Eva S.; Smith, Robert G.

2012-01-01

Observations are presented of emission lines from organic molecules at frequencies 32-50 GHz in the vicinity of Chamaeleon MMS1. This chemically rich dense cloud core harbors an extremely young, very low luminosity protostellar object and is a candidate first hydrostatic core. Column densities are derived and emission maps are presented for species including polyynes, cyanopolyynes, sulphuretted carbon chains, and methanol. The polyyne emission peak lies about 5000 AU from the protostar, whereas methanol peaks about 15,000 AU away. Averaged over the telescope beam, the molecular hydrogen number density is calculated to be 10(exp 6) / cubic cm and the gas kinetic temperature is in the range 5-7 K. The abundances of long carbon chains are very large and are indicative of a nonequilibrium carbon chemistry; C6H and HC7N column densities are 5.9(sup +2.9) (sub -1.3) x 10(exp 11) /cubic cm and 3.3 (sup +8.0)(sub -1.5) x 10(exp 12)/sq cm, respectively, which are similar to the values found in the most carbon-chain-rich protostars and prestellar cores known, and are unusually large for star-forming gas. Column density upper limits were obtained for the carbon chain anions C4H(-) and C6H(-), with anion-to-neutral ratios [C4H(-)]/[C4H] < 0.02% and [C6H(-l)]/[C6H] < 10%, consistent with previous observations in interstellar clouds and low-mass protostars. Deuterated HC,3 and c-C3H2 were detected. The [DC3N]/[HC,N] ratio of approximately 4% is consistent with the value typically found in cold interstellar gas.

J-type Carbon Stars: A Dominant Source of 14 N-rich Presolar SiC Grains of Type AB

DOE PAGES

Liu, Nan; Stephan, Thomas; Boehnke, Patrick; ...

2017-07-21

Here, we report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB ( 14N/ 15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takesmore » place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. And because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%–15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.« less

J-type Carbon Stars: A Dominant Source of {sup 14}N-rich Presolar SiC Grains of Type AB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Nittler, Larry R.; Alexander, Conel M. O’D.

We report Mo isotopic data of 27 new presolar SiC grains, including 12 {sup 14}N-rich AB ({sup 14}N/{sup 15}N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s -process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s -process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture processmore » ( i -process) takes place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show {sup 13}C and {sup 14}N excesses but no s -process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%–15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.« less

J-type Carbon Stars: A Dominant Source of 14 N-rich Presolar SiC Grains of Type AB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Stephan, Thomas; Boehnke, Patrick

Here, we report Mo isotopic data of 27 new presolar SiC grains, including 12 14N-rich AB ( 14N/ 15N > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takesmore » place, as their stellar source. On the other hand, low-mass CO novae and early R- and J-type carbon stars show 13C and 14N excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. And because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%–15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.« less

J-type Carbon Stars: A Dominant Source of 14 N-rich Presolar SiC Grains of Type AB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Nan; Stephan, Thomas; Boehnke, Patrick

We report Mo isotopic data of 27 new presolar SiC grains, including 12 N-14-rich AB (N-14/N-15 > 440, AB2) and 15 mainstream (MS) grains, and their correlated Sr and Ba isotope ratios when available. Direct comparison of the data for the MS grains, which came from low-mass asymptotic giant branch (AGB) stars with large s-process isotope enhancements, with the AB2 grain data demonstrates that AB2 grains show near-solar isotopic compositions and lack s-process enhancements. The near-normal Sr, Mo, and Ba isotopic compositions of AB2 grains clearly exclude born-again AGB stars, where the intermediate neutron-capture process (i-process) takes place, as theirmore » stellar source. On the other hand, low-mass CO novae and early R-and J-type carbon stars show C-13 and N-14 excesses but no s-process enhancements and are thus potential stellar sources of AB2 grains. Because both early R-type carbon stars and CO novae are rare objects, the abundant J-type carbon stars (10%-15% of all carbon stars) are thus likely to be a dominant source of AB2 grains.« less

Carbon and nitrogen in Type 2 supernova diamonds

NASA Astrophysics Data System (ADS)

Clayton, Donald D.; Eleid, Mounib; Brown, Lawrence E.

1993-03-01

Abundant diamonds found in meteorites seem either to have condensed within supernova interiors during their expansions and coolings or to have been present around those explosions. Either alternative allows implantation of Xe-HL prior to interstellar mixing. A puzzling feature is the near normalcy of the carbon isotopes, considering that the only C-rich matter, the He-burning shell, is pure C-12 in that region. That last fact has caused many to associate supernova carbon with C-12 carbon, so that its SUNOCONS have been anticipated as very C-12-rich. We show that this expectation is misleading because the C-13-rich regions of Type 2's have been largely overlooked in this thinking. We here follow the idea that the diamonds nucleated in the C-12-rich He shell, the only C-rich site for nucleation, but then attached C-13-rich carbon during turbulent encounters with overlying C-13-rich matter. That is, the initial diamonds continued to grow during the same collisional encounters that cause the Xe-HL implantation. Instead of interacting with the small carbon mass having 13/12 = 0.2 in the upper He zone, however, we have calculated the remnants of the initial H-burning core, which left behind C-13-rich matter as it receded during core hydrogen burning. Howard et al. described why the velocity mixing would be essential to understanding the implantation of both the Xe-H and Xe-L components. Velocity mixing is now known to occur from the X-ray and gamma-ray light curves of supernova 1987A. Using the stellar evolution code developed at Goettingen, we calculated at Clemson the evolution of a grid of massive stars up to the beginning of core He burning. We paid attention to all H-burning reactions throughout the star, to the treatment of both convection and semiconvection, and to the recession of the outer boundary of the convective H-burning core as the star expands toward a larger redder state. This program was to generate a careful map of the CNO isotope distribution as He burning begins. Our result for the 30 solar mass star is shown.

Siderophile Element Partitioning between Sulfide- and Silicate melts.

NASA Astrophysics Data System (ADS)

Hackler, S.; Rohrbach, A.; Loroch, D. C.; Klemme, S.; Berndt, J.

2017-12-01

Different theories concerning the formation of the Earth are debated. Either Earth accreted mostly `dry' or volatile elements were delivered late after core formation was largely inactive [1, 2], or volatile rich material was accreted during the main stages of accretion and core formation [3, 4, 5]. The partitioning behavior of siderophile volatile elements (SVE; S, Se, Te, Tl, Ag, Au, Cd, Bi, Pb, Sn, Cu, Ge, and In) may provide first order constraints whether these element concentrations in Earth's mantle were established before or after core-mantle differentiation or perhaps during both periods by multi stage core formation [6]. A special interest is laid into chalcophile element behavior with respective to the possible formation and segregation of a hadean matte [7]. To examine the influence of sulfur on SVE partitioning between metal-silicate melts, we performed experiments simulating a magma ocean stage evolving from sulfur poor- (low fO2) to more oxidizing sulfur rich- (Fe, Ni)-S melts ( 20 wt% S) towards the end of accretion. We carried out partitioning experiments under various P-T-fO2 conditions with a Bristol type end loaded piston cylinder apparatus (<3 GPa) and a 1000 t walker-type multi-anvil press (3-20 GPa). Our results will be presented at the meeting. References: [1] Albarède F. (2009) Nature, 461, 1227-1233. [2] Ballhaus C. et al. (2013) EPSL, 362, 237-245. [3] Fischer-Gödde M. and Kleine T. (2017) Nature, 541, 525 527. [4] Wade J. and Wood B. J. (2005) EPSL, 236, 78-95. [5] Rubie D. et al. (2016) Science, 253, 1141-1144. [6] Rubie D. et al. (2011) EPSL, 301, 31-42. [7] O'Neill H. St. C. (1991) GCA, 55, 1159-1172.

Current Status of Nuclear Physics Research

NASA Astrophysics Data System (ADS)

Bertulani, Carlos A.; Hussein, Mahir S.

2015-12-01

In this review, we discuss the current status of research in nuclear physics which is being carried out in different centers in the world. For this purpose, we supply a short account of the development in the area which evolved over the last nine decades, since the discovery of the neutron. The evolution of the physics of the atomic nucleus went through many stages as more data became available. We briefly discuss models introduced to discern the physics behind the experimental discoveries, such as the shell model, the collective model, the statistical model, the interacting boson model, etc., some of these models may be seemingly in conflict with each other, but this was shown to be only apparent. The richness of the ideas and abundance of theoretical models attests to the important fact that the nucleus is a really singular system in the sense that it evolves from two-body bound states such as the deuteron, to few-body bound states, such as 4He, 7Li, 9Be, etc. and up the ladder to heavier bound nuclei containing up to more than 200 nucleons. Clearly, statistical mechanics, usually employed in systems with very large number of particles, would seemingly not work for such finite systems as the nuclei, neither do other theories which are applicable to condensed matter. The richness of nuclear physics stems from these restrictions. New theories and models are presently being developed. Theories of the structure and reactions of neutron-rich and proton-rich nuclei, called exotic nuclei, halo nuclei, or Borromean nuclei, deal with the wealth of experimental data that became available in the last 35 years. Furthermore, nuclear astrophysics and stellar and Big Bang nucleosynthesis have become a more mature subject. Due to limited space, this review only covers a few selected topics, mainly those with which the authors have worked on. Our aimed potential readers of this review are nuclear physicists and physicists in other areas, as well as graduate students interested in pursuing a career in nuclear physics.

Compound ultrarefractory CAI-bearing inclusions from CV3 carbonaceous chondrites

NASA Astrophysics Data System (ADS)

Ivanova, Marina A.; Krot, Alexander N.; Nagashima, Kazuhide; MacPherson, Glenn J.

2012-12-01